Research On Interference Suppression Techniques In MIMO Cellular Systems

MIMO (Multiple Input Multiple Output, MIMO) technology can utilize multi-patheffects, and improve the channel capacity substantially without increasing thetransmission power and spectrum resources, thus it improves the spectrum efficiency.This advantage makes it become one of the key technologies for the next-generationwireless communication systems. However, when the MIMO technology is applied to amulti-cell MIMO system, due to each cell with a unity frequency reuse factor, thecell-edge users away from the base site will be affected by adjacent co-channelinterference, they which leads to that they cannot communicate properly. Thus, theco-channel interferenceseriously affects the performance of the whole system, whichmakes the system an interference limited system. Therefore, co-channel interferencesuppression becomes a very important issue in the multi-cell MIMO system.First, the background, significance and research status of MIMO technology indomestic and overseas are introduced. Next, the wireless communication channelmodelsfor single-user MIMO, single-cell multi-user MIMO and multi-cell MIMOsystems are discussed, and the formulations of the received signal under differentsystems are deeply discussed. Since the MIMO technology can significantly improvespectrum efficiency, thechannel capacityfor different systems is discussed in detail andcompared through simulations.In the discussion of multiple cell interferencesuppression between MIMO systems.This thesis firstly studies a variety of detectiontechnologies in single-user MIMO systems and single-cell multi-user MIMO systempre-coding technology based on the sending terminal, and makes a simulationcomparison of their property. Then, with regard to multi-cell MIMO systems, the thesisresearches the traditional methods of multi-cell MIMO system interference suppression,and compares different methodsfor multi-cell interference suppression under single-cellmode and combined treatment mode of multi-cell, and also analyzes their advantagesand disadvantages. Due to poor BER performance of thesingle-cell mode and the highercomplexity of the combined treatment mode of multi-cell, these two methods are notgood schemes for multi-cell interference suppression.The thesis researches a proactive processing algorithm for interference suppressionprimarily, which suppresses interference caused by a base station at this interfering basestation. There will be the best overall system performance when all cells take this method. Compared with the single-cell mode, the proactive processing method greatlyimproves the BER performance of the system and reduces system complexity andmaintains the system BER performance when compared with the conventionalmulti-cell joint processing. There are two algorithms of proactive processing.One isnamed proactive zero-forcing pre-coding, by which all of the subspaces of interferingchannel are zero-forced; Another algorithm mitigates the co-channel interference basedon the elimination of the maximum eigenmode of interfering channels, this methodincreases the base station’s spatial freedom degrees for sending effective messages,compared with the proactive zero-forcing pre-coding.If the numbers of effectivemessages which are transmitted by transmitting antennas are not increased, then thenumbers of transmitting antennas will reduce greatly.