1 / 16

Ongoing e-VLBI D evelopments with K5 VLBI System

Ongoing e-VLBI D evelopments with K5 VLBI System. Hiroshi Takeuchi, Tetsuro Kondo, Yasuhiro Koyama, and Moritaka Kimura Kashima Space Research Center/NICT. Outline. What is K5 VLBI system? VLBI@home (Internet-based distributed computing approach for VLBI correlator)

nicholasmendez
Download Presentation

Ongoing e-VLBI D evelopments with K5 VLBI System

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Ongoing e-VLBI Developments with K5 VLBI System Hiroshi Takeuchi, Tetsuro Kondo, Yasuhiro Koyama, and Moritaka Kimura Kashima Space Research Center/NICT

  2. Outline • What is K5 VLBI system? • VLBI@home (Internet-based distributed computing approach for VLBI correlator) • Software baseband converter • Summary

  3. VLBI Systems developed at Kashima K4 Correlator K5 Data Acquisition Terminal K5 System K4 Terminal K4 (KSP) System K3 Correlator (Center) K3 Recorder (Right) 2000~ Real-time e-VLBI with IP PC based system Hard Disk Drives Software Correlator 1990~ Real-time e-VLBI with ATM Operational data rate: 256Mbps Max data rate: 2048Mbps Hardware Correlator K3 System 1983~ Longitudinal Recorder Open Reel Tapes Hardware Correlator

  4. K5 Family : Concept ADS1000 (1024Msample/sec 1ch 1bit or 2bits) PC-VSI Board (K5/VSI) (Supports VSI-H specifications) Correlator other DAS (Mark5) VSI VSI Internet IP-VLBI Board (K5 or K5/VSSP) (~16Msample/ch·sec, ~4ch, ~8bits) ADS2000 (64Msample/ch·sec ,16ch, 1bit or 2bits) PC : Data Acquisition & Software Correlator

  5. Specifications of K5/VSI VLBI system Single channel VSI Data Acquisition System Multi-channel VSI Data Acquisition System

  6. Specifications of K5/VSI VLBI system VSI Data Capture Board (PC-VSI board) VSI Data Recording System (PC-VSI board +RAID)

  7. Architecture of K5 data input module • In K5 system, captured data is not directly recorded to HDD, but transferred to PC’s shared memory. So, multiple software applications can access the data simultaneously in real-time. • Because of this function, various kinds of real-time operations are possible by writing PC software. Such as spectrometer, total power meter, oscilloscope, software correlator, p-cal detector, baseband converter, real-time data transfer, real-time recording, and so on.

  8. Software correlator by distributed computing Merit of software method: No limitations on correlator parameters (number of lags, number of stations, integration time, FX or XF …) VLBI@home:Screensaver-type distributed correlator program runs during the idle time.

  9. VLBI@home -Distributed correlator system over the Internet • Proceduresofdistributed correlation process • A client PC queries the control server about the location of K5 data file to be processed. • The control server determines the files to be processed based on the information in the database server and sends back the URL of the files. • The client PC downloads indicated K5 files from the VLBI stations by FTP. • Correlate the received data. • Correlator results, client conditions, and network status are sent to the control server. • Control server stores the results to the database server. Processing conditions are updated and published to the Internet. Return to 1. SQL ？

  10. Required network speed for VLBI@home • Distributed computing method is effective only in the environment, where Network bit rate ＞ Data processing rate • Current processing speed of software correlator(32 lags) : 15Mbps(Pentium4 3GHz) • 　・Network between Institutes (Dedicated network) • 1Gbps～100Mbps ＞ 15Mbps 　　→ Effective • 　・Network to the home (Public network) • 1 ～ 10Mbps　　　 ＜15Mbps 　　→ Not Effective! Empirical rule, Guilder’s law, says, “Network bandwidth grows at least three times faster than computer power”.

  11. Application：Rapid UT1-UTC estimation (June 29,2004) • After this session, Mark-5 data at Westford was transmitted to Kashima by FTP. • Received Mark-5 data was converted to K5 format, and correlated with VLBI@home. • Average processing speed:58.6Mbps (8 consumer PCs) • UT1 – UTC estimation was completed 4hours and 30 minutes after the last observation in the session.

  12. Development of software baseband converter • Conventional BBC(baseband converter) system Analog BBC Multi-channel A/D samplers after image rejection mixers.Demerit: Gain and phase fluctuations caused by the variations of ambient temperatures. Digital BBC(FPGA,ASIC) Digital baseband converters after a single-channel broadband A/D sampler. Demerit: Less flexibility for band selections.Highdevelopment and maintenance cost.

  13. Software BBC(SBBC) by K5/VSI system If sampling rate is lower than 2 Gbps, SBBC is realized by a current PC. Merit: High flexibility, low cost, integrated to network transmission system and recording system.

  14. SBBC - Specifications and algorithm • Lookup table method (Floating point) • Written in assembly language • Using vector operations(SSE2) and prefetch functions • Multi-thread(8 threads) Current speed: By using a current PC(Xeon 3GHz), 2 baseband channels can be extracted in real-time from 1Gbps of IF signals.

  15. Test experiment using the SBBC • April 18, 2004 • Parkes(PC-EVN) – Kashima(K5, SBBC) • At Kashima, 256-MHz of IF-signals were directly sampled and converted to 16-MHz of baseband signals by the software BBC system. • It is easy to perform the experiments between different VLBI systems, because of the flexibility of the software method.

  16. Summary • K5 VLBI system is a low-cost and high-performance pc-based VLBI system. • Because of the recent developments of consumer PCs, we can use software methods for the VLBI backend processes. For example, distributed software correlator and software BBCs.

More Related