WO2017162810A1

WO2017162810A1 - In-floor distributed antenna and positioning system

Info

Publication number: WO2017162810A1
Application number: PCT/EP2017/056962
Authority: WO
Inventors: Christophe Reithler; Igor BRANKOV
Original assignee: Tarkett Gdl
Priority date: 2016-03-25
Filing date: 2017-03-23
Publication date: 2017-09-28

Abstract

A distributed antenna system comprises a plurality of directional wireless local area network (WLAN) antennas integrated in or arranged under a walk-on-able floor covering, wherein each WLAN antenna has a radiation pattern with a main lobe oriented upwardly so as to serve a cell associated with and located above the WLAN antenna. In addition, a positioning and/or navigation system comprising such a distributed antenna system is disclosed.

Description

IN-FLOOR DISTRIBUTED ANTENNA AND POSITIONING SYSTEM

Field of the Invention

[0001 ] The invention generally relates to a novel smart flooring technology incorporating wireless local area network (WLAN) antennas. Background of the Invention

[0002] "Flooring" or "floor covering" generally designates a substantially planar material applied over a floor structure (subfloor) to provide a decorative walk-on-able surface. Examples of flooring include fitted carpet, wood flooring, stone flooring, bamboo flooring, synthetic (e.g. vinyl) flooring, ceramic tiles, linoleum, laminate, etc. [0003] Relatively recently, so-called "smart" or "intelligent" floor coverings have emerged, which exhibit additional functionality in comparison to their traditional counterparts.

[0004] For instance, EP 2 263 217 discloses an object tracking system, comprising a dense sensor field in the floor. The object tracking system detects sensor activations and links an object to each activation. It further produces event information describing events for immediate or later use. The system detects events according the conditions defined for them, on the basis of sensor observations. The conditions can relate to the essence of the objects, e.g. to the strength of the observations linked to the object, to the size and/or shape of the object, to a temporal change of essence and to movement. The system can be used e.g. for detecting the falling, the getting out of bed, the arrival in a space or the exit from it of a person by tracking an object with the dense sensor field, and for producing event information about the treatment or safety of the person for delivering to the person providing care.

[0005] US 8 138 882 discloses an electronic multi-touch floor covering that has numerous sensors arranged in a dense two-dimensional array to identify shapes. The electronic multi-touch floor covering identifies the shape of an object that is in contact with the surface of the electronic multi-touch floor covering. An entity record is then retrieved from a data store, such as a database, with the retrieved entity record corresponding to the identified shape. Actions are then retrieved from a second data store with the actions corresponding to the retrieved entity record. The retrieved actions are then executed by the computer system. For instance, if the system detects that the family dog has entered an area that is "off-limits" for it, a notification to the owner can be dispatched in order to have the dog removed from the off-limits location.

[0006] US 6 515 586 relates to a floor covering integrated with a tactile sensory layer so as to form a tactile sensory surface. The tactile sensory layer has a plurality of sensors arranged in a dense two-dimensional array. A controller is connected to the tactile sensory surface to track a person or object. The tactile sensory surface may be flexible and manufactured in bulk on a roll, so that it is adjustable in both length and width.

[0007] WO 90/10920 A1 discloses an intelligent floor having a matrix of pressure sensitive sensors, means to detect changes in state of the sensors, means to determine the position of the sensors, clock means, and means to detect changes in sensor state within time periods determined by the clock means.

[0008] JP 2002-076740 relates to a wireless communication system and a communication range control method. JP 2002-076740 teaches a false floor which is composed of non-metallic floor panels, a metallic box which is attached at the bottom of the floor panels and has an opening at its top, and an access point antenna which is placed in the metallic box. The shape and the size of the opening controls the range of communication radio waves. An access point antenna provides wireless LAN for a surface of approximately 300 m². [0009] US 2009/0168733 teaches a floor chamber for use in building construction. The floor chamber includes a cavity and a movable lid supporting one or more electronic components and/or an aerial whereby to define at least part of an access point in or on the floor chamber. Furthermore, a floor construction including one or more floor members defining a floor and including therein a wireless access point and a floor-level wireless access point network is also described. The floor-level wireless access point network comprises two or more access points connected together by an under-carpet cable system.

