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WO1998037717A1 - Securing of short message information during handover - Google Patents

Securing of short message information during handover Download PDF

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Publication number
WO1998037717A1
WO1998037717A1 PCT/FI1997/000117 FI9700117W WO9837717A1 WO 1998037717 A1 WO1998037717 A1 WO 1998037717A1 FI 9700117 W FI9700117 W FI 9700117W WO 9837717 A1 WO9837717 A1 WO 9837717A1
Authority
WO
WIPO (PCT)
Prior art keywords
specifications
fixed part
switching centre
message
services switching
Prior art date
Application number
PCT/FI1997/000117
Other languages
French (fr)
Inventor
Tuomo Sipilä
Ari Kontio
Original Assignee
Nokia Telecommunications Oy
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 Nokia Telecommunications Oy filed Critical Nokia Telecommunications Oy
Priority to AU18813/97A priority Critical patent/AU1881397A/en
Priority to PCT/FI1997/000117 priority patent/WO1998037717A1/en
Publication of WO1998037717A1 publication Critical patent/WO1998037717A1/en

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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
    • H04W4/12—Messaging; Mailboxes; Announcements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/12—Reselecting a serving backbone network switching or routing node
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W92/00—Interfaces specially adapted for wireless communication networks
    • H04W92/02—Inter-networking arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W92/00—Interfaces specially adapted for wireless communication networks
    • H04W92/04—Interfaces between hierarchically different network devices
    • H04W92/14—Interfaces between hierarchically different network devices between access point controllers and backbone network device

