Patent Description:
Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (such as bandwidth, transmit power, etc.).

A wireless communication network may include a number of base stations (BSs) that can support communication for a number of user equipments (UEs). As will be described in more detail herein, a BS may be referred to as a Node B, a gNB, an access point (AP), a radio head, a transmit receive point (TRP), a New Radio (NR) BS, a <NUM> Node B, or further examples, or combinations thereof.

New Radio (NR), which also may be referred to as <NUM>, is a set of enhancements to the LTE mobile standard promulgated by the Third Generation Partnership Project (3GPP). NR is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP) (CP-OFDM) on the downlink (DL), using CP-OFDM or SC-FDM (also known as discrete Fourier transform spread OFDM (DFT-s-OFDM)) on the uplink (UL), as well as supporting beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation.

<CIT> discloses receive an RRC connection release message including paging area (PA)-related information from a first base station and receive system information from a second base station; and check whether a PA has been changed, on the basis of the PA-related information and PA-related information included in the system information, and transmit an RRC connection resume request message to the second base station when the PA has been changed.

3GPP TDoc R2-<NUM> discusses the main principles for inter-RAT mobility from NR to E-UTRA, for both inter-system (the source and target nodes are connected to different CNs) and intra-system (the source and target nodes are connected to the same CN) cases.

3GPP TS <NUM> specifies the Radio Resource Control protocol for the radio interface between UE and NG-RAN.

3GPP TDoc S2-<NUM> proposes to introduce returning back to 5GS in case of handover for voice (EPS/RAT fallback).

The invention is defined by the subject-matter of the appended independent claims. Advantageous embodiments are covered by the dependent claims.

Each of the figures is provided for the purposes of illustration and description.

This disclosure may, however, be implemented in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to one having ordinary skill in the art.

These apparatuses and techniques will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as "elements").

It should be noted that while aspects may be described herein using terminology commonly associated with 3Gor <NUM> wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems, such as <NUM> and later, including New Radio (NR) technologies.

In some deployments of <NUM> NR, a <NUM> next generation nodeB (gNB), may not support voice over NR (VoNR). To support a voice call in a <NUM> NR deployment, a procedure for voice fallback, from <NUM> NR to another radio access technology (RAT) (Long Term Evolution (LTE) or <NUM>, for example), may be implemented to service the voice call. The procedure may include a handover or redirection from the gNB to an LTE evolved nodeB (eNB) (VoNR to voice over LTE (VoLTE) voice fallback), a handover or redirection from the gNB to a 3GnodeB (VoNR to <NUM> circuit switched voice fallback), or another type of <NUM> NR voice fallback procedure.

In some cases, during a <NUM> NR voice fallback procedure, a source BS (the BS that is serving a UE) may not inform the UE or a target BS (the BS that the UE is to be handed over to or redirected to) that the handover or redirection is for purposes of <NUM> NR voice fallback. As a result, the target BS may not be aware that the target BS is to prioritize radio resource allocation, to the UE, for supporting a voice call associated with the UE, which may cause a delay in the setup of the voice call, may cause degraded performance in servicing the voice call, and the like. Moreover, if the handover or redirection fails, and the UE is not aware the handover or redirection is for purposes of <NUM> NR voice fallback, the UE may return to the source BS (which does not support voice calls) without reattempting to connect with the target BS or another BS that supports voice calls, which may cause further delays establishing the voice call.

Some aspects described herein provide techniques and apparatuses for voice fallback in <NUM> NR. In some aspects, a source BS may receive an indication that a UE is establishing a voice call. The source BS may include a gNB or another type of BS that does not support VoNR. Accordingly, the source BS may initiate a <NUM> NR voice fallback procedure, which may include a handover or redirection of the UE to a target BS associated with a RAT that supports another type of voice service, such as LTE (VoLTE), <NUM> (circuit switched voice), or further examples. During the <NUM> NR voice fallback procedure, the source BS may transmit, to the UE and the target BS, a command of mobility, which may include an indication that the handover or redirection is for purposes of <NUM> NR voice fallback.

