PROXIMITY AWARENESS IN SIDELINK COMMUNICATION

Description

[0001] The present invention relates to the field of wireless communication systems or networks, more specifically to the improvements and enhancements regarding a sidelink communication among network entities, like mobile user devices or other user equipment, UE. Embodiments relate to a proximity awareness in sidelink communications, like V2X communications, with regard to a quality of service to be provided or with regard to a feedback mechanism, like the HARQ mechanism, for such sidelink communications.

[0002] Fig. 1 is a schematic representation of an example of a terrestrial wireless network 100 including, as is shown in Fig. 1 (a), a core network 102 and one or more radio access networks RANi, RAN 2 , ... RAN N . Fig. 1(b) is a schematic representation of an example of a radio access network RAN n that may include one or more base stations gNB 1 to gNB 5 , each serving a specific area surrounding the base station schematically represented by respective cells 106 1 to 106 5 . The base stations are provided to serve users within a cell. The term base station, BS, refers to a gNB in 5G networks, an eNB in UMTS / LTE / LTE-A / LTE-A Pro, or just a BS in other mobile communication standards. A user may be a stationary device or a mobile device. The wireless communication system may also be accessed by mobile or stationary loT devices which connect to a base station or to a user. The mobile devices or the loT devices may include physical devices, ground based vehicles, such as robots or cars, aerial vehicles, such as manned or unmanned aerial vehicles (UAVs), the latter also referred to as drones, buildings and other items or devices having embedded therein electronics, software, sensors, actuators, or the like as well as network connectivity that enables these devices to collect and exchange data across an existing network infrastructure. Fig. 1(b) shows an exemplary view of five cells, however, the RAN n may include more or less such cells, and RAN n may also include only one base station. Fig. 1(b) shows two users UE 1 and UE 2 , also referred to as user equipment, UE, that are in cell 106 2 and that are served by base station gNB 2 . Another user UE 3 is shown in cell 106 4 which is served by base station gNB 4 . The arrows 108 1 , 108 2 and 108 3 schematically represent uplink / downlink connections for transmitting data from a user UE 1 , UE 2 and UEs to the base stations gNB 2 , gNB 4 or for transmitting data from the base stations gNB 2 , gNB 4 to the users UE 1 , UE 2 , UEs. Further, Fig. 1(b) shows two loT devices 110 1 and 110 2 in cell 106 4 , which may be stationary or mobile devices. The loT device 110 1 accesses the wireless communication system via the base station gNB 4 to receive and transmit data as schematically represented by arrow 112 1 . The loT device 110 2 accesses the wireless communication system via the user UE 3 as is schematically represented by arrow 112 2 . The respective base station gNB 1 to gNB 5 may be connected to the core network 102, e.g. via the S1 interface, via respective backhaul links 114 1 to 114 5 , which are schematically represented in Fig. 1(b) by the arrows pointing to "core". The core network 102 may be connected to one or more external networks. Further, some or all of the respective base station gNB 1 to gNB 5 may connected, e.g. via the S1 or X2 interface or the XN interface in NR, with each other via respective backhaul links 116 1 to 116 5 , which are schematically represented in Fig. 1(b) by the arrows pointing to "gNBs".

[0003] For data transmission a physical resource grid may be used. The physical resource grid may comprise a set of resource elements to which various physical channels and physical signals are mapped. For example, the physical channels may include the physical downlink, uplink and sidelink shared channels (PDSCH, PUSCH, PSSCH) carrying user specific data, also referred to as downlink, uplink and sidelink payload data, the physical broadcast channel (PBCH) carrying for example a master information block (MIB) and a system information block (SIB), the physical downlink, uplink and sidelink control channels (PDCCH, PUCCH, PSSCH) carrying for example the downlink control information (DCI), the uplink control information (UCI) and the sidelink control information (SCI). For the uplink, the physical channels may further include the physical random access channel (PRACH or RACH) used by UEs for accessing the network once a UE synchronized and obtained the MIB and SIB. The physical signals may comprise reference signals or symbols (RS), synchronization signals and the like. The resource grid may comprise a frame or radio frame having a certain duration in the time domain and having a given bandwidth in the frequency domain. The frame may have a certain number of subframes of a predefined length, e.g. 1ms. Each subframe may include one or more slots of 12 or 14 OFDM symbols depending on the cyclic prefix (CP) length. A frame may also consist of a smaller number of OFDM symbols, e.g. when utilizing shortened transmission time intervals (sTTI) or a mini-slot / non-slot-based frame structure comprising just a few OFDM symbols.

[0004] The wireless communication system may be any single-tone or multicarrier system using frequency-division multiplexing, like the orthogonal frequency-division multiplexing (OFDM) system, the orthogonal frequency-division multiple access (OFDMA) system, or any other IFFT-based signal with or without CP, e.g. DFT-s-OFDM. Other waveforms, like non-orthogonal waveforms for multiple access, e.g. filter-bank multicarrier (FBMC), generalized frequency division multiplexing (GFDM) or universal filtered multi carrier (UFMC), may be used. The wireless communication system may operate, e.g., in accordance with the LTE-Advanced pro standard or the 5G or NR, New Radio, standard.

[0005] The wireless network or communication system depicted in Fig. 1 may by a heterogeneous network having distinct overlaid networks, e.g., a network of macro cells with each macro cell including a macro base station, like base station gNB 1 to gNB 5 , and a network of small cell base stations (not shown in Fig. 1), like femto or pico base stations.

[0006] In addition to the above described terrestrial wireless network also non-terrestrial wireless communication networks exist including spaceborne transceivers, like satellites, and / or airborne transceivers, like unmanned aircraft systems. The non-terrestrial wireless communication network or system may operate in a similar way as the terrestrial system described above with reference to Fig. 1, for example in accordance with the LTE-Advanced Pro standard or the 5G or NR, new radio, standard.

[0007] In mobile communication networks, for example in a network like that described above with reference to Fig. 1, like an LTE or 5G / NR network, there may be UEs that communicate directly with each other over one or more sidelink (SL) channels, e.g., using the PC5 interface. UEs that communicate directly with each other over the sidelink may include vehicles communicating directly with other vehicles (V2V communication), vehicles communicating with other entities of the wireless communication network (V2X communication), for example roadside entities, like traffic lights, traffic signs, or pedestrians. Other UEs may not be vehicular related UEs and may comprise any of the above-mentioned devices. Such devices may also communicate directly with each other (D2D communication) using the SL channels.

