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G. Mapp

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UCL Institute of Education

Patrick Lowenthal

Boise State University

S. Sadi SEFEROGLU

Hacettepe University

Hacettepe University

Arab Academy for Banking and Financial Sciences

Mediterranean University of Reggio Calabria

Salvador Millaleo

Universidad de Chile

Lancaster University

Queen Mary, University of London

Vassilios Vassilakis

University of York

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Papers by G. Mapp

Exploring multi-homing issues in heterogeneous environments

Proceedings - 25th IEEE International Conference on Advanced Information Networking and Applications Workshops, WAINA 2011, 2011

Full bibliographic details must be given when referring to, or quoting from full items including ... more Full bibliographic details must be given when referring to, or quoting from full items including the author's name, the title of the work, publication details where relevant (place, publisher, date), pagination, and for theses or dissertations the awarding institution, the degree type awarded, and the date of the award.

Performance Analysis of Handovers to Provide a Framework for Vertical Handover Policy Management in Heterogeneous Enviroments

Society for Computer Simulation International, Mar 26, 2012

ABSTRACT The rapid development and deployment of integrated heterogeneous networking environments... more ABSTRACT The rapid development and deployment of integrated heterogeneous networking environments such as third generation (3G) cellular WANs and WLANs will soon become commonplace. Users will demand connectivity without disruption anywhere and anytime. Mobility implies that this can only be done using either horizontal or vertical handover techniques where connections will be seamlessly switched between available networks. However, handover policies must consider issues such as network coverage, mobility, as well as Quality of Service (QoS). Analytical models are therefore required to deal with this complexity. However, there have been no analytical models that could be used as part of an overall framework. This paper addresses these issues by developing an analytical model to study vertical handover between a WLAN and a cellular system such as 3G. This model includes mobility of the users as well as decision making probabilities about handover between the two networks. In this paper the cellular network is modelled as a multi-channel queuing system while the WLAN is depicted as a single channel queuing system, both with finite buffering limits. The exact spectral expansion method is employed to solve this model. The proposed analytical model and its solution can be used to evaluate the QoS measures of such systems efficiently and accurately. Numerical results for mean queue length and blocking probability are computed and presented for both systems.

Exploring efficient seamless handover in VANET systems using network dwell time

EURASIP Journal on Wireless Communications and Networking, 2014

Vehicular ad hoc networks are a long-term solution contributing significantly towards intelligent... more Vehicular ad hoc networks are a long-term solution contributing significantly towards intelligent transport systems (ITS) in providing access to critical life-safety applications and services. Although vehicular ad hoc networks are attracting greater commercial interest, current research has not adequately captured the real-world constraints in vehicular ad hoc network handover techniques. Therefore, in order to have the best practice for vehicular ad hoc network services, it is necessary to have seamless connectivity for optimal coverage and ideal channel utilisation. Due to the high velocity of vehicles and smaller coverage distances, there are serious challenges in providing seamless handover from one roadside unit (RSU) to another. Though other research efforts have looked at many issues in vehicular ad hoc networks (VANETs), very few research work have looked at handover issues. Most literature assume that handover does not take a significant time and does not affect the overall VANET operation. In our previous work, we started to investigate these issues. This journal provides a more comprehensive analysis involving the beacon frequency, the size of beacon and the velocity of the vehicle. We used some of the concepts of Y-Comm architecture such as network dwell time (NDT), time before handover (T BH) and exit time (ET) to provide a framework to investigate handover issues. Further simulation studies were used to investigate the relation between beaconing, velocity and the network dwell time. Our results show that there is a need to understand the cumulative effect of beaconing in addition to the probability of successful reception as well as how these probability distributions are affected by the velocity of the vehicle. This provides more insight into how to support life critical applications using proactive handover techniques.

