Can beam pattern affect 5G cell capacity?
I know no of beams can affect capacity due to SS/PBCH overhead, but particular beam pattern can affect capacity of cell?
(For both Analog & Digital BF)
I think it can.
The narrower is the beam the higher is the gain (so higher will be the MCS and throughput) and more MU-MIMO can be scheduled in same time (pairing them for MU-MIMO in different spatial location).
For example there’s a difference between 16 beams covering the whole footprint of cell or 64 beams covering the whole footprint of cell.
Gain of an AAU is anything between 20 dB to 30 dB where 20 goes for large beams and 30 goes for narrow beams.
So we can say that higher the no of beams -> higher cell capacity?
But will the cell capacity be limited by interference due to more number of beams, Shannons Theorem?
Cell capacity is given not only by gain but also by number of simultaneous PDSCH layers.
Yes, beams will not be totally ortogonal meaning will degrade the SINR of each other but will still be a gain for MU-MIMO with spatial multiplexing.
It all depends where users are located. For example for peak throughput tests of the cells in MU-MIMO spatial multiplexing, users are specially located to be as orthogonal possible one from each other ( meaning if user A is in the max of beam1 then user B shoudl be in a min of beam1 and so on)
Okay so my understanding is that higher beams will eat higher PDSCH resources but due to higher layers we can achieve higher T’put as remaining PDSCHs will be used by same users in same time/freq.
One user can have to 4 PDSCH layers ( 4x4 DL MIMO) but this is very rare to see in real life.
More likely an user will have 2 PDSCH layers (2x2 DL MIMO) so a total of 8 such users can be accomodated.
Also narrow beams are given by number of csi rs ports.
The more csi-rs ports there are the narrower will be the beam and so higher will be the gain/MCS/Throughput.