Patent Publication Number: US-11050801-B2

Title: Call to meeting upgrade

Description:
BACKGROUND 
     Mobile phones and other user equipment (UE) can be connected to a telecommunication network to engage in many forms of communication. For example, a call session can connect UEs through the telecommunication network. Such call sessions can include one-to-one audio and/or video calls. 
     UEs can also be connected in a meeting session. Meeting sessions can provide users with access to additional features that go beyond what is available in routine one-to-one audio calls or video calls. For example, meeting sessions can provide whiteboard functions that allow users to create drawings on their UE that can be shared with other UEs, screen sharing functions that allow users of other UEs to view what is being displayed on some or all of a particular UE&#39;s screen, recording functions, group conferencing functions, and/or any other type of meeting function. 
    
    
     
       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 an example environment in which user equipment (UE) can connect to a telecommunication network. 
         FIG. 2  depicts an example of user interface (UI) modes for a communication application that can provide functions for both call sessions and meeting sessions during dialogs between UEs. 
         FIG. 3  depicts an example of a message flow that can be used during a call to meeting upgrade process to transition from a call session to a meeting session. 
         FIG. 4  depicts an example system architecture for a UE. 
         FIG. 5  depicts an example system architecture of an application server. 
         FIG. 6  depicts a flow chart of an example process for upgrading a call to a meeting based on user input at a first UE. 
         FIG. 7  depicts a flow chart of an example process for upgrading multiple calls to a single meeting based on user input at a first UE. 
         FIG. 8  depicts a flow chart of an example process for upgrading a call to a meeting automatically at a first UE when a second UE initiates a call to meeting upgrade process. 
         FIG. 9  depicts a flow chart of an example process by which a call application server can assist in upgrading a call between two UEs to a meeting between the two UEs. 
     
    
    
     DETAILED DESCRIPTION 
     Introduction 
     User equipment (UE) connected to wireless communication networks can engage in calls, including audio calls and video calls, natively through the wireless communication networks. For example, wireless communication networks can have call application servers that assist in setting up and managing call sessions between UEs. 
     However, while conventional audio or video calls can be useful ways for users to communicate, users may desire to instead have their UEs connect to a meeting session that provides features that conventional calls may not allow or support. For example, meeting sessions may provide a whiteboard function that allows users to create drawings on their UEs that can be seen on and/or edited by other UEs. As another example, meeting sessions may provide a screen sharing function, in which images displayed on the screen of one UE can be shared and viewed on other UEs. Meeting sessions can also provide recording functions, group conferencing functions, file sharing functions, collaborative document editing functions, and/or any other type of meeting function. 
     Although standalone applications exist that can provide such meeting functions to UEs if the UEs have the applications installed or connect via a website to a meeting portal, users who are already engaged in a conventional audio or video call may need to end their current audio or video call, load the standalone meeting application, and then begin a new meeting session through the standalone meeting application. This process of ending one form of communication and manually taking steps to begin another form of communication can take time and can be frustrating to users. For example, while users may have engaged in the original audio or video call using phone numbers, the users may need to ask each other for usernames associated with a particular standalone meeting application in order to connect with each other through a separate session using that separate standalone meeting application. 
     Described herein are systems and methods that allow users to upgrade an existing call session to a meeting session, such that the users can seamlessly transfer from an audio or video call to a meeting session that provides additional meeting features. 
     Example Environments 
       FIG. 1  depicts an example environment in which user equipment (UE)  102  can connect to a telecommunication network to make or receive calls, transmit or receive data, and/or perform any other network operation. A UE  102  can be any device that can wirelessly connect to the telecommunication network. For example, a UE  102  can be 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. 
     Elements of the telecommunication network can be compatible with one or more wireless access technologies, such as fifth generation (5G) technologies, 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, and/or any other previous or future generation of wireless access technology. 
     Although not shown in  FIG. 1 , the telecommunication network can include base stations to which UEs  102  can wirelessly connect, as well as a core network connected to the base stations. For example, in an LTE network, a base station can be an evolved Node B (eNB), while the core network can be an Evolved Packet Core (EPC). In some examples, UEs  102  can connect to the telecommunication network via other types of access points and connections, such as a connection over the Internet via a Wi-Fi access point. 
     The telecommunication network can also include an Internet Protocol (IP) Multimedia Subsystem (IMS) linked to the core network. The IMS can have one or more elements that can set up and/or manage communication sessions for UEs  102 . Elements of the IMS can use Session Initiation Protocol (SIP) messages to exchange information with each other and/or UEs  102 . For example, the IMS can include an IMS core  104  with one or more Call Session Control Functions (CSCFs) that process and/or route SIP messages, including Proxy CSCFs (P-CSCFs), Interrogating-CSCFs (I-CSCFs), and/or Serving-CSCFs (S-CSCFs). 
     The IMS core  104  can be linked to one or more application servers that provide services for communication sessions, including a call application server  106  and a conference application server  108 . In some examples, messages can be sent between a call application server  106  and a conference application server  108  directly, while in other examples such messages sent between a call application server  106  and a conference application server  108  can be routed through the IMS core  104 . In still other examples, functions of the call application server  106  and conference application server  108  can be performed by the same node or server, such that the messages described herein as being exchanged between the call application server  106  and conference application server  108  can be exchanged between functions within a single node or server. 
     The call application server  106  can set up and manage call sessions between UEs  102 . The call application server  106  can exchange SIP messages with UEs  102 , elements of the IMS core  104 , and/or other network elements to set up and/or manage a call session. For example, a call application server  106  can receive a SIP INVITE sent by a first UE  102  to initiate a call session with a second UE  102 , and can forward the SIP INVITE message on to the second UE  102 . A response from the second UE  102 , as well as other messages exchanged between the first UE  102  and the second UE  102  regarding set up or management of a call session, can pass through the call application server  106 . 
     The description herein refers to a call application server  106  processing messages sent to or from a UE  102 , or to or from other network elements. However, in some examples, multiple call application servers  106  can work together to route messages through the telecommunication network. For example, although only one call application server  106  is shown in  FIG. 1 , in some situations a first UE  102  may be associated with a different call application server  106  than a second UE  102 . In these situations, a first call application server  106  associated with the first UE  102  can forward a message for the second UE  102  to the second call application server  106 , which can in turn forward the message on to the second UE  102 . 
