PATENT DOCUMENT

Publication Number: US-10863428-B2
Application Number: US-201514869325-A
Country: US
Kind Code: B2

Title: Apparatus, system and method for optimized tune away procedures

Abstract:
A user equipment and a method performed by the user equipment that has a transceiver configured to enable the user equipment to establish a connection with a first network and a second network. The method including establishing a connection to each of the first network and the second network, tuning away from the first network to the second network, tuning back to the first network from the second network and determining whether to perform a network operation with the first network after tuning back to the first network.

Claims:
What is claimed is: 
     
       1. A method comprising:
 at a user equipment having a transceiver configured to enable the user equipment to establish a connection with a first network and a second network:
 establishing a connection to each of the first network and the second network; 
 tuning away from the first network to the second network,
 wherein the tuning away causes a loss of synchronization with the first network; 
 
 tuning back to the first network from the second network; 
 after tuning back to the first network and prior to a subsequent tuning away from the first network to the second network, determining whether to perform a network operation to reestablish synchronization with the first network based on whether a predetermined condition is met, wherein the determining whether the predetermined condition is met includes determining an amount of data in an uplink buffer of the user equipment; and 
 performing the network operation to reestablish synchronization with the first network during a time duration between the tuning back to the first network and the subsequent tuning away from the first network to the second network only when the predetermined condition is met, wherein the UE does not attempt to reestablish synchronization with the first network during the time duration when the predetermined condition is not met. 
 
 
     
     
       2. The method of  claim 1 , wherein the network operation includes one of transmitting a scheduling request to the first network or initiating a random access channel (RACH) procedure with the first network. 
     
     
       3. The method of  claim 1 , wherein the user equipment omits performing the network operation after tuning back to the first network. 
     
     
       4. The method of  claim 1 , wherein the network operation is performed when the amount of data in the uplink buffer is greater than a threshold. 
     
     
       5. The method of  claim 4 , wherein the threshold is based on one of an amount of data required to maintain the connection to the first network, an identification of the first network, a type of the user equipment, a level of service for the user equipment or a connection quality parameter of the connection to the first network. 
     
     
       6. The method of  claim 1 , wherein the determining whether the predetermined condition is met further includes:
 determining a duration between the tuning away and the tuning back. 
 
     
     
       7. The method of  claim 6 , wherein the network operation is performed when the duration exceeds a threshold, and wherein the threshold is based on the amount of data in the buffer. 
     
     
       8. The method of  claim 1 , wherein the determining whether the predetermined condition is met further includes:
 estimating a duration of an inactivity timer of the first network; and 
 performing the network operation when the tuning away from the first network occurs within a time threshold of an estimated expiration of the inactivity timer. 
 
     
     
       9. The method of  claim 8 , wherein the inactivity timer is a radio resource control (RRC) timer of the first network. 
     
     
       10. The method of  claim 8 , wherein the estimating the duration of the inactivity timer includes one of:
 determining an action was performed by the first network for the user equipment based on the inactivity timer; or 
 determining an action was performed by the first network for other user equipment connected to the first network based on the inactivity timer. 
 
     
     
       11. The method of  claim 1 , wherein the first network is an LTE network and the second network is a CDMA network. 
     
     
       12. A user equipment, comprising:
 an uplink buffer; 
 a transceiver configured to enable the user equipment to establish a connection with a first network and a second network; and 
 a processor configured to:
 instruct the transceiver to establish a connection to each of the first network and the second network; 
 instruct the transceiver to tune away from the first network to the second network,
 wherein the tuning away causes a loss of synchronization with the first network; 
 
 instruct the transceiver to tune back to the first network from the second network; 
 after tuning back to the first network and prior to a subsequent tuning away from the first network to the second network, determine whether to perform a network operation to reestablish synchronization with the first network based on whether a predetermined condition is met, wherein the determining whether the predetermined condition is met includes the processor determining an amount of data in the uplink buffer; and 
 perform the network operation to reestablish synchronization with the first network during a time duration between the tuning back to the first network and the subsequent tuning away from the first network to the second network only when the predetermined condition is met, wherein the UE does not attempt to reestablish synchronization with the first network during the time duration when the predetermined condition is not met. 
 
