This paper introduces WirelessGPT, a pioneering foundation model specifically designed for multi-task learning in wireless communication and sensing. Specifically, WirelessGPT leverages large-scale wireless channel datasets for unsupervised pretraining and extracting universal channel representations, which captures complex spatiotemporal dependencies. In fact, this task-agnostic design adapts WirelessGPT seamlessly to a wide range of downstream tasks, using a unified representation with minimal fine-tuning. By unifying communication and sensing functionalities, WirelessGPT addresses the limitations of task-specific models, offering a scalable and efficient solution for integrated sensing and communication (ISAC). With an initial parameter size of around 80 million, WirelessGPT demonstrates significant improvements over conventional methods and smaller AI models, reducing reliance on large-scale labeled data. As the first foundation model capable of supporting diverse tasks across different domains, WirelessGPT establishes a new benchmark, paving the way for future advancements in multi-task wireless systems.

An improved method to design compact pattern reconfigurable pixel antennas is described. The method introduces a new structure consisting of diagonal connections between pixels to enhance the pattern steering capability of the pixel antennas. These diagonal connections increase the number of independent degrees of freedom available in the design process which results in significantly improved performance as compared to designs with only horizontal and vertical connections between pixels. Furthermore the diagonal structures enable the possible formation of new “cross-over” connections which provide a structure that allows currents to cross each other in the antenna geometry. Simulation and measurement results show that an antenna with 2×6 pixels can steer a beam over 150° in the azimuth plane and 300° beam steering range can be achieved with 3×6 pixels. The use of the diagonal elements increases gains by up to 3 dB and provides a much greater steering range as compared to pixel antenna design without the diagonal connections. Utilizing these diagonal pixel connections can also potentially enhance the performance of pixel antenna designs in a wide variety of other pixel antenna configurations.

An approximate inverse scattering technique is proposed for reconstructing cross-sectional area variation along water pipelines to deduce the size and position of blockages. The technique allows the reconstructed blockage profile to be written explicitly in terms of the measured acoustic reflectivity. It is based upon the Born approximation and provides good accuracy, low computational complexity, and insight into the reconstruction process. Numerical simulations and experimental results are provided for long pipelines with mild and severe blockages of different lengths. Good agreement is found between the inverse result and the actual pipe condition for mild blockages.

Characterizing acoustic waveguide channels is becoming important for the development of communication and signal processing applications across diverse fields ranging from urban water supply systems to oil and gas distribution pipeline networks. These applications include sonar and transmission systems in support of leak detection, blockage location, sensing, monitoring, and signaling for example. In this paper, we provide experimental results and models for the wideband channel characterization of acoustic waveguides formed from gas and water pipelines over the 1-50 kHz frequency band. Experimental results are provided for two straight pipe systems comprising an acrylic pipe filled with air and a steel pipe filled with water. A mode-based analytical model for predicting acoustic wave propagation in rigid and elastic pipes is proposed with deterministic and stochastic characteristics both considered. Good matching is demonstrated between the model predictions and experimental results in terms of dispersion curves, channel spectrograms, and delay spread. A key finding is that acoustic waveguides filled with water should be treated as elastic pipes, and they have significantly different characteristics from those filled with gas, which can usually be treated as rigid pipes. Furthermore for the steel-water waveguide pipeline, link budget calculations and noise power spectral density measurements reveal that a communication range of more than 50 m can be obtained.

We describe a method that uses propagation measurements to reconstruct the spatial profiles of the distributed impedance and shunt conductance parameters of a lossy transmission line. From these reconstructed spatial profiles we can deduce the presence and location of transmission line faults. The method makes use of return loss measurements from both ends of the transmission line as well as the transmission loss between the two ends. An inverse scattering approach based on the Born approximation is utilized to obtain the reconstructions. Its advantage compared to exact formulations, such as those based on the Zakharov-Shabat equations, is that it provides separate analytical expressions for the individual spatial profiles of the distributed impedance and shunt conductance transmission line parameters. It is shown by simulation and experiment that the method performs well in a variety of configurations and has the potential to be used in fault detection for cables and feed networks.

We apply and experimentally verify inverse scattering techniques based on the Born and Rytov approximations for detecting soft faults in lossless transmission lines. The advantages of these approximate approaches compared with exact formulations such as those based on the Zakharov–Shabat equations are that they are straightforward to apply and provide intuitive insight into the reconstruction process. The formulations are also well-posed so the effects of noise and measurement errors on the reconstructions are also well behaved. The approaches are well suited for the detection of soft faults since they are based on the assumption that the medium is weakly scattering. We demonstrate the techniques with both experimental and numerical results. In addition, the application to lossy transmission lines is also investigated to determine the approximations usefulness in realistic settings. These show that surprisingly accurate results can be obtained for a wide range of characteristic impedance distributions even when the transmission lines have loss.