چكيده
Abstract
One of the essential part of wireless communication systems is Multiple-Input Multiple-Output (MIMO) system. Using MIMO system can increase the capacity and diversity gain if the system. On the other hand, as a multi-carrier modulation scheme, Orthogonal Frequency Division Multiplexing (OFDM) technique eliminates the effect of frequency- selective channels. WiMAX is an standard for wide band (up to 50Mb/s) and wide range (up to 50 mile) wireless communication systems. WiMAX technology is based on MIMO/OFDM. WiMAX supports a full-range of smart antenna techniques, including precoding methods. Channel Inversion(CI) scheme is the simplest linear precoding scheme which eliminates all interference from other antennas. Other linear precoding such as Regularized Channel Inversion (RCI) can improve the performance of system by adding a multiple of the identity matrix before inverting. Selective (or dynamic) Channel Inversion (SCI) is a linear precoding method in which, instead of eliminating the whole interference (such as CI method) divide the interference into two parts: constructive and destructive. And then eliminates only the destructive part of interference. Exploiting the constructive interference can enhance the received signal SINR and also the system performance.
In this project, first selective channel inversion scheme is simulated in single-user MIMO/OFDM system. The results of simulation shows that by using SCI method, the system performance improvement is about 7 dB with respect to CI method. In this project, it is proposed that by using other smart antenna techniques with SCI method, the system performance is more improved. Using other smart antenna techniques such as Cyclic Delay Diversity (CDD) or transmit antenna selection could improve the system efficiency. The results of simulation shows that in the case of using SCI method with cyclic delay diversity, the gain of about 8dB and with transmit antenna selection the gain of about 5dB is achieved.
