Research On Implementation Technology Of XPIC And Carrier Synchronization In Wireless Communication System

With the development of the wireless technology application, the wireless mobile communication technology developed rapidly, but it always faces a serious problem that it is short of spetrum. Nowadays improving the spectrum efficiency has been one of the focus of research in the wireless communication system.To improve spectrum efficiency, in addition to adopting QAM modulation technology, it also can use Polarization Wavelength Division Multiplexing. When using Polarization Wavelength Division Multiplexing, it involves cross interference. Cross-Polarization Interference Canceller(XPIC) can be used to offset the cross interference, this paper discusses the Cross-Polarization Interference Canceller algorithms; When using QAM modulation technology, demodulation uses coherent demodulation technology in general, and carrier synchronization loop is one of the indispensable loops to coherent demodulation.Firstly, it introduces the structure and algorithms of cross-polarization interference canceller. In this thesis, it introduces three algorithms, including the Direct Decision(DD) algorithm, the DD-Least Mean Square(DD-LMS) algorithm and the Constant Modulus CMA algorithm. Then discusses the switching algorithm of DD-LMS and CMA, which is based on the advantages of the both. According to the mathematical derivation of the algorithm, it carries out model establishment and simulation respectively for DD-LMS, CMA and switching algorithm by using Simulink, and set certain cross-polarization interference in the channel, then analyzes and compares the performance of these algorithms. After finishing the simulation, adopting Verilog realizes the canceller by DD-LMS algorithm and carries out the function simulation and board-level simulation in the FPGA board.Debugging results is great and right.Secondly, it introduces the principle and algorithm of the carrier synchronization loop. This paper discusses the direct decision(DD) algorithm, polarity decision(PD) algorithm and the switching algorithm of the both. According to the mathematical derivation of the algorithms, by using Simulink, it carriesout model establishment and simulation respectively for DD algorithm, PD algorithm and the switching algorithm, and sets some certain frequency offset in the channel, then analyzes and compares the performance of the algorithms. The simulation shows that the loop carrier synchronization algorithm by using swithing algorithm, it converges slowly, but the phase jitter error is small after convergence, and it can capture frequency offset stability; while the carrier synchronization loop adopts PD algorithm, it can get faster convergence rate, but the phase jitter error is larger after convergence as well as the frequency offset jitter captured; and the switching algorithm can get the advantages of the both. Then using verilog achieve carrier synchronization loop by swithing algorithm to carry out the function simulation and board-level simulation of the single synchronization loop in FPGA board, it proved that the carrier synchronization loop by switching algorithm can achieve great effect to correct the frequency offset. At last, it tests the whole system and the debugging result is correct.