Method for operating a roadside network unit and roadside network unit

Description

State of the art

[0001] The invention relates to a method for operating the roadside network unit and a roadside network unit.

[0002] It is already known that vehicles are capable of exchanging information with other vehicles in their vicinity (V2V: Vehicle to Vehicle). Vehicles can also communicate wirelessly with roadside infrastructure (V2I: Vehicle to Infrastructure). Likewise, the vehicle can communicate wirelessly with a backend server on the internet (V2N: Vehicle to Network) or with a pedestrian device (V2P: Vehicle to Person). This type of communication is collectively referred to as Vehicle-to-Everything (V2X).

[0003] The development of new functions and services in the automotive industry, such as automated driving, benefits from V2X. Traffic safety, driving comfort, and energy efficiency can be improved. This leads to new products and business models for automakers, automotive suppliers, and other service providers.

[0004] The first generation of V2X applications, which will be deployed in the coming years, is primarily focused on road use. Their goal is to provide drivers with information about the road environment. Vehicles periodically provide status information (e.g., position, speed, acceleration, etc.) and / or event information (emergency response, broken-down vehicle, traffic jam). This information is typically sent locally in the form of text messages.

[0005] This event-based information can be sent from neighboring vehicles to a central network unit (base station, backend).

[0006] There are currently two competing technologies for V2X Direct Device-to-Device (D2D) communication. The first technology is based on the IEEE 802.11p standard, which forms the basis for the overarching DSRC (Dedicated Short Range Communication) standards in the USA and ETSI ITS G5 (ETSI: European Telecommunications Standards Institute; ITS: Intelligent Transport Systems) in Europe. The second technology is based on 3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution) and is also known by the abbreviation LTE-V2X. A further development of LTE-V2X technology is expected with 5G (5th generation mobile networks).

[0007] The IEEE 802.11p standard uses the PHY layer of the IEEE 802.11a standard based on Orthogonal Frequency Division Multiplexing (OFDM) with some modifications. The MAC layer is based on Enhanced Distributed Channel Access (EDCA), which is contention-based. Carrier Sense Multiple Access (CSMA) with Collision Avoidance (CSMA / CA) is also used. CSMA / CA follows the Listen-Before-Talk principle to minimize collisions on the channel. When a network device (in this context, a vehicle) has data to transmit, it performs a channel measurement to check whether the channel is occupied. If the channel is detected as empty, the network device waits a randomly determined time before beginning the scheduled transmission and then begins the transmission. If the channel is occupied during the channel measurement, the network device performs a backoff procedure, i.e.It waits a randomly determined period of time before attempting the next channel access. The higher the number of network units attempting to transmit in a geographical area, the higher the probability that a network unit will delay its transmission, leading to overall increased delays in the network. The IEEE 802.11p standard offers advantages over other WLAN standards based on IEEE 802.11 in terms of latency and signaling overhead and is adapted to the V2V use case.

[0008] The LTE extension for V2X starting with 3GPP Release 14 proposes the use of licensed and / or unlicensed spectrum for communication. V2V communication is based on a direct device-to-device interface (also known as a sidelink interface at the physical layer). Unlike 802.11p, transmission is cell-based, meaning it is scheduled by the network. Transmission rights are granted by a scheduler unit located in the base station, thus avoiding collisions and minimizing interference. Base station control can only be exercised in areas where the base station signal is available (in-coverage). In a case where no base station signal is available (out-of-coverage), communication takes place over the sidelink with predefined parameters.

[0009] The 5G Automotive Association (5GAA) wants to use the 5.9 GHz ITS frequency spectrum, where ITS-G5 systems also operate. This poses a threat to the future of ITS-G5 systems and their deployment, as some automakers have already announced plans to install ITS-G5-based systems in their cars. This would result in two different wireless communication systems transmitting in the same unlicensed frequency range, resulting in performance degradation for both technologies.

