Abstract
The inherent property of fluctuant channel conditions in the wireless networks influences the Quality-of-Service (QoS) severely. The Mobile Stations (MS) suffering from rigorous interference could not deliver data successfully and fail to achieve the QoS required by the applications. The occurrence of interference would worsen the performance especially in multihop relay networks. IEEE 802.16j is a promising Multihop Relay (MR) networks which enhance coverage, throughput and system capacity of IEEE 802.16e networks by deploying Relay Stations (RS) to relay data between MSs and the Multihop Relay BS (MR-BS). The scheduling services in IEEE 802.16j may allocate the bandwidth periodically without explicit bandwidth request to each hop along the path between the source and the destination. Once the MS encounters low channel quality in access link, the whole resources scheduled for the MS will waste. This not only breaks the QoS agreements but greatly decreases the system performance. In this paper, we propose a cooperative relaying mechanism to overcome the unstable channel conditions in IEEE 802.16j MR networks. Therefore, a user that is currently experiencing bad channels could survive if a cooperative partner with good channels is willing to relay its data to the destination. In order to find out a cooperative partner with best capacity to relay data, we also propose an adaptive partner selection algorithm. Extensive simulations highlight the superiority of the proposed solutions in terms of packet delay, jitter, system throughput, and packet loss rate.