Patent Description:
Aspects of the present disclosure relate generally to wireless communication networks, and more particularly, to transmitting duplicate data packet units in make before break handovers.

Examples of such multiple-access systems include codedivision multiple access (CDMA) systems, time-division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, orthogonal frequency-division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.

<CIT> relates to methods, systems, and devices that support dual link handover. <CIT> relates to methods and systems to enable media access control based High-Speed Packet Access fast cell switching within a network. <NPL>, relates to DC architecture options to support handover enhancements using packet duplication.

For example, a fifth generation (<NUM>) wireless communications technology (which can be referred to as new radio (NR)) is envisaged to expand and support diverse usage scenarios and applications with respect to current mobile network generations. In an aspect, <NUM> communications technology can include: enhanced mobile broadband addressing human-centric use cases for access to multimedia content, services and data; ultra-reliable-low latency communications (URLLC) with certain specifications for latency and reliability; and massive machine type communications, which can allow a very large number of connected devices and transmission of a relatively low volume of non-delay-sensitive information. As the demand for mobile broadband access continues to increase, however, further improvements in NR communications technology and beyond may be desired.

For example, for NR communications technology and beyond, current handover solutions may not provide a desired level of speed or customization for efficient operation. Thus, improvements in wireless communication operations may be desired.

The present disclosure generally relates to techniques for a handover of a UE from a source base station to a target base station and using bi-casting of PDUs to assist or prevent HOL blocking issues as discussed below. The bi-casting of the PDUs may be applied to downlink data and uplink data. For example, for downlink data, a UPF may bi-cast PDUs to both the source base station and the target base station with corresponding PDUs having the same SN, e.g., the same GTP-U SN. The source base station and the target base station may generate the same SN for the payload of the received PDUs and may forward the PDUs having the same PDCP SN. The source base station may send one or more PDUs having either a GTP-U-SN or a PDCP SN to the target base station. For uplink data, the UE may bi-cast PDUs having the same SNs, e.g., PDCP SNs, to both the source base station and to the target base station. The source base station and the target base station may generate the same SN for the payload of the received PDUs and may forward the PDUs having the same GTP-U SNs to the UPF. The source base station may send one or more PDUs having either a GTP-U-SN or a PDCP SN to the target base station. The UE, UPF and the target base station may include duplication components to discard duplicative PDUs having the same SNs.

Each of the aspects described above are performed or implemented in connection with <FIG> which are described in more detail below. In some aspects, the methods, techniques, or schemes discussed herein may be within the limits of current specifications of various wireless communication standards (e.g., 3GPP standards). In some examples, the techniques or methods discussed herein may be implemented by or reside in hardware or software at a UE, a base station or a UPF.

If implemented in software, the functions may be stored on or encoded as one or more instructions or code on a computer-readable medium, such as a computer storage media. Storage media may be any available media that may be accessed by a computer. By way of example, and not limitation, such computer-readable media may comprise a random-access memory (RAM), a read-only memory (ROM), an electrically erasable programmable ROM (EEPROM), optical disk storage, magnetic disk storage, other magnetic storage devices, combinations of the aforementioned types of computer-readable media, or any other medium that may be used to store computer executable code in the form of instructions or data structures that may be accessed by a computer.

It should be noted that the techniques described herein may be used for various wireless communication networks such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and other systems. The terms "system" and "network" are often used interchangeably. IS-<NUM> Releases <NUM> and A are commonly referred to as CDMA2000 1X, 1X, etc. IS-<NUM> (TIA-<NUM>) is commonly referred to as CDMA2000 1xEV-DO, High Rate Packet Data (HRPD), etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. An OFDMA system may implement a radio technology such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA), IEEE <NUM> (Wi-Fi), IEEE <NUM> (WiMAX), IEEE <NUM>, Flash-OFDM™, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are new releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, and GSM are described in documents from an organization named "3rd Generation Partnership Project" (3GPP). The techniques described herein may be used for the systems and radio technologies mentioned above as well as other systems and radio technologies, including cellular (e.g., LTE) communications over a shared radio frequency spectrum band. The description below, however, describes an LTE/LTE-A and/or <NUM> New Radio (NR) system for purposes of example, and LTE or <NUM> NR terminology is used in much of the description below, although the techniques are applicable beyond LTE/LTE-A and <NUM> NR applications, e.g., to other next generation communication systems).

Referring to <FIG>, an example of a wireless communication network showing delays which can lead to a HOL blocking issue is illustrated. As shown, the wireless communication network <NUM> includes a server <NUM> that may transmit one or more PDUs to a UPF <NUM>. The UPF <NUM> may transmit the one or more PDUs to a serving or source base station <NUM> and to a target base station <NUM> during a handover phase of the UE <NUM>. URLLC service requires PDUs to be delivered with short latency and very high reliability. For example, for remote control applications, a controlled object (e.g., UE <NUM>), such as a drone, flight or car, receives controlling commands every <NUM> with T ms latency. The UE <NUM> transmits status data to the server <NUM> each <NUM> with S ms latency. The continuous data transmission shall be supported in mobility scenarios as well. This can be referred to as <NUM> interruption handover. Make before break handover is an implementation that can achieve <NUM> interruption handovers. However, handover procedures usually has a source to target data forwarding phase before the source stops transmitting which introduces an extra delay. The extra delay can lead to HOL blocking issues.

For example, during handover, a PDUn is delivered to the target base station <NUM> with a delay of TO + Tg, where TO is the delay between the server <NUM> and the UPF <NUM> and Tg is the delay between the UPF <NUM> and the target base station <NUM>. The previous PDU, PDUn-<NUM>, is forwarded by the source base station <NUM> to the target base station <NUM> with a delay of TO + Tg + Tn, with Tn being the delay between the source base station <NUM> and the target base station <NUM>. Due to re-ordering of the PDUs at the target base station <NUM>, PDUn cannot be delivered to high layer (e.g., IP layer) of the UE <NUM> before PDUn-<NUM> is delivered. This scenario is referred to as HOL blocking issue and can lead to Tn interruption from the high layer perspective. Mobile broad band (MBB) service is not sensitive to this interruption. However, for URLLC, this interruption may lead to user-plane interruption due to the packet data convergence protocol (PDCP) re-ordering which may cause the URLLC object, e.g., UE <NUM>, to be out of control (e.g., interruption, packet loss or packet delay). Accordingly, due to the requirements for URLLC, new approaches or procedures may be desirable to avoid such HOL blocking issues.

Additional features of the present aspects are described in more detail below with respect to <FIG>.

