JP5163507B2 - Receiver, communication system and communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiver, a communication system and a communicating method which can improve the quality of radio communication. <P>SOLUTION: A delay profile of a signal to be received in the symbol immediately prior to is predicted, on the basis of a delay profile of signals received in a plurality of the preceding symbols; and when the signal is received, the predicted delay profile is used to compensate the received signal, and in addition, a delay profile of a signal to be received in the next symbol is predicted. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a receiver, a communication system, and a communication method.

  In recent years, mobile stations such as mobile terminals are rapidly spreading, and mobile communication systems are widely used. In such a mobile communication system, fading, which is a phenomenon in which the amplitude and phase of a signal fluctuate as the mobile station moves. Fading is a problem in a mobile communication system because it causes a problem in wireless communication.

  Therefore, in recent mobile communication systems, a technique for estimating characteristics of a propagation path (also referred to as a path) through which a signal propagates is used for the purpose of suppressing the influence of fading (see, for example, Patent Document 1). . The “propagation path characteristics” referred to here are distortions received by signals propagated through the propagation path, such as amplitude characteristics and phase characteristics.

  Specifically, a transmitter such as a base station transmits a known signal (also called a pilot signal) before data transmission. A receiver such as a mobile station holds known data, which is the same signal as the known signal, and estimates the propagation path characteristics of the received signal based on the known signal and the known data when the known signal is received. To do. Thereafter, when receiving the data signal, the receiver compensates the received data signal by using the propagation path estimation value that is the estimation result.

International Publication No. 01/048959 Pamphlet

  However, the conventional propagation path estimation method described above may not be able to sufficiently suppress the influence of fading. Specifically, as described above, the conventional receiver estimates the propagation path estimation value when a known signal is received. However, when the receiver is moving, the characteristics of the propagation path will fluctuate. Therefore, even if the receiver compensates the data signal using the estimated propagation path value, the effect of fading is sufficient. It was not always possible to suppress it. This has caused a problem that the quality of wireless communication is deteriorated.

  In particular, in a fast fading environment in which the receiver moves at high speed, the propagation path characteristics fluctuate drastically. Therefore, the conventional propagation path estimation method may cause a significant deterioration in the quality of wireless communication.

  Accordingly, it is an object to provide a receiver, a communication system, and a communication method that can improve the quality of wireless communication.

  In the first proposal, when a signal propagating through a propagation path is received, a compensation unit that compensates the received signal using a delay profile in the propagation path, a signal compensated by the compensation unit, and the received signal And a prediction unit for calculating a delay profile based on the calculation unit, and a prediction for predicting a delay profile for the compensation unit to compensate for a newly received signal based on a plurality of delay profiles calculated by the calculation unit. Part.

  In addition, what applied the component of the receiver disclosed by this application, expression, or arbitrary combinations of a component to a method, an apparatus, a system, a computer program, a recording medium, a data structure, etc. is effective as another aspect. .

  According to the receiver disclosed in the present application, it is possible to improve the quality of wireless communication.

FIG. 1 is a diagram illustrating a configuration of a communication system including a receiver according to the first embodiment. FIG. 2 is a diagram illustrating an example of a frame configuration. FIG. 3 is a diagram for explaining an example of reception processing by the receiver. FIG. 4 is a diagram for explaining prediction processing by the prediction unit. FIG. 5 is a diagram illustrating a configuration example of the receiver according to the first embodiment. FIG. 6 is a flowchart illustrating a reception processing procedure by the receiver according to the first embodiment. FIG. 7 is a diagram illustrating the configuration of the receiver according to the second embodiment. FIG. 8 is a diagram for explaining selection processing by the selection unit. FIG. 9 is a diagram illustrating the configuration of the receiver according to the third embodiment. FIG. 10 is a diagram illustrating an example of a frame configuration. FIG. 11 is a diagram for explaining an example of reception processing by the receiver. FIG. 12 is a diagram illustrating an example of a frame configuration. FIG. 13 is a diagram illustrating an example in which the prediction process is performed using the least square method. FIG. 14 is a diagram illustrating an example in which a prediction process is performed by weighting a delay profile.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following embodiments, a communication system employing OFDM (Orthogonal Frequency Division Multiplexing) as a communication method will be described as an example, but the application target of the present invention is not limited to this. For example, the present invention can also be applied to a communication system that employs a communication scheme such as OFDMA (Orthogonal Frequency Division Multiplexing Access) or CDMA (Code Division Multiple Access) that compensates a received signal using a propagation path estimation value. .

