LENA LTE: why are the MCS index in DlMacStats.txt all even numbers?

[Dapeng Liu]

Hi,

I am using the fading script generated trace to simulate a varying channel. In the MAC layer trace file, the MCS indexes I saw are all even numbers, like 2, 4, 6,.... 28, any particular reason for this?

Thanks much for your help.

[Marco Miozzo]

Hi,

it depends on many things and especially on the configuration you are using in your simulation. Considering the standard one for instance, the MCSs are selected by the AMC according to the CQIs received, which are 15 values characterizing the channel experienced by each UE. This implies that for simple AMC schemes (lie the one called "Ber" used as default in LENA)  the correspondent MCSs are 15, too. You can find more info on the AMC schemes in the LENA documentation.

Regards,
marco.

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[Vincenzo Rea]

I didn't find anything on the specification documents about how translate from a CQI index to the MCS that will be used. What I saw in Lena code (src/lte/model/lte-amc.cc) is that there is a function for this and it uses tables and spectral efficiency values for calculating the MCS for that user. This function gives you only even values and never it will give the other odd values.

[Marco Miozzo]

The tables in LENA come from R1-081483 (  Conveying MCS and TB size via PDCCH) and 36.213 (table 7.2.3-1).


Regards,
marco.

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