[0010] XP051082085; ZTE "Discussion on eNB type RSU and UE type RSU"; 3GPP TSG-RAN WG2 Meeting #93bis, Dubrovnik, Croatia, 11–16 April 2016; discloses extensions to the X2 interface to support inter-RSU communication for eNB-type RSUs.

[0011] Therefore, an objective technical task could be formulated as creating a coexistence mechanism for the two different wireless communication technologies in order to fairly allocate available resources. Disclosure of the invention

[0012] The problem underlying the invention is solved by a method for operating a roadside network unit according to claim 1 and a roadside network unit according to a subordinate claim.

[0013] According to a first aspect, a method for operating a roadside network unit is proposed, according to claim 1.

[0014] According to a second aspect, a roadside network unit is proposed according to claim 9.

[0015] By sending the payload data on the sidelink channel in the licensed frequency range and / or on the ad hoc channel in the unlicensed frequency range, a beneficial division of communication between the two frequency ranges is achieved. The higher the degree of penetration with network units configured according to the second aspect, the better this separation of communication between the two frequency ranges works. Accordingly, the collision probability on the sidelink channel and the ad hoc channel is reduced, and both channels benefit. Consequently, the advantages of both network technologies can be utilized, while simultaneously reducing the collision probability.

[0016] Further features and advantages can be found in the following description of exemplary embodiments. The drawing shows: Figure 1 shows a first cell-based wireless communication network and a second wireless communication network; Figure 2 shows a schematic flow diagram; Figures 3 and 4 each show a schematic block diagram; Figure 5 shows a schematic sequence diagram; and Figure 6 shows a schematic structure of a data packet.

[0017] Figure 1shows a cell-based wireless communication network CELL and an ad hoc wireless communication network VANET. The cell-based wireless communication network CELL comprises a network infrastructure-side network unit BS, a roadside network unit UE1, and a roadside network unit UE2. The network infrastructure-side network unit BS comprises a processor P_BS, a memory element M_BS, and a transceiver TC_BS. The network infrastructure-side network unit BS can also be referred to as a base station or eNodeB. The network infrastructure-side network unit BS is connected to a stationary antenna A_BS for transmitting data on a downlink channel DC and receiving data on an uplink channel UC. The antenna A_BS comprises, for example, a number of antennas and is implemented, for example, as a Remote Radio Head (RRH).The network infrastructure-side network unit BS and the antenna A_BS provide a cell C, within which the roadside network units UE1 and UE2 communicate with the network unit BS. Of course, the network infrastructure-side network unit BS can also be distributed within the framework of virtualization and consist of individual network units. For example, the network units BS, UE1, and UE2 are configured according to the LTE-V2X standard.

[0018] The roadside network unit UE1 comprises a processor P1, a memory element M1, a transceiver TA1, and a transceiver TC1. The transceiver TA1 is connected to an antenna AA1. The transceiver TC1 is connected to an antenna AC1. In one embodiment, the antennas AA1 and AC1 are implemented as a common antenna element. The roadside network unit UE2 comprises a processor T2, a memory element M2, a transceiver TC2, and an antenna A2. Computer programs are stored on the memory elements M1, M2, and M3, which, when executed on the respective processor P1, P2, and P3, implement the methods disclosed in this description. Alternatively, the processors P1, P2, and P3 are implemented as ASICs.

[0019] The two roadside network units UE1, UE2 are located within cell C and are capable of receiving data on the downlink channel DC and transmitting data on the uplink channel UC. The two roadside network units UE1, UE2 are capable of communicating directly with each other via a sidelink channel SC1 in an unlicensed frequency range NLFB and via a sidelink channel SC2 in a licensed frequency range LFB.

