Scalable Video Coding (SVC) is an extension of H.264/Advanced Video Coding (AVC), which has good characteristics for video transmission over networks. SVC encodes a video into a base layer (BL) and multiple enhancement layers (ELs). With the degree of importance of each layer, in addition to different modulation and coding schemes (MCSs), we can assign different retry attempt limits to each layer to improve quality of experience (QoE) metrics, such as average playback bitrate and buffering ratio. For example, we can assign a slower MCS and a higher retry limit to the BL, to reduce the loss rate and maintain the playback smoothness; whereas, at the same time, we can also assign faster MCSs and lower retry limits to each of the ELs, to reduce the buffering ratio. In this paper, we present a QoE-based link adaptation (QLA) scheme for H.264/SVC video streaming over IEEE 802.11 b/g wireless LANs. We then present a multicast extension of the QLA scheme, multicast QLA (MQLA). We implemented our QLA and MQLA schemes on a Linux-based Wi-Fi protocol driver, mac80211, and built a testbed to conduct our experiments. Experiment results show that both our schemes exhibit an improved QoE performance over the default link adaptation scheme provided by the Linux wireless driver, minstrel.

In-station Wi-Fi AP deployment provides opportunistic Wi-Fi access in underground Mass Rapid Transit (MRT) system. But such vehicular network faces the obstacle of limited connection time from the MS on the train to the BS at the station. Therefore, maximizing the throughput during the tens of second intervals becomes crucial to overcome such hindrance. To achieve the goal, we propose Accelerometer-Assisted Rate Adaptation (AARA) to divide the motion of the train into four phases; each adopts a specific rate adaptation mechanism. The experiments show that the average throughput of AARA outperforms that of the conventional scheme.