WO2019229292A1

WO2019229292A1 - Radio link evaluation for bandwidth parts

Info

Publication number: WO2019229292A1
Application number: PCT/FI2019/050357
Authority: WO
Inventors: Timo Koskela; Jorma Kaikkonen; Dawid Koziol; Lars Dalsgaard
Original assignee: Nokia Technologies Oy
Priority date: 2018-05-29
Filing date: 2019-05-07
Publication date: 2019-12-05

Abstract

According to one example embodiment, a method is provided including: determining, by a user equipment, at least one of: a radio link monitoring resource signal is undefined on at least one first bandwidth part, or radio link monitoring resource signals are not available on at least one second bandwidth part in response to receiving a request at the user equipment to switch from at least one first bandwidth part to the at least one second bandwidth part; and performing a radio link monitoring procedure after the switch or after the radio link monitoring resource signal is determined to be undefined, wherein the radio link monitoring procedure is based at least in part on whether or not a radio link problem has been detected by the user equipment.

Description

RADIO LINK EVALUATION FOR BANDWIDTH PARTS

TECHNICAL FIELD

Various example embodiments relate generally to wireless networks and, more specifically, relates to radio link monitoring in wireless networks.

BACKGROUND

Abbreviations that may be found in the specification and/ or the drawing figures are defined below, after the main part of the detailed description section.

BRIEF SUMMARY

This section is intended to include examples and is not intended to be limiting.

According to an example embodiment, a method is provided including: determining, by a user equipment, at least one of: a radio link monitoring resource signal is undefined on at least one first bandwidth part, or radio link monitoring resource signals are not available on at least one second bandwidth part in response to receiving a request at the user equipment to switch from at least one first bandwidth part to the at least one second bandwidth part; and performing a radio link monitoring procedure after the switch or after the radio link monitoring resource signal is determined to be undefined, wherein the radio link monitoring procedure is based at least in part on whether or not a radio link problem has been detected by the user equipment.

According to another example of an embodiment, an apparatus is provided including: means for determining, by a user equipment, at least one of: a radio link monitoring resource signal is undefined on at least one first bandwidth part, or radio link monitoring resource signals are not available on at least one second bandwidth part in response to receiving a request at the user equipment to switch from at least one first bandwidth part to the at least one second bandwidth part; and means for performing a radio link monitoring procedure after the switch or after the radio link monitoring resource signal is determined to be undefined, wherein the radio link monitoring procedure is based at least in part on whether or not a radio link problem has been detected by the user equipment.

According to another example of an embodiment, an apparatus is provided including at least one processor; and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the apparatus at least to determine, by a user equipment, at least one of: a radio link monitoring resource signal is undefined on at least one first bandwidth part, or radio link monitoring resource signals are not available on at least one second bandwidth part in response to receiving a request at the user equipment to switch from at least one first bandwidth part to the at least one second bandwidth part; and perform a radio link monitoring procedure after the switch or after the radio link monitoring resource signal is determined to be undefined, wherein the radio link monitoring procedure is based at least in part on whether or not a radio link problem has been detected by the user equipment.

According to another example of an embodiment, a computer readable medium is provided including program instructions for causing an apparatus to perform at least the following: determining, by a user equipment, at least one of: a radio link monitoring resource signal is undefined on at least one first bandwidth part, or radio link monitoring resource signals are not available on at least one second bandwidth part in response to receiving a request at the user equipment to switch from at least one first bandwidth part to the at least one second bandwidth part; and performing a radio link monitoring procedure after the switch or after the radio link monitoring resource signal is determined to be undefined, wherein the radio link monitoring procedure is based at least in part on whether or not a radio link problem has been detected by the user equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

Some example embodiments will now be described with reference to the accompanying drawings.

FIG. 1 is a block diagram of one possible and non-limiting exemplary system in which the exemplary embodiments may be practiced;

FIG. 2 shows an example of two BWPs configured on a network resource block grid; and FIG. 3 is a logic flow diagram for radio link evaluation for bandwidth parts, and illustrates the operation of an exemplary method or methods, 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.

DETAIFED DESCRIPTION

Features as described herein occasionally refer to LTE terms, however, it is noted that these features may be used in the future with other types of systems (such as New Radio (NR)/5G wireless systems for example). These other wireless systems may be defined by a relevant wireless standard, such as is the case ofNR/5G systems for example. In this way, references to, for example, an eNB (i.e. an LTE base station) are equally applicable to future base stations of these other wireless networks (such as, for example, base stations in 5G wireless networks referred to as gNB) unless indicated otherwise.

The exemplary embodiments herein describe techniques for radio link evaluation for bandwidth parts. Additional description of these techniques is presented after a system into which the exemplary embodiments may be used is described.