[0020] National authorities, such as the Federal Network Agency of the Federal Republic of Germany, draw up a frequency usage plan, which includes, for example, licenses for a particular network operator. Within the scope of the assigned license, the network operator is permitted to use the network infrastructure and terminal equipment in an assigned, i.e., licensed frequency range or frequency spectrum exclusively or as a member of a user group. In contrast, there are frequency ranges or frequency spectra that are not assigned to any network operator and are freely usable under certain conditions, such as reduced transmission / reception power.

[0021] In this description, reference is made to the single uplink channel UC and the single downlink channel DC. For example, the uplink channel UC and the downlink channel DC comprise respective subchannels, meaning multiple channels are available in both the uplink and downlink. The same applies to the sidelink channels SC1 and SC2.

[0022] The VANET wireless communication network comprises the roadside network unit UE1 and a network unit NE1. The network unit NE1 comprises a processor P3, a memory element M3, a transceiver TA3, and an antenna A3. The transceivers TA1 and TA3 are configured, for example, according to the IEEE 802.11p standard. The network units UE1 and NE1 communicate directly with each other via an ad hoc channel ADCH in the unlicensed frequency range NLFB. The ad hoc channel ADCH is arbitrated by the transceivers TA1 and TA3 using a CSMA / CA protocol (CSMA / CA: Carrier Sense Multiple Access / Collision Avoidance).

[0023] Network units NE1 and UE1 are located in proximity to network unit UE2. This proximity may cause their respective transmission powers to be sufficient for transmissions on ADCH and SC1 channels, which are transmitted in the same unlicensed NLFB frequency range, to adversely affect each other. The objective of this description is to reduce this adverse mutual influence.

[0024] The roadside network units UE1, UE2, and NE1 are arranged in respective motor vehicles vehic1, vehic2, vehic3 and are connected to a control unit (not shown) arranged therein for data exchange. In an alternative embodiment, the roadside network units UE1, UE2, and NE1 are part of the control unit in the respective motor vehicle vehic1, vehic2, vehic3. In a further alternative embodiment, the roadside network units UE1, UE2, and NE1 are arranged in a fixed infrastructure, such as a traffic light, instead of in a motor vehicle.

[0025] The sidelink channels SC1, SC2, and a sidelink in general, are defined, for example, by document 3GPP TS 36.300 V14.2.0 (2017-03), which is incorporated into this description by reference. The sidelink includes sidelink discovery, sidelink communication, and V2X sidelink communication between the network entities UE1 and UE2. The sidelink uses uplink resources and a physical channel structure similar to that of the uplink. The sidelink therefore differs from the uplink in terms of the physical channel.

[0026] The sidelink is limited to single cluster transmissions for the physical sidelink channels. Furthermore, the sidelink uses a one-symbol gap at the end of each sidelink subframe. For V2X sidelink communication, the PSCCH (Physical Sidelink Control Channel) and PSSCH (Physical Sidelink Shared Channel) are transmitted in the same subframe. For example, the sidelink channels SC1 and SC2 are the PSSCH.

[0027] The physical layer processing of transport channels in the sidelink differs from uplink transmission in the following steps: Scrambling: For PSDCH, Physical Sidelink Discovery Channel, and PSCCH, scrambling is not specific to the network entity; Modulation: 64 QAM and 256 QAM are not supported for the sidelink (QAM: Quadrature Amplitude Modulation). The PSCCH specifies sidelink resources and other transmission parameters used by the respective network entity UE1, UE2 for the PSSCH.

[0028] For PSDCH, PSCCH, and PSSCH demodulation, reference signals similar to the uplink demodulation reference signals are transmitted in the 4th symbol of the slot in the normal CP, cyclic prefix, and in the 3rd symbol of the slot in the extended CP. The sidelink demodulation reference signal sequence length corresponds to the size (number of subcarriers) of the allocated resource. For V2X sidelink communication, reference signals are transmitted in the 3rd and 6th symbols of the first slot and in the 2nd and 5th symbols of the second slot in the CP. For PSDCH and PSCCH, reference signals are generated based on a fixed base sequence, cyclic shift, and orthogonal cover code. For V2X sidelink communication, the cyclic shift for PSCCH is randomly selected for each transmission.

