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Wireless optical CDMA lAN: digital design concepts [electronic resource]
, Article IEEE Transaction on Communication ; Vol. 56, No. 12, PP. 2145-2155, December 2008 ; Matinfar, M ; Salehi, J. A ; Sharif University of Technology
Abstract
In this paper we study and present an in-depth analysis on the operability and the viability of a typical wireless optical CDMA (OCDMA) local area network. Three receiver structures for OCDMA systems, using optical orthogonal codes (OOC) with minimum auto and cross-correlations as signature sequence, namely, correlation, correlation with hard-limiter, and chip-level detection are studied and proposed for such a network. For the synchronization circuit design the performance of two algorithms for OOC based OCDMA networks, namely, simple serial-search and multiple-shift in the context of wireless OCDMA LAN are studied. Furthermore, we study a synchronization method based on matched filtering...
Atmospheric optical CDMA via optical orthogonal codes
, Article IEEE Transactions on Communication ; Vol.54, No.9, PP. 1614-1623, September 2006 ; Salehi, J. A ; Sharif University Of Technology
Abstract
We propose and consider using a class of multiple-access sequences, namely, optical orthogonal codes (OOCs) in atmospheric optical code-division multiple-access systems. We obtain analytical solutions to the error probability for various channel models using positive-intrinsic-negative diode and avalanche photodiode photodetectors. In our analysis, the effects of atmospheric turbulence, ambient light, thermal noise, and multiuser interference are considered, in the context of a semiclassical photon-counting approach. The performance of the systems taking advantage of space diversity and error-correcting codes are also evaluated. Two common and widely used optical modulations, on-off keying...
Multiclass, multistage, and multilevel fiber-optic CDMA signaling techniques based on advanced binary optical logic gate elements
, Article IEEE Transactions on Communications ; Volume 57, Issue 5, 2009, Pages 1424-1432 ; Salehi, J. A ; Sharif University Of Technology
Abstract
In this paper we introduce and propose novel signaling methods and receiver structures based on advanced binary optical logic gates for fiber-optic code division multiple access (FO-CDMA) systems using all-optical signal processing. In the proposed system the users of the network are categorized into multiple classes. Users of each class transmit at the same power level but different from the levels of the other classes' users. Using a combination of optical OR, AND and XNOR logic gates for the receiver structure we show that such a network not only takes the full advantages of all-optical signal processing but also demonstrates a considerable throughput efficiency when compared to ordinary...
Statistical analysis of coherent ultrashort light pulse CDMA with multiple optical amplifiers using additive noise model
, Article IEEE/OSA Journal of Lightwave Technology ; Vol. 23, No. 5, PP. 1842-1851, May 2005 ; Salehi, J. A ; Sharif University Of Technology
Abstract
This paper describes a study of the performance of various configurations for placing multiple optical amplifiers in a typical coherent ultrashort light pulse code-division multiple access (CULP-CDMA) communication system using the additive noise model. For this study, a comprehensive performance analysis was developed that takes into account multiple-access noise, noise due to optical amplifiers, and thermal noise using the saddle-point approximation technique. Prior to obtaining the overall system performance, the input/output statistical models for different elements of the system such as encoders/decoders, star coupler, and optical amplifiers were obtained. Performance comparisons...
Emerging OCDMA communication systems and data networks [electronic resource]
, Article Journal of Optical Networking ; Volume 6, Issue 9, 1 September 2007, Pages 1138-1178 ; Sharif University Of Technology
Abstract
I present an in-depth review of the trends and the directions taken by researchers worldwide in optical code-division multiple-access (OCDMA) systems. I highlight those trends and features that I believe are essential to the successful introduction of various OCDMA techniques in communication systems and data networks in the near future. In particular I begin by giving a comprehensive review of the construction of optical orthogonal codes (OOCs). Specifically I discuss the recently developed algorithms that are based on matrix algebra, which simplify and enhance the efficiencies of algorithms in OOC generation. In communication systems studies I first focus on and discuss various OCDMA...
