The Ultimate Enterprise DAS Discovery Checklist: 11 Essential Questions to Ask

Executive Strategic Overview: The Fourth Utility

In the contemporary enterprise landscape, wireless connectivity has transcended its former status as a convenient amenity to become the "fourth utility," ranking in criticality alongside electricity, water, and HVAC. For facility managers, IT directors, and Chief Information Officers (CIOs), the integrity of the in-building wireless (IBW) environment is now a determinative factor in tenant retention, operational efficiency, and legal compliance. As the digital ecosystem evolves toward 5G, the Internet of Things , and private cellular networks, the physical limitations of legacy building infrastructure have collided with the increasing demand for ubiquitous, high-bandwidth, low-latency connectivity, necessitating reliable DAS solutions.

The phenomenon is widespread and acute: modern energy-efficient building standards, utilizing materials such as Low-E glass and high-density concrete, inadvertently create Faraday cages that block macro-cellular signals. Consequently, enterprises face a dichotomy where the demand for wireless data inside buildings is growing exponentially, while the building envelope itself is becoming increasingly hostile to Radio Frequency (RF) penetration. The result is a operational landscape marred by dropped calls, stalled data sessions, and—most critically—the failure of emergency communications.  

Addressing this deficit requires the deployment of a Distributed Antenna System (DAS). However, a DAS is not a commodity product; it is a complex infrastructure project involving RF engineering, regulatory compliance, carrier negotiation, and significant capital expenditure. The difference between a successful deployment and a costly failure lies almost entirely in the Discovery Phase. A rigorous discovery process identifies the precise coverage gaps, capacity requirements, and structural impediments before a single cable is pulled.

This report serves as an exhaustive, expert-level guide and checklist for the Enterprise DAS Discovery process. It synthesizes technical best practices, regulatory mandates (including NFPA and IFC codes), and financial modeling to equip decision-makers with the framework necessary to execute a flawless in-building wireless strategy.

1. The Physics of Exclusion: Why Buildings Fail Connectivity

To conduct an effective discovery audit, one must first understand the physics governing signal propagation and attenuation. The primary adversary of indoor cellular coverage is not the distance from the cell tower, but the composition of the building itself.

1.1 RF Attenuation and Building Materials

Wireless signals operate on specific frequencies, typically ranging from 600 MHz to 39 GHz for commercial cellular use. As these waves encounter physical obstacles, they undergo attenuation—a reduction in signal strength measured in decibels (dB). It is critical to note that the decibel scale is logarithmic; a loss of 3 dB represents a halving of signal power, while a loss of 10 dB represents a ten-fold reduction.

During the discovery phase, an audit of building materials is paramount. Modern "green" construction materials are particularly detrimental to RF propagation:

• Low-Emissivity (Low-E) Glass: Designed to reflect infrared energy for thermal efficiency, Low-E glass contains microscopic layers of metal oxide. These layers act as a shield against RF energy. Research indicates that Low-E glass can attenuate cellular signals by 20 dB to 40 dB. To put this in perspective, a strong outdoor signal of -70 dBm could be reduced to -100 dBm (unusable) merely by passing through the window.  

Concrete and Steel: High-density concrete and steel rebar structures, common in stairwells and elevator shafts, provide attenuation often exceeding 20-30 dB. This creates the "core problem" where the center of the building is a dead zone, even if perimeter offices have marginal coverage.

Metal Cladding and Roofing: Warehouses and industrial facilities often utilize metal skins that effectively block all ingress of RF energy, necessitating internal propagation solutions.  

1.2 Frequency Dependence and 5G

The physics of attenuation is frequency-dependent. Lower frequencies (e.g., 700 MHz, used for LTE and Public Safety) have longer wavelengths and penetrate materials more effectively. Higher frequencies (e.g., C-Band 3.7 GHz and mmWave 24 GHz+, used for 5G) have shorter wavelengths and are easily absorbed or reflected by obstacles.  

Discovery Implication: An existing DAS designed five years ago for 700/800 MHz and 1900 MHz (PCS) may be fundamentally incapable of supporting 5G Mid-Band frequencies. The discovery checklist must therefore include a frequency audit to determine if the existing coaxial cabling and antenna infrastructure can support frequencies up to 4 GHz or 6 GHz without significant signal degradation, especially when comparing private LTE vs 5G.

