JP5293079B2 - Wireless communication system and transmission power and data rate control method thereof - Google Patents

Description

  The present invention relates to a transmission power setting method, a data rate control method, and a reception method in a radio station of a radio communication system that uses a wide band in which propagation path quality tends to be biased and uses a communication path code.

  In order to obtain desired reception quality in a wireless communication system, a technique for performing transmission power control of a wireless communication device is known. For example, in Patent Document 1, a signal reception power from a terminal is measured at a base station, an instruction to increase transmission power is transmitted to a mobile station if it is smaller than a desired value, and an instruction to decrease transmission power is transmitted to a mobile station if larger. A technique is described in which the mobile station controls the transmission power according to the transmission power control instruction to keep the reception power at the base station substantially constant.

  Further, in Patent Document 2, a mobile station measures the reception quality of a pilot signal transmitted by a base station with a known power, and when the reception quality is poor based on the measurement result, the transmission is larger than when the reception quality is good. A transmission power control signal requesting power is transmitted to the base station, and the base station receives a signal from the base station in the mobile station by controlling the transmission power of the signal directed to the mobile station based on the transmission power control signal. Technologies that keep the quality almost constant are shown.

  According to these technologies, the reception quality at the receiving station is controlled to be constant, so that the reception quality is constant, and the reception quality deteriorates due to gain fluctuations in the propagation path and the transmission power in the system is unnecessarily excessive. Interference can be prevented.

  Further, when a wide band is used for communication, the quality of the propagation path may be different for each band due to the influence of frequency selective noise or multipath. In such a case, a technique is considered in which communication is performed at a data rate at which communication is possible according to the quality of the propagation path for each band. Furthermore, in Patent Document 3, data that can be communicated for each band is measured by measuring noise for each band, selecting a band for allocating transmission power, allocating data to the selected band, and eliminating waste of power. Techniques for communicating at a rate are shown.

U.S. Pat.No. 5,267,262 U.S. Pat.No. 5,559,790 JP 2001-186102 A

  In order to increase the communication capacity of the entire communication system, it is desirable that the transmission power be as small as possible because each communication executed simultaneously is likely to interfere with other communication, and the amount of information that can be communicated per power It is desirable to select an encoding / modulation method that enables communication at a high data rate.

  On the other hand, in the conventional technique, the transmission power is controlled so that the reception quality becomes constant for the purpose of providing stable communication in the propagation path where the quality fluctuates. Therefore, it is difficult to reduce the transmission power beyond a certain level. .

  In addition, it is necessary to select a low data rate encoding / modulation method capable of communicating with sufficient quality even in a somewhat poor propagation path so that communication does not cause errors even if the propagation path fluctuates.

  In addition, when performing data transmission to one receiving station using a plurality of frequency bands, according to the conventional technique, the band to which data is allocated is changed based on the measurement result of the propagation path. Because the receiving side needs to know in advance the bandwidth to which data is allocated in order to change the data allocation and the reception, the transmission / reception means becomes complicated and it is difficult to follow high-speed propagation path fluctuations. There is a problem.

  The present invention distributes power in a band according to a propagation path by a relatively simple transmission / reception means in a propagation path whose quality varies, and reduces the total amount of transmission power with respect to the amount of transmission data to cause interference to other communications. The purpose is to increase the communication capacity of the entire system by reducing the amount of information that can be communicated per power.

  By using the error correction capability of the channel code, the reception quality of each symbol in the codeword does not need to be constant within the range of the error correction capability of the channel code, and the amount of information that can be used when decoding the channel code The best communication characteristics can be achieved when maximizing. On the other hand, since error correction capability does not work between codewords, it is necessary to stabilize the quality for each codeword.

  For this reason, when communicating using a wide frequency band, the signal power is controlled so that the channel capacity at each time increases by arranging the signals encoded by the channel code in symbols across multiple bands. In the time direction, control is performed so that the signal transmission power is increased as the quality of the communication path becomes worse so that the communication quality for each codeword is stabilized.

  Also, especially when the speed of fluctuation of the channel quality is small, the signal power is set so that the signal encoded by the channel code is arranged in symbols across multiple bands and the channel capacity at each time increases. Control is performed so that the average signal transmission power is constant in the time direction.

  Furthermore, especially when data rate fluctuations are allowed, such as in data communications, signals encoded with channel codes are arranged in symbols across multiple bands to allow for quality variations. Thus, the signal power is controlled so that the channel capacity increases for the entire communication.

  At this time, by controlling the data rate based on the measured propagation path quality and the communication quality fed back from the receiving side and changing the error correction capability of the code, the amount of information that can be communicated per transmission power in the entire communication Can be increased.