[Configuration of communication system]
First, the configuration of a communication system including the receiver according to the first embodiment will be described. FIG. 1 is a diagram illustrating a configuration of a communication system including a receiver according to the first embodiment. Note that the communication system 1 shown in FIG. 1 adopts OFDM as an example of a communication method. As illustrated in FIG. 1, the communication system 1 includes a transmitter 10 and a receiver 100. Note that, in FIG. 1, illustrations of configurations that are not related to the receiver 100 according to the first embodiment are omitted.

  The transmitter 10 is a base station, for example, and includes a transmission unit 11. The transmission unit 11 transmits a signal to the receiver 100. Specifically, the transmission unit 11 transmits a signal according to a predetermined frame configuration in the wireless interface. FIG. 2 shows an example of the frame configuration. In the frame configuration shown in FIG. 2, the vertical axis indicates the frequency (subcarrier), and the horizontal axis indicates the OFDM symbol (time). In FIG. 2, a graphic indicated by a black circle indicates a known symbol (pilot symbol) to which a known signal is assigned, and a graphic indicated by a white circle indicates a data symbol to which a data signal is assigned.

  That is, when the frame configuration in the communication system 1 is the frame configuration shown in FIG. 2, the transmission unit 11 transmits a known signal in the first symbol and the second symbol, and transmits a data signal in symbols after the third symbol. To do.

  The signal transmitted from the transmitter 10 in this way is propagated through a plurality of propagation paths PT (0) to PT (τ) and received by the receiver 100 as in the example illustrated in FIG. Note that τ indicates the delay time of the signal in each propagation path PT. Specifically, in FIG. 1, signals propagating through the propagation paths are delayed in the order of the propagation paths PT (0), PT (1), PT (2),..., PT (τ). It is shown that.

  The receiver 100 is a mobile station such as a mobile terminal, for example, and receives known signals and data signals transmitted from the transmitter 10 via a plurality of propagation paths PT (0) to PT (τ). A signal received by the receiver 100 may be a signal whose amplitude or phase has changed compared to a signal transmitted from the transmitter 10 due to fading. For this reason, the receiver 100 may not be able to perform high-quality wireless communication with the transmitter 10.

  Therefore, the receiver 100 according to the first embodiment predicts a delay profile for compensating a newly received signal using a delay profile calculated in the past. Specifically, the receiver 100 includes a calculation unit 106, a prediction unit 108, and a compensation unit 110, and compensates a received signal while predicting a delay profile by processing by each processing unit. Hereinafter, processing by each processing unit included in the receiver 100 will be described in detail.

[Reception processing by the receiver 100]
A reception process performed by the receiver 100 will be described with reference to FIG. FIG. 3 is a diagram illustrating an example of reception processing by the receiver 100. The upper part of FIG. 3 shows a delay profile of a signal received via the propagation paths PT (0) to PT (3). The horizontal axis of the delay profile indicates time, the vertical axis indicates power (complex amplitude), and the horizontal axis and the vertical axis indicate the delay time of the received signal. Further, the lower part of FIG. 3 shows a reception processing procedure by the receiver 100. In the example illustrated in FIG. 3, the receiver 100 receives a signal transmitted according to the frame configuration illustrated in FIG. 2.

  As in the example illustrated in FIG. 3, it is assumed that the receiver 100 has received a known signal transmitted in the first symbol (step S11). In such a case, the calculation unit 106 of the receiver 100 estimates a propagation path estimated value based on the received known signal, and calculates a delay profile from the estimated propagation path estimated value (step S12). Specifically, the calculation unit 106 calculates a delay profile by performing IFFT (Inverse Fast Fourier Transform) processing on the estimated channel estimation value.

  Subsequently, it is assumed that the receiver 100 has received a known signal transmitted in the second symbol (step S13). In such a case, the calculation unit 106 estimates a propagation path estimated value based on the received known signal, and calculates a delay profile from the estimated propagation path estimated value (step S14).

  Subsequently, the prediction unit 108 of the receiver 100 predicts a delay profile for compensating a newly received signal based on the delay profile calculated in step S12 and the delay profile calculated in step S14. (Step S15). Specifically, the prediction unit 108 predicts a delay profile for compensating a signal transmitted in the third symbol based on the amount of change between the two delay profiles. Note that the prediction processing by the prediction unit 108 will be described later with reference to FIG.

  Subsequently, it is assumed that the receiver 100 has received the data signal transmitted in the third symbol (step S16). In such a case, the compensation unit 110 of the receiver 100 compensates the received data signal using the delay profile predicted in step S15 (step S17).

  Subsequently, the calculation unit 106 estimates a propagation path estimated value based on the data signal received in step S16 and the data signal compensated in step S17, and calculates a delay profile from the estimated propagation path estimated value. (Step S18).

  Subsequently, the prediction unit 108 predicts a delay profile for compensating the signal transmitted in the fourth symbol, based on the delay profile calculated in step S14 and the delay profile calculated in step S18 ( Step S19). Every time the receiver 100 receives a data signal thereafter, the receiver 100 repeatedly performs the processes in steps S17 to S19 described above.

