Synchronised communication method

Abstract

The invention relates to a method of wireless communication within a network of nodes wherein the activation and communication periods of the nodes are synchronised and minimized to reduce the energy consumption and to allow the use of a single radio frequency. Synchronisation of the activation and communication periods is based on the nodes' internal clocks and a multi-period cycle. In the event of significant clock drift, these internal clocks are recalibrated when communicating with a higher-ranking node.

Description

[0001] Synchronised communication method

[0002] The invention relates to the field of telecommunication, in particular, it relates to a method of wireless communication within a network of nodes.

[0003] Communication protocols are well known for enabling communication of information or requests between nodes of a network. For example, in the field of HVAC systems (heating, ventilation, cooling and air conditioning) , communication protocols are integrated into programmable components to automate regulation of air characteristics in an enclosed space. Such protocols ensure communication of air characteristics and other parameters between the sensor nodes and other components of the associated network. Such protocols ensure communication of requested actions through the network to reach the desired air characteristics.

[0004] Regarding the general principle of a communication protocol, it is a system of rules allowing the transit of information between two or more entities (nodes) of a communication network. According to the Open Systems Interconnection model (OSI model) , communication protocols are split into seven different layers (https: / / fr.wikipedia.org / wiki / Mod%C3%A81e_OSI) . The present invention relates to the first layer, the physical one. This physical layer includes among others the following protocols : ADSL, CSMA, EIA 232 / 422 / 449 / 485, IEEE1394, IrDA, ISDN, SPI, USB, VDSL, V21 / 23 / 42 / 90, Wireless USB, 10 / 100 / 100 BaseT, ZWAVE, ZigBee, ENOCEAN, LoRa, BEACON and SigFox, for example. These protocols are limited in terms of data rate, number of nodes to control, radio frequency range, two-way communication and, above all, energy consumption. Other protocols , such as ZWave , ZigBee , ENOCEAN, LoRA, and SigFox, are widely used by manufacturers . Because they are not synchronised, manufacturers prefer to use several radio frequency channels to avoid interference . One problem is that the number of available channels is limited . Another problem, moreover, unsynchronised protocols lead to high energy consumption because of the long listening period imposed on the network nodes to ensure communication . This makes it impossible to have a battery supply with a li fespan of several years .

[0005] The ENOCEAN protocol claims low energy consumption, however it does not resolve the synchronisation problem . I f the communication fails , it repeats the information until it works . As soon as the number of node increases , the system quickly becomes chaotic and becomes inef ficient .

[0006] The LoRa protocol uses three clas ses of nodes (A, B and C ) . Each class has pre-set transmission and reception wake-up periods to enable two-way communication . These periods are not synchronised between nodes of the network and may be up to several seconds , which is an enormous amount of time for telecommunications and inevitably leads to high power consumption as soon as the number of communications requested increases .

[0007] In short , none of the known protocols of fer time synchronisation between nodes . This lack of synchronisation considerably increases the activity time of each node , beyond what i s necessary, which in turn increases the system ' s energy consumption . In fact , whether a node is active for a longer or shorter period, the power supplied does not vary . As a result , a long activation period leads to high energy consumption .

[0008] The applicant has therefore created a low-power consumption protocol that can handle a large number of nodes for two-way communication within a single radio frequency range . Solution of the invention

[0009] To this purpose the invention relates to a method of wireless communication within a network of nodes , wherein the network comprises at least two nodes :

[0010] - at least one gateway node ,

[0011] - at least one master node assigned in a surj ective manner to a gateway node , wherein each node comprises a programmable component , an identi fication code , and an internal clock, said method characterised in that it comprises the following steps :

[0012] - during a first period, activating each master node sequentially based on its internal clock to communicate with the gateway node that it is assigned, the communication comprising synchronisation information to recalibrate the master node ' s internal clock,

[0013] - wherein the first period forms a cycle that is repeated at least once . _c ommun i c_a t i on

[0014] In a preferred or alternate embodiment , all the wireless communication occurs on the same radio frequency channel or on the same range of radio frequencies , or on the same band of radio frequencies , or any combination of channel , range , and / or band .

[0015] N_odes

[0016] A node comprises a programmable component , an internal clock, and an identi fication code . Internal clocks interact with the programmable component and are used to determine precisely when a speci fic node in the system needs to be activated . The clock frequency, for example , may depend on the type of microprocessor used .

[0017] The identi fication code , which is stored in the programmable component of each node , is included in the communication information exchanged between the nodes .

[0018] An active node is capable of receiving and sending information . In other words , an active node can communicate bi-directionally . An inactive node is " asleep" and is not able to communicate with other nodes in the network . By rendering inactive nodes to sleep, the period of activity of any given node in the network is reduced . This reduction in activity corelates to reduced power consumption . The present method, accordingly, incorporates minimi zing the period of activity of each network node and, thus , reduces the power demand of the wireless network .