[0029] For measurements of the respective sidelink channel SC1, SC2, the following options are available on the network units UE1, UE2: Reception power of the sidelink reference signal (S-RSRP); Reception power of the sidelink discovery reference signal (SD-RSRP); Reception power of the PSSCH reference signal (PSSCH-RSRP); Signal strength indicator for sidelink reference signals (S-RSSI).

[0030] The ad hoc channel ADCH and the ad hoc wireless communication network VANET, for example, are defined by the IEEE standard "802.11p-2010 - IEEE Standard for Information technology--Local and metropolitan area networks--Specific requirements--Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment 6: Wireless Access in Vehicular Environments," which is incorporated into this description by reference. IEEE 802.11p is a standard extending the WLAN standard IEEE 802.11. The objective of IEEE 802.11p is to establish WLAN technology in passenger vehicles and to create a reliable interface for applications in intelligent transport systems (ITS). IEEE 802.11p is also the basis for Dedicated Short Range Communication (DSRC) in the frequency band from 5.85 to 5.925 GHz.To avoid confusion with the European DSRC version, the term ITS-G5 is used instead of DSRC, especially in Europe.

[0031] The document "ETSI EN 302 663 V1.2.0 (2012-11)", which is incorporated into this description by reference, describes the two lowest layers of ITS-G5 technology (ITS G5: Intelligent Transport Systems operating in the 5 GHz frequency band), the physical layer and the data link layer. For example, the TA1 and TA3 transceivers implement these two lowest layers and corresponding functions according to "ETSI TS 102 687 V1.1.1 (2011-07)" to use the ad hoc channel ADCH. The following unlicensed frequency ranges are available in Europe for use of the ad hoc channel ADCH, which are part of the unlicensed frequency range NLFB: 1) ITS-G5A for safety-relevant applications in the frequency range from 5.875 GHz to 5.905 GHz; 2) ITS-G5B for non-safety-critical applications in the frequency range 5.855 GHz to 5.875 GHz; and 3) ITS-G5D for the operation of ITS applications in the frequency range 5.905 GHz to 5.925 GHz.ITS-G5 enables communication between the two network entities UE1 and UE2 outside the context of a base station. ITS-G5 enables the immediate exchange of data frames and avoids the management overhead associated with network setup.

[0032] The document "ETSI TS 102 687 V1.1.1 (2011-07)", which is incorporated into this description by reference, describes a "Decentralized Congestion Control Mechanism" for ITS-G5. The ad hoc channel ADCH is used, among other things, for the exchange of data relating to traffic safety and traffic efficiency. The transceivers TA1 and TA3, for example, implement the functions described in the document "ETSI TS 102 687 V1.1.1 (2011-07)". The applications and services in ITS-G5 are based on the cooperative behavior of the roadside network units that form the ad hoc network VANET (vehicular ad hoc network). The ad hoc network VANET enables time-critical road traffic applications where rapid information exchange is necessary to provide timely warnings and assistance to the driver and / or vehicle.To ensure the proper functioning of the VANET ad hoc network, Decentralized Congestion Control Mechanisms (DCC) are used for the ITS-G5 ad hoc channel ADCH. DCC has functions located at multiple layers of the ITS architecture. The DCC mechanisms rely on channel knowledge. Channel state information is obtained through channel probing. Channel state information can be obtained using the TPC (transmit power control), TRC (transmit rate control), and TDC (transmit data rate control) methods. These methods determine the channel state information based on received signal level thresholds or preamble information from detected packets.

[0033] Figure 2 shows a schematic flow diagram for operating the roadside network unit UE1 from Figure 1In a step 202, payload data is determined for transmission to another roadside network unit. In a step 204, the determined payload data is made available for transmission on the sidelink channel in the licensed frequency range or for transmission on the ad hoc channel in the unlicensed frequency range. In a step 206, the payload data is transmitted either on the sidelink channel in the licensed frequency range or on the ad hoc channel in the unlicensed frequency range.

