Antenna reference signals for distance measurements

Abstract

The present invention provides a method of communicating vehicle positioning information, wherein signals are transmitted from at least one vehicle mounted antenna for indicating a position of the vehicle to another entity, the signals including information concerning at least one of an identity of the at least one antenna and information providing a displacement between the at least one antenna and a boundary of the vehicle.

Claims

1. A method of communicating vehicle positioning information, wherein signals are transmitted from at least one vehicle mounted antenna for indicating a position of the vehicle to another entity, the signals including information concerning at least one of information providing a displacement between the at least one antenna and a boundary of the vehicle, and an identity of the at least one antenna, the identity of the at least one antenna being such as to enable the another entity to determine the information providing the displacement between the at least one antenna and the boundary of the vehicle.

2. The method according to claim 1, wherein the signals include both the information concerning at least one of the identity of the at least one antenna and the information providing the displacement between the at least one antenna and the respective boundary of the vehicle.

3. The method according to claim 1, wherein the information concerning the identity of the at least one antenna comprises at least one of an antenna identifier, an indication of a position of the antenna with respect to the vehicle, a type of the vehicle, a vehicle identifier and a number of antennas on the vehicle.

4. The method according to claim 1, wherein the information providing the displacement between the at least one antenna and the boundary of the vehicle comprises information relating to an identity of the vehicle sufficient for the another entity to derive positioning information of the at least one antenna.

5. The method according to claim 1, wherein the signals are transmitted as sidelink signals over a PC5 air interface and wherein differing antennas of the vehicle are arranged to transmit in a manner such that a first antenna uses a first resource element and a second antenna uses a second resource element different from the first resource element.

6. The method according to claim 5, wherein the signals are transmitted as distance determination reference signals with signals from the first antenna being transmitted in a first time slot and signals from the second antenna being transmitted in a second time slot.

7. The method according to claim 1, wherein the signals are transmitted in response to the vehicle receiving a message from the another entity requesting the vehicle to transmit positioning information.

8. The method according to claim 7, wherein the signals are repeatedly transmitted until the vehicle receives a message from the another entity requesting the vehicle to cease transmission of the signals.

9. The method according to claim 1, wherein the signals are transmitted at a variable frequency, the variable frequency being dependent on a relative velocity between the vehicle and the another entity.

10. The method according to claim 1, wherein the information providing the displacement between the at least one antenna and the boundary of the vehicle is dependent on a current orientation of the vehicle with respect to the another entity.

11. The method according to claim 10, wherein additional antennas are activated if the vehicle changes its orientation with respect to the another entity.

12. The method according to claim 1, wherein the signals are sent by means of at least one of demodulation reference signals, sidelink synchronization signals and distance determination reference signals.

13. The method according to claim 1, wherein the another entity is a second vehicle.

Description

(1) Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

(2) FIG. 1 shows a known sidelink resource grid for use on an LTE PC5 interface including primary and secondary sidelink synchronization signals and a physical sidelink broadcast channel;

(3) FIG. 2 illustrates a first vehicle positioning situation with two vehicles:

(4) FIG. 3 shows a sidelink resource grid for a two-antenna vehicle;

(5) FIG. 4 is a message sequence chart for activating a deactivating vehicle positioning;

(6) FIG. 5 is a second message sequence chart for velocity dependent vehicle positioning; and

(7) FIG. 6 shows an example of a dynamic antenna configuration.

(8) Referring to FIG. 2 there is shown a schematic relation between two vehicles 1 and 2 implementing the present invention. Each of the vehicles has two antennas, A1.1, A1.2, A2.1 and A2.2 with each antenna being positioned at a known position with respect to boundaries of the respective vehicles. As shown, antenna A1.2 is located at a distance AO1.2.sub.long from a rear boundary of vehicle 1 and antenna A2.1 is located a distance AO2.1.sub.long from a front boundary of vehicle 2 (the subscript “long” indicating that the distance is in a longitudinal direction).

(9) In a first embodiment, antenna signals that allow corrections to be performed for high accuracy vehicle positioning are disseminated.

