Abstract: The critical issues in design of routing protocol for Wireless Sensor Network (WSN) are energy awareness and maximizing the lifetime. Focus on those challenges, a new routing algorithm named CTOR was proposed based on time synchronization sleeping schedule with low duty cycle. In CTOR, a node selected several proper forwarders in order to gain assured delivery ratio, and then broadcasted the packets to forwarders; in order to reduce replication packets and yield much gain efficiently, forwarders that received packets forwarded packets according to a probability. Then the sink node broadcasted control messages to make all nodes time synchronized, the other nodes turned into sleeping mode according to the permanent duty cycle. This mechanism can reduce the power consumption and hence the network can work longer. The experimental results show that CTOR can alleviate the routing hole problem, prolong the lifetime of the network and increase the delivery ration of packets.

Key words: Wireless Sensor Network (WSN), time synchronization, duty cycle, opportunistic routing, forward probability

摘要： 针对无线传感器网络(WSN)中存在节点剩余能量不足而导致的路由失效问题，提出一种基于低占空比的汇聚树机会路由算法CTOR。在CTOR中，首先根据网络的传输质量需求确定路由候选节点集；然后，节点以广播方式向所有候选节点传输数据包，收到数据包的候选节点再以一定概率转发该数据包，转发成功的候选节点即为选定的路由节点。概率的引进保证了高数据传输质量与轻网络负载；同时，网关节点发送时间同步控制信息以达到全网时间同步的目的；节点根据固定占空比进行休眠切换，以减少节点的能量消耗，延长网络的生存周期。仿真实验表明，基于低占空比的协议可有效地避免网络空洞问题，延长网络的生存周期；同时，机会性的转发可以有效地提高数据包的成功接收率，降低网络的丢包率。

关键词: 无线传感器网络, 时间同步, 占空比, 机会路由, 转发概率