JPH08172422A - Antenna diversity receiver - Google Patents

Abstract

PURPOSE: To improve communication quality by performing weighting for maximizing the signal-to-noise ratio of reception signals after eliminating unrequired signal components from the reception signals of respective branches. CONSTITUTION: The transmission signals of different propagation paths are received in antennas 10-12. The reception signals 13 of the antenna 10 are inputted to a transmission path impulse response estimation processing part 19, a transmission path impulse response 118 is calculated by a known code sequence on a receiver side and inputted to a distortion elimination means 112 and weighting and phase control means 115. In the means 112, the distortion component of the signals 13 is eliminated by the response 118 and code judged output 130, inputted to the means 115 as the signals 121, weighting and phase control is performed so as to maximize the signal-to-noise ratio of the reception signals and the signals 324 are inputted to an addition means 327. The series of processings are performed for the respective antennas. Then, the inputs 124-126 from the respective antennas 10-12 are simply added in the means 127, the output 128 is passed through a code judgement means 129, a code judged result 130 is outputted and an information sequence is demodulated in a signal sequence demodulation means 131.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna diversity receiver for the purpose of improving the reception characteristic in digital communication, and has a waveform equalization process for compensating the distortion of the received signal from the propagation environment and an improvement of the reception gain. It is intended to improve the communication quality especially in a propagation environment where the wireless communication quality to the mobile is poor.

[0002]

2. Description of the Related Art Recently, there has been an urgent need to construct a system for digital mobile phone service. Along with this, the development of digital mobile communication terminals, wireless communication base stations for communicating with the mobile communication terminals, and the like has been actively conducted. In land mobile communication, the reception characteristics are greatly affected by the complicated radio propagation environment generated by the physical environment surrounding the mobile communication terminal and the radio communication base station. For example, even if the distance between the mobile communication terminal and the wireless communication base station is short, the radio wave is subject to multipath propagation distortion due to multi-reflected radio wave propagation due to reflection from a building near the mobile communication terminal or the wireless communication base station. Will end up. Even if the received signal subjected to the multipath propagation distortion has sufficient power, the communication quality is greatly deteriorated due to the effect of the distortion.

Further, as the portable mobile communication terminal moves away from the wireless communication base station, the radio wave is attenuated and it becomes difficult to receive the radio wave, and the communication quality deteriorates. Since the radio propagation environment in land mobile communication is determined between the radio communication base station and the mobile mobile communication terminal, the reception characteristic from the radio communication base station to the mobile mobile communication terminal is the same as that of the mobile communication terminal. It becomes the reception characteristic to the base station (Tive Division Duplex method).
In these poor radio propagation environments, there are waveform equalization technology and diversity technology as means for improving communication quality. The former is an indispensable technology in large-zone wireless communication services such as cellular mobile communication systems, and mainly compensates for waveform distortion caused by multiple reflection radio wave transmission. In addition, some have been put into practical use due to the advent of high-speed digital signal processors and the optimization of signal processing techniques in recent years. On the other hand, the latter is frequently used in conventional analog type cellular mobile communication systems.

[0004] In mobile communication terminals for mobile communication, there is a strong demand for miniaturization and low power consumption while suppressing transmission power as much as possible to realize long-term standby and long-term communication. It is expected that a small zone system will be realized in recent years to meet such demands (Personal handyphone system). However, in the small zone system, the communicable range (zone radius) becomes extremely short as compared with the existing cellular mobile communication system, so that many wireless communication base stations cannot be provided unless they are arranged quite densely. Further, since the communication method is completely different from the existing cellular mobile communication system, a huge amount of infrastructure must be newly added. Therefore, until the small zone system infrastructure is fully developed, the mobile communication terminal specifications will continue to be compatible with the small zone system, and the transmission / reception performance of wireless communication base stations will be improved to reduce the number of wireless communication base stations. It is desirable to start the service at. This means that the zone that the wireless communication base station must cover expands, so the weaker radio waves transmitted from the mobile communication terminal can be handled by improving the reception sensitivity of the base station. When transmitting from the station, the transmission power is increased to make it easier for the mobile mobile communication terminal to receive. However, the expansion of the zone promotes the multi-reflected radio wave propagation distortion, and simply improves the reception gain at the radio communication base station,
It is not a problem that can be solved by increasing the transmission power.

An equalization diversity receiver in which an equalizer and diversity are combined is provided as a reception system that simultaneously realizes the compensation of the multi-reflected radio wave propagation distortion and the improvement of the reception sensitivity as described above to improve the reception characteristics. Several have been proposed. As one of them, a typical diversity technique disclosed in the paper “Interference cancellation characteristics of DFE type transversal combining diversity method in mobile radio-comparison with metric combining-” is introduced. In this paper, the diversity method shown in FIGS. 1 (a) (b) (c) on page 585 is disclosed in FIG. 7 to FIG. Hereinafter, the diversity receiver of FIGS. 7 to 9 will be described.

