Method for transmitting data via a wireless interface between a field device and a mobile device

Abstract

The invention relates to a method for transmitting data via a wireless interface between a field device and a mobile device, comprising the following steps: providing a field device and a mobile device, the field device having a processing unit and a first wireless interface, the mobile device having a second wireless interface, wherein an internal power limit and a minimum connection robustness are stored in the field device; configuring first connection parameters, the first connection parameters having a first transmission power, a first redundancy and a first data packet length, wherein the first transmission power corresponds to a maximum transmission power, the first redundancy corresponds to a minimum redundancy and the first data packet length corresponds to a minimum data packet length, such that the field device does not exceed the internal power limit; sending a first broadcast message from the field device via the first wireless interface with the first connection parameters; receiving the first broadcast message from the mobile device via the second wireless interface; sending a first response message from the mobile device to the field device.

Description

Technical Field

[0001] This invention relates to a method and a system for transmitting data via a wireless interface between a field device and a mobile device. Background Technology

[0002] In the field of analytical measurement technology, particularly in water management, environmental analysis, industry (e.g., food technology, biotechnology, and pharmaceuticals), and for a wide variety of laboratory applications, measurement variables such as pH, conductivity, or even the concentration of analytes such as ions or dissolved gases in gaseous or liquid measurement media are of great significance. These measurement variables can be acquired and / or monitored, for example, using electrochemical sensors (such as optical sensors, potentiometric sensors, amperometric sensors, voltammetric sensors, or coulometric sensors) or conductivity sensors.

[0003] These sensors are typically connected to what are called transmitters, which process the sensor signals and transmit them, for example, to a control center. One type of connection between the transmitter and the control center uses only two cables. In this case, the transmitter is also referred to as a two-wire device.

[0004] For such two-wire devices, the available power is strictly limited, making them particularly suitable for use in potentially explosive environments. These devices communicate using the energy-efficient HART protocol, designed to transmit signals between 4 and 24 mA via a current loop between, for example, a control center and the two-wire device. At a typical maximum supply voltage of approximately 17 V, the minimum available current is typically limited to 3.6 mA. This results in an available power of approximately 61 mW.

[0005] In many devices, the operating voltage is further reduced to enable power supply for additional equipment such as explosion-proof resistors or other devices in the current loop. This further reduces the available power. For example, the iTEMP TMT72 transmitter from Endershaus can operate at a minimum supply voltage of only about 10 V, resulting in a minimum available power of only 36 mW.

[0006] However, the SoCs currently used in many transmitters with integrated Bluetooth communication modules have peak power consumption of up to about 30 mW for wireless communication, while on average they typically require significantly less than 1 mW of power consumption for their communication tasks.

[0007] While on average, the current loop provides sufficient power for all of the transmitter's device functions except for Bluetooth, only about 6 mW is temporarily available for functions such as measuring sensor values, processing, and fieldbus communication, as the remainder is used for Bluetooth communication. Therefore, the device's total power consumption may temporarily exceed the power provided by the current loop.

[0008] To cover such short-term energy demands, energy is typically stored temporarily in energy storage devices, such as capacitors. The required size of the energy storage depends on the duration and magnitude of the power peak.

[0009] However, this has the following drawbacks: it requires additional or larger electronic components, and furthermore, the power available in the transmitter is increased to a level greater than that provided by the current loop. This makes it difficult to meet explosion-proof (“Ex”) requirements.

[0010] Another possibility is to put the Bluetooth communication module into sleep mode for a higher proportion of the time to save energy. However, this has the following drawbacks: the data rate and latency of the Bluetooth connection will be negatively affected. Summary of the Invention

[0011] Therefore, the object of this invention is to provide a method that allows transmitters to operate in a highly energy-efficient manner while simultaneously allowing optimal data transmission.

[0012] According to the present invention, this objective is achieved by the method for transmitting data via a wireless interface between a field device and a mobile device as described in claim 1.

[0013] The method according to the present invention includes:

[0014] - Provides a field device and a mobile device, the field device having a processing unit and a first wireless interface, and the mobile device having a second wireless interface, wherein internal power limits and minimum connectivity robustness are stored in the field device;

[0015] - Configure first connection parameters, which include a first transmit power, a first redundancy, and a first data packet length.

