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Cooperative Communications

Thu, 27 Nov 2008 10:47:10 -0600

Recent advances in wireless communications have allowed a leap in the development and commercialization of many types of wireless networks, including cellular, sensor, military, emergency and community mesh networks. A main observable theme in many of these applications is a paradigm shift from a rigid regulatory framework of competitive/exclusive usage of network resources to a more cooperative/shared resource-pool paradigm. Cooperation refers to active assistance and joint operation of nodes w

Spectrum Enforcement in Cognitive Radio Systems

Thu, 27 Nov 2008 10:43:16 -0600

The advent of frequency-agile radios holds potential for improving the utilization of spectrum by allowing wireless systems to dynamically adapt their spectral footprint based on the local conditions. Although a number of approaches ranging from market mechanisms to opportunistic usage have been proposed, a clear picture is emerging, that spectral gains can only be realized through real-time adaptation at runtime. However, this leaves open the major problem of how to enforce/incentivize complia

Distributed Cache Management in SNETS

Thu, 27 Nov 2008 10:39:20 -0600

We consider a mobile sensor network monitoring a spatio-temporal field. Given limited cache sizes at the sensor nodes, the goal is to develop a distributed cache management algorithm to efficiently answer queries with a known probability distribution over the spatial dimension. First, we propose a novel distributed information theoretic approach (DEBT) in which the nodes locally update their caches based on full knowledge of the space-time distribution of the monitored phenomenon. At each time

Adaptive Modulation

Thu, 27 Nov 2008 10:34:23 -0600

Link Adaptation refers to transmission schemes in which the transmitter adapts its mode (Constellation size, rate, code, power etc...) based on channel conditions. High rate transmission could take place when the channel is favorable and during deep fades robust schemes are enabled. This invariably requires channel state information (CSI) at the transmitter side. We studied the performance of adaptive modulation schemes in personal communication systems under various fading conditions and practi

Target Tracking

Thu, 27 Nov 2008 10:16:45 -0600

In a typical target tracking problem, the presence of random interference introduces uncertainty into the origin of measurements. Data association techniques, together with state estimation, are thus required to associate each measurement with the appropriate target or discard it as arising from clutter (False alarms). Probabilistic Data Association (PDA) is a well-known technique for single target tracking in clutter. Spurious measurements are rejected based on a validation technique that consi