 
     
     
       13. The user equipment of  claim 12 , wherein the network operation includes one of transmitting a scheduling request to the first network or initiating a random access channel (RACH) procedure with the first network. 
     
     
       14. The user equipment of  claim 12 , wherein the processor determines whether the predetermined condition is met by further determining a duration between the tuning away and the tuning back. 
     
     
       15. The user equipment of  claim 12 , wherein the processor determines whether the predetermined condition is met further by:
 estimating a duration of an inactivity timer of the first network; and 
 performing the network operation when the tuning away from the first network occurs within a time threshold of an estimated expiration of the inactivity timer. 
 
     
     
       16. The user equipment of  claim 15 , further comprising:
 a timer, wherein the timer measures a time since a last uplink transmission by the user equipment, the time being compared to the time threshold. 
 
     
     
       17. The user equipment of  claim 15 , further comprising:
 a memory storing one of:
 an action performed by the first network for the user equipment based on the inactivity timer; or 
 an action performed by the first network for other user equipment connected to the first network based on the inactivity timer. 
 
 
     
     
       18. A non-transitory computer-readable medium comprising a set of instructions that, when executed, cause a processor to perform operations, comprising:
 establishing a connection by a user equipment to each of a first network and a second network; 
 tuning away the user equipment from the first network to the second network,
 wherein the tuning away causes a loss of synchronization with the first network; 
 
 tuning back the user equipment to the first network from the second network; 
 after tuning back to the first network and prior to a subsequent tuning away from the first network to the second network, determining whether to perform a network operation to reestablish synchronization with the first network based on whether a predetermined condition is met, wherein the determining whether the predetermined condition is met includes determining an amount of data in an uplink buffer of the user equipment; and 
 performing the network operation to reestablish synchronization with the first network during a time duration between the tuning back to the first network and the subsequent tuning away from the first network to the second network only when the predetermined condition is met, wherein the UE does not attempt to reestablish synchronization with the first network during the time duration when the predetermined condition is not met and wherein the network operation includes to reestablish synchronization with the first network includes one of transmitting a scheduling request to the first network.

Description:
PRIORITY INFORMATION/INCORPORATION BY REFERENCE 
     This application claims priority to U.S. Provisional Application 62/165,602 entitled “Apparatus, System and Method for Optimized Tune Away Procedures,” filed on May 22, 2015, the entirety of which is incorporated herein by reference. 
    
