Abstract:
In a method and systems for selecting traffic information services that are receivable by at least one mobile receiver and are relevant for a route previously determined by a navigational device linked to at least one receiver, service information, which identifies the services having traffic messages relevant for the route, is read out from a stored list for the determined route. In the case of a plurality of services, a table is created that includes the read-out service information, which is sorted according to a valuation and is able to be modified as the route is followed. A receiver is set, in each case, to the highest-rated service.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method and a system for selecting traffic information services which can be received by at least one mobile receiver and which are relevant for a route previously determined by a navigational device linked to at least one receiver. 
     BACKGROUND INFORMATION 
     Modern navigational devices for motor vehicles are capable today of calculating routes even under consideration of the prevailing traffic conditions. For this purpose, information regarding traffic conditions is to be supplied to the navigational devices; broadcast transmitters having digitally coded traffic messages (TMC messages, TMC=traffic message channel) and other sources and services can be used as message sources. However, for this purpose, it is necessary to tune the receiver that is linked to the navigational device to a service that broadcasts traffic reports relevant for the geographical region traversed by the route. 
     If such a setting is randomly performed, it can happen that a service is tuned to that does not broadcast any or that only broadcasts infrequent messages that are relevant for the route in question. 
     From German Published Patent Application No. 44 42 413, a method for tuning a mobile radio receiver and a radio receiver is described, where the particular position determined by a navigational device is used to fetch out a program identification code from a list, so that a transmitter is found that broadcasts information relevant for the ascertained position. It is true that good results can, in fact, be attained when the user of a radio receiver would like to receive traffic messages pertaining to his or her particular position and, for that, requires the correct transmitter. However, using the known method, it is not possible to tune a plurality of broadcast transmitters along the route calculated in the particular case, the tuning of the transmitter and the route search being carried out dynamically. 
     Broadcasting traffic information services is also possible via broadcast media other than RDS broadcasting, e.g. via digital audio broadcasting (DAB) or via cellular networks according to the GSM standard. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to use a navigational device to choose from the available broadcast media and/or transmitters when searching for a route, thereby enabling an optimum supply of traffic information over the entire route. 
     According to the present invention, this object is achieved in that service information is read out for the determined route from a stored list, the information identifying the services having traffic messages relevant for the route; in that, in the case of a plurality of services, a table is created that contains the read-out service information sorted according to a valuation, and that can be changed as the route is followed; and in that a receiver is set in each case to the highest-rated service. 
     The valuation can be carried out according to features that characterize the services and can be received together with the services themselves or can be retrieved from a memory at the receiver. 
     Using the method according to the present invention, the DAB tuner can preferably be set, for example, in regions serviced by DAB, in the remaining regions, the RDS tuner can be set, and on selected routes or in response to a particular demand from the user, commercial services broadcast via GSM can be set. In addition, in each case for one region, it is also possible to store and use traffic reports received from a plurality of services. 
     One further refinement of the present invention makes it possible when searching for a route with the aid of a navigational device, to select the service that can be received by a receiver in such a manner that the reception of relevant traffic messages is optimized over as much of the entire route as possible. 
     In present-day radio broadcasting, this is achieved, for example, in that at least one receiver is a radio receiver for receiving transmitters having traffic messages; in that program identification codes are fetched out from a stored list for the determined route, the list identifying transmitters having traffic information relevant for the determined route; in that, in the case of a plurality of fetched-out program identification codes, a table is created that includes the fetched-out program identification codes sorted according to a valuation, and that can be changed as the route is followed; and in that the radio receiver is set in each case to the highest-rated, receivable transmitter. 
     In the case of additional services, e.g. DAB, this method can be applied once minimal adaptation to the technical specifications of the particular service has been made. 
     Provided that they are supplied with a sufficient number of traffic messages, navigational devices, which can calculate the route even under consideration of the instantaneous traffic conditions, correct the route on the basis of the traffic messages, both at the start of a trip, as well as during the trip in the case of an initially calculated route. Furthermore, during a trip, it may be necessary to recalculate the route when the vehicle deviates (be it intentionally or not intentionally) from the calculated route. Regardless of this, the method according to the present invention enables the best transmitter available for this purpose to be set. 
     In the method according to the present invention, it is preferably provided that the stored list for the program identification codes includes information regarding the reception area, the region covered by the message content (message area), the known frequencies, and an additional message selection carried out by the transmitter. 
