| The continuous increase of mobile traffic drives researches on new wire-less techonologies for the next mobile communication system.3D MIMO (3 Dimensional MIMO) technique which extends the traditional 2D MIMO tech-nique to 3D can improve the spectrum efficiency of wireless communication systems and be regarded as a key technique for the next communication sys-tem. Researches and evaluations on new wireless techniques need the knowl-edge of wireless channel properties, while field channel measurements is the most effective manner to obtain characteristics of wireless channel. The tradi-tional MIMO technique only focuses on the horizontal plane, so researches on modeling method of 3D MIMO channel is critical and fundamental in research and evaluation of 3D MIMO techniques, the major work and contributions of this dissertation includes:1.3D MIMO channel measurements and data processing. Utilizing chan-nel sounder and 3D antenna array to conduct 3D MIMO channel mea-surements at the center frequency of 3.5 GHz with 100 MHz bandwidth. During our field measurements, the dual-polarized omnidirectional array consisting of 56 antenna elements is implemented at Rx, and the dual-polarized uniform planar array with 32 antenna elements is used at Tx. Furthermore, wireless signals are received under both line of sight and non line of sight conditions. After collecting channel responses, channel parameters including propagation delay, doppler shift, azimuth angles and elevation angles are extracted by using SAGE algrithm.2. Research on statistical characteristics of elevation angles. Based on the extracted elevation angles, statistical characteristics of elevation angles are analyzed in all scenarios. It is proved that the elevation angle spectrum in all scenarios can be well fitted by the Laplace distribution. The mean value of the elevation angle spectrum under NLOS condition is investigated, the results show that the mean value of arrival concentrates at the horizontal plane, while the mean value of departure depends on the horizontal dis-tance between transmitter and receiver and their height. Furthermore the elevation angle spread can be fitted by Lognormal distribution, and the UMi scenario has the largest elevation angle spread.3. Measurement-based 3D MIMO channel mdodling. According to the analysis of elevation angles, a novel elevation angle modeling method is proposed. The maximum value of the elevation angle spectrum and the mean value of the elevation angle spectrum are respectively modeled un-der LOS and NLOS conditions. Elevation angles of multipath components are obtain after moving the discrete elevation angles. For 3D antenna ar-ray, the modeling methodology of linear antenna array, planar antenna ar-ray and cylinder antenna array are illustrated. Finally the novel elevation angle and 3D antenna array are introduced into the traditional 2D channel mdoel to complete the 3D MIMO channel model.4. Evaluation of 3D MIMO channel model. The proposed 3D MIMO chan-nel model is evaluated in terms of statistical characteristics of elevation an-gles, singular value distribution, and channel capacity. The results show that predictions of the proposed 3D channel model can well approximate that of the field measurement channel data. Furthermore comparisons are also made between the 3D channel model and the traditional 2D channel model. It is found that the singular value distribution and the capacity of 2D channel can not fit those of 3D channel. Because the 2D channel model does not take elevation angles into consideration, this model only exploite the multiplexing gains in horizontal dimension. This results in that the 2D channel model has high spatial correlation and underestimates the channel capacity. Estimation errors depend on application scenarios, the largest estimation error only exits in UMi scenario.5. Research on 3D MIMO channel correlation. Based on the field chan-nel measurements, the Kronecker correlation model is evaluated in terms of mean squared error, singular value distribution, and sum rate of MU-MIMO systems. It is proved that the Kronecker correlation model de-creases multiplexing gains of MIMO channel. The sum rate will be under-estimated when this model is applied in MU-MIMO systems, and the es-timation error becomes larger when the number of served users increases. Then analytic expressions of 3D channel correlation are obtained based on the 3D MIMO channel model and impacts of elevation angles and antenna configurations on the channel correlation are analyzed. Due to the larger azimuth angle spread, horizontal antenna arrays have lower channel cor-relaion than vertical antenna arrays. In order to obtain high multiplexing gains, horizontal space should be fully utilized and large element spacing in vertical plane is necessary for 3D antenna array.In summary, the statistical characteristics of elevation angles are analyzed based on field channel measurements. According to the analysis results, the modeling methodology of 3D MIMO channel are proposed, the modeling method is further evaluated in terms of singular value distribution and channel capacity. Finally, the Kronecker product channel correlation model is evaluated and im-pacts of elevation angles and antenna configurations on the channel correlation are analyzed.
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