Understanding DAS
Glossary of Terms

This DAS Glossary of Terms is designed to provide clear explanations and answer commonly asked questions about Distributed Antenna Systems. If you’re unfamiliar with DAS, this resource breaks down key concepts, components, and terminology to help you better understand its purpose and importance. Use this guide to navigate the world of DAS with confidence and clarity.

General DAS Terms

What is DAS?

Distributed Antenna System (DAS):
A network of antennas designed to improve cellular and wireless connectivity within buildings or large areas. It ensures strong, consistent signal coverage, especially in places where traditional signals may struggle to reach.

What is the purpose of a DAS?

A Distributed Antenna System (DAS) is a network of antennas designed to improve cellular signal strength and coverage. By sending and receiving cellular signals on a carrier’s licensed frequencies, a DAS enhances voice and data connectivity for end-users. As the name suggests, it “distributes” signal evenly across an area, ensuring consistent and reliable coverage in spaces where traditional signals may be weak or obstructed.

ERRCS (Emergency Responder Radio Communication System)

A wireless communication system installed in buildings to ensure reliable radio signal coverage for emergency responders, such as firefighters, police, and medical personnel. ERRCS enhances communication in areas where traditional radio signals are weak or obstructed, including basements, stairwells, and large facilities. The system typically includes a Bi-Directional Amplifier (BDA), a Distributed Antenna System (DAS), a donor antenna, and a battery backup to maintain operation during power outages. ERRCS is often required by fire and building codes to improve safety and emergency response capabilities.

PUBLIC SAFETY DAS (ERRCS)

Grab Your Free Copy Now

By submitting this page, you agree to DasWave’s Privacy Policy.

Active Distributed Antenna System (Active DAS)

A type of Distributed Antenna System that uses fiber optic cables to transmit signals from a centralized signal source to multiple remote units (antennas) throughout a building or facility. Active DAS amplifies and converts signals at each remote unit, ensuring strong and consistent coverage for wireless communication, including cellular and public safety networks. This system is ideal for large or complex structures such as airports, stadiums, and hospitals, where maintaining reliable signal strength across vast areas is critical.

Passive Distributed Antenna System (Passive DAS)

A type of Distributed Antenna System that uses coaxial cables, splitters, and passive components to distribute radio frequency (RF) signals from a central source to antennas throughout a building. Unlike Active DAS, Passive DAS does not amplify signals at remote points but relies on the strength of the original signal and proper design to ensure adequate coverage. It is typically used in smaller buildings or facilities with straightforward layouts, where the signal loss over shorter distances is minimal.

Hybrid Distributed Antenna System (Hybrid DAS)

A combination of Active and Passive DAS technologies designed to optimize signal distribution in buildings or facilities with diverse coverage needs. In a Hybrid DAS, fiber optic cables are used to transmit signals from the head-end (signal source) to remote units, where the signals are then distributed through coaxial cables and passive components to antennas. This approach combines the long-distance signal transmission benefits of Active DAS with the cost-effectiveness of Passive DAS, making it suitable for medium-to-large facilities with areas requiring both high performance and budget-friendly solutions.

Signal and Connectivity

Frequency Bands

Specific ranges of electromagnetic spectrum frequencies used for wireless communication. Each band is allocated for different types of services, such as public safety, cellular networks, Wi-Fi, or radio broadcasting. Frequency bands are measured in hertz (Hz) and categorized into bands such as low-frequency (LF), very high frequency (VHF), ultra-high frequency (UHF), and others. In the context of Distributed Antenna Systems (DAS) and Emergency Responder Radio Communication Systems (ERRCS), frequency bands ensure that devices operate without interference, enabling reliable communication for emergency responders and commercial networks. Common public safety bands include 700 MHz, 800 MHz, and 900 MHz.

Licensed Frequencies

Specific radio frequency ranges regulated by government authorities (such as the FCC in the United States) that require a license for use. These frequencies are allocated to organizations, such as public safety agencies, wireless carriers, and private businesses, to ensure controlled and interference-free communication. Licensed frequencies are commonly used in applications like public safety communication, cellular networks, and private radio systems. They offer greater security, reliability, and exclusivity compared to unlicensed frequencies. Examples include the 700 MHz and 800 MHz bands used for emergency responder communication.

Unlicensed Frequencies

Radio frequency ranges that do not require a license for use and are open for public access, as regulated by government authorities (e.g., the FCC in the United States). These frequencies are typically used for short-range wireless communication technologies like Wi-Fi, Bluetooth, and certain IoT devices. While they are cost-effective and easily accessible, unlicensed frequencies are more prone to interference due to their widespread use. Common unlicensed frequency bands include 2.4 GHz, 5 GHz, and 6 GHz, which are popular for wireless networking and consumer electronics.

Signal Amplification

The process of increasing the strength of a wireless signal to enhance its coverage and reliability. In communication systems like Distributed Antenna Systems (DAS) and Emergency Responder Radio Communication Systems (ERRCS), signal amplification is achieved using devices such as Bi-Directional Amplifiers (BDAs) or repeaters. These devices boost weak signals to ensure they can travel longer distances and penetrate obstacles like walls or floors, providing consistent and reliable connectivity in areas with poor signal strength. Signal amplification is essential for maintaining effective communication in large buildings, underground spaces, and remote locations.

