DocumentCode :
1505554
Title :
Iterative construction of optimum signature sequence sets in synchronous CDMA systems
Author :
Ulukus, Sennur ; Yates, Roy D.
Author_Institution :
WINLAB, Rutgers-State Univ. of New Jersey, Piscataway, NJ, USA
Volume :
47
Issue :
5
fYear :
2001
fDate :
7/1/2001 12:00:00 AM
Firstpage :
1989
Lastpage :
1998
Abstract :
Optimum signature sequence sets that maximize the capacity of single-cell synchronous code division multiple access (CDMA) systems have been identified. Optimum signature sequences minimize the total squared correlation (TSC); they form a set of orthogonal sequences, if the number of users is less than or equal to the processing gain, and a set of Welch (1994) bound equality (WBE) sequences, otherwise. We present an algorithm where users update their transmitter signature sequences sequentially, in a distributed fashion, by using available receiver measurements. We show that each update decreases the TSC of the set, and produces better signature sequence sets progressively. We prove that the algorithm converges to a set of orthogonal signature sequences when the number of users is less than or equal to the processing gain. We observe and conjecture that the algorithm converges to a WBE set when the number of users is greater than the processing gain. At each step, the algorithm replaces one signature sequence from the set with the normalized minimum mean squared error (MMSE) receiver corresponding to that signature sequence. Since the MMSE filter can be obtained by a distributed algorithm for each user, the proposed algorithm is amenable to distributed implementation
Keywords :
AWGN channels; cellular radio; channel capacity; code division multiple access; correlation methods; iterative methods; least mean squares methods; multiuser channels; optimisation; sequences; AWGN; MMSE filter; MMSE receiver; Welch bound equality sequences; algorithm; iterative construction; normalized minimum mean squared error; optimum signature sequence sets; processing gain; receiver measurements; signature sequence sets; single-cell CDMA systems; synchronous CDMA systems; synchronous code division multiple access; total squared correlation; transmitter signature sequences; AWGN; Additive white noise; Code division multiplexing; Communication system control; Distributed algorithms; Filters; Interference; Multiaccess communication; Statistics; Transmitters;
fLanguage :
English
Journal_Title :
Information Theory, IEEE Transactions on
Publisher :
ieee
ISSN :
0018-9448
Type :
jour
DOI :
10.1109/18.930932
Filename :
930932
Link To Document :
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