@MASTERSTHESIS\{IMM2005-03859,
    author       = "L. Nie",
    title        = "Comparison of Exact and Approximate Multi-User Detection for {GSM}",
    year         = "2005",
    keywords     = "Adjacent Channel Interference (ACI), Cochannel Interference (CCI), Fully Factorized Mean Field (FFMF), Group SpÕcial Mobile (GSM), Interference Cancellation (IC), Inter-Symbol Interference (ISI), Linear Minimum Mean Squared Error (LMMSE)",
    school       = "Informatics and Mathematical Modelling, Technical University of Denmark, {DTU}",
    address      = "Richard Petersens Plads, Building 321, {DK-}2800 Kgs. Lyngby",
    type         = "",
    note         = "Supervised by associate professor Ole Winther",
    url          = "http://www2.compute.dtu.dk/pubdb/pubs/3859-full.html",
    abstract     = "In today s Group Special Mobile (GSM) system, interference is one of the main constraints in increasing cellular capacity. Multi-User Detection (MUD) is a kind of Interference Cancellation (IC) technique, which can be combined with other {IC} methods, such as antenna diversity, whitening. This dissertation investigates exact and approximate {MUD} {GSM} receivers. It is shown that exact {MUD} solution provides a big Bit Error Rate (BER) gain compared to conventional receivers. However, it has exponential complexity, making it infeasible to implement it on the limited Mobile Station (MS). In this thesis, the approximation to the exact solution is based on Mean Field theory. Two suboptimum algorithms: Fully Factorized Mean Field (FFMF) receiver and Structured Mean Field (SMF) receiver are implemented and evaluated. {FFMF} has very low complexity, comparable to that of the Linear Minimum Mean Squared Error (LMMSE) receiver, but much better {BER} performance for interference dominated scenarios. The {SMF} receiver gives faster convergence speed. However, for one Cochannel Interference (CCI), its performance is only close to that of {FFMF} solution in most of the tested {CIR} range and better than that of {FFMF} receiver at low {CIR} values.

Besides, topics such as digital phase modulation, {GSM} basics, the multi-path fading channel and conventional {GSM} receivers are also studied."
}