Patent Publication Number: US-11032334-B2

Title: Enhanced call downgrade reason indicator

Description:
RELATED APPLICATIONS 
     This application is a continuation of and claims priority to U.S. patent application Ser. No. 15/827,379, filed on Nov. 30, 2017, entitled “ENHANCED CALL DOWNGRADE REASON INDICATOR” which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     Telephone calls have been traditionally been voice calls in which audio content is sent from telephone to telephone. However, telecommunication networks have advanced to allow enhanced calls that include other types of content in addition to audio content. For example, video calls that include both an audio component and a video component can be transmitted over a Long-Term Evolution (LTE) network using Video over LTE (ViLTE) technology. As another example, a real-time text (RTT) call can include the audio content of a voice call along with text characters that are transmitted in real time as a user types them. 
     In some situations, a user equipment (UE) device can downgrade an enhanced call to an audio-only call, either automatically or based on a user&#39;s instruction. For example, a UE can automatically downgrade a video call to an audio-only call if there is a problem with the UE or a telecommunication network, such as if there is insufficient bandwidth available to transmit the video component of the video call. As another example, a UE can downgrade a video call to an audio-only call when a user chooses to deactivate a camera at the UE during the video call. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The detailed description is set forth with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The use of the same reference numbers in different figures indicates similar or identical items or features. 
         FIG. 1  depicts a downgrade from an enhanced call to an audio-only call. 
         FIG. 2  depicts content types in an enhanced call and an audio-only call. 
         FIG. 3  depicts an example of a system architecture for a telecommunication network. 
         FIG. 4  depicts an example of default and dedicated bearers. 
         FIG. 5  depicts a user equipment (UE) device transmitting a downgrade reason indicator to a core network and/or an IP Multimedia Subsystem (IMS). 
         FIG. 6  depicts an example system architecture for a UE. 
         FIG. 7  depicts a flow chart of an exemplary process for sending a downgrade reason indicator via Session Initiation Protocol (SIP) messaging. 
         FIG. 8  depicts a flow chart of an exemplary process for sending a downgrade reason indicator via Non-Access Stratum (NAS) messaging. 
     
    
    
     DETAILED DESCRIPTION 
     Introduction 
     Telecommunication networks can carry enhanced calls between user equipment (UE) devices. An enhanced call can be a Video over LTE (ViLTE) video call or other type of video call, a real-time text (RTT) call, or any other type of call that includes audio content and at least one other type of content. However, during an enhanced call, in some situations a UE can downgrade the enhanced call to an audio-only call. A UE can downgrade an enhanced call to an audio-only call either automatically or based on a user&#39;s instruction. 
     A UE can automatically downgrade an enhanced call upon the occurrence of one or more events or conditions that would impact the UE&#39;s ability to provide at least a threshold quality of service for both the audio content and the additional type of content of the enhanced call. Such events or conditions can include the UE&#39;s available bandwidth falling below a threshold level, a battery power level falling below a threshold level, signal quality falling below a threshold level, a number of lost data packets exceeding a threshold level, and/or any other event or condition. By way of a non-limiting example, a UE can be set to automatically downgrade a ViLTE video call to an audio-only call when the available bandwidth drops below 192 kilobits per second (kbps). 
     A UE can also downgrade an enhanced call when instructed to do so either implicitly or explicitly by a user. For example, during a video call a user can select an option through a user interface at a UE to disable the UE&#39;s camera, thereby implicitly instructing the UE to downgrade the video call to an audio-only call. Alternately, a user can select an explicit option to downgrade a video call to an audio-only call. As another example, during an RTT call a user can select an option through a user interface at a UE to remove the display of a keyboard and/or RTT text from the UE&#39;s screen, thereby implicitly instructing the UE to downgrade the RTT call to an audio-only call. Alternately, a user can select an explicit option to downgrade an RTT call to an audio-only call. 
