First radio terminal, operating method thereof, and method of operating a radio communication network

Abstract

A first radio terminal, an operation method thereof, and a method of operating a radio communication network. A method of operating a first radio terminal of a radio communication network is provided, wherein the method comprises: determining an SPS configuration of the first radio terminal, wherein the SPS configuration indicates a set of radio resources for SPS semi-persistent scheduling of a shared device-to-device radio channel, in particular a side link channel SL‑CH, wherein the indicated SPS radio resources are intended for transmission by the first radio terminal; transmitting data towards at least one second radio terminal via a first subset of the set of SPS radio resources; selecting at least one sensing resource from the set of SPS radio resources; sensing the at least one sensing resource; determining a contention indicator depending on the sensing of the at least one sensing resource; and suppressing transmission of data via a second subset of the set of SPS radio resources if the contention indicator indicates a contention situation at the at least one sensing resource.

Description

[0001] State of the art

[0002] The invention relates to a first radio terminal, a method of operating a first radio terminal and a method of operating a radio communications network.

[0003] Vehicle-to-Everything (V2X) is a system that enables information to be transferred between vehicles, between vehicles and infrastructure, between vehicles and networks, or between vehicles and other mobile devices. The system uses direct communication technology, which is called direct short-range communication (DSRC) in IEEE standards or sidelink communication in 3GPP standards. Generally speaking, the direct sidelink communication channel is a direct channel between two mobile devices or fixed infrastructure nodes. Summary of the invention

[0004] According to a first aspect of the present specification, a first radio terminal of a radio communication network, in particular a V2X UE of a V2X network, is provided, wherein the first radio terminal comprises at least one processor, at least one memory comprising computer program code, at least one communication module and at least one antenna, wherein the computer program code and the memory are configured together with the at least one processor, the at least one communication module and the at least one antenna so that the radio terminal at least: determines an SPS configuration for the first radio terminal, wherein the SPS configuration indicates a set of radio resources for SPS semi-persistent scheduling of a shared device-to-device radio channel, in particular a side link channel SL-CH, wherein the indicated SPS radio resources are intended to be transmitted by the first radio terminal; transmits data toward at least one second radio terminal via a first subset of the SPS radio resource set; selects at least one sensing resource from the SPS radio resource set; senses the at least one sensing resource; determines a contention indicator depending on the sensing of the at least one sensing resource; and if the contention indicator indicates a contention situation at the at least one sensing resource, suppresses the transmission of data via a second subset of the SPS radio resource set.

[0005] For example, the SPS configuration determination involves the first radio terminal determining the SPS configuration, eg (pre-) configuration, via sensing, via control channel decoding and reservation decoding, via upper layer messages, and the like.

[0006] The proposed scheme provides an adaptive distributed SPS scheme. Due to the sensing operation at the expense of omitting the transmission opportunity of a subset of SPS sidelink resources, other radio terminals in the vicinity can start or continue their sidelink transmissions. Both the centralized scheduling case and the distributed scheduling case are beneficial.

[0007] According to an advantageous example, the first radio terminal is further configured to transmit data towards the at least one second radio terminal via a second subset of the set of SPS radio resources if the contention indicator indicates no contention situation at the at least one sensing resource.

[0008] Advantageously, a reselection procedure is provided that allows reselection of SPS resources, ie to avoid communication interruptions or sensing interruptions.

[0009] According to an advantageous example, the first radio terminal is further configured to: determine at least one auxiliary radio resource, wherein the at least one auxiliary radio resource and the set of SPS radio resources are disjoint; transmit data towards the at least one second radio terminal via the at least one auxiliary radio resource.

[0010] The use of auxiliary radio resources to transmit payload data helps to avoid order conflicts of long SPS transmissions of different radio terminals. SPS reservations are protected from degradation. The auxiliary radio resources are determined out of order relative to the SPS radio resources. Therefore, transmission diversity is increased and QoS requirements can be maintained, thereby eliminating or reducing transmissions via sensing resources.

[0011] According to an advantageous example, the data transmitted via the at least one secondary radio resource comprises an out-of-order indicator indicating that the secondary radio resource is a secondary radio resource.

[0012] Other radio terminals sensing the out-of-order indicator acquire the knowledge that the functionality, in particular the secondary radio resource, is not an SPS resource and may refrain from transmitting via the detected secondary radio resource.

[0013] According to an advantageous example, the selection of the at least one sensing resource comprises selecting the at least one sensing resource from the SPS resource set upon expiration of a time period since a first transmission via the SPS resource set or upon reaching a number of transmissions via the SPS resource set.

[0014] This time period provides a deterministic behavior of the first radio terminal in using the SPS radio resources and sensing.

[0015] According to an advantageous example, the time period or the number of transmissions is determined depending on at least one of: a measured channel load of the physical device-to-device channel, a current state of an egress queue of the first radio terminal and a QoS indicator.

[0016] Adaptive sensing is provided by taking into account eg the channel loading.Thus, distributed transmission is beneficial when the first radio terminal adapts its behavior to the radio situation in its surroundings.

[0017] According to a favorable example, determining a contention indicator comprises: decoding SCI side link control information present in at least one received sensing resource; determining a plurality of radio resources, in particular a set of SPS resources, reserved for another radio terminal depending on the decoded SCI; and if a second subset of the set of SPS radio resources and the determined plurality of radio resources do not intersect, determining that the contention indicator indicates that there is no contention.

[0018] Therefore, if the SCI information is used to determine that the second subset of SPS radio resources can be used to resume and continue data transmission.

[0019] According to an advantageous example, determining the contention indicator comprises: determining a received signal strength of the at least one sensing resource; comparing the received signal strength with a threshold; and determining the contention indicator depending on the comparison.

[0020] If the signal strength is above the threshold, the first radio terminal determines a contention situation and may advantageously react in order to overcome the potential resource conflict.

[0021] According to an advantageous example, the sensing comprises: sensing a first part of the sensing resources; and transmitting data in a second part of the sensing resources towards the at least one second radio terminal.

[0022] Advantageously, sub-slot sensing and transmission increases the likelihood of data transmission. Furthermore, if the first part includes SCI, sensing is included and may even be sufficient to perform SCI decoding.

[0023] According to a favorable example, suppression comprises: determining, after the SPS configuration has elapsed, a further SPS configuration for the first radio terminal, wherein the further SPS configuration indicates a further set of further SPS radio resources of a shared device-to-device radio channel, in particular a side link channel SL-CH, wherein the indicated further SPS radio resources are intended to be transmitted by the first radio terminal; and starting transmission of data towards the at least one second radio terminal via the further set of SPS radio resources if a time period has not elapsed since sensing of the at least one sensing resource and before a first transmission via the further set of SPS radio resources.

