Data Access Systems and Wireless Interface Devices Suitable for Use in
Such Systems
Field of the Invention
The present invention relates to data access systems and to wireless interface devices suitable for use in such systems. In particular, the present invention is concerned with the usage and form of wireless interface devices that are capable of wirelessly interfacing with a memory-tag reader.
Background of the Invention
Memory devices in the form of Radio Frequency Identification (RFID) tags are well known in the prior art. RFJD tags (also referred to as memory tags) come in many forms but all are discrete, stand-alone, devices comprising an integrated circuit on which in use information can be stored (from a single bit to many kilobytes), and a wireless interface which enables the tag to be interrogated by a reader. Such tags can be arranged to be powered by a local power source in which case they are referred to as "active" tags; however, most RFID tags are arranged to receive power wirelessly from an interrogating reader and these tags are referred to as "passive" tags. There are many different operating principles for RFID memory tags but the two most important are inductive coupling and backscatter coupling.
Memory tags have been designed to operate at a variety of different frequencies from the kilohertz range up to several gigahertz. The type of modulation used varies considerably and the ranges achieved are from millimetres up to a meter or so.
Generally, when a memory tag (other than the most simple) is interrogated by a memory-tag reader, information passes in both directions between the reader and the tag. This transfer can take place using a half duplex procedure in which the reader and tag take turns to transmit, or using a full duplex procedure in which both the reader and tag can transmit at the same time but using different frequencies. For both the half duplex procedure and the full duplex procedure, where the tag is a passive tag the reader can be arranged to provide power on a continuous basis; however, in the case of the half duplex procedure, an alternative approach is for the reader only to provide power to the tag whilst transmitting, the tag storing sufficient energy during these periods to enable it to transmit its data during periods when the reader is not transmitting.
Further details of RFID memory tags can be found, for example, in the RFII) Handbook, Klaus Finkenzeller, 1999, John Wiley & Sons).
Figure 1 of the accompanying drawings illustrates the main functional components of a known passive memory tag 1 and a memory-tag read/write device 8. The memory tag 1 includes an antenna coil Li and a capacitor Ci connected in parallel therewith to form a resonant circuit. The tag 1 further includes a memory 3 and processing and power circuitry 2, the latter not only being arranged to supply power to the memory 3 but also to exchange control and data signals with it over control and data channels 4 and 5 respectively. The control signals typically comprise read/write signals and address signals (though the latter can be omitted where the memory 7 is designed to be written to, and read from, as a whole always beginning at the base address of the memory, the memory itself taking care of cycling its addresses for such operation).
The memory-tag read/write device 8 includes an antenna coil L2 and a capacitor C2 in parallel therewith to form a resonant circuit, and a processing and signal generating circuitry 9. A signal generator within circuitry 9 generates a signal at the chosen frequency, such as 2.45GHz; this signal is applied to the antenna coil L2 and thus generates an electro-magnetic field which, provided the memory tag 1 is sufficiently close to the memory-tag read/write device 8, penetrates the antenna coil Li of the memory tag 1. By induction a voltage is thus generated in the antenna coil Li. This induced voltage is rectified in circuitry 2 and used to power the memory tag 1. The capacitance of the capacitors Cl and C2 is selected such that the resonant circuits are both resonant at the frequency generated by the signal generator, in order to maximise transmitted signal strength and received signal.
When data is to be written to the memory tag 1 by the memory-tag read/write device 8, the radio frequency signal generated in circuitry 9 is modulated, e.g. amplitude modulated, with the data before being applied to the antenna coil L2 and transmitted.
The signal received by the memory tag 1 by inductive coupling thus both powers the memory tag 1 and communicates with it, the circuitry 2 separating the control and data signals from the carrier and passing them to the memory 3 where the data is stored.
Similarly, if data is to be read from the memory tag 1 the circuitry 2, in response to a read request received from the read/write device, applies a signal indicative of the requested data to the antenna coil Li which is detected, as a result of the inductive coupling, by antenna coil L2 and deciphered in circuitry 9 before being output from the memory-tag read/write device 8. This signal can for example be transmitted using load modulation. In RFID systems such as this the power consumed by the memory tag 1 can be measured as a drop in voltage across the internal resistance of the antenna coil L2 of the memory-tag read/write device 8. A load resistance within the circuitry 2 can be switched on and off, thus altering the power consumed by the memory tag 1 which is then detected as an amplitude modulation of the voltage across the antenna coil L2 of the memory-tag read/write device 8.
