EP1363260A1 - Method for radio frequency communication among multiple devices and monitoring system using the method - Google Patents

Abstract

The method includes, in normal functioning mode, to synchronise at regular intervals, the compatibility modules of the different devices (1 and 2) and establishing a discontinuous radio communication link, during the consecutive separated temporal windows, between this central device (1) and the peripheral devices (2) corresponding to the cyclical limited activation periods of the central device and of these peripheral devices, repeated at regular intervals, with a frequency greater than the repetition frequency of the emission of the synchronisation message.

Description

The present invention relates to the field of communication by radio transmission between several elements in particular, but not exclusively, in the case of surveillance or alarm, and relates to a communication method improved and a surveillance or alarm system implementing such process.

In many applications based on the cooperation of several separate electronic devices located remotely from one of the other, provision should be made for wireless communication over the air between these devices as well as an autonomous power supply for each of them. These provisions may be mandatory for reasons installation, security and / or independence from the network, in particularly in the case of surveillance and alarm systems.

However, the systems of this type currently proposed use generally, for reasons of ease of development and point, as well as cost, unidirectional radio links between the sensors and the control panel.

As a result, the sensors or other peripherals are frequently emitted for all detected detections regardless of how the system is activated (armed or disarmed) because they are not aware of the state of the system defined at the level of the Central.

On the other hand, because of the limited capacity of energy sources of the power plant and the sensors, the reception at the level of the central can only be intermittent and the emission at the level of the sensors also.

To ensure proper transmission, it is essential that the duration of transmission on the sensor side is greater than the duration of the rhythm listening (receiving) side central.

If we choose a slow listening rhythm, we prefer the autonomy from the power plant at the expense of the autonomy of the sensors (each emission must be greater than the listening periods of the plant). On the contrary, the increase in the rate of listening to the plant penalizes the autonomy of the latter in favor of the sensors.

In practice, the values retained are a compromise between two, while providing the system with an acceptable reaction time (time means to inform the central unit of a detection observed by a sensor).

However, such a compromise, constituting the least worst produced by the state of the art, is not satisfactory, nor is it autonomy, neither from the point of view of reactivity, reliability or adaptability.

The present invention aims to meet at least some of the needs expressed above and to provide a responsive solution at least some of the foregoing limitations.

For this purpose, the subject of the present invention is a method of bidirectional communication by radio message transmission frequency in the form of digital frames modulated in frequency between a central or primary device master and several peripheral devices or secondary slave, these devices being all physically independent, with autonomous and at least a radio transmission / reception circuit, as well as a counting the time providing a local time reference, characterized in that it consists, in normal operation, in synchronize the accounting modules at predetermined intervals different devices by sending a radio message from synchronization of the central device to peripheral devices and to establish a discontinuous radio communication link, during predetermined repetitive separate temporal windows between said central device and peripheral devices, corresponding to limited periods of cyclic activation of said central device and at least some of said peripheral devices, repeated at regular intervals and / or predetermined, of duration (s) lower than those (s) intervals separating two successive transmissions of the synchronization message, each activation period including a first phase or interval temporal authorization or obligation to issue message (s) for a peripheral devices and simultaneously listening, at least during a first part of this first phase, for the central device and a second phase or time interval of authorization to issue message (s) for the central device and simultaneously listening for at least one of the peripheral devices, the intended recipient (s) of a such eventual message from the central device, said second phase following immediately said first phase and the synchronization message being transmitted at predetermined intervals during such a second phase.

The repetition of synchronization phases will be preferentially regular, that is to say with a given frequency (simple and robust procedure). However, this repetition can also be irregular and follow a given pattern identical for the device central office and the peripheral devices concerned.

Precise synchronization between devices, periodically refreshed, reduces the windows of emission and listening (state of reception) at minimum values, ideally about the same order of magnitude than the messages exchanged.

In addition, the definition of limited periods of activation affecting only some of the peripheral devices and grouping temporally adjacent transmission and listening phases result, in association with the above mentioned provision, a significant reduction in the consumption at the central level, but especially at the level of peripheral devices. Consumption can be further reduced in providing for the sending of messages from the central device to the devices peripherals only if necessary.

In order to guarantee a message reception free from truncation due to a possible delay between transmission and listening phases simultaneous, each message exchanged between master device and device (s) slave (s) includes a first part forming a preamble whose duration time is greater than the maximum drift of synchronization between the central device and the peripheral devices during the interval separating two successive synchronization messages and the one or more listening device (s) remain activated (s) at least during the duration of this preamble, in a continuous or discontinuous manner, said one or more devices are disabled (s) or paused in the absence of detection of message after this period has elapsed.

According to an advantageous variant embodiment of the invention, the body of the preamble can be constituted by a portion of message digital formed of a repeating pattern having both 1 and 0, preferentially present in a regularly alternating manner, said preamble ending with a particular numeric character pattern different from said repetitive pattern, preferably an extended sequence of one plurality of 1, followed by a prolonged sequence of a plurality of 0's.

In addition, it can be advantageously provided that, for each message sent, the preamble is followed by a synchronization byte for activation of the asynchronous radio transmission interface of the circuit transmission / reception of the device (s) central or peripheral (s) recipient (s), and that said peripheral devices realize, after each receipt of a synchronization radio message, a check of the validity of the message, then an exploitation of its information temporal comparison with the local time reference of the concerned peripheral device and the subsequent modification, in advance or delay, of the local time reference provided by the module of corresponding accounting for the difference observed or fraction of the latter, evaluated taking into account at least the last two previous differences noted.

In any case, the length of the messages sent will be calculated in such a way that in no case shall the assigned emission authorization phase.

In accordance with a preferred embodiment of the invention, corresponding to optimized operation, the device Central is always listening during the first phase of each cyclical activation period. In addition, peripheral devices are allowed to transmit, one by one, in a predetermined cyclic order, for example linked to their identification and registration address with the central device, and with a frequency of repetition, occurrence or achievement corresponding to a sub-multiple of the repetition frequency limited periods of activation and listening phases of said devices devices are repeated with a repetition or occurrence frequency corresponding to a sub-multiple of the frequency of repetition of periods activation limits, said repetition frequencies being different for each type or each of the peripheral devices, the frequencies of the listening phases being, for the same peripheral devices, superior at frequencies, transmission phases all peripheral devices listening to each broadcast of a radio message from synchronization issued by the central device.

