Patent Publication Number: US-2019200208-A1

Title: Method and apparatus for proactive load control

Description:
BACKGROUND 
     In the Fifth Generation (5G) mobile network standards, multiple radio access network configurations must be supported. In this multiple configuration scheme, access and mobility management functions may support user equipment (UE), which has registered with the mobile network. However, the access and mobility management functions may become unbalanced with one or more access and mobility management functions being assigned to support many more UEs than other access and mobility management functions, thereby decreasing the efficiency with which the UEs are supported by the access and mobility management functions. 
     BRIEF SUMMARY 
     In the 5G mobile networks specification, there is no function to support proactive load control. Initial load balancing is done as part of access and mobility management function (AMF) selection which is done at an initial UE registration. Further, when an AMF goes on planned maintenance or when the AMF fails, the Radio Access Network (RAN) is notified and/or detects that the AMF has failed, and then selects a different AMF. Furthermore, when an AMF overload is detected, overload control procedures are implemented. These procedures include a non-access stratum (NAS) reject timer, Radio Resource Control (RRC) reject eWaitTimer, access class barring, and other methods. 
     However, there is no method for an AMF to perform proactive load balancing. Proactive load balancing or rebalancing redirects only a portion of the UE(s) registered to the AMF to an alternate AMF while serving some UE(s). This flexibility in serving UE(s) provides mobile network operators the ability to rebalance UEs without any impact to the network and UE(s). 
     A method, apparatus, and computer program product are provided in accordance with certain example embodiments in order to provide proactive load control in a mobile network. 
     In one embodiment, a method for proactive load control in a mobile network is provided. The method comprises receiving an initial message request at an access and mobility management function (AMF) from user equipment via a radio access network (RAN), determining a pre-overload condition exists in the AMF, and causing a redirection request to be transmitted to the RAN. The redirection request is configured to cause a transmission of the initial message to an alternate AMF. 
     In another example embodiment, an apparatus for proactive load control in a mobile network is provided. The apparatus includes at least one processor and at least one memory including computer program code with at least one memory and the computer program code configured to, with the processor, cause the apparatus to at least: receive an initial message request at an access and mobility management function (AMF) from user equipment via a radio access network (RAN), determine a pre-overload condition exists in the AMF, and cause a redirection request to be transmitted to the RAN. The redirection request is configured to cause a transmission of the initial message to an alternate AMF. 
     In a further embodiment, a computer program product is provided that includes at least one non-transitory computer readable storage medium having computer-executable program code portions stored therein with the computer-executable program code portions including program code instructions configured to provide proactive load control in a mobile network. The program code portions of an example embodiment also include program code instructions configured to receive an initial message request at an access and mobility management function (AMF) from user equipment via a radio access network (RAN), determine a pre-overload condition exists in the AMF, and cause a redirection request to be transmitted to the RAN. The redirection request is configured to cause a transmission of the initial message to an alternate AMF. 
     In yet another example embodiment, an apparatus is provided that includes means for proactive load control in a mobile network. The apparatus includes means for receiving an initial message request at an access and mobility management function (AMF) from user equipment via a radio access network (RAN), determining a pre-overload condition exists in the AMF, and causing a redirection request to be transmitted to the RAN. The redirection request is configured to cause a transmission of the initial message to an alternate AMF. 
     In an example embodiment, an apparatus is provided that comprises at least one processor and at least one memory including computer program code for one or more programs with the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to cause a redirection request to be provided by an access and mobility management function (AMF) to one or more access nodes to cause at least some of user equipment returning from an idle mode to be redirected from the AMF to an alternate AMF within a same AMF set, such as AMFs having the same public land mobile network (PLMN) and AMF Set identifier (ID) value. In response to a subsequent determination to stop redirection, the apparatus is also caused to cause a cease redirection request to be provided by the AMF to one or more access nodes in order to stop redirection of user equipment returning from the idle mode to the alternate AMF. 
     The redirection request is caused, in one example embodiment, to be provided prior to reaching an overload condition. The apparatus of an example embodiment is further caused to cause a weight factor to be provided by the AMF to the one or more access nodes in order to at least partially control selection of the AMF to support the user equipment. In an example embodiment, a probability of the AMF being selected to support the user equipment is proportional to the weight factor. The weight factor is set in an example embodiment according to a capacity of the AMF relative to other AMFs. The method of an example embodiment further comprises permitting the weight factor to be changed based upon changes in capacities of one or more of the AMF and the other AMFs. In another example embodiment, the method further comprises causing the weight factor to be set to zero in order to remove all subscribers from the AMF and to route new entrants to other AMFs within the same AMF set. 
