CN111869310A

CN111869310A - Method and system for performing small data fast path communication

Info

Publication number: CN111869310A
Application number: CN201880091212.1A
Authority: CN
Inventors: 卢飞; 朱进国
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2018-04-10
Filing date: 2018-04-10
Publication date: 2020-10-30
Also published as: WO2019196000A1

Abstract

A method for performing small data fast path communication for a wireless communication device moving from a first radio access network to a second radio access network, the method comprising the second radio access network: receiving a small data fast path parameter and a connection recovery identifier from the wireless communication device during a radio resource control connection establishment procedure; deriving a first radio access network from the recovery identifier; transmitting a radio access network connection request to the first radio access network, the connection request including the small data fast path parameter and a tunnel endpoint identifier for small data fast path downlink data; and receiving a tunnel endpoint identifier for the small data fast path uplink data from the first radio access network.

Description

Method and system for performing small data fast path communication

Technical Field

The present disclosure relates generally to wireless networks and, more particularly, to methods and systems for fast paths for small data transmissions.

Background

In many current wireless networks, particularly those having small data transmissions that communicate infrequently using communications, various techniques have been developed to allow small, fast data transmissions to be sent efficiently. In the context of large wireless networks, such as fifth generation networks, if a wireless device using such transmissions moves to a different radio access network, the new radio access network cannot connect to the user plane functionality (i.e., the radio access network is not in the service area of the user plane functionality).

Drawings

While the appended claims set forth the features of the present technology with particularity, these technologies, together with their objects and advantages, may be best understood from the following detailed description taken in conjunction with the accompanying drawings of which:

FIG. 1 is a block diagram of a system in which various embodiments of the present disclosure are implemented.

Fig. 2 illustrates an example hardware architecture of a communication device.

Fig. 3 is a block diagram of a network environment in which the devices depicted in fig. 1 and 2 may be deployed, according to an embodiment.

Fig. 4 is an example of how small data fast path communications may be established using current prior art techniques.

Fig. 5 and 6 are communication flow diagrams illustrating an example of a current existing process for establishing small data fast path communication in the context of the network environment of fig. 3.

Fig. 7, 8, 9, and 10 are communication flow diagrams illustrating examples of processes for establishing small data fast path communication in the context of the network environment of fig. 3, in accordance with various embodiments.

Detailed Description

In one embodiment, a method for performing small data fast path communication for a wireless communication device moving from a first radio access network to a second radio access network, the method comprising the second radio access network performing the following acts: receiving a small data fast path parameter and a connection recovery identifier from a wireless communication device during a radio resource control connection establishment procedure; deriving a first radio access network from the recovery identifier; transmitting a connection request to the first radio access network, the connection request including the small data fast path parameter and a tunnel termination identifier for small data path downlink data; and receiving, from the first radio access network, a tunnel termination identifier for the small data fast path uplink data.

According to another embodiment, a method for performing small data fast path communication for a wireless communication device moving from a first radio access network to a second radio access network, the method comprising the second radio access network performing the following acts: receiving a small data fast path parameter and a connection recovery identifier from a wireless communication device during a radio resource control connection establishment procedure; deriving a first radio access network from the recovery identifier; receiving small data fast path uplink data from a wireless communication device; and transmitting the small data fast path uplink data to the first radio access network.

According to yet another embodiment, a method for performing small data fast path communication for a wireless communication device moving from a first radio access network to a second radio access network, the method comprising the second radio access network performing the actions of: receiving a small data fast path parameter from the wireless communication device during a radio resource control connection establishment procedure; identifying a user plane function based on the small data fast path parameter; communicating, to a user plane function, a request to establish a tunnel for a small data fast path connection, wherein the request includes small data fast path parameters and a tunnel endpoint identifier for small data fast path downlink data; and receiving a tunnel setup response message from the user plane function, the message including a tunnel endpoint identifier for the user plane function for small data fast path uplink data.

According to yet another embodiment, a method for performing small data fast path communication for a wireless communication device moving from a first radio access network to a second radio access network, the method comprising the second radio access network performing the acts of: receiving a small data fast path parameter from the wireless communication device during a radio resource control connection establishment procedure; identifying a first user plane function based on the small data fast path parameter; receiving, from a wireless communication device, small data fast path uplink data; the small data fast path uplink data, the small data fast path parameters, and the tunnel termination identifier for the downlink data are transmitted to the first user plane function. The method further comprises the first user plane function deriving a second user plane function from the small data fast path parameter; and transmitting the small data fast path uplink data, the small data fast path parameters, and the downlink tunnel information for the small data fast path session to the second user plane function.

