Research On Key Techniques Of Radio Resource Allocation In Relay-enhanced Cellular Networks

Short range wireless technology has been widely used in wireless measurement and wireless sensors, because under some conditions, the signal to be measured or sensed is in so hostile environments that the operators cannot work nearly and the data of measurement or sensors must be transmitted to the processing side by wireless transceivers. This thesis is an example of the short range wireless technology application in measurement.Firstly, this thesis introduces some short range wireless transmission technologies. By making comparison of these technologies, this thesis decides to use micro power wireless transmission technology. After analyses the basic structure of wireless system, this thesis formulates a circuit which can realize the half-duplex transmission of data and synchronizing pulse. In this circuit, data is modulated in the method of OOK and pulse is modulated in the method of FSK. At the same time, this thesis designs the RF link to build an entire wireless system.Because the sample accuracy of this system is easily affected by the jitter of the synchronizing clock, this thesis needs a synchronizing pulse whose jitter is shorter than 30 ns. However, traditional envelop detection circuit is not able to reach the response time, therefore this thesis use a logarithmic amplifier instead, which is sensitive to the power and waste much less time. In addition, this thesis introduces an auto level control circuit to reduce the influence of the receiver input power fluctuation on the pulse jitter.In order to further reduce the pulse jitter, this thesis represents a low-jitter digital pulse transmission method. In this method, on the one way, the Costas loop carrier synchronization technology is introduced to improve the synchronism of reference clock, on the other way, the time to digital converter is introduced to reduce the sample error of the pulse by improving the accuracy of the time measurement.Finally, this thesis describes the results of the circuit assembly, debugging and testing and finds that the wireless system is able to realize the transmission function of data in the distance of 120 m and the transmission function of pulse in the distance of 60 m. The sensitivity of the receiver link is-90 dBm.