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Unformatted text preview: ) a few octets at a time and passing the data straight through. When the
Repetitions parameter of the ChannelAccess.request is greater than one, the encoder also
needs to save the data somewhere, and remember to use the saved data at the next transmission
opportunity. The next transmission opportunity could be after quite a long delay, especially if using
PLOP-1. TCretrans7 2008Sep09 I.B. + M.A. DE LANDE LONG
SOFTWARE + CONSULTANCY
Options for repeated retransmissions for telecommand Page 11 In older systems, FOP-1 is typically implemented in software but the Synchronization and Channel
Coding part of the TC Encoder is sometimes implemented in hardware. The hardware could be
awkward to upgrade for the change, especially for the addition of a new buffer to hold the frame(s) (or
the CLTU) for the systematic retransmission.
In more recent systems, Synchronization and Channel Coding is more likely to be implemented in
software, or perhaps in firmware / programmable FPGA. The addition of a new buffer is easier in this
case. 3.3.6 Setting the Repetitions parameter
The ChannelAccess.request is part of the service interface provided by the Synchronization and
Channel Coding Sublayer to the user in the next layer above, which is usually the Transfer Sublayer.
One of the procedures in the Transfer Sublayer would set the Repetitions parameter as appropriate,
depending on the type of frame and on its own parameters. The procedure could be FOP-1 or it could
be some other procedure in the Transfer Sublayer. For the purpose of updating the standards
documents, it is simpler not to specify which procedure sets the parameter:
− If it is specified that the Repetitions parameter is set by FOP-1, then FOP-1 would also need a new
directive so that users and/or management could set the optional repetition value. − If it is specified more generally that the Repetitions parameter is set by the Transfer Sublayer, then
it could be a managed parameter of a Virtual Channel, within the Transfer Sublayer. TCretrans7 2008Sep09 I.B. + M.A. DE LANDE LONG
SOFTWARE + CONSULTANCY
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This document was uploaded on 03/06/2014.
- Spring '14