In this way, the target BS is made aware that the handover or redirection is for purposes of <NUM> NR voice fallback, which permits the target BS to prioritize radio resource allocation, to the UE, for supporting the voice call, which may reduce delays in establishing the voice call, and may reduce performance degradation in servicing the voice call. Moreover, in this way, the UE is made aware that the handover or redirection is for purposes of <NUM> NR voice fallback, which permits the UE to perform various actions, such as indicating, to the target BS, that the UE is attempting to connect to the target BS for purposes of <NUM> NR voice fallback, such as automatically reattempting to connect to the target BS or another BS that supports voice calls (before returning to the source BS) if the handover or redirection fails, which reduces delays in establishing the voice call.

<FIG> is a block diagram conceptually illustrating an example of a wireless network <NUM> useful for understanding the invention. A BS is an entity that communicates with UEs and also may be referred to as a base station, a NR BS, a NodeB, a gNB, a 5GnodeB (NB), an access point, a transmit receive point (TRP), or further examples, or combinations thereof. In 3GPP, the term "cell" can refer to a coverage area of a BS or a BS subsystem serving this coverage area, depending on the context in which the term is used.

A BS may provide communication coverage for a macro cell, a pico cell, a femto cell, or another type of cell. A macro cell may cover a relatively large geographic area (for example, several kilometers in radius) and may allow unrestricted access by UEs with service subscription. A femto cell may cover a relatively small geographic area (for example, a home) and may allow restricted access by UEs having association with the femto cell (for example, UEs in a closed subscriber group (CSG)). A BS may support one or multiple (for example, three) cells. The terms "eNB", "base station", "NR BS", "gNB", "TRP", "AP", "node B", "5GNB", and "cell" may be used interchangeably herein.

In some examples, the BSs may be interconnected to one another or to one or more other BSs or network nodes (not shown) in the wireless network <NUM> through various types of backhaul interfaces such as a direct physical connection, a virtual network, or further examples using any suitable transport network.

Wireless network <NUM> also may include relay stations. A relay station is an entity that can receive a transmission of data from an upstream station (for example, a BS or a UE) and send a transmission of the data to a downstream station (for example, a UE or a BS). A relay station also may be a UE that can relay transmissions for other UEs. A relay station also may be referred to as a relay BS, a relay base station, a relay, etc..

Wireless network <NUM> may be a heterogeneous network that includes BSs of different types, for example, macro BSs, pico BSs, femto BSs, relay BSs, etc. These different types of BSs may have different transmit power levels, different coverage areas, and different impacts on interference in wireless network <NUM>. For example, macro BSs may have a high transmit power level (for example, <NUM> to <NUM> Watts) whereas pico BSs, femto BSs, and relay BSs may have lower transmit power levels (for example, <NUM> to <NUM> Watts).

The BSs also may communicate with one another, for example, directly or indirectly via a wireless or wireline backhaul.

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

MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, etc., that may communicate with a base station, another device (for example, remote device), or some other entity. A wireless node may provide, for example, connectivity for or to a network (for example, a wide area network such as Internet or a cellular network) via a wired or wireless communication link. Some UEs may be considered Internet-ofThings (IoT) devices, or may be implemented as NB-IoT (narrowband internet of things) devices. UE <NUM> may be included inside a housing that houses components of UE <NUM>, such as processor components, memory components, or further examples, or combinations thereof.

A RAT also may be referred to as a radio technology, an air interface, etc. A frequency also may be referred to as a carrier, a frequency channel, etc. Each frequency may support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs. In some cases, NR or 5GRAT networks may be deployed.

In some examples, access to the air interface may be scheduled, such as when a scheduling entity (for example, a base station) allocates resources for communication among some or all devices and equipment within the scheduling entity's service area or cell.

In some examples, a UE may function as a scheduling entity, scheduling resources for one or more subordinate entities (for example, one or more other UEs). A UE may function as a scheduling entity in a peer-to-peer (P2P) network, or in a mesh network.