     Upon the occurrence of one or more automatic downgrade conditions, or upon a user&#39;s selection of an option that leads to a downgrade of an enhanced call, the UE can inform the telecommunication network that the enhanced call is being downgraded to an audio-only call. However, in previous systems, although a UE could inform a telecommunication network when it was downgrading an enhanced call to an audio-only call, the UE did not inform the telecommunication network why the downgrade occurred. Accordingly, in previous systems it could not be determined from the network side whether a downgrade of an enhanced call occurred due to a user&#39;s instruction, or because there was a problem either with the telecommunication network&#39;s service or with the UE itself. This made it difficult to identify and/or fix such network problems and/or UE problems. 
     Example Environment 
       FIG. 1  depicts a downgrade from an enhanced call  102  to an audio-only call  104 . Two UEs  106  can engage in an enhanced call  102  over a telecommunication network  108 . During an enhanced call  102 , either of the UEs  106  can instruct the telecommunication network  108  to downgrade the enhanced call  102  to an audio-only call  104 . 
     A UE  106  can be any device that wirelessly connects to the telecommunication network  108 , such as a smart phone, a cellular phone, a personal digital assistant (PDA), a personal computer (PC), a laptop, a desktop, a workstation, a media player, a tablet, a gaming device, a smart watch, or any other type of computing or communication device. An example UE  106  is illustrated in greater detail in  FIG. 6  and is described in detail below with reference to that figure. 
     The telecommunication network  108  can include networks of one or more providers or operators. A UE  106  can connect to a base station of the telecommunication network  108  through a wireless access technology, such as Long Term Evolution (LTE)/LTE Advanced technology, High-Speed Data Packet Access (HSDPA)/Evolved High-Speed Packet Access (HSPA+) technology, Universal Mobile Telecommunications System (UMTS) technology, Code Division Multiple Access (CDMA) technology, Global System for Mobile Communications (GSM) technology, WiMax® technology, and/or WiFi® technology. For example, in an LTE network a base station can be an eNode B (eNB). 
       FIG. 2  depicts content types in an enhanced call  102  and an audio-only call  104 . While an audio-only call  104  can include audio content  202 , an enhanced call  102  can include audio content  202  plus one or more types of additional content  204 . An enhanced call  102  or an audio-only call  104  can also be associated with metadata or other data that describes attributes of the call, such as identifiers of the originating and/or terminating UE  106 , or information allowing the call to be connected and/or routed through the telecommunication network  108 . 
     In some examples, an enhanced call  102  can be a video call in which the audio content  202  is an audio component of the video call and the additional content  204  is a video component of the video call. By way of a non-limiting example, when the telecommunication network  108  is an LTE network, the video call can be a Video over LTE (ViLTE) call transmitted in part using an IP Multimedia Subsystem (IMS). In this example, a ViLTE call can be downgraded to an audio-only call  104  for an LTE network, such as a Voice over LTE (VoLTE) call. 
     In other examples, an enhanced call  102  can be a real-time text (RTT) call in which the audio content  202  is voice or other audio data, and the additional content  204  is text that is transmitted in real time as the characters are typed by users of the UEs  106 . For example, a UE  106  can display a keyboard on screen through which users can type messages, as well as display the text of previously sent and/or received characters and messages. As such, in an RTT call, users can hold a voice conversation while simultaneously exchanging text messages. When the RTT call is downgraded to a VoLTE call or other type of audio-only call, the keyboard and/or RTT text display can be removed from the UE&#39;s screen while still allowing the users to continue their voice conversation. 
     In still other examples, the additional content  204  of an enhanced call  102  can be any other type of data, such as non-real-time text, a text transcript of the audio content  202  generated through speech recognition, pictures, map data, advertising content, file transfers, prerecorded video, and/or any other type of additional content  204 . 
     Example Architecture 
       FIG. 3  depicts an example of a system architecture for a telecommunication network  108 . The telecommunication network  108  can comprise one or more base stations  302 , a core network  304 , and an IP Multimedia Subsystem (IMS)  306 . In an LTE network, a base station  302  can be an eNode B (eNB), and the core network  304  can be an evolved packet core (EPC). 