Dynamic Edge-Caching for Mobile Users

Special Issue: PMECT2009/ICCCN 2009

Dynamic Traffic Management for Interactive Cloud Services: Localising Traffic Based on Network Throughput and User Mobility

2014 IEEE/ACM 7th International Conference on Utility and Cloud Computing, 2014

Traffic localisation is an important aspect of traffic management on the Internet. The caching of... more Traffic localisation is an important aspect of traffic management on the Internet. The caching of content and its distribution from localized servers is one mechanism that enables traffic localisation and reduces transit costs for network providers while enhancing service performance. However, personalized, dynamic user content is often uncacheable due to its nature. As we move towards a world of constantly connected mobile devices, these devices will focus more towards Cloud services as a means of adding capabilities that would otherwise be impossible to have in a small mobile package. This leaves us with the potential problem of having to deal with un-cacheable traffic from real-time interactive Cloud services that causes congestion on a global scale. In this paper we present a solution that considers the scenario of an interactive, personal service running on the Cloud and accessed by a mobile user. We attempt to localise traffic by moving the virtual machine in response to the user's estimated network dwell time. Results gathered from a prototype platform are presented as proof of the concept.

Cloud-Based Service Delivery Architecture with Service-Populating and Mobility-Aware Mechanisms

Mobile Networks and Cloud Computing Convergence for Progressive Services and Applications

Advances in Mobile and Cloud technologies have redefined the way we perceive and use computers. M... more Advances in Mobile and Cloud technologies have redefined the way we perceive and use computers. Mobile devices now rely on Cloud technology for storage and applications. Furthermore, recent advances in network technology ensure that mobile devices in the future will have high-bandwidth connectivity at all times. This drives the incentive of doing all the processing and storage in the Cloud and using mobile devices to access the services. In this chapter, the authors argue that always-on connectivity along with increased demand of Cloud services will contest the Internet backbone and create problems in the management of Cloud resources. Client mobility is also a factor that should be taken into account when providing Cloud services to mobile devices. The authors therefore propose a new service delivery architecture that takes into account client mobility as well as the distance between clients and services in order to manage Cloud and network resources more efficiently and provide a better Quality of Experience for the user.

Dynamic Edge-Caching for Mobile Users: Minimising Inter-AS traffic by Moving Cloud Services and VMs

2014 28th International Conference on Advanced Information Networking and Applications Workshops, 2014

In recent years, Cloud technology has revolutionized the way services are delivered to end-users.... more In recent years, Cloud technology has revolutionized the way services are delivered to end-users. The advent of truly mobile computing in the form of smartphones and tablets has also driven the demand for Cloud resources in order to compensate for the inherent lack of local resources on these devices. Furthermore, modern mobile devices are equipped with multiple network interfaces and in combination with the rapid deployment of wireless networks, it is expected that they will always have Internet connectivity and access to Cloud resources. In this paper we will focus on traffic management for interactive multimedia services accessed by a mobile user by means of dynamic migration of a Virtual Machine. Network performance measurements are taken from a network of virtualization-enabled hosts that perform live migrations of a Virtual Machine which hosts multimedia content. The data is used as input to an equation that determines whether a migration would be beneficial in terms of traffic localization based on a user's mobility characteristics and network usage patterns. The contribution of this paper lies in the proposed mechanism of managing traffic for interactive services in the context of mobile cloud computing. This helps alleviate the increased network costs introduced by dynamic migrations driven by Quality of Service parameters and may result in increased network traffic for the benefit of improved QoS.

A Secure Framework for Communications in Heterogeneous Networks

2014 28th International Conference on Advanced Information Networking and Applications Workshops, 2014

ABSTRACT Heterogeneous Networks represent an open archi-tecture in which two different domains ne... more ABSTRACT Heterogeneous Networks represent an open archi-tecture in which two different domains need to cooperate in order to provide ubiquitous connectivity. The first is network operators domain, where multiple network operators share the core network to provide network accessibility over a wide variety of wireless technologies such as WiFi and mobile network tech-nologies. The other is the Application-Service Providers domain, which launches various services ranging from the normal video-streaming to the most confidential E-Commerce services. This highlights the fact that any efficient security solution for hetero-geneous networks has to consider the security in these different domains. Therefore, this paper introduces security framework that comprises two Authentication and Key Agreement protocols to secure transactions at the network and service levels. The proposed protocols have been formally verified using formal methods approach based on Casper/FDR tool.

