Ibrahim Habib - Academia.edu (original) (raw)

Papers by Ibrahim Habib

Ieee Transactions on Wireless Communications, Sep 1, 2009

The demand for high-speed services and multimedia applications anywhere and anytime has led to th... more The demand for high-speed services and multimedia applications anywhere and anytime has led to the rise of wireless communications. In particular, WiMAX technology is nowadays considered one of the most prominent solutions capable to provide a Broadband Wireless Access (BWA) in metropolitan areas with a simpler installation and lower cost than traditional wired alternatives. This paper deals with the proposal of efficient adaptive modulation and coding techniques to be used in WiMAX based wireless networks, that allow to improve network performance in the case of Non Line-of-Sight communications, which are typical in urban environments. Through these techniques it is possible to switch the modulation order and coding rate in order to better match the channel conditions, and, hence, obtaining better performance both in terms of error probability and data throughput.

Wireless Communications and Mobile Computing, Sep 1, 2010

Wireless communications for public safety, emergency communications, and delivery of wideband ser... more Wireless communications for public safety, emergency communications, and delivery of wideband services to rural communities are topics of crucial importance to the welfare of the society. Broadband wireless digital subscriber loop (WDSL) technologies offer complementary and possibly low cost solutions to providing broadband connectivity services even to low densely populated areas that otherwise would be outside the loop. At the same time the availability of broadband wireless technologies can be useful for effective information dissemination in times of natural and man-made disasters thus providing a fundamental tool helping public safety agencies in providing quick response and support to communities needing urgent assistance and relief. The topic has been largely investigated (e.g. see references and references therein) during the last two decades.

Computer Communications, Mar 1, 1999

The Asynchronous Transfer Mode (ATM) principle has been recommended by the ITU as the transport v... more The Asynchronous Transfer Mode (ATM) principle has been recommended by the ITU as the transport vehicle for future Broadband ISDN Networks. One of the most important objectives of ATM-based networks is to support multimedia traffic services. The multimedia traffic is a diverse mixture of several types of traffic (e.g., video, voice, image, data) that have different correlations, burstiness characteristics and quality of services (QoS) requirements form the network. Efficient bandwidth allocation and access control algorithms are required to ensure (and maintain) specific QoS requirements for each type of traffic. In this article, we propose and analyze a dynamic bandwidth allocation and control scheme based upon the virtual path (VP) principle. The scheme exploits the statistical multiplexing gain principle in order to increase the bandwidth utilization per VP. It allocates a certain amount of bandwidth to each VP that is necessary to meet the QoS requirements of the traffic carried by that VP. Each VP carries only homogeneous traffic (i.e., traffic with similar characteristics and QoS requirements are supported by a single VP). To dynamically control the allocated path-bandwidth a Bandwidth Control Period (BCP) rule is proposed to control the scheduling of different types of traffic that are supported by separate VPs. It is shown that with proper choice of the BCP, a pathbandwidth can be allocated to guarantee QoS required by the traffic. The scheme is dynamic in the sense that the bandwidth allocated, per VP, depends upon the number of accepted calls and variations in the traffic characteristics. Further, it is shown that access flow control is essential in order to minimize the cell loss rate and enhance the statistical multiplexing gain per VP. ᭧

