Francisco Fontes

Enhanced Media Independent Handover Framework

The Internet access paradigm is changing and a wide range of overlapping radio access technologies, such as WiMAX, Wi-Fi, 3GPP UMTS/LTE and DVB-H, will soon be available to most users and their multi-access devices. Therefore, novel mechanisms and protocols are needed to provide seamless mobility between different wireless access technologies. This paper presents novel handover procedures, based on media independent schemes, to address seamless mobility in heterogeneous environments. We propose an enhanced media independent handover framework (eMIHF), which extends IEEE 802.21 by allowing for efficient provisioning and activation of QoS resources in the target radio access technology during the handover preparation phase, and efficiently interacts with the mobility processes of different technologies employed. We evaluate eMIHF using the ns-2 simulator, and demonstrate that the proposed handover scheme provides seamless mobility, with low latency and no packet loss.

Context-aware media independent information server for optimized seamless handover procedures

The proliferation of the Internet and wireless access technologies introduced the constant mobile paradigm, in which users want to be always connected making use of the best available networks and technologies. In order to provide seamless connectivity among the new wireless access technologies, such as Wi-Fi, WiMAX and 3GPP (UMTS, HSPA and/or LTE), the IEEE 802.21 standard has defined the media independent handover framework. However, although there is a recognized importance of the IEEE 802.21 framework in the vertical handover optimization procedures, it is still necessary to improve this insofar as the radio access technologies individual features are concerned. Moreover, the IEEE 802.21 standard defines an information server that is only able to manage static network information. It is clear that in current and future environments, dynamic context information from network side entities is very important for the vertical handover decision procedures. This paper presents the integration process of the MIH framework with the aforesaid wireless access technologies, enabling the complete support of all the envisioned IEEE 802.21 handover phases. It describes how IEEE 802.21 can be adapted to the specific characteristics of the access technologies, and the mechanisms required to perform the several handover phases between Wi-Fi, WiMAX and 3GPP. Furthermore, this paper addresses a new concept of a context-aware information server that is able to store, manage and deliver real-time dynamic information retrieved from both the network and the terminal side entities, such as the user preferences, running services, mobile nodes characteristics and available network resources. The purpose of this context-aware information server is to optimize the handover preparation and decision phases. Additionally, a meticulous evaluation of the depicted handover mechanisms optimized by the IEEE 802.21 framework is presented, demonstrating that seamless handover between WiMAX, Wi-Fi and 3GPP access networks is achieved with low latency and no packet loss. Finally, the benefits of integrating a context-aware information server in the seamless handover procedure are also evaluated. To perform this evaluation, significant add-ons, also described in this paper, were implemented in the NS-2 simulator to support all the functionalities defined by the IEEE 802.21 standard, as well as the proposed extensions to the standard.

Superfluidity: a flexible functional architecture for 5G networks

We propose the innovative architecture of Superfluidity, a Horizon 2020 project, co-funded by the European Union. Superfluidity targets 5G networks, by addressing key network operator challenges with a multi-pronged approach, based on the concept of a flexible, highly adaptive, superfluid network. Superfluidity supports rapid service deployment and migration in a heterogeneous network environment, regardless of the underlying hardware. The overall proposal offers advanced capabilities in terms of service deployment and interoperability, while guaranteeing high-performance levels end-to-end. Copyright

WiMAX for Emergency Services: An Empirical Evaluation

WiMAX, as a Broadband Wireless Access technology for Metropolitan Area Networks, supporting fixed and mobile terminals, is very promising for Next Generation Networks. Emergency Services can also strongly benefit from WiMAX features, allowing the exploitation of novel application scenarios and business models. This paper presents a set of scenarios, such as Environmental Monitoring, Telemedicine and Fire Prevention, defined and implemented in several European testbeds, interconnected by the European research network GEANT 2, in the framework of the WEIRD project. In particular, we focus our attention on the scenario implemented in the Portuguese testbed - Fire Prevention - providing a detailed description about the testbed planning, implementation and evaluation.

A vendor-independent resource control framework for WiMAX

In this paper, a novel solution to dynamically control the resources of a WiMAX system is proposed. The presented solution is aligned with the NGN trends, as well as with the WiMAX Forum guidelines and architecture. The interaction with the WiMAX systems is performed through SNMP, supporting the standardized IEEE 802.16 f MIB. Furthermore, the paper defines an horizontal abstraction layer, hiding the WiMAX equipments specific functionalities from the network control plane, thus providing robustness and vendor independency. In order to verify the performance of the proposed framework, a WiMAX testbed has been installed, and a set of measurements have been made, showing that the proposed system ensures a quick resource allocation, even for a large number of simultaneous resource reservation requests.

