WO2023187206A1

WO2023187206A1 - Transmission power management

Info

Publication number: WO2023187206A1
Application number: PCT/EP2023/058581
Authority: WO
Inventors: Maria Rita PALATTELLA; Sebastian BARILLARO
Original assignee: Luxembourg Institute Of Science And Technology (List)
Priority date: 2022-04-02
Filing date: 2023-03-31
Publication date: 2023-10-05
Also published as: LU501777B1

Abstract

The proposed invention provides the possibility to reduce energy consumption during data transmission from an end terminal to a gateway node in a Low-Power Wide-Area data communication network. The proposed device decides dynamically and based on working conditions which transmission parameters to use for communicating with the backbone network, without the need of first consuming energy to receive a corresponding parameter adaptation request from the backbone network.

Description

TRANSMISSION POWER MANAGEMENT

Technical field

The invention lies in the field of Low-Power Wide-Area data communication networks. In particular, the invention relates to transmission power management in end devices participating in a nonce llular Low -Power Wide-Area data communication network.

Background of the invention

A Low-Power Wide-Area Network, LPWAN, is a type of wireless telecommunication wide area network designed to allow long-range communications at a low bit rate between connected objects, such as sensors operated on a battery.

In the context of environmental monitoring and pollution detection , it has been proposed to use connected sensing devices that enable in-situ measurements and observation, rather than relying on remote sensing via satellite observations. For example, floating buoys may be used to collect data for detecting microplastics in open sea water. A sensing device needs to transmit the collected data to a communication backbone, which is used for collecting and evaluating the data from a plurality of connected sensors, among other activities. Such a sensing device needs to be able to transmit data to the communication backbone without wasting power. Indeed, power is a scarce resource because the only electricity that is available once the sensor device is deployed typically comes from an on-board battery.

In such specific applications, but also in the general context of Intemet-of-Things, loT, networks, careful use of available power is important, in particular in consideration of the carbon footprint that is left when power is generated.

One known LPWAN technology is Long-Range-Wide Area Network technology, LoRaWAN™. This technology allows to cover transmission distance beyond 10 km, and may be implemented in devices that have low production costs.

The LoRa™ specification defines the PHY layer used in LoRaWAN and uses a proprietary spreadspectrum modulation technique that offers a trade-off between sensitivity and data rate, while operating in a fixed-bandwidth channel of either 125 KHz or 500 KHz (for uplink channels), and 500 KHz (for downlink channels). Additionally, LoRa uses orthogonal spreading factors. This allows the network to preserve the battery life of connected end devices by making adaptive optimizations of an individual end node’s power levels and data rates. A higher spreading factor provides increased processing gain, and higher reception sensitivity, although the data rate will, necessarily, be lower. The spreading factor controls the chirp (symbol) rate, and thus controls the speed of data transmission. Lower spreading factors mean faster chirps and therefore a higher data transmission rate. For every increase in spreading factor, the chirp sweep rate is halved, and so the data transmission rate is halved. Lower spreading factors reduce the range of LoRa transmissions, because they reduce the processing gain and increase the bit rate. Changing spreading factor allows to increase or decrease data rate for an end device. Higher spreading factors provide higher receiver sensitivity.

Within the LoRa specification, a system for choosing the fastest signal modulation mode, which translates to a reduced energy consumption, called Adaptative Data Rate, ADR, is provided. It is based on the monitoring of the strength of the signal received by one or more gateways (radio base station) from an end device, such as a deployed sensing device, belonging to the same network. While the ADR algorithm is implemented on the static end device, a server withing the backbone communication network needs to monitor the deliveries of several transmissions and needs to decide whether the static end device should adapt its data rate, and instruct it to do so. In a scenario involving moving end devices, this approach is ill-suited as it would involve the repeated transmission of instructions to the end node, due to dynamically changing channel conditions. The system is thus merely reactive in the sense that transmissions using and wasting too much power must first occur before the backbone communication network notifies the correspondingly transmitting end node to adapt its data rate. The reception of this notification itself also uses up scarce power at the end node before it can adapt its transmission rate and operate at a reduced power consumption.

Technical problem to be solved

It is an objective of the invention to present a data processing method which overcomes at least some of the disadvantages of the prior art.

Summary of the invention

In accordance with a first aspect of the invention a data transmission device is provided. The data transmission device comprises data transmission means for transmitting data in a non-cellular low- power wide area communication network and power management means.

