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WO2008050110A1 - Systèmes de communication - Google Patents

Systèmes de communication Download PDF

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Publication number
WO2008050110A1
WO2008050110A1 PCT/GB2007/004039 GB2007004039W WO2008050110A1 WO 2008050110 A1 WO2008050110 A1 WO 2008050110A1 GB 2007004039 W GB2007004039 W GB 2007004039W WO 2008050110 A1 WO2008050110 A1 WO 2008050110A1
Authority
WO
WIPO (PCT)
Prior art keywords
data
packet data
packet
terminal
mode
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/GB2007/004039
Other languages
English (en)
Inventor
Mark Wentworth Rayne
Andrew Iain Nicol
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sepura Ltd
Original Assignee
Sepura Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sepura Ltd filed Critical Sepura Ltd
Priority to EP07824287A priority Critical patent/EP2087750A1/fr
Publication of WO2008050110A1 publication Critical patent/WO2008050110A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/18—Information format or content conversion, e.g. adaptation by the network of the transmitted or received information for the purpose of wireless delivery to users or terminals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W92/00—Interfaces specially adapted for wireless communication networks
    • H04W92/16—Interfaces between hierarchically similar devices
    • H04W92/18—Interfaces between hierarchically similar devices between terminal devices
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W76/00—Connection management
    • H04W76/10—Connection setup
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/02—Terminal devices
    • H04W88/04—Terminal devices adapted for relaying to or from another terminal or user
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/16—Gateway arrangements

Definitions

  • the present invention relates to mobile communications systems and in particular to the transmission of packet data in mobile communications systems .
  • TETRA TErrestrial Trunked RAdio
  • V+D voice and data
  • DMO TETRA direct mode operation
  • a method of operating a mobile communications system in which mobile communications terminals can transmit to each other independently of the fixed network infrastructure, the method comprising: transmitting packet data from or to a mobile terminal that is operating independently of the fixed network infrastructure by sending that data through a non-packet data communications channel that is Supported for transmissions independent of the fixed network infrastructure.
  • a mobile communications terminal of a communications system comprising: means for transmitting to another mobile terminal independently of the fixed network infrastructure of the communications system; and means for, when the mobile terminal is operating independently of the fixed network infrastructure, transmitting packet data or receiving packet data by sending that data through a non-packet data communications channel that is supported for transmissions independent of the fixed network infrastructure .
  • packet data is transmitted by or to direct mode operating terminals (units) using existing communications protocols supported in direct mode operation, by sending the packet data over the existing direct mode communications channels.
  • the packet data is transmitted (or received) by tunnelling the packet data over an existing (already supported) direct mode communications channel or channels (using existing direct mode communications protocols and already specified and supported communications messages or data bursts) .
  • tunneling is intended, as is known in the art, the concept of embedding or placing the packet data inside another (the non-packet data) communications protocol (communications message and/or data burst) .
  • the packet data is embedded in the user or information part of the communications protocol (such as an SDS message) and/or sent via a (non-packet data) circuit mode connection (data call) .
  • This can be used to allow, for example, packet data transmission to be extended to direct mode operating terminals, but without the need to specify or support a specific packet data protocol for direct mode operation.
  • the packet data can be any suitable such data, such as, e.g., IP data.
  • the terminal can preferably both send and receive packet data in this way. Preferably the terminal can send and receive data consecutively or concurrently, as desired.
  • the communications channel (protocol) that the packet data is sent (tunnelled) over can be any suitable such channel (protocol) that is supported for a direct mode operating communications terminal .
  • a TETRA system for example, it could comprise, and preferably does comprise, using a circuit mode connection (e.g. a circuit mode data call) and/or one or more SDS messages (both of which are already supported for TETRA direct mode operation) to transmit the packet data.
  • the packet data is transmitted by using a circuit mode call which is set up to transmit data.
  • a method of operating a mobile communications system in which mobile communications terminals can transmit to each other independently of the fixed network infrastructure comprising: transmitting packet data to or from a mobile terminal that is operating independently of the fixed network infrastructure using a circuit mode call.
  • a mobile communications terminal of a communications system comprising: means for, when the mobile terminal is operating independently of the fixed network infrastructure, transmitting or receiving packet data using a circuit mode call .
  • the packet data is sent (tunnelled) using a circuit mode call
  • any suitable and desired data exchange protocol can be used.
  • the protocol includes acknowledgement and repeat mechanisms, numbering of data blocks and windowing, and/or flow-control mechanisms . Suitable such protocols would include PPP, X-modem, Z-modem, etc.
  • the protocol is preferably transparent (as the higher stack layers can ensure order and content are preserved) .
  • forward data protection is used (i.e. extra data is embedded to help recovery at the receiving end) . This may help the reliability of the data transmission.
  • the packet data is transmitted using a short data message (by embedding it in a short data message) , such as a text message, such as, and preferably, in a TETRA system, using the TETRA SDS (short data service) protocol .
  • a short data message such as a text message, such as, and preferably, in a TETRA system, using the TETRA SDS (short data service) protocol .
  • a method of operating a mobile communications system in which mobile communications terminals can transmit to each other independently of the fixed network infrastructure, the method comprising: transmitting packet data to or from a mobile terminal that is operating independently of the fixed network infrastructure using a short data message.
