Patent Description:
The use of light-emitting diodes (LED) for interior cabin lighting in the aeronautics field increasingly leads to enhanced passenger experience and improved customer satisfaction. Currently, cabin illumination systems in passenger aircraft utilize or rely on pre-programmed setting of colors and intensity of light for specific flight phases, such as landing or departure as well as times of the day and time zones. Amongst others, coordinated control of lighting systems may aid passengers in overcoming fatigue of long-distance travel or in keeping calm and relaxed in potentially stressful moments of the flight, such as landing and departure. Moreover, coordination of other multimedia systems on-board an aircraft with the control of the cabin illumination system may further help in creating a believable and satisfying ambience for aircraft passengers.

Decentralized cabin systems require sophisticated approaches in distribution of control data for controlling the various cabin systems in synchronicity. Several approaches have been made but there has not been a comprehensive solution for distributed on-board networks supporting the advantages of decentralized software architectures.

Document <CIT> discloses a method of operating a lighting fixture in an aircraft. Document <CIT> discloses a timed lighting control network. Document <CIT> discloses an LED strip lighting device for a cabin of a passenger aircraft.

Document <CIT> discloses flight illumination linkage control methods based on a flight illumination linkage control system, the system comprising a flight information management unit, an illumination control unit and a main control unit.

Document <CIT> discloses an aircraft cabin management system comprising a video data distributor for distribution of image and video data on-board an aircraft, a central processing unit and at least one graphics processor coupled to the central processing unit.

Document <CIT> indicates an illumination system with an intelligent light module group controller comprising controls for the illumination levels and an interface for receiving and sending information. Document <CIT> discloses a lighting system and a method for controlling a lighting system, particularly for use in lighting systems of airborne vehicles. Documents <CIT> and <CIT> disclose systems for transmitting audio and lighting control data via a communication data bus between multiple devices in an aircraft, and a method for transmitting data packets on a bus system between multiple devices in an aircraft.

Document <CIT> describes a system and method for providing a digital In-Flight-Entertainment system in an aircraft, that is capable of presenting a video program and associated audio in a synchronized manner to a large number of individual video monitors and speakers. It particularly relates to a system and method for achieving synchronized playback of a video program and associated audio across a large population of video and audio playback devices.

Document <CIT> relates generally to data and multi-media content provisioning for aircraft using wireless networks.

One of the objects of the invention is to find improved solutions for synchronizing the distribution of multimedia content such as video, audio and/or lighting control data within a network of data nodes in a passenger aircraft.

This and other objects are achieved by a multimedia distribution network having the features of Claim <NUM>, by a method of distributing multimedia content via a network on board of a passenger aircraft having the features of Claim <NUM> and by an aircraft with a multimedia distribution network having the features of Claim <NUM>.

According to a first aspect of the invention, a multimedia distribution network for use on board of a passenger aircraft comprises a first network node configured as a head controller, a plurality of second network nodes configured as a plurality of intermediate controllers connected to the first network node, and a plurality of third network nodes configured as a plurality of end device controllers, each connected to one of the plurality of second network nodes. The head controller is configured to transmit a multicast stream of multimedia control signal packets for controlling the plurality of end device controllers to the plurality of intermediate controllers. The plurality of intermediate controllers are configured to periodically transmit unicast delay queries to the head controller, to process the received multimedia control signal packets and to distribute processed multimedia control signal packets to the end device controllers with a controllable delay based on the content of unicast delay indicator signals sent by the head controller to the plurality of intermediate controllers in response to the unicast delay queries.

According to a second aspect of the invention, a method of distributing multimedia content via a decentralized network on board of a passenger aircraft includes the steps of transmitting, by a first network node of the decentralized network configured as a head controller, a multicast stream of multimedia control signal packets for controlling a plurality of third network nodes of the decentralized network configured as a plurality of end device controllers; receiving, by a plurality of second network nodes of the decentralized network configured as a plurality of intermediate controllers, the a multicast stream from the head controller; periodically transmitting, by the plurality of intermediate controllers, unicast delay queries to the head controller; receiving, by the plurality of intermediate controllers, unicast delay indicator signals sent by the head controller to the plurality of intermediate controllers in response to the unicast delay queries; and processing, by the plurality of intermediate controllers, the received multimedia control signal packets to the end device controllers and distributing processed multimedia control signal packets with a controllable delay based on the content of the received unicast delay indicator signals.

