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Data Rates for SonATA
2011-02-22 jj
The total data rate out of each beamformer is 104.8576MHz, but
the usable digital bandwidth is 72 MHz.
104.8576 MHz / 2048 samples/packets = 51,200 packets/sec
1 beam = 51,200 packets/sec*4144 bytes/packet*8 bits/byte*2 pol = 3.395 Gbps
There is only one connection from each beamformer to the 10GbE switch.
It carries both pols for that beamformer.
Each channelizer processes only one polarization from one beam.
The data rate going into each channelizer is half of
the beamformer rate, 1.697 Gbs on a 10GbE connection.
Each channelizer reads the entire 104 MHz and applies a digital filter
bank (DFB) to create 256 400KHz channels or 128 800 KHz channels.
A total of 176 output channels are possible;
The current observing system can process 20 MHz or 24 800 KHz channels.
The outside channels are discarded
Each channel is oversampled, having a bandwidth of 1.0922667 MHz.
Oversampling is reciprocal, so the bandwidth is
.8192 MHz / (1 - .25) = 1.0922667 MHz
The output rate for each single pol channel is:
1.0922667 MHz / 1024 samples/packet = 1067 packets/sec
1067 packets/sec * 4144bytes/packet * 8 bits/byte = 35.37 Mbs
Each Channelizer transmits 49 channels:
49 * 35.37 Mbs = 3.11 Gbs
Each dual pol beam has a data rate of 6.22 Gbs.
The total for 3 dual pol beams is 18.67 Gbs.
This data rate necessitates having 3 10GbE connections
between the 10GbE switch and the fanout switches.
Input to the DX server is 1GbE.
One Dx process receives and processes both polarizations for one channel.
A Dx server can run 12-24 Dx processes depending on the capacity of the Dx server.
Dual Pol channel data rate is 35.36 Mbs.
12 channels per dx host: 12 * 35.36 Mbs = 424.3 Mbs
16 channels per dx host: 16 * 35.34 Mbs = 565.76 Mbs
20 channels per dx host: 20 * 35.34 Mbs = 707.2 Mbs
24 channels per dx host: 24 * 35.36 Mbs = 848.64 Mbs
(24 is probably the absolute maximum we could hope for
over a single 1 GbE interface).