DAS Overview

Distributed antenna systems or DAS are a must-have in massive buildings with poor reception. They improve public cellular wireless network coverage indoors, ensuring that people can get strong and reliable signals wherever they are in the building. 

Why Do Buildings Need Distributed Antenna Systems? 

Though cellular phones have become a lot more than just “phones” these days, they still need to perform the basic function of making and receiving calls without disruption. While this typically isn’t an issue when you’re outdoors or even inside your home, it can be difficult for wireless signals to penetrate office buildings, thereby leading to spotty or inadequate coverage in certain areas. Dropped calls and poor connections can lead to unhappy clients and possibly even lost profits.

Cell phone coverage can also be an issue in heavily populated facilities or venues where thousands of people may be attempting to access the phone network at once. Sports stadiums and convention centers are just a few of the types of facilities that could benefit from more reliable cell coverage, while also improving the fan and attendee experience.

In buildings or venues with poor cell service, a distributed antenna system can serve as a valuable addition.

Distributed Antenna Systems Explained

Also commonly known as in-building wireless (IBW) solutions, distributed antenna systems work like a Wi-Fi router except it boosts cell coverage. 

Think of it like this: If you just have one wireless router in your home, then Wi-Fi-enabled devices located closest to the device get the strongest signal and best connectivity. There may even be a few “dead spots” in your home that get a very spotty signal or can’t pick up the signal at all. To resolve this, you can either move your wireless devices closer to the router, which isn’t always convenient, or you can add additional routers to your home to ensure a strong Wi-Fi signal throughout.

Distributed antenna systems work the same way. However, instead of Wi-Fi routers, DAS systems use strategically-placed antennas to boost cell coverage where they are weakest. 

Distributed antenna systems typically consist of a network of antennas that receive signals from base building service or an outside tower. A distribution system then transmits this signal throughout the venue. This reduces spotty reception when you have a properly designed and implemented DAS system. As a result, tenants, customers, guests, and employees can enjoy consistent, uninterrupted mobile signals anywhere in the building.

Four Types of DAS Network Signal Sources

DAS networks have two primary components: the signal source and a distribution system.

Let’s briefly discuss the signal sources in different DAS networks.

1. Repeater or Off-Air Signal - An antenna installed on the roof of a building that catches signals from nearby cell towers.
   
2. Base Transceiver Station (BTS) - Also referred to as NodeB, eNodeB or gNodeB, this signal source connects to a dedicated fiber connection provided by each network carrier.
   
3. Small Cells -These devices are connected via secure tunnels to carrier networks. They rely on a robust Internet connection to receive and distribute high-quality signals. Like with BTS, small cells are provided by network providers.
   
4. Hybrid Signal Source - A combination of two or all of the above. It’s common practice to mix and match signal sources because it is sometimes more cost-effective to use a repeater for corporate floors, for example, and BTS devices in the main activity areas where tens of thousands of people are texting, calling, and video chatting at the same time.

Four Types of DAS Signal Distribution Systems

1. Passive Distributed Antenna System - This system uses passive components like coaxial cables, splitters, and couplers to distribute signals inside a building. The diagram for passive DAS is simple: the signal source connects directly to the passive amplifiers, which are in charge of distributing the signal throughout the building.
   
2. Active Distributed Antenna System -This system has a master unit that converts the source’s radio frequency (RF) signal into digital before sending them to remote radio units (RRUs) via fiber optic or ethernet cables. The RRUs then convert the signals back to RF to be distributed wirelessly throughout the premises. Active DAS is commonly used to send radio signals to first responders and establish public safety DAS  for buildings and structures like stadiums and arenas.
   
3. System Hybrid Distributed Antenna System- Combines the coaxial cabling in Passive DAS and fiber optics in Active DAS networks. It is essentially a single Passive DAS that connects to an RRU on each floor or section of the building. The RRU transmits analog RF signals via coaxial cables to multiple antennas on the floor, extending the coverage without needing too many expensive RRUs.
   
4. Digital Distributed Antenna System- A Digital DAS uses fiber optic cables throughout the system. It converts each network carrier’s signals into binary data, then combines and transmits them via fiber optic or ethernet cables. Because the signal is mainly digital, this system is less prone to interference or signal attenuation.

Common Problems in DAS

A DAS distributes cell coverage and ensures that a mobile signal is available anywhere in a building. But unfortunately, its function can also be its weakness: signals from DAS systems of neighboring buildings can collide and interfere with one another. This is what happens when you’re in a boutique, for example, and your phone catches the WiFi signal from the cafe next door. 

The wireless ecosystem becomes too crowded when there are many DAS systems in one area. These problems emerge as a result:

• Interference - When the signal for one network provider is stronger than another, it can flood the DAS and block the distribution of the weaker signal inside the building.
• Signal attenuation - Signal attenuation means the loss or weakening of the signal transmitted by a DAS network. It can happen when the signal travels long distances, like when there are too few active antennas or RRUs amplifying coverage on a wide floor. 
• Inefficient signal distribution - Signal interference and attenuation can result in inadequate distribution of network signals, which defeats the purpose of distributed antenna systems. 
• Higher costs for DAS infrastructure - To make up for the weak signals due to distribution inefficiencies, building administrators might install additional signal distribution devices to amplify the reach of the indoor cell coverage. Unfortunately, it is an extra expense that can’t guarantee stronger or more stable signals where they are needed the most.
• Security breaches - Signal interference can be an information security issue. When outsiders detect private networks through a shared DAS, they might try to hack into the network for reasons as simple as leeching Internet services or as nefarious as stealing confidential data. 

So when faced with the problem of distributed antenna systems that work all too well, how do you correct interference and attenuation? Signals Defense offers a solution: RF window films.  

The Role of Window Films in Distributed Antenna Systems

Purpose built RF attenuating window films can help isolate analog RF signals distributed by DAS networks inside the building, preventing outsiders from detecting and leeching the signals inside the premises. Likewise, window films block signals outside the building, eliminating interference from nearby buildings and cell towers.

These window films can attenuate signals from outside the building, eliminating problems regarding interference. At the same time, they can help prevent outsiders from detecting signals inside the premises, boosting cybersecurity for users that handle sensitive information. 

Finally, window films help control how signals are distributed inside buildings that use Hybrid DAS or whose occupants have installed multiple independent DAS networks. For example, tenants who have invested in a private DAS system can isolate the cell signal within the rooms or floors they lease by installing window films on the glass windows, doors, and walls.

About DAS Shield

While distributed antenna systems help enhance cell service within a building, one thing they cannot do is control what is happening outside of the facility. That’s where DAS Shield, a protective type of window film, can help. DAS Shield can be applied to nearly any type of window and it works to separate a signal from a distributed antenna system and stays within your facility. These films can also reduce Wi-Fi signal loss, which helps further minimize wireless interference, safeguard systems from hackers and enable quality coverage throughout. Essentially, DAS Shield helps reduce any external RF interference on the outside, thereby helping a facility's distributed antenna system work up to its full potential. 

Contact Signals Defense today for more information on distributed antenna systems and how DAS Shield can help improve coverage throughout your facility.