Transmission Power Control (TPC) protocols are poised for wide spread adoption in wireless sensor networks (WSNs) to address energy constraints. The link quality properties that need to be captured in order to identify the optimum transmission power (TP) have not been clearly defined and previous works have presented conflicting views on the matter. This has led to several current TPC protocols using vastly different link quality properties and reporting unreliable, unstable and inefficient network performance. In this work, observations from several empirical studies on low-power wireless links are applied to identify the most critical properties of link quality for a TPC protocol. Comparing the requirements against currently available link quality estimators, it is shown that link quality estimation in WSNs is still very much an open challenge and one that must be addressed in order to implement an accurate and reliable TPC protocol.

Abstract-This study investigates the opportunities for transmission power control (TPC) protocols in resource constrained wireless sensor networks (WSNs). The paper begins by creating a generalised model to describe the relationship between transmission power, communication reliability and energy consumption. Applying this model to the performance of state-of-the-art radio hardware, the maximum potential energy savings achievable through the implementation of a TPC protocol are identified. From this, previous assumptions about the limited impact of protocols and mechanisms, such as TPC, which seek to reduce the energy consumed by wireless communication activities through targeting the distance dependent term are disproven. This paper concludes by presenting guidelines on the link conditions which offer the greatest opportunities for a TPC protocol.

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Transmission Power Control (TPC) protocols are poised for wide spread adoption in Wireless Sensor Networks (WSNs) to address energy constraints. Identifying the optimum transmission power is a significant challenge due to the complex and dynamic nature of the wireless transmission medium and this has resulted in several previous TPC protocols reporting poor reliability and energy efficiency in certain scenarios. In line with current studies, this study presents an empirical characterisation of the transmission medium in typical WSN environments. Through this, the sources of link quality degradation are identified and extensive empirical evidence of their effects are presented. The results highlight that low power wireless links are significantly affected by spatio-temporal factors with the severity of these factors being heavily dependent on environment.

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