WO2014068535A2

WO2014068535A2 - Method and apparatus for providing enhanced radio link monitoring

Info

Publication number: WO2014068535A2
Application number: PCT/IB2013/059889
Authority: WO
Inventors: Timo Roman; Tero Henttonen
Original assignee: Renesas Mobile Corp
Current assignee: Renesas Electronics Corp
Priority date: 2012-11-05
Filing date: 2013-11-04
Publication date: 2014-05-08
Anticipated expiration: 2015-05-05
Also published as: WO2014068535A3; GB201219885D0; GB2507570A

Abstract

A method, apparatus, and computer program product are provided to provide enhanced radio link monitoring (RLM). In the context of a method, information regarding one or more respective UE-specific RLM configurationss may be determined for each of one or more UEs and, further, each of the one or more UEs may be caused to be informed of the information regarding its one or more respective UE-specific RLM configurations. Various RLM configuration parameters may be provided, such as one or more criteria, one or more thresholds, one or more reference resources, and/or one or more offsets, so as to provide, for example, various common reference symbols (CRS)-based and/or CRS-less UE-specific RLM configurations.

Description

METHOD AND APPARATUS FOR PROVIDING ENHANCED RADIO LINK

MONITORING

Cross Reference to Related Application

This application claims the benefit under 35 U.S.C. § 119(a) and 37 CFR § 1.55 to UK patent application no. 1219885.9, filed on November 5^th, 2012, the entire content of which is incorporated herein by reference.

Technological Field

An example embodiment of the present invention relates generally to wireless networks and, more particularly, to providing enhanced radio link monitoring.

Background

Radio link monitoring (RLM) in LTE Rel-8/9/10/11 consists of a UE-based assessment of the experienced downlink radio link quality. The primary goal is to track whether the network and a given UE can expect to communicate reliably with each other or not.

RLM is typically based on periodic CRS measurements over a given interval and has used the same procedures since LTE Rel-8. However, a variety of newly considered network deployment scenarios are likely to be introduced in future LTE releases, leading the present RLM procedures to be potentially less useful in many cases. Accordingly, RLM procedures which are more flexible, more robust, and are compatible with a variety of deployment scenarios are needed. Brief Summary

Therefore, methods, apparatuses, and computer program products are provided according to example embodiments in order to provide enhanced RLM procedures. In this regard, a method, apparatus, and computer program product from the perspective of an access point may determine UE-specific RLM configurations for UEs and cause the UEs to be informed of the configurations. A corresponding method, apparatus, and computer program product from the perspective of a UE may receive the UE-specific RLM configuration and cause RLM to be performed based on the UE-specific configuration. Various parameters of each UE-specific RLM configuration may be specifically selected so as to tailor the configuration to any number of deployment scenarios.

In one embodiment, a method is provided that includes determining for each of one or more user equipments (UEs), information regarding one or more UE- specific radio link monitoring (RLM) configurations. The method further includes causing each of the one or more UEs to be informed of the information regarding its one or more respective UE-specific RLM configurations. The method of this embodiment is preferably for use in an access point.

In another embodiment, a method is provided that includes receiving information regarding one or more UE-specific RLM configurations. The method further includes causing RLM to be performed on one or more cells in accordance with at least one of the one or more UE-specific RLM configurations and, based on a result of the RLM, determining whether an in-sync or out-of-sync condition exists. The method of this embodiment is preferably for use in a user equipment.

In a further embodiment, an apparatus is provided that comprises a processing system, which may be embodied by at least one processor and at least one memory storing computer program instruction therein. The processing system is arranged to cause the apparatus to at least determine for each of one or more user equipments (UEs), information regarding one or more UE-specific radio link monitoring (RLM) configurations, and to cause each of the one or more UEs to be informed of the information regarding its one or more respective UE-specific RLM configurations. The apparatus according to this embodiment is preferably embodied in an access point.

In another embodiment, an apparatus is provided that comprises a processing system, which may be embodied by at least one processor and at least one memory storing computer program instruction therein. The processing system is arranged to cause the apparatus to at least receive information regarding one or more UE-specific RLM configurations, to cause RLM to be performed on one or more cells in accordance with at least one of the one or more UE-specific RLM configurations and, based on a result of the RLM, determine whether an in-sync or out-of-sync condition exists. The apparatus according to this embodiment is preferably embodied in a user equipement.

In a further embodiment, a computer program product is provided that includes a non-transitory computer readable medium storing computer program code portions therein, the computer program code portions being configured to, upon execution, cause an apparatus to at least determine for each of one or more user equipments (UEs), information regarding one or more UE-specific radio link monitoring (RLM) configurations. The apparatus is further caused to cause each of the one or more UEs to be informed of the information regarding its one or more respective UE-specific RLM configurations. The computer program product according to this embodiment is preferably executed by a radio access node.

In another embodiment, a computer program product is provided that includes a non-transitory computer readable medium storing computer program code portions therein, the computer program code portions being configured to, upon execution, cause an apparatus to at least receive information regarding one or more UE-specific RLM configurations. The apparatus is further caused to cause RLM to be performed on one or more cells in accordance with at least one of the one or more UE-specific RLM configurations and, based on a result of the RLM, determine whether an in-sync or out-of-sync condition exists. The computer program product according to this embodiment is preferably executed by a user equipment.

In a further embodiment, an apparatus is provided that includes means for determining for each of one or more user equipments (UEs), information regarding one or more UE-specific radio link monitoring (RLM) configurations. The apparatus further includes means for causing each of the one or more UEs to be informed of the information regarding its one or more respective UE-specific RLM configurations.

In another embodiment, an apparatus is provided that includes means for receiving information regarding one or more UE-specific RLM configurations. The apparatus further includes means for causing RLM to be performed on one or more cells in accordance with at least one of the one or more UE-specific RLM configurations and, means for determining, based on a result of the RLM, whether an in-sync or out-of-sync condition exists.

Brief Description Of The Drawings

Having thus described certain example embodiments of the present disclosure in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

Figure 1 is an illustration of a system which may benefit from embodiments of the present invention;

Figure 2 is a block diagram of an apparatus that may be configured in accordance with an example embodiment of the present invention;

Figure 3 is a flowchart depicting operations performed by apparatuses embodied by or otherwise associated with an access point in accordance with embodiments of the present invention;

Figure 4 is a flowchart depicting operations performed by apparatuses embodied by or otherwise associated with a UE in accordance with embodiments of the present invention;

Figure 5 is an example information element (IE) which may be used to inform a UE of a UE-specific RLM configuration according to an example embodiment of the present invention.

