Wireless Networks

Ticket Election Multiple Access (TEMA) is introduced for local machine-to-machine communication that is energy and bandwidth-efficient. TEMA is based on distributed elections held among nodes to gain interference-free access to the channel in either unicast or broadcast mode. Non-transmitting nodes can infer whether or not they are the intended receiver of a transmission and act accordingly to save energy, without the need for particular traffic patterns or explicit future transmission schedules. TEMA is shown to be correct in the sense that the channel access schedules are collision-free at the intended receivers, and intended receivers are always in receiving state. An analytical model of the performance of the protocol is used to show that TEMA attains energy-efficiency and high channel utilization even under heavy traffic and high node density conditions. A simulation-based performance analysis validates the analytical results and shows that TEMA outperforms representatives of contention-based and interference-free protocols in terms of energy efficiency, network goodput, and channel access delay. More specifically, it reduces energy consumption to half of that of state-of-the-art distributed election-based protocols while providing up to 25% increase in goodput and up to 50% decrease in channel access delay.

Communication in Terahertz (THz) band is envisioned as a promising technology to meet the ever-growing data rate demand, and to enable new applications in both nano-scale and macro-scale wireless paradigms. In this study, we propose the first system-level design that is suitable for THz communication in macro-scale range with 100+ Gbps data rate. The design is based on the proposed terahertz pulse-level beam-switching with energy control (TRPLE), and motivated by the rise in Graphene-based electronics, which include not only compact generator and detector for pulse communication, but also the capability of beam scanning aided with nano-antenna-arrays. The very high path loss seen in THz wireless channel requires the use of narrow beam to reach longer transmission ranges. On the other hand, impulse radio that emits femtosecond-long pulses allows the beam direction to steer at pulse-level, rather than at packet-level. For TRPLE, we mathematically analyze the data rate for an arbitrary wireless link under the THz channel characteristics and the energy modulation scheme. Then, a novel optimization model is formulated to solve the parameters of the inter-pulse separation and the inter-symbol separation, in order to maximize the data rate while meeting the interference requirement. With the optimization, the data rate of 167 Gbps is shown achievable for most users in 20-m range. A MAC protocol framework is then presented to harness the benefits of the pulse separation optimization.

The Internet of Things (IoT) frequently exchange data through the Internet by comprising a complex network of smart devices. However, various vulnerabilities of IoT applications are observed which shall keep IoT as a technology in danger. Therefore, IoT applications should go through rigorous testing at the network edge. Python is widely used for programming IoT devices as well as developing the corresponding back-end at the network edge. Due to the difficulty of static program analysis on dynamic languages, the quality of test code in Python libraries for IoT development faces a serious threat, which in turn affects the performance of IoT applications. In order to evaluate test quality of Python libraries for IoT applications, we propose a test analysis framework named Pysta. It uses a hybrid analysis engine to support the multi-dimensional evaluation of Python test code. Based on Pysta, we then conduct an empirical study on test quality in eight Python libraries which are widely used for IoT development to investigate test code composition, test objects, test co-evolution, and test code smells. The study results reveal the major problems and challenge in the tests of Python libraries for IoT applications, including low naming consistency, single form of assertion, lacking edge tests, low test coverage in large-scale projects, delaying test co-evolution, and various code smells in tests. This work can inspire researchers and developers on how to improve test quality of IoT applications and further reduce security risks associated with IoT systems.

The recent development in wireless communication technology and portable devices has led to the development of Mobile Ad-Hoc Network which has unique features such as dynamic topology, open wireless medium, decentralized system etc but these network are susceptible to various denial of service attacks such as black hole, gray-hole, worm hole etc. In order to mitigate black-hole attack, various protocols have been proposed but these protocols have been not analyzed under gray-hole attack. In this paper, we have made classification of denial of service attack and highlighted the key differences among black hole, sequence number based gray-hole and smart gray-hole attack. We simulated two types of attacks namely Attack1 and Attack2 by modifying AODV protocol. The Attack1 (GAODV) is sequence number based gray-hole attack protocol whereas Attack2 (SGAODV) is smart gray-hole attack protocol. In order to observe the impact of gray-hole attacks on AODV, IDS-AODV and MBDP-AODV, NS-2.35 simulator is used. The simulation results show that MBDP-AODV performs well as compared with IDS-AODV and AODV under sequence number based gray-hole attack. Through simulation, it has also been found that the impact of the smart gray-hole attack is low as compared with the sequence number based gray-hole attack.

