M ETHOD AN D SYSTEM FOR I NTERNAL CREW COM M U N ICATION

Technical field

[0001] The present invention relates to methods and systems for providing internal crew communication in a vehicle for public passenger transport, in particular a respective railway vehicle.

Background

[0002] Not least for safety reasons, vehicles for public passenger transport such as trains are often equipped with an analog line based system for internal crew communication, in particular for cab to cab communication and internal communication between a driver and other crew members such as conductors. Accordingly, crew members may communicate with each other from fixed locations in the vehicle, in particular between driver cab(s) and suitably equipped other cabin(s) e.g. provided with fixed handset(s).

[0003] However, this only allows for initiating, responding and participating to the crew communication from fixed locations in the vehicle. Consequently, there may be delays in the communication, for example if a conductor is not in the vicinity of the fixed handsets. A driver who wants to reach a conductor may even be distracted from other important tasks as he may have to call several times.

[0004] Therefore, there is a need for improving existing solutions for crew communication.

Problem to be solved

[0005] It is an objective of the present invention to provide methods, systems and devices allowing for improved internal crew communication within for public passenger transport, in particular trains.

[0006] Said task is solved by the subject matter of the independent claims.

[0007] According to an embodiment of a system for internal crew communication in a vehicle for public passenger transport, in particular a respective railway vehicle, the system includes a local area network typically provided by the vehicle, a wireless interface connectable to the local area network and typically provided by the vehicle, a VoIP server connectable to the local area network and typically provided by the vehicle, an internal communication device provided at a fixed location in the vehicle, and an audio system connectable with the local area network and the internal communication device, and, in a connected state, configured to send an invite message referring to an internal crew communication requested by the internal communication device to the VoIP server, the audio system typically being provided by the vehicle. In the connected state, the VoIP server is configured to receive the invite message from the audio system, and forward a corresponding invite message referring to the internal crew communication to a mobile device connected with the VoIP server via the wireless interface, and to receive from the mobile device an invite message for initiating internal crew communication, and forward a corresponding invite message for initiating the internal crew communication to the audio system.

[0008] Accordingly, at least initiating of internal crew communication may be facilitated between drivers in the cab(s) and other crew members when the other crew members are provided with respective mobile device. Further, the crew members may initiate, respond and participate crew communications from anywhere in the vehicle, even within very short times, if the crew members so decide.

[0009] This may require only comparatively modest hardware and/or software changes for vehicles which are already equipped with an onboard public announcement system (OPAS) providing suitable audio hardware, or even a suitable audio system as well as the infrastructure for voice over IP (VoIP) communication with mobile devices as e.g. described in GB 2590379 A.

[0010] Further, conventional crew communication using the typically existing analog connections typically remains fully operable. For example, in case no mobile device is connected to the VoIP server, the VoIP server may simply refrain from forwarding invite messages at all.

[0011] The VoIP server is, in the connected state, i.e. when connected with the audio system and one or more mobile devices, configured to at least one of, typically several of, even more typically all of: - forward the received invite message for initiating the internal crew communication as corresponding invite message to the audio system and any other mobile device connected with the VoIP server;

- establish, for the respective internal crew communication, a VoIP connection with the audio system;

- establish, for the respective internal crew communication, a VoIP connection with the mobile device(s);

- receive, from the audio system, the number of internal communication devices attending the respective internal crew communication;

- bookkeeping, for the respective internal crew communication, a number of attending mobile devices (mobile devices attending the respective internal crew communication);

- sending a further corresponding invite message to a (typically any) mobile device that has dropped the respective internal crew communication, in particular if the respective internal crew communication is still in progress and/or unless a sum of the number of internal communication devices attending the respective internal crew communication number and the number of attending mobile communication devices is zero;

- sending yet a further corresponding invite message to the audio system if the number of internal communication devices attending the respective internal crew communication is zero and the number of attending mobile communication devices is greater than one;

- sending the number of mobile devices attending the respective internal crew communication to the audio system; and

- informing a connected, non-attending mobile device (connected mobile device not attending the respective internal crew communication) that an internal communication call is in progress.

