TOTEM is Orange’s European TowerCo subsidiary. Operating in France and Spain as of November 1, 2021, TOTEM manages over 27,300 tower sites, flat roofs and other sites in these two countries. A neutral player, TOTEM provides solutions enabling operators to provide connectivity wherever pooling between operators is possible.
TOTEM began installing the 1,000 pieces of 5G equipment that will connect the 16 stations and 33 km of the future “Line 15 South” of the new Parisian metro system. The teams at Société des grands projets, the developer of the Grand Paris Express, incorporated this major industrial project into the design of the future 100% connected metro line.
Deploying a 5G mobile network in the tunnels of a metro is a real technical challenge: it's an indoor space with a high density of people, movements, and very thick (and therefore wave-impermeable) walls. TOTEM is deploying this pooled 5G network for all operators, working within the technical constraints of the tunnels and meeting the specific mobile coverage needs of all operators.
A growing need for indoor connectivity: With 80% of connectivity used indoors, TOTEM has positioned itself as the leading TowerCo in this market, connecting underground transport, stadiums, concert halls, and shopping malls.
The following video is from the press visit to the construction site of Line 15 of the Grand Paris Express at Noisy-le-Grand in April 2024:
Helsiki's radio network currently in use in the metro is being renewed in order to support the future train traffic control system. A cellular network pilot was carried out in 2022/23 with results published in April last year. Based on that it was decided that the new radio network will be implemented with mobile network technology, as it was seen as best suited to the needs of the new train traffic control system and the metro.
The metro is still using many original (dating back over 40 years) systems that are nearing the end of their life-cycle. The current traffic control system, in particular, needs to be updated to ensure the reliable and safe operation of the metro in the future as well. Parts of the system that are now being updated include the train control system and track circuits.
The updating of the train control system will make it possible to increase the number of passengers of the metro by enabling shorter headways between trains than are currently possible. Shortening the headway between trains and other capacity-increasing measures are important, as transport forecasts indicate that the metro’s number of passengers will continue to increase. The current capacity of the metro is simply not enough to meet the increasing demand.
Metro systems have long service lives and their updates have far-reaching impacts. The updates to be implemented now will make it possible to operate the metro safely for another 40 years.
The results and observations from the 'Cellular Network Pilot' is available here. Quoting from that:
This innovative pilot demonstrated that a cellular based communication subsystem is suitable for train control as well as other metro systems applications. The pilot outcomes provided insights into the deployment of such systems and also confirmed the expectation that in order to meet the strict radio communication availability requirements necessary to support safety critical applications, at least two radio network layers should be present. These layers can be presented via implementation combinations of private and public networks including 5G SA slicing, depending on the current and future user requirements.
Ability to support signalling: The pilot test results showed that both the private network (4G or 5G) and the public network are suitable to support ATC performance requirements. In high public network load scenarios, it is advised that QoS is implemented to ensure the reliability of any safety critical streams.
Ability to support current systems: The pilot tests showed that the public network is suitable to support metro’s onboard existing systems. It was observed that when the public network was capacity stressed, with all applications present, the Wi-Fi stream could not reach its maximum intended capacity of 250Mbps. This was due to bandwidth limitations experienced during the Pilot tests and is re-lated to end-to-end connectivity restrictions and by the number of hops between end devices and the Mobile Network Operator’s core. Troubleshooting during the tests revealed that a considerable increase in capacity could be realistically achieved by addressing these limitations.
Ability to support future systems: The pilot tests showed that the private network could not reliably service the critical CCTV stream due to the bandwidth limit of that network and the fact that the CCTV stream was duplicated over the two private routers. At the same time the VoIP stream could be reliably serviced indicating that if there was more capacity the issue with CCTV could be resolved.
Private network deployment observations: In normal operation mode, the band used (2300 MHz) and the density of the radio units was demonstrated to fulfil the requirements for ATC and critical voice communication. For the private network, there was degradation of latency in the coverage area of three out of the four radio positions when these were offline. Most of the service degradation was affecting the Uplink and it was observed in areas were changes in radiating cable topology (changing positions/heights etc.) were occurring. Due to the private nature of the network, lack of external interference caused the system to perform better than expected in low signal situations. The two rooftop macro sites were able to provide good coverage and good handovers to the open track area when the radiating cable radio units in the same area were off. In the 5G SA mode all failures noted for the individual routers occur in areas where the radiating cable is on the opposite side of the respective router’s antennas.
