User equipment and base stations involved in packet replication during handover in NR

Abstract

The present disclosure relates to a user equipment and a base station that participate in packet duplication during a handover of a NR. A user equipment is disclosed, comprising: a processing circuit that obtains a user equipment packet duplication state, which includes information about a state of uplink packet duplication to be performed by the user equipment with at least one base station, wherein the information about the state of the uplink packet duplication is per uplink radio bearer, one or more uplink radio bearers are established between the user equipment and the base station, and wherein the processing circuit, when obtaining the user equipment packet duplication state, determines the state of the uplink packet duplication per uplink radio bearer based on configuration information received from at least one base station, the information about the uplink packet duplication state is in the form of a bitmap including one bit per uplink radio bearer, and the state of the uplink packet duplication is activated or deactivated per uplink radio bearer.

Description

[0001] This application is a divisional application of the Chinese invention patent application with the application date of May 23, 2018, application number 201880042590.0, invention name “User equipment and base station participating in packet replication during NR switching”, and the applicant is Panasonic Electric (USA) Intellectual Property Corporation. Technical Field

[0002] The present disclosure is directed to methods, apparatus and articles in a communication system, such as a 3GPP communication system. Background Art

[0003] Currently, the 3rd Generation Partnership Project (3GPP) is working on the next release (Release 15) of the technical specifications for the next generation of cellular technology, also known as the fifth generation (5G). At the 3GPP Technical Specification Group (TSG) Radio Access Network (RAN) Meeting #71 (March 2016, Gothenburg), the first 5G study item "Study on New Radio Access Technology" involving RAN1, RAN2, RAN3 and RAN4 was approved and is expected to become the Release 15 work item defining the first 5G standard. The purpose of this study item is to develop a "New Radio (NR)" access technology (RAT) that operates in the frequency range up to 100 GHz and supports a wide range of use cases, as defined during the RAN requirements study (see, for example, 3GPP TR38.913 "Study on Scenarios and Requirements for Next Generation Access Technologies", currently Release 14.2.0 available at www.3gpp.org and incorporated herein by reference in its entirety).

[0004] One goal is to provide a single technical framework that addresses all use cases, requirements and deployment scenarios defined in TR 38.913, including at least enhanced mobile broadband (eMBB), ultra-reliable low latency communications (URLLC), massive machine type communications (mMTC). For example, eMBB deployment scenarios may include indoor hotspots, dense urban, rural, urban macro and high-speed; URLLC deployment scenarios may include industrial control systems, mobile health (remote monitoring, diagnosis and treatment), real-time control of vehicles, wide-area monitoring and control systems for smart grids; mMTC may include scenarios with a large number of devices with non-time-critical data transfer, such as smart wearable devices and sensor networks. Services eMBB and URLLC are similar in that they both require very wide bandwidth, but the difference is that URLLC services require extremely low latency.

[0005] The second goal is to achieve forward compatibility. Backward compatibility with long-term evolution (LTE, LTE-A) cellular systems is not required, which facilitates completely new system designs and / or the introduction of novel features.

[0006] The basic physical layer signal waveform will be based on OFDM and may support non-orthogonal waveforms and multiple access. For example, additional functions on top of OFDM such as DFT-S-OFDM and / or variants of DFT-S-OFDM, and / or filtering / windowing are further considered. In LTE, CP-based OFDM and DFT-S-OFDM are used as waveforms for downlink and uplink transmissions, respectively. One of the design goals in NR is to seek common waveforms as much as possible for downlink, uplink and sidelink.

[0007] In addition to the waveform, some basic frame structures and channel coding schemes will be developed to achieve the above objectives. The study should also seek consensus on what is needed in terms of radio protocol structure and architecture to achieve the above objectives. In addition, the technical features necessary for the new RAT to meet the above objectives should be studied, including efficient multiplexing of traffic for different services and use cases on the same continuous spectrum block.

[0008] Since 3GPP's NR standardization for 5th generation systems is still in its infancy, many issues are still unclear. For example, there has been discussion about supporting packet replication for user plane and control plane transmission as a way to ensure reliability and reduce HARQ latency. However, there has been no clear agreement on how to effectively implement packet replication. For example, procedures need to be defined to allow an efficient and seamless packet replication process also in handover scenarios. Summary of the invention

[0009] A non-limiting and exemplary embodiment facilitates providing an improved packet duplication procedure during a handover in which different entities (UE, gNB) are participating.

[0010] In one general aspect, the technology disclosed herein features a source base station. The source base station includes a processing circuit that generates a user equipment packet duplication state. The user equipment packet duplication state includes information about a state of uplink packet duplication performed by the user equipment with the source base station and at least one additional base station. The information about the state of the uplink packet duplication is per uplink radio bearer, one or more uplink radio bearers being established between the user equipment and the source base station. The source base station also includes a sending unit that sends the user equipment packet duplication state to a target base station, the target base station being a target of a handover performed from the source base station for the user equipment.

[0011] In one general aspect, the technology disclosed herein is characterized by a target base station including a receiving unit that receives a user equipment packet duplication state. The user equipment packet duplication state includes information about a state of uplink packet duplication performed by the user equipment with a source base station and at least one additional base station. The target base station is a target for a handover performed from the source base station for the user equipment. The information about the state of the uplink packet duplication is per uplink radio bearer, one or more uplink radio bearers being established between the user equipment and the source base station. The target base station also includes a processing circuit that processes the received user equipment packet duplication state to configure packet duplication of an uplink radio bearer to be established between the user equipment and the target base station after the handover.

[0012] In one general aspect, the technology disclosed herein features a user equipment including a processing circuit that generates a user equipment packet duplication state. The user equipment packet duplication state includes information about a state of uplink packet duplication to be performed by the user equipment with a target base station and at least one additional base station. The target base station is a target for a handover from a source base station to be performed for the user equipment. The information about the state of the uplink packet duplication is per uplink radio bearer, one or more uplink radio bearers being established between the user equipment and the target base station after the handover. The user equipment also includes a sending unit that sends the generated user equipment packet duplication state to the target base station.

[0013] In one general aspect, the technology disclosed herein features a method for operating a source base station. The method includes the following steps performed by the source base station. A user equipment packet duplication state is generated, which includes information about a state of uplink packet duplication performed by the user equipment with the source base station and at least one additional base station. The information about the state of the uplink packet duplication is per uplink radio bearer, one or more uplink radio bearers being established between the user equipment and the source base station. The user equipment packet duplication state is sent to a target base station that is a target of a handover performed for the user equipment from the source base station.

[0014] In one general aspect, the technology disclosed herein is characterized by a method for operating a target base station. The method includes the following steps performed by the target base station. Receive a user equipment packet replication state, which includes information about the state of uplink packet replication performed by the user equipment with a source base station and at least one additional base station, the target base station being the target of a handover performed from the source base station for the user equipment. The information about the state of the uplink packet replication is per uplink radio bearer, one or more uplink radio bearers being established between the user equipment and the source base station. Process the received user equipment packet replication state to configure packet replication of the uplink radio bearers to be established between the user equipment and the target base station after the handover.

[0015] In one general aspect, the technology disclosed herein is characterized by a method for operating a user equipment. The method includes the following steps performed by the user equipment. A user equipment packet duplication state is generated, which includes information about the state of uplink packet duplication to be performed by the user equipment with a target base station and at least one other base station, the target base station being the target of a handover to be performed for the user equipment from a source base station. The information about the state of the uplink packet duplication is per uplink radio bearer, one or more uplink radio bearers being established between the user equipment and the target base station after the handover. The generated user equipment packet duplication state is sent to the target base station.

[0016] In one general aspect, the technology disclosed herein is characterized by a user equipment, comprising: a processing circuit, which obtains a user equipment packet duplication status, the user equipment packet duplication status including information about a status of uplink packet duplication to be performed by the user equipment with at least one base station, wherein the information about the status of the uplink packet duplication is per uplink radio bearer, one or more uplink radio bearers are established between the user equipment and the base station, and wherein the processing circuit, when obtaining the user equipment packet duplication status, determines the status of the uplink packet duplication per uplink radio bearer based on configuration information received from the at least one base station, the information about the uplink packet duplication status is in the form of a bitmap including one bit per uplink radio bearer, and the status of the uplink packet duplication is activated or deactivated per uplink radio bearer.

[0017] In one general aspect, the technology disclosed herein is characterized by a method performed by a user equipment, comprising: obtaining a user equipment packet duplication status, the user equipment packet duplication status including information about a status of uplink packet duplication to be performed by the user equipment with at least one base station, wherein the information about the status of the uplink packet duplication is per uplink radio bearer, one or more uplink radio bearers are established between the user equipment and the base station, and wherein, when obtaining the user equipment packet duplication status, the status of the uplink packet duplication per uplink radio bearer is determined based on configuration information received from the at least one base station, the information about the uplink packet duplication status is in the form of a bitmap including one bit per uplink radio bearer, and the status of the uplink packet duplication is activated or deactivated per uplink radio bearer.

[0018] In one general aspect, the technology disclosed herein is characterized by an integrated circuit for controlling a process of a user equipment, the process comprising: obtaining a user equipment packet duplication state, the user equipment packet duplication state comprising information about a state of uplink packet duplication to be performed by the user equipment with at least one base station, wherein the information about the state of the uplink packet duplication is per uplink radio bearer, one or more uplink radio bearers are established between the user equipment and the base station, and wherein, when obtaining the user equipment packet duplication state, the state of the uplink packet duplication per uplink radio bearer is determined based on configuration information received from the at least one base station, the information about the uplink packet duplication state is in the form of a bitmap comprising one bit per uplink radio bearer, and the state of the uplink packet duplication is activated or deactivated per uplink radio bearer.

[0019] It should be noted that the general or specific embodiments may be implemented as a system, a method, an integrated circuit, a computer program, a storage medium, or any selective combination thereof.

[0020] Other benefits and advantages of the disclosed embodiments will be apparent from the specification and drawings. Benefits and / or advantages may be obtained individually from various embodiments and features of the specification and drawings, and all of them do not need to be provided in order to obtain one or more such benefits and / or advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Hereinafter, exemplary embodiments are described in more detail with reference to the accompanying diagrams and drawings.

[0022] Figure 1 An exemplary architecture for a 3GPP NR system is shown.

