Loading...
Search for:
optical-cdma
0.006 seconds
Total 26 records
The effect of pulse shaping on the performance of non-directed wireless infrareD OOK-CDMA systems
, Article 13th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2002, Lisboa, 15 September 2002 through 18 September 2002 ; Volume 5 , 2002 , Pages 2067-2071 ; 0780375890 (ISBN); 9780780375895 (ISBN) ; Salehi, J. A ; Sbahabadi, M ; Sharif University of Technology
2002
Abstract
In this paper we propose the use of pulse shaping for mitigating the effect of channel distortion on the performance of indoor wireless infrared (IR) CDMA systems. The bit error rate (BER) performance of an on-off keying (OOK)-CDMA system as a function of the average transmitted power is investigate& To this end, photon-counting model is utilized and major noises such as shot noise, ambient light, dark current, and receiver thermal noise are taken into consideration. It is shown that using appropriate pulse shapes, the system performance will be improved and the required transmitter power will be reduced. ©2002 IEEE
Temporal/spatial fiber-optic CDMA systems with post- and pre-optical amplification
, Article IEEE Transactions on Communications ; Volume 50, Issue 10 , 2002 , Pages 1688-1695 ; 00906778 (ISSN) ; Salehi, J. A ; Sharif University of Technology
2002
Abstract
In this paper, we present a thorough analysis based on photon-counting techniques on temporal/spatial fiber-optic code-division multiple-access systems incorporating both post- and pre-optical amplifiers. In this analysis, we consider the effect of shot noise, thermal noise, and source extinction on system bit-error rate. Our results can be used to estimate the maximum tolerable amount of quantum fluctuations in the received signal
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....
Multiple-shift code acquisition of optical orthogonal codes in optical CDMA systems
, Article IEEE Transactions on Communications ; Vol. 53, No. 4, PP. 687-697, April 2005 ; Salehi, J. A ; Sharif University Of Technology
Abstract
In this paper, we introduce a new and advanced algorithm, namely, multiple-shift algorithm for code acquisition in optical code-division multiple access (CDMA) systems using unipolar optical orthogonal codes (OOCs) as signature sequences. We analyze the performance of the newly proposed algorithm and obtain a bound on its performance and show its advantage in reducing the mean time of synchronization when compared with other synchronization methods. The algorithm can be used with many different receiver structures, like active or passive correlator with or without hardlimiter(s). However, in this paper, we only consider the simple active correlator structure for further discussions and...
Optical orthogonal code acquisition in fiber-optic CDMA systems via the simple serial-search method
, Article IEEE Transactions on Communications ; Volume 50, Issue 3 , 2002 , Pages 473-483 ; 00906778 (ISSN) ; Salehi, J. A ; Sharif University of Technology
2002
Abstract
In this paper, we analyze, for the first time, the performance of a serial-search algorithm for optical code-division multiple access (CDMA) systems using optical orthogonal codes (OOC). For our analysis, we use advance photon-counting methods and we consider the effect of shot noise and dark current and multi-access interference (MAI). We introduce a new method for modeling the effect of MAI, then we use two approaches to consider this effect on the performance of the synchronization system. For the first approach, we consider the average effect of interference in our analysis, while for the second approach two specific forms of interference are taken into account where one form represents...
Cellular underwater wireless optical CDMA network: potentials and challenges
, Article IEEE Access ; Volume 4 , 2016 , Pages 4254-4268 ; 21693536 (ISSN) ; Jamali, M. V ; Bani Hassan, N ; Beyranvand, H ; Minoofar, A ; Salehi, J. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
Underwater wireless optical communications are an emerging solution to the expanding demand for broadband links in oceans and seas. In this paper, a cellular underwater wireless optical code division multiple-access network is proposed to provide broadband links for commercial and military applications. The optical orthogonal codes are employed as signature codes of underwater mobile users. Fundamental key aspects of the network, such as its backhaul architecture, its potential applications, and its design challenges, are presented. In particular, a promising underwater localization and positioning scheme based on this cellular network is presented. Furthermore, the proposed network is used...
Statistical analysis of fiber-optic CDMA communication systems - Part I: Device modeling
, Article Journal of Lightwave Technology ; Volume 20, Issue 8 , 2002 , Pages 1304-1316 ; 07338724 (ISSN) ; Salehi, J. A ; Sharif University of Technology
2002
Abstract
In this paper, we present a new methodology for analysis of all-optical fiber-optic code-division multiple-access (FO-CDMA) networks. In this analysis, we propose statistical models, based on photon-counting techniques, for some basic elements of the network, such as splitters, combiners, star couplers, and FO-CDMA passive encoders/decoders. By following the statistical variation of the photon-count of the string of pulses that constitutes the address sequence in an FO-CDMA network, we will be able to reveal the quantum-limited optical signal-to-noise ratio (OSNR) required at the transmitter output to meet the performance limits. Moreover, considering receiver thermal noise and source...
