WO2010045966A1

WO2010045966A1 - Apparatus and method for data transmission in a vehicular communication system

Info

Publication number: WO2010045966A1
Application number: PCT/EP2008/064191
Authority: WO
Inventors: Joachim Sachs; Sabine Sories
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2008-10-21
Filing date: 2008-10-21
Publication date: 2010-04-29

Abstract

The present invention relates to a method and apparatus for transmitting a message in a vehicular communication system while avoiding unnecessary transmissions to improve the communication efficiency in the system. The apparatus comprises an antenna arrangement adapted to operate according to a plurality of antenna radiation patterns and a control unit (620) adapted to select an antenna radiation pattern for transmitting the message as a function of distribution information (510) associated with the message.

Description

APPARATUS AND METHOD FOR DATA TRANSMISSION IN A VEHICULAR COMMUNICATION SYSTEM

TECHNICAL FIELD

The present invention relates to an apparatus and a method for transmitting a message in a vehicular communication system.

BACKGROUND

Conventionally, vehicles communicate using visual and audible signals for roughly a century. Such signals include hazard warning lights, brake lights, high beam flashing, honking signals, etc. For example, the brake lights of a car light up when the brake pedal in the car is pressed indicating to the inmnediately following driver that the car in front decelerates and loses speed. For the driver in the following vehicle to break, it is necessary that the driver perceives break lights quickly and in turn also steps on the brake pedal, thereby a delay of brake information may occur so that in dense traffic a rear end collision accident is highly likely, especially if visibility is poor and road conditions are bad.

The signals mentioned above relate particularly to vehicle safety which receives more and more attention so that effective vehicular communication becomes more important leading in an increasing interest in safety applications.

For example, if a vehicle breaks very hard, the driver of the vehicle behind is warned and possibly, to avoid an accident, an automatic brake can be triggered in the warned vehicle. Furthermore, a warning message may be triggered, e.g. by the same sensors that release an airbag, when a vehicle breaks down or an accident occurs. In another example, traffic lights may be equipped with transmitters which indicate the duration of light phases supporting energy efficient driving behaviours. This may also be used to trigger an automatic emergency stop at a red traffic light. Additionally, fire brigade, ambulance or police vehicles may be equipped with communication units to warn vehicles or influence the light phases of traffic lights.

One major motivation for vehicle communication systems is safety and eliminating excessive costs of traffic collisions. In the examples above, it can be seen that vehicular safety applications have a different scope of how data is transmitted. For example,, break lights are only seen from behind and a siren of a police car may be heard in a certain range around the police car.

For car-to-car and car-to-infrastructure applications, vehicle communication systems are being investigated in which vehicles and roadside units may be regarded as communicating nodes providing each other with information,, such as safety warnings and traffic information, e.g. information relating to traffic conditions. As a cooperative approach, vehicle communication systems may more effectively avoid accidents and traffic congestions than if each vehicle tries to solve these problems individually.

For example, Fig. 1 shows a scenario in a vehicle communication system, namely a two-lane road with nine vehicles driving in left-hand traffic with five vehicles going from left to right and four vehicles going from right to left. As shown in Fig. 1, vehicle 100 constituting a source node may communicate with the roadside unit 120 and other vehicles 110 to 117 using some form of wireless communication to inform each other of potential hazardous situations on the road.

Currently, several vehicular communication systems are based on ad hoc wireless local area networks (WLAN) and standardization activities are ongoing in e.g. IEEE 802. lip and IEEE 1609.

Fig, 2 shows a WLAN based vehicular communication system, wherein vehicle 200 constitutes a source node and sends messages via WLAN to other nodes directly reachable by a first hop {indicated by a solid line), e.g. vehicles 210, 212, 214 and roadside unit 250 constituting infrastructure, which are located within a transmission region 260 covered by the source node transmission. These other nodes (vehicles

210, 212, 214) may then forward the message by a second hop (indicated by a line with large dashes) to the nodes 220, 222, 224 and 226, which are reachable from the nodes 210, 212 and 214. In the example of Fig. 2, in a third hop (indicated by a line with small dashes), node 230 may be reached from nodes 220 and 222. Further, as can be seen with respect to node 222 the message may also be received multiple times via different hops, for example by the second hop from node 214 or by the third hop from node 224. Therefore, the same node may receive the same message several times so that data flooding may occur.

