阅读说明：本技术 低复杂度的空间调制接收端天线选择方法 (Low-complexity spatial modulation receiving end antenna selection method ) 是由 束锋 刘林 夏桂阳 朱玲玲 李嘉钰 王云天 邹骏 于 2020-06-12 设计创作，主要内容包括：本发明提供了低复杂度的空间调制接收端天线选择方法。该方法需要在发射端已知期望用户与窃听者信道状态信息的情况下。假设期望接收端总共有N-(b)根天线,从中选择N-(t)根天线接收数据,然后将此选择模式反馈给发射端。发射机将发送的信息比特中的一部分映射为天线索引,另一部分映射为传统的幅度相位调。同时做预编码和人为噪声投影,发射机发送信号,接收端根据检测到的天线序号和调制符号可以完整的恢复发送信息。本发明与传统的天线选择技术相比安全速率得到了极大的提升,并且期望用户能够很好的解调出有用信号,在非法窃听端难以恢复出有用信号,从而能够更好地提升系统的安全性能。(The invention provides a low-complexity spatial modulation receiving end antenna selection method. This method requires that the transmitting end knows the channel state information of the desired user and the eavesdropper. Assume that the expected receiving end has a total of N b Root antenna from which N is selected t The root antenna receives the data and then feeds back the selected mode to the transmitting end. The transmitter maps a portion of the transmitted information bits to antenna indices and another portion to conventional amplitude phase modulation. Pre-coding and man-made noise projection are carried out simultaneously, the transmitter sends signals, and the receiving end adjusts the signals according to the detected antenna serial numberThe transmitted information can be completely recovered by symbol making. Compared with the traditional antenna selection technology, the invention greatly improves the safety rate, expects that the user can well demodulate the useful signal and cannot recover the useful signal at the illegal eavesdropping end, thereby better improving the safety performance of the system.)

1. The low-complexity spatial modulation receiving end antenna selection method is characterized in that: in the selection of the low-complexity spatial modulation receiving end antenna, the receiving end is expected to select a group of antennas as receiving antennas according to a maximum approximate safe rate criterion, and the specific process comprises the following steps:

s1, in low-complexity spatial modulation receiving end antenna selection, a sending end is provided with N_aRoot antenna, intended receiving end equipped with N_bA root antenna; eavesdropping user equipment N_eA root antenna; the transmitting end transmits a training sequence and simultaneously carries out channel estimation on a channel; expecting a user to obtain channel state information from N according to a low complexity antenna selection method_bSelecting N from root antenna_rThe root antenna is used as a receiving antenna for receiving end space modulation;

s2, the expected user feeds back the transmission mode to the transmitter, the transmitter maps one part of the transmitted information bits as antenna indexes, and the other part of the transmitted information bits as traditional amplitude phase signals, and pre-coding and artificial noise projection are carried out at the same time;

s3, expecting a user receiving end to receive signals, wherein the receiving end can completely recover source information according to the received antenna serial number and the modulation symbol.

2. The method for selecting an antenna at a receiving end of low complexity spatial modulation according to claim 1, wherein: the transmitter adopts precoding to map the signal to a receiving antenna, and artificial noise is added in the transmitted signal, so a precoding matrix and artificial noise beamforming need to be designed; the transmitted signal after the transmitting end performs bit stream mapping, precoding and artificial noise can be expressed as。

3. The method for selecting an antenna at a receiving end of low complexity spatial modulation according to claim 1, wherein: the complexity of selecting the antenna is too high by adopting the criterion of maximizing the safe speed, the achievable speed based on a cut-off speed formula is adopted to replace the average safe speed, and the special mapping mode of the spatial modulation symbol is considered on the basis, namely only one antenna index is activated at each moment, so that the optimization problem is further converted into the optimization problem based on the approximate speedAntenna selection problem of rate

Technical Field

The patent technology of the invention belongs to the technical field of wireless communication, and particularly relates to a method for selecting a receiving antenna in a low-complexity spatial modulation system

Background

The transmission principle of the spatial modulation technique is to map a part of the transmitted information bits to antenna indexes and another part to conventional amplitude phase modulation symbols. The spatial modulation technique is an intermediate route between a space-time division structure and a space-time block code in a Bell laboratory, and can realize good balance of spatial multiplexing and spatial diversity. As a novel multi-antenna technology, because only one transmitting or receiving antenna is activated in each time slot, the problems of inter-channel interference and synchronization of multi-antenna transmission can be effectively avoided.

