Communication device, base station, and methods therefor

Abstract

To provide a method and a device with few session interruption and excellent transmission efficiency for UE being serviced through a directional beam.SOLUTION: A communication device communicates with a base station using at least one of a plurality of beams. Each of the plurality of beams includes a synchronization signal, system information, and a reference signal based on a beam identifier of each beam and a cell identifier corresponding to a communication area provided by the base station. When detecting the degradation of signal quality of a first beam included in the plurality of beams, the communication device executes adjustment for continuing the communication between the base station and the communication device using a second beam included in the plurality of beams and different from the first beam.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a communication system. The present invention relates in particular to a wireless communication system and apparatus operating in accordance with the 3rd Generation Partnership Project (3GPP (registered trademark)) standard or its equivalents or derivatives, but is not limited thereto. The present invention relates in particular to mobility in so-called "next generation" systems that use beamforming, but is not limited thereto.

Background Art

[0002] The latest developments of the 3GPP standard are called Long Term Evolution (LTE) of the Evolved Packet Core (EPC) network and the Evolved UMTS Terrestrial Radio Access Network (E-UTRAN), which is also generally called "4G". Furthermore, the terms "5G" and "new radio" (NR) refer to evolving communication technologies that are expected to support various applications and services. Various details of the 5G network are described, for example, in the "NGMN 5G White Paper" V1.0 by the Next Generation Mobile Networks (NGMN) Alliance, and the document is available from https: / / www.ngmn.org / 5G-white-paper.html. 3GPP intends to support 5G via the so-called 3GPP Next Generation (NextGen) radio access network (RAN) and the 3GPP NextGen core network.

[0003] Under the 3GPP specifications, a Node B (or eNB in LTE and gNB in 5G) is a base station through which a communication device (user equipment or "UE") connects to the core network and communicates with other communication devices or remote servers. For simplicity, this application uses the term base station to refer to such a base station and the term mobile device or UE to refer to such a communication device. The core network (i.e., EPC in the case of LTE) hosts functions for (among other things) subscriber management, mobility management, billing, security, and call / session management, and provides connectivity for communication devices to external networks such as the Internet.

[0004] A communication device can be, for example, a mobile communication device such as a mobile phone, smartphone, user equipment, personal digital assistant, laptop / tablet computer, web browser, e-book reader, etc. Such mobile (or generally stationary) devices are also typically operated by a user, but it is also possible to connect so-called "Internet of Things" (IoT) devices and similar machine-type communication (MTC) devices to the network. For simplicity, this application refers to mobile devices (or UEs) in the description, but it should be understood that the technology described can be implemented on any communication device (mobile and / or generally stationary / data-receiving) that can connect to a communication network for transmission.

[0005] 3GPP Technical Report (TR) 23.799 V0.7.0 describes the possible architectures and general procedures for the NextGen (5G) system planned for Release 14 of the 3GPP specifications. 3GPP is also researching the potential use of frequency bands up to 100 GHz for the new (5G) radio access network. Directional beamforming and massive antenna technologies may also be used to overcome the severe channel attenuation characteristics associated with certain high frequency bands (e.g., millimeter wave bands). The term "massive antenna" refers to an antenna having a large number (e.g., 100 or more) of antenna elements arranged in an array. Effectively, such massive antennas can be used to communicate with multiple users simultaneously, thus facilitating multi-user MIMO (multiple-input and multiple-output) transmission. A base station (also referred to as a transmission and reception point (TRP) in this case) can be configured to form respective beams for communicating with multiple UEs substantially simultaneously and for using the associated directional beams.

[0006] 3GPP has agreed on some of the mobility-related requirements within 5G. Specifically, 3GPP intends to provide one or more TRPs for each new radio (NR) base station (i.e., 5G base station, or gNB). As a baseline, each NR is expected to support a state with network-controlled mobility handling and a state with UE-controlled mobility. The measurement configuration associated with typical network-controlled mobility between gNBs is kept to a minimum. Thus, each UE is required to perform fewer (and perhaps less detailed) measurements for mobility purposes (e.g., avoiding the need to provide detailed "cell" level information). However, more detailed information may be required in some cases. 3GPP also intends to minimize context transfer (between base stations) as a result of UE-based mobility.

[0007] Network control mobility can be RRC-driven (i.e., controlling UE mobility using appropriate radio resource control (RRC) signals between the gNB and the UE at the cell level), or zero / minimal RRC involvement may be provided (e.g., at the MAC / PHY layer).

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] However, especially in high-frequency bands, obstacles in the direct line-of-sight (LOS) path between the transmitter and the receiver (e.g., due to obstacles) and / or the mobility of the UE may cause quality degradation of that UE's radio link. Furthermore, some studies suggest that the radio channel may change very rapidly at millimeter-wave frequencies, which may also lead to an increase in transmission errors and / or the number of handovers for a particular UE. Therefore, UEs served via directional beams tend to lose their connection to their base stations and experience data loss. Furthermore, existing (e.g., LTE) mobility technologies are not applicable to 5G RAN due to technical differences and the bandwidths used.

[0009] With the relatively low reliability of high frequencies and directional beams, it is predicted that frequent changes may occur in the beams used by active UEs and 5G base stations / TRPs. This can lead to, for example, an increase in session interruptions (beam-to-beam handovers), signaling overhead, and / or transmission inefficiencies (e.g., an increased need for retransmissions).

