Mimo Channel Measurement And Modeling Of The New Network Structure

To meet the requirement of high data rate transmission, adequate fre-quency bands should be allocated to the IMT-Advanced system. Moreover, more effords should be devoted to the reformation of the network structure and the improvement of the transmission technique. Relay is considered as one of the most promising candidate techniques because of its various advantages over the conventional cellular system regarding the enhancement of coverage range, diversity, and achievable rates. Since the channel measurement and modeling are vital for the research of the transmission technology and the deployment of the communication system, it is very necessary to carry out the channel mea-surement and modeling in the frequency bands that have been or probably will be allocated to the IMT-Advanced, as well as in the emerging network struc-ture. The research in this paper mainly focuses on the channel measurement and modeling in relay system. The main line of the research consists of three steps, namely field measurement, parameter estimation and statistics, as well as modeling. The main contributions are as follows.(1) The performances of MIMO and relay have been attracting a wide range of concerns. However, most of current theoretical literature hypothesize relatively simple channel conditions, resulting in a deviation between the the-oretically predicted performance and the actual performance that system can achieve in the real propagation environment. The field measurement can ac-quire details from the propagation environment, so the performance analysis and prediction based on the measured channel can achieve high accuracy. Nev-ertheless there are no complete methodology and framework on how to assess the system performance from the measured channel at present. A framework for the performance evaluation based on the measured channel is established. The expressions for performance indices of the measured channel are derived. Based on the framework, the performances of the measured channel in indoor hotspot and outdoor relay scenarios are analyzed in terms of channel gain, channel correlation, eigenvalue statistics, capacity and diversity-multiplexing tradeoff. The achievable signal-to-noise ratio, spatial diversity and capacity of three transmission schemes, i.e., direct transmission, amplify-and-forward and decode-and-forward relaying, are investigated. The impact of the propagation environment on the performance is also analyzed.(2) The slant polarized array can utilize the decorrelation effect introduced by both the space and orthogonal polarization, thus can reduce the signal cor-relation and improve system performance. However, because currently there is no corresponding theoretical solution, the signal correlation in the slant po-larized array can only be gotten by measurement or simulatin. The influence of the channel parameters on the correlation is not entirely clear. For the case where the slant polarized arrays are used, the solution of the correlation con-tributed by both the spatial and cross-polarization correlation with arbitrary an-tenna spacing and slant angle is derived. The approximations for the large and small angular spread are also given to reduce the simulation complexity. The derivative of channel correlation on the angular spread, slant angle and cross-polarization descrimination are obtained. The application scope of exact and approximate expressions are validated by simulation. Finally, the equivalent relationship between the antenna spacing and slant angle is revealed.(3) Generally, the antenna of relay is lower than that of the base station, and higher than that of the mobile station. A change in antenna height makes the propagation environment different from the traditional link between base station and mobile station. However, there are no related measurement re-sults on MIMO relay channel measurement in frequency bands allocated to the IMT-Advanced system. Moreover, the polarization and spatial characteristics, which have an important impact on the system performance are not revealed. Therefore, the applicability of channel properties obtained from the traditional base station and mobile station link and new features of the relay channel pa- 北京邮电大学博士学位论文rameters need to be examined. The spatial and polarization characteristics in the three link constituting the relay channel are compared. The distributions for fitting the cross-polarization descrimination and power azimuth spectrum are obtained by the least-square estimation. The expression of channel corre-lation is extended to the case where the power azimuth spectrum follows the multi-cluster Laplacian distribution. Substituting the measured values describ-ing the statistics of channel parameters into the derived expression, the channel correlation of different antenna configurations is studied in the real propagtion environment.(4) Most of the popular channel models are based on the cluster, and the latest models assign different parameters to the clusters generated by differ-ent propagation mechanisms. However, existing measurements and research have not covered the statistical characteristics and propagation mechanisms in RS(?)MS link. For the propgation mechanism in the RS(?)MS link, the cluster identification and tracking are carried out based on the results of parameter esti-mation. Based on the clustering results, the statistics in cluster and correspond-ing propagation mechanisms are investigated. The methods for improving the cluster identification and tracking are also presented.The analysis and modelling methods proposed in this thesis can be applied widely to channel measurements and modeling. The presented measurement and analysis results can provided references and guidelines for performance evaluation and deployment of the IMT-Advanced system. The measurement results in indoor hotspot and outdoor relay scenarios are adopted by the ITU-R and 3GPP-LTE+ standardization, respectively. All the contributions in this the-sis provide a reliable research base for the simulation, evaluation and network planning of IMT-Advanced system in China.