Patent Publication Number: US-2023144777-A1

Title: Amf based handover decision

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This patent application is a divisional application of U.S. patent application Ser. No. 16/914,108, filed on Jun. 26, 2020, entitled “MME Based Handover Decision,” which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     Many mobile devices such as smartphones access both non-cellular and cellular networks. These mobile devices may disconnect from one network in order to switch to another network. Switching from one network to another is called a handover, and mobile devices are generally configured to automatically switch networks when various network conditions are met. For example, mobile devices may switch from slow or unreliable Wi-Fi networks in order to switch to a 3 rd  Generation Partnership Project (3GPP) network such as Long-Term Evolution (LTE). However, when the available cellular signal is marginal or unstable, transitioning from Wi-Fi to LTE too early can result in a poor or dropped connection. Thus, when handover is triggered in mobile devices, the performance of the cellular network should be determined in order to improve the automatic handover in mobile devices. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The detailed description is described with reference to the accompanying figures, in which the leftmost digit(s) of a reference number identifies the figure in which the reference number first appears. The use of the same reference numbers in different figures indicates similar or identical items. 
         FIG.  1    illustrates an example system for managing handover requests for a user device connected to multiple networks, in accordance with some examples of the present disclosure. 
         FIG.  2    illustrates an example of an LTE network architecture for processing handover requests. 
         FIG.  3    is a protocol flow diagram showing an example handover process from a Wi-Fi network to an LTE network. 
         FIG.  4    illustrates an example of a 5G network architecture for processing handover requests. 
         FIG.  5    is a protocol flow diagram showing an example handover process from a Wi-Fi network to a 5G network. 
         FIG.  6    is a block diagram showing various components of an illustrative computing device that makes handover decisions based on network conditions. 
         FIG.  7    is a flow diagram of an example process for making a handover decision from the perspective of a Mobility Management Entity (MME). 
         FIG.  8    is a flow diagram of an example process for making a handover decision from the perspective of an Access and Management Mobility Function (AMF). 
         FIG.  9    is a flow diagram of an example process  900  for making a handover decision from the perspective of an MME or an AMF. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure is directed to techniques for improving Wi-Fi calling performance during the handover process between non-cellular and cellular networks. The handover process includes an attach procedure as defined in 3GPP specification TS 23.401. Handover can be classified into different types based on various aspects involved. In horizontal handover, mobile devices move from one access point to another of the same type. In vertical handover, user devices move from an access point of one type to a different type. The present disclosure is directed to handover from a first radio access technology (RAT) (e.g., Wi-Fi) to a second RAT (e.g., LTE, 5G, beyond 5G [B5G], etc.), which is a vertical handover. A handover may be mobile-initiated or network-initiated, depending on who initiated the handover process. The present disclosure is directed to mobile-initiated handover. 
     Additionally, handover can be mobile-controlled or network-controlled depending on who has primary control of the process. Further, handover can be also classified based on where it obtains information used to decide to initiate handover. For example, if a handover is network-controlled and information collected by the user device is used to assist, then the handover is mobile-assisted. Conversely, if a handover is mobile-controlled and uses information from the network, the handover is network-assisted. In various embodiments, the present disclosure is directed to a mobile-assisted handover. 
     In some aspects, the techniques include receiving a handover request from a user device. The user device may be initially connected to a network over one or more air interfaces and according to one or more RAT, such as Wi-Fi. The user device may request to connect to a 3GPP network via a second RAT, such as LTE. In the LTE network, several rounds of communication can be undertaken by various network nodes, such as an MME, a Home Location Register (HLR)/a Home Subscriber Server (HSS), evolved Packet Data Gateway (ePDG), etc., for handover to be possible. 