Detailed Description

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. As used in this application, the term "circuitry" refers to all of the following: (a)hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and (b) to combinations of circuits and software (and/or firmware), such as (as applicable):

(i) to a combination of processor(s) or (ii) to portions of processor(s)/software

(including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) to circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present.

This definition of "circuitry" applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term "circuitry" would also cover an implementation of merely a processor (or multiple processors) or portion of a processor and its (or their) accompanying software and/or firmware. The term "circuitry" would also cover, for example and if applicable to the particular claim element, a baseband integrated circuit or application specific integrated circuit for a mobile phone or a similar integrated circuit in a server, a cellular network device, or other network device.

Referring now to Figure 1 , a system that supports communications between a user equipment (UE) 10 and a network 14, such as a Universal Mobile Telecommunications System (UMTS) network, a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, a Global Systems for Mobile communications (GSM) network, a Code Division Multiple Access (CDMA) network, e.g., a Wideband CDMA (WCDMA) network, a CDMA2000 network or the like, a General Packet Radio Service (GPRS) network or other type of network, via one or more access points 12 is shown. As used herein, an access point refers to any communication device which provides connectivity to a network, such as a base station, an access node, or any equivalent, such as a Node B, an evolved Node B (eNB), a transmission point, a relay node, or other type of access point. The term "user equipment" includes any mobile communication device such as, for example, a mobile telephone, portable digital assistant (PDA), pager, laptop computer, a tablet computer, or any of numerous other hand held or portable communication devices, computation devices, content generation devices, content consumption devices, data card, Universal Serial Bus (USB) dongle, or combinations thereof. The communications between the user equipment 10 and the access point 12 may include the transmission of data via an uplink that is granted between the user equipment 10 and the access point 12.

The UE 10 and the access point 12 may embody or otherwise be associated with an apparatus 20 that is generally depicted in Figure 2 and that may be configured in accordance with an example embodiment of the present invention as described below. However, it should be noted that the components, devices or elements described below may not be mandatory and thus some may be omitted in certain embodiments. Additionally, some embodiments may include further or different components, devices or elements beyond those shown and described herein.

As shown in Figure 2, the apparatus 20 may include or otherwise be in communication with a processing system, e.g., processing circuitry, such as the processor 20 and, in some embodiments, the memory 24, which is configurable to perform actions in accordance with example embodiments described herein, such as in conjunction with Figures 3 and 4. The processing circuitry may be configured to perform data processing, application execution and/or other processing and management services according to an example embodiment of the present invention. In some embodiments, the apparatus or the processing circuitry may be embodied as a chip or chip set. In other words, the apparatus or the processing circuitry may comprise one or more physical packages (e.g., chips) including materials, components and/or wires on a structural assembly (e.g., a baseboard). The structural assembly may provide physical strength, conservation of size, and/or limitation of electrical interaction for component circuitry included thereon. The apparatus or the processing circuitry may therefore, in some cases, be configured to implement an embodiment of the present invention on a single chip or as a single "system on a chip." As such, in some cases, a chip or chipset may constitute means for performing one or more operations for providing the functionalities described herein.

In an example embodiment, the processing circuitry may include a processor 22 and memory 24 that may be in communication with or otherwise control a communication interface 26 and, in some cases in which the apparatus is embodied by the UE 10, a user interface 28. As such, the processing circuitry may be embodied as a circuit chip (e.g., an integrated circuit chip) configured (e.g., with hardware, software or a combination of hardware and software) to perform operations described herein. However, in some embodiments taken in the context of the UE 10 or the base station 12, the processing circuitry may be embodied as a portion of the UE or the base station.

In embodiments where the apparatus 20 is embodied by a UE 10 configured to be interacted with by a user, the user interface 28 may be in communication with the processing circuitry to receive an indication of a user input at the user interface and/or to provide an audible, visual, mechanical or other output to the user. Thus, the user interface may include, for example, a keyboard, a mouse, a joystick, a display, a touch screen, a microphone, a speaker, and/or other input/output mechanisms.

The communication interface 26 may include one or more interface mechanisms for enabling communication with other devices and/or networks. In some cases, the communication interface may be any means such as a device or circuitry embodied in either hardware, or a combination of hardware and software that is configured to receive and/or transmit data from/to a network 14 and/or any other device or module in communication with the processing circuitry, such as between the UE 10 and the base station 12. In this regard, the communication interface may include, for example, an antenna (or multiple antennas), such as an antenna (or multiple antennas) capable of communicating over radio frequencies (RF), and supporting hardware and/or software, such as RF circuitry, for enabling communications with a wireless communication network. The communication interface 26 may also or alternatively include a communication modem or other hardware/software for supporting communication via cable, digital subscriber line (DSL), universal serial bus (USB), Ethernet or other methods.

In an example embodiment, the memory 24 may include one or more non- transitory memory devices such as, for example, volatile and/or non-volatile memory that may be either fixed or removable. The memory may be configured to store information, data, applications, instructions or the like for enabling the apparatus 20 to carry out various functions in accordance with example embodiments of the present invention. For example, the memory could be configured to buffer input data for processing by the processor 22. Additionally or alternatively, the memory could be configured to store instructions for execution by the processor. As yet another alternative, the memory may include one of a plurality of databases that may store a variety of files, contents or data sets. Among the contents of the memory, applications may be stored for execution by the processor in order to carry out the functionality associated with each respective application. In some cases, the memory may be in communication with the processor via a bus for passing information among components of the apparatus.

The processor 22 may be embodied in a number of different ways. For example, the processor may be embodied as various processing means such as one or more of a microprocessor or other processing element, a coprocessor, a controller or various other computing or processing devices including integrated circuits such as, for example, an ASIC (application specific integrated circuit), an FPGA (field programmable gate array), DSP (digital signal processor), or the like. In an example embodiment, the processor may be configured to execute instructions stored in the memory 24 or otherwise accessible to the processor. As such, whether configured by hardware or by a combination of hardware and software, the processor may represent an entity (e.g., physically embodied in circuitry - in the form of processing circuitry) capable of performing operations according to embodiments of the present invention while configured accordingly. Thus, for example, when the processor is embodied as an ASIC, FPGA, DSP or the like, the processor may be specifically configured hardware for conducting the operations described herein. Alternatively, as another example, when the processor is embodied as an executor of software instructions, the instructions may specifically configure the processor to perform the operations described herein.