Referring to <FIG>, in accordance with various aspects of the present disclosure, an example wireless communication network <NUM> includes at least one UE <NUM> with a modem having a UE handover component <NUM> for performing a make before break handover. Further, wireless communication network <NUM> includes at least one base station <NUM> with a modem having a base station handover component <NUM> for performing a make before break handover. Thus, according to the present disclosure, a UE <NUM> can be handed off from a source base station <NUM> to a target base station <NUM> using a make before break handoff with the downlink communications and uplink communications being bi-casted.

The one or more UEs <NUM> and/or the one or more base stations <NUM> may communicate with other UEs and/or other base stations via an Evolved Packet Core (EPC) <NUM>.

A network that includes both small cell and macro cells may be known as a heterogeneous network. The base stations <NUM> / UEs <NUM> may use spectrum up to Y MHz (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, etc. MHz) bandwidth per carrier allocated in a carrier aggregation of up to a total of Yx MHz (where x is a number of component carriers) used for transmission in each direction. The carriers may or may not be adjacent to or contiguous with each other. Allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or less carriers may be allocated for DL than for UL).

The small cell <NUM>', employing NR in an unlicensed frequency spectrum, may boost coverage to and/or increase capacity of the network.

A base station <NUM>, whether a small cell <NUM>' or a large cell (e.g., macro base station), may include an eNB, gNodeB (gNB), or other type of base station. Some base stations, such as a gNB <NUM> may operate in a traditional sub <NUM> GHs spectrum, in millimeter wave (mmW) frequencies, and/or near mmW frequencies in communication with the UE <NUM>. When the gNB <NUM> operates in mmW or near mmW frequencies, the gNB <NUM> may be referred to as a mmW base station.

The base station <NUM> may also be referred to as a gNB, Node B, evolved Node B (eNB), an access point, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), or some other suitable terminology. The base station <NUM> provides an access point to the EPC <NUM> for one or more UEs <NUM>. Examples of UEs <NUM> include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA), a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, a tablet, a smart device, a wearable device, a vehicle, an electric meter, a gas pump, a large or small kitchen appliance, a healthcare device, an implant, a display, or any other similar functioning device.

The base stations <NUM> and the UEs <NUM> are able to communicate to a network through a <NUM> core network <NUM>. The core network <NUM> may include an Access and Mobility Management Function/Session Management Function (AMF/SMF) entity <NUM>, User Plane Function (UPF) <NUM> and other entity or components for communicating data packet units (PDUs). The AMF/SMF entity of <FIG> may provide similar functions as the AMF/SMF entity of <FIG>. Although <FIG>, shows a <NUM> core network <NUM>, other core networks can be used. For example, an LTE core network can be used with a Mobility Management Entity (MME) providing similar functions as the AMF/SMF entity <NUM> and a Serving Gateway providing similar functions as the UPF <NUM>. <FIG> and <FIG> show the handover procedures for an LTE based core network and a <NUM> based core network, respectively.

Referring to <FIG>, a schematic diagram of a <NUM> core network is illustrated. As shown, the core network <NUM> may include an Authentication Server Function (AUSF) <NUM>, Unified Data Management (UDM) <NUM>, AMF/SMF entity <NUM> (shown as two elements), Policy Control Information (PCF) <NUM> and Application Function (AF) <NUM>, as well as other components for a network (e.g., IP Services <NUM>) to communicate with a UE <NUM> and a random access network (RAN) (which can include one or more base stations <NUM>).

The AMF <NUM> provides several functions including, but not limited to, registration management, connection management, reachability management, mobility management, access authentication, access authorization, location services management, and EPS bearer ID allocation. The SMF <NUM> provides several functions including, but not limited to, session management, UE IP address allocation and management, ARP proxying and/or neighbor solicitation proxying, selection and control of UP function, configures traffic steering at UPF to route traffic to proper destinations, termination of interfaces towards policy control functions, lawful intercepts, control and coordination of charging data collection at the UPF, termination of SM parts of NAS messages, downlink data notification and roaming functionality. The UPF <NUM> provides several functions including, but not limited to, anchor point for intra/inter-RAT mobility, external PDU session point of interconnect to data network (e.g., IP services <NUM>), packet inspection, user plane part of policy rule information, lawful intercepts, traffic usage reporting, QoS handling for user plane, uplink traffic verification, transport level packet marking in the uplink and downlink, sending and forwarding one or more "end marker," and ARP proxying and/or neighbor soliciting proxying. The AUSF <NUM> handles authentication of the components within the <NUM> core network <NUM>. The UDM <NUM> provides several functions including, but not limited to, generation of authentication credentials, user identification handling, access authorization, support for service/session continuity, subscription management and SMS management. The PCF <NUM> provides several functions including, but not limited to, supports unified policy framework to govern network behavior, provides policy rules to control plane functions for enforcement, and accesses subscription information relevant for policy decision in the Unified Data Repository (UDR). The AF <NUM> provides several functions including, but not limited to, application influence on traffic routing, accessing network exposure function and interacting with policy framework for policy control.

Referring to <FIG>, in one aspect, the wireless communication system <NUM> includes a user equipment (UE) <NUM>, which may be an example of the UE <NUM>, undergoing a make before break handover from a source base station 402A to a target base station 402B, which may be examples of the base stations <NUM>. For instance, the UE <NUM> includes dual radios with a first radio <NUM> configured to communicate with the source base station 402A and a second radio <NUM> configured to communicate with the target base station 402B. In an aspect, the UE <NUM> may wirelessly transmit/receive one or more packet data units (PDUs) to/from both the source base station 402A and the target base station 402B. For instance, for downlink communications, the UE <NUM> may receive one or more PDUs from the source base station 402A using the first radio <NUM> and may receive one or more PDUs from the target base station 402B using the second radio <NUM>. Similarly, for uplink communications, the UE <NUM> may transmit one or more PDUs to the source base station 402A using the first radio <NUM> and may transmit one or more PDUs to the target base station 402B using the second radio <NUM>. In an aspect, the communications between the UE <NUM> and the source base station 402A and the communications between the UE <NUM> and the target base station 402B may use the same or different radio access technologies (RAT). Additionally, the source base station 402A and the target base station 402B may be the same type of base stations (e.g., macrocell, picocell, or femtocell) or may be different types of base stations.

The UE <NUM> can include a modem <NUM> having a handover component <NUM> configured to manage communication exchange signaling associated with the first radio <NUM> and/or the second radio <NUM> via one or more radio frequency (RF) communication resources. For example, the handover component <NUM> can receive a measurement control message from the source base station 402A via the first radio <NUM> and can provide measurement reports to the source base station 402A via the first radio <NUM>. The source base station 402A can use the measurement reports to determine whether to initiate a handover procedure. For downlink communications, the handover component <NUM> can wirelessly receive the one or more PDUs from the source base station 402A and from the target base station 402B, decipher the received one or more PDUs and store the received one or more PDUs in a buffer <NUM>. As explained in more detail below, a duplication component <NUM> may detect and discard one instance of a duplicate PDU stored in the buffer <NUM>. For example, when the duplication component <NUM> detects a duplicate PDU, the duplication component <NUM> may discard the duplicate PDU from the source base station 402A.

