Impact of Neighbor Awareness at the MAC Layer in a Vehicular Ad-hoc NETwork (VANET)

Despite various proposed Medium Access Control (MAC) approaches, efficient medium access in VANET remains a significant challenge, especially for the broadcast of safety messages. A key contributing factor to packet loss is the hidden terminal problem, which is exacerbated by the high node mobility apparent in VANET. Since the hidden terminal problem is fundamentally a problem of lack of awareness, this work evaluates the effects of increased neighbor awareness at the MAC layer. An increased awareness of neighboring nodes' slot allocation in a TDMA-based MAC, directly impacts on the number of available slots. Therefore, the effects of TDMA frame size is also evaluated for different awareness ranges. To support the analysis, a TDMA-based MAC with configurable neighbor awareness and configurable TDMA frame size is used. The impact is assessed using the packet delivery ratio, receiver throughput, and end-to-end latency. The results show packet delivery ratio and receiver throughput to increase for increased awareness ranges, up to an optimal of 3 hops, after which performance worsens. An increase in TDMA frame size leads to an increase in packet delivery ratio for small awareness ranges, and an oscillating increase for large awareness ranges. The receiver throughput also initially increases for an increased TDMA frame size, but reaches an optimum, also at 3 hops.