JP2006121550A - Radio communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress an influence on a transmission spectral caused by frequency selective fading in a radio communication system. <P>SOLUTION: Frequency selective fading occurrence condition detecting means 1, 2 detect the condition of selective fading occurrence in a radio propagation path with a communication partner. A transmission pattern determining means 2 determines a transmission pattern which can be discriminated from an arrangement of symbols in a pair about sequence of symbols as a transmission object, the repeating number of the arrangement of the symbols in a pair, a mode for reversing the polarity if the polarity of symbol is reversed in the repeat, and the shift amount of a central frequency if the central frequency is shifted; so that the influence on the transmission spectral caused by the frequency selective fading can be reduced based on the detected results. Then, radio transmission means 3, 4, 5 transmit by radio the sequence of the symbol to be transmitted with a determined transmission pattern through a radio propagation path. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wireless communication apparatus that communicates wirelessly, and more particularly to a wireless communication apparatus that suppresses an influence on a transmission spectrum due to frequency selective fading.

For example, in a wireless communication system such as a mobile communication system, an audio signal and a data signal are transmitted and received wirelessly by a wireless communication device.
FIG. 13 shows an example of a transmission spectrum of a typical QPSK (Quadri Phase Shift Keying) signal. The horizontal axis of the graph indicates the frequency of the signal, and the vertical axis indicates the power of the signal.
FIG. 13 shows a general transmission spectrum when the center frequency is f0 and the band is fs. fs is a frequency at which fs = 1 / Ns, where Ns is the transmission time of information that can be transmitted at one time. Band limiting is performed at a frequency of {f0 ± (plus / minus) fs / 2}.

In FIG. 14, when the spectrum shown in FIG. 13 is transmitted, signals that have different delays are combined through various propagation paths to receive reception affected by frequency selective fading. An example of the spectrum of the signal is shown. The horizontal axis of the graph indicates the frequency of the signal, and the vertical axis indicates the power of the signal. As shown in the figure, the characteristics of the spectrum deteriorate due to frequency selective fading.
In FIG. 15, when the spectrum shown in FIG. 13 is transmitted, signals that have different delays are combined via various propagation paths, thereby receiving reception affected by frequency selective fading. Another example of the spectrum of the signal is shown. The horizontal axis of the graph indicates the frequency of the signal, and the vertical axis indicates the power of the signal. As shown in the figure, the characteristics of the spectrum deteriorate due to frequency selective fading.

Here, the amount of attenuation of signal power due to frequency selective fading reaches several tens of dB when it is large. For this reason, frequency selective fading can be achieved by using multiple receiving antennas and using space diversity that combines received signals with different propagation characteristics and an array antenna that estimates the direction of incoming waves and controls directivity. Mitigating the impact.
However, in particular, a portable device of a communication system using a low frequency band may not have a plurality of antennas due to the antenna structure, and it is necessary to improve reception quality.

JP-A-9-27832 JP 2002-290246 A

As described above, the conventional wireless communication apparatus has a problem in that the quality of wireless communication deteriorates due to the influence of frequency selective fading.
The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a wireless communication apparatus capable of suppressing the influence on the transmission spectrum due to frequency selective fading.

In order to achieve the above object, the wireless communication apparatus according to the present invention performs the following processing when performing wireless communication.
That is, the frequency-selective fading occurrence state detection means detects the occurrence state of frequency-selective fading in the radio propagation path with the communication partner. Based on the detection result by the frequency selective fading occurrence state detecting means, the transmission pattern determining means has a set of symbol sequences to be transmitted so that the influence of the frequency selective fading on the transmission spectrum is reduced. The number of repetitions of the arrangement of symbols, the number of repetitions of the arrangement of symbols in the set, the mode of reversing the polarity when inverting the polarity of the symbol in the repetition, and the amount of shifting the center frequency when shifting the center frequency Determine the transmission pattern to be performed. The wireless transmission means wirelessly transmits the series of symbols to be transmitted through the wireless propagation path with the transmission pattern determined by the transmission pattern determination means.

