5G/NR - PUCCH                                           Home : www.sharetechnote.com

 

 

 

 

 

PUCCH / UCI

 

PUCCH is an uplink physical channel that carries UCI (Uplink Control Information). As DCI (Downlink Control Information) is carried by PDCCH, UCI is carried by PUCCH.  A big difference between DCI and UCI is that UCI can be carried either by PUCCH or PUSCH depending on situation whereas DCI can be carried only by PDCCH (not by PDSCH in any case).

 

 

Contents of UCI

 

The contents of UCI is as follows (this is same as LTE). Not all of these are carried by single UCI. Depending on situation, sometimes only CSI is carried, sometimes ACK/NACK only, sometimes SR only and sometimes CSI & ACK/NACK etc.

  • CSI
  • ACK/NAK
  • Scheduling Request (SR)

 

 

PUCCH Formats

 

There are 5 different formats of PUCCH and which one of them is used is determined by how many bits of information should be carried and how many symbols are assigned, as summarized in the following table.

 

< Based on 38.211 - Table 6.3.2.1-1: PUCCH formats.>

Format Types

Lengh of Symbols

Number of bits

Descriptions (based on 38.300 - 5.3.3)

Format 0

1~2

<= 2

Short PUCCH.

with UE multiplexing in the same PRB.

Based on sequence selection.

Format 1

4~14

<= 2

Long PUCCH.

with multiplexing in the same PRB.

time-multiplex the UCI and DMRS

Format 2

1~2

> 2

Short PUCCH.

with no multiplexing in the same PRB.

frequency multiplexes UCI and DMRS

Format 3

4~14

> 2

Long PUCCH.

with moderate UCI payloads and with some multiplexing capacity in the same PRB.

time-multiplex the UCI and DMRS

Format 4

4~14

> 2

Long PUCCH.

with large UCI payloads and with no multiplexing capacity in the same PRB

 

 

How to Determine PUCCH location ?

 

Following is the illustration for the description on 38.213 - 9.2.1 PUCCH Resource Sets

 

 

 

How to define PUCCH baseband signal ?

 

RRC Parameters

Related PUCCH Format

Description

PUCCH-F0-F1-initial-cyclic-shift

Format 0 / 1

The index of the cyclic shift = {0,1,...11}
PUCCH-F1-time-domain-OCC

Format 1

The index of the orthogonal cover code
PUCCH-F4-preDFT-OCC-index

Format 4

The index of the orthogonal cover code = {0,1,2,3}
PUCCH-F4-preDFT-OCC-length

Format 4

The length of the orghogonal cover code = {2,4}

 

 

Frequeny Hopping

 

It is possible to enable or disable PUCCH using RRC Parameter PUCCH-frequency-hopping

 

 

Modulation

 

QPSK or BPSK is used depending on cases as below.

  • Long PUCCH with 2 or more bits of information : QPSK
  • Short PUCCH with more than 2 bits of information : QPSK
  • Long PUCCH with 1 bit information : BPSK

 

 

Channel Coding

 

Various types of Channel coding is applied to UCI(Uplink Control Information) depending on the number of bits to be carried.

 

UCI size including CRC, if present

Channel Code

1

Repetition code

2

Simplex Code

3-11

Reed Muller Code

> 11

Polar Code

 

 

Reference

 

[1]