无线Ad Hoc网络中基于阈值的分布式流控制机制

Threshold based distributed flow control scheme in wireless Ad Hoc networks

由于无线Ad Hoc网络的分布式特性,当多个流通过同一个中继节点时,带宽的不公平竞争导致低优先级流的饥饿,堵塞通讯.现有算法大多依赖被动的传输超时(Timeout)来处理拥塞控制和饥饿.通过设置拥塞阈值来主动反馈拥塞状态,提出一种基于阈值的分布式流控制机制(TDFC).在TDFC机制中,数据流抢占带宽的贪婪行为将被中继节点阻塞,由此可以有效抑制贪婪行为,实现公平分配;同时各个中继节点为每个流设置堵塞阈值(block threshold),主动反馈堵塞事件,减少带宽浪费.仿真结果表明:与IEEE 802.11 EDCA协议相比,TDFC可以有效实现流之间带宽的公平分配,而且将网络吞吐量提高20%.

In wireless Ad Hoc networks,when a couple of flows pass through a single relaying node,the severe contention for the bandwidth between flows may block the communication between source nodes and destination nodes and starve the flows with lower priority.Most of the existing flow control schemes depend on the passive timeout message for flow block and starvation.To address this issue,a threshold based distributed flow control（TDFC） scheme was proposed based on setting the blocking threshold for blocking detection.In TDFC,the packets of greedy data flows are blocked by the relaying nodes.Thus,greedy behaviors can be suppressed effectively.Each relaying node sets the block threshold for each flow and then the communication congestion can be detected immediately.In addition,by comparison with IEEE 802.11 EDCA,TDFC can implement the fairness between flows,reduce the flow block and improve the network throughput by 20%.