# Patent

## Title
Network-instructed handover from WLAN to another radio access network

## Abstract

Systems and methods are disclosed for providing a network-instructed handover of a wireless device from a Wireless Local Area Network (WLAN) to a Radio Access Network (RAN) of another Radio Access Technology (RAT), e.g., a 3rd Generation Partnership Project (3GPP) or 3rd Generation Partnership Project 2 (3GPP2) RAT. In one embodiment, a WLAN access node determines that a handover of a wireless device from the WLAN to another RAN of a different RAT is to be performed and transmits a handover instruction to the wireless device that instructs the wireless device to perform a handover from the WLAN to a RAN of a different RAT. In this manner, the WLAN access node is able to steer the wireless device from the WLAN to a RAN of a different RAT.

## Background
RELATED APPLICATIONS
This application claims the benefit of provisional patent application Ser. No. 61/811,732, filed Apr. 13, 2013, the disclosure of which is hereby incorporated herein by reference in its entirety.


FIELD OF THE DISCLOSURE
The present disclosure relates to a network-instructed handover of a wireless device from a Wireless Local Area Network (WLAN) to a Radio Access Network (RAN) of another Radio Access Technology (RAT), e.g., a 3rd Generation Partnership Project (3GPP) or 3rd Generation Partnership Project 2 (3GPP2) RAT.
BACKGROUND
The Institute for Electrical and Electronics Engineers (IEEE) has created and maintains a set of Media Access Control (MAC) and PHYsical layer (PHY) specifications for implementing Wireless Local Area Network (WLAN) communication. This set of MAC and PHY layer specifications is known as the IEEE 802.11 specifications (more specifically known as IEEE Standard for Information technology—Telecommunications and information exchange between systems Local and metropolitan area networks—Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications). WLANs that operate according to the IEEE 802.11 specifications are also known as Wi-Fi® networks. Currently, Wi-Fi® networks mainly operate in the 2.4 Gigahertz (GHz) or the 5 GHz frequency band.
The IEEE 802.11 specifications regulate the MAC layer, the PHY layer, and other aspects of each addressable unit, which is referred to as a station (STA) (e.g., an access point or a wireless device), to secure compatibility and inter-operability between access points and wireless devices. Wireless devices may also be referred to herein as wireless terminals, portable devices, or portable terminals. Wi-Fi® networks are generally operated in unlicensed bands. As such, communication over a Wi-Fi® network may be subject to interference from any number of both known and unknown devices. Wi-Fi® networks are commonly used as wireless extensions to fixed/wired broadband access, e.g., in domestic environments and hotspots such as, for example, airports, train stations, and restaurants.
Recently, Wi-Fi® networks have been subject to increased interest from cellular network operators. In particular, there has been an increased interest in using Wi-Fi® networks as an extension of or as an alternative to cellular Radio Access Networks (RANs) to handle the always increasing wireless bandwidth demands. Cellular network operators that are currently serving mobile devices with, e.g. any of the 3rd Generation Partnership Project (3GPP) technologies, see Wi-Fi® networks as a wireless technology that can provide improved service in their regular cellular networks. The 3GPP technologies include Long Term Evolution (LTE), Universal Mobile Telecommunications System (UMTS)/Wideband Code Division Multiple Access (WCDMA), and Global System for Mobile Communications (GSM).
The term “operator-controlled Wi-Fi®” refers to a Wi-Fi® deployment that on some level is integrated with a cellular network operator's existing network and where the 3GPP RAN and the Wi-Fi® wireless access may even be connected to the same core network and provide the same services. There is currently quite intense activity in the area of operator-controlled Wi-Fi® in several standardization organizations. In 3GPP, connection of Wi-Fi® access points to the 3GPP-specified core network is being pursued. In the Wi-Fi® Alliance (WFA), activities related to certification of Wi-Fi® products are undertaken, which are to some extent driven by the need to make Wi-Fi® networks a viable wireless technology for cellular operators to support high bandwidth offerings in their networks. In this regard, the term “Wi-Fi® offload” is commonly used to refer to a cellular network operator's ability to offload traffic from their cellular networks to Wi-Fi® networks, e.g., in peak traffic hours and in situations when the cellular network for one reason or another needs to be offloaded, e.g., to provide requested quality of service, maximize bandwidth, or simply for coverage.
For a cellular network operator, offering a mix of both Wi-Fi® and cellular (e.g., 3GPP) Radio Access Technologies (RATs) results in new problems. In particular, some of these problems arise from the fact that Wi-Fi® networks and cellular networks (e.g., 3GPP networks) are standardized in isolation from one another. As a result, there is a need for intelligent mechanisms that enable co-existence of the Wi-Fi® and cellular network technologies. One such area is connection management. Further, wireless devices (e.g., LTE User Equipment devices (UEs)) usually support both Wi-Fi® and a number of 3GPP cellular technologies. However, many of these wireless devices are basically behaving as two separate devices from a radio access perspective. The 3GPP RAN and the modems and protocols that are operating pursuant to the 3GPP specifications are basically unaware of the Wi-Fi® protocols and modems that are operating pursuant to the IEEE 802.11 specifications.
In light of the discussion above, there is a need for systems and methods that provide intelligent connection management in a communication system having a mix of both Wi-Fi® and cellular (e.g., 3GPP) RATs.
SUMMARY
Systems and methods relating to a network-instructed handover of a wireless device from a Wireless Local Area Network (WLAN) to a Radio Access Network (RAN) of another Radio Access Technology (RAT), e.g., a 3rd Generation Partnership Project (3GPP) or 3rd Generation Partnership Project 2 (3GPP2) RAT, are disclosed. In one embodiment, a method of operation of a WLAN access node is provided. In one embodiment, the method of operation of the WLAN access node includes determining that a handover of a wireless device from the WLAN to another RAN of a different RAT is to be performed and transmitting a handover instruction to the wireless device that instructs the wireless device to perform a handover from the WLAN to a RAN of a different RAT. In this manner, the WLAN access node is able to steer the wireless device from the WLAN to a RAN of a different RAT.
In one embodiment, the handover is a selective handover. More specifically, in one embodiment, the handover is a handover of at least one but less than all communications sessions (e.g., Internet Protocol (IP) sessions) of the wireless device from the WLAN to a RAN of a different RAT. In another embodiment, the handover is a full handover. More specifically, in one embodiment, the handover is a handover of all communications sessions (e.g., IP sessions) of the wireless device from the WLAN to a RAN of a different RAT.
In one embodiment, the handover instruction is a general instruction to perform a handover from the WLAN to a RAN of a different RAT. In another embodiment, the handover instruction includes information that identifies the different RAT for the handover.
In yet another embodiment, the handover instruction includes information that identifies a target cell in the RAN of the different RAT. In addition, in one embodiment, the handover instruction further includes information that identifies the different RAT and the RAN of the different RAT. In another embodiment, the handover instruction further includes assistance information that assists the wireless device when performing the handover. In one embodiment, the assistance information includes at least some system information of the target cell.
In one embodiment, the different RAT is a 3GPP RAT, and the handover instruction includes one or more parameters that enable the wireless device to connect to a RAN of the 3GPP RAT.
In one embodiment, the handover instruction includes a retry timer value that defines an amount of time that the wireless device should attempt to access the RAN of the different RAT when performing the handover.
In one embodiment, the WLAN is an Institute for Electrical and Electronics Engineers (IEEE) 802.11 wireless network. Still further, in one embodiment, the different RAT is a cellular network RAT. In one embodiment, the cellular network RAT is a 3GPP or 3GPP2 RAT. Further, in one embodiment, transmitting the handover instruction to the wireless device includes transmitting, to the wireless device, a management frame selected from a group consisting of: a Deauthentication Management frame including a reason code that corresponds to the handover instruction and a Disassociation Management frame including a reason code that corresponds to the handover instruction. Still further, in one embodiment, transmitting the management frame further includes transmitting information regarding the handover instruction in one or more vendor-specific elements within the management frame. In one embodiment, the information regarding the handover instruction includes at least one of a group consisting of: a target set of networks for the handover, a target RAT for the handover, a target cell, assistance information that assists the wireless device when performing the handover, and a 3GPP handover command. Notably, a 3GPP handover command may alternatively be referred to herein as a 3GPP handover command message. In another embodiment, the information regarding the handover instruction includes a retry timer value that defines an amount of time that the wireless device should attempt to access the RAN of the 3GPP or 3GPP2 RAT when performing the handover.
In one embodiment, the WLAN is an IEEE 802.11 wireless network, the different RAT is a 3GPP or 3GPP2 cellular network RAT, and transmitting the handover instruction to the wireless device includes transmitting, to the wireless device, an Association Response Management frame including the handover instruction. In another embodiment, the WLAN is an IEEE 802.11 wireless network, the different RAT is a 3GPP or 3GPP2 cellular network RAT, and transmitting the handover instruction to the wireless device comprises transmitting, to the wireless device, a Basic Service Set (BSS) Transition Management frame with zero neighbor report elements. In one embodiment, transmitting the BSS Transition Management frame further includes transmitting information regarding the handover instruction in one or more vendor-specific elements within the BSS Transition Management frame. In one embodiment, the information regarding the handover instruction includes at least one of a group consisting of: a target set of networks for the handover, a target RAT for the handover, a target cell, assistance information that assists the wireless device when performing the handover, and a 3GPP handover command. In another embodiment, the information regarding the handover instruction includes a retry timer value that defines an amount of time that the wireless device should attempt to access the RAN of the 3GPP or 3GPP2 RAT when performing the handover.