[0024] Therefore, depending on the QOS requirement, data transmission continues. The time period since sensing guarantees the QoS requirement.

[0025] According to an advantageous example, the first radio terminal is further configured to transmit a contention indicator towards the at least one second radio terminal, wherein the transmitted contention indicator indicates a contention situation at the at least one sensing resource and an identity of the at least one sensing resource.

[0026] Advantageously, radio terminals in the vicinity have knowledge of the contention situation on the at least one sensing resource and may omit transmission on this resource.

[0027] According to an advantageous example, the data transmitted towards the at least one second radio terminal comprises a reservation indicator indicating an identity of a subsequent SPS radio resource or a subsequent auxiliary radio resource for transmission by the first radio terminal.

[0028] By distributing the identity of subsequent SPS radio resources or subsequent auxiliary radio resources, the at least one second radio terminal can refrain from using these resources for transmission.

[0029] According to an advantageous example, the data transmitted towards the at least one second radio terminal comprises a sensing indicator indicating an identity of a subsequent SPS radio resource for sensing by the first radio terminal.

[0030] By distributing the identities of subsequent sensing resources, the at least one second radio terminal can refrain from using these resources for transmission.

[0031] According to a second aspect of the present specification, a method for operating a first radio terminal of a radio communication network, in particular a V2X UE of a V2X network, is provided, wherein the method comprises: determining an SPS configuration for the first radio terminal, wherein the SPS configuration indicates a set of radio resources for SPS semi-persistent scheduling of a shared device-to-device radio channel, in particular a side link channel SL-CH, wherein the indicated SPS radio resources are intended to be transmitted by the first radio terminal; transmitting data toward at least one second radio terminal via a first subset of the set of SPS radio resources; selecting at least one sensing resource from the set of SPS radio resources; sensing the at least one sensing resource; determining a contention indicator depending on the sensing of the at least one sensing resource; and if the contention indicator indicates a contention situation at the at least one sensing resource, suppressing the transmission of data via a second subset of the set of SPS radio resources.

[0032] According to a third aspect of the specification, there is provided a method of operating a radio communication network, wherein the radio communication network comprises a second radio terminal and a first radio terminal according to the first aspect.

[0033] In each figure,

[0034] Figure 1 depicts a schematic flow chart for operating a first radio terminal;

[0035] Figures 2 to 5each depicts a schematic sequence diagram for operating a radio communications network;

[0036] Figure 6 Describes the problems with the prior art; and

[0037] Figure 7 The structure of a first radio terminal is depicted.

[0038] Figure 1 A schematic flow chart of a first radio terminal for operating a radio communication network, in particular a V2X UE for operating a V2X network is depicted. According to step 102, the first radio terminal determines an SPS configuration for the first radio terminal, wherein the SPS configuration indicates a set of radio resources for SPS semi-persistent scheduling of a shared device-to-device radio channel, in particular a sidelink channel SL-CH. The indicated SPS radio resources are intended for transmission by the first radio terminal.

[0039] The sidelink channel SL-CH includes, for example, a physical sidelink shared channel PSSCH and a physical sidelink control channel PSCCH. The sidelink describes the UE-to-UE interface for sidelink communication, sidelink discovery and V2X sidelink communication. The sidelink corresponds to the PC5 interface for sidelink communication and sidelink discovery as well as V2X sidelink communication. The sidelink communication includes the functionality of enabling ProSe direct communication between two or more neighboring UEs, using E-UTRA technology but without traversing any network nodes.

[0040] The determination according to step 102 is done by a central scheduling unit or in a distributed manner. Thus, according to the example of distributed scheduling, step 102 comprises determining a transmission opportunity in the form of an SPS configuration comprising a set of SPS resource sets rr1-rr4. The determination according to step 102 of the distributed scheme may comprise sensing whether a resource is idle or occupied.

[0041] According to step 104, the first radio terminal transmits data towards at least one second radio terminal via the first subset of the SPS radio resource set. The first radio terminal may reserve only one subsequent look ahead SPS radio resource at a time, i.e., ultimately for the next future transmission. If a stop condition is triggered in step 106, the first radio terminal skips the data transmission of the next transmission opportunity or the subsequent next transmission opportunity with the maximum time. The latter may be allowed to meet QoS, latency requirements or UE capabilities such as processing time.

[0042] According to step 106, the first radio terminal selects at least one sensing resource from the set of SPS radio resources.

[0043] According to step 108, the first radio terminal senses the at least one sensing resource.

[0044] According to step 110, the first radio terminal determines a contention indicator dependent on sensing of said at least one sensing resource.

[0045] According to step 114, if the contention indicator indicates a contention situation at the at least one sensing resource, the first radio terminal refrains from transmitting data via the second subset of the SPS radio resource set. Step 114 includes clearing the configured side link grant at the end of the corresponding SC side link control period. In other words, SPS release is performed for future SPS radio resources.

[0046] The SC cycle consists of the transmission of SCI sidelink control information and its corresponding data. SCI contains sidelink scheduling information such as resource block allocation, modulation and coding scheme, group destination ID (for sidelink communication) and PPPP, ProSe per-packet priority (for V2X sidelink communication).

[0047] The data transmitted towards the at least one second radio terminal comprises control information and a payload.

[0048] According to an example, the data transmitted towards the at least one second radio terminal comprises a reservation indicator indicating an identity of a subsequent SPS radio resource or a subsequent auxiliary radio resource for transmission by the first radio terminal.

[0049] According to an example, the data transmitted towards the at least one second radio terminal comprises a sensing indicator indicating an identity of a subsequent SPS radio resource for sensing by the first radio terminal.

[0050] The selection of sensing resources according to step 106 is exemplified below. According to an example, the selection process is configured via, for example, SIB acquisition (e.g., SIBX, SIBY, SIB21, SIB 26) or via a dedicated RRC message. According to an example, the selection information about the location of the sensing resources and the selection process is configured in a resource pool configuration information element, for example, in a sidelink BWP configuration and or SL operator configuration. The cell may be activated or deactivated during SIB acquisition or reacquisition or during RRC reconfiguration or configuration.

[0051] Skipping transmission of configured SPS radio resources and sensing the sensing resources instead is referred to as skipping in the following.The triggering event for determining the sensing resources is mentioned in the following in relation to a timer or a counter.

[0052] When acquiring SIBs with configuration of skipping and / or configuration of timers, or performing activation of skipping operations or performing activation of said timer / counter operations, the first radio terminal UE1 is expected to perform skipping according to the (pre)configured timer / counter value as specified before.