Similarly, as can be seen in Fig. 3, a distribution of information or data of a vehicular communication application {VCA} via WLAN follows multi-hop paths so that transmission of the same message increase exponentially with the number of hops. In general, the distribution may be limited by the number of hops or other routing mechanisms of the ad hoc network but still all nodes surrounding the source node receive the message. For example, vehicle 300 constituting the source node m Fig. 3 not only transmits the message to vehicles 332, 336, 342 and 348 on the same lane of the same road but also to vehicles 344, 346 and 350 of the opposite lane and even to vehicles on a different road 390 shown m Fig. 3 underneath of and perpendicular to the road 380 on which vehicle 300 is travelling.

In more detail, the transmission region 360 covered by vehicle 300 transmission is indicated by a dashed circle, which includes and intersects vehicles 330, 332, 334 and 336, thereby reached by the first hop. In the following, the message may be spread by several hops, similar to the example discussed with respect to Fig. 2, thereby reaching nodes 340, 342, 344, 346 and 348 at the earliest with the second hop and nodes 350, 352 at the earliest with tne third hop. The overall distribution of the message after several hops is indicated by distribution area 370.

Since bandwidth is generally limited for the above discussed vehicular communication applications (VCA) sending the same messages multiple times to the same node may prevent other data or messages to be transmitted m the network, may lead to interference between nodes and thus constitutes a waste of resources.

SUMMARY

Therefore, the need arises for an apparatus and a method for transmitting a message in a vehicular communication system while avoiding unnecessary transmissions to improve the communication efficiency in the system.

This is achieved by an apparatus having che features of independent claim 1 and by a method having the features of independent claim 12. Advantageous embodiments are described in the dependent claims. According to an embodiment , an apparatus for transmitting a message in a vehicular communication system is provided,, wherein the message is associated with distribution information. The apparatus comprises an antenna arrangement adapted to operate according to a plurality of antenna radiation patterns. The apparatus further comprises a control unit adapted to select an antenna radiation pattern for transmitting the message as a function of the distribution information which is associated with the message.

Accordingly, a direction may be given to the transmission of the message by referring to the distribution information associated with the message. Therefore, by selecting a desired antenna radiation pattern, the message may be transmitted only to selected nodes being located in a certain direction from the apparatus. Furthermore, by limiting the number of receiving nodes and thus also of transmitting nodes, unnecessary usage of available bandwidth resources may be avoided.

According to another embodiment, a method for transmitting a message in a vehicular communication system is described, wherein the message is associated with distribution information. The method comprises selecting an antenna radiation pattern from a plurality of antenna radiation patterns as a function of the distribution information associated with the message and transmitting the message according to the selected antenna radiation pattern.

Accordingly, the message may be transmitted in a selected direction so that messages are only received by nodes in a certain direction. Thereby, the number of receiving nodes and thus also of transmitting nodes is reduced, and unnecessary usage of available bandwidth resources may be avoided. According to another embodiment, a computer program may be provided including instructions adapted to cause data processing means to carry out the method with the above described features.

According to another embodiment, a computer-readable medium may be provided, in which a program is embodied, where the program is to make a computer execute the method with the above described features.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a vehicular communication scenario, in particular depicting several vehicles on a two-lane road.

Fig. 2 shows the vehicles of Fig. 1 communicating in a WLAN based vehicular communication system.

Fig. 3 shows the distribution area of communications in a WLAN based vehicular communication system including the vehicles and the road of Figs . 1 and 2 as well as a second perpendicular road with additional vehicles.

Fig. 4 shows an apparatus for transmitting a message according to an embodiment of the invention.

Fig. 5 shows a flowchart of a method for transmitting a message according to an embodiment of the invention.

Fig. 6 shows an apparatus for transmitting and particularly relaying a message according to another embodiment of the Invention.

