WO2001033721A2

WO2001033721A2 - Data transmission for temporarily inactive receivers

Info

Publication number: WO2001033721A2
Application number: PCT/DE2000/003811
Authority: WO
Inventors: Dietmar Braeuer; Uwe Altenburg; Hans-Juergen Krieger
Original assignee: Wincor Nixdorf Gmbh & Co. Kg
Priority date: 1999-11-03
Filing date: 2000-10-27
Publication date: 2001-05-10
Also published as: DE19952840A1; WO2001033721A3

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

Data transmission for temporarily inactive recipients

Technical field

The invention relates to the transmission of data from one

Transmitter to one or more receivers, the receiving device of which is temporarily inactive, in particular to protect batteries.

State of the art

For price labeling it is e.g. from the patent US 4,002,886 (Sundelin) that an electronic display is attached near the goods on the shelf, which can be controlled from a central office. With these devices, known under the name 'Electronic Shelf Label', ESL, it is possible to change the price displays in a short time and to keep them reliably consistent with the data available for the cash registers.

While the above-mentioned document provides for wired control, wireless signal transmission by means of electromagnetic waves is proposed, for example, in US Pat. No. 4,521,677 (Sarwin). In order to take advantage of such, however, the power supply should not be based on wire connections. Since solar cells do not always provide sufficient energy, it can be assumed that they are supplied by batteries. The LCD displays are less of a problem. The main energy consumer is the receiving circuit including the evaluation logic, which has so far been continuously ready to receive.

The object of the invention is therefore to provide a solution in which the receiving circuit can be switched off for the most part and yet any display can be changed simply and reliably at flexibly selectable times.

Presentation of the invention

The invention uses the knowledge that a relative waiting time, during which the receiving circuit can be deactivated, can be contained in the data packets both explicitly and implicitly, and it is only necessary that this waiting time can be determined as easily as possible and none during the waiting time of the transmitter sends relevant data. For this purpose, two different solutions are given, which are optimally combined, but can also be used individually.

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

On the other hand, several data records, which always consist of an address and the associated user data, are combined into one package. The addresses are sorted, then divided into groups and in ascending order Order sent. According to the invention, however, the ascending sorting is only necessary with respect to the groups among one another; the highest address within the group is sent first.

This enables a recipient to determine at the beginning of the group whether his address can be included in the group (if it is smaller or the same) or not (if it is larger). In the latter case, the receiver deactivates its receiving circuit for the remaining time, in which in particular the user data of the group are sent.

Further features and advantages of the invention will become apparent from the following description, which in connection with the accompanying drawings explains the invention using an exemplary embodiment.

Brief description of the drawings

Show it

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, as indicated in FIG. 1, consists of a transmitter 10 with an antenna 11. Preferably electromagnetic waves in the range of 868 or 915 MHz released for this are used; other frequencies, including infrared light, can also be used without any problems.

1, two price displays 20, 20 'are shown as receivers, which are fastened 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.

2 shows the components of a typical price display 20. 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 watches. 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 typically have one or more power saving modes that are included in the invention can be used appropriately. 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 timer 24 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 switch is opened and closed in a known manner, which can be found in the data sheets and application descriptions of the microcontrollers, in such a way that the microcontroller is stopped in a defined manner (and then switched off, if necessary) and starts its work again in a defined manner 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, the microcontroller 26 can also be switched off if it is Power consumption compared to that of the recipient is negligible.

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 unm -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. The selection is, however, primarily without influence on the invention, so that in the following it is assumed 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, a global waiting package is available. 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.

With a data rate of the transmitter of 8000 bits / sec, less than 3 msec are required for the waiting packet, so that the receiver must be switched on less than 5 msec per 2 seconds; the electricity savings are considerable.

With a waiting packet marked in this way, the sender informs the recipients of the relative time of the next data transmission. The sender simultaneously announces that no relevant data blocks have been sent before this point in time. A receiver that receives such a waiting packet can then switch to a power saving mode for the time specified therein and in particular switch off its receiver circuit.

This waiting packet is sent repeatedly and preferably in close succession to the transmitter, the waiting times contained in subsequent waiting packets being reduced by the past time. It is therefore irrelevant when a recipient activates to determine the time of the next data transmission. In particular, a newly added recipient can wait at any time determine. By specifying the time as the relative time to the respective time of transmission, an absolute time is not necessary.

When the waiting time has passed and the receivers reactivate their receiving circuit and possibly the control, there are two options.

As a first option, new waiting packets are sent that contain a new waiting time. This is the case when no user data have to be sent to the recipients. Is the maximum waiting time e.g. 2 sec, but the average time between two changes is one hour, so in the majority of cases a waiting packet will be sent again. Furthermore, all previously active receivers will then go into the inactive state with the first new waiting package, so that the subsequent waiting packages appear to be superfluous. However, it is clear that a high degree of reliability is achieved in this way, especially for new receivers.

