Device mobility in star topology networks

Abstract

The invention relates to a method for managing the mobility of a communication device (CD), comprising: a gateway (GW) receiving (S1) a message transmitted from a communication device, the gateway (GW) determining (S2) a quality measure for each received message, a gateway manager (GM) collecting (S3) secondary vectors (SV) from all gateways, the gateway manager (GM) selecting (S4) a secondary vector (SV) based on the quality measures, the gateway manager (GM) commanding (S5) to pair a communication device corresponding to the communication device identifier (IdCD) of the selected secondary vector (SV) with a gateway corresponding to the gateway identifier (IdGW) of the selected secondary vector (SV) if the selected secondary vector (SV) has a better quality measure than a given primary vector (PV) having the same communication device identifier (IdCD) in a pairing database (DBP) and if the selected secondary vector (SV) has a gateway identifier (IdGW) different from the gateway identifier (IdGW) of the given primary vector (PV).

Description

Technical Field

[0001] This invention relates generally to industrial automation systems, and more specifically to the mobility of wireless devices in networks with a star topology. Background Technology

[0002] The Internet of Things (IoT) is a fundamental element of a company's digital transformation. In many markets, connected objects capture valuable information. Industrial IoT devices are primarily sensors that link to machines located in different areas of an industrial site, measuring, recording, and transmitting operational data to a data center for analysis. These sensors, for example, are wireless devices powered by internal batteries.

[0003] In a star topology network, communication devices, such as wireless sensors, are permanently connected and paired with a single gateway and communicate only with that paired gateway. Any packet exchange between communication devices must go through the gateway, so packets ideally reach their destination via at most one wireless hop. The disadvantage of this star topology is that the network's operation depends on the gateway, and because all packets must pass through it, the gateway can become a bottleneck.

[0004] When a communication device goes out of range of its paired gateway, the messages sent by the communication device will be lost, and even if the message is received by another gateway (not paired with the wireless sensor), the message will not be processed.

[0005] Therefore, it is necessary to effectively support the mobility of communication devices in networks with star topology. Summary of the Invention

[0006] This overview is provided to introduce concepts relevant to the subject matter of this invention. This overview is not intended to identify essential features of the claimed subject matter, nor is it intended to define or limit the scope of the claimed subject matter.

[0007] In one embodiment, a method for managing the mobility of communication devices is provided, wherein a gateway manager is connected to a set of gateways, each gateway being paired with at least one communication device via a wireless link, and each communication device being paired with only one gateway, wherein a first database linked to the gateway manager includes a master vector containing gateway identifiers, communication device identifiers, and quality metrics, the method comprising:

[0008] The gateway receives messages sent from the communication device, each message containing the communication device identifier.

[0009] The gateway determines a quality metric for each received message, which is related to the radio link between the gateway and the communication device.

[0010] For each received message, the gateway stores a quadratic vector containing the communication device identifier, timestamp, and quality metric.

[0011] The gateway manager collects quadratic vectors from all gateways and stores the collected quadratic vectors in the manager database, corresponding to gateway identifiers.

[0012] The gateway manager selects a quadratic vector from quadratic vectors that include the same communication device identifier and timestamps contained in a predetermined time interval, based on a quality metric.

[0013] If the selected quadratic vector has a better quality metric than the given principal vector, and if the selected quadratic vector has a different gateway identifier than the given principal vector, then the gateway manager command pairs the communication device corresponding to the communication device identifier of the selected quadratic vector with the gateway corresponding to the gateway identifier of the selected quadratic vector, and the given principal vector has the same communication device identifier in the pairing database.

[0014] Advantageously, compared to networks with mesh topology, this system exhibits less wireless pollution and provides a balanced distribution of communication devices among gateways.

[0015] In this embodiment, the gateway manager and the gateway form a network with a star topology.

[0016] In an embodiment, when a gateway is paired with a communication device, the pairing database includes a master vector containing the gateway identifier and the communication device identifier.

[0017] In one embodiment, the gateway manager is also configured to command the unpairing of the communication device corresponding to the communication device identifier of the selected quadratic vector and the gateway corresponding to the gateway identifier of the given primary vector.

[0018] In one embodiment, the gateway manager selects the quadratic vector with the best quality metric from the quadratic vectors being compared.

