| Wireless LAN is an extension of wired networks in wireless domain. It has been extensively deployed in such pubic or private areas as companies, schools, airports, and apartments, for its advantages as flexible deployment, high throughput, easy maintenance and relatively cheap cost. It also has become an effect way for wireless access. The legacy wireless LAN was designed for data traffic, however with the broadening of bandwidth and the increasing of data rate, multimedia, especially real-time multimedia transmission over WLAN has becoming an urgent need by many people.Since the scarce resources and the time varying characteristic of wireless channel, enabling different classes and quality ensured services over WLAN is a challenging topic. This paper focuses on the QoS improvement of multimedia transmission over WLAN. Firstly, it introduces the general status of current WLAN, its performance, and the existing standards for providing QoS support. Secondly it analyzes the structure of two different medium access mechanisms of IEEE802.11e: EDCA and HCCA. According to the different characteristics and requirements of various kinds of services, this paper focuses on the advantages and the disadvantage of the two mechanisms when applying to these services. Based on these analyses, the author generalizes some existing QoS mechanisms and provides his own viewpoints.The main task of this paper is to analyze the QoS performance of IEEE802.11e when supporting VoIP traffics and H.264 video streams. Generalize the existing QoS mechanisms and derive some viewpoints of the author. In the end, the author verified... |
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