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1. An Efficient Pulse Position Modulation Scheme to Improve the Bit Rate of Photoacoustic Communication

   https://doi.org/10.1109/WOCC58016.2023.10139346  

   Islam, Md Shafiqul; Younis, Mohamed; Mahmud, Muntasir; Choa, Fow-Sen (May 2023, IEEE)

   Wireless communication from air-to-underwater is quite challenging because of the lack of proper physical signal that propagates well in both air and water medium. Photoacoustic energy transfer mechanism is the most promising method for such cross-medium communication, where a high energy pulsed light is focused on the water surface, causing the generation of an acoustic signal inside the water. Since acoustic signals can travel a long distance inside the water, this method enables an airborne unit to reach nodes at increased underwater depth. Yet the achievable bit rate for this process is very low. When a pulsed laser light with a higher repetition rate is focused inside the water, a vapor cloud is generated around the focus point, which blocks subsequent generation of acoustic signal and consequently limits the achievable bit rate. This paper opts to overcome such a limitation by proposing a novel pulse position modulation technique which can avoid such generation of vapor cloud and increases the bit rate significantly. 

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2. Lithium Niobate Piezoelectric Micromachined Ultrasonic Transducers for high data-rate intrabody communication

   https://doi.org/10.1038/s41467-022-29355-9  

   Pop, Flavius; Herrera, Bernard; Rinaldi, Matteo (April 2022, Nature Communications)

   Abstract In recent years, there has been an increased interest in continuous monitoring of patients and their Implanted Medical Devices (IMDs) with different wireless technologies such as ultrasounds. This paper demonstrates a high data-rate intrabody communication link based on Lithium Niobate (LN) Piezoelectric Micromachined Ultrasonic Transducers (pMUTs). The properties of the LN allow to activate multiple flexural mode of vibration with only top electrodes. When operating in materials like the human tissue, these modes are merging and forming a large communication bandwidth. Such large bandwidth, up to 400 kHz, allows for a high-data rate communication link for IMDs. Here we demonstrate a full communication link in a tissue phantom with a fabricated LN pMUT array of 225 elements with an area of just 3 by 3 mm square, showing data-rates up to 800 kbits/s, starting from 3.5 cm and going up to 13.5 cm, which covers the vast majority of IMDs. 

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3. Enabling Underwater Acoustic Cooperative MIMO Systems by Metamaterial-Enhanced Magnetic Induction

   Desai, Soham; Sudev, Vaishnendr; Tan, Xin; Wang, Pu; Sun, Zhi (April 2019, 2019 IEEE Wireless Communications and Networking Conference (WCNC))

   The acoustic cooperative multi-input-multi-output (MIMO) systems equipped on the underwater robot swarms (URSs) can enable long-range and high-throughput communications. However, the acoustic communications cannot provide the real-time and accurate synchronization for the distributed transmitters of the cooperative MIMO due to the large delay of acoustic channels. In addition, the narrow bandwidth of the acoustic channel further enlarges the synchronization time and errors. In this paper, we propose the metamaterial magnetic induction (M2I)-assisted acoustic cooperative MIMO to address aforementioned challenges. The synchronization time can be reduced since the M2I has negligible signal propagation delays. To quantitatively analyze the improvement, we deduce the synchronization errors, signal-to-noise ratio (SNR), eective communication time, and the throughput of the system. Finally, the improvement of using M2I-assisted synchronization is validated by the numerical evaluation. 

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4. An Adaptive DPPM for Efficient and Robust Visible Light Communication Across the Air-Water Interface

   https://doi.org/10.1109/WOCC48579.2020.9114944  

   Islam, Md Shafiqul; Younis, Mohamed (May 2020, 2020 29th Wireless and Optical Communications Conference (WOCC))

   The scarcity of the optical power is the main challenge for underwater visible light communication. It becomes worst for communication across the air-water interface because of the reflection of light from the air-water interface. Differential pulse position modulation (DPPM) is one of the power efficient modulation techniques. In L-DPPM a block of M = log 2 L input data is mapped into one of the L distinct waveforms containing only one 'on' chip. The size of the DPPM packet is variable and depends on the value of input data and L, which makes error detection quite challenging. In this paper, we propose a frame structure that efficiently enables error detection within a packet for various symbol length, L, of DPPM. We also propose an algorithm using such a frame structure to enable effective detection of packet errors and for adaptively changing the value of L for optimal power efficiency while meeting a certain bound on the packet error rate (PER). We have named our proposed protocol as adaptive differential pulse position modulation (ADPPM). The Bit rate and PER have been studied for different signal-to-noise ratio (SNR) through simulation. A comparison between ADPPM and OOK, DPPM with fixed L is provided. 

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5. 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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