Determining target cell for handover between neighbor cells based on measurement reports and cell identifiers

Abstract

To provide a method, a base station device, and user equipment (UE), in which the base station device causes the UE to perform measurements of signals transmitted in a plurality of neighbor cells and transmit measurement reports.SOLUTION: In a communication system, UE transmits a measurement report further including an associated unique cell identifier together with a corresponding measurement, regarding a neighbor cell. A base station device identifies the corresponding neighbor cell from a plurality of neighbor cells based on the reported unique cell identifier and triggers a communication procedure involving the UE and the identified neighbor cell. The UE transmits instead of the unique cell identifier (such as CGI) or alternatively, a non-unique cell identifier (for example, PCI) or the non-unique cell identifier, and geographical location information that allows a base station to uniquely identify the neighbor cell based on a neighbor relation table (NRT), together with measurement results.SELECTED DRAWING: Figure 5a

Description

[Technical Field]

[0001] The present invention relates to communication systems. In particular, but not exclusively, to wireless communication systems and devices therein operating in accordance with 3GPP (3rd Generation Partnership Project) standards or equivalent or derivative standards. In particular, but not exclusively, the present invention relates to determining a target cell for handover in so-called "next generation" systems involving multiple home base stations within the coverage of a macrocell. [Background technology]

[0002] The latest developments in 3GPP standards are referred to as LTE (Long Term Evolution) with EPC (Evolved Packet Core) networks and E-UTRAN (Evolved UMTS Terrestrial Radio Access Network), also commonly referred to as "4G." Furthermore, the terms 5G and NR (New Radio) refer to developing communication technologies that are expected to support various applications and services. Various details of 5G networks are described, for example, in the NGMN 5G White Paper V1.0 by the NGMN (Next Generation Mobile Network) Alliance, which is available at https: / / www.ngmn.org / 5g-white-paper.html. 3GPP plans to support 5G through the so-called 3GPP NextGen (Next Generation) RAN (Radio Access Network) and 3GPP Next Generation Core Network.

[0003] In 3GPP standards, a NodeB (or "eNB" in LTE, "gNB" in 5G, etc.) is a base station through which communication devices (user equipment or "UE") connect to the core network and communicate with other communication devices or remote servers. A base station may also be referred to as a TRP (Transmission and Reception Point). For ease of explanation, in this application, the term base station refers to any such base station, and the term mobile device or UE refers to any such communication device. The core network (i.e., EPC in the case of LTE) is responsible for functions such as subscriber management, mobility management, charging, security, and call session management, and connects communication devices to external networks such as the Internet.

[0004] Communication devices include, for example, mobile communication devices such as mobile phones, smartphones, user equipment, personal digital assistants, laptop / tablet computers, web browsers, e-book readers, etc. Such mobile (or generally fixed) devices are typically operated by a user, although so-called Internet of Things (IoT) devices and similar machine-type communication (MTC) devices may also be connected to the network. For ease of explanation, this application will refer to mobile devices (or User Equipment (UE)) throughout the specification, although it is understood that the techniques described herein may be implemented on any (mobile and / or generally fixed) communication device that is capable of connecting to a communication network to send and receive data, whether controlled by human input or by software instructions stored in memory.

[0005] The term macro base station refers to a base station having one or more macro cells (cells covering a relatively large geographic area), while the term small cell refers to a cell covering a relatively small geographic area (e.g., a home or office) that often overlaps with a macro cell. A small cell (or picocell) may be operated by a small cell base station or home base station ("HeNB" or "HNB"), etc. However, such small cells are often indirectly controlled by a macro eNB (e.g., a macro base station that operates a macro cell that the small cell overlaps). Thus, at least in the case of a macro base station, a single base station can operate and / or control a large number of cells (e.g., hundreds in the case of LTE or thousands in the case of NR).

[0006] Each base station is associated with a unique base station identifier (e.g., "eNB-ID"). The base station identifier (which may form part of the corresponding cell identifier or may be identical) may be used to uniquely identify an individual cell. When the cell identifier is combined with a network identifier (e.g., a Public Land Mobile Network (PLMN) identifier), it may provide a substantially globally unique identification. As described in section 8.2 of 3GPP Technical Specification 36.300 V15.0.0, the so-called E-UTRAN Cell Global Identifier (ECGI) may be used to globally identify a cell.

[0007] In 3G / LTE networks, a typical macro base station serves a limited number of cells (e.g., three sectors / cells) but may control a large number of home base stations. However, in NR networks, each macro base station (gNB) may serve a relatively large number of cells. This problem is further complicated by the proposed division of gNB functionality between a Central Unit (CU) and one or more Distribution Units (DUs), where each DU can have multiple cells for itself.

[0008] Each cell can be identified using either a Primary Scrambling Code (PSC) associated with the cell and / or a Physical Cell Identity (PCI) broadcast within the cell. Because the typical cell size of an HNB / HeNB is much smaller than that of a macrocell, there may be multiple HNBs / HeNBs within the coverage area (eNB / gNB cells) of a macrocell with the same PSC / PCI. This leads to a condition called PSC / PCI confusion, where during a mobility procedure (e.g., during handover), the source base station is unable to determine the correct target cell for handover from the PSC / PCI included in a measurement report from a mobile device.

[0009] One way to address the PSC / PCI confusion issue is to configure the mobile device to report the global cell ID of the target HNB / HeNB to the source base station after receiving the measurement results (including the PSC / PCI). This is shown in Figure 4, which corresponds to the procedure described in Section 10.5.1.2 of 3GPP TS 36.300, which is incorporated herein in its entirety. However, reporting the global cell ID of the target base station to the source base station, as shown in steps 5 through 7 of Figure 4, causes handover delays and requires the mobile device to perform additional signaling with the serving base station and to obtain system information from the measured base station (which may also affect the mobile device's power consumption). Summary of the Invention [Problem to be solved by the invention]

[0010] However, the inventors have found a PSC / PCI confusion scenario that cannot be addressed by existing mechanisms. For example, in a network supporting E-UTRAN New Radio-Dual Connectivity (EN-DC) and / or Next Generation-Dual Connectivity (NGEN-DC), when a compatible UE is connected to an E-UTRAN (LTE) cell and is ready to establish dual connectivity between the LTE cell and an NR cell, the UE sends measurement reports about the detected NR cells to the current LTE base station (because it is the LTE base station that makes the decision about adding an SgNB (i.e., adding an NR cell to the UE's dual connectivity configuration)). The measurement results about the detected NR cells are reported together with the NR PCI of these NR cells (the measurement target defines the frequency). However, PCI confusion can occur in at least the following scenarios: 1) Two or more neighboring gNBs have cells with the same NR PCI configuration (lack of uniqueness of coverage of one LTE cell, as shown in Figure 6); 2) Two or more serving NR cells of the target gNB have the same NR PCI configuration (lack of uniqueness of 1gNB, as shown in Figure 7).

[0011] In the first scenario, the serving LTE base station (eNB) cannot determine to which gNB the SgNB addition request should be sent. In the second scenario, the target gNB cannot determine in which NR cell / DU it needs to reserve resources for the UE (even if the eNB can determine the correct gNB based on the PCI of the NR cell).

[0012] The inventors have come to realize that, as more and more NR base stations and HNBs are installed, the above PCI confusion scenarios will become very common and that current mechanisms cannot be employed to address these scenarios. Accordingly, preferred exemplary embodiments of the present invention aim to provide methods and apparatus that address or at least partially address the above problems.