Definitions

  • the invention relates in general to securing uninterrupted and error-free data transmission in a situation in which a terminal of a cellular radio system is handed over from a base station to another.
  • the invention relates to a method and system which attempt to prevent the loss of short messages or parts of them when a cordless phone according to the DECT system moves from a base station cluster to another. Then it is assumed that the base station clusters are connected to a switching centre of a digital mobile phone system.
  • the invention also relates to a cordless phone and a base station in a cordless telephone system, which are equipped so as to operate according to the method disclosed by the invention. Loss of data here means that an error occurs in the transmission so that a data element which was meant to be transmitted does not arrive in its destination.
  • Handover is a known concept in telecommunications systems in which mobile terminals are in radio connection with base stations.
  • the terminals are in general called portable parts (PP) and the base stations and base station cluster controllers that control the operation of the base stations are in general called fixed parts (FP).
  • PP portable parts
  • FP fixed parts
  • this application uses the term fixed part to denote the entity consisting of base stations and a base station cluster controller whenever there is no need to consider the elements of this entity separately.
  • Both cluster controllers control two base stations so that cluster controller 7 controls base stations 3 and 4 and cluster controller 8 controls base stations 5 and 6.
  • the entity comprising a cluster controller and the base stations under its control is called a DECT FP, as described above. In this application that entity is also called a fixed part or, in some cases, a cluster.
  • the standardised interface between each of the cluster controllers 7 and 8 and the switching centre 9 is called the A interface in accordance with the prior art.
  • a portable part 2 changes from base station 6 to base station 5, thus initiating a so-called internal handover inside a cluster.
  • a portable part 1 changes from base station 5 to base station 4, which is a so-called external handover in which not only the radio fixed part but also the cluster is changed.
  • the handover of portable part 1 is more problematic of these two in that it may cause errors in a short message transfer which possibly is being carried out between the portable part and the transmission network.
  • Short message transfer may be mobile originated (MO SM) or mobile terminated (MT SM).
  • Fig. 2 shows a signalling timing diagram wherein a portable part PP sends a short message via a fixed part FP to a switching centre MSC.
  • the diagram and the message designators in it conform to a known arrangement disclosed in documents 12 to 21 of the reference document list accompanying this patent application. Time flows from top down and the designated arrows represent individual signalling messages. From the point of view of the present invention it is important to distinguish the different stages in which a handover may occur because the preservation or loss of short message information depends on what other information the portable part and the transmission network manage to exchange.
  • the stages are below numbered from HO 1/MO to HO 6/MO, where HO stands for handover and MO stands for mobile originated. Furthermore, the "Ext" in the stage designators stands for external handover.
  • Handover occurs after the portable part has sent a CC-SETUP message referring to connection establishment but before the portable part has received from the network a CC-CONNECT message indicating that the connection is ready.
  • Handover occurs after the portable part has sent the first segment of the IWU-INFO message conveying the short message but before the fixed part has received the last segment of the IWU-INFO message in question.
  • Handover occurs after the fixed part has received from the portable part the last segment of the rWU-INFO message but before the fixed part has received from the switching centre a CP-ACK message indicating an acknowledgement.
  • Handover occurs after the fixed part has received from the switching centre the CP- ACK message but before the fixed part has received from the switching centre the whole of a CP-DATA message containing reply data.
  • Handover occurs after the fixed part has received from the switching centre the last segment of the CP-DATA message containing reply data but before the fixed part has sent to the switching centre a CP-ACK acknowledgement message.
  • Fig. 3 shows by way of example a signalling timing diagram wherein a portable part PP receives a short message from a mobile services switching centre MSC via a fixed part FP.
  • the diagram corresponds to that shown in Fig. 2 and the stages in which a handover may occur are numbered from HO 1/MT to HO 6/MT where HO stands for handover and MT stands for mobile terminated.
  • Handover occurs after the fixed part has received from the switching centre the last segment of a CP-DATA message conveying the short message and the fixed part has sent a CC-SETUP message referring to connection establishment but before the fixed part has received from the portable part a CC-CONNECT message indicating that the connection is ready.
  • Handover occurs after the fixed part has received from the portable part the CC- CONNECT message but before the portable part has received the last segment of the IWU-INFO message conveying the short message.
  • Handover occurs after the portable part has received the last segment of the IWU- INFO message conveying the short message but before the fixed part has received from the portable part a new IWU-INFO message containing reply data.
  • Handover occurs after the fixed part has received from the portable part a new IWU-INFO message containing reply data but before the fixed part has sent to the switching centre a CP-DATA message containing reply data.
  • Handover occurs after the fixed part has sent to the switching centre a CP-DATA message containing reply data but before the fixed part has received from the switching centre a CP-ACK acknowledgement message.
  • Interworking units must be provided in the system hardware especially for the interworking of the DECT and GSM systems; said units carry out the conversions of signalling messages and related data fields between the formats of the different systems.
  • the interworking unit in the DECT FP which is important from the point of view of the invention, performs the short message conversions such that data transfer between the fixed part and the mobile services switching centre is carried out in the GSM short message format, and between the fixed part and the DECT portable part the short messages are transferred in ⁇ IWU-INFO ⁇ messages according to the DECT system.
  • a short message may be longer than one ⁇ IWU-INFO ⁇ message that complies with the specifications, in which case it is divided into segments transmitted consecutively. According to the specifications no other control messages may be transmitted between ⁇ IWU-INFO ⁇ messages conveying a short message, so a handover cannot occur before the buffers used for temporarily storing the short message segments both in the portable part and in the old fixed part are empty.
  • the DECT specifications require that in a controlled handover the portable part establishes a connection with the new fixed part in parallel with the old connection so that the connection with the old fixed part can be terminated using the normal CC-RELEASE message in which the portable part includes a code for external handover. It is, however, possible that the old connection is cut off due to a sudden break or fade-out, in which case the portable part has a certain limited period of time to establish a connection with the new fixed part.
  • the aforementioned handover stages HO 1/MO to HO 6/MO and HO 1/MT to HO 5/MT defining whether or not data loss is possible in a controlled handover and, on the other hand, when a break cuts off the connection to the old fixed part. It should be noted that the description below only covers the external handover in which the mobile services switching centre MSC participates.
  • Short message data are not lost since the portable part has not yet sent any part of the short message. Handover is carried out through the mobile services switching centre as in a normal voice call.
  • Break Short message data are not lost since the portable part has not yet sent any part of the short message. Handover is carried out through the mobile services switching centre as in a normal voice call.
  • Short message data are not lost since the messages conveying the short message are in a message buffer and the portable part sends them prior to the terminate message sent via the same message buffer.
  • Break Short message data may be lost because the portable part tries in vain to empty the message buffer through the old fixed part.
  • Short message data are not lost because the messages conveying the short message are in a message buffer and the portable part sends them prior to the terminate message sent via the same message buffer.
  • Break Short message data may be lost because the portable part tries in vain to empty the message buffer through the old fixed part.
  • Controlled Short message data are not lost since the mobile services switching centre sends a CP-ACK message to the new fixed part according to the specifications of the control protocol (CP) layer.
  • CP control protocol
  • Controlled Short message data are not lost since the mobile services switching centre sends a CP-DATA message to the new fixed part according to the specifications of the control protocol (CP) layer. Break: Short message data may be lost because the mobile services switching centre sends the CP-DATA message to the old fixed part instead of the new one.
  • CP control protocol
  • Short message data are not lost because the messages conveying the short message are in a message buffer and the portable part sends them prior to the terminate message sent via the same message buffer. Break: Short message data may be lost.
  • Ext HO 1/MT Controlled: Short message data may be lost if the old fixed part acknowledges the CP-DATA message from the switching centre immediately with a CP-ACK message.
  • Short message data may be lost if the old fixed part acknowledges the CP- DATA message from the switching centre immediately with a CP-ACK message.
  • Short message data are not lost because the messages conveying the short message are in a message buffer and the fixed part sends them prior to the terminate message sent via the same message buffer.
  • Break Short message data may be lost if the old fixed part acknowledges the CP- DATA message from the switching centre immediately with a CP-ACK message.
  • Short message data are not lost because the messages conveying the short message are in a message buffer and the portable part sends them prior to the terminate message sent via the same message buffer.
  • Short message data may be lost if the old fixed part acknowledges the CP- DATA message from the switching centre immediately with a CP-ACK message.
  • Short message data are not lost because the messages conveying the short message are in a message buffer and the portable part sends them prior to the te ⁇ ninate message sent via the same message buffer.
  • Break Short message data may be lost if the old fixed part acknowledges the CP- DATA message from the switching centre immediately with a CP-ACK message.
  • Ext HO 5/MT Controlled: Short message data are not lost since the mobile services switching centre sends a CP-ACK message to the new fixed part according to the specifications of the control protocol (CP) layer. Break: Handling of this abnormal situation is done by the GSM system.
  • CP control protocol
  • An object of this invention is to provide a method for securing the short message data in an external handover situation in a cordless communications system wherein the handover is carried out through a switching centre of a cellular radio system. Another object of the invention is that the method according to the invention does not require unreasonably big changes in the current configuration and protocol specifications of the systems. A further object of the invention is to provide a data transfer system in which the cordless portable part and fixed part operate as specified by the method according to the invention.
  • the objects of the invention are achieved by utilising a short message acknowledgement protocol included in said cellular radio system as part of said cordless communications system.
  • the method according to the invention for conveying short messages from a transmission network to a portable part of a cordless telephone system, said transmission network comprising a fixed part of a cordless telephone system and a mobile services switching centre of a mobile communications system, is characterised in that it comprises stages wherein
  • said portable part in response to the reception of short message data from said mobile services switching centre via said fixed part said portable part sends to said fixed part an acknowledgement message in the format required by the specifications of said cordless telephone system,