The data transmission device further comprises a first memory element in which position data of a plurality of known potential receiving nodes are stored; a second memory element in which, for each of said known potential receiving nodes, and for a plurality of predetermined distances to each known potential receiving node, at least one data transmission parameter set is stored, wherein each data transmission parameter set is associated with a corresponding energy cost. The data transmission device further comprises distance estimation means for estimating distances between the data transmission device and the known potential receiving nodes.

The power management means are configured to select a destination node from the known potential receiving nodes and a corresponding data transmission parameter set for an upcoming data transmission. The selection of the destination node is based on an estimated distance between the data transmission device and the known potential receiving nodes, and the data transmission parameter set having the lowest associated energy cost for covering the estimated distance to said selected destination node is selected.

The second memory element may comprise, for a plurality of predetermined distances to any of the potential receiving nodes, at least one data transmission parameter set.

Preferably, the distance estimation means may comprise position estimation means configured to estimate a position of the data transmission device, and the distance estimation means may further be configured to compute distances between said estimated position and the positions of the known potential receiving nodes.

The position estimation means may preferably comprise a global navigation satellite system, GNSS, receiver.

Preferably, the data transmission parameters may comprise a transmission power and a spreading factor.

According to a second aspect of the invention, a buoy comprising at least one sensor for collecting data and a data transmission device for transmitting collected data to at least one potential receiving node in a non-cellular low-power wide area communication network is provided. The buoy is remarkable in that said data transmission device is a device in accordance with an aspect of the invention.

The buoy may preferably comprise means for harvesting solar energy or wave energy and for storing said energy in a battery.

In accordance with another aspect of the invention, a non-cellular low power wide area communication network is provided, which comprises a plurality of potential receiving nodes having known positions and at least one mobile data transmission device according to an aspect of the invention. The non-cellular low power wide area communication network may preferably comprise a buoy in accordance with aspects of the invention.

According to a further aspect of the invention, a power management method for a data transmission device in a non-cellular low-power wide area communication network is provided. The method comprises the steps of: providing position data of a plurality of known potential receiving nodes in a first memory element of said data transmission device; providing, for each of said known potential receiving nodes, and for a plurality of predetermined distances to each known potential receiving node, data transmission parameter sets in a second memory element, wherein each data transmission parameter set is associated with a corresponding energy cost; estimating a distance between the data transmission device and the known potential receiving nodes using distance estimation means; selecting, using power management means, a destination node from the known potential receiving nodes and a corresponding data transmission parameter set for an upcoming data transmission, wherein the selection of the destination node is based on the estimated distance between the data transmission device and the known potential receiving nodes, and wherein data transmission parameter set having the lowest associated energy cost for covering the estimated distance to said selected destination node is selected scheduling a data transmission from the data transmission device to said destination node using said selected data transmission parameter set.

Preferably, the step of distance estimation may comprise estimating a position of the data transmission device using position estimation means, and computing distances between said estimated position and the respective positions of the known potential receiving nodes using said distance estimation means.

The selection of the transmission parameter set may preferably comprise selecting the set that has the lowest associated energy cost for the predetermined distance that is closest to said computed distance.

Preferably, the method may comprise a preliminary step of determining data transmission sets and measuring corresponding energy costs from a plurality of predetermined positions to each of said potential receiving nodes. Preferably the determined data transmission sets may be stored in a memory element of a data transmission device. The data transmission may preferably be scheduled subject to sufficient energy being available in a battery of said data transmission device, for covering said energy cost.

According to yet another aspect of the invention, a computer program comprising computer readable code means is provided, which, when run on a computer system, causes the computer system to carry out the method according to aspects of the invention.

In accordance with a final aspect of the invention, a computer program product comprising a computer readable medium on which the computer program according to an aspect of the invention is stored.

The proposed invention provides the possibility to reduce energy consumption during data transmission from an end terminal to a gateway node in a Low -Power Wide-Area data communication networks. The proposed device decides which transmission parameters to use for communicating with the backbone network, without the need of first consuming energy to receive a corresponding parameter adaptation request from the backbone network. Therefore, by using the method and device in accordance with aspects of the invention the wasting of energy of unnecessary over-powerful transmissions is reduced. It helps to decrease the waste of energy by reducing both the duration and the power of the transmission on those cases where it is possible to do so, while not degrading the quality of the communication. This is achieved by relying on calibration data providing the best combination of modulation speed (i.e., Spreading Factor, that impacts the duration of the transmission) and the transmission power needed by the end device to reach the closest well-known gateway node.