RF (Radio Frequency)

The range of electromagnetic wave frequencies used for wireless communication. RF signals are commonly used to transmit data, voice, and video over the air in systems such as cellular networks, Wi-Fi, radio broadcasting, and public safety communication. The RF spectrum typically ranges from 3 kHz to 300 GHz and is divided into various bands, such as low-frequency (LF), very high frequency (VHF), and ultra-high frequency (UHF), each suited for specific applications. In systems like Distributed Antenna Systems (DAS) and Emergency Responder Radio Communication Systems (ERRCS), RF signals are managed and distributed to ensure reliable coverage throughout a facility.

RF Propagation

The behavior of radio frequency (RF) signals as they travel through different environments and materials. RF propagation determines how signals move from a transmitter (such as an antenna) to a receiver, and it is influenced by factors like frequency, distance, obstacles, and environmental conditions.

There are several modes of RF propagation:

  • Line-of-Sight (LOS): Signals travel directly between antennas without obstructions.
  • Reflection: Signals bounce off surfaces like walls, buildings, or the ground.
  • Diffraction: Signals bend around obstacles.
  • Scattering: Signals disperse in different directions when encountering small objects or irregular surfaces.

Understanding RF propagation is essential for designing systems like Distributed Antenna Systems (DAS) and Emergency Responder Radio Communication Systems (ERRCS) to ensure strong and consistent signal coverage in complex environments such as buildings, tunnels, and urban areas.

Equipment and Components

Antenna

A device used to transmit or receive radio frequency (RF) signals in wireless communication systems. Antennas convert electrical signals into electromagnetic waves for transmission and vice versa for reception. They are a critical component of systems like Distributed Antenna Systems (DAS) and Emergency Responder Radio Communication Systems (ERRCS), ensuring effective signal distribution and communication coverage.

Types of Antennas:

  1. Omnidirectional Antenna: Radiates signals uniformly in all horizontal directions, ideal for covering wide areas.
  2. Directional Antenna: Focuses signals in a specific direction, providing longer range and reducing interference.
  3. Panel Antenna: Commonly used in DAS to distribute signals within buildings.
  4. Yagi Antenna: Used for long-distance communication and precise targeting.

Antennas vary in size, shape, and functionality based on their intended application, frequency range, and environment. Proper antenna selection and placement are essential for optimizing signal strength and coverage.

Repeater

A device used in wireless communication systems to receive, amplify, and retransmit radio frequency (RF) signals to extend their range and improve coverage. Repeaters are commonly used in systems like Distributed Antenna Systems (DAS) and Emergency Responder Radio Communication Systems (ERRCS) to ensure reliable signal strength in areas with weak or obstructed reception, such as tunnels, basements, or large buildings.

Key Functions of a Repeater:

  1. Signal Reception: Captures weak RF signals from a source.
  2. Amplification: Boosts the strength of the received signal.
  3. Retransmission: Transmits the amplified signal to cover a wider area.

Applications:

  • Enhancing cellular and public safety communication in large or complex facilities.
  • Bridging signal gaps in remote or obstructed locations.
  • Supporting seamless communication for emergency responders.

Repeaters are vital for maintaining consistent and reliable communication in environments where direct line-of-sight to the signal source is limited.

Remote Radio Unit (RRU)

A key component in wireless communication systems, particularly in Distributed Antenna Systems (DAS) and modern cellular networks. An RRU is a remote, decentralized device that is typically installed near antennas to handle radio frequency (RF) processing tasks. It connects to a central baseband unit (BBU) via fiber optic cables, allowing for efficient signal transmission and management.

Key Functions of an RRU:

  1. Signal Amplification: Enhances and amplifies RF signals for better coverage.
  2. Signal Conversion: Converts baseband signals from the BBU to RF signals for transmission and vice versa.
  3. Decentralized Processing: Offloads RF processing from the central unit, reducing latency and improving efficiency.

Benefits of an RRU:

  • Improved Coverage: Extends signal reach in large or complex environments.
  • Scalability: Allows easy network expansion by adding more units.
  • Reduced Power Loss: Minimizes signal degradation by placing the unit close to the antenna.

RRUs are commonly used in large-scale deployments like stadiums, airports, and high-rise buildings to provide reliable and consistent wireless communication.

Splitter

A device used in wireless communication systems, such as Distributed Antenna Systems (DAS), to divide a single input signal into two or more output signals. Splitters are passive components that distribute radio frequency (RF) signals to multiple antennas or other system components, ensuring consistent signal coverage across a building or area.

Key Features of a Splitter:

  1. Signal Distribution: Splits the input signal evenly or at specified ratios to multiple outputs.
  2. Passive Operation: Does not require an external power source.
  3. Frequency Range: Supports specific frequency bands to match system requirements.
  4. Loss Management: Introduces minimal signal loss during distribution.

Types of Splitters:

  • 2-Way Splitter: Divides the signal into two outputs.
  • 3-Way or Multi-Way Splitter: Divides the signal into three or more outputs.
  • Uneven Splitter: Distributes signals in unequal proportions based on design needs.

Applications:

  • Connecting multiple antennas in a DAS to extend coverage.
  • Distributing signals in Emergency Responder Radio Communication Systems (ERRCS).
  • Supporting multi-zone wireless communication in large facilities.

Proper design and placement of splitters are critical to maintaining balanced signal strength and minimizing interference in communication systems.