METHOD AND APPARATUS FOR GEO-LOCATING MOBILE STATION
BACKGROUND
This disclosure relates to providing wireless service to a mobile station in a
wireless network and more particularly, but not exclusively, to estimating a geographic
location for a mobile station within a coverage area of a wireless network.
Geographic location information for mobile stations has tremendous value to
mobile applications, network optimization (e.g., self optimized network (SON)), capacity
management, and drive test substitutions, etc. Although many modern mobile stations
can obtain their own locations from integrated GPS modules, it is still a challenge for the
network to track the locations of a large number of subscribers for an extended period of
time. A frequent location update from mobile stations would increase network overhead
and may overwhelm the network and create bottlenecks. A passive location estimation
technique that leverages measurements from normal network operation is desirable
because it avoids such increases in network overhead.
For example, in third generation (3G) code division multiple access (CDMA)
networks, such as 3G1X, EVDO, UMTS, etc., one can triangulate the geographic
location of a mobile station from the reported round trip delays between the mobile
station and three or more base stations (see FIG. 1). The corresponding round trip
delays are sent back by the mobile stations for call processing, thus no additional
signaling overhead is incurred by the network to collect measurements for triangulation.
However, this triangulation approach does not work in all networks, such as the
fourth generation (4G) long term evolution (LTE) networks. Unlike 3G CDMA networks,
each measurement report in LTE networks only contains the round trip delay from one
cell (i.e., the serving cell of the mobile). Thus, the triangulation technique cannot be
used at all in conjunction with 4G LTE networks.
For these and other reasons, there is a need to provide a technique for
estimating a geographic location of a mobile station for at least 4G LTE networks.
Additionally, it is desirable that the technique be compatible with other types of wireless
networks, especially 3G CDMA networks ft is also desirable that the technique be
more reliable than the triangulation technique.
SUMMARY
In one aspect, a method for estimating a geographic location of a mobile station
within a coverage area of a wireless network is provided. In one embodiment, the
method includes: determining a radial distance of a mobile station from a base station
serving the mobile station, the base station including multiple sector antennas, the radial
distance based at least in part on a round trip measurement associated with elapsed
time between sending an outgoing signal from the base station to the mobile station and
receiving a corresponding acknowledgement signal from the mobile station at the base
station; and calculating a current angular position of the mobile station in relation to the
radial distance from the serving base station based at least in part on a first signal
strength measurement, a second signal strength measurement, and an angular position
reference that extends outward from the serving base station, the first and second
signal strength measurements representative of power characteristics of respective
radio frequency (RF) signals received by the mobile station from corresponding first and
second sector antennas of the serving base station.
In another aspect, an apparatus for estimating a geographic location of a mobile
station within a coverage area of a wireless network is provided. In one embodiment,
the apparatus includes: a distance module for determining a radial distance of a mobile
station from a base station serving the mobile station, the base station including multiple
sector antennas, the radial distance based at least in part on a round trip measurement
associated with elapsed time between sending an outgoing signal from the base station
to the mobile station and receiving a corresponding acknowledgement signal from the
mobile station at the base station; and an angular position module in operative
communication with the distance module for calculating a current angular position of the
mobile station in relation to the radial distance from the serving base station based at
least in part on a first signal strength measurement, a second signal strength
measurement, and an angular position reference that extends outward from the serving
base station, the first and second signal strength measurements representative of
power characteristics of respective RF signals received by the mobile station from
corresponding first and second sector antennas of the serving base station.
ln yet another aspect, a non-transitory computer-readable medium storing
program instructions is provided. The program instructions, when executed by a
computer, cause a corresponding computer-controlled device to perform a method for
estimating a geographic location of a mobile station within a coverage area of a wireless
network. In one embodiment of the non-transitory computer-readable medium, the
method includes: determining a radial distance of a mobile station from a base station
serving the mobile station, the base station including multiple sector antennas, the radial
distance based at least in part on a round trip measurement associated with elapsed
time between sending an outgoing signal from the base station to the mobile station and
receiving a corresponding acknowledgement signal from the mobile station at the base
station; calculating a current angular position of the mobile station in relation to the
radial distance from the serving base station based at least in part on a first signal
strength measurement, a second signal strength measurement, and an angular position
reference that extends outward from the serving base station, the first and second
signal strength measurements representative of power characteristics of respective RF
signals received by the mobile station from corresponding first and second sector
antennas of the serving base station; and identifying a current geographic location of
the mobile station in a coverage area of the wireless network in a geographic notation
based at least in part on combining the radial distance and current angular position of
the mobile station relative to the serving base station.
Further scope of the applicability of this the present invention will become
apparent from the detailed description provided below ft should be understood,
however, that the detailed description and specific examples, while indicating preferred
embodiments of the invention, are given by way of illustration only, since various
changes and modifications within the spirit and scope of the invention will become
apparent to those skilled in the art.
DESCRIPTION OF THE DRAWINGS
The present invention exists in the construction, arrangement, and combination of
various parts of the device, and steps of the method, whereby the objects
contemplated are attained as hereinafter more fully set forth, specifically pointed out in
the claims, and illustrated in the accompanying drawings in which:
FIG. 1 is a functional diagram showing three cells of a wireless network in relation
to an exemplary embodiment of a triangulation technique for estimating the geographic
location of a mobile station;
FfG. 2 is a functional diagram showing a serving cell of a wireless network in
relation to an exemplary embodiment of another technique for estimating the
geographic location of a mobile station;
FIG. 3 is a graph showing a transmit antenna gain characteristic for a sector
antenna of a base station in which normalized gain in dB is plotted in relation to look
angles from the sector antenna to a mobile station in relation to azimuth (i.e., horizontal
gain) and elevation (i.e., vertical gain) positions from the orientation of the sector
antenna;
FIG. 4 is a flow chart of an exemplary embodiment of a process for estimating a
geographic location of a mobile station within a coverage area of a wireless network;
FIG. 5, in combination with FIG. 4, is a flow chart of another exemplary
embodiment of a process for estimating a geographic location of a mobile station within
a coverage area of a wireless network;
F G. 6 is a block diagram of an exemplary embodiment of an apparatus within a
serving base station of a wireless network for estimating a geographic location of a
mobile station within a coverage area of the wireless network;
FIG. 7 is a block diagram of an exemplary embodiment of an apparatus within a
geo-location service node of a wireless network for estimating a geographic location of
a mobile station within a coverage area of the wireless network;
FfG. 8 is a block diagram of an exemplary embodiment of an apparatus within a
network management node associated with a wireless network for estimating a
geographic location of a mobile station within a coverage area of the wireless network;
FIG. 9 is a block diagram of an exemplary embodiment of an angular position
module associated with the apparatus shown in FIGs. 6-8;
FIG. 0 is a flow chart of an exemplary embodiment of a process for estimating a
geographic location of a mobile station within a coverage area of a wireless network
performed by a computer-controlled device executing program instructions stored on a
non-transitory computer-readable medium;
FiG. is a bird's eye view of a coverage area of an exemplary base station in a
wireless network showing an estimated geographic location and a GPS location for a
mobile station; and
FiG. 2 is a set of graphs showing azimuth gain parameter characteristics for two
sector antennas of a base station, elevation gain parameter characteristics for the two
sector antennas, a composite graph showing the difference between gains for the two
sector antennas, and a graph of a function of the angular position of the mobile station
in relation to the delta antenna gain component, a delta transmit parameter component,
and a delta signal strength measurement component.