[0008] When considering two UEs directly communicating with each other over the sidelink, both UEs may be served by the same base station so that the base station may provide sidelink resource allocation configuration or assistance for the UEs. For example, both UEs may be within the coverage area of a base station, like one of the base stations depicted in Fig. 1. This is referred to as an "in-coverage" scenario. Another scenario is referred to as an "out-of-coverage" scenario. It is noted that "out-of-coverage" does not mean that the two UEs are not within one of the cells depicted in Fig. 1, rather, it means that these UEs may not be connected to a base station, for example, they are not in an RRC connected state, so that the UEs do not receive from the base station any sidelink resource allocation configuration or assistance, and / or may be connected to the base station, but, for one or more reasons, the base station may not provide sidelink resource allocation configuration or assistance for the UEs, and / or may be connected to the base station that may not support NR V2X services, e.g. GSM, UMTS, LTE base stations.

[0009] When considering two UEs directly communicating with each other over the sidelink, e.g. using the PC5 interface, one of the UEs may also be connected with a BS, and may relay information from the BS to the other UE via the sidelink interface. The relaying may be performed in the same frequency band (in-band-relay) or another frequency band (out-of-band relay) may be used. In the first case, communication on the Uu and on the sidelink may be decoupled using different time slots as in time division duplex, TDD, systems.

[0010] Fig. 2 is a schematic representation of an in-coverage scenario in which two UEs directly communicating with each other are both connected to a base station. The base station gNB has a coverage area that is schematically represented by the circle 200 which, basically, corresponds to the cell schematically represented in Fig. 1. The UEs directly communicating with each other include a first vehicle 202 and a second vehicle 204 both in the coverage area 200 of the base station gNB. Both vehicles 202, 204 are connected to the base station gNB and, in addition, they are connected directly with each other over the PC5 interface. The scheduling and / or interference management of the V2V traffic is assisted by the gNB via control signaling over the Uu interface, which is the radio interface between the base station and the UEs. In other words, the gNB provides SL resource allocation configuration or assistance for the UEs, and the gNB assigns the resources to be used for the V2V communication over the sidelink. This configuration is also referred to as a mode 1 configuration in NR V2X or as a mode 3 configuration in LTE V2X.

[0011] Fig. 3 is a schematic representation of an out-of-coverage scenario in which the UEs directly communicating with each other are either not connected to a base station, although they may be physically within a cell of a wireless communication network, or some or all of the UEs directly communicating with each other are to a base station but the base station does not provide for the SL resource allocation configuration or assistance. Three vehicles 206, 208 and 210 are shown directly communicating with each other over a sidelink, e.g., using the PC5 interface. The scheduling and / or interference management of the V2V traffic is based on algorithms implemented between the vehicles. This configuration is also referred to as a mode 2 configuration in NR V2X or as a mode 4 configuration in LTE V2X. As mentioned above, the scenario in Fig. 3 which is the out-of-coverage scenario does not necessarily mean that the respective mode 2 UEs (in NR) or mode 4 UEs (in LTE) are outside of the coverage 200 of a base station, rather, it means that the respective mode 2 UEs (in NR) or mode 4 UEs (in LTE) are not served by a base station, are not connected to the base station of the coverage area, or are connected to the base station but receive no SL resource allocation configuration or assistance from the base station. Thus, there may be situations in which, within the coverage area 200 shown in Fig. 2, in addition to the NR mode 1 or LTE mode 3 UEs 202, 204 also NR mode 2 or LTE mode 4 UEs 206, 208, 210 are present.

[0012] In the above-described scenarios of vehicular user devices, UEs, a plurality of such user devices may form a user device group, also referred to simply as group, and the communication within the group or among the group members may be performed via the sidelink interfaces between the user devices, like the PC5 interface. For example, the above-described scenarios using vehicular user devices may be employed in the field of the transport industry in which a plurality of vehicles being equipped with vehicular user devices may be grouped together, for example, by a remote driving application. Other use cases in which a plurality of user devices may be grouped together for a sidelink communication among each other include, for example, factory automation and electrical power distribution. In the case of factory automation, a plurality of mobile or stationary machines within a factory may be equipped with user devices and grouped together for a sidelink communication, for example for controlling the operation of the machine, like a motion control of a robot. In the case of electrical power distribution, entities within the power distribution grid may be equipped with respective user devices which, within a certain area of the system may be grouped together so as to communicate via a sidelink communication with each other so as to allow for monitoring the system and for dealing with power distribution grid failures and outages.

[0013] Naturally, in the above-mentioned use cases sidelink communication is not limited to a communication within a group. Rather, the sidelink communication may be among any of UEs, like any pair of UEs.

[0014] It is noted that the information in the above section is only for enhancing the understanding of the background of the invention and therefore it may contain information that does not form prior art that is already known to a person of ordinary skill in the art. QUALCOMM INCORPORATED, "Discussion on Groupcast for NR V2X", vol. RAN WG2, no. Chengdu, China; 20181008 - 20181012, (20180928), 3GPP DRAFT; R2-1814929; describes design issues for a groupcast in a NR V2X sidelink communication. INTEL CORPORATION, "Design options to support priority for V2V communication", vol. RAN WG1, no. Gothenburg, Sweden; 20160822 - 20160826, (20160821), 3GPP DRAFT; R1-167693; describes a mechanism to support priority handling for PC5 V2V communication considering eNB controlled and UE autonomous modes of operation. Priority signaling details are described and how the priority information in resource reselection procedure and UE transmitter behavior is taken into account.

[0015] ZTE, "Discussion on QoS management for NR V2X", vol. RAN WG2, no. Chengdu, China; 20181008 - 20181012, (20180928), 3GPP DRAFT; R2-1814175; describes the QoS management for advanced V2X services over Uu and PC5.

[0016] INTEL CORPORATION, "On QoS Management for NR V2X Communication", vol. RAN WG1, no. Gothenburg, Sweden; 20180820 - 20180824, (20180811), 3GPP DRAFT; R1-1808701; describes the impact of QoS management on physical layer for NR V2X services.

[0017] Document WO 2017 / 103662 A1 describes data packet reception method in wireless network, which involves controlling transmission of predetermined indicator by second communication device to first communication device based on context information related to data packet.

