Pervasive and Mobile Computing 7 (2011) 584–594 Contents lists available at ScienceDirect Pervasive and Mobile Computing journal homepage: www.elsevier.com/locate/pmc Network selection in a WiMAX–WiFi environment Aggeliki Sgora a , Christos A. Gizelis a,∗ , Dimitrios D. Vergados a,b a Department of Information and Communication Systems Engineering, University of the Aegean, Karlovassi, GR-83200 Samos, Greece b Department of Informatics, University of Piraeus, 80, Karaoli & Dimitriou St., GR-18534 Piraeus, Greece article info Article history: Received 1 April 2010 Received in revised form 12 August 2010 Accepted 1 October 2010 Available online 26 October 2010 Keywords: Network selection Wireless environment MADM WiMAX WiFi abstract The tremendous growth of wireless technologies has introduced the potential of continuous service adaptation to the users’ needs by giving them the ability to be able to select and access the proper network based on different criteria. Moreover, next generation wireless networks have been designed to provide support for multimedia services, with different traffic characteristics and different Quality of Service (QoS) guarantees. However, the expansion of Wireless Local Area Networks (WLANs) and Worldwide Interoperability for Microwave Access (WiMAX) networks poses new research era in the decision of the access network selection. In this paper, the existing access network selection schemes are classified into three categories: the network-centric, the user-centric and the collaborative schemes, and are analyzed respectively. Moreover, we propose a multicriteria access network selection algorithm applied in a WiMAX–WLAN environment, in order to facilitate the provision of high quality services and at the same time to satisfy different types of user Service Level Agreements (SLAs). © 2010 Elsevier B.V. All rights reserved. 1. Introduction The interoperability of heterogeneous wireless technologies will serve as a mean to broaden the telecommunications market, since with the integration of different networks wider ranges and higher Quality of Service (QoS) can be provided to the users. In this context, several heterogeneous networks that consist of Worldwide Interoperability for Microwave Access (WiMAX) [1] and Wireless Fidelity (WiFi) [2] networks, have started to be operated. However, the expansion of WLAN and WiMAX networks also poses new challenges in the decision of the access network selection, since these technologies have their own unique characteristics, in terms of QoS, bandwidth allocation throughput, mobility management, and service availability. Also, next generation wireless networks have been designed to provide support for multimedia services, with different traffic characteristics, different (QoS) guarantees, and to satisfy different types of Service Level Agreements (SLAs) for an increasing number of mobile users. The simultaneous service requests by many users cause sometimes network overload and therefore force the Wireless Service Providers (WSPs) to interrupt the ongoing services of their subscribers or to reject new service requests. To overcome this situation, the WSPs may initiate a decision mechanism to select an available access network in the coverage area and transfer their subscribers to it, in order to satisfy the service requirements in QoS, and the load of the network consequently succeeding in profit maximization. Optimal access network is considered the network that can fulfill the service demand of the subscribers based on different types of SLAs, and ensure profitability to the WSPs. Moreover, since the selection of an access network depends on several parameters with different relative importance, such as the network and the application characteristics, the user preferences, the service cost, etc., the access network selection problem is usually looked at from the aspect of multicriteria analysis, and more specifically by applying different ∗ Corresponding author. E-mail addresses: asgora@aegean.gr (A. Sgora), cgizel@aegean.gr (C.A. Gizelis), vergados@aegean.gr, vergados@unipi.gr (D.D. Vergados). 1574-1192/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.pmcj.2010.10.001