Patent Publication Number: US-2023134052-A1

Title: Modem and Application Interaction for Voice Calls

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation, and claims priority under 35 U.S.C. § 120 from nonprovisional U.S. patent application Ser. No. 16/890,181, entitled “MODEM AND APPLICATION INTERACTION FOR VOICE CALLS”, filed on Jun. 2, 2020, the subject matter of which is incorporated herein by reference. application Ser. No. 16/890,181, in turn, claims priority under 35 U.S.C. § 119 from U.S. Provisional Application No. 62/870,137, entitled “Improvements to Modem and Application interaction for voice calls,” filed on Jul. 3, 2019. The disclosure of each of the forgoing documents is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The disclosed embodiments relate generally to wireless communication, and, more particularly, to modem and application interaction for voice calls. 
     BACKGROUND 
     The wireless cellular communications network has grown exponentially over the years. The fifth-generation system (5GS) is developed to meet the increasing demand for wireless services. The 5GS provides higher speed data services. Voice services and its development and evolution in the era of 5G is also a key component in the evolving wireless network. The 5GS utilizes new radio (NR) access technology. The 5GS provides voice over NR (VoNR) for voice services. 5G will also continue to utilize 4G voice architecture and the IP multimedia subsystem (IMS) to provide voice services. For 4G wireless access we have LTE networks, and its voice service VoLTE. 
     Certain 5GS networks offer the VoPS over 3GPP by evolved packet system (EPS) fallback (EPSFB). When the UE initiates IMS voice call on those networks, the 5GS network starts EPS fallback procedure for the UE and the UE has no control over it. If the EPSFB fails for some reason the UE may stay at the NR 5GS. The UE, especially the upper layers of the UE, does not know that EPSFB was attempted and failed. Similarly, if the EPSFB succeeds and UE connects to the LTE 4G network but fails to setup the voice call, the UE, especially the upper layers of the UE, does not know the EPSFB status. Normally, if the EPSFB fails or the call itself fails after EPSFB, the UE&#39;s upper layers decides in which domain to re-attempt the call. To make the most appropriate action after the EPSFB failure it would be beneficial for the upper layers to get indication whether the EPSFB failed or whether the EPSFB was successful and other EPSFB status information. Currently, there is no EPSFB information available to the upper layers of the UE. 
     A solution is sought for the upper layers of the UE to obtain the EPSFB status information. 
     SUMMARY 
     Methods and apparatus are provided for EPS fallback status report by the modem to the upper layers. In one embodiment, the modem/mobile terminal (MT) initiates a 5G voice call, detects an EPSFB triggered by the wireless network, identifies one or more EPSFB status and sends one or more EPSFB status indicators to at least one upper layer based on the identified one or more EPSFB status. In one embodiment, the EPS fall back is a redirection procedure. In another embodiment, the EPS fallback is a handover procedure. In yet another embodiment, the one or more EPSFB status indicators comprising a redirection to EPS started indicator, a handover to EPS started indicator, a redirection to EPS failed indicator, a handover to EPS failed indicator, a redirection to EPS success indicator, and a handover to EPS success indicator. 
     In one embodiment, the mobile terminal sends the one or more EPSFB status indicators using AT command. In one embodiment, the AT command is a new EPSFB status AT command comprising one or more parameters comprising an EPSFB status field, an EPSFB type field and a reporting field. In another embodiment, the EPSFB status command enables EPSFB unsolicited status report to upper layers by setting a value of the reporting field to be one. In yet another embodiment, the EPSFB status field indicates an EPSFB status comprising: 5GS to EPS fallback started, 5GS to EPS fallback successful, and 5GS to EPS fallback failed. In one embodiment, the EPSFB type field indicates an EPSFB type comprising: a handover and a redirection. In yet another embodiment, the sending one or more EPSFB status indicators is disabled upon receiving one or more disabling indication. 