In an aspect, the handover component <NUM> may include a Packet Data Convergence Protocol Sequence Number (PDCP SN) component <NUM>. For uplink communications, the PDCP SN component <NUM> may include a PDCP SN in the header of each PDU that is transmitted to the source base station 402A and the target base station 402B. During the handover process, the PDCP SN component <NUM> may transmit a PDU having a header with a PDCP SN to the source base station 402A and transmit a PDU having a header with the same PDCP SN to the target base station 402B. In an aspect, the PDU transmitted to the source base station 402A may have a header having an identifier identifying the source base station 402A (e.g., a source base station identifier), the PDCP SN and a payload and the PDU transmitted to the target base station 40B may have a header having an identifier identifying the target base station 402B (e.g., a target base station identifier), the same PDCP SN and the same payload. In another aspect, the PDUs transmitted to the source base station 402A and to the target base station 402B may each have a header having an identifier identifying the source base station 402A (e.g., a source base station identifier), an identifier identifying the target base station 402B (e.g., a target base station identifier), the same PDCP SN and the same payload. As explained below, by transmitting PDUs having the same PDCP and the same payload, the target base station 402B can detect and discard an instance of duplicative PDUs, one PDU received from the UE <NUM> and one PDU forwarded by the source base station 402A. For clarity purposes, when the UE <NUM> has a PDU to transmit during a handover process, e.g., the transition process, the handover component <NUM> transmits the same PDU (e.g., having the same PDCP SN and payload) to both the source base station 402A and the target base station 402B. By transmitting the same PDU to both the source base station 402A and to the target base station 402B, the target base station 402B is able to prevent and/or reduce HOL blocking issues.

Each of the source base station 402A and the target base station 402B include a modem <NUM> having a handover component <NUM>. The handover component <NUM> may include a PDCP SN component <NUM>, a general packet radio service (GPRS) tunneling protocol (GTP) user data (GTP-U) SN component <NUM>, buffer <NUM> and duplication component <NUM>. The PDCP SN component <NUM> generates a PDCP SN for each downlink PDU received from the UPF. The GTP-U SN component <NUM> generates a GTU-U SN for each uplink PDU received by the UE <NUM>. The buffer <NUM> stores received PDUs. The duplication component <NUM> detects and discards duplicative PDUs. For downlink data, PDUs are received from the UPF <NUM> with each received PDU having a GTP-U SN. As explained in further detail below, the UPF <NUM> sends (e.g., bi-casts) the same or similar PDUs to both the source base station 402A and target base station 402B during the handover procedure. For example, the UPF <NUM> sends a PDU to the source base station 402A having a header with a GTP-U SN and sends a PDU to the target base station 402B having a header with the same GTP-U SN. The PDCP SN components <NUM> of the source base station 402A and target base station 402B receive the PDUs having the same GTP-U SN and generate the same PDCP SN for the PDUs. Each of the source base station 402A and target base station 402B then transmits the PDUs having the same generated PDCP SN to the UE <NUM>. For uplink data, both of the source base station 402A and the target base station 402B receive the same or similar PDUs from the UE <NUM>, with the two PDUs having the same PDCP SN and same payload. The GTP-U SN component <NUM> of the source base station 402A and the target base station 402B generate a GTP-U SN for their respective PDUs. The generated GTP-U SNs are inserted into the header of the respective PDU. The source base station 402A then forwards the PDU having the GTP-U SN to the target base station 402B. The target base station 402B deciphers the PDUs from the source base station 402A and stores them in the buffer <NUM> along with the PDUs the target base station 402B has received from the UE <NUM>. The duplication component <NUM> of the target base station 402B then detects and discards duplicative PDUs having the same GTP-U SNs. For example, the duplication component <NUM> detects duplicative PDUs and discards the duplicative PDUs from the source base station 402A. The handover component <NUM> then reorders the remaining PDUs in the buffer <NUM> and sends them to the UPF <NUM>. Because the target base station 402B receives the same PDUs from both the source base station 402A and the UE <NUM>, the target base station 402B is able to prevent and/or reduce HOL blocking issues.

The UPF <NUM> includes a modem <NUM> having a handover component <NUM> with a GTP-U SN component <NUM>, buffer <NUM> and duplication component <NUM>. The GTP-U SN component <NUM> generates a GTU-U SN for each downlink PDU to be sent to the UE <NUM>. The buffer <NUM> stores received PDUs, e.g., uplink PDUs. The duplication component <NUM> detects and discards duplicative PDUs stored in the buffer <NUM>. For downlink PDUs to be sent to the UE <NUM>, the GTP-U SN component <NUM> generates a GTU-U SN. For each downlink PDU, the handover component <NUM> can generate one or more headers for the PDU. In one aspect, the handover component <NUM> may generate a header for the source base station 402A with an identifier identifying the source base station 402A and may generate a header for the target base station 402B with an identifier identifying the target base station 402B. The handover component <NUM> may then bi-cast (e.g., send) the PDUs having the same GTU-U SNs and same payloads to the source base station 402A and target base station 402B, respectively. In another aspect, the handover component <NUM> may generate a header having an identifier identifying the source base station 402A and an identifier identifying the target base station 402B and may send a PDU with the header having both identifiers to source base station 402A and target base station 402B. In another aspect, the handover component <NUM> may generate a header having a GTU-U SN and may multicast the PDU to the source base station 402A and the target base station 402B. For uplink PDUs that originated from the UE <NUM>, the handover component <NUM> may receive one or more PDUs from the source base station 402A and one or more PDUs from the target base station 402B. The handover component <NUM> deciphers the received PDUs and stores them in the same buffer <NUM>. The duplication component <NUM> may detect and discard an instance of a duplicative PDU. For example, the duplication component <NUM> may detect and discard an instance of a duplicative PDU from the source base station 402A. The handover component <NUM> then reorders the remaining PDUs in the buffer <NUM> and sends them to the IP services <NUM>. Because the UPF <NUM> receives the same PDUs from both the source base station 402A and the target base station 402B and transmits PDUs having the same GTU-SN to both the source base station 402A and the target base station 402B, the UPF <NUM> is able to prevent and/or reduce HOL blocking issues.

