Sidelink Intermittent Reception Procedure

Abstract

A user device for a wireless communication system is disclosed. The wireless communication system includes a plurality of user devices. The user devices receive transmissions from one or more further user devices via a sidelink. The user devices operate in a discontinuous reception mode. The user devices enter an inactive mode or a sleep mode when certain criteria are met.

Description

[Technical field]

[0001] The present application relates to the field of wireless communication systems or networks, and more particularly to discontinuous reception (DRX) on a side link (SL). [Background technology]

[0002] FIG. 1 is a schematic diagram of an example of a terrestrial-based wireless network 100 including a core network 102 and one or more radio access networks RAN1, RAN2, ...RANN, as shown in FIG. 1(a). FIG. 1(b) is a schematic diagram of an example of a radio access network RANn that may include one or more base stations gNB1-gNB5. Each base station serves a particular area surrounding the base station, which is represented generally by a respective cell 1061-1065. The base station is provided to serve users in the cell. One or more base stations may serve users in licensed and / or unlicensed bands. The term base station (BS) refers to a gNB in ​​a 5G network, an eNB in ​​UMTS / LTE / LTE-A / LTE-A Pro, or simply a BS in other mobile communication standards. A user may be a fixed or mobile device. The wireless communication system may also be accessed by mobile or fixed IoT devices that connect to the base station or the user. Mobile or fixed devices may include physical devices, ground vehicles such as robots or cars, manned or unmanned aerial vehicles (UAVs), the latter also called drones, and buildings, as well as items or devices that incorporate electronics, software, sensors, or actuators, etc., and network connections that allow the devices to collect and exchange data over an existing network infrastructure. Although FIG. 1(b) shows an exemplary diagram of five cells, RANn may include more or fewer such cells, and RANn may include only one base station. FIG. 1(b) shows two users UE1 and UE2, also called user devices or user equipment, residing in a cell 1062 and served by a base station gNB2. Another user UE3 is shown in a cell 1064, served by a base station gNB4. Arrows 1081, 1082 and 1083 represent diagrammatically uplink / downlink connections for transmitting data from users UE1, UE2 and UE3 to base stations gNB2, gNB4 or for transmitting data from base stations gNB2, gNB4 to users UE1, UE2, UE3.This may be realized on licensed or unlicensed bands. Furthermore, Fig. 1(b) shows two further devices 1101 and 1102, e.g. IoT devices, in the cell 1064, which may be fixed or mobile devices. The device 1101 accesses the wireless communication system via the base station gNB4 and transmits and receives data as represented diagrammatically by the arrow 1121. The device 1102 accesses the wireless communication system via the user UE3 as represented diagrammatically by the arrow 1122.

[0003] Each base station gNB1-gNB5 may be connected to the core network 102 via respective backhaul links 1141-1145, e.g., via an S1 interface. In FIG. 1(b), the backhaul links are represented diagrammatically by arrows pointing to "core". The core network 102 may be connected to one or more external networks. The external network may be the Internet, or may be a private network, e.g., an intranet or any other type of campus network, e.g., a private WiFi communication system or a 4G / 5G mobile communication system. Also, some or all of the respective base stations gNB1-gNB5 may be connected to each other via respective backhaul links 1161-1165, e.g., via an S1 or X2 interface, or an XN interface in NR, which are diagrammatically represented in FIG. 1(b) by arrows pointing to "gNB". Sidelink channels enable direct communication between UEs, also called device-to-device (D2D) communication. The sidelink interface in 3GPP is called PCS.

[0004] For data transmission, a physical resource grid may be used. The physical resource grid may include a set of resource elements onto which various physical channels and physical signals are mapped. For example, the physical channels may include physical downlink, uplink, and sidelink shared channels PDSCH, PUSCH, PSSCH (also referred to as downlink, uplink, and sidelink payload data) carrying user-specific data, a physical broadcast channel PBCH carrying, for example, a master information block MIB, and one or more system information blocks SIB, one or more sidelink information blocks SLIB (if supported), physical downlink, uplink, and sidelink control channels PDCCH, PUCCH, PSSCH carrying, for example, downlink control information DCI, uplink control information UCI, and sidelink control information SCI, and a physical sidelink feedback channel PSFCH carrying a PCS feedback response. The sidelink interface may support two-stage SCI. This refers to a first control area (also called first stage SCI) that contains part of the SCI, and optionally a second control area (also called second stage SCI) that contains a second part of the control information.

[0005] For the uplink, the physical channel may further include a physical random access channel PRACH or RACH, which is used by the UE to access the network after the UE synchronizes and acquires the MIB and SIB. The physical signal may include a reference signal or symbol RS, and a synchronization signal, etc. The resource grid may include a frame or radio frame having a specific duration in the time domain and a given bandwidth in the frequency domain. The frame may have a certain number of subframes of a certain length (e.g., 1 ms). Each subframe may include one or more slots of 12 or 14 OFDM symbols depending on the length of the cyclic prefix CP. The frame may have a smaller number of OFDM symbols, for example when utilizing a shortened transmission time interval sTTI or a minislot / nonslot frame structure that includes only a small number of OFDM symbols.

[0006] The wireless communication system may be any single-tone or multi-carrier system using frequency division multiplexing, such as an orthogonal frequency-division multiplexing (OFDM) system, an orthogonal frequency-division multiple access (OFDMA) system, or any other Inverse Fast Fourier Transform (IFFT) based signal with or without cyclic prefix (CP), such as Discrete Fourier Transform-spread-OFDM (DFT-s-OFDM). Other waveforms, such as non-orthogonal waveforms for multiple access, such as filter-bank multicarrier (FBMC), generalized frequency division multiplexing (GFDM), or universal filtered multi carrier (UFMC), may be used. The wireless communication system may operate, for example, according to the LTE-Advanced pro standard, or the 5G or New Radio (NR) standard, or the New Radio Unlicensed (NR-U) standard.

[0007] The wireless network or communication system shown in FIG. 1 may be a heterogeneous network with different overlay networks (e.g., a macrocell network in which each macrocell includes a macro base station such as base stations gNB1 to gNB5, and small cell base stations such as femto base stations and pico base stations, not shown in FIG. 1). In addition to the above terrestrial wireless networks, there are also non-terrestrial wireless communication networks NTN, such as transceivers operating in space, such as satellites, and / or transceivers operating in the air, such as unmanned aerial systems. The non-terrestrial wireless communication networks or systems may operate in a similar manner to the terrestrial system described above with reference to FIG. 1, for example according to the LTE-AdvancedPro standard or the 5G or NR (new radio) standard.

[0008] In a mobile communication network, e.g., in a network as described above with reference to FIG. 1, as in an LTE or 5G / NR network, there may be UEs that communicate directly with each other over one or more sidelink SL channels, e.g., using a PC5 / PC3 interface or WiFi Direct. UEs that communicate directly with each other over sidelink may include vehicles that communicate directly with other vehicles (V2V communication) and vehicles that communicate with other entities of the wireless communication network, e.g., roadside units RSUs, or roadside entities such as traffic lights, road signs, or pedestrians (V2X communication). The RSUs may have BS or UE functionality depending on the specific network configuration. The other UEs may be UEs not related to vehicles and may include any of the devices listed above. Such devices may also communicate directly with each other using SL channels (D2D communication).

[0009] Consider two UEs communicating directly with each other over the sidelink, for example using a PC5 / PC3 interface. One of the UEs may be connected to the BS and may relay information from the BS to the other UE over the sidelink interface (and vice versa). The relaying may be performed within the same frequency band (in-band relaying) or a different frequency band (out-of-band relaying) may be used. In the first case, the communications on Uu and sidelink may be separated using different time slots, as in a Time Division Duplex (TDD) system.

[0010] Figure 2 is a schematic diagram of an in-coverage scenario where two UEs communicating directly with each other are both connected to a base station. The base station gNB has a coverage area, generally represented by a circle 200, which basically corresponds to the cell generally represented in Figure 1. The UEs communicating directly with each other include a first vehicle 202 and a second vehicle 204, both of which are present within the coverage area 200 of the base station gNB. Both vehicles 202, 204 are connected to the base station gNB and furthermore, both are directly connected to each other via a PC5 interface. Scheduling and / or interference management of V2V traffic is assisted by the gNB by control signals over the Uu interface, which is the radio interface between the base station and the UE. In other words, the gNB provides the UE with SL resource allocation configuration or assistance, and the gNB also allocates resources used for V2V communication over sidelink. This configuration is also called Mode 1 configuration in NR V2X and Mode 3 configuration in LTE V2X.

[0011] FIG. 3 is a schematic diagram of an out-of-coverage scenario in which UEs in direct communication with each other may be physically present within a cell of a wireless communication network, but are not connected to a base station, or some or all of the UEs in direct communication with each other are connected to a base station, but the base station does not provide SL resource allocation configuration or assistance. For example, three vehicles 206, 208, and 210 are shown in direct communication with each other over a sidelink using a PCS interface. Scheduling and / or interference management of V2V traffic is based on algorithms implemented between the vehicles. This configuration is also called Mode 2 configuration in NR V2X and Mode 4 configuration in LTE V2X. As mentioned above, the scenario of FIG. 3, which is an out-of-coverage scenario, does not necessarily mean that a Mode 2 UE in NR or Mode 4 UE in LTE is outside the coverage 200 of a base station, but rather that the Mode 2 UE in NR or Mode 4 UE in LTE is not served by a base station, is not connected to a base station in the coverage area, or is connected to a base station but does not receive SL resource allocation configuration or assistance from the base station. Thus, within the coverage area 200 shown in FIG. 2, there may be a situation where, in addition to UEs 202, 204 in NR mode 1 or LTE mode 3, there are also UEs 206, 208, 210 in NR mode 2 or LTE mode 4. Furthermore, FIG. 3 shows, in schematic form, out-of-coverage UEs using relays to communicate with the network. For example, UE 210 may communicate with UE 212 via a sidelink, and UE 1 may connect to a gNB via a Uu interface. Thus, UE 212 may relay information between the gNB and UE 210.

[0012] 2 and 3 show vehicular UEs, it should be noted that the in-coverage and out-of-coverage scenarios described also apply to non-vehicular UEs, in other words, any UE, such as a handheld device that communicates directly with another UE using an SL channel, can be in-coverage and out-of-coverage. Summary of the Invention

[0013] In the wireless communication systems described above with reference to FIG. 1, FIG. 2 or FIG. 3, a UE communicating via a sidelink may operate in a discontinuous reception (DRX) mode.

[0014] Based on the prior art as described above, there may be a need to enhance or improve UEs that communicate over a sidelink and operate in a discontinuous reception (DRX) mode.

[0015] Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of a wireless communication system. [Diagram 2] FIG. 2 is a schematic diagram of an in-coverage scenario in which two UEs that communicate directly with each other are both connected to a base station; [Diagram 3] FIG. 3 is a schematic diagram of an in-coverage scenario in which UEs communicate directly with each other. [Figure 4] FIG. 4 illustrates a conventional DRX mode in a user device communicating with a base station. [Diagram 5] FIG. 5 is a schematic diagram of a wireless communication system including a transmitter, such as a base station, and one or more receivers, such as user devices (UEs), operable in accordance with an embodiment of the present invention. [Figure 6] FIG. 6 shows an embodiment of an extended on-duration after receiving a control message, such as sidelink control information SCI, over the sidelink, where an early termination indication is performed after reception of the message. [Figure 7] FIG. 7 shows an embodiment in which a RX UE receives respective transmission and early termination notifications from two TX UEs over the sidelink. [Figure 8]FIG. 8 illustrates an embodiment of power saving by monitoring only indicated resources, where FIG. 8(a) illustrates an embodiment of extending on-duration based on future resource reservations, and FIG. 8(b) illustrates an embodiment of active time slots monitored based on future resource reservations. [Figure 9] FIG. 9 shows an example of a computer system in which the units or modules according to the present technique and the method steps can operate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Embodiments of the invention will now be described in more detail with reference to the accompanying drawings, in which the same or similar elements are assigned the same reference numerals, and in which:

[0018] In a wireless communication system or network as described above with reference to FIG. 1, FIG. 2 or FIG. 3, sidelink communication between respective user devices, e.g. vehicle-to-vehicle communication (V2V), vehicle-to-anything communication (V2X) or any device-to-device communication (D2D) between any other user devices, e.g. as described above, may be implemented. However, in sidelink operation, such as NR-Uu operation, or PC5 operation, the UE is always awake and monitors the control channel in every subframe to be able to receive from the network or from another UE. Since the UE is always awake even when there is no data to transmit or receive, this increases the power consumption at the UE. In a vehicular use case such as NR V2X, power saving may not be an issue since the vehicular UE (V-UE) is a device with a sufficient power source, e.g. the vehicle's on-board battery.

