CN109167748B - Partial maximum likelihood detection method based on energy sorting - Google Patents

Partial maximum likelihood detection method based on energy sorting Download PDF

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CN109167748B
CN109167748B CN201811297294.3A CN201811297294A CN109167748B CN 109167748 B CN109167748 B CN 109167748B CN 201811297294 A CN201811297294 A CN 201811297294A CN 109167748 B CN109167748 B CN 109167748B
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CN109167748A (en
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冯兴乐
牛晓珂
朱文霞
段国彬
王相相
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Changan University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • 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
    • 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
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
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    • H04L25/03159—Arrangements for removing intersymbol interference operating in the frequency domain
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
    • H04L27/20—Modulator circuits; Transmitter circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2626—Arrangements specific to the transmitter only
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
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Abstract

The invention discloses a partial maximum likelihood detection method based on energy sorting, which adopts a step demodulation mode, firstly, the number of subcarriers adopts minimum mean square error equalization, then the energy value of each subcarrier is obtained, and sorting is carried out, the number p of selected candidate subcarriers is set, and then the partial subcarrier number, the antenna number and the constellation symbol are detected by adopting the maximum likelihood. The subcarrier blocks can make up the error retransmission defect when a receiving end demodulates, the subcarrier serial number can be demodulated by comparing the power of the balanced symbols on the subcarriers, the number of traversed combinations can be reduced by adding part of the maximum likelihood detection algorithm, the complexity is reduced to a certain extent, and the setting of the P value can achieve good compromise between the error rate and the complexity of the system.

Description

Partial maximum likelihood detection method based on energy sorting
Technical Field
The invention belongs to the technical field of wireless communication, and particularly relates to a partial maximum likelihood detection method based on energy sequencing.
Background
The traditional information transmission resources such as spatial domain, frequency domain and time domain can not meet the requirement of the increasing information transmission rate of 5G. Therefore, the information transmission in the joint space and frequency domain at the same time becomes a new resource in 5G, but the increase of the number of antennas and the number of subcarriers also brings a challenge to detection, and index modulation is generated along with the challenge. Index modulation makes use of the index of the transmission medium, such as the transmit antenna, subcarrier, time slot or linear block code, to modulate the information bits by some mapping rule. Since the power consumption generated by the transmission of index bits is small, index modulation has a great potential for green communication in the fifth generation networks in the future by using a feasible trade-off between Spectral Efficiency (SE) and Energy Efficiency (EE) or between diversity gain and multiplexing gain. The index modulation technology mainly comprises space domain index modulation and carrier index modulation, and the two ideas are that the index modulation technology is utilized to reduce interference, and index bits are introduced to make up for loss of spectrum efficiency. Except that spatial index modulation is used to select antennas and subcarrier index modulation is used to select subcarriers. Spatial index Modulation (SM), which is a novel Multiple Input Multiple Output (MIMO) transmission technique, is a technique suitable for different numbers of transmitting antennas and receiving antennas. SM is a novel two-dimensional modulation mode, selects an antenna from a group of antennas through index bits to activate and send data, detects index bit information by judging the position of the activated antenna at a receiving end, and demodulates received symbols to obtain modulation bit information. Due to the unique transmission characteristic of spatial modulation, namely only one antenna is activated, the interference among multiple antennas does not exist, the detection complexity and the radio frequency link cost of a receiving end are reduced, and the introduced index bit can solve the problem of reduced frequency spectrum efficiency caused by the fact that only one antenna is activated. The idea of spatial modulation is applied to a multi-carrier system to obtain Frequency domain index modulation, namely OFDM-IM, compared with the traditional Orthogonal Frequency Division Multiplexing (OFDM) technology, the OFDM-IM system has better error code performance, and meanwhile, as long as the number of activated sub-carriers is proper, the Frequency spectrum efficiency of the OFDM-IM system greatly exceeds that of the OFDM system.
However, the receiving end of the SM-OFDM-IM system has higher requirements on channel independence, synchronization, and the like, and has poorer real-time performance, and symbol information to be detected also changes, and in the system, the receiving end needs to detect three parts of bit information: antenna index bit information, subcarrier index bit information and modulation bit information, the complexity is higher. Therefore, designing a detection method with low complexity and good error rate performance is an important content of index modulation.
