Hi All
As far as I understand, PMP450m support up to 7 groups (MU-MIMO), in this case what will be the maximum Tx power per antenna lobe / group ?
Thank you
Please assist
10x!
Hi,
I'll give a bit more background information to try and answer this properly.
The 450m has 3 main operation modes in terms of TX.
1) Combinig Mode
2) Sector Mode
3) MU-MIMO Mode
1) Combining Mode
Is used to communicate with a single SM where the channel & azimuth are known.
The beamforming action produces a pattern that is significantly narrower in the azimuth direction than that of a standard sector antenna, allowing the main antenna response to be steered to an individual SM by varying the digital phase weights in the 14 chains. The narrower beamwidth in this mode helps to reduce the inter-cell uplink interference level received at the AP compared with reception using a standard sector antenna. When deployed throughout a network, the narrower downlink beamwidth also tends to reduce overall inter-cell interference levels at SMs.
Control functions in the AP automatically adjust digital transmit gain to take into account array gain of about 8.5 dB in the combining mode, ensuring that the radiated power is never greater than the configured power, and thus never greater than the power allowed by the relevant rules.
The reduction in the drive level that arises as a consequence of utilizing array gain has the beneficial outcome of reducing transmitter distortion and thereby contributing to the use of the most efficient modulation modes in the downlink direction.
2)
Sector mode
The device uses the sector mode when transmitting broadcast data, or when communicating with an SM over an unknown channel. The amplitude and phase weights of the individual chains are pre-selected to provide sector coverage, meaning that overall array gain is close to unity.
Control functions in the AP automatically adjust digital transmit gain to take into account the low level of array gain in the sector mode, ensuring that transmitted field strength is maximized within the constraints of the configured power.
The advantage of the sector mode compared to using a single antenna element, is that it allows the device to exploit the combined transmitter power of all 14 chains.
3)
MU-MIMO mode
The device uses the MU-MIMO mode to establish connections with several SMs at the same time. This mode provides a significant increase in the overall data capacity of the sector.
The MU-MIMO operation consists of forming one beam for each connected SM, such that in each case the main lobe of the beam pattern is directed towards the wanted SM, and nulls in the beam pattern are directed towards the other SMs in the MU-MIMO group. SMs in the MU-MIMO group necessarily have different spatial signatures, and the beams are at different azimuth angles.
Control functions in the AP automatically adjust digital transmit gain to take into account array gain in the MU-MIMO mode, ensuring that the radiated power at any azimuth angle is always less than the configured power, and thus less than the power allowed by the relevant rules.
So basically you are imited to the EIRP set on the unit in any mode.
I hope this answers your question.
Best regards,
Andy.
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@ Andy , thank you
In MU-MIMO mode is it correct to say that each beam Tx (out of 7 ) can reach up to Max EIRP (e.g +38 dBm) ?
Extream scenario, 450m AP will transmitt 7 beams x 38dBm , is it correct ?
10x!
Hi,
You are correct, in theory with the optimal 7 beams we could reach 38dBm peak per beam if all SMs are in the correct position.
In non-ideal situations we take account of any power from one beam contributing to any/all the other beams and reduce the power accordingly to meet regualtory EIRP limits.
Andy.
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@ Andy , Thank you
I read several time your answer regarding combining mode, and I am not sure I undertood
The narrower beamwidth in this mode helps to reduce the inter-cell uplink interference level received at the AP compared with reception using a standard sector antenna. When deployed throughout a network, the narrower downlink beamwidth also tends to reduce overall inter-cell interference levels at SMs.
Extra gain due to narrow beam is on the downlink only (AP--->SM) ? or uplink (AP<--SM) ? or both (AP<-->SM)?
10x!
The 450m can do beamforming both DL & UL so both (AP<-->SM) have a gain.
There is no beamforming done directly in the SM.
The paragraph you quote is saying.
For UL the narrow beam means a better SNR (unless the noise source is directly being the SM)
For DL the narrow beam to the SM means we are causing less noise to adjacent networks.Does this make more sense ?There are some videos on 450m technology that may help you as well. Go to the following link and scroll down to video section.LINKAndy.
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Thanks @ Andy
Just to clarify my question ( I have read your answer few times and still have some doubt ).
As the FCC regulations for DL in ptmp is limited to 36dBm EIRP, how is the power will be distributed between SM in MU-MIMO (optimal mode 7 groups).
Example,
EIRP for SU-MIMO is 36dBm ? what will be the EIRP per MU-MIMO of under optimal situation 7 groups (7 lobes) ?
is it be 36-10log7 (assume the total (for all 7) shall be 36dBM to meet FCC )
Assuming my assumption is correct, we might have an issue when we grow as we go (adding new SM's and reaching MU-MIMO lobes) mainly for the far SM's
Thanks again for all the effort
Hi,
Sorry for the delay in replying I've been out of the office.
Quick answer:
The Rx level at the SM will NOT reduce as you increase the number of MUMIMO groups/lobes, so you should NOT see an issue as the group size increases.
Long answer:
There would be a required reduction (up to 10log7) in a simple conducted test on a simple antenna where there was equal transmit power on each antenna element.
However the PMP 450m is an integrated unit where the transmit power on each antenna element is weighted to produce the wanted transmit mode within the regulatory power limit. As a fully integrated unit measurement of the EIRP was made using Radiated test methods in the far field, in MU-MIMO mode the antenna lobe with the highest EIRP was identified and the Horizontal and Vertical components measured and summed to identify the max EIRP. As a Radiated measurement the contribution of any residual beamforming gain and power (EIRP) from the other MU-MIMO lobes are included in the measurement by measuring the highest MUMIMO lobe we ensure that the other lobes are equal to or slightly less than the measured lobe
I hope that makes it clearer.
Best regards,
Andy.
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