Statistical analysis of fiber-optic CDMA communication systems - Part II: Incorporating multiple optical amplifiers
, Article Journal of Lightwave Technology ; Volume 20, Issue 8 , 2002 , Pages 1317-1328 ; 07338724 (ISSN) ; Salehi, J. A ; Sharif University of Technology
2002
Abstract
In this paper, we study and elaborate on the architectural consideration of using multiple optical amplifiers in an all-optical fiber-optic code-division multiple-access (FO-CDMA) network. Our study and considerations are based on obtaining the statistical characteristic functions for photon-counts of a string of output pulses that constitutes the address code in a FO-CDMA network. Optical orthogonal codes (OOCs) with minimum auto- and cross correlation are employed as the address or signature sequence codes. Our analysis is based on chip-synchronous interference only, which provides an upper bound on the system performance. Shot noise, thermal noise, and extinction ratio are considered in...
Low-rate super-orthogonal channel coding for fiber-optic CDMA communication systems
, Article Journal of Lightwave Technology ; Volume 19, Issue 6 , 2001 , Pages 847-855 ; 07338724 (ISSN) ; Nasiri Kenari, M ; Salehi, J. A ; Sharif University of Technology
2001
Abstract
In this paper, we consider using practical low-rate error correcting codes in fiber-optic code division multiple-access (CDMA) communication systems. To this end, a different method of low-rate channel coding is proposed. As opposed to the conventional coding schemes, this method does not require any further bandwidth expansion for error correction in fiber-optic CDMA communication systems. The low-rate channel codes that are used for demonstrating the capabilities of the proposed method are super-orthogonal codes. These codes are near optimal and have a relatively low complexity. We evaluate the upper bounds on the bit-error probability of the proposed coded fiber-optic CDMA system assuming...
Performance analysis of spectral-phase-encoded optical CDMA system using two-photon-absorption receiver structure for asynchronous and slot-level synchronous transmitters
, Article Journal of Lightwave Technology ; 2007, Volume 25, Issue 6, Pages 1638-1645 ; Salehi, J. A ; Sharif University Of Technology
Abstract
In this paper, we analyze the performance of a nonlinear two-photon-absorption (TPA) receiver and compare its performance with that of a single-photon-absorption (SPA) receiver in the context of spectral-phase-encoded optical code-division multiple access (CDMA) technique. The performances for the above systems are evaluated for two different transmission scenarios, namely, asynchronous and slot-level synchronous transmitters. Performance evaluation includes different sources of degradation such as multiple-access interference, noise due to optical amplification, shot noise, and thermal noise. In obtaining the performance, the mean and variance of the received signal in each of the above...
Two-level OOC-based fiber-optic CDMA systems with QoS using optical Analog-Digital Converter (ADC)
, Article 2009 Asia Communications and Photonics Conference and Exhibition, ACP 2009, 2 November 2009 through 6 November 2009, Shanghai ; 2009 ; 9781557528773 (ISBN) ; Salehi, J. A ; Sharif University of Technology
Abstract
A novel two-level signaling technique in OOC-based fiber-optic CDMA systems is proposed. The users of the system are categorized into two classes. Users of class 1 and 2 transmit the optical pulses at power level P and 2P respectively. At the receiver side using optical ADC multi-access interference is considerably suppressed. © 2009 OSA/ACP
Two-level OOC-based fiber-optic CDMA systems with QoS using optical analog-digital converter (ADC)
, Article 2009 Asia Communications and Photonics Conference and Exhibition, ACP 2009 ; 2-6 November , 2009 ; 21622701 (ISSN) ; 9781557528773 (ISBN) ; Salehi, J. A ; Sharif University of Technology
Optical Society of America
2009
Abstract
A novel two-level signaling technique in OOC-based fiber-optic CDMA systems is proposed. The users of the system are categorized into two classes. Users of class 1 and 2 transmit the optical pulses at power level P and 2P respectively. At the receiver side using optical ADC multi-access interference is considerably suppressed. © 2009 OSA
Two-level OOC-based fiber-optic CDMA systems with QoS using optical analog-digital converter (ADC)
, Article Proceedings of SPIE - The International Society for Optical Engineering, 2 November 2009 through 6 November 2009, Shanghai ; Volume 7632 , 2009 ; 0277786X (ISSN) ; 9780819480347 (ISBN) ; Salehi, J. A ; Sharif University of Technology
Abstract
A novel two-level signaling technique in OOC-based fiber-optic CDMA systems is proposed. Users of the system are categorized into two classes. Users of class 1 and 2 transmit the optical pulses at power level P and 2P respectively. We study two kinds of receiver structure for the proposed two-level system. For the first structure we use ordinary AND logic gate and for the second one we use optical ADC with AND logic gate structure. We obtain the system performance and we show that for the two-level signaling multi-access interference is considerably suppressed. Two-level signaling increase system performance and capacity and also presents different QoS for the users in two classes. © 2009...
