Arrangement and method for optimizing the transmission of digital data in two-wire communication networks

Abstract

Two-wire communication network (KNW1 - KNW4) with two or more network nodes (NK1 - NK12), without additional repeaters or amplifiers, wherein a network node (NK1 - NK12) comprises: - a receiving device (DD) suitable for receiving signals of different data rates, wherein the receiving device (DD) is configured to determine the signal quality of received signals; - a transmitting device (SV) suitable for transmitting signals at different data rates; - a controllable termination impedance (3); wherein a network node (NK1 - NK12) is configured to transmit the detected signal quality to one or more network nodes; wherein at least one network node (NK1 - NK12) in the communication network (KNW1 - KNW4) is designed to record the detected signal qualities and the values ​​of the termination impedances (3) of the respective network nodes (NK1 - NK12); wherein at least one network node (NK1 - NK12) specifies to the other network nodes in the communication network (KNW1 - KNW4) what value they are to set as the termination impedance (3); and wherein at least one network node (NK1 - NK12) comprises means for determining which termination impedances (3) the network nodes (NK1 - NK12) should each set in order to optimize the data rate between the network nodes (NK1 - NK12) and the signal quality at the receiving devices (EV) of the network nodes (NK1 - NK12).

Description

[0001] The invention relates to a communication network with two or more network nodes, a network node in a communication network with at least two network nodes and two-wire connections, and a method for optimizing the transmission of digital data in a two-wire communication network with two or more network nodes.

[0002] Communication networks with two-wire connections (twisted-pair cables) are widely used and are employed in building automation, for example, to connect actuators and sensors within a building. In the standardized KNX Twisted Pair (KNX TP) bus system, for instance, data and the necessary operating voltage are supplied to the bus participants via a single bus line. Two-wire communication networks are used, for example, at the field level in automation, control, monitoring, measurement, and information systems.

[0003] In various applications, cost-effective communication networks (fieldbuses) with complex tree structures and large spans are required at the field level, to which many network nodes (e.g., field devices) can be connected. Simple, inexpensive two-wire cables are typically used for cabling, which do not require active components at the branch points. The frequency response of such two-wire cables shows a significant increase in attenuation depending on the cable length and frequency. This attenuation reduces the signal level and thus the transmission quality in the communication network. Therefore, common fieldbuses (e.g., KNX TP (Twisted-Pair)) can only operate at low data rates (typically 10 kbit / s with a network span of around 1000 m).

[0004] Manually setting termination impedances to reduce attenuation and reflections for the network nodes requires a high level of planning and commissioning effort and is prone to errors.

[0005] US Patent 2004 / 0124996 A1 discloses data communication devices (DCE), specifically the high-speed transmission of electronic data between data terminal equipment (DTE). The disclosure describes a method and a device for transmitting a voltage signal as a sequence of current pulses, for example, onto a communication line. The method includes converting an input voltage signal into a current signal and transmitting the resulting current pulses onto a communication line on which a predetermined bias voltage is maintained.

[0006] US patent 2006 / 0025872 A1 discloses a device, a system, and a method for transmitting safety-relevant data via an open system from a sender to a receiver. Safety-relevant components, including function blocks, flexible function blocks, resource blocks, and converter blocks, as well as safety-relevant objects, are provided.

[0007] US 2008 / 0076353 A1 discloses a cable modem with a cable transceiver that enables bidirectional broadband access to a wide area network according to a first wired communication protocol. An RF transceiver establishes bidirectional communication with a remote device over a short-range radio link. A memory module stores an application for secure access. A processing module executes this application, which reads identification data from the remote device over the short-range radio link.

[0008] US Patent 2012 / 0254475 A1 discloses devices and methods for use in conjunction with a building automation system (BAS). In one embodiment, the disclosure includes an intelligent power node consisting of a Java-enabled device and a serial communication cable, providing a seamless open protocol and an aggregation point for transmitting Internet Protocol communication. In another embodiment, the disclosure enables the energy monitoring and control of individual ports and sockets. A further embodiment describes a method for configuring and operating fieldbus devices.

[0009] WO 2010 / 032214 A2 discloses a communication network with a dynamic impedance monitoring and analysis node that has multiple data ports through which data is transmitted within the network. The impedances of external wire pairs 1, 2, etc., are monitored, and the respective termination impedances are dynamically adjusted to minimize detected distortions. Signal flatness and reflected signal drop at the end of a data packet are used by a microprocessor as indicators of impedance matching or mismatch. The network also includes a "best-route logic" for forwarding data through the node to other data ports. If the network has sufficiently redundant connections, these are linked via the "best-route logic" to a second network through which status data can be transmitted.

[0010] Japanese patent application JP2006074431A discloses a method for regulating termination circuits, e.g., impedances, in a network, which, however, requires a complex transceiver technology for sending and receiving.

[0011] The object of the present invention is therefore to provide cost-effective arrangements and methods for optimizing the transmission of digital data in two-wire communication networks.

[0012] The task is solved by a communication network with two or more network nodes, where a network node comprises: - a receiving device suitable for receiving signals of different data rates, wherein the receiving device is configured to determine the signal quality of received signals; - a transmitting device suitable for sending signals at different data rates; - a controllable termination impedance; wherein a network node is configured to transmit the detected signal quality to one or more network nodes; wherein at least one network node in the communication network is designed to record the detected signal qualities and the values ​​of the termination impedances of the respective network nodes; wherein at least one network node specifies to the other network nodes in the communication network what value they should set as their termination impedance; and where at least one network node includes means for determining which termination impedances the network nodes should set in order to optimize the data rate between the network nodes and the signal quality at the receiving devices of the network nodes. Such communication networks offer a high data transmission rate and are particularly suitable for the new Internet protocols (e.g., IPv6) without the need for additional repeaters or amplifiers. Furthermore, the communication network allows continuity, e.g., from the control level (e.g., operation and monitoring) down to the field level (e.g., to sensors).

