WO2023165970A1 - Performing a transmission or transmitting a sidelink synchronization signal block - Google Patents

Abstract

Methods and apparatus are disclosed. In an example, a method in a first User Equipment (UE) of transmitting a sidelink synchronization signal block (S-SSB) is disclosed. The method comprises detecting transmission of a first S-SSB in a first time slot on a sidelink channel in unlicensed spectrum, wherein the first S-SSB includes first data, and transmitting, on the sidelink channel in unlicensed spectrum in a second time slot after the first time slot, a second S-SSB, wherein the second S-SSB includes second data that is associated with the first data. The second S-SSB is transmitted in the second time slot if the sidelink channel is available, if the sidelink channel is busy, or without performing a clear channel assessment procedure for transmitting the second S-SSB on the sidelink channel in the second time slot.

Description

PERFORMING A TRANSMISSION OR TRANSMITTING A SIDELINK

SYNCHRONIZATION SIGNAL BLOCK

TECHNICAL FIELD

[0001] Examples of this disclosure relate to performing a transmission, or transmitting a sidelink synchronization signal block (S-SSB).

BACKGROUND

[0002] Sidelink is the name in the 3GPP specifications of the interface used for direct communication between devices, also referred to as device-to-device (D2D) communications. This is in comparison to typical cellular communications in which two devices communicate by means of uplink (UL) and downlink (DL) transmissions. The sidelink interface is sometimes referred to as the PC5 interface. The UL/DL interface is sometimes referred to as the Uu interface.

Synchronization

[0003] The NR sidelink specifications include a distributed protocol used by UEs to share their notion of time and frequency allowing them to synchronize to a common time/frequency reference. This protocol defines a sidelink synchronization signals block (S-SSB) and corresponding transmitter and receiver behavior. The protocol is often referred to as SLSS protocol or S-SSB protocol.

Sidelink signals synchronization block (S-SSB)

[0004] The S-SSB is a sidelink transmission that includes:

• Sidelink synchronization signals (SLSS). The SLSS are synchronization sequences that depend on a SLSS identity (SLSSID).

• A physical sidelink broadcast channel (PSBCH).

[0005] The S-SSB is transmitted in a slot and spans 7 to 14 OFDM symbols, including a last OFDM symbol that is not used, and which constitutes the Guard Period (GP).

[0006] The S-SSB is transmitted periodically according to an S-SSB period (e.g., every 160 ms). It may be transmitted one or multiple times within a period (S-SSB repetitions). The number of repetitions is (pre-)configurable. For simplicity, in the following description of the background we consider a single transmission per period, but the description is also applicable if S-SSB repetitions are used. Although the expression S-SSB repetitions is commonly used, the transmissions may actually differ. For example, the PSBCH contents may vary between repetitions (e.g., if one of the fields includes an indication of the time resource in which it is transmitted); or the demodulation reference signals (DM-RS) may change between repetitions; or the synchronization sequences may vary between repetitions. The key point is that there are multiple transmissions of S-SSB within a single S-SSB period and that they are associated with the same synchronization reference. A receiver could combine the multiple repetitions to improve detection accuracy, etc.

[0007] The SLSS ID (in some cases together with the contents of PSBCH) provides an indication of priority associated with the S-SSB. In the absence of an external, more reliably source of synchronization (GNSS-derived or NW-derived synchronization, configured with higher priority), a UE searches for the S-SSB transmission indicating highest priority and synchronizes to it.

[0008] Typically, a UE is configured with two resources where S-SSB may be transmitted. It typically transmits on one and listens to the other one. In this way it can transmit and receive S-SSB signals within one period (e.g., 160 ms). Among the two resources, which one to use for transmission is determined based on the synchronization status of the transmitting UE (e.g., priority value of the used synchronization reference, etc.) and some (pre-)configured parameters. Reception of S-SSB is attempted in the other resource. The SLSSID used for transmission is typically different from the one(s) a UE may expect to receive (if any is received). In some cases, three resource may be configured, the third one being used by UEs deriving synchronization directly from GNSS.

UE behavior as a transmitter of S-SSB

[0009] A UE may be configured to transmit S-SSB in one of the two resources one or a (pre-)configured number of times per period (e.g., 160 ms) using a value of SLSSID and contents of PSBCH that is determined based on the synchronization status of the transmitter UE.

UE behavior as a receiver of S-SSB [0010] A sidelink UE may be configured to perform reception of S-SSB. The purpose of receiving S-SSB is to determine the synchronization reference used by other UEs in their transmission. Depending on:

• the priorities of the synchronization reference used by the receiver and of the synchronization reference indicated by the received S-SSB;

• and on a measurement of the power of the received S-SSB (i.e., an RSRP measurement), the receiving UE decides whether to keep its current synchronization reference or to switch to the new reference indicated by S-SSB. As explained earlier, a change of synchronization reference in turn affects the behavior of the UE as a transmitter of S-SSB (e.g., it determines the values of SLSSID and the contents of PSBCH to be used for transmission of S-SSB).

[0011] Accurate synchronization is critical for proper operation of the system. This is particularly critical when new UEs appear in the scenario. Lacking any other information about the scenario, they need to acquire synchronization from S-SSB. This typically requires a blind search for S-SSB transmissions. To facilitate the task of the receiver, S-SSB transmissions conform to specific patterns (predefined or (pre-)configured) in terms of periodicity and number of repetitions of S-SSB transmissions.

System level considerations

[0012] The distributed protocol is designed to ensure that different UEs using the same synchronization reference transmit S-SSB at the same time with exactly the same contents, including SLSSID and PSBCH contents. Thus, a receiver typically observes a linear superposition of the signals transmitted from multiple UEs. This is sometimes referred to as receiving an SFN combination of signals.

[0013] It is important to emphasize that proper receiver operation relies on coordinated action by the transmitters. That is, if different transmitters would not transmit at the same time (up to a certain precision), the receiver UE would not observe a linear superposition of signals, but rather interfering signals or an unexpected repetition of signals.

Configuration and pre-configuration

[0014] In cellular systems, the network typically configures some parameters used by the UEs. This configuration is typically signaled by a network (NW) node (e.g., a gNB) to the UE (e.g., using RRC signaling, broadcast signaling such as MIB or SIB, or some other type of signaling). This is applicable to UEs performing sidelink transmissions if they are in coverage of a network.

[0015] UEs that are out of network coverage but participate in sidelink communications, may be provided the corresponding parameters by means of a pre-configuration (e.g., stored in the SIM).

[0016] Unless explicitly stated, the terms configuration, pre-configuration, or (pre-)configuration are used to denote both ways of providing the corresponding configuration/parameters to a UE.

NR operation in unlicensed spectrum

[0017] The 5G NR supports performing uplink and downlink transmissions in unlicensed spectrum since Rel-16. In the following, we describe some technical components for operation in unlicensed spectrum.

Channel access and COT sharing

[0018] In unlicensed spectrum (also occasionally referred to as shared spectrum) the transmission medium (i.e., the channel) is shared by multiple users. To avoid conflicts and collisions of transmissions, channel access procedures are defined (sometimes referred to as procedures for shared spectrum access). The channel access procedure typically involves the following steps:

• Sensing the channel for a certain period to detect whether other equipment (e.g., device, network node, etc.) are transmitting. This is sometimes referred to as performing clear channel assessment (CCA)

• If the channel is sensed as busy (i.e., CCA was unsuccessful or failed), the transmitter does not transmit.

• If the channel is sensed as idle (i.e., CCA was successful), the transmitter makes use of the channel (e.g., transmits the information or signals, etc.)

[0019] The channel is utilized for a certain time, referred to as the channel occupancy time (COT).

[0020] In some cases, different equipment may share a COT. For example:

• Equipment 1 performs CCA and gains access to the channel (i.e., CCA is successful), and performs some transmission. o As part of this transmission, equipment 1 informs equipment 2 that it is the COT is shared by equipment 1.

• The COT shared by equipment 1 gives equipment 2 access to the channel. Equipment 2 performs some transmission. This may end the COT or the COT may be shared back to equipment 1.

[0021] In some other exceptional cases (e.g., for very short transmissions that are sparse in time), a transmitter may be allowed to transmit without performing CCA.

[0022] These procedures allow for different NR nodes (e.g., UEs, base stations, etc.) to share the channel among them but also with devices using other technologies (e.g., WiFi). Examples may be found in 3GPP TS 37.213.

SSB / Discovery burst

[0023] In unlicensed spectrum, all downlink transmissions by the gNB are governed by the channel access rules for the band in use. That includes not only downlink transmissions targeting specific users but also transmissions of system information that are relevant for all users in the system (e.g., initial access information, synchronization signal block (SSB), etc.). [0024] To efficiently utilize channel accesses, several pieces of information are grouped in a discovery burst. A discovery burst may contain a synchronization signal block with synchronization signals and broadcast information (in a physical broadcast channel or PBCH) as well as other type of information (including control information) that is not relevant for this disclosure. A discovery burst is confined to a periodically occurring window and has an associated duty cycle (or maximum duty cycle). For example, the window may occur periodically every T ms and span a maximum of M slots (the slot being a unit of time). The actual discovery burst spans N slots (with N < M) inside that window, starting at any suitable time. This is illustrated in Figure 1, which shows an example of discovery burst for NR operation in unlicensed spectrum.

[0025] There currently exist certain challenge(s). For example, From a transmitter point of view:

• In unlicensed spectrum, channel access is only possible according to some channel access rules that typically involve sensing the channel as idle (e.g. aclear channel assessment procedure). Consequently, the UE may not be able to transmit S-SSB at predefined time instances. In unlicensed spectrum, coordinating simultaneous transmissions is difficult due to the use of channel access procedures (e.g., listen-before-talk, LBT) in the different transmitters.

[0026] From a receiver point of view, not knowing when the S-SSB transmissions may take place greatly increases the complexity of the UE.

SUMMARY

[0027] Certain aspects of the disclosure and their embodiments may provide solutions to the above-mentioned (or other) challenges. For example, examples of this disclosure include methods for transmitting/receiving S-SSB in unlicensed spectrum. The methods may in some examples include multiple transmissions of S-SSB, and/or the use of a window in which S- SSB may be transmitted.

