IEEE Signal Processing - May 2018 - 69

Future Tenant

Origin Wireless Center
36.3
Office
1070-9

Office
1070-10

Scale

Open Area
1070-12

180.000°
4.982 m

270.000°
10.982 m

A

Pantry
1070-14

Open Area
1070-13

Office
1070-6

Office
1060-5

Office
1060-4

Open Area
1060-3

Open Area
1060-6

180.000°
0.000 m

Office
1070-7
Open Area
1070-11

Meter

LAN Room
1070-15

Office
1070-8

Office
1060-7
Conference Room
1060-2

Office
1070-5

Conference Room
1070-4

180.000°
20.946 m
Reception Area
1070-1

Office
1070-3

Office
1060-8

Satellite
EWC

270.000°
24.946 m

Electrical

B

Elevator Lobby
Open Area
1060-1

Work Room
1070-2

0.000°
29.928 m

0.000°
39.893 m

68.838 m

Open Area
1060-9

0.000°
54.874 m

90.000°
63.855 m

FIGURE 11. An illustration of the route and the floor plan in evaluating the statistical position error.

Phase 2: Online testing

J
TR (h T, 1, h T, 2) = K
K
K
L

N2
O,
2 O
h T, 2 [l] O
P
(11)

max
(h T, 1 ) g T, 2) [i]
i
N tap -1

/

l =0

h T, 1 [l]

2

N tap -1

/

l =0

1
0.8
0.6
CDF

The objective of a TRIEDS is to detect the occurrence of each
trained indoor event through evaluating the similarity between
the testing and the training CSI in the training database G.
The raw CSI obtained from radio devices is complex-valued
and of high dimensions, which complicates the detection problem and increases the computational intricacy.
With the spatial resonance effect, the TR technique provides
an accurate and simple method for comparing two CSI samples.
As demonstrated in Figure 13, each dot in the CSI logical space
represents an indoor event or location, which is uniquely determined by the multipath profile h. By taking a time-reverse and
conjugate operation over the multipaths, the corresponding TR
signatures g are generated, and the points in the CSI logical space,
as marked by A, B, and C, are mapped into the TR space, a point
logical space, as points Al , Bl , and C l. In the TR space, the similarity between two indoor events or indoor locations is quantified
by the TRRS. The higher the TRRS, the more similar are the two
multipath profiles in the TR space. Similar events defined by a
TRRS threshold will be treated as a single class in the TRIEDS.
Mathematically, the TRRS TR (h T, 1, h T, 2) between two
CIRs h T, 1 and h T, 2 is defined as

0.4
0.2
0

0

0.5

1
1.5
Localization Error (m)

2

FIGURE 12. The empirical CDF of the position error.

where the maximal absolute value appearing in the numerator
can compensate possible synchronization errors; N tap denotes
the length of the CIR vector, i.e., the number of taps; *
denotes the convolution operator; and g T, 2 is the timedomain TR signature of h T, 2, as g T, 2 [k] = h )T, 2 [N tap - k - 1],
k = 0, 1, f, N tap - 1.
During the online monitoring phase, the receiver keeps
searching for the match between the current estimated CSI
and the one in G by locating the strongest TRRS. The TRRS
between the unknown testing CSI H T, test and the trained event
S i is defined as

IEEE Signal Processing Magazine

|

May 2018

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69
Table of Contents for the Digital Edition of IEEE Signal Processing - May 2018
