WO2017068230A1

WO2017068230A1 - Positioning method

Info

Publication number: WO2017068230A1
Application number: PCT/FI2015/050717
Authority: WO
Inventors: Olli KOSKIMIES; Ilari Teikari
Original assignee: Nokia Technologies Oy
Priority date: 2015-10-21
Filing date: 2015-10-21
Publication date: 2017-04-27

Abstract

A method and apparatus are disclosed for: a) storing a first signal strength indicator threshold value and a second signal strength indicator threshold value (7.2), wherein the second signal strength indicator threshold value is less than the first signal strength indicator threshold value; b) storing first geofence information and second geofence information (7.3), wherein the second geofence is nested within the first geofence; c) detecting a velocity value of a mobile tag (7.4); and d) varying the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value, and/or varying the distance between the first geofence and the second geofence based on the velocity of the mobile tag (7.5).

Description

Positioning method Field

Embodiments of the invention relate to positioning methods.

Background

High accuracy indoor positioning requires novel systems and solutions that are specifically developed for indoor positioning. The "traditional" positioning technologies used mainly outdoors, such as GPS, WiFi- and cellular-positioning technologies, generally cannot deliver a satisfactory performance indoors that would enable seamless navigation experience in both environments. Typically, there are issues with accuracy, coverage and floor detection (3D) that are difficult to achieve with systems and signals that were not originally designed for the indoor use cases. Bluetooth Low Energy (BTLE) technology has been proposed to be used in indoor positioning systems for tracking devices. Such systems involve the use of High Accuracy Indoor Positioning (HAIP) which places requirements on hardware infrastructure such as the need for multiple array antennas. Therefore this makes for a simpler and more efficient system that is easier to implement using BTLE hardware technology that is already available in the market. The principles of BTLE are described in the art.

High-Accuracy Indoor Positioning (HAIP) tracks the position of Bluetooth LE tags using ceiling- installed locators which perform Angle-of- Arrival measurement on the signal emitted by the tags. However, the effective tracking area under a locator is a focused conical area), so multiple locators are needed. HAIP also requires relatively intensive computational operations.

Summary

In a first aspect, this specification describes a method comprising: a) storing a first signal strength indicator threshold value and a second signal strength indicator threshold value, wherein the second signal strength indicator threshold value is less than the first signal strength indicator threshold value; b) storing first geofence information and second geofence information, wherein the second geofence is nested within the first geofence; c) detecting a velocity value of a mobile tag; and d) varying the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value, and/or varying the distance between the first geofence and the second geofence based on the velocity of the mobile tag. d) may comprise: if the velocity value is determined to have increased, increasing the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value, and/or increasing the distance between the first geofence and the second geofence; and if the velocity value is determined to have decreased, decreasing the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value, and/or decreasing the distance between the first geofence and the second geofence. Increasing the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value may comprise increasing the first signal strength indicator threshold value.

Increasing the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value may comprise reducing the second signal strength indicator threshold value.

Increasing the distance between the first geofence and the second geofence may comprise shrinking the second geofence.

Increasing the distance between the first geofence and the second geofence may comprise expanding the first geofence.

Decreasing the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value may comprise increasing the second signal strength indicator threshold value.

Decreasing the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value may comprise reducing the first signal strength indicator threshold value.

Decreasing the distance between the first geofence and the second geofence may comprise shrinking the first geofence. Decreasing the distance between the first geofence and the second geofence may comprise expanding the second geofence. Detecting a velocity value for a mobile tag may comprise receiving a velocity value from the mobile tag.

The velocity value from the mobile tag may be obtained from an accelerometer reading.

Detecting a velocity value for a mobile tag may comprise determining a velocity value by analysing a series of wireless messages received from the mobile tag.

Detecting a velocity value for a mobile tag may comprise determining a velocity value by analysing signal strength information from a series of packets received from the mobile tag.

Detecting a velocity value for a mobile tag may comprise determining positioning information of the mobile tag over a period of time using angle-of-arrival calculations based on wireless messages received from the mobile tag and using the positioning information to determine the velocity value. d) may comprise varying the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value, and/or varying the distance between the first geofence and the second geofence, continuously as a function of the mobile tag velocity. d) may comprise: if the velocity value is above a first velocity threshold value, increasing the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value and/or increasing the distance between the first geofence and the second geofence; and if the velocity value is below a second velocity threshold value, decreasing the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value, and decreasing the distance between the first geofence and the second geofence.

In a second aspect, this specification describes an apparatus comprising: at least one processor; at least one memory having computer-readable instructions stored thereon, the computer-readable instructions when executed by the at least one processor causing the apparatus at least to: a) store a first signal strength indicator threshold value and a second signal strength indicator threshold value, wherein the second signal strength indicator threshold value is less than the first signal strength indicator threshold value; b) store first geofence information and second geofence information, wherein the second geofence is nested within the first geofence; c) detect a velocity value of a mobile tag; and d) vary the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value, and/or varying the distance between the first geofence and the second geofence based on the velocity of the mobile tag.

In a third aspect, this specification describes a computer-readable medium having computer-readable code stored thereon, the computer-readable code, when executed by at least one processor, causing performance of: a) storing a first signal strength indicator threshold value and a second signal strength indicator threshold value, wherein the second signal strength indicator threshold value is less than the first signal strength indicator threshold value; b) storing first geofence information and second geofence information, wherein the second geofence is nested within the first geofence; c) detecting a velocity value of a mobile tag; and d) varying the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value, and/ or varying the distance between the first geofence and the second geofence based on the velocity of the mobile tag.

