U.S. patent application number 16/261788 was filed with the patent office on 2019-06-06 for method for transmitting prioritized data and a transmitter.
This patent application is currently assigned to Airbus Operations GmbH. The applicant listed for this patent is Airbus Operations GmbH. Invention is credited to Uwe Bartels, Maurice Girod, Maciej Muhleisen, Christoph Petersen, Marcus Venzke.
Application Number | 20190173801 16/261788 |
Document ID | / |
Family ID | 54557278 |
Filed Date | 2019-06-06 |
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United States Patent
Application |
20190173801 |
Kind Code |
A1 |
Bartels; Uwe ; et
al. |
June 6, 2019 |
Method For Transmitting Prioritized Data And A Transmitter
Abstract
Described is a method for transmitting continuously created data
items from an aircraft to a receiver. The data items are of a
plurality of data types and each have a different priority. For
each data type a live LIFO buffer and a main LIFO buffer are
provided. In a regular operation mode continuously created data
items are continuously stored in the main buffers. In a
transmission operation mode continuously created data items are
continuously stored in the live buffers, consecutive data packets
are transmitted and for each data packet the data is selected from
the buffers, wherein data items stored in live buffers are
transmitted before data items stored in main buffers and data items
of higher priorities are transmitted before data items of lower
priorities. Further, a transmitter and an aircraft are described
and claimed.
Inventors: |
Bartels; Uwe; (Hamburg,
DE) ; Venzke; Marcus; (Hamburg, DE) ; Girod;
Maurice; (Hamburg, DE) ; Muhleisen; Maciej;
(Hamburg, DE) ; Petersen; Christoph; (Hamburg,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Airbus Operations GmbH |
Hamburg |
|
DE |
|
|
Assignee: |
Airbus Operations GmbH
Hamburg
DE
|
Family ID: |
54557278 |
Appl. No.: |
16/261788 |
Filed: |
January 30, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15347975 |
Nov 10, 2016 |
10230655 |
|
|
16261788 |
|
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|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 47/28 20130101;
H04L 47/6245 20130101; H04B 7/18506 20130101; H04L 49/9084
20130101; H04L 47/6295 20130101; H04L 47/24 20130101; H04L 69/04
20130101; H04L 47/6275 20130101 |
International
Class: |
H04L 12/863 20060101
H04L012/863; H04L 12/865 20060101 H04L012/865; H04L 12/861 20060101
H04L012/861; H04L 12/841 20060101 H04L012/841; H04L 12/851 20060101
H04L012/851; H04L 29/06 20060101 H04L029/06 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 13, 2015 |
EP |
15194556.5 |
Claims
1. A method for transmitting continuously created data items from
an aircraft to a receiver, wherein the data items are of a
plurality of data types, wherein each of the plurality of data
types is assigned a different priority ranging from a highest
priority to a lowest priority, the method comprising: providing
last-in-first-out buffers for storage of the continuously created
data items, wherein for each data type a separate live buffer and a
separate main buffer are provided and associated with the
respective data type and data items of a specific data type are
only stored in the associated buffers; in a regular operation mode,
continuously storing continuously created data items of the
plurality of data types in the associated main buffers; and in a
transmission operation mode, continuously storing continuously
created data items of the plurality of data types in the associated
live buffers, transmitting consecutive data packets from the
aircraft to a receiver via a data transmission link, each data
packet comprising a header section and a payload section, and
selecting from the buffers, for each data packet, the data to be
transmitted in the payload section, wherein any data item stored in
a live buffer is transmitted before any data item stored in a main
buffer, wherein of the data items stored in one of the live
buffers, any data item of a data type having a higher priority is
transmitted before any data item of a data type having a lower
priority, and wherein of the data items stored in one of the main
buffers, any data item of a data type having a higher priority is
transmitted before any data item of a data type having a lower
priority.
2. The method according to claim 1, wherein a payload section of a
data packet may comprise data items of different data types,
wherein data items are transmitted as records, each record
comprising a header identifying the data type of the data item and
the length of the record.
3. The method according to claim 1, further comprising switching
from the regular operation mode to the transmission operation mode
when a trigger signal is received.
4. The method according to claim 1, wherein for at least one of the
data types data items are stored in frames of a predetermined
length in the buffers.
5. The method according to claim 4, wherein for at least one data
type for which data items are stored in frames of predetermined
size, a plurality of frames is combined and compressed to a single
compressed frame which is stored in the buffers.
6. A transmitter for transmitting continuously created data items
from an aircraft to a receiver, wherein the data items have a
plurality of data types and each data type has a different priority
ranging from a highest priority to a lowest priority, wherein the
transmitter comprises last-in-first-out buffers for storage of the
continuously created data items, wherein for each data type a
separate live buffer and a separate main buffer are provided and
associated with the respective data type and data items of a
specific data type are only storable in the associated buffers,
wherein the transmitter is operable in a regular operation mode and
a transmission operation mode, wherein in the regular operation
mode the transmitter is adapted to continuously store continuously
created data items of the plurality of data types in the associated
main buffers, wherein in the transmission operation mode the
transmitter is adapted to continuously store continuously created
data items of the plurality of data types in the associated live
buffers, transmit consecutive data packets from the aircraft to a
receiver via a data transmission link, each data packet comprising
a header section and a payload section, and select for each data
packet the data to be transmitted in the payload section from the
buffers, wherein any data item stored in a live buffer is
transmitted before any data item stored in a main buffer, wherein
of those data items stored in one of the live buffers, any data
item of a data type having a higher priority is transmitted before
any data item of a data type having a lower priority, and wherein
of those data items stored in one of the main buffers, any data
item of a data type having a higher priority is transmitted before
any data item of a data type having a lower priority.
7. The transmitter according to claim 6, wherein a payload section
of a data packet may comprise data items of different data types,
wherein data items are transmitted as records, each record
comprising a header identifying the data type of the data item and
the length of the record.