[0019] In this embodiment, the quality metrics include a received signal strength indicator and a link quality indicator.

[0020] In this embodiment, the message is sent by the communication device in a broadcast manner.

[0021] In one embodiment, the pairing database is periodically updated using the secondary vectors stored in the gateway manager database by replacing the quality metric values ​​of the primary vectors of the given identifiers of the gateway and the communication device with the quality metric values ​​of the secondary vectors of the same given identifiers of the gateway and the communication device.

[0022] In one embodiment, the gateway manager compares the quality metric of the selected quadratic vector with the quality metric of the principal vector added to the margin, and if the quality metric of the selected quadratic vector is higher than the sum of the quality metric of the principal vector and the margin, it commands a new pairing of the communication device.

[0023] In this embodiment, the message also includes operation data, and only a gateway paired with a given communication device can process the operation data of the message sent by the given communication device.

[0024] In one embodiment, the gateway paired with the communication device allocates a dedicated channel by reserving a storage area for storing operational data from the communication device.

[0025] In this embodiment, each gateway is paired with at least one communication device via a short-range wireless link.

[0026] In another embodiment, a system is provided, including a gateway manager and gateways connected to the gateway manager, each gateway being paired with at least one communication device via a wireless link, and each communication device being paired with only one gateway. The system includes:

[0027] The pairing database linked to the gateway manager includes a master vector containing gateway identifiers, communication device identifiers, and quality metrics.

[0028] The gateway is configured to receive messages sent from communication devices, each message containing a communication device identifier.

[0029] The gateway is configured to determine a quality metric for each received message, the quality metric relating to the radio link between the gateway and the communication device.

[0030] For each received message, the gateway stores a quadratic vector containing the communication device identifier, timestamp, and quality metric.

[0031] The gateway manager is configured to collect quadratic vectors from all gateways and store the collected quadratic vectors in the manager database, each corresponding to a gateway identifier.

[0032] The gateway manager is configured to select a quadratic vector based on a quality metric from quadratic vectors that include the same communication device identifier and timestamps contained in a predetermined time interval.

[0033] The gateway manager is configured to, if the selected quadratic vector has a better quality metric than the given principal vector, and if the selected quadratic vector has a different gateway identifier than the given principal vector, then command the communication device corresponding to the communication device identifier of the selected quadratic vector and the gateway corresponding to the gateway identifier of the selected quadratic vector to be paired, provided that the given principal vector has the same communication device identifier in the pairing database.

[0034] In another embodiment, a computer-readable medium is provided, having on it a computer program for performing a method for managing the mobility of a communication device. The computer program includes instructions for performing steps of the method according to the invention. Attached Figure Description

[0035] A detailed description is given with reference to the accompanying drawings. In the drawings, the leftmost digit of the reference numerals identifies the first figure in which the reference numeral appears. The same numerals are used throughout the drawings to denote the same features and components. Some embodiments of the system and / or method according to this subject matter will now be described by way of example and with reference to the accompanying drawings, wherein:

[0036] Figure 1 A schematic block diagram of a communication system for managing the mobility of a communication device according to an embodiment of the present invention is shown; and

[0037] Figure 2 A flowchart of a method for managing the mobility of a communication device according to an embodiment of the present invention is shown.

[0038] In all the accompanying drawings, the same reference numerals denote the same elements or elements of the same type.

[0039] Those skilled in the art will understand that any block diagram herein represents a conceptual view of an illustrative system embodying the principles of the subject matter. Similarly, it should be understood that any flowchart, state transition diagram, pseudocode, etc., represents various processes that can be substantially represented in a computer-readable medium and thus executed by a computer or processor, whether or not such computer or processor is explicitly shown. Detailed Implementation

[0040] The accompanying drawings and the following description illustrate specific exemplary embodiments of the invention. It should therefore be understood that those skilled in the art will be able to devise various arrangements, although not explicitly described or shown herein, that embody the principles of the invention and are included within its scope. Furthermore, any examples described herein are intended to aid in understanding the principles of the invention and should be construed as not being limited to these specifically enumerated examples and conditions. Consequently, the invention is not limited to the specific embodiments or examples described below, but is limited by the claims and their equivalents.

