JP5327292B2 - Wireless communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce power consumption required for pilot transmission by making a common pilot not being transmitted in whole bands in a situation where data traffic is light. <P>SOLUTION: A communication system transmits a sub-frame including a pilot to a terminal device from a radio base station device in a radio section of a down link. The radio base station device divides the sub-frame into a first sub-frame transmitting a common pilot in the whole transmission bands and a second sub-frame transmitting the common pilot in a prescribed narrow band in the whole transmission bands. The common pilot is transmitted by transmitting the first and second sub-frames in the radio section of the down link. The terminal device receives the sub-frame from the base station device, extracts the pilot from the received sub-frame and performs a prescribed processing. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a radio communication system, and more particularly, to a radio communication system that transmits a subframe including a pilot from a radio base station apparatus to a terminal apparatus in a downlink radio section.

Mobile communication systems, such as mobile phone systems, are about to evolve from 3rd generation to 4th generation systems. Along with the development, new radio access technologies are introduced, and a wider radio frequency band transmission band is occupied, and the maximum data transmission capacity is expected to increase significantly.
OFDM (Orthogonal Frequency Division Multiplex) is employed in the downlink of the EUTRAN (Evolved UTRAN) radio access unit, which is being studied for specification by 3GPP as the next generation system of the WCDMA system (see Non-Patent Document 1). ). FIG. 13 is an explanatory diagram of a subframe sequence in the downlink of the radio access unit of EUTRAN. The horizontal axis is frequency (downlink transmission band), the vertical axis is time, and five subframes are shown. Each subframe is composed of, for example, 7 symbols (7OFDM symbols) as shown in FIG.
An OFDM signal transmitted in a 20 MHz-wide wireless transmission band (system transmission band) is composed of 1201 subcarriers. Also, the 20 MHz wide transmission band is divided into about 100 subbands, and one or a plurality of subbands that are continuous or distributed on the frequency axis are used for data transmission to a certain terminal. One subband is assumed to be composed of 12 subcarriers. The subframe length is 0.5 ms, and a common pilot is transmitted over the entire system transmission band. The downlink common pilot signal is mainly used for synchronous demodulation (for channel estimation and compensation) of control signals and user data and for measurement of radio channel quality. The common pilot is periodically transmitted every subframe.
The common pilot signal may be transmitted using all subcarriers on a certain OFDM symbol. However, in the EUTRAN downlink radio access unit, one transmission antenna receives 1 signal per 6 subcarriers as shown in FIG. A common pilot signal is transmitted on the subcarrier, and is transmitted in 2 OFDM symbols among 7 OFDM symbols.

FIG. 15 is a configuration diagram of a transmission apparatus in an OFDM communication system. A data modulation unit 1 modulates transmission data (user data or control data), for example, QPSK data, and has a complex baseband signal (symbol) having an in-phase component and a quadrature component. Convert to The time division multiplexing unit 2 time-multiplexes a plurality of symbol pilots into data symbols. The serial / parallel converter 3 converts the input data into parallel data of M symbols and outputs M subcarrier samples. An IFFT (Inverse Fast Fourier Transform) unit 4 performs IFFT (Inverse Fourier Transform) processing on the subcarrier samples input in parallel and synthesizes them, and outputs them as discrete time signals (OFDM signals). The guard interval insertion unit 5 inserts a guard interval into the OFDM signal for M symbols input from the IFFT unit, and the transmission unit (TX) 6 performs DA conversion on the OFDM signal (referred to as OFDM symbol) into which the guard interval is inserted, Next, the frequency of the OFDM signal is converted from the baseband to the radio band, amplified at a high frequency, and transmitted from the antenna 7.
FIG. 16 is a block diagram of an OFDM receiver. The signal output from the transmission antenna 7 in FIG. 15 is received by the reception antenna 8 of the reception device via the fading channel (propagation path) in the radio space, and the reception circuit (Rx) 9 is the RF signal received by the antenna. Is converted into a baseband signal, and the AD converter 10 converts the baseband signal into a digital signal and outputs it. The AFC circuit 11 includes a first AFC circuit 11a using a pilot signal, a second AFC circuit 11b using a synchronization signal, and an AFC signal selection circuit 11c. The carrier frequency deviation between the terminal and the base station is estimated, and a local part with a built-in receiving circuit is provided. Adjust the oscillation frequency of the oscillator.
The symbol cutout unit 12 detects the head of the OFDM symbol, deletes the guard interval GI, cuts out the OFDM symbol, and inputs it to the FFT unit 13. The FFT unit 13 performs FFT processing for each extracted OFDM symbol, and converts it to frequency domain subcarrier samples S _{0 to} S _M−1 . The pilot extraction unit 14 extracts pilot symbols from the FFT output, and the channel estimation circuit 15 performs channel estimation for each subcarrier by calculating the correlation between pilot symbols received at regular intervals and a known pilot pattern. The channel compensation circuit (synchronous detection unit) 16 compensates for channel fluctuation of the data symbol using the channel estimation value. Through the above processing, the transmission data allocated to each subcarrier is demodulated. Thereafter, although not shown, the demodulated subcarrier signal is converted into serial data and then decoded. Optimal subband determination unit 17 measures the reception state (radio channel quality, eg, SIR) of each subband using the received pilot, and determines the optimal subband. Note that the signal processing examples of the transmission device and the reception device in FIGS. 15 and 16 are simple ones. In an actual device, more complicated processing is performed to improve characteristics.