[0019] However, sidelink communication or sidelink PC5 operation is not limited to that of vehicular UEs, other UEs with limited or finite power supplies may also communicate over the sidelink, such as regular user devices that contain batteries that need to be periodically charged. Such UEs may include so-called vulnerable road users (VUEs), such as pedestrian UEs (P-UEs), first responder devices for public safety, or IOT devices, such as general purpose IOT UEs or industrial IOT UEs. Since this kind of UEs are not connected to a constant power source and rely on batteries, power saving is important.

[0020] To reduce power consumption at the UE in NR, discontinuous reception (DRX) is employed in the Uu interface. For example, for NR, further details of DRX operation are defined in 3GPP TS 38.321. DRX is a mechanism whereby the UE goes into sleep mode for a period of time during which it does not transmit or receive data. The UE wakes up for another period during which data can be transmitted or received. One important aspect of DRX is the synchronization between the UE and the network regarding the wake-up and sleep cycles, also called the DRX cycle. In the worst case, the network tries to transmit data to the UE in sleep mode, and when the UE wakes up, there is no data to receive. In the NR-Uu interface, this situation is prevented by maintaining a well-defined agreement between the UE and the network or system regarding the sleep and wake-up cycles. In other words, by configuring DRX in the UE by the gNB, the DRX is synchronized with the gNB. The DRX cycle includes both on-time and off-time within a certain fixed time interval. For the NR Uu interface, short and long DRX cycles are defined, where a short DRX cycle spans a few symbols in a timeslot, while a long DRX cycle may span an entire timeslot or multiple timeslots. The number of consecutive control messages for which the UE goes into active state after successfully decoding a control message indicating a new transmission may be specified by the inactivity timer with the following configuration: The timer is restarted upon reception of a control message for a new transmission and / or other control message directed to the UE (e.g. a message scrambled by a UE-specific RNTI or a group-specific RNTI) or upon reception of a corresponding signal, e.g. from a group leader UE, a base station, a relay node or a road side unit (RSU). · Once the timer expires, the UE will enter DRX mode or off time.

[0021] FIG. 4 illustrates a DRX mode using an inactivity timer. The DRX configuration defines a DRX cycle 250 over a certain time period, including an on-time or period 252 at the beginning of the DRX cycle, and a subsequent off-time or off duration 254. On the Uu interface, the UE is awake or active during the on-time 252. Furthermore, the above timer, also called the inactivity timer, is started whenever a transmission or packet is received during the on-time. In FIG. 4, the reception of a data packet during the on-duration 252 of the DRX cycle starting at time t3 is shown at 256. For example, when DCI 256 is received by the UE on the PDCCH, an inactivity timer is started to add a DRX active time 258, thereby extending the original on-duration 252 defined by the DRX configuration from time t4 to t6. This allows the transmitter to transmit further data associated with DCI 256 on the PSCCH. If the transmitter does not intend to transmit any more data, the transmitter may transmit a DRX command to put the UE into an inactive or sleep mode. For example, at any time during the inactivity timer duration 258, the UE may receive a DRX command indicating that no further data is expected from the transmitter or that the transmitter will not transmit further data. If such a transmission end notification 260 is received, for example, at time t5 prior to the end time t6 of the inactivity timer duration 258, the UE may return to a sleep mode. Note that the transmission end notification 260 may also be received for a transmission that does not trigger the inactivity timer. This may cause the normal on duration 252 defined by the DRX communication to be ended before the set end of the on duration 252 in response to the notification 260.

[0022] The process described above with reference to Figure 4 of putting a UE operating in DRX mode into a sleep or inactive state in response to a transmission end notification 260 and ending the on duration 252 before the set end time or ending the extended on duration before the inactivity timer duration 258 ends works well when the UE is in communication with a base station because the base station is aware of all transmissions for a particular UE and based on this knowledge the base station can decide to inform the UE 260 to end transmissions if no further transmissions are scheduled for the UE. However, the situation is different when considering sidelink communications.

[0023] A UE may communicate over the sidelink with multiple other sidelink UEs that, when acting as transmitters, may transmit unicast, groupcast or broadcast messages, and thus the UE may receive multiple transmissions from other sidelink UEs.

[0024] However, since each transmitter (TX UE) does not know about other ongoing communications of the receiving UE (RX UE), it cannot provide an end transmission notification or sleep command 260 as described above with reference to FIG. 4, because putting the receiving UE in sleep mode would prevent the RX UE from receiving data or packets of another ongoing transmission from a different transmitter. For example, sidelink unicast communication represents a one-to-one communication between two UEs over the sidelink. Thus, when a transmitter sends an end transmission or sleep command 260, the receiver may stop listening for further packets from this transmitter. However, since a receiver may have multiple ongoing communications, receiving an end transmission or sleep command 260 from one transmitter may not be synonymous with a go-to-sleep indication, as is the case for transmission over the Uu interface, because the receiver may still have to listen to ongoing transmissions on the other link. In the case of sidelink groupcast communication, the approach of Uu described with reference to Fig. 4 cannot be applied since multiple UEs in the group may transmit data and the UEs in the group that transmit or transmit data are not aware of other UEs communicating with the receiving UE. Therefore, the UE transmitting the groupcast cannot inform the receiving UE that no further data is expected and that the UE may go to sleep. This also applies to sidelink broadcast communication where one transmitter provides communication to all sidelink UEs, which again does not know if the receiving UE has other ongoing communication on other links and may not be able to transmit the end transmission command 260 in the manner described above with reference to Fig. 4 and request the UE to return to sleep mode or state.

[0025] In order to reduce power consumption in UEs communicating over the sidelink, a DRX mode may also be implemented on the sidelink. As described above with reference to Figures 2 and 3, UEs communicating over the sidelink may be in-coverage or out-of-coverage. If the UE is in-coverage, even if it is operating over the sidelink in DRX mode, the gNB, being aware of the DRX cycle, handles resource allocation for transmissions by the UE on the sidelink. If the UE is out of coverage, e.g., if the UE is operating in mode 2, this is not possible. Therefore, a transmission end notification by a specific transmitter for a UE communicating over the sidelink with other UEs and operating in DRX mode to put it into an inactive or sleep mode is not implemented.

[0026] Therefore, known techniques for the Uu interface of putting the UE into sleep mode as soon as a transmission has finished, thereby improving power saving characteristics, are not applicable for sidelink UEs and the power saving possibilities for sidelink UEs operating in DRX mode may be more limited compared to UEs communicating over the Uu interface.

[0027] The embodiments of the present invention provide enhanced or improved power saving possibilities or capabilities for UEs communicating over a sidelink and operating in a discontinuous reception (DRX) mode. The embodiments of the present invention may be implemented in a wireless communication system such as that shown in FIG. 1, FIG. 2, or FIG. 3 including a base station and a user (e.g., a mobile terminal or an IoT device). FIG. 5 is a schematic diagram of a wireless communication system including a transmitter 300, such as a base station, and one or more receivers 302, 304, such as a user device UE. The transmitter 300 and receivers 302, 304 may communicate over one or more wireless communication links or channels 306a, 306b, 308, such as radio links. The transmitter 300 includes one or more antennas ANT TThe receiver 302, 304 may include an antenna array having one or more antenna elements, a signal processor 300a, and a transceiver 300b, which are coupled to each other. UE 5, an antenna array having antennas, signal processors 302a, 304a, and transceivers 302b, 304b. The base station 300 and the UEs 302, 304 can communicate via respective first wireless communication links 306a and 306b (e.g., wireless links using the Uu interface), while the UEs 302, 304 can communicate with each other via a second wireless communication link 308 (e.g., wireless links using the PC5 or sidelink (SL) interface). When the UEs are not served by or connected to the base station, e.g., when both are not in an RRC connected state, or more generally, when SL resource allocation configuration or assistance is not provided by the base station, the UEs can communicate with each other via the sidelink. The system or network of FIG. 5, the one or more UEs 302, 304 of FIG. 5, and the base station 300 of FIG. 5 can operate in accordance with the inventive teachings described herein.

[0028] Device [RX UE goes into sleep mode / stops listening depending on certain criteria] SL RX UE The present invention provides a user device UE for a wireless communication system, the wireless communication system including a plurality of user devices UE, the UE receiving transmissions from one or more further UEs via a side link SL, the UE operating in a discontinuous reception (DRX) mode and entering an inactive or sleep mode if certain criteria are met.

[0029] According to an embodiment, the specific criteria include one or more of the following: -Receive notification of completion of transmission, All transmissions announced by other UEs have been received, Successful reception of a transmission where further resources are reserved in the future for the retransmission of that transmission (e.g., early ACK, - there is no ongoing transmission from other UE, There is no ongoing transmission from the group leader UE or from a UE with a particular ID, There is no ongoing transmission from the base station or relay node, the content of the transmissions received; The number of times n (n=2, 3, 4, etc.) a transmission containing a particular transmission, e.g., a Cooperative Awareness Message (CAM), a Decentralized Environmental Notification Message (DENM), or a Basic Safety Message (BSM), was received; The UE's battery condition is below a configured or pre-configured threshold; The UE is moving within a specific geographic location (e.g. within a predefined zone or building), The UE is moving or not moving.

[0030] According to an embodiment, the user device comprises an inactivity timer that specifies an inactivity timer duration during which the UE remains in an active state and monitors at least the control channel to detect transmissions. The UE starts the inactivity timer upon receiving a transmission by a first further UE.

[0031] According to an embodiment, the UE extends the inactivity timer duration in response to receiving a further transmission by the first further UE and / or a transmission by the second further UE during the inactivity timer duration, or by a signal from a group leader UE, or by a signal from a base station, a relay node, or a road side unit (RSU). The UE enters an inactive or sleep mode before reaching the end of the extended inactivity timer duration if certain criteria are met, e.g. in response to an end of transmission notification by both the first further UE and the second further UE.

[0032] According to an embodiment, the UE enters an inactive mode or a sleep mode in response to the end of transmission notification, the UE receiving the end of transmission notification from one or more of the following: a further UE which performs the completed transmission; a further UE that has not performed a terminated transmission, e.g. a group leader UE of the UE group to which the UE belongs; Relay nodes, Roadside Units (RSUs) or IOT devices, · Access points (e.g. base stations) of wireless communication systems.

[0033] According to an embodiment, further UE end of transmission notification is indicated by: Further notification of the end of transmission by the UE (e.g. using the DRX command MAC (Medium Access Control), CE (Control Element)), or Indication of the number of resources reserved for further transmission by the UE (e.g. using a time resource indicator value (TRIV) or a frequency resource indicator value (FRIV)), or sidelink control information (SCI), e.g. first stage SCI or second stage SCI, or ·AIM(assistance information message).

[0034] SL-TX-UE The present invention provides a user device UE for a wireless communication system, the wireless communication system including a plurality of user devices UE, the UE transmitting one or more transmissions via a side link SL to one or more further UEs, the one or more further UEs operating in a discontinuous reception (DRX) mode, the UE indicating an end of the one or more transmissions to the further UEs to enable the further UEs to enter an inactive or sleep mode.

[0035] According to an embodiment, the UE indicates the end of one or more transmissions to further UEs by: - further notification of the end of transmission to the UE (e.g. using a DRX command MAC (Medium Access Control), CE (Control Element)), or Indication of the number of resources reserved for further transmission to the UE (e.g. using a time resource indicator value (TRIV) or a frequency resource indicator value (FRIV)), or sidelink control information (SCI), e.g. first stage SCI or second stage SCI, or ·AIM(assistance information message), Buffer status reports (eg indicating the number of transmissions to be sent to further UEs or the amount of data to be sent).