Exploring a New Markov Chain Model for Multiqueue Systems

2010 12th International Conference on Computer Modelling and Simulation, 2010

Full bibliographic details must be given when referring to, or quoting from full items including ... more Full bibliographic details must be given when referring to, or quoting from full items including the author's name, the title of the work, publication details where relevant (place, publisher, date), pagination, and for theses or dissertations the awarding institution, the degree type awarded, and the date of the award.

The Design of a Storage Architecture for Mobile Heterogeneous Devices

International Conference on Networking and Services (ICNS '07), 2007

Full bibliographic details must be given when referring to, or quoting from full items including ... more Full bibliographic details must be given when referring to, or quoting from full items including the author's name, the title of the work, publication details where relevant (place, publisher, date), pagination, and for theses or dissertations the awarding institution, the degree type awarded, and the date of the award.

Modelling and performability analysis of network memory servers

Proceedings - Simulation Symposium, 2006

This paper presents an analytical method for the performability evaluation of a proposed network ... more This paper presents an analytical method for the performability evaluation of a proposed network memory server attached to a local area network. The proposed server is expected to improve data storage and retrieval. However, the underlying network will receive an increased amount of traffic which may have a significant effect on the network's performance. The proposed analytical model and its solution can be used to evaluate the performance of such a system. Mean queue lengths and the probability that the NMS queue is full are calculated and presented.

Modelling network memory servers with parallel processors, break-downs and repairs

Proceedings - Simulation Symposium, 2007

Full bibliographic details must be given when referring to, or quoting from full items including ... more Full bibliographic details must be given when referring to, or quoting from full items including the author's name, the title of the work, publication details where relevant (place, publisher, date), pagination, and for theses or dissertations the awarding institution, the degree type awarded, and the date of the award.

An analytical approach for performance analysis of handoffs in the next generation integrated cellular networks and WLANs

Proceedings - International Conference on Computer Communications and Networks, ICCCN, 2010

Full bibliographic details must be given when referring to, or quoting from full items including ... more Full bibliographic details must be given when referring to, or quoting from full items including the author's name, the title of the work, publication details where relevant (place, publisher, date), pagination, and for theses or dissertations the awarding institution, the degree type awarded, and the date of the award.

Modelling and performability analysis of WLANs as a queuing model with channel/access point failures and reconfiguration

Proceedings - UKSim 5th European Modelling Symposium on Computer Modelling and Simulation, EMS 2011, 2011

Wireless local area networks (WLANs) have experienced great popularity in the past decade. There ... more Wireless local area networks (WLANs) have experienced great popularity in the past decade. There is no doubt that WLANs are prone to failures. In order to improve the quality of service (QoS), performance characteristics of such systems should be considered together with the system availability modelling and evaluation which are associated with failures and recovery. This paper presents an analytical model for performability modelling and evaluation of a WLAN. The spectral expansion method is employed for the exact solution of the analytical model considered. The proposed analytical model and its solution can be used to evaluate the performability measures of such systems efficiently and accurately. Various performability measures such as mean queue length and blocking probability are computed and presented.

