MIMO Wireless Communication Model Based On EM Full Wave Method

With the high-speed development of modern communication technology, wireless communication technique for excellent performance and high capacity is coming to people's great attention in related fields. The wireless resources, especially the frequency resources, have become more and more precious. Many efforts have been taken for improve the utilization of these resources more efficiently in B3G / 4G. Researches have indicated that multiple-input multiple-output (MIMO) systems using multi-element antenna arrays (MEA) at both the transmitter and receiver can provide substantially higher data rates and better spectral efficiency than the traditional systems in rich multi-path environments. Therefore, MIMO has considered the key technology in the future's wireless communication systems.However, there are still several limitations in traditional methods of the study on MIMO systems. One of them is that in nowadays study, the antennas on both sides are always considered as omni-directional only for the simplicity, which neglects the effect between antennas and MIMO signals. It must also be noted that in conventional methods, the expression of the channel impulse response is just based on the assumption of point-to-point transmission using ray-tracing simulations, which neglects the spatial distribution of signals. Furthermore, the ray-tracing method is on the basis of the assumption that the dimension of the scatterers is far larger than the wavelength of the incoming signals, which is difficult to be satisfied in many kinds of situations, especially in the indoor environment. As a result, there is still difference between the theoretical results and the measurements. This has caused many research efforts for presentation of new models to decrease this difference. According to the existing problems in the traditional MIMO researches, it is necessary to find out a more dependable analytical model for the MIMO study, which includes both the transmitting and receiving antennas and the space channel.In this thesis, the theory of electromagnetic field and the full wave methods are used to analyze the characteristics of MIMO wireless communication model. We especially study the characteristics of the transmitting and receiving antennas and their effect on the performance of MIMO systems. The current distributions on antennas are used for the evaluation for the reason that the current distributions contain the effect of both spatial field distributions, the form of antennas and the effect of mutual coupling, by which more channel information can be included. Furthermore, a relationship between full wave modeling and channel information is tightened directly.In order to obtain the accurate current distributions, in this thesis, the specific channel model is established and the full wave methods are introduced for the calculation. First, the accuracy of this method is demonstrated by choosing different kinds of calculation conditions and the most applicable one is chosen for the use of next study.Then, we pay much effort on the study of the effect of the mutual coupling and channel correlation on the performance of MIMO systems. The simulation results by MATLAB show that the current distributions on the coupling antenna arrays fluctuate around the one on the no-coupled antennas, which agrees quite well with the measurement results. Furthermore, the numerical results also verify the rationality of the definition the correlation coefficient from the current distribution point of view. Additionally, it is the first time that a new parameter, the power proportion, is used to set the channel model so that this kind of model can be suitable for different kinds of PAS cases and even applicable in more complex circumstances with irregular angle spread or have more than one beam. All these have revealed the electromagnetic relationship of MIMO systems.Finally, a brief conclusion of the above research is made and an interesting investigation of the possibility is given on the study of MIMO correlation based on the electromagnetic field in spectral domain. All these results can be regarded as a fundament to deeply expand the study of MIMO wireless channel model.