OFDM radar on the USRP platform

About the project

A radar using OFDM modulation – the same as Wi-Fi and 5G. It is implemented on a USRP software-defined radio, so it can be changed in software.

In OFDM, data are transmitted simultaneously on many narrow subcarriers. When the transmitted signal is reflected from a target, the phase of each subcarrier changes: the reflection delay causes a phase slope across the subcarriers, and the target's motion a phase slope from symbol to symbol. The same signal can therefore carry data and serve as a radar at the same time.

How it works

1. Transmission: the USRP transmits an OFDM frame – a grid of subcarriers (frequency) and successive symbols (time).
2. Reception: the reflected signal is received by a second USRP; the two devices are connected in MIMO mode, and the computer is connected to the USRP N210 via a 10 Gbit/s link.
3. Rx / Tx division element by element removes the transmitted data; only the effect of the channel, i.e. the target, remains.
4. 2D FFT: a transform across the subcarriers gives the range and across the symbols the velocity – the result is a range-velocity map.