FAA Plans to Change to Radios with 8.33 MHz spacing?

On Saturday, April 13, 2013 12:26:36 PM UTC-6, Bear wrote:
Bob,



I don't believe that we switch to GSM or whatever.



1. For none of the digital communication techniques it was possible to

find a global frequency range.



2. The relative speed is too high. To my knowledge the highest speed to

which a digital communication system is certified is 500 km/h (310 mph).

This is GSM-R, Global System for Mobile Communications - Railway or

GSM-Railway, for details see Wikipedia.

500km/h would be good enough for us but not for others. We can forget it

in aviation thanks to Doppler effect.



Bear

So, how is digital communication with 17,000 mph satellites possible with Doppler effects?

Nobody suggested GSM as an alternative to a global aviation-specific digital communications protocol.

What is your proposal?


So, how is digital communication with 17,000 mph satellites possible with Doppler effects?

Nobody suggested GSM as an alternative to a global aviation-specific digital communications protocol.

The present 2-meter AM air-band "Party line" originated as a military system in the biplane era. Today's military has many highly secure digital communication nets used for airborne operations from close air support to drone attacks.

The DOD likes the idea of using COTS products so wherever possible, they push military technology into the commercial domain to spread R&D costs and reduce the price they pay per unit. That's where the air-band replacement will come from.

Why would the FAA and ICAO want to do this? Bandwidth. Digital communication uses spectrum far more efficiently and it eliminates channel clutter so pilots hear just what they need to hear.

On Saturday, April 13, 2013 2:13:33 PM UTC-6, Bear wrote:
What is your proposal?





So, how is digital communication with 17,000 mph satellites possible with Doppler effects?



Nobody suggested GSM as an alternative to a global aviation-specific digital communications protocol.

http://en.wikipedia.org/wiki/Orthogo...n_multiplexing

From wikipedia:

Summary of advantages
*High spectral efficiency as compared to other double sideband modulation schemes, spread spectrum, etc.
*Can easily adapt to severe channel conditions without complex time-domain equalization.
*Robust against narrow-band co-channel interference.
*Robust against intersymbol interference (ISI) and fading caused by multipath propagation.
*Efficient implementation using Fast Fourier Transform (FFT).
*Low sensitivity to time synchronization errors.
*Tuned sub-channel receiver filters are not required (unlike conventional FDM).
*Facilitates single frequency networks (SFNs); i.e., transmitter macrodiversity.


On Saturday, April 13, 2013 1:13:33 PM UTC-7, Bear wrote:
What is your proposal?





So, how is digital communication with 17,000 mph satellites possible with Doppler effects?



Nobody suggested GSM as an alternative to a global aviation-specific digital communications protocol.

The satellite ain't goin' 17,000 mph with respect to the ground station.
Doppler will be small with short transmissions.


"Bill D" wrote in message
...
On Saturday, April 13, 2013 12:26:36 PM UTC-6, Bear wrote:
Bob,



I don't believe that we switch to GSM or whatever.



1. For none of the digital communication techniques it was possible to

find a global frequency range.



2. The relative speed is too high. To my knowledge the highest speed to

which a digital communication system is certified is 500 km/h (310 mph).

This is GSM-R, Global System for Mobile Communications - Railway or

GSM-Railway, for details see Wikipedia.

500km/h would be good enough for us but not for others. We can forget it

in aviation thanks to Doppler effect.



Bear

So, how is digital communication with 17,000 mph satellites possible with
Doppler effects?

Nobody suggested GSM as an alternative to a global aviation-specific
digital communications protocol.