WO2019061251A1

WO2019061251A1 - Techniques and apparatuses for quick release of radio resource control connection after session termination

Info

Publication number: WO2019061251A1
Application number: PCT/CN2017/104254
Authority: WO
Inventors: Qingxin Chen; Baojun LU; Reza Shahidi; Yong Xie; Anand Chowdhary KOLLURI; Jiming Guo; Uttam Pattanayak; Ammar Kitabi; Yongsheng Shi; Aiping Zhang
Original assignee: Qualcomm Incorporated
Priority date: 2017-09-29
Filing date: 2017-09-29
Publication date: 2019-04-04
Also published as: WO2019061881A1

Abstract

Certain aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may transmit an extended service request (ESR) message to a base station based at least in part on determining that a session of the UE has been terminated, wherein the session uses a first radio access technology (RAT). The UE may receive a redirection message instructing the UE to switch to a second RAT based at least in part on transmitting the ESR message. The UE may remain camped on the first RAT despite receiving the redirection message. The UE may transmit a tracking area update (TAU) message to the base station while remaining camped on the first RAT, wherein the TAU message includes an indication that the UE does not require a bearer. Numerous other aspects are provided.

Description

[Title established by the ISA under Rule 37.2] TECHNIQUES AND APPARATUSES FOR QUICK RELEASE OF RADIO RESOURCE CONTROL CONNECTION AFTER SESSION TERMINATION

FIELD OF THE DISCLOSURE

Aspects of the present disclosure generally relate to wireless communication, and more particularly to techniques and apparatuses for quick release of a radio resource control (RRC) connection after session termination.

BACKGROUND

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, and/or the like) . Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, orthogonal frequency-division multiple access (OFDMA) systems, single-carrier frequency-division multiple access (SC-FDMA) systems, time division synchronous code division multiple access (TD-SCDMA) systems, and Long Term Evolution (LTE) . LTE/LTE-Advanced is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by the Third Generation Partnership Project (3GPP) .

A wireless communication network may include a number of base stations (BSs) that can support communication for a number of user equipment (UEs) . A user equipment (UE) may communicate with a base station (BS) via the downlink and uplink. The downlink (or forward link) refers to the communication link from the BS to the UE, and the uplink (or reverse link) refers to the communication link from the UE to the BS. As will be described in more detail herein, a BS may be referred to as a Node B, a gNB, an access point (AP) , a radio head, a transmit receive point (TRP) , a new radio (NR) BS, a 5G Node B, and/or the like.

The above multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different user equipment to communicate on a municipal, national, regional, and even global level. New radio (NR) , which may also be referred to as 5G, is a set of enhancements to the LTE mobile standard promulgated by the Third Generation Partnership Project (3GPP) . NR is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP) (CP-OFDM) on the downlink (DL) , using CP-OFDM and/or SC-FDM (e.g., also known as discrete Fourier transform spread OFDM (DFT-s-OFDM) ) on the uplink (UL) , as well as supporting beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE and NR technologies. Preferably, these improvements should be applicable to other multiple access technologies and the telecommunication standards that employ these technologies.

SUMMARY

In some aspects, a method of wireless communication, performed by a user equipment (UE) , may include transmitting an extended service request (ESR) message to a base station based at least in part on determining that a session of the UE has been terminated, wherein the session uses a first radio access technology (RAT) ； receiving a redirection message instructing the UE to switch to a second RAT based at least in part on transmitting the ESR message； remaining camped on the first RAT despite receiving the redirection message； and transmitting a tracking area update (TAU) message to the base station while remaining camped on the first RAT, wherein the TAU message includes an indication that the UE does not require a bearer.

In some aspects, a UE for wireless communication may include memory and one or more processors operatively coupled to the memory. The memory and the one or more processors may be configured to transmit an extended service request (ESR) message to a base station based at least in part on determining that a session of the UE has been terminated, wherein the session uses a first radio access technology (RAT) ； receive a redirection message instructing the UE to switch to a second RAT based at least in part on transmitting the ESR message； remain camped on the first RAT despite receiving the redirection message； and transmit a tracking area update (TAU) message to the base station while remaining camped on the first RAT, wherein the TAU message includes an indication that the UE does not require a bearer.

In some aspects, a non-transitory computer-readable medium may store one or more instructions for wireless communication. The one or more instructions, when executed by one or more processors of a UE, may cause the one or more processors to transmit an extended service request (ESR) message to a base station based at least in part on determining that a session of the UE has been terminated, wherein the session uses a first radio access technology (RAT) ； receive a redirection message instructing the UE to switch to a second RAT based at least in part on transmitting the ESR message； remain camped on the first RAT despite receiving the redirection message； and transmit a tracking area update (TAU) message to the base station while remaining camped on the first RAT, wherein the TAU message includes an indication that the UE does not require a bearer.

In some aspects, an apparatus for wireless communication may include means for transmitting an extended service request (ESR) message to a base station based at least in part on determining that a session of the apparatus has been terminated, wherein the session uses a first radio access technology (RAT) ； means for receiving a redirection message instructing the apparatus to switch to a second RAT based at least in part on transmitting the ESR message； means for remaining camped on the first RAT despite receiving the redirection message； and means for transmitting a tracking area update (TAU) message to the base station while remaining camped on the first RAT, wherein the TAU message includes an indication that the apparatus does not require a bearer.

Aspects generally include a method, apparatus, system, computer program product, non-transitory computer-readable medium, user equipment, wireless communication device, and processing system as substantially described herein with reference to and as illustrated by the accompanying drawings and specification.

The foregoing has outlined rather broadly the features and technical advantages of examples according to the disclosure in order that the detailed description that follows may be better understood. Additional features and advantages will be described hereinafter. The conception and specific examples disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. Such equivalent constructions do not depart from the scope of the appended claims. Characteristics of the concepts disclosed herein, both their organization and method of operation, together with associated advantages will be better understood from the following description when considered in connection with the accompanying figures. Each of the figures is provided for the purpose of illustration and description, and not as a definition of the limits of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description, briefly summarized above, may be had by reference to aspects, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects. The same reference numbers in different drawings may identify the same or similar elements.

