WO2019028728A1 - Enhanced radio link monitoring for new radio - Google Patents

Enhanced radio link monitoring for new radio Download PDF

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Publication number
WO2019028728A1
WO2019028728A1 PCT/CN2017/096771 CN2017096771W WO2019028728A1 WO 2019028728 A1 WO2019028728 A1 WO 2019028728A1 CN 2017096771 W CN2017096771 W CN 2017096771W WO 2019028728 A1 WO2019028728 A1 WO 2019028728A1
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WIPO (PCT)
Prior art keywords
user equipment
serving
base station
radio link
recovery procedure
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PCT/CN2017/096771
Other languages
French (fr)
Inventor
Haitao Li
Li Zhang
Original Assignee
Nokia Solutions And Networks Oy
Nokia Shanghai Bell Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Nokia Solutions And Networks Oy, Nokia Shanghai Bell Co., Ltd. filed Critical Nokia Solutions And Networks Oy
Priority to PCT/CN2017/096771 priority Critical patent/WO2019028728A1/en
Priority to CN201780093740.6A priority patent/CN110999395B/en
Publication of WO2019028728A1 publication Critical patent/WO2019028728A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/24—Reselection being triggered by specific parameters
    • H04W36/30—Reselection being triggered by specific parameters by measured or perceived connection quality data
    • H04W36/305—Handover due to radio link failure
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/06—Reselecting a communication resource in the serving access point
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W76/00—Connection management
    • H04W76/10—Connection setup
    • H04W76/19—Connection re-establishment

Definitions

  • This invention relates generally to wireless communication systems related to multi-antenna technology in New Radio (NR) and, more specifically, to an enhanced radio link quality control mechanism for NR by considering the interaction between radio link monitoring and beam failure recovery procedures.
  • NR New Radio
  • beam management is a set of L1/L2 procedures to acquire and maintain a set of TRP (s) and/or UE beams that can be used for DL and UL transmission/reception, which include at least following aspects:
  • Beam determination is for TRP (s) or UE to select of its own Tx/Rx beam (s) .
  • Beam measurement is for TRP (s) or UE to measure characteristics of received beamformed signals.
  • Beam reporting is for UE to report information ofbeamformed signal (s) based on beam measurement.
  • Beam sweeping is operation of covering a spatial area, with beams transmitted and/or received during a time interval in a predetermined way.
  • UE beam failure recovery mechanism includes beam failure detection, new candidate beam identification, beam failure recovery request transmission, and UE monitoring gNB response for beam failure recovery request.
  • Radio link monitoring is a L3 procedure already used in LTE as specified in section 5.3.11 of 36.331. RLM in NR procedure would be very similar to that of LTE.
  • eNB or eNodeB Evolved Node B LTE base station
  • LTE-M LTE system to support MTC or M2M
  • Node B Node B (NB) Node B (base station in UTRAN)
  • the current invention proposes an enhanced radio link quality control mechanism for NR by considering the interaction between RLM and beam failure recovery procedures.
  • An example of an embodiment of the current invention is a method that comprises interactively performing, by a user equipment in a wireless communications network, radio link monitoring on at least one serving beam from a serving base station and a beam recovery procedure on at least one candidate beam from the serving base station; and determining by the user equipment, in response to the beam recovery procedure and the radio link monitoring with different timing relationships, to perform one of the following: triggering re-establishment procedure, indicating to the network switching by the user equipment to at least one candidate beam, and indicating to the network a return back by the user equipment to at least one serving beam.
  • An example of another embodiment of the present invention is an apparatus that comprises at least one processor and at least one memory including computer program code, where the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to perform at least the following: interactively performing, by a user equipment in a wireless communications network, radio link monitoring on at least one serving beam from a serving base station and a beam recovery procedure on at least one candidate beam from the serving base station; and determining by the user equipment, in response to the beam recovery procedure and the radio link monitoring with different timing relationships, to perform one of the following: triggering re-establishment procedure, indicating to the network switching by the user equipment to at least one candidate beam, and indicating to the network a return back by the user equipment to at least one serving beam.
  • An example of an additional embodiment of the instant invention is a computer program product embodied on a non-transitory computer-readable medium in which a computer program is stored that, when being executed by a computer, is configured to provide instructions to control or carry out at least the following: interactively performing, by a user equipment in a wireless communications network, radio link monitoring on at least one serving beam from a serving base station and a beam recovery procedure on at least one candidate beam from the serving base station; and determining by the user equipment, in response to the beam recovery procedure and the radio link monitoring with different timing relationships, to perform one of the following: triggering re-establishment procedure, indicating to the network switching by the user equipment to at least one candidate beam, and indicating to the network a return back by the user equipment to at least one serving beam.
  • An example of yet another embodiment of the invention disclosed herein is an apparatus, comprising means for interactively performing, by a user equipment in a wireless communications network, radio link monitoring on at least one serving beam from a serving base station and a beam recovery procedure on at least one candidate beam from the serving base station; and means for determining by the user equipment, in response to the beam recovery procedure and the radio link monitoring with different timing relationships, to perform one of the following: triggering re-establishment procedure, indicating to the network switching by the user equipment to at least one candidate beam, and indicating to the network a return back by the user equipment to at least one serving beam.
  • FIG. 1 is a block diagram of one possible and non-limiting exemplary system in which the exemplary embodiments may be practiced;
  • FIG. 2 illustrates a time relationship where the beam recovery procedure continuing after the expiration of a timer used to allow the user equipment to regain synchronization with the serving base station;
  • FIG. 3 illustrates a time relationship timing relationship comprises: the beam recovery procedure finishing before the expiration of the timer used to allow the user equipment to regain synchronization with the serving base station;
  • FIG. 4 is a logic flow diagram for enhanced radio link monitoring for New Radio, and illustrates the operation of an exemplary method, a result of execution of computer program instructions embodied on a computer readable memory, functions performed by logic implemented in hardware, and/or interconnected means for performing functions in accordance with exemplary embodiments.
  • This invention relates generally to wireless communication systems related to Rel-15 WI “New Radio (NR) Access Technology” .
  • NR New Radio
  • 3 GPP is now still discussing beam management procedure to support beam-level mobility and beam failure recovery procedure is considered as part of beam management.
  • RLF Radio Link Interruption indication to Layer 2 to facilitate Mobility without RRC Involvement.
  • R2-1706745 it was proposed that for multi-beam operation, after beam recovery via all UL beam (s) of serving cell has failed, RLF is declared.
  • R2-1706965 it was proposed that during the in-sync /out-of-sync detection in RLF, ifbeam failure recovery is trigged, the timer for RLF can be suspended or paused.
  • a problem addressed in this invention is the interaction between RLM and beam failure recovery procedures, more specifically the UE behavior when a beam failure recovery procedure is ongoing during when T310 timer is running.
  • the T310 timer is LTE nomenclature for a timer that starts while initiating RRC Connection Re-Establishment procedure and stops upon selection of suitable E-UTRA cell OR a cell using another RAT. At expiry it enters RRC IDLE state.
  • T310 and N311 are parameters used in LTE system. The intention is for the present invention to reuse LTE’s RLM mechanism, but this does not necessarily mean that future specifications in NR will reuse the same parameter names. Therefore, this invention utilizes these as general concepts, and not necessarily restricted to the same measurements, when describing these two parameters.
  • N311 is also LTE nomenclature and is also used herein for convenience. In general, N311 represents a number of consecutive in-sync that allows the user equipment to confirm synchronization with the serving base station,
  • an N310 parameter indicates the number of 200 ms intervals when the UE is unable to successfully decode the PDCCH due to low RSRP detected. N310 indicates the number of times in which the UE cannot successfully decode 20 consecutive frames in the downlink. T310 is a timer, in seconds, used to allow the UE to get back in synchronization with the eNodeB. N311 is a parameter that indicates the number of 100 ms intervals that the UE must successfully decode the PDCCH to be back in-synch with the eNodeB.
  • this parameter indicates the number of times in which the UE must successfully decode 10 consecutive frames in the downlink in order for the UE to assume the radio link is in-synch.
  • the UE detects N310 consecutive out-of-sync indications, it starts the T310 timer. If the timer expires, the link has failed. If the UE detects N311 consecutive in-sync indications prior to the T310 timer expiring, then the timer is stopped and the link has not failed.
  • a UE performs radio link monitoring on the serving beam (s) and the procedure is done in a similar way as LTE, i.e., physical layer generates periodic in-sync or out-of-sync indications to the RRC layer, and based on these indications, RRC layer decides how to control the timer T310 and whether to declare RLF.
  • LTE serving beam
  • RRC layer decides how to control the timer T310 and whether to declare RLF.
  • RAN1 is also considering beam failure recovery procedure to handle the exceptional cases, e.g. sudden channel degradation due to blockage or beam misalignment due to fast channel variation, which is beyond the ability of beam management procedure. Therefore, it is possible for a UE to recover the failed beam on a new candidate beam (or the previous beam depending on UE’s mobility) and all subsequent transmissions can be switched to the recovered beam.
  • FIG. 1 is a block diagram of one possible and non-limiting exemplary system in which the exemplary embodiments may be practiced.
  • a user equipment (UE) 110 is in wireless communication with a wireless network 100.
  • a UE is a wireless, typically mobile device that can access a wireless network.
  • the UE 110 includes one or more processors 120, one or more memories 125, and one or more transceivers 130 interconnected through one or more buses 127.
  • Each of the one or more transceivers 130 includes a receiver, Rx, 132 and a transmitter, Tx, 133.
