Research On Delay Propagation Characteristics And MIMO Application Of Radio Channels For IMT-Advanced System

As the guideline and technology standards for future mobile communication system, the candidate radio interface technologies (RITs) of IMT-Advanced system are trending towards the technologies of multiple carries, multiple antennas as well as the cooperative transmission. To assure the effective evaluation for candidate RITs in IMT-Advanced system, the propagation characteristics of radio channels in the novel conditions should be investigated. The wireless channel measurement is the most simple and effective way to obtain the channel information. As the key parameters to reflect the wideband channel characteristics, the parameters involved delay propagation play an important role in the design of multiple carries systems. Considering the features of RITs and based on the wideband multiple-input multiple-output (MIMO) channel measurements, this thesis focuses on the investigation of delay propagation characteristics of wideband channel, as well as the application of MIMO technology in IMT-Advanced system. With diverse methods of measurement, data processing, comparison, theoretical analysis as well as the simulation, the main contributions are as follows.(1) Based on the principle of measured equipments, a platform for processing raw data is designed and realized using Matlab toolbox. The platform with simple user interface extracts the channel impulse response from measurement records. It is able to read the measurement setting, and to match the signal files with corresponding system files automatically, thus easy to operate.(2) Based on series of measurement and data processing, the characteristics related delay propagation is studied. The study consists of two parts. One is investigation of typical scenarios defined by IMT-Advanced system, and the other is that of the novel cooperative transmission channels. Base on the measurement campaign of the four typical scenarios, this thesis compares the results of delay parameters with those of WINNER (Wireless World Initiative New Radio) project. As for the measurements of cooperative channel, the impacts of carried frequency and the multiple floors in indoor environment on delay parameters are studied. Meanwhile, the difference of delay propagation characteristics between relay channels and the traditionally central channels in cellular networks is investigated.(3) Since the application of polarized antennas in MIMO system can reduced the requirement of the size of terminals, a novel polarized-spatial correlation model is proposed. The model with flexible polarized direction resolves the restriction of present models where only a certain polarized configuration is considered, thus possesses more applicability. Based on the novel model, the optimal polarization configurations for polarization diversity scheme are further studied. Considering the tradeoff between diversity gain and signals power, an evaluation model related to system performance is derived. The theoretical analysis and simulation results illustrate that the optimal configuration at receiver is fixed at±45°polarization, whereas the optimal result at transmitter is determined by the power angular spectrum as well as the cross polarized discrimination of radio channel.The conclusion in thesis can be applied to the design of IMT-Advanced system, such as parameters of length of cyclic prefix and the spacing between sub-carriers for orthogonal frequency division multiplexing (OFDM) system, as well as the application and configuration of polarized antennas in reality circumstance, and so on.