Direct Wireless Communication Research Articles

Extraction of Underwater Acoustic Signals across Sea–Air Media Using Butterworth Filtering

Direct wireless communication through sea–air media is essential for constructing an integrated communication network that spans space, air, land, and sea. The amplitude of acoustically induced micromotion surface waves is much smaller than the noise interference in complex sea states, making the accurate extraction of these signals from the raw signals detected by an FMCW millimeter-wave radar a major challenge. In this paper, Butterworth filtering is used to extract underwater acoustic signals from the surface waves detected by radar. The physical processes of the channel were simulated theoretically and verified experimentally. The results demonstrate a fitting coefficient of 0.99 between the radar-detected water surface waves and the simulation outcomes, enabling the effective elimination of noise interference and the extraction of acoustically induced micromotion signals in environments with a signal-to-noise ratio (SNR) of −20 dB to −10 dB. Experiments modifying frequency and linear frequency modulation have verified that the usable frequency range for underwater acoustic signals is at least 400 Hz, meeting the frequency requirements of Binary Frequency Shift Keying (2FSK) modulation encoding methods. This research confirms the accuracy of the simulation results and the feasibility of filtering and extracting underwater acoustic signals, providing a theoretical basis and an experimental foundation for building cross-media communication links.

Analyzing the impact of medium access control protocol design and control-plane uplink in asymmetric RF/OWC networks with RF congestion

As the demand for wireless capacity continues to grow, highly directional wireless communication technologies have the potential to provide massive gains in area spectral efficiency. However, novel challenges arise when considering bidirectional connectivity and multi-cell/multi-user systems with highly directional links. Some of these challenges can be alleviated with the introduction of asymmetric connectivity where the highly directional links are used solely for downlink transmission. As an example, we consider asymmetric links with an optical wireless communication (OWC) downlink and sub-6 GHz RF uplink. More specifically, we consider visible light communication as an instance of OWC, although the presented analysis and validation are applicable to alternative OWC technologies and other simplex downlink transmission technologies. While asymmetric connectivity has been previously demonstrated in scenarios like this, the impact of control-plane asymmetry has not been explored, to our knowledge. In this paper, we first introduce the novel challenges related to local handshaking in wireless networks with control-plane asymmetry. We then develop a theoretical framework for throughput analysis in a network where the sub-6 GHz RF channel is shared between a conventional RF link and an asymmetric RF/OWC link. This analysis is validated via simulation and verified in a testbed system using Mango WARP3 software defined radios and a commercially available RF access point. Finally, we use the derived throughput equations to analyze the impact of various protocol parameters and demonstrate one potential use of the derived equations to evaluate sum throughput in the presence of an unreliable OWC link.

Developing a situation and threat assessment framework for a next generation roadside animal detection system

Collisions involving large animals are a serious safety, economic and ecological concern. Some North American jurisdictions have installed a roadside animal detection system (RADS) that can warn the possible presence of large animals on rural highway sections. This study provides a conceptual framework for developing a next generation (NG) RADS. This study focuses on developing a process that can estimate the varying levels of threat posed by animals on the roadway using real-time data on animal and vehicle positions. To estimate the level of threat, the study used a fuzzy rule-based algorithm that integrates four input indicators (e.g., physical distance between animal and vehicle). The methodology was tested using real-world traffic and animal data collected from a conventional RADS in British Columbia, Canada. The NG RADS has significant advantages over the conventional RADS. In particular, the NG RADS can disseminate varying levels of warning according to the estimated level of the threat rather than the constant level of warning generated by a conventional RADS. The NG RADS can also use a Vehicle-to-Infrastructure communication technology to establish direct wireless communication with vehicles at risk, for instance, to automatically control a vehicle's speed to avoid a collision with a large animal.

