Difference between adaptive and non adaptive UL HARQ, especially in MCS field?

Hi all, I am new in telecom and working in development in 4G technology, so I have a doubt regarding it.

I am working on a feature called adaptive UL HARQ implementation. In case of non adaptive UL harq, the mcs chosen are the reserved ones, but for adaptive UL harq, the spec says we have the same kind of options for mcs field (29,30,31).

Am I wrong about the above point regarding adaptive UL harq? If yes, can I use any mcs I can without affecting the TB size and PRB allocation?

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Hello Pradhan,
No, for LTE and in the case of non-adaptative, the retransmission is performed on the same resource and with the same MCS used for the last transmission attempt.

So in no adaptive Harq you don’t use the reserved MCS ( 29,30,31), and reserved MCS are used in case of adaptive Harq and with the MCS indicated on PDCCH


Thanks a lot, really appreciate your effort to clear my doubt, let me search for it in the specs so that I can show it to my coworkers :grin:.

Please refer to the following specification if further details are required and good luck!
36.321 Section :

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Thanks a lot for the specification reference, appreciate it.