[0041] refer to Figure 1The communication system includes a gateway manager (GM) and a set of gateways (GWs) that communicate with a communication device (CD). The gateway manager (GM) is connected to this set of gateways in a star topology via wired or wireless links, and the gateways (GWs) are paired with the communication device (CD) via wireless links. The gateway manager (GM) and the gateways (GWs) form a network with a star topology, in which all gateways (GWs) are individually connected as nodes to the gateway manager (GM), which serves as the central connection point.

[0042] A Gateway Manager (GM) connects to a group of Gateways (GWs) via wired or wireless links, forming a packet network, such as an IP (“Internet Protocol”) high-speed network, like the Internet or an intranet, or even a company-specific private network. Communication between the Gateway Manager (GM) and the group of gateways can be based on the TCP / IP protocol. The Gateway Manager (GM) dynamically manages the pairing of any communication device with the most suitable Gateway (GW) relative to quality metrics related to the radio link. The Gateway Manager (GM) is able to take into account the quality of the radio link for messages transmitted by the communication device and received by different gateways within the communication device's radio range.

[0043] A gateway (GW) can connect to one or more communication devices via a wireless link, such as based on Zigbee, Bluetooth Low Energy, or other short-range technologies. In another example, the gateway (GW) is part of a telecommunications network, which is a limited-range public wireless network, such as a WLAN (Wireless Local Area Network) or compliant with standard 802.1x, or a medium-range network according to the WiMAX (Global Interoperability Microwave Access) protocol.

[0044] Communication Device CDs (CDs) are capable of transmitting operational data to data centers or local applications for analysis and processing. The CD transmits operational data to the data center via a gateway, towards a gateway manager, the appropriate data center, or an application for data analysis. A communication device CD can be any type of industrial IoT device capable of transmitting operational data. Some communication device CDs may be powered by internal batteries or be self-powered, or use any power source that utilizes energy harvesting solutions (e.g., piezoelectric, electromagnetic generators, photovoltaics, etc.).

[0045] The communication device CD can be any type of sensor, such as a pressure sensor, level detector, ammeter / voltmeter, pH meter, leak / strain detector, event or occurrence counter, or speed / accelerometer. Therefore, any sensor capable of measuring specific sensor values ​​or capturing specific events can be connected to the gateway GW. Furthermore, the communication device CD can be a sensor capable of measuring temperature, humidity, and energy measurements, etc. The communication device CD can also be any type of button or device used as wearable commands.

[0046] A communication device (CD) can be any type of actuator that performs actions to operate or modify the state or behavior of a machine or other entity. For example, an actuator can be associated with a lighting device that issues an alarm or call for action.

[0047] A communication device CD can be paired with only one gateway GW, while a gateway can be paired with multiple communication devices. When a gateway GW is paired with a communication device CD, the gateway allocates a dedicated channel for communication with the communication devices. This dedicated channel reserves storage space in the gateway's memory for storing operational data from the communication devices.

[0048] A gateway (GW) can manage a finite number of "Y" channels, where "Y" is an integer. Each channel is dedicated to data transmission between the gateway and the communication devices paired with it. If the number of paired communication devices is less than the finite number of channels, it is assumed that there is free space available for new commissioning of communication devices that can be paired with the gateway and use the remaining channels.

[0049] During commissioning and operation, the communication device CD broadcasts messages without knowing its paired gateway. The messages sent by the communication device contain the communication device identifier IdCD and operational data, such as measurements from wireless sensors. Because the communication device identifier IdCD is included in the message, the gateway GW paired with the communication device CD can identify the communication device and process the message payload, i.e., the operational data, through a dedicated channel associated with the communication device.

[0050] When a gateway (GW) receives a message from a communication device (CD) that is not paired with the gateway, the message payload is ignored, and therefore the operational data is not processed. However, the gateway (GW) can analyze the signal characteristics of the received message.

[0051] Operational data can be exchanged in messages according to the Modbus / TCP communication protocol. Modbus / TCP is a communication protocol that can exchange frames according to the Modbus protocol at the application layer (layer 7) of the ISO (International Organization for Standardization) model, and transmit these Modbus frames on Ethernet networks using the ISO layer of the TCP / IP standard.

[0052] In one embodiment, the gateway GW manages an operation table called the ModBus table for the communication device it is paired with. This table lists a set of "Z" words for each identifier IdCD of the communication device, where each word contains 2 bytes.

