WO2022006762A1

WO2022006762A1 - A method to detect network out-of-synchronization and fast recovery in a multi-sim device

Info

Publication number: WO2022006762A1
Application number: PCT/CN2020/100765
Authority: WO
Inventors: Ling Xie; Vishal DALMIYA; Ajeet Kumar; Sathish Kumar NALLAMANTI; Krishna Chaitanya Bellam; Vaishakh Rao; Liang Hong; Zhenyu Liu
Original assignee: Qualcomm Incorporated
Priority date: 2020-07-08
Filing date: 2020-07-08
Publication date: 2022-01-13

Abstract

Aspects of the present disclosure relate to wireless communications, and more particularly, to techniques for detecting a network out of synchronization condition by a multi-SIM UE.

Description

A METHOD TO DETECT NETWORK OUT-OF-SYNCHRONIZATION AND FAST RECOVERY IN A MULTI-SIM DEVICE

BACKGROUND

Field of the Disclosure

Aspects of the present disclosure relate to wireless communications, and more particularly, to techniques for detecting a network out of synchronization condition by a multi-subscriber identity module (MSIM) user equipment (UE) .

Description of Related Art

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcasts, etc. These 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, etc. ) . Examples of such multiple-access systems include 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems, LTE Advanced (LTE-A) systems, 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, and time division synchronous code division multiple access (TD-SCDMA) systems, to name a few.

These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. New radio (e.g., 5G NR) is an example of an emerging telecommunication standard. NR is a set of enhancements to the LTE mobile standard promulgated by 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 OFDMA with a cyclic prefix (CP) on the downlink (DL) and on the uplink (UL) . To these ends, NR supports 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 NR and LTE technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.

SUMMARY

The systems, methods, and devices of the disclosure each have several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this disclosure as expressed by the claims which follow, some features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled “Detailed Description” one will understand how the features of this disclosure provide advantages that include improved performance of UEs operating with one or more SIMs.

Certain aspects provide a method for wireless communications by a user-equipment (UE) . The method generally includes suspending data service between the UE and a network via a first subscriber identity module (SIM) to perform operations for a second SIM, resuming the data service between the UE and the network via the first SIM, and taking one or more actions to detect a network out of synchronization (OOS) condition that occurred during the suspension.

Certain aspects provide an apparatus for wireless communications by a user-equipment (UE) . The apparatus generally includes means for suspending data service between the UE and a network via a first subscriber identity module (SIM) to perform operations for a second SIM, means for resuming the data service between the UE and the network via the first SIM, and means for taking one or more actions to detect a network out of synchronization (OOS) condition that occurred during the suspension.

Certain aspects provide an apparatus for wireless communications by a user-equipment (UE) . The apparatus generally includes a processing system configured to suspend data service between the UE and a network via a first subscriber identity module (SIM) to perform operations for a second SIM, resume the data service between the UE and the network via the first SIM, and take one or more actions to detect a network out of synchronization (OOS) condition that occurred during the suspension.

Certain aspects provide a user-equipment (UE) . The UE generally includes at least one antenna; and a processing system configured to suspend data service between the UE and a network via a first subscriber identity module (SIM) to perform operations for a second SIM, resume the data service between the UE and the network via the first SIM, and take one or more actions, via the at least one antenna, to detect a network out of synchronization (OOS) condition that occurred during the suspension.

Certain aspects provide a computer-readable medium for wireless communications by a user-equipment (UE) . The computer-readable medium generally includes codes executable to suspend data service between the UE and a network via a first subscriber identity module (SIM) to perform operations for a second SIM, resume the data service between the UE and the network via the first SIM, and take one or more actions to detect a network out of synchronization (OOS) condition that occurred during the suspension.

Aspects of the present disclosure provide means for, apparatus, processors, and computer-readable mediums for performing the methods described herein.

To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the appended drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed.

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 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.

FIG. 1 is a block diagram conceptually illustrating an example telecommunications system, in accordance with certain aspects of the present disclosure.

FIG. 2 is a block diagram conceptually illustrating a design of an example a base station (BS) and user equipment (UE) , in accordance with certain aspects of the present disclosure.

FIG. 3 illustrates an example multi-SIM deployment for a UE, in accordance with certain aspects of the present disclosure.

FIGs. 4A and 4B illustrate a timeline of an example scenario where a UE is out of synchronization with a network.

FIG. 5 illustrates example operations for wireless communication by a UE, in accordance with certain aspects of the present disclosure.

FIG. 6 illustrates a communications device that may include various components configured to perform operations for the techniques disclosed herein in accordance with aspects of the present disclosure.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one aspect may be beneficially utilized on other aspects without specific recitation.

DETAILED DESCRIPTION

Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for optimizing data delivery in multi-subscriber identity module (MSIM) scenarios where a single radio resource is shared. As will be described in greater detail below, an MSIM UE may take action that allows it to more rapidly detect a condition where the UE is out of synchronization with a network.