  • the one or more buses 127 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, and the like.
  • the one or more transceivers 130 are connected to one or more antennas 128.
  • the one or more memories 125 include computer program code 123.
  • the YYY module allows functionality for the usage of control resources for data transmission where any method or examples of such embodiments discussed herein can be practiced.
  • the UE 110 includes a YYY module 140, comprising one of or both parts 140-1 and/or 140-2, which may be implemented in a number of ways.
  • the YYY module 140 may be implemented in hardware as YYY module 140-1, such as being implemented as part of the one or more processors 120.
  • the YYY module 140-1 may be implemented also as an integrated circuit or through other hardware such as a programmable gate array.
  • the YYY module 140 may be implemented as YYY module 140-2, which is implemented as computer program code 123 and is executed by the one or more processors 120.
  • the one or more memories 125 and the computer program code 123 may be configured to, with the one or more processors 120, cause the user equipment 110 to perform one or more of the operations as described herein.
  • the UE 110 communicates with gNB 170 via a wireless link 111.
  • the gNB (a New Radio 5G NodeB, which would denoted as gNB or possibly some variant of an evolved NodeB) 170 is a base station (e.g., for LTE, long term evolution, or 5G base station) that provides access by wireless devices such as the UE 110 to the wireless network 100.
  • the gNB 170 includes one or more processors 152, one or more memories 155, one or more network interfaces (N/W I/F (s) ) 161, and one or more transceivers 160 interconnected through one or more buses 157.
  • Each of the one or more transceivers 160 includes a receiver, Rx, 162 and a transmitter, Tx, 163.
  • the one or more transceivers 160 are connected to one or more antennas 158.
  • the one or more memories 155 include computer program code 153.
  • the ZZZ module allows functionality for the usage of control resources for data transmission where any method or examples of such embodiments discussed herein can be practiced.
  • the gNB 170 includes a ZZZ module 150, comprising one of or both parts 150-1 and/or 150-2, which may be implemented in a number of ways.
  • the ZZZ module 150 may be implemented in hardware as ZZZ module 150-1, such as being implemented as part of the one or more processors 152.
  • the ZZZ module 150-1 may be implemented also as an integrated circuit or through other hardware such as a programmable gate array.
  • the ZZZ module 150 may be implemented as ZZZ module 150-2, which is implemented as computer program code 153 and is executed by the one or more processors 152.
  • the one or more memories 155 and the computer program code 153 are configured to, with the one or more processors 152, cause the gNB 170 to perform one or more of the operations as described herein.
  • the one or more network interfaces 161 communicate over a network such as via the links 176 and 131.
  • Two or more gNBs 170 communicate using, e.g., link 176.
  • the link 176 may be wired or wireless or both and may implement, e.g., an X2 interface.
  • the one or more buses 157 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, wireless channels, and the like.
  • the one or more transceivers 160 may be implemented as a remote radio head (RRH) 195, with the other elements of the gNB 170 being physically in a different location from the RRH, and the one or more buses 157 could be implemented in part as fiber optic cable to connect the other elements of the gNB 170 to the RRH 195.
  • RRH remote radio head
  • each cell can correspond to a single carrier and a gNB may use multiple carriers. So if there are three 120-degree cells per carrier and two carriers, then the gNB has a total of 6 cells.
  • the wireless network 100 may include a network control element (NCE) 190 that may include MME (Mobility Management Entity) /SGW (Serving Gateway) functionality, and which provides connectivity with a further network, such as a telephone network and/or a data communications network (e.g., the Internet) .
  • the gNB 170 is coupled via a link 131 to the NCE 190.
  • the link 131 may be implemented as, e.g., an S1 interface.
  • the NCE 190 includes one or more processors 175, one or more memories 171, and one or more network interfaces (N/W I/F (s) ) 180, interconnected through one or more buses 185.
  • the one or more memories 171 include computer program code 173.
  • the one or more memories 171 and the computer program code 173 are configured to, with the one or more processors 175, cause the NCE 190 to perform one or more operations.
  • the wireless network 100 may implement network virtualization, which is the process of combining hardware and software network resources and network functionality into a single, software-based administrative entity, a virtual network.
  • Network virtualization involves platform virtualization, often combined with resource virtualization.
  • Network virtualization is categorized as either external, combining many networks, or parts of networks, into a virtual unit, or internal, providing network-like functionality to software containers on a single system. Note that the virtualized entities that result from the network virtualization may still be implemented, at some level, using hardware such as processors 152 or 175 and memories 155 and 171, and also such virtualized entities create technical effects.
  • the computer readable memories 125, 155, and 171 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory.
  • the computer readable memories 125, 155, and 171 may be means for performing storage functions.
  • the processors 120, 152, and 175 may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multi-core processor architecture, as non-limiting examples.
  • the processors 120, 152, and 175 may be means for performing functions, such as controlling the UE 110, gNB 170, and other functions as described herein.
  • the various embodiments of the user equipment 110 can include, but are not limited to, cellular phones such as smart devices, tablets, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, internet appliances permitting wireless Internet access and browsing, tablets with wireless communication capabilities, as well as portable units or terminals that incorporate combinations of such functions.
  • PDAs personal digital assistants
  • image capture devices such as digital cameras having wireless communication capabilities
  • gaming devices having wireless communication capabilities
  • music storage and playback appliances having wireless communication capabilities
  • internet appliances permitting wireless Internet access and browsing tablets with wireless communication capabilities, as well as portable units or terminals that incorporate combinations of such functions.
  • various embodiments of the user equipment include machines, communicators and categories of equipment, which are not primarily or not at all in use by human interaction.
  • LTE networks The current architecture in LTE networks is fully distributed in the radio and fully centralized in the core network.
  • the low latency requires bringing the content close to the radio which leads to local break out and multi-access edge computing (MEC) .
  • 5G may use edge cloud and local cloud architecture.
  • Edge computing covers a wide range of technologies such as wireless sensor networks, mobile data acquisition, mobile signature analysis, cooperative distributed peer-to-peer ad hoc networking and processing also classifiable as local cloud/fog computing and grid/mesh computing, dew computing, mobile edge computing, cloudlet, distributed data storage and retrieval, autonomic self-healing networks, remote cloud services and augmented reality.
  • edge cloud may mean node operations to be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head or base station comprising radio parts. It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. It should also be understood that the distribution of labor between core network operations and base station operations may differ from that of the LTE or even be non-existent. Some other technology advancements probably to be used are Software-Defined Networking (SDN) , Big Data, and all-IP, which may change the way networks are being constructed and managed.
  • SDN Software-Defined Networking
  • Big Data Big Data
  • all-IP all-IP
  • An exemplary embodiment comprises a radio node connected to a server.
  • Exemplary embodiments implementing the system allow the edge cloud server and the radio node as stand-alone apparatuses communicating with each other via a radio path or via a wired connection or they may be located in a same entity communicating via a wired connection.
  • This invention proposes an enhanced radio link quality control mechanism for NR by considering the interaction between RLM and beam failure recovery procedures, specifically teaching what to do if the beam recovery procedure is still ongoing while T310 expires/stops and what to do ifthe beam recovery procedure finishes while T310 is still running.
  • the UE IfN311 consecutive in-sync are received on the serving beam before beam recovery procedure finishes, then the UE aborts ongoing beam recovery procedure and the UE indicates “back to serving beam” to gNB, e.g. by re-using the beam recovery request signaling.
  • the UE switches to the new beam, resets all previous IS/OOS counters, restarts T310 and performs RLM on the new beam. However, if the beam recovery procedure finishes while T310 is still running but the beam recovery fails, then UE continues RLM on the serving beam as ifbeam recovery procedure has not been performed.
  • FIG. 2 presents a block diagram for the case where the beam recovery procedure is still ongoing while T310 expires.
  • Item 202 represents the serving beam while item 204 represents the candidate beam along the same time frame.
  • the beam as represented by item 206 has RLM being performed, but T310 has not started due to good link quality.
  • the T310 is running and consecutive N311 in-sync has not been received on serving beam.
  • the T310 expires.
  • the RLM is continued on serving beam. If N311 consecutive in-sync are received on the serving beam before beam recovery procedure finishes, UE aborts ongoing beam recovery procedure, and indicates ′′back to serving beam′′to gNB, e.g. by re-using the beam recovery request signaling
  • the beam proceeds as usual in item 214 with just some RRM measurement, if so configured, but during the time interval represented by item 216 the beam recovery procedure takes place.
  • the beam recovery procedure ends at the time marked by item 220.
  • While waiting for beam recovery, continuing RLM on the serving beam has the benefit of potential recovery on the serving beam by collecting N311 consecutive in-sync, e.g. in the case of UE moving back to the serving beam, with the intention to increase robustness.
  • the UE If the UE “recovers” the serving beam, which means that serving beam can be reliable again for transmission, then there is no need for further beam recovery attempts and, therefore, the UE should abort the ongoing beam recovery procedure and inform this fact to the gNB, as gNB is not aware of this, and is still handling beam recovery.
  • the indication can be sent on the serving beam by reusing the similar signaling of beam recovery request. When gNB receives this, it knows that beam recovery on a candidate beam can be stopped and the UE has returned back to the serving beam.
  • the UE behavior depends on the outcome of beam recovery procedure.
  • the UE can choose to start T310 and see ifN311 consecutive in-sync can be collected on the new beam. This can be seen as a double-check from RLM’s point of view.
  • FIG. 3 presents a block diagram for the case where the beam recovery procedure finishes while T310 is still running.
