Research And Implement On Real-time Fairness Of MAC In IP Mobilephone

With the rapid development of information technology, the demand for network communication increases. People hope to get data, voice and image communication service at any plac and any time. This makes multimedia communication based information network become the world’s focus. The great success of Internet makes the IP (Internet Protocol) network become one of the pillar industries in the future of information networks. IP based package and the mobile communication based WLAN (Wireless Local Area Network) has become the mainstream of the development direction of next-generation communications.As a new wireless communication technology, VoWLAN has been widely used in wireless communication and is a hot subject and the development trend of wireless communications. Especially, the popularity of VoIP technology and the establishment and improvement of wireless LAN standards provides technical support and protection for the full integration of wireless LAN voice. Currently, the main driver of VoWLAN is the incensement of wireless VoIP handsets and the expand of VoWLAN market. However, at the meanwhile of benefit from VoWLAN, we should also know that the real-time business supported by wireless LAN cannot guarantee its quality of service (QoS). VoIP technology itself also exists these problems such as packaging delay, delay jitter, end to end delay and so on. These problems results transmission delay, bandwidth, data security, data packet loss, network congestion, interconnection switch roaming and other issues.in the VoWLAN system. To solve these problems, IEEE Working Group researched and developed the IEEE802.11 protocols to provide QoS to improve the VoWLAN technology.This paper introduces the knowledge and standard about IEEE802.11 wireless LAN firstly. The IEEE802.11MAC access mechanism (DCF and PCF) is analyzed in detail. The working principle of two mechanisms, the method of data access and limits on QoS is analyzed in detail. The performance of IEEE802.11 is compared with IEEE802.11e. The transmission technology on VoIP is researched. The basic theory and related technology of VoIP is introduced and some unresolved issues for VoIP are also analyzed.An active neighbor number and current bandwidth ratio based method is proposed to adjust the contention window for binary exponential backoff process to overcome the problem of fairness. According to the real-time character of polling mechanism, this paper analysis and improves the polling mechanism on the assignment media access to STAs connected to PC in the status of PCF.A token buffer based method is proposed. The basic structure and process of implement is described. The performance is analyzed. The simulation results implement the improvement of original polling mechanism.