Nrsidelink discontinuous reception

Abstract

A user equipment (UE) for a wireless communication system is described. The wireless communication system includes a plurality of UEs. The UE communicates with one or more additional UEs using a sidelink (SL). To operate in a discontinuous reception (DRX) mode, the UE receives a DRX configuration from one of a plurality of DRX configuration sources. The plurality of DRX configuration sources are ranked such that each of the DRX configuration sources has a different rank from the remaining DRX configuration sources, and the UE is to select the DRX configuration from the DRX configuration source of the available DRX configuration sources that has the highest rank.

Description

Technical Field

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

[0002] Embodiments of the present invention relate to NR SL DRX configuration or synchronization source selection, NR SL DRX cycle length, NR SLDRX alignment, the content of the NR SL DRX on-duration, the NR SL DRX signaling procedure and the use of resources by other user equipment during the on-duration.

[0003] FIG1( a ) is a schematic diagram of an example of a terrestrial wireless network 100. As shown in FIG1( a ), the terrestrial wireless network 100 includes a core network 102 and one or more radio access networks RAN1, RAN2, . . . RAN N Figure 1(b) shows the radio access network RAN n Schematic diagram of an example of a radio access network RAN n One or more base stations gNB1 to gNB5 may be included, each serving a specific area around the base station, schematically represented by the corresponding cells 1061 to 1065. Base stations are provided to serve users within the cell. One or more base stations may serve users in licensed and / or unlicensed frequency 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. Users may be fixed devices or mobile devices. Mobile or fixed IoT devices connected to a base station or user may also access the wireless communication system. Mobile devices or IoT devices may include physical devices, ground vehicles (e.g., robots or cars), aircraft (e.g., manned or unmanned aerial vehicles (UAVs), the latter also known as drones), buildings, and other items and devices embedded with electronics, software, sensors, actuators, etc., as well as network connections that enable these devices to collect and exchange data on existing network infrastructure. Figure 1(b) shows an exemplary diagram of five cells, however, RAN n More or fewer such cells may be included, and the RAN nAlternatively, only one base station may be included. Figure 1(b) shows two users, UE1 and UE2, also referred to as user equipment (UE), in cell 1062, served by base station gNB2. Another user, UE3, is shown in cell 1064, served by base station gNB4. Arrows 1081, 1082, and 1083 schematically represent uplink / downlink connections for transmitting data from users UE1, UE2, and UE3 to base stations gNB2 and gNB4, or for transmitting data from base stations gNB2 and gNB4 to users UE1, UE2, and UE3. This can be implemented in either licensed or unlicensed frequency bands. Furthermore, Figure 1(b) shows two IoT devices 1101 and 1102 in cell 1064. IoT devices 1101 and 1102 can be fixed or mobile devices. IoT device 1101 accesses the wireless communication system via base station gNB4 to receive and transmit data, as schematically indicated by arrow 1121. IoT device 1102 accesses the wireless communication system via user UE3, as schematically indicated by arrow 1122. Each base station gNB1 to gNB5 can be connected to the core network 102, for example, via an S1 interface, and via respective backhaul links 1141 to 1145, schematically indicated by arrows pointing to "Core" in Figure 1(b). The core network 102 can be connected to one or more external networks. Furthermore, some or all of the base stations gNB1 to gNB5 can be connected to each other via respective backhaul links 1161 to 1165, for example, via an S1, X2, or XN interface in NR, schematically indicated by arrows pointing to "gNBs" in Figure 1(b). Sidelink channels allow direct communication between UEs, also known as device-to-device (D2D) communication. The sidelink interface in 3GPP is designated PC5.

[0004] For data transmission, a physical resource grid (PRG) may be used. The PRG may include a set of resource elements to which various physical channels and physical signals are mapped. For example, physical channels may include physical downlink, uplink, and sidelink shared channels (PDSCH, PUSCH, PSSCH) that carry user-specific data (also known as downlink, uplink, and sidelink payload data); physical broadcast channels (PBCH) that carry, for example, one or more of the master information block (MIB) and system information block (SIB); and physical downlink, uplink, and sidelink control channels (PDCCH, PUSCH, PSSCH) that carry, for example, downlink control information (DCI), uplink control information (UCI), and sidelink control information (SCI). Note that the sidelink interface may support 2-stage SCI. This refers to a first control region containing some portion of the SCI, and optionally a second control region containing a second portion of the control information.

[0005] For the uplink, the physical channels may also include a physical random access channel (PRACH or RACH) used by the UE to access the network after synchronization and acquisition of the MIB and SIB. Physical signals may include reference signals or symbols (RS), synchronization signals, etc. The resource grid may include a frame or radio frame having a certain duration in the time domain and a given bandwidth in the frequency domain. A frame may have a certain number of subframes with a predetermined length (e.g., 1 ms). Each subframe may include one or more slots having 12 or 14 OFDM symbols, depending on the cyclic prefix (CP) length. A frame may also consist of a smaller number of OFDM symbols, for example when a shortened transmission time interval (sTTI) or a mini-slot / non-slot-based frame structure including only a few OFDM symbols is used.

[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 IFFT-based signal with or without CP, such as DFT-S-OFDM. Other waveforms such as non-orthogonal waveforms for multiple access, such as filter bank multi-carrier (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 pro-advanced standard, or 5G, or the NR (New Radio) standard, or the NR-U (Unlicensed New Radio) standard.

[0007] The wireless network or communication system depicted in Figures 1(a) and 1(b) may be composed of heterogeneous networks with different overlapping networks, such as a network of macrocells (each macrocell including macro base stations (e.g., base stations gNB1 to gNB5)) and a network of small cell base stations, such as femto or pico base stations (not shown in Figures 1(a) and 1(b)). In addition to the terrestrial wireless networks described above, there are also non-terrestrial wireless communication networks (NTNs) that include space-borne transceivers (e.g., satellites) and / or airborne transceivers (e.g., unmanned aerial vehicle systems). Non-terrestrial wireless communication networks or systems may operate in a manner similar to the terrestrial systems described above with reference to Figures 1(a) and 1(b) (e.g., according to the LTE pro-Advanced standard or the 5G or NR (New Radio) standard).

[0008] In a mobile communication network, for example in a network as described above with reference to Figures 1(a) and 1(b), like an LTE or 5G / NR network, there can be UEs that directly communicate with each other over one or more sidelink (SL) channels (e.g. using a PC5 interface). UEs that directly communicate with each other over the sidelink can include vehicles that directly communicate with other vehicles (V2V communication), vehicles that communicate with other entities of the wireless communication network (e.g. roadside entities like traffic lights, traffic signs, or pedestrians) (V2X communication). Other UEs can not be vehicle-related UEs and can include any of the devices described above. Such devices can also directly communicate with each other using the SL channel (D2D communication).

[0009] When considering two UEs that directly communicate with each other over the sidelink, the two UEs can be served by the same base station, such that the base station can provide the UEs with a sidelink resource allocation configuration or assistance. For example, both UEs can be within the coverage area of a base station (like one of the base stations depicted in Figure 1(b)). This is referred to as an “in-coverage” scenario. Another scenario is referred to as an “out-of-coverage” scenario. It is to be noted that “out-of-coverage” does not mean that the two UEs are not within one of the cells depicted in Figure 1(b), but rather that the UEs:

[0010] - can not be connected to the base station, e.g. they are not in an RRC connected state, so the UEs do not receive any sidelink resource allocation configuration or assistance from the base station, and / or

[0011] - can be connected to the base station, but, for one or more reasons, the base station can not provide the UEs with a sidelink resource allocation configuration or assistance, and / or

[0012] - can be connected to a base station that does not support NR V2X services, e.g. a GSM, UMTS, LTE base station.

[0013] When considering two UEs that directly communicate with each other over the sidelink (e.g. using a PC5 interface), one of the UEs can also be connected with the BS and can relay information from the BS to the other UE via the sidelink interface. The relaying can be performed in the same frequency band (in-band relaying), or can use another frequency band (out-of-band relaying). In the first case, the communication on Uu and on the sidelink can be decoupled using different time slots, like in a time-division duplex, TDD, system.

[0014] Figure 2Figure 1(b) illustrates a scenario where two UEs are directly communicating with each other, both connected to a base station. The base station gNB has a coverage area schematically represented by circle 200, which generally corresponds to the cell schematically represented in Figure 1(b). The UEs directly communicating with each other include a first vehicle 202 and a second vehicle 204, both within the coverage area 200 of the base station gNB. Both vehicles 202 and 204 are connected to the base station gNB and are directly connected to each other via a PC5 interface. Scheduling of V2V traffic and / or interference management is assisted by the gNB via control signaling over the Uu interface, the radio interface between the base station and the UEs. In other words, the gNB provides SL resource allocation configuration or assistance to the UEs, and the gNB assigns resources to be used for V2V communication via the sidelink. This configuration is also known as Mode 1 configuration in NR V2X or Mode 3 configuration in LTE V2X.

[0015] Figure 3 is a schematic diagram of an out of coverage scenario, where UEs communicating directly with each other are not connected to a base station, although they may be physically within a cell of the wireless communication network, or some or all of the UEs communicating directly with each other are connected to a base station, but the base station does not provide SL resource allocation configuration or assistance. Three vehicles 206, 208, and 210 are shown communicating directly with each other via a side link (e.g., using a PC5 interface). Scheduling and / or interference management of V2V traffic is based on algorithms implemented between vehicles. This configuration is also referred to as a Mode 2 configuration in NR V2X or a Mode 4 configuration in LTE V2X. As described above, Figure 3 The scenario described as out of coverage scenario does not necessarily mean that the corresponding Mode 2 UE (in NR) or Mode 4 UE (in LTE) is outside the coverage 200 of the base station. Instead, it means that the corresponding Mode 2 UE (in NR) or Mode 4 UE (in LTE) is not served by the base station, is not connected to the base station in the coverage area, or is connected to the base station but does not receive SL resource allocation configuration or assistance from the base station. Therefore, the following scenarios can exist: Figure 2 In the illustrated coverage area 200 , in addition to NR Mode 1 or LTE Mode 3 UEs 202 and 204 , NR Mode 2 or LTE Mode 4 UEs 206 , 208 , and 210 also exist.

[0016] In the aforementioned scenario involving in-vehicle user equipment (UE), multiple such UEs can form a user equipment group (also referred to as a group). Communication within the group or between group members can be performed via a sidelink interface (such as a PC5 interface) between the UEs. For example, the aforementioned scenario using in-vehicle UEs can be employed in the transportation industry, where multiple vehicles equipped with UEs can be grouped together, for example, for remote driving applications. Other use cases where multiple UEs can be grouped together for sidelink communication include factory automation and power distribution. In the case of factory automation, multiple mobile or stationary machines within a factory can be equipped with UEs and grouped together for sidelink communication, for example, to control the operation of the machines, such as robotic motion control. In the case of power distribution, entities within a power distribution grid can be equipped with corresponding UEs, which can be grouped together within a certain area of ​​the system to communicate with each other via sidelink communication, thereby enabling system monitoring and handling of power distribution grid faults and outages.

[0017] Naturally, in the above use cases, sidelink communication is not limited to intra-group communication. Instead, sidelink communication can be between any UEs, such as between any UE pairs.

[0018] Note that the information in the above section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.

[0019] Starting from the prior art as described above, enhancements or improvements may be needed regarding discontinuous reception DRX on the side link SL. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Now, embodiments of the present invention will be described in further detail with reference to the accompanying drawings:

[0021] FIG1( a ) and FIG1( b ) are schematic diagrams showing examples of wireless communication systems;

[0022] 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.

[0023] Figure 3 is a schematic diagram of an out-of-coverage scenario in which UEs communicate directly with each other;

[0024] FIG4( a ) shows an example of a DRX-config information element IE.

