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—The capacity per unit cost, or equivalently minimum cost to transmit one bit, is a well-studied quantity. It has been studied under the assumption of full synchrony between the transmitter and the receiver. In many applications, such as sensor networks, transmissions are very bursty, with small amounts of bits arriving infrequently at random times. In such… (More)

We consider the 'one-shot frame synchronization problem' where a decoder wants to locate a sync pattern at the output of a channel on the basis of sequential observations. We assume that the sync pattern of length N starts being emitted at a random time within some interval of size A, that characterizes the asynchronism level between the transmitter and the… (More)

—A formulation of the problem of asynchronous point-to-point communication is developed. In the system model of interest, the message codeword is transmitted over a channel starting at a randomly chosen time within a prescribed window. The length of the window scales exponentially with the codeword length, where the scaling parameter is referred to as the… (More)

- Walter Sun, Müjdat Çetin, Raymond C. Chan, Vivek Y. Reddy, Godtfred Holmvang, Venkat Chandar +1 other
- IPMI
- 2005

Having accurate left ventricle (LV) segmentations across a cardiac cycle provides useful quantitative (e.g. ejection fraction) and qualitative information for diagnosis of certain heart conditions. Existing LV segmentation techniques are founded mostly upon algorithms for segmenting static images. In order to exploit the dynamic structure of the heart in a… (More)

- Venkat Chandar
- 2008

In this note, we prove that matrices whose entries are all 0 or 1 cannot achieve good performance with respect to the Restricted Isometry Property (RIP). Most currently known deterministic constructions of matrices satisfying the RIP fall into this category, and hence these constructions suffer inherent limitations. In particular, we show that DeVore's… (More)

—Based on recent work on asynchronous communication , this paper proposes a slotted asynchronous channel model and investigates the fundamental limits of asynchronous communication, in terms of miss and false alarm error exponents. We propose coding schemes that are suitable for various asyn-chronous communication scenarios, and quantify more precisely the… (More)

—An update efficient code is a mapping from messages to codewords such that small perturbations in the message induce only slight changes to the corresponding codeword. The parameter that captures this notion is called update-efficiency. In this paper we study update-efficient error-correcting codes and develop their basic properties. While… (More)

—We consider the recovery of a nonnegative vector x from measurements y = Ax, where A ∈ {0, 1} m×n. We establish that when A corresponds to the adjacency matrix of a bipartite graph with sufficient expansion, a simple message-passing algorithm produces an estimatê x of x satisfying x−ˆx1 ≤ O(n k)x− x (k) 1, where x (k) is the best k-sparse approximation of… (More)

This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Abstract—Several aspects of the problem of asynchronous point-to-point communication without feedback are developed when the source is highly intermittent. In the system model of interest, the… (More)

—Motivated by distributed storage applications, we investigate the degree to which capacity achieving encodings can be efficiently updated when a single information bit changes, and the degree to which such encodings can be efficiently (i.e., locally) repaired when single encoded bit is lost. Specifically, we first develop conditions under which optimum… (More)