WO2016095355A1

WO2016095355A1 - Preserving circuit switched service during location area change

Info

Publication number: WO2016095355A1
Application number: PCT/CN2015/074861
Authority: WO
Inventors: Xuepan GUAN; Shiau-He Tsai; Tim Tynghuei Liou; Ta-Yan Siu
Original assignee: Qualcomm Incorporated
Priority date: 2014-12-19
Filing date: 2015-03-23
Publication date: 2016-06-23
Also published as: WO2016095195A1

Abstract

A method of wireless communication includes initiating a circuit switched (CS) service. The method also includes receiving a message indicating a change of location area from a serving radio network subsystem (RNS) to a target RNS during establishment of the CS service. The method further includes sending a location area update (LAU) including a call save request to preserve a radio bearer after the LAU is accepted. The CS service can then be established on the preserved radio bearer.

Description

PRESERVING CIRCUIT SWITCHED SERVICE DURING LOCATION AREA CHANGE

CLAIM OF PRIORITY

The present Application for Patent claims priority to PCT International Application No.PCT/CN2014/094334 entitled “Preserving Circuit Switched Service During Location Area Change” filed December 19, 2014, which is assigned to the assignee hereof and hereby expressly incorporated by reference herein.

BACKGROUND

Field

Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to preserving circuit switched (CS) service during a location area change.

Background

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 Packet Access (HSPA) , which provides higher data transfer speeds and capacity to associated UMTS networks. HSPA is a collection of two mobile telephony protocols, High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA) , that extends and improves the performance of existing wideband protocols.

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.

SUMMARY

In an aspect of the present disclosure, a method of wireless communication is presented. The method includes initiating a circuit switched service. The method also includes receiving a message indicating a change of location area from a serving radio network subsystem (RNS) to a target RNS. The method further includes sending a location area update (LAU) including a call save request to reinitialize the circuit switched service after the LAU is accepted.

In another aspect of the present disclosure, an apparatus for wireless communication is presented. The apparatus includes a memory and at least one processor coupled to the memory. The one or more processors are configured to initiate a circuit switched service. The processor (s) is (are) also configured to receive a message indicating a change of location area from a serving radio network subsystem (RNS) to a target RNS. The processor (s) is (are) further configured to send a location area update (LAU) including a call save request to reinitialize the circuit switched service after the LAU is accepted.

In yet another aspect of the present disclosure, an apparatus for wireless communication is presented. The apparatus includes means for initiating a circuit switched service. The apparatus also includes means for receiving a message indicating a change of location area from a serving radio network subsystem (RNS) to a target RNS. The apparatus further includes means for sending a location area update (LAU) including a call save request to reinitialize the circuit switched service after the LAU is accepted.

In still another aspect of the present disclosure, a computer program product for wireless communication is presented. The computer program product includes a non-transitory computer-readable medium having encoded thereon program code. The program code includes program code to initiate a circuit switched service. The program code also includes program code to receive a message indicating a change of location area from a serving radio network subsystem (RNS) to a target RNS. The program code further includes program code to send a location area update (LAU) including a call save request to reinitialize the circuit switched service after the LAU is accepted.

This has outlined, rather broadly, the features and technical advantages of the present disclosure in order that the detailed description that follows may be better understood. Additional features and advantages of the disclosure will be described below. It should be appreciated by those skilled in the art that this disclosure may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the teachings of the disclosure as set forth in the appended claims. The novel features, which are believed to be characteristic of the disclosure, both as to its organization and method of operation, together with further objects and advantages, will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

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.

FIGURE 1 is a block diagram conceptually illustrating an example of a telecommunications system.

FIGURE 2 is a block diagram conceptually illustrating an example of a frame structure in a telecommunications system.

FIGURE 3 is a block diagram conceptually illustrating an example of a node B in communication with a UE in a telecommunications system.

FIGURE 4 is a diagram illustrating location areas and routing areas in a wireless network in accordance with aspects of the present disclosure.

FIGURES 5 and 6 are call flow diagrams illustrating wireless communication in accordance with aspects of the present disclosure.

FIGURE 7 is a block diagram illustrating a method for wireless communication according to aspects of the present disclosure.

FIGURE 8 is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system according to one aspect of the present disclosure.

DETAILED DESCRIPTION

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.