FIG. 7 shows a block diagram of a maximum ratio combining antenna diversity receiver. This diversity receiver
This is a combined diversity receiver in which the least square mean value of the error e (t) in FIG. 7 is used as an evaluation function, and the received signal of each branch is multiplied by a weighting coefficient to simply add all the branches. The addition result is determined by the sign determiner,
The coefficient is controlled so that the squared expected value of the difference e (t) between the input and the output of the code determiner is minimized. The maximum ratio combining antenna diversity receiver is a very effective tie diversity technology in that it maximizes the signal-to-noise ratio of the received signal.
For the received signal wave that has passed through the multiple reflection propagation path, only the signal-to-noise ratio of the signal wave component that can be received most strongly can be maximized, and other signal wave components will be treated as noise. There is a problem that the reception characteristics are not improved.

FIG. 8 shows a block diagram of a combining diversity receiver using a decision feedback equalizer. The received signal received by each branch is F of the transversal filter structure.
It is input to an FF (Feed Forward Filter), and the signal components spread by multiple reflection radio wave transmission are multiplied and collected.
Further, since the collected signal component also includes the delayed wave component, the delayed wave component is canceled by the FBF (Feed Back Filter), and the signal-to-noise ratio at the time of input to the code determination unit is improved. However, in this diversity receiver, the direct wave component is effectively collected by the FFF, but the delayed wave component is complicatedly controlled,
There is a problem that the component cannot be completely removed by FBF. Further, there is a problem that a code deciding device error that occurs at a certain time as a code deciding device causes error propagation that affects the subsequent code deciding, and thus branch synthesis fails.

FIG. 9 shows a block diagram of a combining diversity receiver using the maximum likelihood sequence estimator. In this diversity receiver, MLSE (Maximum Likelihood Sequence)
The transmission channel impulse correspondence is estimated by the code sequence candidates generated by the estimation, and the TVE (Transversal Filt
er) produces the estimated received signal. The MLSE process and the estimation of the transmission line impulse response are sequentially performed using the square value of the error obtained by subtracting the received signal estimated in each branch from the actual received signal received in each branch as an evaluation function. However, although this diversity receiver can greatly improve the reception performance, it has a problem that the MLSE processing amount becomes enormous and the device scale and power consumption become enormous.

FIG. 11 shows a block diagram of a post-delay-detection combining diversity receiver which can be easily realized. This diversity receiver is a method in which differential detection is performed on a received signal received by each antenna, the influence of the transmission path characteristic peculiar to each antenna is removed, and then simple combining is performed.
However, the differential detection processing on the received signal has a function of deteriorating the signal-to-noise ratio after the differential detection, which leads to deterioration of the reception characteristic. In addition, when the wireless transmission path is a multipath transmission path having delay dispersion, no processing is performed on the delayed wave, so that there is a problem that the delayed wave component becomes an interference signal component and the reception characteristics are greatly deteriorated. .

FIG. 12 shows a block diagram of a combined diversity receiver which controls the phase of a received signal received by each antenna by a transmission path impulse response estimated by the correlation method. Although this diversity receiver does not suffer from the deterioration of the signal-to-noise ratio unlike the post-delay detection combined diversity receiver of FIG. 11, in the case of a multipath transmission line having delay dispersion in the wireless transmission line, processing for the delayed wave is performed. Since it is not performed at all, the delayed wave component becomes an interference component, which causes a problem that the reception characteristics are significantly deteriorated.

As described above, the technique for shaping the waveform of the received signal and the diversity technique for improving the receiving sensitivity have been devised, but from various problems, it remains doubtful whether it is practical or practical.

[0012]

As described above, the use of the maximum ratio combining antenna diversity receiver does not improve the reception characteristics in the environment where the reception sensitivity is severe and the multiple reflection radio wave propagation is present. . Also, other in-phase combining diversity receivers that combine equalization techniques are very effective, but the problem remains that the configuration is not easy.

The antenna diversity receiver of the present invention has been devised in view of such a point, and particularly in digital radio communication intended for a mobile mobile communication terminal moving at a low speed, a transmission path impulse response is obtained at each branch. While estimating, unnecessary signal components from the received signal received in each branch, i.e., weighting such that the signal-to-noise ratio of the received signal becomes maximum after removing the delayed wave component,
We propose a diversity scheme that simply combines the results. With such a configuration, the influence of the delayed wave component, which has been a problem in the maximum ratio combining diversity receiver, can be eliminated. In addition, it is possible to avoid the unnecessary operation of the delayed wave component by the FFF, which is a problem of the conventional synthetic diversity receiver using the decision feedback equalizer, and further, the synthetic diversity reception using the conventional maximum likelihood sequence estimator. It can be realized with much smaller hardware than the machine. Furthermore, it is possible to realize a diversity receiver that does not lose the advantages of the maximum ratio combining antenna diversity receiver that maximizes the signal-to-noise ratio of the received signal.

