# US 2019/0174385 A1 · System and method for radio link monitoring and radio link recovery

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 2019/0174385 A1
- Document ID: US20190174385A1
- Status: Published application
- Kind: A1
- Application number: 16/111,034
- Filed: 2018-08-23
- Published: 2019-06-06
- Earliest claimed: 2017-06-23
- Applicants: Huawei Technologies Co. Ltd.
- Inventors: Aimin Justin Sang; Bin Liu; Xuelong Wang; Qinghai Zeng
- Web page: https://patentgrep.com/patent/US20190174385A1

## CPC

- H04W 36/305: {Handover due to radio link failure (control signalling for hand-off failure H04W36/0079)}
- H04B 7/088: {using beam selection}
- H04L 41/0668: by dynamic selection of recovery network elements, e.g. replacement by the most appropriate element after failure
- H04W 36/0072: {of resource information of target access point}
- H04W 36/00837: {Determination of triggering parameters for hand-off}
- H04W 40/12: based on transmission quality or channel quality
- H04W 40/16: based on interference
- H04W 40/36: due to handover
- H04W 56/001: {Synchronization between nodes}
- H04W 56/0035: {detecting errors in frequency or phase}
- H04W 76/18: Management of setup rejection or failure
- H04W 76/19: Connection re-establishment
- H04W 76/27: Transitions between radio resource control [RRC] states
- H04B 7/0413: MIMO systems
- H04B 7/08: at the receiving station
- H04W 24/04: Arrangements for maintaining operational condition
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)
- H04B: TRANSMISSION
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

A method is provided for radio link failure (RLF) detection, link failure recovery, beam failure recovery (BFR) and radio link monitoring (RLM), and for interactions between modules for RLF, BFR, RLM and, integration and unification of indications. A device may measure a reference signal received over one or more communication paths of a radio link to generate reference signal measurements, and select, from the one or more communications paths, at least one path for link quality assessment of a radio link operation based on the reference signal measurements and a configured criterion. The device may generate a radio link indication based on an assessed link quality metric or a link recovery operation status associated with the selected at least one path, and send the radio link indication from a physical layer of the device to a upper layer of the device.

## Claims

### Claim 1

A method for determining radio link recovery or beam failure recovery (BFR) indications in a device, comprising:
measuring, by a device, a reference signal received over one or more communication paths of a radio link extending between a user equipment (UE) and one or more network devices in a wireless network to generate reference signal measurements, the one or more communication paths being configured by the wireless network;
selecting, from the one or more communication paths, at least one path for link quality assessment of a radio link operation based on the reference signal measurements and a configured criterion;
generating a radio link indication based on an assessed link quality metric or a link recovery operation status associated with the selected at least one path; and
sending the radio link indication from a physical layer of the device to an upper layer of the device.

### Claim 2 (depends on 1)

The method of claim 1, wherein each of the one or more communication paths is associated with a different reference signal, a different beam pair, a different uplink or downlink direction, a different channel, a different carrier, and/or a different cell than other paths in the one or more communication paths.

### Claim 3 (depends on 1)

The method of claim 1, wherein the radio link operation includes uplink or downlink signaling, link failure detection, new beam identification, link failure recovery request transmission or response monitoring.

### Claim 4 (depends on 1)

The method of claim 1, wherein the radio link indication further indicates a connectivity status based on the assessed link quality metric, or a recovery operation status of a success or failure.

### Claim 5 (depends on 1)

The method of claim 1, wherein the radio link indication is generated as an operation success only if all steps in an underlying link or beam recovery process have been completed prior to expiration of a step-wise counter or timer.

### Claim 6 (depends on 1)

The method of claim 1, wherein the radio link indication is generated as an operation failure if any step in a link or beam recovery process failed before a counter or timer expires.

### Claim 7 (depends on 1)

The method of claim 1, wherein the radio link indication is generated as a periodic connectivity out-of-sync (OOS) when all of signal quality of the selected path(s) drops below a threshold.

### Claim 8 (depends on 1)

The method of claim 1, wherein the radio link indication is generated as a periodic connectivity in-sync (IS) when signal quality of any of the selected at least one path exceeds a threshold.

### Claim 9 (depends on 1)

The method of claim 1, wherein executing link recovery operation or assessing link quality is based only on a specific path including a specific reference signal, a specific beam, a serving control channel, or a combination thereof.

### Claim 10 (depends on 1)

The method of claim 1, wherein the reference signal measurements include reference signal received power (RSRP) measurements, signal to noise and interference ratio (SINR) measurements, reference signal received quality (RSRQ) measurements, or received signal strength indication (RSSI) measurements.