     The conference application server  108  can set up and manage meeting sessions between UEs  102 . The conference application server  108  can exchange SIP messages with UEs  102 , the call application server  106 , elements of the IMS core  104 , and/or other network elements to set up and/or manage a meeting session. For example, as will be discussed further below, the conference application server  108  can receive a SIP message from a UE  102  that requests setup of a new meeting session. In response, the conference application server  108  can prepare network resources for a new meeting session and return a SIP message with details about the new meeting session that the UEs  102  can use to connect to the meeting session. For example, the conference application server  108  can return a SIP message with Session Description Protocol (SDP) information describing a meeting session, including link information such as a Uniform Resource Locator (URL) or Uniform Resource Identifier (URI) indicating where the meeting session can be accessed, a meeting identifier, a dial-in number, an access code, and/or any other meeting information. 
     A UE  102  can run or access a communication application  110  that provides both call and meeting functions. For instance, the communication application  110  can be associated with a subscriber&#39;s account and can be used to make and receive calls instead of, or in addition to, UE  102  systems that rely on a Subscriber Identity Module (SIM) to identify a subscriber and make or receive calls. In some examples, the communication application  110  can be an application that is preinstalled on a UE  102  as the UE&#39;s  102  native phone or call dialing application, or is part of the UE&#39;s  102  operating system. In other examples, the communication application  110  can be a separate application that can be run instead of, or as an augmentation to, a UE&#39;s native phone or call dialing application. In still other examples, the communication application  110  can run on a server on the telecommunication network and can be accessed by a UE  102  as a service through a web browser or other interface. 
     In some examples, the communication application  110  can send or receive information through a Real-Time Communication (RTC) gateway  112  of the telecommunication network. For example, the communication application  110  and the RTC gateway  112  can exchange information using HTTP Hypertext Transfer Protocol (HTTP) or any other protocol, while the RCT gateway  112  can use SIP to exchange information with the IMS core  104 , the call application server  106 , the conference application server  108 , and/or any other network element. Accordingly, an RTC gateway  112  can translate information received from a UE&#39;s communication application  110  into SIP messages, and translate SIP messages from other network elements into HTTP or another protocol understood by the UE&#39;s communication application  110 . As an example,  FIG. 1  depicts a communication application  110  running on UE  102 A, with HTTP traffic from the communication application being converted into SIP traffic by an RTC gateway  112 . 
     In other examples, a UE  102  can send or receive SIP messages for a communication application  110  directly without interpretation by an RTC gateway  112 . For example, the UE  102  may be able to send or receive SIP messages for the communication application natively, such as if the communication application  110  is integrated into a UE&#39;s operating system or if the communication application  110  is otherwise configured to natively send and receive SIP messages. As an example,  FIG. 1  depicts UEs  102 B and  102 C natively sending and receiving SIP messages for their instances of a communication application  110  (not shown). 
     Although the description herein refers to UEs  102  sending and receiving SIP messages, it should be understood that in some examples this can refer to communication applications  110  run on, or accessed by, the UEs  102  sending or receiving the SIP messages. Additionally, it should be understood that, in some examples, messages sent or received by UEs  102  or their communication applications  110  can be in another format, but can be translated to or from SIP by an RTC gateway  112  or other network element. 
     A UE  102 , through an associated communication application  110  and/or an RTC gateway  112 , can use SIP messages to establish a dialog with one or more other UEs  102 . The dialog can represent communications between the UEs  102 , and can include a call session and/or a meeting session. As described herein, when a dialog includes a call session and a new meeting session is created, the dialog can continue via the meeting session even when the call session is terminated, such that communications between the UEs  102  can continue. 
       FIG. 2  depicts an example of user interface (UI) modes for a communication application  110 . As noted above, a communication application  110  can provide functions for both call sessions and meeting sessions during dialogs between UEs  102 . The communication application  110  can accordingly have a call mode UI  202  and a meeting mode UI  204 , and can transition between displaying the two UIs and enabling their corresponding functions depending on whether a call session or a meeting session is active during a dialog between UEs  102 . 
     The call mode UI  202  can display information and/or options related to a current or pending call session. A call mode UI  202  can include a caller identifier  206 , a mute selector  208 , a keypad selector  210 , a speakerphone selector  212 , a meeting upgrade selector  214 , and an end call selector  216 . The caller identifier  206  can display a name, phone number, picture, and/or other information about another party to a call. When the call is a video call, the caller identifier  206  can also display video of the other party. The mute selector  208 , when activated by a user, can turn a mute mode on and off during a call. The keypad selector  210 , when activated by a user, can provide a number pad for dialing a phone number or for entering numbers during a call. The speakerphone selector  212 , when activated by a user, can turn a speakerphone option on and off during a call. The meeting upgrade selector  214 , when activated by a user, can initiate the call to meeting upgrade process described herein, by which UEs  102  engaged in one or more call sessions can be seamlessly transferred to a new meeting session within the same dialog as described herein. When the UE  102  is transitioned from a call session to a new meeting session during a dialog, the communication application&#39;s UI can change from the call mode UI  202  to the meeting mode UI  204  without indicating that the call session has ended. From a user&#39;s perspective, the transition between the call mode UI  202  to the meeting mode  204  can lead to a perception that an existing call has been seamlessly upgraded to a meeting without additional user input to separately set up the meeting. The end call selector  216 , when activated by a user, can end a current call. 
     The call mode UI  202  shown in  FIG. 2  is only an example, and a call mode UI  202  can have more or fewer elements than is shown in  FIG. 2 . The call mode UI  202  may also change depending on the status of the call, with different types of information being displayed when a new call is being dialed, when a call is ringing, when a call is active, or when a call has been hung up. In some examples, the call mode UI  202  may also change based on whether a call is an audio call or a video call, for instance displaying camera options when a video call is active. 
     The meeting mode UI  204  can display information and/or options related to a current or pending meeting session. The meeting mode UI  204  can include a meeting presentation area  218 , a whiteboard selector  220 , a screen sharing selector  222 , a recording selector  224 , group options  226 , and/or an end meeting selector  228 . 