[0013] For the sake of efficiency of understanding by those skilled in the art, the present invention will be described in detail in the context of a 3GPP system (5G network), but the principles of the present invention can also be applied to other systems in which a large number of base stations and cells are installed. [Means for solving the problem]

[0014] In an exemplary aspect, the present invention provides a method performed by a base station apparatus in a communication system including a plurality of cells, each cell having a respective PCI (Physical Cell Identifier) associated therewith, comprising: transmitting to a UE (User Equipment) a measurement configuration for configuring the UE to perform measurements on signals transmitted on each of a plurality of neighboring cells and to transmit a measurement report including at least one result of the configured measurements for at least one neighboring cell of the plurality of neighboring cells; receiving the measurement report including at least one result of the configured measurements and transmitted by the UE based on the measurement configuration, the measurement report including, for each of at least a subset of the at least one neighboring cell for which the at least one measurement result relates, the measurement report further including a respective unique cell identifier (e.g., a globally unique identifier) along with the corresponding at least one measurement; and identifying a corresponding neighboring cell from among the plurality of cells based on the at least one unique cell identifier received in the measurement report to trigger a corresponding communication procedure involving the UE and the identified neighboring cell.

[0015] In another exemplary aspect, the present invention provides a method performed by a base station apparatus in a communication system including a plurality of cells, each cell having a respective PCI (Physical Cell Identifier) associated therewith, comprising: transmitting to a User Equipment (UE) a measurement configuration for configuring the UE to perform measurements on signals transmitted on each of a plurality of neighboring cells and to transmit a measurement report comprising at least one result of the configured measurements for at least one neighboring cell of the plurality of neighboring cells; receiving the measurement report comprising at least one result of the configured measurements and transmitted by the UE based on the measurement configuration, the measurement report further comprising at least one PCI of the at least one neighboring cell for which the at least one measurement result is associated with a corresponding at least one measurement; and identifying a neighboring cell from among the plurality of cells based on a Neighbor Relation Table (NRT) and the received at least one PCI to trigger a corresponding communication procedure involving the UE and the identified neighboring cell.

[0016] In another exemplary aspect, the present invention provides a method performed by a base station device in a communication system including a plurality of cells, each cell having a respective PCI (Physical Cell Identifier) associated therewith, comprising: receiving, from different base station devices, a message for triggering a communication procedure involving a UE (User Equipment) served by the different base station devices and a cell identified by an associated PCI; and determining, based on a Neighbor Relation Table (NRT) and the received PCI, whether the received message relates to a cell controlled by the base station device.

[0017] In another exemplary aspect, the present invention provides a method performed by a base station apparatus in a communication system including a plurality of cells, each cell having a respective PCI (Physical Cell Identifier) associated therewith, comprising: transmitting to a User Equipment (UE) a measurement configuration for configuring the UE to perform measurements on signals transmitted on each of a plurality of neighboring cells and to transmit a measurement report comprising at least one result of the configured measurements for at least one neighboring cell of the plurality of neighboring cells; receiving the measurement report comprising at least one result of the configured measurements and transmitted by the UE based on the measurement configuration, the measurement report further comprising information identifying a geographical location (e.g., GPS coordinates) associated with the UE and a respective PCI associated with each cell for the at least one result; and identifying a neighboring cell from among the plurality of cells based on a Neighbor Relation Table (NRT) and the received measurement report to trigger a corresponding communication procedure involving the UE and the identified neighboring cell.

[0018] In another exemplary aspect, the present invention provides a method performed by a UE (User Equipment) in a communication system including a plurality of cells, each cell having a respective PCI (Physical Cell Identifier) associated therewith, comprising: receiving from a base station device a measurement configuration for configuring the UE to perform measurements of signals transmitted in each of a plurality of neighboring cells and to transmit a measurement report including at least one result of the configured measurements for at least one neighboring cell of the plurality of neighboring cells; and transmitting the measurement report, transmitted by the UE based on the measurement configuration, including at least one result of the configured measurements, wherein the measurement report further includes a respective unique cell identifier for each of at least a subset of the at least one neighboring cell for which the at least one measurement result is associated together with the corresponding at least one measurement used by the base station device in identifying a corresponding neighboring cell from among the plurality of neighboring cells for triggering a corresponding communication procedure involving the UE and the neighboring cell.

[0019] In another exemplary aspect, the present invention comprises a method performed by a User Equipment (UE) in a communication system including a plurality of cells, each cell having a respective Physical Cell Identifier (PCI) associated therewith, comprising: receiving from a base station device a measurement configuration for configuring the UE to perform measurements of signals transmitted in each of a plurality of neighboring cells and to transmit a measurement report comprising at least one result of the configured measurements for at least one neighboring cell of the plurality of neighboring cells; performing signal measurements based on the measurement configuration; and transmitting to the base station device a measurement report comprising at least one result of the configured measurements, the measurement report further comprising information identifying a geographical location (e.g., GPS coordinates) associated with the UE and a respective PCI associated with each cell for which the at least one result relates.

[0020] Exemplary aspects of the invention extend to corresponding systems, apparatus, and computer program products, such as computer-readable storage media, storing instructions operable to program a programmable processor to perform the methods and possibilities described in the exemplary aspects and to program a suitably adapted computer to provide an apparatus as described in any of the claims.

[0021] Each feature disclosed in this specification (including the claims) and / or shown in the drawings may be incorporated into the present invention independently (or in combination with) other disclosed and / or shown features. In particular, but without limitation, the features of claims dependent on a particular independent claim may also be introduced into that independent claim in any combination or individually. [Brief explanation of the drawings]

[0022] Examples of illustrative embodiments of the present invention will now be described with reference to the accompanying drawings, in which:

[0023] [Figure 1] FIG. 1 is a diagram that illustrates schematically a cellular communication system in which exemplary embodiments of the present invention may be applied. [Figure 2] FIG. 2 is a schematic block diagram of a mobile device forming part of the system shown in FIG. [Figure 3] FIG. 3 is a schematic block diagram of a base station forming part of the system shown in FIG. [Figure 4] FIG. 4 is a schematic timing diagram illustrating an exemplary manner in which cell identifiers may be resolved in a cellular communication system (eg, LTE). [Figure 5a] FIG. 5a is a schematic diagram illustrating an exemplary method by which PSC / PCI confusion can be addressed in the system shown in FIG. [Figure 5b] FIG. 5b is a schematic diagram illustrating another exemplary method by which PSC / PCI confusion may be addressed in the system shown in FIG. [Figure 5c]FIG. 5c is a schematic diagram illustrating another exemplary method by which PSC / PCI confusion may be addressed in the system shown in FIG. [Figure 5d] FIG. 5d is a schematic diagram illustrating another exemplary method by which PSC / PCI confusion may be addressed in the system shown in FIG. [Figure 5e] FIG. 5e is a schematic diagram illustrating another exemplary method by which PSC / PCI confusion may be addressed in the system shown in FIG. [Figure 6] FIG. 6 is a diagram illustrating a possible scenario in which PSC / PCI confusion may occur in the system of FIG. [Figure 7] FIG. 7 is a diagram illustrating a possible scenario in which PSC / PCI confusion may occur in the system of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0024] <Summary> FIG. 1 illustrates a schematic diagram of a communications network 1 in which mobile devices 3 (mobile phones and / or other user equipment) can communicate with each other via base stations 5 (e.g., LTE base stations (“eNBs”) and / or 5G base stations (“gNBs”)) and a core network (not shown) using an appropriate Radio Access Technology (RAT). Those skilled in the art will appreciate that, although FIG. 1 illustrates one mobile device 3 and three base stations 5, 5-1, and 5-2 for illustrative purposes, other base stations and communications devices will typically be included when the system is implemented.

