Honeywell International Inc. RTA-50D Manuale Utente
MAINTENANCE MANUAL
965-1696
(6)
The phase difference or D8PSK symbol between successive phase changes can be equal
to 0, 45, 90, 135, 180, 225, 270, or 315 degrees. Since there are eight possible phase
differences, each phase change (D8PSK symbol) represents three bits of information: 000,
001, 011, 010, 110, 111, 101, or 100.
to 0, 45, 90, 135, 180, 225, 270, or 315 degrees. Since there are eight possible phase
differences, each phase change (D8PSK symbol) represents three bits of information: 000,
001, 011, 010, 110, 111, 101, or 100.
(7)
For example, if the phase changes at a 10.5-kHz rate, the bit transmission rate is equal to 31.5
Kbps. The VDL Mode 2 D8PSK modulator uses the bits in the message, three at a time, to
select the carrier phase change at a rate of 10,500 D8PSK symbols each second. A 10.5-kHz
D8PSK phase modulation rate corresponds to a D8PSK bit transmission rate of 31.5 Kbps.
Kbps. The VDL Mode 2 D8PSK modulator uses the bits in the message, three at a time, to
select the carrier phase change at a rate of 10,500 D8PSK symbols each second. A 10.5-kHz
D8PSK phase modulation rate corresponds to a D8PSK bit transmission rate of 31.5 Kbps.
(8)
The VDL Mode 2 channel access protocol is CSMA modified to let all terminals to have
equal chances to access the channel when multiple terminals have data to transmit. The
ability to optimize the CSMA protocol is included in the VDL Mode 2 channel access protocol
specification.
equal chances to access the channel when multiple terminals have data to transmit. The
ability to optimize the CSMA protocol is included in the VDL Mode 2 channel access protocol
specification.
(9)
As in Mode A, the Mode 2 data link channel selection is controlled by the ATSU/CMU through
the same high-speed ARINC 429 interface used to exchange downlink and uplink AOA or
ATN messages. The ATSU/CMU also dynamically controls the switching between Mode
A and Mode 2 operation subject to available coverage. Since the VDL Mode 2 data rate
and modulation scheme differ from those used in Mode A, separate VHF frequencies and
ground-based VHF equipment must be used to give POA and AOA/ATN service coverage. As a
result, the availability of high-speed AOA service depends on the availability of ground stations.
the same high-speed ARINC 429 interface used to exchange downlink and uplink AOA or
ATN messages. The ATSU/CMU also dynamically controls the switching between Mode
A and Mode 2 operation subject to available coverage. Since the VDL Mode 2 data rate
and modulation scheme differ from those used in Mode A, separate VHF frequencies and
ground-based VHF equipment must be used to give POA and AOA/ATN service coverage. As a
result, the availability of high-speed AOA service depends on the availability of ground stations.
E.
VDL Mode 3 (Subtask 23-20-59-870-016-A01)
(1)
VDL Mode 2 is a data link protocol that has been optimized for efficient delivery of as much
data traffic as possible within a 25-kHz channel assignment and with radio transmitters limited
to 15 watts output power. It requires dedicated 25-kHz channel assignments. However, there
is also a need to increase the number of VHF channels available in the 118 to 137-MHz
band. To provide for additional voice and data channels, the FAA is developing a VHF digital
transmission mode known as VDL Mode 3.
data traffic as possible within a 25-kHz channel assignment and with radio transmitters limited
to 15 watts output power. It requires dedicated 25-kHz channel assignments. However, there
is also a need to increase the number of VHF channels available in the 118 to 137-MHz
band. To provide for additional voice and data channels, the FAA is developing a VHF digital
transmission mode known as VDL Mode 3.
(2)
The RTA-50D VDR has been designed to support VDL Mode 3 voice and data operation
through a software upgrade. Although VDL Mode 3 functionality is not available in the current
FAA ground stations, a prototype software upgrade to the RTA-50D VDR has proven the
functionality with FAA VDL Mode 3 test ground stations.
through a software upgrade. Although VDL Mode 3 functionality is not available in the current
FAA ground stations, a prototype software upgrade to the RTA-50D VDR has proven the
functionality with FAA VDL Mode 3 test ground stations.
(3)
VDL Mode 3 takes a 25-kHz frequency assignment and breaks it up into 120-ms frames with
four time slots of 30-ms duration each. Each time slot is a different channel. Each channel
(frequency and time slot) can be assigned for use by a different ATC sector. The selection of
which VDL Mode 3 frequency and time slot to use is initially performed by the Pilot using a
radio control panel in the same way 25-kHz or 8.33-kHz channel selection is now performed.
Frequency division into time slots (channels) and the assigned use of the channels (slots) to
different sectors is called TDMA. The slots can be used to transmit packets of digitized voice or
data sized to fit in the appropriate time slot.
four time slots of 30-ms duration each. Each time slot is a different channel. Each channel
(frequency and time slot) can be assigned for use by a different ATC sector. The selection of
which VDL Mode 3 frequency and time slot to use is initially performed by the Pilot using a
radio control panel in the same way 25-kHz or 8.33-kHz channel selection is now performed.
Frequency division into time slots (channels) and the assigned use of the channels (slots) to
different sectors is called TDMA. The slots can be used to transmit packets of digitized voice or
data sized to fit in the appropriate time slot.
(4)
VDL Mode 3 uses TDMA to allow access to multiple voice and data users on the same 25-kHz
frequency assignment. VDL Mode 3 ground stations can be configured to support different
combinations of voice and data services.
frequency assignment. VDL Mode 3 ground stations can be configured to support different
combinations of voice and data services.
(5)
VDL Mode 3 ground stations can be configured so that each of the four time slots is assigned
to voice traffic only (4V configuration). Slot use can be assigned to a different sector. When an
aircraft enters a sector that has been assigned a particular frequency and time slot (channel),
the Pilot can select the appropriate channel on the radio control panel.
to voice traffic only (4V configuration). Slot use can be assigned to a different sector. When an
aircraft enters a sector that has been assigned a particular frequency and time slot (channel),
the Pilot can select the appropriate channel on the radio control panel.
EFFECTIVITY
ALL
23-20-59
Page 17
1 Mar 2011
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