METHOD FOR TRANSFERRING DATA BETWEEN A NODE AND A BASE STATION IN A COMMUNICATION SYSTEM AND BASE STATION AND NODE

Description

[0001] The present invention relates to a method for transmitting data between at least one node and a base station in a communication system with bidirectional radio transmission. The invention further relates to a correspondingly configured node. The invention is particularly suitable for use in recording the consumption of heat or energy, electricity, gas, or water using autonomous consumption meters. Technological background

[0002] Nodes of a communication system, such as smart meters, are usually assigned to local locations such as residential units or residential buildings. The measurement data generated there can be read out in a variety of ways. For example, measurement data can be read out via the power grid (power line). However, integrating the meters into a supra-local network is not possible in this case. Measurement data can also be transmitted using mobile radio technology in the form of data packets or telegrams. However, this is expensive, requires the installation of mobile radio modules on the meters, and has the disadvantage of high power consumption at the individual meters. Furthermore, measurement data can also be transmitted wirelessly in the form of data packets or telegrams, for example, in the ISM (Industrial, Scientific, Medical) band or the SRD (Short Range Devices) band.These frequency ranges have the advantage that operators only require general approval from the frequency management. However, the problem is that due to the frequency of use of such frequency ranges for a wide variety of technical devices, such as garage door controls, baby monitors, alarm systems, Wi-Fi, Bluetooth, smoke detectors, etc., interference can frequently occur. The measurement data is collected wirelessly by either stationary or mobile data collectors (base stations or collectors), to which the measurement data provided by the transmitters of the consumption meters is transmitted.

[0003] In this process, consumption meters transmit measurement data at specific, very short sampling periods (sample time or sampling point in time including time deviation) to a data collector, and the measurement data received during these sampling periods is used for consumption analysis. A particular challenge here is that communication between the data collector and consumption meters requires very precise time synchronization between the oscillators located in the range of the consumption meters and those of the data collector. For the oscillators of autonomous consumption meters, simple quartz crystals with a relatively low frequency and correspondingly low power consumption are used as frequency transmitters (with a time recording function of a frequency reference device). Such quartz crystals exhibit quartz errors of approximately 10–100 ppm due to manufacturing tolerances, temperature behavior, and aging.For example, with a standard quartz crystal, a quartz error of 50 ppm results in a deviation of 4.3 seconds per day, or 26 minutes per year. This, in turn, results in a deviation in time synchronization even with slight temperature fluctuations, which can be noticeable even over very short periods. The result is poor reception.

[0004] In bidirectional transmission, after an uplink transmission from the nodes to the base station, a narrowband downlink transmission of data takes place from the base station to the respective nodes. The data transmitted in the downlink can be, for example, an acknowledgment of receipt of a data packet or telegram by the base station, a query as to whether further data should be transmitted from the respective node to the base station, control telegrams, or other data / information to be transmitted to the respective node. In both the uplink and the downlink, the data is not transmitted in one piece via a telegram. Rather, the telegram is divided into individual data packets that are shorter than the entire telegram, which are then transmitted individually at certain times and decoded or recombined in the receiver.The particular problem with the downlink is that the number of data packets is greater than with the uplink, and the transmission time for each data packet is therefore longer. Furthermore, the carrier frequency of the data packets must correspond very precisely to the carrier frequency expected by the node in order to suppress the influence of noise as much as possible. Finally, the node must open its reception window for the downlink at the expected time, which, however, presents an additional challenge due to the temperature-induced frequency shift of the node-side frequency generator. Accordingly, due to the temperature and the advancing time until the last data packet of a telegram is received in the downlink, a frequency offset and / or a time offset can occur, which makes good reception of the data packets in the downlink difficult or even impossible. Printed state of the art

[0005] A method according to the preamble of the claim is known from DE 10 2005 020 349 B4. In the consumption recording system described therein, the consumption measuring devices have a first time clock (clock time clock) with lower power consumption for continuous operation and a second clock with higher frequency stability and higher power consumption, which is only operated during short activation phases. According to the idea described therein, during the short activation phases of the second clock, the frequency, the period duration, or a variable derived therefrom is recorded in the consumption measuring device as a clock rate of the first time clock on the basis of a comparison standard derived from the second time clock, and the accumulated time of the first time clock is corrected depending on the detected deviation. As a result, the temporal error then corresponds to the temporal error of the second clock of the consumption measuring device.

