WO2015039281A1

WO2015039281A1 - Methods and apparatus for enhanced network registration

Info

Publication number: WO2015039281A1
Application number: PCT/CN2013/083620
Authority: WO
Inventors: Huan Xu; Shiau-He Tsai; Xuepan GUAN; Lei Shen; Guangming Shi
Original assignee: Qualcomm Incorporated
Priority date: 2013-09-17
Filing date: 2013-09-17
Publication date: 2015-03-26

Abstract

Methods and apparatus for communication include conducting, by a user equipment (UE), a first connection attempt with a target core node (CN) associated with a target CN area, wherein the UE is supported by a source CN associated with a source CN area. Further, the methods and apparatus include receiving a first connection failure message indicating a failure to establish a connection with the target CN based on the first connection attempt. Moreover, the methods and apparatus include initiating a retry timer with a first retry timer interval in response to receiving the first connection failure message. In addition, the methods and apparatus include conducting a second connection attempt with the target CN after expiration of the first timer interval.

Description

METHODS AND APPARATUS FOR ENHANCED NETWORK

REGISTRATION

BACKGROUND

Field

[0001] Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to enhanced network registration.

Background

[0002] Wireless communication networks are widely deployed to provide various communication services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. One example of such a network is the Universal Terrestrial Radio Access Network (UTRAN). The UTRAN is the radio access network (RAN) defined as a part of the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). The UMTS, which is the successor to Global System for Mobile Communications (GSM) technologies, currently supports various air interface standards, such as Wideband-Code Division Multiple Access (W-CDMA), Time Division-Code Division Multiple Access (TD-CDMA), and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). For example, China is pursuing TD- SCDMA as the underlying air interface in the UTRAN architecture with its existing GSM infrastructure as the core network. The UMTS also supports enhanced 3G data communications protocols, such as High Speed Downlink Packet Data (HSDPA), which provides higher data transfer speeds and capacity to associated UMTS networks.

[0003] As the demand for mobile broadband access continues to increase, research and development continue to advance the UMTS technologies not only to meet the growing demand for mobile broadband access, but to advance and enhance the user experience with mobile communications.

[0004] In some wireless communication networks, failures in establishing network communication/connection may result in significant degradations in wireless communication performance and quality. Further, in such scenarios, limitations may exist in remedying the degradations. Thus, improvements in network registration are desired.

SUMMARY

[0005] The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

[0006] In one aspect, a method of communication comprises conducting, by a user equipment (UE), a first connection attempt with a target core node (CN) associated with a target CN area, wherein the UE is supported by a source CN associated with a source CN area. Further, the method comprises receiving a first connection failure message indicating a failure to establish a connection with the target CN based on the first connection attempt. Moreover, the method comprises initiating a retry timer with a first retry timer interval in response to receiving the first connection failure message. In addition, the method comprises conducting a second connection attempt with the target CN after expiration of the first timer interval.

[0007] Further, in an aspect a computer program product comprising a computer- readable medium includes at least one instruction executable to cause a computer to conduct, by a UE, a first connection attempt with a target core node (CN) associated with a target CN area, wherein the UE is supported by a source CN associated with a source CN area. Further, the computer program product computer-readable medium includes at least one instruction executable to cause a computer to receive a first connection failure message indicating a failure to establish a connection with the target CN based on the first connection attempt. Moreover, the computer-readable medium includes at least one instruction executable to cause a computer to initiate a retry timer with a first retry timer interval in response to receiving the first connection failure message. In addition, the computer-readable medium includes at least one instruction executable to cause a computer to conduct a second connection attempt with the target CN after expiration of the first timer interval.

[0008] In another aspect, an apparatus for communication comprises means for conducting, by a UE, a first connection attempt with a target core node (CN) associated with a target CN area, wherein the UE is supported by a source CN associated with a source CN area. Further, the apparatus comprises means for receiving a first connection failure message indicating a failure to establish a connection with the target CN based on the first connection attempt. Moreover, the apparatus comprises means for initiating a retry timer with a first retry timer interval in response to receiving the first connection failure message. In addition, the apparatus comprises means for conducting a second connection attempt with the target CN after expiration of the first timer interval.

[0009] Moreover, in an aspect an apparatus for communication comprising a memory storing executable instructions and a processor in communication with the memory. The processor is configured to execute the instructions to conduct, by a UE, a first connection attempt with a target core node (CN) associated with a target CN area, wherein the UE is supported by a source CN associated with a source CN area. Further, the processor is configured to execute the instructions to receive a first connection failure message indicating a failure to establish a connection with the target CN based on the first connection attempt. Moreover, the processor is configured to execute the instructions to initiate a retry timer with a first retry timer interval in response to receiving the first connection failure message. In addition, the processor is configured to execute the instructions to conduct a second connection attempt with the target CN after expiration of the first timer interval.

[0010] To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The features, nature, and advantages of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference characters identify correspondingly throughout and wherein: [0012] Fig. 1 is a schematic diagram of a communication network including an aspect of a user equipment that may enhance network registration;

[0013] Fig. 2 is a schematic diagram of an aspect of the registration component of Fig.

l;

[0014] Fig. 3 is a conceptual diagram of an example registration connection scheme, e.g., according to Fig. 1;

[0015] Fig. 4 is a flowchart of an aspect of the network registration features at a user equipment, e.g., according to Fig. 1;

[0016] Fig. 5 is a flowchart of another aspect of the network registration features at a user equipment, e.g., according to Fig. 1;

[0017] Fig. 6 is a block diagram conceptually illustrating an example of a wireless communication system including an aspect of the user equipment and network entity described herein;

[0018] Fig. 7 is a block diagram conceptually illustrating an example of a frame structure in a wireless communication system including an aspect of the user equipment and network entity described herein; and

[0019] Fig. 8 is a block diagram conceptually illustrating an example of the network entity of Fig. 1, in communication with the user equipment of Fig. 1, in a wireless communication system.

DETAILED DESCRIPTION

[0020] The detailed description set forth below, in connection with the appended drawings, is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

[0021] The present aspects generally relate to enhancements in network registration.