Fig. 7 shows examples of different antenna configurations that may be adopted by the antenna arrangement of the apparatus of an embodiment of the invention. Fig. 8 shows rhe distribution area of vehicles communicating according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of r.he invention are described with reference to the figures. It is noted that the following description contains examples only and should not be construed as limiting the invention.

Embodiments of the invention generally relate to transmitting data, e.g. a message, in a vehicular communication system, and particularly, to transmitting data in a certain direction determined by an antenna radiation pattern selected based on distribution information so as to control the direction of data distribution. Briefly said, a certain directivity may be given to the distribution of data, e.g. a message to be transmitted in the vehicular communication system.

It is noted that reference is made herein to a specific technology, e.g. WLAN, and standards, such as IEEE 802. lip and IEEE 1609, but such references only serve to indicate preferred examples and are in no way limiting. Rather, the present invention can be generally applied in the context of any vehicular communication system that provides for wireless communication between vehicles and/or roadside units, which transmit and receive messages that may be associated with some type of meta information, e.g. distribution information.

As described above, it may be possible to limit the spread of a message by defining a maximum hop count, which may be dependent on the type of message and its content. Such information may be included in meta information transmitted together with the message.

The inventors have realized that limiting data distribution over several hops, e.g. by semantic routing where meta xnformatxon is included in the messages,, i.e. routing in which the routed information may be interpreted by the router, reduces the bandwidth needed for communication to a certain extent ₌

For example, the meta information may include the indication that a message is only of relevance for cars on route 66 east of position X, and relaying nodes, i.e. the vehicles m Fig, 3 other than vehicle 300, can decide whether to forward the information by matching the received meta information with their own context information, e.g. the relaying node knows that it is west of position X and thus does not forward the message .

Although this approach reduces the bandwidth needed for communication, it constitutes a very complex solution on the network layer and requires very advanced positioning, context sensing and analysis methods . Most importantly, it only intervenes after the first hop, i.e., the first receiving node, e.g. node 330 or 334_f recognizes that the message is meant for other nodes m another direction and thus does not forward the message any longer. However, at that point, an unnecessary transmission to and unnecessary reception at the first receiving node, i.e. at a receiving vehicle or roadside unit, in an undesired direction has already occurred and bandwidth has already been wasted.

Therefore, transmission and reception efficiency may be further improved by using distribution information according to which an antenna radiation pattern of an antenna arrangement may be selected to support directed data distribution m a vehicular communication system.

Basically, using different antenna radiation patterns for a node, i.e. a vehicle on the road or a roadside unit, for transmission of a message may lead to highly directional communication without interference with uninvolved nodes. In the following, an embodiment of the invention will be described with regard to Fig. 4.

Fig. 4 illustrates elements of an apparatus 400 according to an embodiment of the invention, comprising an antenna arrangement 410 and a control unit 420.

The antenna arrangement 410 operates according to a plurality of antenna radiation patterns. For example, the antenna arrangement 410 comprises two antennas, namely an antenna for receiving and an antenna for transmitting data and each antenna may have a different radiation characteristic, i.e. each antenna may have at least one radiation pattern. In a simple case two radiation patterns may be directed in opposite directions of each other, e.g. the radiation pattern of one antenna in the forward direction of the vehicle and the radiation pattern of the other antenna in the backward direction of the vehicle. In another example, the antenna arrangement 410 comprises an adaptive antenna, preferably steerable electronically or mechanically to transmit in different directions so that different antenna modes or patterns may be achieved. These examples will be discussed in detail later with respect to Fig. 7.

The control unit 420 selects at least one antenna radiation pattern of the plurality of antenna radiation patterns of the antenna arrangement 410 for transmitting a message as a function of distribution information associated with the message. A message transmitted in the vehicular communication system by the apparatus 400, which may be included in vehicle 300 shown in Fig. 3, may indicate to other vehicles, such as vehicles 330, 332 and 336 to pay attention because vehicle 300 brakes. As becomes obvious from the two roads and the direction in which the vehicles travel, as shown in Fig. 3 _f it is unimportant for vehicle 330 to receive this information . As discussed above, the message xs associated with distribution information. For example, distribution information may comprise information about the direction and range that should be covered when a message is transmitted. On the one hand, distribution information determines the direction in which a message is to be sent. The desired direction may be realized by selecting a corresponding antenna radiation pattern. On the other hand, also range information may be included m the distribution information, which specifies the range according to which the distribution information is to be transmitted. Therefore, the data sent by the apparatus can be directed to nodes in a certain direction, and it can be further specified that the message should be only relayed for a certain number of hops or should only be relayed until a node receives the message which is spaced apart by a certain distance from the apparatus originally transmitting the message.

