总线控制网络中基于优先级CSMA/CD协议的改进

总线控制网络的MAC层协议对网络实时特性具有重要影响。结合优先级CSMA／CD协议的等级原则与Token Bus协议的均衡思想，提出了一种改进的总线优先级轮循CSMA／CD协议。其高级别的总线优先级类似于Token Bus协议中的令牌，在各节点之间轮循传递；使控制网络在遵循整体分级的原则下，相同类型节点的性能局部能够相对均衡。详细阐明了该改进基本思想，概述其具体实现方式，并给出了对比仿真结果。该改进协议对于CAN等基于优先级CSMA／CD协议的总线控制网络具有一定实用价值。

Improved Priority-Based CSMA/CD Protocal in Bus-Topology Control Network

The MAC protocol of bus topology control network greatly influences network real time. This paper proposes an improved priority rotated CSMA/CD protocol, based on both hierarchy of priority based CSMA/CD and balance of token bus protocols. The highest priority rotates among all nodes just like the token in token bus protocol. It thus makes them possible, for the whole network to operate hierarchically and for the same nodes to act similarly in local. The outlines of improvement are detailed and the implementation method is summarized. The comparative simulation results are also given. This improved protocol is of applied value to control networks adopting priority based CSMA/CD protocols, such as CAN.