Method of transmitting signal over sidelink channel in unlicensed radio band of radio access network

Abstract

A method of transmitting a signal from a first radio node to a second radio node over a sidelink channel in an unlicensed radio band of a radio access network comprises:-performing channel sensing of the sidelink channel by decoding sidelink information of the sidelink channel during a sensing period, to identify at least one transmission resource of a sidelink channel for transmitting a signal to the second radio node; -performing a channel contention of the sidelink channel using a listen before talk mechanism during a contention period preceding the at least one identified transmission resource, where the sensing period and the contention period at least partially overlap; -accessing the sidelink channel for a duration comprising the channel occupancy time of the at least one identified transmission resource based on a positive result of the channel contention; and-transmitting a signal from the first radio node to the second radio node using the at least one identified transmission resource of the sidelink channel.

Description

Technical Field

[0001] The invention relates to two related methods of sending signals over a sidelink channel in an unlicensed radio band of a radio access network, as well as related radio nodes, systems for radio communication, related computer program elements and non-transitory computer-readable media. Background Art

[0002] Connection mobility is the subject of various communication standards, such as IEEE 802.11p / bd and 3GPP LTE / NRV2X. Two scenarios are considered for 3GPP LTE / NRV2X: the user equipment (UE) can be in the communication range of a base station (BS), such as an evolved node BS (eNB) or a 5G-NR-Node BS (gNB), or out of the communication range. Another scenario is that a portion of the connected UEs may be connected to the network, while the remaining connected UEs may be out of network coverage. This is called partially out of coverage.

[0003] Typically, when a UE (e.g., a UE installed in a vehicle) is within coverage, the UE can be configured to perform sidelink communications with other UEs within range. In this case, resource allocation, data control, and communication processes are controlled by the UE. In the case where the UE is outside the coverage of, for example, an EUTRA or 5G-NR cell, the UE is preconfigured with a mandatory configuration to use the sidelink for autonomous communication. For example, the UE can be preconfigured with several out-of-coverage frequencies. For example, out-of-coverage frequencies may include intelligent transportation system (ITS) frequencies. Sidelink communications can operate in licensed or unlicensed radio bands.

[0004] In LTE, Licensed Assisted Access for downlink was initially introduced using Listen Before Talk (LBT) to avoid collisions with existing transmissions in the unlicensed band. On uplink, LBT introduced enhanced Licensed Assisted Access (eLAA). 5G New Radio (NR) introduces unlicensed operation for both uplink (UL) and downlink (DL) in either licensed or unlicensed coverage. In this case, a radio node such as a UE or gNB starts LBT channel sensing to find nearby interference. After winning LBT, the gNB or UE initiates Channel Occupancy Time (COT). The COT depends on many factors like the frequency of LBT-artifacts, number of HARQ-NACKs, etc. During COT, the UE or gNB transmits their UL or DL ​​simultaneously.

[0005] 5G NR for unlicensed operation introduces two channel sharing methods based on the supported traffic requirements: Load Based Events (LBE) or Frame Based Events (FBE) COT. In LBE, the UE or gNB accesses the channel after a successful LBT whenever there is data to be transmitted in uplink or downlink. In this case, the radio node can only start LBT directly before the pre-scheduled UL grant to be able to occupy its scheduled time slot. In FBE, there is no significant difference in the occupation and grant process, while the COT is shared with other devices to send feedback or return traffic.

[0006] The sharing of COT between uplink and downlink must guarantee a short time gap between the traffic direction switch between the first device (initiating COT) and the second device (sharing the same COT), for example no more than 16 μs. After such a time gap, the second device should share the COT and send feedback or return traffic after a short sensing interval (LBT-CAT2) or no sensing (LBT-CAT1). However, if a short LBT (LBT-CAT2) is mandatory, the second device suppresses transmission if the result of the LBT is negative. Summary of the invention

[0007] According to a first aspect, there is provided a method of sending a signal from a first radio node to a second radio node over a sidelink channel in an unlicensed radio band of a radio access network.

[0008] The method according to the first aspect comprises:

[0009] - performing channel sensing of the sidelink channel by decoding sidelink information of the sidelink channel during a sensing period so as to identify at least one transmission resource of the sidelink channel for use in sending a signal to the second radio node;

[0010] - performing channel contention for the sidelink channel using a listen-before-talk mechanism during a contention period preceding at least one identified transmission resource,

[0011] wherein the sensing period and the contention period at least partially overlap;

[0012] - based on a positive result of the channel contention, accessing the sidelink channel for a duration including a channel occupancy time of at least one identified transmission resource; and

[0013] - sending a signal from the first radio node to the second radio node using the at least one identified transmission resource of the sidelink channel.

[0014] Channel sensing of the sidelink channel is performed to identify one or more transmission resources that can be used to send signals through the sidelink channel. To this end, the sidelink information is decoded during a sensing period. The sensing period can be understood as a sensing window of a certain or specific period before the sidelink transmission.

[0015] The sidelink information for identifying at least one transmission resource may include sidelink control information (SCI) or additional sidelink auxiliary information, such as sidelink reference signal information or sidelink pilot signal information.

[0016] In order to identify at least one transmission resource, a specified selection window may be considered for decoding the sidelink information, ie, only transmission resources during the selection window are identified as candidates for transmitting a signal.

[0017] Channel contention for the sidelink channel is performed in order to avoid collisions between transmissions of different radio nodes. To this end, a listen-before-talk mechanism is used, which can detect ongoing transmissions from other radio nodes. The listen-before-talk mechanism or process preferably includes measuring the received energy level of transmissions from other devices. Preferably, channel contention is performed immediately before the transmission of the identified transmission resource. The identified transmission resource may be a candidate resource selected by the first radio node or a reserved periodic resource.

[0018] The result of the channel contention may be positive (won LBT) or negative (lost LBT). If the measured energy level of the transmission from the other device is below a certain specified threshold (won LBT), the first radio node may access the sidelink channel for a period of time called the channel occupancy time (COT). When the channel contention terminates with a positive result (won LBT), the channel occupancy time may start immediately.

[0019] If the measured energy level of the transmission from the other device is equal to or above a certain specified threshold (LBT is lost), the first radio node may not access the sidelink channel. Instead, in order to access the channel and send a signal, channel contention is preferably required to be performed again by the first radio node.

[0020] The contention period of the channel contention is preferably shorter than the sensing period. The contention period preferably starts later than the sensing period. The contention period preferably ends at the same time as the sensing period or later than the sensing period.

