Philips Research doc. IEEE 802.11-02-708r1 1 / 23 IEEE 802.11 session Hawaii November 2002 Alexei...
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Transcript of Philips Research doc. IEEE 802.11-02-708r1 1 / 23 IEEE 802.11 session Hawaii November 2002 Alexei...
PhilipsResearch
doc. IEEE 802.11-02-708r1 1 / 23IEEE 802.11 session Hawaii November
2002
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
PhilipsResearch
doc. IEEE 802.11-02-708r1 2 / 23
Requirements
Higher data rates (> 100Mbps) Increased throughput Extended range
Better coverage
Higher network capacity
Possible solutions
Increase bandwidth per link
Higher order modulation
More powerful CODEC
TX / RX diversity
MIMO
PhilipsResearch
doc. IEEE 802.11-02-708r1 3 / 23
Requirements
Higher data rates (> 100Mbps)Higher data rates (> 100Mbps) Increased throughputIncreased throughput Extended rangeExtended range
Better coverageBetter coverage
Higher network capacity
Possible solutions
Increase bandwidth per linkIncrease bandwidth per link
Higher order modulation
More powerful CODEC
TX / RX diversity
MIMO
Currently 12 channels 2 x rate 6 channels
PhilipsResearch
doc. IEEE 802.11-02-708r1 4 / 23
Requirements
Higher data rates (> 100Mbps)Higher data rates (> 100Mbps) Increased throughputIncreased throughput Extended range
Better coverage
Higher network capacityHigher network capacity
Possible solutions
Increase bandwidth per link
Higher order modulationHigher order modulation
More powerful CODEC
TX / RX diversity
MIMO
Over 64-QAM: severe requirements to analogue & mixed signal circuits
PhilipsResearch
doc. IEEE 802.11-02-708r1 5 / 23
Requirements
Higher data rates (> 100MbpsHigher data rates (> 100Mbps) Increased throughputIncreased throughput Extended rangeExtended range
Better coverageBetter coverage
Higher network capacityHigher network capacity
Possible solutions
Increase bandwidth per link
Higher order modulation
More powerful CODECMore powerful CODEC
TX / RX diversity
MIMO
Higher complexity: power & area
Iterative demodulation with “anti-Gray” maps Turbo coded CODEC
PhilipsResearch
doc. IEEE 802.11-02-708r1 6 / 23
Possible solutions
Increase bandwidth per link
Higher order modulation
More powerful CODEC
TX / RX diversityTX / RX diversity
MIMO
Requirements
Higher data rates (> 100MbpsHigher data rates (> 100Mbps) Increased throughputIncreased throughput Extended rangeExtended range
Better coverageBetter coverage
Higher network capacityHigher network capacity
PhilipsResearch
doc. IEEE 802.11-02-708r1 7 / 23
Requirements
Higher data rates (> 100Mbps)Higher data rates (> 100Mbps) Increased throughputIncreased throughput Extended rangeExtended range
Better coverageBetter coverage
Higher network capacityHigher network capacity
Possible solutions
Increase bandwidth per link
Higher order modulation
More powerful CODEC
TX / RX diversity
MIMOMIMO
PhilipsResearch
doc. IEEE 802.11-02-708r1 8 / 23
TX
RX
Theoretical throughput scales linearlyw.r.t. the # of antennas:
Increased range / coverage in NLOS environments
Cheap RF-CMOS technology:
fractional cost per RF front-end (5.x GHz)
Keep DSP complexity limited
Motivation
Constraint
PhilipsResearch
doc. IEEE 802.11-02-708r1 9 / 23
TX
RX 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,
select out of antennas
optimal selection is rather complex simple sub-optimal selection possible
PhilipsResearch
doc. IEEE 802.11-02-708r1 10 / 23
Receiver Transmitter
4 TX chains 4 RX chains f ~ 5.8GHz BW 20MHz
14 bit ADC 35 dB AGC
PhilipsResearch
doc. IEEE 802.11-02-708r1 11 / 23
DAC/ADC
LNA
mixer
AGC+LPF
Monopoles
PhilipsResearch
doc. IEEE 802.11-02-708r1 12 / 23
1 2 3 4 5 6 7 8 9 10 11 12
“soft” walls, much glass few heavy metallic constructions lots of furniture few concrete walls / blocks
Total TX power 14dBm
PhilipsResearch
doc. IEEE 802.11-02-708r1 13 / 23
0.0
0.5
1.0
1.5
2.0
2.5
3 6 9 12 15 18 21 24 27 30 33 36
Range (m)
RM
S d
ela
y s
pre
ad
[x
sym
bo
l ra
te]
80% quantil
50% quantil
10% quantil 1% quantil
RMS delay spread versus range
