(b)
Message format The format of the messages exchanged between the ground and the aircraft is as follows (in the transmission order):
Start of heading (1 character)
Mode (1 character)
Address (7 characters)
Technical acknowledgement (1 character)
Label (2 characters)
Uplink block identifier (1 character)
Downlink block identifier (1 character)
Start of text (1 character)
Text (220 characters max)
Suffix (1 character)
Block check sequence (BCS) (2 characters)
BCS suffix (1 character)
- Start of heading:
indicates the start of data transmission.
-Mode: enables selection of a ground station or a specific group of ground stations for communication with the aircraft.
-Address: contains the identification of the aircraft which transmits or receives the message.
-Technical acknowledgement: acknowledgement (either positive or negative) related to the last message received.
-Label: identifies a specific type of message.
-Uplink block identifier:
R 1EFF : 106-149, 151-156, 159-199, 201-299, 1 46-21-00Page 43 1301-399, 401-499, 1Aug 01/05 1 1 1CES 1 only appears in the messages transmitted by the ground. Enables the aircraft to detect duplicated ground messages (aircraft-to-ground messages may have a downlink block identifier to enable detection of duplicated aircraft messages on the ground).
-Downlink block identifier: only appears in the message transmitted by the aircraft. Enables the ground to detect duplicated messages.
-Start of text: indicates the start of useful data transmission.
-Text: useful data. Only one part of the ISO 5 characters can be transmitted in this field.
-Suffix: indicates the end of useful data transmission.
-Block check sequence: result of a computation made before transmission on the previous bit set. At reception, the same computation is made and the two results are compared. If they are identical, the transmission is correct.
R 1EFF : 106-149, 151-156, 159-199, 201-299, 1 46-21-00Page 44 1301-399, 401-499, 1Aug 01/05 1 1 1CES 1 **ON A/C 151-158, 201-209,
Post SB 46-1009 For A/C 151-152,201-203,
D. Interface with the ground network
(1) Ground network architecture The airline can exchange data with its aircraft through a ground network which is managed by the following world service providers:
SITA-EUROPE ARINC-EUROPE DEPV-BRAZIL ARINC-South America SITA-USA ARINC-USA AIR CANADA AEROTHAI in Thailand SITA- PACIFIC AVICOM-JAPAN ARINC-KOREA ADDC-CHINA
In this ground network, each service provider is responsible for its
own network.
The networks are interconnected, therefore the data is transferred
over any network.
The aircraft is in liaison with the network through the VHF.
On the ground, each service provider works on a special frequency:
-----------------------------------------------DSP FREQUENCY -----------------------------------------------
SITA EUROPE 131,725 MHz
SITA PACIFIC 131,550 MHz
AVICOM JAPAN 131,450 MHz
ARINC USA 131,550 MHz
AIR CANADA 131.475 MHz
SITA USA 136.850 MHz
ARINC EUROPE 136.925 MHz
ARINC SOUTH AMERICA 131.550 MHZ
ARINC KOREA 131.725 MHz
DEPV BRAZIL 131.550 MHz
AEROTHAI THAILAND 131.450 MHz
ADCC CHINA 131.450 MHz
1EFF : 151-158, 201-209, 1 46-21-00Page 45 1 1 Aug 01/04R 1 1 1CES 1
(2) Data exchange between aircraft and ground network R (Ref. Fig. 011)
(a)
Data coding The signal transmitted by the ATSU to the VHF 3 is modulated with the VHF radio signal and then, sent to the ground. Conversely, the signal transmitted by the VHF 3 to the ATSU is obtained after demodulation of the radio signal from the ground. The transmitted data are characters from the ISO alphabet No.5 except the block check sequence field at the end of transmission.
(b)
Message format The format of the messages exchanged between the ground and the aircraft is as follows (in the transmission order):
Start of heading (1 character) Mode (1 character) Address (7 characters) Technical acknowledgement (1 character) Label (2 characters) Uplink block identifier (1 character) Downlink block identifier (1 character) Start of text (1 character) Text (220 characters max) Suffix (1 character) Block check sequence (BCS) (2 characters) BCS suffix (1 character)
-Start of heading: indicates the start of data transmission.
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