EP0347355B1 - Synchronised multi-topical information broadcasting permitting a reconfigurable listening strategy over a transmitter park and of radio programmes - Google Patents

Description

The field of the invention is that of the dissemination of information messages by a fleet of radio transmitters with distributed transmission frequencies, intended for fixed or mobile receivers.

The invention was more particularly developed for the design of a multi-thematic information system intended for mobile receivers, and more particularly for motorists.

However, the method of synchronized broadcasting of a fleet of radio transmitters, as well as the method of reception of radio messages with configurable listening strategy, according to the invention, can be applied in all situations where it is desired allow a single receiver to listen, in an optimized manner, to several transmitters broadcasting regularly updated information messages. The optimization sought of course consists of allowing the receiver to receive as quickly as possible each update occurring on one of the radio transmitters in the park.

Management systems for the optimized reception of emissions from a fleet of distributed frequency radio transmitters are already known.

Thus, the RDS system is known, described in particular in the document NTZ-NACHRICHTENTECHNISCHE ZEITSCHRIFT, vol 40, n °. 5, May 1987, pages 346-348 and 350-351, which is implemented on the basis of sound broadcasting networks in frequency modulation (FM). This service was developed because of the problems posed by the short range of FM transmitters, and therefore the need to set up a network of transmitters with distributed frequencies to offer a service with large coverage. This technique makes it possible to receive, from all points of the geographical area covered, a given broadcast service, provided that the receiver is tuned to the frequency of the corresponding local transmitter. This causes discomfort for the mobile user (typically the motorist) when he reaches the coverage border of the local transmitter to which it is tuned: he must indeed manually search for another frequency when the reception becomes poor. The RDS system has endeavored to solve this problem by offering an automatic tuning function. The principle consists in putting, on a digital subcarrier added to the basic sound signal, information frames containing in particular the list of so-called alternative frequencies, schematically corresponding to the central frequencies of the surrounding transmitters which broadcast the same program. The receiver therefore acquires the list of alternative frequencies, scans these frequencies and decides according to a tactic of its own, to select the best at all times.

This known system does indeed optimize the listening quality of a given transmitter, but does not allow optimized listening to several transmitters. The objective of the invention is to allow a strategy for listening to several transmitters.

More specifically, the objective is to provide a system adapted to the reception of regularly updated information messages, broadcast by a fleet of thematic transmitters with distributed frequencies.

This objective is achieved, according to the invention, using a process of synchronized dissemination of information messages, by a fleet of thematic radio transmitters, allowing a specialized and reconfigurable listening strategy of several transmitters in the park. , from a single receiver,
characterized in that each transmitter continuously broadcasts a cycle formed by a variable number of messages, each cycle of messages being divided into successive blocks of fixed size and duration and identical for all the transmitters, in that each block includes a marker initial informative, said state marker, and each cycle includes an initial informative marker, said synchronizing marker,
and in that the cycle starts of each transmitter in the fleet are shifted from one transmitter to another, so that the markers of each transmitter are broadcast at different times from the other transmitters so that they can be picked up successively by the same receiver .

According to an advantageous characteristic of the invention, each marker comprises on the one hand a version number of the current cycle of the corresponding transmitter, and on the other hand information on the number of blocks to be broadcast before the next synchronizing marker, it i.e. before the start of the next cycle.

Preferably, each synchronizing and / or status marker includes information on the number of new messages in the current version of the broadcast cycle, compared to the previous version.

According to another embodiment of the invention, each state marker includes information on the number of new messages in the current version of the corresponding block, compared with the previous version of said block.

In one or other of these modes of implementation, it is advantageous that said new messages are broadcast immediately after the broadcast of the synchronizing marker of the current cycle of the status marker of the current block respectively.

Advantageously, the fixed duration of a message block is between 40 and 150 times approximately the duration of transmission of a marker.

• on choisit un ordre de priorité d'écoute pour chacun desdits émetteurs thématiques ;
• on écoute successivement chaque émetteur, selon l'ordre de priorité choisi, jusqu'à réception d'un marqueur de l'émetteur ;
• on écoute les messages modifiés de l'émetteur reçu dans le cas où le marqueur correspondant capté porte un numéro de version différent du numéro de version du cycle d'information précédemment mémorisé dans ledit récepteur ;
• on se met directement à l'écoute de l'émetteur d'ordre suivant de priorité lorsque le marqueur reçu de l'émetteur courant comporte un numéro de version identique au numéro de version du cycle mémorisé dans ledit récepteur.