The proposed method relies on the knowledge of the location of the base stations (i.e., gateway nodes) and the awareness of its own location. All this information is used by the end device to calculate what is the closest radio base station, what is the range needed to reach it, and how powerful the transmission must be to overpass the attenuation of the signal due to the distance between them. If the amount of energy available at the time of the transmission is not sufficient for reaching a radio base station, the transmission is postponed to a later time when conditions become less demanding in terms of energy requirements or when the energy available will have become sufficient to satisfy the demand, by harvesting more energy from the environment. The locations of base stations are predetermined and fixed at the time of deployment. The end device is able to learn its own changing location by position estimation means, such as a GNSS sensor included on the end device architecture. The relative distance between the end device and the radio base stations is calculated based updated information.

On open sea, where the chances of having line of sight between an end device located in a floating buoy and a gateway node located on the short are high, there is almost no construction or natural body that might interfere with the transmission. The distance between the floating device and the radio base station becomes one of the most relevant factors that affects the performance of a transmission. As the method in accordance with aspects of the invention is designed to optimize the energy efficiency of a floating device harvesting energy, for example from wave movements, it is reasonable to rely on the distance to improve the efficiency of the transmission.

The proposed communication network may be applied in many different applications, including in the context of marine monitoring and plastic detection, animals tracking, or tracking of rescue teams in the disaster area. In all these scenarios, the end devices are moving without following specific trajectories. Saving energy and ensuring the reliability of the system for a long time is of foremost importance, given the harsh working environment.

Brief description of the drawings

Several embodiments of the present invention are illustrated by way of figures, which do not limit the scope of the invention, wherein: figure 1 provides a schematic illustration of a communication network including a data transmission device in accordance with a preferred embodiment of the invention; figure 2 provide a schematic illustration of a communication network including a data transmission device in accordance with a preferred embodiment of the invention; figure 3 provide a schematic illustration of a communication network including a buoy in accordance with a preferred embodiment of the invention; figure 4 provides a workflow diagram showing the main steps of a method in accordance with a preferred embodiment of the invention.

Detailed description of the invention

This section describes features of the invention in further detail based on preferred embodiments and on the figures, without limiting the invention to the described embodiments. Unless otherwise stated, features described in the context of a specific embodiment may be combined with additional features of other described embodiments. Similar reference numerals are used to denote the same concept across different embodiments of the invention. For example, reference numerals 100, 200 denote a data transmission device in accordance with the invention, according to two different embodiments thereof. The description puts focus on those aspects that are relevant for understanding the invention. It will be clear to the skilled person that a data transmission device also comprises other commonly known aspects, such as antennas, an appropriately dimensioned power supply, or mechanical holding means for holding the various elements of the device in their respectively required positions, even if those aspects are not explicitly mentioned.

Figure 1 illustrates a data transmission device 100 according to preferred embodiment of the invention. The data transmission device 100 is typically an end device, such as a connected loT object or a sensing device, in a non-cellular Low-Power Wide-Area data communication network 1000. It is capable of transmitting data to base stations, or equivalently gateway nodes 10, 20, 30 of said data communication network.

The data transmission device 100 comprises data transmission means 110 for transmitting data in the non-cellular low-power wide area communication network 1000. The data transmission means 110 are for example implemented by a known modem device having modulation and coding capabilities, at least one transmission antenna and a preconfigured circuitry or microprocessor that is capable of accessing the communication network’s carrier channels, for transmitting a data payload thereon. Optionally, data reception is also possible. The specific functioning of such a modem device is as such known in the art and it will therefore not be explained to further detail in the context of the present invention.