  • a mobile communications terminal of a communications system comprising: means for, when the mobile terminal is operating independently of the fixed network infrastructure, transmitting or receiving packet data using a short data message.
  • the short data messages preferably carry an appropriate indication, such as an appropriate protocol identifier (PID) in TETRA, indicating that they carry packet data.
  • PID protocol identifier
  • the SDS messages may also and preferably do carry sequence numbers to allow the packet data to be reassembled in the correct order.
  • SDS messages to carry the packet data may be particularly advantageous, because it is a supported and reliable communications protocol and, e.g., would allow multiple terminals to transmit packet data to, e.g., a gateway, over a shared transmission channel .
  • a given packet data transmission could use a combination of communications protocols, such as a mixture of circuit mode calls and SDS messages .
  • the choice of medium could, e.g., be made by configuration, or dynamically (in use) . For example, some data of a transmission , could be sent using one medium and then the transmission continued using a different medium.
  • the (packet) data transmission uses two different communications channels (protocols) , such as and preferably, a circuit mode call and short data (e.g. SDS) messages.
  • a given terminal could, e.g., send packet data using two different communications channels (protocols) or could receive packet data using two different communications channels (protocols) or both.
  • one protocol (channel) is used to transmit data in one direction, and the other protocol (channel) is used for transmissions (e.g. signalling) in the other direction.
  • the terminal will send (transmit) packet data using one communications channel (protocol) and receive (packet) data via (using) another (different) communications channel (protocol) .
  • a circuit mode connection may be used to send data in one direction, with short messages being used in the other direction, e.g., to carry data at a lower rate, and/or to send back (packet) acknowledgements of the data being transmitted by the circuit mode call.
  • a preferred embodiment of the present invention comprises setting up a circuit mode connection (call) to perform a data, e.g., a file, transfer to or from the communications terminal, and then using short messages to send back packet acknowledgements, and/or to send data (in the other direction) at a lower rate.
  • a data e.g., a file
  • short messages e.g., a file
  • SDS short
  • the recipient prefferably to return acknowledgements, preferably via a short data message or messages, of packet data that it receives.
  • acknowledgements preferably via a short data message or messages
  • an acknowledgement or acknowledgements of packet data that is received are returned . to the sender.
  • packet data block acknowledgements are sent using a stealing channel, preferably using the U-plane stealing channel (in a
  • TETRA system This would allow a fast switching method for packet data acknowledgements .
  • this is done by inserting (i.e. not replacing user data) a MAC-U-SIGNAL PDU (Protocol Data Unit) , which is used, for example, and preferably, to allocate a timeslot (or multiple timeslots) for the receiving party to transmit a response, and in which the transmitting party pauses transmission.
  • MAC-U-SIGNAL PDU Protocol Data Unit
  • There are spare MAC-U-SIGNAL types which are reserved for proprietary use in TETRA and which could be used for this purpose.
  • the packet data that is transmitted or received by the mobile terminal will have a destination or source, respectively. This could be, for example, another direct mode operating terminal such that, for example, and preferably, two DMO terminals can exchange packet data with each other by sending
  • the packet data is transmitted (via the non-packet data communications channel) to or from another mobile unit (terminal) of the communications system (and preferably to or from another mobile terminal that is operating independently of the fixed network infrastructure (a direct mode terminal) ) .
  • the communication is between the mobile terminal and a device, such as, and preferably, a gateway, that has the ability to convert the packet data transmission between the protocol used to transmit it to or from the mobile terminal and another communications protocol, such as, and preferably, a packet data communications protocol.
  • the packet data is transmitted (via the non-packet data communications channel) to (or from) a device, preferably a gateway device, which device preferably can and preferably does, convert the packet data transmission between the protocol used to transmit it to or from the mobile terminal and another communications protocol, such as, and preferably, a packet data communications protocol.
  • a gateway device which device preferably can and preferably does, convert the packet data transmission between the protocol used to transmit it to or from the mobile terminal and another communications protocol, such as, and preferably, a packet data communications protocol.
  • the (gateway) device connects to a computer network, such as, and preferably, the Internet and/or an
  • Intranet It preferably does so directly. This could then allow, e.g., direct mode operating terminals to connect (e.g. directly) to the Internet without going through the trunked voice and data network, and, e.g., accordingly provide a mechanism for extending direct mode operation packet data transmission to the interior of buildings .
  • the data transmission is to or from a device (a gateway device) that can connect, and that preferably ( is connected, to a computer network independently of (and without the need to connect via) the communications system fixed infrastructure.
  • the computer network is preferably the Internet and/or an Intranet. It is believed that such protocol conversion and gateway arrangements may be new and advantageous in their own right .
  • an apparatus for use in a communications system comprising: means for converting a packet data transmission sent using a non-packet data signalling protocol to a transmission to be sent using a packet data signalling protocol and/or vice-versa.
  • a method of operating a communications system comprising: converting a packet data transmission sent using a non-packet data signalling protocol to a transmission to be sent using a packet data signalling protocol and/or vice-versa.
  • the apparatus or method comprises means for or a step of converting a packet data transmission sent using a non-packet data signalling protocol independently of any fixed communications system infrastructure to a packet data communication to be sent via a computer network, such as, and preferably, the Internet and/or an Intranet (and vice-versa) .