[0019] The gateway node acts as a link between the network of nodes and a server . The gateway node is preferably connected to either the Internet or a central management server, or both .

[0020] A master node acts as an interface between the gateway node and a device . The device can be directly an end device , like for example a sensor or an actuator or any operational element . This would usually be the case in " small" installations . The device can al so be a further node , named a " slave node" which wil l be the node managing the end device .

[0021] In this later case , the network of the invention further comprises at least one slave node assigned in a surj ective manner to a master node and, during a second period, each slave node and its assigned master node are sequentially activated, based on their respective internal clock, enabling communication with each other, the communication comprising providing synchronisation information to recalibrate the slave node ' s internal clock, and the first period and the second period form a cycle that is repeated at least once .

[0022] A slave node is therefore directed by the master node . It can be active or inactive , depending on the moment of the cycle .

[0023] The method is operated through computer means like a centralised management server or an application on the internet .

[0024] Optionally, the operator can modi fy at least some method and / or network parameters via the server or on the application which then relay the useful information to the gateway nodes .

[0025] The internal clock of the gateway node serves as a reference clock .

[0026] Unlike the master and slave nodes , the gateway node is preferably continuously active and therefore substantially continuously able to send and receive information .

[0027] A master node communicates with the gateway node to which it is assigned to manage the overall operation of the network .

[0028] It can be active or inactive , depending on the moment of the cycle .

[0029] Time_ _S_-L 9 _99 l _99999999-_9.9t9-_9.9 _ 99-99^999

[0030] Each of the first and, i f present , the second period are divided in a plurality of discrete time slots . A communication window between two nodes is assigned to a particular time slot . A communication window is dedicated to communication between two nodes , as defined by the method . A communication window includes a period of time during which data is actually exchanged between two activated nodes , in other words , bi-directional communication takes place during the communication window . A communication window between two nodes must be comprised in the time slot dedicated to these same two nodes to ensure that there is no interference between several communication windows . A communication window is preferably as long as or shorter than a time slot . In a preferred embodiment , the time slot is longer than the communication window to create dead zones between each communication window . During the communication window, both nodes involved must be active in order to exchange data . This node activation period is preferably longer than the communication window in order to anticipate clock dri fts . Each node may be activated before the communication window and deactivated when all data has been exchanged or after the window when no data has been received ( for example , activation can occur one or several clock cycles earl ier and deactivation can occur one or several clock cycles after the communication window) . However, an activation period that is too long considerably increases the power consumption of the node in question . It is therefore a trade-of f between reliability and power consumption . Because no communication overlaps , the method allows a large number of nodes to be used on a single radio frequency channel , avoiding the interference that could occur i f several communications took place at the same time on the same radio frequency channel . This also allows the network to avoid us ing many di f ferent frequencies , which are in limited supply .

[0031] In short , for each time slot allocated to two nodes , there is a communication window and a simultaneous activation period for the two nodes . The communication window is dependent on the time slot in the sense that it must be entirely within it . The period of simultaneous activation must ideally, i . e . without clock dri ft , entirely comprise the communication window in order to ensure data exchanges . Any arrangement based on these considerations can be envisaged with the aim of minimising the activation time of the nodes whi le ensuring data exchange . All these time periods are determined according to the components of the nodes . Preferably, these time periods comprise blocks of a certain duration placed end to end . The minimum duration of a period is one block, and it is possible to add as many blocks as desired .

[0032] Communication between master nodes and gateway nodes

[0033] The first period allows communications between at least one gateway node and at least one master node surj ectively assigned to the gateway nodes . Since the distribution is surj ective , several master nodes can be assigned to the same gateway node , but not vice versa . As the gateway nodes are preferably always active , each master node is assigned a time slot with the gateway node and is activated and deactivated sequentially by its programmable components on the bas is of its internal clock and a predetermined time slot . Each time slot comprises a communication window during which data is actually exchanged between each master node and its gateway node . In a preferred embodiment , the gateway nodes are always active , and it is the master nodes that initiate the data exchange , i . e . they activate , send data to the gateway nodes , wait for a response and then deactivate . This signi ficantly reduces the activation time o f the master nodes , which are the most solicited by the method and therefore the most energy consuming . Each master node in turn exchanges at least one message with its gateway node . Depending on when this message is received, the gateway responds with synchronisation information ( advance or retreat of a "block" or complete resynchronisation) . In the event of complete resynchronisation, the master node remains listening until it receives a synchronisation message from the gateway . Its clock is recalibrated in relation to the time of reception of this message . This message is sent by the gateway only i f it has requested resynchronisation of the master node .

