B.5 Estimation of time offset

36.1083GPPEvolved Universal Terrestrial Radio Access (E-UTRA)Release 18Satellite Access Node radio transmission and receptionTS

The observation period for determining the sample timing difference shall be 1 ms.

For 0.37 kHz, the observation period for determining the sample timing difference shall be 6 ms.

For 2.5 kHz, the observation period for determining the sample timing difference shall be 1 ms.

In the following represents the middle sample of the EVM window of length (defined in E.5.1) or the last sample of the first window half if is even.

is estimated so that the EVM window of length is centred on the measured cyclic prefix of the considered OFDM symbol. To minimize the estimation error the timing shall be based on the primary synchronization signal and 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 is odd and if is even.

When the cyclic prefix length varies from symbol to symbol (e.g. time multiplexed MBMS and unicast) then 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.5.1 Window length

Table E.5.1-1 and Table E.5.1-1a below specify EVM window length (W) for normal CP, the cyclic prefix length is 10 for symbols 0 and 9 for symbols 1-6.

Table E.5.1-2 specify the EVM window length (W) for extended CP for 15 kHz, sub-carrier spacing.

Table E.5.1-1: EVM window length for normal CP for E-UTRA

Channel Bandwidth MHz	FFT size		Cyclic prefix length for symbols 0 in FFT samples	Cyclic prefix length for symbols 1‑6 in FFT samples	EVM window length W	Ratio of W to total CP for symbols 1‑6(Note 1) [%]
1.4	128		10	9	5	55.6
Note 1: These percentages are informative and apply to symbols 1 through 6. Symbol 0 has a longer CP and therefore a lower percentage.

Table E.5.1-1a: EVM window length for normal CP for NB-IoT

FFT size	Cyclic prefix length for symbols 0 in FFT samples	Cyclic prefix length for symbols 1‑6 in FFT samples	EVM window length W	Ratio of W to total CP for symbols 1‑6(Note 1) [%]
128	10	9	3	33.3
Note 1: These percentages are informative and apply to symbols 1 through 6. Symbol 0 has a longer CP and therefore a lower percentage.

Table E.5.1-2 EVM window length for extended CP for 15 kHz sub-carrier spacing

Channel Bandwidth [MHz]	FFT size	Cyclic prefix in FFT samples	EVM window length W	Ratio of W to total CP (Note 1) [%]
1.4	128	32	28	87.5
Note 1: These percentages are informative.