EP1840857B1 - Method for broadcasting traffic messages and broadcast receiver - Google Patents

Description

State of the art

The invention is based on a method for broadcasting traffic reports and a radio receiver according to the preamble of the independent claims.

In DE 35 36 820 C2 and the ISO standards 14819-1, -2 and -3, a generic method for broadcasting encoded traffic messages is given. The TMC (Traffic Message Channel) method described there pursues the approach of standard traffic messages in their elementary components, specifically the location of an event, the direction of travel, the extent of the event and the actual event. To disassemble, to catalog these components and to assign the cataloged components of the traffic reports corresponding predetermined codes. Instead of the actual traffic reports, only the codes compiled in accordance with the message to be transmitted are transmitted. For example, particularly important points along important traffic routes, such as entrances and exits, petrol stations, rest areas, etc. along motorways are assigned so-called location codes. In a place table (location table) these place codes are each place names and also references to the place under consideration in the course preceding and subsequent places or their location codes specified. By transmitting such a location code and a direction of travel is thus the location of a traffic-related event on a stretch between two coded locations and a particular direction of travel established. In order to provide only a limited address space for the location codes, various location tables are provided for different countries, with a specific country-specific location table being identifiable via an assigned location table number (LTN).

In the radio, the transmitted codes are assigned to corresponding message components on the basis of decoding tables stored therein and then displayed on the display or converted into spoken messages by means of speech synthesis and output via the connected loudspeakers.

These TMC traffic reports are transmitted, for example by means of the so-called Radio Data System (RDS), which is specified for example in DIN / EN 50 067, inaudible next to a radio program on a broadcast frequency.

RDS-TMC is currently implemented in two variants throughout Europe. On the one hand as a free service, which is receivable in large parts of Europe, on the other hand as payment service (Pay-TMC or conditional access (CA)), which u. A. in France, Great Britain and partly in Germany. This service is often provided by private service providers and requires special software in the receivers so that they can decode the encrypted traffic messages. The providers require that for each device that is to be able to decode CA, a certain fee is paid by the terminal equipment manufacturers to the provider.

The DE 199 05 893 A1 suggests a way to broadcast advanced RDS TMC traffic news. The actual message is preceded by a header, which contains references to possible additions to the actual main message. In this header can also be pointed to an encryption of the actual messages.

The EP 0 818 898 A2 describes a method for the selection of digitally coded traffic reports. Each traffic message is assigned a priority characterizing the degree of the respective traffic disruption. Depending on a number of received traffic reports, traffic reports to be issued are selected according to the priority.

Purpose and advantages of the invention

Since part of the information about TMC is provided free of charge by the police as a security-related service, the demand is now in the room, in particular by the European ministries of transport, that in the future also CA providers transmit certain messages to the terminals and users free of charge Should provide. Since this is currently not possible due to the system - there is either free TMC or CA, but not a mixture of both - a solution must be found.

One obvious and preferred solution by CA providers would be that ministries would only require all terminal manufacturers to offer CA in their devices. Thus all terminals could receive and decode all and thus also the above-mentioned CA-TMC traffic reports. However, this would mean that the terminal equipment manufacturers would automatically have to pay licenses for all end devices to the CA providers. However, this solution is unacceptable from the point of view of terminal manufacturers as well as users who would ultimately have to pay the surcharge for CA capability of the terminals.

The present invention solves the above problem with a different approach.

The core is to be seen in the fact that within a transmission channel, which in addition to transmit conditional access information, which is usually encrypted, to transmit generally accessible unencrypted information. The receiver is designed to recognize in the amount of incoming information or messages those that are transmitted unencrypted and then selectively evaluate this, while encrypted messages are ignored.

In this case, the recipient preferably accesses non-encrypted message components for the purpose of detecting unencrypted messages, which messages contain a direct or indirect indication as to whether the currently incoming messages are encrypted or unencrypted messages.

An indirect indication in the case of TMC traffic announcements, for example, is the event codes, since in the standard, each cataloged traffic event is assigned one of several possible urgencies. In the case of TMC traffic reports, it is proposed here that messages that are cataloged as particularly urgent (x-urgent), such as information about wrong-way drivers on motorways, should always be transmitted unencrypted. The recipient can then determine, by analyzing the event code, whether or not it is a particularly urgent message and, in the case of a particularly urgent message, assume that it has been transmitted unencrypted.