     A UE  106  can connect to a base station  302  to access the core network  304  through the base station  302 , and to access the IMS  306  through the base station  302  and the core network  304 . The core network  304  can have components including a Mobility Management Entity (MME)  308 , one or more Serving Gateways (S-GWs)  310 , and one or more Packet Data Network (PDN) Gateways (P-GWs)  312 . The MME  308  can be a control node in the core network  304  that can set up and manage default and dedicated bearers  314 , authenticate subscribers in conjunction with a Home Subscriber Server (HSS), choose an S-GW  310  for a UE  106 , and/or perform other functions of the core network  304 . In some examples, the MME  308  can communicate with the UE  106  using Non-Access Stratum (NAS) messages. An S-GW  310  can be connected to a P-GW  312 , which connects the core network  304  to the IMS  306 , the Internet, and/or other networks and servers. 
     The IMS  306  can include Call Session Control Function (CSCF) elements, including a Proxy CSCF (P-CSCF) and a Serving CSCF (S-CSCF). The Call Session Control Function elements can process and send Session Initiation Protocol (SIP) messages to control multimedia communications sessions that are carried out through the core network  304 , including sessions for audio-only calls  104 , such as VoLTE calls, and enhanced calls  102 , such as ViLTE video calls or RTT calls. The IMS  306 , and/or a Policy and Charging Rules Function (PCRF) node in communication with both the IMS  306  and core network  304 , can instruct the MME  308  and/or other elements of the core network  304  how to prepare and manage the core network  304  for a communication session. Accordingly, the core network  304  and IMS  306  can work together to establish audio-only calls  104  or enhanced calls  102 , and/or to downgrade an enhanced call  102  to an audio-only call  104 . 
       FIG. 4  depicts an example of default and dedicated bearers  314 . Bearers  314  can be established and managed in the core network  304  by the MME  308  and/or other components of the core network  304 . A default bearer  314  can be established for a call session to transmit SIP messages or other signaling related to the establishment and/or management of the call session. One or more dedicated bearers  314  can also be established for a call session in addition to the default bearer  314 , and the dedicated bearers  314  can be used to transmit specific types of content for the call session, such as audio content  202  and/or additional content  204 . 
     A bearer  314  can define a Quality of Service (QoS) that should be provided to traffic associated with that bearer  314  by base stations  302  and/or elements of the core network  304 . For example, traffic associated with a bearer  314  that has a QoS with a guaranteed minimum bitrate can, if necessary, be prioritized by network elements over traffic associated with another bearer  314  that has a QoS without a guaranteed minimum bitrate. 
     A QoS associated with a bearer  314  can be indicated by a QoS Class Identifier (QCI). In some examples, a bearer  314  with a QCI value from 1 to 4 can indicate that traffic in that bearer  314  should be transmitted at least at a minimum guaranteed bitrate, while a bearer  314  with a QCI value from 5 to 9 can indicate that traffic in that bearer  314  will be transmitted using best effort service without a guaranteed bitrate. For example, in some schemes a default bearer  314  can have a QCI value of 5, indicating that traffic in the default bearer  314  has a high priority but a non-guaranteed bitrate, while a dedicated bearer  314  for audio content  202  can have a QCI value of 1 and a dedicated bearer for video content or other additional content  204  can have a QCI value of 2, indicating that traffic in the dedicated bearers  314  has been given a guaranteed bitrate. 
     In some examples, the IMS  306  can instruct the core network  304  to establish and/or terminate bearers  314  based on SIP messages from a UE  106  to the IMS  306 . For example, a P-CSCF in the IMS  306  can identify the type of call being requested by a UE  106  in a SIP message so that the IMS  306  or a PCRF can instruct the MME  308  in the core network to establish and/or terminate bearers  314  accordingly. In other examples, bearers  314  can be established and/or terminated based on Non-Access Stratum (NAS) messages between a UE  106  and an MME  308 . 
       FIG. 3  depicts one UE  106  in communication with one core network  304  and one IMS  306 , such that the core network  304  can establish bearers  314  for that UE  106  to engage in an enhanced call  102  or audio-only call  104 . Corresponding bearers  314  can also be established in the same core network  304  or a different core network  304  for one or more other UEs  106  engaged in the enhanced call  102  or audio-only call  104 . For example, when an originating UE  106  is connected to a first core network  304  and a terminating UE  106  is connected to a second core network  304 , the IMS  306  connected to the first core network  304  can be in communication with a second IMS  306  connected to the second core network  304 , such that it can instruct the second core network  304  to establish and/or terminate bearers  314  for the terminating UE  106  based on call setup and/or call downgrade SIP messages from the originating UE  106 . 
