# Channel Measurement and Modeling for 5G Urban Microcellular Scenarios
## 1 Introduction  
Fifth generation (5G) mobile networks will need to make use of frequencies above 6 GHz to provide multi-Gbps data rates and realize ultra-high capacity for various deployment scenarios [1; 2; 3]. The targeted frequency bands range up to 100 GHz [4]. Early stage studies have shown the feasibility of millimeter waves for cellular networks [5; 6; 7], and standardization activities for 5G have been kicked off in the Radiocommunication Sector of the International Telecommunication Union (ITU-R) [8] and the 3 rd Generation Partnership Project (3 GPP) [9]. Considerable effort is currently put into the refinement of channel models, since they are essential for accurately assessing the performance of future deployments. Most relevant work builds upon state-of-the-art three-dimensional (3D) geometry-based stochastic channel models (GSCMs) that have been developed recently for lower frequency bands. New model features and extended parameter tables have been proposed to fulfill the requirements for 5G millimeter-wave (mm-wave) channel models, which have to support a much wider frequency range, large antenna arrays, large bandwidth and high mobility [10; 11; 12; 13; 14; 15]. Providing measurement data for their validation that is both statistically reliable [16] and including full directional information is very challenging as long as high performance electronically steerable antennas for various mm-wave frequency bands are not available at reasonable expense. Multiple channel sounding campaigns have been reported in the literature for cellular access scenarios above 10 GHz, e.g., at 11 GHz [17], 28 GHz [18; 19], 38 and 73 GHz [20] and 60 GHz [21]. The amount of available data, however, is still not sufficient to fully substantiate and reliably parameterize the models. Currently, directional information is mainly obtained by successively scanning all (relevant) angleswith mechanically steerable directional antennas [21]. Since the scanning takes a long time, the number of observation points is limited in practice. A different measurement approach, which is also pursued in this work, is to use a channel sounder with a high measurement repetition rate in conjunction with omnidirectional antennas and a mobile receiver (RX). It allows for collecting large data sets and capturing all multipaths even for time-variant channels and aims to support the parameterization and validation of channel models on a reliable statistical basis. Omnidirectional path loss (PL) models can be derived directly from such data, and it is well suited for assessing results from ray tracing (RT) tools, which become increasingly important for channel modeling at higher frequencies [22; 23]. They are capable of generating large data sets with unlimited dynamic range and can provide directional information to complement the measurements. In this paper, data from three recent urban microcellular (UMi) measurement campaigns at 60 and 10 GHz is analyzed with focus on the PL and delay spread (DS). The frequencies were chosen since they represent sample points in the lower and the upper part of the range 6-100 GHz and hence are well suited to investigate frequency dependence. Moreover, a radio license could be obtained with sufficient bandwidth at 10 GHz, 60 GHz is an unlicensed band, and suitable measurement equipment was available. In view of complementing the measurements with validated simulation data, the results are compared with predictions from an in-house RT tool for the same environments. The findings provide valuable insight into the dependence of channel characteristics on the propagation scenario, distance and frequency. The presented modeling approaches and parameters were derived from several million channel observations for each scenario and can be used to refine 5G channel models and for comparative investigations. To the knowledge of the authors, a comparable unified analysis for the UMi channel at 60 and 10 GHz based on such large data sets has not been reported in the literature so far.