Since the currently operating CA-RDS-TMC only the location codes for traffic events are transmitted encrypted, in the case of special Urgent messages, ie those with a corresponding event code, which is cataloged as particularly urgent, the transmitted location codes are used without further decryption. In the case of encrypted location codes, however, these and the associated additional message components are ignored, since the further use of encrypted location codes without decryption would lead to false reports.

Detailed Description of a Preferred Embodiment

The invention is described below using the example of RDS-TMC traffic reports. In principle, however, the invention can also be applied to other broadcast standards such as Digital Broadcasting (DAB), Digital Multimedia Broadcasting (DVB) or other transmission methods such as GSM (Global System for Mobile Communication) , UMTS, etc.) and others.

The structure of the radio data signal, hereinafter RDS signal, as well as the coded TMC traffic information transmitted with it will be explained below FIG. 1 explained in more detail.

The RDS signal 1 is composed of a sequence of data blocks 10, which are also referred to as groups. Each group 10 consists of four blocks 11, 12, 13, 14 of 26 bits each, of which each of the first 16 bits 15 are available for the actual payload, while the remaining 10 bits 16 of the transmission of redundancy information for error detection and correction (checkword) and the synchronization of the receiver (offset) are used. To transfer different types of information different group types are provided. To identify the respective group type, a group type code (GT) 21 is provided which comprises the first four bits X15, X14, X13 and X12 of the second block of each group. Further, a version bit (B0) 22, the fifth bit X11 of the second group, is provided. The combination 20 of group type identifier and version bit BO serves to identify a group type in the strict sense. A particularly important date of the RDS signal, which is why in every one of them Group is transmitted in the first block is the program identification code (PI) 15. This is used to uniquely identify a particular broadcast program and includes a country code that indicates the location of the transmitter and the actual program identifier, which is a particular broadcast program, such as For example, the third program of the South West German Broadcasting Corporation (SWR) called. A detailed description of the Radio Data System (RDS) can be found, for example, in DIN EN 50 067.

• der Ort des Geschehens, location 31, für den die 16 Bit Z15-ZO des letzten Blocks zu Verfügung stehen,
• die Art des Verkehrsereignisses, event 32, z.B. Stau, zähfließender Verkehr, Sperrung usw., zu dessen Codierung die letzten 11 Bit des dritten Blocks reserviert sind,
• die Ausdehnung des Ereignisses, extent 33, gemessen in der Zahl von locations, über die sich das Ereignis bzw. die daraus resultierende Verkehrsstörung erstreckt, umfassend die Bits Y13, Y12 und Y11 des dritten Blocks sowie
• ein Bit Y14 des dritten Blocks zur Codierung der Fahrtrichtung (+/-) 34.

In FIG. 1 is exemplified a group of the type 8A, ie with GT 8, version A shown. This group is for the transmission of coded TMC traffic reports according to the mentioned standard ISO 14819-1, -2, -3. The essential components of such a TMC traffic announcement are included

• the location of the event, location 31, for which the 16-bit Z15 ZO of the last block is available,
• the type of traffic event, event 32, eg congestion, slow traffic, blocking, etc., for the coding of which the last 11 bits of the third block are reserved,
• the extent of the event, extent 33, measured in the number of locations that the event or resulting traffic disruption extends, including bits Y13, Y12, and Y11 of the third block, as well as
• a bit Y14 of the third block for coding the direction of travel (+/-) 34.

The example of FIG. 1 shows a so-called single-sequence message, ie a traffic message, which is transmitted with a single group of the RDS signal. In this case, the bit 35 (F) has the value "1". In contrast, there are also multi-sequence messages in the event that the capacity of a single group 8A of the RDS signal is insufficient to transmit a traffic message. To mark such multi-sequence messages, bit 35 (F) is set to the value "0". A detailed description can be found in ISO 14819-1, -2 and -3. In addition, there are also multi-sequence messages which are explained, for example, in ISO 14819-1, -2, -3.