[0010] Therefore, preferred exemplary embodiments of the present invention aim to provide methods and apparatuses that address or at least partially address the above problems.

[0011] For the sake of efficiency of understanding by those skilled in the art, the present invention is 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.

Means for Solving the Problems

[0012] In one aspect, the present invention is a base station for a communication system, the base station comprising a controller and a communication unit, the controller being configured to control communications within a communication area served by the base station, the communication area covering respective portions of the communication area provided by the base station, each having a different beam identifier, formed by a plurality of directional beams, and the communication unit being configured to communicate control information regarding at least one communication device using at least one directional beam associated with the at least one communication device.

[0013] In another aspect, the present invention is a communication device for a communication system comprising a base station that provides a communication area formed by a plurality of directional beams that cover respective portions of the communication area and each have a different beam identifier, the device comprising a controller and a communication unit, the communication unit being configured to receive control information from the base station using at least one directional beam associated with the communication device.

[0014] Aspects of the present invention also extend to corresponding systems, methods, and computer program products such as computer-readable storage media storing computer-executable instructions for programming a programmable processor to perform the methods described in the above aspects and / or the possibilities described above or in the claims, and / or for programming a computer suitably adapted to provide the apparatus described in any of the claims.

[0015] Each feature disclosed in this specification (including this term in the claims) and / or shown in the drawings can be incorporated into the present invention independently of (or in combination with) other disclosed and / or shown features. In particular, without limitation, any feature of any dependent claim that depends on a particular independent claim can be introduced into that independent claim in any combination or individually.

[0016] Here, exemplary embodiments of the present invention will be described by way of example with reference to the accompanying drawings.

Advantages of the Invention

[0017]

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0019] Overview FIG. 1 schematically shows a communication network 1 in which user devices 3 (mobile phones and / or other mobile devices) can communicate with each other via a base station 5 (denoted as "gNB") using an appropriate radio access technology (RAT). In a 5G system, it should be understood that the base station is also referred to as transmit receive points (TRP). In FIG. 1, for illustrative purposes, five mobile devices 3 and one base station 5 are shown, but when implemented, the system typically includes other base stations and mobile devices as well.

[0020] Each base station 5 operates one or more associated cells via TRPs (and / or one or more remotely located TRPs) located at the base station. In this example, for simplicity, base station 5 operates a single cell. Base station 5 is connected to the core network 7 (e.g., via an appropriate gateway and / or user plane / control functions), and adjacent base stations are also connected to each other (either directly or via an appropriate base station gateway). The core network 7 can include, among other things, a control plane manager entity and a user plane manager entity, one or more gateways (GW) for providing a connection between base station 5 and other networks (such as the Internet), and / or servers hosted outside the core network.

[0021] The mobile device 3 connects to an appropriate cell by establishing a radio resource control (RRC) connection with the base station 5 operating the cell, depending on its location and, in some cases, other factors such as signal strength, subscription data, capabilities, etc. The mobile device 3 and the base station 5 (and other transmission points in the network) communicate via an appropriate radio interface depending on the RAT used. The mobile device 3 communicates with a core network node that is relayed between the mobile device 3 and the appropriate core network node by the base station 5 / TRP that provides services to the mobile device 3 using so-called NAS (Non-Access Stratum) signals.

[0022] In this example, base station 5 operates an associated antenna array (e.g., a massive antenna) to provide a plurality of directional beams for communicating with various mobile devices 3 within the cell of base station 5. Each beam is arranged to spread (transmit) in a different direction (3D including elevation angle). Each beam has a unique associated identifier (e.g., an assigned "beam ID") (at least within the cell).

[0023] The beam configuration used in the cell identifies the number of beams and the associated beam patterns. In this example, the total number of beams is "N", i.e., beams #1 to #N are currently configured for the cell of base station 5 ("N" is a positive integer, at least "1").

[0024] Base station 5 is advantageously configured to transmit a set of beam-specific reference signals (BRS) within its cell (or within each cell if the base station operates multiple cells). Mobile device 3 may be configured to use the associated BRS to perform signal strength and channel estimation measurements for each beam. Such beam-specific measurements are used (by the base station and / or mobile device 3) to configure an appropriate set of (one or more) beams for mobile device 3, and this set is called the Operational Beam Set (OBS) of mobile device 3.

[0025] The OBS may be dynamically updated, for example, according to signal conditions, the load within the cell, the throughput required by the mobile device 3 and / or the quality of service (QoS). Advantageously, in most cases, since there may be at least one directional beam available for the mobile device 3 and / or new beams that are added to the OBS (at least temporarily as needed), if the OBS includes multiple beams, the possibility that the mobile device 3 suffers a radio link failure (RLF), i.e., a connection loss with the base station 5, is significantly reduced.

[0026] Furthermore, the OBS may be advantageously used to support the in-cell mobility of the mobile device 3. Specifically, when the mobile device 3 changes its position within the coverage area (cell) of the base station 5, new beams may be added to the OBS as needed (and beams that are no longer needed may be removed).

