PATENT DOCUMENT

Publication Number: US-11317325-B2
Application Number: US-201815994250-A
Country: US
Kind Code: B2

Title: Call setup time in loaded IMS networks

Abstract:
A device, system, and method improve a call setup time. The method is performed at a device configured to establish first and second network connections where the second network performs circuit switched voice calls. The method includes receiving a call input to perform a call and determining whether the device is registered with a first feature to perform the call based on an Internet Protocol (IP). When the device is registered with the first feature, the method includes determining whether timeouts for attempting previous IP calls is greater than a threshold. When the timeouts are at least the threshold, the method includes deregistering from the first feature and performing a circuit switched fallback (CSFB) procedure including a handover from the first network to the second network. The method includes performing the call as a circuit switched call.

Claims:
What is claimed is: 
     
       1. A method, comprising:
 at a device that is configured to establish a first network connection to a first network and a second network connection to a second network, the second network configured to perform circuit switched voice calls: 
 receiving a call input to perform a call; 
 determining whether the device is registered with a first feature of the first network, the first feature configured to perform the call based on an Internet Protocol (IP); 
 when the device is registered with the first feature, determining whether a number of timeouts for attempting previous calls based on the IP is greater than a threshold; 
 when the number of timeouts is at least the threshold, deregistering from the first feature and starting a delay timer; 
 performing a circuit switched fallback (CSFB) procedure including a handover from the first network to the second network; 
 performing the call as a circuit switched call; and 
 reconnecting to the first network when the circuit switched call is completed, wherein the reconnecting comprises determining whether the delay timer is expired and wherein, when the delay timer is not expired, omitting signaling for a registration with the first feature at each instance that the registration is to otherwise be performed due to the number of timeouts such that the device cannot perform calls using the first network. 
 
     
     
       2. The method of  claim 1 , wherein, when the device is not registered with the first feature, the method further comprises:
 performing the CSFB procedure; and 
 performing the call as the circuit switched call. 
 
     
     
       3. The method of  claim 1 , wherein, when the number of timeouts is less than the threshold, the method further comprises:
 performing the call based on the IP. 
 
     
     
       4. The method of  claim 1 , wherein the delay timer lasts 12 hours. 
     
     
       5. The method of  claim 1 , wherein the delay timer is stopped after an area update is detected. 
     
     
       6. The method of  claim 1 , wherein the threshold is five timeouts within a time period of fifteen minutes relative to a current time. 
     
     
       7. The method of  claim 1 , wherein the timeout is a failure of receiving a response from the first feature within a time window after an invite is transmitted to the first feature. 
     
     
       8. The method of  claim 1 , wherein the first network is a Long Term Evolution (LTE) network, wherein the second network is a legacy network, and wherein the first feature is an IP Multimedia Subsystem (IMS), wherein the legacy network comprises one of a Global System for Mobile Communications (GSM) based network or a Universal Mobile Telecommunications System (UMTS) based network. 
     
     
       9. A device, comprising:
 a transceiver configured to establish a first network connection to a first network and a second network connection to a second network, the second network configured to perform circuit switched voice calls; and 
 a processor communicatively coupled to the transceiver and configured to perform operations comprising:
 receiving a call input to perform a call; 
 determining whether the device is registered with a first feature of the first network, the first feature configured to perform the call based on an Internet Protocol (IP);
 when the device is registered with the first feature, determining whether a number of timeouts for attempting previous calls based on the IP is greater than a threshold; 
 when the number of timeouts is at least the threshold, the processor deregistering from the first feature and starting a delay timer; 
 performing a circuit switched fallback (CSFB) procedure including a handover from the first network to the second network; 
 performing the call as a circuit switched call; and 
 reconnecting to the first network when the circuit switched call is completed, wherein the reconnecting comprises determining whether the delay timer is expired and wherein, when the delay timer is not expired, omitting signaling for a registration with the first feature at each instance that the registration is to otherwise be performed due to the number of timeouts such that the device cannot perform calls using the first network. 
 
 
 
     
     
       10. The device of  claim 9 , wherein, when the device is not registered with the first feature, the processor further performs the CSFB procedure and performs the call as the circuit switched call. 
     
     
       11. The device of  claim 9 , wherein, when the number of timeouts is less than the threshold, the processor further performs the call based on the IP. 
     
     
       12. The device of  claim 9 , wherein the delay timer lasts 12 hours. 
     
     
       13. The device of  claim 9 , wherein the delay timer is stopped after an area update is detected. 
     
     
       14. The device of  claim 9 , wherein the threshold is five timeouts within a time period of fifteen minutes relative to a current time. 
     
     
       15. The device of  claim 9 , wherein the timeout is a failure of receiving a response from the first feature within a time window after an invite is transmitted to the first feature. 
     
     
       16. A processor of a device that is configured to establish a first network connection to a first network and a second network connection to a second network, the second network configured to perform circuit switched voice calls, wherein the processor is configured to perform operations comprising:
 receiving a call input to perform a call; 
 determining whether the device is registered with a first feature of the first network, the first feature configured to perform the call based on an Internet Protocol (IP); 
 when the device is registered with the first feature, determining whether a number of timeouts for attempting previous calls based on the IP is greater than a threshold; 
 when the number of timeouts is at least the threshold, deregistering from the first feature and starting a delay timer, the delay timer preventing the device from registering to the first feature; 
 performing a circuit switched fallback (CSFB) procedure including a handover from the first network to the second network; 
 performing the call as a circuit switched call; 
 reconnecting to the first network when the circuit switched call is completed, wherein the reconnecting comprises determining whether the delay timer is expired and wherein, when the delay timer is not expired, omitting signaling for a registration with the first feature at each instance that the registration is to otherwise be performed due to the number of timeouts such that the device cannot perform calls using the first network. 
 
     
     
       17. The processor of  claim 16 , wherein the first feature comprises a IP Multimedia Subsystem (IMS). 
     
     
       18. The processor of  claim 16 , wherein the delay timer is stopped after an area update is detected. 
     
     
       19. The processor of  claim 16 , wherein the threshold is five timeouts within a time period of fifteen minutes relative to a current time. 
     
     
       20. The processor of  claim 16 , wherein the timeout is a failure of receiving a response from the first feature within a time window after an invite is transmitted to the first feature.

