Back in September 2021 I spent a couple of days travelling round the North West of England testing the time-transfer capabilities of 5G using the Calnex Sentinel tester fitted with a 4G/5G “Over-the-Air” (OTA) module. The 5G sites are all synchronised to UTC-traceable time, either locally via GNSS receivers and/or over the network via PTP/SyncE. The tester’s radio module extracts the SSB signals and compares timing information contained therein with its own 1PPS reference. There is obviously a propagation (“time-of-flight”) delay that has to be taken into account so the tester needs to know how far away the transmitting antenna is.
The work was funded in part by the European Space Agency (ESA) under their NAVISP NAV-T programme (see https://navisp.esa.int/ )
Due to some incompatibility between the tester’s GUI and the EARFCN/GSCN (see https://5g-tools.com/5g-nr-gscn-calculator/) used by certain manufacturers I was restricted to testing on Manufacturer A and Manufacturer B sites only, this significantly reduced the number of available test sites but I selected 4 sites close-ish to home. The tester also has an internal GNSS receiver and Rubidium oscillator – both of these take well over 45mins to get fully locked & ready after the tester is powered on so I decided to use another external 1PPS reference for the testing which gets locked & happy in about 15 mins or less.
The first site I visited was next to a MacDonald’s close to Liverpool’s Albert Dock, plenty of time to get a coffee and chill whilst the test was running.
The second site was close to the home of the Grand National, but on the rural side of the village! Raining too. A random dog-walker stopped to say hello and asked all about what I was up to 🙂
The third site was back in Liverpool City Centre – I wanted to do a test indoors (and it was still raining after all) so I made use of the excellent DoES Liverpool facilities (see https://doesliverpool.com/)
The fourth site was a “lamp post” style and used a different type of backhaul connection – it was a real “inner city” site so I tried to be a little more inconspicuous and sat with the tester on my lap in the car!