Layer 1 / layer 2 triggered mobility for centralized unit user plane relocation within base station

Abstract

Generally, the current subject matter relates to mobility (LTM) of Layer 1 / Layer 2 (L1 / L2) triggers for centralized unit user plane (CU-UP) relocation within a base station. In some implementations, a target distributed unit (DU) of a base station serving a user equipment (UE) may be determined to be served by a target CU-UP of the base station. A serving CU-UP of a base station may serve a serving DU of a base station that is currently serving a UE. A target CU-UP for Layer 1 / Layer 2 triggered Mobility (LTM) may be prepared using a Centralized Unit Control Plane (CU-CP) of a base station, and a target DU for LTM may be prepared using the CU-CP.

Description

Technical Field

[0001] In some implementations, the present subject matter relates to a telecommunication system, and more particularly to Layer 1 / Layer 2 Triggered Mobility (LTM) for Centralized Unit User Plane (CU-UP) relocation within a base station. Background Art

[0002] In today's world, cellular networks provide communication capabilities on demand for individuals and commercial entities. Generally, a cellular network is a wireless network that can be distributed over a land area (called a cell). Each such cell is served by at least one fixed-location transceiver, which is called a cell site or base station. Each cell can use a different set of frequencies from its neighboring cells to avoid interference and provide better service within each cell. When cells are linked together, they provide radio coverage over a vast geographical area, which enables a large number of mobile phones and / or other wireless devices or portable transceivers to communicate with each other and with fixed transceivers and telephones anywhere in the network. Such communication is performed through base stations and can be accomplished even if the mobile transceiver traverses more than one cell during transmission. Major wireless communication providers have deployed such cell sites around the world, allowing communication mobile phones and mobile computing devices to connect to the public switched telephone network and the public Internet.

[0003] A mobile phone is a portable telephone that can receive and / or place calls and / or data calls through a cell site or tower by using radio waves to transmit signals back and forth with the mobile phone. Given the large number of mobile phone users, current mobile phone networks provide limited and shared resources. In this regard, cell sites and mobile phones can change frequencies and use low-power transmitters to allow many callers to use the network simultaneously with less interference. The coverage area of a cell site can depend on the specific geographical location and / or the number of users who may potentially use the network. For example, in a city, the range of a cell site can reach up to about 1 / 2 mile; in rural areas, this range can reach 5 miles; in some areas, users can receive signals from a cell site 25 miles away.

[0004] Examples of some digital cellular technologies used by communication providers are: Global System for Mobile Communications (GSM), General Packet Radio Service (GPRS), cdmaOne, CDMA2000, Evolution-Data Optimized (EV-DO), Enhanced Data Rates for GSM Evolution (EDGE), Universal Mobile Telecommunications System (UMTS), Digital Enhanced Cordless Telecommunications (DECT), Data AMPS (IS-136 / TDMA), and Integrated Digital Enhanced Network (iDEN). Long-Term Evolution or 4G LTE, developed by the 3rd Generation Partnership Project (3GPP) standards body, is the standard for high-speed data wireless communication for mobile phones and data terminals. The 5G standard is currently being developed and deployed. 3GPP cellular technologies such as LTE and 5G NR are the evolution of earlier 3GPP technologies such as GSM / EDGE and UMTS / HSPA digital cellular technologies, and allow for increased capacity and speed through the use of different radio interfaces and core network improvements.

[0005] A cellular network can be divided into a radio access network and a core network. The radio access network (RAN) can include network functions that can handle radio layer communication processing. The core network can include network functions that can handle higher layer communication, such as Internet Protocol (IP), transport layer, and application layer. In some cases, the RAN functions can be split into a baseband unit function and a radio unit function, where, for example, the radio unit connected to the baseband unit via a fronthaul network can be responsible for the lower layer processing of the radio physical layer, while the baseband unit can be responsible for higher layer radio protocols, such as MAC, RLC, etc.

[0006] A base station for a 5G cellular network can include a centralized unit (CU), one or more distributed units (DU) communicatively coupled to the CU, and one or more radio units (RU), each RU communicatively coupled to at least one of the one or more DUs, and each RU being configured to communicatively couple to one or more mobile phones and / or other user equipment (UE). The CU can be logically split into a control plane part CU-CP and one or more user plane parts (CU-UP). In a decomposed architecture, the base station includes more than one CU-UP. During the communication coupling process between the UE and the base station, the CU-UP of the base station that provides support to the UE can change from one CU-UP of the base station to another CU-UP of the base station. However, according to the current standard, a cell service change is triggered by layer 3 (L3) measurements and therefore requires resetting at the lower layers layer 1 (L1) and layer 2 (L2), which results in longer latency, greater overhead, and longer interruption times. Summary of the Invention

[0007] In some implementations, the present subject matter relates to a computer-implemented method. The method may include determining that a target distributed unit (DU) of a base station serving a user equipment (UE) is served by a target central unit user plane (CU-UP) of the base station. The serving CU-UP of the base station may serve the serving DU of the base station currently serving the UE. The method may further include: using a central unit control plane (CU-CP) of the base station, preparing a target CU-UP for layer 1 / layer 2 triggered mobility (LTM); and using the CU-CP, preparing a target DU for LTM.

[0008] When the UE is relocated from one CU-UP of the base station to another CU-UP of the base station for one or more services, the method may allow the base station to provide LTM.

[0009] In some implementations, the present subject matter may include one or more of the following optional features.

[0010] In some implementations, preparing the target CU-UP may include retrieving a security key from the target CU-UP using the CU-CP, and preparing the target DU may include sending the security key from the CU-CP to the target DU. Further, the security key configured by the target CU-UP may be sent from the CU-CP to the target DU in a UE CONTEXT SETUP REQUEST message; and / or retrieving the security key may include the CU-CP sending a BEARER CONTEXT SETUP REQUEST message to the target CU-UP, and the CU-UP sending a BEARER CONTEXT SETUP RESPONSE message to the CU-CP, and the BEARER CONTEXT SETUP RESPONSE message may include a security key that may correspond to the UE served by the target CU-UP. Further, the BEARER CONTEXT SETUP REQUEST message may include an information element (IE) notifying the target CU-UP of LTM.

[0011] In some implementations, preparing the target CU-UP may include sending an information element (IE) from the CU-CP to the target CU-UP, the IE notifying the target CU-UP of LTM to reserve resources for the UE.

[0012] In some implementations, the method may further include, after the preparation of the target CU-UP and the preparation of the target DU, triggering the serving CU-UP to start forwarding data to the target CU-UP. Additionally, the triggering may include sending a control packet data unit (PDU) from the serving DU to the serving CU-UP, and thereafter, the serving CU-UP sending the unsent and unacknowledged data PDUs to the target CU-UP. Further, the method may include sending, from the CU-CP to the serving DU, information for identifying a change of the serving CU-UP for LTM before transmitting the control PDU to trigger data forwarding. Additionally, the information may be sent from the CU-CP to the serving DU in a UE CONTEXT MODIFICATION REQUEST message.

[0013] In some implementations, the method may further include, after the preparation of the target CU-UP and the preparation of the target DU, triggering the target CU-UP to start serving the UE via the target CU. Additionally, the triggering may include sending a control packet data unit (PDU) from the target DU to the target CU-UP to initiate downlink data transmission, and thereafter, the target CU-UP sending data PDUs to the target DU; or, the triggering may include sending a first message from the serving DU to the CU-CP, and thereafter, the CU-CP sending a second message to the serving CU-UP, and thereafter, the serving CU-UP sending a third message to the target CU-UP; and / or serving the UE may include sending a first message from the target DU to the CU-CP, and thereafter, the CU-CP sending a second message to the target CU-UP, and thereafter, the target CU-UP initiating downlink data transmission towards the target DU.

[0014] In some implementations, the determination may include using the CU-CP to analyze a radio resource control (RRC) measurement report received from the UE at the CU-CP.

[0015] In some implementations, the serving CU-UP and the target CU-UP may be different entities.

[0016] In some implementations, the base station may be a new generation radio access network (NG-RAN) node.

[0017] In some implementations, the base station may include at least one processor and at least one non-transitory storage medium.

[0018] A non-transitory computer program product (i.e., a physically embodied computer program product) storing instructions is also described, which when executed by one or more data processors of one or more computing systems, cause at least one data processor to perform the operations herein. Similarly, a computer system is also described, which may include one or more data processors and a memory coupled to the one or more data processors. The memory may temporarily or permanently store instructions that cause at least one processor to perform one or more of the operations described herein. Additionally, the method may be implemented by one or more data processors within a single computing system or distributed between two or more computing systems. Such computing systems may be connected via one or more connections and may exchange data and / or commands or other instructions, etc., including but not limited to connections via a network (e.g., the Internet, wireless wide area network, local area network, wide area network, wired network, etc.), connections via direct connections between one or more of the multiple computing systems, etc.

