Next Generation Wireless Systems and
Smart Antennas
Jack H. Winters
April 25, 2003
jack@jackwinters.com
Goal
• Wireless communications, anywhere, in any form
• In any form:
– high-speed data (Internet)
– voice
– audio (music)
– video
• Anywhere:
– home
– buildings (office)
– pedestrian
– vehicles
2
OUTLINE
• Current Systems
• Current Trends
• Technical Issues
– Smart Antennas
– Radio Resource Management
• ITRI Study on China
• Conclusions
3
Current Systems
Peak Data Rate
High performance/price
UWB
100 Mbps
3.1-10.6 GHz
802.11a
5.5GHz Unlicensed
10 Mbps
802.11b
$/Cell
$/Sub
$ 500,000
$ 500
$ 1000
$ 100
$ 100
$ 10
2.4GHz Unlicensed
1 Mbps
BlueTooth
100 kbps
2.4GHz
High ubiquity and mobility
3G Wireless
~ 2GHz
10 feet
2 mph
100 feet
10 mph
1 mile
30 mph
10 miles Range
60 mph Mobile Speed
4
Cellular Data
•
•
•
•
CDPD (US) < 10 kbps
GPRS = 30-40 kbps
EDGE/1xRTT = 80 kbps
WCDMA = 100 kbps (starting in Japan, but not
for several years in US)
5
WLANs: 802.11b
Barker
Barker
1 ms
11 chips
CCK
CCK
727 ns
8 chips
Key 802.11b Physical Layer Parameters:
Data rate:
Modulation/Spreading:
Transmission modes:
(dynamic rate shifting)
Chip rate:
Frequency band:
Bandwidth:
Channel spacing:
Number of channels:
• 1, 2, 5.5, 11 Mbps
• Direct Sequence Spread Spectrum (DSSS)
• DBPSK, DQPSK with 11-chip Barker code (1, 2 Mbps)
(this mode stems from the original 802.11 standard)
• 8-chip complementary code keying (CCK) (5.5, 11 Mbps)
• optional: packet binary convolutional coding (PBCC), 64 state, rate 1/2 CC
(BPSK 5.5 Mbps, QPSK 11 Mbps)
11 MHz
Industrial, Scientific and Medical (ISM, unlicensed) 2.4 - 2.4835 GHz
22 MHz - TDD
5 MHz
Total of 14 (but only the first 11 are used in the US), with only
3 nonoverlapping channels
6
WLANs: 802.11a (g in 2.4 GHz band)
3.2 ms
FFT
G
4 ms
52=48+4 tones
64 point FFT
Key 802.11a Physical Layer Parameters:
Data rate:
Modulation:
Coding rate:
Subcarriers:
Pilot subcarriers:
FFT size:
Symbol duration:
Guard interval:
Subcarrier spacing:
Bandwidth:
Channel spacing:
Frequency band:
Number of channels:
6, 9, 12, 18, 24, 36, 48, 54 Mbps
BPSK, QPSK, 16QAM, 64QAM
1/2, 2/3, 3/4
User data rates (Mbps):
52
BPSK QPSK QAM16 QAM64
4
R=1/2
6
12
24
64
R=2/3
48
4 ms
R=3/4
9
18
36
54
800 ns
312.5 kHz
16.56 MHz - TDD
20 MHz
Unlicensed national infrastructure (U-NII), 5.5 GHz
Total of 12 in three blocks between 5 and 6 GHz
:
7
WLAN Evolution
•
Start with wireless data access (802.11b) (hotspots)
– Extend range and migrate to:
•
•
•
•
•
Voice
Audio (music)
Video
Mobility
Higher data rates (54 Mbps - 802.11a and higher)
8
Technical Issues
•
•
•
•
•
•
Voice/Music streaming/Video streaming (802.11e)
Universal coverage (Internet roaming)
Range
Higher data rates
Capacity/Interference
Key constraint: Stay within existing standards/standard evolution
(enhance performance within standards and drive standards evolution)
9
Internet Roaming
•
Seamless handoffs between WLAN and WAN
– high-performance when possible
– ubiquity with reduced throughput
Cellular Wireless
•
•
•
•
Management/brokering of consolidated WLAN
and WAN access
Adaptive or performance-aware applications
Nokia GPRS/802.11b PCMCIA card
NTT DoCoMo WLAN/WCDMA trial
Internet
Wireless LAN’s
Enterprise
Home
Public
10
Technical Issues
•
•
•
•
•
•
Voice/Music streaming/Video streaming (802.11e)
Universal coverage (Internet roaming)
Range
Higher data rates
Capacity/Interference
Key constraint: Stay within existing standards/standard evolution
(enhance performance within standards and drive standards evolution)
11
Wireless System Enhancements
Peak Data Rate
UWB
100 Mbps
3.1-10.6 GHz
High performance/price
802.11a
5.5GHz Unlicensed
10 Mbps
802.11b
2.4GHz Unlicensed
1 Mbps
$/Cell
$/Sub
$ 500,000
$ 500
$ 1000
$ 100
$ 100
$ 10
Enhanced
BlueTooth
100 kbps
2.4GHz
High ubiquity and mobility
3G Wireless
~ 2GHz
10 feet
2 mph
100 feet
10 mph
1 mile
30 mph
10 miles
60 mph
Range
Mobile Speed
12
Enhancements
•
Smart Antennas (keeping within standards):
– Range increase
– Interference suppression
– Capacity increase
– Data rate increase using multiple transmit/receive antennas
(MIMO)
•
Radio resource management techniques (using cellular
techniques in WLANs):
– Dynamic packet assignment
– Power control
– Adaptive coding/modulation/smart antennas
13
Smart Antennas
SIGNAL
SIGNAL
OUTPUT
INTERFERENCE
INTERFERENCE
BEAMFORMER
WEIGHTS
Smart Antennas significantly improve performance:
• Higher antenna gain with multipath mitigation (gain of M with M-fold diversity) 
Range extension
• Interference suppression (suppress M-1 interferers)  Quality and capacity
improvement
• With smart antennas at Tx/Rx  MIMO capacity increase(M-fold)
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Smart Antennas for Cellular
• Key enhancement technique to increase system capacity, extend coverage, and
improve user experience in cellular (IS-136)
SIGNAL
Uplink Adaptive Antenna
SIGNAL
OUTPUT
INTERFERENCE
BEAMFORMER
WEIGHTS
