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RFID Portal Test at the Wireless Habitat
Test Bed
Engineering Directorate
Avionic Systems Division
Andrew Chu/NASA
July 28, 2010
National Aeronautics and Space Administration
Lyndon B. Johnson Space Center
Houston, Texas 77058-3696
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Introduction
Radio Frequency Identification (RFID) technology has matured to a level that can be used
reliably to support NASA operations in space and ground segments. The Electronic Product
Code (EPC) Global Class 1 Generation 2 (C1G2) standard has found widespread use throughout
commercial and government sectors. Readers, printers, and tag labels from many manufacturers
operate interchangeably with good performance using the C1G2 standard. To demonstrate the
use of RFID in a habitat portal scenario, a Cargo Transfer Bag (CTB) currently used for the
Space Shuttle and International Space Station Programs has been outfitted with RFID-tagged
items and tested with an RFID portal set up at an entrance of the Wireless Habitat Test Bed
located at the Johnson Space Center Building 14 high bay.
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Wireless Habitat Test Bed
The habitat structure of the Wireless Habitat Test Bed is a horizontal cylinder constructed of ¼
inch aluminum skin. The cylinder measures 10 feet in diameter and 20 feet in length. The
aluminum end caps of the cylinder each contain an aluminum door. The habitat is fitted with a
raised floor of tiles with metal plate backing. Channels at three depths on both cylindrical walls
provide a method to build out walls, cabinets and supports for mounted equipment. The inner
walls are made of 1/8” thick Kydex supported by vertical unistruts. Outside of both doors are a
landing and stairwell made of aluminum. Figure 1 and Figure 2 show the habitat structure.
Figure 1. External view of the habitat structure andportal 1.
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Figure 2. Interior arrangement of the habitat looking out portal 1.
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Portal setup
An RFID portal exists at both doors of the habitat. Each portal consists of an Ultra High
Frequency (UHF) Impinj Speedway reader and four circularly polarized antennas purchased
through Impinj. Only portal 1 was used for this test. The Speedway reader has part number IPJR1000-USA1M and serial number 37008290063. The four antennas, two each of S9028PCL
and S9028PCR, were manufactured by Cushcraft. One or more sensors can be used to trigger
the reader to start reading tags. For this test, a 24” x 60” pressure sensing mat was placed at the
edge of the landing to initiate tag reading. The mat and the two external antennas can be seen in
Figure 1. One antenna is mounted above the door hinge and the other antenna is mounted on the
landing rail by the door. The inside antennas are hidden behind the wall in Figure 2. Figure 3
shows the two internal antennas before the walls are installed. The Speedway reader is installed
below the floor tiles inside the habitat. A laptop computer running the Speedway Multireader
software application is used to control and record the tags read by the reader.
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antenna
Figure 3. Location of the interior RFID antennas of portal 1.
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Pantry CTB
The CTB comes in four sizes with the half size bag being the most common. The outside
dimensions of the half size CTB are approximately 10” x 17” x 9.5” (L x W x H). The pantry
CTB is filled with personal hygiene items and office supplies. One RFID tag is placed on the
outside of the CTB to identify the CTB. Similar items inside the CTB are bagged together in
Ziplock bags. In most cases, RFID tags are placed on individual items inside the Ziplock bags
(item level tagging) as well as on the Ziplock bag itself (bag level tagging). The mixture of
items inside the CTB includes metal foil bags and gel tubes, which tend to be difficult for RFID
interrogation. Previous experience with the pantry CTB has shown which items should be
tagged with general versus specialized tags that are designed for application on metal and
liquid/gel items. Appendix A contains a list of the 52 tags associated with the pantry CTB.
Appendix B shows in layers the “standardized” packing arrangement of the CTB. The standard
packing order is an arbitrary orderly packing of the CTB without regard to the interaction of the
items and tags. Both standard and random packing configurations are tested.
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Portal testing
The Speedway reader at portal 1 was set to output 30 dBm to all four antennas (switched
sequentially), i.e., only a single antenna is powered on at a time. The reader was configured to
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dense reader M = 4 high speed mode, dual target search, and a tags in view estimate of 400. The
standard packed pantry CTB was carried through the habitat, entering at portal 1 and exiting
through the opposite door. The CTB was carried through the habitat in three positions: held by
both hands in the front, carried by a handle using the right hand, and carried by a handle using
the left hand. Figure 4 shows the orientation of the CTB as it was carried through the portal
door. Two scenarios were tested: (i) reader was triggered using the pressure sensing mat on the
landing, and (ii) reader continuously on to read items. In the latter case, the CTB was placed in
the high bay directly in front of the habitat portal at a distance of about 40 feet away, in a
position out of view of the reader antennas. The reader was started and then the CTB was moved
into view and carried through the habitat.
Figure 4. Left picture shows the orientation of the CTB as viewed from inside the portal door as the CTB was
carried in front into the habitat. The right picture shows the orientation of the CTB as viewed from inside
the portal when the CTB was carried by the right and left hands into the habitat.
