A spatial shift keying reflection modulation method

Abstract

The present application provides a spatial shift keying reflection modulation method, which applies spatial shift keying modulation to the transceiver, designs the corresponding reflection constellation points in combination with the transmit antenna index to solve the problems existing in IRS-TSM and IRS-TQSM, and jointly maps the transmit antenna index, the receive antenna index, and the reflection constellation point index to get rid of the restriction that the number of transmit and receive antennas must satisfy an integer power of 2. The present application can detect the signal without obtaining channel state information, and can obtain better bit error rate performance and lower computational complexity compared with likelihood detection that is not a perfect channel estimate.

Description

Technical Field

[0001] The present application relates to the field of modulation technology, and in particular to a spatial shift keying reflection modulation method. Background Art

[0002] As people's requirements for wireless communications become higher and higher, wireless networks are developing towards larger scales and higher frequency bands. Various innovative wireless communication technologies continue to emerge to meet the growing demand for higher transmission rates, such as millimeter wave (mmWave) communication, multiple-input multiple-output (MIMO) systems, index modulation (IM) and other technologies, but they suffer from high hardware costs and power consumption, which puts them at a competitive disadvantage in the development of the sixth-generation mobile communication system (6G).

[0003] In the past decade, spatial modulation (SM) has been widely used as a spatial multiplexing technology in MIMO systems. It transmits a constellation symbol by activating a radio frequency chain and uses the index of the active antenna to transmit information in each time slot, which has high transmission efficiency and low power consumption. In recent years, intelligent reflecting surfaces (IRS) have received widespread attention in the communications industry. IRS consists of a large number of low-cost, passive reflection units. It can reflect the incident signal with a specific reflection coefficient and change the amplitude and phase of the incident signal to improve the quality of the received signal, which makes it possible to improve communication performance in a greener way.

[0004] Inspired by SM and IRS, Basar et al. first proposed the IRS-assisted receiver spatial modulation (IRS-RSM) modulation method by combining spatial modulation technology with IRS. Since only one receiving antenna can be used to map bit information at a time, the system spectrum efficiency is low. Subsequently, Ma et al. considered applying spatial modulation technology to both the transmitter and receiver and proposed IRS-assisted transmitter-receiver spatial modulation (IRS-TSM). However, due to the high correlation between the channel link between the transmitter and IRS, it is difficult for the receiver to correctly detect the receiving antenna index when the constellation symbol and the receiving antenna are correctly detected, resulting in the performance degradation of IRS-TSM. IRS has a natural advantage in realizing SM. Recently, Sanila et al. proposed IRS-assisted transmitter-receiver quadrature spatial modulation (IRS-TQSM), which divides the IRS into two blocks for reflecting the real part of the signal and the imaginary part of the signal to the desired two receiving antennas. Although IRS-TQSM improves the spectrum efficiency compared with IRS-TSM, it is worth noting that when the index of the transmitting and receiving antennas is the same antenna, IRS-TSM is a special case of IRS-TQSM. Therefore, the problems in IRS-TSM still exist in IRS-TQSM, resulting in limited performance improvement of IRS-TQSM. In addition, in the above-mentioned studies, the number of transmitting and receiving antennas must be an integer power of 2, which causes the system to reduce the utilization rate of antenna resources and waste resources when it is not an integer power of 2. Recently, Zhang et al. proposed IRS-assisted generalized spatial shift keying (IRS-RGSSK) at the receiving end, which transmits information by activating multiple receiving antennas at the same time. Although IRS-RGSSK gets rid of the restriction that the number of antennas at the receiving end must be an integer power of 2, since spatial shift keying can only transmit information through antenna indexes and requires a large number of IRS elements to optimize the phase, the spectrum efficiency and performance of IRS-RGSSK are reduced. IRS enables the system to carry more information bits, but as the number of bits increases, decoding the receiver information and the receiver's acquisition of channel state information are also huge challenges. Summary of the invention