The subject of the invention is also a method of receiving messages sent by a fleet of thematic radio transmitters, according to a method of synchronized broadcasting, by means of a receiver provided with means for memorizing and processing the information messages received. , process characterized in that:

• a listening priority order is chosen for each of said thematic transmitters;
• each transmitter is listened to successively, according to the order of priority chosen, until reception of a marker from the transmitter;
• listening to the modified messages of the received transmitter in the case where the corresponding marker picked up carries a version number different from the version number of the information cycle previously stored in said receiver;
• we listen directly to the next priority order transmitter when the marker received from the current transmitter has a version number identical to the cycle version number stored in said receiver.

• la figure 1 illustre la composition d'un cycle d'émission, pour un émetteur donné, avec marqueur synchronisé de début de cycle ;
• les figures 2a, 2b illustrent le décalage des marqueurs de chaque émetteur d'un parc de trois émetteurs synchronisés, selon l'invention.
• la figure 3 donne un exemple d'implémentation de marquer.

Other characteristics and advantages of the invention will appear on the following reading of a preferred embodiment given by way of illustration and not limitation, and of the appended drawings in which:

• FIG. 1 illustrates the composition of a transmission cycle, for a transmitter given, with synchronized start of cycle marker;
• Figures 2a, 2b illustrate the offset of the markers of each transmitter of a fleet of three synchronized transmitters, according to the invention.
• Figure 3 gives an example of marking implementation.

The preferred embodiment described below relates to the transmission of information messages, intended for motorists. These messages are broadcast by a fleet of transmitters, each transmitter being specialized on a given theme (meteorology, road traffic, "paging" or calling people, availability of urban car parks, etc.).

Each of these messages is put on the principle of transmitting information of deviation, compared to an agreed state of equilibrium, and known to the receiver.

The messages broadcast are "commands" addressed to on-board computers.

Each on-board terminal includes processing capacity and an on-board database.

The on-board database is advantageously a cartographic base constituted by a set of objects; a set of attributes is attached to each object. Objects, when they are of a cartographic nature, can be addressed by a message field generally called "location";
A typical object is a road segment, a section of road framed by two crossroads;
The attributes of this object are for example: the length of the segment, the category and the name of the road axis to which it belongs, the number of lanes, the direction of traffic, the fluidity, etc ... certain attributes are very static (for example the length), others are dynamic (for example the fluidity).

The messages can either be messages of fixed length (of the type of messages proposed by the ECMT: European Conference of Ministers of Transport), or of variable length.

As detailed in the joint French patent application, of the same filing date, and concerning the "dissemination of information messages", in particular traffic information, intended for mobile receivers with intermittent listening, the system broadcasts states and not transitions and this dissemination of current states is maintained (to take into account the fact that users are listening to indeterminate instants) as long as the current state is not the equilibrium state. This results in redundancy, that is to say that typically the same message will be broadcast a certain number of times.

If it is assumed that, for a certain period of time, no new message is collected, the diffusion reproduces itself identical several times cyclically.
As shown in Figure 1, a message cycle consists of a succession of messages M1, M2, ... Mn. From one cycle to another, the number n and the content of the messages can be modified.

According to the invention, it is appropriate to insert a particular message called "marker message" 11 which identifies the start of the cycle and the version number of the cycle; later when the cycle is modified following the introduction of new messages, the version number is modified following the introduction of new messages, the version number is modified and the number of new messages indicated.

This marker message 11 is therefore an initial informative marker of the cycle, which will be called a synchronizing marker.
As shown on the time axis of Figure 1, its occurrences 12, 13, 14 of diffusion occur at regular intervals, owing to the fact that the diffusion of the cycle is carried out repeatedly. Of course, the time period separating two successive broadcasts (12, 13; 13, 14) of the synchronizing marker 11 can be variable, because the number of messages 10 in the cycle is variable.

FIG. 2 illustrates the principle of synchronization between different transmitters 21, 22, 23.

Each of the transmitters carries a message transmission cycle E1, E2, E3, as shown in FIG. 2a. A synchronizing marker 24, 25, 26 is broadcast at the start of each cycle of the transmitters 21, 22, 23 respectively.

According to the invention, the synchronization of the transmitters consists in broadcasting synchronizing markers 24, 25, 26 of the transmitters at different times, so that they can be received successively by the same receiver, which locks successively on each of the transmission frequencies of the transmitters 21, then 22, finally 23.