[0018] Starting from the prior art as described above, it is an object of the present invention to provide improvements or enhancements in the communications using a sidelink taking into consideration the proximity among the respective network entities communicating over the sidelink.

[0019] This object is achieved by a user device according to claim 1, by a wireless communication network according to claim 4, and by a method according to claim 6.

[0020] Embodiments of the present invention are now described in further detail with reference to the accompanying drawings: Fig. 1shows a schematic representation of an example of a wireless communication system; Fig. 2is a schematic representation of an in-coverage scenario in which UEs directly communicating with each other are connected to a base station; Fig. 3is a schematic representation of an out-of-coverage scenario in which UEs directly communicating with each other receive no SL resource allocation configuration or assistance from a base station; Fig. 4is a schematic representation of a wireless communication system including a transmitter, like a base station, and one or more receivers, like user devices, UEs; Fig. 5illustrates a pre-configured communication range which is based on a type of a vehicle, like a car shown in Fig. 5(a), a van shown in Fig. 5(b) and a truck shown in Fig. 5(c); Fig. 6illustrates scenarios employing a flexible communication range, wherein Fig. 6(a) illustrates a non-coverage scenario, and Fig. 6(b) illustrates an in-coverage scenario; Fig. 7illustrates a flowchart for adapting the inner proximity and the outer proximity circles described above with reference to Fig. 6(b) or the border between the inner proximity and the outer proximity areas; Fig. 8illustrates an enhanced discovery mechanism; Fig. 9illustrates an example for enhancing the accuracy of the minimum required communication range as determined; Fig. 10illustrates an example of improving the determination of a location of a transmitting UE using triangulation; and Fig. 11illustrates an example of a computer system on which units or modules as well as the steps of the methods described in accordance with the inventive approach may execute.

[0021] Embodiments of the present invention are now described in more detail with reference to the accompanying drawings in which the same or similar elements have the same reference signs assigned.

[0022] In wireless communication systems or networks, like those described above with reference to Fig. 1, one or more users, like mobile users, may communicate with each other over a sidelink. However, conventional sidelink communications do not take into consideration or address a proximity of the respective network entities communicating with each other over the sidelink in terms of certain communication requirements or communication mechanisms to be implemented for certain services provided in the network. So far, the proximity among UEs in a wireless communication system is only tackled for discovering nearby vehicles or UEs in a sense of a discovery mechanism. In D2D scenarios, several discovery mechanisms are applied, for example a direct discovery in accordance with which UEs are able to discover other UEs in close proximity without any help of the core network. Another approach is the Evolved Packet Core EPC, level discovery in accordance with which the core network may collect information from each UE about other UEs in the base station's vicinity. The EPC, using the collected information, may notify UEs about their proximity. Another mechanism is based on a direct communication, i.e., a proximity among two UEs is assumed when two or more UEs are able to exchange data directly without passing the data to the base station. A similar approach is based on a UE-to-network relay or a UE-to-UE relay in which a UE acts as a relay either between another UE and a network or between two other UEs so that, via the relay, the respective UEs or the UE and the network may communicate. Thus, conventional approaches regarding the discovery mechanisms, either determine some kind of proximity among the respective network entities or, based on a possible communication among the entities, a proximity is assumed.

[0023] As mentioned above, a UE may be in one of three modes, namely in-coverage, partial coverage or out-of-coverage, and depending on the mode non-public safety and public safety applications or only public safety applications may take into consideration the proximity among the network entities. For example, when considering the above-mentioned discovery mechanisms including the direct discovery and the EPC-level discovery, for UEs being within the network coverage, both non-public and public safety applications may be employed, while only public safety applications may be employed when being out of coverage or in partial coverage. In case of judging the proximity on the basis of the direct communication, either directly among two UEs or via a relay, as long as the UEs are in network coverage, at least public safety applications may be employed, while only public safety applications are available when being out-of-coverage.

[0024] However, conventional approaches do not at all address the proximity with regard to certain requirements of an application for a communication to be performed among multiple network entities over the sidelink. For example conventional approaches do not take into consideration a Quality of Service, QoS, of a certain application or service that is performed using the one or more UEs over the sidelink and which requires certain latency and reliability requirements that depend on the proximity of the respective UEs. In other words, UEs that communicatie over the sidelink, i.e., are within a direct communication, may perform certain applications requiring a certain QoS only as long as the distance between these two UEs is small enough so as to provide for a desired latency, like a very low latency, and a desired reliability, like a high reliability. This may be the case for Ultra Reliable and Low Latency Communications, URLLC, services or applications. In case the distance between the UEs increases, it may be that the desired parameters associated with the quality of service for a certain service or application is no longer achieved.

[0025] Also, other network mechanisms may depend on the proximity among the UEs, and so far, conventional approaches do not take into consideration that certain network mechanisms, like feedback or retransmission mechanisms, may rely or depend on the proximity of the UEs communicating over the sidelink. When considering, for example, the Hybrid Automatic Repeat Request, HARQ, retransmission mechanism there may be certain requirements regarding the time for sending the acknowledgement / non-acknowledgement and / or for sending the retransmission needed for certain services. For example, in case the distance among the UEs employing such a mechanism is short, the respective requirements may be fulfilled. However, with an increase in the proximity such requirements may not be met anymore so that, for example, any action by the respective communication partners with regard to the feedback mechanism are wasted as the information is not available at the other partner within a certain time so as to make use of the retransmission.

[0026] Moreover, when considering V2X communications, until Rel 15 LTE V2X, all the sidelink communication is broadcast based only. In accordance with NR, further use cases, e.g., the above-described vehicular use cases, like platooning and advanced driving, use a groupcast and unicast based sidelink communication along with a basic broadcast mechanism. For example, in such advanced use cases, the communication requirements, like QoS, and / or certain communication mechanisms to be implement, may be varied and may be stringent. As discussed above, the distance among the UEs may be an issue with regard to the use of certain services or applications in such advanced use cases, for example to make sure that a certain QoS or a certain feedback mechanism is possible.

[0027] In accordance with embodiments, a certain communication range or distance, like a minimum communication range, is defined for allowing a UE to make useful use of certain communication mechanisms, like to use a feedback mechanism.