[0025] FIG4( b ) is a table including a description of the DRX-config field of the DRX-config IE in FIG4( a );

[0026] FIG5( a ) shows an example of assistance information that may be provided or sent by a UE;

[0027] Figure 5(b) shows the delay budget report information element IE sent by the UE as part of the assistance information;

[0028] Figure 6 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 equipment UE capable of operating according to embodiments of the present invention);

[0029] Figure 7 Schematically illustrates a user equipment according to an embodiment of the first aspect of the present invention;

[0030] Figure 8 A UE according to an embodiment of the second aspect of the present invention is schematically shown;

[0031] Figure 9 A UE according to an embodiment of the third aspect of the present invention is schematically shown;

[0032] Figure 10 An example of three DRX cycles with the same start time and the same on-duration but different lengths is shown;

[0033] Figure 11 The embodiment of the third aspect of the present invention is shown at the UE. Figure 10 Alignment of DRX cycles;

[0034] Figures 12(a) and 12(b) show the Figure 10 The consequences of misalignment of one of the DRX cycles;

[0035] Figure 13 An embodiment of a UE according to the fourth aspect of the present invention is shown;

[0036] Figure 14 An embodiment including only the on-duration of the PSCCH is shown;

[0037] Figure 15 shows a portion containing PSSCH and the on-duration of PSCCH;

[0038] Figure 16 The on-duration including only or including PSFCH is shown;

[0039] Figure 17 shows the on-duration including a portion of the PSSCH, the PSCCH and the PSFCH;

[0040] Figure 18 A UE according to an embodiment of the fifth aspect of the present invention is shown;

[0041] Figure 19(a) illustrates a sidelink DRX configuration element;

[0042] Figure 19(b) includes a table including a description of the fields of the SL DRX configuration information element of Figure 19(a);

[0043] Figure 20 Embodiments are illustrated in which a receiving UE is enabled to obtain a retransmission in case of a missing acknowledgement message;

[0044] Figure 21 Embodiments are illustrated in which assistance information is provided to alter the length of a DRX cycle;

[0045] Figure 22 Embodiments are illustrated in which assistance information is provided to alter the start time of a DRX cycle;

[0046] Figure 23 Embodiments are illustrated in which assistance information is provided to alter the length of a DRX on-duration;

[0047] Figure 24(a) is an assistance information IE according to an embodiment of the fifth aspect of the application;

[0048] Figure 24(b) illustrates a delay budget reporting information element IE sent by a UE as part of assistance information;

[0049] Figure 25 Embodiments are illustrated in which assistance information is provided to alter the length of a DRX cycle;

[0050] Figure 26 Examples of computer systems on which the units or modules described according to the methods of the application and the steps of the methods can be executed are illustrated. DETAILED DESCRIPTION

[0051] Embodiments of the application will now be described in more detail with reference to the drawings, in which like or similar elements are identified with the same reference numerals.

[0052] In a wireless communication system or network (such as described above with reference to Figures 1(a), 1(b), Figure 2 or Figure 3In the described wireless communication system or network, sidelink communication between various user equipments can be implemented, e.g., vehicle-to-vehicle communication V2V, vehicle-to-anything communication, or any device-to-device D2D communication between any user equipment, e.g., those mentioned above. However, in NR-Uu operation or sidelink operation, like PC5 operation, the UE is always in an awake state and monitors the control channel in every subframe in order to be able to receive from the network and from another UE, respectively. This increases the power consumption at the UE, since the UE is always on, even when there is no data to transmit or receive. For vehicular use cases, like NR V2X, power saving is not an issue, since a vehicular UE (V-UE) is a device with a sufficient power source, e.g., a vehicle's on-board battery.

[0053] However, sidelink communication or sidelink PC5 operation is not limited to the operation of vehicular UEs, other UEs with a restricted or limited power source, like regular user equipment including a battery that needs to be charged periodically, can communicate over the sidelink. Such UEs can include so-called Vulnerable Road Users VUEs, like pedestrian UEs (P-UEs), or first responder devices for public safety use cases, or IoT devices, like general IoT UEs or industrial IoT UEs. For these types of UEs, power saving is important, since they are not connected to a constant power source but rely on their battery.

[0054] To reduce the power consumption at the UE in NR, discontinuous reception DRX is employed on the Uu interface. DRX is a mechanism where the UE enters a sleep mode for a period of time, during which it does not transmit or receive any data. The UE wakes up for another period of time, where it can transmit and receive data. One key aspect of DRX is the synchronization between the UE and the network in terms of its sleep and wake-up periods, also referred to as DRX cycles. In the worst case, the network tries to transmit data to a UE that is in sleep mode, such that when the UE wakes up, there is no data to receive. In the NR-Uu interface, this scenario is prevented by maintaining an explicit agreement between the UE and the network or system in terms of sleep and wake-up periods. In other words, the DRX is configured to the UE by the gNB, and the DRX is synchronized with the gNB.

[0055] The DRX cycle includes both an on-time and an off-time within a fixed time interval, and for the NR Uu interface, short DRX cycles and long DRX cycles are defined, where the short DRX cycle can span several symbols within a slot, and the long DRX cycle can span an entire slot or multiple slots. For example, when considering a base station, like a gNB, from the gNB side, the DRX cycle can be configured by sending a DRX-config information element to the UE, as illustrated in Figure 4(a). Figure 4(b) is a table including a description of the DRX-config field.

[0056] In addition, the UE may use assistance information to adjust the DRX cycle, and Figure 5(a) shows an example of assistance information that may be provided or sent by the UE. The assistance information includes a delay budget report that indicates the UE's preferred adjustment for connected mode DRX, and the assistance information also includes an indication of a preferred increase / decrease in the long DRX cycle length relative to the current configuration, allowing the UE to indicate to the base station that the DRX cycle duration is to be increased or decreased. Figure 5(b) shows a delay budget report information element sent by the UE as part of the assistance information, which includes a value in milliseconds, i.e., msXX or msMinusXX, indicating an increase or decrease in the DRX cycle length desired by the UE.

[0057] While there are well-implemented mechanisms for DRX between the gNB and UE over the Uu interface, DRX will also be implemented on the sidelink to meet the power saving requirements of sidelink UEs that are not connected to a constant power source (e.g., handheld UEs). However, unlike in Uu operation, in sidelink operation there is not necessarily a central point (e.g., the gNB) that allows synchronization of the DRX cycles of the SL UEs.

[0058] The present invention provides a method for implementing discontinuous reception (DRX) on a side link (SL) in a wireless communication system or network, and aspects of the present invention relate to a DRX synchronization timeline, possible cycle lengths of DRX, alignment with DRX cycles of other SL UEs, contents of the on-duration of NR SL DRX, NR SL DRX signaling procedures, and use of resources for on-duration by other user equipment. Embodiments of the present invention may be shown in FIG1(a), FIG1(b), Figure 2 and Figure 3 The depicted wireless communication system is implemented, and the wireless communication system includes a base station and users, such as mobile terminals or IoT devices. Figure 6 is a schematic diagram of a wireless communication system including a transmitter 300 (e.g., a base station) and one or more receivers 302, 304 (e.g., user equipment UE). The transmitter 300 and the receivers 302, 304 can communicate via one or more wireless communication links or channels 306a, 306b, 308 (e.g., radio links). The transmitter 300 may include one or more antennas ANT T or an antenna array having a plurality of antenna elements, a signal processor 300a and a transceiver 300b, which are coupled to each other. The receiver 302 includes one or more antennas ANT UEor an antenna array having multiple antennas, signal processors 302a, 304a, and transceivers 302b, 302b, which are coupled to each other. The base station 300 and the UE 302 can communicate via respective first wireless communication links 306a and 306b (e.g., radio links using a Uu interface), while the UEs 302, 304 can communicate with each other via a second wireless communication link 308 (e.g., a radio link using a PC5 / sidelink (SL) interface). When the UEs are not being served by or connected to the base station (e.g., they are not in an RRC connected state), or more generally, when the base station does not provide SL resource allocation configuration or assistance, the UEs can communicate with each other via the sidelink (SL). Figure 6 systems or networks, Figure 6 One or more UEs 302, 304 and Figure 6 The base station 300 may operate according to the teachings of the present invention as described herein.

[0059] First Aspect - DRX Configuration Source

[0060] User Equipment

[0061] The present invention provides a user equipment UE for a wireless communication system, wherein the wireless communication system includes a plurality of user equipments UE.

[0062] The UE uses the side link SL to communicate with one or more other UEs.

[0063] In order to operate in discontinuous reception (DRX) mode, the UE receives a DRX configuration from one of the multiple DRX configuration sources, and

[0064] The multiple DRX configuration sources are hierarchical, such that each of the DRX configuration sources has a different rank from the remaining DRX configuration sources, and the UE is to select a DRX configuration from a DRX configuration source with the highest rank among the available DRX configuration sources.

[0065] According to an embodiment, the UE shall:

[0066] • determining an available DRX configuration source to which the UE can connect from among multiple DRX configuration sources,

[0067] • determining the available DRX configuration source having the highest rank from the available DRX configuration sources, and

[0068] • Select the DRX configuration from the available DRX configuration source with the highest rank.

[0069] According to an embodiment, multiple DRX configuration sources are ranked based on one or more of the following:

[0070] • Connect the DRX configuration source to the interface of the user equipment, such as the Uu interface or PC5 interface,

[0071] •Type of DRX configuration source, e.g. gNB, roadside unit (RSU), UE,

[0072] • Certain parameters included in the DRX configuration received from the DRX configuration source, such as a timestamp indicating how recent the DRX configuration is, or a priority.

[0073] According to an embodiment, the multiple DRX configuration sources include one or more of the following:

[0074] • an access point of a wireless communication system, such as a base station gNB or a gateway node, said access point having a hierarchy,

[0075] • one or more first UEs authorized by the wireless communication system to send DRX configuration or coordinate DRX, such as a roadside unit (RSU) or a group leader UE, the first UE having the same rank or a different rank than the access point,

[0076] • one or more second UEs to which the UE is connected for communicating over the SL, the second UEs having the same rank or a different rank than one or more ranks of the first UE,

[0077] • one or more third UEs transmitting assistance information on SL resources of the wireless communication system, the assistance information comprising one or more DRX configurations, the third UEs having the same rank or a different rank than one or more ranks of the second UE,

[0078] • One or more fourth UEs operating in DRX mode and transmitting on SL resources of the wireless communication system, and the UE obtains the DRX configuration from the fourth UE by listening to the DRX cycle used at the fourth UE, the fourth UE having the same rank or a different rank lower than one or more ranks of the third UE.

[0079] According to an embodiment, in case that the UE is connected to a specific DRX configuration source, the UE is to limit available DRX configuration sources to those having the same rank as or a higher rank than the specific DRX configuration source.

[0080] According to an embodiment, the specific DRX configuration source includes the base station with the highest rank, and the UE is to limit the available DRX configuration sources to the base station.

[0081] method

[0082] The present invention provides a method for operating a user equipment (UE) of a wireless communication system in a discontinuous reception (DRX) mode, wherein the wireless communication system includes multiple user equipments (UEs), and the UE communicates with one or more other UEs using a side link (SL). The method includes:

[0083] The UE receives a DRX configuration from one of a plurality of DRX configuration sources,

[0084] The multiple DRX configuration sources are hierarchical, such that each of the DRX configuration sources has a different rank from the remaining DRX configuration sources, and the UE is to select a DRX configuration from a DRX configuration source with the highest rank among the available DRX configuration sources.

[0085] Second aspect - DRX cycle length

[0086] User Equipment

[0087] The present invention provides a user equipment UE for a wireless communication system, wherein the wireless communication system includes a plurality of user equipments UE.

[0088] The UE uses the side link SL to communicate with one or more other UEs.