[0028] One aspect of this disclosure provides a method in a first User Equipment (UE) of transmitting a sidelink synchronization signal block (S-SSB). The method comprises detecting transmission of a first S-SSB in a first time slot on a sidelink channel in unlicensed spectrum, wherein the first S-SSB includes first data; and transmitting, on the sidelink channel in unlicensed spectrum in a second time slot after the first time slot, a second S-SSB, wherein the second S-SSB includes second data that is associated with the first data. The second S-SSB is transmitted in the second time slot if the sidelink channel is available, if the sidelink channel is busy, or without performing a clear channel assessment procedure for transmitting the second S-SSB on the sidelink channel in the second time slot.

[0029] Another aspect of this disclosure provides a method in a first User Equipment (UE) of transmitting a sidelink synchronization signal block (S-SSB). The method comprises detecting one or more transmissions of a first S-SSB in one or more respective first time slots on a sidelink channel in unlicensed spectrum; and if the number of detected transmissions of the first S-SSB is lower than a predetermined number of transmissions for the first S-SSB, performing one or more transmissions of the first S-SSB on the sidelink channel in one or more respective second time slots after the one or more first time slots.

[0030] Another aspect of this disclosure provides a method in a first User Equipment (UE) of performing a transmission. The method comprises performing a transmission on a sidelink channel in unlicensed spectrum, determining that an end of the transmission occurs within a window of time slots for sidelink synchronization signal block (S-SSB) transmission on the sidelink channel, and transmitting at least one S-SSB in at least one time slot of the window of time slots.

[0031] Another aspect of this disclosure provides a method in a first User Equipment (UE) of transmitting a sidelink synchronization signal block (S-SSB). The method comprises detecting whether a S-SSB is transmitted on a sidelink channel in unlicensed spectrum in a first time slot of a window of time slots, and if no S-SSB including first data is detected in the first time slot, transmitting one or more S-SSBs including first data on the sidelink channel in one or more second time slots of the window of time slots.

[0032] Another aspect of this disclosure provides apparatus in a first User Equipment (UE) for transmitting a sidelink synchronization signal block (S-SSB), the apparatus comprising a processor and a memory, the memory containing instructions executable by the processor such that the apparatus is operable to detect transmission of a first S-SSB in a first time slot on a sidelink channel in unlicensed spectrum, wherein the first S-SSB includes first data, and transmit, on the sidelink channel in unlicensed spectrum in a second time slot after the first time slot, a second S-SSB, wherein the second S-SSB includes second data that is associated with the first data. The second S-SSB is transmitted in the second time slot if the sidelink channel is available, if the sidelink channel is busy, or without performing a clear channel assessment procedure for transmitting the second S-SSB on the sidelink channel in the second time slot.

[0033] Another aspect of this disclosure provides apparatus in a first User Equipment (UE) for transmitting a sidelink synchronization signal block (S-SSB), the apparatus comprising a processor and a memory, the memory containing instructions executable by the processor such that the apparatus is operable to detect one or more transmissions of a first S SSB in one or more respective first time slots on a sidelink channel in unlicensed spectrum, and if the number of detected transmissions of the first S SSB is lower than a predetermined number of transmissions for the first S SSB, performing one or more transmissions of the first S-SSB on the sidelink channel in one or more respective second time slots after the one or more first time slots.

[0034] Another aspect of this disclosure provides apparatus in a first User Equipment (UE) for performing a transmission, the apparatus comprising a processor and a memory, the memory containing instructions executable by the processor such that the apparatus is operable to perform a transmission on a sidelink channel in unlicensed spectrum, determine that an end of the transmission occurs within a window of time slots for sidelink synchronization signal block (S-SSB) transmission on the sidelink channel, and transmit at least one S-SSB in at least one time slot of the window of time slots.

[0035] Another aspect of this disclosure provides apparatus in a first User Equipment (UE) for transmitting a sidelink synchronization signal block (S-SSB), the apparatus comprising a processor and a memory, the memory containing instructions executable by the processor such that the apparatus is operable to detect whether a S-SSB is transmitted on a sidelink channel in unlicensed spectrum in a first time slot of a window of time slots, and if no S-SSB including first data is detected in the first time slot, transmit one or more S-SSBs including first data on the sidelink channel in one or more second time slots of the window of time slots.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] For a better understanding of examples of the present disclosure, and to show more clearly how the examples may be carried into effect, reference will now be made, by way of example only, to the following drawings in which:

[0037] Figure 1 shows an example of discovery burst for NR operation in unlicensed spectrum;

[0038] Figure 2 depicts a method in accordance with particular embodiments;

[0039] Figure 3 depicts another method in accordance with particular embodiments;

[0040] Figure 4 depicts another method in accordance with particular embodiments;

[0041] Figure 5 depicts another method in accordance with particular embodiments;

[0042] Figure 6 shows examples of transmission of one S-SSB transmission per S-

SSB period and two S-SSB transmissions per S-SSB period;

[0043] Figure 7 shows examples of one S-SSB window with 4 slots per S-SSB period;

[0044] Figure 8 shows an example of transmission of S-SSBs;

[0045] Figure 9 shows another example of transmission of S-SSBs;

[0046] Figure 10 shows further examples of transmission of S-SSBs;

[0047]

[0048]

DETAILED DESCRIPTION [0049] The following sets forth specific details, such as particular embodiments or examples for purposes of explanation and not limitation. It will be appreciated by one skilled in the art that other examples may be employed apart from these specific details. In some instances, detailed descriptions of well-known methods, nodes, interfaces, circuits, and devices are omitted so as not obscure the description with unnecessary detail. Those skilled in the art will appreciate that the functions described may be implemented in one or more nodes using hardware circuitry (e.g. analog and/or discrete logic gates interconnected to perform a specialized function, Application Specific Integrated Circuits (ASICs), Programmable Logic Arrays (PLAs), etc.) and/or using software programs and data in conjunction with one or more digital microprocessors or general purpose computers. Nodes that communicate using the air interface also have suitable radio communications circuitry. Moreover, where appropriate the technology can additionally be considered to be embodied entirely within any form of computer-readable memory, such as solid-state memory, magnetic disk, or optical disk containing an appropriate set of computer instructions that would cause a processor to carry out the techniques described herein.

[0050] Hardware implementation may include or encompass, without limitation, digital signal processor (DSP) hardware, a reduced instruction set processor, hardware (e.g. digital or analogue) circuitry including but not limited to application specific integrated circuit(s) (ASIC) and/or field programmable gate array(s) (FPGA(s)), and (where appropriate) state machines capable of performing such functions.

[0051] In some examples of this disclosure, the channel occupancy time (COT) is shared between UEs transmitting S-SSB corresponding to the same synchronization reference (indicated by means of same or compatible S-SSB slot(s)/SLSSID/PSBCH contents). The COT is shared in a way that new transmitter UEs start transmitting PSBCH, without necessarily having earlier transmitters stop their transmissions. In this way, multiple superpositions of the same signal are observed by a receiver.

[0052] In some examples, the channel occupancy time (COT) is shared between UEs transmitting S-SSB corresponding to different synchronization references (indicated by means of different S-SSB slot(s)/SLSSID/PSBCH contents).

[0053] In some examples, S-SSB transmission in a S-SSB window is performed together with another sidelink (SL) transmission (e.g., PSSCH/PSSCH). [0054] In some examples, a UE performs S-SSB transmission in a S-SSB window if it does not previously detect another S-SSB transmission in the same window (e.g., corresponding to the same synchronization reference).

[0055] Certain embodiments may provide one or more of the following technical advantage(s). For example, from a transmitter point of view, transmissions of S-SSB may include the use of channel access procedures and can deal with busy channel, and/or transmissions of S-SSB from different UEs may be coordinated in spite of using channel access procedures.

[0056] From a receiver point of view, a clear idea of on when to expect reception of S- SSB on a window-level granularity may be provided, and/or improved detection performance in unlicensed bands may be provided, for example as proposed procedures for channel access at the transmitter may improve the chances of multiple UEs transmitting a S-SSB at the same time.

[0057] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.

[0058] Figure 2 depicts a method 200 in accordance with particular embodiments, e.g. a method in a first User Equipment (UE) of transmitting a sidelink synchronization signal block (S-SSB). The method 200 may be performed by a UE or wireless device (e.g. the UE QQ112 or UE QQ200 as described later with reference to Figures 11 and 12 respectively). The method begins at step 202 with detecting transmission of a first S-SSB in a first time slot on a sidelink channel in unlicensed spectrum, wherein the first S-SSB includes first data, and at step 204, transmitting, on the sidelink channel in unlicensed spectrum in a second time slot after the first time slot, a second S-SSB, wherein the second S-SSB includes second data that is associated with the first data. The second S-SSB is transmitted in the second time slot if the sidelink channel is available, if the sidelink channel is busy, or without performing a clear channel assessment procedure for transmitting the second S-SSB on the sidelink channel in the second time slot.

[0059] Thus, for example, if the UE detects a S-SSB that includes the first data, and which is the same S-SSB (or related to it) as the UE wishes to transmit (which it may not be able to transmit in the first time slot, for example if the UE did not gain access to the channel following a CCA/LBT procedure), the UE may assume that the second time slot may contain a repetition of the S-SSB or a related S-SSB (e.g. with a related ID) and thus transmit the S-SSB in the second time slot regardless of whether the sidelink channel in unlicensed spectrum is available or busy (e.g. either not performing CCA/LBT or ignoring the result). Thus the S-SSB transmitted by the UE may be transmitted on top of the other S-SSB transmitted in the second time slot, e.g. by another UE.

[0060] Figure 3 depicts a method 300 in accordance with particular embodiments, e.g. a method in a first User Equipment (UE) of transmitting a sidelink synchronization signal block (S-SSB). The method 300 may be performed by a UE or wireless device (e.g. the UE QQ112 or UE QQ200 as described later with reference to Figures 11 and 12 respectively). The method begins at step 302 with detecting one or more transmissions of a first S-SSB in one or more respective first time slots on a sidelink channel in unlicensed spectrum, and in step 304, if the number of detected transmissions of the first S-SSB is lower than a predetermined number of transmissions for the first S-SSB, performing one or more transmissions of the first S-SSB on the sidelink channel in one or more respective second time slots after the one or more first time slots.

