scholarly journals FPGA Implementation of Block Parallel DF-MPIC Detectors for DS-CDMA Systems in Frequency-Nonselective Channels

2008 ◽  
Vol 2008 ◽  
pp. 1-5 ◽  
Author(s):  
Adel Omar Dahmane ◽  
Lotfi Mejri
Keyword(s):  
Interference Cancellation ◽  
Multiple Access ◽  
Multiple Access Interference ◽  
Fpga Implementation ◽  
Decision Feedback ◽  
Practical Implementation ◽  
Parallel Interference Cancellation ◽  
Arithmetic Complexity ◽  
Cdma Systems ◽  
Code Division Multiple

Multistage parallel interference cancellation- (MPIC-) based detectors allow to mitigate multiple-access interference in direct-sequence code-division multiple-access (DS-CDMA) systems. They are considered serious candidates for practical implementation showing a good tradeoff between performance and complexity. 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 to MPIC without decision feedback. In this letter, FPGA implementation of block parallel DF-MPIC (BP-DF-MPIC) is proposed allowing better tradeoff between performance and FPGA area occupancy. To reach an uncoded bit-error rate of10−3, BP-DF-MPIC shows a 1.5 dB improvement over the MPIC without decision feedback with only 8% increase in FPGA resources compared to 69% for DF-MPIC.

scholarly journals Suitable Spreading Sequences for Asynchronous MC-CDMA Systems

2018 ◽  
Vol 3 ◽  
pp. 9-13 ◽  
Author(s):  
Mouad Addad ◽  
Ali Djebbari
Keyword(s):  
Communication Systems ◽  
Multiple Access ◽  
Signal To Noise Ratio ◽  
Multiple Access Interference ◽  
High Data ◽  
Research Areas ◽  
Rate Transmission ◽  
Cdma Systems ◽  
Code Division Multiple ◽  
Spreading Sequences

In order to meet the demand of high data rate transmission with good quality maintained, the multi-carrier code division multiple access (MC-CDMA) technology is considered for the next generation wireless communication systems. However, their high crest factor (CF) is one of the major drawbacks of multi-carrier transmission systems. Thus, CF reduction is one of the most important research areas in MC-CDMA systems. In addition, asynchronous MC-CDMA suffers from the effect of multiple access interference (MAI), caused by all users active in the system. Degradation of the system’s bit error rate (BER) caused by MAI must be taken into consideration as well. The aim of this paper is to provide a comparative study on the enhancement of performance of an MC-CDMA system. The spreading sequences used in CDMA play an important role in CF and interference reduction. Hence, spreading sequences should be selected to simultaneously ensure low CF and low BER values. Therefore, the effect that correlation properties of sequences exert on CF values is investigated in this study. Furthermore, a numerical BER evaluation, as a function of the signal-to-noise ratio (SNR) and the number of users, is provided. The results obtained indicate that a trade-off between the two criteria is necessary to ensure good performance. It was concluded that zero correlation zone (ZCZ) sequences are the most suitable spreading sequences as far as the satisfaction of the above criteria is concerned.

scholarly journals Analysis of Multiuser Detectors and Performance improvement in DS-CDMA system using Multistage Multiuser Detection Techniques

2021 ◽  
Author(s):  
Ravindrababu Jaladanki ◽  
Krishnarao Ede ◽  
Raja Rao Yasoda
Keyword(s):  
Computational Complexity ◽  
Multiuser Detection ◽  
System Performance ◽  
Interference Cancellation ◽  
Multiple Access ◽  
Signal Amplitude ◽  
Cdma System ◽  
Parallel Interference Cancellation ◽  
Detection Techniques ◽  
Code Division Multiple

