The spectrum shortage at microwaves has necessitated the use of millimeter-wave (mm-wave) frequencies in future fifth generation (5G) wireless communication systems. In order to evaluate the performance of 5G networks at mm-waves, propagation channels in various scenarios must be properly characterized and modeled. This thesis aims at providing important insights, methods and tools for mm-wave channel modeling. Deterministic field prediction tools, previously used mainly for coverage analysis, are increasingly used also for stochastic channel model parametrization or for evaluating system performance. The prediction accuracy of such tools, e.g., ray tracing, may be compromised due to missing details in the environment databases. In this work, a novel field prediction tool relying on accurate environmental information in the form of point clouds is developed. The prediction method parameters are tuned by measurements, and the performance is validated in several indoor environments by comparing predicted and measured channels in terms of power, delay and angular metrics. The results demonstrate excellent prediction accuracy in both line-of-sight (LOS) and non-line-of-sight links.As the upcoming 5G mm-wave deployment will be made in new scenarios, channel sounding is essential to acquire knowledge about the propagation characteristics and the applicability of existing channel model frameworks. This work presents insights obtained from channel sounding results conducted in environments such as offices and a shopping mall in the 60- and 70-GHz bands. Unlike existing channel models, clustering was not found apparent in the large indoor environments, allowing a simpler spatio-temporal channel model structure to be developed. A parametrization of the WINNER II model at 60 GHz and a study on the depolarization at mm-waves is also presented. The results show that polarization is better preserved at mm-waves than at lower frequencies. Moreover, a novel method to evaluate LOS probability based on point clouds is demonstrated. The last part of the thesis deals with the use of stochastic and site-specific channel models in evaluating the performance of mm-wave wireless systems. The point cloud-based simulation tool is used to study the mutual orthogonality of mm-wave links equipped with large antenna arrays. The result shows that compared to microwave frequencies, the number of active users should be smaller at mm-waves to guarantee efficient spatial multiplexing.
|Translated title of the contribution||Mittauksiin perustuva millimetriaaltoalueen radiokanavasimulointi ja -mallinnus|
|Publication status||Published - 2016|
|MoE publication type||G5 Doctoral dissertation (article)|
- channel modeling
- point cloud