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On Sun, 03 Sep 2006 15:37:38 +0200, Mxsmanic wrote:
Greg Copeland writes: New systems (P25) already do this type of thing. I develop digital radio systems. Police, fire, FBI, CIA, DoD, DoE, various municipal utilities, and various branches of the military are all taking advantage of this technology. In many cases, the old analog systems must co-exist with the newer P25 systems. In some cases, more rural analog systems actually connect with a P25 network via a specialized repeated. Integration is not a problem. So why wouldn't it extend to aviation? Great question. I don't have an answer. I've been planting a seed to have the federal marketing types start sniffing around for FAA/political upstarts...but so far, for my company, it seems to fall on deaf ears. Last I read, an FAA study indicated they need lots and lots of money (sorry, don't remember the amount) to upgrade their infrastructure from analog to digital. They need not upgrade it all at once. I agree with that. I didn't read the whole report and it was a couple of years old. I believe the plan was to upgrade over a number of years...I don't recall the window. [snip] Advantages of this technology include: o call queuing - meaning, PTT places you in a queue so you can get a word in, even when the controllers are very busy. BTW, this also means no more "walked on" transmissions. Do other aircraft hear the transmission when you make it, or when the controller hears it? Granted, they are only supposed to listen to the controller, but in practice they will be listening to other aircraft as well. Sorry. I forgot most people don't know how this stuff works. You are queued when you activate your PTT but you don't actually get your "beep" (think NexTel walkie-talkie sound) back until you're granted your call. Only after you're granted your call do you speak. Otherwise, no one hears you because your radio doesn't xmit. Thusly, no more "stomped on" radio calls. Example: Pilot 1 Pilot 2 PTT PTT "beep" Pilot speaks Hears pilot 1 Release PTT "beep" Pilot Speaks Hears pilot 2 How do you make this work in parallel with analog systems that cannot queue? The repeater initiates the call on your behalf. The repeater is queued rather than the analog radio. Likewise, the reply goes to the repeater, which then re-RXs ("repeats") as analog. For this to work, the analog and digitial systems must have their own frequencies. o call prioritization - All sorts of cool things can be done here - including, most recent exchange receives priority. Also, should IFR traffic receive higher priority over that of VFR? What about commercial traffic? Priority could be adjusted dynamically too. This means planes in distress could be assigned higher priority. So on and so on... It's best not to jump off the deep end with gadgets. Just because something can be done doesn't mean that it should be done. Agreed. I was just tossing stuff out to show the types of things that can be done. A more likely scenario is to give priority to controllers. This allows controllers to pre-empt pilots when the talk group is busy. Which is, more than likely the prefered solution. Also, the concept of "emergency" call is also very useful. For example, it places you at the top of the queue. Combine "emergency" with a GPS source, plus data services, and now your squawking 7700, your GPS position is sent with your PTT, and you now have priority with the controller. o caller id - imagine your tail number, altimeter, heading, and aircraft type provided to the controller on every PTT. Where does this leave people with analog equipment? An anachronism? ![]() is converted, such features would simply be a perk to controllers; with the potential to increase QoS for those that digitally participate. o Limited data services What kind of data services do pilots need? Are they going to be surfing the Web? Oh, most definiately not web browsing. TAFs, METARS, in route weather, PIREPs, TFRs, ATIS, ASOS, TWEB, NAV IDs, etc... [snip] The only con of digitial compared to analog is reception. With analog, you can hear a weak signal. It may sound like absoluete crap, but you can still hear it. With digitial, either you have a strong enough signal to hear it...and it sounds awesome...or you hear absoluetely nothing at all. If the digital threshold is set where the threshold of intelligibility would be in analog, there's no net loss. Doesn't work that way. Nor, would you want it to. One of the key points of digitial radio is that everything is crystal clear. This means lots and lots of filtering takes place to pull out voice from the background. If it's intelligible, chances are, it will be considered background noise and filtered out. Greg |
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Greg Copeland wrote:
On Sun, 03 Sep 2006 15:37:38 +0200, Mxsmanic wrote: Do other aircraft hear the transmission when you make it, or when the controller hears it? Granted, they are only supposed to listen to the controller, but in practice they will be listening to other aircraft as well. Sorry. I forgot most people don't know how this stuff works. You are queued when you activate your PTT but you don't actually get your "beep" (think NexTel walkie-talkie sound) back until you're granted your call. Only after you're granted your call do you speak. Just tell people they would operate it like a telephone: the pilot would direct her call to a particular listener (e.g. ATC) and ATC gets a signal (like a phone ringing!) and can let it ring until they have time to answer the call. But in a pinch, the system could also act like a party line system and after hitting the emergency transmit button in her aircraft, the pilot's distress call would automatically cut in over less-urgent calls to not only ATC, but to any aircraft who have set their receivers to automatically accept emergency calls. In essence, digital systems provide multiple virtual private circuits if needed, but still allow broadcast or "party" line equivalents for situations where that communication mode is more useful. |