       FIG. 5  depicts a UE  106  transmitting a downgrade reason indicator  502  through the base station  302  to the core network  304  and/or the IMS  306 . When a UE  106  downgrades an enhanced call  102  to an audio-only call  104 , either automatically or due to a user&#39;s instruction, the UE  106  can transmit a downgrade reason indicator  502  to the core network  304  and/or IMS  306 . The downgrade reason indicator  502  can identify why the UE  106  is downgrading an enhanced call  102  to an audio-only call  104 , such as that it is automatically downgrading the enhanced call  102  or that a user initiated the downgrade of the enhanced call  102 . 
     The downgrade reason indicator  502  can an encoded bit, flag, code, text description, and/or any other type of indicator or value included in control layer information sent from the UE  106  to the core network  304  and/or IMS  306 . For example, the downgrade reason indicator  502  can an encoded bit or flag in a NAS message, or a code and/or text description in a header of a SIP message. 
     In some examples a downgrade reason indicator  502  can be included in a message sent by a UE  106  to inform the core network  304  and/or the IMS  306  that the UE  106  is downgrading an enhanced call  102  to an audio-only call  104 . For example, a downgrade reason indicator  502  can be included in a SIP message, NAS message, or other type of message that requests the downgrade and/or indicates that one or more dedicated bearers  314  should be modified or terminated. In other examples, a downgrade reason indicator  502  can be sent by a UE  106  to the core network  304  and/or the IMS  306  separately from instructions for modifying or terminating one or more bearers  314 . 
       FIG. 6  depicts an example system architecture for a UE  106 , in accordance with various examples. As shown, a UE  106  can include a memory  602  that stores modules and data  604 , processor(s)  606 , radio interfaces  608 , a display  610 , output devices  612 , input devices  614 , and/or a drive unit  616  including a machine readable medium  618 . 
     In various examples, memory  602  can include system memory, which may be volatile (such as RAM), non-volatile (such as ROM, flash memory, etc.) or some combination of the two. Memory  602  can further include non-transitory computer-readable media, such as volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information, such as computer readable instructions, data structures, program modules, or other data. System memory, removable storage, and non-removable storage are all examples of non-transitory computer-readable media. Examples of non-transitory computer-readable media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium which can be used to store the desired information and which can be accessed by the UE  106 . Any such non-transitory computer-readable media may be part of the UE  106 . 
     In some examples memory  602  can also include a SIM (subscriber identity module) card, which is a removable memory card used to identify a user of the UE  106  to a telecommunication network  108 . 
     The modules and data  604  can be utilized by the UE  106  to perform or enable performing any action taken by the UE  106 . The modules and data  604  can include a UE platform and applications, and data utilized by the platform and applications. 
     In various examples, the processor(s)  606  can be a central processing unit (CPU), a graphics processing unit (GPU), or both CPU and GPU, or any other type of processing unit. Each of the one or more processor(s)  606  may have numerous arithmetic logic units (ALUs) that perform arithmetic and logical operations, as well as one or more control units (CUs) that extract instructions and stored content from processor cache memory, and then executes these instructions by calling on the ALUs, as necessary, during program execution. The processor(s)  606  may also be responsible for executing all computer applications stored in the memory  602 , which can be associated with common types of volatile (RAM) and/or nonvolatile (ROM) memory. 
     The radio interfaces  608  can include transceivers, modems, interfaces, antennas, and/or other components that perform or assist in exchanging radio frequency (RF) communications with a base station  302 . In other examples a processor  606 , other modules and data  604 , and/or other components of the UE  106  can perform or assist in transmitting and/or receiving data, and/or pre-processing or post-processing of such data. 
     The display  610  can be a liquid crystal display or any other type of display commonly used in UEs  106 . For example, display  610  may be a touch-sensitive display screen, and can then also act as an input device or keypad, such as for providing a soft-key keyboard, navigation buttons, or any other type of input. 
     The output devices  612  can include any sort of output devices known in the art, such as a display  610 , speakers, a vibrating mechanism, and/or a tactile feedback mechanism. Output devices  612  can also include ports for one or more peripheral devices, such as headphones, peripheral speakers, and/or a peripheral display. 
