# Patent

## Title
Method, device, system and software product for providing system information to enable packet switched handover

## Abstract

A method, mobile device, network device, system, and software product are presented for providing an indication whether a source radio network controller requests to receive system information from a handover target, and for receiving the system information in a target to source transparent container, if the indication requests to receive the system information.

## Background
CROSS REFERENCE TO RELATED APPLICATION
The present invention claims priority to U.S. Provisional Application 60/721,681 filed Sep. 29, 2005.


FIELD OF THE INVENTION
The invention relates to wireless telecommunications, and more particularly to handover situations in a wireless telecommunications system.
BACKGROUND OF THE INVENTION
The global system for mobile communications (GSM) was designed as a second generation system for enabling voice communication to go wireless. However, customers have increasingly sought additional wireless services, such as text messaging and access to data networks. Therefore, third generation systems are designed to provide multimedia communication, including images and video. For example, enhanced data rates for GSM evolution (EDGE) can provide third generation services, including advanced features that improve spectrum efficiency. Likewise, the universal mobile telecommunications services (UMTS) provides flexible delivery of many different services. The UMTS terrestrial radio access network (UTRAN) includes network elements that handle radio-related functionality for UMTS.
By definition, handover means transfer of a user connection from one radio channel to another. One type of handover is an inter-RAT handover, when a user equipment (UE) moves to a different radio access technology (RAT). For example, when the user equipment (UE) reaches the end of a coverage area for UMTS services, it can handover to a 2G service like GSM (if the UE supports multiple RAT). An inter-RAT handover procedure can be initiated in a variety of ways. For instance, a radio network subsystem (RNS) might send a command explicitly telling the UE to move to a different RAT, or the UE might select a cell that belongs to a different RAT.
In the context of a general packet radio system (GPRS), rules for packet switched (PS) handover have been defined in Release 6 of the Third Generation Partnership Project (3GPP), based on GSM/EDGE Radio Access Network (GERAN) research and development. To support handover between radio access technologies (i.e. to support inter-RAT handovers), such as handovers between UMTS and GSM, signalling has been added in the radio resource control (RRC) with the Uu interface, and in the radio access network application part (RANAP) with the Iu interface. Pertinent details about GPRS can be found in 3GPP TS 48.018 V6.14.0 (2006-07), “BSS GPRS Protocol (BSSGP) (Release 6),” of which pages 52-58 and 106-150 are incorporated by reference herein in their entirety. Also, pertinent details about RANAP signalling can be found in 3GPP TS 25.413 V6.0.0 (2005-06), “UTRAN Iu interface RANAP signalling (Release 6),” of which pages 33-37 and 122-170 are incorporated by reference herein in their entirety.
To support inter-RAT PS handover from UTRAN to GERAN, a serving radio network controller (SRNC) needs system information such as packet system information (PSI/SI which is the same as SI/PSI) blocks of the target GERAN cell. The 3GPP group known as “RAN2” has added a choice structure information element (IE) in RRC handover from the UTRAN command message, in order to transfer these PSI/SI blocks to the user equipment (UE). The assumption about how the SRNC gets these blocks was to reuse a RAN Information Management (RIM) procedure with Network Assisted Cell Change (NACC).
Problematically, the RIM/NACC procedure is optional in the network. Consequently, there is no guarantee that the SRNC will get the PSI/SI blocks in time for the handover.
In the UMTS network, the SRNC may have to get the PSI/SI blocks from a drift radio network controller (DRNC) or controlling RNC (CRNC). Thus, the procedure may be even more complicated, more problematic, and less likely to provide the SRNC with the PSI/SI blocks in time.
The PSI/SI blocks are mandatory information for PS handover, whereas RIM/NACC is an optional feature for optimization. Thus, the criticality of missing PSI/SI blocks is higher in the PS handover than in the RIM/NACC procedure.
SUMMARY OF THE INVENTION
The problem described above can be solved by including PSI/SI blocks in a transparent container from the target base station subsystem (BSS) to the source base station subsystem (BSS) or source RNC. In order to optimize this procedure, a PSI/SI indicator can also be included in a source BSS to target BSS transparent container, for example with a value indicating if the PSI/SI block is required in return.
