Vowlan Qos Optimization And Roaming Switching

Recently,with the fast development of VoIP,users want to experience connectivity brought by the wireless,so VoWLAN appears. The low price VoIP technology and the flexible wireless technology are conbined by VoWLAN,it becomes a strong rival with traditional cellular phones and cable VoIP phones. However, in practical applications, there are two major obstacles in VoWLAN:quality of service and roaming switch.Therefore,this paper expands the research following the two aspects as below:To solve the problem of VoWLAN QoS, the paper has analysed QoS of the specific VoWLAN network,studied classical optimum schemes EDCF and AEDCF mechanism for VoWLAN QoS, learnt the strengths and weaknesses of the mechanisms. On this basis, this paper proposes a new algorithm NEDCF which is based on the improvement of the EDCF, NEDCF uses network conflict rate and threshold to divide network state,then makes different network state with different CW and retreated algorithm. At last,there are simulations for NEDCF, simulations show that NEDCF algorithm can improve the delay, packet loss and jitter effectively, thus improving the performance of VoWLAN.To solve the problem of VoWLAN roaming switch,the paper has analysed the VoWLAN roaming process,studied classical optimum schemes 802.11 f, 802.11r, Mobile IP and Mobile SIP mechanism for VoWLAN roaming switch, learnt the strengths and weaknesses of the mechanisms. For the question of long time roaming switch,this paper proposes a improved mechanism FROAM, which combines 802.11r and Mobile SIP,and adds a roaming mode judging server. FROAM can handle subnetwork interconnection roaming and domain roaming respectively. Furthermore, FROAM makes SIP signaling control process ahead of the link switch process. Thus froam can reduce the delay greatly and improve the performance of VoWLAN roaming switch.