[0006] US 2009 / 0201152 A1 discloses a tamper-proof container localization system using micro-transponders, each attached at different positions on the container, and a base station. A first micro-transponder, in an analysis mode, sends an initial packet at a first time and receives radio signals relating to a subsequent packet at a second time. A distance between the first and second micro-transponders is determined from the time difference between the first and second times. Furthermore, the second micro-transponder receives radio signals relating to the first packet and adjusts the time and carrier frequency for the subsequently sent packet.

[0007] US 2016 / 0164745 A1 relates to a method for wired or wireless communication between a base station and a plurality of subscriber stations located at different distances from the base station. To enable multiple access by the subscriber stations, the data is fragmented and the data fragments are sent sequentially in the uplink in a number of time slots necessary for transmission and recombined in the receiver.

[0008] US 2010 / 0075611 A1 discloses a method and device for wireless communication for an industrial process control system comprising multiple nodes and a gateway. Data packets are extracted from combined baseband signals in the gateway's receiver. Furthermore, a time synchronization unit is provided, which performs bit timing synchronization and synchronizes with the clock pulse of the transmitted data. A sampling time error correction device corrects a sampling time error in the demodulated baseband signals.

[0009] DE 10 2010 031 411 A1 and EP 2 751 526 B1 describe a concept for the wireless transmission of payload data, in which the payload data is divided into a plurality of channel-coded data packets and transmitted within a time interval from a node to a base station via a wireless communication channel. In the base station, the data packets are decoded and recombined into payload data. According to EP 2 751 526 B1, the node for generating data packets can be configured to divide a synchronization sequence into partial synchronization sequences and to provide each data packet with one of the partial synchronization sequences. Synchronization sequences are deterministic or pseudorandom binary data sequences that are sent to the base station together with the actual payload data or sensor data in the data packets. The synchronization sequences are known to the base station.By correlating the received data stream with the known synchronization sequence, the base station can determine the temporal position of the known synchronization sequence in the received data stream. To keep the data packets short, the synchronization sequence can be distributed across the individual short data packets, so that the individual data packet has poorer synchronization properties than synchronization across multiple data packets.

[0010] In DE 10 2016 205 052 A1, in order to improve the channel utilization, a data transmitter is proposed which is designed to specify to another data transmitter a transmission time at which the other data transmitter transmits a transmission data packet, or a time interval between two transmission data packets transmitted by the other data transmitter, using an additional transmission data packet which is transmitted in a gap or pause between two transmission data packets.

[0011] According to DE 10 2016 009 197 B3, in order to transmit telegrams from a data collector to a measuring device in the data collector, the transmitter-side reference frequency is shifted by the frequency difference between the data collector-side reference frequency and a measuring device-side reference frequency after receiving a data telegram from the measuring device.

[0012] DE 10 2018 004 828 A1 describes a method for transmitting data between a terminal device and a data collector by radio, in which, after establishing communication, the terminal device sends a message to the data collector and, after receiving the message, the data collector continues, interrupts or terminates the transmission of the data based on the content of the message during the communication. Object of the present invention

[0013] The object of the present invention is to improve the reception quality in the downlink. Solution to the task

[0014] The above object is achieved by the features of the method according to claim 1. Expedient embodiments of the method according to the invention are claimed in the dependent claims.

[0015] According to the invention, a correction of the transmission time and / or the carrier frequency of at least one of the data packets takes place between the downlink data packets. This enables the base station and nodes to coordinate the transmission of the individual data packets to be sent one after the other with regard to the temporal position of the node's reception window and the transmission time of the data packets and / or the carrier frequency much more precisely than was previously possible. This makes it possible to considerably improve the quality of data transmission in the downlink, despite the existing difficulties. The invention also opens up the possibility of spreading the time interval between the data packets, i.e. pulling them apart, since the influence of time and / or temperature can be compensated for by the method according to the invention. Spreading the time interval between the data packets orStretching them out in the temporal sequence has the advantage that significantly cheaper energy buffers can be used in the nodes, since the available electrical energy of the energy buffer no longer has to be used to process a large number of data packets within a very short period of time, since the time period can now be stretched.

[0016] For the transmission of data packets in the downlink, the second node frequency generator is preferably calibrated via the first node frequency generator, thereby eliminating a time offset caused by the second node frequency generator.

[0017] According to the invention, an intermediate calibration packet is transmitted from the node to the base station via the uplink between data packets for correction, so that the base station knows that this calibration has taken place. From this point on, the base station can thus correct the time intervals between the data packets within the transmission sequence.