(10) In this embodiment, each vehicle antenna disseminates distance determination reference signals (DD-RS) in a sidelink resource grid which is used on the LTE PC5 air interface. These DD-RSs may for instance comprise an antenna ID (that is ideally unique in the respective location), or it may comprise an antenna ID (that is unique per vehicle) plus a vehicle ID (that is ideally unique in the respective area). Here, vehicle 1 has coded the following exemplary antenna IDs on the DD-RS physical signals, which are transmitted on reserved resource elements for its respective antennas: The front antenna is A1.1 and rear antenna is A1.2. Likewise, vehicle 2 uses the following antenna identifiers represented by its DD-RS physical signals: the front antenna is A2.1 and the rear antenna is A2.2.

(11) Furthermore, each vehicle is enabled to transmit over any of the available physical sidelink channels PSxCH, such as the PSBCH, an individual set of (primarily geometrical) ranging information. In one embodiment, such an individual set may be associated with a sidelink discovery message, or included in a SidelinkUEInformation RRC message. In another embodiment, this individual set may be part of (or associated with) a new type of message especially defined for ranging purposes.

(12) In this embodiment, all antennas are mounted very close to the vehicles' outer boundaries and are centrally arranged on the engine hood or on the car's trunk (or, alternatively, at the front and rear bumpers). The height over street level can be omitted in this example for reasons of simplicity.

(13) In the example, vehicle 1 transmits the following set of data: Vehicle-ID: abcd1234 Type of Vehicle: Midsize car Number of active antennas: 2 Antenna A1.1=front antenna, centrally located, 0 mm away from the car's front edge. Antenna A1.2=rear antenna, centrally located, 40 mm away from the car's rear edge.
and vehicle 2 transmits the following set of data: Vehicle-ID: dcba4321 Type of Vehicle: Full size car Number of active antennas: 2 Antenna A2.1=front antenna, centrally located, 75 mm away from the car's front edge. Antenna A2.2=rear antenna, centrally located, 60 mm away from the car's rear edge

(14) In one embodiment, some details of the sets defined above are not transmitted. Instead each vehicle's individually transmitted Vehicle-ID is used to derive the other pieces of information, for example those pertaining to the respective car's outer boundaries, from a data base or by means of an algorithm.

(15) Each of the two involved vehicles can now perform a distance determination method according to the following principles.

(16) Vehicle 1 is aware of the geometrical offset of its own antennas A1.1 and A1.2. For example, these geometrical data were stored in a vehicle internal storage. Vehicle 1 uses its own antenna A1.2 for rear measurements (i.e. in order to determine the distance to following vehicles). From the various DD-RSs transmitted by vehicle 2 as physical reference signals (one per antenna mounted at vehicle 2) and the set of ranging information received over one of the physical sidelink channels PSxCH, vehicle 1 knows which antenna reference signal to use (and which to neglect) for distance measurements plus the respective geometrical antenna offset, namely front antenna A2.1 with an offset of 75 mm. The distance measurement itself (i.e. obtaining the value “D.sub.A1.2-A2.1”) is done by well-known means and not part of this invention, e.g. by calculating the wave travelling time from the received DD-RS and multiplying it with the speed of light.
VD.sub.long=D.sub.A1.2-A2.1−AO2.1.sub.long−AO1.2.sub.long
VD.sub.long=D.sub.A1.2-A2.1−(75 mm+40 mm)
VD.sub.long=D.sub.A1.2-A2.1−115 mm

(17) In order to determine the distance between the two vehicles, the geometrical details pertaining to other antennas (such as antenna A2.2) don't have to be taken into account, and the reference signals transmitted by those antennas (e.g. antenna A2.2) don't have to be analysed. The term D.sub.A1.2-A2.1 is the measured distance between the antennas A1.2 and A2.1, while the subtrahend in the formula above represents a correction factor. The result “VD.sub.long” is the distance between the front edge of vehicle 2 and the rear edge of vehicle 1.

(18) In the exemplary syntax Ax.y chosen above, the letter “x” represents the vehicle and the letter “y” specifies the antenna associated with said vehicle. For the front antenna “y” is set to “1”, for the rear antenna “y” is set to “2”. Other syntactical structures and/or other values are of course also possible.

