EP1296305A1 - Apparatus and system for inter-vehicle communication - Google Patents

Abstract

In a communication system (SYS) each vehicle (V1, V2, V3) comprises a transmitting device (VBD1, VBD2, VBD3) which transmits vehicle-specific signals to all other vehicles with a signal format depending on the vehicle position. Thus, each vehicle can identify at least the position of another vehicle in a geographical area (GA) in accordance with the used signal format.

Description

FIELD OF THE INVENTION

This invention relates to an apparatus installed in a vehicle for providing local communications for vehicles. Furthermore, this invention also relates to a communication system for providing local communications for vehicles wherein each vehicle has installed such an apparatus.

Such a communication system and apparatus are in particular suitable for the future development of advanced driver assistance systems. Nowadays, such driver assistance systems provide the driver of the vehicle with a wide range of information such as information about the driving state of the vehicle, navigation information for route planning, weather information, information about blocked roads or accidents etc.

Whilst a navigation system and can typically determine the geographical location of the vehicle within a certain range (for example using a Global Positioning System GPS), such systems do not provide information about nearby vehicles and/or local conditions, like road constructions or damaged road sections.

Whilst the driver of a vehicle has great interest in what happens at far distances (for example whether there is a traffic jam 20-50 km ahead), he/she is at least as much interested in events within a range of 10 m to 1 km. Examples of such events are that the vehicle driving in front breaks, changes the lane, or turns right or left. These events are of a purely local interest but are very important for increasing the level of automation, like in convoy driving, or for simply issuing alarms in the case of manual driving. Note that an increase of the level of automation is a key requirement for further increasing the traffic density in the future.

Despite the fact that some prior art solutions, as explained below, provide a limited possibility to obtain information about another vehicle in the surrounding, these prior art solutions have the disadvantage that they are not capable of providing such information with a delay that is sufficiently low for applications like convoy driving or collision avoidance on highways, and the like.

BACKGROUND OF THE INVENTION

In a typical scenario, vehicles drive on a road surrounded by many other vehicles, and they encounter obstacles, like road constructions that could easily be tagged. Advanced vehicles are more and more equipped with a navigation system based on GPS (Global Positioning System), which allows each vehicle to determine its own geographical position. This position information is used locally in the car or remotely at a service provider to retrieve relevant global events, like major traffic jams, ice rain, or the like and to continuously update the driving recommendation for reaching a particular destination.

Some experimental systems provide automated driving in convoys. In such systems, the first car is manually driven, and the further cars automatically follow the previous car without driver intervention. Today the methods use a combination of optical sensing and radar. Other experimental driver assistance systems track the white line on the road and generate an alarm if the vehicle is at risk of leaving the road. Still other experimental systems transmit alarms through radio signals towards other vehicles in the case of heavy breaking. Since these alarms are somewhat unspecific it is hardly possible to know about their relevance. The vehicle can be driving in the opposite direction or even on another road.

All of the above experimental systems have inconveniences. Either the information is provided on a vehicle-unspecific basis (the alarm sent on heavy breaking is not linked to a specific vehicle) or the information is derived from the behaviour of the observed vehicle rather than from the controls (cameras observing the vehicle ahead rather than information about steering wheel movements). The latter implies that the information is available later, is less accurate, and is complex to obtain.

Nowadays, many vehicles are equipped with cellular mobile radio communication equipment, e.g., GSM in Europe. One could think about using such equipment for car-to-car communication as well. However, this approach would have two major drawbacks: mobile phones are called by subscriber numbers, which is inappropriate in the present context, and routing the data through a cellular system causes delays that are much too large for driver assistance systems. The first drawback actually exists with all known radio-communication systems. A desired communication party is addressed using some fixed address, like an MS-ISDN, an IP address or a radio frequency. The mapping needed to find the address associated with a vehicle in a particular location is so cumbersome that such an approach is not even worth considering.

Furthermore, the communication in the present context is typically one-to-many. Several surrounding vehicles are typically interested in the position, velocity, direction changes, and similar parameters of a specific vehicle.

Therefore, whilst mobile radio communication systems are very useful in providing general traffic information, they are not suitable for the real-time situation of driver assistance and collision avoidance systems.

SUMMARY OF THE INVENTION

As explained above, the known techniques, which allow a vehicle to obtain information about its surrounding are not adequate, mainly in three aspects, namely they imply a delay with respect to the original actuation, they are inaccurate, and they require complex processing.

Thus, the object of the present invention is to provide an apparatus and a communication system, which overcome the difficulties mentioned above and which allow a fast, reliable and economical supply of relevant information to vehicles for further processing by driver assistance systems.

SOLUTION OF THE OBJECT

This object is solved (claim 1) by an apparatus installed in a vehicle for providing vehicle specific information in a geographical area, comprising a transmitting device for transmitting vehicle-specific signals, indicating vehicle-specific information of the vehicle in which said apparatus is installed; a vehicle position determining device for determining the current vehicle position of the vehicle in which the apparatus is installed; and wherein said transmitting device is adapted for transmitting said transmitted vehicle-specific signals with a signal format which depends on the determined current vehicle position.