[0034] According to preferred or alternative aspects of the method, to run the method, the assignment of time slots and communication windows is integrated into the programmable components . There are a predefined number of gateway nodes G . A number of master nodes M are assigned to each gateway node (not necessarily the same M for each gateway node ) . In other words , the method is predefined for a number GxM of master nodes . The first period then provides a number GxM of time slots and communications windows so that each master node can communicate with its assigned gateway node .

[0035] To optimi ze the process , when more than one gateway node is used, in preferred or alternate aspects of the method, it can be advantageous to program the first period so that communication windows are alternating between gateway nodes . This lowers the chance of interference that may occur when all communication windows of one gateway node would happen following each other, before all the communication windows of the next gateway node . In case more than one gateway node i s used, they can have the same number of time slots . One gateway node may be coupled with more master nodes than another gateway node , for example , due to the spatial distribution of the nodes . In this case , some time slots are not used, i . e . they do not comprise a communication window . This can also allow that new master nodes be added to the network at a later time .

[0036] Communication between master nodes and slave nodes

[0037] When slave nodes are present , the second period, preferably but not necessarily of the same duration as the first period, enables communication between at least one master node and at least one slave node surj ectively assigned to a master node . Since distribution is surj ective , several slave nodes can be assigned to the same master node , but not vice versa . Each slave node and the master node to which it is assigned must be activated and deactivated substantially simultaneously and sequentially as configured by their programmable components on the basis of their internal clocks and a predetermined time slot . Each time slot comprises a communication window during which data is actually exchanged between each slave node and its master node . In a preferred embodiment , the master nodes remain active to communicate with all their slave nodes and the slave nodes can be activated before their time slot and deactivated when all data has been exchanged or after the time slot when no data has been received . Once again, it is the master nodes that initiate the communication, so they are activated at the start of the communication and deactivated when the exchange is complete . In this way, their activation time and therefore their energy consumption are considerably reduced . The shorter the time slots , the less active the master nodes and therefore the less energy they consume .

[0038] As explained above , there is a defined number GxM of master nodes . A number of slave nodes S are assigned to each master node . The number of slave nodes can vary for each master node . In other words , the method is predef ined for a given number GxMxS of slave nodes , with G, M and S being the maximal number of possible elements . The second period then provides a number GxMxS of time slots and communications windows so that each slave node can communicate with its assigned master node .

[0039] In case more than one master node is used, they preferably or alternatively all have the same number of time slots . One master node may be coupled with more slave node than another master node , for example because of the spatial distribution of the nodes . In this case , some time slots are simply not used, i . e . they do not comprise a communication window . This can for example allow that new slave nodes be added to the network at a later time .

[0040] The second period has preferably substantially the same duration as the first period . It is preferable to obtain a rational number by aligning the duration of a period to the frequency of the clocks . For example , the frequency of the clock corresponds to a number of binary elements that should be cleverly divided to rationali ze the number of time slots . On the other hand, the time slots must be long enough to allow the nodes to send and receive all the data .

[0041] There may be more than one type of slave node in a network of nodes . For example , there can be detecting or sensing nodes and actuator nodes . The second period can be run sequentially for each type of slave node communicating with the master nodes , thereby multiplying the number of second periods and inserting in the cycle a third period, a fourth period i f needed, and so forth . There can there fore be as many types of slave nodes as there are periods dedicated to communication between master and slave nodes . f L p l_e t e_ _cy c l_e

[0042] A cycle is then created by repeating the periods one after the other . The cycle therefore comprises a number N+ l of periods depending on the number N of slave node types .

[0043] R_e c a l_i_b r a_t i o n_ _q f _ _i_n t e r_n a 1_ _c 1 o_c k s

[0044] One goal of the method is to minimi ze the waking time of the master and, optionally of the slave nodes , of the network, by proper synchronisation of each node . This is why each communication preferably includes synchronisation information .

[0045] During the first period, the master nodes are activated on the basis of their respective internal clocks . Although all clocks are selected to have the same frequency, these clocks operate stochastically, and clock dri ft may occur . I f nothing is done , this can result , for example , in two master nodes being activated simultaneously . To overcome this , the gateway node , which serves as a reference clock because it is connected to the same network as the other gateway nodes , recalibrates or resynchronises the master node ' s internal clock when it observes dri ft and preferably or alternatively at each communication occurrence . To recalibrate it , the gateway node sends synchronisation information, which is then incorporated into the master node .

[0046] During the N periods dedicated to communication between master and slave nodes , when the network comprises at least one slave node , the slave nodes and master nodes are activated on the basi s of their internal clocks . Additionally, these clocks operate stochastically, and clock dri ft may occur . I f nothing is done , this can result in multiple communication windows overlapping . To overcome this problem, a master node recalibrated during the first period forward synchronisation information to recalibrate its slave nodes during their communication window .

