Nutaq’s Radio420X FPGA mezzanine card (FMC) on the Perseus uTCA carrier allows its users to develop MIMO SDR waveforms on either the Perseus’ FPGA or a host PC. To take advantage of this, Nutaq’s GNU Radio plug-in for the Radio420X permits the configuration and the use of multiple independent RF front ends. It therefore allows its users to develop MIMO or multiband waveforms on the host PC.
MIMO 2×2 on Radio420X with GNU Radio
GNU Radio connects to the Perseus and configures both Radio420X FMCs to the required frequencies, gains and bandwidths. Two data streaming channels are open in each direction, one for each FMC in the stack. The plug-in’s users can therefore transmit and receive data on each channel independently. The FPGA reference design for MIMO, included with Nutaq’s Perseus boards, ensures that the streamed data samples are synchronized between channels in transmission and in reception.
MIMO 4×4 and more
Nutaq’s GNU Radio plug-in allows connections and data streaming to and from multiple Perseus carriers, thereby allowing the development of MIMO waveforms in 4×4 or 8×8 configurations. As in 2×2 MIMO, GNU Radio directly configures each of the Radio420X FMCs and streams data directly to and from the Perseus.
Two possible modes of operation are possible:
- Streaming two MIMO data channels directly to and from each Perseus.
- Streaming data on one channel to and from a master Perseus, where a custom user FPGA IP encodes or decodes MIMO data. The data is exchanged between the master and the other Perseus through the chassis’ backplane. This method allows the plug-in’s user to offload the host PC and move a part of the MIMO processing to the FPGA.
For both methods, Nutaq provides an example of how to synchronize data samples between channels on both the reception and the transmission.
Nutaq’s GNU Radio plug-in also supports multiband operation on multiple RF front ends by allowing each Radio420X FMC in the system to be configured independently. The receiver and the transmitter of each Radio420X FMC can also be configured independently from each other, allowing the user to reconfigure either the receive path or the transmit path of a single radio and not affect the others.
The following parameters are configurable for each Radio420X FMC:
- receiver and transmitter frequencies
- receiver and transmitter gains
- receiver and transmitter bandwidths
The only limitation is that for each Radio420X stack, the same ADC and DAC rate must be used for the two FMCs.
The Radio420X parameters are modifiable dynamically and therefore allow the plug-in’s user to build algorithms such as automatic gain control or frequency hopping within GNU Radio.