[0089] wherein the UE is to operate in a discontinuous reception (DRX) mode according to a DRX configuration comprising one or more DRX patterns, the one or more DRX patterns defining a fixed-length DRX cycle or an adaptive-length DRX cycle for a time period during which the DRX configuration is valid, and

[0090] In which, in the case of a fixed-length DRX cycle, the total duration of the DRX cycle and the on-off duration of the DRX cycle are fixed, and in the case of an adaptive-length DRX cycle, the total duration of the DRX cycle and / or the on-off duration of the DRX cycle are adapted depending on one or more parameters, for example, depending on parameters associated with the UE and / or the environment in which the UE is located.

[0091] According to an embodiment, the one or more parameters include one or more of the following:

[0092] • the speed at which the UE moves, wherein when moving at a speed below a certain threshold, the DRX cycle is adapted to a long DRX cycle, and when moving at a speed equal to or above a certain threshold, the DRX cycle is adapted to a short DRX cycle,

[0093] • the presence of one or more further UEs, wherein the DRX cycle is adapted to a short DRX cycle when the distance to the one or more further UEs is below a certain threshold, and the DRX cycle is adapted to a long DRX cycle when the distance to the one or more further UEs is equal to or above a certain threshold,

[0094] • the location where the UE is located, wherein when the location is an unsafe area, the DRX cycle is adapted to a short DRX cycle, and when the location is a safe area, the DRX cycle is adapted to a long DRX cycle,

[0095] • The nature of the transmission, where a short or long DRX cycle is adopted when data transmission needs to be periodically transmitted at shorter or longer intervals, respectively.

[0096] • Occupancy of one or more used resource pools, wherein the DRX cycle is adapted to a longer or different on-duration if the busyness of the monitored resources exceeds a certain threshold, eg by calculating a channel busy rate CBR on the monitored resources.

[0097] According to an embodiment, adopting an adaptive length DRX cycle includes deactivating the DRX mode within a specific duration, and wherein, when data transmission requires the UE to be turned on for a given duration, the given duration is longer than the on duration of the DRX cycle, the UE is to deactivate DRX within the given duration, and after the data transmission is completed, resume the DRX cycle.

[0098] method

[0099] The present invention provides a method for operating a user equipment (UE) of a wireless communication system, wherein the wireless communication system includes multiple user equipments (UEs), and the UE communicates with one or more other UEs using a side link (SL). The method includes:

[0100] operating the UE in a discontinuous reception (DRX) mode according to a DRX configuration comprising one or more DRX patterns defining a fixed-length DRX cycle or an adaptive-length DRX cycle for a time period for which the DRX configuration is valid,

[0101] In which, in the case of a fixed-length DRX cycle, the total duration of the DRX cycle and the on-off duration of the DRX cycle are fixed, and in the case of an adaptive-length DRX cycle, the total duration of the DRX cycle and / or the on-off duration of the DRX cycle are adapted depending on one or more parameters, for example, depending on parameters associated with the UE and / or the environment in which the UE is located.

[0102] Aspect 3 - DRX Alignment

[0103] User Equipment

[0104] The present invention provides a user equipment UE for a wireless communication system, wherein the wireless communication system includes a plurality of user equipments UE.

[0105] The UE uses the side link SL to communicate with one or more other UEs.

[0106] The UE is to operate in DRX mode, and

[0107] Therein, the UE is to align the DRX cycle with one or more access points of the wireless communication system such as a base station gNB or a gateway node and / or another UE.

[0108] According to an embodiment, in order to align the DRX cycle between the UE and the base station,

[0109] In the case where the UE is connected to the base station, in response to being configured with one or more DRX configurations by the base station, the UE aligns its DRX cycle with that of the base station, and / or

[0110] In the case where the UE aligns its DRX cycle with one or more of the other UEs to which the UE is connected for SL communication, the UE is to signal one or more of the UE's existing DRX cycles to the base station in order to inform the base station.

[0111] According to an embodiment, in order to align the DRX cycle between the UE and one or more other UEs, the UE monitors one or more other UEs in the vicinity of the UE and adapts the DRX cycle of the UE to one or more DRX cycles used by one or more of the other UEs.

[0112] According to an embodiment, in case that monitoring one or more of the other UEs in the vicinity of the UE results in multiple DRX durations, the UE is to enable multiple DRX cycles.

[0113] According to an embodiment, in order to enable multiple DRX cycles, the UE is to create a new DRX pattern formed of multiple DRX cycles.

[0114] According to an embodiment, the new DRX cycle is the least common multiple of the multiple DRX cycles.

[0115] According to an embodiment, each of the available DRX configurations defines a DRX duration having a start time point common to all defined DRX durations, wherein the DRX configuration defines a fixed duration and an on-off duration selected from a set of fixed durations.

[0116] method

[0117] The present invention provides a method for operating a user equipment (UE) of a wireless communication system in a discontinuous reception (DRX) mode, wherein the wireless communication system includes multiple user equipments (UEs), and the UE communicates with one or more other UEs using a side link (SL). The method includes:

[0118] The DRX cycle of the UE is aligned by the UE with one or more of an access point such as a base station gNB or a gateway node and / or another UE of the wireless communication system.

[0119] Aspect 4 - DRX cycle duration

[0120] User Equipment

[0121] The present invention provides a user equipment UE for a wireless communication system, wherein the wireless communication system includes a plurality of user equipments UE.

[0122] The UE uses the side link SL to communicate with one or more other UEs.

[0123] The UE is to operate in DRX mode, and

[0124] The on-duration of the DRX cycle depends on the specific purpose for which the UE uses the on-duration.

[0125] According to an embodiment, the UE is to select the on-duration depending on whether the UE is to process:

[0126] (i) control data only, such as data in the PSCCH, or

[0127] (ii) payload data only, such as data in PSSCH, or

[0128] (iii) Feedback data only, such as data in PSFCH, or

[0129] (iv) A combination of two or more of (i) to (iv).

[0130] According to an embodiment, the specific purpose includes one or more of the following:

[0131] • the UE wants to monitor one or more of the other UEs for sensing purposes,

[0132] • The UE needs to determine the available resources for transmission,

[0133] •UE wants to send control and data,

[0134] • The UE needs to monitor feedback from one or more other UEs,

[0135] • The UE is to receive control from one or more other UEs,

[0136] •UE has to determine the load in a given frequency band.

[0137] According to an embodiment, the on-duration spans one or a combination of:

[0138] • a duration of the PSCCH only, such as the first 2 or 3 symbols of a slot, e.g., for receiving a first stage SCI from one or more further UEs and for decoding one or more first stage SCIs, or

[0139] • a portion of the duration of the PSSCH and the duration of the PSCCH to allow the UE to perform a transmission, for example, to enable the UE to send the first phase SCI in the PSCCH and then send the second phase SCI and data in the PSSCH, or to allow the UE to listen to the first phase control information and the second phase control information sent in the PSCCH and PSSCH respectively, or

[0140] • the duration of the PSFCH only, e.g. in terms of one or more subchannels available for transmission as determined by the UE, or

[0141] • The duration of the PSCCH, a portion of the PSSCH duration and the duration of the PSFCH, e.g. to provide discontinuous on-durations within a timeslot for data transmission without requiring the UE to be active throughout the timeslot and for receiving feedback.

[0142] According to an embodiment, the UE is to signal the OnDuration to one or more of the further UEs.

[0143] method

[0144] The present invention provides a method for operating a user equipment (UE) of a wireless communication system in a discontinuous reception (DRX) mode, wherein the wireless communication system includes multiple user equipments (UEs), and the UE communicates with one or more other UEs using a side link (SL). The method includes:

[0145] The OnDuration of a DRX cycle is set by the UE depending on the specific purpose for which the UE uses the OnDuration.

[0146] Aspect 5 - DRX signaling process

[0147] User Equipment

[0148] The present invention provides a user equipment UE for a wireless communication system, wherein the wireless communication system includes a plurality of user equipments UE.

[0149] The UE uses the side link SL to communicate with one or more other UEs.

[0150] In order to operate in DRX mode, the UE needs to receive one or more DRX configurations from the DRX synchronization source, and

[0151] in,

[0152] • the DRX synchronization source includes a base station, and the UE is to receive a control message, such as a SIB, from the base station, the control message including the one or more DRX configurations, or

[0153] • The DRX synchronization sources include one or more of the further UEs, which are to receive one or more DRX configurations from another UE using, for example, PC5 RRC signaling or SCI for a given transmission.

[0154] According to an embodiment, the one or more DRX configurations include some or all of the following information:

[0155] •DRX cycle duration, the total duration of a single DRX cycle, including on-duration and off-duration,

[0156] • On duration, which indicates the duration that the UE can transmit and receive,

[0157] • Inactivity timer, which indicates the duration that the UE must remain on after receiving a control signal and / or packet transmission, e.g. to wait for HARQ feedback,

[0158] • Retransmission timer, which indicates the duration that the UE must remain on because a control signal has indicated a retransmission of a given packet,

[0159] • Communication range requirements, within which the UE is to expect or send feedback on sent or received transmissions.

[0160] According to an embodiment, in order to operate in DRX mode, in response to receiving one or more DRX configurations, the UE is to activate DRX mode.

[0161] According to an embodiment, the UE is to activate DRX mode in response to:

[0162] • expiration of the inactivity timer, or

[0163] • Explicit signaling by another UE, directly or indirectly, to activate or deactivate DRX mode, or

[0164] • HARQ process is enabled, or

[0165] • Switch to receive-only mode, or

[0166] • a higher layer signals power saving, or

[0167] • a change in QoS, or

[0168] • the UE is located in a specific geographical location.

[0169] According to embodiments, the explicit signaling by another UE comprises:

[0170] • using a dedicated field in the SCI related to a given transmission, and information related to the duration of the DRX activation or deactivation,

[0171] • using the "resource reservation field" in the SCI to indicate that there are further transmissions during which the UE is to remain on to receive these transmissions,

[0172] • using the "priority" field in the SCI to indicate the packet delay budget PDB associated with the transmission during which the UE is to remain on to receive any further retransmissions or HARQ retransmissions.

[0173] According to embodiments, in case the UE is to activate the DRX mode in response to a HARQ process being enabled,

[0174] • when only NACK is enabled, the UE is to remain on while receiving data until the transmission is successfully received, or while transmitting data for a time period for receiving a NACK,

[0175] • when both ACK and NACK are enabled, the UE is to remain on while receiving data until the transmission is successfully received, or while transmitting data for a time period for receiving an ACK or NACK.

[0176] According to embodiments, the duration for retransmission is defined by:

[0177] • the UE activates a HARQ timer upon receiving a HARQ transmission, the HARQ timer defining a time window during which the UE expects a retransmission before entering the off mode or starting the inactivity timer, or

[0178] • extending the inactivity timer, e.g., to be 1 or 2 HARQ RTT long, so that the UE can complete the transmission within the on duration, or

[0179] • a communication range requirement.

[0180] According to embodiments,

[0181] The wireless communication system includes a plurality of DRX configuration sources, the plurality of DRX configuration sources being hierarchical such that each of the DRX configuration sources has a different rank than the remaining DRX configuration sources, and

[0182] In case that the UE receives two or more DRX configurations with different start times and durations, the UE is to select the DRX configuration received from the DRX configuration source with the highest rank.

[0183] According to an embodiment, in response to selecting a DRX configuration from a DRX configuration source with the highest rank, the UE is to send assistance information to one or more other DRX configuration sources to notify the other DRX configuration sources of the existence of the DRX configuration source with a higher rank, thereby enabling the other DRX configuration source UEs to align their timing with the selected DRX configuration source.

[0184] According to an embodiment, the assistance information includes information allowing the characteristics of the DRX cycle to be changed.

[0185] According to an embodiment, the characteristics of the DRX cycle include one or more of the following:

[0186] • the duration of the DRX cycle length, e.g. by maintaining the on-duration and reducing the off-duration,

[0187] • the offset of the DRX cycle used to match the start time,

[0188] • The on-duration of the DRX cycle.

