Cellular Telephone And Satellite Networks

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Chapter 17
Cellular TelephoneAnd Satellite Networks
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17.1 Cellular Telephony
Frequency Reuse Principle
Transmitting
Receiving
Handoff
Roaming
First Generation
Second Generation
Third Generation
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Frequency Band Allocations

• The airwaves are already full of signal
  allocated to agreed bands
• Use of the bands is strictly controlled
• http//www.roke.co.uk/download/datasheets/UK_Radio
  _Frequency_Allocations.pdf
• The ISM (Industrial, Scientific and Medical)
  bands are unlicensed anyone can transmit on
  them
• They are used for Wireless LANS, Bluetooth and
  mobile phones

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Figure 17.1 Cellular system
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Figure 17.2 Frequency reuse patterns
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Note
AMPS Advanced Mobile Phone System was the
first generation technology (1G) analog
cellular phone system using FDMA.
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Figure 17.3 Cellular bands for AMPS
Each band 832 x 30kHz channels shared
between two providers 416 each 416 395 for
calls 21 control channels Reuse factor 7, so
only 395/7 56 channels available in any one
cell per provider
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Figure 17.4 AMPS reverse communication band
Note 3 types of modulation
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Figure 17.5 Second-generation cellular phone
systems
2G Mobile systems used for digitised voice
signals Main advantage less susceptible to
noise
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Figure 17.6 D-AMPS
D-AMPS Backward-compatible with AMPS uses
same bands 324 bits 159 voice 64 control
101 error corr.
25 frames per second 6 x 324 bits 1944
PCM and Compression
Digital to Analogue
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Note
D-AMPS, or IS-136, is a digital cellular phone
system using TDMA to multiplex 3 channels
control error corr. QPSK to convert
digital-analogue FDMA to multiplex 832 channels.
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Figure 17.7 GSM bands
GSM Global System for Mobile Communications A
European standard for 2G phones


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Figure 17.8 GSM
Data Rate 8 users x 156.25 bits x 26
frames/120ms 270.8kbps
D ? A
200k x 124 25MHz
GMSK - Gaussian Minimum Shift Keying
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Figure 17.9 Multiframe components
1 second
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Very efficient !
Note
GSM is a digital cellular phone system using TDMA
and FDMA. Reuse factor 3, as a result of
complex error correction, requiring 114 65 49
error correction bits for 65 bits of data large
overhead better use of frequencies
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Figure 17.10 IS-95 forward transmission
IS-95 uses CDMA to multiplex in the forward
(base to mobile) direction
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Figure 17.11 IS-95 reverse transmission
IS-95 uses DSSS in the reverse (mobile to base)
direction
IS-95 is a digital cellular phone system using
CDMA/DSSS and FDMA.
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Figure 17.12 IMT-2000 radio interfaces
3G Mobile Phone systems
The main goal of third-generation cellular
telephony is to provide universal personal
communication.