Thesis: Relative Positioning, Network Formation, and Routing in Robotic Wireless Networks


Robotic Wireless Networks (RWN) is one of the cutting-edge domain of research that focuses on a range of collaborative autonomous operations such as exploration of an unknown terrain, fire-fighting, temporary wireless communication backbone deployments, and extending existing communication infrastructures. Such application contexts with a group of robots impose a diverse set of stringent requirements to the system designers that include but not limited to efficient infrastructure-less localization, positioning, movement control, connectivity maintenance, and lightweight communication protocols. In this thesis, we identify five key problems in the field of RWN and provide the necessary solutions to meet the end-goal of building a scalable, self-sustained, energy efficient, and controllable RWN system. The first research problem that we focus on is related to the localization of robots in any random deployment arena. A real-world deployment of an RWN relies on the availability of a scalable localization system in the application arena for effective operation. While GPS can provide sufficiently accurate positioning in open outdoor setting, effective operations of an RWN demands an alternative and sufficiently precise relative or absolute localization scheme for an indoor cluttered setting where GPS based global positioning is very flaky and unreliable. Most of the existing RF based alternative indoor localization schemes rely on the presence of an infrastructure for trilateration based localization which, thereafter, restricts the RWN application domain. To this end, we propose Autonomous RSSI based RElative poSitioning and Tracking (ARREST), an RSSI based relative localization and proximity maintenance system for RWN that does not require any pre-deployed infrastructure. To demonstrate the practicality as well as analyze the performance, we have developed a real prototype and performed extensive experimentation. The second key problem that we look into is related to the application of an RWN to support a temporary communication backbone with certain communication guarantees in terms of throughput, loss rate, and latency in a dynamic environment. It is often presumed in such contexts that a sufficient number of robots are present in the network. However, to our knowledge, none of the existing works has addressed this crucial RWN system parameter. In our second study, we first derive an upper bound on the spacing between any transmitter-receiver pair by exploiting the properties of Carrier Sense Multiple Access (CSMA) and thereafter, map this bound to a lower bound on the number of robots to deploy. In the course of our third study, we look into the classic problem of routing but with the sole focus on fulfilling the RWN specific requirements in terms of efficiency, reliability, timeliness, and scalability. Only a few existing solutions can fulfill all these requirements (mainly the delay requirement) imposed upon the networking protocol stack of an RWN. To this end, we propose the Heat Diffusion Collection Protocol(HDCP), a backpressure based routing protocol that uses the classic equations related to the heat flow from a highly heated region to a less heated region towards queue based dynamic packet routing. Through an extensive set of real-world experiments, we demonstrate that the HDCP algorithm can guarantee lower delay and higher throughput compared to the existing contenders under a diverse set of conditions. The robots in an RWN also inherently work under limited communication bandwidth and heavy power constraints which in turn put constraints on the communications hardware and protocols. Therefore, in our fourth study, we concentrate on the design of the Robotic Overlay coMmunicAtioN prOtocol (ROMANO), an efficient lightweight application layer communication protocol with low bandwidth and energy requirement for sensing data collection and control. ROMANO is overlaid on top of the well-known Message Queuing Telemetry Transport for Sensor Nodes (MQTT-SN) publish-subscribe protocol to provide a simple and unified abstraction of control and sensing data communication. Through a set of real-world experiments with real prototypes, we demonstrate different features of ROMANO as well as analyze the performance. In the fifth and final study, we look into a problem of passive RF mapping by employing the hardware developed for ARREST system experimentation. The goal of this study is to exploit a received directional RSSI pattern from an omnidirectional transmitter towards passive localization of unknown RF reflecting surfaces/objects in an unknown environment. To this end, we propose the concept of miniRadar which is a low power IEEE 802.15.4 based bi-static radar type system for RWN. In summary, we have developed systems and algorithmic solutions for an RWN that address five cutting-edge problems in an RWN. The proposed solutions and systems will guide the design of an integrated real-world RWN system with self-sustained localization and relative position control, efficient routing with lower delay, simple abstraction of control and communication, and passive RF sensing.

University of Southern California