2. Technological Architecture and Taxonomy

A critical output of the discovery phase is the determination of the appropriate DAS architecture. There is no "one-size-fits-all" solution; the choice depends on square footage, user density, and budget,often weighing against alternatives like private cellular.

2.1 Passive DAS Architecture

Passive DAS, often referred to as a "signal booster" system, represents the foundational tier of in-building coverage.

• Mechanism: A donor antenna on the roof captures the macro network signal. This signal is fed via coaxial cable to a Bi-Directional Amplifier (BDA), which boosts the signal power. The amplified signal is then distributed via splitters and couplers to indoor antennas.  

Best Fit: Facilities under 100,000 square feet.  

Limitations: The system is "passive" because the distribution network (coax/splitters) has no active electronic amplification. Signal loss occurs over every foot of cable (attenuation). Consequently, if cable runs exceed 100-200 feet, the signal degrades to the point of uselessness. Furthermore, Passive DAS generally does not include sophisticated noise filtering, meaning it amplifies background noise along with the signal, potentially raising the noise floor of the macro tower.  

2.2 Active DAS Architecture

Active DAS is the gold standard for large-scale enterprise and venue deployments.

• Mechanism: The RF signal from the carrier (either off-air or via a direct fiber feed) is converted into a digital optical signal at the "Head-End." This optical signal is transported via fiber optic cables to Remote Units (RUs) located throughout the facility. The RUs reconvert the optical signal back to RF and amplify it for local distribution.  

Best Fit: Facilities over 500,000 square feet, campuses, airports, and stadiums.  

Advantages: Fiber optics have virtually zero signal loss over distance, allowing for runs of kilometers without degradation. This architecture supports massive capacity and provides granular monitoring of the network status down to the specific antenna node.  

Barriers: The cost is significant, often exceeding $2.00 to $4.00 per square foot, and deployment requires extensive carrier coordination.  

2.3 Hybrid DAS Architecture

For the "Middleprise" market—buildings between 50,000 and 500,000 square feet—Hybrid DAS offers a strategic balance.

• Mechanism: Hybrid systems utilize digital transport (like Active DAS) over structured cabling (Cat5e/6 or Fiber) to distribute the signal to edge units, which then broadcast RF. Systems like the Nextivity Cel-Fi QUATRA fall into this category.  

Advantages: It offers the installation ease of structured cabling (which many IT integrators can handle) with the performance benefits of digital signal delivery. It eliminates the interference issues of Passive DAS and is significantly cheaper than full Active DAS, aligning with broader network infrastructure.

3. The Discovery Phase I: Organizational Needs & Business Continuity

Before technical measurements are taken, the organizational discovery must establish the "why" and "what" of the deployment. A failure here leads to scope creep and misaligned expectations.

3.1 Business Continuity and Resilience

Connectivity must be viewed through the lens of Business Continuity Planning (BCP). In the event of a macro network failure or a local disaster, how does the organization communicate?

• Risk Assessment: The discovery process must query the reliance on cellular data for critical operations. If the fiber internet line is cut, does the business fail over to 5G routers? If so, the DAS becomes the primary internet backbone during an outage, often leveraging fixed wireless for resilience, as outlined in the business case for private wireless.
• Emergency Communications: Integration with BCP requires understanding regulatory mandates. The RAY BAUM's Act and Kari's Law mandate that multi-line telephone systems (MLTS) must provide a "dispatchable location" to 911 dispatchers. This means a 911 call made from the 40th floor must identify the specific floor and room, not just the building address. A DAS ensures that mobile devices attempting these calls can actually connect to the network to transmit this location data.  

Disruption Tolerance: The discovery checklist must assess the organization's tolerance for installation disruption. Active DAS installation involves pulling rigid coaxial cable and fiber above drop ceilings in occupied offices. Does the BCP allow for after-hours work? What are the security clearance requirements for installers entering server rooms?  

3.2 Capacity vs. Coverage Analysis

A critical distinction in discovery is whether the problem is coverage (dead zones) or capacity (congestion).

