METHOD AND DEVICE FOR RADIO TRANSMISSION OF DATA

Description

[0001] The invention relates to a method for the radio transmission of data according to the preamble of claim 1 and to devices configured for implementing the method according to claim 8. In the method, the data is sent and / or received in a standard-compliant telegram according to a defined standard that conforms to a standard. The data is thus exchanged using a standard-compliant telegram, whereby the standard may not provide for an error correction method, but rather a manufacturer-specific or proprietary area in the telegram. The defined standard refers to protocols for radio transmission, including the definition of the telegrams, for example, within the framework of the OSI layer model.

[0002] The process of reading consumption values from consumption recording devices, such as heat cost allocators, water meters, heat meters, or similar measuring devices or meters, is becoming increasingly automated. For this purpose, consumption and sensor data, e.g., from heat cost allocators, other consumption recording devices, or more generally from measuring devices or meters, is often transmitted to data collectors, which collect the measurement data, for example, centrally in the building. Such a data collector can be permanently installed in a central location or, for example, in a vehicle (drive-by), or brought by a meter reader (walk-by), or by a remotely controlled aircraft (fly-by) close to the recording devices and / or meters to receive the consumption and / or sensor data transmitted by the measuring devices.

[0003] Today, radio systems are typically used to transmit and, if necessary, forward this building consumption and / or building sensor data within a building sensor network, for example. To ensure compatibility between transmitters and receivers from different manufacturers, standardized telegrams are used for radio transmission. Such standards, such as the OMS standard, do not currently provide for the transmission of error correction data, particularly for forward error correction (FEC).

[0004] Known error correction methods using an FEC method, such as the Reed-Solomon method, can be used to correct any transmission errors that may occur in the transmitted telegram after its reception, for example, directly in the receiver, thus obtaining error-free data. This is achieved by redundantly encoding the data to be transmitted. These methods are particularly suitable for error correction in unidirectional radio systems.

[0005] In the paper "A Flexible Error Correction Scheme for IEEE 802.15.4-based Industrial Wireless Sensor Networks," Kann Yu et al. describes a method for forward error correction (FEC). This method uses error correction in conjunction with a special final error correction when a transmission error is detected by a checksum. The error correction data (FEC bits) are part of the entire telegram to be received. In such a system, error correction can only be implemented within the standard used.

[0006] WO 2015 / 074666 A1 describes an error correction method for telegrams containing two telegram parts containing the payload data and appended error correction data. However, the error correction data is only an optional telegram part that can be received, but is not mandatory. This is achieved by ensuring that the first telegram part conforms to a transmission standard on its own, so that the first telegram part can also be received independently of the other telegram part.

[0007] The standards used today for transmitting consumption, sensor or actuator data in a building via a local building radio network do not provide for this type of error correction for the telegrams and can therefore only be used for error-free transmission within a limited distance between receiver and transmitter. If a greater transmission range is to be achieved with this type of method, a significantly higher transmission power would have to be used. However, this is often not possible because the transmitters are usually battery-operated units. Since their battery capacity is usually low for cost reasons, only a limited battery and therefore transmission power is available to reliably achieve the desired service life of the measuring or consumption recording devices. The level of transmission power can also be limited by regulatory requirements, e.g.European directives may be restricted.

[0008] US 2014 / 0126580 A1 discloses a method according to the preamble of claim 1.

[0009] The object of the present invention is therefore to provide a method with which a radio transmission of data, in particular consumption or sensor data in a building by means of a local building radio network, by means of a standard-compliant telegram is possible even over larger ranges without loss of information, wherein this defined standard may not provide for an error correction method.

[0010] The above object is achieved by a method having the features of claim 1 and devices having the features of claim 8. In particular, it is provided that in addition to the standard-compliant telegram, at least one further, non-standard-compliant telegram is sent and received, which contains an error correction data record with error correction data for the data contained in the standard-compliant telegram, which, due to redundancy, allow error correction of the data in the event of transmission errors.

