CN112425248B - Enhanced RS transmission of RLM in NR unlicensed spectrum - Google Patents

Abstract

Determining, by the transmitter, whether the LBT procedure performed in the current cycle was successful for the unlicensed spectrum, and performing one of: transmitting the first reference signal(s) over the unlicensed spectrum at a predetermined location in the current cycle in response to the LBT procedure being successful; or in response to the LBT procedure being unsuccessful, attempting to transmit the second reference signal(s) over the unlicensed spectrum within the time window in the current cycle based on other LBT procedure(s) operating within the time window in the current cycle. The receiver detects the first reference signal(s), and: in response to the detection success, performing processing using the first reference signal(s); or in response to unsuccessful detection, blindly detecting the second reference signal(s) over the unlicensed spectrum for a time window in the current cycle.

Description

Enhanced RS transmission of RLM in NR unlicensed spectrum

Technical Field

The present invention relates generally to wireless communications, and more particularly to reference signal usage in unlicensed spectrum.

Background

This section is intended to provide a background or context to the application that is discussed below. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Thus, unless explicitly indicated otherwise herein, what is described in this section is not prior art to the description of the present application and is not admitted to be prior art by inclusion in this section. Abbreviations that may be found in the specification and/or drawings are defined at the beginning of the following detailed description section.

In order to monitor the downlink radio link quality to indicate the out-of-sync/in-sync status indication to higher layers, the UE should measure the Reference Signal (RS) and compare it with thresholds Qout and Qin. See, e.g., 3GPP TS 36.133V15.2.0 (2018-03). When the estimated downlink radio link quality becomes worse than a threshold Qout, the physical layer in the UE will send an out-of-sync (OOS) indication to higher layers. When the estimated downlink radio link quality becomes better than the threshold Qin, the physical layer in the UE will send a synchronization (IS) indication to the higher layers. Thus, RS measurement is a key function of Radio Link Monitoring (RLM) of the physical layer.

RS measurements depend on RS design and transmission. In Long Term Evolution (LTE), the physical layer in the UE should monitor the downlink quality based on cell-specific reference signals (CRSs) transmitted at each Downlink (DL) subframe and evaluate the radio link quality of each radio frame. In the NR design, both a Synchronization Signal Block (SSB) and a channel state information reference signal (CSI-RS) may be used as RLM reference signals. See the final report of 3GPP TSG RAN WG1#91: MCC Support, "Draft Report of 3GPP TSG RAN WG1#91v0.2.0 (Reno, USA,27th November-1st December 2017)", printed on 3GPP TSG RAN WG1 Meeting#92,R1-180xxxx, athens, greece,2018, 2 months 26 to 3 months 2 days. In the case of CSI-RS based RLM, the RLM-RS resources are configured UE-specific RRC. In the case of SSB-based RLM, the RLM-RS resources may be configured UE-specific or cell-specific RRC. Both RLM-RSs are transmitted periodically. Thus, the UE should monitor the downlink quality based on SSB or CSI-RS and evaluate the downlink radio link quality per cycle in the NR system.

In the unlicensed spectrum, before transmitting on the unlicensed carrier, the device should apply Listen Before Talk (LBT) to ensure that the target carrier is idle before accessing the unlicensed carrier. Due to LBT failure, the transmission of RLM-RS may be blocked, resulting in RLM measurement inefficiency. To overcome the uncertainty of channel availability due to LBT, multiFire (MF) uses Discovery RS (DRS) to make RLM measurements in a predictable DRS transmission window (DTxW). See MFA TS 36.133V1.0.0 (2017-12), release 1.0, especially section 7.6, "Radio Link Monitoring". The presence of DRSs can be expected since the gNB (base station in NR) will attempt to periodically transmit DRSs in DTxW. On the other hand, CRS is used for RLM measurements outside of DTxW.

Additional details regarding RLM measurements in unlicensed spectrum are described below.

Disclosure of Invention

This section is intended to be illustrative, and not limiting.

An exemplary embodiment is a method comprising: determining, by the base station, whether a listen-before-talk procedure performed in the current loop was successful for the unlicensed spectrum; and in response to the determination, performing, by the base station, one of: transmitting one or more first reference signals over an unlicensed spectrum at a predetermined location in a current cycle in response to a listen-before-talk procedure being successful; or attempting to transmit one or more second reference signals over the unlicensed spectrum within a time window in the current loop based on at least one other listen-before-talk process operating within the time window of the current loop in response to the listen-before-talk process being unsuccessful.

Another exemplary embodiment comprises a computer program comprising code for performing the method of the preceding paragraph when the computer program is run on a processor. A computer program according to the paragraph, wherein the computer program is a computer program product comprising a computer readable medium carrying computer program code embodied therein for use with a computer.

An example apparatus includes one or more processors and one or more memories including computer program code. The one or more memories and the computer program code are configured to, with the one or more processors, cause the apparatus to at least: determining, by the base station, whether a listen-before-talk procedure performed in the current loop was successful for the unlicensed spectrum; and in response to the determination, performing, by the base station, one of: transmitting one or more first reference signals over an unlicensed spectrum at a predetermined location in a current cycle in response to a listen-before-talk procedure being successful; or in response to the listen before talk procedure being unsuccessful, attempting to transmit one or more second reference signals over the unlicensed spectrum within a time window in the current loop based on at least one other listen before talk procedure operating within the time window in the current loop.

An exemplary computer program product includes a computer readable storage medium bearing computer program code embodied therein for use with a computer. The computer program code includes: determining, by the base station, whether a listen before talk procedure performed in a current loop was successful for the unlicensed spectrum; and code for performing, by the base station, one of: transmitting one or more first reference signals over an unlicensed spectrum at a predetermined location in a current cycle in response to a listen-before-talk procedure being successful; or attempting to transmit one or more second reference signals over the unlicensed spectrum within a time window in the current loop based on at least one other listen-before-talk process operating within the time window of the current loop in response to the listen-before-talk process being unsuccessful.

In another exemplary embodiment, an apparatus includes: means for determining, by the base station, whether a listen before talk procedure performed in a current loop is successful for the unlicensed spectrum; and means for performing, by the base station, one of the following in response to the determination: transmitting one or more first reference signals over an unlicensed spectrum at a predetermined location in a current cycle in response to a listen-before-talk procedure being successful; or attempting to transmit one or more second reference signals over the unlicensed spectrum within a time window in the current loop based on at least one other listen-before-talk process operating within the time window of the current loop in response to the listen-before-talk process being unsuccessful.

