Analysis Of Wireless Channels And Its Implement In LTE Downlink Based On Time-Frequency Domain

Research on wireless channel is essential to the planning and the design of mobile network and the promotion and improvement of mobile techniques as well.Wireless channel is a very broad classification,various scenarios and complexed enviroment.With the development of high speed raiway wirless techniques, lacking of effective method in analysis of high speed raiway channel with high mobility and fast time varying characters has blocked the establisment of the high speed railway channel. In fact, the traditional channel analysis method based on impulse response in time domain or power spectrum density in frequency domain can not follow the development of wireless communication.T-hey all have the shortcoming of doing channel research in single time domain or frequency domain. Time-frequency analysis overcomes the shortcoming of doing reasearch in single domain. Signal can be expressed by union function in time-frequency domain and can be analyzed in joint time-frequency domain.This thesis firstly discusses some basic time-frequency anlaysis algorithms like STFT, SPWVD and so on.Meanwhile,this thesis analyzes the classification and characters of wireless channel. The OFDM and MIMO techniques in3GPP-LTE are also introduced in this thesis.Then, based on joint time-frequency domain, the thesis analyzes the characters of narrow-band channel and wide-band channel in small-scale fading respectively. Meanwhile, the time-frequency power distribution of Rice channel is given.Compared with the traditional method which is based on time response in time domain or power spectrum in frequency domain in small-scale channel analysis, this distribution has the benefit of reflecting the time varying character of the channel.Subsequently, based on joint time-frequency domain, the thesis fully discu-sses the Qian Liu channel which can simulate the scene in which the speed of train changes,the SCM channel and3GPP high speed railway channel. Their time-frequency power distributions are also given.The distributions have reflected the time varying character of the channel.It is superior to traditional method which is based on single time domain or frequency domain.Finally, based on the simplified LTE down transmitter link and time-freque- ncy anlaysis method, the time-frequency power distribution of LTE downlink signal before and after passing the narrow-band and wide-band channel is given respectively. The distributions have embodied the charater of data mapping of LTE downlink signal in joint time-frequency domain and is essential to the research of the design and improvement of LTE receiver.