DETAILED DESCRIPTION
Various embodiments of methods and apparatus provide techniques for
estimating a geographic location of a mobile station within a coverage area of a wireless
network. In one embodiment, an algorithm estimates a geographic location of mobile
station that reports signal strength measurements from multiple sector antennas of a
serving base station in a wireless network in which the serving base station reports a
round trip measurement associated with the mobile station. For example, the various
embodiments of the geographic location estimating algorithm can be use to estimate the
location of a mobile station in a 4G LTE network. Various embodiments of the algorithm
can also estimate the location of a mobile station in 3G CDMA wireless networks and
other types of wireless networks that use base stations with multiple sector antennas.
With reference to FIG. 2, in one embodiment, the technique for estimating the
geographic location of the mobile station uses a round trip measurement (e.g., RTD
measurement) from a serving base station (i.e., serving cell) to estimate the distance (d)
of the mobile station from the serving base station. Then, signal strength
measurements from serving and/or neighboring sectors of the serving base station to
estimate an azimuth position (F) of the mobile station in relation to an angular position
reference extending outward from the serving base station. Combining the sector
coverage areas of the same base station forms a corresponding cellular coverage area
for the base station. The individual sector coverage areas may also be referred to as
cells in relation to corresponding sector antennas. If so, the corresponding cells for
sector antennas associated with the same base station are still usually labeled as
sectors (e.g., a, b, g sectors or sectors 1, 2, 3). Normally, the sector antennas
associated with the same base station are mounted on the same cell tower (or building).
Hence, the radio wave travel from these sector antennas to a given mobile station
antenna will experience highly correlated losses (including path loss and shadow
fading). The algorithm described herein uses these RF characteristics (i.e., highly
correlated losses) to estimate an azimuth position of the mobile station in relation to the
serving based station based on the difference of signal strength measurements from
multiple sector antennas of the serving base station.
In one embodiment, the algorithm for estimating a geographic location of a
mobile station within a coverage area of a wireless network begins with estimating a
distance (d) of the mobile station from the serving base station based on a round trip
measurement, such as RTD. Next, the azimuth position ( ) of the mobile station in
relation to the serving base station is estimated based on signal strength measurements
by the mobile station from multiple sector antennas of the serving base station that are
reported back by the mobile station to the serving base station via the serving sector
antenna. Combining the distance (d) and azimuth position (F) forms a geographic
location of the mobile station in relation to the serving base station with respect to vector
represented by a displacement (i.e., distance (d)) and an angular position (i.e., azimuth
position (F)). This polar coordinate-type of geographic notation can be converted to
various other forms of geographic notation, including a latitude/longitude notation, an
address notation, or a geo-bin tile grid notation associated with the coverage area for
the wireless network. For example, the geo-bin tile grid notation may use 50 meter by
50 meter tiles to represent the coverage area for a sector antenna, base station, cluster
of base stations, or the overall wireless network. In other embodiments, any suitable tile
size may be used to provide a higher or lower resolution of the coverage area.
The approximation algorithm for estimating the geographic location of a mobile
station may be based on certain considerations regarding the mobile received power
(Pr) (i.e., signal strength measurements) from multiple sector antennas where the sector
antennas are located in close proximity to each other, such as mounted on the same
cell tower or on the same physical structure at relatively the same elevation. For
example, the mobile received power (Pr) is received by the mobile station from multiple
sector antennas of the serving base station. The mobile station measures the signal
strength of the mobile received power (Pr) signals and may report back the
corresponding signal strength measurements in dBm.
Mobile received power (Pr) may be represented by the following equation:
Pr(d, , Q ) = Pt - PL(d) - X + Gt(d, F , Q ) + Gr ( ) ,
where d is a distance between the serving base station and the mobile station in
kilometers (km), F is an azimuth position of the mobile station in relation to an angular
position reference extending outward from the serving base station, Q is an azimuth
position at which the transmit portion of the corresponding sector antenna is oriented in
relation to the angular reference position, Pt is a transmit power for the corresponding
sector antenna in dBm, and PL(d) is an average path loss in dB for the corresponding
sector antenna. The azimuth position Q of the sector antenna is known and
corresponds to its actual installation. Likewise, the transmit power Pt for the sector
antenna is known at the serving base station based on known characteristics of the
sector antenna or actual measurements by the base station.
The average path loss PL(d) may be represented by the following equation:
PL(d) = K 1 + K2 * log10(d) (2),
where K 1 and K2 are propagation parameters such that K 1 is function of morphology,
frequency, cell antenna height, and mobile antenna height and K2 is function of cell
antenna height.
With reference again to equation ( 1 ) , X is a zero-mean Gaussian distributed
random variable (in dB) with standard deviation s approximately equal to N(0, a ) (in
dB). X may be referred to as the shadowing fading effect. Gt(d, F , Q ) is the transmit
antenna gain at the sector antenna in dB. Gr is receive antenna gain at the mobile
station in dB.
With reference to FIG. 3, Gt(d, F , Q ) reflects that Gt is a function of mobile
distance (d) and an angle between the azimuth position (F ) of the mobile station and
the azimuth position (Q ) of the corresponding sector antenna. Note, the distance (d), in
combination with the sector antenna height, is used to estimate an antenna tile and an
antenna downtile. The azimuth position (F) of the mobile station and the azimuth
position (Q) of the corresponding sector antenna are used to determine a horizontal
gain portion of Gt, where the look angle is F - Q. The distance (d) and the height (i.e.,
elevation) of the corresponding sector antenna are used to determine a vertical gain
component of Gt.
