TITLE OF THE INVENTION:

CHANGING LTE SPECIFIC ANCHOR WITH SIMPLE TUNNEL

SWITCHING

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims priority of United States Provisional Patent

Application Serial No. 60/814,042, filed on June 16, 2006. The subject

matter of the above referenced application is incorporated by reference.

BACKGROUND OF THE INVENTION:

Field of the Invention:

[0002] The present invention relates to long term evolution (LTE) anchor

mobility and transferring of LTE anchors when in an idle state.

Description of the Related Art:

[0003] In the 3rd Generation Partnership Project (3GPP), the evolution from

the existing General Packet Radio Service (GPRS) network architecture is

being studied under the name of System Architecture Evolution (SAE) in

order to enhance the capability of the 3GPP system to cope with the rapid

growth in Internet Protocol data traffic. SAE is envisioned to accommodate

various types of access systems, such as 3GPP access systems and WLAN,

and it supports seamless mobility within and across those access systems. As

one of the 3GPP access systems, a new radio access system called Long

Term Evolution (LTE) is being standardized. A goal of SAE standardization

is to accommodate LTE access and provide higher bit rate packet services

with seamless mobility capability.

[0004] An LTE anchor provides mobility anchor functionality when a user

equipment moves from one user plane entity area to another. The LTE

anchor is the user plane entity closest to the radio access network (RAN).

The LTE anchor terminates packet data convergence protocol (PDCP) and

user plane ciphering/integrity protection for LTE access. However, in the

3GPP architecture, it is not specified how the mobility of user plane

functions may be accomplished, or further, which functional entities can be

changed or relocated when the user is in an idle state or in an active mode.

One such functional entity change that is not specified in 3GPP architecture

is the LTE anchor change-over or mobility, which is a critical component to

the operation of the developing architecture.

[0005] One motivation for an LTE specific anchor change-over could be

route optimization, for example, if an earlier selected LTE specific anchor is

no longer in an optimal path as a result of user mobility. Another motivation

for LTE specific anchor change-over may be a failure in the current LTE

anchor requiring a transition to substitute for the failing component. Other

motivations for LTE specific anchor change-over may be network

congestion in the data path to/from the current LTE anchor or a desire to

share load more evenly in the network across other LTE anchors. Thus, LTE

anchor mobility has a substantial impact on the 3GPP architecture and there

is a need to address the LTE anchor mobility issue if the architecture is to be

successful.

SUMMARY OF THE INVENTION:

[0006] An embodiment of the invention generally provides a method for

LTE anchor mobility. The present invention can provide anchor mobility in

a simple, low cost, and uncomplicated solution, through a simple tunnel

switching method in idle mode. Embodiments of the LTE anchor mobility

method are based on the MME role as an idle mode controlling element, thus

having the information needed for simple tunnel switching between two LTE

anchor points. In embodiments of the invention, the 3GPP anchor generally

remains the same when LTE anchor changes.

[0007] Embodiments of the invention may further provide a method for

transferring an LTE anchor in an idle mode. The method includes an MME

(control plane entity) initiating an LTE anchor change procedure, the MME

first commands the selected new LTE anchor to set up a user plane tunnel

towards the 3GPP anchor and then it updates this information towards the

3GPP anchor. Thereafter, the old tunnel is deleted from the old LTE anchor.

[0008] Another embodiment of the invention is directed to a network entity

for initiating an anchor change-over procedure. The network entity includes

a creation unit configured to direct a creation request to a second anchor to

set up a user plane tunnel towards a third generation anchor and configured

to receive a response from the second anchor. The network entity also

includes an updating unit configured to send an update context request

towards the third generation anchor and to receive an update proxy context

response from the third generation anchor. The network entity further includes

a deletion unit configured to direct a deletion request to a first anchor and to

receive a deletion response from the first anchor. The network entity is

configured to operate in an idle mode.