     Other embodiments and advantages are described in the detailed description below. This summary does not purport to define the invention. The invention is defined by the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, where like numerals indicate like components, illustrate embodiments of the invention. 
         FIG.  1    illustrates an exemplary wireless network and a user equipment (UE) with EPSFB in accordance with one novel aspect. 
         FIG.  2    illustrates an exemplary block diagram of the EPSFB status report by the mobile terminal in accordance with embodiments of the current invention. 
         FIG.  3    illustrates an exemplary diagram for EPS falback form IMS voice when the EPSFB status indication is sent to upper layers in accordance with embodiments of the current invention. 
         FIG.  4    illustrates a simplified block diagram of an architecture of UE comprising a Terminal Equipment (TE) and a Mobile Termination (MT) interfaced by a Terminal Adaptor (TA) in accordance with embodiments of the current invention. 
         FIG.  5    illustrates an exemplary table one of an AT command for EPSFB status in accordance with embodiments of the current invention. 
         FIG.  6    illustrates a simplified block diagram of a Terminal Equipment (TE  600 ) with application layers that receives EPSFB status from the MT in accordance with embodiments of the current invention. 
         FIG.  7    illustrates a simplified block diagram of a Mobile Termination (MT  700 ) that sends EPSFB status to upper layers in accordance with embodiments of the current invention. 
         FIG.  8    illustrates an exemplary flow chart for the mobile terminal to detect and send EPSFB status indication to upper layers in accordance with embodiments of the current invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to some embodiments of the invention, examples of which are illustrated in the accompanying drawings. 
       FIG.  1    illustrates an exemplary wireless network  100  and a user equipment (UE) with EPSFB in accordance with one novel aspect. Wireless network  100  comprises 5GS network with an exemplary base station gNB  102  and an exemplary 5G core (5GC)  106 , and 4G/LTE network with an exemplary base station eNB  101  and an exemplary evolved packet core (EPC)  107 . Mobile stations/UEs  103  and  104  connect with the wireless network  100 . UE  104  is served by eNB  101  with an uplink  111  and down link  112 . UE  103  is served by gNB  102 . When UE  103  is configured with dual connectivity, UE  103  is served by eNB  101  with uplink  116  and downlink  117 . At the same time, UE  103  is also served by gNB  102  with uplink  113  and downlink  114 . The 5GS may support IMS registration locally but it may support voice calls not locally in the 5GS but only over EPS if both the UE and network support voice over EPS. EPS fallback for voice calls can happen when the 5GS network trigger fallback to EPS or is willing to steer voice calls to EPS. The EPSFB can happen for both mobile originated and mobile terminated calls. When UE  103  initiates IMS voice call to IMS network  108 , the 5GS network may initiate EPS fall back procedure. The EPSFB is controlled and triggered by the network and usually, the UE has no control over it and no way to identify when the EPSFB takes in place. In one novel aspect, the mobile terminal part of the UE detects the EPSFB status and sends it to upper layers of the UE. 
       FIG.  1    further illustrates simplified block diagrams for UE  103 , gNB  102 , and eNB  101 . UE  103  has an antenna  136 , which transmits and receives radio signals. An RF transceiver module  137 , coupled with antenna  136 , receives RF signals from antenna  136 , converts them to baseband signals and sends them to processor  132 . RF transceiver  137  also converts received baseband signals from processor  132 , converts them to RF signals, and sends out to antenna  135 . In one embodiment, RF transceiver module  137  has two transceivers, transceiver-1  133  and transceiver-2  135 . Processor  132  processes the received baseband signals and invokes different functional modules to perform features in UE  103 . Memory  131  stores program instructions and data  134  to control the operations of UE  103 . 
     For external applications, the EPSFB status may be provided through an AT command. AT commands are used for controlling Mobile Termination (MT) functions and network services from a Terminal Equipment (TE) through Terminal Adaptor (TA). As an example, UE  103  comprises a TE, a TA, and an MT. TE can use AT commands to control MT to get EPSFB status information. In accordance with one novel aspect, a new AT command interface that can report EPSFB status to the TE is proposed. The EPSFB status information can be provided by the MT to the TE automatically upon enabled. The EPSFB status can be queried by the TE through AT command as well. The report of the EPSFB status can be disabled through AT command as well. 
