Transcript From Marconi to Wireless Internet: The Wireless (R)evolution

From Marconi to Wireless Internet:
The Wireless (R)evolution
Prof. Vijay K. Bhargava
Candidate for 2004 IEEE President-Elect
University of Victoria
Victoria, Canada
Email: [email protected]
Website: http://www.ece.uvic.ca/~bhargava/ieee
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Dear IEEE Member:
The Board of Directors has placed my
name on the ballot for the office of
IEEE President-Elect 2004. I would
be pleased to serve as your president if you honour me with your vote in
September.
I welcome any thoughts you may have
on my position statement and issues
that you feel should be addressed by
the IEEE.
Kind Regards,
Vijay Bhargava ([email protected])
http://www.ece.uvic.ca/~bhargava/ieee
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Position Statement
Improve access to product and services (journals,
standards, conference proceedings and continuing
education courses). They account for 75% of our
revenue
Manage Budget, Reduce Corporate Expenses and
improve our volunteer structure
Expand membership beyond the traditional field of
electrical engineers. There are tremendous
opportunities in information technology and related
areas
Jointly with international engineering community,
make IEEE a force for promoting world peace and a
better life for all.
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ISBN: 1-4020-7251-1
© 2003
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Presentation Outline
1.
2.
3.
4.
5.
6.
7.
Historical Overview
The Three Generations
Beyond 3G/Wireless Internet
Enabling Techniques (Innovations from IT Society)
Malaise Afflicting the Wireless Industry
Possible Recovery Scenario
Conclusions
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6
Maxwell
Hertz
Popov
Fessenden
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8
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Signal Hill, December 12, 2001
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The Three Generations and Beyond (Overview)

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First Generation
: Analog Cellular
(Mainly Speech)
Second Generation : Digital Cellular
(Digital Speech and messaging)
2.5G, 2.75G, …
Third Generation : IMT2000
(Integrated Audio and Video)
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Beyond 3G
The true Wireless Internet
Internet connectivity anytime anywhere
Wireless and mobile extensions to the Internet
Wireless – Wireline BB Transparency
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Claude Elwood Shannon
Father of Information Theory
Electrical engineer, mathematician, and native
son of Gaylord. His creation of information theory,
the mathematical theory of communication,
in the 1940s and 1950s inspired the revolutionary
advances in digital communications and
information storage that
have shaped the modern world.
This statue was donated by the
Information Theory Society of the Institute of
Electrical and Electronics Engineers,
whose members follow gratefully in his footsteps.
Dedicated October 6, 2000
Eugene Daub, Sculptor
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Enabling Techniques (Innovations from IT Society)
Reed Solomon Codes
Viterbi Algorithm
Public Key Crytosystem
Compression Algorithm, Huffman, Lempel-Ziv,
Algebraic Coding
Modem Design with Coded Modulation, Ungerböeck
Turbo Decoding approaches Shannon’s capacity limit
by less than 0.5dB
Theory of CDMA and Multiuser Transmission
Space-Time Coding for Mobiles
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Cryptography
Secret Key System
Public Key System
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Digital Signature
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Source Coding for Voice and Video
Variants of Predictive Coding
For voice CELP, VCELP, RPE-LTP and other Variants
H.261 and H.263 Standards support low bit rate (30-64 kbps)
Video for mobile communication
MPEG-4 (with Reed-Solomon Codes)
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Turbo Codes
Originally Turbo code encoder was built using a parallel
concatenation of two (or more) relatively simple recursive
systematic convolutional (RSC) codes with large interleaving
Although the component codes are weak, the output turbo
codeword is very powerful due to the “Interleaver gain”
which produces a random-like codeword
dk
dk
RSC1
d1,k
Interleaver
p
RSC2
d2,k
Turbo Code Encoder
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Turbo Codes (Iterative Decoding)
Soft Input/Soft Output MAP Decoder
Use “extrinsic information” produced from past decoder as
á priori information
Gradually improvement of knowledge on transmitted
information through iterations
After m
iterations
rk
r1,k
p
Decoder
1
p
r2,k
Decoder
2
d
p-1
Turbo code Decoder
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Turbo Codes
Turbo codes will be used in high data rate services in the next
generation CDMA systems above 32 kbps
There are already existing standards for ½ and 1/3 coding rate
turbo code for 3GPP systems
The same iterative decoding principle can be applied in
various different areas
Turbo equalization
Turbo multiuser detection (for coded CDMA signals)
Turbo decoding with estimation of parameters of an
unknown time-varying channel
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Multiuser Detection (MUD)
Signals from all users are considered useful instead of
only interference to each other
MUD provides important performance gains over the
conventional single-user receiver
Performance of single-user conventional receivers are
limited in fading channel due to the near-far effect which