Specifically, when a UE moves from a source core network (CN) registration area to a target CN registration area, the target CN registration area may be given registration information by the source CN upon receiving the UE's area update. In UMTS, for instance, the UE may change CN registration areas when changing a location area (LA) for the circuit- switched (CS) domain or a routing area (RA) for the packet- switched (PS) domain. When such registration information is not available in time, the UE may receive a location/routing area update reject message or an authentication failure message in the target CN registration area. As per the current UMTS specification, the UE's subscriber identification module (SIM) may be indicated as "invalid" until the SIM is removed and re-inserted into the UE. During the "invalid SIM" period, services to the subscriber will be interrupted except for emergency calls.

[0022] Further, due to CN node synchronization issues, the area updates, as well authentication requests may be mistakenly rejected. As a way to try regaining service without physically removing the SIM from the UE, the present apparatus and methods may provide a mechanism for the UE to mark the SIM to the illegal state as per the UMTS specification, enter a low power mode, and then reset the SIM without users physically removing/re-inserting the SIM to the terminal. The present aspects, which may include but are not limited to hardware-based and/or a software-based soft reset mechanism, may manually be initiated via user interface, or automatically triggered with a fixed number of retries.

[0023] During operation in a suboptimal network deployment, a UE may receive frequent location/routing area update (LAU/RAU) rejects or authentication failures when crossing between CN area boundaries. However, if not for the current UE standardized restraints, some service outages may be recovered from after a relatively short period (e.g., poor synchronization performance between CN nodes - serving GPRS support nodes (SGSNs) for RA, home and visitor location registers (HLR/VLRs)). Additionally, some service outages may last for hours (e.g., due to CN nodes suffering from network down time).

[0024] As such, according to aspects of the present apparatus and methods, an implementation of a retry mechanism after rejection or failure of network registration caused by errors between CN nodes may be made to enhance network registration at a UE. Accordingly, in some aspects, the present methods and apparatuses may provide an efficient solution, as compared to current solutions, to minimize service downtimes on UEs after experiencing network registration failures.

[0025] Referring to Fig. 1, in one aspect, a wireless communication system 10 includes at least one UE 12 in communication coverage of at least first network entity 16 and second network entity 26. UE 12 may communicate with source CN 18 associated with source CN registration area 14 by way of, for instance, network entity 16. Further, UE 12 may communicate with target CN 28 associated with target CN registration area 24 by way of, for example, second network entity 26. For example, one or both of source CN registration area 14 and target CN registration area 24 may be a LA for a CS domain or a RA for a PS domain. In some aspects, source CN 18 may transmit and/or receive communication 29 from target CN 28. Such communication 29 may include, but is not limited to, synchronization information related to, or associated with, UE 12 used for facilitating network registration of UE 12 at target CN 28 when UE 12 enters target CN registration area 24.

[0026] UE 12 may communicate with source CN 18 via one or more communication channels 20 and utilizing one or more radio access technologies (RATs) (e.g., TD- SCDMA). Additionally, UE 12 may communicate with target CN 28 via one or more communication channels 30 and utilizing one or more RATs (e.g., TD-SCDMA). In such aspects, the one or more communication channels 20 and/or one or more communication channels 30 may enable communication on both the uplink and downlink between UE 12 and first network entity 16 and/or second network entity 26.

[0027] In an aspect, UE 12 may be transitioning 22 from source CN registration area

14 to target CN registration area 24. As such, in order to maintain continuity in wireless communication, and to avoid service disconnections or limitations (e.g., illegal SIM), UE 12 may engage in one or more registration procedures/attempts with target CN 28 associated with target CN registration area 24. According to the present aspects, to facilitate registration and/or establishment of communication with target CN 28, UE 12 may include registration component 34, which may be configured to conduct one or more registration/connection attempts with target CN 28 when UE 12 is transitioning 22 into target CN registration area 24.

[0028] Registration component 34 may include connection component 36, which may be configured to conduct one or more registration or connection attempts with target CN 28 when registration component 34 detects or otherwise receives indication that UE 12 is transitioning 22 or is located within target CN registration area 24. Further, registration component 34 may include failure detection component 38, which may be configured to detect or otherwise determine one or more target CN 28 registration or connection failures by receiving, for example, one or more registration/connection failure messages. Such failures may, for instance, result from a rejection by target CN 28 of registration or connection information associated with UE 12. Further, in such cases, due to poor communication conditions or poor synchronization between source CN 18 and target CN 28, target CN 28 may not receive at least the minimum registration/connection information for registration of UE 12 at target CN 28.

[0029] Additionally, registration component 34 may include retry timer 40, which may be configured to initiate a timer of a specified interval in response to receiving one or more registration/connection failure messages. To facilitate registration/connection with target CN 28, retry timer 40 may be configured to determine or otherwise set an interval for further connection attempts based on the number of, or previous connection attempts and/or connection failure messages received. That is, retry timer 40 may set an interval by which registration component 34, and more specifically, connection component 36, must wait or delay subsequent registration/connection attempts with target CN 28. Further aspects of registration component 34 are described herein with respect to Fig. 2.

[0030] UE 12 may include communication component 42, which may be configured to facilitate wireless communication with at least one of first network entity 16 and second network entity 26. For example, communication component 42 may enable UE 12 to communicate with one or both of first network entity 16 and second network entity 26 on one or more uplink and/or downlink data communication channels (e.g., communication channel 20 and/or communication channel 30). Further, communication on the one or more uplink and/or downlink communication channels may be conducted using time slots (e.g., time division multiplexing). Additionally, communication component 42 may be configured to transmit or receive registration information (e.g., transmit connection attempt message and/or receive connection failure message).

[0031] In some aspects, UE 12 may also be referred to by those skilled in the art as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a terminal, a user agent, a mobile client, a client, or some other suitable terminology. Additionally, first network entity 16 and/or second network entity 26 may be a macrocell, picocell, femtocell, relay, Node B, mobile Node B, UE (e.g., communicating in peer-to-peer or ad-hoc mode with UE 12), or substantially any type of component that can communicate with UE 12 to provide wireless network access at the UE 12. [0032] Referring to Fig. 2, an aspect of registration component 34 of UE 12 may include various components and/or subcomponents, which may be configured to enhance network registration/connection from a source CN (e.g., source CN 18) to a target CN (e.g., target CN 28, Fig. 1) by implementing a retry timer 40 to conduct one or more connection attempts at specified time intervals. For example, registration component 34 may be configured to attempt establishment of connection with a source CN at one or more varying or fixed time intervals, and receive one or more messages indicating an attempted establishment of the connection with the target CN failed or was rejected.