[0047] In case the clock dri ft is so extensive that the activation period of the slave node does not overlap with its assigned slot at the master node , the slave node in question can be programmed to progressively widen its activation period over subsequent cycles until it is once again in contact with its assigned master node . When contact is re-established, the master node recalibrates the slave node ' s internal clock . After a defined number of cycles of extending the activation period, it is possible to program the slave node to remain awake unti l resynchronisation occurs .

[0048] Communication windows or time slots are preferably slightly longer ( i . e . by a few ms ) that the actual needed for communication . This allows a limited clock dri ft to be managed ef ficiently at every cycle .

[0049] It can also allow to duplicate the communication content during one communication window, to increase reliability .

[0050] Preferably, the network comprises between 1 and 1000 gateway nodes , preferably between 2 and 500 gateway nodes , sti ll preferably between 3 and 100 gateway nodes .

[0051] Preferably, the network comprises between 1 and 10000 master nodes , preferably between 2 and 1000 master nodes , sti ll preferably between 3 and 500 master nodes .

[0052] Preferably, the network comprises between 1 and 100000 slave nodes .

[0053] In case two nodes are spatially out of range from each other, a relay node can be inserted in between . In case a relay is used, the downstream node ( for example a master node ) is assigned to the relay, and the relay is assigned to the upstream node ( for example the gateway node ) . The communication time between the upstream node and the downstream node is longer than a direct communication as the relay introduces a delay, as is well known by a person skilled in the art .

[0054] An overall cycle preferably or alternatively has a duration in the order of a few minutes , for example , between 1 and 5 minutes or even less . The invention also contemplates a system adapted to execute the method, the system comprising :

[0055] - at least one gateway node ,

[0056] - at least one master node , wherein each node comprises a radiofrequency emitter and receiver, a programmable component , an identi fication code and an internal clock,

[0057] - each master node being arranged to , during a first period, sequentially activate on the basis of its internal clock to communicate with a gateway node to which it is assigned, the communication comprising synchronisation information to recalibrate the master node ' s internal clock,

[0058] Optionally, the system further comprises at least one slave node wherein each slave node is arranged to be assigned to a master node and to , during a second period, sequentially activate on the basis of its internal clock, to communicate with each other, the communication comprising synchronisation information to recalibrate the slave node ' s internal clock .

[0059] Detailed description of the invention

[0060] The invention will be better understood with reference to the detailed description of the method with reference to the drawings where :

[0061] Figure 1 is a flow diagram of the network communications ;

[0062] Figure 2 is a schematic diagram of a system of the invention;

[0063] Figure 3 illustrates the first period synchronisation in the system of figure 2 ;

[0064] Figure 4 illustrates the second period synchronisation in the system of figure 2 ; Figure 5 illustrates the last period synchronisation in the system of figure 3 ;

[0065] Figure 6 illustrates another system according to the invention;

[0066] Figure 7 illustrates the first period synchronisation in the system of figure 6 ;

[0067] Figure 8 illustrates the second period synchronisation in the system of figure 6 ;

[0068] Figure 9 illustrates the last period synchronisation in the system of figure 6 ;

[0069] Referring to Figure 1 , a system arranged to run the method o f the invention, the system comprising :

[0070] - at least one gateway node 102 ,

[0071] - at least one master node 104 ,

[0072] - at least one slave node 107 .

[0073] The invention is here thereby illustrated it a complex implementation with three " layers" of nodes but could as well function the same way without slave nodes .

[0074] Each node comprises means of radiofrequency communication 111 , a programmable component 112 , an identi fication code 113 and an internal clock 114 .

[0075] Each gateway node 102 acts as a link between the network of nodes and a server 101 .

[0076] Each master node 104 is arranged to , during a first period 103 , sequentially activate on the bas is of its internal clock to communicate with a gateway node 102 to which it is assigned, the communication comprising synchronisation information to recalibrate the master node ' s internal clock .

[0077] Each slave node 107 is arranged to be assigned to a master node 104 and, during a second period 105 , to sequentially activate on the basis of its internal clock, to communicate with each other, the communication comprising synchronisation information to recalibrate the slave node's internal clock.

[0078] There may be more than one type of slave node 107, here types 108, 109 and 110 are illustrated. In that case, the first type of slave node 108 communicates with the master nodes 104 during the second period 105, and the so called "second period" is repeated for each type of slave node. This implies that the Nth type of slave node 110 communicates with the associated master nodes 104 during the N+lth period 106.

[0079] Figures 2, 3, 4, and 5 detail an example of a wireless communication method in a home automation system, in particular a HVAC system. The HVAC system comprises two types of slave nodes, the first consisting of sensors 231;232 and the second of actuators 241;242. The sensors, in this example can be temperature or position sensors, such as for detecting the opening of windows, while the actuators are capable of, for example, opening or closing a radiator valve. The master nodes 211;212 are typically thermostats and the gateway nodes 210 are centralised stations.