[0027] The mobile device 3 may be configured to perform and report more frequent signal measurements (e.g., detailed channel state information (CSI) measurements) for those beams included in its OBS than for other beams. Thus, if an obstacle is present (blocking the line of sight for a particular directional beam) between the mobile device 3 and the base station 5 (e.g., temporarily), such a change in the signal state (and the beam identification affected) can be detected relatively quickly. The base station 5 can also perform the necessary adjustments for transmission to the mobile device 3 to avoid interference and / or radio link failure due to the obstacle. However, advantageously, the mobile device 3 is most likely to be able to continue communicating with the base station 5 using other suitable (unaffected) beams in its OBS. If the problem affecting a particular beam within the OBS is not resolved, the base station 5 removes that beam from the OBS (e.g., after the expiration of a predetermined timer and / or after receiving a predetermined number of reports indicating problems with that beam).

[0028] Similarly, the base station 5 may be configured to remove a beam from the OBS of the mobile device 3 (and replace it with a different beam) for the mobility of the mobile device 3.

[0029] Accordingly, providing an OBS (and / or associated beam-specific reference signals) results in flexibility in providing services to mobile devices via the base station's cell, improved tolerance to signal propagation problems (e.g., obstacles) affecting the high-frequency radio beam, loss of signal (e.g., while moving within or between cells), and reduced risk of radio link failures due to faster and more efficient cell / beam acquisition by the mobile device.

[0030] Mobile device FIG. 2 is a block diagram showing the main components of the mobile device 3 (e.g., a mobile phone or other user device) shown in FIG. 1. As shown in the figure, the mobile device 3 has a communication unit circuit 31 operable to transmit and receive signals to and from the base station 5 via one or more antennas 33. The mobile device 3 has 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 communication unit circuit 31. Although not necessarily required for its operation, the mobile device 3 may of course have all the normal functions of a conventional mobile phone 3 (such as a user interface 35), and this may be appropriately provided by any one or any combination of hardware, software, and firmware. The software may be pre-installed in the memory 39 and / or downloaded, for example, via a telecommunications network or from a removable data storage device (RMD).

[0031] In this example, the controller 37 is configured to control the overall operation of the mobile device 3 by program instructions or software instructions stored in the memory 39. As shown in the figure, these software instructions include, among other things, an operating system 41, a communication control module 43, a beam setting module 44, a mobility module 45, and a signal measurement module 46.

[0032] The communication control module 43 is operable to control communication between the mobile device 3 and its serving base station 5 (and other communication devices connected to the base station 5, such as additional mobile devices and / or core network nodes).

[0033] The beam setting module 44 is responsible for operating the OBS (or respective OBSs) for the mobile device 3 used in the current serving cell (or cells). This includes, for example, adding and removing cells (e.g., based on information provided by the base station 5 and / or the signal measurement module 46).

[0034] The mobility module 45 is responsible for maintaining network attachment via an appropriate cell (of the base station 5), while the mobile device 3 is moving within the area covered by the telecommunication network 1. The mobility module 45 maintains the network connection by performing cell / beam reselection and / or handover procedures according to, for example, the signal status. It should be understood that the mobility module 45 can also perform cell / beam reselection and / or handover procedures even when the mobile device 3 is stationary, for example, due to changes in the signal status, network load within the current cell, etc. The mobility module 45 also takes into account the OBS of the mobile device 3 and / or the current beam configuration (e.g., provided by the beam setting module 44) for the current cell and / or potential handover candidate cells.

[0035] The signal measurement module 46 is responsible for acquiring signal quality measurement values for the cell / beam in the vicinity of the mobile device 3, generating related signal measurement reports, and transmitting them to the serving base station 5. The signal quality measurement is performed via the beam-specific reference signal transmitted by the base station 5 based on the appropriate measurement configuration provided by the serving base station 5. The signal quality measurement values may include, for example, (detailed) channel state information (CSI) measurement values, reference signal received power (RSRP), reference signal received quality (RSRQ), received signal-to-noise ratio (SNR), and / or signal-to-interference-plus-noise ratio (SINR) measurement values and related reports.

[0036] Base station Figure 3 is a block diagram showing the main components of the base station 5 shown in Figure 1. As shown in the figure, the base station 5 includes a communication circuit 51 for transmitting and receiving signals to and from a communication device (such as the mobile device 3) via one or more antennas 53 (for example, an antenna array / massive antenna), and a network interface 55 for transmitting and receiving signals to and from network nodes (for example, other base stations and / or nodes in the core network 7). The base station 5 has a controller 57 for controlling the operation of the base station 5. The controller 57 is connected to a memory 59. Software may be pre-installed in the memory 59 and / or downloaded via the telecommunications network 1, for example, from a removable data storage device (RMD). The controller 57 is configured to control the overall operation of the base station 5 by program instructions or software instructions stored in the memory 59 in this example. As shown in the figure, these software instructions include, among other things, an operating system 61, a communication control module 63, a beam control module 64, and a measurement setting module 66.

[0037] The communication control module 63 is operable to control communication between the base station 5, the mobile device 3 (user equipment), and other network entities connected to the base station 5. The communication control module 63 also controls separate flows of downlink user traffic and control data to be transmitted to communication devices associated with this base station 5, for example, control data for core network services and / or the mobility of the mobile device 3 (including general (non-UE-specific) system information and reference signals).

