An Algorithm For Joint Adjusting Of Power, Carrier Sensing Threshold And Rate In 802.11 Networks

IEEE 802.11 is a group of protocols which are based on physical carrier sensing (CSMA) mechanism. In wireless multi-hop networks without AP, physical carrier sensing has hidden terminals and exposed terminals problems which are affect on spatial reuse, and aggregate throughput of the network. In recent years with the widely used of wireless network, improving the aggregate throughput has gained tremendous attention.Past algorithms are all armed to improve spatial reuse through joint carrier sensing threshold and rate or joint power and rate. Because of these algorithms pay all their attentions to improve single links, the assignment of space is so different between links that limits the throughput of network. On the other side, these adjusting strategies of the past algorithms all depend on the information which is loaded by control packages of MAC layer in vary degrees, so that the algorithms become more complex, and the effectiveness of the adjustment strategies also be affected.In this paper, we explore a drop-rate based algorithm which is to optimize the space partition through jointing carrier sensing threshold, power and rate. It can improve the aggregate throughput. Our algorithm optimizes space partition form the perspective of cluster. That is, we can group the nodes according to their locality in the network. Nodes belong to the same group can't transmit in the same time, while belong to different groups are able to transmit in the same time. We can place hidden nodes in some group through change their transmit power. Our algorithm is distributed enables each node to estimate the state of network, which is point to the state of channel and topology. Then choose the optional carrier sensing threshold, power and rate according to the rules of algorithm. Different to other algorithm, there can be different parameters chosen between different nodes. On the other side, the adjustment strategies are based on the drop rate. Each node can estimate the state of network according the drop rate of MAC layer. There is no need to increase the additional control orders, with the control packet of existing 802.11 to load information, and the distance from sending node to receiving node. So it is easier to implement in existing 802.11 protocols.The simulation results show that our algorithm jointing carrier sensing threshold, power and rate can deal with hidden terminals problems effectively. Also our algorithm improves the aggregate throughput and balances the assignment of space obviously.