Abstract
In wireless networks, stations can overhear frames that are sent by their neighboring stations. However, this broadcast nature of wireless signals can allow cooperative transmission to achieve spatial diversity without the need for multiple antennas. When a station with a low transmission rate accesses the shared wireless channel, the overall network throughput is reduced. Here we propose a cooperative MAC protocol called PocMAC that uses a distributed method to select relay stations for forwarding the traffic of such low-transmission-rate stations to improve overall throughput. Before each transmission, stations determine whether cooperative transmission through a relay station would be beneficial. Furthermore, the source must know whether the destination has a partner (relay). If the destination is not assigned a relay before a data frame is transmitted, the relay selection process will be performed during transmission. Then, one relay station will be automatically selected to forward the data frame; its MAC address will be stored in the RelayTable of the source station. For a future transmission to the same destination, the appropriate relay station may thus be directly found in the RelayTable instead of performing relay selection again. We performed a simulation to comparing our mechanism with traditional IEEE 802.11 and another cooperative MAC protocol, CoopMAC. The simulation results show that our mechanism improves overall network throughput, especially in dynamic topologies caused by mobility.