     In response to a determination of an overload condition, the apparatus of an example embodiment is further caused to invoke an N2 overload procedure to the one or more access nodes with which the AMF has N2 connections. During recovery form an overload condition, the apparatus of an example embodiment is further caused to cause a message to be provided that includes a percentage value to permit more traffic to be carried. During an overload condition, the apparatus of an example embodiment is further caused to reject Mobility Management signaling requests from user equipment. During an overload condition and in response to a non-access stratum (NAS) request being rejected, the apparatus of an example embodiment is further caused to cause a Mobility Management back-off timer to be sent to prevent at least some NAS requests for Mobility Management procedures from being initiated by user equipment. 
     The apparatus of an example embodiment is further caused to select the one or more access nodes to which the N2 overload procedure is invoked at random. In this example embodiment, the N2 overload procedure requests the one or more access nodes to reject connection requests. The apparatus of an example embodiment is further caused to cause a paging request to be provided to the user equipment while the Mobility Management back off timer is running in order to cause the user equipment to stop the Mobility Management back-off timer and initiate a Service Request procedure or a Tracking Area Update procedure. In an example embodiment, the apparatus is further caused to reject, by a session management function (SMF), a session management request from the user equipment in response to session management congestion. In this example embodiment, the apparatus is also caused to provide a session management back-off timer to the user equipment to prevent initiation of at least some session management procedures until the session management back-off timer has expired. 
     In another example embodiment, a method is provided that includes causing a redirection request to be provided by an access and mobility management function (AMF) to one or more access nodes to cause at least some of user equipment returning from an idle mode to be redirected from the AMF to an alternate AMF within a same AMF set, such as AMFs having the same public land mobile network (PLMN) and AMF Set identifier (ID) value. In response to a subsequent determination to stop redirection, the method causes a cease redirection request to be provided by the AMF to one or more access nodes in order to stop redirection of user equipment returning from the idle mode to the alternate AMF. 
     The redirection request is caused, in one example embodiment, to be provided prior to reaching an overload condition. The method of an example embodiment further comprises causing a weight factor to be provided by the AMF to the one or more access nodes in order to at least partially control selection of the AMF to support the user equipment. In an example embodiment, the probability of the AMF being selected to support the user equipment is proportional to the weight factor. The weight factor is set in an example embodiment according to a capacity of the AMF relative to other AMFs. The method of an example embodiment further comprises permitting the weight factor to be changed based upon changes in capacities of one or more of the AMF and the other AMFs. In another example embodiment, the method further comprises causing the weight factor to be set to zero in order to remove all subscribers from the AMF and to route new entrants to other AMFs within the same AMF set. 
     In response to a determination of an overload condition, the method of an example embodiment further comprises invoking an N2 overload procedure to the one or more access nodes with which the AMF has N2 connections. In an example embodiment, during recovery form an overload condition, the method further comprises causing a message to be provided that includes a percentage value to permit more traffic to be carried. During an overload condition, the method of an example embodiment further comprises rejecting Mobility Management signaling requests from user equipment. In an example embodiment, during an overload condition and in response to a non-access stratum (NAS) request being rejected, the method further comprises causing a Mobility Management back-off timer to be sent to prevent at least some NAS requests for Mobility Management procedures from being initiated by user equipment. 
     The method of an example embodiment further comprises selecting the one or more access nodes to which the N2 overload procedure is invoked at random. In this example embodiment, the N2 overload procedure requests the one or more access nodes to reject connection requests. The method of an example embodiment further comprises causing a paging request to be provided to the user equipment while the Mobility Management back off timer is running in order to cause the user equipment to stop the Mobility Management back-off timer and initiate a Service Request procedure or a Tracking Area Update procedure. In an example embodiment, the method further comprises rejecting, by a session management function (SMF), a session management request from the user equipment in response to session management congestion. In this example embodiment, the method also provides a session management back-off timer to the user equipment to prevent initiation of at least some session management procedures until the session management back-off timer has expired. 
     In a further example embodiment, a computer program product is provided that comprises at least one non-transitory computer-readable storage medium having computer executable program code instructions stored therein with the computer executable program code instructions comprising program code instructions configured, upon execution, to cause a redirection request to be provided by an access and mobility management function (AMF) to one or more access nodes to cause at least some of user equipment returning from an idle mode to be redirected from the AMF to an alternate AMF within a same AMF set. The computer executable program code instructions also include program code instructions configured, upon execution, to cause, in response to a subsequent determination to stop redirection, a cease redirection request to be provided by the AMF to one or more access nodes in order to stop redirection of user equipment returning from the idle mode to the alternate AMF. 
     The redirection request is caused, in one example embodiment, to be provided prior to reaching an overload condition. In an example embodiment, the computer executable program code instructions further comprise program code instructions configured, upon execution, to cause a weight factor to be provided by the AMF to the one or more access nodes in order to at least partially control selection of the AMF to support the user equipment. In an example embodiment, the probability of the AMF being selected to support the user equipment is proportional to the weight factor. The weight factor is set in an example embodiment according to a capacity of the AMF relative to other AMFs. In an example embodiment, the computer executable program code instructions further comprise program code instructions configured, upon execution, to permit the weight factor to be changed based upon changes in capacities of one or more of the AMF and the other AMFs. In another example embodiment, the computer executable program code instructions further comprise program code instructions configured, upon execution, to cause the weight factor to be set to zero in order to remove all subscribers from the AMF and to route new entrants to other AMFs within the same AMF set. 
