Image Processing Reference
In-Depth Information
With the presented distance vector (DV)-hop method, Niculescu and Nath decreased the impact
of the scaling error and the linearization error noticeable [NN]. They calculate an average hop
size (AHS) at each beacon
B
j
using hop distances and real distances to all
k
known remote beacons
B
i
(
i
≠
j
).
√
(
k
i
x
i
−
x
j
)
+(
y
i
−
y
j
)
=
∑
=
c
j
(.)
k
i
h
i
∑
=
During distance estimation, the calculated AHS
c
j
, the actual hop count to beacon
B
j
,andthebea-
con's position are stored within the DV. A sensor node
i
selects the AHS
c
j
of the nearest beacon
B
j
to compute all distances
d
il
to all
l
remote nodes. hus,
c
i
=
c
j
.
d
il
=
h
il
⋅
c
i
(.)
The unmotivated selection of the nearest beacon and its AHS leads to a loss of potential useful
information. Huang et al. therefore improved the DV-hop method by weighting all
m
known AHS
at a sensor node
i
(weighted DV, WDV-hop [HS]). According to Equation ., the AHS of node
S
is
wc
=(
⋅
.
+
⋅
.
+
⋅
. m
)/(
+
+
)=
. m compared to
c
=
. m of the
original DV-hop method (Figure . ).
m
j
=
∑
h
j
⋅
c
j
=
wc
i
(.)
m
j
h
j
∑
=
The distance information based on hop counts is predestinated for start values of iterative algo-
rithms, e.g., hop terrain [SRL] or collaborative multilateration [SPS]. Further, DV-hop can be
used to approximate positions. But in environments with many obstacles, the accuracy decreases
drasticallyduetohugehopcountproducedbybypassing the holes. Another disadvantage is the
decreasing connectivity to remote sensor nodes [TRV
+
].
6.2.6 Lighthouse Localization System
The lighthouse localization system was introduced by Römer [Röm]. In this system, light beams
rotate around a source point with a fixed width
b
and constant angular speed. he time, a turn takes
is defined as
t
Turn
. Due to the rotating light, a sensor node
S
i
detects depending on its distance to the
source of light for a finite time
t
Beam
,
per round (Figure .a).
Rotation
S
1
S
1
S
2
t
=0
α
1
α
1
b
α
2
d
2
d
1
d
1
Parallel beams of
light
Rotating source
of light
(a)
(b)
FIGURE .
Lighthouse localization system: (a) Angle detection and (b) distance estimation depending on angles.
