The uncontainablefuture development of Smart regions, as a set of Smart cities’ networks assembled, is directly associated with a growing demand of full interactive and connected ubiquitous smart environments. To achieve this global connection goal, large number of transceivers and multiple wireless systems will be involved to provide user services and applications (i.e. Ambient Assisted Living, emergency situations, e-health monitoring or Intelligent Transportation Systems) anytime and anyplace, regardless the devices, networks or systems, they use. Adequate, efficient and effective radio wave propagation tools, methodologies and analyses in complex environments (indoor and outdoor) are crucially required to prevent communication limitations such as coverage, capacity or speed or channel interferences due to nodes’ density or channel restrictions. In this work, radio wave propagation characterization in an urban indoor and outdoor environment, at ISM 2.4GHZ and 5GHz Wireless Sensor Networks (WSNs), has been assessed. The selected scenario is an auditorium placed in a city free open area surrounded by inhomogeneous vegetation. User density within the scenario, in terms of inherent transceivers density, poses challenges in overall system operation, given by multiple node operation which increases overall interference levels. By means of an in-house developed 3D ray launching algorithm, the impact of variable density wireless sensor network operation within this complex scenario is presented. This analysis and the proposed simulation methodology, can lead in an adequate interference characterization, considering conventional transceivers as well as wearables, which provide suitable information for the overall network performance in complex crowded indoor and outdoor scenarios.