8. The transmitter according to claim 6, wherein the transmitter is
adapted to receive a trigger signal and to switch from the regular
operation mode to the transmission operation mode when the trigger
signal has been received.
9. The transmitter according to claim 6, wherein for at least one
of the data types data items are stored in frames of a
predetermined length in the buffers.
10. The transmitter according to claim 6, wherein for at least one
data type for which data items are stored in frames of
predetermined size a plurality of frames can be combined and
compressed to a single compressed frame which is stored in the
buffers.
11. An aircraft comprising a transmitter for transmitting
continuously created data items from an aircraft to a receiver,
wherein the data items have a plurality of data types and each data
type has a different priority ranging from a highest priority to a
lowest priority, wherein the transmitter comprises
last-in-first-out buffers for storage of the continuously created
data items, wherein for each data type a separate live buffer and a
separate main buffer are provided and associated with the
respective data type and data items of a specific data type are
only storable in the associated buffers, wherein the transmitter is
operable in a regular operation mode and a transmission operation
mode, wherein in the regular operation mode the transmitter is
adapted to continuously store continuously created data items of
the plurality of data types in the associated main buffers, wherein
in the transmission operation mode the transmitter is adapted to
continuously store continuously created data items of the plurality
of data types in the associated live buffers, transmit consecutive
data packets from the aircraft to a receiver via a data
transmission link, each data packet comprising a header section and
a payload section, and select for each data packet the data to be
transmitted in the payload section from the buffers, wherein any
data item stored in a live buffer is transmitted before any data
item stored in a main buffer, wherein of those data items stored in
one of the live buffers, any data item of a data type having a
higher priority is transmitted before any data item of a data type
having a lower priority, and wherein of those data items stored in
one of the main buffers, any data item of a data type having a
higher priority is transmitted before any data item of a data type
having a lower priority.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 15/347,975, filed on Nov. 10, 2016, which claims priority from
European Patent Application No. 15194556.5 filed Nov. 13, 2015, the
disclosures of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a method for transmitting
continuously created data items from an aircraft to a receiver, a
transmitter for transmitting continuously created data items from
an aircraft to a receiver and an aircraft comprising such a
transmitter.
BACKGROUND OF THE INVENTION
[0003] Today flight accident investigations largely rely on the
data recorded in the so-called flight recorder. Flight recorders
used onboard commercial aircraft are usually fixed to the aircraft.
Thus, if access to the aircraft itself is difficult, for example,
because the aircraft accident occurred over open water and the
wreckage sunk after the accident, it may be difficult to retrieve
the flight recorder. To overcome this disadvantage, it has been
suggested to transmit at least part of the data stored in the
flight recorder from an aircraft to a receiver, e.g., a ground
station before the accident happens such that at least some
information is readily available well before the flight recorder
has been successfully retrieved.
BRIEF SUMMARY OF THE INVENTION
[0004] In the prior art it has been suggested to continuously
transmit the data stored in the flight recorder from the aircraft
to a ground station. Due to the high cost of satellite data
transmission and the limited bandwidth available, this approach is
not feasible in practice, in particular, as most of the transmitted
data is not required and would be discarded immediately. It has,
therefore, previously been suggested to transmit flight recorder
data only after it has been detected that an accident is likely to
occur. While this approach prevents extensive costs due to
unnecessary data transmission, the bandwidth and the transmission
time available will usually be limited. Thus, a choice has to be
made which kind of the flight recorder data is transmitted from the
aircraft to a ground station.
[0005] It is, therefore, an aspect of the present invention to
provide a method and a transmitter for selectively transmitting
flight recorder data from an aircraft to a receiver before an
aircraft accident takes place that takes into consideration that
various types of data may be transmitted and that the transmission
time and bandwidth are limited.
[0006] In a first aspect the problem is solved by a method for
transmitting continuously created data items from an aircraft to a
receiver. The data items are of a plurality of data types and each
of the plurality of data types is assigned a different priority
ranging from a highest priority to a lowest priority.
Last-in-first-out buffers are provided for storage of the
continuously created data items. For each data type a separate live
buffer and a separate main buffer are provided and associated with
the respective data type. Data items of a specific data type are
only stored in the associated buffers. In a regular operation mode
continuously created data items of the plurality of data types are
continuously stored in the associated main buffers. In a
transmission operation mode [0007] continuously created data items
of the plurality of data types are continuously stored in the
associated live buffers, [0008] consecutive data packets are
transmitted from the aircraft to a receiver via a data transmission
link, each data packet comprising a header section and a payload
section, and [0009] for each data packet the data to be transmitted
in the payload section is selected from the buffers, wherein any
data item stored in a live buffer is transmitted before any data
item stored in a main buffer, wherein of those data items stored in
one of the live buffers, any data item of a data type having a
higher priority is transmitted before any data item of a data type
having a lower priority, and wherein of those data items stored in
one of the main buffers, any data item of a data type having a
higher priority is transmitted before any data item of a data type
having a lower priority.
[0010] In other words, the method according to an aspect of the
present invention transmits continuously created data items of
different data types with different priorities. Within the present
application, the term "continuously" does not necessarily refer to
data items that are created non-intermittently, i.e., there may
even be longer gaps in time between the two consecutive
continuously created data items. The term "continuously" describes
that the data items are created over the entire time of a flight
whenever scheduled or whenever an event occurs that is reflected in
a data item. Continuously created data items have to be seen in
contrast to data items of fixed content, such as, for example, an
identifier of an aircraft.
[0011] A data item may be any kind of grouped information that is
intended for storage in a flight recorder or for transmission with
the method according to an aspect of the present invention. Thus, a
data item in its broadest form is a set of bits of different length
and different content. The length of the bit stream and the content
depends on the data type. Examples of data types are flight data,
air traffic control messages, cockpit voice recordings and cockpit
images. Flight data may comprise, for example, recordings of a
course of an aircraft, an altitude of the aircraft, a roll rate, a
yaw rate and control inputs of pilots. Air traffic control messages
are data messages received by an aircraft and may, for example,
include flight plans, meteorological data or notice to airmen.