[0018] Preferably, the first node frequency generator and the first base station frequency generator, i.e., the two high-frequency frequency generators for the carrier frequency, are also calibrated during the transmission of the intermediate calibration packet. This allows the carrier frequency of the data packets to be precisely tuned. This results in an improved signal-to-noise ratio during narrowband reception of the data packets.

[0019] Typically, the base station, like the node, also has a second base station frequency transmitter (time crystal) whose frequency is lower than that of the first base station frequency transmitter. As a result of the transmission of the intermediate calibration packet, a calibration of the second base station frequency transmitter can also be performed via the first base station frequency transmitter. This can further improve the coordination of the transmission times and the reception window.

[0020] Preferably, the intermediate calibration packet is sent between two data packets of the plurality of data packets. The above-described time and / or carrier frequency compensations can therefore be performed within the sequence of a data telegram, so that the adverse effect of the transmission time of a data telegram and the resulting frequency deviations, particularly those caused by temperature, can be eliminated.

[0021] As a result of receiving the intermediate calibration packet, the base station can readjust the transmission time and / or the carrier frequency of the data packets to be generated after receiving the intermediate calibration packet.

[0022] Furthermore, as a result of the calibration of the first node frequency generator and the second node frequency generator, the node can readjust the reception time for the data packets expected after sending the intermediate calibration packet.

[0023] In particular, the calibration of the first node frequency generator and the second node frequency generator can be performed when the intermediate calibration package is provided in the node.

[0024] In particular, the calibration of the first node frequency generator and the first base station frequency generator can continue to take place upon receipt of the intermediate calibration package in the base station.

[0025] During the transmission of the data packets in the uplink, a calibration of the first node frequency generator and the second node frequency generator and / or a calibration of the first node frequency generator and the second base station frequency generator and / or a calibration of the first base station frequency generator and the second base station frequency generator has advantageously already taken place prior to the intermediate calibration packet, so that the calibrations performed during the transmission of the intermediate calibration packet merely represent readjustments to the aforementioned calibrations. Thus, during the calibration performed during the transmission of the intermediate calibration packet, no re-estimation of previous errors (e.g., hardware errors, correction of the difference from the estimate, or the like) is performed.

[0026] Preferably, an intermediate calibration packet can be sent repeatedly. This ensures an increased probability of reception in the event that an intermediate calibration packet is lost in the uplink due to interference or the like.

[0027] According to an advantageous embodiment of the method according to the invention, the transmission time and / or carrier frequency of the downlink data packets is corrected multiple times in their temporal sequence. This allows for continuous time and / or carrier frequency adjustment.

[0028] The intermediate calibration packet is advantageously significantly shorter than a conventional data packet in a telegram to increase the probability of reception in the transmission channel. In particular, this allows the base station to respond more quickly to a corresponding intermediate calibration packet than to a conventional data packet in the uplink.

[0029] As an intermediate calibration packet, only pilots (bits or bit sequences known to both the node and the base station) and / or ID data and / or packet core data can be sent. This assumes that the frequency has changed only minimally (e.g., < 10 Hz), so that even without an ID, it can be verified that the node (counter) is the same.

[0030] Advantageously, the mean (i.e. average) pause between two data packets of the downlink data packets is greater than 500 ms, preferably greater than 700 ms, particularly preferably greater than 900 ms.

[0031] Preferably, the difference between a calibration of the first node frequency generator and the second node frequency generator and / or a calibration of the first node frequency generator and the first base station frequency generator and / or a calibration of the first base station frequency generator and the second base station frequency generator of a previous transmission of data packets with a corresponding subsequent calibration can be determined with regard to its frequency difference using an intermediate calibration packet and taken into account in the base station and / or in the node. In particular, the relevant difference between the calibration of the first node frequency generator and the first base station frequency generator can be taken into account for the correction of the carrier frequency in the base station.

[0032] The present invention further relates to a node according to the features of claim 16. Description of the invention based on exemplary embodiments

[0033] Specific embodiments of the present invention are explained in more detail below with reference to the drawing figures. For the sake of clarity, recurring features are provided with a reference numeral only once. They show: Fig. 1 is a highly simplified schematic representation of an example of a communication network with a base station and several associated nodes; Fig. 2 is a highly simplified representation of an example of a base station for a communication network according to Fig. 1; Fig. 3 is a highly simplified schematic representation of the basic calibration principle of the present invention; Fig. 4 is a highly simplified schematic representation of the transmission of an intermediate calibration packet according to an exemplary embodiment of the invention; and Fig. 5 is a highly simplified schematic representation of examples of different forms of an intermediate calibration packet according to the invention compared to a conventional data packet.