  • the serving beam 302 during time interval 306 RLM is performed, but T310 is not started due to good link quality, then the T310 runs during interval 308, ends at the time marked by item 312, and the after the T310 run is complete the beam proceeds during interval 310 dependent on the outcome of beam failure recovery procedure and serving beam’s RLM.
  • the candidate beam 304 proceeds during time interval 314 with just some RRM measurement, ifso configured.
  • time interval 316 the beam recovery procedure is taking place.
  • the candidate beam proceeds as before, represented by item 318, proceeds depending on the outcome of beam failure recovery procedure: if successful, then the candidate beam becomes the serving beam and perform RLM, optionally T310 can be started; if failure, then nothing happens on the candidate beam but just some RRM measurement, if so configured.
  • the UE switches to the new beam which is now reliable for transmission.
  • the UE can choose to start T310 and evaluate if N311 consecutive in-sync can be collected on the new beam.
  • RAN1 If beam recovery fails, RAN1 has agreed that UE does not make further beam recovery attempts, then the UE just waits for the outcome of RLM on the serving beam, i.e. the expiration of T310 timer.
  • Embodiments herein may be implemented in software (executed by one or more processors) , hardware (e.g., an application specific integrated circuit) , or a combination of software and hardware.
  • the software e.g., application logic, an instruction set
  • a “computer-readable medium” may be any media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer, with one example of a computer described and depicted, e.g., in FIG. 1.
  • a computer-readable medium may comprise a computer-readable storage medium (e.g., 104, 134, or other device) that may be any media or means that can contain, store, and/or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer.
  • a computer-readable storage medium does not comprise merely propagating signals.
  • FIG. 4 is a logic flow diagram for enhanced radio link monitoring for New Radio, and illustrates the operation of an exemplary method 400, a result of execution of computer program instructions embodied on a computer readable memory, functions performed by logic implemented in hardware, and/or interconnected means for performing functions in accordance with exemplary embodiments. Parts or all of exemplary method 400 could be performed in module YYY or module ZZZ as appropriate.
  • the method mainly takes places in the UE side in terms of the timer handling and RLM. But reporting back to serving beam to gNB will impact gNB as well.
  • Exemplary method 400 comprises step 402, where a UE interactively performs radio link monitoring on at least one serving beam from a serving base station and a beam recovery procedure on at least one candidate beam from the serving base station, and step 404, where the UE determines what to perform in response to the beam recovery procedure and the radio link monitoring with different timing relationships.
  • Item 406 shows that the input into that determination is the time relationship such that the beam recovery procedure continues after the expiration of the timer or it finishes before the timer expires.
  • Another input is item 408 as to whether the beam recovery succeeds or fails.
  • Other inputs not illustrated include such things as whether the UE can confirm synchronization with the serving base station. Based on the determination the UE can perform either triggering re-establishment procedure 410, indicating to the network switching by the UE to the candidate beam 412, and indicating to the network a return back by the UE to the serving beam 414.
  • the different functions discussed herein may be performed in a different order and/or concurrently with each other. Furthermore, if desired, one or more of the above-described functions may be optional or may be combined.
  • an advantage or a technical effect of one or more of the exemplary embodiments disclosed herein of the proposed radio link quality control mechanism is that it provides a comprehensive solution that works for all timing relationships between RLM and beam failure recovery procedures.
  • an advantage or a technical effect of one or more of the exemplary embodiments disclosed herein of the proposed interaction scheme is that the probability of a successful recovery of the link on serving/candidate beam can be improved and unnecessary RLF can be avoided.
  • an advantage or a technical effect of one or more of the exemplary embodiments disclosed herein of the proposed interaction scheme is that RLF is not triggered at T310 expiration as shown in FIG. 2 or at completion of beam failure recovery procedure as shown in FIG. 3, meaning that more chances are allowed for link recovery.
  • an advantage or a technical effect of one or more of the exemplary embodiments disclosed herein of the proposed interaction scheme is that unnecessary beam failure recovery can be avoided.
  • an advantage or a technical effect of one or more of the exemplary embodiments disclosed herein of the proposed interaction scheme compared to the prior work in the field, is that if the serving beam is recovered (N311 in-sync indications are received) , the beam failure recovery procedure is aborted, so the related signaling overhead can be saved.
  • An example of an embodiment of the current invention which can be referred to as item 1, is a method that comprises interactively performing, by a user equipment in a wireless communications network, radio link monitoring on at least one serving beam from a serving base station and a beam recovery procedure on at least one candidate beam from the serving base station; and determining by the user equipment, in response to the beam recovery procedure and the radio link monitoring with different timing relationships, to perform one of the following: triggering re-establishment procedure, indicating to the network switching by the user equipment to at least one candidate beam, and indicating to the network a return back by the user equipment to at least one serving beam.
  • An example of a further embodiment of the current invention which can be referred to as item 2, is the method of item 1, where the timing relationship comprises: the beam recovery procedure continuing after the expiration of a timer used to allow the user equipment to regain synchronization with the serving base station.
  • An example of a further embodiment of the current invention which can be referred to as item 3, is the method of item 2, further comprising: continuing by the user equipment the radio link monitoring in the at least one serving beton and not triggering radio link failure.
  • An example of a further embodiment of the current invention which can be referred to as item 4, is the method of item 3, wherein a number of consecutive in-sync, allowing the user equipment to confirm synchronization with the serving base station, are received on the at least one serving beam before the beam recovery procedure finishes.
  • An example of a further embodiment of the current invention which can be referred to as item 5, is the method of item 4, further comprising: aborting by the user equipment the beam recovery procedure, and indicating a return to the at least one serving beam by the user equipment to the serving base station.
  • An example of a further embodiment of the current invention which can be referred to as item 6, is the method of item 3, wherein the beam recovery procedure finishes and a number of consecutive in-sync, allowing the user equipment to confirm synchronization with the serving base station, have not been received on the at least one serving beam.
  • An example of a further embodiment of the current invention which can be referred to as item 7, is the method of item 6, wherein if beam recovery succeeds, further comprising: switching by the user equipment to the at least one candidate beton; resetting all previous in-sync/out-of-sync counters; and restarting the timer.
  • An example of a further embodiment of the current invention which can be referred to as item 8, is the method of item 6, wherein ifbeam recovery fails, further comprising: indicating by the user equipment to radio resource control protocol layer and declaring radio link failure.
  • An example of a further embodiment of the current invention which can be referred to as item 9, is the method of item 1, wherein the timing relationship comprises: the beam recovery procedure finishing before the expiration of a timer used to allow the user equipment to regain synchronization with the serving base station.
  • An example of a further embodiment of the current invention which can be referred to as item 10, is the method of item 9, wherein if beam recovery succeeds, further comprising: switching by the user equipment to the at least one candidate beam; resetting all previous in-sync/out-of-sync counters; and restarting the timer.
  • An example of a further embodiment of the current invention which can be referred to as item 11, is the method of item 9, wherein ifbeam recovery fails, further comprising: continuing the radio link monitoring by the user equipment on the at least one serving beam as if beam recovery procedure had not been performed.
  • An example of another embodiment of the present invention which can be referred to as item 12, is an apparatus that comprises at least one processor and at least one memory including computer program code, where the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to perform at least the following: interactively performing, in a wireless communications network, radio link monitoring on at least one serving beam from a serving base station and beam recovery procedure on at least one candidate beam from the serving base station; and determining, in response to beam recovery procedure and radio link monitoring with different timing relationships, to perform one of the following: triggering re-establishment procedure, indicating to the network switching to at least one candidate beam, and indicating to the network a return back to at least one serving beam.
  • An example of yet another embodiment of the present invention which can be referred to as item 13, is the apparatus of item 12, where the timing relationship comprises: the beam recovery procedure continuing after the expiration of a timer used to allow the user equipment to regain synchronization with the serving base station.
  • An example of yet another embodiment of the present invention which can be referred to as item 14, is the apparatus of item 13, wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to perform at least the following: continuing by the user equipment the radio link monitoring in the at least one serving beam and not triggering radio link failure.
  • An example of yet another embodiment of the present invention which can be referred to as item 15, is the apparatus of item 14, wherein a number of consecutive in-sync, allowing the user equipment to confirm synchronization with the serving base station, are received on the at least one serving beam before the beam recovery procedure finishes.
  • An example of yet another embodiment of the present invention which can be referred to as item 16, is the apparatus of item 15, wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to perform at least the following: aborting by the user equipment the beam recovery procedure, and indicating a return to the at least one serving beam by the user equipment to the serving base station.
  • An example of yet another embodiment of the present invention which can be referred to as item 17, is the apparatus of item 14, wherein the beam recovery procedure finishes and a number of consecutive in-sync, allowing the user equipment to confirm synchronization with the serving base station, have not been received on the at least one serving beam.
  • An example of yet another embodiment of the present invention which can be referred to as item 18, is the apparatus of item, wherein, ifbeam recovery succeeds, the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to perform at least the following: switching by the user equipment to the at least one candidate beam; resetting all previous in-sync/out-of-sync counters; and restarting the timer.
  • An example of yet another embodiment of the present invention which can be referred to as item 19, is the apparatus of item 17, wherein, ifbeam recovery fails, the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to perform at least the following: indicating by the user equipment to radio resource control protocol layer and declaring radio link failure.
  • An example of yet another embodiment of the present invention which can be referred to as item 20, is the apparatus of item 12, wherein the timing relationship comprises: the beam recovery procedure finishing before the expiration of a timer used to allow the user equipment to regain synchronization with the serving base station.
