michael rice brigham young university
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MICHAEL RICEBRIGHAM YOUNG UNIVERSITY
SPACE-TIME CODING FOR AERONAUTICAL
TELEMETRY
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Outline
The “Two Antenna” Problem Space-Time Coding An Experiment with Space-Time Coding and
Tier-1 Modulations at EAFB Prototype Transmitter Prototype Demodulator Flight Test Results
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The Two-Antenna Problem
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The Two-Antenna Problem
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The Two-Antenna Problem
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The Two-Antenna Problem
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Demonstration
6 feet
5 feet
Aircraft Fuselage
carrier frequency = 2200 MHz
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Demonstration: Aircraft Turn
\mydocs\tier-1\stcdemo0.m
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Solution 1: Frequency Diversity
carrier f0
carrier f1
Requires 2× the bandwidth
Requires 2 receivers (possibly two receive antenna dishes)
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Solution 2: Steerable Beam
Think of the two antennas as a two-element antenna array
Adjust the phases of the signals to steer the beam at the receive antenna
Requires an uplink to tell the transmitter where the receiver is …
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Solution 2: Steerable Beam
Think of the two antennas as a two-element antenna array
Adjust the phases of the signals to steer the beam at the receive antenna
… or requires GPS output to be linked to the telemetry package.
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Solution 3: Space-Time Coding
The space-time code provides transmit diversity.
Transmit two different signals from the two antennas.
The signals are different from each other, but both are related to the data stream.
The relationship is defined through a “space-time code.”
The two signals posses a phase relationship that avoids destructive interference on average.
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Solution 3: Space-Time Coding
The space-time code provides transmit diversity.
Transmit two different signals from the two antennas.
The signals are different from each other, but both are related to the data stream.
The relationship is defined through a “space-time code.”
The two signals posses a phase relationship that avoids destructive interference on average.
The ground-based receiver is much more complex.
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Outline
The “Two Antenna” Problem Space-Time Coding An Experiment with Space-Time Coding and
Tier-1 Modulations at EAFB Prototype Transmitter Prototype Demodulator Flight Test Results
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Abstract Model for Space-Time Coding
space-time
encoder
data
s0(t)
s1(t)
h0
h1space-time
demodulator +
decoder
r(t) = h0s0(t) + h1s1(t) + w(t)
data
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s(k-2) s(k-1) s(k) s(k+1) s(k+2) s(k+3)
s(k-2)
s(k-1)
s*(k-1)
s*(k-2)
Example: the 2 × 1 Alamouti Space-Time Code
space-time
encoder
inphase
quadrature
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s(k-2) s(k-1) s(k) s(k+1) s(k+2) s(k+3)s(k) s(k+1) s(k+2) s(k+3)
s(k)
s(k+1)
s*(k+1)
s*(k)
Example: the 2 × 1 Alamouti Space-Time Code
space-time
encoder
s(k-2)
s(k-1)
s*(k-1)
s*(k-2)
inphase
quadrature
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Why This Works ...
SNR with traditional signaling:
SNR with space-time coding:
0
210 NEhh b
0
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20 N
Ehh b
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Demonstration: Aircraft Turn With STC
\mydocs\tier-1\stcdemo.m
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Outline
The “Two Antenna” Problem Space-Time Coding An Experiment with Space-Time Coding and
Tier-1 Modulations at EAFB Prototype Transmitter Prototype Demodulator Flight Test Results
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binary data
source
ARTM Tier-1
Space-Time Block
Encoder
FQPSK-JR Transmitter
FQPSK-JR Transmitter
PA
PA
to top antenna
to bottom antenna
STC transmitter
aircraft fuselage
S-band downconverter
DMO
100 Msamples/sec
70 MHz
5 Mbits/sec
to DVD
data
data
clock
clock
0h
1h
ts0
ts1
Experimental Configuration
LNA
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C-12 Beechcraft: Airborne Platform
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On-Board Transmit Equipment
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Space-Time Encoder
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The Signal Processing
ts0
ts1
0h
1h
000 tsh
111 tshDigital Signal ProcessingThe demodulator needs to estimate • The channel gains: h0, h1
• The propagation delays: t0, t1
• The frequency offset: Df
System Model
digital signal processingusing MATLAB
data
estimates
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0 5 10 150
0.5
1|h
0|
0 5 10 150
0.5
1
|h1|
time, seconds
Estimated Channel Gain Magnitudes
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0 5 10 150
50
100
150
200
250
300
350 ,
deg
rees
time, seconds
Estimated Channel Gain Phase Difference
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0 5 10 15-1
-0.5
0
0.5
1 /T
s
time, seconds
Estimated Channel Delay Difference
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0 5 10 15 20-70
-60
-50
-40
-30
-20
-10
time (sec)
|h0 +
h1| (
dB)
A Fade Using Traditional Signaling
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Experimental Results
No bit errors Even during signal fade (using traditional
two-antenna transmission) We need to build a prototype receiver to see
if this really works …
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Development Contract
Deseret Morning News 11 March 2005
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Outline
The “Two Antenna” Problem Space-Time Coding An Experiment with Space-Time Coding and
Tier-1 Modulations at EAFB Prototype Transmitter Prototype Demodulator Flight Test Results
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Pilot Structure
D bitsLd samples
D bitsLd samples
data 0
data 0pilot 0 data 0 pilot 0
P bitsLp samples
D bitsLd samples
P bitsLp samples
D bitsLd samples
D bitsLd samples
data 1
data 1pilot 1 data 1 pilot 1
P bitsLp samples
D bitsLd samples
P bitsLp samples
Pilot bits are added to each transmitted waveform for estimating the frequency offset, the timing delays, and the (complex-valued) channel gains.
