DETERMINING ONE OR MORE ROUND-TRIP-TIME POSITIONING SECTIONS

Abstract

A method, apparatus and computer readable storage medium are provided that are configured to obtain or hold available radio map information representing a radio map representing a plurality of radio models for a plurality of radio devices. Each radio model is indicative of an expected radio-signal-strength field of a radio signal transmitted by a respective radio device of the plurality of radio devices. The method, apparatus and computer readable storage medium are also configured to determine, at least partially based on the radio map information, one or more round-trip-time positioning sections of an environment covered by the radio map and to provide round-trip-time positioning information causing estimating a position of a mobile device at least partially based on round-trip-times associated with radio signals observed by the mobile device within one of the one or more round-trip-time positioning sections of the environment covered by the radio map.

Claims

1. A method, comprising: obtaining or holding available radio map information representing a radio map representing a plurality of radio models for a plurality of radio devices, wherein each of said plurality of radio models is indicative of an expected radio-signal-strength field of a radio signal transmitted by a respective radio device of said plurality of radio devices; determining, at least partially based on said radio map information, one or more round-trip-time positioning sections of an environment covered by said radio map; and providing round-trip-time positioning information causing estimating a position of a mobile device at least partially based on round-trip-times associated with radio signals observed by said mobile device within one of said one or more round-trip-time positioning sections of said environment covered by said radio map.

2. Method according to claim 1, wherein said one or more round-trip-time positioning sections of said environment covered by said radio map are determined such that at least one of the following conditions is met for each of said one or more round-trip-time positioning sections: at least a predetermined number of radio signals having a radio-signal-strength value exceeding or being equal to a predetermined radio-signal-strength threshold is expected to be observable within said respective round-trip-time positioning section of said one or more round-trip-time positioning sections; or a maximum dilution-of-precision value for said respective round-trip-time positioning section of said one or more round-trip-time positioning sections is expected to be less than or equal to a predetermined dilution-of-precision threshold.

3. Method according to claim 2, wherein each of said radio signals of said at least predetermined number of radio signals is transmitted by a different radio device of said plurality of radio devices.

4. Method according to claim 2, wherein said method further comprises: determining, for one or more positions within said environment covered by said radio map, a respective number of radio signals transmitted by said plurality of radio devices which is expected to be observable with a radio-signal-strength value exceeding or being equal to said predetermined radio-signal-strength threshold at least partially based on said plurality of radio models.

5. Method according to claim 2, said method further comprising: determining, for one or more positions within said environment covered by said radio map, a respective expected dilution-of-precision value

6. Method according to claim 1, said method further comprising: determining, at least partially based on said radio map information, a respective installation position for each of said plurality of radio devices.

7. Method according to claim 1, wherein said radio map information is indicative of a respective installation position for each of said plurality of radio devices.

8. Method according to claim 1, wherein each of said plurality of radio devices is configured to support round-trip-time based positioning, and/or wherein said radio map information is indicative of which radio devices of said plurality of radio devices are configured to support round-trip-time based positioning.

9. Method according to claim 1, said method further comprising: updating said radio map information by adding said round-trip-time positioning information to said radio map information.

10. Method according to claim 1, said method further comprising: estimating said position of said mobile device at least partially based on round-trip-times associated with radio signals observed by said mobile device within one of said one or more round-trip-time positioning sections.

11. Method according to claim 1, said method further comprising: at least one of receiving or collecting a plurality of radio observation reports captured by one or more mobile devices within said environment covered by said radio map; and generating or updating said radio map information at least partially based on said plurality of radio observation reports.

12. Method according to claim 1, wherein said plurality of radio devices comprises one or more of the following: a Bluetooth radio device; a WLAN radio device; and/or a cellular radio device.

13. An apparatus comprising at least one processor and at least one memory containing computer program code, the at least one memory and the computer program code with the at least one processor configured to cause the apparatus at least to: obtain or hold available radio map information representing a radio map representing a plurality of radio models for a plurality of radio devices, wherein each of said plurality of radio models is indicative of an expected radio-signal-strength field of a radio signal transmitted by a respective radio device of said plurality of radio devices; determine, at least partially based on said radio map information, one or more round-trip-time positioning sections of an environment covered by said radio map; and provide round-trip-time positioning information causing estimating a position of a mobile device at least partially based on round-trip-times associated with radio signals observed by said mobile device within one of said one or more round-trip-time positioning sections of said environment covered by said radio map.

