Error detection based on correlation analysis for BCH encoded UHF RFID communication

To accomplish a reliable detection of goods and items over a couple of meters Long Range Radio Frequency Identification (RFID) is a common used wireless transmission technique. Most of the commercial systems use a transmission with passive transponders (tags) which backscatter their information back to a processing unit (reader). This communication is realized in the Electronic Product Code (EPC) Class-1 Gen-2 protocol. In the Gen-2 protocol only a CRC code is used, which can detect transmission errors very reliably but can not correct any errors. So a possible extension to this protocol is the implementation of Forward Error Correction (FEC). Because of its similarity with the CRC code a BCH code can be used. For the small scale fading characteristic and the dyadic backscatter channel a coding gain up to 8 dB regarding the bit error rate can be achieved during an RFID transmission. The disadvantage of a BCH decoding without any additional error detection is however, that the decoder can not decide if a decoded package is false when the erroneous codeword is wrongly detected as another correct codeword. This may lead to falsely detected packages especially for low SNR. This paper shows a simple technique which uses the information of the spreading sequences in the Gen-2 protocol for a detection of erroneous packets. It is shown that the combination of BCH FEC and reliability detection outperforms the conventional CRC-based transmission regarding the time to read a particular tag population in many cases.