[0016] Wherein, the first transmit power corresponds to the maximum transmit power, the first redundancy corresponds to the minimum redundancy, and the first data packet length corresponds to the minimum data packet length, so that the field equipment does not exceed the internal power limit;

[0017] - A first broadcast message is sent from a field device via a first wireless interface with first connection parameters;

[0018] - Receive the first broadcast message from the mobile device via the second wireless interface;

[0019] - Send the first response message from the mobile device to the field device;

[0020] - Receive the first response message from the field equipment;

[0021] - The processing unit determines the first signal strength and the first data packet error rate based on the first response message;

[0022] - The processing unit determines the first connection robustness between the field device and the mobile device based on the first signal strength and the first data packet error rate;

[0023] - Compare the robustness of the first connection with the robustness of the least connection;

[0024] - If the robustness of the first connection is less than or equal to the robustness of the least connection, then send the first data message with the first connection parameters;

[0025] - Configure second connection parameters, which include a second transmit power, a second redundancy, and a second data packet length.

[0026] The second transmit power is less than the first transmit power, the second redundancy is greater than the first redundancy, and the second data packet length is greater than the first data packet length, so that the field device does not exceed the internal power limit. If the first connection robustness is greater than the minimum connection robustness, the first data message is sent with the second connection parameters.

[0027] The method according to the invention enables optimal data transmission while meeting desired energy consumption.

[0028] According to one embodiment of the present invention, both the first wireless interface and the second wireless interface are Bluetooth Low Energy modules, and both are capable of transmitting data at a first data rate or a second data rate, wherein the second data rate is greater than the first data rate.

[0029] The first connection parameter includes a first data rate, and the second connection parameter includes a second data rate.

[0030] According to another embodiment of the present invention, the first connection parameter has a first number of redundant bits, and the second connection parameter has a second number of redundant bits, wherein the first number of redundant bits is greater than the second number of redundant bits.

[0031] According to one embodiment of the present invention, the first connection parameter has a first message length, and the second connection parameter has a second message length, wherein the first message length is less than the second message length.

[0032] According to one embodiment of the present invention, when the robustness of the first connection is greater than the robustness of the minimum connection, the algorithm, energy model, or error model configures the second connection parameters.

[0033] According to one embodiment of the present invention, after the first data message is sent, all previously performed steps are repeated until the first connection robustness is less than or equal to the minimum connection robustness.

[0034] According to one embodiment of the present invention, the first data message has a first phase position, and the method further includes: receiving the first data message at a mobile device, sending a second data message having a second phase position, receiving the second data message at a field device, evaluating the first phase position and the second phase position, and determining the distance between the field device and the mobile device based on the evaluation.

[0035] According to one embodiment of the present invention, the processing unit stores the transmission time when the first data message is transmitted, and the method further includes: receiving the first data message at a mobile device, transmitting the second data message, receiving the second data message at a field device, storing the reception time of the second data message at the field device by the processing unit, determining the signal propagation time based on the transmission time and the reception time, and determining the distance between the field device and the mobile device based on the signal propagation time.

[0036] The aforementioned objective is further achieved by the system according to claim 9.

[0037] The system according to the present invention includes:

[0038] - Field devices with a first wireless interface;

[0039] - Mobile devices with a second wireless interface

[0040] The internal power limits are stored in the field devices.

[0041] The system is suitable for performing the method according to the invention.

[0042] According to one embodiment of the present invention, both the first wireless interface and the second wireless interface are Bluetooth interfaces, preferably Bluetooth Low Energy interfaces. Attached Figure Description

[0043] The invention will be explained in more detail based on the following description of the accompanying drawings, in which:

[0044] - Figure 1 This is a schematic diagram of a system according to the invention for performing the method according to the invention;

[0045] - Figure 2 This is a flowchart of a method for optimizing energy consumption and connection reliability according to the present invention. Detailed Implementation

[0046] Figure 1A system 100 according to the present invention is schematically shown, which has a field device 1 and a mobile device 2. The field device 1 includes a first processing unit 10, a second processing unit 20, and a first wireless interface 30 for communicating with a second wireless interface 40 of the mobile device 2.

