Fast pscell access for improved user throughput

Abstract

The embodiment of the invention relates to fast PSCELL access for improved user throughput. An apparatus comprises means for, in response to receiving a first secondary node addition request for a user equipment from a first target master node, sending a response to the first target master node based on the received first request, means for, in response to receiving a second secondary node addition request for the same user equipment from a second target master node, sending a response to the second target master node based on the received second request, means for sending a response to the second target master node based on the received second request, and means for, in response to receiving a physical uplink shared channel message from the user equipment, sending a response to the second target master node without information whether the user equipment is available to access the first or second target master node, means for enabling decoding of a physical uplink shared channel message received from the user equipment based on a first target master node key associated with the first target master node.

Description

Technical Field

[0001] The present invention relates to fast access to a primary cell of a secondary cell group (PSCell) for improved user throughput. Background Art

[0002] Conditional Handover (CHO) is a feature supported in LTE (Long Term Evolution) and 5G NR (New Radio). CHO is similar in many ways to the previously known "normal" handover (HO), i.e., conventional HO. The main difference from conventional HO is that in CHO, the user equipment (UE) starts preparing to hand over to the target node only when additional CHO execution conditions are met. Another difference between conventional HO and CHO is that multiple target cells are prepared in CHO. Therefore, CHO reserves more resources in the target cell while waiting to be executed than conventional HO.

[0003] In Multi-Radio Dual Connectivity (MR-DC), CHO is limited to the scenario where the target Master Node (MN) can prepare a single target PSCell under the control of the Secondary Node (SN). This may limit the practicality of the CHO MR-DC feature as the UE may need to access different target PSCells at the same time that CHO needs to be performed. A mechanism is being developed for CHO in MR-DC where the target MN can prepare multiple target PSCells for the same target PCell. The focus is on providing the UE with a configuration consisting of both a conditional handover configuration and a conditional PSCell addition or change (CPAC) configuration. In other words, the UE will perform conditional handover to both the PCell and the PSCell, considering the execution conditions for each cell given in the handover configuration.

[0004] The UE evaluates the CHO and CPC conditions in parallel, and only if both conditions are met, the UE performs CHO+CPC configuration. However, the order of sending random access messages to the target PCell and the target PSCell is not defined. Summary of the invention

[0005] The UE may be enabled, for example by implementation or (remote) configuration (e.g., by a serving node) to send the target PCell random access preamble and the target PSCell random access preamble successively, or may be configured to send the target PCell random access preamble before the target PSCell random access preamble, or to send the target PSCell random access preamble only after completing access to the target PCell, or otherwise.

[0006] In the case where SN random access is triggered before MN random access, security issues may arise, causing target PSCell random access failure and enabling phishing attacks.

[0007] If SN random access is triggered before MN random access, the following problems may occur:

[0008] The UE may be configured with multiple conditional dual connectivity configurations on different target MNs. Each dual connectivity configuration has a separate security key for the configuration of the SN terminated bearer. In order to save resources, the target SN can allocate the same preamble for different CHO configurations because it will be used by the same UE. Therefore, after receiving the random access preamble, the target SN may not be able to identify the UE. In other words, the preamble cannot be used to determine the security key. This will cause the target PSCell random access failure, for example, the target SN will not send any RAR (random access response) message, the UE will not access any RAR message, and after the RAR timer at the UE expires, the PSCell access failure may be detected, or the UE may be configured to resend the preamble, which may cause another failure or delay, for example, if the UE has successfully accessed the target MN during this period and sent access completion information from the target MN to the target SN, the target SN may know the selected target MN and be able to identify the target MN and respond to the UE with a RAR message.

[0009] Another problem is that in order to identify itself in the contention-based random access (CBRA) process, the UE indicates the C-RNTI (Cell Radio Network Time Identifier) ​​to the network. Receiving the C-RNTI, the network matches it with the provided configuration. However, C-RNTI is not a security protection signal, and any UE can indicate the C-RNTI of the UE to copy the configured UE. This is usually solved by the UE using a secure RRC (Radio Resource Control) message to send to the target MN, and the target MN forwards the same message to the target SN, but currently the target SN does not indicate any security control message to complete the access process in dual connectivity handover. Therefore, relying only on the C-RNTI to determine the security key to be used creates exposure to phishing attacks.

[0010] Now, in exemplary embodiments, an improved method and a technical device for implementing the method have been invented, by which at least one of the above problems can be alleviated and / or solved. Various aspects include a method, an apparatus and a non-transitory computer-readable medium including a computer program or a signal stored therein, which are characterized by what is described in the independent claims. Various details of the embodiments are disclosed in the dependent claims and the corresponding images and descriptions.

[0011] The scope of protection sought by various embodiments of the present invention is set out by the independent claims. Embodiments and features described in this specification that do not belong to the scope of the independent claims, if any, should be interpreted as examples useful for understanding the various embodiments of the present invention.

[0012] According to an embodiment, one or more problems are solved by the UE indicating that it supports an enhanced dual connectivity handover execution process (e.g., via UE capability signaling). Since the allocated preamble cannot be used to determine the security key, the target SN adopts blind decoding of the UE physical uplink shared channel (PUSCH) message, in other words, the network adopts blind decoding of the UE PUSCH message using multiple security keys configured for the UE to send a random access response to the UE. The target SN has a list of keys configured for the UE, and attempts to decode the message received from the UE using the key list, and sees if any key causes successful decryption of the received message. If any key causes successful decryption of the received message, the target SN can determine that the UE associated with the key is the correct UE. The UE can be configured with strict requirements to complete the dual connectivity handover process faster than before, thereby reducing interruption time and maximizing UE throughput.

[0013] Contention-free random access (CFRA) configuration may be used instead of CBRA procedure, where the UE allocates CFRA preamble to avoid problems that may be caused by CBRA preamble. The secondary cell group (SCG) configuration for a specific target secondary node (T-SN) contains the same CFRA resources configured for the UE.

[0014] In another option, the network increases the random access response timer to allow a large waiting time so that the RRC Reconfiguration Complete message can be received from the target MN.

[0015] According to another embodiment, one or more of the problems are solved by performing a random access procedure for PCell first or simultaneously with PSCell. In other words, unless the target PCell random access is successfully completed, the UE is not allowed to initiate random access to the target PSCell, the UE can initiate PCell random access before or simultaneously with the PSCell RA, and the target cell Pcell random access is performed before the PSCell, and "simultaneously" is defined as a window within which Pcell and PSCell access are performed. In other words, "simultaneously" does not necessarily mean exactly the same time, but within a defined time window.

[0016] According to yet another embodiment, one or more of the issues are resolved such that the UE is allowed to complete the RA procedure at the target PSCell, but possible data traffic is put on hold at the RAN level until the target PSCell receives an SN-specific RRCReconfigurationComplete message forwarded by the target PCell.

[0017] According to yet another embodiment, one or more of the problems are solved such that the UE directly sends a security control message to the target SN using its configured security key to confirm the completion of the random access procedure.

[0018] According to a first aspect, a user equipment is provided, comprising:

[0019] A component for indicating a conditional handover capability to a serving network node, wherein the capability includes information on whether the user equipment supports accessing a primary cell of a secondary cell group of a target secondary node before or in parallel with accessing a primary cell of a target primary node;

[0020] A component for initiating conditional handover execution in response to receiving a conditional handover configuration for a primary cell of a first target primary node and a primary cell of a first secondary node, and another conditional handover configuration for a primary cell of a second target primary node and a primary and secondary cell of the first secondary node, when the conditional handover configuration for a specific target primary node and a target secondary node is maintained; and

[0021] Means for accessing a primary cell of a target secondary node prior to or in parallel with accessing a primary cell of a specific target primary node if the capability is enabled.

[0022] According to the second aspect, the user equipment comprises at least one processor and at least one memory, wherein the at least one memory has computer program code stored thereon, and the at least one memory and the computer program code are configured to, together with the at least one processor, use the user equipment to at least execute:

[0023] Indicating a conditional handover capability to the serving network node, wherein the capability includes information on whether the user equipment supports accessing a primary cell of a target secondary node before or in parallel with accessing a primary cell of a target primary node;

[0024] In response to receiving a conditional switching configuration for a primary cell of a first target primary node and a primary cell of a first secondary node, and another conditional switching configuration for a primary cell of a second target primary node and a primary and secondary cell of the first secondary node;

[0025] When the conditional switch configuration for the specific target primary node and the target secondary node is maintained, initiating conditional switch execution; and

[0026] In case the capability is enabled, the primary cell of the target secondary node is accessed before or in parallel with accessing the primary cell of the specific target primary node.