[0012] Likewise, the audio system is, in the connected state, configured to at least one of, typically several of, even more typically all of: - forward an invite message received from the VoIP server as corresponding invite signal to the internal communication device;

- establish, for the respective internal crew communication, an audio connection between two (or more) internal communication devices;

- establish, for the respective internal crew communication, a VoIP connection with the VoIP server;

- convert an analog audio signal exchanged between two internal communication devices into RTP-packets;

- send the RTP-packets to the VoIP server;

- receive incoming RTP-packets from the VoIP server;

- convert the incoming RTP-packets into a further analog audio signal;

- broadcast the further audio signal to internal communication device attending the respective internal crew communication;

- bookkeeping, for the respective internal crew communication, a number of attending internal communication devices (currently attending internal communication devices / internal communication devices connected to the audio connection); and

- inform the VoIP server about the number of internal communication devices attending the respective internal crew communication.

[0013] The respective invite message may either refer to a request from an internal communication device for a respective internal crew communication or to a respective internal crew communication currently being held. The latter facilitate joining and rejoining of internal crew communications.

[0014] The mobile device may be a smart phone or a tablet computer.

[0015] Further, the mobile device may be a personal electronic device of a person, in particular an employee such as the conductor or another crew member. This typically means that the person has to log in to the mobile device prior to connecting to the VoIP server. As such the personal electronic device may also be provided by the employer, e.g. a railway company.

[0016] Accordingly, the mobile device may be a personal smart phone or a tablet computer.

[0017] The mobile device may be wirelessly connected to a wireless interface of the vehicle which is connected to the Vol P server, a wireless router of the vehicle which connected to the VoIP server, or any other device of the vehicle connected to the VoIP server and providing a wireless interface for communication with the mobile device. In other words, the mobile device may be (wirelessly) connected to a Wi-Fi network of the vehicle (which is different from the local area network of the vehicle but connected thereto).

[0018] Accordingly, connecting the mobile device to the server typically includes connecting the mobile device to and/or via the wireless interface or the wireless router of the vehicle, and/or the other device providing the wireless interface.

[0019] Further, connecting the mobile device to the server may include login/registration on/with the server, e.g. using a username and a password that may be provided by or via the app.

[0020] Typically, the mobile device is pre-registered as crew-member device at the VoIP server.

[0021] The wireless interface may include a (wireless) router and one or more wireless access points.

[0022] The VoIP server, the audio system, and the wireless interface (in particular the wireless access point(s) and/or the wireless router) are typically connected with each other via a local area network of the vehicle, in particular a local area network that is a wired data network and/or uses the Internet Protocol and/or Ethernet technology.

[0023] For example, the local area network may use coaxial cable, twisted pair links and/or fiber optic links in conjunction with switches as a shared medium for information transfer.

[0024] Accordingly, communication and/or transferring the VoIP message to the server may be facilitated. [0025] Typically, establishing the VoIP data connection between the mobile device and the audio system (and a controller thereof, respectively) may include establishing a first VoIP data connection between the mobile device and the VoIP server, and establishing a second VoIP data connection between the VoIP server and the audio system, typically after sending a respective connection request "SIP INVITE" and receiving a respective response message "SIP 200 OK".

[0026] More particular, the mobile device may initiate establishing the VoIP data connection with the audio system using the signaling protocol (SIP and SDP if desired) via the VoIP server by sending a call initiation request "SIP INVITE" to the VoIP server. Upon receiving the connection request from the mobile device, the VoIP server may send a connection request "SIP INVITE" to the audio system using the signaling protocol (SIP and SDP if desired). Upon receiving the connection request from the VoIP server, the audio system may send a response message "SIP 200 OK" to the VoIP server using the signaling protocol (SIP). Upon successfully receiving the response message "SIP 200 OK" from the audio system, the VoIP server may send a response message "SIP 200 OK" to the mobile device using the signaling protocol (SIP). This may be auto attended.

