beamforming antennas (1)
TRANSCRIPT
Beamforming Antennas for Wireless Communications
Yikun Huang, Ph.D.
ECE/CCB
November 24 2003
Outline
Phased Array Antennas
Vector Antennas
Beamforming antennas for WLAN
Conclusion
IntroductionBeamforming and its applicationsBeamforming antennas vs. omnidirectional antennas
Direction of arrival (DOA) estimationBeamformingBasic configurations: fixed array and adaptive arraysmart antenna systems:switched array and adaptive array
DOA and polarizationsuper CART3-loop and 2-loop vector antenna arrayDirection of arrival (DOA) estimationVector antenna vs. phased array antenna
Infrastructure modeAn indoor WLAN designAd hoc modeAd hoc WLAN for rural area
Applications Description
RADAR Phased array RADAR; air traffic control; synthetic aperture RADAR
SONAR Source location and classification
Communications Smart antenna systems; Directional transmission and reception; sector broadcast in satellite communications
Imaging Ultrasonic; optical; tomographic
Geophysical Exploration Earth crust mapping; oil exploration
Astrophysical Exploration High resolution imaging of universe
Biomedical Neuronal spike discrimination; fetal heart monitoring; tissue hyperthermia; hearing aids
Source: B.D.Van Veen and K.M. Buckley, University of Michigan, “Beamforming: A Versatile approach to spatial filtering”,1988
Applications of beamforming technology
Phased array RADAR
Phased array spike sorting
0.139
0.544
Ey1n t( )
1.2 1040 t
0.056
0.205
Ey2n t( )
1.2 1040 t
0.042
0.187
Ey3n t( )
1.2 1040 t
SortedSpike of
individual neurons.
12
34
1 65
67
89
1 41 5
1 31 2
1 11 0
0.139
0.534
Rn 3 t( )
1.2 1040 t
0.183
0.539
Rn 5 t( )
1.2 1040 t
0.147
0.534
Rn 7 t( )
1.2 1040 t
0.147
0.534
Rn 9 t( )
1.2 1040 t
0.183
0.539
Rn 11 t( )
1.2 1040 t
0.139
0.534
Rn 13 t( )
1.2 1040 t
0.14
0.534
Rn 1 t( )
1.2 1040 t
0.148
0.534
Rn 15 t( )
1.2 1040 t
Neuronal spikes
recorded by electrode
array
Phas
ed a
rray
spi
ke s
ortin
g sy
stem
Center for Computational Biology, MSU
Patterns, beamwidth & Gain
Isotropic dipole
top
view
(hor
izon
tal)
side
vie
w(v
ertic
al)
half-wave dipole beamformer
21 /φ
Half-power beam width
Half-power beam width
Half-power beam width
Main lobe
side lobes
nulls
21 /θ78°
Beamformers vs. omnidirectional antennas
1) Beamformers have much higher Gain than omnidirectional antennas: Increase coverage and reduce number of antennas!
Gain: 2
1
NGGN
0
30
60
90
120
150
180
210
240
270
300
330
6
4
2
0
6
9.961 10 7
Field 6 0 ( )
Field 2 0 ( )
Field 1 0 ( )
Beamformers vs. omnidirectional antennas
2) Beamformers can reject interference while omnidirectional antennas can’t: Improve SNR and system capacity!
3) Beamformers directionally send down link information to the users while omnidirectional antennas can’t: save energy!
user
interference
user
interferencenull
Beamformers vs. omnidirectional antennas
user user
null
multipath
4) Beamformers provide N-fold diversity Gain of omnidirectional antennas: increase system capacity(SDMA)
5) Beamformers suppress delay spread:improve signal quality
DOA estimation
βφkdβφλdπ
kkk sinsinΔ 2
phase delay
1 2 3 4 5 6 7 NN-2 N-1N-3… …
… …
d
kk φdδ sin
kφ
Plane wave
Beamforming
phase shifters
1 2 3 4 5 6 7 NN-2 N-1N-3
… …
… …
kφ
… …
1,,k 2,,k 3,,k 4,,k 5,,k 6,,k 7,,k N-3,,k N-2,,k N-1,,k N,,k
)sin)((Δ , βφkdN kkN 1
phased array (fixed/adaptive) configurations-time domain
Basic phased array configurations
Narrowband
sN(k)
s2(k)
s1(k)
.
.
.
w*N
w*2
w*1
)(ky
broadband
sN(k)
s2(k)
s1(k)
.
.
.
)(ky
w*N,0 w*N,1 w*N,k-1. . .
