JP3537203B2 - Antenna diversity receiver - Google Patents

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 improving reception characteristics in digital communication, and more particularly to a waveform equalization process for compensating for a distortion of a received signal from a propagation environment and an improvement in a reception gain. And at the same time, to improve the communication quality in a propagation environment in which the quality of wireless communication with a mobile object is poor.

[0002]

2. Description of the Related Art In recent years, the construction of a system aimed at a digital cellular phone service has been urgently required. Along with this, development of digital mobile communication terminals and wireless communication base stations for communicating with the mobile communication terminals has been actively conducted. In performing land mobile communication, reception characteristics are greatly affected by a complicated radio propagation environment generated by a physical environment surrounding a portable mobile communication terminal and a wireless communication base station. For example, even when the distance between the portable mobile communication terminal and the wireless communication base station is short, the radio wave is subject to multipath propagation distortion due to multiple reflected radio wave propagation due to reflection from buildings near the portable mobile communication terminal and the wireless communication base station. Would. Even if a received signal subjected to multipath propagation distortion has sufficient power, communication quality is significantly degraded due to the influence of the distortion.

Further, as the portable mobile communication terminal moves away from the radio communication base station, the radio wave is attenuated and it becomes difficult to receive the radio wave, thereby deteriorating communication quality. Since the radio propagation environment in land mobile communication is determined between the radio communication base station and the mobile communication terminal, the reception characteristics from the radio communication base station to the mobile communication terminal are unchanged from the mobile communication terminal to the radio communication base. a reception characteristic of the station (TDD- Ti m e Division Duplex -
method). Means for improving the communication quality in these poor radio propagation environments include a waveform equalization technique and a diversity technique. The former is an indispensable technology in a large zone wireless communication service such as a cellular mobile communication system, and mainly compensates for waveform distortion caused by multiple reflection radio wave transmission. Some of them have been put into practical use due to the recent appearance of high-speed digital signal processors and optimization of signal processing techniques. In contrast, the latter is frequently used in conventional analog cellular mobile communication systems.

[0004] In portable mobile communication terminals in mobile communication, there is a strong demand for miniaturization and low power consumption while minimizing transmission power as much as possible and realizing long-time standby and long-time communication. It is expected that a small zone system that meets such demands will be realized in recent years (Personal handyphone system). However, in the small zone system, the communication range (zone radius) is extremely short as compared with the existing cellular mobile communication system, so that services cannot be provided unless many wireless communication base stations are arranged quite densely. Furthermore, since the communication system is completely different from the existing cellular mobile communication system, a huge amount of infrastructure must be newly developed. Therefore, until the infrastructure of the small zone system is completely developed, the transmission / reception performance of the wireless communication base station is improved while the specifications of the portable mobile communication terminal are compatible with the small zone system, and the number of wireless communication base stations is reduced. It is desired to start the service at. This means that the area that must be covered by the wireless communication base station is expanded, so that 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 portable mobile communication terminal to receive. However, the expansion of the zone promotes multiple reflection radio wave propagation distortion, and simply improves the reception gain at the wireless communication base station,
It is not a problem that can be solved by increasing the transmission power.

[0005] An equalizing diversity receiver combining an equalizer and diversity has been proposed as a receiving method for simultaneously improving the above-described multi-reflected radio wave propagation distortion and improving the receiving sensitivity to improve the receiving characteristics. Some have been proposed. As one of them, a representative diversity technique disclosed in the paper "Interference Cancellation Characteristics of DFE Transversal Combining Diversity System in Mobile Radio -Comparison with Metric Combining-" is introduced. In this paper, the diversity scheme shown in FIGS. 1 (a), 1 (b) and 1 (c) on page 585 is disclosed in FIGS. Hereinafter, the diversity receivers 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 combining diversity receiver that uses the least-mean-square value of the error e (t) in FIG. 7 as an evaluation function. The received signal of each branch is multiplied by a weighting coefficient, and all branches are simply added. The result of the addition is determined by a sign determiner,
The coefficient is controlled such that the expected squared value of the difference e (t) between the input and output of the sign determiner is minimized. Maximum ratio combining antenna diversity receiver is a very effective diversity technology in maximizing 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 the other signal wave components are treated as noise. There is a problem that the reception characteristics are not improved.

