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Title:
METHOD AND APPARATUS FOR TRACKING AREA UPDATE PROCEDURE AND EPS BEARER CONTEXTS REPRESENTATION
Document Type and Number:
WIPO Patent Application WO/2010/078255
Kind Code:
A1
Abstract:
A method and an apparatus for a new use of the active flag bit in tracking area update (TAU) and a new optional or conditional information element (IE) included in the TAU request message is disclosed. A method and apparatus for only maintaining non-access stratum (NAS) signaling in addition to not establishing S1 bearer and radio bearer for all active evolved packet system (EPS) bearer context are also provided. Several new formats representing EPS bearer context identities and a new representation scheme are disclosed to uniquely identify EPS bearer contexts in EPS bearer context status IE.

Inventors:
WATFA MAHMOUD (CA)
WANG PETER S (US)
AGHILI BEHROUZ (US)
Application Number:
PCT/US2009/069592
Publication Date:
July 08, 2010
Filing Date:
December 28, 2009
Export Citation:
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Assignee:
INTERDIGITAL PATENT HOLDINGS (US)
WATFA MAHMOUD (CA)
WANG PETER S (US)
AGHILI BEHROUZ (US)
International Classes:
H04W8/08
Other References:
"3rd Generation Partnership Project;Technical Specification Group Core Network and Terminals;Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3(Release 8)", 18 December 2008 (2008-12-18), pages 74 - 78,177, XP002575548, Retrieved from the Internet [retrieved on 20100324]
"3rd Generation Partnership Project;Technical Specification Group Core Network and Terminals;3GPP System Architecture Evolution;CT WG1 Aspects(Release 8)", 18 December 2008 (2008-12-18), pages 44 - 46, XP002575549, Retrieved from the Internet [retrieved on 20100324]
Attorney, Agent or Firm:
GORADIA, Shefali, D. (P.C.United Plaza, Suite 1600,30 South 17th Stree, Philadelphia Pennsylvania, US)
Download PDF:
Claims:
CLAIMS What is claimed is:

1. A mobility management entity (MME) comprising: a transceiver configured to receive a tracking area update (TAU) request message including an evolved packet system (EPS) update type information element; a processor configured to verify a value of an active flag bit within the EPS update type information element; and on a condition that the value of the active flag bit is equal to one, the processor is further configured to only maintain non-access stratum (NAS) signaling.

2. The MME as in claim 1 wherein on a condition that the value of the active flag bit is equal to one, the processor is further configured to maintain NAS signaling without establishing Sl bearer and radio bearer for all active EPS bearer context.

3. The MME as in claim 1 wherein the processor is further configured to activate radio bearer and Sl bearer on a condition that there is data to be transmitted, the value of the active flag bit is equal to one, and on a condition that there is an EPS bearer context for which the radio bearer and Sl bearer are to be established.

4. The MME as in claim 1 wherein on a condition that the NAS signaling is maintained and an EPS bearer context information element is not included in the TAU request message, radio bearer and Sl bearer are not established.

5. The MME as in claim 1 wherein the transceiver is further configured to transmit a TAU accept message.

6. A wireless/transmit receive unit (WTRU) comprising: a processor configured to perform a tracking area update (TAU) procedure by setting a value for an active flag bit and setting a value for an evolved packet system (EPS) update type in an EPS update type information element; and a transceiver configured to transmit a TAU request message including the value of the active flag bit and the value of the EPS update type in order to indicate whether to maintain NAS signaling, and whether a radio bearer and Sl bearer are to be established for all active EPS bearer context.

7. The WTRU as in claim 6 wherein the value of the active flag bit is set equal to one in order to maintain NAS signaling.

8. The WTRU as in claim 6 wherein on a condition that the value of the active flag bit is set equal to zero, the NAS signaling is not maintained.

9. The WTRU as in claim 6 wherein first three bits of the EPS update type information element represent an EPS update type value.

