What does "wireless telemetry connection" actually indicate?

Rolf · January 12, 2019, 9:24am

According to the documentation, it shows percentage bad packets received (probably mavlink packages with wrong crc ?)
Doc: http://ardupilot.org/planner/docs/mission-planner-ground-control-station.html

In case of telemetry via usb or good wifi connection 100% are indicated. Therefore, shouldn’t it be “good packages” ?

But a bad G4 connection via VPN shows eg about 60% and due to VPN, not a single bad packet should be received !!!

What does the “wireless telemetry connection” actually indicate ? How is the value calculated ?

Rolf

Michael_Oborne · January 12, 2019, 10:11am

it is a % of dropped to received packets.

given you are using 4g, what protocol are you using? tcp or udp? also with the vpn software, are you using tcp or udp?

Rolf · January 12, 2019, 10:30am

Thank you for your prompt reply. For telemetry and video i am using UDP. At VPN, I’m unaware. I use ZeroTier VPN https://www.zerotier.com/ .

ktrussell · January 12, 2019, 3:39pm

Using wireless telemetry, I see the reading at 100% when the vehicle is very close and it drops as the vehicle gets further away and the telemetry starts having trouble communicating. So, isn’t the value maybe 100 minus the % of dropped to received packets?

Michael_Oborne · January 12, 2019, 4:27pm

I might have said it the wrong way. But yes, 100 means no loss. Anything lower indicates loss

Michael_Oborne · January 12, 2019, 4:28pm

Can you supply a tlog. I think it could be because of out of order udp packets

Rolf · January 12, 2019, 4:29pm

you mean a tlog from mp ?

Michael_Oborne · January 12, 2019, 4:30pm

Yes. The tlog should show me the out of order packets. Then I can confirm if that’s the issue

Rolf · January 12, 2019, 4:38pm

The tlog file (Arduplane<> G4 with VPN UDP-Telemtry <>Missionplanner): https://www.magentacloud.de/share/h4zker0rac

vierfuffzig · January 15, 2019, 8:10am

for reference:

github.com

ArduPilot/MissionPlanner/blob/ebb2745dda9113aa5616d6e99cbc64441da3e355/Controls/ConnectionStats.cs#L70




// Packets per second = total number of packets received over the

// last 3 seconds divided by three

// Do that every second

_mavlink.WhenPacketReceived

    .Buffer(TimeSpan.FromSeconds(3), TimeSpan.FromSeconds(1))

    .Select(xs => xs.Sum()/3.0)

    .ObserveOn(SynchronizationContext.Current)

    .Subscribe(x => this.txt_PacketsPerSecond.Text = x.ToString("0")),



// Link quality is a percentage of the number of good packets received

// to the number of packets missed (detected by mavlink seq no.)

// Calculated as an average over the last 3 seconds (non weighted)

// Calculated every second

CombineWithDefault(_mavlink.WhenPacketReceived, _mavlink.WhenPacketLost, Tuple.Create)

    .Buffer(TimeSpan.FromSeconds(3), TimeSpan.FromSeconds(1))

    .Select(CalculateAverage)

    .ObserveOn(SynchronizationContext.Current)

    .Subscribe(x => this.txt_LinkQuality.Text = x.ToString("00%")),



// Bytes per second is the average number of bytes received every second

and

basti.