Figure 2 of the accompanying drawings shows a memory map 9 depicting a typical logical organisation of data within the memory 3 of the memory tag 1. In this example, the memory 3 is logically organised into n pages, here labelled as pages 0 to (n-i). Each page contains subject data and error correcting code (ECC) covering that data. Typically, each page of the memory 3 can be selectively read by an interrogating memory-tag read/write device, the read/write device specifying by page number the page it wishes to read. The memory tag 1 can be arranged to operate in a "selective addressing" mode in which the tag will only respond to an interrogating memory-tag read/write device when the latter specifically addresses the tag by transmitting an address associated with the tag. This tag address is typically stored in the first page age 0) of the tag's memory. Selective addressing is particularly useful where several memory tags are arranged in close proximity and there is a risk that an interrogating read/write device could simultaneously activate more than one tag.
The number of applications for memory tags is increasing rapidly and this growth is expected to continue as the capacity of such tags increases and their size reduces. It is therefore likely that memory-tag readers will become much more widespread and will even come to be incorporated into devices, such as cameras and printers, intended for use by the general public.
It is an object of the present invention to provide systems and devices facilitating access to data using a memory-tag reader.
Summary of the Invention
According to one aspect of the present invention there is provided a data access system comprising: a data store for storing a plurality of content items; a plurality of interface devices each capable of wirelessly interfacing with a memory-tag reader, said plurality of devices comprising a spatial distribution of devices each arranged to be associated with a corresponding said content item in the data store; and a control arrangement for enabling the content item associated with a said device of the spatial distribution that has been interrogated by a memory-tag reader, to be downloaded from the data store, via a device of said plurality of discrete devices, to a memory-tag reader requesting such download.
According to another aspect of the present invention there is provided a passive memory tag comprising: a memory for storing an identifier; a first wireless interface for interfacing, at least for energy transfer, with a memory- tag reader; a second wireless interface for interfacing with an external system different from a memory-tag reader positioned to interface with said first wireless interface; and a control block responsive to the memory tag being interrogated by a memory-tag reader to cause said identifier to be passed via the second wireless interface to said external system; both wireless interfaces being arranged to be powered by energy received via the first wireless interface from said memory-tag reader.
According to a further aspect of the present invention there is provided a device for interfacing with a memory-tag reader operating in a selective addressing mode in which the reader transmits the address of a tag it wishes to interrogate, said device comprising: a wireless interface for interfacing with a memory-tag reader; a memory for storing address data indicative of multiple tag addresses; a control arrangement for comparing an address received via the wireless interface from a memory-tag reader with the address data whereby to place the tag in an active mode upon the received address being an address indicated by said address data; the control arrangement being operative when the tag is in its active mode to access and download to an interfacing memory-tag reader subject data associated with the received address.
Brief Description of the Drawings
Embodiments of the invention will now be described, by way of nonlimiting example only, with reference to the accompanying drawings, in which: Figure 1 is a diagram of a prior art memory tag and memory-tag read/write device; Figure 2 is a diagram illustrating a known memory organisation for the Figure 1 memory tag; Figure 3A is a diagram of a first embodiment of the invention in which a tag array of a data access system is being interrogated by a memory-tag reader; Figure 3B is a diagram similar to that of Figure 3A but showing the memory-tag reader downloading selected image data; Figure 4 is a diagram of a pseudo memory tag used in the data access system of Figures 3A and 3B for downloading data to a memory-tag reader; Figure 5A is a diagram of a second embodiment of the invention in which a tag array of the data access system is being interrogated by a memory-tag reader; Figure 5B is a diagram similar to that of Figure 5A but showing the memory-tag reader downloading selected image data; Figure 6 is a diagram of a memory tag used in a tag array of the data access system of Figures 5A and 5B; Figure 7 is a diagram of a third embodiment of the invention in which a memory- tag reader is downloading image data via a pseudo tag array of the data access system; and Figure 8 is a diagram of a pseudo memory tag used in the tag array of the data access system of Figure 7.
Detailed Description of the Preferred Embodiments
Three embodiments of a data access system are described below. In each embodiment, the data access system is arranged to enable the download of content item data to a memory-tag reader; in the present case the content item data is image data, it being appreciated that the content item data could be any type of content data such as audio data, text data, etc. Communication with the memory-tag reader is via wireless interface devices in the form of memory tags or pseudo memory tags; by "pseudo" memory tag is meant a tag that operates, so far as a memory-tag reader is concerned, as if it were a memory tag but which is not a stand-alone device in that it can obtain data for passing to the tag reader from an external data store.
So far as the wireless interfacing with an interrogating memory-tag reader is concerned, the memory tags and pseudo memory tags of the data access systems to be descnbed can utilise any suitable technology including those referred to above in the
discussion of prior art memory tags.
