ncreases; second generation cellular systems are upgraded to provide higher rate packet-switched data service. 2005- Digital TV will replace analog service and start to provide interactive services in addition to broadcast service; third gen- eration cellular systems and WLAN technologies will provide enhanced data services for mobile users; location-based mobile services will expand, applications for wireless short- haul technologies in homes and offices will increase; global telecommunications network will evolve toward a common packet-switched network platform for all types of services. 1.4 Standardization Communication networks are designed to serve a wide variety of users who are using equipment from many different vendors. To design and build net- works effectively, standards are necessary to achieve interoperability, com- patibility, and required performance in a cost-effective manner. Open standards are needed to enable the interconnection of systems, equipment, and networks from different manufacturers, vendors, and opera- tors. The most important advantages and some other aspects of open tele- communications standards are explained next. Standards enable competition. Open standards are available to any telecom- munications system vendor. When a new system is standardized that is at- tractive from a business point of view, multiple vendors will enter this new market. As long as a system is proprietary, specifications are the property of one manufacturer and it is difficult, if not impossible, for a new manufac- turer to start to produce compatible competing systems. Open competition makes products more cost-effective, therefore providing low-cost services to telecommunications users. Introduction to Telecommunications Network Engineering Standards lead to economies of scale in manufacturing and engineering. Stan- dards increase the market for products adhering to the standard, which leads to mass production and economies of scale in manufacturing and engineer- ing, very large scale integration (VLSI) imp