Turning to FIG. 1 , this figure shows a block diagram of one possible and non-limiting exemplary system in which the exemplary embodiments may be practiced. In FIG. 1 , a user equipment (LTE) 110 is in wireless communication with a wireless network 100. A LTE is a wireless, typically mobile device that can access a wireless network. The EGE 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 EGE 110 includes a determination module (det. module), comprising one of or both parts 140-1 and/or 140-2, which may be implemented in a number of ways. The determination module may be implemented in hardware as determination module 140-1 , such as being implemented as part of the one or more processors 120. The determination 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 determination module may be implemented as determination 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 1 10 to perform one or more of the operations as described herein. The LTE 110 communicates with gNB/eNB 170 (generally referred to as gNB 170 below) via a wireless link 1 11.

The gNB 170 is a base station (for example, for 5G/LTE) that provides access by wireless devices such as the EGE 1 10 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 gNB 170 includes a configuration module, comprising one of or both parts 150-1 and/or 150-2, which may be implemented in a number of ways. The configuration module may be implemented in hardware as configuration module 150-1 , such as being implemented as part of the one or more processors 152. The configuration 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 configuration module may be implemented as configuration 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, for example, link 176. The link 176 may be wired or wireless or both and may implement, for example, 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 will 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 covering 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 one or more network control elements (NCE) 190 that may include MME (Mobility Management Entity) and/or SGW (Serving Gateway) functionality, and which provides connectivity with a further network, such as a telephone network and/or a data communications network (for example, the Internet). The gNB 170 is coupled via a link 131 to the NCE 190. The link 131 may be implemented as, for example, an S l interface. For 5G wireless systems, the link 131 may represent a 5G interface, such as NG2 or NG3 for example. The NCE 190 includes one or more processors 175, one or more memories 171 , and one or more network interfaces (N/W EF(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.

Those skilled in the art will appreciate that the various network elements shown in FIG. 1 may be implemented differently in future wireless network, such as 5G wireless networks. For example, the terms NCE, MME, and SGW are terms generally used for the core elements in a LTE network. In contrast to LTE, future wireless networks may carry out network functions (NFs) by a plurality of cooperating devices. The different NFs, may include for example, Access and Mobility Function (AMF), Session Management Function (SMF), Policy Control Function (PCF), Application Function (AF), Authentication Server Function (AETSF), ETser Plane Function (ETPF), and ETser Data Management (ETDM). These NFs may be a virtualized function instantiated on an appropriate platform, such as a cloud infrastructure. For example, certain protocols (such as non real-time protocols for example) may be performed by one or more centralized units (CETs) in a cloud infrastructure, while one or more distributed units (DETs) operate the remaining protocols (e.g. real-time protocols) ofthe 5G radio interface. In this way, the various NFs may be split between CETs and DETs. Together a CET, underlying DETs, and RRHs may be considered as forming a logical base station (which may be represented by gNB 170 in FIG. 1 for example).

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 are still 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 LIE 110, gNB 170, and other functions as described herein.

In general, the various example embodiments of the user equipment 1 10 can include, but are not limited to, cellular telephones such as smart phones, 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.

Having thus introduced one suitable but non-limiting technical context for the practice of the various exemplary embodiments, the exemplary embodiments will now be described with greater specificity.

Bandwidth Part (B WP)

A bandwidth part is contiguous set of common resource blocks (see 3GPP Section 4.4.4.3 of 38.21 1 for example) of a given numerology on a given carrier. A BWP is determined by a starting position, a number of RBs and a numerology. FIG. 2 shows an example where two BWPs are configured on a network physical RB grid that is defined by Reference point ‘A’ and a numerology. The reference point A serves as a reference point for different grids, such as the RBG grid, control resource set (CORESETs) grid, and CSI sub-band grid for example. It is noted that BWPs can be overlapping or non-overlapping, whereas component carriers are only non-overlapping, and a BWP can also be smaller than BW of network carrier.

A UE that is configured to operate using BWPs is configured with a carrier BWP that defines the UE’s operating bandwidth within the cell's operating bandwidth. For initial access, the UE detects an initial BWP in system information to be used until the UE’s configuration in a cell is received. A UE may be configured up to four BWPs for DL reception and four for UL transmission, of which, only one can be active on a given component carrier for each direction, DL and UL.

Radio Link Monitoring

Procedure

A UE may perform radio link monitoring (RLM) on downlink reference signals such as CSI-RS and/or SS/PBCH block (SSB) for example. RLM-RS may be configured to the UE either implicitly or explicitly.

• In an implicit configuration, the network may configure to the UE a PDCCH TCI state indication. Unless explicitly configured, the UE can implicitly determine the set or list of RLM-RS to be source RS of the PDCCH TCI states, namely, the source reference signal or signals that have the QCL assumption with PDCCH DMRS (target signals) are used as RLM-RS. Each CORESET may have a TCI state for PDCCH configured, and there may be maximum of 3 CORESETs configured for UE. As an example, when signals share the same QCL assumption between each other, they share the same indicted property such as delay spread, Doppler spread, Doppler shift, average delay, and/or spatial reception parameters. As an example, when signals have the spatial RX QCL assumption, it would mean that UE can assume the same RX beam (RX spatial filter) when receiving the signals. When a TCI state for PDCCH indicates multiple source RS (a target signal such as PDCCH DMRS, can have multiple source RS with different QCL assumptions), UE may select the RS that has the QCL type-D (spatial RX) assumption with the PDCCH DMRS. A source RS may be, for example, CSI-RS or SS/PBCH block. SS/PBCH block can be referred with SS/PBCH block index, time location index, or SS/PBCH resource index. SS/PBCH block comprises of synchronization signals (primary and secondary, PSS, SSS) and Physical Broadcast Channel including PBCH DMRS.

