CHAPTER 8 CONCLUSION AND FUTURE ENHANCEMENTS

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1 137 CHAPTER 8 CONCLUSION AND FUTURE ENHANCEMENTS 8.1 CONCLUSION In this thesis, efficient schemes have been designed and analyzed to control congestion and distribute the load in the routing process of MANETs. In order to improve load balancing and control congestion, congestion control schemes have been used. The experimental results show that the proposed schemes are more efficient and suitable to control the congestion. Many factors served as motivation to develop efficient congestion control schemes, where one of the most important issues was related to congestion in MANETs. Congestion reduces the entire network performance and causes heavy packet losses. Nowadays, the need for real-time communication in MANETs is increasing. Real time traffic leads to high bandwidth, and results in congestion. Packet loss and bandwidth degradation are caused by congestion. The goal of this research is to explore efficient multipath routing protocols to provide congestion control mechanisms in mobile ad hoc networks. Congestion and load balancing were the important properties that need to be satisfied by these proposed multi path routing schemes. Some of the other factors that motivated the proposed schemes are fault tolerance, loss recovery, congestion detection and rate control technique.

2 138 In MANETs, an unbalanced load causes end to end delay and packet loss. Load balancing schemes control network congestion by distributing the loads in the network, along multiple paths. The selected path should be reliable and disjoint. In order to provide a solution to the congestion issues, an adaptive congestion control scheme is proposed. The algorithm for finding multi-path routes computes multiple paths, which provide all the intermediate nodes on the primary path with multiple routes to destination. The multiple paths include the nodes with the least load, more bandwidth and residual energy. When the average load of an existing link increases beyond a threshold, or the available bandwidth and residual battery power of a node decreases below a threshold, it distributes the traffic over disjoint multi-path routes, to reduce the traffic load on a congested link. Apart from load balancing, efficient congestion detection and rate control techniques are also necessary for congestion control. A rate based congestion control technique is used, which reduces congestion control in an effective manner. The algorithm uses rate estimation and rate control mechanisms to detect and adjust the rate. The estimate rate can be obtained from the intermediate nodes by the destination node, which in turn, forward this information to the source. Since the sending rate is adjusted based on the estimated rate from the intermediate nodes, this technique is better than the traditional congestion control technique in MANETs. A forward and backward path based multipath routing protocol is proposed and achieved better performance in terms of packet delivery ratio with reduced delay and overhead. A reactive path is set up by the forward request, which provides the routing information of a node. The best path for

3 139 each request is selected based upon the number of hops and travel time. The path which has a lower common node number is chosen as the best path. The probability of breakage is lesser when there is a lesser number of common nodes. After setting up the route, data packets are routed over different paths. Then, the load balancing technique is applied in this protocol to alleviate the congestion. An adaptive multipath loss recovery technique using redundant network coding is proposed, to control packet losses. It helps in recovering packets which are lost during transmission. The redundant network coding scheme is applied on the discovered multiple paths, based on the number of packets received, and the link failure of a node. The redundant network coding avoids the retransmission of lost packets and improves the errorcorrecting capabilities of lost packets. Based only on the knowledge of the loss rates on the output links, the source node and intermediate nodes can make decisions for redundant network coding. In this research work, load balancing and congestion control techniques have been considered in multipath routing. The proposed congestion control schemes increase the overall efficiency of the network by making use of idle nodes and at the same time reduces the burden of overloaded nodes. The aforementioned approaches are simulated in a diverse network scenario, and analyzed to measure their ability and performance. It is found that the AMRCC and FBPMCC schemes give the minimum end-to-end delay, the RBCC has a lower packet drop count, and the MLR and FBPMCC schemes show higher packet delivery ratio and lower overhead. The proposed approaches can achieve better performance by providing proper load balancing and can control congestion efficiently.

4 FUTURE ENHANCEMENTS This section focuses on further developments for future research. The research work can be extended in several directions and some of them are summarized below. The proposed approaches are simulated under different conditions of the MANET. It would be interesting to see the performance of the proposed protocol for different parameters such as average density, average number of link change routes, average length of the paths, variable energy capacity nodes, nodes varying processing capability etc. The Random Way Point Mobility Model (RWPMM) is used in the presented work to obtain the simulation results by varying the different network parameters. The RWPMM can be further improved in its accuracy through steady-state initialization, and the results can then be compared. Further, the mobility model used in the simulation is the RWPMM, which is suitable for a certain scenario. It would be interesting to note the behavior of the proposed secure routing protocol as simulated by different mobility models such as the Random walk, Random point group mobility model or the Manhattan model, which are useful for simulating other real-world scenarios. The proposed schemes are implemented on reactive routing protocols. This can be extended to other categories of routing protocols such as- proactive, hybrid, geographical, and, poweraware routing protocols etc.

5 141 In future this approach can be implemented in security. Security has strong effects on MANETs, and its lack degrades the performance of the network. The unique characteristics of mobile ad hoc networks pose a number of nontrivial challenges to the security design, such as the open peer-to-peer network architecture, shared wireless medium, stringent resource constraints, and highly dynamic network topology. These challenges clearly make a case for building multifarious security solutions, that achieve the desirable network performance. Hence, in future, the security aspects of multi path routing can be implemented in MANETs.