Cockpit voice recordings may, for example, include any oral
communication of pilots via radio or any word spoken in the cockpit
of the aircraft. Finally, cockpit images can, for example, be
images captured by a camera mounted in the cockpit of an aircraft.
In an exemplary, preferred embodiment the method is adapted to
transmit data items of the following data types: flight data, air
traffic control messages and cockpit voice recordings.
[0012] Each data type has an assigned priority selected from a
range of priorities ranging from a highest priority to a lowest
priority. For example, if data items of the data types flight data,
air traffic control messages and cockpit voice recordings shall be
transmitted, air traffic control messages data items could be
assigned the highest priority, cockpit voice recordings data items
could be assigned the lowest priority and flight data data items
could be assigned an intermediate priority.
[0013] The method according to an aspect the present invention uses
buffers for temporary storage of data items. The buffers are all
last-in-first-out (LIFO) buffers or stacks. Thus, data items are
arranged in the buffers in the order in which they were stored in
the buffer, i.e., pushed onto the stack. In other words, the data
items are stored in the buffer in a temporal order and it is only
possible to retrieve the data items stored in the buffer in a
temporal order. Thus, if a data item shall be retrieved from the
buffer, the data item stored last is retrieved, than the data item
stored second to last and so on. In other words, whenever a data
item shall be retrieved from the stack, the data item stored last
is pushed first from the stack and reveals the data item stored
second to last and so on.
[0014] For each of the data types that shall be transmitted at
least two separate associated buffers are provided: a live buffer
and a main buffer. For example, if data items of the data types
flight data, air traffic control messages and cockpit voice
recordings shall be transmitted with the method, a live buffer and
a main buffer are provided for flight data, a live buffer and a
main buffer are provided for air traffic control messages and a
live buffer and a main buffer are provided for cockpit voice
recordings. Data items of a specific data type can only be stored
in the associated buffer, e.g., data items of the data type flight
data can only be stored in a flight data main buffer or a flight
data live buffer. As each live buffer and each main buffer is
associated with a data type, each data type is also associated with
one main buffer and one live buffer.
[0015] The method can operate in two different operation modes: a
regular or normal operation mode and a transmission operation mode.
In the regular operation mode the data items that may be
transmitted according to the method are continuously stored in the
associated main buffers. In other words, whenever a new data item
of a data type that shall be transmitted in the transmission
operation mode is created, the data item is stored in the main
buffer associated with the data type of the data item, i.e., pushed
on top of the stack of the main buffer of the respective data type.
No data is transmitted in the regular operation mode.
[0016] When the method switches from the regular operation mode to
a transmission operation mode, continuously created data items are
not stored in the main buffers associated with the respective data
types anymore, but stored in the live buffers associated with the
respective data types. In other words, once the method has switched
to a transmission operation mode, it stores any created data items
in the live buffer associated with the data type of the created
data items, i.e., an air traffic control message data item received
by the method when it operates in the transmission operation mode
is stored in the air traffic control messages live buffer.
[0017] Further, in the transmission operation mode consecutive data
packets are transmitted from the aircraft to a receiver via a data
transmission link. For example, data packets in form of internet
protocol (IP) data packets are transmitted via a transmission link
in form of a satellite communication data connection to a receiver
in form of a ground station. The data packets comprise a header
section and a payload section. The header section may comprise, for
example, an IP header, a user datagram protocol (UDP) header and an
aircraft identifier. In the payload section of the data packet,
selected data from the data items stored in the buffers is
transmitted.
[0018] This data is selected according to the following rules. Any
data item stored in a live buffer is transmitted before a data item
stored in a main buffer. Any data item stored in a live buffer of a
data type having a higher priority is transmitted before a data
item stored in a live buffer having a relatively lower priority.
Finally, any data item stored in one of the main buffers of a data
type having a higher priority is transmitted before a data item
having a relatively lower priority. For example, if data items of
the data types flight data, air traffic control message and cockpit
voice recordings shall be transmitted and flight data has the
highest priority assigned, air traffic control messages an
intermediate priority and cockpit voice recordings the lowest
priority, any air traffic control message item stored in live
buffer is transmitted before any other data item. Next, if no more
air traffic control message data items are stored in the associated
live buffer, any flight data data item stored in a live buffer is
transmitted followed by any cockpit voice recording data item.
Finally, data items stored in the main buffers are transmitted in
the same order. It should be noted that a data item that is
transmitted will be removed from the respective buffer such that
the buffer comprises one data item less than before.
[0019] While data packets are transmitted, new data items may be
created. Such newly created data items are stored in the live
buffers associated with the respective data types. Every time the
method selects data items for the payload section of the next data
packet to be transmitted, it first selects data items from the live
buffers in the order of the priority of the respective associated
data types before selecting data items from main buffers in the
order of the priority of the respective associated data types.
[0020] In the above example, when a new flight data data item is
created while the method operates in transmission operation mode,
this data item is pushed on top of the stack forming the flight
data live buffer. Now when the method selects data items for the
next data packet, the data item stored last in the live buffer is
selected first. In other words, the latest data item of the data
type having the highest priority is always transmitted first.
Afterwards, all other data items of the data type having the
highest priority and received by the method after the method has
switched into transmission operation mode are transmitted. Next,
all data items of the next lower priority received after the method
has switched to transmission operation mode are transmitted in the
opposite temporal order in which they were created. The further
data items then follow in the same manner. Data items stored in the
main buffer, i.e., data items received by the method before the
method has switched to the transmission operation mode are only
transmitted if all data items received after the method has
switched to transmission operation mode have been transmitted.
[0021] Thus, the use of LIFO buffers and the selection of data
items in the order from live buffers to main buffers and in the
order of the priority of the data type associated with the buffers
advantageously ensures that the latest data items created or
received by the method once the transmission operation mode has
been activated which have been given the highest priority are
transmitted before any other data item having a lower priority or
received before the transmission operation mode has been activated.