FIG. 17 is an explanatory diagram of the first AFC circuit 11a using pilot symbols. The IFFT unit 11a-1 performs IFFT processing on a replica of the pilot signal (known pilot) transmitted by the transmitting station and continues in time. A pilot signal is generated, the correlation calculation unit 11a-2 calculates the correlation between the pilot signal and the received signal, the peak detection unit 11a-3 detects a peak correlation value, and the phase detection unit 11a-4 Using the real part R and imaginary part I of the following equation: θ = tan ^-1 (I / R)
To calculate the phase difference θ. Since θ is caused by a frequency deviation, the oscillation frequency of the local oscillator is controlled based on the phase difference. The AFC circuit shown in FIG. 17 is an example.
18A and 18B are explanatory diagrams of the synchronization signal, where FIG. 18A shows an example in which the synchronization channel SCH (synchronization signal) is repeatedly transmitted twice, and FIG. 18B shows an example in which the synchronization channel SCH (synchronization signal) is repeatedly transmitted at the beginning of the frame It is.
FIG. 19 is an explanatory diagram of the second AFC circuit 11b. The delay unit 11b-1 delays the input signal by one symbol or one frame, the correlation calculation unit 11b-2 calculates the correlation of the repeated portion, and the peak detection unit. 11b-3 detects the peak correlation value, and the phase detection unit 11b-4 uses the correlation value to calculate the phase difference θ in the same manner as in FIG. 17, and based on this phase difference, determines the oscillation frequency of the local oscillator. Control.
The synchronization signal is used not only for adjusting the frequency offset as described above, but also for symbol timing, frame timing, pilot signal pattern detection, and the like. For example, the frequency offset is roughly corrected with the synchronization signal, and then fine correction is performed with the pilot signal.
During a day, the amount of data transmission, including voice data, ie data traffic, varies. Especially at midnight, data traffic is considerably less. During a day, the ratio of traffic when data traffic peaks and when traffic is low, such as at midnight, increases as the maximum data transmission capacity increases from the 3rd generation to the 4th generation. It is thought that it will go.
In a situation where data traffic is low, such as at midnight, the amount of data to be transmitted is reduced, that is, a required amount of radio resources is reduced, and the entire transmission band is not fully used. This becomes more significant as the transmission bandwidth increases. In such a situation where there is little data traffic, there are many subbands that are not used for data transmission, and control signals and data are not transmitted in the subbands that are not used, and pilot signals for the purpose of demodulation of the control signals and data are also transmitted. It is not necessary for subbands.
Also, in a situation where data traffic is low, it is inefficient to transmit pilots for the purpose of measuring radio channel quality in all subbands. This is because, if the subbands used for data transmission are limited, the limited subbands may be used for data transmission to each terminal, and each terminal can perform radio channel quality measurement only for the limited subbands. It is because it is good.
In view of the above, in a situation where data traffic is low, it is inefficient to transmit a downlink common pilot signal with high power in each subframe in the entire transmission band (wide transmission band). In other words, it is inefficient in terms of power consumption required for pilot transmission to transmit a common pilot in every subframe in a situation where data traffic is low.