Referring to <FIG>, an LTE or <NUM> GPP handover call flow <NUM> is illustrated. As shown, the UE is in a connected state with data packets being transferred to/from the UE to/from the network via the source base station in both directions (e.g., downlink and uplink). At step <NUM>, the source base station sends a measurement control request message to the UE to set the parameters to measure and set thresholds for those parameters. The purpose of the measurement control request message is to instruct the UE to send a measurement report to the network as soon as one or more thresholds are detected. At step <NUM>, the UE sends a measurement report to the source base station after the UE meets the measurement report criteria that was previously communicated to the UE. At step <NUM>, the source base station makes the decision to handoff the UE to a target base station using a handover algorithm and the measurement report. At step <NUM>, the source base station can optionally issue a resource status request message to determine the load on the target base station. Based on the received source status response, the source base station can decide to proceed further in continuing the handover procedure using the X2 interface. At step <NUM>, the source base station issues a handover request message to the target base station parsing necessary information to prepare the handover at the target base station. At step <NUM>, the target base station checks for resource availability. If the resources are available, the target base station reserves the resources and sends a handover request acknowledgement message to the source base station. At step <NUM>, the source base station generates and sends a radio resource control (RRC) message to the UE. The RRC message includes instructions to perform the handover and may include a RRC connection reconfiguration message including the mobility control information. At step <NUM>, the source base station sends the target base station a status transfer message to convey the PDCP and hyper frame number (HFN) status of the E-UTRAN radio access bearers (E-RABs). The source base station starts forwarding the downlink data packets to the target base station for all of the data bearers (which are being established in the target base station during the handover request message processing) with the target base station buffering the received packets. In the meantime, at steps <NUM> and <NUM>, the UE tries to access the target base station using a non-contention-based random access procedure. If successful in accessing the target base station, the UE sends the RRC connection reconfiguration complete message to the target base station at step <NUM>. At step <NUM>, the target base station sends a path switch request message to the MME to inform the MME that the UE has changed cells, including the tracking area identity (TAI) and evolved cell global identifier (ECGI) of the target. At step <NUM>, the MME determines that the serving gateway can continue to serve the UE and sends a modify bearer request (target base station and tunnel endpoint identifiers (TEIDs) for downlink user plane for the accepted EPS bearers) message to the serving gateway. The modify bearer request can include the location information for the UE. At step <NUM>, the serving gateway switches the downlink path for the UE. At step <NUM>, the serving gateway sends downlink packets to the target base station using the newly receive addresses and TEIDs (path switched downlink data path to the target base station and a modify bearer response to the MME. The serving gateway can send one or more "end marker" packets on the old path to the source base station and can release any user plane/TNL resources. At step <NUM>, the MME responds to the target base station with a path switch request acknowledgement message to notify the completion of the handover. At step <NUM>, the target base station sends a UE context release message to the source base station to release the resources. After the source base station releases the resources, the handover is complete.

In an aspect, a Path Switch Preparation procedure can be introduced, e.g., after step <NUM> in <FIG>. The Path Switch Preparation procedure can trigger the UPF <NUM> to bi-cast, e.g., transmit the same or similar PDUs (e.g., PDUs having the same payload and same SN) to both the source base station 402A and the target base station 402B. When the source base station 402A sends the SN status transfer message to the target base station 402B, the target base station 402B can obtain information for a GTP-U tunnel between the UPF <NUM> and target base station 402B from the UPF <NUM>. In an aspect, besides the two unicast tunnels, e.g., the tunnel between the UPF <NUM> and the source base station 402A and the tunnel between the UPF <NUM> and the target base station 402B, the UPF <NUM> may carry the GTP-U tunnel over IP multicast, similar to the M1 interface in LTE. For a flow requiring <NUM> interruption handover, the same packet of flow may be bi-casted to both the source base station 402A and the target base station 402B with the same GTP-U SN and same payload. The PDCP SN component <NUM> of the source base station 402A and the PDCP SN component <NUM> of the target base station 402B shall generate the same PDCP SN for the respective PDUs based on the GTP-U SN. In another aspect, separate GTP-U tunnels may be established for each URLLC flow. The UPF <NUM> may bi-cast the same packet to both the source base station 402A and to the target base station 402B using the same GTP-U SN and same payload. When a UE <NUM> receives PDUs from both the source base station 402A and the target base station 402B, the UE <NUM> may store the received PDUs in the same buffer <NUM> for re-ordering and duplication detection. Because the target base station 402B supports duplication detection based on the GTP-U SN, the SN Status Transfer message (e.g., step <NUM> of <FIG>) may be enhanced by the source base station 402A to carry sequence number delta information. The sequence number delta information can be the delta between the PDCP SN and the GTU-U SN. After the RRC connection reconfiguration message is sent to the target base station 402B (e.g., step <NUM> in <FIG>), the UE <NUM> may start bi-casting PDUs, e.g., sending the same or similar PDCP PDUs, to the source base station 402A and to the target base station 402B. The same or similar PDCP PDUs will have the same PDCP SN which allows the target base station 402B to detect and discard duplicative PDUs. The UPF <NUM> supports duplication detection, thus the UPF <NUM> detects and re-orders received PDUs from the source base station 402A and the target base station 402B based on SNs in the GTP-U PDUs. The sequence numbers could be PDCP SNs, GTP-U SNs or flow SNs in GTP-U extension headers. The GTP-U SNs are generated based on the PDCP SNs.

Referring to <FIG>, a make before break URLLC handover call flow <NUM> according to the claimed embodiment is illustrated. As shown, the UE <NUM> transmits uplink PDUs having a PDCP SN to the source base station 402A. For each received PDU, the source base station 402A then generates a GTP-U SN, includes the GTP-U SN in a header and then sends the PDU having the GTP-U SN in the header to UPF <NUM>. When the UE <NUM> sends the source base station 402A a measurement report indicating a handover condition, the source base station 402A sends a handover request to the target base station 402B. The target base station 402B responds by sending a handover command to the source base station 402A. The source base station 402A then sends a RRC reconfiguration message to the UE <NUM>. The target base station 402B sends a Path Switch Preparation Request to the AMF/SMF ENTITY <NUM> requesting tunnel information. The AMF/SMF ENTITY <NUM> responds with a Path Switch Preparation Response along with UPF tunnel information. The AMF/SMF ENTITY <NUM> sends a message to the UPF <NUM> (e.g., UPF <NUM> in <FIG>) to trigger the UPF <NUM> to start bi-casting PDUs to both the source base station 402A and the target base station 402B. The UPF <NUM> sends the same or similar downlink PDUs to both the source base station 402A and target base station 402B over one or more respective tunnels. The same or similar downlink PDUs have the same GTP-U SN and same payload. The source base station 402A and target base station 402B receive the same or similar PDUs, generate a PDCP SN based on the GTP-US SN and send PDCP PDUs having the same PDCP SN to the UE <NUM>. The duplication component <NUM> of the UE <NUM> may perform a duplication detection on the received PDCP PDUs. Once the RRC reconfiguration is complete, the UE <NUM> may transmit a RRC Reconfiguration Complete message to the target base station 402B using the first radio <NUM> or the second radio <NUM>. For uplink PDUs, the UE <NUM> may send PDCP PDUs having the same PDCP SNs to both the source base station 402A and the target base station 402B. The source base station 402A and the target base station 402B may receive the PDCP PDUs having the same PDCP SNs, may generate GTP-U SNs based on the PDCP SNs and each of the source base station 402A and the target base station 402B may forward the GTP-U PDUs having the same GTP-U SNs to the UPF <NUM>. The duplication component <NUM> of the UPF <NUM> may perform a duplication detection on the received GTP-U PDUs. In response to receiving the RRC Reconfiguration Complete message, the target base station 402B may send a Path Switch Request to the AMF/SMF ENTITY <NUM>. The AMF/SMF ENTITY <NUM> and UPF <NUM> may complete a bearer modification to change the target base station to the source base station. The bearer modification process may cause the UPF <NUM> to stop the bi-casting. The AMF/SMF ENTITY <NUM> may send a Path Switch Request Acknowledgement message to the target base station 402B. In response, the target base station 402B may send a UE Context Release message to the source base station 402A which causes the source base station 402A to stop the bi-casting process. In response to the UE Context Release message, the source base station 402A may send a RRC Connection Release message to the UE <NUM> which causes the UE <NUM> to stop the bi-casting.

