The invention relates to a method for acknowledging frames sent by endpoints in a group of endpoints intended for an application server, each endpoint in said group communicating with the application server via a gateway and a centralising server, to devices, and to a system implementing said method.

The internet is gradually being transformed into a wide area network, called the “Internet of Things”, connecting all kinds of objects that have become connectable. New requirements in terms of networks have then appeared, and in particular requirements for wireless networks having greater coverage than conventional cellular networks and making it possible to limit energy consumption of the connected equipment. Among these long-range wireless networks allowing low energy consumption (low power wide area network (LPWAN)), mention can be made of networks based on the LoRa (registered trade mark) (long range) technology. LoRa technology operates on frequency bands known by the term “ISM band” (industry, science and medical) comprising frequency bands that can be used freely for industrial, scientific and medical applications. LoRa technology is based on a spread spectrum technology making it possible to obtain low-bitrate communications having good robustness in a particularly noisy ISM band.

A network based on LoRa technology (hereinafter called a “LoRa network”) uses a protocol called LoRaWAN (LoRaWAN 1.1 Specification, final release, 11 Oct. 2017). A LoRa network is composed of base stations or gateways generally placed on high points in order to cover a large geographical area. The gateways are able to detect messages sent in their area by equipment or endpoints and to transfer them to at least one server (LoRa network server (LNS)), hereinafter referred to as an LNS server or centralising server, which will process them or retransmit them to one or more application servers.

In a conventional functioning of a LoRa network, an endpoint wishing to transmit a message (i.e. data) to the LNS server or to a centralising server via the LNS server, transmits this message in a frame, called an uplink frame, in accordance with the LoRaWAN protocol. The uplink frame in accordance with the LoRaWAN protocol, referred to as an uplink LoRa frame, is transmitted in broadcast mode. This uplink LoRa frame is received by at least one gateway. Each gateway that has received the uplink LoRa frame decodes it and retransmits the message contained in said frame to the server in an HTTP (HyperText Transfer Protocol) request, referred to as an uplink HTTP request. If a plurality of gateways have received the uplink LoRa frame, the LNS server receives a plurality of uplink HTTP requests containing the same message. The LNS server must then designate, among the gateways that received the uplink LoRa frame, the gateway to be used for relaying a response to the message contained in the uplink LoRa frame. The response is transmitted from the LNS server to the designated gateway in a downlink HTTP request, then in unicast, from the designated gateway to the endpoint in a downlink frame in accordance with the LoRaWAN protocol, referred to as a downlink LoRa frame. In a majority of implementations of LoRa networks, the designated gateway is the one offering the best quality of transmission with the endpoint that sent the uplink LoRa frame.

The LoRaWAN protocol defines three operating classes: the classes A, B and C. The class A is the most economical in terms of energy consumption. When an endpoint has data to send it does so without any checks and then opens two successive listening windows for any messages coming from the LNS server. These two windows have recommended durations of 1 and then 2 seconds. These two windows are the only ones during which the server can send to the endpoint data that it previously stored for its attention. The class A must be implemented in all the endpoints for reasons of compatibility.

The class B allows good compromise between energy consumption and the need for bidirectional communication. The endpoints functioning in the class B open reception windows at intervals programmed by periodic messages sent by the LNS server.

The class C has the highest energy consumption since the endpoints are permanently listening out, which makes it possible to make communications at all times.

It should be noted that an item of equipment may change its class during operation.

A plurality of endpoints may contribute to the same application managed by the same application server. Currently, an application server wishing to acknowledge frames received from a plurality of endpoints for the same application must acknowledge each frame one by one. Apart from the tedious aspect of such an acknowledgement method, this method monopolises network resources in a not insignificant way.

It is desirable to overcome these drawbacks of the prior art. It is in particular desirable to propose an efficient acknowledgement method.

It is moreover desirable to propose a method that is simple to implement at low cost.

According to a first aspect of the present invention, the present invention relates to a method for acknowledging frames sent by endpoints in a group of endpoints intended for an application server, each endpoint in said group communicating with the application server via a gateway and a centralising server, the application server being connected to the centralising server via a first communication network, the centralising server being connected to each gateway by a second communication network, the group of endpoints and each gateway forming a third network of the long-range wireless network type affording low energy consumption, each communication between an endpoint in said group and a gateway using a communication protocol adapted to said third network. The method is executed by the centralising server and comprises: receiving at least one acknowledgement message sent by the application server, each acknowledgement message acknowledging a plurality of frames sent by endpoints in said group, each acknowledgement message comprising a plurality of fields, a first field comprising information allowing timesetting of each endpoint receiving the acknowledgement message, a second field comprising information fixing a time of next reawakening of each endpoint receiving the acknowledgement message, a third field comprising information representing an identifier of said group, said identifier having been supplied by the centralising server to each endpoint in said group during a phase of connection to the third network performed by said endpoint, and a fourth field comprising information indicating, for each endpoint in said group, whether each frame that it sent to the application server since a previous acknowledgement is acknowledged; and transmitting a frame in broadcast mode to said group via each gateway making it possible to communicate with an endpoint in said group, said frame comprising, for each field of each acknowledgement message received, information representing the information represented by said field.

