CPDLC in UK Airspace

[acarslogger]

Hi all,

CPDLC now appears to be active over UK airspace -- see http://www.ead.eurocontrol.int/eadbasic/pamslight-18F358E551B5B85912BC952AB9894C0D/7FE5QZZF3FXUS/EN/AIC/W/075-2013/EG_Circ_2013_Y_075_en_2013-09-05.pdf .

Hopefully Kinetic will program the SBS-3 to decode CPDLC and 'digital' acars -- see also http://www.kinetic-avionics.co.uk/forums/viewtopic.php?f=44&t=16029#p131299

Stuart

[alpey]

Hi all, Hi Stuart

Interesting NOTAM :

EGGN-B1918/13
A) EGTT  LONDON FIR
B) 2013 Sep 09  13:00 C) 2013 Sep 16  13:00
E) DURING SEP NATS WILL ASSESS CPDLC AT THE LONDON (EGTT) DOMESTIC
CENTRE WITH SPECIFIED PARTNER AIRLINES ONLY. SUBJECT TO SUCCESSFUL
ASSESSMENT, CPDLC WILL BE MADE AVAILABLE TO ALL APPROPRIATELY
FLIGHT PLANNED AIRLINES. DURING THIS PHASE OF THE ASSESSMENT ONLY
FUTURE AIR NAVIGATION SYSTEM (FANS) EQUIPPED AIRCRAFT FROM THE
FOLLOWING AIRLINES WILL BE ABLE TO RECEIVE A CPDLC SERVICE FROM
EGTT: LUFTHANSA, EASYJET, KLM, UNITED AIRLINES.
ATN EQUIPPED AIRCRAFT FROM THE FOLLOWING AIRLINES WILL ALSO BE ABLE
TO RECEIVE A CPDLC SERVICE FROM EGTT: LUFTHANSA, EASYJET, KLM,
UNITED AIRLINES, SCANDINAVIAN, BRITISH AIRWAYS, AMERICAN AIRLINES
AND EMIRATES.
AIC Y 075/2013 REFERS

[acarslogger]

Hi Alpey,

Thanks for the Notam info.

Running the latest SBS-3 firmware (119) and Basestation v180, I used SDRShark and tuned it to 136.975. Here in SE England there appear to be plenty of data messages - I don't know how many are digital acars and how many (if any) are CPDLC.

From the original linked document I'm not sure how much useful/interesting CPDLC information would be decoded, but the logon requirements include Mode-S Aircraft Id (callsign), Aircraft Id (24 bit Hex Code) and importantly the departure and destination ICAO codes. That information might help confirm some of the routing of the alpha-numeric callsigns (e.g. EZY70AB) that are now used.
 
I assume that Kinetic have some business plan and they will no doubt consider whether to enhance the SBS-3 firmware and Basestation to decode these CPDLC and 'digital' acars messages. I assume the bottom line is if they consider it will increase sales then it may happen; if not ....

Stuart

[alpey]

Hi Stuart, Hi all

Extracts FAQ
http://www.eurocontrol.int/faq/link2000 

Wich parts of the avionics need modfication........

There are three main systems that need to be upgraded or provided on an aircraft in order to offer LINK2000+ Services.
1. The Human Machine interface must include the means to display received messages and to enter responses or new messages. This can be achieved by modifications to an MCDU/DCDU. A dedicated printer and keyboard can also be used.
An alerting mechanism is needed to notify the aircrew of arrival of a message. Audible and/or visual alerts can be integrated with existing audible and/or visual alerting components on the flight deck. Link 2000+ does not specify how this should be implemented.

2. The CMU/ATSU need to include the software for the Services and the ATN. This software contains the applications (e.g. CPDLC, CM) to encode/decode the messages; and contains the ATN end system and router protocols. It is implemented as a software upgrade to the CMU/ATSU or similar systems. The implementation choice is left to the aircraft manufacturer or avionics vendor.

3. A VHF Data Radio implementing VDL-2 and the associated transmit/receive antenna needs to be available. In case of retrofit and dependant on the existing radio, a new radio is required or a software upgrade is sufficient.


Will DATA Link replace voice communications  ?

No, the current plan is to supplement voice communications with data link communications and to allow pilots and controllers the freedom to use either, depending on their judgment of the operational situation. This could be compared to an office situation where telephone and e-mail are used depending on the situation, but very few rules exist to determine which should be used for a specific purpose.

[junglejet]

Decoding VDL-2 (technically the D8PSK 31500 bps protocol that underlies DACARS, CPDLC aso) string is very very challenging.

http://wiki.spench.net/wiki/VDL_Mode_2

[acarslogger]

Let's hope that Kinetic like a challenge.

Stuart

[coyotefxl]

The latest test version of Multipsk decodes very well VDL2. You need a USB with wide 20 KHz BW or a SDR (RTLSDR, Funcube or others) to feed the audio to Multipsk. Before buying Multipsk you can test VDL2 for 5 minutes per session.
http://f6cte.free.fr/MULTIPSK_TEST_26_12_2013.ZIP

Luc

[andyj]

Here's a shot of MultiPSK decoding VDL2 with an RTL dongle and feeding into PlanePlotter.
Works very well.

[acarslogger]

Hi Andy,

What information does PP display from the data that is in the VDL2 MultiPSK feed ?

