CN113114311A - Combined beam forming and spatial modulation method based on intelligent reflecting surface and transmitting end - Google Patents

Combined beam forming and spatial modulation method based on intelligent reflecting surface and transmitting end Download PDF

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CN113114311A
CN113114311A CN202110332655.9A CN202110332655A CN113114311A CN 113114311 A CN113114311 A CN 113114311A CN 202110332655 A CN202110332655 A CN 202110332655A CN 113114311 A CN113114311 A CN 113114311A
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reflecting surface
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CN113114311B (en
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吴贇
高浩然
白恩健
蒋学芹
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Donghua 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
    • 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
    • H04B7/04013—Intelligent reflective surfaces
    • 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
    • H04B7/0615—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 of weighted versions of same signal
    • H04B7/0617—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 of weighted versions of same signal for beam forming
    • 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
    • H04B7/0697—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 spatial multiplexing

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Abstract

The invention relates to a method for combining beam forming and receiving end space modulation based on an intelligent reflecting surface and a transmitting end, which carries out optimization design on beam forming of the transmitting end and a phase angle of the intelligent reflecting surface based on a maximum system receiving signal-to-noise ratio. A greedy detection scheme and a maximum likelihood detection scheme based on exhaustive search are provided for two situations of continuous phase shift and discrete phase shift of an intelligent reflecting surface. The method provided by the invention utilizes spatial modulation, effectively avoids the problem of inter-channel interference in multi-antenna transmission, fully utilizes space domain resources and provides effective data transmission rate. In addition, the joint beam forming on the transmitting end and the intelligent reflecting surface is used, so that the signal quality is improved, and the reliable communication is ensured.

Description

Combined beam forming and spatial modulation method based on intelligent reflecting surface and transmitting end
Technical Field
The invention relates to a spatial modulation and combined beam forming method of an intelligent reflector MIMO wireless communication system, belonging to the field of wireless communication.
Background
The fifth generation mobile communication (5G) technology has been deployed in many countries and regions on a large scale, which greatly increases the information transmission rate, and the existing large-scale Multiple-Input Multiple-output (MIMO) technology realizes the transmission and reception of information through a large-scale antenna array, which increases the power gain; however, the conventional phased array required for beamforming limits the size of the antenna array of MIMO due to power consumption and hardware cost, so that the advantages of the MIMO technology cannot be effectively exerted.
Intelligent reflective surfaces, on which a large number of small, low-cost passive reflective elements reflect incident signals only with adjustable phase shifts, without the use of dedicated energy sources for Radio Frequency (RF) processing, decoding, encoding, etc., are considered as a promising alternative to conventional phased arrays. By intelligently adjusting the phase shift of all the reflecting units to adapt to the dynamic wireless channel, the signal reflected by the intelligent reflecting surface can be superposed or offset with the non-reflected signal on the user receiver so as to improve the required signal power or inhibit the channel interference, thereby greatly improving the wireless network performance. The research of scholars at home and abroad on the intelligent reflecting surface has already produced some achievements in recent years. Specifically, Basar firstly proposes two concepts of using an intelligent reflecting surface as an access point and transmitting auxiliary information of the intelligent reflecting surface in double-hop communication, and the article shows that the signal transmission based on the intelligent reflecting surface can effectively improve the receiving signal-to-noise ratio and realize the ultra-reliable communication. Basar further provides intelligent reflecting surface space shift keying (IRS-SSK) and intelligent reflecting surface space modulation (IRS-SM) schemes, the intelligent reflecting surface is utilized to not only improve signal quality, but also select specific receiving antenna indexes according to information bits to realize Index Modulation (IM). Wu and Zhang et al studied the optimization of the intelligent reflector in a multiple transmit antenna system, and for an intelligent reflector enhanced multiple-input single-output (MISO) wireless system, the total signal power received by the user was improved to the maximum extent by jointly optimizing the (active) transmit beamforming of the access point and the (passive) reflected beamforming of the intelligent reflector, and the discrete phase shift was considered in the subsequent studies.
