SUL (Supplementary Uplink) in LTE

Dear Experts

Can we use Supplementary Uplink in 4G just like we use in 5G. Like if i want DL on 2300 band and UL on 1800/2100 band?

Admin note: this post was updated with image below.

I believe itโ€™s a 5G NR concept.

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When is Supplementary Uplink and Downlink used in 5G?

For SDL and SUL carriers addition what is criteria?

Does it require specific band combo?

SuL is crash story.

Only Chinese drove.

No one else support now.

๐’๐ฎ๐ฉ๐ฉ๐ฅ๐ž๐ฆ๐ž๐ง๐ญ๐š๐ซ๐ฒ ๐”๐ฉ๐ฅ๐ข๐ง๐ค (๐’๐”๐‹) ๐ข๐ง ๐Ÿ“๐†:

๐’๐”๐‹ ๐ข๐๐ž๐š ๐ข๐ฌ ๐ญ๐จ ๐ข๐ง๐ญ๐ซ๐จ๐๐ฎ๐œ๐ž ๐š ๐Ÿ๐ซ๐ž๐ช๐ฎ๐ž๐ง๐œ๐ฒ ๐ข๐ง ๐ญ๐ก๐ž ๐ฅ๐จ๐ฐ ๐›๐š๐ง๐ (900mhz or 1.8Ghz) ๐ฐ๐ก๐ข๐œ๐ก ๐ก๐š๐ฏ๐ž ๐ฅ๐จ๐ฐ๐ž๐ซ ๐ฉ๐š๐ญ๐ก ๐ฅ๐จ๐ฌ๐ฌ ๐ญ๐จ ๐ฌ๐ž๐ซ๐ฏ๐ž ๐ข๐ง ๐”๐‹.

  • ๐’๐”๐‹ is used to enhance the UL coverage & throughput in 5G.

  • ๐”๐„ ๐“๐ฑ ๐ฉ๐จ๐ฐ๐ž๐ซ is always lower than ๐ ๐๐ ๐“๐ฑ ๐ฉ๐จ๐ฐ๐ž๐ซ & it is even worse at the cell edge thatโ€™s why we use uplink from the low band.


  • DL/UL carrier operating in the 3.5 GHz band could be complemented with a supplementary UL carrier in the 1.8 GHz band.
  • So, UE is configured with two frequencies in UL, one is non-SUL (which is the original freq of the cell at 3.5 GHz) and the other one is the SUL at 1.8 GHz, but UE canโ€™t transmit at both frequencies at the same time, as only one frequency is allowed at a time.
  • So, UE can use the non-SUL freq near the site and the SUL freq at the cell edge based on certain thresholds.

Credits: :point_down: