Recently, a lot of research has been done in chaotic cryptography field using different kinds of chaotic systems, like chaotic maps, which are being considered as one of the secure and efficient methods to protect confidential information. This article highlights that the main cryptography requirements demand that the new embedded cryptosystems have to be more efficient and secure, it means that they must be faster and offer greater security. For instance, the new cryptosystems require to be compatible with the new telecommunication protocols and, in addition, to be efficient in energy consumption. In this manner, this article introduces a process to improve the randomness of five chaotic maps that are implemented on a PIC-microcontroller. The improved chaotic maps are tested to encrypt digital images in a wireless communication scheme, particularly on a machine-to-machine (M2M) link, via ZigBee channels. We show that function mod 255 improves the randomness of the pseudo-random number generators (PRNG), which is verified performing NIST SP 800-22 statistical tests, histograms, phase-plane analysis, entropy, correlation of adjacent pixels, differential attacks, and using digital images of size 256 × 256 and 512 × 512 pixels. A comparative analysis is presented versus related works that also use chaotic encryption and classic algorithms, such as: AES, DES, 3DES and IDEA. The security analysis confirms that the proposed process to improve the randomness of chaotic maps, is appropriate to implement an encryption scheme that is secure and robust against several known attacks and other statistical tests. Finally, it was experimentally verified that this chaotic encryption scheme can be used in practical applications such as M2M and Internet of things (IoT).

Randomness improvement of chaotic maps for image encryption in a wireless communication scheme using PIC-microcontroller via Zigbee channels

The Internet of Drones (IoD) recently gained momentum due to its high adaptability to a wide variety of complex scenarios. Indeed, Unmanned Aerial Vehicles (UAVs) can successfully be employed in different applications, such as agriculture, search and rescue missions, surveillance systems, mission-critical services, among others, thanks to some technological and practical advantages: high mobility, capability to extend wireless coverage areas, or ability to reach places inaccessible to humans. Moreover, the employment of drones promisingly improves the performance parameters of different network architectures, e.g., reliability, connectivity, throughput, and delay. Nevertheless, the adoption of networks of drones gives rise to several issues related to the intrinsic unreliability of the wireless medium, the duration of batteries, and the high mobility degree, which may cause frequent topology changes. Also security and privacy issues need to be properly investigated. This explains the very large number of works produced in the recent literature on IoD-related topics. With respect to other surveys on IoD-related topics, the goal of the present work is to categorize the multifaceted aspects of IoD, proposing a classification approach of the IoD environment that develops along two main directions. The IoD is initially introduced according to the possible applications and reference operating scenarios. On top of that, this work discussed with its applicability with a dedicated focus on the economical/social implications that the adoption of drones at scale may have. At a macroscopic level, it follows the structure of the Internet protocol stack, starting from the physical layer and extending to the upper layers, without neglecting cross-layer and optimization approaches. At a finer level, all the most relevant works belonging to each layer of the stack are further classified, according to the different issues that propose a peculiar challenges for each layer, and highlighting the most relevant differences with the other surveys present in literature. To provide a deeper insight, the present work embraces many facets of the IoD, with a thorough examination of privacy and security considerations. Finally, a discussion on the main research challenges and possible future directions is carried out, focusing on both open issues and the most promising technologies that deserve to be further developed in the IoD field.

An extensive survey on the Internet of Drones

While the world still struggles against the devastating effects of the COVID-19 pandemic, governments and organisations are discussing how new technologies can be exploited to relieve its impacts and how future pandemics can be avoided or minimised. Among the envisioned solutions, the development of more efficient and widespread smart city initiatives can improve the way critical data is retrieved, processed, stored, and disseminated, potentially improving the detection and mitigation of outbreaks while reducing the execution time when taking critical actions. In fact, some first responses to this pandemic are exploiting different technological solutions that could be ultimately adopted in more integrated city-scale systems, opening many possibilities. Therefore, this study discusses potential solutions and review recent approaches that can be exploited in this complex scenario, describing feasible and promising development trends for the construction of the new expected health-centric smart cities.

COVID-19 pandemic: a review of smart cities initiatives to face new outbreaks

In recent years, reconfigurable antennas have been sought to improve the performance of multiple-input multiple-output (MIMO) wireless communication systems. Their ability to dynamically reconfigure their radiation pattern adds diversity in a manner that is not possible with fixed antennas. This paper investigates the performance benefits provided by pattern reconfigurable receiving antennas with uniform beam steering capability. Their potential performance is first estimated using simulations, and for the first time, the effect of uniform beam steering on MIMO system performance is evaluated in a real indoor channel using two electrically steerable passive array radiator (ESPAR) antennas. Performance comparison is made against a pair of monopole antennas using a hardware bit error rate (BER) test-bed that incorporates statistical spatial averaging in order to assess performance improvements in a more realistic way, and analyze the effect of antenna diversity on the overall system performance. The MIMO-ESPAR system reduces BER with certain pattern combinations and excels in capacity evaluations. The ESPAR antennas improve the spatially averaged channel capacity by as much as 37% at 10 dB transmit SNR, and gain an additional 1 bit/s/Hz in peak capacity at 10 dB receive SNR from diversity gain alone. These improvements make pattern reconfigurable antennas promising options in MIMO-related applications.

