Wireless networks - Lecture 8: Evolution of wireless networks (Part 1). The main topics covered in this chapter include: 1G wireless cellular networks; 2G cellular systems; evolution tree of wireless systems; pacific digital cellular (PDC); automatic switching (dialing) and handover;...
Trang 1Wireless Networks
Lecture 8 Evolution of Wireless Networks
Dr Ghalib A Shah
Trang 2 Review of previous lecture #7
1G wireless cellular networks
► NMT
► AMPS
► TACS
► GSM
► IS-136
► PDC
► IS-95
Trang 3Last Lecture Review
► Versions of CSMA
► CSMA/CA
► Example
► Frequency Hoping
► Direct Sequence
Trang 4Evolution of Wireless Systems
The worldwide success of cellular telephone
has lead to the development of newer wireless systems and standards for other types of
communications besides mobile voice.
► Cellular networks to facilitate high speed data traffic
► Replace fiber optics and copper lines between fixed
points several kms apart.
► Replacement of wires within homes, offices etc
(evolution of Bluetooth)
Trang 5First-Generation Cellular Networks
Analog systems
Standards
► NMT (Nordic Mobile Telephone)
• used in Nordic countries , Switzerland , Netherlands ,
Eastern Europe and Russia
► AMPS (Advanced Mobile Phone System)
• used in the United States ,
► TACS (Total Access Communications System)
• Used in the United Kingdom ,
► C-450
• in West Germany , Portugal and South Africa ,
► Radiocom 2000 in France
► RTMI in Italy
► In J apan there were multiple systems Three standards,
TZ-801, TZ-802, and TZ-803
Trang 6Evolution Tree of Wireless Systems
Trang 7 First fully-automatic cellular phone system
► Started in 1970, in service 1981
► Corresponds to frequency and the later has higher
bands.
Cell size range from 2 km to 30 km.
► Use smaller size in urban areas for better quality and
larger in less-populated areas.
Automatic switching (dialing) and handover.
Trang 8NMT Contd.
No spec for voice traffic encryption
► Buy a scanner, tune to the desired channel and intercept
NMT also supported a s imple data trans fer mode
called DMS (Data and Messaging Service) or
NMT-Text
Using DMS, also text messaging was possible between
two NMT handsets before SMS service started in GSM
but this feature was never commercially available
except in Russian and Polish NMT networks
NMT Suspended
► In Finland TeliaSonera's NMT on December 31, 2002
► Norway's last NMT network on December 31, 2004
► Sweden's TeliaSonera NMT on December 31, 2007
Trang 9 1G cellular phone used in US, which uses FDMA
Operates in 800 MHz band
► Total of 832 channels;
• 416 in 824–849 MHz for transmissions from mobile to the base
• 416 in 869–894 MHz for transmissions from base to the mobile
• Each channel is 30 KHz wide
Require large bandwidth for large base population.
No protection against eavesdropper
► ESN (Electronic Serial Number) was cloned in 1990s to make
free calls from different cells
Replaced with D-AMPS, GSM and CDMA for better
security and capacity
Trang 10 A variant of AMPS developed by Motorola
It has been used in some European countries
(including the UK & Ireland ), as well as J apan and Hong Kong.
more channels.
was discontinued on 31 May 2001
Trang 11Second-Generation Cellular Networks
Digital system i.e voice is digitized
Unlike 1G that relies on FDMA/FDD, 2G use digital
modulation formats and TDMA/FDD, CDMA/FDD
multiple access techniques
Can be divided into two standards; TDMA and CDMA
The main 2G standards are
► GSM (TDMA-based), originally from Europe but used
worldwide
► IS-136 aka D-AMPS, TDMA-based, used in the Americas
► IS-95 aka cdmaOne, CDMA-based, used in the Americas and
parts of Asia
► PDC (TDMA-based), used exclusively in J apan
Trang 122G Contd.
Using digital signals between the handsets and
the towers increases system capacity in two
key ways:
► Digital voice data can be compressed and
multiplexed much more effectively than analog voice encodings through the use of various CODECs,
allowing more calls to be packed into the same amount of radio bandwidth
► The digital systems were designed to emit less radio
power from the handsets This meant that cells could
be smaller, so more cells could be placed in the same amount of space This was also made
possible by cell towers and related equipment
Trang 132G Advantages
The lower powered radio signals require less
battery power, so phones last much longer
between charges, and batteries can be smaller
The digital voice encoding allowed digital
error checking which could increase sound
quality by reducing dynamic and lowering the
noise floor
Going all-digital allowed for the introduction of
digital data services , such as SMS and email
Better security, harder to be scanned
Trang 14 2.27 billion subscribers across more than 212
countries, 81% of the global mobile market
Its ubiquity provides international roaming very
common
8-slots TDMA with 200 KHz radio channel, with frame
duration of 4.615 ms
The channel data rate is 270.833 kbit/s
Operates in four different bands
► Mostly 900 MHz or 1800 MHz
► US and Canada use 850 MHz and 1900 MHz
► 25 MHz bandwidth of each subdivided into 124 channels
► E.g in 900 MHz, uplink 890-915 MHz, downlink 935-960 MHz
Trang 15Others Systems
IS-136 or D-AMPS
► 3-Slot TDMA, used in North and South America, Australia
► Channel bandwidth is 30 KHz
► Frequency bands (824-849MHz and 869-894 MHz)
Pacific Digital Cellular (PDC)
► J apanese standard similar to IS-136
► 25 KHz channel
► 11.2 kbps at 3-slot and 5.6 kbps at 6-slot
► Operates in 800 MHz downlink 810-888 MHz, uplink 893-958
MHz)
► In 1.5 GHz (downlink 1477-1501 MHz, uplink 1429-1453 MHz)
Trang 16Other Systems Contd
► Supports up to 64 users that are orthogonally coded
► Channel bandwidth is 1.25 MHz
► Widely deployed in N America, Korea, J apan,
China, S America, Australia
► Channel data rate is 1.2288 Mchips/s (Mega Chips )
Trang 19Subscriber base as a function of Cellular technology
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Trang 20Summary of today’s lecture
► NMT
► AMPS
► TACS
► C-450
2G digital cellular systems
► GSM
► IS-136
► IS-95
Next Lecture
► 3G and 4G