The method, therefore, advantageously ensures that the limited
bandwidth is used to its maximum extent to make sure that the most
relevant data items are transmitted first even if the bandwidth is
very low. If a high bandwidth is available when the method switches
into transmission operation mode, the main buffer advantageously
provides at least a limited amount of previously recorded data
items that can be readily transmitted to the ground station.
However, the method advantageously ensures that any newly created
data item is transmitted first.
[0022] In a preferred embodiment for each of the live buffers a
maximum age for data items to be retained in the live buffer is
defined, wherein in the transmission operation mode a data item is
moved from a live buffer to a respective main buffer when an age of
the data item exceeds the maximum age defined for the live buffer,
wherein any data item that has been stored in a live buffer before
an other data item is moved to the main buffer before the other
data item.
[0023] In other words, for each of the live buffers it is defined
how long data items will be stored or kept in the live buffer by
defining a maximum age of data items that are retained in the
buffer. For example, data items of the flight data data type may be
retained for one minute in the respective live buffer. Data items
of the air traffic control message data type may be retained for
five minutes in the respective live buffer. If an age of a data
item stored in a live buffer exceeds the respective maximum age,
i.e., if the data item was created or stored in the buffer longer
ago than the maximum age, the data item is moved to the respective
main buffer. By defining a maximum age for a data item stored in a
live buffer it is ensured that only data items created at a
relevant point in time are transmitted. The age of a data item can
be defined from the point in time when the data item was created or
from the point in time when the data item was stored in a
buffer.
[0024] If data items are continuously created at predetermined time
intervals, i.e., with a fixed frequency, and have a predetermined
size, defining a maximum age corresponds to defining a maximum
storage capacity for a predetermined number of data items. Cockpit
voice recordings may, for example, be continuously created at
predetermined intervals and stored in the form of frames or data
items representing 20 ms of recorded sound. A maximum age of
cockpit voice recording data items stored in the live buffer could,
for example, be set to 1 minute. Thus, the live buffer has a
maximum storage capacity of 3000 cockpit voice recording data
items. This is equivalent to stating that the live buffer stores
only data items not older than 1 minute. Thus, in the transmission
operation mode data items are moved from a live buffer to a
respective main buffer when the maximum amount of data items that
can be stored in the live buffer has been reached, wherein any data
item that has been stored in a live buffer before an other data
item is moved to the main buffer before the other data item. The
maximum storage capacity of the buffer may, for example, be limited
by the physical storage capacity of the memory used for actually
storing the data items.
[0025] In other words, in this case the buffers have a limited
capacity. If the maximum number of data items that can be stored in
a buffer has been reached, the buffer overflows and removes the
oldest data item from the buffer to make space for a new data item.
The oldest data item is the data item stored first in a temporal
order in the buffer. However, data items from the live buffer are
not simply discarded. In the preferred embodiment they are instead
moved to the main buffer, i.e., pushed onto the top of the main
buffer. Thus, if the bandwidth of the transmission link is
temporarily too low to transmit all data items created once the
transmission operation mode has been activated, additional
temporary storage space for data items is provided in the main
buffers. If the bandwidth increases while the method is in the
transmission operation mode, those data items moved or pushed to
the main buffer which are still stored in the main buffer are
available for transmission.
[0026] In a preferred embodiment for each data type a separate
overflow buffer is provided and associated with the respective data
type and for each of the main buffers a maximum age for data items
to be retained in the main buffer is defined. A data item is moved
from a main buffer to a respective overflow buffer when an age of
the data item exceeds a maximum age defined for the main buffer,
wherein any data item that has been stored in a main buffer before
an other data item is moved to the overflow buffer before the other
data item. In the transmission operation mode any data item stored
in a main buffer is transmitted before any data item stored in an
overflow buffer. Of those data items stored in one of the overflow
buffers any data item of a data type having a higher priority is
transmitted before any data item of a data type having a lower
priority. In other words, an additional overflow buffer provides
additional storage space for any data items overflowing from the
main buffers.
[0027] It should be pointed out that in certain embodiments no
maximum age is defined for the live buffers but a maximum age is
defined for each of the main buffers. In other words, any data item
stored in a live buffer is maintained in the live buffer and only
data items stored in the main buffers are moved to the respective
overflow buffers if the age of the data items stored in the main
buffers exceeds a predetermined maximum age. Thus, in this
embodiment in the transmission operation mode any data item of a
higher relevance created after the transmission operation mode has
been triggered is transmitted before a data item of a lower
relevance created after the transmission operation mode has been
triggered.
[0028] In an exemplary preferred embodiment the method is adapted
for transmitting also data items of an additional data type. The
additional data type has a different priority than any of the other
data types selected from a range of priorities ranging from a
lowest to a highest priority. For the additional data type a
separate overflow buffer is provided and associated with the
additional data type. Data items of the additional data type are
stored in the associated overflow buffer in the transmission
operation mode and in the regular operation mode. Data items of the
additional data type are treated like data items of any of the
other data types, i.e., of those data items stored in one of the
overflow buffers including the overflow buffer for an additional
data type any data item of a data type having a higher priority is
transmitted before any data item of a data type having a lower
priority. An additional data type may, for example, be cockpit
images. An overflow buffer for data items of an additional data
type advantageously provides a means of transmitting data items of
a lower priority than other data items if a high bandwidth should
be available. If the method is adapted for also transmitting data
items of an additional data type, the data types for which a live
buffer, a main buffer and an overflow buffer are provided could
also be referred to as first data types and the additional data
type for which only an overflow buffer is provided could also be
referred to as second data type. Consequently, data items of a
first data type could be referred to as first data items and data
items of a second or additional data type could be referred to as
second or additional data items.
[0029] It is further preferred that a payload section of a data
packet may comprise data items of different data types, wherein
data items are transmitted as records, each record comprising a
header identifying the data type of the data item and the length of
the record. In other words, data items of different data types can
be transmitted in the payload section of the same data packet. To
this end, the data items of a data type are packed in records
having a header identifying the data type and a payload comprising
the data item or data items. This advantageously enables the method
to completely fill the payload section of a data packet with data
items of different data types if there should not be enough data
items from a single data type that have to be transmitted first.