FIG. 8 is a block diagram of a combining diversity receiver using a decision feedback equalizer. The received signal received at each branch is transmitted through an F
The signal is input to an FF (Feed Forward Filter), and the signal component spread by multiple reflection radio wave transmission is collected.
In addition, since the collected signal components also include a delayed wave component, the delayed wave component is canceled by an FBF (Feed Back Filter), thereby improving the signal-to-noise ratio at the time of input to the code determiner. However, in this diversity receiver, while the direct wave component is effectively collected by the FFF, the delayed wave component is complicatedly controlled,
There is a problem that the component cannot be completely removed by FBF. Furthermore, there is a problem that a code decision unit error occurring at a certain time, which is a code decision unit, causes error propagation that affects subsequent code decisions, and branch combining breaks down.

[0008] Figure 9 shows a block diagram of a combining diversity receiver using a maximum likelihood sequence estimator. In this diversity receiver, MLSE (Maximum Likelihood S
The generated code sequence candidates equence Estimation), channel impulse response is estimated, TV F (Transv
ersal Filter) generates an estimated received signal. The squared value of the error obtained by subtracting the reception signal estimated in each branch from the actual reception signal received in each branch is used as an evaluation function .
And sequentially performing estimation of the channel impulse response and MLSE process used. However , although this diversity receiver can greatly improve the reception performance, the MLSE
There is a problem that the processing amount becomes enormous, and the device scale and power consumption become enormous.

FIG. 11 is a block diagram of a diversity receiver after differential detection that can be easily realized. In this diversity receiver, a method of performing delay detection on a received signal received by each antenna, removing the influence of transmission path characteristics unique to each antenna, and performing simple combining.
However, the delay detection processing on the received signal has a function of deteriorating the signal-to-noise ratio after the delay detection, which leads to deterioration of reception characteristics. Further, in the case where the radio transmission path is a multipath transmission path having delay dispersion, no processing is performed on the delay wave, so that the delay wave component becomes an interference signal component, and there is a problem that the reception characteristics are greatly deteriorated. .

FIG. 12 is a block diagram of a combining diversity receiver that controls the phase of a signal received by each antenna based on the transmission path impulse response estimated by the correlation method. In this diversity receiver, although the signal-to-noise ratio does not deteriorate as in the post-delay-detection combining diversity receiver of FIG. 11, in the case of a multipath transmission line having delay dispersion in a wireless transmission line, processing on a delay wave is performed. Since it is not performed at all, there arises a problem that the delayed wave component becomes an interference component and the receiving characteristic is greatly deteriorated.

As mentioned above, the waveform shaping technique of the received signal and the diversity technique for improving the receiving sensitivity have been devised. However, it is questionable whether the technique is practical and practically usable due to various problems.

[0012]

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

[0013] The antenna diversity receiver of the present invention has been devised in view of the above point, and particularly in digital radio communication for a low-speed mobile portable communication terminal, the transmission path impulse response is determined at each branch. While estimating, unnecessary signal components from the received signal received in each branch, that is, weighting is performed so that the signal-to-noise ratio of the received signal is maximized after removing the delayed wave component,
We propose a diversity scheme that simply combines the results. With such a configuration, it is possible to remove the influence of the delayed wave component which has become a problem in the maximum ratio combining diversity receiver. Further, unnecessary operation of the delay wave component by the FFF, which is a problem of the conventional combining diversity receiver using the decision feedback type equalizer, can be avoided, and further, the combining diversity reception using the conventional maximum likelihood sequence estimator can be avoided. It can be realized with much smaller hardware than the machine. Furthermore, a diversity receiver that does not lose the advantage of the maximum ratio combining antenna diversity receiver that maximizes the signal-to-noise ratio of the received signal can be realized.