[0027] A method according to a third aspect comprises:

[0028] Indicating a conditional handover capability to the serving network node, wherein the capability includes information on whether the user equipment supports accessing a primary cell of a target secondary node before or in parallel with accessing a primary cell of a target primary node;

[0029] In response to receiving a conditional switching configuration for a primary cell of a first target primary node and a primary cell of a first secondary node, and another conditional switching configuration for a primary cell of a second target primary node and a primary and secondary cell of the first secondary node;

[0030] When the conditional switch configuration for the specific target primary node and the target secondary node is maintained, initiating conditional switch execution; and

[0031] In case the capability is enabled, the primary cell of the target secondary node is accessed before or in parallel with accessing the primary cell of the specific target primary node.

[0032] A network node according to a fourth aspect includes:

[0033] means for, in response to receiving a first secondary node adding request for a user equipment from a first target primary node, sending a response to the first target primary node based on the received first request;

[0034] means for, in response to receiving a second secondary node addition request for the same user equipment from the second target master node, sending a response to the second target master node based on the received second request; and

[0035] A component for enabling decoding of a physical uplink shared channel message received from a user device in response to receiving a physical uplink shared channel message from a user device based on a first target master node key associated with a first target master node in the absence of information available as to whether the user device has access to a first target master node or a second target master node, and for decoding based on a second target master node key associated with a second target master node if decoding of the first key is unsuccessful.

[0036] The network node according to the fifth aspect comprises at least one processor and at least one memory having computer program code stored thereon, the at least one memory and the computer program code being configured to, together with the at least one processor, cause the network node to at least perform:

[0037] In response to receiving a first secondary node adding request for a user equipment from a first target primary node, sending a response to the first target primary node based on the received first request;

[0038] In response to receiving a second secondary node addition request for the same user equipment from a second target master node, sending a response to the second target master node based on the received second request; and

[0039] In response to receiving a physical uplink shared channel message from a user device, in the absence of information available as to whether the user device has access to a first target master node or a second target master node, decoding of the physical uplink shared channel message received from the user device is enabled based on a first target master node key associated with the first target master node, and if decoding of the first key is unsuccessful, decoding is performed based on a second target master node key associated with the second target master node.

[0040] A method according to the sixth aspect, comprising

[0041] In response to receiving a first secondary node adding request for a user equipment from a first target primary node, sending a response to the first target primary node based on the received first request;

[0042] In response to receiving a second secondary node addition request for the same user equipment from a second target master node, sending a response to the second target master node based on the received second request; and

[0043] In response to receiving a physical uplink shared channel message from a user device, in the absence of available information as to whether the user device accesses a first or second target master node, decoding of the physical uplink shared channel message received from the user device is enabled based on a first target master node key associated with the first target master node, and if decoding of the first key is unsuccessful, decoding is performed based on a second target master node key associated with the second target master node.

[0044] According to a further aspect, a computer readable storage medium comprises code for use by an apparatus, which when executed by a processor causes the apparatus to perform the above method. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] For a more complete understanding of example embodiments, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:

[0046] Figure 1 A schematic block diagram of a user equipment device for implementing the functions of various embodiments is shown;

[0047] Figure 2 schematically illustrates a layout of a user equipment device according to an example embodiment;

[0048] Figure 3 A portion of an example radio access network is shown;

[0049] Figure 4 shows a signaling diagram for a conditional handover procedure;

[0050] Figure 5 shows a signaling diagram according to an example embodiment;

[0051] Figure 6 shows a signaling diagram according to another example embodiment;

[0052] Figure 7 shows a signalling diagram according to yet another example embodiment;

[0053] Figure 8a A signaling diagram showing yet another example embodiment based on the CFRA procedure;

[0054] Figure 8b shows a signaling diagram based on a CBRA procedure according to yet another example embodiment;

[0055] Fig. 9 shows a signaling diagram according to a further example embodiment;

[0056] Fig.10a A flow chart of a method for a UE according to an embodiment is shown;

[0057] Fig.10b A flowchart of a method for a target SN according to an embodiment is shown; and

[0058] Fig.11 Shown is a simplified block diagram of a network node according to an embodiment. DETAILED DESCRIPTION

[0059] Suitable means and possible mechanisms for performing operations for conditional switching are described in further detail below. Although the following focuses on 5G networks, the embodiments further described below are by no means limited to being implemented only in the network, but are applicable to any network that supports conditional switching.

[0060] In this regard, first refer to Figure 1 and Figure 2 ,in Figure 1 A schematic block diagram of an exemplary apparatus or electronic device 50 is shown, which may incorporate arrangements according to embodiments. Figure 2 A layout of an apparatus according to an example embodiment is shown. Figure 1 and Figure 2 The elements will be explained next.

[0061] The electronic device 50 may be, for example, a mobile terminal or user equipment of a wireless communication system. The device 50 may include a housing 30 for combining and protecting the device. The device 50 may also include a display 32 and a keyboard 34. In addition to the keyboard, the user interface may also be implemented as a virtual keyboard or as a data input system as part of a touch display.

[0062] The device may include a microphone 36 or any suitable audio input, which may be a digital or analog signal input. The device 50 may also include an audio output device, such as any of the following: headphones 38, speakers, or analog audio or digital audio output connections. The device 50 may also include a battery 40 (or the device may be powered by any suitable mobile energy device, such as a solar cell, a fuel cell, or a clockwork generator). The device may also include a camera 42 capable of recording or capturing images and / or video. The device 50 may also include an infrared port 41 for short-range line-of-sight communication with other devices. In other embodiments, the device 50 may also include any suitable short-range communication solution, such as, for example, a Bluetooth wireless connection or a USB / Firewire wired connection.

[0063] The device 50 may include a controller 56 or processor for controlling the device 50. The controller 56 may be connected to a memory 58, which may store user data and instructions for implementation on the controller 56. The memory may be a random access memory (RAM) and / or a read-only memory (ROM). The memory may store computer-readable, computer-executable software, including instructions that, when executed, cause the controller / processor to perform the various functions described herein. In some cases, the software may not be directly executed by the processor, but may cause the computer (e.g., when compiled and executed) to perform the functions described herein. The controller 56 may also be connected to a codec circuit system 54, which is suitable for performing encoding and decoding of audio and / or video data or assisting in encoding and decoding performed by the controller.

[0064] The device 50 may include a radio interface circuit system 52 connected to the controller, which is suitable for generating wireless communication signals, such as for communicating with a cellular communication network, a wireless communication system or a wireless local area network. The device 50 may also include an antenna 44 connected to the radio interface circuit system 52 for transmitting radio frequency signals generated at the radio interface circuit system 52 to (multiple) other devices, and for receiving radio frequency signals from (multiple) other devices.

[0065] A user equipment (also referred to as user equipment (UE), user terminal, terminal device, wireless device, mobile station (MS), etc.) shows a type of device to which resources on the air interface are allocated and assigned, and therefore, any features described herein with a user equipment can be implemented using a corresponding network device (such as a relay node, eNB, and gNB). An example of such a relay node is a layer 3 relay (self-backhaul relay) toward a base station.

[0066] User equipment generally refers to a portable computing device, which includes wireless mobile communication devices that operate with or without a subscriber identity module (SIM), including but not limited to the following types of devices: mobile stations (mobile phones), smart phones, personal digital assistants (PDAs), mobile phones, devices using wireless modems (alarm or measurement devices, etc.), laptop computers and / or touch screen computers, tablet computers, game consoles, notebooks, and multimedia devices. It should be understood that user equipment can also be almost exclusively uplink-only devices, one example of which is a camera or video camera that loads images or video clips to a network. User equipment can also be a device with the ability to operate in an Internet of Things (IoT) network, which is a scenario in which objects are provided with the ability to transmit data over a network without human-to-human or human-to-computer interaction. Therefore, a user device can be an IoT device. A user device can also utilize a cloud. In some applications, a user device may include a small portable device with a radio component (such as a watch, headset, or glasses), and the calculation is performed in the cloud. A user device (or in some embodiments, a layer 3 relay node) is configured to perform one or more user device functions. A user device may also be called a subscriber unit, a mobile station, a remote terminal, an access terminal, a user terminal, or user equipment (UE), to name a few.

[0067] The various techniques described herein can also be applied to cyber-physical systems (CPS) (systems of cooperating computing elements that control physical entities). CPS can enable the implementation and utilization of a large number of interconnected ICT devices (sensors, actuators, processor microcontrollers, etc.) embedded in physical objects in different locations. Mobile cyber-physical systems are a subcategory of cyber-physical systems in which the physical system in question has inherent mobility. Examples of mobile physical systems include mobile robots and electronic devices transported by humans or animals.

[0068] Furthermore, although these devices have been described as a single entity, different units, processors and / or memory units ( Figure 1 Not all are shown) can be implemented.

