IT Insight: Why Wi-Fi on trains is so bad
Today’s blog, written by our Chairman, outlines the inherent problems in providing a good wifi solution on trains and the challenge of users’ growing and inexhaustible demand for ever more bandwidth.
There are several good reasons and none of them are easy to fix.
Trains are nearly always routed away from areas of high population density so they are rarely near the locations that the Telcos choose for their masts. Their best coverage is consequently not where the trains are. The signal on the train is therefore patchy and unreliable and tunnels really don’t help either.
Another difficulty lies in the provision of the back-haul bandwidth. As trains by their very nature move and, hopefully quickly, they have to rely on some kind of wireless connection to the outside world to get the content passengers want. The options here are quite limited. It’s a choice between satellite, 3G/4G and Wi-Fi or a combination of two or more of these.
The most option most commonly adopted by train operators is 3G/4G because it’s the cheapest. It uses a multi SIM modem on the roof of the train connected to a Wi-Fi access point inside the carriage. Unfortunately adding more SIMs to the modem doesn’t increase the available bandwidth proportionally. That is to say two SIMs are not twice as good as one and so on. The result is that an entire carriage has to communicate via the bandwidth of a couple of SIM connections.
A few brave train operators have added satellite as a backup to the 3G/4G solution to deal with areas where the terrestrial signal is weak. This is expensive and complex and doesn’t help with the problem of tunnels.
A more effective solution is to build a dedicated trackside infrastructure. This can be done with 3G/4G microcells connected by fibre laid alongside the track or it can be done with Wi-Fi access points mounted on trackside furniture such signal gantries and the like (https://goo.gl/YJ3g0M). These access points can communicate with the train and with each other at 80+ Mb/s creating a linear chain along the route thus avoiding the need for laying fibre. Unfortunately both of these are very expensive solutions.
Network Rail is believed to be evaluating a 4G/LTE microcell solution leveraging existing trackside telephony fibre on some routes. There is also government consultation (https://goo.gl/CvKWhk) supporting its initiative (https://goo.gl/yJ6EBU) to have acceptable solution Wi-Fi on trains that will serve passengers needs for the next 10 years. Their hope is that it will encourage more people to travel by rail.
The trouble is that ambition will prove largely self-defeating as, however you back-haul it, Wi-Fi is a shared medium. Whatever bandwidth you provide to the train must be divided between all the Wi-Fi using passengers.
The rules of Wi-Fi, as laid down in the IEEE802.11 standard, set out to manage the shared medium fairly. An automatic process common to all Wi-Fi devices makes each user’s device wait its turn to transmit or receive data so that their signals do not jam each other. So on a full train the service will be much slower than on a near empty one as more devices queue for their turn. If you are a lone user in an otherwise empty carriage you can probably enjoy streaming HD video but on a packed commuter train you could struggle to get enough bandwidth for an email.
Whatever the outcome of the government’s consultation and whatever technology is chosen it will inevitably eventually fail because of the users’ inexhaustible demand for ever more bandwidth.
Written by: Jeff Orr, Chairman of the Stack Group
Jeff Orr founded the Stack Group in 1984, and prior to this owned and ran several other successful IT businesses. He is a qualified chartered engineer and winner of the Bibby Prize for Engineering from the University of Liverpool.
Jeff Orr is highly respected in the industry and consults for some of the biggest football clubs in the world.
About Stack Group
The Stack Group deliver solutions and support in the areas of IT Management and Cloud services, Telecoms, Infrastructure and Networks. If you would like any help and advice regarding any of our solutions please do not hesitate to get in touch and one of our experts will assist you.
Phone: +44 (0) 151 521 2202
Email: [email protected]
Today’s blog, written by our Chairman, outlines the inherent problems in providing a good wifi solution on trains and the challenge of users’ growing and inexhaustible demand for ever more bandwidth.
There are several good reasons and none of them are easy to fix.
Trains are nearly always routed away from areas of high population density so they are rarely near the locations that the Telcos choose for their masts. Their best coverage is consequently not where the trains are. The signal on the train is therefore patchy and unreliable and tunnels really don’t help either.
Another difficulty lies in the provision of the back-haul bandwidth. As trains by their very nature move and, hopefully quickly, they have to rely on some kind of wireless connection to the outside world to get the content passengers want. The options here are quite limited. It’s a choice between satellite, 3G/4G and Wi-Fi or a combination of two or more of these.
The most option most commonly adopted by train operators is 3G/4G because it’s the cheapest. It uses a multi SIM modem on the roof of the train connected to a Wi-Fi access point inside the carriage. Unfortunately adding more SIMs to the modem doesn’t increase the available bandwidth proportionally. That is to say two SIMs are not twice as good as one and so on. The result is that an entire carriage has to communicate via the bandwidth of a couple of SIM connections.
A few brave train operators have added satellite as a backup to the 3G/4G solution to deal with areas where the terrestrial signal is weak. This is expensive and complex and doesn’t help with the problem of tunnels.
A more effective solution is to build a dedicated trackside infrastructure. This can be done with 3G/4G microcells connected by fibre laid alongside the track or it can be done with Wi-Fi access points mounted on trackside furniture such signal gantries and the like (https://goo.gl/YJ3g0M). These access points can communicate with the train and with each other at 80+ Mb/s creating a linear chain along the route thus avoiding the need for laying fibre. Unfortunately both of these are very expensive solutions.
Network Rail is believed to be evaluating a 4G/LTE microcell solution leveraging existing trackside telephony fibre on some routes. There is also government consultation (https://goo.gl/CvKWhk) supporting its initiative (https://goo.gl/yJ6EBU) to have acceptable solution Wi-Fi on trains that will serve passengers needs for the next 10 years. Their hope is that it will encourage more people to travel by rail.
The trouble is that ambition will prove largely self-defeating as, however you back-haul it, Wi-Fi is a shared medium. Whatever bandwidth you provide to the train must be divided between all the Wi-Fi using passengers.
The rules of Wi-Fi, as laid down in the IEEE802.11 standard, set out to manage the shared medium fairly. An automatic process common to all Wi-Fi devices makes each user’s device wait its turn to transmit or receive data so that their signals do not jam each other. So on a full train the service will be much slower than on a near empty one as more devices queue for their turn. If you are a lone user in an otherwise empty carriage you can probably enjoy streaming HD video but on a packed commuter train you could struggle to get enough bandwidth for an email.
Whatever the outcome of the government’s consultation and whatever technology is chosen it will inevitably eventually fail because of the users’ inexhaustible demand for ever more bandwidth.
Written by: Jeff Orr, Chairman of the Stack Group
Jeff Orr founded the Stack Group in 1984, and prior to this owned and ran several other successful IT businesses. He is a qualified chartered engineer and winner of the Bibby Prize for Engineering from the University of Liverpool.
Jeff Orr is highly respected in the industry and consults for some of the biggest football clubs in the world.
About Stack Group
The Stack Group deliver solutions and support in the areas of IT Management and Cloud services, Telecoms, Infrastructure and Networks. If you would like any help and advice regarding any of our solutions please do not hesitate to get in touch and one of our experts will assist you.
Phone: +44 (0) 151 521 2202
Email: [email protected]