The following description provides examples of prioritizing activities on SIM(s) of a UE in a communication system, and is not limiting of the scope, applicability, or examples set forth in the claims. Changes may be made in the function and arrangement of elements discussed without departing from the scope of the disclosure. Various examples may omit, substitute, or add various procedures or components as appropriate. For instance, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. Also, features described with respect to some examples may be combined in some other examples. 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. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration. ” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects.

In general, any number of wireless networks may be deployed in a given geographic area. Each wireless network may support a particular radio access technology (RAT) and may operate on one or more frequencies. A RAT may also be referred to as a radio technology, an air interface, etc. A frequency may also be referred to as a carrier, a subcarrier, a frequency channel, a tone, a subband, etc. 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, a 5G NR RAT network may be deployed.

FIG. 1 illustrates an example wireless communication network 100 in which aspects of the present disclosure may be performed. For example, a UE 120a may support (or operate with) multiple SIMs and may have a SIM controller 122a configured perform (or assist UE 120a in performing) operations 500 of FIG. 5. As will be described in greater detail below, operations 500 may help detect a network out of synchronization scenario sooner than conventional UEs.

As illustrated in FIG. 1, the wireless communication network 100 may include a number of base stations (BSs) 110a-z (each also individually referred to herein as BS 110 or collectively as BSs 110) and other network entities. A BS 110 may provide communication coverage for a particular geographic area, sometimes referred to as a “cell” , which may be stationary or may move according to the location of a mobile BS 110. In some examples, the BSs 110 may be interconnected to one another and/or to one or more other BSs or network nodes (not shown) in wireless communication network 100 through various types of backhaul interfaces (e.g., a direct physical connection, a wireless connection, a virtual network, or the like) using any suitable transport network. In the example shown in FIG. 1, the

BSs

110a, 110b and 110c may be macro BSs for the

macro cells

102a, 102b and 102c, respectively. The BS 110x may be a pico BS for a pico cell 102x. The BSs 110y and 110z may be femto BSs for the femto cells 102y and 102z, respectively. A BS may support one or multiple cells. The BSs 110 communicate with user equipment (UEs) 120a-y (each also individually referred to herein as UE 120 or collectively as UEs 120) in the wireless communication network 100. The UEs 120 (e.g., 120x, 120y, etc. ) may be dispersed throughout the wireless communication network 100, and each UE 120 may be stationary or mobile.

Wireless communication network 100 may also include relay stations (e.g., relay station 110r) , also referred to as relays or the like, that receive a transmission of data and/or other information from an upstream station (e.g., a BS 110a or a UE 120r) and sends a transmission of the data and/or other information to a downstream station (e.g., a UE 120 or a BS 110) , or that relays transmissions between UEs 120, to facilitate communication between devices.

A network controller 130 may couple to a set of BSs 110 and provide coordination and control for these BSs 110. The network controller 130 may communicate with the BSs 110 via a backhaul. The BSs 110 may also communicate with one another (e.g., directly or indirectly) via wireless or wireline backhaul.

FIG. 2 illustrates example components of BS 110a and UE 120a (e.g., in the wireless communication network 100 of FIG. 1) , which may be used to implement aspects of the present disclosure.

At the BS 110a, a transmit processor 220 may receive data from a data source 212 and control information from a controller/processor 240. The control information may be for the physical broadcast channel (PBCH) , physical control format indicator channel (PCFICH) , physical hybrid ARQ indicator channel (PHICH) , physical downlink control channel (PDCCH) , group common PDCCH (GC PDCCH) , etc. The data may be for the physical downlink shared channel (PDSCH) , etc. The processor 220 may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. The transmit processor 220 may also generate reference symbols, such as for the primary synchronization signal (PSS) , secondary synchronization signal (SSS) , and cell-specific reference signal (CRS) . A transmit (TX) multiple-input multiple-output (MIMO) processor 230 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide output symbol streams to the modulators (MODs) 232a- 232t. Each modulator 232 may process a respective output symbol stream (e.g., for OFDM, etc. ) to obtain an output sample stream. Each modulator may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. Downlink signals from modulators 232a-232t may be transmitted via the antennas 234a-234t, respectively.

At the UE 120a, the antennas 252a-252r may receive the downlink signals from the BS 110a and may provide received signals to the demodulators (DEMODs) in transceivers 254a-254r, respectively. Each demodulator 254 may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each demodulator may further process the input samples (e.g., for OFDM, etc. ) to obtain received symbols. A MIMO detector 256 may obtain received symbols from all the demodulators 254a-254r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor 258 may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for the UE 120a to a data sink 260, and provide decoded control information to a controller/processor 280.

On the uplink, at UE 120a, a transmit processor 264 may receive and process data (e.g., for the physical uplink shared channel (PUSCH) ) from a data source 262 and control information (e.g., for the physical uplink control channel (PUCCH) from the controller/processor 280. The transmit processor 264 may also generate reference symbols for a reference signal (e.g., for the sounding reference signal (SRS) ) . The symbols from the transmit processor 264 may be precoded by a TX MIMO processor 266 if applicable, further processed by the demodulators in transceivers 254a-254r (e.g., for SC-FDM, etc. ) , and transmitted to the BS 110a. At the BS 110a, the uplink signals from the UE 120a may be received by the antennas 234, processed by the modulators 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 the UE 120a. The receive processor 238 may provide the decoded data to a data sink 239 and the decoded control information to the controller/processor 240.