Turning now to FIGURE 1, a block diagram is shown illustrating an example of a telecommunications system 100. 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 FIGURE 1 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 102 (e.g., UTRAN) that provides various wireless services including telephony, video, data, messaging, broadcasts, and/or other services. The RAN 102 may be divided into a number of Radio Network Subsystems (RNSs) such as an RNS 107, each controlled by a Radio Network Controller (RNC) such as an RNC 106. For clarity, only the RNC 106 and the RNS 107 are shown； however, the RAN 102 may include any number of RNCs and RNSs in addition to the RNC 106 and RNS 107. The RNC 106 is an apparatus responsible for, among other things, assigning, reconfiguring and releasing radio resources within the RNS 107. The RNC 106 may be interconnected to other RNCs (not shown) in the RAN 102 through various types of interfaces such as a direct physical connection, a virtual network, or the like, using any suitable transport network.

The geographic region covered by the RNS 107 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 108 are shown； however, the RNS 107 may include any number of wireless node Bs. The node Bs 108 provide wireless access points to a core network 104 for any number of mobile apparatuses. Examples of a mobile apparatus include a cellular phone, a smart phone, a session 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 110 are shown in communication with the node Bs 108. 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.

The core network 104, 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.

In this example, the core network 104 supports circuit-switched services with a mobile switching center (MSC) 112 and a gateway MSC (GMSC) 114. One or more RNCs, such as the RNC 106, may be connected to the MSC 112. The MSC 112 is an apparatus that controls call setup, call routing, and UE mobility functions. The MSC 112 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 112. The GMSC 114 provides a gateway through the MSC 112 for the UE to access a circuit-switched network 116. The GMSC 114 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 114 queries the HLR to determine the UE’s location and forwards the call to the particular MSC serving that location.

The core network 104 also supports packet-data services with a serving GPRS support node (SGSN) 118 and a gateway GPRS support node (GGSN) 120. 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 120 provides a connection for the RAN 102 to a packet-based network 122. The packet-based network 122 may be the Internet, a private data network, or some other suitable packet-based network. The primary function of the GGSN 120 is to provide the UEs 110 with packet-based network connectivity. Data packets are transferred between the GGSN 120 and the UEs 110 through the SGSN 118, which performs primarily the same functions in the packet-based domain as the MSC 112 performs in the circuit-switched domain.

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 108 and a UE 110, but divides uplink and downlink transmissions into different time slots in the carrier.

FIGURE 2 shows a frame structure 200 for a TD-SCDMA carrier. The TD-SCDMA carrier, as illustrated, has a frame 202 that is 10 ms in length. The chip rate in TD-SCDMA is 1.28 Mcps. The frame 202 has two 5 ms subframes 204, and each of the subframes 204 includes seven time slots, TS0 through TS6. The first time slot, TS0, is usually allocated for downlink communication, while the second time slot, TS1, is usually 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) 206, a guard period (GP) 208, and an uplink pilot time slot (UpPTS) 210 (also known as the uplink pilot channel (UpPCH) ) are located between TS0 and TS1. Each time slot, TS0-TS6, may allow data transmission multiplexed on a maximum of 16 code channels. Data transmission on a code channel includes two data portions 212 (each with a length of 352 chips) separated by a midamble 214 (with a length of 144 chips) and followed by a guard period (GP) 216 (with a length of 16 chips) . The midamble 214 may be used for features, such as channel estimation, while the guard period 216 may be used to avoid inter-burst interference. Also transmitted in the data portion is some Layer 1 control information, including Synchronization Shift (SS) bits 218. Synchronization Shift bits 218 only appear in the second part of the data portion. The Synchronization Shift bits 218 immediately following the midamble can indicate three cases: decrease shift, increase shift, or do nothing in the upload transmit timing. The positions of the SS bits 218 are not generally used during uplink communications.

FIGURE 3 is a block diagram of a node B 310 in communication with a UE 350 in a RAN 300, where the RAN 300 may be the RAN 102 in FIGURE 1, the node B 310 may be the node B 108 in FIGURE 1, and the UE 350 may be the UE 110 in FIGURE 1. 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. 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 (FIGURE 2) 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 (FIGURE 2) 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.

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 (FIGURE 2) 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.

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 (FIGURE 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.

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 (FIGURE 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. Additionally, a scheduler/processor 346 at the node B 310 may allocate resources to the UEs and schedule downlink and/or uplink transmissions for the UEs.