10. The WTRU as in claim 9 wherein the value of the EPS update type represents TAU by indicating maintaining of NAS signaling for a subsequent NAS signaling message.

11. The WTRU as in claim 6, further comprising: a receiver configured to receive a TAU accept message.

12. The WTRU as in claim 6 wherein the processor is configured to define a format for an information element including a type and value format, which includes an EPS bearer context status information element.

13. The WTRU as in claim 6 wherein the processor is further configured to identify EPS bearer contexts in an EPS bearer context status information element.

14. The WTRU as in claim 6 wherein the transceiver is further configured to transmit an uplink NAS transport message.

15. A method comprising: receiving a tracking area update (TAU) request message including an evolved packet system (EPS) update type information element; verifying a value of an active flag bit within the EPS update type information element; and on a condition that the value of the active flag bit is equal to one, only maintaining non-access stratum (NAS) signaling.

16. The method as in claim 15 wherein on a condition that the value of the active flag bit is equal to one, maintaining NAS signaling without establishing Sl bearer and radio bearer for all active EPS bearer context.

17. The method as in claim 15, further comprising: activating radio bearer and Sl bearer on a condition that there is data to be transmitted, the value of the active flag bit is equal to one, and an EPS bearer context for which radio bearer and Sl bearer are to be established.

Description:
[0001] METHOD AND APPARATUS FOR TRACKING AREA UPDATE

PROCEDURE AND EPS BEARER CONTEXTS REPRESENTATION

[0002] CROSS REFERENCE TO RELATED APPLICATION

[0003] This application claims the benefit of U.S. Provisional

Application Serial No. 61/141,090 filed on December 29, 2008, and U.S. Provisional Application Serial No. 61/153,139 filed on February 17, 2009, both of which are hereby incorporated by reference as if fully set forth herein.

[0004] FIELD OF INVENTION

[0005] This application is related to wireless communications.

[0006] BACKGROUND

[0007] In wireless communications, a procedure used by protocols for mobility management and session management between a wireless transmit/receive unit (WTRU) and a mobility management entity (MME) is described having the protocols belong to a non-access stratum (NAS). One example of this is an evolved packet system (EPS) session management (ESM) protocol, which provides procedures for handling of bearer contexts. In both the session management and mobility management NAS protocols there is a support for inter- system mobility between evolved universal mobile telecommunications system (UMTS) terrestrial radio access network (E- UTRAN) and other third generation partnership project (3GPP) (i.e., global system for mobile communications (GSM) enhanced data rates for GSM evolution (EDGE) radio access network (GERAN) and UTRAN) or non-3GPP access networks.

[0008] Long term evolution (LTE) EPS, defined as part of the 3GPP work item called system architecture evolution (SAE), is an evolution of the 3GPP system architecture. The EPS includes E-UTRAN and evolved packet core (EPC). The E-UTRAN and the EPC may be optimized for the delivery of all services using internet protocol (IP), including voice service using voice over IP (VoIP).

[0009] In E-UTRAN, a model of an EPS bearer context refers to a user plane profile including a set of identities, an associated IP address, a quality of service (QoS) agreement, and a traffic flow template (TFT). Upon attachment to the network, a WTRU obtains a connection to a default packet data node (PDN) gateway, which activates a default EPS bearer context for the WTRU. Accordingly, the WTRU has an active EPS bearer context. The WTRU may also request dedicated EPS bearer contexts to be activated. Each context is identified by a unique identity (i.e., EPS bearer identity), and a dedicated EPS bearer context is linked to the default EPS bearer by a linked EPS bearer identity.

[0010] Additionally, the WTRU may request other PDN connections and dedicated EPS bearers from a new PDN. Accordingly, the WTRU may have several linked EPS bearer identities to which dedicated EPS bearers, identified by EPS bearer identities, are associated or linked. [0011] An EPS bearer context maybe uniquely identified by its EPS bearer identity and linked EPS bearer identity. The linked EPS bearer identity may be four (4) bits long and the EPS bearer identity may also be four (4) bits long. The EPS bearer identity may be located in the bits five (5) to eight (8) (inclusive and hence total of 4 bits) of the first octet of every NAS ESM message. Figure 1 is a representation of the linked EPS bearer identity. The linked EPS bearer identity value is located in the bits one (1) to four (4) of the first octet as seen in Figure 1. The values of the linked EPS bearer identity are defined in Table 1.