  Note that FIG. 3 shows an example in which a delay profile for compensating a newly received signal is predicted based on two calculated delay profiles, but the prediction unit 108 has three or more delays. A delay profile may be predicted based on the profile. A process for predicting a delay profile based on three or more delay profiles will be described in a fifth embodiment.

  Next, the prediction process by the prediction unit 108 described above will be described. FIG. 4 is a diagram for explaining the prediction processing by the prediction unit 108. FIG. 4 shows a delay profile in the propagation path PT (0) shown in FIG. In FIG. 4, a graphic indicated by a white circle indicates the power value of the delay profile calculated by the calculation unit 106, and a graphic indicated by the black circle indicates the power value of the delay profile predicted by the prediction unit 108.

  In the example illustrated in FIG. 4, the prediction unit 108 uses the delay profiles E1 and E2 to predict a delay profile E12 for compensating for a signal received at time t3. For example, it is assumed that the power value of the delay profile E2 is 10% lower than the power value of the delay profile E1. In such a case, the prediction unit 108 predicts that the power value of the delay profile will decrease by 10% even at the next signal reception time. That is, the prediction unit 108 predicts a value that is 10% lower than the power value of the delay profile E2 as the power value of the delay profile E12.

  Similarly, in the example illustrated in FIG. 4, the prediction unit 108 uses the delay profiles E2 and E3 to predict the delay profile E23 for compensating the signal received at time t4. In this way, the prediction unit 108 predicts a delay profile for compensating the signal received at time tn + 1 using the delay profiles En-1 and En.

  As described above, the receiver 100 compensates a newly received signal based on a plurality of previously estimated propagation path values without compensating the received signal using the previously estimated propagation path estimation values. Predict the delay profile for Thereby, the receiver 100 can suppress the influence of fading even in an environment in which the receiver 100 moves and the characteristics of the propagation path fluctuate. As a result, the receiver 100 can improve the quality of wireless communication performed with the transmitter 10.

[Configuration of Receiver 100]
Next, the configuration of the receiver 100 will be described. FIG. 5 is a diagram illustrating a configuration example of the receiver 100 according to the first embodiment. As illustrated in FIG. 5, the receiver 100 includes an antenna 101, a known data storage unit 102, a compensation data storage unit 103, a switch 104, an FFT (Fast Fourier Transform) processing unit 105, a calculation unit 106, The delay profile buffer 107, the prediction unit 108, the FFT processing unit 109, the compensation unit 110, and the hard decision unit 111 are included. In FIG. 5, the illustration of the configuration not related to the receiver 100 according to the first embodiment is omitted.

  The antenna 101 receives a signal transmitted from the transmitter 10. The known data storage unit 102 stores known data that is data for correlating with a known signal. Then, the known data storage unit 102 outputs known data to the calculation unit 106 when a known signal is received by the antenna 101.

  The compensation data storage unit 103 receives the data signal compensated by the compensation unit 110 described later via the hard decision unit 111. Specifically, the compensation data storage unit 103 receives the compensation data subjected to the hard decision process by the hard decision unit 111 and outputs the received compensation data to the calculation unit 106.

  The switch 104 switches the processing unit connected to the estimation unit 106 a to either the known data storage unit 102 or the compensation data storage unit 103. Specifically, when a known signal is received by the antenna 101, the switch 104 switches the connection so that the estimation unit 106a and the known data storage unit 102 are connected. In addition, when a data signal is received by the antenna 101, the switch 104 switches the connection so that the estimation unit 106a and the compensation data storage unit 103 are connected.

  The FFT processing unit 105 performs an FFT process on the signal received by the antenna 101. Then, if the received signal is a known signal, the FFT processing unit 105 outputs the known signal after the FFT processing to the estimation unit 106a. On the other hand, when the received signal is a data signal, FFT processing section 105 outputs the signal after the FFT processing to estimation section 106a and compensation section 110.

  The calculation unit 106 calculates a delay profile based on the received signal, known data, compensation data, and the like. Specifically, the calculation unit 106 includes an estimation unit 106a and an IFFT processing unit 106b.

  The estimation unit 106a estimates a channel estimation value indicating the channel characteristics. Specifically, when the known signal is received by the antenna 101, the estimation unit 106a propagates based on the known signal input from the FFT processing unit 105 and the known data input from the known data storage unit 102. Estimate the road estimate. Further, when the data signal is received by the antenna 101, the estimation unit 106a is configured to estimate the propagation path based on the data signal input from the FFT processing unit 105 and the compensation data input from the compensation data storage unit 103. Is estimated.

