Nested Error Correcting Code Based Highly Reliable Data Reading for UHF RFID

In the current UHF RFID standards, the data transfer on reverse link, from tag to reader, is unreliable in nature since there is only error detection code (CRC) used. With the continuous improvement of sensitivity for tag chip, the unreliable reverse link may become the bottleneck for the whole system. In this paper, a nested error correcting code (ECC) based data transfer method is proposed to enhance the reliability of reverse link while maintaining the acceptable read efficiency. The information bits are encoded in the nested way to get the redundant bits for each layer. The reader writes the original information bits and all redundant bits into the tag. During the reading process, the reader gets the redundant bits at different layer in an incremental manner. The purpose is to correct the errors by requiring as less redundant bits as possible. According to the numerical results, the reliability in terms of residual error probability is improved significantly compared to the normal scheme with only CRC check. However, the efficiency in terms of average time to get information bits is much better than the single code protection scheme. Therefore, the proposed scheme can get a good tradeoff between reliability and efficiency. On the other hand, the proposed scheme can be implemented in software, requiring no modifications on the reader hardware and tag.