Computer Networks and Isdn Systems, Feb 1, 1997

This paper presents an adaptive approach to the problem of congestion control arising at the User... more This paper presents an adaptive approach to the problem of congestion control arising at the User-to Network Interface (UNI) of an ATM multiplexer. We view the ATM multiplexer as a non-linear stochastic system whose dynamics are ill-defined. Real-time measurements of the arrival rate process and the queueing process, are used to identify, and minimize congestion episodes. The performance of the system is evaluated using a performance-index function which is a quantative measure of "how well" the system is performing. A three-layers backpropagation neural network controller generates a signal that attempts to minimize congestion without degrading the quality of the traffic. During periods of buffer over-load the control signal, adaptively, modulates the arrival process such that its peak-rate is throttled-down. As soon as congestion is terminated, the control signal is adjusted such that the coding rates are restored back to their original values. Adaptability is achieved by continuously adjusting the weights of the neural network controller such that the performance of the system, measured by its performance index function, is maximized over a certain optimization period. The performance index function is defined in terms of two main objectives: (1) to minimize the cell loss rate (CLR), i.e., minimize congestion episodes, and (2) to maintain the quality of the video/audio traffic by maintaining its original source coding rate. The neural network learning process can he viewed as a specialized form of reinforcement learning in the sense that the control signal is reinforced if it tends to maximize the performance index function. Performance evaluation results prove that this approach is effective in controlling congestion while maintaining the quality of the traffic. . ferent types of traffic with different quality of services (QoS) requirements, e.g., cell loss rate (CLR), cell delay and delay variability, and different statistical characteristics. Statistical multiplexing requires effective traffic and congestion control policies. Traffic control functions (e.g., call admission control) attempt to avoid congestion by allocating resources to connections. However, they cannot guarantee the QOS delivered for each connection since the statistical fluctuations of the traffic may result in

Computer Networks and Isdn Systems, Sep 1, 1995

Asynchronous Transfer Mode (ATM) Broadband Networks are expected to provide a large number of ser... more Asynchronous Transfer Mode (ATM) Broadband Networks are expected to provide a large number of services and applications. A predominant service will be the support of multimedia traffic applications that integrate different types of traffic (e.g., video, voice and data) over the same connection. The heterogeneous traffic-types differ, widely, not only in their individual bit-rates but also in their corresponding correlations and burstiness parameters. Access flow control algorithms are required to enforce and maintain a specific QOS for each type of traffic. In this paper, we present an effective access flow control algorithm that can be applied at the user to network interface (UNI). The scheme is based upon a preventive control principle and uses a control signal, that is function of the buffer occupancy level, to control the source coder sampling rate. The scheme avoids congestion and enhances the statistical multiplexing gain, consequently providing a higher bandwidth utilization for each QOS. We provide a performance analysis study, supported by simulations, of the access node multiplexer. We studied the resulting Quasi Birth Death queueing process, with state dependant arrivals, using matrix-geometric techniques, and found that both MMPP/Er/l/K and the Poisson Process approximations provided very close results for an ATM multiplexer with small buffer size and access control.

Proceedings International Symposium on Computers and Communications, 2001

High Performance Networking VII, 1997

Bandwidth reservation multiple access protocol (BRMA) resolves access contentions for mobile user... more Bandwidth reservation multiple access protocol (BRMA) resolves access contentions for mobile users in wireless local networks. Bandwidth is assigned to each user dynamically at frame level. In each frame, request channels are deterministically assigned to each user and are therefore contention-free. Data channels are assigned dynamically by base station and are therefore collisionfree. In this paper, BRMA is studied for multimedia traffic through simulations. Traffic patterns of different kinds, such as voice, data, real time high activity video (MPEG movie Star Wars) are used to study the protocol performance. With a proper admission control and with proper design of protocol parameters (service ratio, frame length, etc), traffic with different quality of service (QoS) requirements can be supported.

Wireless Communications Ieee Transactions on, Apr 1, 2007

In this paper, we study the problem of maintaining fairness for TCP connections in wireless local... more In this paper, we study the problem of maintaining fairness for TCP connections in wireless local area networks (WLANs) based upon the IEEE 802.11 standard. Current implementations of 802.11 use the so-called Distributed Coordination Function (DCF), which provides similar medium access priority to all stations. Although this mode of operation ensures fair access to the medium at the MAC level, it does not provide any provisions for ensuring fairness among the TCP connections. TCP unfairness may result in significant degradation of performance leading to users perceiving unsatisfactory quality of service. We propose and analyze two solutions that are capable of enabling TCP fairness with minimal additional complexity. The proposed solutions are based on utilizing a rate-control mechanism in two modes: static or adaptive. They do not require modifying existing standards at the MAC or network layers. Hence, they are fully compatible with existing devices. Our performance analysis results prove the efficaciousness of our proposed solutions in achieving TCP fairness compared to existing approaches. We have, also, implemented the proposed solutions in an ad-hoc experimental test-bed, and performed measurements to demonstrate the validity of our approach and results.