    
     BACKGROUND INFORMATION 
     A user equipment (UE) may be configured to establish a connection with a network. For example, the UE may be mobile device and utilize a wireless communications protocol. Based upon the capabilities of the hardware and software of the UE, the connection may be made with different types of networks. In a first example, the network may be a Long Term Evolution (LTE) network. In a second example, the network may be a Code Division Multiple Access (CDMA) network. 
     The UE may connect to the LTE network for data connectivity and to the CDMA network for voice connectivity. The UE may be a Single Radio LTE (SR-LTE) equipped device. In such a scenario, the UE may establish a connection with the LTE network only to tune away (at least temporarily) to the CDMA network to determine if a voice call is destined for the UE on the CDMA network. Subsequently, the UE may tune back to the LTE network. In a typical scenario, the UE tunes away to the CDMA network based on the CDMA network&#39;s paging cycle (e.g., every 5.12 seconds). The typical duration for the tune away is 80-200 milliseconds (ms). 
     When the UE tunes back to the LTE network, the UE sends a scheduling request to the evolved Node B (eNB) of the LTE network to determine that the uplink (UL) connection is in-sync. If the UE is out of sync, as may be indicated by a UL-OUT_OF_SYNC event, the UE will trigger a Random Access Channel (RACH) procedure to attempt to re-synchronize with the LTE network. The initiation of the RACH procedure causes the UE to use additional battery and transmission resources and also causes the network (e.g., the eNB) to use additional computing and transmission resources. 
     SUMMARY 
     In one exemplary embodiment, a method is performed by a user equipment having a transceiver configured to enable the user equipment to establish a connection with a first network and a second network. The method includes establishing a connection to each of the first network and the second network, tuning away from the first network to the second network, tuning back to the first network from the second network and determining whether to perform a network operation with the first network after tuning back to the first network. 
     In another exemplary embodiment, a user equipment has a transceiver configured to enable the user equipment to establish a connection with a first network and a second network and a processor configured to instruct the transceiver to establish a connection to each of the first network and the second network, instruct the transceiver to tune away from the first network to the second network, instruct the transceiver to tune back to the first network from the second network and determine whether to perform a network operation with the first network after tuning back to the first network. 
     In a further exemplary embodiment, a nonvolatile computer-readable medium comprises a set of instructions that, when executed, cause a processor to perform operations. The operations include establishing a connection by a user equipment to each of a first network and a second network, tuning away the user equipment from the first network to the second network, tuning back the user equipment to the first network from the second network and determining whether to perform a network operation with the first network after tuning back to the first network, wherein the network operation includes one of transmitting a scheduling request to the first network or initiating a random access channel (RACH) procedure with the first network. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an exemplary network arrangement, according to various embodiments. 
         FIG. 2  shows an exemplary user equipment (UE) configured to control whether to initiate a scheduling request or RACH procedure by the UE, according to various embodiments. 
         FIG. 3  shows an exemplary signaling diagram controlling whether to initiate a scheduling request or RACH procedure by the UE when tuning back to an LTE network, according to various embodiments. 
         FIG. 4  shows an exemplary method for controlling whether to initiate a scheduling request or RACH procedure by the UE when tuning back to an LTE network, according to various embodiments. 
     
    
    
