WO2023117080A1

WO2023117080A1 - Master cell group-failure recovery and uplink data transmission via deactivated secondary cell group for wireless networks

Info

Publication number: WO2023117080A1
Application number: PCT/EP2021/087301
Authority: WO
Inventors: Faranaz SABOURI-SICHANI; Subramanya CHANDRASHEKAR; Henri Markus Koskinen; Jarkko Tuomo Koskela; Amaanat ALI; Lars Dalsgaard
Original assignee: Nokia Technologies Oy
Priority date: 2021-12-22
Filing date: 2021-12-22
Publication date: 2023-06-29

Abstract

A method includes configuring, by a user device, dual connectivity including a master cell group associated with a first network node that is configured as a master node for dual connectivity for the user device and a secondary cell group associated with a second network node that is configured as a secondary node; determining, by the user device, that the secondary cell group is deactivated; receiving, by the user device, a small data transmission configuration for the secondary cell group; detecting, by the user device, a need to transmit data to the secondary cell group; determining that the small data transmission configuration for the secondary cell group can be used for a data transmission; and transmitting, by the user device, data via the secondary cell group to the second network node utilizing a small data transmission according to the small data transmission configuration.

Description

DESCRIPTION

MASTER CELL GROUP-FAILURE RECOVERY AND UPLINK DATA

TRANSMISSION VIA DEACTIVATED SECONDARY CELL GROUP FOR WIRELESS

NETWORKS

TECHNICAL FIELD

[1] This description relates to wireless communications.

BACKGROUND

[2] A communication system may be a facility that enables communication between two or more nodes or devices, such as fixed or mobile communication devices. Signals can be carried on wired or wireless carriers.

[3] An example of a cellular communication system is an architecture that is being standardized by the 3^rd Generation Partnership Project (3 GPP). A recent development in this field is often referred to as the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. E-UTRA (evolved UMTS Terrestrial Radio Access) is the air interface of 3GPP's Long Term Evolution (LTE) upgrade path for mobile networks. In LTE, base stations or access points (APs), which are referred to as enhanced Node AP (eNBs), provide wireless access within a coverage area or cell. In LTE, mobile devices, or mobile stations are referred to as user equipments (UE). LTE has included a number of improvements or developments. Aspects of LTE are also continuing to improve.

[4] 5G New Radio (NR) development is part of a continued mobile broadband evolution process to meet the requirements of 5G, similar to earlier evolution of 3G & 4G wireless networks. In addition, 5G is also targeted at the new emerging use cases in addition to mobile broadband. A goal of 5G is to provide significant improvement in wireless performance, which may include new levels of data rate, latency, reliability, and security.

5G NR may also scale to efficiently connect the massive Internet of Things (loT) and may offer new types of mission-critical services. For example, ultra-reliable and low-latency communications (URLLC) devices may require high reliability and very low latency. SUMMARY

[5] According to an example embodiment, a method may include: configuring, by a user device, dual connectivity including a master cell group associated with a first network node that is configured as a master node for dual connectivity for the user device and a secondary cell group associated with a second network node that is configured as a secondary node; determining, by the user device, that the secondary cell group is deactivated; receiving, by the user device, a small data transmission configuration for the secondary cell group; detecting, by the user device, a need to transmit data to the secondary cell group; determining that the small data transmission configuration for the secondary cell group can be used for a data transmission; and transmitting, by the user device, data via the secondary cell group to the second network node utilizing a small data transmission according to the small data transmission configuration.

[6] According to an example embodiment, a method may include: configuring, by a second network node configured as a secondary node as part of a dual connectivity for a user device, a secondary cell group associated with the second network node; determining, by the second network node, that the secondary cell group is deactivated; transmitting, by the second network node to a first network node configured as a master node that provides a master cell group for the dual connectivity for the user device, a small data transmission configuration for the secondary cell group, to be forwarded by the first network node to the user device; and receiving data by the second network node from the user device via the secondary cell group while the secondary cell group is deactivated for the user device, wherein the data is received by the second network node via a small data transmission according to the small data transmission configuration.

[7] Other example embodiments are provided or described for each of the example methods, including: means for performing any of the example methods; a non-transitory computer-readable storage medium comprising instructions stored thereon that, when executed by at least one processor, are configured to cause a computing system to perform any of the example methods; and an apparatus including at least one processor, and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform any of the example methods.

[8] The details of one or more examples of embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[9] FIG. 1 is a block diagram of a wireless network according to an example embodiment.

[10] FIG. 2 is a diagram illustrating a secondary cell group (SCG) deactivation procedure according to an example embodiment.

[11] FIG. 3A is a diagram illustrating a small data transmission using a 4-step random access (RACH) procedure according to an example embodiment.

[12] FIG. 3B is a diagram illustrating a small data transmission using a 2-step random access (RACH) procedure according to an example embodiment.

[13] FIG. 3C is a diagram illustrating a configured grant based SDT procedure according to an example embodiment.

[14] FIG. 4 is a diagram illustrating operation of a system in which data (e.g., data and/or MCG failure information, or other information) may be transmitted via configured grant based small data transmission (SDT) transmission according to an example embodiment.

[15] FIG. 5 is a diagram illustrating operation of a system in which data (e.g., data and/or MCG failure information, or other information) may be transmitted via random access (RACH) procedure based small data transmission (SDT) transmission according to an example embodiment.

[16] FIG. 6 is a flow chart illustrating operation of a user device (or UE) according to an example embodiment.

[17] FIG. 7 is a flow chart illustrating operation of a secondary node according to an example embodiment.

[18] FIG. 8 is a block diagram of a wireless station or node (e.g., AP, BS, RAN node, DU, UE or user device, or network node).

DETAIEED DESCRIPTION

[19] FIG. 1 is a block diagram of a wireless network 130 according to an example embodiment. In the wireless network 130 of FIG. 1, user devices 131, 132, 133 and 135, which may also be referred to as mobile stations (MSs) or user equipment (UEs), may be connected (and in communication) with a base station (BS) 134, which may also be referred to as an access point (AP), an enhanced Node B (eNB), a gNB or a network node. The terms user device and user equipment (UE) may be used interchangeably. A BS may also include or may be referred to as a RAN (radio access network) node, and may include a portion of a BS or a portion of a RAN node, such as (e.g., such as a centralized unit (CU) and/or a distributed unit (DU) in the case of a split BS or split gNB). At least part of the functionalities of a BS (e.g., access point (AP), base station (BS) or (e)Node B (eNB), gNB, RAN node) may also be carried out by any node, server or host which may be operably coupled to a transceiver, such as a remote radio head. BS (or AP) 134 provides wireless coverage within a cell 136, including to user devices (or UEs) 131, 132, 133 and 135. Although only four user devices (or UEs) are shown as being connected or attached to BS 134, any number of user devices may be provided. BS 134 is also connected to a core network 150 via a SI interface 151. This is merely one simple example of a wireless network, and others may be used.

[20] A base station (e.g., such as BS 134) is an example of a radio access network (RAN) node within a wireless network. A BS (or a RAN node) may be or may include (or may alternatively be referred to as), e.g., an access point (AP), a gNB, an eNB, or portion thereof (such as a /centralized unit (CU) and/or a distributed unit (DU) in the case of a split BS or split gNB), or other network node.

[21 ] According to an illustrative example, a BS node (e.g., BS, eNB, gNB, CU/DU, ...) or a radio access network (RAN) may be part of a mobile telecommunication system. A RAN (radio access network) may include one or more BSs or RAN nodes that implement a radio access technology, e.g., to allow one or more UEs to have access to a network or core network. Thus, for example, the RAN (RAN nodes, such as BSs or gNBs) may reside between one or more user devices or UEs and a core network. According to an example embodiment, each RAN node (e.g., BS, eNB, gNB, CU/DU, ...) or BS may provide one or more wireless communication services for one or more UEs or user devices, e.g., to allow the UEs to have wireless access to a network, via the RAN node. Each RAN node or BS may perform or provide wireless communication services, e.g., such as allowing UEs or user devices to establish a wireless connection to the RAN node, and sending data to and/or receiving data from one or more of the UEs. For example, after establishing a connection to a UE, a RAN node or network node (e.g., BS, eNB, gNB, CU/DU, ...) may forward data to the UE that is received from a network or the core network, and/or forward data received from the UE to the network or core network. RAN nodes or network nodes (e.g., BS, eNB, gNB, CU/DU, ...) may perform a wide variety of other wireless functions or services, e.g., such as broadcasting control information (e.g., such as system information or on-demand system information) to UEs, paging UEs when there is data to be delivered to the UE, assisting in handover of a UE between cells, scheduling of resources for uplink data transmission from the UE(s) and downlink data transmission to UE(s), sending control information to configure one or more UEs, and the like. These are a few examples of one or more functions that a RAN node or BS may perform.

[22] A user device (user terminal, user equipment (UE), mobile terminal, handheld wireless device, etc.) may refer to a portable computing device that includes wireless mobile communication devices operating either with or without a subscriber identification module (SIM), including, but not limited to, the following types of devices: a mobile station (MS), a mobile phone, a cell phone, a smartphone, a personal digital assistant (PDA), a handset, a device using a wireless modem (alarm or measurement device, etc.), a laptop and/or touch screen computer, a tablet, a phablet, a game console, a notebook, a vehicle, a sensor, and a multimedia device, as examples, or any other wireless device. It should be appreciated that a user device may also be (or may include) a nearly exclusive uplink only device, of which an example is a camera or video camera loading images or video clips to a network.

[23] In LTE (as an illustrative example), core network 150 may be referred to as Evolved Packet Core (EPC), which may include a mobility management entity (MME) which may handle or assist with mobility /handover of user devices between BSs, one or more gateways that may forward data and control signals between the BSs and packet data networks or the Internet, and other control functions or blocks. Other types of wireless networks, such as 5G (which may be referred to as New Radio (NR)) may also include a core network.