Furthermore, this object is solved by a communication system (claim 5) for providing vehicle-specific information between vehicles and/or other sources in a geographical area, wherein each vehicle has installed an apparatus as defined above.

In accordance with the invention a communication in a short-range system is used in order to broadcast from one vehicle to all other surrounding vehicles inter-vehicle information signals directly, i.e. without using the intermediary of e.g. a mobile radio communication network. In particular, in accordance with the invention, the signal format of the vehicle-specific signals depends from the determined current vehicle position. Thus, other (observing) vehicles (which have preferably installed a receiving device for such signals) can receive this vehicle-specific information.

The effective acquisition of the signal by the receiver is made possible by the position dependence of the signal format. Since the recipient, e.g. the driver of a vehicle, knows about the geographic areas of interest, i.e., the areas for which he/she wants to learn about the presence and intention of other vehicles, the receiver may be tuned to receive exactly those signals of interest. This tremendously speeds up the critical signal acquisition. At the same time, an appropriate allocation of signal formats to geographic locations can also allow to control the interference. Such an adequate association effectively may be implemented with a multiple access scheme.

The combination of fast acquisition of signals from other vehicles, only known through their position, and the direct communication between vehicles creates the desired channel with low delay for conveying relevant information between vehicles. In the present context, "relevant information" (i.e. vehicle specific information) can include information that is directly derived from the actuation of the steering wheel, the break, and accelerator pedal. This information can be provided before the vehicle reacts in a detectable way, and therefore in advance of systems that have to rely on such reactions. Furthermore, the information is tied with a vehicle, which at a given time is in a particular position - but which remains otherwise anonymous.

PREFERRED ASPECTS OF THE INVENTION

According to one embodiment (claim 2) the signal format of the vehicle-specific signals which depends from the determined current vehicle position is the transmission timing, e.g. a time slot in a TDMA communication method, or a transmission frequency, for example in a FDMA communication method, or a spreading code, for example in a CDMA communication method, of the vehicle-specific communication signals.

According to one embodiment the timing of the signal transmission may be chosen as the signal format, which depends on the position of the transmitting vehicle. GPS but also the time provided by cellular systems can be used for the synchronization of the clocks of all vehicles. Therefore, a global time reference becomes available with respect to which all vehicles can align their transmissions, as well as the reception of signals from other vehicles. The allocation of time slots can be fixed over longer periods of time and made known globally, either on a CD-ROM or broadcasted, or computed from the geographic coordinates. In one example, a fixed 2-dimensional regular grid can be defined to cover the surface of the earth. The allocation of the time slots can be performed in such a way, that close locations do not transmit at the same time. Furthermore, it is possible to reuse time-slots at a given fixed reuse distance. More general allocations can also be used. The outstanding property of this kind of time division multiplexing is that a receiver can be run continuously outside the transmission slots, and will automatically capture all signals received with a sufficient level. Thus, there is never the need to retune the receiver.

According to other embodiments there exist possibilities for distinguishing the signals from different sources by the use of different frequencies and/or different spreading codes. In these embodiments, however, a time division component is needed as well, since it would be uneconomical to build a sufficient number of receivers to receive the signal from all relevant sources in parallel and at the same time to transmit as well. However, the use of different frequencies and/or codes reduces the information bandwidth of a single carrier.

In accordance with another embodiment (claim 3) a receiving device is provided for receiving source-specific signals, indicating source specific information from at least one other source in said geographical area wherein said source specific signals are selected by the receiving device depending on the current vehicle position of the vehicle in which said apparatus is installed and depending on the current position of said at least one other source.This allows limiting the activity of the receiver to the reception of relevant data.

In accordance with another embodiment (claim 4) the communication apparatus can comprise a determining device for determining said source-specific information from the received source-specific signals. The source-specific information may be a wide range of information to be transferred to the other vehicle, e.g. the vehicle position, the vehicle velocity and/the vehicle movement direction.

In accordance with another embodiment (claim 6) at least one other source may be also a transmitting device of another vehicle or a geographically stationary station. That is, the source-specific communication signals may also contain source-specific information from fixed stations, e.g. from a stationary traffic light arranged at the side of the road. Therefore, the receiving device can provide to the driver not only information about other vehicles but also information from other sources which are not vehicles. Thus, the driver can also react to traffic situations and to traffic guidance information provided by traffic lights, road signs etc.