[0010] JP 2005-027213 relates to a floor panel such as a floor panel, a floor board or the like used as a radio base station such as a private PHS (Personal Handyphone System) or a wireless LAN (Local Area Network) system.

[001 1 ] US 2007/0096984 relates to a network for locating a wireless tag comprises a plurality of wireless nodes. The nodes are not connected together by a wired network neither to a central node. Each node is included in a floor tile for installation inside a building and configured to be wirelessly connectable to at least one other node. When the floor tiles are installed, the plurality of nodes form a mesh or grid and provide overlapping wireless coverage for locating the tag by reference to mesh. [0012] US 2009/0195461 relates to antennas, including for example the combination of RF radiating elements with dielectric construction materials. In particular, document US 2009/0195461 teaches antenna radiating elements combined with dielectric construction materials, with the radiating elements designed to produce a certain radiation pattern taking into account the construction materials. [0013] US 2010/0052866 relates to a lighting device comprising a light emitting unit and an associated control unit that allows the detection of nearby objects. Moreover, it relates to a traffic control system comprising such a lighting device and to a method for controlling an object carrying a wireless communication device like an RFID-tag and/or an NFC-based device. [0014] The present invention generally aims at providing a smart floor covering with improvedfunctionality.

General Description

[0015] A first aspect of the invention relates to a distributed antenna system comprising a plurality of directional wireless local area network (WLAN) antennas integrated in or arranged under a walk-on-able floor covering, wherein each WLAN antenna has a radiation pattern with a main lobe oriented upwardly so as to serve a cell associated with and located above the WLAN antenna.

[0016] As used herein, the term "cell" designates a volume served by a particular WLAN antenna. The volume of each cell is typically relatively small compared to the entire volume covered by the WLAN (e.g. 1 -5% or even less.) Neighbouring cells may (and typically will) partially overlap each other in such a way that continuous coverage is achieved as from a height of about 80 cm above the floor. Conceptually, the system is similar to the cellular networks used in mobile telephony except that the scale of the system is much smaller. [0017] The WLAN antennas may e.g. be integrated in a building floor, in a decorative floor covering or between a decorative floor covering and a subfloor. The distributed antenna system may comprise or consist of an indoor antenna system, an outdoor antenna system and/or a combined indoor/outdoor antenna system.

[0018] The antennas used by the system are high directional gain antennas or antennas capable of being dynamically tuned or reconfigured to achieve high directional gain. High directional gain antennas show a pattern of radiation maxima, or lobes, pointing in different directions. The most important radiation maximum is called the "main lobe" and points into the desired direction of propagation of the radio waves. According to an embodiment of the invention, the antennas comprise plasma antennas, e.g. PSiAns (plasma silicon antennas), available e.g. from Plasma Antennas Ltd., Winchester, UK. A PSiAn may include one or more plasma silicon devices (PSiDs) to perform azimuth and elevation beam steering. The antennas may also be reconfigurable antennas (software-defined antennas) and/or smart antenna (arrays). It may be worthwhile noting that the distributed antenna system may be configured to dynamically tune or reconfigure the gain pattern (including the main lobe) of each antenna of the system if the antenna permits to do so.

[0019] It should be noted that the system may comprise other antennas than those mentioned beforehand. For instance, the system could include one or more so-called omnidirectional antennas and/or one or more antennas not integrated in or arranged under the walk-on-able floor covering. [0020] Preferably, the WLAN antennas form a regular grid, e.g. a rectangular or a hexagonal grid.

[0021 ] Measures are preferably taken in order to mitigate interference between the signals originating from different antennas of the system. Such measures may include the use of WLAN channels at different frequencies on neighbouring antennas, time- division multiplexing under the authority of a controller (whereby antennas serving overlapping volumes are prevented from emitting at the same time), etc.

[0022] According to an embodiment, the distance between neighbouring (nearest- neighbour) WLAN antennas is comprised in the range from 50 cm to 1 .5 m.

