Playback interruption probability analysis for roadside-to-vehicle media streaming

In this paper, we propose a novel analytical framework for Roadside-to-Vehicle (R2V) media streaming to investigate the interruption probability when playback is performed at a vehicle. The results from such analysis can be used to design an R2V media streaming system with minimum interruption probability. We first introduce a general time-dependent queue model G(t)/G/1 to describe the playout buffer at the vehicle. This model characterizes the dynamic wireless channel conditions in a vehicular environment with time-varying packet arrival intervals. Based on the statistically monotonic behavior of the channel rates as the vehicle moves towards and away from a roadside Access Point (AP), we are able to derive the upper and lower bounds of the interruption probability through a time-dependent queuing analysis with diffusion approximation when the startup state is given. The parameters of startup state include startup delay and the number of cached packets in the playout buffer before playback. We divide the period during which the vehicle is guaranteed with low playback interruption probability into small time intervals. This way, the analysis of the G(t)/G/1 system can be decomposed into a series of transient analysis of stationary G/G/1 systems in a sequential fashion. For each stationary G/G/1 system, diffusion approximation with specified initial conditions is applied to obtain the transient queue length and the interruption probability of the playback. This scheme can be easily implemented since it only requires limited statistical information about fading channel and the playback statistics, such as mean and variance of the rate. The proposed analytical framework has been validated to show accurate characterization of the R2V media streaming system with extensive simulations.