[0069] In the following, different exemplary embodiments will be described using a radio access architecture based on Long Term Evolution Advanced (LTE Advanced, LTE-A) or New Radio (NR, 5G) as an example of an access architecture to which these embodiments can be applied, however, the embodiments are not limited to such architectures. Those skilled in the art recognize that by appropriately adjusting the parameters and processes, these embodiments can also be applied to other types of communication networks with appropriate components. Some examples of other options for suitable systems are Universal Mobile Telecommunications System (UMTS) Radio Access Network (UTRAN or E-UTRAN), Long Term Evolution (LTE, same as E-UTRA), Wireless Local Area Network (WLAN or WiFi), Worldwide Interoperability for Microwave Access (WiMAX), Personal Communications Service (PCS), Wideband Code Division Multiple Access (WCDMA), systems using Ultra-Wideband (UWB) technology, sensor networks, mobile ad hoc networks (MANETs), and Internet Protocol Multimedia Subsystem (IMS), or any combination thereof.

[0070] Figure 3 An example of a simplified system architecture is shown, showing only some elements and functional entities, which are all logical units, the implementation of which may differ from what is shown. Figure 3 The connections shown are logical connections; the actual physical connections may be different. It will be clear to those skilled in the art that the system typically also includes Figure 3 Other functions and structures than those shown. However, the embodiments are not limited to the systems given as examples, but a person skilled in the art may apply the solution to other communication systems provided with the necessary properties.

[0071] Figure 3 The example of FIG. 1 shows a portion of an exemplary radio access network.

[0072] Figure 3 User equipment 300 and 302 are shown configured to wirelessly connect to an access node (such as a gNodeB) 304 providing the cell over one or more communication channels in the cell. The physical link from the user equipment to the gNodeB is referred to as an uplink or reverse link, while the physical link from the gNodeB to the user equipment is referred to as a downlink or forward link. It should be understood that the gNodeB or its functionality may be implemented using any node suitable for such purpose (such as an integrated access and backhaul (IAB) node), host, server, or access point entity.

[0073] The communication system typically includes a plurality of gNodeBs, in which case the gNodeBs may also be configured to communicate with each other via wired or wireless links designed for this purpose. These links may be used for signaling purposes. A gNodeB is a computing device configured to control the radio resources of the communication system to which it is coupled. A NodeB may also be referred to as a base station, an access point, or any other type of interface device, including a relay station capable of operating in a wireless environment. The gNodeB includes or is coupled to a transceiver. From the transceiver of the gNodeB, a connection to an antenna unit is provided, which establishes a bidirectional radio link to a user device. The antenna unit may include a plurality of antennas or antenna elements. The gNodeB is also connected to a core network 310 (CN or next generation core NGC). Depending on the system, the counterpart on the CN side may be a service gateway (S-GW, routing and forwarding user data packets), a packet data network gateway (P-GW), for providing connectivity of a user equipment (UE) to an external packet data network, or a mobile management entity (MME), etc. The CN may include a network entity or node that may be referred to as a management entity. Examples of network entities include at least an access and mobility management function (AMF).

[0074] In 5G NR, the user plane function (UPF) can be used to separate the control plane and user plane functions. Among them, the packet gateway (PGW) control and user plane functions can be decoupled, so that the data forwarding component (PGW-U) can be decentralized, while the PGW-related signaling (PGW-C) remains in the core. This allows packet processing and service aggregation to be performed closer to the edge of the network, thereby improving bandwidth efficiency and reducing network load.

[0075] 5G supports the use of multiple-input multiple-output (MIMO) antennas, many more base stations or nodes than LTE (the so-called small cell concept), including macro sites operating in cooperation with smaller sites, and adopting various radio technologies depending on service requirements, use cases and / or available spectrum. The access nodes of the radio network form transmission / reception (TX / Rx) points (TRPs), and UEs are expected to access at least partially overlapping networks of multiple TRPs, such as macro cells, small cells, micro cells, femto cells, remote radio heads, relay nodes, etc. The access nodes can be provided with massive MIMO antennas, i.e. very large antenna arrays including, for example, hundreds of antenna elements, implemented in a single antenna panel or multiple antenna panels, capable of communicating with the UE using multiple simultaneous radio beams. The UE can be provided with a MIMO antenna with an antenna array including, for example, tens of antenna elements, implemented in a single antenna panel or multiple antenna panels. Thus, the UE can access one TRP using one beam, one TRP using multiple beams, multiple TRPs using one (common) beam, or multiple TRPs using multiple beams.

[0076] 4G / LTE networks support some multi-TRP schemes, but in 5G NR, the multi-TRP feature is enhanced, such as the transmission of multiple control signals via multiple TRPs, which can improve link diversity gain. In addition, high carrier frequencies (e.g., mmWaves) together with massive MIMO antennas require new beam management processes for multi-TRP technology.

[0077] 5G mobile communications support a wide range of use cases and related applications, including video streaming, augmented reality, different ways of sharing data and various forms of machine type applications (such as (massive) machine type communications (mMTC), including vehicle safety, different sensors and real-time control. 5G is expected to have multiple radio interfaces, namely sub-6GHz, cmWave and mmWave, and also be able to integrate with existing legacy radio access technologies (such as LTE). At least in the early stages, integration with LTE can be achieved as a system where macro coverage is provided by LTE and 5G radio interface access comes from small cells through aggregation to LTE. In other words, 5G is planned to support inter-RAT operability (such as LTE-5G) and inter-RI operability (inter-radio interface operability, such as sub-6GHz-cmWave, sub-6GHz-cmWave-mmWave). One of the concepts considered to be used in 5G networks is network slicing, in which multiple independent and dedicated virtual sub-networks (network instances) can be created within the same infrastructure to run services with different requirements for latency, reliability, throughput and mobility.

[0078] The frequency bands used for 5G NR are divided into two frequency ranges: Frequency Range 1 (FR1), which includes the sub-6 GHz bands, i.e. the bands traditionally used by previous standards, but also new bands extended to cover potential new spectrum products from 410 MHz to 7125 MHz, and Frequency Range 2 (FR2), which includes the bands from 24.25 GHz to 52.6 GHz. FR2 thus includes bands in the mmWave range, which, due to their shorter range and higher available bandwidth, require a slightly different approach in terms of radio resource management compared to bands in FR1.

[0079] The current architecture in LTE networks is fully distributed in the radio and fully centralized in the core network. Low-latency applications and services in 5G require bringing content close to the radio, giving rise to local breakthroughs and multi-access edge computing (MEC). 5G enables analysis and knowledge generation to be performed at the data source. This approach requires the use of resources that may not be continuously connected to the network, such as laptops, smartphones, tablets, and sensors. MEC provides a distributed computing environment for application and service hosting. It also enables the storage and processing of content close to cellular subscribers to accelerate response time. Edge computing covers a wide range of technologies such as wireless sensor networks, mobile data collection, mobile signature analysis, collaborative distributed peer-to-peer self-organizing networks and processing, and can also be categorized as local cloud / fog computing and grid / mesh computing, dew computing, mobile edge computing, thin cloud, distributed data storage and retrieval, autonomous self-healing networks, remote cloud services, augmented and virtual reality, data caching, Internet of Things (massive connectivity and / or latency critical), critical communications (autonomous vehicles, traffic safety, real-time analysis, time-critical control, healthcare applications).

[0080] The communication system may also be able to communicate with or utilize services provided by other networks, such as the public switched telephone network or the Internet 312. The communication network may also support the use of cloud services, for example, at least part of the core network operations may be performed as a cloud service (this is in the Figure 3 The communication system may also include a central control entity or the like to provide collaboration facilities for networks of different operators, for example, to collaborate in spectrum sharing.

[0081] Edge cloud can be brought into the radio access network (RAN) by leveraging network function virtualization (NFV) and software defined networking (SDN). Using edge cloud may mean that access node operations are at least partially performed in a server, host or node that is operationally coupled to a remote radio head or base station including radio components. Node operations may also be distributed among multiple servers, nodes or hosts. The application of cloudRAN architecture enables RAN real-time functions to be performed on the RAN side (in distributed units DU) and non-real-time functions to be performed in a centralized manner (in centralized units CU 308).

[0082] It should also be understood that the division of labor between core network operations and base station operations may be different from LTE or even non-existent. Some other technological advances that may be used are big data and all-IP, which may change the way networks are built and managed. 5G (or New Radio, NR) networks are being designed to support multiple hierarchical structures, where MEC servers can be placed between the core and the base station or Node B (gNB). It should be understood that MEC can also be applied to 4G networks. gNB is the next generation Node B (or new Node B) that supports 5G networks (i.e. NR).

[0083] 5G can also utilize non-terrestrial nodes 306 (e.g., access nodes) to enhance or supplement the coverage of 5G services, for example, by providing backhaul, wireless access to wireless devices, service continuity for machine-to-machine (M2M) communications, service continuity for Internet of Things (IoT) devices, service continuity for passengers on board, ensuring service availability for critical communications, and / or ensuring service availability for future railway / maritime / aviation communications. Non-terrestrial nodes can have a fixed position relative to the surface of the earth, or non-terrestrial nodes can be mobile non-terrestrial nodes that can move relative to the surface of the earth. Non-terrestrial nodes can include satellites and / or HAPS. Satellite communications can utilize geostationary orbit (GEO) satellite systems or low earth orbit (LEO) satellite systems, particularly giant constellations (systems in which hundreds of (nano) satellites are deployed). Each satellite in a giant constellation can cover multiple satellite-enabled network entities, which create ground cells. Ground cells can be created by ground relay nodes 304 or by gNBs located on the ground or in satellites.

