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Radio Frequency IDentification (RFID) is intended to supplant legacy (optical) bar code scanning technology found in many logistic and retail applications. RFID is distinguished by inexpensive, low power and compact form factor tags, whose longevity and efficacy are predicated on using passive communication techniques and on-tag power harvesting. Such tags employ backscatter modulation, which does not require any active RF components. As a result, backscatter has become an attractive design choice for short-range communications in power constrained wireless sensor networking scenarios. The purpose of this work is two-fold. First, it aims to expose backscatter communication as an emerging topic to a communication systems-theoretic audience. Since backscatter modulation and on-tag power harvesting efficiency are coupled, it is necessary to re-examine notions of power and spectral efficiency from an energy-constraint perspective; this leads to novel coded modulation schemes for future RFID systems. Further, we investigate RFID MIMO systems where the channel fading encountered has different statistics than the classical Rayleigh fading model. In turn,the trade off between diversity order and spatial multiplexing gains are distinct from wide-area MIMO. [ABSTRACT FROM PUBLISHER]

Radio Frequency Identification (RFID) systems, presently standardized under EPC Global Class-1 Gen-2, have attracted increasing interest as the next-generation technology for tagged object identification. One of the important objectives of this work is to highlight the fact that the performance of the backscatter uplink (determined by constellation choice and forward error correction) is coupled to the downlink via the power harvesting functionality. The concept of normalized power loss per bit is introduced for such RFID communication systems to capture the consequent trade-offs, that form the crux of the results. We explore the use of higher dimensional (4-QAM) modulation schemes in future RFID systems (beyond current binary modulation in Class-1 Gen 2) as a means to improve uplink bit rate. However, this results in significantly increased normalized power loss vis-a-vis 2-PSK, suggesting a role for FEC coding. New coded modulation schemes - based on unequal error protection - are proposed that provides additional degrees of freedom (via choice of code parameters) to trade-off spectral efficiency with normalized power loss. This is explored and quantified, resulting in design recommendations. [ABSTRACT FROM AUTHOR]