Fig. 1 is a block diagram conceptually illustrating an example of a wireless communication network, in accordance with certain aspects of the present disclosure.

Fig. 2 is a block diagram conceptually illustrating an example of a base station in communication with a user equipment (UE) in a wireless communication network, in accordance with certain aspects of the present disclosure.

Fig. 3 is a block diagram conceptually illustrating an example of a frame structure in a wireless communication network, in accordance with certain aspects of the present disclosure.

Fig. 4 is a block diagram conceptually illustrating two example subframe formats with the normal cyclic prefix, in accordance with certain aspects of the present disclosure.

Fig. 5 is a diagram illustrating an example of quick release of an RRC connection after session termination, in accordance with various aspects of the present disclosure.

Fig. 6 is a diagram illustrating an example process performed, for example, by a user equipment, in accordance with various aspects of the present disclosure.

DETAILED DESCRIPTION

Various aspects of the disclosure are described more fully hereinafter with reference to the accompanying drawings. This disclosure may, however, be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Based on the teachings herein one skilled in the art should appreciate that the scope of the disclosure is intended to cover any aspect of the disclosure disclosed herein, whether implemented independently of or combined with any other aspect of the disclosure. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to or other than the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim.

Several aspects of telecommunication systems will now be presented with reference to various apparatuses and techniques. These apparatuses and techniques will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, and/or the like (collectively referred to as “elements” ) . These elements may be implemented using hardware, software, or combinations thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

It is noted that while aspects may be described herein using terminology commonly associated with 3G and/or 4G wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems, such as 5G and later, including NR technologies.

Fig. 1 is a diagram illustrating a network 100 in which aspects of the present disclosure may be practiced. The network 100 may be an LTE network or some other wireless network, such as a 5G or NR network. Wireless network 100 may include a number of BSs 110 (shown as BS 110a, BS 110b, BS 110c, and BS 110d) and other network entities. A BS is an entity that communicates with user equipment (UEs) and may also be referred to as a base station, a NR BS, a Node B, a gNB, a 5G node B (NB) , an access point, a transmit receive point (TRP) , and/or the like. Each BS may provide communication coverage for a particular geographic area. In 3GPP, the term “cell” can refer to a coverage area of a BS and/or a BS subsystem serving this coverage area, depending on the context in which the term is used.

A BS may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or another type of cell. A macro cell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscription. A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs with service subscription. A femto cell may cover a relatively small geographic area (e.g., a home) and may allow restricted access by UEs having association with the femto cell (e.g., UEs in a closed subscriber group (CSG) ) . A BS for a macro cell may be referred to as a macro BS. A BS for a pico cell may be referred to as a pico BS. A BS for a femto cell may be referred to as a femto BS or a home BS. In the example shown in Fig. 1, a BS 110a may be a macro BS for a macro cell 102a, a BS 110b may be a pico BS for a pico cell 102b, and a BS 110c may be a femto BS for a femto cell 102c. A BS may support one or multiple (e.g., three) cells. The terms “eNB” , “base station” , “NR BS” , “gNB” , “TRP” , “AP” , “node B” , “5G NB” , and “cell” may be used interchangeably herein.

In some examples, a cell may not necessarily be stationary, and the geographic area of the cell may move according to the location of a mobile BS. In some examples, the BSs may be interconnected to one another and/or to one or more other BSs or network nodes (not shown) in the access network 100 through various types of backhaul interfaces such as a direct physical connection, a virtual network, and/or the like using any suitable transport network.

Wireless network 100 may also include relay stations. A relay station is an entity that can receive a transmission of data from an upstream station (e.g., a BS or a UE) and send a transmission of the data to a downstream station (e.g., a UE or a BS) . A relay station may also be a UE that can relay transmissions for other UEs. In the example shown in Fig. 1, a relay station 110d may communicate with macro BS 110a and a UE 120d in order to facilitate communication between BS 110a and UE 120d. A relay station may also be referred to as a relay BS, a relay base station, a relay, and/or the like.

Wireless network 100 may be a heterogeneous network that includes BSs of different types, e.g., macro BSs, pico BSs, femto BSs, relay BSs, and/or the like. These different types of BSs may have different transmit power levels, different coverage areas, and different impact on interference in wireless network 100. For example, macro BSs may have a high transmit power level (e.g., 5 to 40 Watts) whereas pico BSs, femto BSs, and relay BSs may have lower transmit power levels (e.g., 0.1 to 2 Watts) .

A network controller 130 may couple to a set of BSs and may provide coordination and control for these BSs. Network controller 130 may communicate with the BSs via a backhaul. The BSs may also communicate with one another, e.g., directly or indirectly via a wireless or wireline backhaul.

UEs 120 (e.g., 120a, 120b, 120c) may be dispersed throughout wireless network 100, and each UE may be stationary or mobile. A UE may also be referred to as an access terminal, a terminal, a mobile station, a subscriber unit, a station, and/or the like. A UE may be a cellular phone (e.g., a smart phone) , a personal digital assistant (PDA) , a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet, a camera, a gaming device, a netbook, a smartbook, an ultrabook, medical device or equipment, biometric sensors/devices, wearable devices (smart watches, smart clothing, smart glasses, smart wrist bands, smart jewelry (e.g., smart ring, smart bracelet)) , an entertainment device (e.g., a music or video device, or a satellite radio) , a vehicular component or sensor, smart meters/sensors, industrial manufacturing equipment, a global positioning system device, or any other suitable device that is configured to communicate via a wireless or wired medium.