Thus, the space available in data packet is used optimally.
[0030] In a preferred embodiment the method switches from the
regular operation mode to the transmission operation mode when a
trigger signal is received. The trigger signal may, for example, be
generated by a method or a system for determining the risk of an
aircraft accident if the risk exceeds a predetermined
threshold.
[0031] It is further preferred if for at least one of the data
types data items are stored in frames of a predetermined length in
the buffers. For at least one data type for which data items are
stored in frames of predetermined size, a plurality of frames can
preferably be combined and compressed to a single compressed frame
which is stored in the buffers. For example, if frames of flight
data data items are received at a buffer, these frames are first
collected in the buffer for a predetermined time span. Once a
sufficiently high number of frames has been collected, these frames
are combined and compressed into a single compressed frame. Thus,
if the compressed frames are later transmitted, more relevant data
can be transmitted in a shorter time frame, i.e., with less data
packets.
[0032] In a second aspect the problem is solved by a transmitter
for transmitting continuously created data items from an aircraft
to a receiver. The data items have a plurality of data types and
each data type has been assigned a different priority ranging from
a highest priority to a lowest priority. The transmitter comprises
last-in-first-out buffers for storage of the continuously created
data items. For each data type a separate live buffer and a
separate main buffer are provided and associated with the
respective data type and data items of a specific data type are
only storable in the associated buffers. The transmitter is
operable in a regular operation mode and a transmission operation
mode. In the regular operation mode the transmitter is adapted to
continuously store continuously created data items of the plurality
of data types in the associated main buffers. In the transmission
operation mode the transmitter is adapted to [0033] continuously
store continuously created data items of the plurality of data
types in the associated live buffers, [0034] transmit consecutive
data packets from the aircraft to a receiver via a data
transmission link, each data packet comprising a header section and
a payload section, and [0035] select for each data packet the data
to be transmitted in the payload section from the buffers, wherein
any data item stored in a live buffer is transmitted before any
data item stored in a main buffer, wherein of those data items
stored in one of the live buffers, any data item of a data type
having a higher priority is transmitted before any data item of a
data type having a lower priority, and wherein of those data items
stored in one of the main buffers, any data item of a data type
having a higher priority is transmitted before any data item of a
data type having a lower priority.
[0036] In a preferred embodiment for each of the live buffers a
maximum age of data items retained in the live buffer is defined.
The transmitter is adapted to move a data item from a live buffer
to a respective main buffer in the transmission operation mode when
an age of the data item exceeds the maximum age defined for the
live buffer, wherein any data item that has been stored in a live
buffer before an other data item is moved to the main buffer before
the other data item.
[0037] It is further preferred that the transmitter comprises for
each data type a separate overflow buffer associated with the
respective data type and that for each of the main buffers a
maximum age for data items to be retained in the main buffer has
been defined. The transmitter is adapted to move a data item from a
main buffer to a respective overflow buffer when an age of the data
item exceeds the maximum age defined for the main buffer, wherein
any data item that has been stored in a main buffer before an other
data item is moved to the overflow buffer before the other data
item. In the transmission operation mode any data item stored in a
main buffer is transmitted before any data item stored in an
overflow buffer, wherein of those data items stored in one of the
overflow buffers, any data item of a data type having a higher
priority is transmitted before any data item of a data type having
a lower priority.
[0038] In an exemplary preferred embodiment the transmitter is
adapted for transmitting data items of an additional data type. The
additional data type has a different priority than any of the other
data types selected from a range of priorities ranging from a
lowest to a highest priority. For the additional data type a
separate overflow buffer is provided in the transmitter and
associated with the additional data type. The transmitter is
adapted to store data items of the additional data type in the
associated overflow buffer in the transmission operation mode and
in the regular operation mode. During transmission data items of
the additional data type are treated like data items of any of the
other data types, i.e., of those data items stored in one of the
overflow buffers including the overflow buffer associated to the
additional data type any data item of a data type having a higher
priority is transmitted before any data item of a data type having
a lower priority stored in an overflow buffer.
[0039] In a preferred embodiment a payload section of a data packet
may comprise data items of different data types, wherein data items
are transmitted as records, each record comprising a header
identifying the data type of the data item and the length of the
record.
[0040] In another preferred embodiment the transmitter is adapted
to receive a trigger signal and to switch from the regular
operation mode to the transmission operation mode when the trigger
signal has been received.
[0041] It is further preferred that for at least one of the data
types data items are stored in frames of a predetermined length in
the buffers. For at least one data type for which data items are
stored in frames of predetermined size a plurality of frames can
preferably be combined and compressed to a single compressed frame
which is stored in the buffers.
[0042] The advantages and exemplary description of the various
methods according to the present invention apply vice versa to the
embodiments of a transmitter according to the present invention
having structural features that correspond to the features of the
methods.
[0043] Finally, in a third aspect the problem is solved by an
aircraft comprising a transmitter according to any of the preceding
embodiments. The advantages of the different embodiments of the
aircraft correspond to the advantages of the transmitter used
therein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] In the following, an exemplary embodiment of a method, a
transmitter and an aircraft according to the present invention will
be explained in more detail with reference to the schematic
drawings, wherein
[0045] FIG. 1 shows a flow chart of an exemplary method according
to the present invention,
[0046] FIG. 2 shows an exemplary embodiment of an arrangement of
live buffers, main buffers and overflow buffers,
[0047] FIG. 3 shows an exemplary embodiment of a live buffer, a
main buffer and an overflow buffer,
[0048] FIG. 4 shows an exemplary embodiment of a buffer and two
data records according to the present invention,
[0049] FIG. 5 shows an exemplary embodiment of a data packet,
[0050] FIG. 6 shows an exemplary embodiment of a transmitter
according to the present invention and
[0051] FIG. 7 shows an exemplary embodiment of an aircraft
according to the present invention comprising an exemplary
embodiment of a transmitter according to the present invention.