[0036] [Transmission restrictions during DRX on duration] The present invention provides a user device UE for a wireless communication system, the wireless communication system including a plurality of user devices UE, the UE transmitting a plurality of transmissions via a side link SL to one or more further UEs, the one or more further UEs operating in a discontinuous reception (DRX) mode, each of the plurality of transmissions including at least an initial transmission, the UE transmitting the plurality of transmissions to the further UEs such that at least more than one of the initial transmissions falls within an on duration of a DRX cycle of the one or more further UEs.

[0037] According to an embodiment, one or more of the plurality of transmissions includes at least one further transmission following an initial transmission at a later time.

[0038] According to an embodiment, the plurality of transmissions are transmissions associated with a particular criterion.

[0039] According to an embodiment, the specific criteria include one or more of the following: - the priority is equal to or exceeds a set or pre-defined threshold; Quality of Service (QoS) requirements are equal to or exceed a set or pre-configured threshold, or Packet quotas (e.g., specific configured or pre-configured data rate thresholds), number of transmissions (e.g. a configured or pre-configured minimum or maximum number of transmissions (e.g. CAM or DENM messages)); · The content of the message (e.g. a specific CAM or a specific DENM).

[0040] [Setting the active time of the DRX cycle] SL RX UE The present invention provides a user device UE for a wireless communication system, the wireless communication system comprising a plurality of user devices UE, the UE receiving transmissions from one or more further UEs via a side link SL, the UE operating in a discontinuous reception (DRX) mode, during a DRX cycle the UE is active for a specific active time, the specific active time being dependent on one or more criteria.

[0041] According to an embodiment, the one or more criteria include one or more of the following: one or more characteristics of the packet of transmission, The logical channel used for transmission, The logical channel group used for transmission, Quality of Service (QoS) flows, · Quality of Service (QoS) requirements associated with the transmission, such as priority, latency, or data rate; geographic location or zone, Channel busy rate, Type of UE, one or more resources used by the initial transmission and / or at least one further transmission; · The current battery status of the UE.

[0042] According to an embodiment, the UE receives a DRX configuration defining a DRX cycle and an active time, the UE may receive the DRX configuration from one or more of the following: a further UE which performs transmission; a further UE that is not transmitting, e.g. a group leader UE of the UE group to which the UE belongs; Relay nodes, Road Side Unit (RSU) or IOT device, · Access points (e.g. base stations) of wireless communication systems.

[0043] [Criteria for determining active hours] Depending on the embodiment, the active time may be set, pre-set, or dynamic.

[0044] According to an embodiment, the UE is configured or preconfigured with multiple on-durations for the DRX cycle and the UE determines which on-duration to use depending on one or more criteria.

[0045] According to an embodiment, the UE is configured or pre-configured with one or more default on durations for the DRX cycle, and the UE extends the default on durations based on a preceding transmission to the extended on durations.

[0046] According to an embodiment, in response to the termination of the transmission that caused the extended on-duration, the UE cancels the extension and reverts to the default on-duration.

[0047] [Sparse / Intermittent active times] According to an embodiment, the transmission includes an initial transmission and at least one further transmission at a later time following the initial transmission, and in response to an indication of one or more resources reserved for use by the at least one further transmission, the UE extends the active time to include at least the indicated one or more resources.

[0048] According to an embodiment, the UE extends the active time by: Extend the on duration of the DRX cycle up to the indicated reserved resources, and / or · Add only the indicated reserved resources that should be monitored during the active time to the on duration of the DRX cycle.

[0049] According to an embodiment, the UE enters an inactive or sleep mode between the on duration and the indicated reserved resources.

[0050] According to an embodiment, the one or more further transmissions are re-transmissions of the initial transmission, and in response to successfully receiving the initial transmission within the on-duration, the UE optionally transmits an acknowledgement or a sidelink assistance information (AIM) before entering an inactive or sleep mode and skipping monitoring of the indicated reserved resources.

[0051] According to an embodiment, the one or more further transmissions are retransmissions of the initial transmission, and in response to not receiving the retransmission on the reserved resources outside the on duration, the UE: Staying active for a certain time interval after the timeslot in which a retransmission was expected, e.g., for the duration of an inactivity timer, or Stay active to receive n retransmissions (n ​​≤ maximum number of announced or preconfigured retransmissions), or Enter inactive or sleep mode and wake up only for the next on duration of the DRX cycle, or Sending assistance information (e.g., AIM) to the transmitter with time and / or frequency information for retransmission, or · Sending aiding information (eg, AIM) to the transmitter with information regarding the additional on-duration.

[0052] According to an embodiment, in addition to the reserved resources, the UE receives a resource reservation period indicating that the reserved resources are to be used for further transmissions during a period following the reservation period, and in response to the indication of the resource reservation period, the UE extends its active time to include the indicated one or more resources during the period following the reservation period.

[0053] According to an embodiment, in response to a resource reservation period having a particular duration, such as zero, indicating that the transmitter has selected other resources for transmission, the UE enters an inactive or sleep mode and wakes up only during the next on duration of the DRX cycle.

[0054] According to an embodiment, the one or more resources to be used by the at least one further transmission are indicated in a control message received by the UE, for example a Sidelink Information (SCI) message.

[0055] According to an embodiment, the SCI indicates resources to be reserved within a certain number of future time slots, e.g. using a time resource indicator value (TRIV) or a format or a frequency resource indicator value (FRIV) format, and optionally a resource reservation period indicates that the reserved resources are to be used for further transmissions during a period following the reservation period.

[0056] SL-TX-UE The present invention provides a user device UE for a wireless communication system, the wireless communication system including a plurality of user devices UE, the UE communicating with one or more further UEs via a side link SL, the UE configuring one or more of the further UEs to operate in a discontinuous reception (DRX) mode, the UE determining the DRX configuration of the further UEs depending on one or more criteria.

[0057] According to an embodiment, the one or more criteria include one or more of the following: one or more characteristics of the packet of transmission, The logical channel used for transmission, The logical channel group used for transmission, Quality of Service (QoS) flows, · Quality of Service (QoS) requirements associated with the transmission, such as priority, latency, or data rate; geographic location or zone, Other UE types, one or more resources used by the initial transmission and / or at least one further transmission; · The current battery status of the UE.

[0058] [Extend / Limit Active Time] The present invention provides a user device UE for a wireless communication system, the wireless communication system including a plurality of user devices UE, the UE receiving transmissions from one or more further UEs via a side link SL, the UE operating in a discontinuous reception (DRX) mode, being active for a certain active time (e.g. on duration) during a DRX cycle, the UE decoding or skipping decoding the transmission depending on one or more criteria.

[0059] According to an embodiment, the one or more criteria include a priority, and / or a destination, and / or a Hybrid Automatic Repeat Request (HARQ) indicator associated with the transmission, and / or a cast type associated with the transmission (e.g., a unicast transmission, a groupcast transmission, or a broadcast transmission).

[0060] According to an embodiment, if the HARQ indicator associated with a transmission indicates that the transmitter has requested feedback for the transmission, the UE decodes the transmission and sends the feedback.

[0061] According to an embodiment, the UE checks the priority field in the first stage SCI on the physical sidelink control channel PSCCH and skips decoding of the associated physical sidelink shared channel PSSCH if the priority field indicates a priority below a certain priority threshold.

[0062] According to an embodiment, the UE checks the destination field in the second stage SCI on the physical sidelink shared channel PSSCH and skips further decoding of the PSSCH if the destination field indicates that the transmission is not intended for the UE or a UE group to which the UE belongs.

[0063] According to an embodiment, the UE checks the cast type in the SCI, such as first stage SCI or second stage SCI, and if the transmission is of the particular cast type, skips further decoding of the PSSCH.

[0064] According to an embodiment, the UE checks the source ID field in the second stage SCI on the physical sidelink shared channel PSSCH and skips further decoding of the PSSCH if the source ID field indicates that the transmission is not from a transmitter from which the UE is attempting to receive communication or that the transmission is not in the list of source IDs to decode.

[0065] According to an embodiment, If decoding of the second stage SCI fails and the priority field of the first stage SCI indicates a priority above a certain threshold, the UE becomes active to receive the retransmission, for example by extending the active time until the retransmission is received, or becomes active on resources indicated or reserved in the first stage SCI for the retransmission, or If decoding of the second stage SCI fails and the transmission is in a resource location previously reserved by a transmission to the UE, the UE extends the active time until a retransmission or another transmission is received, or If the previously reserved resources do not contain the expected transmission, the UE extends the active time until a retransmission or another transmission is received.

[0066] [Actions based on feedback] The present invention provides a user device UE for a wireless communication system, the wireless communication system including a plurality of user devices UE, the UE communicating with one or more further UEs via a side link SL, the one or more further UEs operating in a discontinuous reception (DRX) mode, the UE transmitting one or more HARQ capable transmissions to the further UEs during an on duration of a DRX cycle of the further UE, and if no HARQ feedback is received, the UE refraining from HARQ capable transmissions until a next on duration of the further UE and transmitting a HARQ capable transmission during the next on duration of the further UE.

[0067] According to an embodiment, refraining from HARQ capable transmission includes one or more of the following: no further retransmissions of the current transport block TB; -Do not retransmit until the next on duration, restart the retransmission counter during the next on duration, Use of the initial redundant version RV, Reduce the number of retransmissions depending on the amount of on duration so far.

[0068] According to an embodiment, the UE retransmits the HARQ capable transmission a certain number of times after the default on duration has elapsed, and in response to not receiving the HARQ feedback, the UE refrains from the HARQ capable transmission until the next on duration of the further UE and transmits the HARQ capable transmission during the next on duration of the further UE.

[0069] system The present invention provides a wireless communication system comprising a plurality of inventive user devices UE configured for sidelink communication (e.g., using resources from a set of sidelink resources of the wireless communication system).

[0070] method [RX UE goes into sleep mode / stops listening depending on certain criteria] SL RX UE The present invention provides a method of operating a user device UE for a wireless communication system, the wireless communication system including a plurality of user devices UE, the UE receiving transmissions from one or more further UEs via a side link SL, the UE operating in a discontinuous reception (DRX) mode, the method including entering an inactive or sleep mode if a certain criterion is met.

[0071] SL-TX-UE The present invention provides a method of operating a user device UE for a wireless communication system, the wireless communication system including a plurality of user devices UE, the method comprising: transmitting one or more transmissions via a side link SL to one or more further UEs, the one or more further UEs operating in a discontinuous reception (DRX) mode; and indicating an end of the one or more transmissions to the further UEs to enable the further UEs to enter an inactive or sleep mode.

[0072] [Transmission restrictions during DRX on duration] The present invention provides a method of operating a user device UE for a wireless communication system, the wireless communication system including a plurality of user devices UE, the method comprising transmitting a plurality of transmissions via a side link SL to one or more further UEs, the one or more further UEs operating in a discontinuous reception (DRX) mode, each of the plurality of transmissions including at least an initial transmission, the plurality of transmissions being transmitted to the further UEs such that more than at least the one or more initial transmissions fall within an on duration of a DRX cycle of the one or more further UEs.

[0073] [Setting the active time of the DRX cycle] SL RX UE The present invention provides a method of operating a user device UE for a wireless communication system, the wireless communication system comprising a plurality of user devices UE, the UE receiving transmissions from one or more further UEs via a side link SL, the UE operating in a discontinuous reception (DRX) mode, the method comprising: during a DRX cycle the UE remaining active for a specific active time, the specific active time being dependent on one or more criteria.

[0074] SL-TX-UE The present invention provides a method of operating a user device UE for a wireless communication system, the wireless communication system including a plurality of user devices UE, the UE performing one or more further UE communications via a side link SL, the method including configuring one or more of the further UEs to operate in a discontinuous reception (DRX) mode, the DRX configuration for the further UE being determined in response to one or more criteria.

[0075] [Extend / Limit Active Time] The present invention provides a method of operating a user device UE for a wireless communication system, the wireless communication system including a plurality of user devices UE, the UE receiving transmissions from one or more further UEs via a side link SL, the UE operating in a discontinuous reception (DRX) mode and being active for a certain active time (e.g. on duration) during a DRX cycle, the method comprising decoding or skipping decoding the transmission depending on one or more criteria.

[0076] [Actions based on feedback] The present invention provides a method of operating a user device UE for a wireless communication system, the wireless communication system including a plurality of user devices UE, the UE communicating with one or more further UEs via a side link SL, the one or more further UEs operating in a discontinuous reception (DRX) mode, the method comprising: transmitting one or more HARQ capable transmissions to the further UE during an on duration of a DRX cycle of the further UE; and if no HARQ feedback is received, refraining from the HARQ capable transmission until a next on duration of the further UE and transmitting a HARQ capable transmission during the next on duration of the further UE.