• In an explicit configuration, the network indicates explicitly the list of RLM-RSs (such as NZP-CSI-RS and/or SSB resource indexes for example) used for radio link monitoring. The explicit configuration can be, for example, provided within RRC protocol message.

• In a similar manner, a UE may be configured with beam failure detection RS (BFD- RS) either implicitly or explicitly. Beam failure detection performs similar functions as RLM i.e. it determines based on a list of failure detection resources whether a beam failure has occurred. In beam failure detection case, currently only out of sync condition is detected (when all the reference signals are considered to be in out of sync (OOS) condition). OOS calculation may be similar as for RLM. As an example, with explicit configuration it may be possible to configure the same or different RS (SSB or CSI-RS) for RLM and BFD (beam failure detection) but if implicit configuration is used, the configuration of both RLM-RS and BFD-RS follow the TCI state for PDCCH. In BFD, the Ll indicates the link condition to MAC layer.

For each RLM-RS in the list, the UE may determine the hypothetical PDCCH BLER and may determine whether the respective reference signal is Qin or Qout. For example, the Qin value may correspond to a 2% BLER threshold, and the Qout value may correspond to a 10% BLER threshold (the Qout threshold may be same for beam failure detection). In some examples, these thresholds may be configured by the network.

• If all RLM-RS are above the Qout threshold, then an Out of Sync’ indication is provided by Ll to RRC layer (in case of beam failure detection, the indication is provided to the MAC layer, but no indication is provided when at least one BFD- RS is below Qout threshold);

• If at least one RLM-RS is below Qin threshold, then an Tn-Sync’ indication is provided to RRC layer; and

• If none above, then no indication is provided.

Radio resource control (RRC) has in-sync (IS) and out-of-sync (OOS) counters (the values of which may be configured by the network for example) that may operate in following manner:

• When RRC receives N310 consecutive OOS indications from lower layer it starts the timer T310. Upon expiry, the T310 timer causes UE to declare radio link failure (RLF) and to perform subsequent actions e.g. RRC connection re-establishment

• If T310 is running and RRC receives N311 consecutive IS indications it stops the timer T310. When a UE receives a new explicit RLM-RS configuration via RRC signaling, it may reset all the timers and counters at RRC.

Number of RLM-RS

The maximum number, X, of RLM-RS is applied per configured bandwidth part, and is frequency range dependent based on the following:

• Below 3 GHz the maximum is X= 2

• 3-6GHZ the maximum is X= 4

• Above 6GHZ the maximum is X=8

However, there is currently no consensus on the minimum number of RLM-RS per BWP. If the minimum number is undefined then this allows the possibility to configure a BWP without RLM-RS (X=0). In other words, there is no mandate that a network always define/predefine RLM-RS for each configured BWP.

Scaling of RLM-RS measurements

In non-DRX mode operation, the physical layer in the UE assesses once per indication period the radio link quality, evaluated over the previous time period (such as defined in TS 38.133 for example) against thresholds (Qout and Qin) configured by the higher layer parameter rlmlnSyncOutOfSyncThreshold . The UE determines the indication period as the maximum between the shortest periodicity for radio link monitoring resources and 10 msec (i.e. the indication period is scaled based on the periodicity of the RLM-RS).

In DRX mode operation, the physical layer in the UE shall assess once per indication period the radio link quality, evaluated over the previous time period against thresholds (Qout and Qin). The UE determines the indication period as the maximum between the shortest periodicity for radio link monitoring resources and the DRX period, i.e., in DRX the indication period is scaled by the DRX cycle length.

The requirements for RLM-RS monitoring and indication have not yet been decided, but it might be the case that additional scaling of the RLM-RS measurement and/or indication is applied due to UE RX beam sweeping in certain scenarios, such as when RLM-RS=SSB and SSB period is same as SMTC (SS/PBCH block measurement timing configuration) period for example. Currently, UE behavior in RLM is not defined when the network indicates that the UE is to change BWP and there are no RLM-RS configured on the new BWP. Furthermore, in one example, UE may be switched to a new bandwidth part, or on the currently active BWP UE maybe configured with a TCI state for PDCCH that has the aperiodic or semi -persistent signal (for example, CSI-RS may be aperiodic, semi-persistent, or periodic) as source RS (QCL’d source RS). In this case, the UE may determine not to include the signal in the set of RLM-RS. In other words, if a TCI state configuration for PDCCH indicates a state with aperiodic signal as source RS and CTE has no other TCI state for PDCCH, the RLM-RS would not be defined for the CTE (such as in an implicit configuration). Alternatively, if UE has multiple TCI states for PDCCH but all have aperiodic or semi-persistent signal as source RS, CTE may not include the source in the list of RLM-RS resources. Thus, the RLM- RS would not be defined for the CTE. As discussed above, this situation may occur on current active BWP or when UE switches to new BWP and receives new TCI state configuration. A similar situation may occur when UE has RLM-RS defined based on the multiple indicated TCI states for PDCCH wherein at least one of the TCI states does not define RLM-RS. In this situation, UE may receive an indication of deactivating or de configuring one or more active TCI states for PDCCH wherein the remaining current active state or states define no radio link monitoring reference signal. As an example, with implicit RLM-RS configuration, if UE has two TCI states for PDCCH, one with aperiodic source RS (RLM-RS not defined) and one with periodic source RS (defines RLM-RS) and network de-configures the TCI state with periodic source RS, leaving the RLM-RS undefined for the current BWP.