[0033] In an aspect, registration component 34 may include connection component 44, which may be configured to conduct one or more connection attempts with a target CN associated with a target CN area. In some aspects, such connection attempts may be conducted while UE (e.g., UE 12, Fig. 1) is supported by a source CN (e.g., source CN 18, Fig. 1). In particular, connection component 44 may be configured to conduct one or more registration/connection attempts (e.g., attempti 46, attempt₂ 48, attemptN 50) with a target CN (e.g., target CN 28, Fig. 1) when in a target CN registration area (e.g., target CN registration area 24, Fig. 1). Connection component 44 may, for instance, transmit one or more connection request messages including, for example, area update information and/or registration information, to a source CN and/or target CN. In other words, attempti 46, attempt₂ 48 and attemptN 50, each of which indicates a registration/connection attempt, may include information that facilities registration/connection with target CN. Connection component 44 may provide one or more registration/connection attempts (e.g., attempti 46, attempt₂ 48, attempt_N 50) to communication component 42 for transmission to one or more network entity (e.g., source CN 18 and/or target CN 28, Fig. 1).

[0034] Registration component 34 may further include failure detection component

52, which may be configured to detect or otherwise determine a registration/connection failure with a source CN. For example, failure detection component 52 may be configured to receive one or more failure messages (e.g., failure messagei 54, failure message₂ 56, failure message_N 58) indicating at least a failure in establishing or registering connection with a target CN (e.g., target CN 28, Fig. 1) associated with a target CN registration area 24 (e.g., target CN registration area 24). In some aspects, failure messagei 54, failure message₂ 56, and/or failure message_N 58 may include or indicate a location area update rejection message, a routing area update rejection message, and an authentication failure message. Further, upon receiving one or more failure messages (e.g., failure messagei 54, failure message₂ 56, failure messageN 58), failure detection component 52 may provide or communication indication of the registration/connection failure to one or both of connection component 44 and retry timer 60. Additionally, communication component 42 may provide one or more failure messages (e.g., failure messagei 54, failure message₂ 56, failure messageN 58) to failure detection component 52.

[0035] In additional aspects, registration component 34 may include retry timer 60, which may be configured to manage the frequency of registration/connection attempts by connection component 44. For example, retry timer 60 may be configured with a retry timer interval 71 of a designated duration determined by retry timer interval determiner 62. As such, retry timer 60 may be configured to operate for the determined retry timer interval 71. During such retry timer interval 71, registration component 34, and/or one or more subcomponents thereof, may prevent or inhibit connection component 44 from attempting to register or connect with a target CN (e.g., target CN 28, Fig. 1). Further, in other aspects, connection component 44 may receive an indication or notification from retry timer 60 indicating an expiration of the retry timer interval 71.

[0036] For example, retry timer 60 may include retry timer interval determiner 62, which may be configured to determine one or more retry intervals (e.g., retry intervali 68, retry interval₂ 69, retry interval_N 70) based on one or more interval adjustment parameters 63. That is, retry time interval determiner 62 may be configured to determine a retry interval (e.g., retry intervali 68, retry interval₂ 69, retry intervalN 70) for retry timer interval 71. Retry timer 60 may then set or otherwise adjust retry timer interval 71 with a determined retry interval (e.g., retry intervali 68, retry interval₂ 69, retry interval_N 70). Upon setting or adjusting the time interval of retry timer interval 71, retry timer 60 may be configured to maintain the retry timer interval 71 following expiration and subsequent reception of a failure message, or adjust retry timer interval 71 to another retry interval. In some aspects, for example, retry interval₂ 69 may be longer in length or duration than retry intervali 68. Likewise, subsequent retry intervals (e.g., retry intervalN 70) may be of continuously longer length. In other non- limiting aspects, any one or more of retry intervali 68, retry interval₂ 69 and retry interval_N 70 may be of duration within a range of 10 seconds and 3 minutes and/or 30 minutes and 24 hours. [0037] Further, retry timer interval determiner 62 may determine one or more retry intervals based on one or more interval adjustment parameters 63. For example, retry timer interval determiner 62 may be configured to receive or otherwise maintain a record of the number of registration/connection attempts and/or failure messages received in connection failure counter 64. As such, the number of connection failures indicative of at least the number of failure messages (e.g., failure messagei 54, failure message₂ 56, failure messageN 58) received by failure detection component 52 may be considered by retry timer interval determiner 62 in determining one or more retry intervals. In a non-limiting example, an increase or a higher number of failure messages received may result in a longer retry interval. In such non-limiting example, one or more of retry intervals (e.g., retry interval 68, retry interval₂ 69, retry interval 70) or retry timer interval 71, may be proportional to the number of connection failures.

[0038] Interval adjustment parameters 63 may also include an exponential function 65, a linear function 66, and stochastic function 67, each of which may configure or otherwise be used to configure the retry timer interval 71 with a retry interval at a certain frequency. For example, retry timer interval determiner 62 may select or be configured with exponential function 65. As such, exponential function 65 may manage or regulate the communication or generation of one or more retry intervals (e.g., retry interval 68, retry interval₂ 69, retry interval 70) at a frequency demonstrating or following a substantial exponential manner. In other words, as failure detection component 52 receives or otherwise obtains a number of failure messages, exponential function 65 may be used to configure the frequency at which corresponding retry intervals are generated or determined. In such cases, received failure messages would result in an exponential determination of retry intervals (e.g., more frequent). In other aspects, the relationship between the number of failure messages and the retry intervals may demonstrate or be representative of a linear function 66 and/or a stochastic function 67 (e.g., exponentially distribution random variable under the assumption of CN recovery arrival following a Poisson process).