In order to avoid as much as possible total or partial collisions between messages sent simultaneously or partially overlapping by two different devices, it can be expected that, immediately before each transmission phase of a message by the central device or one of the peripheral devices, the device concerned is in a situation of listening, and is authorized to broadcast only in the absence of any radio message being transmitted.

Generally, in current operation, the messages addressed by the peripheral devices to the central device consist either of in predetermined routine messages indicating a normal situation at the level of the peripheral device concerned and addressed compulsorily to the central device in a repetitive manner at successive instants specific to each peripheral device, either in random messages of signaling an incident, an event or an abnormal situation, each signaling message being transmitted to the central device during the authorization phase of the activation period immediately following the occurrence of the incident, event or situation abnormal and its emission beginner before the beginning of the authorization phase transmission, said signaling messages being provided with preambles extended.

The method according to the invention thus implements a method active monitoring of the radio link between the peripherals and the plant by sending presence messages cyclically.

The devices send their respective message in a sequential using their individual address to determine the instant of emission compared to their reference of local time, itself set periodically on the sequencing of the plant. Similarly, the central determines for itself the moments during which it is supposed to receive the presence messages of the various registered devices.

In order to maintain communication between the central device and all the peripheral devices, despite poor conditions of radiofrequency transmission, of signals interfering or scrambling or electromagnetic environment loaded, the different devices are capable of transmitting and receiving radio signals on at least two frequency channels, namely a channel principal used in normal operation and at least one fallback channel, folding or rescue used in case of difficulty of transmission on the main channel, or by temporal distribution of communications on several channels used alternately.

Thus, according to a first embodiment of the invention, said method may consist of switching radio transmissions between devices of the main channel on the or a fallback channel at the initiative peripheral device, after the latter has diagnosed a cut of its radiofrequency link with the central device, either because lack of reception, possibly repeated, of a radio message from synchronization at one or more predetermined deadline (s), the fact that there is no reply message or acknowledgment of receipt central device following the prior sending, repeatedly, of messages radio, in particular, signaling messages of an incident, a event or abnormal situation, of the peripheral device concerned to said central device.

According to another characteristic of the invention, the changeover transmissions between devices on the or a fallback channel consists, for the peripheral device at the initiative of said failover, to switch on the or a fallback channel at the time of the advent of an authorization phase or obligation to issue messages (s) assigned to it in the order established for the different peripheral devices, to then go into listening situation for a first period at least equal to the sum intervals between two periods of cyclic activation and such a period, and possibly, in a repetitive manner, during the estimated consecutive emission phases of the central device, this up to receive an offset synchronization message transmitted by the device central and setting the new transmission and listening rhythm between peripheral device and said central device on said fold channel.

According to another characteristic of the invention, the switching transmissions between devices on the or a fallback channel consists, for the central device, after noting the repeated absence of receiving any message, in particular a routine message, during successive phases of authorization or obligation allocated to the peripheral device having switched over, to be transmitted during the next scheduled listening phase of said peripheral device a synchronization message shifted on the fold channel, or successively on the various possible fallback channels, to possibly repeat this during successive successive listening phases of peripheral devices on the fallback channel (s), up to receiving a message back from said peripheral device having switched over, and to address one or more messages, in one or more emission authorization phases of said central device, requiring the failover of other peripheral devices on the fallback channel considered, where appropriate in the order of addressing of said other devices peripherals, the successive transmission / reception phases of the different devices on the main channel and the fallback channel being shifted temporally, the order of addressing devices, after their failover, will be the fallback channel being either identical to that prevailing over the main channel, which is different from the latter, the new order being in that last case indicated by the central device to peripheral devices.

This last provision allows the central device to communicate simultaneously with all distributed peripheral devices on both transmission channels.

According to a second embodiment of the invention, the devices are capable of transmitting and receiving radio signals on the minus two different frequency channels and at each time window successively the central device and the peripheral devices are switched to a different channel from the one used for the time window immediately preceding, according to a predetermined order of succession of said channels, which is identical for each device and which runs from synchronously for all said devices.

Thus, each activation period is carried out one jump frequency in a deterministic pattern identical for all devices.

Preferably, the latter use at least four different communication channels and the order of succession of said channels is selected at the start of said devices.

The repetition sequence of the different channels will be preferentially odd when the number of usable channels is even and will have a number of steps greater than the number of usable channels.

For marginal cases where it is necessary to implement a recovery procedure (for example after a breakdown, a shutdown of the central, ...), it may be provided a fallback channel that will be fixed and known to different devices, in addition to the different common channels used during normal communication procedures.

In the context of an initialization phase of the communication or integration of a new peripheral device, the pairing of such a new peripheral device or the re-pairing of a peripheral device having been disconnected from the device exchange, consists of exchanges of asynchronous radio messages to be sent to the central device a message indicating the characteristics of said new peripheral device, in particular the frequency of its activation for the program and listen to it, then to transmit to it an address identification, also fixing its order in the sequence of the phases authorizing the transmission of the different peripheral devices in connection with the central device, an initial synchronization message and a possible site identifier used for secure transmissions.

Similarly, the process according to the invention may consist of a mobile device, having been moved out of the field of coverage of the central device and having received a reactivation signal and / or reconnection or having been the subject of a solicitation of this type, to be issued continuously for a duration greater than the sum of the durations of a activation period of devices and an interval separating two such periods, a signaling frame containing the identifying address or the identifier assigned to said device, then to put itself in listening situation in view of receiving a response from the central device, in the form of a initial synchronization message with request authentication, to repeat the two previous operations for the different transmission channels, starting with the last one channel used by said peripheral device before its disconnection from the central office, until a response is received from the central reaching the predetermined maximum number of attempts, with standby or subsequent deactivation of said peripheral device considered in case not restoring communication with the central device.

Typically these latter measures can be implemented in connection with a peripheral device not fixed, nomadic, such than a remote control or the like.

