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Recently, Multi-User Selection Diversity (MUSDiv) for single-carrier systems has been under extensive study on account of the enhancement it provides to system performance with minimum feedback requirements. However, its application to multichannel systems is considered straightforward and thus, it has not been thoroughly examined. In this paper, the performance of MUSDiv is investigated when applied to the spread-spectrum multi-carrier multiple-access system, where the scheduling has to be performed for all the available channels and self interference must also be considered. Specifically, based on the absolute and normalized Signal-to-Noise-Ratio (SNR) scheduling algorithms, two algorithms are presented, modified and optimized, so that they can be applied on a subband instead of a single-channel basis. Moreover, we propose a new scheduling scheme which constitutes a trade-off between the previous schemes, concerning fairness and capacity performance. The new algorithms are related to the symbol Signal-to-Noise-plus-Interference-Ratio (SNIR) instead of SNR and two interference models were devised to this end. Closed-form expressions for the system capacity are extracted for each case, which are compared with simulation results. The research is also extended to the case of non-identical user power profiles among the available subcarriers. The channel state information required to utilize multi-user selection diversity is already necessary for the most common combining schemes, so no more feedback is actually needed. [ABSTRACT FROM AUTHOR]

In this paper we study and analyze the performance of the RAKE receiver for a typical Ultrawideband (UWB) Spectrally-Encoded Spread-Time (ST) CDMA in the presence of multiple Gaussian Interference (GI) signals. We demonstrate that by combining useful properties of three-level codes, ie., codes with values of -1,0,+1, and RAKE receiver, we can introduce a new strategy in which it can result in superior performance when compared to previous results. In particular, following a discussion on three-level codes we can show that RAKE receiver with optimum multiplicative weights achieves a better performance when compared with simpletwo-level codes. With the help of an example we show various properties of RAKE receiver as well as three-level codes and relate these properties to a number of simple descritive parameters of the communication media. Simulation results obtained in this paper indicate the precision with which the analytical results have been obtained in modeling the above system. [ABSTRACT FROM AUTHOR]

This article focuses on forthcoming research papers to be published in this periodical. One paper "On the Application of Factor Graphs and the Sum-Product Algorithm to ISI Channels," is based on the application of the sum-product algorithm to factor graphs representing the joint a posteriori probability of the transmitted symbols, we propose new iterative soft-input soft-output detection schemes for intersymbol interference channels. Another research called "A Class of Signal Processing Schemes for Reducing the Envelope Fluctuations of CDMA Signals," present a class of nonlinear signal processing schemes to reduce the envelope fluctuations in the downlink transmission within code division multiple access (CDMA) systems. These schemes are compatible with conventional CDMA receivers since they just require some modifications at the transmitter side. The proposed transmitter structure includes a nonlinear operation in the time-domain followed by a linear, frequency-domain filtering operation.