In a fourth aspect, this specification describes an apparatus comprising: a) means for storing a first signal strength indicator threshold value and a second signal strength indicator threshold value, wherein the second signal strength indicator threshold value is less than the first signal strength indicator threshold value; b) means for storing first geofence information and second geofence information, wherein the second geofence is nested within the first geofence; c) means for detecting a velocity value of a mobile tag; a d) means for varying the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value, and/ or varying the distance between the first geofence and the second geofence based on the velocity of the mobile tag.

In a fifth aspect, this specification describes a computer program comprising instructions that, when executed by a computing apparatus, cause the computing apparatus to perform the method of the first aspect.

Brief Description of the Drawings

For a more complete understanding of the methods, apparatuses and computer-readable instructions described herein, reference is now made to the following descriptions taken in connection with the accompanying drawings in which: Figure l is a schematic diagram illustrating an indoor environment; Figure 2A is a schematic plane view of the indoor environment; Figure 2B is a state diagram illustrating movement of a mobile tag;

Figure 3 is a flow chart illustrating steps taken when a mobile tag enters a HAIP area; Figure 4 is a flow chart illustrating steps taken when a mobile tag leaves a HAIP area;

Figure 5 is a state diagram illustrating an embodiment of the invention when a high-speed mobile tag enters a HAIP area;

Figure 6 is a state diagram illustrating an embodiment of the invention when a low-speed mobile tag enters a HAIP area;

Figure 7 is a flow chart illustrating embodiments of the invention;

Figure 8 is a schematic block diagram of an HAIP locator;

Figure 9 is a schematic block diagram of a COIP locator; Figure 10 is a schematic block diagram of a mobile tag; and Figure 11 shows a storage means. Detailed description

Embodiments of the invention provide for effective handover between two positioning modes. The first positioning mode may be a low intensity indoor positioning mode which uses received RSSI values to determine the position of a mobile tag. The first positioning mode may also make use of Time of Flight (ToF) calculations. The second, more power- intensive positioning mode, may use angle-of-arrival calculations. The handover between the two modes is managed efficiently so that power consumption can be optimised.

Furthermore, the handovers are arranged so that they minimise disruption to a user interface (UI), for example a map shown on a display device. The first positioning mode may be termed a cost-optimised indoor positioning (COIP) mode. The second positioning mode may be termed a high accuracy indoor positioning (HAIP) mode. COIP locators and HAIP locators are positioning devices that operate in COIP mode and HAIP mode respectively and may be provided in an indoor environment.

Since the inside of buildings is not free space, the accuracy of indoor positioning systems may be significantly impacted by reflection and absorption from walls and obstacles. Non- stationary objects such as doors, furniture, and people can pose an even greater problem, as they can affect the signal strength in dynamic, unpredictable ways. Therefore, while the COIP mode is useful in situations where a medium level of accuracy is satisfactory, a high accuracy positioning mode may be required in other situations.

The processing steps required to determine whether the HAIP mode should be used consume a similar level of computing resources compared to the resources required to perform the HAIP positioning itself. From the HAIP calculation, tag coordinates are obtained (the accuracy of which depends on how close the mobile tag is to the HAIP area) which can be used to evaluate whether the tag is within the HAIP area. However, it is desirable not to perform these calculations unnecessarily as they are computationally intensive.

When displaying a position on a map using COIP mode, the tag location is displayed as a logical location (e.g. "room 123"). When displaying a position on a map using HAIP mode, the tag location is displayed as coordinates (e.g. x:i23, y:456). It is therefore desirable to prevent situations where a mobile tag's location calculation constantly switches between HAIP and COIP modes. The representation of the location can look very different on a map for COIP and for HAIP, so constantly switching between the two modes would cause the user interface to stutter.

Furthermore, it is also desirable not to frequently switch HAIP calculation on and off for a mobile tag, since that requires reconfiguration of the positioning system which is not instantaneous. Embodiments of the invention address the problem of frequent switching between positioning modes. The velocity of the mobile tag can be taken into account when determining whether to perform HAIP calculation and whether to switch between a first positioning mode and a positioning second mode.

As stated above, COIP locators measure signal strength and deliver only approximate location information (for example, at room-level) rather than using the angle of arrival methods used in HAIP locators. COIP methods can be combined with HAIP methods so that areas where high accuracy positioning is needed are equipped with HAIP locators and other areas are equipped with COIP locators. Embodiments use first and second signal strength thresholds to determine whether HAIP calculation is performed or not. The determination of whether to use HAIP calculation is dependent on whether a mobile tag is approaching an HAIP area or moving away from an HAIP area. Embodiments additionally have two nested geofences which determine whether the tag location is determined and provided to a user using HAIP mode or COIP mode. The determination of whether to use HAIP or COIP is also dependent on whether a mobile tag is approaching an HAIP area or moving away from an HAIP area. In embodiments of the invention, the threshold values and geofence coordinates are variable and are dependent on the velocity of the mobile tag. As such, embodiments of the invention make use of variable hysteresis. The handover from the COIP mode to the HAIP mode is performed using a distinct signal strength (RSSI) threshold value and a distinct geofence from the RSSI threshold value and geofence that are used when handing over from HAIP mode to COIP mode. The values of the threshold values and geofence coordinates depend on the velocity of the mobile tags.

