A FM Radio Based Time Synchronization Scheme For Wireless Sensor Network

Time synchronization is a very critical issue in Wireless Sensor Networks(WSN).Traditional time synchronization methods such as GPS and NTP are very mature,but high energy consumption,high complexity and harsh environment make their shortcomings obvious in WSNs.In order to overcome these shortcomings,this thesis presents a low-power and high-precision time synchronization method for WSNs based on FM time-of-day signal and designs a time synchronization hardware system to verify the effectiveness and feasibility of this method.In this thesis,a time synchronization system based on FM time signal is designed,which is woken up before the arrival of the FM time-of-day signal.After receiving the FM broadcast signal,the FM broadcast signal is demodulated by the demodulation circuit and the FM audio signal is processed.Using the digital signal processing method the FM time-of-day signal is discriminated from the FM audio signal,and then outputs the time synchronization signal.The time synchronization system has the ability of self-wake-up and sleep,wake-up before the FM time-of-day signal,sleep after the end of the time synchronization.Through the test,the time synchronization method has an average precision of 1 millisecond,and the power consumption is 117 milliamperes.What's more,it has been used in a real WSN system.First,this thesis extracts the FM time-of-day signal,analyzes the design difficulties,designs a time synchronization method for the existing difficulties,and verifies with the software simulation.Second it designs a dormancy mechanism for FM time-of-day signal to solve system power consumption.Then it also designs signal processing and control module,base time module and FM receive module to implement the hardware.The design scheme is introduced in detail.Especially,a more stable digital time synchronization module is designed after designing the first edition of FM receive module.Finally,a time synchronization system test platform is set up to test the validity,time synchronization accuracy and power consumption.