In accordance with another embodiment (claim 7) in a communication system where each vehicle is equipped with an apparatus in which the specific signal format for transmitting the vehicle-specific signals is changed dependent on the position of the vehicles, the geographical area is divided in a plurality of cells each having assigned a cell transmission/reception timing with respect to a global reference time; each vehicle further comprises a global reference time determining device for determining the global reference time; said vehicle position determining device determines in which cell of said plurality of cells, the vehicle is positioned; and each vehicle further comprises a transmission/reception control device adapted to control the transmitting device for transmitting the vehicle-specific signals at a transmission timing at which the determined global reference time coincides with the cell transmission/reception timing of the cell in which said vehicle is positioned, and to control the receiving device for receiving source-specific signals if the determined global reference time does not coincide with the cell transmission/reception timing of the cell in which said vehicle is currently positioned. That is, since the cell position and the mapping of the cell positions to transmission/reception times is known beforehand at least in the geographical area considered, the actual transmission timings of the signals will indicate the position of vehicles or sources in specific cells.

Preferably (claim 8), said determining device determines as said source-specific information the source position on the basis of the transmission timing of said received source-specific signals.

In accordance with another embodiment (claim 9), each vehicle can comprise a cell scanning device adapted to select a number of cells based on their transmission/reception timings, wherein said control device enables said receiving device to receive communication signals only at the timings corresponding to the cell transmission/reception timings of the selected cells. Thus, the cell-scanning device is adapted for performing a virtual scanning of only a sub-group of cells in the whole geographical area. For example, the scanning device may only scan cells on or beside the roads because other cells are of no interest (nothing is happening there) and thus the receiver which otherwise would have to be used for the scanning of all other cells in the geographical area can be used for other purposes.

According to another embodiment (claim 10), each vehicle comprises a vehicle-vehicle communication device for addressing a specific vehicle and for setting up a direct communication channel to the addressed vehicle. For example, the aforementioned additional receiver availability can be used for such a vehicle-to-vehicle communication in which two or more vehicles set up a channel for an inter-vehicle communication. Such data communications with neighbouring vehicles may be particularly advantageous in order to obtain maps, weather and road conditions information locally.

Further advantageous embodiments and improvements of the invention can be taken from the dependent claims. Furthermore, it should be noted that the invention is not restricted to the present disclosure and various modifications and variations may be carried out within the scope of this disclosure. Furthermore, it should be noted that the invention also comprises steps and/or features, which have been separately described in a specification and/or claimed in the claims.

Hereinafter, the invention will be explained with reference to its advantageous embodiments as shown in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

Fig. 1

shows a vehicle communication system in accordance with the invention in which the signal format depends on the determined current vehicle position;

Fig. 2a

shows the sub-division of geographical area GA into cells of a cell net CNET in the case of a 2-dimensional arrangement;

Fig. 2ba

shows the association of reception/transmission timings GT with cells C for the general case of dividing the geographical area GA into a plurality of cells;

Fig. 2bb

shows similarly as in Fig. 2ba a cell pattern;

Fig. 2c

shows a flowchart of a vehicle communication method in accordance with the invention when the cell mapping of Fig. 2b is employed; and

Fig. 2d

shows another embodiment of a cell layout improved over the one in Fig. 2a.

In the drawings the same or similar reference numerals denote the same or similar parts throughout.

DESCRIPTION OF THE INVENTION

Hereinafter, the invention is described with respect to its advantageous embodiments. First, however, the general principle of the invention will be discussed with reference to Fig. 1 showing a block diagram of the vehicle communication system SYS in accordance with the invention. It should be noted that the term "communication system" is to designate a system in which at least information is transmitted from one source.

Broadcasting for Providing Information on Position, Velocity, Acceleration and other Relevant Information

As described above, the vehicle industry has over many years developed a wide palette of driver assistance tools. However, the limitation of all these tools is the lack of knowledge about the actions and intentions of the surrounding vehicles.

Fig. 1 shows an overview of a communication system SYS for providing communications between vehicles V1, V2, V3 in a geographical area GA. As an example, Fig. 1 shows a scenario, where three vehicles V1, V2, V3 are driving on road sections RD1, RD2, RD3 interconnected at a road junction RNX. However, the invention is not limited to such a scenario at a road section RNX and generally the communication system SYS is intended to provide communications between vehicles located or driving anywhere within the geographical area GA. As shown in Fig. 1, communication may also be established with geographically fixed installed sources, for example a traffic light TL in the vicinity of the road junction RNX. Thus, communication signals may be transmitted from a vehicle itself or from a fixed installed source.

The intention of the communication system SYS in Fig. 1 is to provide a short-range communication system (for example in the range of a few hundred meters) in which the vehicles V1, V2, V3 and possibly some further sources BS transmit and receive vehicle-specific and source-specific signals CS1, CS2, CS3, CSBD, directly from other vehicles or sources without the intermediary of e.g. facilities of a mobile radio communication network. For this purpose each vehicle V1, V2, V3 and also the fixed source BS comprises an apparatus generally denoted with CA1, CA2, CA3, BSCA in Fig. 1.