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

memory

342 and 392 may store data and software for the node B 310 and the UE 350, respectively. For example, the memory 392 of the UE 350 may store a save module 391 which, when executed by the controller/processor 390, configures the UE 350 for preserving circuit switched (CS) service during a location area change.

Each cell in a wireless network belongs to a Location Area (LA) and a Routing Area (RA) . Location area is used for the Circuit-Switched (CS) domain and routing area is used for the Packet-Switched (PS) domain. A location area can consist of a few cells and a routing area can consist of a few cells. Conventionally, one location area covers a larger area than one routing area. An RNC can request that node Bs in one or more location areas send paging messages for mobile terminated circuit switched call setup. Similarly, the RNC can request that node Bs in one or more routing areas send paging messages for mobile terminated packet switched call setup. When the network pages a particular UE, the paging signal is sent to the most recent location area and/or routing area in which the UE was known to have been located. Similarly, when a UE initiates a circuit switched call, the network checks the UE’s present location area and determines if the UE is properly registered in that location area. In order for the network to know the proper location area, the UE performs location area updating (LAU) procedures when the UE moves to a cell in a new location area different from the one in which the UE previously performed a location area update.

FIGURE 4 is a diagram illustrating location areas and routing areas in a wireless network, such as a TD-SCDMA network. Particular cells (represented by the hexagonal spaces) may transmit for one location area and one routing area. In this example, three routing areas and two location areas are shown. The leftmost cells 402 belong to LA1 and RA1, the middle cells 404 belong to LA2 and RA2, and the right most cells 406 belong to LA2 and RA3. When UE1 moves from cell A in LA1, RA1 to cell B in LA2, RA2, then UE1 performs both location area update and routing area update procedures. When UE2 moves from Cell D in LA2, RA3 to Cell C in LA2, RA2, then UE 2 performs a routing area update procedure.

Preserving Circuit Switched (CS) Service During Location Area Change

The present disclosure is directed to wireless communication and, more particularly, to maintaining a circuit switched (CS) service request when the service request is interrupted by a user equipment (UE) transitioning from a serving radio network subsystem (SRNS) to another radio network subsystem (i.e., location area changes) . The location area changes when a location area indicator (LAI) changes. A circuit switched connection will also be referred to as a signaling connection.

In order to set up a circuit switched connection, a mobility management (MM) connection is first established. However, if a location area changes during the circuit switched establishment procedure, the mobility management connection is conventionally aborted and thus the circuit switched connection will also fail. Aborting the mobility management setup procedure is a simple way to restart the MM protocol state.

More specifically, in conventional wireless communication systems, when a UE has a location area change before a mobility management connection is established, the UE aborts the mobility management connection establishment procedure and sends a circuit switched connection release indicator message to the network. The UE then initiates a location update request procedure for the location area change. In response, the network (NW) may send a location area update accept message. The UE does not attempt to retry the circuit switched connection (i.e., signaling connection) establishment. Thus, the previously requested circuit switched service fails.

Aspects of the present disclosure are directed to saving the previous circuit switched service call. In accordance with aspects of the present disclosure, when the UE receives an indication of a location area change prior to establishing a mobility management connection, the UE may abort the mobility management connection and initiate a location area update request. The location area update request may be configured to include a call save request. For example, the location update request may include a message in which a follow on request (FOR) pending flag is set to 1. The FOR pending flag may indicate to the network that further signaling will follow, and requests that the network maintain the connected radio resource (e.g., radio bearer, signaling connection) .

After the UE receives the location area accept message, the UE may continue the circuit switched service and re-initiate a mobility management connection establish procedure using the same radio bearer that was not released. Thus, the mobility management connection can be established and the circuit switched service established with that mobility management connection.

The mobility management connection may fail or not be allowed after receiving the location area accept message, for example, due to some mobility management state limitation. In this case, a new signaling connection (radio bearer) can be set up when the UE enters a mobility management state. The mobility management state occurs when the UE is expecting a connection release message. A new CS service will be initiated with the new radio bearer. Then, a mobility management connection is established for the new circuit switched service.

