Reliability Evaluation and Analysis of Mobile Ad Hoc Networks

The paper addresses the reliability problem of mobile ad hoc networks under link and node failure model. Node reliability is calculated as a function of no. of neighbor nodes, packet success rate, and device type and packet size. The presence of a link between any node pair is binary and its reliability is computed considering the distance between nodes and signal-to-noise ratio (SNR). An efficient algorithm is proposed to analyze and calculate the reliability of mobile ad hoc networks considering multiple routes from source and destination nodes. The effect of different parameters on node reliability and link reliability are analyzed and discussed. The network is simulated and analyzed using INET frame work. Reliability of two distinct cases of this simulation is evaluated. The simulated results and discussions ensure that evaluation of the reliability of any mobile ad hoc networks can be done easily and in an efficient manner by the proposed method

Adaptive Localized Active Route Maintenance Mechanism to Improve Performance of VoIP over Ad Hoc Networks

An important characteristic of a mobile ad hoc network routing protocol is connectivity maintenance. The protocol’s ability to maintain routes and react to topology changes due to link failures affects the delay, packet loss, and throughput of real-time applications. However, the time required to recover from a link failure in the current AODV protocol is too long for real-time applications. The objective of this paper is to develop a mechanism to allow fast response to link breaks to enable real-time communications, such as Voice over IP. We propose AODVM-ALARM, an adaptive localized route maintenance mechanism, over an existing ad hoc multipath routing protocol. The mechanism dynamically monitors and maintains on-going communications by utilizing special control messages and packet analysis techniques to enable fast response to link breaks. The mechanism can recognize, respond and recover quickly from link breaks due to topology changes. AODV-ALARM has been tested in an ad hoc experimental testbed, and compared with AODV-UU and AODVM protocols. Results show that AODVM-ALARM significantly improves the response time to link failures and achieves an overall improvement in the network performance in terms of the failover delay, failover loss and throughput when compared with the previous ad hoc routing protocols. AODVM-ALARM which is easily deployable, fault tolerant and have a fast response to topology changes can be used to rapidly establish VoIP communications, playing a significant role in emergency response for disaster recovery when the network infrastructure might be broken.YesPeer-reviewed journal articl

Improving network reliability by exploiting path diversity in ad hoc networks with bursty losses

In wireless mobile ad hoc networks, end-to-end connections are often subject to failures which do not make the connection non-operational indefinitely but interrupt the communication for intermittent short periods of time. These intermittent failures usually arise from the mobility of hosts, dynamics of the wireless medium or energy-saving mechanisms, and cause bursty packet losses. Reliable communication in this kind of an environment is becoming more important with the emerging use of ad hoc networks for carrying diverse multimedia applications such as voice, video and data. In this thesis, we present a new path reliability model that captures intermittent availability of the paths, and we devise a routing strategy based on our path reliability model in order to improve the network reliability. Our routing strategy takes the advantage of path diversity in the network and uses a diversity coding scheme in order not to compromise efficiency. In diversity coding scheme, if the original information is encoded by using a (N,K) code, then it is enough for the destination to receive any K bits correctly out of N bits to successfully decode the original information. In our scheme, the original information is divided into N subpackets and subpackets are distributed among the available disjoint paths in the network. The distribution of subpackets among the diverse paths is a crucial decision. The subpackets should be distributed 'intelligently' so that the probability of successful reconstruction of the original information is maximized. Given the failure statistics of the paths, and the code rate (N, K), our strategy determines the allocation of subpackets to each path in such a manner that the probability of reconstruction of the original information at the destination is maximized. Simulation results justify the accuracy and efficiency of our approach. Additionally, simulation results show that our multipath routing strategy improves the network reliability substantially compared to the single path routing. In wireless networks, a widely used strategy is to place the nodes into a low energy consuming sleep mode in order to prolong the battery life. In this study, we also consider the cases where the intermittent availability of the nodes is due to the sleep/awake cycles of wireless nodes. A sleep/awake scheduling strategy is proposed which minimizes the packet latency while satisfying the energy saving ratio specified by the energy saving mechanism