As described above, the object of the present invention is that the receiving sensitivity is strict without improving the performance of the portable mobile communication terminal.
Another object of the present invention is to provide an antenna diversity receiver that can realize good communication quality in a wireless communication environment in which multiple reflection radio wave propagation exists.

[0015]

In order to achieve the above object, in the antenna diversity receiver of the present invention, (1) a digitally modulated transmission signal is received, and a digital signal sequence is demodulated from the reception signal. In the receiver, the receiver has a plurality of antennas for receiving a plurality of reception signals at the same time, and a plurality of reception units connected to the respective antennas, and each of the reception units has the reception signal. Means for estimating a transmission path impulse response specific to the receiving section using, and distortion removal of the received signal received by the receiving section using the estimated transmission path impulse response and a signal-to-noise ratio of the received signal Has a means for performing phase control of the plurality of received signals and weighting so that the maximum An addition means for simply adding the outputs from the means for performing the weighting to maximize the signal-to-noise ratio of the received signals and the phase control of the plurality of received signals, and the sign determination of the outputs from the adding means for the simple addition. And a code determining means for performing.

(2) Further, in the transmission path impulse response estimating means included in the receiving section connected to each of the plurality of receiving antennas in the antenna diversity receiver of the present invention, a signal sequence known in advance on the receiver side is generated. When included in the received signal, the transmission path impulse response of the transversal filter expression with the tap number L is estimated using the received signal corresponding to the known signal sequence, and the known signal sequence is included in the received signal. Even if the transmission line impulse response is estimated based on the maximum likelihood sequence estimation method, the transmission line impulse response can be estimated without being affected by the presence or absence of a known signal sequence. The operation of the antenna diversity receiver of the present invention is guaranteed.

(3) Further, the transmission of the transversal filter representation of the tap number L estimated by the transmission path impulse response estimation means included in the receiving section connected to each of the plurality of antennas in the antenna diversity receiver of the present invention. Of the path impulse responses, L-1 tap gains are used for the code determination result up to time k-1 in the code determination means, which is one element that constitutes the diversity receiver, and the remaining one tap is used. The gain will be used for the received signal at time k.

(4) In the antenna diversity receiver of the present invention, the transmission path impulse response estimation means included in the receiving section connected to each of the plurality of antennas does not use the above-mentioned plurality of operations without using a sequential calculation method. A first transmission path impulse response estimating means for estimating a transmission path impulse response unique to each of the receiving sections, and a first estimating means for estimating the transmission path impulse response unique to each of the plurality of receiving sections using a sequential calculating means. The second transmission path impulse response estimation means is provided, and by using either the first transmission path impulse response estimation means or the second transmission path impulse response estimation means, Estimate the intrinsic channel impulse response. Also, the first
It is also possible to use the transmission path impulse response estimated by the transmission path impulse response estimation means as the initial value of the transmission path impulse response estimation of the second transmission path impulse response estimation means.

(5) The antenna diversity receiver of the present invention includes means for removing distortion of a received signal, weighting processing for maximizing the signal-to-noise ratio of the received signal, and phase control for a plurality of received signals. Of the transmission path impulse responses represented by the transversal filter with the number of taps L estimated by the transmission path impulse response estimation means included in the receiving section connected to each of the plurality of receiving antennas included in the antenna diversity receiver of the present invention, L Multiplying means for multiplying -1 tap gain and the code determination result up to time k-1 in the code determining means included in the antenna diversity receiver of the present invention, and a plurality of antennas of the antenna diversity receiver. Subtraction means for subtracting the output from the multiplication means from the received signal at time k received in By comprising multiplication means for multiplying the gain for controlling the amplitude and phase of the force, unnecessary signal components are removed from each of the reception signals received by the plurality of antennas, and the signal-to-noise ratio is maximized. Weighting and phase control can be realized.

