PATENT DOCUMENT

Publication Number: US-10123372-B2
Application Number: US-201615274038-A
Country: US
Kind Code: B2

Title: Device, system and method to avoid voice call setup failure due to network congestion

Abstract:
Devices and methods for handling phone calls. One device is a user equipment (UE) configured to establish a connection with a first evolved Node B (eNB). A method includes transmitting an invite signal to a further UE for a Voice over LTE (VoLTE) call, receiving an accept signal from the further UE, receiving a fail signal from the first eNB that a dedicated bearer is unavailable, generating a trigger signal in response to receiving the fail signal and transmitting the trigger signal to the first eNB. Another device is a base station (e.g., eNB) that receives a VoLTE call request from a UE, determines whether the eNB has sufficient resources to provide a dedicated bearer. When it is determined the eNB has insufficient resources, the eNB determines whether a further eNB has sufficient resources to provide the dedicated bearer, and determines whether the UE can connect to the further eNB.

Claims:
What is claimed is: 
     
       1. A method, comprising:
 at a user equipment (UE) configured to establish a connection with a Long Term Evolution (LTE) network, the LTE network including a first evolved Node B (eNB) and a second eNB, the UE being associated with the first eNB:
 transmitting an invite signal to a further UE for a Voice over LTE (VoLTE) call; 
 receiving an accept signal from the further UE for the VoLTE call; 
 receiving a fail signal from the first eNB that a dedicated bearer is unavailable; 
 generating a trigger signal in response to receiving the fail signal; and 
 transmitting the trigger signal to the first eNB. 
 
 
     
     
       2. The method of  claim 1 , wherein the trigger signal is one of an A2 event measurement report or an A3 event measurement report. 
     
     
       3. The method of  claim 1 , wherein the trigger signal causes a handover procedure to be performed, wherein a successful completion of the handover procedure results in the UE being associated with the second eNB. 
     
     
       4. The method of  claim 3 , further comprising:
 determining whether the handover procedure is successful; and 
 when the handover procedure is not successful, generating a second trigger signal; and 
 transmitting the second trigger signal to the first eNB. 
 
     
     
       5. The method of  claim 3 , further comprising:
 determining whether the handover procedure is successful; and 
 when the handover procedure is not successful, determining a number of trigger signals that have been transmitted to the first eNB in response to receiving the fail signal; and 
 determining whether the number exceeds a threshold. 
 
     
     
       6. The method of  claim 5 , further comprising:
 when the number exceeds the threshold, generating a further trigger signal; and 
 transmitting the further trigger signal to the first eNB, wherein the further trigger signal causes the UE to connect to a circuit switched network for voice calls. 
 
     
     
       7. The method of  claim 5 , further comprising:
 when the number does not exceed the threshold, generating a further trigger signal; and 
 transmitting the further trigger signal to the first eNB, wherein the further trigger signal causes the handover procedure to be performed. 
 
     
     
       8. The method of  claim 1 , wherein the trigger signal causes the UE to connect to a circuit switched network for voice calls. 
     
     
       9. The method of  claim 8 , further comprising:
 performing an automatic redial corresponding to the invite signal using a circuit switched call. 
 
     
     
       10. A user equipment (UE), comprising:
 a transceiver configured to establish a connection with a Long Term Evolution (LTE) network, the LTE network including a first evolved Node B (eNB) and a second eNB, the UE being associated with the first eNB; and 
 a processor configured to perform operations, comprising:
 generating an invite signal to be transmitted to a further UE for a Voice over LTE (VoLTE) call; 
 receiving an accept signal from the further UE for the VoLTE call; 
 receiving a fail signal from the first eNB that a dedicated bearer is unavailable; and 
 generating a trigger signal in response to receiving the fail signal. 
 
 
     
     
       11. The UE of  claim 10 , wherein the trigger signal is an A3 measurement report that causes a handover procedure to be performed, wherein a successful completion of the handover procedure results in the UE being associated with the second eNB. 
     
     
       12. The UE of  claim 11 , wherein the processor is configured to perform further operations comprising:
 determining whether the handover procedure is successful; and 
 when the handover procedure is not successful, generating a second trigger signal. 
 
     
     
       13. The UE of  claim 11 , wherein the processor is configured to perform further operations comprising:
 determining whether the handover procedure is successful; and 
 when the handover procedure is not successful, determining a number of trigger signals that have been transmitted to the first eNB in response to receiving the fail signal; and 
 determining whether the number exceeds a threshold. 
 
     
     
       14. The UE of  claim 13 , wherein the processor is configured to perform further operations comprising:
 when the number exceeds the threshold, generating a further trigger signal, wherein the further trigger signal causes the UE to connect to a circuit switched network for voice calls. 
 
     
     
       15. The UE of  claim 13 , wherein the processor is configured to perform further operations comprising:
 when the number does not exceed the threshold, generating a further trigger signal, wherein the further trigger signal causes the handover procedure to be performed. 
 
     
     
       16. The UE of  claim 10 , wherein the trigger signal causes the UE to connect to a circuit switched network for voice calls. 
     
     
       17. The UE of  claim 16 , wherein the processor is configured to perform further operations comprising:
 performing an automatic redial corresponding to the invite signal using a circuit switched call. 
 
     
     
       18. A method, comprising:
 at an evolved Node B (eNB) of a Long Term Evolution (LTE) network:
 receiving a Voice over LTE (VoLTE) call request from a user equipment (UE) to place a VoLTE call to a further UE; 
 determining whether the eNB has sufficient resources to provide a dedicated bearer to the UE for the VoLTE call; 
 when it is determined the eNB has insufficient resources to provide the dedicated bearer,
 determining whether a further eNB of the LTE network has sufficient resources to provide the dedicated bearer for the UE, and 
 determining whether the UE is capable of connecting to the further eNB; and 
 
 when the further eNB has sufficient resources and the UE is capable of connecting to the eNB, performing a handover procedure such that the UE is associated with the further eNB. 
 
 
     
     
       19. The method of  claim 18 , wherein the determining whether the eNB has sufficient resources is performed after receiving an indication that the further UE has accepted the VoLTE call. 
     
     
       20. The method of  claim 18 , wherein the determining whether the further eNB has sufficient resources includes:
 sending a request via an X2 interface connecting the eNB and the further eNB; and 
 receiving a response from the further eNB via the X2 interface.

Description:
PRIORITY CLAIM/INCORPORATION BY REFERENCE 
     This application claims priority to U.S. Provisional Application 62/235,077 entitled “Device, System and Method for Performing a Call,” filed on Sep. 30, 2015, the entirety of which is incorporated herein by reference. 
    