Regarding implicit and explicit configuration of BFD-RS and RLM-RS, the implicit RLM- RS configuration may not be possible or allowed when UE is explicitly configured with BFD-RS. In this case, the network can configure the UE with no RLM-RS (i.e. use no explicit signaling, which may be interpreted as no configuration or an empty configuration list). In other words, the network may not be mandated to provide the UE an RLM-RS.

Also, on FR1 (Frequency range 1 , typically refers to operation below 6GHz), the network may not indicate TCI state for PDCCH for UE, thus in this case implicit configuration for BFD-RS is not possible and network would configure BFD-RS list explicitly for beam failure detection, but network is not required to configure RLM-RS for each BWP configured in the UE. Thus, the problem emerges on how the UE should perform radio link monitoring when it has no RLM-RS configured, e.g. when an active BWP is switched. One possible solution is to have the UE use the old measurements of the old BWP until it receives new ones on current active BWP. However, when no RLM-RS are configured UE would experience RLF when the latest result was OOS.

According to some example embodiments, a UE may determine to perform the following in response to receiving a request for a BWP switch (or in general, switching bandwidth part, or alternatively in some example embodiments herein, if the RLM-RS configuration becomes undefined in current bandwidth part, i.e. UE has no RLM-RS) depending on whether a radio link problem has been detected:

• If T310 is running (i.e. RLP, radio link problem detected) and if no RLM-RS is configured, or RLM-RS period is much longer (e.g. evaluation delayed or the evaluation period is N-milliseconds or N times longer than in the previous BWP), then the UE may reset the timer (T3 l0)/counter and stop evaluating RLM, or indicate IS until RLM-RS are configured/obtained and can be measured and/or radio link condition evaluated (also in case no RLM-RS is available). As an example, the evaluation period may be scaled differently per bandwidth part. In one example stopping the timer T310 does not reset the timer, i.e. if OOS is received on new BWP, the timer continues from the same value. In another example when the timer T310 is stopped, it is also reset and any counters (IS/OOS) are reset as well.

o At least one benefit of such an approach is preventing RLF (due to expiry of T310) until the UE is configured with RLM-RS or until it has been able to determine the quality of the link (i.e. the UE is configured with new resources for radio link monitoring or the evaluation is delayed). If the network chooses not configure RLM-RS, aforementioned UE behaviour would not change the outcome as if network chooses not to configure RLM- RS to the new BWP, RLF would not be possible as UE would not evaluate RLM.

• According to some example embodiments, a UE (Ll) may indicate IS until RLM- RS are obtained and measured based on network configuration per BWP. This would allow the UE behavior to be set only for those specific BWPs which may likely provide different radio conditions to the UE (such as the BWPs that are significantly separated in frequency or known by the network to be less loaded/less interfered for example). Such configuration could be provided either in advance via RRC or via BWP switch command via DCI or RRC. For example: if T310 is not running and if no RLM-RS is configured, then the UE may stop evaluating RLM and reset all counters; or if T310 is not running, and regardless whether RLM-RS is or is not configured, then the UE may indicate IS until a new RLM-RS can be evaluated and then the UE may transmit an indication based on the new RLM-RS. If the T310 is not running and at least one out of sync condition has been counted at UE (for example, when Ll indicates OOS indication to RRC) before switching to the BWP or determining that RLM-RS is not defined for current BWP, the counter may be reset and Ll may refrain from any further indication before obtaining new measurements/radio link evaluation on new BWP.

o At least one benefit of the above approach is preventing RLF (i.e. upon expiry of T310) until the UE is configured with RLM-RS or until it has been able to determine the quality of the link, such as until the UE is configured with new resources for radio link monitoring for example.

In some examples, the Ll layer (i.e. layer 1 or physical layer) may know whether RLP recovery or timer T310 is running based on UE internal signalling. In these situations, the UE behaviour could depend on whether the RLP/T310 running is detected or known at Ll . In one example, if RLP is detected/known by the Ll , the Ll may send consecutive IS indications to prevent T310 expiry. If the value N311 is known at Ll , then Ll only needs to send N31 1 IS indications to the higher layer. If the value is not known at Ll, then the Ll sends IS indications to higher layer until obtaining new RLM measurement results. If no RLP is detected (T310 is not running), then the UE may send only one IS indication to reset counters (such as OOS counter, N310), and refrain from sending further indications.

