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

Temporal Stream Logic: Synthesis beyond the Bools

Reactive systems that operate in environments with complex data, such as mobile apps or embedded controllers with many sensors, are difficult to synthesize. Synthesis tools usually fail for such systems because the state space resulting from the discretization of the data is too large. We introduce TSL, a new temporal logic that separates control and data. We provide a CEGAR-based synthesis approach for the construction of implementations that are guaranteed to satisfy a TSL specification for all possible instantiations of the data processing functions. TSL provides an attractive trade-off for synthesis. On the one hand, synthesis from TSL, unlike synthesis from standard temporal logics, is undecidable in general. On the other hand, however, synthesis from TSL is scalable, because it is independent of the complexity of the handled data. Among other benchmarks, we have successfully synthesized a music player Android app and a controller for an autonomous vehicle in the Open Race Car Simulator (TORCS.

Low complexity block processing algorithms for adaptive channel estimation in OFDM systems

For pilot-aided channel estimation in orthogonal frequency-division multiplexing (OFDM) systems, adaptive algorithms enable tracking of a time-varying channel. Using several subcarriers for the update step in the adaptive algorithm, i.e., performing block processing, improves the robustness and convergence speed of the adaptation. To decrease the complexity of these algorithms, simplified versions are deduced as well as versions with real-valued filters. In the latter case the number of required arithmetic operations can be reduced significantly not only in the adaptive algorithm but also in the filtering process itself, which represents a dominating part regarding the complexity due to the huge amount of subcarriers of practical OFDM transmission schemes. Simulation results show that gains w.r.t. the convergence behavior can be achieved by real-valued filters compared to complex-valued filters even in scenarios where real-valued filters are theoretically suboptimum

Optimized delay diversity for fading ISI channels

Abstract — In this paper, we propose an optimized delay diversity (ODD) scheme for fading intersymbol interference (ISI) channels. The novel scheme requires knowledge of the channel impulse response (CIR) autocorrelation matrix at the transmitter, but the CIRs themselves have to be available only at the receiver side. We derive a cost function for optimization of the ODD transmit filters and we provide a steepest descent algorithm for iterative calculation of the filter coefficients. In addition, an upper bound on the cost function is derived and employed to prove the asymptotic optimality of the generalized DD (GDD) scheme in [1] for very high signal–to–noise (SNR) ratios and transmit filters of maximum length. However, for SNRs of practical interest and reasonable filter lengths the novel ODD scheme significantly outperforms GDD for both optimum and suboptimum equalization. I

Optimization of Delay Diversity for Linear Equalization

In this paper, we optimize delay diversity (DD) for the case when simple linear equalization (LE) is used at the receiver. We consider the general case of transmission over a correlated multiple-input multiple-output (MIMO) frequency-selective fading channel. The proposed optimization requires the knowledge of the statistical properties of the wireless channel at the transmitter, but channel state information is only required at the receiver side. Based on an approximation of the bit error rate for LE, we derive a stochastic gradient algorithm that allows us to optimize the DD transmit filters. Simulation results for the GSM/EDGE system show significant performance gains of the proposed optimized DD scheme over the DD schemes reported in [1] and [2], respectively, if LE is used at the receiver

On the throughput of Wireless Underground Sensor Networks using magneto-inductive waveguides

Abstract—Wireless Underground Sensor Networks (WUSNs) present a variety of new research challenges. Recently, a magneto-inductive (MI) waveguide technique has been proposed to cope with the very harsh propagation conditions in WUSNs. This approach allows for an extension of the transmission range, which can be quite limited if relays are not deployed. In this paper, tree-based WUSNs are considered with sensors connected via MI-waveguides. The objective of our work is to determine the optimal system parameters and topology in order to avoid bottlenecks in the system and achieve optimal network throughput. I