基于概率的EPA Wireless时钟同步方法

针对在EPA Wireless协议中采用单报文广播(SPB)的时钟同步方法存在同步时间长、发送报文数目多、协议的宏周期长等问题，提出基于概率的用于EPA Wireless同步（PBS）方法.PBS只须分配较少的同步机会,每个机会中所有节点都以相等的概率发送同步报文.理论上PBS需要很少的时间和报文来保持节点和网关之间的同步,可以减少EPA Wireless的宏周期；此外PBS方法更加节能,并且可以减少网络流量.PBS方法的性能不会随着节点数目增多而明显下降.使用PBS,从节点与网关时钟之间的时钟偏差比SPB大,但是该偏差不会影响到协议的功能.将该方法在组建的无线网络上进行实验,结果表明：基于概率的时钟同步方法在实际上和理论上的性能是一致的.

Probability-based clock synchronization for EPA Wireless protocol

Single packet broadcasting (SPB) method applied in EPA Wireless for synchronization needs a plenty of time and packets and a long macro cycle. A probability-based synchronization (PBS) method was proposed to solve the problem. PBS allocates fewer opportunities for synchronization, in which all nodes send synchronization packets with equal probability. In theory, PBS needs less time and packets to keep nodes in synchronization with the gateway, and it can reduce the macro cycle of EPA Wireless. Besides, PBS is more energy saving and can reduce network flow. The performance of PBS does not decrease dominantly with the increasing nodenumber. PBS has a larger deviation than SPB but it does not affect the performance of EPA Wireless. Experiments were conducted on a real wireless network. The results showed the agreement of the experimental and theoretical performances.