Generalized differential modulation with signal space diversity for m-ary quadrature amplitude modulation (m-qam) constellations.

Abstract

Due to an increase in wireless communication usage on several devices, the demand for high transmission rate and reliable connection has increased. In this dissertation, a generalized differential modulation with signal space diversity (GDM-SSD) for a multi-dimensional M-ary quadrature amplitude modulation (M-QAM) scheme is presented to improve the error performance of non-coherent systems in wireless communications. Signal space diversity (SSD) comprises two fundamental stages: constellation rotation and component interleaving. The angle at which the constellation is rotated is determined based on a design criterion which maximizes the diversity order by minimizing the Euclidean square product or, alternatively, minimizes a symbol error probability (SEP) expression. In this dissertation, an angle of 31.7 degrees is used as an angle of rotation in order to achieve SSD in two dimensions. This dissertation aims to improve the error performance of a non-coherent generalized differential modulation (GDM) wireless communication system. The proposed generalized differential scheme (GDM-SSD) is based on optimal power allocation, signal rotation and component interleaving/de-interleaving. GDM-SSD divides a frame into a reference part and normal part. The reference part is transmitted at a higher power than the normal part, and is used to encode and decode the information in the normal part. Optimal power allocation is applied to the system, and the results demonstrate that the SEP performance of the proposed GDM-SSD scheme losses about 5dB performance gap over coherent SSD scheme. It is observed that the performance of GDM-SSD detection gets better as the number of transmitted symbols in a frame increase.