CN107181512B - Multi-user receiving method aiming at signal number overload - Google Patents

Multi-user receiving method aiming at signal number overload Download PDF

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CN107181512B
CN107181512B CN201710444775.1A CN201710444775A CN107181512B CN 107181512 B CN107181512 B CN 107181512B CN 201710444775 A CN201710444775 A CN 201710444775A CN 107181512 B CN107181512 B CN 107181512B
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CN107181512A (en
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李钊
丁嘉敏
赵林靖
肖丽媛
丁汉清
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Xidian University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0452—Multi-user MIMO systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H04B1/7097—Interference-related aspects
    • H04B1/7103—Interference-related aspects the interference being multiple access interference
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
    • H04B7/0802—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using antenna selection
    • H04B7/0817—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using antenna selection with multiple receivers and antenna path selection
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
    • H04B7/0837—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using pre-detection combining

Abstract

The invention belongs to the technical field of wireless communication, and discloses a multi-user receiving method aiming at signal number overload and application thereof, wherein the number of effective signals at a receiving end is reduced to the number of receiving antennas by utilizing the interaction between signals; designing a plurality of zero forcing receiving filter matrixes according to countable effective interference space characteristics, and respectively filtering and judging and reconstructing mixed signals; subtracting the output of the judgment reconstruction module from the original received mixed signal and passing through a protection module; performing secondary filtering by using the same zero-forcing filter matrix, and judging a received symbol by comparing filtering outputs; the serial interference cancellation method is used to cancel the effect of the decoded symbols on the reception of the remaining components of the received mixed signal until all of the transmitted data is recovered. The invention recovers all the transmitted symbols under the condition that the number of the received signals is overloaded but the space of the effective interference state can be counted, and improves the number of the concurrent communication users supported by the system.

Description

Multi-user receiving method aiming at signal number overload
Technical Field
The invention belongs to the technical field of wireless communication, and particularly relates to a multi-user receiving method aiming at signal number overload and application thereof.
Background
With the rapid development of wireless communication technology and the increase of link density of communication links, the capacity of communication systems needs to be increased to meet the increasing demand of user data transmission. When spectrum resources are limited, in order to improve communication service quality and the number of users accommodated by a system, a Multiple-Input Multiple-Output (MIMO) technology is a breakthrough in the field of wireless communication in recent years, and MIMO utilizes space-domain resources, thereby significantly improving system spectrum efficiency. In the research of MIMO, single-User MIMO cannot meet the rapidly growing demands of users, and multi-User MIMO (MU-MIMO) has better practical significance. In the existing MU-MIMO research, the Degree of freedom (DoF) of the receiver is a large factor affecting the signal receiving capability of the receiver, and when the number of receiver antennas is smaller than the number of signals to be solved, i.e., the number of received signals is overloaded, the receiver does not have enough Degree of freedom to distinguish all signal components. The conventional Zero Forcing (ZF) receiving method requires that the number of receiver antennas is equal to or greater than the number of data streams transmitted independently, i.e. the conventional Zero Forcing is not applicable when the signal is overloaded. The number of receive antennas is an important factor that limits the receiver's ability to receive signals and is also a major factor that limits the system capacity. For receiving Multiple concurrent signals, Interference Alignment and Cancellation (IAC) is a method capable of recovering Multiple data in a system, and the method is applied to a Cognitive MIMO (Cognitive Radio Multiple-Input Multiple-Output, CR-MIMO) system, and uses Interference Alignment (IA) to reduce the dimension of a signal, and then uses Interference Cancellation (IC) to cancel Interference, but requires cooperation between receivers. The recovery of the signal by the uniform filtering (MatchedFilter, MF) is not limited by the number of antennas of the receiver, but the interference cannot be eliminated, so that when the interference is strong, the data transmission performance is greatly influenced. Although a scheduling algorithm may also be used to select a group of users from a plurality of users to transmit data to a receiver, users that are not scheduled cannot perform information transmission. When the electromagnetic waves exhibit a mutually beneficial superposition effect in free space, the intensity of the superposed signal is increased compared to each individual waveform; if the two electromagnetic waves weaken each other, the superimposed effect is a reduction in signal strength. Therefore, superposition of Multiple Radio Frequency (RF) signals can be equivalent to an electromagnetic wave, and the idea can be used for novel multi-user receiving method design.
