Abed Ellatif Samhat

A New Approach of UMTS-WLAN Load Balancing; Algorithm and its Dynamic Optimization

The problem of dynamic load balancing in heterogeneous networks is investigated. The sub-systems considered are a UMTS network with WLAN hotspots. A load balancing algorithm is first proposed that can push traffic between the two sub-systems according to load conditions and predetermined load thresholds. To adapt the algorithm to traffic condition, the load threshold for the UMTS to WLAN vertical handover is auto-tuned. The auto-tuning process is orchestrated by a fuzzy logic controller that is optimized using the fuzzy Q-learning algorithm. Numerical simulations using a semi-dynamic network simulator illustrate the effectiveness of the proposed approach.

Semi-dynamic simulator for large-scale heterogeneous wireless networks

In this paper, we present a multisystem wireless simulator based on a semi-dynamic principle with sequential executions to assess the performance of a large-scale network with tens to hundreds of base stations and WLAN hot spots. The semi-dynamic simulator achieves a fast computation time by exploiting the advantages of both analytical modelling and event driven simulation. The simulator architecture is briefly illustrated and the theoretical background is highlighted as well as the implemented Radio Resource Management (RRM) and Joint-RRM (JRRM) algorithms. The simulator is well suited to guide heterogeneous radio network deployment and design. Simulation results are provided to illustrate the practical use of the simulator as well as its efficiency.

The Celtic Gandalf framework

Third generation mobile systems are driving a multi-system network landscape. Network management is crucial to guarantee optimum cooperation between network sub-systems. The aim of the Gandalf project is to use large scale network monitoring, advanced radio resource management rules and appropriate quality of service evaluation in order to achieve automation of network management tasks in a multi-system environment

Security and AAA Architecture for WiFi-WiMAX Mesh Network

This paper presents a flexible architecture for hybrid wireless network where WiFi and WiMAX in mesh mode are deployed in a complementary way. The end user can access to high bit rate Internet services directly by WiMAX technology through the 802.16 base stations or by WiFi technology through a CPE/AP connected to the 802.16 base station. We provide a brief description of the different functional entities and we investigate several technical issues including infrastructure and aspects related to the AAA (authentication, authorization, accounting) procedures for users as well as the system security.

A Layer 2 Scheme of Inter-RAT Handover between UMTS and WiMAX

The future B3G or 4G mobile networks will consist of heterogeneous networks, including GSM, UMTS, WiMAX and WIFI. In order to realize a seamless vertical handover (inter-RAT handover), a variety of interworking architectures and inter-RAT handover mobility managements have been proposed. Based on the integrated coupling architecture, we propose a novel common interworking sublayer (IW sublayer) at layer 2 on RNC and UE to provide a seamless PS inter-RAT handover between UMTS and WiMAX systems. This IW sublayer scheme focuses on eliminating packet loss and reducing handover latency which are common problems for most inter-RAT handover scenarios. Compared with other context transfer schemes, the simulation results show the IW sublayer with ARQ mechanism can achieve a lossless and prompt handover procedure. In addition, this IW sublayer scheme can eliminate false fast retransmit of TCP traffics which is usually caused by packet losses or out-of-order packet arrivals.

Analytical framework for dimensioning hierarchical WiMax-WiFi networks

Providing diverse, ubiquitous and cost-effective broadband services is a foremost challenge for the telecommunication community. Fixed WiMAX or IEEE 802.16d is one of the most promising radio access technologies, providing high performance similar to wired xDSL systems, yet superior to that of current 3G mobile technologies. Numerous deployment concepts are foreseen for WiMAX networks. They are designed to cover isolated areas, thus embodying an appealing solution for cellular networks or wireless backhaul for WiFi access. The latter concept is of interest in this paper that puts forward an analytical model based on the economical aspects to dimension hierarchical WiMax-WiFi networks. The proposed model consists in replacing a finite number of nodes by an equivalent continuum. Its key feature lies in accounting for the effect of interference as well as for the physical layer and channel characteristics in an easy and straightforward manner. On the one hand, the model takes into consideration frequency planning and scheduling aspects; and on the other hand, it provides tractable formulae of the end-user mean capacity and coverage probability in order to properly dimension the hybrid network. Last but not least, the economical facet of network planning is considered to unravel the design trade-offs between maximizing the service provider profit and satisfying the end user requirements in terms of performance.