  The IFFT processing unit 106b calculates a delay profile by performing IFFT processing on the channel estimation value estimated by the estimation unit 106a. Then, the IFFT processing unit 106 b stores the calculated delay profile in the delay profile buffer 107.

  The delay profile buffer 107 stores the delay profile input from the IFFT processing unit 106b. In the example shown in FIG. 5, the delay profile buffer 107 includes buffers 107a and 107b. When the delay profile is input from the IFFT processing unit 106b, the delay profile buffer 107 stores the input delay profile in the buffer 107a. At this time, if the delay profile is already stored in the buffer 107a, the delay profile buffer 107 stores the delay profile stored in the buffer 107a in the buffer 107b and then inputs the delay profile input from the IFFT processing unit 106b. Is stored in the buffer 107a.

  The prediction unit 108 predicts a delay profile for compensating a newly received signal based on the delay profile stored in the delay profile buffer 107. In the example illustrated in FIG. 5, the prediction unit 108 predicts a delay profile based on the amount of variation between the delay profile stored in the buffer 107 a and the delay profile stored in the buffer 107 b.

  The FFT processing unit 109 performs an FFT process on the delay profile predicted by the prediction unit 108. Then, the FFT processing unit 109 outputs the delay profile after the FFT processing to the compensation unit 110.

  The compensation unit 110 compensates the reception signal input from the FFT processing unit 105. Specifically, the compensation unit 110 compensates the reception signal by multiplying the reception complex signal input from the FFT processing unit 105 and the conjugate complex of the delay profile input from the FFT processing unit 109. Then, the compensation unit 110 outputs the compensated signal to the hard decision unit 111. Note that the signal compensated by the compensation unit 110 is demodulated into an original transmission signal by a demodulation unit (not shown).

  The hard decision unit 111 performs a hard decision process on the compensated signal input from the compensation unit 110 and outputs compensation data, which is data after the hard decision process, to the compensation data storage unit 103.

[Reception Processing Procedure by Receiver 100]
Next, a procedure of reception processing by the receiver 100 according to the first embodiment will be described. FIG. 6 is a flowchart illustrating a reception processing procedure performed by the receiver 100 according to the first embodiment. As shown in FIG. 6, when receiving a signal from the transmitter 10 (Yes at Step S101), the FFT processing unit 105 of the receiver 100 performs an FFT process on the received signal (Step S102).

  Subsequently, when the received signal is a known signal (Yes at Step S103), the FFT processing unit 105 outputs the known signal after the FFT processing to the estimation unit 106a. Subsequently, the estimation unit 106a estimates a propagation path estimation value based on the known signal input from the FFT processing unit 105 and the known data input from the known data storage unit 102 (step S104).

  Subsequently, the IFFT processing unit 106b calculates a delay profile by performing IFFT processing on the propagation path estimation value estimated by the estimation unit 106a (step S105). Then, the IFFT processing unit 106 b stores the calculated delay profile in the delay profile buffer 107.

  Subsequently, when two or more delay profiles are stored in the delay profile buffer 107 (Yes in Step S106), the prediction unit 108 predicts a delay profile for compensating a signal received in the next symbol (Step S106). S107).

  On the other hand, when the received signal is a data signal (No at Step S103), the compensation unit 110 compensates the received data signal using the delay profile predicted by the prediction unit 108 (Step S108).

  The hard decision unit 111 performs a hard decision process on the signal compensated by the compensation unit 110, and outputs compensation data after the hard decision process to the compensation data storage unit 103. Then, the compensation data storage unit 103 outputs the compensation data to the calculation unit 106.

  Subsequently, the estimation unit 106a estimates the propagation path estimation value based on the data signal input from the FFT processing unit 105 and the compensation data input from the compensation data storage unit 103 (step S109). Then, the IFFT processing unit 106b calculates a delay profile by performing IFFT processing on the propagation path estimation value estimated by the estimation unit 106a (step S110).

  Subsequently, when two or more delay profiles are stored in the delay profile buffer 107 (Yes in step S106), the prediction unit 108 predicts a delay profile for compensating a signal received in the next symbol ( Step S107).

[Effect of Example 1]
As described above, the communication system 1 according to the first embodiment compensates for a data signal while predicting a delay profile of a signal received in the next symbol based on a delay profile of a signal received in a plurality of immediately preceding symbols. To do. Thereby, the receiver 100 can suppress the influence of fading, and as a result, the quality of wireless communication can be improved.

  In the first embodiment, an example in which the delay profile calculated by the calculation unit 106 is stored in the delay profile buffer 107 is shown. Here, the receiver may select a delay profile used for the compensation process and store it in the delay profile buffer 107. This is because, generally, a receiver detects a signal reception timing by specifying a propagation path called an effective path based on a delay profile. In other words, the receiver treats the signal propagated through the effective path as an effective signal, and treats other signals as noise and removes them. That is, the receiver only needs to hold the delay profile of the signal propagated through the effective path, and does not need to hold the delay profile of the signal propagated through a propagation path other than the effective path. Therefore, in the second embodiment, an example of the receiver 200 that selects a delay profile and stores it in the delay profile buffer 107 will be described.