Public network deployment observations: Signal quality and signal levels were good to excellent throughout the tunnel during all degraded mode scenarios. At the same time there were a few occurrences of longer than average delays in a certain handover area within the tunnel. This could be attributed to the geometry of the track, the size of the tunnel and the relevant positions of the directional anten-nas providing the coverage in this area which are lower than antennas on the roof of the train. These observations reveal that the radio design within the tunnel could be rationalised (less density but better located cells). Other results showed that the radio design needs to also consider that sufficient coverage is provided to allow handovers between tunnel and macro layers. An overarching observation was that for maximum redundancy the radio design should avoid designing private network cell edge areas at the same location as public network cell edge areas. By overlapping the network design, the reliability of the dual layer network can be maximised. A final observation is that routers/mobile gateways working in high availability mode and/or application devices that can manage packet duplication via multiple routers are recommended in order to increase data communication reliability.
WSP UK Transport & Infrastructure worked with Metropolitan Area Transport Ltd and its suppliers, providing technical leadership and assurance in the deployment of a pioneering 4G and 5G pilot in a brownfield metro environment. Digital connectivity and rail systems experts at WSP developed testing procedures and carried out an assessment of the most suitable technology and network layer combination using a range of key decision indicators.
In our earlier posts we talked about how Wi-Fi 6 is being promoted by South Korea's ministry and also how mmWave has not been very successful in Korea. Having said that, earlier last year, Samsung Electronics announced that it has signed contracts with all three South Korean operators to supply its 5G mmWave network solutions and boost connectivity for passengers on the Seoul subway system:
Over 3.6 million passengers use the Seoul subway daily across over 300 stations. With a population of 9.6 million, Seoul is one of the world’s most densely populated cities, with its subway serving as one of the major means of public transportation for the busy metropolitan area. The subway system is expansive, resembling a spider web network that connects Seoul and the surrounding areas, carrying over 30 percent of the city’s population.
While the Seoul subway system has already been providing stable 5G (3.5GHz), 4G and Wi-Fi services, mobile data demands in subways continue to rise exponentially as Korea’s monthly average 5G data consumption reaches approximately 25GB per person.
Later this year, Samsung’s 5G mmWave solutions will enable the subway’s Wi-Fi services to meet increasing data demands by leveraging mmWave’s wide bandwidth, extensive capacity and massive throughput. Subway passengers will be able to enjoy bandwidth-intensive applications such as high-speed, superior-quality streaming for live sports games, movies, mobile games and video communications. These will be delivered at Wi-Fi speeds up to ten times faster on average than currently provided.
In addition to transforming the daily mobile experience for subway users, Samsung’s advanced 5G mmWave solutions will drive a diversified range of use cases and business opportunities for new entrepreneurs, app development startups and consumers. Utilizing mmWave bandwidth can not only bring to life next-generation services such as the metaverse, cloud gaming and Extended Reality (XR) remote learning, but it can also be expanded beyond transportation to industries like retail, medicine, media and entertainment.
A key component of the Seoul subway commercial deployment is Samsung’s mmWave 5G radio solution, Compact Macro, which brings together a baseband unit, radio and antenna in a single form factor. Optimized for mmWave 5G, it uses in-house modems, radio frequency integrated circuits (RFICs) and digital analog front end (DAFE) ASICs.
Complete press release here. Embedded below is a short promo video on this
Earlier we made a tutorial on Infrastructure required for bringing connectivity to underground rail network. So it was good to see Nick Hudson, Director of Global Partners & Programmes at BAI Communications share some pictures of Mobile Network Infrastructure on London Underground network on his LinkedIn post.
Back in June 2021, BAI Communications (BAI) was awarded a 20-year concession by Transport for London (TfL) to deliver high-speed mobile connectivity across the capital in the most advanced and largest infrastructure project of its type in the world. The press release said:
BAI’s partnership with TfL will establish a long-awaited backbone of connectivity with a city-wide integrated communications network delivering multi-carrier cellular, Wi-Fi, and fibre connectivity services. The 4G-enabled and 5G-ready communications network that BAI will build and operate as a neutral host for fixed and mobile operators will fast-track London’s evolution as a smart city. BAI will also help to create a safer, smarter London by building and operating critical communications infrastructure that will support police, fire, and ambulance services.
