Towards Unified Services in Heterogeneous Wireless Networks Based on Soft-Switch Platform

Introduction

The last two decades, after the telecommunication and computer technology convergence, the world of telecommunication applications has changed dramatically. The traffic needs of the customers have moved from circuit switched applications towards packet switched applications (Cox, 1995). Data traffic, with the characteristics of information transmission in the form of packets and the bursty flow characteristics rather than constant rate, nowadays accounts for slightly more than 60% of the traffic that is transmitted over the backbone telecommunication networks (Esmailzadeh, Nakagawa, & Jones, 2003). In addition to data traffic, multimedia applications like video calls, IP TV, and multimedia messaging traffic (variable rate with real time constraints) was made possible by low cost video digitizing equipment (Houssos, Alonistioti, Merakos, Mohyeldin, Dillinger, Fahrmair, & Schoenmakers, 2003).

Different Radio Access Technology (RAT) networks offer different services to their subscribers. This is a big problem for the multimedia industry since it poses certain constraints to the subscribers regarding specific technology handsets. The ideal solution might be a unified handset with a unified service subscriber identity module (SIM) card (Louvros & Iossifides, 2004). This handset should be able to access the service by any radio access network, like Global System Mobile (GSM) (Siegmund, Redl, Weber, & Oliphant, 1995), General Packet Radio System (GPRS), Universal Mobile Telecommunications System (UMTS), and IEEE802.11 standard (WiFi or WLAN) towards a common core platform. In order to achieve such a unification, the service request should be seamless to the radio access technology network and the core platform should support certain protocols to provide again seamless to the user access to the requested service. Such a platform is already designed and is known as the soft-switch solution. The idea behind the soft-switch solution is the layering of the core network management procedures (mobility management, call control, session management, charging) in such a way that the operator can support all requests as a unified routing process. Moreover the operator can deploy its core switch and transmission network based on a common backbone, designed according to the 3GPP standards on IP or ATM infrastructure, and also to be able to accommodate in the future any new radio access technology network simply and without any serious rearrangement of the existing backbone, thus eliminating cost implementation.

Asynchronous Transfer Mode (ATM) technology is proposed by the telecommunication industry to accommodate multiple traffic types (packet and voice) in a high speed wire-line backbone network. Briefly, ATM is based on very fast (on the order of 2.5 Gbits/sec or higher (Q.2931 ATM Network Signaling Specification, ITU)) packet switching technology with 53 byte long packets called cells being transmitted through wireline networks running usually on fiber optical equipment (Louvros, Karaboulas, Iossifides, & Kotsopoulos, 2003).

This chapter consists of three sections. In the first section there is a quick technical introduction regarding the existing radio access technologies and also the ATM technology. In the second section there is a presentation of the service accessibility regarding the vertical and horizontal integration. Finally in the third section the reader is introduced into the soft-switch solution of the common core platform and the general transport architecture.