[0013] A preferred embodiment of the invention is that the signal quality is determined by evaluating the multiple sampling of the (digital) received signal. Furthermore, the signal quality could be determined, for example, via the signal-to-noise ratio.

[0014] The adjustable termination impedance is advantageously designed to allow the line end to be terminated with a suitable impedance or left open.

[0015] The task is still solved by a network node in a communication network with at least two network nodes and two-wire connections. where the network node includes: - a receiving device suitable for receiving signals of different data rates, wherein the receiving device is configured to determine the signal quality of received signals; - a transmitting device suitable for sending signals at different data rates; - a controllable termination impedance; - a measuring unit (microchip) for determining the signal quality, which can be measured at the receiving device; - a memory for recording the values ​​of the termination impedances and the reception quality that can be assigned to each value for the network nodes in the communication network; - a control unit for specifying a setting value for the termination impedances of the network nodes; - An evaluation and calculation unit for specifying respective settings for the termination impedances of the network nodes to achieve an optimal data rate in the communication network, wherein the evaluation and calculation are based on various data rates. In building automation, the network nodes represent, for example, controllers, actuators, or sensors. For instance, firmware updates in the communication network generate very high data traffic. Communication networks with the network nodes according to the invention enable, in particular, high data traffic in the network without any loss of latency. Preferably, the values ​​of the termination impedances of all network nodes are recorded.

[0016] An advantageous embodiment of the invention lies in the fact that the communication network has a free topology. Any topology (bus, tree, etc.) can be flexibly chosen for the communication network. Furthermore, multiple communication networks with arbitrary topologies can be connected via routers.

[0017] An advantageous embodiment of the invention lies in the fact that data transmission in the communication network is carried out using baseband modulation. Data transmission using baseband modulation is particularly widespread in digital transmission systems, whereby the entire width of the transmission channel can be utilized in the signal.

[0018] An advantageous embodiment of the invention lies in the fact that data encoding in the communication network is carried out using Manchester coding. The Manchester code is self-synchronizing, independent of the DC voltage level, and a clock signal can be precisely regenerated on the receiver side; that is, the clock signal can be derived from the code itself.

[0019] An advantageous embodiment of the invention lies in the fact that the termination impedances of the network nodes are selected depending on the topology of the communication network and / or the transmission method and / or the cable length and / or the characteristic impedance. Advantageously, the selection of the termination impedances is performed automatically, based on an algorithm. The values ​​of the termination impedances of the network nodes are thus specifically determined with respect to the underlying infrastructure of the communication network. Advantageously, the value of the termination impedance is derived from the characteristic impedance of the cable.

[0020] An advantageous embodiment of the invention lies in the fact that the network nodes can be supplied with power via the communication network. This particularly reduces the cabling effort, since no separate lines need to be laid for the power supply of the participants (i.e., the network nodes).

[0021] An advantageous embodiment of the invention lies in the fact that a network node is configured to supply one or more other network nodes in the communication network with energy. This allows the communication network to be easily expanded to include additional participants without the need for additional cabling for power supply.

[0022] An advantageous embodiment of the invention lies in the fact that at least one network node is configured to determine the maximum possible data transmission rate in the communication network based on the reception quality of the network nodes. The inventive method for optimizing the transmission of digital data in a communication network can thus be carried out using the existing network infrastructure, without requiring an additional device or generating additional measurement signals.

[0023] An advantageous embodiment of the invention lies in the fact that at least one network node is configured to establish a connection to one or more further communication networks. Because a network node has router-like properties, the inventive method for optimizing the transmission of digital data across multiple connected communication networks can be carried out.

[0024] The task is also solved by a method for optimizing the transmission of digital data in a two-wire communication network, the method comprising the following steps: Step 1: Analysis of the communication network, consisting of network nodes, each with a switchable termination impedance and two-wire lines for connecting the network nodes, whereby the reception quality is determined for the network nodes by applying an initial data rate to each network node, using a defined setup (output configuration) for the termination impedances; Step 2: Using the initial data rate for each network node, determine whether the respective termination impedance needs to be switched on or off to increase the reception quality of each network node; Step 3: Analysis of the communication network, whereby the reception quality is determined for the network nodes by applying a second data rate to each network node; Step 4: Using the second data rate for each network node, determine whether the respective termination impedance needs to be switched on or off to increase reception quality;

[0025] Repeat steps 3 and 4 until no improvement in reception quality is measurable. The inventors' idea is that if a node without termination impedances exhibits undesirable effects due to reflections—i.e., if the data rate from this node to other nodes is noticeably reduced—then the data rate can be improved by selectively adding termination resistors to the communication network. These added termination impedances increase signal attenuation and are removed when the termination impedance of a neighboring node sufficiently eliminates the reflections.

[0026] It is advantageous to evaluate the reception quality of the signals received from all other network nodes for each network node.

[0027] The adjustable termination impedance is advantageously designed to allow the line end to be terminated with a suitable impedance or left open.

[0028] An advantageous embodiment of the invention lies in the fact that, during operation, it is detected whether a new network node is added to the communication network, whether an existing network node is deactivated, whether a new connection is established, or whether an existing connection is removed. This allows for a quick and flexible response to changes in the communication network.

[0029] An advantageous embodiment of the invention lies in the fact that, after a change is detected, the communication network is re-optimized with regard to reception quality and / or data rate. This ensures that, following a change in the communication network, optimal data transmission is subsequently achieved again.