According to a third aspect of the invention, a passenger aircraft comprises a multimedia distribution network according to the first aspect of the invention. In some embodiments, the aircraft may further comprise cabin lighting units controlled by lighting control data distributed via the multimedia distribution network.

A particular advantage of the solutions according to the invention is that some control settings may be pre-loaded in network nodes lower down in the control hierarchy which may aid in keeping synchronicity of executing multimedia control commands to an improved degree. Moreover, this pre-loading enhances flexibility and intelligence in end devices at the outer edges of any kind of network which advantageously aids in increasing reliability of control in the overall system.

By creating a distributed network topology of more granular hierarchy steps, the network is highly scalable. The standardized network control policies further enable interchangeability of single network nodes without the need for re-designing the network entirely. Standardizing the distribution of partial settings over multiple network nodes in different hierarchy levels in a network will guarantee high real-time capabilities as well as simplified pre-deployment procedures, specifically in retrofit scenarios.

Advantageous configurations and refinements will become understood from the further dependent claims and from the description with reference to the figures.

According to some embodiments of the multimedia distribution network and/or the method of distributing multimedia content, the multimedia control signal packets may indicate audio data content, video data content and/or lighting control data content to be processed by the intermediate controllers. Specifically with regard to central lighting control applications in a cabin management system, the solution for disseminating multimedia control signal packets is advantageous as a central controller may coherently orchestrate pre-defined lighting scenes or effects. The cabin management system may select the pre-defined lighting scenes or effects and pass parameters to the head controller which in turn selects a number of required intermediate controllers connected to the correct lighting units within the cabin. The intermediate controllers are provided with commands to execute the requested scenes or effects. The packets with lighting control data content are locally synchronized within the intermediate controllers with the aid of the unicast delay querying procedure of the second aspect of the invention so that each of the intermediate controllers may execute the correct part of a scene or effect within the correct timing.

According to some embodiments of the multimedia distribution network, a plurality of end devices may be connected to the plurality of end device controllers. In several of those embodiments, the plurality of end device controllers may be configured to control the plurality of end devices on the basis of the audio data content, video data content and/or lighting control data content indicated in the multimedia control signal packets. The end devices may in some cases be included in end device modules, such as lighting modules, which also include one of the end device controllers.

In some embodiments, the multimedia distribution network may further include a plurality of end device interpreters connected between respective ones of the plurality of intermediate controllers and the plurality of end device controllers. In several of those embodiments, the plurality of end device interpreters may be configured to convert the content of the multimedia control signal packets into control signals specific to the plurality of end devices. The end device interpreters may advantageously be used for protocol conversion between the communication protocol used in the multimedia distribution network and the "last mile" of command communication within an end device module, such as a lighting module. This enables retrofit solutions with existing end device modules in an aircraft cabin as well as easy and quick integration and/or replacement of end device modules of various origins.

According to some further embodiments of the multimedia distribution network, the plurality of end device interpreters may be configured to transmit feedback information regarding operation status and/or debug information of the plurality of end device controllers to the respectively connected one of the plurality of intermediate controllers. This advantageously allows for feedback regarding certain information collected within end device modules, such as for example periodic heartbeat information to indicate error-free operation, data indicating the configuration of the end device, debug information or sensor values gathered within the end device module.

According to some further embodiments of the multimedia distribution network, the head controller may be configured to transmit the multicast stream with a configurable delay between subsequent multimedia control signal packets.

According to some further embodiments of the multimedia distribution network, the plurality of intermediate controllers may be configured to distribute the received multimedia control signal packets to the end device controllers in a multicast stream of end device control signal packets. In several of those embodiments, the multicast stream of end device control signal packets may be an IP multicast with to the User Datagram Protocol (UDP) as transport protocol.

