Chapter 16 DAS

Question 1

What is a distributed
antenna system (DAS)?

Answer 1

A DAS transmits and receives or
relays RF signals (e.g., signals from
cellular telephones, private LMR
services, pagers, WLANs) within
buildings, structures, tunnels, or
other areas where wireless
services cannot be provided
because of lack of signal
penetration from outdoor networks
or where no suitable outdoor
network exists.
TDMM: Page 16-25

Question 2

Name 7 components
of a DAS.

Answer 2

I . Transmitters
2. Receivers
3.AmpIifiers
4.Converters
5.Cabling
6.Connectors
7.Antennas
TDMM: Page 16-25

Question 3

Name 5 types of cable that
are commonly recognized
for DAS cabling
distribution.

Answer 3

1 .Singlemode optical fiber cabling
2.Multimode optical fiber cabling
3.Hybrid optical fiber cabling
4.Balanced twisted-pair cabling
5.Coaxial cable
TDMM: Page 16-28

Question 4

What category/class of
balanced twisted-pair
cabling is recommended
for DAS cabling
distribution?

Answer 4

Category 6A/Class EA
TDMM: Page 16-28

Question 5

Excluding the base station
hardware, what is the most
expensive part of a DAS?

Answer 5

The antenna network
TDMM: Page 16-29

Question 6

Name the 4 types of
antennas used in a DAS.

Answer 6

1. Omnidirectional
2. Directional
3. Radiating cable
4. Combination of all three
   TDMM: Page 16-29

Question 7

What type of antenna
broadcasts equally in all
directions of only one cross
section of its toroidal
(doughnut-shaped)
three-dimensional
radiation pattern?

Answer 7

Omnidirectional
TDMM: Page 16-29

Question 8

What type of antenna
concentrates the radiated
signal in one direction more
than in another or receives
a signal more readily from
one direction than from
another?

Answer 8

Directional
TDMM: Page 16-30

Question 9

Why is a radiating coaxial
cabling useful in combined
systems?

Answer 9

Because it has a wide
bandwidth, allowing operation
from 70 MHz to more than
2.4 GHz (with some limitations)
TDMM: Page 16-30

Question 10

True or False
A radiating cable should be
placed in a metal conduit
for protection.

Answer 10

False. A radiating cable cannot
be placed in a metal conduit
because it would block the
radiating signal from the cable.
For this reason, the cable must
conform to the environmental
flame spread and fire code
requirements.
TDMM: Page 16-31

Question 11

Name 5 common types of
active DAS equipment.

Answer 11

1. Transceivers
2. Bidirectional amplifiers
3. Unidirectional amplifiers
4. Repeaters
5. Power supply units
   TDMM: Page 16-34

Question 12

What is a transceiver?

Answer 12

A device that uses many of its
components to transmit and
receive RF signals
TDMM: Page 16-34

Question 13

What function is performed
by the power supply unit?

Answer 13

The power supply unit converts
the commercial ac power to dc
operating voltages.
TDMM: Page 16-34

Question 14

What is the primary
headend device?

Answer 14

Main control unit (MCU)
TDMM: Page 16-35

Question 15

Name 3 suitable
locations for an MCU.

Answer 15

1 .Main equipment room (ER)
2. Telecommunications room (T R)
3.Penthouse near the roof
TDMM: Page 16-36

Question 16

Where is DAS backend
equipment typically
located?

Answer 16

In the TR
TDMM: Page 16-38

Question 17

Name 6 examples of DAS
backend equipment.

Answer 17

1. Secondary processors
2. Power supplies
3. Host ports
4. Amplifiers and transceivers
5. Antenna ports
6. Antennas
   TDMM: Page 16-37

Question 18

Name the 3 primary means
used by active DAS to
transport radio signals.

Answer 18

1. Analog modulation of RF
   signals onto an optical carrier
2. Down conversion of RF
   signals to IF
3. Digital sampling of RF signals
   TDMM: Page 16-39

Question 19

What is an advantage of
analog modulation?

Answer 19

The ability to modulate a large
portion of the radio spectrum
over one optical path
TDMM: Page 16-40

Question 20

What is a major problem
associated with analog
systems?

Answer 20

The direct dependency of the
modulation and recovery of the
RF signal to the optical transport
TDMM: Page 16-40

Question 21

What is the primary
medium used for DAS
analog systems?