Therefore, a transmission pattern is determined such that the influence on the transmission spectrum due to frequency selective fading in the wireless propagation path with the communication partner is reduced, and the sequence of symbols to be transmitted is wirelessly transmitted via the wireless propagation path. By transmitting, the influence on the transmission spectrum due to frequency selective fading can be suppressed, and deterioration of communication quality can be prevented.
For example, it is possible to eliminate or reduce the influence of frequency selective fading by not using the signal component at the frequency position where frequency selective fading has occurred at all or not much in communication.

Here, various devices may be used as the wireless communication device, for example, a device that performs transmission and reception wirelessly.
Various communication partners may be used. For example, other wireless communication devices are used.
In addition, as a wireless propagation path with a communication partner that is a target for detecting the occurrence of frequency selective fading, for example, a wireless propagation path used for transmission to the communication partner is used. Alternatively, the occurrence of frequency selective fading in the radio propagation path used for transmission to the communication partner is detected (estimated) based on the occurrence of frequency selective fading in the radio propagation path used for reception from the communication counterpart. Embodiments may be used.
In addition, for example, a mode in which the state of occurrence of frequency selective fading in a radio propagation path used for transmission to a communication partner is notified from the communication partner by a radio signal may be used.

In addition, as information on the occurrence of frequency selective fading, information on various situations may be detected.For example, information on the frequency at which frequency selective fading has occurred, the number of such frequencies, the degree of fading, etc. Can be detected.
Various transmission patterns may be used to reduce the influence of frequency selective fading on the transmission spectrum. For example, frequency selective fading occurs in the band of the transmission spectrum. A transmission pattern that creates a drop in level at a certain frequency position can be used.

In addition, as a series of symbols to be transmitted, for example, a time-series arrangement of symbols such as voice and data to be originally transmitted is used.
In addition, various numbers of symbols may be used as a set of symbols. For example, a mode in which one symbol is set as one set may be used, or a predetermined number of symbols arranged continuously. A mode in which a plurality of symbols are set as one set may be used.
Various times may be used as the number of times the arrangement of symbols as one set is repeated. For example, one time may be used, or a predetermined number of times may be used.

In addition, various modes may be used as a mode of inverting the polarity of the symbol. For example, with the arrangement of symbols as a unit as a unit, odd-numbered or even-numbered symbols included in a repetition are included. A mode in which the polarity (plus / minus sign) is reversed to perform alternate sign inversion, or the polarity (plus / minus sign) of the odd or even numbered symbols is reversed in units of one symbol. A mode in which the sign inversion is performed can be used.
Note that the reversal of the polarity of the symbol may or may not be performed.

Also, various amounts may be used as the amount of shifting the center frequency. For example, a shift amount that does not affect the communication quality based on the filtering characteristics or the like or is small is used.
Note that the center frequency may be shifted or may not be shifted.
Various transmission patterns may be used. For example, the transmission pattern may be generated based on the detection result of the frequency selective fading occurrence state, or a plurality of transmission patterns are stored in advance. An aspect may be used in which a transmission pattern to be used is selected based on the detection result of the frequency selective fading occurrence state.

  As described above, according to the wireless communication device of the present invention, the occurrence state of frequency selective fading in the wireless propagation path with the communication partner is detected, and transmission by frequency selective fading is performed based on the detection result. When the symbol sequence to be transmitted is repeated, the number of repetitions of the symbol sequence as one set, and the polarity of the symbol is inverted in the repetition so that the influence on the spectrum is reduced Determines the transmission pattern identified by the mode in which the polarity is inverted, and the amount by which the center frequency is shifted when the center frequency is shifted, and the series of symbols to be transmitted is determined by the determined transmission pattern as the radio propagation path. Over the air, so that the influence of the frequency selective fading on the transmission spectrum is suppressed. Rukoto can, it is possible to prevent deterioration of communication quality.

Embodiments according to the present invention will be described with reference to the drawings.
First, an outline of a wireless communication apparatus according to an embodiment of the present invention will be described.
FIG. 1 shows a configuration example of a communication device provided in a wireless communication apparatus according to an embodiment of the present invention.
Note that the wireless communication apparatus according to the present embodiment wirelessly communicates audio signals and data signals using a TDD (Time Division Duplex) method.
The wireless communication apparatus according to the present embodiment includes a spectrum analysis unit 1, a control unit 2, a data generation unit 3, an adaptive modulation unit 4, and a wireless transmission unit 5.

