WO2019029152A1

WO2019029152A1 - Packet data convergence protocol context re-synchronization for multiple subscriber identity module device

Info

Publication number: WO2019029152A1
Application number: PCT/CN2018/076996
Authority: WO
Inventors: Jiming Guo; Arnaud Meylan; Saket BATHWAL; Ling Xie; Liang Hong; Zhenyu Liu; Peng Wu; Reza Shahidi
Original assignee: Qualcomm Incorporated
Priority date: 2017-08-07
Filing date: 2018-02-23
Publication date: 2019-02-14
Also published as: WO2019028587A1

Abstract

A user equipment (UE) may identify a gap between receipt of packet data convergence protocol (PDCP) packet data units (PDUs) and determine a PDCP context is out-of-synchronization with a serving base station. The determination may be made based on a validity check (e.g., via a deciphering procedure) using a current hyper frame number (HFN) and, in some cases, additional HFNs. In cases where a received PDCP PDU is determined to be invalid, the UE may trigger a radio resource control (RRC) connection setup procedure or RRC connection reestablishment procedure between the UE and the serving base station. In cases where received PDCP PDUs are determined to be valid based on attempts to decipher the received PDCP PDUs using the additional HFNs, the UE may reset the current HFN and a PDCP reception window of the PDCP context based on the additional HFN used that resulted in the valid determination.

Description

PACKET DATA CONVERGENCE PROTOCOL CONTEXT RE-SYNCHRONIZATION FOR MULTIPLE SUBSCRIBER IDENTITY MODULE DEVICE

CROSS REFERENCES

The present Application for Patent claims priority to International Patent Application No. PCT/CN2017/096187 to Guo et. al., titled “PACKET DATA CONVERGENCE PROTOCOL CONTEXT RE-SYNCHRONIZATION FOR MULTIPLE SUBSCRIBER IDENTITY MODULE DEVICE” , filed August 7, 2017, assigned to the assignee hereof.

BACKGROUND

The following relates generally to wireless communication, and more specifically to packet data convergence protocol (PDCP) context re-synchronization techniques for multiple subscriber identity module (MSIM) devices.

Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power) . Examples of such multiple-access systems include fourth generation (4G) systems such as a Long Term Evolution (LTE) systems or LTE-Advanced (LTE-A) systems, and fifth generation (5G) systems which may be referred to as New Radio (NR) systems. These systems may employ technologies such as code division multiple access (CDMA) , time division multiple access (TDMA) , frequency division multiple access (FDMA) , orthogonal frequency division multiple access (OFDMA) , or discrete Fourier transform-spread-OFDM (DFT-S-OFDM) . A wireless multiple-access communications system may include a number of base stations or network access nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE) .

A UE (e.g., an MSIM UE) may maintain a PDCP count or a PDCP context (e.g., a hyper frame number (HFN) and a PDCP sequence number) in order to perform ciphering and/or integrity check procedures on communications with a base station (e.g., which may also maintain a PDCP context) . In some cases, PDCP context for a UE (e.g., an MSIM UE) may become misaligned or out-of-synchronization with PDCP context of a serving base station. Such misalignment may result in decreased system performance (e.g., increased base station buffer loads, communication latencies such as data stalls, UE deciphering failures, etc. ) . Improved PDCP context synchronization techniques may thus be desired.

SUMMARY

The described techniques relate to improved methods, systems, devices, or apparatuses that support improved packet data convergence protocol (PDCP) context re-synchronization techniques for multiple subscriber identity module (MSIM) wireless devices. An MSIM user equipment (UE) may identify a gap between receipt of PDCP packet data units (PDUs) or PDCP protocol data units and determine a PDCP context is out-of-synchronization with a serving base station. The determination may be made based on a validity check (e.g., via a deciphering procedure) using a current hyper frame number (HFN) and, in some cases, additional HFNs. In cases where at least one received PDCP PDU is determined to be invalid, the MSIM UE may trigger a radio resource control (RRC) connection setup procedure or RRC connection reestablishment procedure between the MSIM UE and the serving base station (e.g., upon the expiration of some counter or timer) . Such RRC procedures may re-synchronize the PDCP context of the MSIM UE and the serving base station. In cases where received PDCP PDUs are determined to be valid based on attempts to decipher the received PDCP PDUs using the additional HFNs, the MSIM UE may reset the current HFN and a PDCP reception window (e.g., update the PDCP context) based on the additional HFN used that resulted in the determination that the received PDCP PDUs are valid.

A method of wireless communication is described. The method may include identifying, at the MSIM UE, a gap between receipt of PDCP PDUs associated with a first SIM, the gap resulting from an MSIM procedure associated with a second SIM, and determining, based at least in part on an existence of the gap, that a PDCP context for the MSIM UE is out of synchronization with a PDCP context of a serving base station. The method may further include updating, based at least in part on the determination, the PDCP context for the MSIM UE to re-synchronize the PDCP context for the MSIM UE with the PDCP context of the serving base station.

An apparatus for wireless communication is described. The apparatus may include means for identifying, at the MSIM UE, a gap between receipt of PDCP PDUs associated with a first SIM, the gap resulting from an MSIM procedure associated with a second SIM, and means for determining, based at least in part on an existence of the gap, that a PDCP context for the MSIM UE is out of synchronization with a PDCP context of a serving base station. The apparatus may further include means for updating, based at least in part on the determination, the PDCP context for the MSIM UE to re-synchronize the PDCP context for the MSIM UE with the PDCP context of the serving base station.

Another apparatus for wireless communication is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be operable to cause the processor to identify, at the MSIM UE, a gap between receipt of PDCP PDUs associated with a first SIM, the gap resulting from an MSIM procedure associated with a second SIM, and determine, based at least in part on an existence of the gap, that a PDCP context for the MSIM UE is out of synchronization with a PDCP context of a serving base station. The instructions may be further operable to cause the processor to update, based at least in part on the determination, the PDCP context for the MSIM UE to re-synchronize the PDCP context for the MSIM UE with the PDCP context of the serving base station.

A non-transitory computer readable medium for wireless communication is described. The non-transitory computer-readable medium may include instructions operable to cause a processor to identify, at the MSIM UE, a gap between receipt of PDCP PDUs associated with a first SIM, the gap resulting from an MSIM procedure associated with a second SIM, and determine, based at least in part on an existence of the gap, that a PDCP context for the MSIM UE is out of synchronization with a PDCP context of a serving base station. The non-transitory computer-readable medium may further include instructions operable to cause a processor to update, based at least in part on the determination, the PDCP context for the MSIM UE to re-synchronize the PDCP context for the MSIM UE with the PDCP context of the serving base station.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, determining that the PDCP context for the MSIM UE may be out-of-synchronization with the PDCP context of the serving base station comprises receiving a plurality of out-of-window PDCP PDUs. Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for attempting to decipher the plurality of out-of-window PDCP PDUs using a current HFN stored at the MSIM UE. Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for determining that at least one of the plurality of out-of-window PDCP PDUs may be invalid based at least in part on the attempt to decipher the multiple out-of-window PDCP PDUs.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, updating the PDCP context comprises triggering a RRC connection setup procedure or RRC connection reestablishment procedure between the MSIM UE and the serving base station.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for maintaining a counter value based at least in part on the attempt to decipher the multiple out-of-window PDCP PDUs. Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for updating the counter value based at least in part on the determination that at least one of the multiple out-of-window PDCP PDUs may be invalid. Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for updating the PDCP context for the MSIM UE based at least in part on the counter value satisfying a threshold.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for releasing a local RRC connection based at least in part on the counter value satisfying the threshold.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for maintaining a counter value based at least in part on the received plurality of out-of-window PDCP PDUs. Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for updating the counter value based at least in part on the received plurality of out-of-window PDCP PDUs. Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for updating the PDCP context for the MSIM UE based at least in part on the counter value satisfying a threshold.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, determining that the PDCP context for the MSIM UE may be out-of-synchronization with the PDCP context of the serving base station comprises attempting to decipher received PDCP PDUs using a current HFN stored at the MSIM UE. Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for attempting to decipher received PDCP PDUs using one or more additional HFNs based on the stored HFN. Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for determining that the received PDCP PDUs may be valid based on the attempt to decipher the received PDCP PDUs using one of the one or more additional HFNs. Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for updating the PDCP context for the MSIM UE to re-synchronize the PDCP context for the MSIM UE with the PDCP context of the serving base station includes updating the PDCP context for the MSIM UE based on the one of the one or more additional HFNs.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, updating the PDCP context comprises resetting the current HFN and a PDCP receive (Rx) window based at least in part on the one of the plurality of additional HFNs that resulted in the determining that the received PDCP PDUs may be valid.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the one or more additional HFNs may be bounded by a predetermined range based on at least one of a MSIM UE gap size, available downlink bandwidth associated with an HFN, or the current HFN.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, determining that the PDCP context for the MSIM UE may be out-of-synchronization with the PDCP context of the serving base station comprises attempting to decipher received PDCP PDUs using a current HFN stored at the MSIM UE and one or more of additional HFNs. Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for determining that at least one of the received PDCP PDUs may be invalid based on the attempt to decipher the received PDCP PDUs. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, updating the PDCP context comprises triggering an RRC connection setup procedure between the MSIM UE and the serving base station.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for maintaining a counter value based at least in part on the attempt to decipher received PDCP PDUs. Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for updating the counter value based at least in part on the determination that at least one of the received PDCP PDUs may be invalid. Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for updating the PDCP context for the MSIM UE based at least in part on the counter value satisfying a threshold. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the PDCP context includes a HFN and a PDCP sequence number.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for determining, based at least in part on an existence of the gap, that a PDCP context for the MSIM UE may be out of synchronization with a PDCP context of a serving base station includes determining the existence of the gap may be based on a MSIM UE procedure associated with a subscriber identity module (SIM) other than a SIM associated with the serving base station.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a system for wireless communication that supports packet data convergence protocol (PDCP) context re-synchronization techniques for multiple subscriber identity module (MSIM) devices in accordance with aspects of the present disclosure.

FIG. 2 illustrates an example of a wireless communications system that supports PDCP context re-synchronization techniques for MSIM devices in accordance with aspects of the present disclosure.

FIG. 3 illustrates an example of a flowchart for PDCP context re-synchronization techniques for MSIM devices in accordance with aspects of the present disclosure.

FIG. 4 illustrates an example of a flowchart for PDCP context re-synchronization techniques for MSIM devices in accordance with aspects of the present disclosure.

FIG. 5 illustrates an example of a flowchart for PDCP context re-synchronization techniques for MSIM devices in accordance with aspects of the present disclosure.

FIG. 6 illustrates an example of a process flow that supports PDCP context re-synchronization techniques for MSIM devices in accordance with aspects of the present disclosure.

FIGs. 7 through 9 show block diagrams of a device that supports PDCP context re-synchronization techniques for MSIM devices in accordance with aspects of the present disclosure.

FIG. 10 illustrates a block diagram of a system including a user equipment (UE) that supports PDCP context re-synchronization techniques for MSIM devices in accordance with aspects of the present disclosure.

