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Unformatted text preview: actly determine the amount of
delay described in item (a) above).
188.8.131.52 Operation on a Deep Space Link A smaller value of T1_Initial may be useful for deep space communications with long roundtrip light times. It can be used to force automatic retransmission of the entire Sent_Queue a
specified number of times prior to receipt of any acknowledgement CLCWs. Assuming
Timeout_Type is set to ‘1’ (see 184.108.40.206), FOP-1 will be suspended once the maximum
number of transmissions is made. Its operation will then be resumed to process the
acknowledgement CLCWs. In addition, a small value of T1_Initial can be used to allow the
‘Set V(R)’ Control Command to be sent without having to verify its acceptance via a CLCW
before sending the Type-AD Transfer Frames. In this case once the allowed number of
transmissions of the Set V(R) is made, the user shall be alerted and can then issue an ‘Initiate
AD Service (without CLCW Check)’ Directive.
To improve the efficiency of COP-1 for deep space missions on links with long light time
delays, a systematic retransmission mechanism can optionally be provided outside COP-1.
The systematic retransmission can be used for Type-AD or Type-BC Transfer Frames and
operates in addition to any automatic retransmissions performed by COP-1. For a
description of the systematic retransmissions, see reference . The additional transmission
time used by the systematic retransmissions can be taken into account when calculating the
value for T1_Initial.
1 The systematic retransmission is outside FOP-1 and has no effect on FOP-1 behavior
specified in the state table (see 5.3) nor on FOP-1 variables such as the State (see
5.1.2) or the Transmission_Count (see 220.127.116.11). The FOP-1 variables have no effect
on the systematic retransmission mechanism. 2 At the receiving end, if FARM-1 receives a duplicate Type-AD Transfer Frame, as a
result of FOP-1 automatic retransmission or as a result of the systematic
retransmission, then FARM-1 rejects the Transfer Frame. CCSDS 232.1-B-2 Page 5-6 September 2010 RECOMMENDED STANDA...
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This document was uploaded on 03/06/2014.
- Spring '14