As a person skilled in the art knows, a transparent container is an information element that often contains information needed to perform relocation. Relocation is the procedure by which a target RNC or BSS may become a mobile terminal's new serving RNC or BSS, respectively. The transparent container can include, for example, security information regarding the mobile, and/or can include the protocol context that describes the mobile's RRC connection and the mobile's capabilities. A transparent container carries information to an intermediate node, such as a serving GPRS support node (SGSN), so that the intermediate node can copy the contents of the container into a message to the final destination (e.g. to a target node). The present invention involves using the transparent container to convey PSI/SI blocks between a target subsystem and a source subsystem, so as to facilitate PS handover.
In case the SRNC and CRNC are the same RNC, and the CRNC implements RIM/NACC, then the SRNC can indicate that it does not need to receive PSI/SI blocks in the target BSS to source BSS transparent container, because the SRNC would already have the PSI/SI blocks. In this case, absence of a PSI/SI indicator IE in the source BSS to target BSS transparent container IE, or a PSI/SI Indicator with a proper value depending on the type of IE, means that the target BSS has to send the PSI/SI blocks.
Alternatively, the SRNC can indicate that it needs to receive the PSI/SI blocks in the target BSS to source BSS transparent container. In this case, absence of PSI/SI Indicator IE in the source BSS to target BSS transparent container IE, or the PSI/SI Indicator with a proper value, means that the target BSS shall not send the PSI/SI blocks. This PSI/SI indicator IE does not need to be in the source BSS to target BSS transparent container, but it shall be transferred from the source RNC to the target BSS via proper messages. By this mechanism, the SRNC can avoid unnecessary PSI/SI delivery over Iu and Gb interfaces.
It is important to ensure that the SRNC will get all the necessary information for PS handover from the target BSS in case of UTRAN to GERAN PS handover. With the present invention, the SRNC will receive PSI/SI blocks in addition to a PS handover command message, in the target BSS to source BSS transparent container.
One drawback of adding PSI/SI blocks in the target BSS to source BSS transparent container may be in case the SRNC is the same as the CRNC, and the CRNC implements a RIM/NACC procedure. As mentioned, it would be a waste to transfer PSI/SI blocks in the transparent container, because the SRNC would have these blocks. To avoid this situation, the present invention includes a way for the SRNC to indicate whether it needs PSI/SI blocks in the source BSS to target BSS transparent container. With this indication, it becomes possible to avoid unnecessary delivery of PSI/SI blocks from the target BSS to the source RNC.
This present invention can be used not only for inter-RAT PS handover, but also for inter-BSS PS handover as well. This is because the RIM/NACC procedure is optional in the GSM network as well.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows an implementation of PSI/SI indicator, according to the present invention.
FIG. 2 shows a change to 3GPP TS 25.413, section 9.2.1, describing a target BSS to source BSS transparent container, according to a first version of an embodiment of the present invention.
FIG. 3 shows a change to 3GPP TS 48.018, Table 11.3.80.a, describing a target BSS to source BSS transparent container coding, according to the first version of an embodiment of the present invention.
FIG. 4a shows a change to 3GPP TS 48.018, Section 11.3.63.2.1, Table 11.3.63.2.1a, according to the first version of an embodiment of the present invention.
FIG. 4b shows a change to 3GPP TS 48.018, Section 11.3.63.2.1, Table 11.3.63.2.1b, according to the first version of an embodiment of the present invention.
FIG. 4c shows a change to 3GPP TS 48.018, Section 11.3.63.2.1, Table 11.3.63.2.1c, according to the first version of an embodiment of the present invention.
FIG. 5 shows a change to 3GPP TS 25.413, section 9.2.1, describing a target BSS to source BSS transparent container, according to a second version of an embodiment of the present invention.
FIG. 6 shows another change to 3GPP TS 48.018, Table 11.3.80.a, describing a target BSS to source BSS transparent container coding, according to the second solution of the present invention.
FIG. 7 is a flow chart showing a method according to an embodiment of the present invention.
FIG. 8 is a block diagram showing a system according to an embodiment of the present invention.



