Ultra-Wide Band (UWB) is an emerging wireless physical layer technology that uses a very large bandwidth. We are interested in finding the design objectives of the medium access (MAC, namely, power control and scheduling) and routing protocols of a multi-hop, best-effort, UWB network. Our objective is to maximize flow rates (more precisely, log-utility of flow rates) given node power constraints. The specificity of UWB is expressed by the linear dependence between rate and signal-to-noise ratio at the receiver. It is known that, in wireless networks, different routing strategies can imply differences in MAC protocol design. Hence we search for the jointly optimal routing, scheduling and power control.

In mobile ad hoc networks, it is often more important to optimize for energy efficiency than throughput. In this paper, we investigate the effect of transmit range on energy efficiency of packet transmissions. We determine a common range for all nodes such that the average energy expenditure per received packet is minimized. In the first part of this paper, we consider stationary networks. We show that energy efficiency depends on various system parameters that includes path loss exponent of the channel, energy dissipation model and network offered load. In particular, when the path loss exponent is large, energy efficiency decreases when the transmit range increases. Hence, the network should be operated at the critical range that just maintains network connectivity. However, when the path loss exponent is small, operating at the critical range yields inferior throughput and energy efficiency. Our results show that energy efficiency is intimately connected to network connectivity. Three network connectivity regimes are identified as the transmit range of all nodes increases. In the second part, we examine the effect of node mobility on energy efficiency. We show that at normal offered load, an optimal transmit range exists such that energy efficiency is maximized. The optimal range turns out to be insensitive to node mobility, and is much larger than the critical range. We show that the energy expenditure can be reduced by 15% to 73% in different mobility scenarios, if the network is operated at the optimal range.

Battery lifetimes in wireless sensor networks are dictated by usage patterns and the elected transmission power. As batteries fail there is an inevitable devolution of the network characterised by the emergence of isolated nodes, the growth of sensory lacunae or dead spots in the sensor field and, eventually, a breakdown in connectivity between the surviving nodes of the network. A Euclidean random graph model with node extinctions governed by an arbitrary lifetime distribution is introduced to explicate fundamental features of these phenomena. Sharp limit theorems characterising the time at which these phenomena make their appearance are derived and, in particular, threshold functions (or phase transitions) are shown for the time at which isolated nodes, discs, and, more generally, lacunae appear. It is shown that at the critical times the number of emergent lacunae follow an asymptotic Poisson law for any distribution of battery lifetimes (though the location of the threshold depends on the particular distribution). These results provide explicit and fundamental tradeoffs between transmission power, vertex density, field coverage, and network lifetime and suggest how principled choices may be made. 1

We investigate the impact of power control on latency in wireless ad-hoc networks. If transmission power is increased, interference increases, thus reducing network capacity. A node sending/relaying delay-sensitive real-time application traffic can, however, use a higher power level to reduce latency, if it considers information about load and channel contention at its neighboring nodes. Based on this observation, we formulate a new distributed power control protocol, Load-Aware Power Control (LAPC), that heuristically considers low end-to-end latency when selecting power levels. We study the performance of LAPC via simulations, varying the network density, node dispersion patterns, and traffic load. Our simulation results demonstrate that LAPC achieves an average endto-end latency improvement of 54 % over the case when nodes are transmitting at the highest power possible, and an average end-toend latency improvement of 33 % over the case when nodes are transmitting using the lowest power possible, for uniformly dispersed nodes in a lightly loaded network.

Abstract not found

A new protocol is presented for power control in ad hoc networks. The issues in conceptualizing the power control problem are discussed, and an architecturally simple as well as theoretically well founded solution is provided. The solution is shown to simultaneously satisfy the objectives of maximizing the traffic carrying capacity of the entire network, extending battery life through providing low power routes, and reducing the contention at the MAC (media access control) layer. Further, the protocol has the plug-and-play feature that it can be employed in conjunction with any routing protocol that pro-actively maintains a routing table. The protocol called COMPOW (Common Power), is completely distributed, asynchronous and modular, and can dynamically adapt to mobility. The protocol has been implemented in the Linux kernel. The software architecture and implementation are described in detail.

This report summarizestu research andact;fixAP: during 2001 undert he ODDR&E MURI on tAt opic ofDat fusion in Large Arrays of Microsensors (SensorWeb). At t he end of 2001 t01 project was slight ly less tss 1.5 years old. The universitfi# involved int his program aret he MassachusetJ InstJ;AP of Technology (tlogyA whichtq grant isadminist:::/fi td Universit y of Illinois, and PrincetA Universit y. The principal investF-AP:/ for trA grant are Prof. Alan Willsky (MIT), Prof. SanjoyMit;F (MIT), Prof. Sanjeev Kulkarni(PrincetAP: Prof. P.R. Kumar (Illinois), and Prof. Tommi Jaakkola (MIT). In recent years trsA has been an emergence of a number of new sensingconcept: many of which involve inexpensive and small sensorstso can, in principle, be deployed in large numberst o provide enhancedspatedA--- oral sensing coverage in wayst hat areeitfi- prohibit: ely expensive or impossible using conventAqx- sensing asset; Realizingt he pot: t ial of such large,distAx/x;# sensorsystrA- however, requires major advances in tAt heory and fundament alunderstP/xx: ofdistFJAP/x dat fusion in highlyuncert/x environment using sensing/communicatcom nodestA- are severely constFAPqF incomputAPqF and comm unicatPq capabilit:At The overall goal oftA- MURI is tfurtxJ trt basict heory and understAPqfi/ by addressing problems including: consistA t fusion algoritAP fornet worked sensors; adapt; e collaboratF e processing in highlyuncertqq environmentr andtA/fifiJ:A sion of informat/- in large anduncertFA net works. Otq: major goals oft his program are tr treA:/J of graduat stuat t s and postfiJ ctfiJfi associatq sotA/ tA/ are equippedt o tA kle multxx#APqx::qAt challenges such astA-fi embedded int he SensorWeb concept and t communicat our ideas and result t otlt in tA DoD communit y tfurt#F e#ort aimed ...