[0038] The beam control module 64 is responsible for operating the OBS associated with each mobile device 3 within the cell (or cells) of the base station 5. This includes, for example, adding and removing cells (e.g., based on signal measurements provided by the mobile device 3, the mobility of the mobile device 3, and / or other information related to the cell such as load information).

[0039] The measurement setting module 66 is responsible for configuring the mobile device 3 to perform and report signal quality measurements for cells and / or beams in the vicinity of the mobile device 3 (e.g., cells / beams operated by this base station 5 and / or neighboring base stations). The measurement setting module 66 generates appropriate measurement settings and transmits them to a specific mobile device 3, and obtains signal quality measurement values by receiving related measurement reports. The measurement reports may be used, for example, when performing mobility and / or beam configuration procedures including the mobile device 3 that provided the report.

[0040] In the above description, the mobile device 3 and the base station 5 have been described as having several individual modules (such as a communication control module and a beam configuration / control module) for ease of understanding. These modules may be provided in this way in a specific application, for example, in other applications where an existing system has been modified to implement the present invention. However, in a system designed from the beginning with the features of the present invention in mind, these modules may be incorporated into the operating system or the entire code, so these modules may not be recognizable as individual entities. These modules may be implemented in software, hardware, firmware, or a combination thereof.

[0041] Some methods of using a directional beam / OBS for communication between a user device and a TRP (base station) in a network will be described in more detail (with reference to FIGS. 4 to 7).

[0042] Operation The base station 5 is advantageously configured to transmit a set of beam-specific reference signals (BRSs) within its cell (or within each cell if the base station operates multiple cells). For example, the base station 5 may transmit one BRS per beam ID. The mobile device 3 may use the associated BRSs to perform signal strength measurements and channel estimation measurements for each beam. The BRSs are transmitted using the beam pattern of the corresponding beam and using a predetermined time / frequency resource (e.g., periodically). It will be understood that different BRSs may be transmitted at the same time / frequency resource or at different time / frequency resources (e.g., when "beam scanning" is employed). Preferably, the various BRSs within the same cell are orthogonal to each other (across the set of time / frequency resources on which they are transmitted), while the BRSs in different cells have a low cross-correlation with each other. The BRS corresponding to a given beam ID is determined (by the mobile device 3) based on the beam ID and the cell ID. In other words, the mobile device 3 may be enabled to construct the BRS for a particular beam based on the associated beam ID and cell ID (including the set of time / frequency resources on which the BRS is transmitted).

[0043] Idle Mode and Initial Cell Selection When the mobile device 3 is in the idle mode, an initial cell search may be performed using appropriate synchronization signals transmitted by the base station (via each of a plurality of beams configured within the cell / coverage area of the base station).

[0044] FIG. 4 schematically shows an exemplary sequence of subframes (in this example, downlink subframes) transmitted by a base station in each beam. As can be seen from the figure, the subframe includes several (downlink) data subframes 80 within base station 5, which can transmit data to mobile devices 3 within its cell (and be served via this specific beam). (Although not shown in FIG. 4 for simplicity), it should be understood that each data subframe 80 can also carry control signals (e.g., scheduling information) and / or reference signals (for signal measurements).

[0045] Advantageously, the base station is configured to transmit a properly formatted synchronization signal (referred to herein as synchronization subframe 81) periodically in a specific subframe. For example, such a synchronization subframe 81 may be transmitted in a subframe preceding the subframe in which system information (SI) broadcast is transmitted (shown as SI information subframe 82 in FIG. 4). Thus, using the synchronization signal, mobile device 3 can adapt its communication unit to use the correct time / frequency resources within that specific beam before moving on to receive the system information broadcast. This advantageously enables mobile device 3 to find and connect to base station 5 via that beam in a quick and efficient manner.

[0046] Specifically, the following options can be used to facilitate the mobile device 3 to perform a beam search for initial access (by performing a random access procedure). a) Beamformed downlink (DL) synchronization signal The mobile device may be configured to detect the cell ID from the synchronization signal and, optionally, detect the associated beam ID from a beam reference signal (BRS) transmitted in a specific beam. b) Beamforming DL System Information The mobile device 3 may be configured to obtain the necessary system information from the cell and, optionally, some beam-specific system information for communication via specific beams. c) Beamformed UL Physical Random Access Channel (PRACH) Transmission (msg1) The PRACH resources may be configured using the system information that the mobile device obtains in advance (i.e., before initiating the random access procedure by transmitting a so-called "msg1" transmission via a specific beam). And d) Beamformed DL Random Access Message (msg2 / 4) The PRACH resources for transmitting msg2 / 4 (via a specific beam) may be configured using the system information.

[0047] <In-Cell Mobility in Connected Mode> While in the connected mode (e.g., after performing appropriate beam search and random access procedures), it should be understood that the mobile device 3 can connect to its serving cell using one or more beams, referred to as an Operational Beam Set (OBS) for that mobile device 3. Such an OBS may include a (typically small) subset of beams within the cell of the base station 5 that are selected for communication with the mobile device 3 while it is within the cell of the base station.

[0048] However, to account for the mobility of the mobile device 3 within the cell (and / or changes in the signal state within the cell), the base station 5 may modify the OBS of the mobile device 3, for example, by adding or removing beams, based on at least one of the following. Beam measurements (performed and reported by the mobile device 3 and / or derived by the base station 5 from UL transmissions by that mobile device 3). Beam load (traffic overcrowding) And Beam priority (which may be set by a higher layer, for example, for inter-cell interference coordination).