[0039] In additional aspects, registration component 34 may include termination component 72, which may be configured to terminate the registration/connection attempts of connection component 44 based on one or more termination conditions 73. For example, termination component 72 may be configured to terminate or to provide a terminating instruction to registration component 34 upon satisfaction of one or more termination conditions 73. Termination conditions 73 may include, but are limited to, reaching a maximum number of target CN connection attempts, expiration of a maximum target CN duration, and/or or successful establishment of a connection with a target CN.

[0040] Referring to Fig. 3, in an aspect, a diagram of an example registration scheme is illustrated. In this example, UE 12 may be moving or transitioning 22 from source CN registration area 14 to target CN registration 24. Accordingly, registration component 34 in UE 12 may be triggered to conduct at least one registration/connection attempt with target CN 28 (e.g., via second network entity 26). For example, connection component 36 may send one or more registration attempts based at least on indications received or obtained by the failure detection component 38 and retry timer 40.

[0041] Specifically, registration component 34, via connection component 36 may transmit an initial registration/connection attempt REG ATTEMPT_N upon entering target CN registration area 24. However, based upon the success of the initial registration/connection attempt, registration component 34 may be configured to send or attempt subsequent registration/connection with second network entity 26 to register or establish a connection with target CN 28. That is, if UE 12, and specifically failure detection component 38, receives a failure message in response to REG ATTEMPT_N, connection component 36 may send or attempt a subsequent registration/connection REG ATTEMPT_N+i with target CN 28 at INTER VAL_N.

[0042] At such time, retry timer 40 may be initialized to operate for a certain time interval. Upon expiration of the time interval and if a subsequent failure message is received, registration component 34 may send or attempt another registration/connection REG ATTEMPT_N+2 with target CN 28 at INTERVAL_N+i. It should be understood that UE 12 may continue to conduct registration/connection attempts with target CN 28 until termination component 72 (Fig. 2) indicates a termination of the registration/connection attempts.

[0043] Referring to Fig. 4, in operation, a UE such as UE 12 (Fig. 1) may perform one aspect of a method 80 for enhancing network registration and/or connection. While, for purposes of simplicity of explanation, the methods herein are shown and described as a series of acts, it is to be understood and appreciated that the methods are not limited by the order of acts, as some acts may, in accordance with one or more aspects, occur in different orders and/or concurrently with other acts from that shown and described herein. For example, it is to be appreciated that the methods could alternatively be represented as a series of interrelated states or events, such as in a state diagram. Moreover, not all illustrated acts may be required to implement a method in accordance with one or more features described herein. As described in further detail below, the functional block diagram 80 provides a process tailored to avoid, or at least to reduce, service interruption experienced by UE 12 (Figs 1 and 2).

[0044] In an aspect, at block 81, method 80 may include conducting a first connection attempt with target CN. For example, as described herein, registration component 34 (Figs. 1 and 2) may execute connection component 44 to conduct a first connection attempt (e.g., attempti 46) with a target CN (e.g., target CN 28) associated with a target CN area (e.g., target CN registration area 24). In some aspects, UE 12 may be supported by a source CN (e.g., source CN 18) associated with a source CN area (e.g., source CN registration area 14) during at least the first connection attempt.

[0045] Moreover, at block 82, method 80 may include receiving a first connection failure message. For instance, as described herein, registration component 34 (Figs. 1 and 2) may execute failure detection component 52 to receive a first connection failure message (e.g., failure messagei 54) indicating a failure to establish a connection with the target CN (e.g., target CN 28) based on the first connection attempt (e.g., attempti 46).

[0046] In addition, at block 83, method 80 may include initiating a retry timer with a first retry timer interval. For example, as described herein, registration component 34 may execute retry timer 60 with a first retry timer interval (e.g., retry timer intervali 68) in response to receiving the first connection failure message (e.g., failure messagei 54).

[0047] At block 84, method 80 may include conducting a second connection attempt with target CN after expiration of first retry timer interval. For instance, as described herein, registration component 34 (Figs. 1 and 2) may execute connection component 44 to conduct a second connection attempt (e.g., attempt₂ 48) with the target CN (e.g., target CN 28) after expiration of the first timer interval (e.g., retry timer intervali 68).

[0048] Further, at block 85, method 80 may optionally include receiving a second connection failure message. For instance, as described herein, registration component 34 (Figs. 1 and 2) may execute failure detection component 52 to receive a second connection failure message (e.g., failure message₂ 56) indicating a failure to establish a connection with the target CN (e.g., target CN 28) based on the second connection attempt (e.g., attempt₂ 46).

[0049] At block 86, method 80 may optionally include adjusting a retry timer interval to a second retry timer interval. For example, as described herein, retry timer 60 (Figs. 1 and 2) may execute retry timer interval determiner 62 to adjust a retry timer interval (e.g., retry timer interval 71) of the retry timer 60 from the first retry timer interval (e.g., retry timer intervali 68) to a second retry timer interval (e.g., retry timer interval₂ 69).

[0050] Additionally, at block 87, method 80 may optionally include conducting a third connection attempt with target CN after expiration of second retry timer interval. For instance, as described herein, registration component 34 may execute connection component 44 to conduct a third connection attempt (e.g., attempt_N 50) with the target CN (e.g., target CN 28) after expiration of the second timer interval (e.g., retry timer interval₂ 69).

[0051] Referring to Fig. 5, in an aspect, a functional block diagram 90 illustrates example blocks executed in conducting network registration/connection according to one aspect the present disclosure. While, for purposes of simplicity of explanation, the methods herein are shown and described as a series of acts, it is to be understood and appreciated that the methods are not limited by the order of acts, as some acts may, in accordance with one or more aspects, occur in different orders and/or concurrently with other acts from that shown and described herein. For example, it is to be appreciated that the methods could alternatively be represented as a series of interrelated states or events, such as in a state diagram. Moreover, not all illustrated acts may be required to implement a method in accordance with one or more features described herein. As described in further detail below, the functional block diagram 90 provides a process tailored to avoid, or at least to reduce, service interruption experienced by UE 12 (Figs 1 and 2).