  • the communications terminal is preferably a mobile communications system terminal or unit, preferably a TETRA terminal operating in direct mode, and the computer network is preferably the Internet and/or an Intranet.
  • the device with which the direct mode terminal is in communication could comprise, e.g., a computer or device coupled to a computer, which computer may then, for example, relay the packet data on to the
  • Such an arrangement could and preferably does comprise, e.g., a PC connected to the Internet and/or to a private network (e.g. an
  • Intranet by a LAN or wireless LAN.
  • Such an arrangement could, e.g., effectively act as a direct mode to wireless LAN packet data gateway that could then be used indoors, and, e.g., provide a means of extending (e.g. TETRA) packet data coverage to the interior of buildings .
  • the device with which the direct mode terminal is in communication comprises a gateway that can, for example, and preferably, establish a packet data connection with or via the communications system fixed infrastructure (such as, in the case of TETRA, a TETRA V+D network) .
  • the communications system fixed infrastructure such as, in the case of TETRA, a TETRA V+D network
  • a gateway can, for example, and preferably, establish a packet data connection with or via the communications system fixed infrastructure (such as, in the case of TETRA, a TETRA V+D network) .
  • the communications system fixed infrastructure such as, in the case of TETRA, a TETRA V+D network
  • the gateway could, in effect, and preferably does act as a converter between DMO circuit mode data and/or DMO SDS messages and the V+D packet data protocol, thereby allowing packet data to be tunnelled through a DMO circuit mode data traffic channel or SDS messages to the V+D network via the "packet data" ' gateway.
  • a gateway apparatus for use in a TETRA communications system comprising: means for converting packet data into SDS messages and/or circuit mode data for transmission in direct mode operation and/or vice-versa.
  • a method of operating a TETRA communications system comprising: converting packet data into SDS messages and/or circuit mode data for transmission in direct mode operation and/or vice-versa.
  • the communication is with and the system or method further comprises a gateway device that can convert the received non-packet data protocol communication (e.g. circuit mode data or short data service) to packet data for onward transmission and vice-versa.
  • the onward transmission could be and preferably is, e.g., directly onto a communications network (e.g. a TETRA V+D network) , and/or via a computer interface (e.g. RS732 or USB or Bluetooth) to an application connected to the computer or any network supported by the computer, e.g., by Ethernet cable, dial-up MODEM, broadband, Wi-FI, GSM-GPRS, 3G or Bluetooth, etc..
  • a communications network e.g. a TETRA V+D network
  • a computer interface e.g. RS732 or USB or Bluetooth
  • the direct mode operating terminal there could be direct communication between the direct mode operating terminal, and the, e.g., gateway, or such communication could be via a repeater or repeaters, etc..
  • the repeater preferably has appropriate addressing and/or store and forward functions (e.g. for SDS messages) to enable it to pass on the packet data appropriately, and/or to, e.g., allow its buffer, etc., the data if a gateway, etc., is busy or otherwise unavailable.
  • a "packet data" gateway device could, for example, comprise two separate radio transceiver units, one for communicating with the direct mode operating terminals, and one for communicating on the fixed network (V+D) side, or a single transceiver that can switch between the two could be used.
  • the, e.g., gateway is preferably configured to align the timing of these transmissions appropriately.
  • the V+D and DMO TDMA (time division multiple access) structures are preferably aligned so that timeslot 1 in the DMO transmission is delayed by 1 timeslot relative to the V+D uplink slot allocated as the packet data channel.
  • Such timing alignment can be achieved, e.g., by adjusting the timing of the DMO channel as soon as the packet mode gateway is assigned to a packet data channel, for example using the timing adjustment signalling that is specified for voice calls through TETRA gateways.
  • SDS messages are used, the direct mode terminal can discover the "packet-data" gateway's timing from the gateway's presence signals.
  • the gateway,- etc. preferably can identify them as carrying packet data and then unpack the data, so as to allow it to be "converted" to the packet data protocol.
  • the gateway may, and preferably does, include, for example, a data buffer to allow it to • buffer the packet data, to facilitate the conversion process .
  • Such "presence” broadcasts preferably include, for example, information or indications relating to one or more or all of:
  • gateway present gateway supports packet data in SOS messages, gateway supports packet data in circuit mode calls, gateway has spare PDP contexts, gateway has spare traffic capacity, etc.
  • the, e.g., gateway can preferably establish this context, e.g., on a requesting terminal's behalf.
  • the call set-up e.g. circuit mode data call set-up
  • the gateway can preferably maintain an association between the packet data protocol (PDP) context and the terminal in question, so that, for example, incoming packet data can be linked to the correct terminal.
  • PDP packet data protocol
  • the PDP context link is retained after the data transmission is finished, so that it can be used again in the future for the terminal in question.
  • a set of such associations could be maintained, e.g., on a first-in, first out, priority-based or some other basis .
  • the context may be deactivated as soon as the circuit mode data call is terminated, although it is preferred to allow the context to time out or to be able to be explicitly closed (which may, e.g., involve flushing out of any queued data and reporting back) .
  • the context is preferably deactivated a predetermined, short, time period (e.g. 5 minutes) after the direct mode terminal stops communicating.