TABLE 1

[0012] In an E-UTRAN, tracking area (TA) may be defined by a location similar to a routing area in GERAN/UTRAN. When a WTRU is in a radio resource control (RRC)_CONNECTED state, the location of the WTRU is known at the cell level. When the WTRU is in an RRCJDLE state, the location of the WTRU is known at a TA level. Accordingly, the WTRU informs or updates the network whenever it enters a new TA by sending a tracking area update (TAU) message. A TAU message may be normal, or periodic if the WTRU is in the RRCJDLE state. The WTRU may indicate the type of TAU prepared by specifying different values for the EPS update type informational element (IE) that is included in the TAU message.

[0013] The current contents of a TAU message, are illustrated below in

Table 2. The format is in the form of value only (V), type only (T), type and value (TV), length and value (LV), or type, length and value (TLV). The present requirement is indicated by mandatory (M) or optional (O). The length of the IE is represented in octets in the message.

TABLE 2

[0014] The EPS update type IE specifies an area with which the updating procedure is associated. Figure 2 illustrates a way of coding the EPS update type IE. Table 3 describes the EPS update type, which is a type 1 information element.

TABLE 3

[0015] As illustrated above, the fourth bit of the EPS update type IE is called an active flag bit. If a WTRU in an EPS mobility management (EMM)- IDLE mode has an uplink (UL) user data pending when it initiates the TA updating procedure, or UL signaling not related to the TA updating procedure, the WTRU may also set the active flag bit in the TAU request message. The WTRU may set the active flag bit in order to indicate the request to establish the user plane to the network and to keep the NAS signaling connection after the completion of the TA updating procedure. If the active flag bit is included in the TAU request message, the MME may reestablish the radio bearer and Sl bearer for all of the active EPS bearer contexts. Thus, if the active flag bit is set equal to one (1), the MME keeps the NAS signaling active and also establishes radio and Sl bearers for all of the active EPS bearer contexts. [0016] In E-UTRAN, an EPS bearer context status refers to an IE indicating the state of each EPS bearer context that may be identified by an EPS bearer identity (EBI). The EPS bearer context status IE is coded as shown in Figure 3 and in Table 4. The EPS bearer context status information element is a type 4 information element with four (4) octets length.

TABLE 4

[0017] According to the current configuration, a WTRU requires the network to maintain the NAS signaling because the NAS messages are sent shortly after the TAU procedure. Accordingly, the network establishes the radio bearer and the Sl bearer for all active EPS bearer contexts, which leads to reserving network resources that are never used. For example, when the user attempts to send a short message service (SMS) message which is encapsulated in an NAS signaling message, there is no need to re-establish radio bearer and Sl bearers for all active EPS bearer contexts. A new EPS bearer context configuration is necessary to utilize saved network resources. It is desirable to define and configure new EPS bearer contexts, new TAU procedures, and new EPS bearer context statuses. [0018] Another example with consequences is when a user initiates a circuit- switched (CS) call request which kicks-off a CS fallback (CSFB) mechanism via NAS signaling message. For this example, and according to the current specification, radio bearer and Sl bearer for all active EPS bearers may be established by the network, but the WTRU may ultimately fallback to a target radio access technology (RAT). When the WTRU sends the actual NAS message to indicate the CSFB request, it would appear as if the WTRU had an active packet- switched (PS) session in LTE.

