Adaptive routing for mobile ad hoc networks

Developing efficient routing protocols for mobile ad hoc networks remains a challenging task. It is well known that every protocol is capable of outperforming the others depending on the network context under which it is evaluated, since protocols only perform optimally under specific network contains due to their inability to adapt their behavior to the network context, which both varies in time and place. This article builds upon this observation to motivate and propose an adaptive multi-mode routing framework that has multiple compatible modes of operation. Based on this framework, an adaptive protocol has been implemented with the novel feature that individual nodes can adapt their mode of operation at any moment, while an overall consistent state of the routing tables is maintained. Through simulation, the correct behavior of the protocol during mode switches is demonstrated and it is shown that the protocol is capable of minimally offering the performance of either proactive or reactive routing, Its capabilities to dynamically switch, when intelligently applied, allow outperforming these protocols. This is illustrated for one specific application scenario where network conditions are dynamically monitored. Further, the article discusses some challenges encountered during the design and, since no monitoring solution has been developed, identifies existing solutions for monitoring and dissemination of network context are identified, offering directions for further research

Multi-hop Device-to-Device Routing Protocols for Software-Defined Wireless Networks

University of Technology Sydney. Faculty of Engineering and Information Technology.Multi-hop device-to-device (MD2D) communications are an integral part of future wireless networks. Multi-hop communications enable mobile devices in close proximity to communicate directly or through multi-hop connections instead of traversing through a network infrastructure. This provides numerous benefits for cellular networks, such as low-cost communications, enhanced cellular coverage and capacity, reduced total power consumption in devices, and improved spectral efficiency. Consequently, service providers can leverage the advantages of both D2D and cellular networks to enhance the quality of their services. However, tight coupling of control and data functions in cellular equipment and the utilization of proprietary interfaces and protocols in existing cellular infrastructure make integration difficult and rigid. Hence, there is a need for open and reprogrammable frameworks to make the network more flexible and scalable. Software-defined networking (SDN) is a promising technology for future wireless networks that provides an open and reprogrammable framework wherein the control functions are taken from network devices and are logically centralized in a control entity. The open framework of SDN provides an opportunity for service providers to manage networks more intelligently and develop services in a more agile manner. This thesis introduces an SDN-based framework for cellular networks, referred to as virtual ad hoc routing protocol framework (VARP), capable of developing different types of multi-hop routing protocols. In the proposed framework, an SDN controller determines the mode of communication for mobile devices (i.e., cellular or multi-hop modes). Two different multi-hop routing protocols are designed for the proposed framework: source-based virtual ad hoc routing protocol (VARP-S) and SDN-based multi-hop D2D routing protocol (SMDRP). In both protocols, a source of data packet sends a route request to the controller and receives the forwarding information from the controller in response. This thesis then presents a multi-protocol framework capable of developing multiple routing protocols under a single framework. In the proposed framework, an SDN controller logically divides a cell into multiple clusters based on its knowledge of the entire cell. The controller determines which multi-hop routing protocol can provide the best performance for each cluster. The simulation results show that the proposed multi-protocol framework provides better performance than traditional single-protocol architectures. Finally, the thesis presents a novel software-defined adaptive routing algorithm for multi-hop multi-frequency communications in wireless multi-hop mesh networks. The simulation results indicate that the proposed algorithm improves the end-to-end throughput of multi-hop connections by considering the surrounding WiFi traffic and adaptive selection of frequencies and routes

A survey of performance enhancement of transmission control protocol (TCP) in wireless ad hoc networks

This Article is provided by the Brunel Open Access Publishing Fund - Copyright @ 2011 Springer OpenTransmission control protocol (TCP), which provides reliable end-to-end data delivery, performs well in traditional wired network environments, while in wireless ad hoc networks, it does not perform well. Compared to wired networks, wireless ad hoc networks have some specific characteristics such as node mobility and a shared medium. Owing to these specific characteristics of wireless ad hoc networks, TCP faces particular problems with, for example, route failure, channel contention and high bit error rates. These factors are responsible for the performance degradation of TCP in wireless ad hoc networks. The research community has produced a wide range of proposals to improve the performance of TCP in wireless ad hoc networks. This article presents a survey of these proposals (approaches). A classification of TCP improvement proposals for wireless ad hoc networks is presented, which makes it easy to compare the proposals falling under the same category. Tables which summarize the approaches for quick overview are provided. Possible directions for further improvements in this area are suggested in the conclusions. The aim of the article is to enable the reader to quickly acquire an overview of the state of TCP in wireless ad hoc networks.This study is partly funded by Kohat University of Science & Technology (KUST), Pakistan, and the Higher Education Commission, Pakistan