CN109995404B - Differential modulation and demodulation method for space-frequency domain modulation - Google Patents

Differential modulation and demodulation method for space-frequency domain modulation Download PDF

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CN109995404B
CN109995404B CN201811543973.4A CN201811543973A CN109995404B CN 109995404 B CN109995404 B CN 109995404B CN 201811543973 A CN201811543973 A CN 201811543973A CN 109995404 B CN109995404 B CN 109995404B
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CN109995404A (en
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范亚君
贾元启
王宁
韩刚涛
李双志
朱政宇
穆晓敏
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Zhengzhou 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
    • H04B7/0456—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
    • 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
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/068—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission using space frequency diversity
    • 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
    • H04B7/0891—Space-time diversity
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/024—Channel estimation channel estimation algorithms
    • H04L25/0242—Channel estimation channel estimation algorithms using matrix methods

Abstract

The invention provides a differential modulation and demodulation method applied to a space-frequency domain modulation system, which comprises the following steps: s1: according to antenna domain, carrier domain andobtaining space-time signal matrix by symbol modulation mapping rule
Figure DEST_PATH_IMAGE001
And time-frequency signal matrix
Figure DEST_PATH_IMAGE002
(ii) a S2: matrix array
Figure 985863DEST_PATH_IMAGE001
And
Figure 680149DEST_PATH_IMAGE002
respectively obtaining space-time transmission matrixes through differential coding design
Figure DEST_PATH_IMAGE003
And time-frequency transmission matrix
Figure DEST_PATH_IMAGE004
(ii) a S3: a matrix containing spatial domain, time domain and frequency domain three-dimensional information
Figure 394027DEST_PATH_IMAGE003
And
Figure 439344DEST_PATH_IMAGE004
fusion into two-dimensional transmission matrix by using kronecker product
Figure DEST_PATH_IMAGE005
(ii) a S4: designing channel matrix by using two-dimensional transmission matrix characteristics
Figure DEST_PATH_IMAGE006
Obtaining a received signal matrix
Figure DEST_PATH_IMAGE007
(ii) a 5: the transmitting matrix is detected by an exhaustive search method by utilizing the Crohn's product property and the transmitting terminal differential transmission characteristic
Figure DEST_PATH_IMAGE008
And
Figure DEST_PATH_IMAGE009
(ii) a S6: obtaining a detection matrix based on an inverse mapping rule
Figure DEST_PATH_IMAGE010
And
Figure 522969DEST_PATH_IMAGE009
a corresponding bit sequence. The invention expands the transmitting modulation space of the traditional space-frequency domain modulation, and can avoid channel estimation; meanwhile, the method can save spectrum resources and is suitable for high-speed mobile scenes with fast channel response change.

Description

Differential modulation and demodulation method for space-frequency domain modulation
Technical Field
The invention relates to the technical field of communication, in particular to a differential modulation and demodulation method applied to a space-frequency domain modulation system.
Background
With the research of multi-antenna technology, a Multiple-Input Multiple-Output (MIMO) system combined with Index Modulation (IM) has been widely used. Spatial Modulation (SM) is an advanced technology with high transmission rate and low complexity, and the serial number of a transmitting antenna is used as a new mapping resource, and only one transmitting antenna is activated in each time slot of a transmitter by establishing a mapping relation between different input bits and antenna serial numbers, so that the purpose of Spatial Modulation is achieved. On one hand, the structure of the transmitting end is simplified, and the power consumption of the power amplifier is greatly reduced; on the other hand, the problems of Inter-Antenna Synchronization (IAS) and Inter-Channel Interference (ICI) are avoided, the detection of the receiving end is simplified, and the power consumption of signal processing is also reduced. However, detection of SM requires accurate Channel State Information (CSI) estimation, which causes the SM system to suffer performance from Channel estimation errors. Based on this, the scholars propose Differential Spatial Modulation (DSM), and introduce a time domain and make a difference in the time domain, so that the advantage that only one transmitting antenna is activated in each time slot of the SM is retained, and the difficult problem of channel estimation is also perfectly avoided. In recent years, the problems of DSM diversity multiplexing trade-off, constellation design, performance analysis, etc. have received extensive attention and research from academia.
With the good performance of spatial modulation techniques in large-scale mimo systems, many studies have been conducted to apply the techniques to multicarrier systems. The Index Modulation of orthogonal subcarriers, i.e. the Index Modulation orthogonal frequency division multiplexing (SIM), is being studied more. As a new transmission technology, structural optimization and improvement thereof are also receiving much attention. Although the SIM technology is widely studied, there is also a SM-like channel estimation problem, so researchers have proposed a single-input single-output Differential carrier index system (DSIM). Aiming at a single antenna, a frequency domain is introduced, a time-frequency transmission matrix is designed at a transmitting end for differential transmission, and incoherent detection is carried out at a receiving end, so that channel estimation is avoided.
