CSSA MAC: carrier sense with slotted-Aloha multiple access MAC in vehicular network

Abstract

IEEE 802.11p and 1609.4 are key layers in the WAVE architecture. They have been chosen to work as random medium multiple accesses with a multichannel switching scheme between SCH to CCH. This paper tackles the 'start-of-interval contention problem', which is faced during beaconing after switching to the CCH periods. At the beginning of each CCH, a considerable number of vehicles may go into contention in the same to get access to the channel and may result in a high collision rate. Therefore, the performance of all vehicular network applications which are based on beaconing will be affected. The proposed new scheme can be integrated with IEEE 1609.4 to work on top of IEEE 802.11p. The main idea in the proposed solution relies on spreading the starting of access time over the CCH period. This technique, which is an improved version of S-Aloha scheme, helps in minimising the risk of collision. The obtained simulation results show promising improvements when applying the proposed solution compared to the performances given when using S-Aloha or only IEEE 802.11p.