Z-1 Z-1
w*2,0 w*2,1 w*2,k-1. . .
Z-1 Z-1
w*1,0 w*1,1 w*1,k-1. . .
Z-1 Z-1
phased array (fixed/adaptive) configuration-frequency domain
Basic phased array configurations
……
…
sN(k)
s2(k)
s1(k)
.
.
.
-+
IFFT
MSE
FFT
w*N
w*2
w*1
)(ky
)(tdFFT
FFT
FFT
broadband
.
.
.
Smart antenna systems
Military networks
Cellularcommunication
networks
Wireless local area networks
switched array adaptive array
switched array adaptive array
switched array adaptive array
Wi-Fi Data rate:11Mbps3G Data rate:100kbps
Switched array (predetermined)
top view(horizontal)
Smart antenna systems
interference
user
1
2
345
6
7
8
9
10
1112 13
14
15
16
user 1
Interference 1top view(horizontal)
user 2
Smart antenna systems
Interference 2
Adaptive array
Smart antenna system
www.vivato.net
12
100
In door range(Mixed Office)
11 Mbps: up to 300m5.5 Mbps: up to 400m 2 Mbps: up to 500m 1 Mbps: up to 600m
Out door range
(outdoor to indoor)
11 Mbps: up to 1.00km5.5 Mbps: up to 1.25km 2 Mbps: up to 2.00km 1 Mbps: up to 2.50km
Out door range(outdoor to outdoor)
11 Mbps: up to 4.20km5.5 Mbps: up to 5.10km 2 Mbps: up to 6.00km 1 Mbps: up to 7.20km
Active user per switch 100
Example: Vivato 2.4 GHz indoor & outdoor Wi-Fi Switches
(EIRP=44dBm;Gain=25 dBi;3-beam)
Polarizationcircular
E
linear
=0
E
E
ellipse
=45
X
Y
Z
iE
ηji eγE sin
γE i cos
’
E
E
=90
E
SuperCART Compact array radiolocation technologyFlam&Russell,Inc.,1990U.S. Patent No., 5,300,885;1994Frequency range: 2 – 30 MHz
Super CART
3-loopV6
V4
V3
V1 V2
V5
Y
X Le ZIV )0(0
Le ZIV )(
iHz 0ˆ
I
iEy 0ˆ
Ikb0.5
b
2-loop
HE
S
Steering vector
γ
γaη
cosesin
ΘsinΘcosΦcosΦsin
ΘsinΦcosΘcosΦsin
hhe
ej
z
x
z
y
0
0
00
00
04
ζH
ii E00
1222 zyx eee
1222 zyx hhh
Blind point
Vector antennas vs. spatial array antennas
Vector antennas measure: ,,,, and power simultaneously, no phase shift device, or synchronization is needed.
Phased array antennas with omnidirectional element measure: ,, and power
Source: Nehorai,A.,University of Illinois at Chicago
Vector antennas vs. spatial array antennas
VA
SA
VA SA
Vector antennas vs. spatial array antennas
Phased array antennas: spatial ambiguities exist
2211 φfφf sinsin
1 2 3 4 5 6 7… …
kφ
kφ
1 2 3 4 5 6 7… …
1φ
2φ
Pηγθφ ,,,,h,h,h,e,e,e zyxzyx
Vector antenna: no ambiguities for DOA estimation
Vector antennas Vs. phased array antennas
Disadvantages of vector antennas
Cheap?
Can use hardware and software of existing communication systems for performance?
f=2.4GHz, =0.125m; vector antenna size: 0.0125m ~ 0.063m
Phased array:d /2=0.063m;L=(N-1)d: 0.188m-0.69m(N=4…12)
f=800MHz, =0.375m; antenna size: 0.04m ~ 0.19m
Phased array:d /2=0.19m;L=(N-1)d: 0.56m-2.06m(N=4…12)
Low profile?
source:M.R. Andrews et al., Nature, Vol. 409(6818), 18 Jan. 2001, pp 316-318.
Working in scattering environment
(a) 2-dipole(monopole)
Low profile antennas with polarization diversity
(c) dipole-loop
(b) 2-loop
TDD/TDMA
Packet switching
AAP1 AP2
user
Handoff between Aps was not standardized at the same time as 802.11b
Packet switching: 3 beam systemtop view(horizontal)
i
ii
PPPd 11
P. Sanchis, et al. 02
iP
1iP
1iP
φΔ
φΔ
1221
12
1221
dφdφ
dφdφ
dφdφ
φi
i
i
DOA
),/Δ(/
),/Δ(
),/Δ(/ˆ
max
max
max
An indoor WLAN designA 4-story office building (including basement), high 30 m, wide 60m and long 100m. We plan to install a Vivato switched array on the 3rd floor.
