response to reference number 4338

0285-EX-ST-2006 Text Documents

Wal-Mart Stores, Inc.

2006-05-16ELS_76044

To Whom It May Concern:,

Please find attached Exhibit 002 containing addition detail on the emissions and
necessary bandwidth for our FCC Form 422 application. As a result of this more detailed
evaluation we request that section 4(G) of our application be amended to 640K (currently
listed as 500K0). Thank you for your consideration of this application.

Sincerely,

Jane Marlow
Sr. License Manager

Exhibit 002 – Explanation of UHF RFID emissions and bandwidth

Wal*Mart will be evaluating the performance of UHF RFID Readers in our Bentonville,
Arkansas laboratory. Readers destined for deployment at Wal*Mart sites in Europe and
Japan will be tested.

The transmission characteristics of UHF RFID Readers are specified in the standard
“Class-1 Generation-2 UHF RFID Protocol for Communications at 860 MHz – 960
MHz” (hereafter referred to as the Gen2 protocol). The Gen2 protocol has been ratified
and is published by EPCglobal Inc.

The Gen2 protocol specifies three transmit modulation options for Readers, double
sideband (DSB) ASK, single sideband (SSB) ASK, or PSK. Readers send digital
commands to tags using one of these modulation formats then follows the command with
a continuous wave (CW) transmission. Therefore, possible Reader emissions are DSB
ASK, SSB ASK, PSK, and CW as indicated in 4(E) of the application.

Pulse Interval Encoding (PIE) is used to encode the digital bits (binary signaling scheme).
Encoding of “data-0” and “data-1” bits is shown in Figure 1. A data-1 bit is
distinguished from a data-0 by having a duration that is between 1.5 and 2.0 times the
length of a data-0.

1.5 Tari ≤ data-1 ≤ 2.0 Tari
Tari 0.5 Tari ≤ x ≤ Tari

PW PW

data-0

data-1
Figure 1: RFID Gen2 data encoding

The baseband data sequences are pulse shaped (filtered) to meet Japanese and European
radiated emission regulatory requirements prior to modulation of the carrier. Figures 2,
3, and 4 show examples of typical pulse shaping and the resulting Power Spectral Density
(PSD) of the transmitted DSB ASK, SSB ASK, and PSK signal, respectively. The
examples show waveforms and spectra for a 32 kbps data rate signal.

Time Domain Waveforms (pre-filter) Power Spectral Density
1.25 40
1
20

PSD (dBm/0.1 kHz)
0.75
0.5 0
0.25
-20
0
-0.25 -40
-0.5 PIE ASK -60
-0.75
0 25 50 75 100 125 -200 -100 0 100 200
Frequency (kHz)
Time Domain Waveforms (post-filter) Eye Diagram
1.25
1 1
0.75 0.8
0.5
0.6
0.25
0 0.4
-0.25 0.2
PIE ASK (DSB)
-0.5 ABS[signal] 0
-0.75
0 25 50 75 100 125 0 10 20 30 40 50
Time (µsec) Time (µsec)

Figure 2: DSB ASK baseband time and frequency domain waveforms (32kbps data
rate example)

Time Domain W aveforms (pre-filter) Power Spectral Density
1.25 40
1
20
PSD (dBm/0.1 kHz)

0.75
0.5 0
0.25
-20
0
-0.25 -40
-0.5
PIE ASK -60
-0.75
0 25 50 75 100 125 -200 -100 0 100 200
Frequency (kHz)
Time Domain W aveforms (post-filter) Eye Diagram
1.25
1 1
0.75
0.8
0.5
0.25 0.6

0 0.4
-0.25 PIE ASK (SSB)
0.2
ABS[signal]
-0.5 PIE ASK (DSB) 0
-0.75
0 25 50 75 100 125 0 10 20 30 40 50
Time (µsec) Time (µsec)

Figure 2: SSB ASK baseband time and frequency domain waveforms (32kbps data
rate example)

Time Domain Waveforms (pre-filter) Power Spectral Density
1.75 40
1.25
20

PSD (dBm/0.1 kHz)
0.75
0.25 0
-0.25
-20
-0.75
-1.25 -40
-1.75
PIE BPSK -60
-2.25
0 25 50 75 100 125 -200 -100 0 100 200
Frequency (kHz)
Time Domain Waveforms (post-filter) Eye Diagram
1.75 1.5
1.25
1
0.75
0.25 0.5
-0.25 0
-0.75
-0.5
-1.25
PIE BPSK (DSB) -1
-1.75 ABS[signal]
-2.25 -1.5
0 25 50 75 100 125 0 10 20 30 40 50
Time (µsec) Time (µsec)

Figure 3: PSK baseband time and frequency domain waveforms (32kbps data rate
example)

The bandwidth efficiency (bps/Hz) is used to relate the data rate to the 99% signal
bandwidth for each emission type. Bandwidths are listed in Table 1 for typical and
maximum data rates. Typical data rates correspond to modes prevalent in Readers
designed for operation in Japanese and European markets. Maximum bandwidths
correspond to maximum data rates allowed by the Gen2 protocol.

Table 1: Typical and maximum bandwidths for each emission type
Emission Type Bandwidth Typical Maximum Typical Maximum
Efficiency Data Rate Data Rate Bandwidth Bandwidth
(bps/Hz) (kbps) (kbps) (kHz) (kHz)
DSB ASK 0.20 48 128 240 640
SSB ASK 0.40 48 128 120 320
PSK 0.27 48 128 178 474

Baseband signals modulate an RF carrier at a frequency within the range listed in column
4(A) of the application. The carrier is constrained to fall on channel centers that are 200
kHz apart starting 100 kHz inside the 4(A) frequency limits. The peak radiated transmit
power (power assuming no modulation, that is, a CW transmission) is listed in column
4(C). The peak power is constrained by Japanese and European regulations.

Document Created: 2006-05-16 10:17:24
Document Modified: 2006-05-16 10:17:24

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