Bandwidth, Sample Rates, and Networking

Note

Further details to be provided or can be made available upon request.

Each radio chain is fully independent, and uses a 32 bit complex sample

Note

The section on Data Formats provides additional information on the sample and data format used by Cyan.

(I and Q) to provide up to 1GHz of instantaneous stare bandwidth with 16bit resolution at the FPGA. This corresponds to a bit rate of 32Gbps for each active radio channel (Rx or Tx). However, the back haul bandwidth (from Cyan to a client PC) is limited by the underlying quad 40GBASE-R protocol and qSFP+ interface to 40Gbps per qSFP+.

Bandwidth

Each qSFP+ port can sustain a throughput of 40 Gbps transmission bandwidth, for a total of 160 Gbps of throughput bandwidth across the four qSFP+ ports. However, at 32 bits per sample (16 bits I, 16 bits Q), at 1 GSPS = 32 Gbps times the maximum number of channels (16) this exceeds the channel capacity of the standard qSFP+ ports. As a result, in order to transmit data using all ports, we need to decimate by integer multiples.

Sample rate on Crimson TNG

The base sample rate for Crimson TNG Converters is 325MSPS. All of the Rx channels (A, B, C, D), Tx channel A and Tx channel B are sample at that rate. Due to FPGA limitations, the maximum supported sample rate on Tx channels C and D is \frac{1}{4} of this value; or 80.56640625MSPS (325 MSPS/4). Depending on your use case, custom FPGA images may be developed that allow full rate sending over all Tx channels, but this functionality is not included in the stock Crimson TNG image.

The default Crimson TNG FPGA image supports sample rates that are an integer dividers of 325 MSPS. The possible native sample rates may be calculated as; 325 / N, where N = [2,65534]. However, the default image also includes a 4/5 resampler, though it is uncompensated. This allows for additional sample rates that are integer dividers of 257.8125MSPS (this number corresponds to (325*4/5)MSPS), providing for an additional range of sample rates in the form of; 257.8125/N, where N = [1,65534].

Warning

Please note that RF performance may be degraded when using the 4/5 resampler.