FIGs. 11 through 14 illustrate methods for PDCP context re-synchronization techniques for MSIM devices in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

A multiple subscriber identity module (MSIM) user equipment (UE) may have at least two subscriber identity modules (SIMs) , and each SIM may be associated with a subscription. In some cases, UEs may use one or more SIMs, and thus utilize one or more subscriptions simultaneously. Each SIM may contain a unique serial number, security authentication and ciphering information, temporary information related to the local network, a list of available services, a personal identification number (PIN) , a personal unblocking code (PUK) for PIN unlocking, etc. Further, a packet data convergence protocol (PDCP) context may be used by a UE for deciphering and/or integrity check procedures on downlink communications from a serving base station. The PDCP context may include a hyper frame number (HFN) and a PDCP sequence number. PDCP context of a UE and a base station may become misaligned (e.g., lose synchronization) , for example, when an MSIM device experiences a gap between reception of PDCP protocol data units (PDUs) or protocol data units. In some cases, MSIM UE procedures associated with a SIM other than a SIM associated with the serving base station may result in such gaps between reception of PDCP PDUs. As these gaps occur, downlink transmission control protocol (TCP) traffic may still be on-going, such that when downlink packets arrive at the serving base station communication issues may arise (e.g., such as increased base station downlink buffer levels, UE deciphering failures, UE packet drops, etc. ) .

When MSIM UE gaps in reception of PDCP PDUs result in PDCP context loss-of-synchronization, the serving base station may increment the HFN/PDCP sequence number when data for transmission to the UE arrives, and in some cases may drop certain packets when the buffer overflows. Further, the UE may maintain the HFN and PDCP reception window setting established before the gap (e.g., thus losing synchronization with the PDCP context of the serving base station) . When HFN loss-of-synchronization happens, the UE may need to drop certain packets due to deciphering failures until re-synchronization is achieved. When PDCP sequence number loss-of-synchronization happens, the UE may drop certain PDCP PDUs received out of the reception window.

Therefore, upon identification of a gap between receipt of PDCP PDUs (e.g., a gap between receipt of PDCP PDUs associated with a first SIM, the gap resulting from an MSIM procedure associated with a second SIM) , an MSIM UE may determine that a PDCP context for the MSIM UE is out-of-synchronization with a PDCP context of a serving base station (e.g., by performing a validity check or deciphering procedures on received PDCP PDUs) . The MSIM UE may update the PDCP context for the MSIM UE to re-synchronize the PDCP context for the MSIM UE with the PDCP context of the serving base station. In some cases, the PDCP context may be updated by testing different HFNs used for a PDCP PDU validity check, by triggering a radio resource control (RRC) connection setup procedure or RRC connection reestablishment procedure between the MSIM UE and the serving base station, etc. as discussed in more detail below.

The MSIM UE may determine the PDCP context is out-of-synchronization with the PDCP context of the serving base station by attempting to decipher multiple out-of-window PDCP PDUs using a current HFN stored at the MSIM UE and determining that at least one of the out-of-window PDCP PDUs is invalid. In some cases, when the MSIM UE determines there is a PDCP context loss-of-synchronization, the MSIM UE may attempt to decipher received PDCP PDUs using one or more additional HFNs. In some cases, the additional HFNs may be bounded by a predetermined range based on at least one of an MSIM UE gap size, available downlink bandwidth associated with an HFN, or the current HFN. In cases where the MSIM UE determines the received PDCP PDUs are valid based on the use of one of the additional HFNs, the MSIM UE may update the PDCP context to include the additional HFN used. Further, in such cases, the PDCP context may be updated by resetting the current HFN and a PDCP receive window of the PDCP context based on the one or more additional HFNs that resulted in the determination a valid PDCP PDU was received.

In some examples, the MSIM UE may maintain a counter value based on the attempt to decipher the multiple out-of-window PDCP PDUs or the number of PDCP PDUs whose sequence number is out of the current reception (Rx) window. The MSIM UE may update or increment the counter value based on the determination that at least one of the multiple out-of-window PDCP PDUs is invalid. The MSIM UE may continue to update the PDCP context for the MSIM UE as long as the counter value satisfies a threshold (e.g., remains below some predetermined or configured threshold) . However, the MSIM UE may release an RRC connection if the counter value exceeds some threshold (e.g., if the timer or counter expires) .

Aspects of the disclosure are initially described in the context of wireless communications systems. Example flow charts illustrating techniques discussed herein are then described. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to PDCP context re-synchronization techniques for MSIM devices.

FIG. 1 illustrates an example of a wireless communications system 100 in accordance with various aspects of the present disclosure. The wireless communications system 100 includes base stations 105, UEs 115, and a core network 130. In some examples, the wireless communications system 100 may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, or a New Radio (NR) network. In some cases, wireless communications system 100 may support enhanced broadband communications, ultra- reliable (e.g., mission critical) communications, low latency communications, or communications with low-cost and low-complexity devices.

Base stations 105 may wirelessly communicate with UEs 115 via one or more base station antennas. Base stations 105 described herein may include or may be referred to by those skilled in the art as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, an eNodeB (eNB) , a next-generation Node B or giga-nodeB (either of which may be referred to as a gNB) , a Home NodeB, a Home eNodeB, or some other suitable terminology. Wireless communications system 100 may include base stations 105 of different types (e.g., macro or small cell base stations) . The UEs 115 described herein may be able to communicate with various types of base stations 105 and network equipment including macro eNBs, small cell eNBs, gNBs, relay base stations, and the like.

Each base station 105 may be associated with a particular geographic coverage area 110 in which communications with various UEs 115 is supported. Each base station 105 may provide communication coverage for a respective geographic coverage area 110 via communication links 125, and communication links 125 between a base station 105 and a UE 115 may utilize one or more carriers. Communication links 125 shown in wireless communications system 100 may include uplink transmissions from a UE 115 to a base station 105, or downlink transmissions, from a base station 105 to a UE 115. Downlink transmissions may also be called forward link transmissions while uplink transmissions may also be called reverse link transmissions.

The geographic coverage area 110 for a base station 105 may be divided into sectors making up only a portion of the geographic coverage area 110, and each sector may be associated with a cell. For example, each base station 105 may provide communication coverage for a macro cell, a small cell, a hot spot, or other types of cells, or various combinations thereof. In some examples, a base station 105 may be movable and therefore provide communication coverage for a moving geographic coverage area 110. In some examples, different geographic coverage areas 110 associated with different technologies may overlap, and overlapping geographic coverage areas 110 associated with different technologies may be supported by the same base station 105 or by different base stations 105. The wireless communications system 100 may include, for example, a heterogeneous LTE/LTE-A or NR network in which different types of base stations 105 provide coverage for various geographic coverage areas 110.

The term “cell” refers to a logical communication entity used for communication with a base station 105 (e.g., over a carrier) , and may be associated with an identifier for distinguishing neighboring cells (e.g., a physical cell identifier (PCID) , a virtual cell identifier (VCID) ) operating via the same or a different carrier. In some examples, a carrier may support multiple cells, and different cells may be configured according to different protocol types (e.g., machine-type communication (MTC) , narrowband Internet-of-Things (NB-IoT) , enhanced mobile broadband (eMBB) , or others) that may provide access for different types of devices. In some cases, the term “cell” may refer to a portion of a geographic coverage area 110 (e.g., a sector) over which the logical entity operates.

UEs 115 may be dispersed throughout the wireless communications system 100, and each UE 115 may be stationary or mobile. A UE 115 may also be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a subscriber device, or some other suitable terminology, where the “device” may also be referred to as a unit, a station, a terminal, or a client. A UE 115 may also be a personal electronic device such as a cellular phone, a personal digital assistant (PDA) , a tablet computer, a laptop computer, or a personal computer. In some examples, a UE 115 may also refer to a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or an MTC device, or the like, which may be implemented in various articles such as appliances, vehicles, meters, or the like.

Some UEs 115, such as MTC or IoT devices, may be low cost or low complexity devices, and may provide for automated communication between machines (e.g., via Machine-to-Machine (M2M) communication) . M2M communication or MTC may refer to data communication technologies that allow devices to communicate with one another or a base station 105 without human intervention. In some examples, M2M communication or MTC may include communications from devices that integrate sensors or meters to measure or capture information and relay that information to a central server or application program that can make use of the information or present the information to humans interacting with the program or application. Some UEs 115 may be designed to collect information or enable automated behavior of machines. Examples of applications for MTC devices include smart metering, inventory monitoring, water level monitoring, equipment monitoring, healthcare monitoring, wildlife monitoring, weather and geological event monitoring, fleet management and tracking, remote security sensing, physical access control, and transaction-based business charging.

Some UEs 115 may be configured to employ operating modes that reduce power consumption, such as half-duplex communications (e.g., a mode that supports one-way communication via transmission or reception, but not transmission and reception simultaneously) . In some examples half-duplex communications may be performed at a reduced peak rate. Other power conservation techniques for UEs 115 include entering a power saving “deep sleep” mode when not engaging in active communications, or operating over a limited bandwidth (e.g., according to narrowband communications) . In some cases, UEs 115 may be designed to support critical functions (e.g., mission critical functions) , and a wireless communications system 100 may be configured to provide ultra-reliable communications for these functions.

In some cases, a UE 115 may also be able to communicate directly with other UEs 115 (e.g., using a peer-to-peer (P2P) or device-to-device (D2D) protocol) . One or more of a group of UEs 115 utilizing D2D communications may be within the geographic coverage area 110 of a base station 105. Other UEs 115 in such a group may be outside the geographic coverage area 110 of a base station 105, or be otherwise unable to receive transmissions from a base station 105. In some cases, groups of UEs 115 communicating via D2D communications may utilize a one-to-many (1: M) system in which each UE 115 transmits to every other UE 115 in the group. In some cases, a base station 105 facilitates the scheduling of resources for D2D communications. In other cases, D2D communications are carried out between UEs 115 without the involvement of a base station 105.

Base stations 105 may communicate with the core network 130 and with one another. For example, base stations 105 may interface with the core network 130 through backhaul links 132 (e.g., via an S1 or other interface) . Base stations 105 may communicate with one another over backhaul links 134 (e.g., via an X2 or other interface) either directly (e.g., directly between base stations 105) or indirectly (e.g., via core network 130) .

The core network 130 may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. The core network 130 may be an evolved packet core (EPC) , which may include at least one mobility management entity (MME) , at least one serving gateway (S-GW) , and at least one Packet Data Network (PDN) gateway (P-GW) . The MME may manage non-access stratum (e.g., control plane) functions such as mobility, authentication, and bearer management for UEs 115 served by base stations 105 associated with the EPC. User IP packets may be transferred through the S-GW, which itself may be connected to the P-GW. The P-GW may provide IP address allocation as well as other functions. The P-GW may be connected to the network operators IP services. The operators IP services may include access to the Internet, Intranet (s) , an IP Multimedia Subsystem (IMS) , or a Packet-Switched (PS) Streaming Service.

At least some of the network devices, such as a base station 105, may include subcomponents such as an access network entity, which may be an example of an access node controller (ANC) . Each access network entity may communicate with UEs 115 through a number of other access network transmission entities, which may be referred to as a radio head, a smart radio head, or a transmission/reception point (TRP) . In some configurations, various functions of each access network entity or base station 105 may be distributed across various network devices (e.g., radio heads and access network controllers) or consolidated into a single network device (e.g., a base station 105) .

Wireless communications system 100 may operate using one or more frequency bands, typically in the range of 300 MHz to 300 GHz. Generally, the region from 300 MHz to 3 GHz is known as the ultra-high frequency (UHF) region or decimeter band, since the wavelengths range from approximately one decimeter to one meter in length. UHF waves may be blocked or redirected by buildings and environmental features. However, the waves may penetrate structures sufficiently for a macro cell to provide service to UEs 115 located indoors. Transmission of UHF waves may be associated with smaller antennas and shorter range (e.g., less than 100 km) compared to transmission using the smaller frequencies and longer waves of the high frequency (HF) or very high frequency (VHF) portion of the spectrum below 300 MHz.