[0011] By additionally sending a telegram with error correction data, the advantages of error correction can also be used for radio transmission according to a standard without error correction, without the standard itself having to be changed. Of course, the method can be used in the same way if the standard provides for error correction, but this is not to be used or is to be supplemented. To apply error correction, it is sufficient to set up the transmitters and receivers intended for radio transmission so that at least one (and preferably exactly one) additional telegram with the error correction data is sent. In addition, the receiver is set up to receive the additional telegram with the error correction data and to carry out the error correction in the event of a transmission error in the standard-compliant telegram.The method according to the invention thus leads to greater error robustness and thus a greater transmission range. Accordingly, it is possible to reduce the density of receivers used for meter readings, thereby saving costs at the point of consumption. Another possibility is to reduce the transmission power while maintaining the same range. This leads to cost savings in the manufacturing of the devices used as transmitters, since, for example, the battery capacity can be reduced.

[0012] A particular advantage of the method proposed by the invention is that, despite the integration of error correction into the data transmission proposed by the invention, the standard-compliant telegrams remain unchanged. This ensures that data transmission, for example, remains standard-compliant within the scope of consumption value recording or the transmission of other measurement data, so that other transmitting and receiving devices in the transmission system, e.g., the building sensor network, can continue to be used. The advantage of error correction is then reserved for the devices in which the method according to the invention is implemented.

[0013] According to the invention, the at least one additional telegram is sent after the standard-compliant telegram and is received accordingly later. This allows the receiver to decide, after receiving the standard-compliant telegram, whether the additional telegram containing the error correction data also needs to be received. If the data transmission was error-free, the receiver can forgo receiving it.

[0014] Accordingly, according to the invention, the at least one further telegram sent after the standard-compliant telegram is only received if a transmission error was detected in the standard-compliant telegram. This saves energy in the receiver by additionally receiving the error correction data. If, due to the transmission times between the standard-compliant telegram and the subsequent further telegram with error correction data being too short, it is not possible to evaluate whether a transmission error is present in the standard-compliant telegram before the at least one further telegram arrives, the telegram is received as a precaution. The telegram can be buffered and, once the check for transmission errors has been completed, evaluated if necessary or otherwise discarded. In this case, the receiver at least saves energy required to carry out the evaluation.

[0015] In a preferred embodiment of the invention, the at least one further telegram contains, in addition to the actual error correction data of the error correction data set, an identifier. This identifier contains information for implementing the error correction, such as the type of error correction and / or parameters required to implement the error correction, and / or information regarding which components of the telegram were included in the calculation of the error correction data. This allows the error correction or the error correction data set to be designed flexibly and, for example, to have different lengths depending on the correction class to be achieved. The error correction data alone or the combination of error correction data and identifier can be referred to as the correction data set.

[0016] Possible types of error correction include Bose-Chaudhuri-Hocquenghem (BCH) codes, Reed-Solomon (RS), and other systematic forward error correction (FEC) codes. In systematic codes, the information bits are included in the code word generated by the error correction in their unaltered form, making it possible to read the data without performing error correction during an error-free transmission. This is particularly important for decoding the received radio telegrams with low computational effort and thus with low power consumption.

[0017] It can be intended to transmit only one version number of the error correction in the identifier, the meaning of which is known to the recipient of the telegram. The recipient can, for example, maintain a table that contains the type of error correction for each version number, such as the polynomial used, and all the information required to perform the error correction. This can save several bytes in the transmission of the identifier itself, because not all information needs to be transmitted in plain text.

[0018] If the receiver has access to the error correction data in addition to the actual data, specifically the payload data specified in the standard and any additional manufacturer-specific data, it is possible to reconstruct the error-free, standard-compliant telegram despite transmission errors in either the payload data or the error correction data. However, this requires that the receiver knows the type of error correction and the required parameters.

[0019] If this information were transmitted in the identifier according to the invention, it would not be possible to correct an error in the identifier itself. Therefore, a preferred embodiment of the invention provides for the identifier to have its own error correction. For this purpose, separate identifier error correction data is provided in the identifier. For example, if the identifier, also referred to as the FEC header, comprises 1 byte = 8 bits, 3 bits can be provided for the actual identifier and a further 3 bits for identifier error correction data. This identifier error correction data is also referred to as FEC parity bits. According to the invention, this separate error correction of the identifier is completely independent of the error correction of the rest of the telegram, in particular the payload data.It may be provided that the error correction used in the identifier is not changed during the service life of the method so that all receiving systems can assume that there is only one type of error correction in the identifier.

[0020] In one embodiment of the invention, provision can be made for the data to be transmitted in encrypted form. For this purpose, the data to be transmitted is transmitted in encrypted form in the telegram. The error correction data is preferably determined based on the already encrypted data and is no longer encrypted itself. This is unnecessary because it is not possible to determine the original data from the error correction data, as this can only reconstruct the data in encrypted form. According to the invention, the identifier is also not encrypted because the identifier and error correction data must be evaluated at the receiver before decryption in order to be able to carry out error correction in advance if an error occurred during radio transmission.

