Interference and Signal Strenght

[Kelly Bellis]

I've always loved that map - who made it?

BTW, there is also a UHF scanner on the LS too!

I like your avatar Sorin - is that a T2 ? - that's the gun I learned to turn angles on back in the 70's

 

[Nistorescu Sorin]

Hi Kelly,

Thank you very much.
Yes, I keep my T2 in very good conditions.

But things are changing fast! This Triumph LS is quite a machine.
It's better to look forward.

That map it's just a simulated image now. Someday may be..
Graphically speaking, I really don't know who made it. Practically with some drones, could be possible.

Regards,

Sorin.

 

[Nistorescu Sorin]

Perhaps Triumph LS could provide results like this.

 

[Matt Johnson]

Dear Matt,

One day we tried a metal plate (dimensions about 1m x 1.5m) hold vertical between receiver and those radars at about 2 meters from receiver.

You probably don't need to carry around a big heavy metal plate. Metal will reflect most all radio power within the first few atoms of the material. I lose almost all satellite signals by placing a thin piece of aluminum foil over the antenna:

You should be able to block the radar interference with a piece of cardboard covered with foil or an aluminum baking pan.

Javad, when I did this test I am noticing that the U4 screen does not appear to be displaying the correct S/N loss for GPS L1 & L2 and GLN L2. Here are the screenshots before and after placing foil over the antenna. I let the U4 screen average for over 10 minutes:

Before Foil

After Foil: Compare this to the S/N loss shown in my Spectrum Analysis.

 

[Nistorescu Sorin]

Two favorite receivers:

one for monitoring reporting & protecting all GNSS bands against interferences;
http://www.javad.com/jgnss/products/receivers/triumph-ls.html

the other for GNSS Ionospheric Scintillation and TEC Monitor
http://www.novatel.com/products/scintillation-tec-monitor/gpstation-6/#overview

 

[Nistorescu Sorin]

"Interferences do exist in many places" indeed.
As you can see in the pictures is an open environment but we cannot measure. Too few satellites.

We intend to find the source of interferences with a R&S®FSH Handheld Spectrum Analyzer with geotagging function and a directional antenna.
An old electric motor with a 5kV power line is the first that we suspect that produce harmonics and then a small military unit at about 1 km distance.

200m away from the bad place we can instantly obtain fix solution with more than 9+4 GPS/GLONASS satellites.
The major problem is for GPS L1 and GLONASS L1.

We tried in field a Leica GNSS receiver, Stonex S9, Triumph1 and Triumph VS.

 

[Shawn Billings]

Interesting to see L2C and L5 signal strength seems to be enough to overcome the interference, based on the screen shot.

 

[Nistorescu Sorin]

Here is a possible representation of the area affected by a source of interference. Then a trajectory shows partial segments of decreased quality of navigation parameters in the proximity of jamming sources.

J-Field could have an option to store some interferences parameters attached to a coordinate. Many of above results may be achieved by adding an "interference" layer in Justin/Justin Link.

 

[Nistorescu Sorin]

Characterization for the sources of radio frequency allows for the type of interference signal to be identified, which gives a good indication of whether it is unintentional interference or a jammer.

Some sources of radio frequency interference can seriously disrupt GNSS services, but when extra noise is present, a GNSS receiver will encounter more than unpleasant situations:

1. Low noise will affect measurement accuracy;
2. Medium noise will cause problems with tracking, and make it harder to (re-)acquire satellite signals. Satellites at low elevation may be lost;
3. High noise will completely destroy the receiver’s ability to acquire/track the desired signals.

Triumph-LS represents a big step forward, but I think that a GNSS receiver must quickly distinguish between unintentional interference and deliberate jamming and have the ability to detect and characterise the interference signals, using a comprehensive data base.

Interference detection and characterization help us to develop effective mitigation measures for protecting GNSS services and user equipment.

Regards.

 

[Javad]

Please see the "Spectrum" capability of TRIUMPH-LS. It has a very sophisticated built-in spectrum analyzer that looks to the heart of the signal inside the our GNSS chip. See the "Spectrum" button which scans all bands in a 30-Mhz wide with 1Khz steps. We assign up to 100 channels for spectrum analysis.

 

[Nistorescu Sorin]

It is true, Triumph-LS Spectrum analyzer has the ability to look at the heart of the signal inside.

But in some situation I can say that looking at the signal spectrum then interpret it and at last somehow depict the interferences source type (intentional/unintentional) is not a easy task for us.

So when I say characterization I want to mean monitor, report and also possible suggestion about the device that caused the interferences. As far as I know, jammers generate a wide, strong, continuous signal and are therefore relatively easy to identify.

If a surveyor like me is not be able to interpret the LS spectrum, then effective counter-measures can not be taken. For example, we lost a month because of the situation shown at #26. Also in NetView we need to compare the current spectrum results with a previous ones on the same spectrum if it is possible.

Thank you very much for the answer.

Regards.

