Abstract:
In a method for evaluating traffic announcements received in digitally encoded form in a data packet, the data packet is decoded, and after the evaluation the traffic announcements are stored in memory. Under poor broadcasting conditions, it may be uncertain whether all the traffic announcements transmitted have actually been correctly received and evaluated. For confirmation of completeness, data words that, in encoded form, include the nominal number of reports transmitted in one cycle are broadcast within each complete cycle of traffic announcements. The decoded and evaluated reports counted within one cycle are compared with this nominal number.

Description:
Cross-reference to related U.S. patent and applications, the disclosures of which are hereby incorporated by reference: 
     U.S. Pat. No. 3,949,401, HEGELER; U.S. Pat. Nos. 4,435,843 and 4,450,589, EILERS and BRAGAS; 
     U.S. Pat. No. 4,499,603, EILERS; 
     Ser. No. 07/447,378, DUCKECK, filed Dec. 7, 1989 based on German P 38 20 639.0 of June 18, 1988); 
     Ser. No. 07/447,578, DUCKECK, filed Dec. 7, 1989 based on German P 38 20 641.2 of June 18, 1988). 
     FIELD OF THE INVENTION 
     The invention relates to a method for evaluating traffic announcements, received in digitally encoded form in a data packet. The European Broadcasting Union&#39;s SPECIFICATIONS OF THE RADIO DATA SYSTEM RDS FOR VHF/FM SOUND BROADCASTING (March 1984), also known as Technical Publication 3244-E or EBU-3244-E. 
     With the introduction of the RDS system, it is possible to broadcast not only the tone modulation of an FM radio program but also data. A suitable traffic radio decoder that is arranged for processing digital signals is known from German Patent Disclosure Document DE-OS 35 36 820 BRAGAS and BUSCH. The digital signals are obtained by demodulating an auxiliary carrier that is broadcast along with an FM radio program via radio transmitters. As a result, not only information on the stations received and on the content of the program but also traffic announcements can also be decoded. Compared with traffic announcements that are transmitted in the clear or audible form of tone modulation, either after interrupting the ongoing program or at predetermined times, broadcasting of digital signals offers the opportunity of transmitting traffic announcements without interrupting the program. It is possible to transmit short encoded announcements that then address and trigger retrieval of standardized texts stored in memory in the receiver. 
     Preparation and transmission of the traffic announcements are done in the traffic studio, where the incoming reports are fed into a personal computer that forms encoded information from them. The computer then assembles all the reports into a report block, which may be of variable length. The report block is then inserted into the data packet, but it is not broadcast in a continuous sequence; instead, other groups of the data packet that are broadcast more frequently are interspersed in it. 
     Under poor reception conditions, as may be particularly prevalent in vehicle radio receivers, it is possible that parts of the data packet transmitted may not be decoded correctly or may even be lost completely. In practice, only an approximately 20% decoding probability is therefore expected. This means that it is not assured that all the reports of a report block, which is assembled as a cycle of traffic announcements, will be recognized after the block has been broadcast. If the decoded reports are then stored in memory, there is no certainty that all the reports are in fact present. 
     It is the object of the invention to improve a method for evaluating traffic announcements received in digitally encoded form in a data packet in such a way as to improve the certainty of having recognized and evaluated all the reports. 
     Transmitting data words that include the nominal number of reports transmitted in one cycle furnishes a check number or datum whose valve is independent of reception conditions and independent of the accuracy of decoding and evaluation. This datum can then be compared with the number of reports actually decoded and evaluated within one cycle. If the number of reports decoded and evaluated matches the nominal number, there is a high degree of certainty that the reports transmitted have all been received. 
     Preferably, the nominal number of data words transmitted in one cycle is transmitted at the end of the cycle associated with these data words. The advantage of this provision is that by the transmission of these data words, the end of the cycle is simultaneously defined, and in the event that the nominal and actual number of reports match, these reports can then be saved immediately afterward by means of memories. EBU 3244-E defines a data Group 104 bits long, consisting of Block 1 through Block 4, each 26-bit Block having a 16-bit Information word followed by a 10-bit Checkword. 