Journal of High Speed Networks, Oct 1, 1997

Proceedings of ICUPC 97 - 6th International Conference on Universal Personal Communications, 1997

ABSTRACT

Proceedings of ICC/SUPERCOMM '96 - International Conference on Communications, 1996

ABSTRACT

The Fourth IEEE Workshop on High-Performance Communication Systems, 1997

ABSTRACT Not Available

1999 IEEE International Conference on Communications (Cat. No. 99CH36311), 1999

ATM supports a wide range of multimedia traffic. While ATM provides increased flexibility in supp... more ATM supports a wide range of multimedia traffic. While ATM provides increased flexibility in supporting various types of traffic the traffic control problems become more difficult to solve when trying to achieve efficient use of network resources. One of such problem is the bandwidth allocation. This paper presents a new approach to the bandwidth allocation problem for video traffic using

Google, Inc. (search). ...

Journal of High Speed Networks

An adaptive algorithm is proposed for controlling mobile users transmitter power and information ... more An adaptive algorithm is proposed for controlling mobile users transmitter power and information bit rate cooperatively in CDMA networks. The active component of this scheme is called Genetic Algorithm for Mobiles Equilibrium (GAME). Based on an evolutionary computational model, the base station tries to achieve an adequate equilibrium between its users. ThereoJ each mobile can send its traf3c with a suitable power to support it over the different path losses and interference. In the mean time, its battery life is beingpresewed while limiting the interference seen by neighbors. This optimization is based on each user trafic, required signal quality, the channel characteristics and users spatial distribution. A significant enhancement in signal quality and power level has been noticed through several experiments. 0-7803-6521 -6/$10.00 (C) 2000 IEEE

Journal of High Speed Networks

ABSTRACT

Ieee Transactions on Wireless Communications, Sep 1, 2009

The demand for high-speed services and multimedia applications anywhere and anytime has led to th... more The demand for high-speed services and multimedia applications anywhere and anytime has led to the rise of wireless communications. In particular, WiMAX technology is nowadays considered one of the most prominent solutions capable to provide a Broadband Wireless Access (BWA) in metropolitan areas with a simpler installation and lower cost than traditional wired alternatives. This paper deals with the proposal of efficient adaptive modulation and coding techniques to be used in WiMAX based wireless networks, that allow to improve network performance in the case of Non Line-of-Sight communications, which are typical in urban environments. Through these techniques it is possible to switch the modulation order and coding rate in order to better match the channel conditions, and, hence, obtaining better performance both in terms of error probability and data throughput.

Wireless Communications and Mobile Computing, Sep 1, 2010

Wireless communications for public safety, emergency communications, and delivery of wideband ser... more Wireless communications for public safety, emergency communications, and delivery of wideband services to rural communities are topics of crucial importance to the welfare of the society. Broadband wireless digital subscriber loop (WDSL) technologies offer complementary and possibly low cost solutions to providing broadband connectivity services even to low densely populated areas that otherwise would be outside the loop. At the same time the availability of broadband wireless technologies can be useful for effective information dissemination in times of natural and man-made disasters thus providing a fundamental tool helping public safety agencies in providing quick response and support to communities needing urgent assistance and relief. The topic has been largely investigated (e.g. see references and references therein) during the last two decades.