[0052] At block 91, method 90 may include a UE attempting to establish a connection with a target CN node as part of a switch from a source CN area to a target CN area. For example, as described herein, registration component 34 (Figs. 1 and 2) may execute connection component 44 to conduct a connection attempt (e.g., attempti 46) with a target CN (e.g., target CN 28) associated with a target CN area (e.g., target CN registration area 24) as part of a switch from a source CN area to a target CN area. In an aspect in which the switch is associated with a CS domain, the switch may be between location areas. In an aspect in which the switch is associated with a PS domain, the switch may be between routing areas.

[0053] Further, at block 92, method 90 may include the UE receiving a connection failure message associated with establishing a connection with the target CN node. For instance, as described herein, registration component 34 (Figs. 1 and 2) may execute failure detection component 52 to receive a connection failure message (e.g., failure messagei 54) indicating a failure to establish a connection with the target CN (e.g., target CN 28) based on the connection attempt (e.g., attempti 46). In an aspect, the failure message may be a location area updates reject message, a routing area update reject message, and/or an authentication failure message.

[0054] At block 93, method 90 may include the UE determining whether to reattempt to establish the connection with the target CN based at least on reception of the failure message. For example, as described herein, UE 12 may execute registration component 34 (Figs. 1 and 2) to determine whether to continue conducting registration/connection attempts with target CN. In an aspect, for a temporary loss of registration information between CN nodes across area boundaries, retry after a short interval (e.g., retry timer intervali 68) may be performed.

[0055] Additionally or in the alternative, if the short-interval retry also failed, then it may be determined that a comparatively more serious CN node problem (e.g., at source CN or target CN) might exist or have occurred. In such an additional/alternative aspect, a second longer interval between retries may be used (e.g., retry timer interval₂ 69). In an aspect, the longer retry interval may be a fixed value or may increase as the number of retries increases. In another aspect, the long retry interval may be limited to either a maximum number or a maximum period of trials.

[0056] In an aspect, UE 12 may have access to CN area information (e.g., source CN registration area 14 and/or target CN registration area 24). In such aspects, where the UE does not have access to CN area information, the UE may perform a first retry at a first shorter time interval (e.g., retry timer intervali 68) and then may perform a retry based on a second longer time interval (e.g., retry timer interval₂ 69).

[0057] At block 95, method 90 may include the UE retrying to establish the connection with the target CN one or more times based at least on one of the first shorter time interval or the second longer time interval. For example, as described herein, registration component 34 (Figs. 1 and 2) may execute retry timer 60 with a first retry timer interval (e.g., retry timer intervali 68) or second (longer) retry timer interval₂ 69) in response to determining to continue conducting registration/connection attempts with target CN (e.g., target CN 28).

[0058] At block 96, method 90 may include the UE determining whether the retry was successful or whether a maximum number of attempts have been met. For example, as described herein, registration component 34 (Figs. 1 and 2) may execute termination component 72 to determine wither the registration/connection attempts were successful and/or whether a maximum number of attempts has been met. If at block 96, the retry is successful then the process may terminate at block 96. However, if a block 96 at least one of the one or more connection attempts is unsuccessful, then method 90 may return to block 95.

[0059] In an aspect, the UE may continue retrying registration/connection at the longer interval until the retry status is re-initialized by CN area change. In an optional aspect, at block 96 the UE (e.g., termination component 72) may further determine whether a maximum number of attempts or maximum time duration has expired. In such an optional aspect, when the UE determines that maximum number of attempts or maximum time duration have expired, then the process may terminate at block 96.

[0060] Turning now to Fig. 6, a block diagram is shown illustrating an example of a telecommunications system 200 in which UE 12 including registration component 34, may operate, such as in the form of or as a part of UEs 210 and Node Bs 208. The various concepts presented throughout this disclosure may be implemented across a broad variety of telecommunication systems, network architectures, and communication standards. By way of example and without limitation, the aspects of the present disclosure illustrated in Fig. 6 are presented with reference to a UMTS system employing a TD-SCDMA standard. In this example, the UMTS system includes a (radio access network) RAN 202 (e.g., UTRAN) that provides various wireless services including telephony, video, data, messaging, broadcasts, and/or other services. The RAN 202 may be divided into a number of Radio Network Subsystems (RNSs) such as an RNS 207, each controlled by a Radio Network Controller (RNC) such as an RNC 206. For clarity, only the RNC 206 and the RNS 207 are shown; however, the RAN 202 may include any number of RNCs and RNSs in addition to the RNC 206 and RNS 207. The RNC 206 is an apparatus responsible for, among other things, assigning, reconfiguring and releasing radio resources within the RNS 207. The RNC 206 may be interconnected to other RNCs (not shown) in the RAN 202 through various types of interfaces such as a direct physical connection, a virtual network, or the like, using any suitable transport network.

[0061] The geographic region covered by the RNS 207 may be divided into a number of cells, with a radio transceiver apparatus serving each cell. A radio transceiver apparatus is commonly referred to as a Node B in UMTS applications, but may also be referred to by those skilled in the art as a base station (BS), a base transceiver station (BTS), a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), an access point (AP), or some other suitable terminology. For clarity, two Node Bs 208 are shown, however, the RNS 207 may include any number of wireless Node Bs. The Node Bs 208 provide wireless access points to a core network 204 for any number of mobile apparatuses.

[0062] initiation protocol (SIP) phone, a laptop, a notebook, a netbook, a smartbook, a personal digital assistant (PDA), a satellite radio, a global positioning system (GPS) device, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, or any other similar functioning device. The mobile apparatus is commonly referred to as user equipment (UE) in UMTS applications, but may also be referred to by those skilled in the art as a mobile station (MS), a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal (AT), a mobile terminal, a wireless terminal, a remote terminal, a handset, a terminal, a user agent, a mobile client, a client, or some other suitable terminology. For illustrative purposes, three UEs 210 are shown in communication with the Node Bs 208, each of which may include registration component 34 of UE 12 (Fig. 1). The downlink (DL), also called the forward link, refers to the communication link from a Node B to a UE, and the uplink (UL), also called the reverse link, refers to the communication link from a UE to a Node B.

