JP4937186B2 - Wireless communication system, communication apparatus, wireless communication method, wireless communication program, and processor - Google Patents

Description

The present invention relates to a wireless communication system, a communication device, a wireless communication method , a wireless communication program, and a processor .

  Turbo codes and turbo decoding were discovered in 1993, and are attracting attention as error correction codes that approach the Shannon limit, which is the theoretical limit of communication. The turbo code is equipped with two RSC (Recursive Systematic Convolutional) code units having two identical connections, and an information bit is input to two code units, but at this time, before being input to one RSC code unit, an interleaver is provided. Is inserted, and the information bits are rearranged and input to one of the code parts, so that a code bit convolved under two independent constraint conditions is generated. Therefore, in the decoding unit, decoding is performed by two maximum a posteriori probability (MAP) estimation units, and transmission bits can be detected with high accuracy by exchanging the reliability obtained by each decoding.

  From the viewpoint that the characteristics can be gradually improved by repeating these two independent constraint conditions, intersymbol interference in which the signal at the previous time becomes interference due to the impulse response of the radio propagation path. Consider the case of a transmission scheme based on a single carrier scheme that is susceptible to (ISI: Inter-Symbol Interference). In this case, convolution of information bits for the purpose of error correction is assumed to be an outer code, and convolution based on the impulse response of the propagation path is assumed to be an inner code. It is possible to gradually detect signals by iterative processing by using the reliability obtained from each of the equalization unit that compensates for distortion due to the path and the decoding unit as prior information for detection of the transmission bits of each other. Turbo equalization techniques have been proposed.

Conventionally, when a plurality of users are multiplexed in the frequency domain, control has been performed so that subcarriers to be used do not overlap each other. A SORM (Spectrum Overlapped Resource Management) scheme that enables overlapping use of carriers has been proposed. This method is a method that makes it possible to separate the spectrum even when the number of reception antennas is smaller than the number of transmission antennas (hereinafter, this state is referred to as Rank drop), and a method that completely separates users in the frequency domain, It is shown that performance such as communication efficiency is improved.
On the other hand, MIMO (Multiple Input Multiple Output), which is a scheme in which a plurality of users use the same frequency and perform communication by space division, assumes that the number of reception antennas is equal to or greater than the number of transmission antennas. This is a technique that is different from SORM.
Kazunari Yokomakura, et al. “Spectrum overlap resource management using dynamic spectrum control”, 2008 Proceedings of the IEICE General Conference, 437 pages, published by the Institute of Electronics, Information and Communication Engineers, March 5, 2008

However, in the conventional technology, when determining the transmission power of the signal used for wireless communication, whether or not the data subjected to the error correction code can be decoded is not considered, and the determined transmission power depends on the determined transmission power. Has a drawback that data transmitted with an error correction code cannot be decoded.
In the conventional technology, for example, the transmission power of the signal transmitted by the transmission device is determined based on the reception power of the reception device or the reception SNR (Signal to Noise power Ratio). Depending on the transmission power of the signal, the data subjected to the error correction code may not be decoded due to the influence of the propagation path or the influence of interference.
In addition, for example, in the conventional technology, a system that can cope with a Rank drop in which a plurality of transmission apparatuses use subcarriers redundantly and perform communication with the number of reception antennas smaller than the number of transmission antennas, such as a SORM system. Assuming a receiver that performs iterative processing, such as turbo equalization technology, there is no method for performing iterative processing appropriately, and depending on the transmission power of the signal, it is impossible to decode data transmitted with turbo code There is.

The present invention has been made in view of the above points, and an object of the present invention is to control the transmission power of data so that a device that has received data transmitted with an error correction code can decode it. A wireless communication system, a communication apparatus, a wireless communication method , a wireless communication program, and a processor are provided.

(1) The present invention has been made to solve the above-described problems, and one aspect thereof is a first communication device that transmits data subjected to an error correction code, and a transmission from the first communication device. A second communication device that performs equalization processing for compensating distortion of the transmission path and decoding processing using an error correction code to decode the data before the error correction code is applied to the signal of the received data. In the wireless communication system provided, the second communication device includes an equalized data reliability detection unit that detects equalized data reliability information based on a frequency response of a subcarrier to be used and noise in the second communication device. A transmission power determining unit that determines transmission power required when the first communication device transmits the data signal using the equalized data reliability information detected by the equalized data reliability detection unit and, with a, Serial first communication apparatus, the transmission power required when the first communication device transmits a signal of the data, transmission power control is determined based on the information notified from the second communication device It is a radio | wireless communications system characterized by providing a part .

  (2) Further, according to one aspect of the present invention, the wireless communication system includes a plurality of the first communication devices, and the equalized data reliability detection unit is configured to perform the equalized data reliability according to transmission power. The information is detected, and the transmission power determining unit transmits the reliability represented by the equalized data reliability information of each of the data transmitted from the plurality of first communication devices so as to be higher than a predetermined reliability. Determine the power.

(3) Further, according to one aspect of the present invention, the wireless communication system includes a plurality of the first communication devices that transmit data while sharing at least some of the subcarriers, and the equalized data reliability detection A unit detects the equalized data reliability information according to transmission power, and the transmission power determination unit represents the equalized data reliability information of each of data transmitted from the plurality of first communication devices. The transmission power is determined so that the reliability is higher than the predetermined reliability.
According to the above configuration, the wireless communication system can improve communication efficiency because a plurality of the first communication devices transmit data while sharing subcarriers.

  (4) Moreover, 1 aspect of this invention WHEREIN: The said transmission power determination part determines the said transmission power for every subcarrier.

(5) In addition, according to one aspect of the present invention, an error correction code equalizing process that compensates for distortion of a transmission path is performed on the data signal subjected to the error correction code transmitted from the first communication apparatus. In the second communication device that performs the decoding process and decodes the data before applying the error correction code,
Equalized data reliability detector for detecting equalized data reliability information based on frequency response of subcarrier to be used and noise in second communication device, and equalization detected by equalized data reliability detector A communication apparatus comprising: a transmission power determining unit that determines transmission power required when the first communication apparatus transmits the data signal using data reliability information.

(6) Further, according to one aspect of the present invention, an error correction code is used for equalization processing that compensates for distortion of a transmission path for a data signal subjected to an error correction code transmitted from the first communication device. A communication method in a second communication device that performs decoding processing and decodes data before applying an error correction code, wherein the communication device uses a frequency response of a subcarrier used and noise in the second communication device. A first process of detecting equalized data reliability information based on the first data, and the first communication apparatus uses the equalized data reliability information detected by the communication apparatus in the first process. And a second step of determining transmission power required when transmitting a data signal.

(7) One embodiment of the present invention is based on an equalization process for compensating for distortion of a transmission path for an error correction code signal transmitted from a first communication apparatus, and an error correction code. A frequency response of a subcarrier used for communication between the first communication device and the second communication device is sent to a computer of the second communication device that performs decoding processing and decodes data before being subjected to error correction code. And equalized data reliability detecting means for detecting equalized data reliability information based on noise in the second communication device, using the equalized data reliability information detected by the equalized data reliability detecting means The wireless communication program causes the first communication apparatus to function as transmission power determining means for determining transmission power required when transmitting the data signal.

(8) Further, according to one aspect of the present invention, an error correction code is used for equalization processing that compensates for distortion of a transmission path for a data signal that has been subjected to the error correction code transmitted from the first communication device, and the error correction code. A processor mounted on a second communication device that performs decoding processing and decodes data before being subjected to error correction code, and is used for communication between the first communication device and the second communication device Based on the frequency response of the subcarrier and the noise in the second communication device, the transmission power required when the first communication device transmits the data signal is determined using equalized data reliability information. It is a processor characterized by doing.

(9) Further, according to one aspect of the present invention, an error correction code is used for equalization processing that compensates for distortion of a transmission path for a data signal subjected to an error correction code transmitted from the first communication device. Equalized data reliability for detecting equalized data reliability information representing the reliability of the data after the equalization process in the second communication device that performs the decoding process and decodes the data before the error correction code is applied When the equalization data reliability information detected by the detection unit and the equalization data reliability detection unit is lower than the predetermined reliability, the first transmission device is not shared with the other first transmission devices. And a transmission power determining unit that determines to increase the transmission power for a signal to be allocated to a carrier.

(10) One embodiment of the present invention is based on an equalization process for compensating for distortion of a transmission path for a data signal subjected to an error correction code transmitted from the first communication apparatus, and an error correction code. Equalized data reliability for detecting equalized data reliability information representing the reliability of the data after the equalization process in the second communication device that performs the decoding process and decodes the data before the error correction code is applied When the equalization data reliability information detected by the detection unit and the equalization data reliability detection unit is higher than the predetermined reliability, the first transmission device shares with the other first transmission devices. And a transmission power determining unit that determines to reduce the transmission power for a signal to be assigned to a carrier.

(11) One embodiment of the present invention is based on an equalization process for compensating for distortion of a transmission path for a data signal subjected to an error correction code transmitted from the first communication apparatus, and the error correction code. In the second communication device that performs the decoding process and decodes the data before applying the error correction code,
Equalized data reliability information representing the reliability of the data after the equalization processing, such as detecting equalized data reliability information representing the reliability based on the input / output characteristics of the mutual information amount related to the decoding processing, etc. Transmission power required when the first communication device transmits the data signal using the equalized data reliability detection unit and the equalized data reliability information detected by the equalized data reliability detection unit And a transmission power determination unit that determines the transmission power.

(12) One embodiment of the present invention is based on an equalization process for compensating for distortion of a transmission path for a data signal subjected to an error correction code transmitted from the first communication apparatus, and an error correction code. An equalized data reliability detection unit for detecting a mutual information amount calculated from the equivalent amplitude gain after the equalization process in the second communication device that performs decoding processing and decodes the data before applying the error correction code A transmission power determination unit that determines transmission power required when the first communication device transmits the data signal using the mutual information amount detected by the equalization data reliability detection unit; It is a communication apparatus characterized by comprising.

(13) In addition, according to one aspect of the present invention, an error correction code is used for equalization processing that compensates for transmission path distortion for a data signal subjected to an error correction code transmitted from the first communication device. In a second communication device that repeatedly performs decoding processing and decodes data before performing error correction code, equalized data reliability information representing reliability of the data after the equalization processing, Using the equalized data reliability detection unit that detects equalized data reliability information of at least two of the equalization processes, and the equalized data reliability information detected by the equalized data reliability detection unit, A transmission power determining unit configured to determine transmission power required when the first communication apparatus transmits the data signal;

(14) Further, according to one aspect of the present invention, the communication device may be configured such that the equalized data reliability information of the at least two equalization processes is equalized data reliability of the first equalization process. Information and equalization data reliability information for the equalization process when transmission path distortion is completely compensated.

(15) Further, according to one aspect of the present invention, an error correction code is used for equalization processing that compensates for distortion of a transmission path for a data signal subjected to an error correction code transmitted from the first communication device. An equalization data reliability detection unit for detecting equalization data reliability information for the first equalization process in the second communication device that repeatedly performs the decoding process and decodes the data before the error correction code is applied; A transmission power determining unit that determines transmission power required when the first communication device transmits the data signal using the equalized data reliability information detected by the equalized data reliability detection unit And a communication device .