The

memories

242 and 282 may store data and program codes for BS 110a and UE 120a, respectively. A scheduler 244 may schedule UEs for data transmission on the downlink and/or uplink.

The controller/processor 280 and/or other processors and modules at the UE 120a may perform or direct the execution of processes for the techniques described herein. For example, as shown in FIG. 2, the controller/processor 280 of the UE 120a has a SIM controller 122a, which is configured to implement one or more techniques described herein with reference to FIG. 5.

In some examples, access to the air interface may be scheduled. A scheduling entity (e.g., a BS 110) allocates resources for communication among some or all devices and equipment within its service area or cell. 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. BSs 110 are not the only entities that may function as a scheduling entity. In some examples, a UE 120 may function as a scheduling entity and may schedule resources for one or more subordinate entities (e.g., one or more Hiother UEs 120) , and the other UEs 120 may utilize the resources scheduled by the UE 120 for wireless communication. In some examples, a UE 120 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 120 may communicate directly with one another in addition to communicating with a scheduling entity.

In some examples, the communication between the UEs 120 and BSs 110 is referred to as the access link. The access link may be provided via a Uu interface. Communication between devices may be referred as the sidelink.

In some examples, two or more subordinate entities (e.g., UEs 120) may communicate with each other using sidelink signals. Real-world applications of such sidelink communications may include public safety, proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V) communications, Internet of Everything (IoE) communications, IoT communications, mission-critical mesh, and/or various other suitable applications. Generally, a sidelink signal may refer to a signal communicated from one subordinate entity (e.g., UE 120a) to another subordinate entity (e.g., another UE 120) without relaying that communication through the scheduling entity (e.g., UE 120 or BS 110) , even though the scheduling entity may be utilized for scheduling and/or control purposes. In some examples, the sidelink signals may be communicated using a licensed spectrum (unlike wireless local area networks, which typically use an unlicensed spectrum) . One example of sidelink communication is PC5, for example, as used in V2V, LTE, and/or NR.

Various sidelink channels may be used for sidelink communications, including a physical sidelink discovery channel (PSDCH) , a physical sidelink control channel (PSCCH) , a physical sidelink shared channel (PSSCH) , and a physical sidelink feedback channel (PSFCH) . The PSDCH may carry discovery expressions that enable proximal devices to discover each other. The PSCCH may carry control signaling such as sidelink resource configurations, resource reservations, and other parameters used for data transmissions, and the PSSCH may carry the data transmissions. The PSFCH may carry feedback such as CSI related to a sidelink channel quality. In some systems (e.g., NR Release 16) , a two stage SCI may be supported. Two stage SCI may include a first stage SCI (SCI-1) and a second stage SCI (e.g., SCI-2) . SCI-1 may include resource reservation and allocation information, information that can be used to decode SCI-2, etc. SCI-2 may include information that can be used to decode data and to determine whether the UE is an intended recipient of the transmission. SCI-1 and/or SCI-2 may be transmitted over PSCCH.

NR concurrent radio-access technology (RAT) operation generally refers to operating multiple simultaneous active connections with at least one connection being on NR. For example, the two connections may involve LTE and NR connections, or both NR connections. Multi-SIM devices are able to connect to multiple networks independently without network awareness. Different UE behaviors may occur based on different implementations like dual-SIM dual active (DSDA) or dual-SIM dual standby (DSDS) . DSDS generally refers to a dual-SIM deployment where the two SIM cards of the UE may be unable to simultaneously generate traffic. DSDA on the other hand refers to a dual-SIM deployment where both SIM cards of the UE may be active at the same time. As used herein, a SIM generally refers to both virtual and hardware implementations of a SIM. In other words, each SIM may be implemented using hardware (e.g., a physical SIM card) on the multi-SIM device, or implemented virtually using a remote database.

Dual SIM receivers allow the different SIMs to support a variety of different combination options. For example, dual-SIM (DSIM) devices could support the following:

SA-NR + SA-NR: both SIMs could support standalone (SA) NR (SA-NR) ;

NSA-NR + LTE: one SIM supports non-standalone (NSA) while another SIM supports LTE;

LTE + LTE: both SIMs support LTE;

LTE + W: one SIM supports LTE, the other supports wideband CDMA; or any other combination (X RAT + X RAT both SIMs the same RAT or X RAT + Y RAT the SIMs support different RATs) .

In some cases, in a multi-SIM deployment, each SIM of the UE can belong to the same network carrier. For example, two or more SIMs (also referred to herein as subscribers or SUBs) belonging to the same operator can be in the following modes:

(1) Idle + Idle : 2 or more SUBs in Idle camp to the same cell

(2) Connected + Idle : 1 SUB in Idle and 1 Sub Connected camp to the same cell

In conventional multi-SIM deployments, in scenarios where the UE is performing a low priority activity via a first SIM and another high priority activity is triggered on the same or different SIM of the UE, the high priority activity may be delayed, significantly impacting the performance of the UE. For example, assume an out of service indication is triggered on a SIM while another (or same) SIM is performing CSG autonomous search function. In this example, the recovery from the out of service may be delayed due to the CSG autonomous search, which may involve performing measurements for multiple CSG cells, performing a full band scan to obtain a given CSG cell, etc. These measurements and band scans may utilize RF resources of the UE, causing tune aways and increasing the delay time for out of service recovery on the SIM in which the out of service indication is triggered on.