In some aspects, two or more UEs <NUM> (for example, shown as UE 120a and UE 120e) may communicate directly using one or more sidelink channels (for example, without using a base station <NUM> as an intermediary to communicate with one another). For example, the UEs <NUM> may communicate using peer-to-peer (P2P) communications, device-to-device (D2D) communications, a vehicle-to-everything (V2X) protocol (for example, which may include a vehicle-to-vehicle (V2V) protocol, a vehicle-to-infrastructure (V2I) protocol, or further examples, or combinations thereof), a mesh network, or further examples, or combinations thereof. In this case, the UE <NUM> may perform scheduling operations, resource selection operations, or other operations described elsewhere herein as being performed by the base station <NUM>.

<FIG> is a block diagram conceptually illustrating an example <NUM> of a base station <NUM> in communication with a UE <NUM> in a wireless network useful for understanding the invention. Base station <NUM> and UE <NUM> may respectively be one of the base stations and one of the UEs in <FIG>.

At base station <NUM>, a transmit processor <NUM> may receive data from a data source <NUM> for one or more UEs, select one or more modulation and coding schemes (MCS) for each UE based at least in part on channel quality indicators (CQIs) received from the UE, process (for example, encode and modulate) the data for each UE based at least in part on the MCS(s) selected for the UE, and provide data symbols for all UEs. Transmit processor <NUM> also may process system information (for example, for semi-static resource partitioning information (SRPI), etc.) and control information (for example, CQI requests, grants, upper layer signaling, etc.) and provide overhead symbols and control symbols. Transmit processor <NUM> also may generate reference symbols for reference signals (for example, the cell-specific reference signal (CRS)) and synchronization signals (for example, the primary synchronization signal (PSS) and secondary synchronization signal (SSS)). A transmit (TX) multiple-input multiple-output (MIMO) processor <NUM> may perform spatial processing (for example, precoding) on the data symbols, the control symbols, the overhead symbols, or the reference symbols, if applicable, and may provide T output symbol streams to T modulators (MODs) 232a through 232t. Each modulator <NUM> may process a respective output symbol stream (for example, for OFDM, etc.) to obtain an output sample stream. Each modulator <NUM> may further process (for example, convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal.

At UE <NUM>, antennas 252a through 252r may receive the downlink signals from base station <NUM> or other base stations and may provide received signals to demodulators (DEMODs) 254a through 254r, respectively. Each demodulator <NUM> may condition (for example, filter, amplify, downconvert, and digitize) a received signal to obtain input samples. Each demodulator <NUM> may further process the input samples (for example, for OFDM, etc.) to obtain received symbols. A receive processor <NUM> may process (for example, demodulate and decode) the detected symbols, provide decoded data for UE <NUM> to a data sink <NUM>, and provide decoded control information and system information to a controller or processor (controller/processor) <NUM>. A channel processor may determine reference signal received power (RSRP), received signal strength indicator (RSSI), reference signal received quality (RSRQ), channel quality indicator (CQI), etc. In some aspects, one or more components of UE <NUM> may be included in a housing.

On the uplink, at UE <NUM>, a transmit processor <NUM> may receive and process data from a data source <NUM> and control information (for example, for reports including RSRP, RSSI, RSRQ, CQI, etc.) from controller/processor <NUM>. Transmit processor <NUM> also may generate reference symbols for one or more reference signals. The symbols from transmit processor <NUM> may be precoded by a TX MIMO processor <NUM> if applicable, further processed by modulators 254a through 254r (for example, for DFT-s-OFDM, CP-OFDM, etc.), and transmitted to base station <NUM>. Receive processor <NUM> may provide the decoded data to a data sink <NUM> and the decoded control information to a controller or processor (controller/processor) <NUM>. Network controller <NUM> may include communication unit <NUM>, controller or processor (controller/processor) <NUM>, and memory <NUM>.

