Generate CU-Plane Messages for O-RAN Fronthaul Test

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This example shows how to generate fronthaul control and user (CU) plane messages for open radio access network (O-RAN) conformance tests using 5G Toolbox™. These O-RAN compliant messages are considered as split option 7.2x test vectors generated from an O-RAN distributed unit (O-DU). The example generates a packet capture (PCAP) file that contains these messages.

Introduction

This example shows how to build the O-RAN fronthaul CU-plane messages, as defined in TS O-RAN.WG4.CUS, which transmit an NR test model waveform, as defined in TS 38.141-1. These O-RAN compliant messages are considered as split option 7.2x test vectors generated from an O-DU. The example generates a PCAP file, which contains the messages. You can use the generated packets to test an O-RAN radio unit (O-RU) following the conformance test specifications in TS O-RAN.WG4.CONF. You can also analyze the generated PCAP file with third-party packet analysis tools. In this example, Wireshark is used to verify that the content of the CU-plane messages is as expected.

This example builds the CU-plane messages required to transmit the specified NR test model waveform. The example generates a single C-plane message per slot, using Section Type 1, and a single U-plane message per symbol. The U-plane messages encapsulate the IQ data using a single section per symbol. The following diagram shows the flow of the generated CU-plane messages.

GenerateCUPlaneMessagesForORANFronthaulTestPacketGeneration.png

Set Configuration Parameters

The data frame to transmit consists of a full band 5G NR test model waveform, as defined in TS 38.141-1. You can set the test model, the channel bandwidth, and the subcarrier spacing of the test waveform. This example supports FDD duplex mode only and does not apply any precoding or beamforming.

The generated PCAP file includes the Ethernet, eCPRI, and O-RAN protocols. In this section, you can configure parameters available in the three protocols:

O-RAN — Set the compression method and the IQ samples bit-width before and after compression.
eCPRI — Set the extended antenna-carrier identifier (eAxC ID) fields. All packets have the same eAxC ID because this example supports only a single stream.
Ethernet — Set the Ethernet VLAN tag, and the MAC source and destination addresses.

This example does not generate management plane (M-plane) messages. However, the example enables you to set these M-plane parameters: compression mode, byte order, and number of bits per field in eAxC ID.

% Select the NR test waveform parameters
waveConfig.tm = "NR-FR1-TM1.1";  % Test model (must be full band)
waveConfig.bw = "100MHz";  % Channel bandwidth in MHz
waveConfig.scs = "30kHz"; % Subcarrier spacing in kHz

% O-RAN configuration
% Select the compression parameters
oranConfig.method = 'BFP'; % Compression method
oranConfig.IQWidth = 16;                  % IQ samples bit-width before compression
oranConfig.cIQWidth = 9;                  % Compressed IQ samples bit-width (1 to 16)

% eCPRI configuration
% Select the eAxC ID fields
eCPRIConfig.DUPortID = 0;      % Distributed unit identifier
eCPRIConfig.BandSectorID = 0;  % Band and sector identifier
eCPRIConfig.CCID = 0;          % Component carrier identifier
eCPRIConfig.RUPortID = 0;      % Spatial stream identifier

% Ethernet configuration
% Select the Ethernet VLAN tag
ethernetConfig.TPID = 0x8100; % Tag protocol identifier
ethernetConfig.priority = 7;                % Priority level (0 to 7)
ethernetConfig.DEI = 0;  % Drop eligible indicator
ethernetConfig.VID = 1;                     % Unique VLAN identifier (0 to 4095)
% Select the MAC source and destination addresses
ethernetConfig.sourceAddress = ["56","3b","be","a9","92","4c"]; % MAC source address
ethernetConfig.destAddress = ["da","14","de","b0","55","63"];   % MAC destination address

% Select the M-plane parameters
mPlaneConfig.compMode = 0;  % Compression mode
mPlaneConfig.byteOrder = 0; % Byte order
mPlaneConfig.eAxCIDBits = [2 6 4 4];           % Number of bits per field in eAxC ID

% Set the name of the PCAP file
pcapFileName = 'CUMessages'; % PCAP file name

Generate U-Plane Data

Use the hNRReferenceWaveformGenerator class to generate the complete 5G NR configuration of the frame that you selected in the previous section. The resource grid of the NR frame (split option 7.2x) is the data carried in the U-plane messages.

% Create waveform generator object
waveConfig.dm = "FDD"; % FDD duplexing mode
tmWaveGen = hNRReferenceWaveformGenerator(waveConfig.tm,waveConfig.bw, ...
    waveConfig.scs,waveConfig.dm);

% Generate waveform and get resource grid of one frame of data
[~,gridSet] = generateWaveform(tmWaveGen);
grid = gridSet.ResourceGridBWP;

Compress U-Plane Data

Next, compress the generated resource by using the nrORANBlockCompress function. Compression method options include block floating point (BFP), block scaling, and mu-law, as defined in TS O-RAN.WG4.CUS Annex A.1.1, A.2.1, and A.3.1, respectively. Before applying the compression, scale the IQ samples in the resource grid to the bit-width specified by oranConfig.IQWidth.

% Scale the IQ samples in the resource grid using IQWidth
peak = max(abs([real(grid(:)); imag(grid(:))]));
scaleFactor = peak / (0.95*(2^(oranConfig.IQWidth-1)-1));
oranConfig.scaledGrid = round(grid/scaleFactor);

% Apply compression to the scaled resource grid if selected
if ~strcmp(oranConfig.method,'No compression')
    [oranConfig.cGrid,oranConfig.cParam] = nrORANBlockCompress(oranConfig.scaledGrid, ...
        oranConfig.method,oranConfig.cIQWidth,oranConfig.IQWidth);
end

Extract CU-Plane Message Configuration

Use the getCUMessagesConfig local function to get the configuration per CU-plane message:

Ethernet header
eCPRI header
eCPRI payload (O-RAN configuration)

% Get the number of symbols per slot and the number of slots per subframe
waveConfig.symbolsPerSlot = gridSet.Info.SymbolsPerSlot;
waveConfig.slotsPerSubframe = gridSet.Info.SlotsPerSubframe;  

% Obtain set of CU-plane messages 
[cMessagesConfig,uMessagesConfig] = getCUMessagesConfig(waveConfig,oranConfig, ...
    eCPRIConfig,ethernetConfig);