The signal strength measurements for mobile received power Pr may be reported
as received signal reference power (RSRP) measurements, reference signal received
quality (RSRQ) measurements, or Ec/lo measurements. RSRQ is the ratio of received
signal reference power to total received power. Ec/lo is the ratio in dB between the pilot
energy accumulated over one PN chip period ("Ec") to the total power spectral density
in the received bandwidth ("lo").
Mobile received power Pr1 and Pr2 from two sector antennas of the serving base
station in dBm may be represented by the following equations:
Pr1 (d, F, Q1) = Pt1 - PL(d) - X + Gt1 (d, F, Q1) + Gr (3),
Pr2 (d, F, Q2) = Pt2 - PL(d) - X + Gt2 (d, F, Q2) + Gr + e (4).
The path loss and shadowing fading effect from different sector antennas of the
same base station can be assumed to be equal where the sector antennas are mounted
on the same cell tower or building. The close proximity of the sector antennas results in
high correlation of between these components of the mobile received power Pr1 and
Pr2. For example, the differences of shadow fading are expected to be very small and
are counted by e in equation (4). As mentioned above, d, Q1 and Q2 are known
values.
Based on the foregoing, an estimate of the azimuth position (F) of the mobile
station may be based on the difference of mobile received power from the two sector
antennas (Pr1-Pr2) in dB. For example, (Pr1-Pr2) can be (RSRP1 - RSRP2) or
(RSRQ1-RSRQ2) in an LTE network. Similarly, (Pr1-Pr2) can be (Ec/lo) 1 - (Ec/lo) 2 in
a CDMA network. Even though the mobile received power Pr1 and Pr2 are expressed
in absolute received power format (i.e., dBm), the estimation of mobile location does not
require the knowledge of absolute received power information. RSRQ for LTE and pilot
Ec/io for CDMA can be used in the same manner as mentioned above.
Based on the foregoing, the difference between the mobile received power Pr1
and Pr2 can be represented by the following equation:
(Pr1 - Pr2) = (Gt1 (F )- Gt2 (F ) ) + (Pt1 - Pt2 ) (5),
where F can be substituted with a potential azimuth position F for the mobile station
in the range of 0 to 360 degrees. The potential azimuth position Om that results in the
closest match between the right and left sides of equation (5) can be used as estimated
azimuth position of the mobile station.
Based on the foregoing, the azimuth position of the mobile station can be
represented by the following equation:
F(0)=| (Gt1 (F )- Gt2 (F ) )+ (Pt1 - Pt2 )-(Pr1 - Pr2) | (6),
where F can be substituted with a potential azimuth position Fih for the mobile station
in the range of 0 to 360 degrees. The potential azimuth position F n that minimizes
(Fhti ) can be used as estimated azimuth position of the mobile station.
This process can also be expressed in the following equation:
min (Gt1 (F )- Gt2 (F ) )+ (Pt1 - Pt2 )-(Pr1 - Pr2) | (7).
Notably, the value selected for the initial potential azimuth position Fih in
equations (5) through (7) can be based at least in part on the knowledge of the
orientation and azimuth position of the serving sector antenna. Subsequent values
selected for the potential azimuth position Om can be based on whether the subsequent
result is approaching or receding from the desired result. Various techniques can also
be used to select subsequent values for the potential azimuth position Om based on the
magnitude of the difference between the subsequent result and the desired result as
well as the change in the difference between consecutive subsequent results and the
desired result.
With reference to FIG. 1, a bird's eye view of a coverage area of an exemplary
base station A in a wireless network shows an estimated geographic location for a
mobile station (UE) resulting from the process disclosed herein. A geographic location
for the mobile station (UE) based on GPS location is also shown for comparison. The X
and Y axes for the coverage area reflect distance in meters from the base station A.
Notably, the estimated geographic location is close to the GPS location.
The base station A includes a first sector antenna oriented at 27 degrees from
north (i.e., an angular position reference representing 0 / 360 degrees) and a second
sector antenna oriented at 267 degrees. The mobile station reported signal strength
measurements from the first and second sector antennas at - dB and -13 dB,
respectively. The angular position of the mobile station was estimated at 330.6 degrees
using the process disclosed herein. The measurements used to estimate the
geographic location of the mobile station were retrieved from per call measurement data
(PCMD) for an active call associated with the mobile station. For example, the PCMD
data may be stored by a wireless service provider during network operations for billing
purposes. The process disclosed herein may use signal strength measurements and
round trip measurements captured and retained during network operations via any
suitable techniques without requiring additional network overhead for collection of data
to perform the estimate of the geographic location of the mobile station.
With reference to FIG. 12, various data and calculations associated with the
process for estimating the geographic location of a mobile station is provided in a set of
graphs. The upper left graph shows an azimuth gain parameter characteristic for a first
sector antenna of a serving base station. The first sector antenna is oriented at 27
degrees from north (i.e., an angular position reference representing 0 / 360 degrees).
The middle left graph shows an azimuth gain parameter characteristic for a second
sector antenna of a serving base station. The second sector antenna is oriented at 267
degrees from north. The azimuth gain parameter characteristics may be manufacturer's
specifications of power measurements from the sector antennas from relatively close
(e.g., 10 meters) to the base station where little or no path loss is experienced. As
shown, the first and second sector antennas have the same azimuth gain characteristic
merely shifted by the orientation of the antennas. In other base station arrangements,
the sector antennas may have different azimuth gain characteristics.
The upper right graph shows an elevation gain parameter characteristic for the
first sector antenna. The first sector antenna is oriented at 2 degrees down from
horizontal (i.e., an elevation position reference representing 0 / 360 degrees). The
middle right graph shows an elevation gain parameter characteristic for the second
sector antenna. The second sector antenna is also oriented at 2 degrees down from
horizontal. The elevation gain parameter characteristics may be manufacturer's
specifications of power measurements from the sector antennas from relatively close
(e.g., 10 meters) to the base station where little or no path loss is experienced. As
shown, the first and second sector antennas have the same elevation gain
characteristic. In other base station arrangements, the sector antennas may have
different elevation gain characteristics. Also, the sector antennas may be oriented at
different angles from the horizontal in other base station arrangements.
The lower left graph is a composite graph showing the difference between gains
for the first and second sector antennas. The composite graph takes the azimuth and
elevation gain characteristics into account to form a composite delta gain characteristic.