[0025] Each base station 5 operates one or more associated cells 7. A mobile device 3 connects to a suitable cell 7 (depending on the cell's location and possibly other factors, such as signal conditions, subscription data, capabilities, etc.) by establishing an RRC (Radio Resource Control) connection with the appropriate base station 5 operating that cell 7.

[0026] In the example shown in FIG. 1, the base station 5 is an LTE base station (eNB) that operates (controls) a cell 7S serving the current mobile device 3. In this example, the serving cell 7S is a macrocell with a relatively wide coverage area, but in other examples it may be a small cell (e.g., an HNB cell). The base stations 5-1 and 5-2 are NR base stations (gNBs) with an architecture in which base station functionality is divided between a central unit (CU) and corresponding (at least one) distribution unit (DU) (although they may also include an eNB portion). Specifically, the CU is a logical node that performs a subset of base station functions (e.g., user data forwarding, mobility control, radio access network sharing, positioning, session management), while the remaining base station functions are performed by the associated DU. The CU controls the operation of the associated DU via an appropriate front-haul (Fs) interface (which may include separate user and control plane Fs interfaces). The CU may be called a BBU / REC / RCC / C-RAN / V-RAN, and the DU may be called an RRH / RRU / RE / RU.

[0027] The base stations 5 are connected to the core network via suitable core network interfaces, such as the S1 interface (LTE) and / or the N2 / N3 interface (5G). The base stations 5 are also connected to neighbouring base stations (directly or via a (home) base station gateway) via suitable base station interfaces, such as the X2 interface (LTE) or the Xn interface (5G).

[0028] The core network includes one or more appropriate User-Plane Functions (UPFs) and one or more Control-Plane Functions (CPFs) that, among other things, track the location of mobile devices 3 within the communication network 1 (e.g., a Mobility Management Entity (MME) or an Access and Mobility Management Function (AMF)), store subscription-related information for each UE (e.g., information identifying which mobile devices 3 are configured as machine-type communication devices), store control parameters applicable to each mobile device 3, and handle the respective traffic flows of each mobile device 3 according to applicable policies (e.g., including network, subscription, charging policies, etc.). Although omitted from FIG. 1 for simplicity, the core network typically includes one or more gateways for connecting to other (external) networks, such as the Internet, to servers hosted outside the core network, etc.

[0029] The base stations 5-1 and 5-2 operate multiple associated cells 7 via their respective DUs. In this embodiment, each DU has one or more associated cells 7 (all controlled by a CU connected to that DU). Each cell has an associated cell identifier (e.g., PCI). The communication network 1 makes effective use of Automatic Neighbor Relation (ANR) functionality. Accordingly, each base station 5 is configured to store and maintain an appropriate Neighbor Relations Table (NRT) for each cell 7 that the base station 5 operates (directly or via an associated DU). Details of the ANR functionality and NRT are described in section 22.3.2a of 3GPP TS 36.300, and are summarized at the end of the description.

[0030] As described above, mobile device 3 is currently served by cell 7S, which is controlled by base station 5. However, if mobile device 3 moves in the direction indicated by the arrow in FIG. 1 , base station 5 must initiate a handover of mobile device 3 to a suitable target cell 7T. To do so, base station 5 configures mobile device 3 to perform appropriate signal measurements on multiple cells 7 in the vicinity of mobile device 3 and report the results of such measurements (e.g., when certain conditions are met, such as finding a candidate cell 7 with sufficient signal strength during the signal measurements). In another embodiment, cell 7S may serve mobile device 3 as a primary cell or “PCell” (e.g., an LTE cell), and base station 5 may attempt to configure mobile device 3 for dual connectivity involving cell 7T as a secondary cell or “SCell.” Similar to the handover example, base station 5 configures mobile device 3 to perform appropriate signal measurements and report the results of the measurements to base station 5.

[0031] Because there may be a large number of cells (DUs) in a given geographical area (especially in the case of small cells), two or more cells 7 may have the same PCI (or the same PSC) configuration. In this example, both cells 7T and 7A are configured with the same PCI value ("X"). This means that within the coverage of a large cell (e.g., a macro cell) or in the vicinity of the mobile device 3's current serving cell 7S, at least some cells 7 may lack uniqueness. This scenario corresponds to the scenario shown in FIG. 6.

[0032] Furthermore, since multiple cells 7 / DU may be controlled by the same base station 5 (CU), two or more cells 7 of that base station 5 may have the same PCI (or the same PSC) configuration. This means that at least some of the cells 7T and 7A may lack uniqueness within the geographic area served by a particular base station 5 (CU). This scenario corresponds to the scenario shown in Figure 7.

[0033] In this system, the mobile device 3 and base station 5 are advantageously configured to avoid confusion arising in the above scenario by performing appropriate procedures to uniquely identify a particular cell 7 (e.g., a target cell or secondary cell for handover for dual connectivity), regardless of whether a split CU / DU architecture is used and whether PCI (or PSC) uniqueness is ensured over a given area (e.g., among cells 7 in the vicinity of the mobile device 3 and / or among cells controlled by a particular base station 5).

[0034] More specifically, the mobile device 3 and the base station 5 may be configured to follow one (or more) of the following options, or any combination of the following options: The mobile device 3 may be configured to automatically transmit the GCI of at least each subset of reported cells 7 together with the measurements configured for those cells to the serving base station 5 without requiring a separate System Information (SI) request (i.e., an SI request for the subset of reported cells 7 containing the strongest cell). Thus, the base station 5 may be configured to determine the correct cell 7T (the base station 5-1 controlling that cell 7T) based on the GCI without requiring the UE to be separately reconfigured to read the system information (e.g., by sending a separate reconfiguration message including an SI request). The mobile device 3 may be configured to send the PSC / PCI of each reported cell 7 to the serving base station 5 (as part of normal operation) and to send the GCI of one or more cells 7 upon request from the base station 5 (e.g., upon receiving a request from the base station 5 for a GCI for a particular cell 7, or upon receiving a new measurement configuration for a particular cell 7). The base station 5 may be configured to determine the GCI from the reported PSC / PCI and information stored in the neighbor relation table before requesting the GCI from the mobile device 3. The mobile device 3 may be configured to report the GCI of a subset (a predetermined number and / or type of cells) of all measured cells 7, and to report the PSC / PCI associated with the remaining cells. The base station 5 may be configured to determine the correct cell 7T (the base station 5-1 controlling the cell 7T) based on either the GCI or the PSC / PCI available for the cell 7T, without requesting the GCI from the mobile device 3. The base station 5 may be configured to determine the GCI from information stored in the neighbor relation table and the reported PSC / PCI. The mobile device 3 may be configured (in normal operation) to transmit the PSC / PCI of each reported cell 7 to its serving base station 5. If the base station 5 cannot determine the GCI based on the PSC / PCI, the base station 5 may forward the PSC / PCI to one of the neighboring base stations operating a cell with that PCI (e.g., gNB 5-1 or 5-2 operating 7T and 7A, respectively). The neighboring base stations 5-1 / 5-2 may be configured to determine the correct cell 7T from the information stored in their neighbor relation table and the PSC / PCI received from the serving base station 5. The serving base station 5 may be configured to determine the GCI from the information stored in its neighbor relation table and the geographical location of the mobile device 3 (which is reported by the mobile device 3 together with the measurement results or in a separate procedure, e.g., upon request from the serving base station 5). In all options, the base station (eNB / gNB5 controlling the UE's current cell 7S and / or eNB / gNB5-1 controlling the target cell 7T) may be configured to use the GCI (e.g., instead of the associated PSC / PCI) to identify the cell 7T in handover and / or dual connectivity procedures.