[24] In addition, the techniques described herein may be applied to various types of user devices or data service types, or may apply to user devices that may have multiple applications running thereon that may be of different data service types. New Radio (5G) development may support a number of different applications or a number of different data service types, such as for example: machine type communications (MTC), enhanced machine type communication (eMTC), Internet of Things (loT), and/or narrowband loT user devices, enhanced mobile broadband (eMBB), and ultra-reliable and low-latency communications (URLLC). Many of these new 5G (NR) - related applications may require generally higher performance than previous wireless networks.

[25] loT may refer to an ever-growing group of objects that may have Internet or network connectivity, so that these objects may send information to and receive information from other network devices. For example, many sensor type applications or devices may monitor a physical condition or a status, and may send a report to a server or other network device, e.g., when an event occurs. Machine Type Communications (MTC, or Machine to Machine communications) may, for example, be characterized by fully automatic data generation, exchange, processing and actuation among intelligent machines, with or without intervention of humans. Enhanced mobile broadband (eMBB) may support much higher data rates than currently available in LTE.

[26] Ultra-reliable and low-latency communications (URLLC) is a new data service type, or new usage scenario, which may be supported for New Radio (5G) systems. This enables emerging new applications and services, such as industrial automations, autonomous driving, vehicular safety, e-health services, and so on. 3GPP targets in providing connectivity with reliability corresponding to block error rate (BLER) of 10'⁵ and up to 1 ms U-Plane (user/data plane) latency, by way of illustrative example. Thus, for example, URLLC user devices/UEs may require a significantly lower block error rate than other types of user devices/UEs as well as low latency (with or without requirement for simultaneous high reliability). Thus, for example, a URLLC UE (or URLLC application on a UE) may require much shorter latency, as compared to a eMBB UE (or an eMBB application running on a UE).

[27] The techniques described herein may be applied to a wide variety of wireless technologies or wireless networks, such as LTE, LTE-A, 5G (New Radio (NR)), cmWave, and/or mmWave band networks, loT, MTC, eMTC, eMBB, URLLC, etc., or any other wireless network or wireless technology. These example networks, technologies or data service types are provided only as illustrative examples.

[28] In dual-connectivity (or more generally referred to as multi-connectivity), a UE (or user device) may be connected to multiple base stations or network nodes simultaneously, where the network nodes may be of the same or different radio access technologies (RATs). Thus, for multi-connectivity, each of the network nodes may be an eNB, gNB, or other network node. For example, one of the network nodes may be referred to as a master node (MN) (e.g., master gNB (MgNB) or master eNB (MeNB)), while another network node may be referred to as a secondary node (SN) (e.g., a secondary gNB (SgNB) or secondary eNB (SeNB)), e.g, with respect to the classical BS architecture. For dual or multi-connectivity, the UE may, for example, establish a first connection to a MN, and then establish a second connection to a SN. For each of the network nodes (MN or SN) that the UE is connected to, the UE may be able to communicate and/or receive data via multiple (a plurality of) cells, e.g., using carrier aggregation (CA). The cells of the MN may be referred to as a master cell group (MCG), while the cells of a SN may be referred to as a secondary cell group (SCG).

[29] In the case of dual or multi-connectivity, the first cell (of the master cell group (MCG)) within the MN to which the UE connects is typically known as the Primary Cell (PCell), while the first cell (of the secondary cell group (SCG)) within the SN to which the UE connects is typically known as the Primary Secondary Cell (PSCell), which serves as a primary cell as far as the UE’s connectivity to the SN is concerned. The PCell and the PSCell are each allocated physical uplink control channel (PUCCH) resources to allow the UE to send HARQ ACK/NACK (acknowledgement/negative acknowledgement) feedback, and other control information, to the MCG (or MN) and SCG (or SN), respectively.

[30] Handover (HO) (or PCell change) procedures may be used in 5G NR to allow a change or handover of the UE from a source network node to a target network node, e.g., to maintain robustness of connection between a user equipment (UE) and a wireless network over different cells. A primary-cell (PCell) change may be performed for a UE for both MN and SN, e.g., based on measurement reports and/or a cell-change trigger condition being satisfied.

[31] After a secondary cell group (SCG) for the UE (as part of dual connectivity) has been activated, the SCG may subsequently be released, which causes the connection between the UE and the SCG/SN to be released or disconnected (the UE would no longer have an RRC configuration with respect to the secondary cell group (or with respect to the primary secondary cell of the SCG)). After being disconnected from the SCG/SN, the UE may typically be required to perform a random access (RACH) procedure to a (e.g., new) secondary cell group to establish a new connection with a primary secondary cell (PSCell), which may typically introduce or require significant latency and signaling overhead to establish a connection to a SCG or SN, as part of dual connectivity. [32] According to an example embodiment, in order to decrease this latency, rather than releasing the SCG for the UE (which would cause the UE to no longer be connected to the PSCell of the SCG), the SCG may alternatively be deactivated (suspended), e.g., in the event that the SCG is no longer needed for the UE, such as if traffic for the UE decreases below some threshold and/or such SCG is not be needed for a time period for the UE to transmit and/or receive data. By deactivating the SCG for the UE, the radio bearers for the SCG will remain in place (will remain mapped to the SCG for the UE), the UE context may remain stored at the secondary node (SN) for the SCG and UE, and the UE may continue to send neighbor cell measurement reports to the network (e.g., to the SN (secondary node) and MN (master node)). However, after the SCG for the UE is deactivated, the secondary node (SN) will not schedule the UE for uplink or downlink transmission via the SCG, and the UE will not monitor the physical downlink control channel (PDCCH) of the SCG/SN for scheduling information for the UE, in order to allow the UE to conserve power. The SCG may be deactivated, and may later be reactivated.

[33] Also, a SCG may be added or configured by MN in a deactivated state (e.g., a deactivated SCG may be added or configured for UE dual connectivity). Thus, for example, the UE and/or SN may determine that a SCG is deactivated by either: 1) UE or SN sends and/or receives a deactivation request for the SCG (which is currently active); or, 2) a deactivated SCG has been added or configured by MN for the UE (a SCG added that is in a deactivated state).

[34] According to an example embodiment, dual connectivity may be initiated by MN based on traffic requirements or traffic demands for a UE. The procedure to provide dual connectivity may start with a SN-addition request sent by MN to SN. After receiving the SCG configuration from SN (in reply to SN-addition request), the MN may send a RRC reconfiguration to the UE with the received SCG configuration received from SN. The SCG may be added in either an activated or a deactivated state (when added to the dual connectivity for the UE).

[35] FIG. 2 is a diagram illustrating a secondary cell group (SCG) deactivation procedure according to an example embodiment. As shown in FIG. 2, a UE 210 may be operating in dual connectivity and connected (e.g., at step 1) to a master node (MN) 212 and a secondary node (SN) 214. At step 2, inactivity (e.g., lack of transmitting and/or receiving data) over the UE-SCG connection may be detected by either the UE 210 or the network (e.g., SN or MN). Because the radio bearers mapped on the SCG may be anchored at the MN or SN, either the MN or SN may detect SCG inactivity. At step 3, if SN detects inactivity, the SN 214 may send a suspend/deactivate SCG indication to MN 212 (to cause deactivation or suspension of the SCG). At steps 4-5, MN 212 may send SCG suspend (or SCG deactivate) request to UE 210. Alternatively, the UE may send a deactivation (or suspend) request to MN 212 and/or SN 214 to request deactivation or suspension of the SCG. At steps 6-7, the UE may send a SCG suspend/ (or deactivation) complete (confirming that the SCG has been deactivated or suspended) via MN 212 to SN 214. At step 8, the UE 210 continues to measure neighbor cells and send measurement reports to the network (e.g., to SN 214 and/or MN 212), but ceases monitoring (at least while SCG is deactivated) the PDCCH for SCG/SN for control information (e.g., scheduling information directed to the UE 210) that may be transmitted by SN 214 to the UE 210 in order for the UE 210 to save power.

[36] A UE may be in one of multiple (e.g., three) states (for example, one of three Radio Resource Control (RRC) states) with respect to a network. In an Idle state (RRC Idle), there is typically no (or limited) RRC context (where a RRC context may include information or parameters necessary for communication between the UE and gNB/network node) stored in the RAN (radio access network) node (e.g., gNB) or network node, or UE. From a core network perspective, the Idle UE is in an Idle (CM_Idle) state. No data transfer may typically occur between a UE and network node (e.g., gNB) when the UE is in an Idle state. In an Idle state, a UE may typically periodically wake up to receive possible paging messages from the network.

[37] A UE may transition from Idle state (e.g., RRC Idle) to a Connected state (e.g., RRC Connected state) by performing a random access (RACH) procedure with the gNB or network node. As part of the RACH procedure, both the UE and network node (e.g., gNB) may obtain the context, e.g., communication parameters necessary to allow UE-gNB communication. As an example communication parameter, the UE may obtain, e.g., as part of a RACH procedure with gNB, a timing advance to allow the UE to perform uplink transmission to the gNB. The UE may also obtain a UE identity from the network, e.g., such as a cell-radio network temporary identifier (C-RNTI), which may be used by the UE for communication or signaling with the network or gNB.

[38] However, a significant time delay and signaling load is typically required for a UE to perform a random access (RACH) procedure to transition from Idle state to Connected state. Therefore, a third state for a UE was introduced - Inactive state (e.g., RRC Inactive state), in which the RRC context is maintained by both the UE and the network (gNB and core network), to allow the UE to transition to an Active state much faster than from Idle state. However, in Inactive state, the UE is allowed to sleep (a low power state) much of the time, similar to Idle state.

[39] In addition, a small data transmission (SDT), e.g., which may be a data transmission of data that is less than a threshold size or which fits within a payload of a SDT transmission, was introduced to allow both (or either) a RACH (random access procedure) based SDT transmission (using either 2-step RACH procedure or 4-step RACH procedure) or a configured grant based SDT transmission, by a UE that is in an Inactive (e.g., RRC Inactive) state, without requiring the UE to first transition to a Connected state.