[0021] The channel occupancy time may at least partially overlap with a selection window used to identify transmission resources. The channel occupancy time may extend beyond the selection window.

[0022] Transmitting the signal preferably includes transmitting a physical sidelink control channel for transmitting sidelink control information, followed by transmitting a physical sidelink shared channel for transmitting payload data.

[0023] According to a second aspect, there is provided a method of sending a signal from a second radio node to a first radio and / or a third radio node over a sidelink channel in an unlicensed radio band of a radio access network.

[0024] The method according to the second aspect comprises:

[0025] - receiving a signal sent from the first radio node to the second radio node over the side link channel in the unlicensed radio band during a channel occupancy time of the first radio node,

[0026] wherein the received signal comprises information about a channel occupancy time of the first radio node;

[0027] - accessing the sidelink channel during the channel occupancy time of the first radio node; and

[0028] - sending a signal from the second radio node to the first radio node and / or the third radio node via a sidelink channel,

[0029] The signal is transmitted by sharing the channel occupation time of the first radio node.

[0030] Sharing the channel occupation time of the first radio node may be understood as accessing the channel and sending a signal by the second radio node during the channel occupation time of the first radio node, in particular without performing channel contention of 3GPP Category 4. Sharing the channel occupation time means that once the first radio node initiates the channel occupation time and sends at least one signal, the second radio node may send a signal in response to a signal received from the first radio node without performing channel contention by using the listen-before-talk mechanism of 3GPP Category 4.

[0031] According to a third aspect, a first radio node is provided. The first radio node comprises a radio modem, a non-transitory computer-readable medium comprising machine-readable instructions, and a processor configured to load and execute the machine-readable instructions to cause the first radio node to perform the method according to the first aspect or an embodiment thereof, thereby sending a signal from the first radio node to a second radio node over a sidelink channel in an unlicensed radio band of a radio access network.

[0032] According to a fourth aspect, a second radio node is provided. The second radio node comprises a radio modem, a non-transitory computer-readable medium comprising machine-readable instructions, and a processor configured to load and execute the machine-readable instructions to cause the second radio node to perform the method according to the second aspect or an embodiment thereof, thereby transmitting a signal from the second radio node to the first radio and / or the third radio node via a sidelink channel in an unlicensed radio band of a radio access network.

[0033] According to a fifth aspect, there is provided a system for radio communication comprising a first radio node as defined by the third aspect and a second radio node as defined by the fourth aspect.

[0034] According to a sixth aspect, there is provided a computer program element comprising machine readable instructions which, when loaded and executed by a processor, cause the processor to perform the method according to the first aspect and / or the method according to the second aspect.

[0035] According to a seventh aspect, there is provided a non-transitory computer readable medium comprising machine readable instructions of the sixth aspect.

[0036] The methods presented for sending signals via a sidelink channel in an unlicensed radio band of a radio access network allow for the coexistence of different radio access technologies in the unlicensed radio band. The methods allow for reducing intra-system conflicts between transmissions of different radio nodes by avoiding interference. Furthermore, the methods are beneficial due to improved efficiency in the use of transmission resources and reduced response times in sidelink communications. Sending a signal from a second radio node to a first and / or third radio node by sharing the channel occupancy time of the first radio node allows for reducing additional delays introduced by performing channel contention and improving efficiency in the use of the sidelink channel.

[0037] This allows many of the regulatory requirements needed to access unlicensed spectrum to be retained (such as nominal bandwidth and aggregation of contiguous nominal carriers by the same device). The techniques detailed herein are flexible and can be applied to different nominal bandwidths and different nominal aggregate bands specified between regions. For example, ETSI BRAN regulations require nominal frequencies of 20MHz and aggregate bands in the 4, 8, 16, etc., 5GHz and 6GHz bands, although the techniques discussed herein can be generalized to other regions.

[0038] In other words, the first problem solved is that the sidelink communication is limited to dedicated (ITS) and licensed bands. In this case, the unlicensed band can be used to supplement the ITS / licensed band.

[0039] The second problem solved is that there is no specification on how to perform sidelink operations on unlicensed carriers for all communication broadcast types. In this case, unlicensed FBE can be used.

[0040] The third problem solved is to initiate and share the channel occupation time (COT). According to the present specification, if a side link transmission is scheduled, the radio node shares its channel occupation time for sending the side link transmission with other radio nodes, where the other radio nodes use transmission opportunities with short time gaps so as not to lose channel contention. The short time gap is a switching symbol at the end of each side link time slot. If the channel contention by the first radio node is lost, the second radio node will not detect the side link control information of the first radio node and perform CAT-4 LBT.

[0041] Therefore, this specification proposes a technique for accessing unlicensed bands for sidelink communications. The scheme focuses on dedicated unlicensed carrier assisted access, which may force ISM band regulations to be shared fairly between multiple technologies (e.g., 3GPP and WiFi). The dedicated carrier is also used to send broadcast, multicast and / or unicast information; it can also be used to guarantee synchronization between other radio nodes.

[0042] According to an embodiment of the first aspect, performing channel sensing includes:

[0043] - performing first channel sensing of the sidelink channel by decoding sidelink information of the sidelink channel during a first sensing period, and

[0044] - performing second channel sensing of the sidelink channel by decoding the sidelink information of the sidelink channel during a second sensing period,

[0045] The second sensing period and the contention period at least partially overlap. Preferably, the first sensing period precedes the contention period. In particular, the first sensing period and the contention period may not overlap.

[0046] In other words, the sensing period may consist of a first sensing period / window and a second sensing period / window. The first sensing period is preferably before the second sensing period. The first sensing period and the second sensing window may be adjacent or non-adjacent in time. The first sensing period is preferably longer than the second sensing period. The first sensing period allows decoding of possible resource reservations of other radio nodes and identification of possible resource candidates for sending signals within the selection window. The second sensing period allows decoding of possible recent resource reservations of other radio nodes that were not detected during the first sensing period.

[0047] According to an embodiment of the first aspect, sending a signal comprises sending information about a channel occupancy time (i.e., the channel occupancy time of the first radio node). The information may comprise the channel occupancy time, the length of the channel occupancy time, the end of the channel occupancy time, and / or how to share the channel occupancy time with other radio nodes.

[0048] The information about the channel occupancy time may be sent to the second and / or third radio node explicitly or implicitly.The implicit sending may include an index, an indicator, and / or a specific selection of a transmission format, based on which the information about the channel occupancy time may be derived or encoded.