(6) In this antenna diversity receiver, a portion which becomes a digital signal processing section, that is,
Transmission path impulse response estimating means included in each of a plurality of receiving units connected to a plurality of receiving antennas, distortion removal processing of a plurality of received signals by the plurality of receiving antennas, and signal-to-noise of the received signals The means for performing the weighting process for maximizing the ratio and the phase control process for the received signal do not require a number corresponding to the plurality of reception antennas, and the transmission path impulse response means and the distortion removal process for the received signal. By using the means for performing the weighting process for maximizing the signal-to-noise ratio of the received signal and the phase control process for the received signal in time division, the configuration of the antenna diversity receiver of the present invention can be easily and minimized. It is possible to configure with a limited signal processing unit.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram for explaining claim 1 of the present invention. In this figure, the digital signal processing unit is depicted as being directly connected to the receiving antenna, but it should be mentioned in advance that the analog signal processing unit such as the RF unit and the IF unit and the AD converter are omitted. deep. In a receiver that receives a digitally modulated transmission signal and demodulates a digital signal sequence from the reception signal, a plurality of reception antennas 10, 11, and 12 included in the reception signal are transmission signals that arrive through different propagation paths. To receive. In the first reception unit 16, the reception signal 13 received by the reception antenna 10 is input to the transmission path impulse response estimation processing unit 19, and the code determination output 130 of the code determination unit 129 or a code known in advance on the receiver side. The transmission line impulse response 118 is calculated using the sequence. The calculated transmission path impulse response 118 is input to the distortion removal means 112 and the weighting and phase control means 115. The received signal 13 and the code determination output are also input to the distortion removing means 112, and the distortion component is removed from the received signal 13 using the estimated transmission path impulse response 118 and the code determination output 130. The received signal 121 from which the distortion has been removed by the distortion removing means 112 is input to the weighting and phase control means 115, and weighting and phase control are performed so that the signal-to-noise ratio of the received signal is maximized. The weighted and phase-controlled received signal 124 is input to the adding means 127. This series of operations is performed by each receiving antenna. FIG.
Then, similar processing is performed on the reception signal 14 and the reception signal 15 received by the reception antenna 11 and the reception antenna 12, and input signals 125 and 126 to the adding means 127 are generated. The adding means input signals 124, 125, 126 from the respective antennas are all simply added by the adding means, and become the adding means output 128. The addition unit output 128 is input to the code determination unit 129 and the code determination result 130 is output. The information sequence is demodulated by the digital signal sequence demodulation means using the code determination result 130.

FIG. 2 illustrates a method of estimating a channel impulse response when the received signal 22 includes a known signal sequence and a method of estimating a channel impulse response when the received signal 22 does not include a known signal sequence. FIG. The TDMA communication system uses a part of the time axis 20 called a slot 23 to perform communication along the time axis 20, and the time assigned to itself is called a slot time 21. Only communication is done. In general, in order to distinguish one's own slot 23 from another's slot, a known signal sequence 24 is stored in the slot 23.
Is added regularly. When the known sequence 24 is added to the received signal, the transmission line impulse response estimating means 2 is set at the times 27, 28 and 29 at which the known sequence ends.
At 12, the transmission path impulse response 213 is estimated. If the known signal sequence 24 exists, the transmission line impulse response estimation means 212 uses the received signal 210 corresponding to the known signal sequence and the signal sequence 211 when the known signal sequence is received without distortion. Transmission line impulse response 21
3 is estimated. The estimated transmission path impulse response 23
Is generally expressed by a vector, and an element of the vector, that is, a tap gain 2 according to the delay dispersion amount in the transmission path.
The number of 14,215,216,217 is determined. Further, in FIG. 2, the known signal sequence 2 is added to the received signal sequence 22.
When 4 is not added, the transmission path impulse response 213 cannot be easily estimated because all slots 23 are information sequences. In that case, the blind estimation process is performed, and at time 27, 28, 29 when a certain time elapses from the time considered to be the head of the slot, all combinations of signal sequences that will be transmitted within that time are combined. A plurality of transmission candidate sequences 219, 220, 221, 222 generated by the transmission candidate sequence generation unit 218 are sequentially passed through the pseudo transmission line response 223 having an appropriately given initial value, and the transmission candidate sequences are actually transmitted within that time. The maximum likelihood sequence candidate is determined 226 by comparing the received signal sequence 22 received and selecting the transmission candidate sequence having the smallest error and matching. Then, using the maximum likelihood sequence 227, the transmission path impulse response estimation means 2
At 28, a true transmission line impulse response 213 is gradually obtained.

FIG. 3 is a specific example for explaining a method of using the estimated transmission path impulse response. A description will be given of one of a plurality of receiving antennas. Among the received signals received by the receiving antenna 30, the received signal 31 corresponding to the known signal series and the undistorted signal series 33 of the known signal series are used to generate the transmission path impulse response 35 by the transmission path impulse response estimation means 34. Presumed. Estimated transmission path impulse response expressed by multiple tap gains 3
5, the tap gains 37, 38, 39, 310 other than the tap gain 36 corresponding to the current processing time are subjected to code determination by the code determination means 328 one time before 329.
Used for weighting. Then, the weighted results 312, 313, 314, 315 are the simple adder 33.
The addition result 316 is subtracted from the received signal 32 by the subtractor 317. And subtracter output 31
8 is multiplied by the multiplier 319 with a value obtained by taking the complex conjugate of the tap gain 36 corresponding to the current time in the transmission path impulse response 35 estimated by the transmission path impulse response estimation means 34. This multiplication result 320 always exists for the reception signal received by each antenna, and all of them are added by the addition means 32.
Add 6 The addition result 327 is input to the code determination means 328, and the determination result 329 is used again for the processing at the next time.

