ABSTRACT
Contents 13.1 Introduction ................................................................................................................... 338 13.2 Telecommunication Networks ....................................................................................... 338
13.2.1 Fixed Telephone Network ................................................................................... 338 13.2.2 IP Network ......................................................................................................... 342 13.2.3 Wireless and Mobile Networks ........................................................................... 343
13.2.3.1 Wireless Local Area Network ............................................................... 343 13.2.3.2 Global System for Mobile Communication .......................................... 345 13.2.3.3 General Packet Radio Service ............................................................... 347 13.2.3.4 Universal Mobile Telecommunications System ..................................... 348
13.3 NGNs: Convergence of Networks .................................................................................. 349 13.4 Voice-Over IP ................................................................................................................ 351
13.4.1 H.323 Framework ............................................................................................... 351 13.4.2 SIP Framework ................................................................................................... 353 13.4.3 VoIP System........................................................................................................ 355 13.4.4 QoS in VoIP ....................................................................................................... 357
13.5 Future Research Directions ............................................................................................ 358 13.6 Conclusions .................................................................................................................... 359 References ............................................................................................................................... 359
13.1 Introduction In telecommunications, there are many networks, such as the public switched telephone network (PSTN), signaling system 7 (SS7), the integrated services digital network (ISDN), the internet protocol network (IP network), the wireless local area network (WLAN), the global system for mobile communication (GSM), general packet radio service (GPRS), the universal mobile telecommunications system (UMTS), etc. ese telecommunications networks were designed to provide specific services, which are initially distinct and then converge into a single network [1]. Voice-over IP is a clear example of such convergent services [2]. To visualize this convergence, it is necessary to understand the historical development, which is summarized in the following events [3]: the introduction of automatic telephone exchange, the digitalization of telecommunications systems, the integration of circuit-switched technology and packet-switched technology (VoIP emergence), and the evolution of the mobile systems (1G, 2G, 3G, 4G, and beyond).
