Abstract
IEEE 1609/802.11p standard obligates each vehicle to broadcast a periodic basic safety message (BSM). The BSM message comprises a positional and kinematic information of a transmitting vehicle. It also contains emergency information that is to be delivered to all the target receivers. In broadcast communication, however, existing carrier sense multiple access (CSMA) medium access control (MAC) protocol cannot guarantee a high reliability as it suffers from two chronic problems, namely, access collision and hidden terminal interference. To resolve these problems of CSMA MAC, we propose a novel enhancement algorithm called a neighbor association-based MAC (NA-MAC) protocol. NA-MAC utilizes a time division multiple access (TDMA) to distribute channel resource into short time-intervals called slots. Each slot is further divided into three parts to conduct channel sensing, slot acquisition, and data transmission. To avoid a duplicate slot allocation among multiple vehicles, NA-MAC introduces a three-way handshake process during slot acquisition. Our simulation results revealed that NA-MAC improved packet reception ratio (PRR) by 19% and successful transmission by 30% over the reference protocols. In addition, NA-MAC reduced the packet collisions by a factor of 4. Using the real on-board units (OBUs), we conducted an experiment where our protocol outperformed in terms of PRR and average transmission interval by 82% and 49%, respectively.
Highlights
Vehicular communication, often referred to as V2X, is among the main pillars for the imminent era of intelligent transportation systems
We propose a novel protocol called neighbor association-based medium access control (MAC) (NA-MAC), which supports a hybrid of time division multiple access (TDMA) and carrier sense multiple access (CSMA) MAC configuration like hybrid cooperative MAC (HCMAC)
We describe the layout of the experiment with five on-board units (OBUs)
Summary
Often referred to as V2X, is among the main pillars for the imminent era of intelligent transportation systems (e.g., autonomous vehicles). Several standard protocols [1,2] have been developed to realize data communication among the vehicles Most of these protocols allow the vehicles to transmit broadcast and unicast messages through predefined control and service channels [3]. DSRC spectrum is exclusively used by V2X communications This spectrum is further divided into seven orthogonal channels, each of which represents the 10 MHz bandwidth. One of these channels is called a control channel (CCH), which is dedicated to broadcast safety messages. WWhhiillee sscchheedduulliinngg tthhee cchhaannnneellreresosouurcrecse,sR, RSUSUcocnosnidsiedresrtshethheidhdidednetnertmerinmailncaolllciosilolinsi.oInt .avItoaidvsoaidllsocaalltoincgattihneg stahme seacmheanchnaenl rneesloruesrcoeusrctoesmtoumltiuplteipinleteinrfteerrifnegrinvgehviechleisc.leTsh. Te haeutahuothrsoorsf o[1f5[]15in] tirnotdroudcuedcead novel MAC protocol that provides time division multiple access (TDMA)-based broadcasting for safety messages with a coordination of RSUs. The RSU defines the transmission. The proposed method mainly focuses on broadcast V2V communication and it can be extended to V2I communication scenarios
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