In an exemplary embodiment, a method is disclosed that includes: detecting, by the user equipment, one or more first reference signals in the unlicensed spectrum at a predetermined location in the current cycle; and in response to the detecting, performing, by the user equipment, one of: in response to the detection being successful, performing processing using one or more first reference signals; or in response to unsuccessful detection, blindly detecting one or more second reference signals over the unlicensed spectrum for a time window in the current cycle.

Another exemplary embodiment comprises a computer program comprising code for performing the method of the preceding paragraph when the computer program is run on a processor. The computer program according to the paragraph, wherein the computer program is a computer program product comprising a computer readable medium carrying computer program code embodied therein for use with a computer.

An example apparatus includes one or more processors and one or more memories including computer program code. The one or more memories and the computer program code are configured to, with the one or more processors, cause the apparatus to at least: detecting, by the user equipment, one or more first reference signals in the unlicensed spectrum at a predetermined location in the current cycle; and in response to the detecting, performing, by the user equipment, one of: in response to the detection being successful, performing processing using one or more first reference signals; or in response to unsuccessful detection, blindly detecting one or more second reference signals over the unlicensed spectrum for a time window in the current cycle.

An exemplary computer program product includes a computer readable storage medium bearing computer program code embodied therein for use with a computer. The computer program code includes: code for detecting, by a user equipment, one or more first reference signals in an unlicensed spectrum at a predetermined location in a current cycle; and code for performing, by the user equipment, one of: in response to the detection being successful, performing processing using one or more first reference signals; or in response to unsuccessful detection, blindly detecting one or more second reference signals over the unlicensed spectrum for a time window in the current cycle.

In another exemplary embodiment, an apparatus includes: means for detecting, by the user equipment, one or more first reference signals in the unlicensed spectrum at a predetermined location in the current cycle; and means for performing, by the user equipment, one of: in response to the detection being successful, performing processing using one or more first reference signals; or in response to unsuccessful detection, blindly detecting one or more second reference signals over the unlicensed spectrum for a time window in the current cycle.

Drawings

In the 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 one example of RLM-RS transmission in NR-U;

fig. 3 shows one example of the proposed RLM-RS transmission in an NR-U in an exemplary embodiment;

Fig. 4 is a logic flow diagram for enhanced RS transmissions for RLM in an NR unlicensed spectrum performed by a gNB in accordance with an example embodiment;

FIG. 4A is a graphical representation of sub-windows within a time window and possible parameters associated therewith; and

Fig. 5 is a logic flow diagram for enhanced RS transmissions for RLM in an NR unlicensed spectrum performed by a user equipment according to an example embodiment.

Detailed Description

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

3GPP: third generation partnership project

5G: fifth generation of

CRS: cell specific reference signals

CSI-RS: channel state information reference signal

DL: downlink (from base station to UE)

DMRS: demodulation reference signal

DRS: discovery of reference signals

DTxW: DRS transmission window

ENB (or eNodeB): evolved node B (e.g., LTE base station)

GNB (or gNodeB): base station for 5G/NR

I/F: interface

IS: synchronization

L1: physical layer

LBT: listen before talk

LTE: long term evolution

MF：MultiFire

MFA: multiFire alliance

MME: mobility management entity

NCE: network control element

NR: new radio

NR-U: NR unlicensed

N/W: network system

OOS: asynchronous

PDCCH: physical downlink control channel

PDSCH: physical downlink shared channel

RLF: radio link failure

RLM: radio link monitoring

RRC: radio resource control

RRH: remote radio head

RS: reference signal

Rx: receiver with a receiver body

SGW: service gateway

SSB: synchronous signal block

Syn: synchronization

TS: technical specification of

Tx: transmitter

UE: user equipment (e.g., wireless devices, typically mobile devices)

WG: work group

The word "exemplary" is used herein to mean "serving as an example, instance, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described in the detailed description are exemplary embodiments provided to enable persons skilled in the art to make or use the invention and not to limit the scope of the invention which is defined by the claims.

The exemplary embodiments herein describe techniques for enhanced RS transmission for RLM in the NR unlicensed spectrum. After describing the systems in which the exemplary embodiments may be used, additional descriptions of these techniques are presented.

Turning to FIG. 1, a block diagram of one possible and non-limiting exemplary system in which the exemplary embodiments may be practiced is shown. In fig. 1, a User Equipment (UE) 110 is in wireless communication with a wireless network 100. The UE is wireless and typically a mobile device that has access to a wireless network. UE 110 includes one or more processors 120, one or more memories 125, and one or more transceivers 130 interconnected by 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 optic or other optical communications device, or the like. One or more transceivers 130 are connected to one or more antennas 128. The one or more memories 125 include computer program code 123.UE 110 includes RLM module 140, RLM module 140 includes one or both of portions 140-1 and/or 140-2, and RLM module 140 may be implemented in a variety of ways. RLM module 140 may be implemented in hardware as RLM module 140-1, such as being implemented as part of one or more processors 120. RLM module 140-1 may also be implemented as an integrated circuit or by other hardware such as a programmable gate array. In another example, RLM module 140 may be implemented as RLM module 140-2, RLM module 140-2 being implemented as computer program code 123 and executed by one or more processors 120. For example, the one or more memories 125 and the computer program code 123 may be configured, with the one or more processors 120, to cause the user device 110 to perform one or more of the operations described herein. UE 110 communicates with gNB 170 via wireless link 111.