• Coverage Deficits: Manifest as "No Service" or dropped calls. This is a signal strength (RSRP) issue.
• Capacity Deficits: Manifest as full signal bars but inability to load webpages. This is a signal quality (SINR) and throughput issue.
• Discovery Implication: Passive DAS solves coverage but cannot create new capacity; it merely repeats the existing (congested) outdoor signal. If the audit reveals capacity issues (e.g., a stadium or trading floor), Passive DAS is the wrong solution. The discovery team must steer the project toward Active DAS or Small Cells that introduce new capacity sources.  

3.3 User Density and IoT Inventory

The audit must inventory the "things" as well as the people.

• Human Density: Calculate the user-per-square-foot ratio. High density impacts the noise floor.
• Machine Inventory: Are there point-of-sale terminals, smart meters, medical telemetry devices, or autonomous robots relying on cellular backhaul?.  

Future Scaling: Will the facility deploy massive IoT (mIoT) sensors in the next 3-5 years? The DAS design must account for the specific frequencies (e.g., NB-IoT bands) required by these devices, especially in smart campus environments.

4. The Discovery Phase II: The Physical & RF Site Survey

The Site Survey is the empirical backbone of the DAS project. It transitions the project from theoretical needs to physical realities.

4.1 The RF Grid Test

A professional integrator performs a grid test, subdividing the floor plan into manageable sectors (typically 20-40 grids per floor) to measure signal metrics.

• RSRP (Reference Signal Received Power): The absolute power of the LTE/5G signal. An acceptable baseline for reliable voice is typically -95 dBm or better.
• SINR (Signal-to-Interference-Plus-Noise Ratio): This measures signal quality. A low SINR (below 0 dB) indicates high interference, meaning even a strong signal will result in slow data speeds.
• Benchmark Testing: The survey must benchmark all relevant carriers (AT&T, Verizon, T-Mobile). It is common to find one carrier has excellent penetration while another is dead. This data informs whether a single-carrier or multi-carrier solution is required.  

4.2 The Donor Signal Analysis

For Passive and Hybrid systems, the "Donor" signal—the signal taken from the roof—is the lifeblood of the system.

• Line of Sight (LOS): The survey team must visually and electronically identify the location of the nearest macro towers.
• Signal Dominance: The donor antenna must be able to isolate a "dominant" server. If the roof receives signals from three different towers of equal strength, the DAS may experience "pilot pollution," leading to rapid handovers and dropped calls.
• Roof Penetration Audit: The discovery team must identify existing conduit or penetration points to route the cable from the roof to the IT closet. Coring new holes in a post-tension concrete roof is expensive and risky; finding an existing pathway is a key cost-saving discovery.  

4.3 Spectrum Analysis and Interference

Using a spectrum analyzer, the integrator checks for external noise.

• Noise Floor Analysis: If the ambient noise floor is high (e.g., -80 dBm), the DAS must amplify the signal significantly above this level to be usable.
• Passive Intermodulation (PIM) Potential: The survey should identify potential PIM sources, such as rusty rooftop fences or old cabling, which can generate interference when blasted with high-power RF.  

4.4 The "Physique" Audit: Structural Constraints

• Plenum vs. Non-Plenum: The survey must determine if the space above the drop ceiling is used for air return (Plenum). If so, all cabling must be Plenum-rated (CMP), which is significantly more expensive and rigid than standard riser cable (CMR).
• Vertical Risers: Identifying continuous vertical pathways (chases) from the basement to the roof is critical for fiber backbones. Lack of risers may require core drilling, impacting structural engineering reviews and costs.  

Asbestos and Hazardous Materials: In older buildings, the discovery phase must flag potential asbestos in ceiling tiles or insulation, as this triggers abatement protocols that can stall installation.  

5. The Design Phase: Engineering & Simulation

Data from the discovery phase is ingested into specialized software to create the system design. This is not a rough sketch; it is a physics-based simulation.

5.1 iBwave Design Modeling

The industry standard for DAS design is iBwave. During the discovery and planning phase, ensuring the integrator uses iBwave is a primary vetting criterion.  

• 3D Modeling: The engineer builds a 3D model of the building, assigning material properties (e.g., "Concrete - Heavy," "Glass - Low E") to every wall and window.
• Propagation Simulation: Virtual antennas are placed in the model, and the software simulates how RF waves will travel, reflect, and diffract through the building.
• Heat Maps: The output is a heat map predicting coverage (RSRP) and quality (SINR) for every square foot. This allows the client to visualize coverage before purchasing equipment.  