  • said fixed part converts said acknowledgement message to a format required by the specifications of said mobile communications system and sends it to said mobile services switching centre, and - in said mobile services switching centre information about the reception of said acknowledgement message is conveyed to a certain short message protocol layer according to the specifications of said mobile communications system.
  • the invention is also directed to a method for transferring short messages in the opposite direction.
  • the method according to the invention for transferring short messages from a portable part of a cordless telephone system to a transmission network comprising a fixed part of a cordless telephone system and a mobile services switching centre of a mobile communications system is characterised in that it comprises stages wherein - in response to the reception of short message data from said portable part via said fixed part said mobile services switching centre sends to said fixed part an acknowledgement message in the format required by the specifications of said mobile communications system,
  • said fixed part converts said acknowledgement message to a format required by the specifications of said cordless telephone system and sends it to said portable part
  • the idea according to the invention is in this patent application directed particularly to the operation of the DECT and GSM systems but it can also be applied to other corresponding adaptations of communications systems.
  • the idea of utilising short message protocols of the GSM system in the DECT system can be realised in at least three different ways which are disclosed in this patent application as the preferred embodiments of the invention.
  • the first alternative employs the SM-CP protocol layer (Short Message - Control Protocol) of the GSM system, which is a simple "send and wait" type protocol.
  • the transmitting device sends a so-called CP-DATA message answered by the receiving device with a CP-ACK or CP-ERROR message.
  • the CP-DATA message may include a message of a higher protocol layer and the CP-ERROR message may include the cause of the reception error.
  • the SM-CP protocol layer counterparts are in the portable part of the cordless telephone system and in the mobile services switching centre, so that the protocol layer in question is transported through the fixed part and base station unchanged. In an error situation the transmitting device once retransmits an unacknowledged SM-CP layer message after a certain period of time.
  • a particular advantage of this embodiment is that the portable part can utilise all protocol layers specified for short messages in a GSM terminal and that the interworking units (IWU) of both the portable part and fixed part are fairly simple in implementation. The probability of data being lost is very small.
  • the second preferred embodiment of the invention employs the aforementioned SM-CP protocol layer between the mobile services switching centre and the fixed part.
  • the counterparts of the next highest protocol layer (SM-RP, Short Message - Relay Protocol) are in the portable part of the cordless telephone system and in the mobile services switching centre.
  • Communication between the fixed part and portable part complies with the specifications of the DECT system with the exception that the interworking units (IWU) of the devices exchange short message related information between them.
  • IWU interworking units
  • the responsibility for securing the short message information lies primarily with the interworking unit of the fixed part. Indeed, this embodiment requires a little more complex implementation of the interworking units than the first embodiment.
  • the mutual correlation of messages and records as well as the conversions made by the interworking units are described in more detail later on.
  • This embodiment has the special advantage that it requires only slight changes in the current specifications. However, absolute securing of short message data in a handover cannot be guaranteed.
  • the third preferred embodiment of the invention employs a special multimedia messaging service protocol (MMSP), which is specified in document DE/RES- 03038: "Radio Equipment and Systems (RES); Digital European Cordless Telecommunications (DECT) Data Services Profile Multimedia Messaging Service with Specific provision for Facsimile service (service type F, Class 2)".
  • MMSP multimedia messaging service protocol
  • the CM-ACK and CM-ERROR messages of the above-mentioned SM-CP protocol of the GSM system are conveyed across the PP-FP radio interface using the MMSP protocol so that possible error situations are corrected according to the mechanisms of the SM- CP protocol.
  • MMSP protocol is by definition not the same kind of a state machine consisting of well-defined states as e.g. the SM-CP protocol, so its use is not completely in harmony with the original specifications.
  • the loss of short message information is prevented more effectively than in the second embodiment of the invention described above.
  • Fig. 1 schematically shows a known communications system the operation of which can be made more efficient using the invention
  • Fig. 2 shows a known timing diagram for signalling in mobile originated short message transfer
  • Fig. 3 shows a known timing diagram for signalling in mobile terminated short message transfer
  • Fig. 4 shows protocol layers used in a first preferred embodiment of the invention
  • Fig. 5 shows protocol layers used in a second preferred embodiment of the invention
  • Fig. 6 shows protocol layers used in a third preferred embodiment of the invention
  • Fig. 7 shows a timing diagram for short message transfer according to the first preferred embodiment of the invention
  • Fig. 8 shows a timing diagram for short message transfer according to the second preferred embodiment of the invention
  • Fig. 9 shows a timing diagram for short message transfer according to the third preferred embodiment of the invention.
  • Fig. 10 shows messages in a communications situation according to the third preferred embodiment of the invention.
  • Fig. 11 shows messages in a second communications situation according to the third preferred embodiment of the invention.
  • Figs. 1 to 3 so below in the description of the invention and its preferred embodiments reference will be made mainly to Figs. 4 to 11.
  • Like elements in the drawing are denoted by like reference designators.
  • Fig. 4 shows the protocol stacks used in different parts of the system in the case of the first preferred embodiment of the invention.
  • the use of protocol stacks, or the logical OSI (Open Systems Interconnection) architecture, is known to a person skilled in the art.
  • Column PP represents the protocol stack of a portable part of a cordless telephone system
  • column FP represents the protocol stack of the fixed part
  • column MSC represents the protocol stack of a mobile services switching centre
  • column SC represents the protocol stack of a short message service centre.
  • the figure shows only the protocol layers that are essential from the point of view of the invention.
  • the lower protocol layers PHY, MAC and DLC Physical, Media Access Control, Data Link Control
  • PHY, MAC and DLC Physical, Media Access Control, Data Link Control
  • the portable part PP and fixed part FP have, above the aforementioned, a CC (Call Control) protocol layer which in a known manner includes the functions needed for the establishment and maintenance of a telephone connection.
  • CC Common Control
  • MMSP Multimedia Messaging Service Protocol
  • a DECT portable part PP For a DECT portable part PP to be able to use the GSM short message service in accordance with the first embodiment of the invention, it has to have an IWU (Interworking Unit) layer above the CC layer mentioned above.
  • the fixed part FP includes an interworking unit IWU which acts as an intermediary between the CC+MMSP layer of the DECT system and the MM (Mobility Management) layer operating in the direction of the mobile services switching centre MSC.
  • the mobile services switching centre MSC has a counterpart for this MM layer.
  • the fixed part FP has no higher protocol layers in connection with the short message service, but on the next highest layers SM-CP and SM-RP the counterparts are located in the portable part PP and the mobile services switching centre MSC. On the highest protocol layer SM-TP (Short Message - Transport Protocol) the counterparts are found in the portable part PP and short message service centre SC.
  • SM-TP Short Message - Transport Protocol
  • the protocol layers SM-CP, SM-RP and SM-TP operate in a known manner defined in the standards of the GSM system and described in an illustrative manner e.g. in a book titled "The GSM System for Mobile Communications" by Michel Mouly and Marie-Bernadette Pautet, published by the authors, ISBN 2-9507190-0-7, Palaiseau 1992.
  • the inventional idea of bringing GSM standards partly in the DECT domain is applied by forming a stack of the three protocol layers as such in a portable part PP so that e.g.
  • all CP-DATA, CP-ACK and CP-ERROR messages of the SM-CP layer are transmitted as such between the mobile services switching centre MSC and the portable part PP. If any of these messages is lost during a handover, the device that sent the lost message notices that the receiving device sends no acknowledgement and retransmits the message. In certain cases it may be that a message of the SM-CP layer is duplicated during a handover, in which case the receiving device may receive two identical copies of the same SM-RP -layer message conveyed by the SM-CP layer. The situation is corrected when the receiving device compares the eight-bit message identifiers of the SM-RP-layer messages with each other.
  • the interworking units performing the interpretation between the DECT and GSM specifications have to have information about which of the data elements of the different systems cor- respond to each other and how they are inter-converted in the transfer.
  • Table 1 shows the correlation of messages in the interworking unit IWU of the portable part PP in a mobile originated short message transfer.
  • Table 2 shows the correlation of messages in the interworking unit IWU of the fixed part FP in a mobile originated short message transfer.
  • Table 3 shows the correlation of messages in the inter- working unit IWU of the portable part PP in a mobile terminated short message transfer
  • Table 4 shows the correlation of messages in the interworking unit IWU of the fixed part FP in a mobile terminated short message transfer.
  • the reference "message in IWU-to-IWU parameter", which appears in the tables, means that the message is added to the corresponding IWU-INFO type transmission using a known parameter format.
  • a person skilled in the art is able to draw up the necessary message interpretation instructions for the interworking units on the basis of the tables.
  • the SM-CP protocol layer may require some changes in the timing, but suitable timings can be easily found by means of experimentation or simulating real operation.
  • Fig. 7 shows an example of a short message transfer in a handover of a portable part PP from fixed part FP1 to fixed part FP2 under a mobile services switching centre MSC.
  • Time interval 71 comprises connection establishment
  • time interval 72 comprises short message transfer via the old fixed part FP1
  • time interval 73 comprises an external handover.
  • Fig. 5 shows the essential parts of the protocol stacks used in the communications system.
  • the operation of the PHY, MAC, DLC and CC+MMSP layers used in the communications between the portable part PP and fixed part FP is the same as in the first embodiment described above.
  • the portable part PP does not have a SM-CP protocol layer, but above the IWU layer on top of the CC+MMSP layer there is immediately the SM-RP layer and above that, the SM-TP layer.
  • the interworking unit IWU operates between the CC+MMSP layer, which operates in the direction of the portable part PP, and the SM-CP layer, which operates in the direction of the mobile services switching centre MSC.
  • the SM-CP layer Between the fixed part FP and the mobile services switching centre MSC there are, below said SM-CP layer, other layers of which Fig. 5 shows the SCCP/MAP (Signalling Connection Control Part / Mobile Application Part) layer.
  • the SM-RP layer the counterpart of which is the corresponding SM-RP layer of the portable part PP.
  • the counterparts are in the portable part PP and short message service centre SC.
  • the interworking unit IWU of the fixed part FP transfers a CP-DATA message to a mobile services switching centre MSC only when all the IWU-INFO segments that contain parts of the message in question have arrived error-free from the portable part PP. Otherwise the fixed part FP discards the parts of the incomplete CP-DATA message.
  • mobile terminated short message transfer the fixed part FP does not acknowledge the first CP-DATA message from the switching centre MSC until the connection to the portable part is established, i.e. the fixed part FP has received from the portable part PP a ⁇ CC-CONNECT ⁇ message.