The gNB170 is a base station that provides access to the wireless network 100 by wireless devices, such as the UE 110. The gNB170 is a base station for 5G (also referred to as New Radio (NR)). The gNB170 may also be an eNB (evolved NodeB) base station for LTE (Long term evolution), or any other suitable base station. The gNB170 includes one or more processors 152, one or more memories 155, one or more network interfaces (N/W I/F) 161, and one or more transceivers 160 interconnected by one or more buses 157. Each of the one or more transceivers 160 includes a receiver Rx 162 and a transmitter Tx 163. 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 gNB170 includes the RLM module 150, the RLM module 150 includes one or both of the portions 150-1 and/or 150-2, and the RLM module 150 can be implemented in a variety of ways. RLM module 150 may be implemented in hardware as RLM module 150-1, such as being implemented as part of one or more processors 152. RLM module 150-1 may also be implemented as an integrated circuit or by other hardware such as a programmable gate array. In another example, RLM module 150 may be implemented as RLM module 150-2, RLM module 150-2 being implemented as computer program code 153 and executed by one or more processors 152. For example, the one or more memories 155 and the computer program code 153 are configured, with the one or more processors 152, to cause the gNB170 to perform one or more of the operations as described herein. One or more network interfaces 161 communicate over the network, such as via links 176 and 131. Two or more gnbs 170 communicate using, for example, links 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 optic or other optical communication devices, wireless channels, etc. For example, one or more transceivers 160 may be implemented as a Remote Radio Head (RRH) 195, while other elements of the gNB 170 are physically located in a different location than the RRH, and one or more buses 157 may be implemented in part as fiber optic cables to connect the other elements of the gNB 170 to the RRH 195.

The wireless network 100 may include a Network Control Element (NCE) 190, the NCE 190 may include MME (mobility management entity)/SGW (serving gateway) functionality and provide connectivity to other networks such as a telephone network and/or a data communication network (e.g., the internet). gNB 170 is coupled to NCE 190 via link 131. Link 131 may be implemented as, for example, an S1 interface. The NCE 190 includes one or more processors 175, one or more memories 171, and one or more network interfaces (N/W I/F) 180 interconnected by 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, with the one or more processors 175, to cause the NCE 190 to perform one or more operations.

Wireless network 100 may implement network virtualization, a process that combines hardware and software network resources and network functions into a single software-based management entity (i.e., a virtual network). Network virtualization involves platform virtualization, which is typically combined with resource virtualization. Network virtualization may be categorized as external (combining many networks or portions of networks into virtual units) or internal (providing network-like functionality to software containers on a single system). Note that the virtualized entity resulting from network virtualization is still implemented to some extent using hardware such as processors 152 or 175 and memories 155 and 171, and that such virtualized entity also produces technical effects.

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 a memory function. Processors 120, 152, and 175 may be of any type suitable to the local technical environment, and may include, as non-limiting examples, one or more of the following: general purpose computers, special purpose computers, microprocessors, digital Signal Processors (DSPs), and processors based on a multi-core processor architecture. Processors 120, 152, and 175 may be means for performing functions, such as controlling UE 110, gNB 170, and other functions described herein.

In general, various embodiments of user device 110 may include, but are not limited to, cellular telephones (such as smartphones), tablet computers, 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, tablet computers having wireless communication capabilities, as well as portable devices or terminals that incorporate combinations of such functions.

Having thus introduced a suitable but non-limiting technical background for practicing exemplary embodiments of the present invention, the exemplary embodiments will now be described in greater detail.

The exemplary embodiments relate to an NR-U system. For more details on the NR-U system and the frequency bands that may be involved, see, e.g., Qualcomm Incorporated,"Revised SID on NR-based Access to Unlicensed Spectrum",RP-172021,3GPP TSG RAN Meeting#77,Sapporo, Japanese, 2017, 9, 11-14. This is a 3GPP work item description, also known as "studio on NR-based Access to Unlicensed Spectrum".

As described above, CRS is cell-specific and transmitted at each DL subframe. Since there are multiple transmission samples in one radio frame, it can help ensure that the UE can access the radio link quality at least once per radio frame. Thus RLM measurements in MF dependent on DRS and CRS are feasible.

However, in an NR-U system, the RLM-RS (SSB and CSI-RS) may be transmitted once per cycle at a fixed location. Thus, there may be far fewer potential measurement samples than in MF systems, especially for long periods of RS (e.g., where relatively long periods of time have passed between RSs).

Furthermore, due to LBT failure in the unlicensed spectrum, the transmission of the RS may also be dropped, as shown in fig. 2, which indicates that the UE 100 cannot accurately and quickly track the radio link state. Fig. 2 shows an attempted transmission of RLM-RS over time with period 240, and each cycle 210-1 through 210-5 has a period corresponding to period 240. As shown in FIG. 2, gNB 170 sends RLM-RS transmissions 220 in cycle 210-1 (and cycles 210-4 and 210-5), but once gNB 170 misses the RS transmission point due to the discarded RLM-RS transmissions 230 in cycles 210-2 and 210-3 (e.g., due to a corresponding LBT failure), gNB 170 must wait until the next cycle (in this example cycle 210-4) has no opportunity to transmit. In the case of high LBT blocking rate, UE 110 will not know the radio link state for one or several cycles (in this example, several cycles 210-2 and 210-3). Of course, the UE cannot report the indication to higher layers, in which case Radio Link Failure (RLF) declaration may result.

It is beneficial to introduce enough instances of RS transmissions to do RLM evaluation while attempting to reuse existing RSs in the NR. The exemplary embodiments herein aim to provide an option to provide a number of potential RS transmission opportunities for RLM measurements in the NR unlicensed spectrum.

An overview of exemplary embodiments is now provided. One exemplary embodiment proposes a robust RLM-RS transmission scheme based on LBT results to facilitate RLM measurements to reliably monitor radio link quality. When a legacy periodic RLM-RS transmission 220 is blocked by a discarded RLM-RS transmission 230 (e.g., and corresponding LBT failure), an exemplary RS extension transmission scheme may be triggered to transmit opportunistic RLM-RS in a flexible time window. The detailed design of the proposed RS transmission mainly includes two aspects: (1) RS extension scheme, and (2) flexible time window. These will be briefly described below.

(1) RS expansion scheme

Regarding the RS extension scheme, several RSs are introduced in the scheme for opportunistic transmission. The RS includes not only a conventional RLM-RS but also a temporary RLM-RS (and vice versa).

A) The legacy RLM-RS may be different from the original blocked periodic RS. For example, it may not involve retransmission of the original blocked RS. That is, it may be a retransmission of the original blocked RS or other periodic RS. In other words, it is not limited to the original blocked RS. Instead, it may cover more RSs. For example, if the original blocked RLM-RS is SSB1, the legacy RLM-RS may be SSB1 or SSB2.

B) The temporary RLM-RS may be, for example, a group common DMRS in the PDCCH or a UE-specific DMRS in the PDCCH or a DMRS in the PDSCH.