14. Apparatus according to claim 13, wherein said one or more round-trip-time positioning sections of said environment covered by said radio map are determined such that at least one of the following conditions is met for each of said one or more round-trip-time positioning sections: at least a predetermined number of radio signals having a radio-signal-strength value exceeding or being equal to a predetermined radio-signal-strength threshold is expected to be observable within said respective round-trip-time positioning section of said one or more round-trip-time positioning sections; or a maximum dilution-of-precision value for said respective round-trip-time positioning section of said one or more round-trip-time positioning sections is expected to be less than or equal to a predetermined dilution-of-precision threshold.

15. Apparatus according to claim 14, wherein said apparatus is further caused to: determine, for one or more positions within said environment covered by said radio map, a respective number of radio signals transmitted by said plurality of radio devices which is expected to be observable with a radio-signal-strength value exceeding or being equal to said predetermined radio-signal-strength threshold at least partially based on said plurality of radio models.

16. Apparatus according to claim 14, said apparatus further caused to: determine, for one or more positions within said environment covered by said radio map, a respective expected dilution-of-precision value

17. Apparatus according to claim 13, said apparatus further caused to: determine, at least partially based on said radio map information, a respective installation position for each of said plurality of radio devices.

18. Apparatus according to claim 13, wherein each of said plurality of radio devices is configured to support round-trip-time based positioning, and/or wherein said radio map information is indicative of which radio devices of said plurality of radio devices are configured to support round-trip-time based positioning.

19. Apparatus according to claim 13, said apparatus further caused to: update said radio map information by adding said round-trip-time positioning information to said radio map information.

20. A non-transitory computer readable storage medium configured to store computer program code, the computer program code configured, upon execution, to cause an apparatus to: obtain or hold available radio map information representing a radio map representing a plurality of radio models for a plurality of radio devices, wherein each of said plurality of radio models is indicative of an expected radio-signal-strength field of a radio signal transmitted by a respective radio device of said plurality of radio devices; determine, at least partially based on said radio map information, one or more round-trip-time positioning sections of an environment covered by said radio map; and provide round-trip-time positioning information causing estimating a position of a mobile device at least partially based on round-trip-times associated with radio signals observed by said mobile device within one of said one or more round-trip-time positioning sections of said environment covered by said radio map.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0098] FIG. 1 is a block diagram of an exemplary embodiment of a system according to the invention;

[0099] FIG. 2 is a block diagram of an exemplary embodiment of an apparatus according to the invention;

[0100] FIG. 3 is a block diagram of an exemplary embodiment of a radio device;

[0101] FIG. 4 is a block diagram of an exemplary embodiment of a mobile device;

[0102] FIG. 5 is a flow chart illustrating an exemplary embodiment of a method according to the invention;

[0103] FIGS. 6a-6c are exemplary embodiments of a radio map according to the invention; and

[0104] FIG. 7 is a schematic illustration of examples of tangible and non-transitory storage media according to the invention.

DETAILED DESCRIPTION OF THE FIGURES

[0105] The following description serves to deepen the understanding of the present invention and shall be understood to complement and be read together with the description of example embodiments of the invention as provided in the above SUMMARY section of this specification.

[0106] FIG. 1 is a schematic high-level block diagram of a system 100 according to an exemplary aspect of the invention. In the following, it is assumed that system 100 is an indoor radio positioning system for an indoor environment.

[0107] The indoor environment of system 100 is for example inside a building or a complex of buildings like a shopping center, a parking garage, an airport, a company site, etc.

[0108] System 100 comprises a positioning server 200 and a plurality of radio devices 300-1 to 300-5. Optionally, system 100 may comprise a mobile device 400. It is to be understood that system 100 may comprise further radio devices and mobile devices. In the following, it is thus referred to radio devices 300-1 to 300-5 and mobile device 400 without limiting the scope of the invention.

