1. Field of the Invention
The present invention relates to a mechanism for executing a handover for a subscriber between mobility management entities for load balancing reasons. Specifically, the present invention is related to an apparatus, a method and a computer program product which allow, for example, a handover from a current mobility management entity to a new mobility management entity due to load balancing reasons.
2. Related Background Art
Prior art which is related to this technical field can e.g. be found in technical specifications according to 3GPP TS 23.401 (e.g. version 11.4.0), TS 36.413 (e.g. version 11.2.1), and TS 36.300 (e.g. version 11.4.0).
The following meanings for the abbreviations used in this specification apply:
AP: application protocol
BS: base station
CN: core network
CPU: central processing unit
DNS: domain name system
eNB: evolved node B
EPC: evolved packet core
EPS: evolved packet system
E-UTRAN: evolved UTRAN
GUTI: globally unique temporary identity
HFN: hyper frame number
HO: handover
HSS: home subscriber server
IMSI: international mobile subscription identity
LTE: Long Term Evolution
LTE-A: LTE Advanced
MME: mobility management entity
NAS: non-access stratum
O&M: operation and maintenance
PDCP: packet data convergence protocol
PDN: packet data network
PGW: packet data network gateway
RNC: radio network controller
SGW: serving gateway
TA: tracking area
TAI: tracking area identity
TAU: tracking area update
TEID: tunnel endpoint identifier
UE: user equipment
UMTS: Universal Mobile Telecommunication Services
UTRA: UMTS terrestrial radio access
UTRAN: UMTS terrestrial radio access network
In the last years, an increasing extension of communication networks, e.g. of wire based communication networks, such as the Integrated Services Digital Network (ISDN), DSL, or wireless communication networks, such as the cdma2000 (code division multiple access) system, cellular 3rd generation (3G) and fourth generation (4G) communication networks like the Universal Mobile Telecommunications System (UMTS), enhanced communication networks based e.g. on LTE or LTE-A, cellular 2nd generation (2G) communication networks like the Global System for Mobile communications (GSM), the General Packet Radio System (GPRS), the Enhanced Data Rates for Global Evolution (EDGE), or other wireless communication system, such as the Wireless Local Area Network (WLAN), Bluetooth or Worldwide Interoperability for Microwave Access (WiMAX), took place all over the world. Various organizations, such as the 3rd Generation Partnership Project (3GPP), Telecoms & Internet converged Services & Protocols for Advanced Networks (TISPAN), the International Telecommunication Union (ITU), 3rd Generation Partnership Project 2 (3GPP2), Internet Engineering Task Force (IETF), the IEEE (Institute of Electrical and Electronics Engineers), the WiMAX Forum and the like are working on standards for telecommunication network and access environments.
Generally, for properly establishing and handling a communication connection between terminal devices such as a user equipment (UE) and another communication network element or user equipment, a database, a server, etc., one or more intermediate network elements such as communication network control elements, e.g. base stations or eNBs, core network elements, e.g. control nodes, support nodes and service nodes are involved which may belong to different communication network.
Wireless or cellular communication networks, such as 2G, 3G, LTE or LTE-A based networks, are divided in several sub-systems, for example an access network subsystem like UTRAN or E-UTRAN (evolved UTRAN), a core network subsystem (like EPC), etc. While the access network subsystem is mainly responsible for communicating with subscriber terminals or UEs via a wireless connection, the core network subsystem is responsible for overall control of the UEs and the establishment of bearers. The core network subsystem comprises several elements, such as gateways (SGW, PGW), mobility control elements or MME etc.
The MME, for example, is used as a control node for processing the signaling between the UE and the core network. It has functions related to bearer management (establishment, maintenance and release of bearers), connection management and inter-working with other networks. Furthermore, functions related to localizing and management of UEs being in an idle mode are done by the MME. For this purpose, an MME manages all UEs being located in a so called tracking area, wherein each tracking area may consist of one or more cells controlled by a corresponding communication network control element (e.g. an eNB). It is to be noted that a cell may belong to one or more tracking areas. Generally, when a UE enters or changes a tracking area, it conducts a TAU procedure so that the MME is aware of the tracking area where the UE is reachable. If plural MMEs are available for a cell, these MMEs form a MME pool.
In order to support O&M functions related to the communication network system, network management functions are provided. For example, load balancing and load re-balancing mechanisms between different MMEs are used. For example, MME load balancing functionality permits UEs entering into an MME pool area to be directed to an appropriate MME in a manner that achieves load balancing between the MMEs (e.g. by using a weight factor for each MME being set according to a capacity/load of the respective MME). Load re-balancing between MMEs, on the other hand, is used to permit UEs that are registered on one MME (within an MME pool) to be moved to another MME, which is used e.g. in connection with O&M related processes. It is to be noted that in case of load re-balancing all or a part of the UEs (subscribers) attached to the MME can be moved to the other MME.
However, when executing the present load re-balancing procedures, it is possible that a user experience is interrupted since certain services are caused when a UE is moved to a new (target) MME including a TAU procedure (without making handover prior to the TAU) so that a user plane needs to be released for a short period, as resources have not been pre-allocated on the target radio node prior to the new registration. Furthermore, the selection of the target MME relies on the mechanisms like load balancing (e.g. weight factor) which may not lead to an optimal overall selection result inside the MME pool. Also the currently standardized method does not provide means for the load balancing TAU triggering MME to select a specific target MME.
It is an object of the invention to overcome at least some of the above described problems and to provide an enhanced mechanism for executing a handover for a subscriber between mobility management entities for load balancing reasons. Specifically, it is an object of the present invention to provide an improved apparatus, method, and computer program product which allow, for example, a handover from a current mobility management entity to a new mobility management entity due to load balancing reasons while a user experience is not affected.
These objects are achieved by the measures defined in the attached claims.
According to an example of an embodiment of the proposed solution, there is provided, for example, an apparatus comprising at least one processor, and at least one memory for storing instructions to be executed by the processor, wherein the at least one memory and the instructions are configured to, with the at least one processor, cause the apparatus at least to perform: a handover trigger receiving and processing function configured to receive and process a handover trigger message indicating that a change of at least one subscriber attachment from a current mobility management entity to a new mobility management entity is to be executed while a current cell and tracking area of the at least one subscriber is kept unchanged, a handover initiating function configured to initiate a handover of a connection for the at least one subscriber from the current mobility management entity to a new mobility management entity while maintaining the current cell and tracking area of the at least one subscriber, and a handover requirement indicating function configured to create a handover required message and cause transmission of the handover required message to the current mobility management entity, the handover required message indicating a requirement of a relocation of the at least one subscriber to the current cell and tracking area.