     UE  103  also includes multiple modules that carry out different tasks in accordance with embodiments of the current invention. Mobile terminal (MT)  191  initiates a 5G voice call in wireless network  100 , detects an evolved packet system (EPS) fallback (EPSFB) triggered by IMS  108 , identifies one or more EPSFB status, and sends one or more EPSFB status indicators to at least one upper layer based on the identified one or more EPSFB status. Terminal equipment (TE)  192  receives EPSFB status from MT  191  and determines voice call status for UE  103 . EPSFB status module  193  handles EPSFB status information. EPSFB status module  193  may be part of MT  191  or part of TE  192  or a standalone module. The UE modules can be implemented in software, firmware, or hardware/circuits. In another embodiment, EPSFB status module  193  may distribute its function in both MT  191  and TE  192 . 
     Also shown in  FIG.  1    is an exemplary block diagram for eNB  101 . eNB  101  has an antenna  156 , which transmits and receives radio signals. A RF transceiver module  153 , coupled with the antenna, receives RF signals from antenna  156 , converts them to baseband signals and sends them to processor  152 . RF transceiver  153  also converts received baseband signals from processor  152 , converts them to RF signals, and sends out to antenna  156 . Processor  152  processes the received baseband signals and invokes different functional modules to perform features in eNB  101 . Memory  151  stores program instructions and data  154  to control the operations of eNB  101 . eNB  101  also includes multiple function modules that carry out different tasks in accordance with embodiments of the current invention. An EPSFB  155  handles communication with UE  103  for EPSFB and performs EPSFB procedure. 
     Also shown in  FIG.  1    is an exemplary block diagram for gNB  102 . gNB  102  has an antenna  126 , which transmits and receives radio signals. An RF transceiver module  123 , coupled with the antenna, receives RF signals from antenna  126 , converts them to baseband signals and sends them to processor  122 . RF transceiver  123  also converts received baseband signals from processor  122 , converts them to RF signals, and sends out to antenna  126 . Processor  122  processes the received baseband signals and invokes different functional modules to perform features in gNB  102 . Memory  121  stores program instructions and data  124  to control the operations of gNB  102 . gNB  102  also includes multiple function modules that carry out different tasks in accordance with embodiments of the current invention. An EPSFB  125  handles communication with UE  103  for EPSFB and performs the EPSFB procedure. 
     In one novel aspect, the EPSFB status is indicated to the upper layer such that the upper layers can decide in which domain to re-attempt the call if the EPSFB failed. In one embodiment, the modem/mobile terminal (MT) provides the upper layers with an indication information about the status of the EPSFB procedure. 
       FIG.  2    illustrates an exemplary block diagram of the EPSFB status report by the mobile terminal in accordance with embodiments of the current invention. A UE  201  is connected in a 5GS network. UE  201  connects with a 5G radio access station/gNB  202  and a 4G/LTE base station/eNB  203 . The 5GS network also includes network entities  204 , including 5GC, EPC and IMS. At step  221 , UE  201  starts a mobile originated (MO) or a mobile terminated (MT) call and proceeds with media set up. At step  221 , the wireless network initiated an EPS procedure. In one embodiment, the EPSFB procedure is carried out with a redirection procedure at step  222 . In the redirection procedure for EPSFB case, UE  201  releases the call with 5G gNB  202  and re-establishes link with LTE/eNB  203 , where a new radio connection is started for the VoLTE call. In one embodiment, MT  211  identifies the EPSFB starts with redirection by detecting the redirection command. In one embodiment, the redirect command is “Connection Release Command” with Redirection information received on NR during MO/MT call procedure. In another embodiment, the EPSFB procedure is carried out with a handover procedure at step  223 . In the handover procedure for the EPSFB case, UE  201  performs handover from the 5GC to EPC while maintaining the connection with the original 5G gNB. In one embodiment, MT  211  identifies the EPSFB starts with handover by detecting a handover command indicating EPS fallback procedure started. In one novel aspect, MT  211  of UE  201  obtains the EPSFB status information and sends the status indication information to one or more upper layers of UE  201 . At step  281 , upon EPSFB starts, the EPSFB start indicator is obtained by MT  211 . At step  280 , the EPSFB start indicator is sent to upper layers  212  of UE  201 . 
