Khalid Al-Begain

An adaptive QoS framework for integrated cellular and WLAN networks

The design of a network architecture that can efficiently integrate WLAN and cellular networks is a challenging task, particularly when the objective is to make the interoperation between the two networks as seamless and as efficient as possible. To provide end-to-end quality of service (QoS) support is one of the key stages towards such a goal. Due to various constraints, such as the unbalanced capacity of the two systems, handoff from user mobility and unreliable transmission media, end-to-end QoS is difficult to guarantee. In this paper, we propose a generic reservation-based QoS model for the integrated cellular and WLAN networks. It uses an adaptation mechanism to address the above issues and to support end-to-end QoS. The validity of the proposed scheme is demonstrated via simulation experiments. The performance results reveal that this new scheme can considerably improve the system resource utilization and reduce the call blocking probability and handoff dropping probability of the integrated networks while maintaining acceptable QoS to the end users.

Prioritised best effort routing with four quality of service metrics applying the concept of the analytic hierarchy process

In this paper, a new approach that applies the concept of the Analytic Hierarchy Process (AHP) in the area of routing in communication networks is proposed. AHP is a well-known model in the area of decision making with multiple objectives. In addition, a new algorithm called Enhanced Best Effort Quality of Service Routing (QoS) with Multiple Prioritised Metrics is proposed for connection-oriented point-to-point communications. Four QoS metrics have been considered: delay, bandwidth, security and loss probability. The results presented and discussed in this paper are focussed on demonstrating the effects of metric prioritisation on the routing decisions. It is found that changing priority of a metric from 0 (the lowest priority) to 1 (the highest priority) applying the proposed algorithm improves the value of that metric by an average of (20-60)% for 90% of utilisation range.

Modal Properties of an Index Guiding Nematic Liquid Crystal Based Photonic Crystal Fiber

This paper presents the results of the modal analysis of an index guiding soft glass photonic crystal fiber infiltrated with a nematic liquid crystal (NLC-PCF). The modal analysis is carried out using the full vectorial finite difference method which is capable of dealing accurately with anisotropic waveguide problems. The analyzed parameters are the effective index, birefringence, dispersion, effective mode area, and confinement losses for the two fundamental polarized modes. The effects of the structure geometrical parameters, rotation angle of the director of the NLC and temperature on the modal properties are investigated. The numerical results reveal that the proposed design offers high birefringence of 0.012 at the operating wavelength 1.55 mum with low losses for the two polarized modes. In addition, the structure is tailored to obtain a flat dispersion over a wide range of wavelengths with high birefringence.

Analysis of GSM/GPRS Cell with Multiple Data Service Classes

This paper is concerned with the performance modelling and evaluationof a General Packet Radio Service (GPRS) for a wireless Global System forMobile telecommunication (GSM) cellinvolving both voice and multiple class data services under a completepartitioning scheme (CPS). The GPRS is modelled as a system ofaccess and transfer queues in tandem having an external multiple classcompound Poisson bursty traffic with geometrically distributedbatches under first-come-first-served (FCFS) and generalised processor-sharing(PS) scheduling disciplines, respectively. The proposed queueing model isvalid for both uplink and downlink connections and provides multiple classdata services with different arrival rates, interarrival-time squaredcoefficients of variation (SCVs), file (burst) sizes and different PSdiscrimination service levels.Based on the principle of maximum entropy (ME), a product formapproximation is characterised for the two queues in tandem, subject to queueing theoretic mean value constraints. The MEsolution implies a decomposition of the system into individual singleserver building block queues, each of which can be analysed inisolation. Consequently, ME closed form expressions and simulation resultsfor the aggregate state probability together with the marginal mean queuelength and blocking probability are divised to assess the credibility of theME solution and also to study the effect of external GPRS bursty traffic uponthe performance of the wireless cell.