Fig. 1 depicts a communication system 100 in which various embodiments described herein may be implemented. The communication system 100 includes several wireless communication devices (for ease of reference, "wireless communication device" will sometimes be referred to herein simply as a "communication device" or "device"). The depicted communication devices are a first communication device 102 (depicted as a user equipment ("UE")), a second communication device 104 (depicted as a base station), and a third communication device 106 (depicted as a UE). It should be understood that many other communication devices are possible, and those represented in fig. 1 are meant for purposes of example only. In an embodiment, the wireless communication system 100 has many other components not depicted in fig. 1, including other base stations, other UEs, wireless infrastructure, wired infrastructure, and other devices common in wireless networks. Possible implementations of the communication device include any device that can be used for wireless communication, such as smartphones, tablets, laptops and non-traditional devices (e.g., household appliances or other parts of the "internet of things"). When operating as part of a wireless communication system (e.g., part of a radio access network), a wireless communication device may be referred to as a "radio network node". Wireless communication devices communicate primarily by transmitting and receiving wireless signals.

The second communication device 104 operates as a Node of the RAN 108, such as a "Node B" of a fourth or fifth generation RAN. RAN 108 is communicatively linked to CN 110. CN 110 carries many functions and has many components that support RAN 108.

The following description will sometimes refer to nodes and UEs without specific reference to fig. 1. However, it should be understood that all methods described herein may be performed by the communication device of fig. 1, and that the nodes, base stations, and UEs are referred to in a generic manner only for convenience. Additionally, for each described process, in an embodiment, the steps are performed in the order set forth in the language. In other embodiments, the steps are performed in a different order.

Fig. 2 illustrates a basic hardware architecture implemented by each of the wireless communication devices of fig. 1, according to one embodiment. The elements of fig. 1 may have other components as well. The hardware architecture depicted in fig. 2 includes: logic 202, memory 204, transceiver 206, and one or more antennas represented by antennas 208 (including transmit antennas and/or receive antennas). The memory 204 may be or include a buffer that holds the incoming transmission, for example, until the logic is able to process the transmission. Each of these elements is communicatively linked to each other via one or more data paths 210. Examples of data paths include: wires, conductive paths on the microchip, and wireless connections. The hardware architecture of fig. 2 may also be referred to herein as a "computing device.

The term "logic circuit" as used herein refers to a circuit (a piece of electronic hardware) designed to perform a complex function defined in terms of mathematical logic. Examples of logic circuitry include a microprocessor, controller, or application specific integrated circuit. When the present disclosure refers to a device performing an action, it should be understood that this can also mean that logic integrated with the device is actually performing the action.

Turning to fig. 3, a network environment in which the devices depicted in fig. 1 and 2 may be deployed in accordance with various embodiments will now be described. The network environment includes RAN 108, wireless communication device 102, and CN 110. The network environment also includes a data network ("DN") 302.

Continuing with fig. 3, CN 110 includes unified data management server ("UDM") 304, access and mobility management function ("AMF") 306, session management function ("SMF") 308, and user plane function ("UPF") 310.

In one embodiment, the AMF 306 provides the following services: registration management, connection management, reachability management, and mobility management. The AMF also performs access authentication and access authorization. The AMF 306 acts as a non-access stratum ("NAS") security terminal and relays session management ("SM") NAS between the UE and the SMF.

According to an embodiment, SMF 308 provides the following services: session management (e.g., session establishment, modification, and release), UE internet protocol ("IP") address assignment and management (including optional authorization), selection and control of user plane ("UP") functions, and downlink ("DL") data notification.

In an embodiment, the UPF310 provides the following services: packet routing and forwarding, traffic usage reporting, quality of service ("QoS") handling for the user plane, DL data packet buffering, and DL data notification triggering for an anchor point of intra-radio access technology ("RAT")/inter-radio access technology ("RAT") mobility service.