     The MME may identify the ePDG that is serving the user device requesting handover via the HSS, which stores the ePDG address serving the user device. Upon identifying the ePDG that is serving the requesting user device, the MME may interface with the ePDG. For the sake of clarity, a pseudo-acronym “S1x” or “new S1” has been defined to represent a new interface that is configured for communication between the ePDG and the MME. The requesting user device may provide measurement reports to the ePDG. In some aspects, the requesting user device may report received signal strength or power of reference signals (e.g., received signal strength indication [RSSI], reference signals received power [RSRP], reference signal received quality [RSRQ], etc.) at regular intervals to the ePDG. The ePDG may relay the measurement reports to the MME via the S1x interface. Based at least on the measurement reports, the MME may reject or accept the handover request from the user device. 
     In some aspects, the user device requesting handover may be initially connected to a Wi-Fi network and then select a second RAT to connect to a cellular network, wherein the second RAT may be 5G. In the 5G network, several rounds of communication can be undertaken by various network nodes, such as an AMF, Non-3GPP Interworking Function (N3IWF), Unified Data Function (UDM), etc., for handover to be possible. 
     The AMF may identify the N 3 IWF handling the user device session. Upon identifying the N3IWF serving the requesting user device, the AMF may communicate with the N3IWF via the N2 interface. The requesting user device may provide measurement reports to the N3IWF. In turn, the N3IWF may communicate the measurement reports to the AMF. The AMF may reject or accept the handover request from the user device based at least on the measurement reports. 
     Because a handover decision at the MME or the AMF is based on measurement reports of network conditions from the requesting user device, it is less likely that a poor or dropped connection will result after the completion of the handover process. The techniques described herein may be implemented in a number of ways. Example implementations are provided below with reference to the following figures. 
     Example Network Architectures 
       FIG.  1    illustrates an example system  100  for managing handover requests for a user device connected to multiple networks. The system  100  includes a user device  102  that can comprise smartphones, mobile devices, personal digital assistants (PDAs), desktop computers, laptops, tablets, smartwatches, or other electronic devices having a wireless communication function that are capable of receiving input, processing the input, and generating output data. The user device  102  may be equipped with multiple transceivers to connect to multiple wireless networks. 
     The user device  102  is configured to communicate with an access network over a physical communications interface or layer, which can include air interfaces and/or a direct-wired connection. The user device  102  may connect to any sort of access networks, such as a Global System for Mobile Communications (GSM) or Universal Mobile Telecommunications System (UMTS) network, a universal terrestrial radio network (UTRAN) or an Enhanced Data rates for GSM Evolution (EDGE) radio access network (GERAN), an evolved universal terrestrial radio access network (E-UTRAN), a 2G, 3G, 4G, 5G, LTE, LTE advanced network, a Wi-Fi (IEEE 802.11) or other LAN access network, or a satellite or terrestrial wide-area access network. 
     The user device  102  may connect to the wireless networks via multiple wireless base stations. For instance, the user device  102  may connect to 5G network  110  and LTE network  112  via gNodeB  104  and eNodeB  106 , respectively. The network architecture of the LTE network  112  is described further in  FIG.  2   , and the network architecture of the 5G network  110  is described further in  FIG.  4   . In other embodiments, a single base station can include multiple transceivers, with at least one transceiver on each network (e.g., 3G, 4G, LTE, 5G). Additionally, the user device  102  can be configured to connect to additional networks via Wi-Fi, Bluetooth, and other connections. 
     The user device  102  may also communicate via a Wi-Fi access point (AP)  108  or other network devices that are the initial node that the user device  102  communicates with to access the services of a corresponding access network. The user device  102  may connect to different networks (e.g., 5G network  110 , LTE network  112 , Wi-Fi network  114 ) as a user moves in and out of coverage areas of individual access networks. While  FIG.  1    illustrates a user device  102  operating on 5G network  110 , LTE network  112 , and Wi-Fi network  114 , the present disclosure is not so limited, and the user device  102  may operate on other types of networks with disparate power levels, propagation distances, or other differences. 