     Once the network triggers the EPSFB, either through redirection procedure or the handover procedure, the status of the EPSFB needs to be indicated to the upper layers of the UE. At step  231 , the EPSFB procedure succeeds. At step  282 , MT  211  obtains the EPSFB success information and sends the EPSFB success indicator to upper layers  212  at step  280 . In one embodiment, the MT identifies the EPSFB via handover is successful by detecting a handover complete. In another embodiment, the MT identifies the EPSFB via redirection is successful by detecting UE camped on LTE. Similarly, if at step  232 , the EPSFB fails, MT  211  obtains the EPSFB fail information at step  283  and sends the EPSFB fail indicator to upper layer  212  at step  280 . In one embodiment, the MT identifies the EPSFB fail by detecting a handover failure. In another embodiment, the MT identifies an EPSFB fail by detecting that the UE cannot find LTE cell. 
     MT  211  of UE  201  is the modem of UE  201 . It provides the upper layers with an indication or a set of information about the status of the EPSFB procedure, as in step  280 . When the application has initiated an IMS call, the modem will provide application layer or the upper layers EPSFB indicators including a redirection to EPS started indicator, a handover to EPS started indicator, a redirection to EPS failed indicator, a handover to EPS failed indicator, a redirection to EPS success indicator, and a handover to EPS success indicator. In one embodiment, the indication to application/upper layers can be provided by AT-commands or related methods. 
       FIG.  3    illustrates an exemplary diagram for EPS fallback form IMS voice when the EPSFB status indication is sent to upper layers in accordance with embodiments of the current invention. UE  301  is connected in the wireless network with 5GS and LTE networks. The wireless network includes next generation radio access network (NG-RAN)  302 , which provides both NR and LTE radio access; evolved UTRAN (E-TRAN)  303 ; access mobility management function (AMF)  304 , mobility management entity (MME)  305 , serving gateway (SGW)  306 , packet data network gateway (PGW)/session management function (SMF)/user plane function (UPF)  307 , and IMS  308 . At step  311 , the UE starts MO or MT IMS voice session in 5GS. At step  312 , the network initiates PDU session modification to setup QoS flow for IMS voice. At step  313 , the 5GS radion access NG-RAN  302  triggers for EPS fallback procedure. In one embodiment, NG-RAN  302  also triggers measurement report solicitation. At step  314 , the 5GS network entity PGW/SMF/UPF  307  rejects PDU session modification indicating IMS voice fallback in progress and sends the information to NG-RAN  302 . At step  315 , PGW/SMF-UPF  307  starts a redirection or a handover to EPS procedure and signals UE  301 . 
     In one embodiment, the modem of the UE  301  upon detecting the EPSFB signal, at step  321 , sends EPSFB status indication information to upper layers. The EPSFB status indication includes EPSFB starts, EPSFB success and EPSFB fail. At step  316 , the network starts tracking area update (TAU) procedure. At step  326 , the network attaches with PDN connectivity request with request type “HANDOVER”. At step  317 , the network initiates PDN connection modification to setup a dedicated bearer for voice. At step  318 , IMS voice session establishment continues. In one novel aspect, the modem/mobile terminal identifies an EPS fallback triggered by the network. In one embodiment, the modem identifies the event at step  315  when the redirection or handover procedure is initiated. In another novel aspect, the modem identifies the status of EPS fallback triggered by the network, including EPSFB starts, EPSFB succeeded, and EPSFB failed. In another novel aspect, when there is an MT IMS call setup at step  311 , the UE should wait for Network&#39;s redirection or handover command from NR to EPS to make this call on LTE at step  315 . 