[0023] Figure 2shows an exemplary user and control plane architecture for LTE eNB, gNB and UE,

[0024] Figure 3 exemplarily showing the exchange of PDUs and SDUs between layers in the OSI model,

[0025] Figure 4 shows an exemplary PDCP control PDU used by a PDCP entity processing user plane data,

[0026] Figure 5 shows an exemplary and general user plane architecture currently discussed in connection with LTE-NR multi-connectivity with MCG (Master Cell Group) bearers via LTE eNB,

[0027] Fig. 6A The general user plane architecture is shown, where the PDCP entity is located in the LTE (primary) eNB, the secondary side

[0028] Figure 6B shows a general user plane architecture, where the PDCP entity is located on the secondary side.

[0029] Figure 7 shows the control plane connection of eNBs participating in the DC of a certain UE, where S1-MME is terminated in MeNB, and MeNB and SeNB are interconnected via X2-C,

[0030] Figure 8 shows different U-plane connection options for eNBs participating in the DC of a certain UE,

[0031] Fig. 9 shows the LTE contention-based random access process,

[0032] Fig.10 shows the contention-free random access process of 3GPP LTE,

[0033] Fig.11 shows an example signaling flow for the inter-MeNB handover without SeNB change,

[0034] Fig.12 A signaling diagram showing messages exchanged between a UE, a source master gNB and a target master gNB,

[0035] Fig.13A shows the contents of the UE packet duplication status,

[0036] Fig. 13B An alternative embodiment of signaling the content of the UE packet duplication status via the X2 interface is shown,

[0037] Fig.14shows a signaling diagram according to an improved embodiment, wherein the UE packet duplication status is sent by the source MgNB and received by the target MgNB within a handover request message,

[0038] Fig.15 shows a signaling diagram according to an improved embodiment, in which the target MgNB modifies the received UE packet duplication state,

[0039] Fig.16 Shown with Fig.15 Flowcharts related to the signaling diagram,

[0040] Fig.17A shows the contents of the UE packet copy status in MAC CE format,

[0041] Fig. 17B shows the contents of the UE packet copy status in MAC CE format,

[0042] Fig.18A shows the contents of the UE packet copy status in the PDCP control PDU format,

[0043] Fig.18B shows the contents of the UE packet copy status in the PDCP control PDU format,

[0044] Fig.19 shows a signaling diagram according to an alternative embodiment, in which a 4-step RACH procedure is used, the UE packet duplication status is sent by the UE and received by the target MgNB as part of the handover procedure,

[0045] Fig. 20 shows a signaling diagram according to an alternative embodiment, in which a two-step RACH procedure is used, the UE packet duplication status is sent by the UE and received by the target MgNB as part of the handover procedure,

[0046] Fig.21 A flow chart is shown in which a UE packet duplication status message is sent directly from the UE to the target MgNB. DETAILED DESCRIPTION

[0047] Basis of the Disclosure

[0048] 5G NR system architecture and protocol stack

[0049] As described in the background section, 3GPP is working on the next version of the fifth generation of cellular technology, referred to as 5G, which includes the development of new radio access technology (NR) operating in the frequency range up to 100GHz. 3GPP must identify and develop the technical components required to successfully standardize NR systems that meet urgent market needs and longer-term needs in a timely manner. To achieve this, the development of radio interfaces as well as radio network architectures is considered in the study project "New Radio Access Technology". The results and protocols are collected in the technical report TR 38.804v14.0.0, which is incorporated herein by reference in its entirety.

[0050] Among other things, a provisional agreement has been reached on the overall system architecture. NG-RAN (Next Generation Radio Access Network) consists of gNBs, which provide NG Radio Access user plane (SDAP / PDCP / RLC / MAC / PHY) and control plane (RRC) protocol terminations to the UE. gNBs are interconnected with each other via Xn interfaces. gNBs are also connected to NGC (Next Generation Core) via Next Generation (NG) interfaces, more specifically to AMF (Access and Mobility Management Function) via NG-C interface and to UPF (User Plane Function) via NG-U interface. NG-RAN architecture as Figure 1 As shown, it is taken from TS 38.300 v.0.4.1, Section 4, which is incorporated herein by reference.

[0051] Various deployment scenarios are currently being discussed for support, for example, as reflected in 3GPP TR 38.801 v14.0.0, which is incorporated herein by reference in its entirety. For example, a non-centralized deployment scenario is proposed (Section 5.2 of TR 38.801; centralized deployment is described in Section 5.4), where base stations supporting 5G NR can be deployed. Figure 2 An exemplary decentralized deployment scenario is shown, and based on TR 38.301 Figure 5 .2.-1, also showing an LTE eNB and a user equipment (UE) connected to a gNB and an LTE eNB (which will be understood as an eNB according to previous 3GPP standard releases such as LTE and LTE-A). As mentioned above, the new eNB for NR 5G can be exemplarily referred to as a gNB.

[0052] As exemplarily defined in TR 38.801, an eLTE eNB is an evolution of an eNB supporting connections to an EPC (Evolved Packet Core) and an NGC (Next Generation Core).

[0053] The user plane protocol stack of NR is currently defined in Section 4.4.1 of TS 38.300 v0.4.1. The PDCP (Packet Data Convergence Protocol), RLC (Radio Link Control) and MAC (Medium Access Control) sublayers terminate in the gNB on the network side. In addition, as described in Section 6.5 of TS 38.300 v0.4.1, a new access stratum (AS) sublayer (SDAP, Service Data Adaptation Protocol) is introduced on top of PDCP. Section 4.4.2 of TS 38.300 defines the control plane protocol stack of NR. Section 6 of TS38.300 gives an overview of Layer 2 functions. Sections 6.4, 6.3 and 6.2 of TS 38.300 list the functions of the PDCP, RLC and MAC sublayers. Section 7 of TS 38.300 lists the functions of the RRC layer. The above sections of TS 38.300v 0.2.0 are incorporated herein by reference.

[0054] The new NR layer currently assumed for the 5G system can be based on the user plane layer structure currently used in the LTE (-A) communication system. However, it should be noted that no final agreement has been reached on all the details of the NR layer.

[0055] PDCP layer PDU

[0056] Will combine Figure 3 The terms Service Data Unit (SDU) and Protocol Data Unit (PDU) used in this document are explained below. In order to formally describe the exchange of packets between layers in the OSI model (such as the above-mentioned MAC, RLC and PDCP) in a generic way, the SDU and PDU entities have been introduced. An SDU is an information unit (data / information block) sent from a protocol on layer N+1, which requests a service from a protocol located at layer N via a so-called Service Access Point (SAP). A PDU is an information unit exchanged between peer processes of the sender and receiver of the same protocol located at the same layer N.

[0057] A PDU is generally formed of a payload portion consisting of a processed version of the received SDU, a preceding layer N specific header, and optionally terminated by a trailer. Since there is no direct physical connection between these peer processes (except for layer 1), the PDU is forwarded to layer N-1 for processing. Therefore, from the perspective of layer N-1, a layer N PDU is an SDU.

[0058] On the transmitting side, each layer receives SDUs from the higher layers that it provides services for and outputs PDUs to the layers below. The RLC layer receives packets from the PDCP layer. From the perspective of the PDCP, these packets can be called PDCP PDUs, and from the perspective of the RLC, these packets represent RLC SDUs. The RLC layer creates packets that are provided to the layer below, the MAC layer. From the perspective of the RLC, the packets provided by the RLC to the MAC layer are RLC PDUs, and from the perspective of the MAC, they are MAC SDUs. On the receiving side, the process is reversed, with each layer passing the SDUs to the layers above, where they are received as PDUs.

[0059] Some initial and temporary protocols for the PDCP layer of 5G NR can be found in section 6.4 of TS 38.300v0.4.1. The PDCP layer manages the data flows in the user plane as well as in the control plane. As in LTE, it can be exemplarily assumed that two different types of PDCP PDUs are also defined for 5g NR: PDCP data PDU and PDCP control PDU. PDCP data PDU is used for both control and user plane data. PDCP control PDU can be used to transmit feedback information for header compression, as well as for PDCP status reporting, which is used in case of handover and is therefore only used within the user plane.

[0060] Its format is Figure 4 The PDCP Control PDU, exemplarily shown in Figure 2, is used by the PDCP entity that handles user plane data. There are two types of PDCP Control PDUs, distinguished by the PDU Type field in the PDCP header. The PDCP Control PDU carries a PDCP "Status Report" for lossless handover scenarios, or carries ROHC feedback created by the ROHC (Robust Header Compression) header compression protocol. The PDCP Control PDU carrying ROHC feedback is used for user plane radio bearers mapped on RLC UM or RLC AM, while the PDCP Control PDU carrying PDCP status report is only used for user plane radio bearers mapped on RLC AM.

[0061] Dual Connectivity (DC) and Multi Connectivity (MC) Architectures

[0062] Multiple connections between LTE and the new radio access technology NR 5G can be supported and can be based on the concept of dual connectivity (already known from previous 3GPP releases of LTE and LTE-A, briefly explained later). Multi-connectivity can be defined as an operating mode in which a multi-Rx / Tx UE in connected mode is configured to utilize radio resources in E-UTRA and NR provided by multiple different scheduling units (e.g., LTE eNBs and gNBs) connected via non-ideal backhaul links. Multiple connections (also called dual connectivity) can, for example, allow a UE to be simultaneously connected to an LTE(-A) network and a new 5G network (exemplarily referred to as LTE-NR multi-connectivity). In addition, NR-NR multi-connectivity, i.e., simultaneous connection to a primary gNB and at least one secondary gNB, can also be foreseen.

[0063] Dual connectivity between LTE and NR and different options in this regard are currently discussed in TR 38.801 v 14.0.0, section 10.1 “Dual Connectivity between NR and LTE”, which is incorporated herein by reference.

[0064] Figure 5 The current combination with MCG (Master Cell Group) bearer via LTE eNB, split between LTE eNB and gNB (PDCP entity is located in LTE (Master) eNB, see Fig. 6A ) and SCG (Secondary Cell Group) bearers via gNB (see, e.g., Section 10.1 of 3GPP TR 38.801, which is incorporated herein by reference). It should be noted that it is also possible to have the PDCP entity located on the secondary side (i.e., gNB, see also Figure 6B ) to implement split radio bearers (see also TR 38.801, section 10.1). Figure 5 Also shown is an exemplary user plane architecture for a UE, illustrating the various layers in the UE for processing data packets received from LTE eNBs and gNBs via bearers.

[0065] Then, NR-NR dual connectivity is briefly mentioned in Section 10.2.5 "Intra-NR dual connectivity", which is incorporated herein by reference. It can be clearly seen that some or all of the main principles of traditional LTE dual connectivity can be exemplarily inherited by NR intra-dual connectivity with potential enhanced functions. However, the details of the above aspects will still be discussed in the specification stage.