     The meeting presentation area  218  can display information that can be viewable to meeting participants. For example, the meeting presentation area  218  can display a list of meeting participants, a whiteboard space associated with a whiteboard function, screens shared by one or more meeting participants via a screen sharing function, video of one or more meeting participants, files shared by one or more meeting participants, a collaborative document editing screen, and/or any other information associated with a meeting session. 
     The whiteboard selector  220 , when activated by a user, can initiate a whiteboard function that can allow a user to create drawings on their UE  102  that are visible by and/or editable by other participants of a meeting session. In some examples, a whiteboard and/or created drawings can be visible in the meeting presentation area  218  or other portion of the meeting mode UI  204 . In some examples, data associated with drawings created via a whiteboard function during a meeting session can be uploaded to and stored at a conference application server  108  so that it is accessible by other meeting participants. 
     The screen sharing selector  222 , when activated by a user, can initiate a screen sharing function that can allow at least some of the images displayed on a UE  102  to be shared with other participants of a meeting session. For example, when a screen sharing function is activated at a first UE  102 , the UE&#39;s display can be mirrored to other UEs  102  in a meeting presentation area  218  of their communication applications  110 , and users of the other UEs  102  can watch as a user of the first UE  102  interacts with the communication application  110  or other applications on the first UE  102 . In some examples, data associated with the screen sharing function during a meeting session can be uploaded to and stored at a conference application server  108  so that it is accessible by other meeting participants. 
     The recording selector  224 , when activated by a user, can initiate a recording process in which information associated with a meeting session is recorded and stored for later playback or review. In some examples, data recorded during a meeting session can be uploaded to and stored at a conference application server  108  so that it is later accessible by one or more meeting participants. In other examples, data recorded during a meeting session can be stored locally at a UE  102 . 
     The group options  226  can allow a user to invite other meeting participants to a meeting session or otherwise manage the participants to the meeting session. For example, when UE  102 A shown in  FIG. 1  upgrades an audio call session with UE  102 B to a meeting session as described herein, the group options  226  can allow a user to UE  102 A to invite UE  102 C to the meeting session. In some situations, UE  102 A may have had separate audio call sessions with UE  102 B and UE  102 C, can upgrade the call session with UE  102 B to a meeting session using the meeting upgrade selector  214  of the call mode UI  202 , and then use the group options  226  to bring UE  102 C into the meeting session. In other situations, UE  102 C may not have been in an existing call session with UE  102 A, but a user of UE  102 A can use the group options  226  to add UE  102 C after a meeting session has begun. 
     The end meeting selector  228 , when activated by a user, can end a current meeting session. 
     The meeting mode UI  204  shown in  FIG. 2  is only an example, and a meeting mode UI  204  can have more or fewer elements than is shown in  FIG. 2 . The call mode UI  202  may also change depending on the status of a meeting session. For example, the meeting presentation area  218  and/or other elements of the meeting mode UI  204  can change to display different types of information depending on how many participants are connected to the meeting session and/or what meeting features are active or are supported by the conference application server  108  for a particular meeting session. 
       FIG. 3  depicts an example of a message flow that can be used during a call to meeting upgrade process to transition communications associated with a dialog between UE  102 A and UE  102 B from a call session  300  to a meeting session  302 . At the beginning of the message flow, UE  102 A can be engaged in a call session  300  with UE  102 B. The call session  300  can be a session for an audio call or a video call. For example, the call session  300  can be a Real-Time Transport Protocol (RTP) session that uses RTP to transport audio and/or video data over IP-based elements of the telecommunication network. In some examples, the call session  300  may be established between UE  102 A and UE  102 B using SIP messages exchanged between UE  102 A, the call application server  106 , and UE  102 B. For example, UE  102 A can initiate the call session  300  by sending a SIP INVITE message to the call application server  106 , which can forward the SIP INVITE to the UE  102 B. To accept the call, UE  102 B can reply with a SIP message including a “200 OK” response, and the call session  300  can be established between the UEs  102 . 
     In some situations, UE  102 A can put the call session  300  with UE  102 B on hold in order to begin a second call session  300  with a third UE  102 , such as UE  102 C shown in  FIG. 1 . For example, UE  102 A can send a new SIP INVITE to the call application server  106  to initiate a new call session  300  with UE  102 C, or accept a new SIP INVITE that originated from UE  102 C. After the second call session  300  with UE  102 C has been set up, UE  102 A can keep the call session  300  with UE  102 B on hold, place the second call session  300  with UE  102 C on hold and return to the call session  300  with UE  102 B, alternate between the call sessions  300 , and/or end one or both call sessions  300 . In this situation, UE  102 A may have dialogs with both UE  102 B and UE  102 C. 
     While a dialog&#39;s call session  300  for an audio or video call is active, a user of UE  102 A may choose to upgrade the dialog from the call session  300  to a meeting session  302 . For example, the user can input a command to upgrade the current call session  300  to a meeting session  302 , such as selecting a meeting upgrade selector  214  in a call mode UI  202  of a communication application  110 . In response to user input requesting an upgrade from the call session  300  to a meeting session  302 , UE  102 A can send a meeting request  304  to the conference application server  108 . In some examples, the UE  102 A can send the meeting request  304  to the call application server  106 , which can then forward the meeting request  304  on to the conference application server  108  as shown in  FIG. 3 . However, in other examples the UE  102 A can send the meeting request  304  directly to the conference application server  108  without the meeting request  304  passing through the call application server  106 . 
     The meeting request  304  can be sent as a SIP INVITE message, or any other type of message. The meeting request  304  can have a header or message body that specifies information about the requested meeting session  302 , such as a number of participants, participant identifiers, requested meeting features, and/or any other information. For example, a meeting request  304  can include such information in an XML, formatted message body. In some examples, the meeting request  304  can include identifiers of the UE  102  requesting the meeting session  302  and/or identifiers of other expected meeting participants, such as Mobile Station International Subscriber Directory Numbers (MSISDNs) or other identifiers associated with UE  102 A and/or UE  102 B. The meeting request  304  can include the same type of identifier for a UE  102  that would be used to initiate a call session  300 . For example, an MSISDN associated with a UE  102  can be used to set up the initial call session  300 , as well as to set up a new meeting session  304  during a call to meeting upgrade process. 