  The present invention can estimate the quality of a propagation path used for transmission from the quality of a received signal, for example, when applying a TDD (Time Division Duplex) method in which transmission and reception are duplexed by time-sharing the same band. In an environment, a signal whose transmission power is known is transmitted from the receiving station to the transmitting station, and the transmitting station can determine the propagation path quality from the received quality of this signal and control the signal power setting. It is.

  In addition, when the quality of the channel to be transmitted is not estimated from the quality of the received signal as in the case of applying the FDD (Frequency Division Duplex) method in which duplexing is performed using different bands for transmission and reception, from the transmitting station, A signal whose power is known is transmitted to the receiving station, and the receiving station determines the channel quality based on the reception quality of this signal, transmits quality information to the transmitting station, and this quality information is transmitted to the transmitting station. The present invention can be applied by controlling the setting of signal power in the wireless section based on the above.

According to the present invention, by setting the power in the band and time so as to increase the channel capacity, it is possible to reduce the required transmission power on average and reduce the mutual interference between communications.

  First, a transmission power setting method used in the present invention will be described.

  However, log2 (x) represents the logarithm of x with 2 as the base, and log (x) represents the natural logarithm of x.

  It is known that the capacity C of the communication channel having the frequency bandwidth W can be expressed as C = Wlog2 (1 + S / N) using the signal power S and the noise power N.

  Here, the increase rate of the capacity with respect to the increase in the minute signal power is dC / dS = W / (log (2) · (S + N)), which is inversely proportional to the sum of the signal power and the noise power. That is, when the signal power is increased, the capacity can be increased most when the sum of the signal power and the noise power is added to the smallest band or time.

  This relationship is called the water injection theorem. When the noise power varies depending on the band or time, the noise power is measured, and the sum of the measured noise power and signal power (hereinafter referred to as reference power) is equal. By performing communication with power set for each band or time, the communication path capacity per average transmission signal power can be increased. The reference power for obtaining the reception information amount necessary for correctly receiving the transmission data is determined by, for example, the error correction capability of the code used for encoding. In addition, control may be performed such that information about the reception state is fed back from the receiving station, and the reference power is increased when the amount of received information is insufficient.

  FIG. 1 shows how signal power is set for a band or time based on this policy. In the figure, the white rectangle 100 represents the signal power of the signal, and the noise power in the band / time where the hatched rectangle 101 exists.

  Since a negative value cannot be assigned as signal power, power is not assigned to a band or time when the noise power is very large, and the sum of signal power and noise power is calculated for other bands or times. The channel capacity is maximized by allocating power so that it is constant.

  Although FIG. 1 shows power allocation according to noise power, it is possible to consider this for fluctuations in channel gain due to fading or the like. That is, when the signal transmission power is T and the propagation path gain is G, the capacity of the previous communication path can be expressed as C = Wlog2 (1 + T · G / N).

  Therefore, the increase rate of the capacity with respect to the increase of the minute signal transmission power is dC / dT = W / (log (2) · (T + N / G)), and the value obtained by dividing the noise power by the channel gain is equivalently noise. By treating it as power, even when the propagation path gain fluctuates, it can be handled equivalently to when the noise power fluctuates.

  In this case, the variable channel gain and noise power are measured, and the signal transmission power is controlled so that the sum of the quotient and signal transmission power when the noise power is divided by the channel gain is constant. The communication path capacity per transmission signal power can be increased. As a result, the communication path capacity of the entire system can be increased.

  Further, when the fluctuation of the noise power is sufficiently small, the same control can be performed by treating the fluctuation of the reciprocal of the channel gain as the fluctuation of the noise power equivalently. For this reason, hereinafter, equivalent noise power is treated as noise power.

  In the above, the case where the water injection theorem is applied as the power control policy has been shown. Similarly, the signal power in a band or time with a large noise power is reduced, and instead the signal power in a band or time with a small noise power is increased. Thus, it is also within the scope of the present invention to use another control law as long as it is a control law that increases the channel capacity per transmission power.

FIG. 2 shows the relationship between noise power and signal power for each power control method. A solid line 300 is a conventional power control that stabilizes the quality by keeping the SN ratio of the receiving end constant, and uses the signal power proportional to the noise power to stabilize the quality for each band and time.
On the other hand, the broken line 301 shows the relationship between the noise power and the signal power when the water injection theorem is applied. In contrast to the conventional control method, the signal power increases as the noise power decreases, and the noise power cannot exceed a certain value. For example, by setting the signal power to 0, the channel capacity per signal power is increased.
Also, as in the case of the dashed-dotted line 302, when the noise power is above a certain level, control is performed in the same manner as when the water injection theorem is applied. As a result, it is possible to obtain the effect of increasing the channel capacity while preventing extreme concentration of signal power.
In addition, when the noise power is a certain level or more, as in the two-dot chain line 303, the same effect of increasing the channel capacity can be obtained by combining with a control law that sets the signal power to zero.