In one example embodiment, when a UE switches from BWP with no RLM-RS to BWP with RLM-RS and UE has not reset any counters/timers, i.e., has only indicated IS to higher layers (such as if the UE only stops T310), then T310 may be reset.

FIG. 3 is a logic flow diagram for radio link evaluation for bandwidth parts. This figure further illustrates the operation of an exemplary method or methods, 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. For instance, the monitoring module 140-1 and/or 140-2 may include multiples ones of the blocks in FIG. 3, where each included block is an interconnected means for performing the function in the block. The blocks in FIG. 3 are assumed to be performed by the UE 1 10, e.g., under control of the monitoring module 140-1 and/or 140-2 at least in part. According to an example embodiment, a method is provided including: determining, by a user equipment, at least one of: a radio link monitoring resource signal is undefined on at least one first bandwidth part, or radio link monitoring resource signals are not available on at least one second bandwidth part in response to receiving a request at the user equipment to switch from at least one first bandwidth part to the at least one second bandwidth part as indicated by block 300; and performing a radio link monitoring procedure after the switch or after the radio link monitoring resource signal is determined to be undefined, wherein the radio link monitoring procedure is based at least in part on whether or not a radio link problem has been detected by the user equipment as indicated by block 302.

Determining the radio link monitoring resource signals are not available on the at least one second bandwidth part may include at least one of: determining radio link monitoring resource signals have not been configured on the at least one second bandwidth part; and determining a period of radio link monitoring resource signals corresponding to the at least one second bandwidth part exceeds a threshold value. In case the radio link problem is detected, the method may further include: resetting one or more timers and/or one or more counters associated with the radio link monitoring procedure of a radio resource control protocol; and transmitting one or more in-sync indications either when the radio link monitoring resource signals have not been configured or until the radio monitoring resource signals on the at least one second bandwidth part are measured. In response to determining a radio link problem has not been detected, the method may further include: stopping radio link monitoring for either the at least one second bandwidth part after the switch, or for the at least one first bandwidth part after the radio link monitoring resource signal is determined to be undefined; and resetting one or more timers and/or one or more counters associated with the radio link monitoring procedure of a radio resource control protocol. In response to determining a radio link problem has not been detected, the method may further include: transmitting one or more in-sync indications until either a radio link monitoring resource signal configured on the at least one second bandwidth part is measured, or at least one further radio link monitoring resource signal configured on the at least one first bandwidth part is measured after the radio link monitoring resource signal is determined to be undefined, and sending a radio link indication based on the radio link monitoring signal configured on the at least one second bandwidth part or the further radio link monitoring signal configured on the first bandwidth part. Determining the radio link monitoring resource signal is undefined on the at least one first bandwidth part may include: receiving an indication of a new transmission configuration indication state for a physical downlink control channel, wherein no other transmission configuration indication state is configured for the user equipment that defines a radio link monitoring reference signal. The user equipment may be configured with at least two active transmission configuration indication states for a physical downlink control channel, and the method may further include: receiving an indication to deactivate or de -configure one or more of the at least two active transmission configuration indication states, and determining the radio link monitoring signal is undefined when none of the remaining active transmission configuration indication states define a radio link monitoring reference signal. The method may further include determining the radio link problem has been detected when a timer is running; and determining no radio link problem has been detected when the timer is not running. The timer may be started when a predetermined number of out-of-sync indications are received by a radio resource control protocol, and upon expiry of the timer the user equipment may determine radio link failure. The method may include: receiving a configuration for the radio link monitoring procedure that is specific to one or more of a plurality of bandwidth parts.

The means for determining the radio link monitoring resource signals are not available on the at least one second bandwidth part may include at least one of: means for determining radio link monitoring resource signals have not been configured on the at least one second bandwidth part; and means for determining a period of radio link monitoring resource signals corresponding to the at least one second bandwidth part exceeds a threshold value. In case the radio link problem is detected, the apparatus may further include: means for resetting one or more timers and/or one or more counters associated with the radio link monitoring procedure of a radio resource control protocol; and means for transmitting one or more in-sync indications either when the radio link monitoring resource signals have not been configured or until the radio monitoring resource signals on the at least one second bandwidth part are measured. In response to determining a radio link problem has not been detected, the apparatus may further include: means for stopping radio link monitoring for either the at least one second bandwidth part after the switch, or for the at least one first bandwidth part after the radio link monitoring resource signal is determined to be undefined; and means for resetting one or more timers and/or one or more counters associated with the radio link monitoring procedure of a radio resource control protocol. In response to determining a radio link problem has not been detected, the apparatus may further include: means for transmitting one or more in-sync indications until either a radio link monitoring resource signal configured on the at least one second bandwidth part is measured, or at least one further radio link monitoring resource signal configured on the at least one first bandwidth part is measured after the radio link monitoring resource signal is determined to be undefined, and means for sending a radio link indication based on the radio link monitoring signal configured on the at least one second bandwidth part or the further radio link monitoring signal configured on the first bandwidth part. The means for determining the radio link monitoring resource signal is undefined on the at least one first bandwidth part may include: means for receiving an indication of a new transmission configuration indication state for a physical downlink control channel, wherein no other transmission configuration indication state is configured for the user equipment that defines a radio link monitoring reference signal. The user equipment may be configured with at least two active transmission configuration indication states for a physical downlink control channel, and the apparatus may further include: means for receiving an indication to deactivate or de-configure one or more of the at least two active transmission configuration indication states, and means for determining the radio link monitoring signal is undefined when none of the remaining active transmission configuration indication states define a radio link monitoring reference signal. The apparatus may further include means for determining the radio link problem has been detected when a timer is running; and means for determining no radio link problem has been detected when the timer is not running. The timer may be started when a predetermined number of out-of-sync indications are received by a radio resource control protocol, and upon expiry of the timer the user equipment may determine radio link failure. The apparatus may further include means for receiving configuration for the radio link monitoring procedure that is specific to one or more of a plurality of bandwidth parts.