In summary, the problems of the prior art are as follows: conventional zero forcing reception requires that the number of receiver antennas be no less than the constraint on the number of signal components to be resolved.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a multi-user receiving method aiming at signal number overload and application thereof.
The invention is realized in such a way that a multi-user receiving method aiming at signal number overload comprises the following steps:
(1) regarding a part of solvable signals as expected signals, regarding the overall effect of the rest signals as equivalent interference by utilizing the interaction between the signals, and reducing the number of the signals needing to be processed by a receiving end to the number of receiving antennas;
(2) designing a plurality of zero forcing receiving filter matrixes according to countable equivalent interference space characteristics, dividing the received mixed signals into a plurality of branches, and filtering and judging and reconstructing the mixed signals of each branch by adopting the zero forcing receiving filter matrixes; each filter vector f in the zero-forcing receiving filter matrix Gn,n∈S：
Figure BDA0001320956240000021
G comprises NR-1 column vectors, conjugate transpose of G to GHG is common to
Figure BDA0001320956240000022
A possible combination, of which only one is consistent with the actual equivalent interference spatial signature;
(3) subtracting the original received signal from the reconstructed signal, comparing the subtracted signal with a preset noise threshold, if the subtracted signal is smaller than the threshold, adding an offset signal, otherwise, not processing the offset signal, then performing secondary filtering on each branch, comparing the filtering output intensity of each branch to determine a correct branch, and judging a received symbol of the branch after the primary filtering;
(4) using serial interference elimination method to eliminate the influence of decoded symbol on receiving residual component of received mixed signal, and using serial interference elimination method to carry decoded NR-1 symbol
Figure BDA0001320956240000031
The receiver removes the recovered signal from the set N and updates the set N; by repeating the above process for the remaining mix signals,until all the transmitted data is restored.
Further, the multi-user receiving method aiming at the signal number overload comprises the following steps:
in a first step, each transmitter is configured with NTRoot transmitting antenna, NTMore than or equal to 2, adopting a wave beam forming transmitting mode to transmit one path of data, and estimating channel state information h between the transmitter k and the receiver by the transmitter kkWhere K is 0,1, K-1, transmitter K being in accordance with hkComputing a precoding vector pkTransmitter k will be hkReporting the modulation mode information to a receiver together with the modulation mode information, wherein the receiver acquires the modulation mode information of each channel of transmitted data and takes L as the maximum modulation order in the used modulation modes, and the number K of signals transmitted by K transmitters is greater than the number N of antennas of the receiverRThe transmission power of each transmitter is PT；
Secondly, the receiver receives the mixed signal y:
Figure BDA0001320956240000032
wherein x iskRepresenting data transmitted by a transmitter k, n representing additive white gaussian noise; the signal transmitted by the transmitter k shows a spatial characteristic r at the receiving endk＝hkpk(ii) a And forming a set N by all signals to be received by the receiver, wherein the number of the signals contained in the set N is K, M represents the number of elements in the set N, and M is equal to K. Comparing M with NRIf M is less than or equal to NRZero forcing receive filter matrix W for receiver designZFFiltering the mixed signal y directly and outputting M decision symbols;
thirdly, if M is more than NRThe receiver randomly selects N in the set NR-1 signal constitutes a set S of signals to be solved,
Figure BDA0001320956240000041
the rest signals in the set N form an interference set I; by using the interaction between interferences, M- (N)R-1) overall effect of interference as one path of equivalent interference, equivalent interferenceThe spatial characteristics of the disturbance are
Figure BDA0001320956240000042
All possible rThe space characteristic set C forming equivalent interference exists in a plurality of combination situations after the transmitted symbols are modulated, and the space characteristic set C forms equivalent interference at a given hjAnd pjOn the premise that the set C contains
Figure BDA0001320956240000043
Each element, if the modulation constellation has origin symmetry, is included in the set C
Figure BDA0001320956240000044
