The research of safety applications in vehicular networks has been a popular research topic in an effort to reduce the number of road victims. Advances on vehicular communications are facilitating information sharing through real time communications, critical for the development of driving assistance systems. However, the communication by itself is not enough to reach the most desired target as we need to know which safety-related information should be disseminated. In this work, we bring passive sensors and backscatter communication to the vehicular network world. The idea is to increase the driver (or vehicle) awareness regarding the presence of pedestrians in a crosswalk. Passive sensors and backscatter communication technologies are used for the pedestrians’ detection phase, while the vehicular network is used during the dissemination of the detection information to surrounding vehicles. The proposed solution was validated through end-to-end experimentation, with real hardware and in a real crosswalk with real pedestrians and vehicles, demonstrating its applicability.

In this letter, the authors present the first millimeter-wave (mm-wave) high-order backscatter modulator, based on a BiCMOS technology for 5G/Internet of Things (IoT) applications. The design and implementation of the proposed system are described, followed by the considered characterization measurement setup. This work presents a chip that performs different orders of backscatter modulation, M-quadratic-amplitude modulation (QAM), for a wide range of operation both in frequency (20-28 GHz) as well as with multiple values of input power. Besides that, the modulator presents the lowest power consumption compared with the state of the art. An extensive estimation of error vector magnitude (EVM) values for different frequencies and modulations (16, 32, and 64-QAM) is presented. These results show that it will be possible, in a future implementation, to establish low power consumption communication links with a multigigabit data rate in a wide range of frequencies.

A novel over-the-air (OTA) beamforming calibration procedure is proposed, which can be applied to different types of multiple-input multiple-output (MIMO) transmitting antennas. The method consists of using two tones on each antenna element, the main tone, and the tickle tone. The latter one operates in a different frequency for each antenna element and is used to obtain the optimum phase that needs to be set for each element to generate a beam in the desired direction, at the main tone frequency. The novel method was applied to linear, planar, 3-D antennas, and noncollocated multiantennas to validate its applicability to different antenna types. Line-of-Sight (LOS) and non-LOS experimental results demonstrate that the method can be used to retrieve the required phase to fully control the antenna radiation pattern. An optimum radiation pattern and lowest error vector magnitude (EVM) can be achieved even under high multipath effects/non-LOS conditions. A comparison between the performance and the application of the array factor (AF) theory is presented for practical indoor scenarios, demonstrating the effectiveness of the method. It is demonstrated that the method may be an alternative to the calibration of nonstandard MIMO antennas, where the AF computation is complex or not possible.

The backscatter modulation has been used as an emerging technology in the Internet of Things (IoT), due to the hardware simplicity and low power consumption. Moreover, this technology is being combined with wireless power transfer scenarios in order to overcome a large number of batteries used. With recent development of backscatter systems for high bit‐rate communications, the design of a calibrated measurement system to characterise and calculate the optimum performance for M‐ary quadrature amplitude modulations, emerge as a requirement in IoT measurements. The main objective of this work is to characterise a backscatter modulation system, considering two characterisation approaches, a cable test measurement, and an Over‐The‐Air measurement. Thus, the characterisation of high‐order backscatter modulators can be executed to anticipate its performance in real scenarios. In this work, a dual‐band high‐order backscatter modulator will be presented and characterised for different modulations in free‐space, and the Error Vector Magnitude results will be computed.

The main objective of this work is to present a characterization and measurement system using multi-sine to study active antenna array behavior. In the multi-sine approach, a main tone and a tickle tone will be explored. The tickle tones will be used as a reference to characterize each antenna element, which will allows us to study them in terms of amplitude and phase. For this purpose, each antenna element will be excited by a main tone (same frequency at each element) and a tickle tone (different frequency at each element) with lower power. The experimental setup was fully implemented using an of the shelf software defined radio (SDR) approach. With the aid of a synchronized measurement system, a conventional 16 element array was characterized and results are presented and discussed, showing that this approach is relevant for this kind of application.

The main goal of this work is to characterize the coupling effects that occur in MIMO antenna arrays, when the antenna beam is steered along a specific direction. A calibrated measurement system designed to measure such effects, is proposed. Experimental results have been obtained for several beam directions, showing the impact of the beam steering on each MIMO antenna element.