Managing small data transmissions in unlicensed radio frequency spectrum band by wireless device

Abstract

The invention relates to managing small data transmissions (SDT) in an unlicensed radio frequency spectrum band by a wireless device while in a radio resource control (RRC) inactive state. The wireless device performs a timing advance (TA) verification procedure using a measured reference signal received power (RSRP) value. After successfully obtaining DL timing synchronization and after confirming that a portion of the unlicensed RF band is not occupied, the wireless device transmits uplink (UL) data during a configured grant SDT (CG-SDT) occasion. The wireless device may remove or delay transmission of the UL data to a subsequent CG-SDT occasion when DL timing synchronization is not successfully acquired prior to the CG-SDT occasion, or when a Listen Before Talk (LBT) failure is encountered that indicates that the CG-SDT occasion cannot be used. When the time elapsed from the previous TA verification exceeds a TA time threshold, the wireless device may re-measure the RSRP value and re-verify the TA value.

Description

Technical Field

[0001] The described embodiments relate to wireless communications, including methods and apparatus for managing small data transmission (SDT) by wireless devices in unlicensed radio frequency bands. Background Art

[0002] Newer generations (e.g., fifth generation (5G) New Radio (NR)) cellular wireless networks implementing one or more third generation partnership project (3GPP) 5G standards are rapidly developing and being deployed by network operators around the world. Newer cellular wireless networks provide a range of packet-based services, with 5G technology providing increased data throughput and lower latency connections that ensure enhanced mobile broadband services for wireless devices. The higher data throughput and lower latency of 5G are expected to introduce a range of new applications and services and improve existing applications and services. While in a radio resource control (RRC) connected state with a cellular wireless network, it may be inefficient for both the wireless device and the cellular wireless network to pass a small amount of data with the accompanying signaling overhead. In order to improve signaling efficiency, the wireless device may instead transmit a limited amount of data while in an RRC inactive state with the cellular wireless network. The cellular wireless network may provide a configured grant (CG) that allocates a time period for a wireless device to use for a small data transfer (SDT) when it is in an RRC inactive state. Prior to sending uplink (UL) data during a CG-SDT opportunity in an unlicensed radio frequency (RF) band, the wireless device attempts to acquire timing synchronization and listens to determine whether the unlicensed RF band can be used for transmission. Transmissions by other wireless devices in the unlicensed RF band may interfere with timing synchronization acquisition during a time synchronization opportunity prior to the CG-SDT opportunity and may interfere with UL data transmission during the CG-SDT opportunity. When using an unlicensed RF band, a mechanism is needed for wireless devices to manage small data transmissions. Summary of the invention

[0003] The present application relates to wireless communications, including methods and apparatus for managing small data transmission (SDT) in a cellular unlicensed radio frequency band by a wireless device. The wireless device is configured to transmit a limited amount of data using an unlicensed radio frequency (RF) band when in a radio resource control (RRC) inactive state with a cellular wireless network. Since the unlicensed RF band used by the cellular wireless network is shared with a separate non-cellular wireless network, transmissions by other wireless devices in the unlicensed RF band can overlap with downlink (DL) transmissions from the cellular wireless network to the wireless device, and can also overlap with uplink (UL) transmissions from the wireless device to the cellular wireless network. When the wireless device transitions from an RRC connected state to an RRC inactive state (or when in an RRC inactive state), the cellular wireless network can provide the wireless device with a configuration grant (CG) allocating a time period for small data transmission (SDT) in an RRC release message. The RRC release message can also include a timing advance (TA) value for the wireless device for time alignment of UL communications transmitted to the cellular wireless network. In some cases, the cellular wireless network may also provide a TA value to the wireless device in a medium access control (MAC) control element (CE) TA command message. The wireless device calculates a first reference signal received power (RSRP) value within a first measurement window in which the most recent TA value is received. Later, when the wireless device determines that UL data can be used for CG-SDT transmission, the wireless device performs a TA verification process while in an inactive state. The wireless device calculates a second RSRP value and compares the second RSRP value with the first RSRP value to determine whether the previously received TA value remains valid. After a successful TA verification, the wireless device attempts to acquire timing synchronization with the cellular wireless network by receiving a DL synchronization signal block (SSB) during one or more timing synchronization opportunities before the CG-SDT opportunity, during which a portion of the UL data is transmitted. Transmissions from other wireless devices sharing an unlicensed RF band may interfere with the transmission and / or reception of a DL SSB. The cellular wireless network may perform a listen-before-talk (LBT) process to determine whether the unlicensed RF band is not occupied before transmitting a DL SSB to the wireless device. In some cases, DL SSB transmission may not occur or may occur but be interfered with by other wireless device transmissions. When timing synchronization is not successfully acquired before a CG-SDT opportunity, the wireless device may delay the transmission of UL data intended for a portion of the CG-SDT opportunity to a subsequent CG-SDT opportunity or remove the portion of UL data. In some embodiments, before attempting to transmit UL data during a CG-SDT opportunity, the wireless device must acquire timing synchronization within the time range of the CG-SDT opportunity.When timing synchronization is not acquired before the CG-SDT opportunity, the wireless device may ignore the current CG-SDT opportunity and attempt to acquire timing synchronization after the current CG-SDT opportunity and before a subsequent CG-SDT opportunity. Transmissions from other wireless devices sharing an unlicensed RF band may also interfere with UL data transmission, and therefore, the wireless device performs an LBT process before the CG-SDT opportunity to determine whether the unlicensed RF band can be used for UL CG-SDT transmission. When no DL LBT failure occurs (timing synchronization is successfully acquired) and no UL LBT failure occurs (unlicensed RF band that can be used for UL transmission), the wireless device transmits a portion of UL data during the CG-SDT opportunity. When a UL LBT failure occurs, the wireless device may delay the transmission of the portion of UL data to a subsequent CG-SDT opportunity or remove the portion of UL data. In some embodiments, the wireless device may reacquire timing synchronization after a CG-SDT opportunity that cannot be used due to a UL LBT failure and before a subsequent CG-SDT opportunity. In some embodiments, after the UL LBT fails, the wireless device removes the current portion of UL data intended for transmission at the current CG-SDT opportunity, and prepares the new portion of UL data for transmission at the subsequent CG-SDT opportunity. In some embodiments, the wireless device delays the current portion of UL data without performing a new TA verification process before the subsequent CG-SDT opportunity. In some embodiments, before the subsequent CG-SDT opportunity (and after the current CG-SDT opportunity), the wireless device performs a complete or partial TA verification process. In some embodiments, the wireless device performs an additional RSRP measurement and compares the additional RSRP measurement with the stored RSRP measurement corresponding to the most recent TA value to determine the validity of the most recent TA value. In some embodiments, the wireless device performs a complete TA verification process by performing two RSRP measurements and comparing them to each other to determine the validity of the most recent TA value. In some embodiments, the wireless device determines whether the CG-SDT opportunity is within the time range of the most recent TA verification process. When the time elapsed between the next CG-SDT opportunity to transmit UL data and the most recent TA verification procedure exceeds the TA time threshold, the wireless device may perform a full or partial TA verification procedure to verify (or re-verify) the TA value.

[0004] Other aspects and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate by way of example the principles of the described embodiments.

[0005] The present invention content is provided only for the purpose of summarizing some example embodiments, so as to provide a basic understanding of some aspects of the subject matter described herein. Therefore, it should be understood that the above-mentioned features are only examples and should not be construed as narrowing the scope or essence of the subject matter described herein in any way. Other features, aspects and advantages of the subject matter described herein will become apparent through the following detailed description, drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The present disclosure will be more readily understood through the following detailed description taken in conjunction with the accompanying drawings, in which like reference numerals designate like structural elements.