[0023] It will be appreciated that the distributed antenna system enables WLAN- based navigation systems with unpreceded positioning accuracy, in particular WiFi™- based (indoor) positioning systems. The high positioning accuracy is obtained thanks to the high density of WLAN antennas and to the correspondingly small size of the associated cells. For most applications, given that each cell has a "footprint" with a diameter (greatest extension) of about 1 .5 to about 6 m at most, preferably of about 1 .5 to about 3 m at most, the position of the cell currently serving a mobile device (also: mobile station) may be considered sufficiently accurate position information. If, however, more precise position information should be required, that could be derived from signal strength measurements (at the mobile device and/or at the antennas) and/or triangulation. As used herein, the term "footprint" designates the area on the floor corresponding to the orthogonal projection of the cell.

[0024] Preferably, the antennas are arranged in such a way that their main lobes are oriented substantially perpendicular to the walk-on-able floor covering. As used herein, substantially perpendicular means: forming an angle of 90°± 10° with respect to the reference surface.

[0025] Preferably, the antennas are configured to emit beams that are at least approximately rotationally symmetrical (in terms of radiated intensity) about the axis of the main lobe. According to an embodiment, the main lobe has a half-power beam width smaller than or equal to 90°, preferably smaller than or equal to 70°, more preferably smaller than or equal to 65°, and still more preferably smaller than or equal to 60°. The half-power beam width is preferably greater than or equal to 20°, preferably greater than or equal to 25°, more preferably greater than or equal to 30°, and still more preferably greater than or equal to 35°. As used herein, the "half power beam width" is the angle between the half-power (-3 dB) points of the main lobe, when referenced to the peak effective radiated power of the main lobe. In case of a main lobe without rotational symmetry, the above conditions on the half-power beam width are preferably valid for all azimuthal planes. [0026] According to an embodiment, each of the WLAN antennas is part of an access point compliant with IEEE Standard 802.1 1™ (the WiFi™ standard). The term "access point" is used herein with the meaning defined by that standard.

[0027] The walk-on-able floor covering may be arranged inside or outside a building. If arranged inside a building, it may cover one or plural rooms and it preferably comprises a plurality of WLAN antennas in at least one of the rooms. [0028] A second aspect of the invention relates to a communication system comprising a distributed antenna system as presented hereinabove and a controller configured to selectively control the transmission powers of the WLAN antennas.

[0029] The controller may control the transmission powers of the WLAN antennas e.g. by selectively switching the antennas on and off individually. Alternatively or additionally the controller may be configured to gradually and dynamically adjust the transmission powers of the different antennas and/or to steer the beams of the WLAN antennas (if these so permit). As indicated above, the antennas may be reconfigurable antennas (software-defined antennas) and/or smart antenna (arrays). [0030] According to an embodiment, the controller is configured to selectively and dynamically control the transmission power and/or the direction of the main lobe of each WLAN antenna depending on the presence of a WLAN client device (e.g. a mobile phone, a laptop computer, a tablet, etc.) within the cell associated with the WLAN antenna. In a practical implementation that may mean that the controller tracks the position of the client device (also: mobile device) and tries to predict a future position (by extrapolation or similar methods). When the controller determines that the client device will enter another cell of the system with a certain probability, it may activate the corresponding WLAN antenna. Similarly, when the controller determines that the client device has left a cell and will not return to it within a certain time and with a certain probability, it may deactivate the corresponding antenna.

[0031 ] The controller is preferably configured to dynamically adjust the transmission powers and/or the directions of the main lobes of the WLAN antennas in such a way as to achieve a predefined WLAN signal quality (e.g. signal strength) at the WLAN client device while otherwise minimising electromagnetic radiation caused by the WLAN antennas. Turning off antennas that are not currently serving a client device has the advantage that the risk of interference between different antenna signals is reduced.

[0032] The communication system may optionally comprise presence sensors, each presence sensor being associated with one or plural WLAN antennas and configured to detect the presence of a human and/or a mobile device within the cell or cells associated with the one or plural WLAN antennas. The controller may in this case be configured to dynamically control the transmission power and/or the direction of the main lobe of the one or plural WLAN antennas depending upon the presence of a human and/or a mobile device within the respective cell or cells as detected by the presence sensors.