[0014] As described above, an object of the present invention is to provide a portable mobile communication terminal that has a high receiving sensitivity without improving its performance.
Another object of the present invention is to provide an antenna diversity receiver capable of realizing good communication quality in a wireless communication environment in which multiple reflected radio wave propagation exists.

[0015]

In order to achieve the above object, an antenna diversity receiver according to the present invention comprises: a receiving section for receiving a digitally modulated signal; a transmission path impulse from a reception signal received by the receiving section. An estimating unit for estimating a response; and a signal processing unit for performing phase control of the received signal by removing transmission line distortion from the received signal using the transmission line impulse response estimated by the estimating unit. Receiving means, combining means for combining output signals from the receiving means, code determining means for performing code determination based on the output signal from the combining means, and demodulation for demodulating an output signal from the code determining means. Means,
And the signal processing unit is configured by the estimation unit
Transversal filter expression of estimated tap number L
Of the transmission path impulse responses of
Until time k-1 in the tap gain and the sign determination means
Multiplying means for multiplying the sign determination result of
The received signal at time k received by each of the antennas
Distortion by removing the output of the product means
And a distortion removing unit comprising:
Is multiplied by the L-th tap gain at time k.
Weighting unit for correcting the phase of the received signal by
And the following.

(2) In the transmission path impulse response estimating means of the receiving unit 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 used. If the received signal is included in the received signal, the transmission signal impulse response of the transversal filter expression with the number of taps 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 not, the configuration is such that the transmission path impulse response is estimated based on the maximum likelihood sequence estimation method, so that the transmission path impulse response can be estimated regardless of the presence or absence of a known signal sequence. The operation of the antenna diversity receiver of the present invention is guaranteed.

(3) Further, transmission of a transversal filter expression of the number of taps L estimated by the transmission path impulse response estimation means included in the reception unit connected to each of the plurality of antennas in the antenna diversity receiver of the present invention. Of the channel impulse response, 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 of 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 according to the present invention, the transmission path impulse response estimating means included in the receiving unit connected to each of the plurality of antennas is provided 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 second estimating means for estimating a transmission path impulse response unique to each of the plurality of receiving sections using a sequential calculation means. 2 transmission line impulse response estimating means, and by using either the first transmission path impulse response estimating means or the second transmission path impulse response estimating means, Estimate the unique transmission path impulse response. In addition, the first
It is also possible to use the transmission path impulse response estimated by the transmission path impulse response estimation means as the transmission path impulse response estimation initial value of the second transmission path impulse response estimation means.

(5) Means for performing distortion removal processing of the received signal, weighting processing for maximizing the signal-to-noise ratio of the received signal, and phase control of a plurality of received signals provided in the antenna diversity receiver according to the present invention include: The transmission path impulse response of the transversal filter representation of the number of taps L estimated by the transmission path impulse response estimating means of the receiving unit connected to each of the plurality of receiving antennas provided in the antenna diversity receiver of the present invention is represented by L Multiplying means for multiplying -1 tap gain and a code determination result up to time k-1 by a code determining means provided in the antenna diversity receiver of the present invention, and a plurality of antennas of the present antenna diversity receiver Subtraction means for subtracting the output from the multiplying means from the reception signal at time k received at By comprising multiplying means for multiplying the gain for controlling the amplitude and phase of the force, it is possible to remove unnecessary signal components from each of the received signals received by the plurality of antennas and maximize the signal-to-noise ratio. Weighting and phase control can be realized.