Wireless communications system 100 may also operate in a super high frequency (SHF) region using frequency bands from 3 GHz to 30 GHz, also known as the centimeter band. The SHF region includes bands such as the 5 GHz industrial, scientific, and medical (ISM) bands, which may be used opportunistically by devices that can tolerate interference from other users.

Wireless communications system 100 may also operate in an extremely high frequency (EHF) region of the spectrum (e.g., from 30 GHz to 300 GHz) , also known as the millimeter band. In some examples, wireless communications system 100 may support millimeter wave (mmW) communications between UEs 115 and base stations 105, and EHF antennas of the respective devices may be even smaller and more closely spaced than UHF antennas. In some cases, this may facilitate use of antenna arrays within a UE 115. However, the propagation of EHF transmissions may be subject to even greater atmospheric attenuation and shorter range than SHF or UHF transmissions. Techniques disclosed herein may be employed across transmissions that use one or more different frequency regions, and designated use of bands across these frequency regions may differ by country or regulating body.

In some cases, wireless communications system 100 may utilize both licensed and unlicensed radio frequency spectrum bands. For example, wireless communications system 100 may employ License Assisted Access (LAA) , LTE-Unlicensed (LTE-U) radio access technology, or NR technology in an unlicensed band such as the 5 GHz ISM band. When operating in unlicensed radio frequency spectrum bands, wireless devices such as base stations 105 and UEs 115 may employ listen-before-talk (LBT) procedures to ensure a frequency channel is clear before transmitting data. In some cases, operations in unlicensed bands may be based on a CA configuration in conjunction with CCs operating in a licensed band (e.g., LAA) . Operations in unlicensed spectrum may include downlink transmissions, uplink transmissions, peer-to-peer transmissions, or a combination of these. Duplexing in unlicensed spectrum may be based on frequency division duplexing (FDD) , time division duplexing (TDD) , or a combination of both.

In some examples, base station 105 or UE 115 may be equipped with multiple antennas, which may be used to employ techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communications, or beamforming. For example, wireless communication system may use a transmission scheme between a transmitting device (e.g., a base station 105) and a receiving device (e.g., a UE 115) , where the transmitting device is equipped with multiple antennas and the receiving devices are equipped with one or more antennas. MIMO communications may employ multipath signal propagation to increase the spectral efficiency by transmitting or receiving multiple signals via different spatial layers, which may be referred to as spatial multiplexing. The multiple signals may, for example, be transmitted by the transmitting device via different antennas or different combinations of antennas. Likewise, the multiple signals may be received by the receiving device via different antennas or different combinations of antennas. Each of the multiple signals may be referred to as a separate spatial stream, and may carry bits associated with the same data stream (e.g., the same codeword) or different data streams. Different spatial layers may be associated with different antenna ports used for channel measurement and reporting. MIMO techniques include single-user MIMO (SU-MIMO) where multiple spatial layers are transmitted to the same receiving device, and multiple-user MIMO (MU-MIMO) where multiple spatial layers are transmitted to multiple devices.

Beamforming, which may also be referred to as spatial filtering, directional transmission, or directional reception, is a signal processing technique that may be used at a transmitting device or a receiving device (e.g., a base station 105 or a UE 115) to shape or steer an antenna beam (e.g., a transmit beam or receive beam) along a spatial path between the transmitting device and the receiving device. Beamforming may be achieved by combining the signals communicated via antenna elements of an antenna array such that signals propagating at particular orientations with respect to an antenna array experience constructive interference while others experience destructive interference. The adjustment of signals communicated via the antenna elements may include a transmitting device or a receiving device applying certain amplitude and phase offsets to signals carried via each of the antenna elements associated with the device. The adjustments associated with each of the antenna elements may be defined by a beamforming weight set associated with a particular orientation (e.g., with respect to the antenna array of the transmitting device or receiving device, or with respect to some other orientation) .

In one example, a base station 105 may use multiple antennas or antenna arrays to conduct beamforming operations for directional communications with a UE 115. For instance, some signals (e.g. synchronization signals, reference signals, beam selection signals, or other control signals) may be transmitted by a base station 105 multiple times in different directions, which may include a signal being transmitted according to different beamforming weight sets associated with different directions of transmission. Transmissions in different beam directions may be used to identify (e.g., by the base station 105 or a receiving device, such as a UE 115) a beam direction for subsequent transmission and/or reception by the base station 105. Some signals, such as data signals associated with a particular receiving device, may be transmitted by a base station 105 in a single beam direction (e.g., a direction associated with the receiving device, such as a UE 115) . In some examples, the beam direction associated with transmissions along a single beam direction may be determined based at least in in part on a signal that was transmitted in different beam directions. For example, a UE 115 may receive one or more of the signals transmitted by the base station 105 in different directions, and the UE 115 may report to the base station 105 an indication of the signal it received with a highest signal quality, or an otherwise acceptable signal quality. Although these techniques are described with reference to signals transmitted in one or more directions by a base station 105, a UE 115 may employ similar techniques for transmitting signals multiple times in different directions (e.g., for identifying a beam direction for subsequent transmission or reception by the UE 115) , or transmitting a signal in a single direction (e.g., for transmitting data to a receiving device) .

A receiving device (e.g., a UE 115, which may be an example of a mmW receiving device) may try multiple receive beams when receiving various signals from the base station 105, such as synchronization signals, reference signals, beam selection signals, or other control signals. For example, a receiving device may try multiple receive directions by receiving via different antenna subarrays, by processing received signals according to different antenna subarrays, by receiving according to different receive beamforming weight sets applied to signals received at a plurality of antenna elements of an antenna array, or by processing received signals according to different receive beamforming weight sets applied to signals received at a plurality of antenna elements of an antenna array, any of which may be referred to as “listening” according to different receive beams or receive directions. In some examples a receiving device may use a single receive beam to receive along a single beam direction (e.g., when receiving a data signal) . The single receive beam may be aligned in a beam direction determined based at least in part on listening according to different receive beam directions (e.g., a beam direction determined to have a highest signal strength, highest signal-to-noise ratio, or otherwise acceptable signal quality based at least in part on listening according to multiple beam directions) .

In some cases, the antennas of a base station 105 or UE 115 may be located within one or more antenna arrays, which may support MIMO operations, or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be co-located at an antenna assembly, such as an antenna tower. In some cases, antennas or antenna arrays associated with a base station 105 may be located in diverse geographic locations. A base station 105 may have an antenna array with a number of rows and columns of antenna ports that the base station 105 may use to support beamforming of communications with a UE 115. Likewise, a UE 115 may have one or more antenna arrays that may support various MIMO or beamforming operations.

In some cases, wireless communications system 100 may be a packet-based network that operates according to a layered protocol stack. In the user plane, communications at the bearer or PDCP layer may be IP-based. A Radio Link Control (RLC) layer may in some cases perform packet segmentation and reassembly to communicate over logical channels. A Medium Access Control (MAC) layer may perform priority handling and multiplexing of logical channels into transport channels. The MAC layer may also use hybrid automatic repeat request (HARQ) to provide retransmission at the MAC layer to improve link efficiency. In the control plane, the RRC protocol layer may provide establishment, configuration, and maintenance of an RRC connection between a UE 115 and a base station 105 or core network 130 supporting radio bearers for user plane data. At the Physical (PHY) layer, transport channels may be mapped to physical channels.

In some cases, UEs 115 and base stations 105 may support retransmissions of data to increase the likelihood that data is received successfully. HARQ feedback is one technique of increasing the likelihood that data is received correctly over a communication link 125. HARQ may include a combination of error detection (e.g., using a cyclic redundancy check (CRC) ) , forward error correction (FEC) , and retransmission (e.g., automatic repeat request (ARQ) ) . HARQ may improve throughput at the MAC layer in poor radio conditions (e.g., signal-to-noise conditions) . In some cases, a wireless device may support same-slot HARQ feedback, where the device may provide HARQ feedback in a specific slot for data received in a previous symbol in the slot. In other cases, the device may provide HARQ feedback in a subsequent slot, or according to some other time interval.

Time intervals in LTE or NR may be expressed in multiples of a basic time unit, which may, for example, refer to a sampling period of T _s = 1/30,720,000 seconds. Time intervals of a communications resource may be organized according to radio frames each having a duration of 10 milliseconds (ms) , where the frame period may be expressed as T _f = 307,200 T _s. The radio frames may be identified by a system frame number (SFN) ranging from 0 to 1023. Each frame may include 10 subframes numbered from 0 to 9, and each subframe may have a duration of 1 ms. A subframe may be further divided into 2 slots each having a duration of 0.5 ms, and each slot may contain 6 or 7 modulation symbol periods (e.g., depending on the length of the cyclic prefix prepended to each symbol period) . Excluding the cyclic prefix, each symbol period may contain 2048 sampling periods. In some cases a subframe may be the smallest scheduling unit of the wireless communications system 100, and may be referred to as a transmission time interval (TTI) . In other cases, a smallest scheduling unit of the wireless communications system 100 may be shorter than a subframe or may be dynamically selected (e.g., in bursts of shortened TTIs (sTTIs) or in selected component carriers using sTTIs) .

In some wireless communications systems, a slot may further be divided into multiple mini-slots containing one or more symbols. In some instances, a symbol of a mini-slot or a mini-slot may be the smallest unit of scheduling. Each symbol may vary in duration depending on the subcarrier spacing or frequency band of operation, for example. Further, some wireless communications systems may implement slot aggregation in which multiple slots or mini-slots are aggregated together and used for communication between a UE 115 and a base station 105.

The term “carrier” refers to a set of radio frequency spectrum resources having a defined physical layer structure for supporting communications over a communication link 125. For example, a carrier of a communication link 125 may include a portion of a radio frequency spectrum band that is operated according to physical layer channels for a given radio access technology. Each physical layer channel may carry user data, control information, or other signaling. A carrier may be associated with a pre-defined frequency channel (e.g., an E-UTRA absolute radio frequency channel number (EARFCN) ) , and may be positioned according to a channel raster for discovery by UEs 115. Carriers may be downlink or uplink (e.g., in an FDD mode) , or be configured to carry downlink and uplink communications (e.g., in a TDD mode) . In some examples, signal waveforms transmitted over a carrier may be made up of multiple sub-carriers (e.g., using multi-carrier modulation (MCM) techniques such as OFDM or DFT-s-OFDM) .

The organizational structure of the carriers may be different for different radio access technologies (e.g., LTE, LTE-A, NR, etc. ) . For example, communications over a carrier may be organized according to TTIs or slots, each of which may include user data as well as control information or signaling to support decoding the user data. A carrier may also include dedicated acquisition signaling (e.g., synchronization signals or system information, etc. ) and control signaling that coordinates operation for the carrier. In some examples (e.g., in a carrier aggregation configuration) , a carrier may also have acquisition signaling or control signaling that coordinates operations for other carriers.

Physical channels may be multiplexed on a carrier according to various techniques. A physical control channel and a physical data channel may be multiplexed on a downlink carrier, for example, using time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. In some examples, control information transmitted in a physical control channel may be distributed between different control regions in a cascaded manner (e.g., between a common control region or common search space and one or more UE-specific control regions or UE-specific search spaces) .

