On the optimal spreading sequence allocation in flat-fading channels

TitleOn the optimal spreading sequence allocation in flat-fading channels
Publication TypeJournal Article
Year of Publication2003
AuthorsDjonin, D. V., and V. K. Bhargava
JournalWireless Communications, IEEE Transactions on
Volume2
Pagination680 - 689
Date Publishedjul.
ISSN1536-1276
Keywordsasymptotic analysis, channel capacity, code division multiple access, DS-CDMA, fading channels, flat-fading channels, frequency flat fading, group orthogonal optimal sequence allocation, optimal spreading sequence allocation, optimisation, order statistics, power control, sequences, single cell model, spectral efficiency, spread spectrum communication, sum capacity, synchronous code-division multiple-access channels
Abstract

The sum capacity of optimally allocated spreading sequences with and without power control is studied for synchronous code-division multiple-access channels subject to frequency flat fading. Continuing upon the recently derived characterization of sum capacity for asymmetric received powers with no power control at the transmitter, we present an asymptotic analysis of the sum capacity in the wideband limit of a large number of users and evaluate possible gains compared with the random spread sequences. Next, we discuss group orthogonal optimal sequence allocation and analyze its potential to decrease the complexity of the receiver while achieving the sum capacity of optimally allocated equal-energy sequences. For the power controlled case, we give a general characterization of sum capacity and identify the optimal power-control law and sequence allocation that achieves this capacity. These results are also analyzed in the asymptotic limit of a large number of users.

URLhttp://dx.doi.org/10.1109/TWC.2003.814341
DOI10.1109/TWC.2003.814341

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