Research On Downlink Synchronization In 3GPP TD-LTE System

The long term evolution of Evolved Universal Mobile Telecommunications System Terrestrial Radio Access, launched by 3GPP, is designed to achieve high performance of radio communication, including higher data rate, lower latency, performance optimized for IP packets, and performance insurance of cell edge.The layer 1 of the LTE is based on OFDM techniques because of OFDM system's spectrum's inherent flexibility and attractive implementation potential. Those advantages, however, are strongly depending on the accurateness of synchronization. Thus, synchronization, including time and frequency, is a fundamental issue of OFDM system, which imposes severe challenges in the mobile channel conditions particularly.In this paper, the downlink initial synchronization of the TD-LTE system has been systematically researched based on the search of present OFDM synchronization algorithms. By using physical signal of primary synchronization signal (PSS) and secondary synchronization signal (SSS), cell search procedures could be achieved, and cell identification of current accessing cell could be obtained by the UE as well. What's more, this paper proposes a solution combining two different algorithms for primary synchronization, which could achieve the joint detection of time and frequency error.Finally, a TD-LTE physical layer simulation plat has been established based on matlab, to test and verify the performance of the proposed synchronization algorithms. In this paper, we simulate the performance under three kinds of channel conditions: AWGN channel, Rayleigh fading channel, and the corresponding frequency Base Station interference. The simulation results show that the downlink synchronization has been successfully achieved by those algorithms proposed in this paper.