Affiliations: [a] Fraunhofer IMS, Institute for Microelectronic Circuits and Systems, Duisburg, Germany
Institute of Communication Acoustics, Ruhr-Universität Bochum, Bochum, Germany
Corresponding author: Gerd vom Bögel, Fraunhofer IMS, Institute for Microelectronic Circuits and Systems, Finkenstr 61, 47057 Duisburg, Germany. Tel.: +49 203 3783-0; Fax: -153; E-mail: [email protected].
Abstract: In medicine and other high-tech sectors, mobile RFID or sensor transponder systems are designed with high-Q antenna coils to increase the energy efficiency. Hence, the range of inductively coupled systems is improved; however, the bandwidth is decreased by 1 over Q. As a result, the reading performance is not limited by the energy supply, but instead by a high bit error rate. In this paper, we describe how the data detection in such narrow-band systems can be improved by a multilevel decoding scheme composed of an advanced maximum-likelihood receiver in the ?rst stage and a soft Viterbi decoding scheme utilizing time variant reliability information in the second stage. An analysis of potential time-variant reliability information is given. The analysis relies on an underlying Bayesian model, which provides an a-posteriori probability indicating the reliability of the received input. As the final building block, a last decoding stage is discussed, which can be composed of a forward error correction that further exploits the reliability information at the second decoder output. Overall, the suggested system architecture results in a notable improvement of both bit and packet error rate, thus allowing the use of high-quality-factor antennas for efficient and reliable mobile RFID systems.
Keywords: Radio frequency identification, sensors, maximum-likelihood decoding, matched filters, viterbi algorithm, bayes methods