Computer Communications, Mar 1, 1999

The Asynchronous Transfer Mode (ATM) principle has been recommended by the ITU as the transport v... more The Asynchronous Transfer Mode (ATM) principle has been recommended by the ITU as the transport vehicle for future Broadband ISDN Networks. One of the most important objectives of ATM-based networks is to support multimedia traffic services. The multimedia traffic is a diverse mixture of several types of traffic (e.g., video, voice, image, data) that have different correlations, burstiness characteristics and quality of services (QoS) requirements form the network. Efficient bandwidth allocation and access control algorithms are required to ensure (and maintain) specific QoS requirements for each type of traffic. In this article, we propose and analyze a dynamic bandwidth allocation and control scheme based upon the virtual path (VP) principle. The scheme exploits the statistical multiplexing gain principle in order to increase the bandwidth utilization per VP. It allocates a certain amount of bandwidth to each VP that is necessary to meet the QoS requirements of the traffic carried by that VP. Each VP carries only homogeneous traffic (i.e., traffic with similar characteristics and QoS requirements are supported by a single VP). To dynamically control the allocated path-bandwidth a Bandwidth Control Period (BCP) rule is proposed to control the scheduling of different types of traffic that are supported by separate VPs. It is shown that with proper choice of the BCP, a pathbandwidth can be allocated to guarantee QoS required by the traffic. The scheme is dynamic in the sense that the bandwidth allocated, per VP, depends upon the number of accepted calls and variations in the traffic characteristics. Further, it is shown that access flow control is essential in order to minimize the cell loss rate and enhance the statistical multiplexing gain per VP. ᭧

Computer Networks and Isdn Systems, Feb 1, 1997

This paper presents an adaptive approach to the problem of congestion control arising at the User... more This paper presents an adaptive approach to the problem of congestion control arising at the User-to Network Interface (UNI) of an ATM multiplexer. We view the ATM multiplexer as a non-linear stochastic system whose dynamics are ill-defined. Real-time measurements of the arrival rate process and the queueing process, are used to identify, and minimize congestion episodes. The performance of the system is evaluated using a performance-index function which is a quantative measure of "how well" the system is performing. A three-layers backpropagation neural network controller generates a signal that attempts to minimize congestion without degrading the quality of the traffic. During periods of buffer over-load the control signal, adaptively, modulates the arrival process such that its peak-rate is throttled-down. As soon as congestion is terminated, the control signal is adjusted such that the coding rates are restored back to their original values. Adaptability is achieved by continuously adjusting the weights of the neural network controller such that the performance of the system, measured by its performance index function, is maximized over a certain optimization period. The performance index function is defined in terms of two main objectives: (1) to minimize the cell loss rate (CLR), i.e., minimize congestion episodes, and (2) to maintain the quality of the video/audio traffic by maintaining its original source coding rate. The neural network learning process can he viewed as a specialized form of reinforcement learning in the sense that the control signal is reinforced if it tends to maximize the performance index function. Performance evaluation results prove that this approach is effective in controlling congestion while maintaining the quality of the traffic. . ferent types of traffic with different quality of services (QoS) requirements, e.g., cell loss rate (CLR), cell delay and delay variability, and different statistical characteristics. Statistical multiplexing requires effective traffic and congestion control policies. Traffic control functions (e.g., call admission control) attempt to avoid congestion by allocating resources to connections. However, they cannot guarantee the QOS delivered for each connection since the statistical fluctuations of the traffic may result in

Computer Networks and Isdn Systems, Sep 1, 1995

Asynchronous Transfer Mode (ATM) Broadband Networks are expected to provide a large number of ser... more Asynchronous Transfer Mode (ATM) Broadband Networks are expected to provide a large number of services and applications. A predominant service will be the support of multimedia traffic applications that integrate different types of traffic (e.g., video, voice and data) over the same connection. The heterogeneous traffic-types differ, widely, not only in their individual bit-rates but also in their corresponding correlations and burstiness parameters. Access flow control algorithms are required to enforce and maintain a specific QOS for each type of traffic. In this paper, we present an effective access flow control algorithm that can be applied at the user to network interface (UNI). The scheme is based upon a preventive control principle and uses a control signal, that is function of the buffer occupancy level, to control the source coder sampling rate. The scheme avoids congestion and enhances the statistical multiplexing gain, consequently providing a higher bandwidth utilization for each QOS. We provide a performance analysis study, supported by simulations, of the access node multiplexer. We studied the resulting Quasi Birth Death queueing process, with state dependant arrivals, using matrix-geometric techniques, and found that both MMPP/Er/l/K and the Poisson Process approximations provided very close results for an ATM multiplexer with small buffer size and access control.