Critical review of analytical modelling approaches for performability evaluation of the handover phenomena in mobile communication systems

Proceedings - 11th IEEE International Conference on Computer and Information Technology, CIT 2011, 2011

ABSTRACT Perform ability modelling and evaluation of wireless and mobile systems have been of int... more ABSTRACT Perform ability modelling and evaluation of wireless and mobile systems have been of interest for recent research work. Especially, because of the complexity of the next generation wireless and mobile systems, modelling and performance evaluation is essential to improve the architecture according to the quality of service. (QoS ) requirements and performance characteristics. A considerable amount of the existing work in literature focuses on handover phenomena using analytical modelling and/or simulation of mobile communication systems. This paper presents a perform ability evaluation framework of mobile communication systems with different handover strategies using analytical modelling approaches. The availability and mobility issues are also considered in the proposed models. Well-known approximate Markov reward model solution and the exact Spectral expansion solution approaches are considered. Perform ability measures of proposed models, such as blocking probability and mean queue length are presented.

Impacts of Buffering of Voice Calls in Integrated Voice and Data Services

2011 UkSim 13th International Conference on Computer Modelling and Simulation, 2011

Full bibliographic details must be given when referring to, or quoting from full items including ... more Full bibliographic details must be given when referring to, or quoting from full items including the author's name, the title of the work, publication details where relevant (place, publisher, date), pagination, and for theses or dissertations the awarding institution, the degree type awarded, and the date of the award.

Exploring Service and Buffer Management issues to provide integrated voice and data services in single and multi-channel wireless networks

Proceedings - International Conference on Advanced Information Networking and Applications, AINA, 2013

Service and Buffer Management techniques can be used to ensure Quality of Service (QoS) for diffe... more Service and Buffer Management techniques can be used to ensure Quality of Service (QoS) for different traffic flows according to some specific policies. In this study, a single buffer queuing system is considered to model single and multi channel, homogeneous wireless network systems such as wireless local area networks (WLANs) and cellular networks. These systems are now being used to carry both voice and data traffic and hence it is important to optimise these systems in an attempt to reduce the blocking, and minimize the latency to acceptable ranges. Since voice packets are delay sensitive, they have the priority to receive service. Also they require smaller buffering capacities, since the response time to voice requests should be below specific values. In addition, in order to reduce retransmission on reliable data connections, data packets are not usurped by incoming voice packets. In this paper, a mathematical analysis of this scenario is explored. The proposed mathematical model is represented by two dimensions; one for incoming voice packets and one for data packets. The models proposed show that it is possible to store incoming voice packets in the queue in case the channel or channels are busy. Both voice and data packets have finite buffering. Incoming voice packets are blocked when the voice buffer or the common queue is full. Therefore there is an added blocking probability of voice due to the presence of data packets in the system when the common queue is full. The analytical model is validated using simulation. The system proposed attempts to provide minimum delay for voice while reducing the disruption to reliable data connections. Numerical results show that, it is possible to attain these goals with reasonable buffer sizes. This study is useful for understanding the trade-offs and thresholds of single and multi channel systems with voice and data traffic.

A Generic Analytical Modelling Approach for Performance Evaluation of the Handover Schemes in Heterogeneous Environments

Wireless Pers Commun, 2014

In recent years, there has been an increased interest in the integration of different technologie... more In recent years, there has been an increased interest in the integration of different technologies in heterogeneous environments. Modelling heterogeneous systems is a complex task and handover schemes should consider issues such as network coverage, mobility, and Quality of Service (QoS). Analytical models are useful to deal with this complexity. This paper presents a generic framework to model handover in heterogeneous environments for performance evaluation of different handover schemes. The model developed considers mobility of the users, coverage radius of the networks as well as decision making probabilities about handover between the two networks. The interaction between cellular mobile technologies is considered and handover between a WLAN and a cellular system is analysed using the proposed model. Two stage open networks can be used to model this kind of integrated systems. The cellular mobile technologies are modelled as a multi-channel queuing system while the WLAN is depicted as a single channel queuing system, both with finite buffers. The exact spectral expansion method is employed to solve the models. Simulation is also employed for the proposed systems and used for validation of the accuracy of the proposed

Exploring efficient imperative handover mechanisms for heterogeneous wireless networks

NBiS 2009 - 12th International Conference on Network-Based Information Systems, 2009

Full bibliographic details must be given when referring to, or quoting from full items including ... more Full bibliographic details must be given when referring to, or quoting from full items including the author's name, the title of the work, publication details where relevant (place, publisher, date), pagination, and for theses or dissertations the awarding institution, the degree type awarded, and the date of the award.