Because information other than the actual TMC traffic messages can be transmitted in 8A groups, type 3AA groups are preceded by type 3A groups in the RDS data stream (TMC traffic reports). FIG. 2 ). These contain in the fourth block 14 a so-called application identifier (Application ID, AID) 41, which indicates which type of information in the following groups of the type 8A, in the present case TMC messages. Further, these include a location table number (LTN) 42 which indicates which of a plurality of possible location tables has been used for encoding the event locations on the transmitter side and, consequently, should also be used on the receiver side for decoding the location codes. Different location tables are for example to allow the coding of places in several countries, ie for Germany there is a first, France a second, etc. place table.

Finally, the standard also provides for groups of type 8A in which management information (ADMIN 8A) is transmitted. These differ from the groups of the type "8A" carrying the actual traffic reports by the bit "T" 36, which in the case of a management group has the value "1", but in the case of traffic message groups the value "0".

To decode these TMC messages according to the ALERT C standard, as described for example in the aforementioned standards ISO 14819-1, -2 and -3, the country and the valid location table must first be identified. The LTN (Location Table Number) together with the program identification (PI) code of the sender serve this purpose. From these two pieces of information you can determine exactly which country you are in and which LTN is currently in use. This allows each free TMC service to be uniquely identified and decoded.

The standard was later extended backwards compatible to enable Conditional Access TMC. For this purpose, instead of the valid LTN, the code 0 (zero) is transmitted in group 3A, which was defined as "undefined" in the old standard. An old-style device can not handle this code and ignores the CA-TMC traffic messages included in the following 8A groups. One for receiving CA-TMC traffic messages recognizes based on the LTN "0" that the service transmits encrypted traffic reports. The encryption of traffic information is carried out on the transmitter side via an encryption of the location codes according to one of several possible regulations.

To decrypt these encrypted location codes on the receiver side, a special 8A group ( FIG. 3 ) first the actual LTN (before encryption) 51, which can usually be the same number as for the free TMC service. Furthermore, a decryption key number (encryption ID ENCID) 52 is transmitted which is stored in a receiver-side decryption table (FIG. FIG. 4 , Numeral 60) designating one of a plurality of decryption instructions 61 to be used. The decryption table 60 is available to all terminal manufacturers who pay appropriate licenses to use CA-TMC to the service provider. By applying the correct decryption rule, the encrypted received location codes can be assigned the correct location codes, which can then be assigned to places by means of the location table.

The solution is that at least certain, namely particularly urgent messages that are marked as X-Urgent in the event (event) catalog (eg: Ghost driver, danger notifications, people, animals and objects on the road), in principle always as free Messages must be made available. That would also meet the demands of the ministries of transport. These messages must always be transmitted with unencrypted location codes 31. Since future receivers can also recognize LTN 0 and in the appropriate group 8A and the correct LTNBE (before encryption) can read 51, which, as already mentioned, is usually identical to the usual national LTN, then the message can be received correctly because the Code is in unencrypted form and the otherwise required decryption table with the keys is not necessary and thus no license costs for Conditional Access TMC must be paid.

In addition, it is also defined in the RDS-TMC standard that, using an additional label, the "default urgency", ie the default urgency of a message, can be increased here in particular (see EN ISO 14819-1, Chapter 5.5.3, US Pat. Label 1, code 0). With this option, messages with normal urgency can also be converted to X-Urgent and transmitted according to the invention with an unencrypted location code.

FIG. 5 shows an arrangement of radio transmitter 100 and radio receiver 200 for carrying out the method according to the invention.

The transmitter 100 basically codes traffic reports according to the conditional access (CA) method. This means that for traffic events, which are not assigned the highest priority in the event catalog, the associated event, for example accident location, is coded with an encrypted location code. In the case of traffic events, however, in which the event catalog is assigned the highest priority, the event location is encoded unencrypted on the basis of the location table.

The traffic messages thus coded are broadcast as broadcast signal 110 according to the known CA-TMC method. This means that, on the one hand, an RDS group 3A with the location table number (LTN) "0" and, further, a group 8A according to FIG FIG. 3 with the unencrypted location table (LTNBE) and the decryption identification number (ENCID) and another group 8A with the event code (event), the direction of travel (+/-) and the location code (Location) is transmitted. In the case of a particularly urgent message, which is assigned the default urgency "x-urgent" in the event catalog, the transmitted location code is unencrypted, but in the case of lower urgency it is encrypted.