FIGURES 5 and 6 are diagrams illustrating exemplary call flows in which the circuit switched service is preserved in accordance with aspects of the present disclosure. Referring to FIGURE 5, at time 502, a UE radio resource control 522 may receive a reconfiguration message from network 524. The reconfiguration message may initiate a procedure for serving radio network subsystem relocation. The reconfiguration message may include a new location area identification (LAI) . At time 504, and before a mobility management (MM) connection has been established, the UE non-access stratum (NAS) 520 may attempt to start a new circuit switched service. The UE NAS 520 may send a connection management (CM) service request to the UE radio resource control (RRC) 522. In turn, the UE RRC 522 sends an initial direct transfer including the CM service request to the network 524, at time 506.

At time 508, before the mobility management connection is established for the connection management service request, the UE RRC 522 sends a message to the network indicating that the SRNS relocation successfully completed thereby changing the location area (LAI) .

At time 510, the UE NAS 520 aborts the mobility management connection establishment procedure due to the location area (LAI) change. Because the mobility management connection has been aborted and no other mobility management connection exists, the UE NAS 520 also sends a message to the UE RRC 522 requesting that the UE RRC 522 send a circuit switched connection release indicator message to the network. Accordingly, at time 512, the UE RRC 522 sends the circuit switched connection release indicator message to the network 524.

At time 514, the UE NAS 520 initiates a location area update (LAU) request procedure. Because the LAU request is after the mobility management connection establishment has been aborted, the connection is ordinarily dropped. However, in accordance with aspects of the present disclosure, the location area update request includes a save request. The save request may set a follow on request pending flag to a value of one to indicate to the network 524 that further signaling will follow the LAU request. As such, the follow on request (FOR) within the location area update request, requests that the network 524 maintain the circuit switched connection after the location area update. The existing radio bearer may be preserved to retry the mobility management connection request, for example. At time 516, the UE NAS 520 receives a location area accept message from the network 524 indicating that the location area has been updated. The circuit switched service is not terminated and may be reinitialized. That is, the existing radio bearer is used for the CM service request.

Referring now to FIGURE 6, at time 602, the UE NAS 520 attempts to start a new circuit switched service. The UE NAS 520 sends a connection management service request to UE RRC 522. At time 604, the UE RRC 522 sends an initial direct transfer message to the network 524. The initial direct transfer message includes the connection management service request to establish a mobility management connection for the circuit switched service. At time 606, the UE RRC 522 receives a reconfiguration message that initiates a SRNS relocation. At time 608, before the mobility management connection is established, the SRNS relocation completes successfully and the location area identification is changed.

At time 610, the UE NAS aborts the mobility management connection establishment procedure due to the location area (LAI) change. Because the mobility management connection establishment has been aborted and no other mobility management connection exists, the UE NAS 520 also sends a message to request that the UE RRC 522 send a circuit switched connection release indicator message. In turn, the UE RRC 522 sends the circuit switched connection release indicator message to the network 524 at time 612.

At time 614, the UE NAS 520 initiates a location area update (LAU) request procedure. The location area update request may include a save request. For example, the save request may set a follow on request pending flag to a value of one to indicate to the network 524 that further signaling will follow the LAU request. The follow on request (FOR) within the location area update request, requests that the network 524 maintain the circuit switched connection after the location area update and preserve the existing radio bearer for MM connection request retry, for example. At time 616, the UE NAS 520 receives a location area accept message from network 524. Finally, the circuit switched service is not terminated and may be reinitialized for establishing a CS service.

Thus, in accordance with aspects of the present disclosure and as shown in the illustrative examples of FIGURES 5 and 6, the circuit switched service may be preserved by including a call save request in the location area update request message sent to the network. In some aspects, the call save request may comprise an indication of the state of the follow-on request pending flag. The follow-on request pending flag may be used to indicate to the network that further signaling will follow. In one example, the follow-on request flag may be set to one and an indication of the set value may be included with the LAU request. In response, the network may send a location area accept message to the UE. The UE may, in turn, reinitialize the previous circuit switched service request and proceed to establish the mobility management connection.

On the other hand, when the follow-on request flag is not set to one, the signaling connection between the UE and the network is released. As a result, the circuit switched service is reinitiated after the signaling connection is released.

FIGURE 7 shows a wireless communication method 700 according to one aspect of the disclosure. A UE initiates a circuit switched service, as shown in block 702. The UE also receives a message indicating a change of location area from a serving radio network subsystem (RNS) to a target RNS, after the CS service request, but before the CS service is established., as shown in block 704. Further, the UE sends a location area update (LAU) including a call save request to preserve the radio bearer after the location area update is accepted, as shown in block 706. In other words, the signaling connection is not released after the area update. In some aspects, the LAU may include an indication of a value of a follow-on request (FOR) flag. For example, the FOR flag may be set to a value of one to indicate that further signaling will follow, and included with the LAU.

