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Does the NRHDLDownlinkReceiver process TDD (time division duplex) or FDD (frequency division duplex), or does the distinction not matter?

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Attached is the sample code. Does it apply to TDD or FDD?
%% NR HDL Downlink Receiver MATLAB Reference
% This example shows how to model a 5G NR cell search, MIB and SIB1 recovery
% hardware algorithm in MATLAB(R) as a step towards developing a Simulink(R)
% HDL implementation of a downlink receiver.
% This MATLAB code serves as a reference to
% verify the Simulink models of the hardware implementations in the
% <docid:whdl_ug#example-nrhdlCellSearch NR HDL Cell Search>,
% <docid:whdl_ug#example-nrhdlMIBRecovery NR HDL MIB Recovery>,
% <docid:whdl_ug#example-nrhdlSIB1Recovery NR HDL SIB1 Recovery>, and
% <docid:whdl_ug#example-nrhdlSIBRecoveryFR2 NR HDL SIB1 Recovery for FR2> examples.
% The NR HDL Downlink Receiver MATLAB Reference example bridges the gap
% between a mathematical algorithm and its hardware implementation by
% providing a MATLAB model of the algorithms that are implemented in
% hardware. The MATLAB reference is created to evaluate hardware-friendly
% algorithms and generate test vectors for verifying the Simulink
% fixed-point HDL optimized implementation.
% This example is one of a related set, for more information see
% <docid:whdl_ug#mw_5782f1a8-44cd-44ec-b57c-7870b51cc0df NR HDL Reference
% Applications Overview>.
% Copyright 2021 The MathWorks, Inc.
%% Downlink Receiver Overview
% A block diagram of the Downlink Receiver algorithm is shown.
% The algorithm detects, demodulates, and decodes 5G NR synchronization
% signal blocks (SSBs) and recovers SIB1. It is a hardware-friendly version
% of the corresponding steps in the
% <docid:5g_ug#mw_a4db8282-8f25-4802-8b02-548bab69b7dd NR Cell Search and MIB and SIB1 Recovery>
% example. At the top level, the algorithm consists of a Search Controller,
% an SSB Detector, an SSB Decoder, SIB1 grid demodulator and SIB1 decoder.
% This example explains each of these blocks in more detail and
% demonstrates the corresponding MATLAB reference functions,
% which are used to explore algorithms for hardware implementation and to
% verify the streaming fixed-point Simulink models.
% This example focuses on 5G NR frequency range 1 (FR1). See
% <docid:whdl_ug#example-nrhdlSIBRecoveryFR2 NR HDL SIB1 Recovery for FR2>
% for an example of how to use the MATLAB reference for FR2 SIB1 Recovery.
% <<../NRHDLMATLABRefTop.png>>
%% Cell Search
% Cell search consists of carrier frequency recovery, primary synchronization signal (PSS) search,
% OFDM demodulation, and secondary synchronization signal (SSS) search.
% The Search Controller and the SSB Detector work together to perform
% these processing steps.
% The SSB Detector performs all of the high-speed signal
% processing tasks, making it well suited for FPGA or ASIC implementation.
% The Search Controller coordinates the search and operates at a
% low rate, making it well suited for software implementation
% on an embedded processor.
% The algorithm starts by using the PSS to search for SSBs with
% subcarrier spacings of 15 kHz and 30 kHz across a range of coarse frequency
% offsets. The subcarrier spacing and coarse frequency offset search ranges
% are configurable.
% If SSBs are detected, the receiver OFDM demodulates the resource grid
% of the SSB with the strongest PSS and determines its cell ID
% using the SSS. The residual fine frequency offset is corrected during
% the OFDM demodulation phase.
% <<../NRHDLCellSearchAlgorithmIntroBlockDiagram.png>>
% * _SSB Detector_: Searches for and OFDM-demodulates SSBs at
% a given carrier frequency offset and subcarrier spacing and measures
% the residual fine carrier frequency offset.
% * _Digital Down Converter (DDC)_: Performs frequency translation
% to correct frequency offsets in the received waveform and then
% decimates the signal from 61.44 Msps to 7.68 Msps.
% * _PSS search_: Searches for PSS symbols within the waveform.
% * _OFDM demodulation_: OFDM-demodulates an SSB resource grid.
% * _SSS search_: Searches for SSS and determines the overall cell ID.
% * _Search Controller_: Coordinates the cell search by directing the
% SSB Detector to search for PSS symbols at different coarse
% frequency offsets and subcarrier spacings and to demodulate the
% SSB with the strongest PSS.