Each apparatus CA1, CA2, CA3, BSCA comprises a transmitting device VBD1, VBD2, VBD3, BS-BD for transmitting vehicle-specific or source-specific signals CS1, CS2, CS3, CSBD. The vehicle-specific signals indicate vehicle-specific information of the vehicle, in which the apparatus is installed and the source-specific signals indicate source-specific information.

In accordance with another embodiment, each apparatus CA1, CA2, CA3 arranged in the vehicles can comprise a receiving device VRD1, VRD2, VRD3 for generally receiving source-specific signals CS1, CS2, CS3, CSBD from at least one other source in said geographical area GA wherein said source-specific signals CS1, CS2, CS3, CSBD indicate the source-specific information of the respective transmitting source. If the transmitting source is a transmitting device of another vehicle, the received source-specific signals are the vehicle-specific signals CS1, CS2, CS3. In case the transmitting source is the fixed source BS, the signals are generally the source-specific signals of the fixed source BS.

For providing the inter-vehicle communications, it is sufficient if each of the vehicle apparatus CA1, CA2, CA3 comprises the respective transmitting device and preferably the receiving device. However, in accordance with another embodiment of the invention also the fixed source BS may comprise a receiving device BS-RD for receiving the signals CS1, CS2, CS3 from the respective vehicles V1, V2, V3.

Each apparatus CA1, CA2, CA3 arranged in the vehicles also comprises a vehicle-position determining device VBD1, VBD2, VBD3 for determining the current vehicle position CAV1, CVP2, CVP3 of the vehicle in which the apparatus is installed. In accordance with one embodiment of the invention, such a vehicle-position determining device can determine the current vehicle position by means of a GPS (Global Positioning System) schematically shown in Fig. 1. Although not necessary for providing the inter-vehicle communication, also the general e.g. fixed source BS can have a source-position determining device BSPD. If the source BS is stationary, as is the case for the traffic light TL in Fig. 1, this device BSPD may simply be a memory in which the fixed position of the source BS is registered.

The respective apparatus CA1, CA2, CA3, BSCA can also comprise a control device BCD1, BCD2, BCD3, BCDBS and a determining device BSDD1, BSDD2, BSDD3, BS-DD which perform specific functions in accordance with other embodiments of the invention as explained below. For example, the determining device main function may be to determine source-specific information from the received source-specific communication signals.

The transmitting device VBD1, VBD2, VBD3, BSBD in accordance with the invention is adapted for transmitting the vehicle-specific signals CS1, CS2, CS3 BS-CS in a signal format BF1, BF2, BF3, BFB which depends on the determined current vehicle position CVP1, CVP2, CVP3 or source position BSP.

Position Dependent Signal Format

In accordance with the invention, the signal format depends on the determined current vehicle position. The dependency itself can be a function of the multiple access scheme used for the inter-vehicle communications. Three examples in accordance with advantageous embodiments of the invention are described below.

According to a first embodiment, the timing of the signal transmission may be chosen as the signal format, which depends on the position of the transmitting vehicle. GPS but also the time provided by cellular systems can be used for synchronising the clocks of all vehicles. Therefore, a global time reference is available with respect to which all vehicles can align the transmission of their own signal, as well as the reception of signals from other vehicles. The allocation of time slots to geographic locations can be fixed or at least very rarely re-planned. It can be made globally available, either on a CD-ROM or via broadcasting, or it can be derived directly by a simple formula from the geographic coordinates. In one example, a fixed 2-dimensional regular grid can be defined to cover the surface of the earth. The allocation of the time slots can be performed in such a way that close locations do not transmit at the same time. Furthermore, preferably time-slots can be re-used at a sufficient distance. Explicit examples of allocations will be discussed below. The outstanding property of this kind of time division multiplexing is that a receiver can be run continuously outside the time slot used for transmission, and that it will automatically capture all signals received with a sufficient power level. In such a scenario, the receiver needs never be re-tuned.

In accordance with a second and third embodiment, the signals from different sources are distinguished by the use of different frequencies (FDMA) and/or different spreading codes (CDMA). In these cases, however, a time division component is needed as well, since it would be uneconomical if not impossible to build a sufficient number of receivers to receive the signals from all relevant sources in parallel and at the same time to transmit as well. The use of different frequencies and/or codes is an advantage in some cases, e.g., when the distance at which the same signal format is used needs to be increased.

Selective Discontinuous Reception

Hereinafter, "geographical area" is to designate the area in which those transmitters are located, whose signals can be decoded correctly by a given receiver. In principle a receiver can decoded the signals from all transmitters in its geographical area. In accordance with another embodiment of the invention, it is however possible that said receiving device is configured for receiving signals only from a selected predetermined set of sources in said geographical area GA. The receiving device can select the set of sources depending on its own current position (and preferably velocity) and depending on the current position (and preferably velocity) of all others sources in said geographical area. For example, for the vehicle V2 in Fig. 1 it will be sufficient to have information about the vehicle V2 approaching the junction RNX and about the vehicle V3 leaving the junction NRX. That is, each receiving device may only monitor these signals because it is only interested in receiving information about the sources in these locations.