[0019] Details of one or more variations of the subject matter described herein are set forth in the accompanying drawings and the description below. Other features and advantages of the subject matter described herein will be apparent from the specification, the drawings, and the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate certain aspects of the subject matter disclosed herein and, together with the description, help explain some of the principles associated with the disclosed implementations. In the drawings,

[0021] Figure 1a an exemplary conventional Long Term Evolution (LTE) communication system is illustrated;

[0022] Figure 1b illustrates Figure 1a other details of the exemplary LTE system shown;

[0023] Figure 1c illustrates Figure 1a other details of the evolved packet core of the exemplary LTE system shown;

[0024] Figure 1d illustrates Figure 1a an exemplary evolved Node B of the exemplary LTE system shown;

[0025] Figure 2 illustrates Figures 1a - 1d other details of the evolved Node B shown;

[0026] Figure 3 an exemplary virtual radio access network according to some implementations of the current subject matter is illustrated;

[0027] Figure 4 Illustrates an exemplary 3GPP split architecture that provides higher frequency band usage to its users;

[0028] Figure 5a Illustrates an exemplary 5G wireless communication system;

[0029] Figure 5b Illustrates an exemplary layer architecture of a split gNB and / or split ng-eNB (e.g., a next-generation eNB that can be connected to a 5GC);

[0030] Figure 5c Illustrates Figures 5a - 5b An example functional split in the gNB architecture shown;

[0031] Figure 6a Illustrates an exemplary system according to some implementations of the current subject matter;

[0032] Figure 6b Illustrates according to some implementations of the current subject matter Figure 6a An exemplary alternative configuration of the system;

[0033] Figure 7 Illustrates an exemplary method according to some implementations of the current subject matter;

[0034] Figure 8 Illustrates another exemplary system according to some implementations of the current subject matter;

[0035] Figure 9 Illustrates yet another exemplary system according to some implementations of the current subject matter; and

[0036] Figure 10 Illustrates another exemplary method according to some implementations of the current subject matter. Detailed Description

[0037] The current subject matter can provide systems and methods that can be implemented in a wireless communication system. Such systems can include various wireless communication systems, including 5G New Radio communication systems, Long Term Evolution communication systems, etc.

[0038] Generally, the current subject matter relates to layer 1 (L1) / layer 2 (L2)-triggered mobility (LTM) for centralized unit user plane (CU-UP) relocation within a base station.

[0039] In some implementations of the present subject matter, a base station of a wireless communication system can have a split architecture in which the base station includes more than one CU-UP. The base station can be configured to provide LTM when a UE communicatively coupled to the base station is relocated from one CU-UP of the base station to another CU-UP of the base station for one or more services of the UE.

[0040] 3GPP standards that define one or more aspects related to the present subject matter include 3GPP TS 38.321, "NR; Media Access Control (MAC) Protocol Specification", 3GPP TS 38.331, "NR; Radio Resource Control (RRC) Protocol Specification", 3GPP TS 38.463, "NG-RAN; E1 Application Protocol (E1AP)", and 3GPP TS 38.473, "NG RAN F1 Application Protocol (F1AP)". Standards of the O-RAN Alliance can also be related to one or more aspects of the present subject matter.

[0041] One or more aspects of the present subject matter can be incorporated into the transmitter and / or receiver components of a base station (e.g., gNodeB, eNodeB, etc.) in such a communication system. The following is a general discussion of long term evolution communication systems and 5G new radio communication systems.

[0042] Ⅰ. Long Term Evolution Communication System

[0043] Figures 1a - 1c and Figure 2 Illustrated is an exemplary conventional Long Term Evolution (LTE) communication system 100 and its various components. As is commercially known, the LTE system or 4G LTE is governed by standards for high-speed data wireless communication for mobile phones and data terminals. The standard is an evolution of GSM / EDGE (Global System for Mobile Communications / Enhanced Data Rates for GSM Evolution) and UMTS / HSPA (Universal Mobile Telecommunications System / High Speed Packet Access) network technologies. The standard is developed by 3GPP (3rd Generation Partnership Project).

[0044] As Figure 1a shown, the system 100 can include an evolved universal terrestrial radio access network (EUTRAN) 102, an evolved packet core (EPC) 108, and a packet data network (PDN) 101, where the EUTRAN 102 and the EPC 108 provide communication between the user equipment 104 and the PDN 101. The EUTRAN 102 can include a plurality of evolved Node Bs (eNodeB or ENODEB or enodeb or eNB) or base stations 106 (a, b, c) that provide communication capabilities to a plurality of user equipments 104 (a, b, c) (as Figure 1bas shown). The user equipment 104 can be a mobile phone, a smart phone, a tablet computer, a personal computer, a personal digital assistant (PDA), a server, a data terminal, and / or any other type of user equipment, and / or any combination thereof. The user equipment 104 can be connected to the EPC 108 via any eNodeB 106 and ultimately connected to the PDN 101. Generally, the user equipment 104 can be connected to the nearest eNodeB 106 in terms of distance. In the LTE system 100, the EUTRAN 102 and the EPC 108 work together to provide connection, mobility, and services for the user equipment 104.

[0045] Figure 1b illustrates Figure 1a other details of the network 100 shown above. As described above, the EUTRAN 102 includes a plurality of eNodeBs 106, also known as cell sites. The eNodeB 106 provides radio functions and performs key control functions, which include scheduling of air-link resources or radio resource management, active mode mobility or handover, and admission control of services. The eNodeB 106 is responsible for selecting which mobility management entities (MMEs, as Figure 1c shown) will serve the user equipment 104 and is responsible for protocol features such as header compression and encryption. The eNodeBs 106 that make up the EUTRAN 102 cooperate with each other for radio resource management and handover.

[0046] The communication between the user equipment 104 and the eNodeB 106 is carried out via the air interface 122 (also known as the LTE-Uu interface). As Figure 1b shown, the air interface 122 provides communication between the user equipment 104b and the eNodeB 106a. The air interface 122 uses orthogonal frequency division multiple access (OFDMA) and single carrier frequency division multiple access (SC-FDMA), an OFDMA variant, on the downlink and uplink, respectively. OFDMA allows the use of various known antenna technologies, such as multiple input multiple output (MIMO).

[0047] The air interface 122 uses various protocols, including radio resource control (RRC) for signaling between the user equipment 104 and the eNodeB 106 and non-access stratum (NAS) for signaling between the user equipment 104 and the MME (as Figure 1c shown). In addition to signaling, user traffic is transmitted between the user equipment 104 and the eNodeB 106. Both signaling and traffic in the system 100 are carried by physical layer (PHY) channels.

[0048] A plurality of eNodeBs 106 can be interconnected with each other using the X2 interface 130 (a, b, c). As Figure 1bAs shown, the X2 interface 130a provides the interconnection between eNodeB 106a and eNodeB 106b; the X2 interface 130b provides the interconnection between eNodeB 106a and eNodeB 106c; the X2 interface 130c provides the interconnection between eNodeB 106b and eNodeB 106c. The X2 interface can be established between two eNodeBs to provide signal exchange, which may include load or interference related information and handover related information. eNodeB 106 communicates with the evolved packet core 108 via the S1 interface 124(a, b, c). The S1 interface 124 can be split into two interfaces: one interface for the control plane (as shown by the control plane interface (S1-MME interface) 128 in Figure 1c ), and the other interface for the user plane (as shown by the user plane interface (S1-U interface) 125 in Figure 1c ).

[0049] The EPC 108 establishes and enforces quality of service (QoS) for user services, and allows the user equipment 104 to maintain a consistent Internet Protocol (IP) address while moving. It should be noted that each node in the network 100 has its own IP address. The EPC 108 is designed to interoperate with traditional wireless networks. The EPC 108 is also designed to separate the control plane (i.e., signaling) and the user plane (i.e., traffic) in the core network architecture, which allows for greater flexibility and independent scalability of the control and user data functions.

[0050] The EPC 108 architecture is dedicated to packet data and is shown in more detail in Figure 1c . The EPC 108 includes a serving gateway (S-GW) 110, a PDN gateway (P-GW) 112, a mobility management entity (MME) 114, a home subscriber server (HSS) 116 (the subscriber database of the EPC 108), and a policy control and charging rules function (PCRF) 118. Some of these (such as the S-GW, P-GW, MME, and HSS) are usually combined into nodes according to the manufacturer's implementation.

[0051] The S-GW 110 acts as an IP packet data router and is the bearer path anchor for the user equipment in the EPC 108. Thus, when the user equipment moves from one eNodeB 106 to another during a mobility operation, the S-GW 110 remains unchanged, and the bearer path towards the EUTRAN 102 is switched to communicate with the new eNodeB 106 serving the user equipment 104. If the user equipment 104 moves into the domain of another S-GW 110, the MME 114 transfers all the bearer paths of the user equipment to the new S-GW. The S-GW 110 establishes bearer paths for the user equipment to one or more P-GWs 112. If downlink data for an idle user equipment is received, the S-GW 110 buffers the downlink packets and requests the MME 114 to locate and re-establish the bearer paths to and through the EUTRAN 102.

[0052] The P-GW 112 is the gateway between the EPC 108 (as well as the user equipment 104 and the EUTRAN 102) and the PDN 101 (as Figure 1a shown). The P-GW 112 acts as a router for the user traffic and performs functions on behalf of the user equipment. These include the IP address assigned to the user equipment, packet filtering of the downstream user traffic to ensure it is placed on the appropriate bearer path, and enforcement of downstream QoS (including data rate). Depending on the services the subscriber is using, there can be multiple user data bearer paths between the user equipment 104 and the P-GW 112. The subscriber can use services on PDNs served by different P-GWs, in which case the user equipment has at least one bearer path established to each P-GW 112. During the handover of the user equipment from one eNodeB to another, if the S-GW 110 is also changing, the bearer path from the P-GW 112 is switched to the new S-GW.