[0033] According to an embodiment of the communication system, the presence sensors comprise at least one of the following: ferroelectret pressure sensors integrated in the floor, capacitive presence sensors integrated in the floor, thermographic sensors and video cameras. As used herein, the term "ferroelectret pressure sensor" designates a cellular polymer film structure that exhibits piezoelectric properties and, more specifically, that generates an electric potential difference and/or an electrical current between first and second electrode layers applied on its faces in response to pressure being applied on the polymer film structure.

[0034] The WLAN antennas may be controlled selectively by a WLAN node, e.g. a WLAN router or a repeater. The WLAN node may be a component of a wired or over- the-air distribution system, which is made accessible via the wireless medium and the WLAN antennas. [0035] The WLAN antennas are preferably low-power antennas. Preferably the low- power antennas have an output power in the range from 0 dBm (1 mW) to -70 dBm (100 pW). The output power of the antennas is preferably selected in such a way that the received WLAN signal strength in a height of between 0.5 m and 2.5 m above the floor is comprised in the range from -10 dBm (100 [Ml) to -100 dBm (0.1 pW). [0036] A third aspect of the invention relates to a positioning and/or navigation system based on a distributed antenna system and/or on a communication system according to the first and second aspects of the invention. The positioning and/or navigation system could be an indoor positioning system or an outdoor positioning system or a combined indoor-and-outdoor positioning system (e.g. for an industrial site). High positioning accuracy may be obtained by way of a high density of WLAN antennas and to the correspondingly small size of the associated cells. Preferably, each cell has a "footprint" with a diameter (greatest extension) of about 1 .5 to about 6 m at most, more preferably of about 1 .5 m to about 3 m at most. The position of a mobile device connected to one or more of the antennas may be derived from the cell currently serving the mobile device and/or from signal strength measurements (at the mobile device and/or at the antennas) and/or by triangulation and/or by trilateration. Brief Description of the Drawings

[0037] By way of example, preferred, non-limiting embodiments of the invention will now be described in detail with reference to the accompanying drawings, in which:

Fig. 1 is a schematic illustration of a communication system according to an aspect of the present invention;

Fig. 2 is a schematic illustration of a floor structure comprising WLAN antennas;

Figs. 3 to 9 illustrate the tracking of mobile devices using a distributed antenna system according to an aspect of the invention;

Fig. 10 is a flowchart of a preferred embodiment of the tracking process; Fig. 1 1 is a flowchart of a preferred embodiment of a process carried out by a mobile device when using a communication system according to an aspect of the invention;

Fig. 12 is a schematic illustration of a distributed antenna system integrated into (decorative) flooring also comprising pressure sensors. Detailed Description of Preferred Embodiments

[0038] Fig. 1 schematically illustrates an IEEE Standard 802.1 1™-compliant communication system 10 according to an embodiment of the invention. The communication system 10 comprises a distributed antenna system featuring a grid of directional WLAN antennas 12 arranged under a walk-on-able decorative floor 14 covering (not shown in Fig. 1 , cf. Fig. 2). The WLAN antennas 12 are wired group-wise to respective antenna controllers 16. The antenna controllers 16 are connected to a network switch and router 18, which creates a network (e.g. an Ethernet network) and connects to the Internet 20.

[0039] As shown in Fig. 2, the WLAN antennas 12 are arranged in the floor. The floor comprises a subfloor 22 (e.g. of screed concrete) that carries a decorative floor covering 24 (e.g. wood, bamboo, stone, ceramic, laminate, vinyl- or polymer-based flooring). In the illustrated example, the WLAN antennas 12 are located between the subfloor and the decorative floor covering 24. Additionally or alternatively, the WLAN antennas could be integrated into the decorative floor covering or be integrated into the subfloor. Each WLAN antenna 12 has a radiation pattern with an upwardly oriented main lobe and serves a small cell located above the antenna. Fig. 2 schematically illustrates the main lobes of the different antenna patterns at reference numerals 26.