  • An example of yet another embodiment of the present invention which can be referred to as item 21, is the apparatus of item 20, wherein, ifbeam recovery succeeds, the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to perform at least the following: switching by the user equipment to the at least one candidate beam; resetting all previous in-sync/out-of-sync counters; and restarting the timer.
  • An example of yet another embodiment of the present invention which can be referred to as item 22, is the apparatus of item 20, wherein, ifbeam recovery fails, the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to perform at least the following: continuing the radio link monitoring by the user equipment on the at least one serving beam as ifbeam recovery procedure had not been performed.
  • An example of an additional embodiment of the instant invention which can be referred to as item 23, is a computer program that comprises code for interactively performing, by a user equipment in a wireless communications network, radio link monitoring on at least one serving beam from a serving base station and a beam recovery procedure on at least one candidate beam from the serving base station; and code for determining by the user equipment, in response to the beam recovery procedure and the radio link monitoring with different timing relationships, to perform one of the following: triggering re-establishment procedure, indicating to the network switching by the user equipment to at least one candidate beam, and indicating to the network a return back by the user equipment to at least one serving beam.
  • An example of another additional embodiment of the instant invention which can be referred to as item 24, is computer program product embodied on a non-transitory computer-readable medium in which a computer program is stored that, when being executed by a computer, is configured to provide instructions to control or carry out the method of any of items 1-11.
  • An example of a yet further embodiment of the present invention which can be referred to as item 25, is an apparatus, comprising means for interactively performing, in a wireless communications network, radio link monitoring on at least one serving beam from a serving base station and a beam recovery procedure on at least one candidate beam from the serving base station; and means for determining, in response to the beam recovery procedure and the radio link monitoring with different timing relationships, to perform one of the following: triggering re-establishment procedure, indicating to the network switching to at least one candidate beam, and indicating to the network a return back to at least one serving beam.
  • the different functions discussed herein may be performed in a different order and/or concurrently with each other. Furthermore, if desired, one or more of the above-described functions may be optional or may be combined.

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Abstract

A method, apparatus, and computer program product for a user equipment in a wireless communications network to interactively perform radio link monitoring on at least one serving beam from a serving base station and a beam recovery procedure on at least one candidate beam from the serving base station and to determine, for different timing relationships of the beam recovery procedure compared to the radio link monitoring, which of the following to perform: triggering re-establishment procedure, indicating to the network switching by the user equipment to at least one candidate beam, or indicating to the network a return back by the user equipment to at least one serving beam.

Description

ENHANCED RADIO LINK MONITORING FOR NEW RADIO TECHNICAL FIELD
This invention relates generally to wireless communication systems related to multi-antenna technology in New Radio (NR) and， more specifically， to an enhanced radio link quality control mechanism for NR by considering the interaction between radio link monitoring and beam failure recovery procedures.
BACKGROUND
This section is intended to provide a background or context to the invention disclosed below. The description herein may include concepts that could be pursued， but are not necessarily ones that have been previously conceived， implemented or described. Therefore， unless otherwise explicitly indicated herein， what is described in this section is not prior art to the description in this application and is not admitted to be prior art by inclusion in this section.
According to early agreements in RAN1， beam management is a set of L1/L2 procedures to acquire and maintain a set of TRP (s) and/or UE beams that can be used for DL and UL transmission/reception， which include at least following aspects：
Beam determination is for TRP (s) or UE to select of its own Tx/Rx beam (s) . Beam measurement is for TRP (s) or UE to measure characteristics of received beamformed signals. Beam reporting is for UE to report information ofbeamformed signal (s) based on beam measurement. Beam sweeping is operation of covering a spatial area， with beams transmitted and/or received during a time interval in a predetermined way.
UE beam failure recovery mechanism includes beam failure detection， new candidate beam identification， beam failure recovery request transmission， and UE monitoring gNB response for beam failure recovery request.
Radio link monitoring (RLM) ， on the other hand， is a L3 procedure already used in LTE as specified in section 5.3.11 of 36.331. RLM in NR procedure would be very similar to that of LTE.
The current invention moves beyond these techniques.
Abbreviations that may be found in the specification and/or the drawing figures are either defined in the text or defined below in the following list of abbreviations：
2G             Second Generation
3G             Third Generation
3GPP          Third Generation Partnership Project
5G            Fifth Generation
5G-NB         Fifth Generation Node B
ACK           Acknowledged/Acknowledgement
A/N           Acknowledged/Not acknowledged
ARQ           Automatic Repeat-reQuest
BCI           Beam Change Indication
BS            Base Station
BSI           Beam State Information
BRI           Beam Refinement Information
BRS           Beam Reference Signal
BRRS          Beam Refinement Reference Signal
BSR           Buffer Status Report
CB            Contention based
CE            Control Element
CQI           Channel Quality Indicator
CSI           Channel State Information
C-RNTI        Cell Radio Network Temporary Identifier
DCI           Downlink Control Information
DL            Downlink
eNB or eNodeB Evolved Node B (LTE base station) 
EPDCCH        Enhanced Physical Downlink Control Channel
E-UTRAN       Evolved UTRAN
gNB           NR/5G Node B
HARQ          Hybrid Automatic Repeat Request
IS            In-Sync
L1            Physical Layer or PHY
L2            MAC/RLC/PDCP layer
L3            RRC layer
LCID          Logical Channel Identifier
LTE           Long Term Evolution
LTE-A         Long Term Evolution -Advanced
LTE-M         LTE system to support MTC or M2M
Node B (NB)   Node B (base station in UTRAN)
MAC           Medium Access Control
MAC CE        MAC Control Element
MIMO          Multiple In， Multiple Out
MTC           Machine Type Communication
NACK          Not Acknowledged/Negative-acknowledgement
NB            NodeB， base station
NR            New Radio
OOS           Out-of-Sync
PDCP          Packet Data Convergence Protocol
PDSCH         Physical Downlink Shared Channel
PDCCH         Physical Downlink Control Channel
PDU           Protocol Data Unit
PHR           Power Headroom Report
PRACH         Physical Random Access Channel
PRB           Physical Resource Block
PUCCH         Physical Uplink Control Channel
PUSCH         Physical Uplink Shared Channel
QoS           Quality of Service
RACH          Random Access Channel
RAN           Radio Access Network
RAT           Radio Access Technology
RBI           Refinement Beam Index
RRC           Radio Resource Control
RE            Resource Element
Rel           Release
ReTx          Retransmission or retransmitting
RLC           Radio Link Control
RLF           Radio Link Failure
RLM           Radio Link Monitoring
RSRP          Reference Signal Received Power
RSRQ          Reference Signal Received Quality
RSSI          Received Signal Strength Indicator
Rx， RX       Reception or receiving
SB            Sweeping Block
SPS            Semi-persistent scheduling
SR             Scheduling Request
SRS            Sounding Reference Signal
TDD            Time Division Duplexing
TRP            Transmit-Receive Point
TS             Technical Specification or Technical Standard
TTI            Transmission Time Interval
Tx， TX        Transmission or transmitting
TXRU           Transceiver Unit
UCI            Uplink Control Information
UE             User Equipment or mobile station
UL             Uplink
UL-SCH         Uplink Shared Channel
PUSCH          Physical uplink shared channel
BRIEF SUMMARY
This section is intended to include examples and is not intended to be limiting. As discussed in detail below， the current invention proposes an enhanced radio link quality control mechanism for NR by considering the interaction between RLM and beam failure recovery procedures.
An example of an embodiment of the current invention is a method that comprises interactively performing， by a user equipment in a wireless communications network， radio link monitoring on at least one serving beam from a serving base station and a beam recovery procedure on at least one candidate beam from the serving base station； and determining by the user equipment， in response to the beam recovery procedure and the radio link monitoring with different timing relationships， to perform one of the following： triggering re-establishment procedure， indicating to the network switching by the user equipment to at least one candidate beam， and indicating to the network a return back by the user equipment to at least one serving beam.
An example of another embodiment of the present invention is an apparatus that comprises at least one processor and at least one memory including computer program code， where the at least one memory and the computer program code are configured， with the at least one processor， to cause the apparatus to perform at least the following： interactively performing， by a user equipment in a wireless communications network， radio link monitoring  on at least one serving beam from a serving base station and a beam recovery procedure on at least one candidate beam from the serving base station； and determining by the user equipment， in response to the beam recovery procedure and the radio link monitoring with different timing relationships， to perform one of the following： triggering re-establishment procedure， indicating to the network switching by the user equipment to at least one candidate beam， and indicating to the network a return back by the user equipment to at least one serving beam.
An example of an additional embodiment of the instant invention is a computer program product embodied on a non-transitory computer-readable medium in which a computer program is stored that， when being executed by a computer， is configured to provide instructions to control or carry out at least the following： interactively performing， by a user equipment in a wireless communications network， radio link monitoring on at least one serving beam from a serving base station and a beam recovery procedure on at least one candidate beam from the serving base station； and determining by the user equipment， in response to the beam recovery procedure and the radio link monitoring with different timing relationships， to perform one of the following： triggering re-establishment procedure， indicating to the network switching by the user equipment to at least one candidate beam， and indicating to the network a return back by the user equipment to at least one serving beam.