[0049] <OBS measurement of in-cell mobility> To describe the mobility of the mobile device 3 within the cell, the base station 5 may also use beam measurements (executed and reported by the mobile device 3 and / or derived by the base station 5 from the UL transmissions of the mobile device 3).

[0050] In this case, the beam measurement values reported by the mobile device 3 may include, for example, the reference signal received power (RSRP) and / or the signal-to-interference-plus-noise ratio (SINR) associated with each beam (measured using respective BRSs for each beam).).

[0051] The mobile device 3 may be configured (by the serving base station 5 via appropriate measurement configuration signaling) to report measurement values periodically and / or in an event-triggered manner. For example, the report may be triggered when the RSRP of a beam exceeds or falls below a predetermined threshold (absolute or relative to other beams) for a certain period of time. This is similar to LTE handover measurements.

[0052] Optionally, the mobile device 3 may be configured to sort the beams in order of priority based on the measurement values and report measurement values only for the best beams (e.g., a predetermined number of beams) or report the beam IDs associated with the best beams for the mobile device 3 (e.g., as a list).

[0053] However, it will also be understood that the mobile device 3 may be required to add or remove one or more specific beams to its OBS (even without reporting actual measurement values). This can reduce the amount of signaling required between the mobile device 3 and the base station 5. The base station 5 can arbitrarily specify a subset of the beams measured and reported by the mobile device 3 (e.g., before adding to or removing from the OBS).

[0054] In the case of time division multiplexing (TDD) communication, the base station 5 may also be configured to utilize channel reciprocity to select the most appropriate beam for the OBS of the mobile device 3 based on channel measurement values derived from UL transmissions from the mobile device 3.

[0055] Whenever the network (base station 5) modifies the OBS, it notifies the mobile device 3 using a properly formatted control signal (e.g., RRC signal).

[0056] <UE-specific data and control> Advantageously, the OBS may be used for i) UE-specific DL data transmission (similar to how the physical downlink shared channel or "PDSCH" is transmitted in an LTE cell) and ii) UE-specific DL control transmission (similar to the enhanced physical downlink control channel or "E-PDCCH" in LTE).

[0057] The OBS may be useful for at least reducing the amount of CSI signals and facilitating open-loop transmit diversity for a particular mobile device 3.

[0058] Specifically, the reduction in the amount of CSI signals may be achieved as follows. Typically, DL beamforming for the transmission of UE-specific channels is based on CSI reports from the UE (mobile device 3). However, when using the OBS, CSI measurements and signal overhead can be reduced by configuring the mobile device to transmit detailed CSI reports only for the beams within the OBS (using the associated BRSs on those beams for CSI measurements).

[0059] In particularly beneficial cases, the base station 5 may apply appropriate precoding (amplitude and phase weighting) for DL transmission over the beams within the OBS based on the CSI reports from the mobile device 3. In this case, UE-specific DM-RS may be included in the transmission so that the mobile device 3 does not need to know the precoding weights used by the network.

[0060] The base station 5 may be configured to apply transmit diversity over the beams within the OBS. In this case, the mobile device 3 can use the BRS on each beam to extract the transmitted signals from each beam and then combine the transmitted signals before decoding. This approach has the advantage that detailed CSI is not required from the mobile device 3.

[0061] <Common control signal> The mobile device 3 may need to receive specific control information from the network that is not specific to that UE and / or does not need to be broadcast over the entire cell of the base station 5. Such control information may include, but is not limited to, for example, random access response (RAR) messages 2 and 4, power control signals, paging.

[0062] The base station 5 may transmit such common control information on all the beams within the OBS (e.g., using open-loop transmit diversity as described above). In this case, the mobile device 3 may use the BRS on each beam to demodulate the transmission on that beam and then combine the received data to improve communication reliability.

[0063] <In-cell mobility> In FIG. 5(a), a base station 5 operating multiple directional beams and with beams #3 and #4 currently assigned to the OBS of the mobile device 3 is schematically shown. The OBS is shown using solid lines, and the beams not included in the OBS are shown using dotted lines.

[0064] The diversity created by using multi - beams between the base station 5 and the mobile device 3 can significantly reduce the possibility that the mobile device 3 loses connection with the base station 5 due to obstacles and / or mobility even when the base station 5 is operating in a high - frequency band within its cell (while within the cell of the base station 5). That is, even if one (or more) beams are lost, the mobile device 3 is likely to remain connected to at least one beam (or multiple beams) of the base station 5. Therefore, the loss of the received SNR (combined from multiple beams) has to be tolerated.

[0065] More specifically, Fig. 5(a) schematically shows a scenario where the mobile device 3 is currently communicating with the base station 5 using an OBS equipped with beams #3 and #4. Since these are included in the OBS, the mobile device 3 is configured to transmit relatively detailed CSI reports regarding beams #3 and #4 (relatively frequently), while the mobile device 3 transmits only periodic (less frequent) RSRP measurement values for other beams (and / or RSRP measurement values for beams #3 and #4).