[0189] method

[0190] The present invention provides a method for operating a user equipment (UE) for a wireless communication system in a discontinuous reception (DRX) mode, wherein the wireless communication system includes multiple user equipments (UEs), and the UE communicates with one or more other UEs using a side link (SL). The method includes:

[0191] The UE receives one or more DRX configurations from a DRX synchronization source,

[0192] in,

[0193] • When the DRX synchronization source includes a base station, the UE receives a control message, such as a SIB, from the base station, the control message including one or more DRX configurations, or

[0194] • When the DRX synchronization source comprises one or more of the further UEs, one or more DRX configurations are received by the UE from the other UE using, for example, PC5 RRC signaling or SCI for a given transmission.

[0195] Aspect 6 - Non-DRX-UE avoids using on-duration resources

[0196] User Equipment

[0197] The present invention provides a user equipment UE for a wireless communication system, wherein the wireless communication system includes a plurality of user equipments UE.

[0198] The UE uses the side link SL to communicate with one or more other UEs.

[0199] wherein the UE is not operating in a discontinuous reception (DRX) mode but is aware that one or more of the other UEs are operating in a DRX mode, and

[0200] Therein, a UE should avoid using resources used by another UE for transmission during its on-duration.

[0201] According to an embodiment, in order to avoid using resources used by another UE during its On-Duration, the UE is to:

[0202] • exclude resources that appear during the open duration, or

[0203] • Add a penalty for using resources that appear within the opening duration, or

[0204] • Resources present during the on-duration are used only if no other resources are available.

[0205] According to an embodiment, the penalty includes one or more of the following:

[0206] • Limit penalties, e.g. resources can only be used for transmissions above a certain priority,

[0207] • Sensing penalty, for example, a value can be added to the RSSI measurement when performing the measurement,

[0208] • Selection penalties that make one or more specific resources less likely to be selected, for example, because they have decreased in rank after sensing.

[0209] According to an embodiment, the selection penalty is based on the number of UEs using a specific resource during the UE's on-duration, eg, the more UEs using a specific resource, the less likely the specific resource is to be selected.

[0210] method

[0211] The present invention provides a method for operating a user equipment (UE) for a wireless communication system, the wireless communication system including a plurality of user equipments (UEs), wherein the UE communicates with one or more other UEs using a side link (SL), the UE not operating in a discontinuous reception (DRX) mode but knowing that one or more of the other UEs are operating in the DRX mode, the method comprising:

[0212] A UE avoids transmitting using resources used by another UE during the other UE's On-Duration.

[0213] Overview

[0214] According to an embodiment, the UE includes one or more of the following: a power-limited UE, or a handheld UE (such as a UE used by pedestrians and referred to as a vulnerable road user VRU or pedestrian UE (P-UE)), or a body-worn or handheld UE used by public safety personnel and first responders and referred to as a public safety UE (PS-UE), or an IoT UE (for example, a sensor, actuator, or UE set up in a campus network to perform repetitive tasks and requiring input from a gateway node at periodic intervals), or a mobile terminal, or a fixed terminal, or a cellular IoT-UE, or a vehicle-mounted UE, or a vehicle-mounted group leader (GL) UE, or an IoT or narrowband IoT (NB-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 (for example, a sensor or actuator) provided with a network connection that enables the item / device to communicate using a wireless communication network, or any other item or device (for example, a sensor or actuator) provided with a network connection that enables the item / device to communicate using a sidelink wireless communication network, or any network entity supporting a sidelink.

[0215] system

[0216] The present invention provides a wireless communication system comprising a plurality of user equipments UE according to the present invention, the plurality of user equipments UE being configured for sidelink communication using resources, for example, from a sidelink resource set of the wireless communication system.

[0217] According to an embodiment, the wireless communication system includes one or more base stations, wherein the base station includes one or more of the following: 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 a roadside unit (RSU), or a UE, or a group leader (GL), or a relay, or a remote radio head, or an AMF, or an SMF, or a core network entity, or a mobile edge computing (MEC) entity, or a network slice in the context of NR or 5G core, or any sending / receiving point TRP that enables an item or device to communicate using a wireless communication network, and the item or device is provided with a network connection to communicate using the wireless communication network.

[0218] Computer program product

[0219] An embodiment of the present invention provides a computer program product comprising instructions which, when executed by a computer, cause the computer to perform one or more methods according to the present invention.

[0220] Aspect 1 - DRX configuration source

[0221] According to an embodiment of the first aspect of the present invention, the sidelink UE employs DRX and selects a source for DRX configuration from a hierarchical list of sources (also referred to as hierarchical DRX configuration sources).

[0222] Figure 7 The user equipment according to the embodiment of the first aspect of the present invention is schematically shown. The user equipment UE includes an antenna ANT for wireless communication in a wireless communication network or system, as shown in Figures 1(a), 1(b), Figure 2 or Figure 3 The antenna ANT is depicted. The UE can communicate with one or more other UEs (such as UE1 and UE2) via a side link (for example using the PC5 interface). The UE can also be connected to the base station via the Uu interface, such as Figure 7 The gNB shown, for example, in the case where the UE is in Mode 1, as described above with reference to Figure 2 For operation in DRX mode, the UE may receive DRX configuration from a DRX configuration source. Figure 7 In the illustrated embodiment, it is assumed that gNB, UE1 and UE2 are DRX configuration sources, and the UE can obtain DRX configuration from the DRX configuration source for operation in DRX mode. According to the embodiment, the DRX configuration sources are hierarchical, so that each of the DRX configuration sources has a different level from other DRX configuration sources. Figure 7 In an embodiment, the gNB is the DRX configuration source with the highest rank (rank 1). UE1 is also a configuration source, but with a lower rank than the gNB, i.e., rank 2, and UE2 is another DRX configuration source with a rank lower than the rank of UE1 and the rank of the gNB, for example, with rank 3. The UE may determine which DRX configuration sources are available, for example, with which DRX configuration sources communication may be established, and among these available DRX configuration sources, the UE receives or selects a DRX configuration to be adopted from the source with the highest rank. For example, in Figure 7 In the scenario shown, the DRX configuration source with the highest rank is the gNB. Therefore, although the UE can also be connected to UE1 and UE2, it receives the DRX configuration from the gNB due to the highest rank. In the case where the UE is in Mode 2 and is not connected to a gNB, for example, the available DRX configuration sources are UE1 and UE2, and the UE can receive the DRX configuration from UE1 because it has the highest rank among the available DRX configuration sources, i.e., rank 2.

[0223] The various DRX configuration sources may be ranked based on one or more of the following:

[0224] • Connect the DRX configuration source to the interface of the user equipment, such as the Uu interface or PC5 interface,

[0225] • Type of DRX configuration source, for example, a level 1 category source may include a gNB, a level 2 category source may include a roadside unit (RSU), a relay UE that relays the DRX configuration from the gNB to the UE, a base UE (e.g. a police / fire truck or a group leader (GL) UE), and a level 3 category source may be another UE,

[0226] • Specific parameters included in the DRX configuration received from the DRX configuration source, for example, a timestamp indicating how recent the DRX configuration is, or a dedicated priority parameter attached to the DRX source for a given category of UEs, where the category of UEs may be public safety UEs or IoT UEs.

[0227] According to an embodiment, the following DRX configuration sources may be provided, which are hierarchical as follows:

[0228] • An access point of a wireless communication system, such as a base station gNB or a gateway node. An access point has a first level.

[0229] • One or more first UEs authorized by the wireless communication system to send DRX configurations or coordinate DRX, such as roadside units (RSUs) or group leader UEs (GL-UEs). The first UEs may be devices that do not operate in DRX mode but communicate with other UEs, such as pedestrian UEs (P-UEs) or public safety UEs (PS-UEs), via sidelinks. The first UEs may have the same rank or a different rank than the first rank of the access point.

[0230] • one or more second UEs to which the UE is connected for communication over the SL, e.g., a V-UE, a P-UE, or a PS-UE. The second UEs have the same rank or a different rank than one or more ranks of the first UE,

[0231] • One or more third UEs, such as other PS-UEs or P-UEs not in communication with the UE, that transmit assistance information on the SL resources of the wireless communication system. The assistance information includes one or more DRX configurations or information for modifying a DRX configuration. The third UE has the same rank or a different rank than one or more ranks of the second UE,

[0232] • One or more fourth UEs operating in DRX mode and transmitting on SL resources of the wireless communication system, such as other PS-UEs or P-UEs. The UEs monitor the DRX cycle used at the fourth UEs to adapt their DRX cycle. The fourth UEs have the same rank or a different rank that is lower than one or more ranks of the third UEs.

[0233] For example, for a specific UE, the top-level DRX configuration source (i.e., the source with the highest rank) may be a single source providing one or more global DRX configurations, such as a gNB, an infrastructure UE (e.g., a patrol car or fire truck), or a gateway node (e.g., in the case of a campus network). The next level or hierarchy for a specific UE may be a higher category of UEs, such as a V-UE or GL UE, followed by UEs of the same category, such as neighboring UEs. Depending on the embodiment, different types of UEs may be provided with different DRX configuration sources or DRX synchronization sources, which are selected in a hierarchical manner as described above. According to the embodiment, four different types of UEs communicating via the side link PC5 may be considered:

[0234] Vulnerable road users (VRUs), such as pedestrian UEs (P-UEs): These UEs are essentially handheld UEs used by pedestrians, such as mobile phones. The UE can periodically transmit its location to other VRUs, making the UE's location known to these other VRUs. In the event that a VRU is nearby and there is a possibility of a collision, the VRU receives the transmission from the UE.

[0235] • Public Safety UE (PS-UE): This type of UE can be a body-worn or handheld UE used by public safety personnel and first responders (such as police, paramedics, and firefighters). A PS-UE always requires both transmit and receive functionality.

[0236] • IoT-UEs: These UEs may include sensors, actuators or other low-power nodes or powered relays and / or processing nodes in a sensor network.

[0237] • Industrial IoT-UEs: These UEs can be devices in a closed campus network that are designed to perform specific tasks and get input from a gateway node at periodic intervals. An example of an IoT-UE is a robot performing repetitive tasks on a factory floor.

[0238] When considering the above types of UEs, they may adopt different DRX synchronization sources. More specifically, for the above different types of UEs, the hierarchical order of the synchronization sources may be different.

[0239] For example, in the case of a pedestrian UE (P-UE) operating in Mode 1 or Mode 2 but within the coverage of a gNB, the vulnerable road user (VRU) or P-UE can receive DRX synchronization information and the corresponding timeline and DRX configuration from the gNB, for example, via RRC. When the P-UE moves out of coverage, the P-UE can receive DRX synchronization information from another neighboring UE, which can be a vehicle UE (V-UE) or a neighboring P-UE. The DRX synchronization information can be sent from the neighboring UE to the P-UE via the aforementioned assistance information (see Figures 5(a) and 5(b)), or the P-UE can monitor the DRX cycle of the neighboring UE. For the P-UE, the hierarchical order for receiving DRX configuration or synchronization information can be as follows:

[0240] • Level 1: gNB, providing DRX configuration,

[0241] • Level 2: One or more V-UEs, providing assistance information for relaying or modifying DRX configuration from the gNB,

[0242] • Level 3: One or more other P-UEs, the P-UE monitors the DRX cycles of the one or more other P-UEs for adapting its own DRX cycle.

[0243] In addition to the gNB, a public safety UE (PS-UE) can receive DRX configuration or synchronization from the infrastructure UE to which it is connected. This infrastructure UE can be a patrol car, ambulance, or fire truck that provides synchronization information to the PS-UE. The PS-UE can also receive DRX synchronization information from a group leader UE (GL-UE) enabled at a specific location. Therefore, the hierarchical order for receiving DRX synchronization information at the PS-UE can be as follows:

[0244] • Level 1: gNB, providing DRX configuration,

[0245] • Level 2: Base UE to which the PS-UE is connected and which provides the DRX configuration, or another UE that relays the DRX configuration from the gNB,

[0246] • Level 3: GL-UE, participates like PS-UE and provides DRX configuration,

[0247] • Level 4: One or more V-UEs, providing assistance information for modifying the DRX configuration,

[0248] • Level 5: One or more other PS-UEs, the PS-UE monitors the DRX cycles of the one or more other PS-UEs for adapting its own DRX cycle.

