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If a linear block code C of length n has a Tanner graph without cycles, then maximum-likelihood soft-decision decoding of C can be achieved in time O(n 2). However, we show that cycle-free Tanner graphs cannot support good codes. Specifically, let C be an (n, k, d) linear code of rate R = k/n that can be represented by a Tanner graph without cycles. We(More)
Personal Digital Assistants (PDAs) and other mobile computing devices rely on synchronization protocols in order to maintain data consistency. These protocols operate in environments where network resources such as bandwidth, memory and processing power are limited. In this paper, we examine a number of popular and representative synchronization protocols,(More)
We consider the problem of efficiently reconciling two similar sets held by different hosts while minimizing the communication complexity , which we call the set reconciliation problem. We describe an approach to set reconciliation based on a polynomial encoding of sets. The resulting protocols exhibit tractable computational complexity and nearly optimal(More)
— We propose a new framework for providing robust location detection in emergency response systems, based on the theory of identifying codes. The key idea of this approach is to allow sensor coverage areas to overlap in such a way that each resolvable position is covered by a unique set of sensors. In this setting, determining a sensor-placement with a(More)
We propose a novel framework for location detection with sensor networks, based on the theory of identifying codes. The key idea of this approach is to allow sensor coverage areas to overlap so that each resolvable position is covered by a unique set of sensors. In this setting, determining a sensor-placement with a minimum number of sensors is equivalent(More)
Modern Personal Digital Assistant (PDA) architectures often utilize a wholesale data transfer protocol known as " slow sync " for synchronizing PDAs with Personal Computers (PCs). This approach is markedly inefficient with respect to bandwidth usage, latency, and energy consumption, since the PDA and PC typically share many common records. We propose,(More)
— The erasure resilience of rateless codes, such as Luby-Transform (LT) codes, makes them particularly suitable to a wide variety of loss-prone wireless and sensor network applications, ranging from digital video broadcast to software updates. Yet, traditional rateless codes usually make no use of a feedback communication channel, a feature available in(More)
— Modern Personal Digital Assistant (PDA) architectures often utilize a wholesale data transfer protocol known as " slow sync " for synchronizing PDAs with Personal Computers (PCs). This approach is markedly inefficient with respect to bandwidth usage and latency, since the PDA and PC typically share many common records. We propose, analyze, and implement a(More)
— We present novel rateless codes that generalize and outperform LT codes (with respect to overall communication and computation complexity) when some input symbols are already available at the decoding host. This case can occur in data synchronization scenarios, or where feedback is provided or can be inferred from transmission channel models. We provide(More)