nrSRSIndices

Generate uplink SRS resource element indices

Syntax

[ind,info] = nrSRSIndices(carrier,srs)

[ind,info] = nrSRSIndices(carrier,srs,Name,Value)

Description

[ind,info] = nrSRSIndices(carrier,srs) returns resource element indices ind for the uplink sounding reference signal (SRS), as defined in TS 38.211 section 6.4.1.4.3 [1]. The input carrier specifies carrier configuration parameters for a specific OFDM numerology. The input srs specifies SRS configuration parameters.

[ind,info] = nrSRSIndices(carrier,srs,Name,Value) specifies output formatting options using one or more name-value pair arguments. Unspecified options take default values.

Examples

Generate SRS Indices for Two-Port Transmission

Configure the carrier with default configuration parameters.

carrier = nrCarrierConfig;

Configure a two-port SRS transmission of 4 OFDM symbols.

srs = nrSRSConfig;
srs.NumSRSPorts = 2;
srs.NumSRSSymbols = 4;

Set the time-domain starting position of the SRS to 8 and the bandwidth configuration index to 5.

srs.SymbolStart = 8;
srs.CSRS = 5; 

Generate SRS resource element indices for the specified carrier and SRS configuration parameters.

ind = nrSRSIndices(carrier,srs,'IndexStyle','subscript');

Verify that the index matrix has three columns corresponding to the [subcarrier, symbol, antenna] subscripts.

size(ind)

ans = 1×2

   960     3

Generate and Map SRS Symbols to Carrier Grid

Configure the SRS and the carrier with default configuration parameters.

carrier = nrCarrierConfig;
srs = nrSRSConfig;

Generate SRS symbols and indices using the specified carrier and SRS configuration parameters.

srsSym = nrSRS(carrier,srs);
srsInd = nrSRSIndices(carrier,srs);

Create a carrier grid corresponding to the number of subcarriers, OFDM symbols, and number of antenna ports specified in the configuration objects.

K = carrier.NSizeGrid*12;       % Number of subcarriers
L = carrier.SymbolsPerSlot;     % Number of OFDM symbols per slot
P = srs.NumSRSPorts;  % Number of antenna ports
gridSize = [K L P];

Initialize the carrier grid for one slot with all zeros.

slotGrid = complex(zeros(gridSize));

Map the SRS symbols to the carrier grid using the indices.

slotGrid(srsInd) = srsSym;

Input Arguments

carrier — Carrier configuration parameters

nrCarrierConfig object

Carrier configuration parameters for a specific OFDM numerology, specified as an nrCarrierConfig object.

srs — SRS configuration parameters

nrSRSConfig object

SRS configuration parameters, specified as an nrSRSConfig object.

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: 'IndexStyle','subscript','IndexBase','0based' specifies the indexing style and indexing base of the output.

IndexStyle — RE indexing form

'index' (default) | 'subscript'

RE indexing form, specified as one of these values:

• 'index' — The indices are in linear index form.

• 'subscript' — The indices are in [subcarrier, symbol, antenna] subscript row form.

Data Types: char | string

IndexBase — RE indexing base

'1based' (default) | '0based'

RE indexing base, specified as one of these values:

• '1based' — The index counting starts from 1.

• '0based' — The index counting starts from 0.

Data Types: char | string

Output Arguments

ind — SRS resource element indices

N-by-P matrix (default) | M-by-3 matrix

SRS resource element indices, returned as one of these values:

• N-by-P matrix — When 'IndexStyle' is set to 'index' and where P is the number of antenna ports.

• M-by-3 matrix — When 'IndexStyle' is set to 'subscript'. The matrix rows correspond to the [subcarrier, symbol, antenna] subscripts based on the number of subcarriers, OFDM symbols, and number of antennas, respectively.

The number of rows depends on the SRS configuration specified by srs. The NumSRSPorts property of srs determines the number of antenna ports. Depending on 'IndexBase', the indices are either 1-based or 0-based.

Data Types: uint32

info — Information about SRS index generation

structure

Information about the SRS index generation, returned as a structure containing these fields:

Fields	Values	Description
SubcarrierOffset	srs.NumSRSPorts-by-srs.NumSRSSymbols integer matrix	Frequency starting position per antenna port and OFDM symbol (parameter k0 in TS 38.211 Section 6.4.1.4.3)
FreqIndex	(srs.BSRS + 1)-by-srs.NumSRSSymbols integer matrix	Frequency position index per OFDM symbol (parameter nb in TS 38.211 Section 6.4.1.4.3, where b is an integer from 0 to srs.BSRS)
HoppingOffset	(srs.BSRS – srs.BHop)-by-srs.NumSRSSymbols integer matrix	Hopping offset per OFDM symbol (parameter Fb in TS 38.211 Section 6.4.1.4.3, where b is an integer from srs.BHop + 1 to srs.BSRS)
PRBSet	srs.NRBPerTransmission-by-srs.NumSRSSymbols integer matrix	Resource blocks allocated for SRS per OFDM symbol

References

[1] 3GPP TS 38.211. “NR; Physical channels and modulation.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Version History

Introduced in R2020a

R2024a: Specify eight antenna ports and comb offset hopping

The srs input argument enables you to:

• Specify eight antenna ports through the NumSRSPorts property.

• Specify eight-port TDM for SRS transmission through the EnableEightPortTDM property.

• Configure comb offset hopping in SRS transmissions through the CombOffsetHopping, CombOffsetHoppingID, CombOffsetHoppingSubset, and HoppingWithRepetition properties.

R2023a: C/C++ code generation updates

For C/C++ code generation, the limitation to specify name-value arguments as compile-time constants has been removed.