[0249] An IoT-UE or industrial IoT-UE can receive DRX configuration or synchronization information from a gateway node or UE to which it is connected within a network (such as a sensor network or campus network). An IoT-UE may not be connected to an external network and cannot receive DRX information from a gNB. For an IoT-UE, the hierarchical order for receiving DRX synchronization can be as follows:

[0250] • Level 1: Gateway node or UE, providing DRX configuration,

[0251] • Level 2: One or more other IoT-UEs, providing assistance information for modifying the DRX configuration,

[0252] • Level 3: One or more other IoT-UEs, the IoT-UE monitors the DRX cycles of the one or more other IoT-UEs to adapt its own DRX cycle.

[0253] According to other embodiments, the ranking can be based on reception quality, as gNBs can transmit at higher power than UEs and can therefore be easily distinguished from them. For example, typical PHY measurements such as SNR, SINR, correlation peak above a threshold, etc. can be used to assess reception quality.

[0254] The above-mentioned DRX configuration source not only provides DRX configuration for the UE, but also serves as a DRX synchronization source, so as to allow the UE to synchronize its DRX cycle using the DRX synchronization information received from the DRX configuration source.

[0255] According to an embodiment, the UE may disable the hierarchical classification of DRX configuration sources. For example, when the UE is connected to a specific DRX configuration source, lower-ranked DRX configuration sources may no longer be considered. In other words, the UE may limit the available DRX configuration sources to those with the same rank as the currently used DRX configuration source or a higher rank than the currently used DRX configuration source. For example, when the UE uses a gNB as the DRX configuration source with the highest rank, the UE limits the available DRX configuration sources to one source, namely the gNB.

[0256] Therefore, according to an embodiment of the present invention, a UE can determine its DRX configuration or synchronization source in a hierarchical manner from multiple available DRX configurations or synchronization sources, each of which is associated with a specific level in the hierarchical order. This is advantageous because for DRX cycles to work effectively between UEs, the UEs need to be synchronized with each other so that their on-durations are aligned. All UEs that are able to receive a DRX configuration from the highest DRX synchronization source will have their on-durations aligned and effectively communicate with each other, while achieving power savings by going to sleep during the off-durations. This is to ensure that as long as the DRX cycles are synchronized with each other, the UEs will not miss listening to any critical transmissions.

[0257] Furthermore, by using the DRX configuration relayed from the gNB along with assistance information between UEs, all UEs within a specific area but with different synchronization sources can align themselves to a common on-duration to achieve considerable power savings.

[0258] The second aspect - DRX cycle length

[0259] According to an embodiment of the second aspect of the present invention, the DRX cycle may be fixed or adaptive. Figure 8 A UE according to an embodiment of the second aspect of the present invention is schematically shown, the UE comprising an antenna ANT for communicating with one or more other UEs (such as Figure 8 UE1 and UE2 shown in FIG) perform side link communication. Figure 8 The UE operates according to a DRX mode based on a DRX configuration, which includes a fixed-length DRX cycle or an adaptive-length DRX cycle for the period of time during which the DRX configuration at the UE is valid. The DRX cycle contains an on-duration and an off-duration and can be defined in a simple on-off manner or in the form of a DRX pattern.

[0260] A DRX pattern is essentially a series of on-durations and off-durations defined within a fixed DRX cycle. A DRX cycle may span multiple symbols or time slots. Assuming that the UE needs to listen only to periodic transmissions, but each transmission is of different length, the DRX cycle may be adapted to such a pattern by defining on-durations for different times when the UE expects to listen to a transmission and off-durations when the UE is asleep to save power. In one example, the UE may select a specific DRX pattern depending on its current battery status. This may comprise: a longer on-duration in the first part of the pattern, e.g. for decoding a control channel in each time slot of the first time period; and a shorter on-duration in the remaining part. In the shorter on-duration part of the pattern, the UE may decode the control channel only in every nth time slot. This may apply similarly to all channels used in the on-duration part, e.g. PSCCH, PSFCH and / or PSSCH.

[0261] In the case where the DRX configuration indicates a fixed-length DRX cycle, the total duration of the DRX cycle and the on-off duration of the DRX cycle are fixed. On the other hand, in the case where the DRX configuration indicates an adaptive-length DRX cycle, the total duration of the DRX cycle and / or the on-off duration of the DRX cycle may be adapted depending on one or more parameters (e.g., parameters associated with the UE and / or the environment in which the UE is located).

[0262] According to embodiments, an indication whether the DRX cycle is of fixed length or of adaptive length is comprised in the initial DRX configuration received at the UE from the DRX configuration source, e.g. in the manner described above with reference to the first aspect of the application (see Figure 7 and the associated description). According to other embodiments, the configuration of the DRX cycle can change during operation of the UE. For example, in response to DRX synchronization information received at the UE from the DRX synchronization source in the manner described above with reference to Figure 7 the second aspect of the application, a different DRX cycle can be signaled to the UE by the selected DRX synchronization source, as described above with reference to Figure 7 the third aspect of the application. In other words, according to such embodiments, the DRX synchronization information can contain the total duration of the DRX cycle, including the duration of the ON phase, in which the UE can transmit and receive data, and the OFF phase. The DRX synchronization information can signal different cycle durations, so that the cycle length can be fixed or adaptive.

[0263] In case of a fixed length DRX cycle, the total duration and its ON-OFF duration are fixed for the time period for which the DRX configuration is valid, e.g. until new DRX synchronization information is received indicating a different DRX cycle configuration. The ON-OFF duration can also be defined in the form of a pattern.

[0264] In case the DRX synchronization information indicates an adaptive length DRX cycle, the DRX cycle can be a combination of short DRX cycles and long DRX cycles, and the duration can be based on the above mentioned parameters associated with the UE. Again, the time period for which such adaptive length cycle is valid for the current DRX configuration can be valid, and the configuration can change in response to new DRX synchronization information. According to embodiments, the duration of the adaptive length DRX cycle can be based on one or more of the following parameters:

[0265] • the speed at which the UE travels or moves: for example, when the UE is a P-UE and the user is walking, the UE moves at low speed, so a long DRX cycle is adopted. If the user of the UE moves faster, e.g. when he is cycling or on other vehicle, or when he is running, a short DRX cycle can be used, so as to have a longer ON duration, so as to transmit its position to surrounding UEs with higher periodicity.

[0266] • The presence of other UEs (such as V-UEs): For example, a short DRX cycle may be used when the UE is at a traffic intersection, on a busy road, or in an accident-prone area near one or more V-UEs. A long DRX cycle may be used when the UE is far away from the V-UEs, such as in a park or in a safer area. For example, when the UE is indoors or in another area deemed safe for the vehicle, sidelink communication with the V-UE may not be required and therefore may be turned off, or may be turned off entirely.

[0267] • Nature of data transmission: In cases where data transmission requires the UE to be on for a given duration, which is longer than the on-duration of the DRX cycle, the UE may deactivate DRX for the given duration. After the transmission is completed, the DRX cycle may be resumed. According to other embodiments, if data transmission requires periodic transmission at short and longer intervals, a short or long DRX cycle may be used.

[0268] • Occupancy of one or more resource pools used for SL communications. If the monitored resource busyness exceeds a certain threshold, for example, by calculating the Channel Busy Rate (CBR) on the monitored resources, the DRX cycle may be adapted to a longer or different OnDuration. This may be useful to ensure that there are available resources for one or more UE transmissions during the OnDuration of the DRX cycle.

[0269] Embodiments of the second aspect of the present invention that provide fixed or adaptive length DRX cycles via DRX synchronization information are advantageous because this aspect provides versatility to the UE to adapt to its needs at a given point in time while maximizing the power saving capabilities of the DRX cycle. While fixed-length DRX cycles can be used for UEs that only desire periodic transmission of defined packet sizes, adaptive-length DRX cycles enable UEs to vary their on-duration based on their surrounding circumstances while maintaining off-duration to ensure power savings.

[0270] The third aspect - DRX alignment

[0271] According to an embodiment of the third aspect of the present invention, a UE is provided with a DRX configuration that can be aligned with one or more DRX cycles (e.g., the DRX cycle of an access point (e.g., a base station gNB or gateway node) to which it is connected and / or the DRX cycle of one or more UEs with which it communicates via a sidelink). Figure 9A UE according to an embodiment of the third aspect of the present invention is schematically illustrated. The UE includes an antenna that allows the UE to communicate with other UEs (e.g., UE1 and UE2) via a sidelink (e.g., PC5 interface). Furthermore, the UE can communicate with the gNB via the Uu interface. To enable DRX on the sidelink, i.e., for communications with UE1 and / or UE2, the DRX cycle needs to be aligned between the transmitter and receiver of the corresponding SL communications, allowing the transmitter and receiver to communicate with each other during the corresponding on-durations and conserving power during the off-durations.

[0272] like Figure 9 As shown in Figure 1, when a UE is in Mode 1, DRX alignment can be performed between the gNB and the UE. In this scenario, the UE receives the DRX configuration from the gNB, for example, via RRC signaling, and the UE and gNB are synchronized with each other due to the connection over the Uu interface. To facilitate sidelink communication between the UE and UE1 and / or UE2, in this scenario, the gNB provides DCI to the UEs, synchronizing all UEs.

[0273] However, according to other embodiments, the UE may be in Mode 2 and communicate with the Figure 9 UE1 and UE2 communicate in mode 2 without being connected to the gNB. When moving from mode 2 to mode 1, i.e., while connected to the gNB, the UE has DRX cycles aligned with those of UE1 and UE2. When moving from mode 2 to mode 1 while still connected to the gNB, the UE may notify the gNB of one or more DRX cycles existing at the UE. For example, when connected to the gNB, the UE may send DRX cycle information to the gNB via the PUCCH or during the initial access procedure. Depending on the embodiment, once the gNB is notified by the UE of one or more DRX cycles existing at the UE, the gNB may or may not accept the UE's continued use of one or more currently used DRX cycles. For example, the gNB may indicate acceptance of the currently used DRX cycles by not responding to the UE or by sending an acknowledgment message. Alternatively, the gNB may indicate rejection of the currently used DRX cycles by sending a new DRX configuration that the UE intends to use.

[0274] According to other embodiments, the alignment of the DRX cycle may be performed at the SL UE (e.g. Figure 9 For example, when in Mode 2 and not connected to a gNB, alignment can be performed only between the SL UEs just mentioned. To align with UE1 and UE2, Figure 9 The UE in the can monitor UE1 and UE2 in the vicinity of the UE and adapt to the other UEs in use (i.e. Figure 9 In the case of multiple DRX durations, for example, Figure 9UE1 in the Figure 9 In order to enable multiple DRX cycles, the UE may enable multiple DRX cycles in order to use a different DRX duration than the DRX duration adopted by UE2 in the example. According to an embodiment, in order to enable multiple DRX cycles, the UE may create a new DRX pattern formed by multiple DRX cycles. For example, if a third UE (UE3) monitors the DRX cycles from UE1 and UE2 and realizes that the on-duration in the cycle is too long and it does not make sense for the UE to be turned off for a very short period of time, it may remain on for the entire duration. Instead of monitoring multiple DRX cycles, UE3 may create a new DRX pattern that enables it to be on during the on-durations of UE1 and UE2 and defines an off-duration in which the UE can also save power. The ultimate goal of UE3 is to define a DRX cycle that ensures it can receive from all relevant UEs around it while achieving power savings.