A seed interference spatial signature;
fourthly, the receiver firstly resolves the spatial characteristic r of the signal to be resolvedn＝hnpnN ∈ S and the spatial signature r of the equivalent interferencePerforming Schmidt orthogonalization and designing each filter vector f in a zero-forcing receiving filter matrix Gn,n∈S：
Figure BDA0001320956240000045
G comprises NR-1 column vectors, conjugate transpose of G to GHG is common to
Figure BDA0001320956240000046
A possible combination, of which only one is consistent with the actual equivalent interference spatial signature;
in a fifth step, the receiver divides the mixed signal y into
Figure BDA0001320956240000047
Then using the fourth step
Figure BDA0001320956240000048
Each filtering matrix G respectively filters each mixed signal, judges the filtered signals and reconstructs the signals by combining channel state information, and the signal reconstruction is carried out on the signals and the actual equivalent interference space characteristics IThe resulting branch is obtained as a reconstructed signal
Figure BDA0001320956240000049
Wherein
Figure BDA00013209562400000410
Is N R1 transmitter-to-receiver channel matrix for the signal to be solved,
Figure BDA00013209562400000411
indicating that the transmitter is to process the data
Figure BDA00013209562400000412
The precoding matrix of (a) is determined,
Figure 2
for the correct data symbol vector obtained by the judgment, the reconstructed signal of the branch inconsistent with the actual equivalent interference space characteristic is
Figure BDA00013209562400000414
Wherein
Figure 1
Is a data symbol vector obtained by erroneous decision affected by interference;
sixthly, each branch circuit reconstructs the signal
Figure BDA0001320956240000051
Or
Figure BDA0001320956240000052
Subtracting the received mixed signal y respectively, comparing the subtracted output with a preset threshold Th, if the subtracted output is smaller than Th, adding a bias signal to the output, otherwise, directly outputting the output to a post-stage for processing without processing;
seventhly, each branch adopts G which is the same as the G for the first filtering to carry out second filtering on the signal output in the sixth step, the output of each branch is compared, and the branch with the minimum signal intensity is the branch with the same equivalent interference spatial characteristicsJudging and outputting N by adopting the filtering result of the first time in the fifth stepR-1 received symbol
Figure BDA0001320956240000053
Eighthly, the receiver utilizes the recovered data symbols and the channel state information to reconstruct the signal, and then adopts serial interference elimination to carry the decoded NR-1 symbol
Figure BDA0001320956240000054
Is removed from the mixed signal y, the receiver removes the recovered signal from the set N, updates the set N, and returns to the third operation.
Further, the third step is that when the number of the sending signals is more than the number N of the receiving antennasRWhen in use, the interaction between signals is firstly utilized to obtain the overall effect of a plurality of interferences, thus realizing the space dimension reduction of the signals to be processed and reducing the number of the signals to be processed of the receiver to NRAnd then, receiving the multi-user signals by zero forcing and serial interference elimination.
Further, when the modulated symbols have multiple conditions, which causes multiple conditions of the spatial characteristics of equivalent interference generated by interaction between signals, corresponding zero-forcing receiving filter matrixes G can be designed according to different equivalent interference spatial characteristics, the received mixed signals y are divided into multiple paths, different G are adopted to respectively filter and reconstruct each path of mixed signals, the reconstructed result is subtracted from the original mixed signals y, G which is the same as the first filtering is adopted to carry out second filtering on the result, branches with consistent equivalent interference spatial characteristics are judged according to the output size comparison result, and correct received symbols are recovered.
Further, if a branch erroneously reconstructs a signal identical to the original mixed signal and only noise remains in the output subtracted from the received mixed signal, a protection module for judging whether the branch has a signal is added before each branch performs the second filtering, the output subtracted from the received mixed signal is compared with a preset threshold, and if the output subtracted from the branch is smaller than the threshold, a bias signal needs to be added, so that the branch can still be distinguished from the branch identical to the equivalent interference spatial characteristic after the branch is subjected to the second filtering.