According to some further embodiments of the multimedia distribution network, the multicast stream of multimedia control signal packets may be an IP multicast with to the User Datagram Protocol (UDP) as transport protocol.

According to some embodiments of the method, transmitting the multicast stream of multimedia control signal packets may be performed with a configurable delay between subsequent multimedia control signal packets.

According to some further embodiments of the method, distributing the received multimedia control signal packets to the end device controllers may be performed using a multicast stream of end device control signal packets.

The above configurations and refinements may be combined with one another as desired where expedient. Further possible embodiments, refinements and implementations of the invention also encompass combinations, which are not explicitly mentioned, of features of the invention described above or below with regard to the exemplary embodiments. In particular, a person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the present invention.

The present invention will be discussed in more detail below on the basis of the exemplary embodiments shown in the schematic figures. In the figures:.

The appended figures are intended to provide improved understanding of the embodiments of the invention. They illustrate embodiments and serve, in conjunction with the description, for the explanation of principles and concepts of the invention. Other embodiments, and many of the stated advantages, will emerge with regard to the drawings. The elements of the drawings are not necessarily shown true to scale relative to one another. Direction-indicating terminology such as, for instance, "top", "bottom", "left", "right", "above", "below", "horizontal", "vertical", "front", "rear" and similar indications are used only for explanatory purposes and do not serve to restrict the generality to specific configurations as shown in the figures.

In the figures of the drawing, elements, features and components which are identical, functionally identical and of identical action are denoted in each case by the same reference designations unless stated otherwise.

Multicast messaging in the context of this invention comprises any form of one-to-many communication between nodes in a network where datagrams, such as data packets or data frames, are addressed for or directed to a particular group of network nodes subscribed to the multicast service, the so-called multicast group. Members of that group may receive and process any multicast messaging content sent by a specific multicast messaging transmitter within the network. The multicast messaging transmitter will send only one copy/version of the content to be distributed which will be delivered to a plurality of network nodes in the multicast group. Association with a multicast group and labelling of the multicast messages may be affected by means of protocol-specific multicast addresses, such as for example IP addresses. Multicast messaging in the context of this invention may particularly include network-assisted multicasting where copies of multicast messages are automatically created in network segments including multicast group members.

Unicast messaging in the context of this invention comprises any form of one-to-one communication between nodes in a network where datagrams, such as data packets or data frames, are transmitted from one node in the network to another predetermined destination node in the network. Both transmitting and destination network node are identified by an unambiguous network address such as an IP address. Unicast messaging in the context of this invention may be unidirectional or bidirectional.

Datagrams within the context of this invention comprise any type of data transfer unit in a packet-switched network for communication data content without the need for a connection. Datagrams may include a payload section preceded by an administrative header section. Datagrams in the context of this invention may in particular be data packets or data frames, and underlying communication protocols relying on such datagrams may be Ethernet, IP, UDP or TCP.

Transmission of certain commands and/or control signals within the context of this disclosure may be performed under a lightweight messaging protocol for machine-to-machine (M2M) communication, such as the Message Queuing Telemetry Transport (MQTT) protocol. Advantages of using MQTT for transmission of certain commands and/or control signals between participants in a multimedia distribution network are its easy manageable footprint of code and the concomitant low requirements with respect to bandwidth resources and reliability measures of the underlying network. MQTT is based on TCP/IP establishing a connection between server type network nodes (brokers) and other network nodes participating in the communication under MQTT (clients). The brokers act as intermediaries for any communication with the clients and any communication of the clients among each other. Clients may either publish content, i.e. sending out blocks of data with payload content associated with a predefined topic, or subscribe to a certain topic, i.e. querying with the broker for blocks of data published by other clients labelled with the desired topic indicator. Topics may be branched into subtopics. Due to MQTT communication being driven by events (actual subscription queries triggering multicasting of corresponding published data), the bandwidth requirements are kept low since data transmission is not performed continuously or periodically in line with a predefined transmission schedule.