In one embodiment, the WLAN is an IEEE 802.11 wireless network, the different RAT is a 3GPP or 3GPP2 cellular network RAT, and transmitting the handover instruction to the wireless device includes transmitting, to the wireless device, a Wireless Network Management Notification (WNM-Notification) Request frame including the handover instruction within one or more optional subelements formatted as one or more vendor-specific elements. In one embodiment, the handover instruction includes at least one of a group consisting of: information indicative of the 3GPP or 3GPP2 RAT for the handover, a cell identifier of a target cell in the RAN of the 3GPP or 3GPP2 RAT to which the wireless device is to be handed over, and one or more attachment parameters that indicate which communication sessions of the wireless device are to be handed over.
In one embodiment, the WLAN is an IEEE 802.11 wireless network, the different RAT is a 3GPP or 3GPP2 cellular network RAT, and transmitting the handover instruction to the wireless device includes transmitting, to the wireless device, a WNM-Notification Request frame including the handover instruction.
In one embodiment, determining that a handover of the wireless device from the WLAN to another RAN of a different RAT is to be performed includes deciding to initiate a handover to a 3GPP RAT, sending a handover preparation request to a RAN in a RAN of the 3GPP RAT, and receiving a handover preparation response from the RAN comprising a 3GPP handover command. In this embodiment, transmitting the handover instruction includes transmitting the 3GPP handover command to the wireless device. Further, in one embodiment, transmitting the 3GPP handover command includes transmitting a frame selected from a group consisting of: a Deauthorization Management frame including the 3GPP handover command, a Disassociation Management frame including the 3GPP handover command, an Association Response Management frame including the 3GPP handover command, a BSS Transition Management frame including the 3GPP handover command, and a WNM-Notification frame (e.g., a WMN-Notification Request frame) including the 3GPP handover command.
In one embodiment, a WLAN access node includes a processor and memory containing instructions executable by the processor whereby the WLAN access node is operative to determine that a handover of a wireless device from a WLAN to another RAN of a different RAT is to be performed, and transmit a handover instruction to the wireless device that instructs the wireless device to perform a handover from the WLAN to a RAN of a different RAT. The memory may include additional instructions executable by the processor whereby the WLAN access node is operative to, e.g., perform any of the embodiments described above.
In another embodiment, a WLAN access node is adapted to determine that a handover of a wireless device from the WLAN to another RAN of a different RAT is to be performed and transmit a handover instruction to the wireless device that instructs the wireless device to perform a handover from the WLAN to a RAN of a different RAT. The WLAN access node may be further adapted to perform any of the methods described above.
In another embodiment, a WLAN access node includes means for determining that a handover of a wireless device from the WLAN to another RAN of a different RAT is to be performed and means for transmitting a handover instruction to the wireless device that instructs the wireless device to perform a handover from the WLAN to a RAN of a different RAT.
In yet another embodiment, a WLAN access node includes a WLAN communication module configured to provide WLAN communication with a wireless device, a handover decision module configured to determine that a handover of the wireless device from a WLAN to another RAN of a different RAT is to be performed, and a handover instruction module configured to transmit a handover instruction to the wireless device that instructs the wireless device to perform a handover from the WLAN to a RAN of a different RAT.
In another embodiment, a computer program is provided that includes instructions which, when executed on at least one processor, cause the at least one processor to carry out any of the methods of operation of a WLAN access node described above. In one embodiment, a carrier containing the computer program is provided, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium).
In one embodiment, a method of operation of a wireless device is provided. The method of operation of the wireless device includes communicating with a WLAN access node, receiving a handover instruction from the WLAN access node to perform a handover from a WLAN to another RAN of a different RAT, and performing the handover in response to receiving the handover instruction.
In one embodiment, the handover instruction is an instruction for a selective handover from the WLAN to another RAN of a different RAT, and performing the handover comprises performing the selective handover. In another embodiment, the handover instruction is an instruction for a full handover from the WLAN to another RAN of a different RAT, and performing the handover comprises performing the full handover.
In one embodiment, the handover instruction is a general instruction to perform a handover to a RAN of a different RAT, and performing the handover includes performing the handover to a RAN of a different RAT. In another embodiment, the handover instruction includes information that identifies the different RAT for the handover, and performing the handover includes performing the handover to a RAN of the different RAT identified by the information included in the handover instruction.
In yet another embodiment, the handover instruction includes information that identifies a target cell in the RAN of the different RAT, and performing the handover includes performing the handover to the target cell. In one embodiment, the handover instruction further includes information that identifies the different RAT and the RAN of the different RAT. In another embodiment, the handover instruction further includes assistance information that assists the wireless device when performing the handover, and performing the handover to the target cell includes performing the handover to the target cell based on the assistance information. In one embodiment, the assistance information includes at least some system information of the target cell.
In one embodiment, the different RAT is a 3GPP RAT, and the handover instruction includes one or more parameters that enable the wireless device to connect to a RAN of the 3GPP RAT.
In one embodiment, the handover instruction includes a retry timer value that defines an amount of time that the wireless device should attempt to access the RAN of the different RAT when performing the handover. Further, in one embodiment, performing the handover includes retrying the handover for the amount of time defined by the retry timer value, and notifying the WLAN access node of a handover failure if the handover is not successful within the amount of time defined by the retry timer.
In one embodiment, the WLAN is an IEEE 802.11 wireless network. Further, in one embodiment, the different RAT is a cellular network RAT. In one embodiment, the cellular network RAT is a 3GPP or 3GPP2 RAT. Further, in one embodiment, receiving the handover instruction includes receiving a management frame transmitted by the WLAN access node, wherein the management frame is selected from a group consisting of: a Deauthentication Management frame including a reason code that corresponds to the handover instruction and a Disassociation Management frame including a reason code that corresponds to the handover instruction. In another embodiment, receiving the handover instruction includes receiving an Association Response Management frame including the handover instruction from the WLAN access node. In yet another embodiment, receiving the handover instruction includes receiving a BSS Transition Management frame with zero neighbor report elements from the WLAN access node. In yet another embodiment, receiving the handover instruction includes receiving, from the WLAN access node, a WNM-Notification frame (e.g., a WNM-Notification Request frame) including the handover instruction within one or more optional subelements formatted as one or more vendor-specific elements. In yet another embodiment, receiving the handover instruction includes receiving a WNM-Notification frame including the handover instruction from the WLAN access node.
In one embodiment, receiving the handover instruction includes receiving a 3GPP handover command within a WLAN frame.
In one embodiment, a wireless device is provided. In one embodiment, the wireless device includes a transceiver, a processor, and memory containing instructions executable by the processor whereby the wireless device is operative to communicate with a WLAN access node of a WLAN via the transceiver, receive, via the transceiver, a handover instruction from the WLAN access node to perform a handover from the WLAN to another RAN of a different RAT, and perform the handover in response to receiving the handover instruction.
In another embodiment, the wireless device is adapted to communicate with a WLAN access node of a WLAN, receive a handover instruction from the WLAN access node to perform a handover from the WLAN to another RAN of a different RAT, and perform the handover in response to receiving the handover instruction. The wireless device may be further adapted to perform any of the embodiments of the method of operation of the wireless device described above.
In another embodiment, the wireless device includes means for communicating with a WLAN access node of a WLAN, means for receiving a handover instruction from the WLAN access node to perform a handover from the WLAN to another RAN of a different RAT, and means for performing the handover in response to receiving the handover instruction.
In another embodiment, the wireless device includes a WLAN communication module configured to provide WLAN communication with a WLAN access node of a WLAN, a handover instruction reception module configured to receive a handover instruction from the WLAN access node to perform a handover from the WLAN to another RAN of a different RAT, and a handover module configured to perform the handover in response to the handover instruction.
In one embodiment, a computer program is provided. The computer program comprises instructions which, when executed on at least one processor, cause the at least one processor to carry out the method of operation of a wireless device according to any of the embodiments described above. In one embodiment, a carrier containing the computer program is provided, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium).
Those skilled in the art will appreciate the scope of the present disclosure and realize additional aspects thereof after reading the following detailed description of the embodiments in association with the accompanying drawing figures.