(6) In this antenna diversity receiver, a portion serving as a digital signal processing unit, that is,
Transmission path impulse response estimation means provided in each of a plurality of reception units connected to a plurality of reception antennas, distortion removal processing of a plurality of reception signals by the plurality of reception antennas, and signal-to-noise of the reception signals Means for performing weighting processing to maximize the ratio and phase control processing of the received signal does not require the plurality of reception antennas, and the transmission path impulse response means and the distortion removal processing of the received signal; By using time-division means for performing weighting processing for maximizing the signal-to-noise ratio of the received signal and phase control processing for the received signal, the configuration of the antenna diversity receiver of the present invention can be easily and minimized. It can be configured with a limited number of signal processing units.

[0021]

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 from the receiving antenna, but it should be noted 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 received signal, a plurality of receiving antennas 10, 11, and 12 included in the receiver transmit transmission signals arriving on different propagation paths. To receive. In the first receiving unit 16, the received signal 13 received by the receiving 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 that is known in advance on the receiver side. The transmission path impulse response 118 is calculated using the sequence. The calculated transmission path impulse response 118 is input to the distortion removing unit 112 and the weighting and phase control unit 115. The received signal 13 and the sign determination output are also input to the distortion removing unit 112, and the distortion removing unit 112 removes a distortion component from the received signal 13 using the estimated transmission path impulse response 118 and the sign determination output 130. The received signal 121 whose distortion has been removed by the distortion removing means 112 is input to the weighting and phase control means 115, where 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 signals 14 and 15 received by the reception antennas 11 and 12, and input signals 125 and 126 to the addition means 127 are generated. All of the addition means input signals 124, 125, 126 from each antenna are simply added by the addition means to become an addition means output 128. The addition means output 128 is input to the sign judgment means 129 and the sign judgment result 130 is outputted. Using this code determination result 130, the information sequence is demodulated by the digital signal sequence demodulation means.

FIG. 2 illustrates a method of estimating a transmission channel impulse response when the received signal 22 includes a known signal sequence, and a method of estimating a transmission channel impulse response when the received signal 22 does not include a known signal sequence. FIG. In the TDMA communication system, communication is performed along a time axis 20 using a part of the time axis 20 called a slot 23, and a time allocated to itself is called a slot time 21. Only communication is performed. Generally, in order to distinguish between own slot 23 and another's slot, known signal sequence 24
Are added regularly. When the known sequence 24 is added to the received signal, the transmission path impulse response estimating means 2 is used at times 27, 28 and 29 when the known signal sequence ends.
At 12, the transmission path impulse response 213 is estimated. When the known signal sequence 24 exists, the transmission path impulse response estimation unit 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 path impulse response 21
3 is estimated. The estimated transmission path impulse response 23
Is generally represented by a vector, and the element of the vector, that is, the tap gain 2 according to the delay dispersion amount in the transmission path.
The numbers 14, 215, 216, 217 are determined. Also, in FIG. 2, the known signal sequence 2
When 4 is not added, since the slots 23 are all information sequences, the transmission path impulse response 213 cannot be easily estimated. In that case, blind estimation processing is performed, and at times 27, 28, and 29 after a certain time has elapsed from the time considered to be the beginning of the slot, all combinations of signal sequences that will be transmitted within that time are determined. A plurality of transmission candidate sequences 219, 220, 221 and 222 generated by the transmission candidate sequence generation unit 218 are successively passed through the pseudo transmission path response 223 having an appropriately given initial value, and within that time, The maximum likelihood sequence candidate is determined 226 by comparing with the received received signal sequence 22 and selecting a transmission candidate sequence that matches with the least error. Then, using the maximum likelihood sequence 227, the transmission path impulse response estimation means 2
At 28, a true transmission path impulse response 213 is gradually obtained.