[0030] An advantageous embodiment of the invention lies in the fact that in steps 3 and 4, the second data rate is determined by a stepwise increase of the initial data rate. This allows an optimal data rate to be achieved iteratively in the communication network in incremental steps. Incremental, stepwise increases in the data rate are easily implemented.

[0031] An advantageous embodiment of the invention lies in the use of an initial data rate of 50 kbit / s. With an initial data rate of 50 kbit / s as the starting point for stepwise incremental increases in the data rate, an optimal data rate in the communication network is quickly achieved. Advantageously, the initial setup (i.e., the initial configuration) of the termination impedances is determined by a prior test.

[0032] An advantageous embodiment of the invention lies in the fact that in steps 3 and 4, the second data rate is determined by a stepwise reduction of the data rate, starting from the initial data rate. Decremental, stepwise reductions of the data rate are also easily implemented.

[0033] An advantageous embodiment of the invention lies in the use of an initial data rate of 1 Mbit / s. Starting from this initial data rate of 1 Mbit / s, an optimal data rate is quickly reached in the communication network through a stepwise decremental reduction of the data rate.

[0034] An advantageous embodiment of the invention lies in the fact that in step 1 all termination impedances are either switched off or switched on. This allows a first reception quality to be determined very easily and quickly for the network nodes as a reference quality.

[0035] An advantageous embodiment of the invention lies in the fact that the value of the termination impedance is matched to the wave impedance of the network. Thus, the optimal data transmission rate can be achieved for each specific network topology in a dedicated and efficient manner.

[0036] An advantageous embodiment of the invention is that the termination impedance is in the range of 100 ohms. A termination impedance of 100 ohms, or in the range of 100 ohms (± 10%), has proven particularly advantageous for twisted-pair cables.

[0037] An advantageous embodiment of the invention lies in the fact that the value of the termination impedance is variable. This allows the value of the termination impedance to be specifically tailored to the infrastructure and topology of the communication network in order to achieve an optimal data rate.

[0038] An advantageous embodiment of the invention lies in the fact that the determination of which termination impedances must be switched on or off to improve reception quality is carried out by a mathematical optimization method (e.g., linear optimization). By using a mathematical optimization method to decide which termination impedances must be switched on or off to improve reception quality, the efficiency of the method is particularly increased.

[0039] An advantageous embodiment of the invention lies in the fact that the method is applied to each network node. This achieves an optimal data transmission rate for the entire communication network.

[0040] An advantageous embodiment of the invention lies in the fact that the method starts based on an empirical switching on or off of termination impedances for specific network nodes, dependent on the topology of the communication network. In this way, for a known wiring diagram of the communication network, a setting can be found that advantageously exhibits the lowest attenuation and reduced reflections for the desired maximum data rate. Starting from this setting, the method very efficiently achieves an optimal data transmission rate for the communication network. It is advantageous, for example, to terminate spur lines above a certain length. Spur lines are lines that branch off from a signal path.

[0041] An advantageous embodiment of the invention lies in the fact that the method runs in parallel with the data operation. This allows the communication system to operate during optimization.

[0042] The invention and advantageous embodiments of the present invention are explained with reference to the following figures. These show: Fig. 1. A first exemplary communication network for building automation, Fig. 2 the frequency response of an exemplary channel in the communication network of Fig. 1, Fig. 3 a second exemplary communication network for building automation, Fig. 4 Two exemplary communication networks that are linked together via a router, Fig. 5 a block diagram of a first exemplary network node, Fig.6 a block diagram of a second exemplary network node, Fig. 7 an exemplary flowchart for the implementation of the present invention, Fig. 8 an exemplary flowchart for a switching algorithm of termination impedances, Fig. 9 an exemplary flowchart for a switching algorithm of termination impedances, Fig. 10 an exemplary measurement table with termination resistances, and Fig. 11. A block diagram for a third example network node.

[0043] In building automation, networks are used as complex, tree-like structures with multiple nodes, numerous end devices, and varying cable lengths. The cables used are rarely true twisted pairs with correspondingly low attenuation per meter, but often only conventional star quad cables with minimal twisting of the conductors. The frequency response of these cables shows a significant and substantial increase in attenuation per meter with frequency. Furthermore, length-dependent distortions can occur. This limits the maximum data rate. Signals (often DC-free line codings such as Manchester coding), which, depending on the bit sequence, exhibit spectral components with a high frequency at the data rate and significant components up to twice the data rate, consequently suffer from strong amplitude fluctuations over time.

[0044] Fig.Figure 1 shows a first example communication network KNW1 for building automation. For clarity, only some network nodes in the communication network KNW1 are labeled with reference numbers NK1 - NK3.

[0045] In Fig. The numbers 1 to 15 represent, for example, connection, branch, and endpoints in the communication network KNW1. One or more network nodes NK1 to NK3 can be connected to each of these connection, branch, or endpoints.

[0046] In the tree-like communication network KNW1 according to Fig. 1. Signals from a transmitter are reflected at each endpoint unless the line is terminated with a suitable impedance (typically 100 ohms). This is well known from transmission line theory.

[0047] The frequency response, especially of two-wire lines, shows a significant increase in attenuation depending on the line length and frequency. If the individual ends of the branches are not terminated with the characteristic impedance of the line, reflections occur which propagate to all other network nodes and thus distort the signal through summation. If all ends are terminated, the attenuation increases further, as the transmitter (ultimately each node) is subjected to an ever-increasing load. This attenuation and distortion result in a reduction of the signal level and thus the transmission quality in the communication network.

