Distributed
Antenna Systems (DAS)
Objectives:
From this self-study program you should learn:
- How
distributed
antenna systems are designed to maximize
coverage
- How
cabling connects all elements of a distributed
antenna systems
- What
types of cabling (copper or fiber) are used in distributed
antenna systems
- Issues
in designing and installing distributed
antenna systems cabling.
Introduction
The
landscape is covered with cellular towers but the
majority of cellular connections (70-80% for both
voice or data) originate inside buildings, so wireless
coverage inside buildings has become more important.
Cellular wireless signals often cannot penetrate walls
and even windows in large buildings, requiring
low-power cellular antennas placed inside buildings to
provide reliable service.
There are several other reasons for cellular systems
inside buildings or structures. Sometimes the number
of users inside a building like a convention center or
sports facility exceeds the bandwidth of a single
cellular system. In many areas, local laws specify the
need for public safety radio signal coverage (fire,
police, emergency) inside every building that requires
indoor antenna coverage.
Auto or mass transit tunnels are also obvious
applications for cellular distributed antenna systems.
A distributed antenna system is a fairly straightforward
installation, similar to a LAN connected to the Internet
with one major exception - a DAS may be shared by all
cellular service providers rather than be limited to one
user or one ISP. DAS for most facilities will use fiber
backhaul for the cellular connections because of the
bandwidth requirements. Small buildings may use an antenna
on the roof and coax cable for distribution inside the
facility, called a Passive DAS, but they are becoming
rare. DAS
cabling resembles structured cabling or OLAN cabling and
in fact can share the backbone cables if there are
sufficient fibers available. Since most DAS cabling is
singlemode, compatibility with the new generation GPON
OLAN which uses singlemode fiber is easiest.
DAS digital electronics are usually from one of two
standard system types set up by manufacturers for
compatibility. Cabling has no standard although TIA is
working on such a document, but it may take years to be
finished and does not seem to cover the typical digital
system architectures. Manufacturers of the equipment or
service providers generally dictate the cabling
architecture and specifications. So
as is the FOA’s procedure, we will summarize the options
and provide guidance on how the DAS is generally designed
and built and not spend our time on standards that will be
changing continuously! We do however try to keep our
references up to date.
In addition to the information on DAS design and cabling
options, we include links in this self-study program to
information relevant to installation.
Assignments
You
will be instructed to read the references or watch videos
and take the quiz (Test Your Knowledge) to complete the
"classroom" part of the course.
Get
Started
Watch
The Video
FOA
YouTube Video Lecture 40,
Distributed Antenna Systems
Read
The Online FOA Reference
FOA
Reference Guide,
Distributed Antenna Systems
Test
Your Knowledge - DAS
Cabling - Quiz
Lesson
Plans
Read
the materials or watch the videos linked on each lesson
plan and take the quiz.
Lesson 1:
Overview - How Wireless Networks Use Fiber Optics
Lesson 2: Fiber
To The Cell Site And
Fiber To The Antenna
Lesson 3: Distributed Antenna Systems (DAS)
Lesson
4: Small Cells
Lesson 5: WiFi -
Enterprise, Urban and Rural
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