communication system

The invention relates to a method for locating a vehicle to be located. Furthermore, the invention relates to a vehicle to vehicle communication system. To reduce death and injuries caused by vehicle crashes, the U.S. Department of Transportation (USDOT), National Highway Traffic Safety Administration (NHTSA) have considered mandating the use of vehicle to vehicle (V2V) communication systems designed to transmit basic safety information between vehicles to facilitate warnings to drivers concerning impending crashes. Each vehicle is equipped with a GPS receiver to receive the vehicle location from the satellites. V2V system on the vehicle will transmit the vehicle speed, location and other safety information to the other V2V equipped vehicles. In this manner, a vehicle on the road equipped with V2V system is aware of other V2V system equipped vehicle's speed and location information within certain range (such as 300 meters).

A vehicle obtains its own position information through its GPS receiver, and the GPS signal from the satellite is very weak. Therefore, it can be easily interfered with by other sources or blocked by surrounding environment such as tress, bridges, tunnels, and buildings. When this occurs, V2V communication loses vital information.

Accordingly, there is a need for a possibility to locate a vehicle continuously.

The invention provides a method for locating a vehicle to be located by using a vehicle to vehicle communication system, with the following steps:

Providing an equipped vehicle that has at least one vehicle-based antenna system with several antennas,

Providing a vehicle to be located that has at least one vehicle-based antenna system with several antennas, Establishing a multiple in and multiple out communication between both vehicles via their vehicle-based antenna systems, and

Locating the vehicle to be located by analyzing the multiple in and multiple out communication established between both vehicles. The invention further provides a vehicle to vehicle communication system for locating a vehicle to be located by an equipped vehicle, wherein the vehicle to vehicle communication system comprises at least one processing unit and two vehicle-based antenna systems each assigned to a respective vehicle, wherein each vehicle-based antenna system comprises several antennas so that the vehicle to vehicle communication system has a multiple in and multiple out antenna system configured to locate the vehicle to be located.

In general, the multiple in and multiple out antenna system established is used for exchanging signals that are evaluated so as to locate the vehicle to be located, in particular the vehicle in the front. In fact, the environment is categorized in cells that establish the environment matrix compared to the coupling matrix describing the communication between both vehicles. The matrixes are compared with each other so as to identify the location of the vehicle to be located.

Hence, the multiple in and multiple out communication between both vehicles may be defined by a coupling matrix, wherein the coupling matrix is determined by the vehicle to vehicle communication system when the multiple in and multiple out communication is established, in particular wherein the parameters of the coupling matrix are associated with the distance between both vehicles and the relative offset and/or wherein the parameters comprise amplitude and phase information of the signals exchanged. Therefore, each component of the coupling matrix, also called parameter of the coupling matrix, is assigned to a communication between one antenna of the equipped vehicle and one antenna of the vehicle to be located wherein phase and amplitude information of the respective signal (portion) is assigned to the component.

According to another aspect, the environment of the equipped vehicle is divided in cells, wherein the cells represent possible locations of the vehicle to be located in the environment of the equipped vehicle, and wherein the cells establish an environment matrix, in particular wherein each cell of the environment matrix has the same dimension as the coupling matrix. Thus, each cell of the environment matrix may be assigned to the respective location of the vehicle to be located.

Furthermore, each cell of the environment matrix may be assigned to a correlation matrix. Particularly, each cell of the environment matrix is compared with the coupling matrix determined so as to identify the cell of the environment matrix matching the coupling matrix determined in order to locate the vehicle to be located. In other words, the multiple in and multiple out antenna system may be configured to exchange signals evaluated by the processing unit to locate the vehicle to be located based upon a comparison of the signals exchanged with a previously determined environment matrix having several cells assigned to possible locations of the vehicle to be located. Accordingly, the vehicle to be located can be located in an easy and simple manner.

Another aspect provides, prior to the comparing, the coupling matrix determined is converted into a correlation matrix. In other words, the processing unit may be configured to convert a coupling matrix into a correlation matrix, wherein the coupling matrix defines the communication between the vehicle-based antenna systems. The conversion ensures that the correlation matrix obtained can be compared with the cells of the environment matrix easily so that the evaluation and locating is improved.

Particularly, the correlation matrix obtained from the conversion of the coupling matrix is matched against each cell of the environment matrix, and wherein the best match is assigned to the location of the vehicle to be located. In other words, the processing unit may be configured to define the environment of the equipped vehicle by an environment matrix, and wherein the processing unit is configured to compare the environment matrix and the correlation matrix so as to identify the location of the vehicle to be located. The cell of the environment matrix that matches best with the converted coupling matrix, namely the correlation matrix, can be deemed as to be assigned to the location of the vehicle to be located. Depending on the rank or rather the dimension of the environment matrix, the resolution of the locating can be adapted. For instance, a minimum mean square error is used for identifying the best matching. Thus, the best matching cell can be identified in a fast and cost-efficient manner.

Moreover, one of the several antennas may be used as a reference so that the signals of the other antennas are used for providing relative information, in particular relative phases with respect to the reference. When the relative target location is not changing, the absolute received signal phase information is changing at different times. However, the relative phase information among the receiving antennas will remain the same. So, the antenna used as the reference ensures that the other signal phases will be relative phases with respect to the one of the reference. The relative phases are dependent on the distance difference among these antennas from the emitter and the wavelength of the signal.

According to another embodiment, a velocity matrix and/or an acceleration matrix are/is established in addition to the environment matrix used for locating the vehicle to be located. Besides the environment matrix used for locating the vehicle to be located, velocity and/or acceleration matrix mapping may also be applied so as to gather information with regard to the velocity and/or acceleration of the respective vehicle. These matrixes will have correlated to the vehicle speed information sent from the respective vehicle. The processing unit may be configured to perform a method as described above.

