Ayman Kaheel | University of British Columbia (original) (raw)

Papers by Ayman Kaheel

Optical Burst Switching (OBS) is a hybrid technique between coarse grain optical circuit switchin... more Optical Burst Switching (OBS) is a hybrid technique between coarse grain optical circuit switching and fine grain optical packet switching. In OBS networks, user data is switched entirely in the optical domain, while control and management functions are performed in the electrical domain. This separation of the data plane and the control plane allows OBS networks to provide reasonably high levels of utilization while circumventing the need for optical buffering. In spite of OBS favorable features, several issues need to be addressed before OBS can be deployed in the Internet backbone. The objectives of this thesis are twofold: devise new methods for quality-of-service (QoS) provisioning in OBS networks, and develop new wavelength scheduling algorithms for enhancing the blocking probability in OBS networks. QoS provisioning is a major research problem in OBS networks. This is mainly because of the absence of the concept of "packet queues" in OBS networks. This thesis proposes two approaches for QoS provisioning in OBS networks. The first approach is a simple, yet effective scheme, called preemptive prioritized just enough time (PPJET). PP JET provides better service for high priority traffic by dropping reservations belonging to lower priority traffic using a new channel scheduling algorithm called preemptive latest Abstract in available unused channel with void filling (PLAUC-VF). Simulation results show that PPJET outperforms offset-based QoS schemes both in terms of dropping probability and end-to-end delay. As a second approach for solving the QoS problem in OBS networks, we present a detailed architecture for providing quantitative QoS guarantees with respect to endto-end delay, throughput, and packet loss probability in labeled OBS networks. The architecture describes a novel approach for applying fair scheduling algorithms in both the data plane of labeled OBS edge nodes and the control plane of core nodes without the need for optical buffering. In addition, we present analytical results for delay, throughput, and blocking probability in the proposed architecture. Simulation results demonstrate that the proposed architecture provides accurate and controllable service differentiation in labeled OBS networks. The absence of optical buffers in OBS nodes, coupled with the one way nature of OBS signaling protocols, drives the blocking probability to become the main performance measure in OBS networks. This give rise to the need for analytical models for calculating the blocking probability in OBS networks. In this thesis we present an approximate analytical model for calculating the blocking probability in OBS networks. The proposed analytical model takes into consideration the peculiar characteristics of OBS networks. To verify its accuracy, we compared the model results with results from a discrete-event simulation model. The proposed model results are in satisfactory agreement with simulation results.

SPE Annual Technical Conference and Exhibition

2004 IEEE International Conference on Communications (IEEE Cat. No.04CH37577), 2004

In this paper we present a new analytical model for evaluating the blocking probability in Just-E... more In this paper we present a new analytical model for evaluating the blocking probability in Just-Enough-Time-based optical burst switching networks. The proposed analytical model takes into consideration the effects of the burst offset time and the burst length on the blocking probability. We use a (M +1)-state non-homogenous Markov chain to describe the state of an output link carrying M wavelength channels. In addition, we model each wavelength channel by a 2-state Markov chain. The offset time is drawn from a specified distribution so that wavelength reservation requests, made before a given time, build up to be a workload whose mean value declines with the reservation starting time. Furthermore, we express the blocking probability in terms of first passage time distributions to account for the burst length. To verify its accuracy, the model results are compared with the results of a sophisticated discrete-event simulation model. The model results were found to be in satisfactory agreement with simulation results.

IEEE Journal on Selected Areas in Communications, 2000

Abstract This paper presents a new analytical model for calculating the blocking probability in J... more Abstract This paper presents a new analytical model for calculating the blocking probability in Just-Enough-Time (JET)-based optical burst switching networks. Relationship to the problem of calculating the reservation probability in advance reservation systems is also ...

Ieee Journal on Selected Areas in Communications, Dec 1, 2006

Abstract This paper presents a new analytical model for calculating the blocking probability in J... more Abstract This paper presents a new analytical model for calculating the blocking probability in Just-Enough-Time (JET)-based optical burst switching networks. Relationship to the problem of calculating the reservation probability in advance reservation systems is also ...

Mobile Cloud Visual Media Computing, 2015

Classical approaches to quality-of-service (QoS) provi-sioning in IP networks are difficult to ap... more Classical approaches to quality-of-service (QoS) provi-sioning in IP networks are difficult to apply in all-optical networks. This is mainly because there is no optical coun-terpart to the store-and-forward model that mandates the use of buffers for queuing packets during ...

