Automatic reception window for geo-locating WLAN devices
A method for determining reception window timing using a measuring station receiving an antenna beam width, receiving an antenna tilt angle, receiving an altitude A, determining a far projection angle Δf, determining a near projection angle Δn, and determining a far projection range corresponding to the far projection angle Δf and based at least upon the values of Δf and A. The method further includes determining a near projection range corresponding to the near projection angle Δn and based at least upon the values of Δn and A, determining an end time of a reception window based at least upon the value of the far projection range the reception window being a window of time in which a response from the target station is expected to be received, and determining a start time of the reception window based at least upon the value of the near projection range.
1. A method for determining reception window timing using a measuring station, the measuring station comprising a directional antenna having a boresight, the measuring station transmitting signals to a target station, the measuring station receiving response signals from the target station corresponding to the transmitted signals, the method further comprising:
receiving an antenna beam width 2Φ;
receiving an antenna tilt angle θ;
receiving an altitude A, where A is an altitude of the measuring station above ground level;
determining a far projection angle Δf based at least upon a far signal strength at ground level, the far signal strength being a far predetermined fraction of a maximum signal strength at ground level, the far predetermined fraction being based at least in part upon the beam width 2Φ and tilt angle θ;
determining a near projection angle Δn based at least upon a near signal strength at ground level, the near signal strength being a near predetermined fraction of the maximum signal strength at ground level, the near predetermined fraction being based upon the beam width 2Φ and tilt angle θ;
determining a far projection range, Rf, corresponding to the far projection angle Δf and based at least upon the values of Δf and A;
determining a near projection range, Rn, corresponding to the near projection angle Δn and based at least upon the values of Δn and A;
determining an end time of a reception window, Tt, based at least upon the value of the far projection range, Rf, the reception window being a window of time in which a response from the target station is expected to be received; and
determining a start time of the reception window based at least upon the value of the near projection range, Rn.
2. The method of claim 1 , wherein the far projection angle Δf is determined from a formula given by:
(sin 2 (Δ f )cos N (ψ))/(sin 2 (θ+ψmax)cos N (ψmax))=Fraction,
(ψ) being a deviation in degrees from the boresight of the directional antenna,
(ψmax) being a deviation from the boresight of the directional antenna that corresponds to a maximum gain at the ground level,
(θ+ψ) being a pitch angle,
(θ+ψmax) being the pitch angle of the maximum antenna gain at the ground level,
cos N (x) being an antenna gain at angle x, x being an angle from one of a center of the directional antenna and the boresight of the directional antenna, and
Fraction being a predetermined fraction.
3. The method of claim 1 , wherein the near projection angle Δn is determined from a formula given by:
(sin 2 (Δ n )cos N (ψ))/(sin 2 (θ+ψmax)cos N (ψmax))=Fraction,
(ψ) being a deviation in degrees from the boresight of the directional antenna,
(ψmax) being a deviation from the boresight of the directional antenna that corresponds to a maximum gain at the ground level,
(θ+ψ) being a pitch angle,
(θ+ψmax) being the pitch angle of the maximum antenna gain at the ground level,
cos N (x) being an antenna gain at angle x, x being an angle from one of a center of the directional antenna and the boresight of the directional antenna, and
Fraction being a predetermined fraction.
4. The method of claim 1 , wherein the near predetermined fraction of the maximum signal strength at the ground level is 1/15.8, and the far predetermined fraction of the maximum signal strength at the ground level is 1/15.8.
5. The method of claim 4 , wherein the far projection angle Δf is determined as:
Δ f =(−14.83+1.08Φ−0.013Φ 2 )+(1.11−0.061Φ+0.00085Φ 2 )θ+(0.00069+0.00028Φ−0.0000057Φ 2 )θ 2 ,
2Φ being a beam width of the directional antenna.
6. The method of claim 4 , wherein the near projection angle Δn is determined as:
Δ n =(−6.35+3Δ8Φ−0.034Φ 2 )+(1.04−0.019Φ+0.0004Φ 2 )θ+(0.000156+0.000062Φ−0.0000027Φ 2 )θ 2 ,
2Φ being a beam width of the directional antenna.