% In the MATLAB reference, the |nrhdlexamples.cellSearch| function
% implements the cell search algorithm. This function implements the Search
% Controller shown in the diagram, and calls the |nrhdlexamples.ssbDetect|
% function, which implements the SSB Detector.
% The <docid:whdl_ug#example-nrhdlCellSearch NR HDL Cell Search>
% example shows the streaming fixed-point Simulink HDL implementation
% of the SSB Detector.
% In the
% <docid:xilinxzynqbasedradio_ug#mw_b204ff68-0a8b-46d9-82a9-9e0bd6dc7535 5G NR MIB Recovery Using Analog Devices AD9361/AD9364>
% example, the SSB Detector is implemented in programmable
% logic while the Search Controller is implemented in software on the
% integrated processing system.
%% Search Controller
% The Search Controller is responsible for coordinating the
% overall search. The algorithm follows these steps.
% # For each subcarrier spacing, step through each coarse frequency
% offset and use the SSB Detector to search for SSBs
% until one or more is detected. The coarse frequency offset step
% size is half the subcarrier spacing. When SSBs are detected
% at a given frequency, record the residual fine carrier frequency offset
% of the strongest SSB that is returned.
% # Move to the next coarse frequency step and search for SSBs again.
% If the search detects SSBs, choose the coarse frequency offset
% that resulted in the smallest fine frequency offset measurement.
% Otherwise, pick the last coarse frequency offset.
% # Compute the total frequency offset by adding the
% coarse and fine frequency offsets together.
% # Use the SSB Detector to correct the frequency offset and
% perform one more search for SSBs.
% # Pick the SSB with the strongest PSS correlation.
% Use the SSB Detector in demodulation mode
% to find and demodulate the SSB and determine
% its cell ID.
%% SSB Detector
% These diagrams show the SSB Detector structure for FR1,
% and the parameters and data passed to and
% from the Search Controller. The SSB Detector is subdivided into
% two functions: SSB Detector DDC (|nrhdlexamples.ssbDetectDDC|) and
% SSB Detection Search and Demod (|nrhdlexamples.ssbDetectSearchDemod|).
% The DDC accepts samples at 61.44 Msps and performs a frequency shift
% followed by decimation by a factor of 8 using halfband filters.
% The frequency offset, in Hz, is provided by the search controller and is
% used by the algorithm to compensate for both coarse and fine
% frequency offsets.
% <<../NRHDLCellSearchSSBDetectorDDC.png>>
% <<../NRHDLCellSearchSSBDetector.png>>
% SSB Detection Search and Demod accepts samples at 7.68 Msps.
% For 30 kHz subcarrier spacing, it uses the samples
% at this rate. For 15 kHz subcarrier spacing,
% it decimates the input by a factor of two,
% operating at 3.84 Msps.
% SSB Detection Search and Demod has two modes of operation: search and demodulation.
% In search mode, the function searches for SSBs
% at the specified subcarrier spacing using the PSS, and
% returns a list of those detected. For each SSB that
% is found, the function returns these parameters:
% * _NCellID2_: Indicates which of the three possible
% PSS sequences (0,1, or 2) was detected.
% * _timing offset_: The timing offset from the start of
% the waveform to the start of the SSB.
% * _fine frequency offset_: The residual fine frequency offset in Hz
% measured by using the cyclic prefixes of all
% four OFDM symbols in the SSB.
% * _correlation strength_: The measured PSS correlation level.
% * _signal energy_: The total energy in the samples
% in which the PSS was detected.
% In demodulation mode, the function attempts to find a
% specific SSB by using its timing offset and NCellID2.
% If the function finds the specified PSS, the receiver OFDM demodulates the SSB
% resource grid and attempts to detect its SSS. In demodulation
% mode, the function returns these results.
% * Updated parameters for only the specified SSB if the PSS is found.
% * The demodulated SSB resource grid if the PSS is found.
% * The cell ID if the SSS is found.
% The OFDM demodulator uses a 256-point FFT to demodulate
% the SSB resource grid, which contains 240 active subcarriers.
%% Timing Offsets
% The cell search algorithm uses timing offsets to identify positions within the
% received waveform and intermediate signals. A timing offset is the number of
% samples from the start of the waveform to a given position, such as the start
% of an SSB. Timing offsets are given in samples at 61.44 Msps and wrap around
% every 20 ms, or 1228800 samples. In 5G NR, receivers can assume that the SS burst
% periodicity is 20 ms or less for cell search purposes, hence the reason
% for this choice of timing reference periodicity.
