Patent Description:
The basic ITS communication architecture is described in ETSI (European Telecommunications Standards Institute) Standard EN <NUM><NUM> and related ETSI standards. A most recent development in ITS is the so-called Collective Perception Service (CPS) to share information on objects detected by one communication partner, such as a vehicle onboard unit (OBU) or a roadside unit (RSU) (generally called "ITS station", ITS-S), with another communication partner (ITS-S). The CPS in ITS is described in, e.g., ETSI Technical Report TR <NUM><NUM> and ETSI Technical Specification TS <NUM><NUM>.

<FIG> show the present concept of CPS to share "perceptions" (detections, analysis and/or trackings) of objects among participants according to the above-mentioned ETSI standards. In <FIG> a vehicle <NUM> on a road <NUM> perceives an object <NUM>, e.g., another vehicle, by means of an own sensor <NUM> such as a camera, a radar sensor, lidar sensor etc., with a field of view <NUM>. In <FIG> the vehicle <NUM> may be additionally aware of a third vehicle <NUM> around a bend <NUM> of the road <NUM> which obstructs the direct view to the vehicle <NUM>, by means of a wireless communication <NUM> between an ITS-S aboard the vehicle <NUM> and an own ITS-S aboard the vehicle <NUM>. In <FIG> the third vehicle <NUM> around the bend <NUM> perceives a fourth vehicle <NUM> by means of an own sensor <NUM> with a field of view <NUM> and shares information
about this perception over the wireless communication <NUM> with the first vehicle <NUM>. Vehicle <NUM> thus enjoys the benefit of a "Collective Perception" (CP) from other ITS-S-equipped participants so that it becomes aware of objects beyond its own sensor range even when those objects are not equipped with an ITS-S on their own.

Similarly to the perception of objects the CPS standardized in ETSI TR <NUM><NUM> also provides for the sharing of information on free space areas a participant may move into, for example for collision avoidance or maneuvering, which is likewise described in <CIT>.

The messages exchanged in the CPS to share such perceptions of objects and/or free space areas to inform the communication partner about, e.g., the existence, speed, distance, position, direction etc. of a perceived object or the existence, position, shape, size etc. of a perceived free space area are called Collective Perception Messages (CPMs). <FIG> shows the general structure of a CPM as defined in ETSI TR <NUM><NUM>. The CPM <NUM> contains - apart from an ITS PDU (Protocol Data Unit) header <NUM> designating the message as a "CPM package" - a set of CPM parameters <NUM> in the form of one or more data containers <NUM> - <NUM>, in particular:.

Information about perceived free space areas may be transported in either one or more of the sensor information containers <NUM> or one or more of the perceived object containers <NUM>, depending on the implementation of the ETSI TR <NUM><NUM> standard.

In particular, according to ETSI TR <NUM><NUM> a perceived object container <NUM> may contain sensor data such as distance and direction or position, shape and size of a perceived free space area as measured by the ITS-S's sensor, and an indication of the time of measurement of the sensor data. For some data elements, e.g., for distance, speed, angle and object dimension values of a perceived object or for the existence of a free space area, ETSI TR <NUM><NUM> also provides for confidence measures of the respective data values. The receiving ITS-S can then assess the trustworthiness of the collectively shared perception information.

In general, it is up to the receiving ITS-S to make good use of the wealth of collectively shared sensor data to appropriately execute road safety applications, such as driver warnings or automatic braking and steering functions for moving into a free space area for collision avoidance. However, the wealth of information can overload the processing capabilities of receiving ITS-S in heavy traffic situations, leading either to malfunctions or the need for higher processing powers with increased costs.

It is an object of the invention to overcome the shortcomings of the prior art and to provide novel devices for improving CPS in ITS.

To this end, the invention creates a novel ITS service station, comprising:.

The novel ITS service station of the invention aggregates CPMs from surrounding ITS-S into aggregated ("third") CPMs so that other ITS-S listening to these broadcasts are eased from the burden of following a multitude of ITS-S and processing a multitude of CPMs to assess free maneuvering space. The ITS service station of the invention therefore contributes to reduce the complexity of the CPS for listening ITS-S, in particular when the aggregated CPMs of the ITS service station are prioritized over "normal" CPMs during communication or receipt. Listening ITS-S can thus gain a better overview about any possible free space areas in their vicinity without the need to fuse free space area information from a multitude of CPMs themselves.