In order to increase the reactivity and efficiency of the process according to the invention while maintaining a low current activation rate, each peripheral device can have two different frequencies of repetition of its cyclic activation period and radio communication with the central device, namely a low frequency and a frequency high, said peripheral device operating normally with the low repetition rate and said peripheral device tilting towards the high repetition rate when said device is biased or activated or, in advance, when said device determines the occurrence next action that may require or require the establishment of a communication with the central device.

In accordance with a particularly advantageous application, the communication method according to the invention can be implemented by a surveillance or alarm system, the central device consisting of a microprocessor alarm control panel for the execution of the management and control of the said system and provided with an interface external communication and peripheral devices consisting of one or several sensor (s), control organ (s), imaging organ (s) and / or sound, siren (s), horn (s), actuator (s), detector (s) and / or communication device (s) to a network.

The invention also relates to a surveillance system or alarm system comprising a control unit and peripherals, forming independent and self-powered devices, characterized in that implements the communication method as described above.

La figure 1 représente des chronogrammes montrant les signaux émis/reçus au niveau du dispositif central au cours de deux périodes d'activation successives ;

La figure 2A représente des chronogrammes illustrant les décalages pouvant être générés à l'émission et à la réception des messages envoyés par les périphériques pendant le TPP du fait de la dérive de l'horloge locale ;

La figure 2B illustre une variante de réalisation de l'invention selon laquelle l'activation du dispositif central en phase d'écoute est intermittente pendant le TPP ;

La figure 3 est un ordinogramme représentant les étapes effectuées par un dispositif périphérique n'ayant pas reçu un message de synchronisation (top desynchro) émis par le dispositif central à un instant prédéterminé ;

La figure 4 est une représentation sous forme d'un chronogramme d'un exemple de constitution d'une trame de signalisation émis par un dispositif périphérique mobile souhaitant reprendre la liaison avec le dispositif central ;

La figure 5 représente un exemple de possible structure de la trame courante utilisée dans le cadre du procédé selon l'invention ;

La figure 6 est une représentation schématique d'un ensemble comprenant un dispositif central et plusieurs dispositifs périphériques communiquant avec ce dernier selon le procédé objet de la présente ;

La figure 7 montre sous forme de diagramme les différents états possibles pour les dispositifs périphériques en relation avec le premier mode de réalisation de l'invention décrit ci-dessus, et,

La figure 8 montre sous forme de diagramme les différents états possibles pour les dispositifs périphériques en relation avec le second mode de réalisation de l'invention décrit ci-dessus.

The invention will be better understood, thanks to the following description, which refers to a preferred embodiment, given by way of non-limiting example, and explained with reference to the attached schematic drawings, in which:

FIG. 1 represents timing diagrams showing the signals transmitted / received at the central device during two successive activation periods;

FIG. 2A shows timing diagrams illustrating the offsets that can be generated on transmission and reception of the messages sent by the peripherals during the TPP because of the drift of the local clock;

FIG. 2B illustrates an alternative embodiment of the invention according to which the activation of the central device during the listening phase is intermittent during the TPP;

FIG. 3 is a flow chart showing the steps performed by a peripheral device that has not received a synchronization message (top desynchro) transmitted by the central device at a predetermined time;

FIG. 4 is a representation in the form of a timing diagram of an example of constitution of a signaling frame transmitted by a mobile peripheral device wishing to resume the connection with the central device;

FIG. 5 represents an example of possible structure of the current frame used in the context of the method according to the invention;

Figure 6 is a schematic representation of an assembly comprising a central device and a plurality of peripheral devices communicating with the latter according to the method of the present invention;

FIG. 7 shows in diagrammatic form the different possible states for the peripheral devices in relation to the first embodiment of the invention described above, and,

Figure 8 shows in diagrammatic form the different possible states for the peripheral devices in relation to the second embodiment of the invention described above.

The invention will now be described more precisely in relation to with a practical realization in the form of a surveillance system or an alarm device consisting of at least one central or central device 1 to microprocessor (in some cases called base) cooperating with at least a peripheral or peripheral device 2 chosen from the list comprising sensors, control devices, sirens, horns, actuators and communication devices to a network through communications short distance radio (also known as SRD) using a free band of type ISM).

Each element of this system, shown schematically in FIG. 6 is equipped with a radio transmission / reception circuit 1 ', 2' (alternating) and has an independent power source (battery or battery), as well that a 1 ", 2" time accounting module associated with a reference of time (typically a quartz with a counting chain) yet called "local reference".

Central 1 transmits a radio signal periodically containing information representative of the temporal sequencing of said central unit 1 and the peripherals 2 capture this information so to stall their inner workings on an identical or multiple rhythm of that of the central 1 or at least try to approach it. When the central 1 sends the temporal information, it precedes it with a series number of characters (called the preamble) whose transmission duration is greater than the maximum observable drift between a device 2 and the central 1 (given the uncertainties related to the accuracy of quartz, temperature, aging of quartz and various uncertainties), increased by the number of characters needed to ensure receive synchronization, allowing devices 2 in reception to detect the transmission of time information despite the drifts of time references, knowing that the rhythm and timing of transmission are predetermined both in Central 1 and in the devices 2 considered.

Said devices 2 exploit this temporal information after verification of the validity of the latter (use of a "signature" or authentication) by modifying their chain of counting in advance or delay of the latter following the gap observed between the local reference (device 2) and the information temporal value transmitted, of a value equal to that difference or a fraction thereof difference, weighted by the average value calculated in a sliding manner on the previous discrepancies.

According to an exemplary non-limiting practical embodiment of a monitoring system and alarm, the central 1 can operate on a reception rate of one second (interval separating two listening phases successive), for a duration of about 8 ms in the absence of message and 30 ms in the presence of message from a synchronized device 2. The window or listening phase of control panel 1 starts 125 ms (1/8 s) before his speech window. This window is called Peripheral Speech Time (TPP).

This listening period of Central 1 is followed by a time of 40 ms word for the latter called TPC (central speaking time). It is used to synchronize devices every 64 seconds (repeated sending of synchronization message). TPC speaking times do not are used only if the plant has information to transmit. The synchronized devices are not allowed to transmit during the TPC (see figure 1).