(2) Flexible time window

With respect to flexible time windows, the time window may be dynamically triggered when certain conditions are met. After LBT blocks one or several consecutive periods of legacy RS transmission, the time window allows the gNB 170 (e.g., or eNB) to transmit opportunistic RSs in the time window.

The time window may be flexible and may be configured as follows:

a) The time window may be a plurality of consecutive time slots or a plurality of non-consecutive sub-windows. Each sub-window may comprise several consecutive time slots.

B) The location of the time window (including the starting location and length) may be configured by RRC signaling. The starting position may be indicated by a relative offset within the subframe position of the conventional periodic RLM-RS. The offset is relative to the time position of the periodic RLM-RS.

Now, an overview has been provided, and more details will be provided. In particular, exemplary proposals are set forth in the context of using a plurality of embodiments.

In the unlicensed spectrum, the RLM-RS transmission will be blocked by LBT failure and corresponding discarded RLM-RS transmission 230, which will affect the performance of RLM measurements. In the present disclosure, an enhanced RS transmission scheme is proposed to overcome LBT problems in the NR unlicensed spectrum (NR-U) by artificially adding multiple transmission points in addition to the normal periodic RS transmission.

In the present disclosure, an exemplary proposed RS transmission scheme will be described in detail, including in particular: when and where to transmit the opportunistic RLM-RS, which opportunistic RLM-RS to transmit, and detailed operation at the gNB 170 and UE 110. To more clearly illustrate the exemplary proposal, fig. 3 shows an example of the proposed RLM-RS transmission in the NR-U.

FIG. 3 shows five cycles 210-n, 210-n+1, 210-n+2, 210-n+3, and 210-n+4, each cycle having the same period 240. The first cycle 210-n has a normal RLM-RS transmission 220. The second loop 210-n+1 and the third loop 210-n+2 have LBT failure and corresponding discarded RLM-RS transmissions 230. The fourth loop 210-n+3 and 210-n+4 has normal RLM-RS transmissions 220. Due to LBT failure and corresponding discarded RLM-RS transmission 230 in the second and third loops 210-n+1, 210-n+2, an offset 310 is used between the time position of the discarded RLM-RS transmission 230 and the time position of the activated time window 330 (e.g., where it starts), and there are opportunistic RLM-RS transmissions 320-1, 320-2 in each time window 330-1, 330-2, respectively.

(1) When and where to transmit opportunistic RLM-RS 320

The position of the time window 330 may be indicated by a relative frame number that is related to the position of the normal periodic RLM-RS signal. The relative frame number may be indicated by an offset 310 from the location of the periodic RLM-RS signal (e.g., discarded RLM-RS transmission 230). In some embodiments, the time window 330 may be represented by an offset 310 and a time length 380 (also referred to as a length 380) of RRC signaling. In fig. 3, the start of the time window 330-1 between cycle #n+1 (210-n+1) and cycle #n+2 (210-n+2) may be indicated by an offset 310 relative to the position of the periodic RLM-RS signal (i.e., the discarded RLM-RS transmission 230) at cycle #n+1 (210-n+1).

The activated time window 330 is implicitly and dynamically triggered only when one or several consecutive normal periodic RLM-RS transmissions 220 fail. For simplicity of illustration, assume that a time window 330 is triggered after one periodic RLM-RS is lost in the transmission opportunity, as shown in fig. 3. In FIG. 3, in response to the failure of the normal periodic RLM-RS transmission 220 at cycle #n+1 (210-n+1), the time window 330-1 between cycle #n+1 (210-n+1) and cycle #n+2 (210-n+2) has been activated. The gNB 170 will attempt to transmit the opportunistic RLM-RS transmission 320-1 (and corresponding signal) within the active time window 330-1. Similarly, in response to the failure of the normal periodic RLM-RS transmission 220 at cycle #n+2 (210-n+2), the time window 330-2 between cycle #n+2 (210-n+2) and cycle #n+3 (210-n+3) has been activated. The gNB 170 will attempt to transmit the opportunistic RLM-RS transmission 320-2 (and corresponding signal) within the active time window 330-2. Note that in this example, the opportunistic RLM-RS transmissions 320-1, 320-2 are at different (time) locations within their respective time windows 330-1, 330-2.

(2) What kind of opportunistic RLM-RS to transmit

In the present disclosure, in an exemplary embodiment, it is proposed to reuse existing DMRS signals as opportunistic RLM-RS signals in addition to configured RLM-RS signals (in some embodiments). Thus, the opportunistic RLM-RS signal may comprise two parts: DMRS signal 360 and configured RLM-RS signal 350. The configured signal 350 may be an SSB 350-1 or CSI-RS 350-2 in an NR system. DMRS signal 360 may be a common group DMRS in PDCCH360-1, or a UE-specific DMRS in PDCCH 360-2, or a DMRS in PDSCH 360-3.

In the active time window 330, if the DMRS signal 360 is transmitted at the PDCCH or PDSCH, there is no need to transmit the configured RLM-RS signal 350. Transmitting only DMRS signal 360 reduces resource overhead to avoid additional configured RLM-RS signal 350 transmissions, as the gNB 170 only needs to transmit DMRS signal 360. Of course, if DMRS signal 360 is not transmitted within active time window 330, gNB 170 needs to transmit configured RLM-RS signal 350.

It should be noted that the normal RLM-RS transmission 220 will also be referred to as a normal RLM-RS signal 220. Similarly, the opportunistic RLM-RS transmission 320 will be referred to as an opportunistic RLM-RS signal 320.

(3) Exemplary detailed operations at gNB 170 and UE 110

At the gNB transmitter, normal RLM-RS or opportunistic RLM-RS transmission will be performed based on the LBT results. When LBT is successful, the gNB170 will periodically transmit the normal RLM-RS at the predefined location. When a normal periodic RLM-RS transmission is blocked by an LBT failure and a corresponding discarded RLM-RS transmission 230, the time window 330 will be triggered (e.g., instantaneously), and when the gNB170 acquires a channel in the time window 330, the gNB170 will send an opportunistic RLM-RS.