[0048] In contrast to the point-to-point connections most commonly used in telecommunications (e.g., Ethernet, TV coaxial cable), if many end devices participate in such a communication network KNW1, connecting a terminating impedance at each endpoint leads to a very low overall impedance of the communication network KNW1 and thus to an extremely high attenuation of the signals. The transmitter would have to inject a very high power into the low-impedance network KNW1.

[0049] In such communication networks (KNW1), distorted signals and numerous delayed signal copies reflected at other network ends occur at the receiver of each end device. This becomes particularly problematic when a reflected signal with a frequency content at the data rate is superimposed, with a delay, on the signal component actually intended to be received, which has frequencies at twice the data rate. Because the former signal is less attenuated at lower frequencies, it effectively masks the latter. The greater the delay, i.e., the longer the individual branches of the KNW1 communication network, the more critical the situation becomes. This phenomenon is known in theory as intersymbol interference, and its effects are exacerbated here depending on the bit sequence. Therefore, with simple receiver architectures, an upper data rate is limited by the KNW1 network. This limit is currently around 10 kbit / s for networks with lengths up to 1000 m.

[0050] Fig. Figure 2 shows the frequency response of an example channel in the communication network of Fig. 1, with the transmitter at terminal 4 (NK2) and the receiver at terminal 12 (NK3). In the diagram of Fig. 2. The frequency in MHz is plotted on the abscissa axis and the respective amplitude or level (in dB) is plotted on the ordinate axis.

[0051] Intersymbol interference (ISI, or symbol crosstalk) describes interference between symbols transmitted sequentially in digital data transmission. This can also be demonstrated in the frequency domain or frequency response. In addition to the attenuation already mentioned, which increases with frequency, the delayed signal, when added to the direct signal, creates a zero point in the frequency response, depending on the lengths of the spur lines in the KNW1 network. This zero point is located approximately at the frequency f = c / 4L, where c is the propagation speed on the cable and L is the length of the responsible spur line to the originating connection. (See diagram below.) Fig. 2. The dip at 700 kHz can probably be attributed to the reflected signal of the spur line to terminal 10. Fig.1. Branch lines are lines that branch off from a signal path. The signal path can be the connection between any two nodes (e.g., NK2 and NK3) in the network KNW1.

[0052] In particular, new internet protocols (e.g., IPv6) and technologies are driving the desire for seamless communication networks right up to the sensor or actuator, even in building automation. A tenfold increase in data rate would be extremely beneficial, as these protocols introduce significantly more overhead, and new applications (e.g., firmware downloads) demand higher data throughput. Furthermore, network lengths should not decrease, nor should the number of end devices (e.g., sensors) decrease, thus avoiding the need for additional repeaters or amplifiers for cost reasons.

[0053] The inventive method for optimizing the transmission of digital data in a two-wire communication network is usable for different network topologies and for networks with different types of network nodes (e.g., controllers, sensors, actuators, fire detectors, lighting).

[0054] Fig. Figure 3 shows a second exemplary communication network, KNW2, as a standalone two-wire network (e.g., twisted pair) for building automation. The diagram shows... Fig. For clarity, only three network nodes (NK4 - NK6) are shown. The example communication network KNW2 could, for instance, be a KNX system.

[0055] Fig. Figure 4 shows two example communication networks KNW3 and KNW4, which are coupled together via a router NK8. Fig.Figure 4 shows an example of a two-wire network KNW3 connected to the backbone network KNW4 via a router NK8. This is also shown in the diagram according to... Fig. For clarity, only three network nodes (NK7 - NK9) are shown.

[0056] Fig. Figure 5 shows a block diagram of a first exemplary network node NK10. The network node NK10 is connected via a suitable interface SS1 (network connection) to a communication network using two-wire connections (twisted pair connection cables are advantageous).

[0057] The exemplary network node NK10 includes: - a receiving device EV, suitable for receiving signals of different data rates, wherein the receiving device EV is configured to determine the signal quality of signals received via the interface SS1; - a transmitting device SV, suitable for sending signals at different data rates via the SS1 interface; - a controllable termination impedance AI; - a measuring unit or measuring instrument MM for determining the signal quality, which can be measured at the receiving device EV; - a memory M for recording the values ​​of the termination impedances and the reception quality that can be assigned to a respective value for the network nodes in the communication network; - a control unit SM for specifying a setting value for the termination impedances of the network nodes; - An evaluation and calculation unit (AM) for specifying the respective setting values ​​for the termination impedances of the network nodes to achieve an optimal data rate in the communication network, whereby the evaluation and calculation are based on different data rates. Voltage is coupled in or out via a suitable coupling element (K1), and data is coupled in or out via a suitable coupling element (K2).

[0058] Advantageously, the control unit SM, the measuring unit MM, the evaluation and calculation unit AM, and the storage medium M are integrated into a processing unit MP (e.g. a microprocessor) and implemented with suitable hardware or software means.

[0059] The switchable termination impedance AI can be directly controlled by the microprocessor MP. In a further embodiment, the switchable termination impedance AI can also be integrated into the coupling element K2.

[0060] Fig. Figure 6 shows a block diagram of a second example network node, NK11. The example network node NK11 is a router suitable for connecting two communication networks that may have different topologies, protocols, and / or transmission methods. The communication networks to be connected can be connected to the router via corresponding network ports SS2 and SS3, respectively. The example network node NK11 can either have only router functionality, or it can be configured as a normal device (e.g., sensor, actuator) and additionally include router functionality.

[0061] Fig. Figure 7 shows an example flowchart for optimizing the transmission of digital data in a two-wire communication network.