The data transmission device 100 further comprises power management means 120 that are either implemented by an electronic circuit, or by a data processor configured to carry out a power management method. The data processor may either comprise a programmable processing unit that is configured through appropriately formulated software code instructions stored in a memory element to which the processing unit has a read access, or it may comprise an application specific integrated circuit implementing the power management method. The power management means 120 are operatively connected to the data transmission means 110 and to at least one memory element. The memory element may comprise a random-access memory, RAM, module, or a solid-state drive, SSD, allowing it to operate in a stand-alone device where maintenance is generally not possible. The different components of the device are for example connected using a data transmission bus. Two memory elements 130, 140 may be logically structured onboard of a single memory chip. Alternatively, two distinct memory chips may be used to implement memory elements 130 and 140 respectively. The first memory element 130 comprises position data of a plurality of known gateway nodes 10, 20, 30 of the communication network 1000. Three such gateway nodes are illustrated for the sake of illustration, although it will be understood that a real-world deployment may comprises a much larger plurality of gateway nodes. Position data, preferably comprising absolute geographical coordinates, of each gateway nodes 10, 20, 30 is pre-stored in the first memory element during the assembly of the data transmission device 100. Each of the gateway nodes 10, 20, 30 is a potential receiving node for a data transmission originating at the data transmission device 100.

The second memory element 140 stores, for each of said known gateway nodes 10, 20, 30 and for a plurality of predetermined distances between the data transmission device 100 and each known gateway node, at least one data transmission parameter set M. A parameter set comprises, in the example of LoRa, a spreading factor and a transmission power, without being limited to these examples. All parameters that define a specific transmission configuration may be used. Each transmission mode, and therefore each data transmission parameter set M has an associated energy cost E, typically expressed in Watt. The data comprised in the second memory element reflects real- world transmission scenarios between the transmission device 100 and any of the available gateway nodes 10, 20, 30. This calibration data may for example be obtained prior to the production of corresponding transmission device, during a data gathering campaign. A test data transmission device is deployed successively at a plurality of locations, implying different distances to each of the available gateway nodes. During a test data transmission from a given location, all available transmission parameter sets are successively used for transmitting data to each of the gateway nodes 10, 20, 30 that are within transmission range, and the corresponding energy cost is recorded. The tighter the grid of test locations, the more accurate the sampling of this calibration data, which will be made available to the power management means 120 will be.

The data transmission device further comprises distance estimation means 150 for estimating distances D(10), D(20), D(30) between the data transmission device and the known potential receiving nodes 10, 20 30 when it is deployed and operational. By way of a non-limiting example, the data transmission device may comprise an internal clock that is precisely synchronized with the network. In that case, the distance estimation means 150 may be implemented by a data processor capable to calculate the relative distance to a gateway node, by measuring the propagation time that a data transmission (for example a periodically broadcast beacon signal) originating at said gateway node, takes before being received by data transmission device. Alternatively, the distance estimation means 150 may comprise receiver units for receiving signals from other communication networks having fixed infrastructure nodes at positions that are known at the data transmission device 100. These may include cellular data receiver units or WiFi receiver units. WiFi access point and cellular radio base stations send signals periodically. The recognition of these signals is then used at the data transmission device to estimate its own location and to then calculate the distances D(10), D(20), D(30) separating itself from the gateway nodes 10, 20, 30 respectively. While the data in the second memory element 140 may be structured in many different ways without departing from the scope of the present invention, including in the form of a structured database, Table I provides an example of the stored content. For each available gateway (GW), and for an estimated distance (D) between the data transmission device 100 and the gateway, an energy cost (E) is associated with a corresponding set of transmission parameters (M). By way of example, if the estimated distance D(20) to node 20 is the smallest among the estimated distances to each of the gateway nodes, then node 20 is chosen as a destination node. Among the available transmission parameters sets for node 20, the transmission parameter set that is associated with the lowest energy cost is then selected for the data transmission to the selected destination node. So, if D(20) is equal to D 1 or closer to D 1 than to any other distance recorded in the table for gateway node 20, and if the energy cost E6 is the lowest among the energy costs recorded for gateway node 20 at a distance DI, then the chosen transmission parameter set will be the set M2.

Table I

The selection of the destination node is based on an estimated distance D(10), D(20), D(30) between the data transmission device 100 and the position of the known potential receiving nodes 10, 20, 30, wherein typically the closest node is chosen as the destination node. The selection of the data transmission parameter set implies choosing the set that has the lowest associated energy cost for covering the estimated distance to said selected destination node.