[0028] Embodiments of the present invention may be implemented in a wireless communication system as depicted in Fig. 1, Fig. 2, and Fig. 3 including base stations and users, like mobile terminals or loT devices. Fig. 4 is a schematic representation of a wireless communication system including a transmitter 300, like a base station, and one or more receivers 302 1 to 302 n , like user devices, UEs. The transmitter 300 and the receivers 302 may communicate via one or more wireless communication links or channels 304a, 304b, 304c, like a radio link. 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, coupled with each other. The receivers 302 include one or more antennas ANT R or an antenna array having a plurality of antennas, a signal processor 302a 1 , 302a n , and a transceiver 302b 1 , 302b n coupled with each other. The base station 300 and the UEs 302 may communicate via respective first wireless communication links 304a and 304b, like a radio link using the Uu interface, while the UEs 302 may communicate with each other via a second wireless communication link 304c, like a radio link using the PC5 interface. When the UEs are not served by the base station, are not be connected to a base station, for example, they are not in an RRC connected state, or, more generally, when no SL resource allocation configuration or assistance is provided by a base station, the UEs may communicate with each other over the sidelink. The system, the one or more UEs and the base stations may operate in accordance with the inventive teachings described herein.

[0029] Thus, embodiments of the present invention provide improvements and enhancements in the communication over a sidelink by using the proximity awareness of a UE. An advantage of the inventive approach is that it allows meeting for certain use cases, like the above-mentioned platooning, specific low-latency / high-reliability requirements, as well as to fulfill respective QoS levels provided the communication partner is within the minimum required communication range, i.e., the communication range that is required to meet the just mentioned QoS requirements. For example the inventive approach may be applied whenever a communication within the near distance is more important, for example, has a higher priority, than a communication exchange with a communication partner or UE that is further away, so as to ensure the low-latency / high-reliability demands of certain use cases, for example, platooning. When considering the platooning use case, the minimum communication distance may be related to an emergency situation, like an expected breaking, which effects mostly and immediately all the vehicles in close proximity. Thus, when considering a situation in which one vehicle within the platoon performs an expected breaking, this is communicated among the other members of the platoon, and the minimum communication range is selected such that a proximity or distance between the respective UEs allows for transmitting the message about the unexpected breaking to and processing the message by the other platoon members provides sufficient time to avoid crashes or the like.

[0030] The inventive approach is not limited to the QoS requirements or to certain emergency situations, rather, it may be applied to any situation in which the communication from one UE to another UE requires the other UE to perform some action, like breaking or the like, for which time, in addition to the signal processing and the signal transmission, is needed. Besides the QoS mechanism, another issue that may be of interest in accordance with embodiments is the implementation of retransmission mechanisms. To avoid any waste of resources and the like, retransmissions which may not be processed by the UEs within the minimum time are avoided.

[0031] Thus, embodiments of the present invention improve the delivered QoS for V2X based communications taking into consideration the communication range or the distance among the UEs communicating over the sidelink. Another effect is that resource wasting is avoided by taking into consideration the communication range or distance on the sidelink when deciding whether certain mechanisms in the communication are to be activated, like a feedback mechanism, for example a HARQ mechanism.

[0032] In accordance with embodiments, a minimum required communication range may be a range of communication that covers: a relative physical distance measured in meters between the UEs; in this case, the distance information may be conveyed by upper-layers or may be conveyed using control information, for example over the Uu interface or using the Sidelink Control Information, SCI, or a radio distance captured by a UE measurement; the UE measurement may include a measurement of the Received Signal Strength Indicator, RSSI, the Reference Signal Received Power, RSRP, the Reference Signal Received Quality, RSRQ, the path loss, different general-state-information or as a function of the transmitted power, or a targeted geographical area as provided by upper layers, for example, including coverage area and directions, which may be transmitted via the Cooperative Awareness Message, CAM, or the Decentralized Environmental Notification Message, DENM.

[0033] In accordance with embodiments, the minimum required communication range may be employed for unicast and groupcast communications among UEs communicating over a sidelink. The minimum required communication range may be pre-configured and may be provided by higher layers. The pre-configured minimum required communication range may be impacted by the application time or type, the service type or the UE type. For example, when considering vehicles, different vehicle types may be assumed. For example, vehicle type 1 may be associated with a conventional car, vehicle type 2 may be associated with a conventional van, and vehicle type 3 may be associated with a truck. The respective vehicle types are described by respective length, width and height dimensions, for example in meters, of the vehicle. Fig. 5 illustrates an embodiment in accordance with which the pre-configured communication ranges are based on the type of a vehicle. Fig. 5(a) illustrates a car that includes a user device for which a certain minimum communication range is to be employed to see whether certain requirements or mechanisms may be achieved / employed when communicating with another UE, i.e., dependent on whether the UE is outside or inside the minimum communication range. As mentioned above, dependent on the vehicle type, the pre-configured communication range is determined. In Fig. 5(a) the minimum required communication range 402a is indicated. As is shown by the arrow L+W+H, the communication range 402a takes into consideration the dimension of the vehicle, namely its length, its width and its height. In a similar way as Fig. 5(a), Fig. 5(b) also shows a communication range 400b, however, not for a car but for a van 404, and in Fig. 5(c) the communication range 400c is illustrated for a truck 406. In Fig. 5(b) and in Fig. 5(c) the communication range 400b, 400c is preconfigured dependent on the vehicle type, i.e., dependent on the length, the width, and the height of the van 404 and the truck 406, respectively. In Fig. 5, the center of the minimum required communication range 402a to 402c is assumed to be the center of mass of the respective vehicle 400, 404, 406 in consideration.

[0034] In accordance with embodiments not according to the claimed invention, the minimum required communication range may be employed for the sidelink communication among the UEs using slot-based PSCCH and PSSCH for the sidelink communication, wherein the respective sidelink may be adapted by mapping a high priority MCS and TBS to the QoS value and the communication range. For example, a low MCS may be employed for a high QoS and for a low communication range. Also, the power control may be adapted, and as is described with reference to further embodiments below concerning the mapping of the MCS / TBS / TPC (TPC = Transmitter Power Control) to respective communication ranges.

[0035] In accordance with other embodiments not according to the claimed invention, a non-slot transmission may be employed and the communication may be performed on a mini-slot for the same communication range but with a higher power, thereby reducing the transmission time. This requires short-time sensing and may boost the transmission power to coexist with other possible collisions.