[0084] It is understood by those skilled in the art that the depicted system is only an example of a part of a radio access system, and in practice the system may include multiple gNodeBs, a user equipment may access multiple radio cells, and the system may also include other devices, such as physical layer relay nodes or other network elements. At least one gNodeB may be a home gnodeB. In addition, in a geographical area of ​​the radio communication system, multiple different types of radio cells as well as multiple radio cells may be provided. A radio cell may be a macro cell (or umbrella cell), which is a large cell typically having a diameter of up to tens of kilometers, or a smaller cell, such as a micro, femto or pico cell. Figure 1 The gNodeB in the cellular radio system can provide any kind of these cells. The cellular radio system can be implemented as a multi-layer network including multiple cells. Usually, in a multi-layer network, one access node provides one or more cells, so multiple gNodeBs are needed to provide such a network structure.

[0085] The Radio Resource Control (RRC) protocol is used in various wireless communication systems to define the air interface between the UE and the base station (e.g., gNB). The protocol is specified by 3GPP in TS 36.331 for LTE and TS 38.331 for 5G. In terms of RRC, the UE can operate in idle mode or connected mode in LTE and 5G, where the radio resources available to the UE depend on the mode in which the UE is currently residing. In 5G, the UE can also operate in an inactive mode. In RRC idle mode, the UE has no connection for communication, but the UE is able to listen to paging messages. In RRC connected mode, the UE can operate in different states, such as CELL_DCH (dedicated channel), CELL_FACH (forward access channel), CELL_PCH (cell paging channel), and URA_PCH (URA paging channel). The UE can communicate with the gNB via various logical channels, such as broadcast control channel (BCCH), paging control channel (PCCH), common control channel (CCCH), dedicated control channel (DCCH), dedicated traffic channel (DTCH).

[0086] The transitions between states are controlled by the state machine of RRC. When the UE is powered on, it is in disconnected mode / idle mode. The UE can transition to RRC connected mode with initial connection or connection establishment. If the UE is inactive for a short period of time, the gNB can suspend its session by moving to RRC inactive mode and can resume its session by moving to RRC connected mode. The UE can move to RRC idle mode from RRC connected mode or RRC inactive mode.

[0087] The actual user and control data from the network to the UE is sent via downlink physical channels, which in 5G include the Physical Downlink Control Channel (PDCCH) carrying the necessary Downlink Control Information (DCI), the Physical Downlink Shared Channel (PDSCH) carrying user data and system information for users, and the Physical Broadcast Channel (PBCH) carrying the necessary system information that enables the UE to access the 5G network.

[0088] User and control data from the UE to the network are sent via uplink physical channels, which in 5G include physical uplink control channel (PUCCH), physical uplink shared channel (PUSCH) and physical random access channel (PRACH). The physical uplink control channel (PUCCH) is used for uplink control information, including HARQ (Hybrid Automatic Repeat Request) feedback confirmation, scheduling requests and downlink channel state information for link adaptation. The physical uplink shared channel (PUSCH) is used for uplink data transmission. The physical random access channel (PRACH) is used by the UE to request connection establishment, which is called random access.

[0089] Conditional Handover (CHO) is a feature supported in LTE and 5G NR. CHO is similar in many ways to the previously known "normal" handover (HO), i.e., traditional HO. Figure 4 An inter-MN handover with / without MN-initiated SN change according to the example given in TS137 340 V17.5.0 is shown. This inter-MN handover can be used to transfer UE context data from a source MN to a target MN, while the UE context at the SN is retained or moved to another SN. During the handover, the target MN decides whether to retain, change or release the SN.

[0090] At step 1, the source MN starts the handover process by initiating the Xn Handover Preparation process including both MCG and SCG configuration. The source MN includes the source SN UE XnAP ID, SN ID and UE context in the source SN in the Handover Request message.

[0091] At step 2, if the target MN decides to retain the UE context in the source SN, the target MN sends an SN Add Request to the SN, including the SN UE XnAP ID as a reference to the UE context established by the source MN in the SN. On the other hand, if the target MN decides to change the SN to allow incremental configuration, the target MN sends an SN Add Request to the target SN, including the UE context established by the source MN in the source SN. Otherwise, the target MN may send an SN Add Request to the target SN, including neither the SN UE XnAP ID nor the UE context established by the source MN in the source SN.

[0092] In the following, the expression (target) SN represents the original SN in the case where the target MN decides to retain the UE context in the source SN, or the new target SN in the case where the target MN decides not to retain the UE context in the source SN and selects another SN as the target SN. Similarly, the expression (source) SN represents the original SN in the case where the target MN decides to retain the UE context in the source SN, or the new target (and source) SN in the case where the target MN decides not to retain the UE context in the source SN and selects another SN as the target SN.

[0093] The (target) SN replies with a SN Add Request Ack at step 3. The (target) SN may include an indication of a complete or incremental RRC configuration.

[0094] At step 3a, for the SN terminated bearer using MCG resources, the target MN provides the Xn-U DL TNL address information in the Xn-U Address Indication message.

[0095] At step 4, the target MN includes the MNRRC reconfiguration message to be sent to the UE to perform the handover in the handover request confirmation message, and may also provide the forwarding address to the source MN. If PDU session splitting is performed on the target side during the handover process, multiple data forwarding addresses corresponding to each node are included in the handover request confirmation message. If the target MN and SN decide to retain the UE context in the SN in steps 2 and 3, the target MN indicates to the source MN that the UE context in the SN is retained.

[0096] At step 5a / 5b, the source MN sends an SN release request message to the (source) SN, including a reason indicating MCG mobility. The (source) SN acknowledges the release request. If the source MN receives an indication from the target MN, it indicates to the (source) SN that the UE context in the SN is retained. If an indication as to the UE context to be retained in the SN is included, the SN retains the UE context.

[0097] At step 5c, the source MN sends an XN-U address indication message to the (source) SN to convey data forwarding information. If the PDU session is split on the target side, multiple data forwarding addresses may be provided.

[0098] At step 6, the source MN triggers the UE to perform handover and apply the new configuration.

[0099] At step 7 / 8, the UE synchronizes to the target MN and replies with a MN RRC Reconfiguration Complete message.

[0100] At step 9, if configured with bearers requiring SCG radio resources, the UE synchronizes to the (target) SN.

[0101] It should be noted that the order in which the UE performs the random access procedure to the MN (step 7) and performs the random access procedure to the SN (step 9) is not limited.

[0102] At step 10, if the RRC connection reconfiguration procedure is successful, the target MN notifies the (target) SN via an SN reconfiguration complete message.

[0103] At step 11a, the source SN sends a Secondary RAT Data Usage Report message to the source MN and includes the amount of data transmitted to and received from the UE over the NR / E-UTRA radio, as described in clause 10.11.2. The order in which the source SN sends the Secondary RAT Data Usage Report message and performs data forwarding with the MN / target SN is not defined. The SN may send a report when the transmission of the relevant QoS is stopped.

[0104] At step 11b, the source MN sends a Secondary RAT Report message to the AMF to provide information about the used NR / EUTRA resources.

[0105] At step 12, for bearers using RLC AM, the source MN sends an SN status transfer to the target MN, including the SN status received from the source SN if necessary. The target forwards the SN status to the target SN if necessary.

[0106] At step 13, data forwarding is performed from the source side if applicable. If the SN is retained, data forwarding may be omitted for SN terminated bearers or QoS flows retained in the SN.

[0107] At steps 14 to 17, the target MN initiates a path switch procedure. If the target MN includes multiple DL TEIDs for one PDU session in the Path Switch Request message, then in the case of a TEID update in the UPF, multiple UL TEIDs of the UPF for the PDU session should be included in the Path Switch Ack message. If new UL TEIDs for the UPF of the SN are included, the target MN performs a MN-initiated SN modification procedure to provide them to the SN.

[0108] At step 18, the target MN initiates a UE context release procedure to the source MN.

[0109] At step 19, upon receipt of the UE Context Release message from the source MN, the (source) SN releases the C-Plane related resources associated with the UE context to the source MN. Any ongoing data forwarding may continue. If the UE Contention Retention Indication is included in the SN Release Request message in step 5, the SN shall not release the UE context associated with the target MN.

[0110] Dual Connectivity (DC) is a feature supported in LTE and 5G NR that enables aggregation of two radio links at the PDCP (Packet Data Convergence Protocol) layer level. For resource aggregation, a UE in RRC_CONNECTED state is assigned two radio links from two different network nodes, which may be connected via a non-ideal backhaul. The first node, the master node (MN), serves as a mobility and signaling anchor, and the second node, the secondary node (SN), provides additional local radio resources for the UE. These two resource sets are called the primary cell group (MCG, associated with the MN) and the secondary cell group (SCG, associated with the SN). The MN can be an LTE eNB or an NR gNB. The SN can be an LTE eNB or an NR gNB. The MN and the SN can be the same node.