It is clear that the above mentioned DSM systems and DSIM systems bypass any channel estimation from the transmitting end to the receiving end completely. But all use single domain resources, where DSM introduces spatial domain resources and DSIM introduces frequency domain resources. In order to utilize the space domain and frequency domain resources at the same time more effectively, thereby improving the error performance. Researchers have proposed an orthogonal frequency division multiplexing-based spatial Modulation carrier Index Modulation (SM-OFDM with Subcarrier Index Modulation, ISM-OFDM) system, which activates different antennas to transmit Modulation information on activated subcarriers by design. However, the assumption is that perfect CSI is obtained at the receiving end, and in fact, additional resources are also consumed to perform CSI estimation. Therefore, space-time frequency domain resources can be fully utilized, and channel estimation is avoided at a receiving end, which is the purpose of differential modulation and demodulation of the space-frequency domain modulation system.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a differential modulation and demodulation method in a space-frequency domain modulation system, wherein the differential coding modulation of a space-time transmission block and a time-frequency transmission block is designed at a transmitting end in the system, and the fusion of three-domain information is carried out by utilizing a kronecker product, so that the problem of channel estimation in the space-frequency domain modulation system is solved.
In a first aspect, the present invention provides a differential modulation and demodulation method in a space-frequency domain modulation system, where the method includes:
s1: grouping sub-carriers according to transmitting antennas, and then obtaining a space-time signal matrix according to an antenna domain, a carrier domain and a symbol modulation mapping rule
Figure GDA0002079647560000021
And time-frequency signal matrix
Figure GDA0002079647560000022
S2: sending terminal two-dimensional space-time signal matrix
Figure GDA0002079647560000023
And time-frequency signal matrix
Figure GDA0002079647560000024
Respectively obtaining space-time transmission matrixes through differential coding design
Figure GDA0002079647560000031
And time-frequency transmission matrix
Figure GDA0002079647560000032
S3: space-time transmission matrix containing spatial domain, time domain and frequency domain three-dimensional information
Figure GDA0002079647560000033
And time-frequency transmission matrix
Figure GDA0002079647560000034
Two-dimensional transmission matrix fused by utilizing Crohn's product
Figure GDA0002079647560000035
S4: designing channel matrix including frequency domain, transmitting antenna and receiving antenna by using two-dimensional information property
Figure GDA0002079647560000036
And performing a signal matrix
Figure GDA0002079647560000037
Obtaining a matrix of received signals
Figure GDA0002079647560000038
S5: utilizing kronecker product property and space-time transmission matrix at transmitting end
Figure GDA0002079647560000039
And time-frequency transmission matrix
Figure GDA00020796475600000310
Deducing corresponding differential detection formula, and detecting the matrix of the transmitted space-time signals by an exhaustive search method
Figure GDA00020796475600000311
And time-frequency signal matrix
Figure GDA00020796475600000312
S6: obtaining a detection matrix based on regular inverse mapping such as antenna domain, carrier domain and symbol mapping
Figure GDA00020796475600000313
And
Figure GDA00020796475600000314
a corresponding bit sequence.
Preferably, the step S1 specifically includes:
s11 according to the transmitting antenna NtGrouping the subcarrier number L, and sharing G groups, wherein N is L/G is N for each group of subcarrierstFor the g subcarrier group, N is includedtTth transport block of one slot:
first of all, the first step is to,
Figure GDA00020796475600000315
bit information for determining NtObtaining a space-time index matrix according to the antenna activation sequence of each time slot
Figure GDA00020796475600000316
Secondly, the first step is to carry out the first,
Figure GDA00020796475600000317
bit information is used for determining the carrier activation sequence containing N time slots to obtain a time-frequency index matrix
Figure GDA00020796475600000318
Finally, b3＝Nlog2The (M) bit information is mapped to N M-PSK modulation symbols,
Figure GDA0002079647560000041
determining
Figure GDA0002079647560000042
N symbols.
S22 space-time transmission matrix
Figure GDA0002079647560000043
And time-frequency transmission matrix
Figure GDA0002079647560000044
Respectively as follows:
Figure GDA0002079647560000045
Figure GDA0002079647560000046
preferably, the step S2 specifically includes:
setting an initial space-time transmission matrix
Figure GDA0002079647560000047
And time-frequency transmission matrix
Figure GDA0002079647560000048
Are respectively as
Figure GDA0002079647560000049
Wherein
Figure GDA00020796475600000423
Is an identity matrix of dimension N × N. Wherein
Figure GDA00020796475600000411
And
Figure GDA00020796475600000412
can be any one of the transmission signal matrixes belonging to the transmission modulation space and transmits
Figure GDA00020796475600000413
And
Figure GDA00020796475600000414
no bit information is conveyed. The transmitting end can obtain the t space-time transmission matrix of the g carrier group through differential transmission
Figure GDA00020796475600000415
And time-frequency transmission matrix
Figure GDA00020796475600000416
Figure GDA00020796475600000417
Figure GDA00020796475600000418
Preferably, the step S3 specifically includes:
space-time transmission matrix containing spatial domain, time domain and frequency domain three-dimensional information
Figure GDA00020796475600000419
And time-frequency transmission matrix
Figure GDA00020796475600000420
Two-dimensional transmission matrix fused by utilizing Crohn's product
Figure GDA00020796475600000421
Figure GDA00020796475600000422
Wherein
Figure GDA0002079647560000051
Is kronecker product.