FIG. 3 is a specific example for explaining how to use the estimated transmission path impulse response. A description will be given of one of the plurality of receiving antennas. Using a received signal 31 corresponding to a known signal sequence and a non-distorted signal sequence 33 of the known signal sequence among transmission signals received by the receiving antenna 30, a transmission channel impulse response Presumed. Estimated transmission path impulse response 3 expressed by multiple tap gains
5, among the tap gains 37, 38, 39, and 310 other than the tap gain 36 corresponding to the current processing time, the sign determination unit 328 determines the sign 329 up to one time before.
Is used for weighting. Then, the weighted results 312, 313, 314, 315 are added to the simple adder 33.
The result of addition 316 is subtracted from the received signal 32 by a subtractor 317. And subtracter output 31
8 is multiplied by the multiplier 319 with the 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 received signal received by each antenna, and all of them are added to the addition means 32.
Add by 6. The addition result 327 is input to the sign determination means 328, and the determination result 329 is used again for processing at the next time.

FIG. 4 shows an embodiment of a method of using an adaptive algorithm when estimating a transmission path impulse response. In general, there are two types of adaptive algorithms: sequential operation means and non-sequential operation methods. In view of this point, the transmission path impulse response estimating means 42 has a processing part 43 for performing a sequential calculation method and a processing part 44 for performing a non-sequential calculation method, and either one is used.
The inputs to the transmission path impulse response estimating means 42 are the received signal sequence 40 and the determination result from the code determiner (129 in FIG. 1) or the known signal sequence 41. Each is input to the sequential calculation method processing unit 44. Then, the transmission path impulse responses 418 and 419 estimated by the respective processing units 43 and 44 are output via the switch 45 as the estimation result 46 of the transmission path impulse response estimation unit 42. In addition, there are four ways to use the sequential calculation method 43 and the non-sequential calculation method 44. Among the received signal sequence 47, the known signal sequence 4
The method is applied to a time 48 when 10 is received, and to the time 49 when the information signal sequence 411 is received. The method 412 uses the transmission path impulse response 418 estimated by a sequential calculation method in both the section at time 48 and the section at time 49. 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 scheme 414 uses the transmission path impulse response 18 estimated by a sequential calculation method in the section of the time 48, does not perform adaptive estimation of the transmission path impulse response in the time 49, and does not estimate the transmission path impulse response in the time 48. The impulse response is fixedly used. × 42 in the figure
0 means that 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, and does not perform adaptive estimation of the transmission path impulse response in the time 49, but estimates the transmission path impulse in the time 48. Use the response fixedly. As described above, the configuration in which the adaptive transmission path impulse response is not estimated from the middle of the TDMA slot as in the method 414 or the method 415 is effective in mobile communication for low-speed mobile communication. Thus, the implementation of the receiver is simplified.

FIG. 5 shows an 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 estimation unit 52. The transmission path impulse response estimating means 52 receives the sign determination result 538 from the sign determining means 53 or a known signal sequence. Transmission path impulse response estimation means 52
The estimation results 512 to 518 estimated by
11 is input. Sign determining means 5 is connected to these multipliers.
The judgment results 538 from 3 are delayed in the past by the delay elements 545 to 551 and the judgment results 539 to 539 are obtained in the past.
43 is also input. The multiplier outputs 519 to 525 are input to the simple adder 526, and after all of them are added, the subtracters 528 subtract the received signals 51 from each other. The subtraction result 529 is multiplied by 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. The addition result 537 is input to the sign judgment unit 53 to perform sign judgment. It is. 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 in the subsequent time 553 when the information signal sequence 556 is received.
7 is used as the effective transmission path impulse response 558 in the section 553.