     Upon receipt of the meeting request  304 , the conference application server  108  can set up the requested meeting session  302 . For example, the conference application server  108  can dedicate computing and/or network resources for the meeting session  302 , assign a meeting ID number or other identifier to the meeting session  302 , assign an access code for the meeting session  302 , and/or perform any other operation to prepare the meeting session  302 . Although UEs  102  that were already parties to one or more call sessions  300  with UE  102 A can be joined into the meeting session  302  as discussed herein, in some examples the conference application server  108  can also assign a dial-in number for the meeting session  302 , such that users of other UEs  102  may alternately be able to join the meeting session  302  by placing a conventional phone call to the dial-in number. 
     After setting up the meeting session  302 , the conference application server  108  can send a meeting confirmation  306  back to the UE  102 A, such as a SIP message indicating a response code of “200 OK.” In some examples, the conference application server  108  can send the meeting confirmation  306  to the call application server  106 , which can then forward the meeting confirmation  306  on to the UE  102 A as shown in  FIG. 3 . However, in other examples the conference application server  108  can send the meeting confirmation  306  directly to the UE  102 A without the meeting confirmation  306  passing through the call application server  106 . 
     The meeting confirmation  306  sent by the conference application server  108  can include a header and/or message body with details about the meeting session  302 , such as link information, a meeting identifier, a dial-in number, an access code, and/or any other meeting information. For example, the meeting confirmation  306  can include a message body with SDP information that defines a profile for the meeting session  302  and/or XML information about the meeting session  302 . UE  102 A can use the meeting information in the meeting confirmation  306  to join the meeting session  302 . For example, UE  102 A can use link information, a meeting ID, an access code, and/or any other information in the meeting confirmation  306  to join the meeting session  302  set up by the conference application server  108 . 
     When UE  102  receives the meeting confirmation  306  and joins the meeting session  302 , a UI displayed by the UE  102 A can transition from a call mode UI  202  to a meeting mode UI  204 . At this point UE  102 A may be at least temporarily engaged in both the original call session  300  and the new meeting session  302 , however options and information presented to the user may transition to only reflecting the meeting session  302  in a meeting mode UI  204 . Accordingly, from the user&#39;s perspective, an existing call has been seamlessly converted to a meeting without the user needing to end the existing call and separately set up the meeting. The UE  102  and/or its communication application  110  can consider the call session  300  and the meeting session  302  to be part of the same dialog with UE  102 B, such that the beginning of the meeting session  302  does not terminate the dialog and the user is instead transitioned seamlessly from the call to the meeting. 
     After UE  102 A has joined the meeting session  302 , UE  102 A can send a meeting referral  308  to the conference application server  108 . In some examples, the UE  102 A can send the meeting referral  308  to the call application server  106 , which can then forward the meeting referral  308  on to the conference application server  108  as shown in  FIG. 3 . However, in other examples the UE  102 A can send the meeting referral  308  directly to the conference application server  108  without the meeting referral  308  passing through the call application server  106 . 
     The meeting referral  308  can indicate that the conference application server  108  should invite one or more identified UEs  102  to the meeting session  302 . For example, because a user of UE  102 A wanted to upgrade a call session  300  with UE  102 B to the meeting session  302 , UE  102 A can send a meeting referral  308  that instructs the conference application server  108  to invite UE  102 B to the meeting session  302 . If UE  102 A had been engaged in multiple call sessions  300 , such as a call session with UE  102 B that had been on hold and another call session  300  with UE  102 C that was active, the meeting referral  308  can identify both UE  102 B and UE  102 C as UEs  102  that should be invited to the meeting session  302 . 
     In some examples, a meeting referral  308  can be a SIP REFER message. In other examples, a meeting referral  308  can be a SIP INVITE message or any other type of message. The meeting referral  308  can have a header or message body that indicates an identifier for one or more UEs  102  that are to be invited to the meeting session  302 , as well as SDP or other information about the meeting session  302 . For example, the meeting referral  308  can be a SIP REFER message with a header including an MSISDN or other identifier associated with UE  102 B and the meeting ID provided to UE  102 A in the meeting confirmation  306 . As discussed further below, in some examples a meeting referral  308  containing identifiers of UEs  102  that should be invited to a meeting session  302  can be included in an initial meeting request  304  rather than being included in a separate meeting referral  308  message. 
     In some examples, the conference application server  108  can return an acceptance message, directly or through the call application server  106 , to UE  102 A to confirm that it will be inviting the UEs  102  identified in the meeting referral  308  to the meeting session  302 . In some examples, the conference application server  108  may also send messages, such as SIP NOTIFY messages, to UE  102 A directly or through the call application server  106  to indicate that the conference application server  108  is attempting to invite the identified UEs  102  or has succeeded in joining them to the meeting session  302 , and/or to provide any other update about the status of the meeting session  302 . 
     In response to receipt of the meeting referral  308 , the conference application server  108  can send UE  102 B a meeting invitation  310  that invites UE  102 B to the meeting session  302 . The meeting invitation  310  can include a header or message body that includes an identifier of UE  102 B. In some examples, the meeting invitation  310  can be a SIP INVITE message. The meeting invitation  310  can also include SDP information or other information about the meeting session  302 , such as link information, a meeting identifier, a dial-in number, an access code, and/or any other meeting information. 
     In some examples, the conference application server  108  can send the meeting invitation  310  to the call application server  106 , which can then forward the meeting invitation  310  on to UE  102 B as shown in  FIG. 3 . However, in other examples the conference application server  108  can send the meeting invitation  310  directly to UE  102 B without the meeting invitation  310  passing through the call application server  106 . 
     UE  102 B can join the meeting session  302  based on the meeting information in the meeting invitation  310 . In some examples, because UE  102 B is still engaged in its leg of the original call session  300  through the call application server  106 , UE  102 B may interpret the meeting invitation  310  received via the call application server  106  as a re-invite message that modifies the existing dialog according to the new SDP or other information associated with the meeting session  302 . 
     UE  102 B can also send a meeting acceptance  312 , such as a SIP “200 OK” message, to the conference application server  108  in response to the meeting invitation  310 . In some examples, UE  102 B can send the meeting acceptance  312  to the call application server  106 , which can then forward the meeting acceptance  312  on to the conference application server  108  as shown in  FIG. 3 . However, in other examples UE  102 B can send the meeting acceptance  312  directly to the conference application server  108  without the meeting acceptance  312  passing through the call application server  106 . 
