The multi-code (MC) multirate DS-CDMA (direct sequence-code division multiple access) transmission system's performance is analyzed, associated to a multistage parallel interference cancellation (MPIC) structure, MC-MPIC, with hyperbolic tangent decision device in the intermediate stages. Extensive Monte Carlo simulations (MCS) considering total and partial cancellation in additive white Gaussian noise (AWGN) and flat Rayleigh channels indicated great performance gain of the MC-MPIC structure when compared to the conventional MC detection. The results show the feasibility of the proposed structure for future third generation (3G) systems.

This paper proposes to extend the discrete Verhulst power equilibrium approach, previously suggested in [1], to the power-rate optimal allocation problem. Multirate users associated to different types of traffic are aggregated to distinct user classes, with the assurance of minimum rate allocation per user and QoS. Herein, Verhulst power allocation algorithm of [1] was adapted to the DS-CDMA jointly power-rate control problem. The analysis was carried out taking into account static and dynamic channels, as well as the convergence time (number of iterations), quality of solution, in terms of the normalized mean squared error (NSE), when compared to the analytical solution based on interference matrix inversion, and the solution given by classical Foschini algorithm [2] as well, besides the computational complexity analysis.

The multi-code (MC) multirate DS-CDMA (direct sequence-code division multiple access) transmission system's performance is analyzed, associated to a multistage parallel interference cancellation (MPIC) structure, MC-MPIC, with hyperbolic tangent decision device in the intermediate stages. Extensive Monte Carlo simulations (MCS) considering total and partial cancellation in additive white Gaussian noise (AWGN) and flat Rayleigh channels indicated great performance gain of the MC-MPIC structure when compared to the conventional MC detection. The results show the feasibility of the proposed structure for future third generation (3G) systems

A new utilization form for the evolutionary programming (EP) algorithm applied to multi-user DS-CDMA (direct sequence code division multiple access) systems in a synchronous AWGN (additive white Gaussian noise) channel is proposed. In order to find the maximum likelihood (ML) solution, the variance matrix for the generation of new candidates was expressed as a function of the following parameters: E/sub b//N/sub 0/; near-far ratio (NFR); cost function (fitness value). A cloning strategy procedure was introduced where the best vectors with the bit-candidates were cloned, reducing drastically the required time for the algorithm convergence to the single user bound (SuB) performance. An improvement in the convergence process was obtained using a parallel interference canceller with soft decision (SD-PIC) for initial vector generation.

This paper presents a performance analysis of a baseband multiple-input single-output ultra-wideband system over scenarios CM1 and CM3 of the IEEE 802.15.3a channel model, incorporating four different schemes of pre-distortion: time reversal, zero-forcing pre-equaliser, constrained least squares pre-equaliser, and minimum mean square error pre-equaliser. For the third case, a simple solution based on the steepest-descent (gradient) algorithm is adopted and compared with theoretical results. The channel estimations at the transmitter are assumed to be truncated and noisy. Results show that the constrained least squares algorithm has a good trade-off between intersymbol interference reduction and signal-to-noise ratio preservation, providing a performance comparable to the minimum mean square error method but with lower computational complexity. Copyright (C) 2011 John Wiley & Sons, Ltd.

This paper extends the discrete Verhulst power equilibrium method, previously suggested in [1], to the power-rate optimal allocation problem. Multirate users associated with different types of traffic are aggregated to distinct user' classes, with the assurance of target rate allocation per user and QoS. Therein, single-rate Verhulst power allocation algorithm was adapted to the multirate DS/CDMA power control problem. The analysis was carried out taking into account the convergence time (number of iterations) and quality of solution in terms of the normalized square error (NSE), considering static and dynamic realistic mobile channels. Computational complexity was addressed and compared to the analytical solution based on interference matrix inverse and the Foschini solution as well.

We analyze the performance of multirate structures, implemented with a multiple codes (MC) scheme, and associated to multiuser detection (MUD) of successive interference cancellation (SIC) for a group of users (GSIC), considering a hyperbolic tangent (tanh) decision device in the intermediate stages. Extensive Monte Carlo simulations (MCS) were accomplished for the MC-GSIC tanh structure's performance characterization, considering total and partial cancellation (with cancellation factor /spl xi/>1) in additive white Gaussian noise (AWGN) and flat Rayleigh channels.

A 1:4/1:16 demultiplexer IC with an integrated skip circuit has been successfully designed and fabricated employing SCFL standard cells based on 1 /spl mu/m MESFET foundry technology. The circuit was designed to operate at up to 2.5 Gb/s with low power dissipation. The demultiplexer employs a tree type architecture based on 1:2 demux blocks using tristage flip-flops. A new skip circuit without re-timing was proposed and integrated in the demultiplexer for frame alignment. The proposed skip circuit demonstrated its effectiveness and the IC operated either as a 1:4 or a 1:16 demultiplexer at up to 2.5 Gb/s with a power dissipation of 1 W. This IC is applicable for signal processing on SONET STS-12/48 optical communication systems.

In this work a simple and efficient methodology for tuning the input parameters applied to the ant colony optimization multiuser detection (ACO-MuD) in direct sequence code division multiple access (DS-CDMA) is proposed. The motivation in using a heuristic approach is due to the nature of the NP complexity posed by the wireless multiuser detection optimization problem. The challenge is to obtain suitable data detection performance in solving the associated hard complexity problem in a polynomial time. Previous results indicated that the application of heuristic search algorithms in several wireless optimization problems have been achieved excellent performance-complexity tradeoffs. Regarding different system operation and channels scenarios, a complete input parameters optimization procedure for the ACO-MuD is provided herein, which represents the major contribution of this work. Furthermore, the performance of the ACO-MuD is analyzed via Monte-Carlo simulations. Simulation results show that, after convergence, the performance reached by the ACO-MuD is much better than the conventional detector, and somewhat closer to the single user bound (SuB). Rayleigh flat channel is initially considered, but the results are straightforwardly extended to selective fading channels, as well as diversity (time and spatial) wireless channels.