Controller/processor <NUM> of base station <NUM>, controller/processor <NUM> of UE <NUM>, or any other component(s) of <FIG> may perform one or more techniques associated with voice fallback for 5GNR, as described in more detail elsewhere herein. For example, controller/processor <NUM> of base station <NUM>, controller/processor <NUM> of UE <NUM>, or any other component(s) of <FIG> may perform or direct operations of, for example, process <NUM> of <FIG>, process <NUM> of <FIG>, or other processes as described herein. Memories <NUM> and <NUM> may store data and program codes for base station <NUM> and UE <NUM>, respectively. A scheduler <NUM> may schedule UEs for data transmission on the downlink or uplink.

The stored program codes, when executed by controller/processor <NUM> or other processors and modules at UE <NUM>, may cause UE <NUM> to perform operations described with respect to process <NUM> of <FIG> or other processes as described herein. The stored program codes, when executed by controller/processor <NUM> or other processors and modules at base station <NUM>, may cause base station <NUM> to perform operations described with respect to process <NUM> of <FIG> or other processes as described herein. A scheduler <NUM> may schedule UEs for data transmission on the downlink or uplink.

In some aspects, UE <NUM> may include means for receiving, from a first BS <NUM> associated with a <NUM> NR RAT, a command of mobility from the <NUM> NR RAT to a second RAT, means for determining that the command of mobility is for voice fallback, means for transmitting, to a second BS <NUM> associated with the second RAT and based at least in part on determining that the command of mobility is for voice fallback, an RRC connection request communication for attempting to communicatively connect with the second BS <NUM> for voice fallback, or further examples, or combinations thereof. In some aspects, such means may include one or more components of UE <NUM> described in connection with <FIG>.

In some aspects, base station <NUM> may include means for determining that a UE <NUM>, communicatively connected with the BS <NUM>, is establishing a voice call, the BS being associated with a <NUM> NR RAT, means for transmitting, based at least in part on determining that the UE <NUM> is establishing the voice call, a command of mobility from the <NUM> NR RAT to a second RAT, the command of mobility including a voice fallback indication, or further examples, or combinations thereof. In some aspects, such means may include one or more components of base station <NUM> described in connection with <FIG>.

For example, the functions described with respect to the transmit processor <NUM>, the receive processor <NUM>, or the TX MIMO processor <NUM> may be performed by or under the control of controller/processor <NUM>.

<FIG> is a diagram illustrating an example <NUM> of voice fallback for <NUM> NR according to the invention. As shown in <FIG>, example <NUM> may include a UE (such as the UEs 120a-120e depicted and described in <FIG> or the UE <NUM> depicted and described in <FIG>) and a plurality of BSs (such as the BSs 110a-110d depicted and described in <FIG> or the BS <NUM> depicted in <FIG>). In some aspects, BS 110a may include a gNB that is associated with a 5GNR RAT. In some aspects, BS 110b and BS 110c may include another type of BS, such as an eNB associated with an LTE RAT, a <NUM> nodeB associated with a <NUM> RAT, or further examples.

In some aspects, the plurality of BSs may represent a plurality of cells provided by one or more BSs. For example, a single BS may provide the plurality of cells, where a first cell (corresponding to BS 110a) of the BS is associated with a <NUM> NR RAT, a second cell (corresponding to BS 110b) of the BS is associated with an LTE RAT or a <NUM> RAT, and a third cell (corresponding to BS 110c) of the BS is associated with an LTE RAT or a 3GRAT. As another example, the first cell (corresponding to BS 110a) associated with a <NUM> NR RAT may be provided by a first BS, a second cell (corresponding to BS 110b) associated with an LTE RAT or a 3GRAT may be provided by a second BS (different from the first BS or the same BS as the first BS), and a third cell (corresponding to BS 110c) associated with an LTE RAT or a 3GRAT may be provided by a third BS (different from the first BS or the same as the first BS, different from the second BS or the same as the second BS, or further examples).