Figures 3 and 4 are flowcharts illustrating the operations performed by a method, apparatus and computer program product, such as apparatus 20 of Figure 2 in accordance with an example embodiment of the present invention as respectively embodied by an access point, such as access point 12 depicted in Figure 1, and a UE, such as UE 10 depicted in Figure 1. It will be understood that each block of the flowcharts, and combinations of blocks in the flowcharts, may be implemented by various means, such as hardware, firmware, processor, circuitry and/or other device associated with execution of software including one or more computer program instructions. For example, one or more of the procedures described above may be embodied by computer program instructions. In this regard, the computer program instructions which embody the procedures described above may be stored by a memory 24 of an apparatus employing an embodiment of the present invention and executed by a processor 22 in the apparatus. As will be appreciated, any such computer program instructions may be loaded onto a computer or other programmable apparatus (e.g., hardware) to produce a machine, such that the resulting computer or other programmable apparatus provides for implementation of the functions specified in the flowchart blocks. These computer program instructions may also be stored in a non-transitory computer-readable storage memory that may direct a computer or other programmable apparatus to function in a particular manner, such that the instructions stored in the computer-readable storage memory produce an article of manufacture, the execution of which implements the function specified in the flowchart blocks. The computer program instructions may also be loaded onto a computer or other programmable apparatus to cause a series of operations to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide operations for implementing the functions specified in the flowchart blocks. As such, the operations of Figures 3 and 4, when executed, convert a computer or processing circuitry into a particular machine configured to perform an example embodiment of the present invention. Accordingly, the operations of Figures 3 and 4 define an algorithm for configuring a computer or processing circuitry, e.g., processor, to perform an example embodiment. In some cases, a general purpose computer may be provided with an instance of the processor which performs the algorithm of Figures 3 and 4 to transform the general purpose computer into a particular machine configured to perform an example embodiment.

Accordingly, blocks of the flowcharts support combinations of means for performing the specified functions and combinations of operations for performing the specified functions. It will also be understood that one or more blocks of the flowcharts, and combinations of blocks in the flowcharts, can be implemented by special purpose hardware-based computer systems which perform the specified functions, or combinations of special purpose hardware and computer instructions.

In some embodiments, certain ones of the operations above may be modified or further amplified as described below. Moreover, in some embodiments additional optional operations may also be included, some of which are shown in dashed lines in Figures 3 and 4. It should be appreciated that each of the modifications, optional additions or amplifications below may be included with the operations above either alone or in combination with any others among the features described herein.

As mentioned in the Background section, radio link monitoring (RLM) is a process whereby a UE makes an assessment of its experienced radio link quality in either downlink, uplink or both directions. The primary goal is to track whether the network and a given UE can expect to communicate reliably with each other or not. For this purpose, RLM has been defined to comprise two conditions and related sets of procedures: "out-of-sync" and "in-sync." The RLM procedure receives, from the lower layers, a periodic indication of whether the UE is considered to be "in-sync" or "out-of-sync". If UE receives N310 consecutive "out-of-sync" indications from the lower layers, it shall consider that there is a radio problem and start timer T310. If the UE then receives N311 consecutive "in-sync" indications from the lower layers, it shall consider the radio problem to be corrected and will continue normal operation. If, however, the "out-of-sync" condition persists until the timer T310 expires, the UE shall then declare Radio Link Failure (RLF) and start a T311 timer: While the timer T311 is running, the UE will attempt to reselect and re-establish the connection to a suitable cell, e.g., via a suitable access point, so that the connection may still be recovered gracefully, but if the timer expires, the UE shall go to idle mode, which means fully dropping the connection before attempting any subsequent re- establishment actions. Further, in addition to the RLM, there are also other triggers that can cause a RLF to be declared at the UE. For example, if the maximum amount of RLC retransmissions is reached or a RACH problem is detected, the UE will also declare a RLF and proceed with the same actions as for RLF detected based on the RLM procedure.

In an out-of-sync condition, a UE, such as the UE 10 depicted in Figure 1, may not be capable of reliably communicating in the downlink direction with the radio network (e.g., via a serving access point, such as the access point 12 depicted in Figure 1). When the UE detects an out- of-sync condition leading to a RLF (as described above), the UE 10 will start a radio link failure (RLF) procedure. As defined in current LTE standards, when an out-of-sync condition persists for a predetermined time the RLF procedure begins. The out-of-sync is detected whenever an estimated block error rate (BLER) for a hypothetical physical downlink control channel (PDCCH) transmission with downlink control information (DCI) format 1A exceeds the threshold Qout over the previous measurement interval. The value of Qout has been fixed to correspond with a 10% BLER in the 3GPP specification TS 36.133.

In an in-sync condition, the UE 10 is capable of reliably communicating with the radio network (e.g., via the access point 12). As defined in current LTE standards, the UE may consider it is in-sync whenever the estimated BLER over the last measurement interval for a hypothetical PDCCH transmission with DCI format 1C is below the threshold Qin. The value of Qin has been set to correspond with 2% BLER.

