Untitled record

ES 2 344 589 T3

DESCRIPTION

Procedure and apparatus for tracking devices using tags.

Technical field of the invention

This invention relates generally to techniques for tracking articles and, more particularly, to techniques for tracking articles using wireless tags.

Background of the invention

According to an existing technique for tracking articles, a device known as a radio frequency identification tag is mounted on each article, and radio frequency signals are used to communicate information from the tag to a receiver, which is called a reader. The tag can be active or passive. Although existing labels and the systems that use them have generally been adequate for their intended purposes, they have not been satisfactory in all respects.

In this regard, there are situations in which, in determining the specific location of the item bearing the label, it is desirable to have a higher degree of accuracy than can be achieved with existing labels. For example, existing tags can determine the distance to the device based on the magnitude of the signal emitted by the tag, as received at the reader. However, similar existing tags can transmit signals with slightly different magnitudes, and environmental factors can affect the magnitude of the signals transmitted by these tags. As a result, there is a considerable margin of error in the reader's ability to accurately determine the distance to a tag based on the magnitude of the received signal.

Also, it can be even more difficult for the reader to determine the direction to the label. In fact, it is typically necessary to provide multiple readers at spaced locations, and to use a triangulation pattern based on the magnitudes of the signals received at two or three of the readers, to attempt to determine the direction to the tag from each of the readers.

Yet another example of a drawback of existing techniques is that a mobile device being tracked may be held in some other type of mobile device, such as a forklift, making it difficult for existing tracking systems to determine whether a mobile device given is currently held or not on a different mobile device. An additional consideration is that with existing technology it can be difficult to determine whether two mobile devices, such as a tractor and trailer, are currently connected to each other, or are simply in the same general vicinity. Furthermore, when two or more mobile devices, such as containers, are supported by respective different mobile devices, such as trailers, that are all close to each other, with existing technology it can be difficult to determine which mobile device is holding which other mobile device.

Another drawback of existing techniques is that the way a tag transmits radio frequency information can create problems related to compliance with government regulations, because government regulations often strike a balance between factors such as transmission length, power of transmission and transmission speed. In existing labels, the design of the label involves selecting a predetermined balance between transmission duration, transmission power and transmission length, and then the operation of the label is carried out using this predetermined balance.

Yet another drawback of existing techniques is that some existing tags may perform a transmission in response to an interrogation signal but, apart from this, the pre-existing tags generally operate in a predetermined manner that is not subject to external influence. Furthermore, interrogation signals of this type simply cause a transmission by the tag, and do not effect a change in any operating characteristics of the tag. Therefore, other than replacing a given label, there is no convenient way to easily change certain operating characteristics of the label.

Document WO00 / 41333 discloses an active electrostatic transceiver, document WO99 / ​​60512 discloses systems and methods for wirelessly projecting energy to microelectronic devices, document WO98 / 31070 discloses a multi-frame antenna that generates fields that are generally cancellation to distances of one wavelength or more from the antenna and US4112421 discloses a method and apparatus for monitoring vehicles automatically.

Summary of the invention

According to one form of the present invention there is provided an apparatus according to claim 1. According to another form of the present invention a method according to claim 26 is provided.

The method and apparatus may involve: transmitting signaling signals from a signpost, each signaling sign having a signaling code; receiving the signaling signals in a receiving section of the circuitry of a tag that is physically separate from the signpost; transmit from a transmitting section of

ES 2 344 589 T3 circuitry of the tag wireless beacon signals, each of which includes a beacon code associated with the tag, the transmitting step including the step of making the transmitting section responsive to reception by the receiving section of a respective signaling signal for including in at least one radio beacon signal the signaling code from the received signaling signal; receiving the beacon signals at a reader that is physically separate from the signpost and tag; removably holding in a mobile device an item having the tag disposed thereon; securely holding the signpost near a travel path of the mobile device in such a way that the tag passes through a transmission range of the beacon signals from the signpost as the mobile device travels along the signpost with the item in the same; holding near the travel path of the mobile device a sensor that is operatively connected to the signpost; detecting the proximity to the sensor of some of the article and the mobile device; and respond to the detection by the sensor of the proximity of the one of the article and the mobile device to effect a change in the signaling code of the signpost.

The apparatus and method may involve: transmitting signaling signals from a signpost, each signaling signal including a signaling code; receiving the signaling signals in a receiving section of the circuitry of a tag that is physically separated from the signpost; transmitting from a transmitting section of the tag circuits wireless beacon signals, each of which includes a beacon code associated with the tag, the transmitting step including the step of making the transmitting section responsive to reception by the receiving section of a respective signaling signal for including in at least one radio beacon signal the signaling code from the received signaling signal; receiving the beacon signals at a reader that is physically separate from the signpost and tag; hold the signpost on a mobile device; and removably holding on the mobile device an item having the tag disposed thereon at a location such that the tag is within a range of transmission of the signaling signals from the signpost while the item is supported by removable way on mobile device.

The method and apparatus may involve: transmitting signaling signals from a signpost, each signaling signal including a signaling code; receiving the signaling signals in a receiving section of the circuitry of a tag that is physically separate from the signpost; transmitting from a transmitting section of the tag circuits wireless beacon signals, each of which includes a beacon code associated with the tag, the transmitting step including the step of making the transmitting section responsive to reception by the receiving section of a respective signaling signal for including in at least one radio beacon signal the signaling code from the received signaling signal; receiving the beacon signals at a reader that is physically separate from the signpost and tag; removably connecting first and second mobile devices to each other; and holding the signpost on one of the mobile devices and the tag on the other mobile device, such that the tag is within a transmission range of the beacon signals from the signpost while the mobile devices are connected removable way.

The method and apparatus may involve: receiving at a receiving section of a tag wireless signaling signals each including a signaling code; and transmitting from a transmitter section of the tag wireless beacon signals, each of which includes a beacon code associated with the tag. The transmitting activity includes: making the transmitting section responsive to reception by the receiving section of a respective signaling signal to include in at least one beacon signal the signaling code from the received signaling signal; and causing the transmitting section to transmit the beacon signals in a selected format of first and second formats that are different, the transmitting section using the first format in response to receiving one of the signaling signals and using the second format. in response to the absence of reception of any of the signaling signals during a specified time interval, the first format including a signaling field containing the signaling code of the most recently received signaling signal, and the second format lacking the signaling field and being shorter in length than the first format.

The method and apparatus may involve: receiving in a receiver section of a tag wireless signaling signals each including a signaling code; and transmitting from a transmitter section of the tag wireless beacon signals, each of which includes a beacon code associated with the tag. The transmitting activity may include: making the transmitting section responsive to reception by the receiving section of a respective signaling signal to include in at least one beacon signal the signaling code from the received signaling signal; and making the transmitting section responsive to reception by the receiving section of one of the signaling signals to automatically effect variation, in a predetermined manner, of at least one of a transmit power level and a transmit rate for the beacon signals.

The method and apparatus may involve: receiving in a receiver section of a tag wireless signaling signals each including a signaling code and a command part; transmitting wireless beacon signals from a transmitter section of the tag, each of which includes a beacon code associated with the tag, the transmitter section being responsive to reception by the receiving section of a respective signaling signal to include in the minus one radio beacon signal the signaling code from

ES 2 344 589 T3 the received signaling signal; and performing a control function within the tag in response to the command portion of a respective signaling signal received by the tag.

Brief description of the drawings

Figure 1 is a block diagram of an apparatus incorporating features of the present invention, and including a signpost, a beacon tag, a reader, and a control system;

Figure 2 is a schematic view of a digital word that is transmitted by the signpost of Figure 1;

Figure 3 is a schematic view of two different digital words, either of which can be transmitted by the beacon tag of Figure 1;

Figure 4 is a diagram showing a sequence and timing with which the beacon tag of Figure 1 transmits beacon signals;

Figure 5 is a flow chart showing in a different way the sequence of beacon signals that is represented in Figure 4;

Figure 6 is a high-level flow chart showing additional aspects of the operation of the beacon tag of Figure 1;

Figure 7 is a schematic top view of a system representing a practical application of an apparatus of the type shown in Figure 1;

Figure 8 is a schematic top view similar to Figure 7 but showing a system representing another practical application for an apparatus of the type shown in Figure 1;

Figure 9 is a schematic perspective view of one type of container that can be used in association with the invention, and bearing three beacon labels of the type shown in Figure 1;

Figure 10 is a schematic view from above of an installation showing an example of a practical application of a system of the type shown in Figure 1;

Figure 11 is a schematic view of selected parts of a system incorporating the invention and which is suitable for use in association with the installation of Figure 10;

Figure 12 is a schematic view of a train that includes a tractor, three trailers, and a container on each trailer, and incorporating certain aspects of the present invention;

Figure 13 is a schematic side view of a forklift carrying two signposts of the type shown in Figure 1, a roof bearing several radio beacon labels of the type shown in Figure 1, and various items carried by the forklift that each carry a beacon tag of the type shown in Figure 1;

Figure 14 is a schematic side view of the tail section of an aircraft, and a loader that can be used to load or unload the aircraft.

Figure 15 is a schematic side view of an apparatus that includes a conveyor, an indicator post of the type shown in Figure 1 that is mounted on top of the conveyor, and various items that are moving along the conveyor on a pallet, and that each have thereon a beacon tag of the type shown in Figure 1; and Figure 16 is a schematic sectional side view of an apparatus that is an alternative embodiment of the apparatus shown in Figure 7, including the addition of a sensor that may affect the operation of the signpost.

Detailed description of the invention

Figure 1 is a block diagram of an apparatus 10 incorporating features of the present invention. Apparatus 10 includes a signpost 11, a beacon tag 12, a reader 13, and a control system 14. Apparatus 10 actually includes many signposts of the type shown at 11, many tags of the type shown at 12, and various readers of the type shown in 13. However, for clarity in explaining certain fundamental aspects of the present invention, Figure 1 shows only a signpost 11, a tag 12 and a reader 13.

Focusing first on the signpost 11, the signpost 11 includes a microcontroller 21. Those skilled in the art are familiar with the fact that a microcontroller is an integrated circuit that includes a microprocessor, a read-only memory (ROM ) containing a computer program and data

ES 2 344 589 T3 static for the microprocessor, and a random access memory (RAM) in which the microprocessor can store dynamic data during the operation of the system. The signpost 11 also includes a low frequency transmitter 22 which is controlled by the microcontroller 21, and which transmits a low frequency signaling signal 24 through an antenna 23. Transmitter 22 is of a type known to those skilled in the art, and is therefore not illustrated or described in detail in this document. The antenna 23 of the signpost 11 may be a ferrite core and / or flat square antenna of a known type. The antenna 23 is configured to transmit an omni-directional signal, but it will be recognized that the antenna could alternatively be configured to transmit a signal that is directional to some extent.