     The computer executable program code instructions of an example embodiment, further comprise program code instructions configured, upon execution, to invoke, in response to a determination of an overload condition, an N2 overload procedure to the one or more access nodes with which the AMF has N2 connections. In an example embodiment, the computer executable program code instructions further comprise program code instructions configured, upon execution, to cause a message to be provided, during recovery form an overload condition, that includes a percentage value to permit more traffic to be carried. The computer executable program code instructions of an example embodiment further comprise program code instructions configured, upon execution, to reject, during an overload condition, Mobility Management signaling requests from user equipment. In an example embodiment, the computer executable program code instructions further comprise program code instructions configured, upon execution, to cause, during an overload condition and in response to a non-access stratum (NAS) request being rejected, a Mobility Management back-off timer to be sent to prevent at least some NAS requests for Mobility Management procedures from being initiated by user equipment. 
     The computer executable program code instructions of an example embodiment further comprise program code instructions configured, upon execution, to select the one or more access nodes to which the N2 overload procedure is invoked at random. In this example embodiment, the N2 overload procedure requests the one or more access nodes to reject connection requests. The computer executable program code instructions of an example embodiment further comprise program code instructions configured, upon execution, to cause a paging request to be provided to the user equipment while the Mobility Management back off timer is running in order to cause the user equipment to stop the Mobility Management back-off timer and initiate a Service Request procedure or a Tracking Area Update procedure. In an example embodiment, the computer executable program code instructions further comprise program code instructions configured, upon execution, to reject, by a session management function (SMF), a session management request from the user equipment in response to session management congestion. In this example embodiment, the computer executable program code instructions further comprise program code instructions configured, upon execution, to provide a session management back-off timer to the user equipment to prevent initiation of at least some session management procedures until the session management back-off timer has expired. 
     In yet another example embodiment, an apparatus is provided that includes means for causing a redirection request to be provided by an access and mobility management function (AMF) to one or more access nodes to cause at least some of user equipment returning from an idle mode to be redirected from the AMF to an alternate AMF within a same AMF set, such as AMFs having the same public land mobile network (PLMN) and AMF Set identifier (ID) value. In response to a subsequent determination to stop redirection, the apparatus also includes means for causing a cease redirection request to be provided by the AMF to one or more access nodes in order to stop redirection of user equipment returning from the idle mode to the alternate AMF. 
     The redirection request is caused, in one example embodiment, to be provided prior to reaching an overload condition. The apparatus of an example embodiment further comprises means for causing a weight factor to be provided by the AMF to the one or more access nodes in order to at least partially control selection of the AMF to support the user equipment. In an example embodiment, the probability of the AMF being selected to support the user equipment is proportional to the weight factor. The weight factor is set in an example embodiment according to a capacity of the AMF relative to other AMFs. The apparatus of an example embodiment further comprises means for permitting the weight factor to be changed based upon changes in capacities of one or more of the AMF and the other AMFs. In another example embodiment, the apparatus further comprises means for causing the weight factor to be set to zero in order to remove all subscribers from the AMF and to route new entrants to other AMFs within the same AMF set. 
     In response to a determination of an overload condition, the apparatus of an example embodiment further comprises means for invoking an N2 overload procedure to the one or more access nodes with which the AMF has N2 connections. In an example embodiment, during recovery form an overload condition, the apparatus further comprises means for causing a message to be provided that includes a percentage value to permit more traffic to be carried. During an overload condition, the apparatus of an example embodiment further comprises means for rejecting Mobility Management signaling requests from user equipment. In an example embodiment, during an overload condition and in response to a non-access stratum (NAS) request being rejected, the apparatus further comprises means for causing a Mobility Management back-off timer to be sent to prevent at least some NAS requests for Mobility Management procedures from being initiated by user equipment. 