[0040] A mobile device 1 1 (e.g. a portable phone, a tablet, a laptop, a smartwatch, etc.) is served by the antenna associated with the cell in which the mobile device 1 1 is currently located. The shortest distance between two WLAN antennas 12 of the grid is preferably comprised in the range from 50 cm to 1 .5 m. Consequently, a mobile device 1 1 that is carried over the antenna grid will sequentially be served by the different antennas 12 on its path. Assuming that each antenna 12 represents an access point of its own (access point hardware could be installed underfloor at the antenna or at the controller 16), given the density of the antenna grid, the frequency of the handoffs will be much more important than in a conventional wireless network. Accordingly, it is preferred that the wireless network supports fast handoff, e.g. by using opportunistic key caching (OKC) and/or fast transition roaming in accordance with IEEE standard 802.1 1 r. While the mobile device 1 1 roams between antennas connected to the same controller, handoffs could be carried out as over-the-air or over-the-DS (distribution system) intra-controller roams. When the mobile device roams between antennas connected to different controllers, handoffs could be carried out as over-the-air or over- the-DS inter-controller roams. More details on these roaming techniques can be found e.g. in "802.1 1 r, 802.1 1 k, and 802.1 1w Deployment Guide", Cisco IOS-XE Release 3.3, chapter "802.1 1 r Fast Transition Roaming", which is hereby incorporated by reference in its entirety.

[0041 ] According to one embodiment, the antennas 12 are active (ready to transmit and receive frames over the wireless medium) all the time. In this embodiment, the entire grid of antennas is available at any time, allowing a mobile device to connect to any antenna within its reach. Due to the high density of antennas, there is an increased risk of interference associated with such a mode of operation.

[0042] According to a more preferred embodiment, the controllers 16 dynamically control the antennas in such a way as to deactivate antennas that are not serving any client device and/or to adjust the transmission power of each antenna. By deactivating antennas that are not currently in use, controllers considerably reduce the risk of interference compared to the previously discussed mode of operation. Dynamically controlling the states of the antennas requires knowledge at the controller of the current user needs in the covered area. The controllers thus keep track of the WLAN client devices present in their service area and ascertains that the WLAN is available at the current locations of the client devices.

[0043] An illustration of the tracking of WLAN client devices is illustrated in Figs. 3-9. In the illustrated example, the area covered by the distributed antenna system is represented by a quadratic area which comprises 100 antennas arranged to form a 10x10 quadratic grid. For ease of identification of the antennas or cells, the columns and rows of the grid are numbered A to J and 1 to 10, respectively. Each antenna/cell is thus identified by an identifier composed of the letter corresponding to the column and a number corresponding to the row. It will be assumed that the area is a room having a unique entry/exit on the left of cell A8. For the following discussion, it is not important whether the entire area is under the control of a single controller or whether there are plural controllers in charge of subsets of the antennas. However, if there are plural controllers, it is supposed that information on client devices is shared among all controllers (e.g. in a central database 28 as illustrated in Fig. 1 ). [0044] In Fig. 3, the room is empty in the sense that it contains no WLAN client device. All antennas in the room are switched off, except antennas A7, A8, A9, B7, B8, B9 that are located in an entry zone close to the entry/exit. The entry zone is defined in such a way that any mobile device will have to transit through that zone in order to reach any point within the covered area. When a mobile device enters the room, as shown in Fig. 4, it detects the network and collects the SSID (service set identifier). It is now assumed that the WLAN uses MAC-based authentication to grant or deny access to the network. If the mobile device has previously been connected to the network, the network recognises the MAC (media access control) address of the mobile device and proceeds with association. If the mobile device has not previously been connected to the network, the mobile device is requested to register. In case of successful registration access to the network is granted. The controller in charge of the entry access point registers the mobile device with a central tracking server and stores the current position (A8) thereof. The controller also estimates a future position of the mobile device. In Fig. 5, the mobile device has moved from cell A8 to cell B8 (which is already active at that time). The controller now records the new position (B8) of the mobile device and activates the neighbouring antennas that have been inactive thus far (antennas C7, C8, C9). The future position of the mobile device is expected to be cell C8. In Fig. 6, the mobile device has just moved to cell D8 (coming from cell C8). The active antennas are C7, C8, C9, D7, D8, D9 and the controller now switches antennas E7, E8 and E9 active, too. The expected next position of the mobile device is E8. In Fig. 7, the mobile device has just moved to cell E8. As antennas C7, C8 and C9 are no longer in the direct neighbourhood of an antenna currently serving a WLAN client, the controller deactivates them. As antennas F7, F8 and F9 are now in the direct neighbourhood of an antenna currently serving a WLAN client, the controller activates them. The expected next position of the mobile device is F8. It can further be seen in Fig. 7 that another user with a mobile device is about to enter the covered area. The mobile device already present in the room will now be referred to as the first mobile device whereas the newly arrived mobile device will be referred to as the second mobile device. In Fig. 8, the first mobile device has moved to cell F7 (rather than to cell F8 as was expected). The controller has switched antennas D7, D8, D9, E9 and F9 inactive, since they are no longer in the direct neighbourhood of an antenna serving a WLAN client. On the other hand, the controller has switched antennas E6, F6, G6, G7, G8 active, since these are now in the direct neighbourhood of the antenna serving the first mobile device. The expected next position of the first mobile device is G6. The second mobile device has meanwhile entered the room at cell A8, where it connects to the network as described previously with respect to the first mobile device. The expected next position of the second mobile device is B8. In Fig. 9, the first mobile device has moved to cell G6 and antennas E6, E7, E8, F8, and G8 have been deactivated. Newly active antennas are antennas F5, G5, H5, H6, H7. The expected next position of the first mobile device is H5. The second mobile device has moved to cell B7 (rather than to cell B8 as was expected) and the controller has consequently switched antennas A6, B6, C6, C7 and C8 active. As the antennas A9 and B9 belong to the entry zone, the controller keeps them in the active state although they are not directly adjacent an antenna currently serving a WLAN client. The expected next position of the second mobile device is C6.

