Performance of Fountain Codes in Collaborative Relay Networks

Molisch, Andreas F and Mehta, Neelesh B and Yedidia, Jonathan S and Zhang, Jin (2007) Performance of Fountain Codes in Collaborative Relay Networks. In: IEEE Transactions on Wireless Communications, 6 (11). pp. 4108-4119.

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Abstract

Cooperative communications, where parallel relays forward information to a destination node, can greatly improve the energy efficiency and latency in ad-hoc networks. However, current networks do not fully exploit its potential as they only use traditional energy-accumulation, which is often used in conjunction with repetition coding or cooperative space-time codes. In this paper, we show that the concept of mutual- information-accumulation can be realized with the help of fountain codes, and leads to a lower energy expenditure and a lower transmission time than energy accumulation. We then provide an analysis of the performance of mutual information accumulation in relay networks with N relay nodes. We first analyze the quasi-synchronuous scenario where the source stops transmitting and the relay nodes start transmitting after L relay nodes have successfully decoded the source data. We show that an optimum L exists, and is typically on the order of 3 or 4. We also give closed-form equations for the energy savings that can be achieved by the use of mutual-information-accumulation at the receiver. We then analyze and provide bounds for an alternate scenario where each relay node starts its transmission to the destination as soon as it has decoded the source data, independent of the state of the other relay nodes. This approach further reduces the transmission time, because the transmission by the relay nodes helps the other relay nodes that are still receiving.

Item Type:	Journal Article
Publication:	IEEE Transactions on Wireless Communications
Publisher:	IEEE
Additional Information:	Copyright 2008 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.
Keywords:	Cooperative communications;energy accumulation;fountain code; radio networks;relay;transmit energy minimization.
Department/Centre:	Division of Electrical Sciences > Electrical Communication Engineering
Date Deposited:	13 May 2009 05:59
Last Modified:	07 Jan 2013 06:22
URI:	http://eprints.iisc.ac.in/id/eprint/16546

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