     The apparatus of an example embodiment further comprises means for selecting the one or more access nodes to which the N2 overload procedure is invoked at random. In this example embodiment, the N2 overload procedure requests the one or more access nodes to reject connection requests. The apparatus of an example embodiment further comprises means for causing a paging request to be provided to the user equipment while the Mobility Management back off timer is running in order to cause the user equipment to stop the Mobility Management back-off timer and initiate a Service Request procedure or a Tracking Area Update procedure. In an example embodiment, the apparatus further comprises means for rejecting, by a session management function (SMF), a session management request from the user equipment in response to session management congestion. In this example embodiment, the apparatus also provides a session management back-off timer to the user equipment to prevent initiation of at least some session management procedures until the session management back-off timer has expired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Having thus described certain example embodiments of the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
         FIG. 1A  is a networked system in accordance with an example embodiment of the present disclosure 
         FIG. 1B  is an alternate view of the networked system of  FIG. 1A  in accordance with an example embodiment of the present disclosure; 
         FIG. 2  illustrates Radio Access Network (RAN) configurations in accordance with certain example embodiments of the present disclosure; 
         FIG. 3  is a block diagram of a core network apparatus configured in accordance with an example embodiment of the present disclosure; and 
         FIGS. 4-5  are flowcharts illustrating methods for providing proactive load balancing in accordance with an example embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Some embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all, embodiments of the invention are shown. Indeed, various embodiments of the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like reference numerals refer to like elements throughout. As used herein, the terms “data,” “content,” “information,” and similar terms may be used interchangeably to refer to data capable of being transmitted, received and/or stored in accordance with embodiments of the present invention. Thus, use of any such terms should not be taken to limit the spirit and scope of embodiments of the present invention. 
     Additionally, as used herein, the term ‘circuitry’ refers to (a) hardware-only circuit implementations (e.g., implementations in analog circuitry and/or digital circuitry); (b) combinations of circuits and computer program product(s) comprising software and/or firmware instructions stored on one or more computer readable memories that work together to cause an apparatus to perform one or more functions described herein; and (c) circuits, such as, for example, a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation even if the software or firmware is not physically present. This definition of ‘circuitry’ applies to all uses of this term herein, including in any claims. As a further example, as used herein, the term ‘circuitry’ also includes an implementation comprising one or more processors and/or portion(s) thereof and accompanying software and/or firmware. As defined herein, a “computer-readable storage medium,” which refers to a physical storage medium (e.g., volatile or non-volatile memory device), may be differentiated from a “computer-readable transmission medium,” which refers to an electromagnetic signal. 
     A method, apparatus and computer program product are provided in accordance with an example embodiment to provide proactive load control in a mobile network as described herein. 
       FIG. 1A  is a networked system  100  in accordance with an example embodiment of the present disclosure.  FIG. 1A  specifically illustrates User Equipment (UE)  102 , which may be in communication with a Radio Access Network (RAN)  103  and Access and Mobility Management Function (AMF)  104 . The AMF  104  may, in turn, be in communication with core network services  108 . Various methods including the use of an AMF proactive load control  106  may be used by the AMF  104 . 
       FIG. 1B  is an alternate view of the networked system of  FIG. 1A  in accordance with an example embodiment of the present disclosure. As shown in  FIG. 1B , the AMF  104  is a part of the AMF set  205  which includes alternative AMFs  204   a  and  204   b , which provide the same network services and functions to the UE  102  as the AMF  104 . The components of  FIG. 1B  may comprise a network slice of services and functions provided to UE  102 . 
       FIG. 1B  also illustrates an initial message  202  from the UE  102  through the RAN  103 . As shown, the AMF  104  (using AMF proactive load control  106 ) sends a redirection request  203  to the RAN  103  and in response to the redirection request the RAN  103  send a redirected message  204  to alternate AMF  206   a . The AMF proactive load control  106  is configured to permit a cross-section of its UE subscribers that are registered on the AMF  104  (within the AMF Set  205 ) to be moved to another AMF within the same AMF set  205  (e.g., AMF  206   a  or  206   b ) with minimal impact on the network and end users (users of UE  102 ). The AMF  104  may request (such as redirection request  203 ) some or all of the RAN  103  nodes to redirect a cross-section of the UE(s) returning from a IDLE mode to be redirected to another AMF within the same AMF set  205 . In some examples, the AMF  104  may provide a proactive overload control indication in the redirection request if the AMF utilization approaches overload or pre-overload levels. In some examples, the control indication may indicate a predefined percentage or a predefined number of UE(s) that should be redirected to another AMF. For example, the AMF proactive load control  106  may provide a proactive overload control indication as part of the redirection request  203 , with a request to redirect 25% of the IDLE UE(s)  102  to another AMF. When the RAN  103  receives the redirection request  203 , it may be configured to redirect 1 out of 4 next generation application protocol (NGAP) messages from IDLE mode UEs to another AMF or redirect first 25 out of 100 NGAP messages from IDLE mode UEs to another AMF. 
     In some examples, the AMF includes stored UE contexts in a Data Storage network function (UDSF). For UE(s)  102  in IDLE mode, when the UE  102  subsequently returns from IDLE mode and the RAN  103  receives an initial message  203  (which may comprise a NAS message with a 5G SAE-Temporary Mobile Subscriber Identity (S-TMSI) or Globally Unique AMF Identifier (GUAMI) pointing to the AMF  104  that requested for redirection), the RAN  103  should select a different AMF, such as alternate AMF  206   a  from the same AMF set  205  and forward the NAS message (redirected message  204 ) to the alternate AMF  206   a . In some embodiments, the RAN  103  will not reject any request or enable access control restriction when the RAN receives a request for proactive load control or redirection request  202  from the connected AMF(s). 
