1,723 research outputs found
Concurrent Backscatter Streaming from Batteryless and Wireless Sensor Tags with Multiple Subcarrier Multiple Access
This paper proposes a novel multiple access method that enables concurrent sensor data streaming from multiple batteryless, wireless sensor tags. The access method is a pseudo-FDMA scheme based on the subcarrier backscatter communication principle, which is widely employed in passive RFID and radar systems. Concurrency is realized by assigning a dedicated subcarrier to each sensor tag and letting all sensor tags backscatter simultaneously. Because of the nature of the subcarrier, which is produced by constant rate switching of antenna impedance without any channel filter in the sensor tag, the tag-to-reader link always exhibits harmonics. Thus, it is important to reject harmonics when concurrent data streaming is required. This paper proposes a harmonics rejecting receiver to allow simultaneous multiple subcarrier usage. This paper particularly focuses on analog sensor data streaming which minimizes the functional requirements on the sensor tag and frequency bandwidth. The harmonics rejection receiver is realized by carefully handling group delay and phase delay of the subcarrier envelope and the carrier signal to accurately produce replica of the harmonics by introducing Hilbert and inverse Hilbert transformations. A numerical simulator with Simulink and a hardware implementation with USRP and LabVIEW have been developed. Simulations and experiments reveal that even if the CIR before harmonics rejection is 0dB, the proposed receiver recovers the original sensor data with over 0.98 cross-correlation
Performance Evaluation of Variable Bandwidth Channel Allocation Scheme in Multiple Subcarrier Multiple Access
Multiple Subcarrier Multiple Access (MSMA) enables concurrent sensor data streamings from multiple wireless and batteryless sensors using the principle of subcarrier backscatter used extensively in passive RFID. Since the interference cancellation performance of MSMA depends on the Signal to Interference plus Noise Ratio of each subcarrier, the choice of channel allocation scheme is essential. Since the channel allocation is a combinatorial problem, obtaining the true optimal allocation requires a vast amount of examinations which is impracticable in a system where we have tens of sensor RF tags. It is particularly true when we have variable distance and variable bandwidth sensor RF tags. This paper proposes a channel allocation scheme in the variable distance and variable bandwidth MSMA system based on a newly introduced performance index, total contamination power, to prioritize indecision cases. The performance of the proposal is evaluated with existing methods in terms of average communication capacity and system fairness using MATLAB Monte Carlo simulation to reveal its advantage. The accuracy of the simulation is also verified with the result obtained from the brute force method
SecuCode: Intrinsic PUF Entangled Secure Wireless Code Dissemination for Computational RFID Devices
The simplicity of deployment and perpetual operation of energy harvesting
devices provides a compelling proposition for a new class of edge devices for
the Internet of Things. In particular, Computational Radio Frequency
Identification (CRFID) devices are an emerging class of battery-free,
computational, sensing enhanced devices that harvest all of their energy for
operation. Despite wireless connectivity and powering, secure wireless firmware
updates remains an open challenge for CRFID devices due to: intermittent
powering, limited computational capabilities, and the absence of a supervisory
operating system. We present, for the first time, a secure wireless code
dissemination (SecuCode) mechanism for CRFIDs by entangling a device intrinsic
hardware security primitive Static Random Access Memory Physical Unclonable
Function (SRAM PUF) to a firmware update protocol. The design of SecuCode: i)
overcomes the resource-constrained and intermittently powered nature of the
CRFID devices; ii) is fully compatible with existing communication protocols
employed by CRFID devices in particular, ISO-18000-6C protocol; and ii) is
built upon a standard and industry compliant firmware compilation and update
method realized by extending a recent framework for firmware updates provided
by Texas Instruments. We build an end-to-end SecuCode implementation and
conduct extensive experiments to demonstrate standards compliance, evaluate
performance and security.Comment: Accepted to the IEEE Transactions on Dependable and Secure Computin
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