Carrier sense multiple access (CSMA) protocols, such as the IEEE 802.11 protocol, are widely used in wireless ad hoc networks. In this paper, we consider how the parameters of such protocols should be selected. Our primary goal is an increase in spatial reuse. By analyzing conditions for collision prevention, we argue that the product of the transmit power and the carrier sense threshold should remain constant. We then discuss the practical implementation of this principle within the framework of the IEEE 802.11 protocol. Finally, we provide simulation results that compare our scheme to other methods of selecting the protocol parameters. These results indicate that an increase in spatial reuse can indeed be achieved.

In this paper we study the problem of tracking an object moving randomly through a network of wireless sensors. Our objective is to devise strategies for scheduling the sensors to optimize the tradeoff between tracking performance and energy consumption. We cast the scheduling problem as a Partially Observable Markov Decision Process (POMDP), where the control actions correspond to the set of sensors to activate at each time step. Using a bottom-up approach, we consider different sensing, motion and cost models with increasing levels of difficulty. At the first level, the sensing regions of the different sensors do not overlap and the target is only observed within the sensing range of an active sensor. Then, we consider sensors with overlapping sensing range such that the tracking error, and hence the actions of the different sensors, are tightly coupled. Finally, we consider scenarios wherein the target locations and sensors' observations assume values on continuous spaces. Exact solutions are generally intractable even for the simplest models due to the dimensionality of the information and action spaces. Hence, we devise approximate solution techniques, and in some cases derive lower bounds on the optimal tradeoff curves. The generated scheduling policies, albeit suboptimal, often provide close-to-optimal energy-tracking tradeoffs.

This paper addresses the problem of reconstructing wideband speech signals from observed narrowband speech signals. The goal of this work is to improve the perceived quality of speech signals which have been transmitted through narrowband channels or degraded during acquisition. We describe a system, based on linear predictive coding, for estimating wideband speech from narrowband. This system employs both previously identified and novel techniques. Experimental results are provided in order to illustrate the system′s ability to improve speech quality. Both objective and subjective criteria are used to evaluate the quality of the processed speech signals.

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