Public Safety DAS Design Installation Considerations

Public-Safety DAS Design Installation

Maintaining proper communication coverage within large buildings is important to support emergency responders, fire departments, police, and healthcare responders. In isolated areas where coverage is inadequate or non-existent, Distributed Antenna Systems (DAS) are used to support communications. Coverage and capacity are taken into consideration when designing and installing a public-safety DAS solution, as is cost.

Distributed antenna systems are also used to improve an occupants’ access to wireless signals within large buildings. You commonly find them installed, both inside and outside, at locations such as: stadiums, apartment complexes, corporate office buildings, and hotels. Small-cell networks and DAS are becoming essential as more and more users load data-intensive smartphone applications.

public-safety DASWhere cellular data usage is high, such as a stadium or large music venue hosting a major event, the nearby cell tower cannot be relied upon to provide adequate coverage for such a large number of users. The cell tower and local network can quickly become overwhelmed. In these two situations, the solution is to design and install a high capacity DAS.

Coverage verses capacity is commonly the main issue when the cell tower is far away. Also, building materials block cell signals. High-rise buildings often deploy DAS to combat radio frequency noise encountered at higher altitudes.

When designing a DAS system, one of the most important factors to consider is the signal source capabilities supplying the network. Common signal sources include: off-air, BTS, small cell, and NodeB (or eNodeB).

Common Signal Sources

One of the most common signal sources for a DAS is an off-air signal. It takes advantage of a donor antenna to receive and transmit signals from a cell carrier. Basically, it is used to extend network coverage where capacity is not the issue. However, the donor signal must produce a clear and reliable signal. If it does, designing and installing this type of DAS to extend coverage inside a building can be the most cost-effective solution.

There are numerous considerations when designing a DAS solution. For example, public-safety DAS is required where commercial use is typically not required; stairwells, utility rooms, and so on. These remote areas may or  may not be covered in cellular DAS deployments.

When comparing DAS and small cell solutions, cost considerations come into effect. Small cells may be the best choice for smaller, low-density applications where support is needed for a few dozen users and a single carrier.

The DAS tends to become more cost-effective as capacity and coverage requirements increase. For large deployments, it is much less expensive to deploy a DAS for in-building coverage than to deploy dozens or hundreds of cells. Operating expenses are lower as well in a multi-carrier environment.

IBwave public-safety DASIn addition to cost, designing a system must consider and evaluate operational needs, controlling interference, and scalability. There is no one-size fits all solution with public-safety or carrier DAS. In certain situations, the best solution may include both DAS and small cell. At Backhaul Engineering, we are working with design tools such as:

  • iBwave
  • PCTel SeeGull
  • AirMagnet Survey Pro
  • Ekahau Survey/Planner

As DAS designers and installers, we first listen to our client's needs and then begin the process of developing the best, and most cost-effective, DAS solutions.

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