[0061] Figure 4 depicts a method 400 in accordance with particular embodiments, e.g. a method in a first User Equipment (UE) of performing a transmission. The method 400 may be performed by a UE or wireless device (e.g. the UE QQ112 or UE QQ200 as described later with reference to Figures 11 and 12 respectively). The method begins at step 402 with performing a transmission on a sidelink channel in unlicensed spectrum, in step 404, determining that an end of the transmission occurs within a window of time slots for sidelink synchronization signal block (S-SSB) transmission on the sidelink channel, and in step 406, transmitting at least one S-SSB in at least one time slot of the window of time slots.

[0062] Figure 5 depicts a method 500 in accordance with particular embodiments, e.g. a method in a first User Equipment (UE) of transmitting a sidelink synchronization signal block (S-SSB). The method 500 may be performed by a UE or wireless device (e.g. the UE QQ112 or UE QQ200 as described later with reference to Figures 11 and 12 respectively). The method begins at step 502 with detecting whether a S-SSB is transmitted on a sidelink channel in unlicensed spectrum in a first time slot of a window of time slots, and in step 502, if no S-SSB including first data is detected in the first time slot, transmitting one or more S-SSBs including first data on the sidelink channel in one or more second time slots of the window of time slots. [0063] The method 500 may in some examples determine that no S-SSB including first data is detected in the first time slot by detecting a S-SSB and using a corresponding cyclic redundancy (CRC) code for the data carried, e.g., by a PSBCH. For example, if the CRC is different from the expected CRC for the S-SSB with the first data then no S-SSB including first data is detected. Alternatively, for example, no S-SSB may be detected at all in the first time slot. For example, the method may determine that no S-SSB including the first data is detected by failing to detect a sidelink synchronization signal (SLSS).

[0064] Particular example embodiments are now described. Examples of this disclosure provide a procedure for transmitting at least one sidelink synchronization signal block (S-SSB) carrying synchronization signals (e.g., sidelink synchronization signals or SLSS) and/or control information (e.g., a physical sidelink broadcast channel, PSBCH) and the corresponding signaling details.

[0065] In an example, a transmitter procedure combines two features:

• Repetitions, which consist of transmitting the S-SSB multiple times in a given S-SSB period. This is illustrated in Figure 6, which shows examples of transmission of one S-SSB transmission (top, slot in gray) per S-SSB period, and two S-SSB transmissions (bottom, slots in gray) per S-SSB period.

• A S-SSB window, defining the time when transmission of S-SSB is allowed. The S-SSB window is repeated periodically. This is illustrated in Figure 7, which shows examples of one S-SSB window with 4 slots per S-SSB period. In particular, Figure 7 shows examples of one S-SSB transmission (top, slot in gray) per S-SSB window, and two S-SSB transmissions (bottom, slots in gray) per S-SSB window. A UE may be configured with one or several transmissions per S-SSB window.

[0066] As explained above, SL transmissions on an unlicensed channel (e.g. a sidelink channel in unlicensed spectrum) may only take place if the transmitting UE gains access to the channel using some channel access procedure. Typically, for example, this involves detecting that the channel is IDLE (e.g. using a clear channel assessment procedure), meaning that no other device is transmitting in the neighborhood. Thus, it may not be possible to perform a fixed number of transmissions within a group/window of slots.

[0067] If the use of N S-SSB repetitions are configured, in some examples a UE starts transmitting (from the beginning of a slot) as soon as it gains access to the channel and continues transmitting until the slot corresponding to the Nth S-SSB transmission. If the UE gains channel access prior to the first slot, then N S-SSB transmissions are performed. Otherwise, the number may be smaller than N. [0068] If an S-SSB window is used, then the UE may start/stop transmitting at any point (or in any slot) within the window. Typically, the UE may be configured to perform N S-SSB transmissions per S-SSB window. However, unlike simple S-SSB repetitions, the UE need not start in the first slot of the S-SSB window. It does not need to transmit S-SSB until the last slot of the S-SSB window either.

[0069] Nonetheless, the differences between S-SSB repetitions and using S-SSB window are introduced only for the purpose of simplifying the description. The embodiments described herein may be combined in any suitable manner.

Embodiments related to S-SSB repetitions

[0070] In some examples, the system is configured with N slots (per S-SSB period) for S- S SB transmission. We number these slots as

— >> v]- A UE that is expected to transmit S-SSB in these N slots operates in the following way:

• Prior to slot S with i E {1, ... , A], the UE performs clear channel assessment (CCA). o If it succeeds (e.g. the CCA procedure indicates that the channel is idle or available), then it transmits S-SSB using SLSSID value ID1 and PSBCH contents BCH1 in slot S_t o If it fails (e.g. the CCA procedure indicates that the channel is busy or occupied), then it attempts to decode S-SSB using SLSSID value ID1 and PSBCH contents BCH1 in slot S_t (i.e., using the same S-SSB parameters that it would have used for transmission).

• If the UE has transmitted S-SSB in slot S, and/or it has detected S-SSB in slot Si , then it transmits S-SSB using SLSSID value ID1 and PSBCH contents BCH1 in slot S_i+1 (for if i + 1 < N).

[0071] This is illustrated in Figure 8, which shows an example of transmission of S-SSBs. In the first S-SSB period, the UE is successful in performing CCA prior to the first S-SSB slot. Thus, it transmits S-SSB (with SLSSID ID1 and PSBCH contents BCH1) for two slots. In the second S-SSB period, the CCA by the UE fails prior to the first S-SSB slot, but the UE detects S-SSB with SLSSID ID1 and PSBCH contents BCH1 in that slot. Thus, it transmits S-SSB with SLSSID ID1 and PSBCH contents BCH1 in the second slot without performing CCA. In the third S-SSB period, the UE performs CCA prior to each S-SSB slot, but all attempts fail. [0072] In some examples, the N slots are consecutive (though this may not be the case in other examples). This may simplify channel access for transmission of S-SSB in several ways:

• A UE succeeding in CCA can transmit over multiple slots without performing CCA again.

• A UE not succeeding in CCA but detecting S-SSB transmission does not need to perform an additional CCA. This is a form of COT sharing but note that a first UE does not stop transmitting to allow a second UE to transmit. On the contrary, both UEs transmit at the same time.

[0073] Note that with this method, typically the number of UEs transmitting S-SSB increases with i E {1, ... , N}. For example, there may be a single UE transmitting S-SSB in the first slot (e.g., because it is the only one with a successful CCA prior to the first slot). However, other UEs detecting the S-SSB transmission in the first slot may start transmitting in the second slot, and so on.

[0074] In this case, a receiver UE would receive superpositions of the transmitted signals (referred to as SFN combinations of the transmissions). As stated, the number of transmitter UEs would be likely higher for larger values of i. A potential receiver behavior could combine the signals received in different slots or consider performing reception of S-SSB based only one slot (typically the last one, i.e., i = A), or only the p slots (typically the last p, i.e., i E {N — p + 1, N — p + 2, ... , A}), as these include the largest number of contributions. This may result in reduced complexity and/or improved reception for the receiver.

[0075] In some examples, a UE that has detected S-SSB in slot S_t determines based on the detected S-SSB whether or not to transmits S-SSB in slot S_i+1. For example:

• this may depend on an indication in S-SSB (e.g., a field in PSBCH, an SLSSID, etc.). For example, one dedicated field may be used for this purpose; or the behavior may be enabled only if a specific SLSSID is detected, etc. The behavior may be referred as sharing the channel occupancy time.

• this may depend on a measurement on the received S-SSB (e.g., an RSRP or RS SI measurement, a time difference measurement with respect to a time reference, etc). For example, by comparing the measurement to a threshold.

[0076] In some examples, the system is configured so that S-SSB is transmitted in N slots. We number these slots as [S₁₍ S₂, ... , S_w], A UE is expected to transmit S-SSB in half of the N slots. In these N slots, it operates in the following way: • Prior to slot S_t, with i E {1, ... , IV], the UE performs CCA. o If it succeeds, then it transmits S-SSB using SLSSID value ID1 and PSBCH contents BCH1 in slot S_t o If it fails, then it attempts to decode S-SSB using SLSSID value ID2 and PSBCH contents BCH2 in slot S_i+1 (i.e., using different S-SSB parameters from the ones that it would have used for transmission) if i + 1 < N.

• If the UE has detected S-SSB using SLSSID value ID2 and PSBCH contents BCH2 in slot S_i+1, then it transmits S-SSB using SLSSID value ID1 and PSBCH contents BCH1 in slot S_i+2 (if i + 2 < N).

This is illustrated in Figure 9, which shows an example of transmission of S-SSBs. In the first S-SSB period, the UE is successful in performing CCA prior to the first S-SSB slot. Thus, it transmits S-SSB (with SLSSID ID1 and PSBCH contents BCH1) for one slot. In the next (second) slot, the UE detects S-SSB with SLSSID ID2 and PSBCH contents BCH2 in that slot. Thus, it transmits S-SSB with SLSSID ID1 and PSBCH contents BCH1 in the next (third) slot without performing CCA. In the second S-SSB period, the UE does not detect S-SSB with SLSSID ID2 and PSBCH contents BCH2 in any slot. However, it transmits S-SSB with SLSSID ID1 and PSBCH contents BCH1 in the corresponding slots because each corresponding CCA is successful. In the third slot the first CCA attempt fails and there is no transmission in the first slot. However, the UE detects S-SSB with SLSSID ID2 and PSBCH contents BCH2 in the second slot. Thus, it transmits S-SSB with SLSSID ID1 and PSBCH contents BCH1 in the next (third) slot without performing CCA.

[0077] Note that this may include that the two S-SSB resources per period are configured on consecutive resources. This is illustrated in the top of Figure 10, which shows examples of transmission of S-SSBs. Repetitions, if configured, are added two at a time (adjacent to the previous resources or not). This is illustrated in the bottom of Figure 10. In figure 10, the first resource is the gray slot, and the second resource is the check shaded slot.

