WO2007110480A1

WO2007110480A1 - Improved information transfer

Info

Publication number: WO2007110480A1
Application number: PCT/FI2007/050160
Authority: WO
Inventors: Iuliana Marinescu; Rami Vaittinen; Vlora Rexhepi
Original assignee: Nokia Siemens Networks Oy
Priority date: 2006-03-24
Filing date: 2007-03-23
Publication date: 2007-10-04
Also published as: SG136003A1

Abstract

A method of handing over a mobile station in a mobile communication system to at least one target cell. Mapping if facilitated between target cell identification and serving packet radio service support node identification. An identification of allocated packet data resources is included in the handover initiation message. Mapping is utilized in exchanging resource allocation related information between the old and new serving support nodes. Adverse effects due to delays during combined SGSN change for circuit switched and packet switched services may be significantly reduced.

Description

IMPROVED INFORMATION TRANSFER

FIELD OF THE INVENTION

The invention relates to telecommunications, and more particularly to a method, a communication system, a mobile switching centre, a base sta- tion controller, a packet radio serving support node, or a computer program according to the preambles of the attached claims.

BACKGROUND OF THE INVENTION

In telecommunication systems that support both circuit switched and packet switched data transmission a need for enhancing the performance of the handover, especially in connection of the packet switched services, has increased.

The current technical specifications of 3rd Generation Partnership Project (3GPP) define a combined handover of the packet switched and circuit switched services for GERAN A/Gb mode in order to minimize the end-to-end delay of data transmission. An important design factor of the combined handover mechanisms is that the circuit switched handover performance must not degrade due to the packet switched handover procedures. The present experience indicates that at least during a serving packet radio service support node change, due to the chains of information requests between different base station subsystems and core network elements, the accumulated delays tend to be too long.

Another situation where an improved handover performance has been discussed is the restriction of uplink data transfer during routing area update. The specification of packet temporary mobile subscriber identity P-TMSI handling is applicable in case of routing area update, attach, and P-TMSI real- location procedures, when P-TMSI is assigned for a mobile station that already resides in the cell. Abolishing of the restriction has been suggested, but this necessitates that uplink data transfer is made possible also prior to the routing area update procedure.

BRIEF DESCRIPTION OF THE INVENTION

An object of the present invention is thus to provide an improved solution so as to decrease the possible delays that arise from handover procedures involving packet switched resources. The objects of the invention are achieved by a method, a communication system, a mobile switching centre, a base station controller, a packet radio serving support node, or a computer program that are characterized by what is stated in the independent claims. The preferred embodiments of the invention are disclosed in the dependent claims. The invention is based on the idea of establishing an information transfer mechanism whereby essential data can be delivered between the relevant entities without unnecessary inquires and consequent delays.

An advantage of the solution according to the invention is that adverse effects due to delays in handover involving packet switched services may be significantly reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in greater detail by means of preferred embodiments with reference to the attached [accompanying] drawings, in which Figure 1 illustrates the functional architecture of a communication system

Figure 2 illustrates information flows related to combined handover of packet switched and circuit switched services in the embodied communication system of Figure 1 ; Figure 3 illustrates a method according to the embodiment of Figure

2 from the point of view of BSC in the source BSS;

Figure 4 illustrates a method according to the embodiment of Figure 2 from the point of view of MSC;

Figure 5 illustrates a method according to the embodiment of Figure 2 from the point of view of an old SGSN;

Figure 6 illustrates a method according to the embodiment of Figure 2 from the point of view of the new SGSN;

Figure 7 illustrates an embodiment for the configuration of a computer device; and Figure 8 illustrates a further alternative solution where MSC is able to map the target cell ID in the handover information received from the BSS and the new SGSN .

DETAILED DESCRIPTION OF THE INVENTION

In the following, some exemplary embodiments of the invention are described by means of a communication system utilizing GSM (Global System for Mobile Communications), EDGE (enhanced data rates for global evolution) and GPRS (general packet radio service) technologies without limiting the invention to these particular systems and the specific terms used in illustrating the claimed features of the invention. The present invention is applicable to any existing and future telecommunications systems that support combined handover of circuit switched and packet switched data services.