When unsynchronized 2 devices are transmitting, they may accidentally do so during the speaking time of the plant, and for a duration of up to one second. The plant must therefore check before issuing, the presence or absence of a program already engaged.

Thus, energy saving is achieved through the reduction of listening and transmission time for the different devices 1 and 2 constituting the alarm system. This reduction is only possible thanks to the synchronization of peripherals on the rhythm of the power plant.

The inevitable physical inaccuracy of synchronization on which were based the simulations performed by the inventors gives a delta (Δ) of 12 ms per minute, when a 32.768 kHz quartz serves as reference.

When the initial accuracy of the quartz is +/- 30 ppm and the temperature drift is given at +/- 50 ppm in the range -10 ° to + 55 °, the overall tolerance will be +/- 100 ppm to account for other factors (aging, resynchro dispersion, ...).

As previously mentioned, all devices 2 (except possibly a mobile device of the type remote control), are synchronized to the control panel. When getting started of the system, after the installation phase, the devices are keyed on the 60s pace. This synchronization is maintained by the acquisition repeated (systematic) sync signal (sync message) issued by the plant. As the central is in reception every second, devices with a message to be sent to the central must do in the expected TPP interval (see Figure 1).

• message de signalisation ou d'alerte (intrusion, auto protection, défaut d'alimentation, ...)
• message de présence (avec éventuellement indication niveau de pile et niveau de champs).

Messages sent in normal operation can be of two types:

• signaling or warning message (intrusion, auto protection, power failure, ...)
• presence message (possibly with stack level and field level indication).

The first type being unpredictable and exceptional, there is no collision in the vast majority of cases. A mechanism particular to manage the rare collisions is explained further.

• appel systématique des périphériques par la centrale (inconvénient : consommation accrue pour la centrale)
• envoie automatique du message de présence par le périphérique initié par un premier appel (la centrale peut ainsi répartir les périphériques sur les 600 secondes et de ce fait éviter les collisions ultérieures). Cet automatisme peut s'arrêter par l'envoi d'une commande "silence" par la centrale.

The second type is predictable because the devices are set to emit a presence signal at regular intervals (every 600 s for example). Two solutions are possible:

• systematic call of peripherals by the central (disadvantage: increased consumption for the power station)
• automatic sending of the presence message by the device initiated by a first call (the control unit can thus distribute the devices over 600 seconds and thus avoid subsequent collisions). This automation can stop by sending a command "silence" by the central.

For reasons of energy saving and functionality, devices are also listening in an alternating cycle predetermined. While for the central this cycle is one second, it may vary from 2 to 30 seconds depending on the devices.

This means in practice that the plant can not dialogue anytime, with any device, and so must handle in a predictive way its periods of listening devices.

• cycle à 2 secondes : réveil sur les secondes paires (0,2,4,...)
• cycle à 10 secondes : 0, 10, 20, 30, 40, ...
• cycle à 30 secondes : 0 et 30 secondes.

For the sake of simplicity, all devices will be keyed to the same sub-multiples:

• cycle to 2 seconds: waking up on the second pairs (0,2,4, ...)
• cycle at 10 seconds: 0, 10, 20, 30, 40, ...
• cycle at 30 seconds: 0 and 30 seconds.

All devices are therefore listening at least two times per minute (simultaneously for at least some of them).

When the plant needs to interact with several devices (after collision detection, sending an order to several interlocutors, ...) or only one (fast entry of several parameters with the control box), the control unit informs affected devices of the activation of this mode of communication, this which will have the consequence for the peripherals concerned to maintain the receive activated until the transaction or communication in progress is completed or this mode is disabled by the control panel.

• un périphérique particulier
• les périphériques ayant initiés une communication (ou en cours de dialogue) avec la centrale
• tous les périphériques.

In practice, the control unit activates the mode by specifying the devices concerned, namely:

• a particular device
• devices that initiated a communication (or ongoing dialogue) with the central
• all devices.

As indicated previously, such a mode of communication discontinuity requires a precise synchronization between the central 1 and the peripherals 2.

In the practical example mentioned above, the central and devices have a time base of 32768. So all the 64s, the control unit emits a synchronization signal (message) that allows devices to reset the counting channels of their modules counting 2 ".

The sync top coincides with the end of the message word of synchronization (but another convention can be used). The power plant must therefore anticipate the length of the preamble to be "on time". At when a TPC is superimposed with the sending of the sync (once per 64s), the devices go into receive mode at the same pace than that used by the plant during TPP.

The synchronization message can take on the appearance of any message. We can imagine that to reduce the effect of a loss of synchronization, devices software adjust their clock based on the discrepancies noted at the time of synchronization. AT correction error a measure of the difference found (between the signal of sync and the local clock) can help maintain a level of satisfactory performance in case of "prolonged" sync loss, as necessary activation anticipations can be minimized.

In this context of synchronized transmission / reception, two main problems may arise: drifting references local time and the lack of synchronization due to the lack of receiving the cyclic synchronization message forming "top of "sync", which may be due to a loss of connection between central and peripheral.

Concerning the drifts (drifts of local clock), the error will be, in the practical case mentioned above, 6 ms is a delta of 12 ms as mentioned previously.

In a practical way, this means that when the power station listens, a device was able to start a transmission 6 ms plus early, or can start the 6 ms later.

In the extreme case, the control unit is activated first, a device can issue 12 ms later. These 12 ms are advantageously absorbed by the presence of a preamble signal preceding the message proper (see Figure 2A).

• de manifester/détecter une activité radio tout en préservant le message d'une troncature,
• d'effectuer un AFC (contrôle automatique de la fréquence) si la fréquence moyenne vaut f₀ (nombres de 0 et de 1 identiques)
• de synchroniser le récepteur pour activer l'UART (interface d'émission / réception asynchrone) au moment opportun,
• d'absorber les écarts d'horloge entre les éléments constitutifs du système.

This preamble allows in particular:

• to manifest / detect a radio activity while preserving the message of a truncation,
• to perform an AFC (automatic frequency control) if the average frequency is worth f ₀ (numbers of 0 and 1 identical)
• to synchronize the receiver to activate the UART (asynchronous transmit / receive interface) at the appropriate time,
• to absorb the clock differences between the components of the system.