Some UEs may be considered machine-type communication (MTC) or evolved or enhanced machine-type communication (eMTC) UEs. MTC and eMTC UEs include, for example, robots, drones, remote devices, such as sensors, meters, monitors, location tags, and/or the like, that may communicate with a base station, another device (e.g., remote device) , or some other entity. A wireless node may provide, for example, connectivity for or to a network (e.g., a wide area network such as Internet or a cellular network) via a wired or wireless communication link. Some UEs may be considered Internet-of-Things (IoT) devices, and/or may be implemented as may be implemented as NB-IoT (narrowband internet of things) devices. Some UEs may be considered a Customer Premises Equipment (CPE) . UE 120 may be included inside a housing that houses components of UE 120, such as processor components, memory components, and/or the like.

In general, any number of wireless networks may be deployed in a given geographic area. Each wireless network may support a particular RAT and may operate on one or more frequencies. A RAT may also be referred to as a radio technology, an air interface, and/or the like. A frequency may also be referred to as a carrier, a frequency channel, and/or the like. Each frequency may support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs. In some cases, NR or 5G RAT networks may be deployed.

In some examples, access to the air interface may be scheduled, wherein a scheduling entity (e.g., a base station) allocates resources for communication among some or all devices and equipment within the scheduling entity’s service area or cell. Within the present disclosure, as discussed further below, the scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more subordinate entities. That is, for scheduled communication, subordinate entities utilize resources allocated by the scheduling entity.

Base stations are not the only entities that may function as a scheduling entity. That is, in some examples, a UE may function as a scheduling entity, scheduling resources for one or more subordinate entities (e.g., one or more other UEs) . In this example, the UE is functioning as a scheduling entity, and other UEs utilize resources scheduled by the UE for wireless communication. A UE may function as a scheduling entity in a peer-to-peer (P2P) network, and/or in a mesh network. In a mesh network example, UEs may optionally communicate directly with one another in addition to communicating with the scheduling entity.

Thus, in a wireless communication network with a scheduled access to time–frequency resources and having a cellular configuration, a P2P configuration, and a mesh configuration, a scheduling entity and one or more subordinate entities may communicate utilizing the scheduled resources.

As indicated above, Fig. 1 is provided merely as an example. Other examples are possible and may differ from what was described with regard to Fig. 1.

Fig. 2 shows a block diagram of a design of base station 110 and UE 120, which may be one of the base stations and one of the UEs in Fig. 1. Base station 110 may be equipped with T antennas 234a through 234t, and UE 120 may be equipped with R antennas 252a through 252r, where in general T ≥ 1 and R ≥ 1.

At base station 110, a transmit processor 220 may receive data from a data source 212 for one or more UEs, select one or more modulation and coding schemes (MCS) for each UE based at least in part on channel quality indicators (CQIs) received from the UE, process (e.g., encode and modulate) the data for each UE based at least in part on the MCS (s) selected for the UE, and provide data symbols for all UEs. Transmit processor 220 may also process system information (e.g., for semi-static resource partitioning information (SRPI) and/or the like) and control information (e.g., CQI requests, grants, upper layer signaling, and/or the like) and provide overhead symbols and control symbols. Transmit processor 220 may also generate reference symbols for reference signals (e.g., the cell-specific reference signal (CRS) ) and synchronization signals (e.g., the primary synchronization signal (PSS) and secondary synchronization signal (SSS) ) . A transmit (TX) multiple-input multiple-output (MIMO) processor 230 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, the overhead symbols, and/or the reference symbols, if applicable, and may provide T output symbol streams to T modulators (MODs) 232a through 232t. Each modulator 232 may process a respective output symbol stream (e.g., for OFDM and/or the like) to obtain an output sample stream. Each modulator 232 may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. T downlink signals from modulators 232a through 232t may be transmitted via T antennas 234a through 234t, respectively. According to certain aspects described in more detail below, the synchronization signals can be generated with location encoding to convey additional information.

At UE 120, antennas 252a through 252r may receive the downlink signals from base station 110 and/or other base stations and may provide received signals to demodulators (DEMODs) 254a through 254r, respectively. Each demodulator 254 may condition (e.g., filter, amplify, downconvert, and digitize) a received signal to obtain input samples. Each demodulator 254 may further process the input samples (e.g., for OFDM and/or the like) to obtain received symbols. A MIMO detector 256 may obtain received symbols from all R demodulators 254a through 254r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor 258 may process (e.g., demodulate and decode) the detected symbols, provide decoded data for UE 120 to a data sink 260, and provide decoded control information and system information to a controller/processor 280. A channel processor may determine reference signal received power (RSRP) , received signal strength indicator (RSSI) , reference signal received quality (RSRQ) , channel quality indicator (CQI) , and/or the like.

On the uplink, at UE 120, a transmit processor 264 may receive and process data from a data source 262 and control information (e.g., for reports comprising RSRP, RSSI, RSRQ, CQI, and/or the like) from controller/processor 280. Transmit processor 264 may also generate reference symbols for one or more reference signals. The symbols from transmit processor 264 may be precoded by a TX MIMO processor 266 if applicable, further processed by modulators 254a through 254r (e.g., for DFT-s-OFDM, CP-OFDM, and/or the like) , and transmitted to base station 110. At base station 110, the uplink signals from UE 120 and other UEs may be received by antennas 234, processed by demodulators 232, detected by a MIMO detector 236 if applicable, and further processed by a receive processor 238 to obtain decoded data and control information sent by UE 120. Receive processor 238 may provide the decoded data to a data sink 239 and the decoded control information to controller/processor 240. Base station 110 may include communication unit 244 and communicate to network controller 130 via communication unit 244. Network controller 130 may include communication unit 294, controller/processor 290, and memory 292.

In some aspects, one or more components of UE 120 may be included in a housing. Controller/processor 240 of base station 110, controller/processor 280 of UE 120, and/or any other component (s) of Fig. 2 may perform one or more techniques associated with quick release of an RRC connection after session termination, as described in more detail elsewhere herein. For example, controller/processor 240 of base station 110, controller/processor 280 of UE 120, and/or any other component (s) of Fig. 2 may perform or direct operations of, for example, process 600 of Fig. 6 and/or other processes as described herein.