At present, detection methods for SM-OFDM-IM systems are few, and the existing methods can only detect the serial number and constellation symbols of an activated subcarrier but not the serial number of an activated antenna. And cannot be directly applied to the system of the present invention.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a partial maximum likelihood detection method based on energy sorting, which reduces the search range of ML and can reach the compromise between complexity and error rate performance, aiming at the defects in the prior art.
The invention adopts the following technical scheme:
a partial maximum likelihood detection method based on energy sorting adopts a step demodulation mode, firstly, the subcarrier serial number adopts minimum mean square error balance, then the energy value of each subcarrier is obtained, and sorting is carried out, the number p of the selected candidate subcarriers is set, and then the partial subcarrier serial number, the antenna serial number and the constellation symbol are detected by adopting the maximum likelihood.
Specifically, the method comprises the following steps:
s1, receiving sub-block ygMMSE equalization is carried out;
s2, calculating the signal obtained in the step S1
Figure BDA0001851492390000021
The energy values are sorted, and the subcarrier with the largest energy is most likely to be an activated subcarrier;
s3, setting P as the number of candidate subcarriers in each subblock, where P is 1,2, … n, and n is the number of subcarriers in each subblock;
s4, carrying out maximum likelihood detection on the selected P candidate subcarriers, all antennas and constellation modulation, and taking the group with the minimum Euclidean distance as a final judgment result;
s5, when G is G +1, steps S1 to S4 are repeated to obtain the detection results of G subblocks.
In step S1, the equalized signal is obtained
Figure BDA0001851492390000031
Comprises the following steps:
Figure BDA0001851492390000032
Figure BDA0001851492390000033
GMMSE＝(HHH+σ2I)-1HH
wherein G isMMSEAs a weight matrix, σ2For noise variance, I is the unit diagonal matrix, H is the channel, X is the transmit symbol, and W is the noise symbol.
Wherein the g-th receiving sub-block ygComprises the following steps:
yg＝HgXg+Wg
Figure BDA0001851492390000034
wherein G is 1,2, … G, G is total number of sub-blocks, NtFor total number of transmit antennas, NrFor the total number of receiving antennas, the number of subcarriers in each subblock is N ═ N/G, H is the channel, X is the transmission symbol, W is the noise symbol, and the dimension is Nt×n。
Wherein, in step S2, the signal
Figure BDA0001851492390000035
Energy value of
Figure BDA0001851492390000036
Comprises the following steps:
Figure BDA0001851492390000037
wherein, for the obtained energy value of each subcarrier
Figure BDA0001851492390000038
The ordering is as follows:
Figure BDA0001851492390000039
wherein e is1,e2,…,eNAnd sorting the energy values to obtain index values from small to large.
In step S4, the traversal range of the subcarriers is first reduced by energy detection, initial selection is performed, and then partial maximum likelihood detection is performed to reduce the traversal range of the ML.
Wherein, Euclidean distance D is:
Figure BDA0001851492390000041
wherein,
Figure BDA0001851492390000042
for the estimated transmitted symbol of the G-th sub-block, H is the channel, and G is 1,2, …, G, and F are norms.
Specifically, the distribution modulation specifically includes: based on one having NtRoot transmitting antenna, NrAccording to the receiving antenna, N subcarriers are divided into G subcarrier blocks, the length of each subcarrier block is N/G, k subcarriers are selected to be activated and data are sent, the subcarrier configuration is (N, k), and the modulation mode is M-order modulation.