BRIEF DESCRIPTION OF THE DRAWING FIGURES
The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure.
FIG. 1 illustrates a communication system including a mix of both a cellular network and a Wireless Local Area Network (WLAN) that provides a network-instructed handover of a wireless device from the WLAN to the cellular network according to one embodiment of the present disclosure;
FIG. 2 illustrates the operation of the communication system of FIG. 1 to perform a network-instructed handover of the wireless device from the WLAN to the cellular network according to one embodiment of the present disclosure;
FIG. 3 illustrates a frame structure of an Institute for Electrical and Electronics Engineers (IEEE) 802.11 Deauthentication Management frame or an IEEE 802.11 Disassociation Management frame that is utilized to transmit a handover instruction from a WLAN access node to the wireless device according to one embodiment of the present disclosure;
FIG. 4 illustrates the operation of the communication system of FIG. 1 to perform a network-instructed handover of the wireless device from the WLAN to the cellular network according to another embodiment of the present disclosure;
FIG. 5 illustrates a frame structure of an IEEE 802.11 Association Response Management frame that is utilized to transmit a handover instruction from a WLAN access node to the wireless device according to another embodiment of the present disclosure;
FIGS. 6A through 6C illustrate a frame structure of a conventional IEEE 802.11 Basic Service Set (BSS) Transition Management frame;
FIGS. 7A and 7B illustrate a frame structure of an IEEE 802.11 BSS Transition Management frame that is utilized to transmit a handover instruction from a WLAN access node to the wireless device according to another embodiment of the present disclosure;
FIG. 8 illustrates a frame structure of an IEEE 802.11 Wireless Network Management Notification (WNM-Notification) Request frame;
FIG. 9 illustrates a frame structure of an IEEE 802.11 WNM-Notification Request frame with vendor-specific formatting that is utilized to transmit a handover instruction from a WLAN access node to the wireless device according to another embodiment of the present disclosure;
FIG. 10 illustrates a frame structure of an IEEE 802.11 WNM-Notification Request Action frame in which optional subelements are formatted with vendor-specific formatting for transmission of a 3rd Generation Partnership Program (3GPP) handover command according to one embodiment of the present disclosure;
FIGS. 11A and 11B illustrate a frame structure of an IEEE 802.11 WNM-Notification Request frame that is utilized to transmit a handover instruction for multi-band steering according to another embodiment of the present disclosure;
FIG. 12 is a block diagram of one of the base stations of the cellular network of FIG. 1 according to one embodiment of the present disclosure;
FIG. 13 is a functional block diagram of one of the base stations of the cellular network of FIG. 1 according to one embodiment of the present disclosure;
FIG. 14 is a block diagram of the WLAN access node of FIG. 1 according to one embodiment of the present disclosure;
FIG. 15 is a functional block diagram of the WLAN access node of FIG. 1 according to one embodiment of the present disclosure;
FIG. 16 is a block diagram of one of the wireless devices of FIG. 1 according to one embodiment of the present disclosure; and
FIG. 17 is a functional block diagram of one of the wireless devices of FIG. 1 according to one embodiment of the present disclosure.



