Studying And Analysis Of Fast Fading Channel In Wireless Communications

The propagation characteristics is vital for the design of the wireless communication. Especially in the high speed movement condition, the wireless communication will change rapidly. If such a variation cannot be adpapted, the performance of the communication system will degrade. If the communication cannot fit such a change, the performance of the communication system will degrade dramatically. Therefore, in order to improve the performance of the communication system,it is vital to establish accurate channel model. This thesis aims at establishing proper channel model.The propsed model use channel information as less as possible to precisely describe the fast fading channel. In addition, the influence of the speed of mobile station and the multipath effect are investigated. Moreover, the communication system performance under the proposed channel is studied.The main work and contributions of this thesis are as follows:Firstly, we propse a Fourier Basic Extestion Model(CE-BEM) to depict the fast fading channel.Least square method is used to extract the model parameters from the exsiting channel data. We sample the data from the exsiting channel data every K point. This is viewed as the channel estimation interval. In balance of the normalized mean square error(NMSE) and the time complexity of the algorithm, we select the proper estimation interval K.Then, we calculate the order M of the CE-BEM model under different moving speeds. Using least squre method, we obtain the model paramters of CE-BEM model and the NMSE. We draw the conclusion: the proper increasement of the order M can decrease NMSE and the higher speed, the larger NMSE. In addition, we model the amplitude of channel as Rayleigh distribution and phase as uniform distribution. The model parameters of each path is extracted using maximum likelihood estimation.Finnally, using Monte Carlo simulation, we generate sets of random binary sequce at first.Then, they are mapped according to the constellation. Afterwards, the mapped symbols are transmitted over our propoed channel and demapped. By comparing the input and output sequences, the bit error rate is calculated. Additionally, we compare the communication system performances of different constellations and transmitting symbol durations.