Presenting a call admission control algorithm in SIP server to enhance QoS in vocal traffic over 802.11n networks

Transmitting voice over wireless LAN is a useful cost-effective technique that provides vocal conversation service in broadband wireless networks according to the 802.11 standards. In this service, SIP is responsible to provide sessions. Recent researches show that a call admission control algorithm that controls SIP sessions can guarantee the quality of service parameters in transmitting vocal data. State- of-the-art algorithms, deciding at wireless access-points and altering MAC sub-layer parameters, have high complexity and are not efficient in providing quality of service. Therefore, in this paper, we present a new algorithm that decides on accepting or rejecting new calls in a considerably small time. The Proposed algorithm considers dynamic conditions of the network including channel busy rate and the ratio of real-time traffic of channel and makes no change in MAC sub-layer parameters. Testing the proposed method on a real substrate proves its superiority as compared to the best of recent methods in providing requested level of quality of service in terms of call response time, the average duration of calls, packet loss ratio and the delay of real-time traffic.