[0066] The so-called "dual connectivity" concept in LTE refers to an operating mode of a UE (in RRC_CONNECTED state) configured with a primary cell group (MCG) and a secondary cell group (SCG). Dual connectivity is mainly defined in 3GPP technical standard TS36.300, v14.2.0, for example, sections 4.9, 6.5, 7.6, 10.1.2.3.4, 10.1.2.8 and its Annex M, which are incorporated herein by reference. In addition, reference is made to 3GPP TR 38.801, section 10, version 14.0.0, RAN meeting #75, which is incorporated herein by reference.

[0067] E-UTRAN (LTE) supports Dual Connectivity (DC) operation, whereby multiple Rx / Tx UEs in RRC_CONNECTED are configured to utilize radio resources provided by two different scheduling units located in two eNBs connected via a non-ideal backhaul over the X2 interface. An eNB participating in the DC of a certain UE can assume two different roles: the eNB can act as a MeNB or a SeNB. In DC, the UE is connected to at least one MeNB and one SeNB, and the radio protocol architecture used for a specific bearer depends on how the bearer is established. There are three bearer types: MCG bearer, SCG bearer and split bearer. These bearer types are described in Fig. 6A and 6B The inter-eNB control plane signaling of the DC is performed by means of X2 interface signaling. The control plane signaling to the MME is performed by means of S1 interface signaling.

[0068] Each DC UE has only one S1-MME connection between the MeNB and the MME. Each eNB should be able to handle the UE independently, i.e., provide PCell to some UEs while providing SCell for SCG to other UEs. Each eNB participating in the DC of a certain UE controls its radio resources and is primarily responsible for allocating the radio resources of its cells. The corresponding coordination between MeNB and SeNB is performed via X2 interface signaling. Figure 7 The control plane connections of the eNBs participating in the DC of a certain UE are shown: S1-MME is terminated in the MeNB, and the MeNB and SeNB are interconnected via X2-C.

[0069] For dual connectivity, two different user plane architectures are allowed: one where S1-U terminates only at the MeNB and X2-U is used to transfer user plane data from the MeNB to the SeNB; and a second architecture where S1-U may terminate in the SeNB. Figure 8Different U-plane connection options for eNBs participating in the DC of a certain UE are shown. For MCG bearers, the S1-U connection for the corresponding bearer to the S-GW is terminated in the MeNB. The SeNB does not participate in the transmission of user plane data for such bearers over Uu. For split bearers, the S1-U connection to the S-GW is terminated in the MeNB. PDCP data is transmitted between the MeNB and the SeNB via X2-U. The SeNB and the MeNB participate in sending data for this bearer type over Uu. For SCG bearers, the SeNB is directly connected to the S-GW via S1-U. The MeNB does not participate in the transmission of user plane data for such bearers over Uu.

[0070] In the case of DC, the UE is configured with two MAC entities: one MAC entity for the MeNB and one MAC entity for the SeNB.

[0071] RACH Process

[0072] Regarding the RACH (Random Access Channel) procedure in 5G NR, no final agreement has been reached. As described in Section 9.2 of TR 38.804v14.0.0, which is incorporated herein by reference, the NR RACH procedure can support contention-based and contention-free random access in the same or similar manner as defined for LTE. Likewise, the design of the NR RACH procedure should support flexible message 3 sizes, similar to LTE.

[0073] The following will refer to Fig. 9 and Fig.10 The LTE RACH procedure is described in more detail. Uplink transmissions can only be scheduled for a mobile terminal in LTE if its uplink transmission is time synchronized. Therefore, the Random Access Channel (RACH) procedure plays an important role as an interface between an unsynchronized mobile terminal (UE) and the orthogonal transmissions of the uplink radio access. In essence, random access in LTE is used to achieve uplink time synchronization for user equipment that has not yet acquired or lost its uplink synchronization. Once the user equipment has achieved uplink synchronization, the eNodeB can schedule uplink transmission resources for it. One scenario related to random access is that a user equipment in the RRC_CONNECTED state, which is switched from its current serving cell to a new target cell, performs a random access procedure in order to achieve uplink time synchronization in the target cell.

[0074] LTE provides two types of random access procedures, which allow either contention-based access (i.e. implying an inherent risk of collision), or contention-free (non-contention-based) access. A detailed description of the random access procedure can also be found in 3GPP TS 36.321 section 5.1 v14.1.0, which is incorporated herein by reference.

[0075] Next, we will focus on Fig. 9 The LTE contention-based random access procedure is described in more detail. The procedure consists of four "steps". First, the user equipment sends a random access preamble to the eNodeB on the physical random access channel (PRACH) (i.e., message 1 of the RACH procedure). After the eNodeB detects the RACH preamble, it sends a random access response (RAR) message (message 2 of the RACH procedure) on the PDSCH (Physical Downlink Shared Channel) addressed to the PDCCH, where the (random access) RA-RNTI identifies the time-frequency slot in which the preamble was detected. If multiple user equipments send the same RACH preamble in the same PRACH resource (also known as a collision), they will receive the same random access response message. The RAR message can convey the detected RACH preamble, the timing alignment command (TA command) for synchronization of subsequent uplink transmissions, the initial uplink resource assignment (grant) for the transmission of the first scheduled transmission, and the assignment of a temporary cell radio network temporary identifier (T-CRNTI). The eNodeB uses this T-CRNTI to address mobile stations that have detected the RACH preamble until the end of the RACH procedure, since the "real" identity of the mobile station is not yet known to the eNodeB at this point.

[0076] The user equipment monitors the PDCCH within a given time window configured by the eNodeB to receive a random access response message. In response to the RAR message received from the eNodeB, the user equipment sends the first scheduled uplink transmission on the radio resources assigned by the grant in the random access response. This scheduled uplink transmission conveys the actual random access procedure message, such as an RRC connection request or a buffer status report.

[0077] If a preamble collision occurs in the first step of the RACH procedure, i.e., multiple user equipments send the same preamble on the same PRACH resource, the colliding user equipments will receive the same T-CRNTI in the random access response and will collide in the same uplink resource when sending their scheduled transmissions in the third step of the RACH procedure. If the scheduled transmission from one user equipment is successfully decoded by the eNodeB, the contention for the other user equipments remains unresolved. To resolve this type of contention, the eNode B sends a contention resolution message (fourth message) addressed to the C-RNTI or temporary C-RNTI.

[0078] Fig.10The contention-free random access procedure of 3GPP LTE is shown to be simplified compared to the contention-based random access procedure. The eNodeB provides a preamble to the user equipment for random access in the first step so that there is no risk of collision, i.e., multiple user equipments send the same preamble. Therefore, the user equipment then sends the preamble signaled by the eNodeB in the uplink on the PRACH resource. Since the situation where multiple UEs send the same preamble is avoided for contention-free random access, the contention-free random access procedure essentially ends after the UE successfully receives the random access response.

[0079] Therefore, in the future, the new radio technology for 5G can be combined with the above Fig. 9 and Fig.10 3GPP is also investigating a two-step RACH procedure for 5G NR, where message 1 is first sent, corresponding to messages 1 and 3 in the four-step RACH procedure. The gNB will then respond with message 2, which corresponds to messages 2 and 4 of the LTE RACH procedure. Due to the reduced message exchanges, the latency of the two-step procedure can be reduced compared to the four-step procedure. The radio resources used for the messages are optionally configured by the network.

[0080] LTE handover process

[0081] Mobility is a key process in the LTE communication system. In LTE, there are two types of handover procedures for UEs in active mode: S1-handover procedures and X2-handover procedures. For intra-LTE mobility, handover via the X2 interface is usually used for mobility between eNodeBs. Therefore, unless the X2 interface is not established or the source eNodeB is configured to use another handover (e.g., S1-handover), X2 handover is triggered by default. More information about mobility procedures in LTE can be obtained, for example, from Section 5.4 of 3GPP TS 36.331 v14.2.2, which is incorporated herein by reference, and from Section 8.2 of 3GPP 36.423 v14.2.0, which is incorporated herein by reference.

[0082] Considering now the dual and multi-connectivity scenarios, the handover of the MeNB can be performed without changing the SeNB. Such a handover (exemplarily called inter-MeNB handover) is defined in LTE in Section 10.1.2.8.8 "Inter-MeNB handover without SeNB change" of TS 36.300 v14.2.0. Fig.11An example signaling flow for this inter-MeNB handover without SeNB change is shown, which has the following steps described in TS 36.300:

[0083] 1. The source MeNB starts the handover procedure by initiating the X2 Handover Preparation procedure. The source MeNB includes the SCG configuration in the HandoverPreparationInformation. The source MeNB includes the SeNB UE X2AP ID and the SeNB ID as a reference to the UE context in the SeNB, which was established by the source MeNB in ​​the Handover Request message.

[0084] 2. If the target MeNB decides to keep the SeNB, the target MeNB sends a SeNB Add Request to the SeNB, which includes the SeNB UE X2AP ID as a reference to the UE context in the SeNB established by the source MeNB.

[0085] 3. The SeNB replies with a SeNB add request confirmation.

[0086] 4. The target MeNB includes in the Handover Request Confirmation message a transparent container (which also includes the SCG configuration) to be sent to the UE as an RRC message to perform the handover, and may also provide the forwarding address to the source MeNB. If the target MeNB and the SeNB decide in steps 2 and 3 to retain the UE context in the SeNB, the target MeNB indicates to the source MeNB that the UE context in the SeNB is retained.

[0087] 5. The source MeNB sends a SeNB release request to the SeNB. The source MeNB indicates to the SeNB that the UE context in the SeNB is retained. If the indication that the UE context is retained in the SeNB is included, the SeNB retains the UE context.

[0088] 6. The source MeNB triggers the UE to apply the new configuration.

[0089] 7 / 8.UE synchronizes to the target MeNB and replies with RRCConnectionReconfigurationComplete message.

[0090] 9. The UE synchronizes to the SeNB.

[0091] 10. If the RRC connection reconfiguration process is successful, the target MeNB notifies the SeNB.

[0092] 11 / 12. Data forwarding from the source MeNB. Data forwarding can be omitted for SCG bearers. For split bearers, direct data forwarding from the source MeNB to the SeNB is not possible.

[0093] NOTE: Direct data forwarding is possible only for changing bearer type.

[0094] 13-16. The target MeNB initiates the S1 path switching process.

