DE19952840A1 - Data transmission for temporarily inactive recipients - Google Patents

Abstract

The invention relates to the transmission of digital data by sending data packets from a transmitter to one or more receivers whose receiving device is temporarily inactive. The transmitter emits a data packet from which the receiver can determine a waiting time immediately succeeding the data packet, during which no data concerning the receiver are sent, and the receiver determines the waiting time from the data packet and immediately deactivates its receiving device for the duration of this waiting time.

Description

Technical field

The invention relates to the transmission of data from one Sender to one or more receivers whose Receiving device, in particular to protect Batteries that are temporarily inactive.

State of the art

For price labeling it is e.g. B. from the patent US 4,002,886 (Sundelin) known to be close to the goods on the shelf an electronic display is attached by a Head office is controllable. With these under the Designation 'Electronic Shelf Label', ESL, known It is possible to set up price displays in short Change time and with that valid for the cash registers To keep the database reliably and consistently.

While the font above is a wired Control provides for wireless signal transmission by electromagnetic waves z. B. in the patent US 4,521,677 (Sarwin) proposed. To take advantage of one to take advantage of such should also Power supply is not based on wire connections. There Solar cells do not always provide enough energy assuming a battery supply. there LCD displays are less of a problem the receiver circuit is the main energy consumer  including the evaluation logic, which has been are ready to receive.

The object of the invention is therefore to provide a solution where the receiving circuit is mostly turned off can be and yet simple and reliable any ad can be changed at flexibly selectable times.

Presentation of the invention

The invention uses the knowledge that a relative Waiting time during which the reception circuit is deactivated can be both explicit and implicit in the data packets may be included, and it is only necessary that this waiting time can be determined as easily as possible and No relevant data during the waiting period of the transmitters sends. For this, two are different in detail Solutions specified that combine optimally, but also can be used individually.

On the one hand, waiting packets are sent out in which the Time until the next data transfer is encoded. Logically, these times are monotonous falling until the time is reached. A recipient so only needs to receive any of these packets and can then for the time specified in it deactivate.

On the other hand, multiple records are always made up of one Address and the associated user data exist for a Package summarized. The addresses are sorted, then divided into groups and in ascending order  Order sent. According to the ascending Sorting only with respect to the groups among themselves necessary; will be the highest address within the group sent first.

This allows a recipient to be at the beginning of the group determine if his address is in the group at all can be included (if it is less than or equal to) or not (if it's bigger). Deactivated in the latter case the receiver switches its receiving circuit for the remaining time, in which, in particular, sends the group's user data.

Further features and advantages of the invention result from the following description, which in connection with the accompanying drawings, the invention using a Exemplary embodiment explained.

Brief description of the drawings

Show it

Fig. 1 shows the basic arrangement with a transmitter and two receivers,

Fig. 2 shows the structure of a receiver

Description of an embodiment of the invention

The invention will now be described in terms of the preferred ones Embodiment of an electronic system Price labeling ('electronic shelf label', ESL) described.  

Such a system consists, as indicated in FIG. 1, of a transmitter 10 with an antenna 11 . Electromagnetic waves in the approved range of 868 or 915 MHz are preferably used; other frequencies, including infrared light, are also easy to use.

As a receiver 1 has two price displays 20, 20 are shown in FIG. 'Shown, which are mounted on a holder 12.

Any goods stored in the vicinity are not shown. A large number of hundreds to several thousand price displays 20 are used in practice.

In FIG. 2, the components of a typical price display 20 are shown. Visible is the display 21 , which is preferably implemented using LCD technology. This includes a display driver 22 which carries out the necessary control and permanently displays the data transmitted via the connection 29 . These displays are generally known in versions with low power consumption, in particular from clocks. Both are therefore permanently connected to a battery 23 ; a possibly provided main switch is not shown.

A timer 24, which operates a, preferably electronic, switch 25 is also permanently supplied by the battery. The switch switches the power supply for the reception controller 26 and the receiver 27 on and off.

The reception controller 26 is preferably a microcontroller, as is generally known in various versions. Relevant microcontrollers generally have one or more power-saving modes that can be used expediently in the invention. Versions with built-in time control are also known, which can also be used in energy-saving mode and are then used instead of the time control 24 shown separately in FIG. 2.