(19) A vehicle may also use the various antenna identifiers received as physical reference signals from nearby other vehicles to retrieve the desired set(s) of ranging information from a data base, for instance if the transmission of the ranging information by the other vehicles on any of the physical sidelink channels PSxCH over the PC5 air interface was defective, or if there was no transmission at all. The antenna identifiers may be encoded in a form of a reference or link for example pointing to a file's storage location in a data repository. The reference or link may consist of or include a form of uniform resource locator (URL), or derivations thereof. The data base may be a logical entity that consists of several distributed physical memory entities and any set of ranging information may be stored there either in parts or in its entirety. The data base may reside in (at least one of) the vehicle(s) or in some third-party servers on the internet or in both; and the data base queries may take place for example at application layer, for instance over the PC5 air interface or over LTE Uu air interface or over both.

(20) FIG. 3 shows an example sidelink resource grid in which certain resource elements (here: two for each antenna) are reserved for the DD-RS physical signals that may be configured to carry antenna identifiers. The different DD-RS physical signals are distributed in the example sidelink resource grid with an offset in the time domain to one another, whereas different symbols from the same DD-RS physical signal are separated in frequency domain. A resource element Rx.1 that is used by a first antenna Ax.1 for dissemination of its unique DD-RS physical signal is not used by the second antenna Ax.2 (and vice versa). Thus, the receiving antenna is not required to estimate the quality of all spatially separated radio resources; instead the receiving side is only required to measure on resources that are assigned to the DD-RSs (and the related antenna(s)) that are of relevance, as indicated in the set of ranging information (depending on the use case).

(21) In another example, some or all antennas are using the same time-frequency resources with different DD-RSs for each antenna. This is advantageous, as it saves resources.

(22) In yet another example, all antennas use the same DD-RS, but different time-frequency resources. This is advantageous, as the receiver can be built more simply as only one correlator will be used to derive the distance to all antennas, instead of one correlator for each antenna. For this method to work properly, it must be clearly defined which antenna is using which of the time-frequency resources.

(23) A set of (primarily geometrical) ranging information e.g., obtained from higher layers in the protocol stack may be transmitted via any of the physical sidelink channels PSxCH (e.g., on the PSSCH or the PSBCH).

(24) A possible encoding option in ASN.1 notation for the set of ranging information is given below. In the present example with two antennas per vehicle, the variable “maxAntennas” takes on the value of “2”, so that the portion labelled with “AntennaGeoDetails” appears twice, firstly for antenna Ax.1, e.g. the front antenna on vehicle and secondly for antenna Ax.2, e.g. the rear antenna on vehicle ‘x’. The variable “Antenna-ID” is used to correlate the DD-RS transmitted via physical layer reference signals with the corresponding set(s) of ranging information transmitted via any of the physical sidelink channels PSxCH. The DD-RS is generated by using the Antenna-ID. Any sequences with good correlation properties can be used, for example Zadoff-Chu sequences as used in LTE for the random access preambles (cf. 3GPP TS 36.211 chapter 5.7.2.). In this case, an Antenna-ID is mapped to one root sequence number “u” and one value for the cyclic shift “N_CS”. This mapping could either be done static, i.e. it specified in a standard and the mapping table is stored on the mobile devices, or the mapping table is signalled to the mobile devices, or the values for “u” and “N_CS” are signalled directly as part of the ranging information instead of transmitting Antenna-IDs.