[0027] Upon successfully establishing the VoIP data connection between the mobile device and the audio system (upon successfully receiving the response message "SIP 200 OK" from the VoIP server), voice stream(s) may be exchanged via the VoIP server, typically using RTP/SRTP.

[0028] Exchange of voice stream(s) may be ended using the signaling protocol (SIP). This may also be initiated by the mobile device (app).

[0029] In particular, the connected mobile device or audio system may send an end message "SIP BYE" to the audio system/mobile device via the VoIP server.

[0030] More particular, the connected mobile device/audio system may send an end message "SIP BYE" to the VoIP server. Upon receiving the end message "SIP BYE" from the mobile device/audio system, the VoIP server may send an end message "SIP BYE" to the audio system/mobile device. Upon receiving the end message "SIP BYE" from the VoIP server, the audio system/mobile device may send a (further) response message "SIP 200 OK" to the VoIP server using the signaling protocol (SIP). Upon successfully receiving the response message "SIP 200 OK" from the audio system/mobile device, the VoIP server may send a (further) response message "SIP 200 OK" to the mobile device/audio system using the signaling protocol (SIP).

[0031] In this way, a particularly fast and/or efficient transferring the voice message as VoIP message with very low overhead only can be provided.

[0032] Typically, the mobile device(s) includes and/or has access to an app which is, when running on the mobile device, configured to at least one of, typically all of:

- for full duplex VoIP communication;

- to host a SIP user agent;

- register with the VoIP server;

- enquiring a number of mobile devices currently registered the VoIP server; and

- determining a SIP user agent identification based on the number of mobile devices currently registered the VoIP server.

[0033] The (running) app may (further) provide or facilitate one or more or even all of the following features/functionalities:

Public Address: Manual Public Announcement;

Play pre-recorded emergency/normal message;

Internal Communication: Full duplex VoIP communication, typically between a conductor using the mobile device and fixed driver's handset in the train cabs or between two mobile devices using full duplex communication using VoIP;

Passenger Communication: VoIP communication between conductor using a mobile device and passenger who operated Call For Aid (CFA) at a CFA device; and

View/Display existing alarms such as CFA, PEA (Passenger Emergency Alarm), EEH (Emergency Egress Handle).

[0034] The term "app" as used herein shall embrace the terms "web application" and "mobile application". [0035] Further, the mobile device typically includes a (non-volatile) storage storing the app.

[0036] The term "server" as used herein shall refer both to a computer program (software) and a device providing functionality for other programs or devices, typically called "clients", in particular to a respective device including the software for providing server functionality (for clients) in a network, in particular a network using the internet protocol suite, Transmission Control Protocol / Internet Protocol (TCP/IP) and/or User Datagram Protocol / Internet Protocol (UDP/IP). In the following a device providing server functionality in a network is also referred to as "host".

[0037] The typically used signaling protocols include the session initiation protocol (SIP) for initiating, maintaining, and terminating real-time sessions, in particular RFC 3261, more particular the secure SIP signaling protocol (SIPS), and the real-time transport protocol (RTP) such as RFC 3550, in particular the secure real-time transport protocol (SRTP) for transferring the VoIP message as respective data stream. Further, the signaling protocols may include the session description protocol (SDP) for describing session parameters and/or metadata referring to the VoIP message, in particular RFC 4566. Accordingly, transferring of the VoIP message from the mobile device to the audio system can be achieved with very low overhead and at most short time delay.

[0038] Alternatively, the signaling protocol may be based on or include other protocols such as H.323. However, these protocols typically require a larger overhead.

[0039] The data connection between the mobile device and the audio system is typically established via the VoIP server on the vehicle using the signaling protocols.

[0040] In particular, establishing the data connection between the mobile device and the audio system may include establishing a first (VoIP) data connection between the mobile device and the VoIP server using the signaling protocols, and establishing a second (VoIP) data connection between the VoIP server and the audio system. Typically, the VoIP server initiates establishing the second data connection with the audio system using the signaling protocol (after the first data connection is established).