[0034] Figure 3 shows a schematic block diagram for the operation of the roadside network unit UE 1 from Figure 1A block 302 is assigned to an application layer APP. A block 304 is assigned to a facility layer FAC. Block 302 determines payload N1. Block 304 determines payload N2. Payload N1 and N2 can also be referred to as payload. A block 306 decides which of the three queues Q1, Q2, and Q3 the payload N1 and N2 will be provided to. Block 306 can also be referred to as a communications manager, for example.

[0035] Blocks 308 and 310 are assigned to a PDCP layer (PDCP: Packet Data Convergence Protocol). Blocks 308 and 310 comprise, for example, the functionality according to the document "3GPP TS 36.323 V14.3.0 (2017-06)", which is incorporated into this description by reference. Block 310 inserts a corresponding network identifier into the generated PDCP PDU (Protocol Data Unit) data packet to distinguish between the two types of wireless communication networks and corresponding protocol stacks used. This network identifier, which comprises, for example, a single bit, can advantageously be used on the receiver side to distinguish which unit or protocol stack the received data packet can be assigned to and thus provided with.

[0036] A block 312 is assigned to an RLC layer (RLC: Radio Link Control) and includes, for example, the functionality according to the document "3GPP TS 36.322 V14.0.0 (2017-03)", which is incorporated into this description by reference. Block 312 receives the data received from block 308 and determines data, which is forwarded to a block 314. Block 314 is assigned to a MAC layer (MAC: Media Access Control) and includes, for example, the functionality according to the document "3GPP TS 36.323 V14.3.0 (2017-06)", which is incorporated into this description by reference. Block 314 communicates with a block 316, which is assigned to a physical layer PHY. Block 316 includes, for example, the functionality according to the document "3GPP TS 36.201 V14.1.0 (2017-03)", which is incorporated into this description by reference. Block 316 sends the data N1, N2 on the sidelink channel SC2 from Figure 1. For example, the transceiver TC1 includes blocks 314 and 316.

[0037] A block 318 is assigned to the MAC layer MAC and includes, for example, the functionality according to the document "ETSI EN 302 663 V1.2.0 (2012-11)", which is incorporated into this description by reference. Block 318 receives data to be sent from block 310 or from the third queue Q3. Block 320 is assigned to the physical layer PHY and sends the payload data N1, N2 on the ad hoc channel ADCH. Figure 1 For example, block 320 includes the functionality according to document "ETSI ES 202 663 V1.1.0 (2009-11)," which is incorporated into this document by reference. Transceiver TA1, for example, includes blocks 318 and 320.

[0038] If the payload data N1, N2 is present, for example, as an IP packet (IP: Internet Protocol) or as a UDP packet (UDP: User Datagram Protocol), the payload data N1, N2 is placed in one of the two queues Q1, Q2 by block 306. Block 306 makes the decision as to which of the queues Q1, Q2 the payload data N1, N2 is placed in, based on at least one of the following information: 1) the data type within the IP packet, e.g., CAM or DENM; 2) the channel load on the channels SC2, ADCH Figure 1 , for example the channel state information CSI1 and / or CSI2; 3) from transmission requirements such as latency, reliability, data volume, which are known from the application layer; 4) the availability of one and / or the other channel SC2, ADCH from Figure 1 .

[0039] For example, if the payload data N1, N2 are of a type CAM or DENM described below, the payload data N1, N2 are placed in the third queue Q3 by block 306. Of course, other types are possible besides the CAM and DEMN types.

