5G Toolbox TS38.211 Table 6.3.3.1-7 for Short PRACH Preamble Generation

Hi everyone,

I was trying to produce a PRACH preamble and pass it through a TDL channel. For that purpose, I was using the example script given in the link:

5G NR PRACH Detection Test - MATLAB & Simulink (mathworks.com)

However, under the PRACH Configuration section of the link, I obtained an error when trying to obtain the zero correlation zone value. The code segment that I am talking about is below:

% Set PRACH configuration

prach = nrPRACHConfig;

prach.FrequencyRange = 'FR1'; % Frequency range

prach.DuplexMode = 'FDD'; % Frequency Division Duplexing (FDD)

%prach.ConfigurationIndex = 27; % Configuration index for format 0

prach.ConfigurationIndex = 107; % Configuration index for format A1

%prach.SubcarrierSpacing = 1.25; % Subcarrier spacing

prach.SubcarrierSpacing = 15; % Subcarrier spacing

prach.SequenceIndex = 22; % Logical sequence index

prach.PreambleIndex = 32; % Preamble index

prach.RestrictedSet = 'UnrestrictedSet'; % Normal mode

%prach.ZeroCorrelationZone = zeroCorrelationZone; % Cyclic shift index

prach.FrequencyStart = 0; % Frequency location

% Define the value of ZeroCorrelationZone using the NCS table stored in

% the nrPRACHConfig object

switch prach.Format

case {'0','1','2'}

ncsTable = nrPRACHConfig.Tables.NCSFormat012;

ncsTableCol = (string(ncsTable.Properties.VariableNames) == prach.RestrictedSet);

case '3'

ncsTable = nrPRACHConfig.Tables.NCSFormat3;

ncsTableCol = (string(ncsTable.Properties.VariableNames) == prach.RestrictedSet);

otherwise

ncsTable = nrPRACHConfig.Tables.NCSFormatABC;

ncsTableCol = contains(string(ncsTable.Properties.VariableNames), num2str(prach.LRA));

end

NCS = 13;

zeroCorrelationZone = ncsTable.ZeroCorrelationZone(ncsTable{:,ncsTableCol}==NCS);

prach.ZeroCorrelationZone = zeroCorrelationZone; % Cyclic shift index

The changes I made were to set the configuration index from 27 to 107 (therefore, changing the format from 0 to A1) and changing the subcarrier spacing from 1.25 kHz to 15 kHz since I was working with short preamble format. However, I received the error in the last line because the ncsTableCol returned an empty variable from the switch case. I debugged the code further and realized that the Table values were missing in the prach object. What I mean is, in the class definition script, nrPRACHConfig.m, from lines 316 to 324 the tables are defined like so:

Tables = struct('LongPreambleFormats', nr5g.internal.prach.getTable6331x(1), ... % Table 6.3.3.1-1

'ShortPreambleFormats', nr5g.internal.prach.getTable6331x(2), ... % Table 6.3.3.1-2

'NCSFormat012', nr5g.internal.prach.getTable6331x(5), ... % Table 6.3.3.1-5

'NCSFormat3', nr5g.internal.prach.getTable6331x(6), ... % Table 6.3.3.1-6

'NCSFormatABC', nr5g.internal.prach.getTable6331x(7), ... % Table 6.3.3.1-7

'SupportedSCSCombinations', nr5g.internal.prach.getTable6332x(1), ... % Table 6.3.3.2-1

'ConfigurationsFR1PairedSUL', nr5g.internal.prach.getTable6332x(2), ... % Table 6.3.3.2-2

'ConfigurationsFR1Unpaired', nr5g.internal.prach.getTable6332x(3), ... % Table 6.3.3.2-3

'ConfigurationsFR2', nr5g.internal.prach.getTable6332x(4)); % Table 6.3.3.2-4

However, when 'NCSFormatABC' is called, it returns a wrong table because in "nr5g.internal.prach.getTable6331x(7)" the Table 6.3.3.1-7 is defined incorrectly, as below:

% Define TS 38.211 Table 6.3.3.1-7

% Each column represents the following:

% Column 1: zeroCorrelationZoneConfig

% Column 2: NCS value for unrestricted set

% Column 3: NCS value for restricted set type A

% Column 4: NCS value for restricted set type B

t63317 = {

0 0 NaN NaN

1 2 NaN NaN

2 4 NaN NaN

3 6 NaN NaN

4 8 NaN NaN

5 10 NaN NaN

6 12 NaN NaN

7 13 NaN NaN

8 15 NaN NaN

9 17 NaN NaN

10 19 NaN NaN

11 23 NaN NaN

12 27 NaN NaN

13 34 NaN NaN

14 46 NaN NaN

15 69 NaN NaN

};

table63317 = cell2table(t63317,'VariableNames',{'ZeroCorrelationZone','UnrestrictedSet','RestrictedSetTypeA','RestrictedSetTypeB'});

table63317.Properties.Description = 'TS 38.211 Table 6.3.3.1-7: NCS for short preambles';

However, I believe the correct table should be like this:

%% Table 6.3.3.1-7 from TS38.211

% Define TS 38.211 Table 6.3.3.1-7

% Each column represents the following:

% Column 1: zeroCorrelationZoneConfig

% Column 2: NCS value for L_RA = 139

% Column 3: NCS value for L_RA = 571

% Column 4: NCS value for L_RA = 1151

t63317 = {

0 0 0 0

1 2 8 17

2 4 10 21

3 6 12 25

4 8 15 30

5 10 17 35

6 12 21 44

7 13 25 52

8 15 31 63

9 17 40 82

10 19 51 104

11 23 63 127

12 27 81 164

13 34 114 230

14 46 190 383

15 69 285 575

};

table63317 = cell2table(t63317,'VariableNames',{'ZeroCorrelationZone','139','571','1151'});

table63317.Properties.Description = 'TS 38.211 Table 6.3.3.1-7: NCS for short preambles';

The table I proposed above is copied from TS38.211 Table 6.3.3.1-7. Document version is V16.5.0. I think the difference between the two tables is because the old table is from Release 15 and the new table is from Release 16. I solved this issue by writing the table manually in my program however I wonder, is there a planned update to address this issue?

Kind regards,

Dogukan

Answer 1

[Sriram Tadavarty]

Hi Dogukan,

The 3GPP Release 16 updates of PRACH generation are available in 5G Toolbox from MATLAB R2021b release.

Hope this helps.

Regards,

Sriram