Novel selective OFDM-based cooperative techniques for multi-hop systems

In multi-hop systems, the theoretical outage probabilities and diversity orders of novel Orthogonal Frequency Division Multiplexing (OFDM) based Decode and Forward (DF) cooperative techniques are derived for different methods that manipulate the subcarriers in order to improve the performance, while overcoming practical implementation issues and using limited number of relays. First, the outage probability of the Basic Selective OFDM technique is derived for a multi-hop system without the high SNR approximations, and the effect of joint selection in the last two hops is investigated. Then, Subcarrier Ordering technique (SO) is introduced and proved its efficiency in substituting the error correction at the intermediate hops while reducing the computation complexity. Furthermore, we propose alike efficient cooperative methods making use of subcarrier mapping to trade-off between outage performance and practical implementation problems. We also analyze the computation complexity of the different algorithms and we prove that, at high SNR, the proposed Improved Selective OFDMA reduces the complexity by up to NN (Number of subcarriers) times without affecting the outage performance when compared to Selective OFDMA.