Distributed Antenna System (DAS) Cost and Design Considerations for Enterprise Buyers | The Signal Network Blog by Corning

By Art King
Published: October 12, 2022

For many enterprise buyers, approaching the problem of solving for cellular service complaints of employees, guests, and contractors can be like going to an alternate universe.

Here are a few challenges you may face when shopping for a DAS system:

• Cellular vs. enterprise terminology and technology
• Complex  vendor and systems-integration relationships
• Involvement of mobile operators in the problem-solving process

We’ve put this distributed antenna system post together to help enterprise IT people prepare for the conversations with systems integrators, technology suppliers, and mobile operators about shopping for a DAS system. Educated IT buyers make better decisions for their own operation and the people they support across their facilities. 

1. What mobile operator coverage do I need in my building?

This is the key question, as it affects the DAS system cost and the technology decision. It also directly relates to the type of facility that requires better service. Think hospitals,  enterprise buildings, airports, sports venues, higher education campuses, and so on.

For example, venues where the public gathers usually require the three U.S. national mobile operators and, if present, a regional operator. Because the U.S. market share is split into thirds, venues must build for all operators.

Enterprise facilities – typically 100,000- to 500,000-square-foot buildings that are occupied by employees, contractors and their guests – have more flexibility around the mobile operator decision. For example, if the enterprise has a corporate contract with one mobile operator, it may be most practical to support that operator only. Every enterprise is different in their usage and importance of mobility, so we suggest that IT decision makers identify which operators are mandatory or optional. These decisions allow cost-benefit trade-offs to be presented during budgeting so an educated decision can be made for the business.

Tech advice: operator count influences the decision point of a single operator system, such as enterprise indoor small cells, or a multi-operator DAS system.        

2. What are the building size and coverage areas for the proposed DAS system?

This information is critical to the technology decision and ensuring the system meets the desired goals in locations targeted for service improvements. 

In advance of considering a project, enterprise IT should determine:

• How big is the building?
• Is this a campus with multiple buildings?  
• Are there sub-basements and parking structures?

In DAS systems, all the shared equipment is typically called a “headend” and it tends to be the most costly part of the installation. Since the cost of the headend is spread across the square footage that requires services, the more area covered, the lower the costs per square foot.

Also, DAS network design projects involving multiple buildings or areas such as sub-basements or parking, may have special requirements such as extra interfaces, underground fiber capacity, or outdoor housings that need to be considered with potential vendors. When designing and costing the DAS project, it is more cost-effective to have these components in the initial quote vs in later change orders. 

Tech advice: Fully scoping projects enables the best DAS network design to be created in advance. It also promotes collaboration with solutions providers on executing the total project in stages if funding can’t be allocated in the same fiscal year.       

3. What is the density of subscribers (mobile users per square foot)?

Employees of U.S.-based enterprises, on average, occupy about 200 square feet, composed of workspace plus a portion of communal areas. Everyone has at least one mobile device and many may have two (personal and work). The design of a DAS network system is greatly influenced by the density of subscribers, by operator, and needs to be developed as part of the preparation process.  

Subscriber density assumptions can be based on one of the following:

1. Everyone has a contract phone from one mobile operator. Adopt this assumption if an enterprise contract exists or there is only one mobile operator requiring indoor improvement. 
   
   
2. Use the 1/3 market share distribution model. This model applies to venues and commercial real estate where all guests and tenants must be supported. Enterprise adoption of this assumes that the business requires support of all mobile operators, regardless of enterprise mobility contracts.
    

Tech advice: The required headend radio capacity needed to drive a DAS system is related to the number of subscribers attached to each radio. The assumptions above govern the amount of square footage each radio can comfortably accommodate.  This determines the type and number of radios that will be required to provide sufficient capacity and coverage. 

Density changes over time also favor software-driven DAS systems because reconfiguration via network management system is faster and more cost effective than opening the ceilings and re-cabling sections of the DAS itself.

4. What are the performance goals of the DAS system?

Getting the performance goals and underlying assumptions correct is a key factor in success. Imagine having five bars of signal, but calls are hard to make or they drop when employees are on the move. What if business apps are crawling or outright failing? Not good. From an enterprise IT perspective, the design and implementation of the end-to-end DAS system should embody measurable goals. 

Potential performance metrics:

• Speed and latency – both vital to device owner experience 
• Call drops – within the building and entering/exiting
• Capacity usage – backhaul network link, radios, and DAS

Attaching performance goals to the metrics and collaborating with the selected systems integrator on a measurement process for system acceptance is vital. Additionally, long-term monitoring can ensure the enterprise IT owner realizes the performance they expect. 

Two rules of thumb:

• People will consume far more service over time. Data consumption will continue to grow. Plan for extra capacity throughout the system initially and have a roadmap to grow capacity over time.
  
• If the firewalls on the enterprise Wi-Fi are very locked down, plan for the data usage of most all mobile devices switching to cellular indoors for an unedited view of the Internet.

Tech advice: Designing a DAS system to achieve performance goals while balancing DAS system costs takes a seasoned engineer and the right technology choices. The enterprise IT team must own many of the decisions, but the solutions provider helps make those decisions real via technology and design. Ideally, enterprises develop a long-term relationship with a selected cellular technology and solutions provider as cellular networks are continually evolving, and the indoor cellular/DAS network has to evolve in sync with the outdoor networks. Choosing a stable and reliable company with a strong history of service and support is critical.

Summary

Cellular technology is not as well understood by many enterprise IT/Telecom professionals and there is a wealth of knowledge to research before any engagement with vendors begins. This list of four things to know before shopping provides a simple framework to open a conversation with potential solutions integrators and technology suppliers.

There are additional decision points for enterprise IT as the project journey continues. We’ll explore in a future post.

Questions and comments welcome. Also, my colleague, Derek Whitehurst, and I will be discussing this topic in more detail at the BICSI Winter virtual event.