Description:
BACKGROUND INFORMATION 
     A user equipment (UE) may be configured to establish a connection to at least one of a plurality of different networks or types of networks as well as with other UEs to perform a variety of different functionalities via the connection. For example, the UE may connect to a first type of network (e.g., Long Term Evolution (LTE) network) to communicate with a further UE through the network connection (e.g., a user of the UE may perform a voice call or transmit a text to another user of another UE). In establishing a communication pathway with the further UE, the UE may utilize a plurality of different calling applications. For example, the calling applications may utilize a circuit switched call or a voice over Internet Protocol (IP) (VoIP) such as voice over LTE (VoLTE). 
     The VoLTE call provides various benefits for the networks that establish calls and the users performing the calls. For example, the VoLTE call may allow more voice and/or data to be transmitted within a given time period. In another example, the VoLTE call may utilize less bandwidth than other VoIP calls. In a further example, the VoLTE call does not rely on the legacy circuit switched voice network. To complete a VoLTE call, an IP Multimedia Subsystem (IMS) may be used. In scenarios where the IMS fails to establish the call, a protocol used by the UE is to reregister with the IMS and utilize a fallback procedure for the call to be performed using the circuit switched voice network (e.g., a circuit switched fallback procedure (CSFB)). This process may require a relatively substantial amount of time that may impact a user experience. When the UE is situated where a connection path to the IMS (e.g., a loaded IMS) results in the IMS continuously failing to establish a call, the user may constantly experience these long setup times to establish a call. 
     SUMMARY 
     The exemplary embodiments are directed to a method of improving a call setup time. The method is performed at a device that is configured to establish a first network connection to a first network and a second network connection to a second network, the second network configured to perform circuit switched voice calls. The method includes receiving a call input to perform a call. The method includes determining whether the device is registered with a first feature of the first network. The first feature is configured to perform the call based on an Internet Protocol (IP). When the device is registered with the first feature, the method includes determining whether a number of timeouts for attempting previous calls based on the IP is greater than a threshold. When the number of timeouts is at least the threshold, the method includes deregistering from the first feature. The method includes performing a circuit switched fallback (CSFB) procedure including a handover from the first network to the second network. The method includes performing the call as a circuit switched call. 
     The exemplary embodiments are directed to a device that improves a call setup time. The device includes a transceiver and a processor. The transceiver is configured to establish a first network connection to a first network and a second network connection to a second network. The second network is configured to perform circuit switched voice calls. The processor receives a call input to perform a call. The processor determines whether the device is registered with a first feature of the first network. The first feature is configured to perform the call based on an Internet Protocol (IP). When the device is registered with the first feature, the processor determines whether a number of timeouts for attempting previous calls based on the IP is greater than a threshold. When the number of timeouts is at least the threshold, the processor deregisters from the first feature. The processor performs a circuit switched fallback (CSFB) procedure including a handover from the first network to the second network. The processor performs the call as a circuit switched call. 
     The exemplary embodiments are directed to a method of improving a call setup time. The method is performed at a device that is configured to establish a first network connection to a first network and a second network connection to a second network, the second network configured to perform circuit switched voice calls. The method includes receiving a call input to perform a call. The method includes determining whether the device is registered with a first feature of the first network, the first feature configured to perform the call based on an Internet Protocol (IP). When the device is registered with the first feature, the method includes determining whether a number of timeouts for attempting previous calls based on the IP is greater than a threshold. When the number of timeouts is at least the threshold, the method includes deregistering from the first feature and starting a delay timer. The delay timer prevents the device from registering to the first feature. The method includes performing a circuit switched fallback (CSFB) procedure including a handover from the first network to the second network. The method includes performing the call as a circuit switched call. Upon completion of the circuit switched call, the method includes connecting to the first network. The method includes determining whether the delay timer is running. When the delay timer is running, the method includes preventing the device from registering with the first feature. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an exemplary signal diagram when a call is successfully established according to various exemplary embodiments described herein. 
         FIG. 2  shows an exemplary signal diagram when a call is established using a fallback procedure according to various exemplary embodiments described herein. 
         FIG. 3  shows an exemplary network arrangement according to various exemplary embodiments described herein. 
         FIG. 4  shows an exemplary user equipment according to various exemplary embodiments described herein. 
         FIG. 5  shows an exemplary signal diagram to improve call setup time according to various exemplary embodiments described herein. 
         FIG. 6  shows an exemplary method for improving a call setup time in irregular network conditions according to various exemplary 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 improving the manner in which calls are established by a user equipment (UE). During irregular network behavior, there may be a relatively long call setup time that is observed when performing a call using Internet Protocol (IP) and using a circuit switched fallback procedure. Accordingly, the exemplary embodiments provide a mechanism that reduces a call setup time and improves device performance during irregular network behavior. As will be described in detail below, the mechanism according to the exemplary embodiments may utilize a timeout counter and a delay timer to modify and/or bypass select operations resulting in a call setup time being reduced. 
     Initially, it is noted that the exemplary embodiments are described with regard to a UE. However, the UE is only exemplary. The exemplary embodiments may be utilized with any device that may connect to a network used in establishing a call with another UE as well as be configured with the hardware, software, and/or firmware to establish the connection and utilize the mechanism according to the exemplary embodiments. Therefore, the UE as described herein is used to represent any device capable of establishing these connections. 
     It is also noted that the exemplary embodiments are described with regard to irregular network behavior or irregular network conditions being experienced by a UE that causes a call setup time to be longer than under regular network conditions. For illustrative purposes, the irregular network conditions are described as a loaded network feature such as an IP Multimedia Subsystem (IMS). However, those skilled in the art will understand that there may be one or more different factors that may contribute to irregular network conditions such that the mechanism according to the exemplary embodiments may be utilized. Therefore, the loaded IMS may represent one or more factors that result in the irregular network conditions. 
     The exemplary embodiments are also described with regard to a Long Term Evolution (LTE) network and a Voice over LTE (VoLTE) call in which an IMS is used to perform the VoLTE call along with a circuit switched fallback (CSFB) procedure when the VoLTE call is not capable of being established or the VoLTE call is not available. However, the network type, the call type, the use of the IMS, and the CSFB are only exemplary. For example, the call may be any type including voice over IP, voice over WiFi, etc. The exemplary embodiments may be implemented and/or modified for any process in which a first feature may be attempted, a second feature may be used as a secondary approach, and one or more operations in the first feature may be modified to reach the second feature in a more expeditious manner for subsequent uses of the process. 