[0049] Sending the information about the channel occupancy time allows the second and / or third radio node to share the channel occupancy time of the first radio node.

[0050] According to an embodiment of the first aspect, the method according to the first aspect includes:

[0051] receiving a signal sent from the second radio node to the first radio node in an unlicensed band of the radio access network,

[0052] The received signal is sent by the second radio node by sharing the channel occupation time of the first radio node.

[0053] Sharing the channel occupancy time of the first radio node allows reducing the additional delay introduced when performing channel contention and improving the efficiency of the side link channel usage.

[0054] According to an embodiment of the first aspect, the method according to the first aspect includes:

[0055] responding to the received signal by sending another signal to the second radio node and / or the third radio node in an unlicensed band of the radio access network,

[0056] Therein, a further signal is transmitted during the channel occupancy time of the first radio node.

[0057] The further signal may be sent using one or the last transmission resource of the channel occupancy time of the first radio node.

[0058] According to an embodiment of the first aspect, the category of the listen-before-talk mechanism for performing channel contention is one of the following 3GPP categories: category 4, category 2, category 1. Herein, the listen-before-talk mechanism of category 1 can be understood as not using the listen-before-talk mechanism. Other suitable listen-before-talk mechanisms known to those skilled in the art can be used as an alternative.

[0059] For the initial transmission by the first radio node, a listen-before-talk mechanism of category 4 is preferably used. For further transmissions by the first radio node within the channel occupation time, the first radio node may use a listen-before-talk mechanism of category 2 or category 1. Herein, the category of the listen-before-talk mechanism may be selected based on the gap period between the previous transmission in the side link channel and the transmission of another signal sent by the first radio node during the channel occupation time. The gap period may be understood as a period during which the measured energy level of transmissions from other devices is below a certain threshold.

[0060] According to an embodiment of the first aspect and / or an embodiment of the second aspect, the transmission resource for sending a signal by the first radio node and / or the transmission resource for sending a signal by the second radio node belongs to an interleaved structure of multiple transmission resources of the side link channel. The interleaved structure can be understood as a structured allocation of an unlicensed radio band to multiple transmission resources. In this article, the unlicensed radio band can be divided or distributed or allocated to multiple transmission resources so that the multiple transmission resources are interleaved across the frequency range of the unlicensed radio band. In other words, the interleaved structure consists of multiple interleaved interleaving patterns, each of which represents a transmission resource.

[0061] Each radio node may select different transmission resources or interleaving patterns to send signals in the unlicensed radio band. The transmissions of multiple radios may multiplex themselves on the same unlicensed radio band, thereby avoiding collisions between simultaneous transmissions of different radio nodes.

[0062] Advantageously, a predetermined portion of an unlicensed radio band comprising a plurality of transmission resources may be divided into a plurality of contiguous sub-portions, wherein each transmission resource comprises at least two non-contiguous sub-portions of the unlicensed radio band, such that the plurality of transmission resources form an interleaved structure of a side link channel across the predetermined portion of the unlicensed radio band.

[0063] The predetermined portion of the unlicensed radio band may include the entire unlicensed radio band or only a portion of the unlicensed radio band, such as 80%. The sub-portions may be of equal length in frequency. The sub-portions comprised by or allocated to the same transmission resource are non-contiguous or non-adjacent in frequency and may further be equidistant in frequency.

[0064] By forming an interleaved structure of sidelink channels across a predetermined portion of the unlicensed radio band, each of the plurality of transmission resources allows a single transmission to be distributed across the predetermined portion of the frequency range.

[0065] According to a first advantageous alternative,

[0066] Two consecutive sub-parts represent resource blocks of different sidelink subchannels of a sidelink channel,

[0067] Each sidelink subchannel includes a plurality of non-contiguous resource blocks, and

[0068] Each transmission resource includes all resource blocks belonging to the same sidelink subchannel.

[0069] For example, the predetermined portion of the unlicensed radio band may be divided into N=S*M consecutive sub-portions, where S represents the number of different sub-channels. Herein, each S consecutive sub-portion may represent resource blocks of S different sidelink sub-channels, which are preferably arranged in the same order across the predetermined portion of the unlicensed radio band. Thus, the sub-channels themselves are interleaved across the frequency range of the unlicensed radio band.

[0070] According to the second advantageous alternative,

[0071] Each sub-portion represents a different sidelink subchannel of the sidelink channel, and

[0072] Each transmission resource includes at least two non-contiguous sidelink sub-channels.

[0073] In other words, a subchannel consists of a single resource block, or includes only consecutive resource blocks.By combining at least two non-consecutive subchannels into one transmission resource, a plurality of transmission resources are interleaved across the frequency range of the unlicensed radio band.

[0074] Thus, for transmissions over the sidelink channel of the unlicensed-radio band, the interleaving structure is configured to guarantee operation over a minimum nominal bandwidth.

[0075] According to an embodiment of the first aspect and / or an embodiment of the second aspect, performing channel contention includes performing channel contention for multiple subbands of the side link channel, wherein a bandwidth portion of the side link channel is adjusted based on a result of the channel contention for the multiple subbands.

[0076] According to an embodiment of the first aspect and / or an embodiment of the second aspect, the adjusted bandwidth portion may include a subband of a side link channel for which the result of channel contention is positive. For example, a channel may include multiple subbands, wherein for at least one subband, the result of channel contention is positive, and for at least one other subband, the result of channel contention is negative. The adjusted bandwidth portion preferably includes only at least one subband for which channel contention is positive. In other words, the bandwidth portion of the side link channel is adjusted by eliminating at least one subband for which the result of channel contention is negative. The subbands of the adjusted bandwidth portion may be (non)continuous or (non)adjacent in frequency.

[0077] This embodiment solves the problem of designing a bandwidth part (BWP) for wideband operation. In the case of unlicensed bands, wideband operation depends on a successful listen-before-talk mechanism in each subband. Therefore, the BWP design of sidelink Release 16 does not hold perfectly. This embodiment provides flexible bandwidth operation for wideband operation based on listen-before-talk.

[0078] According to an embodiment of the second aspect, the method further comprises:

[0079] Before accessing the side link channel, channel contention for the side link channel is performed using a listen-before-talk mechanism.

[0080] Preferably, the channel contention is performed by the second radio node after the second radio node receives the signal sent from the first radio node.Based on a positive result of the channel contention, the sidelink channel may be evaluated by the second radio node during the channel occupation time of the first radio node.

