Backoff algorithm using relay count in CSMA based wireless mesh networks

Abstract

The wireless mesh networks consist of wireline backbone network, gateways and mobile stations. In wireless mesh networks, all nodes construct multi-hop networks that all can be relay nodes. At the gateway node, bottleneck problem can occur because of gathering of all packets from mobile stations in the local mesh network. Since the gateway node has large capacity compared to that of the mobile stations in the local mesh networks, every packet which are generated from the wireless mobile stations come together at the gateway node. Therefore, we propose an effective CSMA algorithm for reducing this bottleneck in IEEE 802.11 based wireless mesh network. In this thesis, every node updates the relay information constantly in distributed manner. RTS/CTS messages which are used for medium access control (MAC) protocol contain the information of transmitter and destination ID. Therefore, the nodes can count the number of origin nodes dynamically by reading the control message. Based on the concept of relay count awareness, we proposed the modified version of the IEEE 802.11 DCF mode that proposes linear distribution and exponential distribution as a probability density function (pdf) of the contention window size selection rather than using uniform distribution. We analyze the proposed scheme and conventional scheme which use IEEE 802.11 DCF mode that operates on multi-hop wireless mesh networks and perform simulation and get results that our proposed scheme outperforms the conventional scheme.