[40] FIG. 3A is a diagram illustrating a small data transmission using a 4-step random access (RACH) procedure according to an example embodiment. A UE 210 and a gNB 312 are shown in FIG. 3A. The UE is in Inactive state (e.g., RRC Inactive). At step 1, the UE 210 sends (transmits) message (Msg) 1 of the RACH procedure, which is the RACH preamble specifically for SDT. Typically, a RACH preamble is transmission for the purpose of establishing a connection (for the purpose of the UE transitioning to Connected state).

However, a special SDT RACH preamble may be transmitted to indicate a request to transmit (or indicate a transmission of) data via SDT transmission within a RACH procedure message. At step 2, the UE 210 receives a random access response (RAR). At step 3, the UE 210 transmits Msg 2 of the RACH procedure, including SDT transmission, which is data that is less than a threshold size and/or fits within the SDT payload for Msg 3. At Msg 4, the UE 210 may receive Msg 4 of the RACH procedure, which may include a RRC Release message and/or may include suspend (deactivation) indication to confirm that the UE should or will remain in Inactive (RRC Inactive) state. Msg 4 may also include DL (downlink) data.

[41] FIG. 3B is a diagram illustrating a small data transmission using a 2-step random access (RACH) procedure according to an example embodiment. The UE 210 is in an Inactive state. The operation of the 2-step RACH procedure of FIG. 3B is similar to the 4-step RACH procedure of FIG. 3A, except, Msg 1 and Msg 3 are combined into Msg A in the 2-step RACH procedure, and Msg 2 and Msg 4 are combined into Msg B of the 2-step RACH procedure, as shown in FIG. 3B. Thus, as shown in FIG. 3B, the UE 210 may perform SDT transmission by transmitting SDT RACH preamble and data (UL data) within Msg A to gNB 312. The UE 210 may receive Msg B from gNB 312, which may be a RRC release message and/or may include a suspend (deactivation) indication that confirms the UE 210 should remain in Inactive state (and Msg B may also include DL data).

[42] A small data transmission may also be transmitted via a configured grant based SDT transmission. FIG. 3C is a diagram illustrating a configured grant based SDT procedure according to an example embodiment. The UE 210 is in an Inactive state. At step 0, a configured grant configuration for SDT is received by the UE 210. At step 1, the UE transmits data based on a configured grant based SDT (based on or in accordance with the configured grant configuration for SDT), e.g., using radio bearers (e.g., data radio bearers) and/or timefrequency resources that may be indicated by the configured grant configuration for SDT. At step 2, the UE 210 may receive a RRC release message, e.g., which may include a suspend (or deactivation) indication that confirms the UE 210 should remain in Inactive state (and Msg B may also include DL data).

[43] According to an example embodiment, a UE (or user device) may configure dual connectivity including a master cell group (MCG) associated with a first network node that is configured as a master node for dual connectivity for the user device and a secondary cell group (SCG) associated with a second network node that is configured as a secondary node. The UE may determine that the SCG is deactivated, e.g., which may include one or more of the following, for example: 1) the UE receiving, from the first network node, a request to deactivate the SCG associated with the second network node; 2) the UE deactivating the SCG in response to a request to deactivate the SCG; or 3) the UE configuring a deactivated SCG (a SCG in a deactivated state), as part of dual connectivity for the UE. The UE may detect a need to transmit data to the SCG. But, as noted, the SCG may be deactivated. For example, the data may be: 1) a master cell group (MCG) failure information that reports a MCG radio link failure detected by the UE (in the event that the UE detects a MCG radio link failure); 2) data received by the UE for UL transmission to the SCG, and/or 3) a buffer status report (BSR) (e.g., in the event that the UL data to be transmitted does not fit within a pay load of a small data transmission). The UE may determine that the small data transmission (SDT) configuration can be used to for a data transmission to the SCG. The UE may transmit data via the deactivated SCG to the second network node utilizing a small data transmission (SDT) (either RACH based SDT or configured grant based SDT) according to the SDT configuration. Allowing a UE to transmit data via the deactivated SCG to the SN utilizing a SDT, e.g., utilizing either a configured grant based SDT and/or RACH based SDT (while the SCG is deactivated), reduces latency and signaling, by allowing the data to be transmitted without requiring or waiting for the SCG to be activated or reactivated.

[44] For example, the SDT configuration may be transmitted to the UE from the first network node (configured as the master node) as part of a SCG addition in deactivated state, SCG deactivation request message, and/or may be broadcast to the UE (and to other nodes) by the second network node (configured as the secondary node) within system information (e.g., within system information block (SIB)) broadcasted by the second network node, for example.

[45] As noted, the data to be transmitted by the UE via SDT (transmitted utilizing either configured grant based SDT transmission or utilizing RACH based SDT transmission) may include one or more of: 1) a master cell group (MCG) failure information to report, by the UE via the SCG to the second network node, a MCG radio link failure, based on the UE detecting a MCG radio link failure; 2) data received by the UE for uplink transmission by the UE via the SCG to the second network node (that is configured as the secondary node); and/or 3) a buffer status report (BSR) if the UL data to be transmitted via SCG is greater than a threshold size or does not fit within a payload of a SDT according to the SDT configuration. The first network node (configured as the master node for dual connectivity for the UE) is associated with or provides the MCG, while the second network node (configured as the secondary node for the dual connectivity for the UE) is associated with or provides the SCG.

[46] In an example embodiment, the UE may prioritize data transmission via deactivated SCG to second network node in the following order: 1) MCG failure information, if the UE detected a MCG radio link failure; 2) data received by the UE for uplink (UL) transmission by the UE via the SCG to the second network node, if the data (size of the data) for UL transmission is less than or equal to a threshold size or fits within a payload of a SDT according to the SDT configuration; 3) a buffer status report (BSR) if a size of the UL data to be transmitted is greater than a threshold size or does not fit within a payload of a SDT according to the SDT configuration.

[47] According to an example embodiment, a SDT configuration may include, e.g., one or more of: time-frequency resources that may be used for a small data transmission (SDT); SDT bearers (e.g., data radio bearers and/or control radio bearers, which may be used for both RACH based SDT or configured grant based SDT), which may be used for data transmission via a random access procedure based small data transmission or used for data transmission via a configured grant based small data transmission; a timer value for a timing advance for the small data transmission configuration (e.g., expiration of the timer indicates that the timing advance for the SDT configuration is invalid, while a running (non-expired timer) indicates a valid timing advance for the SDT configuration); a buffer status report (BSR) size for a BSR that may be transmitted via SDT; and/or a threshold size of data for a SDT transmission, or a payload size of a SDT transmission.

[48] The UE may prioritize a configured grant based SDT transmission over a RACH based SDT transmission, e.g., if a timing advance for the SDT configuration for the SCG is valid. Thus, according to an example embodiment, the UE may transmit the data via configured grant based SDT if the timing advance (for the SDT configuration for the SCG) is valid (e.g., timer for the timing advance or timer for the SDT configuration, or timer for CG-based SDT, has not expired), and otherwise, the UE may transmit the data via RACH based SDT if the timing advance is invalid (e.g., the timer for the timing advance or for the SDT configuration has expired). For example, the timing advance may be valid only for an indicated amount of time (e.g., the timer value indicated in the SDT configuration), and after this amount of time has passed (e.g., as indicated by the expiration of the timer for the timing advance), the UE assumes that the timing advance for SDT configuration for the SCG is no longer valid (e.g., may be assumed to be inaccurate for UL communications via SCG to SN), and the timing advance can no longer be used by the UE for UL data transmission via configured grant (CG) based SDT. In such case, if the timing advance for the SDT configuration for the SCG is invalid, the UE may instead transmit data via the RACH based SDT, e.g., within a RACH message (Msg) 3 (for 4- step RACH procedure) or within a RACH message A (for 2-step RACH procedure). As noted, the UE may transmit the data via configured grant based SDT (if timing advance for SDT configuration is valid) or RACH based SDT (if timing advance for SDT configuration is invalid), even though the SCG (provided by or associated with the SN) is deactivated (suspended). Allowing SDT transmission of data utilizing a SDT, e.g., utilizing either a configured grant based SDT and/or RACH based SDT, when the SCG is deactivated may reduce latency and/or reduce signaling, by allowing the data to be transmitted without requiring (or waiting for) the SCG to be reactivated.

[49] Thus, for example, the UE may perform the following: determining whether a timing advance for the SDT configuration is valid or invalid; wherein the transmitting comprises performing at least one of the following: transmitting, by the UE via the SCG to the second network node (that is configured as the secondary node), the data utilizing the configured grant-based SDT according to the SDT configuration, if the timing advance for the SDT configuration is valid; otherwise, transmitting, by the UE via the SCG to the second network node, the data utilizing the random access-based SDT within a first random access procedure message (e.g., within Msg 3 for 4-step RACH procedure or Msg A for a 2-step RACH procedure) if the timing advance for the SDT configuration is invalid.

[50] According to an example embodiment, the UE determining that the SDT configuration for the SCG can be used for data transmission may include: determining that a configured grant-based SDT is available (e.g., resources such as radio bearers have been allocated for SDT) and a timing advance for the SDT configuration is valid; and determining that a size of the data to be transmitted is less than a threshold size or fits within a payload of a SDT according to the small data transmission configuration. In such case (e.g., configured grant based SDT is available and timing advance for SDT configuration is valid, and data fits within payload of SDT), the transmitting (by the UE) of data may include the UE transmitting data via the SCG to the second network node utilizing the configured grant-based SDT according to the SDT configuration (e.g., using or according to the radio bearers and/or other parameters indicated by the SDT configuration).

[51] On the other hand, the determining (by the UE) that the SDT configuration for the SCG can be used for data transmission may include: determining that a size of the data to be transmitted is less than a threshold size or fits within a payload of a SDT according to the SDT configuration; and determining that a timing advance for the SDT configuration is invalid. In such case (e.g., where the data fits within SDT payload, and timing advance is invalid), the transmitting may include transmitting, by the UE via the SCG to the second network node, the data utilizing the random access based SDT within a first random access procedure message (e.g., within Msg 3 for 4-step RACH procedure or within Msg A for 2-step RACH procedure).