[0007] Figure 1A A block diagram illustrating different components of an example system configured to perform small data transfer (SDT) communications by a wireless device in accordance with some embodiments.

[0008] Figure 1B A block diagram illustrating radio resource control (RRC) states of a wireless device according to some embodiments.

[0009] Figure 1C A diagram illustrating exemplary communications for performing SDT communications between a wireless device and a cellular wireless network according to some embodiments.

[0010] Figure 2 A diagram illustrating exemplary failures that may occur when performing SDT communications in an unlicensed radio frequency (RF) band, according to some embodiments.

[0011] Figure 3A , Figure 3B and Figure 3C A diagram illustrating an example mechanism for mitigating downlink (DL) timing synchronization failure of a wireless device during SDT communications in accordance with some embodiments.

[0012] Figure 4A , Figure 4B and Figure 4C A diagram illustrating an example mechanism for mitigating uplink (UL) transmission failures of a wireless device during SDT communications according to some embodiments.

[0013] Figure 5 A flow chart illustrating an exemplary method for managing SDT communications by a wireless device according to some embodiments.

[0014] Figure 6 A flow chart illustrating another exemplary method for managing SDT communications by a wireless device according to some embodiments.

[0015] Figure 7A block diagram illustrating exemplary elements of a wireless device according to some embodiments is illustrated. DETAILED DESCRIPTION

[0016] Representative applications of the methods and apparatus according to the present application are described in this section. These examples are provided only to add context and aid in understanding the described embodiments. Therefore, it will be apparent to those skilled in the art that the embodiments may be practiced without some or all of these specific details. In other cases, in order to avoid unnecessarily obscuring the embodiments, well-known processing steps are not described in detail. Other applications are possible, so that the following examples should not be considered restrictive.

[0017] The present application relates to wireless communications, including methods and apparatus for managing small data transmission (SDT) in an unlicensed radio frequency band by a wireless device. The wireless device is configured to transmit a limited amount of uplink (UL) data using an unlicensed radio frequency (RF) band when in a radio resource control (RRC) inactive state with a cellular wireless network. When only a small amount of data can be used for UL transfer, the transmission of UL data by the wireless device when in the RRC inactive state can be more efficient than transitioning to an RRC connected state, particularly with respect to signaling overhead. The limited UL data transmission by the wireless device when in the RRC inactive state can be referred to as small data transmission (SDT). Since the unlicensed RF band used by the cellular wireless network is shared with a separate non-cellular wireless network, transmissions by other wireless devices in the unlicensed RF band can overlap with downlink (DL) transmissions by the cellular wireless network to the wireless device, and can also overlap with UL transmissions by the wireless device to the cellular wireless network. Interference with DL transmissions performed by the cellular wireless network may disrupt the wireless device from acquiring timing synchronization, while interference with UL transmissions performed by the wireless device may interrupt UL data communications to the cellular wireless network.

[0018] When transitioning from the RRC connected state to the RRC inactive state (or when in the RRC inactive state), the cellular wireless network may provide the wireless device with a configured grant (CG) in an RRC release message allocating a time period for SDT, which is referred to herein as a CG-SDT opportunity. The RRC release message may also include a timing advance (TA) value for the wireless device for aligning UL transmissions to the cellular wireless network relative to DL transmissions from the cellular wireless network. In some cases, when the wireless device is in the RRC inactive state, the cellular wireless network may also provide the TA value to the wireless device in a medium access control (MAC) control element (CE) TA command. The wireless device may use the most recently received TA value to adjust the time alignment of UL communications to the cellular wireless network. In order to measure the DL path loss reference value, the wireless device receives and measures a reference signal transmitted by the cellular wireless network and calculates a first reference signal received power (RSRP) value, which is referred to herein as an RSRP1 value. The RSRP1 value may be determined by the wireless device within a first measurement window in which the most recent TA value is received from the cellular wireless network. The RSRP1 value provides a snapshot of the distance between the wireless device and the gNodeB of the cellular wireless network. Later, when the wireless device determines that UL data can be used for CG-SDT transmission while in an inactive state, the wireless device performs a TA verification process to determine whether the most recent TA value can still be considered valid for time alignment of UL transmissions sent to the cellular wireless network. As part of the TA verification process, the wireless device receives and measures another reference signal and calculates a second RSRP value, which is referred to herein as the RSRP2 value. The wireless device then compares the second RSRP value with the first RSRP value, for example by calculating the difference between RSRP1 and RSRP2 and comparing the magnitude of the difference with the CG-SDT RSRP change threshold to determine whether the TA value remains valid. When the TA value is valid, the wireless device continues the SDT session. When the TA verification fails, the wireless device does not initiate an SDT transmission, repeats the measurement of the RSRP2 value and the comparison of the change in the RSRP2 value with the RSRP1 value to determine whether the TA value is verified, after which the wireless device continues the SDT session. In some cases, when the TA value is invalid for a period of time, the wireless device waits for the cellular wireless network to initiate a new SDT session.

[0019] After successful TA verification, the wireless device attempts to acquire timing synchronization with the cellular wireless network by receiving a DL synchronization signal block (SSB) during one or more timing synchronization opportunities before the CG-SDT opportunity, during which a portion of the UL data is transmitted. Transmissions from other wireless devices sharing an unlicensed RF band may interfere with the transmission and / or reception of the DL SSB. The cellular wireless network may perform a listen-before-talk (LBT) process to determine whether a portion of the unlicensed RF band in which the DL SSB will occur can be used for transmission. In some cases, the DL SSB transmission performed by the cellular wireless network may not occur in one or more scheduled DL timing synchronization opportunities before the CG-SDT opportunity, or may be interfered with by other wireless device transmissions. The wireless device may not be able to acquire timing synchronization before the CG-DTS transmission opportunity occurs. When timing synchronization is not successfully acquired before the CG-SDT opportunity, the wireless device may delay the transmission of a portion of the UL data scheduled for transmission during the CG-SDT opportunity to a subsequent CG-SDT opportunity or remove the portion of the UL data. In some embodiments, before attempting to transmit the portion of UL data during the CG-SDT opportunity, the wireless device must acquire timing synchronization within the time range of the CG-SDT opportunity. When timing synchronization is not acquired before the CG-SDT opportunity (or not within the time range of the CG-SDT opportunity), the wireless device can ignore the current CG-SDT opportunity and attempt to acquire timing synchronization after the current CG-SDT opportunity and before the subsequent CG-SDT opportunity. Unless the wireless device successfully acquires timing synchronization before the CG-SDT opportunity, transmission of UL data will not occur during the CG-SDT opportunity.

[0020] Transmissions from other wireless devices that share an unlicensed RF band may also interfere with UL data transmissions to a cellular wireless network performed by the wireless device. The wireless device performs an LBT process before the UL CG-SDT opportunity at which the UL data is to be transmitted to determine whether a portion of the unlicensed RF band used by the wireless device for UL CG-SDT transmission is available. When timing synchronization is successfully acquired and no UL LBT failure occurs (unlicensed RF band that can be used for the relevant portion of UL transmission), the wireless device transmits the first portion of UL data during the CG-SDT opportunity. When a UL LBT failure occurs and the current UL CG-SDT opportunity cannot be used, the wireless device can delay the transmission of the first portion of UL data to a subsequent CG-SDT opportunity or remove the first portion of UL data. In some embodiments, the wireless device can reuse the previously acquired timing synchronization and retry the UL CG-SDT transmission at a subsequent CG-SDT opportunity. In some embodiments, the wireless device can acquire timing synchronization again before a subsequent CG-SDT opportunity (and after a CG-SDT opportunity that cannot be used due to a UL LBT failure). In some embodiments, after UL LBT fails, the wireless device removes a first portion of UL data intended for transmission at a current CG-SDT opportunity and prepares a new portion of UL data for transmission at a subsequent CG-SDT opportunity.