A layer 2 scheme for inter-RAT handover between UMTS and WiMAX in tight coupling architecture

The future B3G or 4G mobile networks will consist of heterogeneous networks, including GSM, UMTS, and WiMAX. In order to realize a seamless vertical handover (inter-RAT handover), a variety of interworking architectures and inter-RAT handover mobility managements have been proposed. In this paper we consider the tight coupling architecture to achieve the interconnection between UMTS and WiMAX systems. A novel common interworking sublayer (IW sublayer) is proposed at layer 2 on RNC, W-RNC and UE to provide a seamless PS inter-RAT handover between UMTS and WiMAX. This IW sublayer scheme, which features SR ARQ mechanism, focuses on eliminating packet loss and reducing handover latency that are common problems for most inter-RAT handover scenarios. The simulation results of the tight coupling architecture show that, compared with other context transfer schemes like buffering-and-forwarding of FMIPv6, the IW sublayer solution can achieve a lossless and prompt handover.

Fluid Model for Wireless Adhoc Networks

In this paper, we propose an analytical fluid model for adhoc wireless networks. Our fluid model consists in replacing a finite number of nodes by an equivalent continuum - characterized by a density of nodes - and disseminated in the network according to some distribution function. The key feature of our model is that it takes into account the effect of interference, the CSMA/CA mechanism and radio propagation aspects in an easy and straightforward way. We will give closed form formulae of the Mean Capacity per node and the Coverage Probability, along with an evaluation of the impact of nodes density, network size and carrier sense range on overall performance.

Performance analysis of the IEEE 802.11 DCF with imperfect radio conditions

IEEE 802.11 Wireless Local Area Networks (WLAN) are widely used in recent years. The basic 802.11 Medium Access Control (MAC) method for controlling the medium access is the Distributed Coordination Function (DCF) which is an access scheme based on the contention principle using Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA). Most of the analytical studies investigating the performance of DCF and the saturation throughput at MAC layer assume ideal channel conditions where the retransmission of a packet only results from a collision. In this paper, we present an analytical model to estimate the saturation throughput at the MAC layer for a fixed number of stations taking into account the imperfections of the radio channels. The latter is investigated for different modulation techniques.

Inter-RAT Handover Between UMTS And WiMAX

The future beyond third generation (B3G) or fourth generation (4G) systems will consist of different radio access technologies, such as GSM/GPRS, UMTS, WiFi, and WiMAX. Many intensive efforts have been made to identify the unsolved issues about the future mobile systems, and one important issue is what the future vertical handover management solution will be. A variety of mobility management solutions have been proposed, such as MIPv6/FMIPv6 (D. Johnson, et al., 2004; R. Koodli, 2005), SCTP (M. Afif, et al., 2006), interRAT (Radio Access Technologies) handover of 3GPP (3GPP TS 43.129; 3GPP TR 25.931). Among these solutions, the layer 2 inter-RAT handover solution of 3GPP is a promising way for its high reliable handover procedure. Unfortunately, the 3GPP inter-RAT solutions only support inter-RAT handover between cellular networks, and do not support inter-RAT handover between WiMAX (Worldwide Interoperability for Microwave Access) and UMTS (Universal Mobile Telecommunications System). Another important issue is the interworking architecture and the coupling scenario that are used to provide an efficient inter-RAT handover management. Depending on where is the coupling point, there are several interworking architectures: no coupling, loose coupling, tight coupling, very tight coupling (integrated coupling) (G. Lanpropoulos, et al., 2005). The loose coupling and tight coupling architectures often use Mobile IP or part of Mobile IP as the handover management protocol. So these two kinds of coupling architectures require less complicated modifications to the existing protocol stacks and are more flexible than integrated coupling. However, they often suffer from longer handover latency varying from some hundreds of milliseconds to some seconds. The integrated coupling generally achieves better handover performance at expense of adding complex modification to existing network protocol stacks. In recent years, the 3GPP and IEEE organizations have proposed their respective interworking solutions for convergence of heterogeneous networks. For instance, the ongoing 3GPP standard for interworking between UMTS and WiFi (3GPP TS 23.234) only focuses on the control plane, and defines the interworking topologies, access gateways, 27