7. The method of claim 1 , wherein the far projection range Rf is determined as:
R
f
=
{
Δ
f
=
0
°
,
R
fmax
A
sin
(
Δ
f
)
>
R
fmax
,
R
fmax
A
sin
(
Δ
f
)
,
Where
Δ
f
=
{
Δ
f
<
0
°
,
0
°
Δ
f
<
θ
,
θ
,
Rfmax being a maximum value for Rf derived from the time between successive transmitted ranging packets.
8. The method of claim 1 , wherein the near projection range Rn is determined as:
R
n
=
{
Δ
n
>
90
°
,
A
A
sin
(
Δ
n
)
.
9. The method of claim 1 , wherein the reception window end time Tt is determined as:
T
t
=
{
Δ
f
=
0
°
,
T
tmax
2
R
f
c
+
t
SIFS
>
T
tmax
,
T
tmax
2
R
f
c
+
t
SIFS
,
Where
Δ
f
=
{
Δ
f
<
0
°
,
0
°
Δ
f
<
θ
,
θ
,
Rf=A/sin(Δf),
c=speed of light,
T max being a maximum value for Tt derived from a time between successive transmitted ranging packets, and
t SIFS being a short interframe spacing time.
10. The method of claim 9 , wherein the maximum value for the reception window end time, T tmax is determined as:
T tmax =( Tp−tp−tr )
Tp being the time between transmitted request packets,
tp being the duration of the request packet, and
tr is the duration of the response packet.
11. The method of claim 7 , wherein a maximum value of the far projection range, Rfmax, is determined as:
Rf max= c ( Tt max− t SIFS )/2
where c=speed of light,
T tmax being a maximum value for Tt, and
t SIFS being the short interframe spacing time.
12. The method of claim 1 , wherein a reception window start time Ts, is determined as:
T
s
=
{
Δ
n
>
90
°
,
2
A
c
+
t
SIFS
2
R
n
c
+
t
SIFS
,
where Rn=A/sin (Δn),
c=speed of light, and
t SIFS being the short interframe spacing time.
13. An apparatus for determining reception window timing using a measuring station, the measuring station comprising a directional antenna having a boresight, the measuring station transmitting signals to a target station, the measuring station receiving response signals from the target station corresponding to the transmitted signals, the apparatus comprising:
processing circuitry in communication with the apparatus, the processing circuitry configured to:
receive an antenna beam width 2Φ;
receive an antenna tilt angle θ;
receive an altitude A, where A is the altitude of the measuring station above ground level;
determine a far projection angle Δf based at least upon a far signal strength at ground level, the far signal strength being a far predetermined fraction of a maximum signal strength at ground level, the far predetermined fraction being based at least in part upon the beam width 2Φ and tilt angle θ;
determine a near projection angle Δn based at least upon a near signal strength at ground level, the near signal strength being a near predetermined fraction of the maximum signal strength at ground level, the near predetermined fraction being based upon the beam width 2Φ and tilt angle θ;
determine a far projection range, Rf, corresponding to the far projection angle Δf and based upon the values of Δf and A;
determine a near projection range, Rn, corresponding to the near projection angle Δn and based at least upon the values of Δn and A; and
determine an end time of a reception window, Tt, based at least upon the value of the far projection range, Rf, the reception window being a window of time in which a response from the target station is expected to be received; and
determine a start time of the reception window based at least upon the value of the near projection range, Rn.
14. The apparatus of claim 13 , wherein the far projection angle Δf is determined from the formula:
(sin 2 (Δ f )cos N (ψ))/(sin 2 (θ+ψmax)cos N (ψmax))=Fraction,
(ψ) being a deviation in degrees from the boresight of the directional antenna,
(ψmax) being a deviation from the boresight of the directional antenna that corresponds to a maximum gain at the ground level,
(θ+ψ) being a pitch angle,
(θ+ψmax) being the pitch angle of the maximum antenna gain at the ground level, and
cos N (x) being an antenna gain at angle x, x being an angle from one of a center of the directional antenna and the boresight of the directional antenna, and
Fraction being a predetermined fraction.