At the UE receiver, two layers of detection are used. First, the UE 110 will first detect if the normal periodic RLM-RS 220 is at a predefined location. Then, if the normal RLM-RS 22 is not detected, the UE 110 starts blind detection of opportunistic RLM-RS within a time window. Take fig. 3 as an example. The normal periodic RLM-RS signal at cycle #n (210-n) has been successfully transmitted and the time window 330 is not triggered. But the normal periodic RLM-RS signal transmission at cycle #n+1 (210-n+1) has been blocked by LBT. Thus, the time window 330-1 between cycle #n+1 (210-n+1) and cycle #n+2 (210-n+2) is triggered to begin after one offset 310 from the location of the discarded RLM-RS transmission 230 at cycle #n+1 (210-n+1). The gNB 170 will then attempt to transmit the opportunistic RLM-RS signal 320-1 within the time window 330-1. If LBT is successful in one of the transmission slots within window 330-1, gNB 170 transmits opportunistic RS signal 320. Similarly, the time window 330-2 between cycle #n+2 (210-n+2) and cycle #n+3 (210-n+3) is triggered to begin after one offset 310 from the location of the discarded RLM-RS transmission 230 at cycle #n+2 (210-n+2). The gNB 170 will then attempt to transmit the opportunistic RLM-RS signal 320-2 within time window 330-2. If LBT is successful in one of the transmission slots within window 330-2, gNB 170 transmits opportunistic RS signal 320.

Accordingly, on the UE side, the UE 110 first detects normal periodic RLM-RSs at cycle #n (210-n), cycle #n+1 (210-n+1), and so on. When UE 110 does not detect a normal periodic RLM-RS 220 in cycle #n+1 (210-n+1) (e.g., detection fails), UE 110 will attempt to blindly detect opportunistic RLM-RS 320 within time window 330-1 between cycle #n+1 and cycle #n+2. Similarly, when UE 110 does not detect a normal periodic RLM-RS 220 in cycle #n+2 (210-n+2) (e.g., detection fails), UE 110 will attempt to blindly detect opportunistic RLM-RS 320 within time window 330-2 between cycle #n+2 and cycle #n+3.

Fig. 4 and 5 describe these exemplary operations in more detail.

Turning to fig. 4, a logic flow diagram for enhanced RS transmissions for RLM in NR unlicensed spectrum performed by a gNB in accordance with an exemplary embodiment. The figure illustrates the operation of one or more exemplary methods, the results of execution of computer program instructions implemented on computer-readable memory, functions performed by logic implemented in hardware, and/or interconnecting components for performing the functions according to the exemplary embodiments. The blocks in fig. 4 are assumed to be performed by the gNB (or eNB or other network node), e.g., at least partially under control of RLM module 150.

In block 410, the gNB 170 determines one or more of the following: offset 310, time length 380 of time window 330, N, and window parameter(s). The parameter N is described below, and the window parameter(s) are described with reference to fig. 4A. In block 420, the gNB 170 sends an indication of these determined parameters to the UE 110, representing one or more of: offset 310, time length 380, N, and window parameter(s). The transmission may be via RRC signaling, for example, although other signaling is possible. It should also be noted that offset 310 and time length 380 may be configured via other means such as those described in the technical specification. For example, for the case where the time window 330 occupies the "entirety" of the time period between the end of the LBT process and the beginning of the next cycle 210, one or both of the offset 310 and the time length 380 may also not be necessary. The parameter N and window parameter(s) may also be communicated or defined by other techniques, such as via a technical specification.

In addition, regarding N, while the example of fig. 3 shows the time window 330 triggered after a single LBT failure and corresponding discarded RLM-RS transmission 230, the time window 330 may be triggered after one or several LBT failures and corresponding discarded RLM-RS transmissions 230. In some embodiments, the detailed number N of failed LBTs and corresponding discarded RLM-RS transmissions 230 may be configured by the network. Thus, the parameter N is used in these embodiments to determine whether transmission (fig. 4) or detection (fig. 5) of opportunistic RLM-RS should be performed. That is, if the number of discarded RLM-RS transmissions 230 is less than N, the time window will not be triggered. Note that this is a comparison of the number of discarded RLM-RS transmissions 230 to a threshold N, and that there are many different ways to perform this comparison. In the examples of fig. 4 and 5, the number of discarded RLM-RS transmissions 230 is compared to N, and in response to the number of discarded RLM-RS transmissions 230 being equal to or greater than N, a time window is triggered. Alternatively, however, the time window may be triggered in response to the number of discarded RLM-RS transmissions 230 being greater than (but not equal to) N. In the examples of fig. 4 and 5, the number of discarded RLM-RS transmissions 230 is indicated by a counter shown as "n". In fig. 4, the counter n is set to 0 (zero) in block 423.

The next box in fig. 4 occurs over one or more cycles 210. In block 425, the gNB170 performs the LBT procedure, and in block 430, the gNB170 determines whether the LBT procedure was successful. If so (block 440 = yes (success)), the gNB170 performs a normal RLM-RS transmission 220 (e.g., a periodic transmission at a predefined location) on the unlicensed spectrum for the current loop 210 in block 450. As described above, the RLM-RS may be one or both of a Synchronization Signal Block (SSB) and a channel state information reference signal (CSI-RS). Note that the predefined location is shown in fig. 3 as being at the beginning of the loop 210, which has a period 240. In response to performing the normal RLM-RS transmission 220, the counter n is set (reset) to zero in block 452. The normal RLM-RS transmission 220 may continue for a number of loops 210 as long as the LBT procedure is successful within consecutive loops 210 (i.e., loops 210 that are adjacent to each other in time and consecutive).

In contrast, if the LBT procedure is unsuccessful (block 440 = no (failure)), then in the case of using parameter N, such as received (or otherwise configured, such as via a technical specification), flow proceeds to blocks 445 and 455. Note that if parameter N is not used, flow may proceed from block 440 to block 460 (and tracking of counter N will not also be performed in blocks 423, 445, 452, and 485). For the example of block 445, the gNB 170 increments the counter n (n=n+1), and in block 455, the gNB 170 compares the number of (e.g., consecutive) discarded RLM-RS transmissions 230 to a threshold. The term "contiguous" refers to "in a row" such that multiple discarded RLM-RS transmissions 230 will be discarded in multiple successive loops 210 (i.e., multiple loops 210 in a row in time). In this case, the comparison is between the number of consecutive discarded RLM-RS transmissions 230 (e.g., N) and N, and the timing window 330 is triggered in response to the number of discarded RLM-RS transmissions 230 (e.g., N) being equal to or greater than N. If the number of discarded RLM-RS transmissions 230 (e.g., N) is less than N (block 455 = yes), then flow proceeds to block 425 where another LBT procedure is performed in the new subsequent loop 210.