[0078] In the different embodiments described above, the number of S-SSB transmissions may be limited by (pre-)configuration or by channel access procedures. For example,

• The UE may be expected to transmit S-SSB in as many of the N slots as possible, subject to gaining access to the channel (by means of CCA or using one of the above embodiments). • The UE may be expected to transmit S-SSB in at most M < N slots, subject to gaining access to the channel (by means of CCA or using one of the above embodiments).

Embodiments related to having a S-SSB window

[0079] In some examples, the S-SSB window consists of N slots (consecutive or non- consecutive). We number these slots as [5₁,S₂, ... , S_W]. Consider a UE configured to transmit S-SSB within that window using SLSSID value ID1 and PSBCH contents BCH1. The UE operates as follows:

• Step 1. If the UE has detected S-SSB transmissions that indicate SLSSID value ID1 and PSBCH contents BCH1 from other UEs within the S-SSB window, the UE does not attempt to transmit S-SSB within the window

• Step 2. Otherwise, the UE attempts to transmit S-SSB within the window. That is, prior to slot S_t, with i G {1, ... , A], the UE performs CCA: o If the channel is deemed IDLE, then the UE transmits S-SSB in slot S_t (potentially also in subsequent slots, up to K repetitions). o Otherwise, the UE attempts to receive S-SSB in slot S_t and goes back to Step 1 (for the next slot in the S-SSB window, until it reaches the end of the S-SSB window).

[0080] As explained above, in some cases the SLSSID value may be a function of ID1 and the radio resource (time, frequency) in which S-SSB is transmitted. Similarly, the PSBCH contents may be a function of BCH1 and the radio resource (time, frequency) in which S-SSB transmitted.

[0081] In one variation, a different SLSSID and/or PSBCH contents may be considered in Step 1. For example, detecting a specific S-SSB (i.e., with a defined SLSSID and/or PSBCH contents) or detecting any S-SSB (i.e., with any valid SLSSID and PSBCH contents).

[0082] In some examples, the UE must detect K S-SSB transmissions that indicate SLSSID value ID1 and PSBCH contents BCH1 to skip transmitting further in the window. K may be (pre-)configured.

[0083] In some examples, a UE determines to skip transmitting further in the S-SSB window based on the detected S-SSB transmission(s). For example: • this may depend on an indication in S-SSB (e.g., a field in PSBCH, an SLSSID, etc.). For example, one dedicated field may be used for this purpose; or the behavior may be enabled only if a specific SLSSID is detected, etc.

• whether transmissions can be skipped or not may depend on a measurement on the received S-SSB (e.g., an RSRP or RSSI measurement, a time difference measurement with respect to a time reference, etc). For example, by comparing the measurement to a threshold.

[0084] In some examples, a SL transmission other than S-SSB (a first SL transmission) within the S-SSB window is followed up by a S-SSB transmission. For example, the transmission may end within the S-SSB window. In one dependnt embodiment, the UE performing the first SL transmission also performs the subsequent S-SSB transmission, for example within the same COT or transmit opportunity (TXOP). This could be done for example without again checking whether the channel is available (e.g. performing CCA) as the UE may already have access to the channel. In some examples, a UE receiving the first SL transmission may perform the subsequent S-SSB transmission.

[0085] Other restrictions determining whether the UE performs S-SSB transmission may apply. For example, only UEs configured to transmit S-SSB in that S-SSB window may do it. [0086] In some cases, there may be an explicit indication provided by the UE performing the SL transmission other than S-SSB so that receiving UEs can transmit the subsequent S- SSB, if applicable. That is, the COT may be explicitly shared.

[0087] In other cases, the COT sharing may be implicit. Any UE receiving the SL transmission other than S-SSB may assume that it is allowed to transmit the subsequent S-SSB. [0088] As described earlier, S-SSB transmissions are periodic. Thus, the preceding embodiment may in some examples be limited to periodic SL transmissions other than S-SSB. [0089] All these procedures may be applied to all slots in the S-SSB window; or only to some of them (e.g., all except the last one); or may include some slots outside the S-SSB window (e.g., the slot right before the start of the S-SSB window).

[0090] Figure 11 shows an example of a communication system QQ100 in accordance with some embodiments.

[0091] In the example, the communication system QQ100 includes a telecommunication network QQ102 that includes an access network QQ104, such as a radio access network (RAN), and a core network QQ106, which includes one or more core network nodes QQ108. The access network QQ104 includes one or more access network nodes, such as network nodes QQl lOa and QQl lOb (one or more of which may be generally referred to as network nodes QQ110), or any other similar 3^rd Generation Partnership Project (3GPP) access node or non- 3GPP access point. The network nodes QQ110 facilitate direct or indirect connection of user equipment (UE), such as by connecting UEs QQ112a, QQ112b, QQ112c, and QQ112d (one or more of which may be generally referred to as UEs QQ112) to the core network QQ106 over one or more wireless connections.

[0092] Example wireless communications over a wireless connection include transmitting and/or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and/or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, the communication system QQ100 may include any number of wired or wireless networks, network nodes, UEs, and/or any other components or systems that may facilitate or participate in the communication of data and/or signals whether via wired or wireless connections. The communication system QQ100 may include and/or interface with any type of communication, telecommunication, data, cellular, radio network, and/or other similar type of system.

[0093] The UEs QQ112 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and/or operable to communicate wirelessly with the network nodes QQ110 and other communication devices. Similarly, the network nodes QQ110 are arranged, capable, configured, and/or operable to communicate directly or indirectly with the UEs QQ112 and/or with other network nodes or equipment in the telecommunication network QQ102 to enable and/or provide network access, such as wireless network access, and/or to perform other functions, such as administration in the telecommunication network QQ102.

[0094] In the depicted example, the core network QQ106 connects the network nodes QQ110 to one or more hosts, such as host QQ116. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. The core network QQ106 includes one more core network nodes (e.g., core network node QQ108) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, network nodes, and/or hosts, such that the descriptions thereof are generally applicable to the corresponding components of the core network node QQ108. Example core network nodes include functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-concealing function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Exposure Function (NEF), and/or a User Plane Function (UPF).

[0095] The host QQ116 may be under the ownership or control of a service provider other than an operator or provider of the access network QQ104 and/or the telecommunication network QQ102, and may be operated by the service provider or on behalf of the service provider. The host QQ116 may host a variety of applications to provide one or more services. Examples of such applications include the provision of live and/or pre-recorded audio/video content, data collection services, for example, retrieving and compiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server.

[0096] As a whole, the communication system QQ100 of Figure 11 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution (LTE), and/or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G); wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and/or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and/or any low-power wide-area network (LPWAN) standards such as LoRa and Sigfox.

[0097] In some examples, the telecommunication network QQ102 is a cellular network that implements 3GPP standardized features. Accordingly, the telecommunications network QQ102 may support network slicing to provide different logical networks to different devices that are connected to the telecommunication network QQ102. For example, the telecommunications network QQ102 may provide Ultra Reliable Low Latency Communication (URLLC) services to some UEs, while providing Enhanced Mobile Broadband (eMBB) services to other UEs, and/or Massive Machine Type Communication (mMTC)/Massive loT services to yet further UEs. [0098] In some examples, the UEs QQ112 are configured to transmit and/or receive information without direct human interaction. For instance, a UE may be designed to transmit information to the access network QQ104 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the access network QQ104. Additionally, a UE may be configured for operating in single- or multi-RAT or multi -standard mode. For example, a UE may operate with any one or combination of Wi-Fi, NR (New Radio) and LTE, i.e. being configured for multi-radio dual connectivity (MR-DC), such as E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) New Radio - Dual Connectivity (EN- DC).

[0099] In the example illustrated in Figure 11, the hub QQ114 communicates with the access network QQ104 to facilitate indirect communication between one or more UEs (e.g., UE QQ112c and/or QQ112d) and network nodes (e.g., network node QQl lOb). In some examples, the hub QQ114 may be a controller, router, a content source and analytics node, or any of the other communication devices described herein regarding UEs. For example, the hub QQ114 may be a broadband router enabling access to the core network QQ106 for the UEs. As another example, the hub QQ114 may be a controller that sends commands or instructions to one or more actuators in the UEs. Commands or instructions may be received from the UEs, network nodes QQ110, or by executable code, script, process, or other instructions in the hub QQ114. As another example, the hub QQ114 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data. As another example, the hub QQ114 may be a content source. For example, for a UE that is a VR headset, display, loudspeaker or other media delivery device, the hub QQ114 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which the hub QQ114 then provides to the UE either directly, after performing local processing, and/or after adding additional local content. In still another example, the hub QQ114 acts as a proxy server or orchestrator for the UEs, in particular in if one or more of the UEs are low energy loT devices.

[0100] The hub QQ114 may have a constant/persistent or intermittent connection to the network node QQ110b. The hub QQ114 may also allow for a different communication scheme and/or schedule between the hub QQ114 and UEs (e.g., UE QQ112c and/or QQ112d), and between the hub QQ114 and the core network QQ106. In other examples, the hub QQ114 is connected to the core network QQ106 and/or one or more UEs via a wired connection. Moreover, the hub QQ114 may be configured to connect to an M2M service provider over the access network QQ104 and/or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with the network nodes QQ110 while still connected via the hub QQ114 via a wired or wireless connection. In some embodiments, the hub QQ114 may be a dedicated hub - that is, a hub whose primary function is to route communications to/from the UEs from/to the network node QQ110b. In other embodiments, the hub QQ114 may be a non-dedicated hub - that is, a device which is capable of operating to route communications between the UEs and network node QQ110b, but which is additionally capable of operating as a communication start and/or end point for certain data channels.