Preferably, the step S4 specifically includes:
channel matrix comprising frequency domain, transmitting antenna and receiving antenna is designed by utilizing two-dimensional transmission matrix characteristic
Figure GDA0002079647560000052
And performing a signal matrix
Figure GDA0002079647560000053
Obtaining a matrix of received signals
Figure GDA0002079647560000054
Figure GDA0002079647560000055
Wherein
Figure GDA0002079647560000056
Is the channel matrix of the g-th subcarrier group.
Preferably, step S5 specifically includes:
utilizing kronecker product property and space-time transmission matrix at transmitting end
Figure GDA0002079647560000057
And time-frequency transmission matrix
Figure GDA0002079647560000058
Deducing corresponding differential detection formula, and detecting the matrix of the transmitted space-time signals by an exhaustive search method
Figure GDA0002079647560000059
And time-frequency signal matrix
Figure GDA00020796475600000510
The detection formula is as follows:
Figure GDA00020796475600000511
wherein psisAnd psifRespectively represent
Figure GDA00020796475600000512
And
Figure GDA00020796475600000513
all possible signal matrices.
Preferably, the step S6 specifically includes:
obtaining a detection matrix based on regular inverse mapping such as antenna domain, carrier domain and symbol mapping
Figure GDA00020796475600000514
And
Figure GDA00020796475600000515
a corresponding bit sequence.
According to the technical scheme, for each subcarrier group g, the differential space-time block and the differential time-frequency block are fused into a two-dimensional transmission matrix by using the kronecker product at the transmitting end for signal transmission, and the differential detection is deduced by using the corresponding kronecker product property at the receiving end. Through the tth receiving block of the receiving end
Figure GDA0002079647560000061
And (t-1) th reception block
Figure GDA0002079647560000062
Exhaustive search to detect transmit space-time signal matrices
Figure GDA0002079647560000063
And time-frequency signal matrix
Figure GDA0002079647560000064
The channel estimation problem is avoided.
Drawings
In order to more clearly illustrate the embodiments or technical solutions of the present invention in the prior art, the drawings used in the description of the embodiments or prior art are briefly introduced below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic flowchart of a differential modulation and demodulation method in a space-frequency domain modulation system according to the present invention;
FIG. 2 is a schematic diagram of bit mapping of a space-time signal matrix at a transmitting end;
FIG. 3 is a schematic diagram of bit mapping of a time-frequency signal matrix at a transmitting end;
FIG. 4 is a schematic diagram of a system for avoiding channel estimation using a kronecker product according to the present invention;
fig. 5 is a graph comparing the simulation of the present invention with the DSM system at a spectral efficiency of 1.5bps/Hz for the case where the receiving antennas are 1 and 2, respectively, and the subcarrier L is 2.
Fig. 6 is a graph comparing simulations of two example sub-schemes of the present invention with an ISM-OFDM system at a spectral efficiency of 2.5bps/Hz, with receive antennas of 3 and 4, respectively, and a subcarrier L of 64.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, a differential modulation and demodulation method in a space-frequency domain modulation system provided for an embodiment of the present invention includes the following steps:
s1: grouping sub-carriers according to transmitting antennas, and then obtaining a space-time signal matrix according to an antenna domain, a carrier domain and a symbol modulation mapping rule
Figure GDA0002079647560000071
And time-frequency signal matrix
Figure GDA0002079647560000072
S2: sending terminal two-dimensional space-time signal matrix
Figure GDA0002079647560000073
And time-frequency signal matrix
Figure GDA0002079647560000074
Respectively obtaining space-time transmission matrixes through differential coding design
Figure GDA0002079647560000075
And time-frequency transmission matrix
Figure GDA0002079647560000076
S3: space-time transmission matrix containing spatial domain, time domain and frequency domain three-dimensional information
Figure GDA0002079647560000077
And time-frequency transmission matrix
Figure GDA0002079647560000078
Two-dimensional transmission matrix fused by utilizing Crohn's product
Figure GDA0002079647560000079
S4: designing channel matrix including frequency domain, transmitting antenna and receiving antenna by using two-dimensional information property
Figure GDA00020796475600000710
And performing a signal matrix
Figure GDA00020796475600000711
Obtaining a matrix of received signals
Figure GDA00020796475600000712
S5: utilizing kronecker product property and space-time transmission matrix at transmitting end
Figure GDA00020796475600000713
And time-frequency transmission matrix
Figure GDA00020796475600000714
The differential transmission characteristics of the differential detection circuit are deduced to obtain corresponding differential detection formulasSearch method for detecting space-time signal matrix
Figure GDA00020796475600000715
And time-frequency signal matrix
Figure GDA00020796475600000716
S6: obtaining a detection matrix based on regular inverse mapping such as antenna domain, carrier domain and symbol mapping
Figure GDA00020796475600000717
And
Figure GDA00020796475600000718
a corresponding bit sequence.
