Permutation Spreading Technique Employing Spatial Modulation for MIMO-CDMA Systems

Abstract

Spatial Modulation (SM) is a spatial multiplexing technique designed for MIMO systems where only one transmit antenna is used at each time. It is considered to be an attractive choice for future wireless communication systems as it reduces Inter Channel Interference (ICI) while maintaining high energy efficiency. It can achieve this goal by mapping block of data bits into constellation points in the spatial and signal domain. Combining this innovative method with multiple access techniques could improve the system performance and enhance the data rate. In Code Division Multiple Access (CDMA) method employing parity bit permutation spreading, the bit error rate (BER) performance could be improved by using the parity bits to select the spreading sequence to use at each signalling interval. In this thesis, a new system model based on SM and CDMA employing parity bit permutation spreading is proposed and investigated. The proposed system takes advantage of the benefits of both techniques. In this system, in addition to use the parity bits to select the spreading sequences, same concept is used to select the combination of antennas to activate at each time instant. By doing so, a reduction of power consumption, Inter-Channel and Inter Symbol Interference effect can be achieved while keeping a certain diversity order compared to SM. Multiuser scenario is also discussed in order to investigate the multiple access interference (MAI) effects in synchronous transmission. In such case, the receiver estimates the desired user's information by considering the other users' signal as additional noise. Simulation results of the proposed MIMO-CDMA system employing permutation spreading show, for single user and multiuser, a significant improvement of the BER performance in low signal to noise ratio (SNR) when SM is implemented.