  According to the present invention, a wireless communication system determines transmission power of a data signal using equalized data reliability information, which is information that can be used to determine whether data transmitted with an error correction code can be decoded. Therefore, the transmission power of the signal can be controlled so that the data transmitted with the error correction code can be decoded.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram of a radio communication system according to the first embodiment of the present invention.
In this figure, mobile station apparatus A (second communication apparatus, communication apparatus) and mobile station apparatuses 1 to 3 (mobile station apparatus X, first communication apparatus, other communication apparatuses) perform wireless communication. As will be described later, the base station apparatus A determines allocation of uplink subcarriers used by the mobile station apparatuses 1 to 3 for communication, and notifies the mobile station apparatuses 1 to 3 of the allocation. Moreover, the mobile station apparatuses 1 to 3 transmit pilot signals used for propagation path estimation to the base station apparatus A.

As an equalization method, the base station apparatus A uses a frequency domain SC / MMSE (Soft Cellular Followed by Minimum Mean Square Error) turbo equalization technique for a single carrier method. However, the present invention is not limited to this. For example, the base station apparatus A can add a cyclic prefix (Cyclic Prefix) to the mobile station apparatus X and use a DFT- An equalization technique may be used for any communication system using an S-OFDM (Discrete Fourier Transform Orthogonal Frequency Division Multiplexing) system, an MC-CDMA system, and an OFDM system.
In addition, regarding the equalization technique, the base station apparatus A is not limited to the frequency domain SC / MMSE, and may use, for example, time domain SC / MMSE or maximum a posteriori probability (MAP) equalization. . In addition, the base station apparatus A employs a technique for performing iterative equalization processing, but a technique that does not perform iterative equalization processing can be employed by considering the number of repetitions as one.

Hereinafter, a communication method for performing communication by selecting subcarriers that are orthogonal to each other on the frequency axis from the bands used for communication by each mobile station device X and base station device A so as not to overlap is referred to as DSC- The FDM (Dynamic Spectrum Control-Frequency Division Multiplexing) method is called, and a communication method that may be selected so as to overlap is called a SORM (Spectrum Overlapped Resource Management) method.
In this embodiment, the communication system is DSC-FDM.

Next, mobile station apparatus X (mobile station apparatuses 1 to 3) will be described.
FIG. 2 is a schematic block diagram showing the configuration of the mobile station apparatus X according to this embodiment. The mobile station apparatus X includes antennas x101 and x114, a reception unit x102, a control unit x103, an encoding unit x104, an S / P (Serial / Parallel) serial conversion unit x105, and a DFT (Discrete Fourier Transform). Unit x106, subcarrier allocation unit x107, transmission power control unit x108, IDFT (Inverse Discrete Fourier Transform) unit x109, CP (Cyclic Prefix) insertion unit x110, P / S (Parallel / Serial) : Parallel / serial) conversion unit x111, D / A (Digital / Analog) conversion unit x112, and RF (Radi) Frequency: is equipped with a radio frequency) section x113.

The reception unit x102 down-converts a reception signal received via the antenna x101 from a radio frequency signal to a baseband signal, and then outputs data converted into a digital signal by analog / digital conversion to the control unit x103. For example, the reception unit x102 outputs the transmission power information notified by the base station device A (base station device A1 in this embodiment) and the subcarrier allocation information to the control unit x103.
The control unit x103 extracts transmission power information (an increase / decrease number SP described later) from the data input from the reception unit x102. Controller x103 stores the power control values associated with increased or decreased number of SP ^g X (SP), using the power control value ^g X (SP) corresponding to the extracted count change SP, the mobile station apparatus X Controls transmission power when transmitting a data signal to the base station apparatus A1. Here, the power control value g ^X (SP) indicates an increase / decrease in the increase / decrease number SP (dB) for simplicity.
The control unit x103 outputs control information for controlling the transmission power of the signal to the transmission power control unit x108 according to the power control value g ^X (SP). This control method is control information for multiplying the transmission power of a signal by g ^X (SP) with respect to the transmission power when a predetermined initial state g ^X (SP = 0) = 1. As an initial state, the average of the previous communication or the previous communication, or the power when the propagation path estimation signal is transmitted is used. Incidentally, the square of the amplitude of the signal is proportional to the transmission power, the transmission power is g ^{X (SP)} times, the square also g ^{X (SP)} times the amplitude of the signal.
Further, the control unit x103 extracts subcarrier allocation information from the data input from the reception unit x102, and outputs control information that causes the subcarrier allocation unit x107 to allocate a signal to the subcarrier of the subcarrier allocation information. To do.

The encoding unit x104 performs encoding such as error correction on the input transmission data, and further, BPSK (Binary Phase Shift Keying), QPSK (Quadrature Amplitude Modulation), etc. To generate a time-axis signal and output it to the S / P converter x105.
The S / P conversion unit x105 serial / parallel converts the time axis signal input from the encoding unit x104 and outputs the result to the DFT unit x106.
The DFT unit x106 performs discrete Fourier transform on the time axis signal input from the S / P conversion unit x105, generates a frequency signal, and outputs the frequency signal to the subcarrier allocation unit x107.

  The subcarrier allocation unit x107 allocates the frequency signal input from the DFT unit x106 to the subcarrier according to the control information input from the control unit x103, and outputs the subcarrier to the transmission power control unit x108.

The transmission power control unit x108 changes the transmission power of the signal allocated for each subcarrier input from the subcarrier allocation unit x107 according to the control information input from the control unit x103, and outputs it to the IDFT unit x109. That is, the transmission power control unit x108 sets the transmission power when transmitting a data signal to the base station apparatus A1 as the transmission power represented by the information notified from the transmission power information notification unit a111 of the base station apparatus A1.
If the signal transmission power is changed by the same amount for all subcarriers at the same time, the signal transmission power may be controlled after the processing of the P / S conversion unit x111, or the D / A conversion unit x112 may You may control transmission power with respect to the analog signal after a process.

The IDFT unit x109 performs inverse discrete Fourier transform on the frequency signal assigned to the subcarrier input from the transmission power control unit x108 to obtain a time signal, and outputs this to the CP insertion unit x110.
CP insertion section x110 inserts a predetermined cyclic prefix (CP) into the signal input from IDFT section x109, and outputs the signal to P / S conversion section x111.
The P / S conversion unit x111 performs parallel / serial conversion on the signal input from the CP insertion unit x110 and outputs the result to the D / A conversion unit x112.
The D / A conversion unit x112 converts the digital signal input from the P / S conversion unit x111 into an analog signal and outputs the analog signal to the RF unit x113.
The RF unit x113 up-converts the analog signal input from the D / A conversion unit x112 into a radio frequency signal, and transmits the signal to the base station apparatus A1 via the antenna x114.

Next, the base station apparatus A1 that is the base station apparatus A (FIG. 1) according to the present embodiment will be described.
FIG. 3 is a schematic block diagram showing the configuration of the base station apparatus A1 according to the first embodiment of the present invention.
The base station apparatus A1 includes antennas a101 and a113, a reception unit a102, a pilot separation unit a103, a propagation path characteristic / dispersion estimation unit a104, a CP (Cyclic Prefix) removal unit a105, an FFT (Fast Fourier Transform). (Conversion) unit a106, equalization / decoding unit a107, subcarrier allocation determination unit a108, transmission power determination unit a109, equalization data reliability detection unit a110, transmission power notification unit a111, and transmission unit a112 .

The receiving unit a102 down-converts the received signal received from the mobile station device X via the antenna a101 from a radio frequency signal to a baseband signal, and outputs it to the pilot separation unit a103.
The pilot separation unit a103 separates the reception signal input from the reception unit a102 into a pilot signal and a reception data signal. The pilot separation unit a103 outputs the separated pilot signal to the propagation path characteristic / dispersion estimation unit a104. The pilot separation unit a103 outputs the separated received data signal to the CP removal unit a105.

The propagation path characteristic / dispersion estimation unit a104 uses the pilot signal input from the reception unit a102 to refer to the frequency response of the propagation path of the mobile station apparatus X (hereinafter referred to as propagation path characteristic ξ ^X (k), where k is k. The first discrete frequency) and the thermal noise variance σ ² (or the average received signal-to-noise ratio of the entire band) in the base station apparatus A1 are estimated. The propagation path characteristic / dispersion estimator a104 obtains information on the estimated propagation path characteristic ξ ^X (k) and thermal noise variance σ ² for each piece of information of the mobile station apparatus X. It outputs to the carrier determination part a108.
Note that the propagation path characteristic / dispersion estimation unit a104 may use the propagation path characteristic ξ ^X (k) estimated in the previous communication when performing continuous communication.

CP removing section a105 removes the cyclic prefix of the received data signal input from pilot separating section a103, and outputs the signal from which the cyclic prefix has been removed to FFT section a106.
The FFT unit a106 converts the received data signal, which is a time signal input from the CP removal unit a105, into a frequency signal by fast Fourier transform, and the converted signal is the subcarrier allocation determined by the subcarrier allocation determination unit a108. Based on the information indicating the assignment, each signal of mobile station apparatus X is output to equalization / decoding section a107.
The equalization / decoding unit a107 performs equalization processing for compensating for distortion in the transmission path and decoding processing using an error correction code, decodes data before the error correction code, and outputs decoded bits. Details of the processing of the equalization / decoding unit a107 will be described later.

The subcarrier allocation determination unit a108 determines allocation of subcarriers used for communication with the mobile station apparatus X.
For example, the subcarrier allocation determination unit a108 allocates, to each mobile station apparatus X, a subcarrier having a large value of the channel characteristic ξ ^X (k) input to the channel characteristic / dispersion estimation unit a104. However, the present invention is not limited to this, and for example, subcarrier allocation may be determined in advance.
The subcarrier allocation determining unit a108 outputs the propagation path characteristic ξ ^X (k) and the thermal noise variance σ ² regarding the determined subcarrier allocation to the transmission power determining unit a109.
Information indicating the subcarrier allocation determined by the subcarrier allocation determination unit a108 is transmitted to the mobile station apparatus X via the transmission unit a112 and the antenna a113. The mobile station apparatus X receives information representing the subcarrier allocation, allocates a transmission signal to the subcarrier of the information, and communicates with the base station apparatus A1.

First, the transmission power determination unit a109 selects a value SP (hereinafter referred to as an increase / decrease number SP) indicating the increase / decrease number of the transmission power when the mobile station apparatus X transmits a data signal to the base station apparatus A1.
The transmission power determination unit a109 stores the power control value g ^X (SP) as a function of SP in advance, and the power control value g ^X (SP) corresponding to the selected increase / decrease number SP and the subcarrier allocation determination unit a108. The channel characteristic ξ ^X (k) and the thermal noise variance σ ² input from are output to the equalized data reliability detection unit a110. The transmission power determination unit a109 may store the power control value g ^X (SP) determined in advance in the communication standard or the like by reading software storing the information, or the base station apparatus A1. When the mobile station apparatus X starts communication, the mobile station apparatus X may be notified of the power control value g ^X (SP) and stored in advance.

The transmission power determination unit a109 includes the power control value g ^X (SP) corresponding to the selected increase / decrease number SP, the propagation path characteristic ξ ^X (k) input from the subcarrier allocation determination unit a108, and the thermal noise variance σ. ² is output to the equalized data reliability detection unit a110.
The transmission power determination unit a109 determines the increase / decrease number SP using the equalizer output mutual information amount I ^X calculated from the information input from the transmission power determination unit a109 by the equalization data reliability detection unit a110 described later. . When the increase / decrease number SP is determined, as described above, the mobile station apparatus X transmits a data signal to the base station apparatus A1 by the power control value g ^X (SP) corresponding to the increase / decrease number SP. To control the transmission power. That is, the transmission power determination unit a109 uses the equalizer output mutual information I ^X (equalization data reliability information) detected by the equalization data reliability detection unit a110 to cause the mobile station device X to change to the base station device A1. The transmission power at the time of transmitting the data signal is determined. A method for determining the transmission power of the signal performed by the transmission power determination unit a109 will be described later.
The transmission power determination unit a109 outputs the determined transmission power information (increase / decrease number SP) to the transmission power information notification unit a111.