     The exemplary embodiments are directed to when a first user using a first UE calls a second user using a second UE. When the first UE is connected to an IMS at the time the call is made, the first UE may attempt to perform the call as a VoLTE call over a LTE network. When the first UE attempts to perform the call as the VoLTE call but the VoLTE call fails from the IMS being unavailable, the first UE may subsequently perform the call using a CSFB procedure through the LTE network so that the circuit switched call is used over the legacy network. When the first UE is not connected to the IMS at the time the call is made, the first UE may perform the call as a circuit switched call over a legacy network via the CSFB procedure. 
     Initially, the VoLTE call procedure may entail a plurality of operations that are performed initially, during, and after the VoLTE call is performed.  FIG. 1  shows an exemplary signal diagram  100  when a call is successfully established as a VoLTE call according to various exemplary embodiments described herein. The signal diagram  100  is described with regard to a UE  2 , a LTE network  4 , an IMS  6 , and a legacy network  8 . As the VoLTE call is successful in the signal diagram  100 , the legacy network  8  may not participate in this exemplary flow. The signal diagram  100  shows a direct exchange between the UE  2  and the IMS  6 . However, those skilled in the art will understand that the UE  2  is capable of communicating with the IMS  6  via the LTE  4 . Therefore, the exchange between the UE  2  and the IMS  6  may include a forwarding functionality performed by the LTE  4  (not shown). 
     An initial process that is performed is the UE  2  registers with the IMS  6 . For example, upon connecting to the LTE network  4  or upon an event occurring (e.g., an area update), the UE  2  may register or reregister with the IMS  6 . Those skilled in the art will understand the plurality of operations that are performed for the IMS registration procedure to be completed for the UE  2  to be registered with the IMS  6 . As illustrated in  FIG. 1 , an IMS registration procedure  10  may include the UE  2  transmitting a register request  12  to the IMS  6 . The IMS  6  may respond with a  401  unauthorized response  14 . This exchange may entail the UE  2  attempting to IMS register but is challenged by the IMS  6  to authenticate itself. The UE  2  may then transmit another register request  16  to the IMS  6 . The IMS  6  may respond with a 200 OK response  18  which completes the IMS registration  10 . This exchange may entail the UE  2  establishing a protected session with the IMS  6  for another attempt at registering to be performed. Thereafter, the UE  2  is registered with the IMS  6 . 
     It is noted that the above IMS registration procedure  10  is a general summary of select operations that are performed. Those skilled in the art will understand that there may be a plurality of other operations that are performed in the IMS registration  10 . For example, in the initial attempt to register with the IMS, the IMS registration procedure may include a proxy call session control function (CSCF) (P-CSCF) and a serving CSCF (S-CSCF). The UE  2  may request a dynamic host configuration protocol (DHCP) server and additionally request a domain name and/or IP address of a P-CSCF as well as domain name system (DNS) servers. By performing a DNS query, a list of P-CSCF IP addresses may be retrieved and one of these IP addresses may be selected which initiates communication with the IMS  6 . Thereafter, once the UE  2  attaches to the IMS  6 , a S-CSCF may be assigned to serve the UE  2 . The S-CSCF may retrieve a profile of the UE  2  (or the user of the UE  2 ) who has an IMS subscription. A subsequent attempt to register with the IMS may be performed to result in the UE  2  registering with the IMS  6 . 
     Once the UE  2  has registered with the IMS  6 , the UE  2  may utilize the various features that the IMS  6  may provide. A particular feature that may be used is performing a VoLTE call. Accordingly, at a subsequent time, the UE  2  may receive a mobile originating (MO) call input from a user (e.g., a public switched telephony network (PSTN) phone number). Since the UE  2  is registered with the IMS  6 , the call may be performed as a VoLTE call. Therefore, the UE  2  may transmit an invite  20  to the P-CSCF of the IMS  6  including data such as a called party and corresponding information (e.g., available codecs, a real-time transport protocol (RTP) port number, an IP address, etc.). The P-CSCF of the IMS  6  may respond by acknowledging the invite  20  with a 100 trying message  22 . Additionally, the IMS  6  may transmit a 183 session progress  24  with network carrying media stream capabilities of the destination along the signaling path, a media gateway (IM-MGW) common codec list, an IP address, a RTP port number, etc. The UE  2  may then confirm the codec selection in a provisional response ACK (PRACK)  26  to which the IMS  6  acknowledges the selected codec in a 200 OK  28 . Upon completion of these operations, a call may be established  28 . Once established, the call may be performed such as ringing  30  the mobile terminating (MT) UE and allowing a conversation  32  (if a user of the MT UE answers the call). Once the call is completed, the call may be terminated  34 . 
     The above process in the signal diagram  100  of  FIG. 1  illustrates when a VoLTE call is successfully established and performed until the call is terminated (regardless of whether the conversation  30  takes place). With the call being completed over the LTE network  4 , the UE  2  remains connected to the LTE network  4  after the call has terminated  34 . However, there are scenarios when the VoLTE call fails. For example, after transmitting the invite  20 , there may be a window in which the 100 trying message  22  is to be received that results in a timeout. The window may vary in size based on a variety of factors (e.g., a global region, network capabilities, etc.). In a particular example, a maximum window may be up to 32 seconds. 
       FIG. 2  shows an exemplary signal diagram  200  when a call is established using a fallback procedure according to various exemplary embodiments described herein. The signal diagram  200  is also described with regard to the UE  2 , the LTE network  4 , the IMS  6 , and the legacy network  8 . The signal diagram  200  relates to a scenario when an initial VoLTE call attempt fails from failure to receive the 100 trying message within the window after transmitting the invite and a CSFB procedure is used. The signal diagram  200  may start in a substantially similar manner as the signal diagram  100 . Specifically, the IMS registration  10  may be performed in which the UE  2  registers with the IMS  6 . Once registered, the UE  2  may perform a call using a VoLTE call. It is again noted that the signal diagram  200  shows a direct exchange between the UE  2  and the IMS  6  but that the exchange between the UE  2  and the IMS  6  may include a forwarding functionality performed by the LTE  4  (not shown). 
     In performing the VoLTE call, again, the UE  2  may transmit an invite  36  to the IMS  6  including the data noted above. However, in this instance, a time  38  may pass where the time  38  corresponds to the window in which the 100 trying message is to be received from the IMS  6 . Due to certain network implementations, there may be occasions when the IMS  6  does not respond to the invite resulting in a call establishment failing and/or a substantial call setup time being observed. Specifically, the window must lapse for subsequent operations to be performed, if a remaining time after the window lapsing allows for the subsequent operations. For example, in France, an invite response timeout value may be set to 3,000 ms by certain networks. Due to this invite response timeout value, once the invite response timeout occurs, the UE  2  may still perform a CSFB procedure. Accordingly, the UE  2  which is IMS registered may initially send an invite to establish a VoLTE call. However, since there is no response from the IMS  6 , the UE  2  attempts to complete the call through the CSFB procedure and using a circuit switched call. This process may require between 8 to 10 seconds from the VoLTE call being attempted and subsequently the circuit switched call being attempted. In other countries, the invite response timeout value may be set higher than France such that the invite response timeout occurring may result in no further operations being performed. As a result, in these other regions, the call being established at all is very low when the VoLTE call fails. With higher invite response timeout values, by the time the session gets terminated between the UE  2  and the IMS  6 , the UE  2  may not perform any further attempts to complete the call, even forgoing the CSFB procedure. 