     When the AMF  104  has determined to stop redirection as described below, the AMF proactive control function  106  can indicate, by sending a cease redirection request, that it can serve all UE(s) in IDLE mode to stop the redirection. 
     In some examples, the AMF Proactive load control function  106  is configured to pro-actively re-balance the AMF  104  load prior to reaching overload in order to prevent an overload situation. 
     In some examples, the AMF Proactive load control function  106  should not issue a redirection request when the AMF  104  becomes overloaded because a Load Balancing function should have ensured that the other AMFs in the AMF set  205  area are similarly overloaded. 
     In general the core network will support Control Plane Congestion and Overload Control, which in addition to proactive load balancing described herein, includes several other complementary procedures. For example, the congestion and overload control includes AMF Load Balancing which permits UE(s)  102  that are entering into an AMF Region/AMF Set  205  to be directed to an appropriate AMF in a manner that achieves load balancing between AMFs. This is achieved by setting a Weight Factor for each AMF, such that the probability of an AMF being selected is proportional to its Weight Factor. The Weight Factor is typically set according to the capacity of an AMF node relative to other AMF nodes. The Weight Factor is sent from the AMF to the RAN  103  (e.g., a 5G access node (AN)) via NGAP messages. 
     In some examples of AMF Load Balancing, an operator of a mobile network may decide to change the Weight Factor after the establishment of NGAP connectivity as a result of changes in the AMF capacities. For example, a newly installed AMF may be given a much higher Weight Factor for an initial period of time making it faster to increase its load. However, in some examples, the Weight Factor is not changed frequently. For example, in a mature network, changes on a monthly basis could be anticipated, due to the addition of RAN or core network (CN) nodes. 
     In some networks, the AMF  104  may be configured to select a specific AMF for UE(s) configured for low access priority with a different load balance than that used for AMF selection for other UEs. 
     When network slicing is deployed, load balancing by the RAN  103  node is only performed between AMFs that belong to the same selected Network Slice Selection Assistance Information (S-NSSAI(s)) within the same AMF set  205 , e.g., AMFs with the same public land mobile network (PLMN) and AMF Set ID value. 
     The RAN  103  node may have Load Balancing parameters adjusted beforehand (e.g., the Weight Factor is set to zero if all subscribers are to be removed from the AMF, which will route new entrants to other AMFs within an AMF Set). 
     The congestion and overload control also includes AMF control of overload. In some examples, the AMF  104  contains mechanisms for avoiding and handling overload situations. This can include proactive load control to avoid overload with minimal impacts on the network load and end users described herein, reactive overload control, restricting UE(s), and NAS congestion control. 
     Under unusual circumstances, if the AMF  104  has reached overload situation, the AMF may be configured to restrict the load that the RAN nodes are generating, if the RAN is configured to enable the overload restriction. This can be achieved by the AMF invoking an N2 overload procedure to all or to a proportion of the RAN nodes with which the AMF has N2 connections. To reflect the amount of load that the AMF wishes to reduce, the AMF can adjust the proportion of RAN nodes which are sent NGAP OVERLOAD START message, and the content of the OVERLOAD START message. 
     In some examples, the AMF should select the RAN nodes at random (so that if two AMFs within an AMF Set are overloaded, they do not both send OVERLOAD START messages to exactly the same set of 5G ANs). Using the OVERLOAD START message, the AMF can request the RAN node to: reject RRC connection requests that are for non-emergency, non-exception reporting and non-high priority mobile originated services; reject new RRC connection requests for 5GS NAS Mobility Management signaling targeted (e.g. for Registration update procedure) for that AMF; or only permit RRC connection requests for emergency sessions and mobile terminated services for that AMF. This AMF configuration blocks emergency session requests from UEs with universal SIMs (USIMs) provisioned with Access Classes 11 and 15 when they are in their Home Public Land Mobile Network/Equivalent Home Public Land Mobile Network HPLMN/EHPLMN and from UEs with USIMs provisioned with Access Classes 12, 13 and 14 when they are in their home country, only permit RRC connection requests for high priority sessions, exception reporting and mobile terminated services for that AMF; or reject new RRC connection requests from UEs that access the network with low access priority. 
     In some examples, the radio resource control (RRC) connection requests listed in this clause also include the request for RRC Connection Resume. In some examples, when rejecting an RRC connection request for overload reasons, the RAN  103  indicates to the UE  102  an appropriate timer value that limits further RRC connection requests for a period of time. 
     In some examples, an RAN node supports rejecting of RRC connection establishments for certain UEs. Additionally, an RAN node may provide support for the barring of UEs. In some examples, during an overload situation, the AMF should attempt to maintain support for emergency services and for a Mobile Positioning System (MPS). 
     In some examples, when the AMF is recovering, the AMF can either: send OVERLOAD START messages with new percentage value that permit more traffic to be carried, or the AMF sends OVERLOAD STOP messages. 