Routing in underwater wireless sensor networks (UWSN) is an important and a challenging activity due to the nature of acoustic channels and to the harsh environment. This paper extends our previous work [Al-Salti et al. in Proceedings of cyber-enabled distributed computing and knowledge discovery (CyberC), Shanghai, pp 331–336, 2014] that proposed a novel multipath grid-based geographical routing (MGGR) protocol for UWSNs. The extended work, EMGGR, viewed the network as logical 3D grids. Routing is performed in a grid-by-grid manner via gateways that use disjoint paths to relay data packets to the sink node. The algorithm consists of three main components: (1) a gateway election algorithm; responsible for electing gateways based on their locations and remaining energy level (2) a mechanism for updating neighboring gateways’ information; allowing sensor nodes to memorize gateways in local and neighboring cells, and (3) a packet forwarding mechanism; in charge of constructing disjoint paths from source cells to destination cells, forwarding packets to the destination and dealing with holes (i.e. cells with no gateways) in the network. The performance of EMGGR has been assessed using Aqua-Sim, which is an NS2 based simulator for UWSNs. Results show that EMGGR is an energy efficient protocol in all simulation setups used in the study. Moreover, EMGGR can also maintain good delivery ratio and end-to-end delay.

This paper proposes a circularly polarized 2 × 2 antenna array for C-band wireless applications. The most attractive feature of the proposed design is that it is only fabricated on a single layer of a dielectric substrate, while maintaining wideband operation and high gain radiation as well. The single-layer design is able to significant reduce the antenna’s complexity. The array element is based on a truncated corner patch and a periodic structure. The final prototype of 2 × 2 antenna array with overall dimensions of 1.2λ × 1.2λ × 0.04λ, where λ is the lowest operating frequency, was fabricated and experimentally validated. The proposed array yields a measured impedance bandwidth of 42.9% (4.4–6.8 GHz) and a measured 3-dB axial ratio bandwidth of 36.4% (4.5–6.5 GHz). Within the operating band, good radiation patterns are achieved and the boresight gain is from 9.5 to 11.5 dBic. Compared with the other reported single-layer sequential-fed antenna arrays in literature, the proposed shows the best operating bandwidth with competitive gain radiation.

A wearable millimetre-wave radar antenna operating in 24.05–24.25 GHz for imaging applications in collision avoidance to assist visually impaired people is presented. Non-uniform excitation for the series end-fed 1 × 10 array antenna is optimized in simulation achieving a modified Dolph–Chebyshev distribution, which provides improved performance in terms of beam width, Side-lobe level and Gain. Commercial RO3003 and eco-friendly polypropylene (PP) are considered as substrates for comparison purposes, being the PP electromagnetically characterized for the first time at such high frequencies. Consistent agreement between simulation and measurement results is achieved for antenna prototypes on both dielectrics. The impedance matching bandwidth is analysed for the antenna on PP also under bent conditions. The overall size of the compact, low-cost, eco-friendly and flexible antenna on PP is 98.68 × 14.4 × 0.52 mm3 and, according to literature survey, it overcomes the state of the art on wearable radar antennas at 24 GHz.

We consider multimedia wireless networks in environments where traffic characterizations and traffic rates are generally time‐varying. For such networks we propose a CDMA transmission policy, in conjunction with a moving boundaries concept induced by a traffic monitoring high‐level protocol. The proposed transmission/traffic management technique is analyzed and numerically evaluated.

We propose Bluemob, a novel algorithm for building ad-hoc networks among mobile devices of passengers on urban buses using the Bluetooth interface. Based on estimates of node permanence onboard, a role-assignment mechanism establishes the nodes more suited to perform a given function in the network (masters, slaves or gateways). The mechanism is flexible and isolated from the algorithm core, allowing the adoption of Bluemob in other small and dynamic environments and applications with minimal changes. Simulation studies indicate improvements of up to 75 % in the times needed to rebuild the network after nodes have left in comparison to an algorithm without the role-assignment mechanism. Performance levels related to the quality of estimates are also evaluated to indicate the accuracy of estimation needed for proper application of the algorithm.