A novel auto-calibration system for wireless sensor motes

In recent years, Wireless Sensor Networks (WSNs) research has undergone a quiet revolution, providing a new paradigm for sensing and disseminating information from various environments. In reality, the wireless propagation channel in many harsh environments has a significant impact on the coverage range and quality of the radio links between the wireless nodes (motes). Therefore, the use of diversity techniques (e.g., frequency diversity and spatial diversity) must be considered to ameliorate the notoriously variable and unpredictable point-to-point radio communication links. However, in order to determine the space and frequency diversity characteristics of the channel, accurate measurements need to be made. The most representative and inexpensive solution is to use motes, however they suffer poor accuracy owing to their low-cost and compromised radio frequency (RF) performance. In this report we present a novel automated calibration system for characterising mote RF performance. The proposed strategy provides us with good knowledge of the actual mote transmit power, RSSI characteristics and receive sensitivity by establishing calibration tables for transmitting and receiving mote pairs over their operating frequency range. The validated results show that our automated calibration system can achieve an increase of 5 . 1 ± dB in the RSSI accuracy. In addition, measurements of the mote transmit power show a significant difference from that claimed in the manufacturer's data sheet. The proposed calibration method can also be easily applied to wireless sensor motes from virtually any vendor, provided they have a RF connector.