E.5 Estimation of time offset

36.1043GPPBase Station (BS) radio transmission and receptionEvolved Universal Terrestrial Radio Access (E-UTRA)Release 18TS

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.

E.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 160 for symbols 0 and 144 for symbols 1-6.

Table E.5.1-2, Table E.5.1-2a ,Table E.5.1-2b ,Table E.5.1-2c and Table E.5.1-2d specify the EVM window length (W) for extended CP for 15 kHz, 7.5 kHz ,1.25 kHz, 2.5 kHz and 0.37 kHz sub-carrier spacing, the cyclic prefix length is 512, 1024 ,6144, 3072 and 9208 respectively.

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
3	256		20	18	12	66.7
5	512		40	36	32	88.9
10	1024		80	72	66	91.7
15	1536		120	108	102	94.4
20	2048		160	144	136	94.4
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
3	256	64	58	90.6
5	512	128	124	96.9
10	1024	256	250	97.7
15	1536	384	378	98.4
20	2048	512	504	98.4
Note 1: These percentages are informative.

Table E.5.1-2a EVM window length for extended CP for 7.5 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	256	64	56	87.5
3	512	128	116	90.6
5	1024	256	248	96.9
10	2048	512	500	97.7
15	3072	768	756	98.4
20	4096	1024	1008	98.4
Note 1: These percentages are informative.

Table E.5.1-2b EVM window length for extended CP for 1.25 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	1536	384	336	87.5
3	3072	768	696	90.6
5	6144	1536	1488	96.9
10	12288	3072	3000	97.7
15	18432	4608	4536	98.4
20	24576	6144	6048	98.4
Note 1: These percentages are informative.

Table E.5.1-2c EVM window length for extended CP for 2.5 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	768	192	168	87.5
3	1536	384	348	90.6
5	3072	768	746	96.9
10	6144	1536	1500	97.7
15	9216	2304	2268	98.4
20	12288	3072	3024	98.4
Note 1: These percentages are informative.

Table E.5.1-2d EVM window length for extended CP for 0.37 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	5184	576	504	87.5
3	10368	1152	1044	90.6
5	20736	2302	2230	96.9
10	41472	4604	4498	97.7
15	62208	6906	6796	98.4
20	82944	9208	9060	98.4
Note 1: These percentages are informative.