Multiuser Detection
Low complexity optimal joint detection for oversaturated multipleaccess communications
IEEE Transactions on Signal Processing
Binary signature sets for increased user capacity on the downlink of cdma systems
IEEE Transactions on Wireless Communications
Spectral efficiency of CDMA with random spreading
IEEE Transactions on Information Theory
Optimal sequences and sum capacity of synchronous CDMA systems
IEEE Transactions on Information Theory
Quasi-orthogonal sequences for code-division multiple-access systems
IEEE Transactions on Information Theory
Iterative construction of optimum signature sequence sets in synchronous CDMA systems
IEEE Transactions on Information Theory
Multiuser signaling in the symbol-synchronous AWGN channel
IEEE Transactions on Information Theory
IEEE Communications Magazine
Wideband DS-CDMA for next-generation mobile communications systems
IEEE Communications Magazine
Extending the capacity of multiple access channels
IEEE Communications Magazine
An Improved OCDMA/OCDMA Overloading Scheme for Cellular DS-CDMA
NEW2AN '08 / ruSMART '08 Proceedings of the 8th international conference, NEW2AN and 1st Russian Conference on Smart Spaces, ruSMART on Next Generation Teletraffic and Wired/Wireless Advanced Networking
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Overloading is a technique to accommodate more number of users than the spreading factor N. This is an efficient way to increase the number of users in a fixed bandwidth, which is of practical interest to mobile system operators. In this paper we have reviewed the different overloading schemes proposed in the literature for the DS-CDMA systems. The performance of an Orthogonal/Orthogonal (O/O) overloading scheme, using two sets of orthogonal codes (O/s-O) has been evaluated. Iterative multistage detector (IMSD) is used to reduce the multiple access interference between the users of two sets. The BER performance of IMSD is evaluated with hard and soft decisions functions using Monte-Carlo simulations. It is found that, this scheme provides 19% and 11% channel overloading for synchronous DS-CDMA system in an AWGN channel, with a SNR degradation of less than 0.5 dB at a BER of 10-5 compared to single user bound for N=16 and 64 respectively.