In some aspects, the UE initiates a mobility management connection as part of the CS service request. The mobility management connection may, for example, be initiated on the preserved radio bearer resource. The UE may further receive the message indicating the change of location area before the mobility management connection is established.

In some aspects, the UE may reinitiate the mobility management connection after sending the LAU with the call save request. The UE may then establish the circuit switched service with the reinitiated mobility management connection when a mobility management connection is established. On the other hand, the UE may release a circuit switched domain connection when no mobility management connection is established and then initiate a new circuit switched service.

FIGURE 8 is a diagram illustrating an example of a hardware implementation for an apparatus 800 employing a processing system 814. The processing system 814 may be implemented with a bus architecture, represented generally by the bus 824. The bus 824 may include any number of interconnecting buses and bridges depending on the specific application of the processing system 814 and the overall design constraints. The bus 824 links together various circuits including one or more processors and/or hardware modules, represented by the processor 822 the

modules

802, 804, 806 and the non-transitory computer-readable medium 826. The bus 824 may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further.

The apparatus includes a processing system 814 coupled to a transceiver 830. The transceiver 830 is coupled to one or more antennas 820. The transceiver 830 enables communicating with various other apparatus over a transmission medium. The processing system 814 includes a processor 822 coupled to a non-transitory computer-readable medium 826. The processor 822 is responsible for general processing, including the execution of software stored on the computer-readable medium 826. The software, when executed by the processor 822, causes the processing system 814 to perform the various functions described for any particular apparatus. The computer-readable medium 826 may also be used for storing data that is manipulated by the processor 822 when executing software.

The processing system 814 includes a service request module 802 for initiating a circuit switched service. The processing system also includes a location area update module 804 for receiving a message indicating a change of location area from a serving RNS to a target RNS. The processing system 814 further includes a call save module 806 for sending a location area update including a call save request to reinitialize the circuit switched service. The modules may be software modules running in the processor 822, resident/stored in the computer readable medium 826, one or more hardware modules coupled to the processor 822, or some combination thereof. The processing system 814 may be a component of the UE 350 and may include the memory 392, and/or the controller/processor 390.

In one configuration, an apparatus such as a UE is configured for wireless communication including means for initiating. In one aspect, the initiating means may be the antennas 352, the channel processor 394, the transmitter 356, the transmit frame processor 382, the transmit processor 380, the controller/processor 390, the memory 392, call save module 391, service request module 802, and/or the processing system 814 configured to perform the initiating of a circuit switched service.

The UE is also configured to include means for receiving. In one aspect, the receiving means may be the antennas 352, the receiver 354, the channel processor 394, the receive frame processor 360, the receive processor 370, the controller/processor 390, the memory 392, call save module 391, service request module 802, location area update module 804, and/or the processing system 814 configured to perform the receiving of a message indicating a change of location area from a serving RNS to a target RNS.

The UE is further configured to include means for sending a location area update. In one aspect, the sending means may be the antennas 352, the transmitter 356, the transmit frame processor 382, the transmit processor 380, the controller/processor 390, the memory 392, call save module 391, service request module 802, location area update module 804, save module 806 and/or the processing system 814 configured to perform the sending of a location area update including a call save request to reinitialize the circuit switched service after the location area update is accepted.

In one configuration, the means functions correspond to the aforementioned structures. In another aspect, the aforementioned means may be a module or any apparatus configured to perform the functions recited by the aforementioned means.

Several aspects of a telecommunications system has been presented with reference to TD-SCDMA systems. 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 including those with high throughput and low latency such as 4G systems, 5G systems and beyond. 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, GSM 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.

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 thevarious 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.

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 non-transitory 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) .

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.

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.

It is also to be understood that the term “signal quality” is non-limiting. Signal quality is intended to cover any type of signal metric such as received signal code power (RSCP) , reference signal received power (RSRP) , reference signal received quality (RSRQ) , received signal strength indicator (RSSI) , signal to noise ratio (SNR) , signal to interference plus noise ratio (SINR) , etc.