[0021] In a further embodiment of the invention, the defined standard provides for the embedding of check values in the telegram by inserting a check block, each with an associated check value for the preceding data block, after a data block containing data and / or manufacturer-specific data, which together are also referred to as payload data. This can also apply to the subsequent telegram containing the error correction data set or at least the error correction data of the error correction data set.

[0022] An example of embedding check values in the telegram is the inclusion of CRC blocks in the standard telegram. After a certain number of bytes containing the actual data to be transmitted (specifically, the payload), a certain number of CRC bytes are provided as a check value in a check block to perform a so-called cyclic redundancy check. This allows the receiver to determine whether the transmission contains errors or not. This makes it possible to perform error correction with the error correction data only if a transmission error has occurred.

[0023] Data transmission telegrams typically contain a sync word in their preamble, which synchronizes the receiver to the sender's transmission clock, so that the actual data (in the sense of the payload) can be transmitted after this sync word. This also applies to the standard-compliant telegram.

[0024] The advantage of the described method is that the additional telegram according to the invention increases the receivability of the standard-compliant telegram by providing error correction for this telegram without changing the standard. Thus, standard-compliant telegrams remain receivable within the framework of the standard without error correction for receivers not configured for the error correction according to the invention.

[0025] According to the invention, at least one additional telegram is sent without a preamble and sync word. The receiver maintains bit synchronization during the short transmission pause, on the order of up to a maximum of 10 bit times, between the standard-compliant telegram or a preceding additional telegram and the additional telegram without a preamble. The bit time is defined as the time required to transmit one bit.

[0026] By eliminating the preamble and the sync word, the energy required for error correction is reduced. This can also be useful if, according to the invention, several additional telegrams are sent for error correction. In principle, it is of course also possible to transmit all data for error correction in just one additional telegram as described, without a preamble (and therefore without a sync word).

[0027] According to the invention, the at least one additional telegram is transmitted at a fixed (in the sense of a defined) time interval from the standard-compliant telegram. This makes it particularly easy for the receiver to assign the at least one additional telegram to the standard-compliant telegram. The fixed temporal relationship can refer to the beginning or end of the standard-compliant telegram.

[0028] However, the time interval is particularly preferably based on the end of the standard-compliant telegram. If the standard-compliant telegram has different lengths, the transmission gap can be designed to be particularly small and, above all, always the same.

[0029] In practice, the length of the time interval or the transmission pause is the result of an optimization task with complex interrelationships. If the distance is shorter than the activation time of the radio chip, which is on the order of 1 ms, this results in an energy advantage compared to a long distance, where the activation time must be invested. Furthermore, the collision rate increases with increasing distance as long as telegrams from other devices do not fit into the distance gap. This means that the collision rate is proportional to the length of the two telegrams plus their time interval (transmission pause). Above a certain size of the distance gap, the collision rate decreases again. The longer the time interval, the longer the receiver has to wait until the telegram can be fully processed in case of transmission errors.The receiver must buffer the first received telegram and can only perform error correction after receiving the second telegram. The longer the time interval, the more telegrams must be buffered on average. If the time interval is chosen too short, the first telegram may not have been processed yet when the second telegram arrives. Against this backdrop, a transmission pause of between 5 and 10 bit times has proven particularly advantageous in practice.

[0030] The invention also relates to devices for the radio transmission of data, comprising a radio transmitter, a data memory for storing the data to be transmitted, and a computing unit, which are configured to compile a standard-compliant telegram and at least one further telegram according to the method described above and to transmit them via the radio transmitter. According to the invention, a device for the radio transmission of data can also be equipped with a radio receiver, a data memory for storing the transmitted data, and a computing unit. The computing unit of the radio receiver is configured to receive a standard-compliant telegram and a further telegram according to the method described above and to use the error correction data set, iethe error correction proposed according to the invention and in particular the error correction data, to correct possible transmission errors in the telegram.

[0031] The computing unit is therefore configured to carry out the above-described method according to the invention or parts thereof.