[0005] In view of the defects existing in the above-mentioned background technology, the present application provides a method of spatial shift keying reflection modulation based on intelligent reflective surface-assisted joint transceiver. This method applies spatial shift keying modulation to the transceiver, and designs the corresponding reflection constellation points in combination with the transmitting antenna index to solve the problems existing in IRS-TSM and IRS-TQSM. The transmitting antenna index, the receiving antenna index, and the reflection constellation point index are jointly mapped to get rid of the restriction that the number of transceiver antennas must satisfy an integer power of 2 and improve the system bit error rate performance. Then, a non-coherent detection method of the receiving end is designed based on energy greedy detection. The receiving end can detect the signal with low computational complexity and without obtaining channel state information, and finally obtains a method of spatial shift keying reflection modulation based on IRS-assisted joint transceiver. The present application adopts the following technical solutions:

[0006] A spatial shift keying reflection modulation method, the method comprising the following steps:

[0007] Step 1: Group the information bit stream input in each time slot;

[0008] Step 2: Use the JTSSK-RM joint mapping table to perform index mapping;

[0009] Step 3: Deploy the IRS near the transmitter to reflect the unmodulated carrier signal from the transmitter, and complete the link modeling between the transmitter and the IRS and between the IRS and the receiver;

[0010] Step 4: Select the transmitting antenna, select the IRS reflection constellation point according to the selected transmitting antenna, and then select the receiving antenna;

[0011] Step 5: The receiving antenna at the receiving end obtains channel state information through channel estimation;

[0012] Step 6: The receiver restores the bit information according to the received signal and uses the incoherent energy detection method to restore the bit information.

[0013] Furthermore, in step 1, the information bit stream is grouped, including: each group includes B bits, and the binary bit B is converted into a corresponding decimal index m, where m=1, 2, ..., 2 B ;

[0014] The B bits satisfy the following relationship:

[0015]

[0016] Where L represents the number of reflection modulation constellation points corresponding to each transmitting antenna. Indicates rounding down.

[0017] Further, in step 2, the decimal index m is used to index the joint mapping combination (i, k, l), where i represents the activated transmit antenna index, k represents the receive antenna index, and l represents the IRS reflection modulation constellation point index; the transmitting end vector is composed of 0 and 1, which is expressed as The i-th element is 1, indicating that the i-th transmitting antenna has been activated, and the remaining N t -1 element is 0 indicating that the transmit antenna is not activated.

[0018] Furthermore, in step 3, the link between the transmitter and the IRS is modeled as a Rice fading channel with a deterministic direct-view Loss component, and the link between the IRS and the receiver is modeled as a Rayleigh fading channel.

[0019] Furthermore, the Rice fading channel satisfies the following relationship:

[0020]

[0021] Where κ represents the Rice factor, represents the direct view path, and its calculation formula is as follows:

[0022]

[0023] Where λ is the wavelength, d is the distance between two adjacent IRS elements, there is no coupling between IRS elements, and ψ AoA represents the angle of arrival; represents the non-line-of-sight path, h NLos Channel matrix from IRS to receiver The elements of have zero mean and independent unit variance, and obey the complex Gaussian distribution CN(0,1);

[0024] The elements of the link channel matrix from the transmitter to the IRS are expressed as The elements of the link channel matrix from IRS to the receiving end are expressed as Where n=1, 2,...,N, i=1, 2,...,N t k = 1, 2, ..., N r .

[0025] Furthermore, in step 4, the number of IRS reflection constellation points is L·N t Each transmitting antenna index i will correspond to a set of constellation points Each constellation point satisfies the following relationship:

[0026]

[0027] Where i = 1, 2, ..., N t,l=1,2,...,L.

[0028] Furthermore, in step 4, transmitting antenna index selection is performed, including:

[0029] No. The constellation point corresponding to the root transmitting antenna is phase rotated by the constellation point corresponding to the i-th transmitting antenna Get, where

[0030] The IRS reflection coefficient matrix is ​​expressed as The IRS reflection coefficient matrix is ​​composed of the beamforming vector of the kth receiving antenna and the lth reflection constellation point, which is expressed as:

[0031]

[0032] in, represents the beamforming vector phase, represents the lth reflection constellation point corresponding to the activation of the i-th transmitting antenna, and diag(·) represents the diagonal matrix whose elements are on the main diagonal;

[0033] The amplitude of each reflection unit in the IRS reflection coefficient matrix satisfies the relationship [Φ] n,n =1 to maximize the reflected power of each element, where n=1, 2, ..., N.