[0041] Further, the VoIP server may be configured to maintain the VoIP data connection with the audio system and/or to terminate the VoIP data connection with the audio system. [0042] As such the VoIP server is typically configured to establish, maintain and/or terminate the second (VoIP) data connection typically forming a second part of the VoIP data connection.

[0043] The VoIP server may even be configured to establish (maintain and/or terminate) the VoIP data connection with the mobile device. However, the (first part of the) VoIP data connection between the mobile device and the VoIP server is typically established on request of (initialized by) the mobile device and an app running on the mobile device, respectively.

[0044] The VoIP server may e.g. be provided by one or more computer devices of a passenger comfort system of the vehicle or a Crew Communication Gateway (CCG) which acts as a SPOC (Single point of contact) for mobile devices to connect to a data network of the train and get the desired functionalities such as Public Address, play pre-recorded messages, internal communication, and/or passenger communication.

[0045] In these embodiments, the CCG may host the VoIP server to carry out the VoIP functionality and may employ SIP over RTP/SRTP.

[0046] Note that the VoIP server may also be implemented as a logical device, for example as part of a controller of the audio system.

[0047] Likewise, the audio system may be implemented as a logical device.

[0048] Typically, at least one of, typically several or even all of: the VoIP server, the audio system, the mobile device(s) and the app running on the mobile device(s), respectively, is configured to use at least one of, typically all of SIP, RTP, in particular SRTP, and SDP.

[0049] Further, at least one of, typically several or even all of: the VoIP server, the audio system, the mobile device(s) and the app running on the mobile device(s), respectively, are operable as a SIP-user agent. In some embodiments, even the internal communication device(s) are operable as respective SIP-user agents.

[0050] The data connection for the internal crew communication(s) typically includes a VoIP data connection between the mobile device(s) and the audio system via the VoIP server, and analog data connection(s) between the audio system and the internal communication device(s). [0051] Typically, the respective VoIP data connection is configured to use the real-time transport protocol (RTP), in particular the secure real-time transport protocol (SRTP) for transferring and/or exchanging voice messages as respective VoIP messages.

[0052] The VoIP server typically provides SIP-server functionality and VolP-server functionality. In the following the VoIP server is also referred to a server for short.

[0053] After establishing the data connection, voice streams may be exchanged between the mobile device(s) and/or the internal communication device(s).

[0054] The voice streams at the end of the mobile device(s) may include respective RTP- streams, in particular SRTP-streams.

[0055] Further, exchanging the voice stream(s) may include converting an analog audio signal, in particular an analog audio signal at the end of the internal communication device(s) into RTP-packets for the RTP-stream and adding the analog audio signal as RTP-packets to the RTP-stream, respectively, and vice versa, i.e. converting RTP-packets and RTP-stream, respectively, into analog audio signals to be broadcast to the internal communication device(s).

[0056] Converting the audio signals (analog to RTP and vice versa) referring to the spoken (live) internal crew communications is typically performed by a controller of the audio system or an audio converter of the audio system, for example a train amplifier of the audio system, but may also be done by individual amplifiers connected with the controller of the audio system and the internal communication devices.

[0057] Accordingly, the controller of the audio system is typically configured to perform Analog to Digital (AD) and Digital to Analog (DA) communication between VoIP Communication channel and an analog communication channel(s) which interface with the respective internal communication device (if not implemented with VolP-functionality).

[0058] According to an embodiment of a method for internal crew communications in a vehicle for public passenger transport, the vehicle including a local area network, a wireless interface connected to the local area network, a VoIP server connected to the local area network, an internal communication device provided at a fixed location in the vehicle, and an audio system connected with the local area network and the internal communication device, in particular a respective railway vehicle, the method includes listening, at the audio system, for an incoming internal crew communication request from the internal communication device, and, in response to receiving the incoming internal crew communication request, sending an invite message referring to the internal crew communication request to the VoIP server, and listening, at the VoIP server, for an invite message for initiating internal crew communication from a mobile device connected with the VoIP server via the wireless interface (and the local area network), and, in response to receiving the invite message, sending a corresponding invite message for initiating the internal crew communication to the audio system.