Memories

242 and 282 may store data and program codes for base station 110 and UE 120, respectively. A scheduler 246 may schedule UEs for data transmission on the downlink and/or uplink.

In some aspects, UE 120 may include means for determining that a session of the UE 120 has been terminated, means for transmitting an extended service request (ESR) message to a base station based at least in part on determining that a session of the UE 120 has been terminated, means for receiving a redirection message instructing the UE 120 to switch to a second RAT, means for remaining camped on the first RAT despite receiving the redirection message, means for transmitting a tracking area update (TAU) message to the base station while remaining camped on the first RAT, and/or the like. In some aspects, such means may include one or more components of UE 120 described in connection with Fig. 2.

As indicated above, Fig. 2 is provided merely as an example. Other examples are possible and may differ from what was described with regard to Fig. 2.

Fig. 3 shows an example frame structure 300 for frequency division duplexing (FDD) in a telecommunications system (e.g., LTE) . The transmission timeline for each of the downlink and uplink may be partitioned into units of radio frames. Each radio frame may have a predetermined duration (e.g., 10 milliseconds (ms) ) and may be partitioned into 10 subframes with indices of 0 through 9. Each subframe may include two slots. Each radio frame may thus include 20 slots with indices of 0 through 19. Each slot may include L symbol periods, e.g., seven symbol periods for a normal cyclic prefix (as shown in Fig. 3) or six symbol periods for an extended cyclic prefix. The 2L symbol periods in each subframe may be assigned indices of 0 through 2L–1.

While some techniques are described herein in connection with frames, subframes, slots, and/or the like, these techniques may equally apply to other types of wireless communication structures, which may be referred to using terms other than “frame, ” “subframe, ” “slot, ” and/or the like in 5G NR. In some aspects, a wireless communication structure may refer to a periodic time-bounded communication unit defined by a wireless communication standard and/or protocol.

In certain telecommunications (e.g., LTE) , a BS may transmit a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) on the downlink in the center of the system bandwidth for each cell supported by the BS. The PSS and SSS may be transmitted in

symbol periods

6 and 5, respectively, in

subframes

0 and 5 of each radio frame with the normal cyclic prefix, as shown in Fig. 3. The PSS and SSS may be used by UEs for cell search and acquisition. The BS may transmit a cell-specific reference signal (CRS) across the system bandwidth for each cell supported by the BS. The CRS may be transmitted in certain symbol periods of each subframe and may be used by the UEs to perform channel estimation, channel quality measurement, and/or other functions. The BS may also transmit a physical broadcast channel (PBCH) in symbol periods 0 to 3 in slot 1 of certain radio frames. The PBCH may carry some system information. The BS may transmit other system information such as system information blocks (SIBs) on a physical downlink shared channel (PDSCH) in certain subframes. The BS may transmit control information/data on a physical downlink control channel (PDCCH) in the first B symbol periods of a subframe, where B may be configurable for each subframe. The BS may transmit traffic data and/or other data on the PDSCH in the remaining symbol periods of each subframe.

In other systems (e.g., such NR or 5G systems) , a Node B may transmit these or other signals in these locations or in different locations of the subframe.

As indicated above, Fig. 3 is provided merely as an example. Other examples are possible and may differ from what was described with regard to Fig. 3.

Fig. 4 shows two example subframe formats 410 and 420 with the normal cyclic prefix. The available time frequency resources may be partitioned into resource blocks. Each resource block may cover 12 subcarriers in one slot and may include a number of resource elements. Each resource element may cover one subcarrier in one symbol period and may be used to send one modulation symbol, which may be a real or complex value.

Subframe format 410 may be used for two antennas. A CRS may be transmitted from

antennas

0 and 1 in

symbol periods

0, 4, 7, and 11. A reference signal is a signal that is known a priori by a transmitter and a receiver and may also be referred to as a pilot signal. A CRS is a reference signal that is specific for a cell, e.g., generated based at least in part on a cell identity (ID) . In Fig. 4, for a given resource element with label Ra, a modulation symbol may be transmitted on that resource element from antenna a, and no modulation symbols may be transmitted on that resource element from other antennas. Subframe format 420 may be used with four antennas. A CRS may be transmitted from

antennas

0 and 1 in

symbol periods

0, 4, 7, and 11 and from

antennas

2 and 3 in

symbol periods

1 and 8. For both

subframe formats

410 and 420, a CRS may be transmitted on evenly spaced subcarriers, which may be determined based at least in part on cell ID. CRSs may be transmitted on the same or different subcarriers, depending on their cell IDs. For both

subframe formats

410 and 420, resource elements not used for the CRS may be used to transmit data (e.g., traffic data, control data, and/or other data) .

The PSS, SSS, CRS and PBCH in LTE are described in 3GPP Technical Specification (TS) 36.211, entitled "Evolved Universal Terrestrial Radio Access (E-UTRA) ； Physical Channels and Modulation, " which is publicly available.

An interlace structure may be used for each of the downlink and uplink for FDD in certain telecommunications systems (e.g., LTE) . For example, Q interlaces with indices of 0 through Q –1 may be defined, where Q may be equal to 4, 6, 8, 10, or some other value. Each interlace may include subframes that are spaced apart by Q frames. In particular, interlace q may include subframes q, q + Q, q + 2Q, and/or the like, where q ∈ {0, …, Q-1} .

The wireless network may support hybrid automatic retransmission request (HARQ) for data transmission on the downlink and uplink. For HARQ, a transmitter (e.g., a BS) may send one or more transmissions of a packet until the packet is decoded correctly by a receiver (e.g., a UE) or some other termination condition is encountered. For synchronous HARQ, all transmissions of the packet may be sent in subframes of a single interlace. For asynchronous HARQ, each transmission of the packet may be sent in any subframe.

