RF measurements and drive tests to verify the coverage of a network already in service.

No. The instrumented vehicle drives the route in normal traffic, at the permitted speeds, and records the measurements without interruption. Most surveys are receive-only: they do not change the configuration of the equipment and they do not interrupt the radio service. Call tests are run with the terminals already in use and have to be arranged in advance with the control room. Only the stationary measurements need to be agreed with the infrastructure operator, because they require stopping in a lay-by or access to the equipment rooms.

Inside the bore the GPS receiver loses the satellites, so the position of the samples cannot be read from the satellite: we reconstruct it along the chainage. Before the survey we note the fixed references inside the tunnel (portal, niches, emergency exits) and use them to place the recording along the route; at the points agreed with the customer we add stationary measurements. At the end every stretch of the bore is matched to the level measured, from the portal to the exit, and can be compared with the values required by the specification.

Two measurements are needed together: the level of the wanted signal and the emissions present on the same channel. If the level is low, the problem is coverage, and it is solved by working on the sites, on the transmit power, or on the antennas. If the level is adequate but communication is still disturbed, an unwanted emission is present on the channel: we identify it with spectrum analysis and track its source with a directional antenna. When the interference appears intermittently we record the spectrum over time, so that we capture it at the moment it occurs.

The instrument records a sample every few metres: if the speed keeps changing, samples bunch up where the vehicle slows and thin out where it accelerates, and the resulting maps are uneven. So we cover the route at a constant 80 km/h, a speed that keeps the sampling regular and remains compatible with traffic. During the day, on busy sections, that speed cannot be held: this is why surveys are scheduled at night. When the customer wants a comparison between different conditions, we repeat the route at peak hours as well.

A phone only reads the cell it is attached to, and it measures with its internal antenna, shielded by the bodywork. The magnetic-mount broadband antenna on the vehicle roof receives about 10 dB more than a phone resting on the dashboard: measuring with a phone therefore underestimates the coverage actually available. The scanner connected to the external antenna instead sweeps the bands and records every carrier present at that point, for every operator, not just the one serving the terminal. It is the only way to establish what alternatives a user really has along a section without coverage.

Besides the technical report we deliver the measurement data in CSV and Excel and the KMZ files, split by section and by operator. The KMZ files open in Google Earth Pro and show the route with a colour scale keyed to the measured levels; selecting a point brings up the list of every technology and carrier active at that position, with level, signal-to-noise ratio, and cell identifier. That way the customer can go back over the measurements independently, without having to ask us for every later check.

The scanner detects the operators that hold their own frequencies: in Italy these are Vodafone, TIM, WindTre, and Iliad. Virtual operators do not appear as separate entries, because they hold no frequencies of their own and ride on the networks of those four: their performance falls within the measurements of the host operator. Near borders we also record the carriers of foreign operators spilling into the area, which is useful because a terminal can latch onto them and roam without the user noticing.

There is no single interval that suits everyone: a survey is repeated whenever something changes that can alter coverage. The recurring cases are the commissioning of a new or modified system, tunnel works affecting the radiating cable or the antennas, the appearance of a new radio installation in the area, and repeated reports from operators about one specific stretch. Where a maintenance contract is in place, the check is scheduled together with the other periodic inspections.