However, the offset of the synchronizing markers 24, 25, 26 is a necessary condition, but not sufficient, to allow a reconfigurable listening strategy according to the invention. Indeed, it has been noted that each of the transmitters' cycles can comprise a variable number of messages, the offset between the times of transmission of the markers 24, 25, 26, must nevertheless remain distinct whatever the size of the cycles E1, E2 , E3 correspondents.

• on considère une unité de temps où "time-slot"; identique pour tous les émetteurs ;
• sur un émetteur donné, la diffusion d'un cycle quelconque s'effectue sur un nombre entier d'unités de temps.

According to the invention, this is obtained by respecting the following principle:

• we consider a unit of time where "time-slot"; identical for all transmitters;
• on a given transmitter, the broadcasting of any cycle takes place over an integer number of time units.

Each time unit corresponds to the transmission of an information block. This means that the messages M1, M2 ... Mn of a cycle are previously cut out, or grouped together, so as to successively fill each of the transmission blocks with a constant time unit.

By respecting this mode of configuration of the broadcasting cycles, and provided that a sufficient relationship is maintained between the duration of emission of a marker on the one hand, and the duration of emission of a block, on the other , of the initial offset between each of the synchronizing markers 24, 25, 26 of the transmitters 21, 22, 23 will be maintained whatever the length variations of the cycles E1, E2, E3.

Advantageously, in addition to the synchronizing markers 24, 25, 26 of the cycle, a state marker broadcast by each block and at the start of the block, this status marker indicates in particular the number of blocks that remain to be broadcast. to meet the cycle synchronizing marker again, as well as a version number of the current cycle.

In the same way as for synchronizing markers, the times at which each transmitter broadcasts its status markers are slightly offset, and allow the same HF head of a given receiving terminal to "jump from one to the other".

This is illustrated in Figure 2B.

• émetteur 1 (21) : émission d'un marqueur synchronisant 24, puis de deux marqueurs d'état 271 et 272 ;
• émetteur 2 (22) : émetteur du dernier marquer d'état du cycle courant 28m , puis marqueur synchronisant 25 et premier marqueur d'état 281 du nouveau cycle ;
• émetteur 3 (23) : émission de trois marqueurs d'état en cours de cycle 29i, 29i+1, 29i+2.

During a given period of time for broadcasting the fleet of three transmitters 21, 22, 23, the situation is as follows:

• transmitter 1 (21): transmission of a synchronizing marker 24, then of two status markers 271 and 272;
• transmitter 2 (22): transmitter of the last status marker of the current cycle 28m, then synchronizing marker 25 and first status marker 281 of the new cycle;
• transmitter 3 (23): transmission of three status markers during the cycle 29i, 29i + 1, 29i + 2.

It can be seen that, in accordance with the invention, the period of time u separating any two markers, for the same transmitter, is identical whatever the transmitter.

It is this condition which allows synchronization between the different transmitters 21, 22, 23, whatever the number of data blocks of the cycles. The offset T between two consecutive markers, from one transmitter to another (for example: between the status marker 28m and of the transmitter 2 and the status marker 29i of the transmitter 3) is such that, if on examining the 28m marker the receiver decides to take an interest in the transmitter 3, it has enough time to agree on the frequency of the transmitter 3 and possibly synchronize its decoder before the broadcast of the marker 29i.

The ratio between the duration u of emission of a block on the one hand, and the duration of emission of a marker on the other hand, must be sufficiently large to allow several transmitters to operate simultaneously. By way of example, it is possible to envisage a duration of approximately 100 ms for the transmission of a marker, and block transmission times of the order of 15 s. The duration T necessary to effect the transition from the agreement of one transmitter to the agreement with another transmitter should be easily reduced within 1 second.