DETAILED DESCRIPTION
The embodiments set forth below represent information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims.
Systems and methods relating to a network-instructed handover of a wireless device from a Wireless Local Area Network (WLAN) to a Radio Access Network (RAN) of another Radio Access Technology (RAT), e.g., a 3rd Generation Partnership Project (3GPP) or 3rd Generation Partnership Project 2 (3GPP2) RAT, are disclosed. In this regard, FIG. 1 illustrates a communication system 10 that includes a cellular RAN 12 and a WLAN 14. The cellular RAN 12 includes base stations 16-1 through 16-5 (generally referred to herein collectively as base stations 16 and individually as base station 16) that operate according to a cellular RAT such as, e.g., a 3GPP or 3GPP2 RAT. Some examples of 3GPP and 3GPP2 RATs are Long Term Evolution (LTE), Universal Mobile Telecommunications System (UMTS)/Wideband Code Division Multiple Access WCDMA), and Global System for Mobile Communications (GSM) RATs. While five base stations 16 are shown in this example, the cellular RAN 12 may include any number of base stations 16.
The WLAN 14 includes a WLAN access node 18 that operates according to a WLAN RAT and provides a connection point for the WLAN 14. The WLAN access node 18 may alternatively be referred to as an access point, a wireless access controller, or the like. In the embodiments described herein, the WLAN RAT is an Institute for Electrical and Electronics Engineers (IEEE) 802.11 WLAN RAT (i.e., the WLAN 14 is an IEEE 802.11 or Wi-Fi® network). For example, the WLAN 14 may be a Wi-Fi® hotspot. However, the present disclosure is not limited thereto. Other WLAN RATs may be used. In one embodiment, the WLAN 14 is an operator controlled WLAN, which at some level is integrated with the cellular network (including the cellular RAN 12) of a cellular network operator. Further, while not illustrated, the WLAN 14 and the cellular RAN 12 may be connected to the same core network (e.g., an Evolved Packet Core (EPC) network for a LTE RAN).
Together, the cellular RAN 12 and the WLAN 14 provide services to a number of wireless devices 20-1 through 20-5 (generally referred to herein collectively as wireless devices 20 and individually as wireless device 20). While five wireless devices 20 are shown in this example, there may be any number of wireless devices 20 served by the cellular RAN 12 and the WLAN 14. In this example, the wireless devices 20-1 and 20-2 are connected to the WLAN 14, whereas the wireless devices 20-3 through 20-5 are connected to the cellular RAN 12. The wireless devices 20, which may also be referred to as wireless communication devices, may represent any suitable type of device capable of wireless communication including, but not limited to, conventional User Equipment devices (UEs) and other types of cellular telephones; Machine Type Communication (MTC)/Machine-to-Machine (M2M) devices (e.g., wireless sensors or meters); Radio Frequency Identifiers (RFIDs); WLAN terminals or Stations (STAs); and wireless-capable laptops, tablets, and other computers.
As discussed below, the WLAN access node 18 initiates a network-instructed handover of the wireless device 20-1 from the WLAN 14 to the cellular RAN 12. Using conventional technology, the wireless device 20-1 would remain connected to the WLAN 14 until a connection with the WLAN 14 is no longer possible. In particular, the wireless device 20-1 would remain connected to the WLAN 14 as long as the wireless device 20-1 is within a coverage area 22 of the WLAN 14. As a result, the wireless device 20-1 would, at least in some scenarios, remain connected to the WLAN 14 even though a connection to the cellular RAN 12 would be better (e.g., provide lower latency, higher data rates, or the like). According to one embodiment of the present disclosure, the WLAN access node 18 operates to initiate a handover of the wireless device 20-1 from the WLAN 14 to the cellular RAN 12 whenever such a handover is desirable. As one example, the WLAN access node 18 may initiate a handover from the WLAN 14 to the cellular RAN 12 when the wireless device 20-1 is greater than a predefined radio distance from the WLAN access node 18 as indicated by dashed line 24 but is still within the coverage area 22 of the WLAN 14. As used herein, radio distance is any value indicative of a quality or strength of a radio signal received by the wireless device 20-1 from the WLAN access node 18 or received by the WLAN access node 18 from the wireless device 20-1 (e.g., a Received Signal Strength Indicator (RSSI)).
As discussed below in detail, in order to initiate the handover of the wireless device 20-1 from the WLAN 14 to the cellular RAN 12, the WLAN access node 18 sends a handover (HO) instruction to the wireless device 20-1. The handover instruction may be for a full handover of all communication sessions (e.g., Internet Protocol (IP) sessions) from the WLAN 14 to the cellular RAN 12 or a selective handover of one or more communications sessions, but potentially less than all communications sessions, from the WLAN 14 to the cellular RAN 12. In response to the handover instruction, the wireless device 20-1 performs the handover by connecting to the cellular RAN 12. In this particular example, the wireless device 20-1 connects to the base station 16-1 (more specifically to a cell served by the base station 16-1). From that point, the handed over communication session(s) are with the cellular RAN 12. Note that while the embodiment of FIG. 1 and many of the other embodiments described below focus on a handover from the WLAN 14 to the cellular RAN 12, the present disclosure is not limited thereto. The handover may be from the WLAN 14 to any RAN of a different RAT.
FIG. 2 illustrates the operation of the communication system 10 of FIG. 1 to perform a network-instructed handover of the wireless device 20-1 from the WLAN 14 to the cellular RAN 12 according to one embodiment of the present disclosure. As illustrated, initially, communication is established between the wireless device 20-1 and the WLAN 14 via the WLAN access node 18 (step 100). At some point, the WLAN access node 18 decides, or determines, that a handover of the wireless device 20-1 from the WLAN 14 to a RAN of a different RAT is desired (step 102). In one embodiment, the handover is a full handover of all communication or traffic (e.g., all IP sessions). In another embodiment, the handover is a selective handover of particular communication or traffic (e.g., only IP sessions of certain types). Further, the decision to perform the handover may be a general decision to perform a handover from the WLAN 14. In other words, the handover decision may be a general decision to perform a handover, where it is left to the wireless device 20-1 to determine a target for the handover. Alternatively, the handover decision may be a specific handover decision. More specifically, a specific handover decision may be a decision to perform a handover to a target RAT (e.g., LTE), a decision to perform a handover to a target RAN of a target RAT type (e.g., a specific LTE RAN), or a decision to perform a handover to a target cell in a target RAN of a target RAT type (e.g., a specific cell in a specific LTE RAN).
Next, the WLAN access node 18 transmits a handover instruction to the wireless device 20-1 (step 104). As discussed below in detail, in one embodiment, the WLAN 14 is an IEEE 802.11, or Wi-Fi®, network, and the handover instruction is transmitted within an IEEE 802.11 frame. The IEEE 802.11 frame may be, for example, a Deauthentication Management frame, a Disassociation Management frame, an Association Response Management frame, a Basic Service Set (BSS) Transition Management Request Action frame, or a Wireless Network Management Notification (WNM-Notification) frame (e.g., a WNM-Notification Request frame). The handover instruction includes information indicating that a handover is to be performed. More specifically, in one embodiment, the handover instruction includes one or more of the following:

    
    
        a code (e.g., a special status code or a special reason code) that indicates that a handover is to be performed,
        information that indicates whether the handover is a full or a selective handover,
        information identifying communications sessions to be handed over in the case of selective handover (e.g., one or more 3GPP Non-Access Stratum (NAS) parameters indicating a subset of ongoing traffic or communications sessions (e.g., Packet Data Network (PDN) connections identified by Access Point Names (APNs), IP sessions identified by Traffic Flow Templates (TFTs)) that are to be handed over),
        information that identifies a target RAT for the handover,
        information that identifies a target RAN for the handover,
        information that identifies a target cell for the handover,
        assistance information that will assist the wireless device 20-1 when performing the handover (e.g., at least some System Information (SI) of a target cell),
        a 3GPP handover command, which may be received by the WLAN access node 18 from, e.g., the base station 16 of a target cell for the handover, or one or more parameters from a 3GPP handover command,
        one or more 3GPP NAS parameters (e.g. attachment type, APN, etc.), and
        a retry timer that defines an amount of time that the wireless device 20-1 should attempt to access a RAN of a different RAT (which, as discussed above, may or may not be specified by the handover instruction) when performing the handover before, e.g., notifying the WLAN access node 18 of a handover failure or attempting to reestablish the handed over communication with the WLAN 14.
    
    


In response to the handover instruction, the wireless device 20-1 performs the handover to, in this example, a cell served by the base station 16-1 in the cellular RAN 12 (step 106). The manner in which the wireless device 20-1 performs the handover may vary depending on the particular implementation. As one example, the wireless device 20-1 synchronizes to the cell served by the base station 16-1, obtains the system information of the cell (if needed), and initiates a random access procedure to establish a connection to the cell served by the base station 16-1. Once the random access procedure is finished, the final steps of the handover are completed. However, the exact details depend on the RAT of the cellular RAN 12 and the particular implementation (e.g., whether assistance information is provided in the handover instruction). Once the handover is complete, the wireless device 20-1 communicates with the base station 16-1 (step 108). In addition, if the handover was a selective handover, the wireless device 20-1 also communicates with the WLAN access node 18 for any communications session(s) or traffic that was not handed over (step 110).
As discussed above, in some embodiments, the handover instruction is transmitted from the WLAN access node 18 to the wireless device 20-1 within a particular type of IEEE 802.11, or Wi-Fi®, frame. In this regard, FIG. 3 illustrates a frame format for both an IEEE 802.11 Deauthentication Management frame and an IEEE 802.11 Disassociation Management frame that can be utilized to transmit the handover instruction according to one embodiment of the present disclosure. These two frames have the same frame format. Notably, the frame format of the Deauthentication Management frame and the Disassociation Management frame are defined in Chapters 8.3.3.12 and 8.3.3.4 of “802.11-2012—IEEE Standard for Information technology—Telecommunications and information exchange between systems Local and metropolitan area networks—Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications,” which is referred to herein as the IEEE 802.11-2012 specification.
Importantly, the frame body of the Deauthentication/Disassociation frame includes a reason code and one or more vendor-specific elements. In one embodiment, the handover instruction includes a special reason code transmitted in the frame body. In particular, the IEEE 802.11-2012 specification defines a number of reason codes in Chapter 8.4.1.7. In this embodiment, a new reason code is defined for a handover instruction from the WLAN 14. Thus, in this embodiment, the WLAN access node 18 transmits the handover instruction by transmitting a Deauthentication/Disassociation Management frame including the new, or special, reason code defined to indicate a handover instruction.
In addition, in some embodiments, the handover instruction includes additional information transmitted in the one or more vendor-specific elements of the Deauthentication/Disassociation Management frame. This additional information may include any information related to the handover of the wireless device 20-1 from the WLAN 14 to, in the example of FIGS. 1 and 2, the cellular RAN 12. In one embodiment, the additional information includes one or more of the following:

    
    