Specifically, for each subcarrier block, index bit p of one antenna is activated1Comprises the following steps:
Figure BDA0001851492390000043
subcarrier index bit p2Comprises the following steps:
Figure BDA0001851492390000044
constellation symbol bit p3Comprises the following steps:
p3＝k log2M
the bit number p carried by one SM-OFDM-IM block is:
p＝p1+p2+p3
a transmission rate R of
Figure BDA0001851492390000045
Frequency domain transmission symbol of g sub-block
Figure BDA0001851492390000046
The following were used:
Figure BDA0001851492390000051
wherein G is 1, … G,
Figure BDA0001851492390000052
denotes the symbol sent by the g-th sub-block on the j-th sub-carrier of the ith transmitting antenna, i is 1,2, …, Nt，j＝1,2,…,n；
If the wireless channel is kept unchanged in the transmission process of the SM-OFDM-IM symbol, the obtained frequency domain receiving signal
Figure BDA0001851492390000053
Comprises the following steps:
Figure BDA0001851492390000054
wherein,
Figure BDA0001851492390000055
representing the channel matrix on the jth subcarrier of the jth subblock, subject to a distribution CN (0,1),
Figure BDA0001851492390000056
Figure BDA0001851492390000057
indicating the received signal and gaussian white noise in the g-th sub-block.
Compared with the prior art, the invention has at least the following beneficial effects:
the partial maximum likelihood detection method based on energy sorting reduces the search range of the traditional ML and reduces the complexity of a receiving end detection algorithm.
Furthermore, detection algorithms with different error rate performances can be obtained according to the selection of the P value, and good compromise between the error rate and the complexity of the system can be achieved.
Further, in order to minimize the mean square error based on the estimated value of the received data and the target data, the estimated value of the transmission symbol on each subcarrier is obtained by frequency domain equalization.
Further, by comparing the power of the equalized symbols on the subcarriers, the corresponding subcarrier with a higher power is considered as an active subcarrier. Thus, the sequence number of the active subcarrier can be demodulated.
Furthermore, the partial maximum likelihood detection algorithm can demodulate accurate subcarrier serial numbers, antenna index serial numbers and constellation symbols, the number of combinations needing to be traversed is reduced, and the complexity is reduced to a certain extent.
Furthermore, there is a significant defect of possible error transmission in demodulation at the receiving end in the transmitting structure when the sub-carriers are not blocked, and the defect can be made up by blocking the sub-carriers.
In summary, the subcarrier blocks of the present invention can make up for the error retransmission defect when the receiving end demodulates, the subcarrier sequence number can be demodulated by comparing the power of the balanced symbol on the subcarrier, the number of traversed combinations can be reduced by adding part of the maximum likelihood detection algorithm, the complexity is reduced to a certain extent, and the setting of the P value can achieve a good compromise between the system error rate and the complexity.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
FIG. 1 is a bit error rate curve diagram of different P values in a partial maximum likelihood detection algorithm based on energy sorting of an SM-OFDM-IM system in the invention;
FIG. 2 is a diagram of an SM-OFDM-IM system model in accordance with the present invention;
FIG. 3 is a graph comparing the bit error rate of the inventive system with that of the initial system at the same spectral efficiency;
fig. 4 is a bit error rate comparison diagram of the energy sorting-based partial maximum likelihood detection algorithm of the SM-OFDM-IM system in the present invention, the classical algorithm ML, and the partial maximum likelihood detection algorithm using ZF equalization.
Detailed Description
The invention provides a partial maximum likelihood detection method based on energy sequencing, which mainly combines space domain index modulation and frequency domain index modulation to form a space-frequency combined index modulation system, namely SM-OFDM-IM.
The invention relates to a partial maximum likelihood detection method based on energy sorting, which adopts the thought of step-by-step demodulation, firstly obtains an energy value for each subcarrier after the subcarrier sequence number adopts minimum mean square error equalization, sorts the energy values, sets a P value as the number of selected candidate subcarriers, and then adopts the maximum likelihood to detect partial subcarrier sequence number, antenna sequence number and constellation symbol.
Based on one having NtRoot transmitting antenna, NrAccording to the receiving antenna, N subcarriers are divided into G subcarrier blocks, the length of each subcarrier block is N/G, k subcarriers are selected to be activated and data are sent, the subcarrier configuration is (N, k), and the modulation mode is M-order modulation.