[0019] According to the CSFB procedure, PS resources may be reserved in the target RAT in order to handover all of the bearer context that are active in E-UTRAN and for which bearers have been established, because of a value of the active flag bit, resulting in delays. The delays add to the process which should have otherwise been completed with less signaling and time. [0020] Moreover, it is possible that the WTRU has UL user data for transmission to establish radio bearer and Sl bearer for a specific bearer context. Currently, the WTRU may not indicate the context for which it wishes to establish the bearers. Instead, the network may establish radio bearers for all active bearer contexts. This is not efficient in the context where a user wishes to interact with only one application corresponding to one bearer context. According to the current architecture, all of the active contexts are provided radio bearer and Sl bearer support without actually being used, thus valuable network resources are wasted.

[0021] Furthermore, there is no current IE that identifies an EPS bearer context as part of an EPS bearer identity. An EPS bearer identity is incorporated in the first octet of every ESM NAS message. The linked EPS bearer identity has a defined IE. Thus, the EPS bearer context identity is split in the ESM messages and there is currently no IE that includes both the linked EPS bearer identity and the EPS bearer identity [0022] The current details of the EPS bearer context status IE do not uniquely define a bearer context in the case where there are connections to multiple PDN gateways. An EPS bearer context is uniquely identified by a linked EPS bearer context identity and an EPS bearer context identity. Thus, the current EPS bearer context status IE does not uniquely identify the EPS bearer contexts of the WTRU.

[0023] A need exists for an enhanced use of an active flag bit of a TAU request message to determine weather only NAS signaling is maintained. Moreover, a new informational element is desired to be included in a TAU message, and new ways to represent the EPS bearer contexts to be used in the context status IE are also desired.

[0024] SUMMARY

[0025] A method and an apparatus for a use of the active flag bit in a

TAU procedure and a new optional IE or a conditional IE included in the TAU request message is disclosed. Several new formats representing EPS bearer context identities and a new representation scheme are disclosed to uniquely identify EPS bearer contexts in EPS bearer context status IE. [0026] An MME comprising a transceiver configured to receive a TAU request message including an EPS update type information element, a processor configured to verify a value of an active flag bit within the EPS update type information element, and on a condition that the value of the active flag bit is equal to one, the processor is further configured to only maintain NAS signaling is provided. On a condition that the value of the active flag bit is equal to one, the processor of the MME is further configured to maintain NAS signaling without establishing Sl bearer and radio bearer for all active EPS bearer context. [0027] BRIEF DESCRIPTION OF THE DRAWINGS

[0028] A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings wherein:

[0029] Figure 1 shows a linked EPS bearer identity in accordance with the prior art;

[0030] Figure 2 shows an EPS update type information element in accordance with the prior art;

[0031] Figure 3 shows an EPS bearer context status information element in accordance with the prior art;

[0032] Figure 4 shows an LTE wireless communication system/access network;

[0033] Figure 5 illustrates an exemplary block diagram of the LTE wireless communication system/access network as shown in Figure 4;

[0034] Figure 6 shows tracking are update procedure according to one embodiment.

[0035] Figure 7 shows tracking are update procedure according to another embodiment.

[0036] Figure 8 shows the IE defined as chosen active EPS bearer contexts IE along with a coding format;

[0037] Figure 9 shows a coding format of each identity of an active bearer context;

[0038] Figure 10 shows a television format representing the EPS context identity according to one embodiment;

[0039] Figure 11 shows an identity of an active bearer context;

[0040] Figure 12 shows a television format representing the EPS context identity according to another embodiment;

[0041] Figures 13 and 14 illustrate a combined linked EPS bearer identity and a EPS bearer identity; and [0042] Figures 15 and 16 separately specify linked EPS bearer identity and EPS bearer context identity.

[0043] DETAILED DESCRIPTION

[0044] When referred to hereafter, the terminology "wireless transmit/receive unit (WTRU)" includes but is not limited to a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, a cellular telephone, a personal digital assistant (PDA), a computer, or any other type of user device capable of operating in a wireless environment. When referred to hereafter, the terminology "base station" includes but is not limited to a Node-B, a site controller, an access point (AP), or any other type of interfacing device capable of operating in a wireless environment.

