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CDMA Receiver







How Cell Sync Works
understanding CDMA time sync technology



Cell Sync includes a CDMA cellular receiver, which receives a signal in a similar manner to a CDMA band cellular telephone. It gets the time information embedded in the cellular broadcast and passes that time information to the Cell Sync software running on the computer. Once Cell Sync has synchronized, it continues to update the computer it is running on regularly.

Our Cell Sync product harnesses the accuracy of GPS via CDMA signals used by digital cellular/PCS telephones. CDMA transmissions must be precisely synchronized within ten microseconds for the protocol to work. Each CDMA base station, maintained by the cellular operating company, has at least one highly accurate GPS receiver. This GPS receiver gets its time from GPS satellites.

 In effect, CDMA base stations act as GPS repeaters for time and frequency applications—an indirect form of GPS. That's why it's sometimes called indirect GPS.

CDMA Technology
In the late 1980's Qualcomm designed a mobile, cellular telecommunications system offering numerous advantages over existing systems. This system has been widely accepted, standardized and deployed throughout the world. It is commonly referred to as CDMA due to its use of Code Division Multiple Access (CDMA) techniques for servicing multiple users on the same frequency. It is sometimes referred to as IS-95 after the TIA/EIA standard which defines its signal structure and protocols.

Comparison with GPS Technology
One of its most noteworthy characteristics is the specification of the GPS timescale as the CDMA mobile telecommunications system timescale. In so doing, Qualcomm in essence designed a system in which each of the base stations became a distributor of GPS time. Transmissions from CDMA base stations are precisely synchronized to UTC time to within ten microseconds. This has profound implications for users of precise time who are within receiving range of one of these base stations. Relative to the signals received by GPS receivers on the earth, signals from the CDMA mobile telecommunications systems are much stronger. This means that they are easily received inside buildings.

While GPS receivers offer similar precision and reliability, GPS antenna installation is often difficult in a business or industrial environment. For the best reception, GPS receivers require that an antenna be installed with a wide-angle view of the sky. In some locations running a cable to the roof or window can be cost-prohibitive.

For more information

Cell Sync Product Information:
  Advanced Features
  Frequently Asked Questions about cellular time syncing
  Cell Sync CDMA Receiver
     Installation Information, User's Guide

   Cell Sync Site Index
   Cell Sync Main Page


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