DETAILED DESCRIPTION OF THE INVENTION
A preferred embodiment of the present invention will now be described, merely to illustrate one way of implementing the invention. This illustration is not meant to limit the scope or coverage of what is described elsewhere in this application.
As explained above, for PS handover, PSI/SI blocks are mandatory information. They must be transferred to the UE before a PS HANDOVER COMMAND message is transferred.
An assumption for a UTRAN to GERAN PS handover case has been that PSI/SI blocks in addition to PS HANDOVER (HO) COMMAND message are included in the HANDOVER FROM UTRAN COMMAND message. To construct this RRC message, the SRNC has to receive the necessary GERAN information. The PS HANDOVER COMMAND message can be included in a target BSS to source BSS transparent container. However, PSI/SI blocks are assumed to be delivered to the SRNC via a RIM/NACC procedure.
The current mandatory procedure for PS handover implicates RIM/NACC, whereas the RIM/NACC procedure is optional in network implementation, according to 3GPP specifications. Thus, according to 3GPP specifications, the SRNC is not guaranteed to receive PSI/SI blocks in time for PS handover, and the SRNC must either delay the PS handover or have a failed PS handover, if the SRNC is the same as the CRNC which did not implement RIM/NACC procedure, or if the SRNC is different from the CRNC which did not implement RIM/NACC procedure.
Accordingly one embodiment of the present invention is a transparent container solution. An optimization for this transparent container solution can be to include a PSI/SI Indicator IE in a source BSS to target BSS transparent container. If the SRNC and the CRNC are the same RNC, and the CRNC implemented RIM/NACC, the SRNC will not need to receive PSI/SI blocks again via a target BSS to source BSS transparent container. So, if the SRNC has PSI/SI blocks for the target GSM cell, the SRNC will not include the PSI/SI Indicator IE. If the SRNC needs to receive PSI/SI blocks via target BSS to source BSS transparent container, it will include the PSI/SI Indicator IE with the value “True”. If the target BSS receives this indicator, it includes the PSI/SIs blocks in the target to source BSS transparent container.
One illustrative implementation of the PSI/SI Indicator is shown in FIG. 1. If the PSI_SI Indicator IE is missing, it means the SRNC does not need to receive PSI/SI blocks. But the meaning of existence of IE can be the other way around; i.e., a missing PSI/SI Indicator IE can mean that the SRNC needs PSI/SI blocks.
Another illustrative implementation of the PSI/SI Indicator is to make the PSI/SI Indicator a mandatory IE. Thus, this PSI/SI Indicator will always be included in the source BSS to target BSS transparent container, and the source RNC/BSS must indicate clearly whether it needs PSI/SI blocks or not. The implementation details can vary to realize PSI/SI Indicator. The importance is that there should be a means for the source RNC/BSS to indicate whether it needs to receive PSI/SI blocks or not from target BSS via transparent container.
A first version of this embodiment of the present invention involves having two parts in a target BSS to source BSS transparent container. The first part of the container includes PS HO COMMAND message in CSN.1 code in an octet string. The second part of the container includes the number of PSI/SIs, type and PSIs or SIs in BSSGP code in an octet string. According to this version, an approved RRC message (HANDOVER FROM UTRAN COMMAND) can be used. Also, no RIM/NACC is needed. The SRNC will always get PSI/SIs in time during PS HO. The SRNC has to interpret the BSSGP command, because only “Number of SI/PSI,” “Type” and “SI/PSI” are needed in RRC message.
In 3GPP TS 25.413, a change could be made as shown in FIG. 2. And, in 3GPP TS 48.018, changes could be made as shown in FIG. 3, which illustrates an information element including information needed in the Source BSS to execute a PS Handover. FIG. 4 further explain the content of FIG. 3. FIG. 4a shows a change to 3GPP TS 48.018, Section 11.3.63.2.1, Table 11.3.63.2.1a.
According to FIG. 4a, A RAN-INFORMATION application container for the NACC application has coding of the Application Container IE within the RAN-INFORMATION RIM container for the NACC application. The reporting Cell Identifier is a field that is encoded as the Cell Identifier defined in sub-clause 11.3.9 of 3GPP TS 48.018.
FIG. 4b shows a change to 3GPP TS 48.018, Section 11.3.63.2.1, Table 11.3.63.2.1b. The TYPE field indicates the type of SI/PSI messages provided by the reporting cell. The TYPE field is coded as shown.
FIG. 4c shows a change to 3GPP TS 48.018, Section 11.3.63.2.1, Table 11.3.63.2.1c. Accordingly FIG. 4c shows a number of SI/PSI coding. This field indicates the number of SI/PSI provided by the reporting cell contained in the SI/PSI field. This number may be zero. For system information messages with multiple instances, each instance is counted as one SI/PSI message. The Number of SI/PSI field is coded as shown. The SI/PSI field contains a list of either system information or packet system information messages valid for the reporting cell. The number of (packet) system information messages is indicated in the Number of SI/PSI field. Furthermore, if the TYPE field indicates that “SI messages as specified for BCCH (3GPP TS 44.018) follow” then the SI/PSI field contains System Information message instances encoded for BCCH as specified in 3GPP TS 44.018. Each System Information message contains the Message type octet followed by all the IEs composing the message payload. Each message is 21 octets long. If the TYPE field indicates that “PSI messages as specified for PBCCH (3GPP TS 44.060) follow” then the SI/PSI field contains Packet System Information message instances encoded for PBCCH as specified in 3GPP TS 44.060. Each Packet System Information message contains the MESSAGE_TYPE field followed by the PSI message content. Each message is 22 octets long.
