Solutions · Indoor radio coverage for buildings
Radio and cellular coverage inside buildings, in every space, including below street level.
We design and install DAS that bring professional radio networks (TETRA, DMR, VHF/UHF) and the LTE and 5G cellular signal into every enclosed space of a building, underground levels, car parks, stairwells, and lifts included. We hand over the system fully commissioned, with the line measurements and call tests floor by floor.
Outdoor radio networks cover streets and forecourts, not building interiors and underground levels. Reinforced concrete and floor slabs attenuate the signal: on the intermediate floors the level drops, and in stairwells and underground car parks the signal does not arrive at all. The consequences show up every day. The technician who goes down to the boiler room on the basement level stops answering the control room. The security team loses contact halfway up a stairwell. Anyone stuck in a lift cannot call for help. And a 112 call from an underground level does not go through: nobody notices until it really matters.
That is why indoor coverage has to be designed, not taken for granted. The work starts with an instrumented survey: we measure the level of the professional radio networks and of the mobile operators floor by floor, identify the spaces the signal does not reach, and size the system on that data. Then we choose the signal source, a donor antenna on the roof or a repeater or dedicated base station in the technical room, and design the distribution: an optical fiber or coaxial riser, floor antennas, radiating cable in long corridors and service routes, and passive components sized on the design calculation. We install with our own technicians and close the job with acceptance testing: line measurements and call tests in every critical space.
Why radio coverage inside a building has to be designed.
What makes it hard to bring the signal into every space of a multi-storey structure.
The spaces left without a signal
On underground levels, in car parks, in stairwells and lift shafts, in technical rooms and archives, the signal from outside does not arrive. These are the same spaces where staff work alone and where an emergency has to be reported straight away.
Several networks on the same system
Inside a building the staff radio network, the emergency services’ networks, and the cellular signal of several operators all coexist. They have to be distributed on the same line without interfering with each other: that takes filters, combiners, and a level calculation done network by network.
Site work inside a building that stays open
A hospital, an airport, or an office complex does not shut down for the installation. We work in the agreed operating windows, use the existing risers and suspended ceilings, and reseal penetrations through slabs and walls as the design specifies.
How an indoor coverage system is built.
A building seen in section: the donor antenna on the roof, the central unit in the underground technical room, and the riser feeding the antennas on every floor, stairwells and lift shafts included.
- Source and riser
- The donor antenna on the roof picks up the signal of the outdoor networks and carries it to the central unit in the technical room. From the central unit the optical fiber or coaxial riser climbs the building and feeds every level.
- Floor antennas
- The ceiling or wall antennas distribute the signal through the rooms on the floor. In long corridors and car parks we use radiating cable in their place.
- Underground levels
- Below ground level the signal from outside does not arrive: car parks, stores, and technical rooms are covered only by the system’s own antennas.
- Stairwells and lift shafts
- Stairwells and lift shafts run through the whole building and are the hardest spaces to cover. We serve them with a dedicated column of antennas, from the head of the shaft down to the pit.
What an indoor coverage system includes.
The systems we build inside a building, from the first survey to monitoring in service.
