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Coverage in mobile communications systems requires an acceptable link gain over a maximum service area, with areas of low link gain being problematic. A standard approach to maximize link gain is to deploy multiple-input–multiple-output (MIMO) antennas that adapt to the changing multipath. There is also recent interest in using active surfaces for adaptive reflections within the multipath environments, and this calls for new ideas at the system and component levels. A critical mechanism in urban propagation is corner diffraction, which illuminates shadow areas but with low link gain. We present a simple add-on system for corners, comprising a simple scattering dipole or scattering array, which can significantly improve link gain in the shadow region over a wide bandwidth. The concept is demonstrated through analysis, simulation, and physical measurement. Only shadowed areas are boosted, and the line-of-sight coverage is not significantly affected. Our demonstration is for a passive, fixed configuration, which is suitable for retrofitting to existing systems. [ABSTRACT FROM AUTHOR]

Waveguide arrays comprise slot radiators cut into hollow, single-mode, standing wave structures. Their impedance bandwidth and compactness are limited by the waveguide cutoff. By using the TEM mode of a coaxial waveguide, a more compact structure with a larger bandwidth is possible at the expense of increased ohmic loss in the waveguide. Using this basis, a new type of slotted coaxial waveguide antenna is presented. A compact waveguide array means that the element and array aspects are not independent, and with no accurate transmission line models for the structure, the design is from a parametric study by simulation. Two basic designs are demonstrated: the first with no constraint on the azimuthal extent of the slots, and the second where some mechanical strength of the waveguide is maintained by constraining the azimuthal extent of the slots to be 90° or less. The parametric studies provide insight for realizing the high bandwidth, and measurements of prototypes confirm the performance. These antennas are useful for integration with cylindrical structures such as masts or bicycle and drone frames. [ABSTRACT FROM AUTHOR]

The automated detection of people having a fall is particularly important for the elderly in indoor care situations. Privacy concerns, and regulations that prohibit cameras in indoor environments, mean that optical sensing must give way, at least in some situations, to less explicit sensing such as radar. Currently, fall detection using radar Doppler signatures has limitations. We demonstrate a radar-based technique that detects breathing and other movements seamlessly, and can detect a fall after it has happened, i.e., even when the person is static. Using a low-cost, ceiling-mounted radar at low microwave frequencies (sub-6 GHz), our results show it is possible to remotely localize a person within a few cm. The sensor system includes a small neural network model that can distinguish a person from other moving objects in an indoor environment. This can reduce false alarms of the fall detection and hence improve system reliability in real-world deployment. In our experiments, the neural network differentiates a person from a pet (an example of a complex moving entity) with an accuracy exceeding 95%. This sensor system demonstration paves a way forward for general indoor fall detection, extending to the well-being of our elderly through real-time, ongoing monitoring of their breathing and other activities of daily living. [ABSTRACT FROM AUTHOR]

The implementation of high-speed wireless networks, such as currently used fourth generation (4G) systems and future 5G systems, feature challenging processing. Field programmable gate arrays (FPGAs) can straddle research and development for these current and future networks since they provide scaling through reconfigurable logic, high parallelism, and low power consumption. This brief demonstrates an FPGA circuit implementation, with measurements, of a minimal system (a 5G element or “unit cell”): a single-user mobile with antenna diversity and a distributed antenna system (DAS) at the base station. The demonstration system has a bandwidth of 20 MHz, runs at 2.4 GHz, and has two antennas at both the transmitting base station and at the receiving mobile. The modulation is orthogonal frequency division multiplexing (OFDM) with space-time block coding (STBC). The FPGA is a Virtex-6, used for software defined radio (SDR), and this can readily be scaled to handle larger-dimensioned, higher-capacity systems. The receiver has time-offset synchronization, frequency-offset, and channel estimation. The high-level algorithm design (Xilinx System Generator) for these functions and the OFDM-STBC, and the resources consumed on the FPGA during real-time implementation, are included. We also compare the use of coax and fiber for linking the distributed antennas, using off-the-shelf components. The approach used here of combining simulations with physical measurement of a minimal system is a practical way forward for assessing candidate systems for 5G. [ABSTRACT FROM AUTHOR]