Signal Processing - November 2016 - 132
device, named the Bot. With the proposed algorithm in the section "Achieving Centimeter Accuracy Via TRRS,"
the Origin estimates the location of the
Bot. Figure 4 shows one Wi-Fi device
used in the proposed IPS.
The experiments are conducted in a
typical office of a multistory building.
The indoor space is filled with a large
number of reflectors, e.g., chairs, desks,
shelves, sofas, walls, and ceilings. The
CSIs of 50 candidate locations are
measured, with 20 measurements for
each location.
To evaluate the performance, the
CSIs at each location are partitioned into
a training set and a testing set, with ten
CSIs for each. The TRRS matrix is calculated using the CSIs collected at the
50 candidate locations. Each element of
the matrix represents the TRRS between
the CSIs at the training location and the
testing location. In other words, the
figure 4. The Wi-Fi device used in the proposed IPS.
Experiment results
Extensive experiments are conducted
to validate the theoretical analysis and
evaluate the performance of the proposed IPS. The proposed system contains two Wi-Fi devices, each equipped
with three omnidirectional antennas. One Wi-Fi device, called Origin,
estimates CSI from the other Wi-Fi
Algorithm 1. Calculating TRRS by exploiting diversities.
Input:
f = 1, 2, f, F
f = 1, 2, f, F
H = {H s, f } s = 1, 2, f, S, Hl = {Hls, f } s = 1, 2, f, S
Output: c [ H, Hl ]
1:
K = 0, K l = 0, h = 0
2:
for s = 1, 2, f, S do
3:
for f = 1, 2, f, F do
4:
K s, f = 0, Kls, f = 0
5:
for k = 1, 2, f, K do
6:
K s, f ! K s, f +| H s, f, k |2
7:
Kls, f ! Kls, f +| H sl, f, k |2
8:
end for
9:
K ! K + K s, f , Kl ! Kl + Kls, f
10:
for n = 1, 2, f, N do
z [n] ! / k = 1 H s, f, k H sl *,f, k e -j
N
11:
12:
end for
13:
n * = argmax |z [n]|
14:
hr s, f = z [n*]
15:
h ! h + hr s, f
n = 1, 2, f, N
16:
132
2rn (k - 1)
N
4
Calculating channel energies
on virtual link (s, f )
4
Calculating modified cross-correlation
on virtual link (s, f )
end for
17:
end for
18:
c [ H, Hl ] ! c
h
K K
2
m
IEEE Signal Processing Magazine
|
November 2016
|
diagonal elements of the matrix indicate
the similarity between CSIs at the same
location, while the off-diagonal elements stand for the similarity between
CSIs of different locations.
Figure 5 illustrates the TRRS vmatrices under effective bandwidths of
10, 40, 120, and 360 MHz. First of
all, it is easily seen from Figure 4 that
the diagonal elements of the matrices are close to one, signifying high
similarities among CSIs of the same
locations. Regarding the off-diagonal
elements, they become smaller with an
increasing effective bandwidth. When
the effective bandwidth is small, e.g.,
10 MHz, some off-diagonal elements
are even larger than the diagonal elements, giving rise to localization errors.
In other words, it is very likely to localize the Bot to incorrect positions when
the effective bandwidth is small. When
the effective bandwidth is increased, the
gap between diagonal and off-diagonal elements enlarges, which provides
a clear watershed between the correct
and incorrect locations and leads to an
enhanced system performance in return.
To provide a statistical point of view,
Figure 6 shows the cumulative density
functions of the diagonal and off-diagonal elements in TRRS matrices under
a variety of effective bandwidths. As
we can see, the gap between the diagonal and off-diagonal elements increases
with the effective bandwidth, indicating a
better distinction between different locations. Whenever there is a gap between
the diagonal and off-diagonal elements, a
perfect localization can be achieved with
an appropriate threshold, i.e., 100% true
positive rate and 0% false positive rate.
In a practical indoor environment,
there usually exists environment dynamics that might degrade the localization
performance. To evaluate the proposed
IPS in a dynamic indoor environment,
the testing CSIs are recollected in the
presence of human activities and large
object movement. In particular, to
emulate dynamics from human activities, one participant was asked to walk
continuously in the vicinity of the Bot.
