This paper proposes a one-way ranging method using reference-based broadcasting messages. The method is based on impulse radio UWB (Ultra-wideband) for wireless sensor networks. The proposed method reduces traffic overheads and increases the ranging accuracy using frequency offsets and counter information based on virtually synchronized counters between RNs (Reference Nodes) and MNs (Mobile Nodes). Simulation results show that the proposed method can alleviate the ranging errors comparing to SDS-TWR (Symmetric Double-Sided Two-Way Ranging) method in terms of the frequency offset.

This paper reports a 24GHz ISM band radar module for pedestrian detection in crosswalks. The radar module is composed of an RF transceiver board, a baseband board, and a microcontroller unit board. The radar signal is a sawtooth frequency-modulated continuous-wave signal with a center frequency of 24.15GHz, a bandwidth of 200MHz, a chirp length of 80µs, and a pulse repetition interval of 320µs. The radar module can detect a pedestrian on a crosswalk with a width of 4m and a length of 14m. The radar outputs the range, angle, and speed of the detected pedestrians every 50ms by radar signal processing and consumes 7.57W from 12V power supply. The size of the radar module is 110×70mm2.