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1. Discrete Time Synchronization Modeling for Active Rectifiers in Wireless Power Transfer Systems

   https://doi.org/10.1109/COMPEL.2019.8769717  

   Cochran, Spencer; Costinett, Daniel (June 2019, IEEE Workshop on Control and Modeling for Power Electronics (COMPEL))

   Active rectifiers in wireless power transfer systems exhibit many benefits compared to diode rectifiers, including increased efficiency, controllable impedance, and regulation capability. To achieve these benefits, the receivers must synchronize their switching frequency to the transmitter to avoid sub-fundamental beat frequency oscillations. Without additional communication, the receiver must synchronize to locally-sensed signals, such as voltages and currents induced in the power stage by the transmitter. However, the waveforms in the receiver are dependent on both the transmitter and receiver operation, resulting in an internal feedback between sensing and synchronization which prohibits the use of traditional phase-locked-loop design techniques. In this digest, a discrete time state space model is developed and used to derive a small signal model of these interactions for the purpose of designing stable closed-loop synchronization control. A prototype 150 kHz wireless power transfer converter is used to experimentally validate the modeling, showcasing stable synchronization. 

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2. Proactive Anti-Eavesdropping With Trap Deployment in Wireless Networks

   https://doi.org/10.1109/TDSC.2022.3141406  

   He, Qiuye; Fang, Song; Wang, Tao; Liu, Yao; Zhao, Shangqing; Lu, Zhuo (January 2022, IEEE Transactions on Dependable and Secure Computing)

   Due to the open nature of wireless medium, wireless communications are especially vulnerable to eavesdropping attacks. This paper designs a new wireless communication system to deal with eavesdropping attacks. The proposed system can enable a legitimate receiver to get desired messages and meanwhile an eavesdropper to hear ``fake" but meaningful messages by combining confidentiality and deception, thereby confusing the eavesdropper and achieving additional concealment that further protects exchanged messages. Towards this goal, we propose techniques that can conceal exchanged messages by utilizing wireless channel characteristics between the transmitter and the receiver, as well as techniques that can attract an eavesdropper to gradually approach a trap region, where the eavesdropper can get fake messages. We also provide both theoretical and empirical analysis of the established secure channel between the transmitter and the receiver. We develop a prototype system using Universal Software Defined Radio Peripherals (USRPs)Experimental results show that an eavesdropper at a trap location can receive fake information with a bit error rate (BER) close to 0, and the transmitter with multiple antennas can successfully deploy a trap area. 

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3. Physical Layer Encryption for Wireless OFDM Communication Systems

   https://doi.org/10.1007/s41635-020-00097-8  

   Jacovic, Marko; Juretus, Kyle; Kandasamy, Nagarajan; Savidis, Ioannis; Dandekar, Kapil R. (July 2020, Journal of Hardware and Systems Security)

   Our everyday lives are impacted by the widespread adoption of wireless communication systems integral to residential, industrial, and commercial settings. Devices must be secure and reliable to support the emergence of large scale heterogeneous networks. Higher layer encryption techniques such as Wi-Fi Protected Access (WPA/WPA2) are vulnerable to threats, including even the latest WPA3 release. Physical layer security leverages existing components of the physical or PHY layer to provide a low-complexity solution appropriate for wireless devices. This work presents a PHY layer encryption technique based on frequency induction for Orthogonal Frequency Division Multiplexing (OFDM) signals to increase security against eavesdroppers. The secure transceiver consists of a key to frequency shift mapper, encryption module, and modified synchronizer for decryption. The system has been implemented on a Virtex-7 FPGA. The additional hardware overhead incurred on the Virtex-7 for both the transmitter and the receiver is low. Both simulation and hardware evaluation results demonstrate that the proposed system is capable of providing secure communication from an eavesdropper with no decrease in performance as compared with the baseline case of a standard OFDM transceiver. The techniques developed in this paper provide greater security to OFDM-based wireless communication systems. 

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4. A 41.5 pJ/b, 2.4GHz Digital-Friendly Orthogonally Tunable Transceiver SoC with 3-decades of Energy-Performance Scalability

   https://doi.org/10.1109/CICC48029.2020.9075915  

   Chatterjee, Baibhab; Sen, Shreyas (April 2020, IEEE Custom Integrated Circuits Conference (CICC))

   null (Ed.)

   Adaptive communication for Internet of Things (IoT) and Wireless Body Area Network (WBAN) technologies is becoming increasingly popular due to the large power-performance trade-offs and highly dynamic channel conditions. Path loss, low signal to noise ratio (SNR) in the channel and network congestion adversely affect the data communication, each of which can be taken care of using different strategies such as reducing the data rate (for reducing congestion), increasing the output power (for increased path loss) and application of error correction coding (ECC, for low SNR). In this paper, we present a digital-friendly Transceiver SoC consisting of an RF-DAC based transmitter with orthogonally tunable output power, data rate and ECC that enables optimum system level bit error rate (BER) and energy for over 3-orders of energy-performance scalability, along with an ultra-low-power OOK receiver that receives the transmitter's control bits from a nearby base station for closed-loop control. The data rate and ECC control is achieved through a digital baseband, while a tapped capacitor matching network controls the output power. The energy efficiency of the transmitter is 27.6pJ/b at 10MSps and at 0.8V supply (~9X improvement over state-of-the-art), while the entire SoC (Transmitter+OOK receiver for controller feedback) consumes only 41.5pJ/b. 

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5. Keyless Covert Communication in the Presence of Non-causal Channel State Information

   Zivari-Fard, H.; Bloch, M.; Nosratinia, A. (August 2019, IEEE Information Theory Workshop)

   We consider the problem of covert communication over a state-dependent channel, for which the transmitter and the legitimate receiver have non-causal access to the channel state information. Covert communication with respect to an adversary, referred to as the “warden,” is one in which the distribution induced during communication at the channel output observed by the warden is identical to the output distribution conditioned on an inactive channel-input symbol. Covert communication involves fooling an adversary in part by a proliferation of codebooks; for reliable decoding at the legitimate receiver the codebook uncertainty is removed via a shared secret key that is unavailable to the warden. Unlike earlier work in state-dependent covert communication, we do not assume the availability of a shared key at the transmitter and legitimate receiver. Rather, a shared randomness is extracted at the transmitter and the receiver from the channel state, in a manner that keeps the shared randomness secret from the warden despite the influence of the channel state on the warden’s output. An inner bound on the covert capacity, in the absence of an externally provided secret key, is derived. 

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