Wireless communications are typically vulnerable to eavesdropping and active malicious attacks due to their broadcast nature. Secure spatial modulation as a security capability to enhance spatial modulation has attracted increased research interest in academia and industry due to its high energy efficiency. The spatial modulation of the receiving end is that the transmitter maps one part of the transmitted information bits to the antenna index of the receiving end by designing precoding, and the other part is mapped to the traditional amplitude phase signal, which utilizes the difference of wireless channels, so that the expected receiver can correctly demodulate the information transmitted by the transmitting end according to the detected antenna serial number and the modulation symbol, and the signal form received by the eavesdropping user at the receiving end is different from that of the expected user, and meanwhile, the eavesdropping user is additionally interfered by artificial noise to cause that the eavesdropping user can not demodulate the transmitted information or can not demodulate the transmitted information, thereby enhancing the security of the spatial modulation. Besides, the signal detection complexity of the user is expected to be low, and the method is suitable for low-power-consumption scenes such as the Internet of things and a wireless sensor network. Although there is a literature on safe receiving-end spatial modulation, the influence of receiving-end antenna selection on the safe rate has not been studied so far. The method is researched to derive the upper bound, namely the safe rate is directly maximized, but the complexity is higher, so that the low-complexity spatial modulation receiving end antenna selection method is provided.

Disclosure of Invention

Aiming at the problems, the invention provides a low-complexity spatial modulation receiving end antenna selection method, which replaces mutual information quantity by using cut-off rate, and simultaneously approximates the safe rate by using a special symbol mapping mode of spatial modulation.

In order to achieve the purpose, the technical scheme adopted by the invention comprises the following specific processes: s1, in low-complexity spatial modulation receiving end antenna selection, a transmitting end is provided with N_aRoot antenna, intended receiving end equipped with N_bA root antenna. Eavesdropping user equipment N_eA root antenna. The transmitting end transmits the training sequence and simultaneously carries out channel estimation on the channel. Because the complexity of selecting the antenna by adopting the criterion of maximizing the safe rate is overhigh, the reachable rate based on a cut-off rate formula is adopted to replace the average safe rate, and the special mapping mode of the spatial modulation symbols is considered on the basis, namely only one antenna index is activated at each moment, so that the optimization problem is further converted into the antenna selection problem based on the approximate safe rate maximizationIt is desirable that a user selects a set of antenna modes according to a low-complexity receiving-end antenna selection method based on approximate safe rate maximization under the condition of obtaining channel state information. S2, expecting the user to feed back the mode to the transmitter, the transmitter maps one part of the sent information bits as antenna indexes, the other part of the sent information bits as traditional amplitude phase modulation, and artificial noise is added in the transmitted signals, so that pre-design is neededEncoding matrices and artificial noise beamforming. The transmitted signal after bit stream mapping, precoding and artificial noise by the transmitter is expressed asS3, expecting a user receiving end to receive signals, wherein the receiving end can completely recover source information according to the received antenna serial number and the modulation symbol.

The method provided by the invention can enable the expected user to correctly demodulate the source information, and an eavesdropper is difficult to detect the transmitted signal due to the difference of channels and the influence of artificial noise. The low-complexity receiving end antenna selection method can obtain higher safety rate and improve the safety transmission performance of the system. The average safe rate performance far exceeds random antenna selection, and is close to the upper bound of theory, namely the performance of the method for directly maximizing the safe rate, but the complexity is far lower than that of the method for directly maximizing the safe rate.

Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Drawings

Fig. 1 is a block diagram of a precoding-assisted receiver-side spatial modulation system.

Fig. 2 shows a safe rate variation curve of a low-complexity receiving-end antenna selection algorithm.