[0111] Dual connectivity can improve user throughput and mobility robustness because users can be connected to both MCG and SCG simultaneously, and improve load balancing between MCG and SCG resources.

[0112] CHO has been specified for UEs configured with dual connectivity. Here, the source MN node (controlling the primary cell, PCell) sends a handover request to the target MN node (controlling the target PCell), which in turn selects a secondary node (controlling the target PSCell) and prepares it as part of the CHO preparation. When the CHO execution conditions are met, the UE performs access to the target PCell and PSCell.

[0113] Hereinafter, several embodiments will be described.

[0114] Figure 5 A signaling diagram according to an example embodiment is shown. In this example, there are two target MNs, namely target MN 1 and target MN 2, but in actual implementation, the number of target MNs participating in CHO may not be two, for example, more than two. At step 501, the UE indicates the fast PSCell access capability to the serving RAN node. The fast PSCell access capability is used as a hint by the RAN node to initiate a procedure on the network side to successfully achieve fast PSCell access. In particular, the procedure needs to be known on the target SN side, so the capability indication goes from the source MN to the target MN, and from the target MN to the target SN.

[0115] At steps 502 to 506, once the UE sends a measurement report to trigger a dual connectivity handover (CHO), the source MN includes the capability in the CHO request, and further, the target MN includes the capability in the SN add request message. For each CHO request, the target SN receives a different SN security key, because the SN key depends on the MN key, and each target MN will have its own MN key.

[0116] At step 507, the target SN uses the fast PSCell access capability information to determine whether to trigger a fast PSCell access procedure for the UE.

[0117] At step 508, the target SN and the target MN reply to the source SN, and the source SN configures the UE with CHO configuration. During this process, the UE may receive two CHO configurations, one CHO for the first target MN (T-MN1) and the other CHO for the second target MN (T-MN2), where each CHO configuration will contain the SCG configuration for the same T-SN. As described in the previous section, the T-SN SCG configurations in both CHO configurations will contain the same CFRA resources configured for the UE. Early data forwarding begins, and after initial preparation, data will be sent from the source to the candidate cell using early data forwarding.

[0118] Early data forwarding is done with respect to target bearer configuration. In early data forwarding, the target SN terminates the bearer flow to the target SN, and the target MN terminates the bearer flow to the target MN. This is achieved by configuring the TEID of the T-SN for the target SN terminated bearer.

[0119] According to an embodiment, the source MN may forward a copy of all DL data to the first target MN1 and another copy of all DL data to the second target MN2. Once the conditional handover to the first target MN1 or the second target MN2 is completed, the buffered DL data will be used for DL ​​data transmission from the first target MN1 and / or the second target MN2 to the UE.

[0120] Possibly, the first target MN1 may decide the splitting of DL data between the first target MN1 and the target SN. Typically, DL data may be forwarded to the target MN, then split, and a portion of the data may be forwarded to the target SN. However, during early data forwarding, the target MN does not speak directly. The network may use direct data forwarding using the TEID of the target SN, or may use indirect data forwarding, where the data first goes to the target MN, and the target MN forwards the data to the target SN. Therefore, at step 508, the source MN knows the different data splittings, and forwards a copy of the first split to the first target MN1, forwards the second split to the target SN, forwards the third split to the second target MN2, and forwards the fourth split to the target SN. The target SN buffers the second and fourth splits until step 515, and uses the second split, for example, if the first target MN1 is detected. Then, at step 516, communication with the UE is started, and the UE receives DL data from the source MN, and in parallel receives part of the DL data from the target SN.

[0121] At step 509, the CHO configuration for the first target MN1 and the target SN is maintained, and the UE initiates a CHO execution.

[0122] At step 510, the PRACH opportunity for the target PSCell occurs first, so the UE sends a preamble to the target PSCell while waiting to send a preamble to the target PCell.

[0123] At steps 511 and 512, the target SN determines to send a random access response because the fast PSCell access procedure will be used to resolve security key ambiguity.

[0124] According to an embodiment, the RRCReconfiguration Complete may be sent to the target MN only after step 512, since there may be no signaling bearer to the target SN. Therefore, the user plane communication will start towards the target SN.

[0125] At step 513, the UE sends a PUSCH message with the resources allocated in the RAR message. At the time of preparation, the uplink TEID towards the user plane function is known. In addition, after successful decoding of the UE PUSCH packet, the selected target MN will be known. Therefore, the data can be forwarded to the correct target MN. Since the CHO condition holds for the first target MN1, the UE uses the SN key corresponding to the first target MN1 CHO configuration.

[0126] At step 514, the target SN employs blind decoding of the PUSCH message using the SN key generated using the keys of the first target MN1 and the second target MN2.

[0127] At step 515, the target SN successfully decodes the PUSCH message using the SN key generated using the key of the first target MN1.

[0128] At step 516, a reply is sent to the UE and communication through the target SN can begin.

[0129] At step 517: At preparation time, the UL TEID towards the UPF is known. In addition, after successful decoding of the UE PUSCH packet, the selected target MN will be known. Therefore, the data can be forwarded to the correct target MN.

[0130] At steps 518 to 521, access to the target PCell is completed simultaneously, and an RRCReconfiguration Complete is sent to the target MN and the target SN.

[0131] Figure 6 FIG. 4 shows a signaling diagram according to another example embodiment, in which a delayed CFRA response is utilized. Figure 5 Similar to the embodiment of , the UE indicates the fast PSCell access capability to the serving RAN node at step 601. The fast PSCell access capability is used as a hint by the RAN node to initiate a procedure on the network side to successfully achieve fast PSCell access. In particular, the procedure needs to be known on the target SN side, so the capability indication goes from the source MN to the target MN, and from the target MN to the target SN.

[0132] Once the UE sends a measurement report to trigger dual connectivity handover (CHO) at step 602 , the source MN includes this capability in a CHO request at step 603 , and furthermore, the target MN includes this capability in an SN add request message and sends it to the target SN at step 604 .

[0133] The target MN also configures a RAR timer, allowing enough time for the RAR timer of the target SN. For example, if the maximum value of the target SN RAR timer is 1000ms, the target MN RAR timer should be less than the maximum value (i.e., less than 1000ms) to allow the target SN to send a RAR after the successful completion of the RA procedure in the target MN. Alternatively, the target MN configures a RAR window and indicates it to the target SN in the SN Add Request, and then the target SN will configure a RAR window large enough for the UE to combine with the MNRAR duration.

[0134] At step 605, the target SN uses the received information to determine to trigger an enhanced random access procedure for the UE. In addition, the target SN configures an extended RAR timer, taking into account the RAR timer configured by the PCell.

[0135] The target MN will know the target SN RAR window and the target MN can allocate the RAR window with respect to what the target SN has allocated. This will allow the UE to complete the MN RAR procedure in a timely manner.

[0136] At step 606, the target SN and target MN reply to the source, and the source configures the UE using the CHO configuration.

[0137] The CHO configuration for the first target MN1 and the target SN is maintained, and the UE initiates a CHO execution at step 607 .

[0138] The PRACH opportunity for the target PSCell (target SN) occurs first, so the UE sends a preamble to the target PSCell at step 608 while waiting until a preamble is sent to the target PCell (first target MN1).

[0139] At step 609, the target SN determines to wait to send a random access response because the UE is configured with an extended RAR timer.

[0140] Meanwhile, in steps 610 to 612, access to the target Pcell is completed, and an RRC Reconfiguration Complete message is sent to the first target MN1 and the target SN.

[0141] At step 613, communication through the target MN may begin.

[0142] At step 614, the target SN initiates a RAR after receiving the RRC Reconfiguration Complete message from the first target MN1.

[0143] At step 615, the target SN sends a RAR to the UE.

[0144] At step 616, the UE sends a PUSCH message with the resources allocated in the RAR message.

[0145] At step 617, the target SN successfully decodes the PUSCH message using the SN key generated using the key of MN1. An acknowledgement is sent to the UE and communication on the target SN can start at step 618.

[0146] If the UE is capable of working with different RAR windows, e.g. RAR windows for source MN, source SN, target MN and target SN, then a cell group specific RACH configuration may be used, e.g. RA-responseWindow is a parameter configured there. An example of such a configuration is as follows:

[0147] ra-ResponseWindow ENUMERATED{sl1,sl2,sl4,sl8,sl10,sl20,sl40,sl80}

[0148] An embodiment includes assigning one RA window that is large enough to cover both the RAR windows of the first target MN1 and the second target MN2 via, for example, the target SN.

[0149] According to an embodiment, when the target SN receives a second SN add request from a second target MN, but for the same UE, an extended RAR window is assigned and then used at step 509, the value of the extended RAR window should be selected to be larger than the RAR windows of the first target MN1, the second target MN2 and the target SN.