Exploring multi-homing issues in heterogeneous environments

Proceedings - 25th IEEE International Conference on Advanced Information Networking and Applications Workshops, WAINA 2011, 2011

Full bibliographic details must be given when referring to, or quoting from full items including ... more Full bibliographic details must be given when referring to, or quoting from full items including the author's name, the title of the work, publication details where relevant (place, publisher, date), pagination, and for theses or dissertations the awarding institution, the degree type awarded, and the date of the award.

Performance Analysis of Handovers to Provide a Framework for Vertical Handover Policy Management in Heterogeneous Enviroments

Society for Computer Simulation International, Mar 26, 2012

ABSTRACT The rapid development and deployment of integrated heterogeneous networking environments... more ABSTRACT The rapid development and deployment of integrated heterogeneous networking environments such as third generation (3G) cellular WANs and WLANs will soon become commonplace. Users will demand connectivity without disruption anywhere and anytime. Mobility implies that this can only be done using either horizontal or vertical handover techniques where connections will be seamlessly switched between available networks. However, handover policies must consider issues such as network coverage, mobility, as well as Quality of Service (QoS). Analytical models are therefore required to deal with this complexity. However, there have been no analytical models that could be used as part of an overall framework. This paper addresses these issues by developing an analytical model to study vertical handover between a WLAN and a cellular system such as 3G. This model includes mobility of the users as well as decision making probabilities about handover between the two networks. In this paper the cellular network is modelled as a multi-channel queuing system while the WLAN is depicted as a single channel queuing system, both with finite buffering limits. The exact spectral expansion method is employed to solve this model. The proposed analytical model and its solution can be used to evaluate the QoS measures of such systems efficiently and accurately. Numerical results for mean queue length and blocking probability are computed and presented for both systems.

Exploring efficient seamless handover in VANET systems using network dwell time

EURASIP Journal on Wireless Communications and Networking, 2014

Vehicular ad hoc networks are a long-term solution contributing significantly towards intelligent... more Vehicular ad hoc networks are a long-term solution contributing significantly towards intelligent transport systems (ITS) in providing access to critical life-safety applications and services. Although vehicular ad hoc networks are attracting greater commercial interest, current research has not adequately captured the real-world constraints in vehicular ad hoc network handover techniques. Therefore, in order to have the best practice for vehicular ad hoc network services, it is necessary to have seamless connectivity for optimal coverage and ideal channel utilisation. Due to the high velocity of vehicles and smaller coverage distances, there are serious challenges in providing seamless handover from one roadside unit (RSU) to another. Though other research efforts have looked at many issues in vehicular ad hoc networks (VANETs), very few research work have looked at handover issues. Most literature assume that handover does not take a significant time and does not affect the overall VANET operation. In our previous work, we started to investigate these issues. This journal provides a more comprehensive analysis involving the beacon frequency, the size of beacon and the velocity of the vehicle. We used some of the concepts of Y-Comm architecture such as network dwell time (NDT), time before handover (T BH) and exit time (ET) to provide a framework to investigate handover issues. Further simulation studies were used to investigate the relation between beaconing, velocity and the network dwell time. Our results show that there is a need to understand the cumulative effect of beaconing in addition to the probability of successful reception as well as how these probability distributions are affected by the velocity of the vehicle. This provides more insight into how to support life critical applications using proactive handover techniques.