    
     BACKGROUND INFORMATION 
     A first user equipment (UE) may be configured to communicate wirelessly with a second UE. Specifically, the first UE may transmit data to and receive data from the second UE through a wired or wireless communications network. The first and second UEs may use the network to communicate using a variety of different applications. For example, the first UE may be a mobile originating (MO) UE while the second UE may be a mobile terminating (MT) UE for a voice call. The voice call may be performed in a variety of different manners. For example, when the MO or MT UE is connected to a legacy network, the voice call may be performed using circuit switching. In another example, when the MO or MT UE is connected to an Internet Protocol (IP) data transmission network, the voice call may be performed using Voice over IP (VoIP). More specifically, when the network is a Long Term Evolution (LTE) network, the VoIP call may be a Voice over LTE (VoLTE) call. 
     When the VoLTE call is performed, the MO and MT UEs may perform a setup procedure. Initially, when the MO and MT UEs connect to the LTE network, each UE may be associated with one or more default bearers with an associated base station of the LTE network to which the UE is connected that provide a best effort service in the exchange of data with the LTE network. Furthermore, when a particular application is being utilized such as the VoLTE call, each UE may be assigned a dedicated bearer with the associated base station that provides a dedicated tunnel for data to be transmitted with regard to the VoLTE call (e.g., the voice data). The dedicated bearer may provide a variety of functionalities such as improving throughput or guaranteeing a bit rate for the data to be transmitted. However, if the base station (e.g., an evolved Node B (eNB) with an LTE network) does not have sufficient resources to provide the dedicated bearer, the VoLTE call fails even when the MT UE has accepted the invite. 
     SUMMARY 
     A method performed by a user equipment (UE) configured to establish a connection with a Long Term Evolution (LTE) network, the LTE network including a first evolved Node B (eNB) and a second eNB, the UE being associated with the first eNB. The method includes transmitting an invite signal to a further UE for a Voice over LTE (VoLTE) call, receiving an accept signal from the further UE for the VoLTE call, receiving a fail signal from the first eNB that a dedicated bearer is unavailable, generating a trigger signal in response to receiving the fail signal and transmitting the trigger signal to the first eNB. 
     A user equipment (UE) having a transceiver configured to establish a connection with a Long Term Evolution (LTE) network, the LTE network including a first evolved Node B (eNB) and a second eNB, the UE being associated with the first eNB; and a processor configured to perform operations. The operations include generating an invite signal to be transmitted to a further UE for a Voice over LTE (VoLTE) call, receiving an accept signal from the further UE for the VoLTE call, receiving a fail signal from the first eNB that a dedicated bearer is unavailable and generating a trigger signal in response to receiving the fail signal. 
     A method performed by an evolved Node B (eNB) of a Long Term Evolution (LTE) network. The method including receiving a Voice over LTE (VoLTE) call request from a user, equipment (UE) to place a VoLTE call to a further UE, determining whether the eNB has sufficient resources to provide a dedicated bearer to the UE for the VoLTE call, when it is determined the eNB has insufficient resources to provide the dedicated bearer, determining whether a further eNB of the LTE network has sufficient resources to provide the dedicated bearer for the UE and determining whether the UE is capable of connecting to the further eNB and when the further eNB has sufficient resources and the UE is capable of connecting to the eNB, performing a handover procedure such that the UE is associated with the further eNB. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a network arrangement according to various embodiments described herein. 
         FIG. 2  shows a Long Term Evolution network according to various embodiments described herein. 
         FIG. 3  shows an evolved Node B of the LTE network of  FIG. 2  according to various embodiments described herein. 
         FIG. 4  shows a signaling diagram for a network operation in performing a call according to various embodiments described herein. 
         FIG. 5  shows a method for a network operation in performing a call according to various embodiments described herein. 
         FIG. 6  shows a user equipment according to various embodiments described herein. 
         FIG. 7  shows a first signaling diagram for a user equipment operation in performing a call according to various embodiments described herein. 
         FIG. 8  shows a first method for a user equipment operation in performing a call according to various embodiments described herein. 
         FIG. 9  shows a second signaling diagram for a user equipment operation in performing a call according to various embodiments described herein. 
         FIG. 10  shows a second method for a user equipment operation in performing a call according to various embodiments described herein. 
     
    
    
