Special Studies Project Report (M.Eng.) - Asian Institute of Technology, 2002

Reducing decoding complexity by combining array processing and space-time codes (STC) helps a communication system using STC to overcome a big obstacle that prevents it from achieving a desired transmission rate. Multi-carrier CDMA (MC-CDMA) is a combination of multi-user access of CDMA and multi-carrier modulation techniques, which allows providing good performance in a channel with high inter-symbol interference. In addition to that, antenna airny, STC and MC-CDMA system have a similar characteristic that transmit-receive data streams are divided into sub-streams. Thus, there may be a noticeable reduction of receiver complexity when we combine them together. In this research study, the combination of array processing and STC in MC-CDMA system over slow selective-fading channel is investigated and compared with corresponding existing MC-CDMA system using STC. Performance comparisons are made in different channel conditions as well as in different transmission rates. All the data are calculated and compared with corresponding simulation parameters in (Maitree, 2000). Simulation results show that combining array processing and STC can provide higher data rate (2 times) while reducing decoding complexity (16 times). However, there is a penalty to be paid for simplified decoding, especially in multipath fading channel. The serious performance degradation is about 10 dB at FER of 0.01 at both the same data transmission rate and double data transmission rate over multipath fading channel in the case of single user system. However, for an A WGN channel combining array processing and STC with 2-STCM shows a negligible degradation (about 1 dB at FER of 0.001) compared with 4-STCM for both single user system and multiuser system.

A research submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Advanced Technologies