[0063] The core network 204, as shown, includes a GSM core network. However, as those skilled in the art will recognize, the various concepts presented throughout this disclosure may be implemented in a RAN, or other suitable access network, to provide UEs with access to types of core networks other than GSM networks.

[0064] In this example, the core network 204 supports circuit- switched services with a mobile switching center (MSC) 212 and a gateway MSC (GMSC) 214. One or more RNCs, such as the RNC 206, may be connected to the MSC 212. The MSC 212 is an apparatus that controls call setup, call routing, and UE mobility functions. The MSC 212 also includes a visitor location register (VLR) (not shown) that contains subscriber-related information for the duration that a UE is in the coverage area of the MSC 212. The GMSC 214 provides a gateway through the MSC 212 for the UE to access a circuit-switched network 216. The GMSC 214 includes a home location register (HLR) (not shown) containing subscriber data, such as the data reflecting the details of the services to which a particular user has subscribed. The HLR is also associated with an authentication center (AuC) that contains subscriber-specific authentication data. When a call is received for a particular UE, the GMSC 214 queries the HLR to determine the UE's location and forwards the call to the particular MSC serving that location.

[0065] The core network 204 also supports packet-data services with a serving GPRS support node (SGSN) 218 and a gateway GPRS support node (GGSN) 220. GPRS, which stands for General Packet Radio Service, is designed to provide packet-data services at speeds higher than those available with standard GSM circuit- switched data services. The GGSN 220 provides a connection for the RAN 202 to a packet- based network 222. The packet-based network 222 may be the Internet, a private data network, or some other suitable packet-based network. The primary function of the GGSN 220 is to provide the UEs 210 with packet-based network connectivity. Data packets are transferred between the GGSN 220 and the UEs 210 through the SGSN 218, which performs primarily the same functions in the packet-based domain as the MSC 212 performs in the circuit- switched domain.

[0066] The UMTS air interface is a spread spectrum Direct-Sequence Code Division

Multiple Access (DS-CDMA) system. The spread spectrum DS-CDMA spreads user data over a much wider bandwidth through multiplication by a sequence of pseudorandom bits called chips. The TD-SCDMA standard is based on such direct sequence spread spectrum technology and additionally calls for a time division duplexing (TDD), rather than a frequency division duplexing (FDD) as used in many FDD mode UMTS/W-CDMA systems. TDD uses the same carrier frequency for both the uplink (UL) and downlink (DL) between a Node B 208 and a UE 210, but divides uplink and downlink transmissions into different time slots in the carrier.

[0067] Fig. 7 shows a frame structure 250 for a TD-SCDMA carrier, which may be used in communications between UE 12 (Fig. 1) and one or both of first network entity 16 (Fig. 1) and second network entity 26 (Fig. 1) discussed herein. The TD- SCDMA carrier, as illustrated, has a frame 252 that may be 10 ms in length. The frame 252 may have two 5 ms subframes 254, and each of the subframes 254 includes seven time slots, TSO through TS6. The first time slot, TSO, may be allocated for inter/intra frequency measurements and/or downlink communication, while the second time slot, TS1, may be allocated for uplink communication. The remaining time slots, TS2 through TS6, may be used for either uplink or downlink, which allows for greater flexibility during times of higher data transmission times in either the uplink or downlink directions. A downlink pilot time slot (DwPTS) 256, a guard period (GP) 258, and an uplink pilot time slot (UpPTS) 260 (also known as the uplink pilot channel (UpPCH)) are located between TSO and TS1. Each time slot, TS0-TS6, may allow data transmission multiplexed on a maximum of, for instance, 16 code channels. Data transmission on a code channel includes two data portions 262 separated by a midamble 264 and followed by a guard period (GP) 268. The midamble 264 may be used for features, such as channel estimation, while the GP 268 may be used to avoid inter-burst interference.

[0068] Fig. 8 is a block diagram of a Node B 310 in communication with a UE 350 in a RAN 300, where RAN 300 may be the same as or similar to RAN 202 in Fig. 6, the Node B 310 may be the same as or similar to Node B 208 in Fig. 6, and the UE 350 may be the same as or similar to UE 210 in Fig. 6 or the UE 12 in Fig. 1 including registration component 34. In the downlink communication, a transmit processor 320 may receive data from a data source 312 and control signals from a controller/processor 340. The transmit processor 320 provides various signal processing functions for the data and control signals, as well as reference signals (e.g., pilot signals). For example, the transmit processor 320 may provide cyclic redundancy check (CRC) codes for error detection, coding and interleaving to facilitate forward error correction (FEC), mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), M-phase- shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM), and the like), spreading with orthogonal variable spreading factors (OVSF), and multiplying with scrambling codes to produce a series of symbols.

[0069] Channel estimates from a channel processor 344 may be used by a controller/processor 340 to determine the coding, modulation, spreading, and/or scrambling schemes for the transmit processor 320. These channel estimates may be derived from a reference signal transmitted by the UE 350 or from feedback contained in the midamble 214 (Fig. 8) from the UE 350. The symbols generated by the transmit processor 320 are provided to a transmit frame processor 330 to create a frame structure. The transmit frame processor 330 creates this frame structure by multiplexing the symbols with a midamble 214 (Fig. 8) from the controller/processor 340, resulting in a series of frames. The frames are then provided to a transmitter 332, which provides various signal conditioning functions including amplifying, filtering, and modulating the frames onto a carrier for downlink transmission over the wireless medium through smart antennas 334. The smart antennas 334 may be implemented with beam steering bidirectional adaptive antenna arrays or other similar beam technologies.

[0070] At the UE 350, a receiver 354 receives the downlink transmission through an antenna 352 and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver 354 is provided to a receive frame processor 360, which parses each frame, and provides the midamble 214 (Fig. 8) to a channel processor 394 and the data, control, and reference signals to a receive processor 370. The receive processor 370 then performs the inverse of the processing performed by the transmit processor 320 in the Node B 310. More specifically, the receive processor 370 descrambles and despreads the symbols, and then determines the most likely signal constellation points transmitted by the Node B 310 based on the modulation scheme. These soft decisions may be based on channel estimates computed by the channel processor 394. The soft decisions are then decoded and deinterleaved to recover the data, control, and reference signals. The CRC codes are then checked to determine whether the frames were successfully decoded. The data carried by the successfully decoded frames will then be provided to a data sink 372, which represents applications running in the UE 350 and/or various user interfaces (e.g., display). Control signals carried by successfully decoded frames will be provided to a controller/processor 390. When frames are unsuccessfully decoded by the receiver processor 370, the controller/processor 390 may also use an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support retransmission requests for those frames.

