Abstract:
C2X communication is made possible efficiently via WLAN by apparatuses and a method for filtering data frames received by a vehicle from a receiver via a WLAN connection, wherein a frame type indicated in a received data frame is used to decide that device to which data in the data frame are transmitted.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the U.S. national phase application of PCT International Application No. PCT/EP2008/059924, filed Jul. 29, 2008, which claims priority to German Patent Application No. 10 2007 059 023.9, filed Dec. 6, 2007, and German Patent Application No. 10 2008 035 419.8, filed Jul. 29, 2008, the contents of such applications being incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to methods and apparatuses for selecting data transmitted via a WLAN connection. 
       BACKGROUND OF THE INVENTION 
       [0003]    The Car-to-Car Communication (C2C-Communication) discussed below is a term defined by the Car-to-Car Communication Consortium (C2C-CC), an affiliation between several automobile manufacturers. C2C-CC is developing an open industrial standard for Car-to-Car Communication and for communication between the vehicles and infrastructure devices (traffic lights, etc). 
         [0004]    A basis for such Car-to-Car radio systems may be wireless communication systems in the form of WLANs (Wireless Local Area Networks) based on the standard defined by the IEEE under the standard descriptor 802.11, for example (see, for example: IT-Wissen, Das groβe Onlinelexikon für Informationstechnologie [IT Knowledge, The big online dictionary of information technology]). 
         [0005]    C2X communication comprises C2C communication (Car-to-Car Communication) and communication between a vehicle and a further device, which is not a vehicle, such as an infrastructure device (traffic lights, etc.) 
         [0006]    For Car-to-X-communication (C2X-communication), a WLAN implementation based on the 802.11p standard is conceivable, said standard not yet having been approved, however. This subform of the WLAN standard 802.11 is distinguished by the opportunity for ad-hoc communication and long ranges. Ad-hoc communication is a mode in which at least two subscribers (radio devices in vehicles, for example) communicate with one another spontaneously (ad hoc), with communication also being able to be effected from a subscriber to a final destination via a plurality of subscribers forwarding the communication as intermediate stations. Besides the ad-hoc mode communication, WLAN is also acquainted with an infrastructure mode, which operates using base stations (access point). 
         [0007]    With the currently used radio standard based on IEEE /802.11a/b/g/n, commercially available WLAN routers have the drawback that they require relatively long setup times for the communication (channel setup latencies), which reduces applicability. However, said 802.11a/b/g/n standards have significantly higher data rates than 802.11p, which in turn makes them of interest for multimedia applications. 
       SUMMARY OF THE INVENTION 
       [0008]    It is an object of the present invention to avoid the aforementioned drawbacks and allow efficient C2X communication. 
         [0009]    The invention allows use of 802.11-WLAN transmission methods (particularly 802.11a or 802.11b or 802.11g or 802.11n) using commercially available WLAN radio engineering both for C2X communication and for communication of other contents (for example for Internet/http/etc. communication, “surfing” the Internet etc.) using the same WLAN radio engineering appliances in a motor vehicle. In this case, the very good range and the relatively short connection setup times of available WLAN standards such as 802.11a/b/g/n can be used efficiently. One significant implementation of the invention is the expansion of the MAC-Layers in the WLAN standard 802.11 (for example 802.11 a/b/g/n), by a data packet type (which can be used for the C2X communication according to aspects of the invention) (for example frame type 3 or frame type 2) with one of the (MAC layer header) frame subtypes 8 to 15 (which have not yet been used), which is ignored by existing WLAN implementations but which allows modified implementations to set up effective C2X communication in parallel (that is to say at the same time and/or by the same WLAN communication terminal, for example) with other WLAN communication (e.g. use of the Internet). 
         [0010]    The invention relates to a method for filtering data transmitted to a receiver in a motor vehicle via a WLAN connection, wherein a filter device (for example an expanded MAC software driver) uses at least the frame type contained in a data frame (e.g. “3”; or “2” with subtypes) to decide about that device (device processing C2X data or device processing http data) to which the respective data frame is transferred. 
         [0011]    In this case, the frame type of a data frame can be used to decide whether the data frame is transferred to a C2X device or to another (vehicle) device (for example device (e.g. Internet browser) processing http or Internet data further). 
         [0012]    The decision about that device to which the data frames are transferred may involve a frame type (“3”) or else a combination of a frame type and a particular (MAC layer header) frame subtype (for the frame type “2”, one of the (MAC layer header) frame subtypes “8”, “9”, “10”, “11”, “12”, “13”, “14”, “15”). 
         [0013]    The data can be transmitted using a 802.11a or b or g or n standard, in particular. 
         [0014]    Besides filtering of received data, the invention also relates to a method for sending data frames via a data link installed in a motor vehicle, wherein from a C2X device (for example a C2X controller module in the vehicle) are provided with a frame type identifier (type 2 with subtypes 8 to 15 or type 3 etc.), whereas data to be sent which come from other vehicle devices (devices processing http/Internet/Multimedia data) are provided with another frame type identifier. 
         [0015]    In addition, the invention relates to a reception device for a vehicle-based implementation with a filter device for deciding about the forwarding of received data frames to a C2X device (C2X) or other device (http/Internet-Browser/Multimedia etc.) using types indicated in the MAC layer header of the data frame (“3”; “2” with particular subtypes). 
