Network Rail intends to spend £1.9bn rolling out high-speed mobile broadband across the busiest parts of the UK's rail network. Julian Turner talks to Ingo Flomer of Axell Wireless about the ambitious project and why distributed antenna system (DAS) technology may provide a cost-effective solution.
Ingo Flomer is director of product marketing at Axell Wireless, a leading provider of distributed antenna systems (DAS) and wireless coverage products for public safety and cellular applications. Flomer is responsible for defining the company's product management strategy and has over 20 years' experience in telecommunication, wireless and fixed line projects.
Julian Turner: Please describe the evolution of Axell Wireless.
Ingo Flomer: Axell Wireless was formed over 40 years ago and is currently one of the top four providers of public safety and cellular wireless coverage solutions in the world.
The company has pioneered the use of fibre-optics to carry radio frequency (RF) signals and uses the technology to propagate wireless coverage in many of the world's leading buildings and transport networks. Axell has designed and supplied DAS systems to over 100 countries.
With the mass proliferation of smartphones, we all expect coverage wherever we are, it is no longer just a 'nice-to-have' feature. However, bringing coverage inside some of these environments can prove to be a challenge. We help mobile, train and metro operators as well as building owners to solve this problem and provide customers with seamless mobile coverage wherever they are.
JT: What specific advantages does DAS technology offer compared with other wireless solutions?
IF: DAS solutions help propagate a mobile operator's network seamlessly inside buildings and tunnels as well as across external environments such railway tracks. A DAS can be connected to an operator's base station housed inside the building, in a basement or 'comms' room for example, or even located several kilometres away. Another option is to 'feed' a DAS using an off-air digital repeater that takes the signal from the air and directs it inside.
Having received the radio signals, the DAS filters, amplifies and redistributes them throughout the building or location using a series of antennas.
A DAS can also incorporate 'leaky feeder' cabling, which emits signals for devices to connect to. This solution provides homogenous coverage, and is the preferred method of covering tunnels and the inside train carriages. The equipment we use on-board trains is compact, is optimised for low power consumption and can easily fit inside existing storage areas or concealed cupboards; it can also be installed during other scheduled train maintenance.
The materials used to build new structures tend to prevent wireless signals from reaching inside, especially on buildings with more than 20 levels. Axell's Fibre DAS can take the external signal and redirect it inside, ensuring coverage throughout the building.
Operators and owners of buildings, metro systems, trains and tunnels all benefit. A DAS system offers an improved customer and business experience, allowing better communication with staff, and the ability to promote products and services to customers using digital media.
JT: What are the most salient benefits for the end-user?
IF: Providing seamless coverage throughout a building allows everyone to fully optimise the use of their mobile device, whether it's to make a call, text or use the internet.
We've all been travelling on a train and trying to make a call when the signal keeps dropping, it can be most frustrating. A fibre DAS solution provides a high-capacity data network, making it easy for people to stream videos, download email and use social media apps on an uninterrupted service.
Axell's DAS solution is a multi-band, multi-operator, multi-technology system that works on any frequency combination. This means that both mobile phone and public safety coverage can be supplied on the same network. Finally, the flexibility of such a system means it's future-proofed.
JT: Is Network Rail's plan to spend £1.9bn rolling out high-speed mobile broadband across the busiest parts of the UK rail network feasible and what are the main challenges?
IF: The UK has significant technological hurdles to overcome to connect rail passengers to the cellular network. The coverage has to extend throughout the entire 14,480km passenger and freight system, and cover notorious black spots in cuttings and tunnels. But UK rail operators, along with Network Rail, can overcome the challenges of installing cellular networks across this extensive area.
As well as logistics, the technical aspect also needs careful consideration. RF signals are usually reflected by trains' multilayered metallic carriages, resulting in a reduced level of RF signal propagation and poor quality mobile coverage for passengers.
For train operators, providing passengers reliable on-board cellular coverage acts as a differentiator in what is a very competitive marketplace. The systems they deploy should prepare them for coping with future technologies such as 4G, without having to replace equipment later down the line.
JT: Is there any reason why DAS technology can't be used successfully on the UK rail network and is Network Rail considering it?
IF: Axell's DAS solution that has been deployed in the Channel Tunnel as well as in more than 70% of the world's metro systems. DAS is a very viable solution when it comes to the UK rail network and it is already deployed on parts of it. Network Rail will likely review all the technological options, but we will need to wait and hear from them as to how they intend to move forward.
JT: Where and how can a DAS save operators money compared with alternative technologies?
IF: The system architecture means less equipment needs to be deployed, resulting in a smaller physical footprint and savings on capital expenditure (CAPEX) and operating expenses (OPEX), as well as simplifying the network design.
A DAS can be shared by all operators on the same system and site requirements are reduced due to the smaller size and power consumption of the equipment, minimising external infrastructure costs.
The signals distributed by a DAS can be higher in quality compared to a classic base station roll-out. For example, 'radio corridors' can be defined, avoiding a load-share with parallel roads running along the same route that could absorb a lot of mobile traffic and, as a result, block the cell.
Handovers between coverage cells, which are critical at high-speed and reduce the data throughput, can be minimised by shaping extra-long cells. These also provide another benefit; the base stations that feed the DAS are better utilised compared with a traditional roll-out, where the cells normally sleep in idle mode, since most of the time no train is present.
On-board repeaters significantly increase the range of existing cells, which reduces the level of investment required for outdoor coverage extension. Instead of increasing the density of sites along the track itself, the on-board repeaters, which can be shared by all operators, provide a comparable or better investment.
JT: How do you envisage 4G and high-speed mobile broadband evolving in the short to mid-term?
IF: The technology is already there to enable train and mobile operators to offer high-speed mobile broadband, it is just a case of deployment.
4G is thought to be robust enough even for dynamic scenarios such as high-speed trains. This is good news, since the bottleneck is the traffic throughput between the outdoor network and the train.
There are railway projects in Europe targeting 1MB/s delivered to the train with the help of 4G.
Essential for the throughput in 4G is the distance of the mobile device to the base station. Here, the on-board repeater plays an important role, as it virtually 'reduces' that distance, resulting in high data speeds for passengers.
Any installation project on a train has a number of complexities that need to be addressed at the planning stage. In an ideal scenario, a single solution would provide coverage across the 2G, 3G and 4G spectrum, so that customers with any major mobile network operator could benefit from it.
The systems that are chosen should be able to cope with future technologies without having to replace any equipment later down the line.