[0077] [Computer program products] An embodiment of the present invention provides a computer program product comprising instructions that, when executed by a computer, cause the computer to perform one or more methods according to the present invention.

[0078] [Implementation of early termination of SL communication] Embodiments of the first aspect of the invention provide an approach to improve the power saving possibilities or capabilities of a UE by allowing a receiver, such as a sidelink UE, communicating with other UEs via a sidelink to enter an inactive or sleep mode if certain criteria are met. In other words, embodiments of the invention provide for the implementation of an early termination of the active time of a DRX cycle also for communications via the sidelink.

[0079] According to an embodiment, a SL RX UE may enter an inactive mode or a sleep mode if one or more of the following criteria are met: - Receive notification that transmission is complete. · All transmissions announced by other UEs have been received. For example, the further UE may send a report such as a Buffer Status Report (BSR) to the RX UE informing it that it is about to transmit a certain amount of data, which upon receiving, the RX UE may consider or assume that there is no further data transmission from this UE. Successful reception of a transmission (e.g., early ACK) where further resources are reserved in the future for one or more retransmissions of that transmission. ·There is no ongoing transmission from other UE on the SL. ·There is no ongoing transmission from the group leader UE or from a UE with the particular ID. ·There is no ongoing transmission from the base station or relay node. An end of transmission indication is received and there is no further transmission from another UE in progress on the SL. The content of the received transmission, e.g. a communication containing a specific message such as a Cooperative Awareness Message (CAM), a message in the 5.9 GHz intelligent transport system (ITS-G5), a Decentralized Environmental Notification Message (DENM) or a Basic Safety Message (BSM). · The number of times a particular communication has been received. For example, after receiving the same transmission multiple times, e.g., two, three, or more generally n times (where n is a configurable or preconfigured natural number N greater than 1), the UE may determine that no further transmissions are necessary and enter a sleep mode until the next on duration. For example, this may apply to transmissions including a Cooperative Awareness Message (CAM), a Decentralized Environmental Notification Message (DENM), or a Basic Safety Message (BSM), where receiving the same message multiple times in different transmissions may cause the UE to determine that no further transmissions are necessary. · The battery condition of the SL RX UE is below the configured or pre-configured threshold. ·SL RX UE is moving within a specific geographic location (e.g. within a predefined zone or building). ·SL RX UE is moving or not moving.

[0080] For example, whether the UE is moving can be determined based on the GPS location of the UE or variations in the channel impulse response. If the UE is not moving, given a frequency flat channel, the channel impulse response remains substantially unchanged.

[0081] Therefore, allowing the SL receiver to sleep or stop listening improves power conservation capabilities in sidelink communications by reducing active time, similar to when communicating over the Uu interface.

[0082] An embodiment of the first aspect of the invention will now be described with reference to a scenario in which a SL RX UE decides whether to enter a sleep or inactive mode in response to receiving an end of transmission notification from a sidelink transmitting UE (SL TX UE), i.e. from the UE sending the transmission. The sidelink receiver SL RX UE, while operating in DRX mode, may decide about an early end of the on-duration in response to the transmitter SL TX UE providing an indication indicating whether and / or where one or more further transmissions are expected following an initial transmission.

[0083] FIG. 6 illustrates an embodiment of an extended on-duration after receiving a control message, such as sidelink control information SCI, over the sidelink, with an early termination notification following receipt of the message. The SL TX UE transmits an initial SCI1 during the on-duration 252 of the SL RX UE. The on-duration begins at time t1, and at time t2 during the on-duration 252, SCI1 is received, followed by a first data transmission PSSCH1 from the TX UE to the RX UE over the sidelink. Once SCI1 is received, the on-duration 252 is extended beyond the original duration, which ends at t4. During the original on-duration 252 or during the extended on-duration, the TX UE may transmit a further transmission associated with SCI2, which is received at time t3. In the illustrated embodiment, time t3 is prior to the end of the original on-duration 252 at time t3. Because the on-duration 252 has been extended, the RX UE remains active for the extended duration and also receives a further data transmission PSSCH2. Further, in response to receiving SCI2, the on-duration is further extended, for example by restarting the inactivity timer. Thus, in the embodiment shown in Figure 6, the overall on-duration extension 262 extends the original on-duration 252 from time t4 to time t6.

[0084] According to an embodiment, in order to enable a RX UE communicating with a TX UE via a sidelink to improve power saving characteristics, the TX UE includes in its transmission to the RX UE an indication that it should not expect further transmissions from the TX UE. The TX UE may indicate a PSSCH early end 260 to the RX UE. For example, at the end of the last data transmission PSSCH2, the end of the transmission from the TX UE may be signaled by transmitting a PSSCH early end 260 to inform the RX UE that it should not expect further transmissions from the TX UE. The RX UE may end the extended on duration 262 at time t5, i.e. after time t5 the RX UE may go to an inactive state. Thus, according to an embodiment, by enabling the sidelink TX UE to signal the end of the transmission to the sidelink RX UE, the sidelink RX UE may end the extended on duration 262, i.e. the RX UE may go to an inactive state since it no longer needs to monitor for further transmissions that are indicated not to occur. This allows the RX UE to reduce its active time to the period from t1 to t5 instead of the period from t1 to t6, thereby saving power.

[0085] Note that with respect to the embodiment of FIG. 6, the termination of transmission 260 may also occur in situations where transmissions from the TX UEs occur only during the on-duration 252. For example, the transmission PSSCH1 may include an early termination 260, e.g., at the end of the transmission, such that the RX UE may enter an inactive state after receiving PSSCH1 in response to a termination notification. Thus, the original on-duration 252 may be terminated before its original termination time at time t4. For example, the termination may occur at time t3 after an early termination indication from the TX UE. In this situation, the active time may be limited to the period from t1 to t3, which may similarly reduce the active time to conserve power.

[0086] During the active time, the RX UE monitors at least the control channel to detect further transmissions, such as the second transmission indicated by SCI2 in FIG. 6. If the end 260 is not received, the RX UE continues monitoring for a period from the end of PSSCH2 until t6, which is the end of the extended on duration 262. If a further transmission is detected, for example by detecting a further SCI, the on duration 262 can be further extended, for example by restarting the inactivity timer. However, as described above, in the example of FIG. 6, in the absence of the end 260, the RX UE further monitors at least the control channel until time t6. This wastes power that could be saved by allowing the RX UE to end the extended on duration 262 or on duration 252 in response to an indication that the RX UE should not expect further transmissions from the TX UE. Thus, during the active time, the TX UE may send one or more transmissions to the receiver or RX UE that trigger an extension of the active time to allow the transmitter to pursue further transmissions during the extended active time. When the transmitter completes a transmission, the receiver does not listen until the dynamically extended active time 262 expires, because the receiver can stop listening for transmissions from the transmitter in response to signal 260 indicating the end of transmission.

[0087] According to an embodiment, as shown in the embodiment of FIG. 6, the notification 260 provided by the TX UE to the RX UE may be an end of transmission indication, for example by sending a MAC control element (CE), such as a DRX command, that explicitly indicates at the end of a transmission that no further transmissions should be expected from the TX UE.

[0088] According to an embodiment, instead of indicating an end of transmission indication as shown in Fig. 6, the TX UE may indicate that there are further transmissions when providing the control information. According to an embodiment, the TX UE may transmit a buffer status report, e.g. a report indicating the number of transmissions to be transmitted or the amount of data to be transmitted to the RX UE. According to another embodiment, the TX UE may indicate the resources reserved for the transmission when providing the control information. For example, assuming that the TX UE is operating in mode 2, the resources reserved for the transmission may be indicated. Thus, instead of indicating or indicating the end of the transmission, a control message associated with a particular transmission, such as an SCI and / or an assistance information message (AIM), may indicate a certain number of resources reserved for the transmission indicated in the control message (e.g. in the form of actual resources reserved). This can be applied, for example, when performing retransmissions of one or more transport blocks (TB), but also for other transmissions.

[0089] For example, as described above with reference to FIG. 3, when assuming operation in Mode 2, a TX UE may have slightly different ways of operating for periodic or semi-persistent transmissions / retransmissions and aperiodic or dynamic transmissions / retransmissions. For example, the maximum number of transmissions / retransmissions N may be limited to 32 for periodic and aperiodic transmissions. One limitation on this number may be the number of available resources in the candidate resource set. Another limitation may be the number of resources that can be specified in the SCI, which may be only a maximum of three resources, including the initial transmission or the resource on which the initial transmission occurs. These resources may be limited to fit into a 32 ms window.

[0090] In mode 2, the UE identifies the resources required for each possible transmission / retransmission among the available resources in the candidate resource set, with possible limitations based on the packet delay budget (PDB) of the TB. Once the UE has identified the list of available candidate resources, the UE selects N candidate resources. The UE first randomly selects one of the N candidate resources. Assuming that the first candidate resource is selected in slot ml, the UE also randomly selects a second candidate resource, with the restriction that the gap between this candidate resource and the first selected candidate resource must be smaller than the window W of 32 slots. This means that the second candidate resource can be located in slot m2 within the slot range [m1-31, m1+31]. This ensures that the first stage SCI of one of the two selected candidate resources can reserve the other candidate resource. If N>2, the UE also randomly selects a third candidate resource, but with the restriction that it is located in slot m3 in the range [m1-31, m1+31] or in the range [m2-31, m2+31]. This chaining procedure is repeated with the aim that all candidate resources for transmission / retransmission are reserved by the preceding SCI. However, if the UE can only select a subset of the N candidate resources according to this procedure, the remaining resources are selected randomly within the selection window, even if they do not satisfy the restriction of the preceding first stage.

[0091] When transmitting TBs of different sizes, the number of subchannels used for transmission may be changed, and the number of subchannels is selected such that the TB and its associated SCIs (including first and second stage SCIs) fit into the candidate resource set, which may be limited by the maximum number of subchannels defined or allowed within the resource pool that defines the resources used for sidelink communication.

[0092] Only the UE transmitting the TB knows the PDB associated with the TB, a selection window may be selected according to the PDB, and all transmissions / retransmissions associated with the TB must be completed within the selection window. In case of aperiodic transmission, the number of transmissions / retransmissions may be tracked by a reselection counter. After the end of transmission of the TB, i.e., after the TB and all possible retransmissions of the TB have been transmitted, the reselection counter may be decremented by one. Before transmitting the last TB, which makes the reselection counter zero, the TX UE may evaluate whether a new resource should be selected for the next TB. If so, the UE may set the resource reservation duration to 0 ms in the first stage SCI, thereby indicating to other UEs that it is not reserving the same resource for the next TB. If not, the UE may keep the same resource already reserved for the next TB, and the same resource reservation duration is included in the first stage SCI.

[0093] In the above example of determining resources for multiple transmissions, e.g. including an initial transmission and one or more retransmissions of the initial transmission, the transmitter may inform the receiving UE of the resources reserved for a particular transmission, so that a UE receiving, e.g. an SCI or AIM, knows when a particular transmission will finish. The resources may be indicated in, e.g., the following ways: For example, resources over time may be indicated in any of the following ways: by a bitmap over time, where the bitmap indicates resources such as OFDM symbols, time slots, subframes, or frames, and the resource set is defined over part or the entire length of one BWP; By starting resource, such as a timeslot or subframe, and the duration of the resource set, By explicit resource number, such as a timeslot or subframe number, By puncturing resources that are explicitly mentioned or that are part of another resource set or RP, By starting resource, and a periodic offset for subsequent occurrences, By symbol, time slot, subframe, or frame pattern, The following formula is used to define the TRIV (time resource indicator value) defined in TS38.214: if N = 1 TRIV = 0 else if N = 2 TRIV = t1 else if (t2-t1-1) ≦ 15 TRIV = 30 (t2- t1- 1) + t1+ 31 else TRIV = 30 (31 - t2+ t1) * 62 - t1 end if end if

[0094] Where: N indicates the number of time slots indicated by the AIM, 0 means the time slot where AIM was received, 1 means the time slot in which the AIM was received and one other future time slot with respect to the time slot in which the AIM was received, 2 means the time slot in which the AIM was received and two other future time slots with respect to the time slot in which the AIM was received, t1 denotes the first future resource time slot with respect to the time slot in which the AIM was received; t2 denotes the second future resource timeslot with respect to the timeslot in which the AIM was received.