     In examples in which the call application server  106  serves as an intermediary between the conference application server  108  and the UEs  102  during exchange of the meeting request  304 , meeting confirmation  306 , meeting referral  308 , meeting invitation  310 , and the meeting acceptance  312 , the call application server  106  can review those messages to determine when both UE  102 A and UE  102 B have joined the meeting session  302 . Accordingly, after UE  102 B sends the meeting acceptance  312 , the call application server  106  can send end call instructions  314  to both UE  10 A and UE  102 B, such as a SIP “BYE” messages. The end call instruction  314  can cause the legs of the call session  300  between UE  102 A and UE  102 B to be terminated, thereby releasing network resources that may have been devoted to those legs. 
     In other examples in which the UEs  102  exchange messages directly with the confirmation application server  108 , after UE  102 A and UE  102 B have both joined the meeting session  302  following UE  102 B&#39;s meeting acceptance  312 , UE  102 A can send an end call instruction  314 , such as a SIP “BYE” message, that causes the original call session  300  to be terminated. 
     At this point, although both legs of the original call session  300  between UE  102 A and UE  102 B have been terminated, the previously existing dialog between UE  102 A and UE  102 B can remain active and both UEs  102  can have joined the meeting session  302 . Users of UE  102 A and UE  102 B can continue communicating through the meeting session  302  using audio or video, as well as through additional meeting features that may not have been available during the original call session  300 . For example, when UE  102 B receives the meeting invitation  310  and joins the meeting session  302 , a UI displayed by UE  102 B can transition from a call mode UI  202  to a meeting mode UI  204 . 
     In some examples, a transition from a previously existing call session  300  to a new meeting session  302 , and an associated UI transition, may occur at UE  102 B without user input at UE  102 B. For example, when UA  102 A and UE  102 B are engaged in a call, a user of UA  102 A can provide user input to initiate a call to meeting upgrade process. As part of that call to meeting upgrade process, UE  102 B can receive a meeting invitation  310  and automatically join a new meeting session  302  in response, such that a user of UE  102 B perceives the call transitioning to a meeting automatically and seamlessly. 
     Although  FIG. 3  depicts the conference application server  108  sending a meeting invitation  310  to UE  102 B, the conference application server  108  may also send a similar meeting invitation  310  to UE  102 C and/or any other UEs  102  identified in a meeting referral  308 . For example, when UE  102 A had a first call session  300  with UE  102 B on hold and had a second call session  300  with UE  102 C active when UE  102 A began the call to meeting process, UE  102 A can send a meeting referral  308  requesting that both UE  102 B and UE  102 C be invited to the meeting session  302  by the conference application server  108 . In this situation, UE  102 B and UE  102 C can both receive a meeting invitation  310  and both can respond by joining the meeting session  302  as active meeting participants along with UE  102 A, even though UE  102 B had been on hold. When UE  102 B and UE  102 C join the meeting session  302  and send meeting acceptances  312  back to the conference application server  108 , messages can also be sent to both UE  102 B and UE  102 C to end their legs of previous call sessions  300 . For example, the call application server  106  can send one end call instruction  314  to UE  102 B to end its leg of the original first call session  300  and another end call instruction  314  to UE  102 C to end its leg of the original second call session  300 . 
     As shown in  FIG. 3 , in some examples UE  102 A can send a meeting request  304  to set up a meeting session  302 , followed later by a meeting referral  308  that identifies other UEs  102 , such as UE  102 B and/or UE  102 C, as meeting participants that the conference application server  108  should invite to the meeting session  302 . However, in other examples, the initial meeting request  304  sent by UE  102 A can include a meeting referral  308  or other information identifying UE  102 B, UE  102 C, and/or any other UEs  102  as meeting participants that should be invited to the meeting session  302 . Accordingly, in situations in which the initial meeting request  304  identifies other UEs  102  as meeting participants that are to be invited to the meeting session  302 , the conference application server  108  can send meeting invitations  310  to the identified UEs  102  in response to the initial meeting request  304  instead of in response to receipt of a later meeting referral  308 . 
     Example Architecture 
       FIG. 4  depicts an example system architecture for a UE  102 , in accordance with various examples. As shown, a UE  102  can include a memory  402  that stores a communication application  110  and other modules and data  404 , processor(s)  406 , radio interfaces  408 , a display  410 , output devices  412 , input devices  414 , and/or a drive unit  416  including a machine readable medium  418 . 
     In various examples, memory  402  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  402  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 discs (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  102 . Any such non-transitory computer-readable media may be part of the UE  102 . 
     The memory  402  can store computer-readable instructions and/or other data associated with a communication application  110  that can provide both call and meeting functions to a user of the UE  102 . In some examples, the communication application  110  can be an application or operating system component that is stored in the memory  402 . In other examples, the communication application  110  can be run through a web browser or other interface from a server or other remote location, however some or all parts of the communication application  110 , or related data, can be at least temporarily stored in the memory  402 . 
     The memory  402  can also store other modules and data  404  that can be utilized by the UE  102  to perform or enable performing any action taken by the UE  102 . The modules and data  404  can include a UE platform and applications, and data utilized by the platform and applications. 
     In various examples, the processor(s)  406  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)  406  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)  406  may also be responsible for executing all computer applications stored in the memory  402 , which can be associated with common types of volatile (RAM) and/or nonvolatile (ROM) memory. 
     The radio interfaces  408  can include transceivers, modems, interfaces, antennas, and/or other components that perform or assist in exchanging radio frequency (RF) communications with a base station of a wireless telecommunication network, or an alternate access point through which the UE  102  can reach a telecommunication network. For example, a UE  102  can have radio interfaces  408  compatible with LTE, Wi-Fi, and/or any other type of wireless connection. 
     The display  410  can be a liquid crystal display or any other type of display commonly used in UEs  102 . For example, display  410  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  412  can include any sort of output devices known in the art, such as a display  410 , speakers, a vibrating mechanism, and/or a tactile feedback mechanism. Output devices  412  can also include ports for one or more peripheral devices, such as headphones, peripheral speakers, and/or a peripheral display. 