[0101] Figure 12 shows a UE QQ200 in accordance with some embodiments. As used herein, a UE refers to a device capable, configured, arranged and/or operable to communicate wirelessly with network nodes and/or other UEs. Examples of a UE include, but are not limited to, a smart phone, mobile phone, cell phone, voice over IP (VoIP) phone, wireless local loop phone, desktop computer, personal digital assistant (PDA), wireless camera, gaming console or device, music storage device, playback appliance, wearable terminal device, wireless endpoint, mobile station, tablet, laptop, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), smart device, wireless customer-premise equipment (CPE), vehiclemounted or vehicle embedded/integrated wireless device, etc. Other examples include any UE identified by the 3rd Generation Partnership Project (3GPP), including a narrow band internet of things (NB-IoT) UE, a machine type communication (MTC) UE, and/or an enhanced MTC (eMTC) UE.

[0102] A UE may support device-to-device (D2D) communication, for example by implementing a 3 GPP standard for sidelink communication, Dedicated Short-Range Communication (DSRC), vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), or vehicle- to-everything (V2X). In other examples, a UE may not necessarily have a user in the sense of a human user who owns and/or operates the relevant device. Instead, a UE may represent a device that is intended for sale to, or operation by, a human user but which may not, or which may not initially, be associated with a specific human user (e.g., a smart sprinkler controller). Alternatively, a UE may represent a device that is not intended for sale to, or operation by, an end user but which may be associated with or operated for the benefit of a user (e.g., a smart power meter).

[0103] The UE QQ200 includes processing circuitry QQ202 that is operatively coupled via a bus QQ204 to an input/output interface QQ206, a power source QQ208, a memory QQ210, a communication interface QQ212, and/or any other component, or any combination thereof. Certain UEs may utilize all or a subset of the components shown in Figure 12. The level of integration between the components may vary from one UE to another UE. Further, certain UEs may contain multiple instances of a component, such as multiple processors, memories, transceivers, transmitters, receivers, etc.

[0104] The processing circuitry QQ202 is configured to process instructions and data and may be configured to implement any sequential state machine operative to execute instructions stored as machine-readable computer programs in the memory QQ210. The processing circuitry QQ202 may be implemented as one or more hardware-implemented state machines (e.g., in discrete logic, field-programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), etc.); programmable logic together with appropriate firmware; one or more stored computer programs, general-purpose processors, such as a microprocessor or digital signal processor (DSP), together with appropriate software; or any combination of the above. For example, the processing circuitry QQ202 may include multiple central processing units (CPUs). The processing circuitry QQ202 may be operable to provide, either alone or in conjunction with other UE QQ200 components, such as the memory QQ210, UE QQ200 functionality. For example, the processing circuitry QQ202 may be configured to cause the UE QQ202 to perform the methods as described with reference to Figure 2, 3, 4 and/or 5.

[0105] In the example, the input/output interface QQ206 may be configured to provide an interface or interfaces to an input device, output device, or one or more input and/or output devices. Examples of an output device include a speaker, a sound card, a video card, a display, a monitor, a printer, an actuator, an emitter, a smartcard, another output device, or any combination thereof. An input device may allow a user to capture information into the UE QQ200. Examples of an input device include a touch-sensitive or presence-sensitive display, a camera (e.g., a digital camera, a digital video camera, a web camera, etc.), a microphone, a sensor, a mouse, a trackball, a directional pad, a trackpad, a scroll wheel, a smartcard, and the like. The presence-sensitive display may include a capacitive or resistive touch sensor to sense input from a user. A sensor may be, for instance, an accelerometer, a gyroscope, a tilt sensor, a force sensor, a magnetometer, an optical sensor, a proximity sensor, a biometric sensor, etc., or any combination thereof. An output device may use the same type of interface port as an input device. For example, a Universal Serial Bus (USB) port may be used to provide an input device and an output device.

[0106] In some embodiments, the power source QQ208 is structured as a battery or battery pack. Other types of power sources, such as an external power source (e.g., an electricity outlet), photovoltaic device, or power cell, may be used. The power source QQ208 may further include power circuitry for delivering power from the power source QQ208 itself, and/or an external power source, to the various parts of the UE QQ200 via input circuitry or an interface such as an electrical power cable. Delivering power may be, for example, for charging of the power source QQ208. Power circuitry may perform any formatting, converting, or other modification to the power from the power source QQ208 to make the power suitable for the respective components of the UE QQ200 to which power is supplied.

[0107] The memory QQ210 may be or be configured to include memory such as random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), magnetic disks, optical disks, hard disks, removable cartridges, flash drives, and so forth. In one example, the memory QQ210 includes one or more application programs QQ214, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data QQ216. The memory QQ210 may store, for use by the UE QQ200, any of a variety of various operating systems or combinations of operating systems.

[0108] The memory QQ210 may be configured to include a number of physical drive units, such as redundant array of independent disks (RAID), flash memory, USB flash drive, external hard disk drive, thumb drive, pen drive, key drive, high-density digital versatile disc (HD-DVD) optical disc drive, internal hard disk drive, Blu-Ray optical disc drive, holographic digital data storage (HDDS) optical disc drive, external mini-dual in-line memory module (DIMM), synchronous dynamic random access memory (SDRAM), external micro-DIMM SDRAM, smartcard memory such as tamper resistant module in the form of a universal integrated circuit card (UICC) including one or more subscriber identity modules (SIMs), such as a USIM and/or ISIM, other memory, or any combination thereof. The UICC may for example be an embedded UICC (eUICC), integrated UICC (iUICC) or a removable UICC commonly known as ‘SIM card.’ The memory QQ210 may allow the UE QQ200 to access instructions, application programs and the like, stored on transitory or non-transitory memory media, to off-load data, or to upload data. An article of manufacture, such as one utilizing a communication system may be tangibly embodied as or in the memory QQ210, which may be or comprise a device-readable storage medium.

[0109] The processing circuitry QQ202 may be configured to communicate with an access network or other network using the communication interface QQ212. The communication interface QQ212 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna QQ222. The communication interface QQ212 may include one or more transceivers used to communicate, such as by communicating with one or more remote transceivers of another device capable of wireless communication (e.g., another UE or a network node in an access network). Each transceiver may include a transmitter QQ218 and/or a receiver QQ220 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth). Moreover, the transmitter QQ218 and receiver QQ220 may be coupled to one or more antennas (e.g., antenna QQ222) and may share circuit components, software or firmware, or alternatively be implemented separately.

[0110] In some embodiments, communication functions of the communication interface QQ212 may include cellular communication, Wi-Fi communication, LPWAN communication, data communication, voice communication, multimedia communication, short-range communications such as Bluetooth, near-field communication, location-based communication such as the use of the global positioning system (GPS) to determine a location, another like communication function, or any combination thereof. Communications may be implemented in according to one or more communication protocols and/or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA), Wideband Code Division Multiple Access (WCDMA), GSM, LTE, New Radio (NR), UMTS, WiMax, Ethernet, transmission control protocol/intemet protocol (TCP/IP), synchronous optical networking (SONET), Asynchronous Transfer Mode (ATM), QUIC, Hypertext Transfer Protocol (HTTP), and so forth.

[0111] Regardless of the type of sensor, a UE may provide an output of data captured by its sensors, through its communication interface QQ212, via a wireless connection to a network node. Data captured by sensors of a UE can be communicated through a wireless connection to a network node via another UE. The output may be periodic (e.g., once every 15 minutes if it reports the sensed temperature), random (e.g., to even out the load from reporting from several sensors), in response to a triggering event (e.g., when moisture is detected an alert is sent), in response to a request (e.g., a user initiated request), or a continuous stream (e.g., a live video feed of a patient).

[0112] As another example, a UE comprises an actuator, a motor, or a switch, related to a communication interface configured to receive wireless input from a network node via a wireless connection. In response to the received wireless input the states of the actuator, the motor, or the switch may change. For example, the UE may comprise a motor that adjusts the control surfaces or rotors of a drone in flight according to the received input or controls a robotic arm performing a medical procedure according to the received input.

[0113] A UE, when in the form of an Internet of Things (loT) device, may be a device for use in one or more application domains, these domains comprising, but not limited to, city wearable technology, extended industrial application and healthcare. Non-limiting examples of such an loT device are devices which are or which are embedded in: a connected refrigerator or freezer, a TV, a connected lighting device, an electricity meter, a robot vacuum cleaner, a voice controlled smart speaker, a home security camera, a motion detector, a thermostat, a smoke detector, a door/window sensor, a flood/moisture sensor, an electrical door lock, a connected doorbell, an air conditioning system like a heat pump, an autonomous vehicle, a surveillance system, a weather monitoring device, a vehicle parking monitoring device, an electric vehicle charging station, a smart watch, a fitness tracker, a head-mounted display for Augmented Reality (AR) or Virtual Reality (VR), a wearable for tactile augmentation or sensory enhancement, a water sprinkler, an animal- or item-tracking device, a sensor for monitoring a plant or animal, an industrial robot, an Unmanned Aerial Vehicle (UAV), and any kind of medical device, like a heart rate monitor or a remote controlled surgical robot. A UE in the form of an loT device comprises circuitry and/or software in dependence on the intended application of the loT device in addition to other components as described in relation to the UE QQ200 shown in Figure 12.

[0114] As yet another specific example, in an loT scenario, a UE may represent a machine or other device that performs monitoring and/or measurements, and transmits the results of such monitoring and/or measurements to another UE and/or a network node. The UE may in this case be an M2M device, which may in a 3GPP context be referred to as an MTC device. As one particular example, the UE may implement the 3GPP NB-IoT standard. In other scenarios, a UE may represent a vehicle, such as a car, a bus, a truck, a ship and an airplane, or other equipment that is capable of monitoring and/or reporting on its operational status or other functions associated with its operation.

[0115] In practice, any number of UEs may be used together with respect to a single use case. For example, a first UE might be or be integrated in a drone and provide the drone’ s speed information (obtained through a speed sensor) to a second UE that is a remote controller operating the drone. When the user makes changes from the remote controller, the first UE may adjust the throttle on the drone (e.g. by controlling an actuator) to increase or decrease the drone’s speed. The first and/or the second UE can also include more than one of the functionalities described above. For example, a UE might comprise the sensor and the actuator, and handle communication of data for both the speed sensor and the actuators.