The composite graph reflects differences in relation to varying azimuth position that
follows the azimuth gain characteristics and a relatively steady state component from
the elevation gain characteristics because the elevation tilt of the antennas is not
changing. The following equation is used to populate the composite graph:
(Gt1 ( )a + Gt1 e, - Gt1 max ) - (Gt2(0) a + Gt2 e, - Gt2 ma ) (8),
where Gt1 (F)3Z is the azimuth gain for the first sector antenna for a given azimuth angle
in relation to the angular position reference, Gt1 e is the elevation gain for the first
antenna associated with the elevation tilt, and Gt1 max is the maximum gain for the first
sector antenna. Similarly, Gt2 ( )az is the azimuth gain for the second sector antenna
for a given azimuth angle in relation to the angular position reference, Gt2e is the
elevation gain for the second antenna associated with the elevation tilt, and Gt2 max is
the maximum gain for the second sector antenna.
The lower right graph shows a function of the angular position of the mobile
station in relation to the delta antenna gain component, a delta transmit parameter
component, and a delta signal strength measurement component as defined above in
equation (7).
With reference to FiG. 4 , an exemplary embodiment of a process 400 for
estimating a geographic location of a mobile station within a coverage area of a wireless
network begins at 402 where a radial distance of a mobile station from a base station
serving the mobile station is determined. The base station includes multiple sector
antennas. The radial distance is based at least in part on a round trip measurement
associated with elapsed time between sending an outgoing signal from the base station
to the mobile station and receiving a corresponding acknowledgement signal from the
mobile station at the base station. At 404, a current angular position of the mobile
station in relation to the radial distance from the serving base station is calculated. The
current angular position is based at least in part on a first signal strength measurement,
a second signal strength measurement, and an angular position reference that extends
outward from the serving base station. The first and second signal strength
measurements representative of power characteristics of respective RF signals
received by the mobile station from corresponding first and second sector antennas of
the serving base station.
With reference to FIGs. 4 and 5, another exemplary embodiment of a process
500 for estimating a geographic location of a mobile station within a coverage area of a
wireless network includes the process 400 of FIG. 4 and continues at 502 where a
current geographic location of the mobile station in a coverage area of the wireless
network is identified in a geographic notation. The geographic notation is based at least
in part on combining the radial distance and current angular position of the mobile
station relative to the serving base station. In one embodiment, the radial distance and
current angular position reflect a polar coordinate-type of geographic notation in
reference to the serving base station. In other embodiments, the radial distance and
current angular position can be converted into various types of geographic notation,
such as a latitude/longitude notation, an address notation, or a geo-bin tile grid notation
associated with the coverage area for the wireless network.
In another embodiment, the process 500 also includes sending the current
geographic location of the mobile station in the geographic notation to a geo-location
storage node associated with the wireless network. In a further embodiment, the
determining, calculating, identifying, and sending are performed by the serving base
station.
In yet another embodiment, the process 500 also includes receiving the round trip
measurement, first signal strength measurement, and second signal strength
measurement from the serving base station via the wireless network at a geo-location
service node associated with the wireless network. In this embodiment, the current
geographic location of the mobile station is sent in the geographic notation to a geolocation
storage device associated with the geo-location service node. In the
embodiment being described, the receiving, determining, calculating, identifying, and
sending are performed by the geo-location service node.
In still another embodiment, the process 500 also includes receiving the round
trip measurement, first signal strength measurement, and second signal strength
measurement from the serving base station via the wireless network at a network
management node associated with the wireless network. In this embodiment, the round
trip measurement, first signal strength measurement, and second signal strength
measurement are stored at a measurements storage device associated with the
network management node. In the embodiment being described, the round trip
measurement, first signal strength measurement, and second signal strength
measurement are retrieved from the measurements storage device in conjunction with
the determining and calculating. In this embodiment, the process 500 also includes
sending the current geographic location of the mobile station in the geographic notation
to a geo-location storage device associated with the network management node. The
receiving, storing, retrieving, determining, calculating, identifying, and sending are
performed by the network management node in the embodiment being described.
With reference again to FIG. 4, in another embodiment of the process 400, the
round trip, first signal strength, and second signal strength measurements are related in
calendar time. In a further embodiment, the radial distance and current angular position
of the mobile station relative to the serving base station are indicative of a current
geographic location of the mobile station in a coverage area of the wireless network in
relation to the calendar time associated with the round trip, first signal strength, and
second signal strength measurements.
In yet another embodiment of the process 400, the first sector antenna is serving
the mobile station and referred to as a serving sector antenna and the second sector
antenna is disposed near the first sector antenna and referred to as a neighboring
sector antenna. In still another embodiment of the process 400, the round trip
measurement is measured by the serving base station. In a further embodiment, the
round trip measurement includes a RTD time measurement. In still yet another
embodiment of the process 400, the first and second signal strength measurements are
measured by the mobile station. In a further embodiment, the first and second signal
strength measurements include RSRP measurements, RSRQ measurements, or Ec/lo
measurements.
In another embodiment of the process 400, the calculating in 404 may include
retrieving first and second transmit parameter values from a storage device associated
with the wireless network. The first and second transmit parameter values
representative of power characteristics of respective communication signals to be
transmitted by the corresponding first and second sector antennas in this embodiment,
the calculating in 404 may also include determining a difference between the first and
second transmit parameter values to obtain a first angular position component.
In a further embodiment of the process 400, the calculating in 404 may also
include retrieving the first and second signal strength measurements from the storage
device. In this embodiment, the calculating in 404 may also include determining a
difference between the first and second signal strength measurements to obtain a
second angular position component.
In a yet further embodiment of the process 400, the calculating in 404 may also
include retrieving a first antenna elevation gain parameter value, a first antenna
maximum gain parameter value, and a first antenna azimuth gain parameter
characteristic from the storage device. The first antenna azimuth gain parameter
characteristic relating first antenna azimuth gain parameter values to variable azimuth
positions with respect to the angular position reference. The variable azimuth positions
representative of prospective azimuth positions of the mobile station in relation to the
angular position reference. The first antenna azimuth gain parameter characteristic
based at least in part on a first antenna position value representative of a first azimuth
position at which the first sector antenna is oriented in relation to the angular position
reference. In this embodiment, a second antenna elevation gain parameter value, a
second antenna maximum gain parameter value, and a second antenna azimuth gain
parameter characteristic are also retrieved from the storage device. The second
antenna azimuth gain parameter characteristic relating second antenna azimuth gain
parameter values to the variable azimuth positions. The second antenna azimuth gain
parameter characteristic based at least in part on a second antenna position value
representative of a second azimuth position at which the second sector antenna is
oriented in relation to the angular position reference.