[0021] In some cases, the wireless device may determine whether a previously verified TA value continues to be valid or needs to be revalidated. In some embodiments, due to a DL LBT failure that prohibits successful timing synchronization or a UL LBT failure that blocks UL data transmission, the wireless device delays the first portion of UL data from the current CG-SDT opportunity to a subsequent CG-SDT opportunity, and retries to transmit the first portion of UL data during the subsequent CG-SDT opportunity without performing a new TA verification process. In some embodiments, before the subsequent CG-SDT opportunity (and after the current CG-SDT opportunity), the wireless device performs a full TA verification process or a partial TA verification process. In some embodiments, the wireless device performs a full TA verification process by taking two separate RSRP measurements and comparing them to each other to determine the validity of the most recent TA value. In some embodiments, the wireless device performs a partial TA verification process by taking an additional RSRP measurement and comparing the additional RSRP measurement with the stored RSRP measurement corresponding to the most recent TA value to determine the validity of the most recent TA value. In some embodiments, the wireless device determines whether the CG-SDT opportunity is within the time range of the most recent TA verification process and sends UL data at this opportunity. When the time elapsed between the CG-SDT opportunity for the next transmission of UL data and the most recent TA verification procedure exceeds the TA time threshold, the wireless device may perform a full TA verification procedure or a partial TA verification procedure to verify (or re-verify) the most recent TA value.

[0022] These and other embodiments are described below with reference to FIGS. Figure 7 Discussion is made; however, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for illustrative purposes only and should not be construed as limiting.

[0023] Figure 1AA block diagram 100 of various components of an exemplary system configured to perform small data transfer (SDT) is illustrated. A wireless device 102 includes wireless circuitry that can receive cellular wireless transmissions in cellular licensed and unlicensed radio frequency (RF) bands from a cellular wireless network. A gNodeB 112 of the cellular wireless network can transmit reference signals, such as synchronization signal blocks (SSBs) 106, that the wireless device 102 can use to obtain timing and frequency synchronization in order to receive and transmit communications from and to the gNodeB 112 of the cellular wireless network. The gNodeB 112 can configure the wireless device to operate in a radio resource control (RRC) inactive state to conserve battery power and free up RF resources for use by other wireless devices 102. Releases 15, 16, and 17 of the 3GPP wireless communication standard introduced a small data transfer (SDT) feature to allow a wireless device 102 to transmit a limited amount of data while in an RRC inactive state without requiring the wireless device 102 to transition to an RRC connected state. Prior to transmitting the SDT 108, the wireless device 102 receives the SSB 106 to determine to acquire DL timing synchronization to allow the wireless device 102 to apply an uplink (UL) time advance (TA) adjustment relative to the downlink (DL) frame boundary to ensure proper reception of the UL transmission by the wireless device 102 to the gNodeB 112. When operating in an unlicensed RF band shared with other wireless devices (including non-cellular wireless devices), the transmission of the SSB 106 by the gNodeB 112 may conflict with the transmissions of the other wireless devices. The gNodeB 112 may use a listen-before-talk (LBT) process to determine whether a portion of the unlicensed RF band that the gNodeB 112 intends to use is available (not used by other wireless devices). When the gNodeB 112 determines that the portion of the unlicensed RF band is available, the gNodeB 112 may transmit a signal (e.g., the SSB 106) to the wireless device 102. When the gNodeB 112 determines that the portion of the unlicensed RF band is not available, the gNodeB 112 may refrain from transmitting in the portion of the unlicensed RF band to the wireless device 102. Even when the gNodeB 112 successfully transmits to the wireless device 102, in some instances, other wireless devices may transmit in the same portion of the unlicensed RF band, causing a time overlap conflict that may cause the wireless device 102 to be unable to receive and successfully decode the SSB 106. When the wireless device 102 has successfully acquired timing synchronization, the wireless device 102 may send UL data to the gNodeB 112 during a configured Granted SDT (CG-SDT) opportunity when a portion of the unlicensed RF band is available for use by the wireless device 102.Other wireless devices using the unlicensed RF band may already be occupying the CG-SDT opportunity, and the wireless device 102 uses the LBT process to determine the availability of the unlicensed RF band. In some cases, the wireless device 102 will not be able to use the allocated CG-SDT opportunity. As further discussed herein, the wireless device 102 may use various techniques to manage SDT communications in the unlicensed RF band when an LBT failure is encountered in the DL direction that affects timing acquisition and / or when an LBT failure is encountered in the UL direction that affects the transmission of UL data at the CG-SDT opportunity.

[0024] Figure 1BA state transition diagram 150 for a wireless device 102 is illustrated. When associated with a cellular wireless network but without an active connection for data transmission and reception, the wireless device 102 can be in an RRC idle state 156. While in the RRC idle state 156, the wireless device 102 can monitor a paging channel, perform cell measurements, and receive system information from the cellular wireless network. The wireless device 102 can send an RRC setup 166 control message to the cellular wireless network to transition from the RRC idle state 156 to the RRC connected state 152, such as to initiate a mobile originating (MO) voice connection, receive a mobile called (MT) voice connection, receive DL data, or send UL data. After completing communications with the wireless device 102 while in the RRC connected state 152, the cellular wireless network can send an RRC release 162 message to return the wireless device 102 to the RRC idle state 156. When the wireless device 102 has only a small amount of UL data to transmit to the cellular wireless network, the signaling overhead of transitioning from the RRC idle state 156 to the RRC connected state 152 and formatting and transmitting the small amount of UL data may be inefficient. Instead of sending the wireless device 102 from the RRC connected state 152 to the RRC idle state 156, the gNodeB 112 of the cellular wireless network may transition the wireless device 102 to the RRC inactive state 154 by sending an RRC release with pause 160 command message. The RRC release with pause 160 command message may include an SDT configuration indicating a CG-SDT opportunity at which the wireless device 102 may transmit a limited amount of UL data while remaining in the RRC inactive state 154 and without requiring the wireless device 102 to transition back to the RRC connected state 152 to transmit the limited amount of UL data. The wireless device 102 may use an SDT process to deliver UL data at one or more CG-SDT opportunities while in the RRC inactive state 154. If the wireless device 102 requires more radio resources than are available via the SDT procedure, the wireless device 102 may return to the RRC connected state 152 via the RRC resume 164 command message. After completing the UL data transmission via the SDT procedure, the wireless device 102 may remain in the RRC inactive state 154 after receiving an additional RRC release with pause 168 command message from the gNodeB 112 of the cellular wireless network. The additional RRC release with pause 168 command message may include an SDT configuration that indicates a future CG-SDT opportunity for the wireless device 102 to use for future small amounts of UL data. Alternatively, the wireless device 102 may transition to the RRC idle state 156 in response to the RRC release 162 command message from the gNodeB 112 of the cellular wireless network (without a pause or SDT configuration).