[0109] Indoor radio positioning system 100 is not limited to a single positioning server 200, but may optionally comprise a plurality of servers (e.g. forming a server cloud). Accordingly, the positioning server 200 may be part of such a plurality of servers (e.g. a server cloud) or may be represented by such a plurality of servers (e.g. a server cloud).

[0110] In system 100, positioning server 200 and mobile device 400 may be configured to communicate with each other as indicated by communication path 101. It is to be understood that communication path 101 may comprise one or more communication links (e.g. one or more wireless communication links or one or more wireline communication links or a combination thereof). For example, communication path 101 may include one or more communication links over one or more communication networks. For example, communication path 101 is or includes a communication link over a cellular communication network like a 2G/3G/4G/5G cellular communication network. The 2G/3G/4G/5G cellular radio communication standards are developed by the 3GPP and presently available under http://www.3gpp.org/.

[0111] Positioning server 200 may be configured for generating and updating radio map information representing a radio map covering the indoor environment of system 100 (e.g. based on a plurality of radio observation reports as disclosed in more detail above). The radio map may be configured to enable mobile device 400 to estimate its position at least partially based on this radio map when the mobile device is located in the indoor environment of system 100 which is covered by the radio map. Positioning server 200 may provide (e.g. transmit) the radio map information to mobile device 400 via communication paths 101.

[0112] Radio devices 300-1 to 300-5 may be WLAN access points fixedly installed in the indoor environment of system 100 and may be configured for transmitting and receiving WLAN radio signals. For example, they may be configured for automatically and repeatedly transmitting WLAN radio signals. In particular, they may be configured to support WLAN according to the IEEE 802.11mc standard which specifies a solution for determining round-trip-time (RTT) values associated with (a) WLAN radio signal(s) travelling between two WLAN devices (e.g. a respective WLAN access point of WLAN access points 300-1 to 300-5 and mobile device 400). It is to be understood that system 100 is not limited to WLAN access points as radio devices 300-1 to 300-5. In the following, it is thus referred to radio devices 300-1 to 300-5 as WLAN access points 300-1 to 300-5 for exemplary purposes only without limiting the scope of the invention.

[0113] For example, mobile device 400 may be one of a smartphone, a tablet computer, a notebook computer, a smart watch and a smart band. Mobile device 400 may be configured for transmitting and receiving WLAN radio signals.

[0114] Moreover, mobile device 400 may be configured for estimating its position based on observed (e.g. received) WLAN radio signals and the radio map represented by the radio map information. In particular, mobile device 400 may for example use the radio map information (e.g. the radio map represented by the radio map information) provided by the positioning server 200 to mobile device 400 to estimate an observation position based on at least three WLAN radio signals observed (e.g. received) by mobile device 400 at the observation position as disclosed above in more detail.

[0115] Furthermore, mobile device 400 may be configured for estimating its position based on round-trip-times associated with observed (e.g. received) WLAN radio signals. To this end, mobile device 400 may be configured to support WLAN according to the IEEE 802.11mc standard. Based on at least three RTT values of WLAN radio signals transmitted by at least three different WLAN access points of WLAN access points 300-1 to 300-5 and observed by mobile device 400 at an observation position, the observation position of mobile device 400 may be estimated as disclosed above in more detail.

[0116] FIG. 2 is a block diagram of an exemplary embodiment of an apparatus according to the invention. In the following, it is assumed that this apparatus corresponds to positioning server 200 of system 100 of FIG. 1.

[0117] Positioning server 200 comprises a processor 201. Processor 201 may represent a single processor or two or more processors, which are for instance at least partially coupled, for instance via a bus. Processor 201 executes a program code stored in program memory 202 (for instance program code causing positioning server 200 to perform one or more of the embodiments of a method according to the invention or parts thereof (e.g. the method or parts of the method disclosed below with reference to flowchart 500 of FIG. 5), when executed on processor 201), and interfaces with a main memory 203. Program memory 202 may also contain an operating system for processor 201. Some or all of memories 202 and 203 may also be included into processor 201.

[0118] One of or both of a main memory and a program memory of a processor (e.g. program memory 202 and main memory 203) could be fixedly connected to the processor (e.g. processor 201) or at least partially removable from the processor, for instance in the form of a memory card or stick.

