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(
−
)
2
(
−
)
2
y
y
∑
x
x
+
i
j
i
j
=
j
≠
i
(1)
HopSize
∑
h
j
j
≠
i
In formula 1, (x
i
, y
i
), (x
j
, y
j
) is the coordinates of reference node i and j, h
j
is the
number of hops among node i and j (j≠i). Third, using triangular measurement method
or maximum likelihood estimation method calculate their position.
It is easy to estimate the rough position of positioning node coordinate through
LDV-HOP positioning technology, then, weighted least squares method with triangu-
lar measurement method can be used to calculate new coordinate, achieve refinement
cycle,. There are two characteristics in this refinement cycle.
First, adding the value of a property right for estimating position of the node. Using
weighted least square method to implement positioning calculate, which make nodes
with large position error have smaller influence on positioning calculating. Second,
node with low connectivity which cause large positioning error was prevented them
from participating in the refinement cycle process in order to eliminate their effect.
Comparing with DV-HOP algorithm, LDV-HOP with the circulation refinement
link obtain positioning information within the local area, it reduce the localization
energy consuming, improve the positioning accuracy and reduce communications
volume. LDV-HOP algorithm with increase circulation refinement link can meet the
low power requirements and simply node of WSNs.
4 Experiment and Simulation
4.1 Simulation and Analysis of Algorithm
Using the Network Simulator version 2 (NS2) in simulation experiment to test the
performance of the LDV-HOP algorithm which increased the refinement cycle.
First decompress the installation package NS2 in the host machine with the Win-
dows operation system which installs Linux OS in VMware virtual machines, then
configure and install, finally set the environment variable. The simulation takes the
MAC type with IEEE802.15.4 protocol, the AODV route protocol. 30 nodes distrib-
ute in the 400m*400m square region, and each node randomly moved with direction
and velocity which the maximum velocity of movement is 50m/s, and the scene con-
tinues 50s set by setdest tool. Using the cbrgen current capacity tool to complete the
following, the current capacity is cbr, the speed of 30 nodes are 1.0 m/s.
The entire simulation process includes the network topology and the process of the
data sending and receiving defined in the tcl script. The actual content is as followed:
1) Define the scenario parameters; 2) Configure the node parameters; 3) Record the
tracking data of simulation process; 4) To create 20 mobile nodes; 5) Define the con-
clusion of process. To open the “nam” animation analog picture with the simulation
NS2 and the executive command after producing the tcl script.
Finally analyzed and processed of data which recorded in the simulation experi-
ment. When the reference node occupies the total nodal point number is certain
(20%), compared the position error and the communication load of the different con-
nection between the DV-HOP algorithm(D) and LDV-HOP algorithm after increasing
the circulation refinement link(L). The simulation experiment results under the differ-
ent connectivity of network show in the table 1.
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