D2D Communication Underlaying Microwave and Millimeter-Wave Cellular Networks Using CIPC

D2D communication is one of the promising technologies to improve network performance through direct wireless communication between users, without, or with limited participation of the base station (BS). In this paper, we investigate the performance of D2D communication underlaying microwave ( μ-wave) and millimeter-wave (mm-wave) cellular networks using stochastic geometry. Rayleigh fading is considered to characterize the μ-wave channels in both links, while the Rician fading is used to characterize the mm-wave channel in the D2D and cellular desired link. The D2D communication is established when the losses between the D2D transmitter and the D2D receiver are lower compared to the losses that exist between the D2D transmitter and the BS receiver. On the other hand, to minimize the interference caused by the coexistence of cellular and D2D communication and increase network performance, the Channel Inversion-Based Power Control (CIPC) is studied. In this way, the Complementary Cumulative Distribution Function (CCDF) for the successful transmission is obtained. Based on the analytical and numerical results, we show an important increase in the probability of successful transmission using the CIPC and considering the channel gains condition to establish the D2D communication compared to the traditional mode in which power control is not used and no conditions are considered to establish the D2D communication.

Coded Cooperative Data Exchange in Multichannel Multihop Wireless Networks

This article investigates the coded cooperative data exchange (CCDE) problem, where a set of nodes initially hold a subset of packets and wish to retrieve all desired packets via direct wireless communication with neighbors. The CCDE problem in multihop wired networks has seen significant research recently and is proved to be NP-hard. The CCDE problem in multihop wireless networks (MWNs) must additionally consider half-duplex constraint, interference constraint, and channel constraint. Channel assignment brings new challenges to the CCDE problem in MWN, since it is also a well-known NP-hard problem even with one channel. In this article, we study the CCDE problem in MWN with multiple channels. We first construct a path network to evaluate the priority for each possible transmission and then construct a conflict graph (CG). This graph depicts the half-duplex, interference, and channel constraints. After that, a greedy channel assignment algorithm is proposed to obtain the nonconflict transmissions based on the constructed CG and assign a channel for each selected transmission. Finally, based on the selected transmissions, we construct a single-source multicast network exploiting the time expanded network, with which the network encoding and decoding schemes can be computed within polynomial time. Extensive simulations are conducted to demonstrate the efficiency of the proposed algorithm.

An efficient multiple access control protocol for directional dense urban traffic surveillance system

Artificial intelligence (AI) methods for traffic video analysis have been widely identified as potential solutions for solving hard problems in intelligent transport systems (ITS). To exploit the advantages of AI, dense cameras to monitor the traffic are required to be deployed along the road and at the intersections. The captured videos of these cameras should be back-hauled to the control center, acting as the inputs of the AI methods. To bear such large data traffic load and to cover long transmission range, directional communication technology can be employed, which concentrate the energy of the wireless signal in a specified direction to provide high data rate and long transmission range (up to hundreds of kilometers). In this paper, the communication time extension problem (CTEP) is identified when directional transmission is applied to the dense urban traffic surveillance system, where the wireless signal propagation time approximates the data transmission time. A link distance division-based time division multiple access (LDD-TDMA) protocol is proposed to address the identified CTEP. Firstly, the directional wireless communication links are classified into categories according to the link distance, where nodes located in the same communication ring belong to the same category. Then a link distance aware (LDA)-based slot allocation algorithm is proposed to assign the time slots to the links. The optimal communication rings’ radius is derived in closed form formula, and the minimum average links’ distance is derived. Simulation results show that LDD-TDMA outperforms TDMA by 13.37% when the ring number is 4.

Development, Implementation, and Characterization of a 64-Element Dual-Polarized Phased-Array Antenna Module for 28-GHz High-Speed Data Communications

Silicon-based millimeter-wave (mm-wave) phased-array technologies are enabling directional wireless data communications at Gb/s speeds. In this paper, we review and discuss the challenges of implementing a multichip phased-array antenna module for mm-wave applications using organic buildup substrate technology. A prototype test vehicle has been fabricated and studied to evaluate the antenna and interconnect performance, dielectric properties, package substrate warpage conditions at different temperatures, chip- and board-level joint process reliability, and thermal management feasibility for cooling. Based on the learning from the test vehicle, an organic-based multilayered phased-array antenna package for 28-GHz mm-wave radio access applications is implemented. The package incorporates 64 dual-polarized antenna elements and features an air cavity common to all antennas. Direct probing measurements on a single-antenna element of the package show over 3 GHz of bandwidth and 3-dBi gain at 28 GHz. A phased-array transceiver module has been developed with the package; the module includes four SiGe BiCMOS ICs attached using flip-chip assembly. Module-level measurements in the TX mode show a 35-dB near-ideal output power increase for 64-element power combining; 64-element radiation pattern measurements are reported with a steering range of ± 50° without tapering in off-boresight directions, and 64-element radiation pattern measurements with tapering show achievement of a sidelobe level lower than −20 dB. The transceiver modules achieved 20.64-Gb/s throughput with 256 QAM and 800-MHz bandwidth in direct over-the-air link measurement results.

