Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/02—Details
  • H04L12/16—Arrangements for providing special services to substations
  • H04L12/18—Arrangements for providing special services to substations for broadcast or conference, e.g. multicast
  • H04L12/1881—Arrangements for providing special services to substations for broadcast or conference, e.g. multicast with schedule organisation, e.g. priority, sequence management
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L51/00—User-to-user messaging in packet-switching networks, transmitted according to store-and-forward or real-time protocols, e.g. e-mail
  • H04L51/58—Message adaptation for wireless communication
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W28/00—Network traffic management; Network resource management
  • H04W28/02—Traffic management, e.g. flow control or congestion control
  • H04W28/06—Optimizing the usage of the radio link, e.g. header compression, information sizing, discarding information
  • H04W28/065—Optimizing the usage of the radio link, e.g. header compression, information sizing, discarding information using assembly or disassembly of packets
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/02—Details
  • H04L12/16—Arrangements for providing special services to substations
  • H04L12/18—Arrangements for providing special services to substations for broadcast or conference, e.g. multicast
  • H04L12/189—Arrangements for providing special services to substations for broadcast or conference, e.g. multicast in combination with wireless systems
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
  • H04W4/12—Messaging; Mailboxes; Announcements
  • H04W4/14—Short messaging services, e.g. short message services [SMS] or unstructured supplementary service data [USSD]