     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 an apparatus, system and method for optimizing tune away procedures of a user equipment (UE) that connects to multiple networks. The UE may be configured to establish a connection with different types of networks such as an LTE network, a CDMA network, a Global System for Mobile Communications (GSM) network, etc. The UE may perform tune-away and tune-back procedures in view of this capability. The exemplary embodiments provide a mechanism to keep the UE in an out of sync state on tune back, under certain circumstances, to save power and resources at the UE and resources at the network. 
       FIG. 1  shows an exemplary network arrangement  100 , according to various embodiments. The exemplary 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, 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. 
     Each of the UEs  110 - 114  may be configured to communicate directly 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 . More specifically, the legacy RAN  120  may be a CDMA network. 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 and may also communicate using a wired connection. With regards to the exemplary embodiments, the UEs  110 - 114  may establish a connection with the LTE-RAN  122  to, among other functionalities, perform data transfers with the LTE network. In another example, the UEs  110 - 114  may communicate with the legacy RAN  120  that is a CDMA network. 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  particularly using the CDMA configuration 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 client stations  110 - 114  to communicate with the WLAN  124 . 
     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 . This subscription information is used to provide the correct multimedia services to the user. 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. 
     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  connecting to the legacy RAN  120  and the LTE-RAN  122 , the connection to the LTE-RAN  122  being via an eNB  122 A. Initially, the UEs  110 - 114  may 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 access point (e.g., the eNB  122 A of the LTE-RAN  122 ). Thus, the UEs  110 - 114  that are associated with the eNB  122 A may utilize the connected state discontinuous reception (“CDRX”) functionality when configured to perform this feature. Subsequently, while associated with the eNB  122 A and connected to the LTE-RAN  122 , the UE may tune away to the legacy RAN  120  for a temporary amount of time. During this tune away time, the UE may check for activity in the legacy RAN  120 . In a specific embodiment where the UE is receiving data connectivity from the LTE-RAN  122  and voice connectivity from the legacy RAN  120 , the activity may be pages from the legacy RAN  120 . The UE may then tune back to the LTE-RAN  122 . 
     From the UE perspective, the connection with the LTE-RAN  122  remains the same. That is, the temporary tuning away from the LTE-RAN  122  to the legacy RAN  120  does not have any impact on the connection. More specifically, upon the UE tuning back to the LTE-RAN  122 , the UE expects a substantially similar connection with the LTE-RAN  122  as if the tune-away procedure was not even performed. With the knowledge of the tune-away procedure being performed, the UE therefore expects no change in service when tuning back to the LTE-RAN  122 . 
     When the UE tunes away to the legacy RAN  120  and then tunes back to the LTE-RAN  122 , the UE may send a scheduling request to the eNB  122 A to determine if the uplink (UL) of the UE remains in-sync with the eNB  122 A. Synchronization of the UE with the eNB  122 A may be considered a time alignment between the UE and eNB  122 A that is a result of the RACH procedure. The determination made by the UE after the tune back is to determine if the time alignment from the last RACH procedure through the last downlink (DL) or UL transmissions is ongoing and remains valid. In one exemplary scenario, the UE may lose synchronization because the UE has not exchanged data with LTE-RAN  122  for a long period of time (e.g., the time of the tune away). In the exemplary embodiments, the LTE-RAN  122  may provide the UE with a time alignment timer (TAT) via, for example, the RRCReconfiguration message. The LTE-RAN  122  is configured to send timing advance commands (TA) with the duration of TAT, such that UE may assume it is in sync with LTE-RAN  122 . On expiry of the TAT (e.g., no receipt of a timing advance command), the UE may consider that it is in the out of sync state (e.g., UL_OUT_OF_SYNC) with the LTE_RAN  122 . In current implementations, when the UE detects it is out of sync, the UE will initiate a RACH procedure with the eNB  122 A to come back into synchronization. 
     However, according to the exemplary embodiments, there may be circumstances where it is more efficient for the UE to remain out of sync with the eNB  122 A. Exemplary circumstances for allowing the UE to remain out of sync will be described in greater detail below. Examples of the potential efficiencies gained by allowing the UE to remain out of sync may include power and resource savings associated with not sending the scheduling request, not performing the RACH procedure, releasing its UL Physical Uplink Control Channels (PUCCH) and not sending other signals (e.g., Channel Quality Indicators (CQI), Rank Indication (RI), Precoding Matrix Indicator (PMI), etc.) to the LTE-RAN  122 . In addition, there may also be resource savings realized on the network side (e.g., at eNB  122 A) because the eNB  122 A may stop transmitting timing advance (TA) commands to the UE, which may also allow the eNB  122 A to increase the cell capacity. Thus, the exemplary embodiments provide apparatus, systems and methods for controlling the frequency of scheduling requests (SR) and RACH triggers after the UE tunes back to the LTE-RAN  122 . 
