# US 12,004,223 B2 · Systems and methods for retransmission of contention free random access beam failure recovery (CFRA-BFR) and cross-CC beam failure detection

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- Number: US 12,004,223 B2
- Document ID: US12004223B2
- Status: Granted
- Kind: B2
- Application number: 17/428,002
- Filed: 2020-02-05
- Published: 2022-04-21
- Granted: 2024-06-04
- Earliest claimed: 2019-02-08
- Assignees: Apple Inc.
- Applicants: Apple Inc.
- Inventors: Yushu Zhang; Gang Xiong; Guotong Wang; Alexei Davydov
- Web page: https://patentgrep.com/patent/US12004223B2

## CPC

- H04B 7/06964: {Re-selection of one or more beams after beam failure}
- H04W 74/0838: using contention-free random access [CFRA]
- H04W 74/0833: Random access procedures, e.g. with 4-step access
- H04B: TRANSMISSION
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)

## Abstract

Some embodiments of this disclosure include systems, apparatuses, methods, and computer-readable media for use in a wireless network for beam failure recovery (BFR). For example, some embodiments are directed to a user equipment (UE). The UE includes radio front end circuitry and processor circuitry coupled to the radio front end circuitry. The processor circuitry can be configured to receive, using the radio front end circuitry, one or more reference signals. The processor circuitry can be further configured to, in response to determining that a beam failure occurred for the one or more reference signals, determine a contention-free (CF) physical random access channel (PRACH) resource for a beam failure recovery (BFR) request. The processor circuitry can be further configured to transmit, using the radio front circuitry, the BFR request using the determined CF PRACH resource.

## Claims

### Claim 1

A user equipment (UE), comprising:
radio front end circuitry; and
processor circuitry, coupled to the radio front end circuitry, and configured to:
receive, using the radio front end circuitry, one or more reference signals;
in response to determining that a beam failure occurred for the one or more reference signals,
determine a contention-free (CF) physical random access channel (PRACH) resource for a first beam failure recovery (BFR) request based on a first newly identified beam (NIB), wherein the first NIB is associated with at least one antenna port quasi-collocation parameter;
transmit, using the radio front end circuitry, the first BFR request using the CF PRACH resource via the first NIB;
monitor, for a BFR response, a first search space that is quasi-co-located with the first NIB; and
responsive to detecting the BFR response via a downlink control information (DCI) associated with a physical downlink control channel (PDCCH) in the first search space, wherein the DCI has a cyclic redundancy check (CRC) scrambled by a cell radio network temporary identifier (C-RNTI) or a modulation and coding scheme C-RNTI (MCS-C-RNTI), then
after 28 symbols from a last symbol of the PDCCH, perform PDCCH monitoring in a control resource set (CORESET) with index 0 using the at least one antenna port quasi-collocation parameter.

### Claim 2 (depends on 1)

The UE of claim 1, wherein the first search space corresponds to a recovery Search Space identity (recoverySearchSpaceid).

### Claim 3 (depends on 2)

The UE of claim 2, wherein the processor circuitry is further configured to:
upon not receiving a BFR response and a BFR timer expiring:
transmit, using the radio front end circuitry, a second BFR request using a contention-based PRACH.

### Claim 4 (depends on 3)

The UE of claim 3, wherein the BFR timer is configured by Radio Resource Control (RRC) signaling.

### Claim 5 (depends on 1)

The UE of claim 1, wherein the processor circuitry is further configured to in response to not receiving a BFR response and before a BFR timer expires, retransmit the first BFR request via the first NIB using the radio front end circuitry.

### Claim 6 (depends on 5)

The UE of claim 5, wherein a transmission power for the retransmission of the first BFR request is based on a reference signal of the one or more reference signals that is associated with the first NIB.

### Claim 7 (depends on 1)

The UE of claim 1, wherein the processor circuitry is further configured to, in response to not receiving a BFR response and before a BFR timer expires, retransmit the first BFR request via a second NIB different from the first NIB using the radio front end circuitry.

