Adaptive Multicast on Mobile Ad Hoc Networks Using Tree-Based Meshes With Variable Density of Redundant Paths

Multicasting has been extensively studied for mobile ad hoc networks (MANETs) because it is fundamental to many ad hoc network applications requiring close collaboration of multiple nodes in a group. A general approach is to construct an overlay structure such as multicast tree or mesh and to deliver a multicast packet to multiple receivers over the overlay structure. However, it either incurs a lot of overhead (multicast mesh) or performs poorly in terms of delivery ratio (multicast tree). This paper proposes an adaptive multicast scheme, called tree-based mesh with k-hop redundant paths (TBM k ), which constructs a multicast tree and adds some additional links/nodes to the multicast structure as needed to support redundancy. It is designed to make a prudent tradeoff between the overhead and the delivery efficiency by adaptively controlling the path redundancy depending on network traffic and mobility. In other words, when the network is unstable with high traffic and high mobility, a large k is chosen to provide more robust delivery of multicast packets. On the other hand, when the network traffic and the mobility are low, a small k is chosen to reduce the overhead. It is observed via simulation that TBM k improves the packet delivery ratio as much as 35% compared to the multicast tree approach. On the other hand, it reduces control overhead by 23–87% depending on the value of k compared to the multicast mesh approach. In general, TBM k with the small value of k offers more robust delivery mechanism but demands less overhead than multicast trees and multicast meshes, respectively

Adaptive Multicast on Mobile Ad Hoc Networks Using Tree-Based Meshes With Variable Density of Redundant Paths

Multicasting has been extensively studied for mobile ad hoc networks (MANETs) because it is fundamental to many ad hoc network applications requiring close collaboration of multiple nodes in a group. A general approach is to construct an overlay structure such as multicast tree or mesh and to deliver a multicast packet to multiple receivers over the overlay structure. However, it either incurs a lot of overhead (multicast mesh) or performs poorly in terms of delivery ratio (multicast tree). This paper proposes an adaptive multicast scheme, called tree-based mesh with k-hop redundant paths (TBM k ), which constructs a multicast tree and adds some additional links/nodes to the multicast structure as needed to support redundancy. It is designed to make a prudent tradeoff between the overhead and the delivery efficiency by adaptively controlling the path redundancy depending on network traffic and mobility. In other words, when the network is unstable with high traffic and high mobility, a large k is chosen to provide more robust delivery of multicast packets. On the other hand, when the network traffic and the mobility are low, a small k is chosen to reduce the overhead. It is observed via simulation that TBM k improves the packet delivery ratio as much as 35% compared to the multicast tree approach. On the other hand, it reduces control overhead by 23–87% depending on the value of k compared to the multicast mesh approach. In general, TBM k with the small value of k offers more robust delivery mechanism but demands less overhead than multicast trees and multicast meshes, respectively

Optimizing Routes Quality and Scattering in the AODV Routing Protocol

An ad-hoc mobile network is a collection of mobile nodes that are dynamically and arbitrarily located in such a manner that the interconnections between nodes are capable of changing on a continual basis. Routing protocols are used to discover routes between nodes. Many mobile ad-hoc networks protocols such as AODV construct route only when desired by the source node (reactively). The advantage hereof is that no prior assumptions of the network topology are required. In highly mobile networks this is an attractive property. Other used protocols (such as OLSR) are said proactive. Such protocols maintain information about routes to all destinations all times. The consequence of this approach is that the amount of control traffic is independent of the actual traffic and mobility in the network. In this paper we describe three major optimization schemes for the well-known AODV routing protocol in order to get some of the proactive protocols features in it. The targeted characteristics are: traffic independent control and shortest path routes.Facultad de Informátic

Spatiotemporal Multicast and Partitionable Group Membership Service

The recent advent of wireless mobile ad hoc networks and sensor networks creates many opportunities and challenges. This thesis explores some of them. In light of new application requirements in such environments, it proposes a new multicast paradigm called spatiotemporal multicast for supporting ad hoc network applications which require both spatial and temporal coordination. With a focus on a special case of spatiotemporal multicast, called mobicast, this work proposes several novel protocols and analyzes their performances. This dissertation also investigates implications of mobility on the classical group membership problem in distributed computing, proposes a new specification for a partitionable group membership service catering to applications on wireless mobile ad hoc networks, and provides a mobility-aware algorithm and middleware for this service. The results of this work bring new insights into the design and analysis of spatiotemporal communication protocols and fault-tolerant computing in wireless mobile ad hoc networks