Furthermore, when the number of antennas configured for each transmitter is different, the data transmission mode of each transmitter is different, and when the number of transmitting antennas is NTWhen the data is equal to 1, the transmitter transmits one path of data in an omnidirectional transmission mode; h corresponding to transmitter with number of transmitting antennas equal to 1kpkShould be replaced by hkThe spatial signature observed by the receiver of the signal transmitted by the transmitter is rk＝hk(ii) a Number of antennas N when transmittingTAnd when the data is more than or equal to 2, the transmitter transmits one path of data by adopting a beam forming transmission mode.
Another object of the present invention is to provide a mimo system using the multiuser receiving method for an overload in the number of signals.
The invention has the advantages and positive effects that: the traditional zero forcing receiving method requires that the number of receiving antennas is not less than the number of signals to be solved, so that the traditional zero forcing receiving method cannot be adopted for receiving when the number of signal components is greater than the number of receiving antennas. The invention utilizes the integral effect shown by a plurality of interference interactions, and when the number K of signals to be solved is more than the number N of antennas of the receiverRIn the case of (1), K- (N) is selectedR-1) using the signals as interference, and using the interaction between the interference to take the overall effect as one path of equivalent interference, thereby reducing the number of signals to be processed by the receiver to NRIt is possible to recover an arbitrary number of transmission data and obtain good data rate performance in the case where the number of reception antennas is not less than 2.
The invention carries out twice filtering on signals, carries out judgment reconstruction on the first filtering result of the original mixed signal, and carries out subtraction with the original mixed signal, only the interference which can be eliminated by a filtering matrix is left at the output of the branch with the equivalent interference space characteristic, only the noise is left after the second filtering, the output of the inconsistent branch can not be filtered, the output after the second filtering has signal components, determines the branch with the equivalent interference space characteristic consistency by comparing the filtering output of each branch, and judges the receiving symbol of the branch after the first filtering.
The invention adopts the serial interference elimination technology, eliminates the influence of the decoded signal on the recovery of other signals by a receiver by subtracting the recovered signal from the received mixed signal, and then combines zero forcing reception to recover the symbols sent by all transmitters, aiming at breaking through the constraint that the number of the antennas of the receiver is not less than the number of the components of the signal to be solved in the traditional zero forcing reception, and realizes the dimension reduction of the signal space to be processed by utilizing the overall effect shown after the interaction of a plurality of interferences, thereby recovering the signal as much as possible by using the limited receiving antenna.
Drawings
Fig. 1 is a flowchart of a multi-user receiving method for overloading the number of signals according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of a multi-user uplink communication scenario model provided in an embodiment of the present invention.
Fig. 3 is a flowchart of a multi-user receiving method for receiving an overload number of signals according to an embodiment of the present invention.
Fig. 4 is a block diagram of a single-stage receiver of the multi-user receiving method for overloading the number of received signals according to the embodiment of the present invention.
Fig. 5 is a diagram of a complete receiver structure of the multi-user receiving method for receiving an overload number of signals according to the embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The following detailed description of the principles of the invention is provided in connection with the accompanying drawings.
As shown in fig. 1, the multi-user receiving method for signal number overload according to the embodiment of the present invention includes the following steps:
s101: reducing the number of effective signals of a receiving end to the number of receiving antennas by utilizing the interaction between the signals;
s102: designing a plurality of zero forcing receiving filter matrixes according to countable effective interference space characteristics, and respectively filtering and judging and reconstructing mixed signals;
s103: subtracting the output of the decision reconstruction module from the original received mixed signal, passing through a protection module, performing secondary filtering by using the same zero-forcing filter matrix, and comparing the filtered outputs to decide a received symbol;
s104: and eliminating the influence of the decoded symbols on the reception of the residual component of the received mixed signal by using a serial interference elimination method, and repeating the process on the residual mixed signal until all the transmitted data are recovered.
The application of the principles of the present invention will now be described in further detail with reference to the accompanying drawings.
FIG. 2 is a system model showing a communication system consisting of three transmitters and one receiver, the receiver being configured with NREach transmitter is configured with N receiving antennasTIn the embodiment of the present invention, binary phase-shift keying (BPSK) is used for all transmitters, that is, the maximum modulation order L is 2, and when the modulation schemes used by different transmitters are different, L is the maximum modulation order in all modulation schemes.