        A target set of networks (e.g., Public Land Mobile Networks (PLMNs) or Network Identifier/System Identifiers (NID/SIDs)) for the handover. The WLAN 14 may belong to a separate network compared to the cellular RAN 12. Furthermore, different equivalent PLMNs may exist in the cellular/3GPP domain.
        A target 3GPP/3GPP2 RAT for the handover (i.e., the 3GPP/3GPP2 RAT to which the wireless device 20-1 should handover to).
        A target 3GPP/3GPP2 RAT and a target cell for the handover. This may indicate both the RAT and the cell that the wireless device 20-1 should handover to. The target cell could be indicated as, e.g., a GSM Cell Global Identity (CGI) (including Mobile Country Code (MCC), Mobile Network Code (MNC), Location Area Code (LAC), and Cell Identity (CI)) or any other RAT specific cell identifier like, e.g., the 28-bit Universal Terrestrial Radio Access Network (UTRAN) Cell Identifier (UC-Id) including both Radio Network Controller Identifier (RNC-ID) and Cell-ID (C-Id). Notably, the UC-Id is 28 bits and parts of the UC-Id are used for the RNC-ID (e.g., 12 bits) and the rest for the C-Id (e.g., 16 bits). Then, the whole UC-Id can identify a cell within a PLMN, and the C-Id can be used to identify a cell within a Radio Network Subsystem (RNS).
        Assistance information for assisting the wireless device 20-1 when performing the handover to a target cell in a target RAT. For example, the assistance information may include at least some SI elements that the wireless device 20-1 would need to first read on the target cell. The wireless device 20-1 may be able to more quickly access the target cell when such assistance information is already provided to the wireless device 20-1 from the WLAN 14.
        A 3GPP handover command as defined in the 3GPP specification for a target RAT. For example, if the target RAT is GSM, then the handover command is defined in 3GPP Technical Specification (TS) 44.018 (e.g., version 12.2.0). The same applies for UTRAN and Evolved UTRAN (E-UTRAN), where the handover command is defined in 3GPP TS 25.331 (e.g., version 12.1.0) and 36.331 (e.g., version 12.1.0), respectively. In this case, the WLAN 14 is integrated into the cellular network in such a way that it is possible to perform handover preparation phase signaling towards the RAN node controlling/handling the target RAT and the target cell. The handover command is created by the target RAN node (e.g., the base station 16-1) and provided to the WLAN access node 18 for transmission to the wireless device 20-1.
        One or more 3GPP NAS parameters (e.g. attachment type, APN, etc.).
        A retry timer that indicates an amount of time that the wireless device 20-1 should attempt to access the target RAT/cell in any of the cases described above. If the wireless device 20-1 is unable to access the target RAN/cell in the amount of time indicated by the retry timer, in some embodiments, the wireless device 20-1 should try to abandon the access attempts to the target RAT/cell and attempt to inform the WLAN 14 (e.g., the WLAN access node 18) of a handover failure.
    
    


As discussed above, in one embodiment, the handover instruction transmitted by the WLAN access node 18 to the wireless device 20-1 may include a 3GPP handover command. In this regard, FIG. 4 illustrates the operation of the communication system 10 of FIG. 1 according to one embodiment in which the handover instruction includes a 3GPP handover command. As illustrated, initially, communication is established between the wireless device 20-1 and the WLAN 14 via the WLAN access node 18 (step 200). In this embodiment, at some point, the WLAN access node 18 decides, or determines, that a handover of the wireless device 20-1 from the WLAN 14 to the cellular RAN 12 is desired (step 202). In one embodiment, the decision is for a full handover. However, in another embodiment, the WLAN access node 18 may decide to initiate a full or selective handover. The WLAN access node 18 then sends a handover preparation request to the base station 16-1 serving a target cell for the handover (step 204). In response, the base station 16-1 sends a handover preparation response including a 3GPP handover command to the WLAN access node 18 (step 206). Note that while the 3GPP handover command is used in this example, one or more parameters that are normally included in a 3GPP handover command may be used instead of a full 3GPP handover command. The communication between the WLAN access node 18 and the base station 16-1 in steps 202 and 204 may be directly between the base station 16-1 and the WLAN access node 18 via a wired or wireless connection, e.g., a cellular connection, or indirectly through, e.g., a common core network of the cellular RAN 12 and the WLAN 14.
Next, the WLAN access node 18 transmits a handover instruction including the 3GPP handover command to the wireless device 20-1 (step 208). As discussed above, in one embodiment, the 3GPP handover command is transmitted in an IEEE 802.11 Deauthentication/Disassociation Management frame. However, the handover command may be transmitted in other types of IEEE 802.11 frames. In this embodiment, the handover instruction may include, e.g., a 3GPP RAT type for the handover, a 3GPP RAT Identifier (ID) for the handover, and one or more attach parameters taking the form of a 3GPP handover command or one or more parameters that are normally included in a 3GPP handover command. Additionally, the handover instruction may include one or more 3GPP NAS parameters to be used in the Attach Request as defined in Section 5.3.2.1 of 3GPP TS 23.401 (version 12.4.0). These parameters include, for example, APN, attach type per APN (initial attach, handover attach, handover attach with IP Flow Mobility (IFOM), etc.), TFT, etc.
In response to the handover instruction including the 3GPP handover command, the wireless device 20-1 performs the handover to, in this example, a cell served by the base station 16-1 in the cellular RAN 12 (step 210). Once the handover is complete, the wireless device 20-1 communicates with the base station 16-1 (step 212). In addition, if the handover was a selective handover, the wireless device 20-1 also communicates with the WLAN access node 18 for any communications session(s) or traffic that was not handed over (step 214).
As discussed above, the handover instruction may be transmitted in various types of IEEE 802.11 frames. In this regard, FIGS. 5, 6A through 6C, 7A, 7B, and 8-10 illustrate various IEEE 802.11 frame formats that can be utilized to transmit the handover instruction from the WLAN access node 18 to the wireless device 20-1 according to additional embodiments of the present disclosure. More specifically, FIG. 5 illustrates a frame format of an IEEE 802.11 Association Response Management frame as defined in Chapter 8.3.3.6 of the IEEE 802.11-2012 specification. As illustrated, the frame body of the Association Response Management frame includes, among other elements, a status code element and one or more vendor-specific elements. In one embodiment, the handover instruction includes a special status code transmitted in the frame body, where the special status code is a new status code defined for a handover instruction from the WLAN 14. Thus, in this embodiment, the WLAN access node 18 transmits the handover instruction by transmitting an Association Response Management frame including the new, or special, status code defined to indicate a handover instruction.
In addition, in some embodiments, the handover instruction includes additional information transmitted in the one or more vendor-specific elements of the Association Response Management frame. This additional information may include any information related to the handover of the wireless device 20-1 from the WLAN 14 to, in the example of FIGS. 1 and 2, the cellular RAN 12. This additional information may include, for example, any of the information described above with respect to the Deauthentication/Disassociation Management frame.
Still further, in another embodiment, the handover instruction may use only the one or more vendor-specific elements (i.e., without any special status code). For example, in one particular embodiment, the information transmitted in the one or more vendor-specific elements includes a code indicative of the handover instruction. Additional information related to the handover may also be transmitted in the vendor-specific element(s), as discussed above.
FIGS. 6A through 6C illustrate a frame format of a BSS Transition Management Request frame as defined in Chapter 8.5.14.9 of the IEEE 802.11-2012 specification. Normally, the BSS Transition Management Request frame includes one or more Neighbor Report elements. As illustrated in FIGS. 7A and 7B, in one embodiment, the handover instruction is transmitted from the WLAN access node 18 to the wireless device 20-1 by transmitting a BSS Transition Management Request frame, and specifically a BSS Transition Management Request frame including a BSS Transition Candidate List Entries field, with zero Neighbor Report elements. This frame will then be interpreted by the wireless device 20-1 as a handover instruction. More specifically, zero Neighbor Report elements may be interpreted as there being no suitable WLAN access nodes to which to transition and, as such, a handover to a RAN of a different RAT (e.g., the cellular RAN 12) is needed. Further, in some embodiments, the handover instruction includes additional information related to the handover in the one or more vendor-specific elements. This additional information may include, e.g., any of the additional information described above with respect to the Deauthentication/Disassociation Management frame.
FIG. 8 illustrates a frame format for an IEEE WNM-Notification Request frame as defined Chapter 8.5.14.28 of the IEEE 802.11-2012 specification. Importantly, the WNM-Notification Request frame includes one or more optional subelements in which the handover instruction is transmitted from the WLAN access node 18 to the wireless device 20-1 according to one embodiment of the present disclosure. More specifically, in one embodiment, the optional subelement(s) of the WNM-Notification Request frame are formatted as vendor-specific element(s), as illustrated in FIG. 9. While not essential for the present disclosure, the optional subelement(s) may be formatted as vendor-specific element(s) as defined in Chapter 8.4.2.28 of the IEEE 802.11-2012 specification. The handover instruction can then be transmitted as the vendor-specific content of the optional subelement(s). The handover instruction may include, as described above, a code that indicates a handover instruction and/or information related to the desired handover (e.g., target RAT, target RAN, target cell, 3GPP handover command, 3GPP NAS parameters, retry timer, or the like, or any combination thereof).
In one embodiment, the vendor-specific element of the WNM-Notification Request frame is formatted in accordance to the Wi-Fi® Alliance (WFA) rules for such frame types, as illustrated in FIG. 10. In this embodiment, the fields of the WFA formatted vendor-specific element includes the following information:

    
    
        A subelement ID set to value “221” (“Vendor Specific,” as specified by the IEEE 802.11-2012 specification).
        An Organization Identifier set to “0x 50 6F 9A” (as requested by the WFA guidelines).
        A “Type” set to “0x01” (in conjunction with “WFA Technology Assignments” instructions).
        The 3GPP RAT Type indicates a handover preference in regard to a specific RAT to be chosen by the wireless device 20-1 (i.e., a target RAT). In one embodiment, the 3GPP RAT Type field can assume the following values:
        
            0: Reserved
            1: Any RAT
            2: Global System for Mobile Communications Enhanced Data Rates for Global Evolution Radio Access Network (GERAN)
            3: UTRAN
            4: E-UTRAN
            5-255: Reserved
        
        
        A 3GPP RAT ID specifies an ID of target 3GPP RAN node for the handover (e.g., an ID of the target base station 16).

Still further, in some embodiments, the handover may be either a full or a selective handover. In this regard, the WFA formatted vendor-specific element may optionally include one or more attachment parameters indicating a subset of ongoing traffic or communications sessions (e.g., IP sessions) that are to be handed over. Examples of such attachment parameters include, but are not limited to, APN(s) to be handed over, attach type per APN (initial attach, handover attach, handover attach with IFOM, etc.), TFTs indicating n-tuples to be handed over, or the like, or any combination thereof. Notably, an APN identifies a PDN that the wireless device 20-1 communicates with via the WLAN 14 such as, for example, the Internet, an IP Multimedia System (IMS) network, an enterprise network, or the like. Note that the information discussed above may be transmitted in other types of IEEE 802.11 frames (e.g., a Deauthentication Management frame, a Disassociation Management frame, an Association Request Management frame, a BSS Transition Management Request Action frame, or the like). Similarly, the information discussed above with respect to the WFA formatted WNM-Notification Request frame of FIG. 10 is only one example of the information included in a handover instruction. Additional or alternative information may be included in the handover instruction.

    
    


The embodiments described above focus on steering wireless devices 20 from the WLAN 14 to the cellular RAN 12 (or at least from the WLAN 14 to a RAN of a different RAT). FIGS. 11A and 11B illustrate a modified IEEE 802.11 WNM-Notification Request frame that can be utilized for multi-band steering according to one embodiment of the present disclosure. More specifically, the WLAN 14 may include multiple WLAN access nodes 18 operating in different frequency bands (e.g., the 2.4 and 5 Gigahertz (GHz) frequency bands) or a single WLAN access node 18 that operates at two or more frequency bands. Multi-band steering is steering wireless devices 20 from one WLAN frequency band to another WLAN frequency band. The WNM-Notification Request frame of FIGS. 11A and 11B includes BSS Transition Management capabilities. Using the BSS Transition Management capabilities, the WNM-Notification Request frame can be transmitted by the WLAN 18 to, e.g., the wireless device 20-2 to steer the wireless device 20-2 from one frequency band of the WLAN 14 to another frequency band of the WLAN 14.
Particular implementations of the embodiments described herein introduce a mechanism by which a WLAN access node can steer a wireless device to another RAT. Some implementations of the embodiments described above are rather simple and can be implemented with a minimum of effort by both network and wireless device vendors. Also, some implementations of the embodiments described herein utilize elements of standardized solutions and thus can be implemented without an excessive amount of substantial changes to, e.g., the IEEE 802.11-2012 specifications.
Some implementations of the embodiments described above introduce a full-fledged solution that can enable a WLAN access node to communicate an all-traffic, or full, handover of all traffic or a selective handover of only certain type(s) of traffic (i.e., the WLAN access node can communicate a handover at a desired level of granularity). Furthermore, some implementations of the embodiments described herein provide the WLAN access node with the ability to specify a target 3GPP RAT for a handover. Still other embodiments provide enhanced WLAN multiband steering that can be communicated with the same type of frame as a handover instruction, requiring less implementation efforts.
While the base stations 16 (or any type of as cellular access nodes) may be implemented in hardware or any combination of hardware and/or software, FIG. 12 is a block diagram of one of the base stations 16 of FIG. 1 according to one embodiment of the present disclosure. Note that while the base stations 16 are discussed herein, the functionality of the base stations 16 described herein can be performed by any type of cellular access node (e.g., a RAN node, a base station, an enhanced Node B (eNodeB), a Radio Network Controller (RNC), or the like). As illustrated, the base station 16 includes a baseband unit 26 including a processor 28, memory 30, and a network interface 32 and a radio unit 34 including a transceiver 36 coupled to one or more antennas 38. In one embodiment, the functionality of the base station 16 described herein is implemented in software stored in the memory 30 and executed by the processor 28. Additionally, the base station 16 may include additional components responsible for providing additional functionality, including any of the functionality described above and/or any functionality necessary to support the embodiments described herein.
In one embodiment, a computer program is provided that includes instructions which, when executed on at least one processor, cause the at least one processor to carry out any of the embodiments of the base station 16 described above. In one embodiment, a carrier containing the computer program is provided, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium).
FIG. 13 is a functional block diagram of one of the base stations 16 of FIG. 1 according to one embodiment of the present disclosure. As illustrated, the base station 16 includes a handover module 40 and a communication module 42, both of which are implemented in software executed by one or more processors (e.g., the processor 28 of FIG. 12). The handover module 40 operates along with, e.g., the wireless device 20-1 to perform the handover of the wireless device 20-1 to a cell served by the base station 16. In addition, in some embodiments, the handover module 40 handles handover preparation requests received from the WLAN access node 18 and builds a 3GPP Handover command message that is sent directly or indirectly to the WLAN access node 18 as part of a handover preparation response. The communication module 42 provides communication with the wireless device 20-1 once the wireless device 20-1 is handed over to the cell served by the base station 16.
While the WLAN access node 18 may be implemented in any type of hardware or any combination of hardware and software, FIG. 14 is a block diagram of the WLAN access node 18 of FIG. 1 according to one embodiment of the present disclosure. As illustrated, the WLAN access node 18 includes a processor 44, memory 46, and a transceiver 48 coupled to one or more antennas 50. In particular embodiments, some or all of the functionality described above as being provided by the WLAN access node 18 may be provided by the processor 44 executing instructions stored on a computer-readable medium, such as the memory 46. Alternative embodiments of the WLAN access node 18 may include additional components responsible for providing additional functionality, including any of the functionality identified above and/or any functionality necessary to support the embodiments described above.
In one embodiment, a computer program is provided that includes instructions which, when executed on at least one processor, cause the at least one processor to carry out any of the embodiments of the WLAN access node 18 described above. In one embodiment, a carrier containing the computer program is provided, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium).
FIG. 15 is a functional block diagram of the WLAN access node 18 of FIG. 1 according to one embodiment of the present disclosure. As illustrated, the WLAN access node 18 includes a WLAN communication module 52, a handover decision module 54, and a handover instruction module 56, each of which is implemented in software that is executed by one or more processors of the WLAN access node 18 to provide the functionality described herein. The WLAN communication module 52 provides communication with wireless devices 20 connected to the WLAN 14. The handover decision module 54 decides when a handover of a wireless device 20 from the WLAN 14 to another RAT is to be performed. The handover instruction module 56 provides handover instructions to wireless devices 20 when appropriate. While not illustrated, the WLAN access node 18 may include additional modules such as, for example, a communication module for communication to and/or from the cellular RAN 12 (e.g., to and/or from the base station 16 in the cellular RAN 12, e.g., directly or via a common core network).
While the wireless devices 20 may be implemented in any type of hardware or any combination of hardware and software, FIG. 16 is a block diagram of one of the wireless devices 20 of FIG. 1 according to one embodiment of the present disclosure. As illustrated, the wireless device 20 includes a processor 58, memory 60, and a transceiver 62 coupled to one or more antennas 64. In particular embodiments, some or all of the functionality described above as being provided by the wireless device 20 may be provided by the processor 58 executing instructions stored on a computer-readable medium, such as the memory 60. Alternative embodiments of the wireless device 20 may include additional components responsible for providing additional functionality, including any of the functionality identified above and/or any functionality necessary to support the embodiments described above.
In one embodiment, a computer program is provided that includes instructions which, when executed on at least one processor, cause the at least one processor to carry out any of the embodiments of the wireless device 20 described above. In one embodiment, a carrier containing the computer program is provided, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium).
FIG. 17 is a functional block diagram of one of the wireless devices 20 of FIG. 1 according to one embodiment of the present disclosure. As illustrated, the wireless device 20 includes a WLAN communication module 66, a handover instruction reception module 68, a handover module 70, and a cellular network communication module 72, each of which is implemented in software that is executed by one or more processors of the wireless device 20 to provide the functionality described herein. The WLAN communication module 66 provides communication with the WLAN access node 18 of the WLAN 14. The handover instruction reception module 68 operates to receive a handover instruction from the WLAN access node 18. The handover module 70 operates to perform a handover form the WLAN 14 to another RAT, e.g., the 3GPP RAT of the cellular RAN 12, when a handover instruction is received by the handover instruction reception module 68. The cellular network communication module 72 provides communication with the cellular RAN 12.
The following acronyms are used throughout this disclosure.