[0025] Figure 1CA diagram 170 of an SDT signaling process including communications between a wireless device 102 and a gNodeB 112 of a cellular wireless network is illustrated. While in the RRC connected state 152, the wireless device 102 may receive an RRC release with suspend 160 command message from the gNodeB 112 including an SDT configuration. At 172, the wireless device 102 may suspend data radio bearers (DRBs) and transition to the RRC inactive state 154. The wireless device 102 may also suspend one or more signaling radio bearers (SRBs) while maintaining (or reestablishing) at least one SRB with the gNodeB 112 of the cellular wireless network. During the time window of transitioning from the RRC connected state 152 to the RRC inactive state 154, the wireless device 102 may also measure and store a first reference signal received power (RSRP) value, referred to herein as RSRP1, for later use as part of a timing alignment (TA) verification process. At 174, the wireless device 102 determines that pending UL data is available for transmission to a gNodeB 112 of the cellular wireless network, and also determines that one or more SDT criteria for using an SDT process while in the RRC inactive state 154 are met. The wireless device 102 may recover the DRB for SDT transmission. At 176, the wireless device 102 sends an initial SDT transmission using a random access channel (RACH) or via a configured grant (CG). At 178, the wireless device 102 sends additional SDT transmissions at one or more CG-SDT opportunities. At the end of the SDT period 180, the gNodeB 112 sends an RRC release with pause 168 command message to the wireless device 102, the RRC release with pause command message including another SDT configuration indicating future CG-SDT opportunities for the wireless device 102 to use for future SDT transmissions while remaining in the RRC inactive state 154. During the time window of the RRC Release 168 command message with the pause, the wireless device 102 may re-measure and store the updated RSRP1 value for later use as part of the timing alignment (TA) verification process.

[0026] Figure 2A diagram 200 illustrates potential failure points that may occur for SDT transmissions of a wireless device 102 in an unlicensed RF band. The wireless device 102 may be in an RRC inactive state 154 that has previously received an RRC release with pause 168 command message that includes an SDT configuration indicating a CG-SDT opportunity 202. The wireless device 102 completes RSRP1 measurements at a time T1′ within the RSRP1 measurement window of receiving the RRC release with pause 168 command message, or after receiving a timing advance (TA) medium access control (MAC) control element (CE) that includes a most recent TA value for the wireless device 102 to align UL transmissions sent to a gNodeB 112 with respect to DL transmissions received from the gNodeB 112. The RSRP1 value may be stored for future use by the wireless device 102 during a timing advance (TA) verification procedure. Subsequently, the wireless device 102 determines that UL data suitable for SDT transmission is available and meets the criteria for sending UL data via the SDT mechanism. The wireless device 102 can only transmit at the CG-SDT opportunity 202 after successfully acquiring timing synchronization with the gNodeB 112. The wireless device 102 can perform timing synchronization acquisition after completing the TA verification process. The wireless device 102 measures a second RSRP value (which is referred to as the RSRP2 value in this article) at time T2' within the RSRP2 measurement window before performing the TA verification process at time T2. The wireless device 102 performs the TA verification process by comparing the RSRP2 value with the previously measured and stored RSRP1 value to determine whether the RSRP has changed (increased or decreased) by more than the CG-SDT RSRP change threshold configured by the gNodeB 112. For example, the wireless device 102 can calculate the magnitude of the difference between the RSRP1 value and the RSRP2 value, and determine whether the magnitude exceeds the CG-SDT RSRP change threshold. The RSRP value provides an indication of the signal strength of the signal received from the gNodeB 112, and the difference between the most recently measured RSRP value RSRP2 and the previously measured RSRP1 value may indicate whether the signal strength has changed such that the most recent TA value received from the gNodeB 112 may no longer be valid. Changes in the received signal strength based on the RSRP value may indicate changes in the path loss (for signal propagation between the gNodeB 112 and the wireless device 102), which may indicate that the previously received, most recent TA value may be stale (no longer considered valid).

[0027] After successfully verifying the most recent TA value, the wireless device 102 may perform timing acquisition by attempting to receive the SSB 106 (or a relevant portion thereof) from the gNodeB 112 during the timing synchronization opportunity 204. Since the wireless device 102 and the gNodeB 112 may communicate in an unlicensed RF band, the gNodeB 112 may perform an LBT procedure prior to transmitting the SSB 106 during the timing synchronization opportunity 204 to determine whether the unlicensed RF band over which the gNodeB 112 intends to transmit the portion of the SSB 106 is unoccupied. Downlink (DL) LBT failure may occur at the timing synchronization opportunity 204 when the unlicensed RF band is occupied by another wireless device or when a transmission by another wireless device overlaps with the transmission of the SSB 106 and affects successful reception and decoding of the SSB 106 by the wireless device 102 during the timing synchronization opportunity 204. Multiple timing synchronization opportunities 204 may be available to acquire DL timing synchronization prior to the CG-SDT opportunity 202. The wireless device 102 may retry acquiring DL timing synchronization at one or more additional available timing synchronization opportunities 204 occurring before the CG-SDT opportunity 202. Figure 2 As shown, DL LBT failure occurs at the first timing synchronization opportunity 204, but the wireless device successfully acquires DL timing at the second timing synchronization opportunity 204. When the wireless device 102 cannot acquire timing synchronization at any timing synchronization opportunity 204 before the CG-SDT opportunity 202, the wireless device 102 can remove the portion of pending UL data or can delay the transmission of the portion of pending UL data to a subsequent CG-SDT opportunity 202. In some embodiments, the wireless device 102 may be required to successfully acquire timing synchronization within the time range of the CG-SDT opportunity 202 within which the transmission of the portion of pending UL data is attempted. Timing synchronization acquired much earlier than the CG-SDT opportunity 202 may be considered unavailable to the wireless device 102, and may need to be reacquired closer to the CG-SDT opportunity 202 for UL data transmission.

[0028] After successfully acquiring DL timing, the wireless device 102 may prepare to transmit a portion of pending UL data at the next available CG-SDT opportunity 202. The wireless device 102 may perform an LBT process before transmitting UL data during the CG-SDT opportunity 202 to determine whether a portion of the unlicensed RF band can be used for transmission. When the unlicensed RF band is occupied by another wireless device 102, an uplink (UL) LBT failure may occur at the CG-SDT opportunity 202. Multiple CG-SDT opportunities 202 are available for the wireless device 102, and in some embodiments, the wireless device 102 may retry and successfully transmit the portion of pending UL data via a subsequent CG-SDT opportunity 202. In some embodiments, when a UL LBT failure occurs, the wireless device 102 removes the portion of pending UL data. In some embodiments, the wireless device 102 delays the portion of pending UL data to a subsequent CG-SDT opportunity 202 and performs a complete TA verification process before the subsequent CG-SDT opportunity 202. In some embodiments, the wireless device 102 delays the portion of the pending UL data to a subsequent CG-SDT opportunity 202, and performs a partial TA verification process before the subsequent CG-SDT opportunity 202. In some embodiments, the wireless device 102 delays the portion of the pending UL data to a subsequent CG-SDT opportunity 202 without performing the TA verification process before the subsequent CG-SDT opportunity 202. In some embodiments, the wireless device 102 delays the portion of the pending UL data to a subsequent CG-SDT opportunity 202, and performs a partial or complete TA verification process within the time range of the subsequent CG-SDT opportunity 202.

[0029] Figure 3A A diagram 300 illustrates an example of mitigating a DL timing synchronization failure for SDT by a wireless device 102. The wireless device 102 may complete TA verification at time T2 and then attempt to acquire DL timing at one or more (or all available) timing synchronization opportunities 204 occurring before the CG-SDT opportunity 202 (and after T2). LBT failure may occur at one or more (or all available) timing synchronization opportunities 204. Figure 3AIn the example shown, DL timing synchronization is successfully acquired at two different timing synchronization opportunities 204, while LBT failure occurs at two other timing synchronization opportunities 204. When the wireless device 102 successfully acquires DL timing at a timing synchronization opportunity 204, the wireless device 102 can transmit UL data at one or more CG-SDT opportunities 202 after completing the successful DL timing acquisition. In some embodiments, the wireless device 102 successfully acquires DL timing at multiple timing synchronization opportunities 204 before the CG-SDT opportunity 202, and uses the most recently acquired DL timing (acquired from the successful timing synchronization opportunity 204 that is closest in time to the CG-SDT opportunity 202). When the wireless device 102 successfully acquires DL timing at at least one timing synchronization opportunity 204, after T2 and before the CG-SDT opportunity 202, the wireless device 102 can transmit at the CG-SDT opportunity 202 (if the relevant portion of the unlicensed RF band is available).