The spectrum analyzer 1 receives a signal wirelessly received by an antenna (not shown) and measures the state of the propagation path from the received signal.
The control unit 2 determines a transmission mode based on the result of the analysis performed by the spectrum analysis unit 1. In addition, the control unit 2 controls the data generation unit 3, the adaptive modulation unit 4, and the wireless transmission unit 5 with control signals.
The data generation unit 3 receives the control signal from the control unit 2 and generates data to be transmitted according to the control signal.
The adaptive modulation unit 4 receives the control signal from the control unit 2 and modulates transmission data generated by the data generation unit 3 according to the control signal.
The radio transmission unit 5 receives a control signal from the control unit 2, converts the transmission modulation signal generated by the adaptive modulation unit 4 into a radio frequency (RF) signal according to the control signal, and converts the transmission modulation signal into an antenna (FIG. (Not shown).

  In the wireless communication apparatus according to the present embodiment, the control unit 2 estimates the propagation path based on the result of analyzing the received signal in the spectrum analysis unit 1, and as a result, when the propagation path is in good condition, for example, 16QAM (Quadrature Amplitude) Information is transmitted at a high communication speed by Modulation), etc. On the other hand, as shown in FIGS. 14 and 15, when frequency selective fading is detected for the state of the propagation path, the transmission signal is transmitted in a band affected by fading. The transmission mode is determined so as to give a drop of the band on the spectrum, and the adaptive modulation unit 4 or the wireless transmission unit 5 performs control so that the determined transmission mode is realized.

  As a transmission mode that causes a drop in the spectrum of a transmission signal in a predetermined band, for example, a mode using a signal that is repeated twice with two information symbols (2 symbols) as one set, or four information symbols (4 A mode that uses a signal that is repeated twice as a set of symbols), a mode that uses a signal that simply repeats one information symbol (one symbol), and the polarity (plus) of the odd-numbered or even-numbered information symbol in these Modes that use signals that are inverted (minus), modes that shift the center frequency according to the drop of the spectrum in order to avoid bands affected by fading, and frequency selectivity by multiplexing these transmission signals A mode that uses only a band that is not affected by fading can be used.

In the receiving side device, when demodulating the received signal, a radio communication system that is less susceptible to frequency selective fading is performed by performing an operation opposite to the symbol operation according to the transmission mode used in the transmitting side device. Can be built.
Note that the receiving side device knows in advance in which transmission mode the transmission pattern is transmitted by the transmitting side device. For example, at the start of transmission, the transmitting side device uses a predetermined format. The transmission mode (transmission pattern) is notified from the apparatus to the receiving apparatus.
In addition, in the wireless communication apparatus according to the present embodiment, the state of the propagation path (frequency selective fading state) with the other wireless communication apparatus based on the signal wirelessly received from the other wireless communication apparatus that is the communication partner. ) And a transmission mode (transmission pattern) for the other wireless communication device is determined based on the estimation result.

Further, for example, in a system using an FDD (Frequency Division Duplex) method, in any transmission mode (transmission pattern) with respect to a radio communication apparatus as a communication partner on the basis of a result of analyzing a measured reception spectrum. It can be configured to instruct whether or not it is desired to be transmitted.
For spectrum analysis, for example, when communication with band limitation is already performed, a signal having a normal spectrum (a spectrum without band limitation) such as a preamble pattern or a pilot symbol pattern is used for analysis. In a communication mode in which band limitation is not performed, it is possible to perform spectrum analysis on the received signal as it is.

  Also, for example, in the case of a transmission system with spatial multiplexing such as space division multiple access (SDMA) or multi-input multi-output (MIMO), for each propagation path, It is possible to communicate adaptively by judging the situation.

  In the wireless communication apparatus according to the present embodiment, the function of the spectrum analysis unit 1 and the function of the control unit 2 constitute frequency selective fading occurrence state detection means, and the function of the control unit 2 provides transmission pattern determination means. The wireless transmission means is configured by the function of the data generation unit 3, the function of the adaptive modulation unit 4, and the function of the wireless transmission unit 5.

