Two different ways to implement the systematic

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Unformatted text preview: specification? Two different ways to implement the systematic retransmission are considered here: − by making changes to the handling of the Sent_Queue (see section 3.2.1) − by using the AD_Accept and BC_Accept events from the Lower Procedures (see section 3.2.2) If either of these two is selected, then there will also be a need for a new FOP-1 parameter (see section 3.2.3). 3.2.1 Systematic retransmission using the Sent_Queue A systematic retransmission with a “cycle” pattern: ABCD ABCD ABCD ABCD … could be implemented for type-AD frames using the Sent_Queue. As there is never more than one type-BC frame on the Sent_Queue, the retransmission pattern for type-BC frames can only be AAAA… Currently, the Sent_Queue has a To_Be_Retransmitted_Flag for each frame on the queue, which is used for the FOP-1 automatic retransmissions. This flag could be replaced or expanded by a new To_Be_Retransmitted_Count for each frame on the queue, to control the systematic retransmissions. This option appears to be more complicated than the one described in section 3.2.2. Also, it does not add the capability for the hammer pattern of retransmissions discussed in section 1.3. 3.2.2 Systematic retransmission using AD_Accept and BC_Accept events A systematic retransmission with a “hammer” pattern: AAAA BBBB CCCC DDDD … could be implemented for type-AD frames using the AD_Accept event. Similarly, the BC_Accept event could be used for type-BC frames. In the current FOP-1, when FOP-1 passes a type-AD frame to the Lower Procedures it also sets the AD_Out_Flag to “Not Ready”. In this option, a count would be added at this point: when the next ADAccept event occurs, the same frame is passed to the Lower Procedures again and the count incremented. This loop continues until the desired number of systematic transmissions is reached or until some other FOP-1 event causes a reset of the count. The main part of this option can be specified by making changes to the FOP-1 actions “Look for FDU” (for type-AD fra...
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This document was uploaded on 03/06/2014.

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