     DETAILED DESCRIPTION 
     The exemplary embodiments may be further understood with reference to the following description and the related appended drawings, wherein like elements are provided with the same reference numerals. The exemplary embodiments are related to a device, system, and method for performing a call. Specifically, the call may be a Voice over Long Term Evolution (LTE) (VoLTE) call where a dedicated bearer is established to perform the VoLTE call when resources are available on a base station to which a mobile originating (MO) user equipment (UE) is connected. The exemplary embodiments provide a first mechanism in which a network operation is used in performing the call, a second mechanism in which a first UE operation is used in performing the call, and a third mechanism in which a second UE operation is used in performing the call. 
     Initially, it is noted that the exemplary embodiments are described with regard to a VoLTE call. However, the VoLTE call is only exemplary. In some exemplary embodiments, the VoLTE call may be a component of the communication performed by the MO UE. For example, the VoLTE call may be a component of a video over LTE functionality. Thus, any use of a VoLTE call or a voice call may be representative of other communication calls including a video call. It is also noted that since the exemplary embodiments relate a VoLTE call, the exemplary embodiments are described with regard to resources and whether a dedicated bearer is capable of being established. However, this is also only exemplary. The dedicated bearer may be an operation utilized in a call operation for the call to be performed properly in an LTE network and may represent any comparable step in other packet switched networks. 
       FIG. 1  shows a network arrangement  100  according to various embodiments described herein. The exemplary network arrangement  100  includes UEs  110 - 114 . In this example, it is assumed that a respective, different user is using each of the UEs  100 - 114 . For example, a first user may be utilizing the UE  110 , a second user may be utilizing the UE  112 , and a third user may be utilizing the UE  114 . Those skilled in the art will understand that the UEs  110 - 114  may be any type of electronic component that is configured to communicate via a network, e.g., mobile phones, tablet computers, desktop computers, smartphones, phablets, embedded devices, wearables, etc. It should also be understood that an actual network arrangement may include any number of UEs being used by any number of users and being associated with any number of these users where the user may be associated with one or more of the UEs. That is, the example of three (3) UEs  110 - 114  is only provided for illustrative purposes. However, as will be understood from the description herein, the exemplary embodiments may relate to when at least two UEs  110 - 114  are present in the network arrangement  100  for a call to be performed. 
     Each of the UEs  110 - 114  may be configured to communicate with one or more networks. In this example, the networks with which the UEs  110 - 114  may communicate are a legacy radio access network (RAN)  120 , a LTE RAN (LTE-RAN)  122 , and a wireless local area network (WLAN)  124 . In this example, each of the networks  120 - 124  is a wireless network with which the UEs  110 - 114  may communicate wirelessly. However, it should be understood that the UEs  110 - 114  may also communicate with other types of networks using a wired connection. With regards to the exemplary embodiments, the UEs  110 - 114  may establish a connection with the LTE-RAN  122  to perform VoLTE calls with other UEs. For example, the UEs  110 - 114  may have a LTE chipset to communicate with the LTE-RAN  122 . Again, the use of three (3) networks is only exemplary and there may be any other number of networks with which the UEs  110 - 114  may communicate. 
     The legacy RAN  120  and the LTE-RAN  122  are portions of cellular networks that may be deployed by cellular providers (e.g., Verizon, AT&amp;T, Sprint, T-Mobile, etc.). These networks  120  and  122  may include, for example, base stations (Node Bs, eNodeBs, HeNBs, etc.) that are configured to send and receive traffic from UEs that are equipped with the appropriate cellular chip set. Examples of the legacy RAN  120  may include those networks that are generally labeled as 2G and/or 3G networks and may include circuit switched voice calls and packet switched data operations. Those skilled in the art will understand that the cellular providers may also deploy other types of networks, including further evolutions of the cellular standards, within their cellular networks. The WLAN  124  may include any type of wireless local area network (WiFi, Hot Spot, IEEE 802.11x networks, etc.). Those skilled in the art will understand that there may be thousands, hundreds of thousands or more of different WLANs deployed in the United States alone. For example, the WLAN  124  may be the user&#39;s home network, the user&#39;s work network, a public network (e.g., at a city park, coffee shop, etc.). Generally, the WLAN  124  will include one or more access points that allow the UEs  110 - 114  to communicate with the WLAN  124 . However, as noted above, the exemplary embodiments relate to the UEs  110 - 114  utilizing the LTE-RAN  122  to perform VoLTE calls. 
     In addition to the networks  120 - 124 , the network arrangement  100  also includes a cellular core network  130  and the Internet  140 . The cellular core network  130 , the legacy RAN  120 , and the LTE-RAN  122  may be considered a cellular network that is associated with a particular cellular provider (e.g., Verizon, AT&amp;T, Sprint, T-Mobile, etc.). The cellular core network  130  may be considered to be the interconnected set of components that manages the operation and traffic of the cellular network. The interconnected components of the cellular core network  130  may include any number of components such as servers, switches, routers, etc. The cellular core network  130  also manages the traffic that flows between the cellular network and the Internet  140 . 
     The network arrangement  100  also includes an IP Multimedia Subsystem (IMS)  150 . The IMS  150  may be generally described as an architecture for delivering multimedia services to the UEs  110 - 114  using the IP protocol. The IMS  150  may include a variety of components to accomplish this task. For example, a typical IMS  150  includes a Home Subscriber Server (HSS) that stores subscription information for a user of the UEs  110 - 114 . Thus, when the corresponding UE of the user registers with the IMS  150  (e.g., connects thereto), the subscription information may be utilized to determine various features. For example, this subscription information is used to provide the correct multimedia services to the user such as a VoLTE call. The IMS  150  may communicate with the cellular core network  130  and the Internet  140  to provide the multimedia services to the UEs  110 - 114 . The IMS  150  is shown in close proximity to the cellular core network  130  because the cellular provider typically implements the functionality of the IMS  150 . However, it is not necessary for this to be the case such as when the IMS  150  is provided by another party. 
     Thus, the network arrangement  100  allows the UEs  110 - 114  to perform functionalities generally associated with computers and cellular networks. For example, the UEs  110 - 114  may perform the VoLTE calls to other parties, may browse the Internet  140  for information, may stream multimedia data to the UEs  110 - 114 , etc. 
     The network arrangement  100  may also include a network services backbone  160  that is in communication either directly or indirectly with the Internet  140  and the cellular core network  130 . The network services backbone  160  may be generally described as a set of components (e.g., servers, network storage arrangements, etc.) that implement a suite of services that may be used to extend the functionalities of the UEs  110 - 114  in communication with the various networks. The network services backbone  160  may interact with the UEs  110 - 114  and/or the networks  120 ,  122 ,  124 ,  130 ,  140  to provide these extended functionalities. 
     The network services backbone  160  may be provided by any entity or a set of entities. In one example, the network services backbone  160  is provided by the supplier of one or more of the UEs  110 - 114 . In another example, the network services backbone  160  is provided by the cellular network provider. In still a further example, the network services backbone  160  is provided by a third party unrelated to the cellular network provider or the supplier of the UEs  110 - 114 . 
     The exemplary embodiments relate to the UEs  110 - 114  performing a VoLTE call. For example, the UE  110  may be the MO UE that invites a further UE such as the UE  112 , which may be a mobile terminating (MT) UE. Initially, the UEs  110 - 114  establish a connection to the LTE-RAN  122 . Those skilled in the art will understand that any association procedure may be performed for the UEs  110 - 114  to connect to the LTE-RAN  122 . For example, as discussed above, the LTE-RAN  122  may be associated with a particular cellular provider where the UE  110 - 114  and/or the user thereof has a contract and credential information (e.g., stored on a SIM card). Upon detecting the presence of the LTE-RAN  122 , the UEs  110 - 114  may transmit the corresponding credential information to associate with the LTE-RAN  122 . More specifically, the UEs  110 - 114  may associate with a specific base station (e.g., an eNB of the LTE-RAN  122 ). 
       FIG. 2  shows the LTE-RAN  122  according to various embodiments described herein. As discussed above, the LTE-RAN  122  may include a plurality of base stations. As illustrated, the LTE-RAN  122  may include a plurality of eNBs  205 - 220 . It should be noted that the LTE-RAN  122  including four eNBs is only exemplary and that the LTE-RAN  122  may include any number of eNBs that provide an access point for UEs to establish a connection to the LTE-RAN  122 . The eNBs  205 - 220  may utilize a communication protocol such as the X2-AP protocol on an X2 interface such that one of the eNBs  205 - 220  may communicate with the other eNBs  205 - 220 . Accordingly, information such as load information or available resource information of a first eNB may be provided when requested by a second eNB. Typically, the X2 interface is a wired interface between the different eNBs  205 - 220 . In the example of  FIG. 2 , a wired X2 interface is depicted between the eNB  210  and each of the other eNBs  205 ,  215  and  220 . However, it is also possible that there are wired X2 interfaces between the other eNBs (e.g., an X2 interface between eNB  205  and eNB  220  that is not shown). It is also possible that the eNBs  205 - 220  may exchange information via a wireless connection. 