[0062] Advantageously, after installation but before the communication network is operational, test data is sent from each network node and received by each of the other network nodes, controlled by a network node designated as the master, and checked for transmission errors. This process can then be performed for various combinations (in principle, even for all) of connected termination impedances. The termination impedances can be individually addressed and electronically switched on and off by a command from the master. This process is also performed during the initial setting of the termination impedances for each data rate. The master can thus determine the maximum data rate for the entire network as well as between the individual nodes, and the termination impedances to be set.After this process, the conditions in the communication network remain constant until a change is made to the communication network, such as adding or removing nodes, or changing the cabling. Only in this case does the process need to be repeated.

[0063] There are 3 possibilities for the starting point of this auto-setting process: 1) All terminations are switched off. The source resistance is always present in each transmitter. 2) All terminations are connected. The source resistance is always present in the transmitter. 3) The terminations found using the empirical theoretical method are established. The source resistance is always present in the transmitter.

[0064] The first and second options do not guarantee that all nodes are reachable (too much reflection or attenuation, respectively). The third option ensures reachability, at least for low data rates, but further improvements may be possible (see section "Further Options").

[0065] The simplest approach would be to try all combinations of ending settings. This would result in 2 N The number of tests (where N is the number of nodes) quickly becomes immeasurably large with a test time of approximately 10 seconds per test. Therefore, algorithms were sought that have a test time that increases only linearly with N.

[0066] The inventors proceed from the following idea: if a node without a termination impedance makes itself undesirably noticeable through reflections, i.e., noticeably reduces the data rate to other nodes, this cannot be better remedied than by setting the termination impedance for that node.

[0067] Based on this idea, two approaches (algorithms) were developed and their effectiveness demonstrated through testing. These are the "Remove RLoad" algorithm, which first sets all terminations and then begins switching off, and the "Add RLoad" algorithm, which has no terminations except for the source resistance and begins switching on.

[0068] The “Remove Rload” algorithm (switch-off algorithm, see Fig. Option 8) is faster and assumes a more forgiving initial configuration, as it terminates the branch lines from the outset. However, with many connected nodes, the attenuation can become very high, potentially rendering some nodes unreachable.

[0069] The “Add Rload” algorithm (switching algorithm, see Fig.9) In its initial configuration, no active termination impedances are used, resulting in a potentially less favorable initial configuration. Due to frequency dips, some nodes may become unreachable. However, activating the termination impedances makes more and more nodes reachable.

[0070] If no manual initial configuration is specified in the communication network, an automated "channel setup" can be used to advantage, as described in Fig. 7 are shown as examples.

[0071] First, an inventory (recording the reachable nodes) is performed to determine which nodes are present in the network. Then, all termination impedances are activated, and another inventory is performed. If all nodes are still reachable, the "Remove Rload" algorithm can be used. Otherwise, the "Add Rload" algorithm is more suitable because it has less attenuation on the transmission channels. It is advantageous for the master to know the number of nodes so it knows when it can communicate with all nodes, but this is not strictly necessary.

[0072] Fig.Figure 8 shows an example flowchart for a removal impedance switching algorithm. To start the removal impedance switching algorithm, the termination resistors of all nodes must first be activated. The algorithm then deactivates one termination impedance after another, performing a speed test after each one (e.g., across all network nodes). If deactivating a termination impedance leaves a spur line unterminated and negatively impacts the network, some nodes will no longer be able to communicate at the same high data rate. This degrades the overall network performance, and the termination impedance is reactivated. If no degradation is observed, the termination impedance remains deactivated. This process continues until all termination impedances have been checked or only one termination impedance remains active.The configuration will also be completed when all nodes can communicate with each other at the maximum data rate, i.e., a sufficient number of termination impedances are enabled.

[0073] With each iteration, an inventory is performed. This allows the identification of nodes that, due to lower attenuation, can be reached by disabling a termination impedance. The termination impedance must be enabled at these newly identified nodes so the algorithm can determine whether or not it needs to be set. In some cases, the termination impedance of a new node may render a previously enabled termination impedance unnecessary. Therefore, the previously checked termination impedances should be re-verified to ensure that a termination impedance is required at the newly discovered node.

[0074] This algorithm typically requires N+2 iterations, meaning a channel setup (configuration) for 64 nodes would take approximately 10 minutes, as a speed test takes about 10 seconds. The speed test is the most time-consuming part of each iteration. (N is the number of network nodes.)

[0075] Branch lines are lines that branch off from a signal path. The signal path can be the connection between any two nodes (e.g., A and B) in a network.

[0076] Fig.Figure 9 shows an example flowchart for an add-on algorithm ("Add Rload") of termination impedances in a communication network. Before the add-on algorithm ("Add Rload") is started, the initial setup is determined. An existing configuration (e.g., manual or predetermined by empirical rules) can be adopted, or the termination impedance of a master can be set (automatically). A master can intelligently control its own termination impedance. If there are multiple potential masters in the network, these network nodes can negotiate or share the master role.

[0077] Afterward, one termination impedance after another is activated, and a speed test is performed for each one. If activating a termination impedance results in an overall deterioration of the communication network, the termination impedance is deactivated again. This process continues until all termination impedances have been tested. Since several termination impedances may be necessary to achieve an improvement, depending on the network topology, termination impedances are kept active as long as they do not negatively impact network performance.

[0078] The configuration also terminates when all nodes can communicate with each other at the maximum data rate. Additionally, an inventory (recording the reachable nodes) is performed with each iteration to identify newly reachable nodes. Newly discovered nodes must have their termination impedance disabled. The algorithm also checks whether the termination impedance should be set for these nodes. Restarting the algorithm is pointless, as these nodes would again be unreachable in the initial configuration.