% The figure shows two 5G waveforms with different SS burst periodicities (5 ms and 20 ms)
% and the receiver timing reference. The MATLAB reference can detect
% SSBs at any position within the received waveform. However, if the waveform is longer
% than 20 ms, ambiguity in the returned timing offsets exists because the
% timing reference wraps around every 20 ms. Additionally, the receiver can
% demodulate only SSBs that begin within the first 20 ms of the waveform.
% <<../NRHDLCellSearchTimingReference.png>>
%% SSB Decoding
% The diagram shows the structure of the SSB decoder, which is implemented
% by the |nrhdlexamples.ssbDecode| function. The algorithm takes the SSB
% resource grid from the OFDM demodulation phase of the SSB detector,
% processes it through PBCH and BCH decoding, and outputs MIB parameters
% and PBCH timing information.
% <<../NRHDLSSBDecodingAlgorithmFlow.png>>
% PBCH decoding takes the demodulated OFDM symbols of the resource grid
% and processes using these steps:
% * _DMRS Search_: Searches for the index used for demodulation reference symbol (DMRS) generation.
% * _Channel Estimation_: Calculates an estimate of the channel using the DMRS.
% * _Channel Equalization_: Equalizes the received data using the channel estimate.
% * _Symbol Demod_: Performs QPSK demodulation to get the PBCH soft bits.
% * _Descramble_: Descrambles the soft bits.
% BCH Decode then processes the descrambled soft bits to recover the MIB
% data using these steps:
% * _Rate Recovery_: Combines repeated soft bits then performs scaling and quantization.
% * _Polar Decode + CRC_: Performs polar decoding to get the message bits
% and CRC decoding to check for errors.
% * _MIB Message Parse_: Interprets the decoded message bits to produce the MIB parameter outputs.
%% SIB1 Demodulation
% The diagram shows the structure of the SIB1 Demodulator algorithm, which
% is implemented by the |nrhdlexamples.sib1Demodulate| function. The
% algorithm accepts samples at 61.44 MHz, and uses the results from the
% previous processing stages to locate and demodulate a grid containing
% CORESET0 and the scheduled SIB1 transmission. The MIB results are used
% to calculate the parameters of
% CORESET0, which includes the frequency offset, number of resource blocks,
% and the monitoring occasion. The frequency offset is relative to the location
% of the detected SSB. The first stage of data processing is a DDC
% which performs a frequency shift to center the SIB1 grid and then
% downsamples to 30.72 MHz - the maximum bandwidth for CORESET0 in FR1.
% The next stage is to wait for the CORESET0 monitoring occasion - the algorithm
% contains a timing reference that is synchronized with the SSB Detector
% timing references to identify the next occurance of the monitioring occasion.
% Once the monitoring occasion is reached the
% received samples are OFDM demodulated to produce a grid CORESET0
% resource blocks wide and two slots in duration.
% <<../NRHDLSIB1GridRecoverAlgorithmBlockDiagram.png>>
%% SIB1 Decoding
% SIB1 decoding is performed on the SIB1 grid output by SIB1 demodulation.
% SIB1 decoding requires decoding of PDCCH to recover the SI-RNTI encoded DCI
% message, and decoding PDSCH to recover SIB1 message. The example shows
% two methods for decoding SIB1, either with or without hardware
% accelerators. The hardware accelerator version splits the each decoding
% stage into two steps.
% First, a setup step to create the input vectors which can be deployed to embedded software.
% Second, the hardware accelerated portion of the algorithm which can be deployed on an FPGA.
% Without hardware accelerators each decoding stage is performed by a single step which can be deployed to embedded software. By default,
% |nrhdlexamples.CORESET0Extract| and |nrhdlexamples.CORESET0Decode| are
% used. Alternatively, |nrhdlexamples.pdcchDecoding| is used. Both methods use
% the SIB1 grid and the parameters
% recovered from the previous decoding stages to locate and decode the
% PDCCH for CORESET0. They return the DCI message which signals the
% location of the PDSCH resources allocated to SIB1, and returns a flag
% indicating whether the DCI was found in the first or second slot of the SIB1
% grid.
% The slot carrying PDSCH and PDSCH for SIB1 is selected from the SIB1 grid
% and |nrhdlexamples.coreset0PhaseAdjustment| corrects for the phase offset
% applied on an OFDM symbol basis by the transmitter, as detailed in TS
% 38.211 section 5.4.
