s-taka.org

Satoshi Takahashi

Lang:

Galileo E6B signal reception with Pocket SDR, a open source software-defined radio

category: gnss
tags: galileo has oem729 pocketsdr qzsl6tool

I extracted the Galileo E6B signal using the open source software-defined radio Pocket SDR published by Professor Tomoji Takasu of Tokyo University of Marine Science and Technology.

Using the method in the screenshot of Professor Takasu’s article Galileo HAS (High Accuracy Service) operation start, I processed the data recorded on 2022-09-30, ch2_20220930_115617.bin (1.4 gigabytes).

$ pocket_trk.py ch2_20220930_115617.bin -f 12 -sig E6B -prn 1-36 -log e6b.txt
$ grep CNAV e6b.txt

$CNAV,1.882,E6B,21,FFFC15C5320C6126982E702F1DC74C3153FACB22B5AA2D0C818AB1A0314C34DB3899A194DE1DE382F4CEF18D8C124110A52CDCAE27B92FB40D18DFBE28
$CNAV,1.883,E6B,27,FFFC15C6601B940FC8843BE505E15FBD0BACF8934613AA08B74750B5B3784B2CC591E515B78B79DACB0B92A0A62DE206033DE8C6E752991EBEF2A10B88
$CNAV,1.887,E6B,19,2B26BCEF0C04F6711BF86137086A12C14F87C07B4C6AA4DE04BCEB8612C34C691BFABCECEB86BCED4F851BFB0C074C68613604BFF48448D33487C2D588
...

Non-stationary data was displayed. When the quasi-zenith satellite system started trial delivery of MADOCA-PPP, it seems that Galileo was also trial delivery of HAS. The Pocket SDR is awesome because it enables me to do what I want to receive new signals. I am very interested in the content of this message, so I will try to write a decoder.

In addition, the navigation data output command GALCNAVRAWPAGE of the E6B signal for the NovAtel OEM729 receiver that Professor Takasu wrote in the article. The command name seems to mean that the C/NAV message for the Galileo satellite is output in raw page format.

The OEM729 receiver has an Ethernet interface that allows multiple receiver outputs to be output individually using multiple TCP ports. Therefore, I sent the above E6B raw data output command to the ICOM1 port (TCP port 3001) of my OEM729 receiver, while the result received at the ICOM4 port (TCP port 3004) was displayed with NovAtel raw data display code, novdump.py. nc (netcat) is a command to access any TCP or UDP port, and its -C option converts line feed code to CR+LF (carry return and line feed).

$ nc -C ssl-oem729 3001
[ICOM1]log icom4 galcnavrawpageb onchanged

<OK
[ICOM1]^C
$ nc ssl-oem729 3004 | novdump.py
MT2239 unknown           70 bytes
MT2239 unknown           70 bytes
MT2239 unknown           70 bytes
MT2239 unknown           70 bytes
MT2239 unknown           70 bytes
MT2239 unknown           70 bytes

[ICOM1] is the OEM729 receiver’s prompt and <OK is its response message. It seems that the C/NAV message on the Galileo E6B signal was output to the ICOM4 port.

Reply email from EUSPA (European Union Agency for the Space Programme) GSC (GNSS Service Centre) regarding Internet delivery of Galileo HAS requested me of “specific research activity” in detail. Regarding this item, I was asked to rewrite it when filling out the application form, and it seemed that the form could not be submitted without the word “R&D” or “project” in the example of this form. I will reread the EUSPA Galileo High Accuracy Service (HAS) page and resubmit the application form.

Related article(s):