The apparatus 400 that transmits the message may be a part of or included in a vehicle, e.g. vehicle 300 as discussed above, or a roadside unit.

In some circumstances, it may turn out that it is advantageous if the apparatus not only transmits a message but may also receive a message or the distribution information or both. In such a case, the apparatus may be adapted for relaying and the antenna arrangement receives at least one of the message and the distribution information from another apparatus either in another vehicle or a static node, such as a roadside unit.

In the following, operations of an apparatus will be described with regard to Fig. 5. Fig. 5 shows a flow diagram of operations for a method for transmitting a message, such as during operation of the apparatus 400 shown m Fig. 4. As described above, the apparatus may be included, attached or mounted to a vehicle or roadside unit so that the method described below can be performed in a vehicle or roadside unit, for example.

In a first operation 210, when starting operations, an antenna radiation pattern from a plurality of antenna radiation patterns is selected as a function of distribution information associated with a message. For example, if the message is to alert following vehicles when the vehicle that transmits the message brakes, the distribution information associated with the message comprises information making the control unit 420 to select a radiation pattern with backward directed distribution.

In a subsequent operation 520, the message is transmitted according to the selected antenna radiation pattern, e.g. in a backward direction with respect to the vehicle transmitting the message.

In one example, transmitting the message may include also transmitting distribution information together with a message or in the message. However, the invention is not limited to this case, since distribution information for a message or sequence of messages can also be transmitted via a dedicated control channel instead of being included in the message, e.g. in the message header. Therefore, it may be sufficient that the message is associated with distribution information and it is feasible that both the message and the distribution information may be transmitted, received or generated from different sources.

Fig. 6 shows an apparatus 600 according to another embodiment, similar to the apparatus 400 of Fig. 4, and apparatus 600 may also be used to perform the operations described above. The apparatus in Fig. 6 comprises a control unit 620, an associating unit 630, a generating unit 640, a receiving unit 612, a transmitting unit 614 and an antenna arrangement 616, 618.

In Fig. 6 the antenna arrangement is shown by two antennas 616 and 618, wherein antenna 616 may be used for receiving data and antenna 618 may be used for transmitting data. Although apparatus 600 shows two antennas for receiving and transmitting data, the antenna arrangement is not limited thereto, and as described above, also a single adaptive antenna may be employed.

The adaptive antenna may be steerable or otherwise configurable to receive and to transmit data. As known in the art, an adaptive antenna may comprise several active elements enabling formation of a beam of a certain shape and direction by electronic control of the elements. In general, active elements or an array of similar antennas make up an adaptive antenna that may change its combined radiation pattern so as to switch among several different modes. Different radiation patterns may thus be achieved by electrically controlling the radiation of individual elements. However, it is also possible to simply steer the antenna mechanically to obtain different radiation patterns, e.g. by turning it by 180°.

Examples of antenna radiation patterns that may be used with the antenna arrangement in the apparatus 600 are described with respect to Fig. 7.

Fig. 7 shows three different antenna beams, i.e. radiation patterns 710, 720 and 730 resulting from the antennas or antenna configurations 740, 750 and 760, respectively. The antennas 740, 750 and 760 shown in Fig. 7 do not necessarily have to be individual antennas but their radiation patterns may also be realized by one adaptive antenna that is configurable to produce the antenna beams 710, 720 and 730, as described above. An example for such an antenna arrangement is a preferably steerable adaptive antenna configurable for at least one of receiving and transmitting data.