When performing wireless communication, it is common to perform encoding using a channel code.
By encoding data of a certain length using a channel code having sufficient correction capability and performing interleaving, the characteristic after reception signal decoding is not reception quality for each symbol in the codeword, for example, SN ratio, Received information amount of the entire codeword represented by Equation 1

Ruled by. Here, k is a proportional constant, SNR (i) represents the reception S / N ratio of symbol i in the code word, and I _m is a value proportional to the sum of the channel capacity obtained from the S / N ratio of all symbols in the code word. . For this reason, when using a channel code, it is desirable not to stabilize the reception quality for each symbol in the code word but to control the amount of communicable information, that is, the channel capacity.

On the other hand, since the error correction capability of the channel code does not work between codewords, it is desirable to control so that the quality is stabilized for each codeword.

  FIG. 12 shows an example of how a codeword generated by encoding with a channel code is divided into a plurality of subcarriers in order to use this property. Transmission data 501 is encoded by a channel code and converted into codeword 502. Codeword 502 is divided by serial-parallel conversion so as to correspond to a plurality of subcarriers as in 503. By using, for example, an inverse FFT on the divided signal, it is possible to perform communication by OFDM (Orthogonal Frequency Division Multiplexing) modulation in which each subcarrier has an orthogonal frequency.

  FIG. 3 shows an example of power distribution for achieving both an increase in channel capacity within a codeword and quality stabilization for each codeword. The data encoded by the channel code is divided and communicated in different bands, and the power distribution between the bands is increased at each time so as to increase the channel capacity, and the total signal transmission power at each time is compared to the noise power. Allocate with positive correlation. For example, a reference power that is the sum of noise power and signal transmission power is determined for each codeword.

  However, it is not necessary to control the sum of the signal power at each time, for example, if the code length of the channel code is sufficiently small with respect to the speed of fluctuation of the propagation channel, the same code word is communicated. The power distribution does not need to be changed while the communication is in progress. The same effect can be obtained even if communication is continued with distribution. This is because if the received information amount of the entire codeword is equal to or greater than a predetermined value, it can be received correctly.

  It is also possible to stabilize the quality of each codeword by changing the error correction capability of the code.

  The error correction capability of the code is generally determined by the signal data rate (encoding rate) before encoding per 1 bit of the encoded signal. The higher the data rate (encoding rate), the lower the correction capability and the data rate. The lower the (coding rate), the higher the correction capability.

  Using this property, if the quality is poor based on the measured channel quality, the data rate is controlled to be low, and if the quality is good, the data rate is controlled to be high. For example, if the decoding fails due to feedback, a data rate reduction, that is, an increase in code length (decrease in coding rate) is requested, so that an optimum data rate is selected according to the quality of the propagation path and the data rate is increased. Although there are fluctuations, stable communication can be performed.

  For this reason, as shown in FIG. 1, the signal power is always set for the purpose of increasing the channel capacity regardless of the bandwidth and time, so that the data rate varies depending on the time but the communication is performed stably. Throughput can be improved.

  Hereinafter, the control system of the present invention, the configuration of a radio station, and the operation of each unit will be described with reference to the drawings. In the following description, a station that transmits a data signal by applying the present invention is referred to as a transmitting station, and a station that receives the data signal is referred to as a receiving station, and is used for data signal communication from the transmitting station to the receiving station. A configuration when the invention is applied will be described. However, the present invention may be applied to communication of data signals in both directions from the transmitting station to the receiving station and from the receiving station to the transmitting station.

  In order to perform the above power control, a propagation path gain or noise power is measured to determine equivalent noise, and control based on the determination result is performed. The control method includes a method in which the transmission station controls the transmission power of the transmission station by measuring the equivalent noise of the propagation path from the reception station to the transmission station, and a propagation path from the transmission station to the reception station. There is a method in which the equivalent noise is measured, the measurement result is notified to the transmitting station, and the transmitting station controls the transmission power based on the notified measurement result.