DETAILED DESCRIPTION
[0052] FIG. 1 shows a flow chart schematically depicting an
exemplary embodiment of a method according to the present
invention. The method is provided for transmitting continuously
created data items, such as data items stored in a flight recorder
of an aircraft, to a ground station. The exemplary embodiment of a
method shown in FIG. 1 is adapted for transmitting data items of
the following data types: flight data, cockpit voice recordings and
air traffic control messages. To these data types may also be
referred to as first data types and to data items of these data
types may also be referred to as first data items. Each of the data
types has been assigned a different priority selected from a range
of priorities extending from a highest priority to a lowest
priority. Air traffic control messages have been assigned the
highest priority, flight data has been assigned the second highest
priority and cockpit voice recordings have been assigned the third
highest priority.
[0053] The method is further adapted for transmitting data items of
an additional or second data type in form of a cockpit images. The
data items of the additional data type may also be referred to as
second data items. Further, the additional data type has also been
assigned a priority from a range of priorities extending from the
highest to a lowest priority. The priority assigned to the
additional data type is different from the priorities assigned to
any of the other data types. In the present example, cockpit images
have been assigned the lowest or fourth highest priority.
[0054] The exemplary embodiment of a method provides
last-in-first-out (LIFO) buffers for the continuously created data
items. As can be seen in FIG. 2, three different kinds of LIFO
buffers are provided: three live buffers 1a, 1b, 1c, three main
buffers 3a, 3b, 3c and four overflow buffers 5a, 5b, 5c, 5d. To
improve the ease of understanding, in the following where no
reference is made to a specific live buffer 1a, 1b, 1c, the live
buffers will generally be indicated by reference numeral 1; where
no reference is made to a specific main buffer 3a, 3b, 3c, the main
buffers will generally be indicated by reference numeral 3; and
where no reference is made to a specific overflow buffer 5a, 5b,
5c, 5d, the overflow buffers will generally be indicated by
reference numeral 5.
[0055] For each of the first data types a separate live buffer 1, a
separate main buffer 3 and a separate overflow buffer 5 are
provided and assigned to the respective data type. In detail, live
buffer 1a, main buffer 3a and overflow buffer 5a are assigned to
the air traffic control messages data type, live buffer 1b, main
buffer 3b and overflow buffer 5b are assigned to the flight data
data type and live buffer 1c, main buffer 3c and overflow buffer 5c
are assigned to the cockpit voice recordings data type. For the
second data type only an overflow buffer 5d is provided and
assigned to this data type, i.e., the overflow buffer 5d is
assigned to the cockpit images data type.
[0056] The method can operate in two different operation modes. A
first or regular operation mode includes a first and a second
method step 7, 9 and a second or transmission operation mode
includes a third, a fourth and a fifth method step 11, 13, 15.
[0057] In the regular operation modes any continuously created data
item of a first data type is continuously stored in the main buffer
3 associated with the respective data type in the first method step
7. Any continuously created data item of the second data type is
continuously stored in the overflow buffer 4d associated with the
second data type. All data items regardless of their type are
stored in frames 17 in the buffers 1, 3, 5. In FIGS. 2, 3 and 4
only a single frame 17 has been provided with a reference numeral
to keep FIGS. 2, 3 and 4 easy to understand.
[0058] In the exemplary embodiment of the method shown in FIG. 1
data items are always stored in the form of frames 17 in the
buffers 1, 3, 5. How the content of the frames 17 is generated
depends on the data type. For example, a frame 17 of flight data
may comprise uncompressed flight data data items created over a
period of 125 ms. Another frame 17 of flight data may comprise
compressed flight data which has, for example, been generated from
eighty uncompressed flight data frames 17. Frames 17 comprising air
traffic control message data items comprise uncompressed data and
frames 17 comprising cockpit voice recordings or cockpit images
only comprise compressed recordings or images, respectively.
[0059] The second method step 9 checks if a trigger signal has been
received from an external source, for example, from a system
determining a risk of an aircraft emergency. If the trigger signal
has been received, the method switches to the transmission
operation mode and continues with the third, fourth and fifth
methods steps 11, 13, 15. If no trigger signal has been received,
the method continues to operate in the regular operation mode. It
should be noted, that FIG. 1 only shows a schematic representation
of the flow of the exemplary embodiment of the method. The first
and the second method step 7, 9 do not have to be executed in
sequence. It is also possible, that the first and the second method
step 7, 9 are parallel processes. The first method step 7
continuously stores continuously created data items in the
respective buffers 3, 5 and the second method step 9 monitors in
parallel whether a trigger signal is received. If a trigger signal
is received, the second method step 9 stops the first method step 7
and the method continues with the third method step 11. The same
applies to the third, fourth and fifth method steps 11, 13, 15,
which are shown in FIG. 1 as sequential method steps. However,
method steps 13 and 15 may be implemented as an independent process
executed in parallel to method step 11.
[0060] In the third step 11 data items of a first data type are
continuously stored in the associated live buffers 1, i.e., any air
traffic control message data items that are created, are stored in
the associated air traffic control message live buffer 1a, flight
data data items are stored in the associated flight data live
buffer 1b and cockpit voice recordings data items are stored in the
associated cockpit voice recordings live buffer 1c. In the same
method step 11, any data item of the second data type is still
stored in the associated overflow buffer 5d.
[0061] In the fourth step 13, data items are selected from the
buffers 1, 3, 5 for transmission in the form of data packets in the
fifth step 15. Data items are selected from the buffers 1, 3, 5
according to the following rules: any data item stored in a live
buffer 1 has to be transmitted before any data item stored in a
main buffer 3 and any data item stored in a main buffer 3 has to be
transmitted before any data item stored in an overflow buffer 5.
