Copyright (c) 2011 All rights reserved. http://works.bepress.com/muhammad_alam Recent documents in Muhammad T. Alam en-us Wed, 16 Feb 2011 21:36:16 PST 3600 http://works.bepress.com/muhammad_alam/12 http://works.bepress.com/muhammad_alam/12 Tue, 16 Nov 2010 16:18:36 PST The PoC (push-to-talk over cellular) application allows point-to-point or point-to-multipoint voice communication between mobile network users. The related work over PoC focuses on the performance analysis only and is ignorant about dimensioning a PoC controller to optimize revenue for service providers. In this paper, we dimension a PoC service with the assumption that the network grade of service is provided. The on-demand sessions should have access priority over pre-established sessions. A PoC controller should be able to terminate a PoC session based on an optimal timer. Moreover, the number of simultaneous session initiations by a PoC client is also a configurable parameter. We derived relations to provide access priority to special PoC sessions based on available transmit/receive units (TRU) and threshold level. Load sharing expressions are reported for a PoC controller using the Lagrange multiplier technique. A simple relation to control the PoC session timer is proposed. Finally, the derivation of maximum number of allowable simultaneous sessions is depicted using two-state Markov models. Numerical results have been computed with the corresponding derivation to provide a useful insight into the system behaviour. APoC service can benefit from these optimal values of our work during the busy hour. Muhammad T. Alam http://works.bepress.com/muhammad_alam/11 http://works.bepress.com/muhammad_alam/11 Tue, 13 Jul 2010 23:25:04 PDT The existing session establishment scenario of IP multimedia subsystem (IMS) suffers from triangular routing for a certain period of time when an end SIP user or terminal is mobile. In this paper, the performance of three possible session establishment scenarios in a mobile environment is investigated by using an analytical model. The model is developed based on the expressions of cost functions, which may represent system delay and overhead involved in sessions establishment. Some numerical results are demonstrated which provides useful insights into the system behavior. Finally, a decision algorithm is demonstrated in this article to select the optimal session set up option. Muhammad T. Alam http://works.bepress.com/muhammad_alam/10 http://works.bepress.com/muhammad_alam/10 Mon, 11 Jan 2010 16:35:10 PST The existing session establishment scenario of IP Multimedia Subsystem (IMS) suffers from triangular routing for a certain period of time when an end IMS user or terminal is mobile. In this paper, the performance of three possible session establishment scenarios in a mobile environment is investigated by using an analytical model. The model is developed based on the expressions of cost functions, which may represent system delay and overhead involved in sessions establishment. Simulation results are demonstrated which provides useful insights into the system behaviour. Finally, a decision algorithm is demonstrated in this paper to select the optimal session set up option. Muhammad T. Alam http://works.bepress.com/muhammad_alam/9 http://works.bepress.com/muhammad_alam/9 Mon, 11 Jan 2010 16:35:09 PST In this paper, we provide complete end-to-end delay analyses including the relay nodes for instant messages. Message Session Relay Protocol (MSRP) is used to provide congestion control for large messages in the Instant Messaging (IM) service. Large messages are broken into several chunks. These chunks may traverse through a maximum number of two relay nodes before reaching destination according to the IETF specification of the MSRP relay extensions. We discuss the current solutions of sending large instant messages and introduce a proposal to reduce message flows in the IM service. We consider virtual traffic parameter i.e., the relay nodes are stateless non-blocking for scalability purpose. This type of relay node is also assumed to have input rate at constant bit rate. We provide a new scheduling policy that schedules chunks according to their previous node’s delivery time stamp tags. Validation and analysis is shown for such scheduling policy. The performance analysis with the model introduced in this paper is simple and straight forward, which lead to reduced message flows in the IM service. Muhammad T. Alam http://works.bepress.com/muhammad_alam/8 http://works.bepress.com/muhammad_alam/8 Sun, 30 Aug 2009 17:48:42 PDT Push-To-Talk can be viewed as an Instant Messaging service, enhanced with voice functionality. Most of the related work available today focuses on the performance analysis over PoC. However, they seemed to be completely ignorant about dimensioning PoC controller to optimize revenue for service providers. The contribution of this proposed work is as follows: 1. Provide access priority to special sessions based on available TRUs (Transmit/Receive Unit); 2. Optimize the session timer for a PoC controller; 3. Optimize number of session initiation for a PoC client during busy hour. We propose to dimension the PoC controller based on the assumption that the network grade of service is provided. This way a PoC server is able to control PoC functionalities to the optimal level. Muhammad T. Alam http://works.bepress.com/muhammad_alam/7 http://works.bepress.com/muhammad_alam/7 Sun, 30 Aug 2009 17:48:41 PDT The IP Multimedia Subsystem (IMS) is the technology that will merge the Internet (packet switching) with the cellular world (circuit switching). It will make Internet technologies, such as the web, email, instant messaging, presence, and videoconferencing available nearly everywhere. Presence is one of the basic services that is likely to become omnipresent in IMS. It is the service that allows a user to be informed about the reachability, availability, and willingness of communication of another user. Push to talk over Cellular (PoC) is another service in IMS that is intended to provide rapid communications for business and consumer customers of mobile networks. In order to become a truly successful mass-market service for the consumer segment, the only realistic alternative is a standardized Push-to-talk solution providing full interoperability between terminals and operators. Instant Messaging (IM) is the service that allows an IMS user to send some content to another user in near real-time. This service works under IETF’s Message Session Relay protocol (MSRP) to overcome the congestion control problem. We believe the efficiency of these services along with the mobility management in IMS session establishment has not been sufficiently investigated.In this research work, we identify the key issues to improve the existing protocols in IMS for better system behaviour. The work is centred on the three services of IMS: (1) Presence Service, (2) Push-to-Talk over cellular and, (3) Instant Messaging and over the issue of (4) IMS session set up. The existing session establishment scenario of IP Multimedia Subsystem (IMS) suffers from triangular routing for a certain period of time when an end IMS user or terminal is mobile. In this thesis, the performance of three possible session establishment scenarios in a mobile environment is compared by using an analytical model. The model is developed based on the expressions of cost functions, which represents system delay and overhead involved in sessions’ establishment. The other problem areas in optimizing presence service, dimensioning a PoC service and analysing service rates of IM relay extensions in IMS are identified. A presence server becomes overloaded when massive number of IMS terminals joins a network to request presence facility. Performance models are developed in this research to mitigate such load during heavy traffic for the presence service. Queuing analyses for different cases are provided while instant messaging chunks go through two consecutive relay nodes. The specific factors such as blocking probability, stability conditions, optimized subscription lifetime etc. in IMS environment parameters have been investigated. We have also elaborated models to dimension a PoC service for service providers with regards to controlling PoC session access, optimal PoC session timer, path optimization and number of allowable simultaneous PoC sessions for given network grade of service.In a nutshell, the contribution of this dissertation are: (a) a proposed robust scheduler to improve performance of the IMS presence service, (b) several derived models to dimension IMS Push-to-talk over cellular service, (c) a new mechanism to reduce cost for the IMS session set ups in mobile environment and (d) evaluation of message blocking and stability in IMS Instant Messaging (IM) service by applying queuing theories. All of these analyses have resulted in recommendations for the performance enhancements with optimal resource utilization in IMS framework. Muhammad Tanvir Alam Computer Science (0984) http://works.bepress.com/muhammad_alam/6 http://works.bepress.com/muhammad_alam/6 Sun, 30 Aug 2009 17:48:41 PDT Presence is one of the basic services which is likely to become omnipresent in IMS (IP Multimedia Subsystem). In this research, we propose a weighted class based queuing (WCBQ) mechanism to provide class differentiation and to reduce the load in the IMS presence server. The tasks of admission controller for the Presence Server (PS) are demonstrated. An optimized dropping time frame has been developed based on Langrange multiplier technique. If the dropping rate of the low prioritized and heavily weighted pre-existing messages is kept at a tolerable rate, then PS benefits significantly from the scheduling algorithm. Various simulation results have been shown that provides useful insight into the system behaviour during heavy traffic. Muhammad T. Alam http://works.bepress.com/muhammad_alam/4 http://works.bepress.com/muhammad_alam/4 Sun, 30 