Investigation on uplink collaborative contention-based bandwidth request for WiMAX three hop relay networks

This paper suggests a collaborative contention bandwidth request (BR) mechanism for worldwide interoperability for microwave access (WiMAX) three-hop relay networks. By complimenting message and code BR in three hops of a link, the proposed framework enables low block error rate (BLER), packet dropping and signaling overhead while preserving the connection throughput and access delay requirements of best effort (BE) services. With three hops between base station (BS) and mobile station (MS) via relay station 1 (RS1) and relay station 2 (RS2), there take place eight possible BR mechanisms with message and code BR. Among eight BR mechanisms, message-message-code (MMC) BR performs better with message dominant BR and code-message-code (CMC) BR performs better with code dominant BR. Further, with CMC BR, the BLER is reduced by 5.88%, packet dropping is reduced by 8.68%, medium access control (MAC) overhead is reduced by 7.6%, MAC wastage is reduced by 4.47%, connection delay is reduced by 28.30%, queuing delay is reduced by 8.65%, queue size is reduced by 15.25% and throughput is improved by 11.51% than MMC BR mechanism.