For sensor network, sensors are running out of their own clocks. How sensors know when to receive packets from other sensors or vice versa when to send packets to other sensors. Obviously sensor won’t do tx/rx all the time unless you want to kill battery in minutes.
Low power is critical to wireless sensor network. Most of time sensors are idle and not talking to each other or sensor network gateway. When idle, sensors should be allowed to go to sleep to save power. These days sensor’s idle current can go to microamps level. How can they do that? They normally shut down high precision and high power clk source and using low precision low power clk source. But it means sensor using low precision clk may wake up too early or too late and miss the window to receive and send packets.
Bluetooth SIG has a good article to address above questions. Although discussion is for Bluetooth, the concept applies to overall sensor network. The article is freely available at: Bluetooth sniff and subrating.
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