Proactive QoS Enhancement Technique for Efficient VoIP Performance over Wireless LAN and Cognitive Radio Network

——VoIP over Wireless LANs is greatly affected by path-loss, RF interference and other sources of signal attenuation in addition to network congestion. The primary factors involved in effective real-time communication, namely delay and loss, must be within certain controlled limits in such a scenario. Wireless LAN Access Points must, therefore, act in tune with the codecs to ensure high quality of the ongoing VoIP sessions. Further deployment of VoIP in opportunistic communication medium like cognitive radio network requires thorough analysis of the factors involved in design and implementation of such networks along with modifications in VoIP parameters. In this paper, the various codec parameters are analyzed with respect to wireless LAN access points. Thereafter, an optimization algorithm is developed based on proactive strategy to keep loss and latency within tolerable limits. The proposed algorithm is hence implemented in the SIP enabled test-bed to provide optimum Voice over IP (VoIP) performance. The proactive strategy is further applied to study VoIP performance over cognitive radio networks. A simulation model is developed for VoIP transmission in cognitive radio networks with two scenarios where the primary and the secondary user involve in VoIP transmission respectively. For each scenario, extensive analysis of both VoIP and CRN parameters is performed and an algorithm is proposed based on codecs and active queues to ensure high throughput of VoIP traffic with enhanced QoS. Results verify significant performance improvement in VoIP call quality under both wireless LAN and cognitive radio network environment. Simulation and measured results have also been included. Index Terms——Voice over IP, Wireless LAN, Cognitive Radio Network, Access Point, Codec, Active Queue Management