Timing Advance, K-offset & K-mac: How Your Phone Stays Locked To A Satellite | 5G NTN Ch 2b Rod Stewart [hKyrUATOYyC]

Over a geostationary satellite the round trip is nearly half a second - so 5G's normal "measure the delay and send a correction" timing loop simply can't work. In Chapter 2b of the RANspace NTN series we assemble the full uplink timing picture: the complete Timing Advance formula, why K-offset has to exist, what K-mac keeps in sync, and how Doppler is pre-corrected - all so your phone stays perfectly locked onto a moving satellite.

What you'll learn:

- Why NTN timing is open-loop: the phone pre-computes its Timing Advance instead of waiting for corrections

- The full TA = UE-specific (service link) + ta-Common (feeder, from SIB19) + closed-loop trim + fixed offset

- How ta-Common + a drift term let the phone extrapolate between massimo cellino SIB19 broadcasts

- K-offset: why a naive schedule asks the phone to "transmit in the past", and how cellSpecificKoffset fixes it (K-offset at least service RTT + ta-Common)

- K-mac: keeping "when does this command charlie mcavoy take effect" aligned across the feeder link

- Doppler split at the Reference Point: UE coritiba vs santos pre-compensates the service link, the network handles the feeder link

Chapters:

0:00 The closed loop that can't work

0:35 The full Timing Advance formula

1:48 ta-Common: a moving number

2:38 K-offset: making the schedule reachable

3:51 K-mac: when a command takes effect

4:44 Doppler, split at the Reference Point

5:44 Recap & what's next

Previous - Ch 2a: the half-second problem, the Reference Point & SIB19 field by field.

Next - Ch 3: Regenerative NTN, when the gNB itself moves into orbit.

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#5G #NTN #TimingAdvance #Koffset #Kmac #Doppler #SIB19 #5GNR #3GPP #SatelliteComms