The first and second embodiments of the present invention will be specifically described below, and fig. 4 is a transmission model, which applies the methods described in the first and second embodiments to a space-frequency domain modulation MIMO legal communication system. The transmitting terminal is configured with NtRoot antenna, receiving end configuration NrAnd L subcarriers are provided for the root antenna. At a transmitting end, performing differential processing on the space-time transmission matrix and the time-frequency transmission matrix respectively, and fusing three-dimensional information by using a kronecker product; the differential detection is carried out at the receiving end by utilizing the property of the kronecker product, thereby perfectly avoiding the estimation of the CSI, wherein the S belongs to the CN×MThe dimension representing the matrix S is N × M.
Example one
In this embodiment, the specific process of step S1 is as follows:
s11 according to the transmitting antenna NtGrouping the subcarrier number L, and sharing G groups, wherein N is L/G is N for each group of subcarrierstFor the g subcarrier group, N is includedtTth transport block of one slot:
first of all, the first step is to,
Figure GDA0002079647560000081
bit information for determining NtObtaining a space-time index matrix according to the antenna activation sequence of each time slot
Figure GDA0002079647560000082
Secondly, the first step is to carry out the first,
Figure GDA0002079647560000083
bit information is used for determining the carrier activation sequence containing N time slots to obtain a time-frequency index matrix
Figure GDA0002079647560000084
Finally, b3＝Nlog2The (M) bit information is mapped to N M-PSK modulation symbols,
Figure GDA0002079647560000085
determining
Figure GDA0002079647560000086
N symbols.
So NtThe information bits transmitted by each time slot are:
Figure GDA0002079647560000087
the spectral efficiency can be expressed as:
Rm＝Dm/(Nt(K+L)) (1)
it should be noted that M is the modulation order of PSK, for convenience of understanding, N modulation symbols employ the same modulation order, and K is the cyclic prefix added at the transmission end.
The mapping method of the space-time index matrix is consistent with that of the time-frequency index matrix, and the mapping method of the space-time index matrix is briefly introduced here. In all Nt| A In the arrangement combination, one of them is selected
Figure GDA0002079647560000091
The combination is effective, and thus, it is necessary to
Figure GDA0002079647560000092
Each ratioTo modulate the position of the non-zero element arrangement. A boolean matrix whose elements are composed of 0 and 1 may be used
Figure GDA0002079647560000093
To indicate such a permutation and combination. For example, if the desired sequence is [1,2 ]](assuming that two transmitting antennas are configured at the transmitting end), that is, the non-zero element of the first column (first time slot) is located in the first row, the non-zero element of the second column (second time slot) is located in the second row, and the corresponding permutation matrix
Figure GDA0002079647560000094
Can be expressed as:
Figure GDA0002079647560000095
Figure GDA0002079647560000096
each element in (1) is Nt×NtThe elements of the boolean matrix of (1) are comprised of 0 and 1, and each row and each column has only one non-zero element.
Figure GDA0002079647560000097
The element in the ith row and the jth column of (a) indicates the activation of the ith antenna in the jth slot. A 1 indicates that this antenna is activated in this time slot and a 0 indicates that no information is transmitted.
S12 space-time transmission matrix
Figure GDA0002079647560000098
And time-frequency transmission matrix
Figure GDA0002079647560000099
Respectively as follows:
Figure GDA00020796475600000910
Figure GDA00020796475600000911
wherein
Figure GDA00020796475600000912
And
Figure GDA00020796475600000913
each row and each column only have one non-zero element;
Figure GDA00020796475600000914
is a signal vector containing N modulation symbols, determines
Figure GDA0002079647560000101
The middle N symbols, namely:
Figure GDA0002079647560000102
FIG. 2 shows a space-time signal matrix at a transmitting end according to an embodiment of the present invention
Figure GDA0002079647560000103
A bit map schematic; FIG. 3 shows a time-frequency signal matrix at a transmitting end according to an embodiment of the present invention
Figure GDA0002079647560000104
Bit mapping schematic diagram. As can be seen from fig. 2 and 3 provided in the embodiment of the present invention, for a given bit stream, the bit stream is first grouped according to the grouping situation of G groups of subcarriers; for the g-th group, first part
Figure GDA0002079647560000105
Bit information for determining NtObtaining a space-time index matrix according to the antenna activation sequence of each time slot
Figure GDA0002079647560000106
Of the second part
Figure GDA0002079647560000107
Bit information is used to determine NtOne slot carrier activation sequence
Figure GDA0002079647560000108
Obtaining a time-frequency index matrix; n log of the third fraction2Generating N modulation symbols from (M) bit information, mapping the N modulation symbols to N M-PSK modulation symbols, and determining
Figure GDA0002079647560000109
N symbols.