[0150] It should be noted that the UE will not access both the first target MN1 and the second target MN2 at the same time. It will select one of them.

[0151] At step 506, the extended RAR window value is communicated to the UE, so the UE will be able to wait longer than usual for the RAR at step 514, but in case of failure, the UE may need to resend the RACH preamble, which will then be delayed.

[0152] Without the extended RAR window, if the PCell access is not completed within the RAR window, the PSCell access towards the target SN will fail because the UE cannot receive the RAR within the RAR window.

[0153] Figure 7 A signaling diagram according to yet another example embodiment is shown.At step 701, the UE is constrained by RAN4 requirements not to initiate PSCell access unless PCell access is completed during dual connectivity handover for CHO with multiple candidate SCGs.

[0154] At step 702, the UE sends a measurement report to the source MN to trigger a dual connectivity handover (CHO). Then, at step 703, the source MN includes the capability in a CHO request and sends it to the first target MN1.

[0155] At step 704, the target MN sends an SN add request to the target SN to maintain dual connectivity for the UE.

[0156] At step 705, the target SN and the target MN reply to the source MN, and the source MN configures the CHO configuration for the UE.

[0157] At step 706, the CHO configuration for the target MN1 and the target SN is maintained, and the UE initiates a CHO execution.

[0158] Now assume that the PRACH opportunity for the target PSCell occurs first. Therefore, even in this case, the UE cannot initiate access to the PSCell due to restrictions, so at step 707, the UE waits for the random access procedure of the PCell to be completed before initiating random access to the PSCell.

[0159] At the same time, access to the target PCell is completed. This may have been completed so that at step 708, the UE sends a preamble to the target Pcell, and at step 709, the target Pcell replies by sending a RAR to the UE. At step 710, an RRCReconfiguration Complete message is sent from the UE to the target MN and to the target SN.

[0160] After sending the RRCREconfiguration complete message to the target SN, communication through the target MN can start at step 711, and the UE determines that the Pcell access is completed and initiates the PSCell access procedure at step 712. In other words, once the UE is able to send RRCREconfigurationComplete to the PCell, after the successful confirmation of RRCREconfigurationcomplete, the UE will send a preamble to the PSCell.

[0161] At step 713, the UE sends a preamble to the target PSCell.

[0162] At step 714, the target SN sends a random access response to the UE.

[0163] At step 715, the UE sends a PUSCH message with the resources allocated in the RAR message to the target PSCell.

[0164] In the following, another embodiment will be referred to Figure 8a (shown as a signaling diagram based on the CFRA process) and Figure 8b (Signaling diagram shown as a CBRA process-based) is described. It is assumed that the UE is able to synchronize with the target PCell and the target PSCell in parallel. The random access procedures to the target PCell and the target PSCell can be performed in parallel. It is also assumed that the CHO / CPC condition holds for both the target PCell and the target PSCell. Before the target PCell is ready (i.e., CHO has not been successfully completed), parallel synchronization with the target PCell and the target PSCell is started, and the random access procedure to the target PSCell is completed.

[0165] At steps 801 to 804, the UE declares that it can perform concurrent access to the target PCell and to the target PSCell. The information is propagated to the target MN1 in a CHO request and then to the target SN in a SN add request.

[0166] At step 805, the target PSCell shall assign resources in the usual way, but it shall indicate to the PDCP (E1AP) that DL traffic shall be suspended. No ciphering or integrity protection shall be applied. PDCP PDUs shall not be forwarded to lower layers (RLC) for transmission, but shall be buffered. A discard timer shall not be started. The target PSCell shall instruct the MAC (F1AP) to avoid UL scheduling (except for UL scheduling related to the RA procedure, i.e. RAR and - in case of CBRA - UL DCI related to the completion of the contention resolution procedure), including ignoring positive SRI transmissions from the UE. The target PSCell shall instruct the RLC (F1AP) that UL traffic shall not be forwarded to higher layers (PDCP) for further processing and buffering.

[0167] At step 806 , the UE configures the CHO configuration in a conventional manner (target MN+target SN) and starts early data forwarding, as shown in steps 807 and 808 .

[0168] At step 807, possible downlink data may be transmitted for the target MN1 terminated bearer, and at step 808, downlink data may be transmitted for the target SN terminated bearer.

[0169] exist Figure 5 At step 513, PUSCH is sent to initiate user plane communication.

[0170] Figure 5The point is to try to decode any PUSCH received via all configured keys, e.g. all target MNs prepared for a specific target SN. At the time of preparation, the UL TEID towards the UPF is known. Additionally, upon successful decoding of the UE PUSCH packet, the selected target MN will be known.

[0171] The UE starts the CHO evaluation phase. At some point in time, it appears that the CHO conditions hold for the target MN1 and the target SN (step 809).

[0172] At steps 810 and 813, the UE performs a random access procedure for the target MN (target PCell). Figure 8a and Figure 8b In the example of FIG. 5 , the random access procedure for the target MN lasts longer than the random access procedure started in parallel by the UE for the target SN (target PSCell).

[0173] The steps at 811 (811.1 to 811.6) illustrate options for the CFRA process.

[0174] At steps 811.1 to 811.2, the UE sends a preamble to the target SN through the PRACH and successfully receives the RAR from the target SN.

[0175] At step 811.3, from the perspective of both the UE and the target SN (target PSCell), the random access procedure has been successfully completed.

[0176] At step 811.4, any downlink (DL) traffic present at the PDCP level is buffered as configured in step 805.

[0177] At step 811.5, the UE sends the traffic using the RAR grant, but the traffic still remains buffered at the RLC level as configured in step 805. It should be noted that the MAC should confirm the transmission by sending a TBS 0 grant for the same HARQ process. It should also be noted that the RLC should be ready for ARQ status transmission if requested, and the ARQ status is allowed to be sent. However, PUCCH transmissions should also be allowed, but positive SRI transmissions should be ignored.

[0178] At step 813, the random access procedure at the target MN (target PCell) is successfully completed. At step 814, the UE sends an RRCReconfigurationComplete message to the target PCell, in which the SN-specific RRCReconfigurationComplete message is embedded, which is forwarded by the target MN to the target SN (target PSCell). This indicates that the PSCell change completion procedure can be started.

[0179] At step 815, the target PSCell shall indicate to the MAC (F1AP) that UL scheduling shall be unblocked and positive SRI transmission shall be processed normally. The target PSCell shall indicate to the RLC (F1AP) that UL traffic shall be processed normally. Forwarding to higher layers (PDCP) is allowed.

[0180] At step 816, the target PSCell indicates to the PDCP (E1AP) that the DL traffic should be handled normally (once the security context is known). A discard timer should be started. The PDCP should be allowed to forward the data to the lower layers (RLC) for transmission.

[0181] Next, the CBRA process will refer to Figure 8b is described, especially the steps at 812 (812.1 to 812.8). Steps 801 to 810 are similar to Figure 8a 801 to 810 of the CFRA option shown in , so the description of these steps is omitted here.

[0182] At steps 812.1 and 812.2, the UE sends a preamble to the target SN through the PRACH and successfully receives the RAR from the target SN.

[0183] At steps 812.3 and 812.4, the UE sends a C-RNTI MCE to the target SN using the RAR grant and receives a UL DCI scrambled with its own C-RNTI from the target SN.

[0184] At step 812.5, from the perspective of the UE and the target SN (target PSCell), the random access procedure has been completed.

[0185] At step 812 . 6 , DL traffic that may occur at the PDCP level is buffered as configured in step 805 .

[0186] At step 812.7, the UE sends traffic using the uplink (UL) DCI associated with the contention resolution completion, but the traffic remains buffered (step 812.8) at the RLC level as configured in step 805. It should be noted that the MAC should confirm the transmission by sending a TBS 0 grant for the same HARQ process, and the RLC should be ready for ARQ status transmission if requested (ARQ status is allowed to be sent). However, PUCCH transmissions should also be allowed, but positive SRI transmissions should be ignored.

[0187] Now, the process ends with Figure 8a The CFRA option continues in the same manner at step 813.

[0188] In another solution with additional security procedures on the target SN side, such as Fig. 9 As shown, at step 901, the UE is configured with a signaling radio bearer 3 (SRB3), which is implemented for specific RRC messages when the UE is in EN-DC (E-UTRAN New Radio Dual Connectivity), all using the DCCH logical channel for dual connectivity handover operations. During SRB3 configuration, the UE can be assigned a separate (e.g., third) identification key by the target SN.

[0189] At step 904, the UE sends a preamble to the target PCell, and at step 905, the target PCell replies by sending a RAR to the UE.

[0190] At step 906, the configuration of SRB3 allows the UE to directly send a security identification message to the target SN to resolve the security issue. The security identification may be an SN RRCReconfiguration Complete message. The message may be a relatively lightweight message carrying an encrypted UE identification message.