[0045] Figure 4 shows an LTE wireless communication system/access network 200 that includes an E-UTRAN 205. The E-UTRAN 205 includes a WTRU 210 and several evolved Node-Bs, (eNBs) 220. The WTRU 210 is in communication with an eNB 220. The eNBs 220 interface with each other using an X2 interface. Each of the eNBs 220 interface with an MME/Serving GateWay (S-GW) 230 through an Sl interface. Although a single WTRU 210 and three eNBs 220 are shown in Figure 4, it should be apparent that any combination of wireless and wired devices may be included in the wireless communication system/access network 200.

[0046] Figure 5 is an exemplary block diagram of an LTE wireless communication system/access network 300 including the WTRU 210, the eNB 220, and the MME/S-GW 230. As shown in Figure 5, the WTRU 210, the eNB 220 and the MME/S-GW 230 are configured to perform a method for TAU procedure and EPS bearer contexts representation.

[0047] In addition to the components that may be found in a typical

WTRU, the WTRU 210 includes a processor 316 with an optional linked memory 322, at least one transceiver 314, an optional battery 320, and an antenna 318. The processor 316 is configured to perform a method for TAU procedure and EPS bearer contexts representation. The transceiver 314 is in communication with the processor 316 and the antenna 318 to facilitate the transmission and reception of wireless communications. In case a battery 320 is used in the WTRU 210, it powers the transceiver 314 and the processor 316. [0048] In addition to the components that may be found in a typical eNB, the eNB 220 includes a processor 317 with an optional linked memory 315, transceivers 319, and antennas 321. The processor 317 is configured to perform a method for TAU procedure and EPS bearer contexts representation. The transceivers 319 are in communication with the processor 317 and antennas 321 to facilitate the transmission and reception of wireless communications. The eNB 220 is connected to the MME/S-GW 230 which includes a transceiver 332 and a processor 333 with an optional linked memory 334.

[0049] In a first embodiment, a new interpretation for the active flag bit is described. If the active flag bit is set by the WTRU 210, the NAS signaling is maintained by the network after performing the TAU procedure. The network may maintain the NAS signaling on a condition that the active flag bit is set equal to one (1) and no radio bearer or Sl bearer are to be established. Otherwise, if the value of the active flag bit is equal to zero (0), then the network may not maintain any NAS signaling after the TAU procedure is completed. The possibilities for interpretation of the active flag bit are as shown in Table 5.

TABLE 5

[0050] If a WTRU 210 desires to establish lower layer support for a specific bearer context, the WTRU may use other NAS messages to do so since the NAS signaling is maintained. Alternatively, to indicate maintenance of NAS signaling for other signaling messages to be sent by the WTRU, code points are defined for the EPS update type IE. The code points, shown in Table 6, are in addition to setting the active flag bit equal to one (1). [0051] Alternatively, one of the values may be used to indicate to the network that the signaling connection is to be maintained and that the radio bearer and Sl bearer for all active EPS bearer contexts may also be established. This is in addition to setting the active flag bit equal to one (1).

TABLE 6

[0052] Figure 6 shows tracking area update procedure 600 according to one embodiment. The WTRU 610 is configured to transmit a TAU request message 612 to the MME 630. The TAU request message 612 includes the active flag bit that is set equal to one (1) and the EPS update type value (as defined in Table 6) is set equal to 111. The EPS update type value represents bits one (1) to three (3) of octet one. The MME 630 is configured to send TAU accept message 614 to WTRU 610. The MME 630 is configured to not establish radio and Sl bearers 615. The MME 630 is configured to maintain NAS signaling 616 on a condition that a value of the active flag bit is one (1) and on a condition that no radio and Sl bearers are to be established. The WTRU 610 is configured to transmit an extended service request to the MME 630. The extended service request may be the required NAS message for CSFB. The MME 630 is configured to move the WTRU 610 to CS domain using the known CSFB procedures 620. The EPS update type value may be one of the values described in Table 6. Alternatively, on a condition that the value of the active flag bit is set to zero (0), then the network may not maintain any NAS signaling after the TAU procedure completes.

