Method for predicting outdoor three-dimensional space signal field strength by extended COST-231-Walfisch-Ikegami propagation model
A method for predicting outdoor three-dimensional space signal field strength by extended COST-231-Walfisch-Ikegami propagation model, comprising: establishing a three-dimensional scene model between a transmitting base station and a predicted region space; performing an on-site measurement according to a certain resolution in a prediction region and recording wireless signal strength information at a height of 1 m above the ground; acquiring a vertical cross section between the transmitting base station and a receiving point at a height of 1 m above the ground, and acquiring therefrom an average roof height, an average street width and an average between-building space; predicting a reception signal strength at a measurement point in a calculation formula of a COST-231-Walfishch-Ikegami propagation model; correcting the COST-231-Walfishch-Ikegami propagation model of the measurement point according to an error Δ between measured data and a prediction result; acquiring a vertical cross section between the transmitting base station and a receiving point at other height of the measurement point, and filtering therefrom buildings outside a Fresnel circle to re-acquire the average roof height, the average street width and the average between-building space; and calculating a reception signal strength at other height of the measurement point according to the corrected COST-231-Walfishch-Ikegami propagation model.
1. A method for predicting outdoor three-dimensional space signal field strength by an extended COST-231-Walfisch-Ikegami propagation model, comprising:
(1) establishing a three-dimensional scene model from a transmitting base station to a predicted region space:
establishing the three-dimensional scene model from the transmitting base station to the predicted region space by importing GIS format map, the three-dimensional scene model comprises street information and three-dimensional building models of all buildings within a scope of the transmitting base station and a prediction region;
wherein the buildings within the scope of the transmitting base station and the prediction region are determined as all buildings within a first Fresnel circle between the transmitting base station and receiving points of the prediction region; radius r of the first Fresnel circle is calculated by
r
=
λ
d
1
d
2
d
,
wherein λ is wavelength of electromagnetic wave, d represents distance from the transmitting base station to a receiving point, S represents an infinite plane that is perpendicular to a line connecting a transmitting point and a receiving point, and d 1 and d 2 represent distances between the transmitting base station and the plane S and between the receiving point and the plane S respectively; the three-dimensional building model information includes building outer envelope information, building height information h roof , and building geographical location information; and the street information includes street width information w, and street geographical location information;
(2) measuring a wireless signal strength at a height of 1 m within the prediction region using existing instruments according to a fixed resolution to form measurement data (x, y, z, M rx ) of each receiving point;
the measurement data of each receiving point includes location information and wireless signal strength information of the receiving point, wherein x is longitude information of the receiving point, y is latitude information of the receiving point, z is height information of the receiving point, and M rx is reception signal strength;
(3) predicting reception signal strength of a measurement point at a height of 1 m according to the COST-231-Walfisch-Ikegami propagation model;
acquiring a vertical cross section between the transmitting base station and a measurement point at a height of 1 m above the ground, and acquiring therefrom key parameters of the COST-231-Walfisch-Ikegami propagation model, wherein the key parameters include an average roof height h roof , an average street width w, an average between-building space b, a base station height h tx , a receiving point height h rx , a base station transmitting power W, a base station transmitting signal frequency f, a distance d between the base station and the measurement point, and an angle φ between an incident direction of a base station direct wave and a direction of a street to which the measurement point belongs;