[0080] This example uses identification codes defined as follows. The first part determines the category of the node, i.e. "M" if it is a master node, "G" if it is a gateway node, "Si" if it is a slave node of the first type and "S2" if it is a slave node of the second type. The second part determines the number of the node in the system. For example, the tenth master node is defined as "M10», or the fifth slave node of the first type is defined as "Si5". This coding is only used as an example and is not restrictive in any way.

[0081] The aim of the network and the method in this specific example is to manage temperature in a building while minimising node energy consumption. The method in the following example is configured for the following parameters G, M, S, and N defined and listed in Table 1. In this case, the method manages up to two (G) gateway nodes (centralised stations) G1 and G2. Up to three (M) master nodes (thermostats) are assigned to each gateway node, here Ml, M2 and M3 assigned to G1 and M4, M5, and M6 assigned to G2. Up to two (S) slave nodes of the first type (sensors) are assigned to each master node (thermostat) , here Sil and Si2 assigned to Ml, Si3 and Si4 assigned to M2, Si5 and Si6 assigned to M3, Si? and Si8 assigned to M4, Si9 and SilO assigned to M5 and, Sill and Sil2 assigned to M6. Up to two (S) slave nodes of the second type (actuators) are assigned to each master node (thermostat) , here S2I and S22 assigned to Ml, 828 and S24 assigned to M2, 826 and S26 assigned to M3, S2 and S18 assigned to M4, S29 and S2IO assigned to M5 and, S2II and S2I2 assigned to M6. The method is configured for two (N) types of slave nodes, so one cycle is made up of three (N+l) periods.

[0082] The first period comprises six (GxM) time slots because the network can have up to six (GxM) master nodes. If the network has fewer than six (GxM) master nodes, some slots are simply not used. The second and third periods comprise twelve (GxMxS) time slots each, as the network can have up to twelve (GxMxS) slave nodes of each type. If the network has fewer than twelve (GxMxS) slave nodes of either type, some slots are simply not used.

[0083] Table 1

[0084] These parameters define the network structure on which the temporal structure is based . This temporal structure designates the duration of the periods - each divided in a number o f time slots , and the time slots comprise communication windows . The repetition of the periods along a de fined pattern represents a cycle .

[0085] To determine the temporal structure of the network, the first step is to identi fy the minimum time required for a communication window to ensure that all the data can be transmitted correctly . In this example , communications are carried out by RF emitter / receiver system and the content of the communication is determined by the programmable component , which can be a microprocessor .

[0086] For the sake of illustration, each communication between a gateway node and a master node takes for example about 30ms , while each communication between a master node and a slave node takes for example about 4ms . The time is determined at least based on the frequency of the communication and the number of bits of the message being communicated . The communication comprises mainly information on synchronisation, identi fication codes of nodes , and data measured by the sensors or orders for the actuators. Let's assume that in this example, depending on the node components, the periods are made up of blocks of 15.625ms placed side by side. The temporal structure of the method (time slots, communication windows, activation periods) , among other possibilities, is determined as follows:

[0087] In this example, during the first period, a communication between a master node and a gateway node takes 30ms. With blocks of 15.625ms, it is appropriate to set communication windows of 31.25ms. To minimise possible interference between master nodes in the event of clock drift, it is advantageous to have a wider time slot, for example by adding 15.625ms on either side of the communication window. In this way, each time slot TMin the first period is 62.5ms. Finally, it remains to determine the activation period for each of the nodes. By preference, gateway nodes are continuously active. During this first period, the master nodes are activated and deactivated in turn to limit their energy consumption. As master nodes initiate communication, they are activated at the start of their communication window, send their data and deactivate after receiving a response. Each master node in turn exchanges at least one message with its gateway node. Depending on when this message is received, the gateway responds with synchronisation information (advance or retreat of a "block" or complete resynchronisation) . In the event of complete resynchronisation, the master node remains listening until it receives a synchronisation message from the gateway. Its clock is recalibrated in relation to the time of reception of this message. This message is sent by the gateway only if it has requested resynchronisation of the master node.

[0088] In this example, during the second and third period, a communication between a master node and a slave node takes 4ms. Suppose that, for reliability reasons, the message is sent twice with a dead time of 5ms between each, then the minimum time required is 13ms. With blocks of 15.625ms, it is appropriate to set communication windows of 15.625ms. To minimise possible interference, it is advantageous to have a wider time slot, for example by adding a 15.625ms death zone after the communication window. In this way, each time slot Tsin the second period is 31.25ms. Finally, it remains to determine the activation period for each of the nodes. By preference, the master nodes remain active for as long as it takes to communicate with all its slave nodes. In this example, each master node has two slave nodes, so each master node activates at the start of its communication window and deactivates as soon as communication with the last slave node ends. The slave nodes are activated and deactivated in turn to limit their energy consumption. To ensure communication in the event of clock drift, their activation period starts 15.625ms before the time slot and ends when all data has been exchanged or 15.625ms after the time slot if no data has been received, i.e. maximum 62.5ms of activation for each .