A first embodiment of the present invention will be described.
Hereinafter, a method for controlling the transmission spectrum by the wireless communication apparatus of this example will be described.
The transmission spectrum shown in FIG. 13 includes transmission symbol sequences “..., S (n−1), S (n), S (n + 1), S (n + 2), S (n + 3), S (n + 4),. This is an example in the case where “.” Is transmitted as it is. Here, S (t) represents a symbol, and t represents time (arrangement order).
The transmission symbol S (t) is transmitted at a time interval of transmission time Ts = (1 / fs), and band limitation is performed at a frequency of {f0 ± (plus / minus) fs / 2}.
Moreover, there is no limitation in particular as a modulation system of the signal transmitted with transmission symbol S (t), For example, QPSK, 16QAM, etc. can be used.

FIG. 2 shows an example of a transmission spectrum when two transmission symbols (two symbols) are transmitted as a set twice. As a specific example, the transmission symbol sequence is “..., S (n−2), S (n−1), S (n−2), S (n−1), S (n), S (n + 1). , S (n), S (n + 1), S (n + 2), S (n + 3), S (n + 2), S (n + 3),. The horizontal axis of the graph indicates the frequency of the signal, and the vertical axis indicates the power of the signal.
In the transmission spectrum shown in FIG. 2, power drops on the spectrum occur at frequencies of {f0 ± (plus / minus) fs / 8} and {f0 ± (plus / minus) 3 × fs / 8} in the band. .

FIG. 3 shows an example of a transmission spectrum in a case where four transmission symbols (4 symbols) are transmitted twice as a set. As a specific example, the transmission symbol sequence is “..., S (n−3), S (n−2), S (n−1), S (n), S (n + 1), S (n + 2), S (n + 3), S (n), S (n + 1), S (n + 2), S (n + 3), S (n + 4),. The horizontal axis of the graph indicates the frequency of the signal, and the vertical axis indicates the power of the signal.
As shown in FIG. 2 and FIG. 3, even if the number of repetitions is the same number (in this example, 2 times), if the number of symbols in one set of the transmission symbol series changes, a drop in power generated on the spectrum The bandwidth and number of

FIG. 4 shows an example of a transmission spectrum when two transmission symbols (two symbols) are transmitted as a set four times repeatedly. As a specific example, the transmission symbol sequence is “..., S (n−2), S (n−1), S (n), S (n + 1), S (n), S (n + 1), S ( n), S (n + 1), S (n), S (n + 1), S (n + 2), S (n + 3), S (n + 2), S (n + 3), S (n + 2), S (n + 3), S ( n + 2), S (n + 3), S (n + 4), S (n + 5),. The horizontal axis of the graph indicates the frequency of the signal, and the vertical axis indicates the power of the signal.
As shown in FIGS. 2 and 4, even if the number of transmission symbol sequences is the same (2 symbols in this example), the spectrum concentrates on a specific frequency as the number of repetitions increases. It has the property of narrowing the band.

FIG. 5 shows an example of a transmission spectrum in a case where information symbols of a transmission symbol series are simply transmitted twice, that is, transmission is performed twice with one transmission symbol (one symbol) as one set. An example of the transmission spectrum in this case is shown. As a specific example, the transmission symbol sequence is “..., S (n−1), S (n−1), S (n), S (n), S (n + 1), S (n + 1), S ( n + 2), S (n + 2), S (n + 3), S (n + 3), S (n + 4), S (n + 4),. The horizontal axis of the graph indicates the frequency of the signal, and the vertical axis indicates the power of the signal.
In the example of FIG. 5, compared with the example of FIG. 2, the communication speed is the same, but the band in which power drops on the spectrum is different, and in FIG. 2, {f0 ± (plus / minus) fs / 8} and { The frequency is f0 ± (plus / minus) 3 × fs / 8}. In FIG. 5, the frequency is {f0 ± (plus / minus) fs / 4}, which is increased in FIG.

