chapter 16 other wireless networks
TRANSCRIPT
Chapter 16
Other Wireless
Networks
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chapter 16: Outline
16.1 WiMAX
16.2 Cellular Telephony
16.3 Satellite Networks
Chapter 16: Objective
The first section discusses the WiMAX, a wireless access
network that can replace the wired access networks we
discussed in Chapter 14. The section first describes
services provided by this network. It then describes the
IEEE 802.16 project as the basis of the network. The
section finally defines the link-layer and the physical layer of
WiMAX.
The second section discusses cellular telephone networks.
It explains the frequency reuse principle. It then describes
the general operations of this network.
The third section discusses satellite networks. It first
describes the operations of the all types of satellites. The
section then defines GEO satellites and their characteristics,
then moves to MEO satellites and shows their applications.
16.4
16-1 WiMAX
People want to have access to the Internet
from home or office (fixed) where the wired
access to the Internet is either not available
or is expensive. People also need to
access the Internet when they are using
their cellular phones. WiMAX (Worldwide
Interoperability for Microwave Access) has
been designed for these types of
applications.
16.5
16.1.1 Services
WiMAX provides two types of services to
subscribers: fixed and mobile.
16.6
Figure 16.1: Fixed WiMAX
16.7
Figure 16.2: Mobile WiMAX
16.8
16.1.2 IEEE Project 802.16
• WiMAX is the result of the IEEE 802.16
project. The standard is sometimes referred
to as wireless local loop, in contrast with
wired local loop (dial-up, DSL, or cable).
• Before we discuss this standard, let us
compare the 802.16 and 802.11 projects.
• First, 802.11 is a standard for a wireless LAN;
802.16 is a standard for a wireless WAN (or
MAN).
• Project 802.11 defines a connectionless
communication; project 802.16 defines a
connection-oriented service.
16.9
16.1.3 Layers in Project 802.16
Figure 16.3 shows the layers in the 802.16
project. IEEE has divided the data-link layer into
three sublayers and the physical layer into two
sublayers.
16.10
Figure 16.3: Data-link and physical layers
16.11
Figure 16.4: MAC frame format
16.12
Figure 16.5: Frame structure at the physical layer
16.13
16-2 Cellular Telephony
Cellular telephony is designed to provide
communications between two moving units,
called mobile stations (MSs), or between
one mobile unit and one stationary unit,
often called a land unit. A service provider
must be able to locate and track a caller,
assign a channel to the call, and transfer
the channel from base station to base
station as the caller moves out of range.
16.14
Figure 16.6: Cellular system
CO
16.15
16.2.1 Operation
Let us first briefly discuss the operation of the
cellular telephony.
• Transmitting: MS–BS–MSC–PSTN-CO- phone
• Receiving: CO-PSTN-MSC-Paging-BS-MS
• Frequency-reuse principle: reuse factor
• Handoff: hard vs. soft
• Roaming
16.16
Figure 16.7: Frequency reuse patterns
16.17
16.2.2 First Generation (1G)
Cellular telephony is now in its fourth generation.
The first generation was designed for voice
communication using analog signals. We
discuss one first-generation mobile system used
in North America, AMPS.
16.18
Figure 16.8: Cellular bands for AMPS
16.19
Figure 616.9: AMPS reverse communication band
16.20
16.2.3 Second Generation (2G)
To provide higher-quality (less noise-prone)
mobile voice communications, the second
generation of the cellular phone network was
developed. While the first generation was
designed for analog voice communication, the
second generation was mainly designed for
digitized voice. Three major systems evolved in
the second generation: D-AMPS, GSM, and IS-
95.
16.21
Figure 16.10: D-AMPS
16.22
Figure 16.11: GSM bands
(Global System for Mobile Communication)
16.23
Figure 16.12: GSM
GMSK: Gaussian Minimum Shift Keying
16.24
Figure 16.13: Multiframe components
16.25
Figure 16.14: IS-95 forward transmission
CDMA
16.26
Figure 16.15: IS-95 reverse transmission
DSSS
16.27
16.2.4 Third Generation (3G)
The third generation of cellular telephony refers
to a combination of technologies that provide
both digital data and voice communication.