Within each buffer category, i.e., live buffer 1, main buffer 3 or
overflow buffer 5, every data item of a data type having a higher
priority has to be transmitted before a data item having a lower
priority. Applied to the exemplary embodiment this means that first
any data item of the live buffer 1a associated with air traffic
control messages is transmitted. Next, any data item stored in the
live buffer 1b associated with flight data is transmitted, followed
by any data item stored in the live buffer 1c associated with
cockpit voice recordings. If all items from the live buffers 1 have
been selected for transmission, the data items stored in the main
buffers 3 are selected in the same order. Finally, if any data item
stored in a main buffer 3 has been selected for transmission, data
items stored in an overflow buffer are selected in the order of the
priority of the data type. In FIG. 2 the order in which data items
are selected from the buffers 1, 3, 5 is indicated by the arrow
19.
[0062] It should be noted that the buffers 1, 3, 5 are LIFO
buffers. Thus, whenever a data item is selected from a buffer 1, 3,
5, the data item is removed that has been stored last in a temporal
order in the buffer 1, 3, 5. In other words, the LIFO buffers 1, 3,
5 advantageously add a temporal prioritization to the selection of
data items as the LIFO buffers 1, 3, 5 make sure that more recently
created data items are always selected first.
[0063] Once the data items for transmission with the next data
packet have been selected in the fourth step, the data items are
stored in the payload of a data packet and transmitted via a data
transmission link in the fifth method step 15. The data
transmission link is a satellite communication network using the IP
protocol for data transmission between aircraft and ground
station.
[0064] It should be noted that every time data items are selected
for transmission with the next data packet, the selection process
starts again at the live buffer 1a having the highest priority and
continuously works its way through the buffers 1, 3, 5 selecting
data items for transmission according to their priority. Thus, it
is ensured that whenever a new data packet can be transmitted, the
most recent and most highly prioritized data items are transmitted
before any data item having arrived earlier or having a lower
priority.
[0065] Further, providing main buffers 3 advantageously ensures
that at the time the method switches from the regular operation
mode to the transmission operation mode, there is always some data
created or recorded before the transmission operation mode was
activated. In particular if the method is used to transmit data
usually stored in a flight recorder, this data may be helpful for
determining the cause of the accident as it was captured right
before it was detected that there is a risk of an aircraft
emergency and the data, therefore, could include an indication why
the transmission operation mode was activated. It should, however,
be pointed out that in the method according to the present
invention any data item of a first data type created after the
transmission operation mode was activated is stored in the liver
buffers 1 and, therefore, transmitted before the historical data
stored in the main buffers 3.
[0066] Part of the transmission and selection method steps 13, 15
are shown in more detail in FIGS. 4 and 5. In FIG. 5, an exemplary
embodiment of a data packet 21 is shown in more detail. The data
packet 21 comprises a header section 23 and a payload section 25.
The header section 23 comprises an IP header 27, a UDP header 29
and an aircraft identifier 31. The IP header 27 and the UDP header
29 are part of the transmission protocols used for transmitting the
data packet 21 via the satellite network. The aircraft identifier
31 is an identifier that unambiguously identifies the aircraft
sending the data packet 21. The payload section 25 comprises the
data items that shall be transmitted packed in several records 33.
Each record comprises a record header 35 and a record payload 37.
The overall maximum allowable size of the data packet 21 is
determined by the transmission link and the transmission protocol.
Each of the elements 27, 29, 31 of the header section 23 has a
predetermined length, i.e., comprises a predetermined number of
bits. The remaining available bits are used for the payload section
25.
[0067] The structure of the records 33 and how the records are
created from the data items stored in the buffers 1, 3, 5 will next
be described in more detail with reference to FIG. 4. FIG. 4 shows
an arbitrary buffer 39 comprising six frames 17 of data items. For
the following description it will be assumed that this buffer 39 is
the buffer 39 from which the next data items have to be selected
according to the rules set out above. From the buffer 39 as many
data items are selected as can be fitted in the payload section 25
of the next data packet 21. The payload section 25 may, for
example, have enough space left to transmit the data stored in four
frames 17. Thus, four frames 17 are selected and added to the
record payload 37 of a first record 33a. Additionally, header
information such as a data type identifier 41, a record payload
length 43 and a time stamp 45 are added to the record header 35.
Once the top four frames 17 have been selected from the buffer 39,
only two frames 17 remain in the buffer 39. Assuming that no new
frames 17 are added to the buffer 39 between the selection of data
items for two consecutive data packets 21, the remaining two frames
17 are added to the record payload 37 of a second record 33b. The
second record 33b comprises the same data type identifier 41 in the
record header 35 as the first record 33b, but the record payload
length 43 and the time stamp 45 are different.
[0068] As can be seen in FIG. 5, if a record 33 comprising data
items of a single data type is not sufficient to fill the entire
payload section 25 of the data packet 21, records 33 of different
data types can be advantageously be added to the same payload
section 25 to maximize the number of data items that is transmitted
with every data packet 21 and optimize the use of the available
bandwidth.
[0069] For each of the buffers a maximum age of data items to be
retained in the buffer has been defined. For flight data data items
and cockpit voice recording data items stored in the respective
main buffers 3b, 3c the maximum age has been defined as five
minutes and for data items of these data types stored in the live
buffers 1b, 1c a maximum age has been defined as one minute. For
air traffic control messages the maximum age has been defined as
two hours for the associated main buffer 3a and 5 minutes for the
associated live buffer 1a. Only data items having an age which is
younger, i.e., smaller, than the maximum age are retained in the
respective buffer.