FIG. 6 shows the center frequency of the transmission signal from f0 for the transmission spectrum shown in FIG. 2, that is, for the transmission spectrum when two transmission symbols (two symbols) are transmitted twice as a set. An example of a transmission spectrum in the case where control is performed so that the drop of the band becomes f0 by shifting by fs / 8).
In the example of FIG. 6, spectrum side lobes appear outside the band and are removed by the filter. However, since most of the power exists in the band, the communication quality is not affected or little.
Note that the center frequency of the transmission signal can be shifted by an arbitrary amount, for example, by shifting the local frequency.

  In the wireless communication device of this example, by transmitting a transmission symbol sequence repeatedly in an arbitrary number of times, it is possible to create a drop in power in a specific band on the transmission spectrum, and to set its center frequency to It is also possible to shift within a range that does not affect the communication quality. In the wireless communication apparatus of this example, using such spectral characteristics, when frequency selective fading occurs, the transmission spectrum is adaptively controlled, and the signal component of the frequency at which frequency selective fading has occurred. The communication is performed so that no or very little is used.

As described above, in the wireless communication device of this example, the occurrence of frequency selective fading in the propagation path is estimated, and the data transmission pattern is changed in accordance with the estimated propagation path condition, whereby a spectrum unique to the band is obtained. This suppresses the influence of the frequency selective fading on the spectrum.
Specifically, in the wireless communication apparatus of this example, a reception quality measurement function that detects the presence / absence of frequency selective fading and identifies a frequency at which attenuation due to fading occurs, and a transmission spectrum at the obtained fading frequency. Transmission signal generation control function that controls the signal pattern of the transmission signal so that the transmission pattern is not distributed, and the transmission pattern is changed based on the analysis result by the spectrum analysis unit that measures the state of the propagation path from the reception signal. To perform adaptive modulation and transmission.

Therefore, the wireless communication apparatus of this example can provide a communication system that is strong against frequency selective fading in a wireless propagation path in which frequency selective fading has occurred.
For example, the wireless communication apparatus of this example is applied to a communication system in which frequency selective fading due to multipath occurs, and when frequency selective fading occurs, data is repeatedly transmitted within the transmission band. A unique spectrum is formed, and the influence of frequency selective fading can be suppressed.
Further, in the wireless communication device of this example, for example, depending on the condition of the propagation path, not only the communication speed is lowered when the communication quality is deteriorated, but also the presence of occurrence of frequency selective fading is examined, and the frequency selection is performed. It is possible to control so that the transmission spectrum of a signal is not allocated to a band in which attenuation is significant due to the influence of sex fading.

Thus, in the wireless communication apparatus of this example, in order to change and avoid the transmission spectrum when frequency selective fading occurs, for example, transmission data is repeatedly transmitted (that is, the data has periodicity). Thus, a unique spectrum is generated in the band, and adaptive modulation is performed to change the periodicity, the center frequency, etc. so as to match the drop with the drop of fading.
Here, it is possible to reduce the error rate by combining the data repeatedly transmitted by the transmission-side device, for example, by the reception-side device.
Also, for example, in voice communication, when the communication speed is reduced to 1/2 or 1/4 compared to normal time, the coding rate is changed, the data is periodically thinned and discarded, In a state where data naturally overflows and disappears from the buffer, it is possible to leave it to error correction in the upper layer, or to switch between full rate and half rate.

A second embodiment of the present invention will be described.
Hereinafter, a method for controlling the transmission spectrum by the wireless communication apparatus of this example will be described.
The transmission spectrum shown in FIG. 13 includes transmission symbol sequences “..., S (n−1), S (n), S (n + 1), S (n + 2), S (n + 3), S (n + 4),. This is an example in the case where “.” Is transmitted as it is. Here, S (t) represents a symbol, and t represents time (arrangement order).
The transmission symbol S (t) is transmitted at a time interval of transmission time Ts = (1 / fs), and band limitation is performed at a frequency of {f0 ± (plus / minus) fs / 2}.
Moreover, there is no limitation in particular as a modulation system of the signal transmitted with transmission symbol S (t), For example, QPSK, 16QAM, etc. can be used.