The User Datagram Protocol (UDP) is established on the transport layer and is part of the Internet Protocol (IP) suite, thus coined as UDP/IP. UDP does not require pre-existent connections prior to any data transmission and is therefore inherently unreliable. However, in UDP transmission, packets may be dropped without the need to wait for or to re-transmit delayed packets. Real-time dissemination of data under UDP is highly efficient both in terms of bandwidth requirements as well as latency, specifically for multimedia distribution networks.

<FIG> shows a schematic diagram of a multimedia distribution network <NUM> for use on-board of a passenger aircraft, such as for example the passenger aircraft A depicted in conjunction with <FIG>. The network <NUM> includes a number of network nodes which are interconnected among each other. By way of non-limiting example, a first network node acts as a head controller <NUM>. A number of second network nodes connected to the first network node act as a plurality of intermediate controllers <NUM>. In the depicted configuration, the multimedia distribution network <NUM> is implemented as a star topology, however, other forms of network topologies are equally possible, such as daisy-chain topologies, cluster topologies, ring topologies, partially or fully connected mesh topologies or any sort of hybrid network topologies as combination of two or more of the aforementioned topology types. For example, the multimedia distribution network <NUM> may be arranged in a star-ring network, a snowflake network or a cluster-mesh network.

The first and second network nodes may be functionally equipped with the necessary elements and features to dynamically take on either the role of a head controller <NUM> or of one of the intermediate controllers <NUM>. In one form of implementation, the role of a head controller <NUM> is pre-determined, however, in other forms the role of the head controller <NUM> may dynamically be re-assigned to a different one of the second network nodes, for example in order to provide functional redundancy in case of permanent or temporary failure or unavailability of the respective first network node acting as head controller <NUM> previously.

Connected to a respective one of the intermediate controllers <NUM> there is a plurality of third network nodes configured as a plurality of end device controllers <NUM>. The end device controllers <NUM> may be internal processors of end device modules <NUM>. The end device modules <NUM> may further include functional units <NUM> that are controlled by the respective end device controller <NUM>, such as for example lighting units, loudspeakers, displays or other multimedia end devices.

The head controller <NUM> is configured to transmit a multicast stream MC of multimedia control signal packets for controlling the plurality of end device controllers <NUM> to the plurality of intermediate controllers <NUM>. To that end, the head controller <NUM> may include a central processor <NUM> that controls various communication interfaces <NUM>, <NUM>, <NUM> and <NUM>. A cabin communication interface <NUM> may receive control data from a cabin management system (not shown) of the aircraft which the multimedia distribution network <NUM> is part of, for example via MQTT. This control data includes commands and parameters to select a pre-defined multimedia scenario for display by a number of end devices <NUM>.

The multicast stream MC may for example be disseminated to a number of selected or subscribed intermediate controllers <NUM> via a multicast output <NUM> of the head controller <NUM> to multicast inputs <NUM> of the intermediate controllers <NUM>. The multicast stream MC may include a stream of multimedia control signal packets indicating audio data content, video data content and/or lighting control data content to be processed by the intermediate controllers. The payload content of the multimedia control signal packets is determined to reach a number of end device controllers <NUM> which in turn are configured to control the plurality of end devices <NUM> on the basis of the payload content included in processed multimedia control signal packets processed by the intermediate controllers according to the indicated content of the original multimedia control signal packets.

As exemplarily depicted in the message sequence chart of <FIG>, the head controller <NUM> is configured to transmit the multicast stream MC with a configurable multicast delay d1 between subsequent multimedia control signal packets. The multicast stream MC of multimedia control signal packets may in some cases be an IP multicast with the User Datagram Protocol (UDP) as transport protocol.

In some cases, the end device modules <NUM> may include an end device interpreter <NUM> each of which is connected between respective ones of the intermediate controllers <NUM> and the end device controllers <NUM>. Those end device interpreters <NUM> are used to convert the payload content of the multimedia control signal packets into control signals specific to the respectively associated end devices <NUM>, for example audio control signals for loudspeakers, video control commands for displays or lighting control signals for lighting units such as LED strips or panels. The end device interpreters <NUM> may in some forms of implementation be configured to transmit feedback information FD regarding operation status and/or debug information of the plurality of end device controllers <NUM> to the respectively connected one of the plurality of intermediate controllers <NUM>, for example via a route through a feedback interface <NUM> of the corresponding intermediate controller <NUM> to a debug interface <NUM> of the head controller <NUM>. The feedback information FD may be used to fine-tune the performance of the end devices <NUM> or by re-arranging the selection of the end devices <NUM> by the head controller <NUM> in order to achieve the desired output of the pre-defined multimedia scenario.