     Also illustrated in the LTE-RAN  122  of  FIG. 2 , the UE  110  may be configured to directly exchange data with select ones of the LTE-RAN  122 . For example, the UE  110  may have established a connection to the LTE-RAN  122  via the eNB  205  in which an association procedure has been performed. However, the LTE-RAN  122  may have the eNBs  210 ,  215  disposed such that the location of the UE  110  relative to the eNBs  210 ,  215  enables data to be exchanged (e.g., signal power information such as a received signal strength indicator (RSSI)). Thus, the UE  110  may be associated with the eNB  205  and be using the eNB  205  to exchange data with the LTE-RAN  122 . However, the UE  110  may also discover the eNBs  210 ,  215  and be able to measure characteristics of the signals being transmitted by the eNBs  210  and  215 . The eNB  220  may also be a base station of the LTE-RAN  122  but may be positioned in such a way that the UE  110  is currently incapable of exchanging data with the eNB  220 . For example, the UE  110  may be located outside an operating area of the eNB  220 , may have interference (e.g., physical structure) that prevents the UE  110  from communicating with the eNB  220 , etc. 
     When the UEs  110 - 114  associate and establish a connection with the LTE-RAN  122  such as the UE  110  associating with the eNB  205 , one or more default bearers may be established for the UEs  110 - 114 . Initially, a bearer may define how data is treated when transmitted through the network. That is, the bearer may be a set of network parameters that define data specific treatment by type or association with an application. Accordingly, the LTE-RAN  122  may treat a first type of data in a first way and treat a second type of data in a second way. For example, the first type of data may be prioritized so that the LTE-RAN  122  treats this data in a special manner. It should be noted that the bearer may also define the treatment based upon user identity or other identification parameters. 
     One type of bearer that is established when initially connecting to the LTE-RAN  122  is a default bearer. The LTE-RAN  122  via the associated eNB may assign the default bearer, which remains so long as the UE is connected to the LTE-RAN  122 . The default bearer may be a best effort service for the data transmitted through the LTE-RAN  122 . Thus, depending upon various network conditions currently being experienced by the LTE-RAN  122 , the data being transmitted through the default bearer may be given whatever resources are available. The default bearer may be associated with a particular IP address and a single UE may have further default bearers established. Each default bearer may be assigned a quality of service (QoS) class indicator (QCI) of 5 to 9 that relates to non-guaranteed bit rate (GBR) bearers. Applications that may utilize the default bearer may be those in which the delivery of data is less time sensitive. For example, signaling messages such as Session Initiation Protocol (SIP) may utilize the default bearer. Other examples include smartphone traffic including video, chat, email, browsing, etc. 
     A further type of bearer that may be established between the UE and the LTE-RAN  122  is a dedicated bearer. The dedicated bearer may provide a dedicated tunnel to specific traffic. One application that utilizes the dedicated tunnel is VoLTE voice data used when performing the VoLTE call. The dedicated bearer may be an additional bearer over the default bearer that is established at a time subsequent to the default bearer being established (e.g., upon performing the VoLTE call). Since default bearers require separate IP addresses and the dedicated bearer is provided over an established default bearer, the dedicated bearer does not require a separate IP address. However, the dedicated bearer is linked to the default bearer established previously. Specifically, a value defined during setup of the dedicated bearer may be used to link the dedicated bearer to the default bearer. The dedicated bearer may utilize the same QCI as the default bearer but may also utilize a different QCI that relates to a GBR bearer. The dedicated bearer may use traffic flow templates (TFT) to provide the special treatment to specific services such as the VoLTE call. That is, the TFT may also define the rules of when the dedicated bearer is to be used based upon the application being executed. 
     When considering the operation of the default bearer and the dedicated bearer, the default bearer is established upon the UE connecting to the LTE-RAN  122 . Specifically, the LTE-RAN  122  assigns the default bearer to the UE. Subsequently, while still connected to the LTE-RAN  122 , the UE may execute the VoLTE call functionality. For example, the UE  110  may be the MO UE while the UE  112  may be the MT UE. As such, the MT UE may also be connected to the LTE-RAN  122  and have a default bearer assigned and established. When the VoLTE call functionality is performed, various signaling messages are transmitted between the UE  110  and the UE  112  via the LTE-RAN  122  and the IMS  150  through the respective default bearer. That is, a VoLTE call setup procedure may be performed. For example, a SIP Invite signal may be transmitted from the MO UE to the MT UE through the LTE-RAN  122 . When the SIP Invite reaches the MT UE, the MO UE and the MT UE may enter a ringing state as to whether the VoLTE call is to be established. If the MT UE accepts the VoLTE call, a SIP 200 OK signal may be transmitted back to the MO UE that indicates that the VoLTE call is to be established. Once the VoLTE call has been established from successfully transmitting the different signaling messages, the UE  110  and the UE  112  may be connected to each other to perform the VoLTE call. Specifically, the dedicated bearer may be established for each of the UE  110  and the UE  112  for the VoLTE data to be transmitted. However, the eNB  205  to which the MO UE  110  is associated must have sufficient resources to provide the dedicated bearer to be used for the VoLTE call that is to be established (e.g., from the SIP 200 OK signal being transmitted). If the eNB  205  has insufficient resources, a conventional approach entails the eNB  205  transmitting another SIP signal (i.e., SIP 503—Insufficient Bearer Resources) indicative of this. Those skilled in the art will understand that the eNB  205  is transparent to the SIP signaling and the dedicated bearer creation process initiates only after the MT UE has picked up the VoLTE call or upon transmitting the SIP 200 OK signal. Therefore, the conventional approach when the VoLTE call is to be established and the eNB  205  has insufficient resources (e.g., the eNB  205  is congested) results in the VoLTE call failing. 
     It is noted that the VoLTE call setup procedure may include a variety of other processes. For purposes of the description herein, it may be assumed that these processes are performed properly and successfully. For example, the UE  110  initially establishes a connection to the IMS  150 . It should be noted that this operation of the setup procedure may be a more general operation that is performed at various other times and not necessarily be performed due to the VoLTE call being performed. For example, the connection to the IMS  150  may occur whenever the UE  110  has established a connection to the LTE-RAN  122 . However, it is also noted that in order to utilize the VoLTE call functionality, a connection to the IMS  150  may be required. 
     The connection to the IMS  150  may be performed through an initial association with the eNB of the LTE-RAN  122 . A subsequent connection may be established to the IMS  150  through various components of the IMS  150 . Specifically, an attach procedure may be performed in connecting the UE  110  to the IMS  150 . For example, the IMS  150  may include a mobility management entity (MME) and a packet data network (PDN) gateway (PGW). These components may be responsible for at least one operation when the VoLTE call functionality is used. Specifically, the MME may be a control-node for the LTE-RAN  122  that performs paging and tagging operations for an idle mode of the UE  110 . More specifically, the MME may perform operations related to bearer activation and/or deactivation. The MME may also select a serving gateway (SGW) at the initial attach with the IMS  150 . The SGW may be configured to route and forward data packets for the UE  110 . For example, the SGW may manage and store contexts for the UE  110  such as parameters of the bearer service, network internal routing information, etc. The MME may also authenticate the UE  110  (via the HSS) such that the services available to the UE  110  are identified including the VoLTE call functionality. The PGW may be configured to provide a connectivity between the UE  110  to an external PDN by being a point of entry/exit for data packet traffic for the UE  110 . It is noted that the IMS  150  may provide a connection to a plurality of PGW to access a corresponding number of PDN. Thus, the UE  110  may be enabled to exchange data packets with multiple PDNs via the PGW of the IMS  150 . During the attach procedure, the UE  110  may attach when a default access point name (APN) is an IMS APN and the IMS PDN is established during the default bearer determination. However, if the default APN is not the IMS APN, the IMD PDN may be established following the attach procedure. 
     Once the attach procedure is performed and the UE  110  has established a connection to the IMS  150 , an IMS registration procedure may be performed. The IMS registration procedure may enable the identified multimedia services to be accessed. Specifically, the IMS registration procedure may entail registering at least one IP Multimedia Public Identity (IMPU) such as a telephone number of the UE  110 . The IMS  150  may then authenticate an IP Multimedia Private Identity (IMPI). The registration process may be initiated by the UE  110  transmitting a SIP registration message to a proxy call session control function (CSCF) (P-CSCF). Using further message passing operations such as through an interrogating CSCF (I-CSCF) and a serving CSCF (S-CSCF), an authentication procedure may be performed via the HSS. With specific regard to the VoLTE call functionality, the IMS registration procedure may incorporate the P-CSCF and a policy and charging rules function (PCRF). The P-CSCF may be a SIP proxy providing a first point of contact for the UE  110  with the IMS  150 . The P-CSCF may also be disposed on a path of all signaling to inspect each signal ensuring that the UE  110  does not misbehave such as changing a known signaling route or disobeying a routing policy. The PCRF may determine policy rules in the IMS  150 . The PCRF aggregates information to and from the IMS  150  to support creation of the rules and make policy decisions for the multimedia services performed by the UE  110 . With particular regard to the VoLTE call functionality, the PCRF may be a mediator of network resources for the IMS  150  to establish the call and allocate the requested bandwidth to the dedicated bearer. 