Enhanced Common Radio Resources Managements Algorithm in Heterogeneous Cellular Networks

Deployment of new radio technologies in the mobile world has not been more critical than it is now. The customers and applications have been starving for more data throughput while operators are struggling to deliver the promised high data rates to customers. Operators are using existing traffic information from GSM/GPRS technologies to deploy WCDMA and HSDPA systems. The deployment of WCDMA in the existing GSM/GPRS cell sites has proven to enhance the network resources available to the operators. The diversity of the services and the availability at the moment of two radio access networks to choose from to deliver these services makes the management of available resources rather complex. Therefore, Common Radio Resources Management (CRRM) has been standardized by 3GPP. Radio Access Technology (RAT) selection is a key element for CRRM. In this paper, we propose a new algorithm to optimize the available network resources in multi radio environment based on service requests. The proposed algorithm efficiently optimizes the radio resources available based on the services supported in 3GPP standards

Opto-VLSI-based correlator architecture for multiwavelength optical header recognition

A novel optical correlator employing an opto-very-large-scale-integration (VLSI) processor to construct the routing lookup table, in conjunction with an array of fiber Bragg gratings (FBGs) for multiwavelength optical header recognition is demonstrated. The FBG array provides wavelength-dependent time delays, whereas the opto-VLSI processor generates wavelength intensity profiles that match arbitrary bit patterns. The recognition of 4-b optical patterns is experimentally demonstrated at 2.2 Gb/s by showing that the correlator produces an autocorrelation waveform of high peak whenever the input bit pattern matches the wavelength intensity profile.

Investigation of the M2/G2/1/∞,N queue with restricted admission of priority customers and its application to HSDPA mobile systems

This paper investigates a queuing system for QoS optimization of multimedia traffic consisting of aggregated streams with diverse QoS requirements transmitted to a mobile terminal over a common downlink shared channel. The queuing system, proposed for buffer management of aggregated single-user traffic in the base station of High-Speed Downlink Packet Access (HSDPA), allows for optimum loss/delay/jitter performance for end-user multimedia traffic with delay-tolerant non-real-time streams and partially loss tolerant real-time streams. In the queuing system, the real-time stream has non-preemptive priority in service but the number of the packets in the system is restricted by a constant. The non-real-time stream has no service priority but is allowed unlimited access to the system. Both types of packets arrive in the stationary Poisson flow. Service times follow general distribution depending on the packet type. Stability condition for the model is derived. Queue length distribution for both types of customers is calculated at arbitrary epochs and service completion epochs. Loss probability for priority packets is computed. Waiting time distribution in terms of Laplace-Stieltjes transform is obtained for both types of packets. Mean waiting time and jitter are computed. Numerical examples presented demonstrate the effectiveness of the queuing system for QoS optimization of buffered end-user multimedia traffic with aggregated real-time and non-real-time streams.

Towards a User-Centric and Quality-Aware Multimedia Service Delivery Implementation on IP Multimedia Subsystem

IP multimedia subsystem (IMS) originating from the 3GPP is pivotal on the road to next generation all-IP networks. Multimedia applications are potential drivers for the adoption of next generation IP multimedia subsystem (IMS) and could be a decisive factor in its deployment. They are expected to generate revenue to the operators and justify their investment in IMS. And, for these multimedia services to be widely accepted by the end users, guaranteed and adaptable quality of service provision across heterogeneous access networks and heterogeneous device types is mandatory. In this paper, a generic, adaptive, controlled service delivery framework implementation for multimedia applications on IMS architecture is proposed. The framework is designed to be user-centric, adaptable to terminal mobility and session mobility with minimum session disruption enabling a better end-to-end QoS. It is at the session-level, completely user-driven and does not account for the network-level QoS. It employs the Session initiation protocol (SIP), which is the signaling protocol for the 3GPP specified IMS. The purpose behind designing the framework is to evaluate the provisioning of quality-adaptive multimedia services on IMS network and analyze the performance with respect to delay induced by quality adaptation procedures during session and terminal mobility which might contribute towards the end-to- end quality of service delivered to the users.

