Optimizing the persistent scheduling in two-hop relay networks

We propose two scheduling protocols which are applicable to two-hop relay networks based on mobile WiMAX system: the first protocol adopts a persistent scheduling (PS) scheme in both hops, called the PS-PS protocol, while the second protocol adopts the PS scheme only in the first hop and the dynamic scheduling (DS) scheme in the second hop, called the PS-DS protocol. We optimize the above two protocols by minimizing their average resource usage (ARU) through appropriate selection of the modulation and coding scheme (MCS) level for given delay and packet error requirements. Taking into account different characteristics in both a source-relay (SR) link and a relay-destination (RD) link, resource usage due to hybrid automatic repeat request (HARQ) retransmissions, and the accompanying signaling overhead, we compare the performance of the proposed optimization methods with that of the conventional method in terms of ARU. The PS-PS protocol outperforms the PS-DS protocol and the conventional method considered in most channel case, while the PS-DS protocol outperforms other schemes in a harsh channel condition.