EP0847154B1 - Method and means for transmitting messages with a variable datarate as a Radio Data Signal - Google Patents

Description

The invention relates to a method and a device for transmitting messages with fluctuating volumes as radio-data signals (RDS), in which specially designated groups are provided for the messages.

The Radio Data System (RDS) enables additional and inaudible transmission of digital data in parallel to broadcast programs in one data channel. Specifications of the radio data system for VHF radio are inter alia in the publication Tech. 3244 - E, March 1984 of the European Union Broadcasting Union (EBU). Radio receivers with suitable RDS decoders can record and decode transmitted data in addition to audio reception with the same receiver. For data transmission, 32 groups of 104 bits each are provided, with each of the transmitted groups being assigned a specific service. Group 8a is currently for the transmission of digitally coded traffic announcements.

A traffic announcement can be encoded in the form of up to five 8A groups. The ALERT-C protocol used for coding permits up to four 8A groups per RDS cycle, which consists of a total of twelve groups. Therefore, in order for enough transmission capacity to be available for other services, broadcasters generally limit the number of 8A groups to only one 8A group per RDS cycle. The transmission of the coded traffic reports is repeated cyclically in order to give newly added receivers access to the message inventory. The period required for the transmission of all coded traffic messages is therefore called the TMC cycle.

The messages are repeated to increase transmission reliability both directly and within the cycle. The frequency of repetition is proportional to the priority of the message, that is, a wrong message is repeated more frequently than a jobsite message. With a low number of messages, one 8A group per RDS cycle is sufficient for the transmission of all messages. However, in the case of large volumes, the addition of a high-priority message leads to a strong delay in the remaining messages. Especially with only one 8A group per RDS cycle, the available channel capacity is insufficient in such cases.

The object of the present invention is therefore to provide more RDS channel capacity for the transmission of digitally coded traffic reports (TMC messages) in these special cases.

This object is achieved in the method according to the invention in that the number of specially designated groups per RDS cycle between a minimum and a maximum allowable number is variable and that the number depending on the occurrence of the messages and / or from The amount of messages flagged as urgent.

The inventive method has the advantage that the service provider can better exploit the scarce RDS channel capacity and that the channel for the TMC messages need not be sized for the highest expected number of traffic reports.

The method according to the invention can be used for various messages with fluctuating volumes, such as radio text, paging and for transparent data channels. However, a preferred application is that the messages are digitally encoded traffic announcements (TMC messages) and that the specially designated groups are 8A groups, it is preferred that the number of 8A groups per RDS cycle be between one and four is changeable and / or that the urgent messages are X-messages.

A further development of the method according to the invention is that, after receipt of a message intended for transmission, it is checked whether this message is marked as urgent, if appropriate the number of specially marked groups per cycle is increased, if the maximum permissible number has not already been reached, and that it does not check, if appropriate, whether a message marked as urgent should be deleted, reducing, if appropriate, the number of specially designated groups per RDS cycle. The 8A groups additionally programmed in the RDS cycle can be regarded as a special channel which is only used by high-priority messages. This allows the service provider to guarantee a minimum access time for these types of messages, which is independent of the particular message inventory.

In a device according to the invention, in which an RDS coder is controlled by a cycle generator which identifies the groups of radio data signals according to their intended purpose, the object is achieved in that the messages are supplied to the cycle generator and that in the cycle generator means for Detecting the occurrence of messages and / or the occurrence of messages marked as urgent and generating RDS cycles, the number of specially marked groups per RDS cycle between a minimum and a maximum allowed number depending on the occurrence of the messages and / or the occurrence of messages marked as urgent.

In the RDS coder, the maximum number of 8A groups tolerated by the broadcaster is set in the RDS cycle. This number is a maximum of four, but may also be in the implementation of the invention two or three. From the cycle generator only one of these groups is used in case of weak message volume. The unused 8A groups are skipped in the RDS cycle, which is an already known feature of the RDS coder.

If a high-priority message - a so-called X-message, as eXtrem urgent - in the TMC cycle recorded (Fig. 1), the cycle generator generates twice as many 8A groups per unit time as before and reached so that now in the RDS -Coder another 8A group is used for the transmission. The RDS cycle is now temporarily made up of thirteen groups. If this capacity is insufficient, the cycle generator can increase this number dynamically up to the maximum number of predefined 8A groups in the RDS cycle. After deleting the X-message or when the number of messages is reduced, the required channel capacity can be gradually reduced to the normal level by the cycle generator.

