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5 Main Components of Active DAS (Distributed Antenna System)

Feb 26, 2018

5 Main Components of Active DAS (Distributed Antenna System)

In-And-Outs of an Active DAS: Basics, Components, and More.

Large concrete structures. Thousands of cellular devices. There never was a better time for DAS. Amidst the rise of 4G technology and the emergence of 5G, the world is in the midst of a digital revolution. The need to serve wireless systems sans the structural and technological limitations is greater than ever.

No wonder DAS systems are thriving now more than ever before. After all, serving multi-band, multi-technology carriers in larger space is achieved only with the help of minimalistic equipment: Signal source at one end and a distribution system at other. Nevertheless, DAS solutions in itself have evolved into various flavors such as off-air DAS, iDAS, eDAS, oDAS, and hybrid DAS. However, active and passive DAS continues to remain at the top-of-their-games even as they serve as the foundation for all the above variations.

In this edition, we dive deeper into an active DAS and explore its components, attempting an understanding at what makes it the perfect choice indoor wireless solution to enhance capacity and coverage for large-scale public places such as airports and football stadiums.

A DAS can simply be understood as a network of distributed antenna-equipped radio units serving an indoor or outdoor location. In essence, a variety of signal sources connected to a head-end unit which in-turn serves multi-band radio units comprise a DAS's overall skeletal structure. Active gain elements in both the uplink and the downlink direction have earned an active DAS its name. So what are these components and how do they function? Here is an in-depth detail.

5 Components Of Active Distributed Antenna Systems:

  1. Signal Sources.

    As powerful as an active DAS is, the system itself is incapable of producing a standalone signal. These signals are fed from sources such as a service provider feed, Node-Bs, and the modern favorite - small cells. These signal sources reside in the head-end equipment room. Multiple service providers can provide their respective signal feed making it a multi-carrier active distributed antenna system. Only major service providers can provide the feed such as AT&T Wireless, Verizon Wireless, Sprint, T-Mobile, etc. in USA. MVNO's or Mobile Virtual Network Operators would not provide such a signal feed themselves - They would need permission from the main service carriers such as those mentioned above. In Canada, those would be Rogers Wireless, Telus Mobility, Bell Mobility, Freedom Mobile, etc.

  2. POI Tray.

    Stationed between the signal sources and the head-end unit, the POI tray combines the RF signals from diverse RF sources before it is delivered to the head-end equipment. These signals differ in nature and their abrupt and direct combination at the head-end unit can result in diversity imbalance. Of course, the same can also be achieved by using standalone hybrid combiners, which is the traditional way. But the POI does more.

    The downlink signal from RF sources is usually powered at 40 W which is much higher than the average head-end unit can handle. The POI tray configurations attenuate these downlink signals before they are delivered to the head-end unit, thereby preventing excessive power-loss and heating.

  3. Head-End Unit.

    In addition to the signal sources, the head-end equipment room houses the head-end unit. On one side, band-specific units called RF modules connect the head-end unit to corresponding uplink and downlink port-pairs on the POI via coaxial cables. These RF modules provide further signal filtration and amplification based on the signal frequencies. Similarly, a series of uplink-downlink port pairs, one for each radio unit, are present on the other end to facilitate zone-wise signal distribution.

    Needless to say, the head-end equipment room houses some of the most critical components of an Active DAS. Not only should it be large enough to house the electronic components, it should also be well-equipped to handle their excessive heating and impart cooling thereafter.

  4. Radio Units.

    Active DAS radio units receive signals from the head-end unit, segregate them based on frequencies, amplify them, and then transmit them to the nearby regions through antennas. These antennas is either mounted on the top of the radio-unit directly or connected to an RF-port. The reverse of this process is carried out in uplink direction. Depending on the transmission power and number of different frequencies supported, different types of radio units are deployed in an active DAS. Radio units are powered by AC or DC supply.

  5. Fiber Optic Cables.

    Distributed antenna systems cannot be complete without connecting all components with fiber-optic cables. Thin, flexible, and light-weight, fiber optic cables are perfect for an Active DAS. They don't take up much space and can easily dwell in even the smallest nooks and crannies. Since the optic signal attenuation in fiber optic cables is low, it grants the freedom to place radio units at a considerable distance from the head-end unit without causing signal loss or loss of signal Gain achieved from signal sources such as a service carrier feed. Depending on the type of signal to be transmitted, Single-Mode (SM) or Multi-Mode (MM) fiber optic cables can be used.

Conclusion.

Now you know what it takes to power a DAS wireless network in a large airport or a multi-storey shopping complex, allowing you to seamlessly carry on with your wireless communication, regardless of the number of concurrent mobile users and regardless of thick concrete walls that surround such large man-made structures.

Active DAS Components


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6 comments

  • Question from Blake: “I’m not sure if this is the right place to ask this, but how do I increase the wifi coverage area of my 4G hotspot?” Answer: Hotspots can be a great way to take a cell signal and make a data connection to any device that works with Wi-Fi, even if said Wi-Fi enabled device isn’t a cellular one. The problem is you need a cellular signal for your hotspot to work so if your signal is weak, you could run into problems. However, you can fiddle with where your hotspot is located, and position it where the cell phone signal is the strongest. You can also consider getting a cell phone signal booster to enhance the signal you’re getting for your hotspot.

    Garrison J. Stone on
  • Right now i search about DAS Network to distribute a signal in a larger building but how can we use the Active DAS System in a efficient way that might be used in a 14 floor building…..

    Faroz Khan on
  • I’m not sure if this is the right place to ask this, but how do I increase the wifi coverage area of my 4G hotspot? I’ve got the hotspot, now I want it to work further than it currently does.

    Blake Urich on
  • I heard the term DAS network and had no idea what it meant. The only thing I remembered was DOS, that old school computer operating system. I had to look it up so after coming up with DAS telecom, I saw DAS stands for “distributed antenna system.” A distributed antenna system design will allow a big building to have the same level of strong cell phone signals throughout it because of distributed antenna system architecture, which runs throughout the building. This can also be set up outdoors by distributed antenna system companies which specialize in this area. Now that I’ve read this blog, I feel like I know all about DAS. Now if I could only remember what I used to know about DOS.

    Riley Benjamin on
  • There’s a lot of information about cell phone boosters, but I’ve heard about DAS and wondered what DAS is and how DAS works. Apparently, the active DAS components are spread throughout a building to make sure there are consistently strong signals, no matter where you go. So for example if you go in a stadium and are on the lower level surrounded by a lot of concrete and metal, you’ll still have a strong cell phone signal and won’t have to worry about dropped calls or slow data.

    Arnold Paulson on
  • It doesn’t seem right that you go to a large building or facility and can’t get a strong signal for your cell phone, but it happens often, whether you’re at a stadium, a mall, or a government building. It’s good to know distributed antenna system design can fix this problem for any building. Congratulations to whoever wrote this article because it explains cellular das systems well, and what equipment and procedures are necessary to make cell phones work throughout the area.

    S. Pendelton on

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