     The input devices  414  can include any sort of input devices known in the art. For example, input devices  414  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  418  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  402 , processor(s)  406 , and/or radio interface(s)  408  during execution thereof by the UE  102 . The memory  402  and the processor(s)  406  also can constitute machine readable media  418 . 
       FIG. 5  depicts an example system architecture of an application server  500 . An application server  500  can be a call application server  106  and/or a conference application server  108 . An application server  500  can have a system memory  502 . The system memory  502  can store data for the application server  500 , including a session manager  504  and/or other modules and data  506 . The application server  500  can also include processor(s)  508 , removable storage  510 , non-removable storage  512 , input device(s)  514 , output device(s)  516 , and/or communication connections  518  for communicating with other network elements  520 . 
     In various examples, system memory  502  can be volatile (such as RAM), non-volatile (such as ROM, flash memory, etc.), or some combination of the two. Example system memory  502  can include one or more of RAM, ROM, EEPROM, a Flash Memory, a hard drive, a memory card, an optical storage, a magnetic cassette, a magnetic tape, a magnetic disk storage or another magnetic storage devices, or any other medium. 
     The session manager  504  can be configured to set up and manage communication sessions that are part of a dialog between UEs  102 . The session manager  504  can manage communication sessions at least in part based on SIP messages received, generated, or forwarded by the application server  500 . For example, when the application server  500  is a call application server  106 , a session manager  504  can set up, manage, and/or tear down legs of a call session  300  between UEs  102  based on SIP messages and/or forward SIP messages to and from a conference application server  108  associated with setup of a meeting session  302  during a call to meeting upgrade process as shown in  FIG. 3 . As another example, when the application server  500  is a conference application server  108 , a session manager  504  can set up and manage a meeting session  302  requested as part of a call to meeting upgrade process, including receiving a meeting request  304  and a meeting referral  308 , and sending meeting invitations  310  as shown in  FIG. 3 . 
     The other modules and data  506  can be utilized by the application server  500  to perform or enable performing any action taken by the application server  500 . The other modules and data  506  can include a platform and applications, and data utilized by the platform and applications. 
     In some embodiments, the processor(s)  508  can be a central processing unit (CPU), a graphics processing unit (GPU), both CPU and GPU, or other processing unit or component known in the art. 
     The application server  500  can also include additional data storage devices (removable and/or non-removable) such as, for example, magnetic disks, optical disks, or tape. Such additional storage is illustrated in  FIG. 5  by removable storage  510  and non-removable storage  512 . Computer storage media may include 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  502 , removable storage  510  and non-removable storage  512  are all examples of computer-readable storage media. Computer-readable storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile discs (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by the application server  500 . Any such computer-readable storage media can be part of the application server  500 . In various examples, any or all of system memory  502 , removable storage  510 , and non-removable storage  512 , store programming instructions which, when executed, implement some or all of the herein-described operations of the application server  500 . 
     In some examples, the application server  500  can also have input device(s)  514 , such as a keyboard, a mouse, a touch-sensitive display, voice input device, etc., and/or output device(s)  516  such as a display, speakers, a printer, etc. These devices are well known in the art and need not be discussed at length here. 
     The application server  500  can also contain communication connections  518  that allow the application server  500  to communicate with other network elements  520 , such as the IMS core  104  or other application servers  500 . For example, a communication connection  518  can allow the application server to exchange SIP messages with UEs  102  through the IMS core  104 . As another example, when the application server  500  is a call application server  106 , the call application server  106  can use a communication connection  518  to forward SIP messages to or from a conference application server  108 . 
     Example Operations 
       FIG. 6  depicts a flow chart of an example process for upgrading a call to a meeting based on user input at a first UE  102 . In some examples, the first UE  102  can be UE  102 A shown in  FIGS. 1 and 3 . 
     At operation  602 , the first UE  102  can be engaged in a call session  300  with a second UE  102 , such as UE  102 B shown in  FIGS. 1 and 3 . For example, the first and second UEs  102  can have exchanged SIP messages through or more call application servers  106  to establish a call session  300  as part of a dialog between the first and second UEs  102 . The first UE  102  can display a call mode UI  202  during the call session  300 , for example via a communication application  110  that can provide both call and meeting functions. 
     At operation  604 , the first UE  102  can receive user input instructing the first UE  102  to initiate a call to meeting upgrade. For example, the user input can be an activation of a meeting upgrade selector  214  displayed in a call mode UI  202  of a communication application  110 . 
     At operation  606 , in response to the user input instructing the first UE  102  to initiate a call to meeting upgrade, the first UE  102  can send a meeting request  304  to a conference application server  108 . In some examples, the first UE  102  can send the meeting request  304  to the conference application server  108  via the call application server  106  to which it is already connected with respect to the call session  300 . However, in other examples, the first UE  102  can send the meeting request  304  directly to the conference application server  108 . 
     At operation  608 , the first UE  102  can receive meeting information about a new meeting session  302  established by the conference application server  108  in response to the meeting request  304 . In some examples, the first UE  102  can receive the meeting information in a meeting confirmation  306  that was received by the call application server  106  from the conference application server  108  and forwarded by the call application server  106  to the first UE  102 . In other examples, the first UE  102  can receive the meeting information in a meeting confirmation  306  sent directly to the first UE  102  from the conference application server  108 . 
     At operation  610 , the first UE  102  can join the meeting session  302  and change the displayed UI to a meeting mode UI  204 . For example, a communication application  110  handling the call session  300  can use the meeting information, such as a link, meeting ID, and/or other information to join the meeting session  302  established by the conference application server  108  and transition its display from the call mode UI  202  to the meeting mode UI  204 . The first UE  102  can join the meeting session  302  as part of the same dialog with the second UE  102 , such that the dialog is not terminated despite the transition from the call session  300  to the meeting session  302 . 
     At operation  612 , the first UE  102  can send a meeting referral  308  to the conference application server  108 . The meeting referral  308  can include the meeting information about the meeting session  302  and an identifier associated with the second UE  102 , such that the conference application server  108  can invite the second UE  102  to the meeting session  302 . In some examples, the first UE  102  can send the meeting referral  308  to the call application server  106 , which can then forward the meeting referral  308  to the conference application server  108 . However, in other examples, the first UE  102  can send the meeting referral  308  directly to the conference application server  108 . In some examples, if a meeting referral  308  or other information identifying the second UE  102  as a meeting participant was included in the meeting request  304  sent at operation  606 , operation  612  can be skipped. 