  • Normal operation may follow one of the following alternative patterns: a) The fixed part FP does not acknowledge the CP-DATA message from the switching centre with a CP-ACK message until a little before the expiration of the TC1N timer of the SM-CP layer specifications so that the fixed part has time to send the short message successfully to the portable part. In this alternative, the portable part PP does not send an acknowledgement to the fixed part FP.
  • the portable part PP When the portable part PP has received a complete short message, its IWU layer acknowledges the fixed part FP either with an empty IWU-INFO message or with a reply message of the SM-RP layer, transferred in parameters of the IWU-INFO message.
  • Said empty IWU-INFO message may contain a copy of the first IWU-INFO segment used in the transfer of a successfully received short message.
  • bit 8 of octet 3 in the «IWU-to- IWU» element can be set to 0 to indicate an acknowledgement or the ⁇ Protocol Discriminator> field in the reply message can be given a value which indicates an acknowledgement to the message sent.
  • the latter two are new specifications that should be included in the standard specifications for the structure of said messages.
  • the fixed part FP receives from the portable part PP a ⁇ CC-RELEASE-COM ⁇ message which includes, if necessary, an indicator for external handover. Then the old fixed part FP immediately sends, in accordance with this embodiment of the invention, to the switching centre MSC a CP-ACK acknowledgement message to prevent the switching centre from unnecessarily retransmitting the same short message via the new fixed part; this is because in a controlled external handover the ⁇ CC-RELEASE-COM ⁇ message indicates, among other things, that the short messages in the transmit buffers have been conveyed across the radio interface prior to the controlled termination of the connection.
  • the portable part PP sends the reply messages from the higher protocol layers via the new fixed part whereby the new fixed part sends to the switching centre the CP- ACK message corresponding to the CP-DATA message transfe ⁇ ed earlier via the old fixed part. Now at the latest the switching centre knows that the short message sent via the old fixed part has been successfully received in the portable part. If the portable part PP receives via the new fixed part an identical copy of an already- received short message, it discards the extra copy and sends to the new fixed part an acknowledgement message of a higher protocol layer (SM-RP). In mobile originated short message transfer the portable part terminates, if necessary, the transfer of segments of a message to the old fixed part if a handover occurs, and sends all segments of that short message to the new fixed part.
  • SM-RP protocol layer
  • the old fixed part does not send a CP- ACK message to the switching centre MSC in this embodiment of the invention.
  • the switching centre attempts to retransmit the unacknowledged CP-DATA message. If the normal handover signalling has sent information about the new base station cluster to the switching centre, the switching centre sends the message to that, so that short message information will not be lost. If, in spite of the fade-out, the portable part PP had received the short message or if it receives it via the new fixed part, it sends a SM-RP-layer acknowledgement via the new fixed part. If necessary, the portable part discards the incomplete short message parts, i.e. those IWU-INFO segments that do not constitute a complete short message.
  • Fig. 8 shows an example of a short message transfer according to the second embodiment of the invention, wherein a handover is performed for portable part PP from fixed part FP1 to fixed part FP2 under a mobile services switching centre MSC.
  • Time interval 81 comprises connection establishment
  • time interval 82 comprises short message transfer via the old fixed part FP1
  • time interval 83 comprises an external handover.
  • Acknowledgement employs the b-alternative described above and timer TC1N of the SM-CP protocol layer in the old fixed part FP1 ("Note 1 " in the figure).
  • Fig. 6 which once again shows the essential parts of the protocol stacks used in the devices of the communications system.
  • the operation of the PHY, MAC and DLC layers used in the communications between the portable part PP and fixed part FP is the same as in the first and second embodiments described above.
  • the SM-CP protocol layer according to the GSM system is used only between the fixed part FP and the mobile services switching centre MSC in the same way as in the second embodiment described above.
  • the MMSP protocol layer is separated according to Fig. 6 into an "auxiliary layer" of its own, which, however, in the standard OSI model belongs to the same layer as the CC layer.
  • the portable part and fixed part use in their mutual communications primitives and acknowledgement rules of the MMSP protocol layer so that an acknowledgement need not be performed "indirectly" by means of timing arrangements and/or messages of the SM-RP layer, as in the second embodiment described above.
  • the interworking unit IWU of the portable part PP operates between the portable part's SM-RP protocol layer and the MMSP layer.
  • the interworking unit IWU makes the necessary conversions between the MMSP/CC layer according to the DECT specifications and the SM-CP layer according to the GSM specifications.
  • Table 6 shows the correlation of messages in the FP's interworking unit IWU when MMSP-layer primitives are used to fully or partially represent the corresponding SM-CP-layer concepts in mobile originated short message transfer.
  • Table 7 shows the correlation of messages in the FP's interworking unit IWU when MMSP-layer primitives are used to fully or partially represent the corresponding SM-CP-layer concepts in mobile terminated short message transfer.
  • MMSP-layer primitives are used to fully represent the corresponding SM-CP-layer concepts refers to an arrangement wherein all SM-CP- layer messages have a well-defined counterpart in the MMSP layer.
  • the MMSP-layer functions follow as accurately as possible the functions and states of the SM-CP layer.
  • the MMSP layer behaves as much as possible in the same way as the SM-CP layer that complies with GSM specifications.
  • a special advantage of this alternative is that the portable part's MMSP layer can be made to operate as a peer entity of the mobile services switching centre's SM-CP layer so that the exchange of acknowledgement messages and other short message related communications between the portable part PP and the mobile services switching centre MSC comply with the known end-to-end functionality.
  • MMSP-layer primitives are used to only partially represent the corresponding SM-CP-layer concepts refers to an arrangement wherein the PP's interworking unit IWU uses MMSP-layer MMS-SEND-RPY primitives to represent the SM-CP-layer messages required in the transmission of acknowledgement messages.
  • MMSP-layer MMS-SEND primitives can be used for conveying RP-ACK messages coming from the SM-RP protocol layer; in the SM-CP layer these would correspond to CP-DATA messages.
  • the mobile services switching centre's SM-CP protocol layer counterpart is mainly in the fixed part.
  • the portable part's MMSP layer implementation is rather simple.
  • a "primitive” refers to communication between different protocol layers in one and the same device, which communication may be either a request (-Req) or an indication (-Ind).
  • the tables show that when the portable part is the receiving device (MT, or mobile terminated transfer), a MMS-SEND-RPY type primitive between the MSSP sub-layer and CC layer conveys the acknowledgement indicating that the portable part has received the segmented short message in full.
  • the fixed part converts the corresponding IWU-INFO message sent by the portable part to a CP-ACK acknowledgement to be sent to the mobile services switching centre MSC.
  • the mobile services switching centre sends a CP-ACK message which the fixed part converts to an IWU-INFO message to be sent to the portable part.
  • the portable part's CC layer further sends the information in the form of a MMS-SEND-RPY type primitive to the MMSP layer.
  • this embodiment may also require minor modifications in the SM-CP-layer timing arrangements, but the most suitable time values can be easily found using ordinary methods of experimentation or simulation.
  • the correlations of the fields in different messages are as follows:
  • the MMSP-layer operation of the portable part can be modelled using a certain state machine.
  • the state machine shall include all items presented in Subclause 5 in document [20] of the reference document list attached to this patent application, so that the CP-DATA message corresponds to MMS-SEND, the CP-ACK message corresponds to MMS-SEND-RPY wherein the ⁇ Command Outcome> field of the «MMS-Generic-Header» element contains a code for "successful", and the CP- ERROR message corresponds to MMS-SEND-RPY wherein the ⁇ Command Outcome> field of the «MMS-Generic-Header» element contains a code for "unsuccessful".
  • the state machine can only have two states, the first of which is "Idle” and the second "Wait for Reply".
  • the first transition from the "Idle” state to the "Wait for Reply” state occurs when the portable part's MMSP layer sends a MMS-SEND primitive.
  • the portable part also starts a MMSP-layer timer TMMS1 that has the same predetermined time limit as the SM-CP-layer timer TC1N according to the GSM specifications.
  • the portable part If the timer expires before the portable part has received the MMS-SEND-RPY type acknowledgement, the portable part retransmits the same MMS-SEND primitive and no state transition occurs. But if the portable part receives the MMS-SEND-RPY type acknowledgement before the timer TMMS 1 expires, the state machine returns to the "Idle" state. Between the MMSP protocol layer and the DECT CC (Call Control) layer there has to be a connection controlling the operation because if there is no data link forward from the MMSP layer, the portable part will not send the MMS-SEND primitive.
  • Fig. 9 shows an example of short message transfer according to the third preferred embodiment of the invention, wherein a portable part PP is handed over from fixed part FPl to fixed part FP2 under a mobile services switching centre MSC.
  • Time interval 91 comprises connection establishment
  • time interval 92 comprises short message transfer via the old fixed part FPl
  • time interval 93 comprises an external handover.
  • time intervals 94 illustrate transfer of data related to the SM-RP protocol layer in IWU-INFO messages sent on the basis of MMS-SEND primitives.
  • Figs. 10 and 11 show two examples of short message transfer according to the third preferred embodiment of the invention, wherein it is illustrated especially the mapping of messages in the PP's protocol layers SM-RP, IWU/MMSP and CC, and in the FP's protocol layers CC and MMSP/IWU.
  • Fig. 10 shows mobile originated (MO) short message transfer
  • Fig. 11 shows mobile terminated (MT) short message transfer.
  • the figures are based on the alternative in which the portable part's SM-CP-layer functions are only partly mapped in the MMSP layer.
  • ETS 300 175-1 2nd edition “Radio Equipment and Systems (RES); Digital European Cordless Telecommunications (DECT) Common Interface Part 1 : Overview”.
  • ETS 300 175-2 2nd edition “Radio Equipment and Systems (RES); Digital European Cordless Telecommunications (DECT) Common Interface Part 2: Physical layer”.
  • ETS 300 175-3 2nd edition “Radio Equipment and Systems (RES); Digital European Cordless Telecommunications (DECT) Common Interface Part 3: Medium access control layer”.
  • ETS 300 175-4 2nd edition “Radio Equipment and Systems (RES); Digital European Cordless Telecommunications (DECT) Common Interface Part 4: Data link control layer”.
  • ETR 015 Digital European Cordless Telecommunications Reference document.
  • ETR 043 Radio Equipment and Systems (RES); Digital European Cordless Telecommunications (DECT) Common Interface Services and Facilities requirements specification.
  • ETR 056 Digital European Cordless Telecommunications System description document.
  • ETS 300 370 2nd edition Radio Equipment and Systems (RES); Digital European Cordless Telecommunications/Global System for Mobile Communications (DECT/GSM) Interworking profile, Access and mapping (Protocol/procedure description for 3.1 KHz speech service).
  • RES Radio Equipment and Systems
  • DECT/GSM Digital European Cordless Telecommunications/Global System for Mobile Communications
  • prETS 300 499 "Radio Equipment and Systems (RES); Digital European Cordless Telecommunications/Global System for Mobile Communications (DECT/GSM) Interworking profile GSM MSC - DECT FP Fixed interconnection”.
  • RES Radio Equipment and Systems
  • DECT/GSM Digital European Cordless Telecommunications/Global System for Mobile Communications
  • ETS 300 536 GSM 03.40: "European digital cellular telecommunication system; Technical Realisation of the Short Message Service (SMS) Point-to-point (PP) phase 2".
  • ETS 300 599 GSM 04.11: "European digital cellular telecommunication system; Point-to- Point (PP) Short Message Service (SMS) Support on Mobile Radio Interface phase 2".

