rosie bolton skads workshop april 10th 2008 skads costing work: beyond the benchmark scenario rosie...

Rosie BoltonSKADS Workshop April 10th 2008

SKADS Costing work: beyond the benchmark scenario

Rosie Bolton

Paul Alexander, Andy Faulkner and SKADS

Costing tool development with Aaron Chippendale, Tim Colegate, Dominic Ford, Peter Hall and CDIT and …


Overview

• SKADS costing work to date– Memo 93, Benchmark scenario

– “Second round” – Tiger Team Preliminary Specification for the SKA, costing of the SKADS “vision” for the SKA

• Current / Future work: The SKA design and costing tool


Previous SKADS costing work

• Benchmark scenario (old)– 12,800 6.1m dishes (ATA), in dish

stations

– 250 Aperture array stations, co-placed with dish stations

– Radius range out to 3,000km

– Low frequency array costed very roughly

– Reduction in data rate for longest distances (for AA),

– Comms very expensive: 300 M€, +500 M€ for full data rate

– Total cost ~1.9 Bn Euros (2011)


Outline Configuration: Tiger team doc

• Follow concentration based on the SKA Draft specification:

– Dish AA-hi AA-lo

– <1Km 20% 30% ~15%

– <5Km 50% 66% 50%

– <180Km 75% 100% 100%

– <3000Km 100%

–

• AAs only out to 180km, frequency bands 70MHz-450MHz and 300MHz-

1,000MHz. AA bandwidth up to full range – set by data transfer spec

• Dishes all correlated, not beam-formed in Stations. 800MHz-10GHz. B/W 4GHz

• 5 spiral arms, with

– 3 to 3,000km, 2 only to 180km (saves trenching cost but configuration studies must

verify / challenge this)

Station

Core ~5km dia

Central ProcessingFacility

Not to scale!

180km

Dishes AA-hi

AA-lo


System design overview

Dishes and feeds in core and in outer

array2400 dishes


array2400 dishes

AA-lo array antennas


AA Station85 Stations, 1 AA-lo, 1 AA-hi

“array” in each

AA Station85 Stations, 1 AA-lo, 1 AA-hi

“array” in each

Digital Signal TransportDigital Signal Transport Central processing and correlator

Central processing and correlator

SKA SKA

First stage Analogue

beam-former


beam-former

First stage digital beam-

forming


forming

Station beam-formerStation beam-former

Analogue data transport


Mechanical infrastructureMechanical infrastructure

AA-hi array antennas


AA-hi

Local digital data transportLocal digital

data transportMechanical

InfrastructureMechanical

InfrastructureAnalogue data

transportAnalogue data

transport

Digital data transport


First stage digital beamforning

First stage digital beamforning

AA-lo

AA CollectorsAA Collectors

AA-hi core165 AA-hi “arrays”


AA-lo core165 AA-lo “arrays”


Processing boxesProcessing boxes

Infrastructure and Trenching

Infrastructure and Trenching


• Central Processing Facility– Correlator

– Back-end computing

– Some station beamforming for AA-lo core


array2400 dishes


array2400 dishes

Digital Signal Transport


SKA SKA

AA CollectorsAA CollectorsInfrastructure

and Trenching

Infrastructure and

Trenching


Station

Core ~5km dia


Comms links

Not to scale!

180km

Dishes spread along spiral arms

Dishes

AA-hi

AA-lo

Central processing and

correlator


correlator


• Digital Signal Transport– Detailed model for

Communications

– Technology choice dependent on link length and data rate

– Development work in progress within SKADS (Roshene McCool and others)


array2400 dishes


array2400 dishes


correlator


correlator

SKA SKA


and Trenching

Infrastructure and

Trenching


Station

Core ~5km dia


Comms links

Not to scale!

180km


Dishes

AA-hi

AA-lo




• Dishes– 15m (in line with Tiger Team

Spec)

– Costed from SKAcost

– Cost of dish and feed

– €200,000 NPV per dish

– 2,400 dishes

– Range




correlator


correlator

SKA SKA


and Trenching

Infrastructure and

Trenching


Station

Core ~5km dia


Comms links

Not to scale!

180km


Dishes

AA-hi

AA-lo


array2400 dishes


array2400 dishes


• AA collectors are SKADS focuses – especially the AA-hi (300-1,000MHz)

• AA collectors sit in central cores (AA-lo and AA-hi separately) and in outer stations (together)


array2400 dishes


array2400 dishes




correlator


correlator

SKA SKA

Infrastructure and

Trenching

Infrastructure and

Trenching


Station

Core ~5km dia


Comms links

Not to scale!

180km


Dishes

AA-hi

AA-lo



Aperture array systems



AA Station85 Stations, 1 AA-lo,

1 AA-hi “array” in each

AA Station85 Stations, 1 AA-lo,

1 AA-hi “array” in each


beam-former


beam-former


forming


forming

Station beam-formerStation beam-former



Mechanical infrastructureMechanical infrastructure



AA-hi

Local digital data transportLocal digital

data transportMechanical

InfrastructureMechanical

InfrastructureAnalogue data

transportAnalogue data

transport



First stage digital

beamforming

First stage digital

beamforming

AA-lo






Processing boxes

Processing boxes

Each AA-lo array is ~180m diameter

Core may be fully-filled for improved temperature sensitivity (EoR signal)

LOFAR high-band

Log-Periodic dipole schematic

Each AA-hi station ~60m diameter


Costed Data Rates

• AA-hi Data rate equivalent to 250 square degrees across the whole band from 300 MHZ to 1,000 MHz. Including 8:10 encoding, 16.5 Tb/s per station

