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DS3-T1 Network Infrastructure & data transmission Simon Garrington University of Manchester/Jodrell Bank Observatory

DS3-T1 Network Infrastructure & data transmission Simon Garrington University of Manchester/Jodrell Bank Observatory, UK. Feasibility study of network for SKA Data link from dishes/stations Monitor & Control links to dishes/station Clock distribution across network Partners:

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DS3-T1 Network Infrastructure & data transmission Simon Garrington University of Manchester/Jodrell Bank Observatory

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  1. DS3-T1Network Infrastructure & data transmissionSimon GarringtonUniversity of Manchester/Jodrell Bank Observatory, UK • Feasibility study of network for SKA • Data link from dishes/stations • Monitor & Control links to dishes/station • Clock distribution across network • Partners: • Manchester/Jodrell Bank: [e-MERLIN] • Spencer, Garrington, Anderson, McCool, Bentley, Davis • ASTRON [LOFAR] • Maat, Gloudemans • IRA/INAF [BEST] • Montebugnoli, Boschi SKADS Review 2006

  2. DS3-T1SKADSDeliverables • Detailed cost models for data/M&C links • COTS technology • Standard protocols & commercial equipment • Component based technology • Protocol-free; mass –market components • Short-distance analogue links • Prototype phase transfer links SKADS Review 2006

  3. EOR AA All Sky AA ~10m Dishes FPA ~10m Dishes WBF 0.1 0.3 1.0 3.0 10.0 30.0 GHz DS3-T1 – Data transfer SKA Reference Design From AF Talk Scale of problem 14-72 Gb/s per beam per dish/station x 4 for parallel operation? 10Gb/s: $300 - $10000 depending on distance $3k per beam per dish/station Nb x Ns ~ 105  $300M Digging+cable: $15/m 5km + 150km arrays -> $15M + $15M/1000km of long links SKADS Review 2006

  4. Initial Cost Model Memo 75: Ralph Spencer - see Ralph’s talk Inner 5km array: 2000 dishes <3GHz 40 beam PAF 300 MHz b/w 8 bits >3GHz 1 beam WBF 2.5 GHz b/w 6 bits $300 10G Tx-Rx pair, $10/m trench+cable $160M Outer array cost comparable for single beam, otherwise dominates SKADS Review 2006

  5. DS3-T1 Approach • Cannot wait for DS3-T2/3 to deliver array configuration, processing topologies then design network • Must provide & refine ‘unit costs’ for various ‘useful links’ and build generic cost model tool • Transmission equipment • Multiplexing: CWDM, DWDM, TDM… • Amplification (>100km) & Regeneration (>400 km) • Connectors & fibre management • Installation & commissioning costs • Multiplexing trade-offs • Clarify cost break-points in terms of data rates, distances and aggregation • Iterate within DS3 SKADS Review 2006

  6. DS3-T1InitialProgress • Initial technology survey for COTS links (ASTRON) • Based on LOFAR experience: 1,10 GigE • Looking at switches, DWDM,CDM • Anticipate move 1/10 G  10/40/100G • Generic WAN modelling tool started (ASTRON) • Use for COTS data links and low bandwidth M&C network • LOFAR: • Arms: 45 stations, 2Gb/s, 50km • Core: 32 stations, 2+ Gb/s, 5km SKADS Review 2006

  7. DS3-T1Data transfer: component based Technology survey for component-based links (Jodrell/Manchester) • Based on e-MERLIN & ALMA experience: 30 -120 Gb/s custom DWDM on single fibre from antenna developed by NRAO/JBO • e-MERLIN: • 600km dark fibre network leased/installed • Looking at Fibre-to-the-Home for cheap short links • VCSELs, Plastic Optical Fibre • mechanical splices, cheap connectors, easier fibre management • Industrial links being sought SKADS Review 2006

  8. Issues emerging No. of bits to transport No of beams on outer stations Cheapest short (0.1 – 5 km) links New Technology (VCSELs, POF) Topology Fibre management SKADS Review 2006

  9. Phase Transfer • Need 1 ps timing control for 1% loss at 20 GHz • Options • Independent clocks (masers): expensive ($200k) • Transmit signal; steer oscillator at remote end; track round trip delay • Fibre • EVLA (2 fibres), ALMA (optical LO distribution) • Temperature control; non-reciprocity; polarisation effects • Multi-hop links • Radio • MERLIN (pulsed 1486.3 MHz) • RFI; scale-up? • 2-way satellite (TWSTT) • USNO clock transfer <100 ps/day over >1000 km • Weinreb et al: few ps • Cost: to rent transponder channels • In practice, may use mixture, depending on distance SKADS Review 2006

  10. Phase Transfer Isolating return signal • Circulators • Simple system tested at JBO • Single freq; 1 GHz modulation; VVM phase measurement • Good circulator: 30dB -> 2dg • Dual freq schemes • Time multiplex • MERLIN L-band link • 1486.3 MHz pulsed at 88 Hz • Pulse length discrimination • Works to few ps over >200km Tests planned • e-MERLIN fibre spans (above & below ground, 300km) • Implement MERLIN 1484.3 MHz TDM on fibre Spencer, Sureshkumar,Strong,STG Two-way – 2(one-way) SKADS Review 2006

  11. Phase Transfervia GPS • GPS Common View being tested for time transfer (USNO, NIST, BIPM,…) using carrier phase • Better than TWSTT for 100s < t < 1d • Used dual-freq geodetic antennas/receivers, final GPS ephemerides • Short timescale limitations • Noise & GPS multipath (rms 50cm) • Want beamforming antenna … • … SKADS Aperture Array (1227,1575 MHz) • High gain: improve SNR • High degree of multipath rejection • Strategies to use this for phase transfer • Next gen. GPS, Galileo Plumb & Larson 2005 SKADS Review 2006

  12. SKADS Review 2006

  13. Allan variance plot GPS stability floor 2 10-13  -0.44 SKADS Review 2006

  14. GPS SKADS Review 2006

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