In this embodiment, step S2 specifically includes:
setting an initial space-time transmission matrix in the g-th subcarrier group
Figure GDA00020796475600001010
And time-frequency transmission matrix
Figure GDA00020796475600001011
Are respectively as
Figure GDA00020796475600001012
Wherein
Figure GDA00020796475600001013
Is an identity matrix of dimension N × N. Wherein
Figure GDA00020796475600001014
And
Figure GDA00020796475600001015
can be any one of the transmission signal matrixes belonging to the transmission modulation space and transmits
Figure GDA00020796475600001016
And
Figure GDA00020796475600001017
no bit information is conveyed. The transmitting end can obtain the t space-time transmission of the g carrier group through differential transmissionInput matrix
Figure GDA00020796475600001018
And time-frequency transmission matrix
Figure GDA00020796475600001019
Figure GDA00020796475600001020
Figure GDA00020796475600001021
In particular, assume that (m, w) represents a matrix
Figure GDA0002079647560000111
Row m, column w; matrix of (n, w)
Figure GDA0002079647560000112
Row n and column w. Then: 1. for space-time blocks
Figure GDA0002079647560000113
Indicating that m-th antennas are activated in the w-th time slot of the g-th group; 2. for time frequency block
Figure GDA0002079647560000114
Indicating the active n-th carrier modulation information f on the active m-th antenna in the w-th time slot of the g-th groupnw；
In this embodiment, step S3 specifically includes:
space-time transmission matrix containing three-dimensional information of space domain, time domain and frequency domain
Figure GDA0002079647560000115
And time-frequency transmission matrix
Figure GDA0002079647560000116
By means of kronecker effectCombined into a two-dimensional transmission matrix
Figure GDA0002079647560000117
Figure GDA0002079647560000118
Wherein
Figure GDA0002079647560000119
Is kronecker product. Here, we assume xsxfAnd xmRepresenting all possible signal matrix values of the matrices S, F and M, respectively. For this embodiment, we need to satisfy the following closed-loop properties:
1. if it is
Figure GDA00020796475600001110
And is
Figure GDA00020796475600001111
The differential encoding equation (5) needs to be satisfied
Figure GDA00020796475600001112
2. If it is
Figure GDA00020796475600001113
And is
Figure GDA00020796475600001114
The differential encoding equation (6) needs to be satisfied
Figure GDA00020796475600001115
To satisfy the above properties, the accumulation of amplitude values during differential coding is avoided, and a space-time matrix is used
Figure GDA00020796475600001116
And time-frequency matrix
Figure GDA00020796475600001117
The non-zero elements in (c) need to satisfy unity magnitude.
In this embodiment, step S4 specifically includes:
channel matrix comprising frequency domain, transmitting antenna and receiving antenna is designed by utilizing two-dimensional transmission matrix characteristic
Figure GDA00020796475600001118
And performing a signal matrix
Figure GDA00020796475600001119
Obtaining a tth frequency domain received signal matrix:
Figure GDA0002079647560000121
wherein
Figure GDA0002079647560000122
Is a complex additive white gaussian noise matrix. Each element is independently and identically distributed in a zero mean value N0The complex Gaussian random variable of the variance is expressed as s-CN (0, N)0)；
Figure GDA0002079647560000123
Expressed as g-th group NNr×NNtThe setting method of the frequency domain channel coefficient matrix comprises the following steps:
Figure GDA0002079647560000124
in particular, it is possible to use, for example,
Figure GDA0002079647560000125
each element thereof is 0;
Figure GDA0002079647560000126
representing g-th groups, N corresponding to N-th sub-carriersr×NtA frequency-domain channel matrix of the dimension,
Figure GDA0002079647560000127
each element of (a) obeys a complex gaussian random distribution of zero mean unit variance.
In this embodiment, step S5 specifically includes:
utilizing kronecker product property and space-time transmission matrix at transmitting end
Figure GDA0002079647560000128
And time-frequency transmission matrix
Figure GDA0002079647560000129
Deducing corresponding differential detection formula, and detecting the matrix of the transmitted space-time signals by an exhaustive search method
Figure GDA00020796475600001210
And time-frequency signal matrix
Figure GDA00020796475600001211
The specific process is as follows:
s51: based on equation (7), the tth received signal matrix can be expressed as:
Figure GDA00020796475600001212
the (t-1) th received signal matrix can be expressed as:
Figure GDA00020796475600001213
by bringing the differential encoding equations (5) and (6) into the equation (10), it is possible to obtain:
Figure GDA0002079647560000131
s52: the above equation is derived and simplified by using the property of the kronecker product.
The precondition for the existence of the property is as follows: assuming that the dimensions of the matrices A, B, C, D form the products AB and CD of the matrices, the equation is satisfied
Figure GDA0002079647560000132
I.e. the interchange between the ordinary matrix product and the kronecker product between the matrices can be performed.