     It is noted that the CSFB procedure may be used for any of a variety of reasons in which a corresponding event triggers the CSFB procedure. For illustrative purposes, the exemplary embodiments are described with regard to the CSFB procedure being triggered when the invite response timeout occurs. However, the exemplary embodiments may be implemented and/or modified with other reasons that the CSFB procedure is triggered. 
     Returning to the signal diagram  200 , since the 100 trying message is not received within the time  38 , the session may be terminated  40 . When the session is terminated  40 , the UE  2  is still connected to the LTE network  4 . Accordingly, the UE  2  may transmit an extended service request  42  to the LTE  4 . As those skilled in the art will understand, the extended service request  42  may be a message sent by the UE  2  to the LTE  4  to initiate the CSFB procedure. Subsequently, the LTE  4  may perform the CSFB procedure  44  for the UE  2  to perform the call as a circuit switched call. As illustrated, by using the CSFB procedure  44 , there may be a legacy handover  46  in which the UE  2  is associated with the legacy network  8 . Thereafter, the call may be stablished  48  where the call is performed as a circuit switched call. The call may then be established  48 , ringing  50  may be performed, a conversation  52  may be performed (assuming the MT user answers the call), and the call may be terminated  54 . After the circuit switched call is terminated, the UE  2  may return to the LTE network. Thus, there may be a legacy teardown  56  and a LTE connect  58  that is performed. Upon returning to the LTE  4 , the UE  2  may again register with the IMS  6  using the IMS registration  60  which is substantially similar to the IMS registration  10 . 
     It is noted that the above set of operations in which the CSFB procedure is used is based on an assumption that the LTE  4  is configured to provide this feature. As those skilled in the art will understand, the CSFB procedure may be provided when there is a bridge between the LTE  4  and the legacy network  8  over which the circuit switched call would be performed. Specifically, an interface (e.g., SGs interface) may connect a mobility management entity (MME) of the LTE  4  to a mobile switching center (MSC) of the legacy network  8 . Thus, upon receiving the extended service request  42 , the LTE  4  may use the SG interface for the CSFB procedure to be performed and the circuit switched call to be performed (e.g., without any user intervention) by the legacy network  8 . However, if the SG interface or bridge is unavailable, the call may be required to be performed as a VoLTE call. 
     As noted above, the call setup time that is required under irregular network conditions (e.g., a loaded IMS) may be substantially long. For example, to establish a call, the operations that are performed may use 8 to 10 seconds before a user hears ringing (indicating that the MT user is being contacted). Again, the operations may include a first set of operations used in attempting to perform a VoLTE call and a second set of operations used in attempting to perform a circuit switched call when the VoLTE call fails. The CSFB procedure may allow for the call to be established but the overall call establishment procedure may benefit from using the circuit switched call at an earlier opportunity to reduce the time to establish the call, rather than use the first set of operations to perform the VoLTE call under conditions when the VoLTE call likely fails (e.g., eliminate the window in waiting for the 100 trying message from the IMS). For example, when the UE is in a location where the IMS may not be capable of establishing a VoLTE call, each instance that a user attempts to place a call while registered to the IMS may result in this extended call setup time where the circuit switched call is ultimately used. For example, a first call may utilize 8 to 10 seconds to establish a call which is ultimately circuit switched. After the call, the UE returns to the LTE network (from the legacy network) and registers with the IMS. A second, subsequent call may again utilize 8 to 10 seconds to establish a call (e.g., from first attempting the VoLTE call since the UE is IMS registered) which also ultimately is circuit switched. This extended call setup time may continue until the conditions of the UE or the IMS changes (e.g., area change). 
     In view of the extended call setup time under irregular network conditions, the exemplary embodiments provide a mechanism to reduce the call setup time in establishing a call by bypassing the VoLTE call attempt and utilizing the circuit switched call. That is, the CSFB procedure may be used without the operations used in attempting the VoLTE call (e.g., the window to receive the 100 trying message). Specifically, the exemplary embodiments introduce a timeout counter that defines when a delay timer is to be used. The timeout counter indicates a threshold of instances that a timeout occurs from attempting the VoLTE call in previous iterations. The irregular network conditions being experienced may be indicated from the threshold being met. Accordingly, the delay timer may be started so that subsequent calls may be attempted immediately with the CSFB procedure. The call that triggered the delay timer may also immediately use the CSFB procedure by deregistering with the IMS to bypass the VoLTE call attempt. The delay timer defines when a UE may register with the IMS. By postponing when the UE registers with the IMS after a call has been completed, the UE may remain unregistered with the IMS such that the VoLTE call is not an option and the CSFB procedure is used at an earlier opportunity for the circuit switched call to be used while the irregular network conditions persist. 
       FIG. 3  shows a network arrangement  100  according to the exemplary embodiments. The network arrangement  100  includes UEs  110 - 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, smartphones, phablets, embedded devices, wearable devices, Cat-M devices, Cat-M1 devices, MTC devices, eMTC devices, other types of Internet of Things (IoT) devices, 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. 
     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 client 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. The legacy RAN  120  may be used for circuit switched calls. For example, the legacy RAN  120  may include a 2G network in which a Global System for Mobile Communications (GSM) is used or a 3G network in which a Universal Mobile Telecommunications System (UMTS) is used. The LTE-RAN  122  may be used to perform Voice over IP (VoIP) calls, specifically VoLTE calls. 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.). 
     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  may further include bridges or a SG interface that connects the LTE-RAN  122  and the legacy RAN  120 . 
     The network arrangement  100  also includes an 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 such as VoLTE calls. 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 . This subscription information is used to provide the correct multimedia services to the user such as the 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 UE  110  performing mobile originating (MO) calls with another UE. In performing the MO call, the VoLTE call may be performed over the LTE-RAN  122  using the IMS  150 , when available, and a circuit switched call may be performed through a CSFB procedure over the legacy RAN  120  when the VoLTE call fails. The exemplary embodiments provide a delay mechanism where operations associated with the IMS  150  may be modified so that a circuit switched call may be used in a more efficient manner under irregular network conditions regarding the IMS  150  when attempting to perform VoLTE calls. 
       FIG. 4  shows the UE  110  of the network arrangement  100  of  FIG. 3  according to the exemplary embodiments. The UE  110  is configured to execute a plurality of engines that perform functionalities to improve call setup times based on previous results in attempting to perform a call and subsequent settings as a result thereof. It is noted that the UE  110  being configured with the features of the exemplary embodiments is only exemplary. That is, the UE  110  may also represent the UEs  112 ,  114 . 