       FIG. 2  shows the UE  110  of the network arrangement  100  of  FIG. 1  that is configured to control the frequency of SRs and RACH triggers after the UE  110  tunes back to the LTE-RAN  122 , according to various embodiments. Specifically, the UE  110  includes functionality that controls when a SR and/or RACH procedure is initiated after the UE  110  tunes back to the LTE-RAN  122  after tuning away to the legacy RAN  120 . For exemplary purposes, the UE  110  may also represent the UEs  112 ,  114 . However, it should be noted that the other UEs  112 ,  114  may not necessarily be capable of performing the functionalities described below with regard to the UE  110 . 
     The UE  110  may represent any electronic device that is configured to perform wireless functionalities and may be representative of one or more of the UEs  110 - 114 . For example, 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 and/or WiFi functionalities. 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, 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, etc. 
     The processor  205  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  225 . The use of the web browser may entail requesting uplink grants to transmit requests to the web browser or downlink grants to receive data from a website. Those skilled in the art will understand that these grants may be LTE data traffic performed while the UE  110  is connected to the LTE-RAN  122  via the eNB  122 A. In yet another example, the processor  205  may execute a tune away application  235  to control when a SR and/or RACH procedure is initiated after the UE  110  tunes back to the LTE-RAN  122  after tuning away to the legacy RAN  120 . 
     It should be noted that the above noted applications being an application (e.g., a program) executed by the processor  205  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. In addition, in some UEs, the functionality described for the processor  205  is split among two processors, a baseband processor and an applications processor. The exemplary embodiments may be implemented in any of these or other configurations of the UE. 
     The memory  210  may be a hardware component configured to store data related to operations performed by the UE  110 . Specifically, the memory  210  may store data related to the tune away function that may be used by the tune away application  235  to perform the functionalities described herein. 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 transmit and receive data with the eNB  122 A. The transceiver  225  may enable communication with the LTE-RAN  122  or with other electronic devices directly or indirectly through the LTE-RAN  122  to which the UE  110  is connected. The transceiver  225  may operate on a variety of different frequencies or channels (e.g., set of consecutive frequencies). For example, the transceiver  225  may connect to the legacy RAN  120  using corresponding frequencies and also connect to the LTE-RAN  122  using corresponding frequencies. Thus, an antenna or multiple antennae (not shown) coupled with the transceiver  225  may enable the transceiver  225  to operate on these frequency bands. 
     As discussed above, the exemplary embodiments utilize the tune away application  235  to control when a SR and/or RACH procedure is initiated after the UE  110  tunes back to the LTE-RAN  122 . In a first exemplary mechanism, the tune away application  235  may control whether to initiate a SR or RACH procedure based on a quantity of data that is in the MAC UL buffer. For example, if there is no data or very little data in the MAC UL buffer, the tune away application  235  may determine that no SR or RACH procedure should be initiated. In a second exemplary mechanism, the tune away application  235  may control whether to initiate a SR or RACH procedure based on the duration of the tune away to the legacy RAN  120 . For example, the longer the tune away, the more likely that a SR or RACH procedure should be initiated. In a third exemplary mechanism, the tune away application  235  may control whether to initiate a SR or RACH procedure based on the radio resource control (RRC) inactivity timer of the network. In this example, the UE  110  may learn about the operation of the RRC inactivity timer and base the decision whether to initiate a SR or RACH procedure on the operation of the RRC inactivity timer. Each of these exemplary mechanisms will be described in greater detail below. 
       FIG. 3  shows an exemplary signaling diagram  300  for controlling whether to initiate a SR or RACH procedure by the UE  110  when tuning back to the LTE-RAN  122 , according to various embodiments. Thus, the signaling diagram  300  relates to when the UE  110  performs a tune-away procedure to tune away from the LTE-RAN  122  to the legacy RAN  120  and tune back from the legacy RAN  120  to the LTE-RAN  122 . 
     The signaling diagram  300  illustrates a generic procedure to first connect to the LTE-RAN  122  by the UE  110 . Specifically, the UE  110  transmits a connection request  305  when the UE  110  is within an operating area of the eNB  122 A and detects the presence of the LTE-RAN  122 . The eNB  122 A may transmit a connection reply  310  to the UE  110 . Subsequently, a connection  315  may be established between the LTE-RAN  122  and the UE  110 . The initiation of the RACH procedure by the UE  110  may occur during the connection request  305  or the connection establishment  315 . However, in any case, the synchronization between the UE  110  and the eNB  122 A is established by the completion of the connection establishment  315 . 