[0191] The UE sends this indication as a result of successful application of the target RRCreconfiguration. Otherwise, it avoids this indication. If it has been allocated, the target SN can use the third identification key to decode the security identification message from the UE, or the target SN should use blind decoding using the key allocated on the target MN1 and the target MN2 (step 907).

[0192] Thereafter, SN link communication may begin (step 908), and the UE may experience a shorter interruption time compared to sequential access.

[0193] At step 909, the UE sends a preamble to the target PSCell.

[0194] At step 910, the target SN sends a random access response to the UE.

[0195] At step 911, an RRCReconfiguration Complete message is sent from the UE to the target MN1 and the target SN.

[0196] According to an embodiment, the method for conditional switching will refer to Fig.10a and Fig.10b A flow chart is described.

[0197] According to an embodiment, in response to receiving an indication that the secondary node does not support blind or parallel decoding or stops user plane transmission of the user equipment, or if the user equipment cannot be configured with SRB3 for security indication, the conditional handover capability is disabled.

[0198] According to an embodiment, the security indication may be sent to the target secondary node using a security key from the user equipment, wherein the security indication is a secondary node key or a specific key used for identification purposes.

[0199] According to an embodiment, UE capabilities may be enabled by a serving network node (e.g., a master node), for example, by being included in a conditional handover configuration, and for example based on feedback from (multiple) target master nodes and / or secondary nodes. For example, the secondary node may not support blind / parallel decoding, so if the UE supports fast SN access, but the network does not, the UE may be remotely configured to complete access to the target master node before accessing the SN. This may be by the network's default configuration, or by disabling the UE capabilities, for example, through information included in the CHO configuration. Therefore, the RACH preamble and RAR message may be optional, for example, in the case where timing advance information is already available in the UE, access may start from RRCReconfigComplete or PUSCH, or other". In this context, the term "fast access" means, for example, that access to the target SN and start of data communication may occur before access to the target MN by the UE.

[0200] Fig.10a The flowchart reflects the operation of the UE, and Fig.10b The flowchart reflects the operation of the target SN (such as gNB).

[0201] At a UE, the method includes indicating (1000) a conditional switching capability to a serving random access network node; in response to receiving a conditional switching configuration for a primary cell of a first target primary node and a primary cell of a first secondary node, and another conditional switching configuration for a primary cell of a second target primary node and a primary secondary cell of the first secondary node; initiating (1002) conditional switching execution when the conditional switching configuration for a specific target primary node and a target secondary node is maintained; and, if the capability is enabled, accessing (1004) the primary cell of a target secondary node before or in parallel with accessing the primary cell of the specific target primary node.

[0202] At a target secondary node of a radio access network, the method includes, in response to receiving a first secondary node add request for a user device from a first target primary node, sending (1020) a response to the first target primary node based on the received first request; in response to receiving a second secondary node add request for the same user device from a second target primary node, sending (1022) a response to the second target primary node based on the received second request; and in response to receiving a physical uplink shared channel message from the user device, in the absence of information as to whether the user device accesses the first target primary node or the second target primary node is available, enabling (1024) decoding of the physical uplink shared channel message received from the user device based on a first target primary node key associated with the first target primary node, and if (1026) decoding of the first key is unsuccessful, then based on a second target primary node key associated with the second target primary node (1028).

[0203] The method and its related embodiments may also be implemented in an apparatus implementing an access point or base station (such as an eNB or gNB) of a radio access network. According to one aspect, an apparatus, such as a gNB, includes a component for receiving requests from a plurality of master nodes, the plurality of master nodes being included as secondary nodes added as part of a conditional handover process for a user equipment; a component for obtaining an identification of a user equipment involved in the conditional handover process from each of the requests; and a component for determining, based on the identification of the user equipment, that the plurality of requests are about the same user equipment.

[0204] Such means may include, for example Fig. 9 The functional unit disclosed in Fig. 9 1 shows a simplified block diagram of a network node (ie, an apparatus) according to aspects and related embodiments. It should be noted that, although the above embodiments are mainly disclosed in conjunction with a target secondary node (SN), Fig. 9 The structures and functional units disclosed in are also applicable to network nodes, such as the source MN, source SN and target MN described above.

[0205] The network node 1100 may be a base station, an access point, an access node, a gNB, an evolved NodeB (eNB), a server, a host, or any other network entity that may communicate with a UE.

[0206] The apparatus may include at least one processor or control unit or module 1102. At least one memory 1104 may be provided in the apparatus. The memory may include computer program instructions or computer code included therein. One or more transceivers 1106 may be provided, and the apparatus may also include antennas 1108, although only one antenna is shown per device, many antennas and multiple antenna elements may be provided to the device. For example, other configurations of the apparatus may be provided. For example, in addition to wireless communication, the network node may also be configured for wired communication with the UE, and in this case, the antenna 1108 may show any form of communication hardware, not limited to just an antenna.

[0207] The transceiver 1106 may be a transmitter, a receiver, or both a transmitter and a receiver, or may be configured as a unit or device for both transmission and reception. The transmitter and / or receiver (in terms of radio components) may also be implemented as a remote radio head, which is not located in the device itself, but is located in, for example, a mast. Operations and functions may be performed in different entities (such as nodes, hosts, or servers) in a flexible manner. In other words, the division of labor may vary from case to case. One possible use is to enable a network node to deliver local content. One or more functions may also be implemented as (multiple) virtual applications in software that can run on a server.

[0208] In some embodiments, the apparatus may include at least one processor and at least one memory including computer program code. The at least one memory including the computer program code may be configured to, together with the at least one processor, cause the apparatus to at least perform any of the processes described herein.

[0209] The processor 1102 may be embodied by any computing or data processing device, such as a central processing unit (CPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a programmable logic device (PLD), a field programmable gate array (FPGA), a digital enhancement circuit, or the like, or a combination thereof. The processor may be implemented as a single controller, or multiple controllers or processors.

[0210] For firmware or software, the implementation may include modules or units (e.g., processes, functions, etc.) of at least one chipset. At least one memory 1104 may independently be any suitable storage device, such as a non-transitory computer-readable medium. A hard disk drive (HDD), random access memory (RAM), flash memory, or other suitable memory may be used. The memory may be combined with the processor on a single integrated circuit or may be separate from the processor. In addition, computer program instructions may be stored in the memory, and they may be processed by the processor, and may be computer program code in any suitable form, such as a compiled or interpreted computer program written in any suitable programming language. The memory or data storage entity is typically internal, but may also be external, or a combination of the two, such as in the case of obtaining additional memory capacity from a service provider. The memory may be fixed or removable.

[0211] The memory and computer program instructions can be configured together with a processor for a specific device to enable a hardware device (such as network node 1100) to perform any of the above processes. Therefore, in some embodiments, a non-transitory computer-readable medium may be encoded with instructions or one or more computer programs (such as added or updated software routines, applets or macros) that can perform a process such as one of the processes described herein when executed in hardware. In other embodiments, a computer program product can encode instructions for performing any of the above processes, or a computer program product and encoded instructions embodied in a non-transitory computer-readable medium that perform any of the above processes when executed in hardware. The computer program can be encoded in a programming language, which can be a high-level programming language such as Objective-C, C, C++, C#, Java, etc., or a low-level programming language such as machine language or assembly language. Alternatively, some embodiments can be executed entirely in hardware.

[0212] According to one embodiment, a computer program includes instructions stored thereon for causing a device to perform at least the following items: receiving an add request from a target master node, the add request having an indication that the request involves a conditional switch, the request including an identifier of a user equipment and an identifier of a source master node; using the identifier of the user equipment and the identifier of the source master node to check whether the device has a control target primary cell prepared for the user equipment; comparing an existing secondary group configuration with the secondary group configuration included in the request; verifying based on the comparison that the same data radio bearer can be allocated for the add request; and responding to the request using an identifier of a tunnel endpoint for downlink data forwarding that has been allocated for a previous add request.

[0213] According to an embodiment, the computer program includes instructions stored thereon for causing the device to perform at least the following items: receiving a tunnel endpoint identifier of the first target master node and a first target tunnel endpoint identifier from a first target master node; receiving a tunnel endpoint identifier of the second target master node and a second target tunnel endpoint identifier from a second target master node; determining that the first target tunnel endpoint identifier and the second target tunnel endpoint identifier correspond to each other; and deciding to send data addressed to a target secondary node only via one of the first target master node and the second target master node.

[0214] According to an embodiment, the computer program includes instructions stored thereon for causing the device to perform at least the following items: sending an add request related to conditional switching to a target secondary node, the add request including information about the requested secondary cell group bearer configuration and information about the identity of the user equipment; receiving an add request confirmation from the target secondary node, the add request confirmation including the secondary cell group configuration and an indication that an identifier of a tunnel endpoint allocated by the target secondary node for downlink data is shared with another target primary node; deciding to use indirect data forwarding based on the indication; and sending an identifier of the tunnel endpoint of the device and a shared identifier of the tunnel endpoint allocated by the target secondary node for downlink data to a source primary node.

