Supporting QoS in MANET by a Fuzzy Priority Scheduler and Performance Analysis with Multicast Routing Protocols

EURASIP Journal on Wireless Communications and Networking 2005:3, 426–436 c 2005 C. Gomathy and S. Shanmugavel
Supporting QoS in MANET by a Fuzzy Priority Scheduler and Performance Analysis with Multicast Routing Protocols C. Gomathy Telematics Lab, Department of Electronics and Communication Engineering, Anna University, Chennai-600 025, India Email: S. Shanmugavel Department of Electronics and Communication Engineering, Anna University, Chennai-600 025, India Email: Received 5 November 2004; Revised 9 March 2005; Recommended for Publication by George Karagiannidis Mobile ad hoc network is an autonomous system of mobile nodes characterized by wireless links. The major challenge in ad hoc networks lies in adapting multicast communication to environments, where mobility is unlimited and failures are frequent. Such problems increase the delays and decrease the throughput. To meet these challenges, to provide QoS, and hence to improve the performance, a scheduler can be used. In this paper we design a fuzzy-based priority scheduler to determine the priority of the packets. The performance of the scheduler is studied with the multicast routing protocols. The scheduler is evaluated in terms of the quantitative metrics such as packet delivery ratio and average end-to-end delay and the results are found to be encouraging. Keywords and phrases: mobile ad hoc networks, scheduling algorithms, multicast routing protocols, fuzzy logic. 1. INTRODUCTION Ad hoc network is a collection of wireless nodes, which form a temporary network without relying on the existing network infrastructure or centralized administration. Ad hoc networks form a multihop network, where the communication is over the wireless channel, hopping over several mobile nodes. In recent years, a number of unicast routing protocols have been proposed. Multicasting routing and packets forwarding in ad hoc networks is a fairly unexplored area. In today’s network, data transmission between multiple senders and receivers is becoming increasingly important. There are many applications which send from a single source to multiple destinations or from multiple senders to multiple receivers. Multicasting reduces the communication costs, link bandwidth consumption, sender and router processing, and delivery delay. In addition, it also provides a simple and robust communication mechanism when the receiver’s individual addresses are unknown or changeable. It also can improve the utilization of the wireless link, when sending mulThis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. tiple copies of messages and exploit the inherent broadcast property of wireless transmission. Hence, multicasting plays an important role in ad hoc networks. Many multicast protocols have been proposed for ad hoc networks [1, 2, 3, 4, 5, 6, 7]. The ad hoc multicast routing protocol (AMRoute) [1] is a shared tree protocol, which allows dynamic core migration based on group membership and network configuration. The protocol utilizing increasing id-numbers, (AMRIS), builds a shared tree to deliver multicast data [7]. A multicast extension of ad hoc on-demand distance vector (MAODV) routing protocol has also been proposed [4]. It is unique in using a destination sequence number for each multicast entry. The sequence number is generated by multicast group head to prevent loops and to discard state routes. The on-demand multicast routing protocol (ODMRP), is an ad hoc multicast protocol based on multicast mesh [5]. ODMRP uses soft states. So, learning a group is automatically handled by timeouts. It relies on frequent network-wide flooding when the number of source nodes is large and this may lead to scalability problem. In ODMRP, the control packet overhead becomes more prominent when the multicast group is small in comparison with the entire network. The core-assisted mesh protocol (CAMP) supports multicasting by creating a shared mesh structure [2]. All nodes in network maintain a set of tables with membership Fuzzy-Based Priority Scheduler for MANET 427 Table 1: Comparison of protocols. Protocol AMRoute AMRIS MAODV LAM ODMRP CAMP MCEDAR NTPMR Multicast topology Hybrid Tree Tree Tree Mesh Mesh Hybrid Mesh Loop free No Yes Yes Yes Yes Yes Yes Yes and routing information. It classifies nodes in the network as duplex or simplex numbers. It relies on underlying unicast routing protocol, which guarantees correct distances to all destinations within finite time. A new on-demand multicast protocol called node transition probability-based multicast routing (NTPMR) is proposed in [3]. It uses a mesh infrastructure instead of a tree. It minimizes the frequency of control message broadcasts. The reduction of channel overhead makes NTPMR more attractive in mobile wireless networks. A comparison of different multicast protocols is shown in Table 1. With routes being decided by these multicasting protocols, the transmission of packets is to be performed. For this, a scheduler is used. A scheduler should schedule the packets to reach the destination quickly, which are at the verge of expiry. Scheduling discipline manages the queue of requests awaiting service. Without a scheduler, packets will be processed in FIFO manner and hence there are more chances that more packets may be dropped and hence the network may not meet the QoS target [8, 9, 11]. Typical metrics for providing QoS include delay, loss rate, jitter, bandwidth and so forth. In the proposed scheduler, end-to-end delay and packet delivery ratio are considered to analyse the performance of the network, thus providing QoS. Ad hoc networks have several features, including possible frequent transmission of control packets due to mobility, the multihop forwarding of packets, and the multiple roles of nodes as routers, sources, and sinks of data, that may produce unique queuing dynamics. The choice of scheduling algorithm to determine which queued packet to process next will have a significant effect on the overall end-to-end performance when traffic load is high. For this, various scheduling algorithms were studied. To experiment and evaluate the scheduler, three multicast protocols, namely, ODMRP, CAMP, and NTPMR, are considered. The protocols are so chosen because they all use mesh configuration but different mechanisms as shown in Table 1. In this paper, a fuzzy-based priority scheduler is designed and implemented. It schedules the data packets based on its priority index. The priority index is attached to the header of the data packets. Its value is based on the queue length of the node, data rate of the source (which is normalized with respect to channel capacity), and expiry time of the packet. This scheduler favors data packets as compared to control packets. It aims to improve the average throughput Dependence on unicast protocol Ye (...truncated)