[0053] Figure 7 shows tracking area update procedure 700 according to another embodiment. The WTRU 710 is configured to set a TAU timer 712. The WTRU 710 is configured to determine whether the TAU timer 712 has expired 714. On a condition that the TAU timer has expired 714, the WTRU 710 is configured to set the EPS update type value to a predefined value 714. On a condition that the TAU timer has not expired 714, the WTRU 710 is configured to check whether the TAU timer has expired. The WTRU 710 is configured to transmit a TAU request message 718 to the MME 730. The TAU request message 718 includes the active flag bit that is set equal to one (1) and the EPS update type value (as predefined in Table 6). The EPS update type value represents bits one (1) to three (3) of octet one. The MME 730 is configured to send TAU accept message 720 to WTRU 710. The MME 730 is configured to not establish radio and Sl bearers 722. The MME 730 is configured to maintain NAS signaling 722 on a condition that a value of the active flag bit is one (1) and on a condition that no radio and Sl bearers are to be established. The WTRU 710 is configured to transmit an uplink NAS transport message 724. Alternatively, on a condition that the value of the active flag bit is set to zero (0), then the network may not maintain any NAS signaling after the TAU procedure completes.

[0054] A method for a new IE used to identify the active bearer contexts for which the network may establish radio bearer and Sl bearer if the active flag bit is set equal to one (1) is disclosed. An IE is defined that may be used to indicate the active bearer context for which the network may establish radio bearer and Sl bearer on a condition that the WTRU 210 has an UL data to transmit and the active flag bit is set equal to one (1). Thus, when an MME 230 is configured to receive the TAU request message, the MME 230 may be configured to verify the value of the active flag bit. If the active flag bit is set equal to one (1), the MME 230 may be configured to check whether an optional IE or a conditional IE is included in the TAU message. If either the optional IE or the conditional IE is included in the TAU message, the MME 230 may be configured to activate the radio bearer and Sl bearer for the active bearer contexts that are identified in the new IE. Alternatively, if the active flag bit has a value of zero (0), the WTRU 210 may not include the IE in the TAU message.

[0055] Figure 8 shows the IE defined as chosen active EPS bearer contexts IE identifier (IEI) (i.e., octet 1) and also shows the IE coding. The octet 2, which is the number of chosen active EPS bearer contexts, holds a number N of active bearer context requiring establishment of radio and Sl bearers, where N is an integer. The identities of active bearer context, which starts from octet three (3) and is the same for the N-I octets that follows the third octet, are defined in Figure 9. The illustration of Figure 8 may be used if the WTRU 210 has more than one PDN connection, and the activation desires to specify EPS bearer contexts on different PDN connections. [0056] A new value may be required for the chosen active EPS bearer contexts IE. A number of chosen active EPS bearer contexts in octet 2 of Figure 8 indicate the number of active bearer contexts the WTRU 210 requires to establish a radio bearer and an Sl bearer. A number of chosen active EPS bearer contexts also indicate the number of active bearer context identities that follow in octet 3. [0057] Each identity of an active bearer context seen in octet 3, for example, in Figure 8 is eight (8) bits long and the coding is shown in Figure 9. Bits five (5) to eight (8) of Figure 9 indicate the linked EPS bearer identity, while bits one (1) to four (4) indicate the identity of the EPS bearer. The actual coding may be vice versa, that is, bits five (5) to eight (8) may indicate the EPS bearer identity and bits one (1) to four (4) may indicate the linked EPS bearer identity. The linked EPS bearer identity and EPS bearer identity are as defined in Table 1.

