Transcript Wireless Communications Research Overview

EE360: Lecture 14 Outline
3G Cellular and Beyond
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1G and 2G
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What is 3G?
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Evolution to 3G
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2.5G, 2.67589G?
“Frequency reuse and coding for GPRS”, Matthias
Unbehaun
“Wireless mobile communications at the start of the 21st
century”, Jeremy Poole
Beyond 3G
1-2 G Cellular Design:
Voice Centric
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Cellular coverage is designed for voice service
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Cellular systems are designed for voice
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Area outage, e.g. < 10% or < 5%.
Minimal, but equal, service everywhere.
20 ms framing structure
Strong FEC, interleaving and decoding delays.
Spectral Efficiency
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around 0.04-0.07 bps/Hz/sector
comparable for TDMA and CDMA
3G Cellular Design:
Voice and Data
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Goal (early 90s): A single worldwide air interface
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Bursty Data => Packet Transmission
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384 Kbps outdoors, 1 Mbps indoors.
Need to provide QOS
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Simultaneous with circuit voice transmisison
Need to “widen the data pipe”:
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Yeah, right
Evolve from best effort to statistical or “guaranteed”
Adaptive Techniques
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Rate (spreading, modulation/coding), power, resources, signature
sequences, space-time processing, MIMO
3G GSM-Based Systems
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EDGE: Packet data with adaptive modulation and
coding
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8-PSK/GMSK at 271 ksps supports 9.02 to 59.2
kbps per time slot with up to 8 time-slots
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Supports peak rates over 384 kbps
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IP centric for both voice and data
3G CDMA Approaches
W-CDMA and cdma2000
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cdma2000 uses a multicarrier overlay for compatibility with IS-95
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WCDMA designed for evolution of GSM systems
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Varying user bit rate is mapped to variable power and spreading
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Different services can be mixed on a single code for a user
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Multiple code operation
CA
CC
CD
5
Cellular Standards Evolution
Japan
st
1 Gen
1st
Gen
nd Gen
Gen
22nd
3rd
rd Gen
3 Gen
TACS
NMT/TACS/Other
PDC
GSM
W-CDMA/EDGE
Converged TDMA/GSM
family of technologies
will have dominant market
share (~80 percent).
Americas
Europe
(EDGE in Europe and Asia
outside Japan)
AMPS
TDMA
CDMA
EDGE
cdma2000
Global strategy
based on W-CDMA and EDGE networks,
common IP based network, and dual mode
W-CDMA/EDGE phones.
W-CDMA and cdma2000
will be optional modes in
one spec. Basic phones
will be one or the other.
Global phones will have
both.
Cellular Systems Evolution
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GSM (TDMA+FH):
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GPRS
EDGE: Enhanced GPRS with adaptive modulation and
coding
IS-95(CDMA):
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Variable processing gain, e.g., WCDMA
HDR (Qualcomm)
 Time slotted data with adaptive modulation
 Data transmissions are scheduled
 No spreading
State-of-the art at the beginning of the 21st century
Beyond 3G
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Need to provide: “beyond data”
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Higher data rates (at least on downlink)
More multimedia contents
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Wideband (10 MHz or more)
Main Candidates
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Voice, data, video, WWW access.
broadcast as well as cellular
WOFDM
WCDMA
Multicarrier CDMA
Other???
How will these systems access the Internet and
coexist with wireless LANs?
Summary
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Wireless data and multimedia are the main drivers
for future generations of cellular systems.
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Several competing standards (as in 2G).
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Evolutionary path unclear.
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Killer application unknown.
What do mobile users want?
 How will cellular users access the Internet?
 Will wireless LANs or cellular systems dominate the
future wireless data landscape?
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