[0059] The method typically further includes listening, at the VoIP server, for the invite message from the audio system, and, in response to receiving the invite message from the audio system, sending a corresponding invite message referring to the internal crew communication to the mobile device.

[0060] Further, the method typically includes listening, at the audio system, for the invite message from the VoIP server, and, in response to receiving the invite message from the VoIP server, sending a corresponding typically analog signal to the internal communication device.

[0061] The incoming internal crew communication request and/or the corresponding signal is typically transmitted via a separate (digital) data connection different to an analog data connection for exchanging analog audio signals.

[0062] Typically, the method includes, at the VoIP server and in response to receiving the invite message from the mobile device, sending a corresponding invite message for initiating the internal crew communication to the audio system and any other mobile device (any other than the mobile from which the invite message is received) connected with the VoIP server.

[0063] The method typically further includes establishing and/or maintaining a respective internal crew communication in response to receiving, at the VoIP server, an acknowledging response message from another mobile device or an acknowledging response message from the audio system.

[0064] Establishing and/or maintaining the internal crew communication may include at least one of or even all of:converting an incoming analog audio signal into outgoing RTP- packets, typically by the audio system; - converting incoming RTP-packets into an outgoing analog audio signal , typically by the audio system; and

- using at least one of SIP, RTP, in particular SRTP, and SDP.

[0065] Prior to exchanging the voice stream(s) in an internal crew communication, data connection(s) may be established using a signaling protocol for initiating, maintaining, and terminating real-time sessions for voice applications, in particular the session initiation protocol, SIP, and/or the session description protocol, SDP, for describing session parameters and/or metadata referring to the voice stream(s).

[0066] In other words, the respective VolP-functionality is typically implemented via SIP and RTP, in particular using SIPS and SRTP, and may be supplemented by the session description protocol SDP, in particular RFC 4566.

[0067] Further, SIP Extension for Instant Messaging (RFC 3428 SIP) and/or RTP Profile for Audio and Video Conferences with Minimal Control (RFC 3551) may be used.

[0068] The VoIP server and the app may support different languages, and are typically configured for a specific language in these embodiments, for example a preselected language such as English. This facilitate communication.

[0069] Other embodiments include on one or more computer-readable storage media, and one or more computer programs recorded on the one or more computer-readable storage media or computer storage devices, and configured to perform the processes of the methods described herein.

[0070] In particular, a computer program and/or a (non-volatile) computer-readable storage medium may include instructions which, when executed by a one or more computing units (processors) of a system, in particular crew-internal communication system disposed in a public transport vehicle, cause the system to carry out the processes of the methods explained herein.

[0071] The above-described embodiments can be combined with each other in any way if not specified otherwise. Those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings. Brief description of the figures

[0072] The attached drawings illustrate embodiments and together with the description serve to explain the principles of the invention. The elements of the drawings are shown relative to each other and are not necessarily to scale.

[0073] The same reference numbers denote similar or even equal components. Arrows shown in the figures typically indicate flow of information and/or connections for exchanging information and data respectively.

[0074] FIG. 1A is a block diagram schematically illustrating a system for internal crew communications according to embodiments.

[0075] FIG. IB is a block diagram schematically illustrating a system for internal crew communications according to embodiments.

[0076] FIG. 2A schematically illustrates operation of the system for internal crew communications shown in FIG. IB according to an embodiment.

[0077] FIG. 2B schematically illustrates operation of the system for internal crew communications shown in FIG. IB according to an embodiment.

[0078] FIG. 2C illustrates a flow chart of a method for internal crew communications according to embodiments.

[0079] FIG. 2D illustrates a flow chart of a method for internal crew communications according to embodiments.

