I have some questions about certain specs of the 5GHz 450m that I just need a little clarification on.
I need this information to correctly answer some questions from CRTC & ISED about our 50/10 coverage. While recording the requested information, it made me second guess my understanding of the 450m’s specs…
The requested information is about the (mTnR) number Transmit and Receive antennas the 450m has. Since AP has one beam-forming antenna, I was initially inclined to state the value is “1T1R”, but given the (7)radio’s and (14)MIMO streams, I was left wondering if this was proper way of recording that.
Second to that, another value that was requested was the Massive MIMO gain factor, and that was unclear to me. As far as I know, this isn’t a requirement, but I’d like to fill it in if I can. Is it 14? Something else? Or is this relevant to 5G base-stations only?
The 450m in 5 GHz uses 14x14 MIMO antenna arrangement - 14 Tx antennas and 14 Rx antennas. The beamforming is accomplished by varying the phase of the signal transmitted or received creating an area of signal enhancement for each SM group, simultaneously creating areas of some level of null for SM groups not on the same azimuth. Then, on top of that, MU-MIMO (multiuser MIMO) groups SM’s so that all SM’s within the same beamforming area are treated as a group, and the AP can transmit to other SM groups at the same time - up to 7 groups, depending on the distribution of SM’s in the 450m sector. I’ve seem 450m’s with 1 SM group operating (the SM’s were in one small area in the 450m sector, or the SM’s are few and scattered across the whole sector, so there were no 2 SM’s that could be grouped together), and I’ve seen 5 SM groups working. Since RF propagation is reciprocal (that is the DL propagation is the same as the UL propagation), the 450m knows the RF location of the SM groups, the RF phase is maintained for both DL and UL for a time period. Then a process called sounding occurs, and any propagation info needed by the AP is updated.
The massive MIMO gain factor has a theoretical value (it can be measured in a proper lab), but is very difficult to measure in a working network. The value is the difference in performance that SM’s experience when the entire sector is covered by a single 2x2 MIMO signal vs the performance experienced when the full MIMO array is in operation. Typical values range from 1-2 dB up to 9 dB or more theoretically. I would not put any value on the form.
Hi Dave,
I am pretty familiar with the details you’ve explained, however I was just slightly confused how to answer the dumbed down version of the question for this silly spreadsheet. There’s no way to explicitly state “beamforming sector” on a spreadsheet, and 14 seemed like it wasn’t entirely truthful because of the dynamic nature of a beamforming antenna. But I think it is indeed the answer CRTC and ISED are looking for when considering the functionality of the AP.