     In one aspect, the user device  102  may be initially connected to the Wi-Fi network  114  over one or more air interfaces (not pictured). The user device  102  may transmit a handover request to connect to a different network such as the 5G network  110  or the LTE network  112 . The user device  102  may provide measurement reports to one or more network entities in the 5G network  110  or the LTE network  112 . For instance, the measurement reports can include received signal strength or power of reference signals (e.g., RSSI, RSRP, RSRQ, etc.). These measurements may be provided to an N3IWF of the 5G network  110  or an ePDG of the LTE network  112 , depending upon embodiments. Based at least on the measurement reports, the AMF or the MME may reject or accept the handover request from the user device. Handover processes from the Wi-Fi network  114  to the 5G network  110  and from the Wi-Fi network  114  to LTE network  112  are further described below. 
     LTE Network Architecture 
       FIG.  2    illustrates an example of an LTE network architecture  200  for processing handover requests from user devices. The architecture  200  may include a user device  202  that may correspond to the user device  102  of  FIG.  1   .  FIG.  2    includes a radio access network (RAN)  206 . The RAN  206  includes a plurality of access points that serve the user device  202  over air interfaces (not pictured). The access points in the RAN  206  can be referred to as access nodes (ANs), access points (APs), base stations (BSs), NodeBs, eNodeBs, and/or so forth. The RAN  206  can include the eNodeB  106  of  FIG.  1   . These access points can be terrestrial access points (or ground stations), or satellite access points. 
     The RAN  206  is configured to connect to the evolved packet core (EPC)  220  that can perform a variety of functions, including bridging circuit-switched (CS) calls between the user device  202  served by the RAN  206  and other user devices (not pictured) served by the RAN  206  or a different RAN (not pictured), and can also mediate an exchange of packet-switched (PS) data with external networks such as a public data network (PDN)  226  (e.g., Internet). The PDN  226  includes a number of routing agents and processing agents (not shown). The user device  202  may also be directly connected to a modem or router (e.g., Wi-Fi router), which can correspond to the access point  208 . The access point  208  can correspond to the access point  108  of  FIG.  1   . 
       FIG.  2    further includes a Serving Gateway (SGW)  210 , an MME  212 , an HLR/HSS  214 , and a PDN Gateway (PGW)  222 . The PGW  222  includes a network device that acts as a router and gateway between the EPC  220  and the PDN  226 , and forwards session data between the PDN  226  and a base band unit in the EPC  220 . The SGW  210  includes a network device that routes and forwards session data between the PGW  222  and the RAN  206  serving the session&#39;s destination user device  202 . 
     The MME  212  can register or unregister user device  202  with the network, to establish user plane bearer channels, to hand off the user device  202  to different eNodeBs, MMES, other networks, and/or to perform other operations. The MME  212  may perform policing operations on traffic destined for and/or received from the user device  202 . The MME  212  may also authenticate a user by interacting with the HLR/HSS  214  and creating billing records. The MME  212  may further provide the user device  202  with mobility management and session management functions using, for example, Network Access Stratum (NAS) signaling. 
     The HLR/HSS  214  is a database that contains user-related and subscription-related information. The HLR/HSS  214  includes a user&#39;s telephone number (i.e., Mobile Subscriber Integrated Services Digital Network [MSISDN] number) and a user&#39;s International Mobile Subscriber Identity (IMSI) that uniquely identifies a subscriber. The IMSI can identify the subscription that is associated with a user. The IMSI includes the Mobile Country Code (MCC) and the Mobile Network Code (MNC). A copy of the IMSI is also stored on the subscriber identity module (SIM) card of the user device  202  that is associated with the subscribers. The HLR/HSS  214  also includes authentication information that is used to authenticate the subscriber and to generate encryption keys on a session basis, Access Point Names (APNs) that the subscriber is allowed to use, IMS-specific information, and/or so forth. Thus, the functions of the HLR/HSS  214  include functionalities such as mobilities management, call and session establishment support, user authentication and access authorization, and/or so forth. 
