NS2-Based Simulation And Study Of Vehicular Networking WAVE Multi-Channel Access Mechanism

To reduce traffic accidents,enhance traffic safety and improve the driving environment,the concept of vehicular ad-hoc networks (VANETs) is proposed to solve the traffic problem based on Internet of Things. WAVE is an important protocol framework of the VANETs.WAVE is comprised of IEEE802.11p and IEEE1609 protocol suite.It considers the characteristics of the actual traffic environment and is applicable to the network environment with high-speed mobile nodes and the fast changing topology structure. WAVE has now become a research hotspot in the intelligent transportation.Mutil-Channel access mechanism is an important aspect of WAVE.IEEE 1609.4 is used to implement mutil-channel access mechanism in WAVE.IEEE1609.4 is compromised of the functions of channel coordination,channel synchronization, channel routing and channel access.With multi-channel access mechanism,the overall network throughput is greatly improved and more vehicles can be accommodated in the network.But the study of multi-channel access mechanism is few at present.Four channel access methods are proposed in IEEE 1609.4:continuous access, alternating SCH and CCH access, immediate SCH access, and extended SCH access. Only alternating SCH and CCH access can be be suitable for both safety-related applications and no-safety related applications. But it has fixed the CCH interval and SCH interval and cann't be well adapted to the fast changing network topology structure.This paper starts from ensuring traffic safety and improve the network throughput,proposes an improved channel access mechanism——the channel reservation mechanism based on negotiation against the drawbacks exsiting in the alternating SCH and CCH access existing in the SCH channel access method at present.Mobile car networking model is established in this paper and NS2 simulation tool is used to implement and validate the channel reservation mechanism based on negotiation.The result shows that the channel reservation mechanism based on negotiation improves the overall network throughput with low average delay and packet loss ratio on the basis of guaranteeing traffic safety.