performed a number of field tests 11 with Tmote Sky sensor nodes in real-world power delivery and distribution systems by measuring background noises, interference levels, and link quality. On the PHY layer perspective, determination of ED and LQI is a good approach to identify the radio condition. IEEE 802.15.4 Based Wireless Sensor Network Design for Smart Grid CommunicationsĬhun-Hao Lo, Nirwan Ansari, in Handbook of Green Information and Communication Systems, 2013 4.4.2.4 ED and LQI Assessment For example, a battery-powered device might be in an excellent location in terms of the link quality, but routing the messages frequently through this device will drain its battery much earlier than the rest of the devices in the same network. Other factors, such as routing energy efficiency considerations, can also influence the route selection. The LQI is only one of the decision factors in selecting a path to route a message. In general, the path that has the highest overall LQI has a better chance of delivering a message to the destination. For example, the NWK layer can use the reported LQI levels of the devices in the network to decide which path to use to route a message. The LQI is reported to the MAC layer and is available to the NWK and the APL layers for any type of analysis. The LQI must have at least eight unique levels. The LQI measurement is performed for each received packet. The link quality can also be judged using both the signal energy and the signal-to-noise ratio. Therefore, a signal with high SNR is considered a high-quality signal. As a general rule, higher SNR translates to lower chance of error in the packet. The ratio of the desired signal energy to the total in-band noise energy (the signal-to-noise ratio, or SNR) is another way to judge the signal quality. The RSS is a measure of the total energy of the received signal. The received signal strength (RSS) can be used as a measure of the signal quality.

The link quality indicator (LQI) is an indication of the quality of the data packets received by the receiver. Shahin Farahani, in ZigBee Wireless Networks and Transceivers, 2008 3.2.4 Link Quality Indicator

Wifi rssi good value