The equalization data reliability detection unit a110 performs equalization, which will be described later, from the power control value g ^X (SP), the propagation path characteristic ξ ^X (k), and the thermal noise variance σ ² input from the transmission power determination unit a109. The output mutual information amount (equalized data reliability information) for the mobile station apparatus X of the unit 12-1 is calculated. That is, equalized data reliability information representing the reliability of the data after equalization processing in the base station apparatus A1 is detected. Hereinafter, the output mutual information amount of the output of the equalizer 12-1 for the mobile station apparatus X is referred to as an equalizer output mutual information amount I ^X. That is, equalized data reliability information representing the reliability of the data after equalization processing in the base station apparatus A1 is detected.
Details of the output mutual information amount and the detection method of the equalization unit output mutual information amount I ^X performed by the equalization data reliability detection unit a110 will be described later.
The equalized data reliability detection unit a110 outputs the calculated equalization unit output mutual information ^IX to the transmission power determination unit a109.

The transmission power information notification unit a111 notifies the mobile station apparatus X of the transmission power information input from the transmission power determination unit a109 via the transmission unit a112 and the antenna a113.
The transmission unit a112 converts a data signal to be transmitted to the mobile station apparatus X into an analog signal by digital / analog conversion, up-converts the signal to a radio frequency signal as a transmission signal, and transmits the signal to the mobile station apparatus X via the antenna a113. Send.

Hereinafter, the equalization / decoding unit a107 will be described. FIG. 4 is a schematic block diagram showing the configuration of the equalization / decoding unit a107.
The equalization / decoding unit a107 includes an equalizer c11-1 that performs equalization processing, a decoder c12 that performs decoding processing, a deinterleaver 14-1, and an interleaver 16-1.
The equalizer c11-1 includes a soft cancellation unit 11-1, an equalization unit 12-1, a demodulation unit 13-1, a soft replica generation unit 17-1, and a propagation path characteristic multiplication unit 18-1. The The decoder c12 includes a decoding unit 15.

The soft cancellation unit 11-1 receives a received signal replica (propagation) having an amplitude proportional to the reliability obtained by the propagation path characteristic multiplication unit 18-1 from the received data signal of the mobile station apparatus X input from the FFT unit a106. Signal of interference component on the road) is canceled, and the received data signal subjected to the cancellation processing is output to the equalization unit 12-1.
In the first process, since the soft replica is not generated by the soft replica generation unit 17-1, a reception signal replica is not generated. Therefore, the soft cancellation unit 11-1 does not perform a cancellation process.

The equalization unit 12-1 includes the propagation path characteristic ξ ^X (k) of the mobile station apparatus X estimated by the propagation path characteristic / dispersion estimation unit a104, the soft replica S _soft generated by the soft replica generation unit 17-1, The received data signal subjected to the cancel process by the soft cancel unit 11-1 is input. The equalization unit 12-1 compensates for distortion of the signal in the propagation path for the received data signal soft-cancelled using the propagation path characteristic ξ ^X (k) and the soft replica S _soft (equalization process). And the received data signal after the equalization processing is output to the demodulator 13-1.

The demodulation unit 13-1 demodulates the reception data signal input from the equalization unit 12-1, calculates a log likelihood ratio (LLR) of each demodulated reception data signal, and calculates The log likelihood ratio LLR is output to the deinterleaver 14-1.
The deinterleaver 14-1 returns the time sequence of the bit string of the received data signal before the rearrangement by the interleaver of the mobile station apparatus X (not shown).

The decoding unit 15 performs error correction processing on the log likelihood ratio LLR of each received data signal that the deinterleaver 14-1 has returned to its original arrangement, and performs the error correction processing to increase the reliability. The log likelihood ratio LLR of the received data signal is calculated and output to the interleaver 16-1.
The interleaver 16-1 rearranges the received data signals input from the decoding unit 15 again.
The soft replica generation unit 17-1 generates a soft replica S _soft having an amplitude proportional to the reliability from the log likelihood ratio LLR that is rearranged by the interleaver 16-1. For example, the soft replica generation unit 17-1 can calculate the _soft replica S _soft by Expression (1).

Here, the equation (1) is a soft replica S _soft when the modulation method is a four-phase phase modulation (QPSK: Quadrature Phase Shift Keying). Further, l ₁ is a log likelihood ratio LLR of the first bit constituting the QPSK signal, and l ₂ is a log likelihood ratio LLR of the second bit.

The soft replica generation unit 17-1 outputs the _soft replica S _soft calculated and generated by the equation (1) to the equalization unit 12-1. Also, the soft replica generation unit 17-1 converts the _soft replica S _soft generated by the equation (1) into a frequency signal by fast Fourier transform, and outputs the converted signal to the propagation path characteristic multiplication unit 18-1. .

The propagation path characteristic multiplication unit 18-1 multiplies the propagation path characteristic ξ ^X (k) input from the propagation path characteristic / dispersion estimation unit a104 by the frequency signal of the soft replica input from the soft replica generation unit 17-1. Then, a received signal replica is generated. The propagation path characteristic multiplication unit 18-1 outputs the generated reception signal replica to the soft cancellation unit 11-1.

  As described above, the soft cancel unit 11-1 again cancels the received signal replica input from the propagation path characteristic multiplying unit 18-1 from the received data signal. The equalization / decoding unit a107 repeats the above process a predetermined number of times, and finally determines the log likelihood ratio LLR obtained by the decoding unit 15 to obtain a decoded bit.

Hereinafter, a method for determining the transmission power of the signal of the mobile station apparatus X performed by the transmission power determination unit a109 will be described.
First, a theoretical mechanism of turbo equalization technology will be described, and then, a detection method of the equalization unit output mutual information I ^X performed by the equalization data reliability detection unit a110 according to the present embodiment will be described, A method for determining the transmission power of the signal of the mobile station apparatus X performed by the transmission power determination unit a109 according to the present embodiment will be described.

First, the theoretical mechanism of turbo equalization technology will be described.
FIG. 5 is a schematic block diagram showing a functional configuration for realizing the turbo equalization technique. FIG. 6 to FIG. 10 are external information exchange (EXIT) charts that visually represent the iterative process of the turbo equalization technique.

As shown in FIG. 5, a general turbo equalization technique is realized by using an equalizer c1 that obtains reliability from convolution of a propagation path and a decoder c2 that obtains reliability by error correction processing.
The equalizer c1 and the decoder c2 mutually exchange a reliability value regarding the data signal, and utilize this reliability value as prior information in mutual signal detection. Therefore, the equalization unit output log likelihood ratio LLR becomes the decoding unit input log likelihood ratio LLR. Also, the decoding unit output log likelihood ratio LLR becomes the equalization unit input log likelihood ratio LLR.
The equalizer c1 corresponds to the equalizer c11-1 surrounded by a dotted line in FIG. The decoder c2 corresponds to the decoder c12 surrounded by a dotted line in FIG. In principle, a deinterleaver 14-1 and an interleaver 16-1 are provided between the equalizer c1 and the decoder c2.

FIG. 6 is an explanatory diagram for explaining a turbo equalization technique. This figure is an EXIT chart that quantifies and visually represents the processing in the equalizer c1 and the decoder c2 in FIG.
In this figure, the horizontal axis of the EXIT chart indicates an equalizer external input mutual information amount (equalizer input mutual information amount) and a decoder external output mutual information amount (decoder output mutual information amount). In this figure, the vertical axis of the EXIT chart indicates the equalizer external output mutual information amount (equalizer output mutual information amount) and the decoder external input mutual information amount (decoder input mutual information amount).

Here, the mutual information amount is a quantitative representation of how much information amount is obtained with respect to the transmission signal Y from the reception signal Z when the transmission signal Y is transmitted and the reception signal Z is obtained. is there.
The external mutual information amount represents a log likelihood ratio LLR obtained by dividing the input log likelihood ratio LLR from the output log likelihood ratio LLR, that is, the mutual information amount improved only by the immediately preceding process. That is, the external mutual information amount represents the mutual information amount improved only by the processing immediately before the equalizer c1 or the decoder c2, and the mutual information amount based on the reliability grasped at the time of input is subtracted. (External mutual information amount is simply called mutual information amount). In this case, the mutual information about the data signal when the log likelihood ratio LLR is obtained is constrained to a value between “0” and “1”.
Further, the mutual information amount being “0” means that information regarding the data signal is not obtained. Further, the mutual information amount being “1” means that information on the data signal is completely obtained, that is, the data signal can be completely reproduced.

  This figure shows the input / output relationship of the mutual information amount of the equalizer c1 as a curve L21, and the input / output relationship of the mutual information amount of the decoder c2 as a curve L22. The iterative process can be visually represented by an arrow (this is referred to as an “EXIT locus”). First, since no prior information is obtained in the first iterative process, the input mutual information amount of the equalizer c1 is “0”. Then, the equalizer c1 obtains an equalizer output mutual information “0.65” according to the arrow A21-1.

Next, since the output mutual information amount of the equalizer c1 becomes the input mutual information amount of the decoder c2, the equalizer output mutual information amount is input to the decoder c2. The decoder c2 obtains an output mutual information amount “0.95” in accordance with the arrow A22-1. Here, since the processes of the equalizer c1 and the decoder c2 are each completed once, the first iteration process is completed.
Next, the equalizer c1 uses the output mutual information amount of the decoder c2 as the input mutual information amount, and obtains the output mutual information amount “0.8” according to the arrow A21-2. The decoder c2 uses the output mutual information amount of the equalizer c1 as the input mutual information amount, and obtains the output mutual information amount “1” according to the arrow A22-2. At this time, since the obtained decoder output mutual information amount reaches “1”, the signal can be detected without error by performing demodulation at this stage.
In the case of this figure, if the decoder c2 operates twice, the decoder output mutual information amount from the decoder c2 becomes “1”, which means that the transmission signal can be decoded without error.

  FIG. 7 is another explanatory diagram for explaining the turbo equalization technique. This figure is an EXIT chart that quantifies and visually represents the processing in the equalizer c1 and the decoder c2 in FIG. In FIG. 7, the horizontal axis of the EXIT chart indicates the equalizer input mutual information and the decoder output mutual information, and the vertical axis of the EXIT chart indicates the equalizer output mutual information and the decoder input mutual information. Show.

  This figure shows the input / output relationship of the mutual information amount of the equalizer c1 as a curve L31, and the input / output relationship of the mutual information amount of the decoder c2 as a curve L32. In this figure, the input / output relationship of the mutual information amount of the equalizer c1 is compared with the input / output relationship of the mutual information amount of the equalizer c1 of FIG. The amount of information is low. This means that the noise power and the interference power in the case shown in this figure are larger than the signal power in the case shown in FIG. In addition, the curve L32 of this figure shows the same curve as the curve L22 in FIG.

The EXIT locus in FIG. 7 will be described.
First, since no prior information is obtained in the first iterative process, the input mutual information amount of the equalizer c1 is “0”. Then, the equalizer c1 obtains the equalizer output mutual information “0.4” according to the arrow A31-1.

  Next, since the output mutual information amount of the equalizer c1 becomes the input mutual information amount of the decoder c2, the equalizer output mutual information amount is input to the decoder c2. The decoder c2 obtains the output mutual information amount “0.2” according to the arrow A32-1. Here, since the processes of the equalizer c1 and the decoder c2 are each completed once, the first iteration process is completed. If the same process is repeated, the EXIT locus cannot be advanced beyond P1 in this figure. This indicates that the amount of mutual information output from the decoder c2 cannot exceed “0.26” no matter how many times the processing is repeated, and a signal can be detected without error in the transmission bits for that packet. It cannot be done and it becomes an error. Such a state is called a stack state.

