Cellular Signal Surveys for Digital Billboards: What to Measure Before You Build

Why Digital Billboards Depend on a Data Connection

There were about 25,000 digital billboards in the United States at the end of 2025, according to OAAA's year-end display count (OAAA 2025 Facts & Figures). Lamar alone reported operating about 5,500 digital billboards across 43 states and Canada (Lamar 2025 Form 10-K). Each one is a computer driving LED faces, and nearly everything that makes it pay depends on a data connection:

• Content and schedules: new ad copy, flight dates, and day-parting changes arrive over the network.
• Programmatic ads: the player asks an ad platform for an ad right before the slot plays. In Place Exchange's integration, for example, an ad request is sent from the player just before the placeholder plays out (DISE documentation).
• Proof of play: the player reports what actually ran. Broadsign's player "reports incidents and proof-of-play statistics back to Broadsign Server" (Broadsign docs).
• Monitoring: once a display is connected, Daktronics' network operations center checks it for module, connectivity, webcam, temperature, and light-sensor issues (Daktronics DB-66XX installation manual).
• Public-safety messages: FBI fugitive and missing-person messages and AMBER Alerts are pushed to digital billboards over the same link.

The money follows the connection. OAAA puts 2025 U.S. out-of-home ad spend at $9.46 billion, with digital at 36% of it and programmatic at 30% of digital. A programmatic slot on a sign that cannot reach the network goes unfilled, and an ad that ran without a proof-of-play report is hard to bill.

Why So Many Billboards Run on Cellular

Billboards stand where the traffic is, beside highways and major arterials, and rarely next to a building with a broadband line. Getting a wired connection to the pole is the expensive part: "In many outdoor environments, however, 'trenching' new lines for power and/or data can end up costing more than the display hardware itself" (Sign Media Canada). The same article points out that when a static sign is converted to digital, power is usually already there but data is not, because static signs never needed it. Even where broadband exists, "it may take up to 90 days to procure a broadband connection" (Semtech).

So sign makers ship cellular. Daktronics' DB-66XX billboard manual lists the display's SmartLink ICCID or MEID number, both cellular identifiers, among the details its help desk may need at first power-up. Watchfire markets cellular hardware and data plans to billboard operators (Billboard Insider). Vantage LED's cell modem guide says that when the manufacturer provides the service, "the carrier will typically be AT&T or Verizon" (Vantage LED). Either way, the sign is only as reliable as the cellular signal at its antenna.

What Weak Signal Looks Like at a Billboard

A sign with a bad connection usually looks fine from the road. Players are built for it: in Adhese's DOOH documentation, "A screen in a lift or a remote billboard may lose connectivity, so players are expected to cache content and keep running offline" (Adhese). The problem shows up elsewhere:

• New campaigns or schedule changes that reach the sign late or not at all, so old copy keeps running.
• Programmatic slots that go unfilled.
• Gaps in proof-of-play reports, and makegoods to cover them.
• Slow or failed remote access. One Daktronics support article lists slow internet to billboard equipment, a flashing red signal light, and an RSSI of -100 as symptoms of an antenna plugged into the wrong connection on the modem (Daktronics KB).
• Offline alarms in the network operations center, and webcam images that stop arriving.

Because these failures look like player or software faults, they often lead to service calls and part swaps that fix nothing. A coverage problem needs a coverage answer.

Why Bars, Coverage Maps, and Address Lookups Are Not Enough

• Bars are not a measurement. OptConnect's antenna guide notes that "An AT&T device may display only 1 bar when signal RSSI is -80 dBm, but the same device on Verizon may display 2 bars at the same -80 dBm RSSI" (OptConnect).
• Manufacturer specs are in bars too. Daktronics' cellular modem guide rates signal by the modem's light, from "Good signal (equivalent to 4-5 bars)" to "Inadequate (equivalent to 0 bars)" (Daktronics modem guide). That tells an installer when to move the modem, but it is not a number you can compare between carriers or sites.
• Coverage maps and address lookups are models. OptConnect says its support team can identify carrier coverage by address but "cannot evaluate how well those signals may penetrate or be received inside the building." A billboard is outdoors, but the same limit applies: maps and lookups predict coverage over large areas, not what reaches one antenna on one structure.
• The modem is on one carrier. The SIM in the sign tells you about that carrier only. The best carrier at the site may be one nobody has checked.

Measure at the Antenna, Not at the Base

Billboard makers already tell installers to prove the signal at the mounting spot before committing to it. Daktronics says to install the modem within 25 feet of the display and to "Permanently fasten the modem vertically with the antenna pointing upward once it has been proven effective in the location." Vantage LED says "Prior to mounting the antenna permanently, make sure the modem is getting good signal strength" and that "The antenna should be facing the nearest cell tower with clear line of sight." OptConnect adds that antennas "should never be placed inside of a metal enclosure."

A survey does that check on every carrier, at the antenna's height, before the install crew is on site. Height matters in both directions. Signal strength usually improves as you go up, but an antenna with a clear view of more distant cells also picks up more interference, so signal quality (SINR) can be worse at the top of a structure than at its base. The side of the structure matters as well, because the display cabinets and steel block signal from the directions they face.