As the speech window of the devices 2 is limited to 125 ms, the message sent by a "late" device should not exceed the limit of the TPP. If the preamble is 14 ms (dispersion delta) + 3 characters (ie ~ 3 ms), the message will be maximum: 125 - 12 - (14 + 3) = 99 ms (~99 bytes to 9600 bds). Advantageously, we will limit ourselves to 31 ms for message length to avoid overflow (Figure 2).

Advantageously, the preamble contains as many as 1 as 0 so that, encoded in frequency modulation, the average value of the signal The radio frequency corresponds to the central value of the radio channel the activation of an automatic frequency control device (AFC) receiver side, at the beginning of the call.

Preferably, the preamble consists of a sequence of characters 55h (101010 ...) allowing faster operation of frequency servoing and can be followed by a pattern consisting of two FFh and 00h characters used to mark the end of the preamble and the beginning data transmitted in the message or frame concerned 2.

The reception of FFh before 00h indicates that synchronization character was achieved from the first 55h.

In practice, said preamble may, for example, be composed of 15 characters or 15.6 ms duration (at 9600 bds).

As a variant, the first 14 characters may be identical and be worth 0xF0 (0000011111 in binary). The ^15th is 0x9C (0001110011 in binary). The beginning of the preamble materializes in the form of positive and negative pulses of equal length (~521 μs). The last character 0x9C indicates the end of the preamble.

To optimize the consumption of the receiver device, activation of the latter can be cut in two periods of 4 ms (instead 15 ms continuous), as shown in Figure 2B.

In addition, a synchronization fault may occur when device 2 misses one or more synchronization message (s) issued by the central 1.

The first time, the device retains its internal reference, but in the next minute he will have to anticipate the TPC in order to to be able to receive the synchronization message even in case of delay.

If the synchronization is missed a second time, the device concerned must initiate a procedure to recover its synchronization, as than that represented for example in FIG.

To implement such a procedure, the system according to the invention will, for example, have to implement a method of managing the multi-channel transmissions with crimping in case of failure of the usual radio link.

Thus, during the installation of the system, the central 1 request to the different devices 2 recorded to measure the signal quality radio on all exploitable channels (measurement of noise floor at the RSSI - signal strength indicator received, so that to be able to determine in a second time what will be respectively the main channel and backup channel (or fallback). After doing the selection, the central unit 1 indicates to all the devices the instructions on the choice of channels.

• par le(s) périphérique(s) concerné(s), pour basculer sur le canal de repli après un nombre prédéterminé d'absence de recalage (non réception de plusieurs messages de synchronisation) ou de répétitions successives d'émission de messages de signalisation d'événement restés sans réponse, et,
• par la centrale, pour rechercher le(s) périphérique(s) aux "abonnés" absents (absence de message de présence ou de non-réponse à une requête).

The radio link faults can be detected, on the one hand, by the peripherals, when the time adjustment is no longer received at the scheduled time or when there is no acknowledgment following the transmission of an event and, d on the other hand, by the central unit, by the repeated absence of presence messages or the absence of acknowledgment following a request. This observation is exploited:

• by the device (s) concerned, to switch to the fallback channel after a predetermined number of no registration (no receipt of several synchronization messages) or successive repetitions of transmission of signaling messages event that remained unanswered, and,
• by the central unit, to search for the device (s) to the "subscribers" absent (absence of message of presence or non-response to a request).

In any case, one of the devices 2 of the system will be the channel change initiative when the requirements are filled, and Central 1 will emit a form of radio beacon on the channel of fallback (after the required conditions), while retaining the management of the main channel.

Each device 2 having switched on the channel of drawdown changes its rhythm and timing of reception. Indeed, while the devices running on the main channel are busy according to different rhythms (depending on the nature of the devices), the rhythm is identical for everyone as soon as they have switched to the fallback channel.

Advantageously, the instants of the listening phases on the channel fallback, are offset from the nominal operation.

Thus, for example, in nominal operation (channel principal), the exchanges (except alerts) are done on second pairs and, in emergency operation (draw channel) and the radio beacon is transmitted by the central unit 1 on odd seconds (which allows it to continue to manage other devices 2 on the main channel).

In the practical example discussed, the link loss procedure is initiated after two synchronization losses (two synchronization messages not received). At first, the isolated device of the plant continues to listen for a synchronization every minute on the initial channel. Anticipation of TPP and TPC intervals are anticipated (or delayed) of the value:
(Number of minutes since last sync) x (average error found).

In a second step, the isolated device switches to the fallback channel when it was supposed to send his message of presence and goes back to receiving mode for a second to try to capture a synchro (the central having noted the absence of a signal of presence, it is programmed to issue a status request (synchronized) on the fold channel.

If this procedure is unsuccessful, the affected device will fall asleep for 32 seconds, then reactivate reception for 40 ms on the fallback channel (during the TPC) and so on (sleep, Rx, ...). These 40 ms are divided into 4 ms periods of Rx separated by standby time of 2 ms.

It should be noted, in this respect in particular, that the presence of a mobile device, such as a remote control, in the surveillance or alarm will be a special case since it could be outside the coverage area at the time of migration (switchover of devices on the fallback channel). As a result, if it is not synchronized, it transmits asynchronously successively on the four channels in starting with the most recently used channel. The show on each channel must be one second to allow listening by the central. The different communication channels that can be used are preferentially located in the 868 MHz band.

In fact, a mobile device such as a remote control will have to be managed in a specific way, particularly with regard to its communication with the plant, since it is likely to leave the Radio coverage area of the plant.

It will therefore be necessary to provide some particular for this device, with repercussions on the general operation of the system.