[0009] Another embodiment of the invention is directed to a method for

initiating an anchor change-over procedure. The method includes directing a

creation request to a second anchor to set up a user plane tunnel towards a

third generation anchor, receiving a response from the second anchor and

sending an update context request towards the third generation anchor. The

method also includes receiving an update proxy context response from the

third generation anchor, directing a deletion request to a first anchor and

receiving a deletion response from the first anchor. A network entity

implementing the elements above is configured to operate in an idle mode.

[0010] Another embodiment of the invention is directed to an apparatus for

initiating an anchor change-over procedure. The apparatus includes directing

means for directing a creation request to a second anchor to set up a user

plane tunnel towards a third generation anchor. The apparatus also includes

receiving means for receiving a response from the second anchor, updating

means for sending an update context request towards the third generation

anchor and receiving means for receiving an update proxy context response

from the third generation anchor. The apparatus further includes directing

means for direction a deletion request to a first anchor and receiving means for

receiving a deletion response from the first anchor. The apparatus is in an idle

mode.

[0011] Another embodiment of the invention is directed to a system for

implementing initiation of an anchor change-over procedure. The system

includes a mobility entity configured to direct a creation request to a second

anchor to set up a user plane tunnel towards a third generation anchor. The

system also includes the second anchor configured to create a tunnel towards

the third generation anchor upon receipt of the creation request and to send a

response to the mobility entity. Upon receipt of the response from the second

anchor the mobility entity is configured to update a context request towards the

third generation anchor. The third generation anchor is configured to update

uplink path toward the second anchor and to send an update proxy context

response to the mobility entity. The mobility entity is configure to directing a

deletion request to a first anchor and to receive a deletion response from the

first anchor. The mobility entity is configured to operate in an idle mode.

BRIEF DESCRIPTION OF THE DRAWINGS:

[0012] The accompanying drawings, which are included to provide a further

understanding of the invention and are incorporated in and constitute a part

of this specification, illustrate embodiments of the invention that together

with the description serve to explain the principles of the invention, wherein:

[0013] Figure 1 illustrates an exemplary system architecture of the

invention;

[0014] Figure 2 illustrates an exemplary system architecture of the

invention including the user equipments communicating with the system

architecture and the mobile LTE anchor;

[0015] Figure 3 illustrates an exemplary simplified implementation of the

anchor mobility method of the invention;

[0016] Figure 4 illustrates a diagram of an exemplary LTE anchor mobility

configuration.

[0017] Figures 5 A and 5B illustrate a flowchart of an exemplary anchor

mobility method of the invention in a roaming case;

[0018] Figure 6 illustrates a schematic for an exemplary inter-base station

handover including an LTE anchor change;

[0019] Figures 7A and 7B illustrate a flow chart of an exemplary method

of inter MME handover with additions to enable UPE=LTE anchor

handovers;

[0020] Figure 8 illustrates a flow chart of an exemplary method of

relocating visited UPE after an inter MME handoff;

[0021] Figures 9A and 9B illustrate an alternative method for LTE anchor

relocation;

[0022] Figures 1OA and 1OB illustrate another alternative method for LTE

anchor relocation; and

[0023] Figure 11 illustrates the steps implemented in the MME for initiating

an anchor change-over procedure

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0024] Reference will now be made to the preferred embodiments of the

present invention, examples of which are illustrated in the accompanying

drawings.

[0025] Figure 1 illustrates an exemplary system architecture in which

embodiments of the invention may be implemented. In 3GPP SAE/LTE, the

supporting architecture is currently being developed. The different

functionalities of the user plane side of the supporting architecture are shown

in Figure 1. The system architecture evolution (SAE) anchor 102 and the

3GPP anchor 104 are each shown in the dashed line box and are in

communication with the MME UPE 106, which is collectively referred to as

the evolved packet core. The core network to radio access network for

transport of user plane and control plane traffic is illustrated as Sl, that is, the

communication link between the MME UPE and the Evolved RAN. The non-

3GPP-access-network, for example, Wireless LAN, to core network for user

plane control and mobility support is illustrated as S2, that is, the connection

between the SAE anchor 102 and the WLAN or non-3GPP IP access

component.