The measurement of equivalent noise used in this control is performed by transmitting a signal whose transmission power is fixed or known to the station measuring the equivalent noise, and the station measuring the reception power and the fixed or known transmission power. And can be measured by estimating the channel gain. When the station measuring the equivalent noise does not know the transmission power, the transmission power is notified at the same time, and the measured transmission power is compared with the transmission power notified by the measuring station. Equivalent noise can be measured by estimating the channel gain. Furthermore, since this control can be performed using the relative magnitude relationship without using the absolute value of the equivalent noise, a signal whose transmission power ratio between signals is fixed with respect to the measuring station. Can be used for control by measuring the relative magnitude relationship of the channel gain from the ratio of the received power between the signals at the station that measures the channel gain. In the present invention, since the data transmission power is controlled for each frequency band or for each time, the propagation path condition is also determined for each frequency band or according to the transmission timing.

  In the following, a signal used for the purpose of the equivalent noise measurement is referred to as a pilot signal. However, as long as the transmission power or the ratio of transmission power between signals can be estimated, the data signal itself and other control signals are used. Can be treated as a pilot signal. This pilot signal may be transmitted for each frequency band, or may be commonly used in a plurality of frequency bands.

  Hereinafter, the control flow of the present invention and the case where the transmitting station measures the equivalent noise from the received signal and controls the transmitted signal will be described as the first embodiment with reference to the drawings.

  FIG. 4 is an example of a processing flow for power setting in the transmitting station and the receiving station in the first embodiment. In process P111, the data receiving station first transmits a signal including a pilot signal for channel quality estimation. The signal including the pilot signal is received and demodulated by processing P101 of the data transmission station. Based on the signal received in process P101, the data transmission station measures the reception quality in process P102, and determines the transmission power of the signal to be transmitted by one of the power setting methods described above based on the measurement result. . In process P103, the data signal is transmitted with the transmission power according to the determination in process P102.

  Here, each process performed in the transmitting station and the receiving station does not have to be a process in which the start and end are completed in order as shown in the flowchart of FIG. 4. A series of processing may be realized.

As an example, the flow of processing at the transmitting station when processing is performed continuously will be described with reference to the sequence diagram of FIG. In the processing at the transmitting station in FIG. 5, the signal transmission processing S101 is continuously performed while a signal is transmitted from the transmitting station to the receiving station, and the received signal demodulation processing S103 is continuously performed while the signal is transmitted from the receiving station to the transmitting station. Continue processing. In the reception signal demodulation process, when a pilot signal sufficient for determining the propagation path quality is received, a reception pilot notification message S110 notifying that the pilot signal has been received is notified to the propagation path quality determination process P102. The propagation path quality judgment process starts upon receiving the reception pilot notification message, and when the propagation path quality is judged, a transmission power setting message S111 for notifying the transmission power used for signal transmission is notified to the signal transmission process. To finish the process. The signal transmission processing can be performed with power corresponding to the pilot signal received during the continuous transmission processing by controlling the power of the signal to be transmitted upon receiving the transmission power setting message.

  FIG. 6 shows a configuration example of the transmitting station and FIG. 7 shows a configuration example of the receiving station in the embodiment of the radio station for realizing the control of the first embodiment according to the present invention.

In the transmitting station of FIG. 6, transmission data is subjected to channel coding and interleaving processing in encoding section 211 and interleaving section 212, and an encoded transmission data signal is created.
The encoded transmission data signal is partially or entirely selected by the coding rate control unit 217 and input to the transmission signal generating unit 210. At this time, the better the channel quality notified from the channel quality determining unit 230, the smaller the ratio can be selected and the coding rate can be increased. In addition, if the decoding quality notified from the received signal demodulator is a decoding failure, select another or the same part of the signal encoded based on the same transmission data as the signal that has failed to be decoded, If the decoding quality is successful, a part or the whole of the encoded signal is selected based on transmission data different from the signal that has been successfully decoded.

  In signal transmitting section 210, the coded word transmission data signal is given transmission power for each band or time output from propagation path quality determining section 230 in data power setting section 215, and pilot signal is multiplexed in multiplexing / modulating section 214. Are multiplexed and modulated to create a baseband transmission signal.

  FIG. 11 shows an example of processing in the multiplexing / modulation unit 214. The coded word transmission data signal and the pilot signal to which transmission power is given by the data power setting unit are multiplexed by multiplexing unit 401, are parallelized, and are output to subcarrier modulation unit 402 for each subcarrier. In subcarrier modulation section 402, the transmission signal for each subcarrier is modulated by, for example, QPSK (Quadri-Phase Shift Keying) or QAM (Quadrature Amplitude Modulation). The signals modulated for each subcarrier are collected in the multicarrier modulation section 403, and the multicarrier modulation section 403 performs frequency-time conversion processing such as inverse FFT, inverse DFT, and inverse DCT.

