中文摘要：

IEEE802.11p突破了传统协议的限制,采取多信道协调的机制,但是控制信道和服务信道的长度是固定的,造成信道资源大量浪费。针对传统IEEE802.11p中信道利用率低的问题,提出了一种非饱和情况下可变的服务信道（Service Channel,SCH）时隙媒质接入控制（Medium Access Control,MAC）机制。在此机制下,可以通过调整控制信道（Control Channel,CCH）和SCH的长度,达到吞吐量最大化的效果。该机制使用三维Markov链模型来计算WAVE服务广播信息（Wave Service Advertisement,WSA）帧的时延,并得出了一个非饱和状态下适用的可变的SCH时隙MAC计算模型。仿真实验表明,该机制不仅提高了信道利用率,增加了吞吐量,同时也降低了信道的时延。

英文摘要：

The emergence of IEEE802.11 p protocol effectively breaks through the limitations of traditional protocol, and the multi-channel coordination mechanism is usually adopted. However, recent research indicates that the fixed length ratio of between CCH and SCHs in IEEE1609.4 protocol would bring about huge waste of channel. This paper proposes a variable SCH interval multichannel medium access control（MAC） scheme under the non-saturated channel. With this scheme, three dimensional Markov chain is used to calculate the delay of WSA frame, control the length of CCH interval and SCH interval and achieve the max throughput. The simulation results indicate that the proposed scheme can help VANETs remarkably naise the unsaturated throughput of SCHs and lower the transmission delay of data frames.