     At operation  614 , the first UE  102  can terminate its leg of the original call session  300 . In some examples, the first UE  102  can receive an end call instruction  314  from the call application server  106  that causes the first UE  102  or its communication application  110  to terminate the first UE&#39;s leg of the call session  300 . In other examples, an end call instruction  314  can be a notification that the call application server  106  has terminated the leg of the call session  300 . In still other examples, after both the first UE  102  and the second UE  102  have joined the meeting session  302 , the first UE  102  can transmit an end call instruction  314  to the call application server  106  and/or the second UE  102  to cause the original call session  300  to be terminated. 
     Despite termination of the call session  300 , due to the switch to presenting the meeting mode UI  204  and/or because the first UE  102  considers the meeting session  302  to be part of the same dialog with the second UE  102  as the original call session  300 , the transition to the meeting session  302  can appear to a user of the first UE  102  to be a seamless upgrade from the call to a meeting. 
       FIG. 7  depicts a flow chart of an example process for upgrading multiple calls to a single meeting based on user input at a first UE  102 . In some examples, the first UE  102  can be UE  102 A shown in  FIGS. 1 and 3 . 
     At operation  702 , the first UE  102  can be engaged in a first call session  300 A with a second UE  102 , such as UE  102 B shown in  FIGS. 1 and 3 . For example, the first and second UEs  102  can have exchanged SIP messages through or more call application servers  106  to establish the first call session  300 A as part of a first dialog between the first and second UEs  102 . 
     At operation  704 , the first UE  102  can also be engaged in a second call session  300 B with a third UE  102 , such as UE  102 C shown in  FIG. 1 . For example, the first and third UEs  102  can have exchanged SIP messages through or more call application servers  106  to establish the second call session  300 B as part of a second dialog between the first and third UEs  102 . In some examples, the first UE  102  may have placed the first call session  300 A with the second UE  102  on hold to initiate the second call session  300 B with the third UE  102  or to accept the third UE&#39;s initiation of the second call session  300 B. 
     During operations  702  and  704 , the first UE  102  can display a call mode UI  202 , for example via a communication application  110  that can provide both call and meeting functions. In some examples, the call mode UI  202  can present options that allow a user to put the active call session  300  on hold and/or return an on-hold call session  300  to being active. 
     At operation  706 , the first UE  102  can receive user input instructing the first UE  102  to initiate a call to meeting upgrade. For example, the user input can be an activation of a meeting upgrade selector  214  displayed in a call mode UI  202  of a communication application  110 . The call to meeting upgrade can apply to any or all of the current call sessions  300 , even if one or more of the call sessions  300  is on hold. For example, a user of the first UE  102  can initiate a call to meeting upgrade while the first call session  300 A is on hold and the second call session  300 B is active, such that both call sessions  300  can be upgraded into a single meeting session  302  between the first UE  102 , the second UE  102 , and the third UE  102 . 
     At operation  708 , in response to the user input instructing the first UE  102  to initiate a call to meeting upgrade, the first UE  102  can send a meeting request  304  to a conference application server  108 . In some examples, the first UE  102  can send the meeting request  304  to the conference application server  108  via a call application server  106  to which it is already connected with respect to either or both call sessions  300 . However, in other examples, the first UE  102  can send the meeting request  304  directly to the conference application server  108 . 
     At operation  710 , the first UE  102  can receive meeting information about a new meeting session  302  established by the conference application server  108  in response to the meeting request  304 . In some examples, the first UE  102  can receive the meeting information in a meeting confirmation  306  that was received by a call application server  106  from the conference application server  108  and forwarded by the call application server  106  to the first UE  102 . In other examples, the first UE  102  can receive the meeting information in a meeting confirmation  306  sent directly to the first UE  102  from the conference application server  108 . 
     At operation  712 , the first UE  102  can join the meeting session  302  and change the displayed UI to a meeting mode UI  204 . For example, a communication application  110  handling the call session  300  can use the meeting information, such as a link, meeting ID, and/or other information to join the meeting session  302  established by the conference application server  108  and transition its display from the call mode UI  202  to the meeting mode UI  204 . The first UE  102  can join the meeting session  302  as part of the first and second dialogs established with the second UE  102  and the third UE  102 , such that the first and second dialogs are not terminated despite the transition from the call sessions  300  to the meeting session  302 . 
     At operation  714 , the first UE  102  can send a meeting referral  308  to the conference application server  108 . The meeting referral  308  can include the meeting information about the meeting session  302  and identifiers associated with the second UE  102  and the third UE  102 , such that the conference application server  108  can invite the second UE  102  and the third UE  102  to the meeting session  302 . In other examples, the first UE  102  can send separate meeting referrals  308  for each UE  102  that is to be invited to the meeting session  302 . In some examples, the first UE  102  can send the one or more meeting referrals  308  to the one or more call application servers  106  associated with the call sessions  300 , which can then forward the one or more meeting referrals  308  to the conference application server  108 . However, in other examples, the first UE  102  can send the one or more meeting referrals  308  directly to the conference application server  108 . In some examples, if a meeting referral  308  or other information identifying the second UE  102  and the third UE  102  as meeting participants was included in the meeting request  304  sent at operation  708 , operation  714  can be skipped. 
     At operation  716 , the first UE  102  can terminate its legs of the first call session  300 A and the second call session  300 B. In some examples, the first UE  102  can receive one or more end call instructions  314  from the one or more call application servers  106  that cause the first UE  102  or its communication application  110  to terminate the first UE&#39;s legs of the call sessions  300 . In other examples, an end call instruction  314  can be a notification that a call application server  106  has terminated a leg of a call session  300 . In still other examples, after the first UE  102  determines that the second UE  102  and/or the third UE  102  have joined the meeting session  302  along with the first UE  102 , the first UE  102  can transmit an end call instruction  314  to the one or more call application servers  106 , the second UE  102 , and/or the third UE  102  to cause the original call sessions  300  to be terminated. 