  • the contexts may be de-activated on the basis of the longest idle period when all the contexts are used up, or when there is only a small number of contexts remaining free (so that the gateway can attempt to advertise free context capacity rather than reserving capacity for idle contexts) .
  • the terminal operating in- direct mode can and preferably does present a packet data interface to the (client) packet data applications running on the terminal (even though, as discussed above, it may not actually transmit that data using a true packet data protocol) .
  • the present invention has been described above with particular reference to packet data transmissions from a direct mode operating terminal to a given destination, it would also or instead be possible for the invention to be applied, analogously, to the reverse process of packet data that is to be transmitted to the direct mode operating terminal.
  • incoming packet data would, e.g., be converted by the, e.g., gateway from a packet data protocol to a circuit mode data call or SDS messages and then transmitted accordingly to the direct mode terminal .
  • the present invention also extends to the reverse processes of transmitting packet data to a terminal using the techniques described herein. It will be appreciated that in a preferred embodiment, and according to a further aspect of the present invention, the present invention provides a method of transmitting packet data in a mobile communications system comprising:
  • a DM-MS Direct mode mobile station
  • a DM-MS application deciding it wants to exchange packet data with a V+D (voice+data) connected data service
  • the DM-MS requesting a circuit-mode call set up for packet data
  • a packet-mode gateway negotiating PDP (Packet data protocol) context activation with the V+D network, and informing the DM-MS that the call setup is successful
  • the DM-MS commencing sending circuit-mode data to the packet-mode gateway
  • the packet-mode gateway buffering the circuit-mode data and locating the first complete data packet
  • the packet-mode gateway asking the V+D network for permission to start transmitting the data packets, and getting allocated to a packet data channel
  • the packet-mode gateway sending timing adjustment messages to the DMO (direct mode operation) channel to align the DMO timing to the allocated packet data channel ; i) the packet mode gateway starting transmitting
  • the present invention provides a method of transmitting packet data in a mobile communications system comprising:
  • the communications terminal in the present invention can take any suitable or desired form. It should be a mobile terminal (mobile station) of a mobile communications system.
  • the mobile station may, e.g., be portable or, e.g., vehicle mounted, etc., as is known in the art.
  • the communications system of the present invention can be any suitable such system.
  • the present invention is particularly applicable to mobile communication systems, such as the TETRA system.
  • the present invention also extends to a communications terminal and to a method of operating a communications terminal of a mobile communications system, and to a mobile communications system and a method of operating a mobile communications system, that is in accordance with and/or that can be operated in accordance with, the present invention.
  • the present invention also extends to a mobile communications system comprising one or more mobile communications terminals that are in accordance with the present invention.
  • the communications system preferably comprises, as discussed above, a gateway apparatus or device to which packet data may be transmitted by a (and preferably each) mobile terminal when the terminal is operating independently of the fixed network infrastructure of the communications system by sending that data through a non-packet data communications channel that is supported for transmissions independent of the fixed network infrastructure, and/or from which packet data may be transmitted to a (and preferably each) mobile terminal , when the terminal is operating independently of the fixed network infrastructure of the communications system by sending that data through a non-packet data communications channel that is supported for transmissions independent of the fixed network infrastructure, and which gateway apparatus or device can convert or translate the packet data transmission between the protocol used to transmit it to or from the mobile terminal and another communications protocol.
  • the gateway apparatus or device preferably comprises, as discussed above, means for connecting to a computer network independently of the communications system's fixed network infrastructure, and/or means for establishing a packet data connection with or via the communications system's fixed infrastructure.
  • the mobile communications system is preferably a TETRA system.
  • TETRA TETRA system
  • all of the aspects and embodiments of the present invention described herein can and preferably do include, as appropriate, any one or more or all of the preferred and optional features of the invention described herein.
  • the methods in accordance with the present invention may be implemented at least partially using software e.g. computer programs. It will thus be seen that when viewed from further aspects the present invention provides computer software specifically adapted to carry out the method or a method herein described when installed on data processing means, a computer program element comprising computer software code portions for performing the method or a method herein described when the program element is run on data processing means, and a computer program comprising code means adapted to perform all the steps of a ' method or of the methods herein described when the program is run on a data-processing system.
  • software specifically adapted to carry out the method or a method herein described when installed on data processing means
  • a computer program element comprising computer software code portions for performing the method or a method herein described when the program element is run on data processing means
  • a computer program comprising code means adapted to perform all the steps of a ' method or of the methods herein described when the program is run on a data-processing system.
  • the invention also extends to a computer software carrier comprising such software which when used to operate a communications system or terminal comprising data processing means causes in conjunction with said data processing means said system or terminal to carry out the steps of the method of. the present invention.
  • a computer software carrier could be a physical storage medium such as a ROM chip, CD ROM or disk, or could be a signal such as an electronic signal over wires, an optical signal or a radio signal such as to a satellite or the like.
  • the present invention provides computer software and such software installed on a computer software carrier for carrying out at least one of the steps of the methods set out herein.
  • the present invention may accordingly suitably be embodied as "a computer program product for use with a computer system.