### Claim 11 (depends on 1)

The method of claim 1, wherein the selected at least one path for the radio link is selected based on a moving average, weighted sum, or threshold comparison of the reference signal measurements.

### Claim 12 (depends on 1)

The method of claim 1, further comprising assessing link quality by deriving carrier-level, channel-level, or cell-level link quality metric based on a single or multiple beam(s) and of a specific reference signal.

### Claim 13 (depends on 1)

The method of claim 1, wherein a criterion for assessing a serving link by considering multiple paths or selecting a path is configured by filtering the metric of individual path, selecting one or multiple paths based on threshold comparison or metric ranking, deriving a single link quality metric by combining selected paths by mathematical methods comprising a weighted summarization, and/or assessing a link quality by comparing a derived metric against a threshold.

### Claim 14 (depends on 1)

The method of claim 1, wherein the radio link indication associates a selected path with a beam or beam pair, a serving channel, a reference signal, a component carrier, and/or a base station or a cell.

### Claim 15 (depends on 1)

The method of claim 1, wherein link failure detection or beam failure detection is triggered when each of a configured synchronization signal block (SSB) measurement, a configured demodulation reference signal (DM-RS) measurement, a configured sounding reference signal (SRS) measurement, and a configured channel state information reference signal (CSI-RS) measurement associated with the radio link is below a corresponding threshold with a time period.

### Claim 16 (depends on 1)

The method of claim 1, wherein new beam identification or new path identification is triggered when any of a configured synchronization signal block (SSB) measurement, a configured demodulation reference signal (DM-RS) measurement, a configured sounding reference signal (SRS) measurement, and a configured channel state information reference signal (CSI-RS) measurement associated with the radio link is above a corresponding threshold with a time period.

### Claim 17 (depends on 1)

The method of claim 1, wherein an indication for link failure operation or a beam failure operation is triggered periodically, aperiodically, or in response to an event.

### Claim 18 (depends on 1)

The method of claim 1, wherein the radio link indication identifies a link connectivity status, the link connectivity status being determined according to a second configured criterion including comparing quality metrics against a threshold for a specific path of the radio link, or a combined indication of multiple paths for a same link by logic (OR or AND) operations.

### Claim 19 (depends on 1)

The method of claim 1, wherein configured derivation or assessment of serving link metrics include filtering such as weighted sum or moving average, or SINR-to-BLER table lookup of multiple beam-specific signal metrics.

### Claim 20 (depends on 1)

The method of claim 1, wherein radio link monitoring (RLM) and link recovery operations work independently.

### Claim 21 (depends on 1)

The method of claim 1, wherein the one or more communication paths comprise multiple beams, the multiple beams comprising at least one of: multiple beams with a network device of the same or different reference signals, multiple beams on same or different frequency carriers, multiple beams of same or different (DL or UL) directions, multiple beams of the same or different reference signals, multiple beams on same or different channels, multiple beams from same or different network devices in a same or different cells, on a same or different radio access technologies (RATs), or any combination of them.

### Claim 22 (depends on 1)

The method of claim 1, wherein a weight is configured for per-reference signal, for per-beam, for per-channel, for per-direction, for per-carrier, or for per-cell, and the weight is a digital number or a linear scalar, and a weight sum is a linear or non-linear function.

### Claim 23 (depends on 1)

The method of claim 1, further comprising configuration methods of at least one of following:
receiving a radio resource control (RRC) configuration signal;
determining what or how indications of link recovery are generated, used, or multi-path considered and selected by following a radio link configuration or by a RRC signal;
deciding a multipath consideration (diversity exploitation) method and parameters;
deciding a filtering criteria and parameters, and IS or OOS indication generation approach for multi-path link recovery;
deciding upwards and downwards mutual indications between RLM and link recovery (in parallel or cascaded processing) relationship; and
influencing change of a link recovery state machine based on indications according to configured upper level status or events.

### Claim 24 (depends on 1)

The method of claim 1, wherein the device is the UE.

### Claim 25 (depends on 1)

The method of claim 1, wherein the device is one of the one or more network devices.

### Claim 26

A device comprising:
a processor; and
a non-transitory computer readable storage medium storing programming for execution by the processor, the programming including instructions to:
measure a reference signal received over one or more communication paths of a radio link extending between a user equipment (UE) and one or more network devices in a wireless network to generate reference signal measurements, the one or more communication paths being configured by the wireless network;
select, from the one or more communication paths, at least one path for link quality assessment of a radio link operation based on the reference signal measurements and a configured criterion;
generate a radio link indication based on an assessed link quality or a link recovery operation status associated with the selected at least one path; and
send the radio link indication from a physical layer of the device to an upper layer of the device.

