Ultra-wideband (UWB) radio is becoming a promising field for new generation's digital communication systems. This technique, based mainly on the impulse radio paradigm, offers great flexibility and shows enormous potential in view of a future broadband wireless access. In this paper, we aim at presenting the main principles to design a multiaccess scheme based on UWB. The potential of UWB is exploited within a distributed ad hoc wireless system, where we describe the principles for the definition of a medium-access control (MAC) for mobile computing applications and we analyze the main performance results derived from simulations. A general framework for radio resource sharing is outlined for classes of traffic requiring both elastic-dynamic and guaranteed-reserved bandwidth. Then, we discuss the issue of supporting the proposed radio resource sharing scheme by means of a distributed MAC protocol. Index Terms-Ad hoc networks, medium access control (MAC) protocols, power control, radio resource sharing.

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Abstract-An IEEE 802.15.4-based Wireless Sensor Network is considered, and the relationship between the IEEE 802.15.4 topology formation mechanism and possible routing strategies at the network layer is studied. Two alternative routing schemes proposed in the framework of the ZigBee Alliance are analyzed. The first is the well-known Ad-hoc On demand Distance Vector (AODV) routing protocol, which was designed for highly dynamic application scenarios in wireless ad-hoc networks. The second is a tree-based routing scheme based on a hierarchical structure established among nodes during the network formation phase. This latter approach, referred to as HERA (HiErarchical Routing Algorithm) in the paper, routes packets from sensors to sink based on the parent-child relationships established by the IEEE 802.15.4 topology formation procedure.An extensive simulation analysis is carried out to compare HERA and AODV. It is shown that a hierarchical routing scheme based on the MAC association procedures offers several benefits with respect to reactive routing in typical sensor network applications. Moreover, it is to be noted that most sensor network scenarios are concerned with delivery of packets from a series of static sensors to a single, static, sink.

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Abstract-This paper deals with scatternet formation in Bluetooth. A scatternet is an ad hoc network of Bluetooth devices. Some works in the literature rely on the single-hop hypothesis, i.e., all devices are in radio visibility of each other. Other works refer to the more likely circumstance that devices are scattered in an area where some of them can not directly communicate. A challenging issue in this latter scenario (often referred to as multi-hop) is the design of a formation algorithm that: i) operates in a distributed way; ii) dynamically adapts the topology to the mobility of devices; iii) forms a scatternet with given topological properties. In this paper a distributed algorithm for scatternet formation that gives rise to a tree-like structure is introduced. The algorithm is shown to present three key properties that make it innovative with respect to the literature in the field: i) it is fully distributed and asynchronous; ii) it can be applied in a multi-hop environment; iii) it operates in order to dynamically adapt the topology to nodes' mobility and failures. The key steps and rules of the algorithm are described and performance results obtained by simulation are discussed.

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