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Station Transmission Constraints on Re-Broadcast

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Admin:
Hi All

I wanted to open a discussion about the constraints for transmission from the OGN-R stations
There are 2 aspects which we need to consider:-
- legal requirement for broadcast (as per ISM EN300/220 Band G)
- useful information for broadcast (what we decide)

The legal requirements are clearly not up for discussion, and as part of the S/W I will monitor the transmission of data from the OGN-R, and ensure we do not bust the duty cycle restrictions - thats easy, and is implemented today

The best case (practical) range you can expect to get from an OGN-R transmission is 30km
but what is useful for re-broadcast, there are 2 parameters to consider:-

1. Traffic Proximity Range
This refers to when to uplink traffic over the OGN-R. So in other words if Glider G1 is within (TPR) km of PAW P1
transmit information about G1 over the PAW Frequency

2. Station Proximity Range
Only transmit data for (any) Glider Traffic when PAW traffic is within (SPR) km of the station

So for an Active OGN-R transmission to occur both TPR and SPR must be satisfied.

An Active transmission is where an OGN-R transmission occured because TPR and SPR were satisfied for a given PAW equiped aircraft, others may still receive those broadcasts 'Passively'

We still have not decided numbers for TPR and SPR and wanted to discuss this with forum members,
We need to be within certain constraints legally (and these are adhered to in software), but in a perfect scenario what should we consider for TPR and SPR ?

My initial thoughts are as follows

1. Traffic Proximity Range   = 5km
2. Station Proximity Range = 30km

These would be for minimum conditions, the legal requirements of duty cycle may bear down on these further.

Up for discussion ...

Thx
Lee

Moffrestorer:
Hi Lee,

I think we’ve got used to a somewhat greater TPR than 5km (3 miles). A 90kt machine will cover this distance in 1.8mins, and this could halve if the glider/contact is flying at the same speed directly toward you. Perhaps we should consider RV speeds here.

I would be happier with a TPR of 10km, if possible and would give better forewarning of glider hotspots.

Thx,

Chris

exfirepro:
Lee,

I concur with Chris. 5Km is pretty close and doesn't give much leeway to allow for poor or intermittent signals. A TPR of 10Km would be much safer, as we need to give sufficient warning to allow PAW pilots to adjust our track to avoid the gliders (especially if there is a concentration around a hotspot), as unless they are also running PAW won't even be aware of our presence and in any case we are obliged to give way to them. The proposal otherwise sounds good.

Regards

Peter

Ian Melville:
I agree with Chris and Pete, 5km is to close. 10km I would accept.

Am I right in thinking that SPR could be reduced if the density of OGN-R stations was high enough? And would it be to much hassle to taylor it station by station, so that high density areas can have a reduced SPR?

T67M:
I'm going to support Lee's original numbers: doubling the TPR from 5km to 10km quadruples the amount of data, making a data rate reduction much more likely. I also challenge anyone to visually acquire a glider at 10km - even at 3km they are nearly invisible in my experience, so 5km gives plenty of notice even at RV speeds.

My only concern is around missed transmissions, and for that reason is prefer the data to be repeated as fast as possible within the legal limits.

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