Performance study of efficient cooperative communication systems

The cooperative relaying technique has gained a lot of research interest recently.It can obtain the spatial diversity and improve the system performance as the multipleinput multiple-output (MIMO) technique does, but without the requirement of installing multiple antennas in mobile devices.However, due to the half-duplex constraint that mobile terminals cannot transmit and receive at the same time over the same frequency band, some conventional cooperative protocols have to sacrifice the spectral efficiency to trade the accurate transmission.In the thesis, we concentrate on analyzing the performance of cooperative relaying systems with efficient and effective transmission protocols, which can achieve the full spatial diversity gain as well as improve the spectrum efficiency significantly.Firstly, to achieve the full cooperative diversity gain of a single-relay system with fixed decode-and-forward (DF) relaying protocol, the cooperative maximal-ratio combining (C-MRC) scheme is employed.The bit-error rate (BER) performance of C-MRC and maximal-ratio combining (MRC) schemes is analyzed in the presence of independent and non-identical Nakagami-m fading channels.The BER upper bounds of both schemes are derived and the achievable diversity orders are compared.It is illustrated that by smartly designing weighting factors, the C-MRC scheme can achieve the full spatial diversity gain of the system.Additionally, C-MRC is shown to achieve higher diversity order than MRC in the fixed DF relaying protocol as well as outperform the adaptive DF relaying protocol.