Activating index bit p of one antenna for each subcarrier block1Comprises the following steps:
Figure BDA0001851492390000071
subcarrier index bit p2Comprises the following steps:
Figure BDA0001851492390000072
constellation symbol bit p3Comprises the following steps:
p3＝k log2M
so the number of bits p that one SM-OFDM-IM block can carry is:
p＝p1+p2+p3
a transmission rate R of
Figure BDA0001851492390000073
The bits per channel use, bpcu, according to the above steps, the frequency domain of the g sub-block sends the symbol
Figure BDA0001851492390000074
As follows
Figure BDA0001851492390000075
Wherein G is 1, … G,
Figure BDA0001851492390000076
denotes the symbol sent by the g-th sub-block on the j-th sub-carrier of the ith transmitting antenna, i is 1,2, …, Nt，j＝1,2,…,n。
The frequency domain received signal obtained assuming that the radio channel remains unchanged during the transmission of the SM-OFDM-IM symbol
Figure BDA0001851492390000077
Comprises the following steps:
Figure BDA0001851492390000078
wherein,
Figure BDA0001851492390000079
represents the g-th subThe channel matrix on the jth subcarrier of the block, which obeys the distribution CN (0,1),
Figure BDA00018514923900000710
Figure BDA00018514923900000711
indicating the received signal and gaussian white noise in the g-th sub-block.
The received signal is detected in units of each sub-block, and the g-th received sub-block y is setgDimension NtX n, wherein
yg＝HgXg+Wg
Figure BDA0001851492390000081
Wherein G is 1,2, …, G is the total number of sub-blocks, and N istFor total number of transmit antennas, NrFor the total number of receiving antennas, the number of subcarriers in each sub-block is N ═ N/G, H is a channel, X is a transmission symbol, and W is a noise symbol.
The method comprises the following specific steps:
s1, for ygPerforming MMSE equalization
MMSE belongs to a linear detection algorithm, is based on an improved result of a zero-forcing detection algorithm, considers the influence of noise on detection, and designs a weight matrix as follows:
GMMSE＝(HHH+σ2I)-1HH
in the formula, σ2I is the unit diagonal matrix for the noise variance.
The noise variance σ needs to be known at the receiving end for the MMSE signal detection algorithm2The equalized signal obtained by using the obtained frequency domain received signal is:
Figure BDA0001851492390000082
Figure BDA0001851492390000083
s2, and the signal after equalization
Figure BDA0001851492390000084
To obtain an energy value, i.e.
Figure BDA0001851492390000085
Obtaining the energy value of each subcarrier
Figure BDA0001851492390000086
And sorting it to obtain
Figure BDA0001851492390000087
The sub-carrier with the largest energy is considered to be the most possible activating sub-carrier;
s3, setting a value P, where P is the number of candidate subcarriers per subblock, and P is 1,2, … n;
the complexity of using energy detection is low and its detection performance is poor due to interference among multiple antennas and the influence of white gaussian noise.
S4, carrying out maximum likelihood detection on the selected P candidate subcarriers, all antennas and constellation modulation
Figure BDA0001851492390000091
Wherein,
Figure BDA0001851492390000092
the combination with the minimum Euclidean distance is the final judgment result according to the sending symbol of the g sub-block estimated in the step;
and S5, repeating the steps until G is equal to G +1, and obtaining the detection results of the G sub-blocks.
Firstly, the traversal range of the subcarrier is reduced by using energy detection, initial selection is carried out, partial maximum likelihood detection is carried out on the basis, the traversal range of the ML is reduced, and the algorithm complexity is reduced.
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 some, but not all, embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The block diagrams of the transmitting end and the receiving end of the SM-OFDM-IM system adopted in the invention are shown in FIG. 2, and the specific modulation process of the transmitter is as follows: firstly, selecting an antenna to be activated according to an antenna index bit, carrying out OFDM-IM modulation on a subcarrier block on the activated antenna, selecting a subcarrier to be activated according to the subcarrier index bit and modulating a constellation symbol, wherein a receiving end is opposite to a transmitting end.
Different from the detection of the traditional MIMO-OFDM system, the receiving end of the SM-OFDM-IM system needs to detect subcarrier index bits, antenna index bits and constellation modulation bits, and the current detection method for index modulation is mainly divided into joint detection and step detection, wherein the research focuses on spatial modulation and frequency domain index modulation. The joint detection method utilizes the maximum likelihood criterion to carry out joint detection on the subcarrier index, the antenna index and the constellation point so as to improve the BER performance of the method. The idea of step detection is to detect the subcarrier index, antenna index and constellation point separately. The detection methods of the SM and the OFDM-IM systems can not be directly used, and the error code rate of the existing energy detection method for the frequency domain index modulation system can reach 10 when the signal-to-noise ratio is 40dB-4And the performance is better. But the performance is poor when the method is directly applied to the SM-OFDM-IM system, and the error rate is always maintained at 10-2On the left and the right sides,on the basis, a partial ML detection method based on energy sorting is provided, an error rate simulation graph of the partial ML detection method is shown in figure 1, and the complexity of the partial ML detection method can be greatly reduced on the premise of slight loss of error rate performance.