[0053] According to an example, in the coverage case, the network provides the timer / counter value, eg via an RRC configuration received by the radio terminal.

[0054] According to another example, in out of coverage case, the UE uses its configuration of preconfigured timer / counter values ​​or information elements received via the sidelink control channel.

[0055] For example, a SIB (e.g., SIBX, SIBY, SIBZ, etc.) includes sl-ConfigCommon, which may, for example, contain sl-BWP-Config and / or SL-BWP-Pool-Config or sl-ResourcePool-Config information elements, which contain the configuration and / or activation / deactivation of the fields, i.e., in (one or more) TX resource pool configurations.

[0056] For example, when a dedicated RRC message configures a skip mechanism or a skip counter / timer, the value of the timer / counter and / or the process for skipping, such as sub-slots, delayed skipping, early skipping, etc. is configured. If not, the configuration in the SIB information and / or the configuration in the SL pre-configuration message may be used.

[0057] According to an example, a cell manager residing, for example, in a base station decides to activate or deactivate said operation / timer / counter. Therefore, the first radio terminal checks the RRC pre-configuration sidelink (or any other SL RRC configuration element) or SIB TX pool configuration (or any configuration element) for at least one of the following fields:

[0058] - SL-Configuration Resource Skip Activation / Deactivation, e.g., Boolean {true or false};

[0059] - SL-configuration resource skip mode, e.g., enum {early skip, late skip, subslot skip (first or last)};

[0060] - SL-Configuration Resource Skip Time Activation / Deactivation or SL-Configuration Resource Skip Counter Activation / Deactivation or

[0061] - SL-Configure Resource Skip Timer / SL-Configure Resource Skip Counter, where timer can enumerate {ms20, ms50, ms100, ms200, ms300, ms400, ms600, ms1000, ms1500, ms2000} counter can enumerate {N5, N10, N20, N30, N40, N60, … and so on}.

[0062] If the first radio terminal UE1 is configured by upper layers (e.g. acquired via RRC dedicated message or during SIB (e.g. SIBX, SIBY, SIBZ, ...)) to perform out-of-order transmission. The first radio terminal UE1, after finding the skip and / or skip timer configuration, checks whether the use of out-of-order operation is "enabled" or "disabled". If the above skip operation or skip timer / counter is configured and "enabled", the first radio terminal UE1 checks the acquired SIB (e.g. SIBX, SIBY, SIBZ, etc.) - if it contains (in one of its information elements, e.g. SL-BWP-PoolConfig), or the RRC pre-configured sidelink - if it contains (in one of its information elements) such as: SL-Configuration Resource Out-of-Order Enable / SL-Configuration Resource Out-of-Order Enable (or a field, e.g. SL-Configuration Resource Out-of-Order with Boolean value {true or false}), and SL-Configuration Resource Out-of-Order Mode, e.g. enumeration {before skip, after skip}.

[0063] According to an example, if out-of-order is configured, a lower layer such as a MAC may generate a MAC PDU including: a MAC control element CE having one logical channel ID (LCID) including:

[0064] - 1 (or more bits) notifies one or more stations that the current message is an out-of-order message for a configured resource;

[0065] - If the out-of-order message is generated after a skip (e.g., when SL-ConfigurationResourcesOut-of-orderMode = AfterSkip}, then this MAC CE may contain N bits to inform other stations about: whether the SPS will continue for another (one or more) cycles; and the interfering station Layer 2 ID or Layer 1 ID and or SPS / ConfiguredResources ID of the skipped process.

[0066] Figure 2 A schematic sequence diagram for operating a radio communication network RCN is depicted.According to arrow 200, the focus of the illustration is on data transmission from a first radio terminal UE1 to a second radio terminal UE2.

[0067] The first subset ss1 is used in steps 104, 105 for transmitting data towards the second radio terminal UE2.

[0068] The selection of step 106 of the at least one sensing resource sr comprises selecting at least one sensing resource sr from the set s1 of SPS resources rr1-rr4 when a time period T1 has expired since the first transmission via the set of SPS resources rr1-rr4, or when the number of transmissions via the set s1 of SPS resources rr1-rr4 is reached.

[0069] According to an example, the time period T1 is determined based on a predefined rule that takes into account a resource reselection counter SL_RESOURCE_RESELECTION_COUNTER and a configurable threshold value probResourceKeep for the probability of keeping SPS radio resources. The threshold value probResourceKeep is selected by an upper layer to maintain SPS radio resources that are initially selected for periodic transmission longer after the expiration of SL_RESOURCE_RESELECTION_COUNTER. The predefined rule is applied when the radio terminal UE1 reserves a limited number of SPS radio resources. As a specific example of a predefined rule, the number of subframes in a set of time and frequency resources associated with a transmission opportunity of the PSSCH can be given as a specific value (e.g., Cresel). At this time, a specific value Cresel may be defined as 10 * SL_RESOURCE_RESELECTION_COUNTER (when a specific counter (e.g., SL_RESOURCE_RESELECTION_COUNTER) is set), otherwise Cresel may be set to 1 (e.g., if SL_RESOURCE_RESELECTION_COUNTER is not set). 5 or more and 15 or less random values ​​of SL_RESOURCE_RESELECTION_COUNTER may be set. For example, when SL_RESOURCE_RESELECTION_COUNTER is 5, a total of 50 subframes may be reserved for transmission of PSSCH. For example, when SL_RESOURCE_RESELECTION_COUNTER is 15, a total of 150 subframes may be reserved for transmission of PSSCH. After reaching the end of these reserved SPS resources, the radio terminal UE1 determines whether to select the next resource following the previously determined SPS scheme as the sensing resource sr by comparing the determined random number with the threshold value probResourceKeep.

[0070] The time period T1 or the number of transmissions is determined depending on at least one of: a measured channel load of a physical device-to-device channel, a current state of an egress queue of the first radio terminal UE1, and a QoS indicator. According to an example, the time period T1 is selected from a set of preconfigured time periods. According to an example, the time period T1 is configured via the network. According to an example, the time period T1 is fixed.

[0071] According to this example, in step 108, the first radio terminal UE1 senses the occupancy of the sensing resource sr because the third radio terminal UE3 transmits at least via a portion of the sensing resource sr. Therefore, the sensing of step 108 includes: sensing the first portion of the sensing resource sr; and transmitting data in the second portion of the sensing resource sr towards the at least one second radio terminal UE2.