An example of yet another embodiment of the invention disclosed herein is an apparatus， comprising means for interactively performing， by a user equipment in a wireless communications network， radio link monitoring on at least one serving beam from a serving base station and a beam recovery procedure on at least one candidate beam from the serving base station； and means for determining by the user equipment， in response to the beam recovery procedure and the radio link monitoring with different timing relationships， to perform one of the following： triggering re-establishment procedure， indicating to the network switching by the user equipment to at least one candidate beam， and indicating to the network a return back by the user equipment to at least one serving beam.
BRIEF DESCRIPTION OF THE DRAWINGS
In the attached Drawing Figures：
FIG. 1 is a block diagram of one possible and non-limiting exemplary system in which the exemplary embodiments may be practiced；
FIG. 2 illustrates a time relationship where the beam recovery procedure continuing after the expiration ofa timer used to allow the user equipment to regain synchronization with the serving base station；
FIG. 3 illustrates a time relationship timing relationship comprises： the beam recovery procedure finishing before the expiration of the timer used to allow the user equipment to regain synchronization with the serving base station； and
FIG. 4 is a logic flow diagram for enhanced radio link monitoring for New Radio， and illustrates the operation of an exemplary method， a result of execution of computer program instructions embodied on a computer readable memory， functions performed by logic implemented in hardware， and/or interconnected means for performing functions in accordance with exemplary embodiments.
DETAILED DESCRIPTION OF THE DRAWINGS
This invention relates generally to wireless communication systems related to Rel-15 WI “New Radio (NR) Access Technology” . Different from LTE， in NR system， multi-beam operation， which is enabled by multi-antenna technology， is introduced for DL and UL transmission/reception. 3 GPP is now still discussing beam management procedure to support beam-level mobility and beam failure recovery procedure is considered as part of beam management.
In the RAN2 NR ad hoc meeting of June 2017， it was agreed that RAN2 understands that beam failure recovery (L1 or MAC) and RLF (RRC) are performed in different layers.
There were a few RAN2 contributions submitted to recent meetings discussed herein. In R2-1706437， it was proposed that RLF is declared ifbeam failure recovery does not succeed and different options are listed for the interaction modeling， e.g. beam failure recovery with or without RRC involvement. In R2-1706680， it was proposed that upon failure of beam failure recovery mechanism for each subset of beams， the UE shall provide a Radio Link Interruption indication to Layer 2 to facilitate Mobility without RRC Involvement. In R2-1706745， it was proposed that for multi-beam operation， after beam recovery via all UL beam (s) of serving cell has failed， RLF is declared. In R2-1706965， it was proposed that during the in-sync /out-of-sync detection in RLF， ifbeam failure recovery is trigged， the timer for RLF can be suspended or paused.
Prior work in this field did not provide a comprehensive solution addressing all timing relationships between RLM and beam failure recovery procedures， which are considered in the present invention. While some prior proposals considered that the failure of beam failure recovery procedure triggers RLF， none of them considered the other way  around， i.e.， RLM procedure should also impact beam failure recovery procedure， as we propose in the current invention.
A problem addressed in this invention is the interaction between RLM and beam failure recovery procedures， more specifically the UE behavior when a beam failure recovery procedure is ongoing during when T310 timer is running. The T310 timer is LTE nomenclature for a timer that starts while initiating RRC Connection Re-Establishment procedure and stops upon selection of suitable E-UTRA cell OR a cell using another RAT. At expiry it enters RRC IDLE state. Please note T310 and N311 (also discussed herein) are parameters used in LTE system. The intention is for the present invention to reuse LTE’s RLM mechanism， but this does not necessarily mean that future specifications in NR will reuse the same parameter names. Therefore， this invention utilizes these as general concepts， and not necessarily restricted to the same measurements， when describing these two parameters. Thus， since New Radio may use a different nomenclature and that the term T310 is used here for convenience. Likewise， N311 is also LTE nomenclature and is also used herein for convenience. In general， N311 represents a number of consecutive in-sync that allows the user equipment to confirm synchronization with the serving base station，
In LTE， to determine ifa Radio Link is out of Synch， an N310 parameter indicates the number of 200 ms intervals when the UE is unable to successfully decode the PDCCH due to low RSRP detected. N310 indicates the number of times in which the UE cannot successfully decode 20 consecutive frames in the downlink. T310 is a timer， in seconds， used to allow the UE to get back in synchronization with the eNodeB. N311 is a parameter that indicates the number of 100 ms intervals that the UE must successfully decode the PDCCH to be back in-synch with the eNodeB. That is， this parameter indicates the number of times in which the UE must successfully decode 10 consecutive frames in the downlink in order for the UE to assume the radio link is in-synch. In LTE， if the UE detects N310 consecutive out-of-sync indications， it starts the T310 timer. If the timer expires， the link has failed. If the UE detects N311 consecutive in-sync indications prior to the T310 timer expiring， then the timer is stopped and the link has not failed.
In NR system， a UE performs radio link monitoring on the serving beam (s) and the procedure is done in a similar way as LTE， i.e.， physical layer generates periodic in-sync or out-of-sync indications to the RRC layer， and based on these indications， RRC layer decides how to control the timer T310 and whether to declare RLF.
Meanwhile， even though beam management procedure (which is still under RAN1 discussion) is intended to well handle beam-level mobility， RAN1 is also  considering beam failure recovery procedure to handle the exceptional cases， e.g. sudden channel degradation due to blockage or beam misalignment due to fast channel variation， which is beyond the ability of beam management procedure. Therefore， it is possible for a UE to recover the failed beam on a new candidate beam (or the previous beam depending on UE’s mobility) and all subsequent transmissions can be switched to the recovered beam.
In this regard， the impact on the radio link monitoring procedure cannot be ignored， and the interaction between RLM and beam failure recovery procedures is not trivial. For example， UE behavior should be defined on whether the UE should continue radio link monitoring on the current beam (s) until RLF happens during the beam failure recovery procedure， and whether beam recovery failure should directly trigger RLF， etc. This invention addresses these issues.
Before turning to a further discussion of the current invention， we turn to FIG. 1， which is a block diagram of one possible and non-limiting exemplary system in which the exemplary embodiments may be practiced.
Please note that the word “exemplary” is used herein to mean “serving as an example， instance， or illustration. ” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described in this Detailed Description are exemplary embodiments provided to enable persons skilled in the art to make or use the invention and not to limit the scope of the invention which is defined by the claims
In FIG. 1， a user equipment (UE) 110 is in wireless communication with a wireless network 100. A UE is a wireless， typically mobile device that can access a wireless network. The UE 110 includes one or more processors 120， one or more memories 125， and one or more transceivers 130 interconnected through one or more buses 127. Each of the one or more transceivers 130 includes a receiver， Rx， 132 and a transmitter， Tx， 133. The one or more buses 127 may be address， data， or control buses， and may include any interconnection mechanism， such as a series of lines on a motherboard or integrated circuit， fiber optics or other optical communication equipment， and the like. The one or more transceivers 130 are connected to one or more antennas 128. The one or more memories 125 include computer program code 123. Note that the YYY module allows functionality for the usage of control resources for data transmission where any method or examples of such embodiments discussed herein can be practiced. The UE 110 includes a YYY module 140， comprising one of or both parts 140-1 and/or 140-2， which may be implemented in a number of ways. The YYY module 140 may be implemented in hardware as YYY module 140-1， such as being implemented as  part of the one or more processors 120. The YYY module 140-1 may be implemented also as an integrated circuit or through other hardware such as a programmable gate array. In another example， the YYY module 140 may be implemented as YYY module 140-2， which is implemented as computer program code 123 and is executed by the one or more processors 120. For instance， the one or more memories 125 and the computer program code 123 may be configured to， with the one or more processors 120， cause the user equipment 110 to perform one or more of the operations as described herein. The UE 110 communicates with gNB 170 via a wireless link 111.
The gNB (a New Radio 5G NodeB， which would denoted as gNB or possibly some variant of an evolved NodeB) 170 is a base station (e.g.， for LTE， long term evolution， or 5G base station) that provides access by wireless devices such as the UE 110 to the wireless network 100. The gNB 170 includes one or more processors 152， one or more memories 155， one or more network interfaces (N/W I/F (s) ) 161， and one or more transceivers 160 interconnected through one or more buses 157. Each of the one or more transceivers 160 includes a receiver， Rx， 162 and a transmitter， Tx， 163. The one or more transceivers 160 are connected to one or more antennas 158. The one or more memories 155 include computer program code 153. Note that the ZZZ module allows functionality for the usage of control resources for data transmission where any method or examples of such embodiments discussed herein can be practiced. The gNB 170 includes a ZZZ module 150， comprising one of or both parts 150-1 and/or 150-2， which may be implemented in a number of ways. The ZZZ module 150 may be implemented in hardware as ZZZ module 150-1， such as being implemented as part of the one or more processors 152. The ZZZ module 150-1 may be implemented also as an integrated circuit or through other hardware such as a programmable gate array. In another example， the ZZZ module 150 may be implemented as ZZZ module 150-2， which is implemented as computer program code 153 and is executed by the one or more processors 152. For instance， the one or more memories 155 and the computer program code 153 are configured to， with the one or more processors 152， cause the gNB 170 to perform one or more of the operations as described herein. The one or more network interfaces 161 communicate over a network such as via the  links  176 and 131. Two or more gNBs 170 communicate using， e.g.， link 176. The link 176 may be wired or wireless or both and may implement， e.g.， an X2 interface.