• . cycle 31 (1 bit) : normal ou lent
• . Type 31 (1 bit) : marqueur d'état ou marqueur synchronisant
• . ID-logique (33)* (6 bits) nombre (modulo 64) croissant de 1 à chaque nouvelle version du cycle. Le numéro de cycle figurant dans les marqueurs d'état est identique au numéro figurant dans le marqueur synchronisant du cycle.
• . ID-Physique (34) (4 bits) : cet identificateur est incrémenté chaque fois que le contenu du cycle est physiquement modifié ; ce champ est destiné à faciliter l'exploitation par le terminal des redondances en transmission.
• . DUREE (35) (6 bits) : ce champ est exprimé en nombre entier de "Time-slots"; la durée du cycle est en réalité ce nombre + 1; quand le marqueur est du type "état", il s'agit du temps nécessaire pour diffuser la fin du cycle, ou plus précisément du nombre de time-slots à s'écouler jusqu'au prochain marqueur synchronisant, quand le marqueur est synchronisant il s'agit du temps nécessaire pour diffuser la totalité du cycle.
• . NB-NOUV (36) (8 bits). Ce champ indique, en binaire, le nombre de messages nouveaux par rapport à la dernière version logique (qui peut être ou pas selon les cas la dernière diffusion) ; la valeur O indique un dépassement de capacité (plus de 255 messages nouveaux) ; les messages nouveaux sont systématiquement diffusés dans les NB-NOUV premières positions du cycle ;
• . NOUVDEP (37) (1 bit) ; ce champ indique si les NBNOUV messages nouveaux sont entièrement placés dans le cycle devant ce marqueur. Il s'agit, surtout pour les marqueurs d'état, de préciser si les nouveautés du cycle suivent ou s'il faut attendre le début du cycle suivant.
• . V.G.P. (38) (1) : Indicateur de présence d'une voie de gestion (valeur 1).
• . AL (39) (1) : indicateur de présence d'un message d'alarme sur un émetteur du service (diffusion en urgence U3).

An example of marker format is shown in Figure 3, in the case of a transmission according to the RDS system discussed above. A cycle marker fits on an RDS group. Each marker (synchronizing or status) carries the following information:

• . cycle 31 (1 bit): normal or slow
• . Type 31 (1 bit): status marker or synchronizing marker
• . Logical ID (33) * (6 bits) number (modulo 64) increasing by 1 with each new version of the cycle. The cycle number in the status markers is the same as the number in the synchronizing cycle marker.
• . Physical-ID (34) (4 bits): this identifier is incremented each time the content of the cycle is physically modified; this field is intended to facilitate the terminal's use of transmission redundancies.
• . DURATION (35) (6 bits): this field is expressed as an integer of "Time-slots"; the duration of the cycle is actually this number + 1; when the marker is of the "state" type, it is the time necessary to broadcast the end of the cycle, or more precisely the number of time-slots to elapse until the next synchronizing marker, when the marker is synchronizing it this is the time required to broadcast the entire cycle.
• . NB-NOUV (36) (8 bits). This field indicates, in binary, the number of new messages compared to the last logical version (which may or may not be the last broadcast); the value O indicates an overflow (more than 255 new messages); new messages are systematically broadcast in the NB-NOUV first positions in the cycle;
• . NOUVDEP (37) (1 bit); this field indicates if the NBNOUV new messages are entirely placed in the cycle in front of this marker. This is, especially for the status markers, to specify whether the new features of the cycle follow or whether to wait for the start of the next cycle.
• . VGP (38) (1): Indicator of the presence of a management channel (value 1).
• . AL (39) (1): indicator of the presence of an alarm message on a transmitter of the service (broadcast in emergency U3).

The last two fields of the marker, as well as the following fields which are described, are not relevant to the present invention. Distinction between the number of the logical identifier 33 on the one hand and the number of the physical identifier 34 on the other hand is related to a particularity of the messages transmitted, not directly relevant to the subject of the present invention. Indeed, and as detailed in the joint patent application, the messages transmitted may include an a priori expiration hour, beyond which they are no longer significant. As a result, these messages are removed from the broadcast cycle at said expiration time. However, it is advisable that the modification of the cycle which results therefrom is not understood by the receiver as signifying an update. Consequently, the logical version number remains unchanged when a message of this type is removed, and it is therefore the logical identifier 33 that is relevant for the listening and updating strategy of each receiver. .

Several listening strategies can be considered.

• on choisit un ordre de priorité d'écoute pour chacun desdits émetteurs thématiques ;
• on écoute successivement chaque émetteur, selon l'ordre de priorité choisi, jusqu'à réception d'un marqueur de l'émetteur ;
• on écoute les messages modifiés de l'émetteur reçu en ce que le marqueur correspondant porte un numéro de version différent du numéro de version du cycle d'information précédemment mémorisé dans ledit récepteur ;
• on se met directement à l'écoute de l'émetteur d'ordre suivant de priorité lorsque le marqueur au-dessus l'émetteur courant comporte un numéro de version identique au numéro de version du cycle mémorisé dans ledit récepteur. Selon une second stratégie :
• on choisit un ordre de priorité d'écoute pour chacun des émetteurs du parc ;
• on écoute successivement, au cours d'une unité de temps, tous les marqueurs diffusés en décalage sur l'ensemble des émetteurs du parc, en fait on captera, durant cette unité de temps, un nmarqueur par émetteur, l'ordre d'écoute des émetteurs étant indépendant des ordres de priorité choisis, mais uniquement dépendant des décalages synchronisés entre émetteurs ;
• on cale enfin le récepteur sur chaque émetteur pour lequel on a capté l'existence d'une nouvelle version, nécessitant une mise à jour de la base de données embarquée, en suivant l'ordre de priorité choisie.