FIG. 6 shows an embodiment in which the proposed antenna diversity receiver has only one digital signal processing unit and uses signals received from each antenna in a time-division manner. The reception signal 66 selected by the switch 64 among the reception signals received by the plurality of reception antennas 60 to 63 is input to the reception unit 65. There is only one receiving unit 65 for M receiving antennas. The selected reception signal 66 is input to the transmission path impulse response estimation means 67 and the reception signal distortion removal means 621. The estimated transmission channel impulse response 68 estimated by the transmission channel impulse response estimation means 67 is sent to the transmission channel impulse response storage unit 69. The transmission path impulse response storage unit 69 has storage areas 610 to 6131 specific to the reception antenna selected by the switch 64, and the estimated transmission path impulse response 68 is stored in storage areas 610 to 613 corresponding to the selected reception antenna. It is memorized. In addition, from the transmission path impulse response storage unit 69, a storage area 610 corresponding to the reception antenna selected by the switch 620 is stored.
Transmission line impulse response 619 stored from 613
Is read and supplied to the received signal distortion removing means 621 and the weighting and phase control means 622. In the distortion removing unit 621, a signal 623 obtained by removing distortion from the received signal 66 received by the selected receiving antennas 60 to 63 is input to the weighting and phase control unit 622. The weighting and phase control means 622 performs weighting and phase control of the received signal so as to maximize the signal-to-noise ratio of the received signal, and outputs a signal 624 to be input to the accumulator 625. In the accumulator 625, each of the receiving antennas 60 to 6
3 has the function of adding all the signals after the distortion removal and the weighted phase control are performed on the signal received in step 3. The output 626 of the accumulator is sent to the sign judgment means 627, where sign judgment is performed. The code determination result 628 is demodulated by the digital signal sequence demodulation section 629 as transmission information. The reason why the signal line 68 connecting the transmission path impulse response estimating means 67 and the transmission path impulse response storage unit is bidirectional is that the proposed antenna diversity receiver sequentially tracks the estimation of the transmission path impulse response. This is to take into account the case where it is made to occur. In other words, the transmission line impulse response once stored is read again by the transmission line impulse response estimation means, 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
3 are weighted gains 710-712 for controlling the amplitude and phase of each received signal.
And the results 713 to 715 are simply added to the adder 7
16 is added. The addition result 717 is a sign decision unit 718
, And the sign is determined. Sign determination result 71
9 and the sign determiner input 717 are obtained by a subtractor 720, and the gain 7 is adaptively determined based on the error 721.
23 is required. Then, the gain 723 is based on the reception signals 74 to 7 received by the reception antennas 71 to 73 at the next time.
6, gains 710 to 712 for controlling the amplitude and phase.

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

FIG. 9 shows a maximum likelihood sequence estimator (MLSE: Maximum L).
FIG. 2 is a diagram illustrating an example of a conventional combined diversity receiver using an ikelihood sequence estimator). Received signals 93 to 95 received by a plurality of receiving antennas 90 to 92
Is calculated by the estimated transmission signal sequence 930 estimated in the MLSE process 929 and the estimated transmission path impulse responses 915 to 917 controlled by the tap gain adaptive control means 932 so that the estimated received signals 99 to 911 are transformed by the transversal filters 912 to 914. Generated. The generated estimated received signals 99 to 911 are input to subtractors 96 to 98, and error signals 918 to 920 from the received signals 93 to 95 are generated. The generated error signals 918 to 920 are supplied to square calculation means 921 to 923, respectively. Outputs 924 to 926 of the multiplication operation means 921 to 923 are added to an adder 927.
And all are added. The addition result 928 is ML
The signal is sent to SE processing section 929 and used for estimating a transmission signal sequence. The branch metric 931 used for selecting 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 of the transversal filters 912 to 914 at the next time is input.
5 to 917 are required. 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 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 signal components 107 to 109 corresponding to the multipath propagation distortion are subtracted by the subtractor 1010. ~
Subtract at 1012. Received signals 1019 to 1021 from which the influence of multipath propagation distortion has been removed are input to multipliers 1022 to 1024 to perform weighting and phase control so as to maximize the signal-to-noise ratio. The multiplier multiplies the gains 1025 to 1027 by the received signals 1019 to 1021, and outputs the outputs 1028 to 1030 to the adder 1031. Output 1032 of adder 1031
Are supplied to a sign determiner 1033 and a subtractor 1038 for generating an error signal 1035. Sign judging device 10
The result 1034 determined by the sign 33 is an error signal 1035
Is supplied to a subtractor 1038 for generating a signal, and an error 1035 with respect to the input signal 1032 of the sign determiner 1033 is obtained. The error signal 1035 is the tap gain adaptive control means 1
036, and a tap gain 1037 at the next time is obtained. Also, the output 1034 of the sign determination unit 1033
Are sent to the backward filters 1013 to 1015 to generate signal components 107 to 109 for removing the multipath distortion components included in the received signals 104 to 106. As described above, the configuration of the antenna diversity receiver of the present invention is greatly different from that of the antenna diversity receiver using the conventional waveform equalization technique (FIGS. 7 to 9). This series of received signal processing procedures is expressed by a mathematical formula. Received signal rk _{, i} 104-1 received at the i-th receiving antenna at time k
Considering relative 06, the input signal r _k, i from 1,028 to 1,030 of adder 1031 in Figure ^{_{10, r'k, i = h *}} o, i {r k, i -h i, t x (k- 1) It becomes｝. Here, _{ho, i} is a direct wave component of the estimated transmission path impulse response. h _i : Estimated transmission channel impulse response vector composed of components obtained by removing h _{o, i} from the estimated transmission channel impulse response. h _i = [h _{1, i} , h _{2, i} ,..., h _{L-1, i} ] ^t * L is the total tap number of the estimated transmission path impulse response. x (k-1): a determination result vector including a result determined by the code determiner 1033 until 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 sign determination unit 1033 at time j. (*): Means complex conjugate. (T): means transposition. It is.