The example provided in Table I implies that each of the available gateway nodes 10, 20, 30 have potentially different transmission and reception features, for example due to having different antenna configurations or due to static impediments on the propagation path from the data transmission device to any specific gateway node. Therefore, for a given estimated distance DI to gateway 10, the preferred transmission parameters may be different from the preferred transmission parameters associated with gateway 20 at the same distance D 1. If all or a subset of the gateway nodes can be considered to have similar characteristics, the corresponding data in the second memory element 140 may be grouped together for these similar gateway nodes, thereby using less storage space. If all gateway nodes are considered of have similar characteristics, the data provided in the memory element 140 will not depend on the gateways 10, 20, 30, but it will be the same for any of these gateways. The power management means will in such a case select the closest gateway as the destination node, and the corresponding transmission parameter set M having the least energy cost E is selected for the corresponding distance.

Figure 2 illustrates a data transmission device 200 according to another preferred embodiment of the invention. Unless otherwise states, the features described for the previous embodiment remain the same. The data transmission device 200 is typically an end device, such as a connected loT object or a sensing device, in a non-cellular Low-Power Wide-Area data communication network 2000. It is capable of transmitting data to base stations, or equivalently gateway nodes 10, 20, 30 of said data communication network.

The data transmission device 200 comprises data transmission means 210 for transmitting data in a the non-cellular low-power wide area communication network 2000. The data transmission device 200 further comprises power management means 220 that are either implemented by an electronic circuit, or by a data processor configured to carry out a power management method. The power management means 220 are operatively connected to the data transmission means 210 and to at least one memory element. Two memory elements 230, 240 may be logically structured onboard of a single memory chip. Alternatively, two distinct memory chips may be used to implement memory elements 230 and 240 respectively. The first memory element 230 comprises position data of a plurality of known gateway nodes 10, 20, 30 of the communication network 2000. Each of the gateway nodes 10, 20, 30 is a potential receiving nodes for a data transmission originating at the data transmission device 200.

The second memory element 240 stores, for each of said known gateway nodes 10, 20, 30 and for a plurality of predetermined distances between the data transmission device 200 and each known gateway node, at least one data transmission parameter set M. Each transmission mode, and therefore each data transmission parameter set M has an associated energy cost E, typically expressed in Watt. The calibration data comprised in the second memory element reflects real-world transmission scenarios between the transmission device 200 and any of the available gateway nodes 10, 20, 30, as explained in the context of the previous embodiment.

In order to select the appropriate destination node and transmission parameter set, which use the least energy, the power management means 220 rely on an estimation of the distance to each of the known gateway nodes 10, 20, 30. The distance estimation means 250 comprise a receiver unit 252 for receiving signals from a Global Navigation Satellite System, GNSS, 01 such as the GPS, the Galileo satellite constellation, other satellite constellations or equivalently High Altitude Platforms, HAPs implementing similar signaling. As is known in the art, the reception of these signals allows the receiver unit to estimate its own absolute position in terms of geographical coordinates. Based on this information, the distance estimation means 250 then computed the distances D(10), D(20), D(30) separating itself from the gateway nodes 10, 20, 30 respectively, by relying on the position data stored in the first memory element 230. This setup is easy to deploy and requires no data transmission from the data transmission device 200 itself, while providing high accuracy position data.

Figure 3 illustrates buoy 300. As shown, the buoy is a floating device, designed for sensing data in the ocean. Typically, it comprises a watertight floating enclosure that houses several components, comprising but not limited to a power supply such as a rechargeable battery, sensing means 310 such as a camera sensor for collecting images, a data processor 320 for analyzing and/or compressing sensed data, and a data transmission device 100, 200 as described in the previous embodiments. The data transmission device 100, 200 is thus configured to transmit collected data to one of a plurality of known gateway nodes 10, 20, 30 of the non-cellular Low-Power Wide-Area data communication network, installed on the shoreline in known predetermined positions. Preferably, the buoy 300 may comprises means for harvesting either wind energy, solar energy through solar panels, or kinetic wave energy, for example by using an integrated pendulum system. The harvested energy is fed into the rechargeable battery and made available for future data transmission. By using energy harvesting on the one hand, and data transmission minimizing energy consumption as proposed by the invention on the other hand, the autonomy of the floating and position-changing device is increased as compared to known architecture, without sacrificing the ability to collect sensed data.