Seamless, reliable, video multicast in wireless ad hoc networks

A wireless ad hoc network is a self-organized and dynamically reconfigurable wireless network without central administration and wired infrastructure. Nodes in a wireless ad hoc network can instantly establish a communication structure while each node moves in an arbitrary manner. A wireless ad hoc network is useful for mobile nodes working in a group to accomplish certain tasks. On the other hand, multicast is a very useful and efficient means of supporting group-oriented applications. Multicast is an essential technology for many applications such as video distribution and group video conferencing, data dissemination, disaster relief and battlefield. Video multicasting over wireless ad hoc networks is bandwidth-efficient compared to multiple unicast sessions. However, video multicasting poses great challenges over wireless ad hoc networks. Video packets are both delay and loss sensitive. In addition, due to nodes mobility, the topology of wireless ad hoc networks is frequently changed. As a result, the established links are continuously broken, causing quality loss and interruption in the received video signal. Other challenges include limited battery life of wireless nodes and lower wireless network capacity compared to wired networks. Video multicast over wireless ad hoc networks has been an active area in recent years. The main objective of these studies is to improve the quality of the received video by exploiting the error resilience properties of Multiple Description Coding (MDC) along with multiple paths. In other words, MD video is encoded and transmitted over two different paths to each destination node. If only one path is broken, packets corresponding to the other description on the other path can still arrive at the destination node on time. Layered Coding (LC) and Multiple Description Coding (MDC) have been proposed as video source coding techniques that are robust against inevitable transmission errors. In contrast to MDC, LC encodes a media source into two or more sub-streams, known as layers, one base layer and several enhancement layers. The base layer can be decoded to provide a basic quality of the received video while the enhancement layers are mainly used to refine the quality of the video that is reconstructed from the base layer. If the base layer is corrupted, the enhancement layers become useless, even if they are received correctly. Therefore, the base layer is critically important and is usually highly protected. For MDC, however, these sub-streams are of equal importance in the sense that each sub-stream, also called a description, can be decoded independently to produce a signal of basic quality. When more descriptions are received, the decoder can gradually increase the quality. One main problem of video multicasting for heterogeneous destinations is the assignment of video descriptions and the construction of multicast tree. However, the assignment of MD video and the construction of multicast tree can greatly affect the user satisfaction (i.e., affect the quality of the received video). In this thesis, we introduce novel approaches to improve the user satisfaction for a set of heterogeneous multicast destinations. The main idea of our approaches is to employ the independent-description property of MDC along with multiple multicast trees. However, many questions are raised: How multiple multicast trees should be constructed? And how MD video should be assigned? Is it better to construct multiple multicast trees first and then assign the video descriptions? Or is it better to assign the video descriptions first and we then construct multiple multicast trees? Should we perform that in a distributed manner or in a centralized one? To answer these questions, we propose different algorithms to construct multiple multicast trees and to assign MD video. The proposed algorithms are: Serial MDC, Distributed MDC, and Centralized MDC. Serial MDC constructs multiple paths, to each destination, and assigns a different video description to each of them. After that, it constructs multiple multicast trees. Distributed MDC assigns MD video and constructs multiple multicast trees in parallel and in distributed fashion. In Centralized MDC, the assignment of MD video and the construction of multiple multicast trees are performed in a centralized manner. However, Centralized MDC first constructs multiple multicast trees and then assigns different video description to each multicast tree. We evaluate and compare our proposed algorithms Under different network conditions. For example, Network size, and multicast group size. Simulation results demonstrate that, indeed, the way of multicast trees construction and the assignment of MD video can greatly affect the user satisfaction. In addition, simulation results show that MDC can achieve higher user satisfaction compared to LC with a small cost in terms of number of pure forwarders nodes, bandwidth utilization, and aggregate tree delay. Furthermore, we use our proposed algorithms to develop different multicast protocols for video multicast over wireless ad hoc networks. Specifically, we propose four protocols, namely, Centralized MDMTR (Multiple Disjoint Multicast Trees Routing), Sequential MDMTR, Distributed MDMTR, and Neighbor-aware MDMTR protocols. These protocols take many issues into consideration, rejoining and joining a multicast group, multicast trees maintenance, and mobility of nodes, for example. We evaluate the performance of our proposed protocols and compare them under different network conditions. For example, multicast group size, and mobility of nodes. Simulation results demonstrate that our protocols perform well compared to other protocols in the literature

Tree Multicast Strategies in Mobile, Multihop Wireless Networks

this paper, we extend the tree multicast concept to wireless, mobile, multihop networks for applications ranging from ad hoc networking to disaster recovery and battlefield. The main challenge in wireless, mobile networks is the rapidly changing environment. We address this issue in our design by: (a) using "soft state"; (b) assigning different roles to nodes depending on their mobility (2-level mobility model); (c) proposing an adaptive scheme which combines shared tree and per-source tree benefits, and; (d) dynamically relocating the shared tree Rendezvous Point (RP ). A detailed wireless simulation model is used to evaluate various multicast schemes. The results show that per-source trees perform better in heavy loads because of the more efficient traffic distribution; while shared trees are more robust to mobility and are more scalable to large network sizes. The adaptive tree multicast scheme, a hybrid between shared tree and per-source tree, combines the advantages of both and performs consistently well across all load and mobility scenarios. The main contributions of this study are: the use of a 2-level mobility model to improve the stability of the shared tree; the development of a hybrid, adaptive per-source and shared tree scheme, and; the dynamic relocation of the RP in the shared tree