Opportunistic Relay Protocol For IEEE 802.11 WLANs

In IEEE802.11,it is the general case that the further away the stations from the access point (AP), the slower the data rate is to transmit to the AP. With the existing IEEE 802.11 MAC, in the long run all stations end up with the same amount of throughput, no matter if they transmit slow or fast. When one host captures the channel for a long time because its bit rate is low, it penalizes other hosts that use the higher rate. As a solution, a novel MAC layer relay protocol, Opportunistic Relay Protocol (ORP) is proposed, to improve the performance of IEEE 802.11. The ORP suggests two hops technique to enable slow transmitting stations to speed up their transmission rates. The simplest explanation is: A single 2 Mbps transmission path is replaced with two 11 Mbps transmissions where an intermediate node is used as a relayer. This way relay protocol offers 5.5 Mbps (ignoring overhead) effective bitrate instead of 2 Mbps. In this thesis, ORP was formalized and analyzed through theoretical work and implemented within a simulation environment to evaluate the performance improvement that ORP offers. It is showed that with ORP, the overall throughput of the BSS improves up to %25. Moreover, ORP inserts negligible amount of overhead to the system while maintaining backward compatibility with IEEE 802.11. Table of