Furthermore, according to an example of an embodiment of the proposed solution, there is provided, for example, a method comprising receiving and processing a handover trigger message indicating that a change of at least one subscriber attachment from a current mobility management entity to a new mobility management entity is to be executed while a current cell and tracking area of the at least one subscriber is kept unchanged, initiating a handover of a connection for the at least one subscriber from the current mobility management entity to a new mobility management entity while maintaining the current cell and tracking area of the at least one subscriber, creating a handover required message for indicating a requirement of a relocation of the at least one subscriber to the current cell and tracking area, and causing transmission of the handover required message to the current mobility management entity.
According to further refinements, these examples may comprise one or more of the following features:
In addition, according to an example of an embodiment of the proposed solution, there is provided, for example, an apparatus comprising at least one processor, and at least one memory for storing instructions to be executed by the processor, wherein the at least one memory and the instructions are configured to, with the at least one processor, cause the apparatus at least to perform: a handover trigger function configured to create a handover trigger message and to cause transmission of the handover trigger message, the handover trigger message indicating that a change of at least one subscriber attachment from a current mobility management entity to a new mobility management entity is to be executed while a current cell and tracking area of the at least one subscriber is kept unchanged, a handover required message processing function configured to receive and process a handover required message, the handover required message indicating a requirement of a relocation of the at least one subscriber to the current cell and tracking area, and a handover processing function configured to continue a handover procedure of a connection for the at least one subscriber from the current mobility management entity to a new mobility management entity.
In addition, according to an example of an embodiment of the proposed solution, there is provided, for example, a method comprising creating a handover trigger message indicating that a change of at least one subscriber attachment from a current mobility management entity to a new mobility management entity is to be executed while a current cell and tracking area of the at least one subscriber is kept unchanged, causing transmission of the handover trigger message, receiving and processing a handover required message, the handover required message indicating a requirement of a relocation of the at least one subscriber to the current cell and tracking area, and continuing a handover procedure of a connection for the at least one subscriber from the current mobility management entity to a new mobility management entity.
According to further refinements, these examples may comprise one or more of the following features:
Moreover, according to an example of an embodiment of the proposed solution, there is provided, for example, an apparatus comprising at least one processor, and at least one memory for storing instructions to be executed by the processor, wherein the at least one memory and the instructions are configured to, with the at least one processor, cause the apparatus at least to perform: a handover function configured to execute a handover procedure for changing at least one subscriber attachment to a new mobility management entity while a current cell and tracking area of the at least one subscriber is kept unchanged, a home subscriber server updating function configured to conduct an update procedure for the at least one subscriber with a home subscriber server of the at least one subscriber when the handover procedure is completed, and a temporary identity reallocating function configured to conduct a reallocation procedure of a temporary identity of the at least one subscriber with a communication element of the at least one subscriber.
Moreover, according to an example of an embodiment of the proposed solution, there is provided, for example, a method comprising executing a handover procedure for changing at least one subscriber attachment to a new mobility management entity while a current cell and tracking area of the at least one subscriber is kept unchanged, conducting an update procedure for the at least one subscriber with a home subscriber server of the at least one subscriber when the handover procedure is completed, and conducting a reallocation procedure of a temporary identity of the at least one subscriber with a communication element of the at least one subscriber.
According to further refinements, these examples may comprise one or more of the following features:
In addition, according to examples of the proposed solution, there is provided, for example, a computer program product for a computer, comprising software code portions for performing the steps of the above defined methods, when said product is run on the computer. The computer program product may comprise a computer-readable medium on which said software code portions are stored. Furthermore, the computer program product may be directly loadable into the internal memory of the computer and/or transmittable via a network by means of at least one of upload, download and push procedures.
By virtue of the proposed solutions, it is possible to provide an enhanced mechanism for executing a handover for a subscriber between mobility management entities for load balancing reasons. Specifically, according to some examples of embodiments of the invention, it is possible to conduct a new type of load balancing handover allowing to provide a seamless mobility to the users. That is, it is possible to avoid a break in the user data flow (which may caused for example by conventional load balancing TAU procedure without a handover) and to provide a seamless mobility. Furthermore, it is possible for the current or old MME to trigger a handover to a new MME, wherein it may also influence the selection of a specific target MME. In addition, a configuration of a handover procedure for offloading purposes may be flexible so that, for example, a signalling load at the network can be adjusted and reduced. Moreover, the handover procedure can be executed transparently for a UE so that service impact can be avoided.
The above and still further objects, features and advantages of the invention will become more apparent upon referring to the description and the accompanying drawings.
In the following, examples and embodiments of the present invention are described with reference to the drawings. For illustrating the present invention, the examples and embodiments will be described in connection with a cellular communication network based on a LTE or LTE-A based communication system. However, it is to be noted that the present invention is not limited to an application using such types of communication system, but is also applicable in other types of communication systems and the like, for example an UMTS based communication system.
A basic system architecture of a communication network where examples of embodiments of the invention are applicable may comprise a commonly known architecture of one or more communication systems comprising a wired or wireless access network subsystem and a core network. Such an architecture may comprise one or more access network control elements, radio access network elements, access service network gateways or base transceiver stations, such as a base station, an eNB etc., which control a coverage area also referred to as a cell and with which one or more communication elements or terminal devices such as a UE or another device having a similar function, such as a modem chipset, a chip, a module etc., which can also be part of a UE or attached as a separate element to a UE, or the like, are capable to communicate via one or more channels for transmitting several types of data. Furthermore, core network elements such as gateway network elements, policy and charging control network elements, mobility management entities and the like are part of the communication network.
The general functions and interconnections of the described elements, which also depend on the actual network type, are known to those skilled in the art and described in corresponding specifications, so that a detailed description thereof is omitted herein. However, it is to be noted that several additional network elements and signaling links may be employed for a communication to or from a communication element or terminal device like a UE and a communication network, besides those described in detail herein below.
Furthermore, the described network elements, such as communication network control elements, like an BS, an eNB and the like, core network elements like an MME, an SGW and the like, as well as corresponding functions as described herein may be implemented by software, e.g. by a computer program product for a computer, and/or by hardware. In any case, for executing their respective functions, correspondingly used devices, nodes or network elements may comprise several means and components (not shown) which are required for control, processing and communication/signaling functionality. Such means may comprise, for example, one or more processor units including one or more processing portions for executing instructions, programs and for processing data, memory means for storing instructions, programs and data, for serving as a work area of the processor or processing portion and the like (e.g. ROM, RAM, EEPROM, and the like), input means for inputting data and instructions by software (e.g. floppy disc, CD-ROM, EEPROM, and the like), user interface means for providing monitor and manipulation possibilities to a user (e.g. a screen, a keyboard and the like), interface means for establishing links and/or connections under the control of the processor unit or portion (e.g. wired and wireless interface means, an antenna, etc.) and the like. It is to be noted that in the present specification processing portions should not be only considered to represent physical portions of one or more processors, but may also be considered as a logical division of the referred processing tasks performed by one or more processors.