Detailed Description

The present invention is further illustrated by the following figures and specific examples, which are to be construed as merely illustrative and not limitative of the remainder of the disclosure, and all changes and modifications that would be obvious to those skilled in the art are intended to be included within the scope of the present invention and the appended claims are intended to be embraced therein.

The invention provides a precoding-assisted receiving end space modulation system model, wherein a transmitting end (Alice) is provided with N_aRoot antenna, intended user (Bob) equipped with N_bA root antenna. Eavesdropping user (Eve) equips N_eA root antenna. Using correlated channel estimationAfter estimating the channel state information, the expected user selects N_rAnd the root antenna then returns the activated antenna combination mode to the transmitting end, and the transmitting end performs bit stream mapping, precoding and artificial noise. At this time, Alice's transmission signal may be represented as

P_SFor total transmitted power, p₁Distribution of the transmission power of the useful signal, p₂＝1-ρ₁Distribution of the transmission power of the artificial noise, e_nExpress identity matrix I_NtOf the nth column, s_m， m∈[1,2,…,M]Representing the mth constellation symbol in an M-dimensional constellation. P_kFor a precoding matrix, P_ANA noise projection matrix. The artificial noise is added to make the interference to the eavesdropper more serious, and the system obtains higher security. The expected channel matrix and the wiretap channel matrix are respectively H and G, and the received signals of the corresponding expected user and wiretap user are as follows:

the receiving end selects the ith antenna to obtain the unit matrixIn the selection of the ith row vector, select N in total_tAnd an antenna selection matrix formed by row vectors. From N_bSelecting N from root antenna_tRoot antenna, in commonThe pattern, where K e (1,. K) denotes the kth combination pattern.

Average safe rate R_sDefined as the average of the differences between the amount of mutual information expected from the user to the transmitter and the amount of mutual information eavesdropped from the user to the transmitter in different channel conditions.

The amount of mutual information I (x; y) desired from the user to the transmitter_b|H,T_kP) is defined as follows:

whereinSince the transmitter injects artificial noise, the noise received by the eavesdropping user is colored noise, and can be processed by a whitening filter W for analysis^-1/2Whitening filtering is carried out, and the filtered noise vector isWhereinEavesdropping on the mutual information quantity I (x; y) of the user to the transmitter_e|G,T_kP) is expressed as follows:

in the above formula

Selecting N in a receiving antenna_rRoot antenna maximizing average safe rateThe optimization problem of (2) is defined as follows:

max R_s subject to T_k∈{T₁,T₂,...,T_K} (7)

since the mutual information amount is calculated in calculating the safe rate, the calculation is carried out by Monte Carlo simulation, and the complexity isN_sampRepresenting the number of simulated noise sample points. We reduce its complexity by replacing the mutual information content of the two with a cut-off rate, which is a valid approximation.

At this point the safe rate is approximatelyThe optimization problem is transformed as follows:

further to account for the particular manner of symbol mapping in spatial modulation, only one receive antenna is activated at a time, then | e_ns_m-e_n′s_m′‖²Distance d of available mapping signal₁,d₂,…,d_JAnd probability of its occurrence f₁,f₂,…,f_JApproximate substitution. Further approximation is made as follows

Wherein Q ═ W^-1/2GP_k。

The final optimization problem turns into

With a complexity ofMuch less complex than equation (7). Simulation results show that the safety rate performance of the low-complexity receiving-end antenna selection method is close to the performance of the method for directly maximizing the safety rate.

Fig. 1 is a block diagram of a precoding-assisted receiver-side spatial modulation system.

Fig. 2 is a diagram showing a safety rate versus signal-to-noise ratio curve of the proposed low complexity algorithm, where the number of transmitter antennas is 7, the number of receiver total antennas is 7, the number of selectively activated receive antennas is 4, and the power distribution coefficients of the signal and the artificial noise are 0.5 and 0.5, respectively. As can be seen from the figure, the proposed low complexity antenna selection algorithm safe rate curve approaches the upper bound, i.e. the method of maximizing the safe rate, but it is less complex. Meanwhile, the proposed low-complexity antenna selection algorithm is far higher than the safety rate obtained by a random antenna selection method. This shows that the proposed low complexity antenna selection method can achieve very good safe transmission performance.