[0053] In other words, the gateway (GW) manages a table containing a data space of Z ModBus words to store operational data from each paired communication device.

[0054] At regular time intervals, such as every “N” seconds, where “N” is an integer, the ModBus table of each gateway GW is transmitted (or read) to the gateway manager GM to feed the ModBus network database.

[0055] The ModBus network database can then be used by different applications that reference communication device identifiers using operational data, such as applications for power monitoring or temperature monitoring.

[0056] The Gateway Manager (GM) and the Gateway Gateway (GW) are synchronized in time, for example, by using a shared clock or by periodically updating the Gateway Gateway's clock.

[0057] A gateway (GW) can receive messages from any communication device within radio range, but can only process operational data sent by communication devices paired with the gateway.

[0058] Any message received by the gateway (GW) is analyzed by the gateway to determine a quality metric of the radio link between the gateway and the communication device that sent the message. Quality metrics may include, but are not limited to, Received Signal Strength Indicator (RSSI) and Link Quality Indicator (LQI). LQI is an indication of the quality of the data packets in the message received by the gateway, while RSSI can be used as a measure of the signal strength of the message received by the gateway.

[0059] For each received message, each gateway stores in its gateway database DBG a communication device identifier (IdCD) that has sent the message, a timestamp corresponding to the message's reception time, and a quadratic vector (SV) of quality metrics.

[0060] At fixed time intervals, such as every “M” seconds, where “M” is an integer, the contents of the gateway database of each gateway GW are transmitted (or read) to the gateway manager GM to feed the manager database DMB.

[0061] The Manager Database (DBM) contains quadratic vectors (SVs) stored, each corresponding to a gateway identifier (IdGW). The Manager Database (DBM) is linked to the Gateway Manager (GM) and is either included within the Gateway Manager or implemented in another entity accessible by the Gateway Manager.

[0062] The Gateway Manager (GM) also manages the Pairing Database (DBP), which contains the Master Vector (PV) corresponding to the Gateway IdGW that has been paired with a communication device.

[0063] The main vector PV contains a gateway identifier IdGW, a channel identifier IdC, a communication device identifier IdCD, a quality metric, and the final encryption key, where the gateway is paired with the communication device.

[0064] Considering the number of gateways "m" and the number of channels "Y" per gateway, it can be assumed that there exists a principal vector of number "m×Y" in the pairing database DBP. If a given channel of a gateway is not used, i.e., there is free space for pairing communication devices, the identifier IdC of the given channel can have a value equal to "0" or "NULL" or any value indicating that the channel is free.

[0065] The pairing database DBP is updated periodically based on the contents of the gateway database of each gateway GW. At fixed time intervals, such as every "L" seconds, where "L" is an integer, the contents of the pairing database DBP are periodically updated with the administrator database DBM.

[0066] If the communication device is still paired with the gateway, the quality metric of the principal vector of the given identifier IdGW of the gateway and the given identifier IdCD of the communication device is replaced with the quality metric of the quadratic vector of the same given identifier IdGW of the gateway and the same given identifier IdCD of the communication device.

[0067] If the communication device is not paired with the previous gateway and is paired with the new gateway, the quality metric value of the principal vector with the previous gateway identifier IdGW, the channel identifier IdC, and the communication device identifier IdCD is replaced with the quality metric value of the secondary vector with the new gateway identifier IdGW, the new channel identifier IdC, and the same communication device identifier IdCD. The new gateway allocates a new channel dedicated to the communication device, and the previous gateway has released the channel previously dedicated to the communication device.

[0068] Typically, for example, every "M" seconds, where "M" is an integer, the Gateway Manager Analysis Manager database DBM contains a quadratic vector with timestamps included in a predetermined time interval. The predetermined time interval should contain a sufficiently long period to detect when a communication device has moved and send a message once it has moved, and should also contain a sufficiently short period to focus only on the most recently moved communication device.

[0069] The Gateway Manager (GM) analyzes the database DBM's quadratic vectors to detect whether a communication device has been moved or whether there are structural changes in the area (such as new walls, new metal assets, etc.), and is now closer to a different gateway (from a radio link quality perspective) than to its paired gateway. It is assumed that the closer the communication device is to the gateway (in a radio context), the better the quality metric of messages received by the gateway from the communication device. However, in some cases, the quality metric of messages received by a more distant gateway may be better than that received by a closer gateway, for example, if there are obstacles between the communication device and the closer gateway that reduce the signal quality carrying the message.