Also in the derivation process, it is assumed that for any g-th group, the channel remains unchanged between consecutive transmissions, i.e. the channel remains unchanged between consecutive transmissions
Figure GDA0002079647560000133
Then, by taking advantage of the property of kronecker product, in combination with formula (11), formula (12) can be converted into:
Figure GDA0002079647560000134
based on formula (11), formula (13) can be further converted into:
Figure GDA0002079647560000135
wherein
Figure GDA0002079647560000136
Is the noise of the g-th group, the t-th receive matrix.
From formula (14), can be
Figure GDA0002079647560000137
And
Figure GDA0002079647560000138
solving for the highest probability by maximum likelihood detection
Figure GDA0002079647560000139
And
Figure GDA00020796475600001310
ML detection is a comparisonCalculating Euclidean distances between the possible modulation matrixes and the received signals, and selecting one with the minimum Euclidean distance as an optimal solution:
Figure GDA00020796475600001311
i | · O in formula (4.18)FRepresents Frobenius norm operation, such that
Figure GDA00020796475600001312
Maximum value
Figure GDA0002079647560000141
And
Figure GDA0002079647560000142
as a result of the detection of the current t. Wherein psisAnd psifRespectively represent
Figure GDA0002079647560000143
And
Figure GDA0002079647560000144
all possible signal matrices.
In this embodiment, step S6 specifically includes:
obtaining a detection matrix based on regular inverse mapping such as antenna domain, carrier domain and symbol mapping
Figure GDA0002079647560000145
And
Figure GDA0002079647560000146
a corresponding bit sequence;
example two
Different from the first embodiment, the second embodiment assumes that the applied examples of the present invention have the same space-time index matrix for all subcarrier groups g, i.e. the space-time index matrix is the same
Figure GDA0002079647560000147
The space-time transmission matrix is thus kept uniform for all subcarrier groups g, i.e.
Figure GDA0002079647560000148
The time-frequency matrix mapping and transmission method is consistent with the embodiment. So that N can be obtainedtThe information bits transmitted in each time slot are:
Figure GDA0002079647560000149
therefore, the spectral efficiency in the second embodiment can be expressed as:
Rs＝Ds/(Nt(K+L)) (17)
description of the embodiments
Specifically, this example mainly addresses the mapping situation of one subcarrier group g in the first embodiment, but is naturally also applicable to the mapping situation of the first subcarrier group in the second embodiment.
Suppose that for a MIMO communication system with a legal space-frequency domain modulation, a transmitting end is configured with NtThe receiving end is configured with N as 2 antennasr2 antennas; grouping the subcarriers L-64, G-32 groups in total, and N-2 subcarriers in each group; and the activated subcarriers modulate the BPSK symbols. The transport bit stream of the g-th group may be divided into b 11 bit and b 21 bit is used to select the antenna activation matrix and the carrier activation matrix of 2 slots, respectively. b32 bits of information are used to select the modulation symbols of two slots. In summary, for any subcarrier group in the first embodiment or the first subcarrier group in the second embodiment, the space-time-frequency transmission matrix carries b in common1+b2+b 34 bits of information.
As shown in fig. 4, assume that the block of bits for the current carrier group is 0110. With the mapping rules of fig. 2 and 3, the first bit '0' is correspondingly arranged as [1,2 ]]That is, in a time slot block containing two adjacent time slots, the first transmitting antenna and the second transmitting antenna are activated in sequence to form a space-time index matrix
Figure GDA0002079647560000151
Similarly, the corresponding arrangement of the second bit '1' is [2,1 ]]That is, in the current time slot block, the second sub-carrier and the first sub-carrier are activated in sequence to form the time-frequency index matrix
Figure GDA0002079647560000152
The last two bits '10' are mapped to a corresponding modulation symbol vector xf，t＝[-1，+1]。
Figure GDA0002079647560000153
And
Figure GDA0002079647560000154
is represented as follows:
Figure GDA0002079647560000155
suppose a (t-1) th transmission matrix
Figure GDA0002079647560000156
And
Figure GDA0002079647560000157
expressed as:
Figure GDA0002079647560000158
the tth space-time transmission matrix and the time-frequency transmission matrix can be expressed as:
Figure GDA0002079647560000159
wherein (20) indicates that in the first of 2 consecutive time slots, the second transmit antenna is activated, and the second subcarrier modulation symbol '-1' is activated on the active antenna; similarly, in the second time slot, the first transmit antenna is activated, and the first subcarrier modulation symbol '+ 1' is activated on this active antenna.
Therefore, the differential modulation and demodulation method in the space-frequency domain modulation system provided by the invention has the advantages that the differential processing of the space-time matrix and the time-frequency matrix is respectively carried out at the sending end, then the three-dimensional information is fused into the two-dimensional matrix for transmission, the differential detection formula is deduced at the receiving end by utilizing the property of the kronecker product, and the transmitted bit is demodulated on the premise that the transmitting end and the receiving end do not need to acquire the channel state information. The method is suitable for any space-time-frequency modulation MIMO system.