However, none of the above studies on the intelligent reflective surface is performed in the MIMO system, and in order to show the advantages of the MIMO system while beamforming, the present invention considers that the intelligent reflective surface is added in addition to spatial modulation to perform communication of the joint beamforming auxiliary MIMO system.
Disclosure of Invention
The purpose of the invention is: the problems of overhigh cost, overlarge complexity and the like of the traditional beam forming and the limit of the traditional beam forming on the scale of the MIMO antenna array are solved, and meanwhile, the signal to noise ratio is further improved and the error rate is reduced.
In order to achieve the above object, the technical solution of the present invention is to provide a method for combining beam forming and spatial modulation based on an intelligent reflecting surface and a transmitting end, which is characterized by comprising the following steps:
(1) establishing an intelligent reflector MIMO wireless communication system model: in a MIMO system, having NTBase station and N of root antennaRThe receiving end of the root antenna is communicated with the aid of the intelligent reflecting surface; the channel between the transmitting and receiving ends of the MIMO system is divided into two sub-channels: sub-channel T between intelligent reflector and base station, and sub-channel between receiving end and intelligent reflector
Figure BDA0002996836900000021
After spatial modulation, the received signal of the kth antenna is:
yk＝rkPTws+nk (1)
wherein, the invention models the reflection phase shift coefficient on the first reflection unit as thetaiE 0,2), the amplitude coefficient rho e 0,1]，
Figure BDA0002996836900000022
Representing a phase-shift reflection matrix on an intelligent reflection surface, under the condition of considering maximum reflection, the method is set to be 1, w is a beam forming vector, s represents a transmission symbol, the mean value of the transmission symbol is 0, and the variance of the transmission symbol is 1; n iskIs Gaussian white noise, has a mean value of 0 and a variance of sigma2。
(2) Considering two schemes of continuous phase shift and discrete phase shift, performing combined beam forming on a transmitting end and an intelligent reflecting surface to maximize the signal-to-noise ratio (received power), and describing beam forming optimization under the continuous scheme as a problem (P1):
(P1)：
Figure BDA0002996836900000023
s.t.‖w‖2≤p (3)
0≤θi<2π,
Figure BDA0002996836900000024
beamforming optimization under discrete scheme is described as a problem (P2):
(P2)：
Figure BDA0002996836900000025
s.t.‖w‖2≤p (6)
θi∈I,
Figure BDA0002996836900000026
wherein p is the maximum transmission power, the invention takes a 3-bit phase shifter as an example to discuss a discrete phase shift scheme, i.e. I ═ {0, pi/4, pi/2, 3 pi/4, pi, 5 pi/4, 3 pi/2, 7 pi/4 } is selected as a discrete phase shift sequence.
(3) And the spatial modulation of a receiving end is adopted to effectively obtain the transmission bit rate while the joint beamforming optimization is carried out. Having N in the systemRRoot receiving antennas and perform M-PSK or M-QAM modulation for transmitting each group b1+2Digital signal of bits, in which the front b1Bit mapping to receive antenna index k, post b2Mapping the bits into constellation point symbols s;
(4) the invention respectively uses two detection algorithms for demodulation, wherein one detection algorithm is a greedy detection algorithm, and the other detection algorithm is a maximum likelihood detection algorithm based on exhaustive search.
Further, the problem (P1) in step (2) can be solved by the following method to realize the step-by-step optimization of beamforming between the base station and the intelligent reflecting surface:
Figure BDA0002996836900000031
is rkRepresents the channel between the kth receiving antenna and the ith reflecting unit, where k is 1,2RAnd i ═ 1, 2., N, βk,iRepresenting the channel amplitude, phik,iRepresenting the channel angle. For any given transmit beam vector
Figure BDA0002996836900000032
The channel between the ith reflection unit and the base station can all be represented as
Figure BDA0002996836900000033
Wherein
Figure BDA0002996836900000034
Is the ith row vector of T,
Figure BDA0002996836900000035
representing the channel amplitude, αiRepresenting the channel angle. The reflection phase shift of the first reflection unit is
Figure BDA0002996836900000036
In view of the maximum reflection, ρ is set to 1. The objective function of the problem (P1) can be expressed as:
Figure BDA0002996836900000037
in formula (8), σ2Representing the noise power.