The block chart of Figure 1 illustrates an example of the functional architecture of a communication system that enables for its subscribers circuit switched calls and packet data transmission. The first leg of the system illus- trates a mobile station (MS) 100 connected to the core network (CN) 105 via General Packet Radio Service (GPRS) system, the GSM system (Global System for Mobile communications) acting as a radio access network (RAN). Generally, the basic structure of a GSM network comprises two parts: a base station system (BSS) 110 and a network subsystem (NSS). The GSM BSS communicates with mobile stations (MS) 100 via radio connections over a radio interface Um 115. In the base station system BSS 110 each cell is served by a base transceiver station (BTS) 120. The base station 120 is connected to a base station controller (BSC) 125, which controls the radio frequencies and channels used by the base station. The base station controller BSC 125 is connected over an A-interface 130 to a mobile switching centre (MSC) 135, i.e. as a part of GSM NSS to the core network CN 105 of the system.

The Serving GPRS Support Node (SGSN) 140 keeps track of the location of individual mobile stations and performs security functions and access control. The SGSN 140 is connected to the GSM base station system through the Gb interface 145. The Gateway GPRS Support Node (GGSN) 150 provides interworking with packet data networks, and is connected with SGSNs via an IP-based packet domain public land mobile network (PLMN) backbone network.

In order to use GPRS services, an MS shall first make its presence known to the network by performing a GPRS attach. This makes the MS available for SMS over GPRS, paging via the SGSN, and notification of incoming packet data. In order to send and receive packet data by means of GPRS services, the MS shall activate the packet data protocol context that it wants to use. This operation makes the MS known in the corresponding GGSN, and interworking with data networks can commence.

A serving GPRS support node 140 (SGSN) is arranged to serve a mobile station by sending or receiving packets via the BSS. Each support node SGSN manages the packet data service in the area of one or more cells in a cellular packet radio network. A mobile station 10, which is in a cell, communicates with the BSS 110 over the radio interface Um 115 and further through the Gb interface 145 with the SGSN 140 to the service area of which the cell belongs. This mode of operation of the MS, when connected to the Core Network via GERAN and the A and/or Gb interfaces, is called A/Gb mode. GE- RAN refers to GSM/EDGE radio access network that includes GPRS and EDGE technologies. As shown in Figure 1 , SGSN may also provide a Gs interface towards MSC. Gs interface exists primarily to support interworking with GSM systems to communicate with MSC on location and routing area changes. Gn interface connects the SGSN to GPRS backbone network and allows SGSN to communicate with the GPRS support nodes (GSN) of the home network. Gp interface provides for communication between SGSNs of different operators' public land mobile networks.

As an example of the enhanced information transfer mechanism, Figure 2 illustrates information flows related to combined handover of packet switched and circuit switched services in the embodied communication system of Figure 1. Source BSS 20 (s-BSS) denotes the base station subsystem to which the mobile station is currently registered. Target BSS 22 (t-BSS) denotes the base station subsystem, to which the mobile station is intended to be handed over. MSC 24 denotes the mobile switching centre managing the handover. Old SGSN 26 (o-SGSN) denotes the SGSN serving the source BSS 20 and new SGSN 28 (n-SGSN) denotes the SGSN serving the target BSS 22. The Handover required -procedure allows a BSS to request a handover to be carried out for a particular MS that currently has been allocated one or more resources. This is done by generating a HANDOVER REQUIRED message and sending it from the source BSS to the MSC. As part of the BSS's functions, the BSS continually monitors all radio information and compares it with parameters such that if the transmission quality of a given parameter (or set of parameters) passes a predetermined threshold (set by O&M) then a HANDOVER REQUIRED message is generated and sent to the MSC.

According to the present embodiment, in order to notify the core network that the mobile station also has some packet switched resources allocated, a corresponding indication is transmitted from the base station subsys- tern to the core network. The indication optimally manifests the existence of the resources, as well as provides necessary information for identifying the resources, as well as the elements involved with allocating these resources. In the embodiment of Figure 2, this is implemented by including in the HAND- OVER REQUIRED -message (step 2-1 ) from the source BSS to the MSC at least the following indications:

- Temporary Logical Link Identity (TLLI) allocated by the old SGSN (hereinafter: old TLLI)

- International Mobile Subscriber Identity (IMSI) of the user - Target cell identifiers associated with the routing area code (RAC).

