Re: New J-10 Thread III
Thanks crobato. I always wondered exactly what type of wireless tech military datalinks used... its too long distance to be wifi-style connections. So it was cell phones all along. How vulnerable are modern data-links to jamming? I know militaries have jammers strong enough to jam an entire city's cell phone networks.
Wireless military links work similarly to civilian wireless telephony with the similarity of principles and technologies. Similar problems confront both, resulting in similar solutions. Like digital celphones, digital packets are sent along with voice.
As telephony technologies move up from 1G to 2G to 3G and now even 4G, they keep getting harder and harder to jam. Much of basic cell telephony are actually designed to prevent interference and jamming, mainly from all the other celphones and towers. That's why you can have millions of handsets able to operate without interference on a single frequency or on a narrow band of frequencies. If you're going to jam a modern network now, the jammer has to be that close to overwhelm the network via sheer amplitude and that powerful since you have to barrage all the frequencies, but you know, it still may not work.
For example with TDMA technologies. TDMA means Time Division Multiple Access. This means different users are allocated different time slots on the same frequency. That would be similar to a classroom where every student is given a minute to stand up and discuss their project. Now when each handset is idle, and not using broadcasting, they will each scan for other handsets and on frequencies on the air. If the current frequency is busy or being interfered, they will move to another frequency, then broadcast when their time slot comes in. What I just described is GSM. Yes, basic handset technology is frequency agile aka hopping and not only that, its LPI (Low Probability of Intercept). Actually with algorithms that exploit Orthogonality, make that zero interception.
Another, which is using pseudo random coding. You got all these handsets sharing the same frequency, each emitting pseudo random waveforms. When pseudo random waveforms are in the same frequency, they do not cancel or jam each other. In fact, pseudo random waveforms are that difficult to jam unless the jamming waveform has to match it exactly with a completely offset phase. So you got millions of handsets emitting pseudo random forms, so how can two parties communicate with each other? The first party and the second party are given a unique special code, and with this code, they are able to recognize each other, and others will be treated as background noise. Sounds fancy? Yet, this is your basic CDMA handset.
Its keeps getting more and more difficult to jam as technology progresses, combining time division, frequency hopping, spread spectrum, pseudo random forms, and the initiative is with the communicating side. Its just easier to blast the communication towers with precision munitions.
