I will use a lot of terms and acronyms in this website and I will define them as we go through the materials. However, some of the words or phrases I will use more frequently than others. I want to go over those frequently used terminologies and the context they are used before we dive into the materials. 

Frequently used terms & phrases in this site

Wireless: 

Everyone knows what wireless means. So I am not talking about wireless in general. 'Wireless' for DAS has a special meaning. 

To explain, let me tell you the difference of WiFi and DAS. People are more used to WiFi – because that is all around them. Both are wireless networks. But WiFi operates on 'unlicensed' or public frequencies - 2.4 GHz for example.  Basically, we don't have to pay for these frequencies. 

When it comes to DAS, the signals we will use those frequencies belong to companies such as AT&T, Sprint, T-Mobile, U.S. Cellular, Vodafone, Verizon, etc. So, wireless frequencies we deal with in DAS are 'licensed'. These companies actually paid the government for the frequencies they use. 

DAS

DAS is also known as in-building wireless system. This is a popular description; but you will soon find out that we have indoor as well as outdoor DAS.

DAS stands for Distributed Antenna Systems. This may sound complicated, but essentially DAS is a signal plumbing system. Just like your building has intricate plumbing system throughout the building for water, DAS is a plumbing system for cellular signal. It's a way to deal with spots of poor signal coverage inside a large building by installing a network of small antennas throughout the building. 

There was a time when DAS pretty much meant in-building 'wireless' system.  But it has evolved and now it can cover both indoor and outdoor. iDAS for indoor DAS, and oDAS for Outdoor DAS.

Throughout this website, I'll refer to 3 generations of DAS, differentiated by cable used. I will identify them as:

1. DAS 1.0 (when we use just coaxial  cable or coax in short), 

2. DAS 2.0 (when we use fiber and coax), and  

3. DAS 3.0 (when we use all fiber). 

Whenever you talk about DAS, people usually understand DAS 2.0 - which uses both fiber and coax for cabling. DAS 2.0 is also known as Active DAS or Fiber DAS. DAS 3.0 is not very well known, but soon most of the DAS you will see are going to be all-fiber or DAS 3.0.

A quick disclaimer, all DAS we will talk about processes cellular and public safety DAS. 

Operators or Carriers:

Operators and carriers are Wireless Service Providers. We will use this term on almost every other page. 

Basically whoever you are paying for your cell phone or the SIM card every month is a Wireless Service Provider.  So in U.S., for example, AT&T, Sprint, T-Mobile, U.S. Cellular, Verizon, are all Wireless Service Providers. Throughout our articles, we will call the Wireless Service Providers as Operators or Carriers in short.   Both of these terms are used frequently in the industry.

So, DAS we will discuss on this website may be beginning to take shape.  We will only focus on carrier-grade DAS that works in ‘licensed’ wireless frequencies. What do I mean by carrier-grade DAS? These are DAS systems where Carriers will most likely provide signal sources. More on this later.

Electronics or 'active' materials:

Whenever I use electronics, you can assume these will need electricity to work. Electronics are also known as Active Materials in DAS.

'Infrastructure' or 'passive' materials:

All other materials for DAS will be grouped under passive or infrastructure materials. Passive because it does not require electricity.

Infrastructure because these passive materials form the underlying framework for the DAS to work.

Example of passive materials will be, coaxial and fiber cable, antennas, connectors, dividers and couplers etc.

Coax:

I use the word Coax quite often ... coax is basically coaxial cable. We will learn more about coax soon.

Signal (RF) Source:

Whenever I say Signal, I mean RF or Radio Frequency signal.

By Signal, I also mean the 'licensed' signal that the operators like Sprint, AT&T, Verizon own. Source of signal or signal source is basically base station, or small cell, or even signal booster. 

Signal source legitimately can only come from Carriers or Operators. Or they have to be explicitly approved by them. 

Single-Carrier DAS:

Most DAS 1.0 systems are single-carrier DAS, because they usually handle 1 carrier or operator (such as Sprint). In other words, for example, if you are getting say just Sprint signal out of a DAS, most likely that is a single-carrier DAS. 

Exceptions always exist. That means you may have a DAS 1.0 system that is a multi-carrier – which is rare, or you may get a DAS 2.0 system which is single-carrier.

Multi-Carrier DAS or Neutral Host DAS:

Most of the time, when I talk about DAS, I am referring to Multi-Carrier or Multi-Operator DAS. Especially, DAS 2.0 and DAS 3.0 systems.

Multi-Carrier or Multi-Operator DAS systems can process or transport cellular signals from multiple operators such as AT&T, Sprint, T-Mobile, Verizon etc. Multi-Carrier DAS is often referred to as Neutral Host DAS. Although this term (i.e., Neutral Host DAS) is more popular, there is no true 'neutral host' DAS. So I prefer the Multi-Carrier DAS.

DL/UL:

DL & UL stand for Downlink and Uplink. When a signal is coming down from the signal source to your cell phone that is downlink signal.

When your cell phone is sending signal back to the signal source for processing, then you are talking about uplink. 

One easy way to remember, what you 'hear' on your phone is coming through downlink, and when you are 'talking' on your phone you are sending your words into uplink.

Explaining Downlink (DL) and Uplink (UL)

Low Voltage Vendor

Low Voltage Vendors are the guys who install Security Systems, Audio/Visual Solutions, Fiber Optics, Networking Systems, Voice & Data Cabling etc. inside buildings. Most of the large commercial buildings or campus have a set of low voltage vendors that they know very well, familiar with their work, and hence trust them.

The same people can be used for installing passive materials for DAS such as cable, antennas, couplers, and even electronics.