[0045] In the scenario described with respect to Figs. 3-9, the controller estimates the future path of the mobile devices using a heading vector or a velocity vector with is added to the current position vector. The heading vector may be computed by subtracting the previous position vector from the current position vector. The velocity vector may be obtained by dividing the above heading vector by the time between the instants of position fixing. The above extrapolation approach is a very simple one to guess the future position of a mobile device. A more elaborate approach could e.g. be based upon statistics of past recorded paths of the mobile device of concern. If there is no (or no recent) history for the specific mobile device, the controller could estimate the future position depending on the most frequently used paths of all mobile devices. Another approach could additionally use navigation data from the mobile device (e.g. a current destination set by the user.)

[0046] Fig. 10 is a flowchart illustrating an embodiment of a method of tracking a mobile device (MD) in the coverage area. The process starts either with a mobile device entering the covered area (step S10). The mobile device then tries (automatically or upon user action on the mobile device) to associate with an access point (step S12). The network then determines whether the mobile device is known (step S14) by looking up the mobile device's MAC address in its database. If the mobile device has never registered to the network before, the mobile device is required to register (step S16) If the registration does not succeed (step S20), the mobile device cannot connect to the network and is not tracked (step S21 ). If the registration is successful the mobile device connects to the network by association with the access point (step S22). After the mobile device has successfully connected to the network, the controller records the position (the current cell) of the mobile device in the central database (step S24). When the controller detects a change relating to a mobile device (an arrival, a leave or a change of position), it determines whether any access points have to be activated or deactivated as a consequence of the detected change (step S28). The network then remains in the new state until a new event (arrival or leave of a mobile device, or a handoff) is detected (step S30). If a mobile device roams from one to another access point, association with the new access point (step S12) is preferably done by fast transition roaming in accordance with IEEE standard 802.1 1 r as described hereinabove. If a mobile device leaves the covered area (step S32), the controller records the leave in the central database.