[0116] Figure 13 shows a network node QQ300 in accordance with some embodiments. As used herein, network node refers to equipment capable, configured, arranged and/or operable to communicate directly or indirectly with a UE and/or with other network nodes or equipment, in a telecommunication network. Examples of network nodes include, but are not limited to, access points (APs) (e.g., radio access points), base stations (BSs) (e.g., radio base stations, Node Bs, evolved Node Bs (eNBs) and NR NodeBs (gNBs)).

[0117] Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling a relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units and/or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS).

[0118] Other examples of network nodes include multiple transmission point (multi-TRP) 5G access nodes, multi -standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, multi-cell/multicast coordination entities (MCEs), Operation and Maintenance (O&M) nodes, Operations Support System (OSS) nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs)), and/or Minimization of Drive Tests (MDTs).

[0119] The network node QQ300 includes processing circuitry QQ302, a memory QQ304, a communication interface QQ306, and a power source QQ308, and/or any other component, or any combination thereof. The network node QQ300 may be composed of multiple physically separate components (e.g., a NodeB component and a RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components. In certain scenarios in which the network node QQ300 comprises multiple separate components (e.g., BTS and BSC components), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeBs. In such a scenario, each unique NodeB and RNC pair, may in some instances be considered a single separate network node. In some embodiments, the network node QQ300 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memory QQ304 for different RATs) and some components may be reused (e.g., a same antenna QQ310 may be shared by different RATs). The network node QQ300 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node QQ300, for example GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z-wave, LoRaWAN, Radio Frequency Identification (RFID) or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node QQ300.

[0120] The processing circuitry QQ302 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and/or encoded logic operable to provide, either alone or in conjunction with other network node QQ300 components, such as the memory QQ304, network node QQ300 functionality.

[0121] In some embodiments, the processing circuitry QQ302 includes a system on a chip (SOC). In some embodiments, the processing circuitry QQ302 includes one or more of radio frequency (RF) transceiver circuitry QQ312 and baseband processing circuitry QQ314. In some embodiments, the radio frequency (RF) transceiver circuitry QQ312 and the baseband processing circuitry QQ314 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital units. In alternative embodiments, part or all of RF transceiver circuitry QQ312 and baseband processing circuitry QQ314 may be on the same chip or set of chips, boards, or units.

[0122] The memory QQ304 may comprise any form of volatile or non-volatile computer- readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and/or any other volatile or non-volatile, non-transitory device-readable and/or computerexecutable memory devices that store information, data, and/or instructions that may be used by the processing circuitry QQ302. The memory QQ304 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and/or other instructions capable of being executed by the processing circuitry QQ302 and utilized by the network node QQ300. The memory QQ304 may be used to store any calculations made by the processing circuitry QQ302 and/or any data received via the communication interface QQ306. In some embodiments, the processing circuitry QQ302 and memory QQ304 is integrated.

[0123] The communication interface QQ306 is used in wired or wireless communication of signaling and/or data between a network node, access network, and/or UE. As illustrated, the communication interface QQ306 comprises port(s)/terminal(s) QQ316 to send and receive data, for example to and from a network over a wired connection. The communication interface QQ306 also includes radio front-end circuitry QQ318 that may be coupled to, or in certain embodiments a part of, the antenna QQ310. Radio front-end circuitry QQ318 comprises filters QQ320 and amplifiers QQ322. The radio front-end circuitry QQ318 may be connected to an antenna QQ310 and processing circuitry QQ302. The radio front-end circuitry may be configured to condition signals communicated between antenna QQ310 and processing circuitry QQ302. The radio front-end circuitry QQ318 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. The radio front-end circuitry QQ318 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters QQ320 and/or amplifiers QQ322. The radio signal may then be transmitted via the antenna QQ310. Similarly, when receiving data, the antenna QQ310 may collect radio signals which are then converted into digital data by the radio front-end circuitry QQ318. The digital data may be passed to the processing circuitry QQ302. In other embodiments, the communication interface may comprise different components and/or different combinations of components.

[0124] In certain alternative embodiments, the network node QQ300 does not include separate radio front-end circuitry QQ318, instead, the processing circuitry QQ302 includes radio front-end circuitry and is connected to the antenna QQ310. Similarly, in some embodiments, all or some of the RF transceiver circuitry QQ312 is part of the communication interface QQ306. In still other embodiments, the communication interface QQ306 includes one or more ports or terminals QQ316, the radio front-end circuitry QQ318, and the RF transceiver circuitry QQ312, as part of a radio unit (not shown), and the communication interface QQ306 communicates with the baseband processing circuitry QQ314, which is part of a digital unit (not shown).

[0125] The antenna QQ310 may include one or more antennas, or antenna arrays, configured to send and/or receive wireless signals. The antenna QQ310 may be coupled to the radio front-end circuitry QQ318 and may be any type of antenna capable of transmitting and receiving data and/or signals wirelessly. In certain embodiments, the antenna QQ310 is separate from the network node QQ300 and connectable to the network node QQ300 through an interface or port.

[0126] The antenna QQ310, communication interface QQ306, and/or the processing circuitry QQ302 may be configured to perform any receiving operations and/or certain obtaining operations described herein as being performed by the network node. Any information, data and/or signals may be received from a UE, another network node and/or any other network equipment. Similarly, the antenna QQ310, the communication interface QQ306, and/or the processing circuitry QQ302 may be configured to perform any transmitting operations described herein as being performed by the network node. Any information, data and/or signals may be transmitted to a UE, another network node and/or any other network equipment.

[0127] The power source QQ308 provides power to the various components of network node QQ300 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). The power source QQ308 may further comprise, or be coupled to, power management circuitry to supply the components of the network node QQ300 with power for performing the functionality described herein. For example, the network node QQ300 may be connectable to an external power source (e.g., the power grid, an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry of the power source QQ308. As a further example, the power source QQ308 may comprise a source of power in the form of a battery or battery pack which is connected to, or integrated in, power circuitry. The battery may provide backup power should the external power source fail.

[0128] Embodiments of the network node QQ300 may include additional components beyond those shown in Figure 13 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and/or any functionality necessary to support the subject matter described herein. For example, the network node QQ300 may include user interface equipment to allow input of information into the network node QQ300 and to allow output of information from the network node QQ300. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for the network node QQ300. [0129] Figure 14 is a block diagram of a host QQ400, which may be an embodiment of the host QQ116 of Figure 11, in accordance with various aspects described herein. As used herein, the host QQ400 may be or comprise various combinations hardware and/or software, including a standalone server, a blade server, a cloud-implemented server, a distributed server, a virtual machine, container, or processing resources in a server farm. The host QQ400 may provide one or more services to one or more UEs.

[0130] The host QQ400 includes processing circuitry QQ402 that is operatively coupled via a bus QQ404 to an input/output interface QQ406, a network interface QQ408, a power source QQ410, and a memory QQ412. Other components may be included in other embodiments. Features of these components may be substantially similar to those described with respect to the devices of previous figures, such as Figures 12 and 13, such that the descriptions thereof are generally applicable to the corresponding components of host QQ400. [0131] The memory QQ412 may include one or more computer programs including one or more host application programs QQ414 and data QQ416, which may include user data, e.g., data generated by a UE for the host QQ400 or data generated by the host QQ400 for a UE. Embodiments of the host QQ400 may utilize only a subset or all of the components shown. The host application programs QQ414 may be implemented in a container-based architecture and may provide support for video codecs (e.g., Versatile Video Coding (VVC), High Efficiency Video Coding (HEVC), Advanced Video Coding (AVC), MPEG, VP9) and audio codecs (e.g., FLAC, Advanced Audio Coding (AAC), MPEG, G.711), including transcoding for multiple different classes, types, or implementations of UEs (e.g., handsets, desktop computers, wearable display systems, heads-up display systems). The host application programs QQ414 may also provide for user authentication and licensing checks and may periodically report health, routes, and content availability to a central node, such as a device in or on the edge of a core network. Accordingly, the host QQ400 may select and/or indicate a different host for over-the-top services for a UE. The host application programs QQ414 may support various protocols, such as the HTTP Live Streaming (HLS) protocol, Real-Time Messaging Protocol (RTMP), Real-Time Streaming Protocol (RTSP), Dynamic Adaptive Streaming over HTTP (MPEG-DASH), etc.

[0132] Figure 15 is a block diagram illustrating a virtualization environment QQ500 in which functions implemented by some embodiments may be virtualized. In the present context, virtualizing means creating virtual versions of apparatuses or devices which may include virtualizing hardware platforms, storage devices and networking resources. As used herein, virtualization can be applied to any device described herein, or components thereof, and relates to an implementation in which at least a portion of the functionality is implemented as one or more virtual components. Some or all of the functions described herein may be implemented as virtual components executed by one or more virtual machines (VMs) implemented in one or more virtual environments QQ500 hosted by one or more of hardware nodes, such as a hardware computing device that operates as a network node, UE, core network node, or host. Further, in embodiments in which the virtual node does not require radio connectivity (e.g., a core network node or host), then the node may be entirely virtualized.

[0133] Applications QQ502 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) are run in the virtualization environment Q400 to implement some of the features, functions, and/or benefits of some of the embodiments disclosed herein.

[0134] Hardware QQ504 includes processing circuitry, memory that stores software and/or instructions executable by hardware processing circuitry, and/or other hardware devices as described herein, such as a network interface, input/output interface, and so forth. Software may be executed by the processing circuitry to instantiate one or more virtualization layers QQ506 (also referred to as hypervisors or virtual machine monitors (VMMs)), provide VMs QQ508a and QQ508b (one or more of which may be generally referred to as VMs QQ508), and/or perform any of the functions, features and/or benefits described in relation with some embodiments described herein. The virtualization layer QQ506 may present a virtual operating platform that appears like networking hardware to the VMs QQ508.

[0135] The VMs QQ508 comprise virtual processing, virtual memory, virtual networking or interface and virtual storage, and may be run by a corresponding virtualization layer QQ506. Different embodiments of the instance of a virtual appliance QQ502 may be implemented on one or more of VMs QQ508, and the implementations may be made in different ways. Virtualization of the hardware is in some contexts referred to as network function virtualization (NFV). NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which can be located in data centers, and customer premise equipment.