Figure 1 shows a system 100 used to determine the location of a mobile tag in accordance with embodiments of the invention. The system 100 comprises positioning devices in fixed positions. These positioning devices include HAIP locators 3O1, 3Ο2, 30₃, 3Ο4 and COIP locators 4O1, 4Ο2. The HAIP locators 30 and COIP locators 40 are controlled by a controller 50 comprising processor circuitry 51 and non-volatile memory 52. The controller 50 may be a server. The non-volatile memory 52 has code 52a stored therein to allow the controller 50 to perform its functionality. The controller 50 also comprises volatile memory 53. Together, the non-volatile memory 52 and volatile memory 53 form a storage device 54. Whilst in Figure 1, the controller is shown proximate the HAIP locators 30 and COIP locators 40, it should be borne in mind that the controller 50 may be located remotely.

A user 1 may carry a BTLE mobile tag 10 into an indoor environment 20 in which the HAIP locators 30 and COIP locators 40 are located. The BTLE mobile tag 10 may be part of a smartphone, a key fob, a PDA and so forth. Example indoor environments include warehouses, hospitals, shopping malls and so forth. Some of the BTLE fixed locators are HAIP locators 30 located in an HAIP area 200 shown in Figure 2A. The HAIP area 200 is the area in which HAIP positioning is used. The area in the indoor environment 20 outside the HAIP area 200 may be termed the COIP area. The remaining BTLE fixed locators are COIP locators 40 that are located in the COIP area. Each of the HAIP locators 30 and the COIP locators 40 comprises processor circuitry, a storage medium and computer code stored therein that allows the functionality of the HAIP locators and COIP locators to be carried out.

In embodiments of the invention, when a mobile tag approaches a HAIP positioning area 200, both HAIP locators 30 and COIP locators 40 receive the radio signal transmitted by the mobile tag 10. The controller 50 of the positioning system 100 is configured to select when to switch from COIP positioning to HAIP positioning and vice versa.

Figure 3 is a flow chart showing the various steps performed by the controller 50 of a positioning system 100 in order to determine the position of a mobile tag as the mobile tag approaches an HAIP positioning area 200 when the mobile tag is moving at an

intermediate velocity. The controller 50 stores upper and lower velocity threshold values. In this, case the mobile tag 10 is determined to have a velocity between the two velocity threshold values. During the following description reference is also made to Figure 2 to illustrate the operation of the various steps.

The process begins at step 3.1.

Step 3.2 is an ongoing step. The positioning system is operating in COIP mode. COIP mode may be thought of as the default mode for the positioning system. In other words, the system operates in COIP mode unless HAIP is activated. This corresponds to the position I shown in Figures 2A and 2B.

At position I, no HAIP calculations are performed. The position of the mobile tag 10 may be displayed on a user interface (such as a map application) as a logical position, for example the room in which the mobile tag 10 is located may be highlighted on the map.

The mobile tag 10 is in an area that is monitored by the system using the COIP mode. Each of the COIP locators is provided with an antenna, a processor and memory. Each COIP locator is configured to measure the RSSI of the packet and relay this information to the controller 50. The controller 50 can collate RSSI information relating to each packet from each COIP locator having a known position. From this information, the controller is able to determine the position of the mobile tag 10 in accordance with the COIP mode.

The mobile tag 10 transmits packets which are detected by COIP locators and HAIP locators that are within range of the mobile tag 10, at step 3.3. The transmission of the packets by the mobile tag 10 is performed periodically. Each of the packets contains a tag identifier, and a transmit timestamp.

As shown in Figures 2A and 2B, the user carrying the mobile tag 10 approaches an area 200 having HAIP locators 30, each of which uses angle of arrival measurements to determine mobile tag positions. As the mobile tag approaches the HAIP positioning area, packets transmitted by the mobile tag 10 are detected but the signal strength of these packets, as detected by the HAIP locators is very weak at first. This may correspond to the position II shown in Figure 2. At position II, no HAIP calculations are performed. Again, the position of the mobile tag 10 may be displayed on a user interface (such as a map application) as a logical position, for example the room in which the mobile tag 10 is located may be highlighted on the map.

At this stage, the packets received from the mobile tag 10 are used to perform positioning according to the COIP mode. That is, the RSSI data that are measured at various COIP locators are used to determine the position of the mobile tag 10 as shown on a user interface (UI) of a user's mobile device such as a smartphone.

As the mobile tag 10 approaches the HAIP positioning area 200, the RSSI values from the periodically transmitted packets detected at the HAIP locators 30 increase in strength. The controller 50 determines that the RSSI value at one or more of the HAIP locators 30 increases above a first threshold SSi at step 3.3.

In response, HAIP calculation is switched on for the mobile tag 10 and the controller 50 activates nested outer and inner geofences GFi, GF2 around the HAIP positioning area 200, at step 3.4.

This may correspond to a mobile tag 10 being located at the position III as shown in Figures 2A and 2B. At this stage, COIP is still performed and the position of the mobile tag that may be displayed to a user on a user interface is still the position determined using COIP. The HAIP calculation is configured by the controller 50 to operate as a background operation. As the mobile tag 10 approaches the HAIP positioning area, it first enters the outer geofence GFi, as shown in position IV in Figures 2A and 2B. At this point, the positioning is carried out in COIP mode. The determination that the mobile tag 10 has entered the outer geofence GFi is performed using the HAIP calculation.

The controller 50 detects that the mobile tag 10 has entered the inner geofence GF2 at step 3.5. This corresponds to the position V shown in Figures 2A and 2B. In response to the mobile tag 10 entering the inner geofence GF2, the controller 50 switches the mobile tag 10 to HAIP positioning at step 3.6. At this stage, the position shown on a user interface is displayed in accordance with HAIP mode. The determination that the mobile tag 10 has entered the inner geofence GF2 is also performed using the HAIP calculation.