As shown in <FIG>, and by reference number <NUM>, UE <NUM> may establish a voice call. In some aspects, the voice call may include a mobile originating (MO) voice call (a voice call originated by UE <NUM>), a mobile terminating (MT) voice call (a voice call terminated at UE <NUM>), or further examples. In some aspects, UE <NUM> may establish the voice call by initiating a quality of service (QoS) flow for a connection with an Internet protocol multimedia subsystem (IMS) to service the voice call. The QoS flow may be associated with one or more QoS parameters for the voice call, such as a packet loss rate parameter, a latency parameter, a throughput parameter, a packet error rate parameter, or other QoS parameters.

In some aspects, BS 110a may determine that UE <NUM> is establishing the voice call. For example, BS 110a may identify the QoS flow for the voice call based at least in part on receiving, from UE <NUM>, an indication of the QoS flow. The indication may include a <NUM> QoS identifier (5QI) or another type of identifier.

In some aspects, BS 110a may determine that BS 110a cannot support the QoS flow because BS 110a is associated with a RAT that does not support voice calls. Accordingly, BS 110a may reject the setup of the QoS flow and may initiate a <NUM> NR voice fallback of UE <NUM> to BS 110b, which may support voice calls. As indicated above, BS 110b may be associated with an LTE RAT, a <NUM> RAT, or another type of RAT that supports voice calls.

As further shown in <FIG>, and by reference number <NUM>, to initiate the <NUM> NR voice fallback, BS 110a transmits a command of mobility to UE <NUM>, to BS 110b, or to a combination of UE <NUM> and BS 110b. The command of mobility is for voice fallback from the <NUM> NR RAT to another RAT that supports voice calls, such as an LTE RAT or a 3GRAT. In some aspects, when the command of mobility is transmitted to UE <NUM>, the command of mobility may include a handover communication or a redirection communication. The handover communication includes a MobilityFromNRCommand NR RRC communication. In some aspects, the redirection communication may include an RRCRelease NR RRC communication or another type of redirection communication. In some aspects, the command of mobility may include a source radio network controller (RNC) to target RNC transparent container or a universal mobile telecommunications system terrestrial radio access network (UTRAN) RRC connection request communication if the other RAT is a 3GRAT.

BS 110a includes, in the command of mobility, a voice fallback indication. The voice fallback indication includes an information element (IE), a voiceFallbackIndication IE, that indicates the command of mobility is for voice fallback from the <NUM> NR RAT to another RAT that supports voice calls.

In some aspects, when the command of mobility is transmitted to BS 110b, the command of mobility may include an s1 application protocol (S1AP) communication, a radio access network application part (RANAP) communication, an RRC communication, or similar type of communication. The RRC communication may include a HandoverPreparationInformation LTE RRC communication or another type of RRC communication. If BS 110b is associated with an LTE RAT, the command of mobility may include a voice fallback indication, a voiceFallbackIndication IE, that indicates the command of mobility is for voice fallback from the <NUM> NR RAT to another RAT that supports voice calls. If BS 110b is associated with a <NUM> RAT or another type of RAT that supports circuit switched voice calls, the command of mobility may include a voice fallback indication, such as a circuit switched fallback (CSFB) Information IE or another type of IE, that indicates the command of mobility is for voice fallback from the <NUM> NR RAT to another RAT that supports voice calls.

As further shown in <FIG>, and by reference number <NUM>, UE <NUM> attempts to communicatively connect with BS 110b by transmitting an RRC connection request communication to BS 110b. In some aspects, UE <NUM> may transmit the RRC connection request communication based at least in part on receiving the command of mobility and determining that the command of mobility is for voice fallback.

In some aspects, UE <NUM> may determine that the command of mobility is for voice fallback based at least in part on identifying a voice fallback indication, included in the command of mobility, that indicates the command of mobility is for voice fallback. In some aspects, UE <NUM> may implicitly determine that the command of mobility is for voice fallback based at least in part on receiving the command for mobility while establishing the voice call, based at least in part on a whether UE <NUM> is capable of implementing a VoNR voice call (for example, UE <NUM> may infer that the handover or redirection is for voice fallback if UE <NUM> is not capable of implementing a VoNR voice call), or further examples, or a combination thereof.