A preferred embodiment of the invention is characterized in that the first sensor data includes a first confidence measure of said first free space area and the at least one second sensor data includes a second confidence measure of said second free space area, wherein the aggregator is configured to calculate a third confidence measure from said first and at least one second confidence measures and to include said third confidence measure in the third sensor data.

An aggregated ("third") data in the aggregated ("third") CPM may have a better aggregated ("third") confidence measure when it had been aggregated from multiple data sources. Therefore, any ITS-S listening to both "normal" CPMs (here: the first and second CPMs) and "aggregated" CPMs (here: the "third" CPM of the inventive ITS service station) can choose to process and consider the CPM showing the best confidence measure for a specific maneuvering space needed, leading to an implicit prioritizing of the CPMs of the ITS service station at the receiving ITS-S. The receiving ITS-S may ignore sensor data regarding the maneuvering space from other CPMs in favor of the sensor data in the aggregated CPM. Processing load in the receiving ITS-S is thus significantly reduced, in particular in heavy traffic situations, e.g., at an intersection, and low-cost ITS-S with modest processing capabilities can be used without compromising safety.

In one embodiment, the aggregator is configured to aggregate said first and second sensor data by geometrically intersecting the first and second free space areas indicated therein and by including the resulting intersection area in the third sensor data. The area of intersection is thus an area which is confirmed by at least two disseminating ITS-S as being "free", i.e., unoccupied by another vehicle or object. This double confirmation increases the trustworthiness of the aggregated CPM on free space area information. Furthermore, if the aggregated (third) CPM contains a (third) confidence measure for the (third) sensor data on the intersection area, then this third confidence measure can be chosen as equal to or better than the better one of the first and second confidence measures of the first and second free space areas which had been intersected. A listening ITS-S can then use the intersection area with high confidence that it is empty.

Alternatively the aggregator is configured to aggregate said first and second sensor data by geometrically merging the first and second free space areas indicated therein and including the resulting merged area in the third sensor data. In this embodiment, the listening ITS-S has a large merged area of free space available for manoeuvring, albeit of lower confidence. In particular, if confidence measures are used in the first, second and third CPMs, the third confidence measure in the aggregated CPM can be set to the worst confidence measure of all first and second free space areas from which the merged area had been built, to be on the safe side.

The third sensor data may additionally include the number of originating sensor data from which the third sensor data has been aggregated, and/or may additionally include the number of first and second ITS-S from whose CPMs the third sensor data has been aggregated. An ITS-S receiving the aggregated CPM can use this information to further assess the confidence of a sensor data indicated therein.

For keeping inventory and tracking of objects in its area of coverage over time, the aggregator of the ITS service station may have a memory for storing first and second CPMs including timestamps of the sensor data therein and may be configured to retrieve, for aggregating said third CPM, all sensor data from the memory having timestamps falling within a selected period of time.

Although the aggregated CPMs of the ITS service station of the invention may implicitly have priority over "normal" CPMs in that they will usually carry sensor data with higher confidence measures than the normal CPMs of other ITS-S, the aggregated CPMs of the ITS service station may additionally be flagged with a higher priority than normal CPMs. This may be done by, e.g., including a "high priority" flag in the header of the aggregated CPM. Receiving ITS-S then do not need to compare confidence measures to prioritize aggregated CPM over normal CPMs, but just will look for the high priority flag, to speed up processing.

The ITS service station of the invention can either be moveable, e.g., in the form of an onboard unit on a vehicle, or stationary, such as a roadside unit or infrastructure. In a particularly preferred embodiment the ITS service station is a roadside unit at an intersection. At intersections high vehicle traffic and hence communication traffic is to be expected so that receiving ITS-S benefit most from the load-reducing and safety-increasing CPM aggregation service of the inventive ITS service station.

The invention will now be described in further detail by means of exemplary embodiments thereof under reference to the enclosed drawings, in which show:.

<FIG> and <FIG> referring to the CPS in ITS and the CPM data structure, respectively, have been explained at outset.

<FIG> and <FIG> each show an ITS service station <NUM> mounted stationarily as a roadside unit (RSU) at a traffic area S, e.g., an intersection, a highway, a parking lot etc. Three exemplary vehicles <NUM> - <NUM> are shown approaching or just about to enter the traffic area S. The positions of the vehicles <NUM> - <NUM> on the area S are designated as PA, PB and PC, respectively.