[0066] As generally shown in Fig. 5(b), an obstacle (e.g., a vehicle) between the mobile device 3 and the base station 5 can cause a decrease in the RSRP of a beam (beam #4 in this example) in the OBS. However, such a change in the signal state is beneficially tracked by CSI measurements of that beam, and the mobile device 3 can still receive DL transmissions via beam #3 (which is not currently affected by signal quality degradation due to the obstacle). Therefore, using the CSI measurement values (#4) for the affected beam, the base station 5 can perform the necessary adjustments (e.g., prioritizing beam #3 over beam #4) in its transmission for the mobile device 3 (at least temporarily). If the CSI measurement values of the affected beam still indicate a poor signal state (e.g., over a predetermined period and / or a period of the number of CSI reports), the base station 5 may be configured to remove the affected beam from the OBS of the mobile device 3.

[0067] Similarly, the base station 5 may be configured to remove the beam from the OBS of the mobile device 3 for the mobility of the mobile device 3. Such a movement scenario is shown in FIG. 5(c). Specifically, in this example, when the mobile device 3 moves within the cell of the base station 5, the network (and / or the mobile device 3) monitors the signal state of the beams included in the OBS (e.g., using beam RSRP measurements and / or CSI), and when the mobile device 3 is no longer within the service area of beam #4, it decides to update the OBS by removing beam #4 and adding beam #2.

[0068] <Inter-connection-mode inter-cell mobility> The mobile device 3 may be configured to perform measurements that take into account the available beamforming gain from the beams used in the neighboring cells in order for the network (base station 5) to determine when to initiate a handover of the mobile device 3 to a neighboring cell. Thus, advantageously, when selecting a handover target cell for the mobile device 3, the serving base station 5 can select the most appropriate beam of the handover target cell, so that the mobile device 3 can continue to communicate via the new cell without experiencing significant data loss and / or delay.

[0069] To facilitate inter-cell mobility, the mobile device 3 may be configured to measure the respective signal strengths of each beam within one or more adjacent cells (at least the cells / beams for which the current base station requests measurements). For example, the mobile device 3 may scan each beam ID (unique BRS) transmitted in an adjacent cell and be configured to report the ID of the strongest beam to the serving base station 5 for each measured adjacent cell. If the serving base station 5 determines that a handover is necessary for the mobile device 3, the serving base station 5 may provide information identifying the beam most suitable for its mobile station 3 to the target cell during the handover procedure. If available from the mobile device 3, the serving base station 5 may also provide detailed measurements regarding such a beam.

[0070] FIG. 6 schematically shows a scenario in which the mobile device 3 performs a handover between a cell (“Cell1”) operated by its current serving base station 5A and an adjacent cell (“Cell2”) operated by the base station 5B.

[0071] As can be seen from the figure, both base stations 5A and 5B operate a number of directional beams. First, the mobile device 3 communicates with the serving base station 5A using the OBS including beams #5 and #6 of cell 1. The mobile device 3 performs appropriate handover measurements for one or more adjacent cells (including cell 2) by measuring the RSRP for all beams within its cell. In this example, the mobile device 3 reports strong RSRP for beams #2 and #3 within cell 2. Therefore, when selecting cell 2 as the handover target cell, the current serving base station 5A can advantageously control the handover of the mobile device 3 to beams 2# and #3 of cell 2 as the optimal beams within that cell.

[0072] Therefore, when the mobile device 3 performs a handover to cell 2, it is potentially possible to connect via the most appropriate beam within that cell (assuming those beams are available to the mobile device 3). Even if not all beams having a good signal state within cell 2 are available to the mobile device 3 (for example, due to the load within cell 2), the new base station 5B can still start providing service to the mobile device 3 via at least some of the appropriate candidate beams (and potentially add other beams to the OBS as the mobile device 3 moves around within the area covered by cell 2).

[0073] <In-cell OBS> In FIG. 7, a scenario is schematically shown in which the mobile device 3 communicates simultaneously via cell 1 operated by the base station 5A and cell 2 operated by the base station 5B. This scenario is in fact a variation of the Coordinated Multipoint (CoMP; inter-cell coordinated transmission and reception) transmission and reception scenario defined for LTE. However, in this case, the base station 5 is configured to allocate specific beams to the mobile device 3 rather than across all component carriers. Such simultaneous transmission / reception can be performed, for example, when the mobile device 3 is located in a cell-edge area and / or when the cells of adjacent base stations overlap. Thus, in such a situation, the mobile device 3 can receive signals from multiple cells (and transmit signals via multiple cells), thereby significantly improving the downlink (or uplink) performance. Simultaneous transmission / reception (CoMP) may be used for two main purposes. i) To improve the signal quality. (By transmitting / receiving the same signal via two or more cells) ii) To improve the throughput (by achieving a higher overall data rate than possible by using only a single cell by transmitting different data via different cells).

[0074] In the scenario shown in FIG. 7, the mobile device 3 is configured to have respective OBSs for each cell within its CoMP measurement set (Cell1 and Cell2 in this example), and to measure and report beam-by-beam CSI for each beam of each OBS. Specifically, in this example, the OBS for the mobile device 3 in Cell 1 includes beams #5 and #6 of this cell, and the OBS for the same mobile device 3 within Cell 2 includes beams #2 and #3 of Cell 2. Thus, the mobile device 3 is configured to perform beam-by-beam CSI measurement and reporting for beams #5 and #6 of Cell 1 and beams #2 and #3 of Cell 2.