By acknowledging a plurality of frames sent by the endpoints in a group of endpoints with a single frame sent in broadcast mode, the acknowledgement method does not monopolise the network resources.

According to one embodiment, when the centralising server receives a single acknowledgement message, the frame transmitted in broadcast mode comprises the acknowledgement message.

According to one embodiment, each frame intended to be transmitted in broadcast mode to said group comprises, in an endpoint address field of said frame, a predefined address, each endpoint receiving a frame comprising the predefined address identifying this frame as a frame sent in broadcast mode.

According to one embodiment, during the connection phase, the centralising server responds to each connection-request frame emanating from an endpoint in said group by a connection-enabling frame transmitted in unicast mode to the endpoint that transmitted the connection-request frame, the connection-enabling frame comprising the identifier of said group in an endpoint address field, a field comprising information enabling timesetting of the endpoint that is the destination of said enabling frame and a field fixing a time of next reawakening of said destination endpoint.

According to one embodiment, the fourth field takes the form of a binary mask wherein each bit corresponds to an endpoint in said group, the endpoint address field of said connection-enabling frame further comprising information indicating to the endpoint that is the destination of said connection-enabling frame a position in the binary mask of the bit corresponding to said destination endpoint.

According to one embodiment, when the application server implements a plurality of applications, each endpoint in said group being able to contribute to each application in the plurality of applications, each application implemented by the application server being associated with an application number known by each endpoint in said group, each acknowledgement message comprises a fifth field comprising an application identifier for identifying the application among the plurality of applications for which frames are acknowledged.

According to a second aspect of the invention, the invention relates to a method for acknowledging frames sent by endpoints in a group of endpoints intended for an application server, each endpoint in said group communicating with the application server via a gateway and a centralising server, the application server being connected to the centralising server via a first communication network, the centralising server being connected to each gateway by a second communication network, the group of endpoints and each gateway forming a third network of the long-range wireless network type affording low energy consumption, each communication between an endpoint in said group and a gateway using a communication protocol adapted to said third network. The method is executed by an endpoint, referred to as the current endpoint, in said group and comprises: receiving an acknowledgement frame, the acknowledgement frame having been transmitted in broadcast mode by the centralising server and comprising an acknowledgement message generated from information supplied by the application server, said message being identical for each endpoint in said group and composed of a plurality of fields, a first field comprising information allowing timesetting of the current endpoint, a second field fixing a time of next reawakening of the current endpoint, a third field comprising information representing an identifier of said group, said identifier having been supplied by the centralising server to the current endpoint during a phase of connection to the third network performed by the current endpoint, and a fourth field comprising information indicating to said current endpoint whether each frame that it has sent to the application server is acknowledged; setting a clock internal to said endpoint using the first field; if the identifier represented by the information representing the identifier of said group contained in the third field corresponds to the identifier received by the current endpoint during the connection phase, checking, using the fourth field, that each frame sent since a previous acknowledgement is acknowledged; and going on standby until the time of next reawakening indicated in the second field.

According to a third aspect of the invention, the invention relates to a method for acknowledging frames sent by endpoints in a group of endpoints to an application server, each endpoint in said group communicating with the application server via a gateway and the centralising server, the application server being connected to the centralising server via a first communication network, the centralising server being connected to each gateway by a second communication network, the group of endpoints and each gateway forming a third network of the long-range wireless network type affording low energy consumption, each communication between an endpoint in said group and a gateway using a communication protocol adapted to said third network. The method executed by the application server comprises: generating an acknowledgement message, the acknowledgement message comprising a plurality of fields, a first field comprising information allowing timesetting of each endpoint receiving said message, a second field comprising information fixing a time of next reawakening of each endpoint receiving said message, a third field comprising information representing an identifier of said group, said identifier having been supplied by the centralising server to each endpoint in said group during a phase of connection to the third network performed by said endpoint, and a fourth field comprising information indicating, for each endpoint in said group, whether each frame that it sent to the application server since a previous acknowledgement is acknowledged; and sending a frame comprising said message, the information included in each field of said message being intended to be transmitted to each endpoint in the group of endpoints via the centralising server and each gateway enabling the centralising server to communicate with each endpoint in the group of endpoints.

According to one embodiment, the long-range wireless network affording low energy consumption is a LoRa network and the communication protocol adapted to said network is the LoRaWAN protocol.