The bi-casting process may avoid the forwarding delay for downlink transmissions. During the transition phase of a make before break handover, the bi-casting by the UPF <NUM> may be enabled in response to a request by the target base station 402B. For example, a Path Switch Preparation procedure may be initiated after step <NUM> of <FIG> which may trigger the UPF bi-casting PDUs to both the source base station 402A and the target base station 402B. The Path Switch Preparation procedure may include the GTP-U tunnel information between the UPF <NUM> and the target base station 402B to be exchanged. Besides the regular two unicast GTP-U tunnels (e.g., the GTP-U tunnel between the UPF <NUM> and the source base station 402A and the GTP-U tunnel between the UPF <NUM> and the target base station 402B), a single GTP-U tunnel over IP multicast, similar to MT interface in LTE, may be used. The bi-casting by the UE <NUM>, source base station 402A, target base station 402B and UPF <NUM> results in data delivered to high layer in sequence, lossless, and without duplication. In current LTE handover, the PDCP SN is assigned by the source base station 402A and target base station 402B in a continuous manner. PDCP SNs can be used for packet loss, duplication detection and re-ordering.

In make before break handover, the PDCP SN components <NUM> in the source base station 402A and the target base station 402B work in parallel in the interim phase of handover. To support duplication detection, the PDCP SN components <NUM> in the source base station 402A and the target base station 402B assign the same SN to the same PDU received from the UPF <NUM>. This requires the UPF <NUM> to bi-cast the same PDU to the source base station 402A and to the target base station 402B using the same SN in the GTP-U PDUs. Each of the source base station 402A and the target base station 402B assign the PDCP SN to the PDUs based on the GTP-U PDU SN.

If the <NUM> interruption is required only for some flows of a PDU session, the flow level SN may be assigned in the GTP-U PDUs. For a flow requiring <NUM> interruption handover, the same packet of the flow is bi-casted to both the source base station 402A and the target base station 402B with the same SN in the GTP-U PDU. The PDCP SN components <NUM> in the source base station 402A and the target base station 402B generate the same PDCP SN based on the SN of the GTP-U-SN.

In another aspect, separate GTP-U tunnels may be established for each URLLC flow. The UPF <NUM> may bi-cast the same PDUs to both the source base station 402A and the target base station 402B using the same GTP-U SN. When a UE <NUM> receives PDCP PDUs from both the source base station 402A and the target base station 402B, the duplication component <NUM> of the UE <NUM> will store the deciphered PDCP PDUs into the same buffer <NUM> and the duplication component <NUM> will perform a duplication procedure to discard duplicative PDCP PDUs and re-order the remaining PDCP PDUs. Even with the UPF <NUM> bi-casting the PDUs, when the channel of the source base station 402A fades too fast, the source base station 402A has to forward some of the unsent packets (e.g., PDUs not sent to the UE <NUM>) to the target base station 402B. In this case, the duplication component <NUM> of the target base station 402B shall perform the duplication process and will discard duplicative PDUs for the forwarded PDUs without PDCP SNs. One process to do this is for the Xn GTP-U to carry the same SN as the GTP-U PDU from the UPF <NUM>. If the SN has to be different for some reason, the SN Status Transfer message, e.g., step <NUM> in <FIG>, is enhanced to carry the delta between the Xn GTP-U SN and the UPF GTP-U SN. The duplication component <NUM> of the target base station 402B may perform the duplication detection process based on the GTP-U SN. The Status Transfer message may be enhanced to carry the SN delta information.

For uplink transmissions, the make before break based <NUM> interruption handover relies on the UE duplication/bi-casting of the same PDUs (or IP packets) to the PDCP SN components <NUM> in the source base station 402A and the target base station 402B with the PDCP PDUs having the same PDCP SNs. The UE <NUM> may start the bi-casting after the RRC Reconfiguration Complete message is sent to the target base station 402B in step <NUM> of <FIG>. The UPF may perform the duplication detection process and perform the re-ordering based on the PDCP SN in GTP-U extension header, GTP-U SN or the flow specific SN in the GTP-U extension header. For the GTP-U SN or flow specific SN detection, the SN in the GTP-U may be assigned based on the PDCP SN. For flow specific SN detections, if the UPF side TEID, UDP port and IP Address are the same for the two tunnels (e.g., the tunnel between the UPF <NUM> and the source base station 402A and the tunnel between the UPF <NUM> and target base station 402B), up to implementation, the UPF <NUM> may treat the two uplink GTP-U tunnels as one GTP tunnel. In this scenario, the re-ordering and duplication detection process may be achieved without extra processing in the UPF <NUM>. The UE <NUM> may start the bi-casting/duplication to the PDCP SN components <NUM> in the source base station 402A and the target base station 402B after the RRC Connection Reconfiguration message is sent to the target base station 402B (e.g., step <NUM> of <FIG>). For the same or similar PDU PDUs (e.g., IP packet or other payload) sent to the source base station 402A and to the target base station 402B have the same PDCP SN. The UPF <NUM> performs the duplication detection procedure and re-orders the received GTP-U PDUs from the source base station 402A and the target base station 402B based on the GTP-U SN. The SN may be the PDCP SN, GTP-U SN or flow SN in the GTP-U extension header. The SN in GTP-U PDUs is generated based on the PDCP SN.

Referring to <FIG>, a flow diagram showing an example method <NUM> of operating a UPF according to the above-described aspects to handover of a UE from a source base station to a target base station includes one or more of the herein-defined actions.