A carrier may be associated with a particular bandwidth of the radio frequency spectrum, and in some examples the carrier bandwidth may be referred to as a “system bandwidth” of the carrier or the wireless communications system 100. For example, the carrier bandwidth may be one of a number of predetermined bandwidths for carriers of a particular radio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 MHz) . In some examples, each served UE 115 may be configured for operating over portions or all of the carrier bandwidth. In other examples, some UEs 115 may be configured for operation using a narrowband protocol type that is associated with a predefined portion or range (e.g., set of subcarriers or RBs) within a carrier (e.g., “in-band” deployment of a narrowband protocol type) .

In a system employing MCM techniques, a resource element may include one symbol period (e.g., a duration of one modulation symbol) and one subcarrier, where the symbol period and subcarrier spacing are inversely related. The number of bits carried by each resource element may depend on the modulation scheme (e.g., the order of the modulation scheme) . Thus, the more resource elements that a UE 115 receives and the higher the order of the modulation scheme, the higher the data rate may be for the UE 115. In MIMO systems, a wireless communications resource may refer to a combination of a radio frequency spectrum resource, a time resource, and a spatial resource (e.g., spatial layers) , and the use of multiple spatial layers may further increase the data rate for communications with a UE 115.

Devices of the wireless communications system 100 (e.g., base stations 105 or UEs 115) may have a hardware configuration that supports communications over a particular carrier bandwidth, or may be configurable to support communications over one of a set of carrier bandwidths. In some examples, the wireless communications system 100 may include base stations 105 and/or UEs that can support simultaneous communications via carriers associated with more than one different carrier bandwidth.

Wireless communications system 100 may support communication with a UE 115 on multiple cells or carriers, a feature which may be referred to as carrier aggregation (CA) or multi-carrier operation. A UE 115 may be configured with multiple downlink CCs and one or more uplink CCs according to a carrier aggregation configuration. Carrier aggregation may be used with both FDD and TDD component carriers.

In some cases, wireless communications system 100 may utilize enhanced component carriers (eCCs) . An eCC may be characterized by one or more features including wider carrier or frequency channel bandwidth, shorter symbol duration, shorter TTI duration, or modified control channel configuration. In some cases, an eCC may be associated with a carrier aggregation configuration or a dual connectivity configuration (e.g., when multiple serving cells have a suboptimal or non-ideal backhaul link) . An eCC may also be configured for use in unlicensed spectrum or shared spectrum (e.g., where more than one operator is allowed to use the spectrum) . An eCC characterized by wide carrier bandwidth may include one or more segments that may be utilized by UEs 115 that are not capable of monitoring the whole carrier bandwidth or are otherwise configured to use a limited carrier bandwidth (e.g., to conserve power) .

In some cases, an eCC may utilize a different symbol duration than other CCs, which may include use of a reduced symbol duration as compared with symbol durations of the other CCs. A shorter symbol duration may be associated with increased spacing between adjacent subcarriers. A device, such as a UE 115 or base station 105, utilizing eCCs may transmit wideband signals (e.g., according to frequency channel or carrier bandwidths of 20, 40, 60, 80 MHz, etc. ) at reduced symbol durations (e.g., 16.67 microseconds) . A TTI in eCC may consist of one or multiple symbol periods. In some cases, the TTI duration (that is, the number of symbol periods in a TTI) may be variable.

Wireless communications systems such as an NR system may utilize any combination of licensed, shared, and unlicensed spectrum bands, among others. The flexibility of eCC symbol duration and subcarrier spacing may allow for the use of eCC across multiple spectrums. In some examples, NR shared spectrum may increase spectrum utilization and spectral efficiency, specifically through dynamic vertical (e.g., across frequency) and horizontal (e.g., across time) sharing of resources.

Each UE 115 may contain one or more SIMs. A SIM may be an entity or component of the UE 115 that contains the International Mobile Subscriber Identity (IMSI) , which uniquely identifies a subscriber to a particular wireless service of a system operator. Without a valid IMSI, service may not be accessible. A SIM may also contain a unique serial number (e.g., an integrated circuit card ID (ICCID) ) , security authentication and ciphering information, temporary information related to the local network, a list of available services, a PIN, a PUK for PIN unlocking, etc. In some cases, a SIM may be a circuit embedded in a removable plastic card. The SIM may provide a means to authenticate the user, but it may also store other subscriber-related information or applications, such as text messages and phone book contacts. A UE 115 may have a subscription to access a particular network or system, and the subscription may be associated with access credentials, user information, billing or charging information, usage information, or the like, for a user. Each SIM may be associated with and include information, access credentials, etc. for a system. In some systems, such as UMTS and LTE, a universal subscriber identity module (USIM) may perform the same or similar functions of a SIM. As used herein, subscriber identity module or SIM may refer to a universal subscriber identity module or USIM.

A SIM may be an integrated circuit that securely stores the IMSI and the related key used to identify and authenticate UE 115-i. MSIM UEs 115 may have at least two SIMs, and each SIM may be associated with a subscription. UEs 115 may use one or more SIMs, and thus one or more subscriptions simultaneously. In some cases, MSIM mobile devices may support operation using separate subscriptions with one or several carriers. In some cases, MSIM UEs 115 may operate using one subscription at a time, keeping the other subscription in an idle state. MSIM UEs 115 have become increasingly popular because of the versatility that they provide, particularly in countries where there are many service providers. For example, an MSIM multi-standby (MSMS) device enables at least two SIMs to be in idle mode waiting to begin communications, but only allows one SIM at a time to participate in an active communication due to sharing of a single radio frequency (RF) resource (e.g., transceiver) . As a result, during an active communication on one SIM, the wireless device may periodically tune away to a network associated with another SIM to monitor signals or to acquire a connection.

Wireless communications system 100 may include several MSIM UEs 115. MSIM UEs 115 may identify a gap between receipt of PDCP PDUs (e.g., resulting from an MSIM UE procedure associated with a second SIM) and determine a PDCP context is out-of-synchronization with a serving base station 105. The determination may be made based on a validity check (e.g., via a deciphering procedure) using a current HFN and, in some cases, using additional HFNs. In cases where at least one received PDCP PDU is determined to be invalid, the MSIM UE 115 may trigger an RRC connection setup procedure or RRC connection reestablishment procedure between the MSIM UE 115 and the serving base station 105. In cases where received PDCP PDUs are determined to be valid based on attempts to decipher the received PDCP PDUs using one or more HFS of the additional HFNs, the MSIM UE 115 may reset the current HFN and a PDCP reception window based on the additional HFN used that resulted in the determination that the received PDCP PDUs are valid. Such techniques for PDCP context re-synchronization, along with other possible embodiments, are discussed in further detail below.

FIG. 2 illustrates an example of a wireless communications system 200 that supports PDCP context re-synchronization techniques for MSIM devices in accordance with various aspects of the present disclosure. Wireless communications system 200 includes base station 105-a, base station 105-b, and UE 115-a, which may be examples of base stations 105 and UEs 115 as described with reference to FIG. 1. Wireless communications system 200 may illustrate PDCP context re-synchronization techniques enabling UE 115-a to synchronize PDCP context information with that of base station 105-a and/or base station 105-b. In some cases, UE 115-a may be referred to as an MSIM device, and base station 105-a and base station 105-b may be associated with different subscriptions (e.g., SIM cards) of UE 115-a.

A PDCP count or PDCP context may be used for PDCP ciphering and integrity check procedures. PDCP context may include HFN (e.g., which may be maintained or stored by each of a communicating UE 115 and base station 105) and PDCP sequence number (e.g., a numbering space such as 4096 for 12 bit sequence number, which may be further enlarged with more air interface overhead) . The PDCP sequence number may refer to a numbering of a PDCP PDU that is transmitted over the air. In some cases, a PDU may refer to a protocol data unit. For example, each packet entering the PDCP layer may assigned a PDCP sequence number. In the example above, the PDCP sequence number may be selected to be 12 bits in length and thus the PDCP sequence number may start at 0 and end at 4095. Further, an HFN may be defined to start at 0 and may be incremented by 1 after every 4096 packets that enter the PDCP layer.

MSIM UE 115-a may communicate with base station 105-a via connection 205-a and may communicate with base station 105-b via connection 205-b. In the present example, each connection (e.g., connection 205-a and connection 205-b) may be associated with a different subscription (e.g., a different SIM card of the UE 115-a) . In some cases, one subscription may interrupt communications associated with another subscription. For example, the subscription associated with base station 105-b may interrupt communications over connection 205-a (e.g., communications between UE 115-a and base station 105-a) . Such interruptions (e.g., due to priority of the other subscription, etc. ) may result in gaps between reception of PDCP PDUs conveyed over connection 205-a. For example, a subscription may be interrupted such that another subscription perform cell reselection procedures, location updates, other cell continuity procedures, etc. Such may be referred to as an MSIM UE procedure. That is, a second subscription (e.g., provided via base station 105-b and connection 205-b) supported by UE 115-a may interrupt communications associated with an active or primary subscription (e.g., provided via base station 105-a and connection 205-a) , such that PDCP PDUs conveyed over connection 205-a may be delayed or associated with a gap. For example, downlink TCP traffic may be ongoing regardless of the interruption from the second subscription. As such, as the downlink packets (e.g., associated with the ongoing TCP traffic) arrive at the base station 105-a, the base station 105-a may buffer the packets (e.g., the buffer level of the base station 105-a may increase during the interruption associated with the second subscription) .

Therefore, PDCP context synchronization issues may arise when an MSIM gap (e.g., discussed above) results in a data stall from the perspective of the UE 115-a. In some cases, carrier aggregation deployments may be especially susceptible to such PDCP context synchronization issues as higher air bandwidth may result in increased downlink TCP traffic delays due to high bandwidth delay product (BDP) . During such gaps, base station 105-a may increment the HFN/PDCP sequence number when data (e.g., PDCP PDUs) continues to arrive and, in some cases, may drop certain packets when the buffer overflows. On the other hand, UE 115-a may maintain the HFN and PDCP Rx window settings that were present prior to the gap, which may result in the loss of PDCP context synchronization between UE 115-a and base station 105-a. When HFN becomes out-of-synchronization, the UE 115-a may drop certain packets upon reception due to deciphering failure until re-synchronization is achieved. That is, such gaps may result in base station 105-a ciphering packets with a HFN that has been incremented, while UE 115-a may attempt to decipher the packets with a HFN stored prior to the gap, which may result in deciphering failures. When PDCP sequence number becomes out-of-synchronization, the UE 115-a may drop certain PDCP PDUs that fall outside of a reception window (e.g., a PDCP Rx window) . The PDCP Rx window associated with the UE 115-a PDCP context may be a function of the size of the PDCP sequence number space (e.g., the PDCP Rx window may be half of the PDCP sequence number search space and may be detected based on last and current received PDCP sequence number) . Therefore, when a PDCP PDU associated with a PDCP sequence number that is outside of an expected window of PDCP sequence numbers, the UE 115-a may drop the PDCP PDU.