  The baseband transmission signal created by the transmission signal creation unit 210 is given an average power that can be received by the receiving station in the transmission power setting unit 213, converted into a radio frequency signal by the radio unit 200, and transmitted from the antenna. The

  A signal received by the transmitting station in FIG. 6 is converted into a baseband signal by the radio unit 200. Among the baseband received signals, the data signal is demodulated in the received signal demodulator 220, and a received data signal is created as a result of the demodulating process. The received data signal is deinterleaved by the deinterleaver 222 and the channel code is decoded by the decoder 221 to generate received data.

  Further, from the baseband received signal, the propagation path estimation unit 223 measures the propagation path gain or noise power for each frequency band, and notifies the propagation path quality judgment unit 230 of the propagation path quality. The propagation path quality determination unit 230 determines the signal power for each band based on the signal power setting method based on the notified propagation path quality, and notifies the data power setting unit 215 of the power set for each band. By doing so, the transmission power is controlled based on the propagation path quality.

  Of the baseband received signal, the decoding quality signal demodulated by the received signal demodulator 220 is notified to the coding rate controller 217.

  On the other hand, in the receiving station of FIG. 7, the decoding quality having pilot signal and transmission data encoded by the encoding unit 211, interleaved by the interleaving unit 212, and decoding success / failure information generated by the decoding quality generation unit 218 The signal is multiplexed and modulated by distributing the signal to each band in the signal transmission unit 210 and transmitted via the radio unit 200 with the power set in the transmission power setting unit.

The radio signal received from the antenna in the receiving station in FIG. 7 is converted into a baseband received signal in the radio unit 200. Among the baseband received signals, the data signal is demodulated in the received signal demodulator 220, and a received data signal is created as a result of the demodulating process. The received data signal is deinterleaved by the deinterleaver 222 and the channel code is decoded by the decoder 221 to generate received data.
At this time, each part of the codeword created from the same transmission data is accumulated in the transmitting station, and decoding is tried as needed.For example, CRC (cyclic redundancy check) or the like is used to determine whether decoding is successful or unsuccessful. The quality determination unit 218 is notified.

  Next, in the case where the receiving station controls the transmission signal of the transmitting station by measuring the propagation path gain from the received signal and notifying the transmitting station of the measurement result, the processing flow and configuration as Example 2 are as follows. This will be described with reference to the drawings.

FIG. 8 shows an example of the processing flow at the transmitting station and the receiving station in the second embodiment.
In step P201, the transmitting station first receives a signal including a pilot signal for propagation path quality estimation. The receiving station receives a signal including the pilot signal in the received signal demodulation process P211, creates a quality information signal based on the pilot signal in the propagation path quality determination process P212, and a signal including the quality information in the signal transmission process P213. Send. Based on the quality information received in the received signal demodulation process P202, the transmitting station determines the quality of the propagation path in the quality information determination process P203, and sets the signal power based on the signal power setting method described above based on the determination result. Data is transmitted in P204.

  Further, the quality information transmitted in the signal transmission process P213 can be transmitted as a relative relationship such as magnitude or phase difference of power with the pilot signal. In this case, the quality information and the pilot are transmitted in the signal transmission process P213. The transmitting station transmits a signal including the signal, and the transmitting station receives the quality information and the pilot signal in the received signal demodulation process P202. In the quality information determination process P203, the quality of the propagation path is determined from the relative relationship between the quality information and the pilot signal. It is possible.

  Here, each process performed in the transmitting station and the receiving station does not need to be a process in which the start and end are completed in order as in the flowchart of FIG. 8, and the processes that operate continuously communicate messages. A series of processing may be realized.

FIG. 9 shows a configuration example of the transmitting station and FIG. 10 shows a configuration example of the receiving station in the embodiment of the radio station for realizing the control of the second embodiment according to the present invention.
Since the processing for the data signal and the decoded quality signal is the same as in the case of the first embodiment, only the processing for the pilot signal and the quality information signal different from the first embodiment will be described below.

In the transmitting station of FIG. 9, transmission data is subjected to channel coding and interleaving processing in encoding section 211 and interleaving section 212, and an encoded transmission data signal is created.
The encoded transmission data signal is partially or entirely selected by the coding rate control unit 217 and input to the transmission signal generating unit 210. At this time, as the channel quality notified from the quality information determination unit 231 is better, a smaller ratio can be selected to increase the coding rate. In addition, if the decoding quality notified from the received signal demodulator is a decoding failure, select another or the same part of the signal encoded based on the same transmission data as the signal that has failed to be decoded, If the decoding quality is successful, a part or the whole of the encoded signal is selected based on transmission data different from the signal that has been successfully decoded.

