Cooperation diversity scenarios for clipped OFDM with iterative destination node reception

A realistic framework for cooperation diversity is presented for Orthogonal Frequency Division Multiplexing (OFDM) systems with clipping type of transmitter non-linearities. The destination node processes together the received information from the source node and a single, selection algorithm dependent relay one (if any of the candidate relays succeeds in decoding the original OFDM packet sent). The relayed packets are the same with the direct ones (repetition coding), so that simpler receiver processing applies. The destination node employs an optimized, iterative receiver structure based on Turbo processing, in which both the channels and the clipping distortion are (iteratively) estimated. The relaying nodes receive the source-node emanating packets in a standard, non-iterative fashion, due to delay constraints. Two methods of relay node selection are considered: a) Random Relay Selection (RRS), and b) Optimal Relay Selection (ORS). High gains are showed for the proposed approach, due to the synergy between clipping distortion, channel estimation and multiple transmission paths, based on node cooperation diversity. In addition, when the number of candidate relay nodes increases, it is shown that ORS performs significantly better than RRS.