In some aspects, UE <NUM> may include, in the RRC connection request, an indication that the voice call is a cause value for the RRC connection request communication. The cause value may indicate, to BS 110b, the purpose of UE <NUM> attempting to communicatively connect with BS 110b. BS 110b may use the indication of the voice call, in the RRC connection request communication, to prioritize radio resource allocation to UE <NUM>. In this way, UE <NUM> may be assigned a higher priority relative to other UEs connected to BS 110b in order to ensure that the <NUM> NR voice callback procedure is successful.

As further shown in <FIG>, and by reference number <NUM>, UE <NUM> detects a failure in the attempt to communicatively connect with BS 110b. For example, UE <NUM> may determine that a connection could not be established within a particular time window for establishing the connection, and may accordingly determine that the attempt to communicatively connect with BS 110b has failed or was unsuccessful.

As further shown in <FIG>, and by reference number <NUM>, UE <NUM>, based at least in part on detecting that failure in the attempt to communicatively connect with BS 110b, performs various actions based at least in part on the command of mobility being for <NUM> NR voice fallback. As shown in <FIG>, attempts to communicatively connect with BS 110c, which may be associated with an LTE RAT, a <NUM> RAT, or another RAT that supports voice calls. As another example, UE <NUM> may reattempt to communicatively connect with BS 110b. In this way, UE <NUM> may reduce the delay caused by the failed connection attempt by attempting to connect to a BS that is associated with a RAT that supports voice calls instead of reconnecting to BS 110a, which is associated with a RAT that may not support voice calls.

As further shown in <FIG>, and by reference number <NUM>, once UE <NUM> is communicatively connected with BS 110c, BS 110c may prioritize UE <NUM> in order to support the voice call. In some aspects, BS 110c may prioritize UE <NUM> based at least in part on the voice fallback indication received from BS 110a, may prioritize UE <NUM> based at least in part on the voice call cause value indicated by UE <NUM>, or a combination thereof. In some aspects, BS 110c may prioritize UE <NUM> when assigning radio resources associated with BS 110c. For example, BS 110c may be configured to prioritize voice calls over other types of packet traffic (for example, to ensure that voice quality and latency parameters are satisfied), and accordingly may prioritize assigning radio resources to UE <NUM> over assigning the radio resources to other UEs communicatively connected with BS 110c.

Accordingly, BS 110a may initiate a <NUM> NR voice fallback procedure, which may include a handover or redirection of UE <NUM> to BS 110b. During the <NUM> NR voice fallback procedure, BS 110a may transmit, to UE <NUM> and BS 110b, a command of mobility, which may include an indication that the command of mobility is for <NUM> NR voice fallback to another RAT that supports voice calls. In this way, BS 110b is made aware that a handover or redirection of UE <NUM> to BS 110b is for purposes of <NUM> NR voice fallback, which permits BS 110b to prioritize radio resource allocation to UE <NUM> for optimizing the cell, associated with BS 110b, for supporting the voice call, which may reduce delays in establishing the voice call, and may reduce performance degradation in servicing the voice call. Moreover, in this way, UE <NUM> is made aware that the handover or redirection is for purposes of <NUM> NR voice fallback, which permits UE <NUM> to perform various actions, such as indicating, to BS 110b, that UE <NUM> is attempting to connect to BS 110b for purposes of <NUM> NR voice fallback, such as automatically attempting to connect to BS 110c (before returning to BS 110a) if the handover or redirection fails, which reduces delays in establishing the voice call.

<FIG> is a diagram illustrating an example process <NUM> performed, for example, by a UE according to the invention. The example process <NUM> shows where a UE (such as UE <NUM>) performs voice fallback for 5GNR.

As shown in <FIG>, the process <NUM> includes receiving, from a first BS associated with a <NUM> NR RAT, a command of mobility from the <NUM> NR RAT to a second RAT (block <NUM>). The command of mobility is included in a MobilityFromNRCommand NR RRC communication. For example, the UE (for example, using receive processor <NUM>, controller/processor <NUM>, memory <NUM>, or further examples, or a combination thereof) may receive, from a first BS associated with a <NUM> NR RAT, a command of mobility from the <NUM> NR RAT to a second RAT, as described above. The second RAT includes an LTE RAT or a <NUM> GRAT.