#3
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Just tell people they would operate it like a telephone: the pilot would
direct her call to a particular listener (e.g. ATC) and ATC gets a signal (like a phone ringing!) "Your call is important to us. Our operators are busy right now giving their full attention to other airlines. We will be with you shortly. Did you know that you can find most of the information you seek on our website? Please log on to www.getlostspamcan.com. In the mean time, we hope you enjoy our new rap hold music." after hitting the emergency transmit button in her aircraft Yanno, this reminds me of what was promised in our health care system about twenty or thirty years ago. Jose -- There are more ways to skin a cat than there are cats. for Email, make the obvious change in the address. |
#4
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Jose writes:
"Your call is important to us. Our operators are busy right now giving their full attention to other airlines. We will be with you shortly. Did you know that you can find most of the information you seek on our website? Please log on to www.getlostspamcan.com. In the mean time, we hope you enjoy our new rap hold music." "If this is an emergency, press one. If this is a normal call, press two. If this is a reply to a previous call directed to you, press three. If the emergency prevents you from maintaining your assigned altitude, press one. If it prevents you from maintaining your assigned heading, press two. If explosive decompression has occurred, press three. If both pilots are unconscious, press four. If the aircraft has exploded in midair, press five. If you have struck a mountainside or structure while waiting for the queued reply to your last call, press six. If none of these apply, please stand by, and a controller will personally address your emergency as soon as possible. The current queue is ... seven ... minutes long. Thank you for waiting. High fashion reigns at Frammis Terminal's Duty Free Mall, with fall colors now in stock! Reserve your table via pilot radio at the Fallingsky lounge for fine dining after touchdown! The current queue is ... six ... minutes long. Thank you for waiting." -- Transpose mxsmanic and gmail to reach me by e-mail. |
#5
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On Thu, 07 Sep 2006 02:19:25 GMT, Jose
wrote in : "Your call is important to us. Our operators are busy right now giving their full attention to other airlines. We will be with you shortly. Did you know that you can find most of the information you seek on our website? Please log on to www.getlostspamcan.com. In the mean time, we hope you enjoy our new rap hold music." Yeah know, I keep hearing "this call may be recorded for quality assurance", but the quality is anything but. :-) |
#6
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Jim Logajan writes:
Just tell people they would operate it like a telephone: the pilot would direct her call to a particular listener (e.g. ATC) and ATC gets a signal (like a phone ringing!) and can let it ring until they have time to answer the call. But in a pinch, the system could also act like a party line system and after hitting the emergency transmit button in her aircraft, the pilot's distress call would automatically cut in over less-urgent calls to not only ATC, but to any aircraft who have set their receivers to automatically accept emergency calls. In essence, digital systems provide multiple virtual private circuits if needed, but still allow broadcast or "party" line equivalents for situations where that communication mode is more useful. What about analog users? What if an analog user transmits while a queued message is being transmitted? -- Transpose mxsmanic and gmail to reach me by e-mail. |
#7
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On Thu, 07 Sep 2006 07:41:55 +0200, Mxsmanic wrote:
Jim Logajan writes: Just tell people they would operate it like a telephone: the pilot would direct her call to a particular listener (e.g. ATC) and ATC gets a signal (like a phone ringing!) and can let it ring until they have time to answer the call. But in a pinch, the system could also act like a party line system and after hitting the emergency transmit button in her aircraft, the pilot's distress call would automatically cut in over less-urgent calls to not only ATC, but to any aircraft who have set their receivers to automatically accept emergency calls. In essence, digital systems provide multiple virtual private circuits if needed, but still allow broadcast or "party" line equivalents for situations where that communication mode is more useful. What about analog users? What if an analog user transmits while a queued message is being transmitted? Normally, the duration between keying and the call grant is very. It's measured in milliseconds. This means, the analog users PTTs and starts talking, assuming he doesn't already hear someone talking. The grant comes back to the repeater and it starts repeating. That means the digital portion is some number of milliseconds behind the analog portion. If someone else on the analog side walks on your analog call, I imagine the DSP will do its best to filter it out. That probably means your call it terminated before you intended or it's removed. If an analog user talks over the P25 repeater, repeating from the digital side (xmiting analog), then you have the classic walked on radio call problem. That is, after all, one of the problems of analog radio. And from my first posting on the topic: How do you make this work in parallel with analog systems that cannot queue? The repeater initiates the call on your behalf. The repeater is queued rather than the analog radio. Likewise, the reply goes to the repeater, which then re-RXs ("repeats") as analog. For this to work, the analog and digitial systems must have their own frequencies. Hopefully this clears things up. Greg |
