Scale Up

K2SDR

Will there be a way to scale up the server part to allow more connections? Perhaps connect device to a desktop server? 20 or more users would be great.

Jeff

jks

Unfortunately not at full bandwidth with the current architecture. With each DDC added (2 needed per user connection: 1 audio, 1 waterfall) additional resources are consumed on the FPGA (logic fabric & memory) and more compute load is placed on the Beagle. So it is not possible to go past the current 4 user limit (unless someone sees some clever optimizations). The goals of this project were full bandwidth, low cost, modest performance, web-enabled and then to maximize the number of connections possible within those constraints.

However, as discussed on this thread: http://forum.kiwisdr.com/discussion/discussion/359/iq-recordings-4-users there is the possibility of running a single channel at a lesser bandwidth (maybe 1 MHz wide) and shipping the raw IQ data off to a PC for FFT-based downconversion that could support many more users. The 1 MHz limit has to do with the capacity of the SPI link from FPGA to Beagle and probably how fast the Beagle can reliably sustain output to the Ethernet. Now there is an unimplemented 8-bit wide GPIO connection from FPGA to Beagle. So you might be able to beat the performance of the 48 MHz SPI. Lots of room for experimentation.

For comparison look at how Twente WebSDR works: http://wwwhome.cs.utwente.nl/~ptdeboer/ham/sdr/#apr2013 The raw IQ from a full bandwidth ADC is resampled by the FPGA to fit the capacity of a gigabit Ethernet link back to a PC with a GPGPU card to do the huge FFT and associated processing. Our colleague Andr?s Retzler, HA7ILM, is working on this exact architecture: http://blog.sdr.hu/2016/03/13/recent-work.html