     The congestion and overload control also includes NAS level Congestion control. In some examples, to protect the network from congestion the AMF has the option of rejecting NAS request messages. NAS level congestion control may contain the functions: “DNN based congestion control” and “General NAS level Mobility Management control”. 
     Under general overload conditions the AMF may reject Mobility Management signaling requests from UEs. When a NAS request is rejected, a Mobility Management back-off timer may be sent by the AMF. While the Mobility Management back-off timer is running, the UE may not initiate any NAS request for Mobility Management procedures except for Detach procedure, requests for UE(s) with high priority access, requests for emergency services and mobile terminated services. After any such Detach procedure, the back-off timer may continue to run. If the UE receives a paging request from the AMF while the Mobility Management back off timer is running, the UE may stop the Mobility Management back-off timer and initiate the Service Request procedure or the Tracking Area Update procedure. 
     In some examples of NAS level Congestion control, the DNN based Session Management congestion control may be activated by a session management function (SMF) due to a congestion situation at the SMF. The congestion control may include configuration, by a restart or recovery condition of a user plane function (UPF), or by a partial failure or recovery of a UPF for a particular UPF(s). 
     In some examples, the SMF may reject the Session Management requests from the UE (e.g. packet data unit (PDU) Session establishment/modification request) with a Session Management back-off timer when SM congestion associated with a data network name (DNN) is detected. If the UE provides no DNN, then the SMF uses a default DNN selected for the PDU session establishment. 
     In some examples, upon reception of the Session Management back-off timer in the NAS Session Management reject, if DNN was provided in the Session Management Request message that was rejected, the UE will not initiate any Session Management procedures for the congested DNN, at least until the timer expires. In some examples, the UE may initiate Session Management procedures for other DNNs. 
     In another example, if a DNN is not provided in the Session Management Request message that was rejected, the UE will not initiate any Session Management requests without DNN. The UE may initiate Session Management procedures for a specific DNN. 
     In some examples, certain network changes, such as a cell or PLMN change do not stop the Session Management back-off timer. 
     In some examples, the UE is allowed to initiate the Session Management procedures for high priority access and emergency services even when the Session Management back-off timer is running. For example, if the UE receives a network initiated Session Management Request message for the congested DNN while the Session Management back-off timer is running, the UE may stop the Session Management back-off timer associated with this DNN and respond to the SMF. In some examples, the UE may support a separate Session Management back-off timer for every DNN that the UE may activate. 
       FIG. 2  illustrates alternate Radio Access Network (RAN) configurations including non-standalone configurations  3 ,  3 A, and  3   x  which are long term evolution (LTE) assisted and evolved packet core (EPC) connected. The non-standalone options of one embodiment also include configurations  7 ,  7   a , and  7   x  which are LTE assisted and 5G core network (CN) connected. Furthermore, configurations  4  and  4   a  are new radio (NR) assisted and 5G CN connected. The standalone options shown include configurations  2  and  5  which are NR/5G CN connected and LTE 5G CN connected, respectively. Table 1 illustrates RAN agreement on the RAN nodes for the various connection options. Each of the architecture configurations shown in  FIG. 2  may be supported by the embodiments described herein. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 NR RAT 
                 E-UTRA RAT 
               
               
                   
                 support 
                 support 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 5GCN connected 
                 gNB 
                 ng-eNB 
               
               
                   
                 EPC connected 
                 en-gNB 
                 eNB 
               
               
                   
                   
               
            
           
         
       
     
     Turning now to  FIG. 3 , examples of an AMF apparatus (including AMF  104 ) may be embodied as a core network apparatus as configured in accordance with an example embodiment of the present disclosure. As described below in conjunction with the flowchart of  FIG. 4 , the AMF  104  of an example embodiment may be configured to perform the functions described herein. In any instance, the AMF  104  may more generally be embodied by a computing device, such as a server, a personal computer, a computer workstation or other type of computing device including those functioning as a user equipment and/or a wireless local area network. Regardless of the manner in which the AMF  104  is embodied, the apparatus of an example embodiment may be configured as shown in  FIG. 3  so as to include, be associated with or otherwise be in communication with processing circuitry  300  including, for example, a processor  302  and a memory  304  and, in some embodiments, and/or a communication interface  306 . 
     In the processing circuitry  300 , the processor  302  (and/or co-processors or any other circuitry assisting or otherwise associated with the processor) may be in communication with the memory device  304  via a bus for passing information among components of the AMF  104 . The memory device may include, for example, one or more volatile and/or non-volatile memories. In other words, for example, the memory device may be an electronic storage device (e.g., a computer readable storage medium) comprising gates configured to store data (e.g., bits) that may be retrievable by a machine (e.g., a computing device like the processor). The memory device may be configured to store information, data, content, applications, instructions, or the like for enabling the apparatus to carry out various functions in accordance with an example embodiment of the present invention. For example, the memory device could be configured to buffer input data for processing by the processor. Additionally or alternatively, the memory device could be configured to store instructions for execution by the processor. 
