Transcript Casper Signal Processing Workshop SKA Signal Processing (Preliminary) Wallace Turner Domain Specialist for Signal Processing.

Casper Signal Processing Workshop
2009
SKA Signal Processing
(Preliminary)
Wallace Turner
Domain Specialist for Signal Processing
Example Configuration (Phase 2)
SPDO
Memo 100 identifies the
following options:
70-200MHz: Sparse AA
200-500MHz: Sparse AA
500MHz-10GHz: 3000
15m dishes
Or
500MHz- 10GHz: 2000
15m dishes with PAFs
plus WBSPF
Or
500MHz-10GHz: 250
Dense AA plus 2400 15m
dishes/ WBSPF
Example Configuration with Dense AA + SPF
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Note: On going
discussions 15m vs 12m
dishes
Reference Design
SPDO
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Dishes+Single Pixel Feeds
SPDO
American: 6m Hydroformed Dish
Canadian: 10m Composite Dish
South Africa: 15m Composite Dish
Note:
On going discussions 12m vs. 15m dish
Required sensitivity 10,000 m2K-1
Correlator processor and dump rate
proportional to Nant2
ADC likely to be at antenna (4 bit ?)
O/Prate = fs.4bits
= 160 G bits/s per antenna
Where fs = sample rate likely to be split into
smaller basebands
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AGN Science Chapter Example
SPDO
AGN Science Chapter
Survey Speed: 1 x 105 m4K-2deg2
Frequency range 500 MHz to 8GHz
Tsys now: Not achieved over bandwidth
Target Tsys: 35K
No. of 15 m dishes needed for AGN and Star Formation for
various aperture efficiencies with single pixel feeds
1600
1400
1200
1000
s
e 800
h
s
i
d 600
.
o
N 400
50%
55%
60%
65%
200
0
30
35
40
45
Achieved Tsys K
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50
55
60
Dishes+Phased Array Feeds
SPDO
ASKAP Australia: Checkerboard Array
Apertif Netherlands: Vivaldi Array
Note:
Some Channelization and Beamforming
likely to be at antenna.
Maximum Field of View limited by
Array size and focal length of dish.
Achievable field of view limited by
network bandwidth.
PHAD Canada: Vivaldi Array
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Example Number PAFs Required
SPDO
Wide Field Polarimetry Science Chapter
Survey Speed: 5 x 108 m4K-2deg2
Max frequency 2GHz
WBSPF would require over 15,000 dishes
No. of 15 m dishes needed for Wide Field Polarimetry for
various aperture efficiencies with PAF
5000
4500
4000
3500
3000
s
e 2500
h
s
i 2000
d
.
o 1500
N
1000
500
0
50%
60%
70%
80%
40
50
60
70
80
90
100
Achieved Tsys K
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Tsys now: 100 K
Target Tsys: 50 K
Simplistic View of PAF Processing
SPDO
•
•
Consider Frequency Domain Beamforming
Channelisation: Nchan ~ 64
– 12 taps gives < 60db aliasing between channels
– Processing load ~ (Ntaps + 3*log2(Nchan)) x Nel x 2pol x fs
– Ntaps = 12, Nel = 96 x 2pol & fs = 1.4 GHz for 700MHz bandwidth
Processing load
= 8 x 1012 MACS
•
Beamformer (per antenna):
– Average beams per channel 30
– Processing Load = Nbms.Nel.2pol.fs. 4Multiplies = 3 x 1013 Macs
•
O/Prate= Nbms.2pol.fs.4bits.8B10B = 420 G bit/s
– 42 10 G bit/s optical cables per antenna
– Includes 25 % extra bandwidth required for 8B/10B Encoding
•
2000 dishes with PAFs (total 840 T bits/s)
Note :*FFT implementation dependent
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Sparse Aperture Arrays
SPDO
LOFAR: Netherlands et al
Note:
Two types of sparse
AA required:
70MHz – 200 MHz
200MHz – 500 MHz
LWA: USA
MWA: USA & Australia
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Only solution for EoR
HI Science Chapter
Dense Aperture Array Station
SPDO
Assumed Dense Aperture Array
~256 tiles x 256 elements per tile
2 polarisations per element
Sample rate ~ 2.5 G Hz
4 bits/ sample
56 m diameter
250 stations
Tsys now 120K
Target 35K Memo 100
Dense AA Detail
300MHz to 1GHz i.e. 700MHz bandwidth
fs=2 x 700 MHz
56m diameter array =>2463 m2
44.4 2pol elements per m^2 (30 cm
wavelength) = 110,000 elements x 2pol per
station, about 2 x 64k elements.
