Author : A. Farhan, Eman
Engineering and Technology Journal,
2015, Volume 33, Issue 5, Pages 1189-1201
Spatial Multiplexing (SM) can be achieved higher transmission rate without allocating higher bandwidth or increasing transmit power, so it is wildly used recently to serve the extremely demand of mobile communications. But multipath fading is major bottleneck in increasing the data rate and reliability of transfer of information over wireless channel. SM suffers from significant degradation in term of Bit Error Rate (BER) in such environments. In this research it has been tested a SM system with three types of detection. The first results show the Maximum Likelihood (ML) is the better one, but the complexity is increased dramatically with increasing of data rate or the level modulation order in addition of delay time. On the other hand, Zero Forcing (ZF) is very simple related to ML and it suitable for real time communications, but the problem is the Bit Error Rate (BER) is very high related to the performance of ML. So that this research proposed to adopt ZF decoder, and to support its performance, Convolutional Codes (CC) is added to this system to overcome this problem. The results show the proposed scheme gives a gain of about 10 dB of Signal to Noise Ratio (SNR) at BER of 10-4 for code rate of ½ of CC. To reduce the redundancy informations of CC, 2/3 code rate is proposed instead of ½. The results illustrates such system gives significant gain at high SNR, but the problem is the BER in increased up to system with code at low SNR. Also the results confirm that this problem decreases with high number of antennas. So that MIMO system is suitable for high data rate.