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NR Unlicensed

 

I think NR-U in concept would be equivalent to LAA in LTE-U. In LTE, it had to develop a few major PHY/MAC features just for this (e.g, frame type 3, symbol level scheduling (DCI 3)), but in NR PHY/MAC change would not be as much as LAA case since NR frame structure and scheduling is already flexible enough to adjust it for various use cases. However, there should be various small modifications or new implimentation of PHY/MAC features for smooth coexistance between NR and other technology(e.g, WiFi, LTE-U)

 

 

 

What is it for ?

 

Main objectives of NRU(NR Unlicensed) based on  RP-201834 can be summarized as follows.

  • Enable access to unlicensed spectrum which enables operation of NR in the 5GHz and the 6GHz (e.g., US 5925 – 7125 MHz, or European 5925 – 6425 MHz
  • (In 5 GHz) Enable fair coexistence between already deployed Wi-Fi generations and NR-U, between NR-U and LTE-LAA, and between different NR-U systems
  • (In 6 GHz) Support the channel access mechanism with energy detection as part of the coexistence mechanism for enabling coexistence amongst RATs including at least NR-U, [LTE-LAA], and WiFi

 

 

 

Deployment Scenario

 

The scenario studied and defined in RP-201834 can be summarized as follows.

    Scenario A: Carrier aggregation between licensed band NR (PCell) and NR-U (SCell).

    • NR-U SCell may have both DL and UL, or DL-only.
    • In this scenario, NR PCell is connected to 5G-CN.

    Scenario B: Dual connectivity between licensed band LTE (PCell) and NR-U (PSCell)

    • In this scenario, LTE PCell connected to EPC as higher priority than PCell connected to 5G-CN.

    Scenario C: Stand-alone NR-U

    • In this scenario, NR-U is connected to 5G-CN.

    Scenario D: A stand-alone NR cell in unlicensed band and UL in licensed band (single cell architecture).

    • In this scenario, NR-U is connected to 5G-CN.

    Scenario E: Dual connectivity between licensed band NR and NR-U.

    • In this scenario, PCell is connected to 5G-CN.

 

The deployment scenario can be summarized in illustration as follows.

 

 

 

 

PHY layer consideration

 

RP-201834 descirbes many aspects of Physical Layer aspects. Followings are what I think is important to notice. (NOTE : I haven't confirmed yet on whether all of these are specified in Release 16 TS document)

  • Multiple DL to UL and UL to DL switching points in frame structure for LBT(Listen Before Talk)
  • Scheduling multiple TTI for PUSCH
  • Data Multiplexing considering LBT and channel access priorities
  • LBT subbands within the wideband carrier. For all wide-band operation cases, CCA is performed in units of 20MHz (at least for 5GHz)
  • NR-U Discovery Reference Signal (DRS)
  • Block-interlaced transmission for PUCCH, PUSCH
  • Support of Multiple PDSCH starting point

 

 

 

Presentations on YouTube

 

[1] Webinar - Fixed 5G: From mmWave to NR-U

[2] 5G NR-U and WiFi

[3] The license-exempt spectrum: An opportunity for 3GPP

[4] Sivers IMA On-Demand Webinar: Fixed Wireless Access (FWA), Licensed or Unlicensed 5G

[5] TWS 2015: Role of Unlicensed Spectrum in 5G

[6] Fixed Broadband LTE in Unlicensed 5 GHz Spectrum with Telrad Webinar

[7] NEWSDR 2019 Technical Presentation 2: 5G NR-U – "Houston, we have a problem here”

[8] 5G NR-U vs WiFi6 video Part 1

[9] 5G NR-U vs WiFi6 - Part 2 |5G | NR-U | WiFi6 | WiFI |

[10] TWS 2015: Role of Unlicensed Spectrum in 5G

 

 

 

Reference :

 

[1] How does support for unlicensed spectrum with NR-U transform what 5G can do for you? (Qualcomm)

[2] Unlicensed Use of the 6 GHz Band (FCC)

[3] FCC Opens Spectrum Horizons for New Services & Technologies (FCC)

[4] FCC Modernizes 5.9 GHz Band to Improve Wi-Fi and Automotive Safety (FCC)

[5] List of WLAN channels (Wikipedia)