What Is a DAS Signal Survey? A Complete Guide

What Is a Distributed Antenna System (DAS)?

A Distributed Antenna System (DAS) is a network of spatially separated antennas connected to a common signal source. Installed inside buildings and across campuses, DAS extends cellular coverage to areas where signals from outdoor macro towers cannot reliably penetrate. Hospitals, airports, stadiums, office towers, and manufacturing facilities are among the most common environments that rely on DAS to deliver consistent voice and data connectivity.

Without DAS, occupants in large or dense buildings frequently experience dropped calls, slow data speeds, and unreliable connectivity. As enterprises increasingly depend on mobile devices for mission-critical applications, the cost of poor indoor coverage extends far beyond inconvenience—it affects productivity, safety, and tenant satisfaction.

Why Signal Surveys Matter Before DAS Deployment

A DAS signal survey is the essential first step in any DAS project. It is a professional, on-the-ground assessment of existing cellular signal strength, quality, and coverage throughout a facility. Rather than relying on theoretical propagation models or vendor estimates, a signal survey documents actual RF conditions with calibrated measurement equipment.

Survey results serve multiple critical purposes:

• Baseline documentation: Establishes the current state of coverage before any system is designed or installed.
• Gap identification: Pinpoints exactly where coverage is weak, degraded, or absent across carriers and frequency bands.
• Design input: Provides DAS engineers with the real-world data needed to determine antenna placement, cable routing, and capacity requirements.
• RFP justification: Gives building owners and facility managers the empirical evidence to justify DAS investment in procurement documents.
• Post-installation validation: Creates a benchmark against which DAS performance improvements can be measured after deployment.

What Gets Measured During a DAS Signal Survey

Professional signal surveys capture a comprehensive set of RF metrics at each test point throughout a facility. Understanding these measurements is key to interpreting survey results and making informed DAS decisions.

RSRP (Reference Signal Received Power)

RSRP measures the power level of the LTE or 5G reference signal received by a device. Expressed in dBm, it indicates raw signal strength. Values above -80 dBm are generally considered good for indoor environments, while values below -110 dBm typically indicate coverage gaps that require DAS intervention.

RSRQ (Reference Signal Received Quality)

RSRQ evaluates signal quality by accounting for interference and noise relative to signal strength. Measured in dB, RSRQ helps identify areas where signal may be present but degraded by interference from competing cells or building-internal reflections. Values above -10 dB are considered acceptable, while values below -15 dB indicate quality issues.

SINR (Signal-to-Interference-plus-Noise Ratio)

SINR measures the ratio of useful signal to background interference and noise. Expressed in dB, SINR is the best predictor of actual data throughput. Higher SINR values correlate directly with faster download and upload speeds. Areas with SINR below 0 dB will experience extremely poor data performance regardless of signal strength.

Additional Measurements

Beyond the core metrics, professional surveys also capture RSSI (total received power), carrier identification, PCI (Physical Cell ID) to map tower connections, network technology generation (5G NR, LTE, 3G), GPS coordinates for precise location mapping, altitude data for multi-floor buildings, and precise timestamps for temporal analysis.

When You Need a DAS Signal Survey

Several scenarios call for a professional signal survey:

• New construction: Before a building is occupied, a survey establishes baseline coverage and identifies whether DAS is needed from day one.
• Renovation or expansion: Changes to building layout, materials, or occupancy patterns can dramatically alter RF propagation. A survey documents the new conditions.
• Tenant complaints: When occupants report poor cellular service, a survey replaces anecdotal reports with precise measurements that quantify the problem and guide the solution.
• DAS RFP preparation: Procurement teams need survey data to write accurate RFP specifications and evaluate vendor proposals against documented baselines.
• Post-installation verification: After DAS deployment, a follow-up survey confirms the system meets design targets and coverage requirements.
• Regulatory compliance: Some jurisdictions require documented in-building coverage for first-responder communications (ERRCS/public safety DAS).

Survey Methodology: How a Professional Survey Works

A professional DAS signal survey follows a structured methodology to ensure complete and accurate results. The process typically includes:

Pre-survey planning: The survey team reviews floor plans, identifies critical areas (lobbies, conference rooms, executive floors, loading docks), and designs a measurement grid with appropriate test point density. Grid spacing varies by facility type—tighter spacing in critical areas, wider spacing in open areas.

On-site measurement: Technicians walk the facility with calibrated measurement devices, collecting RF data at each grid point. Modern survey tools capture data from all available carriers simultaneously, eliminating the need for multiple passes. GPS and indoor positioning systems tag each measurement with precise location data.

Multi-floor coverage: For multi-story buildings, surveys are conducted on every occupied floor. Vertical signal propagation between floors is measured to understand how coverage changes with elevation.

Data validation: Survey data is quality-checked during collection. Anomalous readings are re-measured, and test point coverage is verified against the planned grid to ensure no areas are missed.

How Survey Results Inform DAS Design

Survey data directly drives DAS engineering decisions. Coverage heatmaps overlaid on floor plans show engineers exactly where antennas are needed and where existing signal is adequate. Signal quality metrics determine whether areas need capacity enhancement or just coverage extension. Carrier-specific analysis identifies whether a neutral-host DAS supporting all carriers is required or if a single-carrier solution suffices.

The survey baseline also sets measurable success criteria for the DAS installation. Instead of vague requirements like "improve coverage," RFPs can specify target RSRP, RSRQ, and SINR values based on documented deficiencies, giving both building owners and integrators clear performance benchmarks.

Cost Factors for DAS Signal Surveys

Survey costs vary based on several factors:

• Facility size: Larger buildings and campuses require more test points and more time on site.
• Number of floors: Multi-floor surveys multiply the measurement area and complexity.
• Test point density: Higher-density grids provide more detailed data but require more measurement time.
• Deliverable requirements: Basic survey reports cost less than fully interactive dashboards with heatmaps and compliance scoring.
• Geographic location: Travel requirements affect project costs for facilities outside standard service areas.

Despite the upfront cost, signal surveys consistently save money in the long run by preventing over-engineered or under-performing DAS installations. The survey investment is typically a small fraction of total DAS project cost and pays for itself by ensuring the system is designed correctly the first time.