     With the UE  110  having been attached to and registered with the IMS  150 , the user of the UE  110  may opt to perform the VoLTE call functionality. Thus, the VoLTE call setup procedure may receive the input from the user in performing this operation. For example, the user may launch a VoLTE call application and provide/select an identity of the MT UE  112 . To perform the VoLTE call, the UE  110  may transmit a SIP invite to the UE  112  via the P-CSCF which results in the further SIP signaling that may occur as described above. 
     The exemplary embodiments provide a way to perform the VoLTE call between the UE  110  and the UE  112  where various mechanisms are used in aiding the MO UE  110  to communicate with the MT UE  110 . Initially, the exemplary embodiments may attempt to utilize the VoLTE call for the communication to be performed but may also utilize a failover option such as a single radio voice call continuity (SRVCC) to ensure that a call is still established such as through a circuit switched connectivity (e.g., Wideband Code Division Multiple Access (WCDMA)). 
     According to a first mechanism, a network operation may be used in aiding the MO UE  110  to communicate with the MT UE  110 . Specifically, the eNB  205  may perform operations that provide this feature.  FIG. 3  shows the eNB  205  of the LTE-RAN  122  of  FIG. 2  according to various embodiments described herein. As discussed above, the eNB  205  may be a base station of the LTE-RAN  122  that enables the UE  110  to associate with the eNB  205  to establish a connection to the LTE-RAN  122 . Although the description herein relates specifically to the eNB  205 , it is noted that the neighboring eNBs  210 - 220  may also include the components and perform the operations described herein. Thus, the eNB  205  may represent all of the eNBs  205 - 220 . The eNB  205  may include a processor  305 , a memory arrangement  310 , and a transceiver  315 . 
     The processor  305  may be configured to execute a resource manager  320 , a dedicated bearer application  325 , a handover application  330 , and a failover application  335 . The resource manager  320  may be configured to manage the resources of the eNB  205  (e.g., capacity, parallel processes, bandwidth management, etc.). The resource manager  320  may also determine the available resources and how these available resources are to be used. Specifically, the resource manager  320  may determine whether there are sufficient resources for a dedicated bearer to be established for the MO UE  110 . The dedicated bearer application  325  may be configured to establish the dedicated bearer with the MO UE  110  when an indication is provided by the resource manager  320  of the required resources to perform this functionality. 
     The network operation according to the exemplary embodiments may initially determine whether the VoLTE call may still be established despite the dedicated bearer failing to be established by the eNB  205 . However, as discussed above, the dedicated bearer is required for the VoLTE call to be performed. Thus, the eNB  205  may utilize the handover application  330 . The handover application  330  may be configured to determine whether a neighboring one of the eNBs  210 - 220  may be used to provide the dedicated bearer for the VoLTE call performed by the UE  110  which is currently associated with the eNB  205 . Accordingly, upon receiving an indication from the resource manager  320  that there are not sufficient resources for the eNB  205  to provide the dedicated bearer for the VoLTE call, the eNB  205  via the handover application  330  may proactively assess a load of the neighbor eNBs  210 - 220  and determine whether the eNBs  210 - 220  are congested or have available resources to establish the dedicated bearer for the UE  110 . For example, the load information may be received through the X2-AP protocol over the X2 interface. If the handover application  330  determines that one of the neighboring eNBs  210 - 220  has sufficient resources, the handover application  330  may determine whether the UE  110  is capable of exchanging data with the neighboring eNB (e.g., further information over the X2 interface). For example, the eNB  220  may indicate that data is not currently being exchanged (e.g., through a discovery process). Thus, even if the eNB  220  were to have the available resources, the eNB  220  may be removed from consideration. In another example, the eNB  210  may indicate that data is being exchanged. Thus, if the eNB  210  were to have the available resources, the eNB  210  may be considered. The handover application  330  may provide an indication to the LTE-RAN  122 , which triggers a handover operation from the eNB  205  to the eNB  210 . Accordingly, the resource manager  320  may not utilize a conventional mechanism of transmitting the SIP 503 indicating the bearer setup failure and have the VoLTE call failed. Instead, the VoLTE call may be saved and the dedicated bearer may be established with the eNB  210 . It is noted that the handover operation may also prepare the target handover eNB by providing the necessary data to continue the operation in establishing the VoLTE call. 
     It is possible for the handover application  330  to receive the indication from the resource manager  320  and also determine that the neighboring eNBs  210 - 220  do not have the required resources to provide the dedicated bearer for the VoLTE call of the UE  110 . In a first manner of handling this type of scenario, the eNB  205  may utilize the SIP 503 that results in the call failure. However, in a second manner of handling this type of scenario and according to the exemplary embodiments, the eNB  205  may utilize the failover application  335  to provide yet another mechanism of saving the call. Specifically, the failover application  335  may continue upon a basis that the dedicated bearer failed to be established through congestion at the eNB  205  as well as the neighboring eNBs  210 - 220 . Accordingly, the failover application  335  may trigger a SRVCC operation in a substantially aggressive way so that the call may be completed over a circuit switched connectivity. The failover application  335  may assume that the UE  110  has a capability of performing the call over the circuit switched connectivity. However, the failover application  335  may also perform further operations such as requesting circuit switched measurements (e.g., WCDMA) from the UE  110  to verify the capability. If the UE  110  has the circuit switched capability, then the SRVCC operation may be used. However, if the UE  110  does not have the circuit switched capability, the eNB  205  may continue with the SIP 503. 
       FIG. 4  shows a signaling diagram  400  for a network operation in performing a call according to various embodiments described herein. The signaling diagram  400  illustrates an exemplary process in which the handover application  330  is being used. Thus, the signaling diagram  400  may begin with a conventional process in performing a VoLTE call. The signaling diagram  400  may assume that the UE  110  is the MO UE while the UE  112  is the MT UE, the MO UE  110  is currently connected to the eNB  205 , and the eNB  210  is a neighboring eNB to the eNB  205  and capable of communicating with the MO UE  110 . 
     In performing the setup for the VoLTE call, the MO UE  110  may transmit a SIP invite  405  to the eNB  205 . The eNB  205  may forward the SIP invite  410  to the LTE-RAN  122 . The LTE-RAN  122  may forward the SIP invite  415  to the target destination of the MT UE  112 . The MT UE  112  may respond and accept the invite for the VoLTE call. Accordingly, the MT UE  112  may transmit a SIP 200 OK signal  420  back to the LTE-RAN  122 . The LTE-RAN  122  may forward the SIP 200 OK  425  to the eNB  205 . 
     When the eNB  205  receives the SIP 200 OK  425 , the eNB  205  via the resource manager  320  may perform a resource check  430 . The resource check  430  may determine whether the eNB  205  has sufficient resources. If the eNB  205  determines that there are insufficient resources (e.g., the eNB  205  cannot allocate a dedicated bearer to the UE  110 ), the eNB  205  requests load information  435  from the neighboring eNBs  210 - 220  such as the eNB  210 . The eNB  210  may transmit the resource information  440  to the eNB  205  indicating the load and available resources. The eNB  205  may perform a handover check  445  to determine whether the UE  110  is capable of communicating with the eNB  210 . When the eNB  210  is determined to have the available resources (and is capable of communicating with the UE  110 ), a handover operation  450  may be performed where an association and connection procedure is performed such that the UE  110  is connected to the eNB  210 . The LTE-RAN  122  may transmit a handover indication  455  for the UE  110  to update its connectivity parameters. With the handover is being performed, the dedicated bearer may be established  460  between the eNB  210  and the UE  110  and the VoLTE call may be performed. Thus, even though the original eNB  205  did not have a dedicated bearer to handle the VoLTE call, the call did not fail because it was saved by the handover to the eNB  210 . Thus, the user experience of a VoLTE call is enhanced because a call failure has been avoided. 
     It should be noted that in this signaling diagram and the other signaling diagrams illustrated and described herein, there may be additional network components through which the signals flow and/or are processed. An example of an additional network component may be a telephony application server (TAS). The TAS may be generally described as an entity in a telephone network such as that utilized by providers of the cellular core network that performs functionalities unrelated (or tangential) to the routing of messages through the telephone network. For example, the TAS may perform functionalities associated with voice mail features, toll-free numbers, call forwarding features, bridges, etc. 
       FIG. 5  shows a method  500  for a network operation in performing a call according to various embodiments described herein. The method  500  relates to the first mechanism according to the exemplary embodiments of a network operation aiding the call to be performed initially as a VoLTE call and, if necessary, as a circuit switched call. The method  500  will be described with reference to the eNB  205 . The method  500  will also be described with regard to the network arrangement  100  of  FIG. 1 , the LTE-RAN  122  of  FIG. 2 , and the eNB  205  of  FIG. 3 . 
     In  505 , the eNB  205  receives a VoLTE request from the MO UE  110 . It is noted that the VoLTE request may also relate to when the UE  110  is the MT UE where the dedicated bearer is still established. However, for illustrative purposes, the UE  110  is represented as the MO UE. The VoLTE request may include the target destination. Thus, in  510 , the VoLTE request may be forwarded to the MT UE (e.g., through the eNB  205 , to a PGW, to a MME, to an eNB to which the MT UE  112  is associated, and to the MT UE  112 ). In  515 , the eNB  205  may receive the VoLTE response from the MT UE. Specifically, the VoLTE response may be a SIP 200 OK indicating that the user of the MT UE  112  has accepted the invite. The VoLTE response may also correspond to a reject indication. It is noted that the SIP 200 OK may also be forwarded to the MO UE  110 . 
