Research On The Key Technology Of Coordinated Multiple Points In Downlink LTE-A System

OFDMA technology in downlink LTE-A systems can ensure that the data of differentusers within a cell are transmitted on the mutually orthogonal subcarriers. It follows that themultiple access interference among these users can be restrained，but the interference from theusers of other cells cannot be eliminated. In conventional communication systems a user getserved only by a single cell, and signals from adjacent cells are treated as interference. WithCoordinated multiple point (CoMP) replacing the traditional single point transmission, thegeographically separated cells can cooperatively serve one or more users. By sharinginformation between each other and working cooperatively, base stations (BSs) in differentcells can jointly transmit data to an individual user and turn the inter-cell interference intouseful data, or minimize the inter-cell interference, which can effectively improve the signalto noise ratio (SINR) at the receiver and therefore the system spectrum efficiency. CoMP hasbeen considered as an effective means to improve the performance of the edge users.In this paper we focus on the key technologies of CoMP joint processing (CoMP JP).The details are as follows:1．CoMP system coordinated strategy. Two things are considered: the division of theedge users and the division of the cooperating sets. Methods for determining the edge usersare introduced firstly, which include Geometry method and the difference of antenna gain andlarge scale fading. Then several methods for the division of the cooperating sets are given.2．Precoding algorithms in CoMP systems. Study of precoding algorithms is carried outon the basis of two transmission modes, CoMP-SU-MIMO and CoMP-MU-MIMO. ZFprecoding and MMSE precoding are used in CoMP-SU-MIMO mode, whereas inCoMP-MU-MIMO mode ZF precoding and BD precoding, as well as BD-GMD-THP areapplied. The simulation results show that BD-GMD-THP can effectively reduce the total biterror rate of the system and improve the performance of CoMP-MU-MIMO.3．Scheduling algorithm in CoMP systems. Aimed at the difference between CoMPsystems and traditional LTE systems, traditional non-CoMP mode PF resource schedulingalgorithm, SU-CoMP mode PF resource scheduling algorithm, MU-CoMP mode independentresource scheduling algorithm and MU-CoMP mode joint resource scheduling algorithm are mainly studied. The simulation results show that CoMP can effectively improve the spectrumefficiency of edge users, and joint resource scheduling algorithm can make the systemperformance further improved.