At block <NUM>, the method <NUM> may include establishing a tunnel between the UPF and the target base station based on information in a path switch preparation request for a make before break handover of a UE from a source base station to the target base station, the path switch preparation request being received in response to a request originating by the target base station. In an aspect, for example, the processor <NUM> in conjunction with the UPF handover component <NUM> may establish a tunnel between the UPF <NUM> and the target base station 402B based on information in a path switch preparation request for a make before break handover of the UE <NUM> from the source base station 402A to the target base station 402B, the path switch preparation request being received in response to a request originating by the target base station.

At block <NUM>, the method <NUM> may include bi-casting a downlink PDU to a source base station and to the target base station with a same SN in a tunnel protocol. In an example, the processor <NUM> in conjunction with the handover component <NUM> and/or the GTP-U SN component <NUM> may bi-cast a downlink PDU to the source base station 402A and to the target base station 402B with a same SN in a tunnel protocol, e.g., GTP-U.

At block <NUM>, the method <NUM> may optionally include transmitting a same PDU having the same SN to the target base station and source base station. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM> and/or the GTP-U SN component <NUM> may transmit a same PDU having the same SN to the target base station 402B and source base station 402A.

At block <NUM>, the method <NUM> may optionally include transmitting a first PDU to the target base station over the tunnel between the UPF and the target base station, transmitting a second PDU to the source base station 402A over the tunnel between the UPF and the source base station, wherein the first PDU and the second PDU have the same payload and the same SN, e.g., a GTP-U SN. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM> and/or the GTP-U SN component <NUM>, via transceiver <NUM>, may transmit a first PDU to the target base station 402B over the tunnel between the UPF <NUM> and the target base station 402B, transmit a second PDU to the source base station 402A over the tunnel between the UPF <NUM> and the source base station 402A, wherein the first PDU and the second PDU have the same payload and the same SN, e.g., a GTP-U SN.

At block <NUM>, the method <NUM> may optionally include transmitting a same PDU having a same SN to the target base station and the source base station via multicasting. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM> and/or the GTP-U SN component <NUM>, via the transceiver <NUM>, transmit a same PDU having a same SN to the target base station 402B and the source base station 402A via multicasting.

At block <NUM>, the method <NUM> may include receiving PDUs from the source base station and the target base station with corresponding PDUs having the same SNs in the tunnel protocol, e.g., GTP-U. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM>, via the transceiver <NUM>, may receive PDUs for the source base station 402A and the target base station 402B with corresponding PDUs have the same SNs in the tunnel protocol, e.g., GTP-U.

At block <NUM>, the method <NUM> may include discarding received duplicate PDUs based on the SNs in the tunnel protocol, e.g., GTP-U. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM> and/or duplication component <NUM> may discard received duplicate PDUs based on the SNs in the tunnel protocol, e.g., GTP-U.

At block <NUM>, the method <NUM> may include re-ordering remaining PDUs based on the at least one corresponding SN. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM> and/or duplication component <NUM> may re-order the remaining PDUs based on the at least corresponding SN.

At block <NUM>, the method <NUM> may include transmitting the re-ordered remaining PDUS. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM>, via the transceiver <NUM>, may transmit the remaining PDUs based on the at least corresponding SN.

Referring to <FIG>, a flow diagram showing an example method <NUM> of operating a UE according to the above-described aspects to handover of the UE from a source base station to a target base station includes one or more of the herein-defined actions.

At block <NUM>, the method <NUM> may include transmitting, via a first radio or a second radio, a connection reconfiguration complete message to a target base station for completing a make before break handover of the UE from the source base station to the target base station. In an aspect, for example, the processor <NUM> in conjunction with either the first radio <NUM> or the second radio <NUM> and/or the handover component <NUM> may transmit, via the first radio <NUM> or the second radio <NUM>, a connection reconfiguration complete message to the target base station 402B for completing a make before break handover of the UE <NUM> from the source base station 402A to the target base station 402B.

At block <NUM>, the method <NUM> may include, for uplink transmissions, transmitting, via the first radio, a first PDU to the source base station. In an aspect, for example, the processor <NUM> in conjunction with the first radio <NUM>, the handover component <NUM> and/or PDCP SN component <NUM> may transmit, the first PDU having a PDCP SN to the source base station 402A.

At block <NUM>, the method <NUM> may include, for uplink transmissions, transmitting, via the second radio, a second PDU to the target base station. In an aspect, for example, the processor <NUM> in conjunction with the second radio <NUM>, the handover component <NUM> and/or PDCP SN component <NUM> may transmit, the second PDU having a PDCP SN to the target base station 402B. The first PDU and the second PDU will have the same SN, e.g., PDCP SN.

At block <NUM>, the method <NUM> may include, for downlink transmissions, receiving, via the first radio, one or more PDUs from the source base station, with each receive PDU having at least one corresponding SN, e.g., PDCP SN. In an aspect, for example, the processor <NUM> in conjunction with either the first radio <NUM>, the handover component <NUM> and/or PDCP SN component <NUM> may receive, one or more PDUs from the source base station 402A, with each received PDU having at least one corresponding SN, e.g., PDCP SN.

At block <NUM>, the method <NUM> may include, for downlink transmissions, receiving, via the second radio, one or more PDUs from the target base station, with each receive PDU having at least one corresponding SN, e.g., PDCP SN. In an aspect, for example, the processor <NUM> in conjunction with either the second radio <NUM>, the handover component <NUM> and/or PDCP SN component <NUM> may receive, one or more PDUs from the target base station 402B, with each received PDU having at least one corresponding SN, e.g., PDCP SN.

At block <NUM>, the method <NUM> may include, deciphering the received one or more PDUs from the source base station and the target base station respectively and storing the received one or more PDUs in a buffer. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM> may decipher the received one or more PDUs from the source base station 402A and the target base station 402B respectively and store the received one or more PDUS in a buffer <NUM>.

At block <NUM>, the method <NUM> may include, discarding duplicative PDUs in the buffer based on the at least one corresponding SNs, e.g., PDCP SNs. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM> and/or duplication component <NUM> may discard received duplicative PDUs based on the at least one corresponding SNs, e.g., PDCP SNs.

At block <NUM>, the method <NUM> may include delivering the re-ordered remaining PDUs to upper layer. In an aspect, for example, the processor <NUM> in conjunction with the transceiver <NUM> and/or handover component <NUM> may deliver the remaining PDUs based on the at least corresponding SN.

Referring to <FIG>, a flow diagram showing an example method <NUM> of operating a AMF/SMF ENTITY <NUM> according to the above-described aspects to handover of the UE from a source base station to a target base station includes one or more of the herein-defined actions.

