Abstract
Providing quality-of-service- (QoS-) guaranteed video on demand (VOD) services over wireless access in vehicular environments (WAVEs) is a challenge as WAVE adopts enhanced distributive channel access (EDCA), a contention-based channel access mechanism, for air interface access control. This paper proposes a selective downlink scheduling (SDS) algorithm to enhance the quality of VOD for WAVE networks. According to the importance of video decoding, video packets are categorized into high and low priorities. The categorized packets are put into different queues in roadside units (RSUs) to contend for transmission opportunities. Aiming to improve video playback quality and reduce video playback delay, the proposed SDS algorithm schedules video packets based on their importance, playback deadline, and their real-time parameters of receiving onboard units (OBUs), such as velocity and remaining dwelling time. The effectiveness of SDS algorithm is verified by simulations.
Highlights
Wireless access in vehicular environments (WAVEs) [1] is a generation intelligent transportation technology that aims to improve transportation environments
We have proposed a selective downlink scheduling algorithm, SDS, for wireless access in vehicular environments (WAVEs) networks in order to improve the quality of video on demand (VOD) services
Video packets are marked into high and low priorities before they are fed into WAVE media access control (MAC)
Summary
Wireless access in vehicular environments (WAVEs) [1] is a generation intelligent transportation technology that aims to improve transportation environments. Compressed video streams are able to tolerate small amount of packet loss without degrading the quality of video playback very much, since some packets are less important for video decoding [4] This feature can be used for schedule algorithms to deliver important packets and discard unimportant packets when traffic is heavy, or a wireless channel is unreliable. Inspired by EDF, MFL, and aforementioned video streaming schemes over wireless mechanisms, the SDS algorithm proposed in this paper aims to improve video playback quality and reduce video playback delay in WAVE networks. In the SDS algorithm, video packets destined to different OBUs are coordinately scheduled by their playback deadline This feature can be used to reduce the video playback delay of all OBUs. The proposed mechanism in this paper is not designed for only a specific video codec scheme (such as H.264), but it is applicable to other popular video compression formats, such as H.263, MPEG-2.
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