Previously proposed wavelength scheduling algorithms in optical burst switching networks process ... more Previously proposed wavelength scheduling algorithms in optical burst switching networks process each reservation request individually and in a greedy manner. In this paper we propose a new family of wavelength scheduling algorithms that process a batch of reservation requests together instead of processing them one by one. When a control burst with a reservation request arrives to a free batch scheduler, the scheduler waits for a small amount of time, called the acceptance delay, before deciding to accept or reject the reservation request. After the acceptance delay has passed, the scheduler processes all the reservation requests that have arrived during the acceptance delay, then it accepts the requests that will maximize the utilization of the wavelength channels. We describe an optimal batch scheduler that serves as an upper bound on the performance of batch scheduling algorithms. Furthermore, we introduce two heuristic batch scheduling algorithms. The performance of the proposed algorithms is evaluated using a discrete-event simulation model. Simulation results suggest that batch schedulers could decrease the blocking probability by 25% compared to the best previously known wavelength scheduling algorithm.

Image matching is a cornerstone technology in many image understanding, augmented reality and rec... more Image matching is a cornerstone technology in many image understanding, augmented reality and recognition applications. The state-of-the-art techniques follow a feature-based approach by extracting interest points and describing them by either rotation or affine invariant descriptors. However, requiring rotation or affine invariance comes at an additional computational cost as well as inaccurate estimates in some cases such as out-of-plane rotations. Fortunately, today most mobile devices incorporate 3-D accelerometers that measure the acceleration values along the three axes. In this paper, we propose to employ the acceleration values to calculate the in-plane and tilting rotation angles of the capturing device, in order to alleviate the need for constructing rotationally invariant descriptors. We describe an approach for incorporating the calculated rotation angles in the process of interest point extraction and description. Furthermore, we evaluate empirically the proposed approach, both in terms of computational time and accuracy on standard datasets as well as a dataset collected using a mobile phone. Our results show that the proposed approach provides savings in computational time while providing accuracy gains.

Mobicast: A System for Collaborative Event Casting Using Mobile Phones Ayman Kaheel Microsoft Inn... more Mobicast: A System for Collaborative Event Casting Using Mobile Phones Ayman Kaheel Microsoft Innovation Lab 306, Kornish El Nile, Maadi, Cairo, Egypt aymank@microsoft.com ... Mostafa Ezz Faculty of Engineering Cairo University Giza, Egypt mostafa.3ez@gmail.com ...

Optical Burst Switching (OBS) is a hybrid technique between coarse grain optical circuit switchin... more Optical Burst Switching (OBS) is a hybrid technique between coarse grain optical circuit switching and fine grain optical packet switching. In OBS networks, user data is switched entirely in the optical domain, while control and management functions are performed in the electrical domain. This separation of the data plane and the control plane allows OBS networks to provide reasonably high levels of utilization while circumventing the need for optical buffering. In spite of OBS favorable features, several issues need to be addressed before OBS can be deployed in the Internet backbone. The objectives of this thesis are twofold: devise new methods for quality-of-service (QoS) provisioning in OBS networks, and develop new wavelength scheduling algorithms for enhancing the blocking probability in OBS networks. QoS provisioning is a major research problem in OBS networks. This is mainly because of the absence of the concept of "packet queues" in OBS networks. This thesis proposes two approaches for QoS provisioning in OBS networks. The first approach is a simple, yet effective scheme, called preemptive prioritized just enough time (PPJET). PP JET provides better service for high priority traffic by dropping reservations belonging to lower priority traffic using a new channel scheduling algorithm called preemptive latest Abstract in available unused channel with void filling (PLAUC-VF). Simulation results show that PPJET outperforms offset-based QoS schemes both in terms of dropping probability and end-to-end delay. As a second approach for solving the QoS problem in OBS networks, we present a detailed architecture for providing quantitative QoS guarantees with respect to endto-end delay, throughput, and packet loss probability in labeled OBS networks. The architecture describes a novel approach for applying fair scheduling algorithms in both the data plane of labeled OBS edge nodes and the control plane of core nodes without the need for optical buffering. In addition, we present analytical results for delay, throughput, and blocking probability in the proposed architecture. Simulation results demonstrate that the proposed architecture provides accurate and controllable service differentiation in labeled OBS networks. The absence of optical buffers in OBS nodes, coupled with the one way nature of OBS signaling protocols, drives the blocking probability to become the main performance measure in OBS networks. This give rise to the need for analytical models for calculating the blocking probability in OBS networks. In this thesis we present an approximate analytical model for calculating the blocking probability in OBS networks. The proposed analytical model takes into consideration the peculiar characteristics of OBS networks. To verify its accuracy, we compared the model results with results from a discrete-event simulation model. The proposed model results are in satisfactory agreement with simulation results.

