Marek Miskowicz

The event-triggered integral criterion for sensor sampling

The paper presents the performance evaluation of the event-triggered integral criterion for sensor sampling. The proposed asynchronous sampling pattern is the extension of the simple send on delta strategy used e.g. in LonWorks/EIA-709 control networking technology. The analytical formula for evaluation the mean and the maximum rate of event-based traffic versus the sampling resolution is derived. The simulation results verifying the derived formula are reported. The definition of the integral send on delta concept and the framework of its implementation in Neuron C programming language are presented.

Efficiency of Event-Based Sampling According to Error Energy Criterion

The paper belongs to the studies that deal with the effectiveness of the particular event-based sampling scheme compared to the conventional periodic sampling as a reference. In the present study, the event-based sampling according to a constant energy of sampling error is analyzed. This criterion is suitable for applications where the energy of sampling error should be bounded (i.e., in building automation, or in greenhouse climate monitoring and control). Compared to the integral sampling criteria, the error energy criterion gives more weight to extreme sampling error values. The proposed sampling principle extends a range of event-based sampling schemes and makes the choice of particular sampling criterion more flexible to application requirements. In the paper, it is proved analytically that the proposed event-based sampling criterion is more effective than the periodic sampling by a factor defined by the ratio of the maximum to the mean of the cubic root of the signal time-derivative square in the analyzed time interval. Furthermore, it is shown that the sampling according to energy criterion is less effective than the send-on-delta scheme but more effective than the sampling according to integral criterion. On the other hand, it is indicated that higher effectiveness in sampling according to the selected event-based criterion is obtained at the cost of increasing the total sampling error defined as the sum of errors for all the samples taken.

Efficiency of level-crossing sampling for bandlimited gaussian random processes

The paper presents the analytical estimation of the mean rate and the effectiveness of the level-crossing sampling scheme if the input signal is modelled by the bandlimited Gaussian stationary random process. The level-crossing sampling effectiveness is defined as the reduction of the sampling rate in relation to the periodic sampling. A new measure, called the spectral density of the level crossings, has been introduced and evaluated. It is also derived that the lower bound of the sampling effectiveness (i.e. the guaranteed effectiveness) for a Gaussian lowpass process equals 3.76 and is independent of either the process mean square value, or the cut-off frequency. The guaranteed effectiveness approximates the sample reduction for a high sampling resolution at the same time.

Sampling of signals in energy domain

The paper introduces a new event-based criterion for discrete representations of continuous-time signals, which can be used in intelligent sensors to report the current state of the observed object. The criterion is based on the control of the sampling error energy. The analytic approximation of the mean sampling rate for a given sampling resolution is derived. The formula for the reduction of sampling rate with respect to periodic sampling is found. The analytical calculations are validated by simulation results

Analytical approximation of the uniform magnitude-driven sampling effectiveness

The paper deals with the magnitude-driven sampling, where the signal is sampled when the measurement signal crosses a certain prespecified levels in the value domain. The magnitude-driven sampling effectiveness defined as a ratio of the number of samples taken in periodic and magnitude-driven schemes is studied. The comparison of both sampling patterns is made for the same signal tracking performance. The simulation investigation is performed and the analytical approximation of the simulation results is derived. As it follows from the analytical formula, the uniform magnitude-driven sampling effectiveness is a function of the first time derivative of a sampled continuous-time signal in relation to the time.

Average Channel Utilization of CSMA With Geometric Distribution Under Varying Workload

Performance analysis of fixed-size contention window carrier sense multiple-access (CSMA) protocol with geometric distribution for slot selection probability is addressed in the paper. This MAC scheme, called Sift, was initially proposed for large-scale event-driven wireless sensor networks. The goal of the present paper is to evaluate the standard performance measures (throughput, protocol capacity, collision rate, and mean access delay) for geometrically distributed CSMA both in the context of data-centric dense sensor networks and node-centric industrial automation systems. The analytical approach based on the stochastic analysis has been applied. To demonstrate how the protocol is able to cope with bursty traffic, the average throughput defined over a specified workload range has been introduced and examined. Using the average throughput as the performance criterion, the geometric CSMA has been compared to conventional CSMA schemes with uniform distribution. The latter are represented by the classical p-persistent CSMA and the predictive p-persistent CSMA used in LonWorks control networks. It is shown that G-CSMA is overload-tolerant event-driven MAC protocol since the average throughput may be kept on high level in wide range of workload if the shape of geometric distribution is well chosen.

The event-triggered sampling optimization criterion for distributed networked monitoring and control systems

An overview of signal-dependent sampling methods in control systems with an emphasis on the event-triggered schemes is done. The analysis of either the networked control system performance, or the sampling cost component measures is performed. A new criterion for sampling a continuous-time variable using the event-triggered pattern is presented. The suggested criterion is based on the optimization of a balance between the signal tracking performance and the cost of a networked control system. As the system cost we consider the amount of communication bandwidth dedicated to sending messages and the length of the FIFO output buffer. The evaluation of particular cost components is made on the basis of timing parameters of a sample string, i.e. the average sampling rate and sample string burstiness. The principles of selection of the sampling interval bounds are discussed. The rules of tuning of the objective function coefficients are presented.

Event-based sampling strategies in networked control systems

A postulate of resource-aware design of modern control systems drives an intensified research towards more extensive usage of event-based models. The objective of most research works on event-triggered control is positioned in the context of networked sensor and control systems due to perspective of better bandwidth utilization and reducing computational complexity. The aim of this paper is to review event-based sampling strategies in terms of analytical evaluation of the mean traffic rate produced to the communication channel. The focus is put on the analysis of threshold-based sampling criteria including send-on-delta reporting strategy (Lebesgue sampling), and its extensions (send-on-area, send-on-energy). Next, the Lyapunov sampling as a scheme that addresses control system stability is surveyed. The overview of research studies shows that in many application scenaria the event-based sampling schemes can provide around one order of magnitude of traffic reduction compared to conventional periodic sampling while still keeping similar system performance.

Designing Time-to-Digital Converter for Asynchronous ADCs

Time-to-digital converter designing and analysis for asynchronous ADCs is discussed in the paper. The proposed ADC utilizes two-level conversion scheme consisting in duty-cycle modulation and subsequent time-to-digital conversion (TDC). Three concepts of the asynchronous ADC digital serial output interface are presented. The comparison of minimum transmission rates of the serial output port(s) for each concept is carried out. Finally, the procedure of the evaluation of key ADC design parameters for the speech signal supporting a possible original input signal recovery is exemplified.

Performance of send-on-delta sampling schemes with prediction

In the paper, the performance of the sampling algorithm as a measure that evaluates together the sampling cost and the sampling accuracy is introduced and analyzed. We define the sampling cost as a number of samples in a unit of time and respectively the sampling accuracy as the mean intersampling error. On the basis of the sampling scheme performance measure, we compare the pure send-on-delta scheme and the send-on-delta scheme with prediction because these sampling algorithms are developed on controlling the linear intersampling error. As shown on the basis of simulation results, the send-on-delta schemes with first or second-order prediction outperforms the classical periodic sampling, and the pure send-on-delta scheme.