FIG. 4 is an embodiment relating to a method of using an adaptive algorithm when estimating a channel impulse response. Generally, there are two types of adaptive algorithms: a sequential calculation means and a non-sequential calculation method. In consideration of this point, the transmission path impulse response estimation means 42 has a processing portion 43 for performing a sequential calculation method and a processing portion 44 for performing a non-sequential calculation method, and either one is used.
The input to the transmission path impulse response estimation means 42 is the received signal sequence 40 and the determination result from the code determiner (129 in FIG. 1) or the known signal sequence 41, which are not processed by the sequential calculation method processing unit 43 and It is input to each of the sequential calculation method processing units 44. Then, the transmission path impulse responses 418 and 419 estimated by the respective processing units 43 and 44 are output as the estimation result 46 of the transmission path impulse response estimation means 42 via the switch 45. There are four possible ways of using the sequential calculation method 43 and the non-sequential calculation method 44. Of the received signal series 47, the known signal series 4
The application method is for time 48 when 10 is received and the application method for time 49 when information signal sequence 411 is received. The method 412 uses the transmission path impulse response 418 estimated by the sequential calculation method in both the time 48 section and the time 49 section. Method 413
Uses the transmission path impulse response 419 estimated by the non-sequential calculation method in the section of time 48, and uses the transmission path impulse response 418 estimated by the sequential calculation method in the section of time 49. The method 414 uses the transmission path impulse response 18 estimated by the sequential calculation method in the period of time 48, does not adaptively estimate the transmission path impulse response in time 49, and estimates the transmission path impulse response in time 48. Use impulse response fixedly. X42 in the figure
0 means that the adaptive transmission path impulse response is not updated. The method 415 uses the transmission path impulse response 419 estimated by a non-sequential calculation method in the time 48 section, does not perform adaptive transmission path impulse response estimation at the time 49, and estimates the transmission path impulse response within the time 48. Use the response fixedly. As described above, it is effective in mobile communication for low-speed mobiles to adopt a configuration in which adaptive transmission path impulse response estimation is not performed from the middle of the TDMA slot as in the schemes 414 and 415. Therefore, the implementation of the receiver is simplified.

FIG. 5 shows a more specific embodiment of the antenna diversity receiver of the present invention shown in FIG. The received signal 51 received by each of the receiving antennas is input to the receiving unit 50 and the transmission path impulse response estimating means 52. The code determination result 538 from the code determination means 53 or the known signal sequence is input to the transmission path impulse response estimation means 52. Transmission path impulse response estimation means 52
The estimation results 512 to 518 estimated by
11 is input. The code determining means 5 is connected to those multipliers.
The judgment result 538 from No. 3 is delayed by the delay elements 545 to 551, and the judgment results 539 to 5 are judged in the past.
43 is also input. The multiplier outputs 519 to 525 are input to the simple adder 526, all of which are added, and then subtracted from the received signal 51 by the subtractor 528. The subtraction result 529 is multiplied in the multiplier 531 by the complex conjugate value 530 of the tap gain corresponding to the time when the reception signal 51 estimated by the transmission path impulse response estimation means 52 is received. The multiplication result 532 is input to the adder 54 and is added to the same result as the multiplication result 532 obtained from the other plurality of receiving antennas, and the addition result 537 is input to the code determination unit 53 to perform the code determination. Be done. TDMA slot 554
Among them, the transmission path impulse response estimation 557 is performed within the duration 552 of the known signal sequence 555, and the transmission path impulse response is not performed at the subsequent time 553 at which the information signal sequence 556 is received, and the transmission path impulse response estimation processing 55
The result obtained in 7 is used as the transmission path impulse response 558 effective in the section 553.

FIG. 6 shows an embodiment in which the proposed antenna diversity receiver has only one digital signal processing unit and the received signals from the respective antennas are used by time division switching. Of the received signals received by the plurality of receiving antennas 60 to 63, the received signal 66 selected by the switch 64 is input to the receiving unit 65. The receiving unit 65 exists only for M receiving antennas. The selected received signal 66 is input to the transmission path impulse response estimation means 67 and the received signal distortion removal means 621. The estimated transmission path impulse response 68 estimated by the transmission path impulse response estimation means 67 is sent to the transmission path impulse response storage unit 69. The transmission path impulse response storage unit 69 has storage areas 610 to 6131 unique to the receiving antenna selected by the switch 64, and the estimated transmission path impulse response 68 is stored in the storage areas 610 to 613 that match the selected receiving antenna. Remembered. In addition, from the transmission path impulse response storage unit 69, storage areas 610 that match the receiving antenna selected by the switch 620.
Transmission path impulse response 619 stored from 613
Is read out and supplied to the received signal distortion elimination means 621 and the weighting and phase control means 622. The distortion removing means 621 inputs the signal 623 obtained by removing the distortion from the received signal 66 received by the selected receiving antennas 60 to 63 to the weighting and phase control means 622. The weighting and phase control means 622 performs weighting and phase control of the received signal so that the signal-to-noise ratio of the received signal is maximized, and outputs a signal 624 which is an input to the cumulative adder 625. In the cumulative adder 625, each of the receiving antennas 60-6
It has the role of adding all the signals after distortion removal and weighted phase control have been performed on the signal received in 3. The cumulative adder output 626 is sent to the code determination means 627 and the code determination is performed. The code determination result 628 is demodulated by the digital signal sequence demodulation unit 629 as transmission information. Further, the reason why the signal line 68 connecting the transmission path impulse response estimation means 67 and the transmission path impulse response storage section is bidirectional is that the estimation of the transmission path impulse response is sequentially tracked in the proposed antenna diversity receiver. This is in consideration of the case. That is, the transmission path impulse response once stored is read into the transmission path impulse response estimation means again, updated, and written again in the storage area.