Survey of the existing coverage
- Measurement of the signal level of the professional radio networks, floor by floor, down to the underground levels
- Verification of the operators’ cellular coverage in corridors, stairwells, car parks, and inside the lift car
- Spectrum analysis to detect the carriers already present in the building and any interference
- Survey of the available cable routes: vertical risers, suspended ceilings, trunking, and technical rooms
- A survey report with a map of the spaces without coverage, which is what we size the system on
Signal source
- A donor antenna on the roof, aimed at the radio site or the base station serving the area
- A repeater or dedicated base station in the technical room, where picking up the signal from outside is not enough
- The central unit of the distribution system in the technical room, with its own power board
- Filters, duplexers, and combiners so several networks can share the same distribution line
- Isolation between the donor antenna and the indoor antennas, measured before the system enters service to prevent the repeater from oscillating
Distribution riser
- An optical fiber riser between the central unit and the floor remote units, in larger buildings
- A coaxial riser in the vertical shafts, with a tap-off at every level
- Radiating cable in long corridors, car parks, and service routes, where individual antennas are not enough
- Separate routes for the signal lines and the power lines
- Sealing of penetrations through slabs and walls as the design specifies
Floor antennas
- Ceiling or wall antennas, in the position and the number the design specifies
- Dedicated antennas for shielded rooms and spaces isolated from the rest of the floor
- Antennas in lobbies, corridors, and connecting routes, where communication must not drop while people move around
- Measurement of the levels at every antenna before the suspended ceilings are closed
- Labeling of antennas, cables, and connectors to the design drawings
Passive components and cabling
- Splitters, directional couplers, and terminating loads sized on the design calculation
- Connectors terminated and tightened at every termination, with a continuity check
- The minimum bending radius respected when laying the coaxial cables
- Surge arresters on the lines coming down from the roof antenna
- Bonding of equipment, racks, and antenna supports to the earthing system
Coverage of the critical spaces
- Underground levels and car parks: antennas over the driving lanes, or radiating cable along the route
- Stairwells: antennas distributed on the landings, so communication does not drop on the way up or down
- Lift shafts: antennas at the head of the shaft and in the pit, to keep the link with the car
- Technical rooms, boiler rooms, and electrical substations: dedicated antennas, because staff work in them alone
- Stores, archives, and underground warehouses, covered together with the routes that connect them to the rest of the building
Acceptance testing and measurements
- Standing wave ratio (VSWR) on antennas, downlead lines, and radiating cable sections
- Location of line faults, with a measurement of the distance to the fault point
- Measurement of the signal levels floor by floor, compared with the design calculation
- Call tests in every critical space, together with the staff who work there
- A signed acceptance report and as-built documentation matching the state of the system
Monitoring and maintenance
- TP-CELLX at the critical points of the system: it checks the operators’ 2G, 3G, and 4G cellular coverage
- TP-RFX on the distribution line: it checks the radio carriers, from 15 MHz to 2.7 GHz
- TP-CCV2 on the lines: it reports short circuits and open lines on the radiating cable and the coaxial cables
- Track-TP as the supervision platform, with notifications by email, SNMP traps, WhatsApp, and Telegram
- Scheduled maintenance visits, where we repeat the measurements and compare them with the acceptance figures
Frequently asked questions.
The questions we are asked most often about this type of system.
Can you amplify the cellular signal in a building without agreements with the operators?
No. An operator’s signal can be repeated inside a building only with its consent, because the system works on its frequencies and affects its network outside the building too. Amplifiers sold to the public and installed without a design are a frequent cause of interference: they degrade the coverage of nearby cells, and the operator asks for them to be switched off as soon as it traces the disturbance. The correct route is a system designed and agreed with each operator, which either authorizes the repetition of its own signal or supplies the equipment to connect to the distribution line.
Can you cover only part of the building, for example the underground levels?
Yes. The system is sized on the spaces the survey identifies as lacking coverage, and in many buildings those are only the underground levels, the car parks, and the stairwells, while on the floors above ground the signal arriving from outside is still sufficient. It is worth designing the main line with the whole building in mind, though: installing the riser and the tap-off points during the first job costs far less than laying cables once the work is closed, when suspended ceilings and risers have to be reopened. That way, extending to the other floors becomes a tap-off from the existing line rather than a new system.
Do the antennas installed in the rooms comply with electromagnetic exposure limits?
Yes. An indoor coverage system distributes low power across many antennas instead of concentrating the power in a single source, and the levels expected in the rooms stay within the exposure limits set by law. Compliance is not taken for granted: it is calculated during design, taking into account the power fed into the line and the distance between the antennas and the work positions, and it is verified by the acceptance measurements, which stay attached to the system documentation. Where the client asks for it, we repeat the same measurements with the system in service, during maintenance visits.
What happens to the system if the power fails?
It depends on which parts of the system are powered. The radiating cable, the antennas, and the passive components need no power supply and keep distributing the signal as long as the source stays running. The active equipment, meaning the central unit, the repeater, and the floor remote units, stays in service only if the design provides dedicated lines and uninterruptible power supplies sized for the required autonomy. That is a decision to make during design, because indoor coverage is needed above all in emergencies, and an emergency can happen exactly when the power is out.
Request a proposal for indoor radio coverage for buildings.
For every project we provide a tailored technical and commercial proposal based on your requirements — feasibility analysis, RF coverage study, and intervention planning.