[0071] In the uplink, data from a data source 378 and control signals from the controller/processor 390 are provided to a transmit processor 380. The data source 378 may represent applications running in the UE 350 and various user interfaces (e.g., keyboard). Similar to the functionality described in connection with the downlink transmission by the Node B 310, the transmit processor 380 provides various signal processing functions including CRC codes, coding and interleaving to facilitate FEC, mapping to signal constellations, spreading with OVSFs, and scrambling to produce a series of symbols. Channel estimates, derived by the channel processor 394 from a reference signal transmitted by the Node B 310 or from feedback contained in the midamble transmitted by the Node B 310, may be used to select the appropriate coding, modulation, spreading, and/or scrambling schemes. The symbols produced by the transmit processor 380 will be provided to a transmit frame processor 382 to create a frame structure. The transmit frame processor 382 creates this frame structure by multiplexing the symbols with a midamble 214 (FIG. 2) from the controller/processor 390, resulting in a series of frames. The frames are then provided to a transmitter 356, which provides various signal conditioning functions including amplification, filtering, and modulating the frames onto a carrier for uplink transmission over the wireless medium through the antenna 352.

[0072] The uplink transmission is processed at the Node B 310 in a manner similar to that described in connection with the receiver function at the UE 350. A receiver 335 receives the uplink transmission through the antenna 334 and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver 335 is provided to a receive frame processor 336, which parses each frame, and provides the midamble 214 (FIG. 2) to the channel processor 344 and the data, control, and reference signals to a receive processor 338. The receive processor 338 performs the inverse of the processing performed by the transmit processor 380 in the UE 350. The data and control signals carried by the successfully decoded frames may then be provided to a data sink 339 and the controller/processor, respectively. If some of the frames were unsuccessfully decoded by the receive processor, the controller/processor 340 may also use an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support retransmission requests for those frames.

[0073] The controller/processors 340 and 390 may be used to direct the operation at the Node B 310 and the UE 350, respectively. For example, the controller/processors 340 and 390 may provide various functions including timing, peripheral interfaces, voltage regulation, power management, and other control functions. The computer readable media of memories 342 and 392 may store data and software for the Node B 310 and the UE 350, respectively. A scheduler/processor 346 at the Node B 310 may be used to allocate resources to the UEs and schedule downlink and/or uplink transmissions for the UEs.

[0074] Several aspects of a telecommunications system has been presented with reference to a TD-SCDMA system. As those skilled in the art will readily appreciate, various aspects described throughout this disclosure may be extended to other telecommunication systems, network architectures and communication standards. By way of example, various aspects may be extended to other UMTS systems such as W- CDMA, High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), High Speed Packet Access Plus (HSPA+) and TD-CDMA. Various aspects may also be extended to systems employing Long Term Evolution (LTE) (in FDD, TDD, or both modes), LTE-Advanced (LTE-A) (in FDD, TDD, or both modes), CDMA2000, Evolution-Data Optimized (EV-DO), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Ultra-Wideband (UWB), Bluetooth, and/or other suitable systems. The actual telecommunication standard, network architecture, and/or communication standard employed will depend on the specific application and the overall design constraints imposed on the system.

[0075] Several processors have been described in connection with various apparatuses and methods. These processors may be implemented using electronic hardware, computer software, or any combination thereof. Whether such processors are implemented as hardware or software will depend upon the particular application and overall design constraints imposed on the system. By way of example, a processor, any portion of a processor, or any combination of processors presented in this disclosure may be implemented with a microprocessor, microcontroller, digital signal processor (DSP), a field-programmable gate array (FPGA), a programmable logic device (PLD), a state machine, gated logic, discrete hardware circuits, and other suitable processing components configured to perform the various functions described throughout this disclosure. The functionality of a processor, any portion of a processor, or any combination of processors presented in this disclosure may be implemented with software being executed by a microprocessor, microcontroller, DSP, or other suitable platform.

[0076] Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. The software may reside on a computer-readable medium. A computer- readable medium may include, by way of example, memory such as a magnetic storage device (e.g., hard disk, floppy disk, magnetic strip), an optical disk (e.g., compact disc (CD), digital versatile disc (DVD)), a smart card, a flash memory device (e.g., card, stick, key drive), random access memory (RAM), read only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), a register, or a removable disk. Although memory is shown separate from the processors in the various aspects presented throughout this disclosure, the memory may be internal to the processors (e.g., cache or register).

[0077] Computer-readable media may be embodied in a computer-program product.

By way of example, a computer-program product may include a computer-readable medium in packaging materials. Those skilled in the art will recognize how best to implement the described functionality presented throughout this disclosure depending on the particular application and the overall design constraints imposed on the overall system.

[0078] It is to be understood that the specific order or hierarchy of steps in the methods disclosed is an illustration of exemplary processes. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the methods may be rearranged. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented unless specifically recited therein.

[0079] The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean "one and only one" unless specifically so stated, but rather "one or more." Unless specifically stated otherwise, the term "some" refers to one or more. A phrase referring to "at least one of a list of items refers to any combination of those items, including single members. As an example, "at least one of: a, b, or c" is intended to cover: a; b; c; a and b; a and c; b and c; and a, b and c. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §212, sixth paragraph, unless the element is expressly recited using the phrase "means for" or, in the case of a method claim, the element is recited using the phrase "step for."

Claims

CLAIMS What is claimed is:

1. A method of communication, comprising:

conducting, by a user equipment (UE), a first connection attempt with a target core node (CN) associated with a target CN area, wherein the UE is supported by a source CN associated with a source CN area;

receiving a first connection failure message indicating a failure to establish a connection with the target CN based on the first connection attempt;

initiating a retry timer with a first retry timer interval in response to receiving the first connection failure message; and

conducting a second connection attempt with the target CN after expiration of the first timer interval.