Figure 4 is a flow chart showing the various steps performed by the controller 50 of the positioning system in order to determine the position of a mobile tag 10 as the mobile tag 10 moves away from the HAIP positioning area 200. As before, the controller 50 determines that the mobile tag 10 is moving at an intermediate velocity, i.e. having a velocity between the upper and lower velocity threshold values stored at the controller 50. During the following description reference is also made to Figures 2A and 2B to illustrate the operation of the various steps. In general, once the mobile tag 10 moves away from the HAIP positioning area 200, HAIP positioning and HAIP calculation are deactivated. The process starts at step 4.1. The mobile tag 10 may be located at the position V shown in Figures 2A and 2B. At step 4.2, packets received at the HAIP locators 30 are processed by the controller 50 using HAIP mode. The periodic packets are processed in the HAIP positioning mode as the mobile tag 10 moves inside the inner geofenced area. The periodic packets are also processed in the HAIP positioning mode as the mobile tag 10 if the mobile tag 10 moves outside the inner geofenced area but remains inside the outer geofenced area, as represented by position VI in Figures 2A and 2B. Thus, the position of the mobile tag 10 may be displayed on a map user interface as a coordinate position.

At step 4.3, the positioning system 50 detects that the mobile tag 10 has left the outer geofence GFi. This is represented by position VII in Figures 2A and 2B which is equivalent to position III. In response, at step 4.4, the positioning system switches the positioning mode for the mobile tag 10 to COIP positioning mode. The position displayed on a UI is shown using the COIP positioning mode instead of the HAIP mode. However, HAIP calculations continue to be performed by the positioning system for the mobile tag 10 as a background operation.

As the mobile tag 10 moves further away from the HAIP positioning area 200, the RSSI values of the periodically transmitted packets, as measured by the HAIP locators 30, decrease. Firstly, the received RSSI values drop below the first threshold SSi. At this point, HAIP calculations for the mobile tag 10 are continued. This is represented by position VIII in Figures 2A and 2B.

At step 4.5, the received RSSI values drop below a second threshold SS2 which is less than the first threshold SSi. Once the signal strength drops below the second threshold SS2, HAIP calculation is switched off for the tag, at step 4.6. This may correspond to the position IX shown in Figures 2A and 2B which is equivalent to position I. The process ends at step 4.7.

Therefore, it is apparent from the discussion above that the hysteresis arises from using a first threshold SSi for enabling HAIP calculations and a second, distinct, threshold SS2 for disabling HAIP calculations. Furthermore, an inner geofence GF2 is used to switch from COIP positioning mode to HAIP positioning mode, whilst a distinct outer geofence GFi is used to switch from HAIP positioning mode to COIP positioning mode. Once the controller 50 has determined the location of the mobile tag 10 in either COIP or HAIP mode, the location information may be transmitted as a packet to a user device. The user device may be a mobile device in which the mobile tag 10 is itself contained.

Alternatively, the user device may be a desktop computer, laptop or any other device so that a user can track the position of the mobile tag.

The provision of a variable hysteresis in a positioning system will now be explained. The controller 50 increases or decreases handover hysteresis according to the estimated velocity of mobile tag 10 to avoid thrashing between the HAIP and COIP systems, thereby improving user experience. Each mobile tag may have separate hysteresis values. The term hysteresis value refers to the difference between the two thresholds SSi and SS2 and the distance between the inner and outer geofences.The difference between the first and second thresholds for enabling and disabling HAIP calculation and the gap between inner and outer geofences can be set individually for each respective tag. Alternatively, the hysteresis can also be defined globally according to the speed of the fastest tag. The hysteresis values may be stored by the controller and may be defined beforehand to define the minimum hysteresis at a certain speed that ensures that the minimum time for switching between HAIP to COIP and back to HAIP is long enough. The hysteresis values may be stored at the controller 50, for example in a lookup table.

The hysteresis values may be determined according to the speed of the fastest tag or for each tag separately. In both cases, the speed of the tag is used to look up the correct hysteresis value. In the fastest tag case, the hysteresis value for the fastest tag is applied to all tags detected by the system.

The lookup table may be stored for example in a configuration file or in a database.

Alternatively, instead of a lookup table, a function may be designed based on the measurements, such that the function takes a tag velocity as a parameter and returns hysteresis values as a return value.

The velocity of each tag 10 may be estimated using one or more ways. Firstly, the velocity may be determined from positioning results from the HAIP system. As a series of the BLTE messages are received at the controller 50 from a tag 10 over a given time period, the velocity may be determined.

Another way of determining mobile tag velocity is to use an accelerometer. The mobile tag 10 may comprise an accelerometer 18. Accelerometer results may be delivered to the controller 50 inside positioning packets transmitted by the tag 10 or through other means. For example, standard Bluetooth communication could be used instead of positioning packets, or the tag could have, for example a WLAN or IR transceiver that could be used.

Accelerometer based velocity measurements may be calibrated when the mobile tag 10 is in a HAIP area where the mobile tag 10 can be positioned accurately. The accelerometer based velocity results may be recorded at the same time as the HAIP locators 30 measure the mobile tag position. The HAIP position and the accelerometer results may then be correlated. It is then possible to calculate speed according to the positioning results and then estimate the approximate accelerometer reading that corresponds to a certain speed. Another way of determining mobile tag velocity is to monitor a change in the signal power or received signal strength (RSSI). Whilst the signal strength based results may be less accurate than results derived from HAIP packets, they may be used to distinguish between slow and fast moving tags, especially when fingerprinting data is available, which makes RSSI-based positioning more accurate. Using RSSI data may be useful to improve results acquired from the accelerometer 18 . The change in RSSI during a given time period may be recorded and compared to the change in HAIP position over the same time period. A speed estimate may be calculated from both the accelerometer and from RSSI values. These estimates may be compared to determine if a speed result is reliable. Over time, these reliability estimates can be collected and the least reliable results can be removed by comparing with average speed values.

