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333 setting fop 1 timer if the option for systematic

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Unformatted text preview: al Channel multiplexing, this issue is unimportant. 3.3.3 Setting FOP-1 timer If the option for systematic retransmission is in the Synchronization and Channel Coding Sublayer, then it could be more difficult to set a correct value for the FOP-1 timer, because the delays in the system below FOP-1 could become more unpredictable. This depends on the increased difficulty in predicting delays caused by other Virtual Channels and therefore is similar to the previous item (section 3.3.2). 3.3.4 Multiple frames in a CLTU The change to the ChannelAccess.request primitive looks simple, but it is more complicated when there is more than one frame in a CLTU. In general, a CLTU could carry a mixture of AD and BD frames, and it could carry frames for more that one Virtual Channel. This would need to be restricted when the “Repetitions” parameter is greater than 1, and this would need to be explained in the changes to the standards. For simplicity, it would therefore be helpful to include a general restriction on the use of the optional repetition parameter. So, for ChannelAccess.request (Frames, Repetitions) when Repetitions is greater than 1, then Frames must consist of a single frame. The purpose of the systematic retransmission is to improve the probability that a frame will be accepted at the receiving end. Multiple frames increase the length of the CLTU, which in turn increases the probability that the CLTU will be rejected. Therefore, this restriction reinforces the aim of the systematic retransmissions. (See also section 4.2.1 below.) 3.3.5 Buffering the frame or CLTU If the option for systematic retransmission is in the Synchronization and Channel Coding Sublayer, then some kind of extra buffer is needed in the sublayer, to hold the frame (or CLTU) that is being systematically retransmitted. For a TC Encoder which is implemented so that the lower levels "pull" the next frame when the link is ready, the Synchronization and Channel Coding part of the TC Encoder may be taking the frame(s...
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