[52] Also, the detecting, by the UE, a need to transmit data to the SCG may include, for example: receiving, by the UE, data for uplink transmission via the SCG to the second network node. The method may further include determining whether or not a size of the received data for uplink transmission fits within a payload of a SDT according to the SDT configuration. And, in such case, the transmitting may include at least one of the following: 1) transmitting, by the UE, the received data to the SCG via a SDT according to the SDT configuration if the received data fits within a payload of a SDT transmission according to the SDT configuration; and transmitting, by the UE to the SCG, a buffer status report to allow for a subsequent transmission by the UE of the received data if the received data does not fit within a payload of a SDT transmission according to the SDT configuration.

[53] Also, for example, the detecting, by the UE, a need to transmit data to the SCG may include: detecting, by the UE, a master cell group (MCG) radio link failure, wherein the MCG is associated with the first network node that is configured as the master node for dual connectivity with the UE. The transmitting may include transmitting a MCG failure information to report, by the UE to the first network node or the master node via the second network node, the MCG radio link failure. Also, the method may further include receiving, by the UE from the second network node, a MCG recovery information including a handover command instructing the UE to perform a handover to a target primary cell of a new MCG; and performing, by the UE, a handover to the target primary cell of the new MCG based on the handover command. Also, for example, the UE receiving the MCG recovery information may include at least one of: 1) receiving, by the UE from the second network node via a SCG deactivation message, a MCG recovery information including a handover command instructing the UE to perform a handover to a target primary cell of a new MCG if the MCG failure information is transmitted by the UE via a configured grant-based SDT transmission according to the SDT configuration; and/or 2) receiving, by the UE from the second network node, a message, including the MCG recovery information and a secondary cell group (SCG) deactivation indication that indicates a continued deactivated state of the SCG for the UE, via a second random access (RACH) procedure message (e.g., via Msg 4 of 4-step RACH procedure or via Msg B of 2-step RACH procedure) if the MCG failure information is transmitted by the UE via a random access (RACH) procedure based SDT transmission within the first random access (RACH) procedure message (e.g., within Msg 3 of 4-step RACH or within Msg A of 2- step RACH procedure). Also, for example, the MCG failure information may include: an indication that a MCG radio link failure has been detected, and one or more cell neighbor cell measurements measured by the UE or user device.

[54] From the perspective of the second network node (that is configured as the secondary node for dual connectivity of the UE), the second network node may perform a method that includes: configuring, by a second network node configured as a secondary node as part of a dual connectivity for a user device, a SCG associated with the second network node; determining, by the second network node, that the SCG is deactivated; transmitting, by the second network node to a first network node configured as a master node that provides a master cell group (MCG) for the dual connectivity for the UE, a small data transmission configuration (SDT) for the SCG, to be forwarded by the first network node to the UE; and receiving data by the second network node from the UE via the SCG group while the SCG is deactivated for the user device, wherein the data is received by the second network node via a small data transmission according to the small data transmission configuration.

[55] For example, the determining that the SCG is deactivated may include at least one of the following: receiving a request to deactivate the SCG associated with the second network node; deactivating the SCG in response to a request to deactivate the SCG; or configuring a deactivated SCG or a SCG that is in a deactivated state, as part of dual connectivity for the UE.

[56] Also, the data received by the second network node may include at least one of: 1) a master cell group (MCG) failure information to report, by the UE via the SCG to the second network node, a master cell group (MCG) radio link failure, based on the UE detecting a master cell group (MCG) radio link failure (e.g., in the event the UE detects a MCG Radio link failure); 2) data received by the UE for uplink transmission by the UE via the SCG to the second network node; or 3) a buffer status report if the data (size of the data) to be transmitted is greater than a threshold size or does not fit within a payload of a small data transmission (SDT) according to the small data transmission (SDT) configuration.

[57] According to an example embodiment, the receiving data may include at least one of the following: receiving, by the second network node from the UE via the SCG, the data utilizing the configured grant-based SDT according to the SDT configuration, if a timing advance for the SDT configuration is valid; and/or receiving, by the second network node from the UE via the SCG, the data utilizing the random access based SDT within a first random access procedure message (e.g., Msg 3 or Msg A) if the timing advance for the SDT configuration is invalid. In such case, the method may further include at least one of: 1) transmitting, by the second network node to the UE via the SCG, a SCG deactivation message, if the data is received by the second network node from the UE via a configured grant based SDT transmission according to the SDT configuration; or 2) transmitting, by the second network node to the UE via the SCG, a message, including a SCG deactivation indication that indicates a continued deactivated state of the SCG for the UE, within a second random access (RACH) procedure message (e.g., Msg 4 or Msg B) if the data is received by the second network node from the UE via a random access based small data transmission within a first random access procedure message.

[58] According to an example embodiment, the receiving data may include receiving, by the second network node from the UE via the SCG, a MCG failure information that reports a MCG radio link failure; and wherein the method further includes: forwarding, by the second network node (configured as the secondary node) to the first network node (configured as the master node), the MCG failure information that reports the MCG radio link failure; receiving, by the by the second network node from the first network node, a MCG recovery information including a handover command instructing the UE to perform a handover to a target cell of a new MCG; and transmitting, by the second network node to the UE via the SCG, the MCG recovery information. Also, for example, the transmitting the MCG recovery information may include at least one of: 1) transmitting, by the second network node to the UE via a SCG deactivation message, the MCG recovery information including a handover command instructing the UE to perform a handover to a target primary cell of a new MCG if the MCG failure information is received by the second network node from the UE via a configured grantbased SDT transmission according to the SDT configuration; or 2) transmitting, by the second network node to the UE, a message, including the MCG recovery information and a SCG deactivation indication that indicates a continued deactivated state of the SCG for the UE, via a second random access (RACH) procedure (e.g., Msg 4 for 4-step RACH or Msg B for 2-step RACH) message if the MCG failure information is received by the second network node from the UE via a random access (RACH) procedure based small data transmission within the first random access (RACH) procedure message (Msg 3 of 4-step RACH procedure or Msg A of 2- step RACH procedure).

[59] Further illustrative features and examples will now be described. As noted, example embodiments are described wherein data (e.g., data, buffer status report and/or MCG failure information) may be transmitted by a UE utilizing a small data transmission (SDT) based on a SDT configuration for the secondary cell group (SCG). The UE may configure (or may receive a configuration for, or may be configured for) dual connectivity including a master cell group (MCG) associated with a first network node that is configured as a master node for dual connectivity for the UE and a secondary cell group (SCG) associated with a second network node that is configured as a secondary node. The UE may determine that the SCG is deactivated. For example, the SCG may be added or configured (e.g., in an activated state), and may later be deactivated (e.g., in response to a request or indication to deactivate the SCG associated with the secondary network node), or the SCG may be added or configured in a deactivated state. For example, a SDT configuration may be received by the UE as part of a SCG deactivation request message (e.g., received by the first network node), or via system information received by the UE from the second network node. The UE may transmit data via SDT transmission based on either: 1) a configured grant based SDT (if a timing advance for the SDT configuration is valid) or 2) a random access (RACH) procedure based SDT (if the timing advance is invalid) via the deactivated SCG to the second network node (configured as a secondary node for dual connectivity for the UE). For example, this allows data and/or MCG failure information to be transmitted to a deactivated SCG by utilizing a SDT transmission, without requiring a reactivation of the SCG, which will allow data or control information transmission to deactivated via SDT, while avoiding or reducing latency and signaling overhead that would typically be required to reactivate the SCG.

[60] FIG. 4 is a diagram illustrating operation of a system in which data (e.g., data and/or MCG failure information, or other information) may be transmitted via configured grant based small data transmission (SDT) transmission according to an example embodiment.

[61] For example, the UE is permitted and configured with the corresponding SDT configuration (e.g., including radio bearers to be used for configured grant (CG) based SDT and RACH based SDT) to utilize SDT while SCG is deactivated. When UE uses SDT (either CG or RACH based SDT) to send data (e.g., data, BSR or MCG failure information) via SDT, the UE SCG may typically still be deactivated, for example. After UE sends its data, BSR or MCG failure information via SDT (via CG based SDT or RACH Msg A or Msg 3), the reply from the network may include: 1) a request to deactivate the SCG and 2) MCG failure recovery information (e.g., which may include HO command to new PCell) if UE reported MCG failure information.

[62] The SDT configuration may be used for small data transmission (e.g., to send MCG failure report, or small amount of UL data, that fits within SDT payload size). The UE may be asked to move SCG back to (or remain in) deactivated state (e.g., in case of completed transmission of UL data) or UE may be triggered to move SCG to activated state (e.g. to complete MCG failure recovery, by performing a handover to target PCell of new MCG).

[63] The SDT configuration may be used to transmit a buffer status report (BSR) from the UE and thus trigger scheduling of UL grants by NW or SCG activation from NW side (e.g., if the UL data at UE for transmission is above the maximum pay load size of SDT).

[64] In case MCG failure is observed by UE or if UL data arrived on SCG RLC (UL data arrived on SCG radio link control entity (e.g., from upper layers at UE), for UL transmission to SCG/secondary network node):

[65] If timing advance timer (TAT) for SDT configuration is running (e.g., not expired, and thus timing advance is still valid for UE):

[66] UE applies the configuration of the configured grant typel resources and adds MCGFailurelnformation, SCG UL data, or SCG BSR in PUSCH (physical uplink shared channel, which may be used by UE for UL transmission of data or control information).

[67] Else (TAT is expired):

[68] UE starts normal 4-step or 2-step RACH procedure to SCG and adds MCGFailurelnformation, SCG UL data or SCG BSR in Msg 3 (4-step RACH procedure) or Msg A (2-step RACH procedure);

[69] In case MCG (master cell group) radio link failure is detected by UE, the failure report (MCG failure information) is received by SN (secondary node) and forwarded by SN to MN (master node) over Xn interface (gNB-to-gNB interface) (e.g., within an existing RRC Transfer XnAP message); and, then Fast MCG failure recovery proceeds, e.g., UE may perform handover to indicated target cell.

