NR-U Channel Access Schemes (Candidates)

NR-U Channel Access Schemes (Candidates)

  November 25, 2020    tls123

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 Note: NR-Unlicensed is still in the study phase with barely any work done on the TS. It is expected that by 2022 (so Release 18) we may see some specification for the 6GHz band in Europe. As of now, only potential candidates for NR-U implementation can be guessed. 

The channel access candidate schemes for NR-based access for unlicensed spectrum can be classified into the following categories:

-    Category 1: Immediate transmission after a short switching gap

 -     This is used for a transmitter to immediately transmit after a switching gap inside a COT.

-     The switching gap from reception to transmission is to accommodate the transceiver turnaround time and is no longer than 16 µs.

-    Category 2: LBT without random back-off

-     The duration of time that the channel is sensed to be idle before the transmitting entity transmits is deterministic.

-    Category 3: LBT with random back-off with a contention window of fixed size

-     The LBT procedure has the following procedure as one of its components. The transmitting entity draws a random number N within a contention window. The size of the contention window is specified by the minimum and maximum value of N. The size of the contention window is fixed. The random number N is used in the LBT procedure to determine the duration of time that the channel is sensed to be idle before the transmitting entity transmits on the channel.

-    Category 4: LBT with random back-off with a contention window of variable size

-     The LBT procedure has the following as one of its components. The transmitting entity draws a random number N within a contention window. The size of contention window is specified by the minimum and maximum value of N. The transmitting entity can vary the size of the contention window when drawing the random number N. The random number N is used in the LBT procedure to determine the duration of time that the channel is sensed to be idle before the transmitting entity transmits on the channel.

For different transmissions in a COT and different channels/signals to be transmitted, different categories of channel access schemes can be used.

Related:

1. NR-U Inactive and Idle procedures (Candidates)

2. NR-U Control plane (Candidates)

3. NR-U Layer 2 (Candidates)

4. NR-U Physical layer channel designs(Candidates)

5. NR-U Physical Frame structure (Candidates)