Then, the participant was asked to open
and close a door that blocks the direct
link between the Origin and Bot so as
Table of Contents for the Digital Edition of Signal Processing - November 2016
Signal Processing - November 2016 - Cover1
Signal Processing - November 2016 - Cover2
Signal Processing - November 2016 - 1
Signal Processing - November 2016 - 2
Signal Processing - November 2016 - 3
Signal Processing - November 2016 - 4
Signal Processing - November 2016 - 5
Signal Processing - November 2016 - 6
Signal Processing - November 2016 - 7
Signal Processing - November 2016 - 8
Signal Processing - November 2016 - 9
Signal Processing - November 2016 - 10
Signal Processing - November 2016 - 11
Signal Processing - November 2016 - 12
Signal Processing - November 2016 - 13
Signal Processing - November 2016 - 14
Signal Processing - November 2016 - 15
Signal Processing - November 2016 - 16
Signal Processing - November 2016 - 17
Signal Processing - November 2016 - 18
Signal Processing - November 2016 - 19
Signal Processing - November 2016 - 20
Signal Processing - November 2016 - 21
Signal Processing - November 2016 - 22
Signal Processing - November 2016 - 23
Signal Processing - November 2016 - 24
Signal Processing - November 2016 - 25
Signal Processing - November 2016 - 26
Signal Processing - November 2016 - 27
Signal Processing - November 2016 - 28
Signal Processing - November 2016 - 29
Signal Processing - November 2016 - 30
Signal Processing - November 2016 - 31
Signal Processing - November 2016 - 32
Signal Processing - November 2016 - 33
Signal Processing - November 2016 - 34
Signal Processing - November 2016 - 35
Signal Processing - November 2016 - 36
Signal Processing - November 2016 - 37
Signal Processing - November 2016 - 38
Signal Processing - November 2016 - 39
Signal Processing - November 2016 - 40
Signal Processing - November 2016 - 41
Signal Processing - November 2016 - 42
Signal Processing - November 2016 - 43
Signal Processing - November 2016 - 44
Signal Processing - November 2016 - 45
Signal Processing - November 2016 - 46
Signal Processing - November 2016 - 47
Signal Processing - November 2016 - 48
Signal Processing - November 2016 - 49
Signal Processing - November 2016 - 50
Signal Processing - November 2016 - 51
Signal Processing - November 2016 - 52
Signal Processing - November 2016 - 53
Signal Processing - November 2016 - 54
Signal Processing - November 2016 - 55
Signal Processing - November 2016 - 56
Signal Processing - November 2016 - 57
Signal Processing - November 2016 - 58
Signal Processing - November 2016 - 59
Signal Processing - November 2016 - 60
Signal Processing - November 2016 - 61
Signal Processing - November 2016 - 62
Signal Processing - November 2016 - 63
Signal Processing - November 2016 - 64
Signal Processing - November 2016 - 65
Signal Processing - November 2016 - 66
Signal Processing - November 2016 - 67
Signal Processing - November 2016 - 68
Signal Processing - November 2016 - 69
Signal Processing - November 2016 - 70
Signal Processing - November 2016 - 71
Signal Processing - November 2016 - 72
Signal Processing - November 2016 - 73
Signal Processing - November 2016 - 74
Signal Processing - November 2016 - 75
Signal Processing - November 2016 - 76
Signal Processing - November 2016 - 77
Signal Processing - November 2016 - 78
Signal Processing - November 2016 - 79
Signal Processing - November 2016 - 80
Signal Processing - November 2016 - 81
Signal Processing - November 2016 - 82
Signal Processing - November 2016 - 83
Signal Processing - November 2016 - 84
Signal Processing - November 2016 - 85
Signal Processing - November 2016 - 86
Signal Processing - November 2016 - 87
Signal Processing - November 2016 - 88
Signal Processing - November 2016 - 89
Signal Processing - November 2016 - 90
Signal Processing - November 2016 - 91
Signal Processing - November 2016 - 92
Signal Processing - November 2016 - 93
Signal Processing - November 2016 - 94
Signal Processing - November 2016 - 95
Signal Processing - November 2016 - 96
Signal Processing - November 2016 - 97
Signal Processing - November 2016 - 98
Signal Processing - November 2016 - 99
Signal Processing - November 2016 - 100
Signal Processing - November 2016 - 101
Signal Processing - November 2016 - 102
Signal Processing - November 2016 - 103
Signal Processing - November 2016 - 104
Signal Processing - November 2016 - 105
Signal Processing - November 2016 - 106
Signal Processing - November 2016 - 107
Signal Processing - November 2016 - 108
Signal Processing - November 2016 - 109
Signal Processing - November 2016 - 110
Signal Processing - November 2016 - 111
Signal Processing - November 2016 - 112
Signal Processing - November 2016 - 113
Signal Processing - November 2016 - 114
Signal Processing - November 2016 - 115
Signal Processing - November 2016 - 116
Signal Processing - November 2016 - 117
Signal Processing - November 2016 - 118
Signal Processing - November 2016 - 119
Signal Processing - November 2016 - 120
Signal Processing - November 2016 - 121
Signal Processing - November 2016 - 122
Signal Processing - November 2016 - 123
Signal Processing - November 2016 - 124
Signal Processing - November 2016 - 125
Signal Processing - November 2016 - 126
Signal Processing - November 2016 - 127
Signal Processing - November 2016 - 128
Signal Processing - November 2016 - 129
Signal Processing - November 2016 - 130
Signal Processing - November 2016 - 131
Signal Processing - November 2016 - 132
Signal Processing - November 2016 - 133
Signal Processing - November 2016 - 134
Signal Processing - November 2016 - 135
Signal Processing - November 2016 - 136
Signal Processing - November 2016 - 137
Signal Processing - November 2016 - 138
Signal Processing - November 2016 - 139
Signal Processing - November 2016 - 140
Signal Processing - November 2016 - 141
Signal Processing - November 2016 - 142
Signal Processing - November 2016 - 143
Signal Processing - November 2016 - 144
Signal Processing - November 2016 - 145
Signal Processing - November 2016 - 146
Signal Processing - November 2016 - 147
Signal Processing - November 2016 - 148
Signal Processing - November 2016 - Cover3
Signal Processing - November 2016 - Cover4
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