Complex quadrature spatial modulation transmits two signal symbols at each channel use, each is drawn from a different constellation set. The indices of the antennas from which the symbols are transmitted carry information to the receiver. When both symbols are transmitted from the same antenna, the symbols resulting from the addition of the two signal symbols belong to the Minkowski sum of the original two constellation sets. Therefore, the size of the modulation set at the transmitter increases and the minimum distance between transmitted symbols is reduced, leading to degradation in the error performance. In this study, the authors propose to equip the transmitter with an additional antenna which is used to transmit the second signal symbol only when the information bits representing the antenna indices are identical. The design of the optimum modulation sets that maximise the Euclidean distance is also addressed. Furthermore, based on the probability of antenna use, they advise an antenna ranking algorithm that improves the performance. The simulation results show that the proposed scheme achieves a signal‐to‐noise ratio gain of 6.4 and 9.5 dB using 16 quadrature amplitude modulation and 16 phase‐shift keying, respectively.

Blockchain technology has heralded a new era in digital innovation, revolutionizing our approach to designing and building distributed applications in the digital sphere. Blockchain technology operates as an immutable digital ledger, where each entry representing a digital transaction is indelible and cannot be altered once established. Initially designed as the fundamental framework for cryptocurrencies, blockchain has outgrown its original purpose, demonstrating significant potential in various industries and offering a variety of security and privacy features. Our study provides a thorough and current survey of blockchain applications, security, privacy concepts, primitives, and threat models. It stands out by concentrating on how blockchain technology intersects with emerging fields like IoT, EVs, FinTech, and healthcare systems in a single framework. To provide security and privacy features, blockchain systems employ different foundational notions and primitives while tackling diverse adversarial scenarios with various capabilities and goals. This study presents a fresh examination of the current state of applications, security and privacy notions and primitives, and threat models in blockchain systems. Additionally, this work highlights existing gaps in knowledge and outlines open questions, aiming to stimulate interest in further advancements in the field.

Quadrature spatial modulation (QSM) utilizes the in‐phase and quadrature spatial dimensions to transmit the real and imaginary parts of a single signal symbol, respectively. The improved QSM (IQSM) t...

The proper use of Android app permissions is crucial to the success and security of these apps. Users must agree to permission requests when installing or running their apps. Despite official Android platform documentation on proper permission usage, there are still many cases of permission abuse. This study provides a comprehensive analysis of the Android permission landscape, highlighting trends and patterns in permission requests across various applications from the Google Play Store. By distinguishing between benign and malicious applications, we uncover developers’ evolving strategies, with malicious apps increasingly requesting fewer permissions to evade detection, while benign apps request more to enhance functionality. In addition to examining permission trends across years and app features such as advertisements, in-app purchases, content ratings, and app sizes, we leverage association rule mining using the FP-Growth algorithm. This allows us to uncover frequent permission combinations across the entire dataset, specific years, and 16 app genres. The analysis reveals significant differences in permission usage patterns, providing a deeper understanding of co-occurring permissions and their implications for user privacy and app functionality. By categorizing permissions into high-level semantic groups and examining their application across distinct app categories, this study offers a structured approach to analyzing the dynamics within the Android ecosystem. The findings emphasize the importance of continuous monitoring, user education, and regulatory oversight to address permission misuse effectively.

At each channel use, the complex quadrature spatial modulation (CQSM) transmits two signal symbols drawn from two disjoint modulation sets. The indices of the antennas from which symbols are transmitted also carry information. In the improved CQSM (ICQSM), an additional antenna is used to transmit the second signal symbol only when the indices of the antennas to be used for transmission are equal. Conventionally, the second modulation set is a rotated version of the first, where the rotation angle is optimized such that the average unconditional error probability (AUP) is reduced. In this paper, we propose a low‐complexity method to design the PSK modulation sets based on reducing the AUP. After introducing min‐BER and max‐d_min, two exhaustive search methods, we analytically show that the AUP depends on Euclidean distance between transmitted vectors, which in turn depends on the power of signal symbols, the Euclidean distance between the symbols of each modulation set, and the Euclidean distance between the symbols of the two sets. The optimal rotation angle is analytically derived for any modulation order and the radii of the modulation sets are optimized such that AUP is reduced for a wide range of system configurations. The simulation results show that more than 3 dB of power gain is achieved in the case of 16PSK, where higher gains are achieved for higher modulation orders. These gains are achieved at no computational cost because the optimization does not depend on the channel realization.