TLLI identifies the allocated packet switched resources, IMSI identifies the mobile subscriber and the combination of cell identifiers and routing area codes to facilitate recognition and thus exchange of information between the SGSNs. The HANDOVER REQUIRED -message is generally generated in BSC.

When MSC receives the HANDOVER REQUIRED -message, it initiates the normal handover request (step 2-3) towards the target BSS. After successful conventional location area update procedures MSC receives an acknowledgement message (step 2-4) whereby the target BSS informs that the BSS resources are available and the handover may be executed.

In order to minimize delay in the packet data transmission during the handover, the MSC should parallelly initiate defined procedures for allocation of packet switched resources towards SGSNs. The problem, however, is that MSC is not necessarily able to determine the address of the new SGSN with which to communicate. In the specific case where MSC is able to identify SGSN on the basis of the Location Area Identifier (LAI), and SGSN has already earlier (for example, in connection with location update request for some other mobile station) sent a location update request to MSC, MSC is able to identify the SGSN. Otherwise MSC will not know the new SGSN until the com- bined routing area/location area update (RA/LA update).

According to the present embodiment, this problem is overcome by a new message generated in MSC and transmitted to the old SGSN. The message is generated at least when MSC receives from BSS a handover indication that contains the indication of allocated packet transmission resources. The new message comprises at least information to identify the current packet switched resources, the subscriber and the target cell. In the embodiment of Figure 2, this is implemented by including in a MS INFORMATION REQUEST -message (step 2-2) from MSC to old SGSN at least parameters IMSI, old TLLI, and target cell identity.

In order to be able to perform the necessary actions for allocation of the packet switched resources, the new SGSN needs some valid information on the mobile station operation. In the embodiment of Figure 2, the new SGSN requires information on, for example, the MM context and PDP context related to the mobile station to be handed over. Thus the old SGSN generates a new GPRS tunneling protocol (GTP) message that comprises this essential infor- mation for the new SGSN; MM context, PDP context, VLR number, old TLLI, valid IMSI and target cell ID. The VLR number indicates to the new SGSN the specific MSC to which it should send the new temporary mobile station identity for GPRS services, the Packet-TMSI (P-TMSI). The old SGSN delivers the new GTP message MS Information request to the new SGSN (step 2-5). In the embodiment of Figure 2, the necessary action for allocation of the packet switched resources is a valid TLLI such that the mobile station is able to address the radio resources. New TLLI is derived from new P-TMSI allocated by the new SGSN. The P-TMSI has significance only within a routing area. Outside the routing area it has to be combined with the routing area iden- tification (RAI) to provide for an unambiguous identity. The purpose of the P- TMSI reallocation procedure is to provide identity confidentiality, i.e. to protect a user against being identified and located by an intruder. Usually, P-TMSI re- allocation is performed at least at each change of a routing area, but such choices are generally left to the network operator. While the necessary mobile station information is now available to the new SGSN, it is able to allocate a new P-TMSI. Additionally, it knows MSC that manages the combined RA/LA handover. Thus the new SGSN generates a MS INFORMATION RESPONSE -message comprising at least IMSI and the new p-TMSI and forwards it (step 2-6) to MSC. After successful Handover request and MS information request procedures MSC is able to complete the combined handover procedure and deliver the new P-TMSI to the source BSS, which forwards it to the mobile station.

The new proposed mechanism enables transfer of information re- quired for allocation of packet switched resources from MSC to the new SGSN even if the MSC does not preliminarily know the new SGSN. Thereby the new SGSN is also able to perform necessary actions for the packet switched resource allocation before the combined handover of the circuit switched and packed switched services. In the system of Figure 2, MSC can communicate with the old SGSN, and does not mandatorily have to know the new SGSN at this stage. Due to the availability of the RAC information in the target cell ID, the old SGSN is able to forward the stimulus and essential information to the new SGSN such that allocation of P-TMSI becomes possible. This efficient information transfer mechanisms significantly expedites the handover procedure where packet switched resources are involved. Figure 3 illustrates a method according to the embodiment of Figure

