Bro, can you have a look at the post above this and the link. I have absolutely no background on this. You might be able to throw some light.
Look through the the link. So heavy in mathematical formulae and modelings that I fell asleep, woke up, read again, slept agin....Wah, highly recommended reading for people with insomnia. Nevermind if it sounded Greek to you. It gets much worst when into radio transmission theory. Better than any medicine!
Basically the article talked about use of leaky cable, which I had highligthed in earlier post, of how signals can be transmitted to a moving train, very much alike how a mobile phone network works, except that the leaky cable is a highly tuned cable with very precise slots cut into the sheath to 'leak' the signals along the length of the cable so that the train at any location along the track, will receive the signal. Antenna on the other hand, is a point transmitter/receivers. And the receivers uses bandpass to only allow that band of frequency to be passed (accepted) as signal, the rest blocked out.
Only of interest about jamming in the link is in section V Analysis, part B: Jamming and SINR. To jam a sign transmission, jammers send a signal within the signal frequency that raises the noise level thereby reducing the Signal-to-noise ratio, thereby clashes the signal. The receiving electronics need a good high signal-to-noise ratio to understand the signal. Just like in your radio, the cracking sound is noise. Hence with lots of cracking sounds (means ratio of signal and noise tends towards 1 or below if noise is higher than signal strength, or level that equipment cannot tolerate to make sense of the signals) you will not be able to hear what is being said, hence you ignore the signal. Same thing happens when in jamming attack.
I guess by referencing this article, they are suspecting the cable to be a possible cause, be it signal jamming by attacker(s), or purely a technical issue. Electronics are usually specs to protect against ElecteoMagnetic Interference(EMI) and those used similar in SMRT would be very stringent on this specs, hence interference not likely to be interference on the electronics. I am not sure if there's any spare cables inside the tunnels for them to switch to a spare cable to try isolate that cables is not the source of problem.
Now my view. To have such a jamming attack inside MRT tunnels, the attacker has to be on the train to be near to the signal cables which are mounted on the wall of the tunnels. You can see these cables when inside the train. To generate the jamming signal, you need jamming equipment on board too. Unless the jamming equipment is so high tech that is so small and it can be hidden in pocket, it is not possible to ride the train and send out noise to jam the signal. Assuming the attacker can do that, the timing and location of the signal lose will show a 'travelling' pattern along with the train where the train is at point of signal jam. Unless there's more than 1 attacker riding in other trains at same time, or a purpose-plan attacker changing back and forth along the CCL, it is really hard to imagine is a deliberate attack. And why only on CCL and not the other lines, which will give a huge headache to LTA/SMRT in a even more random attack? I am not privy to the findings and pattern of signal lost hence cannot comment what may be possible cause when signal is lost and the trains emergency brakes kicked in. I can only offer my guess of probability from what was reported.
Unless they put monitoring devises on every train to try capture the jamming signals, and when it happens, search everyone inside the trains, there's really no way anyone can be in the tunnel and activate the jamming signals outside of the trains.
I cannot imagine why anyone want to, or can sabotage the MRT like this. I am more inclined to believe that's some technical faults happening on the signaling networks. More so in the cables for the above reason of EMI specs. The most difficult troubleshooting is intermittent problems due to degraded specifications which just at the edge of functional capabilities. Most times it depended on knowledge of component's characteristics and theory and educated guess to isolate and resolve such problems. Intermittent problems can go away for a period of time and return to haunt the trains some time later if it is not taken out of the network.
Btw, just saw a news break that the MRT been stable since Friday. Fingers crossed.
