Abstract: In order to reduce the problem of collision and cut down the time delay in wireless sensor networks, an improved CSMA/CD protocol based on directed diffusion and orderly competition, namely CSMA/CD-DDOC protocol, is proposed. By dividing the numerous forwarding nodes in the same gradient level into several groups that request the sharing channel orderly, the number of nodes competing for the sharing channel in the same time is reduced, and the intended result is achieved. The theoretical analysis and simulation results validate that the time delay performance of CSMA/CD-DDOC protocol is better than that of CSMA/CD protocol.

Key words: directed diffusion, Wireless Sensor Networks（WSN）, Medium Access Control（MAC） protocol, orderly competition, time delay

摘要： 在定向扩散路由无线传感器网络中，为减轻竞争型MAC协议CSMA/CD的碰撞冲突问题，以及减小MAC协议引入的时延，对CSMA/CD协议进行改进，提出基于定向扩散与有序竞争的传感器网络MAC协议，即CSMA/CD-DDOC，通过将同跳梯度层次内的转发节点进行分组后实施各分组对共享信道的有序竞争，减少同时争用信道的节点数目，以达到减少碰撞和减小时延的目的。理论分析和仿真结果表明，CSMA/CD-DDOC协议具有优于CSMA/CD协议的时延性能。

关键词: 定向扩散, 无线传感器网络, 介质访问控制（MAC）协议, 有序竞争, 时延