     The UE  110  may represent any electronic device that is configured to perform wireless functionalities (e.g., a VoLTE call) and may be representative of one or more of the UEs  110 - 114  (examples of which are noted above). The UE  110  may include a processor  205 , a memory arrangement  210 , a display device  215 , an input/output (I/O) device  220 , a transceiver  225 , and other components  230 . The other components  230  may include, for example, sensors to detect movement and movement related data, an audio input device, an audio output device, a battery that provides a limited power supply, a data acquisition device, ports to electrically connect the UE  110  to other electronic devices, sensors to detect conditions of the UE  110 , etc. 
     The processor  205  may be configured to execute a plurality of engines of the UE  110 . For example, the engines may include a call engine  235 , a registration engine  240 , and a delay engine  245 . The call engine  235  may be configured to perform a call using a variety of different types of calls based on current conditions indicating availability of the different types of calls. The registration engine  240  may be configured to perform registration operations to register the UE  110  to the IMS  150 . The delay engine  245  may be configured to affect the registration engine  240  with regard to when the registration operations may be performed. 
     It should be noted that the above noted engines each being an application (e.g., a program) executed by the processor  205  is only exemplary. The functionality associated with the engines 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. For example, the integrated circuit may include input circuitry to receive signals and processing circuitry to process the signals and other information. The engines may also be embodied as one application or separate applications or as part of one or more multifunctional programs. Accordingly, the applications may be implemented in a variety of manners in hardware, software, firmware, or a combination thereof. In addition, in some UEs, the functionality described for the processor  205  is split among two or more processors such as a baseband processor and an applications processor, as will be described in further detail below. The exemplary embodiments may be implemented in any of these or other configurations of a UE. 
     The memory  210  may be a hardware component configured to store data related to operations performed by the UE  110 . For example, the memory  210  may store a contact list (e.g., PTSN numbers) of different contacts with whom a call may be placed. As will be described in further detail below, the memory  210  may also store data associated with instances of timeouts occurring from invites to the IMS  150 . The memory  210  may further store data associated with when the instances occur and predefined settings to be used in the mechanism according to the exemplary embodiments (e.g., delay increments, a delay reset time, etc.). 
     The display device  215  may be a hardware component configured to show data to a user while the I/O device  220  may be a hardware component that enables the user to enter inputs. It should be noted that the display device  215  and the I/O device  220  may be separate components or integrated together such as a touchscreen. The transceiver  225  may be a hardware component configured to establish a connection with at least one of a base station associated with the legacy RAN  120 , a base station of the LTE-RAN  122  (e.g., an evolved Node B (eNB)), a router of a WLAN  124 , the UE  112 , etc. Accordingly, the transceiver  225  may operate on a variety of different frequencies or channels (e.g., set of consecutive frequencies). 
     As described above, the exemplary embodiments provide an expedited approach that allows the UE  110  to utilize a circuit switched call when performing a call when the UE  110  is experiencing irregular network conditions that result in the IMS  150  not responding within a window after the UE  110  transmits an invite to perform a VoLTE call. The VoLTE call may be bypassed by deregistering the UE  110  from the IMS  150  when a timeout counter has been met. Thus, the present call may proceed to the CSFB procedure. Furthermore, a delay timer may be started that prevents the UE  110  from registering (or re-registering) with the IMS  150  for the duration of the timer or when a register event is detected. Without registering with the IMS  150 , any call that is placed while the delay timer is running is performed as a circuit switched call via the CSFB procedure. With a higher probability that the VoLTE call fails during the delay timer, the call setup time in establishing a call may be reduced to improve a user experience, particularly in view of the waiting time for the IMS  150  being eliminated. The exemplary embodiments are directed to a first set of operations associated with registering with the IMS and a second set of operations associated with performing a call. The first and second set of operations are performed mutually as a result of the first set of operations affecting the second set of operations and vice versa. The first and second set of operations are also based on a call event that indicates a result of attempting to perform a call as a VoLTE call. 
     The call engine  235  may perform a call using a variety of different types of calls based on current conditions indicating availability of the different types of calls. From the perspective of the user and the UE  110 , the call engine  235  may allow an input to be received that indicates that a call is to be performed. From the perspective of network operations, when the UE  110  is registered with the IMS  150 , the call engine  235  may perform a call as a VoLTE call. When the UE  110  is not registered with the IMS  150 , the call engine  235  may perform a call as a circuit switched call. When the UE  110  performs a VoLTE call but fails to establish the VoLTE call, the call engine  235  may utilize a CSFB procedure in which the call is completed as a circuit switched call. In performing a call, the call engine  235  may perform a plurality of signaling operations such as the process described above with regard to the signal diagrams  100 ,  200  of  FIGS. 1, 2 , respectively. The call engine  235  may perform the call for each instance that a user enters an input requesting that the call be performed. As will be described in detail below, the current conditions of the UE  110  may indicate whether the UE  110  is registered with the IMS  150  such that a corresponding type of call is performed. 
     The registration engine  240  may perform registration operations to register the UE  110  with the IMS  150 . The registration engine  240  may also perform a plurality of signaling operations to register the UE  110  with the IMS  150 . For example, the IMS registration  10  of the signaling diagrams  100 ,  200  of  FIGS. 1, 2 , respectively, may include select registration operations that are performed by the registration engine  240 . As will be described in detail below, the registration engine  240  may be configured to perform the registration operations at predefined times, as may be defined by an IMS and/or LTE Specification. However, according to the exemplary embodiments, a registration with the IMS  150  as would be performed by the registration engine  240  may be delayed after completion of a call that is performed as a circuit switched call. 
     The delay engine  245  may affect the registration engine  240  with regard to when the registration operations may be performed. As noted above, the registration engine  240  may be delayed as to when the registration operations to register the UE  110  with the IMS  150  are performed. The delay engine  245  may define a delay timer that is used to indicate when the registration engine  240  performs the registration operations after completion of a call that is performed as a circuit switched call. The delay engine  245  may also monitor each VoLTE call attempt and track instances that VoLTE call attempts resulted in a timeout. Accordingly, the delay engine  245  may also determine when the delay timer is to be used as well as instruct a deregistration procedure from the IMS  150  to be performed. 
     As an overall procedure in which the CSFB procedure is available, the mechanism according to the exemplary embodiments provides a change in which an IMS deregistration may be performed and when an IMS registration is to be performed through a timeout counter and a delay timer. Thus, the UE  110  is enabled to establish a call successfully with a reduced call setup time by immediately using the CSFB procedure and bypassing the VoLTE call attempt (when IMS registered at the time a call input is received). 
     For each call input from a user, the UE  110  may determine whether the UE  110  is registered with the IMS  150 . When registered, the UE  110  may attempt a VoLTE call. When not registered, the UE  110  may use the CSFB procedure and attempt a circuit switched call. When registered, the UE  110  may also determine whether the UE  110  has experienced a threshold number (e.g., a timeout counter) of timeout instances from prior calls being performed as VoLTE calls. When the timeout instances are within the threshold number, the UE  110  may proceed in performing the call as a VoLTE call. However, when the timeout instances exceed the threshold number, the UE  110  may deregister with the IMS  150  and use the CSFB procedure to attempt a circuit switched call. 