[0095] Note: If the new UL TEID of the S-GW is included, the target MeNB performs the MeNB initiated SeNB modification procedure to provide it to the SeNB.

[0096] 17. The target MeNB initiates a UE context release process to the source MeNB.

[0097] 18. Upon receiving the UE Context Release message, the SeNB may release the C-Plane related resources associated with the UE context to the source MeNB. Any ongoing data forwarding may continue. If the indication is included in the SeNB Release Request in step 5, the SeNB will not release the UE context associated with the target MeNB.

[0098] Similar or the same handover procedures may be used in 5G NR.

[0099] NR PDCP layer and packet duplication

[0100] 3GPP is currently discussing dual and multi-connectivity with packet replication across multiple links for 5G NR to ensure high reliability such as required to support URLLC. In URLLC use cases, packets must be received correctly with ultra-high reliability (e.g., 99.999%) and within the required latency target (e.g., 1ms). To meet these requirements, existing technologies such as HARQ may not be sufficient.

[0101] A split bearer is configured with one PDCP entity and two RLC entities, one in the MCG (primary cell group) and the other in the SCG (secondary cell group). Data on the split bearer can be sent to either of the two RLC branches. Therefore, packet duplication is accordingly understood as sending the same data packet on both branches (both RLC branches are active at a given time).

[0102] Packet duplication is not necessarily always beneficial and should be disabled when no gain is available. Therefore, after packet duplication has been configured as SRB / DRB via RRC signaling, dynamic activation and deactivation of packet duplication should be supported (e.g., via MAC CE or PDCP control PDU) to cope with dynamic channel quality changes in both RLC branches.

[0103] Chapter 6.4 of TS 38.300 describes the main functions of the PDCP layer, including duplication detection and duplication of PDCP PDUs. As defined therein, when duplication is configured by RRC for a radio bearer, an additional RLC entity and an additional logical channel are added to the radio bearer to handle the duplicated PDCP PDU. Therefore, duplication on PDCP involves sending the same PDCP PDU twice via two "branches": once on the original RLC entity and a second time on the additional RLC entity. When doing so, the original PDCP PDU and the corresponding copy should not be sent on the same carrier. Two different logical channels may belong to the same MAC entity (CA, carrier aggregation), or may belong to different MAC entities (DC, such as dual connectivity). In the former case, logical channel mapping restrictions are used in the MAC to ensure that the logical channel carrying the original PDCP PDU and the logical channel carrying the corresponding copy are not sent on the same carrier. Once the radio bearer is configured, the duplication function can be activated and disabled via the MAC control element. As a further option, it is discussed to support the activation and disabling of packet duplication with the aid of a PDCP control PDU.

[0104] It should be noted that these definitions are still under discussion and have not yet been finalized. However, the same or similar form of packet replication functionality as just described based on TS 38.300 will be implemented for 5G NR. In particular, packet replication is advantageously used to allow reduced latency and increased reliability for both user data and control signaling, and can be used in place of link selection. The same technology can also improve the robustness of mobility in challenging scenarios such as high mobility and ultra-dense deployments.

[0105] The PDCP function in the transmitting unit accordingly supports packet duplication, while the PDCP function in the receiving unit supports duplicate packet removal, ie, detecting packet duplication and forwarding a single packet to upper layers.

[0106] An optional implementation detail currently under discussion is that the original PDCP PDU and the corresponding copy should not be sent on the same transport block.

[0107] There is no final agreement on how to implement packet duplication. 3GPP is discussing how to define at least a mechanism to start / stop PDCP duplication faster and with less signaling overhead compared to RRC reconfiguration.

[0108] Accordingly, the present disclosure will provide solutions that help overcome one or more disadvantages and / or meet one or more of the above-mentioned needs.

[0109] DETAILED DESCRIPTION OF THE DISCLOSURE

[0110] In the following, the UE, base station and process of the new radio access technology envisioned for the 5G mobile communication system will be described. Different implementations and variants will also be described. The following detailed disclosure is facilitated by the discussions and findings described in the previous section "Foundation of the Disclosure" and may be based at least in part thereon.

[0111] However, in general, it should be noted that there are actually very few things that have been agreed upon about 5G cellular communication systems, so many assumptions must be made in the following in order to be able to explain the basic principles of the present disclosure in a clear and understandable manner. However, these assumptions should be understood as merely examples and should not limit the scope of the present disclosure. Those skilled in the art will appreciate that the principles disclosed below and as described in the claims can be applied in different scenarios and can be applied in ways not explicitly described herein.

[0112] Moreover, the terms for processes, entities, layers, etc. used below are closely related to the terms used in LTE / LTE-A systems or current research projects for 3GPP 5G, even though the specific terms to be used in the context of new radio access technologies for the next 3GPP 5G communication system have not yet been fully decided. Therefore, the terms can be changed at the specification stage without affecting the functionality of the embodiments of the present invention. Therefore, the technicians realize that the present invention and its scope of protection should not be limited to the specific terms used exemplarily in this document due to the lack of updated or ultimately agreed terms, but should be understood more broadly in accordance with the functions and concepts that constitute the functions and principles of the present disclosure.

[0113] For example, a mobile station or mobile node or user terminal or user equipment (UE) is a physical entity within a communication network. A node may have several functional entities. A functional entity refers to a software or hardware module that implements and / or provides a predetermined set of functions to other functional entities of a node or network. A node may have one or more interfaces that attach the node to a communication facility or medium through which the node can communicate. Similarly, a network entity may have a logical interface that attaches a functional entity to a communication facility or medium through which it can communicate with other functional entities or corresponding nodes.

[0114] The term "base station" or "radio base station" refers here to a physical entity within a communication network. The physical entity performs some control tasks with respect to the communication equipment, including one or more of scheduling and configuration. Note that the base station functionality and the communication equipment functionality may also be integrated within a single device. For example, a mobile terminal may also implement the functionality of a base station for other terminals. The term used in LTE is eNB (or eNodeB), while the term currently used for 5G NR is gNB.

[0115] Fig.12A signaling diagram is shown in which messages are exchanged between a UE, a source master gNB (MgNB) and a target MgNB.

[0116] Exemplarily, it is assumed that the uplink radio bearer is a split radio bearer established between the UE and the source MgNB, wherein the split radio bearer may have two branches, one terminating at the user equipment and the other terminating at the source MgNB, wherein the path of one of the two branches is via at least one other gNB, such as a secondary gNB (SgNB). Figure 5 , Fig. 6A and Figure 6B As shown and described in the figure, the PDCP entity can be exemplarily located at the MgNB or at the SgNB.

[0117] Optionally, a Packet Data Convergence Protocol (PDCP) entity of the UE is shared for split radio bearers, wherein the PDCP entity is located at the source MgNB, and wherein the data packet is a PDCP Protocol Data Unit (PDCP PDU).

[0118] like Fig.12 As further shown, uplink packet replication is performed between the UE and the source MgNB. In addition, the UE performs packet replication with at least one other gNB (e.g., a secondary gNB (SgNB)).

[0119] Thereby, the UE performs uplink packet duplication by sending the same data packet to the source MgNB and at least one other gNB (e.g., a secondary gNB (SgNB)), and the source MgNB participates as the receiving side of the uplink packet duplication performed by the UE by generating a single data packet to be forwarded to an upper layer of the source MgNB using the data packets received from the UE and from at least one other gNB.

[0120] according to Fig.12 In the scenario where the PDCP entity is located at one of the other gNBs (e.g. secondary gNBs), a scenario is assumed where it is decided to switch the UE from at least one other gNB (herein referred to as the source SgNB) to the target SgNB instead of switching from the source MgNB to the target MgNB. For ease of explanation, the following mainly assumes the following scenario: the PDCP entity is located at the source MgNB and the UE changes from the source MgNB to the target MgNB while maintaining the same secondary gNB. However, the subsequent embodiments are equally applicable to the case where the PDCP entity is located (not at the MgNB) but at the SgNB and therefore the UE changes from one source SgNB to another target SgNB while maintaining connection with the same primary gNB.

[0121] In order to avoid discarding packet replication for the UE when switching to the target MgNB (or SgNB), the source MgNB can notify the target MgNB of the UE's packet replication status.

[0122] According to an exemplary embodiment, the source MgNB generates a UE packet duplication status, which includes information about the status of uplink packet duplication performed by the UE to the source MgNB and at least one other gNB. Thus, the information about the status of uplink packet duplication is per uplink radio bearer, wherein one or more uplink radio bearers are established between the UE and the source MgNB. The source MgNB then sends the UE packet duplication status to a target MgNB, which is the target of a handover performed from the source MgNB for the UE.

[0123] According to another exemplary embodiment, the target MgNB receives a UE packet duplication status including information about a status of uplink packet duplication performed by the UE to the source MgNB and at least one other gNB. The target MgNB processes the received UE packet duplication status to configure packet duplication of an uplink radio bearer to be established between the UE device and the target MgNB after handover.

[0124] like Fig.12 As further shown in FIG. 1 , the handover involves the source MgNB sending a handover request to the target MgNB, after which the target MgNB responds to the source MgNB with a handover request ACK. Subsequently, the source MgNB sends a handover command to the UE. Fig.12 As exemplarily assumed in , the replication activation is sent after the handover is completed. Accordingly, during the handover process, the target MgNB will assume (e.g., by default) that the UE will not use any packet replication, so the handover request ACK and the corresponding handover command sent by the source MgNB to the UE will indicate that uplink replication is disabled (see Fig.12 "Replication is disabled"). Upon receiving a handover command (such as an RRC connection reconfiguration request), the UE initiates a RACH process to establish a connection with the target MgNB. Once the UE has sent a handover complete message to the target MgNB and established a connection with the target MgNB, the UE can activate uplink replication with the target MgNB and accordingly use uplink packet replication with subsequent uplink data transmission.

[0125] refer to Fig.13A, shows the content of the UE packet duplication status to be sent to the target MgNB, that is, the current duplication status of the UL radio bearer used by the UE. More specifically, according to this exemplary illustration, it is assumed that the UE has established five uplink data radio bearers (DRBs) #0-#4, and the UE packet duplication status can indicate up to five uplink DRBs #0-4.

