Research And Implementation On QoS Of VoIP System In Broadband Wireless MAN

With the rapid development of broadband wireless network technology, the problem of bandwidth is not any longer the choke point. Thereby, the background pushes the development trend of various services over the broadband wireless network towards real-time. As the representative real-time IP service, VoIP (Voice over IP) technology has gained extensive recognition and made quiet great progress. IEEE standard 802.16, a sort of wireless metropolitan area networks (MAN) technology, can provide broadband wireless access for fixed, portable, and mobile devices. Network based-on IEEE standard 802.16 will hold more and more quotient in the future of broadband wireless network. However, there are a good many of difficult subjects and challenges waiting for solution in VoIP system based-on broadband wireless network. For instance, complication and low expansibility with traditional H.323, lack of effective mechanism to assure the quality of service. IEEE standard 802.16 has already defined the message and method of prearranged bandwidth, but do not give the concretely realized scheme. To solve these challenges, the research work mainly focus on the realized schemes of VoIP, common scheduling strategies, mechanisms of prearranged bandwidth in IEEE standard 802.16. On a base of comparing the realized scheme between traditional H.323 and SIP, it is confirmed that the scheme of VoIP based-on SIP will become mainstream. Taking the quality of voice service as a principle, considering the character of SIP flow fully, combining the models of quality of service in existence, integrating the theory of prearranged bandwidth in IEEE 802.16, the thesis classifies and schedules various service flows in order to ensure the quality of voice service. First of all, on the basis of analyzing the foreground of VoIP service and currently popular VoIP token protocol, confirming the status of SIP in VoIP service, expatiating on the hierarchy and network system of VoIP system based-on SIP especially, the thesis analyzes the SIP flow in detailed and proposes a SIP track technology to differentiate voice service from other services in the VoIP system based-on SIP. Secondly, the thesis adopts differentiated model with good expansibility by analyzing several kinds of service models of Quality of Service deeply. At the same time, a priority-transmission scheduling algorithm for assuring voice service was proposed through analyzing the relative scheduling mechanism in the differentiated model. Thirdly, the thesis adopts GPSS mechanism and proposes a realized scheme by combining with the quality of service mechanism of IEEE standard 802.16. Finally, the thesis summarizes the content of former parts and gives a solution of VoIP system in wireless metropolitan area networks based-on IEEE standard to assure the quality of service on the whole. The results indicate that the resolution is reasonable, viable and applicable and promotes the research on the key technology, Quality of Service, in VoIP system. The methodology in the thesis can also be used in VoIP system based-on other networks. Partial content of the solution has already been applied in the cooperative project between Shangyang technology Inc. and WuHan Hanwang high tech Inc. Investigation and practice indicate that the solution has a good capability of transplantable and can be used in vary application of VoIP.