A UE may be located within the coverage of multiple BSs. One of these BSs may be selected to serve the UE. The serving BS may be selected based at least in part on various criteria such as received signal strength, received signal quality, path loss, and/or the like. Received signal quality may be quantified by a signal-to-noise-and-interference ratio (SINR) , or a reference signal received quality (RSRQ) , or some other metric. The UE may operate in a dominant interference scenario in which the UE may observe high interference from one or more interfering BSs.

While aspects of the examples described herein may be associated with LTE technologies, aspects of the present disclosure may be applicable with other wireless communication systems, such as NR or 5G technologies.

New radio (NR) may refer to radios configured to operate according to a new air interface (e.g., other than Orthogonal Frequency Divisional Multiple Access (OFDMA) -based air interfaces) or fixed transport layer (e.g., other than Internet Protocol (IP) ) . In aspects, NR may utilize OFDM with a CP (herein referred to as cyclic prefix OFDM or CP-OFDM) and/or SC-FDM on the uplink, may utilize CP-OFDM on the downlink and include support for half-duplex operation using time division duplexing (TDD) . In aspects, NR may, for example, utilize OFDM with a CP (herein referred to as CP-OFDM) and/or discrete Fourier transform spread orthogonal frequency-division multiplexing (DFT-s-OFDM) on the uplink, may utilize CP-OFDM on the downlink and include support for half-duplex operation using TDD. NR may include Enhanced Mobile Broadband (eMBB) service targeting wide bandwidth (e.g., 80 megahertz (MHz) and beyond) , millimeter wave (mmW) targeting high carrier frequency (e.g., 60 gigahertz (GHz) ) , massive MTC (mMTC) targeting non-backward compatible MTC techniques, and/or mission critical targeting ultra reliable low latency communications (URLLC) service.

A single component carrier bandwidth of 100 MHZ may be supported. NR resource blocks may span 12 sub-carriers with a sub-carrier bandwidth of 75 kilohertz (kHz) over a 0.1 ms duration. Each radio frame may include 50 subframes with a length of 10 ms. Consequently, each subframe may have a length of 0.2 ms. Each subframe may indicate a link direction (e.g., DL or UL) for data transmission and the link direction for each subframe may be dynamically switched. Each subframe may include downlink/uplink (DL/UL) data as well as DL/UL control data.

Beamforming may be supported and beam direction may be dynamically configured. MIMO transmissions with precoding may also be supported. MIMO configurations in the DL may support up to 8 transmit antennas with multi-layer DL transmissions up to 8 streams and up to 2 streams per UE. Multi-layer transmissions with up to 2 streams per UE may be supported. Aggregation of multiple cells may be supported with up to 8 serving cells. Alternatively, NR may support a different air interface, other than an OFDM-based interface. NR networks may include entities such central units or distributed units.

The RAN may include a central unit (CU) and distributed units (DUs) . A NR BS (e.g., gNB, 5G Node B, Node B, transmit receive point (TRP) , access point (AP)) may correspond to one or multiple BSs. NR cells can be configured as access cells (ACells) or data only cells (DCells) . For example, the RAN (e.g., a central unit or distributed unit) can configure the cells. DCells may be cells used for carrier aggregation or dual connectivity, but not used for initial access, cell selection/reselection, or handover. In some cases, DCells may not transmit synchronization signals. In some cases, DCells may transmit synchronization signals. NR BSs may transmit downlink signals to UEs indicating the cell type. Based at least in part on the cell type indication, the UE may communicate with the NR BS. For example, the UE may determine NR BSs to consider for cell selection, access, handover, and/or measurement based at least in part on the indicated cell type.

As indicated above, Fig. 4 is provided merely as an example. Other examples are possible and may differ from what was described with regard to Fig. 4.

Fig. 5 is a diagram illustrating an example 500 of quick release of an RRC connection after session termination, in accordance with various aspects of the present disclosure.

As shown in Fig. 5, a UE 120 may communicate with a base station 110. In some aspects, when a session of the UE 120 (e.g., a call, a data session, a Voice over LTE (VoLTE) call, a multimedia messaging service (MMS) session, and/or the like) is terminated, there may be a long delay (e.g., 10 seconds or longer) between the end of the session and a time when an RRC connection, associated with the session, is released. This may result in poor UE performance, such as by consuming additional battery power or preventing the UE 120 from using radio resources, used for the RRC connection, for another wireless connection (e.g., a wireless wide area network (WWAN) connection, a wireless local area network (WLAN) connection, and/or the like) .

In some aspects, if the UE 120 is a multi-subscriber identity module (SIM) UE with two or more network subscriptions, a long delay to release an RRC connection associated with a first SIM may interfere with UE communications that use a second SIM. For example, the UE 120 may miss pages or other communications on a second subscription if an RRC connection has not yet been release on a first subscription. Some techniques and apparatuses described herein address the long delay associated with releasing an RRC connection after a session is terminated, thereby improving UE performance.

As shown by reference number 505, the UE 120 may determine that a session, that uses a first radio access technology (RAT) , has been terminated. The first RAT may include a packet switched RAT, such as an LTE RAT or another type of RAT. In some aspects, the session may include a Voice over LTE (VoLTE) session (e.g., a VoLTE call) , a multimedia messaging service (MMS) session, and/or the like. In some aspects, to establish the session, an RRC connection may be established between the UE 120 and the base station 110, and one or more bearers may be established for the session. The UE 120 may determine that the session has been terminated based at least in part on signaling and/or messaging with the base station 110 (e.g., to tear down the one or more bearers) . Without employing the techniques described herein, after the session has been terminated, the base station 110 may maintain the RRC connection for a relatively long time, such as 5 seconds, 10 seconds, 15 seconds, or longer. Some techniques and apparatuses described herein assist with quickly releasing the RRC connection associated with the terminated session (e.g., in less than 4 seconds, less than 3 seconds, less than 2 seconds, etc. ) , thereby improving performance of the UE 120.