[0040] CAM (Cooperative Awareness Message) messages are defined in the document "ETSI EN 302 637-2 V1.3.1 (2014-09)", which is incorporated into this specification by reference. In road traffic, cooperative awareness means that road users and the roadside infrastructure inform each other about their position, driving dynamics, and characteristics. Road users include all types of road vehicles such as cars, trucks, motorcycles, bicycles, and pedestrians, as well as roadside infrastructure including traffic signs, traffic lights, barriers, and gates. CAM messages are sent at regular intervals, i.e., periodically. A CAM message indicating an emergency vehicle or a traffic jam serves not only to improve traffic efficiency but also road safety.

[0041] DENM (Decentralized Environmental Notification Message) messages are defined in the document "ETSI EN 302 637-3 V1.2.1 (2014-09)", which is incorporated into this specification by reference. A DEN (Decentralized Environmental Notification) service supports a RHW (Road Hazard Warning) application. The DEN service generates, manages, and processes DENM messages. A DENM message contains information about a road hazard or abnormal traffic situation and its location. The DEN service delivers the DENM as a payload to the ITS network and transport layer for message dissemination. An ITS application disseminates a DENM message to the network entities through direct vehicle-to-vehicle or vehicle-to-infrastructure communication on the ad hoc channel ADCH.On the receiving side, the DEN service of a receiving ITS-S processes the received DENM message and delivers the DENM content to an application. This application transmits the information to the driver or vehicle if the information about the road condition is relevant to the driver. The driver or vehicle is then able to take appropriate actions to respond to the situation.

[0042] Alternatively or in addition to the type of payload data N1, N2, the decision as to which of the three queues Q1 to Q3 the payload data N1, N2 is placed in is made depending on local channel state information CSI1 and / or CSI2. The local channel state information CSI1 is determined by block 314 and includes, for example, a ratio of scheduled radio resources to free radio resources on the sidelink channel in the licensed frequency range. The local channel state information CSI2 is determined by block 318 and includes, for example, a number of roadside network units directly accessible via the ad hoc channel, i.e., a local density of roadside network units. The channel state information CSI2 indicates, for example, that the ad hoc channel in the unlicensed frequency range has a high occupancy, i.e.,The number of detected reachable roadside network units in the vicinity exceeds a threshold. If the ad hoc channel is highly congested, block 306 decides to place the payload data N1, N2 in the first queue Q1.

[0043] In one embodiment, the local channel state information CSI1 and CSI2 are compared with each other and, depending on the comparison, it is determined into which of the queues Q1, Q2 or Q3 the payload data N1, N2 is placed.

[0044] Placing data in queue Q1 means that the stored data is sent on the sidelink channel in the licensed frequency range. Placing data in queue Q2 means that the stored data is sent on the ad hoc channel in the unlicensed frequency range via block 310, which is assigned to the PDCP layer. Placing data in queue Q3 means that the stored data is sent on the ad hoc channel in the unlicensed frequency range, with the stored data being immediately received, i.e., directly fed, by block 318, which is assigned to the MAC layer. This means that the payload data N1, N2, which are fed to queue Q3 from the application layer APP or the facility layer FAC, are provided from there directly to the MAC layer for transmission via the ad hoc channel.

[0045] Blocks 308, 310, 312, 314, and 316 are part of an LTE-V protocol stack (S-LTE-V). Blocks 318 and 320 are part of an ITS-G5 protocol stack (S-ITS-G5), whereby only the two lowest layers, MAC and PHY, are implemented here, and the remaining layers are not exclusively intended for ITS-G5. This advantageously enables only a simplified transceiver (TC1).

[0046] Figure 4 shows a schematic block diagram for the operation of the roadside network unit UE 1 from Figure 1 . In contrast to Figure 3 A reception of payload data N1, N2 is shown. A block 402 determines, depending on the data provided by block 318, whether the payload data N1, N2 is provided directly to blocks 302 or 304, or whether the received data comprises a PDCP packet PDU and is thus provided to block 310.

