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Register a new userLive Streaming of the Uncompressed HD and 4K Videos Using Terahertz Wireless Links
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Added by
Maksim Skorobogatiy
Publication date
2017
fields
Physics
and research's language is
English
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Taming the Terahertz waves (100 GHz-10 THz) is considered the next frontier in wireless communications. While components for the ultra-high bandwidth Terahertz wireless communications were in rapid development over the past several years, however, their commercial availability is still lacking. Nevertheless, as we demonstrate in this paper, due to recent advances in the microwave and infrared photonics hardware, it is now possible to assemble high performance hybrid THz communication systems for real-life applications. As an example, in this work, we present design and performance evaluation of the photonics-based Terahertz wireless communication system for the transmission of uncompressed 4K video feed that is built using all commercially available system components. In particular, two independent tunable lasers operating in the infrared C-band are used as a source for generating the Terahertz carrier wave using frequency difference generation in a photomixer. One of the IR laser beams carries the data which is intensity modulated using the LiNbO3 electro-optic modulator. A zero bias Schottky detector is used as the detector and demodulator of the data stream followed by the high-gain and low-noise pre-amplifier. The Terahertz carrier frequency is fixed at 138 GHz and the system is characterized by measuring the bit error rate for the pseudo random bit sequences at 5.5 Gbps. By optimizing the link geometry and decision parameters, an error-free (BER<10-10) transmission at a link distance of 1m is achieved. Finally, we detail integration of a professional 4K camera into the THz communication link, and demonstrate live streaming of the uncompressed HD and 4K video followed by analysis of the link quality.
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In this work, we present an in-depth experimental and numerical study of the short-range THz communications links that use subwavelength dielectric fibers for information transmission and define main challenges and tradeoffs in the link implementation. Particularly, we use air or foam-cladded polypropylene-core subwavelength dielectric THz fibers of various diameters (0.57-1.75 mm) to study link performance as a function of the link length of up to ~10 m, and data bitrates of up to 6 Gbps at the carrier frequency of 128 GHz (2.34 mm wavelength). We find that depending on the fiber diameter, the quality of the transmitted signal is mostly limited either by the modal propagation loss or by the fiber velocity dispersion (GVD). An error-free transmission over 10 meters is achieved for the bit rate of 4 Gbps using the fiber of smaller 0.57 mm diameter. Furthermore, since the fields of subwavelength fibers are weakly confined and extend deep into the air cladding, we study the modal field extent outside of the fiber core, as well as fiber bending loss. Finally, the power budget of the rod-in-air subwavelength THz fiber-based links is compared to that of free space communication links and we demonstrate that fiber links offer an excellent solution for various short-range applications.
Video live streaming is gaining prevalence among video streaming services, especially for the delivery of popular sporting events. Many objective Video Quality Assessment (VQA) models have been developed to predict the perceptual quality of videos. Appropriate databases that exemplify the distortions encountered in live streaming videos are important to designing and learning objective VQA models. Towards making progress in this direction, we built a video quality database specifically designed for live streaming VQA research. The new video database is called the Laboratory for Image and Video Engineering (LIVE) Live stream Database. The LIVE Livestream Database includes 315 videos of 45 contents impaired by 6 types of distortions. We also performed a subjective quality study using the new database, whereby more than 12,000 human opinions were gathered from 40 subjects. We demonstrate the usefulness of the new resource by performing a holistic evaluation of the performance of current state-of-the-art (SOTA) VQA models. The LIVE Livestream database is being made publicly available for these purposes at https://live.ece.utexas.edu/research/LIVE_APV_Study/apv_index.html.
Metasurfaces are an enabling technology for complex wave manipulation functions, including in the terahertz frequency range, where they are expected to advance security, imaging, sensing, and communications technology. For operation in transmission, Huygens metasurfaces are commonly used, since their good impedance match to the surrounding media minimizes reflections and maximizes transmission. Recent theoretical work has shown that Huygens metasurfaces are non-optimal, particularly for large angles of refraction, and that to eliminate reflections and spurious diffracted beams it is necessary to use a bianisotropic metasurface. However, it remains to be demonstrated how significant the efficiency improvement is when using bianisotropic metasurfaces, considering all the non-ideal features that arise when implementing the metasurface design with real meta-atoms. Here we compare concrete terahertz metasurface designs based on the Huygens and Omega-type bianisotropic approaches, demonstrating anomalous refraction angles for 55 degrees, and 70 degrees. We show that for the lower angle of 55 degrees, there is no significant improvement when using the bianisotropic design, whereas for refraction at 70 degrees the bianisotropic design shows much higher efficiency and fidelity of refraction into the designed direction. We also demonstrate the strong perturbations caused by near-field interaction, both between and within cells, which we compensate using numerical optimization.
Terahertz (THz) band is considered as the next frontier in wireless communications. The emerging THz multiplexing techniques are expected to dramatically increase the information capacity of THz communications far beyond a single channel limit. In this work, we explore the THz frequency-division multiplexing modality enabled by novel add-drop multiplexer (ADM) design. Based on modular two-wire plasmonic waveguides fabricated using additive manufacturing and metallization techniques, we demonstrate four-port THz ADMs containing grating-loaded side couplers for operation at ~140 GHz carrier frequency. Particular attention is payed to the design of plasmonic waveguide Bragg gratings and directional couplers capable of splitting broadband THz light in spectral and spatial domains, respectively. Finally, we demonstrate multiplexing and demultiplexing of THz signals with bit rates up to 6 Gbps using the developed ADMs. We believe that proposed plasmonic circuits hold strong potential to provide robust integrated solutions for analogue signal processing in the upcoming THz communications.
We studied the injection-locking properties of a resonant-tunneling-diode terahertz oscillator in the small-signal injection regime with a frequency-stabilized continuous THz wave. The linewidth of the emission spectrum dramatically decreased to less than 120 mHz (HWHM) from 4.4 MHz in the free running state as a result of the injection locking. We experimentally determined the amplitude of injection voltage at the antenna caused by the injected THz wave. The locking range was proportional to the injection amplitude and consistent with Adlers model. As increasing the injection amplitude, we observed decrease of the noise component in the power spectrum, which manifests the free-running state, and alternative increase of the injection-locked component. The noise component and the injection-locked component had the same power at the threshold injection amplitude as small as $5times10^{-4}$ of the oscillation amplitude. This threshold behavior can be qualitatively explained by Maffezzonis model of noise reduction in general limit-cycle oscillators.
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