IEEE 802.11 session Hawaii November 2002
11-02-708r0-WNG
Alexei Gorokhov, Paul Mattheijssen, Manel Collados,
Bertrand Vandewiele, Gunnar Wetzker
Philips Research
PHY options for high throughput wireless LANs
Right time and place for MIMO?
Performance enhancement via antenna selection
Experimental set-up and channel measurements
MIMO architectures for high data rates
Experimental results
Philips
Research
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Requirements
Possible solutions

Higher data rates (> 100Mbps)

Increase bandwidth per link

Increased throughput

Higher order modulation

Extended range

More powerful CODEC

Better coverage

TX / RX diversity

Higher network capacity

MIMO
Philips
Research
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Requirements
Possible solutions

Higher data rates (> 100Mbps)

Increase bandwidth per link

Increased throughput

Higher order modulation

Extended range

More powerful CODEC

Better coverage

TX / RX diversity

Higher network capacity

MIMO

Currently  12 channels
2 x rate  6 channels
Philips
Research
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Requirements
Possible solutions

Higher data rates (> 100Mbps)

Increase bandwidth per link

Increased throughput

Higher order modulation

Extended range

More powerful CODEC

Better coverage

TX / RX diversity

Higher network capacity

MIMO

Philips
Research
Over 64-QAM: severe requirements
to analogue & mixed signal circuits
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Possible solutions
Requirements

Higher data rates (> 100Mbps)

Increase bandwidth per link

Increased throughput

Higher order modulation

Extended range

More powerful CODEC

Better coverage

TX / RX diversity

Higher network capacity

MIMO



Philips
Research
Higher complexity: power & area
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Iterative demodulation with “anti-Gray” maps
Turbo coded CODEC
11-02-708r0-WNG
Requirements
Possible solutions

Higher data rates (> 100Mbps)

Increase bandwidth per link

Increased throughput

Higher order modulation

Extended range

More powerful CODEC

Better coverage

TX / RX diversity

Higher network capacity

MIMO
Philips
Research
6 / 23
11-02-708r0-WNG
Requirements
Possible solutions

Higher data rates (> 100Mbps)

Increase bandwidth per link

Increased throughput

Higher order modulation

Extended range

More powerful CODEC

Better coverage

TX / RX diversity

Higher network capacity

MIMO
Philips
Research
7 / 23
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Motivation
RX

Theoretical throughput scales linearly
w.r.t. the # of antennas:

Increased range / coverage in NLOS
environments

Cheap RF-CMOS technology:
fractional cost per RF front-end (5.x GHz)
Constraint
TX
Philips
Research

Keep DSP complexity limited
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
RX
select
out of
antennas
TX
Philips
Research
Need for extra degrees of freedom at
RX to ensure enough diversity (

High incremental cost of adding RF
front-end versus the cost of antenna

Use
antennas and
front-ends at
RX, select adaptively a subset of
antennas,


optimal selection is rather complex
simple sub-optimal selection possible
9 / 23
)
11-02-708r0-WNG






Receiver
Philips
Research
Transmitter
10 / 23
4 TX chains
4 RX chains
f ~ 5.8GHz
BW 20MHz
14 bit ADC
35 dB AGC
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LNA
mixer
DAC/ADC
Monopoles
Philips
Research
AGC+LPF
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Total TX power 14dBm
1