     Often, a plurality of transmitters are relevant for one and the same geographical region. In order to also optimize in this context, it is provided in an additional further refinement that the table of the transmitters to be set is established and actualized by comparing positions on the route to regional information in the list. Preferably, the entries in the thus-determined table are sorted in such a manner that transmitters having the most suitable message content are at the top. 
     In detail in this context, it can also be provided that the sorted table is transferred to a control device of the radio receiver and is used there as a basis for a transmitter search, the transmitter at the head of the table being searched first. 
     Transmitters often have different preferences for selecting the traffic messages broadcast by them. Thus, there are transmitters, for example, that only broadcast local traffic reports, or ones that broadcast traffic messages for a larger area. In another further refinement, these characteristics of the transmitter can be taken advantage of in that, in the sorting operation, the particular class of the roads to be traveled are in relation to the other message selection of the transmitter that identifies the road classes for which the transmitter in question broadcasts traffic messages. 
     According to an advantageous embodiment, the different transmitters or PI codes can be geographically selected in a particularly advantageous manner without the relatively complicated storing of coordinates, in that corresponding program identification codes are specified in the list regarding geographical regions into which a digital road map is subdivided for the navigational device, and in that the program identification codes are read out on a region-by-region basis and sorted as the route is followed. 
     In this advantageous embodiment, it is possible to take the road classes into exact consideration in that, in the sorting operation, the particular class of the roads to be traveled is in relation to the other message selection of the transmitter that designates the size of the region for which the transmitter in question broadcasts traffic messages, and in that, in the case of different road classes within one region, those which are most prevalent within one region are used for the sorting. 
     In an advantageous system for implementing the method according the present invention, it is ensured that the current state of the list and the digital road map reliably agree by the list being stored on the same data carrier as a digital road map, preferably on an optically readable disc (CD ROM). 
     To continuously adapt the route to potentially quickly changing traffic conditions, frequent access to TMC transmitters may be necessary. So that this is not associated with disturbing interruptions in the reception of the remaining programs, it is provided in another advantageous system for implementing the method according to the present invention that the radio receiver has two receiving sections, which can be set independently of one another. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a radio receiver and a navigational device set up for implementing the method according to the present invention. 
     FIG. 2 shows a section of a road map for explaining the method according to the present invention. 
     FIG. 3 shows a PI list and tables used in the method according to the present invention. 
     FIG. 4 shows a flow chart of a program for a microprocessor located in the navigational device, the program being designed for implementing the method according to the present invention. 
    
    
     DETAILED DESCRIPTION 
     The radio receiver represented in FIG. 1 has a receiving section  2  having an antenna  1 , the output of the receiving section being linked, on the one hand, via NF processor  4  and output stages  5 ,  6  to speakers  7 ,  8 , and, on the other hand, via an RDS decoder  3  to a microprocessor  13 . The microprocessor is used to control the entire radio receiver and is designed, among other things, to select and decode individual pieces of information, e.g. program identification codes (PI codes) and digital traffic messages, from the RDS signal decoded by  3 . 
     Furthermore, microprocessor  13  is connected to a keyboard  14  and a display  15  with which diverse inputs (setting the transmitter, volume, muting received transmitters) can be carried out, and required information (the operating state of the receiver, the set transmitter, traffic messages represented as text) can be transmitted. Microprocessor  13  also has an output that is linked to a control input of receiving section  2 , so that receiving section  2  can be set by hand using  14  or to transmitters stored in microprocessor  13 . 
     Microprocessor  13  of the radio receiver is linked via a bidirectional data connection  10  to a navigational device, which can also be controlled by a microprocessor, which is not shown. The information for the route search or for adapting the route search to the particular course of the trip is extracted from a mass storage unit  18 , e.g. a CD-ROM, and from a GPS position finding device  17 . In addition to a digital road map, of which a section is shown in FIG. 2, there is a list in mass storage unit  18  of those transmitters broadcasting digitally coded traffic messages (TMC messages). The list is ordered according to PI codes and, for each PI code, includes a reception area, a message area, frequencies at which programs having the respective PI code are broadcast, and other message selection performed by the transmitter, e.g. only local, regional, and national messages. 