predicting a reception signal strength T rx of the receiving point according to a calculation formula of the COST-231-Walfisch-Ikegami propagation model, comprising steps (3-1) to (3-3):
(3-1): calculating propagation losses of line-of-sight propagation and non-line-of-sight propagation between the base station and a test point respectively, by calculating a propagation loss L blos of line-of-sight propagation in accordance with step (3-2) and calculating a propagation loss L bNlos of non-line-of-sight propagation in accordance with step (3-3), therefore propagation loss L b is represented as a following formula:
L
b
=
{
L
blos
,
when
there
is
line
-
of
-
sight
propagation
from
a
transmitting
point
to
a
receiving
point
L
bNlos
,
when
there
is
non
-
line
-
of
-
sight
propagation
from
a
transmitting
point
to
a
receiving
point
(3-2): if there is line-of-sight propagation between the base station and the test point, the propagation loss is calculated by a formula L blos =42.6+26lgd+20lgf;
(3-3): if there is non-line-of-sight propagation between the base station and the test point, the propagation loss is calculated by a formula L bNlos =L bs +L rts +L msd , wherein L bs is propagation loss of a free space, L rts is diffraction and scattering loss from the roof to the street, L msd is diffraction loss of multiple barriers, and L bs , L rts and L msd are calculated by a specific method including steps (3-3-1) to (3-3-3):
(3-3-1): in step (3-3), L bs is calculated by a formula:
L bs =32.45+20 lgd+ 20 lgf;
(3-3-2): in step (3-3), L rts is calculated by a formula:
L
rts
=
{
-
16.9
-
10
lgw
+
10
lgf
+
20
lg
(
h
roof
-
h
rx
)
+
L
ori
,
when
h
roof
>
h
rx
0
,
when
L
rts
<
0
wherein
L
ori
=
{
-
10
+
0.354
ϕ
,
0
°
≤
ϕ
<
35
°
2.5
+
0.075
×
(
ϕ
-
35
)
,
35
°
≤
ϕ
<
55
°
4.0
-
0.114
×
(
ϕ
-
35
)
,
55
°
≤
ϕ
<
90
°
(3-3-3): in step (3-3), L msd is calculated by a formula:
L
msd
=
{
L
bsh
+
K
a
+
K
d
lgd
+
K
f
lgf
-
9
lgb
0
,
when
L
msd
<
0
wherein,
L
bsh
=
{
-
18
lg
(
1
+
h
tx
-
h
roof
)
,
h
tx
>
h
roof
0
,
when
h
tx
≤
h
roof
K
a
=
{
54
,
h
tx
>
h
roof
54
-
0.8
×
(
h
tx
-
h
roof
)
,
d
≥
05
km
and
h
tx
≤
h
roof
54
-
0.8
×
(
h
tx
-
h
roof
)
×
(
d
0.5
)
,
d
<
0.5
km
and
h
tx
≤
h
roof
K
d
=
{
18
,
h
tx
>
h
roof
18
-
15
(
h
tx
-
h
roof
h
roof
-
h
rx
)
,
h
tx
≤
h
roof
K
f
=
-
4
+
{
0.7
×
(
f
925
-
1
)
,
for
a
medium
-
sized
city
and
a
suburban
center
having
trees
of
medium
density
1.5
×
(
f
925
-
1
)
,
for
center
of
a
big
city
(3-4) when there is line-of-sight propagation between the transmitting base station and the test point, the reception signal field strength of the test point is T los =W−L blos ;
when there is non-line-of-sight propagation between the transmitting base station and the test point, the reception signal field strength of the test point is T Nlos =W−L bNlos , therefore the signal field strength of the test point is represented as:
T
rx
=
{
T
los
=
W
-
L
blos
,
when
there
is
line
-
of
-
sight
propagation
from
a
transmitting
point
to
a
receiving
point
T
Nlos
=
W
-
L
bNlos
,
when
there
is
line
-
of
-
sight
propagation
from
a
transmitting
point
to
a
receiving
point
;
(4) calculating an error Δ=M rx −T rx between a measured value and a predicted value according to the actually measured field strength M rx and a predicted field strength T rx of the test point, and correcting the calculation formula of the COST-231-Walfisch-Ikegami propagation model of the test point;
(5) acquiring a vertical cross section between the transmitting base station and the receiving point at an extended height h rx ′ of the test point, and filtering therefrom buildings outside the first Fresnel circle between the transmitting point and the receiving point, to re-acquire key parameters of the COST-231-Walfisch-Ikegami propagation model and calculating the reception signal strength at the extended height h rx ′ according to the corrected COST-231-Walfisch-Ikegami propagation model;
(6) changing height of h rx ′, repeating step (5), and calculating reception signal strength at all extended heights on the receiving point using an algorithm of the corrected COST-231-Walfisch-Ikegami propagation model;
(7) changing the location of the test point, repeating steps (3) to (6), and calculating reception signal strength at all extended heights on all the test points to acquire a prediction signal field strength in a three-dimensional space of an outdoor area of a building within the prediction region.