Since each geographical location, i.e. positions of a vehicle, will always be indicated through the signal format, the preferably arranged receiving device only tunes to the signal formats associated with locations that are of interest. This frees the transceiver for other tasks in the meantime.

Dedicated Vehicle to Vehicle Communication

Examples of other tasks that can be performed include intercom communication with other vehicles, exchange of maps, road- and whether-information, as well as listening to a broadcast channel previously set-up by the front vehicle in a convoy. Furthermore, such a channel can also be used for short voice messages, like "Please drive first, I wait!". For this purposes each vehicle can comprise a vehicle-to-vehicle communication device for addressing a specific vehicle and for setting up a direct communication channel to the addressed vehicle.

Such devices can re-use time-slots that are irrelevant to the communication parties. This can be on the same or a different and code. The call set-up request (including the desired frequency, code and timing) is transmitted on the broadcast channel of the calling party. The reference can be to any free transmission resource foreseen in the system including in particular unused time slots on the same carrier frequency or on other parallel carriers configured for that purpose. Note all vehicles that wish to set-up a call (i.e. address a specific vehicle) must scan the broadcast channel corresponding to other locations for one period T before sending a call set-up request in order to ensure that no other vehicle has reserved a previously free resource. Also note that a new call set-up must be performed if a transmission is interrupted at some stage.

The time used by the calling party shall be chosen in such a way that it does not interfere with the scanning of the called party. In a first step this can be estimated, later on the two vehicles can exchange their scanning patterns (to be described below) in order to increase the available transmit time (roads are narrow beams and not half-planes).

Cell Arrangements, Cell size, Range, and Bandwidth Requirements

The embodiment shown in Fig. 2a, 2ba is based on differentiating vehicle positions by the timing of signals. In this "cell mapping approach" segments or surface areas (hereinafter called "cells") are mapped to an absolute reference time, as, for example, provided by a GPS system.

Regarding the vehicle position determination in Fig. 2a, 2ba it may be noted that with the advent of radio navigation, e.g. GPS for determining the position, it is possible to let a vehicle know its exact position at almost any time. A good GPS system can perform a position determination with a resolution about 20m.

Thus, as shown in Fig. 2a, if a GPS system is used, each vehicle having a position-determining device VPD1, VPD2, VPD3, BSPD cooperating with the GPS can determine its position and can in principle transmit signals with a transmission timing identifying the vehicle position.

As shown in Fig. 2a, the geographical area GA is overlaid with a cell net CNET with vertical lines VL and horizontal lines HL, which form a number of rectangular cells CELL11, CELL21, CELL22. Of course, the cells do not necessarily need to be rectangular and any other shape can be used. Typically, the size of a cell is about 10x10 meters to cover, on the average, only a single car. Of course, merely subdividing the geographical area GA in a plurality of cells still does not attribute any sufficient position information to the communication signals CS1, CS2, CS3, CSBS. The second reference comes from a Global Reference Time GRT available to all vehicles and all transmitting sources. Such a global reference time GRT as shown in Fig. 2a, can also be part of a global positioning system GPS. Furthermore, as clocks become more accurate, there need not even be a global synchronization of all vehicles if the reference time is accurately available within each vehicle. Therefore, generally in this embodiment each vehicle V1, V2, V3, further generally comprises a global reference time determining device GTR1, GTR2, GTR3, GTRB for determining the global reference time GRT in each vehicle.
As shown in Fig. 2ba, each cell C11, C12, C13, ... C1n (in Fig. 2ba: n = 6), C21, C31, Cm1 (in Fig. 6b: m = 5), .... , Cmn has assigned to it a predetermined cell transmission/reception timing GT11, ..., GTmn. Basically, the transmission/reception timing indicates for each cell that a vehicle residing in this cell can only transmit signals at the transmission/reception timing assigned to the specific cell. For example, in Fig. 2ba the vehicle V1 located in cell C52 will only transmit its beacons at the timing GT52. Likewise, vehicles V4, V2, V3 will only transmit at timings GT44, GT35, GT26. The fixed station BS will only transmit at GT43.

Since the vehicles V1-V4 continuously change their position along the road RD each vehicle must know its exact position in the geographical area GA at least with respect to finding out in which cell it is located. Therefore, the vehicle position determining device VPD1, VPD2, VPD3 of the vehicles and BSPD of the fixed station BS determines in which cell of the plurality of cells the vehicle or the fixed station is positioned.

If now the vehicle cell position and the global reference time is available in each vehicle continuously changing position, the respective control device BCD1, BCD2, BCD3, controls the respective transmitting device VBD1, VBD2, VBD3, BS-BD for transmitting signals (beacons) at a transmitting timing at which the determined global reference time GRT coincides with the cell transmission/reception timing GTmn of the cell in which the vehicle is positioned. Preferably, the control device controls the respective receiving device VRD1, VRD2, VRD3, BS-RB for receiving signals (beacon signals) if the determined global reference time GRT does not coincide with the cell transmission/reception timing of the cell in which said vehicle is positioned. Thus, the determining device BS-DD1, BS-DD2, BS-DD3, BS-DD can determine the transmitting source position on the basis of the transmitting timing of the received signal.