% By default, |nrhdlexamples.SIB1Extract| and |nrhdlexamples.SIB1Decode| are used. Alternatively,
% |nrhdlexamples.pdschDecoding| is used. Both methods use the phase corrected slot grid, the DCI
% message, and other information from the previous decoding stages to
% locate and decode the PDSCH resources carrying the SIB1 message. They
% return the SIB1 message bits and the result of the SIB1 CRC
% check. A CRC value of 0 indicates successful recovery of the SIB1.
% <<../NRHDLMATLAB_SIB1Decode.png>>
%% Generate a Test Waveform
% This section shows how to use the MATLAB reference functions to
% search for SSBs in a waveform, demodulate and decode an SSB to recover the MIB, and recover the scheduled SIB1.
% Use the |nrhdlexamples.generateRxWaveform| function to generate
% a 5G FR1 waveform containing SSB bursts and the corresponding SIB1 transmissions.
% Change the |simulationCase| to explore different parameter sets. The full
% set of simulation cases is shown.
disp('Test waveform configurations:')
simulationCase = "SimCase 1";
[rxWaveform,ssbPattern,minChanBW,Lmax,rxSampleRate,txMIB,simCase] = nrhdlexamples.generateRxWaveform(simulationCase);
disp("Selected Simulation case:" + newline);
FoCoarse = 0;
if ssbPattern == "Case A"
scsSSB = 15;
scsSSB = 30;
%% Plot the spectogram of the waveform.
% The plot shows a spectogram of the SSBs, CORESET0s, and PDSCH regions
% carrying SIB1. These regions are generated with different power levels.
% The amplitude of each resource element is indicated by its color.
figure(1); clf;
nfft = rxSampleRate/(scsSSB*1e3);
title('Spectrogram of the Received Waveform')
%% Detect SSBs
% Use the |nrhdlexamples.ssbDetect| function to find SSBs in the waveform
% by searching for PSS symbols. This example calls the function with a
% coarse carrier frequency offset estimate of zero and a subcarrier spacing
% determined from the SSB pattern of the generated waveform. The function
% corrects the coarse frequency offset and measures the
% residual fine frequency offset of each SSB. Frequency offset input and
% output are given in Hz. The function returns a list of detected PSS
% symbols as a structure array.
% Display the structure array contents by converting it to a table.
[pssList,diagnostics] = nrhdlexamples.ssbDetect(rxWaveform,FoCoarse,scsSSB);
% Check if any PSS have been detected
if isempty(pssList)
disp('No PSS found during SSB detection.');
disp('Detected PSS list:')
% The |nrhdlexamples.ssbDetect| function also returns a structure containing
% diagnostic signals. Use this output to plot the PSS correlation
% results. Each peak in the correlator output shown corresponds
% to an entry in the PSS list.
figure(2); clf;
nrhdlexamples.plotUtils.PSSCorrelation(diagnostics,'PSS Correlation');
% Use the |nrhdlexamples.ssbDetect| function to OFDM-demodulate one of the SSBs
% and attempt SSS detection. For this operation, call the function with an optional
% 4th argument that specifies the timing offset and NCellID2 of the desired SSB.
% This example chooses the PSS with the highest correlation metric, however
% you can choose any of the detected SSBs.
% Correct the frequency offset by passing in the sum of the coarse and
% fine frequency offset estimates.
[~,maxCorrIdx] = max(vertcat(pssList.pssCorrelation));
chosenPSS = pssList(maxCorrIdx);
disp('Selected PSS:')
FoFine = chosenPSS.frequencyOffset;
FoEst = FoCoarse + FoFine;
[ssBlockInfo,ssbGrid,diagnostics] = nrhdlexamples.ssbDetect(rxWaveform,FoEst,scsSSB,chosenPSS);
% Check SSB successfully demodulated
if isempty(ssBlockInfo)
disp('Failed to demodulate selected SSB.');
% In demodulation mode, the function returns three outputs instead of
% two. The |ssBlockInfo| structure contains further details of the SSB, such as the
% SSS correlation strength and the overall cell ID. The |ssGrid| output is a matrix
% containing the demodulated OFDM symbols.