Using a small portable device, a person is able
to talk to anyone else in the world with a voice
quality similar to that of the existing fixed
telephone network. A person can download and
watch a movie, download and listen to music,
surf the Internet or play games, have a video
conference, and do much more. The third-
generation concept started in 1992, when ITU
issued a blueprint called the Internet Mobile
Communication 2000 (IMT-2000).
16.28
Figure 16.16: IMT-2000 radio interfaces
W-CDMA CDMA-2000
16.29
16.2.5 Fourth Generation (4G)
• The fourth generation of cellular telephony is
expected to be a complete evolution in
wireless communications. Some of the
objectives defined by the 4G working group:• Spectrum efficiency
• High network capacity
• 100Mbps for moving users, 1Gbps for stationary
users
• All IP, packet-switched network
• New techniques:• OFDMA (Orthogonal FDMA)
• 64-QAM for LTE (Long Term Evolution)
• SDR (Software Defined radio)
• MIMO (Multiple-input multiple-output)
16.30
16-3 Satellite Network
A satellite network is a combination of
nodes, some of which are satellites, that
provides communication from one point on
the Earth to another. A node in the network
can be a satellite, an Earth station, or an
end-user terminal or telephone.
16.31
16.3.1 Operation
Let us first discuss some general issues related
to the operation of satellites.
• Orbits
• Frequency bands
16.32
Figure 16.17: Satellite orbits
What is the period of the moon, according to Kepler’s law?
Example 16.1
Here C is a constant approximately equal to 1/100. The
period is in seconds and the distance in kilometers.
16.33
According to Kepler’s law, what is the period of a satellite
that is located at an orbit approximately 35,786 km above
the Earth?
Example 16.2
16.34
Table 16.1: Satellite frequency bands
16.35
16.36
Figure 16.18: Satellite orbit altitudes
Radiation belt: a layer of energetic charged particles that is held in place
around a magnetized planet, such as the Earth, by the planet's magnetic
field.
16.37
16.3.2 GEO Satellites
Line-of-sight propagation requires that the
sending and receiving antennas be locked onto
each other’s location at all times (one antenna
must have the other in sight). For this reason, a
satellite that moves faster or slower than the
Earth’s rotation is useful only for short periods.
To ensure constant communication, the satellite
must move at the same speed as the Earth so
that it seems to remain fixed above a certain
spot. Such satellites are called geostationary.
16.38
Figure 16.19: Satellites in geostationary orbit
16.39
16.3.3 MEO Satellites
Medium-Earth-orbit (MEO) satellites are
positioned between the two Van Allen belts. A
satellite at this orbit takes approximately 6 to 8
hours to circle the Earth.
16.40
Figure 16.20: Orbits for global positioning system (GPS) satellites
24 satellites in six orbits
At any time, 4 satellites are visible from any point on Earth
16.41
Figure 16.21: Trilateration on a plane
2 2 2
2 2 2
2 2 2
( ) (y )
( ) (y )
( ) (y )
A A A
B B B
C C C
x x y r
x x y r
x x y r
16.42
2 2 2 2
2 2 2 2
2 2 2 2
( ) (y ) ( )
( ) (y ) ( )
( ) (y ) ( )
A A A A
B B B B
C C C C
x x y z z r
x x y z z r
x x y z z r
16.43
2 2 2
1
2 2 2
2 2
2 2 2
3 3 3
( ) (y)
( ) (y)
( ) (y )
x r
x x r
x x y r
16.44
2 2 2
1 1 1
2 2 2
2 2 2
2 2 2
3 3 3
( ) (y )
( ) (y )
( ) (y )
x x y r
x x y r
x x y r
2 2 2 2 2 2
1 2 2 1 1 2 2 1 2 1
2 2 2 2 2 2
1 3 3 1 1 3 3 1 3 1
2 ( ) 2 ( )
2 ( ) 2 ( )
x x x x x y y y y y r r
x x x x x y y y y y r r
16.45
16.3.4 LEO Satellites
• Low-Earth-orbit (LEO) satellites have polar
orbits.
• The altitude is between 500 and 2000km, with
a rotation period of 90 to120 minutes.
• A LEO system usually has a cellular type of
access
• The footprint normally has a diameter of 8000
km
16.46
Figure 16.22: LEO satellite system
ISL: Inter-Satellite Link
UML: User Mobile Link
GWL: gateway Link