The vehicles <NUM> - <NUM> each carry an ITS-S <NUM> - <NUM> in the form of an onboard unit (OBU). Vehicles <NUM>, <NUM> are exemplarily equipped with a sensor <NUM> with a respective field of view, capable of perceiving an object <NUM>i (i = <NUM>, <NUM>,. The sensors <NUM> may be of any kind, e.g., a camera, a radar or lidar sensor, an acoustic sensor, a vibration sensor, an infrared sensor etc. The ITS service station <NUM>, too, may have an own sensor <NUM> to perceive objects <NUM>i in its vicinity, although this is not obligatory. Generally speaking, each of the ITS-S <NUM> - <NUM> and ITS service station <NUM> may have none, one or more sensors <NUM>, also of different sensor types.

Instead of being stationarily mounted as a roadside unit, the ITS service station <NUM> could also be mobile, e.g., aboard a vehicle as an OBU.

The objects <NUM>i perceived by the sensors <NUM> may be of any kind, e.g., a manned or unmanned land, sea or air vehicle, a pedestrian, an animal, a machine, a traffic sign, a radio, a light or infrared beacon, and the like.

In the scenarios depicted in <FIG> and <FIG> each of the ITS-S <NUM>, <NUM> of the vehicles <NUM>, <NUM> perceives the same exemplarily depicted object <NUM>i. At the same time, within their respective fields of views of the sensors <NUM>, the ITS-S <NUM>, <NUM> each perceive a free space area A, B which is devoid of any object <NUM>i. Also the sensor <NUM> of the ITS service station <NUM> perceives a free space area C devoid of any object <NUM>i.

The free space areas A, B, C perceived by the stations <NUM>, <NUM>, <NUM> will have a shape and size depending on the field of view of the respective sensor <NUM> and the objects <NUM>i perceived therein as well as the shadow each object <NUM>i casts within that field of view for the respective sensor <NUM>.

The vehicles <NUM>, <NUM> share their perceptions of the observed free space areas A, B, as detected by their sensors <NUM>, via CPMs <NUM>, <NUM> sent from their ITS-S <NUM>, <NUM> (the "perceiving" or "disseminating" ITS-S) to the ITS-S <NUM> (the "receiving" or "listening" ITS-S) of the vehicle <NUM>. These "normal" CPMs <NUM>, <NUM> are also received by the ITS service station <NUM>, which creates an "aggregated" CPM <NUM> therefrom, as follows.

Within the CPMs <NUM>, <NUM> a perceived free space area A, B can be indicated in any possible geometric definition, e.g., as a circle, square, rectangle, sector, ellipse or polygon. For example, the free space areas A, B are defined by the corner points A<NUM> - A<NUM> and B<NUM> - B<NUM>, respectively. The exemplary free space area C observed by the ITS service station <NUM> is defined by an ellipse.

With reference to <FIG>, <FIG> and <FIG>, the ITS service station <NUM> has a receiver <NUM> with an area of radio coverage <NUM> to receive the CPMs <NUM>, <NUM> from the ITS-S <NUM>, <NUM> in its neighborhood. It goes without saying that the radio coverage area <NUM> will be dependent both on the transmitting power of the disseminating ITS-S <NUM>, <NUM> and the receiving sensitivity of the receiver <NUM>. For ease of description, the various normal CPMs <NUM>, <NUM>. are designated as CP<NUM>, CP<NUM>,. , generally CPm, in the following.

An aggregator <NUM> connected to the receiver <NUM> processes the set {CPm} of the received CPMs CPm and calculates the aggregated CPM <NUM>, called CPΣ in the following, therefrom. The aggregated CPM CPΣ is then broadcast by a transmitter <NUM> connected to the output of the aggregator <NUM> so that it can be received by listening ITS-S in the vicinity, such as (here) the ITS-S <NUM> on the vehicle <NUM>. The transmitter <NUM> and the receiver <NUM> of the ITS service station <NUM> can be implemented by a combined transceiver, too.

To calculate the aggregated CPM CPΣ from the received normal CPMs CPm the aggregator <NUM> has a memory <NUM> which contains - among other programs and data as needed - a table <NUM> storing the CPMs CPm, shown in <FIG>.