At block <NUM>, the method <NUM> may include receiving, from the target base station, a request for downlink bi-casting of duplicative packet data units (PDUs), the request being a path switch preparation request for a make before break handover for the UE from the source base station to the target base station, the path switch preparation request is based on a SN status transfer message and contains target base station information. In an aspect for example, the processor <NUM> of the AMF/SMF ENTITY <NUM> may receive from the target base station 402B, via the transceiver <NUM>, a request for downlink bi-casting of duplicative PDUs, the request being a path switch preparation request for a make before break handover for the UE <NUM> from the source base station 402A to the target base station 402B, the path switch preparation request is based on a SN status transfer message and contains target base station information.

At block <NUM>, the method <NUM> may include configuring the UPF to establish a tunnel between the UPF and the target base station. In an aspect, for example, the processor <NUM> may configure the UPF <NUM> to establish a tunnel between the UPF <NUM> and the target base station 402B.

At block <NUM>, the method <NUM> may include transmitting, to the target base station, UPF information to establish the tunnel between the target base station and the UPF using the target base station information and the UPF information. In an aspect, the processor <NUM>, via the transceiver <NUM>, may transmit, to the target base station 402B, UPF information to establish the tunnel between the target base station 402B and the UPF <NUM> using the target base station information and the UPF information.

Referring to <FIG>, a flow diagram showing an example method <NUM> of operating a target base station according to the above-described aspects to handover of the UE from a source base station to a target base station includes one or more of the herein-defined actions.

At block <NUM>, the method <NUM> may include receiving, from a source base station, a SN transfer message. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM> and via the transceiver <NUM>, may receive, from the source base station 402A, a SN transfer message.

At block <NUM>, the method <NUM> may include transmitting, to the AMF/SMF entity, a path switch preparation request for a make before break handover for the UE from the source base station to the target base station, the path switch preparation request including target base station tunnel information and configured to trigger a UPF to transmit PDUs for the UE to both the target base station and the source base station during the handover. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM>, via the transceiver <NUM>, may transmit, to the AMF/SMF entity <NUM>, a path switch preparation request for a make before break handover for the UE <NUM> from the source base station 402A to target base station 402B, the path switch preparation request including target base station tunnel information and configured to trigger the UPF <NUM> to transmit PDUs for the UE <NUM> to both the target base station 402B and the source base station 402A during the handover.

At block <NUM>, the method <NUM> may include receiving, from the AMF/SMF entity <NUM>, a path switch preparation response including UPF tunnel information. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM>, via the transceiver <NUM>, may receive the path switch preparation response including UPF tunnel information.

At block <NUM>, the method <NUM> may include establishing a tunnel between the target base station and the UPF using the UPF tunnel information. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM>, via the transceiver <NUM>, may establish the tunnel between the target base station 402B and the UPF <NUM> using the UPF tunnel information.

At block <NUM>, the method <NUM> may include receiving, from the UPF, one or more PDUs via the tunnel, each PDU having at least one corresponding SN in the second protocol, e.g., GTP-U. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM>, via the transceiver <NUM>, may receive, from the UPF <NUM>, one or more PDUs via the tunnel, each PDU having at least one corresponding SN in the second protocol, e.g., GTP-U.

At block <NUM>, the method <NUM> may include receiving, from the source base station, one or more PDUs, each PDU having at least one corresponding SN in the second protocol, e.g., GTP-U. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM>, via the transceiver <NUM>, may receive, from the source base station 402A, one or more PDUs, each PDU having at least one corresponding SN in the second protocol, e.g., GTP-U.

At block <NUM>, the method <NUM> may include, deciphering the received one or more PDUs from the UPF and the source base station respectively and storing the received one or more PDUS in a buffer. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM> may decipher the received one or more PDUs from the UPF <NUM> and the source base station 402A respectively and store the received one or more PDUS in a buffer <NUM>.

At block <NUM>, the method <NUM> may include, discarding duplicative PDUs in the buffer based on the at least one corresponding SNs, e.g., GTP-U SNs. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM> and/or duplication component <NUM> may discard received duplicative PDUs based on the at least one corresponding SNs, e.g., GTP-U SNs.

At block <NUM>, the method <NUM> may include converting, for each of the remaining PDUs, the at least one corresponding SN in the second protocol to a SN in the first protocol. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM> and/or PDCP SN component <NUM> may convert, for each of the remaining PDUs, the at least one corresponding SN in the second protocol to a SN in the first protocol. For example, GTP-U SNs may be converted to PDCP SNs based on the GTP-U SN.

At block <NUM>, the method <NUM> may include re-ordering remaining PDUs based on the at least one corresponding SN in the first protocol, e.g., PDCP. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM> and/or duplication component <NUM> may re-order the remaining PDUs based on the at least corresponding SN.

At block <NUM>, the method <NUM> may include transmitting the re-ordered remaining PDUs to the UE. In an aspect, for example, the processor <NUM> in conjunction with the transceiver <NUM> and/or handover component <NUM> may transmit the re-ordered remaining PDUs to the UE <NUM> based on the at least corresponding SN.

At block <NUM>, the method <NUM> may include receiving, from the source base station, one or more PDUs via the tunnel, each PDU having at least one corresponding SN in the first protocol, e.g., PDCP. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM>, via the transceiver <NUM>, may receive, from the source base station 402A, one or more PDUs via the tunnel, each PDU having at least one corresponding SN in the first protocol, e.g., PDCP.

At block <NUM>, the method <NUM> may include receiving, from the UE, one or more PDUs, each PDU having at least one corresponding SN in the first protocol, e.g., PDCP. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM>, via the transceiver <NUM>, may receive, from the UE <NUM>, one or more PDUs, each PDU having at least one corresponding SN in the first protocol, e.g., PDCP.

At block <NUM>, the method <NUM> may include, deciphering the received one or more PDUs from the source base station and the UE respectively and storing the received one or more PDUs in a buffer. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM> may decipher the received one or more PDUs from the source base station 402A and the UE <NUM> respectively and store the received one or more PDUs in a buffer <NUM>.

At block <NUM>, the method <NUM> may include converting, for each of the remaining PDUs, the at least one corresponding SN in the first protocol to a SN in the second protocol. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM> and/or GTP-U SN component <NUM> may convert, for each of the remaining PDUs, the at least one corresponding SN in the first protocol to a SN in the second protocol. For example, PDCP SNs may be converted to GTP-U SNs based on the PDCP SN.

At block <NUM>, the method <NUM> may include re-ordering remaining PDUs based on the at least one corresponding SN in the second protocol, e.g., GTP-U. In an aspect, for example, the processor <NUM> in conjunction with the handover component <NUM> and/or duplication component <NUM> may re-order the remaining PDUs based on the at least corresponding SN.