     The EPSFB status indication provided by the modem to the upper layers would enable the UE to decide in which domain to re-attempt the call or initiate a call. To make the most appropriate action after the EPSFB failure, it would be beneficial for the upper layers to get an indication of the EPSFB status. In one embodiment, the indication to application/upper lawyers is provided by the modem/mobile terminal by AT-commands. 
       FIG.  4    illustrates a simplified block diagram of an architecture of a user equipment UE  400  comprising a Terminal Equipment (TE  401 ) and a Mobile Termination (MT  403 ) interfaced by a Terminal Adaptor (TA  402 ) in accordance with embodiments of the current invention. The TA, MT, and TE may be implemented in the form of separate or integrated entities as needed. The span of control of the defined AT commands allows handling of any physical implementation that may lead to TA, MT and TE as three separate entities; TA integrated under the MT cover, and TE implemented as a separate entity; TA. integrated under the TE cover, and MT implemented as a separate entity; and TA and MT integrated under the TE cover as a single entity. 
     In the example of  FIG.  4   , the AT commands are observed on the link between TE  401  and TA  402 . However, most of the AT commands exchange information about the MT, not about the TA. The Interface between TE  401  and TA  402  operates over existing serial cables, an infrared link, and all link types with. similar behavior. The interface between TA  402  and MT  403  is dependent on the interference within MT  403 . in one embodiment, IF  401  sends an AT command to TA  402 , which converts to an MT control to be sent to MT  403 . The AT commands can be a read command for retrieving EPSFB status from MT  403  or a set command for enabling or disabling automatic EPSFB status reporting for MT  403 . In response, MT  403  sends EPSFB status back to TA  402 , which converts to a response to be sent to IF  401 . The response can include the updated EPSFB status information. 
       FIG.  5    illustrates an exemplary table one of an AT command for EPSFB status in accordance with embodiments of the current invention. As illustrated in  FIG.  5   , the AT+CEPSFB command is a set or read or test command. The set command controls the presentation of an unsolicited result code+CEPSFB: &lt;stat&gt;,&lt;type&gt; when &lt;reporting&gt;=1, and there is a change due to EPS fallback(EPSFB) procedure triggered by the network. Read command returns &lt;reporting&gt;, which indicates whether reporting of EPSFB status (EPSFBS) is enabled or disabled. When reporting is enabled, the parameters &lt;stat&gt; and &lt;type&gt; indicate the most recently received EPSFB status. When reporting is disabled, no EPSFB status is provided. 
     The defined values of the relevant information include:
         &lt;reporting&gt;: integer type, &lt;reporting&gt;=0 disables EPSFB status unsolicited result code, &lt;reporting&gt;=1 enables EPSFB status data unsolicited result code +CEPSFB: &lt;n&gt;,&lt;stat&gt;,&lt;type&gt;.   &lt;stat&gt;: integer type, indicates the EPS fallback (EPSFB) status. When MO/MT call(exclude VoNR) is on-going on NR.
           “0” 5GS to EPS fallback started. (“Handover/Redirection Command” indicating EPS fallback procedure started)   “1” 5GS to EPS fallback successful. (“Handover Complete” sent or “UE camped on LTE cell for Redirection case”)   “2” 5GS to EPS fallback fail. (“Handover Failure” sent or “UE cannot find LTE cell”)   
           &lt;type&gt;: integer type; indicates the EPSFB type
           0 Handover. (“Handover Command” received on NR during MO/MT call(exclude VoNR) is on-going)   1 Redirection. (“Connection Release Command with Redirection information” received on NR during MO/MT call(exclude VoNR) is on-going)   
           Implementation: Optional. This command is applicable to UEs supporting 5GS.       