Definitions

• the invention relates to the transfer of a file conducted in PMR (Private Mobile Radio, Professional Mobile Radio) networks or standalone networks to several recipients.
• PMR Primary Mobile Radio, Professional Mobile Radio
• TETRA is the most widely used PMR network standard in Europe. This application deals with the operation of Tetra networks, but the invention is also useful in connection with most other PMR networks, such as Tetrapol and P25.
• the TETRA network is a time division multiplexing network.
• the radio path between a base station and terminal devices is very narrow in terms of its capacity and the number of available simultaneous speech or data channels is limited. This is partly compensated for by the possibility of a group call, whereby a single channel or time interval enables transmission of one message at a time from a single speaker or message sender to several recipients in such a way that just one radio channel is used within the range of each base station and thereby several recipients receive the call, the radio path not being burdened more than in the case of a single call. It is similarly possible to send a text message along a system control channel to a group, the single message transmitted along a radio path being received by several terminal units at a time. Even with a low-level radio capacity, this enables a sensible communication to be maintained within a group.
• the TETRA network provides a possibility of operating without a base station, directly from one terminal unit to another.
• a picture message or other file must be transmitted to each terminal unit separately by conducting the data transfer over a data link, whereby the base station becomes blocked for a long time should the same base station be used by several recipients. Because the TETRA network has no knowledge of a multicast feature for data channels or packet data along a radio path, the file must be transmitted several times along the radio path between a base station and a terminal unit, resulting in network congestion.
• the current standard does not recognize multicast data transmission functional at radio network level, although the terminal units could support an IP multicast operation, between the base station and the terminal unit there is no addressing mechanism for several recipients' packets or data stream, such that the packets or data stream would only be sent once along the radio path to several recipients.
• the only form of group communication recognized by the TETRA standard between a base station and a terminal unit or between two terminal units comprises group text messages and group calls. Text messages can also be communicated in multiple segments the same way as in a GSM network. Still, in the event that a file is transmitted to several recipients, it is only a notice of the transmission which is sent as a text message, the actual file being retrieved by using a data link.
• the group-transmitted file transfer results in an overload condition of the base stations or an extremely slow file transfer in the event that there are several recipients within the range of a single base station. This is the practical reason why the transmission of a file conducted in a TETRA network to several recipients has been deemed impossible to implement because of a narrow data transfer capacity.
• patent publication GB2443320A describing transmission of IP data in a TETRA network.
• the publication does not teach the use of group messages for making the use of a radio band more efficient.
• the operation according to a preferred embodiment of the invention is based on conducting a file transfer by using SDS group messages known to the network.
• SDS group messages are text messages, which are transmitted by a network within the range of a base station to several recipients over a control channel at one time.
• the transmitting server computer, or the terminal unit operating in a network transmits over a TETRA network several group text messages, such that a file is encoded into a plurality of successive text messages and to at least one of these messages is attached a title tag, on the basis of which the recipients are able to compile and decode the transmitted file from the plurality of messages.
• the file to be transferred can be for example a picture, which enables sending for example a wanted picture to several recipients, or enables sending for example a chart or a map image in support of leading an operation.
• the sender of a message dissects the transmitted file into segments suitable for transmission in the form of group text messages, for example in the form of SDS messages in a TETRA network. This is performed for example with a program means according to the invention.
• a required title tag to the messages is attached a required title tag, at least a file-transmission specifying label or sequence number to at least one of the messages to be transmitted and a label or a sequence number specifying each segment of the text message, on the basis of which the messages are organized in successive order prior to decoding the file.
• the sequence number for successive segments can be for example an integer a single byte or half a byte in length.
• the name of a file, and the description to be sent along with a file are transmitted in just one title message which is generally first to be transmitted. Since a TCTRA network provides no guarantee regarding a transmission delay, nor regarding the incoming order of messages, the first sent message is not necessarily the one first obtained by the recipient.
• the terminal unit after receiving a title message, is possibly forced to compile a file also from messages arrived prior to the title message, which is why the messages must carry for example a sequence number, providing a basis for the terminal unit to identify segments of each file from among the messages coming from a single sender.
• the number of sequence numbers may also be more than one, whereby the segments of each file can be numbered individually and the messages are distinguished from each other by means of a second sequence number or a title tag.
• the method according to the invention enables sending a picture the size of a passport photo for a display presentation typically by means of about 12 successive SDS messages of about 140 bytes in length.
• each terminal unit opens an IP- or circuit switched data channel for the retrieval of a picture or other file
• the system according to the invention enables transmission of files to several recipients without blocking the network.
• the 12 SDS messages needed for the transmission of a picture file result in a reasonably minor burden on the control channel in comparison to the situation that each group transmission recipient within the range of a base station would open his/her own packet- or circuit-switched communication for a retrieval of the file.
• the opening of each data or packet communication burdens both data and control channels, whereby the several separately opened data links for sending one and the same file also congest the control channel as long as there are several recipients within the range of one and the same base station.
• a terminal unit In order to implement a method of the invention according to a TETRA network operating embodiment, a terminal unit must be provided with a program means capable of compiling and decoding a transferable file from several SDS messages. Transmission requires that a server, a gateway device, or a terminal unit be provided with a program means capable of dissecting and encoding the file into several group text messages to be transmitted successively.