It should be understood that although the devices of fig. 3 have names ending in "functions" or "entities," they are actually computing devices that perform functions (e.g., under the control of software). Thus, for example, the UPF310 is a computing device (or computing devices working in concert) that performs the functions described herein.

The various devices in fig. 3 communicate with one another in various ways, including well-known interfaces shown by the lines labeled "Nx". In addition, each device depicted in fig. 3 is meant to be representative. For example, there may be many SMFs and UPFs in the CN, and there may be multiple RANs that the device 102 may encounter when moving from one location to another.

In an embodiment, "small data" refers to a block of data that is less than 200 bytes in size. Furthermore, according to embodiments, "fast path" refers to a data transmission technique in which certain intermediate steps are skipped when compared to conventional data transmission. For example, a conventional data transfer procedure may include a device (e.g., a UE) first sending a service request message to the AMF and requesting a network (e.g., a RAN) to establish a user plane for data transfer.

Turning to fig. 4, an example of how small data fast path ("SDFP") communications may be established using current state of the art will now be described. The SDFP is established by providing relevant UPF (UPF 310 in this example) or protocol data unit ("PDU") session-related information from the SMF to the wireless communication device (device 102 in this example) which will later provide the information to the RAN (RAN 108 in this example). The UPF or PDU session related information allows the RAN to export a path to the UPF (e.g., via interface N3). Upon arrival of uplink ("UL") data, the wireless communication device passes the data to the RAN along with UPF or PDU session related information. The RAN forwards the data (e.g., over the N3 interface). Since all information needed to forward the data is received from the wireless communication device, the RAN need not signal to the AMF, nor need it store any context information about the wireless communication device (e.g., in the UE context).

Turning to fig. 5, an example of a current existing process for establishing SDFP communications will now be described in the context of the network environment of fig. 3. At 501, the device 102 sends a UL NAS TRANSPORT message to the AMF 306. The message includes single network slice selection assistance information ("S-NSSAI"), a data network name ("DNN"), a PDU session identifier ("ID"), a request type, and an N1 SM container (PDU session setup request). The request type indicates "initial request" if the PDU session setup is a request to establish a new PDU session. Device 102 should provide an indication in the UL NA TRANSPORT message that it wants to establish an SDFP PDU session.

At 502, the AMF 306 selects an SMF that supports SDFP (in this example, SMF 308). The AMF 306 also generates an SDFP security background. AMF 306 sends an Nsmf _ pdusesion _ CreateSMContext request (which includes a user permanent identifier ("SUPI"), DNN, S-NSSAI, PDU session ID, AMF ID, request type, N1 SM container (PDU session setup request), user location information, access type, and SDFP indication) to SMF 308.

At 503, SMF308 responds with an Nsmf _ pdusesion _ CreateSMContext response (SMF context indicator) message.

At 504, SMF308 selects a UPF that supports SDFP (UPF 310 in this example). The SMF308 sends an N4 session setup request message to the UPF 310 and provides packet detection, enforcement and reporting rules to be installed on the UPF 310 for the PDU session. If the CN tunnel information is assigned by SMF308, the CN tunnel information is provided to UPF 310 in this step. Also during this step, SMF308 will set up an SDFP security context in UPF 310.

At 505, the UPF 310 replies by sending an N4 session setup/modification response. If the CN tunnel information is assigned by the UPF 310, the CN tunnel information is provided to the SMF 308 in this step.

At 506, the SMF 308 communicates to the AMF 306: namf _ Communication _ N1N2MessageTransfer (including PDU Session ID, Access type, N2SM information (PDU Session ID, QoS flow identifier (S) ("QFI (S))), QoS profile (S), CN Tunnel information, S-NSSAI, Session aggregation maximum bit Rate (" AMBR "), PDU Session type), N1 SM container (PDU Session setup Accept (QoS rule (S), S-NSSAI, allocated IP address, Session AMBR, and selected PDU Session type))). The PDU session setup accept will also include the UPF information for this PDU session.

At 507, the AMF 306 responds with a Namf _ Communication _ N1N2MessageTransfer ACK reply message.

At 508, the AMF 306 transmits to the RAN 108: n2 PDU session request (N2 SM info, NAS message (PDU session ID, N1 SM container (PDU session setup accept))). The AMF 306 sends an N2SM message to the RAN 108 containing the PDU session ID and PDU session setup accept for the device 102 to the RAN 108, as well as received from the SMF 308 within the N2 PDU session request.

