ICEST 2005 June 29 - July 1, 2005, Nis, Serbia and Montenegro Loosely-coupled interworking of GSM/GPRS mobile networks and Wireless LANs Toni Janevski 1 Aleksandar Tudzarov 2 Dusko Temkov 3 Perivoje Stojanovski 4 Abstract – In this paper we propose a solution for interworking of cellular networks, such as GSM/GPRS networks, and Wireless LAN. Proposed interworking is based on so-called loosely- coupled architecture, where the integration is based on the Authentication, Authorization and Accounting i.e. AAA. The applicative solution for GSM/GPRS-WLAN integration includes development of several network nodes, such as WLAN Access Controller and WLAN AAA charging gateway. The proposed solution provides possibility for efficient deployment of WLAN network to existing GSM/GPRS system of the mobile operator. Keywords - AAA, Cellular, Internetworking, Mobile networks, Wireless LAN. I. INTRODUCTION Wireless LAN (WLAN) is a complementary service offering for mobile operators. Mobile operators using GSM and GPRS already have infrastructure that covers wide-area. However, they lack the higher data rates for Internet services that are demanded by most of the users, which are accommodated to the wired Internet and expect similar offer in a wireless environment. WLAN may be deployed in Public, Corporate or Residential environments, where GSM/GPRS systems already are accommodated. In particular it is suitable for indoor public hot spots, hotels, exposition areas, and corporate business. Hence, with a little additional investment mobile operators can further expand the packet (i.e. Internet) service by adding throughput and capacity in hot spots by using WLAN. General Packet Radio Service (GPRS) is a development of GSM that provides packet switched data communications. On the other side, Wireless LAN (WLAN) is a relatively cheap technology and provides many times higher bandwidth than GPRS for packet traffic, but with many times smaller cells (up to 50-100 meters). 1 Toni Janevski is with Faculty of Electrical Engineering, University “Sv. Kiril i Metodij”, Karpos 2 bb, Skopje, R.Macedonia, E-mail: tonij@etf.ukim.edu.mk 2 Aleksandar.Tudzarov is graduate student at the Faculty of Electrical Engineering, Skopje, R.Macedonia, E-mail: Aleksandar.Tudzarov@mobimak.com.mk 3 Dusko Temkov is graduate student at the Faculty of Electrical Engineering, Skopje, R.Macedonia, E-mail: Dusko.Temkov@mt.com.mk 4 Perivoje Stojanovski is graduate student at the Faculty of Electrical Engineering, Skopje, R.Macedonia, E-mail: pstojanovski@mt.net.mk The most used WLAN standard today is IEEE 802.11b, which is relatively cheap and offers high data rate up to 11 Mbps. Wireless LANs IEEE 802.11b are already widely deployed in developed countries and also in some companies in Macedonia. Other currently available WLAN standard for interworking are 802.11a and 802.11g, which offer data rates up to 54 Mbps. Due to interest for WLAN considering lower price than classical cellular infrastructure, large vendors on the telecommunication market have created different solutions for Wireless LAN operated by mobile operators. Some of these solutions are described in [1-51]. In this paper we propose and describe in details efficient and cost-effective system for unified Authentication, Authorization and Accounting (AAA) for loosely-coupled PLMN-WLAN internetworking, in particular, for the scenario where PLMN operator adds its own WLAN network to offer WLAN service. The paper is organized as follows. In Section II we discuss architectures for PLMN-WLAN interworking. Proposed AAA solution is given in Section III. Finally, Section IV concludes the paper. II. ARCHITECTURE FOR PLMN-WLAN INTERWORKING Depending on the degree of inter-dependence that one is willing to introduce between the PLMN network and the 802.11 network, there are two different ways of integrating the two wireless technologies. They are usually defined as [16]: • Loosely-coupled internetworking (loose coupling) • Tightly-coupled internetworking (tight coupling). There are several advantages to the loosely-coupled integration approach. First, it allows independent deployment and traffic engineering for PLMN and WLAN networks. Second, loosely-coupled solution has lower costs and complexity compared to tightly-coupled one. Furthermore, loosely-coupled internetworking provides easy access to WLAN services for all potential types of users, such as postpaid and prepaid users of the mobile operator, as well as provides possibility to use WLAN services to users that have no subscription made with the mobile operator by using WLAN vouchers. Also, tightly-coupled approach demands additional investments in end user equipment for WLAN access (besides traditional 802.11 network cards), while loosely-coupled solution does not.