     The input devices  614  can include any sort of input devices known in the art. For example, input devices  614  can include a microphone, a keyboard/keypad, and/or a touch-sensitive display, such as the touch-sensitive display screen described above. A keyboard/keypad can be a push button numeric dialing pad, a multi-key keyboard, or one or more other types of keys or buttons, and can also include a joystick-like controller, designated navigation buttons, or any other type of input mechanism. 
     The machine readable medium  618  can store one or more sets of instructions, such as software or firmware, that embodies any one or more of the methodologies or functions described herein. The instructions can also reside, completely or at least partially, within the memory  602 , processor(s)  606 , and/or radio interface(s)  608  during execution thereof by the UE  106 . The memory  602  and the processor(s)  606  also can constitute machine readable media  622 . 
     Example Operations 
       FIG. 7  depicts a flow chart of an exemplary process for sending a downgrade reason indicator  502  via SIP messaging when downgrading an enhanced call  102  to an audio-only call  104 . 
     At block  702 , a UE  106  can begin an enhanced call  102  with another UE  106  by sending a SIP setup message to the IMS  306  through a default bearer  314 . For example, the SIP setup message can be a SIP INVITE message. As discussed above, a default bearer  314  can be set up in the core network  304  to transmit SIP messages or other signaling related to the establishment and/or management of a call session, such as the SIP setup message. 
     The SIP setup message can identify the type of the enhanced call  102 , such as whether it is a video call or an RTT call. In some examples the SIP setup message can indicate each type of content in the enhanced call  102 , including the audio content  202  and one or more types of additional content  204 , and/or a requested QoS level for each of the types of content. 
     At block  704 , the IMS  306  can instruct the core network  304  to establish one or more dedicated bearers  314  for the enhanced call  102  in response to the SIP setup message. A component of the IMS  306 , such as the P-CSCF in the IMS  306  can review SIP setup message to determine the types of content in the enhanced call  102 , and/or a QoS level for each of the types of content. Accordingly, a PCRF can instruct the core network  304  to establish dedicated barriers  314  for the type of enhanced call  102  requested by the UE  106 . 
     For example, when the enhanced call  102  is a video call, the IMS  306  can instruct the core network  304  to set up two dedicated bearers  314 , one for the audio component and one for the video component, in addition to the default bearer  314 . As another example, when the enhanced call  102  is an RTT call, the IMS  306  can instruct the core network  304  to set up a single dedicated bearer  314  for both the audio content  202  and the text content, because text may not be expected to use many bits compared to the audio content  202 . Alternately, separate dedicated bearers  314  can be established for the audio content  202  and text content of an RTT call. 
     Once dedicated bearers  314  have been established, the IMS  306  can finish setting up the enhanced call  102  between the UEs  106  and the enhanced call  102  can be active at block  706 . While the enhanced call  102  is active during block  706 , data packets for the audio content  202  and additional content  204  can be passed through the associated dedicated bearers  314  within the core network  304 . As will be discussed below, in some situations block  706  can be skipped when automatic downgrade conditions occur or user downgrade instructions are received after the SIP setup message is sent at block  702  but before the enhanced call  102  becomes active. 
     At block  708 , the UE  106  can determine if any automatic downgrade conditions have been satisfied. A UE  106  can be configured with automatic downgrade conditions that, if satisfied, may indicate that the UE  106  cannot provide at least a threshold QoS for both the audio content  202  and the additional content  204 . For example, an automatic downgrade condition can be when a minimum guaranteed bitrate defined by a QCI value for a dedicated bearer  314  for the audio content  202  and/or additional content  204  cannot be met by the UE  106  and/or the telecommunication network  108 . Other automatic downgrade conditions can be when the UE&#39;s available bandwidth falls below a threshold level, the UE&#39;s battery power level falls below a threshold level, the quality of network signals received by the UE  106  falls below a threshold level, data packets sent to or from the UE  106  become lost or need retransmission at more than a threshold level, or any other condition. 