     The AMF  104  may, in some embodiments, be embodied in various computing devices as described above. However, in some embodiments, the apparatus may be embodied as a chip or chip set. In other words, the apparatus may comprise one or more physical packages (e.g., chips) including materials, components and/or wires on a structural assembly (e.g., a baseboard). The structural assembly may provide physical strength, conservation of size, and/or limitation of electrical interaction for component circuitry included thereon. The apparatus may therefore, in some cases, be configured to implement an embodiment of the present invention on a single chip or as a single “system on a chip.” As such, in some cases, a chip or chipset may constitute means for performing one or more operations for providing the functionalities described herein. 
     The processor  302  may be embodied in a number of different ways. For example, the processor may be embodied as one or more of various hardware processing means such as a coprocessor, a microprocessor, a controller, a digital signal processor (DSP), a processing element with or without an accompanying DSP, or various other circuitry including integrated circuits such as, for example, an ASIC (application specific integrated circuit), an FPGA (field programmable gate array), a microcontroller unit (MCU), a hardware accelerator, a special-purpose computer chip, or the like. As such, in some embodiments, the processor may include one or more processing cores configured to perform independently. A multi-core processor may enable multiprocessing within a single physical package. Additionally or alternatively, the processor may include one or more processors configured in tandem via the bus to enable independent execution of instructions, pipelining and/or multithreading. 
     In an example embodiment, the processor  302  may be configured to execute instructions stored in the memory device  304  or otherwise accessible to the processor. Alternatively or additionally, the processor may be configured to execute hard coded functionality. As such, whether configured by hardware or software methods, or by a combination thereof, the processor may represent an entity (e.g., physically embodied in circuitry) capable of performing operations according to an embodiment of the present disclosure while configured accordingly. Thus, for example, when the processor is embodied as an ASIC, FPGA or the like, the processor may be specifically configured hardware for conducting the operations described herein. Alternatively, as another example, when the processor is embodied as an executor of instructions, the instructions may specifically configure the processor to perform the algorithms and/or operations described herein when the instructions are executed. However, in some cases, the processor may be a processor of a specific device (e.g., an encoder and/or a decoder) configured to employ an embodiment of the present invention by further configuration of the processor by instructions for performing the algorithms and/or operations described herein. The processor may include, among other things, a clock, an arithmetic logic unit (ALU) and logic gates configured to support operation of the processor. 
     In embodiments that include a communication interface  306 , the communication interface may be any means such as a device or circuitry embodied in either hardware or a combination of hardware and software that is configured to receive and/or transmit data from/to a network and/or any other device or module in communication with the AMF  104 , such as UE, core network services, a database or other storage device, etc. In this regard, the communication interface may include, for example, an antenna (or multiple antennas) and supporting hardware and/or software for enabling communications with a wireless communication network. Additionally or alternatively, the communication interface may include the circuitry for interacting with the antenna(s) to cause transmission of signals via the antenna(s) or to handle receipt of signals received via the antenna(s). In some environments, the communication interface may alternatively or also support wired communication. As such, for example, the communication interface may include a communication modem and/or other hardware/software for supporting communication via cable, digital subscriber line (DSL), universal serial bus (USB) or other mechanisms. 
     Referring now to  FIG. 4 , the operations performed, such as by the AMF proactive load control  106  embodied on AMF  104  on a core network apparatus of  FIG. 3  which may be embodied by or in association with processing circuitry  300 , are illustrated in order to provide a warning message via a public warning system. As shown in block  402  of  FIG. 4 , the apparatus of this example embodiment includes means, such as the processing circuitry  300 , the processor  302  or the like, for receiving an initial message request at an access and mobility management function (AMF) from user equipment via a radio access network (RAN). For example, AMF  104  may receive initial message  202  as shown in  FIG. 1B . In some examples, initial message  202  may comprise a NAS message from UE  102  when waking from IDLE mode. In some examples, the RAN  103  may comprise one of the configurations described in relation to  FIG. 2   
     As shown in block  404  of  FIG. 4 , the apparatus of this example embodiment includes means, such as the processing circuitry  300 , the processor  302  or the like, for determining a pre-overload condition exists in the AMF. In some examples, the pre-overload condition will comprise a lower limit which corresponds to the utilization of the AMF approaching an overload condition and an upper limit which corresponds to an overload condition. In some examples, the pre-overload condition may comprise a condition where a predefined percentage or amount, such as 60% (lower limit)-80% (upper limit), of the AMF&#39;s capacity is utilized. For example, 60-80% of the UEs registered to the AMF  104  may be active and using the AMF. In some examples, the lower and upper limits defining the pre-overload condition may be predefined such as by an operator of the mobile network. 