[0119] A program memory (e.g. program memory 202) may for instance be a non-volatile memory. It may for instance be a FLASH memory (or a part thereof), any of a ROM, PROM, EPROM, MRAM or a FeRAM (or a part thereof) or a hard disc (or a part thereof), to name but a few examples. For example, a program memory may for instance comprise a first memory section that is fixedly installed, and a second memory section that is removable from, for instance in the form of a removable SD memory card.

[0120] A main memory (e.g. main memory 203) may for instance be a volatile memory. It may for instance be a DRAM memory, to give non-limiting example. It may for instance be used as a working memory for a processor (e.g. processor 201) when executing an operating system and/or programs.

[0121] Processor 201 further controls a communication interface 204 which is for example configured to communicate via a network like a cellular communication network. Positioning server 200 may use communication interface 204 to communicate with mobile device 400 (e.g. via communication path 101).

[0122] Furthermore, processor 201 controls an optional user interface 205 configured to present information to a user of positioning server 200 and/or to receive information from such a user. User interface 205 may for instance be the standard user interface via which a user of positioning server 200 controls other functionality thereof. Examples of such a user interface are a touch-sensitive display, a keyboard, a touchpad, a display, etc.

[0123] The components 202 to 205 of positioning server 200 may for instance be connected with processor 201 by means of one or more serial and/or parallel busses.

[0124] It is to be understood that positioning server 200 may comprise various other components.

[0125] FIG. 3 is a block diagram of an exemplary embodiment of a radio device according to the invention. In the following, it is assumed that this radio device corresponds to a WLAN access point 300 like WLAN access points 300-1 to 300-5 of system 100.

[0126] WLAN access point 300 comprises a processor 301. Processor 301 may represent a single processor or two or more processors, which are for instance at least partially coupled, for instance via a bus. Processor 301 executes a program code stored in memory 302. Some or all of memory 302 may also be included into processor 301. Memory 302 may for instance be a volatile or non-volatile memory. It may for instance be a RAM or DRAM memory. It may for instance be a FLASH memory (or a part thereof), any of a ROM, PROM, EPROM, EEPROM, MRAM or a FeRAM (or a part thereof) and/or a hard disc (or a part thereof), to name but a few examples. It may for instance be used as a working memory for processor 301 when executing an operating system and/or programs. Memory 302 may also comprise an operating system for processor 301. Memory 302 may for instance comprise a first memory portion that is fixedly installed in WLAN access point 300, and a second memory portion that is removable from WLAN access point 300, for instance in the form of a removable SD memory card.

[0127] Processor 301 further controls a radio interface 303 configured to receive and/or transmit WLAN radio signals. For instance, radio interface 303 may at least comprise a WLAN component including a WLAN transmitter (TX). The radio interface 303 may additionally comprise a WLAN receiver (RX). The transmitter and receiver may also be part of a WLAN transceiver (TRX). The WLAN transmitter enables WLAN access point 300 to transmit WLAN radio signals. Likewise, the WLAN receiver enables WLAN access point 300 to receive WLAN radio signals. Moreover, the radio interface 303 may be configured to support determining one or more round-trip-time values according to the IEEE 802.11mc standard, for example by capturing times-of-arrival and/or times-of-departure as disclosed above in more detail. It is to be understood that any computer program code based processing required for receiving and processing received WLAN radio signals may be stored in an own memory of the radio interface 303 and executed by an own processor of the radio interface 303 or it may be stored for example in memory 302 and executed for example by processor 301.

[0128] The components 302 to 303 of WLAN access point 300 may for instance be connected with processor 301 by means of one or more serial and/or parallel busses.

[0129] It is to be understood that WLAN access point 300 may comprise various other components.

[0130] FIG. 4 is a block diagram of an exemplary embodiment of a mobile device 400 according to the invention. In the following, it is assumed that this mobile device 400 corresponds to mobile device 400 of system 100 of FIG. 1.