Figure 3A shows the first embodiment of the data access system 10. The system comprises an array 11 of passive memory tags 12, and a data handling subsystem 13.
The data handling subsystem 13 comprises an image database 14 storing image data on a plurality of images, a pseudo memory tag 17 serving as a download interface for downloading image data from the image database 14 to a memory-tag reader, and a control arrangement 15, including an authorization unit 16, for enabling the download of a selected image via the pseudo tag 17.
In this first embodiment the array tags 12 are of standard form with a memory organisation similar to that shown in Figure 2, though in this case there is no need to include a tag address in page 0 of the tag memory as the tags as sufficiently spaced to avoid any problem of simultaneous activation of multiple tags by an interrogating tag reader. Bach tag 12 is associated with a respective one of the images for which image data is stored in the database 14. Page 0 of the tag memory of each tag 12 is used to store an image identifier (image ID) of the image with which the tag is associated, whilst the remaining pages of the tag memory are used to store thumbnail data representing a thumbnail of the associated image. As an alternative to each tag storing thumbnail data, a thumbnail of the image could be physically presented over or adjacent the tag itself (for example, printed on a sheet overlying the tags 12); in this case, each tag 12 need only hold the image ID of the associated image.
Figure 3A also depicts a portable memory-tag reader 20 comprising an interface head 21 for wirelessly interfacing with a memory tag, a user interface 22 (here shown as including a small display), a control unit 23 typically microprocessor-based and operating under program control, and a non- volatile memory 24 which can be semiconductor based or use another storage technology such as a hard disc. In Figure 3A the memory-tag reader 20 is shown as positioned juxtaposed a memory tag 12 of the array 11. Upon the user of the reader 20 activating the reader, the reader interrogates the tag 12 and reads in the contents of the tag's memory and, in particular, reads in the ID of the image associated with the tag 12 (see arrow 27). If the tag's memory includes thumbnail data, this data is used to display the corresponding thumbnail on the display of the user interface 22. On the basis of this display (or on the basis of a thumbnail or other data printed or otherwise presented adjacent the tag itself), the user determines whether or not they wish to download the full image data.
If the user decides to download the full image data, the user "locks in" the image ID read from the memory tag 12 by making an appropriate input via the user interface 22; the image ID is thereby stored in the memory 24.
As illustrated in Figure 3B, the user then positions the memory-tag reader 20 juxtaposed the download pseudo memory tag 17 and activates the reader to retrieve the image data corresponding to the image ID just captured from the tag 12 of the array 11. In the present embodiment, this is done by the reader entering a selective addressing mode in which it uses the image ID as the address of the tag it wishes to read, this address/image ID being passed to the pseudo memory tag 17 (see arrow 28).
The pseudo memory tag 17 is shown in block diagram form in Figure 4. The pseudo tag 17 comprises a front end for wirelessly interfacing with the memory tag reader 20 operating in its selective addressing mode, and a back end for receiving data from the image database 14. The front end is similar in form to a standard passive memory tag and here comprises elements Li, Cl, and a processing and power circuit 2 similar to the corresponding elements of the Figure 1 memory tag. The front end further comprises an address data memory 50 that holds data indicative of a set of tag addresses to which the tag is to respond (the data can simply indicate an address range or specif' a list of individual addresses). When the tag 17 is interrogated by the tag reader 20 operating in its selective addressing mode, the circuit 2 compares the tag address received from the reader with the address data held in memory 50 to determine if there is a match - if there is, the tag 17 responds to the reader 20, otherwise the tag does not respond. The backend of the pseudo memory tag 17 comprises a transfer control block 51 and a wired interface 52 for accessing data from the image database 14; both these elements 51 and 52 are preferably externally powered (though it is also possible to arrange for power to be provided by the memory tag reader 20 as for the front end of the pseudo tag 17). The transfer control block 52 is arranged at the command of the circuit 2 to request the transfer from the database 14 of image data corresponding to the tag address provided by the memory tag reader and which has been recognised by the circuit 2 as being an address indicated by the address data held in memory 50. As already noted, the received tag address is also the image ID of the selected image.
Upon the transfer control block 51 requesting particular image data as identified by the image ID (received tag address), the authorization unit 16 of the control arrangement 15 determines whether this request is an authorized request. This determination involves checking one or more conditions; for example, one possible condition could be the payment of a fee and another condition could be that the reader is an authorized reader as indicated by an appropriate reader ID passed via the pseudo tag 17 to the control arrangement 15. The conditions to be satisfied can be made dependent on the identity of the requested image. Provided the authorization unit 16 is satisfied that the required access condition or conditions have been met, the control arrangement proceeds to enable the transfer of the requested image data from the database 14.