The one or more buses 157 may be address， data， or control buses， and may include any interconnection mechanism， such as a series of lines on a motherboard or integrated circuit， fiber optics or other optical communication equipment， wireless channels，  and the like. For example， the one or more transceivers 160 may be implemented as a remote radio head (RRH) 195， with the other elements of the gNB 170 being physically in a different location from the RRH， and the one or more buses 157 could be implemented in part as fiber optic cable to connect the other elements of the gNB 170 to the RRH 195.
It is noted that description herein indicates that “cells” perform functions， but it should be clear that the gNB that forms the cell would perform the functions. The cell makes up part of a gNB. That is， there can be multiple cells per gNB. For instance， there could be three cells for a single gNB carrier frequency and associated bandwidth， each cell coveting one-third of a 360-degree area so that the single gNB’s coverage area covers an approximate oval or circle. Furthermore， each cell can correspond to a single carrier and a gNB may use multiple carriers. So if there are three 120-degree cells per carrier and two carriers， then the gNB has a total of 6 cells.
The wireless network 100 may include a network control element (NCE) 190 that may include MME (Mobility Management Entity) /SGW (Serving Gateway) functionality， and which provides connectivity with a further network， such as a telephone network and/or a data communications network (e.g.， the Internet) . The gNB 170 is coupled via a link 131 to the NCE 190. The link 131 may be implemented as， e.g.， an S1 interface. The NCE 190 includes one or more processors 175， one or more memories 171， and one or more network interfaces (N/W I/F (s) ) 180， interconnected through one or more buses 185. The one or more memories 171 include computer program code 173. The one or more memories 171 and the computer program code 173 are configured to， with the one or more processors 175， cause the NCE 190 to perform one or more operations.
The wireless network 100 may implement network virtualization， which is the process of combining hardware and software network resources and network functionality into a single， software-based administrative entity， a virtual network. Network virtualization involves platform virtualization， often combined with resource virtualization. Network virtualization is categorized as either external， combining many networks， or parts of networks， into a virtual unit， or internal， providing network-like functionality to software containers on a single system. Note that the virtualized entities that result from the network virtualization may still be implemented， at some level， using hardware such as  processors  152 or 175 and  memories  155 and 171， and also such virtualized entities create technical effects.
The computer  readable memories  125， 155， and 171 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology， such as semiconductor based memory devices， flash memory， magnetic  memory devices and systems， optical memory devices and systems， fixed memory and removable memory. The computer  readable memories  125， 155， and 171 may be means for performing storage functions. The  processors  120， 152， and 175 may be of any type suitable to the local technical environment， and may include one or more of general purpose computers， special purpose computers， microprocessors， digital signal processors (DSPs) and processors based on a multi-core processor architecture， as non-limiting examples. The  processors  120， 152， and 175 may be means for performing functions， such as controlling the UE 110， gNB 170， and other functions as described herein.
In general， the various embodiments of the user equipment 110 can include， but are not limited to， cellular phones such as smart devices， tablets， personal digital assistants (PDAs) having wireless communication capabilities， portable computers having wireless communication capabilities， image capture devices such as digital cameras having wireless communication capabilities， gaming devices having wireless communication capabilities， music storage and playback appliances having wireless communication capabilities， internet appliances permitting wireless Internet access and browsing， tablets with wireless communication capabilities， as well as portable units or terminals that incorporate combinations of such functions. In addition， various embodiments of the user equipment include machines， communicators and categories of equipment， which are not primarily or not at all in use by human interaction.
The current architecture in LTE networks is fully distributed in the radio and fully centralized in the core network. The low latency requires bringing the content close to the radio which leads to local break out and multi-access edge computing (MEC) . 5G may use edge cloud and local cloud architecture. Edge computing covers a wide range of technologies such as wireless sensor networks， mobile data acquisition， mobile signature analysis， cooperative distributed peer-to-peer ad hoc networking and processing also classifiable as local cloud/fog computing and grid/mesh computing， dew computing， mobile edge computing， cloudlet， distributed data storage and retrieval， autonomic self-healing networks， remote cloud services and augmented reality. In radio communications， using edge cloud may mean node operations to be carried out， at least partly， in a server， host or node operationally coupled to a remote radio head or base station comprising radio parts. It is also possible that node operations will be distributed among a plurality of servers， nodes or hosts. It should also be understood that the distribution of labor between core network operations and base station operations may differ from that of the LTE or even be non-existent. Some other technology advancements  probably to be used are Software-Defined Networking (SDN) ， Big Data， and all-IP， which may change the way networks are being constructed and managed.
One possible manner to carry out embodiments described herein is with an edge cloud using a distributed computing system. An exemplary embodiment comprises a radio node connected to a server. Exemplary embodiments implementing the system allow the edge cloud server and the radio node as stand-alone apparatuses communicating with each other via a radio path or via a wired connection or they may be located in a same entity communicating via a wired connection.
This invention proposes an enhanced radio link quality control mechanism for NR by considering the interaction between RLM and beam failure recovery procedures， specifically teaching what to do if the beam recovery procedure is still ongoing while T310 expires/stops and what to do ifthe beam recovery procedure finishes while T310 is still running.
Ifbeam recovery procedure is still ongoing while T310 expires/stops， the UE does not trigger RLF but continues RLM in the serving beam.
IfN311 consecutive in-sync are received on the serving beam before beam recovery procedure finishes， then the UE aborts ongoing beam recovery procedure and the UE indicates “back to serving beam” to gNB， e.g. by re-using the beam recovery request signaling.
Ifbeam recovery procedure finishes and N311 consecutive in-sync have not been received on the serving beam， then ifbeam recovery succeeds， the UE switches to the new beam， resets all previous IS/OOS counters， restarts T310 and performs RLM on the new beam.
Ifbeam recovery procedure finishes and N311 consecutive in-sync have not been received on the serving beam， then ifbeam recovery fails， the UE indicates to L3 and declares RLF.
If the beam recovery procedure finishes while T310 is still running and the beam recovery succeeds， then the UE switches to the new beam， resets all previous IS/OOS counters， restarts T310 and performs RLM on the new beam. However， if the beam recovery procedure finishes while T310 is still running but the beam recovery fails， then UE continues RLM on the serving beam as ifbeam recovery procedure has not been performed.
FIG. 2 presents a block diagram for the case where the beam recovery procedure is still ongoing while T310 expires.
Item 202 represents the serving beam while item 204 represents the candidate beam along the same time frame. In serving beam 202， the beam as represented by item 206 has RLM being performed， but T310 has not started due to good link quality. During the time interval represented by item 208 the T310 is running and consecutive N311 in-sync has not been received on serving beam. At the point in time represented by item 212 is when the T310 expires. In the time frame of item 210， the RLM is continued on serving beam. If N311 consecutive in-sync are received on the serving beam before beam recovery procedure finishes， UE aborts ongoing beam recovery procedure， and indicates ″back to serving beam″to gNB， e.g. by re-using the beam recovery request signaling
In candidate beam 204， the beam proceeds as usual in item 214 with just some RRM measurement， if so configured， but during the time interval represented by item 216 the beam recovery procedure takes place. The beam recovery procedure ends at the time marked by item 220.
In the time interval represented by item 218， depending on the beam recovery procedure’s outcome： if successful， then the candidate beam becomes the serving beam and performs RLM； optionally T310 can be started； if failure， then nothing happens on the candidate beam but just some RRM measurement， if so configured.
The rational for not triggering RLF upon T310 expiry is that beam recovery procedure is ongoing and UE still has chance to recover link on the candidate beam.
While waiting for beam recovery， continuing RLM on the serving beam has the benefit of potential recovery on the serving beam by collecting N311 consecutive in-sync， e.g. in the case of UE moving back to the serving beam， with the intention to increase robustness.
If the UE “recovers” the serving beam， which means that serving beam can be reliable again for transmission， then there is no need for further beam recovery attempts and， therefore， the UE should abort the ongoing beam recovery procedure and inform this fact to the gNB， as gNB is not aware of this， and is still handling beam recovery. The indication can be sent on the serving beam by reusing the similar signaling of beam recovery request. When gNB receives this， it knows that beam recovery on a candidate beam can be stopped and the UE has returned back to the serving beam.
Otherwise， ifno “recovery” is achieved on the serving beam before the completion of beam failure recovery procedure， the UE behavior depends on the outcome of beam recovery procedure.
Ifthe beam recovery succeeds， it means that the new candidate beam is reliable for transmission and then the UE should switch to the new beam. For more robust control on the new beam， the UE can choose to start T310 and see ifN311 consecutive in-sync can be collected on the new beam. This can be seen as a double-check from RLM’s point of view.
If beam recovery fails， it means both serving beam and candidate beam are not reliable. In this case， L3 should be informed and RLF should be triggered.
FIG. 3 presents a block diagram for the case where the beam recovery procedure finishes while T310 is still running.
Again， the serving beam， represented by item 302， and the candidate beam， represented by item 304， procedure in the same time domain. The serving beam 302 during time interval 306 RLM is performed， but T310 is not started due to good link quality， then the T310 runs during interval 308， ends at the time marked by item 312， and the after the T310 run is complete the beam proceeds during interval 310 dependent on the outcome of beam failure recovery procedure and serving beam’s RLM.
The candidate beam 304 proceeds during time interval 314 with just some RRM measurement， ifso configured. During time interval 316， the beam recovery procedure is taking place. After the beam recovery finishes， represented by item 320， the candidate beam proceeds as before， represented by item 318， proceeds depending on the outcome of beam failure recovery procedure： if successful， then the candidate beam becomes the serving beam and perform RLM， optionally T310 can be started； if failure， then nothing happens on the candidate beam but just some RRM measurement， if so configured.
