I have a question related to 5G NR numerology and bandwidth part.
I would like to refer to the following article as a reference.
Please refer to the 1st figure in this article.
So, in 5G NR, it appears that each sub-set of sub-carriers (named BW part) can have different numerology.
In the above figure, you can see, the 1st part has 30 KHz, 2nd part has 15 KHz and 3rd part has 60 KHz.
My questions are as follows:
1) in Downlink case, is this only applicable to UE or this is applicable to basestations also?
2) if this is applicable to basestations (in DL case) then I have a question
From the figure, it appears that each sub-set of sub-carriers have a different numerology and hence each of them are transmitted with different symbol duration. Is this a correct assumption?
if yes, once OFDM is done then the notion of sub-carrier is gone as the data is not in time domain.
So, how it is possible to just take a sub-set of sub-carriers and then transmit them with varying symbol duration?
5G is pretty new and here are my thoughts thus far:
For Question 1 you can research the standards and I expect the answer to be directly available somewhere.
My guess is that mixed numerology is meant for either directions of link and that a given UE has limited BW anyway to be mixed but multiple UEs can send each on their numerology.
For Question 2: yes mixed numerology has different symbol time since orthogonality rule is that spacing should be inverse of symbol time.
For the third question (not numbered): For mixed numerology all components of signal must have same sampling rate when generated from various numerologies. This could be done by choosing large enough fft/ifft size for worst case. Any lower numerology can be upsampled through fft/ifft techniques without the hassle of filters.