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assigns the frequencies for a circuit-mode call from its own
pool. However, lack of channel frequency for a call at the GES
results in the initiation of a channel frequency reassignment
request to a central authority which initially made the preassignment.
The central authority can then make an
assignment of frequency to the GES utilizing the frequencies
heU in a common pool. ,
10.4.3.2 C channel power ~ g e m n r
10.4.3.2.1 The GES calculates the initial EIRP of the C
channel accurding to the value derived from the worst case
link budget.
10.4.3.2.2 The GESs can be assigned power budgets
consistent with performance requirements of the channels
operating to the satellite. Once this p e r budget is fully
utilized, the GES management rejects further channeldcall
quests until sufficient power has been released to be assigned
to the new requests or until the log-on request LIDU indicates
AES in distress. The C channel power can be controlled for
example in accordance with the following power control
decision table:
for the 21 000 bids, rate 1/2 FEC channel, if the
average number of errors per 2 560 channel bits (before
decoding) is:
gteater than 172: increase EIRP by 2 dB
between 119 and 172: increase EIRP by 1 dB
between 76 and 1 19: leave EIRP unchanged
between 44 and 76: decrease EIRP by 1 dB
less than 44: decrease EIRP by 2 dB.
Yllfoo
No. 75
Annex 10 - Aeronautical Telecommunic&ns Volume lII
Note.- These values curmspond to the input bit ermr rates GESs within all the satellite service areas provided by the
to a a t e In Kterbi decoder as specdfied for the C channel that satellite system provider, as required. The revision number for
pmvide an ourput bit error mte of loJ (nominal) to 1@ (1 dB a system table and spot ham map are unique to each satellite
above nominal), with a margin of 1.5 dB. service area.
10.4.4 GES PRE-EMPIION MANAGEMENT
10.4.4.1 Voice versus voice pre-emption
The purpose of this capability at the GES is to make resources
available for a higher precedence voice call if there are no
additional resources available at the GES and lower
precedence voice calls are being m i & The GES
management, upon receipt of a request from circuit-mode
services for a channel unit for a voice call, checks -if the
precedence of the new request for voice call set-up is higher
than any call already in progress. If the precedence of new call
request is higher than any one call-in-progress, the GES
management then ruthlessly pre-empts the lowest precedence
call in progress to make resources available for the higher
precedence call. If there are more than one call at the lowest
precedence in progress at a given time then it is at the
discretion of the .GES operator to pre-empt a call. One option
could be to pre-empt the call which has been in progress for
the longest time.
10.4.4.2 Data verscrs voice pm-emption
The purpose of this capability at the GES is to make resources
available to set up an additional P channel for higher
precedence data traffic when there are no additional resources
available at the GES to set up an additional P channel, and
lower precedence vdce calls are being serviced and
transmission of ackhtional data traffic on the already
operational P channels would violate the data transfer delay
requirements specified in Annex 10, Volume Ill, Part I,
Chapter 4, 4.7. However, a higher precedence voice call does
not pre-empt an operational P channel to make resources
available for setting up a higher precedence voice call because
doing so will be detlimental to data transmissions from the
AES.
10.4.5 GES SYsTEM BROADCAST
10.4.5.1 System table broadcast
10.4.5.1.1 This facility at the GES allows the GES to
update the system table infonnation and spot beam map
infomtion stored in an AES. The system table and spot beam
map updates are transmitted to AESs as complete or partial
sequences.
10.4.5.1,Z The initial search data in the system table
contains satellite-identifying P,, channel frequencies for all
satellites. Any changes to the system table are made centrally
by the satellite system provider and are disseminated to all
10.4.5.1.3 The complete sequence is transmitted by the
designated GES on the satellite-identifying P, channel and it
comprises all broadcast LIDUs headed by a broadcast index
LTDU. The partial sequence comprises one or more braadcast
LIDUs headed by a broadcast index LIDU. The partial
sequence contains the most recent updates only. The broadcast
index LDU identifies the presence of individual LIDU series
within both the complete and partial sequences. Each GES
　
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