Pseudo-random Aloha for inter-frame soft combining in RFID systems

Abstract

In this work we consider a recently proposed variant of the classical Framed Slotted-ALOHA where slot selection is based on a pseudo-random function of the message to be transmitted and of the frame index. We couple this feature with convolutional encoding, that allows to perform Inter-frame Soft Combining (ISoC) of multiple (re)transmission attempts of the same payload across different frames. The ISoC scheme, proposed here for the first time, requires less memory usage and computational complexity at the receiver digital signal processor compared to existing techniques based on inter-frame signal cancellation (instead of combining). Numerical simulation results show that the ISoC scheme brings a noticeable throughput gain over traditional schemes in a dense RFID scenario with multiple concurrent Tag transmissions.