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Construction of equiangular signatures for synchronous CDMA systems

Heath, Robert W., Jr. and Tropp, Joel A. and Dhillon, Inderjit S. and Strohmer, Thomas (2005) Construction of equiangular signatures for synchronous CDMA systems. In: International Symposium on Spread Spectrum Techniques and Applications, 8th, Sydney, Australia, 30 August - 2 September 2004. IEEE , Piscataway, NJ, pp. 708-712. ISBN 0-7803-8408-3

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Welch bound equality (WBE) signature sequences maximize the uplink sum capacity in direct-spread synchronous code division multiple access (CDMA) systems. WBE sequences have a nice interference invariance property that typically holds only when the system is fully loaded, and, to maintain this property, the signature set must be redesigned and reassigned as the number of active users changes. An additional equiangular constraint on the signature set, however, maintains interference invariance. Finding such signatures requires equiangular side constraints to be imposed on an inverse eigenvalue problem. The paper presents an alternating projection algorithm that can design WBE sequences that satisfy equiangular side constraints. The proposed algorithm can be used to find Grassmannian frames as well as equiangular tight frames. Though one projection is onto a closed, but non-convex, set, it is shown that this algorithm converges to a fixed point, and these fixed points are partially characterized.

Item Type:Book Section
Tropp, Joel A.0000-0003-1024-1791
Additional Information:© Copyright 2005 IEEE. Reprinted with permission. [Posted online: 2005-01-03]
Subject Keywords:code division multiple access, eigenvalues and eigenfunctions, optimization, radio frequency interference, sequences, spread spectrum communication
Record Number:CaltechAUTHORS:HEAissta04
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9041
Deposited By: Archive Administrator
Deposited On:22 Oct 2007
Last Modified:06 Mar 2015 23:13

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