[0079] Once all termination impedances have been checked, the removal algorithm (“Remove Rload”) is used (see Fig. 8) Used to check if all added termination impedances are necessary. This is needed to remove unnecessary termination impedances and thus reduce attenuation on the channel.

[0080] Redundant termination impedances can arise when a termination impedance is activated and this leads to an improvement in the network, but another termination impedance, checked later, would achieve this improvement better. This is the case, for example, in a bus topology if the termination impedance at the end of the bus line is not checked first.

[0081] This algorithm requires a maximum of 2*N+2 iterations, meaning a channel setup for 64 nodes would take approximately 20 minutes, as a speed test takes about 10 seconds. The speed test is the most time-consuming element of each iteration. N is the number of network nodes.

[0082] This eliminates the need to test all possible configurations (2^N); instead, each termination impedance only needs to be individually enabled or disabled. N is the number of nodes in the network (including the master). The "Remove Rload" algorithm requires at most N iterations, as each impedance is disabled once. The "Add Rload" algorithm could potentially require up to 2*N iterations, since a termination impedance is first enabled and then, if deemed useful, disabled again. Therefore, the computational effort increases linearly with the number of nodes.

[0083] Each iteration requires an inventory, a speed test, and a network configuration. All these elements increase linearly with the number of nodes. This is especially true for the speed test, as a single measurement generates N measurement results. This is achieved by all nodes simultaneously evaluating the measurement packet from the sending node.

[0084] It is also possible to begin operational use before completing the channel setup (channel configuration), as soon as all nodes can communicate with each other at the lowest data rate. The channel setup can then be terminated during operational use. This is achieved, for example, by alternately transmitting user data and performing speed tests. This slows down both processes, but allows the system, i.e., the communication network, to be operational sooner. Order of nodes to be tested

[0085] The order in which the termination impedances are tested has a significant impact on the final configuration. Tests have shown that a good configuration can be found with any order. However, it has also been shown that an intelligent order allows for faster and more reliable configuration improvement.

[0086] At the start of a channel setup, a speed test is always performed with the initial configuration. This speed test also assesses the reception quality of individual network nodes. The better other nodes receive data—that is, the higher the data rates at which the test packets are received—the better the reception quality. During the channel setup, a new speed test is performed with each iteration, thus reassessing the reception quality after each iteration.

[0087] Regarding the switching algorithm (“Add Rload”, see Fig.9), where no termination impedances are enabled in the initial configuration, the nodes with the best reception quality tend not to be affected by spur lines; in other words, they tend to be the cause of frequency-selective dips themselves. If these nodes are checked first, the network will be improved faster and more reliably.

[0088] Regarding the removal algorithm ("Remove Rload", see Fig.8) In the initial configuration where all termination impedances are enabled, the nodes with the best reception quality tend to be those located in the middle of the network. These are the nodes where the termination impedance is generally not needed, as they are not connected to a long spur line. Due to attenuation, the reception quality is worse at nodes connected to long spur lines. Therefore, even in this case, the nodes with the best reception quality must be checked first.

[0089] Furthermore, nodes that are geographically very close to each other can be identified by correlating the reception quality of the individual communication links. Therefore, if two nodes can communicate with the same nodes at the same maximum data rate, there is a high probability that these nodes are geographically close. This means that in the first round, only one neighboring node can be checked, which tends to result in only one node being checked if it is connected to the same spur line, and then another spur line being checked more quickly. Combination with empirical theoretical methods

[0090] Especially when a wiring diagram for the communication network is known, a combination with empirical theoretical methods can be advantageous.

[0091] Since the dips in the frequency response occur at a frequency that is inversely proportional to the line length and the frequency range is given by the data rate < 1 MHz, rules can be empirically established as to where terminations should be placed.

[0092] The following rules can prevent frequency-selective dips of <1 MHz in a network: - Each network must have at least one termination impedance; this can also be the source impedance of the transmitter. - Every spur line >40 m must be terminated. - No terminating impedance may be inserted at branch points. - In the case of a bus or branch as a spur line, only the longest signal path needs to be completed, provided its total length exceeds 40m.

[0093] To prevent dropouts in the frequency range <1 MHz (up to 500 kbit / s Manchester-coded data rate) on spur lines, all points more than 40 m from the nearest branch must be terminated. This prevents reflections that would cause dips of <1 MHz. For 1 Mbit / s, lines longer than 20 m would need to be terminated accordingly. If the spur line consists of a bus or branch (spur line with multiple branches longer than 40 m), it is sufficient to terminate only the longest path. Even in small networks, at least one termination impedance is required to prevent multiple reflections, which in turn lead to frequency-selective dips. The source resistance (series resistance) of the transmitter can, under certain circumstances, also serve as the termination impedance.A branch already appears to have a low impedance, meaning that inserting an additional terminating resistor at the branch point leads to an even lower impedance, i.e., a worse match, and should therefore be avoided. Speed ​​Test Procedure

[0094] The speed test is always started from the master and follows this procedure: Command from the Master Action of the nodes Node response Start Speed ​​Test Initialize internal measurement table, send acknowledgement to master - Send Test Packet 50 kbps Send test packet at 50 kbps Store reception quality of received test packets Send test packet 100 kbps Sending test packet at 100 kbps Store reception quality of received test packets Send test packet 250 kbps Sending test packet at 250 kbps Store reception quality of received test packets Send test packet 500 kbps Sending test packet at 500 kbps Store reception quality of received test packets Send test packet 1000 kbps Sending test packet at 1000 kbps Store reception quality of received test packets End Speed ​​Test Send measurement table to master -

[0095] With the "Start Speedtest" command, each node initializes its own internal measurement table. With each "Send Test Packet" command, each node sends a test packet at the corresponding data rate, and the other nodes store the received test packet's signal quality in their measurement tables. The "End Speedtest" command terminates the speed test and sends the measurement tables to the master.

