US-12628065-B2 - U2U relay UE-initiated dedicated relay discovery for supporting direct-to-indirect path switch

US12628065B2US 12628065 B2US12628065 B2US 12628065B2US-12628065-B2

Abstract

A UE operates in a system where a source UE communicates using SL communications with a destination UE and detects a SL coverage issue with the sidelink communications between the source and destination UEs. The UE sends, to at least the destination UE, an announcement concerning at least one of the sidelink coverage issue or the UE being available as a relay UE candidate for an indirect path to the destination UE. The destination UE receives the announcement and communicates with the UE to set up and use the indirect path.

Inventors

Vinh Van Phan
Ling Yu
Gyorgy Tamas Wolfner

Assignees

NOKIA TECHNOLOGIES OY

Dates

Publication Date: 20260512
Application Date: 20230818

Claims (5)

1 . A method performed by a relay user equipment (UE) operating in a system where a source UE communicates using sidelink communications with a destination UE, the method comprising: receiving, by the relay UE from a network node, a configuration to perform a detecting operation; in response to receiving the configuration, detecting a sidelink coverage issue with the sidelink communications between the source UE and the destination UE by: monitoring Sidelink Control Information (SCI) transmitted by the source UE for one or more Hybrid Automatic Repeat Request (HARQ) retransmissions directed to the destination UE, obtaining, from the monitored SCI, layer 2 identifiers of the source UE and the destination UE, and determining that the source UE has performed a threshold number of consecutive HARQ retransmissions for which the relay UE fails to detect corresponding sidelink HARQ feedback from the destination UE within a monitoring time window; in response to detecting the sidelink coverage issue, sending, by the relay UE to at least the destination UE, a first announcement including the obtained layer 2 identifiers of the source UE and the destination UE, wherein the first announcement is sent using sidelink unicast, and wherein the first announcement comprises: a notification of the detected sidelink coverage issue, and a sidelink discovery announcement that the relay UE is available as a relay UE candidate for an indirect path between the source UE and the destination UE; in response to sending the first announcement, receiving, from the destination UE, one of: a first response comprising a direct communication request (DCR) message for establishing the indirect path, and a second response comprising a sidelink HARQ feedback; in response to receiving the DCR message, establishing the indirect path by: establishing a first sidelink connection between the relay UE and the destination UE; and sending, from the relay UE to the source UE, the DCR message to establish a second sidelink connection between the relay UE and the source UE; and in response to receiving the sidelink HARQ feedback, sending a second announcement to the source UE, wherein the second announcement comprises: a notification of the detected sidelink coverage issue, a notification that the destination UE is reachable by the relay UE, and a sidelink discovery announcement that the relay UE is available as the relay UE candidate for the indirect path; and based on sending the second announcement, causing the source UE to determine whether to switch to the indirect path based on whether the one or more HARQ retransmissions were triggered by a Discontinuous Transmission (DTX) or a Negative Acknowledgement (NACK).
2 . The method according to claim 1 , further comprising: in response to sending the first announcement, when neither the first response nor the second response is received from the destination UE, performing: repeating the detection of the sidelink coverage issue, and resending, the first announcement to the destination UE.
3 . A relay user equipment (UE), comprising: one or more processors; and one or more memories storing instructions that, when executed by the one or more processors, cause the UE, operating in a system where a source UE communicates using sidelink communication with a destination UE, to perform: receiving, from a network node, a configuration to perform a detecting operation; in response to receiving the configuration, detecting, by the relay UE, a sidelink coverage issue with the sidelink communications between the source UE and the destination UE by: monitoring Sidelink Control Information (SCI) transmitted by the source UE for one or more Hybrid Automatic Repeat Request (HARQ) retransmissions directed to the destination UE, obtaining, from the monitored SCI, layer 2 identifiers of the source UE and the destination UE, and determining that the source UE performs the one or more HARQ retransmissions for which the UE fails to detect corresponding HARQ feedback from the destination UE; in response to detecting the sidelink coverage issue, sending, by the relay UE, to at least the destination UE, a first announcement including the obtained layer 2 identifiers of the source UE and the destination UE, wherein the first announcement is sent using sidelink unicast and the first announcement comprises: a notification of the detected sidelink coverage issue, and a sidelink discovery announcement that the relay UE is available as a relay UE candidate for an indirect path between the source UE and the destination UE; in response to sending the first announcement, receiving, from the destination UE, a first response comprising a direct communication request (DCR) message for establishing the indirect path; in response to receiving the DCR message, establishing the indirect path by: establishing a first sidelink connection between the relay UE and the destination UE; and sending, from the relay UE to the source UE, the DCR message to establish a second sidelink connection between the relay UE and the source UE.
4 . The apparatus according to claim 3 , wherein, in response to the first announcement, when neither the first response nor the second response is received from the destination UE, the one or more memories further store instructions that, when executed by the one or more processors, cause the relay UE at least to perform: repeating the detection of the sidelink coverage issue, and resending the first announcement to the destination UE.
5 . A system comprising: a relay user equipment (UE), comprising: a first processor; and one or more memories storing instructions that, when executed by the first processor, cause the relay UE to perform at least the following: receiving, from a network node, a configuration to perform a detecting operation; in response to receiving the configuration, detecting, by the relay UE, a sidelink coverage issue with the sidelink communications between the source UE and the destination UE by: monitoring Sidelink Control Information (SCI) transmitted by the source UE for one or more Hybrid Automatic Repeat Request (HARQ) retransmissions directed to the destination UE, obtaining, from the monitored SCI, layer 2 identifiers of the source UE and the destination UE, and determining that the source UE performs the one or more HARQ retransmissions for which the UE fails to detect corresponding HARQ feedback from the destination UE; in response to detecting the sidelink coverage issue, sending, by the relay UE, to at least the destination UE, a first announcement including the obtained layer 2 of the source UE and the destination UE, wherein the first announcement is sent using sidelink unicast and the first announcement comprises: a notification of the detected sidelink coverage issue, and a sidelink discovery announcement that the relay UE is available as a relay UE candidate for an indirect path between the source UE and the destination UE; in response to sending the first announcement, receiving, from the destination UE, one of: a first response comprising a direct communication request (DCR) message for establishing the indirect path, and a second response comprising a sidelink HARQ feedback; in response to receiving the DCR message, establishing the indirect path by: establishing a first sidelink connection between the relay UE and the destination UE; and sending, from the relay UE to the source UE, the DCR message to establish a second sidelink connection between the relay UE and the source UE; and a destination (UE), comprising: a second processor; and one or more additional memories storing instructions that, when executed by the second processor, cause the destination UE to perform at least the following: receiving from the relay UE, the first announcement; and in response to receiving the first announcement, sending, to the relay UE, the first response comprising the DCR message for establishing the indirect path between the source UE and the destination UE via the relay UE, and establishing a sidelink connection with the relay UE as part of the indirect path; and in response to receiving the first announcement, sending, by the destination UE to the relay UE, the second response comprising a sidelink Hybrid Automatic Repeat Request (HARQ) feedback.