[0275] According to an embodiment, although UEs communicating via the sidelink may adopt different DRX durations, all DRX durations are based on a global starting point and have a set of fixed durations, where their corresponding on / off durations are also defined. For example, three DRX cycles may be defined, such as Figure 10 All DRX cycles have the same global starting point, the same on-duration but different fixed durations, i.e. different off-durations. The duration of DRX cycle 1 is 1 time slot, the duration of DRX cycle 2 is 2 time slots, and the duration of DRX cycle 3 is 3 time slots. Figure 10 For each of the DRX cycles shown, the on-duration is the same and the on-duration is at the beginning of the DRX cycle at t0. Assume that the DRX cycle consists of Figure 9 The UE in the system is connected to each UE via a side link. Figure 9 The UE in FIG is a single RX UE that receives corresponding DRX cycles from three different TX UEs and receives DRX cycles from three different TX UEs. Figure 11 The received DRX cycles are aligned in the manner shown. Three different DRX cycles received from different TX UEs are aligned so that the start time of all cycles is the same. This provides a turn-on time so that the UE turns on to monitor each of the TX UEs. More specifically, as Figure 11As shown, the UE has an OnDuration during each time slot, such that in the first time slot, the UE can receive from / transmit to UE1, UE2, and UE3, all of which have their OnDuration at the beginning of the first time slot. In the second time slot, the UE also has an OnDuration so that it can transmit to / receive from UE1, which also has an OnDuration at the beginning of the second time slot. At time slot 3, the receiving UE has an OnDuration at the beginning of the third time slot so that it can receive from / transmit to UE1 and UE2, and at the beginning of the fourth time slot, the UE can receive from / transmit to UE1 and UE3. At time slot 5, the UE receives from / transmits to UE1 and UE2, and so on.

[0276] Figures 12(a) and 12(b) show the consequences of a receiving UE not being aligned with a DRX cycle. Figure 9 The UE in receives DRX cycle 1, DRX cycle 2 and DRX cycle 3 from three other UEs (i.e., UE1, UE2 and UE3), as shown in the above reference Figure 10 As described, however, as shown in FIG12( a ), the UE is aligned only with respect to time t0 for DRX cycle 1 and DRX cycle 3, while DRX cycle 2 is not aligned and has an offset with respect to time t0 of the on-durations of DRX cycle 1 and DRX cycle 3. Compared to the case where all DRX cycles are aligned, this misalignment results in the situation shown in FIG12( b ), and requires the UE to have an extended on-duration. In order to enable the UE to receive from / transmit to UE1, UE2, and UE3, the on-duration is twice that of the aligned case, so that during the first on-duration, the UE can receive from / transmit to UE1 and UE3, and receive from / transmit to UE2 during the extended on-duration. At time slot 2, since the duration of DRX cycle 2 is two time slots, the situation in the second time slot is the same as Figure 11 However, in the third time slot, an extended on-duration is again required so that the UE can receive / transmit from / to the first UE during the first part of the on-duration and receive / transmit from / to UE2 during the extended on-duration, as well as in time slot 5. While this issue can be addressed by the UE defining a DRX pattern to monitor UE1, UE2, and UE3, it may be more feasible to simply align the DRX cycles and maximize the off-duration to increase power saving gains.

[0277] Therefore, the embodiments of the third aspect of the present invention regarding aligning DRX in the above manner are advantageous because, by aligning the DRX cycles in the above manner, the on-duration at the receiving UE that receives different DRX cycles from each UE communicating via the side link does not need to have an extended on-duration, thereby improving power saving even when different DRX cycles are enabled.

[0278] The fourth aspect - the content of the DRX cycle on-duration

[0279] According to an embodiment of the fourth aspect of the present invention, a sidelink UE operating according to the DRX mode may determine the OnDuration of a DRX cycle depending on the purpose for which the UE uses the OnDuration.

[0280] Figure 13 An embodiment of a UE according to the fourth aspect of the present invention is shown. The UE comprises an antenna ANT for communicating with one or more UEs (such as Figure 10 The UE operates according to the DRX mode, and depending on a specific purpose, the UE may set the on-duration of the DRX cycle accordingly.

[0281] According to an embodiment, the UE selects the on-duration depending on whether it is processing: (i) only control data, such as data in the PSCCH, (ii) only payload data, such as data in the PSSCH, or (iii) only feedback data, such as data in the PSFCH, or any combination of two or more of (i), (ii), and (iii). For example, the UE may decide to monitor only the PSCCH, or PSCCH+PSSCH, or only the PSFCH, or PSCCH+PSSCH+PSFCH, depending on its needs. For example, the motivation for monitoring only the PSFCH is that it is very short, and the UE may only want to check if there are any other unicast UEs in the cell to check whether the band is busy or idle. It may want to transmit emergency messages to these UEs, so camping on an empty band does not make sense.

[0282] According to an embodiment, the on-duration of the DRX cycle may be set depending on the content of the on-duration, which may vary depending on the purpose for which the UE uses the on-duration. For example, the purpose may be one or more of the following:

[0283] • A UE wants to monitor one or more of the other UEs for sensing purposes,

[0284] • The UE needs to determine the available resources for transmission,

[0285] •UE wants to send control and data,

[0286] • the UE is to listen for feedback from one or more of the further UEs,

[0287] • the UE is to receive control from one or more of the further UEs,

[0288] • the UE is to determine a load in a given frequency band.

[0289] To facilitate these purposes, the UE can employ different on durations for different purposes or scenarios.

[0290] According to embodiments, the UE can signal its on duration pattern to one or more of the further UEs. The on pattern can depend on the purpose of the group of UEs, e.g. in case of public safety UEs, it is expected that the group only listens to periodic transmissions from other UEs but with different on duration lengths. Once a UE within the group, e.g. a GL UE, determines the appropriate on duration pattern, it signals this pattern to the other UEs within the group, e.g. using an assistance message.

[0291] According to embodiments, the on duration can only cover or include the PSCCH. Figure 14 An embodiment is shown in which the on duration only includes the PSCCH. Figure 14 A DRX cycle is shown with a duration of one slot, however, longer durations are also possible. As shown, the on duration only includes the PSCCH, and the PSCCH and PSFCH are in the off duration. Thus, the on duration only spans the duration of the PSCCH, e.g. the first two or three symbols of a slot. According to embodiments, in the PSCCH, a first stage SCI can be transmitted by other UEs, like UE1 or UE2 in Figure 13 This enables the receiving UE to decode the received SCI. This can be used to determine whether resources are available for transmission, e.g. for the purpose of sensing, as in mode 2. According to other embodiments, this can also be used to detect any pre-emption control messages intended for the UE.

[0292] According to other embodiments, the on duration can include or comprise at least a portion of the PSSCH and the PSCCH. Figure 15 An on duration is shown which includes a portion of the PSSCH and the PSCCH. Again, a total duration of a DRX cycle of one slot is assumed, however, again, longer durations are possible. The on duration is in the first two symbols of the slot, and the PSSCH is in the third symbol of the slot. The PSSCH is in the off duration. Figure 15The figure shows that it includes PSCCH and about 1 / 3 of PSSCH. Depending on the environment, the portion of the on-duration covering the PSCCH can be longer or shorter. The UE can use the on-duration spanning the portion of the data channel and the control to perform its own transmission. For example, it enables the UE to send data to other UEs (such as Figure 13 The on-duration may be used to allow the UEs to listen to the first and second stage control information sent in the PSCCH and PSSCH, respectively.

[0293] According to other embodiments, the OnDuration may only cover the PSFCH, ie the Physical Sidelink Feedback Channel. Figure 16 The onDurations are shown to include or contain only the PSFCH. Again, a period length of one time slot is assumed, however, longer periods are also possible. As shown, the onDurations contain only the PSFCH. According to an embodiment, this can be done when the UE is aware that the time slot is being used by more than one other UE (e.g. Figure 13 Among the available subchannels, the UE needs to determine which subchannel is available for transmission, which can be inferred from listening to the PSFCH only, because the subchannels within the PSFCH are implicitly mapped to the corresponding subchannels in the PSFCH. The advantage of this embodiment is that the UE can infer the same information by listening to the PSFCH for a much shorter duration than the PSSCH, rather than staying for a longer time to listen to the PSSCH, as can be seen from Figure 16 However, this aspect may only be feasible on resource pools where PSFCH is enabled.

[0294] According to other embodiments, the OnDuration may include a combination of the PSCCH, at least a portion of the PSSCH, and the PSFCH. Figure 17 The on-duration of the PSCCH, part of the PSSCH and the PSFCH is shown. Figure 17 In the example, the cycle length is two time slots, and the on-duration can be such that in the first time slot, part of the PSFCH and the PSCCH are covered by the on-duration, while the PSFCH of the subsequent time slots are covered by the on-duration. According to an embodiment, this combination can be used when the amount of data to be sent by the UE is limited, that is, when the entire PSSCH is not needed. In order to optimize the off-duration to save power, the UE can use the following methods within the time slot: Figure 17discontinuous on-duration illustrated in Fig. 2, where the UE is on for a part of the PSSCH and the PSCCH and then turns on again in a subsequent slot (in the same slot or a subsequent slot) to receive feedback during the PSFCH.

[0295] Embodiments of the fourth aspect of the application are advantageous in defining the duration of the on-period of the DRX cycle depending on the purpose of using the on-duration, as the UE can maximize its power saving capabilities based on its specific needs.

[0296] Fifth aspect - DRX signaling procedures

[0297] According to embodiments of the fifth aspect of the application, one or more DRX signaling procedures are provided. Figure 18 A UE according to embodiments of the fifth aspect of the application is illustrated, which comprises an antenna and is capable of communicating with a gNB over a Uu interface and with respective other UEs (UE1 and UE2) over a sidelink interface, like a PC5 interface. In order to operate in DRX mode, the UE is to receive one or more DRX configurations from a DRX synchronization source, which can be Figure 18 the gNB, UE1 or UE2 in Fig. 1. In case the DRX synchronization source is the gNB, the UE is to receive a control message, e.g. a system information block SIB, including the one or more DRX configurations from the base station. In case the DRX synchronization source is one or more UEs for sidelink communication, like UE1 and UE2 in Fig. 1, the UE is to receive the DRX configurations from UE1 and / or from UE2 using, e.g., PC5 RRC signaling or SCI (like a second stage SCI) for a given transmission. According to embodiments, Figure 18 Figure 18 the synchronization source gNB, UE1 and UE2 in Fig. 1 can be hierarchized in the way described above with reference to the first aspect of the application and explained with reference to Figure 7

[0298] According to the fifth aspect of the application, therefore, in order to enable the DRX mode on sidelink in a UE, the UE needs to receive the DRX configuration or DRX configuration information from a DRX synchronization source, like the sources described above with reference to the first aspect of the application, and once the UE has the DRX configuration, the activation of the DRX mode can be done through additional signaling, according to embodiments.

[0299] According to embodiments, the gNB can signal one or more DRX configurations to the SL UE, e.g. using RRC configuration. The DRX configuration can be transmitted using a SIB, together with a resource pool configuration indicating the resources provided by the gNB for sidelink communication. When the UE is operating in mode 1 or mode 2, the UE can receive the DRX configuration as long as the UE is within the coverage of the gNB. ​​

[0300] According to other embodiments, for example, when the UE is outside the coverage of a gNB, the UE may receive DRX communications from another UE via a sidelink. The UE may receive a DRX configuration from another SL UE via PC5 RRC signaling over the sidelink. When DRX mode is active, the DRX configuration may be a global configuration for any transmission. The UE may receive the DRX configuration using a second-stage SCI for a specific transmission. In such an embodiment, the UE may receive an indication of the second-stage format in the first-stage SCI, so that the receiving UE knows that the transmission from the transmitting SL UE needs to use the DRX configuration provided in the second-stage SCI.