     The ePDG  218  may authorize and authenticate user device  202  with the HLR/HSS  214  via the Authentication, Authorization, and Accounting (AAA) server  216 . The HLR/HSS  214  may store the address of the ePDG  218  that is serving the user device  202 . The ePDG  218  receives, from the user device  202 , measurement report  230  indicating network conditions, such as network edge conditions or end-to-end conditions, such as radio frequency (RF) conditions. The ePDG  218  may interface with the MME  212  via the S1x interface  228  to deliver the measurement report  230  to the MME  212 . 
     The AAA server  216  may perform authentication, authorization, and accounting functions for an untrusted device connecting to the access network. For example, the AAA server  216  may communicate with the HLR/HSS  214  via a Diameter protocol to perform authentication and/or authorization of the user device  202 . The ePDG  218  may send a Diameter Extensible Authentication Protocol (EAP) Request (DER) to the AAA server  216  to authenticate and authorize the user device  202  using the identity and APN information associated with the user device  202 . 
     The AAA server  216  may request subscriber information for the user device  202  from HLR/HSS  214  using a Multimedia Authorization Request (MAR), and HLR/HSS  214  may respond with a Multimedia Authorization Answer (MAA) providing the requested subscriber information. After obtaining the subscriber information, the AAA server  216  may send an authentication challenge with a Diameter EAP Answer (DEA) message. 
     The EPC  220  further includes an AMF  224 , which serves part of the role of the MME  212 . The AMF  224  performs user device-based authentication, authorization, and mobility management for the user device  202  and maintains a NAS signaling connection with the user device  202  and manages the user device registration procedure. The AMF  224  is also responsible for paging. The RAN  206  and the EPC  220  are set to interwork with the New Radio (NR) and the Next Generation Core Network (NGCN) of the 5G network  204 , which will be discussed in detail with respect to  FIG.  4   . 
     In one aspect, the user device  202  may request a handover between access networks. For instance, the user device  202  may request a handover from a Wi-Fi network to the LTE network. A protocol flow diagram showing an example handover process from the Wi-Fi network to the LTE network is shown in  FIG.  3   . 
     At  302 , the user device  202  that is associated with a subscriber is attached to the ePDG  218 . The user device  202  may provide measurement reports to the ePDG  218 , wherein the measurement reports can indicate network conditions (e.g., RF conditions). In some aspects, the user device  202  may report received signal strength or power of reference signals (e.g., RSSI, RSRP, RSRQ, etc.) at regular intervals to the ePDG  218 . 
     At  304 , the HLR/HSS  214  stores ePDG address (e.g., Internet Protocol [IP] address, MAC address, port number, etc.) of the ePDG  218  that is serving the user device  202 . At  306 , the user device  202  may perform LTE attach procedures. At  308 , the user device  202  may send a handover request to a base station. The base station can be a part of the RAN  206  as described in  FIG.  2   . The base station is configured to wirelessly interface with the user device  202  to enable access to the core network, the Internet, and/or other networks. The base station may include one or more radio access nodes, a base transceiver station (BTS) or a base station controller (BSC), a Node-B (NodeB), an evolved NodeB (eNodeB), a Home NodeB, a Home eNodeB, a site controller, an access point (AP), or a wireless router, or a server, router, switch, or other processing entity with a wired or wireless network. In the illustrated embodiment, the base station comprises eNodeB  106 . 
     At  310 , the eNodeB  106  transmits a handover-required message to the MME  212 . The MME  212  may first identify the ePDG  218  that is serving the user device  202  requesting handover. At  312 , the MME  212  may retrieve the ePDG address of the ePDG  218  serving the user device  202  from the HLR/HSS  214 . Upon identifying the ePDG  218  that is serving the user device  202 , the MME  212  may interface with the ePDG  218  via the S1x interface to request and receive the measurement reports as shown at  314 . The measurement reports include one or more measurements obtained via the user device  202  indicating network conditions in real-time or near real-time. For instance, the measurements may indicate whether the available cellular signal is marginal or unstable. Therefore, the MME  212  can determine whether transitioning from Wi-Fi to LTE may likely be successful or result in a poor connection. Based on the measurements in the measurement reports, the MME  212  may reject or accept the handover request from the user device  202  at  316 . 