Congestion-aware route selection in automatic evacuation guiding based on cooperation between evacuees and their mobile nodes

When a large-scale disaster occurs, evacuees have to evacuate to safe places quickly. For this purpose, an automatic evacuation guiding scheme based on cooperation between evacuees and their mobile nodes has been proposed. The previous work adopts shortest-distance based route selection and does not consider the impact of traffic congestion caused by evacuation guiding. In this paper, we propose congestion-aware route selection in the automatic evacuation guiding. We first adopt a traffic congestion model where each evacuee’s moving speed on a road is determined by the population density of the road and his/her order among evacuees traveling in the same direction. Based on this congestion model, each evacuee’s mobile node estimates the cost, i.e., traveling time, of each road in the area. Each mobile node collects information about blocked road segments and positions of other evacuees through communication infrastructures or other mobile nodes. Based on the obtained information, it calculates and selects the smallest-cost route. Through simulation experiments, we show that the congestion-aware route selection can reduce both average and maximum evacuation times compared to the shortest-distance-based route selection, especially under highly congested situations. Furthermore, we show that the congestion-aware route selection can work well even under highly damaged situations where only direct wireless communication among mobile nodes is available.

Air Substrate 2-D Planar Cavity Antenna With Chessboard Structure

In this letter, an air substrate two-dimensional chessboard cavity antenna with scalable radiating aperture is proposed for high-gain applications. The proposed cavity antenna is composed of $M$ × $N$ open cavity units, arranged properly in a planar chessboard topology structure. Benefiting from the structure scalability, a much larger radiating aperture with high gain can be achieved using an appropriate excitation approach. Another merit from the chessboard structure is the air-filled medium without suffering from the high dielectric loss for high-frequency usage. Each unit of the cavity antenna can be supported stably by the shorting sidewalls of itself and adjacent units, not by substrate as usual. To validate the design strategy, a 4 × 5 air-filled chessboard cavity antenna is built and tested. The peak gain of 17.28 dBi is measured in the operation band of 8.35–8.74 GHz (4.56%), exhibiting the potentials in the directional wireless communication applications.

Automatic evacuation guiding scheme based on implicit interactions between evacuees and their mobile nodes

When large-scale disasters occur, evacuees have to evacuate to safe places quickly. They, however, may not be able to afford to obtain sufficient information for their evacuations under such emergent situations. In this paper, we propose an automatic evacuation guiding scheme using evacuees’ mobile nodes, e.g., smart phones. The key idea to achieve automatic evacuation guiding is implicit interactions between evacuees and their mobile nodes. Each mobile node tries to navigate its evacuee by presenting an evacuation route. At the same time, it can also trace the actual evacuation route of the evacuee as the trajectory by measuring his/her positions periodically. The proposed scheme automatically estimates blocked road segments from the difference between the presented evacuation route and the actual evacuation route, and then recalculates the alternative evacuation route. In addition, evacuees also share such information among them through direct wireless communication with other mobile nodes and that with a server via remaining communication infrastructures. Through simulation experiments, we show that 1) the proposed scheme works well when the degree of damage is high and/or road segments are continuously blocked, 2) the average evacuation time can be improved even in small penetration ratio of the proposed system, and 3) the direct wireless communication can support many evacuations at almost the same level as the communication infrastructure when the number of evacuees becomes large.