[0070] Therefore, the Gateway Manager (GM) compares quadratic vectors that have the same communication device identifier (IdCD) and a timestamp included in a predetermined time interval. When a communication device broadcasts a message, different gateways can receive the message, and the corresponding quadratic vectors, which have the same communication device identifier (IdCD) and the gateway identifier (IdGW) that received the message, are stored in the manager database. The Gateway Manager selects the quadratic vector with the higher quality metric from the compared quadratic vectors.

[0071] The selected quadratic vector is then compared with the primary vector in the pairing database DBP that has the same communication device identifier IdCD. The primary vector contains the currently paired gateway identifier IdGW. If the quality metric of the selected quadratic vector is better than that of the primary vector, the gateway manager commands to unpair the communication device from the gateway corresponding to the primary vector's gateway identifier IdGW, and further commands the communication device to pair with the gateway corresponding to the selected quadratic vector's gateway identifier IdGW.

[0072] Pairing of a communication device with another gateway is accomplished by selecting an available channel of that gateway. The pairing database DBP is therefore updated by replacing the gateway identifier IdGW in the primary vector with the gateway identifier IdGW of the selected secondary vector. As previously mentioned, the quality metric value of the primary vector is also replaced with the quality metric value of the selected secondary vector. This pairing update can be performed by the gateway manager GM, or it can be performed the next time the pairing database DBP is updated with the contents of the gateway database for each gateway GW.

[0073] In one embodiment, the gateway manager may further consider other criteria when comparing the quality metrics of the selected quadratic vector and the principal vector. For example, to account for variations in signal strength, the gateway manager may compare the RSSI of the selected quadratic vector with the RSSI of the principal vector with a margin (e.g., 6 dB) added. For a new pairing, the RSSI of the selected quadratic vector should be better than the sum of the RSSI of the principal vector and the margin.

[0074] In another embodiment, load balancing between gateways can be considered, for example by selecting a gateway with more resources or more free channels for a new pairing.

[0075] The payload of messages sent by the communication device can be encrypted, and only the gateway paired with the communication device can decrypt the payload. The encryption key is generated after the communication device is debugged and can be exchanged with the first paired gateway according to different protocols. For example, a user action can be performed on a button on the communication device to trigger the pairing process, during which secure data is exchanged between the communication device and the gateway, allowing the gateway to retrieve the encryption key. In the case of encryption functionality, the encryption key of the communication device can be stored in the pairing database DPB as part of the master vector PV containing the communication device identifier IdCD.

[0076] In one embodiment, the Gateway Manager (GM) can collect the encryption key associated with the communication device from the gateway paired with it. When the communication device unpairs from a previous gateway and pairs with a new gateway, the Gateway Manager can retrieve the encryption key associated with the communication device from the previous gateway and transmit it to the new gateway. This automated mechanism avoids any user intervention in re-pairing the communication device.

[0077] One embodiment includes a gateway GW or gateway manager GM, which takes the form of a device including one or more processors, I / O interfaces, and memory coupled to the processors. The processor can be implemented as one or more microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, state machines, logic circuits, and / or any means of manipulating signals based on operating instructions. The processor can be a single processing unit or multiple units, all of which may also include multiple computing units. Among other capabilities, the processor is configured to fetch and execute computer-readable instructions stored in memory.

[0078] Functionality implemented by a processor can be provided using dedicated hardware and hardware capable of executing software associated with appropriate software. When provided by a processor, functionality can be provided by a single dedicated processor, a single shared processor, or multiple separate processors, some of which may share the functionality. Furthermore, the explicit use of the term "processor" should not be construed as referring specifically to hardware capable of executing software, and may implicitly include, but is not limited to, digital signal processor (DSP) hardware, network processors, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), read-only memory (ROM) for storing software, random access memory (RAM), and non-volatile memory. Other hardware, conventional and / or custom, may also be included.