Figure 5 is a schematic diagram showing the approach of a fast moving tag 10 towards a HAIP area. It is assumed in this example that a mobile tag 10 is outside the HAIP area and is moving fast towards the HAIP area. If it is detected that the mobile tag 10 is moving rapidly, as determined by one or more of the velocity determining methods described above, the upper RSSI threshold SSi used for switching on HAIP calculation on is increased and the lower RSSI threshold SS2 used for switching HAIP calculation off is decreased. Furthermore, the inner geofence GF2 (used to switch to HAIP positioning) is reduced in size and the outer geofence GFi (used to switch to COIP positioning) is increased in size. It should be noted that when increasing the hysteresis it is the differences between threshold values and geofence coordinates that are increased. One or other of the threshold values may be kept constant whilst the other threshold value is varied. Likewise one or other of the geofence coordinates may be kept constant whilst the other set of coordinates is varied.

When the mobile tag 10 is sufficiently close to the HAIP locators 30 that HAIP calculation can deliver high accuracy positioning, the results of the HAIP calculation may be used to determine tag speed. At this point, the mobile tag 10 is likely to be very close to the outer geofence GFi. Therefore, for a mobile tag 10 travelling towards the HAIP area the predominant effect is that the inner geofence GF2 becomes smaller. However, the outer geofence GFi being larger will affect the mobile tag 10 once the mobile tag 10 travels away from the HAIP area. This configuration is particularly useful to handle mobile tags 10 which are quickly crossing a HAIP area (i.e. the mobile tags 10 quickly enter the area, move across it, and exit it again). Figure 6 is a schematic diagram showing the approach of a slow moving tag 10 towards a HAIP area. In this case, the upper RSSI threshold SSi (used for switching HAIP calculation on) is decreased and the lower RSSI threshold SS2 (used for switching HAIP calculation off) is increased. The inner geofence GF2 (used to switch to HAIP positioning) is increased in size and the outer geofence GFi (used to switch to COIP positioning) is reduced in size. Again, one or other of the threshold values may be kept constant whilst the other threshold value is varied. Likewise one or other of the geofence coordinates may be kept constant whilst the other set of coordinates is varied. The velocity of a mobile tag 10 may change between it entering and leaving the geofence. For example, a mobile tag 10 may enter a HAIP area quickly but leave it slowly. Therefore the signal strength thresholds and geofences for a particular tag may be continuously adjusted based on the velocity of the mobile tag 10. It may be particularly important to vary the hysteresis for a mobile tag 10 when it is detected that the mobile tag 10 is near to a HAIP area.

In embodiments of the invention, the effects of crossing an RSSI threshold or crossing a geofence are not cancelled due to the result of a hysteresis adjustment. In other words, if an RSSI value from a mobile tag 10 has crossed a threshold before an adjustment to that threshold, the threshold is considered crossed after the adjustment, even if the RSSI value from the mobile tag 10 has not yet reached the adjusted threshold.

A hysteresis adjustment may affect an immediate crossing of an RSSI threshold or crossing of a geofence. In other words, if a mobile tag 10 did not yet cross an original threshold or geofence and, after hysteresis adjustment, the mobile tag 10 is deemed to have crossed the threshold or geofence, then HAIP calculations may be enabled or disabled and HAIP positioning mode enabled or disabled, as appropriate.

Figure 7 is a flowchart illustrating the operations carried out in various embodiments The process starts at step 7.1. At step 7.2, first and second signal strength indicator threshold values are stored. The second signal strength indicator threshold value is less than the first signal strength indicator threshold value. At step 7.3, information relating to first and second geofences are stored. The second geofence is nested within the first geofence.

At step 7.4, a velocity value of the mobile tag 10 is detected. At step 7.5, the difference between the first and second signal strength indicator threshold values, and/ or the distance between the first geofence and the second geofence is varied, based on the velocity of the mobile tag. The process ends at step 7.6. It should be noted that in some embodiments, the hysteresis values may be varied continuously as a function of the velocity of the mobile tag 10. In other words, the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value, and/or the distance between the first geofence and the second geofence, are varied continuously as a function of the mobile tag velocity. As the velocity is determined to increase, the hysteresis values are increased continuously.

Similarly, as the velocity is determined to decrease, the hysteresis values are decreased continuously. That is, the difference between the two thresholds SSi and SS2 and the distance between the inner and outer geofences can be increased if the velocity is determined to increase and can be decreased if the velocity is determined to decrease.

Example 1

A fast moving mobile tag 10 is moving towards a HAIP area and has just crossed the inner geofence GF2. In response, the controller 50 switches to HAIP positioning. Hysteresis adjustment results in the inner geofence GF2 being made smaller, and the mobile tag 10 is now located between the adjusted inner geofence GF2 and the outer geofence GFi. The controller 50 will continue to use HAIP positioning to determine the position of the mobile tag 10. The situation is considered by the controller 50 to be the same as if the mobile tag 10 had entered the unadjusted inner geofence GF2 and then exited it again but without exiting the outer geofence GFi.

Example 2

A slow moving mobile tag 10 is moving towards a HAIP area and has crossed the outer geofence GFi but not the inner geofence GF2, i.e. it is located between the two geofences. Therefore, the controller 50 continues to use COIP positioning to determine the position of the mobile tag 10. Hysteresis adjustment results in the inner geofence GF2 being made larger, and the mobile tag 10 is now inside the adjusted inner geofence GF2. The controller 50 will immediately switch to HAIP positioning to determine the position of the mobile tag 10.