To deal with such issues, upon detection of a gap and/or PDCP context loss-of-synchronization, RRC connection setup may be triggered by PDCP to get back into PDCP context synchronization with the serving base station. If after a large gap, the PDCP receives multiple out-of-window PDUs (e.g., the PDCP window may be half the sequence number space and detected based on the last and current received sequence number) , the PDUs may be deciphered using a current HFN to check if the PDUs are valid. If consecutive PDUs turn out to be invalid (e.g., deciphering fails) , the base station may have dropped odd multiple of more than half of the PDCP sequence number space of PDUs (e.g., for a 12-bit PDCP sequence number space, 2048*1, 2048*3, 2048*5, etc. may have been dropped) . In such a case, the PDCP may trigger the RRC connection setup which may re-synchronize the PDCP context of the UE 115-a and the base station 105-a (e.g., the UE 115-a and base station 105-a may reflash or reset HFN and/or PDCP sequence numbering) .

In other examples, UE based PDCP context recovery via PDCP PDU deciphering may be performed regardless of the reception window setting. If after a large gap the PDCP receives PDUs which are within the window, but do not pass the validity check, the MSIM UE may try different combinations of HFN and determine which HFN is currently in use by the base station. After certain PDCP PDUs are deciphered successfully, the MSIM UE may restore the HFN and reception window setting accordingly. That is, UE 115-a may attempt to re-synchronize PDCP context without initiating a new RRC connection setup. The UE 115-a may attempt to decipher the PDCP PDUs using a range of HFNs (e.g., additional HFNs based on the gap size) . For example, after detection of a gap and/or PDCP context loss-of-synchronization, UE 115-a may attempt to decipher a received PDCP PDU with a HFN value of the current HFN, the current HFN–1, and the current HFN + 1. The HFN range may be predetermined or configured (e.g., HFN range = [current HFN –lower range, current HFN + upper bound] ) , or based on the gap size. If the UE 115-a is able to successfully decipher the received PDCP PDU using one of the additional HFNs within the range of HFNs, the UE 115-a may re-synchronize the PDCP context based on the successfully utilized HFN.

FIG. 3 illustrates an example of a flowchart 300 for PDCP context re-synchronization techniques for MSIM devices in accordance with various aspects of the present disclosure. In some examples, flowchart 300 may implement aspects of wireless communications system 100 and wireless communications system 200. Flowchart 300 may illustrate RRC connection setup after a gap upon detection of multiple out-of-window PDCP PDUs.

At 305, a concurrent radio access technology (CRAT) UE may operate in a connected mode (e.g., LTE connected mode) . At 310, the UE may receive PDCP PDUs following a gap (e.g., a post LTA gap) . At 315, the UE may determine whether the received PDCP PDUs are out-of-window (e.g., if the received PDCP PDUs have sequence numbers outside of the PDCP Rx window) . If the PDCP PDUs are within the PDCP Rx window, the UE may perform in-window procedures at 320.

If the received PDCP PDUs are out-of-window, a counter may be maintained based on the received out-of-window PDCP PDUs at 325. In some cases, the counter may increment with each out-of-window PDCP PDU received (e.g., the counter may count each received out-of-window PDCP PDU) . In other cases, a counter may be started after a first received out-of-window PDCP PDU. The counter may count the number of out-of-window PDCP PDUs received (e.g., increment with each received out-of-window PDCP PDU) , or may behave similar to a timer (e.g., increment with time) . At 330, if the counter exceeds a threshold (e.g., the number of out-of-window PDCP PDUs exceeds a threshold, a time duration or timer expires, etc. ) , the UE may trigger RRC local release and RRC connection setup to re-synchronize the PDCP context (e.g., the PDCP HFN, and the PDCP Rx window) at 335. If, at 330, the counter has not exceeded the threshold, the UE may continue receiving any PDCP PDUs (e.g., flowchart 300 may cycle back to 310) .

FIG. 4 illustrates an example of a flowchart 400 for PDCP context re-synchronization techniques for MSIM devices in accordance with various aspects of the present disclosure. In some examples, flowchart 400 may implement aspects of wireless communications system 100 and wireless communications system 200. Flowchart 400 may illustrate RRC connection setup after a gap upon detection of multiple out-of-window PDCP PDUs.

At 405, a CRAT UE may operate in a connected mode (e.g., LTE connected mode) . At 410, the UE may receive PDCP PDUs following a gap (e.g., a post LTA gap) . At 415, the UE may determine whether the received PDCP PDUs are out-of-window (e.g., if the received PDCP PDUs have sequence numbers outside of the PDCP Rx window) . If the PDCP PDUs are within the PDCP Rx window, the UE may perform in-window procedures at 420.

If the PDCP PDUs are out-of-window PDCP PDUs, the UE may attempt to decipher (e.g., validate) the PDCP PDUs with the current HFN (e.g., of the UEs PDCP context) at 425. If the deciphering at 425 is successful, the UE may discard the old valid PDCP PDU. If the deciphering was unsuccessful (e.g., if the PDCP PDU is determined invalid) the UE may increment a counter at 435. For example, in some cases, a counter may be started after a first deciphering failure (e.g., after a received PDCP PDU is determined to be invalid) , and the counter may behave similar to a timer (e.g., increment with time) . In other cases, the counter may increment with each deciphering failure (e.g., the counter may count each received PDCP PDU determined to be invalid) . At 440, if the counter exceeds a threshold (e.g., the number of deciphering failures exceeds a threshold, a time duration or timer expires, etc. ) , the UE may trigger RRC local release and RRC connection setup to re-synchronize the PDCP context (e.g., the PDCP HFN, and the PDCP Rx window) at 445. If, at 440, the counter has not exceeded the threshold, the UE may continue receiving any PDCP PDUs (e.g., flowchart 400 may cycle back to 410, and PDCP context re-synchronization techniques may continue) .

FIG. 5 illustrates an example of a flowchart 500 for PDCP context re-synchronization techniques for MSIM devices in accordance with various aspects of the present disclosure. In some examples, flowchart 500 may implement aspects of wireless communications system 100 and wireless communications system 200. Flowchart 500 may illustrate UE based PDCP context re-synchronization (e.g., UE based PDCP context recovery) via PDCP PDU deciphering regardless of Rx window setting.

At 505, a UE may determine or identify that a gap between receipt of PDCP PDUs exists (e.g., resulting from an MSIM UE procedure associated with a second SIM) . At 510, the UE may receive incoming PDCP PDUs. At 515, the UE may attempt to decipher the PDCP PDUs using a current HFN, as well as additional HFNs within some range of the current HFN. At 520, the UE may determine whether the PDCP PDUs are valid based on the deciphering. If the PDCP PDUs are valid, the UE may reset the HFN and PDCP Rx window (e.g., based on the HFN associated with the successful deciphering) , and resume operation according to normal operating procedure (e.g., 525) . If the PDCP PDUs are invalid, the UE may increment a counter at 530. If, at 535, the counter exceeds a threshold (e.g., the counter reaches some predetermined value, the counter expires, etc. ) , the UE may determine radio link failure (RLF) has occurred, and may trigger RRC local release and RRC connection setup to re-synchronize the PDCP context at 540. If, at 535, the count does not exceed the threshold, the UE may resume reception of PDCP PDUs (e.g., 510) , and may resume PDCP context re-synchronization techniques.

FIG. 6 illustrates an example of a process flow 600 that supports PDCP context re-synchronization techniques for MSIM devices in accordance with various aspects of the present disclosure. Process flow 600 includes base station 105-c and UE 115-b, which may be examples of base stations 105 and UEs 115 as described with reference to FIGs. 1 and 2. Process flow 600 may illustrate PDCP context re-synchronization techniques between UE 115-b (e.g., an MSIM UE) and base station 105-c. In the following description of the process flow 600, the operations between the UE 115-b and the base station 105-c may be transmitted in a different order than the exemplary order shown, or the operations performed by UE 115-b may be performed in different orders or at different times. Certain operations may also be left out of the process flow 600, or other operations may be added to the process flow 600.

At 605, base station 105-c may transmit one or more PDCP PDUs to UE 115-b. The PDCP PDUs received at 605 may be either within a window or be out-of-window PDCP PDUs, and may further be determined to be either valid or invalid. Such determinations may be made according to techniques described with reference to FIGs. 2 through 4.

At 610, the UE 115-b may identify a gap between receipt of PDCP PDUs received at 605. In some cases the gap may be based on an MSIM UE procedure associated with a SIM other than a SIM associated with the serving base station (e.g., an MSIM UE procedure associated with a SIM other than a SIM associated with the base station 105-c) .

At 615, the UE 115-b may determine (e.g., based on existence of the gap identified at 610) that a PDCP context for the MSIM UE 115-b is out-of-synchronization with a PDCP context of the serving base station (e.g., base station 105-c) . The PDCP context may include a HFN and a PDCP sequence number. In some cases, the loss-of-synchronization may be determined based on an attempt to decipher the plurality of out-of-window PDCP PDUs (e.g., received at 605) using a current HFN stored at the MSIM UE 115-b. If the attempt to decipher the multiple out-of-window PDCP PDUs results in at least one of the out- of-window PDCP PDUs being invalid, the UE 115-b may determine there is a loss-of-synchronization.

In some cases, the UE 115-b may additionally attempt to decipher received PDCP PDUs using one or more additional HFNs (e.g., the one or more additional HFNs based on the stored/current HFN) . The one or more additional HFNs may be bounded by a predetermined range based on an MSIM UE gap size, available downlink bandwidth associated with an HFN, the current HFN, etc. In such cases, it may be determined that the received PDCP PDUs are valid based on the attempt to decipher the received PDCP PDUs using one of the one or more additional HFNs.

At 620, the UE 115-b may update the PDCP context to re-synchronize the PDCP context for the MSIM UE 115-b with the PDCP context of the serving base station 105-c (e.g., based on the determination at 615) . In some cases (e.g., where at least one received PDCP PDU is determined to be invalid) , updating PDCP context includes triggering an RRC connection setup procedure or RRC connection reestablishment procedure between the MSIM UE 115-b and the serving base station 105-c. In other cases (e.g., where received PDCP PDUs are determined to be valid based on attempts to decipher the received PDCP PDUs using the additional HFNs) , updating PDCP context includes resetting the current HFN and a PDCP Rx window based on the additional HFN that, when used for deciphering, resulted in the determination that the received PDCP PDUs are valid.

In some examples, the UE 115-b may maintain a counter value based on the attempt to decipher the multiple out-of-window PDCP PDUs. The counter value may be updated or incremented based on the determination that at least one of the multiple out-of-window PDCP PDUs is invalid. As discussed herein, the UE 115-b may update the PDCP context as long as the counter value satisfies a threshold (e.g., as long as the counter has not expired, exceeded some threshold, etc. ) . In some cases, the UE 115-b may release the RRC connection if the counter exceeds some threshold (e.g., if the counter or timer expires) .

FIG. 7 shows a block diagram 700 of a wireless device 705 (e.g., an MSIM UE) that supports PDCP context re-synchronization techniques for MSIM devices in accordance with aspects of the present disclosure. Wireless device 705 may be an example of aspects of a UE 115 as described herein. Wireless device 705 may include receiver 710, communications manager 715, and transmitter 720. Wireless device 705 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .

Receiver 710 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to PDCP context re-synchronization techniques for MSIM devices, etc. ) . Information may be passed on to other components of the device. The receiver 710 may be an example of aspects of the transceiver 1035 described with reference to FIG. 10. The receiver 710 may utilize a single antenna or a set of antennas.