In some examples, in scenarios where a PS call/throughput is triggered on a SIM while another (or same) SIM is performing CSG autonomous search function, the triggered SIM may experience throughput degradation due to the CSG autonomous search function. In some examples, in scenarios where a SIM is not running throughput but the network sends measurement to the SIM for NR addition while another (or same) SIM is performing CSG autonomous search function, there may be a delay in NR measurements, additions/deletions/configurations, etc., in the triggered SIM, due to tune aways triggered from the CSG autonomous search function. In some examples, in scenarios where a network is running a timer for a given NR configuration on a SIM and there is a delay on that configuration, the network may delete NR object (s) and deactivate NR from that SIM.

Example Method to Detect a Network Out-of-Sync for Fast Data Transmission Recovery in an MSIM Device

FIG. 3 illustrates an example multi-SIM (MSIM) deployment, in which multiple SIMs share a single radio resource. For example, sharing the same radio resource, one SIM/subscriber module (SUB) may register with a 5G/NR radio access network (RAN) , while another may register with LTE.

In such cases, two subscriber modules (SUBs) share the radio in the time domain, each accessing the shared radio resource at different times. Sharing a single radio resource by multiple SUBs may cause issues.

For example, as illustrated in FIG. 3, when one SUB, such as a data delivery SIM (DDS) , is running time sensitive services, such as online gaming with high definition (HD) video and another SUB, such as a non-DDS (nDDS) needs to access the shared radio resource to monitor for paging, DDS data delivery could be suspended.

For such MSIM devices, where multiple SUBs share the RF resource each of the SUBs typically perform the idle and connected mode activities independently as in the single SIM case. When one SUB takes over the RF resource with a relatively longer duration than the other SUB, there may be a larger impact on the connected SUB connected for packet service (the PS-connected) .

As illustrated in FIG. 4A, when a UE suspends data service for a PS SUB to monitor for activity on the other SUB, the network will see no response from the UE during the suspension. In such cases, the network may declare a radio link failure (RLF) on a radio bearer after a maximum number of radio link control (RLC) retransmissions of the RLC packet.

As illustrated in FIG. 4B, when the UE resumes data service with the PS connected SUB, it may take a relatively long time to detect the mismatch between the network state (RLF on the radio bearer) the UE, which may cause additional round trip time (RTT) delay and transmission outage.

Aspects of the present disclosure, however, techniques that may allow a UE to detect this RLC state mismatch earlier and resume data transmission quickly by keeping retransmit the SDU with SN Tx_Next_Ack after tune-away, which would benefit MSIM performance for throughput heavy or round-trip-time (RTT) sensitive traffic.

FIG. 5 illustrates example operations 500 for wireless communication by a UE, in accordance with certain aspects of the present disclosure. The operations 400 may be performed by a UE (e.g., UE 120a in the wireless communication network 100) equipped with multiple SIMs.

Operations 500 begin, at 502, by suspending data service between the UE and a network via a first subscriber identity module (SIM) to perform operations for a second SIM. As previously described, data service for a PS connected SUB may be suspended to check for paging on another SUB.

At 504, the UE resumes the data service between the UE and the network via the first SIM. At 506, the UE takes one or more actions to detect a network out of synchronization (OOS) condition that occurred during the suspension.

As previously described, during the suspension, the network may have declared an RLF on a radio bearer and, if the UE is unaware, it may waste time after resuming before declaring its own RLF. The actions proposed herein, however, may allow a UE to more quickly detect such a scenario where the UE and network are out of sync (OoS) and recover sooner.

In such cases, the OOS condition may involve an RLC state mismatch between a PS connected SUB and the network associated with a service data unit (SDU) that was transmitted before the suspension for which an acknowledgment has not been received. In such cases, the one or more actions taken by the UE may include retransmitting the same SDU until a threshold number of times is reached, which may allow the UE to more quickly detect and declare an RLF (as the OoS network will not acknowledge the SDU as it has already declared in RLF on the network side) .

In some cases, the RLF may be detected quicker by selecting a particular sequence number (SN) for the SDU to retransmit. This may be understood by considering an example that assumes SUB1 is the PS connected SUB (as in the example of FIGs. 4A and 4B) and is suspended for certain period due to SUB2 activity.

In this example, SUB1 will get the RF resources back after the SUB2 activity is complete and can resume its transmission and receiving. The example again assumes that the network has declared an RLF on a data radio bearer (assume DRBi) used by SUB1 so the network will not respond to (re-) transmission on this DRB.