In embodiments of the invention, threshold adjustments are managed so that a lower threshold is not adjusted to be higher than the former value of the higher threshold.

Similarly, a threshold adjustment does not cause a higher threshold to be lower than the former value of the lower threshold. As such, thrashing may be avoided between the two positioning systems. When a mobile tag 10 is inside a HAIP area, its velocity may be continuously measured using HAIP positioning and compared to RSSI and accelerometer measurements for the purpose of calibrating the RSSI and accelerometer measurements for determining the velocity of the mobile tag 10. However, optimising mobile tag energy consumption may limit this. In some embodiments, the controller 50 may enable continuous accelerometer- based velocity measurement in the mobile tag 10 when the HAIP positioning data indicates that the tag is moving at an abnormal velocity compared to normal velocities for that tag. A velocity may be considered to be abnormal if it deviates significantly from an average velocity for that tag.

Figure 8 is a simplified schematic of an example of the HAIP locator 30 of Figures 1 and 2. The HAIP locator 30 comprises a controller 31, a transceiver 32 and an array of antennas 33. The array 33 of antennas comprises a plurality of antenna elements 33A, 33B, 33C which receive the packets and allow for angle-of-arrival information to be determined. The controller 31 may be of any suitable construction but, in this example, the controller 31 comprises processing circuitry 34 and a storage device 35. The processing circuitry 34 is configured, under the control of computer-readable code 36A stored on the storage device 35, to control the operation of the HAIP locator 30. The storage device 35 comprises a non-volatile memory 36 on which is stored the computer-readable code 36A. The storage device 35 also comprises a volatile memory 37.

Each of the plurality of antenna elements 33A, 33B, 33C connected to a switch (not shown), which is controllable by the processing circuitry 34 operating under the control of computer readable code stored in the storage device 35. The switch is controlled so that only one of the antenna elements 33A, 33B, 33C is connected to the transceiver 32 at any one time.

Figure 9 is a simplified schematic of an example of the COIP locator 40 of Figures 1 and 2. The COIP locator 40 comprises a controller 41, a transceiver 42 and an antenna 43. The controller 41 may be of any suitable construction but, in this example, the controller 41 comprises processing circuitry 44 and a storage device 45. The processing circuitry 44 is configured, under the control of computer-readable code 46A stored on the storage device 45, to control the operation of the COIP locator 40. The storage device 45 comprises a non-volatile memory 46 on which is stored the computer-readable code 46A. The storage device 45 also comprises a volatile memory 47. Figure 10 is a simplified schematic of an example of the mobile tag 10 of Figure 1. The mobile tag 10 comprises a controller 11, a transceiver 12 and an antenna 13. The controller 11 is configured to control the transceiver 12 to transmit via the antenna 13 positioning packets periodically. In some examples in which the mobile tag 10 is in its most simple form, the transceiver 12 may be replaced by a transmitter such that the mobile tag 10 does not have receiving capabilities. The mobile tag 10 may comprise an accelerometer 18.

The controller 11 may be of any suitable construction but, in this example, the controller 11 comprises processing circuitry 14 and a storage device 15. The processing circuitry 14 is configured, under the control of computer-readable code 16A stored on the storage device 15, to control the operation of the mobile tag 10. The storage device 15 comprises a nonvolatile memory 16 on which is stored the computer-readable code 16A. The storage device 15 also comprises a volatile memory 17. The mobile tag 10 additionally comprises a power source (not shown) such as a battery. In other examples, the mobile tag 10 receives power from an external source.

The mobile tag 10 is in some specific examples configured to transmit signals via the Bluetooth Low Energy protocol. That is to say the mobile tag 10 is able to operate in accordance with the BLE standard, currently at version 4.0. Put another way, the mobile tag 10 is "BLE-capable".

The computer readable instructions 52A, 36A, 46A, 16A may be pre-programmed into the apparatuses 50, 30, 40, 10. Alternatively, the computer readable instructions 52A, 36A, 46A, 16A may arrive at the apparatus 50, 30, 40, 10 via an electromagnetic carrier signal or may be copied from a physical entity 1000 (see Figure 11) such as a computer program product, a memory device or a record medium such as a CD-ROM or DVD. The computer readable instructions 52A, 36A, 46A, 16A may provide the logic and routines that enables the devices/apparatuses 50, 30, 40, 10 to perform the functionality described above.

Various terms used above will now be described in more detail. HAIP calculation

Performing an HAIP calculation refers to performing the calculations needed to obtain the coordinates of the tag. However, the result of the calculation may be that the tag is too far away from the HAIP locators for accurate positioning (i.e. the result returns coordinates that may be inaccurate and so positioning may still be performed using COIP). The HAIP calculations are based on angle of arrival (AoA) data obtained from the packets. The HAIP locators 30 each comprise an array of antennas to obtain the AoA data. The format of the positioning packets and determination of the directional information by the HAIP locators 30 may be in accordance with the High Accuracy Indoor Positioning solution for example as provided by the InLocation Alliance of which Nokia is a member. HAIP as developed by Nokia is known in the art. Indeed, it is mentioned, and is described in various levels of detail, in (among other publications) the following published PCT patent applications: WO 2014087196A, WO2013179195A, WO2014087198A, WO

2015013904A, WO 2014107869A, WO2014108753A, WO2014087199A and WO

2014087197A. In view of these and other disclosures, the fundamental principles utilised by the mobile tags 10, HAIP locators 30 to determine the directional information of incoming packets are not described in a great deal of detail in this specification. HAIP positioning

HAIP positioning means that the system delivers the location of a tag using coordinates (as opposed to the logical locations, such as room names, that COIP delivers). The position determined by the HAIP calculations is used as the mobile tag position.

