NR/5G

% Calculate and display the number of SRS subbands configurable by NRRC
NSBTable = hSRSNumberOfSubbandsOrHoppingPatterns(srs);

% Number of SRS subbands (NRRC < 9):  3

% Calculate the frequency origin of the first SRS symbol
f0 = hSRSFrequencyOrigin(srs);

% The frequency origin of the SRS is F0 = 30 RB.

carrier = nrCarrierConfig;
carrier.NSizeGrid = 79;
carrier.SubcarrierSpacing = 15

Create a four-symbol SRS located at the end of the slot. Select the repetition factor to indicate the number of equal consecutive SRS transmissions (OFDM symbols) in a slot. For frequency-hopping configurations, Repetition must be lower than the number of SRS symbols.

srs = nrSRSConfig;
srs.NumSRSSymbols = 4;
srs.Repetition = 1;
srs.SymbolStart = 10; % Time-domain position of the SRS in the slot. (8...13) for normal cyclic prefix (CP) and (6...11) for extended CP

Downlink control information (DCI) can trigger aperiodic SRS transmissions using the higher layer parameter resourceType (see TS 38.331 Section 6.3.2 SRS-Config). As the frequency hopping pattern is reset for aperiodic SRS resource types at each slot, select periodic or semi-persistent SRS resource types to enable inter-slot frequency hopping or aperiodic to disable it. You can configure the slot-wise periodicity and offset of the SRS transmissions by using the property SRSPeriod. For aperiodic resource types, the parameter SRSPeriod controls the periodicity and offset of DCI signals triggering aperiodic SRS transmissions.

srs.ResourceType =  "periodic";
srs.SRSPeriod = [2 0];          % Periodicity in slots (1,2,4,5,8,10,...)
srs.SRSPeriod(2) = 0;           % Offset in slots must be smaller than the periodicity

srs.CSRS = 19; % Bandwidth configuration C_SRS (0...63)
srs.BSRS = 2;  % Bandwidth configuration B_SRS (0...3)
srs.BHop = 0;  % Frequency hopping configuration (0...3). Set BHop >= BSRS to disable frequency hopping
srs.NRRC = 14; % Frequency domain position in blocks of 4 PRB (0...67)

The bandwidth over which the SRS symbols hop increases with the value of CSRS and decreases with BHop (until BHop = BSRS disables hopping). Increasing BSRS reduces the allocated bandwidth per OFDM symbol (property NRBPerTransmission) and can reduce the intra-slot frequency hopping as well. To disable frequency hopping, set BHop >= BSRS. For non-hopping configurations, the roles of CSRS and BSRS are analogous, as the allocated bandwidth increases with CSRS and decreases with BSRS.

You can use the bandwidth configuration table (TS 38.211 Table 6.4.1.4.3-1) to calculate the number of different frequency-hopping patterns configurable by the SRS parameter NRRC as NFHP=NBHop+1⋯NBSRS. The frequency-hopping patterns repeat when NRRC>NFHP⋅NRBT/4.

Set the bandwidth configurations parameters as CSRS = 20, BSRS = 2, and BHop = 1. The condition BHop < BSRS does not guarantee frequency hopping. However, the opposite is true: BHop >= BSRS always disables frequency hopping. You can determine when an SRS bandwidth configuration (CSRS,BSRS,BHop) produces frequency hopping using the Nb parameter from the bandwidth configuration table and evaluating the condition NFHP=NBHop+1⋯NBSRS>1.

carrier = nrCarrierConfig;
carrier.NSizeGrid = 52;
carrier.SubcarrierSpacing = 15;

srs = nrSRSConfig;
srs(1).SRSPeriod = [1 0];
srs(1).SRSPeriod(1) = 4; % Slot periodicity and offset 
srs(1).SRSPeriod(2) = 0; % Slot offset of first SRS

srs(2) = srs(1); % Create a copy of the configured SRS
srs(2).SRSPeriod(1) = 2; % Periodicity in slots
srs(2).SRSPeriod(2) = 1; % Offset in slots

srs = nrSRSConfig;
srs(1).NumSRSSymbols = 1;  % Number of SRS symbols in a slot (1,2,4)
srs(1).SymbolStart = 12; % Time-domain position of the SRS in the slot. (8...13) for normal cyclic prefix (CP) and (6...11) for extended CP

srs(2) = srs(1); % Create a copy of the configured SRS
srs(2).NumSRSSymbols = 2;   
srs(2).SymbolStart = 9;

carrier = nrCarrierConfig;
carrier.NSizeGrid = 52;
carrier.SubcarrierSpacing = 15;

srs = nrSRSConfig;
srs(1).KTC    = 2; % Comb number (2,4). It indicates the allocation of the SRS every KTC subcarriers
srs(1).KBarTC = 1; % Comb offset (0...KTC-1)

srs(2) = srs(1); % Create a copy of the configured SRS
srs(2).KTC    = 4;
srs(2).KBarTC = 0;

srs = nrSRSConfig;
srs.NumSRSSymbols = 4;  % Number of SRS symbols in a slot
srs.SymbolStart =8; % Allocate SRS in OFDM symbols 10:13

srs.CSRS = 10;  % Bandwidth configuration C_SRS (0...63)
srs.BSRS =  2;  % Bandwidth configuration B_SRS (0...3)
srs.BHop =  0;  % Frequency hopping configuration (0...3). Set BHop >= BSRS to disable frequency hopping
srs.ResourceType = "periodic"; % ('periodic','semi-persistent','aperiodic')
srs.Repetition   = 1; % Number of equal consecutive SRS transmissions (1,2,4). It must be lower than NumSRSSymbols

% Configure a 10 MHz bandwidth carrier with 15 kHz SCS.
carrier = nrCarrierConfig;
carrier.NSizeGrid = 52;
carrier.SubcarrierSpacing = 15;

% Create a full-band SRS
srs = nrSRSConfig;
srs.CSRS = hSRSBandwidthConfiguration(srs,carrier.NSizeGrid);

% All SRS share the same physical resources, but they are configured with different cyclic shifts.
for i = 1:8
    srs(i) = srs(1);
    srs(i).CyclicShift = i-1;
end

% Create a resource grid containing SRS
numSlots = 1; % Numer of slots to generate
for ich = length(srs):-1:1
    slotGrid{ich} = hSRSGrid(carrier,srs(ich),numSlots);
end

% Get OFDM modulation related information
ue.NRB = carrier.NSizeGrid;
ue.SubcarrierSpacing = carrier.SubcarrierSpacing;
ue.CyclicPrefix = carrier.CyclicPrefix;
ofdmInfo = hOFDMInfo(ue);

% OFDM modulation
nsrs = length(srs); % Numer of SRS waveforms
numSamples = numSlots*ofdmInfo.SamplesPerSubframe/ofdmInfo.SlotsPerSubframe;
txWaveform = zeros(numSamples,nsrs);
for i = 1:nsrs
    txWaveform(:,i) = hOFDMModulate(ue,slotGrid{i});
end

% Cross correlation of SRS waveforms generated with different cyclic shifts
C = txWaveform'*txWaveform;
srsCorr = C./diag(C);