[0030] Figure 3B A diagram 320 illustrates another example of mitigating DL timing synchronization failure for SDT by the wireless device 102. Figure 3A Unlike the diagram 300 of FIG. 1 , the wireless device 102 cannot acquire DL timing synchronization during any available timing synchronization opportunities 204 occurring after T2 and before the first CG-SDT opportunity 202 due to the DL LBT failure of all timing synchronization opportunities 204. The wireless device 102 cannot transmit UL data at the CG-SDT opportunity 202 until DL timing synchronization is successfully acquired, so the wireless device 102 ignores the first CG-SDT opportunity 202 and retries to acquire DL timing synchronization using one or more timing synchronization opportunities 204 occurring after the ignored CG-SDT opportunity 202 and before the next CG-SDT opportunity 202. In some embodiments, the wireless device 102 removes the first portion of UL data previously prepared for transmission at the first CG-SDT opportunity 202, and prepares the second portion of UL data for the next CG-SDT opportunity 202. In some embodiments, the wireless device 102 delays the first portion of UL data to a next CG-SDT opportunity 202, and transmits the first portion of UL data at the next CG-SDT opportunity 202 after successfully acquiring DL timing synchronization at one or more timing synchronization opportunities 204 before the next CG-SDT opportunity 202. If DL timing synchronization is not successfully acquired before the next CG-SDT opportunity 202, the wireless device 102 may repeat the CG-SDT DL LBT failure process for another CG-SDT opportunity 202. The wireless device 102 may further delay or remove the delayed first portion of UL data.

[0031] Figure 3C A diagram 340 illustrates yet another example of mitigating DL timing synchronization failure for SDT by the wireless device 102. Figure 3A and Figure 3B Unlike the diagrams 300 and 320 of FIG. 340 , the wireless device 102 is required to acquire DL timing synchronization within the timing window before the CG-SDT opportunity 202 (within the time range of the CG-SDT opportunity 202 that sends UL data). In the example of the diagram 340 , the first two timing synchronization opportunities 204 before the corresponding CG-SDT opportunity 202 do not appear within the corresponding timing window, while the last two timing synchronization opportunities 204 before the corresponding CG-SDT opportunity 202 do fall within the corresponding timing window. The wireless device 102 may attempt to acquire DL timing synchronization at least one (and up to all) timing synchronization opportunities 204 that occur within the timing window of the corresponding CG SDT opportunity 202. When any timing synchronization opportunity 204 within the timing window before the first CG-SDT opportunity 202 does not successfully acquire DL timing synchronization, the wireless device 102 may ignore the first CG-SDT opportunity 202 and retry to acquire DL timing synchronization during one or more timing synchronization opportunities 204 that occur with the timing window before the second (subsequent) CG-SDT opportunity 202. In the example of the diagram 340, the wireless device 102 successfully acquires DL timing during at least one timing synchronization opportunity 204 occurring within the required timing window, and transmits UL data at a subsequent CG-SDT opportunity 202. The UL data transmitted by the wireless device 102 at the subsequent CG-SDT opportunity 202 may be the delayed first portion of UL data or the new second portion of UL data (with the first portion of UL data removed).

[0032] Figure 4AA diagram 400 illustrating an example of mitigating UL transmission failure for SDT by a wireless device 102. The wireless device 102 may complete TA verification at time T2 and subsequently successfully acquire DL timing at one or more (or all available) timing synchronization opportunities 204 occurring after T2 and before a first CG-SDT opportunity 202. The wireless device 102 may perform an LBT procedure and incur a UL LBT failure when the portion of the unlicensed RF band intended for UL transmission by the wireless device 102 is unavailable (or available but conflicts when transmitting). The wireless device 102 has several options for mitigating UL LBT failure. The wireless device 102 may transmit delayed UL data (prepared for the first CG-SDT opportunity 202) at a subsequent CG-SDT opportunity, or may transmit new UL data (prepared for the subsequent CG-SDT opportunity 202) at a subsequent CG-SDT opportunity and remove the previously prepared UL data. In some embodiments, the wireless device 102 reuses the DL timing synchronization previously obtained for the first CG-SDT opportunity 202 for the subsequent CG-SDT opportunity 202. In some embodiments, the wireless device 102 obtains (re)DL timing synchronization at one or more timing synchronization opportunities 204 (not shown) before the subsequent CG-SDT opportunity 202. In some embodiments, the wireless device 102 transmits new or delayed UL data at the subsequent CG-SDT opportunity 202 without performing TA verification again before the subsequent CG-SDT opportunity 202. In some embodiments, the wireless device 102 determines whether the time elapsed since T2 (when TA verification occurs) meets (e.g., exceeds) a TA time threshold. When the TA time threshold is met (the elapsed time indicates that the previous TA verification is stale), the wireless device 102 can perform a full TA verification process (re-measure RSRP1 value and RSRP2 value and verify the TA value) or perform a partial TA verification process (re-measure RSRP2 and reuse the previously measured RSRP1 value and verify the TA value). The wireless device 102 measures the RSRP1 value in response to receipt of an RRC release with a suspend message (including a CG-SDT) or in response to receiving a MAC CE TA command, and the wireless device 102 compares the currently measured RSRP2 value (obtained before the SDT transmission) with the most recently calculated (and stored) RSRP1 value to determine whether the most recent TA value is valid.

[0033] Figure 4BA diagram 420 illustrating another example of mitigating a UL transmission failure for SDT by a wireless device 102. The wireless device 102 performs a first TA verification at time T2 and successfully acquires DL timing during a timing synchronization opportunity 204 that occurs after T2 and before a first CG-SDT opportunity 202. The wireless device 102 encounters a UL LBT failure at the first CG-SDT opportunity 202 and re-performs the complete TA verification process by: i) re-measuring RSRP1 at time T1', ii) re-measuring RSRP2 at time T2', and iii) performing TA verification using the RSRP1 value and RSRP2 value re-measured at a second time T2. After re-performing TA verification, in some embodiments, the wireless device 102 re-acquires DL timing synchronization during one or more timing synchronization opportunities 204 prior to a subsequent CG-SDT opportunity 202. In some embodiments, the first portion of UL data intended for transmission at the first CG-SDT opportunity 202 is removed by the wireless device 102, and new (e.g., second portion of) UL data is transmitted at a subsequent CG-SDT opportunity 202. In some embodiments, the first portion of UL data intended for transmission at the first CG-SDT opportunity 202 is delayed and transmitted at a subsequent CG-SDT opportunity 202.

[0034] Figure 4C A diagram 440 illustrating another example of mitigating a UL transmission failure for SDT by a wireless device 102. The wireless device 102 performs a first TA verification at time T2 and successfully acquires DL timing during a timing synchronization opportunity 204 that occurs after T2 and before a first CG-SDT opportunity 202. The wireless device 102 encounters a UL LBT failure at the first CG-SDT opportunity 202 and performs a partial TA verification process by: i) re-measuring RSRP2 at a second time T2' and ii) performing a TA verification at the second time T2 using the re-measured RSRP2 value (from the second time T2') and the RSRP1 value previously measured at time T1'. After performing the partial TA verification, in some embodiments, the wireless device 102 re-acquires DL timing synchronization during one or more timing synchronization opportunities 204 prior to a subsequent CG-SDT opportunity 202. In some embodiments, the first portion of UL data intended for transmission at the first CG-SDT opportunity 202 is removed by the wireless device 102, and new (e.g., second portion of) UL data is transmitted at a subsequent CG-SDT opportunity 202. In some embodiments, the first portion of UL data intended for transmission at the first CG-SDT opportunity 202 is delayed and transmitted at a subsequent CG-SDT opportunity 202.