[0034] Reference number 1 in Fig. 1refers to a radio communication system or radio communication network which comprises a base station 3, e.g. a so-called data collector, and a plurality of individual, autonomously operated nodes 2. The nodes 2 are, for example, sensor devices or meters of any kind, such as water meters, heat meters, gas meters or electricity meters, or actuators. What these nodes 2 have in common is that they have a communication module 17 with antenna 8 and a control and computing unit 19. Furthermore, each node 2 has a first node frequency generator 18 for generating a carrier frequency for radio transmission and a second node frequency generator 21, which is used to determine the times for transmitting data packets 40-1, 40-n in the uplink and for determining the reception window for receiving data packets 50-1, 50-n in the downlink.The first node frequency generator 18 is an HF (high-frequency) quartz crystal, which typically has an error on the order of 20 ppm. In contrast, the second node frequency generator 21 is an LF (low-frequency) quartz crystal, also called a timing quartz crystal, which typically has an error on the order of 100 ppm. This corresponds to a timing error of 100 µs / s.

[0035] The second node frequency generator 21 of node 2 must always be active due to its time measurement or timing function, whereas the first node frequency generator 18 only needs to be activated in transmit and / or receive mode. Otherwise, it is in sleep mode. Each node 2 is operated in an energy-autonomous manner, i.e., it has a battery 22 through which the individual functional units of node 1 are supplied with energy. The communication module 17 or the control and computing unit 19 is not supplied with electrical energy directly from the battery 22, but rather from an energy buffer 5. The latter is supplied with electrical energy, i.e., charged, via a charging unit 4 or a charging circuit to which the battery 22 belongs.

[0036] Each node 2 can, for example, also be provided with a display 9 if desired.

[0037] The radio communication system 1 according to Fig. 1is operated bidirectionally. In the uplink, data packets 40-1, 40-n are transmitted from the respective node 2 to the base station 3, where they are received via its antenna 7. In the downlink, data packets 50-1, 50-n are transmitted from the base station to each individual node 2 and received by their antennas 8.

[0038] The SRD band or the ISM band is preferably used for data transmission, as these provide license-free frequency bandwidths for a wide variety of applications.

[0039] Fig. 2 shows in a highly simplified schematic representation an exemplary structure of an energy-autonomous base station 3 of the communication system 1 according to Fig. 1 The base station 3 comprises a transmitting and receiving section 6 with an antenna 7 and a microprocessor 13, which has a memory 15 and controls the display 23.

[0040] Furthermore, the base station 3 has a first base station frequency transmitter 11 in the form of an HF (high frequency) quartz crystal and a second base station frequency transmitter 12 in the form of an LF (low frequency) quartz crystal. The second base station frequency transmitter 12 is used for time recording and is therefore always active, similar to the second node frequency transmitter 21 of the respective node 2. The second base station frequency transmitter 12 typically also has an error in the order of 100 ppm. The error of the first base station frequency transmitter 11 is in the range of 20 ppm.

[0041] In contrast, the first base station frequency generator 11 is activated analogously to the first node frequency generator 18 of the respective node 2 only at times in which the transmitting and receiving part 6 opens a receiving window for receiving the data packets 40-1, 40-n of the respective node 2.

[0042] The energy source 16 is preferably a battery, in particular a battery with a maximum capacity of 80 Ah. In order to achieve self-sufficient operation over several years with such an energy source, the base station 3 must not always be activated. The base station 3 or its transmitting and receiving section 6 should only be activated, i.e., form a reception window, when the respective node 2 transmits data packets 40-1, 40-n to the base station 3 or the base station 3 transmits data packets 50-1, 50-n in the downlink. During the remaining periods, the transmitting and receiving section 6 of the communication module 10 of the base station 3 should be in sleep mode.

[0043] A timing quartz used for the respective second frequency generator 21 or 12 typically has an error in the order of 100 ppm. This corresponds to a timing error of 100 µs / sec. Assuming that the next data packet will arrive in one hour, this results in an error of 360 ms (60 x 60 x 100 µs) over the duration of one hour. One data packet is approximately 10 ms long. The overhead after one hour would then be approximately 3,600%.

