Reply To: Subcarrier allocation in NOMA

Bashar Tahir


In general, the order in which you enter the UEs determine which subcarrieres they are allocated. For example, consider the following allocation:
scStr.schedule.fixedScheduleDL{1} = ['UE1:12,UE2:60'];
This means that UE1 is allocated the first 12 subcarriers of the BS resources; UE2, on the other hand, is allocated the next 60 subcarriers.

If you now switch this to:
scStr.schedule.fixedScheduleDL{1} = ['UE2:60,UE1:12'];
then this only swaps the positions of the UEs on the resources grid. Meaning that, UE2 occupies the “first” 60 subcarriers, while UE1 occupies the “next” 12 subcarriers.

Now, with NOMA, you define which user is superimposed on which other user. As explained in the user manual, we use the notion of “UEA:UEB”. This means that UEA is superimposed on UEB. So, UEA would be the cell-edge user that is allocated high transmission power. When you enter ‘UE5:UE3,UE6:UE4’, it means that UE5 is superimposed on UE3, while UE6 is superimposed on UE4. If you swap the order to ‘UE6:UE4,UE5:UE3’, then this would result in the same pairing.
If you change it to ‘UE5:UE4,UE6:UE3’, then now UE5 is superimposed on UE4, while UE6 is superimposed on UE3.

Doing something like ‘UE3:36,UE4:36,UE4:UE5,UE3:UE6’ will result in an error, because you already allocated resources to UE3 and UE4, and therefore they are the primary users. It would work, if you make the UE5 and UE6 the primary users (by allocating resources to them first), i.e., ‘UE5:36,UE6:36,UE4:UE5,UE3:UE6’. In this case, UE5 and UE6 would represent the primary (cell-center) users, while UE3 and UE4 would represent the cell-edge.