[0047] Figure 5shows a schematic sequence diagram with sequences S1 and S2. In a step 500, payload N1 is determined in the application layer. In a step 502, a decision is made that the determined payload N1 should be sent on the ad hoc channel ADCH. In a step 504, the payload N1 is provided to the transceiver TA1. In a step 506, the transceiver TA1 arbitrates the ad hoc channel ADCH. If the arbitration is successful, ie, if the ad hoc channel ADCH is free for data transmission, the transceiver TA1 sends the payload N1 on the ad hoc channel ADCH in the unlicensed frequency range in a step 508.

[0048] In a step 510, the payload N1 is determined in the application layer. In a step 512, it is decided that the determined payload N1 should be sent on the sidelink channel SC2. In a step 514, the processor P1 makes the payload N1 available to the transceiver TC1 for transmission. In a step 516, the transceiver TC1 transmits a scheduling request message BSR, for example a buffer status report, on the uplink channel UC to the network infrastructure-side network unit BS. A scheduling grant message G is determined in a step 518 and transmitted in a step 520 on the downlink channel DC to the roadside network unit UE1. The scheduling grant message G1 comprises an allocation of radio resources on the sidelink channel SC2. On the allocated radio resources of the sidelink channel SC2, the determined payload data N1 is sent to the roadside network unit UE2 in a step 522.

[0049] In one embodiment of step 502 and step 512, the determined payload N1 is linked to a transmission request. This request can, for example, be a traffic class of the payload N1, N2, in particular a traffic class according to the document "ESTI 636-4-2 V1.1.1 (2013-10)", which is incorporated into this description by reference. The traffic class that leads to transmission on the ad hoc channel ADCH includes, for example, payload data of the DENM and CAM types, as well as other possible types of payload data / messages. The traffic class that leads to transmission on the sidelink channel SC2 includes payload data of a different type OTH, such as non-traffic-critical information such as advertising to the driver.

[0050] In a further embodiment of steps 502 and 512, the transmission requirement is a size of the payload N1, a latency requirement, and / or a desired reliability of the transmission.

[0051] In a further embodiment of steps 502 and 512, the request comprises a transmission on the two channels SC2 and ADCH, thus increasing the transmission reliability through redundancy.

[0052] In a further embodiment of steps 502 and 512, the channel state information CSI2 of the ad hoc channel is used to determine the decision for provision on one of the channels ADCH, SC2. Provision for transmission on the sidelink channel SC2 occurs when the channel state information CSI2 indicates high occupancy above a predetermined threshold. For example, the number of roadside network units directly accessible via the ad hoc channel ADCH has reached above a threshold, so that reliable delivery of the payload P1 can only be guaranteed via the sidelink channel SC2. Accordingly, if the aforementioned threshold is exceeded, the payload P1 is made available for transmission on the sidelink channel SC2 according to steps 512 and 514.

[0053] In a further embodiment of steps 502 and 512, the channel state information CSI1 of the sidelink channel is used to determine the decision to provide to one of the channels ADHC, SC2.

[0054] In a further embodiment of steps 502 and 512, the channel state information CSI1 and CSI2 are used to determine the decision to provide to one of the channels ADHC, SC2.

[0055] In one embodiment of steps 502 and 512, the payload N1 of the second queue Q2 is Figure 3 provided when the size of the payload N1 falls below a specified threshold. This advantageously allows small amounts of data to be transmitted in the unlicensed frequency range.

[0056] Figure 6shows a schematic structure of a MAC-FRAME data packet according to IEEE 802.11 and explains the interaction between blocks 310 and 318. The MAC-FRAME data packet is transferred from block 318 to Figure 3 created and from Block 318 in Figure 4 read. The MAC-FRAME data packet includes a header H1, a frame body FB1, and a frame check sequence FCS.