FIG. 7 is a block diagram of a conventional maximum ratio combining diversity receiver. Multiple receiving antennas 71 to 7
The received signals 74 to 76 received in No. 3 are weighted gains 710 to 712 for controlling the amplitude and phase of each received signal.
And the result 713-715 is simply the adder 7
16 is added. The addition result 717 is the code determination unit 718.
Is input to and the code is determined. Sign determination result 71
9 and the sign determiner input 717 are obtained by the subtractor 720, and the gain 7 is adaptively adjusted based on the error 721.
23 is required. The gain 723 is the reception signals 74 to 7 received by the reception antennas 71 to 73 at the next time.
Gains 710 to 712 for controlling the amplitude and the phase of No. 6 are obtained.

FIG. 8 is a diagram for explaining a general diversity receiver using a decision feedback equalizer. Received signals 83 to 85 received by the plurality of receiving antennas 80 to 82
Is input to the front filters (FFF) 86 to 88, and the product-sum calculation with the tap gains 89 to 811 is performed. FF
The product-sum operation by F is performed for the purpose of collecting desired signal components scattered on the time axis due to the influence of the delay dispersion characteristic of the transmission line. The reception signals 812 to 814, which have been corrected for the influence of the delay dispersion of the transmission path, are simply added by the adder 815. Since the delayed wave component remains in the adder output 816, the removal signal component 817 from the rear filter 819 is supplied to the adder 818 in order to remove the delayed wave component in order to remove the influence. In the adder 818, the adder 815
The unnecessary component 817 is removed from the signal 816 from the input signal 816 to become the input signal 822 of the code determination unit 820. Code determiner 82
The determination result 821 determined by 0 is supplied to the backward filter 819 and the subtracter 823 that generates an error signal. The code determination result 821 supplied to the rear filter 819 is used to remove an unnecessary signal component from the reception signal received at the next time. In addition, the subtractor 823 generates an error signal 824 between the input signal 822 of the code determination unit 820 and the code determination result 821 of the code determination unit 820, and based on this, it is connected to each of the receiving antennas 80 to 82. The tap gain adaptive control means performs adaptive control of the tap gains 89 to 811 of the front filters 86 to 88 and the tap gain 827 of the rear filter 819. Further, in the rear filter 819, the sum of products operation of the judgment result 821 in the sign judging unit 820 and the tap gain 827 is performed, and the signal component 8 to be removed is
17 is generated.

FIG. 9 shows a maximum likelihood sequence estimator (MLSE: Maximum L).
FIG. 11 is a diagram illustrating an example of a conventional combining diversity receiver using an ikelihood sequence estimator). Received signals 93 to 95 received by the plurality of receiving antennas 90 to 92
Is estimated transmission signal sequence 930 estimated by MLSE processing 929 and estimated transmission path impulse responses 915-917 controlled by tap gain adaptive control means 932, and estimated reception signals 99-911 are obtained by transversal filters 912-914. Is generated. The generated estimated received signals 99 to 911 are input to the subtracters 96 to 98, and error signals 918 to 920 with the received signals 93 to 95 are generated. The generated error signals 918 to 920 are supplied to the square calculation means 921 to 923, respectively. The outputs 924 to 926 of the multiplication calculation means 921 to 923 are adders 927.
Is input to and all are added. The addition result 928 is ML
It is sent to the SE processing unit 929 and is used for estimating the transmission signal sequence. Further, the branch metric 931 used in the selection of the transmission code sequence in the MLSE processing unit 929 is input to the tap gain adaptive control means 932, and the tap gain 91 of each transversal filter 912 to 914 at the next time.
5-917 is required. Further, the estimated transmission candidate sequence determined by MLSE is decoded and output as information sequence 934.

