ADS-B limitations?

[Mike74]

With ADS-B OUT in the process of being mandated in Australia, I have a few questions about the technology behind it. I am new to this area, so its probably a newbiw question.

My understanding is that all planes will transmit their Squitter message on the same 1080 MHz frequency at frequent (0.5 to 1 second) intervals with a range of about 200NM. Will this not lead to significant interference on this frequency around busy airfields?

Or is this just the carrier frequency, and the actual frequency the ADS-B transponder uses is shifted, perhaps using the unique 24bit address?

What is the maximum number of ADS-B transponders you can have active, before the system becomes unusable?

As an aside, does anyone have any estimates about when ADS-B will be mandated in Europe?

Thanks

Mike

[skiesfull]

ADS-B in Europe - provisionally 2015.

[Quokka]

What is the maximum number of ADS-B transponders you can have active, before the system becomes unusable?

The Australian specification was 1000 per ADS-B base-station.

Therefore, the more base-stations that the project delivers, the greater the capacity of the system to cope with future growth in aviation traffic in Australia.

...and hence our support for implementation of the Low-Level ADS-B Project.

By increasing the number of base-stations, it will increase capacity and coverage (coverage being the critical issue for remote areas that are experiencing traffic numbers which have exceeded the maximum number that can be safely and efficiently processed using non-RADAR Procedural Control).

[Mike74]

Thanks for the responses Quokka and Skiesful.

Each basestation may have the capacity to handle 1000 ADS-B transmissions (much like a cell phone base station can), however isn't there also a limitation on bandwidth/saturation of the 1080MHz frequency?

[youngmic]

Is it not 1090 Mhz?

[Quokka]

... it is 1090. I think that someone's been spending a lot of time shopping for 1080p High Definition LCD/Plasma screens recently ;)

[Mike74]

> ... it is 1090. I think that someone's been spending a lot of time shopping for 1080p High Definition LCD/Plasma screens recently

Actually, I was just reading a home theatre magazine :O
I stand corrected, it is 1090MHz

[jumpuFOKKERjump]

...Will this not lead to significant interference on this frequency around busy airfields? Erm, that is the same freq your transponder transmits on now. Noticed any problems???

[Flying Binghi]

ADS-B limitations? - I suppose the biggest limitation would be the future loss of the GPS signal... what will be the back-up plan ?

[Flying Binghi]

I thought I might have the 'thread of knoweledge' here...

Has there been any consideration of the loss of the GPS signal ???

[jumpuFOKKERjump]

Has there been any consideration of the loss of the GPS signal ??? RAIM - Reciever Autonomous Integrity Management

http://en.wikipedia.org/wiki/RAIM

We will get pretty yellow boxes on our radar screens that tell us when to expect not much help from ADS/B. Managing without the GPS is your problem.

[Flying Binghi]

We will get pretty yellow boxes on our radar screens that tell us when to expect not much help from ADS/B. Managing without the GPS is your problem.

jumpuFOKKERjump,

I'm actually refering to the permanent loss of the GPS signal.

[Jabawocky]

So how many satellites in the system have to go U/S all at once for the GPS system to fall over completely.

I am the first to admit that I am no expert on the satellite GPS side of things but I think they operate independent of each other so you would need to have them all go U/S before it all goes pear shaped!

J

[Flying Binghi]

Jaba, my concerns cover the loss of the entire civy GPS over Aus from miss-use.

While I think ADS-B is a good concept, it does have some dangerous limitations.

[Jabawocky]

Binghi

I hear what you are saying but its like the PC world and Microsoft. The yanks can't shut it down or they would never find their way back home from work, let alone anything else.

And ADSB is not to replace terminal radar at all, however in the greater wider spaces its giving ATC tools they just do not have and could well use.

I am really not sure why it scares so many folk. You will never have 100% coverage with anything, but ADSB is likely to give 10 times the cover radar has ever been able to provide. Just like them fancy new car phones of the 80's.......it'l never catch on, its too expensive......etc etc.

J:ok:

[OZBUSDRIVER]

Why would the DoD turn off it's network? Why would the Russians theirs?

[Flying Binghi]

My understanding is, there is a civilian and a military GPS signal.



Hmmm... I went through and edited some of my previous posts in various threads, so I guess nobody knows what it is I'm refering too.

After reading an artcle by S.E. Flinn in the current Forren Afairs mag (I know I carnt spell) I'm thinking now that perhaps I should just state things plainly.

Perhaps Im being a little melodramatic over a possible non-issue.

I'll think about it for a few days.