Enabling determination of proximity based on detectable proximity determiners
It is provided a method for enabling determination of proximity of a mobile device ( 2 a, 2 b ) to a selected proximity determiner ( 3 a ). The method comprises the steps of: determining a base set of proximity determiners ( 3 b - e ) whereby an enlarged set of proximity determiners is defined as the selected proximity determiner and the base set of proximity determiners; receiving beacon measurements of signal strength of other proximity determiners in the enlarged set of proximity determiners; generating a two-dimensional graph based on the beacon measurements; receiving respective device measurements indicating signal strength of a signal from the mobile device at each proximity determiner in the enlarged set of proximity determiners; finding an optimum in a space defined by the two-dimensional graph; and determining the most probable position of the mobile device in the graph based on the optimum.
1 . A method for enabling determination of proximity of a mobile device to a selected proximity determiner, the method being performed by a proximity determiner and comprising:
determining a base set of proximity determiners being detectable from the selected proximity determiner and whereby an enlarged set of proximity determiners is defined as comprising the selected proximity determiner and the base set of proximity determiners;
receiving, from each proximity determiner of the enlarged set of proximity determiners, beacon measurements of signal strength of other proximity determiners in the enlarged set of proximity determiners;
generating a two-dimensional graph based on the beacon measurements;
receiving, from each proximity determiner of the enlarged set of proximity determiners, respective device measurements indicating signal strength of a signal from the mobile device at each proximity determiner in the enlarged set of proximity determiners;
finding an optimum in a space defined by the two-dimensional graph, based on a probability indicator of the mobile device being in a position based on sub-calculations, for each proximity determiner in the enlarged set of proximity determiners, based on a distance in the graph to the respective proximity determiner and the device measurement for the respective beacon; and
determining the most probable position of the mobile device in the graph based on the optimum.
2 . The method according to claim 1 , wherein the finding an optimum comprises finding an optimum based on a numerical optimisation of the probability indicator.
3 . The method according to claim 1 , further comprising determining a finite number of potential positions of the mobile device in the two-dimensional graph, wherein the finding an optimum comprises calculating the probability indicator for each potential position, and determining the optimum to be a most probable of the potential positions, based on the calculated probability indicators.
4 . The method according to claim 1 , wherein the selected proximity determiner is provided by an electronic lock for securing a restricted physical space, and the receiving device measurements, finding an optimum and determining the most probable position are repeated for a plurality of different mobile devices, and wherein the method further comprises:
triggering access control in the electronic lock for the mobile device having the shortest Euclidian distance between its most probable position and the selected proximity determiner in the graph.
5 . The method according to claim 4 , wherein the triggering access control in the electronic lock for the mobile device is only performed when the Euclidian distance between its most probable position and the selected proximity determiner in the graph is less than a threshold distance.
6 . The method according to claim 1 , wherein in the finding an optimum, each sub-calculation is based on a similarity value between the distance in the graph to the respective proximity determiner and the device measurement for the respective beacon.
7 . The method according to claim 1 , wherein the finding an optimum comprises calculating a probability indicator of the mobile device being in that position based on the following formula:
P
p
o
s
=
∑
b
❘
"\[LeftBracketingBar]"
log
(
d
b
r
b
)
❘
"\[RightBracketingBar]"
where P pos is the probability indicator of the mobile device being in position pos, b represents the different proximity determiners, d b is distance in the graph to the proximity determiner b and r b is the device measurement for proximity determiner b.