[0034] Furthermore, in step 4, index selection of the receiving antenna is performed, including:

[0035] Assuming that the receiver activates the kth receiving antenna, the signal-to-noise ratio of the receiving channel of this antenna is expressed as:

[0036]

[0037] Among them, N 0 is the noise variance;

[0038] In order to maximize the signal-to-noise ratio at the kth receiving antenna, IRS uses phase cancellation to optimize the beamforming phase. The phase of the nth reflection unit is expressed as

[0039] Furthermore, in step 5, assuming that the channel state information of the receiving end is completely known, the received signal It is expressed as:

[0040]

[0041] is additive white Gaussian noise AWGN, which follows the distribution in, represents the identity matrix, N 0 is the noise variance, G and h are the Rayleigh fading channel and the Rice fading channel respectively, and f i Represents the transmitting end vector in step 2, which is used to index the i-th transmitting antenna.

[0042] Further, in step 6, restoring bit information according to the received signal includes:

[0043] The maximum likelihood detection method is used to convert the decimal index combination into the corresponding binary bits, and the initial bits sent are restored. The calculation formula is as follows:

[0044]

[0045] in, They represent the detected activated transmitting antenna index, receiving antenna index, and reflection constellation point index, respectively, and y represents the receiving antenna signal;

[0046] In step 6, the bit information is restored using an incoherent energy detection method, including:

[0047] Step 601: Perform energy detection on each receiving antenna to determine the index of a receiving antenna with the largest energy, expressed as:

[0048]

[0049] Let the receiving antenna with the largest energy be the kth receiving antenna activated by the receiving end specified in step 4, that is, index No. The signal of the receiving antenna is expressed as:

[0050]

[0051] Step 602: Detect the index of the reflection constellation point, and Get the constellation point index in and transmit antenna index

[0052] When transmitting, each transmitting antenna has an independent set of reflection constellation points. Therefore, when detecting the transmitting antenna index and the reflection constellation point index, only the reflection constellation point needs to be detected. Contains both the constellation point index Also contains the transmit antenna index

[0053] The detection of the reflection constellation points is achieved through the following formula:

[0054]

[0055] Among them, s m represents all candidate reflection constellation points, represents the detected reflection constellation point; E[β k,n ] represents the expected value of the modulus of the channel matrix element from the IRS to the receiving end, that is, the expected value of the modulus of the Rayleigh fading channel matrix element, and E[α n,i ] represents the expectation of the modulus of the elements of the IRS channel matrix from the transmitter, that is, the expectation of the modulus of the elements of the Rice fading channel matrix, and the calculation formula is as follows:

[0056]

[0057] Among them, I a (x) represents the modified Bessel function of order a;

[0058] The expected value of the Rician fading channel matrix element modulus E[α n,i ] is brought into the detection formula of the reflection constellation point, the reflection constellation point is detected, and the constellation point index is restored and obtained according to the detected constellation point and transmit antenna index Will The corresponding decimal is converted into binary bits, and the original bits sent are restored.

[0059] Through the embodiments of the present application, the following technical effects can be obtained:

[0060] (1) The transmitter and receiver use space shift keying and design the IRS reflection modulation constellation points in combination with the transmit antenna. Compared with the traditional constellation symbols, the IRS reflection constellation points do not need to satisfy the integer power of 2. The transmit antenna index, receive antenna index, and IRS reflection constellation point index are jointly mapped to improve the system bit error rate performance;

[0061] (2) Compared with traditional IRS-TSM and IRS-TQSM, the transmitting and receiving antennas do not need to satisfy the integer power of 2, which improves the bit error rate performance and the spectrum efficiency of the system. This modulation scheme is more general, and IRS-TSM and IRS-RSM can be regarded as a specific form of IRS-JTSSK-RM;

[0062] (3) In order to reduce the detection computational complexity at the receiving end, the present application proposes a non-coherent energy detection, which can detect the signal without obtaining channel state information. Compared with the likelihood detection of imperfect channel estimation, it can obtain better bit error rate performance and lower computational complexity. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the technical solutions in the embodiments of the present application, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0064] Figure 1 It is a schematic diagram of the IRS reflection modulation constellation points under set parameters;