As shown in fig. 3, fig. 4 and fig. 5, the receiving method of the present invention specifically includes the following steps:
in a first step, each transmitter is configured with NTRoot transmitting antenna, NTMore than or equal to 2, all adopt the transmission mode of the beam forming to send a route of data, the transmitter k estimates the channel state information h between it and the receiverkWhere K is 0,1, K-1, transmitter K being in accordance with hkComputing a precoding vector pkTransmitter k will be hkReporting the modulation mode information to a receiver together with the modulation mode information, acquiring the modulation mode information of each path of transmitted data by the receiver, and taking L as 2 as the maximum modulation order in the used modulation modes, wherein the number K of signals transmitted by K transmitters is more than the number N of antennas of the receiverREach ofThe transmitting power of the transmitter is PTIf all transmitters are supposed to transmit according to the main characteristic mode, the precoding vector is selected as a main right singular vector of the channel matrix and corresponds to the maximum singular value of the channel matrix, and each path of transmission is modulated in a BPSK mode;
and secondly, forming a set N by all signals of the receiving end, wherein the number of the signals contained in the initial state set N is 3, M represents the number of elements in the set N, and M is 3 at the moment. Comparing M with the number of receiving antennas N R2, M > NR；
Thirdly, the receiver randomly selects N in the set NR-1 ═ 1 signal h0p0x0Forming a signal set S to be solved, and combining the rest 2 signals h in the set N1p1x1And h2p2x2Forming an interference set I, using the interaction between the interferences to take the overall effect of the 2 interferences as an equivalent interference, wherein the spatial characteristic of the interference state is r＝h1p1x1+h2p2x2All possible rThe set of spatial characteristics C constituting the equivalent interference, the transmitted symbols are modulated in 4 cases, so at a given hjAnd pjIn the case of (j ═ 1,2), 4 cases are shared in total, and in consideration of the spatial symmetry of the modulation constellation, 2 interference state spatial features are shared in C; fourthly, the receiver firstly resolves the spatial characteristic r of the signal to be resolved0＝h0p0State space characteristics r produced by the overall effect of interacting with disturbancesPerforming Schmidt orthogonalization, and obtaining the filter vector in the zero forcing receiving filter matrix G by using the construction method of the zero forcing receiving filter matrix G
Figure BDA0001320956240000091
In addition, r isWith two possible values r1、r2Then g is0There are two, only one of which coincides with the actual transmitted symbol situation;
in a fifth step, the receiver first divides the mixed signal y into
Figure BDA0001320956240000092
Way, then 2 filter matrixes designed in the third step are adopted
Figure BDA0001320956240000093
And
Figure BDA0001320956240000094
filtering each mixed signal, judging the filtered signal and reconstructing the signal by combining the channel state information, and obtaining the correct reconstructed signal by the branch consistent with the actual equivalent interference space characteristic
Figure BDA0001320956240000095
Reconstruction of interference contributions from non-uniform branches
Figure BDA0001320956240000096
Sixthly, each branch subtracts the reconstructed signal from the received mixed signal y
Figure BDA0001320956240000097
Or
Figure BDA0001320956240000098
Comparing the output with a preset threshold Th, and outputting a mixed signal a of the branch with the same equivalent interference space characteristicsi＝h1p1x1+h2p2x2+ n' is greater than Th, then output directly
Figure BDA0001320956240000099
n' represents the updated noise, if the comparison result of the inconsistent branch is less than the noise threshold, the offset is added to the branch, if not, the offset is directly output to obtain
Figure BDA00013209562400000910
Seventh, each branch mixes the signals
Figure BDA00013209562400000911
Or
Figure BDA00013209562400000912
Using the same filtering as the first filtering
Figure BDA00013209562400000913
And
Figure BDA00013209562400000914
performing secondary filtering, comparing the output of each branch, wherein the branch with the minimum signal amplitude (similar to pure noise) is the branch with the same equivalent interference spatial characteristics,
the decision output of the filtering result of the first time in the fifth step can be adopted
Figure BDA00013209562400000915
Eighthly, the receiver uses the decoded symbols and the channel information to reconstruct the signal, and then uses serial interference elimination to decode 1 symbol in the mixed signal y
Figure BDA00013209562400000916
The corresponding signal is removed, the number of signals processed by the receiver is reduced, the receiver deletes the decoded signal from the set N, and returns to the third step of operation by assigning the set N-S to the N update set N.
