Design And Implementation Of The Echo Canceller In LTE Digital Relay System

With the increasing requirement of the communication quality and speed，as a3G long-termevolution technology，LTE has a wide application prospect. In order to meet the high rate oftransmission and full coverage of the wireless signal, the wireless relay technology is introducedin LTE. However, LTE digital relay system has put into use one important technology calledMIMO (Multiple-Input Multiple-Out-put) with more transmitting and receiving antennas. Thetransmitting and receiving antenna’s increase lead to produce multipath echo channels. Relaysystem sends the signals to the user by multiple antennas and the signals are received by thereceiving antenna through the echo channels at the same time. This paper describes an effectivesolution for multi-channel echo cancellation.In this paper, at first the echo cancellation’s kernel adaptive filter is introduced and thealgorithm’s application in echo cancellation is discussed by analysing the adaptive algorithmssuch as LMS, NLMS, DLMS, RLS algorithm. Then the block diagram of two-channel echocanceller is put forward for the digital relay system with two transmitting antennas and onereceiving antenna and the working principle is provided. In order to remove the strongcorrelation between transmitting signals, the signals will be made pretreatment to improve thealgorithm’s convergence speed and accuracy. The two-channel adaptive NLMS algorithm is usedto update the two-channel coefficients at the same time while the base station’s signal and echonoise go into the relay system. Then the echo channel estimation is completed and we can cancelthe echo noise effectively. The results is indicated that the error signal’s convergence curve can play a good convergence effect, and the channels’ estimation also meets the requirement，thatmeans the method of two-channel echo cancellation has realized its function. Finally, the FPGAhardware structure diagram is designed and the overall structure is implemented by everymodule’s design, through the simulation test we can see that the echo canceller successfullyrealizes its function.