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Abstract

To prevent short message information from being lost during a handover in a system in which a portable part of the DECT system takes part in the transfer of short messages according to the GSM system, an acknowledgement arrangement is provided in which short message information is acknowledged using signalling substantially in accordance with the specifications of the GSM system. An interworking unit in connection with a base station or base station cluster controller performs the necessary conversions between the GSM and DECT formats. The inventional idea can be realised in three different ways by arranging the protocol layers participating in the transfer of short messages in different ways in the portable part, fixed part and mobile services switching centre.

Description

Securing of short message information during handover
The invention relates in general to securing uninterrupted and error-free data transmission in a situation in which a terminal of a cellular radio system is handed over from a base station to another. In particular the invention relates to a method and system which attempt to prevent the loss of short messages or parts of them when a cordless phone according to the DECT system moves from a base station cluster to another. Then it is assumed that the base station clusters are connected to a switching centre of a digital mobile phone system. The invention also relates to a cordless phone and a base station in a cordless telephone system, which are equipped so as to operate according to the method disclosed by the invention. Loss of data here means that an error occurs in the transmission so that a data element which was meant to be transmitted does not arrive in its destination.
Handover is a known concept in telecommunications systems in which mobile terminals are in radio connection with base stations. In the DECT system (Digital European Cordless Telephone) the terminals are in general called portable parts (PP) and the base stations and base station cluster controllers that control the operation of the base stations are in general called fixed parts (FP). For simplicity, this application uses the term fixed part to denote the entity consisting of base stations and a base station cluster controller whenever there is no need to consider the elements of this entity separately. Draft standard prETS 300 499 (August 1995) "Radio Equipment and Systems (RES); Digital European Cordless Telecommunications / Global System for Mobile Communications (DECT/GSM) Interworking profile, GSM-MSC ~ DECT-FP Fixed Interconnection" by ETSI (European Telecommunications Standards Institute) discloses interface specifications for connecting a fixed part of the DECT system to operate under a switching centre of the GSM system (Global System for Mobile telecommunications) in the manner shown in Fig. 1. The figure shows by way of example two DECT phones 1 and 2, four RFP (Radio Fixed Part) blocks 3, 4, 5, and 6, two CCFP (Cluster Control Fixed Part) blocks 7 and 8, and an MSC (Mobile services Switching Centre) block 9.
Both cluster controllers control two base stations so that cluster controller 7 controls base stations 3 and 4 and cluster controller 8 controls base stations 5 and 6. The entity comprising a cluster controller and the base stations under its control is called a DECT FP, as described above. In this application that entity is also called a fixed part or, in some cases, a cluster. The standardised interface between each of the cluster controllers 7 and 8 and the switching centre 9 is called the A interface in accordance with the prior art.
Two types of handovers may occur in the system. In Fig. 1, a portable part 2 changes from base station 6 to base station 5, thus initiating a so-called internal handover inside a cluster. A portable part 1, however, changes from base station 5 to base station 4, which is a so-called external handover in which not only the radio fixed part but also the cluster is changed. The handover of portable part 1 is more problematic of these two in that it may cause errors in a short message transfer which possibly is being carried out between the portable part and the transmission network. To illustrate the background of the invention we will now describe signalling related to a short message transfer in a system according to Fig. 1 and the relationship between the signalling and handover.
Short message transfer may be mobile originated (MO SM) or mobile terminated (MT SM). Fig. 2 shows a signalling timing diagram wherein a portable part PP sends a short message via a fixed part FP to a switching centre MSC. The diagram and the message designators in it conform to a known arrangement disclosed in documents 12 to 21 of the reference document list accompanying this patent application. Time flows from top down and the designated arrows represent individual signalling messages. From the point of view of the present invention it is important to distinguish the different stages in which a handover may occur because the preservation or loss of short message information depends on what other information the portable part and the transmission network manage to exchange. The stages are below numbered from HO 1/MO to HO 6/MO, where HO stands for handover and MO stands for mobile originated. Furthermore, the "Ext" in the stage designators stands for external handover.
Ext HO 1/MO:
Handover occurs after the portable part has sent a CC-SETUP message referring to connection establishment but before the portable part has received from the network a CC-CONNECT message indicating that the connection is ready.
Ext HO 2/MO:
Handover occurs after the portable part has received from the network the CC- CONNECT message but before the portable part has sent the short message proper. Ext HO 3/MO:
Handover occurs after the portable part has sent the first segment of the IWU-INFO message conveying the short message but before the fixed part has received the last segment of the IWU-INFO message in question.
Ext HO 4/MO:
Handover occurs after the fixed part has received from the portable part the last segment of the rWU-INFO message but before the fixed part has received from the switching centre a CP-ACK message indicating an acknowledgement.
Ext HO 5/MO:
Handover occurs after the fixed part has received from the switching centre the CP- ACK message but before the fixed part has received from the switching centre the whole of a CP-DATA message containing reply data.
Ext HO 6/MO:
Handover occurs after the fixed part has received from the switching centre the last segment of the CP-DATA message containing reply data but before the fixed part has sent to the switching centre a CP-ACK acknowledgement message.
Fig. 3 shows by way of example a signalling timing diagram wherein a portable part PP receives a short message from a mobile services switching centre MSC via a fixed part FP. As for the reference designators, the diagram corresponds to that shown in Fig. 2 and the stages in which a handover may occur are numbered from HO 1/MT to HO 6/MT where HO stands for handover and MT stands for mobile terminated.
Ext HO 1/MT:
Handover occurs after the fixed part has received from the switching centre the last segment of a CP-DATA message conveying the short message and the fixed part has sent a CC-SETUP message referring to connection establishment but before the fixed part has received from the portable part a CC-CONNECT message indicating that the connection is ready.
Ext HO 2/MT:
Handover occurs after the fixed part has received from the portable part the CC- CONNECT message but before the portable part has received the last segment of the IWU-INFO message conveying the short message. Ext HO 3/MT:
Handover occurs after the portable part has received the last segment of the IWU- INFO message conveying the short message but before the fixed part has received from the portable part a new IWU-INFO message containing reply data.
Ext HO 4/MT:
Handover occurs after the fixed part has received from the portable part a new IWU-INFO message containing reply data but before the fixed part has sent to the switching centre a CP-DATA message containing reply data.
Ext HO 5/MT:
Handover occurs after the fixed part has sent to the switching centre a CP-DATA message containing reply data but before the fixed part has received from the switching centre a CP-ACK acknowledgement message.
Co-operation of different transmission systems is made possible by the interworking unit (IWU). Interworking units must be provided in the system hardware especially for the interworking of the DECT and GSM systems; said units carry out the conversions of signalling messages and related data fields between the formats of the different systems. According to a known proposal, the interworking unit in the DECT FP, which is important from the point of view of the invention, performs the short message conversions such that data transfer between the fixed part and the mobile services switching centre is carried out in the GSM short message format, and between the fixed part and the DECT portable part the short messages are transferred in {IWU-INFO} messages according to the DECT system. A short message may be longer than one {IWU-INFO} message that complies with the specifications, in which case it is divided into segments transmitted consecutively. According to the specifications no other control messages may be transmitted between {IWU-INFO} messages conveying a short message, so a handover cannot occur before the buffers used for temporarily storing the short message segments both in the portable part and in the old fixed part are empty.
The DECT specifications require that in a controlled handover the portable part establishes a connection with the new fixed part in parallel with the old connection so that the connection with the old fixed part can be terminated using the normal CC-RELEASE message in which the portable part includes a code for external handover. It is, however, possible that the old connection is cut off due to a sudden break or fade-out, in which case the portable part has a certain limited period of time to establish a connection with the new fixed part. Below it is described the aforementioned handover stages HO 1/MO to HO 6/MO and HO 1/MT to HO 5/MT defining whether or not data loss is possible in a controlled handover and, on the other hand, when a break cuts off the connection to the old fixed part. It should be noted that the description below only covers the external handover in which the mobile services switching centre MSC participates.
Ext HO 1/MO:
Controlled: Short message data are not lost since the portable part has not yet sent any part of the short message. Handover is carried out through the mobile services switching centre as in a normal voice call.
Break: Short message data are not lost since the portable part has not yet sent any part of the short message. Handover is carried out through the mobile services switching centre as in a normal voice call.
Ext HO 2/MO:
Controlled: Short message data are not lost since the messages conveying the short message are in a message buffer and the portable part sends them prior to the terminate message sent via the same message buffer. Break: Short message data may be lost because the portable part tries in vain to empty the message buffer through the old fixed part.
Ext HO 3/MO:
Controlled: Short message data are not lost because the messages conveying the short message are in a message buffer and the portable part sends them prior to the terminate message sent via the same message buffer.
Break: Short message data may be lost because the portable part tries in vain to empty the message buffer through the old fixed part.
Ext HO 4/MO:
Controlled: Short message data are not lost since the mobile services switching centre sends a CP-ACK message to the new fixed part according to the specifications of the control protocol (CP) layer.
Break: Short message data are not lost since the mobile services switching centre sends a CP-ACK message to the new fixed part according to the specifications of the control protocol (CP) layer. Ext HO 5/MO:
Controlled: Short message data are not lost since the mobile services switching centre sends a CP-DATA message to the new fixed part according to the specifications of the control protocol (CP) layer. Break: Short message data may be lost because the mobile services switching centre sends the CP-DATA message to the old fixed part instead of the new one.
Ext HO 6/MO:
Controlled: Short message data are not lost because the messages conveying the short message are in a message buffer and the portable part sends them prior to the terminate message sent via the same message buffer. Break: Short message data may be lost.
Ext HO 1/MT: Controlled: Short message data may be lost if the old fixed part acknowledges the CP-DATA message from the switching centre immediately with a CP-ACK message.
Break: Short message data may be lost if the old fixed part acknowledges the CP- DATA message from the switching centre immediately with a CP-ACK message.
Ext HO 2/MT:
Controlled: Short message data are not lost because the messages conveying the short message are in a message buffer and the fixed part sends them prior to the terminate message sent via the same message buffer. Break: Short message data may be lost if the old fixed part acknowledges the CP- DATA message from the switching centre immediately with a CP-ACK message.
Ext HO 3/MT:
Controlled: Short message data are not lost because the messages conveying the short message are in a message buffer and the portable part sends them prior to the terminate message sent via the same message buffer.
Break: Short message data may be lost if the old fixed part acknowledges the CP- DATA message from the switching centre immediately with a CP-ACK message.
Ext HO 4/MT:
Controlled: Short message data are not lost because the messages conveying the short message are in a message buffer and the portable part sends them prior to the teπninate message sent via the same message buffer. Break: Short message data may be lost if the old fixed part acknowledges the CP- DATA message from the switching centre immediately with a CP-ACK message.
Ext HO 5/MT: Controlled: Short message data are not lost since the mobile services switching centre sends a CP-ACK message to the new fixed part according to the specifications of the control protocol (CP) layer. Break: Handling of this abnormal situation is done by the GSM system.
So, the handover situations in which short message data may be lost are as follows:
* handover caused by a break, mobile originated short message transfer:
- Ext HO 2/MO, Ext HO 3/MO, Ext HO 5/MO and Ext HO 6/MO.
* handover caused by a break, mobile terminated short message transfer:
- Ext HO 1/MT, Ext HO 2/MT, Ext HO 3/MT and Ext HO 4/MT.
* controlled handover, mobile terminated short message transfer:
- Ext HO 1/MT.
The specifications of the DECT and GSM systems and the draft standards concerning their interworking do not disclose a method for preventing the above- mentioned loss of short message data. An object of this invention is to provide a method for securing the short message data in an external handover situation in a cordless communications system wherein the handover is carried out through a switching centre of a cellular radio system. Another object of the invention is that the method according to the invention does not require unreasonably big changes in the current configuration and protocol specifications of the systems. A further object of the invention is to provide a data transfer system in which the cordless portable part and fixed part operate as specified by the method according to the invention.
The objects of the invention are achieved by utilising a short message acknowledgement protocol included in said cellular radio system as part of said cordless communications system.
The method according to the invention for conveying short messages from a transmission network to a portable part of a cordless telephone system, said transmission network comprising a fixed part of a cordless telephone system and a mobile services switching centre of a mobile communications system, is characterised in that it comprises stages wherein
- in response to the reception of short message data from said mobile services switching centre via said fixed part said portable part sends to said fixed part an acknowledgement message in the format required by the specifications of said cordless telephone system,
