# Evaluation of Deployment Challenges of Wireless Sensor Networks at Signalized Intersections
###### Abstract
The second group are the stochastic channel models (narrowband or wideband) [21], which characterize the channel from a frequency selective perspective. The third group includes the geometry-based stochastic models, which are the most widely used for propagation prediction in mobile communication channels, e.g., the work presented in [22] presents a V2V geometrical channel model considering that the local scatters move with random velocities in random directions. In [23], a new geometric-stochastic channel modeling is presented in which the delay-dependent Doppler probability density functions (pdfs) are derived for general V2V propagation environments, to cope with the non-stationarity of these channels. In reference [24], [PERSON] and [PERSON] presented a non-stationary multipath fading channel model incorporating the effect of velocity variations of the mobile station. Reference [25] presents an adaptive reduced-rank estimation of non-stationary time-variant channels using subspace selection. However, none of the approaches described above consider all the elements of the environment, and because of that, they could fail in specific situations when the surroundings have a great impact on the electromagnetic propagation, such as a complex intersection in a large city, which could have vegetation, different type of scatters including different types of traffic lights, buildings, walking citizens, different materials, etc. Because of that, the fourth group of channel modeling approaches corresponds to deterministic methods, which are widely used for propagation prediction given a specific environment. They can be roughly divided into two categories: those which are based on ray optics (ray launching (RL) or ray tracing (RT) techniques) or the full-wave simulation techniques based on solving the Maxwell's equations (method of moment (MoM), finite difference time domain (FDTD), etc.). These methods are precise but are time-consuming due to inherent computational complexity. Thus, methods based on geometrical optics (ray launching or ray tracing) offer a reasonable trade-off between precision and required calculation time, for radio planning purposes, with strong diffractive elements [26]. The main difference between the RL and RT techniques is that in the RL technique, rays are launched from a transmitter and, at the locations where rays intersect and object; the new reflected, transmitted, diffracted, or scattered rays begin. On the other hand, in the RT approach, the number of possible paths that rays follow from the transmitter to the receiver are encountered by imaging techniques. In this work, deterministic modeling, specifically a RL technique, has been used to characterize the physical channel for radio planning purposes in an urban area for a context-aware system that benefits from traffic light infrastructure, given the ease of deployment as well as the vicinity to users under analysis, i.e., pedestrians as well as vehicles. Such system can obtain information in relation with pedestrian behavior (e.g., density of users in pedestrian crossings, pedestrian speed, incidents in pedestrian movement), vehicle behavior or ambient information, among others. One of the main goals is to model the radio wave propagation adequately in order to optimize the distance between devices in an actual network deployment, by means of an in-house generated application which has been tested under real conditions. A real time monitoring application has been implemented in order to provide context-aware interactivity within the scenario under analysis, in relation with pedestrian/vehicle movement as well as environmental information which can be correlated with pedestrian/vehicle behavior. This paper is divided into the following sections: Section 2 describes the simulation procedure for the channel characterization of the considered scenarios and the scenarios description. Section 3 shows simulation results such as bi-dimensional planes of received power, power delay profiles and delay spread, among others.