3GPP TR25.814

From the above, an object of the present invention is to reduce power consumption required for pilot transmission by not transmitting a common pilot in the entire band (not transmitting in a wide transmission band) in a situation where data traffic is low.
Another object of the present invention is to set a period for transmitting a common pilot in the entire band (wide transmission band) based on the total number of terminals (active mode terminals and DRX / DTX mode terminals) communicating with the base station. Is to control.
Another object of the present invention is to provide a band (narrow band) when a common pilot is not transmitted over the entire band based on the number of terminals (active mode terminals) in a state where data can be constantly transmitted / received to / from the base station. Control the width.
Another object of the present invention is to transmit a narrowband as a subband for transmitting individual data addressed to a terminal, even when transmitting a fullband subframe or a narrowband subframe, as long as the terminal is moving at high speed. Is to assign subbands belonging to.
Another object of the present invention is to transmit an individual pilot together with individual data in a subband when transmitting the individual data in a subband that does not belong to the narrowband when transmitting a narrowband subframe.

The present invention is a radio communication system having a radio base station apparatus and a terminal apparatus that communicates with the radio base station apparatus, wherein the radio base station apparatus transmits a common pilot and data in the entire transmission band, respectively. A subframe generating unit for generating a first subframe and a second subframe for transmitting a common pilot and data in a predetermined narrow band among all transmission bands; and the first and second subframes. Is transmitted in the downlink radio section, thereby transmitting a common pilot.

As described above, according to the present invention, it is possible to prevent the common pilot from being transmitted in the entire band in a situation where the data traffic is low, so that it is possible to reduce power consumption required for pilot transmission. In addition, since the base station always transmits a common pilot at least in a specific narrow band, even a terminal that intermittently transmits and receives data to and from the base station can receive the pilot and perform frequency offset control. it can.
According to the invention, the common pilot can be transmitted in the entire band in a situation where the data traffic is increased such as daytime, and the common pilot is transmitted in a narrow band if the data traffic is low at night. In this way, power consumption required for pilot transmission can be reduced.
According to the present invention, since the bandwidth of the narrow band is controlled based on the number of terminals (active mode terminals) in a state where data transmission / reception can always be performed with the base station, all terminals that wish to communicate Can communicate.
According to the present invention, it is possible to perform processing using highly accurate pilots by averaging channel estimation values obtained based on reception values of common pilots in the preceding and following subframes during high-speed movement.
According to the present invention, when dedicated data is transmitted in a subband not belonging to a narrow band, the dedicated pilot is transmitted in the subband. Therefore, even if the common pilot cannot be used, pilot processing is performed using the dedicated pilot. Is possible.

It is explanatory drawing of the common pilot transmission method which shows the outline | summary of this invention. FIG. 6 is an explanatory diagram of common pilot transmission power when transmission is performed by mixing first and second subframes. It is explanatory drawing of the sub-frame transmission method of this invention. It is a structural example figure of a base station apparatus. It is an example of a structure of a terminal classification management table. It is a terminal type management process flow of a radio | wireless resource management part. It is a change control processing flow of the transmission cycle of the first subframe. It is a control processing flow of the bandwidth of the narrowband NFR that is the transmission bandwidth of the second subframe. It is an individual pilot transmission control processing flow. It is a subband allocation control processing flow of a high-speed mobile terminal. It is a structural example figure of a mobile terminal device. It is a block diagram which shows an example of a pilot extraction part. It is explanatory drawing of the sub-frame row | line | column in the downlink of the radio access part of EUTRAN. It is an example of a sub-frame structure. It is an example of a structure of the transmitter in an OFDM communication system. It is a structural example figure of an OFDM receiver. It is explanatory drawing of the AFC circuit using a pilot symbol. It is explanatory drawing of a synchronizing signal. It is explanatory drawing of the AFC circuit using a synchronizing signal.

