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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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channels and the T channel mode of the transmitter has higher
priority than its R channel mode, the assignment of reservations
on the T channel will affect the R channel transmissions.
The reservations are assigned on the T channel in such a way
that most of the time there is at least one R channel burst
every eight seconds from each AES logged on to the GES
assigning reservations. The burst length and burst interval are
not specified in the AMSS SARPs; they are implementation
dependent.
at both the GES and the AES as. well as coding and decoding
delays. The value for the earliest starting time is implementation
dependent and is computed according to the fornula
given below:
Minimum delay to start of rekrvation = P channel unit
delay + GES processing delay + P channel queuing
delay + R-slot duration + 0.2 set(*) + propagation
delay + AES processing delay.
* 0.2 seconds is the R/l' channel switching time.
A system implementor has obtained the typical values shown
in Table A-10 for some of the components. A typical value for
GES processing delay is in the order of 200 msec.
6.4.3.9 The GES, upon receipt of either a log-on to
another GES or log-off information about an AES which was
logged on to ir, may discard the reservations assigned to the
AES, making the slots available for assignment to its other
logged on AESs.
6.5 Sub-band C channel
to-aircraft and
from-aircraft protocol
6.4.3.7 Qpical values for the length of an individual The sub-band C channel protocol defined in AMSS SARPs
burst are as follows: contained in Annex 10, Volume III, Part I, Chapter 4, 4.6
specifies direct link service (DLS) for signalling SUs. The suba)
18 SUs for a T channel operating at 600 bits/$; band C channel carries signalling for circuit-mode services to
set-up, maintain or release the C channel.
b) 17 SUs for a T channel operating at 1 200 bitds;
c) 3 1 SUs for a T channel operating at 2 400 bitds; and
d) 31 SUs for a T channel operating at 10 500 bitsls.
Qpical values for the burst interval are as ~follows:
a) 16 frames for a T channel operating at 600 bitsls;
7. SATELLITE SUBNETWORK
LAYER
. ,
7.1 General provisions
b) 8 frames for a T channel operating at 1 200 bits/s:
7.1 . I ARCHITECTURE
c) 4 frames for a T channel operating at 2 400 bitds; and
To facilitate the development of interoperability specifications,
d) 1 frame for a T channel operating at 10 500 bitsls. .the subnetwork layer has been divided into functional areas.
This functional division is not intended to preclude implemen-
6.4.3.8 The earliest starting time thst a reservation can tations that aggregate functions in other ways, so long as the
be made by the GES must be such that the AES can receive airborne and ground implementations of the subnetwork layer
the reservation in time to transmit at the start of the assigned each behaves (to an external observer) as if it conformed with
reservation. This time takes into account the processing time the provisions of this section.
Attuchment A to Part I Annex 10 - Aerunauh'cal Telecommunications
Each SSNDPX function contains one or more SSNDPX
entities. Each entity communicates with the peer SSNDPX
entity using the SSNDP.
Each SNAc function contains one or more IS0 8208 DCE
entities. Each IS0 8208 DCE entity communicates with the
peer IS0 8208 data terminal equipment (DTE) entity in the
attached aeronautical telecommunication network (ATN) router
using the IS0 8208 protocol.
7.1.1.3 CN function
Each CN function contains one CN entity. This entity sends
CN event messages to the attached Am routers through the
IS0 8208 DCEs.
7.1.1.4 IW function
Each IW function contains one IW entity. The TW function
perForms the necessary harmonization between the SSND,
SNAc and CN functions. It forwards IS0 8208 packets
between the IS0 8208 DCE and SSNDPX entities. It also
forwards CN event messages to the IS0 8208 DCE entity.
7.1.2 BACKGROUNFDOR THE USE OF
IS0 8208 AND THE ASSOCIATED
SUBNETWORK DEPENDENT PROTOCOL
In the satellite subnetwork, data may be received out-ofsequence
or duplicated. The subnetwork dependent convergence
function (SNDCF) in the ATN router which uses the
services provided by the satellite subnetwork assumes an
underlying connection-mode service which provides sequenced
delivery of data. The SNDCF does not perfom any emr
recovery function to handle-data duplication and data received
out-of-sequence. Therefore, it requires a reliable connectionmode
service which is provided by the IS0 8208 and SSND
protocols. Furthermore, for the satellite subnetwork, it is more
 
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