Short-range ultrasonic communications in air using quadrature modulation

A study has been undertaken of ultrasonic communications methods in air, using a quadrature modulation method. Simulations were first performed to establish the likely performance of quadrature phase shift keying over the limited bandwidth available in an ultrasonic system. Quadrature phase shift keying modulation was then implemented within an experimental communication system, using capacitive ultrasonic sources and receivers. The results show that such a system is feasible in principle for communications over distances of several meters, using frequencies in the 200 to 400 kHz range

Wireless communication using ultrasound in air with parallel OOK channels

The use of airborne ultrasonic transducers for wireless communication was demonstrated. The work used capacitive ultrasonic transducers to transmit coded binary signals through parallel air channels. On-Off Keying modulation was successfully implemented in the system. Within the limited bandwidth of the transducers, six channels were used at frequencies from 50 kHz to 110 kHz with a channel spacing of 12 kHz, allowing 8-bit packets to be transmitted simultaneously. Wireless handshaking was achieved using a simple synchronization signal in front of the information signal. A data rate of 60 kbps was achieved over a short distance and the system Bit Error Rate (BER) was analysed

Feasibility and Security Analysis of Wideband Ultrasonic Radio for Smart Home Applications

Smart home Internet-of-Things (IoT) accompanied by smart home apps has witnessed tremendous growth in the past few years. Yet, the security and privacy of the smart home IoT devices and apps have raised serious concerns, as they are getting increasingly complicated each day, expected to store and exchange extremely sensitive personal data, always on and connected, and commonly exposed to any users in a sensitive environment. Nowadays wireless smart home IoT devices rely on electromagnetic wave-based radio-frequency (RF) technology to establish fast and reliable quality network connections. However, RF has its limitations that can negatively affect the smart home user experience and even cause serious security issue, such as crowded spectrum resources and RF waves leakage. To overcome those limitations, people have to use technology with sophisticated time and frequency division management and rely on the assumptions that the attackers have limited computational power. In this thesis we propose URadio, a wideband ultrasonic communication system, using electrostatic ultrasonic transducers. We design and develop two different types of transducer membranes using two types of extremely thin materials, Aluminized Mylar Film (AMF) and reduced Graphene Oxide (rGO), for assembling transducers, which achieve at least 45 times more bandwidth than commercial transducers. Equipped with the new wideband transducers, an OFDM communication system is designed to better utilize the available 600 kHz wide bandwidth. Our experiments show that URadio can achieve an unprecedentedly 4.8 Mbps data rate with a communication range of 17 cm. The attainable communication range is increased to 31 cm and 35 cm with data rates of 1.2 Mbps and 0.6 Mbps using QPSK and BPSK, respectively. Although the current wideband system only supports short-range communication, it is expected to extend the transmission range with better acoustic engineering. Also, by conducting experiments to measure the ultrasonic adversaries\u27 eavesdropping and jamming performance, we prove that our system is physically secure even when exchanging plaintext data. Adviser: Qiben Ya

Progress in airborne ultrasonic data communications for indoor applications

Capacitive ultrasonic transducers are efficient transmitters and receivers for ultrasonic waves in air, making them ideal devices for signal transmissions in air. Ultrasonic signals are unregulated, difficult to intercept from outside the room, and interference free to most electronic devices. These high security features make ultrasonic communication systems an alternative to radio frequency (RF) based systems for indoor applications. This paper investigated a prototype ultrasonic communication system using a pair of commercially available capacitive ultrasonic transducers in an indoor laboratory environment. Multichannel On-OFF keying (OOK) and binary phase-shift keying (BPSK) modulation schemes were implemented successfully in the system with wireless synchronization, achieving an overall data rate of 60 kb/s using ultrasonic bands from 50 to 110 kHz. The results show that a reliable line-of-sight (LOS) link can be established for communications over distances of 10 and 11 m using multichannel OOK and BPSK, respectively

Experimental Demonstration of Staggered CAP Modulation for Low Bandwidth Red-Emitting Polymer-LED based Visible Light Communications

In this paper we experimentally demonstrate, for the first time, staggered carrier-less amplitude and phase (sCAP) modulation for visible light communication systems based on polymer light-emitting diodes emitting at ~639 nm. The key advantage offered by sCAP in comparison to conventional multiband CAP is its full use of the available spectrum. In this work, we compare sCAP, which utilises four orthogonal filters to generate the signal, with a conventional 4-band multi-CAP system and on-off keying (OOK). We transmit each modulation format with equal energy and present a record un-coded transmission speed of ~6 Mb/s. This represents gains of 25% and 65% over the achievable rate using 4-CAP and OOK, respectively.Comment: 6 pages, 9 figures, IEEE ICC 2019 conferenc

