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时间:2010-07-20 23:38来源:蓝天飞行翻译 作者:admin
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9.3.1 AES TABLE MANAGEMENT
9.3.1.1 Two sets of information are required to be
maintained by the AES. These sets of information are given in
the AMSS SARPs in the form of tables, namely the system
table and the log-on confirm table. The specifics of storing this
information in the AES are not regulated by the AMSS
SARPs, they are implementation dependent.
9.3.1.2 The information listed under "system table" is
provided by the GES. This information contains the necessary
search frequencies to enable the AES to select a satellite, a
beam, and a GES in order to carry out the log-on procedure.
Thus, it is mandatory that this information be current in the
AES prior to logging on. The currency of the system table
information is maintained at the AES by monitoring the
system table broadcast sequences transmitted by the GES as
stated in Annex 10, Volume IU, Part I. Chapter 4. 4.9.3.2.3.1.
9.3.2 AES LOG STATUS MANAGEMENT
9.3.2.1 Satellite, beam and GES selections
9.3.2.1.1 Depending on the geographical location of the
aircraft, the AES may have more than one option for the
selection of a satellite, beam, and GES combination. The
AMSS SARPs provide the flexibility of allowing the AES
management to select the most desirable combination at a
given time. The only requirement imposed on the selection is
the AES capability of receiving an adequate signal on the
selected GES P,,, channel.
9.3.2.1.2 The information used by the AES management
in making its selection is contained in the AES system table.
A GES is uniquely identified by the frequency of its P,,
channel transmitted within a specific beam in the service area
of a given satellite. A satellite is uniquely identified by one or
more sets of satellite/beam-identifying P, channel
frequencies. Each set contains at least two frequencies and is
associated with the ID of the beam within which the associated
P channels are transmitted. If the satellite identification
is made via the global beam (beam ID*), the AES management
may further attempt to select a spot beam, if any exist.
For a satellite service area with spot beam only, the satellite
identification will be made via a spot beam, thus the satellite
and the spot beam selections are made concurrently.
9.3.2.2.1 Log-on initiation. As prescribed by the AES
management AMSS SARPs, the log-on procedure could be
initiated by the receipt of a log-on command. The log-on
command could specify the GES and/or the satellite to be
selected to log on. These AMSS SARPs specify neither the
source nor the format of such command. The source could be
external to the AES relaying the command to the AES
management on a specific interface. The format is implementation
dependent.
9.3.2.2.2 Distress indication. The AES management
AMSS SARPs provide for a capability for the AES to indicate,
at log-on, a distress condition to the GES management. In
order to indicate such a condition, the AES management sets
the "Q number of application" field to 15 in the log-on request
SU. In such a case, the AES would expect the GES not to
reject the log-on. However, the GES may elect not to process
any AES message that is not at the distress precedence level.
9.3.2.2.3 Log-on rejection. Several reasons have been
identified for the GES rejection of an AES log-on request. A
list of these reasons is given in Annex. 10, Volume ID,
Appendix 3 to Chapter 4. No specific AES responses corresponding
to the specified rejection reasons have been given in
the AMSS S M s . Such responses are implementation dependent.
However, the AMSS SARPs further classify the rejection
reasons into three categories: permanent unavailability,
temporary unavailability, and invalid parameters. The response
of the AES management to a rejection reason could be defined
in accordance with the category of the rejection reason in the
following manner:
Atrcrchrne~t A to Part I Annex 10 - Aeronautical Telecommunications
permanent unavailability: cease further log-on attempts
to the same GES;
temporary unavailability: re-attempt log-on to the same
GES, only as a least preference;
invalid parameters: re-attempt log-on to the same GES,
only with different parameters.
9.3.2.3 Universal time broadcast
Some applications on the aircraft may need to be synchronized
with the counterpart applications on the ground. The AMSS
SARPs contain recommendations for support of a time
synchronization facility at the AES and the GES. Thus, for
interoperability consideration, a universal time signal unit
(Annex 10, Volume III, Part I, Appendix 2 to Chapter 4,
 
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