upper antenna
lower antenna
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STC Modulator Block Diagram
bit-levelSTC
encoder
MUXstored pilot bits
(A)
SOQPSK-TG
Modulator
RF(L-Band) PA RF A
RF BMUXstored pilot bits
(B)
clock 2 control
control
control
control
control
bit stream A
bit stream BSOQPSK-
TGModulator
RF(L-Band) PA
frequency locked (minimum)phase locked (preferred)
data
clock
buffer
input clock clock 2 IF/RF
input domain(TTL)
output domain
(RF)
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Prototype Transmitter
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Prototype Transmitter
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Outline
The “Two Antenna” Problem Space-Time Coding An Experiment with Space-Time Coding and
Tier-1 Modulations at EAFB Prototype Transmitter Prototype Demodulator Flight Test Results
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downconvert&
resample
pilotdetector
frequency estimator
from ADC
timing&
channelestimator
Buffer
space-timedecoder(trellis)
derotated data
01 0h 1h
derotated pilots from Buffer
to channel/timing
estimatorto interpolators/
ST decoder
derotated data from Buffer
0
1
to output buffer
interpolator
interpolator
0 1 0h 1h
pilots
data
System Design
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A/DConverter
Sampling at 93.33 MHz
Resampling Filters
Pilot DetectorFrequency
OffsetEstimator
Timing & Channel Estimator
Detection Filters
BufferReindexer
Buffer Buffer
Buffer
Interpolator
Trellis Detector bits
Prototype Demodulator Hardware
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Resampling and Pilot Acquisition
IF to Complex Baseband 70 MHz IF signal 93.3 MHz ADC Resample
Post aliasing DDC is 46.67 Msps Resample to 4 samples/bit = 41.6
Msps Pilot Detection (middle 96 bits)
96 bits → ~66.6 kHz bandwidth Detect Pilot #0 and Pilot #1 Frequency-domain fast correlation
Cover a 200 KHz bandwidth Single 1024-point forward FFT Six 1024-point inverse FFT’s Implements the overlap-and-add fast
correlation algorithm
A/DConverter
Sampling at 93.33 MHz
Resampling Filters
Pilot Detector
Reindexer
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Frequency and Channel Estimations
Data-aided ML frequency offset estimation STC decoding demands RMSEE of
~10 Hertz! Coarse estimation and “bracketing”
followed by fine estimation Received signal derotated based on
estimate Joint Estimation of 0, 1, h0,
and h1 Maximum Likelihood (ML) estimate
of the delays and channel gains Calculate the channel gains h0 and
h1 for the given delay estimates Minimize object function using a
“discrete” simplex algorithm
Frequency Offset
Estimator
Timing & Channel Estimator
Detection Filters
Buffer
Buffer
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Timing and Channel Estimator
Signal Model for Pilot Symbols in Matrix-Vector Form
Maximum-Likelihood Estimator
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Timing Estimator
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Timing and Channel Estimator
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Interpolation and Detection
Interpolation Piece-wise parabolic Farrow filter Outputs 1 sample/bit
Least Squares trellis detector Detector based on a reduced
complexity model of the Tier 1 waveforms Model is the 8 waveform XTCQM
common model for SOQPSK-TG and FQPSK-JR
Trellis accounts for the memory in the signal due to the modulation and the STC
Buffer
Buffer
Interpolator
Trellis Detector bits
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Trellis 0
16 16 32 64 128 128 64 32 16
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Trellis 1
16 16 32 64 128 128 64 32 16
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Prototype Demodulator
IF input (70 MHz)
A/D Converter (93.3 Msamples/s)
FPGAs Vertex 2 Pro Clock and Data Output(10 Mbit/s)
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Outline
