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Does Loss Rate Really Matter? An Experimental Study on Time Synchronization Protocol in Wireless Sensor Networks

In wireless sensor networks, there are many link quality measurement metrics such as RSSI (Received Signal Strength Indicator), LQI (Link Quality Indicator) and PRR (Packet Reception Rate), which can be used under different channel quality and application scenarios. As in time synchronization, channel quality would be essential to the clock synchronization. The broadcast nature of time synchronization algorithm makes channel quality measurement complex. Moreover, the measurement on channel quality would be costly. We make an experimental study on time synchronization in wireless sensor network. Firstly, we use the RSSI and PRR with different packet lengths, secondly, we find that, the PRR would be accurate but costly, and the RSSI is not accurate enough for time synchronization algorithm evaluation. In the end, we propose a channel clustering and categorization mechanism in dealing with the channel measurement difficulties. And we find that, in dealing with the lossy links, the compensation model for synchronization errors is more important than reliable transmissions. Also, the proposed measurement would be helpful to the time synchronization algorithm, especially the FTSP (Flooding Time Synchronize Protocol).