The Telecom Solutions CellCync was designed for providing the Time and Frequency control for the US CDMA2000 cellular networks.

It is a 19” rack device designed to go into a rack of equipment in the cellular base stations, and has connectors that provide different types of time and frequency outputs which are required by other equipment in the base station. The E1 traffic input / output connectors would take the coms traffic in and correct its time and frequency and send it back out again ready to be sent on to the next device in the chain.

GPS works by measuring the time of travel of signals from the GPS satellites with a high degree of accuracy. The GPS Ground Control Segment tracks the GPS satellites and computes accurate orbits for them and calibrations to keep the atomic clocks on the satellites very accurate and stable. In effect the GPS satellites are just very accurate and stable clocks in the sky. In order to get to a GPS position fix, the GPS receiver has to first calibrate its local clock relative to the GPS satellite clocks and so as a by product the GPS receiver also becomes a very accurate clock.

It turns out that using a GPS receiver is a much cheaper way of creating an accurate clock than using a Caesium or Rubidium atomic clocks. Cellular networks and cell towers have to be able to communicate with each other and a large number of cellular devices. In order to do this it needs to have extremely stable clocks in the network so that it known where in terms of Frequency and Time to transmit signals, and similarly where for the recipient to look in term of Frequency and Time for the received signal so that the call and data link stay connected and don’t interfere with all of the other users traffic.

Each cellular base station and tower needs a time and frequency standard to work. These are now almost exclusively provided by a GPS / GNSS reference source. Even transmitting data up and down a wire needs good time and frequency synchronisation to get the data on and off the wire. This synchronisation is the limiting factor for how much data can be sent over a fibre optic.

The ever-increasing demand for larger numbers of simultaneous users and higher network data traffic bandwidth requires tighter and tighter frequency control in all communication network signals. These time and frequency standards are a vital cog in the wheel that delivers 3G, 4G and now 5G audio and video streaming to our phones while on the move.