There's not really a standard, because it's so dependent on what the end user is doing with it. I have sites that need near 100% comms success rates because a flow reading on one site is used to set a pressure setpoint on another. Loss of comms means automatic switching to a less efficient operating mode, which is not ideal.
90% is very low availability. That's over 2 hours a day where you're saying no comms is fine. A properly designed radio network shouldn't have issues like this. Id try to solve these issues by first:
- Setting up a radio pathloss model for all sites on your network. There is free software called RadioMobile for this, which is good enough for this kind of thing. Or engage a specialist consultant to do this with commercial software (expect to pay 3-5k depending on size of your network).
- If the pathloss model shows that comms should work (ideally better than -85dBm but anything up to around -100dBm should work) then investigate why. Hopefully you've got modern radios with built in VSWR and RSSI monitoring. Check there are no issues with antennas, coax, local obstructions. I've seen sites that have been working mostly ok with the antennas pointing 60 degrees off... when aligned properly performance when from OK to perfect. Alignment was hard before the advent of Google Earth. You had to use a compass and paper maps... now, just draw a straight line and find a decent nearby landmark.
If you have sites that have poor or obstructed paths then you may need an additional repeater. Or, with modern IP routable radios, use another site with good coverage to provide a "last mile" point to point link to the troublesome site. A few K for additional radios and installation and problem solved.
Unfortunately all of these require spending some time figuring out the problem, and then possibly spending some time and money fixing the issues. But that in my eyes is much better than simply trying to find a way to say that **** performance is acceptable.
