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RFID is becoming as
ubiquitous as printed bar codes. In fact, in many venues, optically scanned bar codes have been entirely replaced
with embedded RFID tags. Clothing, high value electronics, packaged software, and even books have been using RFID
(sometimes in the form of NFC - near field communications) for many years. Now, major retailers like Wal-Mart have
made a commitment to making RFID ubiquitous. In the not-too-distant future, if you want to have your product sold
by some of these retailers, you will be required to integrate RFID tags.
The magic price mark for RFID is a couple cents per tag. At that level, RFID can be added to every product and
not represent more than a percent or two of the total cost. This table summaries the protocols used in RID
tags that operate in the 800/900 MHz band assigned for ISM (Industrial, Scientific & Medical) use.
| Operating Frequency |
902 MHz - 928 MHz |
902 MHz - 928 MHz |
860 MHz - 930 MHz |
860 MHz - 930 MHz |
| Air Interface |
AM PWM |
AM PWM |
Pulse Interval ASK |
Manchester ASK |
| Bit Period |
NA: 25 µs/12.5 µs EU: 62.5 µs |
NA: 14.25 µs EU: 66.67 µs |
Data ‘0': 20 µs Data ‘1': 40 µs |
125 µs/25 µs |
| Data Rate |
NA: 40/80 kbps EU: 16 kbps |
NA: 70.18 kbps EU: 15.00 kbps |
33 kbps (1) |
8/40 kbps |
| Worst-case Duty Cycle |
52% Data ‘1' low for 6 µs |
62.5% Data ‘1' low for 3To/8 |
50% Data ‘0' low for 10 µs |
50% Manchester code |
| Modulation Depth [Min, Max] |
[20%, 100%] |
[30%, 100%] |
[27%, 100%] |
Nom 15%: [13%, 17% Nom 99%: [90%, 100%] |
| Air Interface |
Passive Backscatter: FSK |
Passive Backscatter: Pulse Interval AM |
Passive Backscatter: Bi-phase Space AM |
Passive Backscatter: Bi-phase Space AM |
| Bit Period |
NA: 25 µs/12.5 µs EU: 62.5 µs |
NA: 7.13 µs EU: 33.33 µs |
25 µs |
25 µs |
| Data Rate |
NA: 40/80 kbps EU: 16 kbps |
NA: 140.35 kbps EU: 30.00 kbps |
40 kbps (1) |
40 kbps (1) |
| Forward-to-reverse Link Turnaround |
Not Applicable (2) |
NA: 114 µs EU: 534 µs |
Shall not exceed 100 µs |
Shall not exceed 100 µs |
| Reset Signal Duration |
800 µs (CW) |
64 µs (CW) |
300 µs (CW) |
400 µs (CW) |
| Collision Arbitration |
Deterministic binary tree search |
Deterministic/Slotted |
Adaptive |
Probabilistic binary tree search (3) |
| Tag Read Speed |
Nom: 200 tags/sec Max: 800 tags/sec |
Not specified |
Nom: 100 tags/sec (~10 ms/tag) |
Nom: 100 tags/sec (~10 ms/tag) |
| Tag Capacity |
Not limited by standard |
~300 (4) |
~300 (4) |
~300 (4) |
| Memory Type |
Read-only |
User programmable |
User programmable |
User programmable |
| Memory Organization |
EPC: 64/96 bits Kill Code: 24 bits Total: >=120 bits |
EPC: 64/96 bits Kill Code: 8 bits Total: >=104 bits |
Up to 256 blocks w/256 bits/block (64 kBits) |
Up to 256 blocks w/8 bits/block (2 kBits) |
| Features |
Moderate D0/ID1 + 24 bit kill passcode |
None Reader broadcasts all or part of ID code. Reader can request kill passcode. |
None Reader broadcasts UID/SUID. Production set block lock bits. No kill command. |
None Reader broadcasts UID/SUID. Production set block lock bits. No kill command. |
(1) No mention of data rates specific to European operation. Reverse link is always
40 kbps. (2) For Auto-ID class 0, the tag data response is always known a priori (i.e., nothing has to be
computed based on the current bit). (3) Probabilistic collision arbitration implies that tag selection speed
will depend on the tag population size. This is a disadvantage. (4) These standards are limited by
the probabilistic nature of their collision arbitration protocols. Most of them assume a tag population
of ~250 tags. Source: RF Design, July 2005 , by Rob
Glidden and John Schroeter. Click
here for the full article.
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