[0053] The MME 114 manages the user equipment 104 within the EPC 108, including managing subscriber authentication, maintaining the context of the authenticated user equipment 104, establishing a data bearer path for user traffic in the network, and tracking the location of idle mobile devices that have not yet detached from the network. For an idle user equipment 104 that needs to reconnect to the access network to receive downstream data, the MME 114 initiates a paging to locate the user equipment and re - establishes the bearer path to and through the EUTRAN 102. The MME 114 for a particular user equipment 104 is selected by the eNodeB 106 when the user equipment 104 initiates system access. For load - sharing and redundancy purposes, the MME is typically part of a pool of MMEs in the EPC 108. In the establishment of a user's data bearer path, the MME114 is responsible for selecting the P - GW 112 and the S - GW 110, which will form the ends of the data path through the EPC 108.

[0054] The PCRF 118 is responsible for policy control decisions and controlling the flow - based charging function in the Policy Control Enforcement Function (PCEF) resident in the P - GW 110. The PCRF 118 provides QoS authorization (QoS Class Identifier (QCI) and bit rate), which determines how a particular data flow will be processed in the PCEF and ensures that it conforms to the user's subscription profile.

[0055] As described above, the IP service 119 is provided by the PDN 101 (as Figure 1a shown).

[0056] Figure 1dFIG. illustrates an exemplary structure of eNodeB 106. eNodeB 106 may include at least one Remote Radio Head (RRH) 132 (usually there may be three RRHs 132) and a Baseband Unit (BBU) 134. The RRH 132 may be connected to an antenna 136. The RRH 132 and the BBU 134 may be connected using an optical interface conforming to the Common Public Radio Interface (CPRI) / Enhanced CPRI (eCPRI) 142 standard specification, or using an RRH-specific customized control and user plane framing method, or using a control and user plane framing method conforming to the O-RAN Alliance. The operation of eNodeB 106 may be characterized using the following standard parameters (and specifications): radio frequency band (Band4, Band9, Band17, etc.), bandwidth (5, 10, 15, 20 MHz), access scheme (downlink: OFDMA; uplink: SC-OFDMA), antenna technology (single-user and multi-user MIMO; uplink: single-user and multi-user MIMO), number of sectors (up to 6), maximum transmission rate (downlink: 150 Mb / s; uplink: 50 Mb / s), S1 / X2 interface (1000Base-SX, 1000Base-T), and mobile environment (up to 350 km / h). The BBU 134 may be responsible for digital baseband signal processing, termination of the S1 line, termination of the X2 line, and call processing and monitoring control processing. IP packets received from the EPC 108 ( Figure 1d not shown in the figure) may be modulated into digital baseband signals and sent to the RRH 132. Conversely, digital baseband signals received from the RRH 132 may be demodulated into IP packets for transmission to the EPC 108.

[0057] The RRH 132 may transmit and receive wireless signals using the antenna 136. The RRH 132 may convert (using a converter (CONV) 140) the digital baseband signal from the BBU 134 into a Radio Frequency (RF) signal and amplify it (using an amplifier (AMP) 138) for transmission to the User Equipment 104 ( Figure 1d not shown in the figure). Conversely, the RF signal received from the User Equipment 104 is amplified (using the AMP 138) and converted (using the CONV 140) into a digital baseband signal for transmission to the BBU 134.

[0058] Figure 2Illustrates other details of the exemplary eNodeB 106. The eNodeB 106 includes multiple layers: LTE layer 1 202, LTE layer 2 204, and LTE layer 3 206. LTE layer 1 includes the Physical Layer (PHY). LTE layer 2 includes Media Access Control (MAC), Radio Link Control (RLC), and Packet Data Convergence Protocol (PDCP). LTE layer 3 includes various functions and protocols, including Radio Resource Control (RRC), dynamic resource allocation, eNodeB measurement configuration and provisioning, radio access control, connection mobility control, and Radio Resource Management (RRM). The RLC protocol is an Automatic Repeat reQuest (ARQ) segmentation protocol used on the cellular air interface. The RRC protocol handles the control plane signaling of LTE layer 3 between the User Equipment and the EUTRAN. RRC includes functions such as connection establishment and release, system information broadcast, radio bearer establishment / reconfiguration and release, RRC connection mobility procedures, paging notification and release, and outer loop power control. The PDCP performs IP header compression and decompression, transmission of user data, and maintenance of the sequence numbers of radio bearers. As Figure 1d shown, the BBU 134 may include LTE layers L1-L3.

[0059] One of the main functions of the eNodeB 106 is radio resource management, which includes scheduling both uplink and downlink air interface resources for the User Equipment 104, controlling bearer resources, and access control. As an agent of the EPC 108, the eNodeB 106 is responsible for the transmission of paging messages used to locate the mobile device when it is idle. The eNodeB 106 also transmits common control channel information over the air, header compression, encryption and decryption of user data sent over the air, and establishes handover reporting and triggering criteria. As described above, the eNodeB 106 can cooperate with other eNodeB 106 via the X2 interface for handover and interference management. The eNodeB 106 communicates with the MME of the EPC via the S1-MME interface and communicates with the S-GW using the S1-U interface. In addition, the eNodeB 106 exchanges user data with the S-GW via the S1-U interface. The eNodeB 106 and the EPC 108 have a many-to-many relationship to support load sharing and redundancy between the MME and the S-GW. The eNodeB 106 selects an MME from a group of MMEs so that multiple MMEs can share the load to avoid congestion.

[0060] II. 5G NR Wireless Communication Network

[0061] In some implementations, the present subject matter relates to a 5G New Radio (NR) communication system. 5G NR is the next telecommunications standard beyond the 4G / IMT-Advanced standard. 5G networks provide higher capacity than current 4G, allowing for more mobile broadband users per unit area and allowing for higher and / or unlimited gigabyte data volumes per month and per user. This can allow users to stream high-definition media on their mobile devices for hours each day, even in situations where Wi-Fi networks are not available. 5G networks have support for improved device-to-device communication, lower costs, lower latency than 4G devices, lower battery consumption, and so on. Such networks have data rates of tens of megabits per second for a large number of users, 100 Mb / s data rates for metropolitan areas, 1 Gb / s data rates for users within a limited area (e.g., an office building) simultaneously, a large number of simultaneous connections for wireless sensor networks, enhanced spectral efficiency, improved coverage, enhanced signaling efficiency, 1 - 10 ms latency, and reduced latency compared to existing systems.

[0062] Figure 3 An exemplary virtual radio access network 300 is illustrated. Network 300 can provide communication between various components, including base stations (e.g., eNodeB, gNodeB) 301, radio devices 303, a centralized unit 302, a digital unit 304, and radio device 306. The components in system 300 can be communicatively coupled to the core using a backhaul link 305. The centralized unit (CU) 302 can be communicatively coupled to the distributed unit (DU) 304 using a midhaul connection 308. The radio frequency (RU) component 306 can be communicatively coupled to the DU 304 using a fronthaul connection 310.

[0063] In some implementations, the CU 302 can provide intelligent communication capabilities to one or more DU units 304. The units 302, 304 can include one or more base stations, macro base stations, micro base stations, remote radio heads, and / or any combination thereof.

[0064] In a lower layer split architecture environment, the CPRI bandwidth requirement for NR can be in the 100s of Gb / s. CPRI compression can be implemented in the DU and RU (as Figure 3 shown). In a 5G communication system, compressed CPRI over an Ethernet frame is called eCPRI and is the recommended fronthaul network. This architecture can enable standardization of fronthaul / midhaul, which can include higher layer splits (e.g., Option 2 or Option 3-1 (upper / lower RLC split architecture)) and fronthaul with an L1 split architecture (Option 7).

[0065] In some implementations, a lower layer split architecture (e.g., Option 7) may include a receiver in the uplink, joint processing of multiple transmission points (TPs) for both DL / UL, and transmission bandwidth and latency requirements that facilitate deployment. Additionally, the lower layer split architecture of the current subject matter may include a split between cell-level processing and user-level processing, which may include cell-level processing in a remote unit (RU) and user-level processing in a distributed unit (DU). Additionally, using the lower layer split architecture of the current subject matter, frequency domain samples may be transmitted via Ethernet fronthaul, where the frequency domain samples may be compressed to reduce fronthaul bandwidth.

[0066] Figure 4 An exemplary communication system 400 is illustrated that may implement 5G technology and may provide the use of higher frequency bands (e.g., greater than 10 GHz) to its users. System 400 may include a macro cell 402 and small cells 404, 406.