     The transmission of the data words containing the nominal number is suitably done in block 4 of the RDS-TMC (traffic message channel) group. According to the &#34;SPECIFICATION OF THE RADIO DATA SYSTEM RDS FOR VHF/FM SOUND BROADCASTING&#34;, EBU, March 1984, pages 12, 14, 15, if the offset word in block 3 is C&#39;, 16 data bits are available in block 4. These 16 bits then can be used to transmit the aforementioned data words. 
     The invention also relates to a radio receiver, in particular a vehicle receiver, having a decoder for decoding traffic announcements received in digitally encoded form, 
     Accordingly, the object of the invention is to improve a radio receiver so as to increase the certainty that all the reports of traffic announcements have been received and evaluated. 
    
    
     DRAWINGS 
     Further features and advantageous embodiments of the invention will become apparent from the further claims, the description and the drawing, which explain the invention in further detail. 
     Shown in the drawing are: 
     FIG. 1, a graphic illustration of a report block as delivered to an encoder; 
     FIG. 2, in chronological succession, the RDS groups occurring in a broadcast data stream; 
     FIGS. 3(a) and 3(b) the layout of the RDS group 8 containing the traffic reports; and 
     FIG. 4 a block circuit diagram of a radio receiver having a decoder. 
     FIG. 5, a flow chart of the traffic report evaluating process according to the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a report block of seven RDS-TMC groups, and this block ends with a further group containing the nominal number of reports present in the report block. The number of reports in the report block is here selected arbitrarily and depends on how many reports are present, based on the current traffic situation. The report block can accordingly have variable lengths. Moreover, the length is dependent on whether the traffic announcements are short enough to be encoded in the form of standardized brief information items, or are more extensive. 
     Statistically, approximately 90% of all traffic announcements can be broadcast in the form of one-sequence reports. Approximately 7 to 8% are two-sequence reports, and the rest are multiple sequence reports. Accordingly, if all the reports are one-sequence reports, then seven of them can be transmitted in the report block. The report block is next fed into an encoder-transmitter 34, which broadcasts the traffic announcements along with other data in the form of a data packet. It is further noted that the encoder-transmitter 34 is also supplied with groups 1 and groups 7. 
     FIG. 2 schematically shows a data stream of RDS groups as they are broadcast in chronological succession. It can be seen that one coherent TMC report block from RDS group 8 is not broadcast as an entire block, but instead is shuffled among other . RDS groups. The other RDS groups are sometimes transmitted more frequently, to increase the transmission certainty for these groups. 
     FIG. 3 shows the layout of an RDS TMC group, that is, group 8. This group includes four blocks, namely block 1, block 2, block 3 and block 4; each block includes 26 bits. Of these bits, the first 16 bits are data words and the last 10 bits are a check word for error recognition and an offset as a synchronizing word. 
     In block 1, the first 16 bits include the program identification PI, that is, information about the transmitter or radio station. In block 2, the first four bits are reserved as a group code GTy. In this case this is group 8. The next bit is the offset code BO. If this bit is 1, then in block 3 the offset is C&#39;. If BO is equal to 0, then in block 3 the offset is C. The offset code is followed by the ARI identification bit TP and another five bits, which are reserved for the program type PTy. C If the offset in block 3 is equal to C&#39;, then in the data part of block 3 the program identification PI is transmitted. From this it can be concluded that 16 bits are free in the data region of the ensuing block 4. These bits can be used for identifying, in encoded form, the nominal number of reports transmitted in one cycle of traffic announcements. 
     Since as already mentioned in conjunction with FIG. 1 the reports may be of variable length, the data words containing the nominal number may include additional information on the length of the reports. The length of the reports is divided into sequences that must be transmitted if a report is to be complete. A one-sequence report can be accommodated within a single RDS group. A two-sequence report requires two RDS groups, which as also noted above may be broadcast with interruptions by other RDS groups. 