According to a fourth aspect of the invention, the invention relates to a device of the centralising server type, making it possible to acknowledge frames sent by endpoints in a group of endpoints to an application server, each endpoint in said group communicating with the application server via a gateway and the centralising server, the application server being connected to the centralising server via a first communication network, the centralising server being connected to each gateway by a second communication network, the group of endpoints and each gateway forming a third network of the long-range wireless network type affording low energy consumption, each communication between an end point in said group and a gateway using a communication protocol adapted to said third network. The device comprises: reception means for receiving an acknowledgement message sent by the application server, said message acknowledging a plurality of frames sent by endpoints in said group, the acknowledgement message comprising a plurality of fields, a first field comprising information allowing timesetting of each endpoint receiving said message, a second field comprising information fixing a time of next reawakening of each endpoint receiving said message, a third field comprising information representing an identifier of said group, said identifier having been supplied by the centralising server to each endpoint in said group during a phase of connection to the third network performed by said endpoint, and a fourth field comprising information indicating, for each endpoint in said group, whether each frame that it sent to the application server since a previous acknowledgement is acknowledged; and transmission means for transmitting a frame in broadcast mode to said group via each gateway making it possible to communicate with an endpoint in said group, said frame comprising, for each field of each acknowledgement message received, information representing the information represented by said field.

According to a fifth aspect of the invention, the invention relates to a device of the endpoint type belonging to a group of endpoints sending frames to an application server, each endpoint in said group communicating with the application server by a gateway and a centralising server, the application server being connected to the centralising server via a first communication network, the centralising server being connected to each gateway by a second communication network, the group of endpoints and each gateway forming a third network of the long-range wireless network type affording low energy consumption, each communication between an endpoint in said group and a gateway using a communication protocol adapted to said third network. The endpoint, referred to as the current endpoint, comprises: reception means for receiving an acknowledgement frame, the acknowledgement frame having been transmitted in broadcast mode by the centralising server and comprising an acknowledgement message generated from information supplied by the application server, said message being identical for each endpoint in said group and composed of a plurality of fields, a first field comprising information allowing timesetting of the current endpoint, a second field fixing a time of next reawakening of the current endpoint, a third field comprising information representing an identifier of said group, said identifier having been supplied by the centralising server to the current endpoint during a phase of connection to the third network performed by the current endpoint, and a fourth field comprising information indicating to said current endpoint whether each frame that it sent to the application server is acknowledged; means for setting a clock internal to said current endpoint using the first field; means for checking, using the fourth field and if the identifier represented by the information representing the identifier of said group contained in the third field corresponds to the identifier received by the current endpoint during the connection phase, that each frame sent is acknowledged; and standby means for putting the current endpoint on standby until the time of next reawakening indicated in the second field.

According to a sixth aspect of the invention, the invention relates to a device of the application server type adapted to acknowledge frames sent by endpoints in a group of endpoints to said application server, each endpoint in said group communicating with the application server via a gateway and the centralising server, the application server being connected to the centralising server via a first communication network, the centralising server being connected to each gateway by a second communication network, the group of endpoints and each gateway forming a third network of the long-range wireless network type affording low energy consumption, each communication between an endpoint in said group and a gateway using a communications protocol adapted to said third network. The device comprises: means for generating an acknowledgement message, the acknowledgement message comprising a plurality of fields, a first field comprising information allowing timesetting of each endpoint receiving said message, a second field fixing a time of next reawakening of each endpoint receiving said message, a third field comprising information representing an identifier of said group, said identifier having been supplied by a centralising server to each endpoint in said group during a phase of connection to the third network performed by said endpoint, and a fourth field comprising information indicating, for each endpoint in said group, whether each frame that it sent to the application server since a previous acknowledgement is acknowledged; said message being intended to be transmitted to each endpoint in the group of endpoints via a centralising server and each gateway enabling the centralising server to communicate with each endpoint in the group of endpoints.

According to a seventh aspect of the invention, the invention relates to a system comprising a group of endpoints according to the fifth aspect sending frames to an application server according to the sixth aspect, each endpoint in said group communicating with the application server via a gateway and a centralising server according to the fourth aspect, the application server being connected to the centralising server via a first communication network, the centralising server being connected to each gateway by a second communication network, the group of endpoints and each gateway forming a third network of the long-range wireless network type affording low energy consumption, each communication between an endpoint in said group and a gateway using a communication protocol adapted to said third network.

According to an eighth aspect of the invention, the invention relates to a computer program, characterised in that it comprises instructions for implementing, by a device, the method according to the first aspect, when said program is executed by a processor of said device.

According to a ninth aspect, the invention relates to storage means, storing a computer program comprising instructions for implementing, by a device, the method according to the first aspect, when said program is executed by a processor of said device.