When the number of antennas configured for each transmitter is different, the data sending mode of each transmitter is different, and when the number of transmitting antennas is NTWhen 1, the transmitter sends one path of data in an omnidirectional transmission mode, and at the moment, the number of the transmitting antennas is equal to 1, and h corresponding to the transmitterkpkShould be replaced by hkThe spatial characteristic of the corresponding transmitted signal at the receiving end of the transmitter is rk＝hk(ii) a Number of antennas N when transmittingTAnd when the data is more than or equal to 2, the transmitter transmits one path of data by adopting a beam forming transmission mode.
FIGS. 4 and 5 show a specific receiver architecture of the present invention, illustrating the present inventionEmbodiment 1 of the invention the operational procedures of filtering reception, successive interference cancellation and signal recovery. Fig. 4 is a specific implementation of the first stage recovered signal of fig. 5. FIGS. 4 and 5 first begin with x0As the expected data to be solved and the rest signals as interference, according to the fifth step, the receiver divides the received mixed signal y into two paths and respectively adopts a zero forcing receiving filter matrix
Figure BDA0001320956240000101
And
Figure BDA0001320956240000102
filtering and judging reconstruction are carried out on y; according to the sixth step, the reconstructed signal is subtracted from the original mixed signal y and is compared with a threshold Th, and whether the output result needs to be increased with bias or not is judged according to the comparison result; according to the seventh step, the outputs of the branches after the second filtering are compared, the first filtering results of the branches with the same equivalent interference space characteristics are selected for judgment and output
Figure BDA0001320956240000103
The first level decoding process ends. FIG. 5 according to an eighth step
Figure BDA0001320956240000104
Feeding back to the receiver, decoding by successive interference cancellation
Figure BDA0001320956240000105
Corresponding signal
Figure BDA0001320956240000106
Is removed from the received mix signal y. Finally, when the number of signals to be solved does not exceed the number of antennas of the receiver, designing a zero forcing receiving filter matrix WZFRestore and output
Figure BDA0001320956240000107
And
Figure BDA0001320956240000108
when the number of antennas configured for each transmitter is different, the data sending mode of each transmitter is different, and when the number of transmitting antennas is NTWhen 1, the transmitter sends one path of data in an omnidirectional transmission mode, and at the moment, the number of the transmitting antennas is equal to 1, and h corresponding to the transmitterkpkShould be replaced by hkThe spatial signature observed by the receiver of the signal transmitted by the transmitter is rk＝hk(ii) a Number of antennas N when transmittingTAnd when the data is more than or equal to 2, the transmitter transmits one path of data by adopting a beam forming transmission mode.
