The Studies Of OFDM System Carrier Frequency Offset Estimation Algorithm

In the Fourth Generation mobile communication systems (4G), the orthogonal frequency division multiplexing (OFDM) technology will be concerned and in of favour. Because it can be against frequency selective fading effectively, has the high spectrum efficiency and has the lower cost. With the growing need for personalized communication, digital, broadband and mobile technology, OFDM technology will be more widely used in the field of integrated wireless access.OFDM technology, however, has two major defects: large PAPR and carrier frequency offset sensitivity. A small carrier frequency offset will result in sharply declined system performance. Therefore, to research the accurate and efficient carrier frequency offset estimation algorithm is imperative, and it is also the work of this thesis.Papers first study some of the current international carrier frequency offset estimation algorithm in-depth, then study the training sequence carrier frequency offset estimation algorithm , last demonstrat and analyz their performance. Its work and the innovations are:First, Papers analyse the basic principles of OFDM system, and the common channel of the OFDM system: AWGN channel, flat fading and frequency selective fading channel, and these channels were modeling and simulation.Secondly, Papers study the impact of each the carrier phase offset and carrier frequency offset on the system, and study the ML algorithm and the Intercarrier Interference Self-Cancellation algorithm in detail. These performances were compared.Finally, Papers study the P. Moose algorithm and Schmidl & Cox algorithm in-depth. On this basis, an improved algorithm was proposed, which based on real training sequence. And it is a data-aided carrier frequency offset estimation algorithm (data-aided) algorithm. The performance of the improved algorithm is more stable, and the computational complexity is much less than P. Moose algorithm and Schmidl & Cox, and it has higher estimation accuracy. It can estimate the small times and integer times of the carrier frequency offset in the time domain. In the case of low signal to noise ratio, the performance of the improved algorithm has more advantages. And it can improve the range of carrier frequency offset algorithm to the half of the maximum signal transmission bandwidth, and its estimation range is quite large. Simulation results show that the carrier frequency offset with the increase of increases the signal bit error rate rapidly. So it is necessary to take effective frequency offset estimation algorithm to reduce the error bit rate communication system. The frequency offset estimation algorithm used based on the training sequences in this paper can effectively estimate the carrier frequency offset value, greatly reducie the system's bit error rate and improve the OFDM system performance.