nrSRS

Generate uplink SRS symbols

Since R2020a

Syntax

[sym,info] = nrSRS(carrier,srs)

[sym,info] = nrSRS(carrier,srs,'OutputDataType',datatype)

Description

[sym,info] = nrSRS(carrier,srs) returns uplink sounding reference signal (SRS) symbols, as defined in TS 38.211 section 6.4.1.4.2 [1]. The input carrier specifies carrier configuration parameters for a specific OFDM numerology. The input srs specifies SRS configuration parameters. The function also returns the structure info, which contains information about the SRS generation process.

[sym,info] = nrSRS(carrier,srs,'OutputDataType',datatype) specifies the data type of the SRS symbols.

Examples

Generate SRS Symbols 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;

The SRS must be located in the last six symbols of the slot. 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 symbols for the specified carrier and SRS configuration parameters.

[sym,info] = nrSRS(carrier,srs);

Verify that the symbols vector contains two columns corresponding to the two-port transmission.

size(sym)

ans = 1×2

   480     2

Verify the number of SRS symbols per port.

isequal(info.SeqLength*srs.NumSRSSymbols,size(sym,1))

ans = logical
   1

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.

datatype — Data type of output symbols

'double' (default) | 'single'

Data type of the output symbols, specified as 'double' or 'single'.

Data Types: char | string

Output Arguments

sym — SRS symbols

complex column vector | complex matrix | []

SRS symbols, returned as a complex column vector, complex matrix, or empty array. The number of transmission antenna ports specified by the NumSRSPorts property of the srs input determines the number of columns. The symbols in a column correspond to one antenna port.

The function returns an empty array when the slot number specified by carrier.NSlot is not a candidate slot, as defined in TS 38.211 Section 6.4.1.4.4, or when the srs.SRSPeriod property is set to 'off'.

Data Types: single | double

info — Information about SRS generation

structure

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

Fields	Description
SeqGroup	Base sequence group number per OFDM symbol (parameter u in TS 38.211 Section 6.4.1.4.2)
NSeq	Base sequence number per OFDM symbol (parameter v in TS 38.211 Section 6.4.1.4.2)
Alpha	Reference signal cyclic shift per port (parameter ɑi in TS 38.211 Section 6.4.1.4.2). When you set the srs.CyclicShiftHopping property to true, Alpha is returned as an srs.NumSRSSymbols-by-srs.NumSRSPorts matrix. (since R2024a)
SeqLength	Zadoff-Chu sequence length (parameter $$M_{sc,b}^{RS}$$ in TS 38.211 Section 6.4.1.4.2)

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™.

Usage notes and limitations:

The datatype input argument must be compile-time constant. For example, when specifying 'single' as the output data type, include {coder.Constant('OutputDataType'),coder.Constant('single')} in the -args value of the codegen function. For more information, see the coder.Constant (MATLAB Coder) class.

Version History

Introduced in R2020a

R2024a: Specify eight antenna ports and enable cyclic shift 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 cyclic shift hopping in SRS transmissions through the CyclicShiftHopping, CyclicShiftHoppingID, CyclicShiftHoppingSubset, and HoppingFinerGranularity properties.

When you set the srs.CyclicShiftHopping property to true, info.Alpha is returned as an srs.NumSRSSymbols-by-srs.NumSRSPorts matrix.