DLSOMAC:一个面向分布式无线链路调度技术的MAC协议

无线网络分布式链路调度技术通过发掘无线传输间的复用达到提高吞吐量的目的. 链路调度策略的形成需要节点间公平地交互含有如节点ID、队列长度等信息的短报文,并且这些短报文同步传输,导致信道拥挤.由于存在信道空闲侦听开销,在拥挤信道中频繁后退,以及隐藏终端和暴露终端的问题,传统的CSMA/CA (Carrier sense multiple access with collision avoidance)协议传输性能低下,难以为分布式无线链路调度技术服务. 针对链路调度策略形成期间报文短、信道拥挤以及公平性要求的挑战.提出了一个简单的随机MAC (Media access control)协议DLSOMAC (Distributed link scheduling oriented MAC). DLSOMAC协议没有信道侦听过程,以降低短报文的传输延迟开销;基于分布式息票收集算法,均匀分散传输时刻来降低冲撞概率和提高公平性,以满足分布式链路调度技术对MAC层的需求.用排队论分析了DLSOMAC的报文传输延迟性能.仿真实验表明, 在短报文情况下,无论网络负载轻重与否, DLSOMAC协议的报文传输延迟明显优于CSMA/CA,并且报文越短,性能相对越好.即使在长报文的情况下,当网络负载很重时, DLOSMAC协议也稍优于CSMA/CA协议,适合于为自组织网络的分布式链路调度技术服务.

DLSOMAC: a MAC Protocol Oriented to Distributed Wireless Link Scheduling Technology

The distributed link scheduling strategy can improve the performance of throughput notably by exploring multiplexing among wireless transmissions. Conceptually, to form a link scheduling strategy, network nodes need fairly exchange short packet embedded with information, such as node identity, queue length, etc. However, synchronous transmissions of these short packets will result in serious channel collision. Due to the weakness of idle listening overhead, frequent back-off in busy channel, and the infamous hidden terminal and exposed terminal, the traditional CSMA/CA (Carrier sense multiple access with collision avoidance) protocol cannot support distributed link scheduling effectively. To overcome these weaknesses, we propose a novel randomized MAC (Media access control) protocol called DLSOMAC (Distributed link scheduling oriented MAC) in this work. In DLSOMAC, the transmission delay is relatively small since DLSOMAC doesn't have idle listening. We use the distributed coupon collection algorithm to disperse transmissions into different slots uniformly. Thus the collision probability is decreased and fairness guaranteed. We also analyse the transmission delay using queuing theory. Simulation results demonstrate that in short packet transmissions, the network throughput of DLSOMAC outperforms that of CSMA/CA notably under any network loads. Especially, the shorter the packet is, the better the relative performance is. Even when the network load is heavy or the packet is long, the network throughput of DLSOMAC is still slightly greater than that of CSMA/CA. The DLSOMAC is a suitable MAC protocol for ad hoc networks to support distributed link scheduling.