As shown in <FIG>, the process <NUM> includes determining that the command of mobility is for voice fallback (block <NUM>). For example, the UE (for example, using receive processor <NUM>, transmit processor <NUM>, controller/processor <NUM>, memory <NUM>, or further examples, or a combination thereof) may determine that the command of mobility is for voice fallback, as described above.

As shown in <FIG>, the process <NUM> includes transmitting, to a second BS associated with the second RAT and based at least in part on determining that the command of mobility is for voice fallback, an RRC connection request communication for attempting to communicatively connect with the second BS for voice fallback (block <NUM>). For example, the UE (for example, using transmit processor <NUM>, controller/processor <NUM>, memory <NUM>, or further examples, or a combination thereof) may transmit, to a second BS associated with the second RAT and based at least in part on determining that the command of mobility is for voice fallback, an RRC connection request communication for attempting to communicatively connect with the second BS for voice fallback, as described above.

Further, the process <NUM> includes detecting a failure in the attempt to communicatively connect with the second BS and attempting to communicatively connect with a third BS associated with the second RAT based at least in part on detecting the failure in the attempt to communicatively connect with the second BS and based at least in part on receiving the command of mobility.

The process <NUM> may include additional aspects, such as any single aspect or any combination of aspects described below or in connection with one or more other processes described elsewhere herein.

In an aspect, determining that the command of mobility is for voice fallback includes determining that the command of mobility is for voice fallback based at least in part on identifying a voice fallback indication included in the command of mobility.

In a further aspect, alone or in combination with a preceding aspect, determining that the command of mobility is for voice fallback includes determining that the command of mobility is for voice fallback based at least in part on at least one of receiving the command of mobility while establishing the voice call or a capability of the UE to implement a VoNR voice call. In another aspect, alone or in combination with one or more of the preceding aspects, the RRC connection request communication indicates a voice call as a cause value.

In an even further aspect, alone or in combination with one or more of the preceding aspects, the first BS and the second BS are different BSs, the <NUM> NR RAT is associated with a cell of the first BS, and the second RAT is associated with a cell of the second BS.

In yet another aspect, alone or in combination with one or more of the preceding aspects, the first BS, the second BS, and the third BS are a same BS, the <NUM> NR RAT is associated with a first cell of the same BS, the second RAT is associated with a second cell of the same BS, and the second RAT is associated with a third cell of the same BS. In a further aspect, alone or in combination with one or more of the preceding aspects, the first BS, the second BS, and the third BS are different BSs, the <NUM> NR RAT is associated with a cell of the first BS, the second RAT is associated with a cell of the second BS, and the second RAT is associated with a cell of the third BS.

In another aspect, alone or in combination with one or more of the preceding aspects, the second BS and the third BS are different BSs, the second RAT is associated with a cell of the second BS, and the second RAT is associated with a cell of the third BS. In an even further aspect, alone or in combination with one or more of the preceding aspects, the second BS and the third BS are a same BS, the second RAT is associated with a first cell of the same BS, the second RAT is associated with a second cell of the third BS.

In yet another aspect, alone or in combination with one or more of the preceding aspects, the first BS and the third BS are a same BS, the <NUM> NR RAT is associated with a first cell of the same BS, and the second RAT is associated with a second cell of the same BS. In a further aspect, alone or in combination with one or more of the preceding aspects, the first BS and the second BS are a same BS, the <NUM> NR RAT is associated with a first cell of the same BS, and where the second RAT is associated with a second cell of the same BS.

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

<FIG> is a diagram illustrating an example process <NUM> performed, for example, by a BS useful for understanding the invention. The example process <NUM> shows where a BS (such as BS 110a or BS 110b) performs operations associated with voice fallback for 5GNR.