[0081] According to an embodiment of the second aspect, the category of the listen-before-talk mechanism for performing channel contention is one of the following 3GPP categories: category 4, category 2, category 1. Herein, the listen-before-talk mechanism of category 1 can be understood as not using the listen-before-talk mechanism. Other suitable listen-before-talk mechanisms known to those skilled in the art can be used as an alternative.

[0082] According to an embodiment of the second aspect, the category of the listen-before-talk mechanism is selected based on the gap period between the previous transmission during the channel occupation time and the transmission of the signal sent by the second radio node. In other words, both the previous signal and the signal sent by the second radio node are sent during the channel occupation time of the first radio node.

[0083] As an example, if there is a gap of less than 16 microseconds between the transmission of the first radio node and the transmission of the second radio node during the channel occupancy time, the second radio node may access and share the side link channel using a listen-before-talk mechanism of category 1. If there is a gap of greater than 16 microseconds and less than 25 microseconds between the transmission of the first radio node and the transmission of the second radio node during the channel occupancy time, the second radio node may access and share the side link channel using a listen-before-talk mechanism of category 2. If there is a gap of greater than 25 microseconds between the transmission of the first radio node and the transmission of the second radio node, the side link channel may be accessed only by the second radio node when using a listen-before-talk mechanism of category 4.

[0084] According to an embodiment of the second aspect, sending a signal comprises sending information about the channel occupation time of the first radio node (preferably about the remaining channel occupation time of the first radio node). Herein, the signal sent by the second radio node by sharing the channel occupation time of the first radio node may comprise information about the channel occupation time of the first radio node.

[0085] The information about the channel occupancy time may be sent to the first and / or third radio node explicitly or implicitly. The implicit sending may include an index, an indicator, and / or a specific selection of a transmission format, based on which the information about the channel occupancy time may be derived or encoded.

[0086] Sending information about the channel occupancy time allows further radio nodes to share the channel occupancy time of the first radio node.

[0087] According to the embodiment of the first aspect or the second aspect,

[0088] - the signal is sent via at least one of a physical sidelink shared channel (PSSCH), a physical sidelink control channel (PSCCH), or a physical sidelink broadcast channel (PSBCH), and

[0089] - Information about the channel occupancy time is sent via the Physical Sidelink Control Channel (PSCCH) or an alternative means for sending sidelink control information.

[0090] Alternative means for transmitting the sidelink control information may include a variation of the sidelink control information or an indicator, index, or format selection representing the sidelink control information.Thus, information about the channel occupancy time may be transmitted in the sidelink control information.

[0091] According to an embodiment of the first aspect and / or the second aspect, if at least one of the signals transmitted during the channel occupancy time is transmitted via a plurality of subbands of the sidelink channel, preferably using wideband operation, at least part of the sidelink control information is transmitted in a physical sidelink control channel (PSCCH), wherein the physical sidelink control channel (PSCCH) is transmitted as follows:

[0092] - at least one subband of a sidelink channel, or

[0093] -The result of channel contention is yes for all subbands.

[0094] One subband in which the PSCCH is transmitted may be a first subband. Part of the sidelink control information may be replicated in all subbands for which the result of channel contention is affirmative.

[0095] According to embodiments of the first aspect or the second aspect, the first radio node and / or the second radio node operates in a frame-based equipment (FBE) mode or a load-based equipment (LBE) mode.

[0096] In LBE mode, the radio node may access the side link channel based on a positive result of channel contention performed whenever there is data to be sent by the radio node over the side link channel. In FBE mode, channel contention is performed only at synchronization frame boundaries. In the case of FBE mode, the information transmitted about the channel occupancy time may include information about the periodicity of the transmission.

[0097] According to one embodiment, the unlicensed radio band may be included in at least one of the following ranges: 410-7125 MHz; 24.25-52.6 GHz; 28-60 GHz; >60 GHz.

[0098] In particular, the unlicensed radio band may be included in at least one of the following ranges: 5150-5925 MHz; 5150-5350 MHz (WAS / RLAN); 5470-5725 MHz (WAS / RLAN); 5725-5855 MHz (FWA); 5855-5875 MHz; 5875-5925 MHz (ITS), 5150-5250 (U-NII-1) 5250-5350 (U-NII-2A) 5350-5470 (U-NII-2B) 5470-5725 (U-NII-2C) 5725-5850 (U-NII-3) or 5850-5925 (U-NII-4).

[0099] In particular, the unlicensed-radio band may be included in at least one of the following ranges: 5925-7125 MHz (eg, in the US) or 5925-6425 MHz (eg, in the EU).

[0100] According to one embodiment, at least the first and second radio nodes are members of a 5G NR radio network. The first and / or second radio nodes may be user devices. The first and / or second radio nodes may include an input interface configured to obtain input data, such as commands from a higher layer, to perform sidelink communications. The first and / or second radio nodes may include a power supply and / or an antenna coupled to a radio modem of the respective radio nodes. The first and / or second radio nodes may support device-to-device, Internet of Things, and / or V2X communications. BRIEF DESCRIPTION OF THE DRAWINGS

[0101] Exemplary embodiments of the invention are depicted in the drawings, which should not be construed as limiting the claims, and are explained in more detail below.

[0102] Figure 1 A, B, and C schematically show three possible options for the listen-before-speak mechanism;

[0103] Figure 2 schematically illustrates an example of sharing channel occupancy time between two radio nodes operating in a frame-based device mode;

[0104] Figure 3 Another example of sharing channel occupancy time between two radio nodes is schematically shown;

[0105] Figure 4 A and B schematically illustrate two alternative interleaving structures of multiple transmission resources of the side link channel;

[0106] Figure 5 A, B, C, D schematically illustrate different bandwidth portion options for broadband operation;

[0107] Figure 6 schematically illustrates an example of a signaling protocol for sharing channel occupancy time on an unlicensed radio band; and

[0108] Figure 7 A and B schematically illustrate the methods according to the first and second aspects. DETAILED DESCRIPTION

[0109] The present invention proposes an independent, self-organizing channel access for sidelink transmission on an unlicensed carrier.The unlicensed carrier can be used for sidelink communication (transmitting data, control and feedback).

[0110] In this case, if the stations send broadcast and synchronization information, they can also synchronize on carrier 2. The synchronization process can have all possible options for 3GPP synchronization, such as synchronization to synchronization master / GNSS, synchronization to gNB (broadcast synchronization signal in licensed or unlicensed band), synchronization to synchronization source UE, etc.