According to another example of an embodiment, an apparatus is provided including at least one processor; and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the apparatus at least to: determine, by a user equipment, at least one of: a radio link monitoring resource signal is undefined on at least one first bandwidth part, or radio link monitoring resource signals are not available on at least one second bandwidth part in response to receiving a request at the user equipment to switch from at least one first bandwidth part to the at least one second bandwidth part; and perform a radio link monitoring procedure after the switch or after the radio link monitoring resource signal is determined to be undefined, wherein the radio link monitoring procedure is based at least in part on whether or not a radio link problem has been detected by the user equipment.

Determination that the radio link monitoring resource signals are not available on the at least one second bandwidth part may include at least one of: determination that radio link monitoring resource signals have not been configured on the at least one second bandwidth part; and determination that a period of radio link monitoring resource signals corresponding to the at least one second bandwidth part exceeds a threshold value. In case the radio link problem is detected, the at least one memory and computer program code may be configured to, with the at least one processor, cause the apparatus to: reset one or more timers and/or one or more counters associated with the radio link monitoring procedure of a radio resource control protocol; and transmit one or more in-sync indications either when the radio link monitoring resource signals have not been configured or until the radio monitoring resource signals on the at least one second bandwidth part are measured. In response to determination that a radio link problem has not been detected, the at least one memory and computer program code may be configured to, with the at least one processor, cause the apparatus to: stop radio link monitoring for either the at least one second bandwidth part after the switch, or for the at least one first bandwidth part after the radio link monitoring resource signal is determined to be undefined; and reset one or more timers and/or one or more counters associated with the radio link monitoring procedure of a radio resource control protocol. In response to determination that a radio link problem has not been detected, the at least one memory and computer program code may be configured to, with the at least one processor, cause the apparatus to: transmit one or more in-sync indications until either a radio link monitoring resource signal configured on the at least one second bandwidth part is measured, or at least one further radio link monitoring resource signal configured on the at least one first bandwidth part is measured after the radio link monitoring resource signal is determined to be undefined, and send a radio link indication based on the radio link monitoring signal configured on the at least one second bandwidth part or the further radio link monitoring signal configured on the first bandwidth part. Determination that the radio link monitoring resource signal is undefined on the at least one first bandwidth part may include: reception of an indication of a new transmission configuration indication state for a physical downlink control channel, wherein no other transmission configuration indication state is configured for the user equipment that defines a radio link monitoring reference signal. The user equipment may be configured with at least two active transmission configuration indication states for a physical downlink control channel, and the at least one memory and computer program code may be configured to, with the at least one processor, cause the apparatus to: receive an indication to deactivate or de-configure one or more of the at least two active transmission configuration indication states, and determine the radio link monitoring signal is undefined when none of the remaining active transmission configuration indication states define a radio link monitoring reference signal. The at least one memory and computer program code may be configured to, with the at least one processor, cause the apparatus to determine the radio link problem has been detected when a timer is running; and determine no radio link problem has been detected when the timer is not running. The timer may be started when a predetermined number of out-of-sync indications are received by a radio resource control protocol, and upon expiry of the timer the user equipment may determine radio link failure. The at least one memory and computer program code may be configured to, with the at least one processor, cause the apparatus to receive a configuration for the radio link monitoring procedure that is specific to one or more of a plurality of bandwidth parts.