[0044] Calibrating the time crystal typically results in a residual error on the order of 20 ppm. This error would therefore be five times smaller than the error mentioned above and would result in an error of 72 ms, or 720% of the 10 ms data packet length.

[0045] Fig. 3shows in the area of ​​node 2 a calibration KAL1', with which the deviation in the node between the second node frequency generator 21 and the first node frequency generator 18 can be reduced from approximately 100 ppm to 20 ppm using the procedure described in DE 10 2005 020 349 B4.

[0046] Furthermore, upon receipt of a data packet 40-1, 40-n from the respective node 2, KAL2' performs a calibration between the first base station frequency generator 11 and the first node frequency generator 18 and stores this calibration in the base station 3. This allows the error in the base station 3 to be significantly reduced from 20 ppm, namely theoretically to an error of 0 ppm. However, since the calibration method only has a finite accuracy in practice (for example, due to temperature fluctuations and the like), a realistic reduction to a range of 5-0 ppm is desirable.

[0047] The additional increase in accuracy achieved thereby corresponds to a factor of at least 4.

[0048] According to the invention, a calibration KAL3' of the second base station frequency generator 12 and the first base station frequency generator 11 is also carried out.

[0049] Fig. 4 shows, by way of example and in a schematic manner, the transmission of a telegram 40 (payload data) in the uplink and of a telegram 50 in the downlink. For the transmission, a plurality of individual data packets 40-1 to 40-n (chunks) are formed from the telegram 40, the length of each of which is smaller than the length of the telegram 40. In node 2, as shown in Fig. 3shown, the first node frequency generator 18 with higher frequency (quartz for carrier frequency) and the second node frequency generator 21 with lower frequency but higher temperature-related offset (quartz for time measurement) are measured against each other (calibration KAL1') and the resulting frequency deviation is stored in a memory of the respective node 2.

[0050] The relevant node 2 sends a data packet, e.g., 40-1, at time t1, wherein the carrier frequency is generated by the first node frequency generator 18.

[0051] The relevant node 2 transmits the data packet 40-1, wherein the time t1 of its transmission is generated by the second node frequency generator 21, and wherein the measured deviation determined by the calibration KAL1' has already been taken into account. The transmission of the data packet 40-1 behaves as if the time t1 of its transmission had been generated by the first node frequency generator 18.

[0052] The data packet 40-1 of the node 2 is received by the base station 3, wherein the deviation between the first node frequency generator 18 and the first base station frequency generator 11 is determined and stored by means of a frequency estimation (KAL2').

[0053] The base station 3 can also determine or correct this deviation (KAL3') by measuring the frequencies of the first base station frequency transmitter 11 and the second base station frequency transmitter 12 and can store it (e.g. in ppm).

[0054] The respective node 2 transmits the next data packet 40-2 with a correction factor based on the deviation between the first node frequency generator 18 and the second node frequency generator 21. In other words, the node transmits in time as if the time had been generated by the first node frequency generator 18 of the node 2.

[0055] Since the determination of the time of the reception window of the base station 3 for the next data packet is made in the base station 3 after the calibration KAL3', the next reception window could also be generated only by the first base station frequency generator 11.

[0056] Based on the reception of the last data packet, base station 3 knows the frequency deviation between the first base station frequency transmitter 11 and the first node frequency transmitter 18. The reception window of base station 3 is corrected as if the first base station frequency transmitter 11 were running at the same speed or frequency as the first node frequency transmitter 18. If the temperature remains constant until the next data packet, it is expected that the reception window will be perfectly matched. In practice, the temperature changes, so deviations of, for example, + / - 5 ppm can occur depending on the time period in between.

[0057] The calibrations CAL1' and CAL3' are not ideal but depend on the calibration length. Thus, a residual calibration error remains.

[0058] To receive the next data packet, the base station 3 adds the time offset between the first base station frequency generator 11 and the first node frequency generator 18 caused by the deviation as well as the time offset between the first base station frequency generator 11 and the second base station frequency generator 12.

[0059] The calibration between the first base station frequency generator 11 and the second base station frequency generator 12 is carried out during the respective open reception windows in the base station 3 and can therefore take longer than in node 2. This allows the residual error in the base station 3 to be further reduced.

[0060] The invention eliminates a difference between the frequencies of the respective first frequency generators 11 and 18.