     5G Network Architecture 
       FIG.  4    illustrates an example of a 5G network architecture  400  for processing handover requests from user devices. Similar to the LTE network architecture as described in  FIGS.  2  and  3   , the 5G network architecture  400  includes a user device  402  that is configured to communicate with an access network. The user device  402  may correspond to the user device  102  and  202  of  FIGS.  1  and  2   , respectively.  FIG.  4    includes a Next Generation RAN (NG-RAN)  406 . The NG-RAN  406  may implement any suitable wireless communication technology or technologies to provide radio access to the user device  402 . For instance, the NG-RAN  406  may operate according to 3GPP NR specifications (i.e., 5G). The NG-RAN  406  includes a plurality of access points that serve the user device over air interfaces. In the illustrated embodiment, the access points in the NG-RAN  406  include base stations such as the gNodeB  104  of  FIG.  1   . The user device  402  may also be directly connected to a modem or router (e.g., Wi-Fi router), which can correspond to the access point  408 . The access point  408  may correspond to the access point  108  and  208  of  FIGS.  1  and  2   , respectively. 
     The NG-RAN  406  is configured to connect to the NGCN  422 , which replaces the EPC  220  of  FIG.  2    in the LTE network. The NG-RAN  406  and the NGCN  422  are set to interwork with RAN and EPC of the LTE network  404 , which are described above with respect to  FIG.  2   . The NGCN  422  includes an AMF  414 , Session Management Function (SMF)  418 , and User Plane Function (UPF)  420 . The AMF  414  provides functions such as NAS security, idle state mobility handling, and/or so forth. The AMF  414  provides functions including those of the MME  212  in  FIG.  2    of the LTE network. The AMF  414  connects to the Authentication Server Function (AUSF)  410  and the Unified Data Function (UDM)  412 . The AUSF  410  provides functions including those of the MME  212  and AAA  216  in  FIG.  2    of the LTE network. 
     Additionally, AUSF  410  manages subscriber authentication during registration or re-registration with the NGCN  422 , which obtains authentication vectors from the UDM  412 . The UDM  412  is the evolution of HLR/HSS  214  in  FIG.  2    and Unified Data Repository (UDR) (not pictured), which is the evolution of the LTE Structured Data Storage (SDS) (not pictured). The UDR can store structured data (e.g., subscriber profile, policy, app data, etc.) that can be exposed to a Network Function (NF) such as the AMF  414  and the SMF  418 , which interface with the UDM  412 . 
     The SMF  418  provides functions such as user device IP address allocation and PDU session control. The SMF  418  interfaces with the Policy Control Function (PCF)  428 , which provides policy control similar to the Policy and Charging Rules Function (PCRF) (not pictured) of an LTE network. The PCF  428  maintains a traditional diameter protocol-based interface to an Application Function (AF)  426  but is also enhanced to allow for resource reservation requests using an HTTP/XML-based interface from other services. 
     The UPF  420  provides functions such as mobility anchoring (e.g., anchoring the user device IP addresses) and protocol data unit (PDU) handling. The UPF  420  also provides the Quality of Service (QoS) enforcement function. The SMF  418  replaces together with the UPF  420  the SGW  210  and PGW  222  in  FIG.  2    of the LTE network. 
     The NGCN  422  further includes a N3IWF  416 . The N3IWF  416  is similar to the ePDG  218  in  FIG.  2    of the LTE network, which serves as a secure gateway for the user device to access non-trusted networks, such as Wi-Fi and the public Internet (e.g., Data Network [DN]  430 ). The AMF  414  may store the address of the N3IWF  416  that is handling the user device session. The address of the N3IWF  416  can include an IP address, MAC address, port number, and/or other such unique identifiers that identify the N3IWF  416 . The N3IWF  416  receives, from the user device  402 , measurement report  432  indicating network conditions (e.g., RF conditions). The N3IWF  416  may interface with the AMF  414  via the N2 interface  434  to deliver the measurement report  432  to the AMF  414 . 