In the embodiment being described, an angular value (e.g., not exceeding 360)
may be selected for the variable azimuth position. The first and second antenna
azimuth gain parameter characteristics may be used to identify the corresponding first
and second antenna azimuth gain parameter values for the variable azimuth position
associated with the selected angular value. In this embodiment, the calculating in 404
may continue by determining a difference between first and second transmit antenna
gains for the selected angular value. The difference may be determined by adding the
first antenna azimuth gain parameter value for the selected angular value to the first
antenna elevation gain parameter value and subtracting the first antenna maximum gain
parameter value to obtain the first transmit antenna gain, adding the second antenna
azimuth gain parameter value for the selected angular value to the second antenna
elevation gain parameter value and subtracting the second antenna maximum gain
parameter value to obtain the second transmit antenna gain, and subtracting the second
transmit antenna gain from the first transmit antenna gain to obtain a third angular
position component.
The angular value selected for the initial variable azimuth position can be based
at least in part on knowledge of which sector antenna is serving the mobile station and
the orientation and azimuth position of the serving sector antenna. Subsequent values
selected for the variable azimuth position can be based on whether the subsequent
result is approaching or receding from the desired result. Various techniques can also
be used to select subsequent values for the variable azimuth position based on the
magnitude of the difference between the subsequent result and the desired result as
well as the change in the difference between consecutive subsequent results and the
desired result.
For example, in a further embodiment of the process 400, the angular value
initially selected for the variable azimuth position may be between the first and second
antenna position values in this embodiment, the initial angular value may be
representative of a mid-point between the first and second antenna position values. In
other words, if the first antenna is oriented to 120 degrees in relation to the angular
reference position, a second antenna may be oriented to 240 degrees, and 180 may be
selected as the initial angular value for the variable azimuth position because it is at a
midpoint between the first and second sector antennas. The selection of other angular
values for the variable azimuth position can take into account whether the results are
getting better or worse to select angular values to obtain better results. The iterative
selection of angular values can be incremental or based on a factor of the difference
between the obtained result and the desired result.
In still another further embodiment of the process 400, the calculating in 404 also
includes adding the first and third angular position components and subtracting the
second angular position component to form an arithmetic result. In the embodiment
being described, the arithmetic result is converted to an absolute value in this
embodiment, if the absolute value is within a predetermined threshold of a desired value
(e.g., zero), the process 400 continues by identifying the angular value substituted for
the variable azimuth position as the current angular position for the mobile station.
Otherwise, the process 400 repeats the selecting with a different angular value, repeats
the determining of the difference between the first and second transmit gains to obtain a
new value for the third angular position component, repeats the adding and subtracting
to form the arithmetic result and the determining of the absolute value, and continues
the repeating until the absolute value is within the predetermined threshold of the
desired value.
In still yet another further embodiment of the process 400, the calculating in 404
also includes adding the first and third angular position components and subtracting the
second angular position component to form an arithmetic result. In this embodiment,
the arithmetic result is converted to an absolute value. In the embodiment being
described, the process 400 repeats the selecting with a different angular value, repeats
the determining of the difference between the first and second transmit gains to obtain a
new value for the third angular position component, repeats the adding and subtracting
to form the arithmetic result and the determining of the absolute value, and continues
the repeating until the absolute value is minimized in this embodiment, the process
400 continues by identifying the corresponding angular value substituted for the variable
azimuth position for which the absolute value is minimized as the current angular
position for the mobile station.
In another further embodiment of the process 400, the calculating in 404 includes
summing the first and third angular position components to form an arithmetic result and
comparing the arithmetic result to the second angular position component in this
embodiment, if the arithmetic result is within a predetermined range of the second
angular position component, the process 400 continues by identifying the angular value
substituted for the variable azimuth position as the current angular position for the
mobile station. Otherwise, the process 400 repeats the selecting with a different
angular value, repeats the determining of the difference between the first and second
transmit gains to obtain a new value for the third angular position component, repeats
the summing of the first and third angular position components to form the arithmetic
result and the comparing of the arithmetic result to the second angular position
component, and continues the repeating until the arithmetic result is within the
predetermined range of the second angular position component.
With reference to FIG. 6, an exemplary embodiment of an apparatus for
estimating a geographic location of a mobile station 600 within a coverage area of a
wireless network 602 includes a distance module 604 and an angular position module
606. The distance module 604 determines a radial distance of the mobile station 600
from a base station 608 serving the mobile station 600. The base station 608 includes
multiple sector antennas (e.g., 610, 612, 614). The radial distance is based at least in
part on a round trip measurement associated with elapsed time between sending an
outgoing signal from the base station 608 to the mobile station 600 and receiving a
corresponding acknowledgement signal from the mobile station 600 at the base station
608. The angular position module 606 is in operative communication with the distance
module 604 and calculates a current angular position of the mobile station 600 in
relation to the radial distance from the serving base station 608. The current angular
position is based at least in part on a first signal strength measurement, a second signal
strength measurement, and an angular position reference that extends outward from the
serving base station 608. The first and second signal strength measurements
representative of power characteristics of respective RF signals received by the mobile
station 600 from corresponding first and second sector antennas 610, 612 of the serving
base station 608. The current angular position may also be based on additional signal
strength measurements from other sector antennas 614 (e.g., sector antenna N).
In this embodiment, the apparatus may also include a location module 616 in
operative communication with the distance module 604 and angular position module
606 for identifying a current geographic location of the mobile station 600 in a coverage
area of the wireless network 602 in a geographic notation based at least in part on
combining the radial distance and current angular position of the mobile station 600
relative to the serving base station 608. In one embodiment, the radial distance and
current angular position reflect a polar coordinate-type of geographic notation in
reference to the serving base station. In other embodiments, the radial distance and
current angular position can be converted into various types of geographic notation,
such as a latitude/longitude notation, an address notation, or a geo-bin tile grid notation
associated with the coverage area for the wireless network.
In the embodiment being described, the apparatus may also include an output
module 618 in operative communication with the location module 616 for sending the
current geographic location of the mobile station 600 in the geographic notation to a
geo-location storage node 620 associated with the wireless network 602. The geolocation
storage node 620 may be internal or external to the wireless network 602. In
this embodiment, the apparatus may include the serving base station 608. In this
embodiment, the serving base station 608 may include the distance module 604,
angular position module 606, location module 616, and output module 618.