With reference to <FIG> and <FIG> a CPM <NUM>, <NUM>, <NUM> or CPm, respectively, contains - apart from the other data depicted in <FIG> - in any sensor information container <NUM> or, preferably, in any perceived object container <NUM>, here called oc<NUM>, oc<NUM>,. , generally ocn, one or more sensor data sdi (i = <NUM>, <NUM>,. ) on free space areas like the free space areas A, B, C. , and optionally corresponding free space area identifiers id, usually assigned by the perceiving ITS-S <NUM>, <NUM>.

The sensor data sdi on any free space A, B, C. perceived by a disseminating ITS-S <NUM>, <NUM> may define the respective free space area in any form of geometrical definition di, e.g., a distance, direction and orientation of the free space area to the sensor <NUM>, a geo-referenced or map-matched region, one or more dimensions of the free space area, a shape and size of the free space area, e.g., in form of a set of polygon corner coordinates A<NUM> - A<NUM>, B<NUM> - B<NUM> etc., as determined by the sensor <NUM>, e.g., as taken by a camera and determined by image processing, etc. For example, any of the data items in the perceived object container <NUM> of a CPM according to ETSI TR <NUM><NUM> can be used for transporting the sensor data definition di on a free space area A, B, C,. , e.g., the data element "FreeSpaceArea" of ETSI TR <NUM><NUM>.

Some of the sensor data sdi which are provided by the respective sensor <NUM> or a suitable processor connected to the sensor/s <NUM> in the ITS-S <NUM>, <NUM> or the ITS service station <NUM> may be provided with a confidence measure cfi, e.g., in form of the "FreeSpaceConfidence" data element according to ETSI TR <NUM><NUM>. Then the sensor data sdi is a pair (d, cf)i comprised of the free space area geometrical definition di and the associated free space area confidence measure cfi.

The confidence measure cfi of a free space area A, B, C,. , or of its definition di, respectively, may be any statistical measure of the confidence, reliability, trustworthiness, non-error rate etc. of this free space area to be a actually empty of objects <NUM>i. For example, the confidence measure cfi can be the <NUM>%-confidence interval, i.e., that with a probability of <NUM>% the free space area with the definition di is empty. Of course, other measures of confidence could be used as explained later on.

If the ITS service station <NUM> has one or more own sensors <NUM> which generate their own sensor data sdk (k = <NUM>, <NUM>,. ), the output of these sensors <NUM> can, e.g., be stored - in the same format as the received CPMs CPm - in data records SD<NUM>, SD<NUM>,. , generally SDk, for example in the same table <NUM>, as shown in <FIG>.

From at least two received CPMs CPm, or at least one received CPM CPm and at least one sensor data record SDk, the aggregator <NUM> calculates the aggregated CPM CPΣ as follows.

With reference to <FIG>, <FIG> and <FIG>, there are basically two possibilities to aggregate free space areas A, B, C,. from at least two different CPMs CPm or at least one CPM CPm and at least one record SDk into an aggregated sensor data sdΣ which is to be included in the aggregated CPM CPΣ. As shown in <FIG>, two or more free space area definitions di, dk can be geometrically intersected, see the resulting intersection area AB of the geometric intersection of the free space areas A and B, the resulting intersection area AC of the geometric intersection of the free space areas A and C, and the resulting intersection area ABC of the geometric intersection of all three free space areas A, B, C. The more free space areas are intersected, the better the confidence or trustworthiness of a resulting (intersected) free space area AB, AC, ABC is, since more participating stations <NUM>, <NUM>, <NUM> indicate that the intersection area is actually devoid of any objects <NUM>i. In the aggregated CPM CPΣ one, more or all of the determined intersection areas AB, AC, ABC can be indicated by respective geometric definitions dΣ.

An alternative possibility to calculate the aggregated CPM CPΣ is shown in <FIG>. The aggregated sensor data sdΣ can be a geometrical merger, combination or fusion D of all individual free space areas A, B, C, indicating for the listening ITS-S <NUM> the maximum area of reported free space which can be used for maneuvering without collision with any object <NUM>i. Of course, the confidence of the trustworthiness of this resulting merged area D will usually not be better than the worst confidence of any of the individual free space areas A, B, C.