- said fixed part converts said acknowledgement message to a format required by the specifications of said mobile communications system and sends it to said mobile services switching centre, and - in said mobile services switching centre information about the reception of said acknowledgement message is conveyed to a certain short message protocol layer according to the specifications of said mobile communications system.
The invention is also directed to a method for transferring short messages in the opposite direction. The method according to the invention for transferring short messages from a portable part of a cordless telephone system to a transmission network comprising a fixed part of a cordless telephone system and a mobile services switching centre of a mobile communications system, is characterised in that it comprises stages wherein - in response to the reception of short message data from said portable part via said fixed part said mobile services switching centre sends to said fixed part an acknowledgement message in the format required by the specifications of said mobile communications system,
- said fixed part converts said acknowledgement message to a format required by the specifications of said cordless telephone system and sends it to said portable part, and
- in said portable part information about the reception of said acknowledgement message is conveyed to a certain short message protocol layer according to the specifications of said mobile communications system.
The idea according to the invention is in this patent application directed particularly to the operation of the DECT and GSM systems but it can also be applied to other corresponding adaptations of communications systems. The idea of utilising short message protocols of the GSM system in the DECT system can be realised in at least three different ways which are disclosed in this patent application as the preferred embodiments of the invention. The first alternative employs the SM-CP protocol layer (Short Message - Control Protocol) of the GSM system, which is a simple "send and wait" type protocol. The transmitting device sends a so-called CP-DATA message answered by the receiving device with a CP-ACK or CP-ERROR message. The CP-DATA message may include a message of a higher protocol layer and the CP-ERROR message may include the cause of the reception error. In the first preferred embodiment of the invention, the SM-CP protocol layer counterparts are in the portable part of the cordless telephone system and in the mobile services switching centre, so that the protocol layer in question is transported through the fixed part and base station unchanged. In an error situation the transmitting device once retransmits an unacknowledged SM-CP layer message after a certain period of time. A particular advantage of this embodiment is that the portable part can utilise all protocol layers specified for short messages in a GSM terminal and that the interworking units (IWU) of both the portable part and fixed part are fairly simple in implementation. The probability of data being lost is very small.
The second preferred embodiment of the invention employs the aforementioned SM-CP protocol layer between the mobile services switching centre and the fixed part. The counterparts of the next highest protocol layer (SM-RP, Short Message - Relay Protocol) are in the portable part of the cordless telephone system and in the mobile services switching centre. Communication between the fixed part and portable part complies with the specifications of the DECT system with the exception that the interworking units (IWU) of the devices exchange short message related information between them. In a handover situation the responsibility for securing the short message information lies primarily with the interworking unit of the fixed part. Indeed, this embodiment requires a little more complex implementation of the interworking units than the first embodiment. The mutual correlation of messages and records as well as the conversions made by the interworking units are described in more detail later on. This embodiment has the special advantage that it requires only slight changes in the current specifications. However, absolute securing of short message data in a handover cannot be guaranteed.
The third preferred embodiment of the invention employs a special multimedia messaging service protocol (MMSP), which is specified in document DE/RES- 03038: "Radio Equipment and Systems (RES); Digital European Cordless Telecommunications (DECT) Data Services Profile Multimedia Messaging Service with Specific provision for Facsimile service (service type F, Class 2)". The CM-ACK and CM-ERROR messages of the above-mentioned SM-CP protocol of the GSM system are conveyed across the PP-FP radio interface using the MMSP protocol so that possible error situations are corrected according to the mechanisms of the SM- CP protocol. It can be said that a disadvantage of this embodiment is that said MMSP protocol is by definition not the same kind of a state machine consisting of well-defined states as e.g. the SM-CP protocol, so its use is not completely in harmony with the original specifications. However, the loss of short message information is prevented more effectively than in the second embodiment of the invention described above.
The invention is described in more detail with reference to the preferred embodiments presented by way of example and to the attached drawing in which
Fig. 1 schematically shows a known communications system the operation of which can be made more efficient using the invention, Fig. 2 shows a known timing diagram for signalling in mobile originated short message transfer,
Fig. 3 shows a known timing diagram for signalling in mobile terminated short message transfer,
Fig. 4 shows protocol layers used in a first preferred embodiment of the invention,
Fig. 5 shows protocol layers used in a second preferred embodiment of the invention,
Fig. 6 shows protocol layers used in a third preferred embodiment of the invention, Fig. 7 shows a timing diagram for short message transfer according to the first preferred embodiment of the invention,
Fig. 8 shows a timing diagram for short message transfer according to the second preferred embodiment of the invention,
Fig. 9 shows a timing diagram for short message transfer according to the third preferred embodiment of the invention,
Fig. 10 shows messages in a communications situation according to the third preferred embodiment of the invention, and
Fig. 11 shows messages in a second communications situation according to the third preferred embodiment of the invention. Above, in connection with the description of the prior art, reference was made to Figs. 1 to 3, so below in the description of the invention and its preferred embodiments reference will be made mainly to Figs. 4 to 11. Like elements in the drawing are denoted by like reference designators.
Fig. 4 shows the protocol stacks used in different parts of the system in the case of the first preferred embodiment of the invention. The use of protocol stacks, or the logical OSI (Open Systems Interconnection) architecture, is known to a person skilled in the art. Column PP represents the protocol stack of a portable part of a cordless telephone system, column FP represents the protocol stack of the fixed part, column MSC represents the protocol stack of a mobile services switching centre and column SC represents the protocol stack of a short message service centre. The figure shows only the protocol layers that are essential from the point of view of the invention.
The lower protocol layers PHY, MAC and DLC (Physical, Media Access Control, Data Link Control) are used in a known manner between the portable part PP and fixed part FP to take care of the physical data transfer and the related functions. In addition, the portable part PP and fixed part FP have, above the aforementioned, a CC (Call Control) protocol layer which in a known manner includes the functions needed for the establishment and maintenance of a telephone connection. It has been proposed that the CC layer be supplemented with a MMSP (Multimedia Messaging Service Protocol) part which extends the applicability of the CC protocol layer to the realisation of other than voice connections. In the system described here, the protocol layers mentioned so far comply with the standards of the cordless telephone system, particularly the DECT system.
For a DECT portable part PP to be able to use the GSM short message service in accordance with the first embodiment of the invention, it has to have an IWU (Interworking Unit) layer above the CC layer mentioned above. Correspondingly, the fixed part FP includes an interworking unit IWU which acts as an intermediary between the CC+MMSP layer of the DECT system and the MM (Mobility Management) layer operating in the direction of the mobile services switching centre MSC. The mobile services switching centre MSC has a counterpart for this MM layer. According to the first embodiment of the invention the fixed part FP has no higher protocol layers in connection with the short message service, but on the next highest layers SM-CP and SM-RP the counterparts are located in the portable part PP and the mobile services switching centre MSC. On the highest protocol layer SM-TP (Short Message - Transport Protocol) the counterparts are found in the portable part PP and short message service centre SC.
In the first embodiment of the invention the protocol layers SM-CP, SM-RP and SM-TP operate in a known manner defined in the standards of the GSM system and described in an illustrative manner e.g. in a book titled "The GSM System for Mobile Communications" by Michel Mouly and Marie-Bernadette Pautet, published by the authors, ISBN 2-9507190-0-7, Palaiseau 1992. The inventional idea of bringing GSM standards partly in the DECT domain is applied by forming a stack of the three protocol layers as such in a portable part PP so that e.g. all CP-DATA, CP-ACK and CP-ERROR messages of the SM-CP layer are transmitted as such between the mobile services switching centre MSC and the portable part PP. If any of these messages is lost during a handover, the device that sent the lost message notices that the receiving device sends no acknowledgement and retransmits the message. In certain cases it may be that a message of the SM-CP layer is duplicated during a handover, in which case the receiving device may receive two identical copies of the same SM-RP -layer message conveyed by the SM-CP layer. The situation is corrected when the receiving device compares the eight-bit message identifiers of the SM-RP-layer messages with each other.
For the transfer of unmodified SM-CP-layer messages between a mobile services switching centre MSC and a portable part PP to be successful, the interworking units performing the interpretation between the DECT and GSM specifications have to have information about which of the data elements of the different systems cor- respond to each other and how they are inter-converted in the transfer. Table 1 shows the correlation of messages in the interworking unit IWU of the portable part PP in a mobile originated short message transfer. Table 2 shows the correlation of messages in the interworking unit IWU of the fixed part FP in a mobile originated short message transfer. Table 3 shows the correlation of messages in the inter- working unit IWU of the portable part PP in a mobile terminated short message transfer, and Table 4 shows the correlation of messages in the interworking unit IWU of the fixed part FP in a mobile terminated short message transfer. The reference "message in IWU-to-IWU parameter", which appears in the tables, means that the message is added to the corresponding IWU-INFO type transmission using a known parameter format. A person skilled in the art is able to draw up the necessary message interpretation instructions for the interworking units on the basis of the tables. The SM-CP protocol layer may require some changes in the timing, but suitable timings can be easily found by means of experimentation or simulating real operation.
Fig. 7 shows an example of a short message transfer in a handover of a portable part PP from fixed part FP1 to fixed part FP2 under a mobile services switching centre MSC. Time interval 71 comprises connection establishment, time interval 72 comprises short message transfer via the old fixed part FP1, and time interval 73 comprises an external handover.
Let us next consider the second preferred embodiment of the invention, referring to Fig. 5 which shows the essential parts of the protocol stacks used in the communications system. The operation of the PHY, MAC, DLC and CC+MMSP layers used in the communications between the portable part PP and fixed part FP is the same as in the first embodiment described above. However, the portable part PP does not have a SM-CP protocol layer, but above the IWU layer on top of the CC+MMSP layer there is immediately the SM-RP layer and above that, the SM-TP layer. In the fixed part FP the interworking unit IWU operates between the CC+MMSP layer, which operates in the direction of the portable part PP, and the SM-CP layer, which operates in the direction of the mobile services switching centre MSC. Between the fixed part FP and the mobile services switching centre MSC there are, below said SM-CP layer, other layers of which Fig. 5 shows the SCCP/MAP (Signalling Connection Control Part / Mobile Application Part) layer. In the mobile services switching centre MSC there are, above said SM-CP layer, the SM-RP layer, the counterpart of which is the corresponding SM-RP layer of the portable part PP. At the highest layer, i.e. the SM-TP layer, the counterparts are in the portable part PP and short message service centre SC.
During normal operation, when no handover is taking place, the interworking unit IWU of the fixed part FP transfers a CP-DATA message to a mobile services switching centre MSC only when all the IWU-INFO segments that contain parts of the message in question have arrived error-free from the portable part PP. Otherwise the fixed part FP discards the parts of the incomplete CP-DATA message. In mobile terminated short message transfer the fixed part FP does not acknowledge the first CP-DATA message from the switching centre MSC until the connection to the portable part is established, i.e. the fixed part FP has received from the portable part PP a {CC-CONNECT} message. Normal operation may follow one of the following alternative patterns: a) The fixed part FP does not acknowledge the CP-DATA message from the switching centre with a CP-ACK message until a little before the expiration of the TC1N timer of the SM-CP layer specifications so that the fixed part has time to send the short message successfully to the portable part. In this alternative, the portable part PP does not send an acknowledgement to the fixed part FP.
b) When the portable part PP has received a complete short message, its IWU layer acknowledges the fixed part FP either with an empty IWU-INFO message or with a reply message of the SM-RP layer, transferred in parameters of the IWU-INFO message. Said empty IWU-INFO message may contain a copy of the first IWU-INFO segment used in the transfer of a successfully received short message. Alternatively, bit 8 of octet 3 in the «IWU-to- IWU» element can be set to 0 to indicate an acknowledgement or the <Protocol Discriminator> field in the reply message can be given a value which indicates an acknowledgement to the message sent. The latter two are new specifications that should be included in the standard specifications for the structure of said messages. When, after the transfer of the short message, the fixed part FP receives from the portable part PP the next {IWU-INFO} message (either empty or a normal SMS message), it acknowledges the CP-
DATA message received earlier from the switching centre MSC using a CP- ACK message.