-10
00
10
20
30
40
50
3 6 9 12 15 18 21 24 27 30 33 36
Range (m)
SN
R p
er
RX
an
ten
na
[d
B]
80% quantil
50% quantil
10% quantil 1% quantil
Signal-to-noise ratio per RX antenna versus range
PhilipsResearch
doc. IEEE 802.11-02-708r1 14 / 23
FEC encoder
interleaver
mapper IFFT
cyclic extension
pulse shaping
FEC encoder
interleaver
mapper IFFT
cyclic extension
pulse shaping
FEC encoder
FFT
sampling
pulse shaping
FEC encoder
FFT
sampling
pulse shaping
MUX
DEMUX
streamcycling
MMSE filter
MRC
+
+
interleaver
mapper FEC encoder
-
-
latency of ~ one TX/RX cycle
deinterleavedemap
TX signal path
RX signal path
deinterleavedemap
PhilipsResearch
doc. IEEE 802.11-02-708r1 15 / 23
space frequency
interleaver
mapper IFFT
cyclic extension
pulse shaping
FEC decoder
FFT
sampling
pulse shaping
FFT
sampling
pulse shaping
FEC encoder
mapper IFFT
cyclic extension
pulse shaping
space frequency
de-interleaver
2 x 2MMSE
filter
TX signal path
RX signal path
demapper
demapper
PhilipsResearch
doc. IEEE 802.11-02-708r1 16 / 23
0
50
100
150
200
250
300
3 6 9 12 15 18 21 24 27 30 33 36
Range (m)
Maxim
um
ra
te [M
bp
s]
1 x 1 RX 11 x 1 RX 42 x 2 RX 22 x 2 RX 43 x 3 RX 33 x 3 RX 44 x 4 RX 4
Outage capacities versus rangeoutage rate 1%
optimal RX antenna selection
S-F modulation / layered RXMIMO channel
0
50
100
150
200
250
300
3 6 9 12 15 18 21 24 27 30 33 36
Range (m)
Maxim
um
ra
te [M
bp
s]
1 x 1 RX 11 x 1 RX 42 x 2 RX 22 x 2 RX 43 x 3 RX 33 x 3 RX 44 x 4 RX 4
PhilipsResearch
doc. IEEE 802.11-02-708r1 17 / 23
0
50
100
150
200
250
300
3 6 9 12 15 18 21 24 27 30 33 36
Range (m)
Maxim
um
ra
te [M
bp
s]
1 x 1 RX 11 x 1 RX 42 x 2 RX 22 x 2 RX 43 x 3 RX 33 x 3 RX 44 x 4 RX 4
Outage capacities versus rangeoutage rate 1%
optimal RX antenna selection
S-F interleaving / MMSE MIMO channel
0
50
100
150
200
250
300
3 6 9 12 15 18 21 24 27 30 33 36
Range (m)
Maxim
um
ra
te [M
bp
s]
1 x 1 RX 11 x 1 RX 42 x 2 RX 22 x 2 RX 43 x 3 RX 33 x 3 RX 44 x 4 RX 4
PhilipsResearch
doc. IEEE 802.11-02-708r1 18 / 23
Outage capacities versus rangeoutage rate 1%
optimal RX antenna selection
S-F interleaving / MMSE S-F modulation / layered RX
0
50
100
150
200
250
300
3 6 9 12 15 18 21 24 27 30 33 36
Range (m)
Maxim
um
ra
te [M
bp
s]
1 x 1 RX 11 x 1 RX 42 x 2 RX 22 x 2 RX 43 x 3 RX 33 x 3 RX 44 x 4 RX 4
0
50
100
150
200
250
300
3 6 9 12 15 18 21 24 27 30 33 36
Range (m)
Maxim
um
ra
te [M
bp
s]
1 x 1 RX 11 x 1 RX 42 x 2 RX 22 x 2 RX 43 x 3 RX 33 x 3 RX 44 x 4 RX 4
PhilipsResearch
doc. IEEE 802.11-02-708r1 19 / 23
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
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 attractivesub-optimal RX antenna selection looks attractive
PhilipsResearch
doc. IEEE 802.11-02-708r1 20 / 23
0
20
40
60
80
100
120
140
160
180
200
3 6 9 12 15 18 21 24 27 30 33 36
Range (m)
Maxim
um
ra
te [M
bp
s]
2 x 2 RX 2
2 x 2 RX 4 (opt)
2 x 2 RX 4 (sub)
2 x 4 RX 4 (MRC)
1 x 1 RX 1
Outage capacities versus rangeoutage rate 1%
S-F modulation with MMSE receiver & sub-optimal RX selection looks attractive
0
20
40
60
80
100
120
140
160
180
200
3 6 9 12 15 18 21 24 27 30 33 36
Range (m)
Maxim
um
ra
te [M
bp
s]
2 x 2 RX 2
2 x 2 RX 4 (opt)
2 x 2 RX 4 (sub)
2 x 4 RX 4 (MRC)
1 x 1 RX 1
S-F modulation / layered RX S-F interleaving / MMSE
PhilipsResearch
doc. IEEE 802.11-02-708r1 21 / 23
Candidate FEC structures
Standard convolutional code rate (1/2) 64-state 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
Turbo- CODEC similar to that of UMTS 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
PhilipsResearch
doc. IEEE 802.11-02-708r1 22 / 23
0.1%
1.0%
10.0%
100.0%
3 6 9 12 15 18 21 24
Range (m)
Ou
tag
e r
ate
[%
]
108 Mbps 96 Mbps 72 Mbps 64 Mbps 36 Mbps 32 Mbps 24 Mbps
108Mbps 64QAM, rate 3/4 96Mbps 64QAM, rate 2/372Mbps 16QAM, rate 3/464Mbps 16QAM, rate 2/336Mbps 16QAM, rate 3/432Mbps QPSK, rate 2/324Mbps QPSK, rate 1/2
Signalling
PhilipsResearch
doc. IEEE 802.11-02-708r1 23 / 23
Observations
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