    
    
        3GPP 3rd Generation Partnership Project
        3GPP2 3rd Generation Partnership Project 2
        APN Access Point Name
        BSS Basic Service Set
        CGI Cell Global Identity
        CI Cell Identity
        C-Id Cell Identifier
        eNodeB Evolved Universal Terrestrial Radio Access Network NodeB
        EPC Evolved Packet Core
        E-UTRAN Evolved Universal Terrestrial Radio Access Network
        GERAN Global System for Mobile Communications Enhanced Data Rates for Global Evolution Radio Access Network
        GHz Gigahertz
        GSM Global System for Mobile Communications
        HO Handover
        ID Identifier
        IEEE Institute for Electrical and Electronics Engineers
        IFOM Internet Protocol Flow Mobility
        IMS Internet Protocol Multimedia System
        IP Internet Protocol
        LAC Location Area Code
        LTE Long Term Evolution
        M2M Machine-to-Machine
        MAC Media Access Control
        MCC Mobile Country Code
        MNC Mobile Network Code
        MTC Machine Type Communication
        NAS Non-Access Stratum
        NID Network Identifier
        PDN Packet Data Network
        PHY PHYsical Layer
        PLMN Public Land Mobile Network
        RAN Radio Access Network
        RAT Radio Access Technology
        RFID Radio Frequency Identifier
        RNC Radio Network Controller
        RNC-ID Radio Network Controller Identifier
        RNS Radio Network Subsystem
        RSSI Received Signal Strength Indicator
        SI System Information
        SID System Identifier
        STA Station
        TFT Traffic Flow Template
        TS Technical Specification
        UC-Id Universal Terrestrial Radio Access Network Cell Identifier
        UE User Equipment
        UMTS Universal Mobile Telecommunications System
        UTRAN Universal Terrestrial Radio Access Network
        WCDMA Wideband Code Division Multiple Access
        WFA Wi-Fi® Alliance
        WLAN Wireless Local Area Network
        WNM-Notification Wireless Network Management Notification
    
    


Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein and the claims that follow.

## Claims

1. A method of operation of a Wireless Local Access Network, WLAN, access node, comprising:
deciding that a handover of a wireless device from a WLAN to another radio access network of a different radio access technology is to be performed; and
transmitting a handover instruction to the wireless device that instructs the wireless device to perform a handover from the WLAN to a radio access network of a different radio access technology, wherein the different radio access technology is a 3rd Generation Partnership Project, 3GPP, radio access technology, wherein the handover instruction comprises information that indicates whether the handover is a full handover of all communication sessions or a selective handover of one or more but less than all communication sessions, and wherein the WLAN can perform both full handovers and selective handovers.

2. The method of claim 1 wherein the handover is a selective handover.

3. The method of claim 1 wherein the handover is a full handover.

4. The method of claim 1 wherein the handover instruction is a general instruction to perform a handover to a radio access network of a different radio access technology.

5. The method of claim 1 wherein the handover instruction comprises information that identifies the different radio access technology for the handover.

6. The method of claim 1 wherein the handover instruction comprises information that identifies a target cell in the radio access network of the different radio access technology.

7. The method of claim 6 wherein the handover instruction further comprises information that identifies the different radio access technology and the radio access network of the different radio access technology.

8. The method of claim 6 wherein the handover instruction further comprises assistance information that assists the wireless device when performing the handover.

9. The method of claim 8 wherein the assistance information comprises at least some system information of the target cell.

10. The method of claim 1 wherein the handover instruction comprises one or more parameters that enable the wireless device to connect to the radio access network of the 3GPP radio access technology.

11. The method of claim 1 wherein the handover instruction comprises a retry timer value that defines an amount of time that the wireless device should attempt to access the radio access network of the different radio access technology when performing the handover.

12. The method of claim 1 wherein the WLAN is an IEEE 802.11 wireless network.

13. The method of claim 12 wherein the different radio access technology is a cellular network radio access technology.

14. The method of claim 13 wherein the 3GPP cellular network radio access technology is a 3rd Generation Partnership Project 2, 3GPP2, radio access technology.

15. The method of claim 14 wherein transmitting the handover instruction to the wireless device comprises transmitting, to the wireless device, a management frame selected from a group consisting of:
a Deauthentication Management frame comprising a reason code that corresponds to the handover instruction; and
a Disassociation Management frame comprising a reason code that corresponds to the handover instruction.

16. The method of claim 15 wherein transmitting the management frame further comprises transmitting information regarding the handover instruction in one or more vendor-specific elements within the management frame.

17. The method of claim 16 wherein the information regarding the handover instruction comprises at least one of a group consisting of:
a target set of networks for the handover;
a target radio access technology for the handover;
a target cell;
assistance information that assists the wireless device when performing the handover;
a 3GPP handover command; and
a Non-Access Stratum, NAS, parameter.

18. The method of claim 16 wherein the information regarding the handover instruction comprises a retry timer value that defines an amount of time that the wireless device should attempt to access the radio access network of the 3GPP or 3GPP2 radio access technology when performing the handover.

19. The method of claim 14 wherein transmitting the handover instruction to the wireless device comprises transmitting, to the wireless device, an Association Response Management frame comprising the handover instruction.