[0036] Another embodiment not according to the claimed invention for the transmission taking into consideration the minimum required communication range may reduce the frequency by maintaining the time to be one slot so that the power is increased which may also be referred to as a data compression.

[0037] The above embodiments may be useful for higher priority information, for example limited data transmission with high / very-high QoS flow values. The data may be allocated to dedicated resources or grant-free resources, which content with other UEs, may be used, or preconfigured resources may be used. The use of grant-free resources or pre-configured resources may use sensing for a short-time or long-time or may use one short sensing.

[0038] In accordance with other embodiments, other than using pre-configured minimum required communication ranges, the communication range may be semi-flexible, i.e., it may be based on fixed values and measurement values. In such embodiments, not only the minimum communication range is provided by an upper layer, rather, a flexible communication range is used by including radio measurements. The radio measurements may be calculated from the RSSI or RSRP or may be based on sidelink measurements with respect to surrounding UEs or vehicles. Also, power measurements available from other sources may be employed, for example, the power may be selected from a plurality of power values based on environmental conditions or based on a sensor input. The sensor input or the environmental conditions may cover speed, weather, vehicle traffic situations, like rush hour, etc., and may further include any upper-layer parameters, e.g., the priority of the packet, the category of the service level or any other QoS flow. The mapping may function as in the previous embodiment, and the transmission taking into consideration the minimum required communication range may be done as described above with reference to the embodiment making use of the pre-configured minimum required communication ranges.

[0039] Another embodiment makes use of flexible communication ranges which, other than the just described embodiment, is completely based on measurements. The advantage of the flexible communication range may be that there is a higher reachability and that adapted distances may be used. Further, there may be more time to collect information for determining the minimum required communication range. Another advantage is that it may adapt with the discovery mechanisms described above, like the direct discovery and the network discovery.

[0040] As mentioned above, the measurements may be based on RSSI, RSRQ or CSI measurements. Further, the measurements may be based on radio range measurements on the sidelink, and the sidelink based radio range measurements may be calculated using the Primary Sidelink Synchronization Channel, PSSS, or the Secondary Sidelink Synchronization Channel, SSSS, or the Demodulation Reference Signals, DMRS.

[0041] The flexible communication range being completely based on measurements is advantageous as it provides the possibility of serving the vehicles in the vicinity with adaptive QoS. Fig. 6 illustrates a scenario employing a flexible communication range being based on measurements performed by the UEs. Fig. 6(a) illustrates a non-coverage scenario, and Fig. 6(b) illustrates an in-coverage scenario. As is shown in Fig. 6(a) a UE1 performs respective measurements on the sidelink, SL, to the other mobile users UE2 to UE5, for example SL-RSRP measurement. Based on these measurements, the UE1 determines the minimum required communication range 402. For example, in case of an emergency, the UE1 is referred to as the emergency notification V-UE (V-UE = vehicular UE), and the closest proximity vehicles are delivered and emergency messages, for example in case of a danger of a crash or the like, to allow the other vehicles to take evasive action. In the example of Fig. 6(a), the respective proximity vehicles are UE2, UE3 and UE4.

[0042] Fig. 6(b) illustrates a scenario employing a flexible communication range when the respective UEs communicate over the sidelink and are in an in-coverage scenario. Fig. 6(b) illustrates the base stations gNB as well as a plurality of UEs, UE1 to UE8, within coverage of the base station. At least some of the UEs may communicate with each other over the sidelink. The base station provides measurements from the respective UEs to the UE1 or to the vehicle including the UE1, as is illustrated by arrow 408. Based on the reported measurements UE1 determines its minimum required communication range that is depicted by the inner circle 402. In addition, Fig. 6(b) illustrates an outer circle 410. For example, in case there is a danger of a crash noticed by a vehicle, like UE1, the base station gNB is immediately requested to grant the resources to UE1 based on a certain quality of service. Using the resources, the closest proximity vehicles are delivered the message notification of a potential crash immediately. Within the inner circle 402, which is derived from the minimum required communication range, the following rules may apply: a reduced transmission power is used because of the limited size of the inner circle 402, grant-free access is employed, for example, resources may be used that are reserved for high priority transmissions, the parameter settings are such that a high reliability is ensured, for example, a suitable MCS is selected, or a feedback mechanism including, for example packet duplication or retransmissions is enabled.

[0043] On the other hand, in the outer proximity circle 410 the following rules may apply: the gNB that also received the emergency message broadcasts this message to the UEs, namely UE2 to UE8 in a usual format, or the notification is sent by UE1 on the sidelink with a timely offset using a high transmission power.

[0044] The setting of the respective circles 402, 410 or, in other words, the setting of the border between the close proximity vehicles and the outer proximity vehicles may be based on one or more measurement thresholds which, in accordance with embodiments, supports identifying a highest priority circle. Fig. 7 illustrates a flowchart for adapting the circles 402, 410 described above with reference to Fig. 6(b) or the border between the inner proximity and the outer proximity areas. Initially, in accordance with embodiments, sidelink measurements may be performed by UE1, for example measurements of the RSRP, RSRQ, CQI and the like as indicated at S1 in Fig. 7. In case the sidelink measurements exceed a certain threshold, as is indicated at S2 in Fig. 7, UEs connected to the measuring UE1 via such sidelinks are considered to be within the inner circle 402, as is indicated at S3 in Fig. 7, and in the example of Fig. 6(b). The sidelink measurements on the sidelinks from UE1 to UE4 and to UE5, respectively, are assumed to be above the threshold so that UE4 and UE5 are within the inner circle 402. On the other hand, in case measurements on sidelinks are below the threshold as is indicated at S4 in Fig. 7, the respective UEs are considered to be in the outer circle 410, as is indicated at S5. In the example of Fig. 6(b) the sidelink measurements or the sidelinks to UE2, UE3, and UE6 to UE8 are less than a certain threshold, for example, the RSRP, RSRQ, CQI measurements are below a threshold, that UE2, UE3 and UE6 to UE8 are considered to be outer proximity vehicles or UEs.

