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A reduced complexity normalized least-mean-square (NLMS) algorithm is presented for blind linear adaptive multiuser detection in synchronous direct-sequence CDMA systems. Selective partial updating is employed to reduce the computational complexity of the NLMS algorithm. The basic idea behind selective partial updating is to update only a small number of the adaptive filter coefficients at each iteration...
Passive communications based on modulated backscatter can dramatically extend the lifespan of wireless sensor networks. Because wireless passive sensor networks reduce the dependence on the batteries, they have great potential to be used in body sensing applications. In a typical sensor network deployment, multiple passive sensor nodes modulate a common carrier. The superimposed reflected signals...
Femtocells, which are low cost low power, stand alone cellular access points, are a potential solution to provide good indoor coverage with high data rate. However, the femtocell deployment may also increase the co-channel interference (CCI) by reducing the distance reuse of the spectrum. In this paper, we introduce methods to cancel out the interference among the femtocells while considering that...
This paper presents an area/energy efficient soft-output MIMO detector that supports the detection of spatial-multiplexing (SM), spatial-diversity (SD), and space-division-multiple-access (SDMA) signals. The developed near-optimal detection algorithms for these three modes share most of the mathematical operations to enable extensive hardware reuse. A unified VLSI architecture is accordingly designed...
In this paper, we propose the low-complexity FPGA implementation of a reconfigurable successive interference cancellation (SIC) detector for combating the effect of multiuser interference in wired/wireless systems. The complexity of various building blocks is reduced and then the whole structure is pipelined. Using the PXI-7842R platform from National Instruments, the SIC detector is implemented and...
A sub-optimum multiuser detector which compares the received samples to reliability thresholds, in order to classify them as reliable or non-reliable, is proposed for CDMA systems. Each one of these classified samples receives a different management in the detection process. This technique presents a good trade-off between performance and complexity in relation to the optimum multiuser detector. In...
Based on the special kind of spreading sequence and semidefinite programming relaxation, A new multiuser detector for asynchronous code division multiple access system is presented. At each transmitter, the special spreading sequence whose second half is the replica of the first is employed. Maximum-likelihood(ML) multiuser detection only need detect 2K once. Then ML detection can be efficiently and...
In this paper, we combine two different multiple access, namely, Space Division Multiple Access (SDMA) and Block-Interleaved Division Multiple Access (B-IFDMA), for uplink transmission, and we name the combined multiple access SD/B-IFDMA. Since SDMA suffers from multiple access interference (MAI) and B-IFDMA from intersymbol interference (ISI), a multi-user detector that can counteract both MAI and...
In this paper, we present a multistage group-decision-aid MUD (MG-MUD) for the uplink multirate code division multiple access (CDMA) systems. To provide good tradeoff between the performance and computational complexity, the new MUD is based on the widely MMSE criterion and constructed by a bank of group detectors in each stage. First, the users are classified into different groups according to their...
In synchronous DS-CDMA systems, multi-access interference (MAI) due to severe frequency-selective fading degrades the system performance. Based on the frequency domain oversampling (FDO) and minimum mean-square error (MMSE) principle, a novel linear per-user MMSE detector is proposed to approximately restore the orthogonality among the spreading sequences and suppress the MAI. Based on a discussion...
This paper presents comprehensive comparisons of interleave division multiple access (IDMA) and direct sequence code division multiple access (DS-CDMA) in terms of performance and complexity using iterative multiuser detection technique, where we restrict ourself to three suboptimum linear detectors: minimum mean square error (MMSE), rake (or matched filter), and soft-rake detectors from practical...
This paper introduces a novel heuristic algorithm for N-user detection in synchronous CDMA multiple access networks. In such systems, the performance of the conventional single-user detection technique (i.e. a rake receiver compounded by a set of matched filters) is clearly bounded by the well-known multiple access interference (MAI). To avoid this limitation, the optimum maximum likelihood (ML) detection...
This paper presents a novel WLAN-based system configuration employing Coded Multi-Carrier Code-Division- Multiplexing technology (CMC-CDM), as a potentially superior alternative to the currently standardized Coded OFDM (COFDM) technology. To further improve the performance of the system and reduce its complexity, a new concept of Chase detection is applied at the receiver. A comprehensive investigation...
Multistage parallel interference cancellation (MPIC) based detectors allow to mitigate multiple access interference and intersymbol interference in direct-sequence code division multiple access (DS-CDMA) systems. Better performance is obtained when decision feedback (DF) is employed. Although MPIC and DF-MPIC have the same arithmetic complexity, DF-MPIC needs much more FPGA resources when compared...
The number of active users in code-division multiple access (CDMA) systems is often much lower than the spreading gain. The present paper exploits fruitfully this a priori information to improve performance of multiuser detectors. A low-activity factor manifests itself in a sparse symbol vector with entries drawn from a finite alphabet that is augmented by the zero symbol to capture user inactivity...
A new transformation matrix technique for reducing the complexity of a multiuser receiver for DS-CDMA system is presented. The reduction in complexity of multiuser receiver would result in better bit error rate (BER) performance. The reduction in error rate would allow us to maximize the data throughput of a communication network by minimizing the packet loss. Our simulation results demonstrate that...
In this paper, combining the endocrine mechanism and immune genetic algorithm immune-endocrine genetic algorithm (IEGA) for multi-user detector problem is proposed. The convergence properties of the IEGA are studied. It is proved that the IEGA converge to global optimum with probability 1. Finally, the experimental results demonstrate that the IEGA is better than some existed algorithms.
Multiuser detection (MUD) techniques are mandatory in direct-sequence code division multiple access (DS-CDMA) systems. They allow to mitigate multiple access interference (MAI) and hence increase the capacity and allow high data rates. Multistage parallel interference cancellation (MPIC) detectors are considered serious candidates for practical implementation showing a good tradeoff between performance...
We propose a new differential recursive update algorithm, which significantly reduces the complexity of iterative minimum mean square error (MMSE) detection and decoding techniques for spread spectrum communication systems. Although the MMSE detector is a less complex suboptimum solution comparing to the optimum one, it is still complex for iterative systems because a large number of matrix inversions...
This paper analyzes the particle swarm optimization multiuser detector (PSO-MUD) under high-order modulation schemes, (particularly for M-QAM), in DS/CDMA systems single-input-single-output (SISO) multipath channels. In order to avoid the computation of complex-valued variables in high-order squared modulation, the optimization problem is reformulated as a real-valued problem. Considering previous...
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