• AA-lo Data rate equivalent to 200 square degrees across the band from 70 MHz to 450 MHz, 12.5 Tb/s

• Complete flexibility in the beams that are sent back

Increase field of view (more beams on the sky)

Decrease the bandwidth


Aperture array sensitivity

A/T total, 250 stations

0

2000

4000

6000

8000

10000

12000

0 200 400 600 800 1000 1200

frequency (MHz)

A/T

sys

AA-lo, Trec 50K, 180m diameter, f(Nyq)=100MHz

AA-hi, Trec 30K, 56m diameter, f(Nyq) = 833MHz

Combined total

Sensitivity averaged over scan angles out to 30º


SKA cost breakdown

No: Infrastructure

Roads, buildings

No: Development costs

NREs, toolingNo: Software development

costsNo: Running costs

No: Project management

costsNo: Contingency(but we do have an uncertainty estimate)


SKA cost breakdown

€162 Million

€394 Million

€526 Million

€165 Million

€92 Million

€63 Million€34 Million

Special Offe

r: 1.52 Billio

n Euros NPV ± 31%


Scaling models: the way forward


Comms cost scaling - DishesComms cost per Dish (80 Gb/s)

0

5

10

15

20

25

30

35

40

45

0 20 40 60 80 100 120 140 160 180 200

Radial distance (km)

Co

mm

s co

st (

tho

usa

nd

eu

ros)

First, second and third amplifiers added

a b

c

a: Cheap VCSELs can be used out to 10km fibre length

RELATIVE COMMUNICATIONS COSTS BECOME MUCH MORE EXPENSIVE AFTER 50KM OF FIBRE DISTANCE

FURTHER BREAK POINT AT 480KM WHERE O-E-O REGEN IS REQUIRED

b: Uncooled, directly modulated lasers out to 50kmc: Cooled, externally modulated lasers > 50 km


Comms cost scaling - AA

AA comms costs with varying 95% radius

0

20

40

60

80

100

120

0 10 20 30 40 50 60 70 80 90

95% radius, km (within which 95% of the stations are)

AA

Co

mm

s c

ost

for

ou

ter

sta

tio

ns

(mil

lio

ns o

f E

uro

s,

2011)

Comms costs are sensitive to station placementConfig work and costing work must be linked

60 million!


Cost scaling: ACost scaling: Aeff eff for AAsfor AAsTotal SKA cost with reduced collecting area

€800,000,000

€900,000,000

€1,000,000,000

€1,100,000,000

€1,200,000,000

€1,300,000,000

€1,400,000,000

€1,500,000,000

€1,600,000,000

0.5 0.6 0.7 0.8 0.9 1

Fraction of spec collecting area

To

tal

SK

A c

ost

(E

uro

s, N

PV

)


Cost scaling: ACost scaling: Aeff eff for AAsfor AAs

010

2030

400 10 20 30 40

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Rel

ativ

e se

nsi

tivi

ty

Offset (x) degrees

Offset (y) degrees

0.9-1

0.8-0.9

0.7-0.8

0.6-0.7

0.5-0.6

0.4-0.5

0.3-0.4

0.2-0.3

0.1-0.2

0-0.1

Variation with scan angle due to:•Projected area•Element responseFixed <Aeff> ...

Amount of collecting area required is a strong function of scan angle requirement: change 30 deg to 45 deg, need 40% more collector: extra ~500 million Euros!

Collecting area requirements vs max angle

139%123%

110%100%

78% 81% 86% 92%

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

10 15 20 25 30 35 40 45

Max angle, degrees

Co

llec

tin

g a

rea

req

uir

emen

ts


Scaling: complex dependencies

Collector costs

Data transport

Correlator Back end computing

Trenching

AA Field of View

Sensitivity ()

Tsys ()

AA Station size ()

Dish size ()

Bandwidth

Layout

Interdependencies are too complex to do with a spreadsheet: we need a more sophisticated model

SKACost


Science Requirements

Engineering Design & Cost

The Job of PrepSKA

Readiness Assessments

Eng. Simulations

Prototypes

Pathfinders & DS

Technical R&D Fou

r Y

ears

Case Studies

SKACost

CourtesyPeter Dewdney


Future work:• SKADS AA model is already scalable on a broad level

– Collecting area requirements

– Bandwidth

– FoV

• Needs more work to make fine details scale:– Operating frequency / Antenna spacing requirements

– Station layout / Configuration

– AA-lo: further design work required for low-freq antennas

– Analogue beamforming / Digital beam-forming

• SKACost costing tool is essential for this– SKACost will be used by selection committee to further define the SKA

spec

– Important that all technologies are adequately represented in SKACost

– Need a shift in approach towards a “model”


Future work:• SKACost developments will include:

– Improved web-tool, with AA costing, in near-term future

– End-August distribution of GUI-based tool• Help required to test this tool - contact us! (Me, Tim Colegate,

Dominic Ford, Aaron Chippendale, Peter Hall, Paul Alexander)

• The better the tool is a describing the technology, the better the merits of that option will show up.

– Longer-term flexible GUI-based tool allowing design blocks and components to be created and an SKA designed from a shopping basket of sub-components


Web-tool plug:

http://www.atnf.csiro.au/projects/ska/cost/

…it’s not perfect but we are working on it, and are keen for feedback

Dominic Rosie Tim Paul

rosie bolton skads workshop april 10th 2008 skads costing work: beyond the benchmark scenario rosie...

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