[0026] The general packet radio service core (GPRS-core) connection to the

evolved packet core network for user and bearer information exchange

during idle and/or active states is illustrated as S3. The GPRS-core

connection to the evolved packet core network for mobility support is

illustrated as S4. The GPRS-core is also connected to GMS/EDGE Radio

Access Network (GERAN) by a Gb interface and to a UTMS Terrestrial

Radio Access Network (UTRAN) by a Iu interface. The Mobility

Management Entity / User Plane Entity connection to the Inter-access-system

anchor for user plane control and mobility support is illustrated as S5a, and

3GPP anchor connection to SAE anchor as S5b. The Home Subscriber

Server connection to the evolved packet core network, which is generally

used to transfer subscriber data for authentication and authorization, is

illustrated as S6. The Policy and Charging Rule Function (PCRF)

connection to the Policy and Charging Enforcement Point for transfer of

quality of service and charging rules is illustrated as S7. PCRF is also

connected to Operational IP Services by an Rx+ interface and the

Operational IP Services is connected to the evolved packet core by a SGi

interface.

[0027] Figure 2 illustrates an exemplary system architecture of the invention

including the user equipments communicating with the system architecture

and the mobile LTE anchor. The LTE anchor 202 communicates with the

3GPP anchor. Thus, the LTE anchor 202 is generally the user plane entity

on the Core Network side closest to the evolved RAN, and operates to

terminate PDCP and user plane ciphering/integrity protection for LTE

access. The termination point currently agreed in 3GPP is to reside on core

network.

[0028] In the exemplary system architecture of Figure 2, the user plane

mobility is considered independently of the control plane, even though both

can be triggered by user mobility to a new base station. Therefore, there are

generally three possible anchor points. First, the LTE specific anchor, which

operates to terminate ciphering, integrity protection, and PDCP for LTE

access. The second is the 3GPP anchor, which is used for switching the user

plane between the defined 3GPP accesses. The third is the global mobility

anchor (the non-3GPP anchor), which is used for switching the user plane

between the 3GPP and non-3GPP accesses, for example, using MIP and HA.

[0029] Figure 3 illustrates an exemplary simplified implementation of the

anchor mobility method of the invention. In the exemplary method, the

Mobility Management Entity (MME)/(control plane entity) initiates an LTE

anchor change procedure. The MME can utilize an external server for

decision making about the time and the new LTE anchor to be selected. The

MME first commands the selected new LTE anchor to set up a user plane

tunnel towards the 3GPP anchor. After it receives tunnel endpoint data from

the new LTE anchor, it updates this information towards the 3GPP anchor.

After that, the old runnel can be deleted from the old LTE anchor. In this

embodiment of the invention, it is assumed that when the MME is in idle

mode it already knows user plane information, including the security

information, and it does not have to request this information from the old

LTE anchor before commanding the LTE anchor change. It should be noted

that this assumption is made because the user equipment is at the moment in

idle mode and it does not thus have any active bearer set up towards the

radio access network.

[0030] More particularly, the exemplary method may include the MME

creating and sending a proxy context request to the new LTE anchor, as Step

14 of Figure 2. The proxy context request may include International Mobile

Station Identity (IMSI) information and IP access context information,

among others. The request operates to command the new LTE anchor to

create a tunnel towards the 3GPP anchor, that is, to prepare to tunneling

behavior as a proxy element between the base station and 3GPP anchor

(when the user equipment moves to active mode for data delivery). The new

LTE anchor responds with the create proxy context response that may

include the new LTE anchor address(es) for user plane delivery, and

allocated Tunnel Endpoint Identifiers (TEID), at Step 15. At step 16, the

MME sends an update context request to the 3GPP anchor. The update

context request includes the new LTE anchor address(es) and the TEID(s)

received from the new LTE anchor. This request operates to instruct the

3GPP anchor to update the user plane path(s) towards the new LTE anchor.