  In the signal transmission unit 210, the coded word transmission data signal is given the transmission power for each band or time output from the quality information determination unit 231 in the data power setting unit 215, and in the multiplexing / modulation unit 214, Multiplexed and modulated to create a baseband transmission signal.

  The baseband transmission signal created by the transmission signal creation unit 210 is given an average power that can be received by the receiving station in the transmission power setting unit 213, converted into a radio frequency signal by the radio unit 200, and transmitted from the antenna. The

  A signal received by the transmitting station in FIG. 9 is converted into a baseband signal by the radio unit 200. Among the baseband received signals, the data signal is demodulated in the received signal demodulator 220, and a received data signal is created as a result of the demodulating process. The received data signal is deinterleaved by the deinterleaver 222 and the channel code is decoded by the decoder 221 to generate received data.

  Further, the quality information determination unit 231 is notified of the channel gain or noise power of each frequency band measured by the channel estimation unit 223 and the quality information extracted by the quality information extraction unit 227 from the baseband received signal. The quality information determination unit 231 determines the signal power for each band based on the notified channel quality and quality information based on the signal power setting method, and sends the power set for each band to the transmission determination unit 215. By notifying, the transmission power is controlled based on the propagation path quality.

  Further, the propagation path gain or noise power is measured from the received baseband signal by the propagation path estimation unit 223, and is notified to the quality information determination unit 231 as the propagation path quality. The quality information determination unit 231 determines signal power for each band based on the signal power setting method based on the notified propagation path quality, and notifies the transmission determination unit 215 of the power set for each band. The transmission power is controlled based on the propagation path quality.

  The transmission power control based on the propagation path quality is performed by notifying the transmission determination unit 215 of the propagation path quality determination result.

  Of the baseband received signal, the decoding quality signal demodulated by the received signal demodulator 220 is notified to the coding rate controller 217.

  On the other hand, in the receiving station of FIG. 10, the decoding quality having the pilot signal and transmission data encoded by the encoding unit 211, interleaved by the interleaving unit 212, and decoding success / failure information generated by the decoding quality generation unit 218 The quality information signal generated by the quality information generation unit 216 is multiplexed and modulated by the signal transmission unit 210 and is determined based on the received signal and the received pilot signal, and the radio unit has the power set in the transmission power setting unit. Sent over 200.

The radio signal received from the antenna in the receiving station in FIG. 10 is converted into a baseband received signal in the radio unit 200. Among the baseband received signals, the data signal is demodulated in the received signal demodulator 220, and a received data signal is created as a result of the demodulating process. The received data signal is deinterleaved by the deinterleaver 222 and the channel code is decoded by the decoder 221 to generate received data.
At this time, each part of the codeword created from the same transmission data is accumulated in the transmitting station, and decoding is tried as needed.For example, CRC (cyclic redundancy check) or the like is used to determine whether decoding is successful or unsuccessful. The quality determination unit 218 is notified.

  Also, the channel quality measurement unit 232 is notified of the channel gain or noise power measured by the channel estimation unit 223 and the quality information extracted by the quality information extraction unit 227 from the baseband received signal. The channel quality measuring unit 232 creates information for notifying the transmitting station of the channel quality measured based on the notified channel quality, and notifies the quality information creating unit 216 of the channel quality measurement result. To do.

  In the first embodiment and the second embodiment, it is desirable to use a channel code having a high error correction capability for the code encoded in the encoding unit 211 and decoded in the decoding unit 221. For example, by applying the Viterbi Algorithm It is possible to use a convolutional code that can be decoded, a Turbo code that can improve error correction capability by repetitive decoding, and the like.

The example of distribution of the transmission signal power of this invention. The example of the relationship between noise power and transmission signal power. The example of distribution of the transmission signal power of this invention. 2 is an example of a processing flow of a transmitting station and a receiving station in the first embodiment. 4 is an example of a transmission station processing sequence in the first embodiment. 2 is a configuration example of a transmission station in the first embodiment. 2 is a configuration example of a receiving station in the first embodiment. 10 is an example of a processing flow of a transmitting station and a receiving station in the second embodiment. 6 is a configuration example of a transmission station in the second embodiment. 6 is a configuration example of a receiving station in the second embodiment. 4 is a configuration example of a multiplexing / modulation unit of a transmission station in the first embodiment. The conceptual diagram of communication using a subcarrier.