Thus, Fig. 2a shows a subdivision of the geographical area GA in rectangular cells CELL11, CELL21, CELL22 as mentioned before. Of course, the cells can have other shapes as well. Fig. 2b shows the boundary of the basic cell arrangement. This basic cell arrangement is repeated periodically. Such an arrangement has the advantage that the cell locations can be computed analytically. On the other hand, this arrangement is not the most effective one for highways in the countryside. In such a case, the cells can only cover the surface of the highway but the allocation of signal formats to locations must then be made explicitly. In all cases, and for all signal formats, there will be a period T after which a given cell, e.g. CELL11, will transmit again. This periodicity is needed both to refresh the information and also for reliability purposes. It appears reasonable to have at least two repetitions in 1 second, which means that the period T must be 0.5 s.

A cell should have a size of the order of the space taken by a typical vehicle. Even with slowly moving cars a size of 4x4 meters will not lead to ambiguities. The position is measured at the beginning of the period T. The alignment of these periods is agreed once and for all with respect to GPS time, for example.

The range at which the radio signals must be received is determined by the manoeuvring time. With a deceleration of 10 m/s² (1 g), a car driving at 50 m/s (180 km/h) can come to stop after 125 m. If we add 1 second for the acquisition of the signal we end up with (175 m). Therefore, in the case of a regular planning, a typical size of the cell arrangement, i.e., of the spatial period will be of the order of 352 m. In this case, a regular arrangement of cells would contain 7744 cells of 4x4 meters. The size of a message for indicating the position, velocity, and acceleration needs no more than 14 bytes, adding some spare leads to 20 bytes. These can be used for communication set-up or for providing additional information on angle, angular velocity and angular acceleration if the car is sliding or spinning, for example. Using a typical rate ½ code implies that 320 x 7744 bits must be transmitted every 0.5 s. With binary shift keying, this implies a required bandwidth of the order of 5 MHz.

A bandwidth of 5 MHz in open environments might lead to inter-symbol interference. In order to cope with this, special modulation techniques, like Orthogonal Frequency Division Multiplexing might be used. Also note that the timing of the transmission correlate to the position of the transmitter and that this can be used to improve the channel estimate, at least in the case of dense traffic.

If the velocity had been 33 m/s (120 km/h), the range required would have been 88 m and the number of cells in the arrangement would have been 1936, implying a bandwidth of 0.6 MHz. The consequences from this small example are that urban and suburban environments can easily be handled with a regular arrangement of cells, and that highways are best addressed with linear cell arrangements, e.g., indexed using the integrated length of the central line from a given reference point. This is one of the types of alternative cell arrangements mentioned previously. Furthermore, the difference in the required range, mentioned above also shows that it is wise to adapt the transmit power depending on the environment. In this process a dependency on the varying type of buildings found in urban and suburban environments must be taken into account.

Power Control and Antenna Steering

In another embodiment, the power control is further refined by also allowing an adaptation based on the importance of the message. The information about an unforeseeable obstacle on the highway, like an accident, or the end of a queue should be indicated with a higher power. The consequence is to increase the signal to interference ratio for such signals, and to make them detectable at larger distances. At the same time the signal to interference ratio for other signals is reduced, which typically has little impact, however.

Every vehicle wants to have the best signal to interference ratio for those signals it is most interested in. As a consequence, the vehicle should steer the antenna to those areas. This is done in another embodiment, in which the vehicle steers the antenna along the road. For that purpose, the vehicle uses an electronic road map and maximizes the signal to interference ratio for the area which transmits the signal at a given time on a given frequency with a given code. In the TDMA scheme, this means that the antenna is steered as a function of time to capture the signal from the area transmitting at that time. In a simplified version, the vehicle steers a sufficiently broad antenna pattern to the front of the vehicle. The pattern must have a breadth to capture signals behind curves. Since only slow vehicles can drive around narrow curves, the breadth of the antenna pattern is made dependent on the velocity of the vehicle.

Allocation of Resources to Cells

So far, we have specified generally how cells are arranged into "arrangements" of cells and how generally the transmitting devices are controlled at timings with respect to a global reference timing. However, we have not yet defined how the radio resources, time, frequency and code are associated with individual cells. For example, in the case of a time division multiplexing, different locations GT11, GT12, ..., GTmn are differentiated by different transmit times. There is great freedom, since there are no restrictions on the availability of information (the simultaneous transmission of relevant information should be avoided), and since the receiver does not need to be retuned. In the case of a 2-dimensional assignment, it is in particular possible to assign the times starting in the upper left corner (0 in Fig. 2bb) and proceeding row by row (0 ... 4; 5 ... 9; 10 ... 14; 15 ... 19; 20 ... 24) down to the lower right corner (24). In the case of a highway, the assignment can be in the form of a zig-zag, i.e., running over all lanes, before going to the next increment in traffic direction.