[0301] According to an embodiment, the DRX configuration may include one or more of the following information:

[0302] •DRX cycle duration – the total duration of a single DRX cycle, including on-duration and off-duration,

[0303] • On duration – the duration that the UE can transmit and receive,

[0304] • Inactivity timer - duration that the UE must remain on after receiving a transmission of a control signal and / or packet, e.g. to wait for HARQ feedback, so that when the timer expires the UE can return to the off duration,

[0305] • Retransmission Timer - the duration that the UE must keep turned on as control signals indicate retransmission of a given packet,

[0306] • Minimum Communication Range - The range within which a UE is to expect or send feedback regarding transmissions sent or received.

[0307] According to an embodiment, the DRX configuration may be signaled to the UE over the sidelink using a Sidelink DRX Configuration element as depicted in Figure 19(a).Figure 19(b) is a table including descriptions of the fields of the SL DRX Configuration information element of Figure 19(a).

[0308] According to another embodiment, in a UE (such as Figure 18 The DRX configuration obtained by the UE in the gNB (e.g., UE1 or UE2) from the gNB or from another SL UE (e.g., UE2) may not be used initially. Instead, the UE may use the DRX mode only when the DRX mode is activated. According to an embodiment, the DRX mode may be activated by:

[0309] • expiration of the inactivity timer, or

[0310] • From another SL UE (e.g. Figure 18 Explicit signaling of UE1 or UE2 in the

[0311] • Enable HARQ process at the UE, or

[0312] • Switch to receive-only mode, or

[0313] • Higher layers signaling to save power, or

[0314] • QoS changes, or

[0315] •The UE is located in a specific geographical location.

[0316] Where an inactivity timer is employed, once the timer expires, the UE switches to the off-duration when it realises that there are no incoming transmissions that it expects to receive and when the UE has no further transmissions planned. This may be achieved once the UE has been idle for a predefined period of time and once the time defined by the inactivity timer has elapsed.

[0317] According to other embodiments, the UE may receive explicit signaling for activating or deactivating the DRX mode. For example, a transmitting or TX UE (e.g. Figure 18 UE1 or UE2) can send a signal to the receiving or RX UE (such as Figure 18 The UE in the DRX mode may signal the TX UE to have a transmission longer than the configured DRX on duration. This requires the RX UE to remain on for a longer duration so that the DRX mode can be deactivated. According to an embodiment, the explicit signaling may be performed as follows:

[0318] • using one or more dedicated fields in the SC associated with a given transmission (e.g. SCI in sidelink, stage 1 SCI, stage 2 SCI, etc.), along with additional information indicating the duration of DRX activation or deactivation, or

[0319] • using the "Resource Reservation field" in the SCI, which indicates that there are further transmissions during which the UE is to remain switched on to receive these transmissions, or

[0320] • Use the “Priority Field” in the SCI to indicate the Packet Delay Budget (PDB) associated with a transmission, during which the UE receiving the transmission must remain switched on in order to receive any further retransmissions or HARQ retransmissions.

[0321] According to further embodiments, the activation of the DRX mode can be made in response to the enabling of the HARQ process. For example, when only NACK is enabled, the UE stays on when receiving data until the transmission is successfully received, or when transmitting data, the UE stays on for a certain time for receiving a NACK. When both ACK and NACK are enabled, the UE stays on when receiving data until the transmission is successfully received, or when transmitting data, the UE stays on for a certain time for receiving an ACK or NACK.

[0322] Figure 20 Embodiments are shown that enable a receiving UE to obtain a retransmission in case of a missing acknowledgement message, the on duration (i.e. the on duration plus the duration of one additional transmission). The TX UE transmits ① data to the RX UE, the RX UE transmits ② an acknowledgement message to the TX UE. In case the acknowledgement is not received at the TX UE, the TX UE assumes that the transmission was not successful and retransmits ③ the data, so that the RX UE can again transmit an acknowledgement, which in the depicted embodiment is successfully read ④ at the TX UE. According to this embodiment, the on duration at the RX UE is chosen so that enough time for at least one additional retransmission is covered, so that the RX UE can read further retransmissions although the data was successfully received the first time. According to embodiments, this can be achieved by enabling a HARQ timer upon reception of a HARQ transmission, which defines a time window in which the UE expects a retransmission before switching from the on duration to the off duration or before starting an inactivity timer. According to another embodiment, the inactivity timer can be set to at least a certain number of HARQ round trip transmission times RTT, for example to one or two HARQ RTT, so that the TX UE can complete the transmission within the prolonged on duration.

[0323] According to yet further embodiments, the duration of a retransmission can depend on the minimum communication range. When the UE is within the minimum communication range, a suitable duration can be set, for example in the above described manner, so that the UE stays on when receiving a transmission to receive a retransmission or performs a retransmission when transmitting. On the other hand, when the UE is outside the minimum communication range, the duration of a retransmission can be set to zero, as the UE is no longer expected to receive a retransmission or to perform a retransmission due to the distance to the sender / receiver.

[0324] According to yet other embodiments, it may be desirable for a UE to activate or deactivate a DRX configuration based on its location. If the UE is within a predefined geographic area where it is desired to receive only periodic transmissions, it may activate the DRX configuration accordingly. When the UE needs to send / receive high QoS transmissions, it may deactivate the DRX configuration to meet the high QoS requirements. Alternatively, the DRX configuration may be activated when the transmissions have low QoS and power conservation is a higher priority for the UE. For example, when the UE is low on power or battery, it may choose to receive only transmissions of a specific QoS based on the DRX configuration to save power.

[0325] According to another embodiment of the fifth aspect, as described above with reference to Figure 18 As explained, the UE may receive DRX configurations from different sources (e.g., from the gNB, UE1, and UE2). According to an embodiment in which some or all of the DRX configuration sources may have the same level, a situation may occur in which multiple DRX configurations with different start times and durations are received at the UE. When such DRX configurations with different start times and durations are received, the UE cannot maintain these multiple DRX configurations. Only if the start times are the same and the durations are multiples of each other, the UE may process the different configurations, for example, in the manner described above with reference to the third aspect, and set the UE accordingly (e.g., Figure 18 The on-duration and off-duration to be used by the UE in the network.

[0326] In case of conflicting DRX configurations having different start times and / or durations which are not multiples of each other, the UE cannot maintain these multiple DRX configurations. An embodiment of the fifth aspect of the present invention provides a solution to such a conflict, assuming that different sources for the DRX configuration have different hierarchies. Thus, according to an embodiment, in case of receiving multiple different DRX configurations, the UE may select the DRX configuration from the DRX configuration source with the highest hierarchy level, as explained above with respect to the first aspect of the present invention. For example, when the highest source is a gNB or a base / leader UE, according to an embodiment, the UE may send assistance information to one or more other DRX configuration sources (which may be another UE) informing the other UEs about the presence of the hierarchical sources. For example, when considering Figure 18 If the gNB, UE1, and UE2 provide conflicting DRX configurations to the UE, the UE selects the DRX configuration provided by the gNB, given that the highest-ranking configuration is associated with the gNB, and notifies UE1 and / or UE2 of the higher-ranking configuration, for example, using assistance information. UE1 and UE2 can then align the timing of their DRX configurations with the gNB's DRX configuration. This process can be repeated to achieve a common start time and duration that is a multiple of each, thereby achieving a synchronized system.

[0327] The auxiliary information can be used to send information from the UE to the receiving UE (for example, from the UE to the Figure 18 The auxiliary information may be used to provide information to a UE1 or UE2 in the DRX cycle to change the characteristics of the DRX cycle for implementing a synchronous system as described above. The characteristics of the DRX cycle may include one or more of the duration of the DRX cycle length (e.g., by maintaining the on-duration and reducing the off-duration), an offset of the DRX cycle for matching the start time, and the on-duration of the DRX cycle. According to an embodiment, the auxiliary information may cause the on-duration of a specific DRX configuration to remain unchanged, while the off-duration may be increased or decreased to match a reference DRX configuration, i.e., a DRX configuration selected by the UE, for example, from the highest level DRX configuration source as described above. This may apply to both long DRX cycle lengths and short DRX cycle lengths. In the case of a long DRX cycle length, the increment or decrement may be in the order of + / - milliseconds, while in the case of a short DRX cycle, the increment or decrement may be in the order of + / - 1 / 32 milliseconds.

[0328] Figure 21 An embodiment of assistance information provided to change the DRX cycle length according to a first type (Type 1) is shown. Figure 21 The current reference DRX configuration is shown in the upper part and the conflicting DRX configuration is shown in the lower part, which is represented by Figure 21 The “change” indicated in is a change that shortens the cycle length, thereby adapting the conflicting DRX configuration to the reference configuration.

[0329] The assistance information may also provide information to align the start time, for example by shifting the entire DRX cycle by a given offset, such as Figure 22 As shown, Figure 22 The current reference configuration is shown in the upper part and the conflicting DRX configuration is shown in the lower part. Figure 20 , the UE assistance information indicates an offset DRX cycle (type 2), which shifts the start of the DRX cycle by the offset in order to match the start time of the reference DRX configuration.

[0330] According to another embodiment, the UE may send a Figure 18 UE1 in ) provides information to change the on-duration of a defined DRX cycle from another source in order to align them, e.g. Figure 23 As shown, Figure 23 UE assistance information for changing the on-duration (type 3) is shown. Figure 23 Again the current reference DRX configuration is shown in the upper part and the conflicting DRX configuration is shown in the lower part, which is represented by Figure 23 The “change” indicated in is changed by shortening the on-duration, thereby adapting the conflicting DRX configuration to the reference configuration.

[0331] UE can use the assistance information IE to Figure 18 UE1 or UE2 in the embodiment of the fifth aspect of the present invention signals the above-mentioned assistance information, and Figure 24 (a) shows such assistance information IE according to an embodiment of the fifth aspect of the present invention, according to which Type 1 changes the DRX cycle length, Type 2 offsets the DRX cycle, and Type 3 changes the on-duration. Figure 24 (b) shows a delay budget report information element sent by the UE as part of the assistance information, which includes a value in milliseconds, i.e., msXX or msMinusXX, indicating an increase or decrease in the DRX cycle length desired by the UE.

[0332] Aspect 6: Non-DRX-UE avoids using on-duration resources

[0333] According to an embodiment of the sixth aspect of the present invention, other UEs (eg UEs not operating in DRX mode) avoid using OnDuration resources to be used in DRX mode. Figure 25 A UE according to an embodiment of the sixth aspect of the present invention is shown. The UE includes an antenna and is capable of communicating with a gNB via a Uu interface and with respective other UEs (UE1 and UE2) via a sidelink interface (e.g., a PC5 interface). The UE may be a V-UE, such that the US does not need to operate in DRX mode. However, the UE is aware of one or more other UEs, such as UE1 and UE2, operating in DRX mode. The UE avoids using resources used by another UE for transmission during its on-duration.

[0334] According to an embodiment, when transmitting on the SL, a UE can avoid using resources used by another UE during its on-duration by excluding resources that occur during the on-duration, or by adding a penalty for using resources that occur during the on-duration, or by using resources that occur during the on-duration only when no other resources are available. The penalty can be in the form of an RSRP / RSSI penalty or a sensing penalty that is added to the actual RSRP / RSSI values ​​measured in the resources during the on-duration to discourage the UE from selecting these resources. The penalty makes these resources less likely to be selected from the entire set of available resources because they are ranked lower after the penalty is added.

[0335] Depending on the embodiment, a restriction penalty may be applied, for example, a resource may only be used for transmissions above a certain priority. According to other embodiments, a selection penalty may be applied, making one or more specific resources less likely to be selected, for example, because they have been downgraded after sensing. The selection penalty may be based on the number of UEs using a specific resource during the UE's on-duration, for example, the more UEs using a specific resource, the less likely it is to be selected.

[0336] Overview

[0337] The embodiments of the present invention have been described above in detail, and each embodiment and aspect may be implemented independently, or two or more embodiments or aspects may be implemented in combination.

[0338] Depending on the embodiment, the wireless communication system may include a terrestrial network, or a non-terrestrial network, or a network or network segment using an airborne vehicle or a spaceborne vehicle or a combination thereof as a receiver.