A Comparative Capacity/Coverage Analysis for CDMA Cell in Different Propagation Environments

In the design of cells in mobile communication systems, path loss prediction models play an important role and have been the subject of the study for some time (M.F. Ibrahim and J.D. Parsons, IEE Proceedings, Vol. 130, No. 5, 1983). This paper presents the analysis of two main factors that affect the capacity bounds in a UMTS cell for different propagation models. These are the (i) interference levels at Node B, which increases with the number of active users, and (ii) the limited sending power of the user equipment (UE) which may not be able to send signals with enough power to reach Node B with the required received power level due to path loss. The aim of this paper is to analyse the capacity/coverage of the uplink of UMTS system in different propagation environments (free space, suburban, urban, dense urban, rural) and derive the capacity bounds for the UMTS cell. The capacity bounds have been extracted based on the extended COST-231 Hata model (http://cost.cordis.lu/src/whatiscost.cfm). COST-231 Hata is an extension of the Okumura—Hata model which covers the higher frequencies (G.L. Stüber, “Principles of Mobile Communications,” Kluwer, 1996) necessary for WCDMA. The basic model describes the propagation loss in an urban environment, but a number of correction factors can be applied to extend its application to a broader range of environments. The analysis takes into account a number of capacity influencing factors such as the CDMA code non-orthogonality, the inter-cell interference, imperfect power control, and different service specific factors. The simulation results show the effect of different system and varying environmental parameters upon the systems capacity in different environments. The results clearly demonstrate that it is too optimistic to rely on studies based on free space assumptions.

Performance Evaluation of Wireless Networks

Wireless technologies are without any doubt shaping the beginning of the new millennium. Cellular networks (2/2.5/3 Generations) have reached global coverage and wireless LANs are providing high speed internet access to city centres and hot spot areas. The principle of computing anytime anywhere is becoming reality. Consequently, there has been tremendous interest recently in the convergence of wired (fixed) networks and mobile wireless and local wireless access systems and networks. B3G and 4G concepts have been the very hot subject of much research and many standardization activities throughout the world. Many B3G/4G related technical committees are taking the initiative to produce enhanced proposals of radio transmission technologies, wireless applications protocols, All-IP wireless network architectures, super signal processing and advanced system prototypes for B3Gwireless and 4Gmobile. However, there are several performance issues that need to be addressed and resolved before a global and widescale integrated broadband infrastructure of convergent multi-service networks can be established towards the next generation Internet with efficient support of multimedia applications. This special issue presents the best six papers from the first workshop on Performance Modelling of Wired and Wireless Mobile Computing and Networks held in conjunction with the 11th ICPADS 2005, Fukuoka, Japan. These papers were selected by the scientific programme committee and extended and revised before undergoing a rigorous period of peer-review. The purpose of this workshop was to provide an international forum for researchers and industry practitioners to present their state-of-art research on performance modelling and evaluation studies in all aspects of wired and wireless networking and computing and to exchange ideas and explore new avenues of collaborations. This workshop attracted a large number of quality papers and the presentations generated very interesting discussions. This special issue comprises of six papers covering experimental studies, analytical modelling, simulation studies, traffic modelling and applications for challenging issues such as routing mechanisms, mobility management, traffic modelling, etc in wireless networks. Pong et al. investigated the relationship between the cell capacity and the station mobility pattern. They chose the most popular and widely implemented Random Waypoint Mobility model for the analysis. They presented an analytical model to study the effect of the Waypoint model on the achievable throughput of a cell and the variability in the channel demand. It was found that the throughput could be over-estimated if the cell coverage was comparable in size to the mobility region, but this effect diminishes as the mobility region becomes relatively larger. They illustrated this effect quantitatively with IEEE 802.11 WLANs as an example. Seah et al. reported an experimental study on the performance of interconnected MANETs running two different routing protocols, namely, the Ad hoc On-Demand Distance Vector (AODV) and Optimized Link State Routing (OLSR) protocols, and showed that with the use of multiple gateways, it is possible to viably interconnect multiple networks running different MANET routing protocols. They validated their experimental study against simulation and presented the credibility of their proposed scheme in large networks. Yassein et al. in their paper carried out a detailed investigation to see the effects of key system parameters in a typical MANET, including node speed, pause time, traffic load, and node density on the performance of probabilistic flooding. In this paper they claimed that the probabilistic flooding, being one of the earliest techniques, has not been considered for broadcasting in MANETs. Their results reveal that most of these parameters have a critical impact on the reachability and the number of International Journal of Wireless Information Networks, Vol. 13, No. 2, April 2006 ( 2006) DOI: 10.1007/s10776-006-0026-1