A comparison of the transmission scheme of the present invention with other existing transmission schemes will be given below to make the advantages and features of the present invention more apparent.
Fig. 5 shows a performance comparison analysis diagram of a Differential space-Frequency Modulation system (DSFM-OFDM) based on Orthogonal Frequency Division Multiplexing (OFDM) in an embodiment of the present invention, where 1 and 2 antennas are respectively configured at a receiving end and 2 transmitting antennas are configured at a transmitting end, and the DSFM-OFDM is used in the embodiment. The DSM uses the signal constellation BPSK and the DSFM-OFDM uses the signal constellation QPSK, both maintaining the same spectral efficiency of 1.5 bps/Hz. Specifically, DSFM-OFDM is assumed to have L2 subcarriers grouped together, while DSM follows single carrier transmission. As can be seen from the simulation results, when 1 and 2 receiving antennas are respectively configured, the error rate performance of the DSFM-OFDM is superior to that of the DSM under the condition of high signal to noise ratio; in addition, the larger the receive antenna, the smaller the performance gap between the two systems. When BER is 10-3The performance difference is reduced from 6dB to 1.5 dB. Under the transmission spectrum efficiency, the performance can be obviously improved under the condition of high signal-to-noise ratio by adopting the technical scheme provided by the embodiment of the invention, and the performance advantage is more obvious along with the increase of the receiving antennas.
Fig. 6 shows that 3,4 antennas are configured at the receiving end, 2 transmitting antennas are configured at the transmitting end, a multi-antenna selection differential space-frequency modulation system (DSFM-OFDM-Multiple, DSFM-OFDM-M) based on OFDM according to an embodiment of the present invention, and a single OFDM based on OFDM according to an embodiment of the present inventionA performance comparison analysis chart of a group antenna selection differential space-frequency modulation system (DSFM-OFDM-Single, DSFM-OFDM-S) and an ISM-OFDM system under the same spectral efficiency of 1.6bps/Hz is shown. Perfect channel state information is assumed to be known to the ISM-OFDM system at the receiving end. Wherein DSFM-OFDM-S system M ═ 8,16]It is indicated that for each set of subcarrier N-2, the first carrier and the second carrier use the signal constellations QPSK and 8PSK, respectively. Specifically, let L be 64 subcarriers and be divided into G be 32 groups; the cyclic prefix length is K-16, v-10, and the MIMO frequency domain selective fading channel follows a complex gaussian distribution with zero mean unit variance. While the variance of the noise distribution is N 01. As can be seen from the simulation results, ISM-OFDM is superior to DSFM-OFDM-M and DSFM-OFDM-S. In addition, when the receiving end is configured with 4 receiving antennas with the BER of 10-4And the ISM-OFDM system has poor performance 5dB and 4dB higher than the DSFM-OFDM-S and DSFM-OFDM-M systems respectively. But we assume here that the ISM-OFDM system knows perfect channel state estimation at the receiving end, but in fact we need as accurate channel response information as possible when the receiving end demodulates in modulation. However, in some cases, it may be difficult to obtain sufficiently accurate channel response estimates. For example, in a high-speed moving scene, the channel response changes too fast, and the accuracy of channel estimation is difficult to guarantee. Although the insertion of more pilots helps to improve the accuracy of channel estimation, too many pilots occupy too many spectrum resources of the transmission system, and the spectrum efficiency is reduced. For another example, to reduce the complexity of the receiving end, we may need to abandon channel estimation and greatly influence the performance of the system by estimating the quality of the channel. Therefore, the differential modulation and demodulation method applied to the space-frequency domain system well avoids the problem of channel estimation and has better practicability.
The above description is only for the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims (7)

1. A method of differential modulation and demodulation of space-frequency domain modulation, the method comprising:
s1: grouping sub-carriers according to transmitting antennas, and then obtaining a space-time signal matrix according to an antenna domain, a carrier domain and a symbol modulation mapping rule
Figure FDA0002946007130000011
And time-frequency signal matrix
Figure FDA0002946007130000012
S2: sending terminal two-dimensional space-time signal matrix
Figure FDA0002946007130000013
And time-frequency signal matrix
Figure FDA0002946007130000014
Respectively obtaining space-time transmission matrixes through differential coding design
Figure FDA0002946007130000015
And time-frequency transmission matrix
Figure FDA0002946007130000016
S3: space-time transmission matrix containing spatial domain, time domain and frequency domain three-dimensional information
Figure FDA0002946007130000017
And time-frequency transmission matrix
Figure FDA0002946007130000018
Two-dimensional transmission matrix fused by utilizing Crohn's product
Figure FDA0002946007130000019
S4: benefit toDesigning channel matrix including frequency domain, transmitting antenna and receiving antenna by using two-dimensional information property
Figure FDA00029460071300000110
And performing a signal matrix
Figure FDA00029460071300000111
Obtaining a matrix of received signals
Figure FDA00029460071300000112
S5: utilizing kronecker product property and space-time transmission matrix at transmitting end
Figure FDA00029460071300000113
And time-frequency transmission matrix
Figure FDA00029460071300000114
Deducing corresponding differential detection formula, and detecting the matrix of the transmitted space-time signals by an exhaustive search method
Figure FDA00029460071300000115
And time-frequency signal matrix
Figure FDA00029460071300000116
S6: obtaining a detection matrix based on regular inverse mapping such as antenna domain, carrier domain and symbol mapping
Figure FDA00029460071300000117
And
Figure FDA00029460071300000118
a corresponding bit sequence.