FIG. 7 shows an example of a transmission spectrum in the case where two transmission symbols (two symbols) are repeated twice as a set and the second polarity (plus or minus sign) is inverted and transmitted. As a specific example, the transmission symbol sequence is “..., S (n−2), S (n−1), −S (n−2), −S (n−1), S (n), S (N + 1), -S (n), -S (n + 1), S (n + 2), S (n + 3), -S (n + 2), -S (n + 3),. The horizontal axis of the graph indicates the frequency of the signal, and the vertical axis indicates the power of the signal.
In the transmission spectrum shown in FIG. 7, power drops on the spectrum occur at frequencies of f0 and {f0 ± (plus / minus) fs / 4} within the band.

FIG. 8 shows an example of a transmission spectrum in a case where four transmission symbols (four symbols) are repeated twice as a set and the second polarity (plus or minus sign) is inverted and transmitted. As a specific example, the transmission symbol sequence is “..., −S (n−3), −S (n−2), −S (n−1), S (n), S (n + 1), S ( n + 2), S (n + 3), -S (n), -S (n + 1), -S (n + 2), -S (n + 3), S (n + 4),. The horizontal axis of the graph indicates the frequency of the signal, and the vertical axis indicates the power of the signal.
As shown in FIGS. 7 and 8, even if the number of repetitions is the same number (two in this example), if the number of symbols in one set of the transmission symbol series changes, a drop in power generated on the spectrum The bandwidth and number of

FIG. 9 shows an example of a transmission spectrum when two transmission symbols (two symbols) are repeated four times as a set, and transmission is performed with the even-numbered polarity (plus or minus sign) inverted. As a specific example, the transmission symbol sequence is “..., −S (n−2), −S (n−1), S (n), S (n + 1), −S (n), −S (n + 1). ), S (n), S (n + 1), -S (n), -S (n + 1), S (n + 2), S (n + 3), -S (n + 2), -S (n + 3), S (n + 2) , S (n + 3), -S (n + 2), -S (n + 3), S (n + 4), S (n + 5),. The horizontal axis of the graph indicates the frequency of the signal, and the vertical axis indicates the power of the signal.
As shown in FIG. 7 and FIG. 9, even if the number of transmission symbol sequences is the same (2 symbols in this example), as the number of repetitions increases, the spectrum concentrates on a specific frequency. It has the property of narrowing the band.

FIG. 10 shows an example of a transmission spectrum in a case where information symbols of the transmission symbol series are simply repeated twice and transmitted with the second polarity (plus or minus sign) inverted. An example of a transmission spectrum in the case of transmitting a transmission symbol (one symbol) as a set by repeating twice and inverting the second polarity is shown. As a specific example, the transmission symbol sequence is “..., S (n−1), −S (n−1), S (n), −S (n), S (n + 1), −S (n + 1). , S (n + 2), -S (n + 2), S (n + 3), -S (n + 3), S (n + 4), -S (n + 4),. The horizontal axis of the graph indicates the frequency of the signal, and the vertical axis indicates the power of the signal.
In the example of FIG. 10, compared with the example of FIG. 7, the communication speed is the same, but the band in which power drops on the spectrum is different. In FIG. 7, f0 and {f0 ± (plus / minus) fs / 4} FIG. 10 shows only the frequency f0, and FIG. 7 shows an increase.

FIG. 11 shows a case where the transmission spectrum shown in FIG. 7 is transmitted, that is, when two transmission symbols (2 symbols) are repeated as a set twice and the second polarity (plus or minus sign) is inverted. An example of the transmission spectrum when the center frequency of the transmission signal is shifted from f0 by (fs / 16) and the band drop is controlled to be {f0− (fs / 16)} is shown. is there.
In the example of FIG. 11, the spectrum of the lower frequency (left side in FIG. 11) is deleted due to the filtering, but the quality is not affected if most of the power exists in the band.
Note that the center frequency of the transmission signal can be shifted by an arbitrary amount, for example, by shifting the local frequency.

  In the wireless communication device of this example, by transmitting a transmission symbol sequence repeatedly in an arbitrary number of times, it is possible to create a drop in power in a specific band on the transmission spectrum, and to set its center frequency to It is also possible to shift within a range that does not affect the communication quality. In the wireless communication apparatus of this example, using such spectral characteristics, when frequency selective fading occurs, the transmission spectrum is adaptively controlled, and the signal component of the frequency at which frequency selective fading has occurred. The communication is performed so that no or very little is used.