15. The first wireless device of claim 13 , wherein the near projection angle Δn is determined from the formula:
(sin 2 (Δ n )cos N (ψ))/(sin 2 (θ+ψmax)cos N (ψmax))=Fraction,
(ψ) being a deviation in degrees from the boresight of the directional antenna,
(ψmax) being a deviation from the boresight of the directional antenna that corresponds to a maximum gain at the ground level,
(θ+ψ) being a pitch angle,
(θ+ψmax) being the pitch angle of the maximum antenna gain at the ground level,
cos N (x) being an antenna gain at angle x, x being an angle from one of a center of the directional antenna and the boresight of the directional antenna, and
Fraction being a predetermined fraction.
16. The apparatus of claim 13 , wherein the near predetermined fraction of the maximum signal strength at the ground level is 1/15.8, and the far predetermined fraction of the maximum signal strength at the ground level is 1/15.8.
17. The apparatus of claim 16 , wherein the far projection angle Δf is determined as:
Δ f =(−14.83+1.08Φ−0.013Φ 2 )+(1.11−0.061Φ+0.00085Φ 2 )θ+(0.00069+0.00028Φ−0.0000057Φ 2 )θ 2 ,
2Φ being a beam width of the directional antenna.
18. The apparatus of claim 16 , wherein the near projection angle Δn is determined as:
Δ n =(−6.35+3Δ8Φ−0.034Φ 2 )+(1.04−0.019Φ+0.0004Φ 2 )θ+(0.000156+0.000062Φ−0.0000027Φ 2 )θ 2 ,
2Φ being a beam width of the directional antenna.
19. The apparatus of claim 13 , wherein the far projection range Rf is determined as:
R
f
=
{
Δ
f
=
0
°
,
R
fmax
A
sin
(
Δ
f
)
>
R
fmax
,
R
fmax
A
sin
(
Δ
f
)
,
Where
Δ
f
=
{
Δ
f
<
0
°
,
0
°
Δ
f
<
θ
,
θ
,
Rfmax being a maximum value for Rf derived from the time between successive transmitted ranging packets.
20. The apparatus of claim 13 , wherein the near projection range Rn is determined as:
R
n
=
{
Δ
n
>
90
°
,
A
A
sin
(
Δ
n
)
.
21. The apparatus of claim 13 , wherein the reception window end time Tt, is determined as:
T
t
=
{
Δ
f
=
0
°
,
T
tmax
2
R
f
c
+
t
SIFS
>
T
tmax
,
T
tmax
2
R
f
c
+
t
SIFS
,
Where
Δ
f
=
{
Δ
f
<
0
°
,
0
°
Δ
f
<
θ
,
θ
,
Rf=A/sin(Δ),
c=speed of light,
T max being a maximum value for Tt derived from a time between successive transmitted ranging packets, and
t SIFS being a short interframe spacing time.
22. The apparatus of claim 13 , wherein the reception window start time Ts, is determined as:
T
s
=
{
Δ
n
>
90
°
,
2
A
c
+
t
SIFS
2
R
n
c
+
t
SIFS
,
where Rn=A/sin (Δn),
c=speed of light, and
t SIFS being the short interframe spacing time.
23. A measuring station for determining reception window timing, the measuring station comprising a directional antenna in communication with a transmitter receiver, the measuring station comprising:
the transmitter receiver configured to:
transmit radio frequency (RF) signals, including RF signals to a target station;
receive RF signals, including RF signals from a target station corresponding to the transmitted RF signals;
a processing circuitry configured to:
receive an antenna beam width 2Φ;
receive an antenna tilt angle θ;
receive an altitude A, where A is the altitude of the measuring station above ground level;
determine a far projection angle Δf based at least upon a far signal strength at ground level, the far signal strength being a far predetermined fraction of a maximum signal strength at ground level, the far predetermined fraction being based at least in part upon the beam width 2Φ and tilt angle θ;
determine a near projection angle Δn based at least upon a near signal strength at ground level, the near signal strength being a near predetermined fraction of the maximum signal strength at ground level, the near predetermined fraction being based upon the beam width 2Φ and tilt angle θ;
determine a far projection range, Rf, corresponding to the far projection angle Δf and based at least upon the values of Δf and A;
determine a near projection range, Rn, corresponding to the near projection angle Δn and based at least upon the values of Δn and A;
determine an end time of a reception window, Tt, based at least upon the value of the far projection range, Rf, the reception window being a window of time in which a response from the target station is expected to be received; and
determine a start time of the reception window based at least upon the value of the near projection range, Rn.