[0065] Figure 2 It is a schematic diagram of a spatial shift keying reflection modulation transmission system;

[0066] Figure 3 For the comparison between the present application and the IRS-RSM and IRS-RGSSK modulation schemes under the system model with the same spectrum efficiency, the same number of transmitting antennas and the same number of receiving antennas;

[0067] Figure 4 For the comparison between the present application and the IRS-TSM and IRS-TQSM modulation schemes under the system model with the same spectrum efficiency, the same number of transmitting antennas and the same number of receiving antennas;

[0068] Figure 5 The bit error rate performance of the incoherent energy detector is compared with the optimal maximum likelihood detector and the maximum likelihood detector with imperfect channel estimation. DETAILED DESCRIPTION

[0069] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0070] This application proposes an intelligent reflecting surface (IRS)-assisted joint transmit-receive end spatial shift keying reflection modulation (IRS-JTSSK-RM) method, which is applied to a multiple-input multiple-output MIMO system assisted by N intelligent reflecting surface units. t Transmitting antennas, N rIn a multiple-input multiple-output MIMO system with multiple receiving antennas, the direct link from the transmitter to the receiver is blocked and there is no direct link; when performing spatial shift keying modulation, the transmitter activates one transmitting antenna in each time slot to transmit an unmodulated carrier signal, and the IRS transmits index information by optimizing the phase shift so that the reflected signal can be coherently superimposed on the desired receiving antenna to realize spatial shift keying at the receiving end. The method includes the following steps:

[0071] Step 1: Group the information bit stream input in each time slot;

[0072] In step 1, the information bit stream is grouped, including: each group includes B bits, and the binary bit B is converted into a corresponding decimal index m, where m = 1, 2, ..., 2 B ;

[0073] The B bits satisfy the following relationship:

[0074]

[0075] Where L represents the number of reflection modulation constellation points corresponding to each transmitting antenna. Indicates rounding down;

[0076] Step 2: Use the JTSSK-RM joint mapping table to perform index mapping;

[0077] In step 2, the decimal index m is used to index the joint mapping combination (i, k, l), where i represents the activated transmit antenna index, k represents the receive antenna index, and l represents the IRS reflection modulation constellation point index; the transmitting end vector is composed of 0 and 1, which is expressed as The i-th element is 1, indicating that the i-th transmitting antenna has been activated, and the remaining N t -1 element is 0, indicating that the transmitting antenna is not activated;

[0078] Step 3: Deploy the IRS near the transmitter to reflect the unmodulated carrier signal from the transmitter, and complete the link modeling between the transmitter and the IRS and between the IRS and the receiver;

[0079] In step 3, the link from the transmitter to the IRS is modeled as a Rice fading channel with a deterministic direct-view Loss component, and the link from the IRS to the receiver is modeled as a Rayleigh fading channel;

[0080] The Rice fading channel satisfies the following relationship:

[0081]

[0082] Where κ represents the Rice factor, represents the direct view path, and its calculation formula is as follows:

[0083]

[0084] Where λ is the wavelength, d is the distance between two adjacent IRS elements, there is no coupling between IRS elements, and ψ AoA represents the angle of arrival; represents the non-line-of-sight path, h NLos Channel matrix from IRS to receiver The elements of have zero mean and independent unit variance, and obey the complex Gaussian distribution CN(0,1);

[0085] The elements of the link channel matrix from the transmitter to the IRS are expressed as The elements of the link channel matrix from IRS to the receiving end are expressed as Where n=1, 2,...,N, i=1, 2,...,N t k = 1, 2, ..., N r ;

[0086] Step 4: Select the transmitting antenna, select the IRS reflection constellation point according to the selected transmitting antenna, and then select the receiving antenna;

[0087] In step 4, the number of IRS reflection constellation points is L·N t Each transmitting antenna index i will correspond to a set of constellation points Each constellation point satisfies the following relationship:

[0088]

[0089] Where i = 1, 2, ..., N t , l = 1, 2, ..., L;

[0090] In step 4, transmit antenna index selection is performed, including:

[0091] No. The constellation point corresponding to the root transmitting antenna is phase rotated by the constellation point corresponding to the i-th transmitting antenna Get, where

[0092] The IRS reflection coefficient matrix is ​​expressed as The IRS reflection coefficient matrix is ​​composed of the beamforming vector of the kth receiving antenna and the lth reflection constellation point, which is expressed as:

[0093]

[0094] in, θ n , n=1,2,...,N represents the beamforming vector phase, represents the lth reflection constellation point corresponding to the activation of the i-th transmitting antenna, and diag(·) represents the diagonal matrix whose elements are on the main diagonal;

[0095] The amplitude of each reflection unit in the IRS reflection coefficient matrix satisfies the relationship |[Φ] n,n |=1 to maximize the reflected power of each element, where n=1, 2, ..., N;

[0096] In step 4, index selection of the receiving antenna is performed, including:

[0097] Assuming that the receiver activates the kth receiving antenna, the signal-to-noise ratio of the receiving channel of this antenna is expressed as:

[0098]

[0099] Among them, N 0 is the noise variance;

[0100] In order to maximize the signal-to-noise ratio at the kth receiving antenna, IRS uses phase cancellation to optimize the beamforming phase. The phase of the nth reflection unit is expressed as

[0101] Step 5: The receiving antenna at the receiving end obtains channel state information through channel estimation;

[0102] Assuming that the channel state information at the receiving end is completely known, the received signal It is expressed as:

[0103]

[0104] is additive white Gaussian noise AWGN, which follows the distribution in, represents the identity matrix, N 0 is the noise variance, G and h are the Rayleigh fading channel and the Rice fading channel respectively, and f i represents the transmitting end vector in step 2, used to index the i-th transmitting antenna;

[0105] Step 6: The receiver restores the bit information according to the received signal and uses the incoherent energy detection method to restore the bit information;

[0106] In step 6, the bit information is restored according to the received signal, including: using the maximum likelihood detection method to convert the decimal index combination into the corresponding binary bits, and restoring the initial bits sent, and the calculation formula is as follows:

[0107]

[0108] in, They represent the detected activated transmitting antenna index, receiving antenna index, and reflection constellation point index, respectively, and y represents the receiving antenna signal;

[0109] In step 6, the bit information is restored using an incoherent energy detection method, including:

[0110] Step 601: Perform energy detection on each receiving antenna to determine the index of a receiving antenna with the largest energy, expressed as:

[0111]

[0112] Let the receiving antenna with the largest energy be the kth receiving antenna activated by the receiving end specified in step 4, that is, index No. The signal of the receiving antenna is expressed as:

[0113]

[0114] Step 602: Detect the index of the reflection constellation point, and Get the constellation point index in and transmit antenna index

[0115] When transmitting, each transmitting antenna has an independent set of reflection constellation points. Therefore, when detecting the transmitting antenna index and the reflection constellation point index, only the reflection constellation point needs to be detected. Contains both the constellation point index Also contains the transmit antenna index

[0116] The detection of the reflection constellation points is achieved through the following formula:

[0117]

[0118] Among them, s m represents all candidate reflection constellation points, represents the detected reflection constellation point; E[β k,n ] represents the expected value of the modulus of the channel matrix element from the IRS to the receiving end, that is, the expected value of the modulus of the Rayleigh fading channel matrix element, and E[α n,i ] represents the expectation of the modulus of the elements of the IRS channel matrix from the transmitter, that is, the expectation of the modulus of the elements of the Rice fading channel matrix, and the calculation formula is as follows:

[0119]

[0120] Among them, I a (x) represents the modified Bessel function of order a;

[0121] The expected value of the Rician fading channel matrix element modulus E[α n,i ] is brought into the detection formula of the reflection constellation point, the reflection constellation point is detected, and the constellation point index is restored and obtained according to the detected constellation point and transmit antenna index Will The corresponding decimal is converted into binary bits, and the original bits sent are restored.