The fifth step of the invention is that when the number K of the transmitted signals is larger than the number N of the receiving antennasRFirst, K- (N) is usedR-1) the overall effect of the interference interaction is taken as one path of equivalent interference, so that the number of signals to be processed at the receiving end is reduced to NRThen, the zero forcing and serial interference elimination are adopted to receive the multi-user data step by step; the invention designs a corresponding zero forcing receiving filter matrix G according to different equivalent interference space characteristics, divides a received mixed signal y into multiple paths, adopts different G paths to respectively carry out filtering and decision reconstruction on each path y, leads the result of the subtraction of the original mixed signal y and the reconstructed signal to firstly pass through a protection module and then carry out secondary filtering, determines branches with consistent equivalent interference space characteristics through the size comparison of the filtering output of each branch, and decides the received symbol after the first filtering of the branch.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (5)

1. A multi-user receiving method for signal number overload, wherein the multi-user receiving method for signal number overload comprises:
(1) regarding a part of solvable signals as expected signals, regarding the overall effect of the rest signals as equivalent interference by utilizing the interaction between the signals, and reducing the number of the signals needing to be processed by a receiving end to the number of receiving antennas;
(2) designing a plurality of zero forcing receiving filter matrixes according to countable equivalent interference space characteristics, dividing the received mixed signals into a plurality of branches, and filtering and judging and reconstructing the mixed signals of each branch by adopting the zero forcing receiving filter matrixes; each filter vector f in the zero-forcing receiving filter matrix Gn,n∈S：
Figure FDA0002693338630000011
G comprises NR-1 column vectors, conjugate transpose of G to GHG is common to
Figure FDA0002693338630000012
A possible combination, of which only one is consistent with the actual equivalent interference spatial signature;
(3) subtracting the original received signal from the reconstructed signal, comparing the subtracted signal with a preset noise threshold, if the subtracted signal is smaller than the threshold, adding an offset signal, otherwise, not processing the offset signal, then performing secondary filtering on each branch, comparing the filtering output intensity of each branch to determine a correct branch, and judging a received symbol of the branch after the primary filtering;
(4) using serial interference elimination method to eliminate the influence of decoded symbol on receiving residual component of received mixed signal, and using serial interference elimination method to carry decoded NR-1 symbol
Figure FDA0002693338630000013
The receiver removes the recovered signal from the set N and updates the set N; repeating (1) to (4) on the residual mixed signals until all the transmission data are recovered;
the multi-user receiving method aiming at the signal number overload comprises the following steps:
first step ofEach transmitter is configured with NTRoot transmitting antenna, NTMore than or equal to 2, adopting a wave beam forming transmitting mode to transmit one path of data, and estimating channel state information h between the transmitter k and the receiver by the transmitter kkWhere K is 0,1, K-1, transmitter K being in accordance with hkComputing a precoding vector pkTransmitter k will be hkReporting the modulation mode information to a receiver together with the modulation mode information, wherein the receiver acquires the modulation mode information of each channel of transmitted data and takes L as the maximum modulation order in the used modulation modes, and the number K of signals transmitted by K transmitters is greater than the number N of antennas of the receiverRThe transmission power of each transmitter is PT；
Secondly, the receiver receives the mixed signal y:
Figure FDA0002693338630000021
wherein x iskRepresenting data transmitted by a transmitter k, n representing additive white gaussian noise; the signal transmitted by the transmitter k shows a spatial characteristic r at the receiving endk＝hkpk(ii) a Forming a set N by all signals to be received by a receiver, wherein the number of the signals contained in the set N is K, M represents the number of elements in the set N, and M is equal to K; comparing M with NRIf M is less than or equal to NRZero forcing receive filter matrix W for receiver designZFFiltering the mixed signal y directly and outputting M decision symbols;
thirdly, if M is more than NRThe receiver randomly selects N in the set NR-1 signal constitutes a set S of signals to be solved,
Figure FDA0002693338630000022
the rest signals in the set N form an interference set I; by using the interaction between interferences, M- (N)R-1) the overall effect of the disturbances as a path of equivalent disturbances, the spatial characteristics of the equivalent disturbances being
Figure FDA0002693338630000023
All possible rThe space characteristic set C forming equivalent interference exists in a plurality of combination situations after the transmitted symbols are modulated, and the space characteristic set C forms equivalent interference at a given hjAnd pjOn the premise that the set C contains
Figure FDA0002693338630000024
Each element, if the modulation constellation has origin symmetry, is included in the set C
Figure FDA0002693338630000025
A seed interference spatial signature;