(25) TABLE-US-00001 -- ASN1START RangingInformation ::= SEQUENCE { Vehicle-ID ::= OCTET STRING, VehicleType ::= ENUMERATED {bicyle, motorcycle, midsize-car, fullsize-car, bus, truck, ...}, Link ::= OCTET STRING, NumberOfAntennas ::= ENUMERATED {1, 2, 4, 8}, Platooning ::= SEQUENCE { MemberOfPlatoon ::= BOOLEAN, PositionInPlatoon ::= ENUMERATED {first, middle, last}, } ShuntingSpace ::= SEQUENCE { ShuntingSpaceFront ::= ENUMERATED {cm10, cm20, cm30, cm40, cm50, ...}, ShuntingSpaceLeft ::= ENUMERATED {cm10, cm20, cm30, cm40, cm50, ...}, ShuntingSpaceRight ::= ENUMERATED {cm10, cm20, cm30, cm40, cm50, ...}, ShuntingSpaceRear ::= ENUMERATED {cm10, cm20, cm30, cm40, cm50, ...}, } LoadingZone ::= SEQUENCE { LoadingZoneFront ::= ENUMERATED {m0.5, m1, m1.5, m2, m2.5, m3, ...}, LoadingZoneLeft ::= ENUMERATED {m0.5, m1, m1.5, m2, m2.5, m3, ...}, LoadingZoneRight ::= ENUMERATED {m0.5, m1, m1.5, m2, m2.5, m3, ...}, LoadingZoneRear ::= ENUMERATED {m0.5, m1, m1.5, m2, m2.5, m3, ...}, } AntennaGeoDetailsList ::= SEQUENCE (SIZE (1..maxAntennas)) OF AntennaGeoDetails } AntennaGeoDetails SEQUENCE { Antenna-ID ::= OCTET STRING, AntennaType ::= ENUMERATED {Static, Dynamic}, OperationMode ::= ENUMERATED {On, Off}, Position ::= ENUMERATED {front, left, right, rear, mid, upper, lower, ...}, DetailedPosition ::= ENUMERATED {front-left, front-centre, front-right, ..., rear-left rear-centre, rear-right}, FrontOffset ::= ENUMERATED {mm5, mm10, mm15, mm20, mm25, mm30, ...}, LeftOffset ::= ENUMERATED {mm5, mm10, mm15, mm20, mm25, mm30, ... }, RightOffset ::= ENUMERATED {mm5, mm10, mm15, mm20, mm25, mm30, ...}, RearOffset ::= ENUMERATED {mm5, mm10, mm15, mm20, mm25, mm30, ...}, Height ::= ENUMERATED {mm100, mm200, mm300, mm400, mm500, ...} } -- ASN1STOP

(26) The ASN.1 structure above also allows for expressing additional space requirements a vehicle might have for shunting or loading/unloading of goods.

(27) The information element “Link” may contain a reference (e.g., a model specific reference in form of a URL) for data base interrogations as described above. Consequently, some parts of the proposed structure above may alternatively be derived from said data base.

(28) Each vehicle transmits an individual set of ranging information. In one embodiment, such an individual set may be associated with (or included in) a sidelink discovery message, or a SidelinkUEInformation RRC message. In another embodiment, this individual set may be part of (or associated with) a new type of message especially defined for ranging purposes.

(29) The two information elements “AntennaType” and “OperationMode” are included in view of a use case described below, in which a vehicle's outer boundaries may change dynamically, for instance when a truck pulling a trailer is taking a turn).

(30) As indicated, a fourth aspect of the invention is the activation and deactivation of the signals on a per need basis. FIG. 4 shows an exemplary signalling flow between vehicles 1 and 2.

(31) Vehicle 1 may request (“Turn On Ranging”) the transmission of at least one of the two pieces of information from vehicle 2, namely the set of (primarily geometrical) ranging information and/or the antenna identifiers. The former may be received from higher layers of the protocol stack and transmitted over the PC5 air interface on any of the physical sidelink channels PSxCH (e.g., associated with or included in a sidelink discovery message or a SidelinkUEInformation RRC message, or it may be part of a new type of message especially defined for ranging purposes). The latter may be directly impressed into the physical layer as reference signals. The order of these two different types of information in FIG. 4 was chosen arbitrarily and may differ in real life deployments. Vehicle 1 may request the two pieces of information from vehicle 2 either once or repeatedly. Each pieces of information may therefore be transmitted only once or repeatedly. This is not shown in FIG. 4 for sake of simplicity.

(32) The trigger message (“Turn On Ranging”) sent by vehicle 1 can be transmitted in a form of a sidelink broadcast message over the PC5 interface to multiple vehicles. In another embodiment the trigger message sent by vehicle 1 is transmitted in form of a sidelink dedicated message over the PC5 interface to a single vehicle.

(33) Based on the information received from vehicle 2, vehicle 1 is enabled to select the relevant antenna(s) A2.y for ranging measurements and to apply a correction factor to arrive at the correct distance between the vehicles in question as described above.

(34) The message sequence of FIG. 4 ends with a termination message (“Turn Off Ranging”) that may be transmitted by vehicle 1 over the PC5 interface either in form of a sidelink broadcast message to multiple vehicles, or in form of a sidelink dedicated message to a single vehicle.