[0122] Figure 1 The N t =3, N r =3, L = 2 parameters, IRS reflection constellation point design example, where N t _Index represents the constellation point corresponding to the i-th transmitting antenna. According to the IRS-assisted joint transmitting and receiving end space shift keying reflection modulation proposed in the present invention, N t =3, N r An example of a joint mapping table with parameters L = 3 and L = 2 is shown in the following table:

[0123]

[0124] Figure 2 The schematic diagram of the IRS-assisted joint transceiver space shift keying reflection modulation transmission system proposed in the present invention is shown in FIG. t The transmitter is equipped with N transmitting antennas. r The receiving end is composed of a receiving antenna. Since there are obstacles between the transmitting end and the receiving end and there is no direct transmission path, an IRS composed of N reflection units is deployed to assist the information transmission from the transmitting end to the receiving end. Among them, h represents the channel link from the transmitting end to the IRS, and G represents the channel link from the IRS to the receiving end.

[0125] In order to demonstrate the superiority of the proposed IRS-JTSSK-RM scheme, Figure 3 The simulation results are used to evaluate the BER performance of the modulation scheme. The IRS-JTSSK-RM scheme is compared with the IRS-RSM and IRS-RGSSK modulation schemes under the maximum likelihood detector with perfect channel estimation. In order to make a fair comparison, the number of transmit antennas N of IRS-JTSSK-RM is t =1 (i.e. single-input multiple-output system). r =12, B = 6 parameters, when the bit error rate drops to 10-4 When N=32, N r =7, B = 5, IRS-JTSSK-RM can obtain more performance gains. The performance difference is mainly due to the fact that IRS-RGSSK requires more IRS elements to optimize the phase and has low spectrum efficiency; at the same spectrum efficiency, IRS-RSM requires more modulation orders, while IRS-JTSSK-RM uses redundant receiving end antenna indexes to reduce the performance impact of constellation symbols and improve the system's bit error rate performance.

[0126] exist Figure 4 In this paper, the IRS-JTSSK-RM scheme is compared with the IRS-TSM and IRS-TQSM schemes in a multi-input and output system, using (N t ,N r ,B) to represent the configuration parameters. First, when the number of transmit and receive antennas is an integer power of 2, IRS-JTSSK-RM has the best bit error rate performance. Compared with IRS-TSM and IRS-TQSM, its performance difference mainly comes from the design of the IRS reflection constellation point, which alleviates the high correlation of the link between the transmitter and IRS. When the number of transmit and receive antennas does not meet the integer power of 2, IRS-JTSSK-RM still has better robustness. The performance difference is mainly that the redundant transmit and receive antennas participate in the joint mapping to reduce the performance impact brought by the constellation point.

[0127] at last, Figure 5 The bit error rate performance comparison of the low complexity non-coherent greedy detection (NCGD) proposed for the IRS-JTSSK-RM modulation scheme with the optimal maximum likelihood detection (ML) and the maximum likelihood detector with imperfect channel estimation is shown. In the previous comparison, a key assumption is that all channel state information is completely known. However, in practice, the acquisition of channel state information is a huge challenge, and perfect channel state information is usually difficult to estimate. In order to analyze the non-coherent greedy detection designed by the present invention, the receiver can detect the signal without obtaining the channel state information. The channel estimation error model used remodels the imperfect channel model as:

[0128]

[0129]

[0130] in, and It is the estimated error of the channel link from the transmitter to the IRS and the error of the channel link from the IRS to the receiver. and The sub-tables show the estimated error matrices of link h and link G, each of which follows zero mean and variance δ 2 The complex Gaussian variable of . Figure 5 It can be seen that in N t =3, N r =3, N=64, L=4, B=5, when the bit error rate drops to 10 -4 When the channel estimation error is δ=0.06, the likelihood detection of imperfect channel estimation performs worse than the incoherent energy detection, and the impact of the estimation error on the bit error rate performance is dominant at high signal-to-noise ratio, which leads to performance degradation. In practical applications, the deviation of channel estimation is often greater. t =5, N r =3, N=64, L=6, B=5, as the spectral efficiency increases, the performance difference between incoherent greedy detection and optimal likelihood detection increases. This is mainly because more receiving antennas make greedy detection increase the probability of misjudging the receiving antenna, while likelihood detection with imperfect channel estimation still performs worse than NCGD at a high signal-to-noise ratio with an estimation error of δ=0.03, and a smaller estimation error is difficult to achieve.