At 509, RAN 108 and device 102 engage in AN access network ("AN") specific signaling exchange related to information received from the SMF. RAN 108 also assigns RAN N3 tunnel information ("Info") for the PDU session. The AN tunnel information includes tunnel endpoints for the involved RAN nodes. In addition, the RAN 108 forwards the NAS message (PDU session ID, N1 SM container (PDU session setup accept)) provided in step 508 to the device 102. RAN 108 only provides NAS messages to device 102 if the necessary RAN resources are established and RAN tunneling information allocation is successful.

At 510, the RAN 108 transmits to the AMF 306: n2PDU session response (PDU session ID, reason, N2SM info (PDU session ID, AN tunnel info, list of QFI(s) accepted/rejected)). The AN tunnel information corresponds to the access network address of the N3 tunnel corresponding to the PDU session.

At 511, the AMF 306 transmits to the SMF 308: nsmf _ pdusesion _ UpdateSMContext request (N2SM info, request type). In this step, AMF 306 forwards the N2SM message received from the RAN to SMF 308. If the list of rejected QFI or QFIs is included in the N2SM message, SMF 308 releases the QoS profile associated with the rejected QFI or QFIs.

At 512, SMF 308 initiates an N4 session modification procedure with UPF 310. SMF 308 provides AN tunnel information, along with corresponding forwarding rules, to UPF 310.

At 513, the UPF 310 provides an N4 session modification response to the SMF 308.

At 514, the SMF 308 communicates to the AMF 306: nsmf _ pdusesion _ UpdateSMContext response (cause).

Turning to fig. 6, an example of a current existing process for establishing SDFP communications will now be described in the context of the network environment of fig. 3.

At 601, the device 102 establishes a radio resource control ("RRC") connection for SDFP transfer. In doing so, device 102 communicates to RAN108 parameters for selecting a UPF for the PDU session for device 102.

At 602, the device 102 ciphers and integrity protects the UL data PDUs and passes them to the RAN 108.

At 603, the RAN108 forwards the UL data PDU to the selected UPF (in this case UPF 310). RAN108 selects a UPF based on SDFP information provided by device 102. The RAN108 will also provide the UPF 310 with RAN N3 DL tunneling information for SDFP sessions.

At 604, the UPF 310 checks the integrity protection and decrypts the UL data PDUs. If the check passes, the UPF 310 forwards the UL data on the N6/N9 interface. Further, the UPF 310 enables subsequent DL data transmission to the RAN node from which the UP data PDU was received.

Problems associated with the above-described arrangement arise when a wireless communication device moves to a new RAN in a fifth generation mobility management ("MM") IDLE state. In that case, the device may have UL data to send, but the new RAN is not able to connect to the UPF as shown in fig. 5 and 6. This will trigger the RAN, AMF and SMF to select a new UPF. However, doing so would trigger a lot of control plane signaling.

In an embodiment, a method for performing small data fast path communication addresses these problems by: when a wireless communication device (e.g., a UE) moves from a first RAN to a second RAN, (1) the wireless communication device connects to the second RAN. (2) (a) the second RAN will establish an Xn connection for SDFP with the first RAN, and the first RAN will send small data to the UPF; or (2) (b) the second RAN will connect to the new UPF (second UPF) and the new UPF will send the small data to the old UPF (first UPF).

Turning to fig. 7, a process performed for performing SDFP communications in the context of the network environment of fig. 3 will now be described, according to an embodiment. In this example, it may be assumed that when the device 102 has connected to the first RAN 108a, it has performed many of the procedures of fig. 5, including step 509, and that the RAN 108a has given the device 102a recovered ID.

At 701, the wireless communication device establishes RRC for SDFP transfer. In doing so, the device 102 will communicate to the second RAN 108b parameters for selecting a UPF for the PDU session for the device 102. The second RAN 108b is not capable of connecting to a UPF, although it is capable of deriving a UPF address. The device 102 includes the recovery ID in its communication with the second RAN 108 b. The device 102 then derives the first RAN using the recovered ID. It should be noted that in some embodiments, the SDFP information includes an identifier of the first RAN. In such embodiments, the first RAN can be derived from the SDFP information. If this method is used, when the device 102 sends a UL NAS TRANSPORT message to the AMF 306 in step 501, the first RAN 108a will include its RAN ID in the message it delivers to the AMF 306, and the AMF 306 will forward the RAN ID to the SMF 308 in step 502. SMF 308 will combine the RAN ID with SDFP information sent to device 102 (PDU session setup accept), as defined in the N1 SM container in step 506.