For example, the antenna arrangement 740_f 750, 760 may transmit at least one of the message and the distribution information described above with an antenna radiation pattern of the plurality of antenna radiation patterns comprising at least one of a forward directed, backward directed and omni directed distribution pattern. If it is assumed in Fig. 7 that the vehicle shown travels from right to left, a forward directed distribution pattern is indicated by beam 710, a backward directed distribution pattern is indicated by beam 730 and an omni directed distribution pattern is indicated by beam 720. Based on the selected radiation pattern, the antenna radiates the message accordingly.

Even if the number of different antenna radiation patterns is limited,, an antenna radiation pattern can still be selected for transmission which fits best to the distribution that is desired by the specific vehicular communication application (VCA) , for example backward direction distribution when braking. Already directing the transmission of a message in a 180 degrees semicircle behind the vehicle reduces the communication in a vehicular communication system by roughly one half, if an even distribution of cars on a two-lane road is assumed.

It is noted that there are several possibilities of antenna radiation patterns in different directions in addition to forward directed and backward directed patterns. In communication between vehicle and roadside unit also a sideward radiation pattern is feasible. For example, when the vehicle 200 passes the roadside unit 250 in Fig. 2, the antenna arrangement of the vehicle may radiate to the roadside unit in a sideward pattern to the left of the vehicle, e.g. diagonally to the left or in a full semicircle to the left. On the other hand, the antenna arrangement of the roadside unit may adapt an antenna radiation pattern to the right in the direction of the passing vehicle, e.g. diagonally to the road or also in a semicircle.

Referring back to Fig. 6, the apparatus 600 having data reception and transmission capabilities may be regarded as an apparatus for relaying a message, since the antenna arrangement may also be adapted to receive at least one of the message and the distribution information.

However, at least one of the message and the distribution information may also be generated directly by the apparatus 600 itself so that the reception capability may not be necessary .

In an example, the generating unit 640 may generate at least one of the message and the distribution information. In more detail, the apparatus 600 may be included in a vehicle which brakes. In response to the braking, the generating unit 640 may generate a message indicating to other drivers that the vehicle is braking and thus decelerating. In this example, the vehicle may be regarded as the source node, since the message is generated by some application function in the generating unit 640.

Further, distribution information may also be created by the generating unit 640 and the message and the corresponding distribution information may be associated with each other by associating unit 630. Corresponding distribution information for the message "attention I am braking" may be a distribution function indicating that the message is to be transmitted in a backward direction of the vehicle, e.g. the beam 730. On the other hand, the apparatus 600 may be regarded as a relaying node, when a message is received by antenna 616 and receiving unit 612, which is then associated by the associating unit 630 with distribution information which may be included in the message or may be received via other means such as a dedicated control channel, for example, as described above.

The following operation performed by the control unit 620 may be the same independent on whether the apparatus may be regarded as a transmitting apparatus or relaying apparatus . Once the message is associated with the corresponding distribution information by the associating unit 630, the control unit 620 selects an antenna radiation pattern for transmitting the message as a function of the distribution information. Next, the transmitting unit may 614 transmit the message to the antenna configured with the selected antenna radiation pattern, e.g. antenna 618 in the example of Fig. 6. Subsequently, the message is transmitted in the desired direction.

It is noted that in some cases it may not be necessary to transmit also the distribution information with the message, for example, in the situation in which only vehicles are to be informed of, for example, braking, which are in a transmission region directly covered by the antenna 618 and relaying or forwarding the message by hopping is not necessary or wanted.

On the other hand, distribution information may be transmitted with the message further comprising range information specifying the range over which distribution information is to be transmitted- For example, distribution information may indicate to the relaying nodes which receive and transmit rhe message, a maximum number of hop counts to limit the number of relaying nodes. In a specific example, in which the apparatus constitutes a WLAK node and the message is transmitted via WLAN to at least another WLAN node, the distribution information includes information regarding a maximum number of hop counts to limit the number of relaying WLAN nodes .

In addition or instead of the generating unit 640, a modification unit (not shown) may be provided in the apparatus 600. The modification unit may modify the distribution information. For example, the apparatus 600 may obtain distribution information, which however needs to be modified by the apparatus 600 because the traffic situation has changed so that the vehicles following the vehicle with apparatus 600 are provided with updated and modified distribution information.

