A Software-Defined Radio System for Backscatter Sensor Networks

Abstract

Abstract-Backscatter radio is proposed for sensor networks. In that way, the transmitter for each sensor is simplified to a transistor connected to an antenna and therefore, the cost for each sensor's communicator becomes negligible, while energy used for wireless communication per sensor is minimized. A software-defined transceiver is built to transmit a carrier, receive the reflections from various sensors and extract their transmitted messages. This work presents a thorough model of the backscatter radio link, the system architecture and a set of data extraction techniques for each sensor's information, testing in practice a sensor communicating through backscatter at a range of approximately 15 meters indoors, with 5 milliwatt transmission power at 10 bits per second. This work highlights the idiosyncrasies of the backscatter channel and provides a new communication perspective in the fertile area of scalable sensor networks, especially when low bit-rate, ultra-low cost sensors are required.Index Terms-RFID, fading channel, bit error rate, wireless sensor networks.

Improving Backscatter Radio Tag Efficiency

“…Specifically, the scattered field at direction when the tag antenna is loaded with can be expressed as [12], [13] (12) (13) (14) where is the current induced by the incoming field at the tag antenna terminals, when the tag is terminated at load , and is the field radiated by the tag antenna when the current at the tag antenna terminals is and no external incident wave is applied to the tag antenna. In (14), denotes the phase of the complex parameter , while the amplitude of is set according to (3).…”

“…Numerous and diverse applications have emerged, spanning RF identifications (RFIDs) in electronic supply chain to electronic music instrumentation [2] or software-defined implementations for ultra-low-cost and ultra-low-power environmental sensor networks [3]- [5].…”

Practical Energy Harvesting for Batteryless Ambient Backscatter Sensors

“…Backscatter radio is a promising solution for the communication aspect of modern WSNs [1]. Utilizing backscatter techniques for achieving communication, requires a RF switch alternating the loads which terminate the sensor's antenna; illumination of the sensor is also needed from a dedicated ( [2][3][4][5]) or a lready-modulated, i.e., ambient (FM [6,7], DTV [8]) RF source.…”

Bistatic architecture provides extended coverage and system reliability in scatter sensor networks

“…Current industry standards (such as UHF EPC Class 1, Generation 2 [5]) focus on the aforementioned applications, disregarding the value of scatter radio in wireless sensor networks (WSNs); the simplicity of the front-end minimizes the energy and monetary cost of each sensor node. Proof of concept systems utilizing scatter radio in WSNs have been presented in [6]- [10].…”

“…Passive tags typically employ energy harvesting to power their electronics and relatively high bit rate, resulting to short range; a monostatic architecture is typically utilized with the reader including both the transmitter of the carrier wave (CW) needed for tag operation and the receiver, responsible for tag information reception. In order to increase network coverage, recent work has proposed semipassive tags (i.e., energy assisted) and low bit rate [6], as well as bistatic architecture with non-coherent [10] or coherent [11] processing, even with exploitation of short block-length channel codes [12], [11], [13]. In the bistatic architecture the reader and the carrier emitter are not co-located.…”