Enhanced Retransmission Scheme Multihop WiMAX Networks

IEEE 802.16j Mobile Multi-hop Relay (MMR) WiMAX network uses Relay Station (RS) to extend the cell coverage area and enhances the link quality and hence the throughput. It allows the number of hops between the SS and the BS to be more than two hops when Non-Transparent RS (NT-RS) is used. Automatic Repeat reQuest (ARQ) protocol is applied to the MAC layer to enhance the wireless link through retransmitting the corrupted packets. The sender realizes that the packet is lost either when it receives negative feedback from the receiver or when the waiting retry timeout is expired. However, when MMR WiMAX is considered, this requires modification to the ARQ retry timeout in order to enhance the link layer and TCP performances. Therefore, this paper presents hop aware ARQ retry timeout adjustment. The proposed scheme aims to decrease the delay of error recovery caused by long retry timeout and avoid un-necessary retransmission due to short retry timeout. The performances of the proposed schemes are simulated using TCP traffic. The results showed that the link layer and TCP performances are improved significantly.