Description

TECHNICAL FIELD Exemplary embodiments herein relate generally to wireless communications and, more specifically, relates to Proximity Service (ProSe) sidelink communications in general including V2X (vehicle-to-everything), public safety, wearable and personal IoT (Internet of things) or industrial IoT applications. BACKGROUND Vehicle-to-Everything (V2X) is a vehicular communication system that supports the transfer of information from a vehicle to moving parts of the traffic system that may affect the vehicle. The main purpose of V2X technology is to improve road safety, energy savings, and traffic efficiency on the roads. In a V2X system, there is a wireless network, typically a cellular network, that communicates with the wireless devices, typically referred to as user equipment (UEs), that are in or part of the vehicles. Additionally, there is an aspect where the wireless devices communicate between themselves, using a “sidelink”, which is a wireless link between the devices. This allows UEs in the vehicles to communicate, such as for traffic, emergency operations, and more. The V2X is also more complex than just moving vehicles. For example, UE-based road side units (RSUs) are good examples which are considered as designated UE devices that can be deployed for facilitating V2X communications. V2X and the sidelink communications there are one set of technologies under Proximity Service (ProSe) sidelink communications in general, which includes V2X along with public safety, wearable and personal IoT (Internet of things) or industrial IoT applications. As an example, in wearables and personal IoT, a smart phone may act as a UE hub for other devices. As another example, in industrial IoT, there may be such a master device in the middle for facilitating communications between sensor or actuator devices. There are issues in these types of systems where UEs are communicating with other UEs but move out of range of those UEs or otherwise have issues on the sidelink with the other UEs. BRIEF SUMMARY This section is intended to include examples and is not intended to be limiting. In an exemplary embodiment, a method is disclosed that includes for a user equipment operating in a system where a source user equipment communicates using sidelink communications with a destination user equipment, detecting by the user equipment a sidelink coverage issue with the sidelink communications between the source user equipment and the destination user equipment; and sending, by the user equipment in response to the detected sidelink coverage issue, to at least the destination user equipment, an announcement concerning at least one of the sidelink coverage issue or the user equipment being available as a relay user equipment candidate for an indirect path to the destination user equipment. An additional exemplary embodiment includes a computer program, comprising instructions for performing the method of the previous paragraph, when the computer program is run on an apparatus. The computer program according to this paragraph, wherein the computer program is a computer program product comprising a computer-readable medium bearing the instructions embodied therein for use with the apparatus. Another example is the computer program according to this paragraph, wherein the program is directly loadable into an internal memory of the apparatus. An exemplary apparatus includes one or more processors and one or more memories storing instructions that, when executed by the one or more processors, cause the apparatus at least to perform: for a user equipment operating in a system where a source user equipment communicates using sidelink communications with a destination user equipment, detecting by the user equipment a sidelink coverage issue with the sidelink communications between the source user equipment and the destination user equipment; and sending, by the user equipment in response to the detected sidelink coverage issue, to at least the destination user equipment, an announcement concerning at least one of the sidelink coverage issue or the user equipment being available as a relay user equipment candidate for an indirect path to the destination user equipment. An exemplary computer program product includes a computer-readable storage medium bearing instructions that, when executed by an apparatus, cause the apparatus to perform at least the following: for a user equipment operating in a system where a source user equipment communicates using sidelink communications with a destination user equipment, detecting by the user equipment a sidelink coverage issue with the sidelink communications between the source user equipment and the destination user equipment; and sending, by the user equipment in response to the detected sidelink coverage issue, to at least the destination user equipment, an announcement concerning at least one of the sidelink coverage issue or the user equipment being available as a relay user equipment candida