[0058] Alternatively, the TV format (i.e., no length indicator field) may be used to represent the EPS context identity as shown in Figure 10. This format does not have a length indicator as seen in Figure 8 as octet 2. Therefore, there may be only one octet for the identity of EPS bearer contexts which may be used to identify only two (2) EPS bearer contexts. The octet 2 showing the identity of active bearer context in Figure 10 holds the identity of at most two (2) EPS bearer contexts when the WTRU 210 has one PDN connection. Bits five (5) to eight (8) hold the identity of the first context and bits one (1) to four (4) hold the identity of the second context. Each of these identities are represented as shown in Table 1.

[0059] The chosen IEI, a different value than the IEI above, may represent a case in which the WTRU 210 has one PDN connection; therefore, the linked EPS context may be derived from the WTRU 210 context in MME 230 and no signaling is required. Figure 11 shows that the one octet space may hold two EPS bearer context IDs, which is sufficient for the reestablishment. Figure 11 shows the identity of active bearer context as EPS bearer ID - 1 (bits five (5) to eight (8) and EPS bearer ID - 2 (bits one (1) to four (4)).

[0060] If only one EPS bearer context is specified, the bits one (1) to (4) for ID - 2 as seen in Figure 11 may all be set equal to zero (0). Alternatively, a different TV format may be used as illustrated in Figure 12. The TV format seen in Figure 12 is three (3) octets long and is used when the WTRU has only one PDN connection. Each bit position maps to the possible EPS bearer identities that exist as defined above in Table 1. Thus, bit positions one (1) to four (4) are reserved while the other bit positions may be used as defined in Table 1.

[0061] Similarly, the chosen IEI indicates that the WTRU 210 has only one PDN connection. Therefore, the linked EPS context may be derived from the WTRU 210 context in MME 230 and no signaling is required. The bits of octets two (2) and three (3), except bits zero (0) to four (4), map to the bearer identities of the WTRU 210. Alternatively, if one (1) EPS bearer context exists, the specific EPS bearer context may be represented by including the proposed IEs in the NAS message.

[0062] In another embodiment, a representation format for EPS bearer contexts is defined. The formats may be used as IEs to refer to a specific bearer context in NAS ESM messages.

[0063] The formats to represent an EPS bearer context identity may include a combined linked EPS bearer identity value and an EPS bearer identity value (i.e., the EPS bearer context identity IEI). The combined term represents the combination of the linked EPS bearer identity and the EPS bearer identity to represent the full EPS bearer context as shown in Figure 13, which uses eight (8) bits. Figure 14 represents a full EPS bearer context identity using four (4) bits for the EPS bearer identity context IEI. [0064] Alternatively, the linked EPS bearer identity and EPS bearer context identity may be specified separately. This is related to the EPS bearer identity described above. Figure 15 and Figure 16 show a representation of the linked EPS bearer identity.

[0065] In another embodiment, a format for the EPS bearer context status IE is described. The EPS bearer context status IE may include both the linked EPS bearer identity and the EPS bearer identity in order to uniquely identify an EPS bearer context. The format may be used to achieve the functionality with the distinction of having a different value for the IEI to reflect an EPS bearer context status IE.

[0066] Alternatively, if one (1) EPS bearer context exists, then the specific EPS bearer context may be represented by including the proposed IEs with respect to the NAS message.

[0067] EMBODIMENTS

1. A mobility management entity (MME) comprising: a transceiver configured to receive a tracking area update (TAU) request message including an evolved packet system (EPS) update type information element.

2. The MME as in embodiment 1, further comprising: a processor configured to verify a value of an active flag bit within the EPS update type information element; and on a condition that the value of the active flag bit is equal to one, the processor is further configured to only maintain non-access stratum (NAS) signaling.

3. The MME as in embodiment 2 wherein on a condition that the value of the active flag bit is equal to one, the processor is further configured to maintain NAS signaling without establishing Sl bearer and radio bearer for all active EPS bearer context.

4. The MME as in any one of embodiments 2-3 wherein the processor is further configured to activate radio bearer and Sl bearer on a condition that there is data to be transmitted, the value of the active flag bit is equal to one, and on a condition that there is an EPS bearer context for which the radio bearer and Sl bearer are to be established. 5. The MME as in any one of embodiments 2-4 wherein on a condition that the NAS signaling is maintained and an EPS bearer context information element is not included in the TAU request message, radio bearer and Sl bearer are not established.