At block <NUM>, the method <NUM> may include transmitting the re-ordered remaining PDUs to the UPF. In an aspect, for example, the processor <NUM> in conjunction with the transceiver <NUM> and/or handover component <NUM> may transmit the re-ordered remaining PDUs to the UPF <NUM> based on the at least corresponding SN.

Referring to <FIG> one example of an implementation of UE <NUM> may include a variety of components, some of which have already been described above, but including components such as one or more processors <NUM> and memory <NUM> and transceiver <NUM> in communication via one or more buses <NUM>, which may operate in conjunction with modem <NUM> and handover component <NUM> to enable one or more of the functions described herein related to make before break handovers. Further, the one or more processors <NUM>, modem <NUM>, memory <NUM>, transceiver <NUM>, RF front end <NUM> and one or more antennas <NUM>, may be configured to support voice and/or data calls (simultaneously or non-simultaneously) in one or more radio access technologies. The one or more antennas <NUM> may include one or more antennas, antenna elements and/or antenna arrays.

In an aspect, the one or more processors <NUM> can include a modem <NUM> that uses one or more modem processors. The various functions related to handover component <NUM> may be included in modem <NUM> and/or processors <NUM> and, in an aspect, can be executed by a single processor, while in other aspects, different ones of the functions may be executed by a combination of two or more different processors. For example, in an aspect, the one or more processors <NUM> may include any one or any combination of a modem processor, or a baseband processor, or a digital signal processor, or a transmit processor, or a receiver processor, or a transceiver processor associated with transceiver <NUM>. In other aspects, some of the features of the one or more processors <NUM> and/or modem <NUM> associated with handover component <NUM> may be performed by transceiver <NUM>.

Also, memory <NUM> may be configured to store data used herein and/or local versions of applications <NUM> or handover component <NUM> and/or one or more of its subcomponents being executed by at least one processor <NUM>. Memory <NUM> can include any type of computer-readable medium usable by a computer or at least one processor <NUM>, such as random access memory (RAM), read only memory (ROM), tapes, magnetic discs, optical discs, volatile memory, non-volatile memory, and any combination thereof. In an aspect, for example, memory <NUM> may be a non-transitory computer-readable storage medium that stores one or more computer-executable codes defining handover component <NUM> and/or one or more of its subcomponents, and/or data associated therewith, when UE <NUM> is operating at least one processor <NUM> to execute handover component <NUM> and/or one or more of its subcomponents.

Receiver <NUM> may include hardware, firmware, and/or software code executable by a processor for receiving data, the code comprising instructions and being stored in a memory (e.g., computer-readable medium). Additionally, receiver <NUM> may process such received signals, and also may obtain measurements of the signals, such as, but not limited to, Ec/Io, SNR, RSRP, RSSI, etc. Transmitter <NUM> may include hardware, firmware, and/or software code executable by a processor for transmitting data, the code comprising instructions and being stored in a memory (e.g., computer-readable medium).

Referring to <FIG>, one example of an implementation of base station <NUM> may include a variety of components, some of which have already been described above, but including components such as one or more processors <NUM> and memory <NUM> and transceiver <NUM> in communication via one or more buses <NUM>, which may operate in conjunction with modem <NUM> and handover component <NUM> to enable one or more of the functions described herein related to handover of a UE <NUM> from a source base station 402A to a target base station 402B.

The transceiver <NUM>, receiver <NUM>, transmitter <NUM>, one or more processors <NUM>, memory <NUM>, applications <NUM>, buses <NUM>, RF front end <NUM>, LNAs <NUM>, switches <NUM>, filters <NUM>, PAs <NUM>, and one or more antennas <NUM> may be the same as or similar to the corresponding components of UE <NUM>/<NUM>, as described above, but configured or otherwise programmed for base station operations as opposed to UE operations.

Referring to <FIG>, one example of an implementation of UPF <NUM> may include a variety of components, some of which have already been described above, but including components such as one or more processors <NUM> and memory <NUM> and transceiver <NUM> in communication via one or more buses <NUM>, which may operate in conjunction with modem <NUM> and handover component <NUM> to enable one or more of the functions described herein related to handover of a UE <NUM>/<NUM> from a source base station 402A to a target base station 402B. In another example, the UPF <NUM> may include a wired communication interface <NUM> which may operate in conjunction with modem <NUM> and handover component <NUM> to enable one or more of the functions described herein related to handover of a UE <NUM>/<NUM> from a source base station 402A to a target base station 402B. The transceiver <NUM>, receiver <NUM>, transmitter <NUM>, one or more processors <NUM>, memory <NUM>, applications <NUM>, buses <NUM>, RF front end <NUM>, LNAs <NUM>, switches <NUM>, filters <NUM>, PAs <NUM>, and one or more antennas <NUM> may be the same as or similar to the corresponding components of UE <NUM>, as described above, but configured or otherwise programmed for UPF operations as opposed to UE operations. Referring to <FIG>, one example of an implementation of AMF/SMF ENTITY <NUM> may include a variety of components, some of which have already been described above, but including components such as one or more processors <NUM> and memory <NUM> and transceiver <NUM> in communication via one or more buses <NUM>, which may operate in conjunction with modem <NUM> and handover component <NUM> to enable one or more of the functions described herein related to handover of a UE <NUM>/<NUM> from a source base station 402A to a target base station 402B. In another example, the AMF/SMF ENTITY <NUM> may include a wired communication interface <NUM> which may operate in conjunction with modem <NUM> and handover component <NUM> to enable one or more of the functions described herein related to handover of a UE <NUM>/<NUM> from a source base station 402A to a target base station 402B. The transceiver <NUM>, receiver <NUM>, transmitter <NUM>, one or more processors <NUM>, memory <NUM>, applications <NUM>, buses <NUM>, RF front end <NUM>, LNAs <NUM>, switches <NUM>, filters <NUM>, PAs <NUM>, and one or more antennas <NUM> may be the same as or similar to the corresponding components of UE <NUM>, as described above, but configured or otherwise programmed for AMF/SMF operations as opposed to UE operations.

Claim 1:
A method (<NUM>) of a make before break handover of a user equipment from a source base station to a target base station in wireless communication executed by a user plane function, UPF, the method (<NUM>) comprising:
receiving a message from one of an access and mobility function, AMF, or a session management function, SMF, wherein in response to receiving the message the method further comprises:
bi-casting (<NUM>) a downlink data packet unit, PDU, to a source base station and to a target base station with a same sequence number, SN, in a tunnel protocol, wherein the downlink PDU is further transmitted by both the source and the target base station to the user equipment;
receiving (<NUM>) PDUs from the source base station and the target base station with corresponding PDUs having the same SNs in the tunnel protocol, wherein the PDUs are received by the source and the target base station from the user equipment; and
discarding (<NUM>) received duplicate PDUs based on the SNs in the tunnel protocol.