Page 728 - 5G Basics - Core Network Aspects

2 Transport aspects

position of the reference sample in the downstream sync symbol of the superframe; see the definition of
the reference sample in clause 8.5.1 and Figure 8-12, and the definition of time event t1 in Figure 8-13.

Figure 8-9 – NTR phase offset estimation

The estimated value of the NTR phase offset (φ) shall be expressed in cycles of a clock running at a
reference frequency FS = 8 192 × fSC (see clause 10.4.2).

The obtained value of φ shall be coded using the following rule:
coded _ value  ( floor   A  MOD() ) A

A  8192 f SC / 8000  52992

The coded value of φ shall be transmitted to the FTU-R using the NTR frequency synchronization eoc
command (represented as a two-byte unsigned integer (see clause 11.2.2.7)). The eoc message shall be
sent over the TPS-TC_MGMT interface as soon as possible but no later than 6 ms after the reference
sample at which the NTR phase offset is measured.

Figure 8-10 shows the NTR offset recording and communication timeline.

Figure 8-10 – NTR offset recording and communication timeline

The FTU-R shall reconstruct the 8 kHz NTR from the received values of the NTR phase offset.

NOTE – The FTU sample clock is proportional to the subcarrier spacing fSC. Therefore, the LTR, being proportional to
the sample clock, will have the same 50 ppm frequency variation as fSC (see clause 10.4.2). The NTR has a maximum
frequency variation of 32 ppm, thus the maximum difference in frequency between the NTR and the LTR will not
exceed 82 ppm. This would result in a maximum NTR phase offset change between two subsequent reference points
-6
for NTR recording of 8210 2TSF = 0.984 µs if TSF = 6 ms, where TSF is the duration of the superframe
(see clause 10.6). This is 0.8% of the 125 µs NTR period.

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