A MIMO (multiple in and multiple out) antenna system is introduced to complement the GPS location function of a vehicle to vehicle system and enhance the location identification of the other vehicles. Using the MIMO antenna system, the vehicle collision warning features for the vehicle to vehicle equipped vehicle can be maintained even when the satellite information is lost, for instance GPS information. The MIMO antenna system can also enhance the signal communication link between vehicle to vehicle equipped vehicles. Generally, the vehicle to vehicle communication system is configured to locate the vehicle when satellite communication is lost. The foregoing aspects and many of the attendant advantages of the claimed subject matter will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: - Figure 1 schematically shows a vehicle to vehicle communication system according to the invention,

Figure 2 illustrates an environment matrix used by a method for locating a vehicle to be located according to the invention,

Figure 3 shows the environment matrix of Figure 2 in more detail, - Figure 4 shows another example for a vehicle to vehicle communication system according to the invention, and

Figure 5 shows a diagram illustrating the scanning results by applying a method for locating a vehicle to be located according to the invention on the system shown in Figure 4. In Figure 1 , a vehicle to vehicle communication system 10 is shown comprising two vehicles A, B each having a vehicle-based antenna system 12, 14 with several antennas A1 -A3, B1 -B3. In the shown embodiment, both vehicle A and vehicle B have three antennas.

Vehicle A transmits signals containing amplitude (A) and phase (B) information. Vehicle B antennas B1 - B3 receive respective signals. The relationship between the antennas A1 -A3, B1 -B3 is governed by the relationship of coupling matrix C as shown by equations (1 ), (2) hereinafter;

Bl rii C12 C13 Al

B2 = C21 C22 C23 A2

-53. C31 C32 C33. .vf 3.

The coupling matrix C parameters are associated with the distance between both vehicles A, B and offset of the two vehicles A, B from the primary vehicle driving directions. Each parameter has signal amplitude and phase information as shown by equation (3) hereinafter:

Cll = Alle ^j911

Furthermore, at least one processing unit 16 may be provided that is connected to one of the vehicle-based antenna systems 12, 14, for instance the one of vehicle B.

Figure 2 illustrates the different positions of the target vehicle, also called vehicle to be located, in the front of the vehicle equipped. For instance, vehicle A corresponds to the vehicle to be located whereas vehicle B corresponds to the equipped vehicle.

The possible positions of the vehicle to be located can be mapped in [m n] cells, where m relates to the distance (amplitude, A) and n represents the vehicle offset (phase, B) from the driving direction. The target at [i,j] position has a correlation matrix Cij as shown by equation (4) hereinafter:

Cijll CijVZ Cij 13

Cij = Cijll Cij22 Ci/23

Ci i l Cij32 Ci/33.

As shown in Figures 2 and 3, the target vehicle positions can be represented in [mn] cells, with each cell represented by [3 by 3] matrix, namely a matrix assigned to the coupling matrix C. Thus, [3 by 3] matrix represents MIMO antenna system of 3 elements at both ends, namely both vehicle-based antenna systems 12, 14.

The correlation matrixes associated with each positions are shown in Figure 3 in more detail. Then, the mapping cell of the environment matrix can be listed as shown by equation (5) hereinafter: CI

Cl»¾.

C2n _ts ^'

Cmn _zs

Cmn ₃₃

When the vehicle to vehicle system 10 receives signals and it forms a correlation matrix as shown by equation (6) hereinafter:

Cyxu Cyx ₁₂ Cyx ₁₃

Cyx Cyx ₂₁ Cyx ₂₂ Cyx ₂₃

lCyx ₃₁ Cyx ₃₂ Cyx ₃₃ The algorithm will match this correlation matrix against each cell in the environment matrix in Eq (5). The best match will be used to identify the vehicle location of the vehicle to be located.

For example, a minimum mean square error between Cyx and Cij (Eq.(4) and Eq.(6)) identifies the best matching of the location of yx to ij. When the relative target location is not changing, the absolute received signal phase information in Eq.(3) is changing at different times. However, the relative phase information among the receiving antennas will remain the same. So, one antenna of the respective antenna system 12, 14 is used as a reference as shown in Figure 3. The other signal phases will be relative phases. This relative phase is dependent on the distance difference among these antennas from the emitter and the wavelength of the signal.

Not only can the position matrix cell be formed, velocity and acceleration matrix mapping can also be applied. These matrixes will have correlated to the vehicle speed information sent from the target vehicle. In the application, there will be predicated location, vector velocity obtained through the history. This information could contain the information obtained from the GPS back to the certain time when the GPS were still available. They could also contain the information purely obtained by vehicle to vehicle MIMO antenna location identification method described above. By combining the history, prediction, and current vehicle to vehicle MIMO antenna vehicle location methods, the system 10 can achieve good vehicle location identification at the time when GPS signal is absent.

Even when the GPS is still available, the vehicle to vehicle MIMO antenna vehicle location identification can provide the second data point as a reference and enhance the system location accuracy and speed of identifying location.

In Figures 4 and 5, an example is shown for illustrative purposes.

Making the illustration simple, two vehicles driving in the same direction on the same lane or two adjacent lanes are assumed. In this case, the two vehicles are driving in the same general direction. Different offset of the vehicle and the distance between them will have different C parameters.

For one antenna on the target vehicle, namely the vehicle to be located, the MIMO antenna output peak searching results can look like in the plot in Figure 5. Two targets at 90 degree (vertical front) and 120 degree orientation.

When there are multiple transmission antennas on the target vehicle, with the multiple receiving antenna, using mean square error to find the best matching and location.