Inductively coupled microsensor networks: relay enabled cooperative communication and localization

In this thesis, we study a novel paradigm for wireless sensor networks: we envision a dense microsensor network, consisting of hundreds or thousands of highly miniaturized wireless nodes with millimeter or sub-millimeter dimensions. Such a microsensor network has many interesting applications ranging from in vivo medical sensing to environmental monitoring. However, the design and operation of the envisioned type of network are challenging: the large number of nodes, in combination with the small form factor, imposes severe constraints on both node complexity as well as power consumption. We propose using inductive neareld coupling as advantageous physical layer choice, allowing an RFID-like operation of the network with wireless power supply from central reader devices and low-complexity tag design. The use of inductive neareld coupling has only rarely been studied in the context of microsensor networks. Our primary goals for inductively coupled microsensors are twofold: we want to enable reliable communication to and between sensor nodes, and perform accurate localization of individual sensors. Both tasks are a ected by the central limitation of a physical layer based on neareld coupling: the severely limited range of interaction. We will show throughout this thesis that the use of wireless relaying allows for overcoming this limitation. Based on a circuit-theoretic communication framework extended to inductively coupled microsensor networks, we rst explore fundamental properties and design limitations. We then investigate suitable approaches to relaying and study their use to increase both the communication range and link reliability. In addition to improving the communication performance of microsensor networks, we demonstrate the capability of inductively coupled relays to enable novel secondary uses of the wireless channel. To this end we show that relay-assisted microsensor networks can achieve distributed computation by introducing a scheme to implement wireless arti cial neural networks over multihop MIMO channels. We continue by showing the feasibility of accurate localization in an RFID-like setting. To this end, we propose a novel method that allows for the localization of a purely passive sensor only consisting of a simple loop antenna and a matching circuit. The unknown position of the sensor is hereby reconstructed from measuring