[0111] Regarding resource allocation, if a gNB is present, configuration and control signaling can be transmitted over the Uu carrier, for example, for a Mode 1 resource allocation scheme where the Uu carrier is the network operating carrier. However, if only the unlicensed band is available and there are no other (one or more) synchronization sources, synchronization between UEs can be performed by configuring a resource pool in Mode 2 (but in the unlicensed band) and exchanging synchronization sequences.

[0112] Sidelink for Load Based Equipment (LBE) in Unlicensed Band

[0113] In this technique, sidelink communications can be sent in a load-based device (LBE) manner, i.e., data is sent on demand. This means that a UE (or a group of UEs) can perform LBT (simultaneously). The UE (or multiple UEs) that find an idle channel wins the LBT. In addition, the winning UE (or a group of UEs) can select resources based on their sensing history of other sidelink transmissions and reserved signals. In this case, the UE (or a group of UEs) that wins the LBT can be allocated 1 of N interlaced patterns in frequency, where the interlaced pattern can be selected randomly. The pattern selected in time and frequency (after a successful LBT) is used to send their control and shared data. Other UEs in the network can receive control and / or data transmissions, or try to capture the channel (based on LBT and sensing based on the sidelink transmission window) to send their sidelink transmissions.

[0114] Sidelink for Frame-Based Equipment (FBE) in Unlicensed Band

[0115] Another option would be to allow any UE that urgently needs a share of the channel occupation time (COT) to send its frame-based equipment (FBE).

[0116] Initial procedure: The initial UE (or a group of asynchronous UEs) should sense the channel with an initial LBT (e.g., the longest with CCA, LBT-4) and perform sliding window based sensing for sidelink communication.

[0117] Based on the success of LBT (for other radio access technologies (RATs)) and longer window based sensing (for equivalent sidelink sensing), the initial UE (or a group of asynchronous UEs) should (randomly) select one of the N interleaving patterns and perform control and data transmission.

[0118] Any other station (or group of stations) sensing the network and being able to decode possible control information (which may contain a certain COT duration) may share the COT initially initiated by UE1. Another UE (or some "other" UEs) sharing the COT may send its (their) sidelink transmissions in an interleaved pattern. Other UEs (or other groups of UEs) may share the initiated initial COT as long as the COT is sufficient to send more sidelink transmissions.

[0119] Furthermore, the initial UE1 (or UE group 1) may transmit on the last transmission opportunity of its (their) initiated COT. In the case of FBE, the initiated COT may send some information about the periodicity of the sidelink transmission configuration grant, i.e., where the initialization process is repeated before each declared period, see Figure 2 .

[0120] Channel access using window-based sensing followed by LBT

[0121] According to one embodiment, a first transmission TRI of a first radio node, for example a first user equipment UE1, needs to be sent on an unlicensed carrier for sidelink communication. To this end, UE1 is configured to perform both channel sensing and channel contention. For channel contention, a listen-before-talk mechanism is used.

[0122] UE1 is configured to perform sidelink (normal - long or short) channel sensing to extract and decode existing (similar) sidelink transmissions from external UEs (other UEs). Herein, UE1 may be configured to perform sidelink sensing using sidelink control channel decoding, e.g., as in Rel-16 (decoding possible sidelink control information (SCI) from other devices with sidelink reservation to select free candidate resources).

[0123] Preferably, UE1 is configured to perform window-based (or sliding window-based) channel sensing using two sensing windows of preferably different sizes (particularly a long sensing window of size W1 and a short sensing window of size W2).

[0124] In sidelink communication, a long sensing window can be used to decode all possible reservations of other UEs to select possible candidate resources within the selection window Sw. In addition, UE1 can start a short sensing window directly before the selected resource. The main role of the short sensing window is to avoid any recent reservations from other UEs that are not detected within the normal (long) sensing window.

[0125] UE1 may be configured to use a listen-before-talk mechanism to accomplish channel contention to detect existing / interfering radio access technologies in unlicensed bands, such as WiFi. The listen-before-talk mechanism is used within or near the end of a short sensing window, or starting from near the end of a short sensing window.

[0126] If a short sensing window is not configured, the UE1 should be required to perform channel contention using a listen-before-talk mechanism directly before selecting candidate resources (either sensing each and all candidate resources or sensing one by one in time sequence).

[0127] Figure 1 Three possible options for a listen-before-talk mechanism that can be used for channel contention are schematically shown. Figure 1 In the example of , channel sensing of the side link channel is performed by the first radio node UE1. The sensing period includes a first sensing window W1 and a second sensing window W2. Herein, the first sensing window W1 precedes the second sensing window W2 and has a longer duration than the second sensing window W2. Performing channel sensing allows identifying at least one candidate transmission resource within a selection window for sending a signal by the first radio node UE1.

[0128] During the second sensing window W2, channel contention using a listen-before-talk mechanism (LBT) is performed. If the listen-before-talk mechanism terminates with a positive result (winning LBT), UE1 is configured to access the sidelink channel, thereby initiating a channel occupation time (COT).

[0129] Figure 1 A shows a first option of a listen-before-talk mechanism assuming that LBE (load-based device) or FBE (frame-based device) has a long transmission gap (larger than the allowed short gap, e.g., 16 microseconds). Then, UE1 is configured to perform channel contention by using a long listen-before-talk mechanism (e.g., based on CAT-4 LBT) during (and / or extended) the short sidelink sensing window W2. As an example, UE1 may be configured to use a listen-before-talk mechanism according to Figure 1 Option A.

[0130] Figure 1 B shows the second option of a listen-before-talk mechanism assuming FBE with a short transmission gap (between the transmission of UE1 initiating the COT and the subsequent transmission of another UE sharing the COT). UE2 is then configured to perform channel contention by using a short listen-before-talk mechanism.

[0131] Figure 1 C shows a third option of a listen-before-talk mechanism assuming FBE with very short transmission gaps (shorter than a predetermined threshold). Then, UE2 does not perform the listen-before-talk mechanism, i.e., UE2 is configured to transmit without any LBT mechanism by sharing the COT initiated by UE1. The third option is also applicable to further transmissions of UE1 after its previous transmission within the same COT.

[0132] Figure 2 An example of sharing channel occupancy time between two radio nodes UE1, UE2 operating in frame-based device mode is schematically shown.