• en l'absence de signal de synchronisation, la télécommande s'endorme et ne se réactive que sur appui d'un bouton,
• un appui bouton "réveille" la télécommande qui n'est donc plus synchronisée ; pour être sûre d'être entendue, elle devra émettre durant une seconde sur chacun des quatre canaux possibles de communication en commençant par le dernier (en date) utilisé
• chaque émission est suivie d'un temps d'écoute pour détecter une possible réponse de la centrale pendant une durée déterminée avant de passer au canal suivant
• pour indiquer cette phase à l'usager, on peut faire clignoter une diode de manière rapide jusqu'à ce que la liaison avec la centrale soit établie
• lorsque la centrale détecte la télécommande, elle répond par une demande d'authentification accompagnée des paramètres de synchronisation

Thus, it can be expected that:

• in the absence of a synchronization signal, the remote control falls asleep and is reactivated only at the touch of a button,
• a button press "wakes" the remote control which is no longer synchronized; to be sure of being heard, it will have to transmit for one second on each of the four possible channels of communication starting with the last one (in date) used
• each transmission is followed by a listening time to detect a possible response of the control unit during a determined duration before moving on to the next channel
• to indicate this phase to the user, it is possible to flash a diode quickly until the link with the plant is established
• when the control unit detects the remote control, it responds with an authentication request accompanied by the synchronization parameters

• trame de signalisation transmise en continu (1 seconde) ne contenant qu'une information simplifiée d'identification de l'envoyeur (pour permettre l'interprétation du message avec un nombre réduit d'octets reçus),
• réponse de la centrale par une demande d'authentification,
• envoi du certificat d'authentification par la télécommande avec les paramètres de celle-ci (id du bouton appuyé, niveau pile, ...).

Since the frame transmitted by the remote control can be picked up at any stage, it is proposed to establish the link in two stages:

• signaling frame transmitted continuously (1 second) containing only simplified information of identification of the sender (to allow interpretation of the message with a reduced number of bytes received),
• response of the central by an authentication request,
• sending the authentication certificate by the remote control with the parameters of the remote control (id of the button pressed, battery level, ...).

An emission frame proposal for the remote control is represented in FIG.

The proposed frame contains 4 bytes repeated 241 times for to obtain a second of emission:

The first byte is a preamble byte, the ^2nd is the same sync byte preamble messages and is 0xf0 (0000011111 in binary. The 3 ^rd and 4 ^th bytes are a fixed value at the time of the remote pairing .

• réponse simultanée de deux périphériques lors du TPP ;
• superposition d'une émission télécommande (asynchrone) avec un dialogue centrale-périphérique.

Moreover, it is also worth mentioning the problems related to possible collisions of radio messages that may occur in the system, namely:

• simultaneous response of two devices during the TPP;
• superposition of a remote control program (asynchronous) with a central-peripheral dialogue.

The first case is identified by the central by the observation of the envelope of superimposed carriers: the signal indicating the level of field should in principle indicate at the end of the TPP the absence of a signal, consecutive to the impossibility of decoding viable data during the TPP. In this case the control unit continues by transmitting in the TPC a message asking for extended listening of devices to allow a call of two.

In the second case, the emission of the remote control is perceived by the plant, at the earliest at the time of the TPP, if not in the process of dialogue. At the end of the TPP, the field level signal will indicate a continuation of the presence of the program, and in the process of dialogue, intervals of silence will not be respected. From these observations, the central interrupts the ongoing dialogues to listen (and decode as soon as as possible) the frame of the remote control. It would be desirable for involved devices can also detect this case for cancel a scheduled broadcast.

At the end of the remote control frame, the control unit responds with a message (in priority on what was being done) to the remote control to initiate a dialogue. This answer must intervene in the standard delay so that the remote control does not switch to the channel next radio. It would be desirable if this collision occurs at moment of a synchro, that the devices having found either the absence sync, or the remote control frame, carries over to the next second the attempt to sync. In case of failure (that is to say of impossibility for the to send the sync), this will be done for the next minute (at this point, in 63 seconds).

Finally, the surveillance or alarm system can also be implement an initial synchronization method for each new device 2 (also called pairing).

In this case, before a device can integrate into the system, it will have to exchange information on its characteristics (type of sensor, identifier, ..) and receive back an address code allowing identify it within the system, as well as a "setting time" of its reference local to central 1.

This is achieved by sending asynchronously a pairing request by the device concerned sweeping successively the different radio channels likely to be used at the time of the initial synchronization.

The emission periods (peripheral side) are interspersed short reception periods in order to test a possible response from the Central 1 (and engage the dialogue ...). Said plant 1 will be previously placed in a specific mode used to install new devices 2, so as not to accidentally take into account a device being installed in another system within range radio.

This initial synchronization mode can also be applied to devices that have left the radio coverage area of Central 1 (remote control, alert locket, etc.). Indeed, if we wish them solicit after returning to the perimeter of Central 1, they must resynchronize to be able to dialogue. Similarly, a device 2 having been stopped (battery replacement) will have to re-engage this procedure.

To complete the description of the example embodiment practice of the invention set out above, a constitution will be described hereinafter possible, as well as an associated format, for the usual messages (from synchronization, routine, signaling) in the form of frames digital, exchanged between the devices 1 and 2 forming the system alarm or surveillance.

Such a frame is shown in FIG. 5 of the drawings annexed, and is normally preceded by a preamble and a byte of synchronization as evoked above (not shown).

The "signaling" fields (signaling _1 and signaling _2) indicate to the recipient device (s) of the frame the conditions and the sequence of the transmission in progress.

These fields can for example indicate the situation of the frame in a transmission (first, last), the number of recipients (frame destined for a specific device or all devices), the type of recipients (device with a transmission in progress), whether or not to write encryption or authentication, and to synchronized or asynchronous nature of the frame.

The length (coded on 6 bits) indicates the number of bytes of the data area.

The Ack flag is an acknowledgment flag indicating that the frame is also used to acknowledge the received frame.

The "type" field makes it possible to identify the nature of the message ("Rfa" is a free bit for any subsequent assignments).

Valid addresses are from 01h to 3Eh, the value 00 being used for broadcast commands and the 3Fh value for unpaired devices. The address of the control panel is always implicit. In the peripheral direction towards the central, the address represents the sender, in the opposite direction, it is the addressee.

The data field forms the area containing the information helpful. Most frames are of fixed length, that is, the data is on 32 bits. To homogenize the formats, the length so in all messages.

The "MAC" field is used to authenticate the message and the calculation of its content can be achieved in different ways, in particular according to those known to those skilled in the art, for example of the type known as AES.

