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286 results on '"Ashish Khisti"'

7. Three-terminal Erasure Source-Broadcast with Feedback

Author

Tan, Louis, Mahdaviani, Kaveh, and Member, Ashish Khisti

Subjects
Computer Science - Information Theory
Abstract

We study the effects of introducing a feedback channel in the erasure source-broadcast problem for the case of three receivers. In our problem formulation, we wish to transmit a binary source to three users over the erasure broadcast channel when causal feedback is universally available to the transmitter and all three receivers. Each receiver requires a certain fraction of the source sequence, and we are interested in the minimum latency, or transmission time, required to serve them all. We propose a queue-based hybrid digital-analog coding scheme that achieves optimal performance for the duration of analog transmissions. We characterize the number of analog transmissions that can be sent as the solution to a linear program and furthermore give sufficient conditions for which optimal performance can be achieved by all users. In some cases, we find that users can be point-to-point optimal regardless of their distortion constraints. When the analog transmissions are insufficient in meeting user demands, we propose two subsequent coding schemes. The first uses a queue preprocessing strategy for channel coding. The second method is a novel chaining algorithm, which involves the transmitter targeting point-to-point optimal performance for two users as if they were the only users in the network. Meanwhile, the third user simultaneously builds "chains" of symbols that he may at times be able to decode based on the channel conditions, and the subsequent reception of additional symbols.

Published
2021

42. Streaming Erasure Codes Over Multi-Access Relayed Networks

Author

Gustavo Kasper Facenda, Elad Domanovitz, Ashish Khisti, Wai-Tian Tan, and John Apostolopoulos

Subjects
FOS: Computer and information sciences, Information Theory (cs.IT), Computer Science - Information Theory, Library and Information Sciences, Computer Science Applications, Information Systems
Abstract

Many emerging multimedia streaming applications involve multiple users communicating under strict latency constraints. In this paper we study streaming codes for a network involving two source nodes, one relay node and a destination node. In our setting, each source node transmits a stream of messages, through the relay, to a destination, who is required to decode the messages under a strict delay constraint. For the case of a single source node, a class of streaming codes has been proposed by Fong et al. [2], using the concept of {\em delay-spectrum}. In the present work we present an in-depth analysis of the properties of delay-spectrum and apply them to develop streaming codes for our proposed setting through a novel framework. Our first scheme involves greedily selecting the rate on the link from relay to destination and using properties of the delay-spectrum to find feasible streaming codes that satisfy the required delay constraints. We provide a closed form expression for the achievable rate region and identify conditions when the proposed scheme is optimal by establishing a natural outer bound. Our second scheme builds upon this approach, but uses a numerical optimization-based approach to improve the achievable rate region over the first scheme. We demonstrate that our proposed schemes achieve significant improvements over baseline schemes based on single-user codes., 47 pages, 8 figures

Published
2023

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