[70] In case of SCG scheduling request, SN informs (possibly within a newly introduced message) or requests MN about SCG activation; In that case, UE’s request for PUSCH (request for UL data transmission) grants on SCG proceeds.

[71] As noted, FIG. 4 is a diagram illustrating operation of a system in which data (e.g., data and/or MCG failure information, or other information) may be transmitted via configured grant based small data transmission (SDT) transmission according to an example embodiment. A UE 210 may be in communication with a master node (MN) 212 and a secondary node (SN) 214. In FIG. 4, it is assumed that the timing advance (TA) is valid (e.g., SDT configuration timer is still running or has not expired). Case 1 of FIG. 4 involves UE transmission of MCG failure information from UE 210 to SN 214, while case 2 of FIG. 4 involves transmission of received UL data (that is directed to SCG) to SCG, via configured grant (CG) based SDT transmission.

[72] Step 0: UE is in RRC_CONNECTED in dual connectivity (with a connection established to each of MN 212 and SN 214).

[73] Step 1: MN, SN or UE decides to deactivate SCG due to traffic load (e.g., due to decreased traffic load for UE, such as an amount of data or traffic for UE that is less than a threshold value). Alternatively, as noted, the SCG may be added or configured in a deactivated state.

[74] Step 2: Usage of SDT is allowed for SCG in deactivated state, and SDT configuration is provided by SN to MN. In case the SCG deactivation signaling is done directly from this step may not be needed or may not be performed.

[75] Step 3 : SCG deactivation request (or SCG deactivation command) is transmitted to the UE to deactivate SCG. The message may include a SDT configuration; or alternatively SDT configuration may be provided or communicated to UE in broadcast signaling, or prior to the deactivation message, or UE may be preconfigured with SDT configuration. The the SCG deactivation signaling may be sent directly from SN to UE, SN can transmit the deactivation command to UE and inform MN about it.

[76] Step 4. UE may transmit a SCG deactivation complete to MN 212, which is forwarded to SN 214, or may be sent directly to SN 214. At this point, the SCG is in deactivated state. Or, the SCG may be in a deactivated state without (or before) UE sending the SCG deactivated complete.

[77] Case 1 :

[78] Step 5. Radio link failure occurs at MCG and the MCG radio link failure may be detected by UE, and the timing advance timer for SDT configuration (or timing advance for configured grant (CG) based SDT) is valid (e.g., indicating that the timing advance known by UE is valid and can be used for UL transmission via configured grant (CG) based SDT.

[79] Step 6. UE applies the configured grant PUSCH (indicating UL time-frequency resources that UE may use to perform CG based SDT transmission) and transmits a MAC (media access control) PDU (protocol data unit) including SCG activation request and MCG failure information (e.g., indicating MCG radio link failure, and providing neighbor cells measurement report) as the (SDT) allowed UL payload of the CG based SDT transmission.

[80] Step 7. The MCG failure information is forwarded by SN 214 to MN 212.

[81] Step 8. MN 212 may provide MCG failure recovery information (e.g., including a handover command requesting a handover of UE 210 to a target cell) for the UE 210 to the SN 214.

[82] Step 9. SN 214 transmits SCG deactivation request (confirming that UE should keep or maintain SCG in deactivated state), as well as MCG failure recovery information to the UE 210, and SCG remains in deactivated state.

[83] Step 10. UE applies the MCG failure recovery information to reestablish its MCG (e.g., which may involve UE performing RACH to target cell as new PCell of MCG) and UE may go back to step 6, if RACH or connection establishment to target cell is not successful.

[84] Case 2:

[85] Step 11. At UE, UL data to be transmitted to SCG arrives on SCG RLC (e.g., from upper layers of UE); UE determines that timing advance for SCG or for SDT configuration is valid (e.g., TA timer for the SDT configuration is not expired or is still running) and the TA timer in SDT configuration (e.g., timing advance (TA) timer for CG-SDT) is valid.

[86] Step 12. UE applies the configured grant PUSCH and transmits a MAC PDU including the arrived UL data (or BSR if data is too large to fit within SDT payload) as payload for configured grant based SDT, including SCG activation request. In an embodiment, the UE may transfer or transmit the UL data utilizing CG (configured grant) based SDT according to (e.g., up to the) maximum allowed payload size for SDT and make subsequent attempt(s) to transfer the rest of the data as long as TA is still valid. In another embodiment, the UE may transmit its buffer status report, BSR, and await the NW to activate SCG and provide necessary UL grants.

[87] Step 13. SN 214 transmits SCG deactivation request to UE 210, e.g., SCG remains in deactivated state. [88] FIG. 5 is a diagram illustrating operation of a system in which data (e.g., data and/or MCG failure information, or other information) may be transmitted via random access (RACH) procedure based small data transmission (SDT) transmission according to an example embodiment. A UE 210 may be in communication with a master node (MN) 212 and a secondary node (SN) 214. The method or procedure illustrated in FIG. 5 may be used to transmit data (e.g., received data for UL transmission to SCG) or MCG failure information. In FIG. 5, it is assumed that the TA is not valid (e.g., the TA timer or timer for the SDT configuration has expired, indicating the timing advance (TA) is invalid and thus CG based SDT transmission cannot be performed, and therefore, RACH based SDT transmission must be used to perform SDT transmission. Case 1 involves transmission of MCG failure information to SN 214, while case 2 involves transmission of UE data that is to be transmitted to SCG, while TA is invalid.

[89] Steps 0-4 of FIG. 5 are the same as in FIG. 4.

[90] Case 1 :

[91 ] Step 5. Radio link failure occurs at MCG, and TA is not valid.

[92] Step 6. UE initiates RACH procedure to SN 214 (Msg. 1) to transmit SDT-specific RACH preamble to SN 214.

[93] Step 7. Random access response (Msg. 2) is transmitted to the UE 210 from SN 214.

[94] Step 8. UE multiplexes the MCG failure information (MCG failure report) in the MAC PDU with other necessary control information in Msg. 3. FIG. 4 illustrates usage of 4- step RACH, but 2-step RACH may be used instead. In this case Msg. 1 & 3 are transmitted together in Msg. A of 2-step RACH. Figure illustrates usage of RACH preamble dedicated for SDT, which will indicate need of SDT transmission to the network. Regular RACH preamble can also be used and introduces a small delay as the UL data can first be transmitted after Msg. 3/Msg. A using the dynamic UL grant received in Msg. 4/Msg. B.

[95] Step 9. The MCG failure is forwarded to MN - similar to the fast MCG recovery procedure with activated SCG.

[96] Step 10. MN 212 may provide MCG failure recovery information (including handover command to request UE to perform handover to target cell) for the UE 210 to the SN [97] Step 11. SN 214 transmits SCG deactivation request, as well as the MCG failure recovery information to the UE 210 and SCG remains in deactivated state.

[98] Step 12. UE applies the MCG failure recovery information to reestablish its MCG (e.g., which may involve UE performing RACH procedure to target cell as new PCell of MCG), and UE may go back to step 6 if RACH or connection establishment to target cell is not successful.

[99] Case 2:

[100] Step 13. At UE, UL data to be transmitted to SCG arrives on SCG RLC (e.g., from upper layers of UE); UE determines that timing advance for SCG or for SDT configuration is invalid (e.g., TA timer for the SDT configuration is expired or is not running).

[101] Step 14. A RACH preamble, such as SDT specific RACH preamble is transmitted by UE 210 via Msg. 1 or Msg. A to SN 214.

[102] Step 15. A random access response is received by UE 210 from SN 214 via Msg. 2 or Msg. B.

[103] Step 16. A SCG activation request and UL data or BSR is transmitted by UE 210 via Msg. 3 or Msg. A to SN 214.

[104] Step. 17. A SCG deactivated message is transmitted by SN 214 to UE 210 via Msg. 4 or Msg B.

[105] Example 1. FIG. 6 is a flow chart illustrating operation of a user device (or UE) according to an example embodiment. Operation 610 includes configuring, by a user device, dual connectivity including a master cell group associated with a first network node that is configured as a master node for dual connectivity for the user device and a secondary cell group associated with a second network node that is configured as a secondary node. Operation 620 includes determining, by the user device, that the secondary cell group is deactivated.

Operation 630 includes receiving, by the user device, a small data transmission configuration for the secondary cell group. Operation 640 includes detecting, by the user device, a need to transmit data to the secondary cell group. Operation 650 includes determining that the small data transmission configuration for the secondary cell group can be used for a data transmission. And, operation 660 includes transmitting, by the user device, data via the secondary cell group to the second network node utilizing a small data transmission according to the small data transmission configuration. [106] Example 2. The method of example 1, wherein the determining that the secondary cell group is deactivated comprises at least one of the following: receiving, by the user device from the first network node, a request to deactivate the secondary cell group associated with the second network node; deactivating, by the user device, the secondary cell group in response to a request to deactivate the secondary cell group; or configuring, by the user device, a deactivated secondary cell group or a secondary cell group that is in a deactivated state, as part of dual connectivity for the user device.

[107] Example 3. The method of any of examples 1-2 wherein the small data transmission comprises a transmission that is less than a threshold size, and which may be transmitted via at least one of a configured grant-based small data transmission or a random access-based small data transmission.

[108] Example 4. The method of any of examples 1-3, wherein the data comprises at least one of: a master cell group failure information to report, by the user device via the secondary cell group to the second network node, a master cell group radio link failure, based on the user device detecting a master cell group radio link failure; data received by the user device for uplink transmission by the user device via the secondary cell group to the second network node; or a buffer status report if the data to be transmitted is greater than a threshold size or does not fit within a payload of a small data transmission according to the small data transmission configuration.