  • Such an implementation may comprise a series of computer readable instructions either fixed on a tangible medium, such as a computer readable medium, for example, diskette, CD-ROM, ROM, or hard disk, or transmittable to a computer system, via a modem or other interface device, over either a tangible medium, including but not limited to optical or analogue communications lines, or intangibly using wireless techniques, including but not limited to microwave, infrared or other transmission techniques .
  • the series of computer readable instructions embodies all or part of the functionality previously described herein.
  • Such computer readable instructions can be written in a number of programming languages for use with many computer architectures or operating systems. Further, such instructions may be stored using any memory technology, present or future, including but not limited to, semiconductor, magnetic, or optical, or transmitted using any communications technology, present or future, including but not limited to optical, infrared, or microwave. It is contemplated that such a computer program product may be distributed as a removable medium with accompanying printed or electronic documentation, for example, shrink-wrapped software, pre-loaded with a computer system, for example, on a system ROM or fixed disk, or distributed from a server or electronic bulletin board over a network, for example, the Internet or .World Wide Web .
  • Figure 1 shows schematically the use of a. packet mode gateway
  • Figures 2 and 3 show alternative embodiments of a packet mode gateway
  • Figure 4 shows a timing diagram for the embodiment of Figure 3.
  • the preferred embodiments of the invention will be described with particular reference to a TETRA. mobile communications system.
  • TETRA Term Evolution
  • the present invention is particularly applicable to TETRA mobile communications systems, as will be appreciated by those skilled in the art, it is not exclusive to those systems and can be applied to other mobile communications systems and communications systems equally.
  • Figure 1 illustrates the use of a packet mode gateway.
  • a fixed data service 2 e.g. a police database of stolen vehicles
  • V+D network 1 using packet data.
  • TETRA terminals 4 and 5
  • Radio equipment 6 acts as a "packet mode" gateway that is able to operate both in TETRA V+D mode and TETRA DMO, either simultaneously, or quasi-simultaneousIy .
  • a TETRA terminal 7 may set up a circuit mode data call with the packet mode gateway 6, and the packet mode gateway establishes a packet data protocol (PDP) context with the TETRA V+D network. Then when the TETRA DMO terminal 7 sends data packets to the packet mode gateway
  • PDP packet data protocol
  • the packet mode gateway sends the data packet on to the database 1 via the TETRA V+D infrastructure using TETRA packet data protocol (and vice versa) .
  • terminal 7 can send the data packets to gateway 6 inside specially labelled SDS messages .
  • This provides a method of extending packet data coverage to black spots in the TETRA V+D coverage.
  • FIG. 2 shows one embodiment of how packet mode gateway 6 may be constructed.
  • the gateway 6 has two separate radio transceiver units .
  • radio transceiver 21 operates on a TETRA direct mode net, communicating with TETRA DMO terminals using DMO frequencies and protocols 23.
  • Radio transceiver 22 operates on a TETRA V+D network, communicating with the TETRA V+D network (and thus with various TETRA services, including data services 2) using TETRA V+D frequencies and protocols.24.
  • the gateway arrangement illustrated in figure 2 may further include, e.g., filters or use increased the physical separation between the two antennas 29 and 30 to help reduce the possibility of receiver blocking, as is known in the art.
  • Radio transceiver 21 can exchange data with TETRA DMO terminals using circuit mode data on a channel dedicated to exchange of data between two terminals (i.e. a "circuit"). It can also exchange SDS messages with terminals . When exchanging data with a DMO terminal (or
  • a data exchange protocol 25 is used that allows blocks of data to be delivered reliably.
  • This protocol includes acknowledgement and repeat mechanisms and numbering of data blocks and windowing mechanisms. Suitable examples of such a protocol include PPP, X Modem, Z-Modem etc.
  • the protocol used is designed to cope efficiently with the type of reliability problems encountered in mobile radio links and operates over a half-duplex link, where the data transmitter has to ' stop transmitting and switch to receive mode from time to time to receive acknowledgement messages from the data receiver.
  • the protocol also provides flow control, so that the flow of circuit mode data can be halted if required to avoid buffer overflow in the packet data gateway 6.
  • the application generating data in the DM-MS (e.g. terminal 7 in figure 1) would generate data packets (e.g. IP packets) .
  • the DM-MS terminal 7 would then collect the IP data packets and send them through the circuit mode channel to the gateway 6 using the circuit mode data exchange protocol.
  • the data packets can be sent in SDS messages .
  • the DM-MS terminal 7 data exchange does not need to take particular account of the data packet boundaries and can send fixed length blocks of data, irrespective of the packet data boundaries. (Alternatively the circuit-mode data blocks may be aligned with packet boundaries, and this may reduce the time delay required to exchange end-to-end packet data acknowledgements.)
  • the receiving packet-mode gateway 6 then assembles the incoming blocks of data in their correct sequence (using the circuit-mode data exchange protocol 25) and stor.es them in a data buffer 27 in the gateway 6 in the correct sequence.
  • the circuit-mode protocol module 25 then informs the V+D transceiver's packet data protocol module 26 via signalling inter-connection 29, that data is now available for transmission.
  • Packet data protocol module 26 now examines the contents of data buffer 27, and locates the packet data protocol headers (e.g. IP, TCP or UDP headers) . Then it extracts successive data packets and transmits them to the TETRA V+D network using the TETRA packet data protocol on a shared, radio channel (or packet data channel) that may also be used by other packet data users, as is known in TETRA.
