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Synchronization for New Services
The telecom network is always evolving, but recently we have seen quite significant strides in technologies like Internet Protocol (IP) and Dense Wavelength Division Multiplexing (DWDM). IP is a packet protocol and, though originally designed for data traffic, is being morphed and adjusted to carry traffic like voice and video, for which the traditional circuit-switched network was considered better suited. In Chapter 1, the sync aspects of IP networks carrying voice-over-IP (VoIP) are discussed.
The ability of fiber strands to carry multiple optical beams, much like frequency-division-multiplexing method used in cable TV to carry multiple video channels, has led to the notion of Wavelength Division Multiplexing (WDM) and variants such as DWDM. The optical beams are, more often than not, SONET/SDH signals, each signal using a distinct wavelength (frequency). The sync aspects arising from this assembly are treated in Chapter 2.
The notion of precision synchronization has been long ignored in Wireless (such as cellular telephony) networks. In Chapter 3, the need for precision synchronization in such networks is discussed primarily from the viewpoint of having to locate, geographically, handsets to within a tight tolerance. Whereas the driver for this location accuracy is to indicate where to send Emergency vehicles like ambulances, other services based on location determination are being developed.
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