     For each call, the UE  110  may also initiate or track a delay timer. When the conditions indicate that the UE  110  is IMS registered and the timeout instances exceed the timeout counter, in addition to deregistering from the IMS  150 , the UE  110  may initiate the delay timer. As noted above, the delay timer may prevent the UE  110  from registering with the UE  110  when the IMS registration procedure would otherwise be used. Specifically, after connecting to the LTE-RAN  122  upon completion of a circuit switched call, the UE  110  may not register with the IMS  150  until the delay timer expires. Accordingly, while the delay timer is running, a further call may be performed. However, since the UE  110  is not registered with the IMS  150 , the UE  110  may utilize the CSFB procedure where the extended service request is transmitted to the LTE-RAN  122  and proceed immediately with performing the call as a circuit switched call. As will be apparent, a result of performing the call in this manner reduces the call setup time as the operations of the VoLTE call may be avoided including the window that the UE  110  waits for a response from the IMS  150 . 
     The timeout counter and the delay timer may be utilized with various features. The timeout counter may track a number of timeouts over a period of time. For example, the timeout counter may have a threshold set to five timeouts within 15 minutes. The 15 minute span may be a moving window such that a timeout that occurred prior to the 15 minute span from a current time may not be considered. However, the use of a moving window is only exemplary. In another implementation, timeout counter may track a number of timeouts while conditions with the IMS  150  remain unchanged. In a further implementation, a combination of the above manner of using the timeout counter may be used. 
     The delay timer may have a duration that lasts for a predetermined time period. For example, the delay timer may be set for a network maintenance period. In an exemplary network, the network maintenance period may be 12 hours. Thus, the delay timer may be set for 12 hours. As those skilled in the art will understand, when the UE  110  experiences substantially similar IMS conditions and remains under these IMS conditions, the next change that may be experienced may be due to a network maintenance event. Accordingly, the delay timer may be set to a corresponding value. It is noted that the delay timer being set to a network maintenance period is only exemplary. In another implementation, the delay timer value may be dynamic and correspond to a time when the network maintenance event is to occur. Thus, the delay timer value may be a remaining duration until the network maintenance event. In a further implementation, the delay timer may be set to any other value and/or using any other basis. 
     The timeout counter may be reset while the delay timer may be stopped based on a respective naturally occurring event and independent events. For example, the timeout counter may constructively be reset when no timeouts are experienced within the time span associated with the timeout counter. In another example, the delay timer may be stopped upon expiry of the duration. In an exemplary independent event, the timeout counter and the delay timer may be reset and stopped, respectively, when an area update is detected. The area update may refer to a tracking area update (e.g., with the LTE-RAN  122 ) or a location/routing area update (e.g., with the legacy RAN  120 ). Thus, the naturally occurring event may independently reset or stop the timeout counter or the delay timer, respectively. The independent event may reset and stop the timeout counter and the delay timer, respectively. It is noted that there may be other types of independent events similar to the area update that triggers the timeout counter to be reset and the delay timer to be stopped. Therefore, the area update as used herein may represent any of these events. The exemplary embodiments may be modified to also incorporate these events as considerations in using the timeout counter and the delay timer. 
       FIG. 5  shows an exemplary signal diagram  500  to improve call setup time according to various exemplary embodiments described herein. The signal diagram  500  is described with regard to the UE  110 , the LTE-RAN  122 , the IMS  150 , and the legacy RAN  120 . The signal diagram  500  relates to an exemplary use of the mechanism according to the exemplary embodiments where a timeout counter and a delay timer are used in bypassing operations to attempt a VoLTE call. For illustrative purposes, the exemplary embodiments are described with a threshold for the timeout counter being two timeouts while conditions of the IMS  150  remain unchanged and that no independent events occur. The delay timer may be set to an arbitrary value with regard to the signal diagram  500 . It is also noted that the signal diagram  500  is described assuming that the CSFB procedure is available and the SG interface between the legacy RAN  120  and the LTE-RAN  122  is available. 
     Although not shown, the signal diagram  500  may start in a substantially similar manner as the signal diagrams  100 ,  200  of  FIGS. 1, 2 , respectively, where the UE  110  connects to the LTE-RAN  122  and registers with the IMS  150  using an IMS registration procedure. Specifically, a substantially similar process to the IMS registration  10  may be performed in which the UE  110  registers with the IMS  150 . Once registered, the UE  110  may perform a call using a VoLTE call when conditions based on the exemplary embodiments allow. Like the signal diagrams  100 ,  200 , the signal diagram  500  shows a direct exchange between the UE  110  and the IMS  150  but that the exchange between the UE  110  and the IMS  150  may include a forwarding functionality performed by the LTE-RAN  122  (not shown). 
     The signal diagram  500  shows four independent calls being made over time. As noted above, the UE  110  may already be connected to the LTE-RAN  122  and registered with the IMS  150 . In a first call, the UE  110  may transmit an invite  502  to the LTE-RAN  122 . Initially, a call input may be received from the user. Being connected to the LTE-RAN  122  and registered with the IMS  150 , the call input may be transmitted as the invite  502 . As with each call, the UE  110  may perform a counter process  504  in determining whether the threshold for the timeout counter has been reached from previous VoLTE call attempts. As this is a first call, the timeout counter may be at 0 instances. Accordingly, the UE  110  may proceed with attempting a VoLTE call for the first call. In attempting the VoLTE call, after the invite  502  is transmitted, the UE  110  may wait for at least a window of time  506  to receive a response from the IMS  150  (e.g., a 100 trying message). As illustrated, the UE  110  may not receive a response from the IMS  150 . Thus, the UE  110  may terminate  508  the VoLTE call session. The UE  110  may also perform a delay process  510  where the instance of the timeout is incremented in the timeout counter (e.g., to 1 instance). Therefore, since the session was terminated  508 , the UE  110  may transmit an extended service request  512  for the LTE-RAN  122  to perform the CSFB procedure  514 . The LTE-RAN  122  and the legacy RAN  120  may perform a legacy handover  516  and the first call may be performed  518  as a circuit switched call using the legacy RAN  120 . Once the call is completed, a teardown  520  with the legacy RAN  120  may be performed and a LTE connect  522  operation may be performed (which may be based on reselection or redirection initiated by the LTE-RAN  122 ). The delay process  510  may further extend until the LTE connect  522  is performed. 
     Specifically, the delay process  510  may determine whether the delay timer is running. At the conclusion of the first call and after connecting  522  to the LTE-RAN  122 , the delay timer is not running. Thus, the UE  110  performs an IMS registration  524 . 
