Biomedical Engineering Reference
In-Depth Information
1
0.1
0.01
1E-3
1E-4
1E-5
1E-6
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
Distance (m)
Fig. 6.12
Experimental BER variations with distance for Scenario 1
6.6.1.1 BER Analysis for Scenario 1
Figure
6.12
depicts the BER variation for Scenario 1. In this scenario, data
communication occurs between four on-body sensor nodes and a coordinator node
placed away from the body. All four sensor nodes are attached to a single user in a
similar experimental setup to that shown in Fig.
6.9
. Each point in Fig.
6.12
represents a BER value recorded for a particular sensor node at a certain distance
away from the coordinator node. Distance between the user's body and the
receiving antenna of the coordinator node is considered as the separation distance
for this experiment. User's body is kept still throughout the BER evaluation
period. BER values recorded by all four sensor nodes for various separation dis-
tances are plotted in Fig.
6.12
. BER evaluation is carried out three times for a
particular distance, and the average BER is plotted for each sensor node.
It can be seen from Fig.
6.12
that the recorded BER values follow a logarithmic
decay. Four sensor nodes used in this experiment recorded BER values with a
slight variation from each other for the same separation distance. These variations
occur mainly due to different orientations of the UWB transmit antennas. Different
antenna orientations cause UWB signals to propagate in different paths towards the
receiving antenna at the coordinator. Fading characteristics and multi-path char-
acteristics of these propagations paths differ from each other causing different BER
values for each sensor node.