[0215] In some embodiments, the device may include a circuit system configured to perform any of the above-described processes or functions. In one example, the circuit system may be a hardware circuit implementation only, such as an analog and / or digital circuit system. In another example, the circuit system may be a combination of hardware circuits and software, such as a combination of (multiple) analog and / or digital hardware circuits with software or firmware, and / or a combination of any part of (multiple) hardware processors with software (including (multiple) digital signal processors), software, and at least one memory, which work together to enable the device to perform various processes or functions. In yet another example, the circuit system may be (multiple) hardware circuits and / or (multiple) processors, such as (multiple) microprocessors or parts of (multiple) microprocessors, which include software for operation, such as firmware. When the operation of the hardware does not require software, the software in the circuit system may not exist.

[0216] Specific examples of circuit systems may be content encoding circuit systems, content decoding circuit systems, processing circuit systems, image generation circuit systems, data analysis circuit systems, or discrete circuit systems. The term circuit system may also refer to, for example, a baseband integrated circuit or a processor integrated circuit for a mobile device, a network entity, or a similar integrated circuit in a server, a cellular network device, or other computing or network equipment.

[0217] On the other hand, it relates to a computer program product stored on a non-transitory storage medium, which includes computer program code, which, when executed by at least one processor, causes the device to at least perform: receiving requests from multiple master nodes to be added as secondary nodes as part of a conditional switching process for a user device; obtaining an identification of the user device involved in the conditional switching process from each of the requests; and determining that multiple requests involve the same user device based on the identification of the user device.

[0218] In general, various embodiments of the present invention may be implemented in hardware or dedicated circuits, or any combination thereof. Although various aspects of the present invention may be illustrated and described in block diagrams or using some other graphical representations, it is well understood that, as non-limiting examples, these blocks, devices, systems, techniques, or methods described herein may be implemented in hardware, software, firmware, dedicated circuits or logic, general purpose hardware or controllers or other computing devices, or some combination thereof.

[0219] Embodiments of the present invention may be practiced in various components, such as integrated circuit modules. The design of integrated circuits is generally a highly automated process. Complex and powerful software tools are available to convert a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

[0220] Programs such as those offered by Synopsys Inc., Mountain View, Calif., and Cadence Design Inc., San Jose, Calif., use well-established design rules and a library of pre-stored design blocks to automatically route conductors and position components on a semiconductor chip. Once the design for a semiconductor circuit has been completed, the final design in a standardized electronic format (e.g., Opus, GDSII, etc.) can be sent to a semiconductor manufacturing plant or "fab" for fabrication.

[0221] The foregoing description provides a complete and informative description of exemplary embodiments of the present invention by way of exemplary and non-limiting examples. However, various modifications and alterations will become apparent to those skilled in the relevant art when the foregoing description is read in conjunction with the accompanying drawings and the accompanying examples. However, all such and similar modifications to the teachings of the present invention will still fall within the scope of the present invention.

Claims

1. A user equipment, comprising at least one processor and at least one memory, wherein the at least one memory stores computer program code, wherein the at least one memory and the computer program code are configured to, together with the at least one processor, cause the user equipment to at least execute: Indicating a conditional switching capability to a serving network node, wherein the capability includes information on whether the user equipment supports accessing a primary cell of a secondary cell group of a target secondary node before or in parallel with accessing a primary cell of a target primary node; In response to receiving a conditional handover configuration for a primary cell of a first target primary node and a primary cell of a first secondary node; When the conditional switching configuration for the specific target primary node and the target secondary node is maintained, initiating conditional switching execution; as well as In case the capability is enabled, the primary cell of the target secondary node is accessed before or in parallel with accessing the primary cell of the specific target primary node.

2. The user equipment according to claim 1, comprising computer program code configured to cause the user equipment to execute: In response to receiving the conditional handover configuration for the primary cell of the first target primary node and the primary cell of the first secondary node and another conditional handover configuration for the primary cell of the second target primary node and the primary and secondary cells of the first secondary node, conditional handover execution is initiated.

3. The user equipment according to claim 1 or 2, comprising computer program code configured to cause the user equipment to execute: The conditional handover capability is enabled based on an indication in a conditional handover configuration received from a serving network node, the indication based in part on an indication of support for fast access to a primary cell of a secondary cell group from one or more target primary or secondary nodes.

4. The user equipment according to claim 3, comprising computer program code configured to cause the user equipment to execute: disabling the conditional switching capability in response to receiving an indication that the secondary node does not support: Blind decoding or parallel decoding, or stopping user plane transmission of the user equipment, or The user equipment cannot be configured with a signalling radio bearer 3 for security indication.

5. The user equipment according to claim 4, comprising computer program code configured to cause the user equipment to execute: Before accessing the secondary node, first complete access to the target primary node.

6. The user equipment according to any one of claims 1 to 5, comprising computer program code configured to cause the user equipment to execute: While waiting to send the preamble to the target primary node, sending the preamble to the target secondary node; receiving a random access response from the target secondary node; sending a physical uplink shared channel message having resources allocated in the random access response message; and Use the secondary node key that corresponds to the corresponding target primary node configuration.

7. The user equipment according to any one of claims 1 to 5, comprising computer program code configured to cause the user equipment to execute: Send a security indication to the target secondary node using a security key, wherein the security indication is Secondary node key or A specific key used for identification purposes.

8. The user equipment according to any one of claims 1 to 7, comprising computer program code configured to cause the user equipment to execute: A determination is made based on the capability whether a conditional switching capability is enabled.

9. The user equipment according to claim 8, comprising computer program code configured to cause the user equipment to execute: In response to the determination, access to the primary node and the secondary node is completed in parallel using the conditional switching capability, or access to the primary node is completed first before accessing the secondary node.

10. A method for communication, comprising: Indicating a conditional switching capability to a serving network node, wherein the capability includes information on whether a user equipment supports accessing a primary cell of a target secondary node before accessing a primary cell of a secondary cell group of the target primary node or in parallel with accessing the primary cell of the secondary cell group of the target primary node; In response to receiving a conditional handover configuration for a primary cell of a first target primary node and a primary cell of a first secondary node; When the conditional switching configuration for the specific target primary node and the target secondary node is maintained, initiating conditional switching execution; as well as In case the capability is enabled, the primary cell of the target secondary node is accessed before or in parallel with accessing the primary cell of the specific target primary node.

11. A network node for a radio access network, the network node comprising at least one processor and at least one memory, the at least one memory having computer program code stored thereon, the at least one memory and the computer program code being configured to, together with the at least one processor, cause the network node to at least perform: In response to receiving a first secondary node adding request for a user equipment from a first target master node, sending a response to the first target master node based on the received first request; In response to receiving a second secondary node adding request for the same user equipment from a second target master node, sending a response to the second target master node based on the received second request; as well as In response to receiving a physical uplink shared channel message from the user equipment, in the absence of information available that the user equipment has access to a first target master node or a second target master node, decoding of the physical uplink shared channel message received from the user equipment is enabled based on a first target master node key associated with the first target master node, and if decoding of the first key is unsuccessful, decoding of the physical uplink shared channel message received from the user equipment is enabled based on a second target master node key associated with the second target master node.

12. The network node according to claim 11, comprising computer program code configured to cause the network node to execute: The conditional handover capability of the user equipment is enabled by an indication included in a conditional handover configuration.

13. The network node according to claim 11 or 12, comprising computer program code configured to cause the network node to execute: The conditional switching capability is disabled by sending an indication to the user equipment that the network node does not support blind decoding or parallel decoding.

14. A network node according to claim 11, 12 or 13, comprising computer program code configured to cause the network node to perform early data forwarding by: A copy of all downlink data related to the user equipment is forwarded to the first target MN1, and another copy of all downlink data related to the user equipment is forwarded to the second target MN2.

15. The network node according to claim 14, comprising computer program code configured to cause the network node to perform early data forwarding by: When the conditional handover to the first target MN1 or the second target MN2 is completed, the buffered DL data is used for downlink data transmission from the first target MN1 and / or the second target MN2 to the user equipment.

16. A network node according to claim 14 or 15, comprising computer program code configured to cause the network node to execute: The TEID of the target secondary node for terminating the bearer for the target SN is configured.

17. A method for communication, comprising: In response to receiving a first secondary node adding request for a user equipment from a first target master node, sending a response to the first target master node based on the received first request; In response to receiving a second secondary node adding request for the same user equipment from a second target master node, sending a response to the second target master node based on the received second request; as well as In response to receiving a physical uplink shared channel message from the user equipment, in the absence of information available that the user equipment has access to a first target master node or a second target master node, decoding of the physical uplink shared channel message received from the user equipment is enabled based on a first target master node key associated with the first target master node, and if decoding of the first key is unsuccessful, decoding of the physical uplink shared channel message received from the user equipment is enabled based on a second target master node key associated with the second target master node.

Images