Ifbeam recovery succeeds， the UE switches to the new beam which is now reliable for transmission. For more robust link control， the UE can choose to start T310 and evaluate if N311 consecutive in-sync can be collected on the new beam.
If beam recovery fails， RAN1 has agreed that UE does not make further beam recovery attempts， then the UE just waits for the outcome of RLM on the serving beam， i.e. the expiration of T310 timer.
Embodiments herein may be implemented in software (executed by one or more processors) ， hardware (e.g.， an application specific integrated circuit) ， or a combination of software and hardware. In an example of an embodiment， the software (e.g.， application logic， an instruction set) is maintained on any one of various conventional computer-readable media. In the context of this document， a “computer-readable medium” may be any media or means that can contain， store， communicate， propagate or transport the  instructions for use by or in connection with an instruction execution system， apparatus， or device， such as a computer， with one example of a computer described and depicted， e.g.， in FIG. 1. A computer-readable medium may comprise a computer-readable storage medium (e.g.， 104， 134， or other device) that may be any media or means that can contain， store， and/or transport the instructions for use by or in connection with an instruction execution system， apparatus， or device， such as a computer. A computer-readable storage medium does not comprise merely propagating signals.
FIG. 4 is a logic flow diagram for enhanced radio link monitoring for New Radio， and illustrates the operation of an exemplary method 400， a result of execution of computer program instructions embodied on a computer readable memory， functions performed by logic implemented in hardware， and/or interconnected means for performing functions in accordance with exemplary embodiments. Parts or all of exemplary method 400 could be performed in module YYY or module ZZZ as appropriate. The method mainly takes places in the UE side in terms of the timer handling and RLM. But reporting back to serving beam to gNB will impact gNB as well.
Exemplary method 400 comprises step 402， where a UE interactively performs radio link monitoring on at least one serving beam from a serving base station and a beam recovery procedure on at least one candidate beam from the serving base station， and step 404， where the UE determines what to perform in response to the beam recovery procedure and the radio link monitoring with different timing relationships. Item 406 shows that the input into that determination is the time relationship such that the beam recovery procedure continues after the expiration of the timer or it finishes before the timer expires. Another input is item 408 as to whether the beam recovery succeeds or fails. Other inputs not illustrated include such things as whether the UE can confirm synchronization with the serving base station. Based on the determination the UE can perform either triggering re-establishment procedure 410， indicating to the network switching by the UE to the candidate beam 412， and indicating to the network a return back by the UE to the serving beam 414.
If desired， the different functions discussed herein may be performed in a different order and/or concurrently with each other. Furthermore， if desired， one or more of the above-described functions may be optional or may be combined.
Although various aspects of the invention are set out in the independent claims， other aspects of the invention comprise other combinations of features from the described embodiments and/or the dependent claims with the features of the independent claims， and not solely the combinations explicitly set out in the claims.
Without in any way limiting the scope， interpretation， or application of the claims appearing below， an advantage or a technical effect of one or more of the exemplary embodiments disclosed herein of the proposed radio link quality control mechanism is that it provides a comprehensive solution that works for all timing relationships between RLM and beam failure recovery procedures.
Moreover， without in any way limiting the scope， interpretation， or application of the claims appearing below， an advantage or a technical effect of one or more of the exemplary embodiments disclosed herein of the proposed interaction scheme is that the probability of a successful recovery of the link on serving/candidate beam can be improved and unnecessary RLF can be avoided.
Furthermore， without in any way limiting the scope， interpretation， or application of the claims appearing below， an advantage or a technical effect of one or more of the exemplary embodiments disclosed herein of the proposed interaction scheme， compared to the prior work in the field， is that RLF is not triggered at T310 expiration as shown in FIG. 2 or at completion of beam failure recovery procedure as shown in FIG. 3， meaning that more chances are allowed for link recovery.
Additionally， without in any way limiting the scope， interpretation， or application of the claims appearing below， an advantage or a technical effect of one or more of the exemplary embodiments disclosed herein of the proposed interaction scheme， is that unnecessary beam failure recovery can be avoided.
Besides， without in any way limiting the scope， interpretation， or application of the claims appearing below， an advantage or a technical effect of one or more of the exemplary embodiments disclosed herein of the proposed interaction scheme， compared to the prior work in the field， is that ifthe serving beam is recovered (N311 in-sync indications are received) ， the beam failure recovery procedure is aborted， so the related signaling overhead can be saved.
An example of an embodiment of the current invention， which can be referred to as item 1， is a method that comprises interactively performing， by a user equipment in a wireless communications network， radio link monitoring on at least one serving beam from a serving base station and a beam recovery procedure on at least one candidate beam from the serving base station； and determining by the user equipment， in response to the beam recovery procedure and the radio link monitoring with different timing relationships， to perform one of the following： triggering re-establishment procedure， indicating to the network switching by  the user equipment to at least one candidate beam， and indicating to the network a return back by the user equipment to at least one serving beam.
An example of a further embodiment of the current invention， which can be referred to as item 2， is the method of item 1， where the timing relationship comprises： the beam recovery procedure continuing after the expiration of a timer used to allow the user equipment to regain synchronization with the serving base station.
An example of a further embodiment of the current invention， which can be referred to as item 3， is the method of item 2， further comprising： continuing by the user equipment the radio link monitoring in the at least one serving beton and not triggering radio link failure.
An example of a further embodiment of the current invention， which can be referred to as item 4， is the method of item 3， wherein a number of consecutive in-sync， allowing the user equipment to confirm synchronization with the serving base station， are received on the at least one serving beam before the beam recovery procedure finishes.
An example of a further embodiment of the current invention， which can be referred to as item 5， is the method of item 4， further comprising： aborting by the user equipment the beam recovery procedure， and indicating a return to the at least one serving beam by the user equipment to the serving base station.
An example of a further embodiment of the current invention， which can be referred to as item 6， is the method of item 3， wherein the beam recovery procedure finishes and a number of consecutive in-sync， allowing the user equipment to confirm synchronization with the serving base station， have not been received on the at least one serving beam.
An example of a further embodiment of the current invention， which can be referred to as item 7， is the method of item 6， wherein if beam recovery succeeds， further comprising： switching by the user equipment to the at least one candidate beton； resetting all previous in-sync/out-of-sync counters； and restarting the timer.
An example of a further embodiment of the current invention， which can be referred to as item 8， is the method of item 6， wherein ifbeam recovery fails， further comprising： indicating by the user equipment to radio resource control protocol layer and declaring radio link failure.
An example of a further embodiment of the current invention， which can be referred to as item 9， is the method of item 1， wherein the timing relationship comprises： the beam recovery procedure finishing before the expiration of a timer used to allow the user equipment to regain synchronization with the serving base station.
An example of a further embodiment of the current invention， which can be referred to as item 10， is the method of item 9， wherein if beam recovery succeeds， further comprising： switching by the user equipment to the at least one candidate beam； resetting all previous in-sync/out-of-sync counters； and restarting the timer.
An example of a further embodiment of the current invention， which can be referred to as item 11， is the method of item 9， wherein ifbeam recovery fails， further comprising： continuing the radio link monitoring by the user equipment on the at least one serving beam as if beam recovery procedure had not been performed.
An example of another embodiment of the present invention， which can be referred to as item 12， is an apparatus that comprises at least one processor and at least one memory including computer program code， where the at least one memory and the computer program code are configured， with the at least one processor， to cause the apparatus to perform at least the following： interactively performing， in a wireless communications network， radio link monitoring on at least one serving beam from a serving base station and beam recovery procedure on at least one candidate beam from the serving base station； and determining， in response to beam recovery procedure and radio link monitoring with different timing relationships， to perform one of the following： triggering re-establishment procedure， indicating to the network switching to at least one candidate beam， and indicating to the network a return back to at least one serving beam.
An example of yet another embodiment of the present invention， which can be referred to as item 13， is the apparatus of item 12， where the timing relationship comprises： the beam recovery procedure continuing after the expiration of a timer used to allow the user equipment to regain synchronization with the serving base station.
An example of yet another embodiment of the present invention， which can be referred to as item 14， is the apparatus of item 13， wherein the at least one memory and the computer program code are further configured to， with the at least one processor， cause the apparatus to perform at least the following： continuing by the user equipment the radio link monitoring in the at least one serving beam and not triggering radio link failure.
An example of yet another embodiment of the present invention， which can be referred to as item 15， is the apparatus of item 14， wherein a number of consecutive in-sync， allowing the user equipment to confirm synchronization with the serving base station， are received on the at least one serving beam before the beam recovery procedure finishes.
An example of yet another embodiment of the present invention， which can be referred to as item 16， is the apparatus of item 15， wherein the at least one memory and  the computer program code are further configured to， with the at least one processor， cause the apparatus to perform at least the following： aborting by the user equipment the beam recovery procedure， and indicating a return to the at least one serving beam by the user equipment to the serving base station.
An example of yet another embodiment of the present invention， which can be referred to as item 17， is the apparatus of item 14， wherein the beam recovery procedure finishes and a number of consecutive in-sync， allowing the user equipment to confirm synchronization with the serving base station， have not been received on the at least one serving beam.
An example of yet another embodiment of the present invention， which can be referred to as item 18， is the apparatus of item， wherein， ifbeam recovery succeeds， the at least one memory and the computer program code are further configured to， with the at least one processor， cause the apparatus to perform at least the following： switching by the user equipment to the at least one candidate beam； resetting all previous in-sync/out-of-sync counters； and restarting the timer.
