Hello, it seems that RPI compute module severely restricts rx and tx bandwidth for LMS7002M (as I know it can handle up to 120 MHz RF bandwidth). And also board has a gigabit ethernet. So I was wondering, is it possible to use limenet micro without RPI compute module and connect it to host pc over ethernet, so it can unlock the full RF bandwith?
Ok, I do not own the hardware, but lets pull up the schematic and look at it.
The board has Ethernet provided by a four port USB 2.0 HUB with integrated 10/100 Ethernet (LAN9514-JZX), so there is no “gigabit ethernet” in the LimeNET Micro.
But let us imagine for one second that you designed and created your own board with actual gigabit Ethernet. What would that mean, well 1,000,000,000 bits/second if you were using a custom protocol, but most people sensibly choose to use IPv4 (or IPv6) which due to their packet headers have overheads.
TCP/IPv4 with a MTU of 1500 bytes (Overhead 5.07%) is at best 94.93% efficient, so a throughput of about 949,284,785 bits/second (theoretical maximum).
TCP/IPv6 with a MTU of 1500 bytes (Overhead 6.37%) is at best 93.63% efficient, so a throughput of about 936,280,884 bits/second (theoretical maximum).
Lets pick the lower of the two throughput numbers, divide that by 12 for the 12-bits for each sample from the LMS7002M and then divide that by 2 for the I and Q channel. 936,280,884/12/2 ~= 39,011,703 IQ samples/second. After you allow for some more reality to leak in you are probably talking closer about 36 MHz of RF bandwidth at most.
What is it that you are trying to do ?
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No, not easily.
If you want to benefit from LimeNET Micro features such as GPSDO, but without using the CM3+ SoM and with processing instead via another host computer, you can connect it to this via USB 3.0.
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Thank you very much for reply. Yes, the idea was in using the benefits of high performance onboard oscillator and 1gb ethernet bandwidth (didn’t find that LimeNet micro has only 10/100 lan before posting question). Now I assume it’s more profitable to use LimeSDR USB with external reference clock
Beneficial? Well, it is 2x2 MIMO instead of SISO and has a bigger FPGA, plus FX3 USB 3.0 controller instead of a simpler FTDI one. Though all of these things may or may not be of benefit, depending upon your particular requirements.
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