     If the UE  106  determines at block  708  that one or more automatic downgrade conditions have been satisfied, at block  710  the UE  106  can prepare a SIP downgrade message that indicates to the IMS  306  that the call session is being modified or updated to downgrade the enhanced call  102  to an audio-only call  104 . For example, the SIP downgrade message can be a SIP re-INVITE message that indicates to the IMS  306  that an existing enhanced call  102  is being downgraded to an audio-only call  104 . In alternate situations in which one or more automatic downgrade conditions are satisfied after an initial SIP setup message was sent at block  702  but before the enhanced call  102  became active at block  706 , the SIP downgrade message can be a SIP UPDATE message. 
     At block  712 , the UE  106  can add or set a downgrade reason indicator  502  in a header and/or body of the SIP downgrade message. For example, the UE  106  can add a code and/or text description to a downgrade reason header in a SIP re-INVITE message or SIP UPDATE message. The code and/or text description can indicate to the IMS  306  that the UE  106  is automatically downgrading the enhanced call  102 . 
     If one or more automatic downgrade conditions were not satisfied at block  708 , the UE  106  can move to block  714  to determine if the UE  106  has received any explicit or implicit instructions from a user to downgrade the enhanced call  102  to an audio-only call  104 . If no explicit or implicit downgrade instructions have been received at block  714 , the UE  106  can return to block  706  and continue to check for the occurrence of automatic downgrade conditions at block  708  and/or user downgrade instructions at block  714  until either the enhanced call  102  is downgraded or the enhanced call  102  ends. In alternate examples, blocks  708  and  714  can be reversed, the UE  106  can check for automatic downgrade conditions and/or user downgrade instructions at preset times or intervals, or the UE  106  can check for automatic downgrade conditions and/or user downgrade instructions using any other method. 
     If the UE  106  determines at block  714  that a user selected a downgrade of the enhanced call  102  through explicit or implicit instructions to the UE  106 , at block  716  the UE  106  can prepare a SIP downgrade message that indicates to the IMS  306  that the call session is being modified or updated to downgrade the enhanced call  102  to an audio-only call  104 . As described above, the SIP downgrade message can be a SIP re-INVITE message indicating that an existing enhanced call  102  is being downgraded to an audio-only call  104 , or a SIP UPDATE message indicating a change from an enhanced call  102  to an audio-only call  104  if the enhanced call  102  has not yet become active. 
     At block  718 , the UE  106  can add or set a downgrade reason indicator  502  in a header and/or body of the SIP downgrade message. For example, the UE  106  can add a code and/or text description to a downgrade reason header in a SIP re-INVITE message or SIP UPDATE message. The code and/or text description can indicate to the IMS  306  that a user initiated the downgrade from the enhanced call  102  to the audio-only call  104 . 
     After a SIP downgrade message has been prepared with a downgrade reason indicator  502  in either blocks  710  and  712  or blocks  716  and  718 , the UE  106  can send the SIP downgrade message to the IMS  306  at block  720 . The IMS  306  can determine from the SIP downgrade message that the enhanced call  102  is being downgraded to an audio-only call, and in response instruct the core network  304  to terminate and/or modify one or more of the dedicated bearers  314 . For example, when the SIP downgrade message is a SIP re-INVITE message indicating that a video call is being downgraded to an audio-only call, the IMS  306  can instruct the core network  304  to terminate a dedicated bearer  314  for the video content while maintaining a separate dedicated bearer  314  for the audio content  202 . 
     The IMS  306  can also determine from the downgrade reason indicator  502  in the SIP downgrade message that the downgrade of the enhanced call  102  was initiated either automatically by the UE  106  or by a user&#39;s instruction. The IMS  306  can store that information in a database, and/or inform the core network  304  that the enhanced call  102  was downgraded automatically or due to a user&#39;s instruction. 
       FIG. 8  depicts a flow chart of an exemplary process for sending a downgrade reason indicator  502  via NAS messaging when downgrading an enhanced call  102  to an audio-only call  104 . 
     At block  802 , a UE  106  can begin an enhanced call  102  with another UE  106  in part by sending one or more NAS setup messages to the MME  308  or other component of the core network  304 . For example, a NAS setup message can be a PDN CONNECTIVITY REQUEST that requests a default bearer  314  for a PDN connection to the IMS  306  or other PDN, or a BEARER RESOURCE ALLOCATION REQUEST message that requests that the core network  304  establish one or more dedicated bearers  314  for the enhanced call  102 . In some examples a NAS setup message can identify QoS levels or QCI values for the requested dedicated bearers  314 . 