[0133] For the first frame, the channel contention using the listen before talk (LBT) mechanism performed by the first radio node UE1 loses (lose LBT). The channel contention using the listen before talk (LBT) mechanism performed by the second radio node UE2 is successful (win LBT). Therefore, the second radio node UE2 initiates a channel occupation time (COT) and sends control data including its COT through the sidelink control channel, and sends further data through the physical sidelink shared channel. The COT of the second radio node UE2 ends without being shared by the first radio node UE1.

[0134] For the second frame, the channel contention using the listen-before-talk (LBT) mechanism performed by the first radio node UE1 is successful (wins LBT). Therefore, the first radio node UE1 initiates a channel occupation time (COT) and sends control data including its COT via the sidelink control channel, and further data via the physical sidelink shared channel. The COT of the first radio node UE1 is shared by the second radio node UE2, i.e. UE2 is configured to send signals without performing channel contention or only within a specified short gap after the transmission of the first radio node UE1 using a short listen-before-talk mechanism of, for example, 3GPP Category 2.

[0135] In other words, UE1 may be configured to transmit information about the initiated COT (e.g., the start and duration of the COT) in its control information. As described above, the LBT mechanism is performed before one or more possible selected candidate resources or before one or more possible reserved periodic resources. The LBT mechanism may also be performed on the candidate resources sequentially (one after another) (i.e., close in time to the first having LBT).

[0136] According to one embodiment, the channel access by the first radio node UE1 can be shared with the second or further radio nodes ("multicast"). To this end, the first radio node UE1 initiates a channel occupation time (COT), sends a signal, and preferably shares its COT with other (one or more) UEs in a dedicated sidelink control field. Thus, each other UE (e.g., in a group communication) that can share the initial COT with UE1 can send control and data of its individual UE within the COT of the first radio node UE1 after a short LBT or no LBT.

[0137] Therefore, the control information initiated by the first radio node UE1 can transmit the COT information to all other UEs in the network (including UEs in the group). Thereafter, for each group member sharing the COT, the control information sent by each group member can transmit the remaining COT to other group members.

[0138] For the remaining COT initiated by the first radio node UE1, another UE (e.g., the second radio node UE2) or other UEs may share the COT in an organized manner. In order to organize the transmissions of other UEs sharing the remaining COT, the following may apply:

[0139] - Coordination of the transmissions of the UEs sharing the COT with the first radio node UE1 may be performed by the first radio node UE1, eg at least for replying to messages of the first radio node UE1.

[0140] - Coordination of transmissions of UEs sharing a COT with the first radio node UE1 may be performed by the first radio node UE1, eg at least for multicast communications.

[0141] - Coordination of transmissions of UEs sharing a COT with the first radio node UE1 may be performed by the first radio node UE1, eg at least for acknowledging messages of the first radio node UE1 with ACK or NACK.

[0142] For the remaining COTs initiated by the first radio node UE1, after the transmissions of all UEs sharing the COT, the first radio node UE1 may acknowledge the transmissions of other UEs in the last transmission opportunity in the initiated COT.

[0143] Figure 3 Another example of sharing channel occupancy time between two radio nodes is schematically shown. Herein, after first performing successful channel sensing (not shown) and secondly performing successful channel contention using a listen-before-talk mechanism, side link control information including the COT of the first radio node UE1 and further data is sent to at least the second radio node UE2. The COT of the first radio node UE1 is shared by the second radio node UE2. The first radio node UE1 uses the last transmission opportunity within the COT initiated by the first radio node UE1 to send a response signal in response to the signal of the second radio node UE2.

[0144] Figure 4 A and B schematically illustrate two alternative interleaving structures of multiple transmission resources of the side link channel.

[0145] The sidelink transmissions may follow a staggered structure, where the staggered structure should cover at least a predetermined portion, e.g., some percentage like 80% of the unlicensed radio band. A sidelink staggered structure for a group of UEs sharing the same timeslot (e.g., UE-Group-X is just a set of UEs that multiplex their sidelink transmissions on a predetermined portion of the nominal frequency (between 18 and 20 MHz)).

[0146] If all UEs in the above set (UE-Group-X) are sending their sidelink transmissions, the entire band is interleaved with the corresponding sidelink resource blocks. Otherwise, only subsequent UEs in the set UE-Group-X (with won LBT) can share the sidelink time slot band with the interleaved frequency structure, as shown in Figure 4 shown.

[0147] Therefore, in unlicensed access, sidelink control and data can be interleaved in an interleaving structure to meet the required bandwidth spanning, where only successful LBT or shared COT users are allowed to interleave their sidelink transmissions.

[0148] Figure 4 A shows the resource pool configuration and subchannel design of the first alternative. Here, the resource pool is configured with multiple sidelink subchannels, where each single subchannel is not continuous in frequency, but interleaved across the nominal frequency. The interleaving width and length of the subchannel are configurable.

[0149] A single radio node may transmit a signal through one of the sub-channels. Multiple radio nodes may transmit signals simultaneously by using different sub-channels, thereby multiplexing their sidelink transmissions.

[0150] Figure 4 B shows the resource pool configuration and subchannel design of the second alternative. Here, the resource pool is configured with multiple adjacent sidelink subchannels, where the subchannels have continuous resources in frequency. The interleaving width may be configurable, but the length of the channel may depend on each time allocation.

[0151] A single radio node may transmit signals with one subchannel interleaving pattern distributed across the nominal bandwidth (ie, comprising, for example, three non-adjacent or non-contiguous subchannels). Multiple radio nodes may transmit signals simultaneously using different interleaving patterns, thereby multiplexing their sidelink transmissions.

[0152] Figure 5 Schematically illustrated are different bandwidth part (BWP) options for wideband operation, depending on the outcome of a listen-before-talk mechanism performed for each sub-band of the unlicensed radio band. Figure 5 The radio band of includes 5 sub-bands. For each sub-band, channel contention is performed by using a listen-before-talk mechanism.

[0153] In unlicensed access, the sidelink BWP is scaled around the LBT subbands (i.e., free or idle subbands) for which the result of the LBT mechanism is positive. In this case, the BWP portion is configured to have a maximum width and a minimum width. Depending on which subbands the result of the LBT mechanism is positive for, the BWP is scaled to one or more or all subbands. The following preferably applies:

[0154] The bandwidth portion may start from the first sub-band for which the result of the LBT mechanism is positive and end after the last consecutive sub-band for which the result of the LBT mechanism is positive.

[0155] Subchannel transmission should start from the first subband for which the result of the LBT mechanism is positive, and end at the last subband for which the result of the LBT mechanism is positive, or vice versa.