[0096] The measurement table maintained by each node contains, for example, N*S fields, each a few bytes in size. Here, N is the number of nodes in the network and S is the number of speed tests performed. Each field stores the signal quality, also known as LQI (Link Quality Indication), of the respective node at the given data rate.

[0097] The speed test procedure can also be changed by the master to check only individual or other data rates.

[0098] It is advantageous to use a time-slot method (e.g. TDMA) for the speed test.

[0099] The process is advantageously controlled by a node designated as the master. Any network node that includes appropriate processing (e.g., a microprocessor with suitable software) and storage (e.g., flash memory) can be used as the master. The initial values ​​of the termination resistors or impedances after the nodes are installed are advantageously chosen according to the selected algorithm as follows: 1) All terminations are switched off. The source resistance is always present at the transmitter. 2) All terminations are connected. The source resistance is always present at the transmitter. 3) The terminations found using the empirical theoretical method are established. Source resistance is always present at the transmitter.

[0100] As in Fig.As described in section 7, the master first performs an inventory (identifying the reachable nodes in the communication network) at the lowest data rate to obtain responses from as many nodes as possible. The master then commands these nodes to add their termination impedance. A subsequent inventory should now make all nodes visible. The master then executes one of two algorithms: Add RLOAD (the switching algorithm, see section 7). Fig. 9) or Remove RLOAD (switch-off algorithm, see Fig. 8), whereby the master transmits to the nodes whether they need to switch their termination impedance on or off.

[0101] For each configuration, a speed test is performed with progressively higher data rates. Short data packets containing synchronization information and parameters such as the TDMA timeslot and data rate are sent to each node. Each node then transmits a data block with a pseudo-noise sequence in its designated timeslot. Any non-transmitting node can receive this data block and verify its accuracy and reception quality. Each node then fills in a table with the results of all received data blocks from other nodes. Once all data rates have been verified, the master collects all these tables and compiles them into a matrix (see...). Fig.(See section 10, upper section). Depending on whether the network speed is higher than in the previous step, the last connected termination impedance is either retained in its position and the achieved speed is either recorded. Each iteration requires an inventory, a speed test, and network configuration.

[0102] This is repeated for each positional variant of the termination impedances RLOAD. If all iteration steps are completed according to the procedures according to... Fig. 8 or Fig. Once steps 9 have been processed, the master node finally decides on the data rate to be used. This can either correspond to the lowest common rate that was still possible without errors for all nodes, or the nodes may individually use the rate determined for this connection, depending on the recipient of a packet to be transmitted.

[0103] The advantage is that only as many termination impedances are set as are necessary to ensure communication between all nodes in the network. The process always attempts to find the optimum.

[0104] Fig. Figure 10 shows an example measurement table with termination impedances. The measurement table is stored and managed in the memory of at least one network node, preferably the respective master. Regarding the measurement table according to... Fig. 10 is an example of a global measurement table that ideally includes all network nodes.

[0105] Fig. Figure 11 shows a block diagram of the section of a third exemplary network node NK12 which serves to switch the optimal termination impedance on or off using the methods described above. Structure of the exemplary network node NK12

[0106] A switchable resistor 3 terminates the transmission line leading to the node, which is connected to terminals 5a and 5b. For example, in Fig. 11 uses an ohmic resistor as the impedance.

[0107] The microprocessor 1 in node NK12 can programmatically control the switching on and off via a logic signal. This logic signal controls a potential-free solid-state relay 2, consisting of an LED and two NMOS FETs with light-sensitive gates. When switched on, resistor 3 is connected between the conductors via relay 2, thus terminating the line with the value of resistor 2. With a line impedance of 100 ohms, the value of resistor 3 is 100 ohms. In practice, the FETs of switch 2 have a non-zero on-resistance when switched on, so the value of resistor 3 is reduced by this value. Capacitors 4a, 4b, 4c, and 4d serve to isolate the DC components at terminals 5a and 5b for the balanced transmission line and at terminals 6a and 6b for the receiver.

[0108] Methods for optimizing the transmission of digital data in a two-wire communication network. Arrangements, in particular communication networks and network nodes, for optimizing the transmission of digital data. Reference sign KNW1 - KNW4 Communication Network NK1 - NK12 Network Nodes 1 MP microprocessor 2 relays 3 Resistance 4a - 4d Capacitor 5a, 5b terminals 6a, 6b terminals SS1 - SS3 interface M Storage AM evaluation tool MM Measuring Instruments SM tax revenue V Power supply SV transmitter EV receiver K1, K2 coupling elements AI termination impedance