L=100m
h=30m
w=60m
Switched array
3
2
1
Basement
An indoor WLAN design
Data rate 1Mbps, 2Mbps, 5.5Mbps, 11Mbps
AP’s EIEP 44dBm
AP’s antenna Gain GA 25 dBi
PC antenna Gain GP 0 dBi
Shadowing 8dB
AP’s antenna receiving sensitivity Smin -95dBm ,-92dBm, ,-89dBm, -86dBm
AP’s Noise floor -178dBm/Hz
Body/orientation loss 2dB
Soft partition attenuate factor (p= number) p1.39 dB
Concrete-wall attenuate factor(q= number) q2.38 dB
Average floor attenuation(floor number) 14.0dB(1),19.0dB(2),23.0dB(3),26.0dB(4)
Frequency 2.4GHz
Reference pathloss PL0 (LOS/NLS, r=1m) 45.9dB/ 50.3dB
Pathloss exponent (LOS/NLS, r=1m) 2.1/3.0
Pathloss standard deviation (LOS/NLS) 2.3dB/4.1dB
Average floor attenuation(floor number) 14.0dB(1),19.0dB(2),23.0dB(3),26.0dB(4)
Data of AP’s antenna is from www.vivato.net
An indoor WLAN designMean pathloss with smin: PGSEIRPL min
osdflsmwallowable LLLLLLPL
Path loss model: )log()(0
0 10rrγPLrPL
alPLrPL )(
The coverage ranges are:r=36m,29m,23m and 18m for date rate at 1Mbps, 2Mbps, 5.5Mbps and 11Mbps respectively
Allowable pathloss:
Case 1: user is on the 3rd floor: 3 concrete walls, 3 soft partitions
The coverage ranges are: r=176m,140m,111m and 88m for date rate at 1Mbps, 2Mbps, 5.5Mbps and 11Mbps respectively .
Case 2: user is in the basement : 3 floors; 2 concrete walls, 3 soft partitions
Beamforming antennas in ad hoc networks
P.Gupta and P.R. Kumar,00
thro
ughp
ut o
btai
ned
by e
ach
node
nn logW~
Beam-forming antennas
?
new routing protocol
new channel access scheme
Beamforming antennas in ad hoc networks
interference
target
Phased patch antenna
D.Lu and D.Rutledge,Caltech,02
Z0=50
Z0=50,L/2
Z0=25,L/2
Series resonant patch array
Phased patch array
Beamforming antennas in ad hoc networks
Medium Access Control Protocol(CSMA/CA)CSMA/CA:carrier sense multiple access/collision avoidance ( for omnidirectional antennas)
(Scheduled/On-demand)Packet routing
Neighbor discovery
No standard MAC protocols for directional antenna
Ad hoc networks may achieve better performance in some cases using beamforming antennas.
No obvious improvement for throughput using beamforming antennas
Neighbor discovery become more complex using beamforming antennas.
Beamforming antennas can significantly increasing node and network lifetime in ad hoc networks.
1) traditional exposed node problem for omnidirectional antennas
Channel access
Source:Y Ko et al., 00
A B C D E
RTS
CTSDATA
ACK
RTS
CTS
DATA
DATA
DATA
ACK
A B C D E
RTS
CTS CTS
DATA
DATAACK
RTS
CTS CTS
DATA
DATA
ACK
1) No coverage change. May save power.2) B may not know the location of C.
The nodes are prohibit to transmit or receive signals
The node is free to transmit or receive signals
The node is blocked to communicate with C
2) Omnidirectional and directional antennas solve the exposed node problem
Channel access
A B C D E
RTS
CTSCTS
DATA
RTS
collision
deafcollision
A B C D E
RTS
CTSDATA
DATA
RTS
3) beamforming antennas create new problems
Neighbor discovery
AB
C
DE
A
t
Nt“Hello”
AP Neighbors
A B,CB A,CC A,B,ED EE C,D
Ad hoc WLAN for rural area
ConclusionBeamforming antenna systems improve wireless
network performance -increase system capacity
-improve signal quality -suppress interference and noise -save powerBeamforming antennas improve infrastructure
networks performance. They may improve ad hoc networks performance. New MAC protocol standards are needed.
Vector antennas may replace spatial arrays to further improve beamforming performance