Implementation Of Adaptive Modem In Cognitive Radio Based On FPGA

Facing with the rapid development of wireless communication, the wireless spectrum resources are becoming deficient along with the ever-increasing requirements of mobile communication and broadband wireless access. And how to improve the spectral efficiency has always been a main challenge in wireless communication research field. Cognitive radio is proposed as an efficient method to resolve this problem. Since the adaptive reconfigurable modem is one of the most important cognitive radio's features, the research of it becomes very significant.Software radio is the ideal platform for implementing the cognitive radio. This thesis firstly introduces the basic principles and key technologies of software radio. Especially, interpolation and decimation in multi-rate signal processing, band-pass sampling, digital down converter and filtering are discussed in detail, which is the theoretical basis of adaptive reconfigurable modem's implementation. After presenting the architecture of cognitive ratio system and basic working modes, the thesis investigates the implementation of communication module based on FPGA. In this section, several modulation and demodulation techniques in cognitive ratio system are analyzed, such as BPSK,π/4 DQPSK, 8PSK and 16QAM. And after this, the thesis introduces the implementation of every function module of the Modem based on DSP+FPGA hardware platform in sequence of signal processing. Based on the analysis of experiment data, the performance evaluation is also presented in this section. According to these results, the thesis proposes a newly designed modulation-variable, bandwidth-variable adaptive reconfigurable Modem to meet the requirements of cognitive ratio in the fourth section. The hardware implementation of several key modules is discussed, and the receiver's policy of baud rate detection is also presented in this section. Finally, the thesis proposes several newly adaptive technologies, like the estimation of baud rate and SNR. And corresponding improvements are also discussed.