[0126] For example, DRB#0 and DRB#1 belong to eMBB services, while DRB#2 belongs to URLLC services. Assume that duplication is enabled for DRB#0, #1, and #2, but not for DRB#3 and #4. For example, such packet duplication status of the UE may be signaled in the form of a bitmap comprising one bit per radio bearer. Fig.13A In the example shown, uplink replication is activated for DRB#0, #1 and #2, which is indicated by a mark "1" in the corresponding bit field. That is, before sending the UE packet replication status, the uplink packet replication for DRB#0, #1 and #2 has been activated / is in an activated state during communication with the source MgNB. Therefore, in the UE packet replication status to be sent to the target MgNB, the corresponding marks of DRB#0, #1 and #2 are set to "1" (in the example shown) so as to notify the target MgNB to use the uplink replication of DRB#0, #1 and #2 after the UE is switched.

[0127] Further for the example of 13A, uplink replication is disabled for DRB#3 and #4, which will be indicated by the flag value "0" in the corresponding bit field. That is, before sending the UE packet replication status, uplink packet replication for DRB#3 and #4 is not used / has been disabled. Therefore, in the UE packet replication status to be sent to the target MgNB, the corresponding flags for DRB#3 and #4 are set to "0" so as to notify the target MgNB not to use uplink replication for DRB#3 and #4 after the UE's handover.

[0128] For this example, uplink replication is activated for signaling radio bearers (SRBs) #0, #1, and #2, which is indicated by a flag "1" in the corresponding bit field of the UE packet replication status. That is, before the UE packet replication status is sent, uplink packet replication for SRBs #0, #1, and #2 has been activated / established. Therefore, in the UE packet replication status to be sent to the target MgNB, the corresponding flags of SRBs #0, #1, and #2 are set to "1" to notify the target MgNB to use uplink replication for SRBs #0, #1, and #2 after UE switching.

[0129] In one embodiment, the status of each established uplink radio bearer is reported. In another exemplary embodiment, the status of a subset of established uplink radio bearers (i.e., not all uplink radio bearers) is reported. Fig.13A In the example of , an eight-bit bitmap, i.e., an eight-bit octet, is used, which can be used to simultaneously inform the target MgNB of the current status of eight UE uplink radio bearers. However, in an alternative embodiment, only a portion of the status of the uplink radio bearers currently used / established by the UE may be implemented in / by the UE packet duplication state.

[0130] In another exemplary embodiment, the state of uplink packet duplication is activated or deactivated per uplink radio bearer. In other words, each field / flag of the bitmap for each uplink radio bearer indicates to the target MgNB that the corresponding radio bearer for which uplink duplication should also be activated (i.e., duplication is turned on or is to be kept activated) / deactivated (i.e., duplication is turned off or is to be kept deactivated) at the target MgNB.

[0131] The uplink radio bearer may be a signaling uplink radio bearer, such as the one described above in conjunction with Fig.13A The SRB referred to is, or data uplink radio bearer, such as the above combined Fig.13A The DRB mentioned.

[0132] In another exemplary embodiment, the bitmap may have a fixed size of one or more octets.

[0133] Fig. 13B An alternative implementation of the content of signaling the UE packet duplication status is shown.

[0134] like Fig. 13B As shown, the content of the UE packet replication status to be sent in the exemplary bitmap as shown in Option 1 includes information related to the combination of DRB replication and SRB replication, that is, the bit field is used to send information about both the DRB replication status and the SRB replication status together in one bitmap. In the exemplary illustration according to Option 1, DRB#0 to DRB#4 are indicated in the bitmap, wherein uplink packet replication for DRB#0 to DRB#2 is activated, and uplink packet replication for DRB#3 and DRB#4 is deactivated, and SRB#0 to SRB#2 are also indicated in the bitmap, and uplink packet replication for all these SRBs is activated.

[0135] like Fig. 13B As further shown in , the content of the UE packet duplication status may alternatively be sent by using two bitmaps as exemplarily shown under option 2.

[0136] One bitmap is used only to send information related to DRB replication, that is, the bit field is dedicated to sending only information related to the DRB replication status in one bitmap. In the exemplary illustration according to option 2, uplink packet replication for DRB#0 to DRB#7 can be indicated in one bitmap, in which case it is activated for DRB#0 to DRB#2 and deactivated for DRB#3 to DRB#7.

[0137] like Fig. 13B As further shown, another bitmap is used only to send information related to SRB duplication, i.e., a bit field is dedicated to sending only information related to the SRB duplication state in one bitmap. In the exemplary illustration according to option 2, uplink packet duplication for SRB#0 to SRB#2 may be indicated in the other bitmap, where it is exemplarily assumed that uplink packet duplication is activated for SRB#0 to SRB#2. According to the exemplary illustration, the remaining bit fields are not allocated to any radio bearer and are reserved, indicated by "R" in the figure.

[0138] In other words, while option 1 refers to the case with combined DRB and SRB mapping in one bitmap, option 2 refers to the case in which DRB and SRB are mapped in separate bitmaps, respectively.

[0139] In Section 9.1 of 3GPP TS 36.423 V14.2.0, the structure of the messages and information elements required by the X2AP protocol is described in a table format. Regarding options 1 and 2 described above, the following message function definitions and contents are exemplarily proposed, as shown in Table 1 below.

[0140]

[0141]

[0142] Table 1

[0143] According to another embodiment, the UE packet duplication status is sent by the source MgNB and received by the target MgNB during a handover procedure initiated by the source MgNB. Fig.14 An exemplary embodiment is shown, in which the UE packet duplication status is sent by the source MgNB and received by the target MgNB within a handover request message sent to the target MgNB to initiate a handover for the UE. Thus, the source MgNB notifies the target MgNB about the UE packet duplication status with a handover request message via the corresponding inter-gNB interface.

[0144] According to yet another embodiment, the UE packet duplication status is sent by the source MgNB within a handover request message sent to the target MgNB to initiate a handover performed on the UE. Fig.14 As shown, a bitmap including the copy information is sent from the source MgNB to the target MgNB within the handover request.

[0145] In response to the handover request, the source MgNB receives from the target MgNB a confirmation of the sent UE packet duplication status. Optionally, the confirmation is received by the source MgNB / sent by the target MgNB within a handover request confirmation message.

[0146] Subsequently, the source MgNB sends a confirmation to the UE to confirm the packet duplication status of the target MgNB. This confirmation can be sent to the UE together with the RRC connection reconfiguration request message as part of a conventional handover process. This confirmation sent from the source MgNB to the UE confirms that the target MgNB has received the packet duplication status previously sent by the source MgNB, and can exemplarily notify the UE about the uplink packet duplication to be used when communicating with the target MgNB. The confirmation can be sent to the UE together with the handover command message. In another exemplary embodiment, the confirmation sent includes information about the status of the uplink packet duplication performed by the UE, wherein the included information corresponds to the same information (e.g., a bitmap) sent by the source MgNB to the target MgNB. Accordingly, the UE is notified that the target MeNB has been notified about the uplink packet duplication status, and can therefore continue to use packet duplication for those uplink radio bearers when communicating with the target MgNB as before.

[0147] As per Fig.14 As further shown in the implementation method, the UE completes the switching process by sending a message indicating the completion of the switching process to the target MgNB (here is an RRC connection reconfiguration completion message), wherein this message indicating the completion of the switching process may have been sent to the target MgNB using uplink packet replication (exemplarily assuming that packet replication is activated for the uplink radio bearer (typically SRB1) used for transmission of the message).

[0148] Usually, as Fig.14 One of the advantages of the embodiment shown in , wherein the UE packet duplication status has been sent during the handover, with Fig.12 Compared with , the waiting time between disabling uplink replication before switching and reactivating uplink replication after switching is significantly reduced.

[0149] In addition, if Fig.14As shown and described above, (re)activation with uplink duplication of the new target MgNB is performed during the handover process and can therefore be used directly during and after the handover process. Thus, the UE performs uplink duplication immediately after the handover process is completed. RRC messages and uplink data are sent by the UE already in packet duplication mode.

[0150] According to another exemplary embodiment, the target MgNB may, upon receiving a handover request together with a packet duplication status, decide to change the uplink packet duplication of the radio bearer reported by the packet duplication status so as to establish a radio bearer with a duplication status different from the notified status and the previously established status between the UE and the source MgNB. In order to allow the target MgNB to decide on such a change, according to an exemplary embodiment, the target MgNB analyzes a measurement report received from the UE, wherein such a measurement report reflects measurements performed by the UE on the radio link between the UE and the target MgNB.

[0151] exist Fig.15 This further exemplary embodiment is shown in FIG. Upon receiving the UE packet duplication status, the target MgNB determines for each uplink radio bearer whether the received UE packet duplication status should be modified. Fig.15 In the illustrated example of, for example, it is shown that the target MgNB decides to update / modify the uplink packet duplication of radio bearers DRB#0 and DRB#1 (as indicated in the received UE packet duplication status) to deactivate them after the handover. According to an exemplary embodiment, this determination as to whether to modify the radio bearers is based on the measurement results performed by the UE on the radio link between the UE and the target MgNB.

[0152] According to an exemplary embodiment, such measurement results performed by the UE and provided to the source MgNB are sent from the source MgNB to the target MgNB using a handover request message, which is also exemplary used to carry the UE packet duplication status. Alternatively, the measurement results can be sent directly to the target MgNB by the UE. According to another exemplary embodiment, such measurement results received from the UE are sent from the UE to the source MgNB, wherein the source MgNB forwards the received measurement results to the target MgNB using a handover request message.

[0153] For example, such measurement results can indicate to the target MgNB that the corresponding link quality of the radio bearers DRB#0 and #1 between the UE and the target MgNB is better than the previous link quality between the UE and the source MgNB. In other words, for the corresponding radio bearers established between the UE and the source MgNB, the target cell quality can be better than the serving cell quality.

[0154] Therefore, the target MgNB may decide that for these two radio bearers, Fig.15 As shown in , for DRB#0 and #1, no uplink replication is required in the target cell. Therefore, the status of DRB#0 and #1 is deactivated, i.e., the corresponding flag is updated from the initially received UE packet replication status "1" to "0". For example, the target MgNB may determine that the target cell quality is good enough for serving eMBB, so that the target MgNB will disable uplink replication for each radio bearer. According to another exemplary embodiment, the target MgNB may also decide to activate several radio bearers, i.e., set several radio bearers to active, if, for example, the target cell quality of the corresponding radio bearer is not good enough compared to the corresponding serving cell quality.

[0155] It is further exemplarily assumed that, when the target MgNB has decided to modify at least one uplink radio bearer, it generates an updated UE packet duplication status and sends the updated UE packet duplication status to the source MgNB, such as Fig.15 As further shown, optionally, the target MgNB sends the updated UE packet duplication status to the source MgNB using a handover request confirmation message.

