Hossam M. H. Shalaby

Bio: Hossam M. H. Shalaby is an academic researcher from Alexandria University. The author has contributed to research in topics: Code division multiple access & Pulse-position modulation. The author has an hindex of 23, co-authored 246 publications receiving 2578 citations. Previous affiliations of Hossam M. H. Shalaby include Laval University & International Islamic University Malaysia.

Modified quadratic congruence codes for fiber Bragg-grating-based spectral-amplitude-coding optical CDMA systems

Abstract: We have constructed a series of new code families for the spectral-amplitude-coding optical code-division multiple-access (CDMA) system, and proposed new transmitter and receiver structures based on tunable chirped fiber Bragg gratings (FBGs). The proposed system has been analyzed by taking into account the effects of phase-induced intensity noise, shot noise, and thermal noise. We have also compared the performance of this system with that of a former system where a Hadamard code is used. It has been shown that the new code families can suppress the intensity noise effectively and improve the system performance significantly. When the effective power is large (i.e., >-10 dBm), the intensity noise is the main factor that limits the system performance. When the effective power is not sufficiently large, thermal and shot noise sources become the main limiting factors and the effect of thermal noise is much larger than that of shot noise.

Chip-level detection in optical code division multiple access

Abstract: A new detector for optical code-division multiple-access (CDMA) communication systems is proposed. This detector is called the chip-level receiver. Both ON-OFF keying (OOK) and pulse-position modulation (PPM) schemes, that utilize this receiver, are investigated in this paper. For OOK, an exact bit error rate is evaluated taking into account the effect of both multiple-user interference and receiver shot noise. An upper bound on the bit error probability for pulse-position modulation (PPM)-CDMA system is derived under the above considerations. The effect of both dark current and thermal noises is neglected in our analysis. Performance comparisons between chip-level, correlation, and optimum receivers are also presented. Both correlation receivers with and without an optical hardlimiter are considered. Our results demonstrate that significant improvement in the performance is gained when using the chip-level receiver in place of the correlation one. Moreover the performance of the chip-level receiver is asymptotically close to the optimum one. Nevertheless, the complexity of this receiver is independent of the number of users, and therefore, much more practical than the optimum receiver.

Performance analysis of optical synchronous CDMA communication systems with PPM signaling

Abstract: Direct-detection optical synchronous code-division multiple-access (CDMA) systems with M-ary pulse-position modulation (PPM) signaling are investigated. Optical orthogonal codes are used as the signature sequences of our system. A union upper bound on the bit error rate is derived taking into account the effect of the background noise, multiple-user interference, and receiver shot noise. The performance characteristics are then discussed for a variety of system parameters. Another upper bound on the probability of error is also obtained (based on Chernoff inequality). This bound is utilized to derive achievable expressions for both the maximum number of users that can communicate simultaneously with asymptotically zero error rate and the channel capacity. Our results show that under average power and bit error rate constraints, there always exists a pulse position multiplicity that permit all the subscribers to communicate simultaneously. >

Multirate optical fast frequency hopping CDMA system using power control

Abstract: This paper addresses the problem of real-time multimedia transmission in fiber-optic networks using code division multiple access (CDMA). We present a multirate optical fast frequency hopping CDMA (OFFH-CDMA) system architecture using fiber Bragg gratings (FBGs). In addition, we argue that, in multimedia applications, different services have different quality of service (QoS) requirements; hence, the user only needs to use the minimum required power to transmit the signal, such that the required signal-to-interference ratio (SIR) is met. We show that a variable bit rate optical communication system with variable QoS can be implemented by way of power control with great efficiency. Present-day multirate optical CDMA systems concentrate on finding the code structure that supports a variable rate system, neglecting the importance of the transmission power of active users on the multiple access interference (MAI) and, therefore, on the system capacity. We assign different power levels to each rate through a power control algorithm using variable optical attenuators, which minimizes the interference and, at the same time, provides variable QoS constraints for different traffic types. Although we are using a code family that preserves good correlation properties between codes of different lengths, simulations show a great improvement in the system capacity when power control is used.