     As shown in block  406  of  FIG. 4 , the apparatus of this example embodiment includes means, such as the processing circuitry  300 , the processor  302  or the like, for transmitting a redirection request to the RAN, wherein the redirection request is configured to cause a transmission of the initial message to an alternate AMF. For example, the RAN  103  may be caused by the redirection request  203  to send the initial message as redirection message  204  to the alternate AMF  206   a . In some examples, the AMF  104  may provide a proactive overload control indication in the redirection request. For example, the control indication may indicate a certain percentage of UE(s) that should be redirected to another/alternate AMF. For example, the AMF proactive load control  106  may provide a proactive overload control indication as part of the redirection request  203 , with a request to redirect a predefined percentage or a predefined amount, such as 25%, of the IDLE UE(s)  102  to another AMF. When the RAN  103  receives the redirection request  203 , it may be configured to take one of the following actions: redirect 1 out of 4 NGAP messages from IDLE mode UEs to another AMF or redirect first 25 out of 100 NGAP messages from IDLE mode UEs to another AMF. 
     In another example, the RAN  103  may only redirect 20% or 1 out of every five initial messages received from UEs  102 . In some examples, the portion of initial messages redirected may increase or decrease over time according to the redirection request or subsequent redirection requests from AMF  104 . For example, as utilization of the AMF increases from 60% to 80%, the AMF proactive load control  106  may be configured to request a higher number of redirections. For example, when the AMF utilization is at 60%, the AMF proactive load control  106  may send a redirect request with a proactive overload control indication requesting redirection of 20% of the IDLE UE(s)  102 . When the utilization is at 75% the AMF proactive load control  106  may send a redirect request with a proactive overload control indication requesting redirection of 30% of the IDLE UE(s)  102 . 
     Referring now to  FIG. 5 , the operations performed, such as by the AMF proactive load control  106  embodied on AMF  104  on a core network apparatus of  FIG. 3  which may be embodied by or in association with processing circuitry  300 , are depicted. As shown in block  502  of  FIG. 5  the apparatus of this example embodiment includes means, such as the processing circuitry  300 , the processor  302  or the like, for determining a pre-overload condition has ceased. In some examples, the pre-overload condition may cease when the capacity of the AMF  104  that is utilized falls below a predefined percentage such as the lower limit. For example, the AMF may become less than 60% utilized. In another example, the pre-overload condition may cease when the capacity of the AMF  104  that is utilized falls below a predefine level lower than the lower limit in order to avoid pre-overload conditions reoccurring quickly. For example, if the lower limit is 60% the pre-overload condition may cease when the AMF utilization is below 55%. In another example, if the AMF  104  becomes overloaded or enters an overload condition (e.g., greater than 80% utilized), the pre-overload condition ceases. 
     As shown in block  504  of  FIG. 5 , the apparatus of this example embodiment includes means, such as the processing circuitry  300 , the processor  302  or the like, for transmitting a cease redirection request to the RAN, this indicates that the AMF  104  can serve all UE(s) in IDLE mode. In some examples, the RAN  103  may then cease redirecting the initial messages received from UEs  102 . In some examples, if the AMF is in an overload condition, the RAN  103  may then reject the initial messages from the UEs  102 . If the AMF is below the pre-overload conditions, the RAN  103  will treat the initial messages normally and forward them from UE(s)  102  to AMF  104 . 
     As described above,  FIGS. 4-5  illustrate flowcharts of an apparatus, method, and computer program product according to example embodiments of the invention. It will be understood that each block of the flowcharts, and combinations of blocks in the flowcharts, may be implemented by various means, such as hardware, firmware, processor, circuitry, and/or other devices associated with execution of software including one or more computer program instructions. For example, one or more of the procedures described above may be embodied by computer program instructions. In this regard, the computer program instructions which embody the procedures described above may be stored by a memory device  304  of an apparatus employing an embodiment of the present invention and executed by processing circuitry  300 , e.g., a processor  302 , of the apparatus. As will be appreciated, any such computer program instructions may be loaded onto a computer or other programmable apparatus (e.g., hardware) to produce a machine, such that the resulting computer or other programmable apparatus implements the functions specified in the flowchart blocks. These computer program instructions may also be stored in a computer-readable memory that may direct a computer or other programmable apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture, the execution of which implements the function specified in the flowchart blocks. The computer program instructions may also be loaded onto a computer or other programmable apparatus to cause a series of operations to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide operations for implementing the functions specified in the flowchart blocks. 
     Accordingly, blocks of the flowcharts support combinations of means for performing the specified functions and combinations of operations for performing the specified functions for performing the specified functions. It will also be understood that one or more blocks of the flowcharts, and combinations of blocks in the flowcharts, may be implemented by special purpose hardware-based computer systems which perform the specified functions, or combinations of special purpose hardware and computer instructions. 
     In some embodiments, certain ones of the operations above may be modified or further amplified. Furthermore, in some embodiments, additional optional operations may be included. Modifications, additions, or amplifications to the operations above may be performed in any order and in any combination. 
     Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. 
     Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.