It can be seen from fig. 1 that as the P value is larger and larger, the search range is larger, the complexity of the detection method is higher and higher, and the error rate performance is better and better, and when P is 4, that is, the maximum likelihood detection is performed, the error rate performance is best, and the complexity is higher.
Table 1 shows the computational complexity of complex multiplication of different detection methods under each sub-block
Figure BDA0001851492390000101
From the above table, it can be seen that the computation complexity of the partial maximum likelihood detection based on the energy sorting detector is lower than that of the conventional maximum likelihood detection method, because the method proposed by the present invention reduces the search range of the maximum likelihood detection by introducing energy detection. Compared with the partial maximum likelihood method adopting ZF equalization, the complexity of the method provided by the invention is slightly higher, which is caused by the difference of selecting the equalization matrix.
Referring to FIG. 2, MATLAB simulation is performed on SM-OFDM-IM, and the number of Monte Carlo simulations is selected to be 107The noise is white gaussian noise. In order to ensure that the OFDM system has the same frequency spectrum efficiency with the OFDM-IM system and the SM-OFDM-IM system, the total number of subcarriers in the OFDM-IM system is 128 and is divided into 64 subblocks, the configuration of the subcarriers in each subblock is (2,1), and BPSK modulation is adopted; adding spatial modulation on the basis of OFDM-IM to form space-frequency joint index modulation, wherein the parameter of the system is set that the total number of subcarriers is 64, the system is divided into 32 subblocks, an antenna system is 2 multiplied by 2, the subcarrier of each subblock is configured to be (2,1), and QPSK modulation is adopted.
Please refer to fig. 3, which is a graph of error rate of OFDM, OFDM-IM, SM-OFDM-IM systems, according to the simulation graph, it can be seen that the error rate is 10 after adding the antenna index under the condition of the same spectrum efficiency-3In comparison to OFDM and OFDM-IM, SM-OFDMIM systems achieve gains of 30dB and 15dB respectively. This is because, compared with the conventional OFDM technology, the SM-OFDM-IM adds subcarrier index information and antenna index information, and selects a part of subcarriers and a part of antennas to transmit data. And other subcarriers and other antennas keep silent states, the sensitivity of the system to frequency offset is reduced due to the sparsity of frequency domain data, the influence of inter-subcarrier interference on transmission performance is reduced, and only one antenna is activated in a space domain, so that inter-antenna interference is avoided.
Under the condition of high signal-to-noise ratio, the error rate performance of the SM-OFDM-IM system is superior to that of OFDM, which shows that the SM-OFDM-IM has better reachable rate. Compared with the bit rate of the transmitting end, the SM-OFDM-IM brings about the reduction of the spectrum efficiency because part of subcarriers and part of antennas are silent, but the introduced index bit information can make up for the problem. The SM-OFDM-IM is a multi-carrier system with more universality than OFDM because of unique system setting and more flexible parameter configuration.
Referring to fig. 4, the parameter setting of the SM-OFDM-IM system is unchanged, and different detection methods are compared, fig. 4 shows BER performance of the SM-OFDM-IM different detection methods, and it can be seen from the figure that, when P is 3, the detection method provided by the present invention obtains better error rate performance than the ML method using ZF equalization because MMSE considers the influence of noise on detection, but has poorer BER performance and lower complexity compared with the maximum likelihood detection method because the increased energy detection reduces the search range of maximum likelihood detection.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.