Aug 2009 17:48:40 PDT IMS (IP Multimedia Subsystem) is the technology that will merge the Internet (packet switching) with the cellular world (circuit switching). Presence is one of the basic services which is likely to become omnipresent in IMS (IP Multimedia Subsystem). It is the service that allows a user to be informed about the reachability, availability, and willingness of communication of another user. The flow of messages will be massive for large amount of publishers and watchers joining the IMS system, because of the security architecture of the IMS. Although the IETF (Internet Engineering Task Force) engineers have proposed several solutions to reduce the signalling overhead to facilitate the presence service, the heavy traffic flows have been compromised with several factors like real time view and information segregation etc. The life time of a watcher subscription has not received any attention so far. The constant time set (both short and long) may create bottleneck because of excessive message flow in the network. In this paper, we propose a mathematical model to analyse the system-performance of the IMS presence service during heavy traffic. The model derives the cost functions that are based on the real parameters of the Presence Server. An algorithm is demonstrated based on the derived model to set up an optimal life time for the Presence Server to assign to its joining IMS watchers during busy traffic. Simulation results have been shown that provide useful insight into the system behaviour. Muhammad T. Alam http://works.bepress.com/muhammad_alam/2 http://works.bepress.com/muhammad_alam/2 Sun, 30 Aug 2009 17:48:39 PDT IMS (IP Multimedia Subsystem) is the technology that will merge the Internet (packet switching) with the cellular world (circuit switching). Presence is one of the basic services which is likely to become omnipresent in IMS (IP Multimedia Subsystem). It is the service that allows a user to be informed about the reachability, availability, and willingness of communication of another user. The flow of messages will be massive for large amount of publishers and watchers joining an IMS system, because of the security architecture of the IMS. Although the IETF engineers have proposed several solutions to reduce the signalling overhead to facilitate the presence service, the heavy traffic flows have been compromised with several factors like real time view and information segregation etc. In this paper, we propose a mathematical model to analyse the system-performance of the IMS presence service during heavy traffic. The model derives the cost functions that are based on the real parameters of the Presence server. Simulation results have been shown that provide useful insight into the system behaviour. Muhammad T. Alam http://works.bepress.com/muhammad_alam/3 http://works.bepress.com/muhammad_alam/3 Sun, 30 Aug 2009 17:48:39 PDT In this research, we propose a weighted class based queuing (WCBQ) mechanism to provide class differentiation and to reduce the load for the IMS (IP Multimedia Subsystem) presence server (PS). The tasks of admission controller for the PS are demonstrated. Analysis and simulation models are developed to quantify the performance of WCBQ scheme. An optimized dropping time frame has been developed based on which some of the pre-existing messages are dropped from the PS-buffer. Cost functions are developed and simulation comparison has been performed with FCFS (First Come First Served) scheme. The results show that the PS benefits significantly from the proposed queuing and dropping algorithm (WCBQ) during heavy traffic. © 2006 World Enformatika Society Muhammad T. Alam http://works.bepress.com/muhammad_alam/1 http://works.bepress.com/muhammad_alam/1 Sun, 30 Aug 2009 17:48:38 PDT In this paper, we provide complete end-to-end delay analyses including the relay nodes for instant messages. Message Session Relay Protocol (MSRP) is used to provide congestion control for large messages in the Instant Messaging (IM) service. Large messages are broken into several chunks. These chunks may traverse through a maximum number of two relay nodes before reaching destination according to the IETF specification of the MSRP relay extensions. We discuss the current solutions of sending large instant messages and introduce a proposal to reduce message flows in the IM service. The analysis presented in this paper is divided into two parts. At the former part, we consider virtual traffic parameter i.e., the relay nodes are stateless non-blocking for scalability purpose. This type of relay node is also assumed to have input rate at constant bit rate. The later part of the analysis considers relay nodes to be blocking and the input parameter to be exponential. The performance analysis with the models introduced in this paper is simple and straight forward, which lead to reduced message flows in the IM service. Also, using our model analysis a delay based optimization problem can be easily deduced. Muhammad T. Alam