For example in a relaying node, such as a vehicle a few hops away, the distribution information may be retrieved from a packet header of the message and may be modified by a semantic routing function of that relaying node, wherein the distribution information may be adapted to a change in the direction of a highway, since a lane of a highway in direction east may temporarily turn west, as described below.

According to a specific example, a relaying node, e.g. a vehicle receiving and transmitting a message, retrieves distribution information from a packet header of the message that may be further modified by a semantic routing function of that node. The semantic routing function may decide that the message is not forwarded any further or it can adapt the directivity, e.g. if a vehicle travels on highway 23 in direction east, the highway may change its direction meaning that "direction east" can mean anything from 1°-179° depending on where the vehicle is travelling on the road (the road may even temporarily turn west) . Intermediate vehicles can adopt the distribution information accordingly. Similarly, the control unit may decide that the obtained message is not relevant to other vehicles and thus may not be transmitted or forwarded.

In other words, in relaying nodes, the distribution information associated with a message can be taken into account for the transmission on the next hop, which may also be combined with other semantic routing functionality, e.g. information regarding the relevance for vehicles on a certain route located at a certain position, as described above.

In a simple example, a received message can be relayed into the same direction as it is received, namely the transmitting antenna is in the opposite direction of the receiving antenna. This may be highly effective for the braking example above and may be realized on lower layers only by using a hop count in message headers. Thereby, directional information is generated at the node itself.

In another example, the VCA may take into account for selection of the antenna radiation pattern information on the area of relevance. In this semantic routing functionality either the desired direction included in the distribution Information is given in the application or the relay itself determines the relevance and the area of relevance for this information .

Further, it is feasible that only certain nodes are authorized to generate a certain message, e.g. official messages by the police or other authorities.

In the following, FIg. 8 shows the distribution area 870 of vehicles communicating according to an embodiment of the invention .

Similar to Fig. 3 nwo two-lane roads perpendicular to each other are shown in Fig. 8. However, as can be readily realized, the vehicles on the second perpendicular road, e.g. vehicles 890, 891 and 892 are not affected by communication originating from the vehicle 800, which constitutes the source node in Fig. 8. Since the transmission of the vehicle 800 is strongly forward directed, only vehicles travelling on the same road and on the same lane are reached, namely in a first hop vehicle 810 and then in a second hop vehicles 820 and 830 and later also vehicles 840, 850 and 860 may be reached. Vehicles 880, 881 and 882 on the opposite lane are unaffected.

Therefore, the bandwidth needed for transmission of one message in this vehicular communication system decreases largely compared to Fig. 3, since only seven vehicles are involved in communication. The example shown in Fig. 8 may correspond to the case in which an ambulance is approaching the vehicles from behind and the last vehicle 800, which also may be the ambulance itself, transmits a message requesting the vehicles 810, 820, 830, 840, 850 and 860 to slow down and move to the side.

Therefore, as can be seen in Fig. 8, the use of directed antennas or steerable antennas reduces the interference at nodes which are anyway not addressed by the certain kind of direction sensitive application, i.e. a certain message. Therefore, the overall system interference is reduced and capacity is increased.

Further, by directing the message, semantic routing may be reduced or even replaced, i.e. information necessary in semantic routing that describes for which node a message is relevant, may be redundant, since the message only reaches nodes in an area for which the message is relevant which is indicated by distribution area 870. Thereby, a simplified network layer which only controls overall transmission by the number of hops, for example, may be realized, and complex routing mechanisms can be neglected. Similar to transmitting a message according to an antenna radiation pattern, it is noted that due to the reciprocal nature of antenna patterns for receiving and transmitting, similar arguments apply for receiving data with a selected antenna radiation pattern. For example, a receiving antenna facing only backwards and expecting messages from the back may not receive messages from the front and thus messages from the front may not interfere with messages from the back.

It should be understood that the control unit 420, 620 may be realized by a microprocessor, computer or integrated circuit and is not limited to the above. For example, the control unit may act as a control] er or processor and may be realized by a hardware arrangement, such as by hardwired circuits, or ASICS (application specific integrated circuits) or software or any suitable combination of the above. Similarly, the associating unit 630 and generating unit 640 and their functions may be integrated in one unit together with a control unit, wherein their functions may be emboαied as a software program. Therefore, the term "unit" in the above described embodiments should not be construed as limiting the individual elements to a separate tangible part of the apparatus but should be understood as a kind of functional entity.