[0131] In summary, in order to improve the transmission reliability and spectrum efficiency of the access system, the IRS embeds additional information bits into the incident signal through the IRS discrete phase while reflecting the unmodulated carrier. The IRS reflection modulation constellation points are designed in combination with the transmitting antenna to alleviate the high correlation between the transmitter and the IRS link, and the spatial shift keying modulation is applied to the transmitting end and the receiving end respectively. Then, the antenna index of the transmitting and receiving ends and the constellation point index are jointly mapped to get rid of the restriction that the number of transmitting and receiving antennas and the number of reflection constellation points must satisfy an integer power of 2. In order to optimize the computational complexity of the detector, after measuring the energy of the receiving antenna, the receiving end retrieves the receiving antenna with the largest energy. In the absence of channel state information, the signal received on the antenna is used to perform linear detection on the reflection constellation point and the transmitting antenna index to solve the large amount of computational complexity of the receiving end and the challenges brought by obtaining channel state information.

[0132] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solution of the present application rather than to limit it. Although the present application has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present application.

Claims

1. A spatial shift keying reflection modulation method, It is characterized in that The method comprises the following steps: Step 1: Group the information bit stream input in each time slot; Step 2: Use the JTSSK-RM joint mapping table to perform index mapping; Step 3: Deploy the IRS near the transmitter to reflect the unmodulated carrier signal from the transmitter, and complete the link modeling between the transmitter and the IRS and between the IRS and the receiver; Step 4: Select the transmitting antenna, select the IRS reflection constellation point according to the selected transmitting antenna, and then select the receiving antenna; Step 5: The receiving antenna at the receiving end obtains channel state information through channel estimation; Step 6: The receiver restores the bit information according to the received signal and uses the incoherent energy detection method to restore the bit information; In step 1, the information bit stream is grouped, including: each group includes B bits, and the binary bit B is converted into a corresponding decimal index m, where m=1, 2, ..., 2B; The B bits satisfy the following relationship: Where L represents the number of reflection modulation constellation points corresponding to each transmitting antenna. Indicates rounding down, N t Represents the number of transmitting antennas, N r Indicates the number of receiving antennas; In step 4, there are L·Nt IRS reflection constellation points in total, and each transmitting antenna index i corresponds to a set of constellation points Each constellation point satisfies the following relationship: Where i = 1, 2, ..., Nt, l = 1, 2, ..., L, N t Represents the number of transmitting antennas, N r Indicates the number of receiving antennas.

2. The method according to claim 1, It is characterized in that In step 2, the decimal index m is used to index the joint mapping combination (i, k, l), where i represents the activated transmit antenna index, k represents the receive antenna index, and l represents the IRS reflection modulation constellation point index; the transmitting end vector is composed of 0 and 1, which is expressed as The i-th element is 1, indicating that the i-th transmitting antenna has been activated, and the remaining Nt-1 elements are 0, indicating that the transmitting antenna is not activated; Among them, N t Represents the number of transmitting antennas, N r Indicates the number of receiving antennas.

3. The method according to claim 1, It is characterized in that In step 3, the link from the transmitter to the IRS is modeled as a Rice fading channel with a deterministic direct-view Loss component, and the link from the IRS to the receiver is modeled as a Rayleigh fading channel.

4. The method according to claim 3, It is characterized in that The Rice fading channel satisfies the following relationship: Where κ represents the Rice factor, represents the direct view path, and its calculation formula is as follows: Where λ is the wavelength, d is the distance between two adjacent IRS elements, there is no coupling between IRS elements, and ψAoA represents the angle of arrival; represents a non-line-of-sight path, hNLos and the elements of the IRS-to-receiver channel matrix have zero mean and independent unit variance, and obey the complex Gaussian distribution CN(0,1); the elements of the link channel matrix from the transmitter to the IRS are expressed as The elements of the link channel matrix from IRS to the receiving end are expressed as Where n=1, 2, ..., N, i=1, 2, ..., Nt, k=1, 2, ..., Nr; α represents the modulus of the element of the Rice fading channel matrix, β represents the modulus of the element of the receiving end channel matrix, φ is the phase parameter of the link channel matrix from IRS to the receiving end, is the phase parameter of the link channel matrix from the transmitter to the IRS.

