Sinh các mô hình toán học của cơ chế FL-FECWe use a mathematical model to formulate the condition and analyze the protection ability of the FL-FEC mechanism. We assume that the number of total packets in one FEC block isn, the number of source packets is k, the number of FEC redundant packets is a function of (n−k), i.e., h and the total number of packets of video streaming is N. Because a lost packet can be recovered not only from its FEC block but also from the previous FEC block, we can consider that a source packet has double FEC mechanism protections in the FL-FEC mechanism. We think that the source packets and the redundant FEC packets in one FEC block have different effective packet loss rates because only subset source packets have double FEC mechanism protections in the FL-FEC mechanism. First, we calculate the average packet loss rate for every FEC block. When the packet loss rate (P) in wireless networks is known, we can get the average packet loss rate in one FEC block by wherebmeans the looking forward ratio. Ifbis two, for example, the FL-FEC mechanism looks forward a half of the source packets in the previous FEC block to generate the FEC redundant packets in the FEC block. Ifbis four, for another example, the FL-FEC mechanism looks forward to the quarter of the source packets in the previous FEC block. Pis the average packet loss rate, so product of Pmultiplying (n−k/b) in the numerator means the source packets not being looked forward by the FEC redundant packet in the next FEC block. Becausek/bmeans the number of source packets looked forward by the FEC redundant packet in the next FEC block, product ofPeffective multiplyingk/bin the numerator represents the effective packet loss rate protected by the FEC redundant packets in the next FEC block. Product of Pmultiplyingk/b the numerator represents the source packets in the previous FEC block looked forward by the FEC redundant packets in its FEC block.
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