Anticollison Steps in ISO 14443B
o ISO 14443B (TYPE 2), has two main components reader (PCD) and tag (PICC).
o At first PCD uses the anti-collision sequence for checking for multiple PICCs.
o Steps
§ PCD sends REQB command with N where N is number slots defined for anti collision.
§ PICC receives REQB and check for N
o ISO 14443B (TYPE 2), has two main components reader (PCD) and tag (PICC).
o At first PCD uses the anti-collision sequence for checking for multiple PICCs.
o Steps
§ PCD sends REQB command with N where N is number slots defined for anti collision.
§ PICC receives REQB and check for N
- If N is 1 then returns ATQB (Answer to Request type B)
- If N is greater than 1 then random number R is generated
- If R is 1 then sends ATQB
- If
R is not 1 then it wait until slot marker sent by PCD is matched
SIGNALLING IN NFC ISO 14443B
o Uses the frequency of 13.56MHz as major carrier.
o Sub carrier if 847.5 KHz is used for carrying data.
o Signal from PICC to PCD is load modulated and used different signaling
than from PCD to PICC.
PCD to PICC signaling
o Uses 10%(8 to 14% practically) amplitude modulation
index, ie there is always a presence of 13.56MHz carrier
o Uses the NRZ encoding for the data
o The signal generated from the smart phone as captured shows modulation
index of 15%
o Uses BPSK (Binary Phase Shift Keying) modulation
o Encoding is NRZ-L for the data.
o Each of the bit is 8 sub carrier period long.
