CQI params

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  • #10322
    lee hyunjee
    Participant

    Hello,
    I want to know about the detail about LTE_get_feedback function.
    I checked UE_output(uu).CQI_bar from LTE_get_feedback, however, it was different UE_scheduling.cqi .
    Then, what is the exactly I can get from LTE_get_feedback?
    Even though I got ‘UE_output(uu).CQI_bar = 10’ from LTE_get_feedback, the transmitter sent ‘cqi 9’ from lteScheduler.m.

    I want to check the CQI Change between CQI(in TX) and CQI(after feedback).
    Which function do I have to check?

    Thanks,

    Sincerely
    Hailey Lee

    • This topic was modified 3 years, 1 month ago by lee hyunjee.
    #10327
    lee hyunjee
    Participant

    I found uplinkChannle.m stored UE_feedback(CQI number) and UE_output(LTE_params.connection_table(bb,:)) = uplinkChannel(bb).receive_feedback; called to get received feedback from the previous subframe, however, this feedback didn’t effect on the TX scheduling.
    In AdaptvieFeedbackScheduler.m > lteScheduler.m, they calculates effective SINR and CQI value.
    I don’t understand this part because they don’t use the feedback value and calculate some values again, then why did they get data in uplinkChannel?

    Best,
    Hailey Lee.

    #10330
    Stefan Schwarz
    Participant

    Dear Hailey Lee,

    the interesting output from the feedback function is UE_output(uu).CQI. This gives you the CQI value that is supported on each resource block (RB) and it will vary over time and frequency. This CQI feedback is then used by the scheduler for RB allocation. As soon as the RBs are allocated, we have to find a modulation and coding scheme that is suitable for transmission over the allocated RBs. This requires averaging over the CQIs of the allocated RBs. For example, if 2 RBs are allocated, one having CQI value 4 the other having CQI value 6, the system might be able to transmit with CQI value 5 over both RBs. This is why the actual CQI employed for transmission is different from the feedback.

    Best,
    Stefan.

    #10332
    lee hyunjee
    Participant

    Dear Stefan,
    I’m really appreciate to your kindess.

    I have one more question,

    In lteScheduler, there is

    SINR_temp = obj.SINR_averager.average(10.^((obj.CQI_mapping_data.table(mod(CQI_temp,20)+1)+(obj.CQI_mapping_data.table(mod(CQI_temp,20)+2)-obj.CQI_mapping_data.table(mod(CQI_temp,20)+1))/3.5)/10),0:15,obj.alphabets); .

    Why it divided by “3.5”?

    Sincererly,
    Hailey Lee

    #10336
    Stefan Schwarz
    Participant

    Thats actually a heuristic value that turned out by simulation to perform well…

    #10419
    lee hyunjee
    Participant

    Hello,
    I have a question to make sure what I understood.
    The simulation parameters are below:
    SUSISO, feedback(true), vehA, PDCCH(false), Bandwidth(1.4MHz) etc..

    When I used the feedback, the SISO.m function was worked.
    There are two part calculating CQI: one is CQI for each RB and the other is average CQI(for subframe).
    Did I understand right way? I want to know exactly about the second CQI(CQI_temp , after calculate CQI per each RB) which is a average CQI per subframe.

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