SMRT temporarily suspends mobile signals on Circle Line
ricky l36 seconds ago
Think that the MRT train signaling, control and communication system with the train management system must be using RF (radio frequency) that clash with the radio comm system used by the telco.
Telco uses 2.4Ghz and 5Ghz radio frequency for WiFi. This RF band is a free-band unlicensed band that are used by Wi-Fi.
Wonder if the MRT signaling and control system uses the same RF?
If yes, there will be radio signal interference.
Wi-Fi have a RF avoidance when they detected channel overlap and clash.
I doubt MRT signaling system may not be so smart to do channel overlapping avoidance when they detect RF signal clashing.
Telco for 3G, 4G, 2.5G also used different RF - quite unlikely this will clash with the MRT signal as they are licensed band and MRT signal unlikely to use this RF that clash with the telco license RF.
ricky l33 seconds ago
For eg. if the MRT system uses 2.4Ghz for the signaling and controlling as their RF for communication and control - it could have been working fine.
Then one day, there is a decision to provide Wi-Fi access point in the MRT for internet access, 2.4Ghz RF band could have been introduce.
Wi-Fi access point will have RF detection capability when they detected other system also running 2.4Ghz with the same channel, it will do avoidance by switching to other channel that will not cause interference.
But MRT system may not have this capability and may have interfere with the Wi-Fi access point also running 2.4Ghz.
When that happen, signaling and control fail.
ricky l23 seconds ago
If understand correctly, the ERP also use 2.4Ghz RF and seem to clash with Wi-Fi.
Adjustment to the 2.4Ghz RF to another frequency band will have solve the problem of RF interference.
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ricky l23 seconds ago
Or else, if the MRT system indeed use the 2.4Ghz RF, then it also possible to inform all Telco to use the 5Ghz RF for Wi-Fi access - and remove the radio access point that receive and transmit 2.4Ghz.
This will prevent the MRT system from clashing with the Wi-Fi - for eg.
Circle Line disruptions due to faulty signalling hardware on one ‘rogue train’
Yahoo Singapore
November 11, 2016
Photo: Reuters
The mystery behind the Circle Line (CCL) disruptions in early November and a few months ago has been solved - it was due to faulty signalling hardware on one train.
The Land Transport Authority and SMRT revealed more details about the investigations undertaken that had led them to reach the conclusion in a joint statement on Friday (11 November).
In early November, SMRT experienced signaling faults on the CCL that caused service delays. The initial investigations by LTA and SMRT showed that the incidents could be linked to similar problems on the CCL in early September.
An initial hypothesis was that interference from telecommunication signals could have caused the trains’ emergency brakes to be activated repeatedly. Mobile network operators suspended services along the CCL for two hours on 3 November and the full day on 4 November to help the authorities carry out their investigations.
Tests later showed that the telecommunication signals were not the cause of the disruptions.
Engineers and data scientists studied various data and found that almost all the faults happened near one particular train, Passenger Vehicle (PV) 46. On Sunday (6 November), tests conducted during train operating hours showed that PV46 caused the loss of communications between nearby trains and the trackside signaling system.
The faulty train, which has been in service since July 2015, has been pulled out of service.
LTA and SMRT said that no other train has been found to have the same problem and will continue to monitor closely.
In a Facebook post, Transport Minister Khaw Boon Wan thanked all the parties that have helped in the investigations to “finally identify the rogue train with faulty signalling hardware as the culprit.”
Khaw said, “The Circle Line’s intermittent loss of signal communication has caused us many sleepless nights.”
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