[0070] FIG. 3 shows in an exemplary fashion how the live buffer 1b,
the main buffer 3b and the overflow buffer 5b associated with the
flight data data type are functionally connected. The buffers 1a,
1c, 3a, 3c, 5a, 5c associated with the air traffic control messages
and the cockpit voice recordings, respectively, are linked in the
same manner. The buffers 1b, 3b, 5b are all LIFO buffers having a
limited capacity. As flight data data items are created
continuously at a fixed rate, i.e., with a predetermined frequency,
providing buffers of a fixed physical storage capacity corresponds
to defining a maximum age for data items to be retained in the
buffer. If one of the buffers has reached its maximum capacity,
i.e., the maximum number of frames 17 that can be stored in the
buffer 1b, 3b, 5b has been reached and a newly created frame 17
shall be stored in the buffer 1b, 3b, 5b, of those frames 17 stored
in the respective buffer 1b, 3b, 5b the frame 47, 49, 51 that has
been stored first in a temporal order in the buffer 1b, 3b, 5b is
removed or pushed from the buffer 1b, 3b, 5b. For example, in the
regular operation mode new data items are continuously added to the
main buffer 3b. As soon as the buffer 3b has been completely filled
with data items or frames 17, the oldest frame 49 is removed from
the main buffer 3b to make space available for the newly added
frame 17.
[0071] In the exemplary embodiment of the method, frames 47 removed
from the live buffer 1b are, however, not immediately discarded but
moved to the main buffer 3b. Likewise, any frame 49 removed from
the main buffer 3b is moved to the overflow buffer 5b. Thus, the
main buffer 3b serves as additional storage space for data items
from the live buffer 1b and the overflow buffer 5b provides
additional storage space for data items from the main buffer 3b.
This could be particularly advantageous if the bandwidth or data
rate available for transmission over the transmission link is
variable. The bandwidth may, for example, for some time be too low
after the transmission operation mode has been activated to
transmit all data items stored in the live buffer 1. At least the
live buffers 1c associated with a data type having the lowest
priority of the first data types will continuously fill up until it
overflows and older data items are pushed to the respective main
buffer 3c. If after some time the bandwidth increases, the data
items stored in the main buffer 3c are still available and could be
transmitted provided that the data rate is high enough. Likewise,
if the main buffers 3 are completely filled, the overflow buffers 5
provide additional storage space such that when a high data rate
should be available, further historic data items can be
transmitted. However, by providing main buffers 3 of limited size,
it is advantageously ensured that first the most relevant data
items of all different data types are transmitted.
[0072] For data items that are continuously created at irregular
intervals such as air traffic control messages the data items are
stored with a time stamp and removed from the respective buffer 1a,
3a, 5a when an age of the data item exceeds the maximum age defined
for the respective buffer. For example, the maximum age for the
live buffer 1a could be set to five minutes, for the main buffer 3a
to two hours and for the overflow buffer 5a to five hours. In other
words, the method continuously compares the age of data items
stored in the buffers 1a, 3a, 5a with maximum age and removes any
data item having a maximum age exceeding the respective maximum age
from the buffer. Any data item removed from the live buffer 1a is
moved to the main buffer 3a and any data item removed from the main
buffer 3a is moved to the overflow buffer 5a. Data items removed
from the overflow buffer are discarded.
[0073] FIG. 6 shows an exemplary embodiment of a transmitter 53.
The transmitter 53 is adapted to carry out the exemplary embodiment
of a method according to the present invention as described with
reference to FIGS. 1 to 5. The transmitter 53 comprises an input 55
which receives the continuously created data items, for example,
from an aircraft's main control system. The input 55 further may
receive a trigger signal for switching the transmitter 53 from a
regular operation mode to a transmission operation mode and back.
Incoming data items are relayed to a distributor 57 which is
adapted to distribute the data items depending on the operation
mode and the data type of the data items to one of the buffers 1,
3, 5 of the transmitter 53. In FIG. 6 the buffers 1, 3, 5 are only
generally indicated and not shown in detail. In particular, the
transmitter 53 comprises a live buffer 1a, 1b, 1c and a main buffer
3a, 3b, 3c for each first data type and an overflow buffer 5a, 5b,
5c, 5d for each first and second data type as required for carrying
out the exemplary embodiment of the method which are not shown
individually in FIG. 6.
[0074] The transmitter 53 further comprises a packetizer 59 which
selects data items or frames 17 from the buffers 1, 3, 5 according
to the rules set out above, adds the data items to the record
payload 37 of records 33 and also adds the necessary header
information to the record header 35. Finally, the packetizer also
packs the records 33 into the payload section 23 of the data packet
21 that is being prepared and adds the necessary header information
to the header section 23. Finally, an output 61 transmits the data
packets 21 via a data transmission link to a ground station.
[0075] With regard to the details of the transmitter 53 reference
is made to the preceding description of the exemplary embodiment of
the method according to the present invention. As the transmitter
53 is adapted to carry out the method as described above, this adds
several limitations to the transmitter 53 that have to be taken
into consideration. As the transmitter 53 is adapted to carry out
the method according to the present invention, the transmitter 53
shares the advantages of the exemplary embodiment of the
method.
[0076] Finally, FIG. 7 shows an exemplary embodiment of an aircraft
63 according to the present invention. The aircraft 63 comprises a
transmitter 53 as shown in FIG. 6. Thus, the above description of
the transmitter 53 fully applies to the aircraft 63. The
transmitter's input 55 is connected to a main control system 65 of
the aircraft 63 and the output 61 of the transmitter 53 is
connected to a satellite antenna 67 for providing a data
transmission link.
[0077] The aircraft 63 according to the present invention shares
the advantages of the exemplary embodiment of a transmitter 53 and
the exemplary embodiment of the method according to the present
invention.
[0078] While at least one exemplary embodiment of the present
invention(s) is disclosed herein, it should be understood that
modifications, substitutions and alternatives may be apparent to
one of ordinary skill in the art and can be made without departing
from the scope of this disclosure. This disclosure is intended to
cover any adaptations or variations of the exemplary embodiment(s).
In addition, in this disclosure, the terms "comprise" or
"comprising" do not exclude other elements or steps, the terms "a"
or "one" do not exclude a plural number, and the term "or" means
either or both. Furthermore, characteristics or steps which have
been described may also be used in combination with other
characteristics or steps and in any order unless the disclosure or
context suggests otherwise. This disclosure hereby incorporates by
reference the complete disclosure of any patent or application from
which it claims benefit or priority.
* * * * *