As described above, the iterative processing by the equalizer c1 and the decoder c2 is performed when the input / output characteristics of the mutual information amounts of the equalizer c1 and the decoder c2 do not intersect (in the case of FIG. 6). “1” can be acquired as a quantity, and transmission bits can be detected without error.
On the other hand, when the input / output characteristics intersect in the middle (in the case of FIG. 7), the repetitive processing stops at the crossing point, and the characteristics are not improved any further, and the transmission bit cannot be detected without error (stack). Status).

  Note that the input / output characteristics of the mutual information of the equalizer c1 (hereinafter referred to as “the input / output characteristics of the equalizer c1” or “the equalizer input / output characteristics”) are the propagation path characteristics and the received signal noise ratio ( Since it is determined on the basis of SNR (Signal to Noise power Ratio), the input / output relationship of the mutual information amount in the equalizer c1 changes for each transmission opportunity. Therefore, in order to perform adaptive control, it is necessary to calculate input / output characteristics for each transmission opportunity. On the other hand, the input / output characteristics of the mutual information amount of the decoder c2 (hereinafter referred to as “the input / output characteristics of the decoder c2” or “decoder input / output characteristics”) are the same error in any data signal by the transmitting device. Since correction encoding is performed, it is uniquely determined.

FIG. 8 is another explanatory diagram for explaining the turbo equalization technique. (EXIT chart). In this figure, the horizontal axis of the EXIT chart indicates the equalizer input mutual information and the decoder output mutual information, and the vertical axis of the EXIT chart indicates the equalizer output mutual information and the decoder input mutual information. Show.
This figure is an EXIT chart for a different mobile station apparatus X. This figure is an example of an EXIT chart when a signal is transmitted at an arbitrary transmission power without using the equalizer output mutual information (equalized data reliability information).

In this case, this figure shows input / output characteristics of the equalizer c11-1 as a curve L41-1 and a curve L41-2. This figure also shows the input / output characteristics of the decoder c12 as a curve L42. Hereinafter, it is assumed that the curve L41-1 is a curve related to the signal of the mobile station apparatus 1, and the curve L41-2 is a curve related to the signal of the mobile station apparatus 2.
An output value when the input mutual information amount of the equalization unit in the EXIT chart is “0” (hereinafter referred to as a start point) is referred to as a start point equalizer output mutual information amount I ^X _S. In this figure, the starting point equalizer mutual information amount I ^X _S of the curve L41-1 and the curve L42-1 is the equalizer output mutual information amount I ¹ , I at the starting point BP41-1 and the starting point BP42-1 respectively. ² .
Further, the output value when the input mutual information amount of the equalization unit in the EXIT chart is “1” (hereinafter referred to as the end point) is referred to as the end point equalizer output mutual information amount I ^X _E. In this figure, the end point equalizer output mutual information amount I ^X _E of the curve L41-1 and the curve L42-1 is the equalizer output mutual information amount I ¹ and I at the end point EP41-1 and the end point EP41-2, respectively. ² .

In this figure, when the curve L41-1 and the curve L41-2 are compared, the start point equalizer output mutual information I ² _S and the end point equalizer output mutual information I ² _E are the start point equalizer output mutual information amount. The value is lower than I ¹ _S and the end point equalizer output mutual information I ¹ _E. Such a situation is a characteristic observed when the received power of the signal from the mobile station apparatus 2 is lower than the received power of the signal from the mobile station apparatus 1. In this case, the curves L41-2 and L42 intersect, that is, a stack state occurs. When communication is performed in such a situation, the decoding process of the signal of the mobile station apparatus 2 causes a stack state as described above, and an error occurs in the decoded data for the data signal of the mobile station apparatus 2.

Next, a method for detecting the equalization unit output mutual information I ^X performed by the equalization data reliability detection unit a110 according to the present embodiment will be described.
First, an expression for detecting the reception signal noise ratio SNR ^X of the mobile station apparatus X is shown, and then an expression for calculating the equalizer mutual information I ^X from the reception signal noise ratio SNR ^X is shown. Here, the equalized data reliability detection unit a110 according to the present embodiment detects a start point equalizer output mutual information amount I ^X _S and an end point equalizer output mutual information amount I ^X _E. That is, the equalization data reliability detection unit a110 performs equalization data reliability information on the initial equalization process and equalization data reliability information on the equalization process when the transmission path distortion is completely compensated. Is detected.

As will be described later, the base station apparatus A1 according to the present embodiment has an equalizer output mutual information I approximated by a start point equalizer output mutual information I ^X _S and an end point equalizer output mutual information I ^X _E. By using ^X , the computational load can be reduced.
The reception signal noise ratio SNR (SNR ^X _S ) at the start point and the reception signal noise ratio SNR (SNR ^X _E ) at the end point are, for example, a value μ ^X _{S at} the start point and a value at the end point of the equivalent amplitude gain μ ^X after equalization. using mu ^X _E, equation (2), represented by (3).

μ ^X is an equivalent amplitude gain calculated by SC / MMSE equalization (MMSE: least square error), and is a value determined by the reliability of the input soft replica. That is, the equalization process in the equalization / decoding unit a107 is a process based on the least square error method in the frequency domain. In Expression (4), δ is “0” at the start point and “1” at the end point, and γ ^X (γ ^X _S ) at the start point and γ ^X (γ ^X _E ) at the end point are respectively expressed by Expression (5), It is represented by (6).

In equations (5) and (6), ξ ^X (k) is a propagation path characteristic at the k-th discrete frequency for the mobile station apparatus X, σ ² is a thermal noise variance value in the base station apparatus A 1, and K is The total number of subcarriers used by each mobile station apparatus X, and N is the total number of subcarriers in the system band used. k is the number of the subcarrier used for communication (k is a natural number from 1 to N), and when not used, ξ ^X (k) is treated as “0”.
The power control value g ^X (SP) using the increase / decrease number SP as a variable is a value used for transmission power control when the mobile station apparatus X transmits a data signal to the base station apparatus A1.

Using the SNR ^X _S (Equation (2)) and SNR ^X _E (Equation (3)) calculated by the above equations, the start point equalizer output mutual information amount I ^X _S and the end point equalizer output mutual information amount I ^X _E is represented by formulas (7) and (8), respectively.

Here, H ₁ , H ₂ , and H ₃ are H ₁ = 0.3073, H ₂ = 0.8935, and H ₃ = 1.1064, respectively. In Equations (7) and (8), 4 × SNR ^X _S , 4 × SNR ^X _E , which is a constant multiple of 4, is a value specific to the modulation method, and is 4 in the case of QPSK or BPSK. Note that since there are similar constants in other modulation schemes, other modulation schemes can be handled by changing this value.

The equalization data reliability detection unit a108 uses the equations (7) and (8) to calculate the start point equalizer output mutual information amount I ^X _S and the end point equalizer output mutual information amount I ^X _E as the mobile station device X. It is calculated for each (for example, mobile station apparatuses 1 and 2). That is, the information representing the reliability of the data is the equalizer output mutual information amount I ^X calculated from the equivalent amplitude gain μ ^X after equalization. Further, the starting point equalizer output mutual information amount I ^X _S and the end point equalizer output mutual information I ^X _E is the frequency response xi] ^X subcarrier k to be used ^(k), the thermal noise at a base station device A1 This is reliability information based on the variance value σ ² .
Normally, it takes a higher value of the end point equalizer output mutual information I ^X _E relative to the start point equalizer output mutual information amount I ^X _S, which is the end point equalizer output mutual information amount I ^X _{This is because E} assumes that the intersymbol interference caused by the propagation path is completely removed, whereas the start point equalizer output mutual information I ^X _S indicates a state where there is intersymbol interference. .

  Next, a method for determining the transmission power of a signal performed by the transmission power determination unit a109 according to the present embodiment will be described. As described above, in the base station apparatus A1 that uses iterative processing, in order to decode data without error, it is necessary not to be in a stacked state. The condition is that the input / output characteristics of the information amount and the input / output characteristics of the mutual information amount of the decoder do not intersect.

In the present embodiment, the transmission power determination unit a109 uses the start point equalizer output mutual information amount I ^X _S and the end point equalizer output mutual information amount I ^X _E detected by the equalization data reliability detection unit a110. The input / output characteristics of the equalizer c11-1 are approximated by a straight line, and the transmission power of the signal of the mobile station apparatus X is determined so that the input / output characteristics of the decoder c12 do not intersect on the EXIT chart.
Originally, the input / output characteristics of the equalization unit in the EXIT chart are calculated using the mutual information input to the equalization unit as a variable with respect to the acquired propagation path information. The computational load is large. According to the present embodiment, the load of the calculation amount can be reduced by approximating using the start point equalizer output mutual information amount I ^X _S and the end point equalizer output mutual information amount I ^X _E. .
In the present embodiment, the allocation of subcarriers is determined using two values of the start point equalizer output mutual information amount I ^X _S and the end point equalizer output mutual information amount I ^X _E. The embodiment is not limited to this. For example, subcarrier allocation may be determined using two or more equalizer output mutual information amounts ^IX . In this case, the start point, the end point, and other equalizers may be determined. The input / output characteristics of the equalizer may be approximated by straight lines connecting the points of the equalizer output mutual information amount I ^X corresponding to several points of the input information amount I ^X. That is, the equalization data reliability detection unit a110 may detect at least two or more equalizer output mutual information amounts ^IX in the repetition.

In the present embodiment, the input / output characteristics of the decoder c12 are measured in advance, and the straight line start point equalizer output mutual information amount I ^X _S and the end point equalizer output mutual information amount I ^X that do not intersect the input / output characteristics are measured. _E advance is calculated, the calculated out starting point equalizer output mutual information I ^X _S and the end point equalizer output mutual information I ^X _E as respective thresholds I _1, I _2, transmission not shown power determiner It is stored in the storage unit a109.

The transmission power determination unit a109 determines the transmission power determined in advance from the start point equalizer mutual information amount I ^X _S and the end point equalizer output mutual information amount I ^X _E detected by the equalization data reliability detection unit a110, respectively. The transmission power of the signal of the mobile station apparatus X is determined so as to be higher than the threshold values I ₁ and I ₂ stored in the storage unit of the unit a109. At this time, with respect to the equalizer input mutual information and the decoder output mutual information having the same value, the equalizer output mutual information corresponding to the equalizer input mutual information becomes the decoder output mutual information. The curve indicating the input / output relationship of the equalizer c11-1 in the EXIT chart is higher than the curve indicating the input / output relationship of the decoder c12.
That is, the equalizer output mutual information I ^{X of} each of the data transmitted from the plurality of mobile station apparatuses X is the predetermined mutual reliability based on the input mutual information amount of the decoder (the input / output characteristics of the mutual information amount related to the decoding process). The transmission power of the signal of the mobile station apparatus X is determined so as to be higher.

Hereinafter, a method for determining the transmission power of signals performed by the transmission power determination unit a109 and the equalized data reliability detection unit a110 will be described with reference to FIG.
FIG. 11 is a flowchart illustrating an example of an operation for determining the transmission power of a signal according to the present embodiment.
First, the transmission power determination unit a109 initializes parameters and sets SP = 0 (S101). The mobile station apparatus X transmits a signal with transmission power controlled according to the power control value g ^X (SP = 0) = 1 in the initial communication with the base station apparatus A1. In the present embodiment, the power control value g ^X (SP) is assumed to be the same power control value g (SP) in all mobile station apparatuses X. It is an increase function of the increase / decrease number SP.
Next, the equalization data reliability detection unit a110 receives the propagation path characteristic ξ ^X (k) of the mobile station device X, the thermal noise variance σ ^{2 of the} base station device A1, and the power control value from the transmission power determination unit a109. g (0) is acquired (S102).