New code families for fiber-Bragg-grating-based spectral-amplitude-coding optical CDMA systems

Abstract: A series of new code families are constructed for spectral-amplitude-coding optical code division multiple access (CDMA) systems. Then structures of both the transmitter and the receiver in such a system are also proposed based on tunable chirped fiber Bragg gratings. Our analysis shows that the proposed new code families can suppress the intensity noise effectively and, hence, improve the overall system performance.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Table Of Integrals Series And Products

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Fundamentals of Queueing Theory

Abstract: Praise for the Third Edition: "This is one of the best books available. Its excellent organizational structure allows quick reference to specific models and its clear presentation . . . solidifies the understanding of the concepts being presented."IIE Transactions on Operations EngineeringThoroughly revised and expanded to reflect the latest developments in the field, Fundamentals of Queueing Theory, Fourth Edition continues to present the basic statistical principles that are necessary to analyze the probabilistic nature of queues. Rather than presenting a narrow focus on the subject, this update illustrates the wide-reaching, fundamental concepts in queueing theory and its applications to diverse areas such as computer science, engineering, business, and operations research.This update takes a numerical approach to understanding and making probable estimations relating to queues, with a comprehensive outline of simple and more advanced queueing models. Newly featured topics of the Fourth Edition include:Retrial queuesApproximations for queueing networksNumerical inversion of transformsDetermining the appropriate number of servers to balance quality and cost of serviceEach chapter provides a self-contained presentation of key concepts and formulae, allowing readers to work with each section independently, while a summary table at the end of the book outlines the types of queues that have been discussed and their results. In addition, two new appendices have been added, discussing transforms and generating functions as well as the fundamentals of differential and difference equations. New examples are now included along with problems that incorporate QtsPlus software, which is freely available via the book's related Web site.With its accessible style and wealth of real-world examples, Fundamentals of Queueing Theory, Fourth Edition is an ideal book for courses on queueing theory at the upper-undergraduate and graduate levels. It is also a valuable resource for researchers and practitioners who analyze congestion in the fields of telecommunications, transportation, aviation, and management science.

Survey on Free Space Optical Communication: A Communication Theory Perspective

Abstract: Optical wireless communication (OWC) refers to transmission in unguided propagation media through the use of optical carriers, i.e., visible, infrared (IR), and ultraviolet (UV) bands. In this survey, we focus on outdoor terrestrial OWC links which operate in near IR band. These are widely referred to as free space optical (FSO) communication in the literature. FSO systems are used for high rate communication between two fixed points over distances up to several kilometers. In comparison to radio-frequency (RF) counterparts, FSO links have a very high optical bandwidth available, allowing much higher data rates. They are appealing for a wide range of applications such as metropolitan area network (MAN) extension, local area network (LAN)-to-LAN connectivity, fiber back-up, backhaul for wireless cellular networks, disaster recovery, high definition TV and medical image/video transmission, wireless video surveillance/monitoring, and quantum key distribution among others. Despite the major advantages of FSO technology and variety of its application areas, its widespread use has been hampered by its rather disappointing link reliability particularly in long ranges due to atmospheric turbulence-induced fading and sensitivity to weather conditions. In the last five years or so, there has been a surge of interest in FSO research to address these major technical challenges. Several innovative physical layer concepts, originally introduced in the context of RF systems, such as multiple-input multiple-output communication, cooperative diversity, and adaptive transmission have been recently explored for the design of next generation FSO systems. In this paper, we present an up-to-date survey on FSO communication systems. The first part describes FSO channel models and transmitter/receiver structures. In the second part, we provide details on information theoretical limits of FSO channels and algorithmic-level system design research activities to approach these limits. Specific topics include advances in modulation, channel coding, spatial/cooperative diversity techniques, adaptive transmission, and hybrid RF/FSO systems.