2 from the point of view of BSC in the source BSS during combined handover of packet switched and circuit switched services. BSC is configured with a set of conditions that trigger handover procedures. In step 30 BSC checks the handover conditions cond_Ho, and if any of them is fulfilled (step 31 ), a hand- over procedure is initiated (step 32). Otherwise the monitoring continues conventionally. BSC checks whether the mobile station has packet switched resources allocated (step 33), and in the positive case (step 34) includes in handover information msg_Msc(para) to MSC the necessary parameters to identify the packet switched resource and information for identification relevant elements participating in the re-allocation of the resources (step 35). In the embodiment of Figure 2 BSC includes in the message IMSI, old TLLI and target cell ID combined with the RAC. In response BSC receives the information infps on new packet switched resource (step 36) and is thereby able to complete (step 37) the handover procedure. In the embodiment of Figure 2, BSC receives the new P-TMSI and as a step of completing the combined circuit switched and packet switched handover, delivers the new P-TMSI to the mobile station. The packet data transmission can continue during the combined handover procedure and no unnecessary delays are caused to the circuit switched handover. Figure 4 illustrates a method according to the embodiment of Figure

2 from the point of view of MSC during combined handover of packet switched and circuit switched services. In step 40 MSC receives from source BSS request req_Ho for handover and in response initiates handover procedures with the target BSS (step 41 ). MSC also checks whether the handover information includes indication PSin_d of allocated packet switched resources (step 42). In the positive case (step 43), MSC generates a message to the old SGSN o- SGSN and includes in the message the necessary parameters to identify the packet switched resource and any information available for identification relevant elements that are needed in the re-allocation of the resources (step 44). In the embodiment of Figure 2 BSC includes in the message IMSI, old TLLI and target cell ID combined with the RAC, as received in the handover information from the BSS. In response MSC receives from the new SGSN a response comprising the information on new packet switched resource (step 45) and is thereby able to complete (step 46) the handover procedure. In the embodiment of Figure 2, MSC receives the new P-TMSI and is thereby able to provide necessary actions for the allocation of resources due to handover. Due to the invented mechanism, MSC is thus able to handle P-TMSI when allocated for the mobile station even before it resides in a cell.

Figure 5 illustrates a method according to the embodiment of Figure 2 from the point of view of an old SGSN during combined handover of packet switched and circuit switched services. In step 50 the old SGSN receives from MSC a request req_Msι for mobile station information. In response to the received request, old SGSN maps the information in the request to information on the same mobile station accessible to the SGSN, and generates (step 51) a new GTP message that comprises the received information and some new information required for re-allocation of the packet switched resources. In the embodiment of Figure 2 the old SGSN includes in the request IMSI, old TLLI and target cell ID combined with the RAC, as received in the handover information from the BSS, and adds MM context, PDP context and VLR number information accessible to it. In step 52, the old SGSN forwards the enhanced request reqMsi to the new SGSN. Due to the invented mechanism, the old SGSN is able to deliver the information required for the allocation of P-TMSI without having to wait for the routing area update procedures.

Finally, Figure 6 illustrates a method according to the embodiment of Figure 2 from the point of view of the new SGSN during combined handover of packet switched and circuit switched services. In step 60 the new SGSN receives from the old SGSN the enhanced request reqMsi÷ for mobile station information. In response to the received request, the new SGSN allocates the the information infps on new packet switched resource (step 61 ). On the basis of the information in infps , the new SGSN is also able to determine the MSC to which the infps is to be sent. In step 62, the new SGSN forwards the information to the determined MSC. In the embodiment of Figure 2 the new SGSN is able to identify the MSC on the basis of the VLR number in the enhanced mobile station information request reqMsi÷- The information delivered from the new SGSN to MSC comprises the P-TMSI required by the mobile station for addressing the packet switched resources. Due to the invented mechanism, the new SGSN is able to implement the necessary actions for allocation of packet switched resources already before the routing area update procedure, and is also able to deliver the results to MSC without unnecessary delays.