[0080] FIG. 3 illustrates a flow chart of a method for internal crew communications according to embodiments.

[0081] FIG. 4 illustrates a flow chart of a method for internal crew communications according to embodiments.

Detailed description

[0082] FIG. 1A is a block diagram schematically illustrating a system 100 and methods for internal crew communications. [0083] In the exemplary embodiment, system 100 includes a mobile device 11 and an exemplary railway vehicle (train) 101 providing a local area network 22, a wireless interface 23 connected to the local area network 22 and a stationary internal communication device 6 (provided at a fixed location in vehicle 101) for internal crew communication, for example an internal communication device 6 arranged in a driver's cabin of train 101. A VoIP server 4 and an audio system 5 (typically including or implemented as an audio system controller ASC) of train 101 are connected with each other via local area network 22 providing a digital data connection DDC. Further, audio system 5 and internal communication device 6 are connected with each other via an analog data connection ADC (analog data line(s)) for exchanging .

[0084] A mobile device 11 of a crew member such as a conductor may be connected with VoIP server 4 via wireless interface 23 and local area network 22.

[0085] In the illustrated connected state, mobile device 11 and an app running on mobile device 11, respectively, may, initiated by the crew member (conductor), may send an invite message I IVI 11_4 for initiating an internal crew communication, in the following also referred to as ICC for short, with another crew member, for example a driver, to server 4.

[0086] Upon receiving invite message IM11_4, server 4 may forward a corresponding invite message IM4_5 for initiating the internal crew communication to audio system 5.

[0087] Upon receiving the corresponding invite message IM4_5, audio system 5 may send (forward) a corresponding analog invite signal S56 such as a ringing signal to internal communication device 6.

[0088] If the other crew member (driver) accepts the invite, an ICC may be set up and carried out.

[0089] Alternatively, the other crew member (driver) may initiate the ICC.

[0090] For this purpose, an analog request R65 for internal crew communication may, initiated by the other crew member (driver), be send from internal communication device 6 to audio system 5.

[0091] Upon receiving request R65, audio system 5 may send (forward) a corresponding invite message IM5_4 to server 4. [0092] Upon receiving invite message IM5_4, server 4 may forward a corresponding invite message IM4_11 for initiating the internal crew communication to connected mobile device 11.

[0093] If the crew member (conductor) accepts the invite (using mobile device 6), a corresponding ICC may be set up and carried out.

[0094] FIG. IB is a block diagram schematically illustrating a system 200 and methods for internal crew communications.

[0095] System 200 is typically similar to system 100 explained above with respect to FIG. 1A. However, train 201 has two internal communication device 6, 7 provided at a respective fixed location. Further, two mobile devices 11, 12 are connected with VoIP server 4 of train 201. Train 201 may also have more than two internal communication device 6, 7 connected with audio system 5 via analog data connection ADC. Likewise, more than two mobile devices 11, 12 may be connected with VoIP server 4 of train 201.

[0096] Accordingly, ICCs may be initiated and held between several crew members.

[0097] In particular any of the mobile devices 11, 12 may send respective invite messages

I Mll_4, IM12_4 to server 4 for initiating ICC. Likewise, any of the internal communication devices 6, 7 may send a respective invite signals S56, S57 to audio system 5 for initiating ICC. This may be achieved via additional, typically digital data connections (not shown) each of which is arranged between audio system 5 and the respective internal communication device 6, 7, and is different to the respective analog data connection ADCanalog data connections ADCrequests R65, R75 and/or signals S56, S57.

