一种基于竞争节点估计的改进DCF机制

对于多跳Mesh网络特有的树状拓扑，距离网关不同跳数的路由器所承载的网络流量不尽相同，与周围节点的竞争情况也不一致，由此传统802．11的DCF机制并不适用。提出了一种基于竞争节点估计的竞争窗调整机制，即利用节点分布式地获取各自的条件碰撞概率，并由此估算其竞争节点个数，在此基础上由最优最小竞争窗与竞争节点个数的关系函数，调整竞争窗大小来提高Mesh网络的总体性能。采用OPNET仿真结果表明，优化后的饱和系统吞吐量可提高70～80％，饱和时延可降低50％以上。

A Modified DCF Protocol based on Competing Node Number Estimation

When the tree-based topology of the mesh network is enabled, the routes would achieve different loads according to their hops to the gateway and their different contention situation. Thus, the traditional 802.11 DCF mechanism is unsuitable. This paper proposes a contention window adjustment strategy based on competing node number estimation. Every node distributively acquires its frame conditional collision probability and from this, estimates the competing nodes number. Then, according to the relation between the optimal contention window and the competing node number, the node adjusts its contention window. Simulation results indicate that the throughput of optimized saturated system is increased by 70-80 %, while system delay is decreased by 50% above.