Finally, the "CRC" is a zone of cyclic redundancy to ensure that the frame has not been faulted during the radio transmission. Its calculation complies with the CCIR standard. The data taken into account in the calculation include all the fields (from signaling_1 to MAC included).

It should be noted that there are two sequences whose format differs from the format described above. They are used in situations where synchronism is not ensured between the sender of the message and the recipient.

The first nonstandard sequence is used by the remote control (and all other mobile devices) to indicate its intention to issue a status frame. Indeed, a prolonged distance of the central causes the synchronization to be lost. The remote control sends a particular sequence for one second on the last used channel and tries to get a response from the plant. Failure results in the issuance of the same sequence on another channel, and so on until exhaustion four possible channels.

The other non-standard sequence is used by the plant for resynchronize devices whose radio link has been interrupted for an extended period (typically> 512 s). This case does not concern mobile devices (remote controls, medallions, etc.). Indeed, after 128 seconds without synchronization and a failed sync request, a device goes into a sleep mode from which it will only come out on solicitation of the plant, in order to preserve the energy of the batteries. AT use, times will be refined not to get a system too sensitive.

Figures 7 and 8 show schematically the different states possible for peripheral devices 2, respectively in relation to the first and second modes of production.

• Rx : réception ;
• Tx : émission ;
• "time-out" : écoulement du délai imparti ;
• "timing" : séquencement ou cycle de répétition ;
• P_stat : trame de statut du périphérique ;
• C_app : trame d'appairage émise par la centrale ;
• P_init : trame de demande d'appairage ;
• P_txt : trame de saisie de texte ;
• synchro ou sync : trame de synchronisation ;
• C_chan : trame de changement de canal émise par la centrale ;
• C_stat : trame de demande de statut émise par la centrale ;
• C_xxx : trame indéterminée ;
• "burst" : salve ;
• "tst" : test.

In these figures, the following terms have the meanings given below:

• Rx: reception;
• Tx: emission;
• "time-out": expiration of the time limit;
• "timing": sequencing or repetition cycle;
• P_stat: device status frame;
• C_app: the pairing frame sent by the plant;
• P_init: pairing request frame;
• P_txt: text entry frame;
• sync or sync: synchronization frame;
• C_chan: channel change frame sent by the plant;
• C_stat: status request frame sent by the central;
• C_xxx: indeterminate frame;
• "burst": salvo;
• "tst": test.

Of course, the invention is not limited to the modes of embodiment described and shown in the accompanying drawings. Modifications remain possible, particularly from the point of view of the constitution of the various elements or by substituting technical equivalents, without going out for as much of the field of protection of the invention.

Claims (17)