Performance analysis of optically bistable thresholders in optical code division multiple access networks
, Article ICONO 2007: Coherent and Nonlinear Optical Phenomena, Minsk, 28 May 2007 through 1 June 2007 ; Volume 6729 , 2007 ; 0277786X (ISSN) ; 081946886X (ISBN); 9780819468864 (ISBN) ; Mehrany, K ; Salehi, J. A ; Rashidian, B ; Sharif University of Technology
2007
Abstract
Optical code division multiple access (OCDMA) is a promising multiple-access technique for future all optical networks. In this manuscript, the usefulness of exploiting bistable optical elements as threshold devices in coherent OCDMA systems is analytically investigated, in which the bistability effect is modeled by a simple square loop
Performance characterization of Relay-Assisted Wireless Optical CDMA Networks in Turbulent Underwater Channel
, Article IEEE Transactions on Wireless Communications ; Volume 15, Issue 6 , 2016 , Pages 4104-4116 ; 15361276 (ISSN) ; Akhoundi, F ; Salehi, J. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
Abstract
In this paper, we characterize the performance of relay-assisted underwater wireless optical code division multiple access (OCDMA) networks over turbulent channels. In addition to scattering and absorption effects of underwater channels, we also consider optical turbulence as a log-normal fading coefficient in our analysis. To simultaneously and asynchronously share medium among many users, we assign a unique optical orthogonal code (OOC) to each user in order to actualize OCDMA-based underwater network. The most significant challenge in underwater optical communication is in the ability to extend the short range of its coverage. In order to expand the viable communication range, we consider...
Digital Design and Implementation of a Multilevel OCDMA System
, M.Sc. Thesis Sharif University of Technology ; Salehi, Javad (Supervisor)
Abstract
Optical Wireless Communication is believed to have a great potential in establishing point to point connection and have attracted an unexpected growth in research , applications and market. Furthermore, Optical wireless systems have recently emerged as a new means of communication, especially in places where electromagnetic interferences is of utmost concern such as in passenger planes and hospitals and in other communications applications where cost could is of concern. In this thesis we build upon previously introduced wireless optical code-division multiple –access communication. In the context of an OCDMA system we begin our study by considering synchronization circuit via a...
Design and Quality of Service Improvement in Optical Code Division Multiple Access Networks
, M.Sc. Thesis Sharif University of Technology ; Pakravan, Mohammad Reza (Supervisor)
Abstract
Considering the advantages of optical communications and code division multiple access technique, Optical Code Division Multiple Access Networks (OCDMANs) was introduced. Thence, many researchers have suggested methods for creating Quality of Service (QoS) differentiated classes in OCDMANs. In this thesis, we have comprehensive review on the QoS assignment methods and enhance them by offering new techniques. In physical layer, we concentrate on variable chip rate OCDMANs and in MAC sub-layer, a new algorithm named Adaptive Level Control (ALC) is introduced. Then, we focus on the physical design of OCDMANs. Firstly, we solve the problem of one-class OCDMAN and introduce few simple and...
Performance of CULP-CDMA Receivers Based on Four Wave Mixers
, M.Sc. Thesis Sharif University of Technology ; Salehi, Javad (Supervisor)
Abstract
In this thesis the performance of the all optical AND gates, based the Four Wave Mixing process (FWM), for application in optical communication and computing systems, has been investigated. In the performance analysis of these AND gates, we mainly focus on its application in the receivers of the Optical Code Division Multiple Access (OCDMA) systems. For analyzing the performance of these receivers we utilize the existing mathematical model for FWM [1-5], which leads to the nonlinear Schrodinger (NLS) coupled equations. The attenuation, chromatic dispersion and Raman scattering effects have been taken into account in this model and the scalar approximation, for approximating the relation...
