SARP: Synchronous Adaptive Routing Protocol for MANETs

AbstractThe aim of a routing protocol is to compute valid routes allowing every couple of nodes in the network to communicate at anytime. When the network topology is evolving over time, routing decisions should be constantly reconsidered. The main goal is to ensure a valid routing through time at the lowest possible cost. Conventional proactive routing protocols periodically recompute their routing tables; but due to their inherent nature based on shortest paths, they select longer links that ensure faster routing but are amenable to rapid breakages as nodes move around. Using short periods certainly allows a better tracking of the topology changes; however, it induces a higher control signaling overhead. An adequate trade-off between the routing period size and the traffic overhead should be found.In this paper, we propose a new mechanism that keeps sensing the network mobility level to properly adjust the routing period size. It relies on a distributed algorithm that collects the network cartography which is then used to self-regulate the routing period size. Simulation results show that our proposed scheme correctly tracks changes and properly adjusts the current routing period size leading to much better performances

Coloured Petrinet for Modelling and Validation of Dynamic Transmission Range Adjustment Protocol for Ad Hoc Network

The IEEE 802.11 standard defines two operational modes for WLANs: infrastructure based and infrastructureless or ad hoc. A wireless ad hoc network comprises of nodes that communicate with each other without the help of any centralized control. Ad hoc implies that the network does not rely on a pre-existing infrastructure but rather each node participates in routing by forwarding data for other nodes. The decentralized nature improves the scalability of wireless ad hoc network as compared to wireless managed networks. Each node acts as either a host or router. A node that is within the transmission range of any other node can establish a link with the later and becomes its immediate neighbour. However, the nodes in the ad hoc networks are constrained with limited resources and computation capability. So it may not be possible for a node to serve more number of neighbours at some instant of time. This enforces a node to remain connected or disconnected with few of its existing neighbours supporting the dynamic restructuring of the network. The presence of dynamic and adaptive routing protocol enables ad hoc networks to be formed quickly. The Dynamic Transmission Range Adjustment Protocol (DTRAP) provides a mechanism for adjusting transmission range of the ad hoc nodes. They maintain a threshold number of registered neighbours based on their available resources. The node protects its neighbourhood relationship during data communication by controlling its transmission range. It registers or de-registers a communicating node as its neighbour by dynamically varying the transmission range. However a node has a maximum limit on its transmission range. If the distance between the node and its neighbour is less than the transmission range and; 1)if the number of neighbours of a node falls short of threshold value, the node dynamically increases its transmission range in steps until it is ensured of an optimal number of neighbours 2)if the number of neighbours of a node exceeds the threshold value, the node dynamically decreases its transmission range in steps until it is ensured of an optimal number of neighbours. Coloured Petri nets (CP-nets) is the modelling language tool used for systems having communication, synchronisation and resource sharing as significant aspects. It provides a framework for the design, specication, validation, and verication of systems. It describes the states in which the system may be in and the transition between these states. The CPN combines Petri nets and programming languages. Petri nets amalgamate the use of graphical notation and the semantical foundation for modelling in systems. The functional programming language standard ML provides the primitives for the definition of data types and manipulation of data values. Besides providing the strength of a graphical modelling language, CP-nets are theoretically well-founded and versatile enough to be used in practice for systems of the size and complexity of industrial projects

On the performance of probabilistic flooding in wireless mobile ad hoc networks

Broadcasting in MANET’s has traditionally been based on flooding, but this can induce broadcast storms that severely degrade network performance due to redundant retransmission, collision and contention. Probabilistic flooding, where a node rebroadcasts a newly arrived one-to-all packet with some probability, p, was an early suggestion to reduce the broadcast storm problem. The first part of this thesis investigates the effects on the performance of probabilistic flooding of a number of important MANET parameters, including node speed, traffic load and node density. It transpires that these parameters have a critical impact both on reachability and on the number of so-called “saved rebroadcast packets” achieved. For instance, across a range of rebroadcast probability values, as network density increases from 25 to 100 nodes, reachability achieved by probabilistic flooding increases from 85% to 100%. Moreover, as node speed increases from 2 to 20 m/sec, reachability increases from 90% to 100%. The second part of this thesis proposes two new probabilistic algorithms that dynamically adjust the rebroadcasting probability contingent on node distribution using only one-hop neighbourhood information, without requiring any assistance of distance measurements or location-determination devices. The performance of the new algorithm is assessed and compared to blind flooding as well as the fixed probabilistic approach. It is demonstrated that the new algorithms have superior performance characteristics in terms of both reachability and saved rebroadcasts. For instance, the suggested algorithms can improve saved rebroadcasts by up to 70% and 47% compared to blind and fixed probabilistic flooding, respectively, even under conditions of high node mobility and high network density without degrading reachability. The final part of the thesis assesses the impact of probabilistic flooding on the performance of routing protocols in MANETs. Our performance results indicate that using our new probabilistic flooding algorithms during route discovery enables AODV to achieve a higher delivery ratio of data packets while keeping a lower routing overhead compared to using blind and fixed probabilistic flooding. For instance, the packet delivery ratio using our algorithm is improved by up to 19% and 12% compared to using blind and fixed probabilistic flooding, respectively. This performance advantage is achieved with a routing overhead that is lower by up to 28% and 19% than in fixed probabilistic and blind flooding, respectively