[0098] For example, a handset may be used as internal communication device 6, 7, in a first setup. Alternatively, a desk microphone and desk loudspeaker may be used as internal communication device 6, 7, in a second setup. For the first setup, the crew member (driver) may, in response to receiving a respective invite signal S56, S57 from audio system 5, remove the handset and possibly also press a button to accept participating the requested ICC. Instead of pressing the button to accept participating the ICC, a cradle switch may be operated by the removal of the handset from the cradle. For the second setup, the crew member (driver) may press also press a respective button for this purpose. Alternatively, the analog audio signal A may, without any interaction of the crew member (driver), be broadcast through the desk loudspeaker. [0099] Upon receiving invite message IM5_4, server 4 may forward corresponding invite messages IM4_11 and IM4_12 to mobile device 11 and 12, respectively. Upon receiving invite message IM11_4, server 4 may forward a corresponding invite message IM4_5 to audio system 5 and a corresponding invite message IM4_12' to mobile device 12. Upon receiving invite message IM12_4, server 4 may forward a corresponding invite message IM4_5' to audio system 5 and a corresponding invite message IM4_11' to mobile device 11. This is explained in more detail below with regard to FIG. 2A to FIG. 2D.

[00100] Likewise, audio system 5, upon receiving the respective invite message IM4_5, IM4_5', may forward corresponding invite signals S56, S57 to both internal communication devices 6, 7, and upon receiving a respective request R65, R75 from one of internal communication devices 6, 7 forward the corresponding invite message IM5_4 to server 4 and a further invite signal (not shown) to the other internal communication device 7, 6.

[00101] In particular and as illustrated in Fig. 2A, upon receiving a respective request from one of internal communication devices, audio system 5 may forward a corresponding invite message IM5_4 to server, and upon receiving server 4 may, via wireless interface 23, forward corresponding invite messages IM4_11, IM4_12 to the connected mobile devices 11, 12.

[00102] Further, if mobile device 11 sends, via wireless interface 23, invite message IM11_4 to server 4, and upon receiving server 4 may, via the local area network, forward a corresponding invite message IM4_5 to audio system 5, and may, via wireless interface 23, forward a corresponding invite message IM4_12' to mobile device 12.

[00103] Likewise, mobile device 12 may send invite message IM12_4 as shown in FIG. IB and Fig. 2C. Upon receiving invite message IM12_4, server 4 may, via the local area network, forward a corresponding invite message IM4_5' to audio system 5, and may, via the local area network and wireless interface 23, forward a corresponding invite message IM4_11' to mobile device 11

[00104] FIG. 2D shows a flow chart of a method 1000 for internal crew communications. Method 1000 may in particular be used for initiating and establishing ICCs using a system 200 as explained above with regard to FIG. IB.

[00105] In a block 1100, an audio system (5 in FIG. IB) of a train or another vehicle for public passenger transport is listening for incoming internal crew communication requests R65, R75 from internal communication device(s) (6, 7 in FIG. IB). [00106] In a block 1200, a VoIP server (4 in FIG. IB) is listening for an invite message IM11_4, IM12_4 for initiating internal crew communication from mobile device 11, 12 which are connected with the VoIP server.

[00107] Blocks 1100, 1200 are typically carried out in parallel (substantially at the same time, i.e. within the same period of time, in particular during a journey, when boarding and deboarding and/or during a stay of the train).

[00108] Further, the VoIP server may, in a block 1300, listen, for an invite message IM5_4 from the audio system, and the audio system may, in a block 1400, listen for the invite message IM4_5, IM4_5' from the VoIP server.

[00109] Typically, blocks 1100, 1200, 1300, 1400 are carried out (substantially) in parallel and within the same period of time, respectively, for example during a journey, in particular as respective real time tasks running on the audio system 5 and the VoIP server 4.

[00110] Upon receiving an incoming internal crew communication request R65, R75, the audio system may send an invite message IM5_4 referring to the internal crew communication request R65, R75 to the VoIP server 4, in a block 1150.

[00111] Likewise, upon receiving an invite message IM11_4 or IM12_4, the VoIP server may send a corresponding invite message IM4_5 or IM4_5' for initiating the internal crew communication to the audio system, and a corresponding invite message to the other mobile device, i.e. a corresponding invite message IM4_12' to mobile device 12, if mobile device 11 has sent invite message IM11_4, and a corresponding invite message IM4_11' to mobile device 11 if mobile device 12 has sent invite message IM12_4, in a block 1250.