Existing
Figure BDA0002996836900000038
Can be set by xiiTo obtain the maximum value, the phase shift of the first reflection unit is seti＝k,i+iTo achieve a maximization of the signal-to-noise ratio;
in this MIMO system, optimization of base station beamforming can be achieved using Maximum Ratio Transmission (MRT), i.e.,
Figure BDA0002996836900000039
by pairsiAnd w are alternately optimized until convergence, so that the aim of maximizing the signal-to-noise ratio under a continuous phase shift scheme can be fulfilled.
Further, the problem (P2) in step (2) can be solved by the following method to realize the step-by-step optimization of beamforming between the base station and the intelligent reflecting surface:
for passive beam forming of the intelligent reflecting surface, the invention adopts an exhaustive and alternative optimization mode. Specifically, N-1 phase shifts in N reflection units are fixed, and the remaining unique reflection unit phase shifts are searched exhaustively in a discrete phase shift sequence; the beamforming optimization at the respective base station is still achieved by maximum ratio transmission; to pairiAnd w is iterated for multiple times until convergence, so that the aim of maximizing the signal-to-noise ratio under a discrete phase shift scheme can be realized.
Further, the greedy detection algorithm and the maximum likelihood detection algorithm in the step (4) are applied in the system as follows:
the greedy detection algorithm firstly demodulates the receiving antenna index k according to the optimization target of signal-to-noise ratio maximization:
Figure BDA0002996836900000041
in the formula (10), ykRepresenting the received signal of the k-th antenna,
Figure BDA0002996836900000042
indicating the detected antenna index.
Then, the transmitted symbol s is demodulated according to the Euclidean distance minimum principle:
Figure BDA0002996836900000043
and the maximum likelihood detection algorithm is joint detection of a receiving antenna index k and a transmitting symbol a:
Figure BDA0002996836900000044
the greedy detection algorithm is simpler and adapts to the optimization target of maximum received power, while the maximum likelihood detection is suitable for situations where the noise impact is small. When the noise condition is larger, the performance of the greedy detection algorithm of the system is superior to that of the maximum likelihood detection algorithm, and the effectiveness of the combined optimization scheme is indirectly proved.
Compared with the prior art, the invention has the following beneficial effects: the intelligent reflector MIMO system designed by the invention effectively utilizes space domain resources by adopting space modulation, improves the data transmission rate, realizes the combined beam forming by the provided alternative optimization algorithm, effectively improves the signal-to-noise ratio, greatly reduces the transmission error rate and improves the system performance.
Drawings
FIG. 1 is a schematic diagram of an intelligent reflector MIMO communication system;
FIG. 2 is a flow chart of a continuous phase shift scheme combined beam forming algorithm based on alternating optimization;
FIG. 3 is a flowchart of a discrete phase shift scheme combined beamforming algorithm based on alternating optimization;
FIG. 4 is a simulation diagram of the signal-to-noise ratio performance of the proposed scheme;
FIG. 5 is a simulation diagram of the effect of different detection methods on the performance of bit error rate in the proposed scheme;
fig. 6 is a simulation diagram of the influence of the number of different receiving antennas on the error rate performance in the proposed scheme.
Detailed Description
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.