[0089] The choice of time durations was determined here in order to obtain first, second and third periods TPof equivalent duration, i.e. 375ms, and therefore a three-periods cycle C of 1125ms. To further reduce energy consumption, a node can deactivate itself before the end of its activation period if communication is completely over.

[0090] In the network of Figure 2, all slots are assigned to a time slot. In other words, there are no blank slots in the temporal structure.

[0091] Figure 3 illustrates the first period of the cycle, intended for communications between master nodes and gateway nodes, i.e. respectively thermostats and centralised stations in this example. Here, the first centralised station G1 communicates 301 with its first thermostat Ml during the first time slot, then the second centralised station G2 communicates 302 with its first thermostat M4 during the second time slot , then the first centralised station G1 communicates 303 with its second thermostat M2 during the third time slot , then the second centralised station G2 communicates 304 with its second thermostat M5 during the fourth time slot , then the first centralised station G1 communicates 305 with its third thermostat M3 during the fi fth time slot and then the second centralised station G2 communicates 306 with its third thermostat M6 during the sixth time slot .

[0092] Each thermostat is activated ( able to receive and send RE messages ) for the duration of its communication and then deactivated to minimi ze energy consumption . This ef fectively results in six communication windows during this first period, spread over the six time slots . The centralised stations are here always active and connected to the data server . As a result , they can, for example , communicate to their thermostats the temperatures to be maintained over speci fic schedules .

[0093] I f an operator modi fies a temperature target via the data server, the concerned centralised station ( s ) inform their thermostats of the new targets during their next communication window . The thermostats also communicate towards the centralised stations , for example : the indoor temperature measured, the position of the radiator valves , the position of the windows , etc . This information can then be sent to the data server and made available to the operator .

[0094] Communication also includes synchroni sation information for the master node ' s internal clock to be recalibrated or realigned on the central clock . Figure 4 illustrates the second period of the cycle , intended for communications between master nodes and slave nodes of the first type , i . e . respectively thermostats and sensors in this example . Preferably, the first thermostat Ml of the first central station G1 is activated to exchange information 401 , 402 with all its sensors Sil and Si2 respectively, then the first thermostat M4 of the second central station G2 is activated to exchange information 403 , 404 with all its sensors Si? and Si8 respectively, then the second thermostat M2 of the first central station G1 is activated to exchange information 405 , 406 with all its sensors Si3 and Si4 respectively, then the second thermostat M5 of the second central station G2 is activated to exchange information 407 and408 with al l its sensors Si9 and Sil O respectively, then the third thermostat M3 of the first central station G1 is activated to exchange information 409 , 410 with all its sensors Si5 and Si6 respectively and then the third thermostat M6 of the second central station G2 is activated to exchange information 411 , 412 with all its sensors Sil l and Sil O respectively . Each sensor is activated for the duration of its communication window, then deactivated to minimise energy consumption . This ef fectively results in twelve communication windows during this second period, spread over the twelve time slots provided by the method . This second period enables the sensors to communicate information to the thermostats about the current state of things , such as the temperature , the position of radiator valves , windows , etc .

[0095] Figure 5 illustrates the third period of the cycle , intended for communication between master nodes and slave nodes of the second type , i . e . respectively thermostats and actuators in thi s example . Preferably, the first thermostat Ml of the first central station G1 is activated to communicate 501 ; 502 with all its actuators S2I and S22 , then the first thermostat M4 of the second central station G2 is activated to 503 ; 504 communicate with all its actuators and S28 , then the second thermostat M2 of the first central station G1 is activated to communicate 505 ; 506 with all its actuators S23 and S24 , then the second thermostat M5 of the second central station G2 is activated to communicate 507 ; 508 with all its actuators S29 and S2I O , then the third thermostat M3 of the first central station G1 is activated to communicate 509 ; 510 with all its actuators 826 and S2 , then the third thermostat M6 of the second central station G2 is activated to communicate 511 ; 512 with all its actuators S2I I and S2I2 . Each actuator is activated for the duration of its communication window and then deactivated to minimise energy consumption . Thi s ef fectively results in twelve communication windows during this third period, spread over the twelve time slots provided by the method . During the first period, the thermostats received targets from the centralised stations and during the second period the thermostats received information on the current state of things ( temperatures , position of radiator valves , windows , etc . ) from the sensors . During this third period, with the information gathered beforehand, the thermostats communicate with the actuators to give them precise instructions . For example , i f a thermostat needs to target a temperature of 22 ° C and has received information that the current temperature is 20 ° C and that the radiator valve i s closed, it can command the actuators to open the radiator valve .