8 . A proximity determiner for enabling determination of proximity of a mobile device to a selected proximity determiner, the proximity determiner comprising:
a processor; and
a memory storing instructions that, when executed by the processor, cause the proximity determiner to:
determine a base set of proximity determiners being detectable from the selected proximity determiner whereby an enlarged set of proximity determiners is defined as comprising the selected proximity determiner and the base set of proximity determiners;
receive, from each proximity determiner of the enlarged set of proximity determiners, beacon measurements of signal strength of other proximity determiners in the enlarged set of proximity determiners;
generate a two-dimensional graph based on the beacon measurements;
receive, from each proximity determiner of the enlarged set of proximity determiners, respective device measurements indicating signal strength of a signal from the mobile device at each proximity determiner in the enlarged set of proximity determiners;
find an optimum in a space defined by the two-dimensional graph, based on a probability indicator of the mobile device being in a position based on sub-calculations, for each proximity determiner in the enlarged set of proximity determiners, based on a distance in the graph to the respective proximity determiner and the device measurement for the respective beacon; and
determine the most probable position of the mobile device in the graph based on the optimum.
9 . The proximity determiner according to claim 8 , wherein the instructions to find an optimum comprise instructions that, when executed by the processor, cause the proximity determiner to find an optimum based on a numerical optimisation of the probability indicator.
10 . The proximity determiner according to claim 8 , further comprising instructions that, when executed by the processor, cause the proximity determiner to:
determine a finite number of potential positions of the mobile device in the two-dimensional graph;
wherein the instructions to find an optimum comprise instructions that, when executed by the processor, cause the proximity determiner to calculate the probability indicator for each potential position, and determine the optimum to be a most probable of the potential positions, based on the calculated probability indicators.
11 . The proximity determiner according to claim 8 , wherein the selected proximity determiner is provided by an electronic lock for securing a restricted physical space, and the proximity determiner comprises instructions that, when executed by the processor, cause the proximity determiner to:
repeat the instructions to receive device measurements, find an optimum and determine the most probable position for a plurality of different mobile devices; and
trigger access control in the electronic lock for the mobile device having the shortest Euclidian distance between its most probable position and the selected proximity determiner in the graph.
12 . The proximity determiner according to claim 11 , wherein the instructions to trigger access control in the electronic lock for the mobile device are only performed when the Euclidian distance between its most probable position and the selected proximity determiner in the graph is less than a threshold distance.
13 . The proximity determiner according to claim 8 , wherein the instructions to find an optimum comprise instructions that, when executed by the processor, cause the proximity determiner to calculate each sub-calculation based on a similarity value between the distance in the graph to the respective proximity determiner and the device measurement for the respective beacon.
14 . The proximity determiner according to claim 8 , wherein the instructions to find an optimum comprise instructions that, when executed by the processor, cause the proximity determiner to calculate a probability indicator of the mobile device being in that position based on the following formula:
P
p
o
s
=
∑
b
❘
"\[LeftBracketingBar]"
log
(
d
b
r
b
)
❘
"\[RightBracketingBar]"
where P pos is the probability indicator of the mobile device being in position pos, b represents the different proximity determiners, d b is distance in the graph to the proximity determiner b and r b is the device measurement for proximity determiner b.
15 . An electronic lock comprising the proximity determiner according to claim 8 .
16 . A non-transitory computer readable medium storing a computer program for enabling determination of proximity of a mobile device to a selected proximity determiner, the computer program comprising computer program code which, when run on a proximity determiner causes the proximity determiner to:
determine a base set of a proximity determiners being detectable from the selected proximity determiner whereby an enlarged set of proximity determiners is defined as comprising the selected proximity determiner and the base set of proximity determiners;
receive, from each proximity determiner of the enlarged set of proximity determiners, beacon measurements of signal strength of other proximity determiners in the enlarged set of proximity determiners;
generate a two-dimensional graph based on the beacon measurements;
receive, from each proximity determiner of the enlarged set of proximity determiners, respective device measurements indicating signal strength of a signal from the mobile device at each proximity determiner in the enlarged set of proximity determiners;
find an optimum in a space defined by the two-dimensional graph, based on a probability indicator of the mobile device being in that position based on sub-calculations, for each proximity determiner in the enlarged set of proximity determiners, based on a distance in the graph to the respective proximity determiner and the device measurement for the respective beacon; and
determine the most probable position of the mobile device in the graph based on the optimum.