[Configuration of Receiver 200]
First, the configuration of the receiver 200 according to the second embodiment will be described. FIG. 7 is a diagram illustrating the configuration of the receiver 200 according to the second embodiment. In the following, parts having the same functions as the constituent parts shown in FIG. 5 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As illustrated in FIG. 7, the receiver 200 newly includes a selection unit 201 as compared with the receiver 100 illustrated in FIG. 5. The selection unit 201 selects a delay profile based on the delay profile calculated by the IFFT processing unit 106b. Specifically, the selection unit 201 sets a propagation path whose signal power is equal to or greater than a predetermined threshold as an effective path. Then, the selection unit 201 selects a delay profile of the signal propagating through the effective path.

  An example of selection processing by the selection unit 201 will be described with reference to FIG. FIG. 8 is a diagram for explaining selection processing by the selection unit 201. Note that the delay profile shown in FIG. 8 is calculated based on the known signal of the first symbol. In the example shown in FIG. 8, the peak value of the power appears at the delay times 0 to 5. A signal having a peak value at the delay time 0 corresponds to a signal propagated through the propagation path PT (0). Similarly, signals having peak values at delay times 1 to 5 correspond to signals propagated through the propagation paths PT (1) to PT (5), respectively.

  When the delay profile is in the state illustrated in FIG. 8, the selection unit 201 selects the propagation paths PT (0) to PT (3) whose signal power value is equal to or greater than the threshold value TH. Then, the selection unit 201 stores the delay profile of the selected propagation paths PT (0) to PT (3) in the delay profile buffer 107. This is because the receiver 200 removes signals propagated through propagation paths other than the propagation paths PT (0) to PT (3), and therefore does not have to hold a delay profile of such signals.

  Note that the selection unit 201 may calculate the threshold value TH based on the delay profile. For example, the selection unit 201 regards a signal received after a predetermined delay time tx as noise in the example illustrated in FIG. Then, the selection unit 201 may calculate the average power of the noise and set a value obtained by multiplying the calculated average power by a predetermined constant as the threshold value TH. In addition, for example, the selection unit 201 may calculate a noise variance value and set a value obtained by multiplying the calculated variance value by a predetermined constant as the threshold value TH.

  The selection unit 201 may perform the above-described selection processing when a known signal is received, may be performed for each predetermined symbol, or may be performed for all symbols.

[Effect of Example 2]
As described above, since the receiver 200 according to the second embodiment selects the delay profile and stores it in the delay profile buffer 107, the quality of the radio communication can be improved and the size of the delay profile buffer 107 can be improved. Can be reduced.

  In the second embodiment, an example in which a valid path is specified and a delay profile is selected has been described. Such a receiver may perform DFT (Discrete Fourier Transform) processing or IDFT (Inverse Discrete Fourier Transform) processing without performing FFT processing or IFFT processing. This is because the amount of computation of DFT and IDFT does not increase if the number of specified effective paths is small. In the third embodiment, an example of a receiver 300 that performs DFT processing and IDFT processing on a delay profile will be described.

[Configuration of Receiver 300]
First, the configuration of the receiver 300 according to the third embodiment will be described. FIG. 9 is a diagram illustrating the configuration of the receiver 300 according to the third embodiment. As illustrated in FIG. 9, the receiver 300 includes a calculation unit 306 instead of the calculation unit 106 and a DFT processing unit 309 instead of the FFT processing unit 109 as compared with the receiver 200 illustrated in FIG. 7. Have.

  The calculation unit 306 newly includes a switch 306a and an IDFT processing unit 306b as compared with the calculation unit 106 illustrated in FIG. The switch 306a switches the processing unit connected to the estimation unit 106a to either the IFFT processing unit 106b or the IDFT processing unit 306b. Specifically, when a known signal is received by the antenna 101, the switch 306a switches the connection so that the estimation unit 106a and the IFFT processing unit 106b are connected. This is because the effective path is often not specified at the time when the known signal is received, so the known signal is input to the IFFT processing unit 106b with a small amount of calculation.

  On the other hand, when the data signal is received by the antenna 101, the switch 104 switches the connection so that the estimation unit 106a and the IDFT processing unit 306b are connected. Note that the switch 104 may connect the estimation unit 106a and the IDFT processing unit 306b when the number of characterized effective paths is smaller than a predetermined threshold. Accordingly, when the amount of computation by the IDFT processing unit 306b increases because the number of valid paths is large, the amount of computation can be reduced by causing the IFFT processing unit 106b to perform IFFT processing.