2. The method of claim 1, further comprising:

receiving a second connection failure message indicating a failure to establish the connection with the target CN based on the second connection attempt;

adjusting a retry timer interval of the retry timer from the first retry timer interval to a second retry timer interval; and

conducting a third connection attempt with the target CN node after expiration of the second retry timer interval.

3. The method of claim 2, wherein the second retry timer interval is longer in duration than the first retry timer interval.

4. The method of claim 2, further comprising determining the second retry timer interval based on one or more interval adjustment parameters.

5. The method of claim 4, wherein the one or more interval adjustment parameters comprise at least one of an exponential function, a linear function, and a stochastic function.

6. The method of claim 1, further comprising terminating the conducting of a subsequent connection attempt upon reaching a maximum number of target CN connection attempts, upon expiration of a maximum target CN duration, or upon a successful establishment of a connection with the target CN.

7. The method of claim 1, wherein the first retry timer interval comprises a time interval within a range of 10 seconds and 3 minutes.

8. The method of claim 2, wherein the second retry timer interval comprises a time interval within a range of 30 minutes and 24 hours.

9. The method of 2, wherein the first connection failure message and the second connection failure message comprise at least one of a location area update rejection message, a routing area update rejection message, and an authentication failure message.

10. The method of claim 1, wherein the source CN area and the target CN area are circuit switched domains, and wherein the conducting of the first connection attempt occurs when the UE switches location areas from the source CN area to the target CN area.

11. The method of claim 1, wherein the source CN area and the target CN area are packet switched domains, and wherein the conducting of the first connection attempt occurs when the UE switches routing areas from the source CN area to the target CN area.

12. A computer program product, comprising:

a computer-readable medium, including:

at least one instruction executable to cause a computer to conduct, by a user equipment (UE), a first connection attempt with a target core node (CN) associated with a target CN area, wherein the UE is supported by a source CN associated with a source CN area;

at least one instruction executable to cause a computer to receive a first connection failure message indicating a failure to establish a connection with the target CN based on the first connection attempt;

at least one instruction executable to cause a computer to initiate a retry timer with a first retry timer interval in response to receiving the first connection failure message; and

at least one instruction executable to cause a computer to conduct a second connection attempt with the target CN after expiration of the first timer interval.

13. The computer program product of claim 12, further comprising:

at least one instruction executable to cause a computer to receive a second connection failure message indicating a failure to establish the connection with the target CN based on the second connection attempt;

at least one instruction executable to cause a computer to adjust a retry timer interval of the retry timer from the first retry timer interval to a second retry timer interval; and

at least one instruction executable to cause a computer to conduct a third connection attempt with the target CN node after expiration of the second retry timer interval.

14. The computer program product of claim 13, wherein the second retry timer interval is longer in duration than the first retry timer interval.

15. An apparatus for communication, comprising:

means for conducting, by a user equipment (UE), a first connection attempt with a target core node (CN) associated with a target CN area, wherein the UE is supported by a source CN associated with a source CN area;

means for receiving a first connection failure message indicating a failure to establish a connection with the target CN based on the first connection attempt; means for initiating a retry timer with a first retry timer interval in response to receiving the first connection failure message; and

means for conducting a second connection attempt with the target CN after expiration of the first timer interval.

16. The apparatus of claim 15, further comprising:

means for receiving a second connection failure message indicating a failure to establish the connection with the target CN based on the second connection attempt; means for adjusting a retry timer interval of the retry timer from the first retry timer interval to a second retry timer interval; and

means for conducting a third connection attempt with the target CN node after expiration of the second retry timer interval.

17. The apparatus of claim 16, wherein the second retry timer interval is longer in duration than the first retry timer interval.

18. An apparatus for communication, comprising:

a memory storing executable instructions; and

a processor in communication with the memory, wherein the processor is configured to execute the instructions to:

conduct, by a user equipment (UE), a first connection attempt with a target core node (CN) associated with a target CN area, wherein the UE is supported by a source CN associated with a source CN area;

receive a first connection failure message indicating a failure to establish a connection with the target CN based on the first connection attempt;

initiate a retry timer with a first retry timer interval in response to receiving the first connection failure message; and

conduct a second connection attempt with the target CN after expiration of the first timer interval.

19. The apparatus of claim 18, wherein the processor is further configured to execute the instructions to:

receive a second connection failure message indicating a failure to establish the connection with the target CN based on the second connection attempt;

adjust a retry timer interval of the retry timer from the first retry timer interval to a second retry timer interval; and

conduct a third connection attempt with the target CN node after expiration of the second retry timer interval.

20. The apparatus of claim 19, wherein the second retry timer interval is longer in duration than the first retry timer interval.

21. The apparatus of claim 19, wherein the processor is configured to execute the instructions to determine the second retry timer interval based on one or more interval adjustment parameters.

22. The apparatus of claim 21, wherein the one or more interval adjustment parameters comprise at least one of an exponential function, a linear function, and a stochastic function.

23. The apparatus of claim 18, wherein the processor is configured to execute the instructions to terminate the conducting of a subsequent connection attempt upon reaching a maximum number of target CN connection attempts, upon expiration of a maximum target CN duration, or upon a successful establishment of a connection with the target CN.

24. The apparatus of claim 18, wherein the first retry timer interval comprises a time interval within a range of 10 seconds and 3 minutes.

25. The apparatus of claim 19, wherein the second retry timer interval comprises a time interval within a range of 30 minutes and 24 hours.

26. The apparatus of 19, wherein the first connection failure message and the second connection failure message comprise at least one of a location area update rejection message, a routing area update rejection message, and an authentication failure message.

27. The apparatus of claim 18, wherein the source CN area and the target CN area are circuit switched domains, and wherein the conducting of the first connection attempt occurs when the UE switches location areas from the source CN area to the target CN area.

28. The apparatus of claim 18, wherein the source CN area and the target CN area are packet switched domains, and wherein the conducting of the first connection attempt occurs when the UE switches routing areas from the source CN area to the target CN area.