5.2 Sectorization and Capacity Planning

For high-density environments, the design must split the building into "sectors."

• Mechanism: Instead of one massive signal covering the whole building, the DAS creates discrete zones (sectors). Sector A covers the conference hall; Sector B covers the offices. This increases total capacity because the same frequencies can be reused in different sectors without interference (if isolation is sufficient).
• Discovery Input: The user density data collected in Phase I directly informs how many sectors are needed. Underestimating this leads to "sector saturation" where users have full bars but cannot load data.  

5.3 Link Budget Analysis

The design includes a "Link Budget"—a mathematical calculation of all gains (amplifiers, antennas) and losses (cables, splitters, walls) in the system.

• Purpose: To ensure that the signal reaching the user's phone is strong enough to maintain a connection, and conversely, that the signal the phone sends back (uplink) is strong enough to reach the DAS antenna.
• Balancing: A critical part of design is balancing the Uplink and Downlink. If the Downlink is too strong, the phone "thinks" it is close to the tower and powers down its transmission, potentially causing the Uplink to fail (the "Near-Far" problem), a key consideration in NaaS (Network as a Service).

6. Regulatory Compliance: Public Safety & E911

A DAS deployment is not merely an IT project; it is a code-compliance construction project. The discovery checklist must rigorously address Public Safety mandates.

6.1 Emergency Responder Radio Coverage Systems (ERRCS)

Building codes (IFC Section 510 and NFPA 72/1221) mandate that new construction and significantly renovated buildings must provide reliable radio coverage for first responders (Fire/Police).  

• Distinct from Cellular: Public Safety DAS operates on different frequencies (typically 700/800 MHz LMR bands) and has stricter survivability requirements than cellular DAS. They usually cannot share the same amplifiers.
• Testing Criteria: The "DAQ" (Delivered Audio Quality) test requires that a firefighter can communicate clearly from 95% of all areas in the building.
• Discovery Action: Check the local "Authority Having Jurisdiction" (AHJ) amendments. Some cities require 99% coverage in critical areas (pump rooms, command centers).  

6.2 Hardening Requirements

Public Safety DAS requires "hardening" that cellular DAS typically does not:

• NEMA-4 Enclosures: Equipment must be housed in water-tight/dust-tight cabinets (often painted red) to survive fire sprinkler activation.  

Battery Backup: The system must remain operational for 24 hours on backup battery power during a main power outage.  

Monitoring: The DAS status (AC fail, Battery Low, Antenna Fail) must be annunciated on the building's main Fire Alarm Panel.  

6.3 E911 and Dispatchable Location

For cellular DAS, compliance with Kari’s Law and RAY BAUM’s Act is essential.

• Requirement: When a 911 call is placed from a mobile device indoors, the system must help facilitate the transmission of location data.
• Technical implication: Passive DAS can obscure location data if not properly sectorized, making the PSAP think the caller is at the donor antenna location (the roof) rather than the basement. Active and Hybrid DAS systems often have better granularity to assist carrier triangulation.  

7. The Carrier Coordination Ecosystem

Perhaps the most underestimated phase in DAS discovery is the bureaucratic hurdle of Carrier Coordination. Operating a signal booster without carrier permission is a violation of FCC regulations (47 CFR Part 20).

7.1 Retransmission Agreements

Every DAS that amplifies a carrier’s signal requires a retransmission agreement.

• The Process: The integrator submits the design (iBwave file) to AT&T, Verizon, and T-Mobile engineering teams for review.
• Timeline: For Active DAS, this process is notoriously slow, taking 6 to 12 months. Carriers prioritize approvals based on their own ROI; a small office building is low priority compared to a stadium.  

• Rejection Risk: Carriers can reject a design if they believe the system will raise the noise floor on their macro tower.

7.2 The "Pre-Approved" Advantage

A key strategic insight for the "Middleprise" is the use of pre-approved hardware.

• Mechanism: Certain Hybrid DAS solutions (like Nextivity’s Cel-Fi) operate on a "network safe" protocol. The equipment intelligently monitors the macro network and shuts down if it detects interference.
• Benefit: Because of this fail-safe, carriers have granted blanket or streamlined approvals for these specific devices. This reduces the coordination timeline from months to weeks, significantly de-risking the project schedule.  