Quality of service differentiation support in WiMAX networks

Ubiquitous broadband Internet access is an important requirement to satisfy user demands and support a new set of real time services and applications. WiMAX, a broadband wireless access solution for wireless metropolitan area networks, covering large distances with high throughputs, is a promising technology for next generation networks. Nevertheless, for the successful deployment of WiMAX based solutions, quality of service (QoS) is a mandatory feature that must be supported. In this paper, the lack of QoS support for WiMAX in NS2- NIST software is addressed. A QoS framework, composed by a packet classification mechanism and a scheduler, has been specified and implemented on the simulator, providing service differentiation over WiMAX networks. Furthermore, in order to validate the developed solutions, a set of QoS oriented scenarios have been simulated and the obtained results show that the implemented model is able to efficiently differentiate between the different traffic classes defined in the WiMAX model.

The Cost of Using IEEE 802.16d Dynamic Channel Configuration

Ubiquitous broadband Internet access is an important requirement to satisfy user demands and support a new set of real time services and applications. IEEE 802.16, as a broadband wireless access technology, can significantly contribute in this area. It is able to provide high throughput over large distances, with intrinsic QoS support, in line-of-Sight and Non- line-of-Sight environments. This paper discusses a network architecture, based on IEEE 802.16 d compliant equipments, which is able to support real-time services with QoS integration through dynamic configuration of the 802.16 channel, using the NSIS framework. Tests have been carried out to evaluate the QoS performance of the defined architecture, demonstrating that it is perfectly capable of handling and supporting real time services, using dynamic configuration of the 802.16 channel, without introducing an excessive cost in the network.

Admission Control in IP Multicast over Heterogeneous Access Networks

Network operators have been reluctant to deploy IP multicast services mainly due to the lack of native control over multicast groups. This lack of control does not only prevent operators from generating revenue from multicast-based services but also hinders regular network management. In this work we identified the network elements where admission control should be enforced for multicast sessions spawning over heterogeneous access networks. The architecture proposed uses existing AAA functionality to perform user identification and multicast session admission control. This control is made at the network layer with no protocol modifications. Three access networks were considered: xDSL, WiMAX and UMTS.

Quality of Service Differentiation in WiMAX Networks

Broadband Wireless Access (BWA) based on the IEEE 802.16 standards [IEEE 802.16, 2004] [IEEE 802.16, 2005], also known as Worldwide Interoperability for Microwave Access (WiMAX), is gaining momentum as more and more field trials are transformed in commercial roll-outs. Very much likely, this is certainly a merit of the combined effort of the IEEE 802.16 standardization community, the WiMAX Forum [WiMAX Forum a, 2008] [WiMAX Forum b, 2008] and the research community. As of today, standards have matured, the WiMAX Forum has setup its certification program in order to foster interoperability, and the research community went through technological details up to an extent, such that many operators consider the risks associated with commercial deployment predictable. Yet, WiMAX is still not deemed as globally established. This technology is very new and a competing system, namely Long-Term Evolution (LTE) [3GPP, 2009], is progressing in a similar pace. Which technology will finally make it through in the market, or will we have even several co-existing ones, is, among others, influenced by the research community. The better a technology is understood, the more likely it will be adopted by manufacturers, vendors and operators. Key to scientific consideration is the availability of reliable simulation tools. This applies equally to WiMAX and any other technology and is embodied by an emerging business of commercial simulators like OPNET [OPNET] and Qualcomm [Qualcomm]. Unfortunately, these simulators are fairly expensive and/or their use is strictly licensed. As monetary considerations and openness frequently prevail, in particular in academia, NS-2 [NS-2], as open-source alternative, still retains its position. Naturally, open-source software rarely approaches commercial standards, especially in terms of completeness and documentation. This is, for example, the case for the public available WiMAX module for NS-2. This module supports several WiMAX features but lacks a very essential one, Quality of Service (QoS) support. The lack of this feature 34

IEEE 802.16 Packet Scheduling with Traffic Prioritization and Cross-Layer Optimization

WiMAX is emerging as a broadband wireless access technology to satisfy end user expectations, containing a new set of advantages in terms of throughput, coverage and QoS support at the MAC level which allows convergence of several different types of applications and services. For that reason, the allocation of resources or scheduling becomes of greater importance. This paper focuses on a cross-layer scheduling optimization solution for IEEE 802.16. The relevant features of the proposed packet scheduling optimization scheme consist: of prioritization of users within the same traffic class, allowing for example to an operator, differentiated treatment among users, for instance distinguishing between premium or gold users and silver users; and also cross layer optimization which implies radio resource optimization and a more effective scheduler decision. Simulation scenarios are presented to demonstrate how the scheduling solution allocates resources through particular WiMAX MAC layer implementation in the NS-2 simulator. Results show that the new mechanism implementation results in an improvement to the simple Round Robin fashion present in the original simulation model, being able to increase differentiation between different classes and decrease packets delay, due to its cross-layer processing and traffic prioritization.