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. 6.13
Experimental BER variations for Scenario 2
channel conditions. It should be noted that BER is marked as '1' for instances
where it is not possible to decode any bits during the experiments.
6.6.1.3 BER Analysis for Scenario 3
Scenario 3 represents experiments carried out by placing both transmitter and
receiver UWB antennas on user's body as shown in Fig.
6.14
. Positions of the
sensor nodes are fixed while position of the receiver UWB antenna is changed
from user's chest area to upper part of user's left leg. Average distance between
sensor and coordinator UWB antennas are taken as the separation distance for this
experiment. User is made to walk at normal speeds during the BER evaluation
period. Figure
6.15
depicts the BER variation for this scenario. It should be noted
that only the BER values for 20 and 50 PPB fixed PPB experiments are plotted in
Fig.
6.15
since only these experiments resulted in a considerable BER value for
this distance range. Results show a degraded BER performance compared that of
Scenario 1. This is mainly caused by the degrations in signal conditions due to the
increased reflections and diffractions caused by complex body motions and
irregular geometry of the human body. Increased attenuation due to the absorption
of UWB signals from human skin and garment materials also degrades the BER