### Claim 8 (depends on 7)

The UE of claim 7, wherein a transmission power for retransmitting the first BFR request is based on a reference signal of the one or more reference signals that is associated with the second NIB.

### Claim 9

A user equipment (UE), comprising:
a memory configured to store program instructions; and
a processor, upon executing the program instructions, configured to:
receive, from a network node, one or more reference signals;
in response to determining that a beam failure occurred for the one or more reference signals,
determine a contention-free (CF) physical random access channel (PRACH) resource for a beam failure recovery (BFR) request based on a first newly identified beam (NIB), wherein the first NIB is associated with at least one antenna port quasi-collocation parameter; and
transmit a first BFR request to the network node using the determined CF PRACH resource; and
monitor, for a BFR response, a first search space that is quasi-co-located with the first NIB; and
responsive to detecting the BFR response via a downlink control information (DCI) associated with a physical downlink control channel (PDCCH) in the first search space, wherein the DCI has a cyclic redundancy check (CRC) scrambled by a cell radio network temporary identifier (C-RNTI) or a modulation and coding scheme C-RNTI (MCS-C-RNTI), then
after 28 symbols from a last symbol of the PDCCH, perform POOCH monitoring in a control resource set (CORESET) with index 0 using the at least one antenna port quasi-collocation parameter.

### Claim 10 (depends on 9)

The UE of claim 9, wherein the first search space corresponds to a recovery Search Space identity (recoverySearchSpaceid).

### Claim 11 (depends on 10)

The UE of claim 10, wherein the processor is further configured to:
upon not receiving a BFR response and a BFR timer expiring:
transmit a second BFR request using a contention-based PRACH.

### Claim 12 (depends on 9)

The UE of claim 9, wherein, to determine that the beam failure occurred, the processor is further configured to:
determine that a plurality of beam failure instances for the one or more reference signals occurred.

### Claim 13

A baseband processor, configured to:
receive one or more reference signals; and
in response to determining that a beam failure occurred for the one or ore reference signals,
determine, based on a first newly identified beam (NIB), a contention-free (CF) physical random access channel (PRACH) resource for a first beam failure recovery (BM) request, wherein the first NIB is associated with at least one antenna port quasi-collocation parameter;
encode, for transmission via the first NIB, the first BFR request, using the CF PRACH resource;
monitor a first search space that is quasi-co-located with the first NIB for a BFR response; and
when the BM response is detected in the first search space via a downlink control information (DCI) associated with a physical downlink control channel (PDCCH), wherein the DCI has a cyclic redundancy check (CRC) scrambled by a cell radio network temporary identifier (C-RNTI) or a modulation and coding scheme (MCS-C-RNTI), then:
after 28 symbols from a last symbol of the PDCCH, perform PDCCH monitoring in a control resource set (CORESET) with index 0 using the at least one antenna port quasi-collocation parameter.

### Claim 14 (depends on 13)

The baseband processor of claim 13, further configured to: to determine that the beam failure occurred, determine one or more beam failure instances for the one or more reference signals occurred.

### Claim 15 (depends on 14)

The baseband processor of claim 14, further configured to determine that a block error rate (BIER) associated with at least one beam failure instance is above a threshold in order to determine the one or more beam failure instances.

### Claim 16 (depends on 13)

The baseband processor of claim 13, wherein a transmission power for retransmitting the first BFR request is based on a reference signal of the one or more reference signals that is associated with the first NIB.

### Claim 17 (depends on 13)

The baseband processor of claim 13, further configured to, when the BFR response is not received before a block error rate (BLER) timer expires, encode the first BFR request for retransmitting via the first NIB.

### Claim 18 (depends on 17)

The baseband processor of claim 17, wherein the BER timer is configured by Radio Resource Control (RRC) signaling.

### Claim 19 (depends on 13)

The baseband processor of claim 13, further configured to, if the BM response is not received before a block error rate (BUR) tinier expires, encode the first BER request for retransmitting via a second NIB different from the first NIB.

### Claim 20 (depends on 19)

The baseband processor of claim 19, wherein a transmission power for retransmitting the first BER request is based on a reference signal of the one or more reference signals that is associated with the second NIB.