     In  520 , the eNB  205  determines whether the VoLTE response is a SIP 200 OK signal. If the eNB  205  determines that the invite is rejected, the eNB  205  may end the method  500 . However, if the eNB  205  determines that the SIP 200 OK is received, the eNB  205  continues the method  500  to  525 . In  525 , the eNB  205  performs a resource check such as with the resource manager  320 . In  530 , the eNB  205  determines if there are sufficient resources to establish the dedicated bearer for the MO UE  110 . If there are sufficient resources, the eNB  205  continues the method  500  to  535  where the eNB  205  establishes the dedicated bearer for the MO UE  110  for the VoLTE call to be performed. However, if there are insufficient resources, the eNB  205  continues the method  500  to  540 . 
     In  540 , the eNB  205  requests information from the neighboring eNBs  210 - 220  such as the load information. The eNB  205  may transmit the request via the X2-AP protocol. The eNB  205  may subsequently receive the information. In  545 , the eNB  205  may determine a handover candidate via the handover application  330 . The handover candidate may be based on whether the neighboring eNB has sufficient resources and is capable of communicating with the UE  110 . For example, the eNBs  210 ,  215  may be candidates at least for their capability of communicating with the UE  110 , whereas the eNB  220  is removed from consideration. Thus, in  550 , the eNB  205  determines whether there are any available handover candidates. 
     If the eNB  205  determines that there are no handover candidates, the eNB  205  continues the method  500  to  555  where the eNB  205  utilizes a failover operation such as a SRVCC in which a circuit switched connectivity is used in performing a circuit switched call. It should be noted that the method  500  may include further operations in which the eNB  205  requests circuit switched capability information to determine whether the SRVCC is to be used. If the eNB  205  determines that there is a handover candidate, the eNB  205  continues the method  500  to  560 . In  560 , the eNB  205  performs a handover operation with a selected neighboring eNB. When the handover is performed, the selected neighboring eNB may be used in establishing the dedicated bearer for the MO UE to perform the VoLTE call. 
     As discussed above, the exemplary embodiments provide a way to perform the VoLTE call between the UE  110  and the UE  112  where various mechanisms are used in aiding the MO UE  110  to communicate with the MT UE  110 . The above description of the first mechanism relates to a network operation. According to a second mechanism, a UE operation may be used in establishing a call by the MO UE  110  to communicate with the MT UE  112 . 
     According to the second mechanism, the MO UE  110  may prepare the connection with the LTE-RAN  122  for a subsequent attempt in performing the VoLTE call to be performed with a higher probability of success. The MO UE  110  may prepare the connection using a first UE operation or a second UE operation. The MO UE  110  may perform a set of operations corresponding to the first UE operation or the second UE operation upon a trigger being received where the trigger is a SIP signaling sequence. Specifically, the MO UE  110  may receive a first indication of the invite for the VoLTE call being accepted to be followed by a second indication that the VoLTE call fails due to unavailable resources on the eNB  205 . 
       FIG. 6  shows the UE  110  according to various embodiments described herein. The UE  110  is configured to execute a plurality of applications that perform the respective functionalities of performing a call and a subsequent call according to the exemplary embodiments. The UE  110  may represent any electronic device that is configured to perform wireless functionalities. Specifically, the UE  110  may perform a VoLTE call when connected to the LTE-RAN  122 . The UE  110  may be a portable device such as a smartphone, a tablet, a phablet, a laptop, a wearable, etc. In another example, the UE  110  may be a client stationary device such as a desktop terminal. The UE  110  may be configured to perform cellular functionalities such as LTE related or circuit switched. The UE  110  may include a processor  605 , a memory arrangement  610 , a display device  615 , an input/output (I/O) device  620 , a transceiver  625 , and other components  630 . The other components  630  may include, for example, an audio input device, an audio output device, a battery, a data acquisition device, ports to electrically connect the UE  110  to other electronic devices, etc. 
     The processor  605  may be configured to execute a plurality of applications of the UE  110 . For example, the applications may include a web browser when connected to a communication network via the transceiver  625 . As such, when connected to the LTE-RAN  122 , the data for the web browser may utilize the default bearer. In another example, the processor  605  may execute a VoLTE call application  635  that enables the UE  110  to perform a VoLTE call functionality such as with the UE  112 . The VoLTE call application  635  may further be configured to perform the VoLTE call setup procedure such as performing the operations described above. In yet another example, the processor  605  may execute a handover trigger application  640 . As will be described in further detail below, the handover trigger application  640  may utilize an operation that causes the LTE-RAN  122  to handover the association of the UE  110  from the currently associated eNB  205  to one of the neighboring eNBs  210 - 220 . In a further example, the processor  605  may execute a failover trigger application  645 . As will be described in further detail below, the failover trigger application  645  may utilize an operation that causes the LTE-RAN  122  to switch to a circuit switched connectivity with the UE  110 . 
     It should be noted that the above noted applications each being an application (e.g., a program) executed by the processor  605  is only exemplary. The functionality associated with the applications may also be represented as a separate incorporated component of the UE  110  or may be a modular component coupled to the UE  110 , e.g., an integrated circuit with or without firmware. 
     The memory  610  may be a hardware component configured to store data related to operations performed by the UE  110 . Specifically, the memory  610  may store data related to the various applications  635 - 645 . For example, the VoLTE call application  635  may utilize a phone book functionality that stores contact information for other users and UEs. The display device  615  may be a hardware component configured to show data to a user while the I/O device  620  may be a hardware component that enables the user to enter inputs. It should be noted that the display device  615  and the I/O device  620  may be separate components or integrated together such as a touchscreen. 
     The transceiver  625  may be a hardware component configured to transmit and/or receive data. That is, the transceiver  625  may enable communication with other electronic devices directly or indirectly through a network based upon an operating frequency of the network. The transceiver  625  may operate on a variety of different frequencies or channels (e.g., set of consecutive frequencies) that are related to the VoLTE call functionality. Thus, an antenna (not shown) coupled with the transceiver  625  may enable the transceiver  625  to operate on the LTE frequency band. 
     The first UE operation according to the exemplary embodiments may determine whether a subsequent call is to be performed as a VoLTE call based upon whether a handover has successfully occurred. As discussed above, the dedicated bearer is required for the VoLTE call to be performed. Also as discussed above, a trigger to perform the first UE operation is based upon receiving the SIP 200 OK signal indicating that the MT UE  112  has accepted the VoLTE call and receiving the SIP 503 signal indicating that the eNB  205  does not have sufficient resources to establish the dedicated bearer for the MO UE  110 . Thus, the MO UE  110  may utilize the handover trigger application  640  for a substantially similar reason as the network operation utilizing the handover application  330  since the eNB  205  is congested. 
     The MO UE  110  may perform the setup procedure for a first VoLTE call using the VoLTE call application  635  including the SIP signaling associated therewith such as the SIP Invite and the SIP 200 OK. The MO UE  110  may subsequently receive a SIP 503 from the eNB  205  that results in the first VoLTE call failing. The MO UE  110  may be configured with settings as to when to perform the subsequent operations. In a first example, MO UE  110  may perform the first UE mechanism whenever the SIP 503 is received. In a second example, the MO UE  110  may perform the first UE mechanism after the SIP 503 is received and when a second VoLTE call is attempted to be performed within a predetermined time period. 
     When the subsequent operations are determined to be performed, the MO UE  110  may generate an A3 event measurement report. Those skilled in the art will understand that event measurement reports for A1-A5 may be utilized for a variety of reasons and to report various events. For example, the A3 event measurement report may indicate that a neighbor eNB becomes better than a serving eNB such as the neighboring eNB  210  is better over the currently associated eNB  205 . In another example, an A2 event measurement report may indicate that a serving eNB becomes worse than a threshold such as the currently associated eNB  205  having network parameters or qualities falling under a predetermined threshold (e.g., RSSI). In this manner, using the handover trigger application  640 , the MO UE  110  may generate the A3 event measurement report indicating that the eNB  210  provides an improved connection over the eNB  205  to the LTE-RAN  122 . It is noted that the handover trigger application  640  may receive information that the eNB  205  in actuality has the better connection. However, to trigger the handover, the handover trigger application  640  may report otherwise. The LTE-RAN  122  may receive the A3 event measurement report and cause the eNBs  205  and  210  to perform a handover process such that the UE  110  associates and connects from the eNB  205  to the eNB  210 . The MO UE  110  may subsequently receive an indication of the handover. Accordingly, a second VoLTE call that is performed may be done with the eNB  210  which may have available resources to provide the dedicated bearer. 