(A) Outline of the Present Invention FIG. 1 is an explanatory diagram of a common pilot transmission method showing an outline of the present invention. In this embodiment, the pilot signal is transmitted using the first frequency band in the first period (in FIG. 1, the first part of the first subframe), and the second period (in FIG. 1, the second subframe is used). In the first part), a pilot signal is transmitted using a second period narrower than the first frequency band.
The downlink radio transmission band has a bandwidth of 20 MHz, and the OFDM signal transmitted in this radio transmission band is composed of 1201 subcarriers. The 20 MHz-wide radio transmission band is divided into about 100 subbands, and one or a plurality of subbands that are continuous or distributed on the frequency axis are used for data transmission to a certain terminal. One subband is composed of 12 subcarriers. The subframe has a length of 0.5 ms and is composed of, for example, 7 OFDM symbols, and transmits a common pilot, a control signal, and user data.
In the present invention, the subframe includes (1) a first subframe (fullband subframe) SF1 for transmitting a common pilot in the full transmission band WFR, and (2) a predetermined narrowband NFR in the full transmission band. The first and second subframes SF1 and SF2 are transmitted in the downlink radio section. In FIG. 1, one of the five subframes is periodically transmitted as the first subframe SF1, and the remaining four are used as the second subframe SF2. That is, the first subframe SF1 is transmitted at a certain period (2.5 ms in the figure), and the second subframe SF2 is transmitted in other time intervals.
The transmission period T of the first subframe SF1 can be 5 ms, 10 ms, and so on. Since the number of terminals communicating in the cell increases in the daytime, T = 0.5 ms, and in the night, the number of terminals communicating in the cell decreases, so T = 2.5 ms. Further, the transmission cycle T of the first subframe SF1 can be controlled to be changed according to the number of terminals communicating in the cell, and T can be changed to 0.5 ms, 1.0 ms, 1.5 ms, 2.0 according to the number of terminals. It can be controlled as ms, 2.5ms, 3.0ms, ....
FIG. 2 is an explanatory diagram of common pilot transmission power when the first and second subframes are mixed and transmitted. During transmission of the first subframe (T1), the transmission power of the common pilot increases, At the time of subframe transmission (T2), the transmission power decreases, and the transmission power decreases in total. As a result, in a situation where data traffic is low (for example, at night), it is possible to reduce power consumption required for pilot transmission by not transmitting the common pilot over the entire band (wide band). Further, since the base station always transmits a common pilot, even a terminal that intermittently transmits and receives data to and from the base station can receive the pilot and perform frequency offset control.

(B) Subframe Transmission Method FIG. 3 is an explanatory diagram of the subframe transmission method, and the same parts as those in FIG.
The first subframe (fullband subframe) SF1 in which the common pilot is transmitted in the entire transmission band WFR is the common pilot CPL, user data position information DTL, common control signal CCS, synchronization signal SYC, individual data UDT for each user, and Includes individual control data UCT. The common pilot CPL is used for SIR measurement and synchronous demodulation on the receiving side, and is transmitted in the entire transmission band WFR. The user data location information DTL is information for notifying the terminal of which subband user data is transmitted, and the terminal refers to this location information DTL to check whether there is data addressed to itself. For example, the individual data UDT and the individual control data UCT addressed to itself are fetched from the designated subband. The common control signal CCS is a control signal common to all terminals, and notifies the transmission cycle of the first subframe SF1, information specifying the narrowband NFR of the second subframe SF2, etc., and the synchronization signal SYC is a terminal. And a signal used for adjusting a frequency offset between the base station and the base station, detecting a symbol timing, a frame timing, a pilot signal pattern, and the like.
The second subframe (narrowband subframe) SF2 in which the common pilot is transmitted in the narrowband NFR includes the common pilot CPL, the user data position information DTL, the individual data UDT and the individual control data UCT for each user, and As appropriate, it includes a voice signal, an ACK / NACK signal, and a common control signal.
The terminal performs reception control of the first and second subframes by switching the reception band based on the transmission period and narrowband information included in the common control signal CCS.

The first subframe (full-band subframe) SF1 is transmitted at a rate of once every 5 subframes, and the second subframe (narrowband subframe) SF2 is transmitted in the other time interval T2. The position of the narrow band NFR is not located at the center of the entire transmission band WFR (shown at the center in the figure), but can be arranged toward the end of the entire band WFR. Moreover, it can also be set as the some divided | segmented narrow band from which a total band becomes narrower than the whole transmission band.
The ratio of the first subframe to all the subframes, or the period T of the first subframe is variable, but when changing the ratio or the period, the base station uses the common control signal CCS in advance to change all terminals It is desirable to notify. For example, when changing the transmission cycle T of the first subframe SF1 according to the total number of terminals communicating in the cell, the base station broadcasts to all terminals in advance using the common control signal CCS. In this case, control is performed so that the intermittent transmission / reception period of a terminal (DRX / DTX mode terminal) in a state of intermittently transmitting / receiving data to / from the base station matches the transmission period T of the first subframe.
Further, the bandwidth of the narrowband NFR is variable, but is not changed in the section T2. Therefore, in FIG. 3, the narrow bandwidths of four consecutive second subframes SF2 following the first subframe SF1 are the same. However, the narrow band of the second subframe SF2 following the next first subframe SF1 can be set to a different bandwidth. However, it is desirable that the base station notifies all terminals in advance using the common control signal CCS which bandwidth is set. For example, when the base station changes the narrowband bandwidth according to the number of terminals communicating in the cell, the base station notifies all terminals in advance using the common control signal CCS.