[0072] Therefore, if sub-slot operation is allowed, the first radio terminal UE1 only skips sub-slots in sensing of the first part of the configured SPS radio resources allocated after the trigger condition is valid. For example, the first radio terminal UE1 may perform at least one of the following:

[0073] - in the second part of sensing, the transmission is postponed to the end of the time slot, thus leaving the beginning symbol of the time slot free for sensing;

[0074] - In the sensing of the second part, an early transmission at the beginning of the time slot and enough symbols left in the remainder of the time slot to allow such symbols to be sensed in the sensing of the first part.

[0075] In both examples, the first radio terminal UE1 is able to transmit on part of the time slot. In these cases, the first radio terminal UE1 must include its SCI for the other radio terminals UE2, UE3 to sense and decode the transmission. The postponed transmission or early transmission within the time slot must include enough information in the SCI to at least identify: the next transmission reservation, the indication of partial time slot skipping. In both examples, the first radio terminal UE1 is listened to for segmentation of resources (because the transmission block size must be reduced to the amount of resources in the sub-time slot duration), or data that cannot be matched in the sub-time slot transmission is discarded. If the UE is requested to sense the SCI and its associated RSRP, the UE can choose to postpone the transmission to the end of the time slot. However, if RSSI sensing is allowed, both examples are suitable for authorized skipping and sensing.

[0076] If the first radio terminal UE1 performs sub-slot resource skipping and identifies a clear channel (i.e. no collision or half-duplex is detected), the first radio terminal UE1 resumes transmission via the configured SPS radio resources. The advantage of having only sub-slot skipping is that reservation continuity is allowed, wherein the other radio terminals UE2 and UE3 will consider that the first radio terminal UE1 always transmits on the indicated SPS radio resources. However, in full-slot skipping, and if not cross-reserved by other transmissions, other UEs may assume a full grant skip and preempt the UE reservation. This can be avoided by partial slot skipping.

[0077] For partial timeslot skipping, whenever the first radio terminal UE1 performs a partial skipping, the first radio terminal UE1 avoids transmission at positions of, in particular, the skipped first part: at the beginning, i.e. decoding of a possibly conflicting SCI or associated PDCCH / PDSCH DMRS; another part of the timeslot (not necessarily the first part), where the first radio terminal UE1 may skip possible DMRS positions (for correlation detection) or RSSI calculation; and the first radio terminal UE1 may decide to skip any part of the timeslot and decide to perform energy detection.

[0078] According to the example, Figure 2 The step 110 of determining the contention indicator CONT, not shown in FIG. 1 , comprises: determining a received signal strength of the at least one sensing resource sr; comparing the received signal strength with a threshold; and determining the contention indicator CONT depending on the comparison.

[0079] According to step 114, the radio terminal UE1 decides to refrain from using the already scheduled resources rr3 and rr4 in order to avoid collisions on the radio channel CH.

[0080] According to the example, suppressing 114 comprises: according to step 202, after the SPS configuration has passed, determining a further SPS configuration for the first radio terminal UE1, wherein the further SPS configuration indicates a further set fs of further SPS radio resources rr10, rr11 of a shared device-to-device radio channel CH, in particular a side link channel SL-CH, wherein the indicated further SPS radio resources rr10, rr11 are intended to be transmitted by the first radio terminal UE1; and if a time period T2 has not passed since the at least one sensing resource sr was sensed 108 and before the first transmission via the further set of SPS radio resources rr10, rr11, then according to steps 416, 418, starting to transmit data towards the at least one second radio terminal UE2 via the further set fs of SPS radio resources rr10, rr11. According to the example, the time period T2 is selected from a set of preconfigured time periods. According to the example, the time period T2 is configured via the network. According to the example, the time period T2 is fixed.

[0081] The first radio terminal UE1 can discard the data transmission in its egress queue, or postpone the data transmission and wait for the resources rr10 and rr11. However, in the sidelink transmission grant resources in the form of sensing resources sr, the data transmission in the egress queue is skipped. Thus, the first radio terminal UE is able to listen to other conflicting transmitters like UE3, i.e. transmitters coexisting on the same reserved periodic resources.

[0082] According to an example, when triggered by the expiration of a timer T1 exceeding a preconfigured threshold, or a period of a continuous number of transmissions of a configured side link resource, the first radio terminal UE skips one (or more) configured side link SPS resources. The relationship between the timer T1, the number of consecutive transmissions after sensing the resource sr, and the reselection counter and resource retention probability for reselecting the radio resource configured by the SPS can be configured. According to an example, once the SPS is started, the timer T1 can be started and allowed to be triggered after the first reselection counter becomes 1 and / or the probability of resource retention is subject to a periodic extension.

[0083] According to an example, based on QoS or latency requirements, the first radio terminal UE1, after determining a trigger condition for the sensing resource sr, extends transmission for at least another configured time / frequency resource (like rr10 and rr11) and delays the skipped transmission until a subsequent configuration grant for the radio resources rr10, rr11.

[0084] According to the example, sub-slot transmission is allowed and the UE only skips part of the time slot to perform sensing. For example, the first part of the time slot can be skipped so that the SCI decoding and the corresponding RSRP measurement can be decoded. For example, the second part of the time slot can be skipped and only the RSSI measurement can be performed. For example, any part of the time slot and more accurately the energy detection of the skipped part. If the radio terminal UE1 identifies a resource conflict or a half-duplex problem, the radio terminal UE1 decides to cancel all remaining configured SPS resources rr3, rr4 and delete the existing configured SPS reservation.

[0085] The conditions for determining the sensing resource sr from the SPS radio resource include at least one of the following:

[0086] - timer T1 started after the first transmission of a periodic transmission opportunity expires before the upcoming transmission opportunity; and / or

[0087] - A counter counting the number of consecutive transmissions in the configured resource set s1 is intervalled with periodicity.

[0088] In order to identify which resources are selected for sensing rather than for transmission, the first radio terminal UE1 selects the following transmission opportunity(s): the subsequent transmission opportunity(s) directly following the triggering event described previously; the subsequent transmission opportunity(s) following one or more transmissions of the configured SPS radio resources, the one or more transmissions being transmitted after the triggering event and not longer than the relaxation time period;

[0089] After the first radio terminal UE1 decides to start sensing the sensing resources sr, the first radio terminal UE1 selects only one configured SPS radio resource for sensing. During the time identified for the at least one sensing resource sr, the UE turns on its receiver and performs sensing, which may include SCI decoding.