[0339] According to an embodiment, the user equipment UE described herein may be one or more of the following: a power-limited UE, or a handheld UE (such as a UE used by pedestrians and referred to as a vulnerable road user VRU or pedestrian UE (P-UE)), or a body-worn or handheld UE used by public safety personnel and first responders and referred to as a public safety UE (PS-UE), or an IoT UE (for example, a sensor, actuator, or UE set up in a campus network to perform repetitive tasks and requiring input from a gateway node at periodic intervals), or a mobile terminal, or a fixed terminal, or a cellular IoT-UE, or a vehicle-mounted UE, or a vehicle-mounted group leader (GL) UE, or an IoT or narrowband IoT (NB-IoT) device, or a WiFi non-access point station (non-AP) 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 roadside unit, or a building, or any other item or device (e.g., a sensor or actuator) provided with a network connection that enables the item / device to communicate using a wireless communication network, or any other item or device (e.g., a sensor or actuator) provided with a network connection that enables the item / device to communicate using a sidelink wireless communication network, or any network entity that supports sidelink.

[0340] The base station BS described in this document can be implemented as a mobile base station or a non-mobile base station, and can be one or more of the following: 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 a roadside unit, or a UE, or a group leader (GL), or a relay, or a remote radio head, or an AMF, or an SMF, or a core network entity, or a mobile edge computing entity, or a network slice in the context of NR or 5G core, or a WiFi AP STA (such as 802.11ax or 802.11be), or any transmission / reception point TRP that enables an item or device to communicate using a wireless communication network, and the item or device is provided with a network connection to communicate using the wireless communication network.

[0341] In the context of cellular communication systems, secure communication systems, and campus networks, embodiments of the method of the present invention are described for sidelink communication. The present invention is not limited thereto; rather, according to further embodiments, the method of the present invention can be used in any type of communication network, such as an ad hoc communication network.

[0342] Although some aspects of the concepts described have been described in the context of an apparatus, it is clear that these aspects also represent descriptions of corresponding methods, where blocks or devices correspond to method steps or features of method steps. Similarly, aspects described in the context of method steps also represent descriptions of corresponding blocks or items or features of corresponding apparatus.

[0343] The various elements and features of the present invention can be implemented in hardware, software using analog and / or digital circuits, by executing instructions through one or more general or special purpose processors, or as a combination of hardware and software. For example, embodiments of the present invention can be implemented in the environment of a computer system or another processing system. Figure 26 An example of a computer system 500 is shown. These units or modules, and the steps of the methods performed by these units, can be executed on one or more computer systems 500. Computer system 500 includes one or more processors 502, such as special-purpose or general-purpose digital signal processors. Processor 502 is connected to a communication infrastructure 504, such as a bus or network. Computer system 500 includes a main memory 506, such as random access memory (RAM), and a secondary memory 508, such as a hard drive and / or a removable storage drive. Secondary memory 508 allows computer programs or other instructions to be loaded into computer system 500. Computer system 500 may also include a communication interface 510 to allow software and data to be transferred between computer system 500 and external devices. Communication can be in the form of electrical, electromagnetic, optical, or other signals capable of being processed by the communication interface. Communication can use wire or cable, fiber optics, telephone lines, cellular phone links, RF links, and other communication channels 512.

[0344] The terms "computer program medium" and "computer readable medium" are used to generally refer to tangible storage media such as removable storage units or a hard disk installed in a hard disk drive. These computer program products are means for providing software to the computer system 500. The computer programs (also known as computer control logic) are stored in main memory 506 and / or secondary memory 508. Computer programs can also be received via a communications interface 510. The computer program, when executed, enables the computer system 500 to implement the present application. In particular, the computer program, when executed, enables processor 502 to implement the processes of the present application, such as any of the methods described herein. Accordingly, such a computer program can represent a controller of the computer system 500. Where the disclosure is implemented using software, the software can be stored in a computer program product and loaded into computer system 500 using a removable storage drive, an interface, like communications interface 510.

[0345] Implementations in hardware or in software can be performed using digital storage media, such as cloud storage, a floppy disk, a DVD, a Blue-Ray, a CD, a ROM, a PROM, an EPROM, an EEPROM or a FLASH memory, having electronically readable control signals stored thereon, which cooperate (or are capable of cooperating) with a programmable computer system such that the respective method is performed. Therefore, the digital storage media can be computer readable.

[0346] Some embodiments according to the application comprise a data carrier having electronically readable control signals, which are capable of cooperating with a programmable computer system, such that one of the methods described herein is performed.

[0347] Generally, embodiments of the present application can be implemented as a computer program product with a program code, the program code being operative for performing one of the methods when the computer program product runs on a computer. The program code can for example be stored on a machine readable carrier.

[0348] Other embodiments comprise the computer program for performing one of the methods described herein, stored on a machine readable carrier. 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.

[0349] Therefore, another embodiment of the method according to the present invention is 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. Therefore, another embodiment of the method according to the present invention is a data stream or a signal sequence representing the computer program for performing one of the methods described herein. The data stream or signal sequence can, for example, be configured to be transmitted via a data communication connection (e.g., via the Internet). Another embodiment comprises a processing device, such as a computer or a programmable logic device, configured or adapted to perform one of the methods described herein. Another embodiment comprises a computer having installed thereon a computer program for performing one of the methods described herein.

[0350] In some embodiments, a programmable logic device (e.g., a field programmable gate array) can be used to perform some or all of the functions of the methods described herein. In some embodiments, the field programmable gate array can cooperate with a microprocessor to perform one of the methods described herein. In general, the methods are preferably performed by any hardware device.

[0351] The above embodiments are merely illustrative of the principles of the present invention. It should be understood that modifications and variations of the arrangements and details described herein will be apparent to others skilled in the art. Accordingly, it is intended that the present invention be limited solely by the scope of the appended patent claims and not by the specific details provided by way of description and explanation of the embodiments herein.

Claims

1. A user equipment (UE) for a wireless communication system, wherein the wireless communication system comprises a plurality of user equipments (UEs), wherein: The UE communicates with one or more other UEs using a side link SL, The UE includes a processor and a memory, the memory containing instructions, and the instructions can be executed by the processor to enable the UE to: To operate in a discontinuous reception (DRX) mode, receiving a DRX configuration from one of a plurality of DRX configuration sources, and The multiple DRX configuration sources are hierarchical such that each of the DRX configuration sources has a different rank from the remaining DRX configuration sources, and the memory further includes instructions that are executable by the processor to cause the UE to select a DRX configuration from a DRX configuration source with a highest rank among the available DRX configuration sources.

2. The user equipment UE according to claim 1, wherein The memory includes instructions executable by the processor to cause the UE to: • determining an available DRX configuration source to which the UE can connect from the plurality of DRX configuration sources, • determining the available DRX configuration source having the highest rank from among said available DRX configuration sources, and • Select the DRX configuration from the available DRX configuration source with the highest rank.

3. The user equipment (UE) according to claim 1, wherein: The multiple DRX configuration sources are ranked based on one or more of the following: • an interface connecting the DRX configuration source to the user equipment, • the type of the DRX configuration source, • Specific parameters included in the DRX configuration received from the DRX configuration source.

4. The user equipment (UE) according to claim 1, wherein: The multiple DRX configuration sources include one or more of the following: • an access point or base station of the wireless communication system, the access point or base station having a hierarchy, • one or more first UEs authorized by the wireless communication system to send DRX configuration or coordinated DRX, the first UEs having the same rank or a different rank than the rank of the access point or base station, • one or more second UEs to which the UEs are connected for communication over the SL, the second UEs having the same rank or a different rank than one or more ranks of the first UE, • one or more third UEs transmitting assistance information on SL resources of the wireless communication system, the assistance information including one or more DRX configurations, the third UEs having the same rank or a different rank than one or more ranks of the second UE, • One or more fourth UEs, operating in the DRX mode and transmitting on the SL resources of the wireless communication system, and the UE obtains the DRX configuration from the fourth UE by listening to the DRX cycle used at the fourth UE, and the fourth UE has the same level or different level lower than one or more levels of the third UE.

5. The user equipment (UE) according to claim 1, wherein: The memory also includes instructions, which are executable by the processor to cause the UE to: if the UE is connected to a specific DRX configuration source, limit the available DRX configuration sources to those available DRX configuration sources having the same rank as or a higher rank than the specific DRX configuration source.

6. The user equipment UE according to claim 5, wherein: The specific DRX configuration source includes a base station with a highest rank, and the memory further includes instructions executable by the processor to cause the UE to limit the available DRX configuration sources to the base station.

7. The user equipment (UE) according to any one of claims 1 to 6, in, The memory also contains instructions executable by the processor to cause the UE to align a DRX cycle with one or more of an access point or base station of the wireless communication system and / or the additional UE.

8. The user equipment (UE) according to any one of claims 1 to 6, in, • the DRX synchronization source comprises a base station, the memory further comprising instructions executable by the processor to cause the UE to receive a control message from the base station, the control message comprising the one or more DRX configurations, or • the DRX synchronization source comprises one or more of the further UEs, the memory further comprising instructions executable by the processor to cause the UE to receive the one or more DRX configurations from another UE.

9. The user equipment UE according to claim 8, wherein: The one or more DRX configurations include some or all of the following information: •DRX cycle duration, the total duration of a single DRX cycle, including on-duration and off-duration, • On duration, which indicates the duration that the UE can transmit and receive, • Inactivity timer, which indicates the duration for which the UE must remain on after receiving a control signal and / or sending a packet, • a retransmission timer, which indicates the duration that the UE must remain on because a control signal has indicated a retransmission of a given packet, • Communication range requirements within which the UE expects or sends feedback regarding sent or received transmissions.

10. The user equipment (UE) according to claim 9, wherein: The memory further includes instructions executable by the processor to cause the UE to: activate the DRX mode in response to receiving the one or more DRX configurations in order to operate in the DRX mode, and The UE is further caused to activate the DRX mode in response to: • expiration of the inactivity timer, or • explicit signalling by another UE, directly or indirectly, to activate or deactivate the DRX mode, or • HARQ process is enabled, or • Switch to receive-only mode, or • Higher layers signaling to save power, or • QoS changes, or • The UE is located in a specific geographical location.

11. The user equipment (UE) according to claim 8, wherein: The wireless communication system includes a plurality of DRX configuration sources, the plurality of DRX configuration sources being hierarchical such that each of the DRX configuration sources has a different rank than the remaining DRX configuration sources, and The memory also includes instructions executable by the processor to cause the UE to: select a DRX configuration received from a DRX configuration source having a highest ranking if the UE receives two or more DRX configurations having different start times and durations.

12. The user equipment (UE) according to claim 11, wherein: The memory further includes instructions that are executable by the processor to cause the UE to: in response to selecting a DRX configuration from a DRX configuration source with the highest rank, send assistance information to one or more other DRX configuration sources to notify the other DRX configuration sources of the existence of the DRX configuration source with a higher rank, thereby enabling the other DRX configuration source UEs to align their timing with the selected DRX configuration source.

13. The user equipment (UE) according to claim 12, wherein: The assistance information includes information that allows changing the characteristics of the DRX cycle.

14. The user equipment (UE) according to claim 13, wherein: The characteristics of the DRX cycle include one or more of the following: • the duration of the DRX cycle length, • an offset of the DRX cycle used to match the start time, • The on-duration of the DRX cycle.

15. A method for operating a user equipment (UE) of a wireless communication system in a discontinuous reception (DRX) mode, wherein the wireless communication system comprises a plurality of user equipments (UEs), and the UE communicates with one or more further UEs using a side link (SL), the method comprising: receiving, by the UE, a DRX configuration from one of a plurality of DRX configuration sources, The multiple DRX configuration sources are hierarchical such that each of the DRX configuration sources has a different rank from the remaining DRX configuration sources, and the UE selects a DRX configuration from a DRX configuration source with a highest rank among the available DRX configuration sources.

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