Method for adapting the transmission interval of a (sensor) node (FN friend node) in a low-energy mesh network (LPN mesh network)

Abstract

Method for adjusting the transmission interval of a (sensor) node (FN friend node) in a low-energy mesh network (LPN mesh network) wherein the (sensor) node in an initial configuration with a first measurement frequency F1 acquires measured values ​​and after each first interval time T1>=1 / F1 transmits a data packet with one or more measured values ​​to a neighboring low power node (LPN) of the network and the low-energy node periodically enters a sleep mode for a duration T2 and during this period T2 cannot receive or send data packets and therefore does not acknowledge the receipt of the data packets that arrive during the period T2, where the sensor node writes the measured values ​​of the unacknowledged data packets into a buffer, characterized in that the (sensor) node detects the exceeding of a set buffer utilization and increases the transmission interval T1.

Description

[0001] The invention relates to a method for adjusting the transmission interval of a (sensor) node (FN friend node) in a low-energy mesh network (LPN mesh network) according to claim 1.

[0002] In Bluetooth, a mesh network means that every node within range communicates with every other node, and therefore data packets are sent multiple times. This is what is usually understood by the term "mesh network." Furthermore, there are also mesh networks with fixed routes (e.g., Wirepas), where each node can receive data from multiple nodes and forward it to only one other node. The topology is similar to a root structure.

[0003] In a low-energy mesh network, there are (sensor) nodes of different categories. There are autonomous, battery-powered nodes and grid-connected nodes. Sending data packets in the mesh network consumes a relatively large amount of energy. This poses no problem for a node with an external power supply. However, for autonomous, battery-powered nodes, this can lead to rapid battery drain.

[0004] An autonomous, battery-powered node regularly enters sleep mode for a duration T2. ​​Afterwards, the node becomes active again. During the active time AZ, the node can forward data packets, provided it has received any. The duration T2 can be set to, for example, 8 seconds. After the active time AZ (AZ = 2 seconds), the node returns to sleep mode.

[0005] A mains-powered sensor node, for example, records a measurement every 100 milliseconds; the transmission interval is correspondingly short. This measurement is forwarded in a data packet directly or via the mesh network to a receiver (gateway).

[0006] When routing data over the mesh network, each node on the routing path must therefore receive and forward a data packet every 100 msec.

[0007] If an autonomous, battery-powered node is located along the routing path, its battery would be depleted relatively quickly (within days or hours, or within a small fraction of its planned lifespan). In certain applications (examples), a lifespan of several years is required. If the node's battery is neither replaceable nor rechargeable, the entire node must be replaced. If the battery is replaceable or rechargeable, this results in maintenance costs.

[0008] When commissioning such a network, it is not immediately clear what data transmission rate each node should operate at.

[0009] Since a mains-powered node has no knowledge of whether its neighboring node is battery-powered or not, it will attempt to transmit its measurements as quickly as possible (short transmission interval). This leads to problems if the neighboring node is battery-powered, because the battery-powered sensor, for example, needs to transmit a data packet every T1 + AZ = 10 seconds.

[0010] If the neighboring node does not transmit a data packet, the sender of the data packet does not receive an acknowledgment.

[0011] Mesh networks are used wherever data is exchanged at many different points and the necessary cabling would be complex and / or expensive. For example, if several (e.g., >50) different and time-insensitive sensor data points need to be collected in an industrial setting, a wireless mesh network is recommended. Battery-powered and mains-powered sensors can be connected to a mesh network, which leads to the problem described earlier.

[0012] One possibility is that a low-power node is no longer allowed to route data and therefore can only send data but not receive it. This negates the advantage of a mesh network that large areas can be covered with few gateways / nodes and a short transmission range.

[0013] Another possibility is to set up separate networks for low-power nodes and for grid-connected nodes, which then reduces the number of nodes per network and again eliminates the advantage of large area coverage.

[0014] Even if a neighboring node shares its power status (low power or mains powered) as information, all nodes in the route before the low-power node would need to receive this information. Since mesh networks are designed and implemented for many thousands of nodes, this can lead to a very high data flow, which in turn negatively impacts battery life.