In
Reference sign 20 denotes a communication network control element such as a base station or eNB controlling a communication area or cell. The UE 10 communicates with the eNB 20 via one or more communication or data paths.
Reference signs 30 and 40 denote mobility management entities or MMEs, i.e. an MME1 and an MME2. In the structure shown in
Reference sign 50 denotes a first gateway element such as an SGW which is connected to the MMEs 30 and 40 and to the eNB 20. The SGW 50 serves, for example, for packet routing and forwarding etc. Reference sign 55 denotes a second gateway element such as an SGW which is connected to MME 240 and the eNB 20.
Reference sign 60 denotes a home subscriber server element such as an HSS. The HSS 60 is a database that contains user-related and subscriber-related information and provides support functions in mobility management, call and session setup, user authentication and access authorization.
Reference sign 70 denotes a packet data network gateway (PDB GW), which is connected to SGW150 and SGW255. The PDN GW 70 is used, for example, for controlling tunnels to an SGW in case of mobility scenarios and for routing user plane packets.
The interfaces or reference points between the elements shown in
As described above, in a conventional implementation example, when a load re-balancing procedure between MMEs is executed, the user experience is interrupted due to the movement of the UE 10 to a new (target) MME including a TAU procedure only, without making a handover prior to the TAU (user plane needs to be released and re-established).
In order to avoid this situation, according to some examples of embodiments of the invention, a handover of a connection of one or more subscribers from one mobility management entity, such as from MME1, to which the subscriber(s) is (are) currently attached, to another mobility management entity, such as from MME2, for load balancing purposes, which is triggered by the current mobility management entity, is conducted. In other words, in the system structure as shown in
According to some examples of embodiments of the invention, the MME to which at least one subscriber (UE 10) is attached is enabled to trigger an inter-MME S1 handover for the UE 10 for load (re-)balancing purposes. That is, the current MME (MME130) is configured to cause a change for one or more UEs attached to it to another MME, for example to reduce the load of the current MME (for O&M purposes, for example). That is, an MME relocation is caused while maintaining the current cell and TA of the UE(s) in question.
According to some further examples of embodiments of the invention, the current MME is also able to select the target MME (i.e. the new MME to which the relocation procedure for the subscribers is to be done in the change process).
As indicated in
According to some examples of embodiments of the invention, the handover trigger message in step S10 comprises a specific cause code indicating that a load balancing handover is triggered.
It is to be noted that according to some examples of embodiments of the invention, an initial instruction or command for conducting a movement of one or more UEs from the current MME130 to another MME (and thus triggering the handover procedure) is given by e.g. a network operator or a further control element, such as an O&M element. This is indicated in
When the eNB 20 receives the handover trigger message comprising e.g. the cause code “Load balancing handover triggered” from the MME130, the eNB 20 triggers or starts in step S20 a S1 handover to itself into the current cell. That is, according to some examples of embodiments of the invention, the eNB 20 is configured to start, in response to the handover trigger message with the specific cause code, an S1 based handover procedure in which the target for the handover of the UE 10 is set to the current cell (i.e. to the eNB 20), wherein also a target TA is set to the current TA, for example.
In step S30, the eNB 20 creates a handover required message and sends it to the MME130 (i.e. the current MME from which also the handover trigger message has been received) for indicating a specific type of handover is to be conducted (which results in that the MME for the specified subscribers (e.g. UE 10) is to be changed).
According to some examples of embodiments of the invention, the handover required message is sent as an S1-AP message and comprises a specific cause code indicating that the handover is triggered by a core network element (instruction).
For example, according to some examples of embodiments of the invention, the handover required message indicates, besides information related, for example, to context information of the UE 10, the current TA as a target TA, the current eNB identity of the eNB 20 as the target eNB identity, and the like. In other words, the handover required message indicates that the current cell and TA of the UE 10 is to be maintained. Furthermore, by means of a further indication, e.g. by means of the cause code, the MME130 determines that an MME relocation for the subscriber (UE 10) is possible to be executed according to MME130 decision (like in case of a “normal” handover, for example). That is, the current MME (MME130) is now able to utilize the handover initiated by the eNB 20 via this message in step S30 for the load re-balancing purposes and triggers e.g. a new MME selection for the at least one subscriber.
As indicated in step S40 of
In step S50, the inter-MME S1 handover procedure is conducted or continued at least between the network elements involved therein, i.e. the UE 10, the eNB 20, the MME130 and the MME240. It is to be noted that according to some examples of embodiments of the invention, the target MME (here MME240) is configured to support a handover cause value which is used by the eNB 20 initially requiring the handover (step S30). In the processing according to step S50, several steps for conducting and continuing the inter MME handover are executed. For example, according to some examples of embodiments of the invention, corresponding steps comprises following parts. A relocation related message is sent, such as a Forward relocation request from the current MME130 to the new MME240 (which comprises e.g. information derived from the handover required message, such as a target eNB identification, the selected TA etc.). The Forward Relocation Request causes the new MME240 to further trigger a handover resource allocation procedure and to send a handover request to the eNB 20, establishing a new S1-AP logical signaling connection (the eNB20 is both the “old” and the “new” eNB in a handover point of view). As a response to the handover request, the eNB 20 sends back to the MME240 an acknowledge message to the handover request. The acknowledgement message triggers a sending-back of a Forward Relocation Response from the new MME240 to the current (or old) MME130. Then the old MME130 sends a handover command message to the eNB 20.
It is to be noted that, according to different examples of embodiments of the invention, the above listed steps can be reduced or added by some steps, or other steps having a similar meaning can be employed. For example, steps described in corresponding specifications and being related to an inter MME handover procedure can be added to the above listed steps, as far as they are suitable. Otherwise, in case a corresponding system where examples of embodiments of the invention are applied does not require certain ones of the above steps, they can be omitted then. The processing described above in connection with step S50 is intended for giving a general overview how an inter MME handover can be executed, and a result of step S50 in a procedure according to examples of embodiments of the invention is to continue the inter MME handover procedure being initiated by the preceding steps S10 to S40.
With regard to the UE 10 connection to the eNB 20, according to some examples of embodiments of the invention, the handover procedure is transparent to the UE 10 and a connection mapping is done in the eNB 20, so that the UE 10 is not aware of the MME change thereof. Alternatively, according to some examples of embodiments of the invention, a “virtual” handover procedure for the UE 10 is executed where the eNB 20 acts as both the old and the new eNB. Consequently, the handover procedure according to some examples of embodiments of the invention provides a seamless mobility.