As shown in <FIG>, in some aspects, the process <NUM> may include determining that a UE, communicatively connected with the BS, is establishing a voice call, the BS being associated with a 5GNR RAT (block <NUM>). For example, the BS (for example, using transmit processor <NUM>, receive processor <NUM>, controller/processor <NUM>, memory <NUM>, or further examples, or a combination thereof) may determine that a UE, communicatively connected with the BS, is establishing a voice call, as described above. In some aspects, the BS is associated with a <NUM> NR RAT.

As shown in <FIG>, in some aspects, the process <NUM> may include transmitting, based at least in part on determining that the UE is establishing the voice call, a command of mobility from the <NUM> NR RAT to a second RAT, the command of mobility including a voice fallback indication (block <NUM>). For example, the BS (for example, using transmit processor <NUM>, controller/processor <NUM>, memory <NUM>, or further examples, or a combination thereof) may transmit, based at least in part on determining that the UE is establishing the voice call, a command of mobility from the <NUM> NR RAT to a second RAT, as described above. In some aspects, the command of mobility may include a voice fallback indication.

In a first aspect, the second RAT includes an LTE RAT or a <NUM> RAT. In a second aspect, alone or in combination with the first aspect, transmitting the command of mobility includes transmitting the command of mobility to at least one of another BS or the UE. In a third aspect, alone or in combination with one or more of the first or second aspects, the command of mobility is included in at least one of a transparent container included in an S1AP communication transmitted to another BS, an RANAP communication transmitted to the other BS, a HandoverPreparationInformation LTE RRC communication transmitted to the other BS, a MobilityFromNRCommand NR RRC communication transmitted to the UE, a HandoverCommand LTE RRC communication transmitted to the UE, or an RRCRelease NR RRC communication transmitted to the UE, a source RNC to target RNC transparent container, or a UTRAN RRC connection request communication.

As used herein, a "processor" is implemented in hardware, firmware, or a combination of hardware and software. As used herein, the phrase "based on" is intended to be broadly construed to mean "based at least in part on" unless explicitly stated otherwise.

The various illustrative logics, logical blocks, modules, circuits and algorithm processes described in connection with the aspects disclosed herein may be implemented as electronic hardware, computer software, or combinations of both.

The hardware and data processing apparatus used to implement the various illustrative logics, logical blocks, modules and circuits described in connection with the aspects disclosed herein may be implemented or performed with a general purpose single- or multi-chip processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor or any conventional processor, controller, microcontroller, or state machine. A processor also may be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some aspects, particular processes and methods may be performed by circuitry that is specific to a given function.

Aspects of the subject matter described in this specification also can be implemented as one or more computer programs, i.e., one or more modules of computer program instructions, encoded on a computer storage media for execution by, or to control the operation of, data processing apparatus.

"Disk" and "disc," as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers.

Various modifications to the aspects described in this disclosure may be readily apparent to those skilled in the art.

Certain features that are described in this specification in the context of separate aspects also can be implemented in combination in a single aspect. Conversely, various features that are described in the context of a single aspect also can be implemented in multiple aspects separately or in any suitable subcombination.

Claim 1:
A method of wireless communication performed by an apparatus of a user equipment, UE (<NUM>), comprising:
receiving (<NUM>) a MobilityFromNRCommand including a voiceFallbacklndication information element, IE, from a first base station, BS, operating a fifth generation New Radio, <NUM> NR, radio access technology, RAT,
wherein the voiceFallbacklndication IE included in the MobilityFromNRCommand indicates that a voice fallback procedure is initiated;
attempting (<NUM>) to connect with a second BS during the voice fallback procedure based at least in part on the MobilityFromNRCommand including the voiceFallbacklndication IE, wherein the second BS is operating another RAT,
wherein the another RAT is one of an Long Term Evolution, LTE, RAT or an third generation, <NUM>, RAT;
failing (<NUM>) to establish an attempted connection with the second BS during the voice fallback procedure; and
attempting (<NUM>) to connect with a third BS during the voice fallback procedure based at least in part on the MobilityFromNRCommand including the voiceFallbacklndication IE and the UE failing to establish the attempted connection with the second BS,
wherein the third BS is operating the another RAT.