Research On Downlink Signal Detection Algorithm In LTE System

In order to meet the performance and higher demand of wireless communication transmission rate, in the end of 2004, 3GPP organization launched the mobile communication technology long term evolution (LTE, long term evolution). LTE uses OFDM and MIMO as the critical technologies. The network end uses multiple antennas to transmit signals. Each receiving antenas at the UE end will receive all data of each transmit antenna which passes through the wireless channel, so the receiver end must uses the signal detection algorithm to recover the transmit signal.Based on the background of national science and technology key project"TD-LTE wireless intergrated tese instument development",this article focuses on the LTE system downlink signal detection algorithm. The signal detection algorithms are divided into signal detection algorithms based on transmit diversity and signal detection algorithms based on spatial multiplexing. Each type signal detection algorithms are included by hard decision algorithms and the receiver design based on soft information. The main work includes several aspects:Firstly, this paper in the second chapter introduces the role of signal detection algorithm, downlink transmission mode, the downlink physical channel and the related downlink transmission mode. The receiver end firstly should ensure the time and frequency charcateristics, and then this paper analyze how to determine the transmission mode of the physical channels. At last, the process of downlink signal detection algorithms of each physical channel is detailed described.Then this paper introduces the signal detection algorithm based on spatial multiplexing in the third and fourth chapter, including the hard decision detection algorithm and the turbo soft detection. For the hard decision detection algorithm, the third chapter mainly describes the traditional V-BLAST algorithm and the QR decomposition algorithm, and then introduces two modified V-BLAST algorithms, described an improved QR cycle iterative algorithm. Finally, the simulation of the improved algorithm confirmed that the relative performance improvement based on the conventional algorithms. In the fourth chapter the turbo receiver in MIMO system is improved, so that it can be applied in the LTE system. A detailed analysis of each module composition is given. Through the turbo soft detection simulation, the impact of each module in this algorithm is displayed. Then a detailed analysis of performance is given.Finally, this paper introduces the signal detection algorithm based on transmit diversity in the fifth chapter. Firstly the precoding for transmit diversity is introduced, and then the traditional maximum ratio merging algorithm is given. Like the turbo receiver, the QR soft detection based on transmit diversity is introduced. The soft detection module is described in detail. At last, the maximum ratio merging algorithm and the turbo soft detection based on QR performance is displayed.Through the improvement of signal detection algorithms and simulation, the algorithms can be applied in the downlink physical layer to constructure the whole link.