A MAC Technique for VoIP Services Using Back off Algorithm in IEEE 802.11e Networks

In the advent of emerging information super highway, voice over Internet Protocol has become a vital service with the demand for high quality of requirements in Wireless Local Area Network(WLANs). The IEEE 802.11e Standard has been recently introduced to mark the Quality of Service (QoS) competence in the ever evolving wireless local area networks. This 802.11e brings contention window, based on Enhanced Distribution Channel Access technique that offers a selected traffic to ensure least bandwidth required for the time specific applications. The EDCA technique resets statistically the contention window of the mobile station after each successful transmission. The static behavior of EDCA does not adapt to the network state hence reduces the network usage which also results in bad performance and reduced link utilization whenever the demand arise for a link utilization increases. In IEEE 802.11 Wireless Local Area Networks (WLANs), network nodes experiencing collisions on the shared channel need to backoff for a random period of time and the Contention Window (CW) is dynamically controlled by the Back off algorithm. The initial step is to design an efficient back off algorithm for wireless ad hoc network is analysis of the existing back off algorithms in wireless ad hoc networks. In this paper, we have considered two important wireless ad-hoc network scenarios: (i) Node Mobility state (ii) Transmission Range state and evaluate both on the impact of mobility i.e. node speed and the impact of transmission range of nodes on the performance. In this paper the performance of the proposed technique and proposed traffic is evaluated and is compared with the original IEEE802.11a technique. The results obtained exhibits that the proposed adaptive technique increases the channel utilization along with the boosted throughput, as well as providing QOS requirements in terms of packet delay, packet drop rate, jitter, packet loss rate.