Explanation of symbols

100 Transmit signal power
101 Noise power
200 Radio section
210 Signal transmitter
211 Encoder
212 Interleave section
213 Transmission power setting section
214 Multiplexer / Modulator
215 Data power setting section
216 Quality Information Creation Department
217 coding rate control unit
218 Decoding quality generator
220 Received signal demodulator
221 Decryption unit
222 Deinterleaving section
223 Propagation path estimation unit
224 Detector / Demodulator
225 Pilot extractor
226 Data extraction unit
227 Quality information extraction unit
228 Decoding quality extraction unit
229 Detector / Demodulator
230 Channel quality judgment unit
231 Quality information judgment unit
300 Relationship between noise power and signal power in conventional transmission power control
301 Example 1 of relationship between noise power and signal power in transmission power control of the present invention
302 Example 2 of relationship between noise power and signal power in transmission power control of the present invention
303 Example 3 of relationship between noise power and signal power in transmission power control of the present invention
401 Multiplexer
402 Subcarrier modulation section
403 Multi-carrier modulator
501 Transmission data string
502 Encoded data (codeword) string
Code word string after dividing into 503 subcarriers
504 1 symbol of signal divided into subcarriers
P101, P201 Received signal demodulation (pilot) processing
P102, P212 Channel quality judgment (pilot) processing
P103, P204 Signal transmission (data) processing
P111, P211 Signal transmission (pilot) processing
P112, P214 Received signal demodulation (data) processing
P213 Signal transmission (pilot / quality information) processing
P202 Received signal demodulation (pilot / quality information) processing
P203 Quality information judgment (pilot / quality information) processing.

Claims (20)