[0090] According to an example, the first radio terminal UE1 performs sensing on a plurality of configured sidelink transmission opportunities (once triggering conditions and events are met). These opportunities may be: a periodic sequence of configured sidelinks of granted transmission opportunities; a subset of resources randomly selected from the original transmission opportunities; a quasi-periodic set of transmission opportunities, which may follow a pattern or they may be selected based on, for example, the traffic density of the first radio terminal UE1, the arrival rate of MAC PDUs at the first radio terminal UE1 and / or the number of MAC PDUs remaining in the egress queue of the first radio terminal UE1.

[0091] Figure 3 A schematic sequence diagram for operating a radio communication network RCN is depicted.

[0092] According to an example, the step 110 of determining the contention indicator CONT comprises: decoding the SCI side link control information present in the received at least one sensing resource sr; determining a set s3 of a plurality of radio resources r2_UE2, r3_UE3, in particular SPS resources r2_UE2, r3_UE3, reserved for the further radio terminal UE3 depending on the decoded SCI; and determining that the contention indicator CONT indicates no contention if the second subset ss2 of the set s1 of SPS radio resources rr1-rr4 and the determined plurality of radio resources r2_UE3, r3_UE3 are disjoint. Decoding the SCI may result in determining a source ID of the third radio terminal UE3 of the transmission and / or a destination ID of the transmission.

[0093] According to steps 112, 116, if the contention indicator CONT indicates no contention situation at the at least one sensing resource sr, the first radio terminal UE1 resumes its transmission and transmits data towards the at least one second radio terminal UE2 via the second subset ss2 of the set s1 of SPS radio resources rr1-rr4.

[0094] As soon as the evaluation results in a positive collision or half-duplex problem, the first radio terminal UE1 sets the contention indicator CONT to parameterize the result of the evaluation process such that: SL_resourceContention = true. In the same example, if the evaluation does not identify any collision and / or half-duplex problem, the contention indicator CONT remains at the default value "false".

[0095] According to an example, in case SL_resourceContention is set to true, the first radio terminal UE1 triggers a reselection procedure if UE1 is allocated to those sidelink resources using autonomous resource mode, i.e. mode 2, or UE1 sends a configured grant reconfiguration request to the network. Additionally, UE1 deletes any remaining configured sidelink grant associated with said periodic transmission.

[0096] A first radio terminal UE1, which skips one transmission for sensing at a sensing resource sr, transmits a contention indicator CONT to other radio terminals UE2, UE3 in the vicinity of the first radio terminal UE1, thereby announcing a possible conflict or half-duplex problem. In this case, the first radio terminal UE1 can only notify the conflicting radio terminal UE3, i.e., the UE1 present in the same SPS reservation period in which the UE1 suspects that the UE3 will conflict or overlap with its own resources. Conflicting radio resources or half-duplex situations can be detected based on: SCI decoding and / or RSRP measurement, RSSI decoding; Physical layer ID (L1 ID) resolution, for example, if one or more UEs transmit in the same time slot (half-duplex problem) and the L1-ID is in the UE L1 ID list; Layer 2 ID (L1 ID) resolution, for example, if one or more UEs transmit in the same time slot (half-duplex problem) and the L1-ID is in the UE L1 ID list. Based on this resolution (and UE decoding capabilities and implementation), the first radio terminal UE1 identifies whether the resources conflict / overlap with resources of other UEs.

[0097] Thus, if the first radio terminal UE1 detects a contention situation with conflicting or overlapping resources, as a result of resolving the situation the first radio terminal UE1 transmits an out-of-sequence transmission such that:

[0098] - The first radio terminal UE1 sends said out-of-sequence message (ie the identified UE causing the collision / overlapping problem) via at least one auxiliary radio resource ar1, ar2 in a unicast transmission.

[0099] - The first radio terminal UE1 transmits the out-of-order message in a multicast transmission (i.e. for those identified UEs causing the conflict / overlapping problem). In this case, those UEs must reside in a certain communication range. The conflict / half-duplex situation resolution communication range is configured for the first radio terminal UE1. Therefore, any UE that may be outside of the communication range may not be requested to perform the resolution of the conflict / half-duplex situation.

[0100] - The first radio terminal UE1 sends said out-of-sequence message in a broadcast transmission (ie to all UEs present in the vicinity of said UE). In this case, the UE may not be able to identify the colliding / overlapping UE-ID(s).

[0101] In all communication broadcast types - unicast, multicast and broadcast - out-of-sequence control information may be carried via physical sidelink control information (SCI) or PC5 (ie, sidelink interface) radio resource control (RRC) signaling.

[0102] According to an example, the first radio terminal UE1 transmits at least an initial transmission and more than one redundant transmission version, which is for example another code version or an identical copy of the initial transmission, on each transmission opportunity according to the SPS radio resource. In each of these transmissions, there may be a reservation including one or more of the following situations:

[0103] - for an initial transmission, there may be a reservation for another redundancy version associated with the initial transmission, and a reservation for another initial subsequent transmission;

[0104] - the redundancy version(s) are reserved only for subsequent transmissions of similar redundancy versions, e.g. of the same level (e.g. RV1), for future subsequent retransmissions;

[0105] - The initial transmission and the redundant version also reserve each other's resources in subsequent transmission opportunities in a chain-based reservation.

[0106] In the last case as stated above, if only one configured time / frequency resource is skipped, then after the skipped transmission slot there will be at least one reservation remaining for a subsequent transmission.

[0107] Data packets are generated by upper layers and are segmented at the RLC layer (after PDCP grouping). A segment is called a transport block (TB) in lower layers (starting from MAC). The transport block size (TBS) is usually calculated after the physical layer modulation and coding scheme selection (i.e., this means that it includes information data and some parity bits). Finally, a cyclic redundancy check is added to the block representing the redundancy version consisting of: some information data, some parity bits, and CRC. The CRC itself is a function of the other two data parts (information and parity). Since channel coding usually uses a low modulation and coding scheme depth, a circular buffer is used to sort the information data and all possible parity bits. In the first redundancy version, some more information bits and some parity bits are selected from the circular buffer. If another retransmission is needed (blind retransmission or confirmation-based retransmission), another redundancy version is used. In this case, the new (second) redundancy version is considering some (other) information bits + some (other) parity bits, which are different from the values ​​of the first transmission, for example. Similar to the first version of the redundancy version, a CRC block is combined to the coded TB.

[0108] Each redundancy version refers to partial information bits and partial parity bits arranged in a circular buffer. The CRC result of each redundancy version is appended to each redundancy version bit forming a complete transport block size, for example according to a provided CRC function polynomial function, i.e., the CRC of each redundancy version is different.

[0109] Figure 4A schematic sequence diagram for operating a radio communication network RCN is depicted.