[0061] The calibration KAL2' between the frequency of the first node frequency generator 18 and the frequency of the first base station frequency generator 11 can also be based on an estimate of at least one parameter of the radio signal transmitted by the communication module 17 and received by the communication module 10 from the following parameter group Carrier frequency and / or bandwidth and / or data rate and / or reception time between two data packets and / or frequency deviation and / or modulation index by the communication module 10 in the base station 3. A corresponding procedure is described in the DE 2016 014 375 A1 described, the contents of which are incorporated by reference in their entirety.

[0062] For example, an estimate can also be made based on several such parameters, e.g. based on the difference between two carrier frequencies or reception times or based on a weighted average of several values, e.g. based on a filtering of N carrier frequencies.

[0063] Following the transmission of the data packets 40-1 to 40-n in the uplink, a telegram 50 is transmitted from the base station 3 to the respective node 2, as shown in Fig. 4 shown in the downlink. Accordingly, the telegram 50 is divided into individual data packets (chunks) 50-1 to 50-n, each of which is smaller than the length of the telegram 50, which, as shown in Fig. 4 shown, can be transmitted on different frequencies. Alternatively, data packets 50-1 to 50-n could also be sent on a single frequency.

[0064] The time period between the last calibration KAL1' of the first node frequency generator 18 and the second node frequency generator 21 (around time t1) until the reception of the last data packet 50-n at time tn can be relatively long. It can be several seconds or even minutes. The temperature during this period particularly influences the frequency of the second node frequency generator (time crystal) and thus the position of the time window of node 2 for receiving the data packets 50-1, 50-n. Furthermore, the higher frequency (carrier frequency) of the first frequency generator is also influenced.

[0065] According to the invention, node 2 performs a recalibration KAL1 of the first node frequency generator 18 and the second node frequency generator 21 between two data packets, e.g., between data packets 50-3 and 50-4, of the individual data packets 50-1 to 50-n of the telegram, i.e., for example, at time t3. This corrects the error in the second node frequency generator 21 that has occurred since the previous calibration KAL1'. At the same time, node 2 sends an intermediate calibration packet 60 in the uplink to base station 3 at time t3. Based on the intermediate calibration packet 60, the base station can thus correct the time interval with respect to the opening of the node's reception window.

[0066] When sending the intermediate calibration packet 60, a calibration KAL2 of the first node frequency generator 18 and the first base station frequency generator 11 can also be performed, whereby the deviations of the carrier frequency of the individual nodes 2 of the network from the frequency of the first frequency generator 11 of the base station 3 can be adjusted. This allows the respective carrier frequency to be precisely adjusted, thus ensuring that the downlink signal fits very precisely into the narrow filter of the base station. As a result, the signal-to-noise ratio of the input signal at node 2 can be optimized, thus ensuring optimized reception.

[0067] In addition, an adjustment KAL3 of the first base station frequency generator 11 and the second base station frequency generator 12 can also be carried out in the base station 3.

[0068] The data packets 50-4 to 50-n sent after receiving the intermediate calibration packet 60 thus have a significantly higher probability of precisely hitting the reception window of the respective node 2 or of being received by the respective node with significantly suppressed noise. The time- or temperature-related offset (delay) of the time frequency and carrier frequency can therefore be significantly reduced with respect to the reception of data packets in the downlink.

[0069] The invention also makes it possible to spread the temporal arrangement of the individual data packets 50-1 to 50-n, i.e., to pull them apart. This, in turn, allows significantly more cost-effective energy buffers to be used in the respective node and base station compared to the previous approach, since the electrical energy of the energy buffer for transmitting or receiving the data packets 50-1 to 50-n no longer needs to be provided over a comparatively short period of time.

[0070] The previously described spreading makes it possible to make the pauses between two data packets significantly longer than before. The invention makes it possible to spread the data packets 50-1 to 50-n so far apart that the average pause between two data packets is greater than 500 ms, preferably greater than 700 ms, and particularly preferably greater than 900 ms.

[0071] The intermediate calibration packet 60 has a significantly shorter length than the conventional uplink data packets 40-1, 40-n, as shown in Figures 5a to 5c. This further increases the probability that the intermediate calibration packet 60 can be successfully received by the respective node 2.

[0072] Fig. 5 shows the structure of a data packet using data packet 40-1 as an example, which is transmitted from node 2 via the uplink to base station 3. The data packet comprises packet core data 400-3, which in turn contains pilots 400-1 and the respective node-specific ID. Area 400-4 contains the packet payload data.

