Research Into The Suppression Inter-cell Asynchronous Interference Of Precoding In LET

The capacity of communication system has been greatly improved by cellular systemcompared with large coverage system, but cell edge users are under the severeinterference resulted from inter-cell interference (ICI), thus inter-cell interferencebecomes an inherent problem for cellular mobile communication system. Recently,Cooperative Base Station System(precoding is utilized to achieve Co-BS systemconfiguration) which based on MIMO technology is proposed to greatly improve spectralefficiency and cell edge users’ performance, meanwhile it can also reach the optimalperformance in theory. However, Co-BS system holds some shortcomings, such as highlysynchronization requirement, the channel information required by the transmitter, andmass information exchange between the cells. Because of the different propagation timeresulted from the distinct distances between the BSs and MSs, even if the useful signalscan reach their target at the same time, it is still very difficult to realize that theinterference signals simultaneously arrive at the target. This means it is asynchronizationbetween the cells that results in inter-cell asynchronous interference. LTE system adoptsOFDM technology which is sensitive to the carrier offset. When the delay has beenbeyond the scope of CP length, additional seriously Inter-cell asynchronous interference isimported to OFDM system. So how to make the most of MIMO, OFDM technology tosuppress or eliminate inter-cell asynchronous interference is very important in Co-BSenvironment.SLNR delay-tolerance precoding is investigated in this thesis to suppress inter-cellasynchronous interference in the downlink of Co-BS LTE system. Inter-cell asynchronousinterference can be reduced and system’s transmission performance can be improved bypre-treating the delay situation.Firstly, the LTE physical layer downlink simulation platform is constructed, and itsperformance is simulated and analyzed. Secondly，A framework of Co-BS with flat fadingchannel environment is developed and the delay expression between the cells is educed,then a delay-tolerance SLNR precoding is brought forward to suppress inter-cellasynchronous interference in the system where there exists delay. Simulations validate theperformance of the method based on cooperative base station LTE systems. Simulationresults show that the scheme can preferably mitigate inter-cell asynchronous interference. Further more, inter-cell asynchronous interference suppression strategy is discussed underthe frequency selective fading channel. Cooperative base station MIMO-OFDM systemmodel is given and the influence of delay to the OFDM modulation matrix is analyzed.On this basis, equivalent channel is made and delay-tolerance SLNR precoding algorithmis deduced in this way. Simulation conclusions indicate that the work achieves the desiredeffect and simultaneously reduces BER. SLNR precoding is a relatively simpler linearprecoding to achieve. It not only can improve system performance, but also can reduceterminal complexity.