RLM is typically based on periodic common reference symbols (CRS) measurements over a given interval (typically once per radio frame, i.e. 10 ms, but the given measurement interval length depends on whether discontinuous reception (DRX) is used or not; the measurement sampling rate and interval changes when DRX is being used, as specified in TS 36.133). Measurements are filtered at layer 3 over a sliding window and the network can control when a RLF should occur (e.g., how many Qout indications will trigger RLF, and how many Qin indications are required for RLF recovery). Test cases and minimum requirements for radio link monitoring in LTE are specified in Section 7.6 of TS36.133. See 3GPP TS 36.133, Requirements for support of radio resource management (Release 10), V10.7.0 (2012-06) (hereinafter "TS 36.133"). According to TS 36.133, when DRX is not being used, Layer 1 of the UE 10 is to send an out-of-sync indication for the primary cell (PCell) to the higher layers within 200 ms Qout evaluation period when the downlink radio link quality of the PCell estimated over the last 200 ms period becomes worse than the threshold Qout. A Layer 3 (L3) filter shall be applied to the out-of-sync indications. Furthermore, when the downlink radio link quality of the PCell estimated over the last 100 ms period becomes better than the threshold Qin, Layer 1 of the UE is to send an in-sync indication for the PCell to the higher layers within 100 ms Qin evaluation period. An L3 filter shall be applied to the in-sync indications. The out-of-sync and in-sync evaluations of the PCell are to be performed as specified in section 4.2.1 of TS 36.213. See 3 GPP TS 36.331 : "Evolved Universal Terrestrial Radio Access (E- UTRA); Radio Resource Control (RRC) protocol specification." Two successive indications from Layer 1 are to be separated by at least 10 ms.

LTE specifications from Rel-10 onwards have introduced the possibility of an eNodeB setting measurement restrictions for RLM. This finds application in network deployments implementing enhanced inter-cell interference coordination techniques (elCIC) through time domain (TDM) resource partitioning. The main use case for the elCIC techniques can be exemplified with a macro-pico scenario, which consists of pico cells under the footprint of a macro cell with TDM coordination between them. The macro cells are interfering with the UEs served by the pico cells, so to protect those UEs, the macro cells may periodically mute their downlink transmissions (except for CRS and system information/paging transmissions). Such muted occasions are called almost blank subframes (ABS) and they follow a given periodic pattern (40 ms period for FDD, 20/60/70 ms period for TDD depending on which TDD configuration is used). During these instances of ABS, the UEs in the pico cells, especially those offloaded from the macro cells through cell range extension (CRE) mechanism (with which the UEs are effected to be connected to the pico cell even though they would normally be connected to the macro cell) can be served better thanks to the reduced macro cell interference due to the ABS reducing the macro cell transmissions and hence, the interference power. Thus, the pico cell range extension UEs experience mainly two types of interference levels: highly interfered subframes over non-ABS subframes of the macro cell and lowly interfered subframes over ABS subframes. UEs may then perform restricted RLM/RRM as well as CSI measurements according to given patterns signaled by the eNodeB. These patterns define the allowed time instances for UE measurement occasions and typically coincide with a subset of the ABS pattern in use at the interfering macro eNodeB.

Up to LTE Re 1-11, the above measurement restrictions represent the one of the only enhancements proposed to RLM since Rel-8. Indeed, since Rel-8, RLM has been based on CRS and has used the very same procedures since Rel-8. Potential problems may arise in using the existing, inflexible, RLM procedures in future releases (e.g. Rel-12 and beyond) due to the variety of newly considered network deployment scenarios and associated signal/interference conditions. In short, the RLM as we know is starting to become rather inflexible and it is becoming clear that existing RLM procedures may not be useful in all deployment scenarios. For example, decreases in CRS density for new carrier types (NCT), CRS cancellation, and the potential use of single frequency networks (SFN) - where a plurality of access points share the same cell ID and thereby the same CRS resources - may all cause RLM determinations being made on CRS resources to be less reliable. One possible reason is that shared CRS resources may not depict precisely the quality of the radio link for a given UE, such as when the given UE is in communication over user-specific reference symbols with a subset of these access points. Considering another example, in Re 1-10 elCIC and Rel-11 felCIC, during ABS subframe instances of interfering cells, OFDM symbols carrying CRS in the serving pico cell experience higher interference level than other OFDM symbols in the same subframe (because the CRS transmissions are not muted and may collide with the pico cell CRS transmissions). The difference between these two interference levels depends on many parameters such as the network deployment scenario, the degree of ABS utilization in the network, whether the CRS transmissions are colliding, etc. In the case of a large difference, one may see that interference measured over CRS may not reflect the one experienced over the majority of PDCCH/PDSCH resource elements (RE). Inaccurate interference measurements over CRS could lead to RLF in some cases or delay the UE entering in-sync state. For example, the UE could perform CRS-based RLM measurements in an instance in which CRS subcarriers just happen to be more interfered than other resource elements over other subcarriers or OFDM symbols within the subframe. Thus, this may lead to the UE getting an overly pessimistic picture of the interference conditions. Such mismatches were encountered for RLM determination during RAN4 work on Rel-10 elCIC performance requirements because the considered baseline receiver was unaware of CRS interference from the dominant interferer and had no means to mitigate the latter. The solution found at that time was to increase margins to account for such possible mismatches, but at the expense of less precise RLM determination.

Additionally, e.g., for coordinated multi-point transmission (CoMP) where channel state information reference signal (CSI-RS) measurements may be used to quantify the channel conditions, it may be more desirable to base RLM on those CSI- RS resources since RLM based on those resources may better match the enhanced physical downlink control channel (EPDCCH)/physical downlink shared channel (PDSCH) transmission quality than if the RLM would be based on CRS broadcast over a large geographical area (e.g. as in CoMP scenario 4 comprising of a macro cell area with low power nodes/transmission points, CRS being transmitted in SFN fashion from all the transmission points, each transmission point transmitting its own CSI-RS resources). Finally, as LTE systems continue to evolve more towards a direction where CRS are transmitted less frequently, e.g. for overhead and energy saving reasons, it can be beneficial to reduce the dependency of the systems on CRS in general. Thus, new RLM mechanisms will need to be established in upcoming releases to support such gradual reductions in reliance on CRS, while still retaining as much backward compatibility with existing releases as possible.

Thus, referring now to Figure 3, the operations performed by a method, apparatus, and computer program product of an example embodiment are illustrated from the perspective of an apparatus 20 that may be embodied by or otherwise associated with an access point, such as the access point 12 depicted in Figure 1, in order to provide enhanced RLM procedures are depicted. In this regard, the apparatus 20 may include means, such as the processing system, e.g., processing circuitry, the processor 22, the memory 24, the communications interface 26 or the like, for determining, for each of one or more UEs, information regarding one or more respective corresponding UE-specific RLM configurations. See operation 300. In a general sense, the possible UE-specific RLM configuration "sets" may include, for example, at least one of (1) a no RLM configuration (e.g., the network, such as via one or more access points such as the access point 12 depicted in Figure 1 , may detect RLM conditions); (2) a CRS-based RLM configuration; and/or (3) a CRS-less RLM configuration. Thus, embodiments of the present invention may accommodate various deployment scenarios, such as those discussed above in which CRS-less RLM may be preferred, while maintaining compatibility with existing deployment scenarios. Furthermore, RLM configurations may be UE-specific. That is, any one UE may or may not share an RLM configuration with another UE (it will be understood, however, that multiple UEs may of course share the same UE-specific RLM configurations in some cases).