[0073] For example, only pilots 60-1, 60-2, i.e., individual pilot sequences, can be transmitted as an intermediate calibration packet 60. Pilots are bits or bit sequences that are known to both the respective node 2 and the base station 3. For example, two pilots 60-1, 60-2, sent at a defined interval, can be provided as an intermediate calibration packet 60. For example, 15-bit pilot sequences can each be sent with a 30-bit interval. Since data packets are usually more than 30 bits long, the communication module 10 or the sync detection of the base station 3 knows that the received pilots 60-1, 60-2 are an intermediate calibration packet 60.

[0074] Alternatively, for example, several, e.g. two pilot sequences 60-1, 60-2 can be sent immediately one after the other, i.e. without any gap, as shown in Fig. 5cThis also allows the communication module 10 or the sync detection of the base station 3 to recognize that this is an intermediate calibration packet 60. The power and / or carrier frequency of the pilot sequences should be approximately the same to ensure that the pilot sequences originate from the same node.

[0075] Alternatively, together with one or more pilots 60-1, 60-2, as in Fig. 5d shown, the ID of the respective node 2 is also sent.

[0076] No further payload is required for Intermediate Calibration Package 60.

[0077] An intermediate calibration packet 60 can preferably also be sent repeatedly between two different data packets 50-1 to 50-n during the transmission of telegram 50 in the downlink. If an intermediate calibration packet 60 is lost, calibration can still be performed with increased probability during the transmission of telegram 50 in the downlink.

[0078] The correction of the transmission time and / or the carrier frequency of the data packets 50-1, 50-n can also be carried out several times in the temporal sequence of the same.

[0079] Preferably, the difference between a calibration of the first node frequency generator and the second node frequency generator and / or a calibration of the first node frequency generator and the first base station frequency generator and / or a calibration of the first base station frequency generator and the second base station frequency generator of a previous transmission of data packets with a corresponding subsequent calibration can be determined with regard to its frequency difference using an intermediate calibration packet and taken into account in the base station and / or in the node. In particular, the relevant difference between the calibration of the first node frequency generator and the first base station frequency generator can be taken into account for the correction of the carrier frequency in the base station. LIST OF REFERENCE SYMBOLS

[0080] 1 Communication system 2 Node 3 Base station 4 Charging unit (node) 5 Energy buffer (node) 6 Transmitting and receiving section 7 Antenna 8 Antenna 9 Display 10 Communication module (base station) 11 First base station frequency generator 12 Second base station frequency generator 13 Microprocessor (base station) 14 Reception window 15 Memory 16 Battery 17 Communication module (node) 18 First node frequency generator 19 Control and processing unit (node) 21 Second node frequency generator 22 Battery 23 Display 40Telegram uplink 40-1 to 40-nData packet uplink 50Telegram downlink 50-1 to 50-nData packet downlink 60Intermediate Calibration Package 60-1Pilot Sequence 60-2Pilot Sequence 400-1Pilot sequence 400-2ID 400-3Packet core data 400-4Packet payload CAL1'Calibration LF / HF in the node CAL2'Calibration HF node / HF base station CAL3'Calibration LF / HF base station CAL1 Calibration LF / HF in the node CAL2 Calibration HF node / HF base station CAL3 Calibration LF / HF base station

Claims

1. Method for transmitting data, in particular sensor data, by radio between at least one battery-operated node (2), which is preferably permanently installed at a fixed location, and a base station (3) in a communication system (1) using bidirectional radio transmission operation, the base station (3) having a communication module (10) having a first base station frequency generator (11), the node (2) having a communication module (17) having a first node frequency generator (18) and a second node frequency generator (21) with a lower frequency than that of the first node frequency generator (18), the communication module (17) of the node (2) being intended to transmit data to the communication module (10) of the base station (3) in the uplink by splitting a radio telegram (40) into at least two data packets, preferably into a multiplicity of data packets (40-1, 40-n), which are transmitted successively at intervals of time and are recombined in the receiver, the communication module (10) of the base station (3) being intended to transmit data to the communication module (17) of the node (2) in the downlink by splitting a radio telegram (50) into at least two data packets, preferably into a plurality of data packets (50-1, 50-n), which are transmitted successively at intervals of time and are recombined in the receiver, characterized in that an intermediate calibration packet (60) is transmitted to the base station (3) in the uplink between the data packets (50-1, 50-n), and the transmission time and / or the carrier frequency of at least one of the data packets (50-1, 50-n) is / are corrected between the data packets (50-1, 50-n).

