Abstract-Vehicular communication is characterized by a dynamic environment, high mobility, and comparatively low antenna heights on the communicating entities (vehicles and roadside units). These characteristics make the vehicular propagation and channel modeling particularly challenging. In this survey paper, we classify and describe the most relevant vehicular propagation and channel models, with a particular focus on the usability of the models for the evaluation of protocols and applications. We first classify the models based on the propagation mechanisms they employ and their implementation approach. We also classify the models based on the channel properties they implement, where we pay special attention to the usability of the models, including the complexity of implementation, scalability, and the input requirements (e.g., geographical data input). We also discuss the less-explored aspects in the vehicular channel modeling, including modeling specific environments (e.g., tunnels, overpasses, parking lots) and types of communicating vehicles (e.g., scooters, public transportation vehicles). We conclude the paper by identifying the under-researched aspects of the vehicular propagation and channel modeling that require further modeling and measurement studies.

Red, green, and blue (RGB) light-emitting diodes (LEDs) are widely used in everyday illumination, particularly where color-changing lighting is required. On the other hand, digital cameras with color filter arrays over image sensors have been also extensively integrated in smart devices. Therefore, optical camera communications (OCC) using RGB LEDs and color cameras is a promising candidate for cost-effective parallel visible light communications (VLC). In this paper, a single RGB LED-based OCC system utilizing a combination of undersampled phase-shift on-off keying (UPSOOK), wavelength-division multiplexing (WDM), and multiple-input-multiple-output (MIMO) techniques is designed, which offers higher space efficiency (3 bits/Hz/LED), long-distance, and nonflickering VLC data transmission. A proof-of-concept test bed is developed to assess the bit-error-rate performance of the proposed OCC system. The experimental results show that the proposed system using a single commercially available RGB LED and a standard 50-frame/s camera is able to achieve a data rate of 150 bits/s over a range of up to 60 m.Index Terms: Optical camera communication (OCC), visible light communications (VLC), non-flickering communication, red, green, and blue (RGB) light-emitting diode (LED), undersampled phase shift on-off keying (UPSOOK), wavelength division multiplexing (WDM), multiple-input-multiple-output (MIMO).

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