Biomedical Engineering Reference
In-Depth Information
10
Cha
m
ber
9
Indoor1
Indoor2
Indoor3
8
Ref
7
6
5
4
3
2
1
0
Back
Chest
Locations of Rx Antenna with respect to Tx on Waist
Head
Wrist
Ankle
Fig. 5
Comparison of maximum-ratio combining (MRC) diversity gain (DG) for different links
for position 1 and three locations at 0.34
λ
0
spacing in an indoor environment in comparison with
narrow band in an indoor environment presented in [
1
]
subject is present in rich multi-path environments. Also, moderate values of DG in
the anechoic chamber confirms both the presence of multi-path components due to
the movement of body parts and the fact that their contribution to DG is not the
dominant factor in more realistic environments.
Effect of Indoor Locations on the Ultra-Wideband Diversity Gain
Table
4
shows the diversity parameters for 0.34
λ
0
spacing between the diversity
branch antennas at three different locations in an indoor environment (Fig.
3
; Loc.
1, Loc. 4 and Loc. 7). The highest DG values are obtained for location 1, because
the subject is close to the walls and pillar in this case, leading to stronger multi-path
reflections. The wrist-to-waist channel is the exception: here, DG is low, compared
to other locations, due to the higher power imbalance and higher correlation in this
case, as the wrist was very close to the wall.
The highest value of DG (i.e. 6.97 dB using MRC) is obtained for the back-to-waist
link (NLOS case), compared to the other links for location 1. The higher value of DG
and lower power imbalance (0.63 dB) for the back-to-waist link suggests that signals
are reasonably uncorrelated and also that movements of body parts result in a higher
decorrelation between the two branch signals. The same reasoning as described in
“Reliability of Diversity Measurements with Respect to Small On-Body Position
Changes” can be applied to account for DG variation for all other links. The results
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