Simulation of an anti-collision algorithm for RFID systems using a code division multiple access with adaptive interference cancellation (CDMA/AIC) approach with dynamic processing gain (Gp)
Benitez Gutierrez, Natalia Margarita
Radio Frequency Identification (RFID) Systems are modern wireless communication systems that transmit information from a transponder (tag) to a reader. RFID systems are well known because of their contactless feature. However, tag performance is limited by collision problems when multiple tags transmit simultaneously. Due to the collision problem, much research has been developed using anti-collision algorithms to enhance the systems' efficiency, save energy, and ensure the correct transmission of information. Most research has used a Time Division Multiple Access (TDMA) approach with anti-collision ALOHA-type algorithms. The time slots and frames of the tags are manipulated to deal with the collision problem. They work with different ALOHA protocol variants that are always trying to reduce the number of collisions compared to the previous techniques. The most promising of the ALOHA protocol variants is Dynamic Frame Slotted ALOHA (DFSA). In addition, research has been conducted with a Code Division Multiple Access (CDMA) approach, called CDMA with Adaptive Interference Cancellation (CDMA/AIC). The time slots are not used for this anti-collision algorithm; instead, Spread Spectrum (SS) technology and Processing Gain (Gp) were employed. In previous work, the Gp was a fixed value equal to sixty-four (64). In contrast, this research involved a CDMA/AIC approach with a dynamic Gp reached by generating different chip rates. This technique depended on the number of collisions from the previous run to resize the Gp for a subsequent run. CDMA gave the flexibility to use Spread Spectrum. The modulated signal was spread across the channel using orthogonal pseudorandom (PN) codes (generated for each tag) and was demodulated at the reader using the same PN code. The more spread the signal was in the channel, the greater the Gp. The research proved an enhancement in the system's performance compared to the previous work. The system's efficiency enhancement and the anti-collision algorithm were proven using MatLab as the simulation software. No hardware implementation was developed in this research. Both the CDMA and the modified DFSA code were exposed to the same conditions of noise (12, 9, 6 dB SNR), number of tags (20, 60, 80, 100, 150, and 200), number of simulations (1000), and Gp/slots (32, 64, 128, and 256). After the data was collected and processed, the performance of CDMA in noisy scenarios and with a large number of tags was faster and more efficient than DFSA. CDMA presented stability and fast information processing due to its error correction and code spreading features.
CDMA/AIC, dynamic processing gain, Rayleigh distribution, MATLAB, DFSA, frame size, ALOHA protocol
Benitez Gutierrez, N. M. (2022). Simulation of an anti-collision algorithm for RFID systems using a code division multiple access with adaptive interference cancellation (CDMA/AIC) approach with dynamic processing gain (Gp) (Unpublished thesis). Texas State University, San Marcos, Texas.