  • packet data protocol headers e.g. IP, TCP or UDP headers
  • a terminal sending packet data must first establish a PDP (packet data protocol) context by negotiation with the TETRA V+D network. Therefore when the DM MS terminal 7 first decides that it wishes to exchange packet data through the gateway 6, it may request the gateway 6 to create a PDP context .on its behalf.
  • the request includes relevant information such as is described in the primitives in EN 300 392-2 clause 28 for the requesting PDP context activation by an application above the SNDCP layer.
  • the request also includes the DM-MS's terminal 7 TETRA address so that the packet-mode gateway 6 can link incoming packet data to the correct DM-MS terminal 7 (however this is not necessary if the lifetime of the PDP context is limited to the lifetime of a DMO circuit mode data call) .
  • Some new signalling could be defined between the DM-MS terminal and the packet-mode gateway to allow the DM-MS to establish a "proxy" PDP context in the gateway.
  • the packet mode gateway 6 could activate a PDP context automatically then the ' DM-MS requests a circuit mode call setup or starts sending data.
  • the packet-mode gateway 6 is able to signal to advertise its ability to act as a packet mode gateway to nearby DM-MSs .
  • the packet mode gateway retains the PDP context (remembering the TETRA address of the applicable DM-MS) for future use by the DM-MS.
  • TETRA V+D supports the existence of up to fourteen co-existing PDP contexts, so the packet data gateway 6 maintains PDP contexts for up to fourteen different DM-MSs at any one time. If a fifteenth DM-MS requests a PDP context, the packet data gateway 6 can refuse the fifteenth request or can erase the oldest or the least recently used PDP context, etc., as desired. Some kind of priority mechanism could also be used if desired.
  • the packet mode gateway 6 can immediately and automatically request a packet data channel from the V+D network, using standard TETRA V+D packet data protocol (as described in clause 28 of EN 300 392-2) .
  • the packet mode gateway 6 waits until it detects that it has one or more complete data packets in its ' buffer 27 and then requests a packet data channel (in line with the TETRA packet data protocol, where the SNDCP layer waits until it receives a first data packet before requesting permission to start transmitting data packets) .
  • the packet-mode gateway 6 can reject the circuit mode call request or SDS message, or can attempt to set up the PDP context immediately and automatically.
  • circuit mode data call set-up signalling when the call is required for packet data operation. This would permit the packet-mode gateway 6 to operate in alternative modes (e.g. to act as a circuit-mode voice call gateway as well) .
  • the data service 2 connected to the V+D network 1 it will also be possible for the data service 2 connected to the V+D network 1 to send packet data to the DM-MS terminal 7, either spontaneously, or in response to packet data received from the DM-MS terminal 7.
  • These could be IP protocol acknowledgements, or application level data.
  • the data service 2 linked to the V+D network 1 does not need to know the DM-MS ' s 7 TETRA address or the packet-mode gateway's TETRA address because the V+D network's SNDCP entity stores the cross reference between the DM-MS . application' s IP address and the packet mode gateway's address and PDP context number.
  • the packet-mode gateway 6 thus determines the DM-MS ' s TETRA address from the data stored with the relevant PDP context and then stores the incoming data in a buffer dedicated to storing data for the correct destination DM-MS terminal 7.
  • the packet data gateway 6 can commence transmitting the data packet (s) to the DM-MS on its next DMO transmit opportunity.
  • the circuit-mode data transmission protocol preferably supports sending circuit-mode data in both directions in alternate half-duplex transmissions along with transmitting acknowledgments for the data travelling in the opposite direction to facilitate this .
  • the packet mode gateway can attempt to send SDS messages to the relevant DM-MS at the next available opportunity on the DMO channel .
  • the packet-mode gateway 6 may attempt to setup a circuit-mode data call with the appropriate DM-MS terminal 7.
  • the DM-MS terminal 7 can be configured to recognise that a circuit-mode data call setup received from the gateway 6 must be for the purposes of exchanging packet data, or, for example, the call setup could indicate that the call is for the purposes of exchanging packet data, so that the DM-MS terminal 7 can use the correct protocol to handle the incoming data and can route it to its packet data applications.
  • the packet mode gateway 6 may continue to receive and buffer the incoming data.
  • the packet data gateway 6 can stop the flow to the particular PDP context avoid buffer overflow when required, by deactivating the affected PDP context.
  • the PDP context is allowed to time out once the circuit-mode data call is terminated. This is also the case with respect to migration from one packet-data gateway to another as it can avoid the complication of there being activated PDP contexts for a single IP address on more than one packet-mode gateway.
  • the PDP context is deactivated as soon as possible following a short delay (e.g. 5 minutes) after the DM-MS stops communicating with the packet mode gateway.
  • a short delay e.g. 5 minutes
  • the process of sending packet data as circuit mode data is essentially the reverse of the process, already described, of sending the circuit mode data as packet data.
  • the DMO transceiver 21 When the DMO transceiver 21 receives an indication from the TETRA V+D transceiver 22 via signalling connection 29 that one or more data packets have been received for the current circuit-mode call, the DMO transceiver 21 takes a suitably sized block of data from the packet data receiving buffer 28, and attempts to transmit it as a block of circuit-mode data or SDS data to the DMO terminal 7.