         [0016]    The invention also relates to a transmission device for implementation in a vehicle and for sending data frames, with a distinguishing device for distinguishing (prior to sending) data packets originating from a C2X device with (only or at least) one frame type (“2” with subtype 8 to 15 or “3”) and for distinguishing data packets with another frame type which originate from another vehicle-based device (Internet/http/Multimedia etc.). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0017]    The invention is best understood from the following detailed description when read in connection with the accompanying drawings. Included in the drawings is the following features: 
           [0018]      FIG. 1  schematically shows the sending and receiving of data packets by a vehicle via a WLAN connection taking account of frame types. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0019]    The 802.11 standard essentially defines two layers: 
         [0020]    (a) the physical layer defines the physical transportation medium (frequency, modulation . . . ) and the rudimentary transportation of databytes. 
         [0021]    (b) the MAC-layer is responsible for data protection, data flow control and subscriber management at a slightly higher level, this taking place, inter alia, by means of various types of data packets/frames (a data frame may be a data packet, for example a datagram on layer 2 of the OSI model). Hence, the MAC layer allows data packets to be transported safely via WLAN to defined receiving stations (for example in a vehicle), inter alia. 
         [0022]    Data originating from higher layers (in the OSI standard model) (for example data originating from (http-based applications) are packed by a MAC layer device into a frame which comprises a header, the actual data (user data) and a frame check sequence. The header in turn contains a “Frame Control” field ( 35 ), inter alia, which in turn contains the type of the frame (for example data frame or control frame) and the subtype of the frame. This design is the same for all 802.11 MAC frames. 
         [0023]    For some types and subtypes of frames, the 802.11 standard has still not defined any applications, which means that these are free for future expansions and such types and subtypes of current implementations (http/Internet Browser, Multimedia, etc.) are ignored, so that they can be used within the context of this invention. By way of example, the general type number 3 could be used to distinguish data frames relating to C2X communication, or subtypes 8 to 15 of a data frame (for a frame with frame type number 2) could be used to distinguish data frames relating to car-to-X (C2X communication) and hence to allow selection of these frames for C2X applications/devices. 
         [0024]    An MAC software driver can be used for the implementation. Such an expanded MAC software driver could then filter out frames or accordingly all packets with the relevant C2X type identifier from the packet stream which it obtains from a physical layer and could forward them directly to a C2X controller module (for example via a software interface or Ethernet, etc) and could package packets which come from a C2X controller into frames of appropriate design and forward them to the physical layer for further sending. This would get around the normal MAC access control or the connection setup for C2X frames, which although safe is lengthy. The C2X controller module could use mechanisms/algorithms, such as that developed by NOW (Network On Wheel), to set up C2X communication—with C2X-specific functions such as geographical routing. Other sources for mechanisms/algorithm are the C2C-CC and the IEEE 1609. For simple functions, such as warning about emergency vehicles by means of a broadcast, these mechanisms/algorithms are not necessary, however. By using an already available field for type recognition in the MAC packets for the expansion, a router modified in this manner would furthermore also allow other communication (for example http/Internet/Multimedia communication). C2X communication would be a simple software add-on for commercially available WLAN routers. When installing WLAN radio engineering in vehicles, this would mean that the hardware which is then present could actually be used for C2X communication only by changing the software. 
         [0025]    In this case, it is possible to use conventional hardware as a router. The ever greater prevalence of mobile appliances with WLAN means that it is also possible to couple them to vehicle appliances using Bluetooth, for example, and then to use the WLAN of the mobile appliances as a router, however. 
         [0026]    Previous approaches to producing C2X communication using commercially available WLAN routers with commercially available Ethernet protocols (UDP) without other (for example http/Internet/Multimedia) communication in parallel, or the alternative use of routers specified for C2X (for example in the case of the NOW Network On Wheels approach) do not achieve the advantages according to aspects of the invention. 
         [0027]      FIG. 1  schematically shows a data frame  31  with a physical layer based on 802.11-PHY (reference  32 ), an MAC layer based on 802.11-MAC with user data  33  and a header  34 , which header  34  contains a frame control data record  35  which contains the frame type  16  (for example type number “2” or type number “3”) and an indication of the subtype (for example “8” to “15”) with the reference symbol  17  and other details (“ . . . ”). The data record (frame etc. “1”) is sent or received by a transmission/reception device  18  (with a transmitter  19  and a receiver  20 ) which is arranged or mounted in a motor vehicle  21 . 
         [0028]    When a data frame  31  is received by a transmission/reception device  18  in the vehicle  21 , the data type  16  indicated in the data frame  31  is used on its own—or on the basis of the data type  16  (“2”) indicated in the data frame  31  and a subtype  17  (“8”, “9”, “10” . . . “15”) indicated in the data frame  31 —to decide whether the data frame is transmitted to a C2X device  22  (for example which can process/display data relating to arriving emergency vehicles or a set of traffic lights with a particular traffic light phase in the direction of travel) or to another communication device  23  (e.g. for surfing the Internet). Accordingly, data coming from the C2X device  22  are provided with an indication  16  of a frame type (“2”) representing the C2X communication by the transmitter  19 —or with an indication  16  of a frame type (“3”) and an indication  17  of a frame subtype (“8” to “15”)—and are transmitted via an air interface  30  (that is to say through the air by radio) to a receiver  45  (in a vehicle or in an infrastructure device), where they are received and processed further.