[0067] A mobile device 408 may be configured to communicate with one or more of the small cells 404, 406. System 400 may allow for splitting of the control plane (C-plane) and user plane (U-plane) between the macro cell 402 and the small cells 404, 406, where the C-plane and U-plane use different frequency bands. In particular, the small cells 404, 406 may be configured to utilize a higher frequency band when communicating with the mobile device 408. The macro cell 402 may utilize an existing cellular frequency band for C-plane communication. The mobile device 408 may be communicatively coupled via the U-plane 412, where a small cell (e.g., small cell 406) may provide higher data rates and more flexible / cost-effective / energy-efficient operation. The macro cell 402 may maintain good connectivity and mobility via the C-plane 410. Additionally, in some cases, LTE and NR may transmit on the same frequency.

[0068] Figure 5a An exemplary 5G wireless communication system 500 is illustrated in accordance with some implementations of the current subject matter. According to Option 7-2, system 500 may be configured to have a lower layer split architecture. System 500 may include a core network 502 (e.g., 5G Core) and one or more gNodeBs (or gNBs), where a gNB may have a centralized unit gNB-CU. The gNB-CU may be logically split into a control plane portion gNB-CU-CP 504 and one or more user plane portions gNB-CU-UP 506. The control plane portion 504 and the user plane portion 506 may be configured to be communicatively coupled using an E1 communication interface 514 (as specified in the 3GPP standard). The control plane portion 504 may be configured to be responsible for executing the RRC protocol and the PDCP protocol of the radio stack.

[0069] According to the higher-layer split architecture, the control plane and user plane portions 504, 506 of the central unit of the gNB can be configured to be communicatively coupled to one or more distributed units (DUs) 508, 510. The distributed units 508, 510 can be configured to execute the upper parts of the RLC, MAC, and PHY layer protocols of the radio stack. The control plane portion 504 can be configured to be communicatively coupled to the distributed units 508, 510 using the F1-C communication interface 516, and the user plane portion 506 can be configured to be communicatively coupled to the distributed units 508, 510 using the F1-U communication interface 518. The distributed units 508, 510 can be coupled to one or more remote radio units (RUs) 512 via a fronthaul network 520 (which can include one or more switches, links, etc.), which in turn communicate with one or more user devices ( Figure 5a not shown in). The remote radio unit 512 can be configured to execute the lower part of the PHY layer protocol and provide antenna capabilities to the remote unit for communication with the user device (similar to the discussion in Figures 1a - 2 above).

[0070] Figure 5b An exemplary layer architecture 530 of the split gNB is illustrated. The architecture 530 can be implemented in the Figure 5a shown communication system 500, which can be configured as a virtualized decomposed radio access network (RAN) architecture, whereby layers L1, L2, L3, and radio processing can be virtualized and decomposed in the (multiple) central units, (multiple) distributed units, and (multiple) radio units. As Figure 5b shown, the gNB-DU 508 can be communicatively coupled to the gNB-CU-CP control plane portion 504 (also shown in Figure 5a ), and the gNB-CU-UP user plane portion 506. Each of the components 504, 506, 508 can be configured to include one or more layers.

[0071] The gNB-DU 508 may include an RLC layer, a MAC layer, and a PHY layer, as well as various communication sub-layers. These may include an F1 Application Protocol (F1-AP) sub-layer, a GPRS Tunneling Protocol (GTPU) sub-layer, a Stream Control Transmission Protocol (SCTP) sub-layer, a User Datagram Protocol (UDP) sub-layer, and an Internet Protocol (IP) sub-layer. As described above, the distributed unit 508 may be communicatively coupled to the control plane portion 504 of the centralized unit, which may also include an F1-AP, SCTP, and IP sub-layers, as well as a Radio Resource Control and PDCP Control (PDCP-C) sub-layer. Additionally, the distributed unit 508 may also be communicatively coupled to the user plane portion 506 of the centralized unit of the gNB. The user plane portion 506 may include a Service Data Adaptation Protocol (SDAP), a PDCP User (PDCP-U), GTPU, UDP, and IP sub-layers.

[0072] Figure 5c illustrates Figures 5a - 5b an example functional split in the gNB architecture shown. As Figure 5c shown, the gNB-DU 508 may be communicatively coupled to the gNB-CU-CP 504 and the gNB-CU-UP 506 using an F1-C communication interface. The gNB-CU-CP 504 and the gNB-CU-UP 506 may be communicatively coupled using an E1 communication interface. The higher part of the PHY layer (or layer 1) may be performed by the gNB-DU 508, while the lower part of the PHY layer may be performed by the RU ( Figure 5c not shown in the figure). As Figure 5c shown, the RRC and PDCP-C parts may be performed by the control plane portion 504, and the SDAP and PDCP-U parts may be performed by the user plane portion 506.

[0073] Some of the functions in the PHY layer of a 5G communication network may include error detection on the transport channel and indication to higher layers, FEC encoding / decoding of the transport channel, hybrid ARQ soft combining, rate matching of the coded transport channel to the physical channel, mapping of the coded transport channel onto the physical channel, power weighting of the physical channel, modulation and demodulation of the physical channel, frequency and time synchronization, radio characteristic measurement and indication to higher layers, MIMO antenna processing, digital and analog beamforming, RF processing, and other functions.

[0074] The MAC sublayer of layer 2 can perform beam management, random access procedures, mapping between logical channels and transport channels, concatenating multiple MAC service data units (SDUs) belonging to one logical channel into a transport block (TB), multiplexing / demultiplexing of SDUs belonging to logical channels into / from the TB passed to / from the physical layer on the transport channel, scheduling information reporting, error correction via HARQ, priority handling between logical channels of a UE, priority handling between UEs by means of dynamic scheduling, transport format selection, and other functions. The functions of the RLC sublayer can include the transmission of higher layer protocol data units (PDUs), error correction via ARQ, reordering of data PDUs, duplication and protocol error detection, reconstruction, etc. The PDCP sublayer can be responsible for the transmission of user data, various functions during the reconstruction process, retransmission of SDUs, SDU discard in the uplink, transmission of control plane data, etc.

[0075] The RRC sublayer of layer 3 can perform the following functions: broadcasting system information to the NAS and AS, establishing, maintaining, and releasing RRC connections, security of point-to-point radio bearers, establishing, configuring, maintaining, and releasing, mobility functions, reporting, and other functions.

[0076] III. LTM for CU-UP Relocation within a Base Station

[0077] In some implementations of the present subject matter, a base station (e.g., a gNodeB such as Figure 5a in a wireless communication system (e.g., a 5G wireless communication system, a 6G or higher generation wireless communication system, etc.)) can have a split architecture in which the base station includes more than one CU-UP (e.g., a gNB-CU-UP 506 such as Figures 5a - 5c ). The base station can be configured to provide LTM when a UE communicatively coupled to the base station relocates from one CU-UP of the base station to another CU-UP of the base station for one or more services.

[0078] Figure 6a FIG. illustrates an exemplary system 600 configured to provide LTM for CU-UP relocation within a base station. In the illustrated implementation, the base station 624 is a gNB in a 5G wireless communication system configured to be similar to the above-described Figure 5a 5G wireless communication system 500, but other base stations can be similarly configured and used to provide LTM for CU-UP relocation within a base station. In Figure 6aIn the illustrated implementation, base station 624 includes multiple CU-UPs 606a, 606b, 606c. In the illustrated implementation, base station 624 includes three CU-UPs 606a, 606b, 606c, but may also include other multiple CU-UPs. The CU of base station 624 including multiple CU-UPs 606a, 606b, 606c is configured to be communicatively coupled to a core network ( Figure 6a not shown in the figure, such as Figure 5a 5GC 502, etc.).

[0079] The CU of base station 624 also includes a CU-CP 604 configured to be communicatively coupled to the user plane portions 606a, 606b, 606c of the CU using an E1 communication interface 614. In the illustrated implementation, the E1 interface 614 includes three communication links to reflect that the CU-CP 604 can be configured to communicate with three CU-UPs 606a, 606b, 606c.

[0080] Base station 624 also includes multiple DUs 608, 610. In the illustrated implementation, base station 624 includes two DUs 608, 610, but may also include other multiple DUs. The CU-CP 604 is configured to be communicatively coupled to DUs 608, 610 using an F1-C communication interface 616. The CU-UPs 606a, 606b, 606c are configured to be communicatively coupled to DUs 608, 610 using an F1-U communication interface 618. In the illustrated implementation, the F1-U interface 618 associated with each of DUs 608, 610 includes three communication links to reflect that each of DUs 608 and 610 can be configured to communicate with three CU-UPs 606a, 606b, 606c.

[0081] Base station 624 also includes multiple RUs 612. In the illustrated implementation, base station 624 includes five RUs 612, but may also include other multiple RUs. The RUs 612 are configured to be communicatively coupled to DUs 608, 610 via a fronthaul network 620. Additionally, each of the RUs 612 is configured to be communicatively coupled to one or more UEs 622. In the illustrated implementation, two of the RUs 612 are shown communicatively coupled to one UE 622, two of the RUs 612 are shown communicatively coupled to two UEs 622, and one of the RUs 612 is shown communicatively coupled to three UEs 622, but each of the RUs 612 can be coupled to a different number of other UEs that may be the same as or different from any other RU 612.

