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access delay figure is possible provided that the terrestrial
network facilities can provide an equivalent improvement in
performance.
8.8.2 Ground-originated calls. The AES and GES logic
procedures for ground-originated AMS(R)S calls are essentially
identical to those of the prevalent non-safety AMSS
procedures. The expected access delay component that is attributable
to the AMS(R)S subnetwork in the absence of any
significant contending P channel traffic is projected to be six
seconds (95 per cent). (Inclusive of three seconds for GES
C channel demodulator acquisition overhead). A terrestrial
network facility delay component of four to six seconds will
result in an expected end-to-end access delay of 10 to 12
seconds (95 per cent). Improvements in either terrestrial
network or GES demodulator overhead will yield an equivalent
improvement in the end-to-end delay performance.
8.8.3 Projections of AMS(R)S subnework call set-up
delay. The call processing delays in Annex 10, Volume 111,
Part I, Chapter 4, 4.8.4.1 specify only the components of
AMS(R)S call set-up delay attributable to the performance of
AES and GES equipment. These performance parameters,
while not entirely deterministic in nature, are not likely to
exhibit a significant statistical variance. This is because the
parameters are specified as maximum internal processing
delays exclusive of any transmission delays or queuing delays
for link layer service such as that which might be experienced
by a telephony signalling CM-LIDU awaiting P channel transmission.
However, the over-all AMS(R)S subnetwork delay
to establish an air or ground-originated call, which will be
subject to the statistical performance of the link layer, is hkely
to be of interest to system planners. Based on simulation
studies using a traffic model identical to that used to determine
the packet-mode performance requirements in Annex 10,
Volume 111, Chapter 4, 4.7. AMS(R)S subnetwork call set-up
delay performance for air and ground-originated calls is
projected to be as depicted in Table A-I 3 of this guidance
material.
Note.- Each perfomnce parameter is applicable to all
AMS(R)S priorities except for those parameters exp~sseda s
a range of ~~alufeosr highest to lowest priority.
8.9 Subjective voice
quality evaluation
8.9.1 General. The end-to-end performance requirements
that were used to establish a basis for the BT laboratories
voice encoding algorithm have been characterized in terms of
intelligibility and acceptability. Intelligibility has been
measured using the diagnostic rhyme test (DRT) or modified
rhyme test (MRT), and acceptability has been measured using
the diagnostic acceptability measure (DAM) or mean opinion
score (MOS).
8.9.2 Intelligibility. Intelligibility based on DRT or MRT
was demonstrated to be 92 per cent or better under quiet
conditions and 87 per cent or better when subjected to noise
levels of up to 87 dB, referenced to 0.0002 rnicrobar using a
C-weighted curve.
8.9.3 Acceptability, Acceptability based on DAM (or
MOS) was demonstrated to be 58 (3.75 out of 5.0) or better
under quiet conditions and 53 (3.25 out of 5.0) or better when
subjected to noise levels of up to 87 dB, referenced to 0.0002
microbar using C-weighted curve.
Note 1,- 87 dB is the ambient noise level of the military
E4B aircraft, The 87 per cent DRT is based on using a noise
cancelling microphone in an aircraft noise environment and
an intermediate reference system (IRS, CCITT Red Book,
Recommendatiotz P.48, Volume C: 1985) handset in an oflce
or ATC room environment.
Note 2.- These voice qualiry standards are minimum
standards measured at a BER of 1x10".
Annex 10 - Aeronautical Telecommunicatioris Volume III
9. AIRCRAFT EARTH STATION
(AES) MANAGEMENT
9.1 General .
Annex 10, Volume 111, Part I, Chapter 4, 4.9 defines the
minimum set of requirements that the AES management must
meet in order to ensure interoperabiljty. This chapter of the
guidance material describes issues related to the AES
management SARPs.
9.2 AES management interfaces
The AES management is described in the AMSS SARPs as an
entity which interfaces to other AES entities, such as the link
and subnetwork layers. The interfaces are defined in terms of
the information exchanged between the AES management and
these other entities and are shown in Figure A-20 of this
guidance material. No formats of the exchanged information
are specified in the AMSS SARPs. Such formats are
considered to be implementation dependent.
93 AES management functions
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