  The IDFT processing unit 306b calculates a delay profile by performing IDFT processing on the channel estimation value estimated by the estimation unit 106a. Specifically, the IDFT processing unit 306b performs IFFT processing on the propagation path estimated value at a reception timing for receiving a signal propagating through the effective path.

  The DFT processing unit 309 performs DFT processing on the delay profile predicted by the prediction unit 108. Specifically, the DFT processing unit 309 performs DFT processing on the delay profile at a reception timing for receiving a signal propagating through the effective path.

[Effect of Example 3]
As described above, the receiver 300 according to the third embodiment is switched to perform the DFT process and the IDFT process according to the number of effective paths, so that the quality of the wireless communication can be improved and the circuit scale can be improved. Can be reduced.

  In the first to third embodiments, the case where the receivers 100, 200, and 300 receive signals transmitted according to the frame configuration illustrated in FIG. 2 has been described. However, the receivers 100, 200, and 300 can perform the above-described compensation processing even when receiving signals transmitted according to other frame configurations. In the fourth embodiment, an example of a receiver that receives a signal transmitted according to a frame configuration other than the frame configuration illustrated in FIG. 2 will be described. In the fourth embodiment, of the receivers 100, 200, and 300, the receiver 100 will be described as an example.

[Another example of frame configuration 1]
First, the case where the receiver 100 receives a signal transmitted according to the frame configuration shown in FIG. 10 will be described. FIG. 10 is a diagram illustrating an example of a frame configuration. In the example illustrated in FIG. 10, the transmitter 10 transmits a known signal in the first symbol and transmits a data signal in symbols after the second symbol.

  A reception process performed by the receiver 100 when a signal is transmitted according to the frame configuration illustrated in FIG. 10 will be described with reference to FIG. FIG. 11 is a diagram illustrating an example of reception processing by the receiver 100.

  As in the example illustrated in FIG. 3, it is assumed that the receiver 100 has received a known signal transmitted in the first symbol (step S21). In such a case, the calculation unit 106 of the receiver 100 estimates a propagation path estimation value based on the received known signal, and calculates a delay profile from the estimated propagation path estimation value (step S22).

  Subsequently, it is assumed that the receiver 100 has received the data signal transmitted in the second symbol (step S23). In such a case, the compensation unit 110 of the receiver 100 compensates the received data signal using the delay profile calculated in step S22 (step S24).

  Subsequently, the calculation unit 106 estimates a propagation path estimation value based on the data signal received in step S23 and the compensation data compensated in step S24, and calculates a delay profile from the estimated propagation path estimation value. (Step S25).

  Subsequently, the prediction unit 108 of the receiver 100 compensates for the signal transmitted in the third symbol based on the delay profile calculated in step S22 and the delay profile calculated in step S25. Is predicted (step S26).

  Subsequently, the receiver 100 receives the data signal transmitted in the third symbol (step S27). In such a case, the compensation unit 110 compensates the received data signal using the delay profile predicted in step S26 (step S28).

  Subsequently, based on the data signal received in step S27 and the data signal compensated in step S28, the calculation unit 106 estimates a propagation path estimated value and calculates a delay profile (step S29).

  Subsequently, the prediction unit 108 predicts a delay profile for compensating a signal transmitted in the fourth symbol based on the delay profile calculated in step S25 and the delay profile calculated in step S29 ( Step S30). Each time the receiver 100 receives a data signal thereafter, the receiver 100 repeatedly performs the processes in steps S28 to S30 described above.

  That is, when the compensation unit 110 of the receiver 100 according to the fourth embodiment receives the data signal of the second symbol, the compensation unit 110 compensates the received data signal using the delay profile calculated by the calculation unit 106. On the other hand, when receiving the data signal after the third symbol, the compensation unit 110 compensates the received data signal using the delay profile predicted by the prediction unit 108.

  As described above, the receiver 100 can compensate for the data signal transmitted after the third symbol while predicting the delay profile even when the known signal is transmitted only in the first symbol.

[Another example 2 of frame configuration]
Next, the case where the receiver 100 receives a signal transmitted according to the frame configuration shown in FIG. 12 will be described. FIG. 12 is a diagram illustrating an example of a frame configuration. When a signal is transmitted according to the frame configuration shown in FIG. 12, the receiver 100 performs propagation by performing linear interpolation between the known signal transmitted in the first symbol and the known signal transmitted in the second symbol. A road estimation value is calculated.

  For example, in the example illustrated in FIG. 12, the estimation unit 106a of the receiver 100 calculates the propagation path estimation values in the symbols Sy12 to Sy14 by performing linear interpolation of the known signals received in the symbols Sy11 and Sy15. Also good.