The invention provides a combined beam forming and spatial modulation method (IRS-JBSM) based on an intelligent reflecting surface and a transmitting end aiming at an intelligent reflecting surface MIMO system, and particularly, the combined beam forming is carried out by utilizing an alternative optimization algorithm on the basis of carrying out spatial modulation on a receiving end through a built system model. The performance advantage of the MIMO system receiving and transmitting end combined design provided by the invention is verified through simulation, and the method specifically comprises the following steps:
the method comprises the following steps: an intelligent reflecting surface MIMO system model as shown in figure 1 is established, an intelligent reflecting surface with N reflecting units reflects incident signals with specific phase shift, active beam forming is carried out at a transmitting end to concentrate the signals to the intelligent reflecting surface with a larger area, and passive beam forming is carried out again on the intelligent reflecting surface to concentrate the signals to a required antenna. With the aid of the intelligent reflecting surface, the energy consumption and complexity caused by directly performing beam forming on the transmitting end to the required receiving end can be greatly reduced. At the same time, spatial modulation based on the receive antenna index is employed for signals having NNRoot transmitting antenna and NRIn the MIMO system with multiple receive antennas, at the k-th selected receive antenna, the received signal may be represented as:
yk＝rkPTws+nk (1)
wherein r iskRepresenting the channel between the kth antenna and the intelligent reflecting surface, and modeling the reflection phase shift coefficient on the first reflecting unit as thetaiE 0,2), the amplitude coefficient rho e 0,1]，
Figure BDA0002996836900000051
Representing a phase-shifted reflection matrix on an intelligent reflective surface. In the case of considering the maximum reflection, the present invention will be set to 1, w is the beamforming vector, s represents the transmitted symbol, its mean is 0, and the variance is 1; n iskIs Gaussian white noise, has a mean value of 0 and a variance of sigma2。
Step two: and performing combined beam forming on the intelligent reflector MIMO system by taking the maximized signal-to-noise ratio as an optimization target. From the received signal equation (1), the signal-to-noise ratio of the kth receiving antenna can be modeled as:
Figure BDA0002996836900000052
for the continuous case, the interior of the above formula is first refined,
Figure BDA0002996836900000053
is rkRepresents the channel between the kth receiving antenna and the ith reflecting unit, where k is 1,2RAnd i ═ 1, 2. For any given transmit beam vector
Figure BDA0002996836900000061
The channel between the ith reflection unit and the base station can all be represented as
Figure BDA0002996836900000062
Wherein
Figure BDA0002996836900000063
Is the ith row vector of T. The reflection phase shift of the first reflection unit is
Figure BDA0002996836900000064
In view of the maximum reflection, ρ is set to 1. The above formula can be further expressed as:
Figure BDA0002996836900000065
in order to maximize the signal-to-noise ratio, the present invention requires the pair θiMaking settings, as is now known
Figure BDA0002996836900000066
Figure BDA0002996836900000067
By setting xiiThe left end of the formula can be maximized, from which we can set
Figure DA00029968369055960401
And realizing the optimization target of reflected beam forming.
For this MIMO system, Maximum Ratio Transmission (MRT) is the optimal way for beamforming at the transmitting end, i.e.,
Figure BDA0002996836900000068
by pairsiAnd w are alternately optimized until convergence, so that the aim of maximizing the signal-to-noise ratio under a continuous phase shift scheme can be fulfilled.
The detailed flow is shown in fig. 2 and algorithm 1.
Figure BDA0002996836900000069
Figure BDA0002996836900000071
For the discrete phase shift case, we use the "exhaustive" + "alternate optimization" approach. Specifically, N-1 phase shifts in N reflection units are fixed, and exhaustive search is performed on the remaining unique reflection unit phase shifts in a discrete phase shift sequence, that is, the phase shifts of other reflection units are fixed, an optimal discrete value of each reflection unit under the condition is searched in a medium round, and a corresponding transmit beamforming vector w is determined according to a maximum ratio transmission principle.
To pairiAnd w is iterated for multiple times until convergence, so that the aim of maximizing the signal-to-noise ratio under the discrete phase shift condition can be realized.
The detailed flow is shown in fig. 3 and algorithm 2.
