CDMA Timing

GPS-synchronized products require you to install a view-of-the-sky antenna.
CDMA-synchronized products work great with the antenna inside your building, just like your cell phone.
(No subscriber fees required.)

Cell Tower
CDMA cell phone towers
transmit the timing signal.

The vast majority of precise timing products use GPS as their timing source.  These products require an antenna installed with a large view-of-the-sky.  Installing and maintaining the antenna can range from being merely a nuisance to being impossible.  In many downtown locations running a cable to the roof can cost several thousands of dollars and leasing rooftop space can cost hundreds of dollars a month.

How Is CDMA Used For Timing?

Our products harness the accuracy of GPS via CDMA signals used by digital cellular/PCS telephones.  Each CDMA base station has at least one GPS receiver because its' transmissions must be precisely synchronized within ten microseconds in order for the cell phone system to work properly.  Our products synchronize themselves to the CDMA base station transmissions, which means they are also synchronized to the GPS transmissions.  So, in effect, CDMA base stations act as GPS repeaters for precise timing applications. That's why we sometimes call it "Indirect GPS".

Where Are CDMA Signals Available?

These very reliable signals are easily received inside buildings and are extensively available throughout the U.S.A., China, Hong Kong, Japan and Korea.  If you are located in one of these areas then chances are good that you have CDMA cellular/PCS coverage.  If in doubt contact us.  You can also check the worldwide coverage map at  Any area listed on the charts with "Type of System" shown as 800 MHz or 1900 MHz will probably work with our products.  (If the "Technology" column shows LTE, this will NOT work with our products.)


How long will CDMA be Around?

CDMA service in the United States is provided by Sprint and Verizon.  As of March 2019, Sprint has not made any announcements regarding changes to their CDMA network.  Verizon, however, plans to discontinue CDMA cell phone service by the end of 2019 but will continue service for M2M customers through the end of 2022.  How extensive Verizon's network coverage will be during this period is unknown. 

CDMA-based network time servers acquire a UTC time sync from signals broadcast from a CDMA base station.  The time server is user configured to use either the North American Cellular (NAC) channel set (Verizon) or the North American PCS (NAP) channel set (Sprint).  The factory default channel set today is NAP.  

Sprint completed a large investment in their Network Vision project in 2014 that completely upgraded 38,000 cell sites.  Sprint said at that time it plans to maintain its 2G CDMA network capability for the long term as part of their Network Vision strategy.  We are unaware of any public announcements since then.  The potential merger with T-Mobile is pending as of March 2019 and potential impact to the CDMA network unknown.

Verizon's last public announcement that we are aware of regarding their CDMA network was in 2016.  Verizon stated that a goal was set to discontinue operations of it's CDMA 1X network by December 31, 2019 but would consider operating into 2020 to serve M2M customers.  M2M includes communications for alarm systems, industrial equipment, vending machines, power company meters, and other "smart" equipment.  In 2018, some of the major M2M vendors that are in the Verizon Partner program announced that Verizon will continue CDMA service to their systems through 2022.  Network coverage could change post-2019 as some of the spectrum may be re-farmed for LTE.

Reference articles:
Telecom Engine:  Sprint to Continue Supporting 2G for M2M Customers
SecureCom Wireless:  CDMA M2M products will have service until Dec. 31, 2022
Honeywell - Verizon CDMA Activations UPDATE for AlarmNet Accounts
StarLink Verizon CDMA Communicator Sunset Date Extended through December 31, 2022