Ubiquitous, Yet Deceptive: Hardware-Based Channel Metrics on Interfered WSN Links

The ease of acquiring hardware-based link quality indicators (LQIs) is an alluring property for fast channel estimation in time- and safety-critical wireless sensor network (WSN) applications, such as closed-loop control and interlocking. The two rudimentary hardware-based channel quality metrics, i.e., received signal strength (RSS) and LQI, are the key constituents of channel estimation and a plethora of other WSN functionalities, from routing to transmit power control. Nevertheless, this paper highlights three deficient aspects of these two indicators: 1) Overall deceptiveness, i.e., the inability to reveal the presence of interference, falsely indicating excellent channel conditions in an unacceptably high fraction of cases; 2) the burstiness of missed detection which compromises the attempts to eliminate the deceptiveness by averaging; and 3) high mutual discrepancy of the two indicators, which is observed in 39%-73% of packets, throughout different scenarios. The ability of RSS and LQI to indicate IEEE 802.11 interference is scrutinized in a variety of scenarios in typical industrial environments using commercial-off-the-shelf hardware and realistic network topologies, giving the findings of this paper high general validity and practical relevance.