What a Billboard Site Survey Measures

A cellular signal survey for a billboard records the following at each candidate antenna position, separately for each carrier:

• RSRP (Reference Signal Received Power): signal strength, in dBm. The main number to check against a modem or router spec.
• RSRQ (Reference Signal Received Quality): signal quality relative to interference and load, in dB.
• SINR (Signal-to-Interference-plus-Noise Ratio): how clean the signal is, in dB. A strong signal with poor SINR still drops connections and slows uploads.
• Serving band and technology: whether the site is served on LTE or 5G, and on which band. Low bands reach farther, which matters at rural highway sites.
• Cell ID and PCI: which tower sector serves the antenna, so a site that flips between sectors, or hangs on one distant sector, shows up.
• Position, height, and time: GPS position, the height and side of the structure where each reading was taken, and when, so every reading ties to an antenna position and can be compared with a later survey.

What Signal Level Does a Digital Billboard Need?

We have not found a billboard manufacturer that publishes a minimum signal level in dBm. The specs that exist are in bars or in words like "good signal strength." Router makers do publish ratings for LTE, and they disagree with each other:

• Digi: RSRP above -90 dBm is excellent, -90 to -105 dBm good, -106 to -115 dBm fair, -116 to -120 dBm poor, and below -120 dBm no service (Digi).
• Teltonika: RSRP of -80 dBm or better is excellent, -80 to -90 dBm good, and -90 to -100 dBm fair to poor, where "marginal data with drop-outs is possible." For RSRQ, -10 to -15 dB is good. For SINR, 13 to 20 dB is good, and "A minimum of SINR should be ≥ 0 dB for basic operation" (Teltonika).

A reading of -100 dBm is "good" on one table and the edge of "poor" on the other. A billboard has to stay connected around the clock from a spot it cannot move away from, so the cautious reading is the right one. If your modem or router has a published spec, use it as the pass line. If not, treat RSRP weaker than about -95 dBm, RSRQ weaker than about -13 dB, or SINR near 0 dB as a position that needs attention.

Take readings more than once at each position. Signal at a roadside site moves with traffic and network load, and the worst consistent reading matters more than the best one.

How a Billboard Survey Works

1. Collect the plan. The site location, structure drawings or the planned structure location and height, which way the faces point, the sign make and model, the modem or router and its carrier if known, and whether wired broadband is available.
2. Measure at the antenna. Readings on AT&T, Verizon, and T-Mobile at the existing or planned antenna height, on each side of the structure where an antenna could go.
3. Check the ground equipment. Readings at the base, where any cabinet or router will sit.
4. Repeat. Readings through the visit, including heavy-traffic hours, so the report shows how much the signal moves.
5. Report by carrier and position. A pass, marginal, or fail call for each carrier at each antenna position, against the hardware spec or the defaults above, with a map of the readings and the raw data.
6. Verify after installation. Optionally, measure again once the sign is live, to document the signal it is working with.

When to Survey a Billboard Site

• During the lease and permit stage. One developer interviewed by Billboard Insider puts a new sign at "a year to two years" with a supportive city and "5-6 years" for complicated projects (Billboard Insider). Connectivity is not on the permitting checklist, so it is easy to leave until the steel is up. Measuring during that window is when the results can still move the antenna, change the carrier, or justify ordering a wired line.
• Before a static-to-digital conversion. The site has power but has never needed data.
• When a sign keeps dropping offline. Stale copy, missed programmatic slots, proof-of-play gaps, or slow remote access.
• Before changing modems, routers, or carriers. So the new hardware and SIM are chosen on measured data.
• Across a portfolio. The same report for every site shows which signs sit on the weakest connections.

What to Do When a Site Comes Up Short

• Change the carrier. If another carrier is strong at the antenna, ask the sign maker or data provider for that carrier's SIM.
• Add a second carrier. A dual-SIM modem or router can fail over when one carrier drops.
• Move or re-aim the antenna. The other side of the structure, clear of the cabinets and steel and facing the serving tower, can be worth more than a new carrier.
• Use a better antenna. A higher-gain external antenna aimed at the serving sector can help at fringe sites.
• Go wired. Where broadband is available, order it early. It can take months, and it is the most dependable option.

Signal boosters are sometimes suggested for signs. A booster only helps where there is a usable outdoor signal to amplify, and it must be a carrier-approved, FCC-compliant unit, so measure before buying one.

Networks Change After You Build

A billboard outlives several generations of cellular technology. In 2022 AT&T shut down its 3G network on February 22, T-Mobile shut down Sprint's 3G CDMA network on March 31 and its own 3G UMTS network on July 1, and Verizon shut down 3G CDMA on December 31 (Light Reading). Any sign still on a 3G modem lost its connection. As recently as 2015, Watchfire was offering sign customers "an exclusive data plan through Verizon Wireless that allows customers to purchase 3G data at below-market prices" (Digital Signage Today).

A survey on file records which bands and cell sectors served the site on each carrier when it went live. When a sign that used to work starts dropping, a repeat survey shows what changed.

What to Send Before a Survey

• The site address or coordinates, and structure drawings or the planned structure location, height, and face directions.
• The sign make and model, and the modem or router model with its minimum signal spec if it has one.
• The carrier on the SIM and who provides the data plan, if known.
• Whether wired broadband is available at the site.
• For existing signs: when copy goes stale or proof-of-play reports go missing, and any offline logs from the network operations center.

Next Steps

Cell Surveys runs cellular signal surveys for digital billboards and on-premise LED signs across the United States: RSRP, RSRQ, and SINR on every carrier at the antenna's height, reported against your hardware's spec. We are independent and measurement-only. We do not sell signs, modems, routers, antennas, boosters, or data plans, so the report says what the signal is, not what to buy. For other roadside equipment that depends on cellular, see our EV charging station surveys. To scope one site or a portfolio, contact us.