       FIG.  6    illustrates a simplified block diagram of a Terminal Equipment (TE  600 ) with application layers that receive EPSFB status from the MT in accordance with embodiments of the current invention. TE  600  comprises a processor  601 , memory  602 , and protocol stacks  610 , including Application (APP) layer, Transport (TCP/UDP) layer, Network (IP) layer, Data Link layer, and Physical (PHY) layer. TE  600  further comprises system control modules  620  including a user interface, a configuration and control module, a connection handler, and a congestion control handler. Processor  601  processes different applications and invokes different system control modules to perform various features of TE  600 . Memory  602  stores program instructions and data  303  to control the operations of TE  600 . The system control modules and circuits can be implemented and configured to carry out functional tasks of TE  600 . TE  600  includes the application layers that receive EPSFB status information from the modem. In one example, TE  600  sends an AT read command to retrieve EPSFB status from the modem. In another example, TE  600  sends an AT set command to enable or disable EPSFB status reporting option. The TE  600  thus can determine whether EPSFB is applicable before sending subsequent EPSFB status related requests and parameters. 
       FIG.  7    illustrates a simplified block diagram of a Mobile Termination (MT  700 ) that sends EPSFB status to upper layers in accordance with embodiments of the current invention. MT  700  has an antenna  706 , which transmits and receives radio signals. An RF transceiver module  704 , coupled with the antenna, receives RF signals from antenna  706 , converts them to baseband signals and sends them to processor  701  via baseband module  705 . RF transceiver  704  also converts received baseband signals from processor  701  via baseband module  705 , converts them to RF signals, and sends out to antenna  706 . Processor  401  processes the received baseband signals and invokes different functional modules to perform features in MT  700 . Memory  702  stores program instructions and data  703  to control the operations of MT  700 . 
     MT  700  also comprises a set of protocol stacks  710  and control circuits including various system modules  720  to carry out functional tasks of MT  700 . Protocol stacks  710  comprises Non-Access-Stratum (NAS) layer, Radio Resource Control (RRC) layer, Packet Data Convergence Protocol/Radio Link Control (PDCP/RLC) layer, Media Access Control (MAC) layer, and Physical (PHY) layer. System modules  720  comprises multiple function modules/circuits. A network interface circuit initiates a 5G voice call in a wireless network. A detector circuit detects an evolved EPSFB triggered by the wireless network. A status circuit identifies one or more EPSFB status. An EPSFB report circuit sends one or more EPSFB status indicators to at least one upper layer based on the identified one or more EPSFB status. 
     In one embodiment, MT  700  further comprises a Terminal Adaptor (TA  730 ) that receives and transmits AT commands and converts the AT commands to be processed by processor  701  for controlling MT functions. In another embodiment, TA may reside in TE or as a sperate entity. In one example, TA  730  receives an AT read command from a TE for the MT to retrieve EPSFB status. In another example, TA  730  receives an AT set command from a TE for setting EPSFB status reporting option such that the MT can detect EPSFB status change and report the updated EPSFB applicability status information accordingly. 
       FIG.  8    illustrates an exemplary flow chart for the mobile terminal to detect and send EPSFB status indication to upper layers in accordance with embodiments of the current invention. At step  801 , the mobile terminal initiates a 5G voice call in a wireless network. At step  802 , the mobile terminal detects an evolved packet system (EPS) fallback (EPSFB) triggered by the wireless network. At step  803 , the mobile terminal identifies one or more EPSFB status according to the result of step  802  or network&#39;s indicator. At step  804 , the mobile terminal sends one or more EPSFB status indicators to at least one upper layer based on the identified one or more EPSFB status. 
     Although the present invention has been described in connection with certain specific embodiments for instructional purposes, the present invention is not limited thereto. Accordingly, various modifications, adaptations, and combinations of various features of the described embodiments can be practiced without departing from the scope of the invention as set forth in the claims.