The “Two Antenna” Problem Space-Time Coding An Experiment with Space-Time Coding and
Tier-1 Modulations at EAFB Prototype Transmitter Prototype Demodulator Flight Test Results
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Prototype Testing
QuasonixSTC
Transmitter
atten
Combiner
atten
atten
Noise+
InterferenceTest Set
TelemetryReceiver
BYUSTC
DemodBERT
Laptop PC
RF1485 MHz
RF1485 MHz
IF70 MHz
EAFB Telemetry Lab Configuration
FastBit FB2000
Channel MicrowaveIsolator LS3211
Hewlett-PackardStep Attenuator
HP8495B
Narda 4322-2
BERT
Fireberd 6000A
atten
atten
PasternackPE7017-40
Reach TechnologiesVBERT-50S-1-R
M/A Comm 5550i
Channel MicrowaveIsolator LS3211
PasternackPE7017-40
Hewlett-PackardStep Attenuator
HP8495B
Hewlett-PackardStep Attenuator
HP8495B
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BER Tests (EAFB Telemetry Lab)
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Flight Tests: Block Diagram
STCTransmitter
SOQPSKTransmitter
+
+÷
L-band isolator
L-band isolator
L-band isolator
L-band isolator
L-band isolator
3 dB
3dB
attenuator
attenuator
splitter
combiner
combiner
upper antenna
lower antenna
10 W
10 W
5 W
5 W
5 W
5 W
10 W
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Flight Tests: Transmit Antennas
Lower Telemetry Antenna(behind the antenna looking forward)
Upper Telemetry Antenna(looking across the fuselage)
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Flight Tests: Idealized Gain Patterns
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More on Space Time Coding for Aero-T/M
Michael Jensen, Michael Rice, and Adam Anderson, "Aeronautical Telemetry Using Multiple-Antenna Transmitters," IEEE Transactions on Aerospace and Electronic Systems, vol. 43, no. 1, pp. 262 - 272, January 2007.
Tom Nelson and Michael Rice, "MIMO Communications Using Offset Modulations," in Proceedings of the IEEE International Waveform Diversity and Design Conference, Lihue, HI, 23 - 27 January 2006.
Tom Nelson, Michael Rice, and Michael Jensen, "Experimental Results for Space-Time Coding Using ARTM Tier-1 Modulation," in Proceedings of the International Telemetering Conference, Las Vegas, NV, October 2005, pp. 90-100.
Tom Nelson, Michael Rice, and Michael Jensen, "Experimental Results with Space-Time Coding Using FQPSK," in Proceedings of the European Test and Telemetry Conference, Toulouse, France, June 2005.
Michael Jensen and Michael Rice, "Alamouti and Differential Transmit Diversity for Air-to-Ground Communications," in Proceedings of the IEEE/ACES International Conference on Wireless Communications and Applied Computational Electromagnetics, pp. 468 - 471, April 2005, Honolulu, Hawaii.
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More on Space Time Coding for Aero-T/M
Tom Nelson and Michael Rice, "Detection of SOQPSK in a Space-Time Coded System With Arrival Time Differences," in Proceedings of IEEE Military Communications Conference, Monterey, CA, November 2004.
Michael Jensen, Michael Rice, Tom Nelson and Adam Anderson, "Orthogonal Dual-Antenna Transmit Diversity for SOQPSK in Aeronautical Telemetry Channels," in Proceedings of the International Telemetering Conference, San Diego, CA, October 2004, pp. 337-344.
Michael Jensen, Michael Rice, and Adam Anderson, "Comparison of Alamouti and Differential Space-Time Codes for Aeronautical Telemetry Dual-Antenna Transmit Diversity," in Proceedings of the International Telemetering Conference, San Diego, CA, October 2004, pp. 345-354.
Tom Nelson and Michael Rice, "Space-Time Coded SOQPSK in the Presence of Differential Delays," in Proceedings of the International Telemetering Conference, San Diego, CA, October 2004, pp. 738 - 747.
Ron Crummett, Michael Jensen, and Michael Rice, "Transmit Diversity Scheme for Dual-Antenna Aeronautical Telemetry Systems," in Proceedings of the International Telemetering Conference, San Diego, CA, October 2002, pp. 113 - 121.
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