Upon expiration of a retransmission timer (t-PollRetransmit) on DRBi, the UE may be able to choose one of different SDUs to retransmit on SUB1. For example, the UE could choose to retransmit the SDU with the highest sequence number (SN) or any SDU that has not been positively acknowledged.

If the UE selects the SDU with the highest SN, however, detection of the NW OoS state may be delayed. This is because the SN keeps increasing, so the UE would transmit an SDU with a different (increasing) SN and the maximum RLC retransmission (reTx) may never be reached (since the maximum RLC retransmission is counted per SN) .

Therefore, to more quickly detect the NW OoS state, it may be more efficient for the UE to retransmit the SDU to always retransmit the SDU with an SN set to the next SN after the last SN acknowledged before the tune-away. In other words, the UE may decide to retransmit an SDU with the smallest SN, for which a positive acknowledgment (ACK) has not yet been received.

By transmitting the same SDU (e.g., with the smallest SN) , if no RLC ACK is received and the number of reTx for this SN (TX_Next_Ack) reaches the maximum RLC reTx count, SUB1 would declare an RLF.

Potential benefits of the techniques proposed herein are that the UE may detect a network OoS state sooner by retransmitting an SDU with a particular SN.

Assuming there are continuous new data packets arriving in the UL buffer after the UE tunes away from the PS SUB1 and SUB1 has not received the NW RLC ACK response yet then:

At the 1 ^st expiration of t-PollRetransmit, the RLC Tx window may be {TX_Next_Ack, …TX_SN1}

At the k-th expiration of t-PollRetransmit, the RLC Tx win is {TX_Next_Ack, …TX_SN1, TX_SN2, …TX_SNk} .

Thus, if the Tx window is full or no more new packets come in, the highest SN would be fixed at TX_SNk from the k-th expiration. If the UE were to retransmit the SDU with the highest SN (as allowed) , then the SN of retransmitted SDUs would be:

TX_SN1, TX_SN2 …TX_SNk, TX_SNk …#max_rlc_reTx of Tx_SNk.

Thus, the whole duration before the UE triggers an RLF and recovers (re-establishes synchronization) would be:

(k+ #max_rlc_reTx-1) *t-PollRetransmit,

which is also the extra outage for effective data transmission.

A similar outage duration as this may occur if the UE were to choose to retransmit any SDUs with a changing SN. Therefore, using the techniques proposed herein, since the smallest SN (TX_Next_Ack) is not changed before the NW RLC response, the UE could potentially reduce the outage by:

k*t-PollRetransmit;

which could be a significant reduction in time (e.g., if k is large) , especially in usage cases involving sparse but continuous data packets, such as network ping or gaming packets.

FIG. 6 illustrates a communications device 600 that may include various components (e.g., corresponding to means-plus-function components) configured to perform operations for the techniques disclosed herein, such as the operations illustrated in FIG. 5. The communications device 600 includes a processing system 602 coupled to a transceiver 608. The transceiver 608 is configured to transmit and receive signals for the communications device 600 via an antenna 610, such as the various signals as described herein. The processing system 602 may be configured to perform processing functions for the communications device 600, including processing signals received and/or to be transmitted by the communications device 600.

The processing system 602 includes a processor 604 coupled to a computer-readable medium/memory 612 via a bus 606. In certain aspects, the computer-readable medium/memory 612 is configured to store instructions (e.g., computer-executable code) that when executed by the processor 604, cause the processor 604 to perform the operations illustrated in FIG. 5, or other operations for performing the various techniques discussed herein. In certain aspects, computer-readable medium/memory 612 stores code 614 for suspending data service between the UE and a network via a first subscriber identity module (SIM) to perform operations for a second SIM; code 616 for resuming the data service between the UE and the network via the first SIM; and code 618 for taking one or more actions to detect a network out of synchronization (OOS) condition that occurred during the suspension. In certain aspects, the processor 604 has circuitry configured to implement the code stored in the computer-readable medium/memory 612. The processor 604 includes circuitry 626 for suspending data service between the UE and a network via a first subscriber identity module (SIM) to perform operations for a second SIM; circuitry 628 for resuming the data service between the UE and the network via the first SIM; and circuitry 630 for taking one or more actions to detect a network out of synchronization (OOS) condition that occurred during the suspension.

The techniques described herein may be used for various wireless communication technologies, such as NR (e.g., 5G NR) , 3GPP Long Term Evolution (LTE) , LTE-Advanced (LTE-A) , code division multiple access (CDMA) , time division multiple access (TDMA) , frequency division multiple access (FDMA) , orthogonal frequency division multiple access (OFDMA) , single-carrier frequency division multiple access (SC-FDMA) , time division synchronous code division multiple access (TD-SCDMA) , and other networks. The terms “network” and “system” are often used interchangeably. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA) , cdma2000, etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM) . An OFDMA network may implement a radio technology such as NR (e.g. 5G RA) , Evolved UTRA (E-UTRA) , Ultra Mobile Broadband (UMB) , IEEE 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, Flash-OFDMA, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS) . LTE and LTE-A are releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described in documents from an organization named “3rd Generation Partnership Project” (3GPP) . cdma2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2) . NR is an emerging wireless communications technology under development.