In the following, with regard to S50 where the inter MME S1 handover procedure is indicated to be conducted, further examples of embodiments will be described regarding alternative aspects for the execution or continuation of the handover procedure. Specifically, reference is made to an inter MME S1 handover procedure as illustrated in
As discussed above, according to examples of embodiments being based on a processing as described in connection with steps S10 to S40, an MME has triggered a handover for load balancing purpose wherein also a target MME for the UE may be selected.
According to the now described examples of embodiments, the handover used for load rebalancing is optimized by modifying a configuration of the handover procedure e.g. in comparison to a configuration of a default handover procedure (e.g. an inter MME S1 based handover procedure not being triggered by the MME but by the eNB). In detail, according to some examples of embodiments, at least parts of the handover related signaling is modified or even skipped.
For example, signaling related to data forwarding, PDCP status related signaling, UE related radio interface signaling is a target for the modification. Furthermore, measurement related signalling, status transfer signaling, SGW relocation signaling and handover notification signalling is a target.
According to examples of embodiments of the invention, the eNB 20 and the MMEs (i.e. MME130 and MME240) are aware of the special type of handover procedure initiated by means of the processing related to steps S10 to S40. This is achieved, for example, by means of the indications comprised in the related signalling, such as the special cause code values in the handover trigger message (S10) or the handover required message (S30), which indicate an offloading purpose handover. Thus, in order to optimize the handover procedure with regard to a signalling or processing load, the configuration of a default handover procedure may be modified or adjusted in such a manner that the special conditions regarding this special handover type (e.g. same TA, same cell or eNB) are considered.
Specifically, according to some examples of embodiments, the eNB 20 and the MME130 as well as the MME240 may adapt the configuration of the handover procedure to be conducted in this case in such a manner that they act differently. For example, content of signals or whole signalling sequences are modified or skipped on the sending side, wherein the receiving side accepts this modification or skipping and continues the handover processing e.g. on the basis of internally stored data.
It is to be noted that according to some examples of embodiments the examples of modifications described in the following are optional for a load balancing handover procedure. Unless explicitly stated otherwise, all optimizations indicated in the following may be implemented separately and independently from each other. Basically, a load balancing handover procedure can also be performed without such modifications, i.e. in accordance with a default handover procedure.
Referring to
Furthermore, with regard to eNB 20, as discussed above, since the cell (and due to that, also not the eNB) is not to be changed in the handover procedure, the eNB 20 represents both a source eNB and a target eNB in the handover procedure. For indicating this double role, two lines indicated by “old” (for the source eNB role) and “new” (for the target eNB role) are provided.
It is assumed that a load rebalancing handover procedure as described e.g. in connection with steps S10 to S40 of
For example, according to some examples of embodiments, since the handover to be executed for load rebalancing purposes is made as a handover to the eNB 20 itself and thus the handover target cell is identical to the handover source cell, it is not necessary that the eNB requests any measurements from the UE 10 or that measurement reports received from the UE 10 are to be evaluated in connection with the handover procedure. This represents a first example of options for modifying a default handover procedure, for example.
Referring now to
In S5030, based on the selection made e.g. in step S40, the source MME MME130 sends a forward relocation request message to the target MME (MME 240). The forward relocation request message comprises e.g. information related to MME UE context, Source to Target transparent container (which may be omitted, see also step S5020), target eNB ID, closed subscriber group related information, target TAI, UE time zone, direct forwarding flag, etc. The target TAI is sent to the target MME to help it to determine whether SGW relocation is needed (and, if needed, aid SGW selection). The MME UE context may include information related to IMSI, UE security context, UE network capability, (current) SGW address and TEID for control signaling, and EPS Bearer context(s) (comprising e.g. PDN GW related information like addresses and TEIDs for uplink traffic, SGW addresses and TEIDs for uplink traffic, etc.). Furthermore, the forward relocation request may include an indication related to the type of the handover (e.g. a cause code or the like) indicating the specific type of handover.
The target MME (MME240) may be set as the instance regarding a decision of keeping or changing the SGW (i.e. change from SGW150 to e.g. SGW255. For example, as the UE has not moved, the SGW may be kept. Nevertheless, according to some examples of embodiments, the final decision regarding conducting or not an additional further relocation of the SGW (i.e. to keep the SGW or to enable SGW relocation) may reside in the target MME. For example, this decision is based on further configuration settings, such as a coupling of the target MME with a specific SGW, or more generally a certain TA coupling with a certain SGW. As the TA is not changed in this special type of handover, the validation whether to change SGW may also be skipped. That is, based on the information received in S5030, the target MME MME240 verifies whether the current source SGW (SGW150) can continue to serve the UE 10. If not, MME240 selects a new SGW, e.g. SGW255. This may be based e.g. on a SGW selection function, a pre-set coupling to a specific SGW defined in DNS configuration. This represents a third example of options for modifying a default handover procedure, for example.
In case a new SGW (i.e. SGW255) is determined or selected, the target MME MME240 sends in S5040 a create session request message to the SGW255 which includes information about bearer context(s) with PDN GW addresses and TEIDs for uplink traffic, UE time zone etc. per PDN connection. The target SGW SGW255 allocates the SGW addresses and TEIDs for the uplink traffic on S1_U reference point (one TEID per bearer). The target SGW (SGW255) sends a create session response in S5045 back to the target MME (MM240) which includes e.g. information about SGW addresses and uplink TEID(s) for user plane. Of course, in case the SGW does not change, messages according to S5040 and S5045 are not sent.
According to a default handover procedure, the target MME (MME240) sends in S5050 a handover request message to the target eNB. The handover request comprises in the default handover procedure, for example, information related to EPS bearers to setup, Source to Target transparent container, handover restriction list, etc., for creating the UE context in the target eNB, including information about the bearers, and the security context. However, since according to some examples of embodiments, in the special handover procedure, the source or “old” eNB is identical to the target or new eNB (i.e. eNB 20), the “target eNB” is already aware about the UE context. Therefore, the complexity of the Handover Request message can be reduced by referencing e.g. to the available UE context, instead of providing a full new configuration of the related UE. In other words, the amount of information provided with the handover request message can be reduced. This represents a fourth example of options for modifying a default handover procedure, for example.
