Beamforming for Magnetic Induction based Wireless Power Transfer Systems with Multiple Receivers

Magnetic induction (MI) based communication and power transfer systems have gained an increased attention in the recent years. Typical applications for these systems lie in the area of wireless charging, near-field communication, and wireless sensor networks. For an optimal system performance, the power efficiency needs to be maximized. Typically, this optimization refers to the impedance matching and tracking of the split-frequencies. However, an important role of magnitude and phase of the input signal has been mostly overlooked. Especially for the wireless power transfer systems with multiple transmitter coils, the optimization of the transmit signals can dramatically improve the power efficiency. In this work, we propose an iterative algorithm for the optimization of the transmit signals for a transmitter with three orthogonal coils and multiple single coil receivers. The proposed scheme significantly outperforms the traditional baseline algorithms in terms of power efficiency.Comment: This paper has been accepted for presentation at IEEE GLOBECOM 2015. It has 7 pages and 5 figure

On Capacity of Active Relaying in Magnetic Induction based Wireless Underground Sensor Networks

Wireless underground sensor networks (WUSNs) present a variety of new research challenges. Magnetic induction (MI) based transmission has been proposed to overcome the very harsh propagation conditions in underground communications in recent years. In this approach, induction coils are utilized as antennas in the sensor nodes. This solution achieves longer transmission ranges compared to the traditional electromagnetic (EM) waves based approach. Furthermore, a passive relaying technique has been proposed in the literature where additional resonant circuits are deployed between the nodes. However, this solution is shown to provide only a limited performance improvement under practical system design contraints. In this work, the potential of an active relay device is investigated which may improve the performance of the system by combining the benefits of the traditional wireless relaying and the MI based signal transmission.Comment: This paper has been accepted for presentation at IEEE ICC 2015. It has 6 pages, 5 figures (4 colored), and 17 reference

Error Control in Wireless Sensor Networks: A Cross Layer Analysis

Error control is of significant importance for Wireless Sensor Networks (WSNs) because of their severe energy constraints and the low power communication requirements. In this paper, a cross-layer methodology for the analysis of error control schemes in WSNs is presented such that the effects of multi-hop routing and the broadcast nature of the wireless channel are investigated. More specifically, the cross-layer effects of routing, medium access, and physical layers are considered. This analysis enables a comprehensive comparison of forward error correction (FEC) codes, automatic repeat request (ARQ), and hybrid ARQ schemes in WSNs. The validation results show that the developed framework closely follows simulation results. Hybrid ARQ and FEC schemes improve the error resiliency of communication compared to ARQ. In a multi-hop network, this improvement can be exploited by constructing longer hops (hop length extension), which can be achieved through channel-aware routing protocols, or by reducing the transmit power (transmit power control). The results of our analysis reveal that for hybrid ARQ schemes and certain FEC codes, the hop length extension decreases both the energy consumption and the end-to-end latency subject to a target packet error rate (PER) compared to ARQ. This decrease in end-to-end latency is crucial for delay sensitive, real-time applications, where both hybrid ARQ and FEC codes are strong candidates. We also show that the advantages of FEC codes are even more pronounced as the network density increases. On the other hand, transmit power control results in significant savings in energy consumption at the cost of increased latency for certain FEC codes. The results of our analysis also indicate the cases where ARQ outperforms FEC codes for various end-to-end distance and target PER values

XLP: A Cross-Layer Protocol for Efficient Communication in Wireless Sensor Networks

Severe energy constraints of battery-powered sensor nodes necessitate energy-efficient communication in Wireless Sensor Networks (WSNs). However, the vast majority of the existing solutions is based on classical layered protocols approach, which leads to significant overhead. It is much more efficient to have a unified scheme which blends common protocol layer functionalities into a cross-layer module. In this paper, a cross layer protocol (XLP) is introduced, which achieves congestion control, routing, and medium access control in a cross-layer fashion. The design principle of XLP is based on the cross-layer concept of initiative determination, which enables receiver-based contention, initiative-based forwarding, local congestion control, and distributed duty cycle operation to realize efficient and reliable communication in WSNs. The initiative determination requires simple comparisons against thresholds, and thus is very simple to implement, even on computationally impaired devices. To the best of our knowledge, XLP is the first protocol that integrates functionalities of all layers from PHY to transport into a cross-layer protocol. A cross-layer analytical framework is developed to investigate the performance of the XLP. Moreover, in a cross-layer simulation platform, the state-of-the- art layered and cross-layer protocols have been implemented along with XLP for performance evaluations. XLP significantly improves the communication performance and outperforms the traditional layered protocol architectures in terms of both network performance and implementation complexity

XLP: A Cross-Layer Protocol for Efficient Communication in Wireless Sensor Networks

Severe energy constraints of battery-powered sensor nodes necessitate energy-efficient communication in Wireless Sensor Networks (WSNs). However, the vast majority of the existing solutions is based on classical layered protocols approach, which leads to significant overhead. It is much more efficient to have a unified scheme which blends common protocol layer functionalities into a cross-layer module. In this paper, a cross layer protocol (XLP) is introduced, which achieves congestion control, routing, and medium access control in a cross-layer fashion. The design principle of XLP is based on the cross-layer concept of initiative determination, which enables receiver-based contention, initiative-based forwarding, local congestion control, and distributed duty cycle operation to realize efficient and reliable communication in WSNs. The initiative determination requires simple comparisons against thresholds, and thus is very simple to implement, even on computationally impaired devices. To the best of our knowledge, XLP is the first protocol that integrates functionalities of all layers from PHY to transport into a cross-layer protocol. A cross-layer analytical framework is developed to investigate the performance of the XLP. Moreover, in a cross-layer simulation platform, the state-of-the- art layered and cross-layer protocols have been implemented along with XLP for performance evaluations. XLP significantly improves the communication performance and outperforms the traditional layered protocol architectures in terms of both network performance and implementation complexity

Fourier–Galerkin domain truncation method for Stokes’ first problem with Oldroyd four-constant liquid

AbstractUsing the Fourier–Galerkin method with domain truncation strategy, Stokes’ first problem for Oldroyd four-constant liquid on a semi-infinite interval is studied. It is shown that the Fourier–Galerkin approximations are convergent on the bounded interval. Moreover, an efficient and accurate algorithm based on the Fourier–Galerkin approximations is developed and implemented in solving the differential equations related to the present problem. Also, the effects of non-Newtonian parameters on the flow characteristics are obtained and analyzed. The method developed here is so general that it can be used to study the mathematical models that involve the flow of viscous fluids with shear rate-dependent properties: For example, models dealing with polymer processing, tribology & lubrication, and food processing

Joint energy harvesting and communication analysis for perpetual wireless nanosensor networks in the terahertz band

Abstract—Wireless nanosensor networks (WNSNs) consist of nanosized communicating devices, which can detect and measure new types of events at the nanoscale. WNSNs are the enabling technology for unique applications such as intrabody drug delivery systems or surveillance networks for chemical attack prevention. One of the major bottlenecks in WNSNs is posed by the very limited energy that can be stored in a nanosensor mote in contrast to the energy that is required by the device to communicate. Recently, novel energy harvesting mechanisms have been proposed to replenish the energy stored in nanodevices. With these mechanisms, WNSNs can overcome their energy bottleneck and even have infinite lifetime (perpetual WNSNs), provided that the energy harvesting and consumption processes are jointly designed. In this paper, an energy model for self-powered nanosensor motes is developed, which successfully captures the correlation between the energy harvestin