 

[Javad]

We can only report on the frequency, the bandwidth and the strength of the interfering signal. We can never say which device generates it. Also, as we showed in one of our advertisements, if several TRIUMPH-LS is deployed in any area, by triangulation on the strength of the interfering signal in different locations, one can identify the approximate location of the jammer. Please see the video on our website about spectrum.

 

[Nistorescu Sorin]

My previously post is somehow related to automotive industry. Recently I had to fix my car. Speaking with those people, I realized that there is an intense concern in radio frequency interference detection. They want to prepare and evaluate the benefit of upcoming Galileo satellites on their work in the near future.

So, the Aldenhoven Testing Center (Germany) is a testing ground for positioning systems. Road applications using a series of pseudolites, ensures that three or more Galileo signals are available at any position inside the test bed (http://www.atc-aldenhoven.de/en/track-elements.html).

Then, jammers with known and configurable characteristics are deployed both in road gantries along the circuit and in the moving vehicles.

Low-cost devices for detecting GNSS interference and jamming within road transport applications are used in different configurations (nsl_probe_and_tablet). A software receiver front end called Stereo (Nottingham Scientific Limited) which can be configured to cover all GNSS frequency bands, performs the GNSS receiver front end processing.

The system is composed of two major elements: networked field sensors or probes, and a server at the back-office for data storage, processing and analysis, wich also monitor the state of the ionosphere to identify disturbances which could impact many receivers and prevents this from incorrectly being attributed to intentional interference.

Triumph-LS analysis capacity for jamming interference caracterisation could be increased with a server support.

Regards.

 

[Nistorescu Sorin]

An interesting project for superfast broadband access is taking place around here.
http://www.batsproject.eu/index.php?option=com_content&view=article&id=76&Itemid=437

Again, interference represents an important issue, but if the project will succeed, it will be part of the general picture of the near future with direct impact for our jobs.

 

[Nistorescu Sorin]

The spoofing attack is potentially more hazardous than jamming since the target receiver is not aware of this threat and it is still providing position/navigation solutions which seem to be reliable.

For GPS, the P-code, (used by military and other so-called authorized users), was designed to be encrypted to prevent straightforward spoofing. The anti-spoofing is implemented using an encryption code, resulting in the P(Y) code. Regarding modernization process a new military signal called M-code was designed to further improve the military GPS signals.

But for civilians, as far as I know, the GPS C/A code and the newer L2C and L5 codes do not have such protection; hope that the Galileo authentication service will inform the end-user about the origin of the signals (if signals come from the Galileo satellites or not), thus representing a real protection against spoofing.

Designing a general approach for a anti-spoofing method is not easy because of many different parameters involved. So how resilient is Triumph LS to spoofing? Here are some examples of this kind of attacks and the countermeasures against them:

 

[Nistorescu Sorin]

Now a project for interference monitoring at a global scale was born. Also, international standards in the area of GNSS threat reporting and receivers testing will be created.

Finally I hope that these projects will reach and help people like us.

 

[Nistorescu Sorin]

This will apply only in EU.

From Spirent blog about ETSI EN 303 413 V1.1.1 (2017-06) standard (ETSI-European Telecommunications Standards Institute):
https://www.spirent.com/Blogs/Posit...our-GNSS-Device-Complies-with-ETSI-EN-303-413

Migrating LS to Linux means a "significantly changed" GNSS-reliant device, or it refers only to any hardware changes? I will understand this term in the case of the Javad OMEGA receiver (if not released yet) which probably must become compliant with the EU Radio Equipment Directive (RED).

I didn't find "significantly changed" term in ETSI EN 303 413 standard. Any clarification will be useful and again, this will apply only in EU.

 

[Matt Johnson]

To comply with this standard which is for protecting against interference from RF bands adjacent to the GNSS bands the Javad antenna needs to have the J-Shield option installed. The Triumph-Omega does not have an integrated antenna. It would comply with this standard if the GNSS antenna attached to it has J-Shield.

To answer your question I feel that "significantly changed" means major hardware changes, not firmware or software upgrades.

 

[Nistorescu Sorin]

Probably J-Shield+ must be included as a standard configuration in all Javad devices at least in EU.
Firmware could also add anti-jamming and anti-spoofing capabilities.

 

[Nistorescu Sorin]

Don't know if this mean something, but starting from the second half of May 2017, my receiver have some weird behaviour at startup. The satellite LED shows red even several minutes, and onto controller polar plot I can see some satellites jumping all around. Their signals shown under polar plot isn't stable.

I will believe that could happen in one specified location, but it seems to be location-independent. It is true that I use a GPS-first approach (set,/par/pos/pd/gpsfirst) and delay GLONASS within 1min, but the problem seems to be when acquiring GPS signal. After a while my receiver fixes.

This behaviour is not permanent and I could not observe it in July (because of holiday). I didn't manage to make a small movie with this behaviour at receiver startup, but I'll watch if it happens again. Just to mention that normally my receiver fixes before I type the name of job in the controller.