Robust power control for IEEE 802.15.4 wireless sensor networks with round-trip time-delay uncertainty

This paper presents a novel, practically implementable robust Power Control (PC) technique that is generally applicable to a variety of IEEE 802.15.4 infrastructure and peer-to-peer wireless sensor networks (WSNs) where there is a round-trip time-delay uncertainty. In this methodology, robust stability and performance constraints are cast as a set of exclusion regions on the Nichols chart. The desired PC strategy is achieved through an iterative shaping of the system frequency response until these constraints are satisfied. A Smith Predictor (SP) is also adopted to mitigate the effects of time delay that occurs quite naturally in this type of problem. Such an approach is shown to be entirely appropriate for the discrete time controller design problem at hand. The designs are validated experimentally using a fully compliant 802.15.4 testbed where mobility is introduced using autonomous robots. This testbed provides a good basis for a formal comparison of the new approach against a number of existing strategies.