The base station transmits the common control signal CCS and the synchronization signal SYC of the first subframe SF1 in the same band as the narrowband NFR of the second subframe SF2. In FIG. 3, the synchronization signal is transmitted only in the first subframe SF1, but the synchronization signal can also be transmitted in the second subframe SF2. In this way, it is possible to perform frequency offset control using a synchronization signal in a subframe period, detection of symbol timing, frame timing, pilot signal pattern, and the like.
The base station transmits data for high-speed mobile terminals in a narrowband NFR subband in all subframes. In the case of a high-speed mobile terminal, radio channel fluctuations become severe. By doing this, channel estimation accuracy is obtained by averaging the common pilots of the preceding and following subframes as shown by A in the figure during data demodulation. And the data demodulation characteristics can be improved.
When transmitting the second subframe, if the amount of data to be transmitted increases, the base station transmits data (individual data, individual control data) in subbands other than the narrowband NFR, as indicated by B in the figure. At the same time, the dedicated pilot is transmitted in the subband. In this way, the terminal can perform synchronous demodulation and SIR measurement using the dedicated pilot even if the common pilot cannot be used when receiving the dedicated data. In FIG. 3, a band adjacent to the narrow band NFR is used as the band B other than the narrow band NFR, but it can be separated from the narrow band NFR as indicated by a dotted line B ′.
The first subframe is not necessarily limited to the format shown in FIG. 3, and the common control signal and the synchronization signal can be transmitted in the entire band.

(B) Type of terminal In the present invention, it is necessary to identify whether the communicating terminal is an active mode terminal or a DRX / DTX mode terminal (intermittent reception / intermittent transmission end). Therefore, first, an active mode terminal, a DRX / DTX mode terminal, and an idle mode terminal are defined.
Active mode terminal An active mode terminal is a communicating terminal that is always ready to receive data. A common control signal is received every 1 TTI (Transmission Time Interval), which is a subframe period, in order to confirm whether data is transmitted to the user. In addition, if there is a transmission instruction from the base station, it is in a state where data can be transmitted immediately by uplink UL. The network knows in which cell the active mode terminal exists. The active mode terminal maintains synchronization in the radio section for both downlink and uplink, and is always in a state where data can be transmitted / received to / from the base station.
・ DRX / DTX mode terminal
The DRX / DTX mode terminal is a communicating terminal in a state where data can be intermittently transmitted to and received from the base station. When there is data to be transmitted to the DRX / DTX mode terminal, the base station notifies that fact by a control signal at a predetermined cycle timing. The DRX / DTX mode terminal receives / decodes the control signal at this predetermined period and confirms whether the data addressed to itself is transmitted. When transmitting control information to the base station, the DRX / DTX mode terminal transmits at the timing of the predetermined period.
The DRX / DTX mode terminal is necessary for the base station to shift to the active mode as necessary, for example, when there is an instruction from the base station or when transmitting data on the uplink. A control signal (for example, a random active signal) is transmitted. The network knows in which cell this DRX / DTX mode terminal exists. A DRX / DTX mode terminal is basically synchronized in the radio section for both downlink and uplink, but may request a frequency offset correction signal from the base station to correct the uplink synchronization. is there.
-Idle mode terminal An idle mode terminal is a terminal which is not communicating with a base station. If there is data to be transmitted to the idle mode terminal, the base station transmits a paging signal at the timing of a predetermined period, and notifies the idle mode terminal that there is transmission data using the paging signal (calling). . When it is found that there is data addressed to itself, the idle mode terminal transmits a random access signal to the base station in order to shift to the active mode. Since the network needs to send a paging signal, it knows in which cell tracking area the idle mode terminal exists.