It may be noted that where there are no conditions to be tested by the authorization unit 16, the role of the control arrangement 15 is, in this embodiment, minimal and can in appropriate cases be reduced to passing on the request from the transfer control block 51 of the tag 17 to the image database 14.
Once image data transfer has been enabled by the control arrangement 15, the transfer control block 51 oversees the transfer of the data via the front end of the pseudo memory tag 17 to the memory-tag reader 20 (see arrow 29 of Figure 3B). Precisely how the transfer is conducted depends on how the memory- tag reader 20 is arranged to receive data. Preferably, the reader 20 is arranged to continue cycling read operations until it receives a transfer complete signal from the tag 17; in this way, any size of image data file can be transferred.
The second embodiment of the data access system 10 is shown in Figures 5A and 5B and is similar to the first embodiment except that now the identity of the image associated with an activated array tag is transferred from the corresponding tag of the tag array 11 directly to the control arrangement 15.
More particularly, the tag array 11 of the second embodiment comprises passive memory tags 32 of the form shown in Figure 6. Each tag 32 comprises two wireless interfaces, namely the memory-tag reader interface formed by the elements Li, Cl and circuit 2 in the example tag of Figure 1, and a further wireless interface 56 for interfacing with a complementary interface 34 of the data handling system 13 (see Figure 5A). The interface 34 is connected to the control arrangement 15. In this manner, a communications channel 33 can be established between an activated tag 32 and the control arrangement 15.
It will be appreciated that the characteristics of the tag interface 56 will generally be different to those of the tag interface to the memorytag reader 20 as the interface 34 of the data-handling subsystem 13 will generally be further spaced from the tags 32 than the memory-tag reader 20. Furthermore, as will be apparent to persons skilled in the art, appropriate measures are needed to prevent interference between the two interfaces of the tag 32; for example, the interface 56 can be arranged to operate in a different frequency band to that used by the reader interface of tag 32, and/or the interface 56 can be arranged to transmit at times when the reader interface is not transmitting or receiving data (this interface may still, however, need to receive a powering signal from the reader 20 whilst the tag is transmitting on the interface 56 although it is also possible to arrange for the interface 56 to operate off stored energy previously received from the reader 20).
When the memory-tag reader 20 is juxtaposed a tag 32 and activated, the tag 32 is powered up and, in standard manner, can be read by the reader 20; in addition, the powered-up tag 32 also sends the image ID of the image associated with the tag 32 via the wireless interface 56 to the interface 34 and thus to the control arrangement (see arrow 36). The control arrangement 15 is arranged to respond to receipt of an image ID via the interface 34 by displaying the corresponding image on a display 35. As a result, there is no need to provide thumbnail data in the tags 32 or to have the such data displayed via the user interface 22 of the memory-tag reader 20. Indeed, the image ID stored by the activated tag 32 need not even be passed to the reader 20 though this can still be advantageous.
With the foregoing arrangement, a user can pass their memory-tag reader 20 over tags of the array 11 and be successively displayed the corresponding images. Upon the user deciding that they wish to download the image data of a particular image, then assuming this image is that associated with the last activated tag 32, the user can simply move the reader to the pseudo memory tag 17 and activate the reader 20 resulting in activation of the tag 17. In this embodiment, the reader 20 is not activated in a selective addressing mode but simply tries to read the tag 17. Upon this occurring, the tag 17 notifies the control arrangement 15 and the latter assumes that the user wishes to access the image associated with the most recently activated one of the array tags 32.
Assuming that any authorization checks are passed, the control arrangement 15 next enables the download and the transfer control block 51 proceeds as described above to control the transfer of image data from the image database 14 to the reader 20 (see arrow 37 in Figure SB).
As an alternative to the control arrangement 15 assuming that the user wishes to download the image associated with the most-recently activated tag 32, the same procedure can be adopted as used in the first embodiment - that is, the reader 20 can be arranged to store in memory 24 the image ID of an image that the user wishes to download, this image ID then being passed by the reader 20 to the pseudo tag 17 using selective addressing (in this alternative, no account is taken of the identity of the image most recently notified to the control arrangement 15 via the channel 33).