[0096] The three-period cycle is then repeated in a loop . In this way, information and instructions are rapidly propagated to all levels of the network, in this example , a complete cycle is completed in j ust 1125ms . Each communication window being allocated to j ust two nodes means that a single radio frequency channel can be used without any risk of interference and ensures that information is received correctly . The cycle described above being run so rapidly, and from using all time available for communication, it is easy for a person skilled in the art to understand that the overall number of nodes can be increased very easily, like multiplied by 10 or even 100 more without compromising the process, and all this using one single radiofrequency range.

[0097] Figure 6 shows a schematic representation of a second network of nodes, very similar to the network of figure 2 (the same reference numbers being used for the same elements) , but without the nodes Ms, Si3, Si9, SilO, S29 and S2IO. The number of required communication windows is therefore effectively less than the number of time slots provided by the method. Figures 7, 8 and 9 illustrate the communications between the nodes of this second network during the three periods of each cycle of the method.

[0098] Figure 7 illustrates the first period of the cycle, intended for communications between master nodes and gateway nodes, i.e. respectively thermostats and centralised stations, of the second network. The order of the communications is identical to that of the first network shown in Figure 3. The only notable difference is that there is no Ms thermostat. In this case, there are five communication windows to be spread over the six time slots provided by the method. As a result, one time slot is not used. This unused slot depends on the unassigned identification code. This means that a thermostat can be added to the network at any time by giving it the Ms identification code, without disrupting the wake-up time of all the other nodes. Furthermore, if a node is dysfunctional, it has no impact on the other nodes.

[0099] Figure 8 illustrates the second period of the cycle, intended for communications between master nodes and slave nodes of the first type, i.e. respectively thermostats and sensors, of the second network. The order of the communications is identical to that of the first network shown in Figure 4. The only notable difference is that there is no Si3, Si9 and SilO sensors. In this case, there are nine communication windows to be spread over the twelve time slots provided by the method. As a result, three time slots are not used. These unused slots depend on the unassigned identification codes. This means that sensors can be added to the network at any time by giving them the identification codes Si3, Si9 and SilO, without disrupting the wake-up time of all the other nodes.

[0100] Figure 9 illustrates the third period of the cycle, intended for communications between master nodes and slave nodes of the second type, i.e. respectively thermostats and actuators, of the second network. The order of the communications is identical to that of the first network shown in Figure 5. The only notable difference is that there is no S29 and S2IO sensors. In this case, there are ten communication windows to be spread over the twelve time slots provided by the method. As a result, two time slots are not used. These unused slots depend on the unassigned identification codes. This means that sensors can be added to the network at any time by giving them the identification codes S29 and S2IO, without disrupting the wake-up time of all the other nodes.

[0101] In another embodiment, the system comprises no slave nodes. In this case, the master nodes also take on the role of the slave nodes. For example, the first master node is a thermostat, the second a window and the third a radiator valve. The three nodes are in the same rank and can therefore communicate exclusively via their gateway node. The thermostat can therefore communicate its data with its gateway node, which controls the valve and the window opening system. Each communication slot between the gateway node and the master node comprises synchronisation information. This simple implementation can be advantageous for networks of a limited size. Relay nodes can be used for master nodes that would be out of reach of the gateway node.

[0102] In another embodiment, the method manages up to ten gateway nodes (G) , up to sixteen master nodes (M) are assigned to each gateway node, up to six slave nodes of a first type (Si) are assigned to each master node and up to six slave nodes of a second type (S2) are assigned to each master node. The first period comprises one hundred and sixty time slots (GxM) , each of which is intended to host a communication window between the gateway nodes and the master nodes. The second period comprises nine hundred and sixty time slots, each of which is intended to host a communication window between the master nodes and the slave nodes of the first type. The third period comprises nine hundred and sixty time slots, each of which is intended to host a communication window between the master nodes and the slave nodes of the second type. In this example, during the second and third period, a communication between a master node and a slave node takes 4ms. Suppose that, for reliability reasons, the message is sent twice with a dead time of 5ms between each, then the minimum time required is 13ms. With blocks of 15.625ms, it is appropriate to set communication windows of 15.625ms. To minimise possible interference, it is advantageous to have a wider time slot, for example by adding a 15.625ms death zone after the communication window. In this way, each time slot in the second and third period is 31.25ms. Finally, it remains to determine the activation period for each of the nodes. By preference, master nodes remain active for as long as it takes to communicate with all its slave nodes. In this example, each master node has six slave nodes, so each master node activates at the start of its communication window and deactivates as soon as communication with the last slave node ends. The slave nodes are activated and deactivated in turn to limit their energy consumption. To ensure communication in the event of clock drift, their activation period starts 15.625ms before the time slot and ends when all data has been exchanged or 15.625ms after the time slot if no data has been received, i.e. maximum 62.5ms of activation for each. In order to obtain periods of equal length, each time slot in the first period is set to 187.5ms while a communication between a master node and a gateway node takes only 13ms. In this case, it is sufficient, for example, to set a communication period of 31.25ms. As master nodes initiate communication, they are activated at the start of their communication window, send their data and deactivate after receiving a response. This considerably limits the activation time for each master node. Finally, each period lasts 30 seconds and the complete cycle 90 seconds .