The equalized data reliability detection unit a110 uses the propagation path characteristic ξ ^X (k) acquired in step S102, the thermal noise variance σ ^{2 of the} base station apparatus A1, and the power control value g (0) to From (7) and equation (8), start point equalizer output mutual information amount I ^X _S and end point equalizer output mutual information amount I ^X _E are calculated (S103). Although the variance of thermal noise is estimated here, the average received SNR ^X over the entire band may be calculated and replaced with the reciprocal thereof.

Next, the transmission power determination unit a109 stores the threshold I ₁ stored in advance in the starting point equalizer mutual information amount I ^X _S calculated in step S103 (in this embodiment, I ₁ = 0.35). As described above, it is determined whether or not a condition that the endpoint equalizer output mutual information I ^X _E is equal to or greater than a threshold I ₂ (in this embodiment, I ₂ = 0.8) that is stored in advance is satisfied ( S104). Here, when the condition of step S105 is satisfied, the transmission power determination unit a109 performs control to reduce the excessive signal transmission power so as not to generate a stack state, and when the condition of step S105 is not satisfied, the transmission power determination unit a109 sets the stack state. This means that control should be performed to increase the transmission power of a signal that is insufficient to prevent generation.

When the condition of S105 is satisfied, the transmission power determination unit a109 selects the increase / decrease number SP obtained by reducing the increase / decrease number SP by 1 (S105).
Next, the equalization data reliability detection unit a110 uses the power control value g (SP) corresponding to the increase / decrease number SP selected by the transmission power determination unit a109 in the process of step S105, and outputs the start point equalizer outputs to each other. The information amount I ^X _S and the end point equalizer output mutual information amount I ^X _E are calculated (S106).
Next, the transmission power determination unit a109 determines that the start point equalizer output mutual information amount I ^X _S calculated in step S106 is less than the threshold value I ₁ = 0.35 or the end point equalizer output mutual information amount I ^X. It is determined whether or not the condition that _E is less than the threshold value I ₂ = 0.8 is satisfied (S107).
When the condition of step S107 is not satisfied, the transmission power determination unit a109 performs the process of step S105. On the other hand, when the condition of step S107 is satisfied, when the increase / decrease number SP is the previous value, the equalizer output mutual information amount ^IX is the minimum optimum value so as not to generate a stack. The increase / decrease number SP is increased by 1 (S108), and the process is terminated.

On the other hand, when the condition of step S105 is not satisfied, the transmission power determination unit a109 selects a value SP obtained by increasing the increase / decrease number SP by 1 (S110).
Next, the equalization data reliability detection unit a110 uses the power control value g (SP) selected by the transmission power determination unit a109 in the process of step S110, and the start point equalizer output mutual information amount I ^X _S , The end point equalizer output mutual information I ^X _E is calculated (S111).
Next, the transmission power determination unit a109 determines that the start point equalizer mutual information amount I ^X _S calculated in step S111 is equal to or greater than the threshold I ₁ = 0.35 and the end point equalizer output mutual information amount I ^X. It is determined whether or not _E satisfies a condition that threshold I ₂ = 0.8 or more (S112).
When the condition of S112 is not satisfied, the transmission power determination unit a109 performs the process of step S110. On the other hand, if the condition of step S110 is satisfied, the process ends.
The transmission power determination unit a109 determines the increase / decrease number SP selected by the above operation as the increase / decrease number SP used by the mobile station apparatus X for transmission power control.

Hereinafter, the operation shown in FIG. 11 will be described using specific numerical values. However, in order to simplify the description, the mobile station apparatus X is assumed to be the mobile station apparatus 1, the total number of subcarriers N is “8”, and the number of subcarriers K used by each mobile station apparatus X is “4”. Also, the case where σ ² that is the variance of noise is “0.631” is shown.
Table 1 shows a subcarrier number k (hereinafter referred to as subcarrier k) for each subcarrier number k (k = 1 to 8) between the mobile station device 1 (TX1) and the base station device A1. The absolute value | ξ ^X (k) |

The subcarrier allocation determination unit a108 determines subcarriers having a large value of the propagation path characteristic | ξ ¹ (k) | input to the propagation path characteristic / dispersion estimation unit a104, that is, subcarriers 1, 2, 3, and The subcarrier to be assigned to the mobile station device 1 is determined. In step S103 in FIG. 11, the equalized data reliability detecting unit a110 calculates the equalizer output mutual information amount I ¹ as I ¹ _S = 0.77 and I ¹ _E = 0.78.
The transmission power determination unit a109 determines that the condition of step S104 is not satisfied in the determination of step S104 in FIG. The transmission power determination unit a109 sets the increase / decrease number SP = + 1 in S110 in FIG. Equalized data reliability detecting unit a110 is a S111 in the FIG. 11, by using the increase and decrease the number of SP = + 1, the equalizer output mutual information amount _{^{I 1 I 1 S = 0.84,}} I 1 E = 0. It is calculated as 85.
The transmission power determination unit a109 determines that the condition of step S112 is satisfied in the determination of step S112 in FIG. 11, and ends the process.
The transmission power determination unit a109 determines +1 selected by the above operation as the increase / decrease number SP.

Here, the case where the condition of step S104 in FIG. 11 is not satisfied has been described. However, when the condition of step S104 is satisfied, the number of increases / decreases that decreases the transmission power of the signal by performing steps S105 to S108. SP will be selected.
In FIG. 11, the method of determining the increase / decrease number SP in one process has been described. However, the present invention is not limited to this. For example, when communication is continuously performed, the optimal increase / decrease number is gradually increased. A method of approaching SP may be used. In this case, the set value of the increase / decrease number SP in S101 may be the value used for the previous communication, and the determination in step S107, the process in step S108, and the determination in step S112 may be eliminated. In addition, if the determination in step S112 is eliminated and it is determined that the condition in step S107 is not satisfied, the process may be terminated.

In the present embodiment, the base station apparatus A1 repeats the equalization process, and determines the signal transmission power based on the start point equalizer output mutual information amount I ^X _S and the end point equalizer output mutual information amount I ^X _E. is doing. However, the present invention is not limited to this. For example, when the base station apparatus A1 does not repeat the equalization process, the I ^X _S repeats the equalization process using only the start point equalizer output mutual information I ^X _S. In this case, the power control value g (SP) may be determined so as to satisfy the condition of the end point equalizer output mutual information I ^X _E , that is, I ^X _S ≧ I ^X _E = 0.8.
In addition, in the present embodiment, the flow asymptotically approaches the desired mutual information amount is shown, but a flow showing the relationship between the mutual information amount and the output power is prepared, and the transmission power of the signal is determined based on the table. Is also possible.

FIG. 12 is a flowchart showing an example of the operation of the wireless communication system according to the present embodiment.
First, the base station apparatus A1 receives a pilot signal from each mobile station apparatus X (S201).
The base station apparatus A1 detects the propagation path characteristics ξ ′ ^X (k) of each mobile station apparatus X and the thermal noise variance σ ² of the base station apparatus A1, and outputs the equalizer output mutual information (starting point equalizer output). The mutual information amount I ^X _S and the end point equalizer output mutual information amount I ^X _E ) are calculated (S202).
The base station apparatus A1 determines an increase / decrease number SP for each mobile station apparatus X so that the stack state does not occur for the signal of each mobile apparatus X (S203).
The base station device A1 notifies each mobile device x10 of the increase / decrease number SP determined to be assigned in step S203 (S204).
Each mobile device X communicates with the base station device A1 by controlling the transmission power of the signal by the power control value g (SP) corresponding to the increase / decrease number SP notified in step S204 (S205).
The base station apparatus A1 receives and decodes the signal transmitted in step S205 (S206).

Thus, according to the present embodiment, the base station apparatus A1 detects the equalizer output mutual information amount ^IX corresponding to the power control value g (SP), and detects the detected equalizer output mutual information amount. The transmission power of the signal of the mobile station apparatus X is determined so that I ^X becomes a value higher than the decoder output mutual information amount, that is, the stack state does not occur. Thereby, base station apparatus A1 can decode the data transmitted by applying the error correction code from mobile station apparatus X.

  In addition, the base station apparatus A1 reduces the signal transmission power to a power lower than the transmission power for the mobile station apparatus X that uses transmission power that is equal to or higher than the minimum required signal transmission power so that a stack state does not occur. Determine the transmission power. As a result, the radio communication system can prevent a large interference with other cells from being generated by the strong signal transmitted by the mobile station apparatus X with excessive transmission power. The power consumption used for transmission can be reduced.

(Second Embodiment)
The second embodiment of the present invention will be described below with reference to the drawings.
In the present embodiment, the wireless communication system is a SORM wireless communication system that allows other users to use some subcarriers by using turbo equalization technology. That is, the wireless communication system includes a plurality of mobile station apparatuses X that transmit data while sharing at least some subcarriers.
The conceptual diagram of the wireless communication system according to the present embodiment is the same as FIG. Further, the mobile station apparatus X according to the present embodiment is the same as that of the first embodiment. In addition, the base station apparatus A2 according to the present embodiment is a base station apparatus when decoding transmission signals from two mobile station apparatuses X (for example, mobile station apparatuses 1 and 2) (hereinafter referred to as “two-user multiplexing”). It is.
Note that the mobile station apparatus X according to the present embodiment is the same as the mobile station apparatus X (FIG. 2) of the first embodiment, and thus description thereof is omitted.

First, the base station apparatus A2 which is the base station apparatus A (FIG. 1) according to the present embodiment will be described.
FIG. 13 is a schematic block diagram showing the configuration of the base station apparatus A2 according to the second embodiment of the present invention.
When the base station apparatus A2 (FIG. 15) according to the present embodiment is compared with the base station apparatus A1 (FIG. 3) according to the first embodiment, the equalization / decoding unit a207, the transmission power information determination unit a208, and the equalization The data reliability detection unit a210 is different. However, other components (antennas a101, a112, receiving unit a102, pilot separating unit a103, propagation path characteristic / dispersion estimating unit a104, CP removing unit a105, FFT unit a106, subcarrier allocation determining unit a108, transmitting unit a1121) Since the functions possessed by are the same as those of the first embodiment, description of the same functions as those of the first embodiment will be omitted.

The equalization / decoding unit a207 performs equalization processing that compensates for distortion of the transmission path and decoding processing using error correction, and decodes and outputs data before the error correction code is applied. Details of the processing of the equalization / decoding unit a207 will be described later.
The transmission power determination unit a209 has the same function as the transmission power determination unit a109 of the first embodiment, but may be another operation (FIG. 18) as described later.

The equalization data reliability detection unit a210 performs equalization, which will be described later, from the power control value g ^X (SP), the propagation path characteristic ξ ^X (k), and the thermal noise variance σ ² input from the transmission power determination unit a209. The equalizing unit output mutual information I ^X output by the unit 12-1 is calculated.
The equalized data reliability detection unit a210 outputs the calculated equalization unit output mutual information ^IX to the transmission power determination unit a209.