     The N3IWF  416  also transports NAS messages from the user device over non-trusted networks and AMF selection. The user device  402  may perform a network registration from networks other than the NG-RAN  406  (e.g., LTE network of  FIG.  2   ). When the user device  402  is connected to the NG-RAN  406  and Wi-Fi (e.g., via the access point  408 ), the user device  402  will have two distinct active NAS connections with the AMF  414 . 
     In one aspect, the user device  402  may request a handover between access networks. For instance, the user device  402  may request a handover from a Wi-Fi network to the 5G network. A protocol flow diagram showing an example handover process from the Wi-Fi network to the 5G network is shown in  FIG.  5   . 
     At  502 , the user device  402  that is associated with a subscriber is attached to the N3IWF  416 . The user device  402  may provide measurement reports to the N3IWF  416 , wherein the measurement reports can indicate network conditions. In some aspects, the user device  402  may report received signal strength or power of reference signals (e.g., RSSI, RSRP, RSRQ, etc.) at regular intervals to the N3IWF  416 . 
     At  504 , the AMF  414  stores N 3 IWF address of the N3IWF  416  that is handling the user device session. At  506 , the user device  402  may perform 5G attach procedures. At  508 , the user device  402  may send a handover request to a base station. The base station can be a part of the NG-RAN  406  as described in  FIG.  4   . The base station is configured to wirelessly interface with the user device  402  to enable access to the core network, the Internet, and/or other networks. The base station may include one or more radio access nodes, a site controller, an access point (AP), or a wireless router, or a server, router, switch, or other processing entity with a wired or wireless network. In the illustrated embodiment, the base station comprises gNodeB  104 . 
     At  510 , the gNodeB  104  transmits a handover-required message to the AMF  414 . The AMF  414  may identify the N3IWF  416  that is handling the user device session based at least on the N3IWF address. Upon identifying the N3IWF  416  that is serving the user device  402 , the AMF  414  may interface with the N3IWF  416  via the N2 interface to receive the measurement reports, as shown at  512 . The measurement reports include one or more measurements obtained via the user device  202  indicating network conditions in real-time or near real-time. For instance, the measurements may indicate whether the available cellular signal is marginal or unstable. Based at least on the measurement reports, the AMF  414  may reject or accept the handover request from the user device  402  at shown at  514 . 
     Example Computing Device Components 
       FIG.  6    is a block diagram showing various components of illustrative computing devices  600 , wherein the computing devices  600  can comprise an MME or an AMF, depending upon embodiments. It is noted that the computing devices  600  as described herein can operate with more or fewer of the components shown herein. Additionally, the computing devices  600  as shown herein or portions thereof can serve as a representation of one or more of the computing devices of the present system. 
     The computing devices  600  may include a communication interface  602 , one or more processors  604 , device hardware  606 , and memory  608 . The communication interface  602  may include wireless and/or wired communication components that enable the computing devices  600  to transmit data to and receive data from other networked devices. In at least one example, the one or more processor(s)  604  may be a central processing unit(s) (CPU), graphics processing unit(s) (GPU), both a CPU and GPU or any other sort of processing unit(s). Each of the one or more processor(s)  604  may have numerous arithmetic logic units (ALUs) that perform arithmetic and logical operations as well as one or more control units (CUs) that extract instructions and stored content from processor cache memory, and then execute these instructions by calling on the ALUs, as necessary during program execution. 
     The one or more processor(s)  604  may also be responsible for executing all computer applications stored in the memory, which can be associated with common types of volatile (RAM) and/or nonvolatile (ROM) memory. The device hardware  606  may include additional user interface, data communication, or data storage hardware. For example, the user interfaces may include a data output device (e.g., visual display, audio speakers), and one or more data input devices. The data input devices may include but are not limited to, combinations of one or more of keypads, keyboards, mouse devices, touch screens that accept gestures, microphones, voice or speech recognition devices, and any other suitable devices. 