The timing control 2, 4 normally receives a time value from the microcontroller 26 . With the transfer of the same, the switch 25 is opened and the time value is loaded into a register which is counted with clock signals. When a predetermined counter reading, in particular zero, is reached, the switch 25 is closed again. The opening and closing of the switch takes place in a known manner, the data sheets and application descriptions of the microcontroller can be removed in such a way that the microcontroller is stopped in a defined manner (and then switched off, if necessary) and its work is restarted after the set time. When using a counter, it is also ensured that the microcontroller is activated at the latest after the counter has run through once, even if the time control has not been set by the microcontroller 26 after a battery change. A timer 24 is certainly also possible, in which a capacitor is charged to a voltage that can be determined by the microcontroller 26 and thus an adjustable time is reached.

Both the receiver 27 and the microcontroller 26 are switched on and off with the switch 25 .

If necessary, switching off the microcontroller 26 can also be dispensed with if its power consumption is negligible compared to that of the receiver.

An antenna 28 shown symbolically in FIG. 2 is connected to the receiver 27 . This antenna 28 is to be designed according to the reception area used and according to the state of the art; in the 868 or 915 MHz range, for example as a planar antenna, which can be integrated on printed circuit boards.

In the following it is assumed that data transmission from transmitter 10 to receiver 27 is made possible in a known manner. It is irrelevant which type of modulation and bit coding is chosen. An example is a two-frequency technique in which a center frequency of 868 MHz is changed by +100 kHz for a 1-bit and by -100 kHz for a 0-bit. The simplest coding is as an asynchronous method, in which the transmitter and receiver are clocked plesiosynchronously for the time of a character that has started with a start bit. However, phase coding, also known as Manchester code, is preferably used, since it is self-clocking and allows a high transmission speed in relation to the bandwidth. However, the selection is primarily without influence on the invention, so that it is assumed in the following that the transmitter sends a data block which consists of characters which, for the sake of clarity, are represented below as 8-bit bytes.

In a first variant of the invention, the first character identifies the type of data block. The character "W" specifies that a waiting time follows, that is to say a global waiting packet is present. This waiting time is preferably specified in a predetermined unit, for example milliseconds or the period of a 32768 Hz crystal. Alternatively, additional digits before or after time can be used to encode a selection of units, or a logarithmic measure can be used. In the latter case, the time control is expediently designed such that the microcontroller switches on the receiver and manages the logarithmic time coding. In the case of a 32768 Hz crystal and a 16-bit counter, the maximum waiting time is 2 seconds.

At a data rate of the transmitter of 8000 bit / sec less than 3 msec is required for the waiting packet, so that the Receiver must be switched on for less than 5 msec per 2 sec got to; the electricity savings are considerable.

With a waiting package marked in this way, the sender sends the Recipients the relative time of the next data transmission communicated. The transmitter thus simultaneously announces that no relevant data blocks were sent before this time become. A recipient who receives such a waiting packet can then for the time specified therein Switch to power saving mode and especially its receivers switch off circuit.

This waiting packet is sent repeatedly by the transmitter preferably in close succession, the included Waiting times for subsequent waiting packages around the past times are reduced. So it doesn't matter when a recipient activates at the time of the to determine the next data transmission. In particular, it can a newly added recipient can wait at any time  determine. By making time relative to each Sending time is an absolute time unnecessary.

When the waiting time has passed and the recipients have theirs Receiving circuit and possibly the control more reactive, are given two options.

As a first option, new waiting packets are sent, the included a new wait. This is the case if no user data has to be sent to the recipient. Is the maximum waiting time z. B. 2 sec, but the average time between two changes one Hour, so in the vast majority of cases a waiting packet will be sent again. Continue to be then all previously active receivers with the first one change the new waiting package into the inactive state so that the subsequent waiting packages appear to be superfluous. But it is clear that this is a high level of Reliability especially for newcomers Recipient is reached.