[0015] DE 11 2012 004 936 B4 discloses a method for forwarding at least one data packet in a wireless sensor network. DE 10 2007 055 195 A1 and EP 2 252 110 A1 disclose a method for operating a radio network.

[0016] The object of the invention is to adjust the transmission interval of a sensor node without data exchange between the nodes in order to reduce the energy consumption of a neighboring battery-powered node.

[0017] This problem is solved by the method specified in claim 1.

[0018] The key idea of ​​the invention is that the battery operation of the neighboring node is detected first. This allows the first node to change its transmission interval, and subsequently the node transmitting to it, and so on. This way, all nodes in the routing path upstream of the battery-powered sensor node change their transmission interval without the battery-powered sensor consuming any energy. If only one node were to change its transmission interval, it would be of little use if the preceding node in the routing path is constantly transmitting data. Therefore, the transmission interval of all nodes in the routing path upstream of the battery-powered sensor is automatically adjusted, as their buffers are also being filled.

[0019] Detection is achieved by writing the measurement values ​​of the unacknowledged data packets into a buffer and inferring the battery status of the neighboring node from the number of buffer values. This allows the transmission interval to be increased, thus conserving the battery of the neighboring node.

[0020] The invention is described in more detail below using an exemplary embodiment.

[0021] Fig. Figure 1 shows an LPN mesh network with multiple nodes and two data receivers (gateway), namely a smartphone and a tablet. • In mesh networks for low power communication (e.g. BLE mesh or wirepas), the devices send messages at the set transmission interval. • This works well if all devices in the mesh network are of the same device class (e.g. R, F or P) • If you have different device classes (e.g., battery-powered, short transmission interval, mains connection, long interval), these must be defined and characterized so that, for example, the LPNs only transmit and do not forward messages from other devices.

[0022] Fig. Figure 2 shows a concrete network with different nodes of different categories, which illustrates the invention in more detail.

[0023] Battery-powered sensors (data path 1 in) can be used. Fig. ) nevertheless transmit data from mains-powered sensors, but in this case the mains-powered sensors must automatically adjust their transmission interval to the transmission interval of the battery-powered sensor, or to a transmission interval that guarantees the expected lifespan of the battery-powered sensor.

[0024] The mains-powered sensor has a transmission interval of, for example, 1 second, while the battery-powered one has a transmission interval of 1 hour.

[0025] Since the mains-powered sensor writes its data to the buffer, and this buffer fills up because the data cannot be transferred to a sleep-activated sensor, the mains-powered sensor automatically reduces its transmission intervals. The new transmission interval can be determined by the sensor measuring the time between "internal sending buffer is filling" and "buffer gets empty." This calculation of the optimal transmission interval can also be performed periodically, once per day, and the transmission interval adjusted accordingly.

[0026] The transmission interval of the sensor node is either changed to a set interval or the sensor measures the time between filling and emptying the buffer and adjusts the interval accordingly.

[0027] In addition, a test function can be integrated into the (sensor) node, which sends test data during execution and thus determines the time between filling and emptying the buffer for testing purposes.

[0028] Alternatively, the prioritization of the low-energy node can be changed to send data packets via other data paths (if available).

[0029] Fig. Figure 3 shows a mesh network. A specific network (e.g., Wirepas) communicates only via the solid lines. The dashed lines represent other possible connections, which would then replace the existing one. Bluetooth would communicate simultaneously via both solid and dashed lines, thus increasing network traffic.

Claims

[1] Method for adjusting the transmission interval of a (sensor) node (FN friend node) in a low-energy mesh network (LPN mesh network) wherein the (sensor) node in an initial configuration with a first measurement frequency F1 acquires measured values ​​and after each first interval time T1>=1 / F1 transmits a data packet with one or more measured values ​​to a neighboring low power node (LPN) of the network and the low-energy node periodically enters a sleep mode for a duration T2 and during this period T2 cannot receive or send data packets and therefore does not acknowledge the receipt of the data packets that arrive during the period T2, where the sensor node writes the measured values ​​of the unacknowledged data packets into a buffer, characterized by , that the (sensor) node detects the exceeding of a set buffer load and increases the transmission interval T1.

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