Hereinafter, the equalization / decoding unit a207 will be described. FIG. 14 is a schematic block diagram showing the configuration of the equalization / decoding unit a207 according to the present embodiment. In this embodiment, since two-user multiplexing is assumed, the processing configuration is two systems. However, the present invention is not limited to this.
In this figure, a soft cancellation unit 21-2, an equalization unit 12-2, a demodulation unit 13-2, a deinterleaver 14-2, an interleaver 16-2, a soft replica generation unit 17-2, and propagation path characteristic multiplication The functions provided in the unit 28-2 are respectively the soft cancellation unit 21-1, the equalization unit 12-1, the demodulation unit 13-1, the deinterleaver 14-1, the interleaver 16-1, and the soft replica generation unit 17-. 1 and the function of the propagation path characteristic multiplication unit 28-1.
The equalizer c21-1 includes a soft cancellation unit 21-1, an equalization unit equalization unit 12-1, a demodulation unit 13-1, a soft replica generation unit 17-1, and a propagation path characteristic multiplication unit 28-1. It is comprised including. The equalizer c21-2 includes a soft cancel unit 21-2, an equalization unit equalization unit 12-2, a demodulation unit 13-2, a soft replica generation unit 17-2, and a propagation path characteristic multiplication unit 28-1. It is comprised including. The decoder c12 includes a decoding unit 15.

  When the equalization / decoding unit a207 (FIG. 14) according to the present embodiment is compared with the equalization / decoding unit a107 (FIG. 4) according to the first embodiment, the soft cancellation unit 21-1, the propagation path characteristic multiplication unit 28-1 is different. However, the functions of other components (equalization unit 12-1, demodulation unit 13-1, deinterleaver 14-1, decoding unit 15, interleaver 16-1, soft replica generation unit 17-1) are Since it is the same as that of the first embodiment, description of the same function as that of the first embodiment is omitted.

The soft cancel unit 21-1 receives a received signal replica (in the propagation path) having an amplitude proportional to the reliability obtained by the propagation path characteristic multiplication units 28-1 and 28-2 from the data signal input from the FFT unit a106. Signal of the interference component) is canceled, and the data signal subjected to the cancellation processing is output to the equalization unit 12-1.
In the first process, since the soft replica is not generated by the soft replica generation unit 17-1, a reception signal replica is not generated. Therefore, the soft cancel unit 21-1) does not perform a cancel process.

The propagation path characteristic multiplication unit 28-1 multiplies the propagation path characteristic ξ ^X (k) input from the propagation path characteristic / dispersion estimation unit a104 by the soft replica frequency signal input from the soft replica generation unit 17-1. Then, a received signal replica is generated. The propagation path characteristic multiplication unit 28-1 outputs the generated reception signal replica to the soft cancellation unit 21-1.
In addition, since the SORM base station apparatus A2 according to the present embodiment presupposes that subcarriers are used repeatedly, the propagation path characteristic multiplication unit 28-1 uses the generated received signal replica as a soft cancellation unit 21. Output to -2.

  Hereinafter, the input / output characteristics of the SORM equalizer will be described first, and then the transmission power determination method for the signal of the mobile station apparatus X performed by the transmission power determination unit a209 according to the present embodiment will be described.

FIG. 15 and FIG. 16 are diagrams (EXIT chart) for explaining the input / output characteristics of a SORM equalizer. In these diagrams, the horizontal axis of the EXIT chart indicates the equalizer input mutual information and the decoder output mutual information, and the vertical axis of the EXIT chart indicates the equalizer output mutual information and the decoder input mutual information. Indicates.
FIG. 15 is a diagram (EXIT chart) for explaining the cases where the SORM method is applied and not applied.
In this figure, the curve L41-1 is a curve (for example, the mobile station apparatus 1) showing the input / output characteristics of the equalizer c1 when not multiplexed. A curve L81-1 indicates that the mobile station device X is multiplexed in the same band of the other mobile station device X, and some of the subcarriers are overlapped with the other mobile station device X. , Is a curve showing the input / output characteristics of the equalizer c1 when user multiplexing is performed by SORM. This figure also shows the input / output characteristics of the decoder as a curve L42.
In this figure, the curves L41-1 and L42 are the same as the curves in FIG.

In this figure, when the curve L41-1 and the curve L81-1 are compared, the start point BP81-1 of the curve L81-1 subjected to user multiplexing by SORM is lower than the start point BP41-1 of the curve L41-1. This is because, in the first stage of repeated turbo equalization, the mutual signals interfere with each other for the subcarriers that have been used repeatedly.
Note that the end points EP41-1 of the curve L41-1 and the curve L81-1 substantially coincide with each other. This shows a state where the signal of the mobile station apparatus X can completely cancel the interference from the signal of the other mobile station apparatus X in the overlapping subcarrier even when multiplexed. That is, in the case of the input / output characteristic (curve L41-1) of the equalizer shown in FIG. 8, even if user multiplexing is performed by SORM, the input / output characteristic of the equalizer is the input / output characteristic shown by the curve L81-1. In the end, it means that it is possible to obtain the same characteristics as when no multiplexing is performed. However, when calculating the input / output characteristics of this decoder, the output mutual information amount of the decoder that decodes the signal of the mobile station apparatus X is the decoding process of the signal of another mobile station apparatus X that uses the subcarrier redundantly. May match the output mutual information amount of the decoder.

FIG. 16 is a diagram (EXIT chart) for explaining the case where the SORM method is applied and not applied in the case of two-user multiplexing.
For example, as shown in FIG. 16, an equalizer c21-1 and a decoder c12, and an equalizer c21-2 and a decoder c12 are arranged as shown in FIG. This is a configuration provided.
In this figure, the curve L91-1 and the curve L91-2 are curves when the SORM method is not applied. Curve L91-1 is a curve related to the reception data signal of mobile station apparatus 1, and curve L91-2 is a curve related to the reception data signal of mobile station apparatus 2. Curves L91-1 and L91-2 are curves indicating the input / output characteristics of the equalizer c1 when the start points are different and the end points are the same.
The input / output characteristics of the equalizer are shifted up and down depending on the ratio with the noise power in the base station apparatus A2 including the equalizer. When the mobile station apparatus 1 and the mobile station apparatus 2 overlap and use subcarriers, that is, when the SORM method is applied, the start point equalizer output mutual information I ¹ _S and I are respectively affected by the overlapping subcarriers. ² _S goes down.
BP1 in this figure indicates the starting point when the SORM method is applied to the mobile station apparatus 1, and BP2 in this figure indicates the starting point when the SORM method is applied to the mobile station apparatus 2.

In the case of FIG. 16, unlike the case of FIG. 15, the assumption that the mutual information amounts obtained from the respective decoders that perform the decoding processing of the signal of the mobile station apparatus X that is used redundantly is not valid. Therefore, when user multiplexing by SORM is performed, it is difficult to express the EXIT chart in two dimensions.
When the noise power with respect to the signal power fluctuates, the curve indicating the input / output characteristics of the equalizer moves vertically in parallel. Therefore, when the received power is reduced, it is clear that a stack is first generated in the signal of the mobile station apparatus X having a low starting point equalizer output mutual information I ^X _{S. If} the stack occurs, the subcarriers are duplicated. This also affects other mobile station apparatuses X having a high starting point equalizer output mutual information I ^X _S to be used.

Next, a method for detecting the equalizer output mutual information I ^X performed by the equalized data reliability detection unit a210 according to the present embodiment will be described.
First, an expression for detecting the reception signal noise ratio SNR ^X of the mobile station apparatus X is shown, and then an expression for calculating the equalizer mutual information I ^X from the reception signal noise ratio SNR ^X is shown. The equalization data reliability detection unit a <b> 210 detects the start point equalizer output mutual information amount I ^X _S and the end point equalizer output mutual information amount I ^X _E for the mobile station apparatus X.
For the mobile station apparatus X, the reception signal noise ratio SNR ^X _S at the start point and the reception signal noise ratio SNR ^X _{E at} the end point are, for example, the value μ ^X _{S at} the start point and the value at the end point of the equivalent amplitude gain μ ^X after equalization. using mu ^X _E, equation (9), represented by (10).

μ ^X is an equivalent amplitude gain calculated by SC / MMSE equalization (MMSE: least square error), and is a value determined by the reliability of the input soft replica. Here, K is the total number of subcarriers used by each mobile station apparatus X, and N is the total number of subcarriers in the system band used. K is the number of a subcarrier used for communication (k is a natural number from 1 to N). The power control value g ^X (SP) is a value used for transmission power control when the mobile station apparatus X using the increase / decrease number SP as a variable transmits a data signal to the base station apparatus A2.
Also, ξ ^X (k) is a propagation path characteristic at the k-th discrete frequency in the mobile station apparatus X, and in the equation (9), the term of Σ of the denominator is only for the subcarrier used in the mobile station apparatus X. Calculated. Further, in the equations (9) and (10), the multiplexed signal is also calculated with the replica signal power at the start point being 0 and the replica signal power being 1 at the end point. In the formula (11), [delta] is 0 at the start, a 1 at the end, gamma ^X (gamma ^X _S) and gamma at the end ^X (gamma ^X _E) is at the starting point, respectively, formula (12), (13) expressed.

In Expressions (5) and (6), σ ² is a thermal noise variance value in the base station apparatus A2.
Using SNR ^X _S (Equation (9)) and SNR ^X _E (Equation (10)) calculated by the above equations, the start point equalizer output mutual information amount I ^X _S and the end point equalizer output mutual information amount I ^X _E is represented by formulas (14) and (15), respectively.

Here, H ₁ , H ₂ , and H ₃ are H ₁ = 0.3073, H ₂ = 0.8935, and H ₃ = 1.1064, respectively. In Equations (14) and (15), a constant multiple of 4 of 4 × SNR ^X _S and 4 × SNR ^X _E is a value specific to the modulation scheme, and is 4 in the case of QPSK or BPSK. Note that since there are similar constants in other modulation schemes, other modulation schemes can be handled by changing this value.

The equalization data reliability detection unit a210 uses the equation (14) and the equation (15), the start point equalizer output mutual information I ^X _S and the end point of each mobile station device X (mobile station devices 1 to 3). The equalizer output mutual information I ^X _E is calculated.
Equation (10) shows the equalizer mutual information amount I ^X after the interference of the mobile station apparatus X that uses the subcarriers in an overlapping manner is completely removed. Therefore, the equation (10) completely agrees with the equation (3). Yes. Equation (9) is more complex than equation (2). In order to easily process this, the equalized data reliability detection unit a210 uses Expression (2) instead of Expression (9), and for subcarriers that are used in duplicate, the calculation of Expression (2) is performed. It may not be taken into consideration.

  Next, a method for determining the transmission power of the signal of the mobile station apparatus X performed by the transmission power determination unit a209 according to the present embodiment will be described. As described above, in the base station apparatus A2 using the iterative process, in order to decode data without error, it is necessary that the stack state does not occur. To prevent the stack state from being generated, an equalizer is used. The condition is that the input / output characteristic of the mutual information amount does not intersect with the input / output characteristic of the decoder mutual information amount.

Also, the input / output characteristic of the decoder c12 according to this embodiment is the curve L42 in FIG. 17 (FIG. 8), as in the first embodiment, and the subcarrier allocation determination unit a108 determines the curve L42. Then, the threshold I ₁ obtained by linear approximation is stored as I ₁ = 0.35, and the threshold I ₂ is stored as I ₂ = 0.8.
The transmission power determination unit a209 determines that the start point equalizer output mutual information amount I ^X _S and the end point equalizer output mutual information amount I ^X _E detected by the equalization data reliability detection unit a210 are the threshold values “0. 35 ”and the transmission power of the signal of the mobile station apparatus X is determined so as to be higher than the threshold“ 0.8 ”.