The intermediate controllers <NUM> may include control interfaces <NUM> used to distribute the received multimedia control signal packets to the end device controllers <NUM>, optionally supported by the end device interpreters <NUM>. In order to provide for synchronicity of the distribution of the multimedia control signal packets to the various end devices modules <NUM> across the host of intermediate controllers <NUM>, each intermediate controller <NUM> includes a query interface <NUM> over which the intermediate controller <NUM> may periodically transmit unicast delay queries DC to the head controller <NUM>.

As exemplarily illustrated in the message sequence chart of <FIG>, the head controller <NUM> receives a unicast delay query DC at the query interface <NUM> and immediately returns a timestamped unicast delay indicator signal back to the querying intermediate controller <NUM>. The round-trip time (RTT) of the unicast delay query DC and the corresponding unicast delay indicator signal is evaluated by the intermediate controller <NUM> so that the distribution of the received multimedia control signal packets to the end device controllers <NUM> may be performed with a controllable delay based on the evaluated RTT. As illustrated in the message sequence chart of <FIG>, the received multimedia control signal packets may in some cases be distributed using a multicast stream LC of end device control signal packets which in some forms of implementation be an IP multicast with the User Datagram Protocol (UDP). The controllable delay d3 may then be set by the intermediate controllers <NUM> to improve synchronicity of the decentralized multicast streams LC from different intermediate controllers <NUM>.

One application scenario for the multimedia distribution network <NUM> is an overall system architecture envisioned for the lighting units and panels in passenger cabin of a passenger aircraft, such as for example the aircraft A of <FIG>. The head controller <NUM> acts as a central light controller receiving lighting scenario commands via MQTT from the cabin management system. These commands select a pre-defined scene or effect and pass some parameters to the head controller <NUM>. The head controller <NUM> then selects the required intermediate controllers <NUM> within the aircraft cabin and commands those to execute the requested scene. Beforehand, the intermediate controllers <NUM> are programmed with the necessary settings needed to know how a certain scene or effect should be executed. The packets send from the head controller <NUM> to the intermediate controllers <NUM> also synchronize the state of the intermediate controllers <NUM>, so that each of the intermediate controllers <NUM> executes the right part of a scene or effect at the right time. Dynamically adjusting the delays for each of the intermediate controllers <NUM> on the basis of the delay polling with the head controller <NUM> greatly aids in achieving that level of synchronicity.

Packets generated by the intermediate controllers <NUM> command the associated end devices <NUM>, for example lighting units and/or LED panels or strips, to display certain colours, hues, brightness etc. Additionally, each end devices <NUM> may provide certain feedback information FD to the associated intermediate controller <NUM> via MQTT. All or most of this feedback information FD is then passed to the head controller <NUM> by the intermediate controllers <NUM> for further evaluation and action.

The unicast delay querying procedure initiated by the intermediate controllers <NUM> from time to time with a delay d2 provides the intermediate controllers <NUM> with information about the network delay that the received multimedia control signal packets experience when received from the head controller <NUM>.

<FIG> shows a flowchart of the method steps of a method M of distributing multimedia content via a network on board of a passenger aircraft, for example the multimedia distribution network <NUM> as shown in <FIG>. The method M may advantageously be carried out on-board of a passenger aircraft, such as the aircraft A as exemplarily depicted in <FIG>. Specifically, the method M may be used to disseminate lighting control among lighting modules distributed and installed in various places of a passenger cabin within the passenger aircraft A.