#8
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On Thu, 07 Sep 2006 02:11:51 +0000, Jim Logajan wrote:
Greg Copeland wrote: On Sun, 03 Sep 2006 15:37:38 +0200, Mxsmanic wrote: Do other aircraft hear the transmission when you make it, or when the controller hears it? Granted, they are only supposed to listen to the controller, but in practice they will be listening to other aircraft as well. Sorry. I forgot most people don't know how this stuff works. You are queued when you activate your PTT but you don't actually get your "beep" (think NexTel walkie-talkie sound) back until you're granted your call. Only after you're granted your call do you speak. Just tell people they would operate it like a telephone: the pilot would direct her call to a particular listener (e.g. ATC) and ATC gets a signal (like a phone ringing!) and can let it ring until they have time to answer the call. That would be very frowned upon. A unit to unit call (like a non-party line telephone) would tie up resources which should otherwise be shared. That's not to say they don't have their place, but it's not something you would want happening all the time. But in a pinch, the system could also act like a party line system and after hitting the emergency transmit button in her aircraft, the pilot's distress call would automatically cut in over less-urgent calls to not only ATC, but to any aircraft who have set their receivers to automatically accept emergency calls. Emergency calls can be group calls just as they are today with their analog equivalent. The point of an emergency call is to give priority to your conversation with someone on the other end. Anything beyond that is a perk. In essence, digital systems provide multiple virtual private circuits if needed, but still allow broadcast or "party" line equivalents for situations where that communication mode is more useful. I would emphasize it the other way around. A unit to unit call ties up an entire channel for its duration. So you would not want that to be the common case. Greg |
#9
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Greg Copeland writes:
The repeater initiates the call on your behalf. The repeater is queued rather than the analog radio. Likewise, the reply goes to the repeater, which then re-RXs ("repeats") as analog. For this to work, the analog and digitial systems must have their own frequencies. Is there a guarantee that transmissions will occur within a certain period? Are these systems verified for safety-of-life applications? Also, the concept of "emergency" call is also very useful. For example, it places you at the top of the queue. Combine "emergency" with a GPS source, plus data services, and now your squawking 7700, your GPS position is sent with your PTT, and you now have priority with the controller. Interesting. This does bring to mind something else, though: If your channels are so crowded that you need a system to queue messages and give priority for emergencies, you need more channels. It's much safer to have multiple channels that don't require queuing than it is to queue on a single channel. Also, how do you deal with analog users who have no queuing? They will still walk over the simultaneous transmissions in digital and analog. An anachronism? ![]() Actually they would be, since practices extended to digital users would naturally tend to affect analog users, even though they don't have the same advantages. This would put them at a safety risk. Until everyone is converted, such features would simply be a perk to controllers; with the potential to increase QoS for those that digitally participate. Quality of service has to translate to increased safety in my book. As I've said, if fancy queuing systems are required just to manage traffic on the channel, then there are not enough channels, digital or otherwise. Oh, most definiately not web browsing. TAFs, METARS, in route weather, PIREPs, TFRs, ATIS, ASOS, TWEB, NAV IDs, etc... As long as someone is still actually flying the plane. A beautiful digital display of weather 300 nm ahead doesn't help if it distracts you from the mountainside looming just ahead through the cockpit window. -- Transpose mxsmanic and gmail to reach me by e-mail. |
#10
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"Mxsmanic" wrote in message
... SNIP As long as someone is still actually flying the plane. A beautiful digital display of weather 300 nm ahead doesn't help if it distracts you from the mountainside looming just ahead through the cockpit window. If you're flying something that requires you to be concerned (near term) with Wx that is 300nm ahead...and you are low enough to hit something that is part of Earth...you've got larger issues to deal with than how you are communicating. ;O) Jay B |
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