[0057] The frame body FB1 comprises the data packet PDCP PDU, which has a header H2 and a data part D, which includes, for example, the payload data. The network identifier K is located in the header H2, indicating which of the protocol stacks S-LTE-V, S-ITS-G5 a respective data packet PDCP PDU is assigned to. Accordingly, on the receiver side, in block 402, depending on the network identifier K, it is determined whether the received frame body FB1 is provided to block 310 or to one of blocks 302 and 304. In an alternative embodiment not shown, the network identifier K is located in an optional parameter field of the header H1.

Claims

1. Method for operating a roadside network unit (UE1), wherein the roadside network unit (UE1) is designed to send payload data (N1, N2) on a sidelink channel (SC2) of a cell-based wireless communication network (CELL) in a licensed frequency band (LFB) and on an ad hoc channel (ADCH) of an ad hoc wireless communication network (VANET) in an unlicensed frequency band (NLFB); the method comprising: - determining (302; 500; 512) payload data (N1, N2) for sending to at least one other roadside network unit (UE2; NE1); - delivering (304; 504; 514) the payload data (N1, N2) for sending on a sidelink channel (SC2) of a cell-based wireless communication network (CELL) in a licensed frequency band (LFB) and for sending on an ad hoc channel (ADCH) of an ad hoc wireless communication network (VANET) in an unlicensed frequency band (NLFB); and - sending (304; 508; 522) the payload data (N1, N2) on the sidelink channel (SC2) in the licensed frequency band (NLFB) and on the ad hoc channel (ADCH) in the unlicensed frequency band (NLFB).

2. Method according to Claim 1, wherein the payload data (N1, N2) are linked to a request for transmission, and wherein the delivery (504; 514) for sending on the sidelink channel (SC2) or for sending on the ad hoc channel (ADCH) is made on the basis of the request.

3. Method according to Claim 2, wherein the request comprises a traffic class of the payload data (N1, N2), in particular a traffic class according to ETSI TS 102 636-4-2 V1.1.1 (2013-10).

4. Method according to either of Claims 2 to 3, wherein the request for transmission comprises a size of the payload data (N1, N2) and / or a latency request and / or a reliability of the transmission of the payload data (N1, N2).

5. Method according to one of the preceding claims, wherein local channel status information (CSI2) pertaining to the ad hoc channel (ADCH) is determined, and wherein the delivery (504; 514) is made on the basis of the local channel status information (CSI2).

6. Method according to the preceding claim, wherein the payload data (N1, N2) are delivered for sending on the sidelink channel (SC2) when the local channel status information (CSI2) indicates an occupancy of the ad hoc channel (ADCH) above a threshold value.

7. Method according to one of the preceding claims, wherein the payload data (N1, N2) are delivered to a PDCP layer for sending on the ad hoc channel (ADCH) when the size of the payload data (N1, N2) is below a threshold value.

8. Method according to one of the preceding claims, wherein a protocol stack (S-ITS-G5) according to ITS-G5 comprises no protocol layers above layer 2 that are exclusively associated with ITS-G5.

9. Roadside network unit (UE1) comprising: - a processor for determining (302; 500; 512) payload data (N1, N2) for sending to at least one other roadside network unit (UE2; NE1), for delivering (304; 504; 514) the payload data (N1, N2) for sending on a sidelink channel (SC2) of a cell-based wireless communication network (CELL) in a licensed frequency band (LFB) and for delivering (304; 504; 514) the payload data (N1, N2) for sending on an ad hoc channel (ADCH) of an ad hoc wireless communication network (VANET) in an unlicensed frequency band (NLFB); and - a transceiver (TC1) for the cell-based wireless communication network (CELL) for sending (304; 522) the payload data (N1, N2) on the sidelink channel (SC2) in the licensed frequency band (NLFB) and a transceiver (TA1) for the ad hoc wireless communication network (VANET) for sending (304; 508) the payload data (N1, N2) on the ad hoc channel (ADCH) in the unlicensed frequency band (NLFB).

10. Network unit (UE1) according to Claim 9, designed for carrying out the method according to one of Claims 2 to 8.