     The handover trigger application  640  may perform the above-described operations based upon an attempt threshold. For example, the A3 event measurement report may be transmitted at least a number of times less than the attempt threshold value to trigger the handover. Thus, if the MO UE  110  receives the handover indication prior to transmitting the A3 event measurement report a predetermined number of times, the MO UE  110  may now utilize the newly associated eNB. However, if the MO UE  110  does not receive the handover indication even after the A3 event measurement report has been transmitted the predetermined number of times, the MO UE  110  may perform yet further operations to prepare the connection for the call. Specifically, the MO UE  110  may utilize the failover trigger application  645 . The failover trigger application  645  may receive an indication from the handover trigger application  640  that the number of attempts has been performed at least the predetermined number of times. For example, the neighboring eNBs  210 - 220  may be unavailable (e.g., at capacity) for a handover. In another example, the LTE-RAN  122  may deny or ignore the request for the handover based upon the A3 event measurement report. The failover trigger application  645  may accordingly utilize a substantially similar mechanism as the handover trigger application  640  by transmitting the A2 event measurement report. As noted above, the A2 event measurement report may indicate that the currently associated eNB  205  is no longer providing a minimum threshold connection. Again, the eNB  205  may in actuality have a sufficient connection but still use the A2 event measurement report to be transmitted to the LTE-RAN  122 . Accordingly, the LTE-RAN  122  may cause the eNB  205  to switch to a circuit switched connectivity for the MO UE  110 . Therefore, a further attempt at a call may be performed over the circuit switched connection. The failover trigger application  645  may initially perform further operations such as determining a circuit switched capability (e.g., WCDMA measurements) to verify whether this option is available. If the UE  110  has the circuit switched capability, then the failover trigger application  645  may perform the above operations. However, if the UE  110  does not have the circuit switched capability, the failover trigger application  645  may continue to transmit the A3 event measurement report in the hopes of a handover or may continue with the connection to the currently associated eNB  205 . 
       FIG. 7  shows a first signaling diagram  700  for a UE operation in performing a call according to various embodiments described herein. The signaling diagram  700  illustrates an exemplary process in which the handover trigger application  640  is being used. Thus, the signaling diagram  700  may begin with a conventional process in performing a VoLTE call. The signaling diagram  700  may assume that the UE  110  is the MO UE while the UE  112  is the MT UE, the MO UE  110  is currently connected to the eNB  205 , and the eNB  210  is a neighboring eNB to the eNB  205  and capable of communicating with the MO UE  110 . 
     In performing the setup for the VoLTE call, the MO UE  110  may transmit a SIP invite  705  to the eNB  205 . The eNB  205  may forward the SIP invite  710  to the LTE-RAN  122 . The LTE-RAN  122  may forward the SIP invite  715  to the target destination of the MT UE  112 . The MT UE  112  may respond and accept the invite for the VoLTE call. Accordingly, the MT UE  112  may transmit a SIP 200 OK signal  720  back to the LTE-RAN  122 . The LTE-RAN  122  may forward the SIP 200 OK  725  to the eNB  205 . The eNB  205  may forward the SIP 200 OK  730  to the MO UE  110 . The eNB  205  may perform a resource check  735  to determine whether there are sufficient resources to provide the dedicated bearer. If there are insufficient resources (e.g., the dedicated bearer cannot be established), the eNB  205  may transmit a SIP 503  740  to the MO UE  110 . 
     As discussed above, the MO UE  110  may perform subsequent operations upon receiving the SIP 200 OK and the SIP 503. The first signaling diagram  700  may also relate to performing the subsequent operations upon receiving the SIP 503. As described above, the receipt of the SIP 200 OK followed by the SIP 503 indicates to the MO UE  110  that the currently connected eNB  205  cannot set up the dedicated bearer. Thus, the MO UE  110  may transmit the A3 event measurement report  745  where the A3 event measurement report  745  indicates that the eNB  210  provides a better connection than the eNB  205 . The eNB  205  may forward the A3 event measurement report  750  to the LTE-RAN  122 . The LTE-RAN  122  may cause a handover procedure  760  such that the MO UE  110  is associated and connected to the eNB  210 . The LTE-RAN  122  may transmit a handover indication  760  regarding a successfully performed handover from the eNB  205  to the eNB  210 . The MO UE  110  may update its connectivity information such that a further VoLTE call may be attempted where a further SIP invite  765  is transmitted to the eNB  210  and the VoLTE call will be attempted with the UE  110  being attached to the eNB  210 . 
       FIG. 8  shows a first method  800  for a UE operation in performing a call according to various embodiments described herein. The method  800  relates to the second mechanism according to the exemplary embodiments of a UE operation aiding the call to be performed initially as a VoLTE call and, if necessary, as a circuit switched call. In particular, the method  800  relates to the first UE operation of the second mechanism. The method  800  will be described with reference to the UE  110 . The method  800  will also be described with regard to the network arrangement  100  of  FIG. 1 , the LTE-RAN  122  of  FIG. 2 , and the UE  110  of  FIG. 6 . 
     In  805 , the MO UE  110  transmits a VoLTE request to the currently associated eNB  205 . Specifically, a SIP Invite may be transmitted including the target destination. In  810 , the MO UE  110  may receive a VoLTE response from the MT UE  112 . Specifically, the VoLTE response may be a SIP 200 OK indicating that the user of the MT UE  112  has accepted the invite. The VoLTE response may also correspond to a reject indication. 
     In  815 , the MO UE  110  determines whether the VoLTE response is a SIP 200 OK signal. If the MO UE  110  determines that the invite is rejected, the MO UE  110  may end the method  800 . However, if the MO UE  110  determines that the SIP 200 OK is received, the MO UE  110  continues the method  800  to  820 . In  820 , the MO UE  110  determines whether the VoLTE call fails. Specifically, the MO UE  110  determines whether a SIP 503 is received from the currently associated eNB  205  indicating that there are insufficient resources for the dedicated bearer to be used in the VoLTE call. If the call has not failed (a SIP 503 is not received and the MO UE  110  is connected to the MT UE  110  over a VoLTE call), the MO UE  110  continues the method  800  to  825  where the VoLTE call is performed using the currently associated eNB  205 . However, if the call does fail (a SIP 503 is received), the MO UE  110  continues the method  800  to  830 . 
     In  830 , the MO UE  110  performs a handover trigger operation. As discussed above, the handover trigger operation relates to the handover trigger application  640  generating an A3 event measurement report indicating that one of the neighboring eNBs such as the eNB  210  has a better connection than the currently associated eNB  205 . Again, it is noted that this may not be true in actuality but used for purposes of this feature. The transmission of the A3 event measurement report to the LTE-RAN  122  may therefore cause the LTE-RAN  122  to perform a handover procedure. In  835 , the MO UE  110  determines whether an indication is received confirming the handover has been performed. If the MO UE  110  determines that the handover indication has been received, the MO UE  110  continues the method  800  to  840 . In  840 , the MO UE  110  establishes a connection with the further eNB to which the handover procedure is performed. 
     If the MO UE  110  determines that the handover indication has not been received (e.g., within a time period following the transmission of the A3 event measurement report), the MO UE  110  continues the method  800  to  845 . In  845 , the MO UE  110  determines a number of attempts of performing the handover trigger operation. If the number of attempts is within a predetermined threshold, the MO UE  110  returns the method  800  to  830  where another attempt is performed. However, if the number of attempts is beyond the predetermined threshold, the MO UE  110  continues the method  800  to  850 . In  850 , the MO UE  110  performs a failover trigger operation. As discussed above, the failover trigger operation relates to the failover trigger application  645  generating an A2 event measurement report indicating that the currently associated eNB  205  does not provide a sufficient connection (based upon a connection threshold). Again, it is noted that this may not be true in actuality but used for purposes of this feature. The transmission of the A2 event measurement report to the LTE-RAN  122  may therefore cause the LTE-RAN  122  to change the connection to a circuit switched connectivity. Of course, this operation assumes that the UE  110  has a circuit switched capability and a possible connection to a circuit switched network, e.g., a legacy RAN  120  is available for connection. 
     As discussed above, the first UE operation of the second mechanism may be used to increase a probability of a following call to be successful through a handover procedure or failover procedure being performed. Thus, a current VoLTE call resulting in a failure may trigger the first UE operation to be used. A second UE operation in the second mechanism may utilize an abbreviated version of the first UE operation. However, the second UE operation may be used to minimize an effort of the user as well as hide a call failure that may result. The MO UE  110  used in the second UE operation may include substantially similar components and perform substantially similar operations as the MO UE  110  of the first UE operation. However, the processor  605  may not execute a handover trigger application  640 . 
     The second UE operation according to the exemplary embodiments may determine whether a current call is to be attempted again after a set of operations are performed based upon whether the attempt for a VoLTE call has succeeded. It is again noted that a trigger to perform the second UE operation is upon receiving the SIP 200 OK signal indicating that the MT UE  112  has accepted the VoLTE call and receiving the SIP 503 signal indicating that the eNB  205  does not sufficient resources to establish the dedicated bearer for the MO UE  110 . Thus, the MO UE  110  may utilize the failover trigger application  645 . 
