How to Measure Cell Signal Before Buying a Signal Booster

Most booster projects start with a sentence like “the signal is bad in the warehouse.” That sentence is not design input. A supplier cannot tell whether the site needs a larger host, a different donor antenna, more service antennas or a different technology until the signal is expressed in numbers and locations.

This guide explains what to measure, where to measure it, and how to present the result so that the first quotation is based on the site rather than on a guess. You do not need a laboratory. A phone, a floor plan and twenty minutes of walking are enough to start.

What numbers should you record?

Five values turn a complaint into a measurement:

1. RSRP (Reference Signal Received Power) in dBm — the strength of the serving cell.
2. SINR (Signal-to-Interference-plus-Noise Ratio) in dB — how clean the signal is.
3. Band — the LTE or 5G band number the phone is using.
4. Cell ID / PCI — which sector is serving the phone.
5. Location — where the reading was taken, with a description such as “roof edge, north side” or “aisle 12, 1.5 m height”.

If your phone also shows RSSI, RSRQ, EARFCN or NR-ARFCN, record them. More context helps, but RSRP, SINR, band and cell ID are the minimum useful set.

Do not use phone bars for design. Bars are vendor-specific and non-linear. Two phones side by side can show different bar counts for the same RSRP.

How do you read RSRP and SINR on a phone?

On many Android phones, the field-test screen is reached through a dial code such as *#*#4636#*#*, and the exact menu varies by manufacturer. On iPhone, the field-test screen is usually reached through *3001#12345#*, but the available pages and labels change between iOS versions. Measurement apps can also display RSRP, SINR, band and cell ID, often with a map or logging function.

Use whichever method you can repeat. The important thing is to record the phone model, the operator, the band and the location, not to find the most advanced screen. If a reading is taken on a different phone or a different band, it is not directly comparable.

A practical RSRP interpretation for LTE planning:

SINR is equally useful:

These ranges are planning guidance, not operator guarantees. Different networks and load conditions shift the boundaries.

Where should you test around the building?

Test outdoors first, then indoors. The outdoor reading establishes whether a booster has anything useful to amplify. The indoor reading establishes how much the building removes.

Take at least three readings at each outdoor position, a metre or two apart. A single reading can land in a local null. If the values vary by more than 10 dB within a small area, note it; antenna placement will matter.

For a multi-floor building, sketch the floors and mark the readings. A table of numbers without a plan is hard to design against. A plan with five or six readings is enough to start.

How should you document a walk test?

A walk test turns a set of readings into a design document. Use a floor plan and mark every reading with the time, phone model, operator, band, RSRP, SINR and cell ID. Walk at working height, not eye level: scanners sit at 1.2-1.5 m, phones are held at head height, and a reading taken while standing on a mezzanine may not represent the aisle below.

For a warehouse, follow the pick aisles and stop at each rack row or workstation. For an office, walk the corridor, enter the worst rooms and test near the window as well as at the desk. For a hotel, walk from the lobby to a guest room and test the lift lobby and the room. Photograph each problem area so the supplier can see the ceiling, walls and any metal structure.

At the end, rank the zones by severity: no service, dropped calls, data stalls, usable but slow, and acceptable. That ranking becomes the acceptance list for the project. Keep the before readings in a table and repeat the same route after commissioning. A marked plan with numbers lets a supplier size the system without a site visit; a description such as “bad signal” does not.

What photos and drawings should you send?

A supplier can learn a lot from four photos and one simple drawing:

• Building exterior from the side where the donor antenna is likely to go.
• Roof or mounting position, including the parapet, nearby structures and the cable route.
• Equipment room or the place where the booster will be installed.
• Interior of the worst area, showing the ceiling, walls and any obvious metal or concrete structure.
• Floor plan with dimensions, floor count, and the rooms or aisles that need coverage.

Mark the proposed donor position, the cable route and the indoor antenna positions on the plan if you can. Even a hand sketch is useful. The goal is not a professional drawing; it is to remove ambiguity about where the numbers came from.

Also note the building materials: concrete, brick, metal cladding, coated glass, basement slab, metal racking. The materials guide explains why these details change the design.

How do you compare before and after installation?

Use the same phone, the same operator and the same band at the same points. Record the values before installation, then repeat after commissioning. Do not compare a before reading on one network with an after reading on another; the difference will be meaningless.

A simple acceptance record:

The exact targets depend on the operator and the service requirement. For voice, a usable signal with stable call retention matters more than a peak number. For scanners and POS terminals, test the actual device, not only the phone. A coverage design that satisfies a phone may still leave a handheld terminal with a marginal link.

What if your phone does not show engineering data?

You have three options:

1. Use a measurement app that reports RSRP, SINR, band and cell ID. Record the app name and phone model.
2. Use a USB modem or a dedicated test phone with a field-test screen that you can operate consistently.
3. Ask for remote guidance. A supplier can walk you through the available screens or interpret a set of readings taken with a simpler app.

What you should avoid is a single bar-count description with no dBm value. “Two bars” can mean a usable -85 dBm signal or a hopeless -110 dBm signal depending on the phone. The number is what makes the conversation technical.

If you can only collect one value, collect outdoor RSRP at the proposed donor position. That single number determines whether the project is a booster project, a donor-antenna project or a different technology conversation.

Send the readings, the plan and the photos together. The next step is a diagnosis, not a product list: the supplier should be able to say which of the three causes your site matches and what should be measured next.