[109] Example 5. The method of any of examples 1-4, wherein the small data transmission configuration is provided for a configured grant-based small data transmission and a random access-based small data transmission; the method further comprising: determining whether a timing advance for the small data transmission configuration is valid or invalid; wherein the transmitting comprises performing at least one of the following: transmitting, by the user device via the secondary cell group to the second network node, the data utilizing the configured grant-based small data transmission according to the small data transmission configuration, if the timing advance for the small data transmission configuration is valid; otherwise, transmitting, by the user device via the secondary cell group to the second network node, the data utilizing the random access-based small data transmission within a first random access procedure message if the timing advance for the small data transmission configuration is invalid. [110] Example 6. The method of any of examples 1-5, further comprising: receiving, by the user device from the second network node, a secondary cell group deactivation message, if the data is transmitted by the user device via a configured grant-based small data transmission according to the small data transmission configuration; and receiving, by the user device from the second network node, a message, including the secondary cell group deactivation indication that indicates a continued deactivated state of the secondary cell group for the user device, within a second random access procedure message if the data is transmitted by the user device via a random access-based small data transmission within a first random access procedure message.

[111] Example 7. The method of any of examples 1-6, wherein determining that the small data transmission configuration for the secondary cell group can be used for data transmission comprises: determining that a configured grant-based small data transmission is available and a timing advance for the small data transmission configuration is valid; and determining that a size of the data to be transmitted is less than a threshold size or fits within a payload of a small data transmission according to the small data transmission configuration.

[112] Example 8. The method of example 7, wherein the transmitting comprises: transmitting, by the user device via the secondary cell group to the second network node, the data utilizing the configured grant-based small data transmission according to the small data transmission configuration.

[113] Example 9. The method of any of examples 1-6, wherein determining that the small data transmission configuration for the secondary cell group can be used for data transmission comprises: determining that a size of the data to be transmitted is less than a threshold size or fits within a payload of a small data transmission according to the small data transmission configuration; and determining that a timing advance for the small data transmission configuration is invalid.

[114] Example 10. The method of example 9 wherein the transmitting comprises: transmitting, by the user device via the secondary cell group to the second network node, the data utilizing the random access-based small data transmission within a first random access procedure message.

[115] Example 11. The method of any of examples 1-6 wherein the transmitted data comprises a buffer status report for the user device to transmit additional data if the additional data to be transmitted is greater than a threshold size or does not fit within a payload of a small data transmission according to the small data transmission configuration.

[116] Example 12. The method of any of examples 1-6 wherein the detecting, by the user device, a need to transmit data to the secondary cell group comprises: receiving, by the user device, data for uplink transmission via the secondary cell group to the second network node; the method further comprising determining whether or not a size of the received data for uplink transmission fits within a payload of a small data transmission according to the small data transmission configuration; wherein the transmitting comprises at least one of: transmitting, by the user device to the secondary cell group, the received data to the secondary cell group associated with the secondary node via a small data transmission according to the small data transmission configuration if the received data fits within a payload of a small data transmission according to the small data transmission configuration; and transmitting, by the user device to the secondary cell group, a buffer status report to allow for a subsequent transmission by the user device of the received data if the received data does not fit within a payload of a small data transmission according to the small data transmission configuration.

[117] Example 13. The method of any of examples 1-6 wherein the detecting, by the user device, a need to transmit data to the secondary cell group comprises: detecting, by the user device, a master cell group radio link failure, wherein the master cell group is associated with the first network node that is configured as the master node for dual connectivity for the user device.

[118] Example 14. The method of example 13, wherein the transmitting comprises: transmitting a master cell group failure information to report, by the user device to the first network node or to the second network node, the master cell group radio link failure.

[119] Example 15. The method of example 13, further comprising: receiving, by the user device from the second network node, a master cell group recovery information including a handover command instructing the user device to perform a handover to a target primary cell of a new master cell group; and performing, by the user device, a handover to the target primary cell of the new master cell group based on the handover command.

[120] Example 16. The method of example 15, wherein the receiving the master cell group recovery information comprises at least one of: receiving, by the user device from the second network node via a secondary cell group deactivation message, a master cell group recovery information including a handover command instructing the user device to perform a handover to a target primary cell of a new master cell group if the master cell group failure information is transmitted by the user device via a configured grant-based small data transmission according to the small data transmission configuration; and receiving, by the user device from the second network node, a message, including the master cell group recovery information and a secondary cell group deactivation indication that indicates a continued deactivated state of the secondary cell group for the user device, via a second random access procedure message if the master cell group failure information is transmitted by the user device via a random access procedure-based small data transmission within the first random access procedure message.

[121] Example 17. The method of any of examples 14-16, wherein the master cell group failure information comprises an indication that a master cell group radio link failure has been detected, and one or more neighboring cell measurements measured by the user device.

[122] Example 18. The method of any of examples 1-17, wherein the small data transmission configuration comprises information indicating one or more of the following: time-frequency resources that may be used for a small data transmission; small data transmission bearers, which may be used for data transmission via a random access procedure based small data transmission or used for data transmission via a configured grant based small data transmission; a timer value for a timing advance for the small data transmission configuration; a buffer status report size; and a threshold size of data for a small data transmission, or a payload size of a small data transmission.

[123] Example 19. A non-transitory computer-readable storage medium comprising instructions stored thereon that, when executed by at least one processor, are configured to cause a computing system to perform the method of any of examples 1-18.

[124] Example 20. An apparatus comprising means for performing the method of any of examples 1-18.

[125] Example 21. An apparatus comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform the method of any of examples 1-18.

[126] Example 22. An apparatus comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: configure, by a user device, dual connectivity including a master cell group associated with a first network node that is configured as a master node for dual connectivity for the user device and a secondary cell group associated with a second network node that is configured as a secondary node; determine, by the user device, that the secondary cell group is deactivated; receive, by the user device, a small data transmission configuration for the secondary cell group; detect, by the user device, a need to transmit data to the secondary cell group; determine that the small data transmission configuration for the secondary cell group can be used for a data transmission; and transmit, by the user device, data via the secondary cell group to the second network node utilizing a small data transmission according to the small data transmission configuration.

[127] Example 23. FIG. 7 is a flow chart illustrating operation of a secondary node according to an example embodiment. Operation 710 includes configuring, by a second network node configured as a secondary node as part of a dual connectivity for a user device, a secondary cell group associated with the second network node. Operation 720 includes determining, by the second network node, that the secondary cell group is deactivated.

Operation 730 includes transmitting, by the second network node to a first network node configured as a master node that provides a master cell group for the dual connectivity for the user device, a small data transmission configuration for the secondary cell group, to be forwarded by the first network node to the user device. And, operation 740 includes receiving data by the second network node from the user device via the secondary cell group while the secondary cell group is deactivated for the user device, wherein the data is received by the second network node via a small data transmission according to the small data transmission configuration.

[128] Example 24. The method of example 23, wherein the determining that the secondary cell group is deactivated comprises at least one of the following: receiving a request to deactivate the secondary cell group associated with the second network node; deactivating the secondary cell group in response to a request to deactivate the secondary cell group; or configuring a deactivated secondary cell group or a secondary cell group that is in a deactivated state, as part of dual connectivity for the user device.

[129] Example 25. The method of any of examples 23-24, wherein the data received by the second network node comprises at least one of: a master cell group failure information to report, by the user device via the secondary cell group to the second network node, a master cell group radio link failure, based on the user device detecting a master cell group radio link failure; data received by the user device for uplink transmission by the user device via the secondary cell group to the second network node; or a buffer status report if the data to be transmitted is greater than a threshold size or does not fit within a pay load of a small data transmission according to the small data transmission configuration.

[130] Example 26. The method of any of examples 23-25, wherein the small data transmission comprises a transmission that is less than a threshold size or fits within a payload of a small data transmission according to the small data transmission configuration, and wherein the small data transmission may be transmitted via at least one of a configured grant-based small data transmission or a random access-based small data transmission.

[131] Example 27. The method of any of examples 23-26, wherein the receiving data comprises at least one of the following: receiving, by the second network node from the user device via the secondary cell group, the data utilizing the configured grant-based small data transmission according to the small data transmission configuration, if a timing advance for the small data transmission configuration is valid; receiving, by the second network node from the user device via the secondary cell group, the data utilizing the random access-based small data transmission within a first random access procedure message if the timing advance for the small data transmission configuration is invalid.

[132] Example 28. The method of example 27, further comprising: transmitting, by the second network node to the user device via the secondary cell group, a secondary cell group deactivation message, if the data is received by the second network node from the user device via a configured grant-based small data transmission according to the small data transmission configuration; and transmitting, by the second network node to the user device via the secondary cell group, a message, including a secondary cell group deactivation indication that indicates a continued deactivated state of the secondary cell group for the user device, within a second random access procedure message if the data is received by the second network node from the user device via a random access-based small data transmission within a first random access procedure message.

[133] Example 29. The method of any of examples 23-28, wherein the receiving data comprises: receiving, by the second network node from the user device via the secondary cell group, a master cell group failure information that reports a master cell group radio link failure; and wherein the method further comprises: forwarding, by the second network node to the first network node, the master cell group failure information that reports the master cell group radio link failure; receiving, by the by the second network node from the first network node, a master cell group recovery information including a handover command instructing the user device to perform a handover to a target cell of a new master cell group; and transmitting, by the second network node to the user device via the secondary cell group, the master cell group recovery information with a secondary cell group deactivation indication.

[134] Example 30. The method of example 29, wherein the transmitting the master cell group recovery information comprises at least one of: transmitting, by the second network node to the user device via a secondary cell group deactivation message, the master cell group recovery information including a handover command instructing the user device to perform a handover to a target primary cell of a new master cell group if the master cell group failure information is received by the second network node from the user device via a configured grantbased small data transmission according to the small data transmission configuration; and transmitting, by the second network node to the user device, a message, including the master cell group recovery information and a secondary cell group deactivation indication that indicates a continued deactivated state of the secondary cell group for the user device, via a second random access procedure message if the master cell group failure information is received by the second network node from the user device via a random access procedure based-small data transmission within the first random access procedure message.