Determining the radio link monitoring resource signals are not available on the at least one second bandwidth part may include at least one of: determining radio link monitoring resource signals have not been configured on the at least one second bandwidth part; and determining a period of radio link monitoring resource signals corresponding to the at least one second bandwidth part exceeds a threshold value. In case the radio link problem is detected, the program instructions may cause the apparatus to perform resetting one or more timers and/or one or more counters associated with the radio link monitoring procedure of a radio resource control protocol; and transmitting one or more in-sync indications either when the radio link monitoring resource signals have not been configured or until the radio monitoring resource signals on the at least one second bandwidth part are measured. In response to determining a radio link problem has not been detected, the program instructions may cause the apparatus to further perform: stopping radio link monitoring for either the at least one second bandwidth part after the switch, or for the at least one first bandwidth part after the radio link monitoring resource signal is determined to be undefined; and resetting one or more timers and/or one or more counters associated with the radio link monitoring procedure of a radio resource control protocol. In response to determining a radio link problem has not been detected, the program instructions may cause the apparatus to further perform: transmitting one or more in-sync indications until either a radio link monitoring resource signal configured on the at least one second bandwidth part is measured, or at least one further radio link monitoring resource signal configured on the at least one first bandwidth part is measured after the radio link monitoring resource signal is determined to be undefined, and sending a radio link indication based on the radio link monitoring signal configured on the at least one second bandwidth part or the further radio link monitoring signal configured on the first bandwidth part. Determining the radio link monitoring resource signal is undefined on the at least one first bandwidth part may include: receiving an indication of a new transmission configuration indication state for a physical downlink control channel, wherein no other transmission configuration indication state is configured for the user equipment that defines a radio link monitoring reference signal. The user equipment may be configured with at least two active transmission configuration indication states for a physical downlink control channel, and the program instructions may cause the apparatus to further perform: receiving an indication to deactivate or de -configure one or more of the at least two active transmission configuration indication states, and determining the radio link monitoring signal is undefined when none of the remaining active transmission configuration indication states define a radio link monitoring reference signal. The program instructions may cause the apparatus to further perform determining the radio link problem has been detected when a timer is running; and determining no radio link problem has been detected when the timer is not running. The timer may be started when a predetermined number of out-of-sync indications are received by a radio resource control protocol, and upon expiry of the timer the user equipment may determine radio link failure. The program instructions may cause the apparatus to further perform receiving a configuration for the radio link monitoring procedure that is specific to one or more of a plurality of bandwidth parts.

Without in any way limiting the scope, interpretation, or application of the claims appearing below, a technical effect of one or more of the example embodiments disclosed herein is preventing RLF when switching BWPs such as until a UE is configured with RLM-RS or until it has been able to determine the quality of the link for example.

It may be possible, when applicable, to use the example techniques described herein for the link evaluation using beam failure detection procedure. In some cases for BFD instead of the IS indication (as in RLM), the UE may not send any indication to higher layer (MAC) which is then interpreted as non-failure condition at higher layer. In a similar manner, the MAC layer counter counting BFI (beam failure indications) may be reset when UE switches BWP or, when the BFD-RS is undefined in the current BWP, and/or the indications are not provided to higher layer. In case IS condition is applied/defined forBFD similar rules may apply as for radio link monitoring.

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 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., memories 125, 155, 171 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 propagating signals.

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.

The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:

eNB (or eNodeB) evolved Node B (e.g., an FTE base station)

BLER block error rate

BWP bandwidth part

BFD Beam Failure Detection

BFD-RS Beam Failure Detection Reference Signal

BFI Beam Failure Indication

CORESET control resource set

CSI-RS channel state information reference signal

DCI downlink control information

DL downlink

DMRS demodulation reference signal

DRX discontinuous reception

gNB next generation node B

I/F interface

IS in-sync

LTE long term evolution

MME mobility management entity

NCE network control element

N/W network

oos out-of-sync

PDCCH physical downlink control channel

PRB physical resource block

RBG resource block group

RLM radio link monitoring RRH remote radio head

QCL quasi-co -location

Rx receiver

RLF radio link failure

RLP radio link problem

RRC radio resource control

RS reference signal

SGW serving gateway

SS/PBCH Block Synchronization Signal/Physical Broadcast Channel Block

SSB SS/PBCH Block

TB transport block

TCI transmission configuration indication

Tx transmitter

UE user equipment (e.g., a wireless, typically mobile device)

Claims

1. A method, comprising:

determining, by a user equipment, at least one of:

a radio link monitoring resource signal is undefined on at least one first bandwidth part, or

radio link monitoring resource signals are not available on at least one second bandwidth part in response to receiving a request at the user equipment to switch from at least one first bandwidth part to the at least one second bandwidth part; and

performing a radio link monitoring procedure after the switch or after the radio link monitoring resource signal is determined to be undefined, wherein the radio link monitoring procedure is based at least in part on whether or not a radio link problem has been detected by the user equipment.

2. The method as in claim 1 , wherein determining the radio link monitoring resource signals are not available on the at least one second bandwidth part comprises at least one of: determining radio link monitoring resource signals have not been configured on the at least one second bandwidth part; and

determining a period of radio link monitoring resource signals corresponding to the at least one second bandwidth part exceeds a threshold value.

3. The method as in any one of claims 1-2, wherein, in case the radio link problem is detected, the method further comprises:

resetting one or more timers and/or one or more counters associated with the radio link monitoring procedure of a radio resource control protocol; and

transmitting one or more in-sync indications either when the radio link monitoring resource signals have not been configured or until the radio monitoring resource signals on the at least one second bandwidth part are measured.