5. The method according to claim 1, It is characterized in that In step 4, a transmit antenna index is selected, including: No. The constellation point corresponding to the root transmitting antenna is phase rotated by the constellation point corresponding to the i-th transmitting antenna Get, where The IRS reflection coefficient matrix is ​​expressed as The IRS reflection coefficient matrix is ​​composed of the beamforming vector of the kth receiving antenna and the lth reflection constellation point, which is expressed as: in, θn,n=1,2,...,N represents the beamforming vector phase, represents the lth reflection constellation point corresponding to the activation of the i-th transmitting antenna, and diag(·) represents the diagonal matrix whose elements are on the main diagonal; The amplitude of each reflection unit in the IRS reflection coefficient matrix satisfies the relationship |[Φ]n,n|=1 to maximize the reflection power of each element, where n=1, 2, ..., N; Among them, N t Represents the number of transmitting antennas, N r Indicates the number of receiving antennas.

6. The method according to claim 4, It is characterized in that In step 4, index selection of the receiving antenna is performed, including: Assuming that the receiver activates the kth receiving antenna, the signal-to-noise ratio of the receiving channel of this antenna is expressed as: Where N0 is the noise variance; Where α represents the modulus of the elements of the Rice fading channel matrix, and β represents the modulus of the elements of the receiving end channel matrix; In order to maximize the signal-to-noise ratio at the kth receiving antenna, IRS uses phase cancellation to optimize the beamforming phase. The phase of the nth reflection unit is expressed as 7. The method according to claim 1, It is characterized in that In step 5, assuming that the channel state information of the receiving end is completely known, the received signal It is expressed as: is additive white Gaussian noise AWGN, which follows the distribution Where, INr represents the unit matrix, N0 is the noise variance, G and h are the Rayleigh fading channel and the Rice fading channel respectively, and fi represents the transmitter vector in step 2, which is used to index the i-th transmitting antenna.

8. The method according to claim 1, It is characterized in that In step 6, the bit information is restored according to the received signal, including: The maximum likelihood detection method is used to convert the decimal index combination into the corresponding binary bits, and the initial bits sent are restored. The calculation formula is as follows: in, They represent the detected activated transmitting antenna index, receiving antenna index, and reflection constellation point index respectively, and y represents the receiving antenna signal; In step 6, the bit information is restored using an incoherent energy detection method, including: Step 601: Perform energy detection on each receiving antenna to determine the index of a receiving antenna with the largest energy, expressed as: Let the receiving antenna with the largest energy be the kth receiving antenna activated by the receiving end specified in step 4, that is, index No. The signal of the receiving antenna is expressed as: Where α represents the modulus of the elements of the Rice fading channel matrix, and β represents the modulus of the elements of the receiving end channel matrix; Step 602: Detect the index of the reflection constellation point, and Get the constellation point index in and transmit antenna index When transmitting, each transmitting antenna has an independent set of reflection constellation points. Therefore, when detecting the transmitting antenna index and the reflection constellation point index, only the reflection constellation point needs to be detected. Contains both the constellation point index Also contains the transmit antenna index The detection of the reflection constellation points is achieved through the following formula: Among them, sm represents all candidate reflection constellation points, represents the detected reflection constellation point; E[βk,n] represents the expected value of the modulus of the channel matrix element from the IRS to the receiving end, that is, the expected value of the modulus of the Rayleigh fading channel matrix element, and E[αn,i] represents the expectation of the modulus of the elements of the IRS channel matrix from the transmitter, that is, the expectation of the modulus of the elements of the Ricean fading channel matrix. The calculation formula is as follows: Where Ia(x) represents the modified Bessel function of order a, and κ represents the Rice factor; The expected value E[αn,i] of the Rician fading channel matrix element modulus is substituted into the detection formula of the reflection constellation point, the reflection constellation point is detected, and the constellation point index is restored and obtained according to the detected constellation point. and transmit antenna index Will The corresponding decimal is converted into binary bits, and the original bits sent are restored.

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