[0082] When one of the UEs 622 communicatively coupled to the base station 624 relocates from one of the CU-UPs 606a, 606b, 606c to another one of the CU-UPs 606a, 606b, 606c for one or more services, in-base-station CU-UP relocation can be configured. One of the CU-UPs 606a, 606b, 606c that is currently serving the UE 622 is referred to as the "serving CU-UP" because it is currently serving the UE 622, e.g., currently servicing the UE 622. One of the CU-UPs 606a, 606b, 606c to which the service of the UE is moved during the relocation is referred to as the "target CU-UP" because its goal is to serve the UE 622.

[0083] For example, when one of the UEs 622 is being served by a first DU in the DU 608 (via one of the RUs 612), the first DU is served by a first CU-UP in the CU-UP 606a and has at least one service moved to a second DU in the DU 612 (via the same RU in the RUs 612 or a different RU in the RUs 612), and the second DU is served by a second CU-UP in the CU-UP 606b, an in-base-station CU-UP relocation scenario may occur. The DU 608 that is currently serving the UE 622 is referred to as the "serving DU" because it is currently serving the UE 622, e.g., currently servicing the UE 622. The DU 610 to which the service of the UE is being moved is referred to as the "target DU" because its goal is to serve the UE 622. Each of the CU-UPs 606a, 606b, 606c has a different security key for use in secure communication with the DU. Therefore, before the target DU 610 can serve the UE 622, the target DU 610 needs the security key of the second CU-UP 606b.

[0084] In the following scenarios, in-base-station CU-UP relocation will not need to occur. For example, one of the UEs 622 is being served by one of the first DU 608 and the second DU 610, the DU is being served by one of the CU-UPs 606a, 606b, 606c and has at least one service moved to the other DU in the DUs 608, 610, and the other DU is also served by the same CU-UP among the CU-UPs 606a, 606b, 606c. Therefore, one of the DUs 608, 610 serving the UE 622 may be changing, but the CU-UP 606a, 606b, 606c serving the UE 622 remains unchanged.

[0085] Reference Figure 6b Further describe the scenarios for configuring the occurrence or non-occurrence of in-base-station CU-UP relocation.Figure 6b illustrates Figure 6a the CU-CP 604 and CU-UP 606a, 606b, 606b, but in Figure 6b the implementation shown, the base station 624 includes more than two DUs. In Figure 6b the implementation shown, the base station 624 includes 66 DUs 626, 628. Three of the DUs 628a, 628b, 628c are macro cells (labeled macro1, macro2, and macro3 in Figure 6b ), and 63 of the DUs 626 are small cells (nine of which are labeled gNB-DU10, gNB-DU20, gNB-DU30, gNB-DU40, gNB-DU50, gNB-DU60, gNB-DU70, gNB-DU80, and gNB-DU90 in Figure 6b ). The base station 624 may include other numbers of macro cells and / or other numbers of small cells. The macro1 DU 628a, macro2 DU 628b, and 21 small cell DUs 626 including gNB-DU10, gNB-DU20, and gNB-DU30 are configured to be served by the first CU-UP 606a (labeled CU-UP1 in Figure 6b ). The macro1 DU628a, macro2 DU 628b, macro3 DU 628c, and 21 small cell DUs 626 including gNB-DU40, gNB-DU50, and gNB-DU60 are configured to be served by the second CU-UP 606b( Figure 6b labeled CU-UP2 in Figure 6b ). The macro2 DU 628b, macro3 DU 628c, and 21 small cell DUs 626 including gNB-DU70, gNB-DU80, and gNB-DU90 are configured to be served by the third CU-UP 606c (labeled CU-UP3 in

[0086] An example of a scenario where in-cell CU-UP relocation is not configured to occur is when at least one service of a UE moves from one macro cell served by a specific CU-UP to another macro cell also served by the same CU-UP. For example, moving from macro1 DU 628a served by the first CU-UP 606a to macro2 DU 628b also served by the first CU-UP 606a, from macro3 DU 628c served by the second CU-UP 606b to macro2 DU 628b also served by the second CU-UP 606b, and so on. Another example of a scenario where in-cell CU-UP relocation is not configured to occur is when at least one service of one of the UEs 622 moves from one small cell served by a specific CU-UP to another small cell also served by the same CU-UP. For example, moving from gNB-DU10 626 to gNB-DU20 626, from gNB-DU50 626 to gNB-DU40 626, from gNB-DU50 626 to gNB-DU60 626, from gNB-DU70 626 to gNB-DU80 626, from gNB-DU80 626 to gNB-DU70 626, and so on.

[0087] An example of a scenario where in-cell CU-UP relocation is configured to occur is when at least one service of one of the UEs moves from one macro cell served by a specific CU-UP to another macro cell served by another CU-UP. For example, moving from macro1 DU 628a served by the first CU-UP 606a to macro3 DU 628c served by the second CU-UP 606b, from macro3 DU 628a served by the second CU-UP 606a to macro3 DU 628c served by the third CU-UP 606c, and so on. Another example of a scenario where in-cell CU-UP relocation is configured to occur is when at least one service of one of the UEs moves from one small cell served by a specific CU-UP to another small cell served by another CU-UP. For example, moving from gNB-DU10 626 served by the first CU-UP606a to gNB-DU40 626 served by the second CU-UP 606b, from gNB-DU80626 served by the third CU-UP606b to gNB-DU40 626 served by the second CU-UP 606b, from gNB-DU90 626 served by the third CU-UP606c to gNB-DU30 626 served by the first CU-UP 606a, from gNB-DU50 626 served by the second CU-UP606b to gNB-DU20 626 served by the first CU-UP 606a, and so on.

[0088] In Figure 6b the implementation shown, each CU-UP 606a, 606b, 606c serves a subset of DUs 626, 628a, 628, 628c for all services. However, a CU-UP can serve all DUs of a base station for one service (e.g., enhanced mobile broadband (eMBB)), while serving a subset of DUs for another service (e.g., vehicle-to-everything (V2X) or ultra-reliable low-latency communication (URLLC)).

[0089] The above scenarios regarding Figure 6a and Figure 6b demonstrate examples of CU-UP relocation within a base station. The CU-UP relocation within a base station described herein is equally applicable to L1 / L2-based inter-cell mobility covering the intra-DU scenario within a CU. An example of such a scenario is that at least one service of one of the UEs moves from a small cell served by a specific CU-UP to another small cell served by the same CU-UP. For example, from gNB-DU10 626 served by the first CU-UP 606a to gNB-DU20 626 served by the first CU-UP 606a, from gNB-DU40 626 served by the second CU-UP 606b to gNB-DU60 626 served by the second CU-UP 606b, from gNB-DU90 626 served by the third CU-UP 606c to gNB-DU80 626 served by the third CU-UP 606c, and so on.

[0090] In some implementations, providing an LTM for CU-UP relocation within a base station may include a preparation phase and a data forwarding phase that occurs after the preparation phase. In some implementations, the preparation phase may include the CU-CP of a base station (e.g., Figure 5a the gNodeB of Figure 6a and Figure 6b the gNB 624, etc.) preparing the target DU (e.g., Figures 5a - 5c DU 508 of Figure 6a and Figure 6b the CU-CP 604 of Figures 5a - 5c DU 510 of Figure 5a the DU 608 of Figure 6a the DU 610 of Figure 6a the DU 626 of Figure 6b the DU 628 of Figure 6b etc.) and the target CU-UP (e.g., Figures 5a - 5c gNB-CU-UP506 of Figure 6a and Figure 6bsuch as CU-UPs 606a, 606b, 606c, etc.)

[0091] The preparation of the target DU may include the CU-CP providing the security key of the UE provided by the target CU-UP to the target DU, thereby allowing the target DU to securely communicate with the UE and the target CU-UP using the security key. The CU-CP may provide the security key to the target DU before the serving cell change is executed, and at least one service of the UE (e.g., Figure 6a such as UE 622, etc.) has been relocated to the target CU-UP, so that after the serving cell change has occurred, the target DU can securely communicate with the UE and the target CU-UP without delay. In some implementations, the CU-CP may be configured to provide the security key to the target DU in the F1:UE CONTEXT SETUP REQUEST message. The F1:UE CONTEXT SETUP REQUEST message is defined by 3GPP. Therefore, according to the 3GPP standard, the security key can be sent from the CU-CP to the target DU using the message that has been sent from the CU-CP to the target DU.

[0092] The preparation of the target CU-UP may include the CU-CP providing the target CU-UP with a notification that relocation of a given UE will occur. This notification may allow the CU-CP to receive the security key of the UE's target CU-UP from the target CU-UP, e.g., as a response to the notification, so that the CU-CP can provide the security key to the target DU during the LTM target cell preparation. In some implementations, the CU-CP may be configured to provide this notification to the target CU-UP in the BEARER CONTEXT SETUP REQUEST message, such as in the information element (IE) of the BEARER CONTEXT SETUP REQUEST message. The BEARER CONTEXT SETUP REQUEST message is defined by 3GPP. Therefore, according to the 3GPP standard, this notification can be sent from the CU-CP to the target CU-UP using the message that has been sent from the CU-CP to the target CU-UP. The same message can also be used to reserve the resources required for the CU-UP relocation of the UE.