Indoor airborne ultrasonic wireless communication using OFDM methods

Concerns still exist over the safety of prolonged exposure to radio frequency (RF) wireless transmissions and there are also potential data security issues due to remote signal interception techniques such as Bluesniping. Airborne ultrasound may be used as an alternative to RF for indoor wireless communication systems for securely transmitting data over short ranges, as signals are difficult to intercept from outside the room. Two types of air-coupled capacitive ultrasonic transducer were used in the implementation of an indoor airborne wireless communication system. One was a commercially available SensComp series 600 ultrasonic transducer with a nominal frequency of 50 kHz, and the other was a prototype transducer with a high-k dielectric layer operating at higher frequencies from 200 to 400 kHz. Binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), and quadrature amplitude modulation (QAM)-based orthogonal frequency division multiplexing modulation methods were successfully implemented using multiple orthogonal sub-channels. The modulated ultrasonic signal packets were synchronized using a wireless link, and a least-squares channel estimation algorithm was used to compensate the phase and amplitude distortion introduced by the air channel. By sending and receiving the ultrasonic signals using the SensComp transducers, the achieved maximum system data rate was up to 180 kb/s using 16-QAM with ultrasonic channels from 55 to 99 kHz, over a line-of-sight transmission distance of 6 m with no detectable errors. The transmission range could be extended to 9 and 11 m using QPSK and BPSK modulation schemes, respectively. The achieved data rates for the QPSK and BPSK schemes were 90 and 45 kb/s using the same bandwidth. For the high-k ultrasonic transducers, a maximum data rate up to 800 kb/s with no measurable errors was achieved up to a range of 0.7 m. The attainable transmission ranges were increased to 1.1 and 1.2 m with data rates of 400 and 200 kb/s using QPSK and BPSK, respectively

Multichannel ultrasonic data communications in air using range-dependent modulation schemes

There are several well-developed technologies of wireless communication such as radio frequency (RF) and infrared (IR), but ultrasonic methods can be a good alternative in some situations. A multichannel airborne ultrasonic data communication system is described in this paper. ON-OFF keying (OOK) and binary phase-shift keying (BPSK) modulation schemes were implemented successfully in the system by using a pair of commercially available capacitive ultrasonic transducers in a relatively low multipath indoor laboratory environment. Six channels were used from 50 to 110 kHz with a channel spacing of 12 kHz, allowing multiple 8-bit data packets to be transmitted simultaneously. The system data transfer rate achieved was up to 60 kb/s and ultrasonic wireless synchronization was implemented instead of using a hard-wired link. A model developed in the work could accurately predict ultrasonic signals through the air channels. Signal root mean square (rms) values and system bit error rates (BERs) were analyzed over different distances. Error-free decoding was achieved over ranges up to 5 m using a multichannel OOK modulation scheme. To obtain the highest data transfer rate and the longest error-free transmission distance, a range-dependent multichannel scheme with variable data rates, channel frequencies, and different modulation schemes, was also studied in the work. Within 2 m, error-free transmission was achieved using a five-channel OOK with a data rate of 63 kb/s. Between 2 and 5 m, six-channel OOK with 60 kb/s data transfer rate was error free. Beyond 5 m, the error-free transmission range could be extended up to 10 m using three-channel BPSK with a reduced data rate of 30 kb/s. The situation when two transducers were misaligned using three-channel OOK and BPSK schemes was also investigated in the work. It was concluded that error-free transmission could still be achieved with a lateral displacement of less than 7% and oblique angles of less than 7°, and three-channel BPSK proved to be more robust than three-channel OOK with transducer misalignment

The high frequency flexural ultrasonic transducer for transmitting and receiving ultrasound in air

Flexural ultrasonic transducers are robust and low cost sensors that are typically used in industry for distance ranging, proximity sensing and flow measurement. The operating frequencies of currently available commercial flexural ultrasonic transducers are usually below 50 kHz. Higher operating frequencies would be particularly beneficial for measurement accuracy and detection sensitivity. In this paper, design principles of High Frequency Flexural Ultrasonic Transducers (HiFFUTs), guided by the classical plate theory and finite element analysis, are reported. The results show that the diameter of the piezoelectric disc element attached to the flexing plate of the HiFFUT has a significant influence on the transducer's resonant frequency, and that an optimal diameter for a HiFFUT transmitter alone is different from that for a pitch-catch ultrasonic system consisting of both a HiFFUT transmitter and a receiver. By adopting an optimal piezoelectric diameter, the HiFFUT pitch-catch system can produce an ultrasonic signal amplitude greater than that of a non-optimised system by an order of magnitude. The performance of a prototype HiFFUT is characterised through electrical impedance analysis, laser Doppler vibrometry, and pressure-field microphone measurement, before the performance of two new HiFFUTs in a pitch-catch configuration is compared with that of commercial transducers. The prototype HiFFUT can operate efficiently at a frequency of 102.1 kHz as either a transmitter or a receiver, with comparable output amplitude, wider bandwidth, and higher directivity than commercially available transducers of similar construction

Study on High-Speed Ultrasound Communication

In this work we have studied energy flow in acoustic billiards, focusing on irregular billiards with and without current effects. The open systems were modeled with an imaginary potential as a source and drain. We have used the finite difference method to model the billiards. General features of the systems are reported and effects of the measuring probe on the wave function are discussed