MAC Enhancements to Support Quality of Services (QoS) in Ad Hoc Wireless Networks: EMACA (Enhancement of Multiple Accesses with Collision Avoidance)

Ad hoc wireless network (AWN) is a collection of mobile hosts forming a temporary network on the fly, without using any fixed infrastructure [1], [2], [3], [4], [5], [6]. QoS (Quality of Service) is the idea that transmission rates, error rates, and other characteristics can be measured, improved, and to some extent guaranteed in advance in ad hoc network however in particular concern for the continuous transmission of high bandwidth video and multimedia information this kind of content dependably transmitting is difficult in public networks using ordinary "best effort‖ protocols [1], [2], [3], [4], [7], [8]. MACA (Multiple Accesses with Collision Avoidance) Protocol is a Contention based Sender initiated Protocol which uses Three way handshaking means that RTS—CTS—Data packet exchange [2]. It used in network congestion avoidance to help in determining the correct sending rate by binary exponential back off (BEB) Algorithm in which if a packet transmitted by a node is lost, the node uses the binary exponential back-off (BEB) algorithm to back off a random interval of time before retrying which is then also inadequate trustworthy because of data sending acknowledgement is not received, hence Enhancement of Multiple Accesses with Collision Avoidance (EMACA) Protocol based on MACA with some modifications over it have been proposed. Instead of three way handshaking in MACA, EMACA protocol propose five way handshaking RTS – CTS – DSSI – DSSI_ACK – DATA Sending - ACK. A comparative study was done on QualNet 4.0 Version simulator [9], [10] over MACA & EMACA. AODV routing protocol was used to evaluate the MACA and EMACA performance [4], [5], [11]. Results show that the EMACA simulation performs well as compared to MACA in sense of Throughput, Total Packet Received and Drop Packet Ratio under varying conditions of no. of nodes and pause time.