At step 702, the second RAN 108 transmits a request to the first RAN 108a to establish an Xn connection to the first RAN 108 a. The second RAN 108b may use the resume ID and SDFP information (or only SDFP information if it contains a RAN ID) to derive the first RAN 108a (e.g., determine the identity of the first RAN 108a, etc.). In the request message, the second RAN 108b also includes SDFP information and a tunnel endpoint identifier ("TEID") for SDFP DL data.

At 703, the first RAN108a responds with an Xn connection response. In this message, the first RAN108a includes the old RAN TEID for SDFP UL data.

At 704, the device 102 ciphers and integrity protects the UL data PDUs and transmits them to the second RAN108 b.

At 705, the second RAN108b forwards the UL data PDUs to the derived first RAN108 a.

At 706, the first RAN108a forwards the UL data PDUs to the selected UPF (UPF 310 in this example). The first RAN108a selects a UPF based on the SDFP information provided by the device 102. The first RAN108a will also provide the UPF310 with RAN N3 DL tunneling information for the SDFP session.

At 707, the UPF310 checks the integrity protection and decrypts the UL data PDUs. If the check passes, the UPF310 forwards the UL data on the N6 interface. Further, the UPF310 enables subsequent DL data transmission to the RAN node from which the UP data PDU was received.

Turning to fig. 8, a process performed for performing SDFP communications in accordance with another embodiment will now be described in the context of the network environment of fig. 3. As with the previous example, it may be assumed that when the device 102 has connected to the first RAN108a, it has performed many of the procedures of fig. 5, including step 509, and that the RAN108a has given the device 102a recovered ID.

At 801, the device 102 establishes RRC for SDFP transfer. The parameters for selecting a UPF for a PDU session for the device are passed to the second RAN108 b. The device 102 provides the recovery ID to the second RAN108 b. The device 102 then derives the first RAN108 a using the recovered ID.

At 802, the device 102 ciphers and integrity protects the UL data PDUs and passes them to the second RAN108 b. The second RAN108b cannot connect to the UPF, although it can derive the UPF address. The device 102 includes the recovery ID in its communication with the second RAN108 b. The device 102 then derives the first RAN using the recovered ID.

At 803, the second RAN108b derives information for the first RAN108 a based on the SDFP information and forwards the UL data PDUs to the first RAN108 a. In data, the second RAN108b also provides Xn DL tunnel information for the SDFP session to the first RAN108 a.

At 804, the first RAN108 a forwards the UL data PDUs to the selected UPF (UPF 310 in this example). The first RAN108 a selects a UPF based on the SDFP information provided by the device 102. The first RAN108 a will also provide the UPF 310 with RAN N3 DL tunneling information for the SDFP session.

At 805, the UPF 310 checks the integrity protection and decrypts the UL data PDUs. If the check passes, the UPF 310 forwards the UL data on the N6 interface. Further, the UPF 310 enables subsequent DL data transmission to the RAN node from which the UL data PDU was received.

Turning to fig. 9, a process performed for performing SDFP communications according to yet another embodiment will now be described in the context of the network environment of fig. 3, with the following appended: there is an initial UPF (first UPF310 a) and a new UPF (second UPF310 b).

At 901, device 102 establishes RRC for SDFP transfer. The parameters for selecting a UPF for a PDU session for the device are passed to the second RAN108 b. RAN108 is not capable of connecting to a UPF, although it is capable of deriving a UPF address.

At 902, the RAN108 selects a UPF (UPF 310b in this example) and requests to establish an N3 tunnel with the UPF. The RAN108 may derive the second UPF310b based on the SDFP information. In some embodiments, the UPF can also be a default UPF configured at the RAN108 for SDFP transmissions. In the request message to the second UPF310b, the RAN108 also includes SDFP information and a RAN TEID for SDFP DL data.

At 903, the second UPF310b responds with an N4 tunnel setup response. In this message, the second UPF310b includes its UPF TEID for SDFP UL data.