fourthly, the receiver firstly resolves the spatial characteristic r of the signal to be resolvedn＝hnpnN ∈ S and the spatial signature r of the equivalent interferencePerforming Schmidt orthogonalization and designing each filter vector f in a zero-forcing receiving filter matrix Gn,n∈S：
Figure FDA0002693338630000026
G comprises NR-1 column vectors, conjugate transpose of G to GHG is common to
Figure FDA0002693338630000027
A possible combination, of which only one is consistent with the actual equivalent interference spatial signature;
in a fifth step, the receiver divides the mixed signal y into
Figure FDA0002693338630000031
Then using the fourth step
Figure FDA0002693338630000032
Each filtering matrix G respectively filters each mixed signal, then judges the filtered signals and reconstructs the signals by combining channel state information, and branches consistent with actual equivalent interference space characteristics obtain reconstructed signals
Figure FDA0002693338630000033
Wherein
Figure FDA0002693338630000034
Is NR1 transmitter-to-receiver channel matrix for the signal to be solved,
Figure FDA0002693338630000035
indicating that the transmitter is to process the data
Figure FDA0002693338630000036
The precoding matrix of (a) is determined,
Figure FDA0002693338630000037
for the correct data symbol vector obtained by the judgment, the reconstructed signal of the branch inconsistent with the actual equivalent interference space characteristic is
Figure FDA0002693338630000038
Wherein
Figure FDA0002693338630000039
Is a data symbol vector obtained by erroneous decision affected by interference;
sixthly, each branch circuit reconstructs the signal
Figure FDA00026933386300000310
Or
Figure FDA00026933386300000311
Subtracting the received mixed signal y respectively, comparing the subtracted output with a preset threshold Th, if the subtracted output is smaller than Th, adding a bias signal to the output, otherwise, directly outputting the output to a post-stage for processing without processing;
seventhly, each branch adopts G which is the same as the G for the first filtering to carry out the second filtering on the signal output by the sixth step, the output of each branch is compared, and the signal intensityThe minimum branch is the branch with the same equivalent interference space characteristics, and the filtering result of the first time in the fifth step is adopted to judge and output NR-1 received symbol
Figure FDA00026933386300000312
Eighthly, the receiver utilizes the recovered data symbols and the channel state information to reconstruct the signal, and then adopts serial interference elimination to carry the decoded NR-1 symbol
Figure FDA00026933386300000313
Is removed from the mixed signal y, the receiver removes the recovered signal from the set N, updates the set N, and returns to the third operation.
2. The multi-user receiving method for overloading the number of signals according to claim 1, wherein said third step is performed when the number of transmitted signals is greater than the number N of receiving antennasRWhen in use, the interaction between signals is firstly utilized to obtain the overall effect of a plurality of interferences, thus realizing the space dimension reduction of the signals to be processed and reducing the number of the signals to be processed of the receiver to NRAnd then, receiving the multi-user signals by zero forcing and serial interference elimination.
3. The multi-user receiving method for signal number overload according to claim 1, wherein when there are multiple conditions of the modulated symbols, which cause multiple conditions of the spatial characteristics of the equivalent interference generated by the interaction between the signals, the corresponding zero-forcing receiving filter matrix G is designed according to the different spatial characteristics of the equivalent interference, the received mixed signal y is divided into multiple paths, different G are used to filter and reconstruct each path of mixed signal, the reconstructed result is subtracted from the original mixed signal y, the result is filtered for the second time by G which is the same as the first filtering, the branch with the consistent spatial characteristics of the equivalent interference is judged according to the comparison result of the output size, and the correct received symbol is recovered.
4. The multi-user receiving method for signal number overload according to claim 1, wherein if a branch erroneously reconstructs a signal identical to the original mixed signal and the output subtracted from the received mixed signal has only noise, a protection module for determining whether the branch has a signal is added before performing the second filtering on each branch, the output subtracted from the received mixed signal is compared with a preset threshold, and if the output subtracted from the received mixed signal is smaller than the threshold, an offset signal needs to be added, so that the branch can be still distinguished from a branch identical to the equivalent interference spatial characteristic after performing the second filtering.
5. The multi-user receiving method for signal number overload according to claim 1, wherein when the number of antennas configured for each transmitter is different, the manner of transmitting data by each transmitter is different, and when the number of transmitting antennas is N, the number of antennas is differentTWhen the data is equal to 1, the transmitter transmits one path of data in an omnidirectional transmission mode; h corresponding to transmitter with number of transmitting antennas equal to 1kpkShould be replaced by hkThe spatial signature observed by the receiver of the signal transmitted by the transmitter is rk＝hk(ii) a Number of antennas N when transmittingTAnd when the data is more than or equal to 2, the transmitter transmits one path of data by adopting a beam forming transmission mode.
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