In S5055, the target eNB (eNB 20) sends a handover request acknowledge message to the target MME (MME240) including information related to EPS bearers (e.g. a list of addresses and TEIDs allocated at the eNB for downlink traffic on S1-U reference point (one TEID per bearer) and addresses and TEIDs for receiving forwarded data if necessary). According to some examples of embodiments, in the special handover procedure, S5055 may be modified further by using it as a trigger for e.g. starting a modify bearer request procedure (described later) between the target MME (MME240) and a new SGW (SGW255) in case of an SGW change. Furthermore, S5055 may be used also as a trigger for conducting a GUTI reallocation and HSS update procedure (to be described later in connection with S60 of
In a default handover procedure, S5060 and S5065 may be executed which are related to indirect forwarding in case of SGW relocation, and which concern a create indirect data forwarding tunnel request and response. However, according to some examples of embodiments, the target MME and the eNB can skip indirect data forwarding in the special handover procedure for load rebalancing. As the target eNB is the same as source eNB, data forwarding can be handled completely eNB internally so that external transport resources are saved and a delay is reduced. Consequently, processing and signalling according to S5060 and S5065 can be omitted. This represents a sixth example of options for modifying a default handover procedure, for example.
In S5070, the target MME (MME240) sends to the source MME (MME130) a forward relocation response message including information related to a cause, a SGW change indication (if any), EPS bearer setup list, addresses and TEIDs.
In a default handover procedure, S5080 and S5085 may be executed which are related, similar to S5060 and S5065, to indirect forwarding. That is, in case indirect forwarding applies, the source MME sends a create indirect data forwarding tunnel request to the (source) SGW (in case of SGW relocation, also tunnel identifier to the target SGW is included). The SGW responds with a create indirect data forwarding tunnel response to the source MME. However, according to some examples of embodiments, as indicated above, the target MME and the eNB can skip indirect data forwarding in the special handover procedure for load rebalancing. As the target eNB is the same as source eNB, data forwarding can be handled completely eNB internally so that external transport resources are saved and a delay is reduced. Consequently, processing and signalling according to S5080 and S5085 can be omitted. This represents an eighth example of options for modifying a default handover procedure, for example.
In the default handover procedure, in S5090, the source MME sends a handover command message to the source eNB, wherein the handover command may include information related to a target to source transparent container, bearers subject to forwarding, and bearers to be released. In the target eNB, a handover command for the UE is constructed and sent in S5095 to the UE. However, according to some examples of embodiments, in the special handover procedure for load rebalancing, the UE 10 remains in the same cell and there is consequently no need to force the UE 10 to perform an access procedure to a new cell (e.g. a RACH access procedure to the eNB). Hence, the eNB 20 may skip the UE related signalling during the handover procedure. This saves resources and makes also the whole special handover procedure transparent to the UE 10. In other words, the UE 10 can be kept not aware of the offloading triggered handover. Making handover transparent to the UE 10, as an advantage of the special handover procedure, results in that the UE 10 does not suffer from the a user plane interruption time during handover (which may be caused in case of the default handover procedure where typically a service impact by e.g. increased delay, reduced data rate or even data loss is the result). Consequently, processing and signalling according to S5095 can be omitted, and that according to S5090 can be modified. This represents a ninth example of options for modifying a default handover procedure, for example.
In S5100, S5102, S5104 and S5106, according to a default handover procedure, the source eNB sends an eNB status transfer message to the target eNB via the MME(s) to convey information such as PDCP and HFN status. The source MME sends this information to the target MME via forward access context notification message (S5102) which the target MME acknowledges (S5104). The target MME, sends the information to the target eNB via MME status transfer message (S5106). However, according to some examples of embodiments, in the special handover procedure for load rebalancing, as the source eNB is the same as target eNB, the eNB 20 and the MMEs are able to skip a PDCP sequence number delivery and thus the eNB/MME status transfer procedure of S5100 to S5106. A PDCP status may be exchanged internally in the eNB 20, or it is not needed at all if handover is performed transparently to UE 10. Consequently, processing and signalling according to S5100 to S5106 can be omitted or at least modified. This represents a tenth example of options for modifying a default handover procedure, for example.
Referring to
In the default handover procedure, in S5115, the UE detaches from the old cell and synchronizes to the new target cell. After the UE has successfully synchronized to the target cell, it sends in S5120 a handover confirm message to the target eNB. Then, in S5125, DL packets forwarded from the source eNB can be sent to the UE. Also, UL packets can be sent from the UE (see S5127), which are forwarded to the (target) SGW and on to the PDN GW. However, according to some examples of embodiments, as also discussed in connection with S5095, in the special handover procedure for load rebalancing, the UE 10 remains in the same cell and there is consequently no need to force the UE 10 to perform an access procedure to a new cell (e.g. a RACH access procedure to the eNB). Thus, the eNB-UE related signalling during the handover procedure may be skipped, and the whole special handover procedure is transparent to the UE 10. The UE 10 does not suffer from a user plane interruption time during handover. Consequently, processing and signalling according to S5115 to S5127 can be omitted or modified. This represents a twelfth example of options for modifying a default handover procedure, for example.
In the default handover procedure, in S5130, the target eNB sends a handover notify message to the target MME. It is to be noted that in case the handover is performed transparently to the UE, according to some examples of embodiments, a separate handover notify message can be skipped, since the MME can assume that a handover has been completed immediately when sending e.g. the handover command (according to S5090). Consequently, processing and signalling according to S5130 can be omitted. This represents a thirteenth example of options for modifying a default handover procedure, for example.
Furthermore, it is to be noted that a negotiation between the eNB 20 and the target MME240 may be executed according to some examples of embodiments where it is negotiated whether the handover notify message can be cancelled. This negotiation may be executed, for example, by using any of the messages regarding handover required (S5020), handover request (S5050), handover request acknowledge (S5055) or handover command (S5090). Consequently, the contents of these messages may be modified. This represents a fourteenth example of options for modifying a default handover procedure, for example.
In the default handover procedure, in S5140, the target MME sends a forward relocation complete notification message to the source MME. The source MME sends in S5145 a forward relocation complete acknowledge message to the target MME. However, according to some examples of embodiments, as the UE is not really detected in a new cell and handover notify may be skipped, the processing and signaling in S5140 and S5145 may be not required and can be skipped. This represents a fifteenth example of options for modifying a default handover procedure, for example.
In the default handover procedure, in S5150, the new MME sends a modify bearer request message to the target SGW for each PDN connection including the PDN connections that need to be released. The modify bearer request message may comprise information related to an eNB address and TEID allocated at the target eNB for DL traffic. As indicated above, according to some examples of embodiments, S5140 and S5145 may be omitted. In this case, the trigger for sending send a modify bearer request, i.e. to start a bearer modification at the SGW, may be provided by the signaling in S5055. This represents a sixteenth example of options for modifying a default handover procedure, for example.
In case the SGW is relocated, according to the default handover procedure, the target SGW assigns addresses and TEIDs (one per bearer) for DL traffic from the PDN GW. In S5160, a modify bearer request message per PDN connection is sent to the PDN GW 70. The PDN GW 70 updates its context field and returns a modify bearer response in S5165 to the target SGW.