(C) Configuration of Base Station Device FIG. 4 is a configuration diagram of the base station device. The radio reception unit 51 down-converts the frequency of the radio signal received by the antenna ATR to a baseband frequency, and then AD-converts the frequency to be input to the OFDM demodulation unit 52. The OFDM demodulator separates and outputs user data and control signals sent from each user and random access signals sent from idle terminals and DRX / DTX mode terminals. When the random access signal processing unit 53 receives a random access signal from an idle terminal or a DRX / DTX mode terminal, the random access signal processing unit 53 performs a known random access process and inputs the identification number of the terminal to the radio resource management unit 54.
The radio resource management unit 54 includes a terminal type management table 54a, and a terminal in communication is an active mode terminal in a state where data can be constantly transmitted / received to / from the base station or intermittently from / to the base station. Manages the type of DRX / DTX terminal that can send and receive data. When receiving a random access signal from the idle terminal and the DRX / DTX terminal, the radio resource management unit 54 registers these terminals as active mode terminals in the terminal type management table 54a, and data per predetermined time of the active mode terminals. The communication amount is monitored, and when the data communication amount becomes equal to or less than the set value, the active terminal is changed to a DRX / DTX terminal, and the terminal whose communication is completed is deleted from the terminal type management table 54a. FIG. 5 shows an example of the configuration of the terminal type management table 54a, in which the terminal type is recorded in correspondence with the identification number of the communicating terminal.

The control unit 55 (1) control for determining the period T of the first subframe and the bandwidth of the narrowband NFR, and (2) control for determining in which subband the individual data / individual control signal of each terminal is transmitted. (3) Transmission control of dedicated pilots at the time of second subframe transmission, (3) Subband allocation control of dedicated data of terminals moving at high speed, etc.
The all-band common pilot generation unit 56 creates and outputs a common pilot signal for all bands at the timing instructed by the control unit 55, and the narrow-band common pilot generation unit 57 generates a narrow-band common pilot signal instructed by the control unit 55. The common pilot signal is generated and output at the instructed timing, and the selection unit 58 selectively generates the common pilot signal for the entire band and the common pilot signal for the narrow band at the timing instructed by the control unit. Channel generation unit) 59. Further, the synchronization signal generator 60, the common control signal generator 61, the user data position information generator 62, and the individual pilot generator 63 respectively generate predetermined signals according to instructions from the controller 55 and send them to the subframe generator 59. input. That is, the synchronization signal generation unit 60 generates the synchronization signal SYC having the bandwidth specified by the control unit, the common control signal generation unit 61 generates the control signal CCS specified by the control unit, and the user data position information generation unit 62 creates user data position information DTL for specifying a subband for transmitting each user data, and an individual pilot creation unit 63 creates an individual pilot and inputs it to the subframe creation unit 59. The individual data / individual control signal creation unit 64 creates data and control signals to be individually transmitted to the user terminal and inputs them to the subframe creation unit 59.

The subframe creation unit 59 is configured to transmit the first subframe based on the transmission period T of the first subframe notified from the control unit 55, the band information of the narrowband NFR, the subband information for transmitting the individual data / individual control signal, and the like. At the time of frame transmission, the first subframe SF1 including the information shown in FIG. 3 is created and output. Similarly, the subframe creation unit 59 creates and outputs a second subframe SF2 including the information shown in FIG. 3 when transmitting the second subframe.
The OFDM modulation unit 65 performs OFDM modulation on the first and second subframes input from the subframe creation unit 59, and the wireless transmission unit 66 transmits the OFDM signal wirelessly from the transmission antenna ATT.
In FIG. 4, it is assumed that an OFDM signal is used in the uplink, but it is not always necessary to use the OFDM signal in the uplink.

(D) Control of base station equipment
(a) Terminal Type Management FIG. 6 is a terminal type management process flow of the radio resource management unit 54.
Based on the signal from the random signal processing unit 53, the radio resource management unit 54 checks whether there is a terminal that has transmitted the random access signal (step 101), and if there is, the terminal that generated the random access signal (idle mode terminal) ) Is registered in the terminal type table 54a as an active mode terminal (step 102). If the terminal that generated the random access signal is a DRX / DTR mode terminal, the terminal is changed from the DRX / DTR mode terminal to the active mode terminal.
Next, it is checked whether there is a terminal with a small amount of data transmission among the active mode terminals (step 103). If there is, the active mode terminal is changed to a DRX / DTR mode terminal (step 104), and the above processing is repeated thereafter. .
The control unit 55 notifies the terminal whose terminal type has been changed from the RX / DTR mode to the active mode, and the terminal that has changed from the active mode to the DRX / DTR mode, using the individual control signal.