A second version of this embodiment of the present invention involves having many parts in a target BSS to source BSS transparent container. The first part of the container includes how many blocks it has, as an integer (2 to 11). The second part of the container includes PS HO COMMAND message in CSN.1 code, in an octet string. The third part to the nth part of the container include the PSIs or Sis, in BSSGP code in an octet string; i.e., one of these n parts contains one PSI or SI. No RIM/NACC is needed. The SRNC will always get PSI/SIs in time during PS HO. Blocks are transparent to the SRNC, and the SRNC only needs to read the number of blocks. Then it just copies the content into a GSM message list IE in HANDOVER FROM UTRAN COMMAND in the RRC.
To accommodate this version of the invention, a GSM message list must be extended to cover a maximum of eleven (11) GSM messages, and the UE must distinguish whether PSIs or SIs are included. Thus, a RRC change request (CR) is needed, in order to remove PSI/SI choice IE in HANDOVER FROM UTRAN COMMAND message, in addition to a RANAP change request and a BSSGP change request.
FIG. 5 shows a change to 3GPP TS 25.413, section 9.2.1, describing a target BSS to source BSS transparent container, according to a second version of an embodiment of the present invention.
FIG. 6 shows another change to 3GPP TS 48.018, Table 11.3.80.a, describing a target BSS to source BSS transparent container coding, according to the second solution of the present invention. This information element contains the information needed in the Source BSS to execute a PS handover, and the element coding is as shown in FIG. 6. The SI/PSI field contains a list of either system information or packet system information messages valid for the reporting cell. The number of (packet) system information messages is indicated in the Number of SI/PSI field specified above. Furthermore, if the Type field indicates that “SI messages as specified for BCCH (3GPP TS 44.018) follow” then the SI/PSI field contains System Information message instances encoded for BCCH as specified in 3GPP TS 44.018. Each System Information message contains the Message type octet followed by all the IEs composing the message payload. Each message is 21 octets long. If the Type field indicates that “PSI messages as specified for PBCCH (3GPP TS 44.060) follow” then the SI/PSI field contains Packet System Information message instances encoded for PBCCH as specified in 3GPP TS 44.060. Each Packet System Information message then contains the MESSAGE_TYPE field followed by the PSI message content. Each message is 22 octets long.
Turning now to FIG. 7, a method 700 is shown according to an embodiment of the invention. An indication is provided 705 indicating whether or not SI/PSI is requested from a PS handover target via transparent container. No such request is made if the SRNC is a CRNC that implements RIM/NACC. If the indication requested the PSI/SI, then that is received 720 in a target to source transparent container. A relocation command is received 725 with the SI/PSI. Then at least part of the contents of the target to source transparent container is sent 730 to a user equipment (e.g. mobile device).
A system for implementing this type of method is shown in FIG. 8. A source RNC 860 (e.g. an SRNC) includes a network element 845 which includes a transmitting module 870 and a receiving module 880. The source RNC sends an indication to a target BSS 850 as to whether SI/PSI is requested. If so, the SI/PSI is provided from the target BSS 850 to the source RNC 860. The source RNC then provides SI/PSI to a mobile device 800, which is received by a receiving module 810 of the mobile device, and is stored in a memory 820. Then a processor 840 can access that SI/PSI in order to have a transmitting device 830 perform handover signalling.
The embodiments described above can be implemented using a general purpose or specific-use computer system, with standard operating system software conforming to the method described herein. The software is designed to drive the operation of the particular hardware of the system, and will be compatible with other system components and I/O controllers. The computer system of this mobile device embodiment includes the CPU processor 840, comprising a single processing unit, multiple processing units capable of parallel operation, or the CPU can be distributed across one or more processing units in one or more locations, e.g., on a client and server. Memory 820 may comprise any known type of data storage and/or transmission media, including magnetic media, optical media, random access memory (RAM), read-only memory (ROM), a data cache, a data object, etc. Moreover, similar to the CPU, the memory may reside at a single physical location, comprising one or more types of data storage, or be distributed across a plurality of physical systems in various forms. The computer system for the network element 845 has a similar description, as a person skilled in the art will understand.
It is to be understood that the present figures, and the accompanying narrative discussions of best mode embodiments, do not purport to be completely rigorous treatments of the method, system, mobile device, and software product under consideration. A person skilled in the art will understand that the steps and signals of the present application represent general cause-and-effect relationships that do not exclude intermediate interactions of various types, and will further understand that the various steps and structures described in this application can be implemented by a variety of different sequences and configurations, using various different combinations of hardware and software which need not be further detailed herein.

