1,721,029 research outputs found
Optimized Over-the-Air Computation for Wireless Control Systems
No full textThe over-the-air controller was recently proposed to enable efficient computation of the control signal for control systems, by leveraging the over-the-air computation concept. This paper introduces a transmit power allocation scheme for the over-the-air controller, where the wireless channel directly produces the control gain of a discrete-time linear control system. The proposed design scheme essentially minimizes the worst effect of the channel noise to the desired control system output, subject to the transmit power limit over the wireless channel. Despite the non-convexity of the problem, we derive the control cost criterion as linear matrix inequalities with transmit power constraints. We comprehensively investigate the control performance and the transmit power cost of the proposed scheme in various scenarios. The proposed optimization scheme shows significant control performance gain against the state-of-the-art solution, while having a comparable transmit power consumption
Outage Performance of Power Controlled DS-CDMA Wireless Systems with Heterogeneous Traffic Sources
No full text
Approximation for a Sum of On-Off Log-Normal Processes with Wireless Applications
No full textIn this paper, a lognormal approximation is proposed
for the sum of lognormal processes weighted by binary processes.
The analytical approach moves from the method early proposed
by Wilkinson for approximating first-order statistics of a sum of
lognormal components, and extends to incorporate second-order
statistics and the presence of both time-correlated random binary
weights and cross-correlated lognormal components in moments’
matching. Since the sum of weighted lognormal processes models
the signal-to-interference-plus-noise ratio (SINR) of wireless
systems, the method can be applied to evaluate in an effective and
accurate way the outage occurrence rate and outage duration for
different wireless systems of practical interest. In a frequencyreuse-
based cellular system, the method is applied for various
propagation scenarios, characterized by different shadowing
correlation decay distances and correlations among shadowing
components. A further case of relevant interest is related to
power-controlled wideband wireless systems, where the random
weights are binary random variables denoting the activity status
of each interfering source. Finally, simulation results are used to
confirm the validity of the analysis
Wireless for Control: Over-the-Air Controller
No full textIn closed-loop wireless control systems, the state-of-the-art approach prescribes that a controller receives by wireless communications the individual sensor measurements, and then sends the computed control signal to the actuators. We propose an over-the-air controller scheme where all sensors attached to the plant simultaneously transmit scaled sensing signals directly to the actuator; then the feedback control signal is computed partially over the air and partially by a scaling operation at the actuator. Such over-the-air controller essentially adopts the over-the-air computation concept to compute the control signal for closed-loop wireless control systems. In contrast to the state-of-the-art sensor-to-controller and controller-to-actuator communication approach, the over-the-air controller exploits the superposition properties of multiple-access wireless channels to complete the communication and computation of a large number of sensing signals in a single communication resource unit. Therefore, the proposed scheme can obtain significant benefits in terms of low actuation delay and low wireless resource utilization by a simple network architecture that does not require a dedicated controller. Numerical results show that our proposed over-the-air controller achieves a huge widening of the stability region in terms of sampling time and delay, and a significant reduction of the computation error of the control signal
Outage Performance of Power Controlled DS-CDMA Wireless Systems with Heterogeneous Traffic Sources
No full textMobile Node Localization via Pareto Optimization : Algorithm and Fundamental Performance Limitations
No full textAccurate estimation of the position of network nodes is essential, e.g., in localization, geographic routing, and vehicular networks. Unfortunately, typical positioning techniques based on ranging or on velocity and angular measurements are inherently limited. To overcome the limitations of specific positioning techniques, the fusion of multiple and heterogeneous sensor information is an appealing strategy. In this paper, we investigate the fundamental performance of linear fusion of multiple measurements of the position of mobile nodes, and propose a new distributed recursive position estimator. The Cramer-Rao lower bounds for the parametric and a-posteriori cases are investigated. The proposed estimator combines information coming from ranging, speed, and angular measurements, which is jointly fused by a Pareto optimization problem where the mean and the variance of the localization error are simultaneously minimized. A distinguished feature of the method is that it assumes a very simple dynamical model of the mobility and therefore it is applicable to a large number of scenarios providing good performance. The main challenge is the characterization of the statistical information needed to model the Fisher information matrix and the Pareto optimization problem. The proposed analysis is validated by Monte Carlo simulations, and the performance is compared to several Kalman-based filters, commonly employed for localization and sensor fusion. Simulation results show that the proposed estimator outperforms the traditional approaches that are based on the extended Kalman filter when no assumption on the model of motion is used. In such a scenario, better performance is achieved by the proposed method, but at the price of an increased computational complexity.</p
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