[0093] In some implementations, the data forwarding phase may include the serving DU (e.g., Figures 5a - 5c DU 508, Figure 5a DU 510, Figure 6a DU 608, Figure 6a DU 610, Figure 6b DU 626, Figure 6b DU 628, etc.) sending data to the serving CU-UP (e.g., Figures 5a - 5cThe gNB-CU-UP 506, Figure 6a and Figure 6b the CU-UPs 606a, 606b, 606c, etc.) indicate when to initiate data forwarding to the target CU-UP. The data forwarding phase may also include the CU-CP identifying the target CU-UP for a given target cell to the serving DU, which may allow the serving DU to identify the target CU-UP corresponding to the target cell at the target DU to the serving CU-UP, so that the serving CU-UP can communicate with the target CU-UP to trigger data forwarding to the target CU-UP. In some implementations, the CU-CP may be configured to identify the target CU-UP for a given target cell to the serving DU in a UE CONTEXT MODIFICATION REQUEST message. The UE CONTEXT MODIFICATION REQUEST message is defined by 3GPP. Thus, according to the 3GPP standard, the identity of the target CU-UP for a given target cell can be provided from the CU-CP to the serving DU using a message that has already been sent from the CU-CP to the serving DU.

[0094] Figure 7 FIG. illustrates an exemplary method 700 according to some implementations of the current subject matter. As Figure 7 shown, method 700 includes a preparation phase 716 and a data forwarding phase 718. Method 700 will be described with respect to Figure 8 the exemplary system 800 shown, but can be similarly implemented using other systems, such as Figure 6a and Figure 6b systems, etc. Figure 8 The system 800 is a 5G system, but as described above, the LTM for CU-UP relocation within a base station described herein can be performed using other types of wireless communication systems (such as 6G or higher generation wireless communication systems).

[0095] In system 800, the UE 802 (e.g., Figure 6a the UE 622, etc.) is configured 814 with an LTM that has one or more target cells in one or more DUs 804, 806 of a base station (e.g., gNodeB (e.g., Figure 5a the gNodeB, Figure 6a and Figure 6b the gNodeB 624, etc.) (e.g., Figures 5a - 5c the DU 508, Figure 5a the DU 510, Figure 6a the DU 608, Figure 6a the DU 610, Figure 6b the DU626, Figure 6b the DU 628, etc.). For ease of explanation,Figure 8 System 800 is shown, in which one UE 802, two DUs 804, 806, and two CU-UPs 810, 812 of the base station are communicatively coupled to the base station (e.g., Figures 5a - 5c gNB-CU-UP 506 of Figure 6a and Figure 6b CU-UPs 606a, 606b, 606c, etc. of Figures 5a - 5c gNB-CU-CP 504 of Figure 6a and Figure 6b CU-CP604 of Figure 5a RU 512 of Figure 6a RU 612 of Figure 8 etc. (not shown in

[0096] UE 802 is currently served by serving DU 804 and serving CU-UP 810.

[0096] Method 700 includes CU-CP 808 determining 702 that the target DU 806 of UE 802 is served by a CU-UP (target CU-UP 812) different from the serving CU-UP 810 that is currently serving serving DU804. The determination 702 by the CU-CP may include CU-CP 808 analyzing 818 the radio resource control (RRC) measurement report 816 sent by UE 802 to CU-CP 808 according to 3GPP standards. According to 3GPP standards, the RRC measurement report may include layer 3 (L3) measurements, which may be analyzed by CU-CP 808 in making resource control decisions, which may include a service change, where UE 802 will be served by a DU (e.g., target DU 806) for at least one service instead of serving DU 804. According to 3GPP standards, CU-CP 808 knows the serving CU-UP 810 that is currently serving serving DU 804 and the CU-UP 812 that is currently serving target DU 806. Therefore, CU-CP 808 knows that in this scenario, since the CU-UP serving UE 802 will be changed, the LTM for CU-UP relocation within the base station is properly executed.

[0097] In response to determining that the target DU 806 of the UE 802 is served by a CU-UP (target CU-UP 812) different from the serving CU-UP 810 currently serving the serving DU 804, the CU-CP 808 prepares the target CU-UP 812 for LTM. The preparation of the target CU-UP 812 may include the CU-CP 808 requesting the target CU-UP 812 to reserve the necessary resources for the UE 802 and retrieving the security key of the UE 802 from the target CU-UP 812. As Figure 8 shown, preparing the target CU-UP 812 for LTM and retrieving the security key may include the CU-CP 808 sending an E1:BEARER CONTEXT SETUP REQUEST message to the target CU-UP 812 using the E1 communication interface. Also as Figure 8 shown, the E1:BEARER CONTEXT SETUP REQUEST message may include an IE that notifies the target CU-UP 812 that a CU-UP relocation will occur, so that the target CU-UP 812 can reserve resources for the UE 802.

[0098] In response to receiving the E1:BEARER CONTEXT SETUP REQUEST message, for example, in response to receiving an IE indicating that a CU-UP relocation will occur, the target CU-UP 812 sends an E1:BEARER CONTEXT SETUP RESPONSE message to the CU-CP 808, which includes the security key of the target CU-UP of the UE 802. The E1:BEARER CONTEXT SETUP RESPONSE message is defined by 3GPP. Therefore, according to the 3GPP standard, the security key can be sent from the target CU-UP 812 to the CU-CP 808 using the message that has been sent from the target CU-UP 812 to the CU-CP 808.

[0099] After retrieving the security key of the target CU-UP of the UE 802, the CU-CP 808 sends the security key of the UE 802 to the target DU 806 to prepare the target DU 806 for LTM. As Figure 8As shown, the transmission 706 of the security key to the target DU 806 may include the CU-CP 808 sending 824 a UE CONTEXT SETUP REQUEST message using the F1 communication interface, which message includes the security key of the target CU-UP of the UE 802. In response to receiving the F1:UE CONTEXT SETUP REQUEST message, the target DU 806 reserves the necessary resources and sends 826 an F1:UE CONTEXT SETUP RESPONSE message. As Figure 8 shown, the F1:UE CONTEXT SETUP RESPONSE message may include cell group configuration information of the target DU 806. Both the F1:UE CONTEXT SETUP REQUEST and F1:UE CONTEXT SETUP RESPONSE messages are defined by 3GPP. Thus, the security key can be sent from the CU-CP 808 to the target DU 806 and confirmed by the target DU 806 to the CU-CP 808 using the messages that have been sent according to 3GPP standards.

[0100] The CU-CP 808 also notifies 708 the serving DU 804 of the change of the CU-UP of a given target cell by identifying the target CU-UP 812 and the corresponding target cell or target DU 806 to the serving DU 804. As Figure 8 shown, the notification to the serving DU 804 may include the CU-CP 808 sending 828 a UE CONTEXT MODIFICATION REQUEST message to the serving DU 804 using the F1 communication interface. As Figure 8 shown, the UE CONTEXT MODIFICATION REQUEST message may include cell identification information and target CU-UP mapping information.

[0101] In response to receiving the UE CONTEXT MODIFICATION REQUEST message, the serving DU 804 stores 830 the received information identifying the target CU-UP 812 and sends 832 a UE CONTEXT MODIFICATION RESPONSE message to the CU-CP 808. As Figure 8As shown, the UE CONTEXT MODIFICATION RESPONSE message includes the combined cell group configuration information of all target cells identified by the CU-CP 808 to the UE 802. Both the UE CONTEXT MODIFICATION REQUEST message and the UE CONTEXT MODIFICATION RESPONSE message are defined by 3GPP. Therefore, the serving DU 804 can receive information about the target CU-UP 812 from the CU-CP and confirm this reception to the CU-CP 808 using a message that has already been sent according to 3GPP standards.

[0102] The CU-CP 808 also notifies the UE 802 of a security key change (indirectly, a CU-UP change) corresponding to the target cell at 710. As Figure 8 shown, according to 3GPP standards, this notification to the UE 802 can include the CU-CP 808 sending an 834 RRC reconfiguration message to the UE 802. As Figure 8 shown, the RRC reconfiguration message includes target cell configuration information, which includes the security key corresponding to the target cell, for example, the security key provided to the CU-CP 808 from the target DU 806 in the UE CONTEXT SETUP RESPONSE message. The RRC reconfiguration message containing the target cell configuration information (LTM preparation) indicates to the UE 802 that the security key is different for the new target cell served by the target CU-UP 812. For this scenario, the PDCP (Packet Data Convergence Protocol) entity needs to be reset.

[0103] In response to receiving the RRC reconfiguration message, the UE 802 sends an 836 intra-frequency or inter-frequency L1 measurement report to the serving DU 804 according to 3GPP standards. The intra-frequency or inter-frequency L1 measurement report provides the serving DU 804 with radio condition information measured by the UE, which indicates when the serving DU 804 should trigger the serving CU-UP 810 to perform data forwarding to the target DU 806.

[0104] Thereafter, based on the intra-frequency or inter-frequency L1 measurement report indicating a predefined threshold for the criteria that should trigger what should occur, the serving DU 804 triggers data forwarding from the serving CU-UP 810 to the target CU-UP 812 by notifying 712 the serving CU-UP 810 when to initiate data forwarding to the target CU-UP 812. As Figure 8As shown, according to the 3GPP standard, the serving DU 804 can notify the serving CU-UP 810 by sending an 840 control packet data unit (PDU) to the serving CU-UP 810. The control PDU is a user plane data packet including control plane information and thus is not a control signaling message. As Figure 8 shown, the control PDU includes information identifying the target CU-UP 812 (e.g., by including the ID of the CU-UP 812 provided to the serving DU 804 in the UE CONTEXT MODIFICATION REQUEST message), and information indicating that data forwarding to the target CU-UP 812 should start.

