Possible Bug - Link Planner 60GHz RX too low?

By all of my calculations and using a few other calculators it appears the receive power is way too low in Link Planner when using the cnWave Vx000 series radios at 60GHz. The RX level never goes above -60dBm even though it clearly should. Nothing in the user guide or anything else I have found would indicate they are limited to -60dBm RX. Are the calculations being performed correctly?

Hi Eric,

Thank you for bringing this to our attention, it looks like we do need to make some enhancements to our 60 GHz cnWave User Guide to make this clearer. There are several references in the User Guide to the fact that the radios use Automatic Power Control, but you are correct it doesn’t mention the reference level, which is indeed -60 dBm. Links that are very short can operate up to -40 dBm (using minimum transmit power), but typically most links will be power controlled to -60 dBm during operation.

In addition the 60 GHz antennas are patch antennas and the RSSI is reported at the single patch level and therefore doesn’t include all the antenna gain on the receive side quoted for each antenna. This means that to use a conventional link budget calculation, you need to add in additional loss on the receive side. In LINKPlanner we are currently reducing the receive gain by 10 dB. There is still ongoing validation and calibration of this value and we may be conservative by 1 or 2 dB in LINKPlanner, but consider that preferable to being too optimistic.

Regards,

Rachel

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Just to add to Rachel’s answer. There are some slight differences in the LINKPlanner UI when a product is using ATPC, but they are easy to miss so I’ll mention them here in case they are useful for anyone.

The “Predicted Receive Power” label changes to “Operational Power”. For 60 GHz cnWave the tooltip shows “Predicted Receive Power is the receive level of a single patch”.

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We also show a help icon, which links to Performance Summary — Cambium LINKPlanner Online Help (5.6.0). This is the important section:

Operational Power: For PTP 8xx when ATPC (APC) is set to Enabled or cnWave 60 GHz where APC is always enabled, the Receive Power displayed is the Operational Power. When ATPC (APC) is enabled the Maximum Power may be reduced depending on the link conditions, resulting in lower measured receive powers, which can vary over time. The value shown is a typical value at the high end of what may be achieved. The tolerance levels shown are the same as given for the Predicted Receive Power.

The installation report will show the Predicted Receive Power during alignment (without ATPC) as well as the Operational Receive Power.

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Thanks,

Andy

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