Within the above general characterizations of UE-specific RLM configurations, many variations may exist. For example, UE-specific RLM configurations may include one or more criteria to be used for RLM, one or more reference resources to be used for RLM, one or more thresholds to be used for RLM, one or more offsets, and/or one or more other parameters, characteristics or the like. Examples of possible criteria may include, for example, a real or hypothetical BLER. The BLER, whether real or hypothetical, may, for example, be of a downlink control channel, such as of a physical downlink control channel (PDCCH) or an enhanced PDCCH (EPDCCH) or more generally of a given downlink physical channel (e.g. PCFICH, PDSCH or any other downlink channel). With respect to a BLER based on an EPDCCH, the EPDCCH configuration may, for example, be predefined, e.g., tied to an EPDCCH common or UE-specific search space, or it may be signaled (e.g., by signaling information such as a physical resource block (PRB) location, aggregation level, whether transmission is localized or distributed, etc.). Examples of possible reference resources may include, for example, a CSI-RS resource or CSI-RS process, such as a CSI-RS resource and interference measurement resource (IMR).

Examples of possible thresholds may, for example, include Qin and/or Qout. Qin and/or Qout may, for example, be either predefined (e.g., as in current LTE standards, where Qin=2% and Qout=10%) or may be configurable, such as by selecting from a plurality of predefined options or by configuring a particular value. One or more offsets may additionally or alternatively be provided, for example, to bias RLM determinations (e.g., to make them more optimistic or more pessimistic). Offsets may, for example, be in the signal-to-interference-and-noise ratio (SINR) domain. The UE may apply such an offset, for example, prior to a BLER computation, thus influencing the out-of-sync/in-sync determination. This may, for example, allow an access point to bias RLM in either direction (e.g., more optimistic or pessimistic) to improve robustness of network operation. For instance, the access point may be aware that in a given elCIC deployment the CRS symbols will tend to see significantly higher interference level compared to other symbols in the subframe, which could trigger excessive RLF from some terminals. Thus, in this case, a UE- specific RLM configuration may include an offset to make RLM determinations more optimistic. Another use case for such biasing is when UE-specific reference symbols (RS) are in use for EPDCCH and/or PDSCH. In this case, the beamforming gain experienced over UE-specific RS (e.g., due to a closed-loop precoding operation) introduces a mismatch between the experienced SINR conditions and those measured over CRS or CSI-RS which are typically not beamformed. The network could be aware of such mismatch and configure the offset, e.g., bias, parameter so that, e.g., it may be roughly equivalent to the experienced beamforming gain, thus improving the consistency of RLM with respect to the experienced radio link quality.

Various configuration variations may, for example, by restricted to or otherwise associated with one or more of the three configuration sets mentioned above. Thus, for example, a CRS-based RLM configuration set may include RLM being based on a real BLER of a PDCCH. As another example, a CRS-less RLM configuration set may include RLM being based on reference symbols or reference- symbol based processes besides CRS, such as, for example, CSI-RS or CSI-RS processes (e.g., a CSI-RS resource and interference measurement resource (IMR)); a real BLER of an EPDCCH; or a hypothetical BLER of an EPDCCH. As another example, a CRS-less RLM configuration set may include RLM being based on any signal originated by the UE such as, e.g., a hybrid automatic request report, a channel state information report or a transmission of sounding reference symbols. In all cases, that is, whether various UE-specific configurations are restricted or unrestricted by configuration set, UE-specific RLM configurations include multiple combinations of collections of reference resources, criteria, and/or thresholds. That is, the determination of an in-sync/out-of-sync condition may be based on multiple combinations of collections of reference resources, criteria, and/or thresholds. By way of example, a UE-specific RLM configuration may provide that an out-of-sync condition may be determined only when a hypothetical BLER of a PDCCH exceeds a first threshold given a first offset and a real BLER of an EPDCCH exceeds a second threshold with no offset. According to another example, the out-of-sync condition may be determined when either of the above occurs. Any number of other examples of combinations will immediately be apparent, and combinations may include three or more collections of reference resources, criteria, and/or thresholds and in-sync/out-of- sync determinations may be based on any logical relationships between these collections. Thus, given collections A, B, and C of reference resources, criteria, and/or thresholds, an in-sync determination may, for example, require A and B and C, or a more complex logical relationship, such as A and (B XOR C), etc.

It will be understood that more than one UE-specific RLM configuration may correspond with any given UE. That is, the apparatus 20 that may be embodied by or otherwise associated with an access point may determine more than one UE-specific RLM configuration for each of one or more UEs and (as discussed below) cause those UEs to be informed of information regarding their corresponding multiple UE- specific RLM configurations. This may, for example, be useful in deployment scenarios which utilize carrier aggregation, in which a UE is in communication with multiple cells, such as a primary cell (Pcell) and secondary cell (SCell). In this case, the PCell and SCell may, for example, be configured differently. Thus, apparatus 20 may determine multiple UE-specific RLM configurations, such as one associated with the PCell and one associated with the SCell. Thus, the UE may perform RLM on the PCell according to the UE-specific RLM configuration associated with the PCell, and similarly for the SCell. Thus, for example, if the PCell were utilizing normal CRS- based legacy transmission mode, the UE could utilize a legacy RLM procedure on the PCell, but at the same time the Scell might be operating under CSI-RS-based ePDCCH operation, and therefore the UE could utilize a CSI-RS-based RLM procedure on the SCell. Other possibilities can also be envisioned easily, e.g. where RLM for either carrier is operated according to one or more configured RLM procedures, and the configuration of those procedures can be different for each carrier.