Do as I dance

Robotics The conditions under which a multirobot search and rescue team might be most needed are also the conditions in which communication between robots might be the most challenging and prone to failure. For example, direct wireless communication or long-range visual observation from one robot to another may be blocked by debris, smoke, or other obstacles. Das et al. engineered their unmanned autonomous vehicles to behave like honey bees, in which a forager bee communicates through a wiggle dance to explain a pattern of motion to follower bees. Three different flight patterns were tested and conveyed with high precision, although some errors arose because of limitations of uncorrected computer vision in perceiving specific shapes. ![Figure][1] One of a group of unmanned autonomous vehicles. PHOTO: © BRENDAN FITTERER/TAMPA BAY TIMES/[ZUMAPRESS.COM][2] Robotics Auton. Syst. 10.1016/j.robot.2016.04.002 (2016). [1]: pending:yes [2]: http://ZUMAPRESS.COM

Array of patch-antennas with meandering-gaps on optical modulator for wireless millimeter-wave beam-steering

An array of patch-antennas with meandering-gaps on an optical modulator is proposed for wireless millimeter-wave beam-steering through high-speed radio-over-fiber systems. Wireless millimeter-wave can be received by the array of patch-antennas and directly modulated to lightwave by the optical modulator. The wireless millimeter-wave can be steered using the meandering-gaps at the patch-antennas by controlling interaction between millimeter-wave and lightwave electric fields in electro-optic modulation. The basic operation and analysis of the proposed device are discussed. In the experiment, 5 × 5 antenna array in 40 GHz millimeter-wave bands was designed and realized for device characterization and demonstration to wireless millimeter-wave beam-steering. There were five variations of wireless millimeter-wave beam-steering for one-dimensional in xz- or yz-planes that can be obtained with wireless millimeter-wave steerable beams of about ±30°. Additionally, 25 variations of wireless beam-steering can be obtained for two dimension in xyz-space through orthogonal optical modulation. The proposed device is promising to be applied in millimeter-wave/tera-hertz bands for future directional wireless communication and sensing with high-speed and high-resolution operation.

Performance of power allocation schemes in an amplify-and-forward single-relay system with diversity at destination

Different strategies can be followed to achieve efficient power allocation in wireless systems. While optimising the average received SNR would directly result in an optimised average BER and outage probability in a direct wireless communication link, it is not clear whether we can achieve an optimised average BER and/or outage probability in a relaying system by optimising the average received SNR. In this paper, the problem of power allocation in a single-relay amplify-and-forward wireless system with maximal ratio combining MRC at the destination terminal is investigated via optimising three different objective functions: average SNR, average BER and outage probability. The average SNR, average BER and outage probability expressions are first derived as a function of source and relay transmit powers and variance of the channel gains. Based on these expressions, closed-form expressions are derived for optimum transmit power allocation between source and relay. It is observed that the BER-based and outage-based power allocation schemes achieve performance improvement over the SNR-based scheme when the relay is closer to the source; however, all the three schemes perform equally when the relay is close to the destination.

Opportunistic Spatial Reuse in IEEE 802.15.3c Wireless Personal Area Networks

The IEEE 802.15.3c wireless personal area network (WPAN) standard is designed to support highly directional wireless communications at the 60-GHz frequency band. Highly directional communications are helpful to reduce interference; hence, great potentials are provided for aggregate network throughput improvement via spatial reuse (SR). However, in 802.15.3c WPANs, the SR is limited in use since the 802.15.3c standard does not specify an explicit procedure for the SR. We design a new and simple scheme exploiting the SR, thus improving aggregate network throughput. In the proposed scheme, the 802.15.3c devices measure and report the measured channel status. Then, a controlling device, which is called the piconet coordinator (PNC) in the 802.15.3c WPAN, schedules resources available for each device. The simulation results demonstrate that the proposed scheme contributes to significant aggregate network throughput improvement. The proposed scheme is so simple that it can be easily employed for practical 802.15.3c devices. In addition, it is guaranteed to work well without conflicting with existing 802.15.3c operations.

Identifying Neighbor and Connectivity of Wireless Sensor Networks with Poisson Point Process

Identifying neighbor and connectivity are the fundamental requirements in wireless sensor networks. The sensor nodes are scattered randomly over the area of interest and their first step is to identify their immediate neighbors, i.e., the nodes with which they have direct wireless communication. On the other hand, connectivity ensures that sensor nodes can communicate with each other in order to aggregate sensing data hop by hop to the base stations (sink nodes). In this paper, we study identifying neighbor and connectivity in the context of wireless sensor networks, using Poisson point process theory.