A further alternative is to arrange for the user to indicate via the user interface 22 of the reader 20 when the image associated with the currently- activated tag 32 is one they wish to download, this indication then being passed by the reader via the currently activated tag 32 and the channel 33 to the control arrangement 15 which stores a record indicating that the image concerned has been selected for download. The user may then go on to activate other array tags 32 before moving the reader 20 to the download tag 17 to download the selected image data; in this case, when the tag 17 indicates to the control arrangement 15 that it has been activated, the latter looks up the record of the image selected for download and proceeds as described above. In fact, it is possible with this alternative to allow the user to select several images for download, the control arrangement 15 storing a record of all these images and subsequently interacting with the transfer control block 51 to bring about the download of the image data of all selected images when the reader is interfaced with the download tag 17.
The wireless communications channel 33 between the tags 32 and the control arrangement 15 can be replaced by a wired channel, though this is not preferred. Where a wired channel is provided, the wired media is preferably in common to all tags 32; however, it would alternatively be possible to provide each tag 32 with its own communication link wiring to the control arrangement 15. In this latter case the control arrangement 15 can determine which tag 32 has been activated simply by reference to the link on which a signal is received; the identity of the associated image can then be looked up in a table held by the control arrangement 15 whereby it is no longer necessary for the tags to transmit image IDs to the control arrangement. Of course, where the tags 32 and the control arrangement 15 communicate over a wired connection, the tags 32 can be active tags receiving power from the system 10.
The third embodiment of the data access system 10 is shown in Figure 7. In this embodiment, the tag array 11 is made up of pseudo memory tags 42. Like the pseudo tag 17, each pseudo tag 42 (see Figure 8) has a front end Li, Cl, 2 for interfacing with a memory-tag reader, and a back end, comprising transfer control block 51 and wired interface 52, for accessing image data from the database 14 for transfer to an interrogating memory-tag reader. However, unlike the pseudo tag 17, each pseudo tag 42 is only intended to access image data of an image with which the tag 42 is associated, the identity of this image being stored in a memory 3 of the tag. Furthermore, the tags are not intended to operate in a selective addressing mode but, like the tags 32, are arranged to respond to a general interrogation by a memory-tag reader 20 by passing the image ID stored in tag memory 3 to the control arrangement 15; in the case of tag 43, the image ID is passed to the control arrangement 15 via the interface 52 of the tag, a wired communications channel 43, and an interface 44 of the control arrangement 15 (see arrow 46). As with the second embodiment of the data access system, in the Figure 7 embodiment upon the control arrangement receiving an image ID via the interface 44, it causes the corresponding image to be displayed on display 35.
If the user of the memory-tag reader 20 wishes to download the image data associated with a currently-interrogated tag 42, the user uses the user interface 22 of the reader 8 to send a download request via the tag 42 to the control arrangement 15. Subject to any required authorization checks being passed, the control arrangement 15 then enables the transfer of the image data associated with the interrogated tag 42 from the database 14, via the tag 42, to the reader under the control of the transfer control block of the tag 42 (see arrow 47).
It would be possible, though not preferred, to replace the wired communication between the tags 42 and control arrangement 15 with wireless communication by providing each tag 42 with a wireless interface in a manner similar to the tags 32 of the second embodiment with each tag 42 being powered from the memory-tag reader 20 via the front end wireless interface of the tag.
Many variants are, of course, possible to the above-described embodiments. Thus, with respect to the first embodiment illustrated in Figures 3A, 3B, and 4, rather than the pseudo memory tag 17 only responding to requests for images with an ID matching a tag address indicated by the address data in memory 50, the pseudo tag 17 can be arranged to leave the checking of requests entirely up to the control arrangement 15.
With regard to the second embodiment illustrated in Figures 5A, SB and 6, the tags 32 of the tag array need not send or receive any data to/from the memory-tag reader, each tag 332 being simply arranged to send its associated image ID to the control arrangement 15 whenever the tag is interrogated by the memory-tag reader. In this case, the wireless interface between the tag and the reader simply serves as a power transfer interface. The image IDs stored by the tags of the tag arrays can be subject to
translation by the control arrangement 15 (for example, using a look-up table) whereby the file names used for storing the image data in image database 14 can differ from the image IDs stored in the tags. This is useful as it enables the image IDs stored in the tags to remain unaltered when the images are changed without having to change the image data file names to match the image IDs in the tags.
In the above-described embodiments, the tags of the array 11 are arranged in a regular pattern; however, other spatial distributions of these tags are possible - for example, the tags could be positioned to correspond to features of interest on a map that is superimposed on the tags.
As already noted, the above-described data access systems can be used for accessing any desired type of content item and are not limited to image items. Of course, different content types will need appropriate output arrangements for their presentation. Thus, for example, where the content items are audio items the display of the second and third embodiments would be replaced by an audio output arrangement.