(b) Control of changing transmission cycle of first subframe FIG. 7 is a flowchart of processing for changing the transmission cycle of the first subframe.
The control unit 55 refers to the terminal type management table 54a of the radio resource management unit 54 to obtain the total number of active mode terminals and DRX / DTR mode terminals, that is, the total number of communicating terminals (step 201), and the total number is set. Whether the number is less than or equal to the number (step 202). If the number is less than the set number, the transmission period T of the first subframe SF1 is set to an initial value, for example, 5 ms (step 203). On the other hand, if the total number is equal to or greater than the set number, the transmission period T of the first subframe SF1 is shortened as the total number increases (step 204). A correspondence table between the total number and the period T is stored in advance, and the period T can be determined based on the correspondence table.
In this case, the DRX / DTR mode terminal performs control so that the intermittent transmission / reception period in which data is intermittently transmitted / received to / from the base station is the same as the transmission period T of the first subframe.
In the above, the period of the first subframe is controlled based on the total number of terminals in communication. However, the number of consecutive first subframes can be controlled with a constant period.

(c) Narrowband Bandwidth Control FIG. 8 is a control processing flow of the bandwidth of the narrowband NFR that is the transmission band of the second subframe.
The control unit 55 refers to the terminal type management table 54a of the radio resource management unit 54, acquires the number of active mode terminals (step 301), checks whether the number of terminals is equal to or less than the set number (step 302), and sets the set number. If it is below, the bandwidth and band position of the narrow band NFR are set as initial values (step 303). On the other hand, if the number of active mode terminals is equal to or greater than the set number, the greater the number of active mode terminals, the wider the bandwidth of the narrowband NFR (step 304). Note that a correspondence table of the number of active mode terminals, bandwidths, and bandwidth positions can be stored in advance, and bandwidths and bandwidth positions can be determined based on the correspondence tables.
Thereafter, the control unit 55 assigns the determined narrowband NFR subband to the active mode terminal when transmitting the second subframe SF2 (step 305).

(d) Dedicated pilot transmission control In the second subframe transmission period T2 (see FIG. 3), the data transmission amount of the active mode terminal increases and the bandwidth of the narrowband NFR may be insufficient. In such a case, it is necessary to transmit dedicated data and dedicated pilots in subbands other than the narrowband NFR subband.
FIG. 9 is a transmission control processing flow of the individual data and the individual pilot. The control unit 55 monitors whether the data transmission of the active mode terminal is possible with the bandwidth of the narrowband NFR (step 401), and if not, it is adjacent to the narrowband NFR so that all data transmission is possible. Thus, a predetermined bandwidth is secured (see B in FIG. 3, step 402). Then, each active mode terminal is allocated to the narrowband NFR and the extended band subbands, and the allocation information is input to the subframe creating unit 59 (step 403). The subframe creating unit 59 creates and transmits the second subframe SF2 (see FIG. 3) so that the dedicated pilot and dedicated data addressed to each terminal can be transmitted in the subband indicated by the allocation information (step 404). ).
By transmitting the dedicated pilot, the terminal can perform synchronous demodulation and SIR measurement using the dedicated pilot even when the common pilot cannot be used when receiving the dedicated data / dedicated control signal.

(e) Subband allocation control of high-speed mobile terminal FIG. 10 is a flowchart of subband allocation control processing of the high-speed mobile terminal.
The control unit 55 refers to the control signal transmitted from the terminal that is the individual data transmission destination, and determines whether the terminal is a high-speed mobile terminal (step 501). If the mobile terminal is moving at high speed, a subband belonging to the narrowband NFR is allocated to the high-speed mobile terminal even when transmitting the first subframe SF1 (step 502). On the other hand, if the mobile terminal is not moving at high speed, a subband not belonging to the narrowband NFR is allocated to the terminal when transmitting the first subframe SF1 (step 503). In the above, it is determined whether or not the terminal is moving at high speed and notified to the base station by a control signal, but it can also be determined by the base station based on measurement of a pilot signal transmitted by the terminal .
By doing as described above, when moving at high speed, the terminal can average the common pilots of the previous and subsequent subframes to obtain a highly accurate pilot and improve the reception quality.
(f) Consideration for common pilots of adjacent base stations The control unit 55 receives a common pilot transmission method (transmission timing and bandwidth information of common pilots for all and narrow bands) in the adjacent base stations from adjacent base stations and networks, The SIR measurement result can be evaluated based on the received information. This is because, for example, the reliability of the SIR measurement result changes depending on whether or not the SIR measurement timing matches the common pilot transmission timing in the adjacent base station.