[0035] Thus, advantageously, the serving base station 5 can determine which cell 7T / which base station 5-1, 5-2 (CU1, CU2) to communicate with, and the target base station 5-1 can determine the cell 7T for which resources need to be reserved for the mobile device 7 (for handover and / or dual connectivity including that cell 7T).

[0036] <Mobile devices> Figure 2 is a block diagram illustrating the major components of the mobile device 3 (e.g., mobile telephone, other user equipment, etc.) shown in Figure 1. As shown, the mobile device 3 includes transceiver circuitry 31 operable to transmit and receive signals to and from a base station 5 via one or more antennas 33. The mobile device 3 includes a controller 37 that controls the operation of the mobile device 3. The controller 37 is associated with a memory 39 and is connected to the transceiver circuitry 31. Although not necessary for operation, it will be apparent that the mobile device 3 may include all of the standard functionality of a typical mobile telephone 3 (e.g., user interface 35), which may be implemented by any one or combination of hardware, software, and firmware, as appropriate.

[0037] The software may be pre-installed in memory 39 and / or may be downloaded, for example, via a communications network or from a Removable Data Storage Device (RMD). Controller 37 is configured in this embodiment to control the overall operation of mobile device 3 via program or software instructions stored in memory 39. As shown, these software instructions include, among other things, an operating system 41, a communications control module 43, a cell ID module 45, and an optional Global Navigation Satellite System (GNSS) module 47.

[0038] The communication control module 43 is operable to control communication between the UE 3 and its base station 5 (and with other communication devices, such as other mobile devices, network nodes, etc., connected to that serving base station 5). The communication control module 43 is also responsible for obtaining system information (of the current serving cell and optionally neighboring cells), performing appropriate signal measurements in cells 7 for which such measurements have been configured by the serving base station 5, and reporting the results of the signal measurements to the serving base station 5.

[0039] The cell ID module 45 is responsible for obtaining information identifying each cell 7 (at least multiple cells 7 in the vicinity of the mobile device 3) and using the information in subsequent procedures involving the cell 7 (e.g., when reporting measurements for the cell 7, during handover to the cell 7, etc.). The information identifying a particular cell 7 may include one or more of the following: an appropriate PLMN ID associated with the cell 7, an ECI / NCI (cell identifier) associated with the cell 7, a PCI associated with the cell 7, a PSC associated with the cell 7, a GCI / EGCI (global cell identifier) associated with the cell 7, and a TAC associated with the cell 7. The cell ID module 45 may obtain the information identifying a given cell 7 from system information obtained by the communication control module 43.

[0040] The GNSS module 47, if present, is responsible for obtaining information for determining the current geographical position (e.g., GPS coordinates) of the mobile device 3. The GNSS module 47 may be realized in the form of a GPS (Global Positioning System) module, a GLONASS (Global Navigation Satellite System) module, a Galileo module, a Beidou module, etc.

[0041] <Base station> FIG. 3 is a block diagram illustrating the main components of one of the base stations 5 shown in FIG. 1. As shown, the base station 5 includes transceiver circuitry 51 for transmitting and receiving signals to and from communication devices (e.g., mobile devices 3 / user equipment) via one or more antennas 53, and a network interface 55 for transmitting and receiving signals to and from the core network (via an appropriate core network interface, such as an S1 / N2 / N3 interface) and neighboring base stations (via an appropriate base station interface, such as an X2 / Xn interface). The base station 5 includes a controller 57 for controlling the operation of the base station 5. The controller 57 is associated with a memory 59. Although not shown in FIG. 3, it is clear that the base station 5 has all the conventional functions of a conventional cellular telephone network base station, which may be implemented by any one or any combination of hardware, software, and firmware, as appropriate. The software may be pre-installed in the memory 59 or may be downloaded, for example, via the communication network 1 or from a removable data storage device (RMD). The controller 57, in this embodiment, is configured to control the overall operation of the base station 5 by means of program or software instructions stored in memory 59. As shown, these software instructions include, among other things, an operating system 61, a communication control module 63, a cell ID module 65, and an NRT (Neighbor Relation Table) 69. Although not shown in Figure 3 for simplicity, some of these functions and modules may be split between the CU and one or more DUs as needed, and other functions (such as a transceiver / controller) and modules may be provided in both the CU and the DU.

[0042] The communication control module 63 is operable to control communications between the base station 5 and the mobile devices 3 (user equipment) and other network entities connected to the base station 5. The communication control module 63 also controls the respective flows of downlink user traffic and control data transmitted (via associated data radio bearers) to communication devices associated with this base station 5. The communication control module 63 is also responsible for configuring appropriate signal measurements for the mobile devices 3 served by the base station 5 and obtaining the results of the signal measurements (e.g. via appropriate higher layer signaling such as RRC).

[0043] The Cell ID module 65 is responsible for obtaining and storing (in the NRT 69) information identifying cells 7 of the communication system 1 (at least its own cell and any neighboring cells) and for using such information in procedures involving these cells 7. The information identifying a particular cell 7 may include one or more of the following: an appropriate PLMN ID associated with that cell 7, an ECI / NCI (cell identifier) associated with that cell 7, a PCI associated with that cell 7, a PSC associated with that cell 7, a GCI / EGCI (global cell identifier) associated with that cell 7, and a TAC associated with that cell 7. The Cell ID module 65 is also responsible for broadcasting information about its own cell 7 via system information.

[0044] The NRT module 69 is responsible for the automatic neighbor relation procedures and contains a properly formatted neighbor relation table (for each cell).

[0045] In the above description, the mobile device 3 and base station 5 have been described, for simplicity of explanation, as comprising a number of separate modules (e.g., a communications control module, a cell ID module, etc.). While these modules may be implemented in the manner described above for certain applications, e.g., in an existing system modified to implement the present invention, for other applications, e.g., a system designed from the beginning with the features of the present invention in mind, these modules may be incorporated into the overall operating system or code and may not be recognized as separate entities. These modules may be implemented in software, hardware, firmware, or a combination thereof.

[0046] <Operation> Exemplary ways in which mobile device 3 and base station 5 may avoid PCI confusion according to exemplary embodiments of the present invention are described below.

[0047] Option 1 In E-UTRAN, the global cell ID of each cell contains 28 bits and is composed of the identifier of the PLMN (Public Land Mobile Network) to which the cell belongs and the CI (Cell Identity) of the cell (within that PLMN). In E-UTRAN, the cell ID is known as ECI (E-UTRAN Cell Identity). For macro cells (and small cells controlled by a macro base station), each (E)CI contains the eNB ID of the macro base station controlling the cell (in the leftmost 18, 20, 21 or 28 bits), and the remaining bits (if present) are the cell identifier of the cell (unique under that base station).

