A method of communicating a chirp signal from a transmitter suitable for receipt at a proximal receiver and a distal receiver, the chirp signal including a plurality of packets, each packet including at least one symbol, each symbol including one or more identical chirps, the method including: generating the chirp signal by interleaving constituent packets of: (i) a first set of packets encoded with first data, each packet including one or more symbols having a first time period t1, and (ii) a second set of packets encoded with second data, each packet including one or more symbols having a second time period t2, where t1