According to a first strategy:

• a listening priority order is chosen for each of said thematic transmitters;
• each transmitter is listened to successively, according to the order of priority chosen, until reception of a marker from the transmitter;
• the modified messages from the received transmitter are listened to in that the corresponding marker carries a version number different from the version number of the information cycle previously stored in said receiver;
• we listen directly to the next priority order transmitter when the marker above the current transmitter has a version number identical to the cycle version number stored in said receiver. According to a second strategy:
• a listening priority order is chosen for each of the transmitters in the park;
• we listen to successively, during a unit of time, all the markers diffused in offset on all the transmitters of the park, in fact we will capture, during this unit of time, a nmarker per transmitter, the listening order transmitters being independent of the orders of priority chosen, but solely dependent on the synchronized offsets between transmitters;
• we finally wedge the receiver on each transmitter for which we have detected the existence of a new version, requiring an update of the on-board database, following the order of priority chosen.

The invention therefore has the advantage, in a preferred application, of allowing a motorist to choose from the thematic transmitters which are proposed to him, those from which he preferentially receives information, and in particular updated information.

Claims (9)

1. Method of synchronised broadcasting of information messages by a fleet of thematic radio transmitters, allowing a specialised and reconfigurable strategy for listening to several transmitters of the fleet, from a single receiver,
   characterised in that each transmitter (21,22,23) permanently broadcasts a cycle formed of a variable number of messages, each message cycle being partitioned into successive blocks of fixed size and fixed duration and which are identical for all the transmitters,
   in that each block includes an initial informative marker, termed the state marker, and each cycle includes an initial informative market (24,25,26), termed the synchronising marker, the said state marker and the said synchronising marker containing a version number for the current cycle of the corresponding transmitter,
   and in that the cycle commencements (24,25,26) for each transmitter (21,22,23) of the fleet are shifted from one transmitter to the next, in such a way that the markers of each transmitter are broadcast at instants which differ from the other transmitters so as to be able to be picked up in succession by the same receiver.
2. Method according to claim 1, characterised in that each state marker includes the information for the number of blocks remaining to be broadcast up to the next synchronising marker.
3. Method according to claim 1, characterised in that each synchronising marker includes the information for the number of blocks to be broadcast before the next synchronising marker.
4. Method according to claim 1, characterised in that the said fixed duration of a message block is between around 40 and 150 times the duration of transmission of a marker.
5. Method according to claim 1, characterised in that each synchronising marker and/or each state marker includes the information for the number of new messages in the current version of the broadcasting cycle with respect to the previous version.
6. Method according to claim 1, characterised in that each state marker includes the information for the number of new messages in the current version of the corresponding block, with respect to the previous version of the said block.
7. Method according to claim 5 or 6, characterised in that the said new messages are broadcast immediately after the broadcasting of the synchronising marker of the current cycle, and of the state marker of the current block respectively.
8. Method of receiving messages transmitted by a fleet of thematic radio transmitters according to a method of synchronised broadcasting according to any one of claims 1 to 7, by means of a receiver equipped with means for storing and processing the information messages received,
   a method characterised in that:

   - an order or priority of listening is chosen for each of the said thematic transmitters;

   - each transmitter is listened to in succession, according to the chosen order of priority, until a marker is received from the transmitter;

   - the modified messages from the received transmitter are listened to in the case where the corresponding marker picked up carries a version number which differs from the version number of the information cycle previously stored in the said receiver;

   - listening to the transmitter with succeeding order of priority is begun directly when the marker received from the current transmitter includes a version number identical to the version number of the cycle stored in the said receiver.
9. Method of receiving messages transmitted by a fleet of thematic radio transmitters according to a method of synchronised broadcasting according to any one of claims 1 to 7, by means of a received equipped with means of storing and processing information messages received, a method characterised in that:

   - an order of priority of listening is chosen for each of the transmitters of the fleet;

   - in the course of one time unit, all the markers broadcast with shift are listened to over the set of transmitters of the fleet in order of phase-shift;

   - the receiver is locked onto each transmitter for which the existence of a new version, requiring an updating of the storage means, has been picked up in accordance with the chosen order of priority.

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