If the anticipated waiting time exceeds the codable value, then either, as described above, the waiting time can be set to the maximum codable value and then reduced in each waiting packet, so that all receivers leave the waiting state synchronously and receive a new maximally coded waiting packet until the envisaged total waiting time is exhausted except for a remainder that can be coded. Alternatively, of course, without leaving the idea of the invention, only waiting packets of the maximum codable waiting time can be sent, in which the coded waiting time is not with everyone Package is decreased. If a data transmission is pending, the following waiting packets are sent with a decreasing waiting time until the planned transmission time for data blocks is reached.

As a second possibility, the transmission time for data blocks is reached, e.g. to transfer a new price for a price display. The transmitter then begins sending data blocks, which are identified, for example, by the letter "D" in the first place. This is followed in a known manner by the recipient address, i.e. the price tag number and the price to be displayed. These data blocks are sent with the respective recipient number concerned as long as price changes are to be entered. After that, the transmission of waiting packets begins again, so that the receivers can go back to the power saving mode.

In particular, in cases where the price changes cannot be acknowledged by a return channel, a repeated and regular transmission of the current prices is necessary, which are only entered by the price tags, for example, after the price has been transmitted identically several times. In the case of a large number of several thousand price tags, data blocks with useful data would predominantly be sent, so that there is no space for the previously described embodiment of the invention, in which the waiting time is coded explicitly and globally for all recipients.

Therefore, the alternative embodiment of the invention also allows the receiver to recognize that for one of the Recipient easily determinable time no data intended for the recipient are to be expected.

The preferred embodiment of this variant of the invention transmits the addresses and data in groups, e.g. consist of sixteen addresses and associated user data. An optimal variant consists in first transferring the addresses and then in the order of the addresses the user data. If the recipient does not find his address in the addresses, he can switch off the recipient for the rest of the group. This is facilitated if, as preferred, the useful data have a fixed length, so that the entire data block of a group of addresses takes a predetermined time.

An improvement is achieved in that the addresses are sent out sorted. The fact that a descending sort can be used instead of the ascending sort described below certainly does not require any further description.

In the case of sorted transmission in groups, the addresses used in each group are always larger than the addresses in the previous groups. For example, the

Addresses sorted in ascending order and grouped into groups of 16 each. However, the largest address within a group is then sent first; the order of the others is practically irrelevant. Therefore, the largest address comes for each group immediately after the indicator for the type of data packet and any other important administrative information. The recipient does not wait for the entire group to be received, but compares it with its own address immediately after receiving the first address. If your own address is larger, it is ensured that the following addresses do not affect the recipient. So he can switch off the receiver for the rest of the group. The waiting time can be determined in advance since the addresses and data have a fixed length. In contrast to the previous variant, in which the addresses are unsorted, but are transmitted in the group before the user data, this is not necessary for the sorted transmission; the user data can immediately follow each address. Only the largest address must be sent first.

A closer look reveals that both variants have in common that the waiting time is fixed before the start of the user data associated with the first address. This also applies if variable long user data are used in which the length of the user data is transmitted before the user data, in particular by means of a field for the user data length in the data block. In the case of sorted transmission, the address must also be sent here, which either has a fixed length or is delimited by a closing character. Since the first address must be received in full anyway, an end sign is possible. Before or after, the total length of the group block is transmitted in coded form. The waiting time can be calculated from this using the data rate.

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 using more energy than a receiver with a very small address, the sorting term is reversed in the next series of data blocks, i.e. The following groups are sent after the next waiting time:

11,14,13,12 7,10,9,8 1,4,3,2

It is assumed here that the same recipients will be addressed again next time; this is of course not necessary; This means that a different set of recipients can be addressed during the second transmission of groups.

In this case, the transmitter is useful in any one

Form in the transmitted packets encoded the address order, e.g. 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, i.e. between two waiting times, a mixed one

Sending possible; i.e. that the sorting is noted in the data packet for each data packet.

However, a common sorting of all data packets within a shipment has the advantage of further improvement. This applies if not all recipients are always addressed, as is usually the case. As soon as, for example, ascending sorting all addresses of a data packet are larger than your own address, all subsequent data packets are of no importance until the next waiting packet. If the second address is the smallest in the package, the recipient needs only evaluate the first two; It is therefore expedient to send all addresses first. In this development, the waiting time until the next broadcast is included in the data packet. The sender, who knows the number of receivers to be addressed, can determine this before sending out the first data packet and can then record the waiting time accordingly in the data packet as an additional field. If the precalculated waiting time exceeds the maximum codable waiting time, the maximum waiting time is encoded in the sense of the first embodiment of the invention above; after the expiry, the recipient immediately finds a data packet whose addresses all exceed their own, takes the waiting time and returns to the waiting state. Otherwise, as described above for waiting packets, the maximum codable waiting time can first be sent in the data blocks if this is before the planned end of the transmission of all pending data blocks, and the waiting time is only coded towards the end. In this way, a nesting of both variants is possible, in which two waiting times are usually coded; firstly, until the next data block in a group and secondly, until the end of the transmission of a sequence of data blocks.

