Non-ideal Characteristics of Low-Cost Radio Transceivers in Wireless Sensor Networks

Some important supporting techniques for wireless sensor networks including link quality estimation, channel modeling and node localization depend on the accuracy of transceiver parameters such as transmit power and receive power. Unfortunately, the low-cost transceivers used by sensor nodes are non-ideal and usually cannot provide accurate and consistent parameter values. As far as we know, there is still no systematical study on the non-ideal characteristics of such transceivers in the literature. In this paper, accuracy and consistency of transmit power, receive power and channel frequency are evaluated through measurements. The results show that channel frequency has good accuracy and consistency. The measured receive power has little difference from the actual input power. Its calibration curve is approximately linear, although there are relatively obvious nonlinear regions. For a single node, there is nearly no difference between the calibration curves of different channels. However, there are obvious offsets between different nodes. Actual transmit power is much lower than the nominal one. There are not only significant differences between the calibration curves of different nodes, but also certain differences between different channels of a single node. It means that calibration of the transmit power is more difficult than the receive power. Fortunately, these calibration curves are overall offset and can be calibrated by only measuring the offset of a single power point. The results also show that if these parameters are not calibrated carefully, performance of link quality estimation, channel modeling and node localization would be affected inevitably.