PROJECT TITLE:

PERFORMANCE ANALYSIS OF OFDM RELAY AND OFDM COOPERATIVE DIVERSITY SYSTEMS

Founded by: Ministry of Education and Science

Head of project: Doc. dr Zoran Veljovic

Research type: Fundamental

Institution University of Montenegro, Faculty of Electrical Engineering

Research topic: Performance analysis of OFDM relay and OFDM cooperative diversity systems, with the relay station performing subcarrier mapping according to the channel conditions on the first and the second hop. The fixed gain amplify-and-forward (AF), variable gain AF, and decode-and-forward (DF) relaying methods will be examined. Performance of interest are: bit error rate (BER), system capacity, as well as system complexity. It is already proven that OFDM relay system maximize achieavable capacity if the subcarrier with the highest signal-to-noise ratio (SNR) from the first hop is mapped at the relay station to the subcarrier with the highest SNR on the second hop, second best – to – second best, etc. However, when the BER performance is the one of interest, then this kind of subcarrier mapping appears to be optimal only for the low SNRs, while for the medium and high SNR regime the subcarriers should be mapped in the opposite way. The performance of different relaying strategies, all including subcarrier mapping, are going to be examined and compared analytically and through simulations, assuming Rayleigh fading channel, which corresponds to signal propagation in case when there is no line of sight between transmitter and receiver.

Research goals: The research goal is to propose the optimal solution for the OFDM relay and cooperative diversity systems, as the potential candidate for the next generation of WWAN and WLAN networks. The optimal solution will be identified through analytical and simulation performance comparison of different OFDM relaying strategies implementing subcarrier mapping at the relay. The performances of interest are BER and system capacity, but optimality condition also assumes analysis of system complexity. Besides, this research project may open many new related research topics, like: time and frequency synchronization in the analyzed OFDM relaying systems, channel estimation in the assumed systems, optimal power allocation, preamble structure, design of the MIMO-OFDM receivers for the OFDM cooperative systems, etc. Also, one of the goals is to present the research results, as well as state of the art in this research area, to students and researchers at the Faculty of Electrical Engineering in Podgorica.