(35) In yet another embodiment, the relative velocity between two vehicles is used to alter the symbol rate of the reference signals. The relative velocity could for example be derived in the following way. Vehicle 1 may inform (cf. “Velocity Indication #1” in FIG. 5) vehicle 2 about its velocity V1 (or about a desired periodicity for the transmission of the set of (primarily geometrical) ranging information and/or the DD-RS). Vehicle 2 may then calculate the relative velocity VR between the vehicles and use this value to control the DD-RS dissemination pattern on its own antennas A2.y. In the next step vehicle 2 may inform vehicle 1 about its own velocity V2 or about the relative velocity VR or both (cf. Velocity Indication #2 in FIG. 12). Vehicle 1 in turn may now itself calculate the relative velocity VR′ (and verify the relative velocity VR received from vehicle 2) and use the result of these operations to control the DD-RS dissemination pattern on its own antennas A1.y. If needed, vehicle 1 may inform vehicle 2 about the verification results and possibly provide a modified relative velocity VR* to vehicle 2 (cf. Velocity Indication #3 in FIG. 5). This feedback may be used to fine tune the DD-RS dissemination pattern from vehicle 2. In another example, the relative velocity is derived from the Doppler frequency of the received sidelink signals. In yet another example, the relative velocity is calculated from the changes over time in the measured distance.

(36) The message sequence of FIG. 5 may be repeated several times either partially or in its entirety. The vehicles may also negotiate a duration for the dissemination of a sequence of the DD-RS with a fixed periodicity. This is not shown in FIG. 5 for sake of simplicity.

(37) In this approach, the relative velocities VR, VR′ or VR* between the two vehicles may determine the dissemination periodicities of the antenna identifiers. That means, if vehicle 1 is running at low speed and vehicle 2 is running at high speed, then the dissemination periodicity of the various DD-RS on the various antennas may need to be increased. On the other hand, if vehicle 1 is running at a given speed and vehicle 2 is running at a similar speed, then the dissemination periodicity of the various DD-RS on the various antennas can be reduced. For this, thresholds pertaining to the relative velocity between the vehicles may be provisioned and used in the respective vehicles to control the DD-RS occupation patterns in the resource grid and with this also the symbol rate (i.e. the dissemination periodicity).

(38) Alternatively or in addition to the relative velocity, the change of the symbol rate and/or the occupation pattern for insertion of the signals in the time domain can be controlled by the velocity over ground of the respective vehicle, e.g. in a way that more symbols of the DD-RS are sent for fast moving vehicles and less for slow moving or parking vehicles.

(39) Depending on the type of vehicle, there may be static and dynamic antenna configurations for the method as will be explained below.

(40) FIG. 6 shows a tractor/trailer combination in a curve. As one can easily see from FIG. 6, the outer boundaries of this vehicle change dynamically as the vehicle moves. For example, new edges appear in zone Z1. It is therefore another aspect of the present invention to activate and deactivate antennas in a dynamic fashion to cover cases like the one shown in FIG. 6.

(41) The change of the vehicle's outer boundaries can be detected by performing distance measurement between antennas associated with the same vehicle (here, the tractor/trailer combination of FIG. 6 is regarded as being one vehicle). In case of the example in FIG. 6, the antennas A2.1 and A1.2 will detect that they move closer to each other when the tractor/trailer combination turns right. Likewise, the antennas A2.4 and A1.3 can detect that they move further apart in the same situation.

(42) An additional aspect of the present invention is therefore intra-vehicle distance measurements (i.e. configuring relevant antennas that are mounted at the same vehicle with reference signals so that they are able to determine the distance between each other antennas). Alternatively, the rotation angle α in the coupling could be used to detect a variation in a vehicle's outer boundaries.

(43) In zone Z1 one can assume that the antennas A1.2 (left rear antenna of the tractor) and A2.1 (left front antenna of the trailer) are mounted on the edges so that they can be easily used for the method—they just have to be activated, if they haven't been used so far.

(44) In respect of the above, the names and encoding variants of the information elements (IE) discussed in the present document shall be understood to merely serve as examples. There are many other options for the encoding of parameters and their values. This invention is by no means restricted to the encoding examples disclosed here.

(45) Furthermore, the parameters may be sub-divided in one way or another, for example they may be collated in a new or already existing hierarchical structure, or grouped together with other information elements for instance in form of a list.