[0131] Mobile device 400 comprises a processor 401. Processor 401 may represent a single processor or two or more processors, which are for instance at least partially coupled, for instance via a bus. Processor 401 executes a program code stored in program memory 402 and interfaces with a main memory 403. Program memory 402 may also comprise an operating system for processor 401. Some or all of memories 402 and 403 may also be included into processor 401.

[0132] Processor 401 controls a communication interface 404 which is for example configured to communicate via a network like a cellular communication network. Mobile device 400 may use communication interface 404 to communicate with positioning server 200 (e.g. via communication path 101).

[0133] Moreover, processor 401 controls radio interface 405 configured to receive and/or transmit WLAN radio signals. For instance, radio interface 405 may at least comprise a WLAN component including a WLAN transmitter (TX). The radio interface 405 may additionally comprise a WLAN receiver (RX). The transmitter and receiver may also be part of a WLAN transceiver (TRX). The WLAN transmitter enables mobile device 400 to transmit WLAN radio signals. Likewise, the WLAN receiver enables mobile device 400 to receive WLAN radio signals. Moreover, the radio interface 405 may be configured to support determining one or more round-trip-time values according to the IEEE 802.11mc standard, for example by capturing times-of-arrival and/or times-of-departure as disclosed above in more detail. It is to be understood that any computer program code based processing required for receiving and processing received WLAN radio signals may be stored in an own memory of the radio interface 405 and executed by an own processor of the radio interface 405 or it may be stored for example in memory 402 and executed for example by processor 401.

[0134] The components 402 to 405 of mobile device 400 may for instance be connected with processor 401 by means of one or more serial and/or parallel busses.

[0135] It is to be understood that mobile device 400 may comprise various other components. For example, mobile device 400 may optionally comprise a user interface (e.g. a touch-sensitive display, a keyboard, a touchpad, a display, etc).

[0136] FIG. 5 is a flow chart 500 illustrating an exemplary embodiment of a method according to the invention. Without limiting the scope of the invention, it is assumed in the following that positioning server 200 of indoor radio positioning system 100 as described above with respect to FIG. 1 performs the steps of flowchart 500.

[0137] In a step 501, radio map information representing the radio map representing a plurality of radio models for the plurality of WLAN radio access points 300-1 to 300-5 is obtained or hold available. In the following, it is assumed that the radio map information representing the radio map has been obtained as a result of generating or updating the radio map and stored in program memory 202. Accordingly, the radio map may be considered to be an existing radio map.

[0138] Each of the plurality of radio models for the plurality of WLAN radio access points 300-1 to 300-5 is indicative of an expected radio-signal-strength field of a WLAN radio signal transmitted by a respective WLAN access point of the plurality of WLAN radio access points 300-1 to 300-5. To this end, each of the plurality of radio models may represent at least one of (1) the expected radio-signal-strength value of a WLAN radio signal transmitted by a respective WLAN access point of the plurality of WLAN radio access points 300-1 to 300-5 at one or more positions (e.g. at any position or at any position of a plurality of predetermined positions like a predetermined grid of positions) in the environment covered by the radio map or (2) the expected path-loss (and, optionally, transmission power) of a radio signal transmitted by a respective radio device of the plurality of radio devices or (3) a combination thereof. To give a non-limiting example, such a radio model may be a soft-boundary model like a parametric model like a path-loss model or a grid model like a radio-signal-strength heatmap.

[0139] In the following, it is assumed that each of the plurality of radio models is a respective path-loss model for a WLAN radio signal transmitted by a respective WLAN access point of the plurality of WLAN radio access points 300-1 to 300-5 which is represented by a respective path-loss exponent experienced by the WLAN radio signal transmitted by the respective WLAN access point, a respective transmission power value used by the transmitter of the respective WLAN access point and an installation position of the respective WLAN access point (e.g. in the form of geographical coordinates).

[0140] In a step 502, one or more round-trip-time positioning sections of the indoor environment of system 100 covered by the radio map are determined at least partially based on the radio map information.