The techniques described herein may be used for the wireless networks and radio technologies mentioned above as well as other wireless networks and radio technologies. For clarity, while aspects may be described herein using terminology commonly associated with 3G, 4G, and/or 5G wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems.

In 3GPP, the term “cell” can refer to a coverage area of a Node B (NB) and/or a NB subsystem serving this coverage area, depending on the context in which the term is used. In NR systems, the term “cell” and BS, next generation NodeB (gNB or gNodeB) , access point (AP) , distributed unit (DU) , carrier, or transmission reception point (TRP) may be used interchangeably. A BS may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or other types of cells. 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 an association with the femto cell (e.g., UEs in a Closed Subscriber Group (CSG) , UEs for users in the home, etc. ) . 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.

A UE may also be referred to as a mobile station, a terminal, an access terminal, a subscriber unit, a station, a Customer Premises Equipment (CPE) , a cellular phone, 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 computer, a camera, a gaming device, a netbook, a smartbook, an ultrabook, an appliance, a medical device or medical equipment, a biometric sensor/device, a wearable device such as a smart watch, smart clothing, smart glasses, a smart wrist band, smart jewelry (e.g., a smart ring, a smart bracelet, etc. ) , an entertainment device (e.g., a music device, a video device, a satellite radio, etc. ) , a vehicular component or sensor, a smart meter/sensor, 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) devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, etc., that may communicate with a BS, 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, which may be narrowband IoT (NB-IoT) devices.

Certain wireless networks (e.g., LTE) utilize orthogonal frequency division multiplexing (OFDM) on the downlink and single-carrier frequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDM partition the system bandwidth into multiple (K) orthogonal subcarriers, which are also commonly referred to as tones, bins, etc. Each subcarrier may be modulated with data. In general, modulation symbols are sent in the frequency domain with OFDM and in the time domain with SC-FDM. The spacing between adjacent subcarriers may be fixed, and the total number of subcarriers (K) may be dependent on the system bandwidth. For example, the spacing of the subcarriers may be 15 kHz and the minimum resource allocation (called a “resource block” (RB) ) may be 12 subcarriers (or 180 kHz) . Consequently, the nominal Fast Fourier Transfer (FFT) size may be equal to 128, 256, 512, 1024 or 2048 for system bandwidth of 1.25, 2.5, 5, 10, or 20 megahertz (MHz) , respectively. The system bandwidth may also be partitioned into subbands. For example, a subband may cover 1.8 MHz (e.g., 6 RBs) , and there may be 1, 2, 4, 8, or 16 subbands for system bandwidth of 1.25, 2.5, 5, 10 or 20 MHz, respectively. In LTE, the basic transmission time interval (TTI) or packet duration is the 1 ms subframe.

NR may utilize OFDM with a CP on the uplink and downlink and include support for half-duplex operation using TDD. In NR, a subframe is still 1 ms, but the basic TTI is referred to as a slot. A subframe contains a variable number of slots (e.g., 1, 2, 4, 8, 16, …slots) depending on the subcarrier spacing. The NR RB is 12 consecutive frequency subcarriers. NR may support a base subcarrier spacing of 15 KHz and other subcarrier spacing may be defined with respect to the base subcarrier spacing, for example, 30 kHz, 60 kHz, 120 kHz, 240 kHz, etc. The symbol and slot lengths scale with the subcarrier spacing. The CP length also depends on the subcarrier spacing. Beamforming may be supported and beam direction may be dynamically configured. MIMO transmissions with precoding may also be supported. In some examples, 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. In some examples, 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.

In some examples, access to the air interface may be scheduled. A scheduling entity (e.g., a BS) allocates resources for communication among some or all devices and equipment within its service area or cell. 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. In some examples, a UE may function as a scheduling entity and may schedule resources for one or more subordinate entities (e.g., one or more other UEs) , and the other UEs may utilize the resources scheduled by the UE for wireless communication. In some examples, 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 communicate directly with one another in addition to communicating with a scheduling entity.

In some examples, two or more subordinate entities (e.g., UEs) may communicate with each other using sidelink signals. Real-world applications of such sidelink communications may include public safety, proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V) communications, Internet of Everything (IoE) communications, IoT communications, mission-critical mesh, and/or various other suitable applications. Generally, a sidelink signal may refer to a signal communicated from one subordinate entity (e.g., UE1) to another subordinate entity (e.g., UE2) without relaying that communication through the scheduling entity (e.g., UE or BS) , even though the scheduling entity may be utilized for scheduling and/or control purposes. In some examples, the sidelink signals may be communicated using a licensed spectrum (unlike wireless local area networks, which typically use an unlicensed spectrum) .

The methods disclosed herein comprise one or more steps or actions for achieving the methods. The method steps and/or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims.

As used herein, 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) .

As used herein, the term “determining” encompasses a wide variety of actions. For example, “determining” may include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure) , ascertaining and the like. Also, “determining” may include receiving (e.g., receiving information) , accessing (e.g., accessing data in a memory) and the like. Also, “determining” may include resolving, selecting, choosing, establishing and the like.

