GNU Radio Testbed

Software Defined Radio platform

Software Defined Radio is a technology that combines software and hardware to provide an efficient technique for building wireless communication networks. The system software performs the signal processing and the hardware is not modulation specific. Software defines radios come with extreme flexibility and on-the-fly or run-time reconfiguration. They have a fast development cycle and can perform multiple tasks simultaneously.

The GNU radio is a popular toolkit for designing software defined radio platforms. It helps bridge the hardware with signal processing modules for different kinds of protocols.

GNU Radio Architecture

The hardware front end for the GNU radio is the Universal Software Radio Peripheral (USRP). The USRP consists of a small motherboard containing up to four 12-bit 64M sample/sec ADCs, four 14-bit, 128M sample/sec DACs, a gate-field programmable gate array (FPGA) and a programmable USB 2.0 controller. Each USRP motherboard can support four daughterboards, two of which are used to transmit and the other two to receive. RF front ends are implemented on the daughterboards. The USRP is small and portable with an open design. It can support multiple coherent channels.

GNU Radio consists of several complex signal processing flow graphs that are made up of simple signal processing building blocks. GNU Radio can link the software with hardware such as the USRP and various ADC/DAC pci cards. Signal processing blocks are written in C++, while Python can be used for creating flow graphs and connecting signal blocks. Graphical interfaces for GNU Radio applications are built in Python. Interfaces may be built using any toolkit you can access from Python.

A picture of the USRP is shown below.