[0047] IEEE standard 802.1 1™ requires that handoffs are initiated by the mobile devices rather than by the access point or the distribution system. Fig. 1 1 is a flowchart illustrating a possible process carried out on a mobile device. It is assumed that the mobile device is already connected to the network. The mobile device periodically scans for available access points (step S36). If no access point is detected (step S38), the mobile device checks whether there is an error (step S40) and then either retries a scan (step S36) or issues an error message (step S42). If available access points are detected, the mobile devices measures their signal strengths (step S44) and populates or updates a corresponding table (step S46). The mobile device then determines which one of the available access points is optimal in terms of signal strength (step S48) and checks whether it should roam to that access point (step S50). That decision is not necessarily taken using the signal strength as the sole criterion (but it could be). Other criteria could be whether the candidate access point lies on the expected path of the mobile device (if that is known), whether the current AP provides satisfactory service (in terms of signal strength or data throughput or the like). If no handoff is required (that is in particular the case if the current access point is the optimal one) the mobile device remains connected to the current access point. If a handoff is deemed necessary, the mobile device roams to the new access point (step 52).

[0048] The process carried out on the mobile device may comprise an aspect of position-fixing and navigation. The signal strengths of the different access points within range allow the mobile device to fix its position (step S54). Position fixing may be carried out on the mobile phone itself if it has a local copy of a map of the covered area containing the positions of the different antennas. If a destination has been entered by the user (check at step S56), the mobile device issues navigation instructions that guide the user to destination. The current position is made available to applications ("apps") installed on the mobile device that have been granted access to that kind of information (step S58). If a destination has been specified, the mobile device checks whether it has been reached (step S60). If yes, arrival at destination is announced to the user and the specified destination is removed (step S62). If the destination has not been reached, the mobile device updates the path from the current position to the specified destination (step S64) and issues the corresponding navigation instructions to the user and/or to any app having been granted access to that type of information.

[0049] As an alternative to standalone position-fixing, position-fixing may be provided as a network service. In this case, the mobile device communicates the received signal strengths and the identifiers of the available access points to a positioning server, which responds by providing the current position. As an additional service, the positioning server may provide a map of the surroundings of the mobile device. If the mobile device includes into its request for position-fixing any specified destination, the positioning server may take over all or part of the navigation tasks. For instance, the positioning server could provide a map showing the path from the current position to the destination.

[0050] The current position and/or any specified destination could be used by the mobile device and/or the network to offer location-based services to the user, including but not limited to: location-aware browsing, location-aware advertising, finding acquaintances in the neighbourhood, etc.

[0051 ] One may object that the above-described modes of operation of the communication system does not allow reliably detecting mobile devices that are switched on or woken up from flight mode in an arbitrary cell of the covered area. Indeed, unless further measures are taken, the user might be forced to take his mobile device to the entry zone or hold it close to a colleague's mobile device in order to connect to the network. In order to address that issue, the controller could be configured to periodically switch on the inactive antennas, thereby "scanning" the covered area for potential WLAN client devices. [0052] Fig. 12 illustrates an embodiment of a distributed antenna system 10 that does not suffer from the above-mentioned drawback because it comprises presence sensors 30 that are also integrated into the floor covering. Each presence sensor 30 is associated with one cell/antenna 12 and detects variations in pressure exerted on the floor. If pressure variations satisfying predefined conditions are detected, the presence sensor 30 (or a pressure sensor controller connected to it) concludes that there is activity in the associated cell. The list of cells in which there currently is activity is communicated to the antenna controllers 16 and/or written into the central database (cf. Fig. 1 ), whereupon the antenna controllers activate the corresponding antennas (in case they are not active already). [0053] The pressure sensors 30 are preferably of the ferroelectret type but other sheet-type pressure sensors, e.g. capacitive or resistive pressure transducers, may be suitable as well. In addition or as an alternative to pressure sensors in the floor, the covered area could be monitored using one or more video cameras, thermographic cameras, 3D-cameras (e.g. 3D time-of-flight cameras), stereoscopic cameras, laser scanners, etc.

[0054] While specific embodiments have been described herein in detail, those skilled in the art will appreciate that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof.

Claims

[WO 2017/1628102/pC 16 PCT/EP2017/056962 Claims

1 . A distributed antenna system comprising a plurality of directional wireless local area network (WLAN) antennas integrated in or arranged under a walk-on-able floor covering, wherein each WLAN antenna has a radiation pattern with a main lobe oriented upwardly so as to serve a cell associated with and located above the WLAN antenna.

2. The distributed antenna system as claimed in claim 1 , wherein the WLAN antennas form a regular grid, e.g. a rectangular or a hexagonal grid.

