Help with Long Range control and digital video streaming for UAV - Page 1
Forum section: electronics / projects

author: Rafael2884
author_rank: Newbie
timestamp: December 30, 2019, 01:35:57 pm
content: So I'm a novice electronics enthusiast, 16 years old, entering the rc world.I made a flying wing of a wingspan of 2 meters designed to go low speed long range, planing missions, with an autopilot I made myself with arduino, gps and some 2.4ghz transceivers modules (laptop communicating thru arduinos), currently with old-school analog video transmissionat 5.8ghz.I wanted to know how to do a wireless communication system that can tell you how strong the signal is, with carrier signal of 900mhz and binary data, that is capable of streaming 360p or 144p 30fps and be controlled, if possible with less than 100ms lag. Distance wanted 5km, with clear line of sigth.I know its very difficult, but I want to know it all from the very beginning. Also, I plan experimenting with pcb building, analog video to digital video, rf comunication, gps based antena tracking and much more.Ebooks, web pages, forums, youtube tutorials or any kind of source that will help me do this very tedious project are welcome.

author: OwO
author_rank: Super Contributor
timestamp: December 30, 2019, 03:00:52 pm
content: What you described is doable but it's a big project in itself because it's not easily doable with off the shelf solutions. If you used a MJPEG stream (or any MPEG without i-prediction) the typical bytes per frame needed for a reasonably clear image is 20KB, which at 30fps is 600KB/s or 5Mb/s. I'll not consider i-prediction schemes for now because it comes with its problems (bursty transmissions, which forces high latency if you add buffering; low robustness to bit errors). For the comms it basically boils down to two choices - single chip transceivers (e.g. CC1200, AX5043) or software defined radio. Existing single chip transceivers don't reach the bit rate needed, and the ones that come close all have shitty sensitivity (over 20dB above shannon). You are left with not much choice but to implement the modulation yourself with a SDR based solution, which is its own can of worms. Lastly you have to design the RF infrastructure components (power amplifier, filters, LNA, antennas, etc) because there are no good off the shelf offerings. To do all this while keeping power consumption and weight low is the challenge.You mentioned range requirements, which is a totally different can of worms. Ideal propagation formulas for free space line of sight do NOT come anywhere close to real world conditions even if you have clear line of sight. The reason for that is the earth that is a reflector. Propagation will be far better when your aeroplane is directly above you or close to that, compared to if it's 5km away and near the ground. Height above ground (of both transmitter and receiver) is extremely important (look up fresnel zone) but also any obstructions in the path even if it's not blocking line of sight. In my experiments if the transmitter is a few hundred meters above ground and the receiver is at ground level, you can expect 5km @ 140dB link budget. That's transmitter at 1W (30dBm) and receiver sensitivity -110dBm.