A wireless communication system that performs data transmission using a plurality of subcarriers in parallel from a transmitting station to a receiving station,
The transmitter station
A channel quality determining unit that determines a channel quality between the transmitting station and the receiving station for each of the plurality of subcarriers and for each timing based on at least one of a channel gain and noise power;
An encoding unit that encodes a data signal into a codeword;
A multiplexing unit that distributes so that at least one of the codewords is divided into a plurality of subcarriers;
A subcarrier modulation unit for performing subcarrier modulation for modulating each of the plurality of subcarriers and outputting a plurality of symbols;
A multicarrier modulation unit that generates a transmission signal by combining the plurality of subcarrier modulated symbols by frequency time conversion;
The transmission power for each of the plurality of subcarriers is transmitted according to the output of the propagation path quality determining unit, and the determined subcarrier having a high first propagation path quality for the plurality of symbols transmitted at the same timing. The plurality of symbols transmitted at different timings such that the transmission power of the symbol corresponding to the carrier is higher than the transmission power of the symbol corresponding to the subcarrier having the low second propagation path quality of the determined subcarrier. First control is performed so that the transmission power of a symbol corresponding to a timing with a low propagation path quality at each determined timing is greater than the transmission power of a symbol corresponding to a timing with a high propagation path quality. A data power setting unit for setting based on the law,
The receiving station is
A demodulator that demodulates the signal received from the transmitting station;
A wireless communication system, comprising: a decoding unit that decodes the demodulated received signal. The wireless communication system according to claim 1,
The wireless communication system, wherein the propagation path quality determination unit determines the propagation path quality based on reception power of a signal transmitted from the reception station to the transmission station. The wireless communication system according to claim 1,
The receiving station has a propagation path quality measurement unit,
The propagation path quality measurement unit measures the propagation path quality based on an output of the demodulation unit that demodulates a signal transmitted from the transmission station to the reception station,
The receiving station notifies the measurement result to the transmitting station,
The wireless communication system, wherein the propagation path quality determination unit determines the propagation path quality based on the measurement result. The wireless communication system according to claim 1,
A wireless communication system, wherein a code rate of the codeword is changed according to the propagation path quality. The wireless communication system according to claim 1,
The propagation path quality determination unit determines a reference power based on noise power for a signal transmitted on a plurality of subcarriers between the transmitting station and the receiving station, and the noise in each subcarrier is determined from the reference power. A wireless communication system, wherein a value obtained by subtracting power is output as signal transmission power, and the reference power is determined by a second control law having the same value in each codeword. The wireless communication system according to claim 5, wherein
The reference power is a reference corresponding to the first codeword in the first codeword transmitted at the timing when the total sum of noise power is large and the second codeword transmitted at the timing when the total sum of noise power is small. A wireless communication system, wherein power is set to a larger value. The wireless communication system according to claim 5, wherein
The wireless communication system, wherein the reference power is a value common to a plurality of consecutive code words. A data transmission control method by a transmitting station in a wireless communication system that performs data transmission using a plurality of subcarriers in parallel from a transmitting station to a receiving station,
Determining a channel quality between the transmitting station and the receiving station for each of the plurality of subcarriers and each timing based on at least one of a channel gain and noise power;
The transmitting station generates a code word by encoding a data signal to be transmitted to the receiving station,
Distributing at least one of the codewords so as to be divided into a plurality of subcarriers;
Modulating for each of the plurality of subcarriers to generate a plurality of symbols,
A plurality of symbols are combined by frequency time conversion to generate a transmission signal,
The transmission power for each of the plurality of subcarriers according to the determined channel quality,
For the plurality of symbols transmitted at the same timing, the transmission power of the symbol corresponding to the subcarrier having the high first propagation path quality of the determined subcarrier is the second propagation path of the determined subcarrier. The transmission power of a symbol corresponding to a subcarrier with low quality is set to be larger than the transmission power of the symbol corresponding to the timing with low propagation path quality for each of the determined timings. The transmission power is set based on a first control law that causes transmission power to be larger than the transmission power of a symbol corresponding to a timing with high propagation path quality, and the transmission signal is transmitted to the receiving station. Data transmission control method. A data transmission control method according to claim 8, wherein
The data transmission control method, wherein the propagation path quality is determined based on reception power of a signal transmitted from the receiving station to the transmitting station. A data transmission control method according to claim 8, wherein
The data transmission control method, wherein the propagation path quality is measured at the receiving station and notified to the transmitting station. A data transmission control method according to claim 8, wherein
The data transmission control method, wherein the propagation path quality is determined using a reception-to-noise ratio power of a signal transmitted between the transmitting station and the receiving station. A data transmission control method according to claim 8, wherein
The transmission power is a value obtained by subtracting the noise power in each subcarrier from the reference power determined based on noise power for a signal transmitted on a plurality of subcarriers between the transmission station and the reception station. Yes,
The data transmission control method, wherein the reference power is determined by a second control law having the same value in each codeword. A data transmission control method according to claim 12, comprising:
The reference power is a reference corresponding to the first codeword in the first codeword transmitted at the timing when the total sum of noise power is large and the second codeword transmitted at the timing when the total sum of noise power is small. A data transmission control method, wherein power is set to a larger value. A data transmission control method according to claim 12, comprising:
The data transmission control method, wherein the reference power is a value updated for each of a plurality of codewords. A data transmission control method according to claim 8, wherein
The data transmission control method, wherein when the propagation path quality is higher than a predetermined reference, the transmission power is set lower than the transmission power when the propagation path quality is a predetermined reference. A data transmission control method according to claim 8, wherein
A data transmission control method, wherein a code rate of the codeword is controlled in accordance with the propagation path quality. A transmitting station that transmits data to a receiving station using a plurality of subcarriers in parallel,
A channel quality determining unit that determines a channel quality between the transmitting station and the receiving station for each of the plurality of subcarriers and for each timing based on at least one of a channel gain and noise power;
An encoding unit that encodes a data signal into a codeword;
A multiplexing unit for distributing the codeword to a plurality of subcarriers;
A subcarrier modulation unit for performing subcarrier modulation for modulating each of the plurality of subcarriers and outputting a plurality of symbols;
A multicarrier modulation unit for generating a transmission signal by frequency-time converting the plurality of subcarrier modulated symbols;
A data power setting unit that sets transmission power for each of the plurality of subcarriers according to the output of the propagation path quality determination unit;
The multiplexing unit distributes so that one codeword is divided into a plurality of subcarriers,
For the plurality of symbols transmitted at the same timing, the transmission power is determined so that the transmission power of the symbol corresponding to the subcarrier having the first propagation path quality of the determined subcarrier is higher than that of the determined subcarrier. Timing with low propagation path quality for each of the determined timings for the plurality of symbols transmitted at different timings so as to be larger than the transmission power of symbols corresponding to subcarriers with low second propagation path quality. A transmission station characterized in that the transmission power of a symbol corresponding to is determined by a first control law that makes the transmission power of a symbol corresponding to a timing with high propagation path quality higher . The transmitting station according to claim 17, wherein
The transmission channel quality determining unit determines the channel quality based on received power of a signal transmitted from the receiving station to the transmitting station. The transmitting station according to claim 18, wherein
The transmission station characterized in that the propagation path quality determination unit determines the propagation path quality based on reception quality information at the reception station notified from the reception station. The transmitting station according to claim 17, wherein
The propagation path quality determination unit determines a reference power based on noise power for a signal transmitted on a plurality of subcarriers between the transmitting station and the receiving station, and the noise in each subcarrier is determined from the reference power. Output the value minus power as signal transmission power,
The transmitting station, wherein the reference power is determined by a second control law having the same value in each codeword.

Images