wi-fi radio link design

[vimcma]

Hello guys!

Is not a trivial task appears in front of me.
I need to calculate the wi-fi radio link to the flying mobile unit for organizing telemetry of that small aircraft it's self.
It is modelling club come to me with this task, they want to build quite big sample of aircraft to show it on their competition.

I need to choose the land station antennas (most probably parabolic (Gain +/-30 dBi) with auto azimuth correction system) and on the flight object is possible to install only omni antenna (with gain 3-5 dB).

Could you please advice me how to calculate this kind of link.
Max distance 50+ km (best case 100km)
Link capacity 30+ Mbps
Flight height 1500 - 3000 m
Flight time 3+ hours

as a transmitting equipment will be used routers with access points like MicroTik or some other with Tx power +27 ... +31 dBm

This all what I've got as an input.

Thank you in advance!!!

[alkoma]

My try:
Using the calculator on the website below, assuming that the distance is 100 km and the omni antenna gain is 5 dBi, the path loss is 105 dB.
This means that the signal at the receiver is going to be around -75 dBm, assuming that the TX power is 30 dBm.
http://www.radio-electronics.com/inf...a-equation.php

[dekili]

Just to add,

For achieving throughput you need to take into count C/I and RSS for the link you are planning. Check modulations that you have, see in vendor documentation required C/I and RSS and heck if you can achieve it with -75dBm of RSS and requested C/I for the modulation that will provide to you 30Mbps. You can expect -75dBm, excluding any signal variation (fading, obstacles etc.) an in case of line of sight links. It all depends on the height that your mobile unit will be lying, because on 100km away from ground unit, due to Earth curvature, you can't have LoS conditions. Your losses will be much higher and I don't expect that you can achieve reliable link (a connection at all) on such large distance. I am not sure if Wi-Fi is the best solution for telemetry on planes and other units unless it is a drone. If you have a real plane, then you can use band close to 350MHz for communication with it and for telemetry data transmission. Those are narrowband channels so no chance of 30Mbps but if it is pure telemetry (no video) than it is OK. For Wi-Fi pay attention to C/I and RSS and be aware that on a 100km distance you might have problems with other users using the same channel, poor propagation conditions due to non-LoS and it is very high data rate to guarantee to mobile unit on such high distance.
cheers

[vimcma]

First of all thank you for your ideas!
Good article with basics of radio wave propagation modelling thanks ...

About interference can say that it is not a problem because 99% of equipment in our country working on 2.4GHz here will be 5GHz band.

This is really not a standard task as for me, before it was RRL networks built for mobile operators (P2P and P2MP RRL links).
Here it will be mobile object if I understand correct for the management of it is enough couple of kbps channel.
But they want to watch video in real time trough the channel.
It is for the fire department to check situation in the forests at the summer time ...

I think that the biggest problem for them will be correct azimuthing from the ground toward object.