Distributed Space Time Block Coding for Asynchronous Cooperative Communication Systems

Multiple-Input-Multiple-Output (MIMO) communication techniques have been an important area of focus for 4th generation wireless systems. This is mainly because of their potentials for high capacity, increased diversity, and interference suppression. The cooperative communication techniques can avoid the difficulties of implementing actual antenna arrays and convert the single-input single-output (SISO) system into a virtual MIMO system. In this scheme, the user explores its other neighbor users to act as relaying nodes and forming virtual MIMO system. Space-Time Block Coding (STBC) is used to improve the transmission reliably and spectral efficiency of MIMO systems. When STBC is applied to a cooperative diversity, the system termed as Distributed Space Time Block Code (D-STBC). Most of the existing research assumes perfect synchronization among cooperative users in D-STBC. This means that they have identical timing, carrier frequency, and propagation delay, which is almost impossible to be achieved. The lack of common timing reference can badly influence the performance of the D-STBC system. There are different research efforts to overcome this problem; most of which have high decoding complexity. In this research, two low decoding complexity detection schemes of D-STBC have been proposed and they have proven their efficiency in mitigation the impact of imperfect synchronization between the relay nodes. The first one is based on Parallel Interference Cancellation (PIC) method and the other is based on Successive Interference Cancellation (SIC) method.