[0141] In the following, it is assumed that the one or more round-trip-time positioning sections of the indoor environment covered by the radio map are determined such that the following conditions are met for each of the one or more round-trip-time positioning sections: [0142] (1) at least a predetermined number of 3 radio signals having a radio-signal-strength value exceeding or being equal to a predetermined radio-signal-strength threshold of 65 dBm is expected to be observable within the respective round-trip-time positioning section of the one or more round-trip-time positioning sections; [0143] (2) a maximum dilution-of-precision (DOP) value for the respective round-trip-time positioning section of the one or more round-trip-time positioning sections is expected to be less than or equal to a predetermined dilution-of-precision threshold of 2.5.

[0144] If each of the one or more round-trip-time positioning sections meets both conditions, it may be expected that round-trip-time based positioning is possible (e.g. with a predetermined or desired minimum accuracy) in each of one or more round-trip-time positioning sections. In particular, the predetermined number of 3 WLAN radio signals, the predetermined radio-signal-strength threshold of 65 dBm and the predetermined dilution-of-precision threshold of 2.5 may be predetermined (e.g. predefined) such that it is expected that round-trip-time based positioning is possible (e.g. with a predetermined or desired minimum accuracy) in each of one or more round-trip-time positioning sections meeting both conditions.

[0145] As disclosed in the following with reference to FIGS. 6a to 6c, the one or more round-trip-time positioning sections of the environment covered by the radio map may be determined at least partially based on the plurality of radio models represented by the radio map represented by the radio map information obtained or hold available in step 501. As disclosed above, it is assumed in the following that each of the plurality of radio models is a respective path-loss model for a WLAN radio signal transmitted by a respective WLAN access point of the plurality of WLAN radio access points 300-1 to 300-5 and that each of the plurality of path-loss models is represented by a respective path-loss exponent experienced by the WLAN radio signal transmitted by the respective WLAN access point, a respective transmission power value used by the transmitter of the respective WLAN access point and an installation position of the respective WLAN access point.

[0146] FIGS. 6a to 6c show exemplary radio map views 600a to 600c which represent (intermediate) results of determining the one or more round-trip-time positioning sections of the indoor environment of system 100 covered by the radio map at least partially based on the plurality of path-loss models for the plurality of WLAN radio access points 300-1 to 300-5 represented by the radio map represented by the radio map information.

[0147] Installation positions 601 to 605 of radio map views 600a to 600c correspond to the installation positions of WLAN radio access points 300-1 to 300-5, respectively, as represented by the plurality of path-loss models for the plurality of WLAN radio access points 300-1 to 300-5.

[0148] To determine the one or more round-trip-time positioning sections of the environment covered by the radio map such that the first condition is met, the determining in step 502 may for example comprise: [0149] determining, for one or more positions (e.g. any position or any position of a plurality of predetermined positions like a predetermined grid of positions) within the indoor environment of system 100 covered by the radio map, a respective number of WLAN radio signals transmitted by the plurality of WLAN radio access points 300-1 to 300-5 which is expected to be observable with a radio-signal-strength value exceeding or being equal to the predetermined radio-signal-strength threshold of 65 dBm; and [0150] determining the one or more round-trip-time positioning sections such that the one or more round-trip-time positioning sections only comprise the one or more positions within the environment covered by the radio map for which it is determined that the respective number of WLAN radio signals transmitted by the plurality of WLAN radio access points 300-1 to 300-5 which is expected to be observable with a radio-signal-strength value exceeding or being equal to the predetermined radio-signal-strength threshold of 65 dBm is equal to or exceeds the predetermined number of 3 WLAN radio signals.

[0151] A result of these determining steps is represented by radio map view 600a of FIG. 6a. Each of circular sections 606 to 610 of radio map view 600a represents a respective section of the indoor environment of system 100 covered by the radio map within which it is expected that a respective WLAN radio signal transmitted by a respective WLAN radio access point of the plurality of WLAN radio access points 300-1 to 300-5 is observable (e.g. receivable) at any position at least with the predetermined radio-signal-strength threshold of 65 dBm. For example, it may be expected, based on the path-loss model of WLAN radio access point 300-1 installed at installation position 601, that a WLAN radio signal transmitted by WLAN radio access point 300-1 is observable (e.g. receivable) at any position within circular section 606 at least with the predetermined radio-signal-strength threshold of 65 dBm. For example, the respective radius of each of the circular sections 606 to 610 may be determined in step 502 based on the respective path-loss exponent and the respective transmission power value represented by the respective path-loss model of the plurality of radio models as well as the predetermined radio-signal-strength threshold of 65 dBm.