     The memory  608  may be implemented using computer-readable media, such as computer storage media. Computer-readable media includes, at least, two types of computer-readable media, namely computer storage media and communications media. Computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules, or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD), high-definition multimedia/data storage disks, or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information for access by a computing device. In contrast, communication media may embody computer-readable instructions, data structures, program modules, or other data in a modulated data signal, such as a carrier wave, or other transmission mechanisms. The memory  608  may also include a firewall. In some embodiments, the firewall may be implemented as device hardware  606  in the computing devices  600 . 
     The processors  604  and the memory  608  of the computing devices  600  may implement an operating system  610 , a mapping module  612 , a decision making module  614 , and a data store  616 . The operating system  610  may include components that enable the computing devices  600  to receive and transmit data via various interfaces (e.g., user controls, communication interface, and/or memory input/output devices), as well as process data using the processors  604  to generate output. The operating system  610  may include a presentation component that presents the output (e.g., display the data on an electronic display, store the data in memory, transmit the data to another electronic device, etc.). Additionally, the operating system  610  may include other components that perform various additional functions generally associated with an operating system. 
     The mapping module  612  and the decision making module  614  may include routines, program instructions, objects, and/or data structures that perform particular tasks or implement particular abstract data types. The mapping module  612  may include one or more instructions, which when executed by the one or more processors  604  direct the computing devices  600  to perform operations related to identifying ePDGs serving user devices or N3IWF handling user device session. In one example, the mapping module  612  may request, from the HLR/HSS, the address of the ePDG serving the user device that requests handover. Upon receiving the ePDG address of the serving ePDG, the mapping module  612  may associate the ePDG address with the serving ePDG in order to identify the ePDG corresponding to the ePDG address. 
     In another example, the computing devices  600  may store the address of the ePDG and/or the N3IWF in the data store  616 . The data store  616  can comprise a data management layer that includes software utilities for facilitating the acquisition, processing, storing, reporting, and analysis of data from multiple data sources. For example, the data store  616  may request ePDG addresses from the HLR/HSS. The mapping module  612  may, in turn, identify the serving ePDG or the N3IWF based at least on the stored address of the ePDG or the N3IWF, respectively. 
     The decision making module  614  may include one or more instructions, which when executed by the one or more processors  604 , direct the computing devices  600  to perform operations related to accepting or rejecting handover requests from user devices. In some aspects, the decision making module  614  may be configured to accept or reject a handover request from a user device based at least on one or more measurements in a measurement report from the requesting user device. The measurements in the measurement report may indicate network conditions such as RF conditions. The measurement report can include RSSI, RSRP, and/or RSRQ levels. In one example, if the measurement report indicates that the RSRP level exceeds a first predetermined signal strength threshold, then the decision making module  614  may accept the handover request. In another example, if the measurement report indicates that the RSSI level does not exceed a second predetermined signal strength threshold but the RSRP level exceeds a third predetermined signal strength threshold, then the decision making module  614  may accept the handover request. However, in such an example if the measurement report indicates that the RSSI level exceeds the second predetermined signal strength threshold, then the decision making module  614  may reject the handover request. In other instances, the decision making module  614  may make use of other combinations signal measurement levels and corresponding predetermined signal measurement thresholds to accept or reject handover requests. 
     Example Processes 
       FIGS.  7 - 9    present illustrative processes  700 - 900  for making handover decisions. The processes  700 - 900  are illustrated as a collection of blocks in a logical flow chart, which represents a sequence of operations that can be implemented in hardware, software, or a combination thereof. In the context of software, the blocks represent computer-executable instructions that, when executed by one or more processors, perform the recited operations. Generally, computer-executable instructions may include routines, programs, objects, components, data structures, and the like that perform particular functions or implement particular abstract data types. The order in which the operations are described is not intended to be construed as a limitation, and any number of the described blocks can be combined in any order and/or in parallel to implement the process. For discussion purposes, the processes  700 - 900  are described with reference to  FIGS.  1 - 6   . 