20. The method of claim 14 wherein transmitting the handover instruction to the wireless device comprises transmitting, to the wireless device, a Basic Service Set, BSS, Transition Management frame with zero neighbor report elements.

21. The method of claim 20 wherein transmitting the BSS Transition Management frame further comprises transmitting information regarding the handover instruction in one or more vendor-specific elements within the BSS Transition Management frame.

22. The method of claim 21 wherein the information regarding the handover instruction comprises at least one of a group consisting of:
a target set of networks for the handover;
a target radio access technology for the handover;
a target cell;
assistance information that assists the wireless device when performing the handover;
a 3GPP handover command; and
a Non-Access Stratum, NAS, parameter.

23. The method of claim 21 wherein the information regarding the handover instruction comprises a retry timer value that defines an amount of time that the wireless device should attempt to access the radio access network of the 3GPP or 3GPP2 radio access technology when performing the handover.

24. The method of claim 14 wherein transmitting the handover instruction to the wireless device comprises transmitting, to the wireless device, a Wireless Network Management Notification, WNM-Notification, Request frame comprising the handover instruction within one or more optional subelements formatted as one or more vendor-specific elements.

25. The method of claim 24 wherein the handover instruction comprises at least one of a group consisting of:
information indicative of the 3GPP or 3GPP2 radio access technology for the handover;
a cell identifier of a target cell in the radio access network of the 3GPP or 3GPP2 radio access technology to which the wireless device is to be handed over; and
one or more attachment parameters that indicate which communication sessions of the wireless device are to be handed over.

26. The method of claim 14 wherein transmitting the handover instruction to the wireless device comprises transmitting, to the wireless device, a Wireless Network Management Notification, WNM-Notification, Request frame comprising the handover instruction.

27. The method of claim 1 wherein:
deciding that a handover of the wireless device from the WLAN to another radio access network of a different radio access technology is to be performed comprises:
deciding to initiate a handover to the 3rd Generation Partnership Project, 3GPP, radio access technology;
sending a handover preparation request to a radio access node in a radio access network of the 3GPP radio access technology; and
receiving a handover preparation response from the radio access node comprising a 3GPP handover command; and

transmitting the handover instruction comprises transmitting the 3GPP handover command to the wireless device.

28. The method of claim 27 wherein transmitting the handover instruction comprises transmitting a frame selected from a group consisting of:
a Deauthorization Management frame comprising the 3GPP handover command;
a Disassociation Management frame comprising the 3GPP handover command;
an Association Response Management frame comprising the 3GPP handover command;
a Basic Service Set, BSS, Transition Management frame comprising the 3GPP handover command; and
a Wireless Network Management Notification, WNM-Notification, Request frame comprising the 3GPP handover command.

29. A wireless Local Access Network WLAN, access node comprising: a processor; and memory containing instructions executable by the processor whereby the WLAN access node is operative to:
decide that a handover of a wireless device from a WLAN to another radio access network of a different radio access technology is to be performed; and
transmit a handover instruction to the wireless device that instructs the wireless device to perform a handover from the WLAN to a radio access network of a different radio access technology, wherein the different radio access technology is a 3rd Generation Partnership Project, 3GPP, radio access technology, wherein the handover instruction comprises information that indicates whether the handover is a full handover of all communication sessions or a selective handover of one or more but less than all communication sessions, and wherein the WLAN can perform both full handovers and selective handovers.

30. A method of operation of a wireless device, comprising:
communicating with a Wireless Local Access Network, WLAN, access node;
receiving a handover instruction from the WLAN access node to perform a handover from a WLAN to another radio access network of a different radio access technology, the handover instruction being decided by the WLAN access node; and
performing the handover in response to receiving the handover instruction, wherein the different radio access technology is a 3rd Generation Partnership Project, 3GPP, radio access technology; wherein the handover instruction comprises information that indicates whether the handover is a full handover of all communication sessions or a selective handover of one or more but less than all communication sessions, and wherein the wireless device can perform both full handovers and selective handovers.

31. The method of claim 30 wherein the handover instruction is an instruction for a selective handover from the WLAN to another radio access network of a different radio access technology, and performing the handover comprises performing the selective handover.

32. The method of claim 30 wherein the handover instruction is an instruction for a full handover from the WLAN to another radio access network of a different radio access technology, and performing the handover comprises performing the full handover.

33. The method of claim 30 wherein the handover instruction is a general instruction to perform a handover to a radio access network of a different radio access technology, and performing the handover comprises performing the handover to a radio access network of a different radio access technology.

34. The method of claim 30 wherein the handover instruction comprises information that identifies the different radio access technology for the handover, and performing the handover comprises performing the handover to a radio access network of the different radio access technology identified by the information included in the handover instruction.

35. The method of claim 30 wherein the handover instruction comprises information that identifies a target cell in the radio access network of the different radio access technology, and performing the handover comprises performing the handover to the target cell.

36. The method of claim 35 wherein the handover instruction further comprises information that identifies the different radio access technology and the radio access network of the different radio access technology.

37. The method of claim 35 wherein the handover instruction further comprises assistance information that assists the wireless device when performing the handover, and performing the handover to the target cell comprises performing the handover to the target cell based on the assistance information.

38. The method of claim 37 wherein the assistance information comprises at least some system information of the target cell.

39. The method of claim 30 wherein the handover instruction comprises one or more parameters that enable the wireless device to connect to the radio access network of the 3GPP radio access technology.

40. The method of claim 30 wherein the handover instruction comprises a retry timer value that defines an amount of time that the wireless device should attempt to access the radio access network of the different radio access technology when performing the handover.

41. The method of claim 40 wherein:
performing the handover comprises re-trying the handover for the amount of time defined by the retry timer value; and
notifying the WLAN access node of a handover failure if the handover is not successful within the amount of time defined by the retry timer.

42. The method of claim 30 wherein the WLAN is an IEEE 802.11 wireless network.

43. The method of claim 42 wherein the different radio access technology is a cellular network radio access technology.

44. The method of claim 43 wherein the 3GPP cellular network radio access technology is a 3rd Generation Partnership Project 2, 3GPP2, radio access technology.

45. The method of claim 44 wherein receiving the handover instruction comprises receiving a management frame transmitted by the WLAN access node, the management frame selected from a group consisting of:
a Deauthentication Management frame comprising a reason code that corresponds to the handover instruction; and
a Disassociation Management frame comprising a reason code that corresponds to the handover instruction.

46. The method of claim 44 wherein receiving the handover instruction comprises receiving an Association Response Management frame comprising the handover instruction from the WLAN access node.

47. The method of claim 44 wherein receiving the handover instruction comprises receiving a Basic Service Set, BSS, Transition Management frame with zero neighbor report elements from the WLAN access node.

48. The method of claim 44 wherein receiving the handover instruction comprises receiving, from the WLAN access node, a Wireless Network Management Notification, WNM-Notification, Request frame comprising the handover instruction within one or more optional subelements formatted as one or more vendor-specific elements.

49. The method of claim 44 wherein receiving the handover instruction comprises receiving a Wireless Network Management Notification, WNM-Notification, frame comprising the handover instruction from the WLAN access node.

50. The method of claim 30 wherein receiving the handover instruction comprises receiving a 3rd Generation Partnership Project, 3GPP, handover command within a WLAN frame.

51. A wireless device comprising:
a transceiver;
a processor; and
memory containing instructions executable by the processor whereby the wireless device is operative to:
communicate with a Wireless Local Access Network, WLAN, access node of a WLAN via the transceiver;
receive, via the transceiver, a handover instruction from the WLAN access node to perform a handover from the WLAN to another radio access network of a different radio access technology, the handover instruction being decided by the WLAN access node; and
perform the handover in response to receiving the handover instruction, wherein the different radio access technology is a 3rd Generation Partnership Project, 3GPP, radio access technology, wherein the handover instruction comprises information that indicates whether the handover is a full handover of all communication sessions or a selective handover of one or more but less than all communication sessions, and wherein the wireless device can perform both full handovers and selective handovers.