Design and Evaluation of Pattern Reconfigurable Antennas for MIMO Applications

Machine learning toward advanced energy storage devices and systems.

This paper proposes an interference detection method for multiuser-multiple input multiple output (MU-MIMO) transmission, which utilizes periodical preamble signals in the frequency domain and the concept of full-duplex transmission when assuming idle antennas at the access point (AP) in MU-MIMO. In the propose method, collision detection (CD) of MU-MIMO is achieved by utilizing asynchronous MU-MIMO called random access MU-MIMO. In random access MU-MIMO, several antennas that are not used for the transmission exist, due to asynchronous MU-MIMO. Hence, idle antennas at the AP can receive preamble signals while the transmit antennas at the AP transmit the preamble signals: this procedure is regarded as full-duplex transmission, which cancels the self-interference between AP antennas. The interference can be detected by subtracting the short preamble signal, which is multiplied by the estimated channel response using the received signal after the FFT processing. Moreover, we utilize dual polarization to reduce the mutual coupling between transmit and receive antennas at the AP. Through a computer simulation, it is shown that the proposed method can successfully detect collision from other user terminals (UTs) with OFDM signals when the interfering power from the interfering user terminal (IT) is greater than the noise power. In addition, the interfering power from IT at the AP and the desired user terminal (DT) is measured in an actual indoor environment, and the possibility of using the proposed method at the AP is discussed by using the measurement results.

Collision Detection Method Using Self Interference Cancelation for Random Access Multiuser MIMO

In this letter, we introduce a method that uses the radar system to observe the waves reflected from the target with the single-input-multiple-output (SIMO) array configuration to estimate living-body directions in a multipath environment for applications such as elderly monitoring. Directions of living body are estimated by the MUltiple SIgnal Classification (MUSIC) method, where the Fourier transformed channel matrix is used. Our use of the 2.4-GHz band allows greater miniaturization of the antenna than is possible with the low-frequency band used by conventional systems. Also, this method can be used in multipath-rich environments such as indoors. The experiments are carried out in a specific indoor environment as a demonstration, and the SIMO channel is measured with various subject numbers and positions. The results indicate that the proposed method can estimate living-body directions with high accuracy even in multipath environments.

Experimental Evaluation of Estimating Living-Body Direction Using Array Antenna for Multipath Environment

In this paper, we propose an uplink multiuser-multiple input multiple output (MU-MIMO) cooperative retransmission control scheme for the reliable and efficient communication of autonomous unmanned aerial vehicles (i.e., flight communication and drone-to-drone communication). This scheme is a key element in the design of a drone-based ad-hoc network. Because drone relay transmission operates in the air, flexible wireless relay networks over large areas can be achieved without interference from multipath signals caused by buildings and obstacles in ground-based communication. However, two main challenges exist. First, the relay transmission system occupies bandwidth every time the drone relays information. Therefore, because the radio channel is shared by multiple relay stations, the throughput is greatly reduced. To improve throughput, it is better to transmit using the minimum number of relay stations. Ultimately, long-distance direct transmission is the best. The other issue is a direct result of the first issues solution: the propagation loss increase when relaying information directly over a long distance. Moreover, because the frequency of interference waves from the ground increases, transmission signal errors are an important issue. To solve this issue, a transmission scheme to reduce errors is required. The scheme proposed in this study achieves high transmission reliability and efficiency even under high transmission error conditions. The results of a computer simulation reveal that the proposed method achieves a direct transmission throughput that is 1.5 times better than that of a conventional scheme. It is also shown that the proposed scheme requires only about three stations to achieve acceptable results.

A Cooperative Transmission Scheme in Drone-Based Networks

This paper proposes a method that uses bistatic MultipleInput Multiple-Output (MIMO) radar to locate living-bodies. In this method, directions of living-bodies are estimated by the MUltiple SIgnal Classification (MUSIC) method at the transmitter and receiver, where the Fourier transformed virtual Single-Input Multiple-Output (SIMO) channel matrix is used. Body location is taken as the intersection of the two directions. The proposal uses a single frequency and so has a great advantage over conventional methods that need a wide frequency band. Also, this method can be used in multipath-rich environments such as indoors. An experiment is performed in an indoor environment, and the MIMO channels yielded by various subject numbers and positions are measured. The result indicates that the proposed method can estimate multiple living-body locations with high accuracy, even in multipath environments. key words: MIMO, living-body location, DOA estimation, microwave sensor, array antenna

Estimating Living-Body Location Using Bistatic MIMO Radar in Multi-Path Environment

Disclosed is an antenna apparatus which can control directivity of a plurality of radiation elements using one parasitic element. The antenna apparatus includes two radiation elements arranged on a base parallel to each other, and a parasitic element disposed between the two radiation elements. Radiation directivity of the two radiation elements is controlled according to the length of the parasitic element. This configuration provides a small-sized antenna apparatus including a plurality of radiators with desired directivity.

Tsutomu Mitsui

Papers

Collision Detection Method Using Self Interference Cancelation for Random Access Multiuser MIMO

Experimental Evaluation of Estimating Living-Body Direction Using Array Antenna for Multipath Environment

A Cooperative Transmission Scheme in Drone-Based Networks

Estimating Living-Body Location Using Bistatic MIMO Radar in Multi-Path Environment

Antenna apparatus and wireless communication terminal