With reference to FIG. 7, an exemplary embodiment of an apparatus for
estimating a geographic location of a mobile station 700 within a coverage area of a
wireless network 702 includes a distance module 704 and an angular position module
706. The distance module 704 determines a radial distance of the mobile station 700
from a base station 708 serving the mobile station 700. The radial distance is based at
least in part on a round trip measurement associated with elapsed time between
sending an outgoing signal from the base station 708 to the mobile station 700 and
receiving a corresponding acknowledgement signal from the mobile station 700 at the
base station 708. The angular position module 706 is in operative communication with
the distance module 704 and calculates a current angular position of the mobile station
700 in relation to the radial distance from the serving base station 708. The current
angular position is based at least in part on a first signal strength measurement, a
second signal strength measurement, and an angular position reference that extends
outward from the serving base station 708. The first and second signal strength
measurements representative of power characteristics of respective RF signals
received by the mobile station 700 from corresponding first and second sector antennas
710, 712 of the serving base station 708. The current angular position may also be
based on additional signal strength measurements from other sector antennas 714
(e.g. , sector antenna N).
In this embodiment, the apparatus may also include a location module 716 in
operative communication with the distance module 704 and angular position module
706 for identifying a current geographic location of the mobile station 700 in a coverage
area of the wireless network 702 in a geographic notation based at least in part on
combining the radial distance and current angular position of the mobile station 700
relative to the serving base station 708.
In the embodiment being described, the apparatus may include a geo-location
service node 722 associated with the wireless network 702 and in operative
communication with the serving base station 708. In this embodiment, the geo-location
service node 722 may include the distance module 704, angular position module 706,
and location module 716.
The geo-location service node 722 may also include an input module 724 and an
output module 718. The input module 724 in operative communication with the distance
module 704 and angular position module 706 for receiving the round trip measurement,
first signal strength measurement, and second signal strength measurement from the
serving base station 708 via the wireless network 702. The output module 718 in
operative communication with the location module 716 for sending the current
geographic location of the mobile station 700 in the geographic notation to a geolocation
storage device 726 associated with the geo-location service node 722. The
geo-location storage device 726 may be internal or external to the geo-location service
node 722. If the geo-location storage device 726 is external to the geo-location service
node 722, the geo-location storage device 726 may be internal or external to the
wireless network 702.
With reference to FIG. 8, an exemplary embodiment of an apparatus for
estimating a geographic location of a mobile station 800 within a coverage area of a
wireless network 802 includes a distance module 804 and an angular position module
806. The distance module 804 determines a radial distance of the mobile station 800
from a base station 808 serving the mobile station 800. The radial distance is based at
least in part on a round trip measurement associated with elapsed time between
sending an outgoing signal from the base station 808 to the mobile station 800 and
receiving a corresponding acknowledgement signal from the mobile station 800 at the
base station 808. The angular position module 806 is in operative communication with
the distance module 804 and calculates a current angular position of the mobile station
800 in relation to the radial distance from the serving base station 808. The current
angular position is based at least in part on a first signal strength measurement, a
second signal strength measurement, and an angular position reference that extends
outward from the serving base station 808. The first and second signal strength
measurements representative of power characteristics of respective RF signals
received by the mobile station 800 from corresponding first and second sector antennas
810, 812 of the serving base station 808. The current angular position may also be
based on additional signal strength measurements from other sector antennas 814
(e.g., sector antenna N).
In this embodiment, the apparatus may also include a location module 816 in
operative communication with the distance module 804 and angular position module
806 for identifying a current geographic location of the mobile station 800 in a coverage
area of the wireless network 802 in a geographic notation based at least in part on
combining the radial distance and current angular position of the mobile station 800
relative to the serving base station 808.
In the embodiment being described, the apparatus may include a network
management node 828 associated with the wireless network 802 and in operative
communication with the serving base station 808. In this embodiment, the network
management node 828 may include the distance module 804, angular position module
806, and location module 816.
The network management node 828 may also include an input module 824, a
measurements storage device 830, and an output module 818. The input module 824
for receiving the round trip measurement, first signal strength measurement, and
second signal strength measurement from the serving base station 808 via the wireless
network 802. The measurements storage device 830 in operative communication with
the input module 824, distance module 804, and angular position module 806 for storing
the round trip measurement, first signal strength measurement, and second signal
strength measurement. In this embodiment, the distance module 804 retrieves the
round trip measurement from the measurements storage device 830 in conjunction with
determining the radial distance. Similarly, the angular position module 806 retrieves the
first and second signal strength measurements from the measurements storage device
830 in conjunction with calculating the current angular position. The output module 818
in operative communication with the location module 816 for sending the current
geographic location of the mobile station 800 in the geographic notation to the geolocation
storage device 826. The geo-location storage device 826 may be internal or
external to the network management node 828. if the geo-location storage device 826
is external to the network management node 828, the geo-location storage device 826
may be internal or external to the wireless network 802.
With reference to FIG. 9, an exemplary embodiment of an angular position
module 906 associated with the apparatus of FIGs. 6-8 may include a source data
communication sub-module 932 and a first angular component sub-module 938. The
source data communication sub-module 932 for retrieving first and second transmit
parameter values from a storage device 936 associated with the wireless network. The
first and second transmit parameter values representative of power characteristics of
respective communication signals to be transmitted by the corresponding first and
second sector antennas (e.g., 610, 612). in this embodiment, the first angular
component sub-module 938 is in operative communication with the source data
communication module 932 for determining a difference between the first and second
transmit parameter values to obtain a first angular position component.
ln a further embodiment of the angular position module 906, the source data
communication module may retrieve the first and second signal strength measurements
from the storage device 936. In this embodiment, the angular position module 906 may
also include a second angular component module 940 in operative communication with
the source data communication module 932 for determining a difference between the
first and second signal strength measurements to obtain a second angular position
component.
In a yet further embodiment of the angular position module 906, the source data
communication sub-module 932 may also retrieve a first antenna elevation gain
parameter value, a first antenna maximum gain parameter value, and a first antenna
azimuth gain parameter characteristic from the storage device 936. The first antenna
azimuth gain parameter characteristic relating first antenna azimuth gain parameter
values to variable azimuth positions with respect to the angular position reference. The
variable azimuth positions representative of prospective azimuth positions of the mobile
station 900 in relation to the angular position reference. The first antenna azimuth gain
parameter characteristic based at least in part on a first antenna position value
representative of a first azimuth position at which the first sector antenna 910 is oriented
in relation to the angular position reference.