In the embodiment of Figure 1, the transmitter 22 generates the signaling signal 24 by effecting amplitude modulation of a carrier signal, which may have a frequency in a range of about 30 kHz to 30 MHz. In the embodiment of Figure 1, and with due regard to compliance with government regulations of various countries regarding electromagnetic emissions, the carrier frequency is selected to be 132 kHz, but alternatively it could be another frequency, such as 132 kHz or 13.56 MHz. An additional consideration in selecting the indicated frequency range is that the signaling signals 24 will exhibit near-field characteristics. The localized nature of the signals in this frequency range helps to facilitate compliance with government regulations in the specific context of the present invention, and also helps to minimize the reception of these signals by other labels of the type shown at 12, which are in the general vicinity of the signpost 11 but are beyond an intended transmission range of the signposts 24. As is known to those skilled in the art, a signal with near-field characteristics has a roll-off that is approximately three times the roll-off for a signal with far-field characteristics. Accordingly, the signaling signals 24 intentionally have a relatively short transmission range, which in the disclosed embodiment is adjustable but typically is around four to twelve feet (1.22 to 3.66 meters). Due to the fact that the signaling signals 24 exhibit near field characteristics, the transmission and reception of the signaling signals 24 can be viewed more as a magnetic coupling between two antennas, rather than a radio frequency coupling.

The signpost 11 also includes a power source 26, which would typically be a battery that is capable of supplying power to the signpost for several years. However, in situations where the signpost 11 is fixed rather than movable, it is alternatively possible to supply power to the signpost 11 from a standard 120V AC power source, as schematically indicated in Figure 1 by a dashed line.

As shown schematically by a dashed line 27 in Figure 1, the microcontroller 21 of the signpost 11 may optionally be connected to the control system 14 by a standard RS-232 serial interface. The RS-232 interface would typically be present only where the signpost 11 is fixedly mounted in a stationary location, as opposed to a situation where the signpost 11 is mounted on some form of mobile device. Alternatively, the RS-232 interface could connect the signpost 11 to the reader 13, because the reader 13 would typically be closer to the signpost 11 than the control system 14. In that case, when the control system 14 wishes to communicate with the signpost 11 would do so through reader 13. Although interface 27 in Figure 1 is an RS-232 interface, it will be recognized that it could alternatively be some other suitable interface, such as an Ethernet interface, an RS-485 interface, or a wireless interface.

The signpost 11 transmits the signpost signal 24 at periodic intervals. The time interval between successive transmissions can be configured to be relatively small, such as 100 ms, or relatively large, such as 24 hours, depending on the particular circumstances of a given signpost 11 relative to the rest of the system. Each signaling signal 24 transmitted by the signpost 11 includes a number of different pieces of information, which will be discussed below in association with Figure 2.

More specifically, Figure 2 is a schematic view of a digital word 36 having several different information fields which are discussed below. The bits of the digital word 36 are transmitted in the signaling signal 24 by serially modulating the bits of the word 36 onto the 132 kHz carrier using amplitude modulation, as mentioned above. The bits of the words 36 are transmitted serially from left to right in Figure 2. The first field is a preamble 41, which is a predefined bit pattern that will allow a device to receive the signal to recognize that the signaling signal is starting, and to synchronize with the signaling signal. In the disclosed embodiment, the preamble is approximately 8 bits, but the specific number of bits may vary depending on the characteristics of the particular receiver that is expected to be used to receive the signaling signal.

The next field 42 in word 36 is a signaling code, which in the disclosed embodiment is a 12-bit integer value that uniquely identifies the particular signpost 11 that is transmitting word 36. As mentioned above, the system 14 may have multiple signposts 11, and the use of different signpost codes 42 by different signposts allows the system to distinguish signposts transmitted by one signpost from those transmitted by another, in an analyzed manner. later in more detail.

This does not mean that this system could never have two signposts with exactly the same signal code. For example, two signposts could be fixedly mounted one in the vicinity of the other and configured to independently transmit truly identical signaling signals 24, not in sync,

ES 2 344 589 T3 to increase the probability that a receiver will pick up the signaling signal from at least one of the two signposts. In effect, this represents a level of redundancy, to increase reliability and accuracy. A different possible scenario is where two signposts 11, which are fixedly mounted at respective locations remote from each other, could conceivably use exactly the same signaling code 42. For example, if each of them communicated with the control system 14 through a respective different reader 13, the control system 14 would have the ability to distinguish them from one another.

The next field in word 36 of Figure 2 is a tag command 43, which is a command for beacon tag 12 that can affect the operation of beacon tag 12. Tag command field 43 is a field 2-bit. Since the purpose of the tag command field 43 is to affect the operation of the beacon tag 12, a discussion of specific examples of these commands will be deferred until after the beacon tag 12 has been described in more detail. The next two fields in word 36 they are a control command 44 and a parameter 45, which are related. In the embodiment discussed, the control command 44 is a 4-bit field, and a parameter 45 is an 8-bit field. Control command 44 is similar to tag command 43, to the extent that each of them instructs tag 12 to do something. The difference is that control commands 44 generally require a companion parameter 45, while label commands 43 do not use parameters. A discussion of the control commands 44 is deferred until later, after the label 12 has been discussed in more detail.

The next field in word 36 is an extension field 46, which is a 1-bit field. In the disclosed embodiment, this field is always a binary "0" for the word format 36 of Figure 2. It is provided for the purpose of facilitating future compatibility. For example, if it were necessary at some future time to modify the format of word 36, the indicator 46 would be set to a binary "1" in each word that has the new format, so that a device that receives the signaling signal 24 it could determine whether word 36 received on that signal had the original format shown at 36 in Figure 2, or the new format.

The next field in word 36 is an error control field 47. As communications between signpost 11 and other devices are essentially one-way transmissions, and as many applications for apparatus 10 of Figure 1 involve environments that have levels of relatively high noise levels, it is important that a receiving device can assess whether the word 36 it received in a signaling signal is correct, or has errors. Accordingly, the error control field 47 is included to provide a degree of early error correction (FEC). In the disclosed embodiment, error control field 47 contains eight parity bits, but the number of parity bits may be different if the total number of bits in word 36 is changed, or if one of several is selected for use. well known parity schemes. In addition to the use of the error control field 47, the overall level of reliability and accuracy can also be increased by having a device receiving the signaling signal 24 save and compare two successive transmissions of a given signaling signal 24, to verify that they are completely identical.

The last field in word 36 is an end-of-packet field 48. This field indicates to a receiving device that the transmission is ending. In the embodiment of Figure 2, the packet end field 48 has eight bits that are all set to a binary "0".

As mentioned above, the signaling signal 24 is typically transmitted in a relatively noisy environment. To ensure reliable signal detection, known techniques can be employed to improve signal-to-noise ratio (SNR). In the disclosed embodiment of Figure 1, the amplitude modulation of the 132 kHz carrier is effected using the well-known technique of amplitude shift modulation (aSk), to improve SNR. Alternatively, frequency shift keying (FSK) or phase shift keying (PSK) could be used to achieve an even higher SNR. However, FSK or PSK would typically require additional analog input circuits on each tag 12. Therefore, and as an object of the present invention is to implement both the signpost 11 and tag 12 at low cost, ASK is used. in the embodiment of Figure 1.

As noted above, the communications between the signpost 11 and the beacon tag 12 are one-way communications involving the signaling signals 24. With this in mind, it is desirable to provide a degree of security that ensures that the beacon tag 12 only it will react to valid signaling signals 24, especially with respect to commands in fields 43-45. Therefore, fields 42-47 of word 36 can be subjected to security protection using well known encryption and / or password techniques.

As discussed above, the signpost 11 in the embodiment of Figure 1 transmits the signaling signal 24 at a frequency of 132 kHz, to provide those signals with an effective range not exceeding approximately twelve feet (3.66 meters). In some applications, however, there may be a need for a somewhat longer range for the signaling signals. In that case, the signaling signals 24 could be transmitted using a different carrier, for example a high frequency microwave carrier of about 2.4 GHz, which would be effective in providing a range of about twenty-five feet (7.62 meters). ). Of course, the use of signals at this microwave frequency means that signpost 11 must generally have a line-of-sight relationship to each tag 12 that it is transmitting on.

ES 2 344 589 T3

Returning to the beacon label 12, the label 12 includes a receiving antenna 61 that receives the signaling signals 24 transmitted by the signpost 11. The antenna 61 is connected to a low-frequency receiver 62 of a known type, which is designed to receive the signaling signals 24, extract from them the information shown in word 36 of Figure 2, and then supply this information to a microcontroller 63 of the label 12. Label 12 also includes a timer 66 that can be used by microcontroller 63 to measure time intervals to be analyzed later. The tag 12 further includes a power source 67, which is typically a battery. However, in a situation where the label 12 is fixedly mounted, the power supply 6 could alternatively be an AC / DC adapter that is powered by an external 120 V AC power supply, as schematically indicated by a line discontinuous in Figure 1.

The microcontroller 63 controls an ultra high frequency (UHF) transmitter 68 of a known type, which in turn is connected to a transmitting antenna 71 of a known type. In the disclosed embodiment, antenna 71 is omnidirectional, but it will be recognized that antenna 71 could alternatively be configured to be directional. Using transmitter 68 and antenna 711, microcontroller 63 of tag 12 can transmit beacon signals 72 to reader 13. In the embodiment of Figure 1, beacon signals 72 are generated by FSK modulation of certain beacon information on a carrier signal having a frequency of 433.92 MHz. A suitable alternative frequency is 915 MHz, but in the disclosed embodiment it is used the 433.92 MHz frequency because it is available for use in a greater number of countries than 915 MHz according to the prevailing government regulations for the transmission of electromagnetic signals. The transmission range for beacon signals 72 is substantially longer than for signaling signals, and in the disclosed embodiment can be up to about 300 feet (91.44 meters). Beacon signals 72 are transmitted using a technique known in the art as a slotted ALOHA protocol, to reduce interference between beacon signals transmitted by different beacon labels.

In the disclosed embodiment, the beacon information transmitted in the beacon signals 72 can take one of two different forms, both of which are shown in Figure 3. More specifically, if the beacon tag 12 has received a valid signaling signal 24 Via antenna 61 and receiver 62, the beacon information transmitted in beacon signal 72 will have the word format shown at 81 in Figure 3. On the other hand, during the periods of time in which the beacon label 12 is outside the transmission range of the signaling signals 24 of any signpost 11, the beacon information transmitted in the signal 72 will have the word format shown in 82 in Figure 3. In the disclosed embodiment, fields 87-88, 91-92 and 97 (and fields 93 and 96 in the case of word 81) are all transmitted using FSK modulation with Manchester encoding at 27.7 kbps.

