| Summary: | 碩士 === 國立清華大學 === 資訊系統與應用研究所 === 94 === File sharing is a basic and popular operation of most applications. Recent years, people have study file sharing issues from wired network to wireless Mobile Ad Hoc networks (MANETs). In which, users can construct the network by them self in an infrastructure-less, any time, any where manner. However, it is not easy to finish a reliable file transmission under such inefficient wireless network condition that have high packet loss rate. We focus on the study of reliable file broadcasting and survey several topics about how to improve the performance of reliable broadcasting, finally we find that people almost solve this problem by designing routing protocols or enhanced MAC-layer, Transport-layer functionality. We think the basic solution to finish reliable file broadcasting is to use control messages like Acknowledge (ACK) or Negative Acknowledge (NACK). In this thesis, we study the effects of NACK packets on reliable file broadcasting in MANETs. We set up seven approaches to use NACK packets: Two are aim at increase the NACK validity (S1, S2), one is aim at reducing packets number in the network (S3), three are aim at reducing the requested packets (S4, R1, R2), and last one is aim at reducing the numbers of NACK packets (R3). The simulations show that each approach has its own special effects on reliable file broadcasting, and different combinations of above seven approaches also have diverse performance results. The bandwidth consumption is not related to average finish time so closely as our imagination before simulation results carries out.
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