At 904, the second UPF310b requests the establishment of an N9 tunnel with the first UPF310 a. The second UPF310b may use the SDFP information to derive the first UPF310 a. In the request message, the second UPF310b also includes SDFP information and the N9 UPF TEID for SDFPDL data.

At 905, the first UPF 310a responds with an N9 tunnel setup response. In this message, the first UPF 310a includes the new UPF TEID for SDFP UL data.

At 906, the device 102 ciphers and integrity protects the UL data PDU and passes it to the RAN 108.

At 907, the RAN 108 forwards the UL data PDU to the derived new UPF (UPF 310b in this example).

At 908, the second UPF 310b forwards the UL data PDU to the old UPF (the first UPF 310 a). The second UPF 310b selects the first UPF based on the SDFP information provided by the device 102. The second UPF 310b will also provide the first UPF 310a with UPF N9 DL tunneling information for the SDFP session.

At 909, the first UPF 310a checks the integrity protection and decrypts the UL data PDUs. If the check passes, the first UPF 310a forwards the UL data over the N6 interface. Further, the first UPF 310a enables transmission of subsequent DL data to the RAN node from which the UL data PDU was received.

Turning to fig. 10, an example of how a wireless communication device establishes an RRC connection for SDFP transfer according to an embodiment will now be described. The steps shown in FIG. 10 are depicted in the context of the network environment of FIG. 3, with the following added: there is an initial UPF (first UPF 310a) and a new UPF (second UPF 310 b). Parameters for selecting a UPF for a PDU session for the UE are communicated to the RAN.

At the beginning, the RAN 108 cannot connect to the UPF, although it can derive the UPF address. At 1002, the device 102 ciphers and integrity protects the UL data PDUs and passes them to the RAN 108.

At 1003, the RAN 108 forwards the UL data PDU to the derived new UPF (second UPF310 b). In the message to the second UPF310, the RAN will include the RAN N3 TEID for DL data. RAN 108 derives the UPF based on the SDFP information provided by device 102.

At 1004, the second UPF310b forwards the UL data PDU to the old UPF (the first UPF310 a). The second UPF310b derives the first UPF310 a based on the SDFP information provided by the device 1002. The second UPF310b will also provide the first UPF310 a with UPF N9 DL tunneling information for the SDFP session.

At 1005, the first UPF310 a checks the integrity protection and decrypts the UL data PDUs. If the check passes, the first UPF310 a forwards the UL data over the N6 interface. Further, the first UPF310 a enables transmission of subsequent DL data to the RAN node from which the UL data PDU was received.

Any and all methods described herein are performed by one or more computing devices. Further, instructions for performing any or all of the methods described herein may be stored on a non-transitory computer-readable medium, such as any of the various types of memories described herein.

It should be understood that the exemplary embodiments described in this disclosure should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should generally be considered as available for other similar features or aspects in other embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope defined by the following claims. For example, the steps of the various methods can be reordered in a manner apparent to those skilled in the art.

Claims

1. A method for performing small data fast path communication for a wireless communication device moving from a first radio access network to a second radio access network, the method comprising:

the second radio access network

Receiving a small data fast path parameter and a connection recovery identifier from the wireless communication device during a radio resource control connection establishment procedure;

deriving the first radio access network from the recovery identifier;

transmitting a connection request to the first radio access network, the connection request including the small data fast path parameter and a tunnel endpoint identifier for small data fast path downlink data; and

Receiving, from the first radio access network, a tunnel endpoint identifier for small data fast path uplink data.

2. The method of claim 1, further comprising receiving small data fast path uplink data from the wireless communication device.

3. The method of claim 2, further comprising transmitting the small data fast path uplink data to the first radio access network using the tunnel endpoint identifier received from the first radio access network.

4. The method of claim 2, further comprising the first radio access network:

selecting a user plane function based on the small data fast path parameter; and is

The downlink tunnel information for the small data fast path session is communicated to the selected user plane function.

5. The method of claim 4, further comprising the user plane function:

checking integrity protection of the small data fast path uplink data;

decrypting the small data fast path uplink data; and is

Forwarding the small data fast path uplink data.