Word format 81 will be discussed first. It begins with a preamble 86, which is functionally comparable to preamble 41 of word 36 shown in Figure 2. In the disclosed embodiment, preamble 86 is 1.296 microseconds long, and includes 20 cycles. that each include a 30 microseconds high logic level and a 30 microseconds low logic level, followed by a cycle that includes a 42 microseconds high logic level and then a 54 microseconds low logic level. The next field in word 81 is a 1-bit format field 87, which is provided to indicate to a receiving device which of the two formats 81 and 82 of Figure 3 is the format used for the instantaneous beacon signal. Thus, field 87 is always a "1" bit in word 81, and a "0" bit in word 82.

The next field in word 81 is a 4-bit tag field 88, which is a code that provides some information about how the particular tag 12 is being used in the system. In this sense, the code may indicate that the tag is fixedly mounted, for example on a ceiling, or it may indicate that the tag is mounted on some form of mobile device. Additionally, when the tag is mounted on a mobile device, the tag type code 88 can provide some information about that mobile device, such as whether that mobile device is a standard height, or has a taller raised profile height.

The next field in word 81 is a 3-bit resource type field 91. When tag 12 is attached to some type of mobile device, the resource type field 91 can identify the specific type of mobile device to which it is attached the tag. For example, field 91 may indicate that the resource is attached to some form of container, to a trailer or truck on which a container can be transported, or to a tractor capable of pulling trailers that have containers on them.

The next field in word 81 is a signaling code 93. This is identical to the signaling code extracted at 42 from signaling word 36 that was most recently received by beacon tag 12. In the disclosed embodiment, word 81 it has only one 93 signaling code field. Accordingly, a system according to the disclosed embodiment must be configured such that each beacon tag 12 is within transmission range of only one signpost at any given time. However, it will be recognized that additional fields for additional signaling codes could be provided in word 81, such that tag 12 could be within transmission range of multiple signposts the same time, while codes are being received and reported. signposts for all those signposts.

The next field in word 81 is a last command field 96, which is identically the last command that was received in either field 43 or 44 of signal word 36 provided by the signpost.

ES 2 344 589 T3 having the signaling code that is present in field 93. This provides confirmation to control system 14 that tag 12 received this particular command from signpost 11.

The next field in word 81 is an error control field 97. In the disclosed embodiment, this is a 16-bit field containing a cyclic redundancy code (CRC) of a known type, which is calculated using the information from fields 87-88, 91-93 and 96. The beacon signals 72 transmitted by tag 12 to reader 13 are essentially one-way signals, and the error control field 97 is therefore provided to give reader 13 a degree of ability to detect and correct some errors in a received word 81. Reader 13 can also increase accuracy and reliability by receiving and comparing two successive beacon signals 72 and verifying that they are identical.

The last field in word 81 is an end-of-packet field 98, which in the disclosed embodiment is 36 microsecond low-level logic. The end of packet field 98 indicates to a receiving device that field 98 is the end of the word 81 that is currently being received.

Returning to the alternative format 82 of the beacon word, the basic difference from word 81 is that fields 93 and 96 of word 81 are omitted from word 82. This is because fields 93 and 96 contain information extracted from the last received signal word 36. Instead, as mentioned above, the beacon word 82 is used in situations where the beacon tag 12 is not currently receiving any signaling signals, and thus has no current information to put into fields 93 and 96. For Therefore, fields 93 and 96 are ignored in the 82 word format.

In theory, it would be possible to use the 81 word format even when tag 12 is not currently receiving information from any signposts, and simply put a "dummy" code as all zeros in each of the 93 and 96 fields. However, government regulations regarding radio transmissions tend to involve a balance between factors such as the power level at which a beacon signal 72 is transmitted, the time interval between successive transmissions of beacon signals 72, and the amount of information present in each radio beacon signal. Using the 82 beacon word format when fields 93 and 96 are not needed reduces the duration of the transmission of the beacon 72 signal, which in turn facilitates compliance with government regulations.

There are two other differences between beacon word format 82 and beacon word format 81. First, field 87 is always a binary "1" in word 81, and a binary "0" in word 82 , as discussed above. Second, the CRC value used in error control field 97 is calculated using fields 87-88 and 91-92 in beacon word 82, because fields 93 and 96 are not present, and therefore not can be taken into account.

Each transmission of the beacon signal 72 is similar to the transmission of a signaling signal 24, in that it is a short burst at the carrier frequency that includes an occurrence of word 81 or word 82 (Figure 3). Beacon tag 12 uses one technique to sequence beacon transmissions 72 when tag 12 is not currently receiving any valid signaling signals 24, and uses a different technique to sequence beacon signals 72 in response to receiving a signal. valid signaling 24.

In this sense, during any given time interval, several different beacon tags 12 may all be attempting to transmit respective different beacon signals 72 to a given reader 13, and it is inevitable that two or more of these tags will attempt to transmit beacon signals. 72 at the same time, so that the signals interfere or "collide" with each other at the reader 13. Each of the two different techniques used to transmit the beacon signals 72 attempts to reduce the probability that any two tags 12 will transmit beacon signals 72 in a synchronized manner that causes successive beacon transmissions 72 from each of these two labels collide repeatedly. Accordingly, each technique is intended to ensure that, even if two tags each happen to transmit a beacon signal 72 at approximately the same time, subsequent successive beacon signals from these two tags will not occur at the same time. same moment.

In more detail, and starting with the situation where tag 12 is not currently receiving any valid beacon signals 24, tag 12 operates in a normal mode of transmission in which it divides the current time into a succession of time slots having equal durations, for example 60-second time slots, and in which it transmits a beacon signal 72 within each time slot, at a randomly selected time within each time segment. In the disclosed embodiment, the random selection is actually done with a pseudo-random calculation of a known type, which closely approximates a truly random determination. In this document, the intent of references to random determinations is to include techniques such as pseudo-random determinations.

When the tag 12 receives a valid signaling signal 24, it immediately interrupts the normal mode of transmission and switches to a special mode of transmission. At the end of the special transmission mode, it returns to normal mode. The special mode is discussed in association with Figure 4, in which the horizontal axis at the bottom represents the progression of time from left to right. The vertical line on the left side of Figure 4

ES 2 344 589 T3 represents the moment when a valid signaling signal is received, and represents the moment when the tag 12 responds by changing from normal mode to special mode. The special mode involves five successive time slots 111-115, each discussed separately later. After the last time interval 115 of the special mode, the label 12 returns from the special mode to the normal mode, where operation in the normal mode is represented by the time interval 116.

Time slot 111 involves N1 successive time slots each having a duration of T1. In the disclosed embodiment, N1 is 5, and T1 is 0.1 seconds. Tag 12 transmits beacon signal 22 once during each of these five time slots, at a randomly selected point within that time slot. These five time segments are schematically represented in Figure 4 by the spaces between the short vertical lines within the time interval 111 along the horizontal axis at the bottom of Figure 4.

It will be appreciated that the operation of the tag during interval 111 is somewhat similar to the operation of the tag during its normal mode, but there are two basic differences. First, each of the time slots in normal mode is approximately 600 times longer than the time slots in time slot 111, and therefore the beacon signal 72 is being transmitted an average of 600 times. more often than in normal mode.

Second, during the time interval 111, the tag 12 transmits each beacon signal 72 at a power level P1, which is 24 dB lower than a power level P2 used during normal operation. As mentioned above, government regulation for UHF transmissions may imply a degree of balance between the duration of each transmission, the time interval between successive transmissions, and the power level of the transmissions. Therefore, how transmissions in time slot 111 have a longer duration than transmissions in normal mode (because they involve the beacon word 81 of Figure 3 instead of the beacon word 82), and how they are sent At an average frequency of 600 times, the reduced power level P1 is used for these transmissions to facilitate compliance with government regulations. The power level that is being used at any given time is set across the top of Figure 4.

Time slot 111 is followed by time slot 112, which is a delay or wait state having a duration of T5, where T5 is 1 second in the disclosed embodiment. During the time interval 112, the tag 12 does not transmit any radio beacon signals 72.

Time slot 112 is followed by time slot 113, which is treated similarly to time slot 111, except that some parameters are different. In particular, the time slot 113 includes N2 successive time slots each having a duration of T2. In the disclosed embodiment, N2 is 3, and P2 is 1 second. During each time slot T2 a single beacon signal 72 is transmitted, at a randomly selected time within that time slot. Beacon signals 72 that are transmitted during time slot 113 are transmitted at the reduced power level P1 that was used in time slot 111.

Time slot 113 is followed by time slot 114, which is a delay or waiting state similar to time slot 112. In particular, no beacon signals 72 are transmitted, and the time slot has a duration of T6, which in the disclosed embodiment is 10 seconds.

Time slot 114 is followed by time slot 115, which involves activity similar to time slot 111 and 113. In particular, time slot 115 includes N3 time slots each having a duration of T3. In the disclosed embodiment, N3 is 3, and P3 is 10 seconds. During each of these time slots a single beacon signal 72 is transmitted, at a randomly selected point within the time slot. At time interval 115, label 12 returns to the highest power level of P2. In this regard, it will be noted that the average transmission speed of beacon signals in time slot 115 is approximately one tenth of the average transmission speed of radio beacon signals in time slot 113, and is approximately one hundredth of the average transmission speed in time slot 111. Therefore, and with reference to the previously discussed balance between the duration of transmissions, the time interval between transmissions and the power level, the label 12 can return to the higher power level P2 as a result of the significant decrease in speed. average of transmissions, still complying with government regulations.

Time slot 115 is followed by time slot 116 which, as mentioned above, represents a return to normal mode of operation. In particular, the tag 12 continuously divides the current time into successive time segments each having a duration T4, where T is 60 seconds. Each of these beacon signals is transmitted at the highest power level P2, using the shorter format of the beacon word shown at 82 in Figure 3. The time interval 116 does not have a specified duration, and it will continue until tag 12 receives a new valid signaling signal causing it to switch back to special mode and carry out the beacon sequence shown in Figure 4.

ES 2 344 589 T3

The preceding discussion mentions several parameters, including N1-N3, T1-T6, and P1-P2, and gives specific values ​​for some of these parameters. The specific values ​​given for these parameters are those used in the disclosed embodiment, but it is within the scope of the present invention to vary these parameters.

Figure 5 is a flow chart showing in a different way the beacon sequence discussed above in association with Figure 4. In Figure 5, the microcontroller 63 of the beacon tag 12 enters block 131 in response to the reception of a valid signaling signal 24. Block 131 corresponds to time slot 111 in Figure 4. At block 131, the beacon tag transmits a P1 power level beacon signal at a random time within each of N1 successive time slots each having a duration T1.

The system then proceeds to block 132 of Figure 5 which corresponds to time slot 112 in Figure 4. In particular, the beacon tag waits for a time slot T5, without transmitting any beacon signal. The system then proceeds to block 133, which corresponds to time slot 113 in Figure 4. At block 113, the beacon tag transmits a P1 power level beacon signal at a random time within each of N2 successive time slots each having a duration T2.