[0156] According to another exemplary embodiment, the target MgNB processes the updated UE packet duplication state in order to configure the packet duplication of the uplink radio bearer to be established between the UE and the target MgNB after the handover. Optionally, the measurement result includes a measurement of a reference signal received quality RSRQ or a reference signal received power RSRP or a signal to noise ratio SNR.

[0157] like Fig.15 As further shown, the source MgNB sends the updated UE packet duplication status to the UE. Optionally, the updated UE packet duplication status is sent to the UE in a handover command message (such as, for example, in an RRC connection reconfiguration request message).

[0158] As described above in conjunction with FIG. 13 , it is exemplarily assumed that the updated UE packet copy status sent by the source MgNB to the UE is in the same form as the bitmap of the original UE packet copy status before being modified by the target MgNB.

[0159] The main advantage of the target MgNB being able to react to measurements from the UE and thereby modify the UE packet duplication state is that it allows for flexibility in reacting to changing situations / cell conditions on the target MgNB side, thereby improving the application of uplink packet duplication only when necessary, and allowing for saving of additional resources spent on uplink packet duplication where possible.

[0160] Fig.16 Shows Fig.15 A general and simplified flow chart of an exemplary embodiment of a signaling diagram of FIG. 1601. In step S1601, the target MgNB receives the UE packet duplication status. In step S1602, the target MgNB analyzes the bitmap mapping according to the received UE packet duplication status. According to step S1603, the target MgNB analyzes the measurement report received from the UE, which measurement report is either received directly from the UE or received via the source MgNB.

[0161] In step S1604, the target MgNB decides whether the cell quality of the relevant radio bearer indicated in the received packet duplication status is better than a predetermined threshold. In other words, in step S1604, it is decided by the target MgNB whether the cell quality for each radio bearer, as seen from the UE and reflected by the UE in its measurement report, exceeds a certain threshold with respect to the target cell.

[0162] If it is determined that the cell quality of each radio bearer in the target cell is not better than the predetermined threshold or is lower than the predetermined threshold, the target MgNB proceeds to step S1605, in which it is determined not to modify the UE packet duplication state. Therefore, in this case, the target MgNB uses the same duplication state as it received in advance through the UE packet duplication state.

[0163] Otherwise, if it is determined that the cell quality of each radio bearer in the target cell is better than the predetermined threshold, the target MgNB proceeds to step S1606 and modifies the UE packet replication state for the radio bearer from the activated state to the deactivated state. In other words, it changes the corresponding value in the field of the bitmap from the value "1" to "0" so as to deactivate the packet replication for each radio bearer whose cell quality in the target cell is better than the threshold.

[0164] In this regard, if the cell quality is better than a threshold, deactivation of the previously indicated activation of the radio bearer avoids unnecessary uplink packet duplication, since the associated service still meets the quality criteria since the respective radio bearer has a better link quality in the target cell. Such deactivation of unnecessary uplink packet duplication advantageously conserves radio resources.

[0165] According to another exemplary embodiment, after the UE packet duplication state has been modified and when the handover is completed, it is assumed that the UE may be able to decide in step S1607 whether the corresponding duplication of the relevant radio bearer that has been modified to be deactivated by the target MgNB is still deactivated, and whether the serving cell quality of the corresponding radio bearer is still better than the threshold. This can be regarded as a confirmation step for the target MgNB to make a decision.

[0166] If it is determined by the UE in step S1607 that the serving cell quality is still better than the threshold, the target MgNB may continue to use the current UE packet duplication configuration (step S1608), ie it continues to use the UE packet duplication state for the established radio bearer modified in step S1606.

[0167] Otherwise, if the UE determines in step S1607 that the quality of the serving cell is no longer better than the threshold, then in step S1609, the UE sends a packet duplication activation command to the target MgNB for the corresponding radio bearer. Fig.16 In the description, it is noted that several steps may also be performed for the case where the target MgNB modifies the corresponding packet duplication state from "deactivated" to "activated" for the corresponding radio bearer.

[0168] More specifically, in this case, it may be determined in alternative step S1604 whether the cell quality of the radio bearer concerned indicated in the received packet duplication status is not better than a predetermined threshold. If not, the target MgNB will continue with the same UE packet duplication status as received in step S1605. Otherwise, if it is determined that the cell quality of the corresponding radio bearer is not better than a predetermined threshold in the target cell, the target MgNB proceeds to alternative step S1606 and modifies the UE packet duplication status from a deactivated state to an activated state for the radio bearer concerned. In other words, it will change the corresponding value within the field of the bitmap from a value of "0" to "1" so as to activate packet duplication for each radio bearer whose cell quality in the target cell is not better than the threshold. The UE will perform subsequent monitoring / decision accordingly in steps S1607 to S1609.

[0169] As an alternative or additional embodiment, a UE packet duplication status message is sent directly from the UE to the target MgNB, rather than having the source MgNB send the UE packet duplication status message. According to this alternative embodiment, the UE generates a UE packet duplication status, which includes information about the status of uplink packet duplication to be performed by the UE for the target MgNB and at least one further gNB. As previously explained, the target MgNB is the target of a handover from the source MgNB to be performed for the UE. Assuming that one or more uplink radio bearers are now established with the source MgNB and will be established between the UE and the target MgNB after the handover, the information about the uplink packet duplication status can again be per uplink radio bearer.

[0170] Exemplarily assume that when generating the UE packet duplication state, the UE determines the state of uplink packet duplication per uplink radio bearer based on the results of measurements performed by the UE for the radio link to the target MgNB. Optionally, the measurement results of the radio link to the target MgNB are compared with the measurement results performed by the UE for the radio link to the source MgNB, or can be compared with one or more thresholds, so as to be able to decide how to use uplink packet duplication in the target cell for the target MgNB.

[0171] For this embodiment in which the UE is responsible for sending the UE uplink packet copy to the target MgNB, many of the exemplary embodiments described in detail previously may be similarly assumed. For example, it is further exemplarily assumed that the information about the status of the uplink packet copy is in the form of a bitmap, the bitmap comprising one bit per uplink radio bearer. Optionally, the status of each established radio bearer will be reported, or the status of a subset of established radio bearers will be reported. Optionally, the status of the uplink packet copy is only activated or deactivated per uplink radio bearer. Optionally, the uplink radio bearer in this context is a signaling uplink radio bearer or a data uplink radio bearer. Optionally, the bitmap has a fixed size of one or more eight-bit bytes. Optionally, the UE packet copy status is sent as a medium access control MAC control element or a packet data convergence protocol PDCP control packet data unit PDU.

[0172] Fig.17A and Fig. 17B As a combination of the above Fig.13A and Fig. 13B An alternative format to the discussed format shows the contents of such a UE packet duplication status. According to this exemplary embodiment, Fig.17A The message format shown relates to a MAC CE format for activating and deactivating a packet duplication configuration, wherein the MAC CE is used for a bitmap including an "activation / deactivation flag" for each established radio bearer.

[0173] like Fig.17AAs shown, the content of the UE packet replication status to be sent in the MAC CE format as exemplarily shown includes information related to the combination of DRB replication and SRB replication, that is, the bit field is used to send information about both the DRB replication status and the SRB replication status in one bitmap, and the LCID field includes the corresponding LCID value that identifies the MAC CE as containing the UE packet replication status. In the exemplary illustration, DRB#0 to DRB#4 are indicated in the bitmap, wherein uplink packet replication for DRB#0 to DRB#2 is activated, and uplink packet replication for DRB#3 and DRB#4 is deactivated, and uplink packet replication for SRB#0 to SRB#2 is also indicated in the bitmap, wherein uplink packet replication of all these SRBs is activated.

[0174] like Fig. 17B As further shown in the upper part of the Fig. 13B In the exemplary embodiment of the description, a separate MAC CE may be used to send the UE packet duplication status for the data radio bearer and the signaling radio bearer, respectively. For example, as shown in the exemplary embodiment, the content of the UE packet duplication status to be sent in the MAC CE format includes only information related to DRB duplication, that is, the bit field is dedicated to sending only information about the DRB duplication status and the LCID field in one bitmap. In the exemplary illustration, DRB#0 to DRB#7 may be indicated in the bitmap, wherein uplink packet duplication for DRB#0 to DRB#2 is activated, and uplink packet duplication for DRB#3 to DRB#7 is deactivated.

[0175] like Fig. 17B As further shown in the lower part, the content of the UE packet duplication status to be sent in the MAC CE format as exemplarily shown includes only information related to SRB duplication, that is, the bit field is dedicated to sending only information about the SRB duplication status and the LCID field in one bitmap. In this example, the LCID field includes a corresponding LCID value that identifies the MAC CE as containing the UE packet duplication status for the data radio bearer. In the exemplary illustration, SRB#0 to SRB#2 can be indicated in the bitmap, where uplink packet duplication for SRB#0 to DRB#2 is activated. According to the exemplary illustration, the remaining bit fields are not assigned to any radio bearer and are reserved, indicated by "R" in the figure.

[0176] As another alternative implementation, the UE packet duplication status sent from the UE to the target MgNB may also be carried by another alternative message format, such as Fig.18A and Fig.18B shown.

[0177] According to an alternative embodiment, Fig.18A The message format shown is related to the PDCP control PDU format used to carry the UE uplink packet duplication status (i.e., activation and deactivation of uplink packet duplication). Figure 4 The format of the PDCP control PDU is described in the background section. Accordingly, the PDCP control PDU may be in the first eight bit byte ( Fig.18A The D / C flag is included in the PDU ("Oct 1" in the PDU). If the value of such D / C flag is "0", it thereby indicates that the PDU is related to the control PDU. If the value of such D / C flag is "1", it thereby indicates that the PDU is related to the data PDU.

[0178] In addition, the field of the second to fourth bits of the first eight-bit byte may relate to a specific "PDU type". For example, in the current 3GPP specification, bit values ​​100 to 111 of the PDU type field are reserved and are not currently used to indicate a specific PDU type. Any of these bit values ​​can be used to achieve the purpose of the UE uplink packet duplication status message. According to one example, the PDU type indicated by the bit value 100 means that the PDCP control PDU indicates UE packet uplink duplication for both DRBs and SRBs.

[0179] about Fig.18A In the example shown, the remaining bits of the first octet may reflect the activation or deactivation status of the SRB and / or DRB. Fig.18A In the example shown, the second octet ("Oct 2") reflects the activation or deactivation status of the DRB and / or SRB. According to another alternative embodiment of this example, if the status of additional SRBs and / or DRBs can be sent in the PDCP Control PDU, an additional octet can be used.