[00112] Further, the audio system may, in a block 1450, upon receiving the invite message IM4_5, IM4_5' from the VoIP server, send a corresponding signal S56, S57 to the internal communication device.

[00113] Likewise, the VoIP server may, upon receiving the invite message IM5_4 from the audio system, sending a corresponding invite message IM4_11, IM4_12 to the mobile devices.

[00114] FIG. 3 illustrates a method 2000 for internal crew communications according to embodiments. Method 2000 is typically similar to method 1000 but is more detailed with respect to VoIP call sequences (as function of time t). [00115] In the exemplary embodiment, two mobile devices 11, 12 (with exemplary SIP user agent identities 1001 and 1002, respectively) are connected with a VolP-server 4 of a train. Further, an audio system 5 (with exemplary SIP user agent identity 9003) of the train is connected with VolP-server 4 via a local area network of the train. Audio system 5 is, via analog data lines, connected with internal communication device (not shown) at a fixed train location, and represents the VoIP End Point for ICCs. The internal communication device may in particular be fixed handsets or the like.

[00116] Via mobile device 11 an invite message I Mll_4 is sent to server 4.

[00117] Upon acceptance, an RTP data connection for full duplex VoIP communication may be established between mobile devices 11 and server 4.

[00118] Thereafter, VoIP server 4 may send corresponding invite messages IM4_5, IM4_12 to audio system 5 and the other mobile device 12.

[00119] In the illustrated embodiment, crew member(s) at the fixed train location accept the invitation and an ICC is established. Different thereto, the user of the other mobile device 12 does not accepts the invitation.

[00120] If the (bookkeeped) number of participating devices (participants) becomes 1, the ICC may be terminated by server 4.

[00121] FIG. 4 illustrates a method 3000 for internal crew communications according to embodiments. Method 3000 is typically similar to method 2000 and method 1000 but is more detailed with respect to VoIP call sequences (as function of time t) as method 1000.

[00122] In the exemplary embodiment of FIG. 4, ICC is initiated via a not shown internal communication device. Accordingly, an invite message IM5_4 is send from audio system 5 to server 4 which forwards corresponding invite message IM4_11, IM4_12 to the two connected mobile devices 11, 12.

[00123] As shown in FIG. 4 for mobile device 11, participants of the ICC may leave and rejoin the ICC if desired by the respective crew member.

[00124] Leaving the ICC is initiated by sending a "BYE" SIP-message to server 4.

[00125] After leaving, VolP-server 4 may, while the ICC is continued between the internal communication device and mobile device 12 via server 4 and audio system 5 which exchange RTP-packets for this purpose (as indicated by the respective arrow), send invite SIP-messages to mobile device 11. This allows for mobile device 11 to rejoin the ICC by responding a "200 OK" SIP-message to server 4, which in turn may acknowledge the received "200 OK" SIP- message by sending an "ACK" SIP-message to mobile device 11 to establish a full duplex VoIP communication with mobile device 11 again.

[00126] Accordingly, ICCs can be flexibly established and handled in vehicles for public passenger transport.

[00127] Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof.

List of reference numbers

11, 12 mobile device

4 host / server

5 audio system

6, 7 internal communication device

22 local area network

23 wireless interface typically comprising a (wireless) router and wireless access point(s)

100, 200 system

101, 201 vehicle, train

1000 -3000 method steps

A analog audio signal (during internal crew communication)

ADC analog data connection

ASC audio system controller

DDC digital data connection (using TCP/IP) / VoIP data connection for

RTP/SRTP streams

IMx_y (corresponding SIP) invite message send from device x to device y

R65, R75 (analog) request for internal crew communication (ICC) from internal communication device 6, 7 to audio system 5

RTP Realtime Transmission Protocol

556 invite signal from audio system 5 to internal communication device 6 indicating a request for ICC

557 invite signal from audio system 5 to internal communication device 7 indicating a request for ICC Table of SIP command used in figures