Claims

[1] Two-wire communication network (KNW1 - KNW4) with two or more network nodes (NK1 - NK12), without additional repeaters or amplifiers, wherein a network node (NK1 - NK12) comprises: - a receiving device (DD) suitable for receiving signals of different data rates, wherein the receiving device (DD) is configured to determine the signal quality of received signals; - a transmitting device (SV) suitable for transmitting signals at different data rates; - a controllable termination impedance (3); wherein a network node (NK1 - NK12) is configured to transmit the detected signal quality to one or more network nodes; wherein at least one network node (NK1 - NK12) in the communication network (KNW1 - KNW4) is designed to record the detected signal qualities and the values ​​of the termination impedances (3) of the respective network nodes (NK1 - NK12); wherein at least one network node (NK1 - NK12) specifies to the other network nodes in the communication network (KNW1 - KNW4) what value they are to set as the termination impedance (3); and wherein at least one network node (NK1 - NK12) comprises means for determining which termination impedances (3) the network nodes (NK1 - NK12) should each set in order to optimize the data rate between the network nodes (NK1 - NK12) and the signal quality at the receiving devices (EV) of the network nodes (NK1 - NK12). [2] Network node in a communication network (KNW1 - KNW4) with at least two network nodes (NK1 - NK12) and two-wire connections, without additional repeaters or amplifiers, wherein the network node (NK1 - NK12) comprises: - a receiving device (DD) suitable for receiving signals of different data rates, wherein the receiving device (DD) is configured to determine the signal quality of received signals; - a transmitting device (SV) suitable for transmitting signals at different data rates; - a controllable termination impedance (3); - a measuring unit (MM) for determining the signal quality, which can be measured at the receiving device; - a memory (M) for recording the values ​​of the termination impedances (3) and the reception quality that can be assigned to each value for the network nodes (NK1 - NK12) in the communication network (KNW1 - KNW4); - a control unit (SM) for specifying a setting value for the termination impedances (3) of the network nodes (NK1 - NK12); - an evaluation and calculation unit (AM) for specifying respective setting values ​​for the termination impedances (3) of the network nodes (NK1 - NK12) to achieve an optimal data rate in the communication network (KNW1 - KNW4), whereby the evaluation and calculation is based on different data rates. [3] Arrangement according to one of the preceding claims, wherein the communication network (KNW1 - KNW4) has a free topology. [4] Arrangement according to one of the preceding claims, wherein data transmission in the communication network (KNW1 - KNW4) is carried out using baseband modulation. [5] Arrangement according to one of the preceding claims, wherein data encoding in the communication network (KNW1 - KNW4) is carried out using Manchester encoding. [6] Arrangement according to one of the preceding claims, wherein the termination impedances (3) of the network nodes (NK1 - NK12) are selected depending on the topology of the communication network (KNW1 - KNW4) and / or the transmission method and / or the cable length and / or the wave impedance. [7] Arrangement according to one of the preceding claims, wherein the network nodes (NK1 - NK12) can be supplied with energy via the communication network (KNW1 - KNW4). [8] Arrangement according to one of the preceding claims, wherein a network node (NK1 - NK12) is configured to supply energy to one or more other network nodes (NK1 - NK12) in the communication network (KNW1 - KNW4). [9] Arrangement according to one of the preceding claims, wherein at least one network node (NK1 - NK12) is configured to determine the maximum possible data transmission rate in the communication network (KNW1 - KNW4) based on the reception quality of the network nodes (NK1 - NK12). [10] Arrangement according to one of the preceding claims, wherein at least one network node (NK1 - NK12) is configured to establish a connection to one or more further communication networks (KNW1 - KNW4). [11] Method for optimizing the transmission of digital data in a two-wire communication network (KNW1 - KNW4) without additional repeaters or amplifiers, the method comprising the following steps: Step 1: Analysis of the communication network (KNW1 - KNW4), consisting of network nodes (NK1 - NK12) each with a switchable termination impedance (3, AI) and two-wire lines for connecting the network nodes (NK1 - NK12), whereby the reception quality is determined for the network nodes (NK1 - NK12) by applying an initial data rate to each network node (NK1 - NK12), using a defined setup for the termination impedances; Step 2: Using the initial data rate for each network node (NK1 - NK12), determine whether the respective termination impedance (3) needs to be switched on or off to increase the respective reception quality of a network node (NK1 - NK12); Step 3: Analysis of the communication network (KNW1 - KNW4), whereby the reception quality is determined for the network nodes (NK1 - NK12) by applying a second data rate to each network node (NK1 - NK12); Step 4: using the second data rate for each network node (NK1 - NK12), determine whether the respective termination impedance (3) needs to be switched on or off to increase the reception quality; Repeat steps 3 and 4 until no improvement in reception quality is measurable. [12] Method according to claim 11, wherein during operation it is detected whether a new network node (NK1 - NK12) is added to the communication network (KNW1 - KNW4) or an existing network node (NK1 - NK12) is switched off or whether a new connection is connected or whether an existing connection is removed. [13] Method according to claim 12, wherein after the detection of a change the communication network (KNW1 - KNW4) is again optimized with respect to reception quality and / or data rate. [14] Method according to one of claims 11 to 13, wherein in steps 3 and 4 the second data rate is determined from the initial data rate by a stepwise increase of the data rate. [15] Method according to any one of claims 11 to 14, wherein the initial data rate is 50 kbit / s. [16] Method according to one of claims 11 to 13, wherein in steps 3 and 4 the second data rate is determined from the initial data rate by a stepwise reduction of the data rate. [17] Method according to one of claims 11 to 13 or according to claim 16, wherein the initial data rate is 1 MBit / s. [18] Method according to any one of claims 11 to 17, wherein in step 1 all termination impedances are either switched off or switched on. [19] Method according to any one of claims 11 to 18, wherein the value of the termination impedance is adapted to the wave impedance of the network. [20] Method according to any one of claims 11 to 19, wherein the value of the termination impedance (3) is in the range of 100 ohms. [21] Method according to any one of claims 11 to 20, wherein the value of the termination impedance (3) is variable. [22] Method according to one of claims 11 to 21, wherein the determination of which termination impedances (3) must be switched on or off to increase the reception quality is carried out by a mathematical optimization method. [23] Method according to any one of claims 11 to 22, wherein the method is applied to each network node (NK1 - NK12). [24] Method according to one of claims 11 to 23, wherein the method starts based on an empirical switching on or off of termination impedances (3) for certain network nodes (NK1 - NK12) depending on the topology of the communication network (KNW1 - KNW4). [25] Method according to any one of claims 11 to 24, wherein the method runs in parallel with the data operation.

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