• the TETRA network itself does not require any modifications, the system and method according to the invention using the group messages of a TCTRA network as such, and the method according to the invention being usable in all TCTRA standard complying networks equipped for the transmission of standard complying SDS group text messages.
• the method is also usable in any other network equipped with a transmission feature operating across a radio path, the method being limited neither to a TCTRA network nor to SDS messages.
• a terminal unit and terminal unit software of the invention operable in a TCTRA network are characterized in that the terminal unit or the software is provided with means for the reception of several successive SDS text messages and for compiling a file encoded therein.
• a preferred TCTRA network embodiment for a transmission program of the invention is characterized by means which encode a file to be transmitted into several successive SDS messages, and by means for the transmission of several successive SDS messages in the form of a group text message to several recipients.
• a terminal unit or a computer device for connecting the same to a network which uses group speech messages of a TCTRA or some other PMR network.
• a speech encoder in the transmitting device and a speech decoder in the receiving device must be replaced with a program means, which encodes into the speech channel not the speech but the data of a discussed file.
• This enables sending preferably larger amounts of data but, on the other hand, the implementation requires a modification in the firmware of a receiving terminal unit so as to enable storing the speech data or sending it to the disposal of a file decoding application.
• the application designer has no control over the operation of an actual base station network, which is why terminal unit applications and data network applications in a present-day TETRA network are forced to operate on top of the presently available features at least until the use of a radio path for data transfer is improved. It would be beneficial to determine a mode of data transfer, in which the multicast messages are transmitted from a base station or a terminal unit as a data transfer addressed to several recipients the same way as the group call is now working. In this case, each base station is able to buffer the transmission of data to terminal units within its own range with a possibility of giving speech a priority.
• a data call or a data packet transfer for several recipients would also enable, for example during the operation, the transfer of a picture directly from one terminal unit to others, whereby, for example prior to the penetration into a hazardous space, the first to establish a visual contact can send a picture in the form of a data broadcast transmission to other terminal units present within the audio range of the same group, and possibly by way of the base station, also to a command center. This way, the important information can be transferred to several recipients in a single procedure directly from terminal to terminal, putting the radio path to efficient overall use.
• the above-described transfer of a file conducted by means of text messages can be carried out preferably as a Java program, which can be uploaded into a terminal unit without making other modifications in the hardware or firmware of terminal units.
• the method according to the invention can also be implemented by means of a terminal unit firmware modification or by means of a special terminal unit, whereby the transfer of a file is managed by means of data encoded into the data stream of a group call to be transmitted in a speech channel. Even in this case, the infrastructure of a TCTRA network remains otherwise unchanged and, as far as the network is concerned, the transfer of a file equals to the transfer of speech, whereby the terminal unit application manages the reception and transmission of multicast data economically to several recipients in existing TCTRA networks without modifications to the network itself.
• the solution according to the invention accomplishes the transfer of a picture sufficient for example for the transfer of a mugshot even to a large number of recipients in a standard time. According to tests, the transmission and reception of typically required 12 SDS messages takes about 14 seconds irrespective of the number of recipients. In the event that the control channel of a base station has become congested for other reasons, this particular base station will naturally slow down the file transfer as messages settle in a queue.
• the program means according to the invention such as a program receiving and compiling SDS messages, for example a java application, does not preferably acknowledge a successful receipt as a default value, because, in the event that there are a large number of recipients, the network would become overloaded by acknowledgements of receipt.
• the unsuccessful reception is preferably followed by waiting a randomly set period of time prior to a retransmission request.
• the time period can be for example within the range of 1 to 20 seconds, whereby, in the case of a large number of recipients, the time is preferably extended for example by a request supplied by means of a title tag transmitted in the message, or by using a group size for establishing a randomly selected maximum time.
• the sender can retransmit a missing or faulty file segment either as a group transmission or to a single recipient also as a single message in the likelihood that a group message would burden the network more than a single message.
• the message or a segment thereof is worth sending in the form of a group message even before the expiry of a random maximum time and, on the other hand, if just one fault report arrives during the maximum waiting time, there is no use to send a group message.
• the network be capable of informing a sender about base stations used by the terminal units, this knowledge can be utilized in deciding the mode of retransmission.
• the entire message can be sent again in the form of a group transmission.
• the retransmission is evident from a title tag of the message, whereby the recipients learn not to send a retransmission request for missing or faulty segments of the previous message prior to receiving the retransmission in its entirety.
• the recipient can use the data of both transmissions for the compilation and error correction of a file.
• the file-transmitting program means can be a gateway computer, which is linked with a PMR network and for example with the data network of an authority.
• the transmitting program means may also be part of a terminal unit or an emergency center, an order dispatch center or the like.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Mobile Radio Communication Systems (AREA)

Applications Claiming Priority (2)

Publications (2)

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Family Cites Families (9)

• 2009
  • 2009-05-25 FI FI20095572A patent/FI123200B/fi active IP Right Grant
• 2010
  • 2010-05-21 WO PCT/FI2010/050416 patent/WO2010136645A1/en not_active Ceased
  • 2010-05-21 EP EP10780105.2A patent/EP2436199A4/de not_active Ceased

Non-Patent Citations (1)

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