     While connected to the LTE-RAN  122 , the UE  110  may perform a tune-away procedure  320  to the legacy RAN  120  such as a CDMA network to check for activity. The tune-away procedure may be performed in a variety of manners such as periodically, aperiodically, upon request, etc. In one exemplary embodiment, the frequency and timing of the tune away procedure is based on the paging schedule of the legacy RAN  120 . When the UE  110  eventually tunes back  325  to the LTE-RAN  122 , the UE  110  determines  330  whether the UE  110  should initiate a SR or RACH procedure. Examples of mechanisms for making the SR/RACH determination were provided above and will be described in greater detail below. 
     In the exemplary signaling diagram  300 , it may be considered that the UE  110  determination  330  indicates that no SR/RACH initiation should be performed at the time of tune back. Thus, the UE  110  will not initiate a SR or RACH procedure and no corresponding signals (e.g., signals associated with SR or RACH) will be exchanged between the UE  110  and the eNB  122 A. Those skilled in the art will understand that the determination  330  may have resulted in the opposite determination (e.g., SR and/or RACH should be initiated) and the appropriate steps for initiating the SR and/or RACH will be performed. An example of this signaling will be provided below. It should also be noted that the determination  330  may be performed one time at tune back  325  or be an ongoing process. For example if the determination is an ongoing process, the UE  110  may continuously perform the determination  330  after the tune back  325  and not wait until the next tune back. To provide a specific use case, if the mechanism used to perform the SR/RACH determination is the quantity of data in the MAC UL Buffer, the quantity may be below a threshold at the time of tune back  325 , but may exceed the threshold before the onset of the next tune away  335 . In such a situation, if the UE  110  is continuously performing the determination  330  when the UE  110  is connected to the LTE-RAN  122  after tune back  325 , the UE  110  may determine that the SR or RACH procedure should be performed when the amount of data in the UL buffer reaches a threshold amount. 
     At a later time, the UE  110  will once again tune away  335  to the legacy RAN  120  and then tune back  340  to the LTE-RAN  122 . After the tune back  340 , the UE  110  will once again determine  345  whether the UE  110  should initiate a SR or RACH procedure. In this exemplary signaling diagram  300 , it is considered that the UE  110  determines that an SR or and/or RACH procedure should be initiated. Thus, the UE  110  will initiate  350  either the SR or RACH procedure and UL synchronization  355  will be established between the UE  110  and the eNB  122 A such that the UE  110  may send data over the UL channel to the eNB  122 A. 
     Accordingly, the UE  110  does not automatically perform the SR (after tune back) or RACH procedure (when out of sync), but rather performs an analysis to determine if the SR and/or RACH procedure is needed after tune back. As described above, this selective use of SR and/or RACH may improve the performance of both the UE  110  and the eNB  122 A. 
       FIG. 4  shows an exemplary method for controlling whether to initiate a scheduling request or RACH procedure by the UE when tuning back to an LTE network, according to various embodiments. The method  400  will be described with reference to the UE  110  performing the various functionalities. The method  400  will also be described with reference to the network arrangement  100  of  FIG. 1 , the UE  110  of  FIG. 2 , and the signaling diagram  300  of  FIG. 3 . 
     In  405 , the UE  110  establishes a connection with the LTE-RAN  122  via the eNB  122 A. As discussed above, any association process may be used. While the UE  110  is connected to the LTE-RAN  122 , the UE  110 , in  410 , may perform a tune-away procedure  410 . Because the UE  110  may be configured to establish a connection to different types of networks, the tune-away procedure may be performed such that the UE  110  tunes away from the LTE-RAN  122  to the legacy RAN  120  that may be a CDMA network. The tune-away procedure may enable the UE  110  to check for activity on the legacy RAN  120  prior to tuning back. 
     In  415 , the UE  110  tunes back from the legacy RAN  120  to the LTE-RAN  122 . When the UE  110  tunes back, the UE  110  determines, in  420 , whether an SR or RACH procedure should be performed. As described above, there may be multiple manners or mechanisms for determining whether an SR or RACH procedure should be performed. In a first exemplary mechanism, the tune away application  235  may monitor the MAC UL Buffer to determine the amount of data in the buffer when the UE  110  resumes operation of the LTE stack. Those skilled in the art will understand that the MAC UL buffer holds the data that the UE  110  will send via the UL channel to the eNB  122 A. The amount of data in the buffer may be a variable that is included in the internal statistics of the MAC UL buffer and the variable may be available for the tune away application  235 . If there is no data in the MAC UL buffer, then the tune away application  235  may determine that there is no need to perform the SR and/or RACH procedure because the UE  110  has no data that needs to be communicated via the UL channel. Those skilled in the art will understand that the MAC UL buffer is only exemplary and that other buffers or storage mechanisms may be used to store or queue data that is to be transmitted on the UL channel by the UE  110 . Any of these buffers or storage mechanisms may be used in the same manner as described for the MAC UL buffer. 