3. The distributed antenna system as claimed in claim 1 or 2, wherein each cell associated with and located above a WLAN antenna has a diameter less than or equal to 6 m, preferably less than or equal to 4.5 m and even more preferably less than or equal to 3 m.

4. The distributed antenna system as claimed in any one of claims 1 to 3, wherein the distance between neighbouring WLAN antennas is comprised in the range from 50 cm to 1 .5 m.

5. The distributed antenna system as claimed in any one of claims 1 to 4, wherein the main lobe is oriented substantially perpendicular to the walk-on-able floor covering.

6. The distributed antenna system as claimed in any one of claims 1 to 5, wherein the main lobe has a half-power beam width smaller than or equal to 90°, preferably smaller than or equal to 70°, more preferably smaller than or equal to 65°, and still more preferably smaller than or equal to 60°.

7. The distributed antenna system as claimed in any one of claims 1 to 6, wherein the main lobe has a half-power beam width greater than or equal to 20°, preferably greater than or equal to 25°, more preferably greater than or equal to

30°, and still more preferably greater than or equal to 35°.

8. The distributed antenna system as claimed in any one of claims 1 to 7, wherein each of said WLAN antennas is part of an access point compliant with IEEE Standard 802.1 1™. [WO 2017/1628102/pC 17 PCT/EP2017/056962

9. The distributed antenna system as claimed in claim 2, wherein the walk-on-able floor covering covers plural rooms and comprises a plurality of WLAN antennas in at least one of the rooms.

10. A communication system comprising a distributed antenna system as claimed in any one of claims 1 to 9 and a controller configured to selectively control the transmission powers of said WLAN antennas and/or to steer the beams of the WLAN antennas.

1 1 . The communication system as claimed in claim 10, wherein the controller is configured to selectively switch said WLAN antennas on and off.

12. The communication system as claimed in claim 10 or 1 1 , wherein the controller is configured to selectively and dynamically control the transmission power and/or the direction of the main lobe of each WLAN antenna depending on the presence of a WLAN client device within the cell associated with the WLAN antenna.

13. The communication system as claimed in claim 12, wherein the controller is configured to selectively and dynamically control the transmission power and/or the direction of the main lobe of each WLAN antenna depending additionally on a prediction of the presence of a WLAN client device within the cell associated with the WLAN antenna.

14. The communication system as claimed in claims 12 or 13, wherein the controller is configured to dynamically adjust the transmission powers and/or the directions of the main lobes of the WLAN antennas in such a way as to achieve a predefined WLAN signal quality at the WLAN client device while otherwise minimising electromagnetic radiation caused by the WLAN antennas.

15. The communication system as claimed any one of claims 10 to 14, comprising presence sensors, each presence sensor being associated with one or plural WLAN antennas and configured to detect the presence of a human and/or a mobile device within the cell or cells associated with said one or plural WLAN antennas, and wherein the controller is configured to dynamically control the transmission power and/or the direction of the main lobe of the one or plural WLAN antennas depending upon the presence of a human and/or a mobile device within the respective cell or cells.

16. The communication system as claimed in claim 15, wherein the presence sensors comprise at least one of the following: ferroelectret pressure sensors integrated in the floor, capacitive presence sensors integrated in the floor, thermographic sensors and video cameras.

17. An positioning and/or navigation system comprising a distributed antenna system as claimed in any one of claims 1 to 9 and/or a communication system as claimed in any one of claims 10 to 16.

18. The positioning and/or navigation system as claimed in claim 17, wherein the position of a mobile device is determined as the position of the antenna to which the mobile device is connected or derived by triangulation or trilateration from the positions of plural antennas within the reach of which the mobile device is located.

19. The positioning and/or navigation system as claimed in claim 17 or 18, wherein the position of a mobile device is determined from signal strength measurements.

20. The positioning and/or navigation system as claimed in any one of claims 17 to 19, wherein the positioning and/or navigation system is an indoor positioning and/or navigation system and/or a combined indoor and outdoor positioning and/or navigation system.

21 . The positioning and/or navigation system as claimed in any one of claims 17 to 19, wherein the positioning and/or navigation system is an outdoor positioning and/or navigation system.