Continuing to refer to Figure 3, the apparatus 20 may further include means, such as the processing system, e.g., processing circuitry, the processor 22, the memory 24, the communications interface 26 or the like, for causing each of the one or more UEs to be informed of the information regarding its one or more respective UE-specific RLM configurations. See operation 310. In this regard, each of the UEs may be informed, for example, via explicit or implicit signaling according to example embodiments, such as by causing one or more indications of the information to be explicitly or implicitly signaled to the UEs. Explicit signaling may include, for example, dedicated signaling such as, for example, radio resource control (RRC) signaling. Explicit signaling may also include, for example, broadcast signaling such as, for example, system information signaling. Implicit "signaling" may, for example, refer to the association of particular RLM configuration options to one or more contexts, system configurations, or the like. Thus, for example, a particular UE- specific RLM configuration may be associated with a particular transmission mode, a carrier aggregation configuration, usage of a specific set of reference resources, or the usage of a new carrier type (NCT). In this way, UE-specific RLM configurations may be implicitly signaled to the various UEs merely by the various UEs being informed, in some way, of a context, system configuration, or the like. Thus, by way of a simplified example, if UE were to be somehow informed that carrier aggregation or new carrier type configuration "A" is being used, e.g., in a particular carrier, this may implicitly signal that the UE should use UE-specific RLM configuration "B," e.g., in that particular carrier. In another example, given legacy carriers and/or legacy transmission modes may be associated with a UE-specific RLM configuration that is compatible with the given legacy carriers and/or transmission modes, while non- legacy carriers and/or transmission modes may be associated with other, and possibly specific, RLM configurations. By legacy it is meant here for instance to include carriers supporting up to a given release of an applicable standard. More complicated logical implicit signaling relationships may also be used according to example embodiments.

Apparatus 20 may further include means for making adjustments to UE- specific RLM configurations based on UE feedback. Thus, apparatus 20 may include means, such as the processing system, e.g., processing circuitry, the processor 22, the memory 24, the communications interface 26 or the like, for receiving a signal from a particular UE of the one or more UEs, for determining, based on the received signal, adjusted information regarding a UE-specific RLM configuration for the particular UE, and for causing the particular UE to be informed of the adjusted information regarding its UE-specific RLM configuration. See operations 320, 330, and 340. For example, the UE may be informed that it is not to declare RLF based on the RLM procedure at all, and instead rely on the network detecting the bad radio conditions based on, e.g., configured CQI reporting sent to the eNB. As another example, apparatus 20 may receive some indication from a UE that e.g., RLF-like conditions or RLF has occurred, such as, for example, a re-establishment request (e.g., due to RLF) or a RLF report. Based on the indication that a RLF has occurred, the apparatus 20 may determine one or more parameters of the UE-specific RLM configuration which should be adjusted. For example, apparatus 20 may modify one or more conditions based on which the reference resources are given to the UE. As another example, apparatus 20 may receive hybrid automatic repeat request (HARQ) feedback or UE channel state information (CSI) reporting. The HARQ feedback or CSI reporting may, for example, indicate a result of the UE's RLM determination (e.g., in-sync/out-of- sync). Based on the HARQ feedback or UE CSI reporting, the apparatus 20 may, for example, determine that one or more thresholds should be adjusted. The determination may be made, for example, based on a single input or according to some filtered value of the HARQ feedback or CSI reporting. Thus, in general, the apparatus 20 may adjust one or more parameters of the UE-specific RLM configuration based on any signal originated by the UE, including for example, but not limited to HARQ, CSI reports, sounding reference signals (SRS) or the like.

Having thus described various operations of embodiments from the perspective of an apparatus 20 embodied by or otherwise associated with an access point, attention will now be turned to Figure 4 in order to describe various embodiments from the perspective of a UE.

In this regard, as depicted in Figure 4, an apparatus 20 embodied by or otherwise associated with a UE, such as the UE 10 depicted in Figure 1, may include means, such as the processing system, e.g., processing circuitry, the processor 22, the memory 24, the communications interface 26 or the like, for receiving information regarding one or more UE-specific RLM configurations. See operation 400. As discussed above, the UE-specific RLM configurations may contain one or more criteria to be used for RLM, one or more reference resources to be used for RLM, one or more thresholds to be used for RLM, one or more offsets, and/or one or more other parameters, characteristics or the like, or one or more combinations of these.

According to an example embodiment in which the apparatus 20 embodied by or otherwise associated with the UE receives information regarding two or more UE- specific RLM configurations, the apparatus 20 may receive one or more indications of the information regarding first and second UE-specific RLM configurations via explicit signaling. For example, the apparatus 20 may receive information regarding a first UE-specific RLM configuration for use with a first transmission mode and/or information regarding a second UE-specific RLM configuration for use with a second transmission mode via explicit signaling. In another example, the apparatus may receive one or more indications of the information regarding said first and second UE- specific RLM configurations via implicit signaling. For example, a first UE-specific RLM configuration may be implicitly tied to a first transmission mode and a second UE-specific RLM configuration may be implicitly tied to a second transmission mode, and these relationships may be known in advance to both the UE and the access point. In one example, upon reconfiguration from a first transmission mode to a second transmission mode, the UE could, in response, implement a second UE- specific RLM configuration associated with the second transmission mode, such that subsequent RLM will be performed in accordance with the second UE-specific RLM configuration that is associated with the second transmission mode. As a specific example, one or more transmission modes (TM), e.g., TM1 to TM9 in LTE Release 11, could share the same UE-specific RLM configuration where RLM is performed in the same way as in LTE systems to date (e.g., based on CRS and PDCCH hypothetical BLER) while transmission mode 10 (e.g., used for CoMP) and above could base their RLM on CSI-RS and EPDCCH hypothetical BLER.

According to another example, one or more UE-specific RLM configurations may be tied to other configuration information of the UE, e.g., similarly to how measurement events are currently handled in the UE. In other words, one or more UE- specific RLM configurations may be adjusted depending on conditions that may occur. The adjustments to a UE-specific RLM configuration may be made, e.g., independently, such as by the apparatus 20 embodied by or otherwise associated with the UE, or in response to signaling received from an access point, For example, the occurrence of RLF in one carrier may lead to a different RLM configuration in another carrier, such as the use of another UE-specific RLM configuration in another carrier or the adjustment of a UE-specific RLM configuration which is already tied to that other carrier. For instance, the occurrence of RLF in one carrier could lead to a UE-specific RLM configuration associated with another carrier being adjusted for stricter monitoring, e.g., by adjusting thresholds, applying a bias, etc., or or even being adjusted to an entirely different RLM mode, e.g., by adjusting one or more resources or criteria used for RLM. In another related example, the UE could be monitoring one or more RLM procedures simultaneously, and the triggering of RLF according to one or more of the RLM procedures could trigger changes in the way the one or more RLM procedures behave.