     However, the determination may not be limited to a Boolean determination of data or no data in the MAC UL buffer. There may also be a threshold value of data. This threshold value of data is an amount of data below which the tune away application  235  determines that there is no need to perform the SR and/or RACH procedure and above which the tune away application  235  determines that the SR and/or RACH procedure should be performed. The threshold amount of data may be set based on any number of factors. For example, the threshold may be set to a value where it is likely that critical information to keep the connection between the UE  110  and the eNB  122 A active is in the MAC UL buffer and needs to be communicated via the UL channel. In another example, the threshold may be set based on performance parameters wherein it is determined that not sending the UL data results in a degraded user experience. The threshold may be set individually based on the carrier network, type of device, level of service for device, connection quality parameters, etc. 
     In a second exemplary mechanism, the determination by the tune away application  235  of whether to initiate a SR and/or RACH procedure may depend on the duration of the tune away (e.g., the time between tune away  320  and tune back  325 ). For example, if the duration of the tune away is below a threshold time (e.g., 80 ms), it may be assumed that the UE  110  may have remained in sync with the eNB  122 A and there is no need to initiate an SR and/or RACH procedure. On the other hand, a delay of longer than the threshold may indicate that it is likely that the UE  110  is out of sync and therefore the SR and/or RACH procedure should be initiated. Those skilled in the art will understand that the threshold of 80 ms is only exemplary and that other duration thresholds may be set based on any number of factors. 
     In addition, it should be noted that the first and second mechanisms may both be used in the determination in  420 . For example, the tune away application  235  may evaluate both mechanisms when making the determination in  420 . If either condition is satisfied (e.g., the amount of information in the buffer is greater than the threshold or if the duration of the tune away is greater than the threshold), the tune away application may determine that the UE  110  should initiate the SR and/or RACH procedure. In another example, the thresholds of the first or second mechanisms may be variable based on the value of the other mechanism. For example, if there is no data in the buffer, the threshold for the duration may be longer. However, if there is data in the buffer that is below the buffer data threshold, the threshold for the duration may be set lower. Those skilled in the art will be able to determine other combinations of variables and values based on these examples. 
     In a third exemplary mechanism, the tune away application  235  may learn about the operation of the RRC inactivity timer. The RRC inactivity timer is a timer that is controlled by the network (e.g., LTE-RAN  122 ). In LTE networks, when the RRC inactivity timer times out (e.g., the eNB  122 A has not received any communication from the UE  110  for the duration of the timer), the eNB  122 A releases the RRC connection between the eNB  122 A and the UE  110 . However, the setting for RRC inactivity timers may vary across provider networks or even within the same provider network based on a variety of factors such as congestion, time of day, etc. Thus, the UE  110  may not have specific knowledge of when its connection will be released based on the RRC inactivity timer. The goal of the UE  110  is to not be released if the UE  110 , in fact, has data that is to be sent to the eNB  122 A. If the UE  110  does not perform the SR and/or RACH procedure, the RRC connection may be released because there was no UL communication between the UE  110  and the eNB  122 A before the expiration of the RRC inactivity timer of the LTE-RAN  122 . However, as will be described in greater detail below, the tune away application  235  may learn about the operation of the RRC inactivity timer (e.g., predict when the eNB  122 A is likely to release the RRC connection) and consider this when making the determination in  420  whether to initiate the SR and/or RACH procedure. 
     In one exemplary embodiment, the tune away application  235  may determine the current release pattern for the UE  110 . That is, the tune away application  235  may record when the eNB  122 A has released the RRC connection with the UE  110  and the duration of the UL inactivity when the connection is released. Those skilled in the art will understand that not every RRC connection release is driven by the RRC inactivity timer, there may be other reasons for the connection release such as a radio link failure (RLF), the UE  110  moving to a different cell, etc. Thus, the tune away application  235  may factor these possibilities when estimating the duration of the RRC inactivity timer based on its previous experience with the eNB  122 A. Moreover, the tune away application  235  may not be limited to only using its experience with the eNB  122 A, but may also factor in its experience with neighboring cells or cells within a certain geographical area because it is likely that these cells have a similar RRC inactivity timer duration. In addition, the tune away application  235  may also factor in current operating conditions such as time of day, the strength of signals being received from the eNB  122 A, etc. 