Communications manager 715 may be an example of aspects of the communications manager 1015 described with reference to FIG. 10. Communications manager 715 and/or at least some of its various sub-components may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions of the communications manager 715 and/or at least some of its various sub-components may be executed by a general-purpose processor, a digital signal processor (DSP) , an application-specific integrated circuit (ASIC) , an field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure. The communications manager 715 and/or at least some of its various sub-components may be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations by one or more physical devices. In some examples, communications manager 715 and/or at least some of its various sub-components may be a separate and distinct component in accordance with various aspects of the present disclosure. In other examples, communications manager 715 and/or at least some of its various sub-components may be combined with one or more other hardware components, including but not limited to an I/O component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof in accordance with various aspects of the present disclosure.

Communications manager 715 may identify a gap between receipt of PDCP PDUs associated with a first SIM, the gap resulting from an MSIM procedure associated with a second SIM, and determine, based on an existence of the gap, that a PDCP context for the MSIM UE is out-of-synchronization with a PDCP context of a serving base station. The communications manager 715 may, based on the out-of-synchronization determination, update the PDCP context for the MSIM UE to re-synchronize the PDCP context for the MSIM UE with the PDCP context of the serving base station.

Transmitter 720 may transmit signals generated by other components of the device. In some examples, the transmitter 720 may be collocated with a receiver 710 in a transceiver module. For example, the transmitter 720 may be an example of aspects of the transceiver 1035 described with reference to FIG. 10. The transmitter 720 may utilize a single antenna or a set of antennas.

FIG. 8 shows a block diagram 800 of a wireless device 805 (e.g., an MSIM UE) that supports PDCP context re-synchronization techniques for MSIM devices in accordance with aspects of the present disclosure. Wireless device 805 may be an example of aspects of a wireless device 705 or a UE 115 as described with reference to FIG. 7. Wireless device 805 may include receiver 810, communications manager 815, and transmitter 820. Wireless device 805 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .

Receiver 810 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to PDCP context re-synchronization techniques for MSIM devices, etc. ) . Information may be passed on to other components of the device. The receiver 810 may be an example of aspects of the transceiver 1035 described with reference to FIG. 10. The receiver 810 may utilize a single antenna or a set of antennas.

Communications manager 815 may be an example of aspects of the communications manager 615 and/or the communications manager 1015 described with reference to FIGs. 6 and 10, respectively. Communications manager 815 may also include PDCP PDU manager 825 and PDCP context manager 830.

PDCP PDU manager 825 may identify a gap between receipt of PDCP PDUs associated with a first SIM, the gap resulting from an MSIM procedure associated with a second SIM. In some cases, determining an existence of the gap is based on an MSIM UE procedure associated with a SIM other than a SIM associated with the serving base station. In some cases, the PDCP PDU manager 825 may receive a set of out-of-window PDCP PDUs, which may be used to determine that the PDCP context for the MSIM UE is out-of-synchronization with the PDCP context of the serving base station (e.g., based on a validity check) .

PDCP context manager 830 may determine, based on an existence of the gap, that a PDCP context for the MSIM UE is out-of-synchronization with a PDCP context of a serving base station. PDCP context manager 830 may then update, based on the determination, the PDCP context for the MSIM UE to re-synchronize the PDCP context for the MSIM UE with the PDCP context of the serving base station. In some cases, the PDCP context includes a HFN and a PDCP sequence number. In some cases, updating the PDCP context (e.g., for the MSIM UE to re-synchronize the PDCP context for the MSIM UE with the PDCP context of the serving base station) may include updating the PDCP context for the MSIM UE based on usage of one or more additional HFNs. In some cases, updating the PDCP context includes resetting a current HFN and a PDCP Rx window based on one of the set of additional HFNs that resulted in the determining that the received PDCP PDUs are valid. In some cases, PDCP context manager 830 may update the PDCP context for the MSIM UE based on a counter value satisfying a threshold. In some cases, updating the PDCP context includes triggering an RRC connection setup procedure between the MSIM UE and the serving base station.

Transmitter 820 may transmit signals generated by other components of the device. In some examples, the transmitter 820 may be collocated with a receiver 810 in a transceiver module. For example, the transmitter 820 may be an example of aspects of the transceiver 1035 described with reference to FIG. 10. The transmitter 820 may utilize a single antenna or a set of antennas.

FIG. 9 shows a block diagram 900 of a communications manager 915 that supports PDCP context re-synchronization techniques for MSIM devices in accordance with aspects of the present disclosure. The communications manager 915 may be an example of aspects of a communications manager 715, a communications manager 815, or a communications manager 1015 described with reference to FIGs. 7, 8, and 10. The communications manager 915 may include PDCP PDU manager 920, PDCP context manager 925, PDCP PDU deciphering manager 930, PDCP PDU validating manager 935, RRC connection manager 940, and PDCP context synchronization counter 945. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses) .

PDCP PDU manager 920 may identify a gap between receipt of PDCP PDUs associated with a first SIM, the gap resulting from an MSIM procedure associated with a second SIM. In some cases, determining, based on an existence of the gap, that a PDCP context for the MSIM UE is out-of-synchronization with a PDCP context of a serving base station includes determining the existence of the gap is based on an MSIM UE procedure associated with a SIM other than a SIM associated with the serving base station. In some cases, determining that the PDCP context for the MSIM UE is out-of-synchronization with the PDCP context of the serving base station includes receiving a set of out-of-window PDCP PDUs.

PDCP context manager 925 may determine, based on an existence of the gap, that a PDCP context for the MSIM UE is out-of-synchronization with a PDCP context of a serving base station. The PDCP context manager 925 may update, based on the determination, the PDCP context for the MSIM UE to re-synchronize the PDCP context for the MSIM UE with the PDCP context of the serving base station. In some cases, the PDCP context includes a HFN and a PDCP sequence number. In some cases, updating the PDCP context for the MSIM UE to re-synchronize the PDCP context for the MSIM UE with the PDCP context of the serving base station includes updating the PDCP context for the MSIM UE based on usage of one of the one or more additional HFNs. In some cases, updating the PDCP context includes resetting the current HFN and a PDCP Rx window based on the one of the set of additional HFNs that resulted in the determining that the received PDCP PDUs are valid. In some cases, updating the PDCP context includes triggering an RRC connection setup procedure between the MSIM UE and the serving base station. In some cases, updating the PDCP context for the MSIM UE may be based on a counter value satisfying a threshold.

PDCP PDU deciphering manager 930 may attempt to decipher the set of out-of-window PDCP PDUs using a current HFN stored at the MSIM UE. In some cases, determining that the PDCP context for the MSIM UE is out-of-synchronization with the PDCP context of the serving base station includes attempting to decipher received PDCP PDUs using a current HFN stored at the MSIM UE. In some cases, PDCP PDU deciphering manager 930 may attempt to decipher received PDCP PDUs using one or more additional HFNs based on the stored HFN. In some cases, the one or more additional HFNs are bounded by a predetermined range based on at least one of an MSIM UE gap size, available downlink bandwidth associated with an HFN, or the current HFN. In some cases, determining that the PDCP context for the MSIM UE is out-of-synchronization with the PDCP context of the serving base station includes attempting to decipher received PDCP PDUs using a current HFN stored at the MSIM UE and one or more additional HFNs.

In some cases, PDCP PDU validating manager 935 may determine that at least one of the set of out-of-window PDCP PDUs is invalid based on the attempt to decipher the multiple out-of-window PDCP PDUs. In some cases, PDCP PDU validating manager 935 may determine that the received PDCP PDUs are valid based on the attempt to decipher the received PDCP PDUs using one of the one or more additional HFNs, and/or determine that at least one of the received PDCP PDUs is invalid based on the attempt to decipher the received PDCP PDUs.

RRC connection manager 940 may release a local RRC connection based on the counter value satisfying the threshold. In some cases, updating the PDCP context includes triggering an RRC connection setup procedure or RRC connection reestablishment procedure between the MSIM UE and the serving base station.

PDCP context synchronization counter 945 may maintain the counter value based on the attempt to decipher the multiple out-of-window PDCP PDUs. PDCP context synchronization counter 945 may update the counter value based on the determination that at least one of the multiple out-of-window PDCP PDUs is invalid. PDCP context synchronization counter 945 may maintain the counter value based on the attempt to decipher received PDCP PDUs and update the counter value based on the determination that at least one of the received PDCP PDUs is invalid. The PDCP context synchronization counter 945 may update (e.g., trigger the PDCP context manager 925 to update) the PDCP context for the MSIM UE based on the counter value satisfying a threshold.

FIG. 10 shows a diagram of a system 1000 including a device 1005 that supports PDCP context re-synchronization techniques for MSIM devices in accordance with aspects of the present disclosure. Device 1005 may be an example of or include the components of wireless device 705, wireless device 805, or a UE 115 as described above, e.g., with reference to FIGs. 7 and 8. Device 1005 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including communications manager 1015, processor 1020, memory 1025, software 1030, transceiver 1035, antenna 1040, and I/O controller 1045. These components may be in electronic communication via one or more buses (e.g., bus 1010) . Device 1005 may communicate wirelessly with one or more base stations 105.

Processor 1020 may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a central processing unit (CPU) , a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof) . In some cases, processor 1020 may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into processor 1020. Processor 1020 may be configured to execute computer-readable instructions stored in a memory to perform various functions (e.g., functions or tasks supporting PDCP context re-synchronization techniques for MSIM devices) .

Memory 1025 may include random access memory (RAM) and read only memory (ROM) . The memory 1025 may store computer-readable, computer-executable software 1030 including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory 1025 may contain, among other things, a basic input/output system (BIOS) which may control basic hardware or software operation such as the interaction with peripheral components or devices.

Software 1030 may include code to implement aspects of the present disclosure, including code to support PDCP context re-synchronization techniques for MSIM devices. Software 1030 may be stored in a non-transitory computer-readable medium such as system memory or other memory. In some cases, the software 1030 may not be directly executable by the processor but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

Transceiver 1035 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 1035 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 1035 may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1040. However, in some cases the device may have more than one antenna 1040, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

I/O controller 1045 may manage input and output signals for device 1005. I/O controller 1045 may also manage peripherals not integrated into device 1005. In some cases, I/O controller 1045 may represent a physical connection or port to an external peripheral. In some cases, I/O controller 1045 may utilize an operating system such as

or another known operating system. In other cases, I/O controller 1045 may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some cases, I/O controller 1045 may be implemented as part of a processor. In some cases, a user may interact with device 1005 via I/O controller 1045 or via hardware components controlled by I/O controller 1045.

FIG. 11 shows a flowchart illustrating a method 1100 for PDCP context re-synchronization techniques for MSIM devices in accordance with aspects of the present disclosure. The operations of method 1100 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1100 may be performed by a communications manager as described with reference to FIGs. 7 through 10. In some examples, a UE 115 may execute a set of codes to control the functional elements of the device to perform the functions described below. Additionally or alternatively, the UE 115 may perform aspects of the functions described below using special-purpose hardware.

At block 1105 a UE 115 (e.g., an MSIM UE) may identify a gap between receipt of PDCP PDUs associated with a first SIM, the gap resulting from an MSIM procedure associated with a second SIM. The operations of block 1105 may be performed according to the methods described herein. In certain examples, aspects of the operations of block 1105 may be performed by a PDCP PDU manager as described with reference to FIGs. 7 through 10.

At block 1110 the UE 115 may determine, based at least in part on an existence of the gap, that a PDCP context for the MSIM UE is out-of-synchronization with a PDCP context of a serving base station. The operations of block 1110 may be performed according to the methods described herein. In certain examples, aspects of the operations of block 1110 may be performed by a PDCP context manager as described with reference to FIGs. 7 through 10.