[0048] In NR, the global cell ID is defined in the same way as in LTE. However, in NR, the cell ID is called NCI (NR Cell Identity), and the ECGI of each cell contains 36 bits (composed of the associated PLMN ID and NCI). Each NCI contains the gNB ID (22 to 32 bits) of the macro base station that controls that cell, and the remaining bits are the cell identifier of that cell (unique under that base station).

[0049] The global cell ID associated with a given cell 7 is broadcast via System Information (SI) by the base station 5 that controls that cell 7. Thus, by obtaining the SI from each measured cell 7 (e.g., step S1b), the mobile device 3 can obtain the corresponding global cell ID.

[0050] One way to address the PCI confusion issue is shown in Figure 5a. In this option, as shown generally in step S1, the mobile device 3 is configured to (automatically) report the global cell ID (GCI or ECGI) of the target cell 7T to the serving base station 5 along with the measurement results (e.g., in addition to or instead of the PCI). For example, the cell ID module 45 of the mobile device 3 may be configured to include the global cell ID corresponding to each cell 7T in the measurement report to the base station 5 (sent via the communication control module 43 in step S2). In other words, step S2 of Figure 5a can be considered a modification of step 4 of Figure 4 (in that it includes the global cell ID of each measured cell 7T).

[0051] Since the global cell ID (e.g., ECGI) can be used to uniquely identify a cell throughout the network, the base station 5 can determine the correct cell 7T (and the base station 5-1 controlling that cell 7T) based on the information included in the measurement report and perform handover / cell addition (step S4). On the other hand, reporting the global cell ID of each cell 7 included in the measurement report to the serving base station 5 may cause a handover delay. This may require the mobile device 3 to obtain additional System Information (SI) for multiple cells, which may affect the power consumption of the mobile device 3. However, in this embodiment, steps 5 and 7 can be omitted (and step 6 is performed first) compared to FIG. 4, thereby reducing the handover delay and associated signaling.

[0052] Option 2 In this option, the mobile device 3 is configured to provide global cell IDs for a subset of the cells 7 from which it reports (although it can also be configured to report only PCIs).

[0053] More specifically, the mobile device 3 may be configured to report (using its cell ID module 45 and communication control module 43) in its measurement report to the base station 5 the global cell IDs of a predetermined (predetermined number) subset of cells 7 (e.g., the cells 7 with the strongest signal strength or "N" cells 7, and / or cells 7 that are likely to experience PCI confusion issues). This substantially corresponds to the scenario described with reference to FIG. 5a. In this case, the measurement report from the mobile device 3 identifies the remaining cells 7 (e.g., cells 7 with non-strongest signal strength) by their associated PCIs (and thus the mobile device 3 does not need to obtain system information for these remaining cells 7).

[0054] If the base station 5 cannot find a suitable handover cell among the cells 7 with reported global cell IDs and the selected (suitable) handover target cell 7T has potential PCI confusion issues, the base station 5 may either proceed with a (potentially successful) handover to that cell 7T or may request the mobile device 3 to obtain and report a global cell ID for that particular cell 7T (as will be explained below with reference to FIG. 5c). This option is particularly useful when attempting to set up dual connectivity for the mobile device 3 (in which case the mobile device 3 will maintain its existing connection with its current serving cell 7S, with a relatively low risk of losing connectivity if the serving base station 5 does not select the correct cell 7T based on the associated PCI).

[0055] Option 2-1 As a variation of option 2, shown in Figures 5b and 5c, the mobile device 3 does not report the global cell ID of any of the cells 7 in the measurement report (although the mobile device 3 may be configured to report the global cell ID of a subset of the cells 7, as in option 2).

[0056] In this embodiment, the current cell 7S of the mobile device may be an LTE / E-UTRAN cell controlled by the base station 5 (or may be a cell provided via an NR cell / DU, as in FIG. 1), and the target cell 7T (one of the UE's candidate cells) may be an NR cell (which may be controlled by the same base station 5 or a different base station 5-1).

[0057] In this case, the serving base station 5 (using the communications control module 63 in step S1 of FIG. 5b) configures the mobile device 3 to perform appropriate signal measurements for one or more neighboring cells 7.

[0058] The mobile device 3 is configured to report (using the communication control module 43) measurements that meet certain predetermined criteria (this is known as an event trigger). As shown in step S2 of Figure 5b / step S1 of Figure 5c, when reporting the measurements, the mobile device 3 also reports the PCI associated with the target cell 7T (or multiple PCIs if reporting more than one candidate cell 7) to the serving base station 5. Beneficially, in this case, it is not necessary for the mobile device 3 to acquire system information (step 1b) at this stage.

[0059] In step S3 of Figure 5b, the base station 5 checks whether it can determine a target cell 7T (in case of handover) / suitable secondary cell 7T (in case of dual connectivity) based on the reported PCI and the information held in its NRT 69. If the correct cell 7T can be determined from the measurement report (or if the risk of PCI confusion is determined to be low), the base station 5 triggers a handover to that cell 7T and configures that cell 7T as a secondary cell for the mobile device 3 in step S4.

[0060] 5c, if the correct cell 7T cannot be determined from the PCI included in the measurement report (S1 in FIG. 5c), the base station 5 generates and transmits (using the communication control module 63) a properly formatted request instructing the mobile device 3 to report the GCI of one or more cells 7T (e.g., cells reported in NRT 69 as not having a unique PCI) by including information identifying the one or more cells 7T (e.g., the associated PCI). In this example, the base station 5 requests the mobile device 3 to obtain and report the (E)CGI of cell 7T with PCI=5T (the cell reported in step S1 as having a sufficiently strong signal strength, although not necessarily the strongest signal).

[0061] The mobile device 3 can acquire the GCI of a particular cell by acquiring (reading) the system information of the cell 7. Thus, essentially, the base station request in step S2 configures the mobile device 3 to acquire system information of the cell 7T associated with the particular PCI (PCI=5 in this example). As shown schematically in step S2b, the mobile device 3 performs SI acquisition using an autonomous gap. That is, the mobile device 3 may temporarily stop transmitting and receiving with the base station 5 in order to acquire relevant system information from the target cell 7T. The SI acquisition (step S2b) may be performed at any time, even before receiving the base station request in step S2 (e.g., in step S1b of FIG. 5b).

[0062] In step S3, the mobile device 3 generates and transmits an appropriately formatted response (e.g., a new measurement report) including the GCI ("Global-CID") of the target cell 7T. In this example, the GCI value reported by the mobile device 3 (for the cell 7T with PCI=5) is "19". Therefore, advantageously, the base station 5 can determine the correct cell 7T to trigger handover / dual connectivity for the mobile device 3 based on the PCI value "5" (which is not necessarily unique within the area served by the base station 5) and the GCI value "19".

[0063] Based on the determined GCI (step S3 in Figure 5b) or the reported GCI (step S3 in Figure 5c), the serving base station 5 can select the correct cell 7T (and the correct base station 5-1) to trigger handover / add S cell (step S4).

[0064] Option 2-2 This variant is similar to that shown in FIG. 5b.