[135] Example 31. A non-transitory computer-readable storage medium comprising instructions stored thereon that, when executed by at least one processor, are configured to cause a computing system to perform the method of any of examples 23-30.

[136] Example 32. An apparatus comprising means for performing the method of any of examples 23-30.

[137] Example 33. An apparatus comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform the method of any of examples 23-30. [138] Example 34. An apparatus comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: configure, by a second network node configured as a secondary node as part of a dual connectivity for a user device, a secondary cell group associated with the second network node; determine, by the second network node, that the secondary cell group is deactivated; transmit, by the second network node to a first network node configured as a master node that provides a master cell group for the dual connectivity for the user device, a small data transmission configuration for the secondary cell group, to be forwarded by the first network node to the user device; and receive data by the second network node from the user device via the secondary cell group while the secondary cell group is deactivated for the user device, wherein the data is received by the second network node via a small data transmission according to the small data transmission configuration.

[139] FIG. 8 is a block diagram of a wireless station (e.g., AP, BS or user device/UE, or other network node) 1200 according to an example embodiment. The wireless station 1200 may include, for example, one or more (e.g., two as shown in FIG. 8) RF (radio frequency) or wireless transceivers 1202A, 1202B, where each wireless transceiver includes a transmitter to transmit signals and a receiver to receive signals. The wireless station also includes a processor or control unit/entity (controller) 1204 to execute instructions or software and control transmission and receptions of signals, and a memory 1206 to store data and/or instructions.

[140] Processor 1204 may also make decisions or determinations, generate frames, packets or messages for transmission, decode received frames or messages for further processing, and other tasks or functions described herein. Processor 1204, which may be a baseband processor, for example, may generate messages, packets, frames or other signals for transmission via wireless transceiver 1202 (1202A or 1202B). Processor 1204 may control transmission of signals or messages over a wireless network, and may control the reception of signals or messages, etc., via a wireless network (e.g., after being down-converted by wireless transceiver 1202, for example). Processor 1204 may be programmable and capable of executing software or other instructions stored in memory or on other computer media to perform the various tasks and functions described above, such as one or more of the tasks or methods described above. Processor 1204 may be (or may include), for example, hardware, programmable logic, a programmable processor that executes software or firmware, and/or any combination of these. Using other terminology, processor 1204 and transceiver 1202 together may be considered as a wireless transmitter/receiver system, for example.

[141] In addition, referring to FIG. 8, a controller (or processor) 1208 may execute software and instructions, and may provide overall control for the station 1200, and may provide control for other systems not shown in FIG. 8, such as controlling input/output devices (e.g., display, keypad), and/or may execute software for one or more applications that may be provided on wireless station 1200, such as, for example, an email program, audio/video applications, a word processor, a Voice over IP application, or other application or software.

[142] In addition, a storage medium may be provided that includes stored instructions, which when executed by a controller or processor may result in the processor 1204, or other controller or processor, performing one or more of the functions or tasks described above.

[143] According to another example embodiment, RF or wireless transceiver(s) 1202A/1202B may receive signals or data and/or transmit or send signals or data. Processor 1204 (and possibly transceivers 1202A/1202B) may control the RF or wireless transceiver 1202 A or 1202B to receive, send, broadcast or transmit signals or data.

[144] The embodiments are not, however, restricted to the system that is given as an example, but a person skilled in the art may apply the solution to other communication systems. Another example of a suitable communications system is the 5G concept. It is assumed that network architecture in 5G may be similar to that of LTE-advanced. 5G is likely to use multiple input - multiple output (MIMO) antennas, many more base stations or nodes than LTE (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and perhaps also employing a variety of radio technologies for better coverage and enhanced data rates.

[145] It should be appreciated that future networks will most probably utilise network functions virtualization (NFV) which is a network architecture concept that proposes virtualizing network node functions into “building blocks” or entities that may be operationally connected or linked together to provide services. A virtualized network function (VNF) may comprise one or more virtual machines running computer program codes using standard or general type servers instead of customized hardware. Cloud computing or data storage may also be utilized. In radio communications this may mean node operations may be carried out, at least partly, in a server, host or node may be operationally coupled to a remote radio head. It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. It should also be understood that the distribution of labour between core network operations and base station operations may differ from that of the LTE or even be non-existent.

[146] Embodiments of the various techniques described herein may be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. Embodiments may be implemented as a computer program product, i.e., a computer program tangibly embodied in an information carrier, e.g., in a machine readable storage device or in a propagated signal, for execution by, or to control the operation of, a data processing apparatus, e.g., a programmable processor, a computer, or multiple computers. Embodiments may also be provided on a computer readable medium or computer readable storage medium, which may be a non-transitory medium. Embodiments of the various techniques may also include embodiments provided via transitory signals or media, and/or programs and/or software embodiments that are downloadable via the Internet or other network(s), either wired networks and/or wireless networks. In addition, embodiments may be provided via machine type communications (MTC), and also via an Internet of Things (IOT).

[147] The computer program may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, distribution medium, or computer readable medium, which may be any entity or device capable of carrying the program. Such carriers include a record medium, computer memory, read-only memory, photoelectrical and/or electrical carrier signal, telecommunications signal, and software distribution package, for example. Depending on the processing power needed, the computer program may be executed in a single electronic digital computer or it may be distributed amongst a number of computers.

[148] Furthermore, embodiments of the various techniques described herein may use a cyber-physical system (CPS) (a system of collaborating computational elements controlling physical entities). CPS may enable the embodiment and exploitation of massive amounts of interconnected ICT devices (sensors, actuators, processors microcontrollers, . . .) embedded in physical objects at different locations. Mobile cyber physical systems, in which the physical system in question has inherent mobility, are a subcategory of cyber-physical systems. Examples of mobile physical systems include mobile robotics and electronics transported by humans or animals. The rise in popularity of smartphones has increased interest in the area of mobile cyber-physical systems. Therefore, various embodiments of techniques described herein may be provided via one or more of these technologies.

[149] A computer program, such as the computer program(s) described above, can be written in any form of programming language, including compiled or interpreted languages, and can be deployed in any form, including as a standalone program or as a module, component, subroutine, or other unit or part of it suitable for use in a computing environment. A computer program can be deployed to be executed on one computer or on multiple computers at one site or distributed across multiple sites and interconnected by a communication network.

[150] Method steps may be performed by one or more programmable processors executing a computer program or computer program portions to perform functions by operating on input data and generating output. Method steps also may be performed by, and an apparatus may be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

[151] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer, chip or chipset. Generally, a processor will receive instructions and data from a read-only memory or a random access memory or both. Elements of a computer may include at least one processor for executing instructions and one or more memory devices for storing instructions and data. Generally, a computer also may include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magnetooptical disks, or optical disks. Information carriers suitable for embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magnetooptical disks; and CDROM and DVD-ROM disks. The processor and the memory may be supplemented by, or incorporated in, special purpose logic circuitry.

[152] To provide for interaction with a user, embodiments may be implemented on a computer having a display device, e.g., a cathode ray tube (CRT) or liquid crystal display (LCD) monitor, for displaying information to the user and a user interface, such as a keyboard and a pointing device, e.g., a mouse or a trackball, by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, or tactile input.

[153] Embodiments may be implemented in a computing system that includes a backend component, e.g., as a data server, or that includes a middleware component, e.g., an application server, or that includes a frontend component, e.g., a client computer having a graphical user interface or a Web browser through which a user can interact with an embodiment, or any combination of such backend, middleware, or frontend components. Components may be interconnected by any form or medium of digital data communication, e.g., a communication network. Examples of communication networks include a local area network (LAN) and a wide area network (WAN), e.g., the Internet.

[154] While certain features of the described embodiments have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the various embodiments.

Claims

1. A method comprising: configuring, by a user device, dual connectivity including a master cell group associated with a first network node that is configured as a master node for dual connectivity for the user device and a secondary cell group associated with a second network node that is configured as a secondary node; determining, by the user device, that the secondary cell group is deactivated; receiving, by the user device, a small data transmission configuration for the secondary cell group; detecting, by the user device, a need to transmit data to the secondary cell group; determining that the small data transmission configuration for the secondary cell group can be used for a data transmission; and transmitting, by the user device, data via the secondary cell group to the second network node utilizing a small data transmission according to the small data transmission configuration.

2. The method of claim 1, wherein the determining that the secondary cell group is deactivated comprises at least one of the following: receiving, by the user device from the first network node, a request to deactivate the secondary cell group associated with the second network node; deactivating, by the user device, the secondary cell group in response to a request to deactivate the secondary cell group; or configuring, by the user device, a deactivated secondary cell group or a secondary cell group that is in a deactivated state, as part of dual connectivity for the user device.

3. The method of any of claims 1-2 wherein the small data transmission comprises a transmission that is less than a threshold size, and which may be transmitted via at least one of a configured grant-based small data transmission or a random access-based small data transmission.

36

4. The method of any of claims 1-3, wherein the data comprises at least one of: a master cell group failure information to report, by the user device via the secondary cell group to the second network node, a master cell group radio link failure, based on the user device detecting a master cell group radio link failure; data received by the user device for uplink transmission by the user device via the secondary cell group to the second network node; or a buffer status report if the data to be transmitted is greater than a threshold size or does not fit within a pay load of a small data transmission according to the small data transmission configuration.

5. The method of any of claims 1-4, wherein the small data transmission configuration is provided for a configured grant-based small data transmission and a random access-based small data transmission; the method further comprising: determining whether a timing advance for the small data transmission configuration is valid or invalid; wherein the transmitting comprises performing at least one of the following: transmitting, by the user device via the secondary cell group to the second network node, the data utilizing the configured grant-based small data transmission according to the small data transmission configuration, if the timing advance for the small data transmission configuration is valid; otherwise, transmitting, by the user device via the secondary cell group to the second network node, the data utilizing the random access-based small data transmission within a first random access procedure message if the timing advance for the small data transmission configuration is invalid.