[0079] Memory may include any computer-readable medium known in the art, including, for example, volatile memory such as static random access memory (SRAM) and dynamic random access memory (DRAM), and / or non-volatile memory such as read-only memory (ROM), erasable programmable ROM, flash memory, hard disk, optical disk, and magnetic tape. Memory includes modules and data. These modules include routines, programs, objects, components, data structures, etc., that perform specific tasks or implement specific abstract data types. Among other things, data serves as a repository for storing data processed, received, and generated by one or more modules.

[0080] Those skilled in the art will readily recognize that the steps of the methods described above can be performed by a programmed computer. In this document, some embodiments are also intended to cover program storage devices, such as digital data storage media, which are machine- or computer-readable and encode machine-executable or computer-executable programs of instructions that perform some or all of the steps of the described methods. Program storage devices can be, for example, digital memories, magnetic storage media such as disks and magnetic tapes, hard disk drives, or optically readable digital data storage media.

[0081] refer to Figure 2 A method for managing the mobility of communication devices in a network with a star topology according to an embodiment of the present invention includes steps S1 to S5.

[0082] In step S1, the communication device CD sends messages in the form of broadcasts, for example at regular time intervals, after a specific action (such as a measure) has been performed, or when an event occurs, such as a. human action, the end of a counter, or the detection of an object.

[0083] Each message contains a communication device identifier (IdCD) and operational data, such as status, action reports, or measurements.

[0084] Messages are received by a gateway (GW) within the radio range of the communication device. Messages sent by the communication device can be received by one or more gateways, but only one gateway is paired with the communication device.

[0085] In step S2, each gateway GW analyzes the received message by first extracting the communication device identifier (IdCD) contained in the received message. Using the IdCD, the gateway GW can distinguish whether the received message comes from a communication device paired with or not paired with the gateway.

[0086] For messages sent by communication devices paired with the gateway, the gateway stores the operation data contained in the message in the operation table along with the communication device's IdCD and the identifier IdC of the channel associated with that communication device.

[0087] For each message received by the gateway, the gateway determines a quality metric relating to the radio link between the gateway and the communication device that sent the message. This quality metric may include, but is not limited to, Received Signal Strength Indicator (RSSI) and Link Quality Indicator (LQI).

[0088] For each received message, the gateway stores the communication device identifier (IdCD), the determined quality metric, and the timestamp in the gateway database (DBG). The timestamp corresponds to the message's reception time. For each received message, the communication device IdCD, the determined quality metric, and the timestamp together form the message's quadratic vector (SV).

[0089] Every N seconds, the operation table of each gateway (GW) is sent to the gateway manager (GM), and in parallel, every M seconds, the contents of the gateway database (DBG) of each gateway (GW) are sent to the gateway manager (GM). Also, every L seconds, in parallel, the paired database (DBP) of the gateway manager (GM) is updated by reading the contents of the gateway database of each gateway (GW). The operation tables are aggregated in a global database, which is accessed by different applications using the operation data.

[0090] In step S3, the gateway manager GM collects quadratic vectors SV from all gateways GW and stores the collected quadratic vectors SV in the manager database DBM, corresponding to the gateway identifiers IdGW.

[0091] In step S4, the gateway manager GM compares the quality metrics of quadratic vectors SV that have the same communication device identifier IdCD and include timestamps in a predetermined time interval.

[0092] Because messages sent by a communication device can be received by different gateways, comparing the quality metrics of the same communication device highlights the differences in packet quality and signal quality between the messages received by different gateways. To effectively utilize communication devices in the ecosystem, each communication device should be paired with a gateway to provide the best possible received signal quality from the communication device.

[0093] The Gateway Manager (GM) selects the quadratic vector (SV) with the best quality metric from the compared quadratic vectors. Considering RSSI and LQI as quality metrics, the SV with the higher RSSI and / or LQI is selected.

[0094] In step S5, the gateway manager GM identifies the gateway currently paired with the communication device. To this end, the gateway manager GM identifies the principal vector PV that has the same communication device identifier IdCD as the selected quadratic vector.

[0095] If the selected quadratic vector and the identified principal vector have the same gateway identifier IdGW, the gateway manager GM will replace the quality metric of the principal vector with the quality metric of the selected quadratic vector.

[0096] If the selected quadratic vector and the identified principal vector have different gateway identifiers (IdGW), the gateway manager (GM) will compare the quality metric of the selected quadratic vector with the quality metric of the principal vector (PV).