2. Method according to Claim 1, characterized in that a calibration (KAL1) for the first node frequency generator (18) and the second node frequency generator (21) takes place between the data packets (50-1, 50-n) and / or a calibration (KAL2) for the first node frequency generator (18) and the first base station frequency generator (11) takes place between the data packets (50-1, 50-n).

3. Method according to Claim 1 or 2, characterized in that the communication module (10) of the base station (3) has a second base station frequency generator (12), the frequency of which is lower than that of the first base station frequency generator (11), and a calibration (KAL3) for the first base station frequency generator (11) and the second base station frequency generator (12) takes place for the correction.

4. Method according to Claim 2 or 3, characterized in that the intermediate calibration packet (60) is sent between two data packets of the plurality of data packets (50-1, 50-n).

5. Method according to one of preceding Claims 2 to 4, characterized in that as a result of reception of the intermediate calibration packet (60), the base station (3) readjusts the transmission time and / or the carrier frequency of the data packets (e.g. 50-4, 50-n) to be generated following receipt of the intermediate calibration packet (60).

6. Method according to one of preceding Claims 2 to 5, characterized in that as a result of the calibration (KAL1) of the first node frequency generator (18) and the second node frequency generator (21), the node (2) readjusts the reception time for the data packets (e.g. 50-4, 50-n) expected after the intermediate calibration packet (60) has been sent.

7. Method according to one of preceding Claims 2 to 6, characterized in that provision of the intermediate calibration packet (60) in the node results in the calibration (KAL1) for the first node frequency generator (18) and the second node frequency generator (21) taking place.

8. Method according to one of preceding Claims 2 to 7, characterized in that the calibration (KAL2) for the first node frequency generator (18) and the first base station frequency generator (11) takes place in the base station (3) when the intermediate calibration packet (60) is received.

9. Method according to one of the preceding claims, characterized in that a previous transmission of data packets (40-1, 40-n) in the uplink has already resulted in a calibration (KAL1') for the first node frequency generator (18) and the second node frequency generator (21) and / or a calibration (KAL2') for the first node frequency generator (18) and the first base station frequency generator (11) and / or a calibration (KAL3') for the first base station frequency generator (11) and the second base station frequency generator (12) having taken place.

10. Method according to one of preceding Claims 2 to 9, characterized in that an intermediate calibration packet (60) is sent repeatedly.

11. Method according to one of the preceding claims, characterized in that the correction of the transmission time and / or the carrier frequency of the data packets (50-1, 50-n) takes place multiple times in the chronological order of same.

12. Method according to one of preceding Claims 2 to 11, characterized in that the intermediate calibration packet (60) is shorter than the data packets (e.g. 50-4, 50-n).

13. Method according to one of preceding Claims 2 to 12, characterized in that the intermediate calibration packet (60) sent is exclusively pilots (60-1, 60-2) and / or ID data and / or packet core data, there being provision in particular for the pilots (60-1, 60-2) to be sent at specific intervals from one another or directly successively.

14. Method according to one of the preceding claims, characterized in that the mean pause between two data packets of the data packets (50-1, 50-n) is greater than 500 ms, preferably greater than 700 ms, particularly preferably greater than 900 ms.

15. Method according to Claim 9, characterized in that a difference between the calibration (KAL1') for the first node frequency generator (18) and the second node frequency generator (21) and the calibration (KAL1) for the first node frequency generator (18) and the second node frequency generator (21) and / or a difference between the calibration (KAL2') for the first node frequency generator (18) and the first base station frequency generator (11) and the calibration (KAL2) for the first node frequency generator (18) and the first base station frequency generator (11) and / or a difference between the calibration (KAL3') for the first base station frequency generator (11) and the second base station frequency generator (12) and the calibration (KAL3) for the first base station frequency generator (11) and the second base station frequency generator (12) is determined and taken into account in the base station (3) and / or in the node (2), in particular taken into account for the correction of the carrier frequencies in the base station (3).

16. Radio-capable node (21) for transmitting data, in particular sensor data and / or actuator data, to a base station (3) via a wireless communication channel, comprising a control and computing unit (19), a first node frequency generator (18), a second node frequency generator (21), a communication module (17) with an antenna (8) and a battery (22), characterized in that the control and computing unit (19) is programmed to operate the method according to at least one of the preceding claims.