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materialisticgumneckElectronics - Devices

Nov 27, 2013 (3 years and 8 months ago)

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Review Questions

1.

A wireless _____ area network is designed for hand
-
held and portable devices
that transmit at slow to moderate speeds.

a.

personal

b.

wide

c.

metropolitan

d.

small

2.

Communications between one sender and multiple receivers is known as _____
transmis
sion.

a.

point
-
to
-
point

b.

point
-
to
-
multipoint

c.

multipoint
-
to
-
router

d.

bridge
-
to
-
point

3.

Each of the following is a wireless personal area network technology except

a.

IrDA

b.

IEEE 802.15.1 (Bluetooth)

c.

IEEE 802.15.4

d.

UART
-
705

4.

One type of 802.15.1 (Bluetooth) network is a
(n)


a.

piconet

b.

meshnet

c.

corenet

d.

linknet

5.

IEEE 802.15.1 (Bluetooth) uses

a.

Orthogonal Frequency Distribution Spectrum

b.

Resource Device Allocation Spectrum

c.

Frequency Hopping Spread Spectrum

d.

Direct Sequence Spread Spectrum

6.

Ultrawideband (IEEE 802.15.3a) is faster t
han IEEE 802.15.3.
True

or
False?

7.

There currently is no IEEE standard to address sensors that require low power
consumption and low cost.
True

or

False
?

8.

RFID tags can be either passive or active.
True

or False?

9.

Devices based on the Infrared Data Associati
on (IrDA) standards can transmit at
much higher rates than IEEE 802.11g networks.
True

or
False
?

10.

Free space optics (FSO) uses radio frequency (RF) transmissions.
True

or
False
?

11.

_____ is a wireless technology similar to Local Multipoint Distribution Service

(LMDS) except that it can transmit at greater distances.
Multichannel
Multipoint Distribution Service (MMDS)

12.

A WMAN technology that can transmit shared data rates of 70 Mbps is _____.
WiMAX (IEEE 802.16)

13.

The type of satellite that is closest to the earth
when it orbits is _____.
low earth
orbiting (LEO) satellite

14.

A wireless _____ area network is designed for devices in an area up to 50
kilometers (31 miles) using RF or infrared transmissions.
metropolitan

15.

The three main categories of WPAN technologies are

IEEE 802.15 standards,
IrDA and _____.
Radio frequency ID (RFID)

16.

Explain how an IEEE 802.15.1 (Bluetooth) pionet functions.

There are two types of 802.15.1 network topologies; the most common is known as a
piconet. When two 802.15.1 devices come within r
ange of each other, they
automatically connect with one another. One device is the master, which controls all
of the wireless traffic. The other device is known as a slave, which takes commands
from the master. An 802.15.1 network that contains one master
and at least one
slave and that use the same channel forms a piconet. 802.15.1 slave devices that are
connected to the piconet and are sending transmissions are known as active slaves;
devices that are connected but are not actively participating are calle
d parked
slaves.


17.

What is Ultrawideband and what is its design goal?

While work on the 802.15.3 standard was ongoing, it was decided that an alternative
study group would be formed to look at even higher data rates than 55 Mbps.
Known as the IEEE 802.15.3
a, it will support data transfers up to 110 Mbps
between a maximum of 245 devices at a distance of 10 meters. Also known as
Ultrawideband, one of its goals is to make
the 802.15.3a standard compelling
enough to entice personal computer hardware vendors to

incorporate the
technology into their computers and compete against USB 2.0 (480 Mbps) and
Firewire or IEEE 1394 (393 Mbps). Currently the 802.15.3a group is working on a
faster rate of 200 Mbps at 4 meters (12 feet).


18.

What is the difference between passi
ve RFID tags and active RFID tags?

Passive RFID tags do not have their own power supply. Instead, the tiny electrical
current induced in the antenna by the incoming signal from the transceiver provides
enough power for the tag to send a response. Because
it does not require a power
supply, passive RFID tags can be very small, some of which are only 0.4 mm × 0.4
mm and thinner than a sheet of paper. However, the amount of data which is sent
back must also be very small, typically just an ID number. Passive
tags have ranges
that vary from about 10 millimeters up to 6 meters. Active RFID tags must have
their own a power source. Although this makes the tags larger (such as the size of a
coin), it enables the tags to have longer ranges and larger memories than
passive
tags, as well as the ability to store additional information sent by the transceiver.
Many active tags have a range of 30 or more meters and a battery life of several
years.


19.

Describe the last
-
mile connection.

This refers to the connection that b
egins at a fast Internet service provider, goes
through the local neighborhood, and ends at the home or office. Whereas the
connections that make up the nation’s data transmission infrastructure are very fast
and well established, the last mile connection
that links these high
-
speed
transmission lines to the home or office are much slower and not universally
available. These slow last mile connections are bottlenecks for users: any high
-
speed
traffic must be throttled back to the slow speed of the last
-
mile

connection, which
reduces the overall speed of the connection.


20.

Explain how atmospheric conditions can impact Free Space Optics (FSO).

The primary disadvantage of FSO is that atmospheric conditions can have an
impact on FSO transmissions. Turbulence caus
ed by wind and temperature
variations can create pockets of air with rapidly changing densities. These air
pockets can act like prisms and lenses to distort an FSO signal. Inclement weather is
also a threat. Although rain and snow can distort a signal, fog

does the most damage
to transmission. Fog is composed of extremely small moisture particles that act like
prisms upon the light beam, scattering and breaking up the signal. However, FSO
can overcome turbulence by sending the data in parallel streams from

several
separate laser transmitters. These transmitters are all mounted in the same link
head but separated from one another by distances of several inches. It is unlikely
that while traveling to the receiver all the parallel beams will encounter the same

pocket of turbulence since the pockets tend to be small.