Methods for a radio-frequency SIM card with low-frequency magnetic communication to trigger a transaction according to determined distance thresholds

A method for a radio-frequency Subscriber Identity Module (SIM) card with low-frequency magnetic communication to trigger a transaction according to determined distance thresholds, wherein the radio-frequency SIM card carries out a distance control of a short-distance communication with a corresponding card reader through a low-frequency channel and conducts the transaction with the card reader through the radio-frequency channel, the method comprising:

• Step a:
• setting a Threshold 1 as a low-frequency magnetic field intensity value corresponding to a distance to trigger the transaction;
• setting a Threshold 2 as a low-frequency magnetic field intensity value corresponding to an effective communication distance of the low-frequency magnetic field;
• and setting a Threshold 3 as a low-frequency magnetic field intensity value corresponding to a farthest transaction distance;
• wherein the Threshold 1 is greater than or equal to the Threshold 3, and the Threshold 3 is greater than or equal to the Threshold 2;
• Step b:
• examining continuously, by the radio-frequency SIM card, an intensity of the low-frequency magnetic field transmitted by the card reader;
• determining whether the intensity is greater than or equal to the Threshold 2;
• and upon determining that the intensity is greater than or equal to the Threshold 2, receiving and storing information of the low-frequency magnetic field;
• Step c:
• further determining, by the radio-frequency SIM card, whether an intensity of the low-frequency magnetic field transmitted by the card reader is greater than or equal to the Threshold 1;
• and upon determining that the intensity is greater than or equal to the Threshold 1, initiating, by the radio-frequency SIM card, a transaction process;
• Step d:
• during the transaction process, examining, by the radio-frequency SIM card, an intensity of the low-frequency magnetic field transmitted by the card reader;
• determining whether the intensity is less than the Threshold 3;
• and upon determining that the intensity is less than the Threshold 3, interrupting the transaction;
• and
• wherein in the Step a, the steps for determining the Threshold 1, the Threshold 2, and the Threshold 3 are as follows:
• A. through experiments, measuring, using a radio-frequency SIM card, intensities of a low-frequency magnetic field transmitted by a card reader that matches with the radio-frequency SIM card;
• determining a correspondence relationship between the intensities and distances;
• and establishing a correspondence table between the intensities and the distances;
• and
• B. based on the correspondence table and requirements for a transaction-triggering distance, setting a low-frequency magnetic field intensity value corresponding to the transaction-triggering distance as the Threshold 1;
• based on a communication rate of the low-frequency magnetic field and a data size that a data transmission needs in the low-frequency magnetic field for the radio-frequency SIM card, calculating an effective communication distance of the low-frequency magnetic field and setting a low-frequency magnetic field intensity value corresponding to the effective communication distance as the Threshold 2;
• based on requirements for a farthest transaction distance control, setting a low-frequency magnetic field intensity value corresponding to the farthest transaction distance as the Threshold 3.