% Display the SSB info to confirm that the cell ID is
% correctly decoded.
disp('SSB info for demodulated SSB:')
% Display the resulting SSB resource grid.
figure(3); clf;
axis xy;
xlabel('OFDM symbol');
title('SSB Resource Grid');
% The |diagnostics| output includes SSS correlation results for all
% 336 possible sequences. Plot the SSS correlation results.
figure(4); clf;
nrhdlexamples.plotUtils.SSSCorrelation(diagnostics,'SSS Correlation')
%% Search for Cells
% This section shows how to use the |nrhdlexamples.cellSearch| function
% to search for and demodulate SSBs when the frequency
% offset and subcarrier spacing are not known.
% As described previously, the |nrhdlexamples.cellSearch| function builds on
% the |nrhdlexamples.ssbDetect| function by adding a search controller
% that looks for SSBs at different subcarrier spacings
% and frequency offsets.
% Apply a frequency offset to test the coarse and fine frequency
% recovery functionality.
Fo = 10000;
t = (0:length(rxWaveform)-1).'/61.44e6;
rxWaveform = rxWaveform .* exp(1i*2*pi*Fo*t);
% Define the frequency range endpoints and subcarrier spacing search space
% and call the |nrhdlexamples.cellSearch| function. The function displays
% information on the search progress as it runs.
% The frequency range endpoints must be multiples of half the
% maximum subcarrier spacing.
frequencyRange = [-30 30];
subcarrierSpacings = [15 30];
[ssBlockInfo,ssbGrid] = nrhdlexamples.cellSearch(rxWaveform,frequencyRange,subcarrierSpacings,struct(...
% Check cell search successfully found and demodulated SSB.
if isempty(ssBlockInfo)
disp('Cell search failed to find or demodulate SSB.');
% As shown in the summary, the receiver returned the correct
% subcarrier spacing of 30 kHz, a cell ID of 249, and the measured frequency offset is close to the
% expected value of 10 kHz.
%% Decode SSB
% Use the |nrhdlexamples.ssbDecode| function to decode the SSB resource grid and recover the MIB.
% The |nrhdlexamples.ssbDecode| function is based on the BCH decoding
% stages of the <docid:5g_ug#mw_a4db8282-8f25-4802-8b02-548bab69b7dd NR Cell Search and MIB and SIB1 Recovery> example.
[mibInfo,decodeDiags] = nrhdlexamples.ssbDecode(ssbGrid,ssBlockInfo.NCellID,Lmax);
% Check MIB successfully decoded from SSB.
if mibInfo.err
disp('Failed to decode MIB from SSB.');
% Plot the correlation peaks for the DMRS search. DMRS search is performed
% to determine ibar_ssb and the SSB index.
figure(5); clf;
title('DMRS Search Correlation');
xlabel('ibar ssb');
ylabel('Correlation strength');
% Plot the PBCH QPSK constellation after phase equalization.
figure(6); clf;
xlim(max(abs(real(decodeDiags.qpskSymb))).*[-1.1 1.1]);
ylim(max(abs(imag(decodeDiags.qpskSymb))).*[-1.1 1.1]);
title('PBCH Symbol Constellation');
% Display the decoded information and compare the transmitted and received MIB structures.
% These results show that the information was successfully decoded.
disp(['BCH CRC: ' num2str(mibInfo.err) newline]);
disp('Decoded information');
disp('Decoded MIB');
disp('Expected MIB');
%% Demodulate the SIB1 Grid
% The |nrhdlexamples.sib1Demodulate| function determines the location of
% CORESET0, using information decoded from previous stages, and OFDM
% demodulates the SIB1 grid. The SIB1 grid contains CORESET0 and the PDSCH
% resources allocated to the SIB1 message.
ssbFrequencyOffset = ssBlockInfo.frequencyOffset;
ssbResults = struct(...
'SubcarrierSpacing', scsSSB, ...
'TimingOffset', ssBlockInfo.timingOffset, ...
'FrequencyOffset', ssbFrequencyOffset);
bandCfg = struct( ...
'ssbPattern', ssbPattern, ...
'Lmax', Lmax, ...