  The number of symbols per set and the number of repetitions are not particularly limited. For example, even if the second polarity is reversed twice with 3 symbols as a set and the polarity is inverted for the second time, one set of 2 symbols. If the polarity is inverted at the even number of times by repeating 5 times, or the polarity is inverted at the even number of times and the odd number of times simply by chronologically, the same characteristics on the spectrum are obtained. This is practical by performing modulation / demodulation according to a specific rule between transmission and reception.

As described above, in the wireless communication device of this example, the occurrence of frequency selective fading in the propagation path is estimated, and the data transmission pattern is changed in accordance with the estimated propagation path condition, whereby a spectrum unique to the band is obtained. This suppresses the influence of the frequency selective fading on the spectrum.
Specifically, in the wireless communication apparatus of this example, a reception quality measurement function that detects the presence / absence of frequency selective fading and identifies a frequency at which attenuation due to fading occurs, and a transmission spectrum at the obtained fading frequency. Transmission signal generation control function that controls the signal pattern of the transmission signal so that the transmission pattern is not distributed, and the transmission pattern is changed based on the analysis result by the spectrum analysis unit that measures the state of the propagation path from the reception signal. To perform adaptive modulation and transmission.

Therefore, the wireless communication apparatus of this example can provide a communication system that is strong against frequency selective fading in a wireless propagation path in which frequency selective fading has occurred.
For example, the wireless communication apparatus of this example is applied to a communication system in which frequency selective fading due to multipath occurs, and when frequency selective fading occurs, data is repeatedly transmitted within the transmission band. A unique spectrum is formed, and the influence of frequency selective fading can be suppressed.
Further, in the wireless communication device of this example, for example, depending on the condition of the propagation path, not only the communication speed is lowered when the communication quality is deteriorated, but also the presence of occurrence of frequency selective fading is examined, and the frequency selection is performed. It is possible to control so that the transmission spectrum of a signal is not allocated to a band in which attenuation is significant due to the influence of sex fading.

Thus, in the wireless communication apparatus of this example, in order to change and avoid the transmission spectrum when frequency selective fading occurs, for example, transmission data is repeatedly transmitted (that is, the data has periodicity). Thus, a unique spectrum is generated in the band, and adaptive modulation is performed to change the periodicity, the center frequency, etc. so as to match the drop with the drop of fading.
Here, it is possible to reduce the error rate by combining the data repeatedly transmitted by the transmission-side device, for example, by the reception-side device.
Also, for example, in voice communication, when the communication speed is reduced to 1/2 or 1/4 compared to normal time, the coding rate is changed, the data is periodically thinned and discarded, In a state where data naturally overflows and disappears from the buffer, it is possible to leave it to error correction in the upper layer, or to switch between full rate and half rate.

A third embodiment of the present invention will be described.
FIG. 12 shows an example of the correspondence between the position of the frequency where the spectrum level drops due to frequency selective fading and the repetitive pattern (transmission pattern) employed for transmission. In this example, the center frequency is not shifted.
In FIG. 12, x indicates the position of deviation from the center frequency when the band is divided into 32 (that is, frequency f = f0 + x × fs / 32).
In FIG. 12, “0” (zero) or “˜0” (approximately zero) is shown at the position where the transmission spectrum falls, and a repetitive pattern (transmission that is adopted corresponding to the position of the frequency where frequency selective fading occurs) (Pattern) is enclosed in a square.

In addition, each repetition pattern has the number of symbols (sym), the number of repetitions, and the polarity (plus or minus sign) alternately inverted ("reverse") or without inverting the polarity. It is specified by whether to transmit as it is ("non").
As a specific example, “1 sym, twice, anti” indicates a pattern in which one symbol is set as a set twice and is transmitted with the polarity reversed alternately, and “4 sym, twice, non” indicates four symbols. A pattern is shown in which a set is repeated twice and transmitted as it is without inverting the polarity.