The system then proceeds to block 134, which corresponds to time slot 114. At block 134, the system waits for a time slot T6 without transmitting any beacon signal, and then proceeds to block 135. Block 135 corresponds to the time slot. time 115 in Figure 4. At block 135, the system transmits a P2 power level radio beacon signal at a random time within each of N3 successive time slots each having a duration P3.

From block 135, the system advances to block 136, which corresponds to time slot 116 of Figure 4. The system remains in block 136 indefinitely, until a new valid signaling signal is received. While at block 136, the beacon tag transmits a beacon signal with power level P2 at a random time within each of a series of successive time slots each having a duration of T4. If a new valid signaling signal is received, then the beacon tag immediately ceases its activity at block 136 and returns to block 131, as indicated schematically by the dashed line 137, to again carry out the beacon sequence that it is represented by blocks 131-135.

Figure 6 is a high-level flow chart depicting the operation of beacon tag 12. Referring to Figure 1, beacon tag 12 has a reduced power mode in which transmitter 68 is off, timer 66 is active, receiver 62 is active, and microcontroller 63 is in a reduced power or "latent" mode, from which it can be pulled out by receiver 62 or the expiration of timer 66. The flow chart of Figure 6 begins at a time when beacon tag 12 exits reduced power mode, because receiver 62 has received a signaling signal, or because timer 66 has expired.

Microcontroller 63 of tag 12 proceeds from block 151 to block 152, where it checks if timer 66 has just expired. If not, then it knows that receiver 62 has received a signaling signal, and goes to block 153, where it extracts and stores the signaling code (42 in Figure 2) from the received signaling signal. Control then passes to block 156, where the beacon tag checks if the received signaling signal also includes a command in any of fields 43 and 44 (Figure 2). If so, then the label goes to block 157, where it executes the command. The tag then proceeds to block 158, where it reverts to its reduced power "latent" mode.

Looking again at block 156, if the beacon tag were to determine that the signaling signal did not include a command, then the beacon tag would have to proceed to block 161, where it reinitializes the beacon sequence. This corresponds to the dashed line 137 in Figure 5, where the tag exits the normal mode of operation represented by block 136, and returns to block 131 to carry out the special beacon sequence that is represented by blocks 131-135 in Figure 5 and by the time intervals 111-115 in Figure 4.

Then, at block 162, the beacon tag determines the next time to transmit its beacon signal according to the beacon sequence. Since the beacon sequence has just been reset at block 161, this will be a determination of the timing of transmitting the beacon signal within the first time slot of time slot 111 in Figure 4. As discussed above, this will involve a random determination of a moment within the time segment, for example, using a pseudo-random technique of a known type. Once this time has been selected, beacon tag 12 sets timer 66 (Figure 1) at block 163 of Figure 6, so that the timer will expire at the appropriate time to allow transmission of the next alarm signal. beacon, and then beacon tag 12 returns to dormant mode at block 158.

Returning to block 152 of Figure 6, if it was determined that microcontroller 63 was brought out of dormant mode because timer 66 expired, microcontroller 63 would have moved from block 152 to block 167. At block 167 a determination is made as to whether the timer expired because it is time to transmit the next beacon signal. If not, then the beacon tag goes directly to block 158, where it returns to mode.

ES 2 344 589 T3 latent. If not, it goes from block 167 to 168, where it transmits its radio beacon signal 72 (Figure 1). It then proceeds to block 162, where it captures the transmission moment for its next successive beacon signal. Then, at block 163, you set the timer to expire at each time you determined. Then, at block 158, it returns to the reduced power latent mode.

At an initial point in this discussion, in association with the discussion in Figure 2, it was indicated that command fields 43-45 would be described in due course. What follows is a discussion of those fields.

The tag command field 43 is a 2-bit field that can be used to instruct a beacon tag 12 (1) to turn off (which is actually a low-power latent mode in which no beacon signals are transmitted. ), (2) to turn on (which is a mode in which beacon signals are transmitted in the manner described above in association with Figures 4-6), (3) to operate at a fast beacon speed, or (4) operating at a slow beacon speed (where slow speed uses a duration for each time segment T4 in Figure 4 that is longer than the duration used for fast speed).

Returning to control command field 44 and parameter field 45, it was mentioned above that parameter field 45 contains a parameter necessary to implement a command specified by control command field 44. A command that can be specified in control command field 44 is an instruction to beacon label 12 to set the beacon code that it puts into field 92 (Figure 3), and in that case parameter field 45 would contain the new code for the radio beacon. Another command that can be specified by control command field 44 is an instruction to beacon tag 12 to set a password or encryption key used for security, as discussed above, and parameter field 45 would contain the new one. password or encryption key. Yet another command that can be specified by control command field 44 is an instruction to beacon tag 12 to set the tag type code that it puts into field 88 (Figure 3), or the resource type code. which it puts inside field 91, and parameter field 45 would contain the new tag type code or resource type code. Still other commands in control command field 44 could instruct the beacon tag to change any one of the various parameters discussed above in association with Figures 4 and 5, including P1, P2, N1, N2, N3, T1, T2, T3, T4, T5, and T6, and parameter field 45 would contain the new value for the specified parameter. It will be recognized that still other commands could be sent to tag 12 using control command field 44 and, when necessary, parameter field 45.

Referring again to Figure 1, the reader 13 will be described in more detail below. The reader 13 includes two antennas 211 and 212 which are of a known type, and each of which is suitable for receiving UHF wireless signals. Reader 13 also includes two UHF receivers 213 and 214, each of which has an input connected to a respective antenna of antennas 211 and 212. The reason that the reader 13 has two UHF antennas 211-212 and two UHF receivers 213-214 is that the antennas 211-212 are arranged to extend perpendicular to each other. Reader 13 is able to determine which of the two antennas 211-212 is producing the strongest output in response to a given beacon signal 72. Reader 13 then selects the strongest output for use as the received version of that radio signal. particular radio beacon.

The reader 13 also includes a decoder 217 of a known type, which has two inputs that are each connected to an output of a respective receiver of the receivers 213-214. The decoder 217 processes the signals received by each of the receivers 213-214, to extract usable information from them, which can then be passed to a microcontroller 221 of the reader 13. A real time clock circuit (RTC) 222 is connected to microcontroller 221. In addition, the reader 13 includes a network interface 223. A network 226 is of a type known in the industry as an Ethernet network, and connects the network interface 223 of the reader 13 to the control system 14, to facilitate communication between the reader 13 and control system 14. The basic function of reader 13 is to receive beacon signals 72 from various beacon tags (such as tag 12), verify that each received beacon signal is valid, perform error detection and correction when necessary, extract information as one or more than the fields shown at 87-88, 91-93 and 96 in Figure 3, and then pass this extracted information to the control system 14.

Figure 7 is a schematic top view of a system 240 depicting a practical application of an apparatus of the type shown at 10 in Figure 1. The system 240 of Figure 7 includes a plurality of signposts, sixteen of which are shown at 241-256 in Figure 7. Each of the 241256 signposts is identical to the signpost shown at 11 in Figure 1, except that each uses a respective unique marking code 42 (Figure 2). Signposts 241-256 have been given different reference numbers in Figure 7 to facilitate a discussion of how system 240 works.

Each of the signposts 241-256 is fixedly mounted, for example on the ceiling of a warehouse or other industrial facility. The sixteen signposts 241-256 are arranged in a regular 4x4 formation. The dotted line circle extending around each signpost in Figure 7 is a schematic representation of the effective outer limit of the transmission range of the signposts emitted by that signpost. As discussed above, each signpost has a limited transmission range of only about 12 feet (3.66 meters) or less, and the spacing between signposts 241-256 has been intentionally selected so that two signposts do not have overlapping transmission ranges. Although sixteen signposts 241-256 are shown in Figure 7, this 4x4 formation is only part of

ES 2 344 589 T3 a much larger formation covering a much larger area. However, the formation shown in Figure 7 is sufficient for purposes of explaining certain principles of the present invention.

A reader 261 is fixedly mounted within the array of signposts 241-256, for example on the same roof that supports the signposts. Reader 261 is identical to the reader shown at 13 in Figure 1, but is given a separate reference number here for clarity. System 240 would actually include a number of other equivalent readers in separate locations, but only one reader 261 is illustrated in Figure 7 to facilitate a clear explanation of certain features of the invention.

Five 271-275 radio beacon labels are also depicted in Figure 7. Each of the beacon labels 271-275 is actually identical to the beacon label shown at 12 in Figure 1, but they have been given separate reference numbers for clarity in the discussion that follows. For the purposes of the following explanation, it is assumed that each of the 271-275 beacon tags is mounted on a different mobile device, such as a container, a pallet, a forklift, a trailer that can hold a container, a tractor that You can pull a trailer, or some other type of mobile device.

Focusing first on beacon tag 271, it will be seen from Figure 7 that this tag is currently within transmission range of signpost 241. Consequently, beacon tag 271 will be receiving beacon signals 281 from the pole. indicator 241, and it will be transmitting signals from beacon 282 to reader 261. The beacon signals 282 will include the unique beacon code for beacon tag 271, as well as the unique beacon code for signpost 241. Consequently, since this signaling code and this beacon code are received in combination with each other on beacon signal 282, the control system associated with reader 261 can determine that beacon tag 271 is currently within the range. transmission range of the signpost 241. This means, in turn, that the mobile device bearing the beacon tag 271 is currently very close to the signpost 241. Since the control system knows the physical location of the signpost 241, the system can make a relatively accurate determination of the current location of the mobile device bearing the beacon tag 271, located in the transmission range of the signpost 241. In particular, the system can determine the current location of the beacon tag 271 and its associated mobile device to an accuracy of approximately 12 feet (3.66 meters), which is the radius of the transmission range of the signpost 21. It will be recognized that this capability is due in part to the fact that signaling signals have a relatively local transmission range, whereas beacon signals have a transmission range that is approximately 30 times farther than the transmission range of radio beacons. signaling signs.

For purposes of comparison, suppose for a moment that all signposts 241-256 were omitted from the system 240 of Figure 7. In that case, each of the beacon signals 282 from the beacon tag 271 would include the code of Unique EPIRB from tag 271, but would not include any signaling code. By analyzing the intensity of beacon signal 282, as received at reader 261, the control system associated with reader 261 could make a very rough estimate of the distance between tag 271 and reader 261. However, it would be difficult for the control system to determine exactly which direction the beacon signal 282 is coming from. In this sense, even though reader 261 has two orthogonal antennas (equivalent to those shown at 311-312 in Figure 1), reader 261 would not know if beacon signal 282 came from one direction or from a diametrically opposite direction.