     After the first call, the UE  110  may be connected to the LTE-RAN  122  and registered with the IMS  150 . In a second call, the UE  110  may transmit an invite  526  to the LTE-RAN  122 . Again, a call input may have been entered and the invite  526  may be used as the UE  110  is registered with the IMS  150 . The UE  110  may perform a counter process  528  in determining whether the threshold for the timeout counter has been reached from previous VoLTE call attempts. With the first call resulting in a timeout from the VoLTE call attempt, the timeout counter may be at 1 instance which is under the threshold for the timeout counter. Accordingly, the UE  110  may proceed with attempting a VoLTE call for the first call. In attempting the VoLTE call, after the invite  526  is transmitted, the UE  110  may wait for at least a window of time  530  to receive a response from the IMS  150  (e.g., a 100 trying message). As illustrated, the UE  110  may not receive a response from the IMS  150 . Thus, the UE  110  may terminate  532  the VoLTE call session. The UE  110  may also perform a delay process  534  where the instance of the timeout is incremented in the timeout counter (e.g., to 2 instances). Therefore, since the session was terminated  532 , the UE  110  may transmit an extended service request  536  for the LTE-RAN  122  to perform the CSFB procedure  538 . The LTE-RAN  122  and the legacy RAN  120  may perform a legacy handover  540  and the first call may be performed  542  as a circuit switched call using the legacy RAN  120 . Once the call is completed, a teardown  544  with the legacy RAN  120  may be performed and a LTE connect  546  operation may be performed (which may be based on reselection or redirection initiated by the LTE-RAN  122 ). The delay process  534  may further extend until the LTE connect  546  is performed. 
     Specifically, the delay process  534  may determine whether the delay timer is running. At the conclusion of the second call and after connecting  546  to the LTE-RAN  122 , the delay timer is not running. Thus, the UE  110  performs an IMS registration  548 . 
     After the second call, the UE  110  may be connected to the LTE-RAN  122  and registered with the IMS  150 . In a third call, the UE  110  may transmit an invite  550  to the LTE-RAN  122 . Again, a call input may have been entered and the invite  526  may be used as the UE  110  is registered with the IMS  150 . The UE  110  may perform a counter process  552  in determining whether the threshold for the timeout counter has been reached from previous VoLTE call attempts. For the third call, the timeout counter may be at 2 instances which satisfies the threshold for the timeout counter. Thus, instead of proceeding with attempting the VoLTE call, the UE  110  performs an IMS deregistration  556  to deregister from the IMS  150 . The UE  110  may also initiate the delay timer  554 . Once deregistered, the UE  110  may proceed to transmitting an extended service request  558  for the LTE-RAN  122  to perform the CSFB procedure  560 . The LTE-RAN  122  and the legacy RAN  120  may perform a legacy handover  562  and the first call may be performed  564  as a circuit switched call using the legacy RAN  120 . Once the call is completed, a teardown  566  with the legacy RAN  120  may be performed and a LTE connect  568  operation may be performed (which may be based on reselection or redirection initiated by the LTE-RAN  122 ). A delay process  570  may be performed to determine whether the delay timer is running. At the conclusion of the third call and after connecting  568  to the LTE-RAN  122 , the delay timer is running. Thus, the UE  110  does not perform an IMS registration. 
     After the third call, the UE  110  may be connected to the LTE-RAN  122  but not registered with the IMS  150 . In a fourth call, the UE  110  may receive a call input  572  from the user to perform a call. The UE  110  may perform a counter process  574  in determining whether the threshold for the timeout counter has been reached from previous VoLTE call attempts. For the fourth call, the timeout counter may still be at 2 instances which satisfies the threshold for the timeout counter. The counter process  574  may also identify that the UE  110  is not registered with the IMS  150 . Thus, the UE  110  may proceed to transmitting an extended service request  576  for the LTE-RAN  122  to perform the CSFB procedure  578 . The LTE-RAN  122  and the legacy RAN  120  may perform a legacy handover  580  and the first call may be performed  582  as a circuit switched call using the legacy RAN  120 . Once the call is completed, a teardown  584  with the legacy RAN  120  may be performed and a LTE connect  586  operation may be performed. A delay process  588  may be performed to determine whether the delay timer is running. At the conclusion of the fourth call and after connecting  586  to the LTE-RAN  122 , the delay timer is running. Thus, the UE  110  does not perform an IMS registration. 
     At a later time, the delay timer  554  may expire. Based on this event, the UE  110  may determine that, if still connected to the LTE-RAN  122 , the UE  110  is to perform an IMS registration  590 . Thus, the UE  110  may again attempt to perform VoLTE calls for subsequent call inputs. 
     It is noted that the delay timer  554  expiring after the conclusion of a call is only exemplary. As the delay timer  554  may be a duration that is triggered upon determining that the timeout counter satisfies a threshold and the arbitrary times at which calls are made by a user, the delay timer may expire during a call. Thus, a delay process that is performed may indicate that the delay timer is not running. Accordingly, at the conclusion of a call during which the delay timer had expired, the UE  110  may perform an IMS registration. 
       FIG. 6  shows an exemplary method  600  for improving a call setup time in irregular network conditions according to various exemplary embodiments described herein. The method  600  may utilize a timeout counter and a delay timer to improve the call setup time by utilizing a CSFB procedure at an earlier opportunity. The method  600  may also eliminate a window associated with attempting a VoLTE call that significantly reduces the call setup time. The method  600  may be performed by the call engine  235 , the registration engine  240 , and the delay engine  245 , and/or other components of the UE  110 . The method  600  will be described with regard to the network arrangement  100  of  FIG. 3  and the UE  110  of  FIG. 4 . 
     In  605 , the UE  110  connects to the LTE-RAN  122 . Those skilled in the art will understand the various operations that are performed for the UE  110  to associate with a network. Once connected to the LTE-RAN  122 , in  610 , the UE registers with the IMS  150 . As described above, the registration with the IMS  150  may be performed using a plurality of requests that result in the UE  110  being registered with the IMS  150  and being configured to utilize the features that the IMS  150  provides. 
     At a later time, in  615 , the UE  110  receives a call input from a user to place a call to another user using a further UE (e.g., UE  112 ,  114 ). The call input may be a selection from a contact list where the selection is associated with a PSTN number that is linked to the further UE. In using the mechanism according to the exemplary embodiments, an initial determination may be performed as to whether the VoLTE call option is available. Thus, in  620 , the UE  110  determines whether the UE  110  is registered to the IMS  150 . Since the UE  110  has performed  605  and  610 , in this pass of the method  600 , the UE  110  is registered to the IMS  150 . 
     In  625 , the UE  110  may then determine a number of prior timeout instances as being tracked with a timeout counter. In  630 , the UE  110  determines whether the number of prior timeout instances is at least a threshold. As noted above, the threshold for the timeout counter may be based on a time window or IMS conditions. For example, the threshold may be 5 timeout instances in a 15 minute time window. In another example, the threshold may be 2 timeout instances while the IMS conditions remain unchanged. Assuming this is a first pass of the method  600  when  605  and  610  are performed, there may not be any prior timeout instances. Thus, the UE  110  continues to  635 . 
     In  635 , with the UE  110  being registered with the IMS  150  and the timeout counter being under the threshold, the UE  110  attempts to place the call as a VoLTE call. Specifically, the UE  110  may transmit an invite to the LTE-RAN  122  which is processed by the IMS  150  (if available). In  640 , the UE  110  determines whether the VoLTE call has been established. Specifically, the UE  110  may determine whether a response (e.g., 100 trying message) to the invite has been received within an available response window. For example, the response window may be 3,000 ms. If the VoLTE call has been established, the UE  110  continues to  645  where the call is performed as a VoLTE call. Thereafter, upon completion of the call, the UE  110  returns to  615 . After performing  645 , the UE  110  may remain connected to the LTE-RAN  122  and remain registered to the IMS  150 . 
