Video Quality Over 802.11e with a Multi-Rate 802.11g Physical Layer

摘要

Many homes now have an 802.11 wireless local area network (WLAN) with a high speed internet connection. 802.11e enhanced distributed channel access (EDCA) allows for traffic prioritisation over 802.11 WLANs which can allow for the QoS demands of the increasing number of multimedia applications on the home network to be met. Providing quality of service (QoS) for delay constrained video applications can be especially challenging due to the bursty nature of video streams. Wireless networks, having a time varying channel, can suffer from physical layer rate switching which can cause a sudden drop in channel capacity and therefore a possible increase in congestion. In this paper we investigate how video quality varies as the number of parallel video streams is increased over a multi-rate 802.11e WLAN. Several traffic mapping schemes are compared from two distinct groups: The non-differentiated schemes treat all video packets equally and the differentiated schemes prioritise video packets based on their frame type. When congestion increases, due to an increase in the number of parallel video streams or due to a drop in physical layer rate, it is found that the non-differentiated schemes suffer from a steep drop in quality while the differentiated schemes offer a much gentler decline. While the differentiated schemes offer the best performance during congestion the success of each scheme is greatly affected by the content of the streamed video sequence.