16.1

Chapter 16

Wireless WANs: Cellular Telephone and Satellite Networks

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

16-1 CELLULAR TELEPHONY

16.2

Cellular telephony is designed to one stationary unit, often called a land unit.

provide communications between two moving units, called mobile stations (MSs), or between one mobile unit and Topics discussed in this section:

Frequency-Reuse Principle Transmitting Receiving Roaming First Generation Second Generation Third Generation

16.3

Figure 16.1

Cellular system

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Figure 16.2

Frequency reuse patterns

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16.6

16.7

1G 2G 2.5G

2.75G

3G 3.5G

4G AMPS GSM D-AMPS IS-136 CDMA IS-95 iDEN Nextel GPRS 30-50 kbps UMTS Wideband-CDMA Wireless-CDMA 384kbps; AT&T, T-Mobile HSPA High speed packet access 400-700kbps (or 3G ?) 1xRTT CDMA2000 1x IS-2000 144 kbps EDGE 75-135kbps iPhone (1st generation) CDMA2000 EV-DO 1xEV EV IS-856 2.5 Mbps down 154 kbps up Verizon, Sprint CDMA2000 EV-DV Dead?

3.1 Mbps down 1.8 Mbps up EV-DO Rev.A

Up to 3.1Mbps

LTE?

Long-term Evolution 3-5 Mbps UMB ??

Ultra Mobile Broadband WiMax??

Wi-Fi???

AT&T, Verizon, and Alltel now support LTE.

What about WiMax for 4G?

16.8

Note

AMPS is an analog cellular phone system using FDMA.

16.9

Figure 16.3

Cellular bands for AMPS

Figure 16.4

AMPS reverse communication band

16.10

Figure 16.5

Second-generation cellular phone systems

16.11

Figure 16.6

D-AMPS

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16.13

Note

D-AMPS, or IS-136, is a digital cellular phone system using TDMA and FDMA.

Figure 16.7

GSM bands

16.14

Figure 16.8

GSM

16.15

GSM uses TDMA and FDMA concepts GMSK (Gaussian minimum shift keying): a form of FSK used in European systems

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.

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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

16.19

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

2.5 Generation GPRS 16.20

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

16.21

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

16.22

3 rd 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

16.23

3 rd 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

16.24

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

LTE 16.25

LTE (3GPP LTE – Long Term Evolution)

• 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 end user 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.

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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, geosynchronous orbit.

as we will see, is called a

16.31

Figure 16.14

Satellite categories

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Figure 16.15

Satellite orbit altitudes

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Table 16.1

Satellite frequency bands

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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

Figure 16.16

Satellites in geostationary orbit

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Figure 16.17

Orbits for global positioning system (GPS) satellites

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Figure 16.18

Trilateration

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Figure 16.19

LEO satellite system

16.38

UML: user mobile link GWL: gateway link ISL: intersatellite link

Figure 16.20

Iridium constellation

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16.40

Note

The Iridium system has 66 satellites in six LEO orbits, each at an altitude of 750 km.

16.41

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.

Figure 16.20

Teledesic

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16.43

Note

Teledesic has 288 satellites in 12 LEO orbits, each at an altitude of 1350 km.