Research On D2D Synchronization Signal Detection And Synchronization Mechanism

The core idea of the Device to Device (D2D) technology is to establish a direct communication link between the terminals to complete the communication. Introducing D2D communication in the cellular network can better reduce the base station load, covering the blind area of the network and increase the total throughput of the network.Synchronization is the basic function of a communication network.Firstly, this thesis designs the D2D synchronization signal detection algorithm and completes the performance simulation. Then this thesis analyzes the D2D network system level synchronization technology.The system synchronization model is established, and the corresponding conclusion is obtained by simulation. The main contributions and innovations of this thesis are as follows:First of all, this thesis studies and designs a D2D synchronization signal (SLSS) detection algorithm. According to good correlation properties of the synchronous signal, this thesis designs the SLSS detection algorithm. Firstly, the complexity of the PSLSS detection algorithm is reduced by using the frequency-domain product instead of the time-domain correlation method, and then the complexity of the SSLSS detection algorithm is reduced by using the non-correlation detection algorithm. At last, by using two consecutive PSLSS symbols and SSLSS symbols, the idea of time domain diversity is used to improve the performance of detection algorithm. This thesis builds the link level platform to carry on the simulation to the detection algorithm.The result shows that the detection algorithm has 1.6dB performance promotion compared with the requirement in 3GPP protocol.Secondly, this thesis studies the D2D network system level synchronization technology. At first, this thesis analyzes the typical scenes in system synchronization and designs the synchronization state mechanism according to the description of system synchronization in the protocol. In order to meet the requirement of system level synchronization, the system synchronization model is established innovatively by borrowing the idea of frequency reuse in cellular system.The mathematical theory is used to analyze the relationship between the synchronization performance and the synchronous diffusion threshold.Then a resource allocation algorithm based on minimum interference is proposed to allocate the subframe of the synchronization signal. This thesis builds a static system-level simulation platform, which proves that the proposed algorithm can improve the performance of the synchronous system. Considering the effect of user density on system performance in actual scene, the optimal threshold of synchronous diffusion is obtained in the particular simulation scenario.Thirdly, according to the influence of user density on system performance, this thesis gets the optimal length of subframe pool for the synchronization signal. Different from the theoretical model, in the actual scene, user density will affect the location of the diffusion source,thus affecting the performance of the synchronous system. In this thesis,the optimal lengths of subframe pool corresponding for scenarios of different user density are obtained by simulation, which provides a reference for the resource allocation scheme in engineering practice.