Dynamic Edge-Caching for Mobile Users

Special Issue: PMECT2009/ICCCN 2009

Dynamic Traffic Management for Interactive Cloud Services: Localising Traffic Based on Network Throughput and User Mobility

2014 IEEE/ACM 7th International Conference on Utility and Cloud Computing, 2014

Traffic localisation is an important aspect of traffic management on the Internet. The caching of... more Traffic localisation is an important aspect of traffic management on the Internet. The caching of content and its distribution from localized servers is one mechanism that enables traffic localisation and reduces transit costs for network providers while enhancing service performance. However, personalized, dynamic user content is often uncacheable due to its nature. As we move towards a world of constantly connected mobile devices, these devices will focus more towards Cloud services as a means of adding capabilities that would otherwise be impossible to have in a small mobile package. This leaves us with the potential problem of having to deal with un-cacheable traffic from real-time interactive Cloud services that causes congestion on a global scale. In this paper we present a solution that considers the scenario of an interactive, personal service running on the Cloud and accessed by a mobile user. We attempt to localise traffic by moving the virtual machine in response to the user's estimated network dwell time. Results gathered from a prototype platform are presented as proof of the concept.

Cloud-Based Service Delivery Architecture with Service-Populating and Mobility-Aware Mechanisms

Mobile Networks and Cloud Computing Convergence for Progressive Services and Applications

Advances in Mobile and Cloud technologies have redefined the way we perceive and use computers. M... more Advances in Mobile and Cloud technologies have redefined the way we perceive and use computers. Mobile devices now rely on Cloud technology for storage and applications. Furthermore, recent advances in network technology ensure that mobile devices in the future will have high-bandwidth connectivity at all times. This drives the incentive of doing all the processing and storage in the Cloud and using mobile devices to access the services. In this chapter, the authors argue that always-on connectivity along with increased demand of Cloud services will contest the Internet backbone and create problems in the management of Cloud resources. Client mobility is also a factor that should be taken into account when providing Cloud services to mobile devices. The authors therefore propose a new service delivery architecture that takes into account client mobility as well as the distance between clients and services in order to manage Cloud and network resources more efficiently and provide a better Quality of Experience for the user.

Dynamic Edge-Caching for Mobile Users: Minimising Inter-AS traffic by Moving Cloud Services and VMs

2014 28th International Conference on Advanced Information Networking and Applications Workshops, 2014

In recent years, Cloud technology has revolutionized the way services are delivered to end-users.... more In recent years, Cloud technology has revolutionized the way services are delivered to end-users. The advent of truly mobile computing in the form of smartphones and tablets has also driven the demand for Cloud resources in order to compensate for the inherent lack of local resources on these devices. Furthermore, modern mobile devices are equipped with multiple network interfaces and in combination with the rapid deployment of wireless networks, it is expected that they will always have Internet connectivity and access to Cloud resources. In this paper we will focus on traffic management for interactive multimedia services accessed by a mobile user by means of dynamic migration of a Virtual Machine. Network performance measurements are taken from a network of virtualization-enabled hosts that perform live migrations of a Virtual Machine which hosts multimedia content. The data is used as input to an equation that determines whether a migration would be beneficial in terms of traffic localization based on a user's mobility characteristics and network usage patterns. The contribution of this paper lies in the proposed mechanism of managing traffic for interactive services in the context of mobile cloud computing. This helps alleviate the increased network costs introduced by dynamic migrations driven by Quality of Service parameters and may result in increased network traffic for the benefit of improved QoS.

A Secure Framework for Communications in Heterogeneous Networks

2014 28th International Conference on Advanced Information Networking and Applications Workshops, 2014

ABSTRACT Heterogeneous Networks represent an open archi-tecture in which two different domains ne... more ABSTRACT Heterogeneous Networks represent an open archi-tecture in which two different domains need to cooperate in order to provide ubiquitous connectivity. The first is network operators domain, where multiple network operators share the core network to provide network accessibility over a wide variety of wireless technologies such as WiFi and mobile network tech-nologies. The other is the Application-Service Providers domain, which launches various services ranging from the normal video-streaming to the most confidential E-Commerce services. This highlights the fact that any efficient security solution for hetero-geneous networks has to consider the security in these different domains. Therefore, this paper introduces security framework that comprises two Authentication and Key Agreement protocols to secure transactions at the network and service levels. The proposed protocols have been formally verified using formal methods approach based on Casper/FDR tool.