In response, the 3GPP anchor sends a message back to the MME indicating

that the update is OK, at Step 17. Thereafter, at step 19, the MME sends a

delete proxy context request (IMSI) to the old LTE anchor to terminate

operations with the old LTE anchor. The old LTE anchor, in response to the

request, releases the resources needed to transfer to the 3GPP anchor. At

step 19 of the exemplary method, the old LTE anchor sends a delete proxy

context response acknowledgement to the MME, which finalizes the

transition of the LTE anchor point from the old LTE anchor to the new LTE

anchor.

[0031] An advantage of the exemplary embodiment of the invention is the

simplicity of the operational steps required to transition from an old LTE

anchor to a new LTE anchor. For example, in the exemplary embodiment,

only dialog messages and responses are needed to establish a new tunnel

endpoint (or multiple in case there are several bearers for that user

equipment) from a new LTE anchor point. Further, since the invention is

primarily directed to conducting LTE anchor changes in idle mode, complex

PDCP endpoint relocation is not required. Also, by using idle mode for the

transition, tunnel updates towards the base station (BS) are not needed, as no

data tunnels exist then between LTE anchor and BS in the idle mode.

[0032] Returning to the basic configuration and system layout of the

invention, Figure 4 illustrates a diagram of an exemplary LTE anchor

mobility configuration. In the exemplary anchor configuration, the X2

interface (the eNB-eNB interface) is used for signaling as well as for data

forwarding. The system layout illustrates that an advantage of the present

invention is that it significantly improves load sharing for LTE specific

anchors and improves LTE anchor failure or congestion. For example,

embodiments of the invention do not generally consider a case where a base

station, after handoff, is not able to communicate with the old LTE anchor.

Embodiments of the invention are generally directed to avoiding longer

delays in the situation, for example, where, due to user equipment mobility,

the currently selected LTE anchor is situated in a non-optimal path in the

network topology so that a more optimal user plane route is achieved by

using another LTE anchor.

[0033] The process of LTE anchor change is generally conducted in the idle

mode. However, active mode changeovers are possible and would generally

be triggered by a base station change. The base station is the node initiating

the LTE anchor change-over, and the process of the changeover will

generally require a PDCP endpoint relocation from the old LTE anchor to

the new LTE anchor. For this process to be efficient, at least one control

plane interface between the respective LTE anchors is necessary. The user

plane forwarding interface could be required, and similar principles for base

station handover would need to be applied. Additionally, buffering is

required at the new LTE anchor until it receives the PDCP/ciphering

information (sequence numbers) at which point the old LTE anchor is

finished. Further, for lossless delivery, data forwarding between the LTE

anchors would also be a requirement. Thus, it is apparent that the LTE

anchor transition, although possible in active mode, is much less complicated

if conducted in the idle mode, as illustrated in the method of Figure 3. For

example, by switching LTE anchors in an idle mode, the process may be

triggered by the tracking area update. Generally the MME is the initiating

node, and the base station is generally not capable of initiating a changeover

while in an idle mode and the MME can utilize an external service to make

the decision change. Further, by conducting the LTE anchor changeover in

an idle mode, the PDCP endpoint move is simplified, and no bearers are

active toward the RAN, as a simple tunnel switching via the MME

accomplishes the changeover.

[0034] Figures 5A and 5B illustrate a flowchart of an exemplary anchor

mobility embodiment of the invention in a roaming case. In the embodiment

illustrated in Figures 5A and 5B, there will be no observed changes to

signaling in the handover. The visiting user plane entity (UPE) is updated

with the new base station (BS) information, but the home UPE does not see

the change at all. For example, at Step 1 in Figures 5A and 5B, a

measurement report is sent to the Source eNode B from the user equipment

in an L1/L2 signaling process. The eNode B (eNB) makes the handoff

decision to move the user equipment to a cell in the target eNB. Then, at

Step 2, the eNB sends a context data (user equipment RAN context) message

to the Target eNB in an L2/L3 signaling process. The target eNode B stores

the UE RAN context and reserves the RLID, and then sends a context

confirm message back to the Source eNB in an L2/L3 signaling process, at

Step 3. Thereafter, the source eNB sends an handover command to the user

equipment, which then detaches from the old cell and synchronizes to the

new cell at Step 4. The user equipment then sends a handover confirm

message to the Target eNB at Step 5. At this stage, the buffered data in

transit is sent from the Source eNB to the Target eNB, and the Target eNB

sends a handover complete message to the Source eNB at Step 6. The

Source eNB may then flush the DL buffer and finalize delivery of any in

transit packets that were buffered.