Array efficiency 80%, Bore efficiency 75%
& Tsys = 35K -> 250 stations for
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10,000m2K-1 sensitivity
Processing Bunker
Simplistic View of Dense Aperture
Array Processing
•
SPDO
Consider Frequency Domain Beamforming
– Delay is implemented as a phase slope in frequency domain.
– Alternative time domain with tuned lengths of co-ax.
•
Channelisation: Nchan 1024,
– 12 taps gives < 60db aliasing between channels
– Ntaps = 12, Nant = 64k x 2pol & fs = 1.4 GHz for 700MHz bandwidth
– Processing ~ (Ntaps + 3*log2(Nchan)) x Nant x 2pol x fs**=8 x 1015 MACS
•
Beamformer (per station):
– Average 1437 beams per channel to cover 250 sq degrees FoV
– Processing Load = Nant.2pol.Nbms.fs. 4MACS = 1 x 1018 MACS
•
O/Prate**= Nbms.2 pol.fs.4bits.8B10B = 20 T bit/s
– Over 2000 10 G bit/s optical cables, 8B/10B Encoding factor 1.25
•
Up to 250 Dense AA Stations (total 10 peta bits/s)
Note :*FFT implementation dependent
**Ignores upsampling of channelizer
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Correlator Processing Loads
SPDO
•
Channelisation (700MHz bandwidth):
– SPF 4 x 1014 (105 channels)
– PAF 4 x 1012 (4096 fine channels giving ~ 105 total)
– Dense AA 6 x 1015 (128 fine channels ~ 105 total)
•
Correlation load (700 MHz bandwidth)
– SPF load = 6 x 1016 MACS
– PAF load = 1 x 1018 MACS
– Dense AA = 2 x 1018 MACS
•
Correlator Dump Rate (Dish Solution)
– 2280 15 m dishes + 40 x 18 dish stations and 3000 km baseline:
– Integration time ~ 200ms for < 1% smearing
5 x 106/2 baselines x 105 channels x 4 bytes x 5 Hz = 9 T Bytes/s
Not calculated for other configurations yet
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Signal Processing Overview
Memo 100 Option a*
SPDO
Local
Monitoring
Timing
Sparse
AA
1680
Dishes
Timing
OptoElectrical
Conversion
Delays
PolyPhase
Filter
Monitoring &
Control
OptoElectrical
Conversion
70 MHz 500 MHz
TBA
10 G bit/s
Optical
Connections
Sparse AA
Channelizer
Optical Rx
Visibilities
OptoElectrical
Conversion
Multipier
Integrator
xx,xy,yx,yy
Full Stokes Correlator
500 MHz 10 GHz
600 Core
SPF Dish
Dishes
40
Stations
OptoElectrical
Conversion
Delays
PolyPhase
Filter
OptoElectrical
Conversion
74240
10 G bit/s
Optical
Connections
Multipier
Integrator
Visibilities
xx,xy,yx,yy
Dish
Channelizer
Optical Rx
OptoElectrical
Conversion
Full Stokes Correlator
SPF Dish
18 Dishes
per
station
PolyPhase
Filter
Beam
Former
OptoElectrical
Conversion
OptoElectrical
Conversion
Pulsar
Search
& Timing
Processing
Candidates
Pulsar & Transient Processing
Beamformer (core)
* Sparse AAs + 3000 15-m dishes with SPFs
TBA
10 G bit/s
Optical
Connections
Pulsar
Candidate
Data
13
Signal Processing Overview
Memo 100 option b*
SPDO
Local
Monitoring
Timing
Sparse
AA
1080
PAF
Timing
OptoElectrical
Conversion
Delays
PolyPhase
Filter
Monitoring &
Control
OptoElectrical
Conversion
70 MHz 500 MHz
TBA
10 G bit/s
Optical
Connections
Sparse AA
Channelizer
Optical Rx
Visibilities
OptoElectrical
Conversion
Multipier
Integrator
xx,xy,yx,yy
Full Stokes Correlator
500 MHz 10 GHz
600 Core
SPF Dish
PAF
40
Stations
OptoElectrical
Conversion