FIG. 10 is an example of a diagram for explaining the present invention shown in FIG. 1 in detail. Since it is drawn with the same elements as in FIGS. 7 to 9, it is easy to compare and evaluate and it is easy to grasp the difference. Since the received signals 104 to 106 received by the plurality of receiving antennas 101 to 103 are affected by the multipath propagation distortion received on the transmission path, the subtractor 1010 subtracts the signal components 107 to 109 corresponding to the multipath propagation distortion. ~
Subtract with 1012. Received signals 1019 to 1021 from which the influence of multipath propagation distortion is removed are input to multipliers 1022 to 1024 for weighting and phase control so that the signal-to-noise ratio is maximized. In the multiplier, the gains 1025 to 1027 are multiplied by the received signals 1019 to 1021, and the outputs 1028 to 1030 are sent to the adder 1031. Output 1032 of adder 1031
Is supplied to the sign determiner 1033 and the subtractor 1038 for generating the error signal 1035. Code determiner 10
The result 1034 of which the sign is determined in 33 is the error signal 1035.
Is supplied to a subtractor 1038 for generating the error, and an error 1035 from the input signal 1032 of the code determiner 1033 is obtained. The error signal 1035 is the tap gain adaptive control means 1
036, and tap gain 1037 at the next time is obtained. Also, the output 1034 of the code determiner 1033
Is sent to the rear filters 1013 to 1015, and signal components 107 to 109 for removing multipath distortion components included in the received signals 104 to 106 are generated. As described above, the antenna diversity receiver of the present invention is largely different in configuration from the antenna diversity receiver (FIGS. 7 to 9) using the conventional waveform equalization technique. This series of received signal processing procedures is mathematically expressed. Received signal r _{k, i} 104-1 received by the i-th receiving antenna at time k
Considering No. 06, the input signals r _{k, i} 1028 to 1030 of the adder 1031 of FIG. 10 are r ′ _{k, i} = h ^* _{o, i} {r _{k, i} −h _i, ^t x (k− 1)}. Where h _{o, i} is the direct wave component of the estimated transmission path impulse response. h _i : An estimated transmission path impulse response vector composed of components obtained by removing h _{o, i} from the estimated transmission path impulse response. h _i = [h _{1, i} , h _{2, i} , ..., h _{L-1, i} ] ^t * L is the total number of taps of the estimated transmission path impulse response. x (k-1): A determination result vector configured by the results determined by the code determination unit 1033 by time k-1. x (k−1) = [x _k−1 , x _k−2 , ..., X _{k−L + 1} ] ^t * x _j is the result 1034 determined by the code determination unit 1033 at time j. (*): Meaning of complex conjugate. (T): Means transposition. Is.

Then, r'k _{, i} is obtained for each received signal received by each receiving antenna, and the adder 1031
Makes a simple addition.

FIG. 11 is a block diagram for explaining a post-delay detection combined diversity receiver. The post-delay detection combined diversity receiver has a very simple structure and is the most easily realized combined diversity receiver system. Received signals 1104 received by the plurality of receiving antennas 1101 to 1103
1106 are subjected to delay detection (differential decoding) by delay detectors (differential decoders) 1129 to 1131 connected to the respective antennas. Specifically, the received signal 1104-
1106 designates multipliers 1119 to 1121 and a delay element 110.
7 to 1109. Delay element output 1110-1
Reference numeral 112 represents complex conjugate signals 1116 to 1118 at complex conjugate elements 1113 to 1115, and multipliers 1119 to 11
21 is input. Multiplication results 1122-1 of the reception signals 1104-1106 and the complex conjugate signals 1116-1118
All of 124 are added by the adder 1125, and the addition result 1126 is supplied to the code determination unit 1127. The code determination result 1128 of the code determiner 1127 becomes the demodulated signal sequence.

FIG. 12 is a command showing the configuration of a conventional antenna diversity receiver which estimates the transmission path impulse response by the correlation calculation means and performs the in-phase combining diversity receiver from the result. Multiple receiving antennas 1200
Received signals 1203 to 1205 received at
Multipliers 1210-1212 and correlation calculation means 1206
To 1028. Correlation calculation means 1206 to 12
The outputs 1220 to 1222 of 08 are the multipliers 1210 to 1
It is input to 212 and is multiplied by the received signals 1203 to 1205. The multiplication results 1213 to 1215 are added by the adder 121.
At 6 all are added. The addition result 1217 is subjected to code determination by the code determination unit 1218, and the code determination result 1219 is obtained.
Is output. Also, the correlation calculation means 1206-1208
Correlation sequence 1209 required for the correlation calculation performed in 1. is supplied from correlation sequence generation means 1223.

FIG. 13 shows a code error rate characteristic for explaining the effect of the 4-branch antenna diversity receiver of the present invention. The vertical axis of the figure indicates the bit error rate (BE
R) 1300, and the horizontal axis of the figure shows the multipath delay amount (τ / T) 1301 in the wireless propagation path. △ in the figure
A mark 1302 is an in-phase combining diversity receiver which has a simple structure shown in FIG. 11 and can be easily realized. The characteristics of the combined diversity receiver after delay detection are shown, and the cross mark 1303 shows the characteristics of the antenna diversity receiver of the present invention. In the figure, E _b / N _o = 5.0 (d
B) characteristic curve 1304 and E _b / N _o = 10.
Characteristic curve 1305 at 0 (dB) and E _b / N _o =
A characteristic curve 1306 at 15.0 (dB) is drawn. From this figure, it can be understood that the antenna diversity receiver of the proposed system can realize a good code error rate in all multipath propagation environments.