[0032] For this purpose, a device designed as a radio transmitter (hereinafter also referred to simply as a transmitter) can transmit a standard-compliant telegram. According to the invention, this transmitter can be configured to generate the error correction data for this telegram and transmit it in a further telegram. The device according to the invention can also be configured as a radio receiver (hereinafter also referred to simply as a receiver), which can receive the at least one further telegram in addition to the standard-compliant telegram. This device is configured to correct transmission errors in the standard-compliant telegram using the error correction data from the at least one further telegram.

[0033] The invention is explained below using exemplary embodiments and with reference to the figures. Fig. 1 shows the structure of the telegrams as used in a method not belonging to the invention, in which the second telegram has a preamble with a sync word. Fig. 2 shows an inventive structure of the telegrams according to an embodiment of the invention, wherein the second telegram has no preamble and no sync word. Fig. 3 shows an inventive error correction identifier with its own error correction identifier data according to an embodiment of the invention.

[0034] In Fig. 1 The structure of telegrams 1, 2 is shown schematically according to an embodiment not belonging to the invention, as they can be transmitted in a method. The standard-compliant telegram 1 has a preamble with sync word 7 and the individual data 3 specified in the standard, which can be divided, for example, as indicated, into different data areas, e.g., a standard data area and a proprietary area for transmitting manufacturer-specific data. Another telegram 2, also referred to as an error correction telegram, has (unlike the invention) a preamble with its own sync word 8.

[0035] Error correction data 4 is transmitted in error correction telegram 2. In addition to the actual error correction data 6, error correction telegram 2 also contains an identifier 5. This identifier 5 transmits a version number, which provides the receiver with the information necessary to perform error correction. Error correction data 4 and identifier 5 are collectively referred to as the error correction data set.

[0036] Fig. 1 also shows, from top to bottom, the chronological sequence of a method for radio transmission of data 3, 4, 5, for example in a local building radio network. The data can be building consumption, building sensor and / or building actuator data 3, error correction data 4 and / or an identifier 5 of the error correction.

[0037] As in the implementation of the method according to the invention, the standard-compliant telegram 1 to be sent is first compiled in a transmitter with the corresponding preamble 7 (containing the sync word). The consumption, sensor, and / or other data 3 for the data points of telegram 1 specified in the standard are first provided. This data can then be encrypted if necessary. This data 3, 7 is inserted into the standard-compliant telegram, with check values (not shown) being calculated from the data if necessary and incorporated into the DataLink layer of the transmission protocol (according to the OSI layer model).

[0038] Next, the error correction data 4 is calculated using the designated error correction method. This data takes into account all data 3, preferably already in encrypted form, as well as, if applicable, the check values and / or the preamble 7. In this case, the error correction data 4 is calculated from the entire telegram 1.

[0039] The error correction data 4 thus obtained are provided in error correction telegram 2. Together with the error correction data 4, the identifier 5, which contains information for implementing the error correction, is provided in error correction telegram 2. To ensure that the identifier 5 can be transmitted, it is provided with its own error correction.

[0040] The Fig. 1 Preamble 8, which is optionally also included in the further telegram 2 (error correction telegram), is not provided for in the method according to the invention.

[0041] Both telegrams 1, 2 are sent with a defined time interval Δt from each other.

[0042] The receiver first receives the standard-compliant telegram 1 and checks for transmission errors, for example, using a cyclic redundancy check using CRC bytes as check values. If an error occurred during the transmission of telegram 1, the second telegram 2 is also received with the error correction data 6, or any signals already received and buffered are evaluated.

[0043] For error correction, it is necessary to determine in advance which error correction method was used. To do this, identifier 5 must be read out with the error correction information. If an error occurred during the transmission of identifier 5, it can be restored using the identifier's own error correction. This provides the receiver with information about the type of error correction, the position of error correction data 4, all parameters, and all other information necessary for error correction. The receiver can then use error correction data 4, which is contained in the subsequent telegram 2, to perform error correction. If the transmission errors do not exceed any existing limit for the number of maximum errors during error correction, the original, error-free, standard-compliant telegram 1 can be reconstructed.

[0044] Fig. 2 shows the inventive structure of telegrams 1 and 2. Error correction telegram 2 is sent without its own preamble and sync word. To receive these telegrams, the receiver maintains bit synchronization after receiving the standard-compliant telegram. After the time Δt known to the receiver, error correction telegram 2 can also be received. Otherwise, the procedure corresponds to the previously described case.