In S5170, according to the default handover procedure, the SGW returns a modify bearer response message to the MME as a response to a modify bearer request message. In S5175, DL packets can be sent to the UE 10.
In the default handover procedure, in S5180, the UE initiates a TAU procedure based on certain conditions. Also the target MME performs a TAU procedure. However, according to some examples of embodiments, in the special handover procedure, a TAU procedure is not performed by the UE 10 as the TA in which the UE 10 camps on is not to be changed. Consequently, processing and signalling according to S5180 can be omitted. This represents a seventeenth example of options for modifying a default handover procedure, for example.
Referring to
In the default handover procedure, in case an indirect forwarding was used, the source MME is triggered in S5200 to send a delete indirect data forwarding tunnel request message to the SGW to release the temporary resources used for indirect forwarding that were allocated at S5080 and S5085. This is responded in S5205 by the target SGW by a delete indirect data forwarding tunnel response message. Similarly, in S5210 and S5215, in case indirect forwarding was used and the SGW is relocated, then the target MME is triggered to send a delete indirect data forwarding tunnel request message to the target SGW to release temporary resources used for indirect forwarding that were allocated at S5060. This is responded by the target SGW by a delete indirect data forwarding tunnel response message. However, according to some examples of embodiments, in the special handover procedure, the MME and the eNB may skip any direct or indirect data forwarding in the load balancing handover procedure (target eNB is the same as source eNB, so that data forwarding can be handled internally in the eNB). Consequently, processing and signalling according to S5200, S50205, S5210, and S5215, respectively can be omitted. This represents a twentieth example of options for modifying a default handover procedure, for example.
As illustrated in connection with
Back to
In view of the fact that the UE 10 is not aware of the MME change or is at least not subjected to a TA change, bearer change or the like (it is still connected to the same cell), there is no reason for it to conduct a TAU (which would be the case when a handover with cell change is conducted in a conventional processing). Nevertheless, when executing the handover procedure for changing the MME as described above, it is necessary to update for example the control point of the bearer (MME) as well as a HSS registration for the subscriber (UE 10) moved to the new MME240.
Therefore, according to some examples of embodiments of the invention, in step S60, immediately after the inter MME handover is completed in step S50, the new MME240 further updates the HSS 60 by informing about the change of the MME, for example by sending an update location request message via the S6a interface to update the HSS registration. In response, the HSS 60 answers to the MME240 with an update location answer (comprising e.g. the IMSI of the UE 10 and subscription date) in case the registration update to new MME (MME240) is successful.
According to some examples of embodiments of the invention, in connection with the update location request/answer exchange with the new MME240, the HSS 60 conducts also a cancel location processing with the old MME130, which comprises for example to send from the HSS 60 to the old MME130 a cancel location message including a cancellation type indication and the IMSI of the UE 10. The MME130 removes then the mobility management and the bearer contexts of the UE 10 and acknowledges this by sending from the old MME130 to the HSS 60 a cancellation location acknowledgement, for example.
Furthermore, in step S60, after receiving the update location answer from the HSS 60, i.e. when the HSS update procedure is completed, the new MME240 conducts a, identity reallocation procedure, such as a GUTI reallocation procedure, with the UE 10. GUTI reallocation is usable for allocating a (new) GUTI and/or a (new) TA list to the UE. For this purpose, the new MME240, sends a reallocation command message, such as a NAS GUTI reallocation command to the UE 10, to allocate a new GUTI with the new TA list from new MME240. The UE responds with a corresponding answer message, such as a GUTI reallocation complete message. Consequently, the UE 10 can be triggered to conduct a TAU procedure, but since the UE location does not change, the required parts of the TAU procedure are executable from MME point of view in a manner that UE gets a new temporary identity and TA list allocated.
It is to be noted that in the handover procedure of step S50 or in the HSS update procedure also a rejection is a possible result for some reasons. In this case, the change of the MME from MME130 to MME240 is stopped or cancelled.
In step S100, a handover trigger message is received and processed which indicates that a change of at least one subscriber attachment from a current mobility management entity to a new mobility management entity (i.e. an MME relocation) is to be executed while a current cell and tracking area of the at least one subscriber is kept unchanged (in other words, a handover with MME relocation but to the same eNB). The handover trigger message is received from the current mobility management entity. According to some examples of embodiments of the invention, the handover trigger message comprises a first specific cause code indicating that the change of the at least one subscriber attachment from the current mobility management entity is due to a load balancing process.
In step S110, a handover of a S1 connection for the at least one subscriber from the current mobility management entity to a new mobility management entity is initiated (while maintaining the current cell and tracking area of the at least one subscriber). According to some examples of embodiments of the invention, for maintaining the current cell and tracking area of the at least one subscriber, a handover procedure for the at least one subscriber is started to the same cell (i.e. the same eNB 20) to which the subscriber is currently attached (e.g. by setting the current cell (eNB 20) and the current TA as the target cell and TA).
In step S120, a handover required message for indicating the requirement of a relocation of the at least one subscriber attachment to the current (same) cell and tracking area (i.e. the cell and TA are maintained even though a relocation is to be done) is created and send to the current mobility management entity (MME130). According to some examples of embodiments of the invention, the handover required message comprises a second specific cause code indicating that the requirement of the relocation of the at least one subscriber attachment to the current cell and TA is due to a command from a core network element.
In step S130, a handover procedure is executed. That is, communication with the current mobility management entity and a new mobility management entity is conducted for completing (or terminating) the handover of the S1 connection for the at least one subscriber from the current mobility management entity to the new mobility management entity while maintaining the current cell and tracking area (i.e. at eNB 20) of the at least one subscriber. For example, the current cell identity and TA indication are used as target values for the handover procedure.
According to some examples, a type of a handover procedure to be executed is determined as being either a default handover procedure or a special handover procedure in which a change from a current mobility management entity to a new mobility management entity is to be executed while a current cell and tracking area of the at least one subscriber is kept unchanged. In case the special handover procedure is determined, a configuration of the handover procedure to be executed can modified from a default setting to a modified setting being different to the default setting. According to some examples, the determination of the type of the handover procedure to be conducted is based on an indication received in the handover trigger message (such as the specific cause code indicated above). Furthermore, the modified setting may comprises at least one of: at the sender side (i.e. messages sent from the eNB 20), a modification of a content of at least one signaling sent in the handover procedure by at least one of adding, amending and omitting of at least one parameter or at least one value comprised in a corresponding signaling sent in the default handover procedure, at the receiver side (i.e. messages received and processed at the eNB 20), the acceptance and processing of a modified content in at least one signaling received in the handover procedure, the modified content being changed in comparison to a content received in the default handover procedure by at least one of adding, amending and omitting of at least one parameter or at least one value comprised therein, at the sender side (i.e. messages sent from the eNB 20), skipping of at least one signaling being sent in the default handover procedure, and, at the receiver side (i.e. messages received and processed at the eNB 20), the acceptance of a skipping of at least one signaling being received in the default handover procedure, and using data being internally stored instead of the at least one skipped signaling.