### Claim 27

A method for radio link monitoring (RLM) in a device, comprising:
measuring, by the device, reference signals received over one or more beams of a serving link between a user equipment (UE) and one or more network devices in a wireless network to generate reference signal measurements;
selecting, from the one or more beams, at least one beam based on the measured reference signals in accordance with a network configured RLM criterion;
deriving a serving link quality from the selected at least one beam according to the network configured RLM criterion;
assessing the derived serving link quality by following the network configured RLM criterion to generate one or more first or periodic RLM indications; and
sending the one or more first or periodic RLM indications to a same layer or an upper layer of the device.

### Claim 28 (depends on 27)

The method of claim 27, wherein the network configured RLM criterion comprises beam-specific metrics filtering, or X best beam(s) selection based on filtered metrics above configured thresholds, or both.

### Claim 29 (depends on 27)

The method of claim 27, wherein the network configured RLM criterion for deriving the serving link quality is for a specific reference signal, beam, carrier, channel, or cell.

### Claim 30 (depends on 27)

The method of claim 27, wherein configured derivation or assessment of serving link metrics comprises filtering such as weighted sum or moving average, or SINR-to-BLER table lookup of multiple beam-specific signal metrics.

### Claim 31 (depends on 27)

The method of claim 27, wherein the network configured RLM criterion comprises a beam-specific metric filtering criterion, a beam selection criterion for comparing filtered metrics of filtered beams against a threshold, and/or a criterion for deriving RLM indications by comparing link metrics of selected beams against a threshold, wherein the link metrics include RSRP, RSRQ, RSSI, SINR, or control channel BLER.

### Claim 32 (depends on 27)

The method of claim 27, wherein the one or more first or periodic RLM indications comprise beam-specific signal metrics (RSRP, RSRQ, RSSI, SINR), multi-beam combined link metrics, RLM criteria generated In-Sync (IS) or Out-Of-Sync (OOS).

### Claim 33 (depends on 27)

The method of claim 27, wherein the one or more first or periodic RLM indications comprising signal metrics or link metrics are utilized by link recovery operations comprising beam or link failure detection, or new beam identification.

### Claim 34 (depends on 27)

The method of claim 27, wherein RLM and link recovery operations work independently.

### Claim 35 (depends on 27)

The method of claim 27, wherein the one or more beams comprise at least one of: multiple beams with a network device of the same or different reference signals, multiple beams on same or different frequency carriers, multiple beams of same or different (DL or UL) directions, multiple beams of the same or different reference signals, multiple beams on same or different channels, multiple beams from same or different network devices in a same or different cells, on a same or different RATs, or any combination of them.

### Claim 36 (depends on 27)

The method of claim 27, wherein a weight is configured for per-reference signal, for per-beam, for per-channel, for per-direction, for per-carrier, or for per-cell, and the weight is a digital number or a linear scalar, and weight sum is a linear or non-linear function.

### Claim 37 (depends on 27)

The method of claim 27, further comprising configuration methods of at least one of below:
receiving a radio resource control (RRC) configuration signal;
determining what or how indications of link recovery or RLM are generated, used, or multi-path considered (diversity exploited) by following a radio link configuration or by a RRC signal;
deciding a multipath consideration (diversity exploitation) method and parameters;
deciding a filtering criteria and parameters, and IS or OOS indication generation approach for multi-beam RLM or multi-path link recovery;
deciding upwards and downwards mutual indications between RLM and link recovery (in parallel or cascaded processing) relationship; and
influencing change of a link recovery state machine based on indications based on configured upper level status or events.

### Claim 38 (depends on 27)

The method of claim 27, wherein the device is the UE.

### Claim 39 (depends on 27)

The method of claim 27, wherein the device is one of the one or more network devices.

### Claim 40

A device comprising:
a processor; and
a non-transitory computer readable storage medium storing programming for execution by the processor, the programming including instructions to:
measure, by the device, reference signals received over one or more beams of a serving link between a user equipment (UE) and one or more network devices in a wireless network to generate reference signal measurements;
select, from the one or more beams, at least one beam based on the measured reference signals in accordance with a network configured RLM criteria;
derive a serving link quality from the selected at least one beam according to the network configured RLM criteria;
assess the derived serving link quality by following the network configured RLM criteria to generate one or more first or periodic RLM indication(s); and
send the one or more first or periodic RLM indication(s) to a same layer or an upper layer of the device.