[0035] Figure 5 A flowchart 500 of an exemplary method for managing SDT transmissions by a wireless device 102 while in an RRC inactive state 154 is illustrated. At 502, the wireless device 102 determines whether there is pending uplink (UL) data that can be used for transmission. At 504, the wireless device 102 verifies a timing advance (TA) value recently received from a cellular wireless network. At 506, the wireless device 102 acquires downlink (DL) timing synchronization during a timing synchronization opportunity 204 within a time range and before a configured grant small data transmission (CG-SDT) opportunity 202. At 508, the wireless device 102 determines whether an unlicensed radio frequency (RF) band is unoccupied before the CG-SDT opportunity. When the unlicensed RF band is unoccupied (and therefore can be used for transmission), at 510, the wireless device 102 transmits a portion of the UL data to the cellular wireless network during the CG-SDT opportunity 202. When the unlicensed RF band is occupied (and therefore unavailable for transmission), at 512 the wireless device 102 either delays transmission of the portion of UL data to a subsequent CG-SDT opportunity 202 or removes the portion of UL data.

[0036] In some embodiments, after delaying transmission of the portion of UL data, the wireless device 102 acquires DL timing synchronization during a second DL timing synchronization opportunity 204 within a second time range of a subsequent CG-SDT opportunity 202, and the wireless device 102 transmits the portion of UL data to the cellular wireless network during the subsequent CG-SDT opportunity 202 when the unlicensed RF band is available for transmission. In some embodiments, the wireless device 102 determines the validity of the TA value by determining whether the most recently measured RSRP value differs from the previously measured and stored RSRP value by more than an RSRP change threshold. In some embodiments, after delaying transmission of the portion of UL data, the wireless device 102: i) measures one or more RSRP values, ii) re-determines the validity of the TA value most recently received from the cellular wireless network based on the one or more RSRP values, and iii) transmits the portion of UL data to the cellular wireless network during the subsequent CG-SDT opportunity 202 when the unlicensed RF band is available for transmission. In some embodiments, the one or more RSRP values ​​include only a single RSRP value, and the wireless device 102 re-determines the validity of the TA value by determining whether the single RSRP value differs from a previously measured and stored RSRP value by more than an RSRP change threshold. In some embodiments, the one or more RSRP values ​​include a first RSRP value and a second RSRP value measured after the first RSRP value, and the wireless device 102 re-determines the validity of the TA value by determining whether the second RSRP value differs from the first RSRP value by more than an RSRP change threshold. In some embodiments, after removing the portion of UL data, the wireless device 102: i) acquires DL timing synchronization during a second DL timing synchronization opportunity within a second time range of a subsequent CG-SDT opportunity 202, and ii) transmits a second portion of UL data to the cellular wireless network during a subsequent CG-SDT opportunity 202 when the unlicensed RF band is available for transmission.

[0037] Figure 6A flowchart 600 is illustrated of another exemplary method for managing SDT transmissions by a wireless device 102 while in an RRC inactive state 154. At 602, the wireless device 102 determines that UL data is available for transmission to a cellular wireless network. At 604, the wireless device 102 performs a first TA verification process to determine the validity of a TA value most recently received from the cellular wireless network. At 606, the wireless device 102 determines (based on the TA verification process) whether the most recently received TA value is valid. When the most recently received TA value is not valid, the method ends. When the most recently received TA value is valid, at 608, the wireless device 102 attempts to acquire DL timing synchronization during one or more timing synchronization opportunities 204 within a time range of the CG-SDT opportunity 202. At 610, the wireless device 102 determines whether DL timing synchronization was successfully acquired during at least one DL timing synchronization opportunity 204 within a time range of the CG-SDT opportunity 202. When DL timing synchronization is successfully acquired within the time range of the CG-SDT opportunity 202, at 612, the wireless device 102 uses the LBT process to determine whether the unlicensed RF band is unoccupied prior to the CG-SDT opportunity 202. At 616, when the LBT process indicates that the unlicensed RF band can be used for transmission, the wireless device 102 transmits the first portion of UL data to the cellular wireless network during the CG-SDT opportunity 202. When DL timing synchronization is not successfully acquired within the time range of the CG-SDT opportunity 202, at 614, the wireless device 102 either delays transmission of the first portion of UL data to a subsequent CG-SDT opportunity 202 or removes the first portion of UL data.

[0038] In some embodiments, when the TA value is determined to be valid and DL timing synchronization is successfully acquired during at least one DL timing synchronization opportunity 204 before and not within the time range of the CG-SDT opportunity 202, the wireless device 102 uses the LBT process to determine whether the unlicensed RF band is not occupied before the CG-SDT opportunity 202, and when the LBT process indicates that the unlicensed RF band can be used for transmission, transmits the first portion of UL data to the cellular wireless network during the CG-SDT opportunity. In some embodiments, after delaying the first portion of UL data to a subsequent CG-SDT opportunity 202, the wireless device 102 uses the LBT process to determine whether the unlicensed RF band is not occupied before the subsequent CG-SDT opportunity 202, and when the LBT process indicates that the unlicensed RF band can be used for transmission, the wireless device 102 transmits the first portion of UL data to the cellular wireless network during the subsequent CG-SDT opportunity 202. In some embodiments, after removing the first portion of the UL data, the wireless device 102 uses an LBT process to determine whether the unlicensed RF band is not occupied before a subsequent CG-SDT opportunity 202, and when the LBT process indicates that the unlicensed RF band can be used for transmission, the wireless device 102 transmits a second portion of the UL data to the cellular wireless network during the subsequent CG-SDT opportunity 202. In some embodiments, after removing the first portion of the UL data, the wireless device 102 performs a second TA verification process to re-determine the validity of the TA value most recently received from the cellular wireless network. When the TA value is re-determined to be valid, the wireless device 102 uses an LBT process to determine whether the unlicensed RF band is not occupied before a subsequent CG-SDT opportunity 202, and when the LBT process indicates that the unlicensed RF band can be used for transmission, the wireless device 102 transmits the second portion of the UL data to the cellular wireless network during the subsequent CG-SDT opportunity 202. In some embodiments, when DL timing synchronization is successfully acquired during two or more DL timing synchronization opportunities 204 before a CG-SDT opportunity 202, the wireless device 102 uses the DL timing synchronization acquired from the DL timing synchronization opportunity 204 that is closest in time to the CG-SDT opportunity 202. In some embodiments, after successfully acquiring DL timing synchronization during at least one DL timing synchronization opportunity 204 before one or more CG-SDT opportunities 202, the wireless device 102 transmits one or more portions of UL data at one or more CG-SDT opportunities 202.In some embodiments, after successfully acquiring DL timing synchronization during at least one DL timing synchronization opportunity 204 prior to one or more CG-SDT opportunities 202 occurring within a TA time range of a first TA verification process, the wireless device 102 transmits one or more portions of UL data at one or more CG-SDT opportunities 202. In some embodiments, the wireless device 102 performs a first TA verification process by determining whether a magnitude of a difference between a current reference signal received power (RSRP) value and a previously stored RSRP value satisfies an RSRP change threshold. In some embodiments, when a time elapsed after the first TA verification process satisfies a TA time threshold, the wireless device 102 performs a second TA verification process to re-determine the validity of a TA value most recently received from the cellular wireless network. In some embodiments, after successfully acquiring DL timing synchronization during at least one DL timing synchronization opportunity 204 prior to one or more CG-SDT opportunities 202 occurring within a TA time range of a second TA verification process, the wireless device 102 transmits one or more portions of UL data at one or more CG-SDT opportunities 202. In some embodiments, the wireless device 102 performs a second TA verification procedure by determining a current reference signal received power (RSRP) value and determining whether a magnitude of a difference between the current RSRP value and a previously stored RSRP value satisfies an RSRP change threshold. In some embodiments, the wireless device 102 performs a second TA verification procedure by: i) determining a first reference signal received power (RSRP) value, ii) determining a second RSRP value after determining the first RSRP value, and iii) determining whether a magnitude of a difference between the second RSRP value and the first RSRP value satisfies an RSRP change threshold.

