Source-Channel Communication Protocols and Tradeoffs in Active Wireless Sensing

Active Wireless Sensing (AWS) is motivated by emerging advances in wireless technology and offers an alternative and complementary approach to in-network processing for rapid and energy-efficient information retrieval in wireless sensor networks. The basic architecture in AWS consists of: i) a wireless information retriever (WIR), equipped with an antenna array, that interrogates a select ensemble of wireless sensors with space-time waveforms, ii) the sensors acting as active scatterers – modulating the acquired waveforms with their (possibly encoded) measured data – to generate a multipath response to the WIR’s interrogation signal, and iii) the WIR retrieving the sensor data by exploiting the space-time characteristics of the resulting multipath sensing channel. An important feature of AWS is its flexibility in tailoring the space-time interrogation waveforms, sensor encoding strategies, and associated processing of the received multipath signal at the WIR for energy-efficient information retrieval. A key mechanism for energy efficiency is distributed source-channel matching: generating a coherent response from sub-ensembles of sensors with highly correlated data, based on the spatial smoothness or correlation in the signal field or on the spatial scale of local cooperation in the network. In this paper, we will discuss a family of source-channel matching protocols in AWS and associated tradeoffs involving rate, reliability and energy consumption of information retrieval.