The receiver 200 receives the broadcast signal 110 broadcast by the transmitter 100, which contains encrypted (CA-) TMC traffic reports, via an antenna 210. In a subsequent receiver 220, which is well known in the art and therefore not described here, the Broadcast signal demodulated and the RDS signal isolated. From this, the actual RDS information, in this case in particular the TMC information, is obtained in a subsequent RDS demodulator 230. These are in turn processed in a downstream processor 240.

The processor 240 then analyzes a group 3A obtained from the RDS signal to determine if it contains the LTN "0". If this is the case, then the received broadcast signal is one which includes TMC traffic messages according to the conditional access method. On the other hand, if the obtained group 3A contains another LTN, it is not a CA-TMC signal but a freely accessible, unencrypted TMC signal.

In the latter case, ie if unencrypted TMC traffic reports are received, they can be decoded and output in a conventional manner (260) or further processed, eg for being taken into account in a vehicle navigation system as part of a driving route calculation.

In the former case, ie when encrypted CA-TMC traffic messages are received, the location table number (LTNBE) 51 is obtained from a subsequent management group 8A of the RDS signal.

In the subsequent groups 8A, the event code 32 is evaluated in each case and then checked whether the associated event is an event with normal, low or particularly high urgency (x-urgent). If it is an event of less than particularly high urgency, the processor 240 assumes that the associated location code of that message has been transmitted in encrypted form. Since using it without decryption would result in erroneous messages, the entire message is ignored.

If, on the other hand, this is a particularly urgent event, the processor 240 can assume that the associated location code has been transmitted unencrypted and evaluates it using the location table 250, whose number it obtained in the form of the LTNBE, in a manner known per se taking into account the country code of the PI code obtained from any group of the RDS signal. Likewise, the other message components, in particular direction and event are evaluated.

According to the development described above, even messages with standard low or normal urgency can be assigned the highest priority. For this purpose, a corresponding urgency increase bit (label 1) is set in the context of a multi-sequence message in a following group 8A. The processor 240 for this capability is designed to evaluate this bit and increase the urgency of the event. If the event then has the highest urgency, the processor again proceeds from an unencrypted location code and decodes the message in a known manner.

Claims (11)

1. Method for transmitting coded traffic messages using a data channel for transmitting encrypted traffic messages,
   characterized in that a particular subset of traffic messages is transmitted principally in an encrypted form using the data channel, wherein the encryption of a traffic message involves only a respective one of at least two components of the traffic message being encrypted, wherein the unencrypted second component contains a piece of information about an urgency of the traffic message, wherein the first component of the traffic message is an event location which is encrypted on the basis of the urgency of the traffic message, and wherein the piece of information about the urgency is obtained from an event code as a second component and the piece of information about the encryption of the first component is obtained from the urgency.
2. Method according to Claim 1, characterized in that the first component is not encrypted if the urgency of the traffic message has a stipulated value.
3. Method according to Claim 2, characterized in that the stipulated value is a high urgency, particularly the value "X-Urgent".
4. Method according to one of the preceding claims, characterized in that the traffic messages are coded on the basis of the TMC standard.
5. Method according to Claim 1, characterized in that the urgency of the traffic message is obtained from an event code as a second component in conjunction with a possibly present piece of urgency elevation information for the second component.
6. Method according to one of the preceding claims, characterized in that the data channel for transmitting encrypted traffic messages comprises all the traffic messages for which a location table number, which comprises an association with locations, has the value 0, which corresponds to transmission of TMC traffic messages using the conditional access method.
7. Traffic message station having means for transmitting traffic messages according to one of the preceding claims.
8. Method for receiving coded traffic messages using a data channel for transmitting partially encrypted traffic messages,
   characterized in that

   - at least two components of a traffic message are received, of which only the first component can be encrypted in each case,

   - wherein the second unencrypted component provides an event code which provides an urgency of the traffic message,

   - wherein the first component of the traffic message is an event location which is processed further without decryption on the basis of the urgency of the traffic message.
9. Method according to Claim 8, characterized in that the first component is processed further without decryption if the urgency of the traffic message has a stipulated value.
10. Method according to one of Claims 8 and 9, characterized in that the urgency of the traffic message is obtained from an event code as the second component in conjunction with a possibly present piece of urgency elevation information for the second component.
11. Receiver having means for receiving traffic messages according to the method in one of Claims 8 to 10.

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