[0035] At Step 7 of the exemplary roaming embodiment, the Target eNB

sends a message to the visited UPE to change the mapping (UE ID, BS

TEID, BS IP address, etc.), and the visited UPE updates the user plane

routing in accordance with the message. At Step 8, the Target eNB sends a

relocation indication to the new MME, which then forwards the relocation

indication to the old MME, at Step 9. At Step 10, the visited UPE sends a

mapping acknowledge message to the Target eNb and, at Step 11, sends a

user plane notification to the old MME. At Step 12, the old MME sends a

relocation acknowledge message to the new MME and the new MME

forwards the relocation acknowledge message to the Target eNB, at step 13.

At this point, all of the packet data travels to the user equipment through the

Target eNB and the exemplary embodiment is completed without any

changes being required to the HOME UPE, as the tunnel endpoint is updated

only at the visited UPE.

[0036] In a roaming case where home services are used and the visited UPE

is the same as the LTE anchor changed after the handover, the UPE selection

in the initial setup is the core network and MME functionality. The MME is

the natural element to detect the need for visited UPE change and to select a

new visited UPE. The same procedures for a stand alone UPE may be used.

Attempts to make the UPE equivalent to LTE anchor relocation with simple

tunnel switching is generally not useful without making the proper PDCP

endpoint relocation, as provided in the above noted embodiment.

[0037] Figure 6 illustrates a schematic for an exemplary inter-base station

handover including an LTE anchor change. The data path before the

handover is illustrated as 61 and includes bi-directional communication

between the 3GPP anchor, the old LTE anchor, the Source base station, and

the user equipment. In the handover method, the Source base station starts

forwarding downlink (DL) data toward the target base station, as illustrated

by 62. A radio link is established and the target base station can send data

via the new radio link towards the user equipment, as illustrated by 63. The

data path is updated from the target base station to the old LTE anchor and

data flows (uplink and downlink) via the new radio link via the target base

station, as illustrated by 64. The MME first requests the new LTE anchor to

setup tunnels towards the 3GPP anchor and the target base station at 65, and

the new LTE anchor is ready to receive data. After the new LTE anchor is

set up, MME requests (generally simultaneously) both target the base station

and 3GPP anchor to update data paths towards the new LTE anchor, all of

which takes place at step 65. Thereafter, at step 66 the MME requests that

the old LTE anchor release the resources after a timer expires. The timer is

set up such that the data already sent can be passed before the timer expires.

[0038] Figures 7A and 7B illustrate a flow chart of an exemplary

embodiment of inter MME handover with additions to enable UPE

equivalent to LTE anchor handovers. At Step 71, a measurement report is

sent, and at Step 72, the context data message is sent, in similar fashion to

the above discussed method. At Step 73, the context is confirmed and the

handover command is sent, at Step 74. At Step 75, the handover confirm

message is sent, and at Step 76, the handover is completed. At Step 77, the

Target eNB sends a message to the old LTE anchor to change the mapping

(UE ID, BS TEID, BS IP address, etc.) and the old LTE updates the user

plane routing. At Step 78, the relocation indication (UE id) is sent from the

Target eNb to the new MME and the relocation indication is sent form the

new MME to the old MME, at Step 79. At Step 80, the old LTE anchor

sends a change mapping acknowledge message to the Target eNB, and a user

plane notification message to the old MME. The user plane notification

message includes the user equipment ID and the PDCP related information

incase the MME initiates uplink handover, that is, to get prepared to relocate

the PDCP and ciphering point, which takes place at Step 81. At Step 82, the

old MME sends a relocation acknowledge message to the new MME, and at

Step 83, the new MME acknowledges relocation to the target eNB.