     In another exemplary embodiment, the tune away application  235  may have access to the RRC inactivity timer information that is collected by other UEs that have connected to the eNB  122 A. For example, each UE that performs the analysis described above with respect to the first exemplary embodiment, may report this information to a central database so that other UEs have access to this information. The central database may be controlled by the network provider, by the provider of the device (e.g., provider of UE  110 ) or by any other entity to which the UEs send the information. The UE  110  (and tune away application  235 ) may access this database and search the database for RRC inactivity timer information for similarly situated UEs (e.g., geographic location, mobile country code (MCC), mobile network code (MNC), etc.). Based on this information, the tune away application  235  may estimate the duration of the RRC inactivity timer for the eNB  122 A. It should be noted that the tune away application may use both the specific information collected by the UE  110  and the information included in the central database to estimate the duration of the RRC inactivity timer for the eNB  122 A. 
     Once the tune away application  235  estimates the length of the RRC inactivity timer of the eNB  122 A, the tune away application may start a corresponding timer on the UE  110  side. For example, after a last UL transmission, the tune away application  235  may start a UE RRC inactivity timer having a duration of the estimated duration of the eNB  122 A RRC inactivity timer. The tune away application  235  may monitor the MAC level activity of the UE  110  (e.g., the UL transmissions) and reset the UE RRC inactivity timer based on the MAC level activity. If the tune away (e.g., tune away  320 ) occurs within a threshold (e.g., 200 ms) of the UE RRC inactivity timer expiring, then the tune away application may determine in  420  that the UE should perform a SR and/or RACH procedure upon tuning back to the LTE-RAN  122 . 
     As described above, a general goal of the UE  110  is not to have the RRC connection released. If the network side RRC inactivity timer were to time out after the UE  110  tuned back to the LTE-RAN  122  because the UE  110  did not perform the SR and/or RACH procedure, this may generally be considered a degraded condition. Thus, by estimating when this RRC connection release may occur and performing the SR and/or RACH procedure after tune back, but prior to the release, the network side RRC inactivity timer may be reset and the RRC connection release may be prevented. The threshold having a value of 200 ms is only exemplary and may be set to any value based on any number of factors. In one exemplary embodiment, the threshold may be variable based on the level of confidence in the estimate of the duration of the network RRC inactivity timer. 
     It should be understood that similar to the first and second exemplary mechanisms described above, this third exemplary mechanism may also be used alone or in conjunction with the other described mechanisms. It should also be understood that the three described mechanisms for determining in  420  whether to initiate an SR or RACH procedure are only exemplary. Those skilled in the art will understand that other mechanisms may be used in accordance with the principles described herein. 
     Returning to the method  400 , if it is determined in  420  that the UE  110  should not initiate the SR or RACH procedure, the method  400  returns to  410  where, after a predetermined period of time, the UE  110  will tune away from the LTE-RAN  122  to the legacy RAN  120 . The method  400  will then proceed in the same manner as described above. As noted previously, the determination in  420  may occur a single time or multiple times after any individual tune back and before the next tune way. 
     If it is determined in  420  that the UE  110  should initiate the SR or RACH procedure, the method proceeds to  425  where the UE  110  performs the SR to determine if the UE  110  is synchronized with the eNB  122 A and the RACH procedure to synchronize with the eNB  122 A if it is not currently synchronized. After the completion of the SR and/or RACH procedure in  425 , the method  400  returns to  410  where, after a predetermined period of time, the UE  110  will tune away from the LTE-RAN  122  to the legacy RAN  120 . 
     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 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: 20150929
Publication Date: 20201208
Grant Date: 20201208
Priority Date: 20150522
Inventors: BHATTACHARJEE, DEEPANKAR
VALLATH, SREEVALSAN
SHARMA, PRATEEK
Assignee: APPLE INC
CPC Classifications: [{"code": "H04W74/0833", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W56/0015", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W56/0015", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W76/16", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W74/0833", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W76/16", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W48/18", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W88/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W88/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W56/0015", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W74/0833", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W88/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W76/16", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W48/18", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 57325901