FDMA and CDMA components can be added in order to increase the separation between transmitters using the same signal. An important restriction from practical radio transceiver design is that a transceiver cannot receive and transmit at the same time. Therefore, the planning must be such that no location has to transmit at a time at which any information relevant to it is transmitted from another location. One arrangement, which fulfils this requirement, is shown in Figure 2bb. The cells are shown as being quadratic for simplicity, in reality, one would prefer hexagonal cells, but other shapes are possible as well. A vehicle or other source that is in a position corresponding to the cell GT₃₁ will scan cells numbered 5, 6, 11, 16, 15 of the present geographical area GA1 and also cells 9, 14, 19 of the adjacent geographical area GA'. The switching from one code to the other from cell numbered 9 in GA' to cell numbered 10 in GA1 can easily be performed in the baseband receiver. If different frequencies where used in neighbouring arrangements, the synthesizer would need to be re-tuned, however. In order to allow for such a re-tuning, an allocation of times to locations is shown in Fig. 2bb.

Fig. 2d would be more advantageous. In this arrangement, adjacent locations are never allocated to adjacent times. This provides the necessary time for re-tuning the synthesizer in order to scan adjacent cells, e.g., when the vehicle is in cell numbered 5 in GA1 it will scan the cells numbered 15, 3, 18, 8, 20 of the present area GA1 but also the cells numbered 17, 7, 22 of the precious area GA'. In conclusion, we note that the re-tuning will make the receiver blind for some locations in the own and neighbouring cell arrangements, whereas code division just prevents to detect one position in each neighbouring cell arrangements, namely the position corresponding to the own transmission.

Description of the Processes in the Vehicle Apparatus

The method for vehicle communication in accordance with the invention is shown in Fig. 2c. The flow chart in Fig. 2c is performed by each vehicle. In step S1 each vehicle synchronizes its clock, and updates its own position, e.g., using GPS or information from the cellular system. This is performed at predefined times nT (n and integer). Note that if none of the latter system is available, the vehicular system relies on the stability of its build-in oscillator and integrates the motion of the car for estimating the kinetic data.

In step S2 the vehicles determine the surroundings it is interested in, either by consulting a map or by using fixed preferences, e.g., at a given velocity, this and that distance ahead, so and so much on the sides and behind the vehicle. Furthermore, it also determines the timing of its own transmission. For each of those locations it determines the times at which the receptions starts tRXi and the parameters, like code cRXi, and frequency fRXi. The latter can also include resources for dedicated communication between vehicles. Correspondingly, it determines the resources of its broadcast transmission tTX0, cTX0, fTX0 as well as resources for dedicated transmissions tTXj, cTXj, and fTXj. The retuning might need some addition time called tLOk.

Step S3 shows the time-counter increment t<-t+tau, where tau is the duration of the shortest operation that might occur.

In step S4, the vehicle checks whether it needs to re-tune the synthesizer (t=tLOi?), it yes it tunes the frequency to fLOi.

In step S5, the vehicle checks whether it has to transmit in the next burst (t=tTXi?), if yes it configures its transmitter (selects the code cTXi) and sends its information.

In step S6, the vehicles checks whether it should listen (t=tRXi?), if yes it configures its receiver to the code cRXi.

Finally in step S7, the vehicle tests whether the time for updating its own position is reached, if yes it branches to step S1 otherwise it proceeds to step S3.

Note that this scheme addresses both the transmission of broadcast information and of information dedicated to a particular vehicle.

INDUSTRIAL APPLICABILITY

The approach described above uses the global time and position information in order to synchronize the transmission and reception of the vehicle such that a fast acquisition and interference control is possible. This approach is extremely simple and cost-effective both in frequency utilization and transceiver hardware. All that is necessary is the determination position of the vehicles and the determination of the global time GRT as well as the appropriate reception/transmission timing GTmn in each cell.

As described, the vehicle communication system in accordance with the invention is a rather low complexity communication system, which allows in almost real-time (as regards the vehicle position) to exchange vehicle-specific information among vehicles. This is principally achieved by using a transmitting technique, i.e. a one-to-many transmission from each vehicle.

An inconvenience of the invention is that it deploys its full benefit only with a large penetration of the system. The introduction could be accelerated by the introduction of lanes reserved for equipped cars, like the car pool lanes in the US. This is more than justified by the increased traffic densities, which become possible if cars are equipped.

It may be noted, that such a system is not necessarily limited to vehicles constituted by cars. The vehicles could also be cyclists, motorcyclists or even pedestrians because it may be of utmost importance for a vehicle to recognize the movements and positions of pedestrians within in road sections. Furthermore, the system may also apply to communications between vehicles constituted by trains, ships of aircrafts.