[0110] According to step 402, the first radio terminal UE1 determines at least one auxiliary radio resource ar1, ar2, wherein the at least one auxiliary radio resource ar1, ar2 and the set s1 of SPS radio resources rr1-rr4 are disjoint.

[0111] According to an example, step 402 includes randomly selecting time and frequency resources for SL-SCH and SCI for the sidelink grant from the selected resource pool. The random function should be such that each allowed selection can be selected with equal probability.

[0112] According to steps 404, 406, the first radio terminal UE1 transmits data via the at least one auxiliary radio resource ar1; ar2 towards the at least one second radio terminal UE2.

[0113] According to step 404, the data transmitted via the at least one secondary radio resource ar1; ar2 comprises an out-of-order indicator OOS indicating that the secondary radio resource ar1; ar2 is a secondary radio resource ar1; ar2.

[0114] According to step 406, the first radio terminal UE1 transmits a contention indicator CONT towards the at least one second radio terminal UE2, wherein the transmitted contention indicator CONT indicates a contention situation at the at least one sensing resource sr and an identity of the at least one sensing resource sr.

[0115] According to the example, according to step 114, the suppression comprises: according to step 412, after the SPS configuration has passed, determining an additional SPS configuration for the first radio terminal UE1, wherein the additional SPS configuration indicates an additional set fs of additional SPS radio resources rr10, rr11 of the shared device-to-device radio channel CH, in particular the side link channel SL-CH, wherein the indicated additional SPS radio resources rr10, rr11 are intended to be transmitted by the first radio terminal UE1; and if a time period T2 has not passed since the at least one sensing resource sr was sensed 108 and before the first transmission via the additional set of SPS radio resources rr10, rr11, then according to steps 416, 418, starting to transmit data towards the at least one second radio terminal UE2 via the additional set fs of SPS radio resources rr10, rr11.

[0116] The auxiliary radio resources ar1, ar2 are located before and after the sensing resources sr for performing sensing measurements. Of course, only one of the auxiliary radio resources ar1, ar2 may be used for transmitting data towards the second radio terminal UE2.

[0117] According to an example, according to step 402, the first radio terminal UE1 selects out-of-order transmission time / frequency resources in the auxiliary radio resources ar1, ar2 sensing within a selection window of length T_slots, which resources do not include any of the configured SPS sidelink resources rr1 to rr4.

[0118] According to an example, the first radio terminal UE1 extends the transmission of data, the first radio terminal UE1 transmitting via the at least one auxiliary radio resource ar1 , ar2 which may be reserved by the next configured resource following the triggering condition.

[0119] Once the trigger condition occurs, the first radio terminal UE1 selects a radio resource for transmission from the new or old configured or pre-configured sensing window radio resources, which may be:

[0120] - in the sensing of the sensing resource sr, a single radio resource that is transmitted once in the selection window directly after the triggering event and before the skipped transmission opportunity;

[0121] - a single radio resource that transmits once in the selection window directly after a triggering event and after skipping the next possible transmission opportunity in sensing of the sensing resource sr after said triggering event;

[0122] - a single radio resource (which is transmitted in more than one selection window, i.e. the current following event and the subsequent event). This can be sent before or after the skipped transmission opportunity;

[0123] - Resources within the same selection window, i.e. following the transmission time / frequency pattern. Those resources or those sub-resources can be used to ensure that there are enough transmission opportunities for other UEs to detect an out-of-order situation.

[0124] According to an example, if retransmission, eg HARQ retransmission, is activated, according to step 402 the first radio terminal UE1 selects at least one retransmission opportunity occurring before or after the skipped configured sidelink grant as the at least one auxiliary radio resource ar1 , ar2 .

[0125] According to an example, the first radio terminal UE1 randomizes the position of the at least one auxiliary radio resource ar1 , ar2 if data is transmitted more than once during the time of the configured SPS sidelink resources rr1 - rr4 .

[0126] According to an example, the data transmitted via the at least one auxiliary radio resource ar1 , ar3 specifically comprises a preconfigured or configurable pattern if data is transmitted more than once during the time of the configured sidelink resource in order to identify that the data transmission is repeated.

[0127] The data transmitted via the at least one auxiliary radio resource ar1, ar2, in particular out-of-order transmission content, message side link control information (SCI) sent via a physical control channel or a message control channel sent via a shared data channel, comprises at least one of the following:

[0128] - an identifier or field or at least one bit in the sidelink control information indicating that the transmission is out of order configured (periodic) sidelink resource, where the contention field can be either "true" if present or "false" if not present; additionally, an identifier of the contention resource affected by the contention (as reserved in time / frequency) or an identifier of the SPS / configured grant index, if present;

[0129] - reservation of skipped (and cancelled) transmission slots in the sensing of the sensing resource sr in order to reserve the originally configured resources;

[0130] - reservation for subsequent transmissions within the configured SPS radio resources rr3, rr4, where the first radio terminal UE1 intends to resume the configured (periodic) transmission; if UE1 wants to resume (e.g. after indicating an intention to resume), and UE1 decides to resume on the same, previously reserved, SPS / configured grant resources, requesting UE1 to send a reservation for subsequent transmissions within the same configured resources, where UE1 intends to resume the same configured (periodic) SPS transmission. This is important for those UEs that can only decode out-of-sequence transmissions;

[0131] - otherwise, if UE1 wants to resume (e.g. after indicating an intention to resume), and UE1 decides to resume on the time-frequency resources, requesting UE1 to send a new periodic reservation interval for use of said configured resources after UE1 indicates to continue (periodic) transmission;

[0132] - The QoS of the UE transmission, or a new QoS for the continuation of the transmission sequence, i.e. if the UE has to increase the QoS of the SPS transmission to resolve the conflict

[0133] - a periodic reservation interval for said configured SPS radio resources rr3, rr4 to be used after the first radio terminal UE1 has indicated to continue with the (periodic) transmission; and

[0134] - If the first radio terminal UE1 identifies a possible conflict, or resource contention for a higher QoS transmission of another UE, or a half-duplex problem, the remaining configured resources rr3, rr4 are cancelled.

[0135] The first radio terminal UE1 notifies other radio terminals, such as the radio terminal UE3, about their conflict or half-duplex problems by transmitting a corresponding indicator like OOS toward at least one radio terminal UE3 near the first radio terminal UE1. According to an example, the first radio terminal UE1 sends unicast sidelink control information or sidelink radio resource control (RRC) information to the conflict / half-duplex UE3. According to another example, the first radio terminal UE1 sends multicast sidelink control information or multicast sidelink radio resource control (RRC) to all possible conflict / half-duplex UEs or UEs associated with the communication range of the first radio terminal UE1. The conflict / half-duplex problem solving communication range can be configured / preconfigured for the first radio terminal UE1. According to another example, the first radio terminal UE1 sends broadcast sidelink control information or broadcast sidelink radio resource control (RRC) information or sidelink master information blocks to all UEs in the domain.