Assuming still that no signposts are present in the system, but that a second reader is provided in such a way that both readers receive the signals from beacon 282, the control system could estimate the distances from beacon tag 271 to each. one of the two readers. With this information, it would be possible to perform a standard triangulation calculation to attempt to estimate the location of the 271 radio beacon tag. But due to the fairly wide tolerances in the ability to estimate distances from the beacon tag to each reader based on the intensity of the beacon signal, even triangulation only produces a very rough estimate of the location, which is not particularly accurate and reliable. . Therefore, it will be recognized that, by using the signposts 241-256 of Figure 7, a significantly more accurate and reliable determination can be made of the current location of the beacon tag 271.

In Figure 7, the mobile device associated with beacon tag 275 is currently at a location where beacon tag 275 is not within transmission range of any of the signposts 241-256. Thus, reader 261 is receiving a beacon signal from beacon tag 275, but the beacon signal includes only the beacon code from tag 275, and does not include a beacon code from either post. indicators 241-256. Therefore, the tag 275 is temporarily located where the system cannot determine its location as accurately as if it were currently within transmission range of any of the signposts. However, the system 240 can still have a relatively accurate idea of ​​the current location of the tag 275 by tracking it over time.

For example, the system may know that tag 275 arrived at its current location by scrolling through the transmit range of signpost 243 and then through the transmit range of signpost 242, and the system can thus predict that tag 275 will soon enter. in the transmission range of the 245 signpost. Therefore, even though tag 275 is not currently within transmission range of any signpost, the system still has a better idea of ​​tag 275's current location than would be the case if there were no posts.

ES 2 344 589 T3 indicators at all. An additional consideration in this regard is that, within the warehouse or other industrial facility, there are often defined paths that mobile devices have to follow through the facility. Accordingly, the system can fully realize that there is a defined path successively extending through signpost 243, signpost 242, and signpost 245. This will provide the system with an even better ability to accurately estimate the current location of tag 275, even though it is not currently within transmission range of any of the 251-256 signposts.

It is possible that two or more beacon tags are simultaneously within the transmission range of a single signpost, so that all those beacon labels are simultaneously receiving the same beacon signal emitted by that signpost. This is the case with beacon tags 272-274 of Figure 7, which are all within transmission range of signpost 248. The reader 261 receives a separate beacon signal from each of the tags 271-274, and each of these beacon signals includes the unique beacon code of the corresponding beacon tag, in combination with the signaling code of the pole. indicator 248. In this way, the control system associated with the reader 261 can distinguish the beacon tags 272-274 from each other, due to their unique beacon codes, and can also determine that all of these beacon tags are currently in locations within range. indicator pole transmission 248.

Although Figure 7 shows an array of signposts 241-256 that are fixed, and various beacon labels 271-275 that are movable, the fixed and movable characteristics of the signposts and beacon labels can be reversed. In this regard, Figure 8 is a schematic top view of a system 300 having sixteen fixed beacon labels 301-316, each of which is equivalent to beacon label 12 of Figure 1. These beacon tags are arranged in a 4x4 array, spaced equivalent to that used for signposts 241-256 of Figure 7. A reader 319 is provided at a central location within the array, and is also stationary. A signpost 322 is mounted on a mobile device, which is movable within the facility, and thus movable relative to the stationary beacon labels 301-316. At the time depicted in Figure 8, the mobile device carrying the signpost 322 is at a location near the beacon tag 301, such that the beacon tag 301 is within transmission range of the signpost 322.

Signpost 322 is transmitting a signaling signal, but the only beacon tag that can currently receive that signal is beacon tag 301. Therefore, each of the beacon tags 301-316 is transmitting a respective beacon signal to the reader 319, and each of these beacon signals includes a unique beacon code, but only the beacon signal from the tag. 301 also includes the unique signaling code that you are receiving in the signaling signal from signpost 322. The control system associated with the reader 319 will know the physical location of each of the fixed beacon tags 301-316. Therefore, the location of the mobile device associated with the signpost 322 can be determined with the same degree of accuracy achieved in the system of Figure 7, because the control system for the embodiment of Figure 8 knows that the distance between the Signpost 322 and the beacon tag 301 should be less than the transmission radius of the signaling signals from the signpost 322 or, in other words, approximately 12 feet (3.66 meters). If the signpost 322 is moved until it is close to the beacon tag 302, then the beacon tag 301 will no longer be within transmission range of the signaling signals from the signpost 322, but the beacon tag 302 will be within that transmission range. Consequently, beacon tag 301 will stop transmitting the signaling code from signpost 322 in its beacon signal, and beacon tag 302 will begin transmitting this signaling code in its beacon signal. As a result, the control system associated with reader 19 can track the movement of the mobile device associated with signpost 322.

One difference between the systems of Figures 7 and 8 is that since the beacon signal from the beacon tag is configured to include only one signaling code, each beacon tag should never be within the transmission range of more than a signpost at any given time. In the system of Figure 7, this is ensured by the fixed mounting of the indicator posts 241-256, with appropriate spacing provided between them. Instead, since the signposts can be moved in the Figure 8 system, care must be taken to ensure that two or more signposts do not approach the same marker at the same time. This is not to suggest that the procedure of Figure 7 is more advantageous than the procedure of Figure 8. One of these procedures may be better for some applications, and the other may be better for other applications. In fact, it should be apparent from the discussion that follows that, in some applications, it would be possible to use a combination of the two procedures.

Additional aspects of the present invention will be discussed below. These additional aspects are believed to be more clearly understood if presented in the context of an example of a specific application. Therefore, the discussion that follows will focus on a private company that is in the business of overnight package delivery. As is well known, companies of this type provide a service in which they collect a package from one sender in one day, and then deliver it to a recipient the next day, typically before noon. The sender can be in one city, like Boston, and the recipient can be in a different city, like Tucson.

ES 2 344 589 T3

On the day a package is picked up in Boston, the company will typically also pick up several other packages in Boston, which will go to a variety of different cities across the country. The next day, the company will have several packages to deliver in Tucson, which were picked up the day before in several different cities across the country. To efficiently handle the routing of all these packets, existing carriers typically provide some form of centralized facility at a major airport. During the night, a container will arrive from a city like Boston, containing various packages that have to be delivered to many different cities. The container will be unloaded at the centralized facility, and then the packages will be classified, to group the packages classified by destination city. Thus, for example for Tucson, the sorting procedure will produce a group of packages destined for delivery in Tucson, which arrived at the centralized facility in a variety of different containers from a variety of different source cities. The group of packages destined for Tucson will be packed in a container, and that container will be transported to Tucson, where the packages will be delivered locally.

With respect to a centralized facility of the type discussed above, most containers will typically arrive in one of two different ways. First, containers from cities that are not too far from the centralized facility will typically arrive by road, in various types of trucks. These trucks are commonly called feeders. Containers from more distant cities will typically arrive by plane. The shapes and sizes of containers that arrive by plane and truck can vary greatly. Figure 9 is a schematic perspective view of a type of container 381 that is particularly suitable for use in aircraft, because it has a shape that facilitates the packaging of several such containers within the somewhat rounded shape of an aircraft fuselage.

Container 381 of Figure 9 has an approximately square bottom wall 382, ​​and an upper wall defined by a horizontal central portion 383, and two inclined portions extending down an inclined plane from opposite sides of portion 383, being visible at 384 one of the sloping parts. Container 381 has four side walls each extending vertically upward from one edge of the bottom wall to one edge of the top wall, and two of these side walls are visible at 387 and 388 in Figure 9. Container 381 it also has two doors 391 and 392, each of which can pivot between an open position and a closed position. A latch, not shown, is provided to secure doors 391-392 in a closed position, and is configured in a known manner to allow the doors to be locked or sealed in their closed positions, so that packages cannot be removed. by unauthorized person when the containers are being transported to or from the centralized facility.

Container 381 itself is a known device. In accordance with the invention, three beacon tags 395-397 are fixedly secured to container 381 at separate locations therein. Each of the labels 395397 is equivalent to the label 12 of Figure 1. The label 395 is provided in the central portion 383 of the top wall of the container. Labels 396 and 397 are provided on respective opposite side walls of container 381, closely adjacent to diagonally opposite corners of bottom wall 382. Each of the various types of containers that travel to and from the centralized facility by truck and plane may be referred to as a unit load device (ULD). Container 381 of Figure 9 is an example of a ULD.

Figure 10 is a schematic top view of a facility 400 including a centralized facility 401 of the type discussed above. In centralized facility 401, packages that are transported by an overnight delivery service are received from many source cities, unpacked, sorted, repackaged, and then transmitted to many destination cities. That is, the centralized facility 401 of Figure 10 is essentially a building where packages are unloaded from containers, sorted, and then reloaded into other containers. The general facility 400 includes an arrival section 403 and an exit section 404, which are both external to the physical building of the centralized facility 401. The arrival section 403 is related to the reception and initial processing of the incoming containers, and the exit section 404 handles the processing of the outgoing containers.

A tracking system of the general type discussed above in association with Figure 7 is used by facility 400, but is not shown in Figure 10 for clarity. This tracking system includes a plurality of separate signposts mounted on the roof of the facility. centralized facility 401, and at other selected locations throughout facility 400, as discussed below. In addition, throughout the facility 400 a plurality of readers are provided. In centralized installation 401, the readers are mounted on the ceiling. In the arrival and departure sections, readers are mounted at entry and exit gates, on or near unloading equipment, on utility poles, in buildings, on fences, on special supports, or other suitable structure that may be present. In general, signposts are provided in areas where very accurate estimates of tag location are needed, using techniques of the type discussed above in association with Figure 7. In contrast, in areas where a more rough estimate of the tag location is sufficient, the signposts may be omitted so that the beacon signals do not include marking codes, and the location estimates may be based on the intensity of the signals. beacon signals as they are received by the readers.

Returning in more detail to the flow of materials through facility 400, an arriving aircraft taxis to arrival section 403, where it is parked at 411. The aircraft can be parked in one of two different types of locations. One is commonly called a "wing" location. This means that the aircraft is parked closely adjacent to a building, which typically has a built-in charger or unloader that can be

ES 2 344 589 T3 extended to an aircraft door to facilitate loading and unloading. The other type of location is known as a "ramp" location. This means that the aircraft is parked on the runway in a separate location from any building. Loading and unloading of such an aircraft are carried out using known types of mobile loaders and unloaders that can exit onto the aircraft and then return to a building.

A government requirement is that most electronic devices that are traveling on airplanes must be deactivated during the flight, so that they do not produce any type of wireless electromagnetic signal that could interfere with the operation of the plane. Therefore, to the extent that any signpost or radio beacon tag of the type shown at 11-12 in Figure 1 is traveling by plane, it must be turned off during flight, or at least it must be in an operating mode in the one that does not transmit electromagnetic signals. As discussed above, beacon labels 395-397 are provided on ULDs of the type shown at 381 in Figure 9. Consequently, when these ULDs are unloaded from an aircraft, the beacon tags have to be turned on. As discussed above, the tag command field 43 (Figure 2) of a signaling signal can turn a beacon tag on or off. Accordingly, signposts may be provided at or near each unloading device, or in the area of ​​the aircraft unloading operation, to light all the beacon tags that are present on the ULDs being unloaded. Alternatively, a manual signpost could be used manually by an operator to turn on all the beacon tags that are on the equipment being unloaded. The beacon labels of the downloaded ULDs thus begin to transmit their beacon signals.