The outlined architecture may preferably be implemented using LoRaWAN technology, without being limited thereto. LoRa is asymmetric by design and puts most of the effort needed for the communication on the network side. This allows keeping the energy consumption of the end device (the data transmission device 100, 200) very low, resulting in an energy-efficient technology. Consequently, several network components are needed on the network side to perform a successful communication. A typical LoRaWAN network architecture comprises several end devices ( the data transmission device 100, 200), several LoRa gateways (the available nodes 10, 20, 30) and a LoRaWAN Network Server, LNS, and several LoRaWAN Application Servers. As previously described, LoRaWAN gateways 10, 20, 30 are deployed along the coast. For each of them, a LoRa Gateway transceiver connected to a high gain antenna is placed preferably at high altitude on the shore, along the coast to receive the signals from the buoy 300. The best location to place this device 10, 20, 30 is on the shore, along the coast at high altitude (for instance over a wind turbine), near the area where the buoy would be floating. The LoRa Gateway 10, 20, 30 must be constantly powered, either with a power grid or with other mechanisms that provide uninterrupted power supply, like a photovoltaic solar panel with batteries. The LoRa Gateway 10, 20, 30 receives messages agnostically from any LoRa device 100, 200 within its coverage range. All the messages received are forwarded to the LoRaWAN Network Server, LNS, using a regular IP network as backhaul. This is most of the times implemented on 3G/4G, WiFi, or Ethernet. The backhaul may be implemented locally within the same device (on which both the gateway and the LNS are implemented). The LoRa Gateway Lorix ONE may for example be used as an inexpensive outdoor energy-efficient device. Alternatively, Raspberry Pi based gateway demonstrated to be more flexible and capable of integrating all the components in the same device. This comes at the cost of a higher energy consumption, compared to the LoRix ONE.

All the messages captured by the LoRa Gateways are forwarded (locally or remotely) to the LoRaWAN Network Server, LNS, which is the network operator of the architecture. This submodule decrypts the messages received, discards duplicates and aliens’ messages, acknowledges those message that require it, and finally passes the information received to the Application Server. There are many LNS available. Among them one may for example use ChirpStack, which is largely adopted by the LoRaWAN community, and which is able to meet the requirements of the proposed communication system.

The LoRaWAN Application Server is responsible of storing and displaying the data received. Like the LNS, the Application Server is usually installed in a different computer, in the Cloud, or any other remote system. However, the Application Server may be installed in the same Outdoor Portable Monitoring device. The Application Server stores the information received using a database. Time-series based databases demonstrated to be suitable for Wireless Sensor Data.

Another piece of the software is responsible for operating the post-processing of the data stored (data analytics), and for the representation/visualization of the data. Chronograph - part of the InfluxDB time series platform - is in charge of those tasks. It is worth mentioning that InfluxDB (including Chronograph) has the benefit of not only being lightweight, well adopted by the community, but also (and especially) it can work offline, without the need of Internet connectivity. In remote coastal marine area, it may be the case Internet connectivity is not available.

Figure 4 illustrates the main steps of the proposed power management method for a data transmission device in a non-cellular low-power wide area communication network, in accordance with a preferred embodiment of the invention.

At a first step i), position data of a plurality of known potential receiving nodes is provided in a first memory element of the data transmission device in accordance with embodiment of the invention. At step ii), for each of said known potential receiving nodes, and for a plurality of predetermined distances to each known potential receiving node, data transmission parameter sets are provided in a second memory element, wherein each data transmission parameter set is associated with a corresponding energy cost.

At step iii), a distance between the data transmission device and the known potential receiving nodes is estimated using distance estimation means.

At step iv), using power management means, a destination node is selected from the known potential receiving nodes and a corresponding data transmission parameter set is selected for an upcoming data transmission. The selection of the destination node is based on the estimated distance between the data transmission device and the known potential receiving nodes. The data transmission parameter set having the lowest associated energy cost for covering the estimated distance to said selected destination node is selected.

Finally, at step v), a data transmission from the data transmission device to said destination node is using said selected data transmission parameter set is scheduled, preferably subject to sufficient energy being available in an energy storage device of the data transmission device.

Using the provided description and figures, a person with ordinary skills in computer programming will be able to implement the described methods in various embodiments without undue burden and without exercising additional inventive skill.

It should be understood that the detailed description of specific preferred embodiments is given by way of illustration only, since various changes and modifications within the scope of the invention will be apparent to the skilled person. The scope of protection is defined by the following set of claims.

