Duty-Cycled, Sub-GHz Wake-up Radio with -95dBm Sensitivity and Addressing Capability for Environmental Monitoring Applications

Abstract

A novel approach for duty-cycled wake-up radios (WuRs) is proposed with focus on environmental monitoring applications involving wireless sensing devices left unattended in harsh conditions. In this scenario, a higher data latency (on the order of seconds or minutes) is potentially acceptable if significant improvements are achieved in terms of a) communication range, b) reliability, and c) energy-efficiency. The solution is solely based on off-the-shelf components with two main novelties implemented by software. First, the Receiver Bandwidth Filter of a commercial sub-GHz radio transceiver is configured with a small value typically not used in data communications (e.g., 9.5 kHz). Such action leads to a higher reliability of the WuR operation in outdoors where longer distances are involved and multiple signal interfering factors may be present. Second, the WuR addressing feature is achieved at the analog domain without requiring data decoding of any symbol. Nonetheless, more than 1,000 nodes can still be individually awoken with the proposed solution considering the 915MHz-ISM band. The preliminary empirical results from five outdoors sites involving more than 30 nodes show no false-positives and less than 3% of false-negative cases for distances higher than 225m and non line-of-sight (NLOS) and obstructed line-of-sight (OLOS) due to vegetation, rocks, and topography. By accepting a longer wake-up latency (e.g., 1 minute), the proposed solution which combines WuR and duty-cycling techniques can excel existing commercial WUR solutions in terms of energy-efficiency by more than one order of magnitude.