If the number of discarded RLM-RS transmissions 230 (e.g., N) is equal to or greater than N (block 455 = no), then flow proceeds to block 460. In block 460, the gNB 170 triggers (e.g., activates) the time window 330 for a time length 380 after the offset 310. During the time length 380 of the time window 330, the gNB 170 attempts to transmit (block 470) the opportunistic RLM-RS 320 in the time window 330, and if the LBT procedure is successful, the opportunistic RLM-RS 320 will be transmitted on the unlicensed spectrum. The transmission of the RLM-RS 320 may include one or both of a configured RLM-RS signal 350 and a DMRS signal 360. If there is a transmission of an opportunistic RLM-RS (block 480 = yes), then the counter n is set (reset) to zero in block 485 and flow proceeds to block 425 where another LBT procedure is performed for the new subsequent loop 210. If there is no transmission of opportunistic RLM-RS 320 (block 480 = no), the gNB 170 determines whether the time length 380 has expired. If the time length 380 has expired (block 490 = yes), then flow proceeds to block 495 where no transmission of opportunistic RLM-RS is performed in the time window, since all LBTs are unsuccessful (i.e., any LBT is unsuccessful). Flow then proceeds to block 425 where another LBT process is performed for the new subsequent loop 210 in block 425. If the time length 380 has not expired (block 490 = no), then flow returns to block 470 where the gNB 170 attempts to transmit the opportunistic RLM-RS 320 in the time window 330.

The description above with respect to fig. 4 assumes a single time window 330. However, the time window 330 may be divided into a plurality of sub-windows. This is illustrated by fig. 4A, which is a diagram of a sub-window 415 within the time window 330, and also shows possible parameters associated therewith. The larger time window 330 may include a number of discrete sub-windows 415 (where a discontinuity indicates that there is a time gap between the sub-windows). In this example, there are three sub-windows 415-1, 415-2, and 415-3. The number of sub-windows 415 is shown by the number 417 of sub-windows 417. It should be noted that three are merely exemplary and that more or fewer sub-windows may be used.

Regarding a simple way for indicating the position of the sub-windows 415, the distances between the sub-windows 415 (shown as intervals SP) may be equally spaced and the same length of the sub-windows (shown as length L _SW of the sub-windows) may be designed. Thus, only parameters including the interval (SP) between two sub-windows, the number of sub-windows in a large time window (417), or the length 380 of the time window 330 need to be configured by the network. Many other options are possible. For example, the window parameters may include the length 380 of the large time window 330, the number 417 of sub-windows 415, and the length L _SW of the sub-windows. As another example, the window parameters may include the length 380 of the large time window 330, the length L _SW of each sub-window, and the length (e.g., SP) of the interval 418. The number of sub-windows may be calculated based on this information. Other examples are also possible.

The gNB 170 will perform LBT sequentially in time in the sub-window 415, and if LBT is successful, the gNB 170 will transmit the opportunistic RLM-RS 320 in the sub-window 415. For example, for each iteration through block 470, the gNB 170 attempts to transmit the opportunistic RLM-RS 320 sequentially in time in one of the sub-windows 415. For UE 110, UE 110 will detect opportunistic RLM-RS 320 sequentially in time in sub-window 415.

Referring to FIG. 5, the diagram illustrates operations of one or more exemplary methods, results of execution of computer program instructions implemented on computer-readable memory, functions performed by logic implemented in hardware, and/or interconnecting components for performing the functions according to the exemplary embodiments. The blocks in fig. 5 are assumed to be performed by the user equipment 110, e.g., at least partially under control of the RLM module 140.

In block 520, UE 110 receives an indication of parameters set by the network. These parameters may include one or more of the following: offset 310, time length 380, N, and window parameter(s). As also previously described, some or all of these may not be used or may be defined in other ways, such as via technical specifications. If N is used, UE 110 sets counter N to 0 (zero) in block 522 (n=0).

In block 530, UE 110 detects a normal periodic RLM-RS220 at a predefined location. If RLM-RS220 is detected (block 540 = yes), UE 110 performs normal RLM-RS processing in block 550 and also sets (resets) counter n to zero (n = 0) in block 555. If RLM-RS220 is not detected (block 540 = no), and if N is used, UE 110 increments a counter N (N = N + 1) in block 542 and compares the number of consecutive discarded RLM-RS transmissions 230 (e.g., N) with parameter N in block 545. In this example, if the number of discarded RLM-RS transmissions 230 (e.g., N) is less than N (block 545 = yes), flow proceeds to block 530 where another detection of a normal periodic RLM-RS is performed in a new subsequent loop 210 in block 530. Note that if N is not used, flow may proceed from block 540 to block 560 and blocks 522, 542, 555, and 592, which manipulate the counter, will not be used.

If the number of discarded RLM-RS transmissions 230 (e.g., N) is equal to or greater than N (block 545 = no), then flow proceeds to block 456. In block 560, UE 110 blindly detects opportunistic RLM-RS 320 after offset 310 within time window 330 (with time length 380). If opportunistic RLM-RS 320 is found (block 570 = yes), then UE 110 performs opportunistic RLM-RS processing in block 590 and sets (resets) counter n to zero (n = 0) in block 592. If opportunistic RLM-RS 320 is not found (block 570 = no), UE 110 determines if time length 380 is over. If the time length 380 does not end (block 580 = no), then UE 110 returns to blindly detecting opportunistic RLM-RS 320 within time window 330. As described with reference to fig. 4A, if the time window 330 is divided into sub-windows 415, then for each iteration through block 560, UE 110 will detect opportunistic RLM-RS 320 sequentially in time in one of sub-windows 415. If the time length 380 ends (block 580 = yes), then the blind detection of opportunistic RLM-RS within the time window fails in block 595. UE 110 returns to block 530 and detects a normal periodic RLM-RS220, e.g., in the next cycle 210.

