Hong Kong consumers expect constant access to high-speed wireless data on demand, including when they ride underground public transport. Yet providing broadband confined coverage networks in one of the world’s busiest rapid transit railways in the world involves highly sophisticated precision-engineered systems – particularly to span large complicated areas and support multi-band, multicarrier services.

The Challenge: Bringing connectivity to a complex underground network
That is the challenge that Radio Frequency Engineering (RFE), a BAI Communications company, has been solving for over 20 years. It has been delivering market-leading solutions to the Hong Kong’s MTR Corporation Ltd (MTR) since 1997, with continuous essential radio systems upgrades, state-of-the-art mobile phone system installations and critical system updates for Hong Kong’s underground subway network.

In 2014, RFE was tasked with a new challenge: design a brand new confined coverage solution for its new MTR West Island Line, which is an extension of the existing Island Line, consisting of three new underground stations with approximately 3km of new dual-bore tunnels.

The pioneering Distributed Antenna System (DAS) network requested by the MTR and the Mobile Network Operators (MNO) was substantially more complex than previously deployed networks, requiring the highest quality standards in engineering design, installation and sophisticated interference control management.

The Solution: MIMO in the metro
RFE’s unparalleled experience and expertise in interference management of combined public safety and cellular systems was used to design a cutting-edge solution, believed to be the world’s first MIMO-LTE development in an underground transit system.

RFE worked closely with MTR and Hong Kong Telecommunications (HKT) – which operates leading mobile carrier CSL – to design, implement and commission a six band 2G, 3G, and 4G (LTE) subway DAS network adopting Multiple In Multiple Out (MIMO) LTE technology for all mobile users in Hong Kong.

The new DAS network was built with the highest traffic capacity of four to six sectors per station covering over 20 sub-bands from 800 to 2,700 MHz. The network covers the new extension’s stations, tunnels, high speed elevators and public access areas.

The benefit: World’s fastest data speed underground
Thanks to the MIMO method, the new extensions have helped deliver extremely fast data services of up to 600 MBps, the fastest wireless data speeds available worldwide.

The network system built by RFE for the West Island Line is capable of delivering the highest cellular data throughput of over 5 Gbps for each station and connecting tunnels.

The West Island Line project was completed in time and on budget, and RFE earned the coveted Gold Quality Award in the Hong Kong MTR Projects Quality, Safety, Environmental and Stakeholder Engagement Awards Presentation Ceremony for its work on the radio systems.