Furthermore, it should be noted that various modifications and variations of the invention are possible on the basis of the above-described teachings. In particular, the invention may comprise features and/or steps, which have been separately described in the specification and in the claims.

Reference numerals in the claims only serve clarification purposes and do not limit the scope of these claims.

Claims (10)

1. An apparatus (CA1,CA2, ..., Can) installed in a vehicle (V1, V2, ..., Vn) for providing vehicle specific information in a geographical area (GA), comprising:

   a transmitting device (VBD1, VBD2, ..., VBDn) for transmitting vehicle-specific signals (CS1, CS2, CSn), indicating vehicle-specific information of the vehicle in which said apparatus is installed;

   a vehicle position determining device (VPD1, VPD2, ..., VPDn) for determining the current vehicle position (CVP1, CVP2, ..., CVPn) of the vehicle in which the apparatus is installed; and wherein

   said transmitting device (VBD1, VBD2, ...; VBDn) is adapted for transmitting said transmitted vehicle-specific signals (CS1, CS2, CSn) with a signal format which depends on the determined current vehicle position (CVP1, CVP2, ..., CVPn).
2. An apparatus according to claim 1,
   characterized in that
   said signal format of said vehicle-specific signals (CS1, CS2, CSn) which depends from the determined current vehicle position (CVP1, CVP2, ..., CVPn) is the transmission timing or a transmission frequency or a spreading code of the vehicle-specific communications signals (CS1, CS2, CSn).
3. An apparatus according to claim 1,
   characterized in that
   a receiving device (VRD1,VRD2, ..., VRDn) is provided for receiving source-specific signals (CS1, CS2, CSn), indicating source specific information from at least one other source (VBD1, VBD2, ..., VBDn; BS) in said geographical area (GA); wherein
   said source specific signals are selected by the receiving device depending on the current vehicle position of the vehicle in which said apparatus is installed and depending on the current position of said at least one other source (VBD1, VBD2, ..., VBDn; BS)
4. An apparatus according to claim 3,
   characterized by
   a determining device (BSDD1, BSDD2, BSDD3, BS-DD) for determining said source-specific information from the received source-specific signals (CS1, CS2, CSn).
5. A communication system (SYS) for providing vehicle specific information between vehicles (V1, V2, ..., Vn) and/or other sources in a geographical area (GA), wherein each vehicle has installed an apparatus in accordance with one or more of claims 1-4.
6. A system (SYS) according to claim 5,
   characterized in that
   at least one other source (VBD1, VBD2, ..., VBDn; BS) is a transmitting device (VBD1, VBD2, ..., VBDn) of another vehicle (V1, V2, ..., Vn) or a geographically stationary station (BS).
7. A system (SYS) according to claim 5 or 6,
   characterized in that
   said geographical area (GA) is divided into a plurality of cells (C11, C12, ..., Cmn) each having assigned a cell transmission/reception timing (GT11; GT12, ..., GTmn);
   each vehicle (V1, V2, ..., Vn) further comprises a global reference time determining device (GTR1, GTR2, GTR3) for determining the global reference time (GTR);
   said vehicle position determining device (VPD1, VPD2, ..., VPDn) determines in which cell of the plurality of cells (C1, C2, ..., Cn) said vehicle is positioned; and
   each vehicle (V1, V2, ..., Vn) further comprises a transmission/reception control device (BCD)

   to control the transmitting device (VBD1, VBD2, ..., VBDn) for transmitting vehicle-specific signals (CS1, CS2, CSn) at a transmitting timing at which the determined global reference time (GRT) coincides with the cell transmission/reception timing (GT11; GT12, ..., GTmn) of the cell in which said vehicle is currently positioned, and

   to control said receiving device (VRD1, VRD2, ..., VRDn) for receiving said source-specific signals (CS1, CS2, CSn) if the determined global reference time (GRT) does not coincide with the cell transmission/reception timing (GT11; GT22, ..., GTmn) of the cell in which said vehicle is currently positioned.
8. A system (SYS) according to claim 7,
   characterized in that
   said determining device (BSDD1, BSDD2, BSDD3, BS-DD) determines as said source-specific information the source position on the basis of the transmission timing of said received source-specific signals (CS1, CS2, CSn).
9. A system according to claim 8,
   characterized in that
   each vehicle (V1, V2, ..., Vn) comprises a cell scanning device adapted to select a number of cells (C1, C2, ..., Cmn) based on their transmission/reception timings (GTRmn) wherein said control device (BCD) enables said receiving device to receive communication signals only at the timings corresponding to the cell transmission/reception timings (GTRmn) of the selected cells.
10. A system according to claim 5-9,
    characterized in that
    each vehicle (V1, V2, ..., Vn) comprises a vehicle-vehicle communication device for addressing a specific vehicle and for setting up a direct communication channel to the addressed vehicle.

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