Note that in blocks 550 and 590 of fig. 5, UE 110 performs processing on the reference signal. This process can be described as follows. In RLM, after the UE has measured the RS, UE 110 compares the measured value with thresholds Qout and Qin. When the estimated downlink radio link quality becomes worse than a threshold Qout, the physical layer in the UE will send an out-of-sync (OOS) indication to higher layers. When the estimated downlink radio link quality becomes better than the threshold Qin, the physical layer in the UE will send a synchronization (IS) indication to the higher layers. For higher layers, after receiving enough consecutive OOS indications from L1, a timer is started. If a sufficient consecutive IS indication IS not received before the timer expires, a Radio Link Failure (RLF) IS declared. Statement of RLF results in consideration or taking other actions, such as a handover or other action.

Without limiting the scope, interpretation, or application of the claims appearing below in any way, a technical effect and advantage of one or more of the example embodiments disclosed herein is that the proposed mechanism increases RS measurement samples by transmitting opportunistic RLM-RS in a configured time window when normal RLM-RS is blocked by a failed LBT. Another technical effect and advantage of one or more of the example embodiments disclosed herein is that one time window for opportunistic RLM-RS transmissions is introduced to reduce complexity of UE detection by avoiding blind detection in all subframes between two normal RLM-RS transmission locations. Another technical effect and advantage of one or more example embodiments disclosed herein is that the proposed RS transmission scheme reuses existing DMRS within a time window in which DMRS is present in PDCCH or PDSCH. Thus, by avoiding additional RLM-RS transmissions in the time window, resource overhead may be reduced.

The following are additional examples.

Example 1. A method, comprising:

determining, by the base station, whether a listen-before-talk procedure performed in the current loop was successful for the unlicensed spectrum; and

In response to the determination, one of the following is performed by the base station:

Transmitting one or more first reference signals over the unlicensed spectrum at predetermined locations in the current cycle in response to the listen-before-talk procedure being successful; or alternatively

Responsive to the listen-before-talk procedure being unsuccessful, attempting to transmit one or more second reference signals over the unlicensed spectrum within a time window in the current loop based on at least one other listen-before-talk procedure operating within the time window in the current loop.

Example 2. The method of example 1, further comprising:

The one or more second reference signals are transmitted over the unlicensed spectrum within the time window in response to one of the at least one other listen-before-talk processes operating within the time window of the current cycle being successful.

Example 3. The method of example 1, further comprising

In response to all other listen before talk procedures operating within the time window in the current loop being unsuccessful, the one or more second reference signals are not transmitted over the unlicensed spectrum.

Example 4 the method of any one of examples 1-3, wherein attempting to transmit the one or more second reference signals over the unlicensed spectrum within the time window in the current cycle is performed only in response to a number of discarded first reference signals in a plurality of (e.g., previous) cycles meeting a threshold, the discarded first reference signals resulting from the listen-before-talk procedure being unsuccessful within the plurality of (e.g., previous) cycles. In this case, the previous cycle is the (e.g., consecutive) cycle preceding the current cycle.

Example 5. A method, comprising:

Detecting, by the user equipment, one or more first reference signals in the unlicensed spectrum at a predetermined location in the current cycle; and

In response to the detecting, one of the following is performed by the user equipment:

In response to the detection being successful, performing processing using the one or more first reference signals; or alternatively

One or more second reference signals are blindly detected over the unlicensed spectrum for a time window in the current cycle in response to the detection being unsuccessful.

Example 6. The method of example 5, further comprising:

The one or more second reference signals are processed in response to the blind detection being successful.

Example 7 the method of example 5, further comprising

In response to the blind detection not being successful within the time window in the current cycle, the detection of the one or more first reference signals is performed in the unlicensed spectrum at the predetermined location in a subsequent cycle.

Example 8 the method of any one of examples 5-7, wherein blindly detecting the one or more second reference signals over the unlicensed spectrum within the time window in the current cycle is performed only in response to a number of discarded first reference signals in a plurality of cycles satisfying a threshold, the discarded first reference signals determined by the first reference signals not being detected within the plurality of cycles.

Example 9. The method of any of examples 1-8, wherein the time window is offset from a time position at which a first reference signal in the current loop would have been transmitted if the listen before talk procedure was successful but was discarded due to failure of the listen before talk procedure.

Example 10 the method of example 9, wherein the time window has a length of time, and wherein the method further comprises: an indication of the length of time and the offset is transmitted between the base station and the user equipment.

Example 11 the method of example 10, wherein the transmitting is performed using radio resource control signaling.

Example 12 the method of any one of examples 1 to 11, wherein the one or more first reference signals comprise one or both of: at least one synchronization signal block and at least one channel state information reference signal.

Example 13 the method of any one of examples 1 to 12, wherein the one or more second reference signals comprise one or both of: the configured radio link monitors reference signals and demodulation reference signals.

Example 14. The method of example 13, wherein the demodulation reference signal comprises one or more of: a common set of demodulation reference signals in a physical downlink control channel; a user equipment specific demodulation reference signal in the physical downlink control channel; and demodulation reference signals in a physical downlink shared channel.

Example 15. The method of example 14, wherein the one or more first reference signals are only the demodulation reference signals, not the configured radio link monitoring reference signals.

Example 16 the method of any one of examples 13 or 14, wherein the configured radio link monitoring reference signal comprises one or both of: at least one synchronization signal block and at least one channel state information reference signal.

Example 17 the method of any one of examples 1 to 16, wherein the time window comprises a plurality of non-contiguous sub-windows.

Example 18. A computer program comprising program code for performing the method of any of examples 1 to 17.

Example 19. The computer program of example 18, wherein the computer program is a computer program product comprising a computer readable medium bearing computer program code embodied therein for use with a computer.

Example 20. An apparatus, comprising:

Means for determining, by the base station, whether a listen before talk procedure performed in a current loop is successful for the unlicensed spectrum; and

Means for performing, by the base station in response to the determination, one of:

Transmitting one or more first reference signals over the unlicensed spectrum at predetermined locations in the current cycle in response to the listen-before-talk procedure being successful; or alternatively

Responsive to the listen-before-talk procedure being unsuccessful, attempting to transmit one or more second reference signals over the unlicensed spectrum within a time window in the current loop based on at least one other listen-before-talk procedure operating within the time window in the current loop.

