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Quantifying, generating and mitigating radio interference in Low-Power Wireless Networks
Ref: CISTER-TR-151012       Publication Date: 28, Oct, 2015

Abstract:
Radio interference affects the performance of low-power wireless networks (LPWN), leading to packet loss and reduced energy-efficiency, among other problems. Reliability of communications is key to expand application domains for LPWN. Since most LPWN operate in the license-free Industrial Scientific and Medical (ISM) bands and hence share the spectrum with other wireless technologies, addressing interference is an important challenge.
In this context, we present JamLab: a low-cost infrastructure to augment existing LPWN testbeds with accurate interference generation in LPWN testbeds, useful to experimentally investigate the impact of interference on LPWN protocols.
We investigate how interference in a shared wireless medium can be mitigated by performing wireless channel energy sensing in low-cost and low-power hardware. For this pupose, we introduce a novel channel quality metric—dubbed CQ—based on availability of the channel over time, which meaningfully quantifies interference. Using data collected from a number of Wi-Fi networks operating in a library building, we show that our metric has strong correlation with the Packet Reception Rate (PRR). We then explore dynamic radio resource adaptation techniques---namely packet size and error correction code overhead optimisations---based on instantaneous spectrum usage as quantified by our CQ metric.
To conclude, we study emerging fast fading in the composite channel under constructive baseband interference, which has been recently introduced in low-power wireless networks as a promising technique. We show the resulting composite signal becomes vulnerable in the presence of noise, leading to significant deterioration of the link, whenever the carriers have similar amplitudes.
Overall, our results suggest that the proposed tools and techniques have the potential to improve performance in LPWN operating in the unlicensed spectrum, improving coexistence while maintaining energy-efficiency. Future work includes implementation in next generation platforms, which provides superior computational capacity and more flexible radio chip designs.

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