As noted above, arrival section 403 has a plurality of readers of the type shown at 13 in Figure 1 at appropriately selected locations throughout arrival section 403. These readers are provided on or near the aircraft's unloading equipment, on utility poles, on buildings, on fences, on special supports, or on another structure. The beacon signals generated by the labels in each ULD will be received by one or more of these readers, each of which will send the information received to a central control system of the type shown at 14 in Figure 1. As the system of control knows which beacon tags are mounted on which ULD, the control system can determine which ULDs have arrived by plane. The control system can then begin planning how to route each ULD through facility 400.

In this sense, there are occasional situations in which a ULD comes from a city of origin that has so many packages going to a single destination city that all these packages have been packaged in a single ULD. In that case, the control system can arrange for the ULD to be transferred directly from the arrival section 403 to the exit section 404, because there is no need to do any unpacking, sorting or repackaging. However, the vast majority of ULDs will have to be unpacked and sorted, and therefore will have to be routed to the centralized 401 facility.

As for all the ULDs that arrive, the control system will have received electronically from each city of origin an identification of the ULDs that are sent, and a list of the specific packages in each such ULD. In this way, depending on the departure times for the planes that travel to the destination cities, the control system can prioritize the order of handling of the arriving ULDs, so that the ULDs that contain packages that have to be in earlier departing flights can be handled earlier than non-packaged ULDs that have to be on earlier departing flights. Based on the electronic information received from the cities of origin, the control system knows which ULDs should be on each arriving aircraft, and can determine if one of the expected ULDs is missing, or if an extra and unexpected ULD is present. The arrival time of each ULD can also be recorded.

When the aircraft is ramp parked, the ULDs can be transported to the centralized facility using a train that includes several removably connected trailers or "trolleys", and a tractor or tug that can pull the trailers. Each ULD can be transferred to a respective train trailer. A train of this type is described in more detail later. In Figure 10, block 142 reflects this transfer of ULDs onto trailers. The train then transports the ULDs to the centralized facility 401. Conversely, if the aircraft is wing parked, the ULDs may or may not be transferred to such a train. Instead, they can be transported by conveyor, by a device such as a cart that can be pushed manually, or by some other transport apparatus. Block 413 of Figure 10 represents the transfer of ULDs from the aircraft to some form of appropriate device that will facilitate the transport of the ULDs.

At block 416 at 403, the manifest of each arriving ULD is manually checked for the arriving flight. Then, in block 417, the ULDs destined for the centralized installation are moved to the centralized installation. As mentioned above, readers are provided at selected locations throughout facility 400, including arrival section 403, centralized facility 401, and exit section 404. In addition, signposts of the type shown at 11 in Figure 1 are provided in a variety of selected locations throughout the facility 400, especially in locations that ULDs must pass through as they are routed through the facility 400. Thus, for example, signposts are provided along typical travel paths, at entrances, and at various stations where ULDs may temporarily wait for attention, which are referred to as "parking" areas. Using the basic procedure discussed above in association with Figure 7, the control system can accurately track each ULD throughout the entire facility 400.

ES 2 344 589 T3

Each of the ULDs coming from parking area 418 is finally transported to one of several unloading stations 421. At each unloading station, an operator opens the ULD, and also presses a pushbutton on an adjacent control panel, to indicate to the control system that has started the download procedure. The operator then unloads all the packages from the ULD, placing them on conveyor belts that take them to a package sorting section 422. When the operator finishes unloading a ULD, the operator presses a new button on the control panel, to signal to the control system that the manual unloading procedure has been completed. In the disclosed embodiment, the control panel at each unloading station is a physical part of the unloading station. However, it may alternatively be provided in the form of a wireless device carried by the operator. Each of the empty ULDs is taken to a parking area 426, and finally they are moved to a parking area 427, directly or through a new parking area 428, which is outside the physical building of the centralized facility 401.

Referring back to arrival section 403, and as discussed above, packages can arrive not only by air, but also by truck. As noted above, trucks are called feeders. The feeders can contain ULDs, in which case the ULDs can be unloaded and handled in a manner very similar to that discussed above in association with an arriving aircraft being parked off the ramp. More typically, however, feeders include packages that are not packed in ULDs. In that case, the feeder itself is treated as the container for the packages, and the lower part of Figure 10 deals with how this type of feeder is handled.

In particular, at block 436 the feeder is checked into the gate of the arrival section 403. A temporary radio beacon tag similar to that shown at 12 in Figure 1 is attached to the feeder, for example, using some special mounting bracket. . At the same time, the person in charge of the gate makes an annotation on a computer, which informs the central control system of the arrival of the feeder, and also informs the control system of the particular beacon tag that has been attached to that feeder, to allow the control system to associate the electronic manifest for that feeder with the actual physical feeder as it travels through facility 400.

If the feeder is a truck in the form of a cab pulling a trailer, commonly known as a tractor-trailer combination, the trailer can be detached from the cab and moved by facility 400 using small local tractors of a type commonly referred to as yardbird. On the other hand, if the cab is an integral part of the feeder, the entire truck can move through facility 400.

In any case, in block 437 the feeder moves from the arrival section 403 to a parking area 441 that is adjacent, but exterior, to the building that serves as a centralized facility 401. The control system schedules the movement of these feeders to feed the discharge stations, one of which is shown at 442. Each feeder is discharged, in a manner similar to that described above for the ULD discharge stations 421. Packages removed from the feeders travel to the parcel sorting section 442, for example by conveyor, while the empty feeders are routed to an empty feeder parking area 443.

In the parcel sorting section 422, all parcels addressed to a given destination city are routed to a selected unloading station from several unloading stations 451. An empty ULD is taken from the parking area 427, and loaded with packages with letterhead for that destination city, until the ULD is full or until it contains all the packages gathered for that destination city. Then that ULD is transferred to a 452 ULD scale section, where each ULD is weighed. Scale 452 is connected to the central control system, so that the control system will know the weight of each loaded ULD, and thus can carry out proper planning regarding how much total weight is being loaded on each departing aircraft.

After each ULD has been weighed at 452, it is moved to an exit parking area 453. From there, in due course it is taken out of the building through a door that has a signpost nearby, and the system is alerted. control of its exit from the centralized facility 401 by virtue of the radio beacon signals that come from a label on the ULD and include the signpost signaling code. Then, as schematically represented by blocks 456, 457 and 458, these ULDs are transported by trains of the type discussed above to departure section 404, where each is loaded onto an aircraft traveling to the destination city for all packages in that ULD.

As mentioned above, government regulations prohibit devices such as radio beacon tags from emitting wireless electromagnetic signals during the flight of the aircraft. Consequently, as each ULD is loaded onto an aircraft, all of the beacon tags associated with it are turned off, or at least put into a mode where they do not emit any beacon signals. This can be accomplished by using a fixed signpost in the aircraft charger area, or by using some form of portable signpost operated by a person involved in the charging procedure. As noted above, one of the commands that may be present in the tag command field 43 (Figure 2) of a signaling signal is a command that turns off any beacon tag that receives the signal. When an aircraft has been loaded with all the ULDs that it is scheduled to carry, the aircraft taxis out of exit section 404, and then takes off for its destination city.

ES 2 344 589 T3

Some of the packages sorted in sorting section 422 are scheduled to depart by truck rather than by plane, for example when they are to be delivered to destinations not far from facility 400. The sorting procedure routes these packages to station stations. feeder loading, one of which is shown at 461. An empty feeder from feeder parking area 443 is moved to one of feeder loading stations 461, where it is loaded with sorted packages to be transported to one or more relatively local delivery centers. The loaded feeder is then moved from centralized facility 401 to exit section 404, where the temporary beacon tag is removed from that feeder, and an appropriate notation is made at a terminal connected to the control system. Then the feeder exits the outlet section 404. In this sense, if the feeder is a trailer that is moved by a yardbird, it is separated from the yardbird and connected to an available cab, and then the cab pulls it to its destination.

As mentioned above, the system that tracks ULDs and feeders through facility 400 is not shown in Figure 10. This system is called the ULD Tracking System (UTS), and Figure 11 is a schematic view of selected parts of this UTS system, which is generally designated in Figure 11 by reference numeral 500. In more detail, the UTS 500 system includes a UTS 502 server, the hardware of which is a suitable computer system of a commercially available type. The server 502 is associated with a database 503, which may be stored on a hard disk of the server 502 itself, or on some type of physically separate storage device that is operatively connected to the server 502. System 500, including server 502, is fault tolerant in the disclosed embodiment, including the provision of a degree of redundancy, to allow the system to automatically reconfigure itself in a known manner to avoid localized faults that may occur. In this sense, it will be recognized that, as all packages that are handled in facility 400 absolutely have to be delivered the next day, it is simply unacceptable that a failure within system 500 stops facility 400 from operating. Obtaining fault tolerance capabilities are of a known type, and are therefore not disclosed in detail in this document.

Server 502 is interconnected at 504 to various other systems, which are not technically part of the UTS 500 system itself, and are therefore shown in dashed lines in Figure 11. One is the scale section of ULDs 452, which was mentioned above in association with Figure 10. Another is an airport transfer control system (AHCS) 506, which is a separate computer system that provides general control for facility 400 of Figure 10, including functions other than tracking feeders and ULDs within facility 400. The Server 502 is also connected to a weighing and balancing system 507, and a planning and operation control (OPC) system 508. Server 502 could also optionally be connected to some other type of computer system 509 used in facility 400.

Returning in more detail to the UTS 500 system, and as mentioned above, there are a plurality of readers that are each equivalent to the reader shown at 13 in Figure 1. Ten of these readers are shown in Figure 11 at 521-530, but this is merely a representative sample of the total number of readers provided throughout the entire installation 400. Six readers 521-526 of this group are each connected to the server 502 via cables of a network 536. In the disclosed embodiment, network 536 is of a type commonly known in the art as an Ethernet network. Two reader controllers 537-538 are also connected to the network, to facilitate communications between the server 502 and the readers. The structure and operation of the 537-538 reader controllers are known to those skilled in the art, and therefore are not described in detail in this document.

The remaining readers 527-530 in Figure 11 are not directly connected to the 536 network. Instead, each is connected to a respective wireless receiver / transmitter 541-544, each of which communicates via wireless signals with a respective one of two additional wireless receivers / transmitters 547-548, serving as access points to the network 536. These wireless links conform to a well-known standard that was propagated by the Institute of Electrical and Electronics Engineers (IEEE), and is commonly known as the IEEE 802.11 standard. As persons skilled in the art are already familiar with this standard, a detailed discussion is unnecessary in this document .