4. The method as in any one of claims 1-3, wherein, in response to determining a radio link problem has not been detected, the method further comprises:

stopping radio link monitoring for either the at least one second bandwidth part after the switch, or for the at least one first bandwidth part after the radio link monitoring resource signal is determined to be undefined; and resetting one or more timers and/or one or more counters associated with the radio link monitoring procedure of a radio resource control protocol.

5. The method as in any one of claims 1 -3, further comprising, in response to determining a radio link problem has not been detected:

transmitting one or more in-sync indications until either a radio link monitoring resource signal configured on the at least one second bandwidth part is measured, or at least one further radio link monitoring resource signal configured on the at least one first bandwidth part is measured after the radio link monitoring resource signal is determined to be undefined, and

sending a radio link indication based on the radio link monitoring signal configured on the at least one second bandwidth part or the further radio link monitoring signal configured on the first bandwidth part.

6. The method as in any one of claim 1 -5, wherein determining the radio link monitoring resource signal is undefined on the at least one first bandwidth part comprises:

receiving an indication of a new transmission configuration indication state for a physical downlink control channel, wherein no other transmission configuration indication state is configured for the user equipment that defines a radio link monitoring reference signal.

7. The method as in any one of claim 1-5, wherein the user equipment is configured with at least two active transmission configuration indication states for a physical downlink control channel, and wherein the method comprises:

receiving an indication to deactivate or de-configure one or more of the at least two active transmission configuration indication states, and

determining the radio link monitoring signal is undefined when none of the remaining active transmission configuration indication states define a radio link monitoring reference signal.

8. The method as in any one of claims 1 -7, further comprising:

determining the radio link problem has been detected when a timer is running; and determining no radio link problem has been detected when the timer is not running.

9. The method as in claim 8, wherein the timer is started when a predetermined number of out-of-sync indications are received by a radio resource control protocol, and where upon expiry of the timer the user equipment determines radio link failure.

10. An apparatus comprising:

means for determining, by a user equipment, at least one of:

means for performing a radio link monitoring procedure after the switch or after the radio link monitoring resource signal is determined to be undefined, wherein the radio link monitoring procedure is based at least in part on whether or not a radio link problem has been detected by the user equipment.

11. The apparatus as in claim 10, wherein the means for determining the radio link monitoring resource signals are not available on the at least one second bandwidth part comprises at least one of:

means for determining radio link monitoring resource signals have not been configured on the at least one second bandwidth part; and

means for determining a period of radio link monitoring resource signals corresponding to the at least one second bandwidth part exceeds a threshold value.

12. The apparatus as in any one of claims 10-11 , wherein, in case the radio link problem is detected, the apparatus further comprises:

means for resetting one or more timers and/or one or more counters associated with the radio link monitoring procedure of a radio resource control protocol; and means for transmitting one or more in-sync indications either when the radio link monitoring resource signals have not been configured or until the radio monitoring resource signals on the at least one second bandwidth part are measured.

13. The apparatus as in any one of claims 10-12, wherein, in response to determining a radio link problem has not been detected, the apparatus further comprises: means for stopping radio link monitoring for either the at least one second bandwidth part after the switch, or for the at least one first bandwidth part after the radio link monitoring resource signal is determined to be undefined; and means for resetting one or more timers and/or one or more counters associated with the radio link monitoring procedure of a radio resource control protocol.

14. The apparatus as in any one of claims 10-12, wherein, in response to determining a radio link problem has not been detected:

means for transmitting one or more in-sync indications until either a radio link monitoring resource signal configured on the at least one second bandwidth part is measured, or at least one further radio link monitoring resource signal configured on the at least one first bandwidth part is measured after the radio link monitoring resource signal is determined to be undefined, and

means for sending a radio link indication based on the radio link monitoring signal configured on the at least one second bandwidth part or the further radio link monitoring signal configured on the first bandwidth part.

15. The apparatus as in any one of claim 10-14, wherein the means for determining the radio link monitoring resource signal is undefined on the at least one first bandwidth part comprises:

means for receiving an indication of a new transmission configuration indication state for a physical downlink control channel, wherein no other transmission configuration indication state is configured for the user equipment that defines a radio link monitoring signal.

16. The apparatus as in any one of claim 10-14, wherein the user equipment is configured with at least two active transmission configuration indication states for a physical downlink control channel, and wherein the apparatus further comprises:

means for receiving an indication to deactivate or de-configure one or more of the at least two active transmission configuration indication states, and

means for determining the radio link monitoring signal is undefined when none of the remaining active transmission configuration indication states define a radio link monitoring reference signal.

17. The apparatus as in any one of claims 10-16, further comprising: means for determining the radio link problem has been detected when a timer is running; and

means for determining no radio link problem has been detected when the timer is not running.

18. The apparatus as in claim 17, wherein the timer is started when a predetermined number of out-of-sync indications are received by a radio resource control protocol, and where upon expiry of the timer the user equipment determines radio link failure.

19. A computer readable medium comprising program instructions for causing an apparatus to perform at least the following:

determining, by a user equipment, at least one of: