Polling scheme for reliable broadcasting in vehicular networks

Broadcasting plays vital role in vehicle-to-vehicle communication. However, it must face to challenges such as lack of acknowledgment, no retransmission, hidden terminals and low link quality that leads to unreliable communication because of message loss caused by collisions and poor link conditions. It is especially critical for safety messages in vehicular networks. To make broadcast more reliable, some rebroadcast methods have been proposed but they have to deal with problems of broadcast redundancy, delay and requirement of cross-layer information. In this work, we propose a new rebroadcast method, at MAC layer level, that uses a polling scheme where messages are retransmitted only when requested. To evaluate our scheme, we propose an analytical model specified for IEEE 802.11p with multichannel operations. We compute packet delivery rate in two cases: the case of one access category as in DCF and the case of prioritized broadcasting with several access categories based on EDCA. Our polling scheme shows significant improvement in both cases compared to standard even in limited operating time due to the switching channel.