  The IFFT processing unit 106b calculates a delay profile by performing IFFT processing on the channel estimation value calculated by linear interpolation. Subsequent prediction processing by the prediction unit 108, compensation processing by the compensation unit 110, calculation processing by the calculation unit 106, and the like are the same as the processing described in the first embodiment.

[Effect of Example 4]
As described above, the receivers 100, 200, and 300 can perform a delay profile prediction process, for example, even when communication is performed using the frame configuration illustrated in FIG. 10 or FIG. As a result, the quality of wireless communication can be improved. In particular, the frame configurations shown in FIGS. 10 and 12 are interfaces with many data symbols and few known symbols. Therefore, when communication is performed using the frame configuration shown in FIGS. 10 and 12, the receivers 100, 200, and 300 can transmit and receive a large amount of user data.

  In the first to fourth embodiments, an example has been described in which the prediction unit 108 predicts a delay profile for compensating a newly received signal using two delay profiles. However, the prediction unit 108 may perform the prediction process using three or more delay profiles. In the fifth embodiment, an example of a receiver that performs prediction processing using three or more propagation path estimation values will be described. In the fifth embodiment, the receiver 100 will be described as an example.

[Another example 1 of prediction processing]
For example, the prediction unit 108 may perform the prediction process from three or more delay profiles using the least square method. FIG. 13 shows an example in which prediction processing is performed using the least square method. In the example illustrated in FIG. 13, the prediction unit 108 predicts a delay profile for compensating a signal received at time tn + 1 from the delay profiles calculated at times t1, t2,. Specifically, the prediction unit 108 predicts a delay profile by approximating a polynomial by least square approximation from the delay profiles calculated at times t1, t2,..., Tn.

[Another example 2 of prediction processing]
For example, the prediction unit 108 may perform prediction processing by weighting a plurality of delay profiles. FIG. 14 shows an example in which the prediction process is performed by weighting the delay profile. In the example illustrated in FIG. 14, the prediction unit 108 multiplies the delay profiles calculated at times t11 to t14 by weights W11 to W14, respectively. Then, the prediction unit 108 predicts a value obtained by adding the multiplied values as a delay profile for compensating the signal received at time t15.

  Note that the value of the weight assigned to each delay profile may be increased as the delay profile of the signal received immediately before, for example. For example, the weight value may be decreased as the error between the predicted value of the delay profile and the actually received signal increases.

  Further, when performing the prediction process using three or more delay profiles, the receivers 100, 200, and 300 store three or more delay profiles in the delay profile buffer 107.

[Effect of Example 5]
Thus, the receivers 100, 200, and 300 can predict the delay profile with high accuracy when performing the prediction process using three or more delay profiles. Thereby, the receivers 100, 200, and 300 can further improve the quality of wireless communication.

  The following supplementary notes are further disclosed with respect to the embodiments including the above examples.

(Supplementary Note 1) When a signal propagating through a propagation path is received, a compensation unit that compensates the received signal using a delay profile in the propagation path;
A calculation unit that calculates a delay profile based on the signal compensated by the compensation unit and the received signal;
A receiver comprising: a prediction unit that predicts a delay profile for the compensation unit to compensate for a newly received reception signal based on a plurality of delay profiles calculated by the calculation unit.

(Supplementary Note 2) The calculation unit
Supplementary note 1 characterized in that a characteristic of the propagation path is estimated based on the signal compensated by the compensation unit and the received signal, and a delay profile is calculated using a propagation path estimation value that is an estimation result The listed receiver.

(Supplementary Note 3) The calculation unit
Supplementary note 1 or 2 characterized in that when a known signal that is a predetermined signal is received, a delay profile is calculated based on the known signal and known data held in advance by the receiver. The listed receiver.

(Supplementary Note 4) The prediction unit
4. The reception according to claim 1, wherein a delay profile is predicted using a plurality of delay profiles calculated based on a signal received immediately before the reception signal by the calculation unit. Machine.

(Additional remark 5) It further has the selection part which selects the delay profile of the propagation path whose signal power is more than a predetermined threshold based on the delay profile computed by the calculation part,
The receiver according to any one of appendices 1 to 4, wherein the prediction unit predicts a delay profile based on the delay profile selected by the selection unit.

(Supplementary Note 6) The prediction unit
The receiver according to any one of appendices 1 to 5, wherein a delay profile is predicted from the plurality of delay profiles by approximating a polynomial by least square approximation.

(Appendix 7) The prediction unit
Any one of appendices 1 to 6, wherein a weight is assigned to each of the plurality of delay profiles, a weight corresponding to each delay profile is multiplied, and a multiplication result is added to predict a delay profile. Receiver described in 1.