[0095] Resources across frequencies can be indicated in one of the following ways: indicated by a bitmap, the bitmap indicating multiple resources across one BWP, e.g. a resource block, Depending on the starting resource (e.g. resource block) and the number of resources in the resource set, If the resource set is non-contiguous in frequency, then multiple starting resources (e.g., resource blocks) and multiple ending resources are used. By explicit resource indexing, such as resource block indexing, By puncturing resources that are explicitly mentioned or that are part of another resource set or RP, By starting resource, and a periodic offset for subsequent occurrences, Depending on the resource block or subchannel pattern, The following formula is used to define the frequency resource indicator value (FRIV) defined in TS38.214:

number

[0096] Thus, using the above format, the resources reserved for transmission by the TX UEs may be signaled, for example, in SCI1 in FIG. 6. Upon receiving an indication of reserved resources, the RX UE may determine the time when no further transmissions are expected from the TX UE. SCI1 may contain assistance information or the RX UE may receive additional AIMs (assistance information messages), which inform the RX UE about the resources reserved for transmission from the TX UE. This allows the RX UE to know that it should not expect further transmissions from the TX UE after transmission PSSCH2, and therefore to enter the inactive state at t5. Similarly, if SCI1 only indicates resources for PSSCH1, the RX UE may enter the inactive state at t3, since it does not expect further transmissions from the TX UE after PSSCH1.

[0097] According to a further embodiment, when an RX UE receives an indication that transmission by one TX UE is to end, it may enter an inactive state as described above if there is only one ongoing transmission from one TX UE to the RX UE via the sidelink. However, the RX UE may also communicate with one or more further sidelink TX UEs and may receive transmissions from another TX UE. Thus, according to an embodiment, an RX UE communicating with multiple TX UEs via the sidelink may enter an inactive state in response to an indication of early end of transmission 260 from one TX UE only if the RX UE has confirmed that there are no other ongoing transmissions with another TX UE. In other words, in response to an indication of end of transmission from one TX UE, the RX UE may transition to a sleep mode or an inactive state if it is not active due to transmissions from another TX UE.

[0098] 7 illustrates an embodiment of the present invention in which a RX UE receives transmissions over a sidelink from a first TX UE A and a second TX UE B. During an ON period 252 from t1 to t4, the RX UE receives SCIs associated with one or more transmissions from TX UE A over the sidelink. * Receive SCI * Upon receiving the first early termination 260A, the on-duration 252 is extended from time t4 to time t7. At time t3, the RX UE receives a further SCIB associated with one or more transmissions by the further TX UE B, which further extends the on-duration or active time from time t7 to time t8. According to the embodiment shown in FIG. 7, TX UE B can indicate a PSSCH MAC_CEB indicating that the RX UE should not expect further transmissions from TX UE B. This can be received at time t5, and in response to this indication, the RX UE can enter an inactive mode, i.e., terminate the extended on-duration. However, since the RX UE has not yet received an indication from TX UE A that it should not expect further transmissions from TX UE A, due to the ongoing transmission by TX UE A, according to the embodiment of the present invention, the RX UE does not take any action in response to the first early termination 260A at t5, i.e., it remains in an active state and continues to monitor the control channel for further transmissions. At time t6, TX UE A transmits a PSSCH MAC.CEA indicating that no further transmissions are expected from TX UE A, which allows the RX UE to initiate early termination 260A at time t7 and enter an inactive mode before the actual end of the extended on-duration at time t8, thereby allowing power savings. At time t6, the RX UE knows that the transmission from TX UE A is the only ongoing transmission since all other transmissions, such as the transmission from TX UE B, have already ended, as notified by TX UE B. Thus, once the early termination signal is sent by TX UE A, the RX UE may enter a sleep or inactive mode at time t7.

[0099] Thus, by each TX UE providing an indication that no further transmissions are expected from it, the receiver can reliably detect when to actually go into a sleep or inactive mode or stop listening to the control channel for further transmissions. This allows for reduced power consumption as the RX UE does not need to be active for the entire extended on-duration, as described with reference to Figures 6 and 7.

[0100] The present invention is not limited to the above embodiment in which the end of transmission notification is provided by the SL TX UE sending the transmission. According to other embodiments, the end of transmission notification may be provided by one or more of the following entities of the wireless communication network: Further UEs that have not performed a terminated transmission, e.g. the group leader of the UE group to which the UE belongs. · Relay node. ·Roadside unit (RSU). IoT devices. · An access point such as a base station of a wireless communication system (for example, when the SL TX UE is a Mode 1 UE).

[0101] [TX UE transmission limit for on-duration] An embodiment of the second aspect of the present invention provides a technique to allow a RX UE communicating with a transmitter over a sidelink to save power by avoiding unused ON durations. More specifically, considering the situation as shown in Fig. 6, if a TX UE transmits at any time, e.g., outside the RX UE's ON period 252, the transmission by the TX UE will not be received. The TX UE can then, if configured to do so, transmit a retransmission that may eventually be detected by the RX UE during the next ON period. However, this may result in the RX UE initially monitoring an ON duration during which no transmission occurs, and thus no power may be saved during this time.

[0102] According to an embodiment of the second aspect, such a situation can be avoided and power can be saved by making sure that the RX UE receives the start of transmission during the ON period 252 (see FIG. 6). Thus, an embodiment of the present invention provides a TX UE that starts transmitting during the time that the RX UE is active, i.e., during the ON period. The transmission operation can be performed in the MAC scheduler, and as also described above, the PHY layer reports a set of candidate resources to the MAC scheduler. When deciding which candidate resource to use for a transmission or data packet, or when deciding which data packet to transmit next, the MAC scheduler takes into account the corresponding one or more ON durations of the DRX cycle used by the RX UE and the potential extension obtained by the inactivity timer.

[0103] According to an embodiment, this approach may be applied to transmissions associated with a priority having a certain set or pre-set threshold or level, also referred to as high priority transmissions. To increase the reliability of such high priority transmissions, the RX UE reliably detects the transmission. If the RX UE does not receive a high priority transmission during the ON period, the RX UE enters a sleep or inactive mode. To ensure that such transmissions are reliably detected, and to obtain additional active time by extending the ON duration for potential retransmissions, if necessary, the TX UE places the initial transmission within the ON duration of the RX UE. This reduces the chance that the RX UE misses the transmitter's transmission altogether. Thus, while ensuring that the transmission is received at the RX UE, it is also ensured that the transmission is received during the initial ON duration, thus avoiding the waste of power when only retransmitting without transmitting the initial transmission during the ON duration.

[0104] According to a further embodiment of the second aspect, the approach may be applied as follows. for transmissions whose Quality of Service (QoS) requirements are equal to or exceed a set or pre-configured threshold, or for transmissions that have a particular packet quota (e.g., a particular configured or pre-configured data rate threshold), or Depending on a set or pre-configured number of transmissions, e.g. a minimum or maximum number of transmissions (e.g. CAM, DENM, or BSM), Depending on the content of the message (e.g. a specific CAM or a specific DENM). TX UE sets active time In the above embodiment, the active time is defined by either the on duration 252 or the extended on duration 262. According to an embodiment of the third aspect of the invention, the active time may be determined as a function of one or more of the following: Characteristics or features of the data packets to be transmitted, e.g. one or more characteristics of the transmitted packets; Destination RX UE (e.g. UE type), The logical channel used for transmission, Quality of Service (QoS) flows, · Quality of Service (QoS) requirements associated with the transmission, such as priority, latency, or data rate; The logical channel group used for transmission, - UE battery status, The UE is moving within a specific geographic location (e.g. within a predefined zone or building), Channel busy rate, Type of UE, · One or more resources used by the initial transmission and / or at least one further transmission.

[0105] Thus, depending on one or more of the above criteria, the active time of the DRX cycle may vary. For example, the RX UE may be configured or preconfigured with multiple different ON durations 252 that may be periodic, and the TX UE may be aware of the configured / preconfigured ON durations available to the RX UE. Thus, depending on the service or communication link, the TX UE may indicate the active time or ON duration that the RX UE should apply along with the control information associated with the transmission. For example, a notification in an SCI, such as a first stage SCI or a second stage SCI, may cause the RX UE to select an indicated ON duration for a transmission received from the TX UE from multiple configured or preconfigured ON durations.

[0106] For example, a RX UE may receive a DRX configuration that defines a DRX cycle and an active time. A RX UE may receive one or more of the following DRX configurations: a further UE which performs transmission; a further UE that is not transmitting, e.g. a group leader UE of the UE group to which the UE belongs; Relay nodes, RSU or IOT device, · Access points (e.g. base stations) of wireless communication systems.

[0107] For example, the TX UE may configure one or more of the RX UEs to operate in a discontinuous reception (DRX) mode and select or determine a DRX configuration for configuring the RX UE according to one or more of the above criteria.

[0108] According to other embodiments, the active time can be dynamically controlled, e.g., based on a previous transmission. This allows the received packet to extend the on duration (e.g., inactivity timer), which allows the TX UE to transmit a new packet, as described above with reference to Figs. 6 and 7. In other words, in such an embodiment, the initially set or pre-configured on duration 252 (e.g., by DRX configuration information) can be extended in response to a transmission or reception of a data packet, thereby creating an extended on duration 262 that replaces the initially set on duration 252 for the DRX operation. For example, the actual length of time of the on duration 252 of a DRX cycle may be extended for each subsequent DRX cycle, i.e., the extended on duration 262 is used instead of the periodic initial on duration 252 after reception of a packet.

[0109] According to a further embodiment, the extension may be cancelled once the TX UE indicates the end of transmission, i.e. after notification of the end notification 260 as described above with reference to Figures 6 and 7, the DRX cycle may stop using the extended on duration 262 and revert to the default on duration 252, also referred to as the default on duration.

[0110] According to this immediately preceding embodiment, a configured or pre-configured active time is used by the RX UE to determine the on-duration or extended on-duration during the DRX cycle. According to other embodiments, rather than defining a specific period for which resources should be monitored, a specific characteristic of the SL transmission may be used, i.e., the resources indicated or reserved for the SL transmission and potential future transmissions. The embodiment exploits this characteristic to enable a reduction in power consumption by monitoring only the resources actually indicated or reserved for sidelink transmissions. The parameters used to indicate such future resources may be time and frequency resource allocation parameters. Such parameters may be defined using SCI format 1-a, the first stage SCI. This may indicate the resources reserved in the next 32 time slots, for example, using the above TRIV format and the above FRIV format, respectively, or using any of the above formats for signaling reserved resources. Information regarding the reserved resources may be included in an assistance information message (AIM), which may be part of the SCI message, the first and / or second stage SCI, or may be separate from the SCI message (e.g., transmitted in the data or PSSCH).

[0111] Based on the information about the actual resources used for further transmissions by the TX UE, the RX UE may monitor resources indicated by the TX UE for one or more transmissions in addition to monitoring the resources during the on-duration. Thus, the power saving characteristics of the RX UE can be improved by restricting the additional monitoring of resources other than the on-duration resources to only the resources indicated for transmission.

[0112] According to the embodiment, power savings with respect to monitoring only the indicated resources can be achieved by extending the on-duration based on future resource reservation or by listening only to the indicated resources for future transmissions. In the first case, there is no fixed extension of the on-duration, but only up to the last resource signaled by the TX UE, so that the RX UE can stop monitoring other resources after the last indicated resource without needing to receive an end of transmission notification.

[0113] Since only resources where transmission occurs after the on duration are monitored, and resources with no transmission between the on duration and the extended time do not need to be monitored, the UE may enter a sleep or inactive mode during such time.

[0114] Figure 8 illustrates an embodiment of power saving by monitoring only indicated resources: Figure 8(a) illustrates an embodiment of extending on-duration based on future resource reservations, and Figure 8(b) illustrates an embodiment of active time slots monitored based on future resource reservations.