  • FIG. 3 illustrates a second embodiment of the packet-mode gateway 6 that is constructed using a single transceiver 41. This gateway uses a single transmitting and receiving antenna 42 connected to a single transmitter and receiver, so that it is connected alternately to the transmitter or receiver, as required.
  • the gateway is able to switch rapidly between receive and- transmit and between the frequency of the DMO net and the frequency of the V+D network.
  • the gateway 6 operates using the TETRA TDMA structure, where a multiframe is divided into eighteen frames, and a frame is subdivided into four slots, each slot having duration 85/6 ms .
  • the V+D and DMO TDMA (time division multiple access) structures are aligned so that timeslot 1 in the DMO transmissions is delayed by 1 timeslot relative to the V+D uplink slot allocated as a packet data channel (like the alignment used by TETRA gateways for relaying speech calls between DMO and V+D) .
  • FIG 4 shows an example of this operation in terms of circuit-mode data. However, similar timings will apply to the use of SDS messages.
  • row 69 indicates transmissions by the packet data gateway 6 on the DMO frequency and row 70 indicates transmissions by a DM-MS to the packet mode gateway.
  • Row 67 indicates the TDMA frame number on the DMO channel, and row 68 indicates the slot number on the DMO channel.
  • the DM-MS transmits some circuit-mode data, labelled cd5, to the packet-mode gateway.
  • the DM-MS transmits further portions of circuit-mode data cd ⁇ , cd7 , cd ⁇ and cd9 , etc. (At some times the DM-MS may have to pause to receive acknowledgements sent from the gateway to the DM-MS in slot 1; this is not shown in figure 4. )
  • Row 66 indicates transmissions by the packet-mode gateway 6 on the uplink frequency of the V+D network.
  • Row 64 indicates the V+D uplink frame number, and row 65 indicates the V+D uplink slot number .
  • the packet mode .gateway has been allocated to use a packet data channel located on slot 3 of the V+D channel, and the DMO timing is aligned, as shown, so that DMO slot 1 occurs one timeslot after V+D uplink slot 3.
  • V+D uplink frame 3 the packet mode gateway discovers it has received enough data from the DM-MS to start transmitting one or more complete data packets to the V+D network.
  • V+D uplink frame 3 slot 3 i.e. the packet data uplink slot
  • the packet mode gateway transmits a first part or segment of packet data pdl to the V+D network. (This data need not comprise a complete packet, as the packet data protocol does not require packet boundaries to correspond to slot boundaries.)
  • the gateway transmits further packet data segments pd2 , pd3, pd4, pd5. , etc.
  • the contents of the packet data segments do not need to correspond exactly to the data received from the DM-MS, as they can be delayed by a greater or lesser degree, and the quantity of data per slot can (and almost certainly will) differ between the DMO slots and the V+D slots.
  • Data rate mismatch can ' be accommodated by missing out packet data up-link slots, or by pausing the delivery of circuit mode data from the DM MS using the flow control features of the circuit mode data protocol.
  • Row 63 of figure 4 indicates transmissions by the V+D base station (BS)' on the downlink frequency of the V+D network.
  • Row 62 indicates the V+D downlink frame ⁇ number
  • row 61 indicates the V+D downlink slot number.
  • the V+D BS sends the packet-mode gateway acknowledgement message ackl that acknowledges receipt of the packet data delivered in data segments pdl, pd2 and pd3.
  • the V+D transmits null PDUs (Protocol Data Units) , but it might equally well send other signalling messages or packet data, perhaps to other MSs.
  • null PDUs Protocol Data Units
  • the packet mode gateway achieves transmitting and receiving . on the DMO channel and on the V+D uplink and downlink frequencies always at different times, once per frame, allowing it to relay packet data between V+D and DMO. This is achieved using a single transceiver and single antenna that is shared between receive and transmit. Since the packet-mode gateway 6 never receives and transmits at the same time, the packet-mode gateway receiver is never blocked by the packet-mode gateway transmitter.
  • the packet-mode gateway 6 is allocated to a single-slot packet data channel.
  • a multi-slot packet data channel could be used, particularly, e.g., if the capacity of DMO circuit-mode data or SDS messages supports it.
  • the correct alignment between the DMO and V+D timing in these . arrangements can be attained by adjusting the timing of the DMO channel as soon as the packet mode gateway is assigned to a packet data channel.
  • the timing must be adjusted such that DMO slot 1 occurs one timeslot after the V+D uplink packet data slot. This timing adjustment can be performed, e.g., using the timing adjustment signalling that is specified for voice calls through TETRA gateways.
  • DM-MSs would discover ⁇ the packet-mode gateway's present timing from the packet mode gateway's presence signals (gps) in figure 4, and then adjust their timing accordingly.
  • each SDS message carrying packet data is given a special protocol identifier (PID) labelled "packet data" so that the DM-MS 7 and the packet-mode gateway 6 know how to handle these particular SDS messages .
  • PID protocol identifier
  • the SDS messages also contain sequence numbers, to facilitate reassembly of the data in the correct order.
