Development and Performance Study of Sender- Based Loss Recovery Techniques for VoIP systems

Voice over Internet Protocol (VoIP) is a technology that transports voice data packets across packet-switched networks using the Internet Protocol (IP). Losing packets in the network is inevitable, and losing voice packets degrades audio quality. The main goal of quality of service (QoS) is to reduce or eliminate delay and loss of voice packets that travels across a network. Researchers proposed many techniques for improving quality of service (QoS) in the face of packet loss . One of these techniques is sender-based loss-recovery techniques (SBLR), whereby the sender assumes an active role to help the receiver recover lost data to improve QoS when packet loss occurs. In this thesis we developed new threshold/Ppersistent sender-based loss recovery techniques for VoIP network. Three loss threshold categories for improving sender– based loss recovery were proposed which are: Random, Adaptive and Fixed threshold metrics respectively. These categories control the volume of the replicated data based on threshold value. A simulation study was carried out using NS2 simulator to evaluate the techniques performance and its impact on QOS for calls delivered through the network. The proposed categories were tested with both conventional sender-based and the P-Persistence techniques through six performance measures of SBLR techniques namely: MOS, Throughput, Delay, Jitter, Cost of technique, and Power Ratio. The new threshold/P-Persistence redundant based techniques achieved better performance than conventional redundant for low to medium loss rate value (up to 5% loss rate), and with appropriate setting improvement can also be realized up to 7.5% loss rate. Also the new threshold/P-Persistence duplicate based techniques achieved also a better performance than conventional duplicate for medium to high loss rate value (up to 10% loss rate) . In general, the new techniques also achieved better voice quality when compared to the plain technique and a higher throughput than conventional duplicate and redundant techniques.