[0156] The PSCCH should start from the first subchannel in the BWP, consuming one or more subchannels (filling towards the last subchannel), or vice versa (from the last to the first).

[0157] Figure 5 A shows the BWP option where the result of the LBT mechanism is positive for all subbands. Therefore, the bandwidth part starts from the first subband and ends at the fourth subband.

[0158] Figure 5 B shows a BWP option where the result of the LBT mechanism is negative for the first subband and positive for the last three subbands. Therefore, the bandwidth part starts from the second subband and ends at the fourth subband.

[0159] Figure 5 C shows a BWP option where the result of the LBT mechanism is positive for the first three sub-bands and negative for the fourth sub-band. Therefore, the bandwidth part starts from the first sub-band and ends at the third sub-band.

[0160] Figure 5 D shows a BWP option where the result of the LBT mechanism is negative for the first and fourth sub-bands and positive for the second and third sub-bands. Therefore, the bandwidth part starts from the second sub-band and ends at the third sub-band.

[0161] Figure 6 An example of a signaling protocol for sharing channel occupancy time on an unlicensed radio band is schematically shown.

[0162] In the example of Figure 10, the first radio node UE1, the second radio node UE2 and the third radio node UE3 communicate via a sidelink channel in an unlicensed radio band F1 of the radio access network. Initially, the resource pool in the unlicensed band F1 is configured by a pre-configuration or a previously stored configuration received from a UE or a gNB.

[0163] The first radio node UE1 forms channel contention using a listen-before-talk mechanism (LBT), and if successful, sends a short control to configure subsequent signaling, and sends a first signal to at least the second radio node UE2 and an optional third radio node UE3 (the third radio node UE3 can passively receive all signals sent by the first radio node UE2). The first signal includes information about the channel occupation time (COT) of the first radio node UE1 and additional data.

[0164] The second radio node UE2 transmits its signal within the allowed gap without performing channel contention, thus sharing the channel occupation time of the first radio node UE1. The first radio node UE1 and optionally the third radio node UE3 receive the signal transmitted by the second radio node UE2.

[0165] If an amount of time greater than the allowed gap has passed, the third radio node UE3 must perform a new channel contention operation to access the unlicensed band.After completing channel contention, the third radio node UE3 sends a short control to configure subsequent signaling and further signals to at least the second radio node UE2 and optionally the first radio node UE3.

[0166] Figure 7 a schematically illustrates a method according to the first aspect. According to the first aspect, there is provided a method 100 of sending a signal from a first radio node to a second radio node over a sidelink channel in an unlicensed radio band of a radio access network.

[0167] The method 100 according to the first aspect comprises:

[0168] - performing 110 channel sensing of the sidelink channel by decoding sidelink information of the sidelink channel during a sensing period in order to identify at least one transmission resource of the sidelink channel for sending signals to the second radio node;

[0169] - performing 120 channel contention for the sidelink channel using a listen-before-talk mechanism during a contention period prior to at least one identified transmission resource,

[0170] wherein the sensing period and the contention period at least partially overlap;

[0171] - based on a positive result of the channel contention, accessing 130 the sidelink channel for a duration comprising a channel occupancy time of at least one identified transmission resource; and

[0172] - Sending 140 a signal from the first radio node to the second radio node using the at least one identified transmission resource of the sidelink channel.

[0173] Figure 7 b schematically illustrates the method according to the second aspect.

[0174] According to a second aspect, a method 200 is provided of sending a signal from a second radio node to a first radio and / or a third radio node over a sidelink channel in an unlicensed radio band of a radio access network.

[0175] The method 200 according to the second aspect comprises:

[0176] - receiving 210 a signal sent from the first radio node to the second radio node over a side link channel in an unlicensed radio band during a channel occupancy time of the first radio node,

[0177] wherein the received signal comprises information about a channel occupancy time of the first radio node;

[0178] - Optionally, performing 220 channel contention for the side link channel using a listen-before-talk mechanism, and based on a positive result of the channel contention:

[0179] - accessing 230 the sidelink channel during the channel occupancy time of the first radio node; and

[0180] - sending 240 a signal from the second radio node to the first radio node and / or the third radio node via a side link channel,

[0181] The signal is transmitted by sharing the channel occupation time of the first radio node.

[0182] The examples provided in the accompanying drawings and described in the foregoing written description are intended to provide an understanding of the principles of this specification. Therefore, it is not intended to limit the scope of the appended claims. This specification describes changes and modifications to the illustrated examples. Only preferred examples are given, and it is desired to protect all changes, modifications and further applications thereof within the scope of the specification.

Claims

1. A method (100) of sending a signal from a first radio node (UE1) to a second radio node (UE2) via a sidelink channel in an unlicensed radio band of a radio access network, comprising: - performing (110) channel sensing of the sidelink channel by decoding sidelink information of the sidelink channel during a sensing period in order to identify at least one transmission resource of the sidelink channel for transmitting signals to the second radio node (UE2); - performing (120) channel contention for the sidelink channel using a listen-before-talk (LBT) mechanism during a contention period prior to at least one identified transmission resource, wherein the sensing period and the contention period at least partially overlap; - based on a positive result of the channel contention, accessing (130) a sidelink channel for a duration of a channel occupation time (COT) including at least one identified transmission resource; as well as - sending (140) a signal from the first radio node (UE1) to the second radio node (UE2) using at least one identified transmission resource of the sidelink channel.

2. The method (100) according to claim 1, The performing (110) of channel sensing comprises: - performing first channel sensing of the sidelink channel by decoding sidelink information of the sidelink channel during a first sensing period, and - performing second channel sensing of the sidelink channel by decoding sidelink information of the sidelink channel during a second sensing period, The second sensing period and the contention period at least partially overlap.

3. The method (100) according to claim 1 or 2, Wherein sending (140) the signal includes sending information regarding a channel occupancy time (COT).

4. The method (100) according to any of the preceding claims, further comprising: A signal transmitted from a second radio node (UE2) to a first radio node (UE1) in an unlicensed band of a radio access network is received, wherein the received signal is transmitted by the second radio node (UE2) by sharing a channel occupation time (COT) of the first radio node (UE1).

5. The method (100) according to claim 4, further comprising: responding to the received signal by sending another signal to the second radio node (UE2) and / or the third radio node in an unlicensed band of the radio access network, Therein, the further signal is sent during a channel occupation time (COT) of the first radio node (UE1).

6. The method (100) according to one of the preceding claims, The category of the listen-before-talk (LBT) mechanism used to perform (120) channel contention is one of the following 3GPP categories: category 4, category 2, category 1.

