Posted 2008-02-03 Print this article Print

Checklist: When to Consider DAS Deployment

As mobile communications in the workplace become standard, IT managers need to weigh their wireless options and assess the need for a DAS. Considerations include:

Mobile Environment

You have mobile staff, clients and visitors, and their productivity depends on wireless services from a variety of wireless operators.

Poor Coverage

Your existing coverage footprint relies on macro networks and your indoor RSSI (received signal strength indication) is well below -85dBm, typically available only around building windows.

WLAN Expansion

You're considering expanding your existing WLAN footprint beyond the boardroom or adopting voice over WLAN applications, making it a good time to evaluate a multiservice-capable DAS.

Public Safety Needs

Since Sept. 11, 2001, many jurisdictions have mandated strong indoor coverage for public safety radios.  You may need to support 450MHz radios and emerging frequencies (for example, 700/800MHz radios) for compliance.

Future Service Requirements

Supporting new multimedia applications using Mobile WiMax services (operates in the 2.5GHz band) means you'll need to ensure strong indoor coverage since these higher frequencies experience more energy loss.

If your organization meets some of the above criteria, then you're a strong candidate for DAS deployment.

Selecting a DAS Solution: Two Design Options

Depending on the size of your building and wireless requirements or "service mix," you can pursue two paths: a narrowband or broadband solution. These two DAS varieties differ on cabling media used for transporting signals and the type of equipment handling wireless signals.

Narrowband DAS

Narrowband DAS solutions typically use Cat. 5/6 cabling that may be complemented by fiber optics to improve scalability. Narrowband architectures use electronics on either end of the Cat. 5/6 cabling to manipulate (re-band) wireless signals for transport over narrowband media. Characteristics include:

  • Lower installation costs for Cat. 5/6 cabling
  • Intensive equipment requirements
  • Highly scalable in size when combined with fiber optic transport
  • Can only handle 1-2 wireless bands simultaneously before the need for parallel networks, which affect operating expense and aesthetics
Broadband DAS

Broadband DAS approaches rely on broadband media like coaxial cable and fiber optics, which enable a single cabled infrastructure to simultaneously carry multiple wireless services spanning a frequency range from 400MHz to 6GHz. These solutions come in two variations: those that use passive media exclusively (coax) and those that combine broadband media like fiber and coax complemented by active elements (hybrid). 

Two Flavors of Broadband DAS


  • Supports multiple frequencies and services simultaneously
  • Coax losses of 3-4dB per 100 feet make rapid power loss inevitable and limit scalability (well-suited for facilities less than 250,000 square feet)
  • With varied loss levels and no adjustable or "active" elements, system design is complex and inflexible to changes
  • Often lacks proactive management
    Hybrid Broadband:

  • Supports multiple frequencies and services simultaneously
  • Use of low-loss fiber makes solution expandable
  • Simpler equipment but higher media costs than narrowband DAS
  • Consistent design rules and adjustable power simplify deployment/design
  • Proactive management helps assure maximum uptime
Since each DAS model offers unique benefits, IT managers need to consider building size, budget, service mix, staffing levels and future needs when selecting a DAS.


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