The 521-526 readers that are connected directly to the 536 network cables are likely to be readers provided within the physical building of the 401 centralized facility, while the 527-530 readers that are connected to the 536 network by 541 wireless links - 544 and 547-548 are more likely to be readers in arrival section 403 and exit section 404. This is because the additional expense of wireless equipment is more likely to be economical in outdoor locations, where some significant cost would be involved in running cables to isolated locations. However, the present invention does not preclude the use of wireless links within the centralized facility 401 building, or the use of direct network connections at locations outside of the centralized facility 401.

In Figure 11, a bottleneck reader system 549 is connected to the network 536. It can cooperate with at least some of the readers 521-530, to provide an immediate and accurate record of the specific time and location that a label of EPIRB passed through a certain point called "bottleneck". A bottleneck is a location that many or all of the beacon tags must pass through, an example being an entrance through which all ULDs must pass to enter the centralized facility 401. The reader system 549 ensures that they are immediately record an exact record of the time and location, because the 502 server will sometimes be too busy with other tasks to respond quickly enough to record exactly the

ES 2 344 589 T3 time and location. As the bottleneck reader system 549 collects information, it passes the information to the server 502 in due course.

Server 502 is also connected via a new network 561 and two network controllers 562-563 to various wireless base stations, four of which are shown at 566-569. Base stations of the type shown at 566-569 are provided throughout the facility 400, and allow the server 502 to communicate wirelessly with various wireless handheld devices 571-578. Each of the 571-578 handhelds includes a keyboard and display and are used for various purposes.

One such purpose is to allow people throughout the facility to obtain information about a ULD, a mobile device, or some other item associated with a given tag. The control system 14 maintains information in an electronic form about the items associated with each tag, and thus can easily provide pertinent portions of this information when requested from any of the 571578 handheld devices. Likewise, the control system could be configured to provide this information via the Internet to a standard web browser program.

Another purpose of handheld devices 571-578 is to allow server 502 to give instructions to people who are working within facility 400. For example, a person operating a mobile device such as a forklift carrying an ULD may be I have to give you instructions on what to do with the ULD. In this sense, if the ULD is to be taken to one of the unloading stations 421 (Figure 10), the operator has to know to which specific unloading station the ULD should be delivered. Similarly, if a ULD is waiting in a parking area, and the operator has to pick it up, the operator has to know which specific ULD to pick up. The server 502 can transmit this information to the operator through one of the handheld devices 571-578 carried by that operator.

The 571-578 handheld devices also have the ability to function as beacon tag readers. This allows an operator, with or without assistance from the server 502, to identify whether a particular ULD close to the operator is an ULD that the system wants the operator to do something with.

Manual units 571-578 can also be used by an operator to alert server 502 of the equipment the operator is currently using. For example, if the operator takes control of a yardbird to move the feeders around facility 400, the identification codes for the operator and yardbird can be entered manually at the keyboard, or they can be scanned in an appropriate manner such as scanning barcodes on the yardbird and on the operator identification card with a barcode scanner on the handheld device, so that the server 502 knows what equipment that particular operator is currently using. Server 502 can then use that handheld device to give the operator specific instructions as to what the operator should do with that equipment.

Figure 12 is a schematic view of a train 600, which is of a type that has been mentioned above, and which can be used to transport ULDs within the facility 400 of Figure 10. The train 600 of Figure 12 includes a tractor or tugboat 601 pulling the train, and three trailers or trolleys 602-604. Tractor 601 and trailers 602-604 are each one type of mobile device.

All 602-604 trailers are identical. Trailer 602 has at its front end a tab, which is removably connected to a hitch at the rear of tractor 601. Trailer 603 has at its front end a tab that is removably connected to a hitch at the rear. rear of trailer 602, and trailer 604 has at its forward end a tab that is removably connected to a hitch at the rear of trailer 603. Although the train 600 of Figure 12 has three trailers, it will be recognized that the number of trailers could be more or less. Each of the trailers 602-604 has a respective ULD 606608 removably supported thereon. Each of the ULDs 606-608 is identical to the ULD 381 discussed above in association with Figure 9.

Tractor 601 has thereon a beacon tag 611, which is provided on top of a post to raise the beacon tag 611 so that it is relatively close to the signposts provided on the roof, one of which is shown at 612 on a ceiling shown schematically as a dotted line 613. The dotted line circle around the signpost 612 represents the transmission range of the signpost 612. It should be noted that the transmission range of the signpost 612 is specifically configured such that trailers 602-604 will pass under the bottom of the transmission range of the signpost 612. Three 616-618 beacon labels are each provided on top of one. of the respective ULDs 606-608.

As Tractor 601 travels through Facility 400, the 611 Marker Tag on it will enter and exit the transmission ranges of various signposts throughout the facility, thus allowing the location of Tractor 601 be tracked exactly in the manner described above in association with Figure 7. The 616-618 beacon labels provided on top of the respective 606-608 ULDs will also pass through the transmission ranges of various signposts, thus facilitating direct and accurate tracking of the location of each of the 606-608 ULDs.

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The 601 tractor has a 623 signpost located near the hitch on its rear. Each of the trailers 602-603 has a respective signpost 626-628 in a right rear corner thereof. Each of the trailers 602-604 also has a respective beacon tag 631-633 held on the tongue of the trailers. As discussed above, each of the roof signposts, like the 612 signpost, has a transmission range that ends at a height vertically above the trailers. Therefore, the 631-633 beacon labels on the trailer tabs do not pass through the transmission ranges of the roof signposts.

The beacon label 631 on the tongue of the trailer 602 is within the transmission range of the signpost 623 on the rear of the tractor 601, but is outside the transmission range of the signpost 626 on the same trailer 602, because the label beacon 631 and signpost 626 are near opposite ends of trailer 602. Similarly, the beacon tag 632 from trailer 603 is within the transmission range of the signpost 626 at the rear of the trailer 602, but is outside the transmission range of the signpost 627 at the rear end of the trailer 603. Also, the 633 radio beacon tag from trailer 604 is within transmission range of signpost 627 at the rear of trailer 603, but is out of transmission range of signpost 628 which is at the rear of trailer 604.

With this in mind, it will be recognized that, while tractor 601 and trailer 602 are removably connected to each other, the trailer beacon tag 631 will periodically transmit a beacon signal that includes its own unique beacon code and also It includes the unique signaling code of the 623 signpost of the 601 tractor. In this way, based on the beacon signals from tag 631, server 502 (Figure 11) will know that trailer 602 is currently directly connected to tractor 601.

Similarly, beacon signals from tag 632 inform the system that trailer 603 is currently directly connected to trailer 602. Additionally, beacon signals from tag 633 inform the system that trailer 604 is currently directly connected to the trailer 603. With all this information, the control system knows not only that tractor 601 and trailers 602-604 are currently all connected together to form train 600, but it also knows the precise order in which they appear respectively in the train from ahead to behind. That is, the control system knows that tractor 601 precedes trailer 602, which in turn precedes trailer 603, which in turn precedes trailer 604. When the trains are assembled and disassembled, to meet the varying needs of the facility, the control system always has immediate direct knowledge of exactly which tractor and which trailers are combined to form any particular train.

As discussed above in association with the ULD 381 of Figure 9, each of the ULDs 606-608 has two additional beacon labels attached to a bottom of it, on opposite side walls near diagonally opposite corners of the bottom wall. . One such marker tag is visible in Figure 12 on each of the ULDs 606-608, and these tags are respectively identified by reference numerals 641-643.

The beacon tag 641 of the ULD 606 is within transmission range of the signpost 626 of the trailer 602 carrying that ULD. Tag 641 thus transmits a beacon signal that includes its own unique beacon code, and also the unique tagging code for signpost 626. In this way, the control system knows that the ULD 606 is currently supported on the trailer. 602. Similarly, beacon labels 642 and 643 transmit respective beacon signals including respective signaling codes from signposts 627 and 628, and informing the control system respectively that ULDs 607 and 608 are held respectively at trailers 603 and 604. The 641-643 beacon labels are low enough on 606-608 ULDs to pass under the transmitting ranges of rooftop signposts 613, such as signpost 612.

If the ULD 606 has been placed on the trailer 602 with an orientation rotated 180 ° about a vertical axis from the orientation shown in Figure 12, then the beacon label 641 would be near the front left corner of the trailer 602, and the ULD 606's third beacon tag (not visible in Figure 12) would be near signpost 626 in the rear right corner of trailer 602. That third beacon tag would thus perform the function of transmitting beacon signals containing the signaling code from the signpost 626 and informing the control system that the ULD 606 is currently supported on the trailer 602. With the ULD 606 in this alternate position, the beacon tag 641 would be out of the transmission ranges of the signposts 623 and 626, and thus would not include any signaling codes in its beacon signal. Therefore, by providing two beacon labels at diagonally opposite locations on the bottom of each ULD, each ULD can be placed on a trailer in either of two different orientations, and therefore no need for facility employees to worry. to ensure a particular orientation of each ULD when placed on a trailer.

The control system knows the location of the tractor 601 by virtue of the beacon signals emitted by the beacon tag 611 of the tractor 601, which typically include the signaling code of one of the roof signposts, such as the signpost 612. Additionally, since the control system also knows which trailers are currently connected to tractor 601, and in what order, the system also knows the location of each of the 602-604 trailers that are connected to tractor 601 as tractor 601 scrolls through the facility shown in Figure 10. In addition, the system knows the location of each of the 606-608 ULDs that are transported

ES 2 344 589 T3 by train 600, not only based on beacon signals transmitted by tags 616-618 on top of ULDs, but also based on beacon signals transmitted by beacon tags 641-643 in the lower parts of the ULDs, because these associate the ULDs with the train 600, and the control system knows the location of the train.

Figure 13 is a schematic side view showing a forklift 651 having a signpost 652 provided on its vertically movable forklift. A 6654 pallet is removably supported on the forklift, and has a 653 radio beacon tag provided on it. The transmission range of the signpost 652 is indicated by a dotted circle in Figure 13, and it will be seen that the label 653 of the pallet 654 is within this transmission range when the pallet is supported on the forklift. Accordingly, tag 653 will transmit beacon signals that include its own unique beacon code and also the signpost 652 signaling code. In this way, the control system will know from these radio beacon signals that pallet 654 is currently being transported by forklift 651. If the control system knows which items are currently supported on the pallet, the system will also know where those items are.

It would also be possible to provide beacon labels 656 and 657 on each of the items 658 and 659 on pallet 654. If the transmission range of the signpost 652 is configured so that the labels 656 and 657 are within transmission range, the Tags 656-657 will transmit respective beacon signals that directly inform the system that items 658-659 are being transported by forklift 651. Alternatively, the signpost 652 could be provided on the pallet 654, and the beacon tag 653 could be omitted from the pallet 654. In that case, the beacon signals from the tags 656-657 would inform the control system of the fact that items 658-659 are currently on a mobile device which is pallet 654.