2. The space-frequency domain modulated differential modulation and demodulation method according to claim 1, wherein the step S1 specifically comprises:
s11: according to the transmitting antenna NtGrouping the subcarrier number L, and sharing G groups, wherein N is L/G is N for each group of subcarrierstFor the g subcarrier group, N is includedtTth transport block of one slot:
first of all, the first step is to,
Figure FDA00029460071300000119
bit information for determining NtObtaining a space-time index matrix according to the antenna activation sequence of each time slot
Figure FDA00029460071300000120
Secondly, the first step is to carry out the first,
Figure FDA00029460071300000121
bit information is used for determining the carrier activation sequence containing N time slots to obtain a time-frequency index matrix
Figure FDA00029460071300000122
Finally, b3＝Nlog2(M) bit information mapping to N M-PSK modulation symbols
Figure FDA00029460071300000123
Determining
Figure FDA00029460071300000124
N symbols;
s22: space-time transmission matrix
Figure FDA0002946007130000021
And time-frequency transmission matrix
Figure FDA0002946007130000022
Respectively as follows:
Figure FDA0002946007130000023
Figure FDA0002946007130000024
3. the space-frequency domain modulated differential modulation and demodulation method according to claim 1, wherein the step S2 specifically comprises:
setting an initial space-time transmission matrix
Figure FDA0002946007130000025
And time-frequency transmission matrix
Figure FDA0002946007130000026
Are respectively as
Figure FDA0002946007130000027
Wherein
Figure FDA0002946007130000028
An identity matrix of dimension NxN; wherein
Figure FDA0002946007130000029
And
Figure FDA00029460071300000210
can be any one of the transmission signal matrixes belonging to the transmission modulation space and transmits
Figure FDA00029460071300000211
And
Figure FDA00029460071300000212
does not convey any bit information; the transmitting end can obtain the t space-time transmission matrix of the g carrier group through differential transmission
Figure FDA00029460071300000213
And time-frequency transmission matrix
Figure FDA00029460071300000214
Figure FDA00029460071300000215
Figure FDA00029460071300000216
4. The space-frequency domain modulated differential modulation and demodulation method according to claim 1, wherein the step S3 specifically comprises:
space-time transmission matrix containing spatial domain, time domain and frequency domain three-dimensional information
Figure FDA00029460071300000217
And time-frequency transmission matrix
Figure FDA00029460071300000218
Two-dimensional transmission matrix fused by utilizing Crohn's product
Figure FDA00029460071300000219
Figure FDA00029460071300000220
Wherein
Figure FDA00029460071300000221
Is kronecker product.
5. The space-frequency domain modulated differential modulation and demodulation method according to claim 1, wherein the step S4 specifically comprises:
channel matrix comprising frequency domain, transmitting antenna and receiving antenna is designed by utilizing two-dimensional transmission matrix characteristic
Figure FDA00029460071300000222
And performing a signal matrix
Figure FDA00029460071300000223
Obtaining a matrix of received signals
Figure FDA00029460071300000224
Figure FDA00029460071300000225
Wherein
Figure FDA00029460071300000226
Is the channel matrix of the g-th subcarrier group.
6. The space-frequency domain modulated differential modulation and demodulation method according to claim 1, wherein the step S5 specifically comprises:
utilizing kronecker product property and space-time transmission matrix at transmitting end
Figure FDA00029460071300000227
And time-frequency transmission matrix
Figure FDA00029460071300000228
Deducing corresponding differential detection formula, and detecting the matrix of the transmitted space-time signals by an exhaustive search method
Figure FDA0002946007130000031
And time frequencySignal matrix
Figure FDA0002946007130000032
The detection formula is as follows:
Figure FDA0002946007130000033
wherein psisAnd psifRespectively represent
Figure FDA0002946007130000034
And
Figure FDA0002946007130000035
all possible signal matrices.
7. The space-frequency domain modulated differential modulation and demodulation method according to claim 1, wherein the step S6 specifically comprises:
obtaining a detection matrix based on regular inverse mapping such as antenna domain, carrier domain and symbol mapping
Figure FDA0002946007130000036
And
Figure FDA0002946007130000037
a corresponding bit sequence.
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