FBMC doesn't work

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  • #9874
    chai
    Participant

    Hi

    When try to run FBMC modulation technique, this error pops out “Frame durations of cells do not match!”

    It happens for both genericscenario and numerology, can anyone help me with this?

    #9877

    Dear Chai,

    as described in the documentation, our simulator works on a frame basis. Therefore, frames of all cells need to have an at least approximately equal frame duration. This becomes critical when different numerologies or waveforms are used in different cells.

    What parameters are you using for the two cells? Did you change anything other than the waveform in the two mentioned scenarios?

    best
    Stefan

    #9931
    chai
    Participant

    Dear Mr Stefan,

    i used the parameter in the numerology and the parameter are as below:
    scStr.modulation.subcarrierSpacing = [15e3, 60e3]; % select a four times bigger subcarrier spacing in the second cell
    scStr.modulation.numerOfSubcarriers = [208, 52]; % to have the same bandwidth, the total number of subcarriers must be one fourth on the second cell
    scStr.modulation.nSymbolsTotal = [15, 60]; % to have the same frame duration, the total number of symbols must be four times higher in the second cell
    scStr.modulation.nGuardSymbols = [1, 4];

    the same case happens when i try using the ‘genericscenario’:
    scStr.modulation.numerOfSubcarriers = [72, 72]; % per BS; number of used subcarriers
    scStr.modulation.subcarrierSpacing = [15e3, 15e3]; % per BS; per base station in Hz
    scStr.modulation.nSymbolsTotal = [15, 15]; % per BS; total number of time-symbols per frame, the frame duration will be nSymbolsTotal/subcarrierSpacing
    scStr.modulation.nGuardSymbols = [1, 1];

    Chai

    #10053
    chai
    Participant

    Dear Mr Stefan,

    I used the same parameter for OFDM, f-OFDM and UFMC. In this case why is FBMC not working? (How does the frame duration does not match with each other but it match with the other 3 modulation)

    Please reply soon. Thank you.

    Chai

    #10267

    Dear Chai,

    the problem related to the frame duration is, that different waveforms apply different filters in time domain. However, the whole simulator processes data on a frame-basis. Therefore, if different waveforms are applied in different cells, they still have to be similar across cells such that the frame processing is still possible.

    I am sorry for my late reply. I will look into this issue. Are you using a single waveform, that is, FBCM, in all cells?

    best
    Stefan

    #10275

    Dear Chai,

    thanks for your comment. Unfortunately there was a bug concerning the use of FBMC. I fixed this bug and re-uploaded the files. Please consider to re-download the simulator files. There were changes in the User.m as well as in the simulationParameters.m.

    However, in the case of FBMC, only real valued symbols are transmitted. To obtain the same time duration as in a cell with OFDM modulation, the number of symbols in the FBMC cell has to be twice as large compared to the OFDM one. So, to obtain LTE like settings, you should use 15 symbols in the OFDM cell while you set 30 symbols in the FBMC cell. Further, as FBMC has no guard symbol (or CP), you should set the number of guard symbols for the FBMC cell to zero.

    Hope that solves your problem.

    best
    Stefan

    #10284
    chai
    Participant

    Dear Mr. Stefan,

    After i redownload the simulator and used all the setting you mention, unfortunately it still doesn’t work. I still cannot run a simulation comparing OFDM with FBMC.

    Below are the parameter i used:
    “scStr.modulation.subcarrierSpacing = [15e3, 30e3]; % select a four times bigger subcarrier spacing in the second cell
    scStr.modulation.numerOfSubcarriers = [104, 52]; % to have the same bandwidth, the total number of subcarriers must be one fourth on the second cell
    scStr.modulation.nSymbolsTotal = [15, 30]; % to have the same frame duration, the total number of symbols must be four times higher in the second cell
    scStr.modulation.nGuardSymbols = [1, 0]; ”

    it comes with an error:”Error using Parameters.SimulationParameters/checkParameters (line 173)
    Invalid ratio of subcarrier spacing, number of subcarriers, number of total symbols and number of guard symbols across
    cells.”

    and the same case where i use 1 symbols and 2 symbols

    Chai

    #10291

    Dear Chai,

    as I already explained, the number of FBMC symbols has to be doubled compared to any other waveform, as it uses only real valued symbols. Further, as you employ a subcarrier spacing for cell 2 that is twice as large as cell 1, you again have to double the number of symbols to match the frame duration. Therefore, I suggest the following parameters

    scStr.modulation.subcarrierSpacing = [15e3, 30e3]; % select a four times bigger subcarrier spacing in the second cell
    scStr.modulation.numerOfSubcarriers = [104, 52]; % to have the same bandwidth, the total number of subcarriers must be one fourth on the second cell
    scStr.modulation.nSymbolsTotal = [15, 60]; % to have the same frame duration, the total number of symbols must be four times higher in the second cell
    scStr.modulation.nGuardSymbols = [1, 0];

    I just tried these settings on the current simulator version and it worked. Let me know if you encounter further problems.

    best
    Stefan

    #10300
    chai
    Participant

    Dear Mr. Stefan,

    I follow exactly the same parameter u suggested and redownload the simulator, i still get an error of

    “Error using zeros
    NaN and Inf not allowed.

    Error in Channel.FastFading (line 117)
    PowerDelayProfileTemp = zeros(length(IndexDelays),max(IndexDelays));

    Error in Parameters.SimulationParameters/checkParameters (line 212)
    Channel.FastFading( obj.modulation.samplingRate, … % sampling rate

    Error in Parameters.SimulationParameters (line 27)
    obj.checkParameters();

    Error in main (line 19)
    simParams = Parameters.SimulationParameters( simulationScenario );”

    what should i do?

    Chai

    #10312

    Dear Chai,

    I just tried again; using the currently available simulator with the following changes in the generic scenario:

    scStr.modulation.waveform                   = { 'OFDM', ...             % waveform for each BS:
                                                    'FBMC' }; 
    
    scStr.modulation.subcarrierSpacing = [15e3, 30e3]; % select a four times bigger subcarrier spacing in the second cell
    scStr.modulation.numerOfSubcarriers = [104, 52]; % to have the same bandwidth, the total number of subcarriers must be one fourth on the second cell
    scStr.modulation.nSymbolsTotal = [15, 60]; % to have the same frame duration, the total number of symbols must be four times higher in the second cell
    scStr.modulation.nGuardSymbols = [1, 0];
    
    scStr.modulation.samplingRate               = 30e3*104*2;
    
    scStr.schedule.fixedSchedule{1}             = [ 'UE1:104' ];     % schedule for BS1
    scStr.schedule.fixedSchedule{2}             = [ 'UE2:52' ];     % schedule for BS2

    works perfectly fine. It seems the error occurs since you are using automatic sampling rate calculation.

    Thank you for your comment, we will fix this issue. For now I advise to use the largest subcarrier spacing times the maximum number of subcarriers times two as sampling rate.

    best
    Stefan

    #10337
    chai
    Participant

    Thank you so much Mr. Stefan, i works.

    last question from me, in the result of BER, there is this UE1, UE2, coded and uncoded, can i know what does the coded and uncoded stands for?

    Chai

    #10484

    Dear Chai,

    uncoded means that there is no channel coding involved, while coded means there is. So for the coded BER, the data bits before the channel encoder at the transmitter are compared to the decoded bits after the decoder at the receiver side. For the uncoded BER, the encoded bits at the transmitter after the channel coder are compared to the received bits before the channel decoder at the receiver.

    best
    Stefan

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