FIG. 17 is a flowchart showing an example of an operation for determining the transmission power of the signal of the mobile station apparatus X according to this embodiment.
Comparing the operation of the present embodiment (FIG. 17) and operation of the first embodiment (FIG. 11), it determines that the processing is the starting point equalizer output mutual information amount I ^X _S and the end point equalizer output Only the calculation formula of the mutual information amount I ^X _E is different. That is, steps S103, S106, and S111 in FIG. 11 correspond to steps S303, S306, and S311 in FIG. 17, respectively, and the equations (7) and (8) used in steps S103, S106, and S111 are In S303, S306, and S311, respectively, Expressions (14) and (15) are obtained. However, since other processes and determination are the same as those in the first embodiment, description thereof will be omitted.

FIG. 18 is a flowchart showing another example of the operation for determining the transmission power of the signal according to this embodiment.
The operation of FIG. 17 is simple because the mobile station apparatus X to be multiplexed can be handled independently. In the operation of FIG. 18, the mobile station apparatus X controls the transmission power of signals for the subcarriers that are used repeatedly, so that the start point equalizer output mutual information I ^X _S can be greatly improved compared to the operation of FIG. 17.

First, the transmission power determination unit a209 initializes parameters and sets a value SP (X, k) = 0 indicating increase / decrease in power (S401). Here, X is a variable indicating the mobile station apparatus X, and k is a variable indicating a subcarrier number used for communication. The mobile station device X transmits a signal with transmission power controlled according to the power control value g ^X (SP = 0) = 1 in the initial communication with the base station device A2. In the present embodiment, the power control value g ^X (SP) is assumed to be the same power control value g (SP) in all mobile station apparatuses X. It is an increase function of the increase / decrease number SP.
Next, the equalization data reliability detection unit a210, from the transmission power determination unit a209, the propagation path characteristic ξ ^X (k) of the mobile station device X, the thermal noise variance σ ^{2 of the} base station device A2, and the power control value g (0) is acquired (S402).

  The transmission power determination unit a209 and the equalized data reliability detection unit a210 perform the processing of steps S104 to S106 for one mobile station device X, and then perform steps S405 to S412 for the other mobile station device X. Perform the process. The transmission power determination unit a209 and the equalized data reliability detection unit a210 terminate the processing when the processing of steps S405 to S412 is completed for all the mobile station devices X that determine the transmission power of the signal (S404, S413). .

The transmission power determination unit a209 is greater than or equal to a threshold I ₁ (in this embodiment, I ₁ = 0.35) stored in advance by the start point equalizer output mutual information I ^X _S calculated in step S403, and Then, it is determined whether or not a condition that the end point equalizer output mutual information I ^X _E is equal to or greater than a threshold I ₂ (in this embodiment, I ₂ = 0.8) that is stored in advance is satisfied (S405).
When the condition of step S405 is satisfied, the transmission power determination unit a209 decreases the increase / decrease number SP (X, l) by 1, and selects the decreased power control value g (SP) (S406). Here, l indicates a subcarrier that is used overlapping with another mobile station apparatus X. That is, the transmission power determination unit a209 reduces the increase / decrease number SP of the subcarriers selected to be used redundantly, and reduces the power control value g (SP), so that the start point equalizer outputs of the other mobile station devices X can be compared with each other. The information amount I ^X _S can be improved. That is, when the equalizer output mutual information amount I ^X is higher than the threshold value I ₁ and the threshold value I ₂ , the transmission power determining unit a209 assigns a signal to be assigned to a subcarrier shared by the other mobile station device X. The transmission power is reduced.

Next, the equalization data reliability detection unit a210 uses the power control value g (SP) selected by the transmission power determination unit a209 in the process of step S406, and the start point equalizer output mutual information amount I ^X _S , The end point equalizer output mutual information I ^X _E is calculated (S407).
Next, the transmission power determination unit a209 determines that the start point equalizer output mutual information amount I ^X _S calculated in step S407 is less than the threshold value I ₁ = 0.35 or the end point equalizer output mutual information amount I ^X. It is determined whether or not a condition that _E is less than the threshold value I ₂ = 0.8 is satisfied (S408).
When the condition of step S408 is not satisfied, the transmission power determination unit a209 performs the process of step S406. On the other hand, when the condition of step S408 is satisfied, when the increase / decrease number SP is the previous value, the equalizer output mutual information ^IX is the minimum optimum value required to prevent the stack from being generated. The increase / decrease number SP is increased by 1, and the process is terminated.

On the other hand, when the condition of step S405 is not satisfied, the transmission power determination unit a209 increases the increase / decrease number SP (X, m) by 1, and selects the increased power control value g (SP) (S410). Here, m indicates a subcarrier that is not used redundantly with other mobile station apparatuses X. That is, the transmission power determination unit a209 increases the power control value g (SP) by increasing the increase / decrease number SP of subcarriers other than the subcarriers selected to be used redundantly, thereby affecting other mobile station apparatuses X. Without giving, it is possible to improve the start point equalizer output mutual information I ^X _S.
That is, when the equalizer output mutual information amount I ^X is lower than the threshold value I ₁ or the threshold value I ₂ , the transmission power determination unit a209 assigns a signal to be assigned to a subcarrier that is not shared with other mobile station devices X. For the above, the transmission power is increased.

Next, the equalization data reliability detection unit a210 uses the power control value g (SP) selected by the transmission power determination unit a209 in the process of step S410, and the start point equalizer output mutual information amount I ^X _S , The end point equalizer output mutual information I ^X _E is calculated (S411).
Next, the transmission power determination unit a209 determines that the start point equalizer mutual information amount I ^X _S calculated in step S411 is equal to or greater than the threshold value I ₁ = 0.35 and the end point equalizer output mutual information amount I ^X. It is determined whether or not _E satisfies a condition that the threshold value I ₂ = 0.8 or more (S412).
When the condition of step S412 is not satisfied, the transmission power determination unit a209 performs the process of step S410. On the other hand, when the condition of step S410 is satisfied, the process proceeds to step S413.
The transmission power determination unit a209 determines the increase / decrease number SP by the above operation, and determines the transmission power when the mobile station apparatus X transmits a data signal to the base station apparatus A2.

Hereinafter, the operation shown in FIG. 17 will be described using specific numerical values. However, in order to simplify the description, the mobile station apparatus X is assumed to be the mobile station apparatus 1, the total number of subcarriers N is “8”, and the number of subcarriers K used by each mobile station apparatus X is “4”. Further, the case where σ ² that is the variance of noise is “0.501” is shown.
Table 2 shows, for each of the subcarrier numbers k (k = 1 to 8) between the base station devices A2 for the mobile station device 1 (TX1) and the mobile station device 2 (TX2), Hereinafter, the absolute value | ξ ^X (k) | of the propagation path characteristic in the subcarrier k) is shown.

The subcarrier allocation determination unit a108 is a subcarrier having a large value of the channel characteristic ξ ^X (k) input to the channel characteristic / dispersion estimation unit a104, that is, subcarriers 2, 3, 4 and 5 are determined as the subcarriers assigned to the mobile station apparatus 1 and the subcarriers 1, 2, 3 and 4 for the mobile station apparatus 2. At this time, the subcarriers not used redundantly are subcarrier 5 in mobile station apparatus 1 and subcarrier 1 in mobile station apparatus 2.
In step S403 in FIG. 18, the equalized data reliability detection unit a210 sets the equalizer output mutual information I ^X to I ¹ _S = 0.54, I ¹ _E = 0.84, I ² _S = 0. 31 and I ² _E = 0.73.

The transmission power determination unit a209 determines that the equalizer output mutual information I ¹ (I ¹ _S , I ¹ _E ) of the mobile station apparatus 1 satisfies the condition of step S405 in the determination of step S405 in FIG. It is determined that the equalizer output mutual information I ² (I ² _S , I ² _E ) of the mobile station apparatus 2 does not satisfy the condition of step S405.
In this case, the mobile station apparatus 1 is subjected to the processes of steps S406 to S409 in FIG. 18, and the mobile station apparatus 2 is subjected to the processes of steps S410 to S412 in FIG.

First, the process performed by the mobile station apparatus 1 will be described.
In step S406 in FIG. 18, the transmission power determination unit a209 decreases the increase / decrease number SP (1, 5) by 1, and sets the increase / decrease number SP (1, 5) =-1. Note that the variable value 5 of the increase / decrease number SP (1, 5) is a value indicating the subcarrier 5 that is used redundantly. The equalization data reliability detection unit a210 uses the increase / decrease number SP (1,5) = − 1 to change the equalizer output mutual information I ¹ to I ¹ _S = 0.53, I ¹ _E = 0.82. And calculate.
In this case, the transmission power determination unit a209 determines that the condition of step S408 is not satisfied in the determination of step S408 in FIG. 18, and further increases or decreases SP (1, 5) by 1 in the process of step S406. Decrease and increase / decrease number SP (1,5) = − 2. The equalization data reliability detection unit a210 uses the increase / decrease number SP (1,5) = − 2, and sets the equalizer output mutual information I ¹ to I ¹ _S = 0.51 and I ¹ _E = 0.81. And calculate.
In this case, the transmission power determination unit a209 determines that the condition of step S408 is not satisfied in the determination of step S408 in FIG. 18, and further increases or decreases SP (1, 5) by 1 in the process of step S406. Decrease and increase / decrease number SP (1,5) = − 3. Equalized data reliability detecting unit a210 is increased or decreased number of SP (1,5) = - 3 was used to calculate the equalizer output mutual information amount _{^{I 1, I 1 S = 0.51}} , I 1 E < 0.8.
Next, the transmission power determination unit a209 determines that the condition of step S408 is satisfied in the determination of step S408 in FIG. 18, and increases the increase / decrease number SP (1, 5) by 1 in the process of step S406. The increase / decrease number SP (1, 5) is set to −2, and the process for the mobile station apparatus 1 is terminated.

Next, processing performed by the mobile station apparatus 2 will be described.
In step S410 in FIG. 18, the transmission power determination unit a209 increases the increase / decrease number SP (2, 1) by 1, and sets the increase / decrease number SP (1, 5) = + 1. Equalized data reliability detecting unit a210, using the increase and decrease the number of SP (2,1) = + 1, the equalizer output mutual information amount ^{I ₁ I 1} S = ^0.32, and _I 1 E = 0.75 calculate.
In this case, the transmission power determining unit a209 determines in step S412 in FIG. 18 that the condition in step S412 is not satisfied, and further increases the increase / decrease number SP (2, 1) by 1 in the process in step S410. Increase or decrease SP (1,5) = + 2. Equalized data reliability detecting unit a210, using the increase and decrease the number of SP (2,1) = + 2, the equalizer output mutual information amount ^{I ₁ I 1} S = ^0.32, and _I 1 E = 0.79 calculate.
In this case, the transmission power determining unit a209 determines in step S412 in FIG. 18 that the condition in step S412 is not satisfied, and further increases the increase / decrease number SP (2, 1) by 1 in the process in step S410. Increase / decrease number SP (1,5) = + 3. Equalized data reliability detecting unit a210, using the increase and decrease the number of SP (2,1) = + 3, the equalizer output mutual information amount ^{I ₁ I 1} S = ^0.32, and _I 1 E = 0.82 calculate.
In this case, the transmission power determination unit a209 determines that the condition of step S412 is satisfied in the determination of step S412 in FIG. 18, and ends the process for the mobile station apparatus 2.
Note that the operation of the wireless communication system according to the present embodiment is the same as that of the first embodiment (FIG. 12), and a description thereof will be omitted.