If the waiting time exceeds the codable value, so either, as described above, each Wait for the maximum codable value and then be reduced in each waiting package so that all Receiver leave the waiting state synchronously and a new one maximum coded waiting packet received until the intended Total waiting time except for a rest that is codable, is exhausted. Alternatively, of course, without leaving the idea of the invention, initially only Waiting packets of the maximum codable waiting time sent where the coded wait is not with everyone  Package is decreased. If a data transmission is pending, the following waiting packages with decreasing waiting time sent until the scheduled time for data blocks to be sent is reached.

So the second option is the time of transmission for Data blocks reached, e.g. B. a new price for one Price display, transfer. Then the transmitter starts with the transmission of data blocks, for example, by the letters "D" are identified in the first place. This is followed in a known manner by the recipient address, i.e. H. the price tag number and the price to be displayed. These data blocks are affected with each one Recipient number sent as long as price changes are to be entered. After that, the transmission of Waiting packages so that the recipients are back in the Can enter power saving mode.

Especially in cases where the price changes are not can be acknowledged by a return channel is one repeated and regular transmission of the current prices necessary from the price tags, for example entered after the price has been transferred identically several times become. With a large number of several thousand Price tags would therefore mostly contain data blocks User data are sent so that for the previously described embodiment of the invention, in which the Waiting time explicitly and globally coded for all recipients is, there is no space.

Therefore, the alternative embodiment of the invention allows it also recognizes to the recipient that for one of the  Recipient easily determinable time none for the recipient certain dates are expected.

The preferred embodiment of this variant of Invention transfers the addresses and data in groups that e.g. B. from always sixteen addresses and associated user data consist. An optimal variant is initially the addresses and then the order of the addresses Transfer user data. The recipient finds his address not in the addresses so he can be for the rest of the group turn off the receiver. This will be easier if, like preferred, the user data have a fixed length, so that the entire data block of a group of addresses one in advance determinable time needed.

An improvement is achieved in that the addresses are sent out sorted. That instead of the following described ascending sorting also a descending can certainly be used further description.

When sorted in groups, they are in everyone Group used addresses always larger than the addresses in the previous groups. For example, the Addresses sorted in ascending order and in groups of 16 each summarized. However, within a group the largest address sent first; the order of the others is practically meaningless. Hence comes with every group immediately after the indicator for the type of data packet and possibly other important administrative information largest address. The recipient does not wait to receive the entire group, but compares immediately Receive the first address with your own address.  

If your own address is larger, it is ensured that the following addresses do not affect the recipient. So he can be the recipient for the rest of the group switch off. The waiting time can be determined in advance because the Addresses and data have a fixed length. In contrast to the previous variant where the addresses are unsorted, but this is transmitted in the group before the user data not necessary for sorted mailing; on every The user data can immediately follow the address. Only the largest address must be sent first.

A closer look reveals that both variants common is that the waiting time before the start of the user data associated with the first address. this applies even if variable long user data are used for which the length of the user data is ahead of the user data is transmitted, in particular through a field for the User data length in the data block. Here too is sorted First send the address to send either has a fixed length or is delimited by a closing character. Because the first address will be fully received anyway a final sign is possible. Before or after the total length of the group block is transmitted coded.

The waiting time can be calculated from this using the data rate become.

A further improvement is possible by alternately using ascending and descending sorting. For example, if addresses 1 , 2 , 3 , 4 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 are sent in groups of four, the following groups are sent:
4, 1, 2, 3;
10, 7, 8, 9;
14, 11, 12, 13.

In order to prevent a receiver with a very large address from having to wait a very long time and thus consuming more energy than a receiver with a very small address, the sorting term is reversed in the next series of data blocks, that is to say the following after the next waiting time Groups sent:
11, 14, 13, 12;
7, 10, 9, 8;
1, 4, 3, 2.

It is assumed here that the same recipient at be addressed again next time; this is natural unnecessary; d. that is, on the second broadcast of groups a different set of recipients can be addressed. In this case, the transmitter is useful in any one Form the address order in the sent packets encoded, e.g. B. instead of "D" as a data packet Indicator "A" for ascending and "Z" for descending Sorting. In this case it is even within one Shipment, d. H. between two waiting times, a mixed one Sending possible; d. that is, the sorting for each data packet is noted in the data packet.