[0105] In response to the serving DU 804 notifying the serving CU-UP 810 to start data forwarding, the serving CU-UP 810 initiates 714 data forwarding to the target CU-UP 812 by sending 842 unsent and unacknowledged data PDUs to the target CU-UP 812. Due to the CU-UP ID provided by the serving DU 804 to the serving CU-UP 810, the serving CU-UP 810 knows which CU-UP of the base station to contact as the target CU-UP 812.

[0106] In some implementations, instead of the serving DU 804 sending an 840 control PDU to the serving CU-UP 810, the serving DU 804 can send a signaling message to the CU-CP 808 using the F1-C communication interface, and then the CU-CP 808 initiates data forwarding to the target CU-UP 812 by sending a message to the serving CU-UP 810 using the E1 communication interface, and then the serving CU-UP 810 initiates data forwarding to the target CU-UP 812. Different from Figure 8 the implementation shown, this alternative implementation uses one more message transmission than Figure 8 the implementation shown, but utilizes the E1-C communication interface when triggering data forwarding.

[0107] Referring again to Figure 7 , after the serving DU 804 has triggered data forwarding, for example, after the serving DU 804 sends an 840 control PDU to the serving CU-UP 810 (or to the CU-CP 808 in the alternative implementation), the serving DU 804 notifies the UE 802 of 716 a serving cell change, e.g., an LTM secondary component carrier (SCC) must be performed on the target DU 806 of the UE 802. As Figure 8 shown, the UE notification 716 can include the serving DU 804 sending an 844 MAC control element (MAC CE) to the UE 802, which includes a serving cell change command. Also as Figure 8As shown, the MAC CE may include a security key change indication, which may be a 1-bit indicator in the MAC CE.

[0108] In response to receiving the MAC CE, the UE 802 sends an 846 random access channel (RACH) message to the target DU 812 according to 3GPP standards, and the UE 802 sends an 852 RRC reconfiguration confirmation message to the CU-CP 808. In response to the successful completion of the RACH procedure, the target DU 812 sends an 848 control PDU to the target CU-UP 812, and the target DU 812 sends an 850 serving cell change notification message to the CU-CP 808 using the F1 communication interface. As Figure 8 shown, the control PDU may include an SCC and a RACH completion notification. This notification allows the start of downlink data transmission to the UE 802. Also as Figure 8 shown, the serving cell change notification message may include the ID of the target DU 812.

[0109] Figure 8 The base station of Figure 8 (not shown in the figure) is communicatively coupled to the core network. The method 700 may further include performing a PATH SWITCH procedure to the core network, which may be performed in the CU-UP relocation scenario within the gNB according to 3GPP standards.

[0110] In some implementations, as Figure 9As shown, the current subject matter can be configured to be implemented in system 900. System 900 can include one or more of processor 910, memory 920, storage device 930, and input / output device 940. Each of components 910, 920, 930, and 940 can be interconnected using system bus 950. Processor 910 can be configured to process instructions for execution within system 600. In some implementations, processor 910 can be a single-threaded processor. In alternative implementations, processor 910 can be a multi-threaded processor. Processor 910 can also be configured to process instructions stored in memory 920 or on storage device 930, including receiving or emitting information via input / output device 940. Memory 920 can store information within system 900. In some implementations, memory 920 can be a computer-readable medium. In alternative implementations, memory 920 can be a volatile memory unit. In some other implementations, memory 920 can be a non-volatile memory unit. Storage device 930 can be capable of providing mass storage for system 900. In some implementations, storage device 930 can be a computer-readable medium. In alternative implementations, storage device 930 can be a floppy disk device, a hard disk device, an optical disk device, a magnetic tape device, a non-volatile solid-state memory, or any other type of storage device. Input / output device 940 can be configured to provide input / output operations to system 900. In some implementations, input / output device 940 can include a keyboard and / or a pointing device. In alternative implementations, input / output device 940 can include a display unit for displaying a graphical user interface.

[0111] Figure 10 Illustrated is an exemplary method 1000 for LTM for CU-UP relocation within a base station according to some implementations of the present subject matter. For example, method 1000 can use Figures 5a - 8 the implementations shown and described above to execute.

[0112] Method 1000 includes determining 1002 a target distributed unit of a base station (e.g., Figure 6a UE 622 of Figure 8 , UW 802 of Figure 5a gNodeB of Figure 6a and Figure 6b gNodeB 624 of Figure 8 , gNodeB of Figures 5a - 5c DU 508 of Figure 5a DU 510 of Figure 6a DU 608 of Figure 6a DU 610 of Figure 6b DU 626 of Figure 6b DU 628 ofFigure 8 The target DU 806, etc., is served by the target centralized unit user plane of the base station (e.g., Figures 5a - 5c the gNB-CU-UP 506, Figure 6a and Figure 6b the CU-UP 606a, 606b, 606c, the target CU-UP 812, etc.). The serving CU-UP of the base station (e.g., Figures 5a - 5c the gNB-CU-UP 506, Figure 6a and Figure 6b the CU-UP 606a, 606b, 606c, the serving CU-UP 810, etc.) serves the serving DU of the base station that is currently serving the UE (e.g., Figures 5a - 5c the DU 508, Figure 5a the DU 510, Figure 6a the DU 608, Figure 6a the DU 610, Figure 6b the DU 626, Figure 6b the DU 628, Figure 8 the serving DU 804, etc.). The method 1000 further includes preparing the target CU-UP for LTM 1004 using the centralized unit control plane of the base station (e.g., Figures 5a - 5c the gNB-CU-CP 504, Figure 6a and Figure 6b the CU-CP 604, CU-CP 808, etc.), and preparing the target DU for LTM 1006 using the CU-CP.

[0113] In some implementations, the current subject matter may include one or more of the following optional features.

[0114] In some implementations, preparing the target CU-UP may include retrieving a security key from the CU-CP for the target CU-UP, and preparing the target DU may include sending the security key from the CU-CP to the target DU. Additionally, the security key configured by the target CU-UP may be sent from the CU-CP to the target DU in the UE CONTEXT SETUP REQUEST message; and / or retrieving the security key may include the CU-CP sending a BEARER CONTEXT SETUP REQUEST message to the target CU-UP, and the CU-UP sending a BEARER CONTEXT SETUP RESPONSE message to the CU-CP, and the BEARER CONTEXT SETUP RESPONSE message may include the security key that may correspond to the UE served by the target CU-UP. Additionally, the BEARER CONTEXT SETUP REQUEST message may include an information element (IE) for notifying the target CU-UP of the LTM.

[0115] In some implementations, preparing the target CU-UP may include sending an information element (IE) from the CU-CP to the target CU-UP that notifies the target CU-UP of the LTM to reserve resources for the UE.

[0116] In some implementations, the method may further include, after the preparation of the target CU-UP and the preparation of the target DU, triggering the serving CU-UP to start forwarding data to the target CU-UP. Additionally, the triggering may include sending a control packet data unit (PDU) from the serving DU to the serving CU-UP to initiate downlink data transmission, and thereafter, the serving CU-UP sending the unsent and unacknowledged data PDUs to the target CU-UP. Additionally, the method may further include sending, from the CU-CP to the serving DU, information for identifying a change of the serving CU-UP for the LTM before the transmission of the control PDU to trigger data forwarding. Additionally, the information may be sent from the CU-CP to the serving DU in the UE CONTEXT MODIFICATION REQUEST message.

[0117] In some implementations, the method may further include, after the preparation of the target CU-UP and the preparation of the target DU, triggering the target CU-UP to start serving the UE via the target CU. Additionally, the triggering may include sending a control packet data unit (PDU) from the target DU to the target CU-UP, and thereafter, the target CU-UP sending a data PDU to the target DU; or, the triggering may include sending a first message from the serving DU to the CU-CP, and thereafter, the CU-CP sending a second message to the serving CU-UP, and thereafter, the serving CU-UP sending a third message to the target CU-UP; and / or serving the UE may include sending a first message from the target DU to the CU-CP, and thereafter, the CU-CP sending a second message to the target CU-UP, and thereafter, the target CU-UP initiating a downlink data transmission towards the target DU.

[0118] In some implementations, the determination may include using the CU-CP to analyze a radio resource control (RRC) measurement report received from the UE at the CU-CP.

[0119] In certain implementations, the serving CU-UP and the target CU-UP may be different entities.

[0120] In some implementations, the base station may be a next-generation radio access network (NG-RAN) node (e.g., gNodeB).

[0121] In some implementations, the base station may include at least one processor and at least one non-transitory storage medium.