As shown by reference number 510, the UE 120 may transmit an extended service request (ESR) message to the base station 110. For example, the UE 120 may transmit the ESR message based at least in part on determining that the session of the UE has been terminated. Typically, a UE 120 may transmit an ESR message to initiate a circuit switched fallback (CSFB) procedure for the UE 120 to fall back to a circuit switched RAT (e.g., a 2G RAT, a 3G RAT, and/or the like) when the UE 120 fails to establish a call on a packet switched RAT (e.g., a 4G RAT, a 5G RAT, and/or the like) . However, in this case, the ESR message may be used to quickly release the RRC connection associated with the terminated session.

As shown by reference number 515, the UE 120 may receive a redirection message from the base station 110 in response to the ESR message. The redirection message may instruct the UE 120 to switch to a second RAT. In some aspects, the second RAT may be a circuit switched RAT. For example, the redirection message may include an RRC connection release message with redirection information for circuit switched fallback, may include a packet switched handover message, and/or the like. In some aspects, the base station 110 may terminate an RRC connection associated with the terminated session based at least in part on receiving the ESR message from the UE 120. In this way, the RRC connection may be quickly released, thereby improving UE performance.

As shown by reference number 520, the UE 120 may ignore the redirection message by remaining camped on the first RAT despite receiving the redirection message. For example, the UE 120 may release an RRC connection associated with the session to enter an idle mode on the first RAT. In some aspects, the UE 120 may release the RRC connection based at least in part on receiving the redirection message. In some aspects, the UE 120 may autonomously release the RRC connection. For example, the UE 120 may initialize a timer (e.g., an ESR timer) based at least in part on transmitting the ESR message, may determine that the timer has expired before receiving a redirection message (e.g., without receiving a redirection message) , and may release the RRC connection based at least in part on determining that the timer has expired.

As shown by reference number 525, the UE 120 may transmit a tracking area update (TAU) message to the base station 110 while remaining camped on the first RAT. The TAU message may include an indication that the UE 120 does not require a bearer (e.g., that a bearer is not to be established for the UE 120) . For example, the UE 120 may set a field of the TAU message to indicate that the UE 120 does not require a bearer, such as by setting an active flag field of the TAU message to a particular value (e.g., a value of zero) . Typically, the UE 120 may transmit such a TAU message to initiate a return to the first RAT after performing a CSFB procedure and falling back to a second RAT. However, in this case, the UE 120 may send the TAU message without first falling back to the second RAT, thereby permitting the UE 120 to remain synchronized with the base station 110 in addition to the quick release of the RRC connection associated with the terminated session, thereby improving UE performance.

In some aspects, the UE 120 may release a first RRC connection, associated with the session, as described above (e.g., based at least in part on receipt of a redirection message or expiration of an ESR timer) . The UE 120 may then initiate a second RRC connection, from an idle mode on the first RAT, to permit the UE 120 to transmit the TAU message. In some aspects, the UE 120 may release the second RRC connection based at least in part on receiving an RRC connection release message. In some aspects, the UE 120 may autonomously release the second RRC connection. For example, the UE 120 may initialize a timer (e.g., a TAU timer) based at least in part on transmitting the TAU message, may determine that the timer has expired before receiving an RRC connection release message (e.g., without receiving the RRC connection release message) , and may release the second RRC connection based at least in part on determining that the timer has expired. In some aspects, the procedure from determining that the session has been terminated until releasing the second RRC connection may occur relatively quickly (e.g., less than 4 seconds, less than 3 seconds, less than 2 seconds, etc. ) , thereby improving UE performance and network performance as compared to waiting 10 seconds or longer for release of an RRC connection upon termination of the session.

In some aspects, the UE 120 may transmit the TAU message without first transmitting the ESR message. For example, upon determining that the session has been terminated, the UE 120 may locally release an RRC connection associated with the session (e.g., without transmitting an ESR message) . After locally releasing the RRC connection, the UE 120 may transmit the TAU message, in a similar manner as described above. In some aspects, this technique may result in even faster release of the RRC connection associated with the session because the UE 120 does not need to transmit the ESR message and wait for a response to the ESR message. However, transmitting the ESR message and waiting for a response to the ESR message may improve reliability of the techniques described herein.

In some aspects, the UE 120 is a multi-SIM UE with multiple network subscriptions. For example, the UE 120 may include a dual SIM dual active (DSDA) UE, a dual SIM dual standby (DSDS) UE, and/or the like. In this case, some techniques described herein for quick release of an RRC connection associated with a terminated session may permit the UE 120 to quickly switch between networks associated with different SIMs and/or subscriptions, thereby improving performance. Furthermore, such techniques may reduce inter-network interference.

In some aspects, the UE 120 may be associated with a dedicated data subscription (DDS) and a non-DDS. For example, a multi-SIM UE may include a first SIM associated with a DDS, which may provide voice and/or data service, and a non-DDS (or voice-only service) , which may not provide data service. In some aspects, the UE 120 may transmit the ESR message, as described above, based at least in part on determining that the session has been terminated on the non-DDS. In this way, the UE 120 may assist with quick release of an RRC connection associated with a session on the non-DDS so that the UE 120 can communicate via the DDS with improved performance (e.g., due to a lower likelihood of missing a communication via the DDS, such as a paging message) .

In some aspects, the UE 120 may be a multi-RAT UE capable of communicating on multiple RATs. Additionally, or alternatively, the UE 120 may be a single SIM UE. In some aspects, the UE 120 may be capable of communicating via a WWAN (e.g., a 2G network, a 3G network, a 4G/LTE network, a 5G/NR network, and/or the like) and a WLAN (e.g., a Wi-Fi network and/or the like) . In this case, some techniques described herein for quick release of an RRC connection associated with a terminated session may permit the UE 120 to quickly switch between a WWAN connection and a WLAN connection, thereby improving performance.

As indicated above, Fig. 5 is provided as an example. Other examples are possible and may differ from what was described with respect to Fig. 5.

Fig. 6 is a diagram illustrating an example process 600 performed, for example, by a UE, in accordance with various aspects of the present disclosure. Example process 600 is an example where a UE (e.g., UE 120 and/or the like) performs quick release of an RRC connection after session termination.