[0039] Representative exemplary devices

[0040] Figure 7 An exemplary computing device 700 that can be used to implement the various components and techniques described herein according to some embodiments is illustrated in a block diagram format. In particular, a detailed view of the exemplary computing device 700 illustrates various components that can be included in the wireless device 102. Figure 7As shown, the computing device 700 may include one or more processors 702 representing a microprocessor or controller for controlling the overall operation of the computing device 700. In some embodiments, the computing device 700 may also include a user input device 708 that allows a user of the computing device 700 to interact with the computing device 700. For example, in some embodiments, the user input device 708 may take a variety of forms, such as buttons, keypads, dials, touch screens, audio input interfaces, visual / image capture input interfaces, input in the form of sensor data, etc. In some embodiments, the computing device 700 may include a display 710 (screen display) that can be controlled by the processor 702 to display information (e.g., information related to incoming, outgoing, or active communication sessions) to the user. The data bus 716 may facilitate data transfer between at least the storage device 740, the processor 702, and the controller 713. The controller 713 can be used to interact with and control different equipment through the equipment control bus 714. The computing device 700 may also include a network / bus interface 711 coupled to the data link 712. In the case of a wireless connection, the network / bus interface 711 may include wireless circuitry, such as a wireless transceiver and / or a baseband processor. The computing device 700 may also include a secure element 724. The secure element 724 may include an eUICC.

[0041] The computing device 700 also includes a storage device 740, which may include a single storage device or multiple storage devices (e.g., a hard drive), and includes a storage management module that manages one or more partitions within the storage device 740. In some embodiments, the storage device 740 may include flash memory, semiconductor (solid-state) memory, etc. The computing device 700 may also include a random access memory (RAM) 720 and a read-only memory (ROM) 722. The ROM 722 may store programs, utilities, or processes to be executed in a non-volatile manner. The RAM 720 may provide volatile data storage and store instructions related to the operation of the computing device 700.

[0042] Wireless Terminology

[0043] According to various embodiments described herein, the terms "wireless communication device", "wireless device", "mobile device", "mobile station", and "user equipment (UE)" may be used interchangeably herein to describe one or more common consumer electronic devices that may be capable of performing the processes associated with various embodiments of the present disclosure. According to various specific implementations, any of these consumer electronic devices may relate to: a cellular phone or smart phone, a tablet computer, a laptop computer, a notebook computer, a personal computer, a netbook computer, a media player device, an e-book device, Devices, wearable computing devices, and any other type of electronic computing device with wireless communication capabilities, which wireless communication capabilities may include communication via one or more wireless communication protocols, such as protocols used to communicate on the following networks: wireless wide area networks (WWAN), wireless metropolitan area networks (WMAN), wireless local area networks (WLAN), wireless personal area networks (WPAN), near field communication (NFC), cellular wireless networks, fourth generation (4G) LTE, advanced LTE (LTE-A) 5G, and / or 5G advanced or other currently or future developed advanced cellular wireless networks.

[0044] In some embodiments, the wireless communication device may also operate as part of a wireless communication system, which may include a group of client devices, which may also be referred to as stations, client wireless devices, or client wireless communication devices, interconnected to an access point (AP) (e.g., as part of a WLAN), and / or interconnected to each other (e.g., as part of a WPAN and / or "ad hoc" wireless network). In some embodiments, the client device may be any wireless communication device capable of communicating via WLAN technology (e.g., according to a wireless local area network communication protocol). In some embodiments, the WLAN technology may include a Wi-Fi (or more generally, a WLAN) wireless communication subsystem or radio component, which may implement the Institute of Electrical and Electronics Engineers (IEEE) 802.11 technology, such as one or more of the following: IEEE 802.11a; IEEE 802.11b; IEEE 802.11g; IEEE 802.11-2007; IEEE 802.11n; IEEE 802.11-2012; IEEE 802.11ac; or other currently or future developed IEEE 802.11 technology.

[0045] In addition, it should be understood that the UE described herein may be configured as a multi-mode wireless communication device that is also capable of communicating via different third generation (3G) and / or second generation (2G) RATs. In these cases, the multi-mode user equipment (UE) may be configured to prefer attaching to an LTE network that provides a faster data rate throughput over other 3G legacy networks that provide a lower data rate throughput. For example, in some specific implementations, the multi-mode UE may be configured to fall back to a 3G legacy network, such as an evolved high speed packet access (HSPA+) network, or a code division multiple access (CDMA) 2000 evolution-data only (EV-DO) network when 5G, LTE, and LTE-A networks are otherwise unavailable.

[0046] It is understood that the use of personally identifiable information should be subject to privacy policies and practices that are generally recognized to meet or exceed industry or government requirements for maintaining user privacy. Specifically, personally identifiable information data should be managed and processed to minimize the risk of unintentional or unauthorized access or use, and the nature of the authorized use should be clearly stated to users.

[0047] The various aspects, embodiments, specific implementations or features of the embodiments may be used individually or in any combination. The various aspects of the embodiments may be implemented by software, hardware, or a combination of hardware and software. The embodiments may also be implemented as computer readable code on a non-transient computer readable medium. A non-transient computer readable medium is any data storage device that can store data, which can then be read by a computer system. Examples of non-transient computer readable media include read-only memory, random access memory, CD-ROM, HDD, DVD, magnetic tape, and optical data storage devices. Non-transient computer readable media may also be distributed on a network coupled computer system so that the computer readable code is stored and executed in a distributed manner.

[0048] For the purpose of illustration, the foregoing description uses specific nomenclature to provide a thorough understanding of the embodiments. However, it will be apparent to those skilled in the art that specific details are not required in order to practice the embodiments. Therefore, the foregoing description of specific embodiments is presented for the purpose of illustration and description. The foregoing description is not intended to be exhaustive or to limit the embodiments described to the precise form disclosed. It will be apparent to those of ordinary skill in the art that, in view of the above teachings, many modifications and variations are feasible.

Claims

1. A method for managing small data transmission (SDT) by a wireless device using an unlicensed radio frequency band of a cellular wireless network, the method comprising: When inactive, the wireless device: determining that uplink (UL) data is available for transmission to the cellular wireless network; performing a first timing advance (TA) verification procedure to determine the validity of a TA value most recently received from the cellular wireless network; When the TA value is determined to be valid: attempting to acquire downlink (DL) timing synchronization during one or more timing synchronization opportunities within a time range of a configured Granted SDT (CG-SDT) opportunity; When DL timing synchronization is successfully acquired during at least one DL timing synchronization opportunity within the time range of the CG-SDT opportunity: determining whether the unlicensed radio frequency band is unoccupied using a listen-before-talk (LBT) process prior to the CG-SDT opportunity; and When the LBT process indicates that the unlicensed radio frequency band can be used for transmission, transmitting the first portion of the UL data to the cellular wireless network during the CG-SDT opportunity; as well as When acquisition of DL timing synchronization fails in all DL timing synchronization opportunities before the CG-SDT opportunity: i) delaying the transmission of the UL data of the first part to a subsequent CG-SDT timing, or ii) removing the UL data of the first part.