A method of bidirectional communication by transmission of radio frequency messages in the form of frequency-modulated digital frames between a master or master primary device and a plurality of slave peripheral or secondary devices, all of which devices are physically independent, provided with autonomous power sources and at least equipped with a radio transmission / reception circuit, as well as a time accounting module providing a local time reference, characterized in that it consists, in normal operation, in synchronizing the accounting modules at predetermined intervals different devices (1 and 2) by transmitting a synchronization radio message from the central device (1) to the peripheral devices (2) and establishing a discontinuous radio communication link during predetermined repetitive separate time windows, between said cen device tral (1) and peripheral devices (2), corresponding to limited periods of cyclic activation of said central device (1) and at least some of said peripheral devices (2), repeated at regular and / or predetermined intervals, of duration (s) less than that (s) intervals between two successive transmissions of the synchronization message, each activation period comprising a first authorization phase or obligation to issue message (s) for a peripheral devices (2) and simultaneously listening, at least during a first part of this first phase, for the central device (1) and a second message issuing authorization phase (s) for the central device ( 1) and simultaneously listening for at least one of the peripheral devices (2), recipient (s) programmed (s) of such a possible message of the central device (1), said second phase immediately following said first phase se and the synchronization message being transmitted at predetermined intervals during such a second phase. Method according to Claim 1, characterized in that each message exchanged between the master device (1) and the slave device (s) (2) comprises a first preamble part whose temporal duration is greater than the maximum drift of the synchronization between the central device (1) and the peripheral devices (2) during the interval separating two successive synchronization messages and in that the device (s) in the listening phase remain activated (s) for at least the duration of said preamble, continuously or discontinuously, said device or devices being disabled (s) or put on standby in the absence of message detection after this period has elapsed. Process according to Claim 2, characterized in that the body of the preamble is constituted by a portion of a digital message formed of a repeating unit comprising as many as 1 as 0, preferably present in a regularly alternating manner, said preamble ending in a pattern of particular digital characters different from said repeating pattern, preferably a prolonged sequence of a plurality of 1, followed by a prolonged sequence of a plurality of 0's. Method according to claim 3, characterized in that , for each transmitted message, the preamble is followed by a synchronization byte for the activation of the asynchronous radio transmission interface of the transmission / reception circuit (1 ', 2 ') of the central device (s) (1) or peripheral (s) (2) recipient (s), and in that said peripheral devices (2) perform, after each reception of a synchronization radio message, a checking the validity of said message, then exploiting its temporal information by comparing it with the local time reference of the peripheral device (2) concerned and the consequent modification, in advance or delay, of the local time reference provided by the accounting module corresponding (2 ") according to the difference observed or a fraction of the latter, evaluated taking into account at least the last two previous differences noted. Method according to one of Claims 1 to 4, characterized in that the central device (1) is always listening during the first phase of each cyclic activation period, in that the peripheral devices (2) are authorized to transmit, one by one, in a predetermined cyclic order, for example linked to their identification and registration address with the central device (1), and with a repetition frequency, occurrence or embodiment corresponding to a sub-multiple of the frequency of repetition of the limited periods of activation and in that the listening phases of said peripheral devices (2) are repeated with a frequency of repetition or occurrence corresponding to a submultiple of the frequency repetition of the limited activation periods, said repetition frequencies being different for each type or each of the peripheral devices (2), the frequencies for the same peripheral devices (2), the listening phases are greater than the frequencies of the transmission phases, all the peripheral devices (2) being attentive on each transmission of a synchronization radio message transmitted by the central device (1). Method according to one of Claims 2 to 5, characterized in that , immediately before each transmission phase of a message by the central device (1) or one of the peripheral devices (2), the device (1 or 2) concerned puts itself in listening situation, and is authorized to emit only in the absence of any radio message being transmitted. Method according to any one of claims 1 to 6, characterized in that the messages addressed by the peripheral devices (2) to the central device (1) consist either of predetermined routine messages indicating a normal situation at the peripheral device ( 2) concerned and addressed compulsorily to the central device (1) repeatedly at successive times specific to each peripheral device (2), or in random messages for signaling an incident, an event or an abnormal situation , each signaling message being transmitted to the central device (1) during the authorization phase of the activation period immediately following the occurrence of the incident, the event or the abnormal situation and its emission beginning before the start of the transmission authorization phase, said signaling messages being provided with extended preambles. Method according to any one of claims 1 to 7, characterized in that the different devices (1 and 2) are able to transmit and receive radio signals on at least two frequency channels, namely a main channel used in normal operation and at least one folding, folding or emergency channel used in case of difficulty of transmission on the main channel, and in that said method consists in switching the radio transmissions between devices (1 and 2) of the main channel on the or a folding channel on the initiative of a peripheral device (2), after the latter has diagnosed a cut of its radiofrequency link with the central device (1), or because of the absence of reception, possibly repeated, synchronization radio message to one or more predetermined deadline (s), either because of the absence of response message or acknowledgment of receipt of the central device (1) following the in repeatedly forwarding radio messages, in particular messages signaling an incident, an event or an abnormal situation, from the peripheral device (2) concerned to said central device (1). A method according to claim 8, characterized in that the switching of the transmissions between devices (1 and 2) on the or a foldback channel consists, for the peripheral device (2) at the initiative of said tilting, to switch on the or fallback channel at the time of the advent of an authorization phase or message transmission obligation (s) assigned to it according to the order established for the various peripheral devices (2), to be put then in listening situation for a first duration at least equal to the sum of the lengths of the interval separating two cyclic activation periods and of such a period, then possibly, repeatedly, during the estimated consecutive transmission phases of the central device (1), until receiving an offset synchronization message transmitted by the central device (1) and setting the new transmission and listening rhythm between said peripheral device (2) and led it central device (1) on said fold channel. Method according to any one of claims 8 and 9, characterized in that the tilting of the transmissions between devices (1 and 2) on the or a fallback channel consists, for the central device (1), after having noted the absence repeated reception of any message, in particular of a routine message, during several successive phases of authorization or transmission obligation allocated to the peripheral device (2) having switched, to be transmitted during the listening phase next provided said peripheral device (2) a synchronization message shifted on the fold channel, or successively on the various possible foldback channels, possibly repeat this issue during several successive corresponding listening phases of the peripheral devices (2) on the or the fallback channels, until receiving a message back from said device device (2) having flipped, and to address one or s messages, in one or more transmission authorization phases of said central device (1), requiring the switching of the other peripheral devices (2) on the relevant fallback channel, if necessary in the addressing order of said other peripheral devices (2), the successive transmission / reception phases of the different devices on the main channel and on the fallback channel being temporally offset, the addressing order of the peripherals (2), after their switching, will be the channel of fallback being either identical to that prevailing on the main channel, or different from the latter, the new order being in the latter case indicated by the central device (1) peripheral devices (2). Method according to any one of claims 1 to 7, characterized in that the devices (1 and 2) are able to transmit and receive radio signals on at least two different frequency channels and in each successive time window. the central device (1) and the peripheral devices (2) are switched to a channel different from that used for the immediately preceding time window, in a predetermined order of succession of said channels, which is identical for each device (1, 2) and which takes place synchronously for all said devices (1 and 2). Method according to Claim 11, characterized in that the devices (1 and 2) use at least four different communication channels and in that the order of succession of said channels is selected at the start of said devices (1 and 2). ). Method according to one of Claims 8 to 10, characterized in that the pairing of a new peripheral device (2) or the re-pairing of a peripheral device (2) has been disconnected from the central device (1) consists, by exchanges of asynchronous radio messages, to send to the central device (1) a message indicating the characteristics of said new peripheral device (2), in particular the frequency of its activation for transmission and listening, and then to transmit to the latter an identification address, also setting its order in the sequence of the transmission authorization phases of the various peripheral devices (2) in connection with the central device (1), an initial synchronization message and a possible identifier of site used for secure transmissions. Method according to one of Claims 1 to 13, characterized in that it consists of a mobile peripheral device (2) which has been moved out of the field of coverage of the central device (1) and which has received a reactivation signal and / or reconnection or having been the subject of such a request, to transmit continuously for a duration greater than the sum of the durations of an activation period of the devices (1 and 2) and of a interval separating two such periods, a signaling frame containing the identification address or the identifier assigned to said device (2), then to put itself in a listening situation in order to receive a response from the central device ( 1), in the form of an initial synchronization message with an authentication request, to repeat the two previous operations for the different possible transmission channels, starting with the last channel used by said peripheral device (2) before it is disconnected from the central unit (1), until a response is received from the central device (1) or reaches the predetermined maximum number of attempts, with the device being put on standby or subsequently deactivated device (2) considered in case of non-restoration of communication with the central device (1). Method according to one of Claims 1 to 14, characterized in that it is implemented by a monitoring or alarm system, the central device (1) consisting of a microprocessor alarm unit for execution of the management and control program of said system and equipped with an external communication interface, in that the peripheral devices (2) consist of one or more sensor (s), control organ (s), organ (s) image taking and / or sound, siren (s), buzzer (s), actuator (s), detector (s) and / or device (s) for communication to a network. Method according to any one of claims 1 to 15, characterized in that each peripheral device (2) has two different frequencies of repetition of its cyclic activation period and radio communication with the central device (1), ie a low frequency and a high frequency, said peripheral device (2) operating normally with the low repetition rate and said peripheral device (2) tilting towards the high repetition rate when said device (2) is solicited or activated or, in advance when said device (2) determines the next occurrence of an action likely to solicit it or to require the establishment of a communication with the central device (1). Surveillance or alarm system comprising a central unit and peripherals, forming independent devices and with autonomous power supplies, characterized in that it implements the communication method according to any one of Claims 1 to 16.

Images