       FIG.  7    is a flow diagram of an example process  700  for making a handover decision from the perspective of an MME. At block  702 , the MME receives a handover request comprising from a user device. At block  704 , the MME identifies an ePDG serving the user device. In one aspect, the MME requests an ePDG address from the HLR/HSS and identifies the serving ePDG based at least on the ePDG address. The user device provides a measurement report to the ePDG, wherein the measurement report indicates network conditions. In some aspects, the user device populates RSSI, RSRP, and/or RSRQ measurements at regular intervals to the ePDG. At block  706 , the MME receives the measurement report from the ePDG serving the user device. In some examples, the MME and the ePDG may interact via a newly created interface such as the S1x interface. At decision block  708 , the MME determines whether a measurement (e.g., RSSI level, RSRP level, or RSRQ level) in the measurement report is above a predetermined threshold. If the measurement is above the threshold (“yes” from block  708 ), then the MME accepts the handover request, as indicated in block  710 . If the measurement is below the threshold (“no” from block  708 ), then the MME rejects the handover request, as indicated in block  712 . 
       FIG.  8    is a flow diagram of an example process  800  for making a handover decision from the perspective of an AMF. At block  802 , the AMF receives a handover request comprising from a user device. At block  804 , the AMF identifies N 3 IWF handling the user device session. In one aspect, the AMF may identify the serving N3IWF based at least on the N3IWF address. The user device provides a measurement report to the N3IWF, wherein the measurement report indicates network conditions. In some aspects, the user device populates RSSI, RSRP, and/or RSRQ at regular intervals to the N3IWF. At block  806 , the AMF receives the measurement report from the N3IWF serving the user device. In some aspects, the AMF may request and receive the measurement report via the N2 interface that exists between the AMF and the N3IWF. At decision block  808 , the AMF determines whether a measurement (e.g., RSSI level, RSRP level, or RSRQ level) in the measurement report is above a predetermined threshold. If the measurement is above the threshold (“yes” from block  808 ), then the AMF accepts the handover request, as indicated in block  810 . If the measurement is below the threshold (“no” from block  808 ), then the AMF rejects the handover request, as indicated in block  812 . 
       FIG.  9    is a flow diagram of an example process  900  for making a handover decision from the perspective of an MME or an AMF. At block  902 , the MME or the AMF may receive a measurement report that includes one or more measurements. For instance, the measurement report can include RSSI levels and RSRP levels. The individual measurements may correspond to a predetermined threshold. Accordingly, the MME or the AMF may engage in multiple decision making process to determine whether to accept or reject the handover request based at least on one or more measurements. 
     For example, at decision block  904 , the MME or the AMF may determine whether a first measurement (e.g., RSRP level) is above or below a first predetermined threshold. If the first measurement is below the first predetermined threshold (“no” from block  904 ), then the MME or the AMF may determine whether a second measurement (e.g., RSSI level) is above or below a second predetermined threshold as shown in decision block  906 . If the first measurement is above the first predetermined threshold (“yes” from block  904 ), then the MME or the AMF may deny the handover request as shown in block  910 . 
     If the second measurement is below the second predetermined threshold (“no” from block  906 ), then the MME or the AMF determines whether the first measurement (e.g., RSRP level) is above or below a third predetermined threshold as shown in decision block  908 . For example, the third predetermined threshold is a threshold that is higher than the first predetermined threshold. If the second measurement is above the second predetermined threshold (“yes” from block  906 ), then the MME or the AMF denies the handover request as shown in block  910 . If the first measurement is above the third predetermined threshold (“yes” from block  908 ), then the MME or the AMF may accept the handover request as shown in block  912 . Conversely, if the first measurement is below the third predetermined threshold (“no” block block  908 ), then the MME or the AMF may reject the handover request as shown in block  910 . 
     CONCLUSION 
     Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as exemplary forms of implementing the claims.