Figure BDA0002996836900000072
Step three: two detection methods are used for demodulating the system, one is a classical maximum likelihood detection algorithm, and the idea of the algorithm is to perform joint detection on a receiving antenna index k and a transmitting symbol s:
Figure BDA0002996836900000081
the second is a greedy detection algorithm based on maximum energy, which firstly detects a receiving antenna index k:
Figure BDA0002996836900000082
detecting a transmission symbol s on the basis of a reception antenna index k:
Figure BDA0002996836900000083
fig. 4 shows the signal-to-noise performance of the proposed algorithm. Setting the number of receiving antennas to N R2, and performing binary modulation, and the number of transmitting antennas is NTAnd carrying out multi-group setting, and verifying the influence of the number N of the reflecting units on the signal-to-noise ratio performance. It can be seen from the figure that the signal-to-noise ratio increases with the number of reflecting units in both the discrete case and the continuous case, except that due to the quantization in the discrete phase shift scheme, the signal from the transmitting end cannot achieve complete phase cancellation at the receiving end, resulting in power loss, and the signal-to-noise ratio performance of the continuous phase shift scheme is slightly better than that of the discrete scheme. Furthermore, an increase in the number of transmit antennas will lead to an increase in SNR performance due to beamforming. The resulting curve of the discrete phase shift scheme is slightly meandering due to the finite stage phase shifters used, but as N increases, this non-smoothness is compensated for. Finally, by increasing the value of N from 30 to 120, the SNR performance is significantly improved, which demonstratesThe effectiveness of the intelligent reflecting surface in creating a 'signal hot spot' is clear.
Fig. 5 to 6 show the bit error rate performance of the successive schemes proposed by the present invention. Similarly, the number of receiving antennas is set to N R2, the number of transmitting antennas is set to NTAnd 3, setting the number of the reflecting units to be N to be 64, and performing binary modulation. Fig. 5 compares the performance of the two demodulation modes under the parameter settings of this example. As mentioned above, the greedy detection algorithm is more suitable for the optimization target of the invention, so that the performance of the greedy detection algorithm of the system is better than that of the maximum likelihood detection algorithm when the noise influence is large, and the effectiveness of the joint optimization scheme of the invention on signal-to-noise ratio improvement is indirectly proved. FIG. 6 compares the number of different receiving antennas NRImpact on error rate performance: the more receive antennas, the slightly worse bit error rate performance. Meanwhile, the two graphs show that the error rate is reduced along with the increase of the number of the reflecting units, and the advantage of the intelligent reflecting surface in the aspect of ensuring reliable communication is displayed.

Claims (4)

1. A combined beam forming and spatial modulation method based on an intelligent reflecting surface and a transmitting end is characterized by comprising the following steps:
(1) establishing an intelligent reflector MIMO wireless communication system model:
configuring N in a MIMO systemTBase station and N of root antennaRThe receiving end of the root antenna is communicated with the aid of the intelligent reflecting surface; the channel between the receiving end and the transmitting end of the MIMO system is divided into a sub-channel T between the intelligent reflecting surface and the base station and a sub-channel between the receiving end and the intelligent reflecting surface
Figure FDA0002996836890000011
After spatial modulation, the received signal of the kth antenna is:
yk＝rkPTws+nk (1)
in the formula (1), the reflection phase shift coefficient on the i-th reflection unit is modeled as θiE [0,2 pi ]), and amplitude coefficient p e [0,1 ]]，
Figure FDA0002996836890000012
Representing a phase-shifted reflection matrix on the intelligent reflective surface; w is a beamforming vector; s represents a transmission symbol, the mean value of which is 0 and the variance of which is 1; n iskIs Gaussian white noise, has a mean value of 0 and a variance of sigma2；
(2) Considering two schemes of continuous phase shift and discrete phase shift, performing combined beam forming on a transmitting end and an intelligent reflecting surface to maximize the signal-to-noise ratio, and describing beam forming optimization under the continuous scheme as a problem (P1):
Figure FDA0002996836890000013
s.t.‖w‖2≤p (3)
Figure FDA0002996836890000014
beamforming optimization under discrete scheme is described as a problem (P2):
Figure FDA0002996836890000015
s.t.‖w‖2≤p (6)
Figure FDA0002996836890000016
in formulas (2) to (7), p is the maximum transmission power; i is a discrete phase shift sequence;
(3) the method comprises the steps that when the combined beam forming is optimized, the spatial modulation based on a receiving end is adopted to effectively obtain the transmission bit rate; the system has NRRoot receiving antennas and perform M-PSK or M-QAM modulation for transmitting each group b1+b2Digital signal of bits, in which the front b1Bit mappingFor the receiving antenna index k, post b2Mapping the bits into constellation point symbols s;
(4) and demodulating by using two detection algorithms respectively, wherein one detection algorithm is greedy detection, and the other detection algorithm is a maximum likelihood detection algorithm based on exhaustive search.