[0065] Similar to the above option, the mobile device 3 may be configured to report the global cell IDs of a predetermined (predetermined number of) subset of cells 7 in its measurement report to the base station 5 (e.g., a single cell 7 or "N" cells 7 with the strongest signal, and / or cells 7 with potential PCI confusion issues). If the base station 5 cannot find a suitable handover cell among the cells 7 with reported global cell IDs, and if the selected (suitable) handover target cell 7T has potential PCI confusion issues, the base station 5 attempts to determine the GCI of the correct target cell 7T based on the NRT 69.

[0066] However, rather than using its own NRT 69, the serving base station 5 of the serving cell 7S is configured to check the NRT 69 of one of the reported cells 7, preferably a small cell (or NR cell), since such a cell has fewer neighboring cells than a macrocell. In a particularly useful example, the serving base station 5 is configured to check the NRT 69 of the strongest cell 7 (preferably a small / NR cell with a relatively small number of neighboring cells) for which a GCI was reported from the mobile device 3. In this case, the base station 5 can assume that the target cell 7T (which potentially has PCI confusion issues) is likely to report similar good signal strength / quality as the strongest cell 7 and that the target cell 7T is very likely to be a neighbor cell of the strongest cell for which a GCI was reported.

[0067] More specifically, the mobile device 3 is configured to report the results of the signal measurements to the base station 5 (i.e., each reported cell can be identified by its PCI or GCI), as described with reference to step S2 of Figure 5a or 5b. When the serving base station 5 selects a cell 7T for the mobile device 3 for which no GCI has been reported, the base station 5 is configured to determine the GCI of the cell 7T based on the NRT 69 (instead of requesting the GCI of the cell 7T from the mobile device 3, as described with reference to steps S2-S3 of Figure 5c).

[0068] Table 1 shows some of the fields that may be included in an exemplary neighbor relation table 69 in accordance with this option. A similar NRT 69 may be stored in memory 59 for each cell 7 controlled by base station 5 and for each neighboring cell (which may be obtained via network interface 55 from the base station controlling that neighboring cell). Thus, for each neighboring cell 7, the NRT 69 for a given cell includes, among other things, an associated index (#1 to #6 in this example), an associated GCI, information identifying the operating frequency of that cell 7, and an associated PCI.

[0069] [Table 1]

[0070] Because the base station 5 is responsible for configuring the mobile device's signal measurements (including configuring the frequency to measure), the base station 5 can determine the frequency of the reported cell 7T from the applicable measurement configuration and the reported measurement results. Thus, by considering the frequency and PCI of the cell 7T, the base station 5 can determine the GCI of the cell 7T based on the information contained in the NRT 69 and the reported PCI. Specifically, the base station's determination is based on the NRT 69 of the strongest cell 7T for which a CGI is reported. In the example NRT 69 shown in Table 1, there are two cells (i.e., #1 and #5) with PCI value "x," but both cells are associated with different frequencies. Therefore, in this embodiment, the correct neighbor cell 7T is the cell that is adjacent to both the UE's current serving cell 7S and the strongest cell and has the frequency for which measurements are configured. It is understood that other techniques can also be used to identify the correct neighbor cell 7T based on the PCI and NRT 69 of the strongest cell 7T for which a CGI is reported. In some embodiments, the base station 5 may be configured to check the PCI in the NRT 69 of more than one cell 7 .

[0071] Therefore, in step S4, when the base station 5 triggers a handover (or dual connectivity) of the mobile device 3 in the cell 7T, the base station 5 can beneficially use the GCI of that cell to manage the handover (or dual connectivity), thereby avoiding connection failures resulting from PCI confusion.

[0072] Instead of the frequency of the neighboring cell 7, the base station 5 may use any other suitable information (from the NRT 69 and / or other sources, including other nodes) to determine the GCI of the correct cell 7T regardless of the mobile device 3.

[0073] Advantageously, with this option, even if the NRT of the serving cell 7S is insufficient due to, for example, a large number of neighboring cells listed in the NRT of the serving cell 7S (e.g., in the case of a macro / LTE cell), the base station 5 may still be able to resolve the correct neighboring cell 7T (based on the NRT 69 of the strongest cell).

[0074] Option 2-3 This option is illustrated schematically in Figure 5d. In this embodiment, the other base station 5-1 (e.g., a gNB) is configured to determine the GCI of the correct target cell 7T based on the #NRT 69 of the cell 7T, rather than the serving base station 5 configured to signal measurements for the mobile device 3. This option is particularly useful when setting up a secondary cell in dual connectivity. If the UE's current cell 7S (PCell) is an LTE / E-UTRAN cell and the selected cell 7T (SCell) is an NR cell, the dual connectivity is called an EN-DC scenario. If both cells 7S and 7T are NR cells, the dual connectivity is called an NGEN-DC scenario.

[0075] More specifically, the mobile device 3 may be configured to report the global cell IDs of at least a predetermined subset (a predetermined number) of the cells 7 in a measurement report for the cells 7 to the base station 5. This step is similar to the previous option (e.g. steps S1 to S2 of Figure 5a or 5b).

[0076] However, in this embodiment, when the serving base station 5 (e.g., the eNB controlling the UE's current cell 7S) selects a cell 7T with no reported GCI as a candidate secondary cell for dual connectivity for the mobile device 3, the serving base station 5 checks whether there is PCI confusion associated with the PCI of that cell 7T. If there is no PCI confusion, the base station 5 proceeds according to normal operation.

[0077] If there is known PCI confusion in the selected cell 7T, the base station 5 continues adding secondary cells to the particular base station 5-1 that controls the cell 7 that the mobile device 3 reported as having the strongest signal strength. The cell 7 with the strongest signal strength is most likely the cell for which the mobile device 3 reported a GCI, and therefore the base station 5-1 that controls that cell 7 can be determined based on that GCI.

[0078] Accordingly, the serving base station 5 generates and transmits a request to add a secondary cell to the base station 5-1 in step S4. The request (e.g., "SCell Addition Request") identifies the strongest cell 7 (e.g., by GCI or PCI) and also identifies the cell 7T by its PCI (e.g., as a preferred cell). The serving base station 5 may optionally include information (e.g., one or more PCIs) identifying one or more preferred cells 7 in the request. In other words, the serving base station 5 may be configured to indicate the priority order (e.g., from most preferred to least preferred in the form of a cell / PCI list) of the strongest cell and different candidate secondary cells 7.

[0079] The other base station 5-1 may add the cell 7 with the strongest strength as a secondary cell for the mobile device 3 and reserve appropriate resources for communicating with the mobile device 3 via the cell 7. Alternatively, according to the priority indicated by the serving base station 5, if there is no PCI confusion, the other base station 5-1 may add the cell 7T (having a PCI value of "X" in FIG. 6) as a secondary cell for the mobile device 3 and reserve appropriate resources for communicating with the mobile device 3 via the cell 7T.

[0080] However, there is a possibility of PCI confusion with respect to the priority cell 7T, for example, as shown in Figure 6, the cell 7A controlled by the base station 5-2 has the same PCI value "X", or as shown in Figure 7, two cells 7A and 7T controlled by the same base station 5 have the same PCI value "X".

[0081] Advantageously, even if there is PCI confusion affecting the priority cell 7T, the base station 5-1 can determine the GCI of the correct cell (e.g., cell 7A or cell 7T) based on the NRT 69 (e.g., as shown in Table 1).