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. 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 (f) 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. ”

The various operations of methods described above may be performed by any suitable means capable of performing the corresponding functions. The means may include various hardware and/or software component (s) and/or module (s) , including, but not limited to a circuit, an application specific integrated circuit (ASIC) , or processor. Generally, where there are operations illustrated in figures, those operations may have corresponding counterpart means-plus-function components with similar numbering. For example,

processors

258, 264 and 266, and/or controller/processor 280 of the UE 120a and/or

processors

220, 230, 238, and/or controller/processor 240 of the BS 110a shown in FIG. 2 may be configured to perform operations 500 of FIG. 5.

Means for receiving may include a transceiver, a receiver or at least one antenna and at least one receive processor illustrated in FIG. 2. Means for transmitting, means for sending or means for outputting may include, a transceiver, a transmitter or at least one antenna and at least one transmit processor illustrated in FIG. 2. Means for suspending, means for resuming, means for taking one or more actions, means for retransmitting, and means for declaring may include a processing system, which may include one or more processors, such as

processors

258, 264 and 266, and/or controller/processor 280 of the UE 120a and/or

processors

220, 230, 238, and/or controller/processor 240 of the BS 110a shown in FIG. 2.

In some cases, rather than actually transmitting a frame a device may have an interface to output a frame for transmission (a means for outputting) . For example, a processor may output a frame, via a bus interface, to a radio frequency (RF) front end for transmission. Similarly, rather than actually receiving a frame, a device may have an interface to obtain a frame received from another device (a means for obtaining) . For example, a processor may obtain (or receive) a frame, via a bus interface, from an RF front end for reception.

The various illustrative logical blocks, modules and circuits described in connection with the present disclosure may be implemented or performed with a general purpose processor, a digital signal processor (DSP) , an application specific integrated circuit (ASIC) , a field programmable gate array (FPGA) or other programmable logic device (PLD) , discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any commercially available processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

If implemented in hardware, an example hardware configuration may comprise a processing system in a wireless node. The processing system may be implemented with a bus architecture. The bus may include any number of interconnecting buses and bridges depending on the specific application of the processing system and the overall design constraints. The bus may link together various circuits including a processor, machine-readable media, and a bus interface. The bus interface may be used to connect a network adapter, among other things, to the processing system via the bus. The network adapter may be used to implement the signal processing functions of the PHY layer. In the case of a user terminal 120 (see FIG. 1) , a user interface (e.g., keypad, display, mouse, joystick, etc. ) may also be connected to the bus. The bus may also link various other circuits such as timing sources, peripherals, voltage regulators, power management circuits, and the like, which are well known in the art, and therefore, will not be described any further. The processor may be implemented with one or more general-purpose and/or special-purpose processors. Examples include microprocessors, microcontrollers, DSP processors, and other circuitry that can execute software. Those skilled in the art will recognize how best to implement the described functionality for the processing system depending on the particular application and the overall design constraints imposed on the overall system.

If implemented in software, the functions may be stored or transmitted over as one or more instructions or code on a computer readable medium. Software shall be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Computer-readable media include both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. The processor may be responsible for managing the bus and general processing, including the execution of software modules stored on the machine-readable storage media. A computer-readable storage medium may be coupled to a processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. By way of example, the machine-readable media may include a transmission line, a carrier wave modulated by data, and/or a computer readable storage medium with instructions stored thereon separate from the wireless node, all of which may be accessed by the processor through the bus interface. Alternatively, or in addition, the machine-readable media, or any portion thereof, may be integrated into the processor, such as the case may be with cache and/or general register files. Examples of machine-readable storage media may include, by way of example, RAM (Random Access Memory) , flash memory, ROM (Read Only Memory) , PROM (Programmable Read-Only Memory) , EPROM (Erasable Programmable Read-Only Memory) , EEPROM (Electrically Erasable Programmable Read-Only Memory) , registers, magnetic disks, optical disks, hard drives, or any other suitable storage medium, or any combination thereof. The machine-readable media may be embodied in a computer-program product.

A software module may comprise a single instruction, or many instructions, and may be distributed over several different code segments, among different programs, and across multiple storage media. The computer-readable media may comprise a number of software modules. The software modules include instructions that, when executed by an apparatus such as a processor, cause the processing system to perform various functions. The software modules may include a transmission module and a receiving module. Each software module may reside in a single storage device or be distributed across multiple storage devices. By way of example, a software module may be loaded into RAM from a hard drive when a triggering event occurs. During execution of the software module, the processor may load some of the instructions into cache to increase access speed. One or more cache lines may then be loaded into a general register file for execution by the processor. When referring to the functionality of a software module below, it will be understood that such functionality is implemented by the processor when executing instructions from that software module.

Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) , or wireless technologies such as infrared (IR) , radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, include compact disc (CD) , laser disc, optical disc, digital versatile disc (DVD) , floppy disk, and

disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Thus, in some aspects computer-readable media may comprise non-transitory computer-readable media (e.g., tangible media) . In addition, for other aspects computer-readable media may comprise transitory computer-readable media (e.g., a signal) . Combinations of the above should also be included within the scope of computer-readable media.

