Beacon design for GPS-Free wireless sensor networks

A beacon for ranging in GPS-Free sensor networks is described, Combining the advantages of both narrowband and high distance estimation accuracy. The system uses the same frequency band for both communication and ranging purposes so that no separate dedicated ranging transceiver is needed. The special designed waveform of the signal is introduced, and the algorithms in the receiver module, especially the TOA estimation method, are described in detail. Simulation results show that the proposed beacon performs well under interference of AWGN.