Stuart

[andyj]

Hi Stewart,

It's pretty much the same format as acars but there are a lot more position reports.
The messages display in PlanePlotter with the normal acars messages.

11/Ø3/15 Ø7:31:56 UTC
Destination address (hexa): 1Ø914A (Ground Station, delegated address)
Source address (hexa): 4Ø6A91 (Aircraft airborne , command frame)
I (Information) frame N(R)=6  N(S)=4 P=Ø
ACARS message ("AOA")
Data (hexa): FFFFØ132AEC7AD45DA57DØ15B5D534Ø2CD31BØC1D532B6B5C4D945C2C2522Ø45C852C42Ø45C7D3D32Ø45C7C757ADD3C183CØ367F
Mode: 2   Identifier: G-EZWP   Ack.: {NAK}
Message type: 5U (Downlink - Weather request)   Block: 4 (Downlink)
Message: M1ØAU265DYEBBR  EHRD  EGSS  EGGW-SA

11/Ø3/15 Ø7:59:26 UTC
Destination address (hexa): 1Ø914A (Ground Station, delegated address)
Source address (hexa): 4Ø6442 (Aircraft airborne , command frame)
XID (Exchange Identification) frame F=1
Data (hexa): 828ØØØ14Ø1Ø9383838353A31393933Ø2Ø2ØØØ1Ø3Ø32ØA48ØFØØØ18ØØØ156Ø1Ø1Ø1Ø3Ø116Ø4Ø12583Ø44C49434384Ø42ØBFEE19
Destination Airport identifier: LICC CATANIA/FONTANAR (ITALY)
Current position (+/- 3') and altitude of the aircraft: 52°18'N ØØ1°48'W   25ØØØ feet (762Ø m)

[andyj]

Here's a shot of mixed VDL2 and ACARS data in Plane Plotter.
The ACARS data is being supplied by acarsdeco2
It might be a bit too small to read but you'll get the idea.

Andy

[acarslogger]

Thanks Andy.

I've been decoding VDL2 transmissions using MultiPSK for some time - I use a SBS-3 > SDRSharp > MultiPSK and then feed the network output into a little application I have written.

I was really interested whether PP managed to decode any of the other CPDLC messages.

As a background for other forum members, the VDL2 frequency (136.975MHz here in SE England) is used for 2 separate types of data; CPDLC and AOA (ACARS Over AVLC = Digital Acars).

AOA - MultiPSK successfully decodes the AOA messages and the output can be reformatted into conventional analogue acars messages e.g. SBS-3 and Airmaster format. During a 12 hour period I received 15,248 Acars transmissions on the analoque frequencies entered into the SBS-3 (131.525, 131.725, 131.825 and 136.750), while for the same period I received 12,427 Acars transmissions on the one VDL2 frequency. There is lots of Acars activity on the VDL2 frequency!

CPDLC - MultiPSK only decodes some of the transmissions associated with CPDLC (CONTROLLER PILOT DATALINK COMMUNICATIONS). It can decode destination airport, altitude and position, but there are many message types defined in NATS AIC document that MultiPSK doesn't decode. See http://www.nats-uk.ead-it.com/public/index.php%3Foption=com_content&task=blogcategory&id=160&Itemid=57.html and then select Y085/2013.

There are many MultiPSK messages similar to this ...

10/03/15 11:08:45 UTC
Destination address (hexa): 275D37 (Ground Station, delegated address)
Source address (hexa): 461F9A
(Aircraft airborne , command frame)
I (Information) frame N(R)=2  N(S)=2 P=0
ISO 8208 message
Data (hexa):
1BFF00815101289C008F325B1447002701534954000000010001080020FFBA4500144700274146494E00461F9A00005341414200000000870000008C050100C301D6C50DC00606042B1B000004010F0160CD010E85003E010000000100000000030071C81FE4EDCFF2B0509C92EC20B34B120103840BB80B4700274146494E00461F9A01010E00080606042B1B0000000001

Currently MultiPSK doesn't decode this type of data stream into anything meaningful. I wondered if PP managed to decode this type of message. If anyone knows how to decode it, please let me know.

Patrick, the author of MultiPSK obviously enjoys decoding all sorts of obscure transmission types and what he has done is with VDL2 is an excellent start, but to get all the data out of the VDL2 transmissions I think it needs someone with an interest and knowledge of aviation to exploit the full potential.

Regards
Stuart
p.s. my application is not in a fit state to make publicly available.

[andyj]

Thanks Stuart. That's interesting stuff.

Yes, it would be nice to be able to decode the rest of the data in there.
I think there's a list of hex id's for ground stations availabe from ARINC but it costs a fortune ! I believe the author of display launcher was looking for a cheaper source.

Programming is not my scene so we'll have to wait for someone else to fix that problem.

Cheers
Andy

[acarslogger]

Hi all,

A second VDL2 frequency is now in use in SE England.
We now have 136.875 and 136.975.

These are both used for CPDLC and 'digital' acars messages.

Stuart

[Radio2.0]

http://radarspotting.com/forum/index.php/topic,5220.0.html
that are the ACARS Freq for 136mhz band:
136.575
136.600
136.625
136.650
136.675
136.700
136.725
136.750
136.775
136.800
136.825
136.850
136.875
136.900
136.925
136.950
136.975

when you look on the .doc I post there you see the Freq.

Is there any free Program available for decoding VDL Mode 2/ 4?