Fig 2 - uploaded by William M. D. Wright
Content may be subject to copyright.
Source publication
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...
Context in source publication
Context 1
... = 4, if QPSK modulation is applied. Π(t) represents a rectangular pulse with a duration of T s . This rectangular window in the time domain produces a sinc-shape spectrum in the frequency domain which makes the subcarriers heavily overlap each other without any interference. The block diagram of OFDM modulation and demodulation is illustrated in Fig. 2. In practice, the encoded bits in series are mapped onto a modulation constellation producing complex values that represent the modulated subcarriers in parallel. The modulation and multiplexing can then be achieved digitally using an inverse fast Fourier transform (IFFT). The OFDM demodulation is virtually the inverse operation of the ...
Similar publications
The invariance of the Lyapunov exponent of a chaotic signal as it propagates along a wireless transmission channel provides a theoretical base for the application of chaos in wireless communication. In additive Gaussian channel, the chaotic signal is proved to be the optimal coherent communication waveform in the sense of using the very simple matc...
Citations
... OFDM is described in [22] as a multicarrier multiplexing technique that transmits data over a range of small frequency channels with equal bandwidth. To provide the orthogonality of all subcarrier signals during the symbol period Ts. ...
The goal of modern communication systems is to transmit information from one point to another through a communication channel quickly and effectively. Mobile wireless users will move around while always being connected to the network. This necessitates the transmission of digital material through wireless networks and satellites, which has grown to be a significant problem over time. The main goal of this study is to compare the performance and efficiency of OFDM to that of other coding schemes, such as LDPC, Turbo, and Convolution. In this simulation, multiple forms of modulation, such as 4 QPSK with a coding rate of 0.663 and a BER of 0.001 at 0.59 dB Eb/No and an efficiency of 1.326, were compared with LDPC, Turbo, and Convolution codes. The performance is improved in the following simulated comparison of 16 QAM with a coding rate of 0.479, which has a BER of 0.001, an Eb/No of 3.26 dB, and an efficiency of 1.914. Using unique, not tried before LDPC code rate of 0.313, with efficiency of 1.25, 0.001 BER, and Eb/No, of 0.65 dB, the simulation proved that the performance of BER and Eb/No, using LDPC and 16 QAM results in a more efficient coding compared with Convolution code and Turbo code. This work has the unique contribution of using untried rates from the 3GPP sheet under three different coding techniques (LDPC, Turbo, and Convolution), which resulted in a lower BER per AWGN channel under OFDM, QPSK, and 16 QAM. The simulation implemented a regular OFDM system over AWGN channel noise, which was done in MATLAB.
... The use of ultrasonic signals as an information carrier is widely known in medical and non-destructive testing fields. Using ultrasound in some environments like underwater, underground [1] and inside the human body is beneficial since no other option is proposed. Using those waves for communicating through solid structures is effective also in many industrial applications, such as nuclear, aerospace [2] and smart vehicles. ...
Transmission of digital data in solid structures is effective
in many industrial applications such as nuclear, aerospace
and smart vehicles. Traditional wireless communication
using electromagnetic waves becomes ineffective in the
presence of metals due to Faraday shielding. Ultrasonic
guided waves, such as Lamb waves, may be an alternative
solution for communicating through metallic structures
and may provide also useful information about the
health of the structure itself. The objective of this work is
to give a proper analogy scheme between telecommunication
and ultrasound domains by doing experimental tests
on healthy and damaged aluminum plates. To ensure this
analogy, an experimental platform for ultrasonic guided
wave communication is built and an automated application
using Matlab Graphical User Interface (GUI) is developed
for modulation and demodulation. Different experimental
tests on healthy plates are realized at first for Amplitude
Shift Keying (ASK), On-Off Keying (OOK) and Binary
Phase Shift Keying (BPSK) to chose the best modulation
technique at optimal bit rate. After this, a demodulation
algorithm based on cross-correlation concept from signal
processing is developed and tested to ensure communication
in damaged plates. Results show that digital data can
be recovered even in the presence of a large damage in the
transmission channel.
... Accordingly, an implementation of a high speed WLAN system based on an asynchronous OFDM, at real-time DSP, has been presented. The implementation of an airborne ultrasonic communication system was proposed by [22], where the OFDM technologh was investigated with different modulation schemes such as BPSK, QPSK and 16-QAM. The work proved that ODFM has a superior behaviour especially with 16-QAM modulation. ...