Abstract Among the various interferences, the Multiple Access Interference (MAI) is a significant issue in Direct Sequence Code Division Multiple Access (DS-CDMA) system due to its users. When the number of users is increasing the MAI is likewise increments, subsequently the system performance progressively diminishes particularly in fading environment. In this paper, the system performance is improved by the proposed multistage multiuser detection technique called Multistage Multiuser Differencing Partial Parallel Interference Cancellation (DPPIC). This is the combination of Partial Parallel Interference Cancellation (PPIC) and Differencing Parallel Interference Cancellation (DPIC). Multistage Multiuser Parallel Interference Cancellation (PIC) and Multistage Multiuser PPIC techniques that exist gave improved system performance meaning as the number of stages increases the MAI decreases but at the cost of increased computational complexity. The computational complexity was reduced by utilizing Multistage Difference PIC (DPIC) technique but with no improvement in the performance. To improve the system performance as well as reduce the computational complexity Multistage Multiuser Partial Differencing Parallel Interference Cancellation (PDPIC) method can be used. The simulation results show that the proposed DPPIC technique performs better than PIC, PPIC and PDPIC in terms of Bit Error Rate (BER) versus normalized signal amplitude ( i.e., E b / N 0 ), but computational complexity slightly more than PDPIC in fading environment.

scholarly journals A proposed method for determination of weighted despreading sequences for a DS/CDMA system

2007 ◽  
Vol 3 (3) ◽  
Author(s):  
Younes Jabrane ◽  
Radouane Iqdour ◽  
Brahim Ait Es Said ◽  
Najib Naja
Keyword(s):  
Interference Cancellation ◽  
Fuzzy Systems ◽  
Code Division Multiple Access ◽  
Multiple Access ◽  
Additive White Gaussian Noise ◽  
Multiple Access Interference ◽  
Code Division Multiple ◽  
Parameter Values ◽  
Gaussian Noise Channels

The steeping chip weighting waveforms are used in multiple access interference cancellation by emphasizing the received spreading signal, therefore, that allows to solve the problem of orthogonality for the chip waveforms. Our paper presents a useful method based on fuzzy systems to determine the despreading sequences weighted by the steeping chip weighting waveforms for Direct Sequence Code Division Multiple Access DS/CDMA. The validity of our proposed method has been tested by numerical examples for an Additive White Gaussian Noise channels and shows that the parameter values of the chip weighting waveforms are good and the Bit Error Rate performance of the system does not undergone any degradation.

A Review on Successive Interference Cancellation Scheme Based on Optical CDMA Network

2014 ◽  
Vol 35 (4) ◽  
Author(s):  
N. Alsowaidi ◽  
T. Eltaif ◽  
M. R. Mokhtar
Keyword(s):  
Interference Cancellation ◽  
Multiple Access ◽  
Direct Detection ◽  
Multiple Access Interference ◽  
Successive Interference Cancellation ◽  
Optical Cdma ◽  
Spectral Amplitude ◽  
Cdma System ◽  
Spectral Amplitude Coding ◽  
Code Division Multiple

AbstractDue to various desirable features of optical code division multiple access (OCDMA), it is believed this technique once developed and commercially available will be an integral part of optical access networks. Optical CDMA system suffers from a problem called multiple access interference (MAI) which limits the number of active users, it occurs when number of active users share the same carriers. The aim of this paper is to review successive interference cancellation (SIC) scheme based on optical CDMA system. The paper also reviews the system performance in presence of shot noise, thermal noise, and phase–induced intensity noise (PIIN). A comprehensive review on the mathematical model of SIC scheme using direct detection (DS) and spectral amplitude coding (SAC) were presented in this article.

Blind Multiuser Receivers for Chaos Based Communications

2003 ◽  
Vol 13 (08) ◽  
pp. 2353-2359 ◽  
Author(s):  
Francisco Argüello ◽  
Manuel Bugallo ◽  
Juan López
Keyword(s):  
Communication Systems ◽  
Multiple Access ◽  
Good Deal ◽  
Multiple Access Interference ◽  
Detection Techniques ◽  
Multiuser Receivers ◽  
Cdma Systems ◽  
Blind Receivers ◽  
Code Division Multiple ◽  
The Impact

Recently, there has been a good deal of interest in the use of chaotic signals for direct sequence code division multiple access (DS-CDMA) communication systems. The capacity of DS-CDMA systems is interference-limited, and can therefore be increased by techniques that suppress interference. This letter is devoted to the evaluation of the impact of blind multiuser detection techniques on chaos based DS-CDMA systems. Blind receivers can suppress multiple access interference and do not require knowledge of the code sequences and propagation channels of the interference. We demonstrate that, for chaotic sequence-based communications, blind multiuser receivers significantly improve the BER with respect to single-user receivers, and that their use is practically essential with a high number of users.