In this embodiment, the source data communication sub-module 932 may also
retrieve a second antenna elevation gain parameter value, a second antenna maximum
gain parameter value, and a second antenna azimuth gain parameter characteristic
from the storage device 936. The second antenna azimuth gain parameter
characteristic relating second antenna azimuth gain parameter values to the variable
azimuth positions. The second antenna azimuth gain parameter characteristic based at
least in part on a second antenna position value representative of a second azimuth
position at which the second sector antenna 912 is oriented in relation to the angular
position reference.
In the embodiment being described, the angular position module 906 may also
include a third angular component sub-module 934 in operative communication with the
source data communication sub-module 932. The third angular component sub-module
934 for selecting an angular value (e.g., not exceeding 360) for the variable azimuth
position. The third angular component sub-module 934 using the first and second
antenna azimuth gain parameter characteristics to identify the corresponding first and
second antenna azimuth gain parameter values for the variable azimuth position
associated with the selected angular value.
In this embodiment, the third angular component sub-module 934 may also
determine a difference between first and second transmit antenna gains for the selected
angular value. The difference may be determined by adding the first antenna azimuth
gain parameter value for the selected angular value to the first antenna elevation gain
parameter value and subtracting the first antenna maximum gain parameter value to
obtain the first transmit antenna gain, adding the second antenna azimuth gain
parameter value for the selected angular value to the second antenna elevation gain
parameter value and subtracting the second antenna maximum gain parameter value to
obtain the second transmit antenna gain, and subtracting the second transmit antenna
gain from the first transmit antenna gain to obtain a third angular position component.
The angular value selected for the initial variable azimuth position can be based
at least in part on knowledge of which sector antenna is serving the mobile station and
the orientation and azimuth position of the serving sector antenna. Subsequent values
selected for the variable azimuth position can be based on whether the subsequent
result is approaching or receding from the desired result. Various techniques can also
be used to select subsequent values for the variable azimuth position based on the
magnitude of the difference between the subsequent result and the desired result as
well as the change in the difference between consecutive subsequent results and the
desired result.
For example, in a further embodiment of the angular position module 906, the
angular value initially selected for the variable azimuth position by the third angular
component sub-module 934 may be between the first and second antenna position
values. In this embodiment, the initial angular value may be representative of a mid
point between the first and second antenna position values. In other words, if the first
antenna is oriented to 120 degrees in relation to the angular reference position, a
second antenna may be oriented to 240 degrees, and 180 may be selected as the initial
angular value for the variable azimuth position because it is at a midpoint between the
first and second sector antennas. The selection of other angular values for the variable
azimuth position can take into account whether the results are getting better or worse to
select angular values to obtain better results. The iterative selection of angular values
can be incremental or based on a factor of the difference between the obtained result
and the desired result.
In a yet further embodiment, the angular position module 906 may include an
arithmetic sub-module 942 and a control sub-module 944. In this embodiment, the
arithmetic sub-module 942 is in operative communication with the first, second, and
third angular component modules 938, 940, 934 for adding the first and third angular
position components and subtracting the second angular position component to form an
arithmetic result. In the embodiment being described, the arithmetic sub-module 942
converts the arithmetic result to an absolute value. The control sub-module 944 is in
operative communication with the arithmetic sub-module 942 and the third angular
component sub-module 934 for identifying the angular value substituted for the variable
azimuth position as the current angular position for the mobile station 900 if the
arithmetic result is within a predetermined threshold of a desired value (e.g., zero).
Otherwise, the control sub-module 944 may causes the third angular component
module 934 to repeat the selecting with a different angular value and the determining of
the difference between the first and second transmit gains to obtain a new value for the
third angular position component, causes the arithmetic sub-module 942 to repeat the
adding and subtracting to form the arithmetic result and the determining of the absolute
value, and causes the repeating to continue until the arithmetic result is within the
predetermined threshold of the desired value.
In an alternate further embodiment, the arithmetic sub-module 942 may be in
operative communication with the first, second, and third angular component modules
938, 940, 934 for adding the first and third angular position components and subtracting
the second angular position component to form an arithmetic result in the embodiment
being described, the arithmetic sub-module 942 converts the arithmetic result to an
absolute value. In this embodiment, the control sub-module 944 may be in operative
communication with the arithmetic sub-module 942 and the third angular component
module 934 for causing the third angular component sub-module 934 to repeat the
selecting with a different angular value and the determining of the difference between
the first and second transmit gains to obtain a new value for the third angular position
component, causing the arithmetic sub-module 942 to repeat the adding and subtracting
to form the arithmetic result and the determining of the absolute value, and causing the
repeating to continue until the absolute value is minimized. In the embodiment being
described, the control sub-module 944 identifies the corresponding angular value
substituted for the variable azimuth position for which the absolute value is minimized
as the current angular position for the mobile station 900.
In another alternate further embodiment, the arithmetic sub-module 942 may be
in operative communication with the first, second, and third angular component modules
938, 940, 934 for summing the first and third angular position components to form an
arithmetic result. In the embodiment being described, the arithmetic sub-module 942
compares the arithmetic result to the second angular position component 940. In this
embodiment, the control sub-module 944 may be in operative communication with the
arithmetic sub-module 942 and the third angular component sub-module 934 for
identifying the angular value substituted for the variable azimuth position as the current
angular position for the mobile station if the arithmetic result is within a predetermined
range of the second angular position component. Otherwise, the control sub-module
944 causes the third angular component module 934 to repeat the selecting with a
different angular value and the determining of the difference between the first and
second transmit gains to obtain a new value for the third angular position component,
causes the arithmetic sub-module 942 to repeat the summing of the first and third
angular position components to form the arithmetic result and the comparing of the
arithmetic result to the second angular position component, and cause the repeating to
continue until the arithmetic result is within the predetermined range of the second
angular position component.
