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Broadband Tests John Conway FABRIC F2F-2 Poznan, Sept 25th 2006

This document discusses the goals and specifications for broadband eVLBI testing and demo at Onsala. It covers topics such as hardware design, Onsala-MERLIN link, channelization, recording options, and future EVN correlation. The document also outlines the timeline for the demo and progress on the project.

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Broadband Tests John Conway FABRIC F2F-2 Poznan, Sept 25th 2006

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  1. Broadband TestsJohn ConwayFABRIC F2F-2 Poznan, Sept 25th 2006 • Month 7 PC-EVN demo • Goals for broadband eVLBI • Specification and design of hardware for Onsala-MERLIN demo. • Procuring 10Gbit/s Onsala link. • Use of Onsala FABRIC resources manpower/money – in project context

  2. Month 7 Demo • EU forced test to demonstrate/re-establish a baseline PC-EVN performance – soaks up contributed manpower for us. Have now got an (almost) working PC-EVN at Onsala. • Scheduled for Friday Oct 20th. Need to start testing NOW • Part 1 – At 6cm, 256Mbit/s, record to disk at On and Jb. Then transfer to JIVE. Convert to Mk5 input and correlate. Should be easy...done several year ago. Who is ensuring this happens at JIVE ? • Part 2 – At 1.3cm, Mh does ’remote recording’ to PC disk at JIVE. Jb records to disk, later transfer, translate at correlator for fringes. I

  3. FABRIC broadband goals-1 • What are we trying to do???? A prototype future eVLBI production system? • Will it also do disk recording or just real time?? Major decision between PC-based or FPGA routes. • Ideally must service a future EVN correlator which does not exist – can we guess its channelization? • Meanwhile we do have MERLIN and LOFAR correlators – maybe we should use them (esp MERLIN) as template.

  4. FABRIC broadband goals-2 • Research project in distributed correlation, a part of the JRA but presently more useful conceptually to seperate from Broadband part. • Channelisation. Present system - many tunable filters and parallel bits streams. Old reasons, tape track limit, geodesy no longer valid? eMERLIN, eVLA one thick BW. Forget past start from scratch? To minimise complexity a few chanelisation modes only for transmitter? No specific ’spectral line modes’? • No of bits. eVLBI without dark fibre (unlike eMERLIN and LOFAR) is still transmit channel limited. Do RFI filtering at station end and just transmit 2bit/sample? • Must decide above issues SOON/TODAY to define exact specifications of what we will build!!

  5. FABRIC broadband goals-3 • No recording, FPGA technology is the way we go???? • iBoB ADC does 8bit and can digitise at Nyquist rate either 1pol of 1GHz BW or 2pol of 512MHz BW. • Transmitter wil lhave smart RFI rejection and outputs 2bits/sample. ’Notch out’ filtering and outputs a limited number of digitally filtered bandwidths. Say four corresponding to 1024MHz, 512,256,128 MHz? ( 4 to 1 Gbit/s). • Lower limit set by spread of OH maser lines (112MHz) , and whether network costs for 1Gbit/s are negligble when operational. • At input to correlator further channelisation may be done prior to high spectral resolution correlation of multiple narrow channels.

  6. Interim Goal- EVN stations to eMERLIN • Can prototype a new astronomy capability + test out concept prior to new EVN correlator. • In general seems reasonable when planning for EVN2010+ – converge on eMERLIN specs BW and freq ranges for L,C,K, (+add other bands) • Operational system at L-band. 1 iBoB 512Hz x 2pol giving 4Gbit/s • Could expand to have at C and K bands 2 iBoBs, sampling 1GHz of spanned BW at each pol, 2bit sampling, giving 8Gbit/s - get sqrt(2) sensitivity of eMERLIN – can eMERLIN obs 2GHz BW same time as 1GHz external.

  7. UV Coverage Left. UV (km)– Coverage for 6 stations MERLIN + Onsala + Wb1 at dec +40deg Right . UV (lambda) shows result of MFS Multi-frequency thesis for L-band 1300-1800MHz (4Gbit/s data rate). Other possible combinations MERLIN + Onsala only, or include Bonn or Irish telescope.Not a competitor to full EVN or EVN+MERLIN, which even just in Europe has three times the resolution and 16 stations.

  8. Parameters of 4Gbit/s Demo • Dual Polarization, 512MHz spanned BW, Nyquist sampled, 2bit giving 4Gbit/s. • Correlate versus eMERLIN 8bit sampled data (16Gbit/s)- potentially has same sensitivity as full 16Gbits/s but no RFI protection – less important on long baselines and can ’notch out’ any strong RFI at Onsala?? • Would be very useful L-band production system, with 25m connected to MERLIN (SEFD=370Jy) . Initial test. • The C and K-band eMERLIN system normally works at 3bit sampling, 2GHz spanned BW and 24Gbit/s, can it be switched to the 16Gbit/s, 8bit sampling mode for test • Option 1 – test at K-band, no new fibre of LO system needed. • Option 2 – Fibre to 25m, and broadband L and C band LO system. Better for operational system.

  9. Timeline • DOW has ’Prototype at Onsala station’ and ’overall broadband demo’ by Month 23 (Feb 2008). • Also has eMERLIN interfaces available by Month 30 (Sept 2008) – inconsistent. • eMERLIN prototype correlator arrives end of 2007. Very hard to meet Month 23 fringe deadline • Have DAR at Onsala by March 2008, software integration and transmitting data from 25m to Jb at 4Gbit/s by that time. By Sept 2008 fringes?? • Hire Onsala manpower by June 2007 for 1+ year????

  10. Link Progress • Discussions through SUNET on upgrading our 1Gbit/s to 10Gbit/s (they will negotiate with vendors for us, still waiting for a cost but expect to get this and order soon). • Two options, link all the way into Chalmers in Gothenburg (55km) or connect to trunk in Kungsbacka. • Not absolutely needed until test in Month 23, Febuary 2008. Purchase depends on price falling/depreciation. • Meanwhile Mh has 10Gbit/s already. Traffic goes through Stockholm just like Onsala data– hence can test most of the route in Mh-Jb tests, all except internal Swedish part.

  11. OPTOSUNET • SUNET historically double BW every year. OPTOSUNET is successor to GIGASUNET. • Dark fibres leased for a 40Gbit/s backbone- fully implemented end of 2006 • Most universities connected at 10Gbit/s • Allow both IP and dedicated point-to-point wavelengths (cost stucture?) • For international transmissions go through NORDUNET

  12. NORDUNET Staus as of April 2006, signals go through Stockholm to rest of world, nor sure a direct connection via Copenhagen possible – NORDUNET congress Sept 25th -30th in Göteborg

  13. Use of Onsala Resources • Onsala has from EU 1 man-year and 10kEuro for Equipment – how to use that? • Option 1 – Recruit electronic engineer help work on iBoB with Mh. Ex Intl Masters student now at Berkely Wireless research group. • Option 2 – Use to broadband the 25m, fibre plus new IF system. Software control of iBoB. Testing of network.

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