[0045] In accordance with further embodiments not according to the claimed invention, the above-described conventional discovery mechanisms may be enhanced by employing the above-described principles placing respective UEs dependent on the sidelink measurements within certain proximity circles. Likewise, the principle may be used to enhance the discovery mechanism and in such a case, the discovery may consider all the physical layer parameters, for example it may include measurements and physical layer IDs. For example, the above-described outer circle 402 may be considered a new discovery mechanism where the UEs are discovered and associated to different circles, for example by splitting the outer circles 410 into one or more regions. Fig. 8 illustrates an embodiment for an enhanced discovery mechanism in accordance with embodiments of the present invention. For example, whenever a certain measurement of the sidelink, like a measured SL power / RSSI / RSRP is larger than a certain threshold, the discovery circles 1 to M illustrated in Fig. 8 apply, and the UEs may be sorted according to the geographic locations. In Fig. 8 UEs having an RSSI above the threshold T1 are associated with a first discovery circle, while UEs with a RSSI between thresholds T1 and T2 are associated with a second discovery level, and so on.

[0046] The discover circles mentioned above with reference to Fig. 8 represent a coverage area or communication range, and the number of circles may depend on the QoS and / or on the required communication range. The complied sorted list may be used for discovery enhancement mechanisms, for example to introduce proximity and distance based aware communications.

[0047] The sorting of the UEs in accordance with the discovery list of Fig. 8 may be done based on the above-mentioned measurements on the sidelink, for example on the basis of power, RSSI, RSRP measurements, or it may be based on distance information obtained otherwise. The UE IDs may be the physical destination ID of the UEs for a unicast communication or the group ID for a groupcast communication. This information may be conveyed using the SCI.

[0048] In case a physical ID is not available, the discovery mechanism may refer to upper layers, for example using the L2 destination ID, or it may allocate a virtual ID for every discovered UE which may then be used for certain messages, like safety messages and / or for broadcast only.

[0049] In accordance with further embodiments, to further enhance the physical layer discovery, the communication to the UEs in the discovery list may be adapted to the actual QoS and the actual communication range as defined, for example, by the circles mentioned above.

[0050] In the following, embodiments for mapping the minimum required communication range and the QoS requirements is described in more detail. With regard to the minimum required communication range, it is noted that this may be the pre-configured communication range, the semi-flexible communication range or the flexible communication range mentioned above. The mapping, in accordance with embodiments, may be between the minimum required communication range and one or more of certain QoS characteristics, like reliability, Block Error Rate, BLER, latency, E2E latency, priority, and the system or application QoS requirements.

[0051] In accordance with an embodiment not according to the claimed invention, a communication range is determined as described above and is mapped to different MCS / TBS / power control levels which is, in turn, a map to different QoS flows. A QoS flow means packets are classified and marked using a QFI (QoS Flow Identifier). The 5G QoS flows are mapped in the AN (Access Network) to DRBs (Data Radio Bearers). In case of a sidelink the radio bearers are termed as Sidelink Radio Bearers (SLRBs). It supports: GBR QoS flow, requires guaranteed flow bit rate, Non-GBR QoS flow, does not require guaranteed flow bit rate.

[0052] For example, table 1 below illustrates a first mapping possibility for a QoS flow 1. Table 1QoS 1Range 1 (0 < L1 < Lmax1)1- MCS1 / TBS1 / TPC1 → BLER 11- MCS2 / TBS2 / TPC2 → BLER 22- MCS3 / TBS3 / TPC3 → BLER 3

[0053] Table 1 illustrates the flow QoS 1, which defines certain QoS requirements, BLER 1, BLER 2, BLER 3, for the system or an application or a service to be performed. For this QoS, the UE communicating with other UEs being in a range L1 that is between 0 and a maximum range, which is the minimum required range for the UE, fulfils the BLER 1of QoS 1 when using MCS1 / TBS1 / TPC1, the BLER 2 of QoS 1 when using MCS2 / TBS2 / TPC2 and the BLER 3 of QoS 1 when using MCS3 / TBS3 / TPC3 as is indicated in the right-hand column of Table 1.

[0054] In accordance with other embodiments not according to the claimed invention, the mapping may be between the QoS flows and one or more communication ranges which are mapped to one or more MCS / TBS / TPC parameters, as is illustrated in table 2 below. Table 2Range 1 (0 < L1 < Lmax1)1- MCS1 / TBS1 / TPC1 -- QoS 11- MCS2 / TBS2 / TPC2 -- QoS 22- MCS3 / TBS3 / TPC3 -- QoS 3

[0055] In Table 2, a UE communicating with other UEs over the sidelink which are within range L1 may achieve the QoSs 1, 2 or 3 when using MCS1 / TBS1 / TPC1, MCS2 / TBS2 / TPC2 and MCS3 / TBS3 / TPC3, respectively, as is indicated in the right-hand column of Table 2.

[0056] In accordance with other embodiments, the minimum required communication range may not be employed only for unicast or groupcast communications, but it may also be used for a broadcast communication over the sidelink. For a broadcast communication no measurements of any vehicles in the proximity may be available to other vehicles. However, to ensure that all vehicles within the defined minimum required communication range receive a notification on the sidelink from the transmitting UE, in accordance with embodiments, the defined minimum required communication range is mapped on a defined transmit power. In accordance with embodiments a basic mapping between each defined minimum required communication range and a predefined transmit power is suggested. In accordance with further embodiments, this mapping may be further enhanced based, for example, on the RF conditions, like an interference or traffic load, based on environmental conditions, like weather or mountains in the vicinity of the transmitting UE, which may be derived, for example, from vehicular measurements and from channel state information. In addition to the distance or communication range a driving direction may also be employed for improving the communication range. The driving direction may be available from CAM or DENM messages. For example, when considering vehicles, on the basis of a driving direction, notifications may only be provided for vehicles driving in parallel to the transmitting vehicle or vehicles driving in the same direction.

[0057] In accordance with embodiments, the vehicles or vehicular UEs may be assumed to have several antennas or antenna ports mounted by a vehicle, and in case a directional communication range is employed, the appropriate antenna / antenna port and, if supported, beamforming may also be employed to enhance the required communication range. In other words, in accordance with embodiments, for example the circles described above may be modified so as to extend more in a driving direction of the vehicles, i.e., they become more elliptic, as less communication range may be needed in the direction traverse to the traveling direction due to the limited widths of the street on which the vehicles may travel while longer communication ranges may be needed along the street.