Successive Interference Cancellation for DS-Optical PPM-CDMA Systems

2016 ◽  
Vol 37 (2) ◽  
Author(s):  
N. Alsowaidi ◽  
Tawfig Eltaif ◽  
M. R. Mokhtar
Keyword(s):  
Interference Cancellation ◽  
Code Division Multiple Access ◽  
Multiple Access ◽  
Successive Interference Cancellation ◽  
Pulse Position Modulation ◽  
Direct Sequence ◽  
Signature Sequence ◽  
Cdma Systems ◽  
The One ◽  
Code Division Multiple

AbstractIn this paper we introduce a successive interference cancellation (SIC) scheme for direct sequence optical code division multiple access (DS-OCDMA) systems using pulse position modulation (PPM). Considering double-padded modified prime code (DPMPC) as a signature sequence code, results show that the system has better performance in terms of both capacity and bit error rate (BER) as compared to the one without cancellation scheme, where the system with SIC scheme can support up to 88 users while the system without SIC scheme can support only 38 users at similar BER=10

A Review on Successive Interference Cancellation-Based Optical PPM-CDMA Signaling

2017 ◽  
Vol 38 (1) ◽  
Author(s):  
Naif Alsowaidi ◽  
Tawfig Eltaif ◽  
Mohd Ridzuan Mokhtar
Keyword(s):  
Interference Cancellation ◽  
Multiple Access ◽  
Multiple Access Interference ◽  
Successive Interference Cancellation ◽  
Optical Cdma ◽  
Quadratic Congruence ◽  
Random Location ◽  
High Intensity Signal ◽  
Code Division Multiple ◽  
The Impact

AbstractThis paper presents a comprehensive review of successive interference cancellation (SIC) scheme using pulse position modulation (PPM) for optical code division multiple access (OCDMA) systems. SIC scheme focuses on high-intensity signal, which will be selected after all users were detected, and then it will be subtracted from the overall received signal, hence, generating a new received signal. This process continues till all users eliminated one by one have been detected. It is shown that the random location of the sequences due to PPM encoding can reduce the probability of concentrated buildup of the pulse overlap in any one-slot time, and support SIC to easily remove the effect of the strongest signal at each stage of the cancellation process. The system bit error rate (BER) performance with modified quadratic congruence (MQC) codes used as signature sequence has been investigated. A detailed theoretical analysis of proposed system taking into account the impact of imperfect interference cancellation, the loss produced from the splitting during encoding and decoding, the channel loss and multiple access interference is presented. Results show that under average effective power constraint optical CDMA system using SIC scheme with

Performance Analysis of SAC Optical PPM-CDMA System-Based Interference Rejection Technique

2016 ◽  
Vol 37 (1) ◽  
Author(s):  
N. Alsowaidi ◽  
Tawfig Eltaif ◽  
M. R. Mokhtar
Keyword(s):  
Interference Cancellation ◽  
Code Division Multiple Access ◽  
Multiple Access ◽  
Multiple Access Interference ◽  
Spectral Amplitude ◽  
Cdma System ◽  
Pulse Position Modulation ◽  
Interference Rejection ◽  
Spectral Amplitude Coding ◽  
Code Division Multiple

AbstractIn this paper, we aim to theoretically analyse optical code division multiple access (OCDMA) system that based on successive interference cancellation (SIC) using pulse position modulation (PPM), considering the interference between the users, imperfection cancellation occurred during the cancellation process and receiver noises. Spectral amplitude coding (SAC) scheme is used to suppress the overlapping between the users and reduce the receiver noises effect. The theoretical analysis of the multiple access interference (MAI)-limited performance of this approach indicates the influence of the size of

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