Here, the configurations of the wireless communication apparatus and the wireless communication system according to the present invention are not necessarily limited to those described above, and various configurations may be used. The present invention can also be provided as, for example, a method or method for executing the processing according to the present invention, a program for realizing such a method or method, or a recording medium for recording the program. It is also possible to provide various devices and systems.
The application field of the present invention is not necessarily limited to the above-described fields, and the present invention can be applied to various fields.
In addition, as various processes performed in the wireless communication apparatus and the wireless communication system according to the present invention, for example, a control program stored in a ROM (Read Only Memory) by a processor in a hardware resource including a processor, a memory, and the like. A configuration controlled by execution may be used, and for example, each functional unit for executing the processing may be configured as an independent hardware circuit.
The present invention can also be understood as a computer-readable recording medium such as a floppy (registered trademark) disk or a CD (Compact Disc) -ROM storing the control program, and the program (itself). The processing according to the present invention can be performed by inputting the program from the recording medium to the computer and causing the processor to execute the program.

It is a figure which shows the structural example of the radio | wireless communication apparatus which concerns on the Example of this invention. It is a figure which shows an example of the transmission spectrum at the time of transmitting repeatedly 2 times by making 2 symbols which concern on 1st Example of this invention as 1 set. It is a figure which shows an example of the transmission spectrum in case the 4 symbols which concern on 1st Example of this invention are repeatedly transmitted 2 times as 1 set. It is a figure which shows an example of the transmission spectrum at the time of transmitting repeatedly 2 times by making 2 symbols which concern on 1st Example of this invention as 1 set. It is a figure which shows an example of the transmission spectrum in case one symbol which concerns on 1st Example of this invention is transmitted twice. It is a figure which shows an example of the transmission spectrum at the time of shifting the center frequency based on 1st Example of this invention, and transmitting repeatedly 2 times by making 2 symbols into 1 set. It is a figure which shows an example of the transmission spectrum in case the polarity of the 2nd time which concerns on 2nd Example of this invention is reversed, and it transmits repeatedly 2 times by making 2 symbols into 1 set. It is a figure which shows an example of the transmission spectrum in the case of inverting the polarity of the 2nd time which concerns on 2nd Example of this invention, and transmitting repeatedly 4 times as a set of 4 symbols. It is a figure which shows an example of the transmission spectrum in case the polarity of the even number which concerns on 2nd Example of this invention is reversed, and it transmits repeatedly 4 times by making 2 symbols into 1 set. It is a figure which shows an example of the transmission spectrum at the time of inverting the polarity of the 2nd time which concerns on 2nd Example of this invention, and transmitting one symbol twice. It is a figure which shows an example of the transmission spectrum at the time of shifting the center frequency based on 2nd Example of this invention, reversing the polarity of the 2nd time, and transmitting repeatedly 2 times by making 2 symbols into 1 set. It is a figure which shows an example of a response | compatibility with the repetition pattern of the symbol which concerns on 3rd Example of this invention, and the position of the fall of a spectrum. It is a figure which shows an example of the transmission spectrum of a QPSK signal. It is a figure which shows an example of the reception spectrum when the transmission spectrum of a QPSK signal receives frequency selective fading. It is a figure which shows an example of the reception spectrum when the transmission spectrum of a QPSK signal receives frequency selective fading.

Explanation of symbols

  1 .... spectrum analysis unit, 2 .... control unit, 3 .... data generation unit, 4 .... adaptive modulation unit, 5 .... wireless transmission unit,

Claims (1)

In a wireless communication device that communicates wirelessly,
Frequency selective fading occurrence status detection means for detecting the occurrence status of frequency selective fading in a radio propagation path with a communication partner;
Based on the detection result by the frequency selective fading occurrence state detecting means, the arrangement of symbols as one set for the sequence of symbols to be transmitted so that the influence on the transmission spectrum due to frequency selective fading is reduced, Determine the transmission pattern identified by the number of repetitions of the arrangement of symbols in one set, the mode of reversing the polarity when inverting the polarity of the symbol in the repetition, and the amount of shifting the center frequency when shifting the center frequency A transmission pattern determining means to perform,
Wireless transmission means for wirelessly transmitting the series of symbols to be transmitted through the wireless propagation path in the transmission pattern determined by the transmission pattern determination means;
A wireless communication apparatus comprising:

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