[0047] The first processing unit 10 and the second processing unit 20 are connected to each other to exchange instructions and / or data, which in Figure 1 The two processing units are represented by double arrows. For example, they are connected to each other via a bidirectional wired communication interface. The second processing unit 20 is suitable for performing computational tasks, such as creating or processing data packets and cryptographic computation tasks.

[0048] Furthermore, the first processing unit 10 is connected to the first wireless interface 30 to transmit instructions and / or data to the first wireless interface 30. The first wireless interface 30 is preferably a Bluetooth module, particularly advantageously a Bluetooth Low Energy module or a module for wireless communication using other protocols (such as ZigBee, Wireless HART, or communication protocols based on the IEEE 802.15.4 transmission protocol). The first wireless interface 30 can be housed in the same system-on-a-chip (SoC) with one or two processing units, or it can be implemented as a separate IC.

[0049] Field device 1 is suitable for connection to an external energy source 3 having an external power level, and is suitable for operation at an internal power level, wherein the internal power level is less than or equal to the external power level. The external energy source 3 is, for example, a current loop having a current of 4 to 20 mA. The current loop is in... Figure 1 The diagram is shown in an abstract manner only. For example, the external power rating is between 36 mW and 61 mW. Of course, field device 1 is also suitable for operation with an internal power source, such as a battery. However, operating field device 1 without a battery has the following advantages: field device 1 can be used, for example, in an explosion-proof environment without any additional measures. Furthermore, the battery does not need to be replaced during the service life of field device 1.

[0050] Field device 1 is preferably a two-wire device, which is suitable for communicating with the control center via the HART protocol through a current loop and is simultaneously supplied with power.

[0051] Field device 1 is connected to sensor 4, for example, and sensor 4 supplies electrical signals, such as voltage or potential, to field device 1. These signals are processed by field device 1 and transmitted via current loop to a control center and / or via first wireless interface 30 to mobile device 2.

[0052] System 100 preferably includes a repeater 6, which is adapted to amplify signals exchanged between field device 1 and mobile device 2 or to increase communication range by transmitting signals via two independent hops. Therefore, repeater 6 can allow communication over longer distances.

[0053] The method for transmitting data via a wireless interface 30 between a field device 1 and a mobile device 2 according to the present invention will now be described in more detail. The objective of this method is, in particular, to transmit a first data message DN1 from the field device 1 to the mobile device 2. The first data message DN1 preferably has a predetermined number of payload data bits and a predetermined number of redundant bits.

[0054] First, the system 100 described above is provided, which includes a field device 1 having a processing unit 10 and a first wireless interface 30, and a mobile device 2 having a second wireless interface 40, wherein internal power limits are stored in the field device 1.

[0055] Communication range during connection establishment:

[0056] Subsequently, the field device 1 sends a first broadcast message WN1 via the first wireless interface 30. This first broadcast message WN1 is a so-called broadcast announcement, that is, information about the existence of the field device 1 and, for example, the fact that sensor data can be obtained from the field device 1. This can also be referred to as a broadcast.

[0057] The first broadcast message WN1 contains, for example, information about the serial number of field device 1, the device name, and / or information about the sensor 4 connected to field device 1.

[0058] Furthermore, the first broadcast message WN1 is received by the mobile device 2 via the second wireless interface 40. For this purpose, it is assumed that the mobile device 2 is naturally within range of the signal (here: the first broadcast message WN1) transmitted by the field device 1.

[0059] When sending broadcast messages, various connection parameters such as transmit power and the number of data packets can be varied. Sending as few broadcast messages as possible with the lowest possible transmit power achieves the lowest possible power consumption for field devices. However, reduced communication range can be problematic. For example, if a Bluetooth device is mounted on a storage tank at high altitude, reducing the transmit power may result in insufficient wireless range to reach a smartphone / tablet on the ground. This would prevent both connection establishment and reception of broadcast data transmitted via broadcast announcements and scans. Therefore, if a connection has not yet been established, it is recommended to always send the broadcast data packets needed to detect the device's presence at a high transmit power (preferably the maximum transmit power), such as the first broadcast message WN1 described herein. However, this means that, with a limited energy budget, only a reduced number of data packets can be sent per unit time (e.g., per minute). For example, if 60 data packets can be sent per unit time at the maximum transmit power, then 600 data packets could be sent per unit time at the minimum transmit power. Because the transmission is performed at maximum power, high latency may occur when establishing a connection. That is, it may take a long time for the smartphone to successfully receive the first data message DN1 from the field device and exchange the message pairs required to establish a connection.