[0136] The control information for data transmitted via the secondary radio resources ar1, ar2 includes identifiers of contention / half-duplex issues regarding: the reservation period / SPS index (if any), the QoS of the UE transmission, the UE1's intention to resume or cancel the transmission.

[0137] According to an example, once the first radio terminal UE1 periodically starts transmission via the auxiliary radio resources ar1, ar2 in a plurality of selection windows, the first radio terminal UE1 transmits a plurality of out-of-sequence transmissions until it recovers the originally configured SPS resources, such as Figure 5 . Thus, if the first radio terminal UE1 transmits more than one out-of-order transmission before resuming transmission via the authorized SPS radio resource, the first radio terminal UE1 may also be configured to select: a random radio resource for each out-of-order transmission (a plurality of out-of-order transmissions), or a set of resources mapped following the configured time / frequency resource pattern for a plurality of out-of-order transmissions. However, if N consecutive configured resources have passed, the first radio terminal UE1 performs reselection and deletes the originally reserved SPS radio resource. In another example, the first radio terminal UE1 chooses to perform out-of-order transmissions until a completely newly configured SPS radio resource is selected.

[0138] For selecting out-of-order resources, a selection window of length T_slots may be considered for this procedure as follows: either the same window size and position as the original SPS / configured sidelink resource selection window, or a window different from the original SPS / configured sidelink resource selection window, which may also be considered to include any reserved configured sidelink resources, but exclude them during resource selection, or a short selection window excluding all originally reserved resources. In the latter option, i.e., the sensing window for the out-of-order transmission(s) does not include the original resources; the first radio terminal UE1 may consider a short sensing window for this operation.

[0139] According to an example, if the first radio terminal UE1 Figure 5 For example, if the first radio terminal UE1 extends its transmission for its originally reserved SPS resources for QoS or strict latency requirements, the first radio terminal UE1 may only consider continuing the original resource reservation after no more than T_relax time slots have passed. Therefore, after the triggering event plus time T2 (with a maximum value of T_relax), the radio terminal UE1 performs a grant skip and allows sensing in such a situation. Additionally, as described above, the first radio terminal UE1 transmits out-of-sequence transmissions via the auxiliary radio resources ar1, ar2.

[0140] Figure 5 A schematic sequence diagram for operating a radio communication network RCN is depicted.

[0141] According to step 502, the first radio terminal UE1 determines the at least one auxiliary radio resource ar1, ar2, wherein the at least one auxiliary radio resource ar1, ar2 and the set s1 of SPS radio resources rr1-rr4 are disjoint.

[0142] According to steps 504, 506, the first radio terminal UE1 transmits data towards the at least one second radio terminal UE2 via the at least one auxiliary radio resource ar1; ar2.

[0143] According to an example, the first radio terminal UE1 is configured to send data via more than one auxiliary radio resources ar1 and ar2 before resuming transmission via SPS resources rr3 and rr4. In this case, the first radio terminal UE1 is configured to: select a random auxiliary radio resource ar1, ar2 for each out-of-order transmission, and / or select a resource pattern for the auxiliary radio resources ar1, ar2.

[0144] Figure 6The problems of the prior art are described. For periodic data transmission in mode 2 resource allocation, semi-persistent scheduling SPS is used. In this case, the UEA performs a sensing mechanism, in which the UEA selects transmission resources in terms of time and frequency. Similar identical copies of these resources (in terms of both time and frequency) are repeated at a period selected from an enumerated (configured or preconfigured value). Once the initial transmission is selected, the UEA adds the time resource (e.g., a time slot index in a resource pool), the frequency resource (e.g., as a subchannel start index and the number of consecutive N subchannels) and the reservation period P_resv to its sidelink control information (SCI). The initial transmission does not indicate how many periods these resources are reserved.

[0145] The UEB's ability to successfully decode the initial SCI (or any subsequent SCI) may indicate that those resources are reserved for multiple cycles.

[0146] However, if the UEC cannot successfully receive the initial SCI or subsequent SCI on the physical sidelink control channel PSCCH, the UEC will fail to indicate those resources as reserved. In this case, the UE3 is allowed to reselect those resources that conflict on the physical sidelink shared channel PSSCH for their own transmission.

[0147] UE3 may not be able to decode the SCI if any of the following situations occurs: the transport block (including the intended SCI) overlaps with the UE's own transmission in the same time and frequency resources; the transport block (including the intended SCI) overlaps with the UE's own transmission in the same time resources but different frequency resources; due to channel path loss and propagation errors.

[0148] Figure 7 The structure of a radio terminal UE1 is depicted. The radio terminal UE1 comprises at least one processor P, at least one memory M comprising a computer program code CP, at least one communication module C and at least one antenna A, wherein the computer program code CP is configured to interact with the at least one processor P, the at least one communication module C and the at least one antenna A so as to cause the radio terminal UE1 to perform the above method.

Claims

1. A first radio terminal (UE1) of a radio communication network (RCN), wherein the first radio terminal (UE1) comprises at least one processor, at least one memory including computer program code, at least one communication module and at least one antenna, wherein the computer program code and the memory together with the at least one processor, the at least one communication module and the at least one antenna are configured so that the radio terminal (UE1) at least: determining (102) an SPS configuration for a first radio terminal (UE1), wherein the SPS configuration indicates a set (s1) of SPS semi-persistently scheduled radio resources (rr1-rr4) of a shared device-to-device radio channel (CH), wherein the indicated SPS radio resources (rr1-rr4) are intended for transmission by the first radio terminal (UE1); transmitting (104) data towards at least one second radio terminal (UE2) via a first subset (ss1) of a set (s1) of SPS radio resources (rr1-rr4); selecting (106) at least one sensing resource (sr) from a set (s1) of SPS radio resources (rr1-rr4); sensing (108) the at least one sensing resource (sr); determining (110) a contention indicator (CONT) dependent on sensing (108) of the at least one sensing resource (sr); and If the contention indicator (CONT) indicates a contention situation at the at least one sensing resource (sr), transmitting data via a second subset (ss2) of the set (s1) of SPS radio resources (rr1-rr4) is suppressed (114).