Example 21 the apparatus of example 20, further comprising:

Means for transmitting the one or more second reference signals over the unlicensed spectrum within the time window in response to one of the at least one other listen-before-talk processes operating within the time window of the current cycle being successful.

Example 22 the apparatus of example 20, further comprising

Means for not transmitting the one or more second reference signals over the unlicensed spectrum in response to all other listen-before-talk procedures running within the time window in the current loop being unsuccessful.

Example 23 the apparatus of any one of examples 20-22, wherein attempting to transmit the one or more second reference signals over the unlicensed spectrum within the time window in the current cycle is performed only in response to a number of discarded first reference signals in a plurality of cycles satisfying a threshold, the discarded first reference signals resulting from the listen-before-talk procedure being unsuccessful in the plurality of cycles.

Example 24 an apparatus, comprising:

Means for detecting, by the user equipment, one or more first reference signals in the unlicensed spectrum at a predetermined location in the current cycle; and

Means for performing, by the user equipment, one of:

In response to the detection being successful, performing processing using the one or more first reference signals; or alternatively

One or more second reference signals are blindly detected over the unlicensed spectrum for a time window in the current cycle in response to the detection being unsuccessful.

Example 25 the apparatus of example 24, further comprising:

means for processing the one or more second reference signals in response to the blind detection being successful.

Example 26 the apparatus of example 24, further comprising

Means for performing the detection of the one or more first reference signals in the unlicensed spectrum at the predetermined location in a subsequent cycle in response to the blind detection not being successful within the time window in the current cycle.

Example 27 the apparatus of any one of examples 24 to 25, wherein blindly detecting the one or more second reference signals over the unlicensed spectrum within the time window in the current cycle is performed only in response to a number of discarded first reference signals in a plurality of cycles satisfying a threshold, the discarded first reference signals determined by the first reference signals not being detected within the plurality of cycles.

Example 28 the apparatus of any one of examples 20-27, wherein the time window is offset from time at which a first reference signal in the current loop would have been transmitted if the listen before talk procedure was successful but was discarded due to failure of the listen before talk procedure.

Example 29 the apparatus of example 28, wherein the time window has a length of time, and wherein the apparatus further comprises means for transmitting an indication of the length of time and the offset between the base station and the user equipment.

Example 30 the apparatus of example 29, wherein the transmitting is performed using radio resource control signaling.

Example 31 the apparatus of any one of examples 20 to 30, wherein the one or more first reference signals comprise one or both of: at least one synchronization signal block and at least one channel state information reference signal.

Example 32 the apparatus of any one of examples 20 to 31, wherein the one or more second reference signals comprise one or both of: the configured radio link monitors reference signals and demodulation reference signals.

Example 33 the apparatus of example 32, wherein the demodulation reference signal comprises one or more of: a common set of demodulation reference signals in a physical downlink control channel; a user equipment specific demodulation reference signal in the physical downlink control channel; and demodulation reference signals in a physical downlink shared channel.

Example 34 the apparatus of example 33, wherein the one or more first reference signals are only the demodulation reference signals and not the configured radio link monitoring reference signals.

Example 35 the apparatus of any one of examples 32 or 34, wherein the configured radio link monitoring reference signal comprises one or both of: at least one synchronization signal block and at least one channel state information reference signal.

Example 36 the apparatus of any one of examples 20 to 35, wherein the time window comprises a plurality of non-contiguous sub-windows.

Example 37 a base station comprising examples 20 to 23 and any one of the examples subordinate thereto.

Example 38. A user equipment includes examples 24 to 27 and any of the examples subordinate to these examples.

Example 39 an apparatus, comprising:

One or more processors; and

One or more memories, including computer program code,

The one or more memories and the computer program code are configured to, with the one or more processors, cause the apparatus to perform the method of any of examples 21-17.

Example 40. An apparatus, comprising:

One or more processors; and

One or more memories, including computer program code,

The one or more memories and the computer program code are configured to, with the one or more processors, cause the apparatus to implement an apparatus according to any of examples 20-36.

Embodiments herein may be implemented in software (executed by one or more processors), hardware (e.g., application specific integrated circuits), or a combination of software and hardware. In an example embodiment, software (e.g., application logic, instruction set) is stored on any of a variety of conventional computer-readable media. In the context of this document, a "computer-readable medium" can be any medium or means that can contain, store, communicate, propagate, or transport the instructions for use by or in connection with the instruction execution system, apparatus, or device (such as a computer), an example of which is described and depicted, for example, in fig. 1. A computer-readable medium may include a computer-readable storage medium (e.g., memory 125, 155, 171, or other device) that may be any medium or means that can contain, store, and/or communicate instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer. The computer-readable storage medium does not include a propagated signal.

The different functions discussed herein may be performed in a different order and/or concurrently with each other, if desired. Furthermore, one or more of the above-described functions may be optional or may be combined, if desired.

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 should also be noted herein that while the above describes example embodiments of the invention, these descriptions should not be viewed in a limiting sense. Rather, various modifications and adaptations may be made without departing from the scope of the invention as defined in the appended claims.

Claims (3)

1. A communication method performed by a base station, comprising:

determining whether a listen-before-talk procedure performed in a current loop is successful for an unlicensed spectrum;

Transmitting one or more first reference signals over the unlicensed spectrum at predetermined locations in the current cycle in response to the listen before talk procedure being successful, the one or more first reference signals comprising a synchronization signal block SSB and a channel state information reference signal CSI-RS; and

Attempting to transmit one or more second reference signals over the unlicensed spectrum within a time window in the current cycle, based on at least one other listen-before-talk procedure operating within the time window in the current cycle, the one or more second reference signals including demodulation reference signals DMRS,

Wherein attempting to transmit the one or more second reference signals over the unlicensed spectrum within the time window in the current cycle is performed only in response to a number of discarded first reference signals in a plurality of cycles meeting a threshold, the discarded first reference signals resulting from the listen-before-talk procedure being unsuccessful in the plurality of cycles.

2. The method of claim 1, further comprising:

The one or more second reference signals are transmitted over the unlicensed spectrum within the time window in response to one of the at least one other listen-before-talk processes operating within the time window of the current cycle being successful.

3. The method of claim 1, further comprising:

in response to all other listen before talk procedures operating within the time window in the current loop being unsuccessful, the one or more second reference signals are not transmitted over the unlicensed spectrum.