FIG. 14 shows a code error rate characteristic for explaining the effect of the two-branch antenna diversity receiver of the present invention. The vertical axis of the figure indicates the bit error rate (BE
R) 1400, and the horizontal axis of the figure shows the multipath delay amount (τ / T) 1401 in the wireless propagation path. △ in the figure
The mark 1402 shows the characteristics of the post-delay-detection combining diversity receiver, which is a common-mode combining diversity receiver that is simple and easy to realize the configuration shown in FIG. 11, and the mark 1403 shows the characteristics of the antenna diversity receiver of the present invention. There is. In the figure, E _b / N _o = 5.0 (dB) as an evaluation parameter
Characteristic curve 1404 and E _b / N _o = 10.0
Characteristic curve 1405 at (dB) and E _b / N _o = 1
Characteristic curve 1406 at 5.0 (dB) and E _b / N
A characteristic curve 1406 when _o = 20.0 (dB) is drawn. From this figure, it can be understood that the antenna diversity receiver of the proposed system can realize a good code error rate in all multipath propagation environments.

[0036]

As described in detail above, according to the antenna diversity receiver of the present invention, the influence of multipath propagation distortion in which the received signal is peculiar to the propagation environment of mobile communication and frequently occurs, and the reception gain are eliminated. Can be improved at the same time. This is because in a conventional diversity diversity receiver after differential detection or in a diversity diversity receiver based on correlation calculation, the delayed arrival signal component was treated as noise, so the reception characteristic was greatly deteriorated. By effectively utilizing the incoming signal component, the reception characteristic is greatly improved. In addition, the diversity receiver using the conventional decision feedback equalizer and the diversity receiver using the maximum likelihood sequence estimator, which takes into account the influence of multipath propagation distortion, has a problem that the configuration becomes complicated. However, it can be realized with a simpler configuration than these, and is particularly effective for wireless communication with a low-speed moving body.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating an outline of the configuration of an antenna diversity receiver of the proposed system.

FIG. 2 is a diagram for explaining a transmission path impulse response estimation method when a received signal includes a known signal sequence and a transmission path impulse response estimation method when a received signal does not include a known signal sequence.

FIG. 3 is an example of a diagram specifically showing a method of using an estimated transmission path impulse response.

FIG. 4 is a diagram showing an example of a method of using an adaptive algorithm when estimating a channel impulse response.

FIG. 5 is a diagram showing an embodiment in which the proposed antenna diversity receiver shown in FIG. 1 is further embodied.

FIG. 6 is a diagram showing an example of a case where the proposed antenna diversity receiver shown in FIG. 1 is used with one digital signal processing unit and time division.

FIG. 7 is a block diagram showing a configuration of a maximum ratio combining diversity receiver.

FIG. 8 is a block diagram showing a configuration of an antenna diversity receiver using a decision feedback equalizer.

FIG. 9 is a block diagram showing a configuration of an antenna diversity receiver using a maximum likelihood sequence estimator.

FIG. 10 is a block diagram of the proposed antenna diversity receiver shown in FIG. 1 and a diagram specifically showing a signal processing method.

FIG. 11 is a block diagram showing the configuration of a conventional diversity diversity receiver after differential detection.

FIG. 12 is a diagram showing a configuration of an antenna diversity receiver that estimates a transmission path impulse response by a conventional correlation calculation means and performs in-phase combining diversity from the result.

13 is a diagram of code error rate characteristics showing the effect of the 4-branch antenna diversity receiver using the present invention shown in FIG.

FIG. 14 is a diagram of code error rate characteristics showing the effect of the two-branch antenna diversity receiver utilizing the present invention shown in FIG.

[Explanation of symbols]

10, 11, 12 Receiver (antenna) 16, 17, 18 Receiver (receiver) 19, 110, 111 Estimator (transmission path impulse response estimator) 112, 113, 114 Signal processor (distortion remover) 127 Combining means (adding means) 129 Code judging means 131 Demodulating means (digital signal sequence demodulating means)

Claims (2)

[Claims] 1. A receiving section for receiving a digitally modulated signal, an estimating section for estimating a channel response using the received signal received by the receiving section, and a channel response estimated by this estimation. A plurality of receiving means having a signal processing unit for performing phase control of the received signal by removing transmission path distortion from the received signal; a combining means for combining output signals from the receiving means; An antenna diversity receiver, comprising: a code determination means for determining a code based on an output signal from the means; and a demodulation means for demodulating an output signal from the code determination means. 2. An estimating unit for estimating a channel impulse response from a received signal received by the receiving unit, distortion removal for the received signal, weighting for maximizing a signal-to-noise ratio of the received signal, and the plurality of units. 2. The antenna diversity receiver according to claim 1, wherein the single signal processing unit for controlling the phase of a plurality of received signals connected to the antenna is performed by time division using the single antenna.