[0103] In another embodiment, the network and method comprise more than two types of slave nodes. In this case, the number of periods is adapted so that each type of slave node communicates with the master nodes. For example, if the network has three types of slave node, the complete cycle of the method comprises four periods. The first is for communication between master and gateway nodes and the next three are for communication between each of the three types of slave node and the master nodes.

[0104] In another embodiment, some master nodes may be out of range of their gateway nodes for direct radio frequency communication. In this case, relays are used as intermediaries to increase the communication range of the nodes. Each master node requiring a relay to communicate with its gateway node is preferably assigned a dedicated relay, i.e., a relay may be assigned to a single master node or may be used for more than one master node. Given the delay introduced by a relay, the communication window and time slot must be increased or shifted if necessary, so that each node can send and receive all the data. Although the method has been here illustrated in the field of HVAC, it can be applicable to any field where a communication network between elements is needed . For example , the method can be applied to a smart city for waste management , street lighting, monitoring air quality, tracking parking spaces , etc . The method can also be applied in the energy sector for managing electricity networks , monitoring electricity meters , managing energy equipment , etc . The areas of application of the method are not limited to the examples presented .

Claims

AMENDED CLAIMS received by the International Bureau on 10 December 2024 (10.12.2024)1 . Method of wireless communication within a network of nodes , wherein the network comprises :- at least one gateway node ,- a plurality of master nodes assigned in a surj ective manner to the at least one gateway node , and- a plurality of slave nodes assigned in a surj ective manner to the plurality of master nodes , wherein each node comprises a programmable component , an identi fication code , and an internal clock, said method comprising the following steps :- during a first period, activating each master node sequentially by its programmable component based on its internal clock to communicate with the gateway node that it is assigned, the communication comprising synchronisation information to recalibrate the master node ' s internal clock,- during a second period, activating each slave node and its assigned master node sequentially by their programmable components based on their respective internal clock, enabling them to communicate with each other, the communication comprising synchronisation information to recalibrate the slave node ' s internal clock .- wherein the first period and the second period form a cycle that is repeated at least once .2 . Method according to claim 1 , wherein each master node initiates the data exchange with its gateway node , and the gateway node recalibrates the master node ' s internal clock when it observes clock dri ft , preferably at each communication occurrence , and wherein the recalibrated master node forwardssynchronisation information to its slaves nodes during their communication .3 . Method according to one of the previous claims , wherein i f the clock dri ft of a slave node is so that the activation period of the slave node does not overlap with its assigned master node , the slave node progressively widens its activation period over subsequent cycles until it overlaps again with its assigned master node , and, i f it overlaps again, the master node recalibrates the slave node ' s internal clock through the communication comprising synchronisation information .4 . Method according to claim 3 , wherein after a predefined number of cycles of extending the activation period of the slave node , the slave node remains awake until resynchronisation occurs .5 . Method according to one of the previous claims , wherein all the wireless communication occurs on the same radio frequency channel or on the same range o f radio frequencies , or on the same band of radio frequencies .6 . Method according to one of the previous claims , wherein a period is divided in a plurality of discrete time slots each dedicated to a single pair of nodes .7 . Method according to claim 6 , wherein each time slot within a period has the same duration .8 . Method according to one of the previous claims , wherein an active node is arranged to communicate bi-directionally .9 . Method according to one of the previous claims , wherein gateway nodes are connected to either the Internet or a central management server, or both .10 . Method according to one of the previous claims , wherein gateway nodes are continuously active .11 . Method according to one of the previous claims , wherein there is more than one type of slave node , the communication of each additional type of slave node with the master nodes taking place during an additional period of the cycle .12 . Method according to one of the previous claims , wherein a relay node can be inserted between two nodes spatially out of range from each other .13 . A system adapted to execute the method according to one of claims 1 to 12 , the system comprising :- at least one gateway node ,- a plurality of master nodes , and- a plurality of slave nodes , wherein each node comprises a radiofrequency emitter and receiver, a programmable component , an identi fication code and an internal clock, each master node being arranged to , during a first period, sequentially activate by its programmable component on the basis of its internal clock to communicate with a gateway node to which it is assigned, the communication comprising synchronisation information to recalibrate the master node ' s internal clock, and wherein each slave node is arranged to be assigned to a master node and to , during a second period, sequentially activate by their programmable components on the basis of their respective internal clock, to communicate witheach other, the communication comprising synchronisation information to recalibrate the slave node's internal clock.

14. A home automation system comprising the system of claim 13.

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