The methods of network elements of Figure 3, 4, 5, and 6 can be implemented by means of a computer device. Figure 7 illustrates an embodi- ment for the configuration of such computer device. The computer device comprises processing means 71 , an element that comprises an arithmetic logic unit, a number of special registers and control circuits. Connected to the processing means are memory means 72, a data medium where computer- readable data or programs or user data can be stored. The memory means typically comprise memory units that allow both reading and writing (RAM), and a memory whose contents can only be read (ROM). The unit also comprises an interface block 73 with input means 74 for inputting data for internal processing in the unit, and output means 75 for outputting data from the internal processes of the unit. Examples of said input means comprise a plug-in unit acting as a gateway for information delivered to its external connection points. For receiving information on the operator of the application server, the application server may also comprise a keypad, or a touch screen, a microphone, or the like. Examples of said output means include a plug-in unit feeding information to the lines connected to its external connection points. For outputting information to the operator of the application server, they may also comprise a screen, a touch screen, a loudspeaker, or the like. The processing means 71 , memory means 72, and interface block 73 are electrically interconnected for performing systematic execution of operations on the received and/or stored data according to the predefined, essentially programmed proc- esses of the unit. In solutions according to the invention, the operations comprise functions of the base station controller, the mobile switching centre, and the serving GPRS support node described above with Figures 3, 4, and 5. The functions of the network elements, implemented by the controlled co-operation of the elements of Figure 7, can also be considered to form logical units that implement, for example, mapping and control functions in the network elements. As discussed above, information on the mapping between a cell ID and the corresponding SGSN is needed to enable exchange of information between the old and new SGSN. The invented mechanism supports several alternative solutions for providing this information, which alternatives can be applied in any of the earlier discussed embodiments. One alternative solutions is to provide MSC with prior knowledge of the mapping between the cell IDs and SGSNs. Such mapping could be implemented, for example, as a database accessible to MSC. Solutions where the information of the mapping is received from the BSS in form of routing area code combined with the target cell identi- fier can be implemented, for example, by using operation and management system for managing the information in the BSS, or RIM applications. Implementation of these alternative solutions are generally known to a person skilled in the art and will not be described in more detail herein.

Figure 8 illustrates a further alternative solution available in configu- rations where MSC is able to map the target cell ID in the handover information received from the BSS and the new SGSN. In step 8-1 , MSC receives a HANDOVER REQUIRED -message from source BSS, as in Figure 2. This time the MSC is able to map the target cell ID to the new SGSN, and forwards (step 8-2) to the new SGSN a message comprising IMSI, old TLLI and target cell ID, as discussed in connection with Figure 2. In addition, MSC implements normally the handover request with the new BSS (steps 8-3, 8-4). Reception of the message indicates to the now SGSN that a new P-TMSI is required for the specific mobile station. However, the new SGSN does not have the adequate information for the allocation and it thus generates a request for mobile station information, includes in the message the information received from MSC, and forwards it (step 8-5) to the old SGSN. On the basis of the information of the message, the old SGSN identifies the mobile station, accesses the additional information on the packet switched resources of the mobile station available to it, and forwards (step 8-6) them back to the new SGSN. On the basis of the received information, the new SGSN allocates the new P-TMSI, and forwards it to the MSC (step 8-7) that correspondingly forwards (step 8-8) it to the source BSS for execution of the handover.

It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The in- vention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

1. A method of handing over a mobile station in a mobile communication system comprising a base station subsystem and a core network, comprising: initiating handover for a mobile station to at least one target cell; allocating resources in the base station subsystem of the target cell; executing the handover; characterized by providing mapping between cell identifications and serving packet radio service support node identifications of the core network; including in the handover initiation message at least one target cell identification and an identification of allocated packet data resources; mapping the target cell identifier into one or more serving packet radio service support nodes; exchanging packet switched resource allocation information between the mapped serving packet radio service support nodes.

2. A method according to claim 1, characterized in that the identification of allocated packet data resources is the identity of the logical link between the mobile station and the serving support node.

3. A method according to claim 1 or 2, characterized in that mapping between target cell identification and serving packet radio service support node identification is facilitated by including both routing area code and target cell identification in the handover initiation message.

4. A method according to claim 1 or 2, characterized by providing mapping in a database system accessible to the mobile switching centre of the communication system, and accessing the mapping in response to a received handover initiation message comprising an identification of allocated packet data resources.

5. A method according to any of claims 1 to 3, character- i z e d by the step of information exchange comprises delivery of mobile station information request message from the mobile switching centre to the old serving packet radio service support node , said mobile station information request message comprising at least the identification and mapping information for identifying the new serving support node; and delivery of an enhanced mobile station information request message from the old serving packet radio service support node to the new serving support node, said enhanced mobile station information request also comprising mobile station information required for resource allocation of a packet switched service in the new serving support node.