Philips
Research
“soft” walls, much glass
few heavy metallic constructions
lots of furniture
few concrete walls / blocks
2
3
4
5
6
7
8
9 10 11 12
12 / 23
SNR per RX antenna [dB]
50
80%
50%
10%
1%
40
quantil
quantil
quantil
quantil
30
20
10
00
-10
Philips
Research
3
6
9
12 15 18 21 24 27 30 33 36
RMS delay spread [x symbol rate]
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2.5
80%
50%
10%
1%
2.0
quantil
quantil
quantil
quantil
1.5
1.0
0.5
0.0
3
6
9
12 15 18 21 24 27 30 33 36
Range (m)
Range (m)
Signal-to-noise ratio per RX
antenna versus range
RMS delay spread versus range
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TX signal path
FEC
encoder
interleaver
FEC
encoder
interleaver
IFFT
cyclic
extension
pulse
shaping
mapper
IFFT
cyclic
extension
pulse
shaping
MMSE
filter
FFT
sampling
pulse
shaping
FFT
sampling
pulse
shaping
mapper
stream
cycling
DEMUX
RX signal path
FEC
encoder
deinterleave
demap
FEC
encoder
deinterleave
demap
MUX
+
MRC
+
-
FEC
encoder
interleaver
mapper
latency of ~ one TX/RX cycle
Philips
Research
11-02-708r0-WNG
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TX signal path
FEC
encoder
space
frequency
mapper
IFFT
cyclic
extension
pulse
shaping
interleaver
mapper
IFFT
cyclic
extension
pulse
shaping
RX signal path
FEC
decoder
Philips
Research
space
frequency
deinterleaver
demapper
demapper
2x2
MMSE
filter
FFT
sampling
pulse
shaping
FFT
sampling
pulse
shaping
11-02-708r0-WNG
300
1
1
2
2
3
3
4
250
200
x
x
x
x
x
x
x
1
1
2
2
3
3
4
RX
RX
RX
RX
RX
RX
RX
1
4
2
4
3
4
4
150
100
50
Maximum rate [Mbps]
Maximum rate [Mbps]
300
1
1
2
2
3
3
4
250
200
x
x
x
x
x
x
x
1
1
2
2
3
3
4
RX
RX
RX
RX
RX
RX
RX
1
4
2
4
3
4
4
150
100
50
0
0
3
6
9
12 15 18 21 24 27 30 33 36
3
6
9
12
MIMO channel
15
18
21
24
Range (m)
Range (m)
S-F modulation / layered RX
Outage capacities versus range
outage rate 1%
optimal RX antenna selection
Philips
Research
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27
30
33
36
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1
1
2
2
3
3
4
250
200
x
x
x
x
x
x
x
1
1
2
2
3
3
4
RX
RX
RX
RX
RX
RX
RX
1
4
2
4
3
4
4
150
100
50
0
300
Maximum rate [Mbps]
Maximum rate [Mbps]
300
1
1
2
2
3
3
4
250
200
x
x
x
x
x
x
x
1
1
2
2
3
3
4
RX
RX
RX
RX
RX
RX
RX
1
4
2
4
3
4
4
150
100
50
0
3
6
9
12 15 18 21 24 27 30 33 36
3
6
9
12
Range (m)
MIMO channel
15
18
21
24
Range (m)
S-F interleaving / MMSE
Outage capacities versus range
outage rate 1%
optimal RX antenna selection
Philips
Research
17 / 23
27
30
33
36
11-02-708r0-WNG
300
1
1
2
2
3
3
4
250
200
x
x
x
x
x
x
x
1
1
2
2
3
3
4
RX
RX
RX
RX
RX
RX
RX
1
4
2
4
3
4
4
150
100
50
0
Maximum rate [Mbps]
Maximum rate [Mbps]
300
1
1
2
2
3
3
4
250
200
x
x
x
x
x
x
x
1
1
2
2
3
3
4
RX
RX
RX
RX
RX
RX
RX
1
4
2
4
3
4
4
150
100
50
0
3
6
9
12
15
18
21
24
27
30
33
36
3
6
9
12
Range (m)
S-F modulation / layered RX
15
18
21
24
Range (m)
S-F interleaving / MMSE
Outage capacities versus range
outage rate 1%
optimal RX antenna selection
Philips
Research
18 / 23
27
30
33
36
11-02-708r0-WNG
MIMO capacities




MIMO capacity scales almost linearly w.r.t. the number of TX/RX antennas
space-frequency modulation with layered RX : ~90% of theoretical limit
space-frequency interleaving with MMSE:
~60% of theoretical limit
…………… with adaptive RX selection:
~80% of theoretical limit
Feasibility aspects



Philips
Research
channel processing beyond 2 x 2 system is hardly feasible (baseband)
layered reception yields higher complexity & processing latency,
seems prohibitive beyond 2 x 2 systems
sub-optimal RX antenna selection looks attractive
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11-02-708r0-WNG
200
180
2 x 2 RX 2
180
2 x 2 RX 2
160
2 x 2 RX 4 (opt)
2 x 2 RX 4 (sub)
160
2 x 2 RX 4 (opt)
2 x 2 RX 4 (sub)
140
2 x 4 RX 4 (MRC)
1 x 1 RX 1
120
100
80
60
40
Maximum rate [Mbps]
Maximum rate [Mbps]
200
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140
120
100
80
60
40
20
20
0
0
3
6
9
12
15
18
21
24
27
30
33
2 x 4 RX 4 (MRC)
1 x 1 RX 1
36
3
6
9
Range (m)
12
15
18
21
24
27
30
33
Range (m)
S-F interleaving / MMSE
S-F modulation / layered RX
Outage capacities versus range
outage rate 1%

Philips
Research
S-F modulation with MMSE receiver & sub-optimal RX selection looks attractive
36
11-02-708r0-WNG
Candidate FEC structures

Standard convolutional code






Turbo- CODEC similar to that of UMTS





Philips
Research
rate (1/2) 64-state (NASA) code [133,171]8
puncture to achieve mandatory / supplementary rate modes
soft-input Viterbi decoding at RX
easy to implement, IEEE 802.11 acceptance
expected to be sensitive to SINR discrepancy
rate (1/3) PCCC with 8-state components [13,15]8
puncture to achieve desired rates
iterative SISO decoding (Max-Log-MAP)
reduced SINR margin, less sensitive to SINR discrepancy
rather high complexity
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Outage rate [%]
100.0%
108
72
36
24
Mbps
Mbps
Mbps
Mbps
96 Mbps
64 Mbps
32 Mbps
10.0%
1.0%
Signalling
0.1%
3
6
9
12
15
Range (m)
Philips
Research
18
21
24
108Mbps  64QAM, rate 3/4
96Mbps  64QAM, rate 2/3
72Mbps  16QAM, rate 3/4
64Mbps  16QAM, rate 2/3
36Mbps  16QAM, rate 3/4
32Mbps  QPSK, rate 2/3
24Mbps  QPSK, rate 1/2
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Observations
Philips
Research

Maximum data rate scales linearly w.r.t. to the
number of antennas

Receive antenna selection improves substantially
maximum data rates (limited number of TX/RX chains)

2 x 2 space division multiplexing with selection 2 of 4 RX
antennas  200%-300% of single-antenna rates
23 / 23