A previously less attractive variant uses a grouping based on other criteria, for example the last or the first bits of the address, generally by means of a bit mask instead of a full sorting of the addresses. In this generalized form of the invention, the total length and the selection mask for the group are transmitted after the identifier for the data block of a group. The recipient masks his own address and calculates the waiting time from the total length if the masking shows that its own address is not affected. Basically, the selection criterion can be designed to be of any complexity, for example also as regular expressions or a program code (byte code) which is interpreted or executed by the microcontroller. However, this complexity has so far not been required when applied to price tags. In any case, the term "sorting" is to be understood in this general sense, according to which a sorting determines an order of a predetermined type in the set of addresses. Otherwise, the total length is nothing more than an encoding of the waiting time that the receiver must wait at least before data relevant to him are sent. Instead of the length in bits or bytes, a waiting time can therefore also be explicitly specified in a previously agreed unit or in a unit introduced or added to the number.

It can be seen that the receiver determines a waiting time in each case from the data block sent. This can be explicit and can be significantly longer than the transmission time of the data block if there are waiting packets. Or it can correspond to the length of the data block if it does not need to be observed based on a criterion sent at the beginning of the data block.

If one abstracts the idea of the invention further, it can be seen that the data record indicator “T” for a waiting packet effectively represents a selection criterion “for all”. This results as an abstract basic idea of the invention that the one of the recipient of the data set Selection code which is evaluated as 'waiting' or 'not waiting' and takes a waiting time and waits for the waiting time when the selection code is evaluated as 'waiting', the waiting time, depending on the selection code, if necessary, implicitly, ie predetermined, or can be explicitly coded.

The mixed use already indicated above is thus possible, in which relative waiting times directed to a fixed point in time between useful data transmissions and relative waiting times to the next group are transmitted during useful data transmissions.

The previous description used a transmission method in which whole characters with a fixed number of bits, in particular 8-bit bytes, were always transmitted and therefore the asynchronous method comes into question. The waiting blocks are also distinguished from the data blocks by the first character in order to enable a quick decision. Alternatively, of course, the address zero or another reserved address can serve as an indicator that it is a waiting block.

As indicated above, an alternative transmission method is, in particular, phase coding or the HDLC method, which are self-clocking and allow better utilization of the channel capacity. Frame formats are also possible here, in which the data are divided into groups of bits of different widths, and in particular by means of the first bit, after a possibly necessary preamble, a distinction is made between waiting blocks and those with addresses and user data. The selection the transmission method therefore depends essentially on the technical conditions in the transmitter and the receiver and influences the application of the present invention only marginally.

In the previous description, only the transmission channel from the transmitter to the receiver is shown. In the preferred form of use, a return channel from the price display to the "transmitter" is also used, with which the data transmission can be acknowledged in order to increase the reliability. The techniques used for this, including the treatment of collisions, 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, other areas of application are possible in which economical energy consumption together with defined accessibility are required. Applications from telemetry are to be mentioned in which one or more sensors have to record measurements at times that are not fixed in advance, but in each case at the same times, for example in environmental monitoring. Here, the data transmission is reduced to the amount of data of one bit, namely to the instruction: "perform measurement".

It is also possible to use it in large-scale radio location of animals that are equipped with a battery-powered transponder, where the time of location is also not predictable and a very large number of transponders are in use.

Claims

claims

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 for the duration of this waiting time

Receiver device deactivated.

2. The method of claim 1, wherein a waiting time is encoded in the data packet.

3. The method according to claim 2, wherein series of data packets are used, in which the waiting times are descending and the remaining time corresponds to a common 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 includes 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, the largest or smallest address appears in the data block as the first or the other addresses are smaller or larger than the first, according to a predetermined sort or coded before the address.

7. The method according to any one of claims 1 or 3 to 5, wherein 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 claim 4, wherein the waiting time is determined by multiplying the number of addresses by the transmission time required for an address with a maximum useful data length.

10. The method according to any one of claims 6 to 8, wherein series of data blocks are sent, in which a second waiting time is additionally encoded, which comprises 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, whereby

- The transmitter emits a data packet from which the receiver can determine a waiting time while

-whose data concerning him are not sent.

12. The transmitter of claim 1, wherein a waiting time is encoded in the data packet.

13. The transmitter of claim 12, wherein the transmitter emits series of data packets, a time counter determines the remaining time up to a respectively set point in time, and this remaining time is entered in each data packet of the series.

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 is predetermined to be constant.

16. The transmitter of claim 14, wherein the waiting time is encoded in the data packet.

17. The method according to any one of claims 14 to 16, wherein series of data blocks are sent, in which a second waiting time is additionally encoded, which comprises 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 one

Selection code extracted from the received data, interpreted and, depending on the result, the filter for the waiting time activated.

20. Receiver according to claim 18 or 19, wherein - a separate address is stored non-volatile in the receiver,

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 filter depending on a code in the data set

Returns waiting time as a predetermined constant.

23. Receiver according to claim 21 or 22, wherein the waiting time is determined by multiplying the number of addresses by the useful data length required for an address.

24. Receiver according to one of claims 18 to 23, for use in a display for electronic price labeling.