Underwater physical medium is a challenging environment for communication using radio frequency (RF) or acoustic waves due to strong attenuation, delay, multi-path fading, power and cost limitations. Discovered a century ago, magnetoinductive (MI) communication technique stands as a strong alternative paradigm due to its independence of environmental impairments including multi-path fading, dynamic channels and high propagation delays experienced by acoustic waves. Furthermore, MI technique yields networking solutions exploiting low-cost, easily-deployable and flexible antenna structures, and the possibility of forming networks of magnetic waveguides defeating path loss. In this work, highly power efficient and fully connected underwater communication networks (UWCNs) composed of transceiver and relay induction coils are presented. Three dimensional (3D) UWCNs are analysed in terms of basic communication metrics, i.e, signal-to-noise ratio, bit-error rate, connectivity and communication bandwidth. The performance studies of realistic 3D networks covering hundreds of meters sea depths and a few km 2 areas show that fully connected multicoil networks with communication bandwidths extending from a few to tens of KHz are possible. Furthermore, the performance dependence on coil properties and network size is theoretically modelled. Results show that MI wireless communication is a promising alternative for UWCNs and future research challenges are pointed out.

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Due to copyright restrictions, the access to the full text of this article is only available via subscription.Graphene resonators are future promising in terms of ultra-low weight, high Young's modulus, strength and wideband resonance frequencies. Besides that, nanoscale optical wireless channels including visible light spectrum are alternatives to radio-frequency communications promising energy efficiency and high data rates. In this article, vibrating multi-layer graphene nanoelectromechanical resonators are combined with designed vibrating Forster resonance energy transfer (VFRET) mechanism to achieve a nanoscale acousto-optic modulator converting vibrations to multi-color photon emissions. The frequency, color and the vibration sensitivity of emission are tunable while vibrations are realized either passively or actively by exploiting acoustic, thermo-acoustic or opto-acoustic properties of graphene. The light is generated by FRET mechanism with oscillating donor-acceptor distance where donor molecules attached on graphene are chosen as CdSe/ZnS core-shell QDs with significant properties of broad absorption spectrum, large cross-sections, tunable emission spectra, size dependent emission wavelength, high photochemical stability and improved quantum yield. The designed modulator achieves acoustic and ultrasound frequencies between several KHz and tens of MHz and radiation power reaching several nanowatts with resonator sizes of hundreds of micrometers for ambient light intensity of 0.1 W/m2/nm. The proposed system promises significant applications including nanoscale acousto-optic communication, transduction, sensing, energy harvesting and biomedical nanoscale communications.Vestel Electronics Inc

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Internet-of-things (IoT) architectures connecting a massive number of heterogeneous devices need energy efficient, low hardware complexity, low cost, simple and secure mechanisms to realize communication among devices. One of the emerging schemes is to realize simultaneous wireless information and power transfer (SWIPT) in an energy harvesting network. Radio frequency (RF) solutions require special hardware and modulation methods for RF to direct current (DC) conversion and optimized operation to achieve SWIPT which are currently in an immature phase. On the other hand, magneto-inductive (MI) communication transceivers are intrinsically energy harvesting with potential for SWIPT in an efficient manner. In this article, novel modulation and demodulation mechanisms are presented in a combined framework with multiple-access channel (MAC) communication and wireless power transmission. The network topology of power transmitting active coils in a transceiver composed of a grid of coils is changed as a novel method to transmit information. Practical demodulation schemes are formulated and numerically simulated for twouser MAC topology of small size coils. The transceivers are suitable to attach to everyday objects to realize reliable local area network (LAN) communication performances with tens of meters communication ranges. The designed scheme is promising for future IoT applications requiring SWIPT with energy efficient, low cost, low power and low hardware complexity solutions.Index Terms-Simultaneous wireless information and power transfer, magneto-inductive communication, network topology modulation, internet-of-things