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From-aircraft 11 through 14 150 s
7 through 10 250 s
11.2.4 Ground station networking
11.2.4.1 Recommendation.- HFDL ground station
sub-systems should interconnect tf~rougha common ground
management sub-system.
Note.- This provides a distributed subnerwork, with a
subnenvark point of attachment (SNPA), depending on the
method of implen~entation, which allows for the ntaintenance
oj. virtual circuit connecrions as aircrufi stations transition
between designated operational coverage areas. The
distribution may be multi-regional or world-wide.
11.2.5 Ground station synchronization
Synchronization of HFDL ground station sub-systems shall be
to within *25 ms of UTC. For any station not operating within
+25 ms of UTC, appropriate notification shall be made to all
aircraft and ground station sub-systems to allow for continued
system operation.
11.2.6 Quality of service
11 .2.6.1 RESIDUAPLA CKET ERROR RATE
The undetected error rate for a network user packet which
contains between 1 and 128 octets of user data shall be equal
to or less than I in lo6.
11.2.6.2 SPEED OF SERVICE
Transit and tiansfer delays for network user packets
(128 octets) with priorities defined in Part I, Chapter 4,
Note.- The HFDL protocol is a layered protocol and is
compatible with the open system interconnection (OSI)
relfcrence model. It permits the HFDL to function us an
aeronautical felecommunication network (ATN)-compatible
subnetwork. The details of the protocol are described in the
Manual on Detailed Technical Specifications for the High
Frequency Data Link (HFDL).
11.3.1 Physical layer IU? characteristics
The aircraft and ground stations shall access the physical
medium operating in simplex mode.
11 .3.1.1 FREQUENCBYA NDS
HFDL installations shall be capable of operating at any single
sideband (SSB) carrier (reference) frequency available to the
aeronautical mobile (R) service in the band 2.8 to 22 MHz,
and in compliance with the relevant provisions of the Radio
Regulations.
11.3.1.2 CHANNELS
Channel utilization shall be in conformity with the table of
carrier (reference) frequencies of Appendix S27 to the ITU
Radio Regulations.
The equipment shaH be capable of operating on integral
multiples of 1 kHz.
338A 4/11/99
No. 74
Annex 10 - Aeronautical Telecommunications Volume 111
The sideband used for transmission shall be on the higher side
of its carrier (reference) frequency.
WDL shall employ M-ary phase shift keying (M-PSK) to
modulate the radio frcquency carrier at the assigned frequency.
The symbol rate shall be 1 800 syrnbols per second &I0 parts
per million (i.e. 0.018 symbols per second). The value of M and
the information data rate shall be as specified in Table 11-2.
Table 11-2. Value of M and information data rate
Information data rate
M (bits per second)
2 300 or 600
4 1 200
8 1 800
where the spectral roll-off parameter, b = 0.31, has been
chosen so that the -20 dB points of the signal are at SSB
carrier (reference) + 290 ~k and SSB carrier (reference) +
2 590 Hz and the peak-to-average power ratio of the waveform
is less than 5 dB.
The basic frequency stability of the transmitting function shall
be such that the diffcrence.between the actual carrier of the
PSK transmission and the SSB assigned frequency shall not
exceed:
a) 20 Hz for HFDL aircraft station sub-systems; and
b) 10 Hz for HFDL ground station sub-systems.
Note.- Wherr M equals the value 2, the data rate may be 1 1.3.1.7 RECEIVER STABILITY
300 or 600 bits per second as determined by the channel
coding rate. The vahe of M may change fmm one data The basic frequency stability of the receiving function shall be
transmission to another depending or1 the duta rate selected. such that, with the transmitting function stability specified iu
The chanrtel coding rute is described in the Manual on 1 1.3.1.6, the over-all frequency difference between ground and
Detailed Technical Specifications for the High Frequency Data airborne functions achieved in service does not exceed 70 Hz.
Link (HFDL).
The M-PSK carrier expressed mathematically shall be defined 4 15 a desired to undesired (D/u) signal ratio shall apply for
as : the protection of co-channel assignments for HFDL as follows:
where:
K- 1
a) data versus data;
b) data versus voice; and
N = number of M-PSK symbols in transmitted
C) voice versus data.
physical layer protocol data unit (PPDU)
~ ( t ) = analog waveform or signal at time t
A = peak amplitude
f n = SSB canier (reference) + 1 440 Hz
T = M-PSK symbol period (111 800 s)
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