[0097] If the selected quadratic vector SV has a higher quality metric than the given principal vector, the gateway manager GM command pairs the communication device corresponding to the communication device identifier of the selected quadratic vector with the gateway identifier IdGW corresponding to the selected quadratic vector. Typically, the result of having a higher quality metric means that the communication device has moved and is now closer to the gateway corresponding to the selected quadratic vector, rather than its currently paired gateway.

[0098] To instruct a communication device to pair with a gateway, the gateway manager (GM) sends a command to the gateway to allocate a dedicated channel for communication with the communication device. Based on the received command, the pairing process is completed only at the gateway level. More specifically, the command may include a channel identifier (IdC) and an encryption key associated with the communication device.

[0099] In another embodiment, load balancing between gateways can be considered, for example by selecting a gateway with more resources or more free channels for a new pairing.

[0100] In another embodiment, the type of communication device can be considered, since the gateway can support only a limited number of communication devices of a given type. The type of communication device can be retrieved from the communication device identifier IdCD.

[0101] In one embodiment, the gateway manager GM compares the selected quadratic vector with the primary vector PV only if the gateway corresponding to the selected quadratic vector has at least one free channel for the new pairing.

[0102] In one embodiment, the gateway manager compares the RSSI of the selected secondary vector with the RSSI of the primary vector added to a margin (e.g., 6 dB). If the RSSI of the selected secondary vector is higher than the sum of the RSSI of the primary vector and the margin, the gateway manager (GM) commands a new pairing of the communication devices.

[0103] Furthermore, if the selected quadratic vector SV has a higher quality metric than the given principal vector, the gateway manager GM command unpairs the communication device corresponding to the communication device identifier of the selected quadratic vector from the gateway corresponding to the gateway identifier IdGW of the principal vector. In other words, the gateway manager GM command unpairs the communication device from the currently paired gateway.

[0104] The pairing and unpairing processes of communication devices can be performed in essentially parallel, that is, the unpairing process can precede the pairing process, or the pairing process can precede the unpairing process.

[0105] In order to command the communication device to unpair from the currently paired gateway, the gateway manager (GM) sends an instruction to the gateway to remove the dedicated channel used for communicating with the communication device and optionally delete the encryption key associated with the communication device.

[0106] Although the invention has been described above with reference to specific embodiments, it is not intended to be limited to the particular forms set forth herein. Rather, the invention is limited only by the appended claims, and other embodiments besides the specific embodiments described above are also possible within the scope of these appended claims.

[0107] Furthermore, although exemplary embodiments have been described in some exemplary combinations of components and / or functions, it should be understood that alternative embodiments may be provided by different combinations of components and / or functions without departing from the scope of this disclosure. In particular, it is contemplated that specific features described individually or as part of an embodiment may be combined with other separately described features or portions of other embodiments.

Claims

1. A method for managing the mobility of a communication device (CD), wherein a gateway manager (GM) is connected to a set of gateways (GW), each gateway being paired with at least one communication device (CD) via a wireless link and each communication device (CD) being paired with only one gateway (GW), wherein a pairing database (DBP) linked to the gateway manager includes an identifier (IdGW) of a given gateway, an identifier (IdCD) of a given communication device paired with the given gateway, and a principal vector (PV) of a quality metric relating to the wireless link between the given gateway and the given communication device, the method comprising: The gateway (GW) receives messages broadcast from communication devices. Each message contains a communication device identifier (IdCD) and operation data. Only the gateway (GW) paired with a given communication device (CD) can process the operation data of the message sent by that given communication device to send the operation data for application use to the gateway manager. The gateway (GW) determines a quality metric for each received message, which is related to the radio link between the gateway and the communication device. For each received message, the gateway (GW) stores a communication device identifier (IdCD), a timestamp, and a quadratic vector (SV) of quality metrics. The Gateway Manager (GM) collects quadratic vectors (SVs) from all gateways and stores each collected SV in the Manager Database (DBM) along with a corresponding gateway identifier (IdGW). The Gateway Manager (GM) selects a quadratic vector (SV) from quadratic vectors that contain the same Communication Device Identifier (IdCD) and include timestamps included in a predetermined time interval, based on a quality metric. If the selected quadratic vector (SV) has a better quality metric than a given principal vector (PV) with the same communication device identifier (IdCD) in the pairing database (DBP), and if the selected quadratic vector (SV) has a different gateway identifier (IdGW) than the given principal vector (PV), the gateway manager (GM) commands a new pairing, pairing the communication device corresponding to the communication device identifier (IdCD) of the selected quadratic vector (SV) with the gateway corresponding to the gateway identifier (IdGW) of the selected quadratic vector (SV), instead of the gateway that the communication device corresponding to the identifier of the communication device of the selected quadratic vector is being paired with.

