| Summary: | 碩士 === 逢甲大學 === 資訊工程所 === 95 === The integration of Mobile IP standard and VoIP functions makes the Mobile Voice over IP (Mobile VoIP) service feasible. In Mobile VoIP applications, the mobile users can dynamically move around different networks, and thus result in handoffs. Handoff events will interrupt the communication, and thus introduce packet lost temporarily. Specially, the quality of service (QoS) with communications will be significantly affected. As a consequence, it is very critical to improving the communication QoS caused by the handoff. In this thesis, we propose a packet recovery mechanism against handoff issue, and analyze its hardware requirements on user’s, mobile node, for providing the reference of performance improvements and designing considerations. We first integrate Mobile IP standard with SIP-based VoIP service to formulate our experimental platform. In order to avoid packet loss and thus improve the communication QoS, we propose a two-buffer packet retransmission recovery scheme. Furthermore, for realizing the effects of handoff time on backup buffer overhead, several realistic experiments with various wireless parameters, such as different access point signaling strengths, different traffic loads, and different advertisement frequencies, were conducted. Experimental results show that, with our packet recovery scheme, the size of extra designated backup buffer of mobile node in general ranges from 7 to 10 Kilo bytes. We thus conclude that our proposed two-buffer recovery scheme is practical for current Mobile VoIP services.
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