Thus, certain aspects may comprise a computer program product for performing the operations presented herein. For example, such a computer program product may comprise a computer-readable medium having instructions stored (and/or encoded) thereon, the instructions being executable by one or more processors to perform the operations described herein, for example, instructions for performing the operations described herein and illustrated in FIG. 5.

Further, it should be appreciated that modules and/or other appropriate means for performing the methods and techniques described herein can be downloaded and/or otherwise obtained by a user terminal and/or base station as applicable. For example, such a device can be coupled to a server to facilitate the transfer of means for performing the methods described herein. Alternatively, various methods described herein can be provided via storage means (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or floppy disk, etc. ) , such that a user terminal and/or base station can obtain the various methods upon coupling or providing the storage means to the device. Moreover, any other suitable technique for providing the methods and techniques described herein to a device can be utilized.

It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes and variations may be made in the arrangement, operation and details of the methods and apparatus described above without departing from the scope of the claims.

Claims

A method for wireless communications by a user equipment (UE) , comprising:

suspending data service between the UE and a network via a first subscriber identity module (SIM) to perform operations for a second SIM;

resuming the data service between the UE and the network via the first SIM; and

taking one or more actions to detect a network out of synchronization (OOS) condition that occurred during the suspension.
The method of claim 1, wherein the OOS condition comprises a radio link control (RLC) state mismatch between the first SIM and the network associated with a service data unit (SDU) that was transmitted before the suspension for which an acknowledgment has not been received.
The method of claim 2, wherein the one or more actions comprise:

retransmitting the same SDU until a threshold number of times; and

declaring a radio link failure (RLF) if the acknowledgment has not been received after retransmitting the same SDU the threshold number of times.
The method of claim 3, wherein the retransmitted SDU comprises a smallest sequence number (SN) for which the acknowledgment has not been received.
The method of any of claims 2-4, wherein the acknowledgment comprises a positive acknowledgment.
The method of claim 2, wherein the SDU is retransmitted after an expiration of a retransmission timer on a given data radio bearer (DRB) .
An apparatus for wireless communications by a user equipment (UE) , comprising:

means for suspending data service between the UE and a network via a first subscriber identity module (SIM) to perform operations for a second SIM;

means for resuming the data service between the UE and the network via the first SIM; and

means for taking one or more actions to detect a network out of synchronization (OOS) condition that occurred during the suspension.
The apparatus of claim 7, wherein the OOS condition comprises a radio link control (RLC) state mismatch between the first SIM and the network associated with a service data unit (SDU) that was transmitted before the suspension for which an acknowledgment has not been received.
The apparatus of claim 8, wherein the one or more actions comprise:

means for retransmitting the same SDU until a threshold number of times; and

means for declaring a radio link failure (RLF) if the acknowledgment has not been received after retransmitting the same SDU the threshold number of times.
The apparatus of claim 9, wherein the retransmitted SDU comprises a smallest sequence number (SN) for which the acknowledgment has not been received.
The apparatus of any of claims 8-10, wherein the acknowledgment comprises a positive acknowledgment.
The apparatus of claim 8, wherein the SDU is retransmitted after an expiration of a retransmission timer on a given data radio bearer (DRB) .
An apparatus for wireless communications by a user equipment (UE) , comprising:

a processing system configured to:

suspend data service between the UE and a network via a first subscriber identity module (SIM) to perform operations for a second SIM;

resume the data service between the UE and the network via the first SIM; and

take one or more actions to detect a network out of synchronization (OOS) condition that occurred during the suspension.
The apparatus of claim 13, wherein the OOS condition comprises a radio link control (RLC) state mismatch between the first SIM and the network associated with a service data unit (SDU) that was transmitted before the suspension for which an acknowledgment has not been received.
The apparatus of claim 14, wherein the one or more actions comprise:

retransmitting the same SDU until a threshold number of times; and

declaring a radio link failure (RLF) if the acknowledgment has not been received after retransmitting the same SDU the threshold number of times.
The apparatus of claim 15, wherein the retransmitted SDU comprises a smallest sequence number (SN) for which the acknowledgment has not been received.
The apparatus of any of claims 14-16, wherein the acknowledgment comprises a positive acknowledgment.
The apparatus of claim 14, wherein the SDU is retransmitted after an expiration of a retransmission timer on a given data radio bearer (DRB) .
A user equipment (UE) , comprising:

at least one antenna; and

a processing system configured to:

suspend data service between the UE and a network via a first subscriber identity module (SIM) to perform operations for a second SIM;

resume the data service between the UE and the network via the first SIM; and

take one or more actions, via the at least one antenna, to detect a network out of synchronization (OOS) condition that occurred during the suspension.
A computer-readable medium for wireless communications by a user equipment (UE) , comprising codes executable to:

suspend data service between the UE and a network via a first subscriber identity module (SIM) to perform operations for a second SIM;

resume the data service between the UE and the network via the first SIM; and

take one or more actions to detect a network out of synchronization (OOS) condition that occurred during the suspension.