Exploring a New Markov Chain Model for Multiqueue Systems

2010 12th International Conference on Computer Modelling and Simulation, 2010

Full bibliographic details must be given when referring to, or quoting from full items including ... more Full bibliographic details must be given when referring to, or quoting from full items including the author's name, the title of the work, publication details where relevant (place, publisher, date), pagination, and for theses or dissertations the awarding institution, the degree type awarded, and the date of the award.

The Design of a Storage Architecture for Mobile Heterogeneous Devices

International Conference on Networking and Services (ICNS '07), 2007

Full bibliographic details must be given when referring to, or quoting from full items including ... more Full bibliographic details must be given when referring to, or quoting from full items including the author's name, the title of the work, publication details where relevant (place, publisher, date), pagination, and for theses or dissertations the awarding institution, the degree type awarded, and the date of the award.

Modelling and performability analysis of network memory servers

Proceedings - Simulation Symposium, 2006

This paper presents an analytical method for the performability evaluation of a proposed network ... more This paper presents an analytical method for the performability evaluation of a proposed network memory server attached to a local area network. The proposed server is expected to improve data storage and retrieval. However, the underlying network will receive an increased amount of traffic which may have a significant effect on the network's performance. The proposed analytical model and its solution can be used to evaluate the performance of such a system. Mean queue lengths and the probability that the NMS queue is full are calculated and presented.

Modelling network memory servers with parallel processors, break-downs and repairs

Proceedings - Simulation Symposium, 2007

Full bibliographic details must be given when referring to, or quoting from full items including ... more Full bibliographic details must be given when referring to, or quoting from full items including the author's name, the title of the work, publication details where relevant (place, publisher, date), pagination, and for theses or dissertations the awarding institution, the degree type awarded, and the date of the award.

An analytical approach for performance analysis of handoffs in the next generation integrated cellular networks and WLANs

Proceedings - International Conference on Computer Communications and Networks, ICCCN, 2010

Full bibliographic details must be given when referring to, or quoting from full items including ... more Full bibliographic details must be given when referring to, or quoting from full items including the author's name, the title of the work, publication details where relevant (place, publisher, date), pagination, and for theses or dissertations the awarding institution, the degree type awarded, and the date of the award.

Modelling and performability analysis of WLANs as a queuing model with channel/access point failures and reconfiguration

Proceedings - UKSim 5th European Modelling Symposium on Computer Modelling and Simulation, EMS 2011, 2011

Wireless local area networks (WLANs) have experienced great popularity in the past decade. There ... more Wireless local area networks (WLANs) have experienced great popularity in the past decade. There is no doubt that WLANs are prone to failures. In order to improve the quality of service (QoS), performance characteristics of such systems should be considered together with the system availability modelling and evaluation which are associated with failures and recovery. This paper presents an analytical model for performability modelling and evaluation of a WLAN. The spectral expansion method is employed for the exact solution of the analytical model considered. The proposed analytical model and its solution can be used to evaluate the performability measures of such systems efficiently and accurately. Various performability measures such as mean queue length and blocking probability are computed and presented.

Critical review of analytical modelling approaches for performability evaluation of the handover phenomena in mobile communication systems

Proceedings - 11th IEEE International Conference on Computer and Information Technology, CIT 2011, 2011

ABSTRACT Perform ability modelling and evaluation of wireless and mobile systems have been of int... more ABSTRACT Perform ability modelling and evaluation of wireless and mobile systems have been of interest for recent research work. Especially, because of the complexity of the next generation wireless and mobile systems, modelling and performance evaluation is essential to improve the architecture according to the quality of service. (QoS ) requirements and performance characteristics. A considerable amount of the existing work in literature focuses on handover phenomena using analytical modelling and/or simulation of mobile communication systems. This paper presents a perform ability evaluation framework of mobile communication systems with different handover strategies using analytical modelling approaches. The availability and mobility issues are also considered in the proposed models. Well-known approximate Markov reward model solution and the exact Spectral expansion solution approaches are considered. Perform ability measures of proposed models, such as blocking probability and mean queue length are presented.

