Improving Multicast Communications Over Wireless Mesh Networks

In wireless mesh networks (WMNs) the traditional approach to shortest path tree based multicasting is to cater for the needs of the poorest performingnode i.e. the maximum permitted multicast line rate is limited to the lowest line rate used by the individual Child nodes on a branch. In general, this meansfixing the line rate to its minimum value and fixing the transmit power to its maximum permitted value. This simplistic approach of applying a single multicast rate for all nodes in the multicast group results in a sub-optimal trade-off between the mean network throughput and coverage area that does not allow for high bandwidth multimedia applications to be supported. By relaxing this constraint and allowing multiple line rates to be used, the mean network throughput can be improved. This thesis presents two methods that aim to increase the mean network throughput through the use of multiple line rates by the forwarding nodes. This is achieved by identifying the Child nodes responsible for reducing the multicast group rate. The first method identifies specific locations for the placement of relay nodes which allows for higher multicast branch line rates to be used. The second method uses a power control algorithm to tune the transmit power to allow for higher multicast branch line rates. The use of power control also helps to reduce the interference caused to neighbouring nodes.Through extensive computer simulation it can be shown that these two methods can lead to a four-fold gain in the mean network throughput undertypical WMN operating conditions compared with the single line rate case

Network coding meets multimedia: a review

While every network node only relays messages in a traditional communication system, the recent network coding (NC) paradigm proposes to implement simple in-network processing with packet combinations in the nodes. NC extends the concept of "encoding" a message beyond source coding (for compression) and channel coding (for protection against errors and losses). It has been shown to increase network throughput compared to traditional networks implementation, to reduce delay and to provide robustness to transmission errors and network dynamics. These features are so appealing for multimedia applications that they have spurred a large research effort towards the development of multimedia-specific NC techniques. This paper reviews the recent work in NC for multimedia applications and focuses on the techniques that fill the gap between NC theory and practical applications. It outlines the benefits of NC and presents the open challenges in this area. The paper initially focuses on multimedia-specific aspects of network coding, in particular delay, in-network error control, and mediaspecific error control. These aspects permit to handle varying network conditions as well as client heterogeneity, which are critical to the design and deployment of multimedia systems. After introducing these general concepts, the paper reviews in detail two applications that lend themselves naturally to NC via the cooperation and broadcast models, namely peer-to-peer multimedia streaming and wireless networkin

Application-Aware Cross-Layer Framework for Wireless Multihop Networks

Current and future mobile and social communications require a rethinking in the development of wireless communication. Optimizing the radio transmission method is not going to scale with the ever increasing user demands. The future internet requires a wireless communication network which can adapt seamlessly to changing environments and service requirements. Especially, service requirements driven by user demand and expanding user device diversity raise a key challenge with respect to content distribution. In this work, research is conducted to improve wireless communication by considering four main aspects: The first aspect is to build a multi layer solution, instead of a conventional single layer solution to achieve higher throughput gains. Here, the physical layer, the medium access layer and the network layer are studied together to utilize capabilities across all these three layers. Thus, a unified graph model is formulated to adapt available mechanisms on the lower three layers in a joint manner. The second aspect is to envision a wireless multihop network which can scale with the increasing number of mobile devices. On the one hand, the number of mobile devices is ever increasing and so is the density of mobile devices in any given network. On the other hand, the requirements and capabilities of mobile devices are becoming more diverse and hence the heterogeneity in a wireless network is growing. This leads to the conclusion that a wireless multihop network is more future proof compared to a wireless network composed only of several base stations. Therefore, the research is focused on wireless multihop scenarios where multiple wireless devices form the network and communication between them occurs over multiple hops. The third aspect is to incorporate different requirements of applications and capabilities of applications. The plethora of applications used in wireless networks come with different sets of requirements, e.g. bandwidth, and capabilities, e.g. adaption of the video quality. Taking into account these requirements and capabilities in addition to a multi layer solution can further increase the performance. In this work, the requirements and capabilities of adaptive video streaming are integrated into an application-aware cross-layer framework. More precisely, scalable video coding and dynamic adaptive streaming over HTTP are integrated into the aforementioned framework. The novel application-aware cross-layer framework adapts network support structures at the network layer, performs resource allocation at the medium access layer, switches between communication types at the physical layer and takes into account the capabilities and requirements of applications, e.g. adaptive video-streaming, at the application layer. The fourth aspect is to utilize aggregation of distributed content, where content is cached over the whole network and can than be aggregated to be consumed by users in the network. Recent research shows promising gains achievable when content is cached at mobile devices, but mostly for single hop wireless networks. Hence, the impact of mobile content caching where popular content is cached and aggregated over multiple devices in a network is investigated in this work. In more detail, a content delivery framework which jointly exploits content already cached at mobile devices as well as switching between mechanisms at the physical layer and the network layer in order to optimally deliver the content to all destinations under changing network conditions is proposed

Mobile Ad Hoc Networks

Guiding readers through the basics of these rapidly emerging networks to more advanced concepts and future expectations, Mobile Ad hoc Networks: Current Status and Future Trends identifies and examines the most pressing research issues in Mobile Ad hoc Networks (MANETs). Containing the contributions of leading researchers, industry professionals, and academics, this forward-looking reference provides an authoritative perspective of the state of the art in MANETs. The book includes surveys of recent publications that investigate key areas of interest such as limited resources and the mobility of mobile nodes. It considers routing, multicast, energy, security, channel assignment, and ensuring quality of service. Also suitable as a text for graduate students, the book is organized into three sections: Fundamentals of MANET Modeling and Simulation—Describes how MANETs operate and perform through simulations and models Communication Protocols of MANETs—Presents cutting-edge research on key issues, including MAC layer issues and routing in high mobility Future Networks Inspired By MANETs—Tackles open research issues and emerging trends Illustrating the role MANETs are likely to play in future networks, this book supplies the foundation and insight you will need to make your own contributions to the field. It includes coverage of routing protocols, modeling and simulations tools, intelligent optimization techniques to multicriteria routing, security issues in FHAMIPv6, connecting moving smart objects to the Internet, underwater sensor networks, wireless mesh network architecture and protocols, adaptive routing provision using Bayesian inference, and adaptive flow control in transport layer using genetic algorithms

Mobile Ad-Hoc Networks

Being infrastructure-less and without central administration control, wireless ad-hoc networking is playing a more and more important role in extending the coverage of traditional wireless infrastructure (cellular networks, wireless LAN, etc). This book includes state-of-the-art techniques and solutions for wireless ad-hoc networks. It focuses on the following topics in ad-hoc networks: quality-of-service and video communication, routing protocol and cross-layer design. A few interesting problems about security and delay-tolerant networks are also discussed. This book is targeted to provide network engineers and researchers with design guidelines for large scale wireless ad hoc networks