Then, r ′ _{k, i} is obtained for each of the received signals received by each of the receiving antennas.
Performs a simple addition.

FIG. 11 is a block diagram for explaining a post-delay detection combining diversity receiver. The post-delay detection combining diversity receiver has a very simple configuration and is the most easily implemented combining diversity receiver system. Received signal 1104 received by a plurality of receiving antennas 1101 to 1103
To 1106 are differentially detected (differentially decoded) by delay detectors (differential decoders) 1129 to 1131 connected to the respective antennas. Specifically, received signals 1104 to
1106 denotes multipliers 1119 to 1121 and delay element 110
7-1109. Delay element output 1110-1
Numeral 112 denotes complex conjugate signals 1116 to 1118 at complex conjugate elements 1113 to 1115, and multipliers 1119 to 11
21. Multiplication results 1122-1 of received signals 1104-1106 and complex conjugate signals 1116-1118
124 are all added by an adder 1125, and the addition result 1126 is supplied to a sign determination unit 1127. The code determination result 1128 in the code determiner 1127 is a demodulated signal sequence.

FIG. 12 is a command showing the configuration of a conventional antenna diversity receiver for estimating the transmission path impulse response by the correlation calculating means and performing an in-phase combining diversity receiver from the result. Multiple receiving antennas 1200
The received signals 1203 to 1205 received by
Multipliers 1210 to 1212 and correlation operation means 1206
To 1028. Correlation calculation means 1206 to 12
08 are output from multipliers 1210-1
212 and multiplied by the received signals 1203 to 1205. The multiplication results 1213 to 1215 are added to an adder 121.
At 6 all are added. The sign result of the addition result 1217 is judged by a sign judgment unit 1218, and the sign judgment result 1219 is obtained.
Is output. Further, correlation calculation means 1206-1208
The correlation sequence 1209 required for the correlation calculation performed in step (1) is supplied from the correlation sequence generation unit 1223.

FIG. 13 shows a bit error rate characteristic for explaining the effect of the four-branch antenna diversity receiver of the present invention. The vertical axis in the figure is the bit error rate (BE
R) 1300, and the horizontal axis in the figure indicates the amount of multipath delay (τ / T) 1301 in the radio channel. △ in the figure
Reference numeral 1302 denotes an in-phase combining diversity receiver whose configuration shown in FIG. 11 is simple and easy to realize. The characteristics of the combining diversity receiver after differential detection are shown, and the 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), the characteristic curve 1304 and E _b / N _o = 10.
The 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 method can achieve a good bit error rate in all multipath propagation environments.

