All you need to know about DAS

Distributed Antenna Systems (DAS) are critical tools to ensure that areas with high user density maintain consistent cellular signals.

The key benefit of a DAS is that it overcomes challenges such as building materials, complex layouts, and interference that can disrupt or weaken a single cell tower’s coverage. By distributing the signal, the DAS ensures reliable, high-quality cellular connectivity throughout the entire facility.

A DAS works by taking a single, strong cellular signal and distributing it throughout a building or venue using a network of individual antennas.

Here’s what it entails in more detail:

1. The DAS receives the wireless signal from the cellular carrier’s main cell tower or base station.
2. This signal is then processed and amplified at the central equipment hub of the DAS system.
3. From there, the enhanced signal is sent through fiber optic or coaxial cables to multiple remote antenna units or nodes placed strategically around the building or venue.
4. Each of these remote units converts the signal back into a radio frequency (RF) signal and broadcasts it using its own antenna.

This distributed network of antennas ensures that the cellular signal is evenly dispersed and maintained, even in areas with very high user density and demand, typically such as stadiums, convention centers, malls, underground transportation, or large office buildings.

DAS helps ensure users have reliable connectivity even in locations with walls, flooring, and other obstacles that degrade cellular coverage. DAS technology is most commonly used in indoor, high-density locations, such as airports, hotels, offices, and other commercial buildings, stadiums or arenas, and outdoor spaces such as urban areas and campuses for first responder communication.

1. Improves wireless coverage and capacity in the designated area via a network of antennas connected to a single signal source.
2. Designed to provide consistent cellular coverage in locations with signal interference.
3. Simultaneously supports 4G, LTE, 5G, other technologies, and multiple wireless carriers, ensuring users have smooth communication.
4. Ensures seamless 5G connectivity indoors that might otherwise be blocked by materials like concrete and glass.
5. Offers greater capacity and multi-carrier coverage than small cells, but can have more expensive installation and difficult upgrades.
6. Most common locations for DAS are large, high-density venues, such as stadiums, college campuses, hospitals, and hotels.
7. Benefits include greater indoor cell coverage, increased network capacity, improved user experience, scalability and flexibility, long-term cost savings, and support for emergency services.
8. There are three types of DAS — active (fiber optic cables and remote antennas), passive (coaxial cables), and hybrid (a combination of both).
9. There are three main types of DAS signal sources — off-air antennas, on-site base transceiver stations, and small cells.
10. The type of DAS and DAS signal sources used will depend on factors such as the size of the coverage area, the type of system used, signal strength requirements, and number of carriers supported.

There are three types of DAS:

• Active DAS can share signals across long distances using powered components such as fiber/ethernet cabling.
• Passive DAS uses non-powered components such as coaxial cabling for smaller locations.
• Hybrid DAS is a combination of active and passive components to cover large, low-density areas.

There are three main types of DAS signal sources.

The first is off-air antennas, or donor antennas, which are installed on the exterior of a building to capture wireless signals from cell towers. These antennas are cost-effective, especially for passive DAS, but rely on existing cellular signals to be consistently available and strong.

The second is on-site base transceiver stations (BTS), which uses fiber optic cables to connect to a wireless carrier’s network. BTS are used most commonly for active DAS because of their higher capacity and greater control over signal distribution. Usually, buildings install one BTS for each supported carrier.

The final DAS signal source is small cells, which are cellular radio access nodes similar to macro cells. On their own, small cells expand coverage and capacity by amplifying and distributing wireless signals. These can act as a localized signal source for DAS and provide a balance between the cost-effective off-air antennas and the control of BTS.

How to choose a DAS signal source.

When choosing a signal source, decision makers should consider factors such as capacity requirements, desired level of control over signal distribution, DAS implementation budget, and available wireless carrier coverage. Sometimes, a combination of signal sources should be used to optimize performance.

While both DAS and small cells amplify and distribute source signals, DAS technology has several key advantages. DAS has greater capacity, coverage, and multi-carrier capabilities, making it better-suited for high-density venues that require support for multiple mobile operators.

The distributed network of DAS allows for greater scalability and flexibility than small cells because antennas can be placed to overcome specific signal blockages and expand coverage as the network demand increases. The dedicated signal source in DAS ensures a consistent, strong signal in the entire coverage area, whereas the individual backhaul connections used by small cells are more prone to capacity limitations and interference.

Additionally, the channels created by DAS ensure more reliable first responder communication during an emergency than small cells.

In essence, although small cells are a cost-effective option for smaller coverage areas, DAS technology provides greater performance, flexibility, and support, especially in locations that have high capacity requirements and a large scale.

The process to implement a DAS is complex and requires experienced professionals for successful and compliant implementation.

There are seven steps for a business to implement a DAS.

1. Self-evaluation and cost determination: assess its specific needs and create a realistic budget.
2. Site survey and location determination: determine the building’s layout to identify signal weak spots and determine optimal installation locations for DAS components.
3. System design and planning: design the DAS architecture based on the site survey, choose the appropriate DAS technology, and obtain necessary approvals.
4. Equipment procurement and installation: purchase the required equipment and install according to the system design. The entire installation process should be documented.
5. Commissioning and integration: perform comprehensive testing of the installed system and integrate with the signal source or sources.
6. Training: train building staff to conduct maintenance.
7. Ongoing maintenance and support: implement a regular maintenance schedule and monitor the system for any issues.

5G cellular coverage uses millimeter wave and mid-band frequencies. These have a shorter range and can be blocked by common construction materials, such as concrete and glass. DAS helps circumvent these blockages by distributing multiple 5G signals from a source to the antennas placed within the building, ensuring there are no dead zones. Additionally, while 5G offers higher data rates, greater capability for bandwidth-intensive applications, and new use cases like virtual reality and industrial IoT, DAS is required for all of that to work properly, ensuring reliable indoor 5G connectivity.

A DAS uses a network of antennas connected to a central signal source, such as an off-air antenna, base station, or small cell, to improve indoor cellular coverage. The source signal is processed and then distributed via cables to remote antenna units through the building, overcoming signal obstructions to provide reliable connectivity in high-density venues such as airports, stadiums, and offices. Key benefits of DAS include eliminating dead zones, increasing capacity, enabling seamless indoor 5G connectivity, and improving overall user experience.