Design of Volume Holographic Code Division Multiple Access (CDMA) Systems
, M.Sc. Thesis Sharif University of Technology ; Salehi, Javad (Supervisor)
Abstract
The amount of assigned computation to data centers, which generally process data streams in a parallel manner has grown in recent years. Switches are one of the most important components in such centers, and their appropriate design can reduce the power loss and increase the processing gain. Among such devices, holographic CDMA switches, which exploit the high storage capability of thin holograms to reduce the size of switches, are suitable alternatives to the traditional electronic switches. In this research, the fairly high power loss of such switches has significantly decreased by modifying the output filter. This modification includes two steps. In the first, the typical matched filter...
Multi-Service Provisioning and Quality of Service (QoS) Guarantee in Optical Code Switched GMPLS Core Networks
, M.Sc. Thesis Sharif University of Technology ; Salehi, Javad (Supervisor)
Abstract
The growth of the word wide Internet causes to increase the request of subscribers for various applications of multimedia which having different traffic characteristics. In order to provide such applications which generate divers data traffic with different transmission rate and quality of service, we need to design a network supporting multi-rate and multi-quality (multi-service) transmission. In this study we present two schemes to support multi-service transmission in generalized multi-protocol label switched (GMPLS) core networks. In the first scheme we use multi-length variable-weight optical orthogonal codes (MLVW-OOC) as signature sequences of optical code division multiplexing system...
Multiuser Interference Mitigation for Performance Enhancement in OCDMA and OFDMA Systems
, Ph.D. Dissertation Sharif University of Technology ; Marvasti, Farokh (Supervisor)
Abstract
Due to the extremely fast growth in high speed data rate demand in the recent years, it is necessary to make use of the optical technologies in telecommunication access networks. Passive optical networks (PONs) has got much attention compared to other optical access architectures due to some advantages such as low installation and maintenance expenses, and providing more reliable network transmission.
In this thesis, we will study two multiple access techniques, namely optical code division multiple access (OCDMA) and optical orthogonal frequency division multiple access (OOFDMA). Since the system performance of these techniques are mainly limited by multiple access interference, we...
In this thesis, we will study two multiple access techniques, namely optical code division multiple access (OCDMA) and optical orthogonal frequency division multiple access (OOFDMA). Since the system performance of these techniques are mainly limited by multiple access interference, we...
Achievable Rates in CDMA and OFDM Based Optical Networks
, M.Sc. Thesis Sharif University of Technology ; Salehi, Jawad (Supervisor)
Abstract
Regarding the increasing trend of network costumers and services, requirement of high-speed and high quality seems to be inevitable. Therefor much effort has been put to issue the problem properly in recent years. Optical fiber networks are attending more attention and optical fiber channels are dominating the world of networking and data. Applying new methods such as CDMA and OFDM raise the issue of maximum achievable rate and quality of these systems.These include the main concentration of this project. First, optical channels are modeled.Then, applying OFDM and CDMA methods, lower and upper bound of channel capacity will be determined
Multirate, differentiated QOS, and multilevel fiber-optic CDMA system via optical logic gate elements
, Article IEEE Journal of Lightwave Technology ; Vol. 27, No. 19 , 1 October , 2009 , PP. 4348-4359 ; 0733-8724 ; Ghaffari, B. M ; Salehi, J. A ; Sharif University of Technology
Abstract
In this paper, we present a novel multirate, differentiated quality of service (QoS) optical CDMA (OCDMA) system using multilevel signaling technique. The emphasis is on OCDMA systems employing multi-length variable-weight optical orthogonal codes (MLVW-OOC) as signature sequence. We begin by presenting a two-class variable-weight OCDMA system in which all users have the same energy level in one bit duration. As a consequence, high weight users transmit their corresponding optical pulses at a lower power while low weight users transmit their corresponding optical pulses at a higher power level. We show that using this multilevel signaling technique, while employing the well known optical AND...