[0075] The beam-by-beam CSI measurement values may be reported to the same (e.g., master) base station 5 regardless of which base station operates that beam, and / or the CSI measurement values may be reported to that particular base station. Regardless of which base station 5 the mobile device 3 reports to, the base stations 5 may be configured to exchange CoMP-related signals with each other via an inter-base-station interface provided therebetween. The CoMP-related signals may include, for example, beam-by-beam CSI and similar information related to the OBS of the mobile device 3 (e.g., beam IDs included in the OBS).

[0076] Furthermore, when simultaneous transmission / reception is used, the decision to add / remove cells to / from the 3CoMP measurement set of the mobile device may be based on RSRP measurements for each relevant beam (which may be obtained as described above). Thus, beneficially, together with appropriate coordination between serving base stations, the signal state of the mobile device can be improved (while using narrow, high-frequency directional beams), and / or throughput can be improved by communicating through multiple cells using beam-specific reference signals and respective OBS configurations within each cell.

[0077] Variations and Alternatives Forms and alternative forms Detailed exemplary embodiments have been described above. As will be understood by those skilled in the art, many modifications and alternatives can be made to the above exemplary embodiments while still benefiting from the invention embodied therein. For purposes of illustration, only some of these alternatives and modifications will be described.

[0078] It will be understood that the beam configuration can vary from cell to cell depending on the coverage / throughput requirements for a particular cell. For example, when the cell radius is large, a large number of very narrow beams may be used, or a relatively small number of relatively wide beams may be used to facilitate cell acquisition and reduce the overhead for transmitting beam-specific reference signals. In some cases, the beam configuration may consist of a single cell and define the coverage of the entire cell (similar to a conventional cell).

[0079] It will also be understood that the beam configuration of a given cell may vary semi-statically for purposes such as self-organising network (SON) adaptation, such as capacity and coverage optimisation (CCOpt). In this case, the reconfiguration of a particular beam configuration may include changing the beam width of one or more beams and / or changing the number of beams (e.g., switching a beam on or off).

[0080] When preparing for handover between cells, if such information is available, the serving base station may inform the mobile device of the number of beams currently operating in the adjacent cell, whereby the mobile device knows the range of beam IDs that need to be scanned / measured. However, if such information is not available or not transmitted to the mobile device, the mobile device may be configured to perform beam measurements assuming that the adjacent cell has the maximum possible number of beams. In any case, using the information identifying the most appropriate beam in the target cell, the mobile device already has a potential set of beams that may be considered for its OBS in the target cell, so it is not necessary to perform extensive beam measurements when entering the target cell.

[0081] In the above exemplary embodiment, the base station is described as transmitting multiple directional beams. It will be understood that the data may be transmitted substantially simultaneously via multiple beams. However, in some cases, for example when hybrid (partially analog and partially digital) beamforming is used, it may not be possible to transmit all the beams at once. In this case, it will be understood that a technique called "beam sweeping" (i.e., transmitting one beam at a time) can be used.

[0082] Instead of the network (base station) determining the OBS based on measurements from the mobile device, the mobile device may be configured to select a beam for its own OBS and (unless otherwise configured), report channel state information (CSI) only for the beam selected for its OBS by the mobile device 3. In this case, advantageously, the network can implicitly determine the OBS from the beams (beam IDs) included in the CSI report. In any case, since CSI reporting of the beams in the OBS may be required, this method has the advantage that no additional signals are required when the mobile device updates its OBS.

[0083] In the above-described embodiment, the base station communicates with the mobile device using 3GPP wireless communication (radio access) technology. However, other wireless communication technologies (i.e., WLAN, Wi-Fi, WiMAX, Bluetooth (registered trademark), etc.) can be used between the base station and the mobile device according to the above embodiment. The above exemplary embodiment is also applicable to "non-mobile" or generally stationary user devices.

[0084] In the above description, the mobile device and the base station are described as having several individual functional components or modules for ease of understanding. These modules may be provided in this way for a specific application, for example, in an existing system that has been modified to implement the present invention, or in a system designed from the beginning with the features of the present invention in mind. However, in a system designed from the beginning with the features of the present invention in mind, these modules may be incorporated into the operating system or the entire code, so these modules may not be recognizable as individual entities.

[0085] In the above exemplary embodiment, several software modules are described. As will be understood by those skilled in the art, the software modules may be provided in compiled or uncompiled form and may be supplied to the base station, the mobility management entity, or the mobile device as a signal on a computer network or a recording medium. Furthermore, the functions executed by some or all of this software may be executed using one or more dedicated hardware circuits. However, the use of software modules is preferred because it facilitates the update of the base station or the mobile device to update their functions.

[0086] Each controller can include, for example, but not limited to, any suitable form of processing circuitry, a microprocessor central processing unit (CPU), an arithmetic logic unit (ALU), input / output (IO) circuitry, internal memory / cache (program and / or data), processing registers, a communication bus (e.g., control, data, and / or address bus), a direct memory access (DMA) function, a counter, a pointer, and / or a timer implemented by hardware or software, and / or the like.

[0087] The controller of the base station may be operable to control, for each communication device, each operational beam set (OBS) including at least one directional beam associated with that communication device.

[0088] The communication unit of the base station is operable to receive, from at least one communication device, measurement results performed on each reference signal transmitted via each beam, and the controller may be operable to determine each beam within the OBS based on the results of the measurements performed on the reference signals.

