High-speed acoustic communication by multiplexing orbital angular momentum

Abstract

Long-range acoustic communication is crucial to underwater applications such as collection of scientific data from benthic stations, ocean geology, and remote control of off-shore industrial activities. However, the transmission rate of acoustic communication is always limited by the narrow-frequency bandwidth of the acoustic waves because of the large attenuation for high-frequency sound in water. Here, we demonstrate a high-throughput communication approach using the orbital angular momentum (OAM) of acoustic vortex beams with one order enhancement of the data transmission rate at a single frequency. The topological charges of OAM provide intrinsically orthogonal channels, offering a unique ability to multiplex data transmission within a single acoustic beam generated by a transducer array, drastically increasing the information channels and capacity of acoustic communication. A high spectral efficiency of 8.0 ± 0.4 (bit/s)/Hz in acoustic communication has been achieved using topological charges between −4 and +4 without applying other communication modulation techniques. Such OAM is a completely independent degree of freedom which can be readily integrated with other state-of-the-art communication modulation techniques like quadrature amplitude modulation (QAM) and phaseshift keying (PSK). Information multiplexing through OAM opens a dimension for acoustic communication, providing a data transmission rate that is critical for underwater applications.high-speed acoustic communication | high spectral efficiency | orbital angular momentum | multiplexing | demultiplexing W ith the increasing amount of human activities underwater including unmanned vehicle exploration, off-shore industrial applications, and remote ocean environment monitoring, the development of underwater communication has become essential. The intrinsic strong absorption of microwave and mid-and far-infrared radiations by water molecules limits the propagation distance of radio frequencies to mere centimeters (1-4), making rf wireless communication approaches impossible. On the other hand, optical waves are scattered by objects in the ocean such as small particles, debris, and marine life due to the shorter wavelengths, limiting the range of optical communication underwater to be within just 200 m (5-7). Presently, acoustic waves are the only option for long-range (over 200 m) underwater communications. However, the applicable bandwidth of acoustic waves is limited within 20 kHz because the higher damping loss of high-frequency acoustic waves in water reduces the propagation distance to less than a kilometer range (8). Such a low carrier frequency limits drastically the spectral bandwidth and data rate accessible for data transmission. Although spectral efficiency has been improved through recent advanced communication technologies such as differential phase-shift keying (PSK) and quadrature amplitude modulation (QAM), the number of available data transmission channels remains tied to the low carrier frequency (9-13).We propose to overcome such ...

Waves, modes, communications, and optics: a tutorial

“…In communications, we continually want larger amounts of useful bandwidth. This need is strong for wireless radio-frequency transmission [13], for optical signals in fibers [14 -17] or free space [17 -20], and even for acoustic information transmission [21][22][23]. Recent progress in novel optical ways to separate different [16] and even arbitrary modes [24 -29], including automatic methods [24 -29], gives additional motivation to consider the use of different modes (or "spatial degrees of freedom") in communications.…”

Acoustic topological devices based on emulating and multiplexing of pseudospin and valley indices

“…resolution of linear differential equations, was demonstrated both theoretically and experimentally in an acoustic system that is protected by nontrivial topology against disorders and perturbations. When integrated with this and other state-of-the-art communication techniques [45][46][47], the building blocks proposed in our work may suggest a significant step towards acoustic communication circuits with complex functionalities.…”

“…For many industrial applications for acoustic devices, robust and controllable transport of acoustic signals along preferred paths is highly demanded. It is also desired that these signal channels are immune to ambient disorders and defects, and it would be even better if an enhanced data transmission rate can be realized at the same time [45].…”

“…Other related acoustic devices are also demonstrated and studied, such as a sorting and routing platform and strongly asymmetric propagation of edge states. All these interesting devices are designed based on the same platform and under the principle of topology, when integrated with other state-of-the-art communication techniques [32,33,[45][46][47], may boost the performance of existing acoustic devices to an unprecedented level.…”

Breaking the barriers: advances in acoustic functional materials

“…By designing the phase distribution in the emitting plane, the phased array is capable of generating com- plex acoustic beams, such as acoustic vortex beams and self-bending beams with arbitrary trajectories [156,157]. Acoustic vortex beams with different 'topological charges' can be utilized as orthogonal channels to improve the data transmission rate for underwater acoustic communication [157]. In a recent work, an acoustic phased array was also employed to generate the desired field for trapping and translating levitated particles by optimizing the phase profile applied to the transducers [158].…”