[0152] In hatched sections 611 and 612 of radio map view 600a, at least 3 sections of circular sections 606 to 610 overlap such that it is expected that at any position of hatched sections 611 and 612 at least 3 WLAN radio signals (i.e. the predetermined number of 3 radio signals) are observable with a radio-signal-strength value exceeding or being equal to the predetermined radio-signal-strength threshold of 65 dBm. Accordingly hatched sections 611 and 612 may be determined in step 502 to meet the first condition as specified above.

[0153] To determine the one or more round-trip-time positioning sections of the environment covered by the radio map such that the second condition is met, the determining in step 502 may for example comprise: [0154] determining, for one or more positions (e.g. any position or any position of a plurality of predetermined positions like a predetermined grid of positions) within the indoor environment of system 100 covered by the radio map, a respective expected dilution-of-precision (DOP) value; and [0155] determining the one or more round-trip-time positioning sections such that the one or more round-trip-time positioning sections only comprise the one or more positions within the indoor environment of system 100 covered by the radio map for which it is determined that the respective expected dilution-of-precision (DOP) value is less than or equal to the predetermined dilution-of-precision threshold of 2.5.

[0156] A result of these determining steps is represented by radio map view 600b of FIG. 6b. Each of cross-hatched sections 613 and 614 of radio map view 600b represents a respective section of the indoor environment of system 100 covered by the radio map within which the respective expected DOP value is equal to 1.0 at any position. Moreover, hatched section 615 of radio map view 600b represents a section of the indoor environment of system 100 covered by the radio map within which the respective expected dilution-of-precision value is less than or equal to the predetermined DOP threshold of 2.5. Accordingly hatched section 615 may be determined in step 502 to meet the second condition as specified above.

[0157] For example, hatched section 615 of radio map view 600b may be determined in step 502 by determining for any position within the indoor environment of system 100 covered by the radio map the respective expected dilution-of-precision value. As disclosed above, the respective expected dilution-of-precision (DOP) values for any position within the indoor environment of system 100 covered by the radio map may be a respective expected geometric dilution-of-precision (GDOP) value or a respective expected positional dilution-of-precision (PDOP) value which may for example be determined (e.g. estimated and/or computed) as outlined in the article Dilution of precision. (i.e. Langley, Richard B. Dilution of precision. GPS world 10.5 (1999): 52-59.).

[0158] The one or more round-trip-time positioning sections 616 and 617 of radio map view 600c of FIG. 6c may then be determined in step 502 to correspond to the overlapping portions of (1) hatched sections 611 and 612 of radio map view 600a of FIG. 6a and (2) hatched section 615 of radio map view 600b of FIG. 6b. By this, the first condition and the second condition are both met in round-trip-time positioning sections 616 and 617.

[0159] This is for example advantageous because it provides a simple solution for determining the one or more round-trip-time positioning sections, in particular for determining the one or more round-trip-time positioning sections of the indoor environment of system 100 covered by an already existing radio map.

[0160] In a step 503, round-trip-time positioning information is provided. For example, the round-trip-time positioning information is provided in step 503 by transmitting the round-trip-time positioning information via communication paths 101 to mobile device 400.

[0161] The round-trip-time positioning information cause estimating a position of mobile device 400 at least partially based on round-trip-times associated with WLAN radio signals observed by mobile device 400 within one of the one or more round-trip-time positioning sections 616 and 617 of the indoor environment of system 100 covered by the radio map. This may be understood to mean that the round-trip-time positioning information are configured to control mobile device 400 to estimate an observation position of mobile device 400 at least partially based on round-trip-times associated with WLAN radio signals observed by mobile device 400 at this observation position if these WLAN radio signals are observed by mobile device 400 within one of round-trip-time positioning sections 616 and 617 (i.e. the observation position is within one of round-trip-time positioning sections 616 and 617). To this end, the round-trip-time positioning information may be indicative of round-trip-time positioning sections 616 and 617 of the indoor environment of system 100 covered by the radio map, for example by representing round-trip-time positioning sections 616 and 617 (e.g. by representing geographic coordinates defining round-trip-time positioning sections 616 and 617). Accordingly, if mobile device estimates, based on the radio map represented by the radio map information and WLAN radio signals observed at an observation position, that the observation position is within one of round-trip-time positioning sections 616 and 617 indicated by the round-trip-time positioning information, mobile device may be caused (e.g. controlled) by the round-trip-time positioning information to proceed with estimating the observation position based on round-trip-times associated with the WLAN radio signals observed at the observation position.

