| 摘要 |
PURPOSE: An adaptive FEC(Forward Error Correction) algorithm for a mobile wireless network is provided to heighten a reliability and an efficiency by actively changing addition amount of error correcting redundant data according to a propagation state. CONSTITUTION: An adaptive FEC algorithm is divided into three levels. As the level goes up, an amount of error correcting redundant data added to an original transmission data increases. When three packets are consecutively lost during 3*Tr, Lcnt is changed from 0 to 3. At this time, Tr time value is a timeout value required for a data link layer to re-transmit a packet. After a successive FEC level adaptation, an adaptive FEC maintains Lcnt as 3 until a withdrawal timer operates. When the withdrawal timer operates at time S3, the adaptive FEC algorithm changes Lcnt to 2 in order to check whether a channel state has been better. If the adaptive FEC undergoes another packet loss, the adaptive FEC restores Lcnt to 3 and multiplies an increase factor α thereto to increase the withdrawal timer S3 of the level 3. Because the increase factor α is greater than 1, α*S3 becomes greater than S3, maintaining the level 3 for a longer time.
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