7.3 Connection Types: Off-Air vs. Small Cell

• Off-Air (Donor Antenna): The most common method. The DAS picks up the signal from the roof. Requires a decent outdoor signal to work.
• Small Cell / BTS (Base Transceiver Station): For large venues, the carrier installs a dedicated signal source (a mini cell tower) inside the building. This provides massive capacity but requires the carrier to pay for a backhaul circuit (fiber connection) to the building.
• Discovery Question: "Does the building have dedicated fiber backhaul available for a BTS, or are we relying on the macro network?". For advanced setups, consider how to deploy private 5G with CBRS.

8. Financial Modeling & ROI

Moving the conversation from "cost" to "investment" requires a transparent breakdown of the total cost of ownership (TCO).

8.1 CAPEX: Hardware and Installation

Cost varies significantly by architecture.

• Passive DAS: $0.75 - $1.00 per sq. ft. Low hardware cost, but labor-intensive cable runs.
• Hybrid DAS: $1.00 - $1.50 per sq. ft. The sweet spot for performance/cost.  

Active DAS: $2.00 - $10.00+ per sq. ft. High hardware costs (optical conversion units) and expensive fiber splicing labor.  

8.2 Soft Costs and Hidden Fees

The discovery budget must account for:

• Design Fees: Professional iBwave design services.
• Permitting: Electrical and low-voltage permits from the city.
• Carrier Integration Fees: Some carriers charge fees to review active DAS designs or inspect the final installation.
• After-Hours Labor: If installation must occur at night to avoid disrupting tenants, labor rates can increase by 1.5x to 2x.  

8.3 Operational Expenditure (OPEX)

• Maintenance Contracts: Annual inspection and re-optimization.
• Monitoring Subscriptions: Cloud-based monitoring fees for Hybrid/Active systems.
• Backhaul Costs: If using a Small Cell signal source, who pays for the dedicated internet circuit? (Often the building owner).  

8.4 ROI Drivers

• Tenant Lease Value: WiredScore and other certifications increase price-per-square-foot leasing potential.
• Productivity: Eliminating the "window wander" (employees leaving desks to find signal) recovers significant man-hours.
• Liability Mitigation: Ensuring E911 compliance reduces legal exposure.  

9. Installation, Commissioning & Optimization

The physical deployment is a construction project requiring strict management.

9.1 Construction Milestones

• Phase 1: Cabling (Rough-In): Running coax or fiber above ceilings. This is the most disruptive phase. Dust mitigation and ceiling tile management are critical in occupied spaces.  

Phase 2: Equipment Mounting: Installing antennas and Remote Units. Aesthetics are key here—antennas should be unobtrusive or painted to match the ceiling.  

Phase 3: Head-End Build: Racking and stacking the main equipment in the IT room. Ensuring proper cooling and UPS (Uninterruptible Power Supply) power.  

9.2 Commissioning and The "Shakedown"

Once powered on, the system is not "done." It must be commissioned.

• Uplink/Downlink Balancing: Engineers adjust the gain settings to ensure the DAS talks to the tower without shouting (causing noise) or whispering (dropping calls).
• PIM Testing: A PIM test is conducted on cable lines to ensure no interference is being generated by the installation itself.  

9.3 Acceptance Testing (ATP)

The final step is the Acceptance Test Plan (ATP).

• Grid Test Redux: The integrator repeats the initial grid test. The "After" map is compared to the "Before" map to prove coverage guarantees (e.g., "95% coverage at -95 dBm").  

• Carrier Walk-Test: For Active DAS, carrier representatives may visit the site to conduct their own verification before allowing the system to go live. Explore our case studies for real-world examples of successful optimizations.

10. Operational Management & Future-Proofing

A DAS is a living system. The RF environment changes as carriers modify their outdoor towers or neighbors install new systems.

10.1 Monitoring and Maintenance

• NOC Monitoring: Modern systems (especially Hybrid/Active) connect to a cloud portal. A Network Operations Center (NOC) can remotely monitor for alarms (e.g., antenna disconnection, overheating).
• Annual Re-commissioning: It is best practice to re-test the system annually. If a carrier changes a tower frequency (e.g., refarming 3G spectrum to 5G), the DAS may need to be re-tuned.  