Policy-Based Adaptive Routing in Mobile Ad Hoc Wireless Networks

Abstract-This paper investigates policy-based adaptive routing for mobile ad hoc networks (MANET's), in which routing metric, routing algorithm parameters and/or protocol selection can be controlled in response to observed performance and external service needs. We propose an adaptive routing framework which allows introduction of adjustable parameters and programmable routing modules. Control information is disseminated through the network to exchange state variables, and a global distributed policy manager is responsible for the adaptive operations at nodes of the network. The proposed architecture can support two types of adaptive mechanisms: the first involves switched selection between a set of routing protocols options or metrics, while the second is based on an integrated routing algorithm which incorporates adaptation of key network state parameters such as link speed or congestion. Example algorithms and simulation results are given, which show that adaptive routing help achieve the desired system performance under the dynamically changing network conditions

Dynamic routing discovery scheme for high mobility in mobile ad hoc wireless networks

An innovative technology that is widely used in many applications is the Mobile Ad-hoc Network (MANET). Discovery and maintenance of routes at MANET are important issues. Within MANET, broadcasting is used to discover a path within on-demand routing protocols. Establishing and maintaining a route periodically among the nodes is the challenge that requires the transmitting of control packets across a network. This state leads to the issue of broadcasting storms. Broadcasting control packets increase control packets overhead and decrease network performance. In this paper, we proposed a scheme called AODV-Velocity and Dynamic (AODV-VD) for effective broadcast control packets. The routing protocol for the ad-hoc on-demand distance victor (AODV) is used to implement the proposed AODV-VD scheme. AODV-VD scheme reduces both the excessive route discovery control packets and network overhead. Network simulator version 2.35 (NS2.35) was used to compare the proposed AODV-VD scheme to the AODV routing protocol in terms of end-to-end latency, average throughput, packet transmission ratio and overhead ratio

Bandwidth and Energy-Efficient Route Discovery for Noisy Mobile Ad-Hoc Networks

Broadcasting is used in on-demand routing protocols to discover routes in Mobile Ad-hoc Networks (MANETs). On-demand routing protocols, such as Ad-hoc On-demand Distance Vector (AODV) commonly employ pure flooding based broadcasting to discover new routes. In pure flooding, a route request (RREQ) packet is broadcast by the source node and each receiving node rebroadcasts it. This continues until the RREQ packet arrives at the destination node. Pure flooding generates excessive redundant routing traffic that may lead to the broadcast storm problem (BSP) and deteriorate the performance of MANETs significantly. A number of probabilistic broadcasting schemes have been proposed in the literature to address BSP. However, these schemes do not consider thermal noise and interference which exist in real life MANETs, and therefore, do not perform well in real life MANETs. Real life MANETs are noisy and the communication is not error free. This research argues that a broadcast scheme that considers the effects of thermal noise, co-channel interference, and node density in the neighbourhood simultaneously can reduce the broadcast storm problem and enhance the MANET performance. To achieve this, three investigations have been carried out: First, the effect of carrier sensing ranges on on-demand routing protocol such as AODV and their impact on interference; second, effects of thermal noise on on-demand routing protocols and third, evaluation of pure flooding and probabilistic broadcasting schemes under noisy and noiseless conditions. The findings of these investigations are exploited to propose a Channel Adaptive Probabilistic Broadcast (CAPB) scheme to disseminate RREQ packets efficiently. The proposed CAPB scheme determines the probability of rebroadcasting RREQ packets on the fly according to the current Signal to Interference plus Noise Ratio (SINR) and node density in the neighbourhood. The proposed scheme and two related state of the art (SoA) schemes from the literature are implemented in the standard AODV to replace the pure flooding based broadcast scheme. Ns-2 simulation results show that the proposed CAPB scheme outperforms the other schemes in terms of routing overhead, average end-to-end delay, throughput and energy consumption