(E) Configuration of Terminal Device FIG. 11 is a configuration diagram of a mobile terminal device.
The radio reception unit 81 down-converts the frequency of the radio signal received by the antenna ATR to a baseband frequency, and the AD converter 82 AD-converts the baseband signal and inputs it to the OFDM demodulation unit 84. The AFC circuit 83 performs control similar to the AFC circuit 11 of FIG. 16 so that the frequency offset becomes zero.
As shown in FIG. 16, the OFDM demodulation unit 84 includes a symbol cutout unit, an FFT, a pilot extraction unit, a channel estimation unit, a channel compensation unit (synchronous demodulation unit), and the like, and a common control signal CCS sent from the base station, Data / individual control signal, user data position information DTL, and common pilot CPL are demodulated and output.
The control unit 85 extracts the common pilot transmission method information included in the common control signal CCS, identifies the reception timing and the bandwidth of the common pilot of the entire band and the narrow band of the common pilot based on the information, and the AFC circuit 83 and the OFDM Notify the demodulator 84. The pilot extraction unit 84a of the OFDM demodulation unit 84 extracts and outputs a common pilot based on the timing and band notified from the control unit 85. Further, the channel estimation unit 84b of the OFDM demodulation unit 84 performs channel estimation based on the common pilot, and the synchronous demodulation unit 84c performs channel compensation.
Further, the control unit 85 identifies the subband to which the individual data / individual control signal addressed to itself is transmitted based on the user data position information DTL, and inputs it to the user data selection unit 86. The user data selection unit 86 selects and outputs individual data or individual control signals addressed to the user from the subband designated by the control unit 55.
Furthermore, if the recognized subband does not belong to the narrowband NFR, the control unit 85 notifies the OFDM demodulator 84 of the subband. The pilot extraction unit 84a of the OFDM demodulation unit 84 extracts the dedicated pilot from the notified subband, the channel estimation unit 84b performs channel estimation based on the dedicated pilot, and the channel compensation unit 84c performs channel compensation.
Optimal subband determining section 87 determines a subband having the best reception quality using the common pilot, and terminal speed measuring section 88 measures the terminal moving speed by a known method using the common pilot. The control signal generation unit 89 creates a control signal including subband information, terminal moving speed, etc., the OFDM modulation unit 90 performs OFDM modulation on the control signal and user data input by time division multiplexing, and the wireless transmission unit 91 transmits the OFDM signal. Is transmitted from the transmitting antenna ATT wirelessly.
As described above, FIG. 11 shows the case of transmitting by OFDM modulation, but it is not always necessary to transmit by OFDM modulation.

FIG. 12 is a block diagram showing an example of the pilot extraction unit 84a, which has a configuration in which pilot signals in the preceding and following subframes are averaged and output. The common pilot extraction unit 84a-1 extracts and outputs a common pilot based on the timing and band information notified from the control unit 85, and the pilot delay unit 84a-2 outputs the pilot signal with a delay of one subframe period. To do. The average unit 84a-3 calculates the average value of the common pilots extracted from the preceding and following subframes, and in the case of a high-speed mobile terminal, the pilot selection unit 84a-4 selects a pilot output from the average unit, and the high-speed mobile terminal Otherwise, the common pilot output from the common pilot extraction unit 84a-1 is selected and output. With this configuration, even when moving at high speed, the terminal can perform channel compensation control and SIR measurement using a highly accurate pilot, and reception quality can be improved.
When transmitting an individual pilot signal in addition to the individual data / individual control signal for a high-speed mobile terminal, a pilot with higher accuracy is extracted by averaging the individual pilot in the averaging unit 84a-3. It becomes possible.

WFR total transmission bandwidth
NFR narrow band
SF1 First subframe (full-band subframe)
SF2 Second subframe (Narrowband subframe)

Claims (1)

A wireless communication system comprising a wireless base station device and a terminal device that communicates with the wireless base station device,
The wireless base station device
The first sub-frame and the subframe generated second subframe, the transmitted at the predetermined narrow band in the entire transmission band each common pilot and data to be transmitted common pilot and data in all transmission band respectively Generator,
A radio transmitter for transmitting a common pilot by transmitting the first and second subframes in a downlink radio section;
A wireless communication system comprising:

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