Answer 21

Singlemode optical fiber
TDMM: Page 16-40

Question 22

How do DAS analog
systems compensate for
the dependency on optical
losses?

Answer 22

By using an automatic gain
control (AGC) as a feedback
loop to maintain constant
optical strength over the optical
fiber plant
TDMM: Page 16-40

Question 23

How is passive distribution
equipment in a DAS
defined?

Answer 23

As equipment that does not
require external power input
TDMM: Page 16-41

Question 24

What is a
directional coupler?

Answer 24

A linear device that uses
induction or another method to
differentially split downlink
power from an input connector
to two or more output
connectors
TDMM: Page 16-41

Question 25

What piece of passive DAS equipment combines dc power with the ac RF signal on a coaxial cable and taps it off at the other end?

Answer 25

Bias tee TDMM: Page 16-41

Question 26

What piece of passive DAS equipment is used to combine two wireless bands to a single antenna feed or distribution cable?

Answer 26

Hybrid coupler TDMM: Page 16-41

Question 27

Which piece of passive DAS equipment accepts an input signal and delivers multiple output signals with specific phase and amplitude characteristics?

Answer 27

Power splitter TDMM: Page 16-41

Question 28

Name 3 characteristics of output signals in passive distribution equipment.

Answer 28

1. Equal amplitude 2. Zero degree phase relationship between any two output signals 3. High isolation between each output signal TDMM: Page 16-41

Question 29

Name 2 common topologies that serve a DAS within a building structure.

Answer 29

1 .Star topology 2.Tapped trunk topology TDMM: Page 16-42

Question 30

Name 3 factors that may affect the selection of a cabling topology for a DAS.

Answer 30

1 .DAS equipment 2.Cabling medium used in a new installation 3.Legacy cabling system in a previous installation TDMM: Page 16-42

Question 31

What cabling mediums may be used in the installation of a star topology?

Answer 31

*Balanced-twisted pair *Coaxial *Optical fiber *Combination TDMM: Page 16-42

Question 32

What types of cabling may be used to install a tapped trunk topology?

Answer 32

*Coaxial *Optical fiber TDMM: Page 16-42

Question 33

What component is used to "tap" into the coaxial cable of a tapped trunk topology?

Answer 33

Splitter or vampire tap TDMM: Page 16-42

Question 34

Name 2 potential problems associated with using a DAS to support mobile communications in buildings.

Answer 34

1 .Availability and usability of RF signals in the intended coverage areas (coverage) 2.Ability to support the demands of the system users and recipients (capacity) TDMM: Page 16-42

Question 35

Name the 3 phases associated with DAS design.

Answer 35

1. Pre-Installation 2.Installation 3.Acceptance/implementation TDMM: Page 16-42

Question 36

What is the purpose of conducting RF measurements during an on-site survey of the radio environment?

Answer 36

To identify existing signals and their frequency and strength TDMM: Page 16-46

Question 37

Name 2 factors that determine the overall usability and capability of an installed DAS.

Answer 37

1 .Antenna Selection 2.Antenna Location TDMM: Page 16-46

Question 38

What is the link loss budget (operating margin)?

Answer 38

The sum of ICT gains and losses in an ITS, beginning with the transmitter and continuing to the receiver, including transmission line loss and antenna gains TDMM: Page 16-46

Question 39

Name 3 objectives of diplexing.

Answer 39

1 .Maintain proper transmission limits set by the manufacturer or regulatory body 2.Provide adequate bandwidth at each frequency that is diplexed 3.Control and minimize signal loss TDMM: Page 16-48

Question 40

What is duplexing?

Answer 40

Combining the forward and reverse signal paths into a single cable TDMM: Page 16-48

Question 41

Name 6 applications where battery backup for the DAS is typically required.

Answer 41

1 .Private security services 2.Hospitals and health care facilities 3.Mining and mine operations 4.Government and military installations 5.Financial markets 6.Life safety issues TDMM: Page 16-49

Question 42

Name 6 strategies for mitigating interference between a DAS and other RF frequencies that are in use in the area.

Answer 42

1 .ReIocate transmission devices 2.Adjust or reassign transmission frequency 3.RepIace receiving antennas 4.Discontinue the use of an interfering frequency 5. Install RF filters or chokes 6. Install RF shielding material TDMM: Page 16-50