In step S200 (which is optional according to some examples of embodiments of the invention), the current MME receives and processes a command for initiating a change of at least one subscriber attachment from a current mobility management entity to a new mobility management entity due to load re-balancing reasons. The command is received e.g. from a network operator or an operation and maintenance element. Furthermore, according to some examples of embodiments of the invention, the command further comprises an indication of an identity of a target mobility management entity to be used as a new mobility management entity in the handover procedure.
In step S210 (e.g. in reaction to the command in step S200, or by a decision made in the current MME130 itself), a handover trigger message is created and sent to a cell (eNB 20) where a subscriber (UE 10) to be moved to a new MME is located. The handover trigger message indicates that a change of at least one subscriber attachment from a current mobility management entity to a new mobility management entity is to be executed while a cell and tracking area of the at least one subscriber is kept unchanged.
According to some examples of embodiments of the invention, the handover trigger message comprises a first specific cause code indicating that the change of the at least one subscriber attachment from the current mobility management entity is due to a load balancing process.
In step S220, a handover required message is received and processed. The handover required message is received from the eNB 20 to which the subscriber in question is attached, and concerns an indication of a requirement of a relocation to the current cell and tracking area (i.e. an MME relocation while the current cell and TA are maintained). The current MME now may utilize this handover initiated by the eNB for the load re-balancing purposes and trigger new MME selection for the at least one subscriber. According to some examples of embodiments of the invention, the handover required message comprises a second specific cause code indicating that requirement of the relocation of the at least one subscriber attachment to the current cell and tracking area is due to a command from a core network element.
In step S230 (which is also optional according to some examples of embodiments of the invention), the current MME (e.g. MME130) selects the new mobility management entity to which the handover of the S1 connection for the at least one subscriber from the current mobility management entity is to be continued. According to some examples of embodiments of the invention, the selection of the new mobility management entity is based on an internal selection algorithm (e.g. related to a result that an SGW does not need to be switched due to the MME handover), or an indication of an identity of a target mobility management entity to be used as the new mobility management entity received from an operation and maintenance element (e.g. in step S200).
In step S240, the handover procedure of the S1 connection for the at least one subscriber from the current mobility management entity to the new mobility management entity is continued. For example, according to some examples of embodiments of the invention, when step S230 is implemented, the handover procedure of the connection is continued to the selected mobility management entity. According to some examples of embodiments of the invention, for continuing the handover procedure, a communication with the communication network control element (eNB 20) to which the at least one subscriber is attached and the new mobility management entity (MME240) is conducted for continuing the handover procedure for the connection for the at least one subscriber from the current mobility management entity to the new mobility management entity while maintaining the current cell and tracking area of the at least one subscriber.
According to some examples of embodiments, the handover procedure continued in S240 may comprise a determination of a type of a handover procedure to be continued as being a default handover procedure or a special handover procedure in which a change from a current mobility management entity to a new mobility management entity is to be executed while a current cell and tracking area of the at least one subscriber is kept unchanged. In case it is the special handover procedure, a configuration of the handover procedure to be continued may be modified from a default setting to a modified setting being different to the default setting. For example, the determination of the type of the handover procedure to be continued is based on an indication received in the handover required message, for example by means of the specific cause code. Furthermore, the modified setting may comprises at least one of: at the sender side (i.e. messages sent from the MME130), a modification of a content of at least one signaling sent in the handover procedure by at least one of adding, amending and omitting of at least one parameter or at least one value comprised in a corresponding signaling sent in the default handover procedure, at the receiver side (i.e. messages received and processed at the MME130), the acceptance and processing of a modified content in at least one signaling received in the handover procedure, the modified content being changed in comparison to a content received in the default handover procedure by at least one of adding, amending and omitting of at least one parameter or at least one value comprised therein, at the sender side (i.e. messages sent from the MME130), skipping of at least one signaling being sent in the default handover procedure, and, at the receiver side (i.e. messages received and processed at the MME130), the acceptance of a skipping of at least one signaling being received in the default handover procedure, and using data being internally stored instead of the at least one skipped signaling.
In step S300, a handover procedure is executed for changing at least one subscriber attachment to a new mobility management entity while a current cell and tracking area of the at least one subscriber is kept unchanged. For example, according to some examples of embodiments of the invention, the handover procedure is conducted in accordance with the description related to step S50 of
According to some examples of embodiments, the handover procedure executed in S300 may comprise a determination of a type of a handover procedure to be continued as being a default handover procedure or a special handover procedure in which a change from a current mobility management entity to a new mobility management entity is to be executed while a current cell and tracking area of the at least one subscriber is kept unchanged. In case it is the special handover procedure, a configuration of the handover procedure to be executed may be modified from a default setting to a modified setting being different to the default setting. For example, the determination of the type of the handover procedure to be executed is based on an indication received in the handover procedure, for example by means of the specific cause code. Furthermore, the modified setting may comprises at least one of: at the sender side (i.e. messages sent from the MME240), a modification of a content of at least one signaling sent in the handover procedure by at least one of adding, amending and omitting of at least one parameter or at least one value comprised in a corresponding signaling sent in the default handover procedure, at the receiver side (i.e. messages received and processed at the MME240), the acceptance and processing of a modified content in at least one signaling received in the handover procedure, the modified content being changed in comparison to a content received in the default handover procedure by at least one of adding, amending and omitting of at least one parameter or at least one value comprised therein, at the sender side (i.e. messages sent from the MME240), skipping of at least one signaling being sent in the default handover procedure, and, at the receiver side (i.e. messages received and processed at the MME240), the acceptance of a skipping of at least one signaling being received in the default handover procedure, and using data being internally stored instead of the at least one skipped signaling.
It is to be noted that the target MME (MME240) may be set as the instance regarding a decision of keeping or changing the SGW (i.e. change from SGW150 to e.g. SGW255. For example, as the UE has not moved, the SGW may be kept. Nevertheless, according to some examples of embodiments, the final decision regarding conducting or not an additional further relocation of the SGW (i.e. to keep the SGW or to enable SGW relocation) may reside in the target MME. For example, this decision is based on further configuration settings, such as a coupling of the target MME with a specific SGW.
