ABSTRACT
318In vehicle ad hoc networks (VANETs), channel coordination scheme is a key technology related to the utilization of channels, which to some extent increases the system throughput. But the available multichannel scheme still suffers from some obvious drawbacks, such as control channel (CCH) congestion, poor channel utilization, multichannel hidden terminal, and missing receiver problems. In this chapter, we study the infrastructure-coordinated multichannel schemes to solve the aforementioned problems with regard to VANETs. Generally, the multichannel schemes are divided into two categories: synchronous multichannel and asynchronous multichannel. For the synchronous scheme, we present a novel synchronous roadside unit (RSU) coordinated multichannel MAC scheme (SRCMC) to allow channel rendezvous on the CCH during the whole synchronization intervals for alleviating the CCH congestion problem. SRCMC also supports simultaneous transmissions on different service channels (SCHs) to increase SCHs utilization. Moreover, we utilize the RSU to record the rendezvous information and broadcast it to the surrounding vehicles on the CCH. Thus, the collision problem on the SCHs can be further avoided. For the asynchronous scheme, we propose a novel asynchronous RSU-coordinated multichannel MAC scheme (ARCMC) to allow RSU switching between different SCHs and retransmitting messages to OBUs which miss rendezvous information. It solves the message loss and rendezvous conflict problems. It is noted that an analytical model is developed to evaluate the aggregate throughput of V2V communications in these different scenes and the performances are analyzed in terms of multichannel hidden terminal, missing receiver, and CCH congestion problems. Simulation results demonstrate that the proposed schemes can provide better performance in channel utilization, system throughput, and avoiding multichannel hidden terminal and missing receiver problem, than that of the existing approaches in the literature.
