> "Putin told me that he would not sell Weapons to Iran." WHO ELECTED THIS FUQING IMBECILE?

China is selling Iran chip sets for their drones and missiles to utilize the BeiDou navigation and communications satellites which provide one meter accuracy (better than L2 band GPS).

BeiDou also uses frequency hopping and advanced anti-spoofing algorithms to nullify electronic countermeasures.

Putin told the fool the truth

He's not SELLING Iran the weapons

He's GIVING them the weapons as recompense for the Shahed drones Iran provided Putin to pound the fuq out of Ukraine

https://x.com/mb_ghalibaf/status/2080300668611416499

VP_Spiro_T_Cheney wrote:

China is selling Iran chip sets for their drones and missiles to utilize the BeiDou navigation and communications satellites which provide one meter accuracy (better than L2 band GPS).

BeiDou also uses frequency hopping and advanced anti-spoofing algorithms to nullify electronic countermeasures.

BeiDou is objectively the best GNSS that currently exists - the Chinese took a long hard look at all the previous ones (GPS, GLONASS and Galileo) and looked at which parts of each worked best. Then they build a V1 system, did live testing on it, took the stuff they learnt from it and designed the current version. Since the V1 system was basically only being used by official entities in China at this point they also took the really drastic step of completely ignoring backwards compatibility with the currently installed receivers and doing a complete redesign of the ranging code structure.

This is the biggest reason it works so well - modernized GPS is using a lot of the same approaches that BeiDou does, but because of the huge numbers of L1 C/A code only receivers it has it fit the modulation around the requirement to keep as much power as possible out of places where it might interfere with the C/A code. Since the Chinese dropped all the V1 stuff completely they don't need to do this and can structure their downlink purely around best performance.  They also lucked out - the frequencies that BDS is using overlap with the ones used by the European Galileo system and the Chinese originally assumed they would have secondary user status - but the EU fuqed around for so long that the Chinese ended up being the first people with a fully operational system in this band and hence the ITU assigned them the primary user status and Galileo is secondary.

They also have a multiple constellation satellite structure - there is a (very GPS like) 24 satellite constellation in MEO with a similar orbital period (it's slightly longer than GPS so they can fly the satellites a bit lower in a less congested orbit - the original "exactly 12 hours" that GPS used was because it made computation simpler, but that's a complete non-issue now).  They also have 3 satellites in GEO orbits that are visible from the whole of China and another 3 in an IGSO that improve accuracy in the whole Asia-Pacific region.

Those 3 GEO satellites are a large part of the reason that they have such good accuracy inside China - They have effectively zero orbit error being in GEO and can be constantly monitored by multiple ground stations to provide clock steering and updated tropospheric delay models.  The IGSO ones provide similar advantages in the whole area and also help with "urban canyon" effects in heavily built-up areas where satellites at higher elevation angles are especially useful because the lower angle satellites are blocked by buildings.  Note that this is similar in approach and intent to the Japanese QZSS system - but with the advantage of not having to operate within a system like GPS that has basic signal structure that was defined over 50 years ago.

And I am absolutely not attacking the people at Rockwell, TI and Magnavox that designed the original GPS code structure - they were highly constrained by what was technically feasible at the time and they did an amazing job within those constraints, which is why a lot of the basic design principles they came up with are still used by every GNSS on the planet. They were also well aware that the C/A code was an ugly hack - but the technology to achieve the same result in a non-hacky way wouldn't really exist for about another 10 years.