2. The method according to claim 1, wherein, The Gateway Manager (GM) and the Gateway (GW) form a network with a star topology.

3. The method according to any one of the preceding claims, wherein, The gateway manager (GM) is also configured to command the communication device with the communication device identifier (IdCD) corresponding to the selected quadratic vector (SV) to the gateway with the gateway identifier (IdGW) corresponding to the given master vector (PV).

4. The method according to any one of the preceding claims, wherein, The gateway manager (GM) selects the quadratic vector (SV) with the best quality metric from the quadratic vectors being compared.

5. The method according to any one of the preceding claims, wherein, The quality metrics include a received signal strength indicator and a link quality indicator.

6. The method according to any one of the preceding claims, wherein, The pairing database (DBP) is periodically updated using the quadratic vectors (SVs) stored in the gateway, by replacing the quality metric values ​​of the primary vectors with the given gateway identifier (IdGW) and the given communication device identifier (IdCD) with the quality metric values ​​of the secondary vectors with the same given gateway identifier (IdGW) and the same given communication device identifier (IdCD).

7. The method according to any one of the preceding claims, wherein, The gateway manager compares the quality metric of the selected quadratic vector with the quality metric of the principal vector added to the margin, and if the quality metric of the selected quadratic vector is higher than the sum of the quality metric of the principal vector and the margin, it commands a new pairing of the communication devices.

8. The method according to any one of the preceding claims, wherein, A gateway (GW) paired with a communication device (CD) allocates a dedicated channel by reserving a storage area for storing operational data from the communication device (CD).

9. The method according to any one of the preceding claims, wherein, Each gateway (GW) is paired with at least one communication device (CD) via a short-range wireless link.

10. A system comprising a gateway manager (GM) and gateways (GW) connected to the gateway manager (GM), each gateway (GW) being paired with at least one communication device (CD) via a wireless link, each communication device (CD) being paired with only one gateway (GW), the system comprising: The pairing database (DBP), linked to the gateway manager, includes the identifier (IdGW) of a given gateway, the identifier (IdCD) of a given communication device paired with the given gateway, and the principal vector (PV) of the quality metric associated with the wireless link between the given gateway and the given communication device. A gateway (GW) is configured to receive messages broadcast from communication devices. Each message contains a communication device identifier (IdCD) and operational data. Only a gateway (GW) paired with a given communication device (CD) can process the operational data of the message sent by that given communication device to send operational data for use by the application to the gateway manager. The gateway (GW) is configured to determine a quality metric for each received message, which relates to the radio link between the gateway and the communication device. The gateway (GW) is configured to store a quadratic vector (SV) for each received message, including the communication device identifier (IdCD), timestamp, and quality metric. The Gateway Manager (GM) is configured to collect quadratic vectors (SVs) from all gateways and store the collected quadratic vectors (SVs) in the Manager Database (DBM) along with corresponding gateway identifiers (IdGWs). The Gateway Manager (GM) is configured to select a quadratic vector (SV) from quadratic vectors that contain the same Communication Device Identifier (IdCD) and include timestamps included in a predetermined time interval, based on a quality metric. The Gateway Manager (GM) is configured to, if the selected quadratic vector (SV) has a better quality metric than a given primary vector (PV) with the same communication device identifier (IdCD) in the Pairing Database (DBP), and if the selected quadratic vector (SV) has a different gateway identifier (IdGW) than the given primary vector (PV), command a new pairing, pairing the communication device corresponding to the communication device identifier (IdCD) of the selected quadratic vector (SV) with the gateway corresponding to the gateway identifier (IdGW) of the selected quadratic vector (SV), rather than the gateway that the communication device corresponding to the identifier of the communication device of the selected quadratic vector is being paired with.

11. A computer-readable medium having thereon a computer program for performing a method for managing the mobility of a communication device according to any one of claims 1 to 9.

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