Method and apparatus for determining the location of a node in a wireless system
View Patent ↗A method and apparatus for determining the location of a node within a wireless communication system is provided herein. In order to determine the location of a node, a series of GSM network measurement reports (NMRs) received at multiple base stations are analyzed by location-finding equipment. Multiple reports from the same mobile unit are analyzed for their received signal strength and multiple location estimates are then determined for the node. The location estimates are then averaged and weighted to determine an accurate location estimate for the node.
1. A method for determining a location of a node, the method comprising the steps of:
receiving a plurality of GSM network measurement reports;
determining a call group from those network measurement reports having a same identification;
determining signal-strength measurements from the plurality of GSM network measurement reports within the call group;
determining a location from the signal-strength measurements, wherein the location comprises an (x,y) location:
averaging a plurality of locations to produce an average location, ( x , y ) as:
x
_
=
1
N
∑
i
=
1
N
x
i
y
_
=
1
N
∑
i
=
1
N
y
i
where x i is a x location calculated from an ith network measurement report, y i is a y location calculated from the ith network measurement report, and N is a number of network measurement reports within the call group;
calculating ({circumflex over (x)} i ,ŷ i ) based on weighting the ( x , y ) location where
x
^
i
=
w
x
_
+
(
1
-
w
)
x
i
and
y
^
i
=
w
y
_
+
(
1
-
w
)
y
i
,
where
w
=
exp
(
-
n
2
c
)
and where n=N/N max and the parameter c>0 and controls a rate of fall-off of w having a call-group size of N.
2. An apparatus for determining a location of a node, the apparatus comprising:
a receiver receiving a plurality of GSM network measurement reports;
logic circuitry determining a call group from those measurement reports having a same identification, determining signal-strength measurements from the plurality of GSM network measurement reports within the call group, determining a location from the signal-strength measurements, wherein the location comprises an (x,y) location, averaging a plurality of locations to produce an average location, ( x , y ) as:
x
_
=
1
N
∑
i
=
1
N
x
i
y
_
=
1
N
∑
i
=
1
N
y
i
x i is a x location calculated from an ith network measurement report, y i is a y location calculated from the ith network measurement report, and N is a number of network measurement reports within the call group, and calculating ({circumflex over (x)} i ,ŷ i ) based on weighting the ( x , y ) location where
x
^
i
=
w
x
_
+
(
1
-
w
)
x
i
and
y
^
i
=
w
y
_
+
(
1
-
w
)
y
i
,
where
w
=
exp
(
-
n
2
c
)
and where n=N/N max and the parameter c>0 and controls a rate of fall-off of w having a call-group size of N.