As shown in Fig. 6, in some aspects, process 600 may include transmitting an extended service request (ESR) message to a base station based at least in part on determining that a session of a UE has been terminated, wherein the session uses a first radio access technology (RAT) (block 610) . For example, the UE may transmit an ESR message to a base station based at least in part on determining that a session of a UE has been terminated, as described above in connection with Fig. 5. In some aspects, the session uses a first RAT.

As further shown in Fig. 6, in some aspects, process 600 may include receiving a redirection message instructing the UE to switch to a second RAT based at least in part on transmitting the ESR message (block 620) . For example, the UE may receive a redirection message based at least in part on transmitting the ESR message, as described above in connection with Fig. 5. In some aspects, the redirection message may instruct the UE to switch to a second RAT.

As further shown in Fig. 6, in some aspects, process 600 may include remaining camped on the first RAT despite receiving the redirection message (block 630) . For example, the UE may remain camped on the first RAT despite receiving the redirection message, as described above in connection with Fig. 5.

As further shown in Fig. 6, in some aspects, process 600 may include transmitting a tracking area update (TAU) message to the base station while remaining camped on the first RAT, wherein the TAU message includes an indication that the UE does not require a bearer (block 640) . For example, the UE may transmit a TAU message to the base station while remaining camped on the first RAT, as described above in connection with Fig. 5. In some aspects, the TAU message includes an indication that the UE does not require a bearer.

In some aspects, the indication in the TAU message is included in an active flag field of the TAU message. In some aspects, the UE is a multi-subscriber identity module (SIM) UE. In some aspects, the UE is a single subscriber identity module (SIM) UE that supports communications on multiple RATs. In some aspects, the UE is associated with a dedicated data subscription (DDS) and a non-DDS. In some aspects, the ESR message is transmitted based at least in part on determining that the session has been terminated on the non-DDS.

In some aspects, the session includes at least one of: a Voice over Long Term Evolution (VoLTE) session, a multimedia messaging service (MMS) session, or some combination thereof. In some aspects, the UE may release a first radio resource control (RRC) connection associated with the session and camp on the first RAT in idle mode after receiving the redirection message； and may initiate a second RRC connection, from the idle mode, to transmit the TAU message.

In some aspects, the UE may initialize a timer based at least in part on transmitting the ESR message； may determine that the timer has expired before receiving the redirection message； may release a first radio resource control (RRC) connection associated with the session and camp on the first RAT in idle mode based at least in part on determining that the timer has expired； and may initiate a second RRC connection, from the idle mode, to transmit the TAU message.

In some aspects, the UE may initialize a timer based at least in part on transmitting the TAU message； and may release a radio resource control (RRC) connection, established to transmit the TAU message, based at least in part on one of: receiving an RRC connection release message prior to expiration of the timer, or determining that the timer has expired prior to receiving the RRC connection release message.

In some aspects, the redirection message includes at least one of: a radio resource control connection release message with redirection information for circuit switched fallback, a packet switched handover message, or some combination thereof.

Although Fig. 6 shows example blocks of process 600, in some aspects, process 600 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in Fig. 6. Additionally, or alternatively, two or more of the blocks of process 600 may be performed in parallel.

The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit the aspects to the precise form disclosed. Modifications and variations are possible in light of the above disclosure or may be acquired from practice of the aspects.

As used herein, the term component is intended to be broadly construed as hardware, firmware, or a combination of hardware and software. As used herein, a processor is implemented in hardware, firmware, or a combination of hardware and software.

Some aspects are described herein in connection with thresholds. As used herein, satisfying a threshold may refer to a value being greater than the threshold, greater than or equal to the threshold, less than the threshold, less than or equal to the threshold, equal to the threshold, not equal to the threshold, and/or the like.

It will be apparent that systems and/or methods, described herein, may be implemented in different forms of hardware, firmware, or a combination of hardware and software. The actual specialized control hardware or software code used to implement these systems and/or methods is not limiting of the aspects. Thus, the operation and behavior of the systems and/or methods were described herein without reference to specific software code—it being understood that software and hardware can be designed to implement the systems and/or methods based, at least in part, on the description herein.

Even though particular combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the disclosure of possible aspects. In fact, many of these features may be combined in ways not specifically recited in the claims and/or disclosed in the specification. Although each dependent claim listed below may directly depend on only one claim, the disclosure of possible aspects includes each dependent claim in combination with every other claim in the claim set. 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-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c) .

No element, act, or instruction used herein should be construed as critical or essential unless explicitly described as such. Also, as used herein, the articles “a” and “an” are intended to include one or more items, and may be used interchangeably with “one or more. ” Furthermore, as used herein, the terms “set” and “group” are intended to include one or more items (e.g., related items, unrelated items, a combination of related and unrelated items, and/or the like) , and may be used interchangeably with “one or more. ” Where only one item is intended, the term “one” or similar language is used. Also, as used herein, the terms “has, ” “have, ” “having, ” and/or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.

Claims

A method of wireless communication performed by a user equipment (UE) , comprising:

transmitting an extended service request (ESR) message to a base station based at least in part on determining that a session of the UE has been terminated, wherein the session uses a first radio access technology (RAT) ；

receiving a redirection message instructing the UE to switch to a second RAT based at least in part on transmitting the ESR message；

remaining camped on the first RAT despite receiving the redirection message； and

transmitting a tracking area update (TAU) message to the base station while remaining camped on the first RAT, wherein the TAU message includes an indication that the UE does not require a bearer.
The method of claim 1, wherein the indication in the TAU message is included in an active flag field of the TAU message.
The method of claim 1, wherein the UE is a multi-subscriber identity module (SIM) UE.
The method of claim 1, wherein the UE is a single subscriber identity module (SIM) UE that supports communications on multiple RATs.
The method of claim 1, wherein the UE is associated with a dedicated data subscription (DDS) and a non-DDS.
The method of claim 5, wherein the ESR message is transmitted based at least in part on determining that the session has been terminated on the non-DDS.
The method of claim 1, wherein the session includes at least one of:

a Voice over Long Term Evolution (VoLTE) session,

a multimedia messaging service (MMS) session, or

some combination thereof.
The method of claim 1, further comprising:

releasing a first radio resource control (RRC) connection associated with the session and camping on the first RAT in idle mode after receiving the redirection message； and

initiating a second RRC connection, from the idle mode, to transmit the TAU message.
The method of claim 1, further comprising:

initializing a timer based at least in part on transmitting the ESR message；

determining that the timer has expired before receiving the redirection message；

releasing a first radio resource control (RRC) connection associated with the session and camping on the first RAT in idle mode based at least in part on determining that the timer has expired； and

initiating a second RRC connection, from the idle mode, to transmit the TAU message.
The method of claim 1, further comprising:

initializing a timer based at least in part on transmitting the TAU message； and

releasing a radio resource control (RRC) connection, established to transmit the TAU message, based at least in part on one of:

receiving an RRC connection release message prior to expiration of the timer, or

determining that the timer has expired prior to receiving the RRC connection release message.
The method of claim 1, wherein the redirection message includes at least one of:

a radio resource control connection release message with redirection information for circuit switched fallback,

a packet switched handover message, or

some combination thereof.
A user equipment (UE) for wireless communication, comprising:

memory； and

one or more processors operatively coupled to the memory, the memory and the one or more processors configured to:

transmit an extended service request (ESR) message to a base station based at least in part on determining that a session of the UE has been terminated, wherein the session uses a first radio access technology (RAT) ；

receive a redirection message instructing the UE to switch to a second RAT based at least in part on transmitting the ESR message；

remain camped on the first RAT despite receiving the redirection message； and

transmit a tracking area update (TAU) message to the base station while remaining camped on the first RAT, wherein the TAU message includes an indication that the UE does not require a bearer.
The UE of claim 12, wherein the indication in the TAU message is included in an active flag field of the TAU message.
The UE of claim 12, wherein the UE is a multi-subscriber identity module (SIM) UE.
The UE of claim 12, wherein the UE is a single subscriber identity module (SIM) UE that supports communications on multiple RATs.
The UE of claim 12, wherein the UE is associated with a dedicated data subscription (DDS) and a non-DDS.
The UE of claim 16, wherein the ESR message is transmitted based at least in part on determining that the session has been terminated on the non-DDS.
The UE of claim 12, wherein the session includes at least one of:

a Voice over Long Term Evolution (VoLTE) session,

a multimedia messaging service (MMS) session, or

some combination thereof.
The UE of claim 12, wherein the memory and the one or more processors are further configured to:

release a first radio resource control (RRC) connection associated with the session and camping on the first RAT in idle mode after receiving the redirection message； and

initiate a second RRC connection, from the idle mode, to transmit the TAU message.
The UE of claim 12, wherein the memory and the one or more processors are further configured to:

initialize a timer based at least in part on transmitting the ESR message；

determine that the timer has expired before receiving the redirection message；

release a first radio resource control (RRC) connection associated with the session and camping on the first RAT in idle mode based at least in part on determining that the timer has expired； and

initiate a second RRC connection, from the idle mode, to transmit the TAU message.
The UE of claim 12, wherein the memory and the one or more processors are further configured to:

initialize a timer based at least in part on transmitting the TAU message； and

release a radio resource control (RRC) connection, established to transmit the TAU message, based at least in part on one of:

receiving an RRC connection release message prior to expiration of the timer, or

determining that the timer has expired prior to receiving the RRC connection release message.
The UE of claim 12, wherein the redirection message includes at least one of:

a radio resource control connection release message with redirection information for circuit switched fallback,

a packet switched handover message, or

some combination thereof.
A non-transitory computer-readable medium storing instructions for wireless communication, the instructions comprising:

one or more instructions that, when executed by one or more processors of a user equipment (UE) , cause the one or more processors to:

transmit an extended service request (ESR) message to a base station based at least in part on determining that a session of the UE has been terminated, wherein the session uses a first radio access technology (RAT) ；

receive a redirection message instructing the UE to switch to a second RAT based at least in part on transmitting the ESR message；

remain camped on the first RAT despite receiving the redirection message； and

transmit a tracking area update (TAU) message to the base station while remaining camped on the first RAT, wherein the TAU message includes an indication that the UE does not require a bearer.
The non-transitory computer-readable medium of claim 23, wherein the indication in the TAU message is included in an active flag field of the TAU message.
The non-transitory computer-readable medium of claim 23, wherein the UE is associated with a dedicated data subscription (DDS) and a non-DDS, and wherein the ESR message is transmitted based at least in part on determining that the session has been terminated on the non-DDS.
The non-transitory computer-readable medium of claim 23, wherein the session includes at least one of:

a Voice over Long Term Evolution (VoLTE) session,

a multimedia messaging service (MMS) session, or

some combination thereof.
An apparatus for wireless communication, comprising:

means for transmitting an extended service request (ESR) message to a base station based at least in part on determining that a session of the apparatus has been terminated, wherein the session uses a first radio access technology (RAT) ；

means for receiving a redirection message instructing the apparatus to switch to a second RAT based at least in part on transmitting the ESR message；

means for remaining camped on the first RAT despite receiving the redirection message； and

means for transmitting a tracking area update (TAU) message to the base station while remaining camped on the first RAT, wherein the TAU message includes an indication that the apparatus does not require a bearer.
The apparatus of claim 27, wherein the indication in the TAU message is included in an active flag field of the TAU message.
The apparatus of claim 27, wherein the apparatus is associated with a dedicated data subscription (DDS) and a non-DDS, and wherein the ESR message is transmitted based at least in part on determining that the session has been terminated on the non-DDS.
The apparatus of claim 27, wherein the session includes at least one of:

a Voice over Long Term Evolution (VoLTE) session,

a multimedia messaging service (MMS) session, or

some combination thereof.