(Appendix 8) A communication system having a transmitter and a receiver,
The transmitter is
A transmission unit that transmits a signal in a symbol unit that is a predetermined time unit;
The receiver
When a signal transmitted by the transmission unit is received, a compensation unit that compensates the received signal using a delay profile in the propagation path;
A calculation unit that calculates a delay profile based on the signal compensated by the compensation unit and the received signal;
And a prediction unit that predicts a delay profile for the compensation unit to compensate for a newly received signal based on a plurality of delay profiles calculated by the calculation unit.

(Supplementary note 9) When performing communication with the receiver, the transmission unit transmits a known signal that is a predetermined signal in the first symbol, and data other than the known signal in the second and subsequent symbols. Send a signal,
When the calculation unit receives the known signal transmitted by the transmission unit, the calculation unit calculates a delay profile based on the known signal;
The compensation unit compensates the received data signal using the delay profile calculated based on the known signal by the calculation unit when the data signal transmitted in the second symbol by the transmission unit is received. The communication system according to appendix 8, wherein

(Appendix 10) A communication method using a transmitter and a receiver,
The transmitter is
A transmission step of transmitting a signal in a symbol unit which is a predetermined time unit,
The receiver
A compensation step of compensating a received signal using a delay profile in the propagation path when the signal transmitted in the transmission step is received;
A calculation step of calculating a delay profile based on the signal compensated in the compensation step and the received signal;
And a prediction step of predicting a delay profile for the compensation step to compensate for a newly received signal based on a plurality of delay profiles calculated by the calculation step.

(Additional remark 11) The said transmission step transmits the known signal which is a predetermined signal in the first symbol when communicating with the receiver, and data other than the known signal in the second and subsequent symbols. Send a signal,
The calculation step calculates a delay profile based on the known signal when the known signal transmitted by the transmission step is received;
The compensation step compensates the received data signal using the delay profile calculated based on the known signal in the calculation step when the data signal transmitted in the second symbol in the transmission step is received. The communication method according to supplementary note 10, characterized by:

DESCRIPTION OF SYMBOLS 1 Communication system 10 Transmitter 11 Transmitter 100, 200, 300 Receiver 101 Antenna 102 Known data storage unit 103 Compensation data storage unit 104 Switch 105 FFT processing unit 106 Calculation unit 106a Estimation unit 106b IFFT processing unit 107 Delay profile buffer 107a, 107b buffer 108 prediction unit 109 FFT processing unit 110 compensation unit 111 hard decision unit 201 selection unit 306 calculation unit 306a switch 306b IDFT processing unit 309 DFT processing unit

Claims (7)

When a signal propagating through a propagation path is received, a compensation unit that compensates the received signal using a delay profile in the propagation path;
A calculation unit that calculates a delay profile based on the signal compensated by the compensation unit and the received signal;
A receiver comprising: a prediction unit that predicts a delay profile for the compensation unit to compensate for a newly received reception signal based on a plurality of delay profiles calculated by the calculation unit. The calculation unit includes:
2. The characteristic of the propagation path is estimated based on the signal compensated by the compensation unit and the received signal, and a delay profile is calculated using a propagation path estimation value as an estimation result. As described in the receiver. The calculation unit includes:
3. A delay profile is calculated when a known signal that is a predetermined signal is received, based on the known signal and known data held in advance by the receiver. As described in the receiver. The prediction unit
The delay profile is predicted using a plurality of delay profiles calculated based on a signal received immediately before the reception signal by the calculation unit. Receiving machine. Based on the delay profile calculated by the calculation unit, further comprising a selection unit that selects a delay profile of a propagation path whose signal power is equal to or greater than a predetermined threshold,
The receiver according to claim 1, wherein the prediction unit predicts a delay profile based on the delay profile selected by the selection unit. A communication system having a transmitter and a receiver,
The transmitter is
A transmission unit that transmits a signal in a symbol unit that is a predetermined time unit;
The receiver
When a signal transmitted by the transmission unit is received, a compensation unit that compensates the received signal using a delay profile in a propagation path through which the signal has propagated ;
A calculation unit that calculates a delay profile based on the signal compensated by the compensation unit and the received signal;
And a prediction unit that predicts a delay profile for the compensation unit to compensate for a newly received signal based on a plurality of delay profiles calculated by the calculation unit. A communication method between a transmitter and a receiver,
The transmitter is
A transmission step of transmitting a signal in a symbol unit which is a predetermined time unit,
The receiver
When receiving a signal transmitted by the transmission step, a compensation step for compensating the received signal using a delay profile in a propagation path through which the signal has propagated ;
A calculation step of calculating a delay profile based on the signal compensated in the compensation step and the received signal;
And a prediction step of predicting a delay profile for the compensation step to compensate for a newly received signal based on a plurality of delay profiles calculated by the calculation step.

Images