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. §112, 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. ”

WHAT IS CLAIMED IS:

Claims

A method of wireless communication, comprising:

initiating a circuit switched (CS) service；

receiving a message indicating a change of location area from a serving radio network subsystem (RNS) to a target RNS after initiating the CS service but before establishing the CS service； and

sending a location area update (LAU) including a call save request to reinitialize the CS service after the LAU is accepted.
The method of claim 1, in which sending the LAU comprises setting a follow-on request (FOR) .
The method of claim 1, in which initiating the CS service comprises initiating a mobility management (MM) connection； and

in which receiving the message comprises receiving the message before the mobility management connection is established.
The method of claim 3, further comprising reinitiating the mobility management connection on a preserved radio bearer resource after sending the LAU with the call save request, the radio bearer resource being preserved in response to the call save request.
The method of claim 4, further comprising establishing the CS service with the reinitiated mobility management connection when the mobility management connection is established.
The method of claim 4, further comprising:

releasing the preserved radio bearer resource when no mobility management connection is established and then

initiating a new CS service.
An apparatus for wireless communication, comprising:

a memory； and

at least one processor coupled to the memory, the at least one processor being configured:

to initiate a circuit switched (CS) service；

to receive a message indicating a change of location area from a serving radio network subsystem (RNS) to a target RNS after initiating the CS service but before establishing the CS service； and

to send a location area update (LAU) including a call save request to reinitialize the CS service after the LAU is accepted.
The apparatus of claim 7, in which the at least one processor is further configured to send the LAU including a setting of a follow-on request (FOR) .
The apparatus of claim 7, in which the at least one processor is further configured: to initiate the CS service by initiating a mobility management (MM) connection； and to receive the message before the mobility management connection is established.
The apparatus of claim 9, in which the at least one processor is further configured to reinitiate the mobility management connection on a preserved radio bearer resource after sending the LAU with the call save request, the radio bearer resource being preserved in response to the call save request.
The apparatus of claim 10, in which the at least one processor is further configured to establish the CS service with the reinitiated mobility management connection when the mobility management connection is established.
The apparatus of claim 10, in which the at least one processor is further configured to release the preserved radio bearer resource when no mobility management connection is established and then to initiate a new CS service.
An apparatus for wireless communication, comprising:

means for initiating a circuit switched (CS) service；

means for receiving a message indicating a change of location area from a serving radio network subsystem (RNS) to a target RNS after initiating the CS service but before establishing the CS service； and

means for sending a location area update (LAU) including a call save request to reinitialize the CS service after the LAU is accepted.
The apparatus of claim 13, in which the sending means sets a follow-on request (FOR) .
The apparatus of claim 13, further comprising means for initiating a mobility management (MM) connection； and

means for receiving the message before the mobility management connection is established.
The apparatus of claim 15, further comprising means for reinitiating the mobility management connection on a preserved radio bearer resource after sending the LAU with the call save request, the radio bearer resource being preserved in response to the call save request.
The apparatus of claim 16, further comprising means for establishing the CS service with the reinitiated mobility management connection when the mobility management connection is established.
The apparatus of claim 16, further comprising means for releasing the preserved radio bearer resource when no connection is established and then initiating a new CS service.
A computer program product for wireless communication, comprising:

a non-transitory computer readable medium having encoded thereon program code, the program code being executed by a processor and comprising:

program code to initiate a circuit switched (CS) service；

program code to receive a message indicating a change of location area from a serving radio network subsystem (RNS) to a target RNS after initiating the CS service but before establishing the CS service； and

program code to send a location area update (LAU) including a call save request to reinitialize the CS service after the LAU is accepted.
The computer program product of claim 19, further comprising program code to send the LAU including a setting of a follow-on request (FOR) .
The computer program product of claim 19, further comprising:

program code to initiate the CS service by initiating a mobility management (MM) connection； and

program code to receive the message before the mobility management connection is established.
The computer program product of claim 21, further comprising program code to reinitiate the mobility management connection on a preserved radio bearer resource after sending the LAU with the call save request, the radio bearer resource being preserved in response to the call save request.
The computer program product of claim 22, further comprising program code to establish the CS service with the reinitiated mobility management connection when the mobility management connection is established.
The computer program product of claim 22, further comprising:

program code to release the preserved radio bearer resource when no mobility management connection is established and then to initiate a new CS service.