Thus, according to the present embodiment, the base station apparatus A2 detects the equalizer output mutual information amount ^IX corresponding to the transmission power of the signal, and the detected equalizer output mutual information amount ^IX is The transmission power of the signal of the mobile station apparatus X is determined so as to be a value higher than the decoder output mutual information amount, that is, so as not to cause a stack state. Thereby, even the base station apparatus A2 to which the SORM method is applied can decode the data transmitted by applying the error correction code from the mobile station apparatus X.
The flow in FIG. 18 shows a case where control is performed so that an appropriate transmission power can be obtained even for a terminal that satisfies the condition of S405. It is also possible to omit steps.

  In each of the above embodiments, an FDD (Frequency Division Duplex) system in which frequencies are different between upstream and downstream has been described. However, the present invention is not limited to this, and transmission power alone as in the first embodiment is used. May be applied to a TDD (Time Division Duplex) system. At that time, a function for determining transmission power (for example, transmission power determination units a109 and a209, equalization data reliability detection units a110 and a210) is provided in the mobile station apparatus X (first transmission apparatus) that performs actual transmission. May be.

  Note that the base station devices A1 and A2, a part of the mobile station device X, the transmission power determination units a109 and a209, the equalized data reliability detection units a110 and a210, the transmission power information notification unit a111, the transmission power in the above-described embodiment. The control unit x108 may be realized by a computer. In that case, a program for realizing this control function is recorded in a computer-readable recording medium, and the program recorded in this recording medium is read into a computer system built in the base station apparatus and mobile station apparatus, It may be realized by executing. The “computer system” here is a computer system built in a mobile station device or a base station device, and includes hardware such as an OS and peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” is a medium that dynamically holds a program for a short time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, In this case, it is also possible to include one that holds a program for a certain time, such as a volatile memory inside a computer system that serves as a server or client. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.

  As described above, the embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to the above, and various design changes and the like can be made without departing from the scope of the present invention. It is possible to

1 is a conceptual diagram of a communication system according to a first embodiment of the present invention. It is a schematic block diagram which shows the structure of the mobile station apparatus which concerns on this embodiment. It is a schematic block diagram which shows the structure of the base station apparatus which concerns on this embodiment. It is a schematic block diagram which shows the structure of the equalization / decoding part which concerns on this embodiment. It is a schematic block diagram which shows the function structure for implement | achieving a turbo equalization technique. It is explanatory drawing for demonstrating a turbo equalization technique. It is another explanatory drawing for demonstrating a turbo equalization technique. It is another explanatory drawing for demonstrating a turbo equalization technique. It is a figure for demonstrating the calculation method of the threshold value of a starting point equalizer output mutual information amount and an end point equalizer output mutual information amount. It is another figure for demonstrating the calculation method of the threshold value of a start point equalizer output mutual information amount and an end point equalizer output mutual information amount. It is a flowchart which shows an example of the operation | movement which determines the transmission power of the signal which concerns on this embodiment. It is a flowchart which shows an example of operation | movement of the radio | wireless communications system which concerns on this embodiment. It is a schematic block diagram which shows the structure of the base station apparatus which concerns on 2nd Embodiment of this invention. It is a schematic block diagram which shows the structure of the equalization / decoding part which concerns on this embodiment. It is a figure for demonstrating the input-output characteristic of the equalizer of a SORM system. It is another figure for demonstrating the input-output characteristic of the equalizer of a SORM system. It is a flowchart which shows an example of the operation | movement which determines the determination method of the transmission power of the signal which concerns on this embodiment. It is a flowchart which shows an example of another operation | movement which determines the transmission power of the signal which concerns on this embodiment.

Explanation of symbols

A, A1, A2 ... base station apparatus a101, a113 ... antenna, a102 ... receiving part, a103 ... pilot separation part, a104 ... propagation path characteristic / dispersion estimation part, a105 ... CP removal unit, a106 ... FFT unit, a107, a207 ... equalization / decoding unit, a108 ... subcarrier allocation determination unit, a109, a209 ... transmission power determination unit, a110, a210, ... Equalized data reliability detection unit, a111 ... transmission power information notification unit, a112 ... transmission unit 11-1, 11-2, 21-1, 21-2 ... soft cancellation unit, 12-1 , 12-2... Equalizer, 13-1, 13-2 ... Demodulator, 14-1, 14-2 ... Deinterleaver, 15 ... Decoder, 16-1, 16 -2 ... Interleaver, 17-1, 7-2... Soft replica generation unit, 18-1, 18-2, 28-1, 28-2... Propagation path characteristic multiplication unit c11-1, c11-2, c21-1, c21-2, c1... equalizer, c12, c2... decoder X (1, 2, 3)... mobile station apparatus x101, x114... antenna, x102. Part, x104 ... encoding part, x105 ... S / P conversion part, x106 ... DFT part, x107 ... subcarrier allocation part, x108 ... transmission power control part, x109 ... IDFT Part, x110 ... CP insertion part, x111 ... P / S conversion part, x112 ... D / A conversion part, x113 ... RF part

Claims (15)

By a first communication device that transmits data subjected to error correction code, an equalization process that compensates for distortion of the transmission path for the data signal transmitted from the first communication device, and error correction code In a wireless communication system comprising: a second communication device that performs decoding processing and decodes data before performing error correction code;
The second communication device is:
An equalized data reliability detection unit for detecting equalized data reliability information based on a frequency response of a subcarrier to be used and noise in the second communication device ;
A transmission power determining unit that determines transmission power required when the first communication device transmits a signal of the data, using the equalized data reliability information detected by the equalized data reliability detection unit; ,
With
The first communication device is:
A transmission power control unit that determines transmission power required when the first communication device transmits the data signal based on information notified from the second communication device. Wireless communication system. The wireless communication system includes a plurality of the first communication devices,
The equalized data reliability detection unit detects the equalized data reliability information according to transmission power,
The transmission power determining unit determines the transmission power such that reliability represented by the equalized data reliability information of each of data transmitted from the plurality of first communication devices is higher than a predetermined reliability. The wireless communication system according to claim 1. The wireless communication system includes a plurality of the first communication devices that transmit data while sharing at least some subcarriers,
The equalized data reliability detection unit detects the equalized data reliability information according to transmission power,
The transmission power determining unit determines the transmission power such that reliability represented by the equalized data reliability information of each of data transmitted from the plurality of first communication devices is higher than a predetermined reliability. The wireless communication system according to claim 1. The wireless communication system according to claim 3, wherein the transmission power determination unit determines the transmission power for each subcarrier. Before applying the error correction code to the signal of the data subjected to the error correction code transmitted from the first communication device by performing equalization processing for compensating distortion of the transmission path and decoding processing by the error correction code In the second communication device for decoding the data of
An equalized data reliability detection unit for detecting equalized data reliability information based on a frequency response of a subcarrier to be used and noise in the second communication device ;
A transmission power determining unit that determines transmission power required when the first communication device transmits a signal of the data, using the equalized data reliability information detected by the equalized data reliability detection unit; ,
A communication apparatus comprising: Before applying the error correction code to the signal of the data subjected to the error correction code transmitted from the first communication device by performing equalization processing for compensating distortion of the transmission path and decoding processing by the error correction code A communication method in the second communication device for decoding the data of:
A first process in which the communication device detects equalized data reliability information based on a frequency response of a subcarrier to be used and noise in the second communication device ;
The communication device uses the equalized data reliability information detected in the first process to determine a transmission power required when the first communication device transmits the data signal. and the process of,
A wireless communication method comprising: Before applying the error correction code to the signal of the data subjected to the error correction code transmitted from the first communication device by performing equalization processing for compensating distortion of the transmission path and decoding processing by the error correction code To the computer of the second communication device for decoding the data of
Equalized data reliability for detecting equalized data reliability information based on a frequency response of a subcarrier used for communication between the first communication device and the second communication device and noise in the second communication device Detection means,
Transmission power determining means for determining transmission power required when the first communication device transmits the data signal using the equalized data reliability information detected by the equalized data reliability detecting means. ,
Wireless communication program to function as. Before applying the error correction code to the signal of the data subjected to the error correction code transmitted from the first communication device by performing equalization processing for compensating distortion of the transmission path and decoding processing by the error correction code A processor mounted on a second communication device for decoding the data of
Using equalized data reliability information based on frequency response of subcarriers used for communication between the first communication device and the second communication device and noise in the second communication device, the first communication device A processor for determining transmission power required when a communication device transmits a signal of the data. Before applying the error correction code to the signal of the data subjected to the error correction code transmitted from the first communication device by performing equalization processing for compensating distortion of the transmission path and decoding processing by the error correction code In the second communication device for decoding the data of
An equalized data reliability detector for detecting equalized data reliability information representing the reliability of the data after the equalization processing;
When the equalized data reliability information detected by the equalized data reliability detection unit is lower than the predetermined reliability, a signal that the first transmission device allocates to a subcarrier that is not shared with the other first transmission devices A transmission power determination unit that determines to increase the transmission power,
A communication apparatus comprising: Before applying the error correction code to the signal of the data subjected to the error correction code transmitted from the first communication device by performing equalization processing for compensating distortion of the transmission path and decoding processing by the error correction code In the second communication device for decoding the data of
An equalized data reliability detector for detecting equalized data reliability information representing the reliability of the data after the equalization processing;
When the equalized data reliability information detected by the equalized data reliability detection unit is higher than the predetermined reliability, a signal assigned to a subcarrier shared by the first transmission device with the other first transmission devices A transmission power determination unit that determines to reduce the transmission power;
A communication apparatus comprising: Before applying the error correction code to the signal of the data subjected to the error correction code transmitted from the first communication device by performing equalization processing for compensating distortion of the transmission path and decoding processing by the error correction code In the second communication device for decoding the data of
Equalized data reliability information representing the reliability of the data after the equalization processing, such as detecting equalized data reliability information representing the reliability based on the input / output characteristics of the mutual information amount related to the decoding processing, etc. Data reliability detector,
A transmission power determining unit that determines transmission power required when the first communication device transmits a signal of the data, using the equalized data reliability information detected by the equalized data reliability detection unit; ,
A communication apparatus comprising: Before applying the error correction code to the signal of the data subjected to the error correction code transmitted from the first communication device by performing equalization processing for compensating distortion of the transmission path and decoding processing by the error correction code In the second communication device for decoding the data of
An equalization data reliability detection unit for detecting mutual information calculated from the equivalent amplitude gain after the equalization processing ;
A transmission power determination unit that determines transmission power required when the first communication device transmits a signal of the data, using the mutual information amount detected by the equalization data reliability detection unit;
A communication apparatus comprising: An error correction code is applied to the data signal subjected to the error correction code transmitted from the first communication device by repeatedly performing an equalization process for compensating for distortion of the transmission path and a decoding process using the error correction code. In the second communication device for decoding the previous data,
Equalized data reliability information representing the reliability of the data after the equalization processing, and detecting equalization data reliability information of at least two or more equalization processing among the repetitions A detection unit;
A transmission power determining unit that determines transmission power required when the first communication device transmits a signal of the data, using the equalized data reliability information detected by the equalized data reliability detection unit; ,
A communication apparatus comprising: The equalized data reliability information of the at least two equalization processes includes the equalized data reliability information for the first equalization process, and the equalization data when distortion of the transmission path is completely compensated The communication apparatus according to claim 13, wherein the communication apparatus is equalized data reliability information regarding equalization processing. An error correction code is applied to the data signal subjected to the error correction code transmitted from the first communication device by repeatedly performing an equalization process for compensating for distortion of the transmission path and a decoding process using the error correction code. In the second communication device for decoding the previous data,
An equalized data reliability detector for detecting equalized data reliability information for the first equalization process ;
A transmission power determining unit that determines transmission power required when the first communication device transmits a signal of the data, using the equalized data reliability information detected by the equalized data reliability detection unit; ,
A communication apparatus comprising:

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