[0162] This is for example advantageous because round-trip-time based positioning is expected to be more accurate (than position estimating based on the radio map and the observed radio signals) in round-trip-time positioning sections of the environment of indoor positioning system 100 meeting one or both of the conditions specified above.

[0163] It is to be understood that the orders of the steps of flowchart 500 is only exemplary and that the steps may also have a different order if possible. Furthermore, it is also possible that two or more steps may be performed in one step.

[0164] FIG. 7 is a schematic illustration of examples of tangible and non-transitory computer-readable storage media according to the present invention that may for instance be used to implement memory 202 of FIG. 2, memory 302 of FIG. 3 and memory 402 of FIG. 4. To this end, FIG. 7 displays a flash memory 700, which may for instance be soldered or bonded to a printed circuit board, a solid-state drive 701 comprising a plurality of memory chips (e.g. Flash memory chips), a magnetic hard drive 702, a Secure Digital (SD) card 703, a Universal Serial Bus (USB) memory stick 704, an optical storage medium 705 (such as for instance a CD-ROM or DVD) and a magnetic storage medium 706.

[0165] Any presented connection in the described embodiments is to be understood in a way that the involved components are operationally coupled. Thus, the connections can be direct or indirect with any number or combination of intervening elements, and there may be merely a functional relationship between the components.

[0166] Further, as used in this text, the term circuitry refers to any of the following: [0167] (a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) [0168] (b) combinations of circuits and software (and/or firmware), such as: (i) to a combination of processor(s) or (ii) to sections of processor(s)/software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone, to perform various functions) and [0169] (c) to circuits, such as a microprocessor(s) or a section of a microprocessor(s), that re-quire software or firmware for operation, even if the software or firmware is not physically present.

[0170] This definition of circuitry applies to all uses of this term in this text, including in any claims. As a further example, as used in this text, the term circuitry also covers an implementation of merely a processor (or multiple processors) or section of a processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example, a baseband integrated circuit or applications processor integrated circuit for a mobile phone.

[0171] Any of the processors mentioned in this text, in particular but not limited to processors 201, 301 and 401 of FIGS. 2, 3 and 4, could be a processor of any suitable type. Any processor may comprise but is not limited to one or more microprocessors, one or more processor(s) with accompanying digital signal processor(s), one or more processor(s) without accompanying digital signal processor(s), one or more special-purpose computer chips, one or more field-programmable gate arrays (FPGAS), one or more controllers, one or more application-specific integrated circuits (ASICS), or one or more computer(s). The relevant structure/hardware has been programmed in such a way to carry out the described function.

[0172] Moreover, any of the actions or steps described or illustrated herein may be implemented using executable instructions in a general-purpose or special-purpose processor and stored on a computer-readable storage medium (e.g., disk, memory, or the like) to be executed by such a processor. References to computer-readable storage medium should be understood to encompass specialized circuits such as FPGAs, ASICs, signal processing devices, and other devices.

[0173] The wording A, or B, or C, or a combination thereof or at least one of A, B and C may be understood to be not exhaustive and to include at least the following: (i) A, or (ii) B, or (iii) C, or (iv) A and B, or (v) A and C, or (vi) B and C, or (vii) A and B and C.

[0174] It will be understood that all presented embodiments are only exemplary, and that any feature presented for a particular exemplary embodiment may be used with any aspect of the invention on its own or in combination with any feature presented for the same or another particular exemplary embodiment and/or in combination with any other feature not mentioned. It will further be understood that any feature presented for an example embodiment in a particular category may also be used in a corresponding manner in an example embodiment of any other category.