Biomedical Engineering Reference
In-Depth Information
Table 1
Diversity parameters for five different links at location 1 with different spacings in an
indoor environment
Links
Results
Antenna spacing (in terms of
λ
0
)
0.116
0.23
0.34
0.48
0.58
0.73
Chest-waist
MRC (dB)
4.03
2.85
2.98
2.32
2.59
1.22
EGC (dB)
2.91
2.10
2.45
2.09
1.71
0.5
SC (dB)
1.92
2.04
1.38
1.21
0.83
0.25
ρ
e
0.625
0.684
0.686
0.630
0.668
0.711
Imbalance (dB)
2.37
1.13
2.13
3.14
3.87
3.04
Head-waist
MRC (dB)
3.45
3.34
5.02
4.33
2.17
2.16
EGC (dB)
2.73
1.02
4.93
3.42
0.79
1.90
SC (dB)
1.96
0.48
4.19
2.14
0.49
1.17
ρ
e
0.631
0.675
0.645
0.638
0.686
0.677
Imbalance (dB)
3.99
2.47
1.11
1.34
1.92
2.22
Wrist-waist
MRC (dB)
1.65
2.23
2.98
2.99
3.22
3.44
EGC (dB)
0.68
1.49
2.09
1.81
1.40
2.93
SC (dB)
0.57
0.90
0.92
1.01
0.98
2.45
ρ
e
0.691
0.730
0.697
0.736
0.734
0.755
lmbalance (dB)
2.55
3.83
2.75
3.53
3.20
4.47
Ankle-waist
MRC (dB)
3.24
3.70
4.02
2.56
3.96
3.03
EGC (dB)
2.1
2.35
2.79
2.32
2.73
2.14
SC (dB)
1.54
1.28
2.11
1.40
2.65
1.01
ρ
e
0.613
0.621
0.637
0.626
0.649
0.733
lmbalance (dB)
3.77
4.84
4.95
6.56
6.0
4.63
Back-waist
MRC (dB)
4.10
6.75
6.97
6.03
6.69
5.94
EGC (dB)
3.56
6.38
5.76
5.53
6.21
4.88
SC (dB)
1.33
4.90
4.11
3.97
4.15
3.72
ρ
e
0.604
0.614
0.618
0.627
0.630
0.626
Imbalance (dB)
3.83
0.28
0.63
0.95
0.31
0.67
EGC
equal-gain combining,
MRC
maximum-ratio combining,
SC
selection combining
for the channels that have a line of sight (LOS), or partial LOS, link with Tx; this
percentage is calculated by taking the difference between maximum and minimum
DG for each link. The exception is the ankle case, where reflections from the ground
make the DG process more stable.
Reliability of Diversity Measurements with Respect to Small
On-Body Position Changes
In order to ensure that all measurements are reliable, a small grid incorporating the
Rx antenna was made, to see how small variations in the position of the diversity
antenna affect the measurement of DG. For specific cases, such as the chest and
the back (see Fig.
2
), a 2
2 grid was applied with an approximate spacing of
5 mm; in the case of the ankle and the head, a one dimensional grid was used, with a
similar spacing. These grids were adopted in this work to investigate the correlation
coefficient between the received signals on different branches and to highlight the
stability of the channel within a small window of positions in on-body measurements.
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