Abstract
IEEE 802.11e was proposed to provide differentiated transmission guarantee for various types of streams, using a mechanism called EDCA. Existed schemes tried to improve video transmission quality by occupying scheduling opportunities of streams with other types, recognizing the importance of each video packet and perform unequal protection and tuning EDCA parameters according to the environment. However, an important factor – the cache size, which may influence packet loss significantly, is often ignored. In this paper, the impact of cache size on video transmission under standard IEEE 802.11e EDCA and two of its enhancements (named ICM and Lin) are analyzed and evaluated. Simulations were performed under three scenarios using the integrated platform of ns-2 and Evalvid. Results show that: (1) Impact of cache size on video transmission performance mainly depends on the scheme adopted. Specifically, cache size has great impact on EDCA and ICM. And Lin shows its adaptability to cache size. (2) Lin is not always the best scheme, and parameter setting influences its performance significantly. (3) Other environment parameters such as traffic source/destination pair, data rates of best effort and background streams also have their own impact on video transmission performance.
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