Determining of model parameters for positioning purposes

1. A method performed by at least one apparatus, said method comprising:

obtaining measurement data on a location-specific quantity of a signal transmitted by a transmitter;

obtaining location information associated with said measurement data on said location-specific quantity; and

determining, based on said obtained measurement data and said obtained location information, one or more model parameters of a model describing said location-specific quantity in dependence of location, wherein said model assumes a location dependence of said location-specific quantity in a form of a linear combination of a first location-specific function and a second location-specific function,

wherein said determination of said model parameters at least in part comprises:

determining a reliability of at least a part of said determined model parameters associated with said first location-specific function; and

determining at least a part of said model parameters associated with said second location-specific function only in an instance in which said reliability of at least a part of said determined model parameters associated with said first location-specific function satisfies a reliability threshold.

2. The method according to claim 1 , wherein said determining of said model parameters comprises

determining at least a part of said model parameters associated with said first location-specific function; and

subsequently determining at least a part of said model parameters associated with said second location-specific function.

3. The method according to claim 1 , wherein said first location-specific function describes a global trend of said location dependence of said location-specific quantity in said model.

4. The method according to claim 1 , wherein said first location-specific function is based on a radio propagation model.

5. The method according to claim 1 , wherein a-priori information is imposed on at least a part of said model parameters associated with said first location-specific function.

6. The method according to claim 5 , wherein said a-priori information is based on at least one of:

legislative requirements;

technical requirements; and

empirical values.

7. The method according to claim 1 , wherein a-priori information is not directly imposed on at least one of said model parameters associated with said first location-specific function.

8. The method according to claim 1 , wherein said first location-specific function accounts for a different propagation of the signal in the vertical direction.

9. The method according to claim 1 , wherein said determination of said model parameters associated with said first location-specific function comprises

choosing starting values for said model parameters associated with said first location-specific function; and

using an iterative algorithm for determining said model parameters associated with said first location-specific function.

10. The method according to claim 9 , wherein said determining of said model parameters associated with said first location-specific function is repeated with different starting values of said model parameters associated with said first location-specific function.

11. The method according to claim 1 , wherein said model parameters

associated with said first location-specific function comprise at least one of:

a path loss constant;

a pass loss exponent;

a location of an said transmitter; and

a floor loss parameter.

12. The method according to claim 1 , wherein said second location-specific function describes local variations of said location dependence of said location-specific quantity in said model.

13. The method according to claim 1 , wherein said second location-specific function is based on a covariance function.

14. The method according to claim 1 , wherein said determining of said model parameters of said second location-specific function is based on residuals of at least a part of said obtained measurement data on said location-specific quantity.

15. The method according to claim 14 , wherein said second location-specific function is a weighted linear combination of said residuals of said obtained measurement data on said location-specific quantity.

16. The method according to claim 1 , wherein said transmitter is part of one of:

a cellular communication system and a non-cellular communication system.

17. The method according to claim 1 , wherein said measurement data on

said location-specific quantity is representative of or comprises at least one of:

a received signal strength;

a timing measurement;

an angle of arrival;

a timing measurement,

a magnetic field strength and/or direction; and

an identification of said transmitter.

18. The method according to claim 1 , wherein said location information is

derived from at least one of:

a Global Navigation Satellite System (GNSS);

a Wireless Local Area Network (WLAN) system;

a Bluetooth (BT) system;

a Radio Frequency Identification (RFID) system;

a cellular network system;

one or more sensors; and

a manual input.

19. A computer readable storage medium in which computer program code is stored, the computer program code when executed by a processor causing an apparatus to:

obtain measurement data on a location-specific quantity of a signal transmitted by a transmitter;

obtain location information associated with said measurement data on said location-specific quantity; and

determine, based on said obtained measurement data and said obtained location information, one or more model parameters of a model describing said location-specific quantity in dependence of location, wherein said model assumes a location dependence of said location-specific quantity in a form of a linear combination of a first location-specific function and a second location-specific function,

wherein said determination of said model parameters at least in part comprises:

determining a reliability of at least a part of said determined model parameters associated with said first location-specific function; and

determining at least a part of said model parameters associated with said second location-specific function only in an instance in which said reliability of at least a part of said determined model parameters associated with said first location-specific function satisfies a reliability threshold.

20. An apparatus configured to realize or comprising respective means for realizing the method of claim 1 .

21. An apparatus comprising at least one processor and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause an apparatus at least to:

obtain measurement data on a location-specific quantity of a signal transmitted by a transmitter;

obtain location information associated with said measurement data on said location-specific quantity; and

determine, based on said obtained measurement data and said obtained location information, one or more model parameters of a model describing said location-specific quantity in dependence of location, wherein said model assumes a location dependence of said location-specific quantity in a form of a linear combination of a first location-specific function and a second location-specific function,

wherein said determination of said model parameters at least in part comprises:

determining a reliability of at least a part of said determined model parameters associated with said first location-specific function; and

determining at least a part of said model parameters associated with said second location-specific function only in an instance in which said reliability of at least a part of said determined model parameters associated with said first location-specific function satisfies a reliability threshold.

22. The apparatus according to claim 21 , wherein the apparatus is one of a server or a part thereof; and

a mobile terminal or a part thereof.

23. A system comprising an apparatus according to claim 21 , and at least one of:

a mobile device configured to provide said measurement data on said location-specific quantity of said signal from said transmitter and to provide said location information associated with said measurement data on said location-specific quantity;

a memory configured to store said measurement data on said location-specific quantity of said signal from said transmitter and to store location information associated with said measurement data on said location-specific quantity; and

a memory configured to store said determined model parameters of said model describing said location-specific quantity in dependence of location.

24. The method according to claim 1 , wherein said model further assumes a location independent component which is a zero mean variable.