The aim of this thesis is to investigate network coding techniques on network-stack components such as Links and Transport Layers. As networks are required to provide reliability and efficiency in their performances in a cost effective manner, the capability of such network in achieving such objective is becoming highly significant in the relevant literature. Moreover, proving reliability and delivery of fast services in any networks settings is very challenging due to the nature of wireless links, mobility, collision and frequent topology changes. Nevertheless, a Multi-Hop network possesses specifics advantages such as easy deployment, extended coverage, and low implementation costs compared to other approaches. Therefore, this research sets out to explore the effective and practical use of Xor network coding in Multi-Hop wireless networks to achieve improved throughput and reduce latency in networks by investigating MAC, Transport and proposed Cross-layers in the presence of Xor network coding in Multi-Hop wireless networks. The findings of this thesis provide that one problem with the reliance of Wireless Multi-Hop networks on IEEE 802.11 technology is the inefficiency of Distributed Coordination Function (DCF) applied in IEEE 802.11 settings, leaving a room to employ a Network Coding technique to improve performance. DCF is found fair to nodes than carrying out Network Coding. Hence, applied a new approach based on DCF mechanism on MAC layer has provided more access to the medium, and also gave a better share of medium for relay nodes which enabled bidirectional traffic flows in saturated multi-hop network traffic’s scenario. The proposed scheme has provided a maximum of 255% throughput improvement compared to COPE with the MAC layer priority over ten hops. Moreover, moving the focus from throughput to Ratio of Loss Packet (RLP), delay and jitters are found to be important factors as they are capable of explaining the impact on throughput and ratio of lost packets. Hence, the thesis has proposed a Transport layer-based scheme called WeNC-TCP. This scheme found to enable the use of network coding functionality, and permit better interactions between TCP at Transport layer and network coding functionality. The scheme was found to provide a better ratio of loss packets, and "end-to-end" Delays have been achieved. The average ratio of loss packets has improved up to 72%, and end-to-end Delays have reduced to up to 48%. Furthermore, TCP is found to provide better network congestion management in a wired network. However, in wireless networks, TCP is found not to work well when Xor network coding is applied. This is due to the absence of the MAC layer’s role to assist TCP packet flow. Therefore, a cross-layer interaction solution is investigated. The simulated results have shown performance improvement concerning throughputs, delays, and jitter. The scheme has provided 100% RLP reduction compared to other TCP variants. The proposed scheme has also provided a minimum delay of 93%, and the jitters have also been reduced to the average of 42%.
|Date of Award||12 May 2020|
- The University of Bristol
|Supervisor||Robert J Piechocki (Supervisor)|