Protocols for Impulse Radio UWB Ad Hoc Networks

Ultra Wideband (UWB) technology offers an unprecedented opportunity to further accelerate the evolution of wireless communication and expand the application landscape by enabling outstanding capabilities. UWB radio is fundamentally different from most radio technologies, e.g., Bluetooth, WLAN, etc. UWB has many forms. A promising but, not well explored form is single-band impulse radio UWB (IR-UWB). In IR-UWB data is transmitted by using a series of very narrow pulses rather than by modulating the data onto a carrier. IR-UWB has considerable potential benefits for high-bandwidth, low-power, low-cost and short-range communications, that make it a candidate for high-performance Wireless Personal Area Networks (WPAN). On the road to IR-UWB based ad hoc networking, there are technical and implementation challenges to be faced. Whether the capabilities and features of IR-UWB systems can be exploited in ad hoc networking has not been systematically investigated and how the network design takes IR-UWB peculiarities into account is kept open. This thesis concentrates on those open research topics. With IR-UWB technology, the richness of simultaneous non-interfering physical channels and the capability of full-duplex are the features that can bring real benefits in network design. Furthermore, impulse radio has an intrinsic flexibility, because the parameters of the physical layer can be explicitly controlled by the upper layers. Therefore, the IR-UWB features allow a simplified medium access control and the network topology can be either organized in a structured or a less structured way. A fundamental topic in designing self-organizing IR-UWB ad hoc networks is the automatic discovery of in-range devices and the dynamic organization of the access to radio resources shared among the devices. In this thesis a data link layer protocol based on time hopping is proposed to enable a device to discover most of its neighboring devices within a short discovery time and avoid collisions. The performance measures (delay time, network throughput) of the proposed protocol are evaluated using both simulations and analytical models to understand the behavior of such self-organizing processes. WPANs are usually ad hoc networks; we consider in this thesis ad hoc IR-UWB WPANs. They require a timely network establishment without relying on any infrastructure. An IR-UWB system can accomplish multiple access by using code division multiplexing, allowing multiple simultaneous transmissions. We propose and investigate a data link layer protocol for single-hop, high data rate IR-UWB WPANs to achieve efficient network initialization and channel management with low control overhead and limited interference. As an extension of our research on single-hop IR-UWB networks, we address the problem that IR-UWB device participating in a WPAN are not always reachable in a single-hop. A network architecture and a set of protocols are proposed to resolve the multi-hop communication among IR-UWB devices as well as enhance channel utilization efficiency. In summary, the essential research activity carried out in this thesis is the data link layer design for IR-UWB ad hoc networks for short-range, high data rate wireless applications. Our results facilitate self-configuration and topology adaptation in a timely fashion, and achieve efficient medium access and multi-hop communications.Department of Telecommunications, Wireless and Mobile Communications GroupElectrical Engineering, Mathematics and Computer Scienc