[0060] According to the present invention, this problem can be mitigated by the following process: most broadcast packets (i.e., broadcast messages) are transmitted at low transmit power. Simultaneously, individual, low-frequency broadcast packets are transmitted at high transmit power. Here, the term "low frequency" means, for example, one packet per 100 packets, preferably one packet per 200 packets, or even less. This only slightly increases average power consumption and therefore has only a minor impact on latency during connection establishment. Meanwhile, the remote device can still establish a connection—despite the increased latency. When using Bluetooth, extended broadcast announcements can also be utilized for a greater communication range. This is only compatible with newer devices supporting Bluetooth 5 or later, but allows the use of a coded physical layer with forward error correction even during connection establishment (which includes broadcast announcements). This connection establishment method for communication range optimization is preferably enabled or disabled by the user to adapt the device to requirements regarding communication range, throughput, and latency.

[0061] Adaptive adjustment of connection parameters:

[0062] After receiving the broadcast message WN1, the mobile device 2 sends a first response message AN1 to the field device 1. The first response message AN1 may contain, for example, a request for further data from the field device.

[0063] Response messages can also be used to request a synchronization connection between two devices so that further data packet pairs can be exchanged after this synchronization. During asynchronous message exchange (referred to as "broadcast announcements and scans" in Bluetooth Low Energy) and during synchronous connections, the configuration of connection parameters determines the power consumption of wireless communication. This also determines the performance of the wireless connection. Conversely, the required transmit power largely determines the necessary configuration of the connection parameters. The following describes a method designed to adaptively estimate the necessary transmit power and optimize the relevant connection parameters based on it.

[0064] Estimation of transmission power:

[0065] If a synchronization connection does not yet exist, i.e., if broadcast and response messages are still being exchanged, the first processing unit 10 or the second processing unit 20 determines a first distance E1 between the field device 1 and the mobile device 2. Here, the first distance is equivalent to the first connection quality or the first connection robustness. In the case of unobstructed communication, connection quality and connection robustness are generally naturally higher over short distances.

[0066] The determination of the first distance E1 is based on the first response message AN1. Preferably, the first response message AN1 includes the original transmitted signal strength and / or packet error rate.

[0067] Preferably, when determining the first distance E1, the signal strength (also referred to as Received Signal Strength Indication (RSSI)) of the received first response message AN1 is determined. As expected, the RSSI is between -30 and -90 dBm. If it does not reach a value close to -30 dBm, the signal strength is considered good, while if it reaches a value close to -90 dBm, the signal strength is considered particularly poor. The first distance E1 is estimated based on the signal strength. For example, if the RSSI is close to -30, the distance is assumed to be very close. For example, if the RSSI is close to -90, the distance is assumed to be very far.

[0068] Preferably, in addition to determining the signal strength of the first response message AN1 in the field device 1, the original transmitted signal strength when the mobile device 2 sent the first response message AN1 is also stored, and / or the original transmitted signal strength is appended to or included in the first response message AN1. In this case, the first distance E1 can be determined based on this signal strength and the original transmitted signal strength. Here, it is assumed that there are no obstacles on the transmission path.

[0069] The initial transmit signal strength of the first response message AN1 is preferably at its maximum value. This is particularly advantageous because the mobile device 2 has fewer power limitations.

[0070] Preferably, the packet error rate of the first response message AN1 is also determined. A high packet error rate indicates a potentially long distance. A low packet error rate indicates a potentially short distance. The packet error rate can be determined, for example, by evaluating the cyclic redundancy check (CRC) of the received packet content.

[0071] Then, the first distance E1 can be estimated based on the determined packet error rate or the determined RSSI of the first response message AN1.

[0072] If a synchronous connection has been established, RSSI and packet error rate can also be used to determine the distance.

[0073] According to alternative and / or supplementary embodiments, the first distance E1 is determined based on a phase or signal propagation time measurement (referred to as channel detection when using Bluetooth) performed during the connection established after the broadcast message exchange.