However, all data packets have to be sorted together the benefit of another within one shipment Possibility of improvement. This applies if not always all recipients are addressed, as in the Is usually the case. As soon as at z. B. ascending Sorting all addresses of a data packet are greater than is the own address, all subsequent data packets are up to the next waiting package does not matter. Is the second The recipient then needs the smallest address in the package  only evaluate the first two; expediently therefore preferably all addresses are sent first. In this Further training is the waiting time in the data packets until next broadcast included. The sender can who knows the number of recipients to be addressed is determined before sending the first data packet and then the waiting time accordingly in the data packet can accommodate additional field. If the pre-calculated Waiting time exceeds the maximum codable waiting time, is in the sense of the first embodiment above Invention encodes the maximum wait time; after their expiration the recipient immediately finds a data packet again Addresses all exceed your own are taken from the Waiting time and goes back to the waiting state. Furthermore can then, as described above for waiting packages, initially the maximum codable waiting time in the data blocks be sent if this is before the planned end of the All pending data blocks are sent, and only against End of the waiting time. This is one Both variants can be nested, in the case of Usually two waiting times are encoded; first the by next data block of a group and secondly the up to End of the transmission of a sequence of data blocks.

A previously less attractive variant used instead a full sorting of the addresses a group formation over other criteria, for example the last or the first bits of the address, generally through a bit mask. In this generalized form of the invention is after the Identifier for the data block of a group of the Transfer total length and the selection mask for the group. The recipient masks his own address and calculates  the waiting time from the total length when masking shows that his own address is not affected. in the Basically, the selection criterion can be of any complexity , for example, as regular expressions or a Program code (bytecode) by the microcontroller interpreted or executed. This complexity will however, so far not when applied to price tags needed. In any case, the term "sorting" is in to understand this general sense, according to the one Sorting an order of predetermined kind in the set of Addresses determined. Otherwise, the total length is nothing other than an encoding of the waiting time that the recipient must at least wait before data relevant to him be sent. Instead of the length in bits or bytes therefore explicitly a waiting time in a previous arranged or presented in one of the numbers or attached unit.

It can be seen that the recipient is in any case from the sent data block determines a waiting time. This can be explicit and much longer than that Transmission time of the data block when waiting packets available. Or it can be the length of the data block if this is based on one at the beginning of the Data blocks sent criterion to be ignored needs.

If one abstracts the idea of the invention further, it is determine that the record indicator "T" for a Waiting package effectively a selection criterion 'for everyone' represents. This results in the abstract basic idea of Invention that the one of the recipient of the record  Selection code that evaluates to 'wait' or 'do not wait' and takes a waiting time and waits for the waiting time, if the selection code to 'wait' is evaluated, with the Waiting time, depending on the selection code, implicitly, d. H. can be predetermined or explicitly encoded.

So this is the mixed one already indicated above Use possible in the period between User data transmissions aimed at a fixed point in time relative waiting times and during user data transfers transfer relative waiting times to the next group become.

The previous description used - a Transmission method in which whole characters are always included a fixed number of bits, in particular 8-bit bytes, were transferred and therefore the asynchronous process in Question is coming. The waiting blocks are also used by the Data blocks are distinguished by a by the first character enable quick decision. Alternatively, you can of course the address zero or another reserved address serve as an indicator that it is is a waiting block.

In particular, alternative transmission methods include as indicated above, a phase coding or that HDLC methods in question, which are self-clocking and one allow better utilization of the channel capacity. Also are here frame formats possible, in which the data in differently wide bit groups are divided and so especially by the first bit after a possible necessary preamble between waiting blocks and those with A distinction is made between addresses and user data. The selection  the transfer process therefore essentially depends on the technical conditions in the transmitter and the receiver and affects the application of the present invention only marginal.

In the previous description, only the Transmission channel from sender to receiver shown. In the preferred form of use is also a return channel from the price display to the "transmitter" with which the Data transfer can be acknowledged to the Increase reliability. The used for this Techniques including collision handling can be used in addition to the described invention and can be found in the prior art.