Max-min utility fair flow management for networks with route diversity

A regional central manager is employed to set aside, for the regional (or back-bone) network that it manages, for each flow class, communications capacity resources for a specific future time horizon. In the context of such a traffic management operation, a longer temporal scale is involved in controlling the admission and distribution of flows across the network. For management scal-ability purposes, flows are aggregated into flow classes. Furthermore, we consider a network operation under which multiple simultaneously activated routes are employed, across possibly distinct segments, to distribute traffic between identified source-destination pairs. We aim to ensure that the utility assigned to each class is as high as feasibly possible while striving to raise the utility gained by all classes in a maxmin fair manner. In doing so, we incorporate the communications capacity constraints that are imposed by the underlying hybrid of directional and/or multiple-access wireline and wireless communications media employed across the network system. We develop and present in this paper an optimal algorithm for solving such a traffic management problem. It yields multi-utility-based max-min fair distributions of flow rates, per each class, across the specified multitude of simultaneously activated multi-segment routes. To guarantee that admitted flows are granted their desired capacity resources (and targeted corresponding utility levels), the selection of optimal flow distributions across the network routes is combined with the use of a flow admission control scheme that serves to optimally limit the aggregate rate of flows admitted for each flow class. As illustrative examples, we demonstrate the effectiveness of our solution in comparing its performance with that obtained under the use of a traffic regulation scheme that is not overlaid with a traffic management mechanism that serves to set aside resources for the support of flow classes. We also illustrate the use of our optimal algorithm for determining the optimal placement of unmanned aerial vehicle platforms that serve to supplement a terrestrial transport segment with a space-based one.

A secure coverage area expansion scheme for public wireless LAN services

An ad-hoc network style connection can be utilised to expand the coverage area of public wireless LAN (WLAN) services. By relaying the messages among user nodes, a node can obtain an internet connection, even though the node is located outside the AP's direct wireless communication area. This concept has been realised by using the ad-hoc on-demand distance vector (AODV) routing protocol and mobile IP. However, it has some drawbacks in terms of security. The AODV has no functions for confirming the validity of routing messages; therefore, there are many threats due to faked or forged routing messages. In contrast, if a secure ad-hoc routing protocol is used for message routing in the WLAN service, the message route can be appropriately maintained. However, in order to employ secure ad-hoc routing protocols, a key and IP address have to be securely delivered to each WLAN node in advance. For this purpose, in this paper, the authors propose a secure address and public key certificate allocation scheme for WLAN services.

Direct cellular vs. indirect pager communication during orthopaedic surgical procedures: A prospective study

Cellular phone use within the hospital setting has increased as physicians, nurses, and ancillary staff incorporate wireless technologies in improving efficiencies, cost, and maintaining patient safety and high quality healthcare [11]. Through the use of wireless, cellular communication, an overall improvement in communication accuracy and efficiency between intraoperative orthopaedic surgeons and floor nurses may be achieved. Both communication types occurred while the surgeon was scrubbed in the operating room (OR). Indirect communication occurred when the pager call was answered by the OR circulating nurse with communication between the surgeon, circulating nurse, and floor nurse. Direct communication consisted of cell phone and Jabra Bluetooth BT200 wireless ear piece used by the surgeon. The surgeon answered the floor nurse's cellular call by phone ring-activated automatic answering. The study was conducted during scheduled orthopaedic procedures. An independent observer measured time variables with a stop-watch while orthopaedic nurses randomly called via pager or cell phone. The nurses asked for patient caregiver confirmation and answers to 30 different patient-care questions. Sixty trials were performed with 30 cell and 30 page communications. Direct cellular communication showed a better response rate than indirect page (Cell 100%, Page 73%). Indirect page communication allowed a 27% and 33% error rate with patient problem and surgeon solution communications, respectively. There were no reported communication errors while using direct wireless, cellular communication. When compared to page communications, cellular communications showed statistically significant improvements in mean time intervals in response time (Cell = 11s, Page = 211s), correct patient identification (Cell = 5s, Page = 172s), patient problem and solution time (Cell = 13s, Page = 189s), and total communication time (Cell = 32s, Page = 250s) (s = seconds, all P < 0.001). Floor nurse satisfaction ratings (dependent on communication times and/or difficulties) were improved with direct cellular communication (Cell = 29 excellent, Page = 11 excellent). Intraoperative case interruptions (defined as delaying surgical progress) were more frequent with indirect page communication (10 page v. 0 cell). Our study demonstrates that direct wireless communication may be used to improve intraoperative communication and enhance patient safety. Direct wireless, cellular intraoperative communication improves communication times, communication accuracy, communication satisfaction, and minimizes intraoperative case interruption. As a result of this study, we hope to maintain our transition to direct wireless, cellular intraoperative orthopaedic communication to reduce medical errors, improve patient care, and enhance both orthopaedic surgeon and nursing efficiencies.

