Multi-channel routing protocols for wireless body area networks

Wearable sensors connected through Wireless Body Area Networks (WBANs) have emerged as a promising enabling technology for many healthcare applications in recent years. A WBAN utilises wearable sensors on the human body to route information between a sensor and a central control unit (CCU) which can be connected to remote stations for further analysis. The routing schemes used in WBANs face challenges due to limited energy and excessive traffic overhead constraints. Most routing protocols for WBANs use a single-channel which limits network performance in terms of interference among links, throughput, end-to-end delay, and congestion. As opposed to single-channel communication, multiple channels increase the number of paths that can be active simultaneously between nodes and increase bandwidth capacity with reduced inter and intrachannel interference. Multi-channel routing protocols can overcome many of the limitations mentioned above for single-channel routing protocols improving traffic congestion, energy consumption, network lifetime, and link stability. However, several challenges still need to be solved when utilising multiple channels, such as channel selection methods for multiple routes and optimising routing metric. In this thesis, various multi-channel routing protocols have been proposed for WBANs to improve the performance over traditional single-channel protocols commonly used in WBANs. Firstly, the thesis develops multi-channel versions of existing routing protocols, such as single-path, single-channel AODV (Ad-hoc On-demand Distance Vector) and REL (Routing based on Remaining Energy and Link quality indicator) to overcome bottlenecks at intermediate nodes. Secondly, new performance metrics are proposed such as a channel-diversity metric named Weighted Multi-Channel Hop-Count (WMHC) and a lexical composite metric named Dual-CHannel REL (DCHREL) for route selection combining hop count, link quality, and nodes residual energy. Lastly, channel selection methods based on Link Quality Estimators (LQEs) such as Link Quality Indicator (LQI) and Received Signal Strength Indicator (RSSI) for static as well as mobile nodes are proposed, which outperform random channel selection in WBANs with a small number of channels. The implementation of the proposed multi-channel routing protocols was carried out in the OMNet++ based Castalia. Simulation results show that the multi-channel routing protocols with the LQE based channel selection at network layer outperform their corresponding single-channel protocols. Similarly, it is shown that the multi-channel routing protocols with the LQE based channel selection efficiently utilise multiple channels to reduce the number of retransmissions needed for route establishment and data forwarding. Moreover, significant improvements in network performance are observed in terms of packet delivery with less control overhead, routing stability in the presence of link fluctuations caused by mobility, and less co-channel interference with balanced and low energy consumption.