[0180] According to another alternative embodiment, Fig.18B The message format shown is related to the PDCP control PDU format for activating and deactivating packet duplication configuration, where the PDCP control PDU is used to send the activation / deactivation status of DRB and SRB respectively.

[0181] According to this alternative embodiment, the PDCP Control PDU may comprise one octet of bits. As an option, the first bit field (having a bit field length of 1 bit) is associated with the D / C flag, followed by the second to fourth bits associated with a specific "PDU type". Thus, the number of bit fields used for the PDU type is variable. For example, a bit value of 102 may indicate that the PDCP Control PDU is associated with a specific PDU type used only to signal the UL packet duplication status of the activation or deactivation of the DRB, as reflected in the Fig.18B Regarding this example, the last four bits of the PDCP control PDU may be used to indicate the activation / deactivation status of the DRB.

[0182] According to another example, a bit value of 101 for the PDU type may indicate that the PDCP control PDU is related to a specific PDU type used only for transmitting an activated or deactivated UL packet duplication state of an SRB, which is reflected in Fig.18B Regarding this example, the last four bits of the PDCP Control PDU may be used to indicate the activation / deactivation status of the SRB, optionally together with the reserved bit field "R".

[0183] Fig.19 A signaling diagram according to an alternative embodiment is shown, wherein the UE packet duplication status is sent directly from the UE to the target MgNB as part of the handover procedure. According to an exemplary embodiment, the UE packet duplication status is sent to the target MgNB as part of a RACH procedure performed by the UE with the target MgNB. It is exemplarily assumed that the RACH procedure comprises four steps and that the UE packet duplication status is sent together with any uplink signaling message of the RACH procedure.

[0184] like Fig.19 As shown, after receiving the RRC connection reconfiguration request notifying the UE about the new target MgNB, the UE sends a RACH preamble to the target MgNB, wherein the RACH preamble corresponds to the above combination Fig. 9 and Fig.10 The UE then receives a message from the target MgNB, which is a random access response message. Thereafter, the UE sends the RRC connection reconfiguration complete message together with the UE packet duplication status to the target MgNB as a third message. Therefore, the third message can be regarded as the above combined message. Fig. 9 and Fig.10 The message 3, however, is in a modified form, since the Duplicate Activate message is sent together with the RRC Connection Reconfiguration Complete message as the UE Packet Duplicate Status. Fig.17A or Fig. 17B According to another alternative exemplary embodiment, the content of the UE packet duplication status has the above combined Fig.18A or Fig.18B The format discussed. After having completed the RACH procedure, the UE performs uplink packet duplication with the target MgNB.

[0185] Fig. 20Another signaling diagram according to an alternative embodiment is shown, wherein the UE packet copy status is sent directly from the UE to the target MgNB as part of the handover procedure. According to another exemplary embodiment, the UE packet copy status is sent to the target MgNB as part of a RACH procedure performed by the UE with the target MgNB. It is exemplarily assumed that the RACH procedure comprises two steps and that the UE packet copy status is sent together with the RACH preamble and the handover complete message of the RACH procedure.

[0186] As above combined Fig. 9 and Fig.10 As illustrated, the two-step RACH process uses the combined message 1 and message 3 of the four-step RACH process as the first message. Fig. 20 As shown, the UE sends the UE packet duplication status to the target MgNB together with the combined message (i.e., the combination of messages 1 and 3). Therefore, the first step of this two-step RACH procedure is the transmission of the RACH preamble, the RRC connection reconfiguration complete message, and the activation duplication message. The use of system information broadcast makes it known in the radio cell that the radio resources available for the UE to send this first message of the two-step RACH procedure. According to an exemplary embodiment, the content of the UE packet duplication status has the above combined Fig.17A According to another alternative exemplary embodiment, the content of the UE packet duplication status has the above combined Fig.18A or the format discussed in 18B.

[0187] In response to this message from the UE including the UE packet duplication status, the target MgNB responds with a message relating to the second step of the two-step RACH procedure corresponding to the combination of message 2 and message 4 of the four-step RACH procedure. After having completed the RACH procedure, the UE performs uplink packet duplication with the target MgNB.

[0188] Fig.21 An exemplary simplified flow chart relating to an exemplary implementation of an alternative embodiment is shown, wherein a UE packet duplication status message is sent directly from the UE to the target MgNB.

[0189] In step S2101, the source MgNB (serving MgNB) sends an RRC connection reconfiguration message (which includes a handover message) and information about the target MgNB to be used by the UE after the handover to the UE.

[0190] Subsequently, in step S2102, the UE uses its own measurement results for the target MgNB to determine whether to modify the uplink replication state of one or more radio bearers currently used with the source MgNB. In an example embodiment, the UE compares the measurement results for the target MgNB with the measurement results for the source MgNB (serving MgNB). Alternatively, the UE may compare the measurement results with a specific threshold (e.g., a cell quality parameter such as RSRP, RSRQ, SNR) so as to be able to determine whether to continue using the same uplink packet replication state previously used for communication with the source MgNB.

[0191] In step S2103, depending on the implementation of the comparison in step S2102, the UE may then determine for each radio bearer whether the target cell measurement result exceeds a certain threshold or exceeds the source cell measurement result. If it is determined that the corresponding measurement result related to the target MgNB exceeds a predetermined threshold, it is determined that the link quality of the corresponding radio bearer to the target MgNB is good enough, for example. If it is determined that the target cell measurement result is better than the source cell measurement value, the link quality in the target cell is better and the UE may not need packet duplication.

[0192] In either case, step S2104 is then performed, in which the UE packet duplication state to be sent to the target MgNB is modified so as to change the duplication configuration from activated to deactivated for the corresponding radio bearers in the UE packet duplication state.

[0193] However, if it is determined that the measurement result related to the target MgNB does not exceed the predetermined threshold of the corresponding radio bearer, it is determined that the link quality of the corresponding radio bearer to the target MgNB is not good enough. If it is determined that the target cell measurement result is not better than the source cell measurement value, the link quality in the target cell is not better and the UE may still need packet replication. Then, proceed to step S2105, where the UE uses the same uplink replication configuration for the target MgNB as previously used for the source MgNB.

[0194] In any case, as previously explained, the UE packet duplication status (whether modified or not compared to that used with the source MgNB) is sent to the target MgNB together with the corresponding activated or deactivated radio bearer indications using a MAC CE or PDCP control PDU.

[0195] It should be noted that, as described above in conjunction with FIG. 17 to FIG. Fig.21One advantage of the described alternative embodiment of sending the UE packet duplication status message directly from the UE to the target MgNB is that it gives the UE certain flexibility in deciding whether duplication of the corresponding radio bearer is to be activated or deactivated in the UE packet duplication status to be sent to the target MgNB.

[0196] As a further advantage of this alternative embodiment, no inter-gNB coordination is required, i.e. no new signalling formats via the inter-gNB interface are required.

[0197] Similarly, combined with the above Fig.12 This alternative embodiment described above in conjunction with Figures 17 to 21 advantageously achieves a reduction in the latency of using duplication for each radio bearer after a handover compared to the aforementioned embodiment.

[0198] Other aspects

[0199] According to a first aspect, a source base station is provided. The source base station comprises a processing circuit that generates a user equipment packet duplication status, the user equipment packet duplication status comprising information about a status of duplication of uplink packets performed by the user equipment with the source base station and at least one further base station. The information about the status of uplink packet duplication is per uplink radio bearer, one or more uplink radio bearers being established between the user equipment and the source base station. The source base station further comprises a sending unit that sends the user equipment packet duplication status to a target base station, the target base station being a target of a handover performed for the user equipment from the source base station.

[0200] According to a second aspect provided in addition to the first aspect, the user equipment packet copy state is transmitted by the transmitting unit during a handover procedure.

[0201] According to a third aspect provided in addition to the second aspect, the user equipment packet duplication state is sent by a sending unit in a handover request message sent to a target base station to initiate handover performed for the user equipment.

[0202] According to a fourth aspect provided in addition to the second or third aspect, the source base station further comprises a receiving unit, which optionally receives a confirmation of the sent user equipment packet duplication status from the target base station in a handover request confirmation message. The sending unit, optionally in a handover command message, sends a confirmation to the user equipment to confirm the packet duplication status of the target base station, wherein optionally, the confirmation includes information about the status of the uplink packet duplication performed by the user equipment.

[0203] According to a fifth aspect provided in addition to any one of the first to fourth aspects, the information about the status of uplink packet duplication of the user equipment is in the form of a bitmap including one bit per radio bearer. Optionally, the status of each established radio bearer is reported. Optionally, the status of a subset of established radio bearers is reported. Optionally, the status of the uplink packet duplication is activated or deactivated per uplink radio bearer. Optionally, the uplink radio bearer is a signaling uplink radio bearer or a data uplink radio bearer. Optionally, the bitmap has a fixed size of one or more eight bits.

[0204] According to a sixth aspect provided in addition to any one of the first to fifth aspects, the user equipment performs uplink packet duplication by sending the same data packet to a source base station and at least one other base station. The source base station participates as a receiving side of the uplink packet duplication performed by the user equipment by generating a single data packet to be forwarded to an upper layer of the source base station using the data packets received from the user equipment and from the at least one other base station.

[0205] According to a seventh aspect provided in addition to any one of the first to sixth aspects, the source base station is a source primary base station or a source secondary base station.

[0206] According to an eighth aspect provided in addition to any one of the first to seventh aspects, the source base station further comprises a receiving unit, which receives an updated user equipment packet duplication state from a target base station, the target base station having modified the received user equipment packet duplication state for at least one uplink radio bearer to generate an updated user equipment packet duplication state, optionally wherein the updated user equipment packet duplication state is received in a handover request confirmation message. A sending unit, which sends the updated user equipment packet duplication state to the user equipment, optionally wherein the updated user equipment packet duplication state is sent to the user equipment within a handover command message.

[0207] According to a ninth aspect provided in addition to the eighth aspect, the updated user equipment packet duplication status is in the form of a bitmap including one bit per uplink radio bearer. Optionally, the updated status of each established radio bearer is reported. Optionally, the updated status of a subset of established radio bearers is reported. Optionally, the updated status of the uplink packet duplication is activated or deactivated per uplink radio bearer. Optionally, the uplink radio bearer is a signaling uplink radio bearer or a data uplink radio bearer. Optionally, the bitmap has a fixed size of one or more eight bits.