[0115] FIG. 8 illustrates a DRX cycle 250 for a RX UE. The DRX cycle 250 includes a periodic on-duration 252 that may be extended according to an embodiment depending on future resources reserved for transmissions by the TX UE. In the embodiment of FIG. 8, assume that an initial transmission is received from the TX UE in time slot (1) during the on-duration 252, as shown in the center of the figure. The initial transmission is associated with control information that also indicates resources reserved for further transmissions of the TX UE that transmitted the initial transmission. Such further transmissions may be retransmissions of the initial transmission in time slots (2) and (3), or may include other initial transmissions of the TX UE according to other embodiments. In the embodiment shown in FIG. 8(a), the transmission of two retransmissions is assumed, where the initial transmission in time slot (1) indicates to the RX UE, for example using assistance information, that retransmissions will occur in time slots (2) and (3). The RX UE realizes that the first retransmission in time slot (2) is still within the on-duration 252, but the second retransmission in time slot (3) is outside the on-duration 252. The RX UE extends the on duration 252 by extending the active time until the time slot (3) where the last retransmission occurs, creating an extended on duration 262 depending on the actual resources to be monitored. Thus, according to the embodiment of FIG. 8(a), a packet (e.g., an initial transmission in time slot CD) received during the active time or on duration 252 extends the on duration 252 by a duration (illustrated by two time slots in this embodiment) that depends on the indicated future time slot reservation for further transmissions. Thus, in the embodiment of FIG. 8(a), one further transmission in time slot (3) outside the default on duration 252 is signaled by the TX UE, and the RX UE extends its active time until the end of the reserved packet in time slot (3).

[0116] Figure 8(b) illustrates an embodiment where the RX UE only listens to additional resources outside the on-duration instructed by the TX UE or the default on-duration 252. The situation in Figure 8(b) is similar to that in Figure 8(a) except that the RX UE only monitors the instructed timeslot (3) for the second retransmission outside the default on-duration 252, but the two timeslots between the end of the default on-duration 252 and the extended active timeslot (3) are not monitored by the RX UE.

[0117] Thus, according to FIG. 8(a), the power saving properties of the RX UE are enhanced because the default ON period is actually extended only to the last reserved resource for transmission (e.g., timeslot (3)), while in FIG. 8(b) the power saving properties can be further enhanced by not listening or monitoring the timeslots between the default ON duration and the actual and retransmission in timeslot (3). Thus, to save power at the RX UE, it is ensured that the RX UE receives a transmission or transport block within the ON period 252, but once the ON period 252 ends, the RX UE listens only to the timeslots indicated (e.g., by the TRIV format), otherwise the RX UE goes into an inactive or sleep mode between the indicated resources. This improves the power saving capabilities.

[0118] According to further embodiments, as described above, the transmission of the TX UE to the RX UE over the sidelink may include an initial transmission and a retransmission of the initial transmission, as shown in FIG. 8. According to further embodiments, when transmitting the initial transmission and the retransmission, after receiving the first transmission within the on duration 252, the RX UE may enter a sleep or inactive mode when the transmission is successfully received. That is, the RX UE stops listening to future retransmissions of that transport block since the transmission has already been successfully decoded. Thus, assuming FIG. 8, if the initial transmission in timeslot (1) is successfully received at the RX UE, the RX UE may enter a sleep or inactive mode after timeslot (1) since there is no need to further monitor timeslots (2) and (3). According to embodiments, if the TX UE transmission is a HARQ enabled transmission, the transition to the inactive / sleep mode may be postponed for one or more timeslots after the initial transmission is successfully received. Thereby, in response to the successful initial transmission in timeslot CD, the RX UE transmits an acknowledgement (ACK) or sidelink assistance information (AIM) and enters a sleep mode. The same process may be applied if the first retransmission received in time slot (2) is successfully decoded, even if the initial transmission was not successfully received.

[0119] According to further embodiments, the TX UE may reserve resources for a further or second transmission or transport block by performing periodic transmissions as defined in Rel-16. For example, the above mentioned formats such as TRIV parameters may be used to indicate resources for further transmissions. In such a case, the control information may contain, in addition to the indication of the actual reserved resources, as a further parameter, a so-called resource reservation period, for example contained in SCI format 1-a. In this period, the same resources may be used for further transmissions after the indicated reservation period. According to such an embodiment, the TX UE may need to change the resources used for the transmission of the second or further transport block, and in such a situation the TX UE may transmit a reservation period with a certain duration, for example with zero as the indicated duration. This informs the RX UE that no further transmissions are received or expected from the TX UE, so that the RX EU can stop monitoring the resources for the mentioned transmission and enter a sleep or inactive mode.

[0120] According to further embodiments, a RX UE monitoring a time slot indicating a reserved resource (e.g., a time slot after the on duration or an actual time slot for a retransmission (e.g., time slot (3) in FIG. 8(b))) may not receive a transmission or retransmission in that time slot. In such a situation, according to an embodiment, if a transmission or retransmission is not received in a reserved resource (3) outside the on duration 252, the RX UE may remain active for a short period of time, for example, by starting an inactivity timer after the time slot (3) in which it was expecting the transmission. Since the missing retransmission in time slot (3) may be due to a reevaluation of resources used by the TX UE, the initially notified resource (3) may have been determined by the TX UE to be no longer available for transmission for some reason. A UE remaining active for a short period of time after the indicated resource (3) may detect the missing retransmission on the reevaluated resource selected by the TX UE. A retransmission may also not be received if it cannot be decoded by the RX UE.

[0121] According to another embodiment, the RX UE can remain active for the reception of n retransmissions, where n is less than or equal to the notified or preset maximum number of retransmissions. According to another embodiment, the RX UE can directly enter a sleep or inactive mode and wake up only during the next on-duration. According to yet another embodiment, the RX UE can transmit assistance information such as AIM (including information regarding one or more on-durations of the RX UE) to the TX UE, including time and / or frequency information during which the RX UE is active and can receive retransmissions or assistance information such as AIM.

[0122] [Extending / Limiting Active Time by TX UE] According to an embodiment of the fourth aspect of the present invention, the power saving properties of a RX UE communicating with other UEs via sidelink may be further enhanced by determining whether a particular transmission of a TX UE should actually be processed by the RX UE or not.

[0123] For example, if a transmission received at the RX UE is determined to be of a particular type, have particular characteristics, or meet particular criteria, the RX UE may monitor only those messages or transmissions that align with the requirements of the transmission to be processed by the RX UE and discard other transmissions or messages in order to conserve power. For example, the UE may determine whether to decode a transmission or skip decoding a transmission depending on one or more criteria. This reduces power consumption because necessary decoding of the particular message or transmission is not performed.

[0124] For example, whether a transmission is of interest to a RX UE may be determined based on a destination ID (e.g., based on whether the transmission is a unicast or groupcast transmission), and / or depending on a priority associated with the transmission, and / or based on whether a Hybrid Automatic Repeat Request (HARQ) indicator is associated with the transmission, and / or based on a cast type associated with the transmission (e.g., a unicast transmission, a groupcast transmission, or a broadcast transmission).

[0125] For example, a destination ID and priority may be indicated in an SCI associated with a transmission and received in a monitored control channel during the on duration. For example, when considering the priority of an application, a field in a first stage SCI transmitted on a PSCCH may be evaluated. By evaluating the priority field of the first stage SCI, a RX UE may skip PSSCH decoding if the specified priority does not reach a certain level. For example, a power saving RX UE may only monitor transmissions or messages above a certain priority and discard or not decode PSSCH messages or transmissions of lower priority.

[0126] When considering the destination, the RX UE can evaluate the destination field included in the second stage SCI transmitted on the PSSCH. For example, the RX UE can determine whether a particular transmission is indeed addressed to the RX ID and needs to be decoded based on the indicated destination ID. Furthermore, the RX UE can check whether the transmission is a group or unicast transmission based on, for example, the group ID and unicast ID indicated in the destination field. For example, the RX UE may determine that unicast transmissions should be decoded but groupcast transmissions do not need to be decoded.

[0127] If the HARQ indicator associated with the transmission indicates that the transmitter requests feedback for the transmission, the RX UE decodes the transmission and transmits feedback. Otherwise, i.e., if the HARQ indicator indicates that the transmitter does not request feedback, the UE may skip decoding to save power. In a further embodiment, the UE may skip decoding even if feedback is requested. This may be useful, for example, in groupcast communications where members of a power-saving group skip low priority messages. However, if feedback is not sent to the transmitter expecting feedback from all group members, the transmitter retransmits the message. In this case, to avoid the above behavior, an ACK may be sent even if the message was not successfully decoded, thereby avoiding unnecessary retransmissions.

[0128] According to another embodiment, the RX UE can skip a certain cast type, which may be configured by the TX UE or the base station or preconfigured on a resource pool. The RX UE checks the cast type in the SCI, e.g., the first stage SCI or the second stage SCI, and if the transmission is of the certain cast type, skips further decoding of the PSSCH.

[0129] According to a further embodiment, the RX UE may skip further PSSCH decoding if the second stage SCI indicates a source ID different from the UE's list of interested communication partners. For example, the RX UE checks the source ID field in the second stage SCI on the physical sidelink shared channel PSSCH and skips further decoding of the PSSCH if the source ID field indicates that the transmission is not from a transmitter for which the RX UE is attempting to receive communication or that the transmission is not on the list of source IDs to decode.

[0130] Further embodiments address the situation where the RX UE decides to decode the second stage SCI on the PSSCH based on information from the first stage SCI, but the decoding fails. In such a situation or scenario, if the priority indicated in the first stage SCI is high priority, i.e. at a certain priority level, the RX UE may stay active for a certain time, for example by triggering an inactivity timer, to receive retransmissions of packets. The RX UE may stay active for a certain time by extending the active time or by checking the reservation field in the first stage SCI that indicates when and where the retransmission is expected, so that the UE stays active until the resource indicated in the reservation field (Figure 8(a)) or becomes active again when the resource where the retransmission occurs is reached (Figure 8(b)).

[0131] According to another embodiment, the RX UE knows, for example thanks to the reserved resource indication, that the transmission at which the decoding failed was in fact previously reserved for a transmission from the TX UE to the RX UE. If the decoding failed, a collision or preemption of a transmission destined for the RX UE may have occurred. In this case too, the active time during which the RX UE monitors the resource after the ON period is extended, allowing the next transmission in case of a collision or an alternative transmission in case of a preemption to be detected and received. This also applies if the reserved resource did not contain the expected transmission at all, i.e. the decoding failed because of the absence of a transmission.

[0132] [Action by TX UE based on HARQ feedback] According to an embodiment of the fifth aspect of the present invention, a TX UE communicating with other UEs via sidelink may transmit one or more transmissions or data packets during the on duration of the RX UE and request feedback. For example, the TX UE may transmit a HARQ-enabled transmission. If the RX UE does not report the required HARQ feedback for any of the received packets or transmissions, the TX UE may assume that the RX UE may not have received the transmission or packet or that this is due to another problem, e.g., half-duplex problem. In such a case, the TX UE may assume that the RX UE missed the transmission or packet and therefore did not extend the active time. In other words, the TX UE assumes that the default ON period of the DRX cycle applies, so the TX UE does not consider an immediate retransmission but waits until the next ON period of the DRX cycle of the RX UE. In other words, the TX UE may suspend the HARQ-enabled transmission, where the suspension may include one or more of the following: -Do not retransmit until the next on duration. no further retransmissions of the current transport block TB; Instead of waiting until the next On Duration, retransmissions for this TB are stopped immediately. ·Restart the retransmission counter during the next on duration. · Use initial redundant version RV.

[0133] For example, if the initial transmission is missed, the UE does not have a copy of the initial RV, but the code is designed such that if the UE misses the initial RV, the decoding performance degrades.

[0134] Therefore, the initial RV is transmitted again since it alone has the best performance for successful decoding. Reduce the number of retransmissions depending on the amount of on duration so far. According to other embodiments, the TX UE may assume that the RX UE extended the default on-duration, e.g. by activating an inactivity timer, because it is deemed likely that the RX UE will receive transmissions from two or more other transmitters over the sidelink. The TX UE may also assume that the RX UE did not respond due to a half-duplex problem. In either case, despite the default on-duration having elapsed, the TX UE may retransmit the same transmission or packet a set or pre-configured number of times based on these assumptions due to the extended on-duration that is assumed to have been triggered by the RX UE. If the RX UE still does not respond to these retransmissions, the TX UE may withhold the packet or transmission until the next default on-duration.