Forklift 651 has a signpost 661 mounted on a pole that extends upward from the top of the cab. Signpost 661 transmits signaling signals that have a transmission range that does not reach items 658-659 supported on the forklift of forklift 651. However, beacon labels 662-664 are provided at separate locations on the roof, and each will be within transmission range of the signpost 661 when the forklift 651 is disposed approximately below it. Thus, based on beacon signals from tags 662-664, the control system can track the movement of forklift 651 through the facility using a technique of the type described above in association with Figure 8. Alternatively, it will be recognized that signpost 661 may be substituted for a beacon tag, and beacon tags 662-664 may be substituted for signposts, in which case the control system would track forklift 651 using a technique of the type described above in association with Figure 7.

Figure 14 is a schematic side view showing the tail section of an aircraft 671, and also a device 672 which is commonly known as a loader, and which can be used to load or unload an aircraft. The aircraft has a hatch or door 674 that has been pivoted downward to create an approximately horizontal platform. The loader has a horizontal platform 676, and has a motorized scissor support for the platform that is capable of vertically raising and lowering the platform, so that it can be vertically aligned with the hatch 674 of the aircraft.

The platform 676 of the loader 672 supports a pallet 677, and the pallet in turn supports several articles, one of which is designated by reference number 678. Each of the articles on the pallet has a radio beacon label on it, being one of the beacon labels indicated by reference numeral 679. The platform supports a signpost 682. In response to the signaling signals from the signpost 682, the tags 679 of the items 678 transmit respective beacon signals that inform the control system that all of these items are currently on the magazine 672 having the signpost 682. A Operator 683 carries a manual unit 684, which is equivalent to the manual units 571-574 discussed above in association with Figure 11. Additionally, the operator carries a portable signpost 686, which can be used to turn off all tags 679 as items 678 are loaded onto the aircraft. The control system can verify whether or not all tags have in fact been turned off by evaluating whether any of the tags are still transmitting beacon signals, and can provide feedback via the 684 handheld as to whether any tags that should still be turned off. are on. Conversely, of course, if the aircraft was being unloaded, the portable signpost could be used to turn on the 679 tags, and the 679 tags would then begin to transmit respective beacon signals containing the 682 signpost signaling code, to alert the control system that all associated items are on magazine 672.

Figure 15 is a schematic side view of an apparatus 700 that includes a conveyor 702 and a signpost 703 that is fixedly mounted above the conveyor 702 on some non-illustrated support, such as a ceiling. The signpost 703 is equivalent to the signpost shown at 11 in Figure 1. The effective transmission range of the signaling signals transmitted by the signpost 703 is indicated by a broken line in Figure 15.

A pallet 706 is supported on the conveyor 702, and is being moved in a direction 704 by the conveyor. Pallet 706 has multiple items on it, one of which is designated by reference number

ES 2 344 589 T3

707. Each of the items 707 is a container for packages that are subject to overnight delivery. Each of the items 707 has on it a respective beacon label, one of which is indicated by reference numeral 708. Each of the beacon labels is equivalent to the beacon label shown at 12 in Figure 1.

As pallet 706 is moved in direction 704 by conveyor 702, each of the items 707 on the pallet will pass through the transmission range of the signaling signals from the signpost 703. Thus, each of the beacon tags 708 will transmit to a non-illustrated reader a beacon signal that includes the unique beacon code for that particular beacon tag, and also the signpost signaling code 703. In this way, the control system connected to the reader will be able to determine, based on the reception of all these radio beacon signals within a certain time window, which articles 707 are currently arranged on the pallet 706. The control system also you will know that these 707 items and the pallet

706 They are currently at a location where they are passing the 703 fixed signpost.

It would also be possible to provide an additional marker tag 711 on the pallet 706 itself. As pallet 706 passes in front of signpost 703, tag 711 will transmit a beacon signal that includes its own unique beacon code, as well as the signaling code from signpost 703, so that the control system you know precisely which pallet is currently passing signpost 703 with items 707 supported on it.

In some circumstances, a problem may be encountered than the arrangement shown in Figure 15, where successive pallets are traveling along conveyor 702 with relatively little spacing between them. In this sense, after the beacon labels 708 of the items 707 leave the transmission range of the signpost 703, they will still continue to transmit beacon signals that include the signpost signaling code 703, for the period of time required to complete the beacon sequence that was previously discussed in association with Figures 4 and 5. If another pallet is moving along the conveyor

702 a short distance behind the illustrated pallet 706, the items on that next pallet can enter the transmission range of the signpost 703 and begin transmitting beacon signals with their signaling code while the beacon labels on the illustrated pallet 706 are still setting. end your beacon sequences. In that case, the control system would find it difficult to distinguish which items are on which of the two pallets. Figure 16 is a schematic sectional side view of an apparatus 730 that is intended to avoid this problem.

More specifically, apparatus 730 is an alternate embodiment of apparatus 700 shown in Figure 15. Apparatus 730 includes all of the elements discussed above in association with apparatus 700. In addition, it includes a sensor 732 that is fixedly mounted, for example, to the same ceiling or bracket as 703 signpost. Sensor 732 is positioned upstream of indicator post 703 with respect to the direction 704 in which materials travel along conveyor 702. In fact, sensor 732 is positioned so that it can detect a new pallet 706 and the Articles on it, just ready the moment they first begin to enter the transmission range of the 703 signpost. Sensor 732 can be any of several different types of known sensors, such as a sensor that detects the movement of the pallet 706, or a proximity sensor that detects the distance to the closest item below it.

Sensor 732 is wired to signpost 703. When sensor 732 detects that a new pallet 706 with items 707 on it is about to enter the transmission range of signpost 703, sensor 732 sends a signal to the signpost 703, and signpost 703 responds by altering its signpost code. Signpost 703 could, for example, increase your signaling code. Thus, to the signpost

703 It could be assigned several unique and successive signaling codes that the control system knew were all associated with a single signpost, and it could cycle through those codes in succession. Alternatively, it would be possible to simply toggle the most significant bit of the signaling code.

As the labels 708 on the new pallet come into the transmission range of the signpost 703, they will begin to receive signposts from the signpost 703 that contain the modified signpost code, and will begin to transmit beacon signals that include their own unique beacon codes, and also the modified signaling code from the 703 signpost. It will be recognized that if all the labels 708 on the preceding pallet have gone out of the transmission range of the signpost 703 before the signpost 703 modifies its flagging code, it will be very easy for the control system to distinguish the items.

707 of a pallet of items 707 from the next successive pallet. However, even though the pallets are closer than this, as illustrated in Figure 16, some of the labels 708 on each of the two adjacent pallets are all within transmission range of the signpost 703 at the time As signpost 703 changes its signaling code, the control system can still accurately distinguish items on one pallet from items on another pallet.

In more detail, and as noted above, the control system will be aware of all possible signaling codes associated with the signpost 703. In addition, each of the beacon labels on the first pallet will have transmitted beacon signals containing the old signaling code. If those beacon labels suddenly start transmitting beacon signals with the modified signaling code, the control system can detect this and ignore those beacon signals. Instead, the beacon labels on the next pallet will have been sending beacon signals that do not contain any signaling codes, and

ES 2 344 589 T3 will suddenly start transmitting beacon signals that include the modified signaling code. The control system can detect this and thus distinguish the beacon labels of articles arranged on one pallet from the beacon labels of articles arranged on the other pallet.

The present invention provides several technical advantages. One such technical advantage is that the location of an item being tracked can be determined with a significantly higher degree of accuracy than with pre-existing procedures. Furthermore, it is possible to accurately determine the location of an article based on information from a single reader, without any need to carry out a complicated triangulation calculation based on information from multiple readers.

Another advantage relates to the fact that the beacon labels embodying the invention receive and transmit signals at respective different frequencies. In this sense, there is an advantage when the tag receives signals at a lower frequency than at which it transmits signals. The received signals have a roll-off characteristic that is significantly greater than the roll-off characteristics of higher frequency signals transmitted by the tag. Yet another related advantage occurs when the low-frequency signals received by the tag are primarily magnetic in nature, making them less susceptible to interference than would be the case for radio-frequency signals. Yet another advantage occurs when the tag is battery powered, allowing it to have and use memory, exhibit higher sensitivity to incoming signals, provide better transmit power, and provide more control over transmitted signals.

Another technical advantage is the ability to more accurately determine the location and relationship of two or more items. For example, it is possible to determine exactly whether a particular mobile device, such as a container, is currently being carried by some other mobile device, such as a forklift or trailer. Furthermore, it is possible to determine whether two or more mobile devices, such as a tractor and one or more trailers, are currently connected to each other and in what order. On the other hand, when two mobile devices, such as containers, are supported on different mobile devices, such as trailers, that are in the same general vicinity, it is possible to determine exactly which mobile device is carrying which mobile device.

Another technical advantage results from the ability to dynamically vary the duration of the signals transmitted by the tag. For example, the amount of information transmitted, and therefore the duration, may be shorter when the tag is not currently receiving a signal from any signpost, while the duration may be longer when the tag is receiving a signal. signaling signal and has to include a signaling code in the transmitted signals. This helps reduce the cumulative amount of time the label is actively broadcasting, which in turn can facilitate compliance with government regulations.

Yet another advantage results from the ability for the tag to vary at least one of its transmission speed and its transmit power in a dynamic manner, based on operating conditions such as whether the tag is currently receiving signals from a signpost. This also helps facilitate compliance with government regulations. Furthermore, these types of variations can help reduce the probability of collisions with signals transmitted by other tags, while ensuring that the reader reliably receives at least one transmission from each tag within a reasonably short period of time.

Yet another technical advantage results from the ability to vary the transmission speed and / or the transmission power of the beacon tag by external control. Another advantage is the ability to vary an identification code that is included in the signals transmitted by the tag, where the change is made under external control. Yet another advantage involves the ability to vary a password and / or encryption code used by the tag, based on external control. Yet another benefit is the ability to switch the tag between normal and restricted modes of operation, where the tag transmitter is disabled in restricted mode. A related advantage occurs when the tag consumes less power in restricted mode.

Another advantage of the invention occurs when a signpost is provided and transmits signaling signals that are received by the tag, the signaling signals including information that effects external control of an operating characteristic of the tag. A related advantage is that it is possible to connect a reader receiving the radio beacon signals to a central control system which in turn is functionally connected to the signpost, so that the control system can exert control over the transmission of control commands. within the signaling signals sent from the signpost to the tag.

Although various selected embodiments have been illustrated and described in detail, it will be understood that various other substitutions and alterations are also possible without departing from the scope of the present invention, as defined by the following claims.