In a first step M1, a head controller <NUM> which is selected as a first network node from a multiplicity of nodes in the multimedia distribution network <NUM> transmits a multicast stream MC of multimedia control signal packets to other nodes in the multimedia distribution network <NUM> selected and configured as intermediate controllers <NUM>. The multimedia control signal packets are intended to control nodes in the multimedia distribution network <NUM> which are configured as end device controllers <NUM>. Specifically, the multimedia control signal packets may indicate audio data content, video data content and/or lighting control data content, i.e. payload with respect to audio data, video data and/or commands for controlling lighting units. In some cases, the head controller <NUM> introduces a configurable delay d1 between subsequent multimedia control signal packets during transmission of the multicast stream MC.

In a second step M2, the intermediate controllers <NUM> receive the multicast stream MC from the head controller <NUM>. The multicast stream MC may for example be an IP multicast with the User Datagram Protocol (UDP) as transport protocol. Upon receipt of the multicast stream MC, the receiving intermediate controllers <NUM> periodically transmit unicast delay queries DC to the head controller <NUM> in a third step M3. The unicast delay queries DC elicit responses by the head controller <NUM> which in turn sends out unicast delay indicator signals targeted to the specific intermediate controllers <NUM> from where the unicast delay queries DC had been obtained. The unicast delay indicator signals are received in a fourth step M4 by the querying intermediate controllers <NUM>.

The unicast delay indicator signals enable the receiving intermediate controllers <NUM> to measure the delay a received multimedia control signal packet of the multicast stream MC is subject to when transmitted from the head controller <NUM> to the respective intermediate controller <NUM>. The timestamps of the unicast delay queries DC and the unicast delay indicator signals may be evaluated by the intermediate controllers <NUM> to estimate the difference between the clocks in the head controller <NUM> and the intermediate controller <NUM>. The intermediate controllers <NUM> may further measure the time it took to receive the unicast delay indicator signal in response to the unicast delay query DC. For example, assuming equal network load in upstream (towards the head controller <NUM>) and downstream (towards the intermediate controller <NUM>), half of the measured Round-Trip-Time (RTT) for one unicast delay querying cycle can be determined as the packet delay time. Subsequent packet delay times may be measured and subject to a moving window averaging procedure in order to smoothen out the measured delay times when there are high fluctuations in the measurements.

The intermediate controllers <NUM> then process the received multimedia control signal packets and distribute the processed multimedia control signal packets to the end device controllers <NUM> in a fifth step M5. The distribution may be performed using a multicast stream LC of end device control signal packets. The intermediate controllers <NUM> use the currently determined packet delay times from the last unicast delay querying cycle(s) to set a controllable delay of the end device control signal packets. That way, synchronicity between the end device controllers <NUM> may be established based on the content of the received unicast delay indicator signals for each of the intermediate controllers <NUM> individually.

In order to improve the stringency of the representation, various features were combined in one or more examples in the detailed description above. However, it should be clear in this case that the description above is only of an illustrative and in no way restrictive nature. It is used to cover all alternatives, modifications and equivalents of the various features and exemplary embodiments. Many other examples will be immediately and directly clear to a person skilled in the art on the basis of his technical knowledge in view of the description above.

Claim 1:
Multimedia distribution network (<NUM>) on board of a passenger aircraft (A), the network (<NUM>) comprising:
a first network node configured as a head controller (<NUM>);
a plurality of second network nodes configured as a plurality of intermediate controllers (<NUM>) connected to the first network node;
a plurality of third network nodes configured as a plurality of end device controllers (<NUM>), each connected to one of the plurality of second network nodes,
the head controller (<NUM>) being further configured to transmit a multicast stream (MC) of multimedia control signal packets for controlling the plurality of end device controllers (<NUM>) to the plurality of intermediate controllers (<NUM>), characterized in that the plurality of intermediate controllers (<NUM>) being further configured to periodically transmit unicast delay queries (DC) to the head controller (<NUM>), to process the received multimedia control signal packets and to distribute processed multimedia control signal packets to the end device controllers (<NUM>) with a controllable delay based on the content of unicast delay indicator signals sent by the head controller (<NUM>) to the plurality of intermediate controllers (<NUM>) in response to the unicast delay queries (DC).