Autonomous reconfiguration and control in directional mobile ad hoc networks

Requirements for increasingly complex, scalable, and dynamic wireless networks, which provide assured end-to-end broadband connectivity in a wide range of scenarios, have been emerging. In this context, we have been investigating wireless technologies that provide extremely high data rates through the use of narrow-beam free space optical (FSO) and/or radio-frequency (RF) point-to-point links. The use of directional wireless communications to form flexible backbone networks, which provide broadband connectivity to capacity- limited wireless networks or hosts using omnidirectional transmission, promises to circumvent the scalability limitations of traditional flat wireless networks. We have been investigating backbones of base stations, in which topologies and mobility can be controlled for purposes of assured communications. We refer to these as Directional Mobile Ad Hoc Networks (DMANET). Our work considers the use of topology control to assure robust end-to-end broadband connectivity in heterogeneous and dynamic environments. Topology control is defined as the autonomous network capability to dynamically reconfigure its physical topology. In the case of directional wireless backbone (DWB) networks, the physical topology can be reconfigured through: Autonomous 1) Topology Reconfiguration (ATR): dynamic redirection of point-to-point links using heuristic algorithms for creating new topologies and pointing, acquisition and tracking of links. Topology reconfiguration algorithms, which compute minimum energy configurations by determining optimal link assignments between backbone nodes, are presented. The pointing, acquisition and tracking (PAT) process needed to physically redirect point-to-point links is also addressed. 2) Mobility Control (MC): dynamic reposition and "morphing" of backbone nodes. In this model, communication links define physical interactions between network nodes. Control mechanisms are designed to mimic physical systems' natural reaction to external excitations, which drive the network topology to minimum energy configurations Using both ATR and MC, networks are completely selforganizing. They can autonomously adapt their physical topology to maximize coverage to terminals or hosts while maintaining robust backbone connectivity. In this paper, we present the design, implementation and evaluation of our novel approaches to autonomous reconfiguration and control.

A quadratic optimization method for connectivity and coverage control in backbone-based wireless networks

The use of directional wireless communications to form flexible mesh backbone networks, which provide broadband connectivity to capacity-limited wireless networks or hosts, promises to circumvent the scalability limitations of traditional homogeneous wireless networks. The main challenge in the design of directional wireless backbone (DWB) networks is to assure backbone network requirements such as coverage and connectivity in a dynamic wireless environment. This paper considers the use of mobility control, as the dynamic reposition of backbone nodes, to provide assured coverage-connectivity in dynamic environments. This paper presents a novel approach to the joint coverage-connectivity optimization problem by formulating it as a quadratic minimization problem. Quadratic cost functions for network coverage and backbone connectivity are defined in terms of the square distance between neighbor nodes, which are related to the actual energy usage of the network system. Our formulation allows the design of self-organized network systems which autonomously achieve energy minimizing configurations driven by local forces exerted on network nodes. The net force on a backbone node is defined as the negative energy gradient at the location of the backbone node. A completely distributed algorithm is presented that allows backbone nodes to adjust their positions based on information about neighbors’ position only. We present initial simulation results that show the effectiveness of our force-based mobility control algorithm to provide network configurations that optimize both network coverage and backbone connectivity in different scenarios. Our algorithm is shown to be adaptive, scalable and self-organized.