[0122] The systems and methods disclosed herein may be embodied in various forms, including, for example, a data processor, such as a computer, which also includes a database, digital electronic circuitry, firmware, software, or a combination thereof. Additionally, the above-described features and other aspects and principles of the implementations of the present disclosure may be implemented in various environments. Such environments and related applications may be specifically constructed to perform various processes and operations in accordance with the disclosed implementations, or they may include a general-purpose computer or computing platform that is selectively activated or reconfigured by code to provide the necessary functionality. The processes disclosed herein have no inherent relationship with any particular computer, network, architecture, environment, or other device, and may be implemented through a suitable combination of hardware, software, and / or firmware. For example, various general-purpose machines may be used with programs written in accordance with the teachings of the disclosed implementations, or, more conveniently, a specialized device or system may be constructed to perform the required methods and techniques.

[0123] The systems and methods disclosed herein can be implemented as a computer program product, i.e., a computer program tangibly embodied in an information carrier, e.g., in a machine-readable storage device or a propagated signal, for execution by, or to control the operation of, a data processing apparatus, e.g., a programmable processor, a computer, or multiple computers. The computer program can be written in any form of programming language, including compiled or interpreted languages, and can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for a computing environment. The computer program can be deployed to be executed on one computer or multiple computers, which are located at one site or distributed among multiple sites and interconnected by a communication network.

[0124] As used herein, the term "user" can refer to any entity, including a person or a computer.

[0125] Although in some cases, ordinal numbers such as first, second, etc. can be related to order; as used in this document, ordinal numbers do not necessarily denote order. For example, ordinal numbers can only be used to distinguish one item from another. For example, to distinguish a first event and a second event, but no temporal order or fixed reference system needs to be implied (such that the first event in one paragraph of the specification can be different from the first event in another paragraph of the specification).

[0126] The foregoing description is intended to illustrate but not limit the scope of the invention, the scope of protection of the invention being defined by the scope of the appended claims. Other implementations are within the scope of the following claims.

[0127] These computer programs (which may also be referred to as programs, software, software applications, applications, components, or code) include machine instructions for a programmable processor and can be implemented in a high-level programming and / or object-oriented programming language and / or assembly / machine language. As used herein, the term "machine-readable medium" refers to any computer program product, apparatus, and / or device for providing machine instructions and / or data to a programmable processor, such as, for example, a disk, an optical disk, a memory, and a programmable logic device (PLD), including a machine-readable medium that receives the machine instructions as a machine-readable signal. The term "machine-readable signal" refers to any signal for providing machine instructions and / or data to a programmable processor. The machine-readable medium can non-transitorily store such machine instructions, such as, for example, a non-transitory solid-state memory or a magnetic hard disk drive or any equivalent storage medium. The machine-readable medium can alternatively or additionally store such machine instructions in a transitory manner, such as, for example, a processor cache or other random access memory associated with one or more physical processor cores.

[0128] To provide interaction with a user, the subject matter described herein can be implemented on a computer having a display device for displaying information to the user, such as, for example, a cathode ray tube (CRT) or a liquid crystal display (LCD) monitor; and a keyboard and pointing device, such as, for example, a mouse or trackball, through which the user can provide input to the computer. Other types of devices can also be used to provide interaction with the user. For example, the feedback provided to the user can be any form of sensory feedback, such as, for example, visual feedback, auditory feedback, or tactile feedback; and the input from the user can be received in any form, including but not limited to sound, voice, or tactile input.

[0129] The subject matter described herein may be implemented in a computing system that includes a back-end component, such as, for example, one or more data servers; or includes a middleware component, such as, for example, one or more application servers; or includes a front-end component, such as, for example, one or more client computers with a graphical user interface or a web browser, through which a user can interact with an implementation of the subject matter described herein; or includes any combination of such back-end components, middleware components, or front-end components. The components of the system may be interconnected by any form or medium of digital data communication, such as, for example, a communication network. Examples of communication networks include, but are not limited to, a local area network (LAN), a wide area network (WAN), and the Internet.

[0130] A computing system may include clients and servers. Clients and servers are typically (but not limited to) remote from each other and typically interact through a communication network. The relationship of client and server arises from computer programs running on the respective computers and having a client-server relationship to each other.

[0131] The implementations set forth in the above description do not represent all implementations consistent with the subject matter described herein. Instead, they are merely some examples consistent with aspects related to the described subject matter. Although some variations are described in detail above, other modifications or additions are also possible. In particular, other features and / or variations may be provided in addition to those described herein. For example, the above implementations may be directed to various combinations and subcombinations of the disclosed features and / or combinations and subcombinations of several other features described above. In addition, the logical flows described in the accompanying drawings and / or herein do not necessarily require the specific order shown or in a sequential order to achieve the desired results. Other implementations may be within the scope of the following claims.

Claims

1. A device, comprising: at least one processor, and at least one non-transitory storage medium storing instructions that, when executed by the at least one processor, cause the at least one processor to perform operations, the operations including: determining that a target distributed unit (DU) of a base station serving a user equipment (UE) is served by a target central unit user plane (CU-UP) of the base station, wherein the serving CU-UP of the base station serves the serving DU of the base station currently serving the UE; using the central unit control plane (CU-CP) of the base station to prepare the target CU-UP for layer 1 / layer 2 triggered mobility (LTM); and using the CU-CP to prepare the target DU for LTM.

2. The device according to claim 1, wherein preparing the target CU-UP comprises: using the CU-CP to retrieve a security key from the target CU-UP; and preparing the target DU comprises: sending the security key from the CU-CP to the target DU.

3. The device according to claim 2, wherein the security key configured by the target CU-UP is sent from the CU-CP to the target DU in a UE CONTEXT SETUP REQUEST message.

4. The device according to claim 2, wherein retrieving the security key comprises: the CU-CP sending a BEARER CONTEXT SETUP REQUEST message to the target CU-UP, and the CU-UP sending a BEARER CONTEXT SETUP RESPONSE message to the CU-CP; and the BEARER CONTEXT SETUP RESPONSE message includes: the security key corresponding to the UE served by the target CU-UP.

5. The device according to claim 4, wherein the BEARER CONTEXT SETUP REQUEST message comprises: an information element (IE) notifying the target CU-UP of the LTM.

6. The device according to claim 1, wherein preparing the target CU-UP comprises: sending an information element (IE) from the CU-CP to the target CU-UP, the IE notifying the target CU-UP of the LTM to reserve resources for the UE.

7. The device according to claim 1, wherein the operations further comprise: after the preparation of the target CU-UP and the preparation of the target DU, triggering the serving CU-UP to start forwarding data to the target CU-UP.

8. The device according to claim 7, wherein the triggering comprises: sending a control packet data unit (PDU) from the serving DU to the serving CU-UP, and thereafter, the serving CU-UP sending unsent and unacknowledged data PDUs to the target CU-UP.

9. The apparatus according to claim 1, wherein the operation further comprises: after the preparation of the target CU-UP and the preparation of the target DU, triggering the target CU-UP to start serving the UE via the target CU.

10. The apparatus according to claim 9, wherein the triggering comprises: sending a control packet data unit (PDU) from the target DU to the target CU-UP to initiate downlink data transmission, and thereafter, the target CU-UP sending a data PDU to the target DU.

11. The apparatus according to claim 8, wherein the operation further comprises: before the transmission of the control PDU to trigger data forwarding, sending information for identifying a change of the serving CU-UP for LTM from the CU-CP to the serving DU.

12. The apparatus according to claim 11, wherein the information is sent from the CU-CP to the serving DU in a UE CONTEXT MODIFICATION REQUEST message.

13. The apparatus according to claim 9, wherein the triggering comprises: sending a first message from the serving DU to the CU-CP, and thereafter, the CU-CP sending a second message to the serving CU-UP, and thereafter, the serving CU-UP sending a third message to the target CU-UP.

14. The apparatus according to claim 9, wherein serving the UE comprises: sending a first message from the target DU to the CU-CP, and thereafter, the CU-CP sending a second message to the target CU-UP, and thereafter, the target CU-UP initiating downlink data transmission towards the target DU.

15. The apparatus according to claim 1, wherein the determining comprises: using the CU-CP to analyze a radio resource control (RRC) measurement report received from the UE at the CU-CP.

16. The apparatus according to claim 1, wherein the serving CU-UP and the target CU-UP are different entities.

17. The apparatus according to claim 1, wherein the base station is a next generation radio access network (NG-RAN) node.

18. The apparatus according to claim 1, wherein the base station comprises the at least one processor and the at least one non-transitory storage medium.

19. A computer-implemented method, comprising: determining that a target distributed unit (DU) of a base station serving a user equipment (UE) is to be served by a target central unit user plane (CU-UP) of the base station, wherein the serving CU-UP of the base station serves the serving DU of the base station currently serving the UE; using a central unit control plane (CU-CP) of the base station to prepare the target CU-UP for layer 1 / layer 2-triggered mobility (LTM); and using the CU-CP to prepare the target DU for LTM.

20. A non-transitory storage medium storing at least one instruction which, when executed by at least one processor, causes the at least one processor to perform operations, the operations comprising: determining that a target distributed unit (DU) of a base station serving a user equipment (UE) is served by a target central unit user plane (CU-UP) of the base station, wherein the serving CU-UP of the base station serves the serving DU of the base station currently serving the UE; using a central unit control plane (CU-CP) of the base station, preparing the target CU-UP for layer 1 / layer 2-triggered mobility (LTM); and using the CU-CP, preparing the target DU for LTM.

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