However, the UI may still display the position to the user as a logical position (such as a room number) in accordance with a COIP mode.

HAIP user interface

Using HAIP positioning in the UI means that the UI displays the location of a tag using coordinates rather than a logical location such as a room number. For example, when COIP positioning is used to locate a tag, the entire room might be highlighted on the map, whereas when HAIP positioning is used, a small blinking dot might be shown at the coordinates of the tag.

Hence, a situation may arise whereby an HAIP calculation is performed, but because the tag is not yet close enough to provide an accurate position, COIP positioning is still used, i.e. the tag location is delivered as a logical location (e.g. a room).

The COIP position may, in this case, be calculated based on either the inaccurate coordinates that are used to determine a logical location or based on RSSI measurements as determined by the HAIP locators 30.

COIP mode COIP mode provides lower accuracy positioning than HAIP mode. However, the infrastructure is less expensive and can involve less complex computational operations to determine a tag location. COIP is therefore convenient for locations and situations where lower accuracy is acceptable to a user.

COIP can rely on RSSI values from packets transmitted by the mobile tags 10. As packets are received at the various COIP locators 40, positioning approaches may be used to determine the tag location such as multilateration or fingerprinting using the RSSI data received at each of the COIP locators 40.

Alternatively, COIP mode may use Time of Flight calculations. Alternatively, COIP mode may make use of coordinates calculated using HAIP mode where it is known that the coordinates are likely to below an accuracy threshold, for example if the calculated coordinates are beyond a distance threshold from the fixed locators.

Whilst embodiments have been described using BTLE messages and HAIP systems, alterative low-power radio technologies may be used such as ZigBee.

The term 'memory' when used in this specification is intended to relate primarily to memory comprising both non-volatile memory and volatile memory unless the context implies otherwise, although the term may also cover one or more volatile memories only, one or more non-volatile memories only, or one or more volatile memories and one or more non-volatile memories. Examples of volatile memory include RAM, DRAM, SDRAM etc. Examples of non-volatile memory include ROM, PROM, EEPROM, flash memory, optical storage, magnetic storage, etc.

Embodiments of the present disclosure may be implemented in software, hardware, application logic or a combination of software, hardware and application logic. The software, application logic and/or hardware may reside on memory, or any computer media. In an example embodiment, the application logic, software or an instruction set is maintained on any one of various conventional computer-readable media. In the context of this document, a "computer-readable medium" may be any media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer. A computer-readable medium may comprise a computer-readable storage medium that may be any tangible media or means that can contain or store the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer as defined previously.

According to various embodiments of the previous aspect of the present disclosure, the computer program according to any of the above aspects, may be implemented in a computer program product comprising a tangible computer-readable medium bearing computer program code embodied therein which can be used with the processor for the implementation of the functions described above.

Reference to "computer-readable storage medium", "computer program product", "tangibly embodied computer program" etc, or a "processor" or "processing circuit" etc. should be understood to encompass not only computers having differing architectures such as single/multi processor architectures and sequencers/parallel architectures, but also specialised circuits such as field programmable gate arrays FPGA, application specify circuits ASIC, signal processing devices and other devices. References to computer program, instructions, code etc. should be understood to express software for a programmable processor firmware such as the programmable content of a hardware device as instructions for a processor or configured or configuration settings for a fixed function device, gate array, programmable logic device, etc.

By way of example, and not limitation, such "computer-readable storage medium" may mean a non-transitory computer-readable storage medium which may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage, or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. It should be understood, however, that "computer-readable storage medium" and data storage media do not include connections, carrier waves, signals, or other transient media, but are instead directed to non-transient, tangible storage media. Disk and disc, as used herein, include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc, where disks usually reproduce data magnetically, while discs reproduce data optically with lasers.

Combinations of the above should also be included within the scope of "computer- readable medium". Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term "processor," as used herein may refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein. In addition, in some aspects, the functionality described herein may be provided within dedicated hardware and/or software modules. Also, the techniques could be fully implemented in one or more circuits or logic elements. If desired, the different steps discussed herein may be performed in a different order and/or concurrently with each other. Furthermore, if desired, one or more of the above- described steps may be optional or may be combined.

Although various aspects of the present disclosure are set out in the independent claims, other aspects of the present disclosure comprise other combinations of features from the described embodiments and/or the dependent claims with the features of the independent claims, and not solely the combinations explicitly set out in the claims.

Claims

1. A method comprising:

a) storing a first signal strength indicator threshold value and a second signal strength indicator threshold value, wherein the second signal strength indicator threshold value is less than the first signal strength indicator threshold value;

b) storing first geofence information and second geofence information, wherein the second geofence is nested within the first geofence;

c) detecting a velocity value of a mobile tag; and

d) varying the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value, and/or varying the distance between the first geofence and the second geofence based on the velocity of the mobile tag.

2. The method of claim l, wherein d) comprises: if the velocity value is determined to have increased, increasing the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value, and/or increasing the distance between the first geofence and the second geofence; and

if the velocity value is determined to have decreased, decreasing the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value, and/ or decreasing the distance between the first geofence and the second geofence.

3. The method of claim 2, wherein increasing the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value comprises increasing the first signal strength indicator threshold value.

4. The method of claim 2 or 3, wherein increasing the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value comprises reducing the second signal strength indicator threshold value.

5. The method of any of claims 2-4, wherein increasing the distance between the first geofence and the second geofence comprises shrinking the second geofence.