[0058] In accordance with further embodiments not according to the claimed invention, an accuracy with which the above-described minimum required communication range is determined may be enhanced. More specifically, the above-described semi-flexible communication range and the flexible communication range may be determined with an enhance accuracy. Basically, the just-mentioned approaches for determining the communication range in a semi-flexible way or in a flexible way may give a rough estimate of the distance between the transmitting UE and the receiving UE. In accordance with embodiments, to increase the accuracy of the distance between the receiving UE and the transmitting UE, GNSS information and a Roundtrip Time of Flight, RTF, are employed. In accordance with an embodiment, neighboring vehicles may be provided with active reflectors, similar as in the secondary radar principle. In case such neighboring vehicles receive a request from the transmitting vehicle, like a feedback request or a positioning request, the receiving UE may respond with a fixed time offset, which allows the determination of the RTF on the basis of which the distance between the transmitting UE and the receiving UE may be determined. In addition, within the response window determined by the time offset, the receiving UE includes its GPS coordinates. Based on the RTF and the coordinates the transmitting UE may more accurately determine the actual distance between the transmitting UE and the receiving UE. In accordance with embodiments, this may be extended to multiple receiving UEs that respond with a fixed time offset along with their respective GPS coordinates.

[0059] Fig. 9 illustrates an embodiment not according to the claimed invention for enhancing the accuracy of the minimum required communication range as determined in accordance with the semi-flexible or flexible approach as described above. Fig. 9 illustrates a transmitting UE as well as respective receiving UEs RxUE1 to Rx UE n . In the example of Fig. 9 it is assumed that the Tx UE broadcasts the request, as indicated at 420 to all Rx UEs, however, in accordance with other embodiments, the request may be transmitted also using a unicast communication to a dedicated one of the Rx UEs or using a groupcast communication for transmitting the request 420 to a number of Rx UEs forming groups. Responsive to the request, each a Rx UE returns a message 422, to 422 n including the time at which the request 420 is received and the offset required at the Rx UE to process the request 420 and to transmit the response 422, so that on the basis of this information, the distance from Tx UE to the respective Rx UE may be calculated. In addition, in accordance with embodiments, the GPS coordinates also may be included in the response 422 as mentioned above.

[0060] When employing multiple Rx UEs, as is depicted in Fig. 9, the Tx UE may average out GPS errors from all receiving UEs and of the transmitting UE itself, as is indicated in the lower part of Fig. 9 at 424. Accurate_Location = P req 1 + Δ P offset 1 + GPS 1 1 + P req 2 + Δ P offset 2 + GPS 2 2 + ⋯ … … … … + P reqN + Δ P offsetN + GPS N N + GPS own N where in the equation above, the variables are as follows: P reqN denotes the request for feedback or positioning, ΔP offsetN indicates the time offset by which the UE's send the response, GPS N indicates the GPS location of the receiver UE, Nis varying between 1.... and an integer value, denoting the number of vehicles included in the communication, GPS own indicates the GPS location of the transmitter UE.

[0061] It is mainly based on the idea of central limit theorem.

[0062] In accordance with embodiments not according to the claimed invention, the request 420 may be sent periodically, a periodically or totally randomly.

[0063] In accordance with embodiments not according to the claimed invention, only responses from those receiving UEs that include a time offset are considered to be valid responses. This avoids collisions in multiple responses.

[0064] The time offset may be included or transmitted using the control channel of the sidelink in a second stage of the SCI, or in case only a single stage SCI is used, it may be transmitted using the normal SCI format. In accordance with other embodiments, rather than transmitting the time offset information in the control channel, it may also be included in any of the other defined sidelink channels.

[0065] The GPS coordinates may be included in a CAM message or a DENM message or for a message defined specifically for groupcast or unicast communications.

[0066] In accordance with further embodiments not according to the claimed invention, the accuracy of the determination of the minimum required communication range may be further enhanced by more accurately determining the location of a transmitting UE. In accordance with embodiments not according to the claimed invention, the location of the transmitting UE may be determined by a triangulation on the basis of signals transmitted from one or more stationary network entities in the vicinity of the transmitting UE, for example from a roadside unit or a base station or from any static UE location. In accordance with embodiments, it is preferred that for the triangulation no other moving receiving UEs are within the communication range. Fig. 10 illustrates an embodiment of improving the determination of a location of a transmitting UE using triangulation. The transmitting Tx UE, in the example of Fig. 10, is assumed to be a vehicular UE close to an intersection of two streets at which respective roadside units 426a to 426c are located which, in a similar way as described with reference to Fig. 9, responsive from a request to Tx UE respond with a response including the time offset and, optionally, the GPS coordinates. The first roadside unit 426a may be a traffic light provided at an elevated location at the center of the intersection, while the other two roadside units 426b, 426c may be respective street lamps.

[0067] Based on the information from the roadside units 426a to 426c the Tx UE may calculate its location by triangulation and, based on this more accurate location also the distance to the receiving UEs may be determined more accurately thereby enhancing the accuracy with which it may be determined whether a certain UE is within or outside a minimum required communication range.

[0068] In accordance with embodiments according to the claimed invention, the minimum required communication range is associated with the use of a feedback mechanism during the communication. As there may be many UEs around the transmitting UE which are not part of a groupcast or of a unicast communication, it is desired to reduce or limit the number of receiving UEs that are expected or allowed to send a feedback to the transmitting UE. Limiting the number of receiving UEs allowed to send a feedback is advantageous as it increases the reliability as the retransmission is directed to the correct one of the receiving UEs or to the correct group of receiving UEs. Another advantage of limiting the number of receiving UEs allowed to send feedback is that this limits the number of retransmission requests at the transmitting UE which may improve the network performance and avoid congestions.

[0069] The following embodiments according to the claimed invention concerning the feedback mechanism may be used together with the above-described embodiments concerning the desired QoS to be achieved, or may be used independent therefrom. In order to increase the reliability of a communication, a feedback mechanism, like a HARQ feedback is used at least for groupcast and unicast communications in V2X communications.

[0070] To avoid signaling overhead, it is desired to identify and limit the number of receiving UEs that may send feedback to the transmitting UE. The limiting of the number of receiving UEs that may send back a feedback to the transmitting UE is based on the above-described minimum required communication range. In accordance with embodiments one of the pre-configured, semi-flexible or flexible communication ranges are employed and dependent on whether a UE is within the range or outside the range, it is identified whether such a UE is to send a feedback or not. UEs making use of the flexible communication range approach described above in more detail may set up thresholds responsive to which the feedback is triggered, and the thresholds may be pre-configured or may be set up by the network. For example, in case a threshold for the feedback is exceeded, like an RSRP measurement for certain group members or a unicast member, the feedback may be initiated.