[0136] In the context of NFV, a VM QQ508 may be a software implementation of a physical machine that runs programs as if they were executing on a physical, non-virtualized machine. Each of the VMs QQ508, and that part of hardware QQ504 that executes that VM, be it hardware dedicated to that VM and/or hardware shared by that VM with others of the VMs, forms separate virtual network elements. Still in the context of NFV, a virtual network function is responsible for handling specific network functions that run in one or more VMs QQ508 on top of the hardware QQ504 and corresponds to the application QQ502.

[0137] Hardware QQ504 may be implemented in a standalone network node with generic or specific components. Hardware QQ504 may implement some functions via virtualization. Alternatively, hardware QQ504 may be part of a larger cluster of hardware (e.g. such as in a data center or CPE) where many hardware nodes work together and are managed via management and orchestration QQ510, which, among others, oversees lifecycle management of applications QQ502. In some embodiments, hardware QQ504 is coupled to one or more radio units that each include one or more transmitters and one or more receivers that may be coupled to one or more antennas. Radio units may communicate directly with other hardware nodes via one or more appropriate network interfaces and may be used in combination with the virtual components to provide a virtual node with radio capabilities, such as a radio access node or a base station. In some embodiments, some signaling can be provided with the use of a control system QQ512 which may alternatively be used for communication between hardware nodes and radio units.

[0138] Figure 16 shows a communication diagram of a host QQ602 communicating via a network node QQ604 with a UE QQ606 over a partially wireless connection in accordance with some embodiments. Example implementations, in accordance with various embodiments, of the UE (such as a UE QQ112a of Figure 11 and/or UE QQ200 of Figure 12), network node (such as network node QQl lOa of Figure 11 and/or network node QQ300 of Figure 13), and host (such as host QQ116 of Figure 11 and/or host QQ400 of Figure 14) discussed in the preceding paragraphs will now be described with reference to Figure 16.

[0139] Like host QQ400, embodiments of host QQ602 include hardware, such as a communication interface, processing circuitry, and memory. The host QQ602 also includes software, which is stored in or accessible by the host QQ602 and executable by the processing circuitry. The software includes a host application that may be operable to provide a service to a remote user, such as the UE QQ606 connecting via an over-the-top (OTT) connection QQ650 extending between the UE QQ606 and host QQ602. In providing the service to the remote user, a host application may provide user data which is transmitted using the OTT connection QQ650.

[0140] The network node QQ604 includes hardware enabling it to communicate with the host QQ602 and UE QQ606. The connection QQ660 may be direct or pass through a core network (like core network QQ106 of Figure 11) and/or one or more other intermediate networks, such as one or more public, private, or hosted networks. For example, an intermediate network may be a backbone network or the Internet.

[0141] The UE QQ606 includes hardware and software, which is stored in or accessible by UE QQ606 and executable by the UE’s processing circuitry. The software includes a client application, such as a web browser or operator-specific “app” that may be operable to provide a service to a human or non-human user via UE QQ606 with the support of the host QQ602. In the host QQ602, an executing host application may communicate with the executing client application via the OTT connection QQ650 terminating at the UE QQ606 and host QQ602. In providing the service to the user, the UE's client application may receive request data from the host's host application and provide user data in response to the request data. The OTT connection QQ650 may transfer both the request data and the user data. The UE's client application may interact with the user to generate the user data that it provides to the host application through the OTT connection QQ650.

[0142] The OTT connection QQ650 may extend via a connection QQ660 between the host QQ602 and the network node QQ604 and via a wireless connection QQ670 between the network node QQ604 and the UE QQ606 to provide the connection between the host QQ602 and the UE QQ606. The connection QQ660 and wireless connection QQ670, over which the OTT connection QQ650 may be provided, have been drawn abstractly to illustrate the communication between the host QQ602 and the UE QQ606 via the network node QQ604, without explicit reference to any intermediary devices and the precise routing of messages via these devices.

[0143] As an example of transmitting data via the OTT connection QQ650, in step QQ608, the host QQ602 provides user data, which may be performed by executing a host application. In some embodiments, the user data is associated with a particular human user interacting with the UE QQ606. In other embodiments, the user data is associated with a UE QQ606 that shares data with the host QQ602 without explicit human interaction. In step QQ610, the host QQ602 initiates a transmission carrying the user data towards the UE QQ606. The host QQ602 may initiate the transmission responsive to a request transmitted by the UE QQ606. The request may be caused by human interaction with the UE QQ606 or by operation of the client application executing on the UE QQ606. The transmission may pass via the network node QQ604, in accordance with the teachings of the embodiments described throughout this disclosure. Accordingly, in step QQ612, the network node QQ604 transmits to the UE QQ606 the user data that was carried in the transmission that the host QQ602 initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In step QQ614, the UE QQ606 receives the user data carried in the transmission, which may be performed by a client application executed on the UE QQ606 associated with the host application executed by the host QQ602.

[0144] In some examples, the UE QQ606 executes a client application which provides user data to the host QQ602. The user data may be provided in reaction or response to the data received from the host QQ602. Accordingly, in step QQ616, the UE QQ606 may provide user data, which may be performed by executing the client application. In providing the user data, the client application may further consider user input received from the user via an input/output interface of the UE QQ606. Regardless of the specific manner in which the user data was provided, the UE QQ606 initiates, in step QQ618, transmission of the user data towards the host QQ602 via the network node QQ604. In step QQ620, in accordance with the teachings of the embodiments described throughout this disclosure, the network node QQ604 receives user data from the UE QQ606 and initiates transmission of the received user data towards the host QQ602. In step QQ622, the host QQ602 receives the user data carried in the transmission initiated by the UE QQ606.

[0145] One or more of the various embodiments improve the performance of OTT services provided to the UE QQ606 using the OTT connection QQ650, in which the wireless connection QQ670 forms the last segment. More precisely, the teachings of these embodiments may improve the transmission of S-SSB and thereby provide benefits such as more reliable S-SSB decoding, improved synchronization, etc.

[0146] In an example scenario, factory status information may be collected and analyzed by the host QQ602. As another example, the host QQ602 may process audio and video data which may have been retrieved from a UE for use in creating maps. As another example, the host QQ602 may collect and analyze real-time data to assist in controlling vehicle congestion (e.g., controlling traffic lights). As another example, the host QQ602 may store surveillance video uploaded by a UE. As another example, the host QQ602 may store or control access to media content such as video, audio, VR or AR which it can broadcast, multicast or unicast to UEs. As other examples, the host QQ602 may be used for energy pricing, remote control of non-time critical electrical load to balance power generation needs, location services, presentation services (such as compiling diagrams etc. from data collected from remote devices), or any other function of collecting, retrieving, storing, analyzing and/or transmitting data.

[0147] In some examples, a measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection QQ650 between the host QQ602 and UE QQ606, in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connection may be implemented in software and hardware of the host QQ602 and/or UE QQ606. In some embodiments, sensors (not shown) may be deployed in or in association with other devices through which the OTT connection QQ650 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software may compute or estimate the monitored quantities. The reconfiguring of the OTT connection QQ650 may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not directly alter the operation of the network node QQ604. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling that facilitates measurements of throughput, propagation times, latency and the like, by the host QQ602. The measurements may be implemented in that software causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connection QQ650 while monitoring propagation times, errors, etc.

[0148] This disclosure includes the following enumerated embodiments:

1. A method in a first User Equipment (UE) of transmitting a sidelink synchronization signal block (S-SSB), the method comprising: detecting one or more transmissions of a first S-SSB in one or more respective first time slots on a sidelink channel in unlicensed spectrum; and if the number of detected transmissions of the first S-SSB is lower than a predetermined number of transmissions for the first S-SSB, performing one or more transmissions of the first S-SSB on the sidelink channel in one or more respective second time slots after the one or more first time slots.

2. The method of embodiment 1, comprising performing one or more transmissions of the first S-SSB in one or more respective second time slots after the one or more first time slots until the predetermined number of transmissions of the first S-SSB have been performed. 3. The method of embodiment 1 or 2, wherein detecting one or more transmissions of a first S-SSB in one or more respective first time slots on a sidelink channel in unlicensed spectrum comprises detecting the one or more transmissions of the first S-SSB from one or more other UEs.

4. The method of any of embodiments 1 to 3, wherein the one or more transmissions of the first S-SSB on the sidelink channel in one or more respective second time slots are performed if the sidelink channel is available, if the sidelink channel is busy, or without performing a clear channel assessment procedure for one or more transmissions on the sidelink channel in one or more respective second time slots.

5. The method of any of embodiments 1 to 4, comprising: performing a clear channel assessment procedure for one or more transmissions on the sidelink channel in one or more of the one or more first time slots; and determining that the channel is busy in the one or more of the one or more first time slots.

6. The method of any of embodiments 1 to 5, wherein the first S-SSB is transmitted simultaneously with a transmission of the second S-SSB by at least one other UE in the one or more second time slots.

7. The method of any of embodiments 1 to 6, wherein one or more first time slots and/or the one or more second time slots are consecutive time slots.

8. The method of any of embodiments 1 to 7, wherein the one or more first time slots and the one or more second time slots comprise time slots in a window of time slots for S-SSB transmissions.

9. The method of embodiment 8, wherein the window of time slots occurs periodically.

10. The method of any of embodiments 1 to 9, wherein detecting the one or more transmissions of the first S-SSB in the one or more first time slots comprises successfully decoding the one or more transmissions of the first S-SSB received in the one or more first time slots.

11. The method of any of embodiments 1 to 10, wherein performing the one or more transmissions of the first S-SSB in the one or more second time slots is performed after determining that an indication in the first S-SSB indicates that the first UE should transmit the second S-SSB in the one or more second time slots, and/or after determining that a signal strength measurement of the first S-SSB in at least one of the one or more first time slots is lower than a first threshold.

12. Apparatus in a first User Equipment (UE) for transmitting a sidelink synchronization signal block (S-SSB), the apparatus comprising a processor and a memory, the memory containing instructions executable by the processor such that the apparatus is operable to: in a first User Equipment (UE) of transmitting a sidelink synchronization signal block (S- SSB), the method comprising: detect one or more transmissions of a first S SSB in one or more respective first time slots on a sidelink channel in unlicensed spectrum; and if the number of detected transmissions of the first S SSB is lower than a predetermined number of transmissions for the first S SSB, performing one or more transmissions of the first S-SSB on the sidelink channel in one or more respective second time slots after the one or more first time slots.