[0074] When measuring signal propagation time, field device 1 determines a first time interval (also known as signal propagation time) between sending a message and receiving a response message, which includes a known delay in processing and responding to the data packet. The propagation speed is assumed to be the speed of propagation in air. This propagation speed and the first time interval are then used to determine a first distance. In phase-based measurements using Bluetooth channel probing, one of the two communication participants (field device or mobile device) sends a message with a known phase position. The receiver of this message replies with a message whose phase matches the phase measured in the received data packet. If the phase of the received response message is measured at different frequencies, the distance between the field device and the mobile device can be calculated from this.

[0075] Adaptive adjustment of connection parameters:

[0076] After determining the first distance E1 using one of the two techniques mentioned above, determine the required transmit power, the data rate of the wireless interface, the redundancy of the payload data, the number of payload bytes per data packet, and the interval between data packet exchanges.

[0077] First, the procedure for adjusting these connection parameters is described, such as... Figure 2 As shown. Then, the effect of each connection parameter to be adjusted will be described in detail.

[0078] Algorithms are used to adjust connection parameters. The algorithm used to find optimal settings works as follows (see...). Figure 2First, the most energy-intensive but robust configuration of the connection parameters is assumed. This ensures the maximum communication range during transmission, i.e., the maximum possible distance between the field device and the mobile device. Based on the estimated first distance E1, the measured attenuation or measured packet error rate, and the error model, it is estimated whether the communication using these connection parameters is robust enough, i.e., whether it has minimum connection robustness. If not, the required robustness (i.e., minimum connection robustness) for communication cannot be achieved, and the algorithm terminates with the most robust configuration supported by the wireless interface 30. However, if the required robustness (minimum connection robustness) is achieved, it is checked whether there is a more energy-efficient configuration of the connection parameters supported by the wireless interface 30. The next more energy-efficient configuration of transmit power, physical layer (also known as PHY), and the number and length of packets within each connection interval is investigated. Here, a connection interval is understood to mean one exchange of messages sent by and received by field device 1. Simultaneously, only configurations where the error model proves that the configuration still achieves the required robustness are allowed.

[0079] If no more energy-efficient configuration can achieve the required robustness (least connectivity robustness), the previous configuration is retained and the algorithm is adjusted. Otherwise, the next more energy-efficient configuration with the connectivity parameters supported by the wireless module is selected, and the above process is followed. This continues until the most energy-efficient configuration with the required robustness has been determined.

[0080] Because this method is based on an error model, the algorithm can iterate multiple times to find the most efficient configuration without gradually adjusting the connection parameters of the wireless interface 30. Since the model can only approximate real-world conditions, iterative adaptation and measurement of robustness data, i.e., connection robustness (based on packet error rate and received power), can also be performed. The two approaches can also be combined.

[0081] Since the mobile device 2 may move away from the field device 1 or change its position at any time, causing the line of sight between the two devices to be at least partially blocked, the above-described process for adapting the connection parameters to the propagation time is continuously repeated.

[0082] The effects of connection parameters on wireless interface 30 and its power consumption are as follows.

[0083] Transmit power determines packet error rate and communication range. Higher transmit power potentially reduces the error rate and increases the communication range. The physical layer used also affects the communication range of the wireless connection. When using Bluetooth, for example, there are different physical layers with different data rates: 1 Mbps and 2 Mbps. At higher data rates, packets require shorter transmission times. The time taken to transmit a certain number of bytes via the first wireless interface 30 is also reduced, which in turn reduces power consumption. However, at the same time, the transmission range and its robustness against interference also decrease. Furthermore, forward error correction (FEC) can be used to correct damaged symbols after reception. In Bluetooth technology, this is achieved, for example, by using coded physical layer S2 (double redundancy) and coded physical layer S8 (octet redundancy) modes.

[0084] For example, the coding physical layer S2 introduces 2 redundant bits per payload data bit, and the coding physical layer S8 introduces 8 redundant bits per payload data bit. This reduces the data rate and increases energy consumption. However, the communication range and interference immunity are greatly increased. Therefore, the physical layer can be selected based on the desired data rate, robustness, and energy-efficient optimized transmit power.

[0085] In addition to defining the physical layer (and therefore the rate of bit transmission in the message), the initial message length is defined based on a first distance E1. When defining the initial message length, the number of payload bytes in the transmitted message is determined. Furthermore, the Bluetooth standard allows the interface to selectively operate with exceptionally long data packets using Data Length Extension (DLE).