In step S310, when it is determined that the handover procedure is completed, an update procedure for the at least one subscriber with a home subscriber server of the at least one subscriber is conducted. For example, according to some examples of embodiments of the invention, an update location request message for informing the home subscriber server of the at least one subscriber about the change to the new mobility management entity is sent, and a corresponding update location acknowledgement message is received and processed for completing the update procedure. That is, according to some examples of embodiments of the invention, for example, the MME240 updates with the HSS 60 via an S6a Update Location Request and receives a response by means of an Update Location Answer.
In step S320, a reallocation procedure of a temporary identity of the at least one subscriber is conducted with the UE (UE 10) of the at least one subscriber. That is, according to some examples of embodiments of the invention, when the temporary identity is a GUTI, a GUTI reallocation command message is sent to the UE of the at least one subscriber for reallocating a GUTI and a TA list of the at least one subscriber, and a corresponding GUTI reallocation complete message is received and processed for completing the reallocation procedure.
In
The communication network control element shown in
The processor 21 is configured to execute processing related to the above described MME changing procedure. In particular, the processor 21 comprises a sub-portion 211 as a processing portion which is usable for receiving and processing a handover trigger message. The portion 211 may be configured to perform processing according to step S100 of
In
The mobility management entity or MME130 may comprise a processing function or processor 31, such as a CPU or the like, which executes instructions given by programs or the like related to the MME changing procedure. The processor 31 may comprise one or more processing portions dedicated to specific processing as described below, or the processing may be run in a single processor. Portions for executing such specific processing may be also provided as discrete elements or within one or more further processors or processing portions, such as in one physical processor like a CPU or in several physical entities, for example. Reference signs 32 and 33 denote transceiver or input/output (I/O) units (interfaces) connected to the processor 31. The I/O units 32 are used for communicating with one or more communication network control elements like the NodeB 20. The I/O units 33 are used for communicating with one or more core network like another MME. The I/O units 32 and 33 may be a combined unit comprising communication equipment towards several network elements, or may comprise a distributed structure with a plurality of different interfaces for different network elements. Reference sign 34 denotes a memory usable, for example, for storing data and programs to be executed by the processor 31 and/or as a working storage of the processor 31.
The processor 31 is configured to execute processing related to the above described MME changing procedure. In particular, the processor 31 comprises a sub-portion 311 as a processing portion which is usable for conducting a triggering of a handover. The portion 311 may be configured to perform processing according to step S210 of
In
The mobility management entity or MME240 may comprise a processing function or processor 41, such as a CPU or the like, which executes instructions given by programs or the like related to the MME changing procedure. The processor 41 may comprise one or more processing portions dedicated to specific processing as described below, or the processing may be run in a single processor. Portions for executing such specific processing may be also provided as discrete elements or within one or more further processors or processing portions, such as in one physical processor like a CPU or in several physical entities, for example. Reference signs 42 and 43 denote transceiver or input/output (I/O) units (interfaces) connected to the processor 41. The I/O units 42 are used for communicating with one or more communication network control elements like the NodeB 20. The I/O units 43 are used for communicating with one or more core network like another MME or the HSS 60. The I/O units 42 and 43 may be a combined unit comprising communication equipment towards several network elements, or may comprise a distributed structure with a plurality of different interfaces for different network elements. Reference sign 44 denotes a memory usable, for example, for storing data and programs to be executed by the processor 41 and/or as a working storage of the processor 41.
The processor 41 is configured to execute processing related to the above described MME changing procedure. In particular, the processor 41 comprises a sub-portion 411 as a processing portion which is usable for conducting a handover procedure. The portion 411 may be configured to perform processing according to step S300 of
It is to be noted that while in the above described examples of embodiments of the invention the functions of the current (old) MME (MME130) and of the new MME (MME240) are described to be located in separate network elements, according to some further examples of embodiments of the invention, a network node acting as a mobility management entity (i.e. a MME) is configured to comprise functions and devices according to both the current (old) MME (MME130) and of the new MME (MME240). In other words, a mobility management entity according to some examples of embodiments of the invention is configured to become both a source and a target for the MME handover procedure as described above.
According to some further examples of embodiments of the invention, there is provided an apparatus comprising handover trigger receiving and processing means for receiving and processing a handover trigger message indicating that a change of at least one subscriber attachment from a current mobility management entity to a new mobility management entity is to be executed while a current cell and tracking area of the at least one subscriber is kept unchanged, handover initiating means for initiating a handover of a connection for the at least one subscriber from the current mobility management entity to a new mobility management entity while maintaining the current cell and tracking area of the at least one subscriber, and handover requirement indicating means for creating a handover required message and for causing a transmission of the handover required message to the current mobility management entity, the handover required message indicating a requirement of a relocation of the at least one subscriber to the current cell and tracking area.
In addition, according to some examples of embodiments of the invention, there is provided an apparatus comprising handover trigger means for creating a handover trigger message and for causing a transmission of the handover trigger message, the handover trigger message indicating that a change of at least one subscriber attachment from a current mobility management entity to a new mobility management entity is to be executed while a current cell and tracking area of the at least one subscriber is kept unchanged, handover required message processing means for receiving and processing a handover required message, the handover required message indicating a requirement of a relocation of the at least one subscriber to the current cell and tracking area, and handover processing means for continuing a handover procedure of a connection for the at least one subscriber from the current mobility management entity to a new mobility management entity.
Moreover, according to some examples of embodiments of the invention, there is provided an apparatus comprising handover means for executing a handover procedure for changing at least one subscriber attachment to a new mobility management entity while a current cell and tracking area of the at least one subscriber is kept unchanged, home subscriber server updating means for conducting an update procedure for the at least one subscriber with a home subscriber server of the at least one subscriber when the handover procedure is completed, and temporary identity reallocating means for conducting a reallocation procedure of a temporary identity of the at least one subscriber with a communication element of the at least one subscriber.
For the purpose of the present invention as described herein above, it should be noted that
As described above, there is provided a mechanism for executing a handover for a subscriber between mobility management entities for load balancing reasons. A current mobility management entity sends a handover trigger message to a communication network control element like an eNB for indicating a relocation to the current cell and tracking area of the subscriber. The eNB starts a handover procedure to itself and sends a handover required message to the current mobility measurement entity. The current mobility measurement entity continues a handover procedure of a connection for the at least one subscriber from the current mobility management entity to a new mobility management entity, wherein the new mobility management entity is selectable at the current mobility management entity. The handover procedure can be modified in comparison to a default handover procedure by modifying and/or omitting handover related signaling. After the handover is completed, the new mobility management entity initiates a location update at a home subscriber server and reallocates the subscriber's UE a new temporary identity and tracking area list.
Although the present invention has been described herein before with reference to particular embodiments thereof, the present invention is not limited thereto and various modifications can be made thereto.
Number | Date | Country | Kind |
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PCT/EP2013/054557 | Mar 2013 | EP | regional |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2013/060020 | 5/15/2013 | WO | 00 |