     If the VoLTE call has not been established and no response from the IMS  150  is received within the response window, the UE  110  continues from  640  to  650 . In  650 , the UE  110  determines that a timeout instance has occurred and increments the timeout counter. In  655 , in view of the VoLTE call attempt failing, the UE  110  transmits an extended service request so that the CSFB procedure may be performed. Thus, in  660 , the call is performed as a circuit switched call. As noted above, based on the extended service request, the LTE-RAN  122  may perform a handover to the legacy RAN  120  for the circuit switched call to be performed. 
     Once the call has completed, in  665 , the UE  110  connects to the LTE-RAN  122 . For example, a teardown of the connection to the legacy RAN  120  is performed so that the UE  110  may connect to the LTE-RAN  122 . Once reconnected to the LTE-RAN  122 , in  670 , the UE  110  determines whether a delay timer is running. In this pass of the method  600 , the delay timer is not running. Accordingly, the UE  110  returns to  610  where the UE  110  registers with the IMS  150 . 
     At a later time, when another call input is received and a plurality of passes of the method  600  are performed, the UE  110  may be registered to the IMS  150  and the timeout counter may indicate that the number of instances of timeouts from attempting VoLTE calls has exceeded the threshold. That is, for the previous calls that are performed, the method  600  may have been performed through  635 - 655  until a current call where the timeout counter has reached the threshold. Thus, in this next call, in  630 , the UE  110  continues from  630  to  675 . 
     In  675 , the UE  110  deregisters from the IMS  150 . By deregistering from the IMS  150 , the UE  110  may bypass performing an attempt of the call as a VoLTE call. Furthermore, in  680 , the UE  110  starts the delay timer. As noted above, the delay timer may be set to a network maintenance period of 12 hours or implementation specific. After deregistering from the IMS  150  and starting the delay timer, the UE  110  continues to  655  where the extended service request is transmitted and the CSFB procedure is performed, then to  660  to perform the call as a circuit switched call, and after the call is completed, to  665  where the UE  110  connects to the LTE-RAN  122 . 
     In this pass of the method  600 , in  670 , the UE  110  may determine that the delay timer is running since the delay timer was started from performing  680 . With the timer running, the UE  110  continues from  670  to  685  where the UE  110  connects to the LTE-RAN  122  but remains unregistered with the IMS  150 . The UE  110  then returns to  615 . 
     While the delay timer is running and the UE  110  is not registered with the IMS  150  after completing a circuit switched call, a further call input may be received in  615 . In this instance, in  620 , the UE  110  determines that the UE  110  is not registered with the IMS  150 . Thus, the UE  110  continues from  620  to  655  to transmit an extended service request for the CSFB procedure to be performed. 
     The method  600  may be used for each call input that is received and may proceed based on the conditions being experienced by the UE  110  at the time the call input is received. Thus, when IMS registered and the IMS  150  being responsive, the VoLTE call may be used. When IMS registered and the IMS  150  being unresponsive, the timeout counter may be tracked. When IMS registered and the timeout counter satisfying the threshold, the UE  110  may deregister from the IMS  150 , start the delay timer, and immediately perform the CSFB procedure without performing a VoLTE call attempt (e.g., including using a window of time to wait for a response from the IMS  150 ). When not registered to the IMS  150 , the UE  110  may immediately perform the CSFB procedure without performing a VoLTE call attempt as this option is not available. After each completing each circuit switched call and after reconnecting to the LTE-RAN  122 , the UE  110  may determine whether the delay timer is still running so that the IMS registration may be performed if the delay timer is not running or remain unregistered with the IMS  150  if the delay timer is running. 
     The method  600  may be modified to incorporate a LTE-RAN  122  that does not include or utilize the SG interface. That is, the LTE-RAN  122  may not be capable of using the CSFB procedure. Thus, after  640 , when the VoLTE call is not established, prior to  650 , the method  600  may determine if the LTE-RAN  122  is LTE only or is capable of providing the CSFB procedure. If the LTE-RAN is capable of providing the CSFB procedure, the UE  110  may continue to  650 . However, if the LTE-RAN  122  is LTE only, the UE  110  may again attempt to perform the call as a VoLTE call or indicate a failed call. 
     The method  600  may also include further operations that run independently of the calls being performed. 
     Specifically, the method  600  may also incorporate operations involved in determining whether the delay timer is to be stopped. For example, the method  600  may incorporate the naturally occurring event that stops the delay timer (e.g., when the delay timer expires). When the delay timer expires, the UE  110  may then perform the IMS registration, particularly when between calls. The method  600  may also incorporate independent events that stop the delay timer. For example, when the UE  110  registers an area update, this event may trigger the delay timer to stop and the IMS registration to be performed, particularly when between calls. 
     The exemplary embodiments provide a device, system, and method of improving a call setup time. By tracking a number of timeout instances that occur from attempting VoLTE calls, the exemplary embodiments may determine whether a UE is experiencing irregular network conditions that result in continued failures of VoLTE call attempts. Rather than continuing to try to use VoLTE calls, the exemplary embodiments may bypass the VoLTE call attempt and instead use a CSFB procedure to perform the call as a circuit switched call. Accordingly, when the timeout instances reach a threshold, the CSFB procedure may be used while the VoLTE call attempt may be bypassed. Furthermore, upon the timeout instances reaching the threshold, a delay timer may be started that defines a duration of time in which the UE  110  is prevented from registering with the IMS after completion of a circuit switched call. Thus, after a circuit switched call, if the delay timer is running, the UE may reconnect to the LTE-RAN but remain unregistered with the IMS. Any call placed while the delay timer is running and the UE remaining unregistered to the IMS may be performed as a circuit switched call using the CSFB procedure. In using the mechanism according to the exemplary embodiments, the call setup time may be reduced significantly (e.g., reduced by 6 to 8 seconds), thereby improving user performance. Furthermore, the UE may avoid signaling for IMS registrations at each instance that the IMS registration is to otherwise be performed due to a timeout, thereby reducing IMS signaling. 
     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 to the present disclosure, without departing from the spirit or the scope of the exemplary embodiments. Thus, it is intended that the present disclosure cover modifications and variations of the exemplary embodiments invention provided they come within the scope of the appended claims and their equivalent.

Metadata:
Filing Date: 20180531
Publication Date: 20220426
Grant Date: 20220426
Priority Date: 20180531
Inventors: BALASUBRAMANIAN, SUNDARRAMAN
VENKATARAMAN, VIJAY
KADRI, NORDINE
MCFARLANE, ALISTAIR
Assignee: APPLE INC
CPC Classifications: [{"code": "H04W36/00224", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/1045", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W36/26", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/1069", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W76/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L43/16", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/1046", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/1073", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W76/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/80", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W60/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04L65/1016", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/1016", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W36/26", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W60/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W36/0022", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04L65/1069", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/1016", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W76/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L43/16", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/1069", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W36/00224", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 68693480