The apparatus 20 embodied by or otherwise associated with the UE may further include means, such as the processing system, e.g., processing circuitry, the processor 22, the memory 24, the communications interface 26 or the like, for causing RLM to be performed on one or more cells, e.g., serving cells, in accordance with at least one of the one or more UE-specific RLM configurations and, based on a result of the RLM, determining whether an in-sync or out-of-sync condition exists. See operation 420. According to an example embodiment, the apparatus 20 embodied by or otherwise associated with the UE may receive information regarding two or more UE-specific RLM configurations, such as a first UE-specific RLM configuration associated with a first carrier, carrier type, transmission mode, or cell, and a second UE-specific RLM configuration associated with a second carrier, carrier type, transmission mode, or cell. These two or more UE-specific RLM configurations may, for example, be different from one another in one or more ways. Thus, the UE may, for example, cause RLM to be performed on a first cell according to the first UE- specific RLM configuration, and may cause RLM to be performed on a second cell according to the second UE-specific RLM configuration. For example, the UE may cause RLM to be performed on a PCell according to one UE-specific RLM configuration and cause RLM to be performed on an SCell according to another configuration. In another example, the UE may be configured to transmit according to a first transmission mode out of two or more available transmission modes and may cause RLM to be performed according to a first UE-specific RLM configuration. In another example, the UE may be configured to transmit according to a second transmission mode out of two or more available transmission modes and may cause RLM to be performed according to a second UE-specific RLM configuration. In one example, said first and second RLM configurations may be tied to respective ones of said first and second transmission mode, such that, for example, the UE may implicitly receive information regarding the first and second RLM configurations, as discussed above.

The apparatus 20 may further include means, such as those just mentioned, for causing RLF procedures to be performed in an instance in which an out-of-sync condition is determined and/or means, such as those just mentioned, for causing in- sync procedures to be performed in an instance in which an in-sync condition is determined. See operations 430 and 440. The out-of- and in-sync procedures may, for example, involve causing one or more signals to be transmitted, such as those discussed above (e.g., a re-establishment request, RLF report, HARQ feedback, CSI reporting, etc.).

The apparatus 20 may further include means, such as the processing system, e.g., processing circuitry, the processor 22, the memory 24, the communications interface 26 or the like, for receiving adjusted information regarding a UE-specific RLM configuration. See operation 450. As discussed above, the adjusted UE-specific RLM configuration may be determined by an apparatus 20 embodied by or otherwise associated with an access point based on signaling discussed above.

Turning briefly to Figure 5, an example of how UEs may be informed of information regarding UE-specific RLM configurations via explicit, dedicated signaling is depicted. This particular example depicts one example of a possible RadioResourceConfigDedicated information element (IE). Portions which are added and/or modified with respect to a standard RadioResourceConfigDedicated IE are encircled with dotted lines. Note that this example only covers the case in which one and only one RLF method is applied for each serving cell. Many other example embodiments without such, and which allow more complex ways to define when RLF is detected, are possible and will be apparent to one skilled in the art to which these inventions pertain.

Embodiments according to the invention may provide many benefits in a wireless communication system. For example, example embodiments of the present invention may provide for UE-specific RLM configurations. Thus, example embodiments may provide a more flexible and robust RLM procedure which can be tailored to a variety of deployment scenarios. Embodiments may allow for RLM procedures to be used with NCTs, and may allow for RLF triggering based on CSI- RS, which may be more effective than CRS-based RLM for CoMP. Further, example embodiments may allow more network control over RLF thresholds, which may be used, for example, to extend UE operation in conditions where there is a mismatch between measured and actual interference conditions.

Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing descriptions and the associated drawings describe example embodiments in the context of certain example combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and/or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

What Is Claimed: 1. A method for use in an access point, the method comprising:

determining, for each of one or more user equipments (UEs), information regarding one or more respective corresponding UE-specific radio link monitoring (RLM) configurations; and

causing each of the one or more UEs to be informed of the information regarding its one or more respective UE-specific RLM configurations.

2. An apparatus for use in an access point, the apparatus comprising a processing system arranged to cause the apparatus to at least:

determine, for each of one or more user equipments (UEs), information regarding one or more respective corresponding UE-specific radio link monitoring (RLM) configurations; and

cause each of the one or more UEs to be informed of the information regarding its one or more respective UE-specific RLM configurations.

3. The apparatus of claim 2, wherein the apparatus is caused to determine, for each of the one or more UEs, information regarding one or more respective UE- specific RLM configurations by determining, for a particular UE, information regarding at least first and second UE-specific RLM configurations, the first UE- specific RLM configuration being associated with a first carrier, carrier type, transmission mode, or cell and the second UE-specific RLM configuration being associated with a second carrier, carrier type, transmission mode, or cell.

4. The apparatus of claims 2 or 3, wherein the information regarding the one or more respective UE-specific RLM configurations comprises or further comprises one or more reference resources to be used for RLM measurements.

5. The apparatus of claim 4, wherein the one or more reference resources comprise a channel state information reference signal (CSI-RS) or channel state information (CSI) process.

6. The apparatus of claim 4, wherein the one or more reference resources comprise a reference symbol.

7. The apparatus of claim 4, wherein the one or more reference resources comprise a common reference symbol (CRS).

8. The apparatus of any of claims 2 to 7, wherein the information regarding the one or more respective UE-specific RLM configurations comprises or further comprises one or more criteria to be used for RLM.

9. The apparatus of claim 8, wherein the one or more criteria comprise a real block error rate (BLER).

10. The apparatus of claim 8, wherein the one or more criteria comprise a hypothetical block error rate (BLER).

11. The apparatus of either of claims 9 or 10, wherein the BLER comprises a BLER of a physical downlink control channel (PDCCH).

12. The apparatus of claims 9 or 10, wherein the BLER comprises a BLER of an enhanced physical downlink control channel (EPDCCH).

