Energy efficient physical layer design for passive RFID system

In forward link, to cooperate with ASK modulation, a new data coding method for carrying out more energy to passive tag is presented for passive RFID system in this paper. The basic idea of the coding is to set adjustable and asymmetric high and low level duration within a symbol cycle, and a longer duration for high level. The performance analysis results show the energy of baseband data transmitted from reader to tags increased by 84% at most, compared with that of Manchester coding at typical 40 kbps. The system performance can be increased by using this coding. The same results are showed by the testbed and theoretical analysis. In return link, the scheme of coded OOK and coded BPSK is proposed. The cutoff rate is used to study the influence of encoding on system performances. Analysis results show that coded modulation is more energy efficient than uncoded modulation in Passive RFID return link and the system performance is improved with almost no increase in chip complexity. The gains of encoding in system information rates and communication range for different cutoff rate is analyzed and evaluated.