B.5 Estimation of time offset
38.1083GPPNRRelease 17Satellite Access Node radio transmission and receptionTS
B.5.1 General
The observation period for determining the sample timing difference 
shall be 1 slot.
In the following 
represents the middle sample of the EVM window of length W (defined in annex B.5.2) or the last sample of the first window half if W is even.
is estimated so that the EVM window of length W is centred on the measured cyclic prefix of the considered OFDM symbol. To minimize the estimation error the timing shall be based on demodulation reference signals. To limit time distortion of any transmit filter the reference signals in the 1 outer RBs are not taken into account in the timing estimation
Two values for 
are determined:
and
where 
if W is odd and 
if W is even.
When the cyclic prefix length varies from symbol to symbol then T shall be further restricted to the subset of symbols with the considered modulation scheme being active and with the considered cyclic prefix length type.
B.5.2 Window length
Table B.5.2-1, B.5.2-2, B.5.2-3 specify the EVM window length (W) for normal CP.
Table B.5.2-1: EVM window length for normal CP, FR1, 15 kHz SCS
|
Channel |
FFT size |
CP length for symbols 1‑6 and 8-13 in FFT samples |
EVM window length W |
Ratio of W to total CP length for symbols 1‑6 and 8-13 (Note) (%) |
|
5 |
512 |
36 |
14 |
40 |
|
10 |
1024 |
72 |
28 |
40 |
|
15 |
1536 |
108 |
44 |
40 |
|
20 |
2048 |
144 |
58 |
40 |
|
NOTE: These percentages are informative and apply to a slot’s symbols 1 to 6 and 8 to 13. Symbols 0 and 7 have a longer CP and therefore a lower percentage. |
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Table B.5.2-2: EVM window length for normal CP, FR1, 30 kHz SCS
|
Channel |
FFT size |
CP length for symbols 1‑13 in FFT samples |
EVM window length W |
Ratio of W to total CP length for symbols 1‑13 (Note) (%) |
|
|
5 |
256 |
18 |
8 |
40 |
|
|
10 |
512 |
36 |
14 |
40 |
|
|
15 |
768 |
54 |
22 |
40 |
|
|
20 |
1024 |
72 |
28 |
40 |
|
|
NOTE: These percentages are informative and apply to a slot’s symbols 1 through 13. Symbol 0 has a longer CP and therefore a lower percentage. |
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Table B.5.2-3: EVM window length for normal CP, FR1, 60 kHz SCS
|
Channel |
FFT size |
CP length in FFT samples |
EVM window length W |
Ratio of W to total CP length (Note) (%) |
|
10 |
256 |
18 |
8 |
40 |
|
15 |
384 |
27 |
11 |
40 |
|
20 |
512 |
36 |
14 |
40 |
|
NOTE: These percentages are informative and apply to all OFDM symbols within subframe except for symbol 0 of slot 0 and slot 2. Symbol 0 of slot 0 and slot 2 may have a longer CP and therefore a lower percentage. |
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Table B.5.2-4 below specifies the EVM window length (W) for extended CP. The number of CP samples excluded from the EVM window is the same as for normal CP length.
Table B.5.2-4: EVM window length for extended CP, FR1, 60 kHz SCS
|
Channel |
FFT size |
CP length in FFT samples |
EVM window length W |
Ratio of W to total CP length (Note) (%) |
|
|
10 |
256 |
64 |
54 |
84 |
|
|
15 |
384 |
96 |
80 |
83 |
|
|
20 |
512 |
128 |
106 |
83 |
|
|
NOTE: These percentages are informative. |
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