With reference to FIG. 10, an exemplary embodiment of a non-transitory
computer-readable medium storing program instructions that, when executed by a
computer, cause a corresponding computer-controlled device to perform a process
1000 for estimating a geographic location of a mobile station within a coverage area of a
wireless network in one embodiment, the process 1000 begins at 1002 where a radial
distance of a mobile station from a base station serving the mobile station is
determined. The base station including multiple sector antennas. The radial distance is
based at least in part on a round trip measurement associated with elapsed time
between sending an outgoing signal from the base station to the mobile station and
receiving a corresponding acknowledgement signal from the mobile station at the base
station. At 1004, a current angular position of the mobile station in relation to the radial
distance from the serving base station is calculated. The current angular position is
based at least in part on a first signal strength measurement, a second signal strength
measurement, and an angular position reference that extends outward from the serving
base station, the first and second signal strength measurements representative of
power characteristics of respective RF signals received by the mobile station from
corresponding first and second sector antennas of the serving base station. Next, a
current geographic location of the mobile station in a coverage area of the wireless
network may be identified in a geographic notation (1006).
In various embodiments, the program instructions stored in the non-transitory
computer-readable memory, when executed by the computer, may cause the computercontrolled
device to perform various combinations of functions associated with the
various embodiments of the processes 400, 500 for estimating a geographic location of
a mobile station described above with reference to FIGs. 4 and 5 . in other words, the
various embodiments of the processes 400, 500 described above may also be
implemented by corresponding embodiments of the process 1000 associated with the
program instructions stored in the non-transitory computer-readable memory.
Likewise, in various embodiments, the program instructions stored in the nontransitory
computer-readable memory, when executed by the computer, may cause the
computer-controlled device to perform various combinations of functions associated
with the various embodiments of the apparatus for estimating a geographic location of a
mobile station described above with reference to FIGs. 6-8 and the angular position
module 906 described above with reference to FIG. 9.
For example, the computer-controlled device may include a base station (see
FIG. 6, 608), a geo-location service node (see FIG. 7, 722), a network management
node (see FIG. 8, 828), or any suitable communication node associated with the
wireless network. Any suitable module or sub-module described above with reference
to FIGs. 6-9 may include the computer and non-transitory computer-readable memory
associated with the program instructions. Alternatively, the computer and non-transitory
computer-readable memory associated with the program instructions may be individual
or combined components that are in operative communication with any suitable
combination of the modules and sub-modules described above with reference to FIGs.
6-9
The above description merely provides a disclosure of particular embodiments of
the invention and is not intended for the purposes of limiting the same thereto. As such,
the invention is not limited to only the above-described embodiments. Rather, it is
recognized that one skilled in the art could conceive alternative embodiments that fall
within the scope of the invention.

We claim:
1. A method for estimating a geographic location of a mobile station within a
coverage area of a wireless network, comprising:
determining a radial distance of a mobile station from a base station serving the
mobile station, the base station including multiple sector antennas, the radial distance
based at least in part on a round trip measurement associated with elapsed time
between sending an outgoing signal from the base station to the mobile station and
receiving a corresponding acknowledgement signal from the mobile station at the base
station; and
calculating a current angular position of the mobile station in relation to the radial
distance from the serving base station based at least in part on a first signal strength
measurement, a second signal strength measurement, and an angular position
reference that extends outward from the serving base station, the first and second
signal strength measurements representative of power characteristics of respective
radio frequency (RF) signals received by the mobile station from corresponding first and
second sector antennas of the serving base station.
2. The method of claim 1, further comprising:
identifying a current geographic location of the mobile station in a coverage area
of the wireless network in a geographic notation based at least in part on combining the
radial distance and current angular position of the mobile station relative to the serving
base station.
3. The method of claim 2, further comprising:
sending the current geographic location of the mobile station in the geographic
notation to a geo-location storage node associated with the wireless network.
4. The method of claim 2, further comprising:
receiving the round trip measurement, first signal strength measurement, and
second signal strength measurement from the serving base station via the wireless
network at a geo-location service node associated with the wireless network; and
sending the current geographic location of the mobile station in the geographic
notation to a geo-location storage device associated with the geo-location service node;
wherein the receiving, determining, calculating, identifying, and sending are
performed by the geo-location service node.
5. The method of claim 2, further comprising:
receiving the round trip measurement, first signal strength measurement, and
second signal strength measurement from the serving base station via the wireless
network at a network management node associated with the wireless network;
storing the round trip measurement, first signal strength measurement, and
second signal strength measurement at a measurements storage device associated
with the network management node;
retrieving the round trip measurement, first signal strength measurement, and
second signal strength measurement from the measurements storage device in
conjunction with the determining and calculating; and
sending the current geographic location of the mobile station in the geographic
notation to a geo-location storage device associated with the network management
node;
wherein the receiving, storing, retrieving, determining, calculating, identifying,
and sending are performed by the network management node.
6. The method of claim , the calculating comprising:
retrieving first and second transmit parameter values from a storage device
associated with the wireless network, the first and second transmit parameter values
representative of power characteristics of respective communication signals to be
transmitted by the corresponding first and second sector antennas; and
determining a difference between the first and second transmit parameter values
to obtain a first angular position component.
7. The method of claim 6, the calculating further comprising:
retrieving the first and second signal strength measurements from the storage
device; and
determining a difference between the first and second signal strength
measurements to obtain a second angular position component.
8. An apparatus for estimating a geographic location of a mobile station within a
coverage area of a wireless network, comprising:
a distance module for determining a radial distance of a mobile station from a
base station serving the mobile station, the base station including multiple sector
antennas, the radial distance based at least in part on a round trip measurement
associated with elapsed time between sending an outgoing signal from the base station
to the mobile station and receiving a corresponding acknowledgement signal from the
mobile station at the base station; and
an angular position module in operative communication with the distance module
for calculating a current angular position of the mobile station in relation to the radial
distance from the serving base station based at least in part on a first signal strength
measurement, a second signal strength measurement, and an angular position
reference that extends outward from the serving base station, the first and second
signal strength measurements representative of power characteristics of respective
radio frequency (RF) signals received by the mobile station from corresponding first and
second sector antennas of the serving base station.
9. The apparatus of claim 8, further comprising:
a location module in operative communication with the distance module and
angular position module for identifying a current geographic location of the mobile
station in a coverage area of the wireless network in a geographic notation based at
least in part on combining the radial distance and current angular position of the mobile
station relative to the serving base station.
0. The apparatus of claim 8, the angular position module comprising:
a source data communication sub-module for retrieving first and second transmit
parameter values from a storage device associated with the wireless network, the first
and second transmit parameter values representative of power characteristics of
respective communication signals to be transmitted by the corresponding first and
second sector antennas; and
a first angular component sub-module in operative communication with the
source data communication sub-module for determining a difference between the first
and second transmit parameter values to obtain a first angular position component.