SIGNAL
In 1999, combining at base stations changed
from MRC to MMSE for capacity increase
INTERFERENCE
BEAMFORMER
Downlink Switched Beam Antenna
BEAM
SELECT
SIGNAL
OUTPUT
Multiple-Input Multiple-Output (MIMO) Radio
•
•
With M transmit and M receive antennas, can provide M independent channels, to
increase data rate M-fold with no increase in total transmit power (with sufficient
multipath) – only an increase in DSP
–
Indoors – up to 150-fold increase in theory
–
Outdoors – 8-12-fold increase typical
AT&T measurements show 4x data rate & capacity increase in all mobile &
indoor/outdoor environments (4 Tx and 4 Rx antennas)
–
216 Mbps 802.11a (4X 54 Mbps)
–
1.5 Mbps EDGE
–
19 Mbps WCDMA
16
MIMO Channel Testing
Test Bed Receivers with Rooftop
Antennas
Mobile Transmitters
W1
Tx
W2
Tx
W3
• Perform timing
recovery and
symbol
synchronization
Rx
• Record 4x4
complex channel
matrix
Rx
Tx
• Evaluate capacity
and channel
correlation
Rx
Tx
W4
Synchronous
test
sequences
Rx
LO
Terminal Antennas
on a Laptop
LO
11.3 ft
Prototype Dual
Antenna Handset
Rooftop Base Station Antennas
Mobile Transmitters
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DIVERSITY TYPES
Spatial: Separation – only ¼ wavelength needed at
terminal
Polarization: Dual polarization (doubles number of
antennas in one location
Pattern: Allows even closer than ¼ wavelength
 4 or more antennas on a PCMCIA card
 16 on a handset
 Even more on a laptop
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MIMO Antennas
Base Station Antennas
Laptop Prototype
• 4 patch antennas at 1900 MHz separated
by 3 inches (/2 wavelengths)
• Laptop prototype made of brass with
adjustable PCB lid
• Antennas mounted on 60 foot tower on 5 story office
building
• Dual-polarized slant 45 1900 MHz sector antennas and
fixed multibeam antenna with 4 - 30 beams
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MIMO Field Test Results
• Measured capacity
distribution is close to the
ideal for 4 transmit and 4
receive antennas
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Smart Antennas for WLANs
Smart
Antenna
AP
Smart
Antenna
AP
Interference
Smart Antennas can significantly improve the performance of WLANs
• TDD operation (only need smart antenna at access point or terminal for performance improvement
in both directions)
• Interference suppression  Improve system capacity and throughput
–
Supports aggressive frequency re-use for higher spectrum efficiency, robustness in the ISM band (microwave
ovens, outdoor lights)
• Higher antenna gain  Extend range (outdoor coverage)
• Multipath diversity gain  Improve reliability
• MIMO (multiple antennas at AP and laptop)  Increase data rates
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Smart Antennas
•
•
•
•
•
Adaptive MIMO
– Adapt among:
• antenna gain for range extension
• interference suppression for capacity (with frequency
reuse)
• MIMO for data rate increase
With 4 antennas at access point and terminal, in 802.11a have the
potential to provide up to 216 Mbps in 20 MHz bandwidth within
the standard
In EDGE/GPRS, 4 antennas provide 4-fold data rate increase (to 1.5
Mbps in EDGE)
In WCDMA, BLAST techniques proposed by Lucent, with 19 Mbps
demonstrated
In UWB, smart antennas at receiver provide range increase at data
rates of 100’s Mbps
22
Radio Resource Management
•
Use cellular radio resource management techniques in
WLANs: Adaptive coding/modulation, dynamic packet
assignment, power control
•
Use software on controller PC for multiple access points to
analyze data and control system
• Power control to permit cell ‘breathing’ (for traffic spikes)
• Dynamic AP channel assignment
– Combination of radio resource management and smart antennas
yields greater gains than sum of gains
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International Technology Research Institute
Study on Wireless Communication
Technology and Systems
• ITRI Wireless Comm. Technology (EU, Japan, 2000)
• ITRI Asian Telecomm. Update (HK, Taiwan, 2001)
• ITRI Asian Telecomm. Update (PRC, March-April, 2003)
http://itri2.org
Asia Telecommunications Study
Comparing the observed R&D trends in Asia with those from
the previous wireless study in Europe and Japan we may
conclude:
• Magnitude of R&D activities in Europe and Japan is
much larger
• System-based R&D is limited in Asia
• Growing activities to support development of Asia’s
expertise in 3G systems are questionable
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Conclusions
• We
are evolving toward our goal of universal high-speed wireless
access, but technical challenges remain
• These challenges can be overcome by the use of:
– Smart antennas to reduce interference, extend range, increase data
rate, and improve quality, without standards changes
– Radio resource management techniques, in combination with smart
antennas, and multiband/multimode devices
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