In a controlled handover, the fixed part FP receives from the portable part PP a {CC-RELEASE-COM} message which includes, if necessary, an indicator for external handover. Then the old fixed part FP immediately sends, in accordance with this embodiment of the invention, to the switching centre MSC a CP-ACK acknowledgement message to prevent the switching centre from unnecessarily retransmitting the same short message via the new fixed part; this is because in a controlled external handover the {CC-RELEASE-COM} message indicates, among other things, that the short messages in the transmit buffers have been conveyed across the radio interface prior to the controlled termination of the connection. The portable part PP sends the reply messages from the higher protocol layers via the new fixed part whereby the new fixed part sends to the switching centre the CP- ACK message corresponding to the CP-DATA message transfeπed earlier via the old fixed part. Now at the latest the switching centre knows that the short message sent via the old fixed part has been successfully received in the portable part. If the portable part PP receives via the new fixed part an identical copy of an already- received short message, it discards the extra copy and sends to the new fixed part an acknowledgement message of a higher protocol layer (SM-RP). In mobile originated short message transfer the portable part terminates, if necessary, the transfer of segments of a message to the old fixed part if a handover occurs, and sends all segments of that short message to the new fixed part.
If the portable part suddenly disappears from the range of the old fixed part thus making the external handover uncontrolled, the old fixed part does not send a CP- ACK message to the switching centre MSC in this embodiment of the invention. When a certain SM-CP-layer time limit in the switching centre is exceeded the switching centre attempts to retransmit the unacknowledged CP-DATA message. If the normal handover signalling has sent information about the new base station cluster to the switching centre, the switching centre sends the message to that, so that short message information will not be lost. If, in spite of the fade-out, the portable part PP had received the short message or if it receives it via the new fixed part, it sends a SM-RP-layer acknowledgement via the new fixed part. If necessary, the portable part discards the incomplete short message parts, i.e. those IWU-INFO segments that do not constitute a complete short message.
Fig. 8 shows an example of a short message transfer according to the second embodiment of the invention, wherein a handover is performed for portable part PP from fixed part FP1 to fixed part FP2 under a mobile services switching centre MSC. Time interval 81 comprises connection establishment, time interval 82 comprises short message transfer via the old fixed part FP1, and time interval 83 comprises an external handover. Acknowledgement employs the b-alternative described above and timer TC1N of the SM-CP protocol layer in the old fixed part FP1 ("Note 1 " in the figure).
Let us next consider the third preferred embodiment of the invention, referring to Fig. 6 which once again shows the essential parts of the protocol stacks used in the devices of the communications system. The operation of the PHY, MAC and DLC layers used in the communications between the portable part PP and fixed part FP is the same as in the first and second embodiments described above. In the third embodiment now disclosed the SM-CP protocol layer according to the GSM system is used only between the fixed part FP and the mobile services switching centre MSC in the same way as in the second embodiment described above. Between the portable part PP and fixed part FP the MMSP protocol layer is separated according to Fig. 6 into an "auxiliary layer" of its own, which, however, in the standard OSI model belongs to the same layer as the CC layer. The idea is that the portable part and fixed part use in their mutual communications primitives and acknowledgement rules of the MMSP protocol layer so that an acknowledgement need not be performed "indirectly" by means of timing arrangements and/or messages of the SM-RP layer, as in the second embodiment described above.
The interworking unit IWU of the portable part PP operates between the portable part's SM-RP protocol layer and the MMSP layer. In the fixed part FP the interworking unit IWU makes the necessary conversions between the MMSP/CC layer according to the DECT specifications and the SM-CP layer according to the GSM specifications.
In the method according to the third embodiment possible errors caused by an external handover are corrected substantially according to the specifications of the SM-CP protocol layer. Detection and correction of errors are performed between the portable part PP and mobile services switching centre MSC in such a manner that between the portable part PP and fixed part FP it is used MMSP-layer primitives and corresponding IWU-INFO messages to fully or partially represent the corresponding SM-CP-layer concepts. Table 5 shows the correlation of messages in the PP's interworking unit IWU when MMSP-layer primitives are used to fully or partially represent the corresponding SM-CP-layer concepts. Table 6 shows the correlation of messages in the FP's interworking unit IWU when MMSP-layer primitives are used to fully or partially represent the corresponding SM-CP-layer concepts in mobile originated short message transfer. Table 7 shows the correlation of messages in the FP's interworking unit IWU when MMSP-layer primitives are used to fully or partially represent the corresponding SM-CP-layer concepts in mobile terminated short message transfer.
The alternative where MMSP-layer primitives are used to fully represent the corresponding SM-CP-layer concepts refers to an arrangement wherein all SM-CP- layer messages have a well-defined counterpart in the MMSP layer. In this case the MMSP-layer functions follow as accurately as possible the functions and states of the SM-CP layer. In other words, the MMSP layer behaves as much as possible in the same way as the SM-CP layer that complies with GSM specifications. A special advantage of this alternative is that the portable part's MMSP layer can be made to operate as a peer entity of the mobile services switching centre's SM-CP layer so that the exchange of acknowledgement messages and other short message related communications between the portable part PP and the mobile services switching centre MSC comply with the known end-to-end functionality.
The alternative in which MMSP-layer primitives are used to only partially represent the corresponding SM-CP-layer concepts refers to an arrangement wherein the PP's interworking unit IWU uses MMSP-layer MMS-SEND-RPY primitives to represent the SM-CP-layer messages required in the transmission of acknowledgement messages. MMSP-layer MMS-SEND primitives can be used for conveying RP-ACK messages coming from the SM-RP protocol layer; in the SM-CP layer these would correspond to CP-DATA messages. Then the mobile services switching centre's SM-CP protocol layer counterpart is mainly in the fixed part. In this alternative the portable part's MMSP layer implementation is rather simple.
In Tables 5 to 7, a "primitive" refers to communication between different protocol layers in one and the same device, which communication may be either a request (-Req) or an indication (-Ind). The tables show that when the portable part is the receiving device (MT, or mobile terminated transfer), a MMS-SEND-RPY type primitive between the MSSP sub-layer and CC layer conveys the acknowledgement indicating that the portable part has received the segmented short message in full. The fixed part converts the corresponding IWU-INFO message sent by the portable part to a CP-ACK acknowledgement to be sent to the mobile services switching centre MSC. In mobile originated (MO) transfer the mobile services switching centre sends a CP-ACK message which the fixed part converts to an IWU-INFO message to be sent to the portable part. The portable part's CC layer further sends the information in the form of a MMS-SEND-RPY type primitive to the MMSP layer. Like the first embodiment, this embodiment may also require minor modifications in the SM-CP-layer timing arrangements, but the most suitable time values can be easily found using ordinary methods of experimentation or simulation. In short, the correlations of the fields in different messages are as follows:
a) the Message Identifier field in a SM-CP message corresponds to the MMS Message Identifier field, b) the User data field in a SM-CP message corresponds to the MMS User data field, and c) the CP-ACK and CP-ERROR correlations in the MMS-SEND-RPY primitives are realised using the Command Outcome field of the MMS-SEND-RPY primitive so that field contents indicating success correspond to the CP-ACK message and failure corresponds to the CP-ERROR message. In connection with the third embodiment of the invention, the MMSP-layer operation of the portable part can be modelled using a certain state machine. In the alternative in which all SM-CP-layer functions of the portable part are fully mapped in the MMSP layer, the state machine shall include all items presented in Subclause 5 in document [20] of the reference document list attached to this patent application, so that the CP-DATA message corresponds to MMS-SEND, the CP-ACK message corresponds to MMS-SEND-RPY wherein the <Command Outcome> field of the «MMS-Generic-Header» element contains a code for "successful", and the CP- ERROR message corresponds to MMS-SEND-RPY wherein the <Command Outcome> field of the «MMS-Generic-Header» element contains a code for "unsuccessful".
In the alternative in which the portable part's SM-CP layer functions are only partly mapped in the MMSP the state machine can only have two states, the first of which is "Idle" and the second "Wait for Reply". The first transition from the "Idle" state to the "Wait for Reply" state occurs when the portable part's MMSP layer sends a MMS-SEND primitive. Then the portable part also starts a MMSP-layer timer TMMS1 that has the same predetermined time limit as the SM-CP-layer timer TC1N according to the GSM specifications. If the timer expires before the portable part has received the MMS-SEND-RPY type acknowledgement, the portable part retransmits the same MMS-SEND primitive and no state transition occurs. But if the portable part receives the MMS-SEND-RPY type acknowledgement before the timer TMMS 1 expires, the state machine returns to the "Idle" state. Between the MMSP protocol layer and the DECT CC (Call Control) layer there has to be a connection controlling the operation because if there is no data link forward from the MMSP layer, the portable part will not send the MMS-SEND primitive.
Fig. 9 shows an example of short message transfer according to the third preferred embodiment of the invention, wherein a portable part PP is handed over from fixed part FPl to fixed part FP2 under a mobile services switching centre MSC. Time interval 91 comprises connection establishment, time interval 92 comprises short message transfer via the old fixed part FPl, and time interval 93 comprises an external handover. In addition, time intervals 94 illustrate transfer of data related to the SM-RP protocol layer in IWU-INFO messages sent on the basis of MMS-SEND primitives.
Figs. 10 and 11 show two examples of short message transfer according to the third preferred embodiment of the invention, wherein it is illustrated especially the mapping of messages in the PP's protocol layers SM-RP, IWU/MMSP and CC, and in the FP's protocol layers CC and MMSP/IWU. Fig. 10 shows mobile originated (MO) short message transfer, and Fig. 11 shows mobile terminated (MT) short message transfer. The figures are based on the alternative in which the portable part's SM-CP-layer functions are only partly mapped in the MMSP layer.
Above it was described three embodiments that illustrate the application possibilities of the invention when a terminal of the DECT system is adapted to use the short message services of the GSM system. It is obvious to one skilled in the art that the embodiments disclosed are presented by way of example only and they can be modified within the scope of the inventional idea defined by the claims set forth below.
References:
[I] ETS 300 175-1 2nd edition: "Radio Equipment and Systems (RES); Digital European Cordless Telecommunications (DECT) Common Interface Part 1 : Overview". [2] ETS 300 175-2 2nd edition: "Radio Equipment and Systems (RES); Digital European Cordless Telecommunications (DECT) Common Interface Part 2: Physical layer".
[3] ETS 300 175-3 2nd edition: "Radio Equipment and Systems (RES); Digital European Cordless Telecommunications (DECT) Common Interface Part 3: Medium access control layer". [4] ETS 300 175-4 2nd edition: "Radio Equipment and Systems (RES); Digital European Cordless Telecommunications (DECT) Common Interface Part 4: Data link control layer".
[5] ETS 300 175-5 2nd edition: "Radio Equipment and Systems (RES); Digital European Cordless Telecommunications (DECT) Common Interface Part 5: Network layer".
[6] ETS 300 175-6 2nd edition: "Radio Equipment and Systems (RES); Digital European Cordless Telecommunications (DECT) Common Interface Part 6: Identities and addressing".
[7] ETS 300 175-7 2nd edition: "Radio Equipment and Systems (RES); Digital European Cordless Telecommunications (DECT) Common Interface Part 7: Security features".
[8] ETS 300 175-8 2nd edition: "Radio Equipment and Systems (RES); Digital European Cordless Telecommunications (DECT) Common Interface Part 8: Speech coding and trans- mission".
[9] ETR 015: "Digital European Cordless Telecommunications Reference document".
[10] ETR 043: "Radio Equipment and Systems (RES); Digital European Cordless Telecommunications (DECT) Common Interface Services and Facilities requirements specification".
[I I] ETR 056: "Digital European Cordless Telecommunications System description document". [12] ETS 300 370 2nd edition: Radio Equipment and Systems (RES); Digital European Cordless Telecommunications/Global System for Mobile Communications (DECT/GSM) Interworking profile, Access and mapping (Protocol/procedure description for 3.1 KHz speech service).
[13] prETS 300 499: "Radio Equipment and Systems (RES); Digital European Cordless Telecommunications/Global System for Mobile Communications (DECT/GSM) Interworking profile GSM MSC - DECT FP Fixed interconnection".
[14] DE/RES-03071 (September 1995): "Radio Equipment and Systems; Digital European Cordless Telecommunications (DECT),/Global System for Mobile communications (DECT/GSM) inter-working profile, Implementation of bearer services".
[15] (DE/RES-03049) prETS 300 499 (August 1995): "Radio Equipment and Systems (RES); Digital European Cordless Telecommunications / Global System for Mobile Communications (DECT/GSM) Interworking profile, GSM-MSC - DECT-FP Fixed Interconnection"
[16] (DE/RES-03050) (June 1995): "Radio Equipment and Systems (RES); Digital European Cordless Telecommunications / Global System for Mobile Communications (DECT/GSM) Interworking profile, GSM Phase 2 supplementary services implementation" [17] (DE/RES-03057): "Radio Equipment and Systems (RES); Digital European Cordless Telecommunications / Global System for Mobile Communications (DECT/GSM) Interworking profile, Implementation of Short message services, point to point and Cell broadcast" [18] (DE/RES-03058): "Radio Equipment and Systems (RES); Digital European Cordless Telecommunications / Global System for Mobile Communications (DECT/GSM) Interworking profile, Implementation of facsimile group 3"
[19] ETS 300 536 (GSM 03.40): "European digital cellular telecommunication system; Technical Realisation of the Short Message Service (SMS) Point-to-point (PP) phase 2". [20] ETS 300 599 (GSM 04.11): "European digital cellular telecommunication system; Point-to- Point (PP) Short Message Service (SMS) Support on Mobile Radio Interface phase 2".
[21] DE/RES-03078 (June 1995): "Radio Equipment and Systems; Digital European Cordless Telecommunications (DECT), Data services profile, Low Rate Messaging Service (Service type E, Class 2)". [22] (DE/RES-03038): "Radio Equipment and Systems (RES); Digital European Cordless Telecommunications (DECT) Data Services Profile Multimedia Messaging Service with Specific provision for Facsimile service (service type F, Class 2)"
Table 1:
Figure imgf000024_0001
Table 2:
Figure imgf000025_0001
Table 3:
Figure imgf000026_0001
Table 4:
Figure imgf000027_0001
Table 5:
Figure imgf000028_0001
NOTE 1): One higher-layer primitive is associated with two lower-layer primitives.
NOTE 2): Release Reason and Cause codes are mapped to each other.
NOTE 3): RPDU is carried as such in the User field of the MMS-SEND message. A code indicating this shall be added to the MMS SEND message.
Table 6:
Figure imgf000029_0001
Table 7:
Figure imgf000030_0001