Optical Rx
Delays
OptoPolyPhase Electrical
Filter Conversion
144,480
10 G bit/s
Optical
Connections
OptoElectrical
Conversion
Multipier
Integrator
Visibilities
xx,xy,yx,yy
PAF/WBSPF
Channelizer
Full Stokes Correlator
SPF Dish
18 PAFS
per
station
Possibly include a beam
former for the core
TBA
10 G bit/s
Optical
Connections
OptoElectrical
Conversion
Pulsar
Search
& Timing
Processing
Pulsar
Candidate
Data
Candidates
Pulsar & Transient Processing
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* Sparse AAs + 2400 15-m dishes with PAFS & WBSPF
Signal Processing Overview
Memo 100 option c*
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* Sparse AAs + 250 Dense AA + 2000 15-m dishes with SPFs
SPDO
Technology Options
SPDO
•
FPGA
– Virtex 6 (available 2010):
2016 x DSP slices clocked at 600 MHz -> 1200 G MACS
~ 25 G MACs per Watt
1018 MACS requires ~ 106 FPGAS
=> 48 W per device and ~ 48 M Watts for 1018 MACS
Operating cost 1$ per Watt per year => $48M per annum
Plus cost of cooling and delivering power
•
ASIC
– 22nm (available 2010):
2.5 nW/MHz/Gate
> 40 T MACS (4 bit) per device => 25,000 devices
Assuming < 50 % gates switching at any one time: 600kW
Operating cost $600k per annum
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What would F or X unit look like?
SPDO
Baseline Board (rear)
Baseline Board (front)
Station Board
EVLA style boards might be an optiton ?
64 ASICS or FPGAs on board (~1.5 kW
card)
~ 190 boards for Dense AA ASIC correlator
14 cards per shelf -> 14 shelves
Is production yield an issue?
Could use smaller 8 processor chip board
As per ASKAP or Uniboard
Inter-board Communication links increase
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Pictures courtesy Brent Carlson
Multichip Module
SPDO
•SKADS have developed a promising Multichip Module:
4 x 4 antenna array currently,
Current RFI Protection shows -57dB per M (in air)
Could be developed and used in several areas of the SKA
(Note that the key components are ADC and Optical I/O, although the others
could be useful in some applications.)
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Picture courtesy of Kris Zarb Adami
Correlator Centre Build Cost
SPDO
ASIC solution
•1 cabinet per 30 sq ft
•Between 80 & 160
cabs?
•Factor of 4 for air
con &PSU units,
offices
•~ 50 W per sq ft
Data Centre Build Cost
100000000
90000000
80000000
Build Cost $
70000000
60000000
50000000
50W/sq ft
100W/ sq ft
40000000
ASIC Solution
400W sq ft
30000000
20000000
10000000
0
0
20000
40000
60000
80000
Total sq feet of data centre
Kevin Wohlever 2006
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100000
120000
SPDO Team
SPDO
Project Director
Project Engineer
Executive Officer
Project Scientist
System Engineer
Domain Specialist Receptors
Domain Specialist Signal Transport
Domain Specialist Computing & Software
Domain Specialist Signal Processing
Site Engineer
Project Management Officer
Industry Relations Manager
Office Manager
20
Richard Schilizzi
Peter Dewdney
Colin Greenwood
Joe Lazio
Kobus Cloete
Neil Roddis
Roshene McCool
Duncan Hall
Wallace Turner
Rob Millenaar
Billy Adams
Phil Crosby
Lisa Bell