Comparison of AIr and IEEE 802.11 with optical CDMA in wireless infrared communication
, Article 2008 International Conference on Telecommunications, ICT, St. Petersburg, 16 June 2008 through 19 June 2008 ; October , 2008 ; 9781424420360 (ISBN) ; Pakravan, M. R ; Sharif University of Technology
2008
Abstract
Optical Code Division Multiple Access has recently received considerable attention in wireless infrared communication. Previously introduced algorithms for wireless indoor infrared communication such as Advanced Infrared and IEEE 802.11 infrared standard use specific media access control (MAC) layer algorithms to coordinate transmission of multiple users. In this paper, we compare the multiple access performance of OCDMA with that of these algorithms and demonstrate the relative strengths and weaknesses of each algorithm. It is demonstrated that when MAC delay is an important issue, OCDMA provides a much better performance. Furthermore, OCDMA requires no coordination between users as they...
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...
Interference cancellation in overloaded optical CDMA systems using unipolar walsh codes
, Article 2013 20th International Conference on Telecommunications, ICT 2013 ; May , 2013 , Page(s): 1 - 5 ; Sedaghat, M. A ; Marvasti, F ; Ghassemian, M ; Sharif University of Technology
IEEE Computer Society
2013
Abstract
In this article, the authors introduce and propose an overloaded Synchronous Optical Code Division Multiple Access (SOCDMA) based on Unipolar Walsh Code (UWC) for fiberoptic communication systems. Given μ as the number of chips, it is shown that 2L - 2 active users can be supported by the proposed system. In this system the users of the network are categorized into two groups. Users of each group transmit at the same power level but different from the level of the other group's users. Using the UWC properties we propose a simple receiver that cancels multiple-user interference (MUI) completely. Moreover, we obtain the optimal power level of each group in order to minimize the probability of...
Interference cancellation in optical CDMA systems via advanced binary optical logic gate elements
, Article IEEE Communications Magazine ; Volume 50, Issue 8 , 2012 , Pages 96-101 ; 01636804 (ISSN) ; Marvasti, F ; Ghaffari, B. M ; Salehi, J. A ; Sharif University of Technology
2012
Abstract
In this article we present an all passive optical iterative interference cancellation method for optical CDMA. We propose the receiver structure based on advanced binary optical logic gates (ABOLGs). Since the performance bottleneck in optical communication systems is the conversion from optical to electronic domains for optical detectors, the interference cancellation has been performed in the optical domain. In incoherent optical communication systems, we have only the positive values for the optical signals. In the proposed system, we bypass the negative values using logic arrays. In the simulations we consider multiple access interference and neglect other sources of noise. Simulation...
An internally coded TH/OCDMA scheme for fiber optic communication systems and its performance analysis - Part II: Using frame time hopping code
, Article IEEE Transactions on Communications ; Volume 57, Issue 1 , 2009 , Pages 50-55 ; 00906778 (ISSN) ; Nasiri Kenari, M ; Sharif University of Technology
2009
Abstract
In Part I, a new internally coded time hoping optical code division multiple access (TH/OCDMA) scheme for fiber optic communication systems has been proposed and its multiple access performance has been evaluated using optical orthogonal code (OOC). Due to low cardinality of OOCs with a correlation value of 1, the capability of the proposed scheme could not be utilized effectively for an increasing number of simultaneous users. In this part, we consider applying the internally coded technique introduced in part one to the frame time hopping/OCDMA scheme. We evaluate the multiple access performance of the system for the three detectors introduced in Part I. Our results demonstrate the...
Performance analysis of internally coded time-hopping coherent ultrashort light pulse CDMA scheme in fiber-optic communication systems
, Article Journal of Lightwave Technology ; Volume 25, Issue 4 , 2007 , Pages 1095-1106 ; 07338724 (ISSN) ; Aghajanzadeh, S. M ; Nasiri Kenari, M ; Karimi, M ; Sharif University of Technology
2007
Abstract
We consider an internally coded time-hopping coherent ultrashort light pulse code division multiple access scheme (TH-CULP CDMA) and analyze its performance in the fiber-optic communication systems. This system combines the TH and CULP CDMA techniques and exploits the advantages of both. In our method, each bit time interval is divided into Ns frames, and the spectral phase-coded pulse is transmitted in one of these frames. Two exclusive PN sequences are assigned to each user. One is added to a superorthogonal convolutional encoder output to select the transmission frame, and the other is used to encode the phase of the ultrashort pulse in the spectral domain. We evaluate the bit error rate...
Performance analysis of slotted ALOHA random access packet-switching optical CDMA networks using generalized optical orthogonal codes and M-ary overlapping PPM signaling
, Article Journal of Optical Communications and Networking ; Volume 3, Issue 7 , July , 2011 , Pages 568-576 ; 19430620 (ISSN) ; Khazraei, S ; Pakravan, M. R ; Sharif University of Technology
2011
Abstract
In this paper we study slotted ALOHA random access optical code division multiple access packet-switching networks with a chip-level receiver structure. We use generalized optical orthogonal codes (GOOCs) and the overlapping pulse position modulation (OPPM) signaling technique to improve system performance. The impact of physical layer parameters such as the GOOC cross-correlation value and the OPPM overlapping index on key performance benchmarks such as network throughput and delay are analyzed. We also study the stability of the network based on the number of backlogged users, using the expected state drift. It has been shown that using GOOC instead of strict optical orthogonal codes...