Furthermore, the control unit 420, 620 may comprise or be connected to a memory, such as a RAM, ROM, hard disk, (E)EPROM, a disk, a flash memory, etc. A Program code stored in the memory may be a program including instructions adapted to cause a processor in tne control unit 420, 620 to carry out the operations of the methods described above.

In other words, according to another embodiment, a program may be provided including Instructions adapted to cause a processor, such as the processor of the control unit, to carry out combinations of the above described operations . Moreover, a computer readable medium may be provided in which the program is embodied. The computer readable medium may be tangible, such as a disk or other data carrier or may be intangible, constituted by signals suitable for electronic, optic or any other type of transmission. A computer program product may comprise the computer readable medium.

Λs described above, the embodiments and examples of the invention allow for transmitting and relaying, respectively, a message in a vehicular communication system, wherein the message is transmitted according to an antenna radiation pattern selected as a function of distribution information associated with the message. Therefore, the invention provides a simple solution to control the direction of data distribution for vehicular communication applications .

It will be apparent to those skilled in the art that various modifications and variations can be made in the described apparatuses and methods of the invention as well as in the construction of this invention without departing from the scope or spirit of the invention.

The invention has been described in relation to particular embodiments and examples which are intended in all aspects to be illustrative rather than restrictive. Those skilled in the art will appreciate that many different combinations of hardware, software and firmware will be suitable for practicing the invention.

Moreover, other implementations of the invention will be apparent to chose skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and the examples be considered as exemplary only. To this end, it is to be understood that inventive aspects lie in less than all features of the single foregoing disclosed implementation or configuration. Thus, the true scope and spirit of the invention is indicated by the following claims.

Claims

1. An apparatus for transmitting a message in a vehicular communication system, wherein said message is associated with distribution information, the apparatus comprising:

an antenna arrangement adapted to operate according to a plurality of antenna radiation patterns; and

a control unit adapted to select an antenna radiation pattern for transmitting said message as a function of said distribution information associated with said message .

!. The apparatus of claim 1, further comprising:

an associating unit for associating said message with said distribution information.

3. The apparatus of claim 1 or 2, wherein

said apparatus is an apparatus for relaying said message and said antenna arrangement is adapted to receive at least one of said message and said distribution information.

4. The apparatus of one of claims 1 to 3, further comprising:

a generating unit for generating at least one of said message and said distribution information.

5. The apparatus of one of claims 1 to 4 _f further comprising:

a modification unit for modifying said distribution information.

6. The apparatus of one of claims 1 to 5 , wherein

the antenna arrangement comprises an antenna for receiving and an antenna for transmitting,

7. The apparatus of one of claims 1 to 5, wherein

the antenna arrangement comprises an adaptive antenna configurable for at least one of receiving and transmitting .

8. The apparatus of one of claims 1 to 7, wherein

the antenna arrangement is adapted to transmit at least one of said message and said distribution information with an antenna radiation pattern of said plurality of antenna radiation patterns comprising at least one of a forward directed, backward directed and omni-directed distribution pattern.

9. The apparatus of one of claims 1 to 8, wherein the distribution information further comprises range information specifying the range over which the distribution information is to be transmitted.

10. The apparatus of one of claims 1 to 9, wherein

said apparatus constitutes a WLAN-node and said message is transmitted via WLAN to at least another WLAN-node.

11. The apparatus of claim 10, wherein

said distribution information includes information regarding a maximal number of hop counts to limit the number of relaying WLAN-nodes .

12. A method for transmitting a message in a vehicular communication system, wherein said message is associated with distribution information, the method comprising:

selecting an antenna radiation pattern from a plurality of antenna radiation patterns as a function of said distribution information associated with said message;

transmitting said message according to said selected antenna radiation pattern.

13. A computer program including instructions adapted to cause data processing means to carry out the method of claim 12.

14. A computer readable medium, in which a program is embodied, where the program is to make a computer execute the method of claim 12.