     In contrast to the first UE operation, the MO UE  110  may immediately utilize the failover trigger application  645  without attempting a handover procedure. Accordingly, the A2 event measurement report may be transmitted to the LTE-RAN  122  to change the connection to a circuit switched connectivity. The second UE operation may also utilize an auto-redial feature that does not require any user intervention. For example, if the second UE operation is a user selected feature, the user of the MO UE  110  may attempt to perform a VoLTE call with the MT UE  112 . However, the failure of the VoLTE call (e.g., receiving the SIP 503) may trigger the failover trigger application  640  to be used. Upon setting the connection to the circuit switched connectivity, the failover trigger application  645  may automatically perform an auto-redial operation with the MT UE  112  using the circuit switched connectivity. In this manner, this set of calls may appear as a single call to the user. 
       FIG. 9  shows a second signaling diagram  900  for a UE operation in performing a call according to various embodiments described herein. The signaling diagram  900  illustrates an exemplary process in which the failover trigger application  645  is being used with an auto-redial feature. Thus, the signaling diagram  900  may begin with a conventional process in performing a VoLTE call. The signaling diagram  900  may assume that the UE  110  is the MO UE while the UE  112  is the MT UE and the MO UE  110  is currently connected to the eNB  205 . 
     In performing the setup for the VoLTE call, the MO UE  110  may transmit a SIP invite  905  to the eNB  205 . The eNB  205  may forward the SIP invite  910  to the LTE-RAN  122 . The LTE-RAN  122  may forward the SIP invite  915  to the target destination of the MT UE  112 . The MT UE  112  may respond and accept the invite for the VoLTE call. Accordingly, the MT UE  112  may transmit a SIP 200 OK signal  920  back to the LTE-RAN  122 . The LTE-RAN  122  may forward the SIP 200 OK  925  to the eNB  205 . The eNB  205  may forward the SIP 200 OK  930  to the MO UE  110 . The eNB  205  may perform a resource check  935  to determine that there are insufficient resources to provide the dedicated bearer. Thus, the eNB  205  may transmit a SIP 503  940  to the MO UE  110 . 
     As discussed above, the MO UE  110  may perform subsequent operations upon receiving the SIP 200 OK and the SIP 503. The second signaling diagram  900  may also relate to performing the subsequent operations upon receiving the SIP 503. Thus, the MO UE  110  may transmit the A2 event measurement report  945  where the A2 event measurement report  945  indicates that the eNB  205  provides an insufficient connection. The eNB  205  may forward the A2 event measurement report  950  to the LTE-RAN  122 , which then subsequently forwards the A2 report  955  to the core network  130 . The core network  130  may cause a connection change such that the MO UE  110  is changed to a circuit switched connectivity by sending a connection update  960  to the legacy RAN  120  (e.g., the circuit switched network). The legacy RAN  120  may forward the connection update  965  to a base station (e.g., Node B  120 A) of the legacy RAN  120  to which the UE  110  may attach. This may cause the UE  110  and the Node B  120 A to crate an SRVCC connection  970  that may be used for a circuit switched call. The MO UE  110  may then re-attempt the call  975  using the SRVCC connection  970 . 
       FIG. 10  shows a second method  1000  for a UE operation in performing a call according to various embodiments described herein. The method  1000  relates to the second mechanism according to the exemplary embodiments of a UE operation aiding the call to be performed initially as a VoLTE call and performing a circuit switched call if the VoLTE call fails. In particular, the method  1000  relates to the second UE operation of the second mechanism. The method  1000  will be described with reference to the UE  110 . The method  1000  will also be described with regard to the network arrangement  100  of  FIG. 1 , the LTE-RAN  122  of  FIG. 2 , and the UE  110  of  FIG. 6 . 
     In  1005 , the MO UE  110  transmits a VoLTE request to the eNB  205 . Specifically, a SIP Invite may be transmitted including the target destination. In  1010 , the MO UE  110  may receive a VoLTE response from the MT UE  112 . Specifically, the VoLTE response may be a SIP 200 OK indicating that the user of the MT UE  112  has accepted the invite. The VoLTE response may also correspond to a reject indication. 
     In  1015 , the MO UE  110  determines whether the VoLTE response is a SIP 200 OK signal. If the MO UE  110  determines that the invite is rejected, the MO UE  110  may end the method  1000 . However, if the MO UE  110  determines that the SIP 200 OK is received, the MO UE  110  continues the method  1000  to  1020 . In  1020 , the MO UE  110  determines whether the VoLTE call fails. Specifically, the MO UE  110  determines whether a SIP 503 is received from the eNB  205  indicating that there are insufficient resources for the dedicated bearer to be used in the VoLTE call. If the call has not failed (a SIP 503 is not received and the MO UE  110  is connected to the MT UE  110  over a VoLTE call), the MO UE  110  continues the method  1000  to  1025  where the VoLTE call is performed using the eNB  205  that provides a dedicated bearer. However, if the call does fail (a SIP 503 is received), the MO UE  110  continues the method  1000  to  1030 . 
     In  1030 , the MO UE  110  performs a failover trigger operation. As discussed above, the failover trigger operation relates to the failover trigger application  645  generating an A2 event measurement report indicating that the eNB  205  is providing an insufficient connection. Again, it is noted that this may not be true in actuality but used for purposes of this feature. The transmission of the A2 event measurement report to the LTE-RAN  122  and to the cellular core network  130  causing a failover procedure where an SRVCC connection is setup with the legacy RAN  120  to change the voice connection to a circuit switched connectivity. Subsequently, in  1035 , the MO UE  110  may perform an auto-redial using the circuit switched connectivity. 
     It is noted that the MO UE  110  may utilize various graphics shown on the display device  615  to indicate to the user of the various changes occurring. For example, the MO UE  110  may utilize the LTE-RAN  122  to perform the VoLTE call but may also be utilizing the LTE-RAN  122  to perform data related operations (e.g., web browser). However, a failure of the VoLTE call may cause the handover which may update the connection. This may prompt a graphic to be shown to the user of the change in connection (which may be less efficient). The failure of the VoLTE call may also cause the circuit switched connectivity to be used which may affect the data connection. This may prompt a graphic to be shown to the user of the change in connection. In another example, the failure of the VoLTE call and an automatic re-dial over the circuit switched connectivity may prompt a graphic to be shown to indicate the status of the call no longer being a VoLTE call. 
     The exemplary embodiments provide a device, system, and method of performing a call. In a first mechanism, a network operation may be used to preserve a call and attempt to connect the MO UE to the MT UE using a variety of operations. Specifically, when a VoLTE call is attempted but fails due to a dedicated bearer being unavailable, the network may perform a handover procedure to a neighboring base station, which may have resources to provide the dedicated bearer. In a second mechanism, a UE operation may be used to prepare a connection for a further attempt to connect the MO UE to the MT UE. Specifically, when a VoLTE call is attempted but fails due to a dedicated bearer being unavailable, in a first UE operation, the UE may perform a handover trigger procedure to associate with a neighboring base station that may provide the dedicated bearer. In a second UE operation, the UE may perform a failover trigger procedure to utilize a circuit switched connectivity for a subsequent call attempt to be performed. 
     It is noted that the above exemplary embodiments relate to operations performed by the UE and eNB. However, this is only exemplary. The exemplary embodiments may also be performed by a separate component or device that performs the above operations that affects the UE and/or the eNB. For example, a different LTE network component may perform the operations of the first mechanism and generates commands for the eNBs. 
     Those skilled in the art will understand that the above-described exemplary embodiments may be implemented in any suitable software or hardware configuration or combination thereof. An exemplary hardware platform for implementing the exemplary embodiments may include, for example, an Intel x86 based platform with compatible operating system, a Windows OS, a Mac platform and MAC OS, a mobile device having an operating system such as iOS, Android, etc. In a further example, the exemplary embodiments of the above described method may be embodied as a program containing lines of code stored on a non-transitory computer readable storage medium that, when compiled, may be executed on a processor or microprocessor. 
     It will be apparent to those skilled in the art that various modifications may be made in the present invention, without departing from the spirit or the scope of the invention. Thus, it is intended that the present invention cover modifications and variations of this invention provided they come within the scope of the appended claims and their equivalent.

Metadata:
Filing Date: 20160923
Publication Date: 20181106
Grant Date: 20181106
Priority Date: 20150930
Inventors: SHARMA, PRATEEK
VALLATH, SREEVALSAN
BHATTACHARJEE, DEEPANKAR
Assignee: APPLE INC
CPC Classifications: [{"code": "H04W36/22", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W36/0022", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04L65/1069", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W76/18", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04L65/1006", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04L65/1016", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W36/0022", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W76/18", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04L65/1016", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W36/22", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W76/18", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04L65/1069", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/1016", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/1069", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/1104", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04L65/1104", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W36/22", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W36/0022", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 58407695