Performance analysis and enhancements of VoIP service schemes in IEEE 802.16 broadband wireless access system

Abstract

IEEE 802.16 standard, based on the DOCSIS standard for cable network, was designed to provide high data-rate up to 54Mbps for nomadic users, and voice over IP service is expected to be one of the most prominent service in commercial 802.16 network. Even though voice traffic has been served with dedicated channel in circuit-switched fashion traditionally, it is packetized through voice codec to utilize the wireless resources efficiently, and evolves toward IP-based VoIP service. Naturally, analytic method and enhancements for accommodating VoIP users efficiently in 802.16 system are required. In the this dissertation, traffic characteristics are studied in case that enhanced technologies such as header compression, silence suppression, and adaptive modulation and coding are adopted, and analyzed by queuing model. In addition, enhanced UGS scheduling schemes for supporting header compression and silence suppression are proposed and analyzed. VoIP has a problem that the amount of payload header from RTP, UDP and IP is much larger than payload from voice codec. Several header compression schemes have been proposed as a remedy for the inefficiency, and they are strongly required for wireless access system that supports IP-based multimedia services. The 802.16 system has the payload header suppression (PHS) as an option, but PHS has less performance than Robust header compression (ROHC). We propose a convergence sublayer and enhanced UGS scheme for supporting ROHC. Then, the performance of UGS scheme supporting header compression is analyzed. Silence suppression detects silence period and holds off generating VoIP payload. With considering that silence period has about 65% duration during voice call, the amount of voice traffic could be greatly reduced by silence suppression. After silence suppression, VoIP traffic has different characteristic from non-suppressed one. We investigate queuing model for describing changed arrival process and analyze the sy...