2. The first radio terminal (UE1) according to claim 1, the first radio terminal (UE1) being further configured to: If the contention indicator (CONT) indicates that there is no contention situation at the at least one sensing resource (sr), data is transmitted (112, 116) towards the at least one second radio terminal (UE2) via a second subset (ss2) of the set (s1) of SPS radio resources (rr1-rr4).

3. The first radio terminal (UE1) according to claim 1 or 2, the first radio terminal (UE1) being further configured to: determining (402; 502) at least one auxiliary radio resource (ar1; ar2), wherein the at least one auxiliary radio resource (ar1; ar2) and the set (s1) of SPS radio resources (rr1-rr4) are disjoint; Data is transmitted (404, 406; 504, 506) towards the at least one second radio terminal (UE2) via the at least one auxiliary radio resource (ar1; ar2).

4. The first radio terminal (UE1) according to claim 3, wherein: Data transmitted via the at least one secondary radio resource (ar1; ar2) includes an out-of-order indicator (OOS) indicating that the secondary radio resource (ar1; ar2) is a secondary radio resource (ar1; ar2).

5. The first radio terminal (UE1) according to claim 1, wherein: The first radio terminal (UE1) is a V2X UE of the V2X network.

6. The first radio terminal (UE1) according to claim 1, wherein: The shared device-to-device radio channel (CH) is the sidelink channel SL-CH.

7. The first radio terminal (UE1) according to one of the preceding claims 1-2, wherein The at least one sensing resource (sr) is selected depending on a resource reselection counter and a threshold of a probability of retaining the SPS radio resource.

8. The first radio terminal (UE1) according to one of the preceding claims 1-2, wherein the selection (106) of the at least one sensing resource (sr) comprises: When a time period (T1) since the first transmission via the set of SPS resources (rr1-rr4) expires, or when the number of transmissions via the set (s1) of SPS resources (rr1-rr4) is reached, the at least one sensing resource (sr) is selected from the set (s1) of SPS resources (rr1-rr4).

9. The first radio terminal (UE1) according to claim 8, wherein: The time period (T1) or the number of transmissions is determined depending on at least one of: a measured channel load of a physical device-to-device channel, a current state of an egress queue of the first radio terminal (UE1), and a QoS indicator.

10. The first radio terminal (UE1) according to one of the preceding claims 1 - 2, wherein determining (110) the contention indicator (CONT) comprises: decoding SCI sidelink control information present in at least one received sensing resource (sr); determining a plurality of radio resources (r2_UE2, r3_UE3) reserved for a further radio terminal (UE3) depending on the decoded SCI; and If the second subset (ss2) of the set (s1) of SPS radio resources (rr1-rr4) and the determined plurality of radio resources (r2_UE3, r3_UE3) are disjoint, then determining that the contention indicator (CONT) indicates that there is no contention.

11. The first radio terminal (UE1) according to claim 10, wherein the plurality of radio resources (r2_UE2, r3_UE3) is a set (s3) of SPS resources (r2_UE2, r3_UE3).

12. The first radio terminal (UE1) according to one of the preceding claims 1 - 2, wherein determining (110) the contention indicator (CONT) comprises: determining a received signal strength of the at least one sensing resource (sr); comparing the received signal strength with a threshold; and A contention indicator (CONT) is determined depending on the comparison.

13. The first radio terminal (UE1) according to one of the preceding claims 1-2, wherein the sensing (108) comprises: sensing a first portion of a sensing resource (sr); and Data in a second portion of the sensing resources (sr) is transmitted towards the at least one second radio terminal (UE2).

14. The first radio terminal (UE1) according to one of the preceding claims 1 - 2, wherein suppressing (114) comprises: After the SPS configuration has passed, determine (202; 412) a further SPS configuration for the first radio terminal (UE1), wherein the further SPS configuration indicates a further set (fs) of further SPS radio resources (rr10, rr11) of the shared device-to-device radio channel (CH), wherein the indicated further SPS radio resources (rr10, rr11) are intended for transmission by the first radio terminal (UE1); and If a time period (T2) has not elapsed since sensing (108) the at least one sensing resource (sr) and before a first transmission via the further set of SPS radio resources (rr10, rr11), transmission (206, 208; 416, 418) of data towards the at least one second radio terminal (UE2) via the further set (fs) of SPS radio resources (rr10, rr11) is started.

15. The first radio terminal (UE1) according to one of the preceding claims 1-2, the first radio terminal (UE1) being further configured to: A contention indicator (CONT) is transmitted (406) towards the at least one second radio terminal (UE2), wherein the transmitted contention indicator (CONT) indicates a contention situation at the at least one sensing resource (sr) and an identity of the at least one sensing resource (sr).

16. The first radio terminal (UE1) according to one of the preceding claims 1-2, wherein The data transmitted towards the at least one second radio terminal (UE2) comprises a reservation indicator indicating an identity of a subsequent SPS radio resource (rr2; rr3; rr4) or a subsequent auxiliary radio resource (ar1; ar2) for transmission by the first radio terminal (UE1).

17. The first radio terminal (UE1) according to one of the preceding claims 1-2, wherein The data transmitted towards the at least one second radio terminal (UE2) comprises a sensing indicator indicating an identity of a subsequent SPS radio resource (sr) for sensing by the first radio terminal (UE1).

18. A method of operating a first radio terminal (UE1) of a radio communications network (RCN), wherein the method comprises: determining (102) an SPS configuration for a first radio terminal (UE1), wherein the SPS configuration indicates a set (s1) of SPS semi-persistently scheduled radio resources (rr1-rr4) of a shared device-to-device radio channel (CH), wherein the indicated SPS radio resources (rr1-rr4) are intended for transmission by the first radio terminal (UE1); transmitting (104) data towards at least one second radio terminal (UE2) via a first subset (ss1) of a set (s1) of SPS radio resources (rr1-rr4); selecting (106) at least one sensing resource (sr) from a set (s1) of SPS radio resources (rr1-rr4); sensing (108) the at least one sensing resource (sr); determining (110) a contention indicator (CONT) dependent on sensing (108) of the at least one sensing resource (sr); and If the contention indicator (CONT) indicates a contention situation at the at least one sensing resource (sr), transmitting data via a second subset (ss2) of the set (s1) of SPS radio resources (rr1-rr4) is suppressed (114).

19. The method according to claim 18, wherein: The first radio terminal (UE1) is a V2X UE of the V2X network.

20. The method according to claim 18, wherein: The shared device-to-device radio channel (CH) is the sidelink channel SL-CH.

21. Method of operating a radio communication network (RCN), the radio communication network (RCN) comprising a first radio terminal (UE1) according to one of claims 1 to 17 and a second radio terminal (UE2).

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