ANTICOLLISION STEPS IN NFC ISO14443B

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

• 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.