[0089] The communication unit of the base station may be operable to receive, from at least one communication device, OBS-specific measurement results (e.g., channel state indicator, CSI, measurement values) for the beams included in the OBS for at least one communication device.

[0090] The controller of the base station may be operable to control a handover for a specific communication device based on at least one of the OBS and beam-specific reference signals associated with the communication device.

[0091] The controller of the base station may be operable to control coordinated multipoint (CoMP) for a specific communication device based on at least one of the OBS and beam-specific reference signals associated with the communication device.

[0092] The communication unit of the base station may be operable to transmit respective control information including a reference signal via each beam. In this case, each reference signal transmitted via each beam may be a beam-specific reference signal. The communication unit of the base station may be configured to periodically transmit each reference signal within each beam using pre-defined resources (e.g., time / frequency resources). The predetermined resources may be specific to a particular beam. Alternatively, the pre-defined resources may be common to a plurality of (e.g., a subset or all) beams.

[0093] Each reference signal transmitted via each beam may depend on the corresponding beam identifier and cell identifier associated with the communication area, and the resources used to transmit each reference signal via each beam may depend on the corresponding beam identifier and the cell identifier associated with the communication area.

[0094] The controller of the base station may be operable to control the beam configuration associated with the communication area of the base station, and the communication unit of the base station may be operable to transmit (e.g., broadcast) the beam configuration associated with the communication area within the communication area. The beam configuration may be defined to define at least one of the number of beams within the communication area, the beam pattern within the communication area, the respective widths associated with each beam, whether a particular beam is on or off, the resources used to transmit a reference signal (or set of reference signals) within a particular beam, and the resources allocated for the random access procedure for each beam.

[0095] The communication unit of the base station may be operable to communicate each beam-specific system information using each directional beam. The communication unit of the base station may be operable to communicate information for identifying resources for random access procedure signals via each beam, via that beam. The communication unit of the base station may be operable to receive random access procedure signals from at least one communication device via at least one beam using the identified resources.

[0096] The communication unit of the base station may be operable to apply transmit diversity to at least one communication device using a plurality of directional beams associated with the at least one communication device. In this case, the processor of the communication device may be operable to combine each data received using each of the plurality of directional beams before decoding the data.

[0097] The communication unit of the base station may be operable to transmit signals (e.g., RAR message 2 and message 4, power control and / or paging) that are not specific to at least one communication device using a plurality of directional beams associated with the at least one communication device.

[0098] The base station may include a massive antenna for forming a plurality of directional beams. The base station may be a base station of a next-generation (NextGen or 5G) radio access network.

[0099] The controller of the communication device may be operable to perform measurements on each reference signal transmitted via each beam, and the communication unit of the communication device may be operable to transmit the measurement results to the base station. The controller of the communication device may be operable to perform measurements (e.g., channel state indicator, CSI, measurement) on the beams included in the OBS of the communication device, and the communication unit of the communication device may be operable to transmit the results of the communication device to the base station.

[0100] The controller of the communication device may be operable to control inter-cell coordinated transmission and reception, CoMP, via a base station, based on at least one of an OBS and a beam-specific reference signal associated with the communication device within a communication area.

[0101] Various other modifications will be apparent to those skilled in the art and are not described in further detail herein.

[0102] This application claims priority from UK Patent Application No. 1613902.4, filed on 12 August 2016, the disclosure of which is incorporated herein in its entirety.

Claims

1. A communication device, comprising: means for communicating with a base station using at least one of a plurality of beams, wherein each of the plurality of beams includes a synchronization signal, system information, a beam identifier of each beam, and a reference signal based on a cell identifier corresponding to a communication area provided by the base station; means for performing an adjustment to continue communication between the base station and the communication device using a second beam included in the plurality of beams and different from the first beam when the communication device detects that the signal quality of the first beam included in the plurality of beams has deteriorated; A communication device comprising the above.

2. A method in a communication device, comprising: communicating with a base station using at least one of a plurality of beams, wherein each of the plurality of beams includes a synchronization signal, system information, a beam identifier of each beam, and a reference signal based on a cell identifier corresponding to a communication area provided by the base station; and performing an adjustment to continue communication between the base station and the communication device using a second beam included in the plurality of beams and different from the first beam when the communication device detects that the signal quality of the first beam included in the plurality of beams has deteriorated. A method comprising the above.

3. A base station, comprising: means for providing a communication area via a plurality of beams, wherein each of the plurality of beams includes a synchronization signal, system information, a beam identifier of each beam, and a reference signal based on a cell identifier corresponding to the communication area; means for performing an adjustment to continue communication between the base station and the communication device using a second beam included in the plurality of beams and different from the first beam when a communication device detects that the signal quality of the first beam included in the plurality of beams has deteriorated; A base station comprising the above.

4. A method in a base station, comprising: providing a communication area via a plurality of beams, wherein each of the plurality of beams includes a synchronization signal, system information, a beam identifier of each beam, and a reference signal based on a cell identifier corresponding to the communication area; and When the communication device detects that the signal quality of the first beam included in the plurality of beams has deteriorated, an adjustment for continuing communication between the base station and the communication device is executed using a second beam included in the plurality of beams and different from the first beam. A method comprising the above.

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