What is Supplementary Uplink in 5G ?

Question

They say it is unique identifier of ENB but where it will be useful?

Answer 1

SUL (Supplementary Uplink) is using a lower-frequency carrier for NR UL transmission in addition to NR’s dedicated UL carrier. Due to the lower frequency, the UL coverage can be significantly improved by transmission on SUL.

Supplementary uplink (SUL): In SUL, one downlink is paired with two possible uplink carrier candidates (one is in low-band and the other is in high-band). Similar to CA concept, better uplink coverage can be achieved by selecting low-band carrier for uplink transmission. However, unlike CA concept, there is no direct reference from downlink carrier.

"n78 -> 3300 MHz – 3800 MHz & n80 -> 1710 MHz – 1785 MHz" will be used as a SUL carrier for NR.

Comments

Does it mean that in case operator allocates part of low band spectrum as SUL, that allocated spectrum cannot be used anymore by  LTE UEs? LTE UEs does not support unpaired FDD and consequence is losing spectrum in band 3 for instance for them.

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n80 overlaps with 3GPP Band 3 in LTE, therefore can't be used in Europe and any other country using 1800 FDD for GSM/LTE