     At block  804 , the core network  304  can establish a default bearer  314  and one or more dedicated bearers  314  for the enhanced call  102  in response to the NAS setup messages. For example, when the enhanced call  102  is a video call, the core network  304  can establish two dedicated bearers  314 , one for the audio component and one for the video component. As another example, when the enhanced call  102  is an RTT call, the core network  304  can establish a single dedicated bearer  314  for both the audio content  202  and the text content of the RTT call, or establish separate dedicated bearers  314  for the audio content  202  and text content. 
     After the dedicated bearers  314  have been established, the enhanced call  102  can be active at block  806 . While the enhanced call  102  is active during block  806 , data packets for the audio content  202  and additional content  204  can be passed through the associated dedicated bearers  314  within the core network  304 . 
     At block  808 , the UE  106  can determine if any automatic downgrade conditions have been satisfied. A UE  106  can be configured with automatic downgrade conditions that, if satisfied, may indicate that the UE  106  cannot provide at least a threshold QoS for both the audio content  202  and the additional content  204 . For example, an automatic downgrade condition can be when a minimum guaranteed bitrate defined by a QCI value for a dedicated bearer  314  for the audio content  202  and/or additional content  204  cannot be met by the UE  106  and/or the telecommunication network  108 . Other automatic downgrade conditions can be when the UE&#39;s available bandwidth falls below a threshold level, the UE&#39;s battery power level falls below a threshold level, the quality of network signals received by the UE  106  falls below a threshold level, data packets sent to or from the UE  106  become lost or need retransmission at more than a threshold level, or any other condition. 
     If the UE  106  determines at block  808  that one or more automatic downgrade conditions have been satisfied, at block  810  the UE  106  can prepare a NAS downgrade message that indicates to the core network  304  that one or more dedicated bearers  314  should be terminated and/or modified in order to downgrade the enhanced call  102  to an audio-only call  104 . For example, the NAS downgrade message can be a PDN DISCONNECT REQUEST message to end a PDN connection for the enhanced call  102  in order to set up a separate PDN connection for the downgraded audio-only call  104 , or a BEARER RESOURCE MODIFICATION REQUEST message that indicates a dedicated bearer  314  should be terminated or modified. For example, a NAS downgrade message can indicate that a dedicated bearer  314  for video content of a video call should be terminated while leaving a dedicated bearer  314  the audio content  202  in place, such that transmission of the audio content can be continued when the video call is downgraded to an audio-only call  104 . As another example, a NAS downgrade message can indicate that a dedicated bearer  314  for an RTT call that was used to transmit both audio content  202  and text content should be modified to carry just the audio content  202  when the RTT call is downgraded to an audio-only call  104 . 
     At block  812 , the UE  106  can add or set a downgrade reason indicator  502  in the NAS downgrade message. In some examples, the UE  106  can set a particular bit in the NAS downgrade message to “1” to indicate that the UE  106  is automatically downgrading the enhanced call  102 . In other examples, a flag, code, or other value can be similarly set in the NAS downgrade message to indicate that the UE  106  is automatically downgrading the enhanced call  102 . 
     If one or more automatic downgrade conditions were not satisfied at block  808 , the UE  106  can move to block  814  to determine if the UE  106  has received any explicit or implicit instructions from a user to downgrade the enhanced call  102  to an audio-only call  104 . If no explicit or implicit downgrade instructions have been received at block  814 , the UE  106  can return to block  806  and continue to check for the occurrence of automatic downgrade conditions at block  808  and/or user downgrade instructions at block  14  until either the enhanced call  102  is downgraded or the enhanced call  102  ends. In alternate examples, blocks  808  and  814  can be reversed, the UE  106  can check for automatic downgrade conditions and/or user downgrade instructions at preset times or intervals, or the UE  106  can check for automatic downgrade conditions and/or user downgrade instructions using any other method. 