Impacts of Buffering of Voice Calls in Integrated Voice and Data Services

2011 UkSim 13th International Conference on Computer Modelling and Simulation, 2011

Full bibliographic details must be given when referring to, or quoting from full items including ... more Full bibliographic details must be given when referring to, or quoting from full items including the author's name, the title of the work, publication details where relevant (place, publisher, date), pagination, and for theses or dissertations the awarding institution, the degree type awarded, and the date of the award.

Exploring Service and Buffer Management issues to provide integrated voice and data services in single and multi-channel wireless networks

Proceedings - International Conference on Advanced Information Networking and Applications, AINA, 2013

Service and Buffer Management techniques can be used to ensure Quality of Service (QoS) for diffe... more Service and Buffer Management techniques can be used to ensure Quality of Service (QoS) for different traffic flows according to some specific policies. In this study, a single buffer queuing system is considered to model single and multi channel, homogeneous wireless network systems such as wireless local area networks (WLANs) and cellular networks. These systems are now being used to carry both voice and data traffic and hence it is important to optimise these systems in an attempt to reduce the blocking, and minimize the latency to acceptable ranges. Since voice packets are delay sensitive, they have the priority to receive service. Also they require smaller buffering capacities, since the response time to voice requests should be below specific values. In addition, in order to reduce retransmission on reliable data connections, data packets are not usurped by incoming voice packets. In this paper, a mathematical analysis of this scenario is explored. The proposed mathematical model is represented by two dimensions; one for incoming voice packets and one for data packets. The models proposed show that it is possible to store incoming voice packets in the queue in case the channel or channels are busy. Both voice and data packets have finite buffering. Incoming voice packets are blocked when the voice buffer or the common queue is full. Therefore there is an added blocking probability of voice due to the presence of data packets in the system when the common queue is full. The analytical model is validated using simulation. The system proposed attempts to provide minimum delay for voice while reducing the disruption to reliable data connections. Numerical results show that, it is possible to attain these goals with reasonable buffer sizes. This study is useful for understanding the trade-offs and thresholds of single and multi channel systems with voice and data traffic.

A Generic Analytical Modelling Approach for Performance Evaluation of the Handover Schemes in Heterogeneous Environments

Wireless Pers Commun, 2014

In recent years, there has been an increased interest in the integration of different technologie... more In recent years, there has been an increased interest in the integration of different technologies in heterogeneous environments. Modelling heterogeneous systems is a complex task and handover schemes should consider issues such as network coverage, mobility, and Quality of Service (QoS). Analytical models are useful to deal with this complexity. This paper presents a generic framework to model handover in heterogeneous environments for performance evaluation of different handover schemes. The model developed considers mobility of the users, coverage radius of the networks as well as decision making probabilities about handover between the two networks. The interaction between cellular mobile technologies is considered and handover between a WLAN and a cellular system is analysed using the proposed model. Two stage open networks can be used to model this kind of integrated systems. The cellular mobile technologies are modelled as a multi-channel queuing system while the WLAN is depicted as a single channel queuing system, both with finite buffers. The exact spectral expansion method is employed to solve the models. Simulation is also employed for the proposed systems and used for validation of the accuracy of the proposed

Exploring efficient imperative handover mechanisms for heterogeneous wireless networks

NBiS 2009 - 12th International Conference on Network-Based Information Systems, 2009

Full bibliographic details must be given when referring to, or quoting from full items including ... more Full bibliographic details must be given when referring to, or quoting from full items including the author's name, the title of the work, publication details where relevant (place, publisher, date), pagination, and for theses or dissertations the awarding institution, the degree type awarded, and the date of the award.