## Claims

1. A method comprising:
providing an indication in a source to target transparent container from a source radio network controller indicating whether the source radio network controller requests system information from a handover target, wherein no request is made if the source radio network controller is a controlling radio network controller that implements Radio Access Network Information Management procedure with Network Assisted Cell Change (RIM/NACC);
receiving the system information in a target to source transparent container from the handover target when the indication indicates that the source radio network controller requests the system information; and
sending to a user equipment at least a part of the system information that is received in the target to source transparent container.

2. The method of claim 1, wherein the system information includes information required by a mobile station for a packet switched handover.

3. The method of claim 2, wherein the packet switched handover is a handover to a different radio access technology.

4. The method of claim 2, wherein the packet switched handover is a handover to a different base station subsystem.

5. The method of claim 1, wherein the target to source transparent container is sent from a target radio network controller with a relocation command.

6. The method of claim 1, wherein the target to source transparent container is received at the source radio network controller.

7. The method of claim 1, wherein providing the indication is accomplished by including an indicator or alternatively by omitting an indicator.

8. The method of claim 1, wherein the indication indicates that the source radio network controller requests to not receive the system information from the handover target, if the source radio network controller is a controlling radio network controller that implements a radio access network information management procedure with network assisted cell change.

9. A computer program product comprising a non-transitory tangible computer readable storage structure having computer program code embedded therein for execution by a processor; the computer program product including instructions for:
providing an indication in a source to target transparent container from a source radio network controller indicating whether the source radio network controller requests system information from a handover target, wherein no request is made if the source radio network controller is a controlling radio network controller that implements Radio Access Network Information Management procedure with Network Assisted Cell Change (RIM/NACC);
receiving the system information in a target to source transparent container from the handover target when the indication indicates that the source radio network controller requests the system information; and
sending to a user equipment at least a part of the system information that is received in the target to source transparent container.

10. The computer program product of claim 9, wherein the system information includes information required by a mobile station for a packet switched handover.

11. The computer program product of claim 9, wherein the target to source transparent container is sent from a target radio network controller with a relocation command.

12. An apparatus comprising:
means for providing an indication in a source to target container from a source radio network controller indicating whether the source radio network controller requests system information from a handover target, wherein no request is made if the source radio network controller is a controlling radio network controller that implements Radio Access Network Information Management procedure with Network Assisted Cell Change (RIM/NACC);
means for receiving the system information in a target to source transparent container from the handover target when the indication indicates that the source radio network controller requests the system information; and
means for sending to a user equipment at least a part of the system information that is received in the target to source transparent container.

13. The apparatus of claim 12, wherein the system information includes information required by a mobile station for a packet switched handover.

14. The apparatus of claim 12, wherein the target to source transparent container is sent from a target radio network controller with a relocation command.

15. A network element comprising:
at least one transmitting module, wherein at least one of the at least one transmitting module is configured to provide an indication in a source to target transparent container from a source radio network controller indicating whether the source radio network controller requests system information from a handover target, wherein no request is made if the source radio network controller is a controlling radio network controller that implements Radio Access Network Information Management procedure with Network Assisted Cell Change (RIM/NACC); and
a receiving module configured to receive the system information in a target to source transparent container from the handover target when the indication indicates that the source radio network controller requests the system information,
wherein at least one of the at least one transmitting module is configured to send to a user equipment at least a part of the system information that is received in the target to source transparent container.

16. The network element of claim 15, wherein the system information includes information required by a mobile station for a packet switched handover.

17. The network element of claim 15, wherein the target to source transparent container from a target radio network controller conveys a relocation command.

18. A system comprising:
a source radio network controller configured to provide an indication in a source to target transparent container indicating whether the source radio network controller requests system information from a handover target, wherein no request is made if the source radio network controller is a controlling radio network controller that implements Radio Access Network Information Management procedure with Network Assisted Cell Change (RIM/NACC); and
a target radio network controller configured to provide the system information in a target to source transparent container to the source radio network controller when the indication indicates that the source radio network controller requests the system information,
wherein the source radio network controller is further configured to send to a user equipment at least a part of the system information that is received in the target to source transparent container.

19. The system of claim 18, wherein the system information includes information required by a mobile station for a packet switched handover.