13. The apparatus of any of claims 2 to 12, wherein the information regarding the one or more respective UE-specific RLM configurations comprises or further comprises one or more thresholds to be used for RLM.

14. The apparatus of claim 13, wherein the one or more thresholds to be used for RLM comprise at least one of a Qin or Qout value.

15. The apparatus of any of claims 2 to 14, wherein the information regarding the one or more respective UE-specific RLM configurations comprises or further comprises one or more offsets.

16. The apparatus of any of claims 2 to 15, wherein the apparatus is caused to cause each of the one or more UEs to be informed of the information regarding its one or more respective UE-specific RLM configurations by causing one or more indications of the information to be explicitly signaled.

17. The apparatus of any of claims 2 to 15, wherein the apparatus is caused to cause each of the one or more UEs to be informed of the information regarding its one or more respective UE-specific RLM configurations by causing one or more indications of the information to be implicitly signaled.

18. The apparatus of any of claims 2 to 17, wherein the apparatus is further caused to receive a signal from a particular UE of the one or more UEs and, based on the received signal:

determine for the particular UE, adjusted information regarding at least one UE-specific RLM configuration; and

cause the particular UE to be informed of the adjusted information regarding the at least one UE-specific RLM configuration.

19. The apparatus of claim 18, wherein the signal comprises a re-establishment request or a radio link failure (RLF) report.

20. The apparatus of claim 18, wherein the signal comprises at least one of a hybrid automatic repeat request (HARQ) feedback, a UE CSI report, or a sounding reference signal.

21. A computer program product for use in an access point, the computer program product comprising a non-transitory computer-readable storage medium storing program code portions therein, the program code portions being arranged to, upon execution, cause an apparatus to at least:

22. A method for use in a user equipment (UE), the method comprising:

receiving one or more indications of information regarding one or more UE- specific radio link monitoring (RLM) configurations;

causing RLM to be performed on one or more cells in accordance with at least one of the one or more UE-specific RLM configurations; and

determining, based on a result of the RLM, whether an in-sync or out-of-sync condition exists.

23. An apparatus for use in a user equipment (UE), the apparatus comprising a processing system arranged to cause the apparatus to at least:

receive one or more indications of information regarding one or more UE - specific radio link monitoring (RLM) configurations;

cause RLM to be performed on one or more cells in accordance with at least one of the one or more UE-specific RLM configurations; and

determine, based on a result of the RLM, whether an in-sync or out-of-sync condition exists.

24. The apparatus of claim 23, wherein the information regarding the one or more UE-specific RLM configurations comprises one or more reference resources to be used for RLM measurements.

25. The apparatus of claim 24, wherein the one or more reference resources comprise a channel state information reference signal (CSI-RS) or channel state information (CSI) process.

26. The apparatus of claim 24, wherein the one or more reference resources comprise a reference symbol.

27. The apparatus of claim 24, wherein the one or more reference resources comprise a common reference symbol (CRS).

28. The apparatus of any of claims 23 to 27, wherein the information regarding the one or more UE-specific RLM configurations comprises or further comprises one or more criteria to be used for RLM.

29. The apparatus of claim 28, wherein the one or more criteria comprise a real block error rate (BLER).

30. The apparatus of claim 28, wherein the one or more criteria comprise a hypothetical block error rate (BLER).

31. The apparatus of claims 29 or 30, wherein the BLER comprises a BLER of a physical downlink control channel (PDCCH).

32. The apparatus of claims 29 or 30, wherein the BLER comprises a BLER of an enhanced physical downlink control channel (EPDCCH).

33. The apparatus of any of claims 23 to 32, wherein the information regarding the one or more UE-specific RLM configuration comprises or further comprises one or more thresholds to be used for RLM.

34. The apparatus of claim 33, wherein the one or more thresholds to be used for RLM comprise at least one of a Qin or Qout value.

35. The apparatus of any of claims 23 to 34, wherein the information regarding the one or more UE-specific RLM configurations comprises or further comprises one or more offsets to be used for RLM biasing.

36. The apparatus of any of claims 23 to 35, wherein the apparatus is caused to receive the one or more indications of the information regarding the one or more UE- specific RLM configurations via explicit signaling.

37. The apparatus of any of claims 23 to 35, wherein the apparatus is caused to receive the one or more indications of the information regarding the one or more UE- specific RLM configurations via implicit signaling.

38. The apparatus of any of claims 23 to 37, wherein the apparatus is further caused to cause a signal to be transmitted and, following transmission of the signal, receive adjusted information regarding at least one of the one or more UE-specific RLM configurations.

39. The apparatus of claim 38, wherein the signal comprises a re-establishment request or a radio link failure (RLF) report.

40. The apparatus of claim 38, wherein the signal comprises at least one of a hybrid automatic repeat request (HARQ) feedback, a UE CSI report, or a sounding reference signal.

41. The apparatus of any of claims 23 to 40, wherein the information regarding the one or more UE-specific RLM configurations comprises information regarding at least first and second UE-specific RLM configurations, the first UE-specific RLM configuration being associated with a first carrier, carrier type, transmission mode, or cell and the second UE-specific RLM configuration being associated with a second carrier, carrier type, transmission mode, or cell.

42. The apparatus of claim 41, wherein the apparatus is caused to cause RLM to be performed on one or more cells in accordance with at least one of the one or more UE-specific RLM configurations by causing RLM to be performed on a primary cell (PCell) in accordance with the first UE-specific RLM configuration and causing RLM to be performed on a secondary cell (SCell) in accordance with the second UE- specific RLM configuration.

43. The apparatus of any of claims 23 to 42, wherein the apparatus is further caused to determine, based on the result of the RLM, adjusted information regarding at least one of the one or more UE-specific RLM configurations.

44. A computer program product for use in a user equipment (UE), the computer program product comprising a computer readable storage medium having program code portions stored therein, the program code portions being arranged to, upon execution, cause an apparatus to at least:

receive one or more indications of information regarding one or more UE- specific radio link monitoring (RLM) configurations;

cause RLM to be performed on one or more cells in accordance with at least one of the one or more UE-specific RLM configurations; and determine, based on a result of the RLM, whether an in-sync or out-of-sync condition exists.