The first phase of the project will see the rollout of modern multi-carrier infrastructure. This will allow fixed and mobile operators to immediately provide continuous 4G coverage to their customers across the London Underground stations and tunnels. The new wireless infrastructure will also be 5G ready. Work on the project will begin immediately, with all stations and tunnels due to have mobile coverage in four years.
Additionally, a new high-capacity fibre network running throughout the London Underground will enable fibre service providers to provide full fibre connectivity to premises across the city. The network will connect to buildings and street assets housing small cells to leverage the power of 5G and the IoT, and deliver improvements in areas like traffic congestion, public safety, and city planning.
Uses leaky feeder / DAS system to link base station hotels on the Tube
Through this concession, BAI will help the transport authority support London’s post-covid recovery as travel resumes, delivering seamless 5G ready connectivity that will enable people to move around the city more efficiently, safely, and securely. More specifically, this project will enable TfL to reduce overcrowding and manage station flow, while improving safety with real-time information and reliable ‘from anywhere’ communications.
BAI was awarded the concession after a competitive tender process. The company has proven experience deploying mission critical communications networks in highly dense urban environments, including the underground rail networks in New York, Toronto, and Hong Kong. This project supports BAI’s strategic intent to sustainably accelerate growth globally. This is achieved through our work deploying outdoor neutral host infrastructure and developing 5G-driven offerings that introduce and scale connectivity solutions for emerging services and fresh revenue opportunities. Ultimately, our work supports our customers by delivering better connectivity and enhanced customer experiences. BAI’s ambitious plans include expanding its wireless infrastructure business across the public transport sector and growing its private network services portfolio.
Last month, BAI announced that they have completed the first milestone of its rollout of high-speed mobile coverage across the London Underground as it launches a permanent 4G service on the eastern section of the Jubilee Line. The press release said:
Customers of Three and EE are the first to be confirmed to have permanent access to 4G and 5G-ready communications between Westminster and Canning Town. The connectivity has been available as part of a pilot service since March 2020. This follows agreements made last year by both mobile operators to join BAI’s network, making them the first to cement their commitment to providing coverage to London Underground passengers.
Whilst on this section of the Jubilee Line, customers will continue to be able to check the latest travel information, keep on top of their emails, catch up on social media, live stream videos wherever they are on the Underground.
Cities all over the world are improving connectivity for subways and metros. With London already a centre of mobile connectivity, it's surprising that getting coverage in the Tube took so long.
It's always been a challenge to bring mobile connectivity to commuters in the underground rail network. The same challenges extend to mines and other facilities under the ground. One solution that has been widely adopted is the use of leaky feeders as antennas.
This solution is also used to compliment the existing terrestrial network in case of tunnels. We made a small tutorial looking at this from metro point of view but the same solution is applicable in many different scenarios.
5G presents a small challenge for this as it is tricky to go beyond 4T4R easily. Each T/R requires a leaky feeder which makes it expensive as well as challenging in other scenarios.
An Ericsson blog post some time back talked about the 2 hop solution for trains. Thinking about it, I quite like the idea. The post talks about 3 main challenges on high speed trains:
There are mainly three reasons communication services on high-speed trains is challenging:
First, large penetration loss via the shield of the train. This penetration loss is expected to be 20 to 30 dB.
Second, large numbers of handovers in very short time. This is due to hundreds or thousands of users needing handover from one site to another concurrently/sequentially. This phenomenon affects system stability and eats up capacity.
Third, high power consumption of user equipment (UE). This is because UE-s on the train need higher power to overcome the large penetration loss in uplink as well.
A common currently adopted solution for high speed trains is to densify the network along the railway to combat the large penetration loss. However, this will make the second issue more severe, as handover frequency is increased due to smaller site- to-site distance. Another way is to increase the transmission power of the base stations, which helps to solve the large penetration loss as well. However this cannot solve the third issue. And neither of these solutions are cost-effective.
Another solution I have discussed before is the Mobile Relay Node which was designed with avoiding multiple handovers when the vehicle moves between different macro cells. Not sure about its status in the standardisation process right now.
Anyway, coming back to the Ericsson post on Small cells on the train, while the Macro cells provide the TD-LTE backhaul outside, Radio Over Fiber (ROF) is used inside the tunnels to provide the same coverage.
Within the train Small cells (I guess multiple small cells will be needed in practical deployments, one for each carriage) can provide good coverage to the users and avoid the need for handovers.
Embedded is the video from Ericsson Taiwan that provides more details about this trial