Fig. 1

die Verteilung der 8A-Gruppen als Funktion der Zeit bei niedrigem Meldungsaufkommen,

Fig. 2

die Verteilung der 8A-Gruppen als Funktion der Zeit bei hohem Meldungsaufkommen,

Fig. 3

ein Ablaufdiagramm zur Erläuterung eines Ausführungsbeispiels des erfindungsgemäßen Verfahrens und

Fig. 4

ein Blockschaltbild einer Einrichtung zur Durchführung des erfindungsgemäßen Verfahrens.

Embodiments of the invention are illustrated in the drawing with reference to several figures and explained in more detail in the following description. It shows:

Fig. 1

the distribution of 8A groups as a function of time with low message volume,

Fig. 2

the distribution of 8A groups as a function of time with high message volume,

Fig. 3

a flowchart for explaining an embodiment of the method according to the invention and

Fig. 4

a block diagram of a device for carrying out the method according to the invention.

In Figures 1 and 2, radio data signals are schematically illustrated over a period of about six seconds, with the non-hatched sections representing other than 8A groups. 11.4 groups / s will be sent. Cross-hatching indicates 8A groups while skipped 8A groups are hatched horizontally. A 4A group, which is hatched vertically, includes a minute mark.

In the case of Fig. 1, the input of the messages, which are each marked with an arrow, takes place with a relatively small amount, so that correspondingly many 8A groups are skipped. With higher message volume according to FIG. 2, considerably more 8A groups are used and only a few are skipped. Despite the Higher message volumes avoid larger waiting times, while with low message volumes (Figure 1) more transmission capacity is available for other services.

3 shows a flowchart for explaining an embodiment of the method according to the invention, wherein after a start 1 at 2 a message is read from a communication unit into the cycle generator and decoded. At 3 it is checked whether the message has an urgency flag (X-urgent). If this is the case, the program branches at 4 depending on whether the X-mode has been activated. X mode means that more than one 8A group is inserted into the data stream compared to normal mode.

In the case of an already activated X mode, it is checked at 5 whether the highest level Xmax is already active. If this is the case, the X-mode is not changed. If it is determined at 4 that the X-mode is not active, it is activated at 6. This is followed by an increase of the X-mode by one level at 7, which is already the case with previously activated X-mode, when at 5 the highest level has not yet been reached.

If it is determined at 3 that the decoded message has no urgency, it is checked at 8 whether a previously sent urgency message should be deleted. If this is the case, at 9 the X-mode is reduced by one level.

After the X mode has been left unchanged, increased or decreased, the message is inserted into the message list or deleted at 10. Then it is queried at 11 whether there are further messages. If applicable, the program will be at 2 repeated, otherwise at 12 ended.

4 schematically shows a device for carrying out the method according to the invention with an RDS cycle generator 14 and an RDS coder 15. The RDS coder is supplied with various messages to be sent, for which inputs 17 are provided for messages other than TMC messages. The TMC messages are first fed from the input 16 to the RDS cycle generator 14, the function of which is known per se but has been extended by the functions described in connection with FIG. In the RDS cycle generator 14, the RDS cycles are thus supplied to the RDS cycles thus adapted to the message volume. At 18, the coded RDS signals may be extracted and fed to a transmitter.

Claims (6)

1. Method for sending messages in fluctuating volume as radio data signals (RDS), with specially marked groups being provided for the messages, characterized in that the number of specially marked groups per RDS cycle can be changed between a minimum permissible number and a maximum permissible number, and in that the number is raised or lowered on the basis of the volume of the messages and/or on the basis of the volume of messages marked as urgent.
2. Method according to Claim 1, characterized in that the messages are digitally coded traffic messages (TMC messages), and in that the specially marked groups are 8A groups.
3. Method according to Claim 2, characterized in that the number of 8A groups per RDS cycle can be changed between one and four.
4. Method according to either of Claims 2 and 3, characterized in that the messages marked as urgent are X messages.
5. Method according to one of the preceding claims, characterized in that following the arrival of a message which is intended to be sent a check is performed to determine whether this message is marked as urgent, in that if this is the case then the number of specially marked groups per cycle is increased if the maximum permissible number has not already been reached, and in that if it is not the case then a check is performed to determine whether a message marked as urgent needs to be deleted, and if this is the case then the number of specially marked groups per RDS cycle is decreased.
6. Device for sending messages in fluctuating volume as radio data signals (RDS), with specially marked groups being provided for the messages, where an RDS coder (15) is controlled by a cycle generator (14) which marks the groups of radio data signals according to their intended use, characterized in that the cycle generator (14) can be supplied with the messages, and in that the cycle generator (14) contains means for detecting the volume of the messages and/or the volume of messages marked as urgent and for generating RDS cycles, with the number of specially marked groups per RDS cycle being raised or lowered between a minimum permissible number and a maximum permissible number on the basis of the volume of the messages and/or on the basis of the volume of messages marked as urgent.

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