Adaptive level control to improve QoS in OCDMA local area networks
, Article 2013 21st Iranian Conference on Electrical Engineering ; May , 2013 , Page(s): 1 - 5 ; 9781467356343 (ISBN) ; Pakravan, M. R ; Sharif University of Technology
2013
Abstract
In this paper, we propose a new method for creating more distinguishable QoS levels in OCDMA networks. The key idea behind the proposed scheme is to adaptively control the transmit power level in each chip based on OCDMA channel state. The structure of the transmitter and receiver are proposed. We provide performance analysis of the recommended scheme and show that it can reduce the system BER and provide better QoS differentiation in a multiclass network. We provide simulation results and demonstrate that they have a good match with the results obtained from mathematical analysis
Theoretical Studies of Ultrashort Light Pulse Spectrally-Phase-Encoded OCDMA System Using Power-Cubic Optical Nonlinear Preprocessor
, Article Journal of Lightwave Technology ; Volume 33, Issue 24 , October , 2015 , Pages 5062-5072 ; 07338724 (ISSN) ; Salehi, J. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
In this paper, a spectral-phase-encoded ultrashort light pulse optical code division multiple access (SPE-OCDMA) system employing a novel nonlinear power-cubic optical preprocessor at its receiver's front end is theoretically investigated. The system's mathematical model and the statistical distribution of the decision variable Y, prior to the decision module of the receiver, are discussed. The first three moments of the random decision variable Y are obtained in the context of the above OCDMA system and subsequently used in an appropriate Log-Pearson type 3 (LP3) distribution to represent the random decision variable $Y$. Multiple access interference (MAI) and amplified spontaneous emission...
Code family for modified spectral-amplitude-coding OCDMA systems and performance analysis
, Article Journal of Optical Communications and Networking ; Volume 2, Issue 6 , May , 2010 , Pages 344-354 ; 19430620 (ISSN) ; Jamshidi, K ; Sharif University of Technology
2010
Abstract
A novel family of codes for modified spectral-amplitude-coding optical code division multiple access (SAC-OCDMA) is introduced. The proposed codes exist for more processing gains than the previously reported codes do. In the network using these codes, the number of users can be extended without any essential changes in the previous transmitters. In this study, we propose a construction method for these codes and compare their performance with previously reported codes
Wireless optical CDMA LAN: digital implementation analysis
, Article IEEE Journal on Selected Areas in Communications ; Volume 27, Issue 9 , 2009 , Pages 1676-1686 ; 07338716 (ISSN) ; Matinfar, M. D ; Salehi, J. A ; Sharif University of Technology
Abstract
In this paper we present and investigate a digital design and implementational details of a wireless optical CDMA (OCDMA) system based on generalized optical orthogonal codes (OOCs). A detailed digital implementation analysis and transmitter/receiver architectures in the context of the above design are fully studied. We analyze various subsystems for a wireless OCDMA system including detector and receiver structure, acquisition, and tracking blocks as well as evaluating their performance in a typical wireless OCDMA communication system. By analyzing two main parts of the system, namely, chip-level detector and OCDMA receiver blocks we evaluate the performance of the overall system....
Multirate, differentiated-qoS, and multilevel fiber-optic CDMA system via optical logic gate elements
, Article Journal of Lightwave Technology ; Volume 27, Issue 19 , 2009 , Pages 4348-4359 ; 07338724 (ISSN) ; Ghaffari, B. M ; Salehi, J. A ; Sharif University of Technology
2009
Abstract
In this paper, we present a novel multirate, differentiated quality of service (QoS) optical CDMA (OCDMA) system using multilevel signaling technique. The emphasis is on OCDMA systems employing multi-length variable-weight optical orthogonal codes (MLVW-OOC) as signature sequence. We begin by presenting a two-class variable-weight OCDMA system in which all users have the same energy level in one bit duration. As a consequence, high weight users transmit their corresponding optical pulses at a lower power while low weight users transmit their corresponding optical pulses at a higher power level. We show that using this multilevel signaling technique, while employing the well known optical AND...