Claims

1. A data transmission device (100, 200) comprising data transmission means ( 110, 210) for transmitting data in a non-cellular low-power wide area communication network and power management means (120, 120), characterized in that the data transmission device further comprises a first memory element (130, 230) in which position data of a plurality of known potential receiving nodes (10, 20, 30) are stored; a second memory element (140, 240) in which, for each of said known potential receiving nodes (10, 20, 30), and for a plurality of predetermined distances (D) to each known potential receiving node, at least one data transmission parameter set (M) is stored, wherein each data transmission parameter set (M) comprises a transmission power and a spreading factor and is associated with a corresponding energy cost (E); distance estimation means (150) for estimating distances (D(10), D(20), D(30)) between the data transmission device and the known potential receiving nodes (10, 20 30); and wherein said power management means (120, 220) are configured to select a destination node from the known potential receiving nodes (10, 20, 30) and a corresponding data transmission parameter set (M) for an upcoming data transmission, wherein the selection of the destination node is based on an estimated distance (D(10), D(20), D(30)) between the data transmission device (100, 200) and the known potential receiving nodes (10, 20, 30), and wherein the data transmission parameter set (M) having the lowest associated energy cost (E) for covering the estimated distance to said selected destination node is selected.

2. The data transmission device (200) according to claim 1, wherein the distance estimation means (250) comprise position estimation means (252) configured to estimate a position of the data transmission device (200), and wherein the distance estimation (250) means are further configured to compute distances (D(10), D(20), D(30)) between said estimated position and the positions of the known potential receiving nodes (10, 20, 30).

3. The data transmission device (200) according to claim 2, wherein said position estimation means (252) comprise a global navigation satellite system, GNSS, receiver.

4. A buoy (300) comprising at least one sensor (310) for collecting data and a data transmission device (100, 200) for transmitting collected data to at least one potential receiving node (10, 20, 30) in a non-cellular low-power wide area communication network, characterized in that said data transmission device (100, 200) is a device in accordance with any of claims 1 to 3. The buoy (300) in accordance with claim 4, further comprising means for harvesting solar energy or wave energy (320) and storing said energy in a battery. A non-cellular low power wide area communication network (1000, 2000, 3000) comprising a plurality of potential receiving nodes (10, 20, 30) having known positions and at least one mobile data transmission device (100, 200) according to any of claims 1 to 3. The non-cellular low power wide area communication network (3000) according to claim 7, comprising a buoy (300) in accordance with any of claims 4 or 5. A power management method for a data transmission device in a non-cellular low-power wide area communication network, comprising the steps of: i) providing position data of a plurality of known potential receiving nodes in a first memory element of said data transmission device; ii) providing, for each of said known potential receiving nodes, and for a plurality of predetermined distances to each known potential receiving node, data transmission parameter sets in a second memory element, wherein each data transmission parameter set comprises a transmission power and a spreading factor and is associated with a corresponding energy cost; iii) estimating a distance between the data transmission device and the known potential receiving nodes using distance estimation means; iv) selecting, using power management means, a destination node from the known potential receiving nodes and a corresponding data transmission parameter set for an upcoming data transmission, wherein the selection of the destination node is based on the estimated distance between the data transmission device and the known potential receiving nodes, and wherein the data transmission parameter set having the lowest associated energy cost for covering the estimated distance to said selected destination node is selected v) scheduling a data transmission from the data transmission device to said destination node using said selected data transmission parameter sets. The power management method according to claim 8, wherein the distance estimation comprises estimating a position of the data transmission device using position estimation means, and computing distances between said estimated position and the respective positions of the known potential receiving nodes using said distance estimation means. The power management method according to any of claims 8 or 9, wherein the selection of the transmission parameter set comprises selecting the set that has the lowest associated energy cost for the predetermined distance that is closest to said computed distance. The power management method according to any of claims 8 to 10, comprising the preliminary step of determining data transmission parameter sets and measuring corresponding energy costs from a plurality of predetermined positions to each of said potential receiving nodes. The power management method according to any of claims 8 to 11, wherein the data transmission is scheduled subject to sufficient energy being available in a battery of said data transmission device, for covering said energy cost. A computer program comprising computer readable code means, which, when run on a computer system, causes the computer system to carry out the method according to any of claims 8 to 12. A computer program product comprising a computer readable medium on which the computer program according to claim 13 is stored.