GPS: Synchronizing Our Telecommunications Networks

Ed Butterline, Sally L. Frodge

Abstract:	Increasingly, the Global Positioning (and timing) System (GPS) is part of the critical infrastructure of the United States in a number of systems. This same trend is seen internationally. GPS not only supports many transportation and related positioning systems, but it increasingly the timing synchronization networks necessary for the viable functioning of the telecommunications and power industries as well as a host of other services 1. This paper discusses some aspects of network synchronization for telecommunications services and how GPS has an increasing, critical role within today's telecommunications – in and of itself a critical component of modern society. GPS provides a global ubiquitous and cost effective source for critical timing and synchronization for operation of telecommunications networks, including the global fiber networks (SDH and SONET) and the global wireless networks (PCS, GSM, TDMA, CDMA, Wideband CDMA). Degradation of network operation can occur when timing or synchronization is lost or corrupted. The user could experience a number of problems stemming from noise in voice communications, loss of information content for faxes, forcing data re-transmission, freeze frames in video, as well as other impacts. The importance of reliable telecommunications to our daily lives is hard to quantify -- it is of such high value. If the reliability of service degrades or is interrupted, dependent industries such as banking and Internet services will also be adversely affected. Lack of telecommunication can also lead to diminished safety, particularly since so much of the transportation and public safety systems are increasingly dependent upon wireless communications. GSM wireless and CDMA wireless communications, enhanced emergency service (E911), digitized video services distribution, telemedicine, video conferencing are all services which are corrupted or lost completely if the primary reference source of telecommunications synchronization is lost, unavailable, or corrupted. Issues affecting GPS can have a commensurate affect on telecommunications services, both wireless and wireline. GPS is a rising utility and requires protection and promotion as a utility both domestically and internationally to insure the continued smooth and reliable operations of dependent industries such as telecommunications. Degradation of the GPS signal can cause degradation of the GPS-based synchronization signal. Issues such as loss of GPS spectrum, interference from other systems, as well as GPS modernization all can have lasting effects on the telecommunications systems around the world. For example, loss of spectrum in the 1559-1567 Megahertz (MHz) band to mobile satellite services (MSS), could adversely affect the ability of the telecommunications industry to provide voice and data services. Conversely, GPS modernization, specifically, the addition of a separate and protected civil frequency, L5=1176.45 MHz, can have future benefits for the expansion and economic growth of the telecom industry and its services. Digital communications demands better and better synchronization. The current standard for interfaces of 1.0 in 10 -11 suffices for today. Does it address future growth and expansion requirements? Additional GPS frequencies can add additional services and levels of service reliability. From the 1960s to today, the telecommunications industry has moved towards an all-digital network. The industry has moved from analog to asynchronous digital to synchronous digital architectures to keep up with the ever-increasing demand for reliable telecommunications services. The divestiture of the Bell System changed the overall industry from one major provider to a number of carriers providing a variety of telecommunications services -- all requiring accurate synchronized timing that can be successfully distributed over many networks.
Published in:	Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999) September 14 - 17, 1999 Nashville, TN
Pages:	597 - 606
Cite this article:	Butterline, Ed, Frodge, Sally L., "GPS: Synchronizing Our Telecommunications Networks," Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999), Nashville, TN, September 1999, pp. 597-606.
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