[0208] According to the tenth aspect provided in addition to the eighth aspect or the ninth aspect, the sending unit sends the result of measurement performed by the user equipment on the wireless link between the user equipment and the target base station to the target base station, optionally, the measurement result is sent using a switching request message; optionally, the measurement result is received from the user equipment.

[0209] According to an eleventh aspect, there is provided a target base station, the target base station comprising a receiving unit that receives a user equipment packet duplication state, the user equipment packet duplication state comprising information about a state of uplink packet duplication performed by the user equipment to a source base station and at least one other base station, the target base station being a target of a handover performed from the source base station for the user equipment. The information about the state of the uplink packet duplication is per uplink radio bearer, one or more uplink radio bearers being established between the user equipment and the source base station. The target base station further comprises a processing circuit that processes the received user equipment packet duplication state to configure packet duplication of an uplink radio bearer to be established between the user equipment and the target base station after the handover.

[0210] According to a twelfth aspect provided in addition to the eleventh aspect, wherein the user equipment packet copy state is received by the receiving unit during a handover process.

[0211] According to a thirteenth aspect provided in addition to the twelfth aspect, wherein the user equipment packet duplication state is received by the receiving unit in a handover request message from a source base station initiating a handover performed for the user equipment.

[0212] According to a fourteenth aspect provided in addition to any one of aspects eleven to thirteen, the target base station further comprises a sending unit, which optionally sends a confirmation of the received user equipment group copy status to the source base station within a switching request confirmation message.

[0213] According to the fifteenth aspect provided in addition to any one of the eleventh to fourteenth aspects, the processing circuit determines whether to modify the received user equipment packet duplication state per uplink radio bearer, optionally, wherein the determination is based on the result of a measurement received from a source base station or a user equipment and performed by the user equipment for a radio link between the user equipment and a target base station. When it is determined to modify the received user equipment packet duplication state for at least one uplink radio bearer, the processing circuit generates an updated user equipment packet duplication state, and the sending unit optionally uses a handover request confirmation message to send the updated user equipment packet duplication state to the source base station, optionally, wherein the processing circuit processes the updated user equipment packet duplication state to configure the packet duplication of the uplink radio bearer to be established between the user equipment and the target base station after the handover.

[0214] According to the sixteenth aspect provided in addition to any one of the eleventh to fifteenth aspects, measurement results are received from the source base station using a switching request message, optionally wherein the measurement results include measurement of a reference signal received quality RSRQ or a reference signal received power RSRP or a signal-to-noise ratio SNR.

[0215] According to a seventeenth aspect, there is provided a user equipment, the user equipment comprising a processing circuit that generates a user equipment packet duplication status, the user equipment packet duplication status comprising information about a status of uplink packet duplication to be performed by the user equipment with a target base station and at least one further base station, the target base station being a target of a handover to be performed for the user equipment from a source base station. The information about the status of the uplink packet duplication is per uplink radio bearer, one or more uplink radio bearers being established between the user equipment and the target base station after the handover. The user equipment further comprises a sending unit that sends the generated user equipment packet duplication status to the target base station.

[0216] According to an eighteenth aspect provided in addition to the seventeenth aspect, wherein the processing circuit, when generating the user equipment packet duplication status, determines the state of uplink packet duplication per uplink radio bearer based on the result of measurement performed by the user equipment for the radio link to the target base station. Optionally, the measurement result of the radio link to the target base station is compared with the measurement result performed by the user equipment on the radio link to the source base station.

[0217] According to a nineteenth aspect provided in addition to the seventeenth or eighteenth aspect, wherein information about the status of uplink packet duplication is in the form of a bitmap comprising one bit per uplink radio bearer, optionally wherein the status of each established radio bearer is to be reported, optionally wherein the status of a subset of established radio bearers is to be reported, optionally wherein the status of the uplink packet duplication is activated or deactivated per uplink radio bearer, optionally wherein the uplink radio bearer is a signalling uplink radio bearer or a data uplink radio bearer, optionally wherein the bitmap has a fixed size of one or more eight-bit bytes, optionally wherein the user equipment packet duplication status is sent as a medium access control MAC control element or a packet data convergence protocol PDCP control packet data unit PDU.

[0218] According to the twentieth aspect provided in addition to any one of the seventeenth to nineteenth aspects, the user equipment packet copy state is sent to the target base station as part of a random access channel RACH process performed by the user equipment with the target base station. Optionally, the RACH process includes four steps, and the user equipment packet copy state is sent together with any signaling message of the RACH process. Optionally, the RACH process includes two steps, and the user equipment packet copy state is sent together with the RACH preamble and the handover completion message of the RACH process.

[0219] According to a twenty-first aspect, a method for operating a source base station is provided, wherein the method includes generating a user equipment packet replication state, the user equipment packet replication state including information about a state of uplink packet replication performed by the user equipment with the source base station and at least one further base station. The information about the state of the uplink packet replication is per uplink radio bearer, one or more uplink radio bearers being established between the user equipment and the source base station. The method also includes: sending the user equipment packet replication state to a target base station, the target base station being a target of a handover performed for the user equipment from the source base station.

[0220] According to a twenty-second aspect, a method for operating a target base station is provided, wherein the method comprises: receiving a user equipment packet replication state, the user equipment packet replication state comprising information about a state of uplink packet replication performed by the user equipment with a source base station and at least one other base station, the target base station being a target of a handover performed for the user equipment from the source base station. The information about the state of the uplink packet replication is per uplink radio bearer, one or more uplink radio bearers being established between the user equipment and the source base station. The method further comprises: processing the received user equipment packet replication state to configure packet replication of an uplink radio bearer to be established between the user equipment and the target base station after the handover.

[0221] According to a twenty-third aspect, a method for operating a user equipment is provided, wherein the method comprises: generating a user equipment packet duplication state, the user equipment packet duplication state comprising information about a state of uplink packet duplication to be performed by the user equipment with a target base station and at least one further base station, the target base station being a target of a handover from a source base station to be performed for the user equipment. The information about the state of the uplink packet duplication is per uplink radio bearer, one or more uplink radio bearers being established between the user equipment and the target base station after the handover. The method further comprises sending the generated user equipment packet duplication state to the target base station.

[0222] Hardware and software implementations of the present disclosure

[0223] The present disclosure can be implemented by software, hardware or software in collaboration with hardware. Each functional block used in the description of each of the above embodiments can be partially or completely implemented by an LSI such as an integrated circuit, and each process described in each embodiment can be partially or completely controlled by the same LSI or a combination of LSIs. LSI can be formed as a chip alone, or a chip can be formed to include some or all functional blocks. LSI may include data input and output coupled to it. According to the difference in integration, the LSI here may be referred to as IC (integrated circuit), system LSI, super LSI or ultra LSI. However, the technology for implementing integrated circuits is not limited to LSI, and can be implemented by using a dedicated circuit, a general-purpose processor, or a dedicated processor. In addition, an FPGA (field programmable gate array) that can be programmed after LSI manufacturing or a reconfigurable processor that can reconfigure the connection and setting of the circuit unit arranged inside the LSI can be used. The present disclosure can be implemented as digital processing or analog processing. If future integrated circuit technology replaces LSI due to the development of semiconductor technology or other derivative technologies, future integrated circuit technology can be used to integrate functional blocks. Biotechnology can also be applied.

[0224] Furthermore, various embodiments may also be implemented with the aid of software modules executed by a processor or directly in hardware. Combinations of software modules and hardware implementations are also possible. Software modules may be stored on any kind of computer-readable storage medium, such as RAM, EPROM, EEPROM, flash memory, registers, hard disk, CD-ROM, DVD, etc. It should also be noted that individual features of different embodiments may be the subject of another embodiment, either alone or in any combination.

[0225] Those skilled in the art will appreciate that various changes and / or modifications may be made to the present disclosure as shown in the specific embodiments. Therefore, the present embodiments should be considered in all aspects as illustrative and not restrictive.

Claims

1. A user equipment, comprising: processing circuitry to obtain a user equipment packet duplication state, the user equipment packet duplication state comprising information about a state of uplink packet duplication to be performed by the user equipment with at least one base station, wherein the information about the status of uplink packet duplication is per uplink radio bearer, one or more uplink radio bearers being established between the user equipment and the base station, and wherein the processing circuit determines the state of uplink packet duplication per uplink radio bearer based on configuration information received from the at least one base station when obtaining the user equipment packet duplication state, The information on the uplink packet duplication status is in the form of a bitmap comprising one bit per uplink radio bearer, and The state of uplink packet duplication is activated or deactivated per uplink radio bearer.

2. The user equipment according to claim 1, in, The uplink radio bearer is a data uplink radio bearer.

3. The user equipment according to claim 2, in, The bitmap has a fixed size of one or more octets.

4. The user equipment according to claim 3, in, The user equipment packet duplication status is sent as a medium access control MAC control element.

5. The user equipment according to claim 4, in, The user equipment packet duplication state is dynamically updated through the MAC control element.

6. The user equipment according to claim 4, in, In the MAC control element, "1" indicates that the state of uplink packet duplication is activated, and "0" indicates that the state of uplink packet duplication is deactivated.

7. A method performed by a user equipment, comprising: obtaining a user equipment packet duplication state, the user equipment packet duplication state comprising information about a state of uplink packet duplication to be performed by the user equipment with at least one base station, wherein the information about the status of uplink packet duplication is per uplink radio bearer, one or more uplink radio bearers being established between the user equipment and the base station, and wherein, when obtaining the user equipment packet duplication status, determining the status of uplink packet duplication per uplink radio bearer based on configuration information received from the at least one base station, The information on the uplink packet duplication status is in the form of a bitmap comprising one bit per uplink radio bearer, and The state of uplink packet duplication is activated or deactivated per uplink radio bearer.

8. An integrated circuit for controlling a process of a user equipment, the process comprising: obtaining a user equipment packet duplication state, the user equipment packet duplication state comprising information about a state of uplink packet duplication to be performed by the user equipment with at least one base station, wherein the information about the status of uplink packet duplication is per uplink radio bearer, one or more uplink radio bearers being established between the user equipment and the base station, and wherein, when obtaining the user equipment packet duplication status, determining the status of uplink packet duplication per uplink radio bearer based on configuration information received from the at least one base station, The information on the uplink packet duplication status is in the form of a bitmap comprising one bit per uplink radio bearer, and The state of uplink packet duplication is activated or deactivated per uplink radio bearer.

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