Multichannel Medium Access Control for Dedicated Short-Range Communications

This paper describes a medium access control (MAC) protocol to enable multichannel operation for dedicated short-range communications (DSRCs). In particular, we focus on the challenge of supporting potentially high-bandwidth commercial or infotainment communications between vehicles and the roadside in hotspots over several service channels, while concurrently enabling time-critical vehicle-vehicle communications for safety in a separate channel. In our architecture, within hotspots, the communication is aided by one of the access points in the hotspot. This access point is designated as the coordinating access point (CAP). Outside the hotspots, the communication is for safety only and is conducted in an ad hoc fashion. The CAP protocol design leverages IEEE 802.11 point coordination function (PCF) and distributed coordination function (DCF), which are modified for multichannel operation. The design objective is to maximize the utilization of the service channel that is used for nonsafety communications while meeting the quality-of-service (QoS) constraints of the safety communications. The performance of the IEEE 802.11 DCF and PCF and the CAP extension is quantified by simulation in NS-2. The mobility model represents a four-lane freeway at maximum vehicular traffic flow that is derived from the SHIFT traffic simulator. The CAP design is shown to significantly enhance the performance of safety and nonsafety communications.