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where f, is the carrier (reference) frequency. slot synchronization is maintained, each HF data link
modulator shall begin outputting a pre-key segment at the
beginning of a time slot plus or minus 10 milliseconds.
1 1.3.1.14 RECEIVERRE SPONSE TO TRANSIENTS
Recommendation.- The receiving function should
11.3.2.3.1 TDMA STRUCTU~
- .
recover from an instantaneous increase in RF power at the Each TJ3MA frame shall be 32 seconds. Each TDMA frame
anterzn'l terminal of 60 dB within 10 milliseconds. The be divided into thifleen equal duration as fo,lows:
receiving finction should recover from nn instantaneous
decrease in RF power at the antenna terminal of 60 dB within
25 milliseconds. a) the first slot of each TDMA frame shall be reserved for
use by the HFDL ground station sub-system to broadcast
link management data in SPDU packets; and
11.3.2 Physical layer functions b) the remaining slots shall be designated either as uplink
slots, downlink slots reserved for specific HFDL aircraft
station sub-systems, or as downlink random access slots
11.3.2.1 FUNCTIONS for use by all HFDL aircraft station sub-systems on a
contention basis. These TDMA slots shall be assigned
The functions provided by the physical. layer shall include the on a dynamic basis using a combination of reservation,
following: polling and random access assignments.
a) transmitter and receiver control;
b) transmission of data; and
c) reception of data.
The HFDL ground station sub-system shall broadcast a
squitter protocol data unit (SPDU) every 32 seconds on each of
its operating frequencies.
11.3.2.2 TRANSMITTER AND RECEIVER CONTROL Note.- Details on the TDMA frame and slot structures,
pre-key segment, data structures, including the SPDU, are
The HFDL physical layer shall implement the trans- contairted in the Manual on Detailed Technical Specifications
mitter/raceiver switching and frequency tuning as commanded for the High Frequency Data Link (HFDL).
4/11/99
No. 74
Part I Annex 10 - Aeronnutical Telecommunications
1 1.3.2.4 RECEPTIONO F DATA
1 1.3.2.4.1 FREQUENSECARYC H
Each HFDL aircraft station shall automatically search the
assigned frequencies until it detects an operating frequency.
Recommendation.- The number of HFDL MPDUs
received with one or more bit errors should not exceed
5 per cent of the total number of MPDUs received, when
using a 1.8 second interleaver under the conditions shown in
Table 11 -3u.
11.3.3 Link Layer
The HF data Link receiver shall provide the means to detect,
synchronize. demodulate and decode PPDUs modulated
according to the waveform defined in 11.3.1.5, subject to the
following distortion:
a) the 1440 Hz audio carrier offset by plus or minus
. 70 Hz;
b) discrete andlor diffuse multipath distortion with up to
5 ms multipath spread;
C) rnultipath amplitude fading with up to 2 Hz two-sided
RMS Doppler spread and Rayleigh statistics; and
Note.- Details on link layer functiom are contained in the
Manual on Detailed Technical Specifications for the High
Frequency Data Link (HFDL).
The fink layer shall provide control functions for the physical
layer, link management and data service protocols.
1 1.3.3.1 CONTROFLU NCTIONS
The link layer shall pass commands for frequency tuning,
transmitter keying and transmitterireceiver switching to the
physical layer.
d) additive Gaussian and broadband impulsive noise with
varying amplitude and random arrival times.
1 1.3.3.2 LINK MANAGEMENT
Note.- Reference CCJR Report 549-2.
Upon receipt of the preamble segment the receiver shall:
a) detect the beginning of a burst of data;
b) measure and correct the frequency offset between the
transmitter and receiver due to Doppler shift and
transrnittedreceiver frequency offsets;
c) determine the data rate and interleaver settings to use
during data demodulation;
d) achieve M-PSK symbol synchronization; and
The link layer shall manage TDMA slot assignments, log-on
and log-off procedures, ground station and aircraft station
TDMA synchronization, and other functions necessary, taking
into account message priority, for the establishment and
maintenance of communications.
1 1.3.3.3 DATA SERVICE PROTOCOLS
The link layer shall support a reliable link service (RLS)
protocol and a direct link service (DLS) protocol.
The RLS protocol shall be used to exchange acknowledged
user data packets between aircraft and ground peer link layers.
e) train the equalizer.
Each HFDL aircraft station sub-system shall synchronize its
slot timing to that of its corresponding ground station with
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