[0135] [General matters] Although the embodiments of the present invention have been described in detail above, each embodiment and aspect may be implemented individually, or two or more of them may be combined and implemented.

[0136] According to an embodiment, the wireless communication system may include a terrestrial based network, or a non-terrestrial based network, or a network or part of a network that uses an aircraft or space vehicle as a receiver, or a combination thereof.

[0137] According to an embodiment, the user device UE described herein may be a UE with limited power, or a handheld UE, such as a UE used by pedestrians, called Vulnerable Road User (VRU) or Pedestrian UE (P-UE), or a wearable or handheld UE, such as a UE used by public safety officers and first responders, called Public safety UE (PS-UE), or an IoT UE (e.g., a sensor, actuator, or UE that is provided in a campus network to perform repetitive tasks and that periodically requires input from a gateway node), or a mobile terminal, or a fixed terminal, or a cellular IoT-UE, or a vehicular UE, or a vehicular group leader (GL) UE, or an IoT or narrowband IoT (NB-IoT) device, or a WiFi non-access point station (non-AP The sidelink may be one or more of a wireless LAN access point (WAN), a STA (e.g., 802.11ax or 802.11be), or a ground vehicle, or an aircraft, or a drone, or a mobile base station, or a road side unit (RSU), or a building, or any other item or device (e.g., a sensor or actuator) that has a network connection that enables the item / device to communicate using a wireless communication network, or any other item / device (e.g., a sensor or actuator) that has a network connection that enables it to communicate using a sidelink, or any sidelink-enabled network entity.

[0138] The base station BS described in this specification may be implemented as a mobile or non-mobile base station and may be one or more of a macro cell base station, or a small cell base station, or a central unit of a base station, or a distributed unit of a base station, or an Integrated Access and Backhaul (IAB) node, or a roadside unit, or a UE, or a group leader GL, or a relay, or a Remote Radio Head (RRH), or an AMF, or an MME, or an SMF, or a core network entity, or a mobile edge computing entity, or a network slice such as in a NR or 5G core context, or a WiFi AP STA (e.g., 802.11ax or 802.11be), or any transmission / reception point TRP that enables an item or device to communicate using a wireless communication network, the item or device having a network connection for communicating using a wireless communication network.

[0139] While some aspects of the above concepts are described in the context of an apparatus, it will be apparent that these aspects also represent descriptions of corresponding methods, where a block or device corresponds to a method step, or a feature of a method step. Similarly, aspects described in the context of a method step also represent descriptions of a corresponding block, item, or feature of a corresponding apparatus.

[0140] The various elements and features of the invention may be implemented as hardware using analog and / or digital circuitry, as software through the execution of instructions by one or more general purpose or dedicated processors, or as a combination of hardware and software. For example, embodiments of the invention may be implemented in the environment of a computer system or another processing system. FIG. 9 shows an example of a computer system 600. The units or modules, as well as the steps of the methods performed by these units, may be executed on one or more computer systems 600. The computer system 600 includes one or more processors 602, such as a dedicated or general purpose digital signal processor. The processors 602 are connected to a communication infrastructure 604, such as a bus or a network. The computer system 600 includes a main memory 606, such as a random access memory RAM, and a secondary memory 608, such as a hard disk drive and / or a removable storage drive. The secondary memory 608 may allow computer programs or other instructions to be loaded into the computer system 600.

[0141] Computer system 600 may further include a communications interface 610 that allows software and data to be transferred between computer system 600 and external devices. Communications may have the form of electronic, electromagnetic, optical, or other signals that can be processed by the communications interface. Communications may use wire or cable, fiber optics, a phone line, a cellular phone link, an RF link, and other communications channels 612.

[0142] The terms "computer program medium" and "computer readable medium" are generally used to refer to tangible storage media, such as a hard disk installed in a removable storage unit or a hard disk drive. These computer program products are means for providing software to the computer system 600. Computer programs, also called computer control logic, are stored in the main memory 606 and / or the secondary memory 608. Computer programs may also be received via the communication interface 610. The computer programs, when executed, enable the computer system 600 to implement the present invention. In particular, the computer programs, when executed, enable the processor 602 to implement the processes of the present invention, such as any of the methods described herein. Such computer programs may thus represent the controller of the computer system 600. When the present disclosure is implemented using software, the software may be stored in a computer program product and loaded into the computer system 600 using an interface, such as a removable storage drive, the communication interface 610, or the like.

[0143] The hardware or software implementation may be performed using a digital storage medium, such as cloud storage, floppy disk, DVD, Blu-ray, CD, ROM, PROM, EPROM, EEPROM, or FLASH memory, on which electronically readable control signals are stored that cooperate or can cooperate with a programmable computer system to execute the respective method. Thus, the digital storage medium may be computer readable.

[0144] Some embodiments of the present invention include a data carrier having electronically readable control signals capable of cooperating with a programmable computer system to cause one of the methods described herein to be performed.

[0145] In general, embodiments of the present invention may be implemented as a computer program product having program code operable to perform one of the methods when the computer program product is run on a computer. The program code may for example be stored on a machine readable carrier.

[0146] Other embodiments include the computer program stored on a machine readable carrier for performing one of the methods described herein. In other words, an embodiment of the inventive method is therefore a computer program having a program code for performing one of the methods described herein, when the computer program runs on a computer.

[0147] A further embodiment of the method of the present invention is therefore a data carrier or a digital storage medium or a computer readable medium having recorded thereon a computer program for performing one of the methods described herein.A further embodiment of the method of the present invention is therefore a data stream or a sequence of signals representing a computer program for performing one of the methods described herein.The data stream or the sequence of signals may be arranged to be transferred via a data communication connection, for example the Internet.A further embodiment comprises a processing means, for example a computer or a programmable logic device, configured or adapted to perform one of the methods described herein.A further embodiment comprises a computer having installed thereon a computer program for performing one of the methods described herein.

[0148] In some embodiments, some or all of the functionality of the methods described herein may be implemented using a programmable logic device such as a field programmable gate array. In some embodiments, a field programmable gate array may cooperate with a microprocessor to implement one of the methods described herein. In general, the methods are preferably performed by any hardware apparatus.

[0149] The above-described embodiments are merely illustrative of the principles of the present invention. It is to be understood that modifications and variations of the arrangements and details described herein will be apparent to those skilled in the art. It is therefore intended to be limited only by the scope of the present claims and not by the specific details presented by the description and illustration of the embodiments herein.

Claims

1. A user device for a wireless communication network, the wireless communication network including a plurality of user devices, the user device receiving a transmission from one or more further user devices via a sidelink; said user device operating in a discontinuous reception mode; The user device enters an inactive or sleep mode when certain criteria are met.

2. The specific criteria are: - The transmission completion notification has been received, - that all transmissions announced from the further user device have been received; - successful reception of a transmission where further resources in the future are reserved for retransmission of said transmission, such as an early ACK; - there is no ongoing transmission from said further user device; - there is no ongoing transmission from the group leader user device or from a user device with a particular ID; - there is no ongoing transmission from the base station or relay node; - the contents of the transmissions received, Receipt of a particular transmission n times (n=2, 3, 4, . . .), such as a transmission containing a Cooperative Awareness Message (CAM), a Decentralized Environmental Notification Message (DENM), or a Basic Safety Message (BSM); - the battery condition of the user device is below a set or pre-set threshold; - the user device is moving within a particular geographic location, such as within a predefined zone or building; - the user device is mobile or stationary; The user device of claim 1 , comprising one or more of:

3. the user device comprising an inactivity timer that specifies an inactivity timer duration during which the user device remains in an active state and monitors at least a control channel to detect transmissions; 3. The user device of claim 1 or 2, wherein the user device starts the inactivity timer in response to receiving a transmission by a first further user device.

4. the user device extends the inactivity timer duration in response to receiving a further transmission by the first further user device and / or a transmission by a second further user device during the inactivity timer duration, or by a signal from a group leader user device, or by a signal from a base station, a relay node, or a roadside unit; 4. The user device of claim 3, wherein the user device enters the inactive or sleep mode before reaching an end of the extended inactivity timer duration in response to the particular criterion being met, such as an end of transmission notification by both the first further user device and the second further user device.

5. the user device responds to an end of transmission notification by entering the inactive mode or the sleep mode; The user device comprises: a further user device which performs the completed transmission; a further user device that has not performed the terminated transmission, such as a group leader user device of a user device group to which the user device belongs; relay node, Roadside unit or IoT device, - Access points of wireless communication systems such as base stations, 5. A user device according to claim 2, further comprising: a first receiving unit configured to receive a transmission end notification from one or more of the first receiving unit and the second receiving unit;

6. Further notification of end of transmission by the user device may be - an end of transmission notification by said further user device using DRX commands MAC (Medium Access Control), CE (Control Element) etc., or - an indication of the number of resources reserved for said transmission by said further user device, for example using a time resource indicator value (TRIV) or a frequency resource indicator value (FRIV), or - SCI, such as first stage SCI (sidelink control information) or second stage SCI, or ・AIM (assistance information message), The user device of claim 5 , wherein:

7. A user device for a wireless communication network, the wireless communication network including a plurality of user devices, the user device sending one or more transmissions via a sidelink to one or more further user devices, the one or more further user devices operating in a discontinuous reception mode; The user device indicates termination of the one or more transmissions to the further user device so that the further user device can enter an inactive or sleep mode.

8. The user device comprises: - an end of transmission notification to said further user device using a discontinuous reception command MAC (Medium Access Control), CE (Control Element) or the like, or - notification of the number of resources reserved for said transmission to said further user device, for example using a time resource indicator value (TRIV) or a frequency resource indicator value (FRIV), or - SCI, such as first stage SCI (sidelink control information) or second stage SCI, or ・AIM (assistance information message), - indicating a buffer status report such as the number of transmissions sent to the further user device or the amount of data sent; 8. The user device of claim 7, further comprising: a signal indicating to the further user device an end of the one or more transmissions by:

9. A user device for a wireless communication network, the wireless communication network including a plurality of user devices, the user device sends a plurality of transmissions over a sidelink to one or more further user devices, the one or more further user devices operating in a discontinuous reception mode, each of the plurality of transmissions including at least one initial transmission; The user device transmits the plurality of transmissions to the further user devices such that at least one or more of the initial transmissions fall within an on duration of a discontinuous reception cycle of the one or more further user devices.

10. The user device of claim 9 , wherein one or more of the plurality of transmissions includes at least one further transmission following the initial transmission at a later time.

11. The user device of claim 9 or 10, wherein the plurality of transmissions are transmissions associated with a particular criterion.

12. The specific criteria are: - The priority is equal to or exceeds a set or pre-defined threshold; - Service quality requirements are equal to or exceed a set or pre-defined threshold; Packet quotas, such as specific settings or pre-configured data rate thresholds; - the number of transmissions, such as a set or pre-set minimum or maximum number of transmissions; The contents of messages, such as a specific Cooperative Awareness Message (CAM) or a specific Decentralized Environmental Notification Message (DENM); The user device of claim 11 , comprising one or more of:

13. A user device for a wireless communication network, the wireless communication network including a plurality of user devices, the user device receiving transmissions from one or more further user devices via a sidelink; said user device operating in a discontinuous reception mode; During a discontinuous reception cycle, the user device is active for a particular active time, the particular active time being dependent on one or more criteria.

14. The one or more criteria are: - one or more characteristics of the packets of the transmission; The logical channel used for transmission, the logical channel group used for transmission, - Service quality flow, - Quality of service requirements related to the transmission, such as priority, delay, or data rate; - geographic location or zone, - Channel busy rate, - the type of user device, one or more resources used by the initial transmission and / or at least one further transmission; - the current battery state of the user device; The user device of claim 13 , comprising one or more of:

15. The user device receives a discontinuous reception configuration defining the discontinuous reception cycle and the active time, the user device: - a further user device which performs said transmission; a further user device that has not performed said transmission, such as a group leader user device of a user device group to which the user device belongs; relay node, Roadside unit or IoT device, - Access points of wireless communication systems such as base stations, 15. The user device of claim 13 or 14, wherein the discontinuous reception configuration can be received from one or more of:

16. The user device of claim 13 , wherein the active time is set, pre-set or dynamic.

17. 17. The user device of claim 16, wherein the user device has a plurality of on durations configured or preset for the discontinuous reception cycle, and the user device determines the on duration to be used in response to one or more criteria.