6. The method of any of claims 1-5, further comprising: receiving, by the user device from the second network node, a secondary cell group deactivation message, if the data is transmitted by the user device via a configured grant-based small data transmission according to the small data transmission configuration; and

37 receiving, by the user device from the second network node, a message, including the secondary cell group deactivation indication that indicates a continued deactivated state of the secondary cell group for the user device, within a second random access procedure message if the data is transmitted by the user device via a random access-based small data transmission within a first random access procedure message.

7. The method of any of claims 1-6, wherein determining that the small data transmission configuration for the secondary cell group can be used for data transmission comprises: determining that a configured grant-based small data transmission is available and a timing advance for the small data transmission configuration is valid; and determining that a size of the data to be transmitted is less than a threshold size or fits within a payload of a small data transmission according to the small data transmission configuration.

8. The method of claim 7, wherein the transmitting comprises: transmitting, by the user device via the secondary cell group to the second network node, the data utilizing the configured grant-based small data transmission according to the small data transmission configuration.

9. The method of any of claims 1-6, wherein determining that the small data transmission configuration for the secondary cell group can be used for data transmission comprises: determining that a size of the data to be transmitted is less than a threshold size or fits within a payload of a small data transmission according to the small data transmission configuration; and determining that a timing advance for the small data transmission configuration is invalid.

10. The method of claim 9 wherein the transmitting comprises: transmitting, by the user device via the secondary cell group to the second network node, the data utilizing the random access-based small data transmission within a first random access procedure message.

11. The method of any of claims 1-6 wherein the transmitted data comprises a buffer status report for the user device to transmit additional data if the additional data to be transmitted is greater than a threshold size or does not fit within a pay load of a small data transmission according to the small data transmission configuration.

12. The method of any of claims 1-6 wherein the detecting, by the user device, a need to transmit data to the secondary cell group comprises: receiving, by the user device, data for uplink transmission via the secondary cell group to the second network node; the method further comprising determining whether or not a size of the received data for uplink transmission fits within a pay load of a small data transmission according to the small data transmission configuration; wherein the transmitting comprises at least one of: transmitting, by the user device to the secondary cell group, the received data to the secondary cell group associated with the secondary node via a small data transmission according to the small data transmission configuration if the received data fits within a payload of a small data transmission according to the small data transmission configuration; and transmitting, by the user device to the secondary cell group, a buffer status report to allow for a subsequent transmission by the user device of the received data if the received data does not fit within a pay load of a small data transmission according to the small data transmission configuration.

13. The method of any of claims 1-6 wherein the detecting, by the user device, a need to transmit data to the secondary cell group comprises: detecting, by the user device, a master cell group radio link failure, wherein the master cell group is associated with the first network node that is configured as the master node for dual connectivity for the user device.

14. The method of claim 13, wherein the transmitting comprises: transmitting a master cell group failure information to report, by the user device to the first network node or to the second network node, the master cell group radio link failure.

15. The method of claim 13, further comprising: receiving, by the user device from the second network node, a master cell group recovery information including a handover command instructing the user device to perform a handover to a target primary cell of a new master cell group; and performing, by the user device, a handover to the target primary cell of the new master cell group based on the handover command.

16. The method of claim 15, wherein the receiving the master cell group recovery information comprises at least one of: receiving, by the user device from the second network node via a secondary cell group deactivation message, a master cell group recovery information including a handover command instructing the user device to perform a handover to a target primary cell of a new master cell group if the master cell group failure information is transmitted by the user device via a configured grant-based small data transmission according to the small data transmission configuration; and receiving, by the user device from the second network node, a message, including the master cell group recovery information and a secondary cell group deactivation indication that indicates a continued deactivated state of the secondary cell group for the user device, via a second random access procedure message if the master cell group failure information is transmitted by the user device via a random access procedure -based small data transmission within the first random access procedure message.

17. The method of any of claims 14-16, wherein the master cell group failure information comprises an indication that a master cell group radio link failure has been detected, and one or more neighboring cell measurements measured by the user device.

18. The method of any of claims 1-17, wherein the small data transmission configuration comprises information indicating one or more of the following: time-frequency resources that may be used for a small data transmission; small data transmission bearers, which may be used for data transmission via a random access procedure based small data transmission or used for data transmission via a configured grant based small data transmission; a timer value for a timing advance for the small data transmission configuration; a buffer status report size; and a threshold size of data for a small data transmission, or a pay load size of a small data transmission.

19. A non-transitory computer-readable storage medium comprising instructions stored thereon that, when executed by at least one processor, are configured to cause a computing system to perform the method of any of claims 1-18.

20. An apparatus comprising means for performing the method of any of claims 1-18.

21. An apparatus comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform the method of any of claims 1-18.

22. An apparatus comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: configure, by a user device, dual connectivity including a master cell group associated with a first network node that is configured as a master node for dual connectivity for the user device and a secondary cell group associated with a second network node that is configured as a secondary node; determine, by the user device, that the secondary cell group is deactivated;

41 receive, by the user device, a small data transmission configuration for the secondary cell group; detect, by the user device, a need to transmit data to the secondary cell group; determine that the small data transmission configuration for the secondary cell group can be used for a data transmission; and transmit, by the user device, data via the secondary cell group to the second network node utilizing a small data transmission according to the small data transmission configuration.

23. A method comprising: configuring, by a second network node configured as a secondary node as part of a dual connectivity for a user device, a secondary cell group associated with the second network node; determining, by the second network node, that the secondary cell group is deactivated; transmitting, by the second network node to a first network node configured as a master node that provides a master cell group for the dual connectivity for the user device, a small data transmission configuration for the secondary cell group, to be forwarded by the first network node to the user device; and receiving data by the second network node from the user device via the secondary cell group while the secondary cell group is deactivated for the user device, wherein the data is received by the second network node via a small data transmission according to the small data transmission configuration.

24. The method of claim 23, wherein the determining that the secondary cell group is deactivated comprises at least one of the following: receiving a request to deactivate the secondary cell group associated with the second network node; deactivating the secondary cell group in response to a request to deactivate the secondary cell group; or configuring a deactivated secondary cell group or a secondary cell group that is in a deactivated state, as part of dual connectivity for the user device.

42

25. The method of any of claims 23-24, wherein the data received by the second network node comprises at least one of: a master cell group failure information to report, by the user device via the secondary cell group to the second network node, a master cell group radio link failure, based on the user device detecting a master cell group radio link failure; data received by the user device for uplink transmission by the user device via the secondary cell group to the second network node; or a buffer status report if the data to be transmitted is greater than a threshold size or does not fit within a pay load of a small data transmission according to the small data transmission configuration.

26. The method of any of claims 23-25, wherein the small data transmission comprises a transmission that is less than a threshold size or fits within a payload of a small data transmission according to the small data transmission configuration, and wherein the small data transmission may be transmitted via at least one of a configured grant-based small data transmission or a random access-based small data transmission.

27. The method of any of claims 23-26, wherein the receiving data comprises at least one of the following: receiving, by the second network node from the user device via the secondary cell group, the data utilizing the configured grant-based small data transmission according to the small data transmission configuration, if a timing advance for the small data transmission configuration is valid; receiving, by the second network node from the user device via the secondary cell group, the data utilizing the random access-based small data transmission within a first random access procedure message if the timing advance for the small data transmission configuration is invalid.

28. The method of claim 27, further comprising: transmitting, by the second network node to the user device via the secondary cell group, a secondary cell group deactivation message, if the data is received by the second network node

43 from the user device via a configured grant-based small data transmission according to the small data transmission configuration; and transmitting, by the second network node to the user device via the secondary cell group, a message, including a secondary cell group deactivation indication that indicates a continued deactivated state of the secondary cell group for the user device, within a second random access procedure message if the data is received by the second network node from the user device via a random access-based small data transmission within a first random access procedure message.

29. The method of any of claims 23-28, wherein the receiving data comprises: receiving, by the second network node from the user device via the secondary cell group, a master cell group failure information that reports a master cell group radio link failure; and wherein the method further comprises: forwarding, by the second network node to the first network node, the master cell group failure information that reports the master cell group radio link failure; receiving, by the by the second network node from the first network node, a master cell group recovery information including a handover command instructing the user device to perform a handover to a target cell of a new master cell group; and transmitting, by the second network node to the user device via the secondary cell group, the master cell group recovery information with a secondary cell group deactivation indication.

30. The method of claim 29, wherein the transmitting the master cell group recovery information comprises at least one of: transmitting, by the second network node to the user device via a secondary cell group deactivation message, the master cell group recovery information including a handover command instructing the user device to perform a handover to a target primary cell of a new master cell group if the master cell group failure information is received by the second network node from the user device via a configured grant-based small data transmission according to the small data transmission configuration; and transmitting, by the second network node to the user device, a message, including the master cell group recovery information and a secondary cell group deactivation indication that

44 indicates a continued deactivated state of the secondary cell group for the user device, via a second random access procedure message if the master cell group failure information is received by the second network node from the user device via a random access procedure based-small data transmission within the first random access procedure message.

31. A non-transitory computer-readable storage medium comprising instructions stored thereon that, when executed by at least one processor, are configured to cause a computing system to perform the method of any of claims 23-30.

32. An apparatus comprising means for performing the method of any of claims 23- 30.

33. An apparatus comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform the method of any of claims 23-30.

34. An apparatus comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: configure, by a second network node configured as a secondary node as part of a dual connectivity for a user device, a secondary cell group associated with the second network node; determine, by the second network node, that the secondary cell group is deactivated; transmit, by the second network node to a first network node configured as a master node that provides a master cell group for the dual connectivity for the user device, a small data transmission configuration for the secondary cell group, to be forwarded by the first network node to the user device; and

45 receive data by the second network node from the user device via the secondary cell group while the secondary cell group is deactivated for the user device, wherein the data is received by the second network node via a small data transmission according to the small data transmission configuration.

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