6. A method according to any of claims 1 to 3, further c h a r a c t e r i z e d by : mapping the target cell identifier into at least the new serving packet radio service support node; delivery of mobile station information request message from the mobile switching centre to the new serving packet radio service support node , said mobile station information request message comprising at least the identification of a packet switched resource; delivery of request for mobile station information necessary for the resource allocation by the new serving packet radio service support node to the old serving support node; delivery of response for mobile station information from the old serving packet radio service support node to the new serving support node.

7. A communication system comprising a base station subsystem and a core network, the base station subsystem being configured to initiate handover for a mobile station to at least one target cell; a mobile switching centre of the core network being configured to request allocation of resources in the base station subsystem of the target cell; c h a r a c t e r i z e d by the communication system comprising at least one core network element configured to provide mapping between cell identifications and serving packet radio service support node identifications of the core network; a base station subsystem element configured to include in the handover initiation message at least one target cell identification and an identi- fication of allocated packet data resources; the at least one core network element being configured to map the target cell identifier into one or more serving packet radio service support nodes; the mapped serving packet radio service support nodes being configured to exchange packet switched resource information for allocation of re- sources.

8. A mobile switching centre for a communication system compris- ing a base station subsystem and a core network, the base station subsystem being configured to initiate handover for a mobile station to at least one target cell; the mobile switching centre belonging to the core network and being configured to request allocation of resources in the base station subsystem of the target cell; characterized by the mobile switching centre comprising a mapping unit for providing mapping between target cell identification and serving packet radio service support node identification; a control unit for detecting in the handover initiation message an identification of allocated packet data resources, and in response to the identification, initiate exchange of resource allocation related information between the source and target serving support nodes; said control unit being configured to utilize the mapping unit in the information exchange.

9. A base station controller for a communication system comprising a base station subsystem and a core network, the base station controller belonging to the base station subsystem and being configured to initiate handover for a mobile station to at least one target cell; characterized by the base station controller comprising a control unit for including in the handover initiation message at least one target cell identification and an identifica- tion of allocated packet data resources.

10. A serving packet radio service support node comprising communication means for exchanging information with the mobile switching centre and other packet radio system serving support nodes, characterized by a interface unit for exchanging packet switched resource allocation information between the mapped serving packet radio service support nodes; and control unit configured to map between target cell identifications and serving packet radio service support node identifications for the information exchange .

11. A serving packet radio service support node according to claim 10, characterized by receiving unit for receiving mobile station information request message from the mobile switching centre comprising an identification of allocated packet data resources, and mapping information for identifying the new serving support node; and transmitting unit for transmitting an enhanced mobile station information request message to the new serving support node, said enhanced mobile station information request also comprising mobile station information required for the resource allocation in the new serving support node.

12. A serving packet radio service support node according to claim

10, c h a r a c t e r i z e d by receiving unit for receiving mobile station information request message from the mobile switching centre comprising at least the identification and mapping information for identifying the new serving support node; and transmitting unit for transmitting a request for mobile station information required for the resource allocation to the old serving support node; said receiving unit being also configured to receive a response for mobile station information required for the resource allocation from the old serving support node.

13. A computer program product, executable in a computer device, c h a r a c t e r i z e d in that execution of the computer program product in the computer device causes the computer device to perform the functions of a mobile switching centre, including the steps providing mapping between target cell identification and serving packet radio service support node identification; and detecting in the handover initiation message an identification of allocated packet data resources, and in response to the identification, initiate exchange of resource allocation related information between the source and target serving support nodes; said control unit being configured to utilize the mapping unit in the information exchange.

14. A computer program product, executable in a computer device, c h a ra c t e r i z e d in that execution of the computer program product in the computer device causes the computer device to perform the functions of a base station controller, including the step of including in the handover initiation message at least one target cell identification and an identification of allocated packet data resources.

15. A computer program product, executable in a computer device, c h a r a c t e r i z e d in that execution of the computer program product in the computer device causes the computer device to perform the functions of a packet radio serving support node, including the step of exchanging packet switched resource allocation information between the mapped serving packet radio service support nodes; and mapping between target cell identifications and serving packet radio service support node identifications for the information exchange.