     The partial list represented in FIG. 3 a  shows entries of the five transmitters Sa through Se having the PI codes PI 1  through PI 5 . In FIG. 2, the reception areas of transmitters Sa through Se are represented as to be synonymous with the transmitters. In the exemplary embodiment, the data file is set up in a particularly simple manner in that the regions of the digital map (FIG. 2) are partitioned into areas, also referred to as PI areas in the following, and in that, for each of these areas, the appertaining transmitters are identified in the list. Thus, according to the list in FIG. 3 a,  for example, transmitter Sa broadcasts traffic messages for area C 2 , and transmitter Sb broadcasts traffic messages for areas C 1 , C 2 , and B 2 . As a result, it is not necessary to assign the message areas of the individual transmitters to the geographical coordinates. 
     Based on its own position, navigational device  16  determines in which PI area the vehicle is located and can jump directly to the appropriate section of the PI-code table, where the navigational device then finds one or more PI codes, e.g., as in FIG. 3 a,  the PI codes PI 1  through PI 4  for area C 2 . 
     If a plurality of PI codes are present, the trip route is first checked to determine which road classes are being used, whether, for example, highways or city roads are being used. In the following, this process is elucidated further on the basis of FIGS. 2 and 3. FIG. 2 shows a section of a total of 16 PI areas, i.e., A 1  through D 4 , of the digital road map. For a trip from a location X to a location Y, searching for a route produced the results that from X, a local road  21  is first followed to a highway junction  22 , then highway  23  is traveled to junction  24 , and finally a local road  25  is again used. Another road  26 , which also leads from X to Y, is not suggested to the driver, since this is a curvaceous route and would require more time. The reception areas of transmitters Sa through Se are indicated with circles or ellipses. If the major portion of a PI area is in the reception area, it is listed in the table according to FIG. 3 a  at the respective transmitter. 
     Transmitters Sa and Se are local transmitters, while transmitters Sb, Sc, and Sd can be received supraregionally. At the onset, the receiver is in region C 2 . According to the list, transmitters Sa through Sd should be able to be received there. Since the first road  21  is not a highway, local transmitter Sa is initially given the highest priority. The remaining transmitters are assessed according to the valuation of their receivability in the subsequent PI areas B 2  and A 2 . Since transmitter Sd can be received in all three PI areas, the transmitters are relayed in the sequence represented in FIG. 3 b,  i.e., Sa, Sd, Sc, to microprocessor  13  of the radio receiver. 
     Prior to reaching the highway at  22 , the ratio of city/local roads  21  to highway  23  is already reduced so dramatically that the prioritization of transmitter Sa is eliminated. As a result, transmitter Sd is then set, although transmitters Sb and Sc may offer a higher field intensity. Transmitter Sd remains set until the transition to PI area A 2 . There, the navigational device determines that, for the rest of the trip, mainly side roads will again be used and, therefore, prioritizes transmitter Se, which is favorable for this PI area (FIG. 3 c ) and remains set until destination Y. 
     FIG. 4 shows a flow chart of a program that is provided in a microprocessor of the navigational device, for implementing the method according to the present invention. After starting at  31  and inputting X and Y at  32 , the route is calculated at  33  with the result X,  22 ,  24 , Y. Then, the program waits for an input as to whether a dynamic navigation is desired. If this is not the case, the program is ended at  35 . However, if a dynamic navigation is desired, the PI areas, in the present case C 2 , B 2 , and A 2 , are determined at  36 . 
     At  37 , corresponding PI codes are then determined on the basis of the table according to FIG. 3 a.  At  38 , the program branches as a function of whether the number NPI of determined PI codes is greater than zero. If a suitable PI code is not previously found, no list is transferred to the radio receiver. In this case, the radio receiver itself, i.e., using the method customary to date, searches for suitable transmitters having traffic messages. 
     However, if PI codes are found, branch  38  is followed by the PI list (FIG. 3 b ) being transferred to the radio receiver. At  40 , a check is made to determine whether the destination has been reached, and, where applicable, the program is ended at  35 . However, as long as the destination has not been reached, the position is actualized at  41  and, thus, also the route still to be traveled. In this context, received TMC messages are also taken into consideration, so that other routes can be selected if necessary in the event of traffic disturbances. If the receiver enters a new PI area as a result of traveling on the originally calculated route or on a newly calculated route, it is once again determined after branch  42 , at  36  through which PI areas the continuing route travels, the corresponding PI codes being subsequently determined at  37 . As long as the receiver has not reached any new areas at  42  and the destination has not yet been reached, the position and the route are actualized at  41  without requiring that the PI  41 , code be newly determined.