Highlights from the Workshop Pervasive Broadband Wireless Access: Toward Long-Term Evolution

The Final Workshop of the CROSSNET (Cross-Layer Design and Network Planning for B3G Systems, http://www.e-projects.ubi.pt/crossnet/) project took place on February 19, 2008, at Instituto de Telecomunicações, Portugal. There were 133 participants, 31 percent from academia, 22 percent from R&D laboratories, 15 percent from telecommunication services and maintenance, 11 percent from manufacturers, 11 percent from regulators, 7 percent from operators, and 3 percent from public bodies and safety ser- vices. From the feedback received from participants, the adhesion to the event was justified by their need to access discussion fora on technology trends and challenges in the telecommunications sector, and research on deployment strategies for pervasive broadband wireless access was faced as an endeavor. The keynote speakers were Prof. Elvino de Sousa, University of Toronto; Dr. Tom Rondeau, Trinity College Dublin; Prof. Loutfi Nuaymi, Telecom Bretagne; and Prof. Javier Gozalvez, Uwicore, University Miguel Hernandez, Spain, covering the topics of 4G visions, broadband wireless access, cognitive radio, and dynamic spectrum access. Presentations also covered opportunities, challenges, and visions for long-term evolution, vehicular communications, and future spectrum management. One of the proposals is to deploy base stations (or access points) organically building autonomous infrastructure wireless networks. The Workshop was sponsored by Ordem dos Engenheiros (Colégio de Engenharia Electrotécnica and Especialização de Telecomunicações), IEEE (Portugal Section and VTS Portugal Chapter), Academia de Ciências — Instituto de Altos Estudos, Academia de Engenharia, Advanced Resources, Alcatel-Lucent, ANACOM, Ericsson, FCT, Instituto Superior Técnico, Microsoft, POSC, PT Inovação, Rhode & Schwarz, University of Aveiro, and University of Beira Interior, Portugal. A copy of abstracts and the majority of presentations are available for download at http://www.e-projects.ubi.pt/ crossnet/workshop.html The coexistence scenario across heterogeneous networks should be seen by the end user as the ability to attain a plethora of multimedia services under a single platform in a ubiquitous and transparent fashion, providing the impetus for system solutions addressing network discovery, selection, con- nection, and reselection as the terminal equipment migrates between collocated networks. In the scope of CROSSNET, interoperability among B3G, IEEE 802.11, and IEEE 802.16 is investigated, since these technologies are widely seen as the enablers for converging the wireless and mobile worlds. By using the existing simulation platforms for different systems such as high-speed downlink packet access (HSDPA) and WiFi, a common radio resource management (RRM) module is being developed in order to provide a step toward network convergence to hide the heterogeneity between operators and technologies. CROSSNET has implemented an HSDPA system-level evaluation tool for evaluating RRM protocol performance. Furthermore, cross-layer scheduling and link adaptation provide key output to enhance the effective capacity and coverage in a more cost-effective way. The IEEE 802.11 WLAN (also known as WiFi) technology has seen high penetration in the broadband fixed wireless access (BFWA) market to provide data services to hotspot areas, mainly due to ease of network deployment and low cost. However, with the quality of service (QoS) constraints becoming evermore stringent, the IEEE opted to evolve the 802.11 standard to 802.11e, a WLAN technology for QoS support. The key enhancement in this evolved standard can be found in the MAC layer, which now provides support for differentiated service classes and proposes techniques to enhance the ability of the physical (PHY) layer to deliver time-critical multimedia traffic. CROSSNET is addressing innovative enhancement to IEEE 802.11e by pursuing research studies on the application of cross-layer signaling to improve QoS delivery, and provide more efficient usage of radio resources by adapting such parameters as arbitrary interframe spacing, a differentiated backoff procedure, and transmission opportunities, as well as acknowledgment policies. A key output from this work is also the development of an event-driven system-level simulator for IEEE 802.11e. Radio access technology (RAT) selection algorithms have been studied in the literature, and nowadays equipment with several RATs incorporated is already common. Results on the gains obtained by using WiFi as a backup network for HSDPA have been obtained. The coexistence of the two standards allows prevention of QoS deterioration when in a low mobility scenario. The proposed RAT selection algorithm is based on the load of each system, and the results show a gain of 60 percent on supported network load with the implementation of this QoS procedure over the HSDPA-alone system. As a consequence, when there is heavy load on the IEEE 802.11e network, acceptance of high-priority services will affect the delay in low-priority services like FTP. Worldwide Interoperability for Microwave Access (WiMAX) is the commonly used name for broadband wire- less access based on the IEEE 802.16 family of standards. WiMAX provides full QoS constrained service types with provisioning for high-data-rate applications targeted toward wide area coverage, and is widely considered to be a strong competitor in the mobile world. Following wireless trends toward ever more efficient networks, CROSSNET designed, implemented, and validated advanced scheduling algorithms based on a cross-layer framework architecture, exploiting information between the PHY and MAC layers. The scheduling policy, considered pivotal in controlling the trade-off between maximizing capacity and QoS delivery, uses cross-layer information to provide preferential treatment to mobile users according to QoS profile, channel conditions, and service classes. A key achievement from CROSSNET is the development of a C++ based mobile WiMAX system simulator that is being used to pursue this line of study.

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