This paper introduces the design and implementation of a wireless communication system with MATLAB based on orthognal frequency division multiplexing technique (OFDM). The constructed system is consisting of transmitter, fading channel and receiver. At the transmitter, the transmitted signal first modulated with PSK modulation, and then multiplexed with OFDM technique to achieve a higher bit rates transmission. The signal was then transmitted through a frequency selective channel with 6 taps. In the receiver parity. The received faded signal processed to be de-multiplexed and de-modulated. Then, a frequency domain equalizer was adopted to remove the fading noise and the inter-symbol interference from the received signal that introduced due to the fading channel. In order to inspect the performance of the frequency equilizer, bit error rate for the overall system was calculated at the receiving point and to recover the original information signal. The simulation results of the designed system as well as the frequency equilizer showed a robustness against the frequency selective faded channel effects. The maximum obtained bit error rate was around 10-5, which means that original signal was effectively recovered.
... Early work in airborne communications has been done by Holm et al. [2], [3], who investigated ultrasonic communications in an indoor localization application and with a 4 kHz bandwidth transducer at a 40 kHz center frequency. More recently, Jiang and Wright [4]- [6] demonstrated reliable communications over a short range (0.2-1.2 meters) at speeds of 60 kbit per seconds using frequencies in the 50-110 Hz band using coded on-off keying. In the field of biomedical engineering research published in [7], [8] targets specifically intra-body or through-tissue communications applications. ...
... The aim of this work was to investigate more efficient and reliable airborne wireless ultrasonic communication methods using advanced orthogonal frequency division multiplexing (OFDM) modulation algorithms, achieving more practical data transfer rates and transmission ranges in an indoor environment. Note that this article is an extension of the previously published International Ultrasonics Symposium paper [11]. In Section II, the implementation of the OFDM system including signal modulation, demodulation, channel estimation and synchronization technique is described. ...
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 kHz to 400 kHz. Binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK) and quadrature amplitude modulation (QAM) based orthogonal frequency division multiplexing (OFDM) modulation methods were successfully implemented using multiple orthogonal subchannels. The modulated ultrasonic signal packets were synchronised 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 modulation with ultrasonic channels from 55 kHz 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 m and 11 m using QPSK and BPSK modulation schemes, respectively. The achieved data rates for the QPSK and BPSK schemes were 90 kb/s 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 m and 1.2 m with data rates of 400 kb/s and 200 kb/s using QPSK and BPSK, respectively.
Wireless communication systems are widely known particularly in telecommunication field, where simply, information can be transmitted without using any wires or cables. The wireless communication systems are mainly used for mobile communication and networking and not widely adopted in other mediums such as solid or liquid. Furthermore, using these different mediums for communication has become interesting when no other option is proposed, such as underwater communication or through solid metallic channels (cylinders or plates). The use of guided ultrasonic waves such as Lamb waves for solid medium may be an attractive solution since it can propagates through long distances. The objective of this work is to compare the behavior of different modulation and demodulation techniques at different frequencies and different bit rates by building an experimental platform for ultrasonic guided wave communication.
A pulse-resonance On-Off keying ultrasound communication microsystem is presented. It is a viable alternative to today’s widely used RF technologies in order to avoid the associated health risks for a specific group of interest, namely babies. Special signal processing and circuit techniques are proposed to overcome drawbacks of classical ultrasound communications; such as echoes and excess ringing, achieving a measured communication range of 28m with a 50bits/s data rate and bit error rate (BER) of 0.01. Targeting a biomedical sensory pacifier, the proposed design needs to be insulated, small size, and low power. Utilizing a 40 kHz ultrasound transducer and a 5-pin low-power controller, a wirelessly-charged high-accuracy remote temperature sensor system with nominal average current consumption of 0.416μA is designed and tested. Multiple subsystems were merged in total volume of 12mm diameter and 15mm height, excluding the charging coil, which is designed as the pacifier’s handler. Thanks to echo avoidance, ringing suppression, dynamic detection threshold adjustment techniques along with 3-bit preamble synchronization; the proposed low-power sub-sampling IQ demodulation of OOK bits results in high-sensitivity robust ultrasound communication system without any alignment requirement for the transducers. The lifetime of the sensor prototype with 8mAh LiR battery is about 27 months.