At block 1115 the UE 115 may update, based at least in part on the determination, the PDCP context for the MSIM UE to re-synchronize the PDCP context for the MSIM UE with the PDCP context of the serving base station. The operations of block 1115 may be performed according to the methods described herein. In certain examples, aspects of the operations of block 1115 may be performed by a PDCP context manager as described with reference to FIGs. 7 through 10.

FIG. 12 shows a flowchart illustrating a method 1200 for PDCP context re-synchronization techniques for MSIM devices in accordance with aspects of the present disclosure. The operations of method 1200 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1200 may be performed by a communications manager as described with reference to FIGs. 7 through 10. In some examples, a UE 115 may execute a set of codes to control the functional elements of the device to perform the functions described below. Additionally or alternatively, the UE 115 may perform aspects of the functions described below using special-purpose hardware.

At block 1205 a UE 115 (e.g., an MSIM UE) may identify a gap between receipt of PDCP PDUs associated with a first SIM, the gap resulting from an MSIM procedure associated with a second SIM. The operations of block 1205 may be performed according to the methods described herein. In certain examples, aspects of the operations of block 1205 may be performed by a PDCP PDU manager as described with reference to FIGs. 7 through 10.

At block 1210 the UE 115 may receive a plurality of out-of-window PDCP PDUs. The operations of block 1210 may be performed according to the methods described herein. In certain examples, aspects of the operations of block 1210 may be performed by a PDCP context manager as described with reference to FIGs. 7 through 10.

At block 1215 the UE 115 may attempt to decipher the plurality of out-of-window PDCP PDUs using a current HFN stored at the MSIM UE 115. The operations of block 1215 may be performed according to the methods described herein. In certain examples, aspects of the operations of block 1215 may be performed by a PDCP PDU deciphering manager as described with reference to FIGs. 7 through 10.

At block 1220 the UE 115 may determine that at least one of the plurality of out-of-window PDCP PDUs is invalid based at least in part on the attempt to decipher the multiple out-of-window PDCP PDUs. The operations of block 1220 may be performed according to the methods described herein. In certain examples, aspects of the operations of block 1220 may be performed by a PDCP PDU validating manager as described with reference to FIGs. 7 through 10.

At block 1225 the UE 115 may trigger an RRC connection setup procedure or RRC connection reestablishment procedure between the MSIM UE 115 and the serving base station based on the determination at block 1220. The operations of block 1225 may be performed according to the methods described herein. In certain examples, aspects of the operations of block 1225 may be performed by a PDCP context manager as described with reference to FIGs. 7 through 10.

FIG. 13 shows a flowchart illustrating a method 1300 for PDCP context re-synchronization techniques for MSIM devices in accordance with aspects of the present disclosure. The operations of method 1300 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1300 may be performed by a communications manager as described with reference to FIGs. 7 through 10. In some examples, a UE 115 may execute a set of codes to control the functional elements of the device to perform the functions described below. Additionally or alternatively, the UE 115 may perform aspects of the functions described below using special-purpose hardware.

At block 1305 a UE 115 (e.g., an MSIM UE) may identify a gap between receipt of PDCP PDUs associated with a first SIM, the gap resulting from an MSIM procedure associated with a second SIM. The operations of block 1305 may be performed according to the methods described herein. In certain examples, aspects of the operations of block 1305 may be performed by a PDCP PDU manager as described with reference to FIGs. 7 through 10.

At block 1310 the UE 115 may receive a plurality of out-of-window PDCP PDUs. The operations of block 1310 may be performed according to the methods described herein. In certain examples, aspects of the operations of block 1310 may be performed by a PDCP context manager as described with reference to FIGs. 7 through 10.

At block 1315 the UE 115 may attempt to decipher the set of out-of-window PDCP PDUs using a current HFN stored at the MSIM UE. The operations of block 1315 may be performed according to the methods described herein. In certain examples, aspects of the operations of block 1315 may be performed by a PDCP PDU deciphering manager as described with reference to FIGs. 7 through 10.

At block 1320 the UE 115 may maintain a counter value based on the attempt to decipher the multiple out-of-window PDCP PDUs. The operations of block 1320 may be performed according to the methods described herein. In certain examples, aspects of the operations of block 1320 may be performed by a PDCP PDU validating manager as described with reference to FIGs. 7 through 10.

At block 1325 the UE 115 may determine that at least one of the set of out-of-window PDCP PDUs is invalid based on the attempt to decipher the multiple out-of-window PDCP PDUs. The operations of block 1325 may be performed according to the methods described herein. In certain examples, aspects of the operations of block 1325 may be performed by a PDCP context synchronization counter as described with reference to FIGs. 7 through 10.

At block 1330 the UE 115 may update the counter value based on the determination that at least one of the multiple out-of-window PDCP PDUs is invalid. As discussed in more detail with reference to FIG. 3, in some cases, the UE 115 may maintain and update the counter based on reception of the out-of-window PDCP PDUs. That is, in some examples, block 1315 and block 1325 may be omitted, such that the counter value is maintained based on reception of out-of-window PDCP PDUs, and the counter value is updated (e.g., incremented) based on the received out-of-window PDCP PDUs (e.g., the counter is incremented with each received out-of-window PDCP PDU) . The operations of block 1330 may be performed according to the methods described herein. In certain examples, aspects of the operations of block 1330 may be performed by a PDCP context synchronization counter as described with reference to FIGs. 7 through 10.

At block 1335 the UE 115 may update the PDCP context for the MSIM UE based on the counter value satisfying a threshold. The operations of block 1335 may be performed according to the methods described herein. In certain examples, aspects of the operations of block 1335 may be performed by a PDCP context manager as described with reference to FIGs. 7 through 10.

FIG. 14 shows a flowchart illustrating a method 1400 for PDCP context re-synchronization techniques for MSIM devices in accordance with aspects of the present disclosure. The operations of method 1400 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1400 may be performed by a communications manager as described with reference to FIGs. 7 through 10. In some examples, a UE 115 may execute a set of codes to control the functional elements of the device to perform the functions described below. Additionally or alternatively, the UE 115 may perform aspects of the functions described below using special-purpose hardware.

At block 1405 a UE 115 (e.g., an MSIM UE) may identify a gap between receipt of PDCP PDUs associated with a first SIM, the gap resulting from an MSIM procedure associated with a second SIM. The operations of block 1405 may be performed according to the methods described herein. In certain examples, aspects of the operations of block 1405 may be performed by a PDCP PDU manager as described with reference to FIGs. 7 through 10.

At block 1410 the UE 115 may receive a plurality of out-of-window PDCP PDUs. The operations of block 1410 may be performed according to the methods described herein. In certain examples, aspects of the operations of block 1410 may be performed by a PDCP context manager as described with reference to FIGs. 7 through 10.

At block 1415 the UE 115 may attempt to decipher received PDCP PDUs using a current HFN stored at the MSIM UE. The operations of block 1415 may be performed according to the methods described herein. In certain examples, aspects of the operations of block 1415 may be performed by a PDCP context manager as described with reference to FIGs. 7 through 10.

At block 1420 the UE 115 may attempt to decipher received PDCP PDUs using one or more additional HFNs based on the stored HFN. The operations of block 1420 may be performed according to the methods described herein. In certain examples, aspects of the operations of block 1420 may be performed by a PDCP PDU deciphering manager as described with reference to FIGs. 7 through 10.

At block 1425 the UE 115 may determine that the received PDCP PDUs are valid based on the attempt to decipher the received PDCP PDUs using one of the one or more additional HFNs. The operations of block 1425 may be performed according to the methods described herein. In certain examples, aspects of the operations of block 1425 may be performed by a PDCP PDU validating manager as described with reference to FIGs. 7 through 10.

At block 1430 the UE 115 may update the PDCP context for the MSIM UE based on the HFN of the one or more additional HFNs by resetting the current HFN and a PDCP Rx window based at least in part on the HFN of the one or more additional HFNs that resulted in the determining that the received PDCP PDUs are valid. The operations of block 1430 may be performed according to the methods described herein. In certain examples, aspects of the operations of block 1430 may be performed by a PDCP context manager as described with reference to FIGs. 7 through 10.

It should be noted that the methods described above describe possible implementations, and that the operations and the steps may be rearranged or otherwise modified and that other implementations are possible. Further, aspects from two or more of the methods may be combined.

Techniques described herein may be used for various wireless communications systems such as 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) , and other systems. A CDMA system may implement a radio technology such as CDMA2000, Universal Terrestrial Radio Access (UTRA) , etc. CDMA2000 covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releases may be commonly referred to as CDMA2000 1X, 1X, etc. IS-856 (TIA-856) is commonly referred to as CDMA2000 1xEV-DO, High Rate Packet Data (HRPD) , etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. A TDMA system may implement a radio technology such as Global System for Mobile Communications (GSM) .

An OFDMA system may implement a radio technology such as Ultra Mobile Broadband (UMB) , Evolved UTRA (E-UTRA) , Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunications System (UMTS) . LTE and LTE-Aare releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, NR, and GSM are described in documents from the organization named “3rd Generation Partnership Project” (3GPP) . CDMA2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2) . The techniques described herein may be used for the systems and radio technologies mentioned above as well as other systems and radio technologies. While aspects of an LTE or an NR system may be described for purposes of example, and LTE or NR terminology may be used in much of the description, the techniques described herein are applicable beyond LTE or NR applications.

A macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs 115 with service subscriptions with the network provider. A small cell may be associated with a lower-powered base station 105, as compared with a macro cell, and a small cell may operate in the same or different (e.g., licensed, unlicensed, etc. ) frequency bands as macro cells. Small cells may include pico cells, femto cells, and micro cells according to various examples. A pico cell, for example, may cover a small geographic area and may allow unrestricted access by UEs 115 with service subscriptions with the network provider. A femto cell may also cover a small geographic area (e.g., a home) and may provide restricted access by UEs 115 having an association with the femto cell (e.g., UEs 115 in a closed subscriber group (CSG) , UEs 115 for users in the home, and the like) . An eNB for a macro cell may be referred to as a macro eNB. An eNB for a small cell may be referred to as a small cell eNB, a pico eNB, a femto eNB, or a home eNB. An eNB may support one or multiple (e.g., two, three, four, and the like) cells, and may also support communications using one or multiple component carriers.

The wireless communications system 100 or systems described herein may support synchronous or asynchronous operation. For synchronous operation, the base stations 105 may have similar frame timing, and transmissions from different base stations 105 may be approximately aligned in time. For asynchronous operation, the base stations 105 may have different frame timing, and transmissions from different base stations 105 may not be aligned in time. The techniques described herein may be used for either synchronous or asynchronous operations.

Information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

The various illustrative blocks and modules described in connection with the disclosure herein 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 conventional 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, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration) .

The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the disclosure and appended claims. For example, due to the nature of software, functions described above can be implemented using software executed by a processor, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations.

Computer-readable media includes both non-transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A non-transitory storage medium may be any available medium that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, non-transitory computer-readable media may comprise random-access memory (RAM) , read-only memory (ROM) , electrically erasable programmable read only memory (EEPROM) , flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. 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, 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 CD, laser disc, optical disc, digital versatile disc (DVD) , floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media.

