Vehicle-to-Pedestrian (V2P) communication is essential to enable a reliable collision avoidance system for vehicles and vulnerable road users (VRUs). In order to develop a reliable communication system accurate channel models are required. However, no dedicated channel model for V2P communication in critical scenarios has been proposed so far. To develop a channel model, we conducted wideband channel sounding measurements considering a typical collision scenario between a vehicle and a pedestrian in line-of-sight (LoS) and non-LoS (NLoS) situations. The wideband measurement data is used to study the characteristics of large-scale or shadow fading, pathloss and diffraction loss. The spatial correlation of shadow fading is examined and different models are proposed. For NLoS scenario, a 3D scenario model is designed to simulate the diffraction at a row of parked vehicles. The diffraction loss due to parked vehicles is analyzed and modeled based on multiple knife-edge diffraction model combined with a two-ray pathloss model. The results show that the proposed diffraction model provides a good match to the measured pathloss.

The radio channel modeling and location system are the focus of many research fields. However, their performance is largely limited by line-of-sight (LOS) and non-line-of-sight (NLOS) conditions. Currently, the most popular LOS/NLOS identification algorithm is based on the channel impulse response (CIR) feature. The decision threshold is applied to identify between LOS and NLOS conditions on this basis. However, the features around the threshold are usually very similar, which leads to low LOS/NLOS accuracy. In this work, the feature extracted from the CIR is used to fit its distribution with the Gaussian mixture function. Then, a soft decision algorithm is used to classify the signal. In the experimental simulations, the algorithm is tested according to the measured data. The results reveal that by choosing different feature combinations, the algorithm effectively improves the accuracy of LOS and NLOS identification.

Thousands of fatalities among pedestrians are caused every year by traffic accidents. Vehicle-to-pedestrian (V2P) communication promises to prevent accidents by enabling collision avoidance application. To develop and test a V2P communications system, accurate knowledge of the propagation channel is essential. However, only limited analysis of V2P channel have been reported in the literature. To fill this gap, the German Aerospace Center conducted an extensive channel sounding measurements campaign in a controlled environment. The measurements were performed at 5.2 GHz with a bandwidth of 120 MHz. In parallel to the channel sounding measurements, performance measurements were carried out using ITS-G5 system at 5.9 GHz and with a bandwidth of 10 MHz. This paper describes the setup and the scenarios for the two measurements. First results on channel evaluation in different scenarios as well as path loss models are presented.

Vehicular ad hoc network (VANET) brings an excellent solution to ensure road safety and transportation efficiency in critical environment like tunnel. Particularly, radio link connectivity of vehicle-to-vehicle (V2V) significantly influences the performance of VANETs. The communication range of the radio systems is a random variable in reality due to the channel fading effect. Therefore, the connectivity model between vehicles in realistic environment is a key for accurate evaluation of system performances. In this paper, we study the V2V connectivity performance in the presence of channel randomness for tunnel environment. Firstly, based on channel measurement campaign, empirical path loss (PL) and small-scale fading channel models are established. Secondly, we study the influence of large-scale fading parameters on V2V connectivity. Thirdly, based on real small-scale fading characteristics, we derive the V2V connectivity probability between any two vehicles under Nakagami fading channel for one-dimensional VANET, and give the closed-form of V2V connectivity probability. Finally, we study the influences of various parameters (i.e., Nakagami fading factor, vehicle density, and neighbor order) on V2V connectivity performance. Results show that with the Nakagami fading shape factor increases, the connectivity probability increases. The shadowing fading can improve connectivity in the VANET; the path loss exponent, transmission distance, and signal-to-noise ratio (SNR) threshold have a negative impact on connectivity probability. The transmit power, vehicle density, and path loss threshold value have a positive impact on connectivity.

Vehicle‐to‐vulnerable‐road‐user (V2VRU) communications have the ability to provide of awareness to both vehicles and vulnerable road users to prevent accidents. An accurate V2VRU channel model in critical accident scenarios is essential to develop a reliable communications system. Therefore, extensive wideband single‐input and single‐output channel measurement campaigns at 5.2 GHz were carried out in open‐field and urban environments. Accident prone scenarios between a vehicle and a cyclist as well as between a vehicle and a pedestrian are considered. In this study, locations of the scatterers in the propagation environment are estimated. The authors propose a method to extract specular multipath components (MPCs) from the estimated time‐variant channel impulse response based on the density of neighbouring MPCs. The specular MPCs are then tracked using a novel tracking algorithm based on the multipath component distance approach. Each path is then related to a physical scatterer in the propagation environment by employing a joint delay‐Doppler estimation. According to the results, single and double bounce reflections from buildings and parked vehicles are identified in line‐of‐sight (LoS) situation. In non‐LoS(NLoS) situation, scattering from nearby trees as well as reflections from traffic signs and lampposts beneath the trees canopy are identified.

The impulse response of the radio channel can typically be decomposed into a specular part and diffuse part. Neglecting the diffuse multipath components (DMC) in the channel model may result in underestimating the received power and the channel capacity. Therefore, it is important to analyze the power contribution of the DMC. This work presents an analysis of the fractional DMC power. A wideband channel measurement campaign was conducted at 5.2 GHz. The Kalman enhanced super resolution tracking (KEST) algorithm is used to estimate the parameters of the specular multipath components (SMC). The results show that the value of the fractional DMC power depends on the shadowing condition. While the DMC contributes as low as 5 % in line-of-sight (LoS) situation prior to the collision, it varies between 15 % and 40 % in obstructed-LoS (OLoS), and it can reach up to 90 % in non-LoS (NLoS) situation.