2. The method of claim 1, wherein the problem (P1) is solved by the following method, and the step-by-step optimization of beamforming between the base station and the intelligent reflecting surface is realized:
Figure FDA0002996836890000021
is rkRepresents the channel between the kth receiving antenna and the ith reflecting unit, where k is 1,2RAnd i ═ 1, 2., N, βk,iRepresenting the channel amplitude, phik,iRepresenting a channel angle; for any given transmit beam vector
Figure FDA0002996836890000022
The channel between the ith reflection unit and the base station can all be represented as
Figure FDA0002996836890000023
Wherein
Figure FDA0002996836890000024
Is the ith row vector of T, liRepresenting the channel amplitude, αiRepresenting a channel angle; the reflection phase shift of the ith reflection unit is
Figure FDA0002996836890000025
P is set to 1 in view of the maximum reflection, the objective function SNR of the problem (P1)kCan be expressed as:
Figure FDA0002996836890000026
in formula (8), σ2Representing the noise power;
existing
Figure FDA0002996836890000027
Can be set by xiiObtain the maximum value xi, so set up the phase shift theta of the ith reflection uniti＝φk,i+αiTo achieve a maximization of the signal-to-noise ratio;
in this MIMO system, the optimisation of base station beamforming is achieved with maximum ratio transmission, i.e.,
Figure FDA0002996836890000028
by pair of thetaiW until convergence, the goal of maximizing the signal-to-noise ratio under a continuous phase shift scheme can be achieved.
3. The method of claim 1, wherein the problem (P2) is solved by the following method, and the step-by-step optimization of beamforming between the base station and the intelligent reflecting surface is realized:
for passive beam forming of the intelligent reflecting surface, fixing N-1 phase shifts in N reflecting units, and exhaustively searching the phase shifts of the rest unique reflecting units in a discrete phase shift sequence; correspondingly, the beamforming optimization at the base station is realized by the maximum ratio transmission principle; to thetaiAnd w is iterated for multiple times until convergence, so that the aim of maximizing the signal-to-noise ratio under a discrete phase shift scheme can be realized.
4. The method of claim 1, wherein the application of a greedy detection algorithm and a maximum likelihood detection algorithm in the MIMO system is as follows:
the greedy detection algorithm firstly demodulates the receiving antenna index k according to the optimization target of signal-to-noise ratio maximization:
Figure FDA0002996836890000031
in the formula (10), ykRepresenting the received signal of the k-th antenna,
Figure FDA0002996836890000032
indicating the detected antenna index;
then, the transmitted symbol s is demodulated according to the Euclidean distance minimum principle:
Figure FDA0002996836890000033
the maximum likelihood detection algorithm is the joint detection of the received antenna index k and the transmitted symbol s:
Figure FDA0002996836890000034
the greedy detection algorithm is simpler and more adaptive to the optimization target of the maximum signal-to-noise ratio, and the maximum likelihood detection is suitable for the case of less noise influence.
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CN114124172A (en) * 2021-12-09 2022-03-01 电子科技大学 Intelligent reflector wave beam shaping and phase shift design method based on alternate direction
CN114900252A (en) * 2022-04-22 2022-08-12 西安邮电大学 Received signal detection method for enabling radio frequency reflector to receive and transmit combined spatial modulation
CN116016074A (en) * 2022-12-14 2023-04-25 东华大学 Intelligent reflecting surface phase shift design method based on cosine similarity
WO2023214797A1 (en) * 2022-05-04 2023-11-09 Samsung Electronics Co., Ltd. Method and device for beam training for an intelligent reflecting surface (irs) assisted cellular system

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