Jean-François Bousquet

A compact low-power underwater magneto-inductive modem

In this work, a magneto inductive (MI) link design is studied to achieve high speed transmission applied to a high density underwater network. For a small loop antenna, a design procedure is described to define the optimal operating frequency constrained on the system bandwidth and range. A coherent link is established between two nodes in a controlled underwater environment. For a small coil with radius of 5 cm, simulation results indicate that a range above 10 meters can be achieved in the low frequency spectrum spanning 10 kHz to 1 MHz. The design procedure is validated through measurements in seawater: a very high output SNR equal to 31.4 dB is realized at the output of the equalizer, and in these conditions a perfectly reliable 8-kbps link is demonstrated at a center frequency of 22.5 kHz.

Time-variant acoustic propagation characterization in seaport deployments

This paper presents a methodology to characterize the time-variant underwater acoustic channel for the development of coherent communication systems. The channel impulse response is extracted during trials in the Halifax harbour. To account for time-variance a fast tracking equalizer enhanced with spread spectrum technology is described and its ability to extract the channel variations is evaluated. The end-to-end bit error rate is used as a figure-of-merit to quantize the equalizer performance. As will be shown, the equalizer is capable of compensating for the Doppler effect as well as rapid changes in the multipath profile.

Ultra-low voltage and low power ring oscillator for wireless sensor network using CMOS varactor

This paper presents two low-voltage and low-power CMOS voltage controlled ring oscillators (VCOs) for use in portable wireless sensor applications. The frequency is controlled using an inversion mode MOS voltage controlled capacitor (varactor) to generate a large tuning range between 166 MHz to 600 MHz for the first design and from 250 MHz to 850 MHz for the second one and consume only 151.2 μW and 146.19 μW respectively. The proposed three-stage VCOs are designed and simulated in TSMC 65nm technology. Both operate on a 0.6 V power supply.

Wireless transmitter bandwidth extension using dynamically varying capacitors

In this paper a technique to reduce the effect of distortion due to a band-limited front-end is proposed. The technique relies on dynamically varying the filter response at a rate that is a multiple of the symbol rate. Time-variant convolution has been used to determine a strategy to vary the filter capacitance, and two alternative circuit designs relying on switching capacitors is proposed. It has been shown that the distortion error can be reduced to 2% for a system bandwidth 7.8 times greater than the transmit front-end bandwidth.

A 69-Mbps dual tuning 8PSK/QPSK transmitter using injection locking and RF phase modulation

This work presents a high data rate, energy efficient quadrature phase shift keying (QPSK) transmitter suitable for biomedical applications. The transmitter includes a dual tuning mechanism to enable flexible phase/frequency control by direct modulation of a class-E oscillator while maintaining synchronization by using injection locking. The circuit is implemented in TSMC 65-nm CMOS technology with a core size 1 mm2. Using a 1.3-V supply, a transmit power of 14.1 dBm. For an injection frequency of 2.2 GHz, the circuit achieves a high throughput data rate equal to 69 Mbps.

Measurement of a Space-time Noise Mitigation Technique

To evaluate the performance of a communication link, signals are often modeled using software and validated against actual data measurements for a more reliable analysis. In this work a measurement campaign is run to analyze the effect of noise on a communication system. A 3-day sea experiment, Dalcomm1, that was run on the South Shore of Nova Scotia will be described. The data recorded will be used to analyze the impact of noise on a 5-element receiver.

Entropy Minimization Based Synchronization Algorithm for Underwater Acoustic Receivers

This paper presents a new entropy minimization criterion and corresponding algorithms that are used for both symbol timing and carrier frequency recovery for underwater acoustic receivers. It relies on the entropy estimation of the eye diagram and the constellation diagram of the received signal. During the parameter search, when perfect synchronization is achieved, the entropy will reach a global minimum, indicating the least intersymbol interference or a restored constellation diagram. Unlike other synchronization methods, this unified criterion can be used to build an all-in-one synchronizer with high accuracy. The feasibility of this method is proven using a theoretical analysis and supported by sea trial measurement data.

A Compact Magneto-Inductive Coil Antenna Design for Underwater Communications

Magnetic induction (MI) has shown a great potential for underwater communications due to its immunity to acoustic noise and low latency. However, the transmission distance of MI is limited since the magnetic field attenuates very fast in the near field. In this work, a magneto inductive antenna design is studied to achieve two modes of operation: 1) a static quasi omni-directional magnetic coupling; 2) a dynamic rotation of magnetic coupling. A design procedure is described to define the strength of the magnetic field, bandwidth (BW) and the path loss (PL) of the underwater communication link. Both modes are simulated and the corresponding antenna configurations are described. The proposed antenna has three coils separated between each other by 120 degrees. The coils have a radius of 5 cm and a length of 8 cm. The simulation results illustrate how this design can provide an omni-directional magnetic coupling and a more directional performance in the rotation mode. In the rotation mode, simulations also confirmed that the magnetic field can be controllable by changing the phases of input currents.

Reliable Acoustic Link using Non-coherent Turbo-coded Frequency Shift Keying

Low-data rate, non-coherent algorithms were tested at 10 km distances to measure reliability and robustness when combined with convolutional turbo encoding techniques. The system was constrained to hardware specifications limiting bandwidth at low frequencies. Simulations were used to verify the performance of varying algorithms in Bellhop modeled channel impulse responses. The algorithms were tested at sea to compare simulation capabilities with real environmental characteristics. The objectives: (1) define a modulation scheme for robust communication in underwater environments, (2) simulate its performance in multipath and Doppler rich environments, and (3) test performance of modulation scheme in actual ocean environment.

Channel model for wideband time-varying underwater acoustic systems

In this paper a wideband underwater acoustic (UWA) channel simulator is developed based on the geometry of the system deployment and by considering the statistics of the random amplitude variation of the channel. This channel simulator is capable of modeling any relative motion between the transmitter and receiver. The delays of multipath arrivals are calculated based on the geometrical and physical parameters of the deployment. The time-varying fractional delay line (TVFDL) is utilized as a flexible and low-complexity software tool to model time-scaling observed on individual paths. The fading characteristics of the channel which is extracted from the measurements is utilized to model the time-varying amplitudes of paths. Also, an orthogonal frequency division multiplexing (OFDM) system is tested throughout a sea trial. The geometrical and statistical parameters of the sea trial are utilized to test the OFDM system using the proposed channel simulator. The bit error rate (BER) of the system is calculated in both measurements and simulations and it will be shown that the assessment of the communication performance realized using simulations is very close to that of the measured performance.