'MinChanBW', minChanBW ...
centerFrequency = 0;
sib1Grid = nrhdlexamples.sib1Demodulate(rxWaveform,ssbResults,mibInfo,bandCfg,centerFrequency);
% Plot the OFDM demodulated SIB1 grid.
figure_SIB1grid = figure(7); clf;
axis xy;
xlabel('OFDM symbol');
title('SIB1 Grid');
%% Decode the SIB1 Grid
% The SIB1 grid consists of 2 slots. Only one of these slots carries
% CORESET0 and the PDSCH with SIB1. Depending on _useHardwareAccelerators_
% either |nrhdlexamples.CORESET0Extract| and |nrhdlexamples.CORESET0Decode|
% or
% |nrhdlexamples.pdcchDecoding| searches within each of the slots for DCI
% messages encoded with SI-RNTI. Once decoded, the SI-RNTI
% encoded DCI message provides information on the location of the SIB1
% message within the PDSCH. Depending on _useHardwareAccelerators_
% either |nrhdlexamples.SIB1Extract| and |nrhdlexamples.SIB1Decode|
% or
% |nrhdlexamples.pdschDecoding| uses the DCI and information from the
% previous stages to locate and decode the SIB1 message within the PDSCH.
% If successfully decoded the sib1CRC will be 0, and the SIB1 message bits
% output.
useHardwareAccelerators = true;
if ~useHardwareAccelerators
% Decode PDCCH and recover DCI message
[dci,dciCRC,NSlot,secondSlotFlag,coresetNRB,muxPattern] = nrhdlexamples.pdcchDecoding(sib1Grid,ssBlockInfo.NCellID,mibInfo.ssbIndex,scsSSB,mibInfo.mib,minChanBW);
% Check DCI successfully decoded from PDCCH.
if dciCRC
disp('Failed to decode DCI from PDCCH.');
% Select slot containing SIB1 message
slotGrid = sib1Grid(:,(1:14)+(14*secondSlotFlag));
% Decode PDSCH and recover SIB1 message bits
[sib1bits,sib1CRC] = nrhdlexamples.pdschDecoding(slotGrid,ssBlockInfo.NCellID,mibInfo.mib,coresetNRB,dci,NSlot,muxPattern);
% Extract the CORESET0 search space candidates from the SIB1 grid to pass to
% the CORESET0 decoding hardware accelerator
searchSpaces,numSlots,coresetDuration,coresetNRB,coresetNSlot,muxPattern] = ...
% Run the CORESET0 decoding hardware accelerator
[dci,dciCRC,secondSlotFlag] = ...
% Check DCI successfully decoded from PDCCH.
if dciCRC
disp('Failed to decode DCI from PDCCH.');
% Select slot containing SIB1 message
slotGrid = sib1Grid(:,(1:14)+(14*secondSlotFlag));
% Extract the SIB1 LDPC codeword from the SIB1 grid to pass to the SIB1
% decoding hardware accelerator
[ldpcCW,tbsLength] = nrhdlexamples.sib1Extract(slotGrid,ssBlockInfo.NCellID,mibInfo.mib,coresetNRB,dci,coresetNSlot+secondSlotFlag,muxPattern);
% Run the SIB1 decoding hardware accelerator
[sib1Bits,sib1CRC] = nrhdlexamples.sib1Decode(ldpcCW,tbsLength);
% Update SIB1 grid plot to highlight PDCCH and PDSCH areas
if sib1CRC == 0
disp('SIB1 successfully decoded');
disp('SIB1 decoding failed');

Answers (1)

akshatsood on 19 Mar 2024
Edited: akshatsood on 19 Mar 2024
I understand that you are inquiring about the code included with the "NR HDL Downlink Receiver MATLAB Reference" tutorial, specifically asking whether it is applicable to both TDD (Time Division Duplex) and FDD (Frequency Division Duplex) modes. To my knowledge, it focuses on 5G NR (New Radio) downlink receiver modeling, including cell search, MIB (Master Information Block), and SIB1 (System Information Block Type 1) recovery processes. These processes are essential for a UE (User Equipment) to initially acquire system information from a network and are applicable to both TDD (Time Division Duplex) and FDD (Frequency Division Duplex) operation modes in 5G NR.
However, the code itself does not explicitly specify whether it is for TDD or FDD. This is because the processes of cell search, MIB, and SIB1 recovery are fundamental to both TDD and FDD systems in 5G NR. The main difference between TDD and FDD lies in how the uplink and downlink transmissions are arranged:
  • TDD systems use a single frequency band for both uplink and downlink transmissions, with time slots allocated for each direction. The direction of transmission switches over time.
  • FDD systems use separate frequency bands for uplink and downlink transmissions, allowing simultaneous transmission in both directions.
The code provided is focused on the downlink part of the communication, which is common to both TDD and FDD systems in terms of cell search and system information recovery. The distinction between TDD and FDD would become more relevant in the context of the overall communication system design, especially when dealing with uplink and downlink configurations, scheduling, and duplexing methods.
I hope this helps.




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