     Despite termination of the first and the second call sessions  300 , due to the switch to presenting the meeting mode UI  204  and/or because the first UE  102  considers the meeting session  302  to be part of the same dialogs with the second UE  102  and the third UE  102  as the original call sessions  300 , the transition to the meeting session  302  can appear to a user of the first UE  102  to be a seamless upgrade from the calls to a meeting. 
       FIG. 8  depicts a flow chart of an example process for upgrading a call to a meeting automatically at a first UE  102  when a second UE  102  initiates a call to meeting upgrade process. In some examples, here the first UE  102  can be UE  102 B shown in  FIGS. 1 and 3 , while the second UE  102  can be UE  102 A shown in  FIGS. 1 and 3 . 
     At operation  802 , the first UE  102  can be engaged in a call session  300  with the second UE  102 . For example, the first and second UEs  102  can have exchanged SIP messages through or more call application servers  106  to establish a call session  300  as part of a dialog between the first and second UEs  102 . The first UE  102  can display a call mode UI  202  during the call session  300 , for example via a communication application  110  that can provide both call and meeting functions. 
     At operation  804 , the first UE  102  can receive a meeting invitation  310  that originated from a conference application server  108 . In some examples, the conference application server  108  may have sent the meeting invitation  310  to the call application server  106  associated with the call session  300  between the first UE  102  and the second UE  102 , and the call application server  106  may have forwarded the meeting invitation  312  to the first UE  102 . In other examples, the conference application server  108  may have sent the meeting invitation  310  directly to the first UE  102 . The meeting invitation  310  can indicate meeting information about a meeting session  302  established by the conference application server  108  in response to a call to meeting upgrade process initiated by the second UE  102 . In some examples, the second UE  102  may have placed the call session  300  with the first UE  102  on hold prior to initiating the call to meeting upgrade, while in other examples the call session  300  between the first UE  102  and the second UE  102  may have been active when the second UE  102  initiated the call to meeting upgrade. 
     At operation  806 , the first UE  102  can return a meeting acceptance  312  to the conference application server  108  in response to the meeting invitation  312 . In some examples, the first UE  102  can send the meeting acceptance  312  to the call application server  106 , which can in turn forward the meeting acceptance  312  to the conference application server  108 . In other examples, the first UE  102  can send the meeting acceptance  312  to the conference application server  108  directly. 
     At operation  808 , the first UE  102  can join the meeting session  302  and change the displayed UI to a meeting mode UI  204 . For example, a communication application  110  handling the call session  300  can use the meeting information, such as a link, meeting ID, and/or other information to join the meeting session  302  established by the conference application server  108  and transition its display from the call mode UI  202  to the meeting mode UI  204 . The first UE  102  can join the meeting session  302  as part of the same dialog with the second UE  102 , such that the dialog is not terminated despite the transition from the call session  300  to the meeting session  302 . In some cases, the first UE  102  can join the meeting session  302  and transition to displaying the meeting mode UI  204  even though the call to meeting upgrade was requested by the second UE  102 . 
     At operation  810 , the first UE  102  can receive an end call instruction  314  that causes the first UE  102  to end its leg of the original call session  300 . In some examples, the end call instruction  314  can originate from the call application server  106  after both the first UE  102  and second UE  102  have joined the meeting session  302 . In other examples, the end call instruction  314  can originate from the second UE  102  after both the first UE  102  and second UE  102  have joined the meeting session  302 . In some examples, the first UE  102  or its communication application  110  can terminate its leg of the call session  300  with the call application server  106  in response to the end call instruction  314 . In other examples, the end call instruction  314  can be a notification that the call application server  106  has terminated the leg of the call session  300 . 
       FIG. 9  depicts a flow chart of an example process by which a call application server  106  can assist in upgrading a call between two UEs  102  to a meeting between the two UEs that is managed by a conference application server  108 . 
     At operation  902 , the call application server  106  can manage a call session  300  between a first UE  102  and a second UE  102 , such as UE  102 A and UE  102 B shown in  FIGS. 1 and 3 . For example, the call application server  106  can route SIP messages between the first and second UEs  102  during setup of the call session  300  and/or during the call session  300 . 
     At operation  904 , the call application server  106  can receive a meeting request  304  from the first UE  102 . The call application server  106  can forward the meeting request  304  to a conference application server  108 . 
     At operation  906 , the call application server  106  can receive a meeting confirmation  306  from the conference application server  108 . The call application server  106  can forward the meeting confirmation  306  to the first UE  102 . 
     At operation  908 , the call application server  106  can receive a meeting referral  308  from the first UE  102 . The call application server  106  can forward the meeting referral  308  to the conference application server  108 . The meeting referral  308  can be a request from the first UE  102  to have the second UE  102  invited to the meeting session  302 . In some examples, if a meeting referral  308  or other information identifying the second UE  102  as a meeting participant was included in the meeting request  304  received at operation  904 , operation  908  can be skipped. 
     At operation  910 , the call application server  106  can receive a meeting invitation  310  from the conference application server  108 . The meeting invitation  310  can identify the second UE  102  and include meeting information about the meeting session  302 . The call application server  106  can forward the meeting invitation  310  to the second UE  102 . 
     At operation  912 , the call application server  106  can receive a meeting acceptance  312  from the second UE  102 . The call application server  106  can forward the meeting acceptance  312  to the conference application server  108 . The meeting acceptance  312  can be a response from the second UE  102  indicating that it has joined the meeting session  302  or will be joining the meeting session  302 . 
     At operation  914 , the call application server  106  can send end call instructions  314  to the first UE  102  and the second UE  102  to terminate their legs of the call session  300 . The call application server  106  can determine that the end call instructions  314  should be sent based on information indicating that both the first UE  102  and the second UE  102  have joined the meeting session  302 . For example, the call application server  106  can determine that the first UE  102  has joined the meeting session  302  based on the receipt of the meeting confirmation  306  from the conference application server  108  and/or the meeting referral  308  from the UE  102 . The call application server  106  can determine that the second UE  102  has joined the meeting session  302  based on the receipt of the meeting acceptance  312 . Although in some examples the end call instructions  314  can instruct the first UE  102  and the second UE  102  to release their legs of the call session  300 , in other examples the call application server  106  can terminate the legs of the call session  300  and the end call instructions  314  can be notifications to the first UE  102  and the second UE  102  that the legs of the call session  300  have been terminated. 
     CONCLUSION 
     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.