Proceedings International Symposium on Computers and Communications, 2001

High Performance Networking VII, 1997

Bandwidth reservation multiple access protocol (BRMA) resolves access contentions for mobile user... more Bandwidth reservation multiple access protocol (BRMA) resolves access contentions for mobile users in wireless local networks. Bandwidth is assigned to each user dynamically at frame level. In each frame, request channels are deterministically assigned to each user and are therefore contention-free. Data channels are assigned dynamically by base station and are therefore collisionfree. In this paper, BRMA is studied for multimedia traffic through simulations. Traffic patterns of different kinds, such as voice, data, real time high activity video (MPEG movie Star Wars) are used to study the protocol performance. With a proper admission control and with proper design of protocol parameters (service ratio, frame length, etc), traffic with different quality of service (QoS) requirements can be supported.

Wireless Communications Ieee Transactions on, Apr 1, 2007

In this paper, we study the problem of maintaining fairness for TCP connections in wireless local... more In this paper, we study the problem of maintaining fairness for TCP connections in wireless local area networks (WLANs) based upon the IEEE 802.11 standard. Current implementations of 802.11 use the so-called Distributed Coordination Function (DCF), which provides similar medium access priority to all stations. Although this mode of operation ensures fair access to the medium at the MAC level, it does not provide any provisions for ensuring fairness among the TCP connections. TCP unfairness may result in significant degradation of performance leading to users perceiving unsatisfactory quality of service. We propose and analyze two solutions that are capable of enabling TCP fairness with minimal additional complexity. The proposed solutions are based on utilizing a rate-control mechanism in two modes: static or adaptive. They do not require modifying existing standards at the MAC or network layers. Hence, they are fully compatible with existing devices. Our performance analysis results prove the efficaciousness of our proposed solutions in achieving TCP fairness compared to existing approaches. We have, also, implemented the proposed solutions in an ad-hoc experimental test-bed, and performed measurements to demonstrate the validity of our approach and results.

Journal of High Speed Networks, Oct 1, 1997

Proceedings of ICUPC 97 - 6th International Conference on Universal Personal Communications, 1997

ABSTRACT

Proceedings of ICC/SUPERCOMM '96 - International Conference on Communications, 1996

ABSTRACT

The Fourth IEEE Workshop on High-Performance Communication Systems, 1997

ABSTRACT Not Available

1999 IEEE International Conference on Communications (Cat. No. 99CH36311), 1999

ATM supports a wide range of multimedia traffic. While ATM provides increased flexibility in supp... more ATM supports a wide range of multimedia traffic. While ATM provides increased flexibility in supporting various types of traffic the traffic control problems become more difficult to solve when trying to achieve efficient use of network resources. One of such problem is the bandwidth allocation. This paper presents a new approach to the bandwidth allocation problem for video traffic using

Google, Inc. (search). ...

Journal of High Speed Networks

An adaptive algorithm is proposed for controlling mobile users transmitter power and information ... more An adaptive algorithm is proposed for controlling mobile users transmitter power and information bit rate cooperatively in CDMA networks. The active component of this scheme is called Genetic Algorithm for Mobiles Equilibrium (GAME). Based on an evolutionary computational model, the base station tries to achieve an adequate equilibrium between its users. ThereoJ each mobile can send its traf3c with a suitable power to support it over the different path losses and interference. In the mean time, its battery life is beingpresewed while limiting the interference seen by neighbors. This optimization is based on each user trafic, required signal quality, the channel characteristics and users spatial distribution. A significant enhancement in signal quality and power level has been noticed through several experiments. 0-7803-6521 -6/$10.00 (C) 2000 IEEE

Journal of High Speed Networks

ABSTRACT