Chapter 16
Wireless WANs:
Cellular Telephone
and Satellite Networks
16.1
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
16-1 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.
Topics discussed in this section:
Frequency-Reuse Principle
Transmitting
Receiving
Roaming
First Generation
Second Generation
Third Generation
16.2
Figure 16.1 Cellular system
16.3
Figure 16.2 Frequency reuse patterns
16.4
16.5
16.6
1G
2G
GSM
AMPS
2.5G
GPRS
30-50 kbps
D-AMPS
IS-136
CDMA
IS-95
iDEN
Nextel
2.75G
3G
UMTS
Wideband-CDMA
Wireless-CDMA
384kbps; AT&T,
T-Mobile
EDGE
75-135kbps
iPhone (1st
generation)
1xRTT
CDMA2000
1x
IS-2000
144 kbps
CDMA2000
EV-DO
1xEV
EV
IS-856
2.5 Mbps down
154 kbps up
Verizon, Sprint
AT&T, Verizon, and Alltel now support LTE.
What about WiMax for 4G?
16.7
3.5G
HSPA
High speed
packet access
400-700kbps
(or 3G ?)
CDMA2000
EV-DV
Dead?
3.1 Mbps down
1.8 Mbps up
4G
LTE?
Long-term
Evolution
3-5 Mbps
UMB ??
UltraMobile
Broadband
WiMax??
EV-DO Rev.A
Up to 3.1Mbps
Wi-Fi???
Note
AMPS is an analog cellular phone
system using FDMA.
16.8
Figure 16.3 Cellular bands for AMPS
16.9
Figure 16.4 AMPS reverse communication band
16.10
Figure 16.5 Second-generation cellular phone systems
16.11
Figure 16.6 D-AMPS
16.12
Note
D-AMPS, or IS-136, is a digital cellular
phone system using TDMA and FDMA.
16.13
Figure 16.7 GSM bands
16.14
Figure 16.8 GSM
GSM uses TDMA and FDMA concepts
GMSK (Gaussian minimum shift keying):
a form of FSK used in European systems
16.15
Figure 16.9 GSM Multiframe components
Lots of overhead!!
16.16
Figure 16.10 IS-95 CDMA forward (base to mobile) transmission
19.2 ksps = 19.2 kilosignals per second
19.2 ksps signal converted to 64-chip
sequence, giving 1.228 Mcps (mega-chips)
ESN: electronic serial
number of handset
ESN is used to generate 2^42 pseudorandom chips, each having
42 bits. Decimator chooses 1 bit out of the 64, and then is
scrambled with digitized voice to create privacy.
16.17
Figure 16.11 IS-95 CDMA reverse (mobile to base) transmission
Each 6 symbols are used to index into a 64x64 Walsh matrix; thus each 6-symbol chunk
is replaced (not multiplied as it would be with CDMA) with a 64-chip code.
A 42-bit unique code is generated by the mobile
hand set and combined with the 307.2 kcps signal
creating a 1.228 Mcps signal.
Note: CDMA not used here because no way of syncing all mobile devices together!
Frequency reuse is 1, since neighboring channels cannot interfere with CDMA or
DSSS transmission.
16.18
2.5 Generation iDEN
iDEN (Integrated Dispatch
Enhanced Network)
• Functionally the same as MIRS
(Motorola Integrated Radio
System)
• A high-capacity digital trunked
radio system providing integrated
voice and data services to its
users
• Used by Nextel Communications
16.19
2.5 Generation GPRS
GPRS (General Packet Radio
Service)
• The 2.5G version of GSM
• Theoretically allows each user
access to 8 GSM data channels at
once, boosting data transfer speeds
to more than 100 Kbps (30 Kbps in
the real world since it only uses 2
GSM channels)
• AT&T Wireless, Cingular, T-Mobile
16.20
2.5 Generation 1xRTT
1xRTT (CDMA2000) 1x Radio
Transmission Technology
• The 2.5G backwards compatible
replacement for CDMA
• 1xRTT will replace CDMA and iDEN
• 1x means that it requires only the
same amount of spectrum as 2G
networks based on CDMA (IS-95)
•Sprint and Verizon
16.21
3rd Generation UMTS
UMTS (Universal Mobile
Telecommunications System)
• Also called Wideband CDMA
• The 3G version of GPRS
• UMTS is not backward compatible
with GSM, so first UMTS phones will
have to be dual-mode
• Based on TDMA, same as D-AMPS
and GSM
16.22
3rd Generation 1xEV
1xEV (1x Enhanced Version)
• The 3G replacement for 1xRTT
• Will come in two flavors
• 1xEV-DO for data only
• 1xEV-DV for data and voice
16.23
EDGE
EDGE (Enhanced Data rates
for Global Evolution)
• Further upgrade to GSM
• Possible 3G (no – 2.75G)
replacement for GPRS
• Uses improved modulation to triple
the data rate where reception is
clear
16.24
LTE
LTE (3GPP LTE – Long Term
Evolution)
16.25
• 3G upgrade to UMTS
• 3GPP – third generation partnership
project
• LTE actually an architecture – contains
EPS (evolved packet system), EUTRAN
(evolved UTRAN), and EPC (evolved
packet core)
•OFDM, QPSK, 16QAM, 64QAM, MIMO
16-2 SATELLITE NETWORKS
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 enduser terminal or telephone.
Topics discussed in this section:
Orbits
Footprint
Three Categories of Satellites
GEO Satellites
MEO Satellites
LEO Satellites
16.26
Figure 16.13 Satellite orbits
16.27
Example 16.1
What is the period of the Moon, according to Kepler’s
law?
Here C is a constant approximately equal to 1/100. The
period is in seconds and the distance in kilometers.
16.28
Example 16.1 (continued)
Solution
The Moon is located approximately 384,000 km above the
Earth. The radius of the Earth is 6378 km. Applying the
formula, we get.
16.29
Example 16.2
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?
Solution
Applying the formula, we get
16.30
Example 16.2 (continued)
This means that a satellite located at 35,786 km has a
period of 24 h, which is the same as the rotation period of
the Earth. A satellite like this is said to be stationary to the
Earth. The orbit, as we will see, is called a
geosynchronous orbit.
16.31
Figure 16.14 Satellite categories
16.32
Figure 16.15 Satellite orbit altitudes
16.33
Table 16.1 Satellite frequency bands
L: GPS
S: weather, NASA, Sirius/XM satellite radio
C: open satellite communications
Ku: popular with remote locations transmitting back to TV studio
Ka: communications satellites
16.34
Figure 16.16 Satellites in geostationary orbit
16.35
Figure 16.17 Orbits for global positioning system (GPS) satellites
16.36
Figure 16.18 Trilateration
16.37
Figure 16.19 LEO satellite system
UML: user mobile link
GWL: gateway link
ISL: intersatellite link
16.38
Figure 16.20 Iridium constellation
16.39
Note
The Iridium system has 66 satellites in
six LEO orbits, each at an
altitude of 750 km.
16.40
Note
Iridium is designed to provide direct
worldwide voice and data
communication using
handheld terminals, a service similar to
cellular telephony but on a global scale.
16.41
Figure 16.20 Teledesic
16.42
Note
Teledesic has 288 satellites in 12 LEO
orbits, each at an altitude of 1350 km.
16.43