10.2 Future-Proofing for 5G and IoT

• C-Band Support: Ensure the installed antennas support up to 4GHz to accommodate new 5G Mid-Band deployments.  

Scalability: Can the system accept new frequency cards? Active and Hybrid systems are generally modular—you can slide in a new "blade" to add T-Mobile 5G, whereas Passive systems might need hardware replacement.  

Neutral Host & Private 5G: Advanced DAS setups can support "Private LTE" (CBRS) networks alongside public carrier signals. This allows the enterprise to run secure, internal industrial IoT networks on the same infrastructure used for employee cell phones, often comparing favorably to Wi-Fi alternatives.

11. Vendor Vetting & Selection Framework

The final component of the discovery checklist is selecting the partner who will execute this vision. The market is saturated with low-quality installers who treat DAS like simple low-voltage cabling. Use this vetting framework to identify true RF integrators, and review testimonials from satisfied clients.

‍11.1 Critical Vetting Questions

11.2 The "Red Flags"

• "We don't need a site survey." Impossible. You cannot design a DAS without measuring the existing RF environment.
• "We guarantee 5 bars everywhere." RF physics makes 100% coverage physically impossible (elevators are notoriously difficult). Honest integrators guarantee specific dBm levels (e.g., -95 dBm over 95% of the floor).
• "We use cheap boosters." Consumer-grade boosters (FCC Part 20 consumer) are illegal for large-scale enterprise use if they cause interference. Ensure the equipment is "Industrial Class" (FCC Part 20 Industrial or Part 90).  

The Strategic Imperative

In 2025, the connectivity of a building is as defining a characteristic as its architecture. The "Fourth Utility" dictates the viability of the workspace for modern tenants, the safety of its occupants during emergencies, and the operational efficiency of the enterprise.

The Enterprise DAS Discovery Checklist is not merely a list of technical steps; it is a risk mitigation strategy. By rigorously assessing the physical environment, understanding the specific "pain profile" of the users, selecting the appropriate architecture (Passive, Hybrid, or Active), and navigating the regulatory maze of NFPA codes and Carrier approvals, stakeholders can transform a potential liability into a strategic asset.

Metro Wireless, specializing in the agile "Middleprise" sector with Hybrid DAS solutions, recognizes that the most critical phase of deployment is Discovery. It is in these initial audits, surveys, and regulatory reviews that the foundation for a robust, future-proof, and compliant wireless network is laid. The cost of disconnection is too high to leave to chance; the path to connectivity begins with a checklist.

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Frequently Asked Questions (FAQ)

What is the difference between Passive and Active DAS? 

Passive DAS uses coaxial cable to distribute signal; it is cost-effective for buildings under 100k sq. ft. Active DAS converts signal to light for transport over fiber optics; it is required for large venues (stadiums, airports) or buildings over 250k sq. ft. to prevent signal loss over long distances.

Do I need carrier approval to install a DAS? 

Yes. It is a federal requirement to obtain a retransmission agreement to rebroadcast a carrier's signal. Metro Wireless manages this coordination process for you to ensure compliance.

Can you install the system without disrupting our daily operations? 

Absolutely. Our installation teams frequently perform cabling and mounting work during nights or weekends to ensure your business operations continue uninterrupted.

Does a DAS help with 5G? 

Yes. Modern DAS infrastructure is designed to support 5G frequencies. However, 5G (especially mmWave) has different propagation characteristics, so an updated site survey and design are critical, as highlighted in emerging 5G trends.

Why can't I just use a cheap signal booster from Amazon? 

Consumer boosters are not designed for enterprise loads. They often cause interference (noise) on the carrier's tower, leading to shutdowns. Enterprise DAS systems are "network safe" and engineered to handle hundreds of simultaneous users without crashing.

Take the First Step Today

If poor cellular signal, dropped calls, or slow data is slowing down your operations, you are paying for it in lost productivity.

Don't guess at the solution. Use the Metro Wireless DAS Discovery Checklist to document your needs, and let our engineering team design a network that works as hard as you do.

Ready to eliminate dead zones? Explore our options for seamless connectivity. Discover how private cellular networks can enhance your setup. Learn more about fixed wireless internet for reliable failover. 

Contact us and send your floor plans and checklist responses to our Sales Engineering team.