Claims

Claims
1. A method for transferring short messages from a communications network to a portable part of a cordless telephone system, said communications network comprising a fixed part of a cordless telephone system and a mobile services switching centre of a mobile communications system, wherein short message information is transferred
- between said mobile services switching centre and said fixed part in the format required by the specifications of said mobile communications system and
- between said fixed part and said portable part in the format required by the specifications of said cordless telephone system, characterised in that it comprises stages wherein
- in response to the reception of short message information from said mobile services switching centre via said fixed part said portable part sends to said fixed part an acknowledgement message in the format required by the specifications of said cordless telephone system,
- said fixed part converts said acknowledgement message to a format required by the specifications of said mobile communications system and sends it to said mobile services switching centre, and
- in said mobile services switching centre information about the reception of said acknowledgement message is conveyed to a certain short message protocol layer according to the specifications of said mobile communications system.
2. A method for transferring short messages from a portable part of a cordless telephone system to a communications network which comprises a fixed part of a cordless telephone system and a mobile services switching centre of a mobile communications system, in which system short message information is transferred
- between said portable part and said fixed part in the format required by the specifications of said cordless telephone system,
- between said fixed part and said mobile services switching centre in the format required by the specifications of said mobile communications system, characterised in that it comprises stages wherein
- in response to the reception of short message information from said portable part via said fixed part said mobile services switching centre sends to said fixed part an acknowledgement message in the format required by the specifications of said mobile communications system, - said fixed part converts said acknowledgement message to a format required by the specifications of said cordless telephone system and sends it to said portable part, and
- in said portable part information about the reception of said acknowledgement message is conveyed to a certain short message protocol layer according to the specifications of said mobile communications system.
3. The method of claim 1 or 2, characterised in that said mobile communications system is the GSM system and said cordless telephone system is the DECT system.
4. The method of claim 3, characterised in that said portable part comprises protocol layers SM-CP, SM-RP and SM-TP according to the specifications of the GSM system and said mobile services switching centre comprises protocol layers SM-CP and SM-RP according to the specifications of the GSM system so that said acknowledgement message is a CP-ACK message according to the specifications of the GSM system, sent at the SM-CP protocol layer of the device receiving the short message in question.
5. The method of claim 3, characterised in that said portable part comprises protocol layers SM-RP and SM-TP according to the specifications of the GSM system and protocol layer CC according to the specifications of the DECT system, said fixed part comprises protocol layer CC according to the specifications of the DECT system and, parallel with it, protocol layer SM-CP according to the specifications of the GSM system and an interworking unit operating between said protocol layers CC and SM-CP, and said mobile services switching centre comprises protocol layers SM-CP and SM-RP according to the specifications of the GSM system, so that when said portable part has received short message information from said mobile services switching centre via said fixed part, said acknowledgement message is an empty {IWU-INFO} message according to the specifications of the DECT system whereby in response to the reception of said empty {IWU-INFO} message said fixed part sends to said mobile services switching centre a CP-ACK message.
6. The method of claim 3, characterised in that said portable part comprises protocol layers SM-RP and SM-TP according to the specifications of the GSM system and protocol layer CC according to the specifications of the DECT system, said fixed part comprises protocol layer CC according to the specifications of the DECT system and, parallel with it, protocol layer SM-CP according to the specifications of the GSM system and an interworking unit operating between said protocol layers CC and SM-CP, and said mobile services switching centre comprises protocol layers SM-CP and SM-RP according to the specifications of the GSM system, so that when said mobile services switching centre has received short message information from said portable part via said fixed part, said acknowledgement message is a CP-ACK message according to the specifications of the GSM system whereby in response to the reception of said CP-ACK message said fixed part sends to said portable part an empty {IWU-INFO} message according to the specifications of the DECT system.
7. The method of claim 3, characterised in that said portable part comprises protocol layers SM-RP and SM-TP according to the specifications of the GSM system and protocol layer CC according to the specifications of the DECT system, said fixed part comprises protocol layer CC according to the specifications of the DECT system and, parallel with it, protocol layer SM-CP according to the specifications of the GSM system as well as an interworking unit operating between said protocol layers CC and SM-CP, and said mobile services switching centre comprises protocol layers SM-CP and SM-RP according to the specifications of the GSM system, so that when said portable part has received short message information from said mobile services switching centre via said fixed part, said acknowledgement message is an {IWU-INFO} message according to the specifications of the DECT system which comprises a SM-RP acknowledgement message according to the specifications of the GSM system whereby in response to the reception of said {IWU-INFO} message said fixed part transfers the included SM-RP acknowledgement message to said mobile services switching centre.
8. The method of claim 3, characterised in that said portable part comprises protocol layers SM-RP and SM-TP according to the specifications of the GSM system and protocol layer CC according to the specifications of the DECT system, said fixed part comprises protocol layer CC according to the specifications of the DECT system and, parallel with it, protocol layer SM-CP according to the specifications of the GSM system and an interworking unit operating between said protocol layers CC and SM-CP, and said mobile services switching centre comprises protocol layers SM-CP and SM-RP according to the specifications of the GSM system, so that when said mobile services switching centre has received short message information from said portable part via said fixed part, said acknowledgement message is a SM-RP message according to the specifications of the GSM system whereby in response to the reception of said SM-RP acknowledgement message said fixed part transfers to said portable part an {IWU-INFO} message according to the specifications of the DECT system which includes said SM-RP acknowledgement message.
9. The method of claim 3, characterised in that said portable part comprises protocol layers SM-RP and SM-TP according to the specifications of the GSM system and protocol layers CC and MMSP according to the specifications of the DECT system, said fixed part comprises protocol layers CC and MMSP according to the specifications of the DECT system and, parallel with them, protocol layer SM-CP according to the specifications of the GSM system and an interworking unit operating between said protocol layers CC/MMSP and SM-CP, and said mobile services switching centre comprises protocol layers SM-CP and SM-RP according to the specifications of the GSM system, so that said acknowledgement message is - a M-MMS-SEND--RPY message according to the specifications of the DECT system when said portable part has received short message information from said mobile services switching centre via said fixed part whereby in response to the reception of said M-MMS-SEND--RPY message said fixed part sends to said mobile services switching centre a CP-ACK message according to the specifications of the GSM system, and
- a CP-ACK message according to the specifications of the GSM system when said mobile services switching centre has received short message information from said portable part via said fixed part whereby in response to the reception of said CP- ACK message said fixed part sends to said portable part a M-MMS-SEND--RPY message according to the specifications of the DECT system.
10. The method of any one of the preceding claims, characterised in that a mobile services switching centre which has sent a first short message information via a fixed part to a portable part waits for a certain first delay and if said mobile services switching centre does not receive an acknowledgement message from said portable part during said first delay it retransmits said first short message information.
11. The method of any one of claims 1 to 9, characterised in that a portable part which has sent a first short message information via a fixed part to a mobile services switching centre waits for a certain second delay and if said portable part does not receive an acknowledgement message from said mobile services switching centre during said second delay it retransmits said second short message information.
12. Use of the method of any one of the preceding claims during an external handover wherein a portable part of a cordless telephone system changes from a radio connection with a first base station cluster to a radio connection with a second base station cluster, said first and second base station clusters communicating with a mobile services switching centre of a mobile communications system.
AMENDED CLAIMS
[received by the Internat ional Bureau on 02 February 1998 (02.02.98) ; orig inal c laims 1 -12 repl aced by amended cl aims 1 - 13 (5 pages ) ]
1. A method for transferring short messages from a first mobile communications system to a portable part of a second mobile communications system, the first mobile communications system comprising a fixed part of the second mobile communications system and a mobile services switching centre, wherein short message information is transferred
- between the mobile services switching centre and the fixed part in the format required by the specifications of the first mobile communications system and
- between the fixed part and the portable part in the format required by the specifications of the second mobile communications system, characterised in that it comprises stages wherein
- in response to the reception of short message information from the mobile services switching centre via the fixed part the portable part sends to the fixed part an acknowledgement message in the format required by the specifications of the second mobile communications system,
- the fixed part converts said acknowledgement message to a format required by the specifications of the first mobile communications system and sends it to the mobile services switching centre, and
- in the mobile services switching centre, information about the reception of said acknowledgement message is conveyed to a certain short message protocol layer according to the specifications of the first mobile communications system.
2. A method for transferring short messages from a portable part of a second mobile communications system to a first mobile communications system which comprises a fixed part of the second mobile communications system and a mobile services switching centre, in which method short message information is transferred
- between the portable part and the fixed part in the format required by the specifications of the second mobile communications system and
- between the fixed part and the mobile services switching centre in the format required by the specifications of the first mobile communications system, characterised in that it comprises stages wherein
- in response to the reception of short message information from the portable part via the fixed part the mobile services switching centre sends to the fixed part an acknowledgement message in the format required by the specifications of the first mobile communications system, - the fixed part converts said acknowledgement message to a format required by the specifications of the second mobile communications system and sends it to the portable part, and
- in the portable part, information about the reception of said acknowledgement message is conveyed to a certain short message protocol layer according to the specifications of the first mobile communications system.
3. The method of claim 1 or 2, characterised in that the second mobile communications system is a cordless communications system.
4. The method of claim 1 or 2, characterised in that the first mobile communications system is the GSM system and the second mobile communications system is the DECT system.
5. The method of claim 4. characterised in that the portable part comprises protocol layers SM-CP, SM-RP and SM-TP according to the specifications of the GSM system and the mobile services switching centre comprises protocol layers SM-CP and SM-RP according to the specifications of the GSM system so that said acknowledgement message is a CP-ACK message according to the specifications of the GSM system, sent at the SM-CP protocol layer of the device receiving the short message in question.
6. The method of claim 4, characterised in that the portable part comprises protocol layers SM-RP and SM-TP according to the specifications of the GSM system and protocol layer CC according to the specifications of the DECT system, the fixed part comprises protocol layer CC according to the specifications of the DECT system and, parallel with it, protocol layer SM-CP according to the specifications of the GSM system and an interworking unit operating between said protocol layers CC and SM-CP, and the mobile services switching centre comprises protocol layers SM-CP and SM-RP according to the specifications of the GSM system, so that when the portable part has received short message information from the mobile services switching centre via the fixed part, said acknowledgement message is an empty {IWU-INFO} message according to the specifications of the DECT system whereby in response to the reception of said empty {IWU-INFO} message the fixed part sends to the mobile services switching centre a CP-ACK message.
7. The method of claim 4, characterised in that the portable part comprises protocol layers SM-RP and SM-TP according to the specifications of the GSM system and protocol layer CC according to the specifications of the DECT system, the fixed part comprises protocol layer CC according to the specifications of the DECT system and, parallel with it, protocol layer SM-CP according to the specifications of the GSM system and an interworking unit operating between said protocol layers CC and SM-CP, and the mobile services switching centre comprises protocol layers SM-CP and SM-RP according to the specifications of the GSM system, so that when the mobile services switching centre has received short message information from the portable part via the fixed part, said acknowledgement message is a CP-ACK message according to the specifications of the GSM system whereby in response to the reception of said CP-ACK message the fixed part sends to the portable part an empty {IWU-INFO} message according to the specifications of the DECT system.
8. The method of claim 4, characterised in that the portable part comprises protocol layers SM-RP and SM-TP according to the specifications of the GSM system and protocol layer CC according to the specifications of the DECT system, the fixed part comprises protocol layer CC according to the specifications of the DECT system and, parallel with it, protocol layer SM-CP according to the specifications of the GSM system as well as an interworking unit operating between said protocol layers CC and SM-CP, and the mobile services switching centre comprises protocol layers SM-CP and SM-RP according to the specifications of the GSM system, so that when the portable part has received short message information from the mobile services switching centre via the fixed part, said acknowledgement message is an {IWU-INFO} message according to the specifications of the DECT system which comprises a SM-RP acknowledgement message according to the specifications of the GSM system whereby in response to the reception of said {IWU-INFO} message the fixed part transfers the included SM-RP acknowledgement message to the mobile services switching centre.
9. The method of claim 4, characterised in that the portable part comprises protocol layers SM-RP and SM-TP according to the specifications of the GSM system and protocol layer CC according to the specifications of the DECT system, the fixed part comprises protocol layer CC according to the specifications of the DECT system and, parallel with it, protocol layer SM-CP according to the specifications of the GSM system and an interworking unit operating between said protocol layers CC and SM-CP, and the mobile services switching centre comprises protocol layers SM-CP and SM-RP according to the specifications of the GSM system, so that when the mobile services switching centre has received short message information from the portable part via the fixed part, said acknowledgement message is a SM-RP message according to the specifications of the GSM system whereby in response to the reception of said SM-RP acknowledgement message the fixed part transfers to the portable part an {IWU-INFO} message according to the specifications of the DECT system which includes said SM-RP acknowledgement message.
10. The method of claim 4, characterised in that the portable part comprises protocol layers SM-RP and SM-TP according to the specifications of the GSM system and protocol layers CC and MMSP according to the specifications of the DECT system, the fixed part comprises protocol layers CC and MMSP according to the specifications of the DECT system and, parallel with them, protocol layer SM- CP according to the specifications of the GSM system and an interworking unit operating between said protocol layers CC/MMSP and SM-CP, and the mobile services switching centre comprises protocol layers SM-CP and SM-RP according to the specifications of the GSM system, so that said acknowledgement message is - a M-MMS-SEND— RPY message according to the specifications of the DECT system when the portable part has received short message information from the mobile services switching centre via the fixed part whereby in response to the reception of said M-MMS-SEND--RPY message the fixed part sends to the mobile services switching centre a CP-ACK message according to the specifications of the GSM system, and - a CP-ACK message according to the specifications of the GSM system when the mobile services switching centre has received short message information from the portable part via the fixed part whereby in response to the reception of said CP- ACK message the fixed part sends to the portable part a M-MMS-SEND--RPY message according to the specifications of the DECT system.
11. The method of any one of the preceding claims, characterised in that a mobile services switching centre which has sent a first short message information via a fixed part to a portable part waits for a certain first delay and if said mobile services switching centre does not receive an acknowledgement message from said portable part during said first delay it retransmits said first short message information.
12. The method of any one of claims 1 to 10, characterised in that a portable part which has sent a first short message information via a fixed part to a mobile services switching centre waits for a certain second delay and if said portable part does not receive an acknowledgement message from said mobile services switching centre during said second delay it retransmits said second short message information.
13. Use of the method of any one of the preceding claims during an external handover wherein a portable part of a cordless telephone system changes from a radio connection with a first base station cluster to a radio connection with a second base station cluster, said first and second base station clusters communicating with a mobile services switching centre of a mobile communications system.
PCT/FI1997/000117 1997-02-21 1997-02-21 Securing of short message information during handover WO1998037717A1 (en)

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WO2000074403A1 (en) * 1999-06-01 2000-12-07 Siemens Aktiengesellschaft Method and system for sending short messages
AU2003200146B2 (en) * 2002-01-29 2004-07-29 Samsung Electronics Co., Ltd. Interactive short message service system in a private wireless network and routing method therefor
KR100659196B1 (en) * 1999-07-28 2006-12-21 유티스타콤코리아 유한회사 Control station handling Layer 3 protocol for handoff between asynchronous UTRAN and synchronous CN
TWI461077B (en) * 2010-01-11 2014-11-11 Mediatek Inc Wireless messaging method and mobile station

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WO1996041490A1 (en) * 1995-06-07 1996-12-19 Nokia Mobile Phones Ltd. Implementation of mutual rate adaptations in data services between gsm and dect

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000074403A1 (en) * 1999-06-01 2000-12-07 Siemens Aktiengesellschaft Method and system for sending short messages
KR100659196B1 (en) * 1999-07-28 2006-12-21 유티스타콤코리아 유한회사 Control station handling Layer 3 protocol for handoff between asynchronous UTRAN and synchronous CN
AU2003200146B2 (en) * 2002-01-29 2004-07-29 Samsung Electronics Co., Ltd. Interactive short message service system in a private wireless network and routing method therefor
TWI461077B (en) * 2010-01-11 2014-11-11 Mediatek Inc Wireless messaging method and mobile station
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US9629043B2 (en) 2010-01-11 2017-04-18 Mediatek Inc. Wireless messaging method and mobile station

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