6. The method of any of claims 2-5, wherein increasing the distance between the first geofence and the second geofence comprises expanding the first geofence.

7. The method of any of claims 2-6, wherein decreasing the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value comprises increasing the second signal strength indicator threshold value.

8. The method of any of claims 2-7, wherein decreasing the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value comprises reducing the first signal strength indicator threshold value.

9. The method of any of claims 2-8, wherein decreasing the distance between the first geofence and the second geofence comprises shrinking the first geofence.

10. The method of any of claims 2-9, wherein decreasing the distance between the first geofence and the second geofence comprises expanding the second geofence.

11. The method of any preceding claim, wherein detecting a velocity value for a mobile tag comprises receiving a velocity value from the mobile tag.

12. The method of claim 11, wherein the velocity value from the mobile tag is obtained from an accelerometer reading.

13. The method of any preceding claim, wherein detecting a velocity value for a mobile tag comprises determining a velocity value by analysing a series of wireless messages received from the mobile tag.

14. The method of claim 13, wherein detecting a velocity value for a mobile tag comprises determining a velocity value by analysing signal strength information from a series of packets received from the mobile tag.

15. The method of claim 13 or 14, wherein detecting a velocity value for a mobile tag comprises determining positioning information of the mobile tag over a period of time using angle-of-arrival calculations based on wireless messages received from the mobile tag and using the positioning information to determine the velocity value.

16. The method of any preceding claim, wherein d) comprises varying the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value, and/or varying the distance between the first geofence and the second geofence, continuously as a function of the mobile tag velocity.

17. The method of any of claims 1-15, wherein d) comprises:

if the velocity value is above a first velocity threshold value, increasing the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value and/or increasing the distance between the first geofence and the second geofence; and

if the velocity value is below a second velocity threshold value, decreasing the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value, and decreasing the distance between the first geofence and the second geofence.

18. Apparatus comprising:

at least one processor;

at least one memory having computer-readable instructions stored thereon, the computer-readable instructions when executed by the at least one processor causing the apparatus at least to:

a) store a first signal strength indicator threshold value and a second signal strength indicator threshold value, wherein the second signal strength indicator threshold value is less than the first signal strength indicator threshold value;

b) store first geofence information and second geofence information, wherein the second geofence is nested within the first geofence;

c) detect a velocity value of a mobile tag; and

d) vary the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value, and/or varying the distance between the first geofence and the second geofence based on the velocity of the mobile tag.

19. The apparatus of claim 18, wherein d) comprises: if the velocity value is

determined to have increased, increasing the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value, and/or increasing the distance between the first geofence and the second geofence; and

if the velocity value is determined to have decreased, decreasing the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value, and/or decreasing the distance between the first geofence and the second geofence.

20. The apparatus of claim 19, wherein increasing the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value comprises increasing the first signal strength indicator threshold value.

21. The apparatus of claim 19 or 20, wherein increasing the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value comprises reducing the second signal strength indicator threshold value.

22. The apparatus of any of claims 19-21, wherein increasing the distance between the first geofence and the second geofence comprises shrinking the second geofence.

23. The apparatus of any of claims 19-22, wherein increasing the distance between the first geofence and the second geofence comprises expanding the first geofence.

24. The apparatus of any of claims 19-23, wherein decreasing the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value comprises increasing the second signal strength indicator threshold value.

25. The apparatus of any of claims 19-24, wherein decreasing the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value comprises reducing the first signal strength indicator threshold value.

26. The apparatus of any of claims 19-25, wherein decreasing the distance between the first geofence and the second geofence comprises shrinking the first geofence.

27. The apparatus of any of claims 19-26, wherein decreasing the distance between the first geofence and the second geofence comprises expanding the second geofence.

28. The apparatus of any of claims 18-27, wherein detecting a velocity value for a mobile tag comprises receiving a velocity value from the mobile tag.

29. The apparatus of claim 28, wherein the velocity value from the mobile tag is obtained from an accelerometer reading.

30. The apparatus of any of claims 18-29, wherein detecting a velocity value for a mobile tag comprises determining a velocity value by analysing a series of wireless messages received from the mobile tag.

31. The apparatus of claim 30, wherein detecting a velocity value for a mobile tag comprises determining a velocity value by analysing signal strength information from a series of packets received from the mobile tag.

32. The apparatus of claim 30 or 31, wherein detecting a velocity value for a mobile tag comprises determining positioning information of the mobile tag over a period of time using angle-of-arrival calculations based on wireless messages received from the mobile tag and using the positioning information to determine the velocity value.

33. The apparatus of any of claims 18-32, wherein d) comprises varying the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value, and/or varying the distance between the first geofence and the second geofence, continuously as a function of the mobile tag velocity.

34. The apparatus of any of claims 18-32, wherein d) comprises:

35. A computer-readable medium having computer-readable code stored thereon, the computer-readable code, when executed by at least one processor, causing performance of:

c) detecting a velocity value of a mobile tag; and

36. Apparatus comprising:

a) means for storing a first signal strength indicator threshold value and a second signal strength indicator threshold value, wherein the second signal strength indicator threshold value is less than the first signal strength indicator threshold value;

b) means for storing first geofence information and second geofence information, wherein the second geofence is nested within the first geofence;

c) means for detecting a velocity value of a mobile tag; and

d) means for varying the difference between the first signal strength indicator threshold value and the second signal strength indicator threshold value, and/or varying the distance between the first geofence and the second geofence based on the velocity of the mobile tag.

37. A computer program comprising instructions that, when executed by a computing apparatus, cause the computing apparatus to perform the method of any preceding claim.