[0039] Figure 8 illustrates a flow chart of an exemplary embodiment of

relocating visited UPE after an inter MME handoff. This embodiment

continues from the previous embodiment and generally begins at Step 100,

where the new MME sends a PDCP information request to the old LTE

anchor and receives a response from the old LTE anchor. This messaging

may be piggybacked onto other messaging between the two entities shown in

previous figures. At Step 140, the new MME sends a create proxy request

message to the new LTE anchor, which creates the required tunnels between

the 3GPP anchor and the base station. The new LTE anchor responds with a

create proxy context response at Step 150, and the new MME sends an

update context response message to the 3GPP anchor, at Step 160. At

generally the same time, the new MME also sends an update user plane

indication to the target eNB to update towards the new LTE anchor. The

3GPP anchor updates uplink path towards the new LTE anchor and sends an

update proxy context message to the new MME at Step 170. At Step 180,

the target eNB acknowledges the user plane update, and at Step 190, the new

MME sends a delete proxy context request to the old LTE anchor, which

responds with an acknowledge message and releases the resources subject to

a timer expiring.

[0040] Figures 9A and 9B illustrate an alternative method for LTE anchor

relocation, and Figures 1OA and 1OB illustrate another alternative method for

LTE anchor relocation. The method illustrated in Figures 9A and 9B are

configured to perform UPE (LTE anchor) relocation totally combined with

MME. Although this method is effective, it may not be preferred, as the

handover may be delayed. The method of Figures 1 OA and 1 OB are directed

to the scenario where the visited UPE is relocated in case of roaming and the

home services are used. Both of the methods illustrated in Figures 9A, 9B

and Figures 1OA and 1OB are similar to the previously discussed methods,

with minor changes to account for the different configurations and situations.

[0041] Figure 11 illustrates the steps implemented in the MME for initiating

an anchor change-over procedure. In Step 1110, the MME directs a creation

request to the new LTE anchor to set up a user plane tunnel towards 3GPP

anchor and receives a response from the second anchor. In Step 1120, the

MME sends an update context request towards the 3GPP anchor and receives

an update proxy context response from the 3GPP anchor. At Step 1130, the

MME sends a deletion request to the old LTE anchor and receives a deletion

response from the old LTE anchor. The MME is in an idle mode.

[0042] Therefore, embodiments of the invention generally provide a method

for transferring an LTE anchor in an idle mode. The method includes an

MME (control plane entity) initiating an LTE anchor change procedure, the

MME first commands the selected new LTE anchor to set up a user plane

tunnel towards the 3GPP anchor and then it updates this information towards

the 3GPP anchor. Thereafter, the old tunnel is deleted from the old LTE

anchor.

[0043] Other embodiments of the invention generally provide a method for

transferring an LTE anchor in an idle mode, wherein the method includes a

source base station forwarding downlink data toward the target base station,

a radio link is established and the target base station sends data via the new

radio link towards the user equipment, and the data path is updated from the

target base station to the old LTE anchor and data flows (uplink and

downlink) via the new radio link via the target base station. The method

further includes the MME requesting the new LTE anchor to setup tunnels

towards the 3GPP anchor and the target base station, the new LTE anchor

starts receiving data, and the MME requests both target BS and 3GPP anchor

to update data paths towards the new LTE anchor. The MME then requests

that the old LTE anchor release communication resources after a timer

expires.

[0044] It should be appreciated by one skilled in art, that the present

invention may be utilized in any network where there is a changeover in the

LTE anchors, as described above. The foregoing description has been

directed to specific embodiments of this invention. It will be apparent;

however, that other variations and modifications may be made to the

described embodiments, with the attainment of some or all of their

advantages. Therefore, it is the object of the appended claims to cover all

such variations and modifications as come within the true spirit and scope of

the invention.