[0071] In order to find out the UEs which may send feedback and which may not send feedback, an accurate distance between the transmitting UE and the receiving UEs is to be calculated, and dependent on the distance, it may be judged whether the UE is actually within the pre-configured minimum required communication range, the semi-flexible communication range or the flexible communication range which have been described in detail above.

[0072] When it is determined that a UE is outside the minimum required communication range the feedback mechanism is deactivated or not initialized, i.e., the UE is not to send any retransmission requests (in case the UE is a receiving UE), or any retransmissions (in case the UE is a transmitting UE). On the other hand, for a predefined groupcast and / or dynamic groupcast and / or unicast communication on a sidelink to one or more UEs that are within the communication range, the receiving UEs are allowed to send feedback, for example a HARQ feedback, so as to increase the reliability of the transmission. The transmitting UE uses a flexible communication range approach as described above and may set up thresholds that may be pre-configured or defined by the network, for triggering the feedback transmissions. If the threshold for the feedback is exceeded, for example if the RSRPs of the UEs of a certain group or a unicast UE is exceeded, a feedback is activated or initiated. In accordance with the present invention, the feedback is explicitly signaled, e.g., in a control channel. More specifically, a transmitting UE determines certain UEs that are within the minimum required communication range and may signal, using for example the sidelink control channel, to those UEs that they are to activate their feedback mechanism so as to send ACK / NACK in response to a transmission so as to allow the transmitting UE to make a retransmissions within a useful time frame, i.e., within a timeframe during which the retransmission may be processed by the receiving UE while still providing, for example, sufficient time for the vehicular UE to react to the fully decoded message, like an emergency message to avoid, for example, a crash situation.GENERAL

[0073] Embodiments of the present invention have been described in detail above, and the respective embodiments and aspects may be implemented individually or two or more of the embodiments may be implemented in combination. It is noted that a UE may have multiple destination L2 IDs and / or multiple source L2 IDs depending on different transmission / receptions, e.g. unicast, groupcast and multicast.

[0074] Embodiments of the present invention have been described in detail above with reference to a sidelink communication using the PC5 interface. However, the present invention is not limited to the use of the PC5 interface. Any other interface allowing for a direct communication among one or more UEs may be employed, e.g., interfaces according to the IEEE 802.11p standard, the IEEE 802.15.4 standard (Zigbee), and others.

[0075] In some of the embodiments described above, reference has been made to respective vehicles being either in a mode in which SL resource allocation configuration or assistance is provided by a base station, e.g., the connected mode, also referred to as NR mode 1 or LTE mode 3 configuration, or vehicles being in a mode in which when no SL resource allocation configuration or assistance is provided by a base station, e.g., the idle mode, also referred to as NR mode 2 or LTE mode 4 configuration. However, the present invention is not limited to V2V communications or V2X communications, rather it is also applicable to any device-to-device communications, for example non-vehicular mobile users or stationary users that perform a sidelink communication, e.g., over the PC5 interface. Also, in such scenarios, the inventive aspects described above may be employed.

Claims

1. A user device, UE, (3021) for a wireless communication system, wherein the UE (3021) is configured to be connected to at least one further UE (302n) via a sidelink (304c) for a sidelink communication with the further UE (302n), and for transmitting to the further UE (302n) via the sidelink (304c), the UE (3021) is configured to obtain distance information representing a certain communication range or a certain distance around the UE (3021), initiate a HARQ feedback mechanism for the sidelink communication when the further UE (302n) is at or within the certain communication range or the certain distance, not initiate the HARQ feedback mechanism for the sidelink communication when the further UE (302n) is outside the certain communication range or the certain distance, and when determining the further UE (302n) to be within the minimum required communication range, explicitly signal to the further UE (302n) to activate the HARQ feedback mechanism so as to send the HARQ feedback in response to a sidelink transmission by the UE (3021).

2. The user device, UE, (3021) according to claim 1, wherein the UE (3021) is to explicitly signal an activation of the HARQ feedback mechanism via a control channel to the further UE (302n).

3. The user device, UE, according to any one of the preceding claims, wherein the UE (3021, 302n) comprises one or more of a mobile terminal, or a stationary terminal, or a cellular IoT-UE, or a vehicular UE, or an loT or narrowband loT, NB-IoT, device, or a ground based vehicle, or an aerial vehicle, or a drone, or a moving base station, or road side unit, or a building, or any other item or device provided with network connectivity enabling the item / device to communicate using the wireless communication network.

4. A wireless communication system comprising: one or more base stations, and a plurality of user devices, UEs, at least some of the UEs comprising a UE (3021) according to any one of the preceding claims.

5. The wireless communication system of claim 4, wherein the base station comprises one or more of a macro cell base station, or a small cell base station, or a central unit of a base station, or a distributed unit of a base station, or a road side unit, or a UE, or a remote radio head, or an AMF, or an SMF, or a core network entity, or a network slice as in the NR or 5G core context, or any transmission / reception point, TRP, enabling an item or a device to communicate using the wireless communication network, the item or device being provided with network connectivity to communicate using the wireless communication network.

6. A method for operating a user device, UE, (3021) for a wireless communication system, wherein the UE (3021) is connected to at least one further UE (302n) via a sidelink (304c) for a sidelink communication with the further UE (302n), wherein, for transmitting to the further UE (302n) via the sidelink, the method comprises: obtaining distance information representing a certain communication range or a certain distance around the UE (3021), initiating a HARQ feedback mechanism for the sidelink communication when the further UE (302n) is at or within the certain communication range or the certain distance, not initiating the HARQ feedback mechanism for the sidelink communication when the further UE (302n) is outside the certain communication range or the certain distance, and when determining the further UE (302n) to be within the minimum required communication range, explicitly signaling to the further UE (302n) to activate the HARQ feedback mechanism so as to send the HARQ feedback in response to a transmission by the UE (3021).

7. The method according to claim 6, comprising explicitly signaling an activation of the HARQ feedback mechanism via a control channel to the further UE (302n).

8. A non-transitory computer program product comprising a computer readable medium storing instructions which, when executed on a computer, perform the method of claim 6 or 7.