NGN: The Evolution of Wireless Networks Research Brief Abstract: Operators of mobile phone networks are already working through the financial and technical challenges of their own next generation of networks. They will have to wait for the fixed network to catch up. By Jason Chapman Recommendations Operators should carefully balance the required performance of data services against the costs of extra base stations. Operators should ensure that future infrastructures can be integrated with legacy infrastructures and interfaces to external networks. Publication Date: 21 February 2003
2 NGN: The Evolution of Wireless Networks Introduction Operators of mobile networks are already familiar with migrating from one generation of equipment to another. In 2003, they are looking at moving to their third generation (3G) and already talking about a fourth. In Europe, mobile communications networks have evolved in stages: In the first generation, mobile networks based on analog technology are connected to the fixed lines of the public switched telephone network (PSTN). Both the mobile network and the PSTN are circuit-switched. For the second generation (2G), mobile networks are digital but circuit-switched, following the Global System for Mobile Communications (GSM) standard. These are connected to the circuit-switched PSTN. In a stage often referred to as 2.5G, mobile networks use a digital, packetswitched overlay to GSM, giving rise to the "always on" general packet radio service (GPRS). Mobile networks are connected to the circuit-switched PSTN and the packet-based Internet. For 3G, mobile networks are wholly digital and completely packet-switched. They connect to the circuit-switched PSTN and the packet-based Internet. Eventually, there will be a fourth generation, in which mobile networks connect with fixed line networks that are also fully based on a packet-switched infrastructure. Third-Generation Challenges In 1999 and 2000, operators of mobile phone services in Europe spent over $120 billion on acquiring licenses to use new radio spectrum and to expand their geographic coverage. Their business case rested on a continuation of exponential growth in mobile and Internet use. But the reality has been a slowing of mobile subscriber growth and the bursting of the dot-com bubble. As a result, operators have become more cautious about whether finance and equipment will be available and whether the market will want new data services. They are postponing the launches of 3G networks and services based on the technology of wideband code division multiple access (W-CDMA). They now see this technology not as a revolution, but as an evolution from intermediate technologies. Gartner expects that W-CDMA will be a truly commercial proposition in Europe in 2004 to 2005 and in North America in 2007 to 2008. In migrating to 3G, the largest change will occur in the radio network. Operators will need new radio access equipment to support the higher, 2GHz, frequencies of W-CDMA's broadband spectrum. The equipment will be fundamentally different from earlier generations that used time division multiple access (TDMA). The introduction of this new technology, with its different propagation and coverage properties, will require different network design techniques. In some cases, carriers will face higher costs, as they will be unable to use their existing property rights for locating base stations and antennas. And there are other design issues: Cell "breathing." Designers will need to review how the radio coverage area varies depending on the number of subscribers within a base station's coverage area. 2003 Gartner, Inc. and/or its Affiliates. All Rights Reserved. 21 February 2003
Handovers. Transferring a moving user from one base station to another is handled differently in W-CDMA. It uses a "softer" handover, where multiple radios monitor signals from the terminal and adjust power outputs and switch between radios to ensure the best quality coverage. This is different to the model used in GSM, where calls are firmly switched from one radio to another as the radio signal reduces. Balancing signal-to-noise ratios, adjusting power transmission levels and controlling system-critical timing to synchronize the network with terminals all add to the complications of upgrading the radio network to support W-CDMA. These are fundamental differences in the air interface. In addition, network designers will have to review the number and designs of base stations required in light of the data rates that the operator wants to support. The higher the data rates, the more base stations will be needed. A controlling factor is the data rate from mobile terminal to base station (the uplink). Higher uplink rates will require significantly more base stations. Mobile operators are already installing and testing new W-CDMA base stations, called node Bs, along with new radio network controllers. The next move toward the next-generation network will occur within the core network, where the current separation of packet and circuit traffic will migrate toward an all-ip core and ultimately to version six of the Internet Protocol (IPv6). 3 Separation of Planes for Control, Access and Applications Many operators have already taken the first step in migrating the network to packet-switched traffic by introducing general packet radio services (GPRS) and separating circuit-switched from packet-switched traffic. With the full introduction of 3G services, this separation of functions is taken further. Functionality associated with accessing the network is separated from that controlling subscribers' access, such as charging. And these are separate from the platforms for services and applications (see Figure 1). This model of multiple functional planes, running over an all-ip infrastructure, will help realize the vision of common applications being available over different access technologies, be they W-CDMA, 802.11 standards for wireless LANs, or fixed connections. Session management and access capabilities will be controlled within different planes to the access medium. For example, a user might initiate a videoconference call on a handheld device while accessing an 802.11 wireless LAN in a coffee shop's public "hot spot." When the user leaves the 802.11 coverage area, he or she should be able to maintain the video call. Access should be switched from 802.11 to 3G without the user being aware of the different supporting technologies. A user only wants to know it will work smoothly and seamlessly. 2003 Gartner, Inc. and/or its Affiliates. All Rights Reserved. 21 February 2003
4 NGN: The Evolution of Wireless Networks Figure 1 Separation of Functional Planes in a Next-Generation Wireless Environment Applications SIP Applications Applications, Multimedia SIP Applications, Applications Multimedia and IP Servers Applications and IP Servers Control Control Authentication Servers, Authentication Charging Gateways Servers, Charging Gateways Access Access Mobile Mobile Gateways, Gateways, GGSNs, GGSNs, IP IP Backbone Backbone Radio Access Network IP Network/ IP Network/ Internet Internet 111531-02-04 GGSN = gateway GPRS support node; IP = Internet Protocol; SIP = Session Initiation Protocol Source: Gartner Dataquest (December 2002) Gartner Dataquest Perspective Eventually, an all-ip environment will mean lower operating costs. Leased lines and circuit-switched networks will be replaced by cost-effective, carrier-grade IP infrastructure and applications platforms. The development of core network devices that span multiple access technologies will mean platform commonality and higher volumes, hence lower network costs. Drivers such as enhanced security, improved quality of service for conversational communications (voice or videoconferencing over IP) as well as demand for more IP addresses are seen as helping the move toward all-ip networks. Operators will incur lower capital and operational costs with carrier-grade IP routers, an all-ip backbone network and common applications servers using the Session Initiation Protocol (SIP). The only downside will be the impact on the associated backhaul networks which, given the potentially large increase in data traffic, will need further investment, particularly when applications based on SIP become prevalent. This vision of an all-ip network will not be realized overnight. There are major hurdles to be overcome. Integration with legacy infrastructures and interfaces to other external networks remain technical challenges. Capital spending constraints will continue to be an inhibitor. Most incumbents already have core network infrastructures and will find it hard to justify a migration before there is a strong return on these past investments. Key Issue How will the evolution of wireless technologies, infrastructures and devices affect enterprises, homes and public premises? 2003 Gartner, Inc. and/or its Affiliates. All Rights Reserved. 21 February 2003
2003 Gartner, Inc. and/or its Affiliates. All Rights Reserved. 21 February 2003 5
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