Claims (4)

1. A partial maximum likelihood detection method based on energy sorting is characterized in that a step-by-step demodulation mode is adopted, firstly, the number of subcarriers is balanced by the minimum mean square error, then the energy value of each subcarrier is obtained, sorting is carried out, the number P of selected candidate subcarriers is set, and then the partial subcarrier number, the antenna number and the constellation symbol are detected by the maximum likelihood;
the distribution modulation specifically comprises: based on one having NtRoot transmitting antenna, NrDividing N sub-carriers into G sub-carrier blocks according to a receiving antenna, selecting k sub-carriers to activate and send data, wherein the sub-carriers are configured as (N, k), and the modulation mode is M-order modulation; the step-by-step demodulation mode comprises the following steps:
s1, receiving sub-block ygMMSE equalization is performed, and the equalized signal
Figure FDA0003023072480000011
Comprises the following steps:
Figure FDA0003023072480000012
Figure FDA0003023072480000013
GMMSE＝(HHH+σ2I)-1HH
wherein G isMMSEAs a weight matrix, σ2I is the unit diagonal matrix, H is the channel,
Figure FDA0003023072480000014
for transmitting symbols, W is a noise symbol and dimension Nt×n；
S2, calculating the signal obtained in the step S1
Figure FDA0003023072480000015
Energy value, and sorting the energy values, the subcarrier with the highest energy is most probably the activation subcarrier, signal
Figure FDA0003023072480000016
Energy value of
Figure FDA0003023072480000017
Comprises the following steps:
Figure FDA0003023072480000018
s3, setting P as the number of candidate subcarriers in each subblock, where P is 1,2, … n, and n is the number of subcarriers in each subblock;
s4, carrying out maximum likelihood detection on the selected P candidate subcarriers, all antennas and constellation modulation, taking the group with the minimum Euclidean distance as a final judgment result, firstly using energy detection to reduce the traversal range of the subcarriers, carrying out initial selection, carrying out partial maximum likelihood detection on the basis, reducing the traversal range of ML, wherein the Euclidean distance D is as follows:
Figure FDA0003023072480000021
wherein,
Figure FDA0003023072480000022
h is the estimated transmission symbol of the G-th sub-block, G is 1,2, …, G, and F are norms;
s5, when G is G +1, steps S1 to S4 are repeated to obtain the detection results of G subblocks.
2. The partial maximum likelihood detection method based on energy sorting of claim 1, wherein in step S1, the g-th received sub-block ygComprises the following steps:
yg＝HgXg+Wg
Figure FDA0003023072480000023
wherein G is 1,2, … G, and G is the total number of sub-blocks.
3. The partial maximum likelihood detection method based on energy sorting as claimed in claim 1, wherein in step S2, the obtained energy value of each sub-carrier is used
Figure FDA0003023072480000024
The ordering is as follows:
Figure FDA0003023072480000025
wherein e is1,e2,…,eNAnd sorting the energy values to obtain index values from small to large.
4. The partial maximum likelihood detection method based on energy sorting according to claim 1, characterized in that, for each subcarrier block, the index bit p of one antenna is activated1Comprises the following steps:
Figure FDA0003023072480000026
subcarrier index bit p2Comprises the following steps:
Figure FDA0003023072480000027
wherein,
Figure FDA0003023072480000028
selecting the combination condition of k subcarriers from n subcarriers;
constellation symbol bit p3Comprises the following steps:
p3＝klog2M
the bit number p carried by one SM-OFDM-IM block is:
p＝p1+p2+p3
a transmission rate R of
Figure FDA0003023072480000031
Frequency domain transmission symbol of g sub-block
Figure FDA0003023072480000032
The following were used:
Figure FDA0003023072480000033
wherein G is 1, … G,
Figure FDA0003023072480000034
denotes the symbol sent by the g-th sub-block on the j-th sub-carrier of the ith transmitting antenna, i is 1,2, …, Nt，j＝1,2,…,n；
If the wireless channel is kept unchanged in the transmission process of the SM-OFDM-IM symbol, the obtained frequency domain receiving signal
Figure FDA0003023072480000035
Comprises the following steps:
Figure FDA0003023072480000036
wherein,
Figure FDA0003023072480000037
representing the channel matrix on the jth subcarrier of the jth subblock, subject to a distribution CN (0,1),
Figure FDA0003023072480000038
Figure FDA0003023072480000039
representing the received signal and the Gaussian white in the g-th sub-blockNoise.
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