18. 18. The user device of claim 16 or 17, wherein the user device has one or more default on durations set or pre-set for the discontinuous reception cycle, and the user device extends the default on durations based on a preceding transmission to result in an extended on duration.

19. 20. The user device of claim 18, wherein in response to termination of the transmission that caused the extended on-duration, the user device cancels the extension and reverts to the default on-duration.

20. the transmission includes an initial transmission and at least one further transmission following the initial transmission at a later time; 16. The user device of claim 13, wherein in response to an indication of one or more resources reserved for use by the at least one further transmission, the user device extends the active time to include at least the indicated one or more resources.

21. The user device comprises: Extending the on duration of the discontinuous reception cycle up to the indicated reserved resources; and / or Adding only the indicated reserved resources that are to be monitored during the active time to the on duration of the discontinuous reception cycle 21. The user device of claim 20, wherein the active time is extended by:

22. The user device of claim 21 , wherein the user device enters an inactive or sleep mode between the on-duration and the indicated reserved resources.

23. the one or more further transmissions are re-transmissions of the initial transmission; 23. The user device of claim 21 or 22, wherein in response to successfully receiving the initial transmission within the on-duration, the user device optionally transmits an acknowledgement or a sidelink assistance information (AIM) before entering an inactive or sleep mode and skipping monitoring of the indicated reserved resources.

24. the one or more further transmissions are re-transmissions of the initial transmission; In response to not receiving a retransmission on a reserved resource outside the on duration, the user device: remain active for a certain time interval after the timeslot in which the retransmission was expected, such as for the duration of an inactivity timer, or Stay active to receive n retransmissions (n≦maximum number of advertised or preconfigured retransmissions), or Entering an inactive or sleep mode and waking up only for the next on duration of said discontinuous reception cycle, or Sending assistance information to the transmitter, such as assistance information (AIM), with time and / or frequency information for retransmissions; or A user device according to claim 21 or 22, adapted to transmit assistance information to the transmitter comprising information regarding additional on-duration such as an AIM.

25. In addition to reserved resources, the user device receives a resource reservation period, the resource reservation period indicating that the reserved resources are to be used for further transmissions during a period following the reservation period; 25. The user device of claim 20, wherein in response to the indication of a resource reservation period, the user device extends the active time to include the indicated one or more resources during a period following the reservation period.

26. A user device as described in claim 25, wherein in response to a resource reservation period having a particular duration, such as zero, indicating that the transmitter has selected another resource for the transmission, the user device enters an inactive or sleep mode and wakes up only during the next on duration of the intermittent reception cycle.

27. 27. The user device of claim 20, wherein the one or more resources used by the at least one further transmission are indicated in a control message received by the user device, such as a Sidelink Information (SCI) message.

28. 28. The user device of claim 27, wherein the SCI indicates the resources reserved within a certain number of future time slots, such as using a time resource indicator value (TRIV) or format or a frequency resource indicator value (FRIV) format, and optionally the resource reservation period indicates that the reserved resources are used for further transmissions during a period following the reservation period.

29. A user device for a wireless communication network, the wireless communication network including a plurality of user devices, the user device communicating with one or more further user devices via a sidelink; the user device configuring one or more of the further user devices to operate in a discontinuous reception mode; The user device determines a discontinuous reception setting of the further user device depending on one or more criteria.

30. The one or more criteria are: - one or more characteristics of the packets of the transmission; The logical channel used for transmission, the logical channel group used for transmission, - Service quality flow, - Quality of service requirements related to the transmission, such as priority, delay, or data rate; - geographic location or zone, - the type of other user devices, one or more resources used by the initial transmission and / or at least one further transmission; - the current battery state of the user device; 30. The user device of claim 29, comprising one or more of:

31. A user device for a wireless communication network, the wireless communication network including a plurality of user devices, the user device receiving transmissions from one or more further user devices via a sidelink; the user device operates in a discontinuous reception mode and is active for a particular active time, e.g., an on duration, during a discontinuous reception cycle; The user device decodes a transmission or skips decoding a transmission depending on one or more criteria.

32. 32. The user device of claim 31 , wherein the one or more criteria include a priority, and / or a destination, and / or a Hybrid Automatic Repeat Request (HARQ) indicator associated with the transmission, and / or a cast type associated with the transmission, such as a unicast transmission, a groupcast transmission, or a broadcast transmission.

33. 33. The user device of claim 32, wherein if a HARQ indicator associated with the transmission indicates that a transmitter has requested feedback for the transmission, the user device decodes the transmission and sends the feedback.

34. 33. The user device of claim 32, wherein the user device checks a priority field in a first stage SCI on a physical sidelink control channel and skips decoding of an associated physical sidelink shared channel if the priority field indicates a priority below a certain priority threshold.

35. 35. The user device according to claim 34, wherein the user device checks a destination field in a second stage SCI on a physical sidelink shared channel and skips further decoding of the physical sidelink shared channel if the destination field indicates that the transmission is not intended for the user device or a user device group to which the user device belongs.

36. 36. The user device of claim 34 or 35, wherein the user device checks a cast type in an SCI, such as a first stage SCI or a second stage SCI, and if the transmission is of a particular cast type, skips further decoding of the physical sidelink shared channel.

37. 37. The user device of claim 34 or 36, wherein the user device checks a source ID field in a second stage SCI on a physical sidelink shared channel and skips further decoding of the physical sidelink shared channel if the source ID field indicates that the transmission is not from a transmitter from which the user device is attempting to receive communications or that the transmission is not in a list of source IDs to decode.

38. if decoding of the second stage SCI fails and the priority field of the first stage SCI indicates a priority equal to or above a certain threshold, the user device becomes active to receive the retransmission, for example by extending an active time until a retransmission is received, or becomes active on resources indicated or reserved in the first stage SCI for the retransmission, or if decoding of the second stage SCI fails and the transmission is in a resource location previously reserved by a transmission to the user device, the user device extends an active time until the retransmission or another transmission is received; or 38. The user device of claim 35, wherein if previously reserved resources do not contain the expected transmission, the user device extends an active time until the retransmission or another transmission is received.

39. A user device for a wireless communication network, the wireless communication network including a plurality of user devices, the user device communicating with one or more further user devices via a sidelink, the one or more further user devices operating in a discontinuous reception mode; the user device transmitting one or more HARQ enabled transmissions to the further user device during an on duration of a discontinuous reception cycle of the further user device; In response to not receiving HARQ feedback, the user device refrains from a HARQ capable transmission until a next on-duration of the further user device, and transmits the HARQ capable transmission during the next on-duration of the further user device.

40. The refraining from HARQ-enabled transmission comprises: no further retransmissions of the current transport block; - Do not retransmit until the next on duration; restarting the retransmission counter during said next on duration; Use of the initial redundancy version, - Reduce the number of retransmissions depending on the amount of on-duration so far, 40. The user device of claim 39, further comprising one or more of:

41. 40. The user device of claim 39, wherein the user device retransmits the HARQ-enabled transmission a certain number of times after a default on-duration has elapsed, and in response to not receiving HARQ feedback, the user device refrains from the HARQ-enabled transmission until the next on-duration of the further user device and transmits the HARQ-enabled transmission during the next on-duration of the further user device.

42. The user device operates in an out-of-coverage mode, and in the out-of-coverage mode, the user device: is not connected to a base station of a wireless communication system, e.g. the user device operates in mode 2 or is not in an RRC connected state, so that the user device does not receive a sidelink resource allocation configuration or assistance from the base station; and / or is connected to a base station of the wireless communication system that is unable to provide sidelink resource allocation configuration or assistance for said user device for one or more reasons; and / or A user device according to any one of claims 1 to 41, connected to a base station of the wireless communication system that does not support sidelink services, such as NR V2X services, such as a GSM, UMTS or LTE base station.

43. The user device may be a user device with limited power, or a handheld user device, such as a user device used by pedestrians, called Vulnerable Road User (VRU) or Pedestrian UE (P-UE), or a wearable or handheld user device, such as a public safety UE (PS-UE), used by public safety officers and first responders, or an IoT user device, such as a sensor, actuator, or user device located in a campus network to perform repetitive tasks and that periodically requires input from a gateway node, or a mobile terminal, or a fixed terminal, or a cellular IoT-user device, or a vehicular user device, or a vehicular group leader user device (GL-UE), or a narrowband IoT or NB-IoT (NB-IoT) 43. The user device of any one of claims 1 to 42, comprising one or more of: a wireless communication network (IoT) device, or a ground vehicle, or an aircraft, or a drone, or a mobile base station, or a roadside unit (RSU), or a building, or any other item or device having a network connection enabling it to communicate using a wireless communication network such as a sensor or actuator, or any other item / device having a network connection enabling it to communicate using a sidelink such as a sensor or actuator, or any sidelink enabled network entity.

44. 44. A wireless communication system comprising a user device according to any one of claims 1 to 43, the wireless communication system being configured for sidelink communication, e.g. using resources from a set of sidelink resources of the wireless communication system.

45. The wireless communication system comprises one or more base stations, the base stations being a macro cell base station, or a small cell base station, or a central unit of a base station, or a distributed unit of a base station, or an IAB (Integrated Access and Backhaul) node, or a roadside unit, or a user device, or a group leader user device (GL-UE), or a relay, or a RRH (Remote Radio Head), or an AMF, or an MME, or an SMF, or a core network entity, or a mobile edge computing entity, or a network slice such as in a NR or 5G core context, or any transmission / reception point that enables an item or device to communicate using the wireless communication network, the item or device having a network connection for communicating using the wireless communication network. The wireless communication system of claim 44.

46. 1. A method of operating a user device for a wireless communication system, the wireless communication system comprising a plurality of user devices, the user devices receiving transmissions from one or more further user devices via a sidelink, the user devices operating in a discontinuous reception mode, the method comprising: A method comprising entering an inactive or sleep mode if certain criteria are met.

47. 1. A method of operating a user device for a wireless communication network, the wireless communication network including a plurality of user devices, the method comprising: sending one or more transmissions via a side link (SL) to one or more further user devices, said one or more further user devices operating in a discontinuous reception mode; and indicating termination of the one or more transmissions to the further user device so that the further user device can enter an inactive or sleep mode.

48. 1. A method of operating a user device for a wireless communication network, the wireless communication network including a plurality of user devices, the method comprising: sending a plurality of transmissions via a sidelink to one or more further user devices, the one or more further user devices operating in a discontinuous reception mode, each of the plurality of transmissions including at least one initial transmission; and transmitting the plurality of transmissions to the further user devices such that at least one or more of the initial transmissions fall within an on duration of a discontinuous reception cycle of the one or more further user devices.

49. A method of operating a user device for a wireless communication system, said wireless communication system comprising a plurality of user devices, said user devices receiving transmissions from one or more further user devices via a side link (SL), said user devices operating in a discontinuous reception mode, said method comprising the steps of:

11. A method comprising the step of: remaining active for a particular active time during a discontinuous reception cycle, said particular active time being dependent on one or more criteria.

50. A method of operating a user device for a wireless communication system, said wireless communication system comprising a plurality of user devices, said user devices communicating with one or more further user devices via a side link (SL), said method comprising the steps of: configuring one or more of the further user devices to operate in a discontinuous reception mode; A method, wherein the discontinuous reception setting of the further user device is determined in dependence on one or more criteria.

51. A method of operating a user device for a wireless communication system, the wireless communication system comprising a plurality of user devices, the user devices receiving transmissions from one or more further user devices via a side link (SL), the user devices operating in a discontinuous reception mode and being active for a certain active time, such as an on duration, during a discontinuous reception cycle, the method comprising the steps of:

11. A method comprising: decoding a transmission or skipping decoding the transmission depending on one or more criteria.

52. 1. A method of operating a user device for a wireless communication system, the wireless communication system including a plurality of user devices, the user devices communicating with one or more further user devices via a sidelink, the one or more further user devices operating in a discontinuous reception mode, the method comprising: transmitting one or more HARQ capable transmissions to a further user device during an on duration of a discontinuous reception cycle of the further user device; in response to not receiving a HARQ feedback, refraining from a HARQ capable transmission until a next on-duration of the further user device, and transmitting the HARQ capable transmission during the next on-duration of the further user device.

53. A computer readable medium storing instructions which, when executed on a computer, perform the method of any one of claims 46 to 52.

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