Therefore, if free space area definitions di, dk with respective confidence measures cfi, cfk are used in the aggregation, the aggregated confidence measure cfΣ of the aggregated area AB, AC, ABC, D in the aggregated sensor data sdΣ with the geometrical definition dΣ may be.

The aggregated confidence measure cfΣ, can also be a composite field or concatenation of the confidence measure cfΣ as calculated above and other information such as the number of data sources responsible for that confidence measure cfΣ, their positions, speeds and/or headings with respect to the free space areas A, B, C,. , the fields of view of the respective sensors <NUM>, etc. For example, the more different the positions of the data sources, i.e. the positions of the sensors <NUM> and/or the positions of the stations <NUM>, <NUM>, <NUM>, with respect to an intersected free space area AB, AC, ABC are, the better the data quality and hence trustworthiness of that intersected free space area is.

The aggregation performed by the aggregator <NUM> may take into account timing aspects. Each CPM CPm and record SDk, and in particular each perceived object container ocn or even each individual sensor data sdi, sdk, may contain a timestamp t indicative of the time of measurement of the respective sensor data sdi, sdk. The timestamp t may be indicated in any suitable format, be it relatively to a time of sending the respective CPm or the time of storing the respective record SDk, or absolutely in terms of a systemwide reference clock.

The timestamps t can also take into account the track or estimated movement of a perceived object <NUM>i and the sensor shadow it casts in the respective sensor's field of view, i.e., its influence on the respective perceived free space areas A, B, C,. , as well as possible calculation, processing or transmission delays. In this way, the "age" of a sensor data sdi, skk can be accounted for by the aggregator <NUM> when calculating the aggregated CPM CPΣ. For example, the aggregator <NUM> may, when aggregating the CPM CPΣ, only use sensor data sdi, sdk from its memory <NUM> whose timestamps t fall within a selected period of time, for example into a past cycle interval, when the ITS service station <NUM> cyclically sends CPMs CPΣ.

In the aggregated CPM CPΣ the aggregator <NUM> may optionally include the number (count) of originating sensor data sdi, sdk from which a specific aggregated sensor data sdΣ had been aggregated, and/or the number (count) of disseminating ITS-S <NUM>, <NUM> from whose CPMs CPm that specific aggregated sensor data sdΣ had been aggregated. The numbers (counts) can be, e.g., attached as data field/s to the respective aggregated confidence value/s cfΣ, in the aggregated CPM CPΣ. These numbers (counts) can then be used by a receiving ITS-S <NUM> to select if or which one of several received aggregated CPM CPΣ is to trust most regarding a specific sensor data.

Usually, the receiving ITS station <NUM> will select and use that aggregated sensor data sdΣ which has the best confidence measure cfΣ attributed to it, e.g., the smallest confidence interval or the highest confidence level, when the confidence measure is expressed in such terms. However, with the additional knowledge of the numbers (counts) of originating sensor data or ITS-S, from which the sensor data sdΣ had been aggregated, the receiving ITS-S <NUM> can improve the selection, e.g., by weighting the confidence measures cfΣ, by their respective numbers (counts) of underlying data. On the other hand, said numbers (counts) may be particularly useful for sensor data sdΣ which does not comprise a confidence measure cfΣ, at all.

Claim 1:
Intelligent Transportation System, ITS, service station (<NUM>), comprising:
a receiver (<NUM>) having an area of radio coverage (<NUM>) and being configured to receive a first Collective Perception Message, CPM, (<NUM>) from a first ITS station (<NUM>) at a first position (PB) within the coverage area (<NUM>), the first CPM (<NUM>) including first sensor data (sdi) on at least one first free space area (A) perceived by the first ITS station (<NUM>), and
an aggregator (<NUM>) connected to the receiver (<NUM>) and configured to aggregate said first sensor data (sdi) with at least one second sensor data (sdi, sdk) on at least one second free space area (B, C) into a third sensor data (sdΣ), which second sensor data (sdi, sdk) either is received via the receiver (<NUM>) in a second CPM (<NUM>) from a second ITS station (<NUM>) at a second position (PC) within the coverage area (<NUM>) or is determined by a sensor (<NUM>) of the ITS service station (<NUM>),
wherein the ITS service station (<NUM>) further comprises a transmitter (<NUM>) connected to the aggregator (<NUM>) and configured to broadcast said third sensor data (sdΣ) in a third CPM (<NUM>).