7. The method (100) according to one of the preceding claims, The transmission resources used to send signals belong to the interleaved structure of multiple transmission resources of the side link channel.

8. The method (100) according to claim 7, wherein: - a predetermined portion of the unlicensed radio band comprising a plurality of transmission resources is divided into a plurality of contiguous sub-portions, and - Each transmission resource comprises at least two non-contiguous sub-portions of the unlicensed radio band, such that a plurality of transmission resources forms an interleaved structure of the sidelink channel across predetermined portions of the unlicensed radio band.

9. The method (100) according to claim 8, wherein: - two consecutive sub-parts represent resource blocks of different sidelink subchannels of said sidelink channel, - each sidelink subchannel comprises a plurality of non-contiguous resource blocks, and - Each transmission resource includes all resource blocks belonging to the same sidelink subchannel.

10. The method (100) according to claim 8, wherein: - each sub-portion represents a different sidelink subchannel of said sidelink channel, and - Each transmission resource comprises at least two non-contiguous sidelink sub-channels.

11. The method (100) according to one of the preceding claims, wherein performing (120) channel contention includes performing channel contention for a plurality of subbands of the sidelink channel, The bandwidth portion of the side link channel is adjusted based on a result of channel contention of the plurality of sub-bands.

12. The method (100) according to claim 11, The adjusted bandwidth portion includes the subband of the side link channel for which the result of channel contention is affirmative.

13. A method (200) of sending a signal from a second radio node (UE2) to a first radio node (UE1) and / or a third radio node through a sidelink channel in an unlicensed radio band of a radio access network, comprising: - receiving (210) a signal sent from the first radio node (UE1) to the second radio node (UE2) over a sidelink channel in an unlicensed radio band during a channel occupation time (COT) of the first radio node (UE1), wherein the received signal comprises information about a channel occupation time (COT) of the first radio node (UE1); - accessing (230) the sidelink channel during a channel occupation time (COT) of the first radio node (UE1); and - sending (240) a signal from the second radio node (UE2) to the first radio node (UE1) and / or the third radio node via the sidelink channel, The signal is sent by sharing a channel occupation time (COT) of the first radio node (UE1).

14. The method (200) of claim 13, further comprising: Prior to accessing (230) the sidelink channel, channel contention for the sidelink channel is performed (220) using a listen-before-talk (LBT) mechanism.

15. The method (200) according to claim 14, The category of the listen-before-talk (LBT) mechanism used to perform (220) channel contention is one of the following 3GPP categories: category 4, category 2, category 1.

16. The method (200) according to claim 15, The type of the Listen Before Talk (LBT) mechanism is selected based on a gap period between a previous transmission during a Channel Occupancy Time (COT) and a transmission of a signal sent by the second radio node (UE2).

17. The method (200) according to any one of claims 13 to 16, Wherein sending (240) the signal comprises sending information about a channel occupied time (COT) of the first radio node (UE1), preferably information about a remaining channel occupied time (COT) of the first radio node (UE1).

18. The method (200) according to any one of claims 13 to 17, The transmission resources used to send signals belong to the interleaved structure of multiple transmission resources of the side link channel.

19. The method (200) of claim 18, wherein: - a predetermined portion of the unlicensed radio band comprising a plurality of transmission resources is divided into a plurality of contiguous sub-portions, and - Each transmission resource comprises at least two non-contiguous sub-portions of the unlicensed radio band, such that a plurality of transmission resources forms an interleaved structure of the sidelink channel across predetermined portions of the unlicensed radio band.

20. The method (200) of claim 19, wherein: - two consecutive sub-parts represent resource blocks of different sidelink subchannels of said sidelink channel, - each sidelink subchannel comprises a plurality of non-contiguous resource blocks, and - Each transmission resource includes all resource blocks belonging to the same sidelink subchannel.

21. The method (200) of claim 19, wherein: - each sub-portion represents a different sidelink subchannel of said sidelink channel, and - Each transmission resource comprises at least two non-contiguous sidelink sub-channels.

22. The method (200) according to any one of claims 13 to 21, wherein performing (220) channel contention includes performing channel contention for a plurality of subbands of the sidelink channel, and The bandwidth portion of the side link channel is adjusted based on a result of channel contention of the plurality of sub-bands.

23. The method (200) according to claim 22, The bandwidth portion to be adjusted includes the subband for which the result of the channel contention is affirmative.

24. The method (100, 200) according to one of claims 1 to 12 and / or one of claims 13 to 23, wherein: - the signal is sent via at least one of a physical sidelink shared channel (PSSCH), a physical sidelink control channel (PSCCH), or a physical sidelink broadcast channel (PSBCH), and - Information about the Channel Occupancy Time (COT) is sent via the Physical Sidelink Control Channel (PSCCH) or an alternative means for sending sidelink control information.

25. The method (100, 200) according to one of claims 1 to 12 and / or one of claims 13 to 24, in, In the case where at least one of the signals transmitted during a channel occupancy time (COT) is transmitted over a plurality of sub-bands of said sidelink channel, wideband operation is preferably used, At least part of the sidelink control information is sent in a physical sidelink control channel (PSCCH), Among them, the physical side link control channel (PSCCH) is sent as follows: - at least one subband of the sidelink channel, or - All subbands for which the result of channel contention is positive.

26. The method (100, 200) according to one of claims 1 to 12 and / or one of claims 13 to 25, The first radio node (UE1) and / or the second radio node (UE2) operate in a frame-based device mode or a load-based device mode.

27. A first radio node (UE1), comprising: - Radio modems; - a non-transitory computer-readable medium comprising machine-readable instructions; - a processor configured to load and execute the machine-readable instructions to cause the second radio device to perform the method (100) according to one of claims 1 to 12.

28. A second radio node (UE2), comprising: - Radio modems; - a non-transitory computer-readable medium comprising machine-readable instructions; - a processor configured to load and execute the machine-readable instructions to cause the second radio device to perform the method (200) according to one of claims 13 to 26.

29. A system for radio communication, comprising: - a first radio node (UE1) as defined in claim 27; and - A second radio node (UE2) as defined in claim 28.

30. A computer program element comprising machine-readable instructions which, when loaded and executed by a processor, - causing the processor to execute the method (100) according to one of claims 1 to 12 and / or - causing the processor to execute a method (200) according to one of claims 13 to 26.

31. A non-transitory computer readable medium comprising machine readable instructions as defined in claim 30.

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