| Summary: | 碩士 === 輔仁大學 === 電機工程學系 === 100 === Due to the incremental requirements of multimedia applications transmitted via wireless communications, the transmission fashions of multimedia streamings based on 802.11 mesh networks will become more and more popular. In the standard 802.11 MAC frame, there is a 4-byte CRC-32 checksum attached behind it. Using the CRC checksum, ACK frame, and retransmission mechanism, wireless networks can provide a reliable transmission. However, in most of multimedia streaming environments, the characteristic of real-time transmission does not allow such reliable transmission based on retransmission mechanism. It also implicates that it does not require using CRC-32 checksum in real-time multimedia streaming environments. However, if the checksum mechanism is totally removed from an MAC frame, each forwarding node cannot detect error occurrence of frames during transmission, and still forward the corrupted and other useless frames to the destination. In this proposal, we will investigate a simple and low overhead error detection mechanism for 802.11 mesh networks. Attaching few CRC-32 checking bits behind MAC frames but obtaining high error detection ability. In real-time multimedia streaming environments, each forwarding node only requires using its original hardware architecture, it can detect error occurrence on an MAC frame via a simple shift and calculation. Then it discards the corrupted frame in time without retransmission. Concurrently, a chase mechanism is performed to make that the following nodes can chase other useless frames belonging to the same UDP datagrams, and then discard them early before arriving at the destination.
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