     If the UE  106  determines at block  814  that a user selected a downgrade of the enhanced call  102  through explicit or implicit instructions to the UE  106 , at block  816  the UE  106  can prepare a NAS downgrade message that indicates to the core network  304  that one or more dedicated bearers  314  should be terminated and/or modified in order to downgrade the enhanced call  102  to an audio-only call  104 . As described above, the NAS downgrade message can be a NAS message, such as a PDN DISCONNECT REQUEST message, a BEARER RESOURCE MODIFICATION REQUEST message, or any other type of NAS message. 
     At block  818 , the UE  106  can add or set a downgrade reason indicator  502  in the NAS downgrade message. In some examples, the UE  106  can set a particular bit in the NAS downgrade message to “0” to indicate that a user initiated the downgrade from the enhanced call  102  to the audio-only call  104 . In other examples, a flag, code, header, or other value can be similarly set in the NAS downgrade message to indicate that a user initiated the downgrade from the enhanced call  102  to the audio-only call  104 . 
     After a NAS downgrade message has been prepared with a downgrade reason indicator  502  in either blocks  810  and  812  or blocks  816  and  818 , the UE  106  can send the NAS downgrade message to the MME  308  or other element of the core network  304  at block  820 . In response, the core network  304  can terminate and/or modify one or more of the dedicated bearers  314 . For example, when the NAS downgrade message requests that a dedicated bearer  314  for the video content of a video call, the core network  304  can terminate the dedicated bearer  314  for the video content while maintaining a separate dedicated bearer  314  for the audio content  202 . 
     The MME  308  or other element of the core network  304  can also determine from the downgrade reason indicator  502  in the NAS downgrade message that the downgrade of the enhanced call  102  was initiated either automatically by the UE  106  or by a user&#39;s instruction. The core network  304  can store that information in a database and/or use it to identify problems with the UE  106  or the telecommunication network&#39;s service. 
     Although  FIG. 7  depicts an enhanced call  104  being set up and downgraded using SIP messages and  FIG. 8  depicts an enhanced call  104  being set up and downgraded using NAS messages, in some examples an enhanced call  104  can be set up using one type of message and downgraded with another type of message. For example, a telecommunication network  108  can be configured to let a UE  106  initiate an enhanced call  104  through SIP messages sent to the IMS  306 , but later downgrade the enhanced call  104  to an audio-only call  102  using NAS messages sent directly to the MME  308 , or vice versa. In still other examples an enhanced call  104  can be set up using any other type of message, and/or a downgrade reason indicator  502  can be communicated from the UE  106  to the core network  104  and/or IMS  306  using any other type of message. 
     CONCLUSION 
     When a UE  106  includes a downgrade reason indicator  502  when it informs a telecommunication network  108  that it is downgrading an enhanced call  102  to an audio-only call  104 , the telecommunication network  108  can track whether downgrades of enhanced calls  102  are occurring automatically or due to user choices. The telecommunication network  108  can also associate individual downgrades of enhanced calls  102  with other information it has about identities and/or locations of UEs  106  that initiated the downgrades, as well as identities and/or locations of base stations or other network equipment to which the UEs  106  were connected when the downgrades occurred. The telecommunication network  108  can use this information to diagnose problems with network service and/or individual UEs  106 . 
     For example, in some situations a telecommunication network  108  can ignore downgrades of enhanced calls  102  that were initiated due to users&#39; instructions, because such instructions may be the result of user choices and preferences and not indicate problems with UEs  106  or the telecommunication network  108 . However, the telecommunication network  108  can correlate downgrades of enhanced calls  102  that were automatically initiated by UEs  106  against identities and locations of the downgrading UEs  106  and/or base stations  302  or other network equipment to which they were connected when the downgrades occurred. When such a correlation shows a high or unexpected number of automatic enhanced call  102  downgrades in a certain area, it can indicate that poor network service may be leading to automatic downgrades of enhanced calls  102 . Personnel of the telecommunication network  108  can then investigate reasons for poor service in that area and/or take steps to improve network service in that area. Similarly, when one UE  106  reports a larger number or a higher percentage of automatic enhanced call  102  downgrades compared to other UEs  106 , it can indicate that the UE  106  may be failing and may need to be replaced. 
     Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example embodiments.