[0086] The advantage of long messages (i.e., first data messages DN1 with a larger first data length) is that the ratio between protocol overhead and payload data becomes more favorable for longer messages. However, if a bit is transmitted incorrectly when using a physical layer without FEC, the entire message is discarded and must be retransmitted. With FEC, some errors can be corrected; however, if the bit error rate is too high, uncorrectable errors will occur, and the entire packet must be retransmitted. This retransmission significantly increases energy consumption. The bit error rate depends in particular on attenuation in the wireless channel and therefore on the distance between the transmitter and receiver. At a given bit error rate, the longer the message, the higher the probability that it contains at least one incorrectly transmitted bit.

[0087] Therefore, from an energy consumption perspective, using longer messages is advantageous for short distances and low bit error rates over wireless channels. For longer distances and therefore higher bit error rates, shorter packet lengths are more advantageous. Thus, for a given bit error rate, the minimum possible energy consumption is always determined by the optimal combination of the physical layer used and the packet length. The optimal combination for a given scenario can be calculated based on a mathematical model of propagation time. This is why the first processing unit 10 preferably continuously optimizes the physical layer and packet length (i.e., the first data length) for propagation time.

[0088] Advantageously, a communication protocol is used that first breaks down the serial byte stream into variable-sized individual datagrams on the transmitter side, then reassembles these variable-sized datagrams on the receiver side, and initiates retransmission if individual datagrams are lost. This use of the data link layer makes it possible to continue using application layer protocols at higher layers without considering the length of the data packets transmitted over radio; that is, long transmission distances are achieved using short datagrams at the application layer, and short transmission distances are achieved using long datagrams, while the application itself does not need to change the size of the data to be transmitted.

[0089] Subsequently, a first data rate is set accordingly based on the first distance E1. For this purpose, the first processing unit 10 changes the data packet rate, i.e., the number of messages per unit time. When using Bluetooth, this is achieved by setting a period. If no connection has been established, broadcast messages will be exchanged approximately according to this period. Therefore, during a connection, the connection interval is set accordingly. After each connection interval, one or more data packet pairs can be exchanged between the field device and the mobile device. If the supported data packet length is longer than the data packet length supported by the Bluetooth standard or radio hardware, multiple data packet pairs can be exchanged one after another. The optimal number of data packets is also derived from an energy model.

[0090] By adaptively adjusting transmit power, physical layer data rate and redundancy, message length, packet rate, and the number of consecutive packet pairs, the lowest possible energy consumption for wireless communication is achieved while maintaining optimal performance. The energy saved in this way is invested in higher message exchange rates at the same energy consumption, resulting in lower latency for the wireless connection. Furthermore, a portion of the saved energy can be used by the device for other functions unrelated to wireless communication.

[0091] The above method is preferably repeated periodically because the mobile device 2 may have moved, and the first distance E1 may therefore no longer be up-to-date. As described above regarding the determination of the first distance E1, the second distance E2 or the second connection robustness is thus determined. For example, a second broadcast message WN2, a second response message AN2, and a second data message DN2 may be exchanged. Figure 2 The illustrated preferred procedure can be modified to render the use of an error model redundant: instead of evaluating the fit of connection parameters based on a model, the parameters of the wireless interface can also be adapted, and the received signal power and packet error rate can be monitored during propagation. If performance is too low or the error rate is too high, the system will revert to the previous configuration.

[0092] The proposed method can increase the data rate and reduce the latency of Bluetooth devices by adapting the transmit power to the required transmit power. This results in higher performance, or, within the same power budget, improved communication robustness (connectivity robustness).

