Mobility and Multi-channel Communications in Low-Power Wireless Networks

The prospect of replacing existing fixed networks with cheap, flexible and even mobile low-power wireless network has been a strong research driver in recent years. However, many challenges still exist: reliability is hampered by unstable and bursty communication links; the wireless medium is getting congested by an increasing number of wireless devices; and life-times are limited due to difficulties in developing efficient duty-cycling mechanisms. These challenges inhibit the industry to fully embrace and exploit the capabilities and business opportunities that low-power wireless devices offer. In this thesis, we propose, design, implement, and evaluate protocols and systems to increase flexibility and improve efficiency of low-power wireless communications.

First, we present MobiSense, a system architecture for energy-efficient communications in micro-mobility sensing scenarios. MobiSense is a hybrid architecture combining a fixed infrastructure network and mobile sensor nodes. Simulations and experimental results show that the system provides high throughput and reliability with low-latency handoffs.

Secondly, we investigate if and how multi-channel communication can mitigate the impact of link dynamics on low-power wireless protocols. Our study is motivated by a curiosity to reconcile two opposing views: that link dynamics is best compensated by either (i) adaptive routing, or (ii) multi-channel communication. We perform a comprehensive measurement campaign and evaluate performance both in the single link and over a multi-hop network. We study packet reception ratios, maximum burst losses, temporal correlation of losses and loss correlations across channels. The evaluation shows that multi-channel communication significantly reduces link burstiness and packet losses. In multi-hop networks, multi-channel communications and adaptive routing achieves similar end-to-end reliability in dense topologies, while multi-channel communication outperforms adaptive routing in sparse networks where re-routing options are limited.

Third, we address the problem of distributed information exchange in proximity-based networks. First, we consider randomized information exchange and assess the potential of multi-channel epidemic discovery. We propose an epidemic neighbor-discovery mechanism that reduces discovery times considerably compared to single-channel protocols in large and dense networks. Then, the idea is extended to deterministic information exchange. We propose, design and evaluate an epidemic information dissemination mechanism with strong performance both in theory and practice.

Finally, we apply some of the concepts from epidemic discovery to the design of an asynchronous, sender-initiated multi-channel medium access protocol. The protocol combines a novel mechanism for rapid schedule learning that avoids per-packet channel negotiations with the use of burst data transfer to provide efficient support of 'multiple contending unicast and parallel data flows. Thesis in PDF

1. A. Gonga, T. Charalambous and M. Johansson, “Fast information exchange in proximity-based multichannel wireless networks”, in Proc. of the IFIP Wireless Mobile and Networking Conference (WMNC 2015), Munich, Germany, Oct. 5-7, 2015.

2. A. Gonga, T. Charalambous and M. Johansson, “Deterministic neighbor discovery with epidemics in multihop wireless networks”, in IEEE Transactions on Mobile Computing , July, 2015, Submitted.

3. A. Gonga, T. Charalambous and M. Johansson, “Neighbor Discovery in Multichannel Wireless Clique Networks: An Epidemic Approach”, in Proc. of the IEEE International Conference on Mobile Ad-hoc and Sensor Systems, IEEE MASS 2013, Oct 14-16, Hangzhou, China

4. A. Gonga, O. Landsiedel, P. Soldati and M. Johansson, “Revisiting Multi-Channel Communication to Mitigate Interference and Link Dynamics in Wireless Sensor Networks”, In Proc. of the IEEE Distributed Computing in Sensor Systems (DCOSS’12), May 16-19, 2012, Hangzhou, China, 2012

5. A. Gonga, O. Landsiedel, P. Soldati and M. Johansson, “Poster Abstract: Multi-Channel Communication vs. Adaptive Routing for Reliable Communication in WSNs”, in Proc. of the ACM/IEEE IPSN’12, April 16-19, Beijing, PRC, 2012

6. A. Gonga, O. Landsiedel, and M. Johansson, “MobiSense: Power-efficient micro-mobility in wireless sensor networks”, in Proc. of the IEEE Conference on Distributed Computing in Sensor Systems and Workshops (DCOSS’11), 2011

7. A. Gonga, M. Johansson and A. Dunkels, “Poster Abstract: MobiSense: power-efficient micro-mobility in IPv6-based sensor networks”, In Proc. of the ACM/IEEE International Conference on Information Processing in Sensor Networks (IPSN’10), April, 2010, Stockholm