6. A method for performing small data fast path communication for a wireless communication device moving from a first radio access network to a second radio access network, the method comprising:

The second radio access network

deriving the first radio access network from the recovery identifier;

receiving, from the wireless communication device, small data fast path uplink data; and

transmitting the small data fast path uplink data to the first radio access network.

7. The method of claim 6, further comprising the first radio access network:

selecting a user plane function based on the small data fast data parameter; and is

Downlink tunnel information for the small data fast path session is communicated to the selected user plane function.

8. The method of claim 7, further comprising the user plane function:

checking integrity protection of the small data fast path uplink data;

decrypting the small data fast path uplink data; and is

Forwarding the small data fast path uplink data.

9. A method for performing small data fast path communication for a wireless communication device moving from a first radio access network to a second radio access network, the method comprising:

The second radio access network

Receiving a small data fast path parameter from the wireless communication device during a radio resource control connection establishment procedure;

identifying a user plane function based on the small data fast path parameter;

transmitting, to the user plane function, a request to establish a tunnel for a small data fast path connection, wherein the request includes the small data fast path parameters and a tunnel endpoint identifier for small data fast path downlink data; and

receiving a tunnel setup response message from the user plane function, the message comprising a tunnel endpoint identifier for the user plane function, the tunnel endpoint identifier being for small data fast path uplink data.

10. The method of claim 9, wherein the user plane function is a first user plane function, the method further comprising the first user plane function requesting from a second user plane function, the request to tunnel a small data fast path data downlink.

11. The method of claim 10, further comprising the first user plane function deriving the second user plane function from the small data fast path parameter.

12. The method of claim 10, wherein the tunnel setup request includes the small data fast path parameter and a tunnel endpoint identifier for downlink data.

13. The method of claim 10, further comprising the first user plane function receiving a tunnel setup response message from the second user plane function, the tunnel setup response message including a tunnel endpoint identifier for small data fast path uplink data.

14. The method of claim 9, further comprising the second radio access network:

receiving uplink data from the wireless communication device; and is

Forwarding the received uplink data to the user plane function.

15. The method of claim 14, further comprising the first user plane function transmitting the uplink data to the second user plane function.

16. The method of claim 15, further comprising the second user plane function:

checking integrity protection of the small data fast path uplink data;

decrypting the small data fast path uplink data; and is

Forwarding the small data fast path uplink data.

17. A method for performing small data fast path communication for a wireless communication device moving from a first radio access network to a second radio access network, the method comprising:

the second radio access network

identifying a first user plane function based on the small data fast path parameter;

receiving small data fast path uplink data from the wireless communication device;

transmitting the small data fast path uplink data, the small data fast path parameters, and a tunnel endpoint identifier for downlink data to the first user plane function;

the first user plane function

Deriving the second user plane function from the small data fast path parameter;

transmitting the small data fast path uplink data, the small data fast path parameters, and downlink tunnel information for a small data fast path session to the second user plane function.

18. The method of claim 17, further comprising the second user plane function:

Checking integrity protection of the small data fast path uplink data;

decrypting the small data fast path uplink data; and is

Forwarding the small data fast path uplink data.

19. A method for performing small data fast path communication for a wireless communication device moving from a first radio access network to a second radio access network, the method comprising:

the second radio access network

Receiving small data fast path information from the wireless communication device during a protocol data unit session establishment procedure;

deriving the first radio access network from the small data fast path information;

transmitting a connection request to the first radio access network, the connection request including the small data fast path information and a tunnel endpoint identifier for small data fast path downlink data; and is

Receiving a tunnel endpoint identifier for small data fast path uplink data from the first radio access network.

20. The method of claim 19, further comprising receiving small data fast path uplink data from the wireless communication device.

21. The method of claim 20, further comprising transmitting the small data fast path uplink data to the first radio access network using the tunnel endpoint identifier received from the first radio access network.

22. The method of claim 20, further comprising the first radio access network:

selecting a user plane function based on the small data fast path information; and is

Transmitting downlink tunnel information for the small data fast path session to the selected user plane function.

23. The method of claim 22, further comprising the user plane function:

checking integrity protection of the small data fast path uplink data;

decrypting the small data fast path uplink data; and is

Forwarding the small data fast path uplink data.

24. A system configured to perform the method of any one of claims 1 to 23.

25. A non-transitory computer readable medium having stored thereon computer executable instructions for performing the method of any one of claims 1 to 23.