[0082] In particular, in this embodiment, the base station 5-1 is configured to check the NRT 69 of the strongest cell 7 (preferably a small cell / NR cell with a relatively small number of neighboring cells) for which a GCI has been reported by the mobile device 3. In this case, the base station 5-1 can assume that the preferred cell 7T is likely to report similar good signal strength / quality as the strongest cell 7, and that the preferred cell 7T is very likely to be a neighboring cell of the strongest cell 7 for which a GCI has been reported (this is indicated by the NRT 69 of the strongest cell 7).

[0083] If the base station 5-1 determines in step S5 that the requested PCI belongs to the cell 7A, it may be configured to forward the received SCell addition request to the correct base station 5-2 (based on the GCI of the cell 7A, if known). Alternatively, the base station 5-1 may be configured to inform the requesting base station 5 about the GCI of the correct cell 7A, or may return an error with an appropriate failure reason (e.g., "SCell addition failed").

[0084] If the base station 5-1 determines in step S5 that the requested PCI belongs to its own cell 7T, it may add the cell 7T as a secondary cell for the mobile device 3 and reserve resources for communicating with the mobile device 3 via the cell 7T. The base station 5-1 may be configured to notify the requesting (primary) base station 5 of the successful addition of the preferred cell 7T as a secondary cell.

[0085] Additionally, if the message received in step S4 includes priorities for different candidate secondary cells 7, the base station 5-1 may be configured to select a different cell 7 from one or more other cells 7 listed in the cell addition request (e.g., if the requested cell 7T or the strongest cell 7 does not have sufficient resources).

[0086] Option 3 This option is illustrated in Figure 5e. In this embodiment, the mobile device 3 is configured to include information identifying the geographic location of the mobile device 3 (e.g., latitude / longitude obtained by the GNSS module 47) in the measurements of at least a subset of the cells 7 being reported (step S2). Therefore, it may not be necessary for the mobile device 3 to obtain and report the GCI associated with the reported cells 7 (step S1b is optional).

[0087] Table 2 shows some of the fields that may be included in an exemplary neighbor relation table 69 of a serving base station 5 in accordance with this option. A similar NRT 69 may be stored in memory 59 of each cell 7 controlled by the base station 5. As can be seen, for each neighbor cell 7, the NRT 69 includes information identifying (among other things) the geographic location of that cell 7.

[0088] [Table 2]

[0089] Advantageously, in the case of PCI confusion, the serving base station 5 may be configured to determine the GCI of the correct cell 7T in step S3 based on information identifying the location of the mobile device and information (in the NRT 69) identifying the location of each cell having the same reported PCI. For example, the base station 5 may be configured to determine which cell 7T is closest to the location of the mobile device 3 (although the base station 5 may take into account other information, such as the power level associated with each cell, to fine-tune this determination).

[0090] <Modifications and alternatives>

[0033] Exemplary embodiments have been described in detail above. As will be appreciated by those skilled in the art, numerous variations and alternatives to the exemplary embodiments are possible and may still benefit from the inventions embodied therein. For purposes of explanation, only some examples of these variations and alternatives are provided.

[0091] In the above exemplary embodiments, the base stations communicate with the mobile devices using 3GPP wireless communication (radio access) technologies. However, the base stations and mobile devices may be configured to communicate with each other using other suitable wireless communication technologies (i.e., WLAN, Wi-Fi, WiMAX, Bluetooth, etc.). The above embodiments are also applicable to "non-mobile" or generally fixed user equipment.

[0092] 1, 6 and 7, for purposes of illustration, each DU is associated with a single cell, however, in implementation each DU may be associated with multiple cells.

[0093] In the above exemplary embodiment, the mobile device is described as reporting to the base station the global cell IDs of a predetermined number of cells (or a subset of all cells for which measurements have been taken), reporting the global cell IDs associated with the cells with the strongest signal strength and / or cells likely to experience PCI confusion issues. However, the mobile device may also be configured to report (e.g., include in a measurement report) the global cell IDs of a predetermined set / type of cells, including one or more of NR cells, home base station cells (small cells), CSG cells, non-CSG cells, and cells associated with PCIs within a predetermined range.

[0094] The geographical location of the mobile device (option 3) may be included in the initial measurement report (as shown in FIG. 5e). Alternatively, the geographical location of the mobile device may be provided in response to a request from the serving base station, similar to steps S2 and S3 of FIG. 5c. In this case, step S2 may be modified to request the geographical location of the mobile device, and step S3 may be modified to report the GPS coordinates of the mobile device (e.g., instead of or in addition to the GCI of the reported cell).

[0095] For all options, the mobile device's GCI / GPS reporting may be turned on / off by the base station via appropriately formatted measurement configuration signaling. For example, GCI / GPS reporting may be turned off when PCI confusion is unlikely (e.g., when NR cell deployment is relatively sparse). In this case, the base station may be configured to determine the number of neighboring NR cells (if any) that share the same PCI based on its NR neighbor list (within its NRT). For example, if the base station determines that no NR cells or a relatively small number (e.g., below a predetermined threshold) of NR cells share the same PCI, the base station may turn off the mobile device's GCI / GPS reporting (or may be configured not to turn on any GCI / GPS reporting if the default is off).

[0096] The above exemplary embodiments address one or more possible PCI confusion scenarios. However, the above exemplary embodiments may also be used to address similar PSC confusion scenarios (e.g., scenarios involving Closed Subscriber Group (CSG) cells, typically identified by an associated PSC).

[0097] For ease of understanding, the mobile device and base station have been described above as having a number of separate modules. While these modules may be provided in the manner described above for certain applications, e.g., by modifying an existing system to implement the present invention, for other applications, e.g., systems designed from the beginning with the features of the present invention in mind, these modules may be incorporated into the overall operating system or code, and may not be recognized as separate entities.

[0098] The above exemplary embodiments describe multiple software modules. As will be appreciated by those skilled in the art, the software modules may be provided in compiled or uncompiled form, or may be supplied to the base station or communication device as a signal over a computer network or on a recording medium. Furthermore, the functions performed by some or all of this software may be performed using one or more dedicated hardware circuits. However, the use of software modules is recommended to speed up updates to the base station or mobile device.

[0099] The measurement report may further include a PCI of the at least one neighboring cell for the at least one measurement result, along with the corresponding at least one measurement and any corresponding GCI.

[0100] The measurement report may include measurement results of multiple neighboring cells, and a GCI may be included in the measurement report for all neighboring cells related to the measurement results in the measurement report.

[0101] The measurement report includes measurement results of multiple neighboring cells, and the GCI is included in the measurement report for one subset of the multiple neighboring cells related to the measurement results in the measurement report, and is not included in a further subset of the multiple neighboring cells related to the measurement results in the measurement report.

[0102] The subset of neighboring cells for which a GCI is included in the measurement report may include at least one cell having a greater measured signal strength or quality than the further subset of neighboring cells.

[0103] The subset of the plurality of neighboring cells whose GCI is included in the measurement report may include at least one of predetermined neighboring cells, cells of a predetermined type (e.g., NR cells / home base station cells), and cells having PCI values from a predetermined range of PCI values.

[0104] The method may further comprise sending a request to obtain GCI for the cells of the further subset from system information broadcast for the cells.

