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• #8970
lee hyunjee
Participant

Hello,

I got the 256-QAM BICM capacity curves from the Vienna SLS and stored data, and then add them into MIdata_loader.m in LLS.
In MIdata_loader.m, there are function and variables which is “[k d] = load_k_d_not_from_file(obj)”.
However, I don’t have any idea about ‘k’ and ‘d’, and there is no explain about them.
Please explain this two variable and what is it.

Moreover, If i have to change “[k d] = load_k_d_not_from_file(obj)” for 256-QAM, how can i get the data?

Thanks,
sincerely, hailey.

#8983
Stefan Schwarz
Participant

Dear Hailey,

great to hear that you were able to get 256 QAM running.

The [k,d] value-pair corresponds to slope (k) and intercept (d) of a linear approximation of the BICM curves around the SNR regime relevant for a given CQI.

Basically, you should take a look at the following two papers to understand what I mean:

– Fig. 1 of “Low Complexity Approximate Maximum Throughput Scheduling for LTE” shows the linear approximation of the BICM curves over CQI that is employed for calculation of [k,d].

– Actually, the BICM curves are a function of SNR rather than CQI as used in Fig. 1. above. However, there is an approximate linear relationship btw. SNR and CQI according to Fig. 4 of “System level simulation of LTE networks”.

–> To calculate the [k,d] values for 256 QAM, you first of all have to determine the appropriate extended SNR to CQI mapping (Fig. 4). Provided this is still linear for the CQIs corresponding to 256 QAM, you can then determine the [k,d] values by linearly approximating the 256 QAM BICM curve similar to Fig. 1.

Hope that helps.

Best,
Stefan.

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