necessitates use of strict power control
In certain cases multiuser receivers can even benefit
from the diversity in powers of the received users and
have better performances than in the case of equal
received powers of users
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Multiuser Detection (MUD)
•In the single user approach,
each detector focuses on
extracting the data of a single
user
•Other users are considered as
interference
•Simple
oscillator
Rx
oscillator
Rx
Rake
Receiver
b1
Detector
h(t)
bK
Detector
b1
Multiuser
Detector
Kth
Rake
Receiver
Kth Rake
Receiver
1st Rake
Receiver
h(t)
1st
•
•
bK
•In the multi-user detection
approach, the common
detector uses available
information from all users to
detect each user
•Complex
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Multiuser Detection (MUD)
Benefits of using multiuser detection
More efficient spectrum utilization (in some
situations we can expect ten fold increase in
spectrum efficiency)
Reduced precision requirement for power control
More efficient power utilization
Main difficulties in implementing multiuser detection
Existence of the other-cell multiple-access
interference (MAI)
Difficulty in implementing multiuser detection on
the downlink (cost, size, weight are of much larger
concern for mobile terminals)
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Multiuser Detection (MUD)
Some of the MUD algorithms are
Maximum Likelihood (Optimal) Decoding (complexity
increases exponentially with the number of users)
Linear detectors (similar to the linear equalization techniques)
decor relating detector
MMSE detector
• MMSE detector can be implemented as an adaptive
filter to reduce complexity
• Blind adaptive implementation of the MMSE detector
Decision Feedback Detectors where past decisions are used to
improve the current ones
Conventional Decision Feedback or Successive
Interference Cancellation
Parallel Interference Cancellation
Optimum Decision Feedback Receiver (has the spectral
efficiency equal to the optimum detector)
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Multiuser Detection (MUD)
Implementation examples of multistage parallel
interference cancellation multiuser detection:
DSP implementation [Buehrer, Woerner, 1999]
VLSI implementation [Aazhang et al., 2000]
The parallel interference cancellation is prefered due to
its performance complexity tradeoff
However, MUD research is still in a phase that would not
justify to make it a mandatory feature for 3G WCDMA
standards
Most probably, its practical implementation and
standardization is going to be defered for 4G systems
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Space-Time Codes
Capacity of a multi-antenna systems far exceeds that
of single-antenna system
Multiple transmit/receive antennas provide diversity
in the space domain (space diversity)
Channel coding designed for wireless communication
systems with multiple transmit/receive antennas
provide both space and time diversity  Space-time
codes
Two categories of space-time coding
1) space-time trellis codes 2) space-time block codes
Decoding of space-time codes requires channel
estimation
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Space-Time Codes
c1(k)
Information s(k
)
source
s’(k)
Space-time
encoder
cN(k)
rN(k)
Receiver
Space-time coding system
2
3
r1(k)
1
Input: 0 1 5 7 6 4
Tx 1: 0 0 5 1 3 6
Tx 2: 0 1 5 7 6 4
4
0
5
7
6
0
1
2
3
4
5
00,01,02,03,04,05,06,07
50,51,52,53,54,55,56,57
20,21,22,23,24,25,26,27
70,71,72,73,74,75,76,77
40,41,42,43,44,45,46,47
10,11,12,13,14,15,16,17
6
7
60,61,62,63,64,65,66,67
30,31,32,33,34,35,36,37
Space-time trellis codes (8-PSK) with
two transmit antennas
s(k Constellation
)
Mapper
 c1
[c1 c2]  
c2
- c2* 
c1* 
Space-time block codes with two
transmit antennas (Alamouti’s scheme)
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Space-Time Codes
Bandwidth and power efficient – a codeword is
transmitted simultaneously from different antennas with
the same total transmit power
Channel information is not necessary at the transmitter
Differential scheme is available when channel information
is not known at the receiver
Can be concatenated with other codes such as ReedSolomon, TCM, turbo code
Can be applied in broadband channel – CDMA, OFDM
Adopted in standards – IS-136, W-CDMA, CDMA2000
Tested in WLAN 802.11a. Increase in link layer
throughput and improving TCP performance
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The Malaise Afflicting The Communications Industry*
A convergence of five key factors
1. Greed
2. Corporate Crime
3. Misguided Regulations
4. Too Much Debt
5. A Broken Business Model
Why did we, the engineers, allow business manipulators
and bureaucrats to drive the show ?
*Peter A. Bernstein, IEEE Spectrum, January 2003
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Possible Recovery Scenario
“Nothing lasts forever”
“This too shall pass”
“Survival of the fattest”!
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Broadband: Alive and Well
Mobile, and Loving it
If Each is Good, Both are Better
If You Build it, Killer Apps will Come
*Steven M.Cherry, IEEE Spectrum, January 2003
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Conclusions
We have presented a historical overview of Wireless
Communication
Innovations from IT Society have been discussed
Reliable high-speed mobile Internet Access will lead to
innovative product and services
“It is dangerous to put limits on Wireless Communications”
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WHY ARE THESE MEN SMILING ?
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