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research affiliate of the Centre de Recherche en Economie et Statistique (Paris). Kaplan is a research economist at the Bureau of Labor Statistics. We are grateful for financial support from the National Science Foundation (SBER 96-18111). We also thank Robert Cho and Brian Dunn for providing some of the Towers Perrin data used in this paper. No(More)
We discuss implementation aspects of a software-defined radio system that allows for dynamic waveform reconfiguration during runtime without interrupting data-flow processing. Traditional software-defined radio systems execute a waveform statically, exactly as it is programmed. Reconfiguration is provided by executing a different waveform, which requires(More)
— We discuss a developing software-defined radio framework and kernel, Surfer, which, among other changes compared with known current frameworks , moves control of when to process a block and how much data to process into the blocks themselves via buffer thresholds. Varying threshold values shows a trade-off between data processing latency and through-put,(More)
We investigate the amount of protocol information required for a communication network to meet an average delay constraint for the delivery of messages that arrive according to a Bernoulli random process. We obtain a lower bound on this overhead as a function of the arrival rate and average delay. Our model is a discretetime analog of the Poisson arrival(More)
We investigate the idea of providing information-theoretic security at the network and data link layers by exploiting the timing information resulting from queuing of packets between a source, an intended receiver, and other users in a network. Specifically, we consider the secure transmission of messages by encoding them onto the interarrival timing of(More)
Processing of earth observation data occur at multiple points across the sensor observation-to-knowledge information flow, including on-board sensor processing, data re-formatting processing, and data analysis processing. Conducting the data flow through web services allows components to be distributed and coupled to form an end-to-end processing chain of(More)
This paper speculates on a perspective for studying overhead in communication systems that contrasts the traditional viewpoint that overhead is the “non-data” portion of transmissions. By viewing overhead as the cost of constraints imposed on a system, information-theoretic techniques can be used to obtain fundamental limits on overhead(More)
—We consider the protocol overhead of meeting an expected delay constraint in sending a bursty source over a binary erasure channel with feedback. In contrast to related work on stability and delay for medium-access control, we focus on physical layer aspects of the problem by jointly considering queuing and message encoding for transmission over the(More)
We summarize the design and implementation of a portable software radio prototype built primarily using commercial off-the-shelf components and open-source software. The device components include a general-purpose processor (GPP) on a small-form-factor motherboard, radio hardware, touchscreen and LCD, audio microphone and speaker, and an internal battery(More)