6. The MME as in any one of embodiments 1-5 wherein the transceiver is further configured to transmit a TAU accept message.

7. A wireless/transmit receive unit (WTRU) comprising: a processor configured to perform a tracking area update (TAU) procedure by setting a value for an active flag bit and setting a value for an evolved packet system (EPS) update type in an EPS update type information element.

8. The WTRU as in embodiment 7, further comprising: a transceiver configured to transmit a TAU request message including the value of the active flag bit and the value of the EPS update type in order to indicate whether to maintain NAS signaling, and whether a radio bearer and Sl bearer are to be established for all active EPS bearer context.

9. The WTRU as in any one of embodiments 7-8 wherein the value of the active flag bit is set equal to one in order to maintain NAS signaling.

10. The WTRU as in any one of embodiments 7-9 wherein on a condition that the value of the active flag bit is set equal to zero, the NAS signaling is not maintained.

11. The WTRU as in any one of embodiments 7-10 wherein first three bits of the EPS update type information element represent an EPS update type value.

12. The WTRU as in any one of embodiments 7-11 wherein the value of the EPS update type represents TAU by indicating maintaining of NAS signaling for a subsequent NAS signaling message.

13. The WTRU as in any one of embodiments 7-12, further comprising: a receiver configured to receive a TAU accept message.

14. The WTRU as in any one of embodiments 7-13 wherein the processor is configured to define a format for an information element including a type and value format, which includes an EPS bearer context status information element.

15. The WTRU as in any one of embodiments 7-14 wherein the processor is further configured to identify EPS bearer contexts in an EPS bearer context status information element.

16. The WTRU as in embodiment 8 wherein the transceiver is further configured to transmit an uplink NAS transport message.

17. A method comprising: receiving a tracking area update (TAU) request message including an evolved packet system (EPS) update type information element.

18. The method as in embodiment 17, further comprising: verifying a value of an active flag bit within the EPS update type information element; and on a condition that the value of the active flag bit is equal to one, only maintaining non-access stratum (NAS) signaling.

19. The method as in embodiment 18 wherein on a condition that the value of the active flag bit is equal to one, maintaining NAS signaling without establishing Sl bearer and radio bearer for all active EPS bearer context.

20. The method as in any one of embodiments 17-18, further comprising: activating radio bearer and Sl bearer on a condition that there is data to be transmitted, the value of the active flag bit is equal to one, and an EPS bearer context for which radio bearer and Sl bearer are to be established.

[0068] Although features and elements are described above in particular combinations, each feature or element can be used alone without the other features and elements or in various combinations with or without other features and elements. The methods or flow charts provided herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable storage medium for execution by a general purpose computer or a processor. Examples of computer-readable storage mediums include a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs). [0069] Suitable processors include, by way of example, a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Application Specific Standard Products (ASSPs); Field Programmable Gate Arrays (FPGAs) circuits, any other type of integrated circuit (IC), and/or a state machine. [0070] A processor in association with software may be used to implement a radio frequency transceiver for use in a wireless transmit receive unit (WTRU), user equipment (UE), terminal, base station, Mobility Management Entity (MME) or Evolved Packet Core (EPC), or any host computer. The WTRU may be used in conjunction with modules, implemented in hardware and/or software including a Software Defined Radio (SDR), and other components such as a camera, a video camera module, a videophone, a speakerphone, a vibration device, a speaker, a microphone, a television transceiver, a hands free headset, a keyboard, a Bluetooth® module, a frequency modulated (FM) radio unit, a Near Field Communication (NFC) Module, a liquid crystal display (LCD) display unit, an organic light-emitting diode (OLED) display unit, a digital music player, a media player, a video game player module, an Internet browser, and/or any Wireless Local Area Network (WLAN) or Ultra Wide Band (UWB) module.