SPE Annual Technical Conference and Exhibition

2004 IEEE International Conference on Communications (IEEE Cat. No.04CH37577), 2004

In this paper we present a new analytical model for evaluating the blocking probability in Just-E... more In this paper we present a new analytical model for evaluating the blocking probability in Just-Enough-Time-based optical burst switching networks. The proposed analytical model takes into consideration the effects of the burst offset time and the burst length on the blocking probability. We use a (M +1)-state non-homogenous Markov chain to describe the state of an output link carrying M wavelength channels. In addition, we model each wavelength channel by a 2-state Markov chain. The offset time is drawn from a specified distribution so that wavelength reservation requests, made before a given time, build up to be a workload whose mean value declines with the reservation starting time. Furthermore, we express the blocking probability in terms of first passage time distributions to account for the burst length. To verify its accuracy, the model results are compared with the results of a sophisticated discrete-event simulation model. The model results were found to be in satisfactory agreement with simulation results.

IEEE Journal on Selected Areas in Communications, 2000

Abstract This paper presents a new analytical model for calculating the blocking probability in J... more Abstract This paper presents a new analytical model for calculating the blocking probability in Just-Enough-Time (JET)-based optical burst switching networks. Relationship to the problem of calculating the reservation probability in advance reservation systems is also ...

Ieee Journal on Selected Areas in Communications, Dec 1, 2006

Abstract This paper presents a new analytical model for calculating the blocking probability in J... more Abstract This paper presents a new analytical model for calculating the blocking probability in Just-Enough-Time (JET)-based optical burst switching networks. Relationship to the problem of calculating the reservation probability in advance reservation systems is also ...

Mobile Cloud Visual Media Computing, 2015

Classical approaches to quality-of-service (QoS) provi-sioning in IP networks are difficult to ap... more Classical approaches to quality-of-service (QoS) provi-sioning in IP networks are difficult to apply in all-optical networks. This is mainly because there is no optical coun-terpart to the store-and-forward model that mandates the use of buffers for queuing packets during ...

Previously proposed wavelength scheduling algorithms in optical burst switching networks process ... more Previously proposed wavelength scheduling algorithms in optical burst switching networks process each reservation request individually and in a greedy manner. In this paper we propose a new family of wavelength scheduling algorithms that process a batch of reservation requests together instead of processing them one by one. When a control burst with a reservation request arrives to a free batch scheduler, the scheduler waits for a small amount of time, called the acceptance delay, before deciding to accept or reject the reservation request. After the acceptance delay has passed, the scheduler processes all the reservation requests that have arrived during the acceptance delay, then it accepts the requests that will maximize the utilization of the wavelength channels. We describe an optimal batch scheduler that serves as an upper bound on the performance of batch scheduling algorithms. Furthermore, we introduce two heuristic batch scheduling algorithms. The performance of the proposed algorithms is evaluated using a discrete-event simulation model. Simulation results suggest that batch schedulers could decrease the blocking probability by 25% compared to the best previously known wavelength scheduling algorithm.

Image matching is a cornerstone technology in many image understanding, augmented reality and rec... more Image matching is a cornerstone technology in many image understanding, augmented reality and recognition applications. The state-of-the-art techniques follow a feature-based approach by extracting interest points and describing them by either rotation or affine invariant descriptors. However, requiring rotation or affine invariance comes at an additional computational cost as well as inaccurate estimates in some cases such as out-of-plane rotations. Fortunately, today most mobile devices incorporate 3-D accelerometers that measure the acceleration values along the three axes. In this paper, we propose to employ the acceleration values to calculate the in-plane and tilting rotation angles of the capturing device, in order to alleviate the need for constructing rotationally invariant descriptors. We describe an approach for incorporating the calculated rotation angles in the process of interest point extraction and description. Furthermore, we evaluate empirically the proposed approach, both in terms of computational time and accuracy on standard datasets as well as a dataset collected using a mobile phone. Our results show that the proposed approach provides savings in computational time while providing accuracy gains.

Mobicast: A System for Collaborative Event Casting Using Mobile Phones Ayman Kaheel Microsoft Inn... more Mobicast: A System for Collaborative Event Casting Using Mobile Phones Ayman Kaheel Microsoft Innovation Lab 306, Kornish El Nile, Maadi, Cairo, Egypt aymank@microsoft.com ... Mostafa Ezz Faculty of Engineering Cairo University Giza, Egypt mostafa.3ez@gmail.com ...