     To enable a distinction to be made among different types of reports, the information on the length of reports is divided into four types; the first type includes the one-sequence reports, the second type includes the two-sequence reports, the third type includes the reports having three and more sequences, and the fourth type includes the special announcements that do not pertain to traffic. Type 1 and 2 reports, on the one hand, and types 3 and 4, on the other, can each be accommodated in the data part of block 4. If reports of all four types are required, then the data words must be broadcast in the form of two-sequences. The distinction between the two data words is made by means of a distinguishing bit U preceding them. If this bit is 0, then the data word includes the numbers of one-sequence and two-sequence reports. Conversely, if the distinguishing bit is 1, then the data word includes the number of reports having more than two sequences and of the announcements not pertaining to traffic. 
     The one-sequence and three-sequence reports occupy eight bits and can thus identify up to 256 reports of the applicable type. The two-sequence reports and announcements not pertaining to traffic occupy seven bits and can thus identify up to 128 reports transmitted in one cycle. The announcements not pertaining to traffic may be CPU information or updating data for the EVA system. 
     The RDS group pertaining to the nominal number of reports within one cycle is transmitted at the end of one cycle, so that here not only the information as to the number of the reports but also the end of the traffic announcement cycle is marked. 
     FIG. 4, finally, shows a block circuit diagram of a radio receiver of a kind suitable for receiving RDS signals. The radio receiver includes a high frequency (HF) part 20, a low frequency (NF) part 22, a loudspeaker 24, a decoder 10 and a display device 26. Signals arriving via the antenna, as transmitted by the encoder-transmitter 34 in FIG. 1 are demodulated in the high frequency part 20, and the tone modulation is delivered to the low frequency part 22, which passes it on to the loudspeaker 24. 
     The demodulated auxiliary carrier is supplied to an RDS decoder 18 that decodes the data packet and is present in the decoder 10. 
     At the output of the decoder, there is an indication as an example of which information or data are available after evaluation of the applicable RDS groups. For instance, RDS group 0 includes information on the transmitter or radio station; RDS group 15 includes information on the frequencies; RDS group 7 includes personal calls, and RDS group 8 includes the traffic announcements under discussion here. Group 8 is called the TMC group, for traffic message channel. 
     The individual groups, in other words including group 8 as well, are evaluated, after the aforementioned decoding in the decoder 18, by a computer 12. The computer 12 is controlled by a control program stored in memory locations 28 of a program memory 16. The evaluated traffic announcements reach memory locations 36 of a memory 14. From the decoded data words, the computer 12 can form standardized traffic announcements, which are delivered to the low frequency part 22 and to the display device 26 and are reproduced via the loudspeaker 24 in the form of synthetic speech and/or via the display device 26 in the form of alphanumeric characters. 
     During the incoming data stream of RDS-TMC groups, the groups are counted and the numbers are recorded in memory locations 38 of the memory 14. At the end of the cycle, if the RDS-TMC group having the nominal number of reports has been received and evaluated, then this number is stored in memory locations 40 of the memory 14. 
     Next, the numbers stored in memory locations 38 and 40, that is, the actual number of reports received and evaluated, are compared with the nominal number. If they match, then the traffic announcements stored in memory locations 36 of the memory 14 can be considered valid. Otherwise, they are marked as invalid. 
     Using the nominal numbers, it is also possible to occupy memory locations 36 inside the memory 14 and, after first temporarily storing the announcements in memory, to inscribe the traffic announcements into these memory locations after finding a match between the actual and nominal numbers. 
     Besides the number of reports, the number of sequences can also be calculated and checked, in the event that traffic announcements, for instance, involve reports of variable length. 
     The evaluation of the data words containing the nominal numbers of reports substantially increases the decoding certainty, so that with a decoding probability of 20%, the case in which a cycle of traffic announcements has been broadcast and evaluated completely can be recognized with certainty. The computer configuration can also be simplified, if the recognition of correctly broadcast traffic announcements makes it possible to reduce the expense and effort for error-correction provisions.