[0093] List of reference numerals

[0094] 1. On-site equipment

[0095] 2 Mobile devices

[0096] 3. External energy source

[0097] 4 sensors

[0098] 5. Memory

[0099] 6 Repeaters

[0100] 10 First Processing Unit

[0101] 20 Second Processing Unit

[0102] 30 First Wireless Interface

[0103] 40 Second wireless interface

[0104] 100 System

[0105] AN1 First Response Message

[0106] AN2 Second Response Message

[0107] DN1 First Data Message

[0108] DN2 Second Data Message

[0109] E1 First Distance

[0110] E2 Second Distance

[0111] WN1 First Broadcast News

[0112] WN2 Second Broadcast Message

Claims

1. A method for transmitting data via a wireless interface between a field device (1) and a mobile device (2), comprising the following steps: - Provide a field device (1) and a mobile device (2), the field device (1) having a processing unit (10) and a first wireless interface (30), and the mobile device (2) having a second wireless interface (40), wherein internal power limits and minimum connectivity robustness are stored in the field device (1); - Configure first connection parameters, which include a first transmit power, a first redundancy, and a first data packet length. Wherein, the first transmit power corresponds to the maximum transmit power, the first redundancy corresponds to the minimum redundancy, and the first data packet length corresponds to the minimum data packet length, so that the field device (1) does not exceed the internal power limit; - A first broadcast message (WN1) is sent from the field device (1) via the first wireless interface (30) with the first connection parameters. - The mobile device (2) receives the first broadcast message (WN1) via the second wireless interface (40); - Send a first response message (AN1) from the mobile device (2) to the field device (1); - Receive the first response message (AN1) from the field device (1); - The processing unit (10) determines the first signal strength and the first data packet error rate based on the first response message (AN1); - The processing unit (10) determines the first connection robustness between the field device (1) and the mobile device (2) based on the first signal strength and the first data packet error rate; - Compare the first connectivity robustness with the minimum connectivity robustness; - If the first connection robustness is less than or equal to the minimum connection robustness, then send the first data message (DN1) with the first connection parameters. - Configure second connection parameters, which include a second transmit power, a second redundancy, and a second data packet length. Wherein, the second transmit power is less than the first transmit power, the second redundancy is greater than the first redundancy, and the second data packet length is greater than the first data packet length, such that the field device (1) does not exceed the internal power limit, and if the first connection robustness is greater than the minimum connection robustness, the first data message (DN1) is sent with the second connection parameters.

2. The method according to claim 1, wherein, Both the first wireless interface (30) and the second wireless interface (40) are Bluetooth Low Energy modules, and both are capable of transmitting data at a first data rate or a second data rate, wherein the second data rate is greater than the first data rate. The first connection parameter further includes the first data rate, and the second connection parameter further includes the second data rate.

3. The method according to claim 1 or 2, wherein, The first connection parameter has a first number of redundant bits, and the second connection parameter has a second number of redundant bits, wherein the first number of redundant bits is greater than the second number of redundant bits.

4. The method according to any one of the preceding claims, wherein, The first connection parameter has a first message length, and the second connection parameter has a second message length, wherein the first message length is less than the second message length.

5. The method according to any one of the preceding claims, wherein, When the robustness of the first connection is greater than the robustness of the minimum connection, the algorithm, energy model, or error model configures the second connection parameters.

6. The method according to any one of the preceding claims, wherein, After the first data message (DN1) is sent, all previously executed steps are repeated until the first connection robustness is less than or equal to the minimum connection robustness.

7. The method according to any one of the preceding claims, wherein, The first data message (DN1) has a first phase position, and the method further includes: receiving the first data message (DN1) at the mobile device (2), sending a second data message (DN2) having a second phase position, receiving the second data message (DN2) at the field device (1), evaluating the first phase position and the second phase position, and determining the distance between the field device (1) and the mobile device (2) based on the evaluation.

8. The method according to any one of the preceding claims, wherein, The processing unit (10) stores the transmission time when the first data message (DN1) is sent, and the method further includes: receiving the first data message (DN1) at the mobile device (2), sending the second data message (DN2), receiving the second data message (DN2) at the field device (1), storing the reception time of the second data message (DN2) at the field device (1) by the processing unit (10), determining the signal propagation time based on the transmission time and reception time, and determining the distance between the field device (1) and the mobile device (2) based on the signal propagation time.

9. A system (100) comprising: - Field device (1) with a first wireless interface (30); - A mobile device (2) with a second wireless interface (40). The internal power limit is stored in the field device (1). The system (100) is adapted to perform the method according to any one of the preceding claims.

10. The system (100) according to claim 9, wherein, Both the first wireless interface (30) and the second wireless interface (40) are Bluetooth interfaces, preferably Bluetooth Low Energy interfaces.

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