13. The apparatus of embodiment 12, wherein the memory contains instructions executable by the processor such that the apparatus is operable to perform the method of any of embodiments 2 to 11.

[0149] Although the computing devices described herein (e.g., UEs, network nodes, hosts) may include the illustrated combination of hardware components, other embodiments may comprise computing devices with different combinations of components. It is to be understood that these computing devices may comprise any suitable combination of hardware and/or software needed to perform the tasks, features, functions and methods disclosed herein. Determining, calculating, obtaining or similar operations described herein may be performed by processing circuitry, which may process information by, for example, converting the obtained information into other information, comparing the obtained information or converted information to information stored in the network node, and/or performing one or more operations based on the obtained information or converted information, and as a result of said processing making a determination. Moreover, while components are depicted as single boxes located within a larger box, or nested within multiple boxes, in practice, computing devices may comprise multiple different physical components that make up a single illustrated component, and functionality may be partitioned between separate components. For example, a communication interface may be configured to include any of the components described herein, and/or the functionality of the components may be partitioned between the processing circuitry and the communication interface. In another example, non-computationally intensive functions of any of such components may be implemented in software or firmware and computationally intensive functions may be implemented in hardware.

[0150] In certain embodiments, some or all of the functionality described herein may be provided by processing circuitry executing instructions stored on in memory, which in certain embodiments may be a computer program product in the form of a non-transitory computer- readable storage medium. In alternative embodiments, some or all of the functionality may be provided by the processing circuitry without executing instructions stored on a separate or discrete device-readable storage medium, such as in a hard-wired manner. In any of those particular embodiments, whether executing instructions stored on a non-transitory computer- readable storage medium or not, the processing circuitry can be configured to perform the described functionality. The benefits provided by such functionality are not limited to the processing circuitry alone or to other components of the computing device, but are enjoyed by the computing device as a whole, and/or by end users and a wireless network generally.

Claims

1. A method in a first User Equipment (UE) of transmitting a sidelink synchronization signal block (S-SSB), the method comprising: detecting transmission of a first S-SSB in a first time slot on a sidelink channel in unlicensed spectrum, wherein the first S-SSB includes first data; and transmitting, on the sidelink channel in unlicensed spectrum in a second time slot after the first time slot, a second S-SSB, wherein the second S-SSB includes second data that is associated with the first data, wherein the second S-SSB is transmitted in the second time slot if the sidelink channel is available, if the sidelink channel is busy, or without performing a clear channel assessment procedure for transmitting the second S-SSB on the sidelink channel in the second time slot.

2. The method of claim 1, comprising: performing a channel access procedure for gaining access to the sidelink channel in a third time slot earlier than the first time slot; if the channel access procedure indicates that the sidelink channel is available, transmitting a third S-SSB including third data in the third time slot; and if the channel access procedure indicates that the sidelink channel is busy, not transmitting in the third time slot.

3. The method of claim 2, wherein the third, first and second time slots are consecutive time slots.

4. The method of claim 2 or 3, wherein: the third data is associated with or related to the second data; the third data is the same as the second data; and/or the third data comprises a S-SSB identifier (ID) and/or a physical sidelink broadcast channel (PSBCH).

5. The method of any of claims 1 to 4, comprising: performing a clear channel assessment procedure for a transmission on the sidelink channel in the first time slot; and determining that the clear channel assessment procedure for a transmission on the sidelink channel in the first time slot indicates that the channel is busy.

6. The method of any of claims 1 to 5, wherein the second S-SSB is transmitted simultaneously with a transmission of the second S-SSB by at least one other UE in the second time slot.

7. The method of any of claims 1 to 6, wherein the first data comprises a first S-SSB identifier (ID) and/or a first physical sidelink broadcast channel (PSBCH), and/or the second data comprises a second S-SSB ID and/or a second PSBCH.

8. The method of claim 7, wherein the second S-SSB ID is the same as the first S-SSB ID or is a modified first S-SSB ID.

9. The method of any of claims 1 to 8, wherein the first and second time slots are consecutive time slots.

10. The method of any of claims 1 to 9, comprising repeating the transmission of the second S-SSB in one or more further time slots after the second time slot.

11. The method of claim 10, wherein the one or more further time slots are consecutive with the second time slot.

12. The method of any of claim 10 or 11, wherein the transmission of the second S-SSB is repeated in the one or more further time slots after the second time slot if the sidelink channel is available, if the sidelink channel is busy, or without performing a clear channel assessment procedure for transmitting the second S-SSB on the sidelink channel in the one or more further time slots.

13. The method of any of claims 1 to 12, wherein the first and second time slots comprise time slots in a window of time slots for S-SSB transmissions.

14. The method of claim 13, wherein the window of time slots occurs periodically.

15. The method of any of claims 1 to 14, wherein detecting the first S-SSB in the first time slot on a sidelink channel in unlicensed spectrum comprises successfully decoding a Physical Sidelink Broadcast Channel (PSBCH) in the first S-SSB received in the first time slot.

16. The method of any of claims I to 15, wherein transmitting the second S-SSB is performed after determining that an indication in the first S-SSB indicates that the first UE should transmit the second S-SSB in the second time slot, and/or after determining that a signal strength measurement of the first S-SSB in the first time slot is lower than a first threshold.

17. A method in a first User Equipment (UE) of performing a transmission, the method comprising: performing a transmission on a sidelink channel in unlicensed spectrum; determining that an end of the transmission occurs within a window of time slots for sidelink synchronization signal block (S-SSB) transmission on the sidelink channel; and transmitting at least one S-SSB in at least one time slot of the window of time slots.

18. The method of claim 17, wherein the S-SSB is transmitted in the at least one time slot of the window of time slots without performing a clear channel assessment procedure for transmitting the at least one S-SSB in at least one time slot of the window of time slots.

19. The method of claim 17 or 18, wherein the at least one time slot of the window of time slots is after the end of the transmission.

20. The method of any of claims 17 to 19, wherein the transmission is a transmission other than a S-SSB transmission.

21. The method of any of claims 17 to 20, wherein the at least one S-SSB is transmitted within a transmit opportunity (TXOP) or channel occupancy time (COT) for transmitting the transmission on the sidelink channel in unlicensed spectrum.

22. The method of any of claims 17 to 21, comprising, before performing the transmission on the sidelink channel in unlicensed spectrum, performing a clear channel assessment procedure for a transmission on the sidelink channel in unlicensed spectrum, and wherein the transmission is performed if the clear channel assessment procedure indicates that the sidelink channel is available.

23. A method in a first User Equipment (UE) of transmitting a sidelink synchronization signal block (S-SSB), the method comprising: detecting whether a S-SSB is transmitted on a sidelink channel in unlicensed spectrum in a first time slot of a window of time slots; and if no S-SSB including first data is detected in the first time slot, transmitting one or more S-SSBs including first data on the sidelink channel in one or more second time slots of the window of time slots.

24. The method of claim 23, wherein transmitting the one or more S-SSBs is performed if no S-SSB including any data is detected in the first time slot.

25. The method of claim 23 or 24, wherein the first time slot and the one or more second time slots are consecutive time slots.

26. The method of any of claims 23 to 25, wherein detecting whether the S-SSB is transmitted on the sidelink channel in the first time slot comprises detecting whether the S-SSB including fist data is transmitted on the sidelink channel in the first time slot.

27. The method of any of claims 23 to 26, wherein the first data comprises a first S-SSB identifier (ID) and/or a first physical sidelink broadcast channel (PSBCH).

28. A computer program comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out a method according to any of claims 1 to 27.

29. A carrier containing a computer program according to claim 28, wherein the carrier comprises one of an electronic signal, optical signal, radio signal or computer readable storage medium.

30. A computer program product comprising non transitory computer readable media having stored thereon a computer program according to claim 28.

31. Apparatus in a first User Equipment (UE) for transmitting a sidelink synchronization signal block (S-SSB), the apparatus comprising a processor and a memory, the memory containing instructions executable by the processor such that the apparatus is operable to: detect transmission of a first S-SSB in a first time slot on a sidelink channel in unlicensed spectrum, wherein the first S-SSB includes first data; and transmit, on the sidelink channel in unlicensed spectrum in a second time slot after the first time slot, a second S-SSB, wherein the second S-SSB includes second data that is associated with the first data, wherein the second S-SSB is transmitted in the second time slot if the sidelink channel is available, if the sidelink channel is busy, or without performing a clear channel assessment procedure for transmitting the second S-SSB on the sidelink channel in the second time slot.

32. The apparatus of claim 31, wherein the memory contains instructions executable by the processor such that the apparatus is operable to perform the method of any of claims 2 to 16.

33. Apparatus in a first User Equipment (UE) for performing a transmission, the apparatus comprising a processor and a memory, the memory containing instructions executable by the processor such that the apparatus is operable to: perform a transmission on a sidelink channel in unlicensed spectrum; determine that an end of the transmission occurs within a window of time slots for sidelink synchronization signal block (S-SSB) transmission on the sidelink channel; and transmit at least one S-SSB in at least one time slot of the window of time slots.

34. The apparatus of claim 33, wherein the memory contains instructions executable by the processor such that the apparatus is operable to perform the method of any of claims 18 to 22.

35. Apparatus in a first User Equipment (UE) for transmitting a sidelink synchronization signal block (S-SSB), the apparatus comprising a processor and a memory, the memory containing instructions executable by the processor such that the apparatus is operable to: detect whether a S-SSB is transmitted on a sidelink channel in unlicensed spectrum in a first time slot of a window of time slots; and if no S-SSB including first data is detected in the first time slot, transmit one or more S- SSBs including first data on the sidelink channel in one or more second time slots of the window of time slots.

36. The apparatus of claim 35, wherein the memory contains instructions executable by the processor such that the apparatus is operable to perform the method of any of claims 24 to 27.