2. The method according to claim 1, further comprising: While in the inactive state, the wireless device: When the TA value is determined to be valid and DL timing synchronization is successfully acquired during at least one DL timing synchronization opportunity that is before the time range of the CG-SDT opportunity and is not within the time range: determining, prior to the CG-SDT opportunity, using the LBT process whether the unlicensed radio frequency band is unoccupied; and When the LBT process indicates that the unlicensed radio frequency band can be used for transmission, the first portion of the UL data is transmitted to the cellular wireless network during the CG-SDT opportunity.

3. The method according to claim 1, further comprising: While in the inactive state, the wireless device: After delaying the UL data of the first part to the subsequent CG-SDT opportunity: determining, prior to the subsequent CG-SDT opportunity, using the LBT process whether the unlicensed radio frequency band is unoccupied; and When the LBT process indicates that the unlicensed radio frequency band can be used for transmission, the first portion of the UL data is transmitted to the cellular wireless network during the subsequent CG-SDT opportunity.

4. The method according to claim 1, further comprising: While in the inactive state, the wireless device: After removing the UL data of the first part: determining, prior to the subsequent CG-SDT opportunity, using the LBT process whether the unlicensed radio frequency band is unoccupied; and When the LBT process indicates that the unlicensed radio frequency band can be used for transmission, a second portion of the UL data is transmitted to the cellular wireless network during the subsequent CG-SDT opportunity.

5. The method according to claim 1, further comprising: While in the inactive state, the wireless device: After removing the UL data of the first part: performing a second TA validation procedure to re-determine the validity of the TA value most recently received from the cellular wireless network; as well as When the TA value is re-determined to be valid: determining, prior to the subsequent CG-SDT opportunity, using the LBT process whether the unlicensed radio frequency band is unoccupied; and When the LBT process indicates that the unlicensed radio frequency band can be used for transmission, a second portion of the UL data is transmitted to the cellular wireless network during the subsequent CG-SDT opportunity.

6. The method according to claim 1, further comprising: While in the inactive state, the wireless device: When DL timing synchronization is successfully acquired during two or more DL timing synchronization opportunities before the CG-SDT opportunity, the DL timing synchronization acquired from the DL timing synchronization opportunity that is closest in time to the CG-SDT opportunity is used.

7. The method according to claim 1, further comprising: While in the inactive state, the wireless device: After successfully acquiring DL timing synchronization during at least one DL timing synchronization opportunity prior to one or more CG-SDT opportunities, one or more portions of the UL data are transmitted at the one or more CG-SDT opportunities.

8. The method according to claim 1, further comprising: While in the inactive state, the wireless device: After successfully acquiring DL timing synchronization during at least one DL timing synchronization opportunity prior to one or more CG-SDT opportunities occurring within a TA time range of the first TA verification procedure, one or more portions of the UL data are transmitted at the one or more CG-SDT opportunities.

9. The method of claim 1, wherein performing the first TA verification procedure comprises determining whether a magnitude of a difference between a current reference signal received power (RSRP) value and a previously stored RSRP value satisfies an RSRP change threshold.

10. The method according to claim 1, further comprising: While in the inactive state, the wireless device: When the time elapsed after the first TA verification process satisfies a TA time threshold, performing a second TA verification process to re-determine the validity of the TA value most recently received from the cellular wireless network; as well as After successfully acquiring DL timing synchronization during at least one DL timing synchronization opportunity prior to one or more CG-SDT opportunities occurring within the TA time range of the second TA verification process, one or more portions of the UL data are transmitted at the one or more CG-SDT opportunities.

11. The method according to claim 10, wherein performing the second TA verification process comprises: Determining a current reference signal received power (RSRP) value; as well as A determination is made as to whether a magnitude of a difference between the current RSRP value and a previously stored RSRP value satisfies an RSRP change threshold.

12. The method according to claim 10, wherein performing the second TA verification process comprises: determining a first reference signal received power (RSRP) value; determining a second RSRP value after determining the first RSRP value; as well as It is determined whether a magnitude of a difference between the second RSRP value and the first RSRP value satisfies an RSRP change threshold.

13. A method for managing small data transmission (SDT) by a wireless device using an unlicensed radio frequency band of a cellular wireless network, the method comprising: When inactive, the wireless device: determining that uplink (UL) data is available for transmission to the cellular wireless network; determining validity of a timing advance (TA) value most recently received from the cellular wireless network; acquiring downlink (DL) timing synchronization during a DL timing synchronization opportunity within a time range of a configured Granted SDT (CG-SDT) opportunity; transmitting a portion of the UL data to the cellular wireless network during the CG-SDT opportunity when the unlicensed radio frequency band is available for transmission; When the unlicensed radio frequency band cannot be used for transmission: i) delaying the transmission of the portion of the UL data to a subsequent CG-SDT timing, or ii) removing the portion of the UL data.

14. The method according to claim 13, further comprising: While in the inactive state, the wireless device: After delaying transmission of the portion of the UL data: acquiring downlink (DL) timing synchronization during a second downlink timing synchronization opportunity within a second time range of the subsequent CG-SDT opportunity; as well as The portion of the UL data is transmitted to the cellular wireless network during the subsequent CG-SDT opportunity when the unlicensed radio frequency band is available for transmission.

15. The method of claim 13, wherein determining the validity of the TA value comprises determining whether a most recently measured RSRP value differs from a previously measured and stored RSRP value by more than an RSRP variation threshold.

16. The method according to claim 13, further comprising: While in the inactive state, the wireless device: After delaying transmission of the portion of the UL data: measuring one or more reference signal received power (RSRP) values; re-determining validity of the TA value most recently received from the cellular wireless network based on the one or more RSRP values; as well as The portion of the UL data is transmitted to the cellular wireless network during the subsequent CG-SDT opportunity when the unlicensed radio frequency band is available for transmission.

17. The method of claim 15, wherein: The one or more RSRP values ​​include only a single RSRP value; and Re-determining the validity of the TA value includes determining whether the single RSRP value differs from a previously measured and stored RSRP value by more than an RSRP variation threshold.

18. The method of claim 15, wherein: The one or more RSRP values ​​include a first RSRP value and a second RSRP value measured after the first RSRP value; and Re-determining the validity of the TA value includes determining whether the second RSRP value differs from the first RSRP value by more than an RSRP variation threshold.

19. The method according to claim 13, further comprising: While in the inactive state, the wireless device: After removing the portion of the UL data: acquiring downlink (DL) timing synchronization during a second downlink timing synchronization opportunity within a second time range of the subsequent CG-SDT opportunity; as well as The second portion of the UL data is transmitted to the cellular wireless network during the subsequent CG-SDT opportunity when the unlicensed radio frequency band is available for transmission.

20. An apparatus configurable for operation in a wireless device, the apparatus comprising one or more processors coupled to a memory storing instructions which, when executed by the one or more processors, configure the wireless device to perform the method according to any one of claims 1 to 19.

21. A wireless device, comprising: a wireless circuit comprising a plurality of antennas; At least one processor communicatively coupled to the wireless circuitry and to a memory storing instructions that, when executed by the at least one processor, configure the wireless device to perform a method according to any one of claims 1 to 19.

22. A non-transitory computer readable medium storing instructions which, when executed by at least one processor of a wireless device, configure the wireless device to perform the method of any one of claims 1 to 19.

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