In addition to the application described for price displays further areas of application are possible in which simultaneously economical energy consumption together with one defined accessibility are required. To be mentioned Applications from telemetry in which one or more Sensor to not fixed from the outset, however have to record measurements at the same times, for example in environmental monitoring. Here is the Data transfer to the amount of data from one bit reduced, namely to the instruction: "Measurement carry out".

Use in large areas is also possible Radio tracking of animals using a battery powered Transponders are provided, where also the time of the Location is unpredictable and a very large number of Transponders is in use.

Claims (24)

1. Method for the transmission of digital data by sending data packets from a transmitter to one or more receivers, the receiving device of which is temporarily inactive, wherein

• the transmitter emits a data packet from which the receiver can determine a waiting time during which no data relating to him are sent,
• - The recipient determines the waiting time from the data packet and deactivates his receiving device for the duration of this waiting time.

2. The method of claim 1, wherein a waiting time in the Data packet is encoded. 3. The method according to claim 2, wherein series of data packets are used where the waiting times are descending are and the remaining time until a common Correspond to the time. 4. The method of claim 1, wherein

• - A selection code is contained in the data packet, which is evaluated by the recipient and
• - The waiting time is activated depending on the result of this evaluation.

5. The method of claim 3, wherein

• - an address is assigned to each recipient,
• the data packet comprises a header which contains one or more addresses,
• - The selection code consists of comparing the addresses from the header with the address of the recipient.

6. The method according to claim 4, wherein in the presence of several addresses - according to a fixed default or sorting coded before the address - largest or smallest address appears first in the data block and the other addresses are smaller or larger than the first. 7. The method according to any one of claims 1 or 3 to 5, the waiting time is predetermined to be constant. 8. The method according to any one of claims 1 to 5, wherein the Waiting time is encoded in the data packet. 9. The method according to any one of claims 4 or 5, wherein the Waiting time by multiplying the number of addresses with that for an address with maximum user data length required airtime is determined. 10. The method according to any one of claims 6 to 8, wherein Series of data blocks are sent in which in addition, a second waiting time is encoded, which is the End of the series or the maximum encodable time. 11. Transmitter for the transmission of digital user data by sending data packets to one or more receivers, the receiving device of which is temporarily inactive, wherein

• - The sender emits a data packet from which the receiver can determine a waiting time during which no data concerning him are sent.

12. The transmitter of claim 1, wherein a waiting time in the Data packet is encoded. 13. The transmitter of claim 12, wherein the transmitter is a series of. Data packets a time counter radiates the remaining time to determined at a time set and this Remaining time entered in each data packet in the series becomes. 14. The transmitter of claim 11, wherein

• - an address is assigned to each recipient,
• the data packet comprises a header which contains one or more addresses,
• - the largest or smallest address appears first, and the other addresses are smaller or larger than the first, according to a predetermined sort or coded before the address.

15. The transmitter of claim 14, wherein the waiting time before is definitely constant. 16. The transmitter of claim 14, wherein the waiting time in the Data packet is encoded. 17. The method according to any one of claims 14 to 16, wherein Series of data blocks are sent in which in addition, a second waiting time is encoded, which is the End of the series or the maximum encodable time. 18. Receiver for receiving data packets, the receiving device being temporarily inactive and

• the receiver comprises a filter to which the received data are fed and which determines a waiting time therefrom,
• - The filter is connected to a time control that deactivates the receiving device for the duration of the waiting time.

19. The receiver of claim 18, wherein

• - The receiver comprises a selector that extracts a selection code from the received data, interprets it and, depending on the result, activates the filter for the waiting time.

20. The receiver of claim 18 or 19, wherein

• - a separate address is permanently stored in the recipient,
• - The selection code comprises one or more addresses;
• - The selector compares its own address with the selection code.

21. The receiver of claim 18, wherein

• - The selection code is the first address coded in the data block and a size comparison of this first address is the result of the selector.

22. Receiver according to one of claims 18 to 21, wherein the Filters depending on a code in the data set Returns waiting time as a predetermined constant. 23. The receiver of claim 21 or 22, wherein the waiting time by multiplying the number of addresses by the length of user data required for an address becomes. 24. Receiver according to one of claims 18 to 23, for Use in an electronic ad Price labeling.