2. The method for predicting outdoor three-dimensional space signal field strength by the extended COST-231-Walfisch-Ikegami propagation model according to claim 1 , wherein a correction value between the actually measured field strength M rx and the predicted field strength T rx in step (4) includes a corrected value Δ los of line-of-sight propagation and a corrected value Δ Nlos of non-line-of-sight propagation:
Δ
=
M
rx
-
T
rx
=
{
Δ
los
=
M
rx
-
T
los
,
when
there
is
line
-
of
-
sight
propagation
from
a
transmitting
point
to
a
receiving
point
Δ
Nlos
=
M
rx
-
T
Nlos
,
when
there
is
non
-
line
-
of
-
sight
propagation
from
a
transmitting
point
to
a
receiving
point
3. The method for predicting outdoor three-dimensional space signal field strength by the extended COST-231-Walfisch-Ikegami propagation model according to claim 1 , wherein step (5) comprises calculating the reception signal strength at the extended height h rx ′ of the test point in step (3) using the calculation formula of the corrected COST-231-Walfisch-Ikegami propagation model in step (4), including steps (5-1) to (5-2):
(5-1) acquiring a vertical cross section between the transmitting base station and the extended height h rx ′ of the test point, and filtering therefrom buildings outside the first Fresnel circle between the transmitting point and the receiving point, a calculation method of the radius r of the first Fresnel circle is the same as that of the step (1),
r
=
λ
d
1
d
2
d
,
wherein, d represents distance from the transmitting base station to the receiving point, S represents the infinite plane that is perpendicular to the line connecting the transmitting point and the receiving point, d 1 and d 2 represent distance between the transmitting base station and the plane S and between the receiving point and the plane S respectively, the first Fresnel radius is a radius of a circle that is formed by intersecting the plane S and a Fresnel ellipsoid;
(5-2) re-acquiring key parameters of the COST-231-Walfisch-Ikegami propagation model according to three-dimensional building and street information after filtered out the first Fresnel circle, calculating field strength T rx ′ of the receiving point using the formula of the step (3), and correcting the receiving point signal field strength using a correction parameter Δ calculated in the step (4), and the corrected receiving point field strength is represented as T rx ″=T rx ′+Δ.
4. The method for predicting outdoor three-dimensional space signal field strength by the extended COST-231-Walfisch-Ikegami propagation model according to claim 1 , wherein step (6) comprises changing a value of h rx ′ at a height interval according to a predicted resolution; repeating calculation procedure of step (5) to calculate prediction results at all extended heights from 1 m to 2h tx :
applying a mirror principle extended model algorithm when the calculated height h rx ′>h tx and there is non-line-of-sight propagation, and replacing actual height h rx ′ with a mirrored height h rx ″ when the COST-231-Walfishch-Ikegami propagation model formula is applied, wherein the mirrored height conforms to formula
h
rx
″
=
{
2
h
tx
-
h
rx
′
,
when
h
rx
′
>
h
tx
h
rx
′
,
when
h
rx
′
≤
h
tx
.
5. A method for predicting outdoor three-dimensional space signal field strength by extended COST-231-Walfisch-Ikegami propagation model, comprising:
establishing a three-dimensional scene model from a transmitting base station to a predicted region space;
performing an on-site measurement according to a certain resolution in a prediction region and recording wireless signal strength information at a height of 1 m above a ground;
acquiring a vertical cross section between the transmitting base station and a receiving point at a height of 1 m above the ground, and acquiring therefrom an average roof height, an average street width and an average between-building space;
predicting a reception signal strength at a measurement point in a calculation formula of a COST-231-Walfishch-Ikegami propagation model;
correcting the COST-231-Walfishch-Ikegami propagation model of the measurement point according to an error Δ between measured data and a prediction result;
acquiring a vertical cross section between the transmitting base station and a receiving point at another height of the measurement point, and filtering therefrom buildings outside a Fresnel circle to re-acquire the average roof height, the average street width and the average between-building space; and
calculating a reception signal strength at the other height of the measurement point according to the corrected COST-231-Walfishch-Ikegami propagation model.