For each combination of three carry positions and two trigger scenarios, the test was performed
five times. Following the test with the standard packing CTB, two random packing tests were
performed. The random packing was accomplished by removing every item from the CTB. The
test personnel randomly grabbed a handful of items-at-a-time and placed them back into the
CTB. A sequential pictorial record of the random packing configurations 1 and 2 are shown in
Appendixes C and D. Thirty RFID test walkthroughs were performed for each of the two
random packing configurations in the same manner as the walkthroughs for the standard packing.
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Portal results
The overall average of the ninety trials shows that at the item level, the read success (tag read/52
total tags) is 75.5%. The overall average at the Ziplock level of 17 tags is 94.5%. There is little
difference in read success between the carrying methods. Similarly, the use of the mat to trigger
the reading versus continuous reader operation has insignificant effects on the read success of the
tags as they pass through the portal.
Table 1. Effects of CTB Carrying Method.
item level
ziplock level
average front
75.5%
95.1%
average right
75.3%
94.7%
average left
75.7%
93.7%
Table 2. Effects of Trigger Mechanism.
item level
ziplock level
average mat trigger
76%
95%
average cont ON
75%
94%
Table 3 shows the effects of packing on the read success. As expected, the read success is
dependent on the arrangement and orientation of the items inside the CTB as is shown by the
packing arrangements. The blocking and tuning effects of adjacent items would affect the
readability of the RFID tags.
Table 3. Packing Effects on Read Success.
item level
ziplock level
7
standard packing
72%
95%
random packing 1
81%
98%
random packing 2
74%
91%
Conclusion
One RFID portal was tested at the Wireless Habitat Test Bed using a pantry CTB with 52 total
tags. The read rate at the item level averages 75.5%, while the read rate at the Ziplock bag level
is 94.5%. The carry method and trigger mechanism are insignificant in terms of read success.
The varying results based on packing order confirm that the read success is dependent on the
arrangement and orientation of the items inside the CTB.
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Appendix A. Items inside the pantry CTB. The item in red font is the CTB level tag. Items in
blue font are the tags on the ziplock bags. Items in black font are the item level tags.
Item
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
Tag Model
2x2
Squiggle
Squiggle
Squiggle
Squiggle
2x2
2x2
2x2
Squiggle
2x2
2x2
2x2
2x2
Squiggle
2x2
2x2
2x2
2x2
Squiggle
2x2
2x2
2x2
Squiggle
Squiggle
Squiggle
Squiggle
Squiggle
Squiggle
Squiggle
TM4
TM4
2x2
2x2
Squiggle
Squiggle
Squiggle
2x2
Squiggle
Squiggle
Squiggle
dog-earred squiggle
Max
Metalcraft squiggle over foam
TM4
2x2
Name
Supply Pantry CTB
Kapton Tape, 1” Bag (1)
Kapton Tape, 1”
Crewmember, Microcassette, Tape Bag (4)
Battery, AA Alkaline (Battery, Size AA, 1.5V) (10)
Cartridge, Ink, Epson Bag (2)
Cartridge, Ink, Tri-color, Epson
Cartridge, Ink, Tri-color, Epson
Hand Cream, Aloe Gel Bag (4)
Hand Cream, Aloe Gel (0.75 oz)
Hand Cream, Aloe Gel (0.75 oz)
Hand Cream, Aloe Gel (0.75 oz)
Hand Cream, Aloe Gel (0.75 oz)
Shave Cream, Edge Gel Bag (4)
Shave Cream, Edge Gel
Shave Cream, Edge Gel
Shave Cream, Edge Gel
Shave Cream, Edge Gel
Deodorant Bag (3)
Deodorant, Shure
Deodorant, Shure
Deodorant, Shure
Toothbrush Bag (5)
Toothbrush, Oral B-40 (Medium)
Toothbrush, Oral B-40 (Medium)
Toothbrush, Oral B-40 (Medium)
Toothbrush, Oral B-40 (Medium)
Toothbrush, Oral B-40 (Medium)
Toothpaste Bag (2)
Toothpaste, Crest
Toothpaste, Crest
Floss, Dental, Glide (Floss, Glide) bag (3)
Hygiene, Towel, Lintless Bag (2)
Hygiene, Towel, Lintless
Hygiene, Towel, Lintless
Hygiene, Towel, Washcloth Bag (2)
Huggies Wipes Assembly (2)
Huggies Wipes Assembly
Huggies Wipes Assembly
No Rinse Body Bath Pouch Bag (4)
No Rinse Body Bath Pouch (No Rinse Body Bath)
No Rinse Body Bath Pouch (No Rinse Body Bath)
No Rinse Body Bath Pouch (No Rinse Body Bath)
No Rinse Body Bath Pouch (No Rinse Body Bath)
Tape, Shurtape, 2” Bag (1)
A-1
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46
47
48
49
50
51
52
2x2
2x2
TM4
Flex
Flex
Prox
Squiggle
Tape, Shurtape, 2”
No Rinse Body Bath (4)
No Rinse Body Bath
No Rinse Body Bath
No Rinse Body Bath
No Rinse Body Bath
Latex Gloves
A-2
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Appendix B. The packing of the standard pantry CTB
B-1
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B-2
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Appendix C. Random packing 1
C-1
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C-2
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Appendix D. Random packing 2
D-1
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D-3