适合关键信息可靠传输的节点拥塞避免算法

A Node-Level Congestion Avoidance Algorithm for Reliable Transmission of Key Information in Wireless Sensor Networks

无线传感器网络节点通信能力有限,有事件发生时,数据产生速率将急剧增大,网络可能会发生拥塞的问题,提出了一种适合关键信息可靠传输的节点拥塞避免算法CAARTKI(Congestion Avoidance Algorithm for Reliable Transmission of Key Information)。算法主要思想是通过引入区分服务,数据包按其重要性不同划分为不同的优先级,高优先级分组优先得到传输。本算法中,节点只有在下一跳节点为其分配了发送窗口才可以发送数据,以避免节点拥塞发生;在链路层考虑拥塞避免的同时,在路由层通过选择可用缓存空间多的邻居节点作为下一跳节点,使关键信息能及时可靠传输到负载较轻的节点,减少由于负载过重时重要信息不能及时传输的可能;在关键信息密集产生时,采用主动丢包策略,丢弃部分低优先级分组,为高优先级分组腾出缓存区间。NS2仿真实验结果表明:CAARTKI可预防拥塞的产生,最高优先级分组的丢包率低,平均网络时延较小,能保证关键信息的及时可靠传输。

The cowanunication ability of a wireless sensor network node is limited, when an event occurs, the data generation rate may increase sharply, which may result in network congestion. While the key information which characterizes the occur- rence of an important event is critical for users, it is very important to transmit them timely and reliably for users ＇ high quality decision-making and effective response. Therefore, the paper puts forward a node-level congestion avoidance algorithm which can guarantee the reliable transmission of key information, named CAARTKI. The main idea of this algorithm is to divide the service by introducing differentiated services, and the packets are divided into different priority according to their importance. In this algorithm, a node sends data only when its next hop node has assigned a sending window for it, which may avoid the occurrence of node congestion, and congestion avoidance is not only considered in link layer, but also, in routing layer, a neighbor node with more buffer spaces is chosen as the next hop node. Thus key information can be transmitted timely and re- liably to nodes with lighter load, and the possibility that important information can not be sent in time due to heavy load can be reduced significantly. When the key information is generated intensively, the algorithm adopts the active loss strategy and frees the cache for packets with higher priority through discarding some packets with lower priority. The NS2 simulation re- sults show that this algorithm can alleviate congestion occurrence, the packet loss rate of the highest priority packets is ex- tremely low and its average network delay is small, and key information can be transmitted reliably and ouieklv.