Opensky Questions

[KD4YGG]

Have never been in an area where Opensky is actually operating.

Do these systems have a dedicated control channel similar to Motorola and EDACS, or is it sent sub-audibly like LTR.

Setting aside the different modulation scheme used by the system (TDMA vs. FDMA), is it theoretrically possible to come up with a version of TRUNKER for Opensky, maybe call it OTRUNKER???

Just curious - any thoughts???

 

[mikey60]

All frequencies in the Opensky system here in Oakland County Michigan are continuously transmitting. Exactly what is being transmitted I don't know as there are very few details available about the inner workings of the OpenSky system.

It could be something similar to LTR as far as control messages go. They wouldn't be subaudible, but part of the data stream that's being transmitted.

Mike

 

[Llwellyn]

Based on my understanding of TDMA technology, you'd need as many receivers simultaneously being fed to the trunker software as there were channels in the system. If Opensky supports as many as a Type II system you're looking at needing 16 receivers on a middle-sized system!

It depends on if all of the same data is sent across all of the frequencies at the same time or not. I would assume that would not be the case and that microseconds of one transmission could be on one frequency and microseconds of another could be on another frequency; with the traffic across the frequency pool loadbalanced.

 

[studgeman]

The biggest OpenSky implimentation is a statewide system in Pennsylvania, however it is 3 years behind schedual and 300Million over budget...

On a more techincal side OpenSky is at least a 2 slot TDMA possibly 4 slot. It is a fully digital system using an end to end VoIP (each subsriber unit has an IP address) One of the biggest challenges to decoding an digital transmission is disecting the packet structure and determining to vocoder algorithm. Because OpenSky is a propritary system this is nearly impossible. OpenSky uses a dedicated control "channel" the same way a TDMA cell system does