28 GHz channel modeling using 3D ray-tracing in urban environments

In this paper, we analyze the radio channel characteristics at mmWave frequencies for 5G cellular communications in urban scenarios. 3D-ray tracing simulations in the downtown areas of Ottawa and Chicago are conducted in both the 2 GHz and 28 GHz bands. Each area has two different deployment scenarios, with different transmitter height and different density of buildings. Based on the observations of the ray-tracing experiments, important parameters of the radio channel model, such as path loss exponent, shadowing variance, delay spread and angle spread, are provided, forming the basis of a mmWave channel model. Based on the analysis and the 3GPP 3D-Spatial Channel Model (SCM) framework, we introduce a a preliminary mmWave channel model at 28 GHz.

I. Introduction

As one of the promising solutions for the next generation of wireless communications (5G), the use of enlarged system bandwidth in the millimeter wave (mmWave) frequency range is discussed [1]. The most fundamental question in mmWave cellular communication systems is the feasibility in outdoor environments, considering the much larger propagation loss compared to legacy cellular systems operating in the below 6 GHz band [1]. In [2], the channel characteristic of mmWave spectrum, based on field measurements, was analyzed at 28 GHz and 38 GHz in outdoor environments. Recently, [3], [4] conducted additional measurement campaigns in urban environment and proposed a mmWave channel model. As an alternative approach to analyze the mmWave channel characteristics and to fill up the gap in statistical description caused by the limited number of samples in measurement campaigns, ray-tracing can be considered since it provides good agreement with real measurement results [5], [6].