As used herein, including in the claims, “or” as used in a list of items (e.g., a list of items prefaced by a phrase such as “at least one of” or “one or more of” ) indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C) . Also, as used herein, the phrase “based on” shall not be construed as a reference to a closed set of conditions. For example, an exemplary step that is described as “based on condition A” may be based on both a condition A and a condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase “based on” shall be construed in the same manner as the phrase “based at least in part on. ”

In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If just the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label, or other subsequent reference label.

The description set forth herein, in connection with the appended drawings, describes example configurations and does not represent all the examples that may be implemented or that are within the scope of the claims. The term “exemplary” used herein means “serving as an example, instance, or illustration, ” and not “preferred” or “advantageous over other examples. ” The detailed description includes specific details for the purpose of providing an understanding of the described techniques. These techniques, however, may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples.

The description herein is provided to enable a person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not limited to the examples and designs described herein, but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.

Claims

A method for wireless communication at a multiple subscriber identity module (MSIM) user equipment (UE) , comprising:

identifying, at the MSIM UE, a gap between receipt of packet data convergence protocol (PDCP) packet data units (PDUs) associated with a first SIM, the gap resulting from an MSIM procedure associated with a second SIM;

determining, based at least in part on an existence of the gap, that a PDCP context for the MSIM UE is out-of-synchronization with a PDCP context of a serving base station; and

updating, based at least in part on the determination, the PDCP context for the MSIM UE to re-synchronize the PDCP context for the MSIM UE with the PDCP context of the serving base station.
The method of claim 1, wherein determining that the PDCP context for the MSIM UE is out-of-synchronization with the PDCP context of the serving base station comprises:

receiving a plurality of out-of-window PDCP PDUs;

attempting to decipher the plurality of out-of-window PDCP PDUs using a current hyper frame number (HFN) stored at the MSIM UE; and

determining that at least one of the plurality of out-of-window PDCP PDUs is invalid based at least in part on the attempt to decipher the multiple out-of-window PDCP PDUs.
The method of claim 2, wherein updating the PDCP context comprises:

triggering a radio resource control (RRC) connection setup procedure or RRC connection reestablishment procedure between the MSIM UE and the serving base station.
The method of claim 2, further comprising:

maintaining a counter value based at least in part on the attempt to decipher the multiple out-of-window PDCP PDUs;

updating the counter value based at least in part on the determination that at least one of the multiple out-of-window PDCP PDUs is invalid; and

updating the PDCP context for the MSIM UE based at least in part on the counter value satisfying a threshold.
The method of claim 2, further comprising:

maintaining a counter value based at least in part on the received plurality of out-of-window PDCP PDUs;

updating the counter value based at least in part on the received plurality of out-of-window PDCP PDUs; and

updating the PDCP context for the MSIM UE based at least in part on the counter value satisfying a threshold.
The method of claim 4, further comprising:

releasing a local radio resource control (RRC) connection based at least in part on the counter value satisfying the threshold.
The method of claim 1, wherein determining that the PDCP context for the MSIM UE is out-of-synchronization with the PDCP context of the serving base station comprises:

attempting to decipher received PDCP PDUs using a current hyper frame number (HFN) stored at the MSIM UE;

attempting to decipher received PDCP PDUs using one or more additional HFNs based on the stored HFN;

determining that the received PDCP PDUs are valid based on the attempt to decipher the received PDCP PDUs using one of the one or more additional HFNs; and

wherein updating the PDCP context for the MSIM UE to re-synchronize the PDCP context for the MSIM UE with the PDCP context of the serving base station includes updating the PDCP context for the MSIM UE based on the one of the one or more additional HFNs.
The method of claim 7, wherein updating the PDCP context comprises:

resetting the current HFN and a PDCP receive (Rx) window based at least in part on the one of the one or more additional HFNs that resulted in the determining that the received PDCP PDUs are valid.
The method of claim 7, wherein the one or more additional HFNs are bounded by a predetermined range based on at least one of an MSIM UE gap size, available downlink bandwidth associated with an HFN, or the current HFN.
The method of claim 1, wherein determining that the PDCP context for the MSIM UE is out-of-synchronization with the PDCP context of the serving base station comprises:

attempting to decipher received PDCP PDUs using a current hyper frame number (HFN) stored at the MSIM UE and one or more additional HFNs; and

determining that at least one of the received PDCP PDUs is invalid based on the attempt to decipher the received PDCP PDUs.
The method of claim 10, wherein updating the PDCP context comprises:

triggering an radio resource control (RRC) connection setup procedure between the MSIM UE and the serving base station.
The method of claim 10, further comprising:

maintaining a counter value based at least in part on the attempt to decipher received PDCP PDUs;

updating the counter value based at least in part on the determination that at least one of the received PDCP PDUs is invalid; and

updating the PDCP context for the MSIM UE based at least in part on the counter value satisfying a threshold.
The method of claim 1, wherein the PDCP context includes a hyper frame number (HFN) and a PDCP sequence number.
The method of claim 1, wherein determining, based at least in part on an existence of the gap, that a PDCP context for the MSIM UE is out-of-synchronization with a PDCP context of a serving base station includes determining the existence of the gap is based on the MSIM UE procedure, wherein the MSIM UE procedure is associated with a SIM other than a SIM associated with the serving base station.
An apparatus for wireless communication at a multiple subscriber identity module (MSIM) user equipment (UE) , comprising:

a processor;

memory in electronic communication with the processor; and

instructions stored in the memory and operable, when executed by the processor, to cause the apparatus to:

identify, at the MSIM UE, a gap between receipt of packet data convergence protocol (PDCP) packet data units (PDUs) associated with a first SIM, the gap resulting from an MSIM procedure associated with a second SIM;

determine, based at least in part on an existence of the gap, that a PDCP context for the MSIM UE is out-of-synchronization with a PDCP context of a serving base station; and

update, based at least in part on the determination, the PDCP context for the MSIM UE to re-synchronize the PDCP context for the MSIM UE with the PDCP context of the serving base station.
The apparatus of claim 15, wherein the instructions executable by the processor to determine that the PDCP context for the MSIM UE is out-of-synchronization with the PDCP context of the serving base station comprises instructions further executable by the processor to:

receive a plurality of out-of-window PDCP PDUs;

attempt to decipher the plurality of out-of-window PDCP PDUs using a current hyper frame number (HFN) stored at the MSIM UE; and

determine that at least one of the plurality of out-of-window PDCP PDUs is invalid based at least in part on the attempt to decipher the multiple out-of-window PDCP PDUs.
The apparatus of claim 16, wherein the instructions executable by the processor to update the PDCP context comprises instructions further executable by the processor to:

trigger a radio resource control (RRC) connection setup procedure or RRC connection reestablishment procedure between the MSIM UE and the serving base station.
The apparatus of claim 16, wherein the instructions are further executable by the processor to:

maintain a counter value based at least in part on the attempt to decipher the multiple out-of-window PDCP PDUs;

update the counter value based at least in part on the determination that at least one of the multiple out-of-window PDCP PDUs is invalid; and

update the PDCP context for the MSIM UE based at least in part on the counter value satisfying a threshold.
The apparatus of claim 16, wherein the instructions are further executable by the processor to:

maintain a counter value based at least in part on the received plurality of out-of-window PDCP PDUs;

update the counter value based at least in part on the received plurality of out-of-window PDCP PDUs; and

update the PDCP context for the MSIM UE based at least in part on the counter value satisfying a threshold.
The apparatus of claim 18, wherein the instructions are further executable by the processor to:

release a local radio resource control (RRC) connection based at least in part on the counter value satisfying the threshold.
The apparatus of claim 15, wherein the instructions executable by the processor to determine that the PDCP context for the MSIM UE is out-of-synchronization with the PDCP context of the serving base station comprises instructions further executable by the processor to:

attempt to decipher received PDCP PDUs using a current hyper frame number (HFN) stored at the MSIM UE;

attempt to decipher received PDCP PDUs using one or more additional HFNs based on the stored HFN;

determine that the received PDCP PDUs are valid based on the attempt to decipher the received PDCP PDUs using one of the one or more additional HFNs; and

wherein the instructions executable by the processor to update the PDCP context for the MSIM UE to re-synchronize the PDCP context for the MSIM UE with the PDCP context of the serving base station includes instructions executable by the processor to update the PDCP context for the MSIM UE based on the one of the one or more additional HFNs.
The apparatus of claim 21, wherein the instructions executable by the processor to update the PDCP context comprises instructions further executable by the processor to:

reset the current HFN and a PDCP receive (Rx) window based at least in part on the one of the one or more additional HFNs that resulted in the determining that the received PDCP PDUs are valid.
The apparatus of claim 21, wherein the one or more additional HFNs are bounded by a predetermined range based on at least one of an MSIM UE gap size, available downlink bandwidth associated with an HFN, or the current HFN.
The apparatus of claim 15, wherein the instructions executable by the processor to determine that the PDCP context for the MSIM UE is out-of-synchronization with the PDCP context of the serving base station comprises instructions further executable by the processor to:

attempt to decipher received PDCP PDUs using a current hyper frame number (HFN) stored at the MSIM UE and one or more additional HFNs; and

determine that at least one of the received PDCP PDUs is invalid based on the attempt to decipher the received PDCP PDUs.
The apparatus of claim 24, wherein the instructions executable by the processor to update the PDCP context comprises instructions further executable by the processor to:

trigger an radio resource control (RRC) connection setup procedure between the MSIM UE and the serving base station.
The apparatus of claim 24, wherein the instructions are further executable by the processor to:

maintain a counter value based at least in part on the attempt to decipher received PDCP PDUs;

update the counter value based at least in part on the determination that at least one of the received PDCP PDUs is invalid; and

update the PDCP context for the MSIM UE based at least in part on the counter value satisfying a threshold.
The apparatus of claim 15, wherein the PDCP context includes a hyper frame number (HFN) and a PDCP sequence number.
The apparatus of claim 15, wherein the instructions executable by the processor to determine, based at least in part on an existence of the gap, that a PDCP context for the MSIM UE is out-of-synchronization with a PDCP context of a serving base station include instructions further executable by the processor to determine the existence of the gap is based on the MSIM UE procedure, wherein the MSIM UE procedure is associated with a SIM other than a SIM associated with the serving base station.
An apparatus for wireless communication at a multiple subscriber identity module (MSIM) user equipment (UE) , comprising:

means for identifying, at the MSIM UE, a gap between receipt of packet data convergence protocol (PDCP) packet data units (PDUs) associated with a first SIM, the gap resulting from an MSIM procedure associated with a second SIM;

means for determining, based at least in part on an existence of the gap, that a PDCP context for the MSIM UE is out-of-synchronization with a PDCP context of a serving base station; and

means for updating, based at least in part on the determination, the PDCP context for the MSIM UE to re-synchronize the PDCP context for the MSIM UE with the PDCP context of the serving base station.
A non-transitory computer readable medium storing code for wireless communication, the code comprising instructions executable by a processor to:

identify, at a multiple subscriber identity module (MSIM) user equipment (UE) , a gap between receipt of packet data convergence protocol (PDCP) packet data units (PDUs) associated with a first SIM, the gap resulting from an MSIM procedure associated with a second SIM;

determine, based at least in part on an existence of the gap, that a PDCP context for the MSIM UE is out-of-synchronization with a PDCP context of a serving base station; and

update, based at least in part on the determination, the PDCP context for the MSIM UE to re-synchronize the PDCP context for the MSIM UE with the PDCP context of the serving base station.