Dynamics of multipath variations in urban environment

The paper analyzes the pace of change for multipath components along a route in urban environment. The direct benefit of the investigation is an insight into the size of visibility regions for multipath components. The problem is considered in time domain, without the impact of antenna patterns or specific frequency band (these can be implemented on the results of the analysis for the purpose of investigating the specific frequency band and specific (MIMO) antenna combination). The analysis was performed using 3D ray tracing tool that calculated the direction of arrival, the length of each multipath component, as well as the power level for each ray. Types of propagation applied were line of sight, reflection and diffraction. Introductory analysis of required number of receiver samples per unit length was performed. Algorithm for tracking or recognising identical or new multipath components along the route based on simple geometry is developed. It was surprisingly observed that the size of visibility regions for most rays was at the level of the receiver sample granulation. This can be explained by the definition of visibility region and its conflict with the nature of diffraction, which was dominant propagation mechanism in this investigation. Based on the results, a modification of 3D geometry based stochastic channel models is suggested.