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1. Enabling Multiple Access in Visible Light Communication Using Liquid Crystal Displays: A Proof-of-Concept Study

   https://doi.org/10.3390/electronics9050826  

   Rahman, MD Rashed; Adedara, Kehinde; Ashok, Ashwin (May 2020, Electronics)

   null (Ed.)

   The directionality of optical signals provides an opportunity for efficient space reuse of optical links in visible light communication (VLC). Space reuse in VLC can enable multiple-access communication from multiple light emitting transmitters. Traditional VLC system design using photo-receptors requires at least one receiving photodetector element for each light emitter, thus constraining VLC to always require a light-emitter to light-receptor element pair. In this paper, we propose, design and evaluate a novel architecture for VLC that can enable multiple-access reception using a photoreceptor receiver that uses only a single photodiode. The novel design includes a liquid-crystal-display (LCD) based shutter system that can be automated to control and enable selective reception of light beams from multiple transmitters. We evaluate the feasibility of multiple access on a single photodiode from two light emitting diode (LED) transmitters and the performance of the communication link using bit-error-rate (BER) and packet-error-rate (PER) metrics. Our experiment and trace based evaluation through proof-of-concept implementation reveals the feasibility of multiple LED reception on a single photodiode. We further evaluate the system in controlled mobile settings to verify the adaptability of the receiver when the LED transmitter changes position. 

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2. A Study of Optical Tag Detection Using Rolling Shutter Based Visible Light Communications

   https://doi.org/10.1109/GLOBECOM38437.2019.9013449  

   Pan, Zijin; Lang, Tian; Li, Zening; Chen, Gang; Wang, Albert (December 2019, Proc. IEEE Global Communications Conference (GLOBECOM))

   null (Ed.)

   In this paper, we present an in-depth study of light emitting diode (LED) based indoor visible light communication positioning system using a smart phone camera with rolling shutter effect, aiming for smart and connected hospital applications. The LED transmits periodical signals with different frequencies as its optical tags. The camera exploits the rolling shutter effect to detect the fundamental frequency of optical signals. The roles of camera parameters determining the rolling effect are studied and a technique to measure the camera readout time per column is presented. Factors limiting the detectable optical frequency range is explained based on the discussion of rolling shutter mechanism. The Fourier spectrum based frequency resolution, which determines the tracking capacity, is analyzed. 

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3. A Single-Aperture, Single-Pixel Reader for Optical Frequency Identification

   https://doi.org/10.1109/ISCAS51556.2021.9401470  

   Fan, Xiaozhe; Hidalgo, James; Leon-Salas, Walter D. (May 2021, 2021 IEEE International Symposium on Circuits and Systems (ISCAS))

   null (Ed.)

   This paper presents a single-aperture, single-pixel reader for communication with Optical Frequency Identification (OFID) tags. OFID tags use solar cells to transmit and receive information wirelessly as well as to harvest radiant energy. Due to its single-aperture architecture, the reader's optical system provides a shared optical path for reception and transmission. Also, physical alignment between the reader and an OFID tag is visually guided using the reader's emitted light, securing a robust data link as long as the OFID tag is illuminated. In this paper, a description of the reader's optical and electronic sub-systems are presented. The transmitter and receiver circuits are described in detail. The transmitter, built with a linear LED driver, achieves a power efficiency of nearly 87%. The receiver, featuring a third-order bandpass filter, reduces both low-frequency and high-frequency ambient noise. A prototype of the reader was fabricated and housed in a custom 3D-printed enclosure. Test results show that the reader is able to receive modulated luminescent signals from an OFID tag at a distance of 1 m and at a data rate of 3 kbps. 

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4. Ordered Gradient Approach for Communication-Efficient Distributed Learning

   https://doi.org/10.1109/SPAWC48557.2020.9153887  

   Chen, Yicheng; Sadler, Brian M.; Blum, Rick S. (May 2020, 2020 IEEE 21st International Workshop on Signal Processing Advances in Wireless Communications (SPAWC))

   null (Ed.)

   The topic of training machine learning models by employing multiple gradient-computing workers is attracting great interest recently. Communication efficiency in such distributed learning settings is an important consideration, especially for the case where the needed communications are expensive in terms of power usage. We develop a new approach which is efficient in terms of communication transmissions. In this scheme, only the most informative worker results are transmitted to reduce the total number of transmissions. Our ordered gradient approach provably achieves the same order of convergence rate as gradient descent for nonconvex smooth loss functions while gradient descent always requires more communications. Experiments show significant communication savings compared to the best existing approaches in some cases. 

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5. Amortizing Rate-1 OT and Applications to PIR and PSI

   https://doi.org/10.1007/978-3-030-90456-2_5  

   Chase, M.; Garg, S.; Hajiabadi, M.; Li, J.; Miao, P. (November 2022, 19th Theory of Cryptography Conference (TCC))

   Nissim, K.; Waters, B. (Ed.)

   Recent new constructions of rate-1 OT [Döttling, Garg, Ishai, Malavolta, Mour, and Ostrovsky, CRYPTO 2019] have brought this primitive under the spotlight and the techniques have led to new feasibility results for private-information retrieval, and homomorphic encryption for branching programs. The receiver communication of this construction consists of a quadratic (in the sender's input size) number of group elements for a single instance of rate-1 OT. Recently [Garg, Hajiabadi, Ostrovsky, TCC 2020] improved the receiver communication to a linear number of group elements for a single string-OT. However, most applications of rate-1 OT require executing it multiple times, resulting in large communication costs for the receiver. In this work, we introduce a new technique for amortizing the cost of multiple rate-1 OTs. Specifically, based on standard pairing assumptions, we obtain a two-message rate-1 OT protocol for which the amortized cost per string-OT is asymptotically reduced to only four group elements. Our results lead to significant communication improvements in PSI and PIR, special cases of SFE for branching programs. - PIR: We obtain a rate-1 PIR scheme with client communication cost of $$O(\lambda\cdot\log N)$$ group elements for security parameter $$\lambda$$ and database size $$N$$. Notably, after a one-time setup (or one PIR instance), any following PIR instance only requires communication cost $$O(\log N)$$ number of group elements. - PSI with unbalanced inputs: We apply our techniques to private set intersection with unbalanced set sizes (where the receiver has a smaller set) and achieve receiver communication of $$O((m+\lambda) \log N)$$ group elements where $m, N$ are the sizes of the receiver and sender sets, respectively. Similarly, after a one-time setup (or one PSI instance), any following PSI instance only requires communication cost $$O(m \cdot \log N)$$ number of group elements. All previous sublinear-communication non-FHE based PSI protocols for the above unbalanced setting were also based on rate-1 OT, but incurred at least $$O(\lambda^2 m \log N)$$ group elements. 

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