An example of yet another embodiment of the present invention， which can be referred to as item 19， is the apparatus of item 17， wherein， ifbeam recovery fails， the at least one memory and the computer program code are further configured to， with the at least one processor， cause the apparatus to perform at least the following： indicating by the user equipment to radio resource control protocol layer and declaring radio link failure.
An example of yet another embodiment of the present invention， which can be referred to as item 20， is the apparatus of item 12， wherein the timing relationship comprises： the beam recovery procedure finishing before the expiration of a timer used to allow the user equipment to regain synchronization with the serving base station.
An example of yet another embodiment of the present invention， which can be referred to as item 21， is the apparatus of item 20， wherein， ifbeam recovery succeeds， the at least one memory and the computer program code are further configured to， with the at least one processor， cause the apparatus to perform at least the following： switching by the user equipment to the at least one candidate beam； resetting all previous in-sync/out-of-sync counters； and restarting the timer.
An example of yet another embodiment of the present invention， which can be referred to as item 22， is the apparatus of item 20， wherein， ifbeam recovery fails， the at least one memory and the computer program code are further configured to， with the at least one processor， cause the apparatus to perform at least the following： continuing the radio link  monitoring by the user equipment on the at least one serving beam as ifbeam recovery procedure had not been performed.
An example of an additional embodiment of the instant invention， which can be referred to as item 23， is a computer program that comprises code for interactively performing， by a user equipment in a wireless communications network， radio link monitoring on at least one serving beam from a serving base station and a beam recovery procedure on at least one candidate beam from the serving base station； and code for determining by the user equipment， in response to the beam recovery procedure and the radio link monitoring with different timing relationships， to perform one of the following： triggering re-establishment procedure， indicating to the network switching by the user equipment to at least one candidate beam， and indicating to the network a return back by the user equipment to at least one serving beam.
An example of another additional embodiment of the instant invention， which can be referred to as item 24， is computer program product embodied on a non-transitory computer-readable medium in which a computer program is stored that， when being executed by a computer， is configured to provide instructions to control or carry out the method of any of items 1-11.
An example of a yet further embodiment of the present invention， which can be referred to as item 25， is an apparatus， comprising means for interactively performing， in a wireless communications network， radio link monitoring on at least one serving beam from a serving base station and a beam recovery procedure on at least one candidate beam from the serving base station； and means for determining， in response to the beam recovery procedure and the radio link monitoring with different timing relationships， to perform one of the following： triggering re-establishment procedure， indicating to the network switching to at least one candidate beam， and indicating to the network a return back to at least one serving beam.
If desired， the different functions discussed herein may be performed in a different order and/or concurrently with each other. Furthermore， if desired， one or more of the above-described functions may be optional or may be combined.
Although various aspects of the invention are set out in the independent claims， other aspects of the invention comprise other combinations of features from the described embodiments and/or the dependent claims with the features of the independent claims， and not solely the combinations explicitly set out in the claims.
It is also noted herein that while the above describes example embodiments of the invention， these descriptions should not be viewed in a limiting sense. Rather， there are several variations and modifications which may be made without departing from the scope of the present invention as defined in the appended claims.

Claims (25)

  1. A method comprising：
    interactively performing， by a user equipment in a wireless communications network， radio link monitoring on at least one serving beam from a serving base station and a beam recovery procedure on at least one candidate beam from the serving base station； and
    determining by the user equipment， in response to the beam recovery procedure and the radio link monitoring with different timing relationships， to perform one of the following：
    triggering re-establishment procedure，
    indicating to the network switching by the user equipment to at least one candidate beam， and
    indicating to the network a return back by the user equipment to at least one serving beam.
  2. The method of claim 1， wherein the timing relationship comprises： the beam recovery procedure continuing after the expiration of a timer used to allow the user equipment to regain synchronization with the serving base station.
  3. The method of claim 2， further comprising： continuing by the user equipment the radio link monitoring in the at least one serving beam and not triggering radio link failure.
  4. The method of claim 3， wherein a number of consecutive in-sync， allowing the user equipment to confirm synchronization with the serving base station， are received on the at least one serving beam before the beam recovery procedure finishes.
  5. The method of claim 4， further comprising： aborting by the user equipment the beam recovery procedure， and indicating a return to the at least one serving beam by the user equipment to the serving base station.
  6. The method of claim 3， wherein the beam recovery procedure finishes and a number of  consecutive in-sync， allowing the user equipment to confirm synchronization with the serving base station， have not been received on the at least one serving beam.
  7. The method of claim 6， wherein ifbeam recovery succeeds， further comprising：
    switching by the user equipment to the at least one candidate beam；
    resetting all previous in-sync/out-of-sync counters； and
    restarting the timer.
  8. The method of claim 6， wherein ifbeam recovery fails， further comprising：
    indicating by the user equipment to radio resource control protocol layer and declaring radio link failure.
  9. The method of claim 1， wherein the timing relationship comprises： the beam recovery procedure finishing before the expiration of a timer used to allow the user equipment to regain synchronization with the serving base station.
  10. The method of claim 9， wherein if beam recovery succeeds， further comprising：
    switching by the user equipment to the at least one candidate beam；
    resetting all previous in-sync/out-of-sync counters； and
    restarting the timer.
  11. The method of claim 9， wherein ifbeam recovery fails， further comprising：
    continuing the radio link monitoring by the user equipment on the at least one serving beam as ifbeam recovery procedure had not been performed.
  12. An apparatus， comprising：
    at least one processor； and
    at least one memory including computer program code，
    the at least one memory and the computer program code configured to， with the at least one processor， cause the apparatus to perform at least the following：
    interactively performing， in a wireless communications network， radio link monitoring on at least one serving beam from a serving base station and beam recovery procedure on at least one candidate beam from the serving base station； and
    determining， in response to beam recovery procedure and radio link monitoring with  different timing relationships， to perform one of the following：
    triggering re-establishment procedure，
    indicating to the network switching to at least one candidate beam， and
    indicating to the network a return back to at least one serving beam.
  13. The apparatus of claim 12， wherein the timing relationship comprises： the beam recovery procedure continuing after the expiration of a timer used to allow the user equipment to regain synchronization with the serving base station.
  14. The apparatus of claim 13， wherein the at least one memory and the computer program code are further configured to， with the at least one processor， cause the apparatus to perform at least the following： continuing by the user equipment the radio link monitoring in the at least one serving beam and not triggering radio link failure.
  15. The apparatus of claim 14， wherein a number of consecutive in-sync， allowing the user equipment to confirm synchronization with the serving base station， are received on the at least one serving beam before the beam recovery procedure finishes.
  16. The apparatus of claim 15， wherein the at least one memory and the computer program code are further configured to， with the at least one processor， cause the apparatus to perform at least the following： aborting by the user equipment the beam recovery procedure， and indicating a return to the at least one serving beam by the user equipment to the serving base station.
  17. The apparatus of claim 14， wherein the beam recovery procedure finishes and a number of consecutive in-sync， allowing the user equipment to confirm synchronization with the serving base station， have not been received on the at least one serving beam.
  18. The apparatus of claim 17， wherein， if beam recovery succeeds， the at least one memory and the computer program code are further configured to， with the at least one processor， cause the apparatus to perform at least the following：
    switching by the user equipment to the at least one candidate beam；
    resetting all previous in-sync/out-of-sync counters； and
    restarting the timer.
  19. The apparatus of claim 17， wherein， ifbeam recovery fails， the at least one memory and the computer program code are further configured to， with the at least one processor， cause the apparatus to perform at least the following：
    indicating by the user equipment to radio resource control protocol layer and declaring radio link failure.
  20. The apparatus of claim 12， wherein the timing relationship comprises： the beam recovery procedure finishing before the expiration of a timer used to allow the user equipment to regain synchronization with the serving base station.
  21. The apparatus of claim 20， wherein， ifbeam recovery succeeds， the at least one memory and the computer program code are further configured to， with the at least one processor， cause the apparatus to perform at least the following：
    switching by the user equipment to the at least one candidate beam；
    resetting all previous in-sync/out-of-sync counters； and
    restarting the timer.
  22. The apparatus of claim 20， wherein， ifbeam recovery fails， the at least one memory and the computer program code are further configured to， with the at least one processor， cause the apparatus to perform at least the following：
    continuing the radio link monitoring by the user equipment on the at least one serving beam as ifbeam recovery procedure had not been performed.
  23. A computer program comprising：
    code for interactively performing， by a user equipment in a wireless communications network， radio link monitoring on at least one serving beam from a serving base station and a beam recovery procedure on at least one candidate beam from the serving base station； and
    code for determining by the user equipment， in response to the beam recovery procedure and the radio link monitoring with different timing relationships， to perform one of the following：
    triggering re-establishment procedure，
    indicating to the network switching by the user equipment to at least one  candidate beam， and
    indicating to the network a return back by the user equipment to at least one serving beam.
  24. A computer program product embodied on a non-transitory computer-readable medium in which a computer program is stored that， when being executed by a computer， is configured to provide instructions to control or carry out the method of any of claims 1-11.
  25. An apparatus， comprising：
    means for interactively performing， in a wireless communications network， radio link monitoring on at least one serving beam from a serving base station and a beam recovery procedure on at least one candidate beam from the serving base station； and
    means for determining， in response to the beam recovery procedure and the radio link monitoring with different timing relationships， to perform one of the following：
    triggering re-establishment procedure，
    indicating to the network switching to at least one candidate beam， and
    indicating to the network a return back to at least one serving beam.
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