Neighbour -Aware, Collision Avoidance MAC Protocol (NCMac) for Mobile Ad Hoc Networks

IEEE 802.11 [1] has become the standard for wireless LAN´s both in infrastructure and in ad hoc mode. The standard specifies the medium access control mechanism, distributed coordination function (DCF). Deploying the 802.11 DCF in wireless multi-hop networks leads to inefficient utilization of bandwidth and energy due to many unnecessary collisions. To attenuate these problems we propose a neighbour -aware collision avoidance MAC protocol (NCMac). The NCMac protocol defines algorithms to estimate minimum and maximum contention window (CW) sizes (CW_min, CW_max) taking into account the number of neighbours in the one-hop neighbourhood and the energy level of the battery. A novel resetting algorithm applied both after a successful and unsuccessful transmission has been also designed. In [3] we have already proposed a similar algorithm to calculate the CW_min (but not CW_max). However, the resetting algorithm of the NCMac is enhanced and unified and the NCMac does not modify the backoff algorithm defined in [1]. The NCMac protocol achieves a better throughput and noticeably reduces the number of collisions resulting in a longer network lifetime and a later dead of the first node as compared with the IEEE 802.11 DCF standard.