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Interference cancellation (IC) is an effective and easy implemented technology in the multi-user system. Previous studies demonstrate the principles of IC and IC process which show a great improvement in the system capacity with IC. However, no research has focused on the IC system's capacity domain by giving an accurate formula. This article carries on the theoretical analysis of CDMA reverse link...
When passed through a high power amplifier (HPA), downlink direct sequence-code division multiple access (DS- CDMA) signals result in additional out-of-band emissions, or spectral regrowth, which could affect adjacent channels. In this paper, we explore which characteristics of the input CDMA signal, in relation to the amplifier characteristics, contribute to spectral regrowth. These characteristics...
The objective of this paper is to combine the antenna downtilt selection with the cell size selection in order to reduce the overall radio frequency (RF) transmission power in the homogeneous High-Speed Packet Downlink (HSDPA) cellular radio access network (RAN). The analysis is based on the concept of small cells deployment. The energy consumption ratio (ECR) and the energy reduction gain (ERG) of...
Robust adaptive multiuser detection schemes are developed for direct-sequence code-division multiple-access (DS-CDMA) multipath frequency-selective fading channels. Multiple access interference (MAI) and intersymbol interference (ISI) are presented in identical format in the expanded signal subspace, which provides convenience for symbol-by-symbol multiuser detection. The proposed multiuse detectors...
Smart antennas have received increasing interest due to its capability for improving the performance of wireless radio systems. In this work we studied the throughput maximization in a CDMA 1xEV-DO cellular system when a smart antenna array is implemented. We focus in the downlink of the CDMA cellular system and consider a packet data direct-sequence code division multiple access (DS-CDMA). We show...
Conventionally, an interweave cognitive radio (CR) system can be developed based on the assumption of spectrum sharing between a wide-band CR system and some narrow-band primary systems. In this paper, we explode this assumption by constructing an interweave CR system using a hierarchical wide-band two-dimensional (2D) spread multi-carrier directed-sequenced code division multiple access (MC-DS-CDMA)...
Continuous growth of cellular subscribers as well as demands for high-speed and high-quality multimedia services have made it necessary to increase system capacity and data rate. On the other hand, the energy consumed goes up accordingly as the data rates increases. Therefore, designing an efficient resources allocation scheme and architecture to improve the output performance and reduce energy consumption...
The performance of multi-hop multiple-input, multiple-output (MIMO) communication scenarios is evaluated for space time block coded (STBC) and the proposed distributed cyclic delay diversity (CDD) technique. By increasing the frequency selectivity, multi-stage CDD with low complexity implementation yields significant performance improvement as relaying network. Both diversity techniques based on frequency-correlated...
A novel Multiuser Detection (MUD) scheme is proposed for DS-CDMA systems employing the so-called Harmony Search (HS) algorithm, which is a novel meta-heuristic optimisation method. We specifically design the HS aided MUD for the communications problem considered and apply it in an iterative joint Channel Estimation (CE), MUD and channel decoding framework. The simulation results demonstrate that a...
Interference cancelation (IC) has been well studied in literature as a potential capacity approaching scheme for uplink code-division multiple-access (CDMA) systems. With the advance of silicon technology, it is becoming implementationally feasible. In this paper, we study a soft IC algorithm which could be iteratively concatenated with Turbo decoding. The algorithm only relies on a conventional single...
This paper evaluates the performance of variable-step closed loop power control algorithm for CDMA communication employing High Altitude Platforms (HAPs). In HAPs, the channel is predicted to have different characteristics compared to that in terrestrial. Users that are distributed within HAPs coverage will have different channel characteristics depending on their elevation angle. In this work, HAPs...
In this paper we propose a multiuser receiver using multistage detection and interference cancellation for direct-sequence code-division multiple-access (DS/CDMA) systems with parity bit selected spreading sequences in synchronous channels. In a CDMA system with parity bit selected spreading sequences (CDMA/PB), the spreading code used by each user depends on the transmitted data bits and it is selected...
The vast literature on power control for CDMA systems ignored the fact that propagation delays occur inevitably during data communication between the base station and the mobile units or viceversa. If these delays are not considered into the power control design stage, the performance of the resulting feedback system can be severely deteriorated or even instability could be triggered in a practical...
In this paper, we propose user grouping algorithms to provide power minimization in grouped MC-CDMA systems. Depending on the channel fading conditions, power control is utilized to minimize the total transmitted power under a bit error rate (BER) constraint. When the allocation is performed without a fair data rate requirement, we provide the optimal solution to the minimization problem. However...
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,...
Using mutually shift orthogonal spreading codes, block spread code division multiple access (BS-CDMA) systems have been shown to achieve multiuser interference (MUI) free reception when signals of all the users arrive at the base station synchronously. In practice, imperfect synchronization destroys the orthogonality among users and causes MUI. We present in this paper the design of spreading and...
Unwanted feedback between the donor (receive) and coverage (service) antennas of a relay (repeater) are created by the radio echoes from the local scatters and direct path antenna isolation limitations. These radio echoes create interference not only in the incoming signal from the base station, but also cause instability in the repeater. In this paper, we present an interference cancellation system...
We propose a call admission control scheme for soft handoff of CDMA networks based on mobility estimation and mobility history of mobile stations. This work is further improvement of the Eliminating Pseudo Handoff Call (EPHC) proposed by Xiaomin Ma et.al. Therefore we named our proposed scheme as Improved EPHC (IEPHC). The proposed scheme not only improves network throughput but also reduces handoff...
In this paper on MIMO-CDMA systems employing permutation spreading, we propose a new method for designing the spreading permutations based on space time block code matrices. We investigate the bit error rate performance of these systems using BPSK and QPSK modulation in single and multiple user situations. The new designs provide full transmit diversity between different message cosets. Compared with...
In this paper, we present an iterative joint channel estimation and data detection technique for multiple-input multiple-output (MIMO) code-division multiple-access (CDMA) systems over Rayleigh fading channels. The proposed receiver performs the channel estimation and data detection using the expectation-maximization (EM) algorithm. We derive a closed-form expression for the optimized weight coefficients...
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