  • the gateway 6 rather than the gateway 6 passing the SDS messages from the DM-MS terminal 7 straight to the V+D infrastructure 1, it unpacks SDS messages with the "packet data" identifier (PID) and stores the packet data they contain in a buffer so that the individual data packets can be extracted and transmitted to the V+D network 1 using the packet data protocol .
  • PID Packet data
  • Use of SDS messages for this purpose also makes it possible for multiple terminals to use the packet mode gateway 6 at the same time. (DM-MSs wishing to send an SDS to a gateway can contend for access using random access.)
  • the SDS method may also make it easier for the packet-mode gateway 6 to send data back to DM-MSs when a DM-MS is actively sending packet data to the packet-mode gateway.
  • the invention comprises and extends to transmitting packet data between mobile terminals operating independently of the fixed network infrastructure by tunnelling that data through a non-packet data communications protocol (such as, and preferably, using a circuit mode connection or SDS signalling) .
  • a non-packet data communications protocol such as, and preferably, using a circuit mode connection or SDS signalling
  • the present invention in its preferred embodiments at least, provides a system for supporting packet data in TETRA DMO.
  • the present invention in its preferred embodiments at least, provides a method of extending packet data services to applications using a TETRA DMO radio terminal by using a packet data gateway that connects to a TETRA V+D network.
  • the proposed packet data gateway acts as a converter between DMO circuit-mode data or DMO SDS messages and V+D packet data protocol, allowing packet data to be tunnelled though a DMO circuit-mode data traffic channel or SDS messages to the packet data gateway.
  • the invention in its preferred embodiments at least, also permits terminals to continue to exchange data with a data service connected to the TETRA V+D network whenever a packet data gateway is present and available.
  • a packet mode gateway is provided that can exchange packet data using a packet data protocol via radio signals with a fixed radio infrastructure on the one hand, and can exchange packet data using a circuit mode protocol or SDS messages via radio signals with a DMO terminal on the other hand, such that packet data is effectively exchanged between the DMO terminal and the fixed radio infrastructure .
  • This is achieved in one embodiment using circuit mode data by a method comprising:
  • DM-MS detects presence of a packet mode gateway
  • DM-MS application decides it wants to exchange packet data with a V+D connected data service.
  • DM-MS requests a circuit-mode call set up for packet data.
  • Packet-mode gateway successfully negotiates PDP context activation with the V+D network, and informs the DM-MS that the call setup is successful .
  • DM-MS commences sending circuit mode data to the packet-mode gateway.
  • the packet-mode gateway buffers the circuit mode data and locates the first complete data packet .
  • the packet-mode gateway asks the V+D network for permission to start transmitting the data packets, and gets allocated to a packet data channel .
  • the packet-mode gateway sends timing adjustment messages to the DMO channel to align the DMO timing to the allocated packet data channel. i) The packet mode gateway starts transmitting the data packets to the V+D network, while continuing to receive circuit mode data containing further data packets . j ) When the DM MS has finished exchanging packet data with the V+D network, it clears the circuit mode data call. k) The packet-mode gateway deactivates the PDP context .
  • the method includes:
  • DM-MS detects presence of a packet mode gateway m) DM-MS application decides it wants to exchange " packet data with a V+D connected data service, n) DM-MS commences sending SDS messages to the packet mode gateway with the "packet data"
  • the packet-mode gateway extracts the data packets from the SDS messages and buffers them, p) Packet-mode gateway successfully negotiates
  • the packet-mode gateway asks the V+D network ⁇ for permission to start transmitting the data packets, and gets allocated to a packet data channel .
  • the packet-mode gateway sends timing adjustment messages to the DMO channel to align the DMO timing to the allocated packet data channel .
  • the packet mode gateway starts transmitting the data packets to the V+D network, while continuing to receive SDS messages containing further data packets.
  • the packet mode gateway deactivates the PDP context .
  • the proposed methods also allow DMO terminals to exchange packet data with each other, e.g., by- tunnelling their IP data to each other through a circuit-mode connection or SDS signalling.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Data Exchanges In Wide-Area Networks (AREA)

Abstract

Un système TETRA (1) a une couverture radio TETRA V+D s'étendant jusqu'à une limite(3). Un terminal TETRA (7) fonctionnant en mode direct peut établir une communication de données en mode circuit avec un mode paquet (passerelle 6). Le terminal TETRA DMO (7) peut alors envoyer des paquets de données à la passerelle en mode paquet (6) au moyen de la voie de données en mode circuit DMO. La passerelle en mode paquet (6) envoie les paquets de données dans, par exemple, une base de données (1), via l'infrastructure TETRA V+D, à l'aide du protocole de paquet de données TETRA. En variante, le terminal (7) peut envoyer des paquets de données à la passerelle (6) à l'intérieur de messages SDS spécialement étiquetés. Ceci fournit un procédé permettant d'étendre la couverture de paquet de données aux points noirs dans la couverture TETRA V+D.
PCT/GB2007/004039 2006-10-23 2007-10-23 Systèmes de communication Ceased WO2008050110A1 (fr)

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GB2539609A (en) * 2014-04-29 2016-12-21 Motorola Solutions Inc Dynamic gateway selection in a wireless communications system
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GB0720747D0 (en) 2007-12-05
GB0621047D0 (en) 2006-11-29

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