FIG. 14 shows a bit error rate characteristic for explaining the effect of the two-branch antenna diversity receiver of the present invention. The vertical axis in the figure is the bit error rate (BE
R) 1400, and the horizontal axis of the figure indicates the amount of multipath delay (τ / T) 1401 in the wireless propagation path. △ in the figure
A mark 1402 indicates the characteristic of the post-delay detection combining diversity receiver, which is an in-phase combining diversity receiver whose configuration shown in FIG. 11 is simple and easy to realize, and a mark 1403 indicates the characteristic of the antenna diversity receiver of the present invention. I have. In the figure, E _b / N _o = 5.0 (dB) is used as an evaluation parameter.
And E _b / N _o = 10.0
The characteristic curve 1405 at (dB) and E _b / N _o = 1
A 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 method can achieve a good bit error rate in all multipath propagation environments.

[0036]

As described above in detail, according to the antenna diversity receiver of the present invention, it is possible to eliminate the influence of the multipath propagation distortion that occurs when the received signal is specific to the propagation environment of the mobile communication and that the reception gain is increased. Can be simultaneously improved. This is because, in the conventional combining diversity receiver after delay detection and the combining diversity receiver based on the correlation operation, the delayed arrival signal component was treated as noise, so that the receiving characteristic was greatly deteriorated. The effective use of the incoming signal component greatly improves the reception characteristics. In addition, a diversity receiver using a conventional decision feedback equalizer or a diversity receiver using a maximum likelihood sequence estimator taking into account the influence of multipath propagation distortion has a problem in that the configuration becomes complicated. However, it can be realized with a simpler configuration than these, and is very effective especially for wireless communication with a low-speed moving object.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an outline of a configuration of an antenna diversity receiver according to a proposed method.

FIG. 2 is a diagram for explaining a transmission path impulse response estimation method when a known signal sequence is included in a received signal, and a transmission path impulse response estimation method when a known signal sequence is not included in the received signal.

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

FIG. 4 is a diagram showing an embodiment of a method of using an adaptive algorithm when estimating a transmission path 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 embodiment in a case where the proposed antenna diversity receiver shown in FIG. 1 uses one digital signal processing unit and uses it in a time-division manner.

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 a configuration of a conventional post-delay detection combining diversity receiver.

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

FIG. 13 is a diagram of a bit error rate characteristic showing an effect of the 4-branch antenna diversity receiver using the present invention shown in FIG. 1;

FIG. 14 is a diagram of a bit error rate characteristic showing an effect of the two-branch antenna diversity receiver using the present invention shown in FIG. 1;

[Description of Signs] 10, 11, 12 Receiving unit (antenna) 16, 17, 18 Receiving unit (receiving unit) 19, 110, 111 Estimating unit (transmission path impulse response estimating unit) 112, 113, 114 Signal processing unit ( (Distortion removing means) 127 combining means (adding means) 129 sign determining means 131 demodulating means (digital signal sequence demodulating means)

Claims (1)

(57) [Claims] 1. A receiving section for receiving a digitally modulated signal, an estimating section for estimating a transmission path impulse response from a received signal received by the receiving section, and a transmission path impulse response estimated by the estimating section. A signal processing unit that performs phase control of the received signal by removing transmission line distortion from the received signal using a plurality of receiving units; a combining unit that combines an output signal from the receiving unit; A code determination unit that performs a code determination based on an output signal from the combining unit; and a demodulation unit that demodulates an output signal from the code determination unit.The signal processing unit is estimated by the estimation unit. Tap
Transmission path impulse of transversal filter expression of several L
L-1 tap gains other than time k in the
Sign determination result up to time k−1 by the sign determination unit;
Product means for multiplying each of the plurality of antennas
From the received signal at time k received by
Subtraction means for removing distortion by subtracting the output,
And the output from the subtraction means
k by multiplying the L-th tap gain of k
An antenna diversity receiver comprising: a weighting unit that corrects a phase of a communication signal .