Asynchronous MAC protocols for Wireless Sensor Networks (WSN)are researched. PBMAC, a new broadcast MAC protocol with shorter preamble, is proposed based on the typical XMAC protocol. PBMAC acquires the sampling schedule by employing neighbor inform mechanism as well as improved preamble sequence. As a result, a shorter preamble is achieved. Evaluated by NS2 simulation, PBMAC is an idea protocol with high performance in terms of energy efficiency and delay compared with BMAC.%本文研究了基于竞争机制的无线传感器网络异步MAC协议,提出了一种新的基于XMAC的异步MAC广播机制--PBMAC(preamble broadcast MAC).PBMAC通过短的带有间隔的前导载波单元序列,结合邻居告知机制以及改进的前导载波单元获知邻居节点的采样时刻,有效地减小了前导载波长度.通过NS2仿真对BMAC和SPBMAC进行了比较和评估.实验结果表明,PBMAC不仅降低了源节点能耗,且减少了数据延迟.
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