Transcript Kashima-Haystack e-VLBI demonstration

Ongoing e-VLBI Developments
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)
Software baseband converter
Summary
VLBI Systems developed at Kashima
K4 Correlator
K5 Data Acquisition
Terminal
K4 Terminal
K5 System
K3 Correlator (Center)
K3 Recorder (Right)
K3 System
1983~
Longitudinal Recorder
Open Reel Tapes
Hardware Correlator
K4 (KSP) System
1990~
Real-time e-VLBI with ATM
Operational data rate: 256Mbps
Max data rate: 2048Mbps
Hardware Correlator
2000~
Real-time e-VLBI with IP
PC based system
Hard Disk Drives
Software Correlator
K5 Family : Concept
ADS1000
(1024Msample/sec 1ch 1bit or 2bits)
PC-VSI Board (K5/VSI)
(Supports VSI-H specifications)
VSI
VSI
Correlator
other DAS (Mark5)
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
Specifications of K5/VSI VLBI system
Single channel VSI Data Acquisition System
D evice N am e
Sam pling rate
Sam ple resolution
External R eference
O utput D ata Form at
Size/W eight
A D S-1000
1024/512M sps
1/2bit
10M H z,1P P S
Starndard V SI-H form at
424 x 400 x 44m m / 5kg
Multi-channel VSI Data Acquisition System
D evice N am e
N um ber of input channels
S am pling R ate
S am ple R esolution
External R eference
O utput D ata Form at
S ize/W eight
Function
A D S -2000
16
2,4,8,16,32,64M sps
2bit
10M H z,1P P S
S tarndard V S I-H form at
482 x 550 x88m m / 12kg
P -C al detection
Specifications of K5/VSI VLBI system
VSI Data Capture Board (PC-VSI board)
D evice N am e
C ontinuous C apture R ate
Input Interface
P C I interface
V SI2000-D IM
2048M bps
1024M bps
512M bps
256M bps
Starndard V SI-H form at
P C I-X(64bit/66M H z)
VSI Data Recording System (PC-VSI board +RAID)
D evice N am e
D isk Storage Interface
M ax R ecording R ate
H D D size
P C -V SI
D ual Fiber C hannel
2048M bps
3TB yte
3hours@ 2048M bps
6hours@ 1024M bps
C ontinuous R ecording Tim e
12hours@ 512M bps
24hours@ 256M bps
Architecture of K5 data input module
RF-signal
ADS-1000 VSI-H
A/D sampler 1-2Gbps
(1Gsps/2bits)


Personal-Computer
PC-VSI
Board
(PCI-X)
DMA
Memory
(1-4GByte)
Network transfer
CPU
Hard Disk
Drive
(RAID)
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.
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.
VLBI@home -Distributed correlator system over the Internet
Procedures of distributed correlation process
Data
Base
Schedule File
WWW
Obs
information
Status
information
1.
A client PC queries the control server about
the location of K5 data file to be processed.
2.
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.
3.
The client PC downloads indicated K5 files
from the VLBI stations by FTP.
4.
Correlate the received data.
5.
Correlator results, client conditions, and
network status are sent to the control server.
6.
Control server stores the results to the
database server. Processing conditions are
updated and published to the Internet. Return
to 1.
SQL
Station 1
Station 3
FTP
Control Server
XML
FTP
XML
Client
FTP
Client
FTP
Station 2
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”.
Application：
Rapid UT1-UTC estimation (June 29,2004)
Kashima station
File transfer
Westford(Mark5)
Mark5→K5
Conversion
File transfer
Client
VLBI@home
FTP
Server
Client




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.
Development of software baseband converter
•Conventional BBC(baseband converter) system
Image Rejection Mixer
A/D
Local signal
IF signal
IF
Distributor
Local signal
..
..
A/D
A/D
Analog BBC Multi-channel
A/D samplers after image
rejection mixers.
Demerit: Gain and phase
fluctuations caused by the
variations of ambient
temperatures.
Local signal
Digital BBC(FPGA,ASIC) Digital baseband converters after a
single-channel broadband A/D sampler.
Demerit:
Less flexibility for band selections. High development and
maintenance cost.
•Software BBC(SBBC) by K5/VSI system
If sampling rate is lower than 2 Gbps, SBBC is realized
by a current PC.
IF-signal
ADS-1000 VSI-H
A/D sampler 1-2Gbps
(1Gsps/2bits)
Personal-Computer
PC-VSI
Board
(PCI-X)
DMA
Memory
(1-4GByte)
CPU
(Software
BBC)
Network transfer
Hard Disk
Drive
(RAID)
Merit: High flexibility, low cost, integrated to network transmission
system and recording system.
SBBC - Specifications and algorithm
IF signal
1024 or 512Mbps (1 or 2bit)
Baseband signal
1MHz ～ 64MHz (1,2,4,8 bit)
Number of taps
127 ～ 8191
Selectable baseband frequency
Discrete (Not arbitrary frequency)
• Lookup table method
(Floating point)
Frequency response of 4095-tap FIR bandpass filter
Gain (dB)
0
• Written in assembly language
-10
-20
• Using vector
operations(SSE2) and
prefetch functions
-30
-40
-50
127
129
131
IF frequency (MHz)
133
135
• 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.
Test experiment using the SBBC
•April 18, 2004
•Parkes(PC-EVN) – Kashima(K5,
SBBC)
•At Kashima, 256-MHz of IFsignals 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.
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.