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The uplink spectral-efficiency of space-division multiple-access (SDMA) cellular systems is studied, when distributed base-station (BS) detection and distributed BS cooperation are employed. In contrast to the related works in literature, which mainly consider the linear and hexagonal Wyner models (or their extensions) with a constant factor for intercell interference (ICI), we address the impacts...
A multiway relay direct-sequence code-division multiple-access (MR-DS-CDMA) system is proposed for exchanging information among a group of distributed mobile terminals (MTs). In order to implement information exchange, a MT having similar distances from the other MTs is chosen to act as a relay, which assists the whole group of MTs to achieve their information exchange within two time-slots. In our...
This paper proposes a fast frequency-hopping M-ary frequency-shift keying dynamic multiple-access (FFH/MFSK DMA) scheme for application in cognitive radios (CRs). For characterising the performance of the FFH/MFSK DMA systems, primary users (PUs) are assumed to become active according to a Poisson process. In our FFH/MFSK DMA system, the noncoherent majority vote assisted single-user detector (MV-SUD)...
Information exchange among a group of users is implemented with the aid of fast frequency-hopping M-ary frequency-shift keying multi-way relay (FFH/MFSK MWR). The FFH/MFSK MWR scheme uses two time-slots per symbol for achieving the information exchange, regardless of the number of users involved. During the first time-slot, all the users communicate with a relay based on the FFH/MFSK principles. Then,...
We propose a novel dynamic multiple-access (DMA) scheme for application in cognitive radios (CRs). This DMA scheme is implemented by fast frequency hopping with Mary frequency-shift keying (FFH/MFSK) associated with suboptimum noncoherent maximum-likelihood multiuser detection (ML-MUD). In our studies, we assume that the primary users (PUs) and the cognitive radio users (CRUs) are operated in the...
The so-called receiver multiuser diversity aided multi-stage minimum mean-square error multiuser detector (RMD/MS-MMSE MUD), which was proposed previously by the author, is investigated in the context of the direct-sequence code-division multiple-access (DS-CDMA) and space-division multiple-access (SDMA) systems that employ in- and quadrature-phase (I-Q) modulation schemes. A detection scheme is studied,...
In this contribution, a novel Ant Colony Optimization (ACO) based Space-Time (ST) Multiuser Detection (MUD) algorithm was proposed in order to improve the Bit Error Ratio (BER) versus Signal-to-Noise Ratio (SNR) performance achieved by the Space-Time Block Code (STBC) assisted two transmit antenna aided fully loaded DS-CDMA system directly employing an ACO based MUD algorithm. Our simulation results...
In this contribution we investigate the spectral-efficiency of a two-hop cooperative network using multicarrier code-division multiple-access (MC-CDMA) transmission scheme. The two-hop network constitutes K source users transmitting signals to K destinations with the aid of N relays. Our focus is on the relay optimization, when assuming that the N relays cooperate or do not cooperate with each other...
In this contribution the asymptotic signal-to-interference-plus-noise ratio (SINR) performance of multicarrier direct-sequence code-division multiple-access systems employing time-frequency-domain spreading, i.e., of the TF/MC DS-CDMA systems, is studied, when separate minimum mean-square error multiuser detection (MMSE-MUD) is considered. The separate MMSE-MUD detects signals first in the time (T)-domain...
In this treatise we propose a three-stage twin-transmit-antenna assisted Multiuser (MU) Direct Sequence Code-Division Multiple Access (DS-CDMA) system employing both a Unitary Rate Code (URC) and a Recursive Systematic Code (RSC) to carry out iterative turbo detection. A Space-Time Block Code (STBC) is used to provide second-order diversity gain in conjunction with a novel soft-output (SO) ant-colony-optimization...
Design of low-complexity detection schemes that can approach near-optimum bit error rate (BER) performance in multiuser or other multiple-input multiple-output (MIMO) systems has always been highly challenging. In this paper we propose and investigate a so-called receiver multiuser diversity aided multi-stage minimum mean-square error multiuser detection (RMD/MS-MMSE MUD) scheme operated in the principles...
In this contribution we propose and study a novel iterative time-frequency-domain (TF-domain) multiuser detector (MUD) for the multicarrier direct-sequence code-division multiple-access system employing both T-domain and F-domain spreading, which, for brevity, is referred to as the TF/MC DSCDMA system. The proposed iterative TF-domain MUD consists of a set of T-domain soft-input soft-output MUDs (SISO-MUDs)...
The downlink minimum bit error rate (MBER) transmit beamforming is directly derived based on the uplink MBER receive beamforming for time division duplex (TDD) space-division multiple-access (SDMA) multiple-input multiple-output systems, where the base station (BS) is equipped with multiple antennas to support multiple single-antenna mobile terminals (MTs). It is shown that the relationship between...
Although multiuser detection (MUD) has received intensive research since its invention by Verdu in 1983, however, the statistical properties in MUD have not received enough attention in research and application. In this contribution, we first study the statistical properties of minimum mean-square error (MMSE)-MUD, maximum likelihood (ML)-MUD and hybrid MMSE/ML-MUD from different aspects in the context...
In this contribution reduced-rank adaptive minimum mean- square error multiuser detector (MMSE-MUD) is proposed and investigated for the hybrid direct-sequence time-hopping ultrawide bandwidth (DS-TH UWB) systems. The adaptive MMSE-MUD is operated based on the normalised least mean-square (NLMS) principles associated with using Taylor polynomial approximation (TPA)-assisted reduced-rank technique...
In this contribution we propose and study a novel multiuser detection (MUD) scheme for multicarrier direct-sequence code-division multiple-access systems employing both time (T)-domain and frequency (F)-domain spreading, which are referred to as the TF/MC DS-CDMA systems. Specifically, a reliability-aided MUD scheme is proposed, which consists of a linear MUD and a so-called L-level maximum-likelihood...
In relay-aided cellular wireless communications mobile terminals (MTs) near the base-station (BS) are usually preferred to being selected as relays for the sake of achieving the relay diversity while simultaneously obtaining a high power-efficiency. However, this strategy may result in a so-called 'bottleneck' problem, when each source MT employs different relays, since the available relays near the...
In this contribution, a novel soft-output Ant Colony Optimization (ACO) based Multi-User Detector (MUD) is proposed for the synchronous Direct-Sequence Code-Division- Multiple-Access (DS-CDMA) uplink. The foraging behaviour of the ant colony in nature motivates the employment of reduced- search ACO-based MUDs, which are capable of approaching the optimum Maximum Likelihood (ML) MUD's performance at...
In this contribution we present a novel ant colony optimization (ACO) based multiuser detector (MUD) designed for synchronous multi-carrier direct sequence code division multiple access (MC DS-CDMA) systems. The operation of the ACO-based MUD is based on the behaviour of the ant colony in nature. The ACO-based MUD aims for achieving the same bit-error-rate (BER) performance as the optimum maximum...
This paper investigates and compares the performance of various ultrawide bandwidth (UWB) systems when communicating over Nakagami-m fading channels. Specifically, the direct-sequence (DS), time-hopping (TH) and hybrid direct-sequence time-hopping (DS-TH) UWB systems are considered. The performance of these UWB systems is studied, when using the conventional single-user correlation detector or the...
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