[0045] In the event that an identifier 5 is required for the application of the error correction proposed according to the invention during the radio transmission of data 3, it is advisable for the identifier 5 to have its own identifier error correction data 4 for the independent error correction of the identifier 5. This allows the identifier 5 to be independently corrected if a transmission error occurs in the identifier 5. A corresponding identifier is shown, for example, in Fig. 3 illustrated.

[0046] There, an identifier 5 with a total of 8 bits (i.e., one identifier byte) is shown with identifier data 9, which describes the type of error correction, can be read directly by the receiver, and contains the information for carrying out the error correction. 3 bits are used for this. Following the identifier data 9, the identifier error correction data 10 is provided, which is calculated on the basis of the identifier data 9 and, in the event of an error due to redundancy, allows the identifier data 9 to be reconstructed. A conventional FEC method can also be used for this. According to the invention, this is clearly predefined and can therefore be used without further parameterization. This method should not be changed in a device generation so that all devices are compatible with one another. 3 bits are also provided for the identifier error correction data 10.

[0047] The remaining Fig. 3Unmarked bits can be used for other purposes, e.g., as a check value for detecting transmission errors, analogous to the previously described method for CRC bytes. Thus, according to the invention, the identifier 5 in telegram 2 is completely self-sufficient with regard to detecting and correcting transmission errors. List of reference symbols:

[0048] 1Standard-compliant telegram 2Further telegram 3Data 4Error correction data 5Identifier 7Preamble with sync word, standard 8Preamble with sync word, error correction (not part of the invention) 9Identifier data 10Identifier error correction data Δt time interval

Claims

1. Method of radio transmission of data, wherein the method comprises the following steps: sending the data in a standard-compliant telegram (1) according to a defined standard by a radio transmitter for radio transmission, wherein the standard is defined according to a protocol for radio transmission including specifying of the telegrams, sending a further telegram (2) by the radio transmitter, wherein the further telegram (2) contains an error correction data set with error correction data (4) for the data (3) contained in the standard-compliant telegram (1), which error correction data (4) allow error correction of the data (3) in the event of transmission errors due to redundancy, receiving the data in the standard-compliant telegram (1) by a radio receiver for radio transmission and detecting a transmission error in the received standard-compliant telegram (1) by the radio receiver, wherein, in the event of a transmission error in the standard-compliant telegram (1), the further telegram (2) is received and evaluated with the error correction data (4) and the error correction is carried out by the radio receiver, wherein the further telegram (2) is sent at a defined time interval after the standard-compliant telegram (1), wherein the further telegram (2) is sent without a preamble and without a sync word, but after a transmission pause which is so short that the radio receiver does not lose bit synchronization during the transmission pause, wherein the short transmission pause is a maximum of 10 bit times and a bit time is defined as the time required for the transmission of a bit, and the further telegram (2) is only received and evaluated if a transmission error was detected in the standard-compliant telegram (1).

2. Method for radio transmission of data according to claim 1, characterized in that the further telegram (2) contains an identifier (5), wherein the identifier (5) contains information for performing the error correction.

3. Method for radio transmission of data according to claim 2, characterized in that the identifier (5) contains its own error correction with identifier error correction data (10) for correcting the identifier (5).

4. Method for radio transmission of data according to claim 2 or 3, characterized in that a version number is transmitted in the identifier (5), based on which the receiver can determine the information for carrying out the error correction.

5. Method for radio transmission of data according to one of the preceding claims, characterized in that at least a further telegram (2) is transmitted at a defined time interval from a preceding further telegram (2).

6. Method for radio transmission of data according to claim 5, characterized in that the defined time interval is related to the end of the preceding further telegram (2).

7. Method for radio transmission of data according to claim 1, characterized in that the defined time interval is related to the end of the standard-compliant telegram (1).

8. Apparatus for the radio transmission of data having a first apparatus designed as a radio transmitter with a data memory for storing the data to be transmitted and with a computing unit of the radio transmitter, wherein the computing unit of the radio transmitter is adapted to compile a standard-compliant telegram (1) and a further telegram (2) according to the steps of sending according to claim 1 and to send them by the radio transmitter, a second apparatus designed as a radio receiver with a data memory for storing the transmitted data and with a computing unit of the radio receiver, wherein the computing unit of the radio receiver is adapted to receive and evaluate the standard-compliant telegram (1) and, in the event of a transmission error in the standard-compliant telegram (1), the further telegram (2) according to the steps of receiving according to claim 1 by the radio receiver.