Xianbing Zou

This paper investigates the reconfigurable intelligent surface (RIS) enhanced millimeter wave (mmWave) communications with spatial modulation (SM). To enhance the bit error ratio (BER) performance, we formulate a joint reflecting coefficients of RIS and the hybrid precoder design problem based on the maximum of minimum Euclidean distance criterion. Unfortunately, the resulting max-min optimization problem turns out to be intractable due to the unit-modulus constraints and intricately coupled variables. However, based on the alternating optimization technique, we show that this problem could be successfully tackled by jointly using the alternating direction method of multipliers (ADMM) and element-wise block coordinate descent (EBCD) algorithms. Numerical results demonstrate that the proposed method achieves a fast convergence rate, and can provide a substantial BER improvement even with 1-bit resolution RIS compared with existing benchmark schemes.

Long-range E-band communication with fiber-equivalent speed is emerging extensively as a critical technology in the next-generation communication. This paper firstly reviews the relevant progress in recent research. A brief survey is presented on high-speed, long-range E-band communication systems and their relevant techniques that are essential to the link design, including antenna, power amplifier (PA), channel, and digital baseband processing. In the second part, we review our recent field trial of a long-range air-to-ground E-band link, which maintains steady transmission from a slow-moving helium balloon to the ground station with a vertical dimension of 20 km. The improvement directions and future research topics are then discussed.

The millimeter-wave frequency band (30∼300 GHz) has received significant attention. Millimeter-wave frequencies have been used for backhaul, cell communication, and other high speed communication. With the advent of 5G communication, millimeter-wave frequencies such as 60-GHz band have been attracting attention as possible candidate for next-generation wireless networks. The traditional application for 60-GHz band is point-to-point communication. Some typical scenarios have been cited in a recent 5G white paper. There exist some traditional channel models for 3G and 4G communication. However, 5G has a new channel model (the outdoor-to indoor channel model, or O2I) that has not been clearly studied. Some conventional channel measurements have been conducted for this new band. Two measurement systems in the 60-GHz band for penetration loss and small-scale measurement for different scenarios are presented. By analyzing our measurement data, we can prove that the O2I channel does not generate new paths and only add some material penetration loss.