Design method of direction modulation signal based on spatial Fourier transform

Abstract

The invention provides a directional modulation signal design method based on spatial Fourier transformation. The method comprises the following steps of establishing desired phase wave beam spatial coverage functions in ideal conditions relative to different communication models; and acquiring a phased array element weighted value according to the spatial Fourier transformation pair relation among phase wave beams and the array element weighted value of a phased array in a directional modulation signal transmitter to achieve a directional modulation signal design in different communication models. By using the directional modulation signals designed by the method, valid users can normally demodulate received directional modulation signals through common digital signal receivers. As to wiretappers in undesirable directions, their wiretapping receivers cannot demodulate useful communication information from received signals due to the relative phase relationship distortion of constellation points in a received signal constellation diagram. The invention provides a safe transmission method for transmitting communication information in wireless channels.

Description

technical field [0001] The invention relates to a design method of a direction modulation signal based on spatial Fourier transform, and belongs to the technical field of wireless communication. Background technique [0002] With the wide application of wireless communication technology in different industries, the security of communication information in the transmission process has attracted more and more attention. Due to the developmental characteristics of the transmission medium, eavesdroppers can receive wireless transmission waves containing the same communication information as legitimate users. Traditional solutions use keys and secure transmission protocols to ensure the security of transmitted information, but with the enhancement of the computing power of eavesdroppers and the inconvenient management and distribution of keys in new decentralized networks, traditional security solutions Programs are increasingly challenged. Physical layer security is a research...

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Problems solved by technology

In this way, the transmitted signal has different modulated signal constellations in different spatial orientations, and the received signal constellation of legal users in the desired direction is the same as the traditional baseband digital modulated signal. The received signal can be demodulated normally by using an ordinary digital communication receiver. ; and the relative phase relationship between the received signal constellation points in the undesired azimuth is distorted, and the eavesdropping receiver cannot demodulate useful communication information from the received signal

However, the design method of direction modulation signal based on genetic algorithm has the following three problems: (1) The objective function of genetic algorithm only considers a single desired direction to design a baseband digital modulation signal, which is only suitable for point-to-point single-user channel model, such as system requirements The direction modulation signal is a broadcast channel covering a certain range, such as a satellite communication system, or an orthogonal channel accessed by multiple users, such as a mobile communication system, which cannot be solved conveniently by using a genetic algorithm; (2) the objective function of the genetic algorithm only considers The digitally modulated signal is designed for the desired azimuth without considering the degree of distortion of the relative phase relationship between the constellation points of the received signals in the undesired azimuth, which is closely related to the eavesdropping performance of the eavesdropping receiver. If some azimuth constellation points in space The degree of distortion of the relative phase relationship between them does not exceed the judgment threshold of the constellation diagram, and the eavesdropping receiver can improve the signal-to-noise ratio of the received signal through multi-antenna reception or accumulation, so that useful communication information can still be demodulated from the received signal; ( 3) The implementation of the genetic algorithm has a certain complexity and needs to search for the solution of the objective function in the whole space. Although Y.Ding published "A Vector Approach for the Analysis and Synthesis of Directional Modulation Transmitters” proposed a directional modulation signal design method based on the vector synthesis method, which greatly reduced the complexity of the algorithm. Issues involved in (1) and (2)

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