[0105] The method may comprise attempting to resolve the GCI based on a Neighbor Relation Table (NRT) before sending the request, and sending the request only if resolution of the GCI based on the NRT is not successful.

[0106] The NRT may be held by the base station device.

[0107] The received measurement results include at least one GCI (Unique Cell Identifier) for at least one neighboring cell, and the identifying step further identifies the identified neighboring cell based on at least one GCI for another neighboring cell.

[0108] The received measurement results may include the at least one GCI for a subset of neighboring cells including at least one of a predetermined neighboring cell, a cell of a predetermined type (e.g., an NR cell / home base station cell), and a cell having a PCI value from a predetermined range of PCI values.

[0109] The method may comprise identifying the neighbouring cell based on the received PCI and information held in the NRT regarding neighbouring cells whose associated signal strength or quality is reported to be greatest (and whose GCI has been reported by the UE).

[0110] The communication procedure involving the UE and the identified neighboring cell may include a handover to the identified neighboring cell or adding the identified neighboring cell as a secondary cell (SCell).

[0111] The base station device may include an LTE base station, and the at least one neighboring cell may be an NR cell.

[0112] The method may comprise configuring E-UTRAN New Radio - Dual Connectivity (EN-DC) for the UE involved in the identified neighboring cell.

[0113] The method may further comprise, when it is determined based on the NRT that the received message does not relate to a cell controlled by the base station device, determining a different cell having the same PCI and a base station device that controls the different cell, and forwarding the received message to the base station device that controls the different cell.

[0114] The received message may include a plurality of PCIs respectively associated with a plurality of cells, and the method may comprise selecting a cell controlled by the base station device based on the received plurality of PCIs, and proceeding with the communication procedure using the selected cell.

[0115] Various other modifications will be apparent to those skilled in the art and will not be described in further detail here.

[0116] <Automatic neighbor relationship> Manually defining and managing neighbor cells in a typical mobile network is a difficult task, and becomes even more challenging as new mobile technologies are deployed alongside existing "legacy" 2G / 3G / 4G cells. As explained in section 22.3.2a of 3GPP TS 36.300, the purpose of the Automatic Neighbor Relation (ANR) feature is to relieve operators of the burden of manually managing neighbor relations.

[0117] For each cell, the base station maintains a conceptual Neighbor Relation Table (NRT). The ANR function resides in the base station (e.g., DU) and includes appropriate functionality for managing the NRT (per cell). The so-called Neighbor Relation Discovery function is responsible for finding new neighbor relations and adding them to the NRT. This typically occurs in the form of the base station configuring appropriate cell measurements for one or more mobile devices served by the base station and receiving corresponding measurement reports from the mobile devices containing information identifying the cell where the measurement was made. If a measurement report identifies a cell not listed in the NRT (for a given cell), the Neighbor Relation Discovery function adds this cell to the NRT (after appropriate communication with other nodes, if necessary).

[0118] The so-called Neighbor Relation Deletion function is responsible for deleting old Neighbor Relations (NR). The Neighbor Relation Detection and Neighbor Relation Deletion functions are implementation specific and may therefore differ from base station to base station.

[0119] Furthermore, the exchange of neighbor cell information between two base stations (e.g., X2 / Xn setup procedure or eNB / gNB configuration update procedure) can also be used for ANR purposes. The ANR function also allows network operators to manage NRTs via O&M (Operation and Maintenance) functions. Operators can use the O&M functions to manually add and remove NRs and / or change the attributes of NRTs as needed. The ANR function may notify the O&M system of changes to NRTs (e.g., changes not made via the O&M function).

[0120] To allow mobile devices to uniquely identify the source of a received signal, each base station is assigned a signature sequence called PCI (Physical Cell ID) or "Physical Layer Cell Identifier." PCI is defined by the carrier frequency and PSC (Primary Scrambling Code) for UTRAN FDD (Frequency Division Duplex) cells, by the carrier frequency and Cell Parameter ID for UTRAN TDD (Time Division Duplex) cells, by Band Indicator + BSIC (Base Station Identity Code) + BCCH (Broadcast Control CHannel) ARFCN (Absolute Radio Frequency Channel Number) for GERAN (GSM EDGE Radio Access Network) cells, and by the PN (Pseudorandom Noise) offset for CDMA2000 cells.

[0121] For each neighbor relationship, the NRT typically includes an associated Target Cell Identifier (TCI) that identifies the cell as a target cell (e.g., for handover and other signaling purposes). In some of the above-mentioned embodiments, the NRT also includes a geographical location (e.g., GPS coordinates) associated with each neighbor cell. In current E-UTRAN systems, the TCI corresponds to the E-UTRAN Cell Global Identifier (ECGI) and PCI. Thus, in a typical ANR implementation, a neighbor relationship from a source cell to a target cell means that the base station controlling the source cell a) knows the ECGI / CI and PCI of the target cell, b) there is an entry for the source cell in the NRT that identifies the target cell, and c) the attributes of the entries in this neighbor relationship table are defined (e.g., defined by O&M or set to initial values).

[0122] This application claims the benefit of priority from UK patent application no. 1800569.4 filed on 12 January 2018, the disclosure of which is incorporated herein in its entirety.

Claims

1. means for managing a cell according to a first Radio Access Technology (RAT); means for receiving, from a user equipment (UE), a measurement report including at least one physical cell identifier (PCI) corresponding to a cell managed by another base station and conforming to a second RAT different from the first RAT; means for sending to the UE a request for at least one Cell Global Identifier (CGI) based on the at least one physical cell identifier; means for receiving from the UE the at least one CGI, each CGI including a corresponding Public Land Mobile Network Identifier (PLMN ID); A base station comprising:

2. means for obtaining an operating frequency of a second cell of the cell according to the second RAT; The base station of claim 1 .

3. 3. The base station according to claim 1, comprising means for obtaining information about the bit length of said at least one CGI.

4. means for transmitting, to a base station managing a cell conforming to a first radio access technology (RAT), a measurement report including at least one physical cell identifier (PCI) corresponding to a cell conforming to a second RAT managed by another base station, the second RAT being different from the first RAT; means for receiving a request for at least one Cell Global Identifier (CGI) from the base station based on the at least one physical cell identifier; means for transmitting to the base station the at least one CGI, each CGI including a corresponding Public Land Mobile Network Identifier (PLMN ID); A user equipment (UE) comprising:

5. Managing a cell according to a first Radio Access Technology (RAT); receiving, from a User Equipment (UE), a measurement report including at least one Physical Cell Identifier (PCI) corresponding to a cell managed by another base station and according to a second RAT different from the first RAT; sending to the UE a request for at least one Cell Global Identifier (CGI) based on the at least one physical cell identifier; receiving the at least one CGI from the UE, each CGI including a corresponding Public Land Mobile Network Identifier (PLMN ID); A method performed by a base station, comprising:

6. transmitting, to a base station managing a cell according to a first radio access technology (RAT), a measurement report including at least one physical cell identifier (PCI) corresponding to a cell managed by another base station and according to a second RAT different from the first RAT; receiving a request for at least one Cell Global Identifier (CGI) from the base station based on the at least one physical cell identifier; transmitting the at least one CGI to the base station, each CGI including a corresponding Public Land Mobile Network Identifier (PLMN ID); A method performed by a User Equipment (UE), comprising:

Images