Stochastic Packet Research Articles

On the Delay-Throughput Tradeoff in Distributed Wireless Networks

This paper deals with the delay-throughput analysis of a single-hop wireless network with $n$ transmitter/receiver pairs. All channels are assumed to be block Rayleigh fading with shadowing, described by parameters $(\alpha,\varpi)$, where $\alpha$ denotes the probability of shadowing and $\varpi$ represents the average cross-link gains. The analysis relies on the distributed on-off power allocation strategy (i.e., links with a direct channel gain above a certain threshold transmit at full power and the rest remain silent) for the deterministic and stochastic packet arrival processes. It is also assumed that each transmitter has a buffer size of one packet and dropping occurs once a packet arrives in the buffer while the previous packet has not been served. In the first part of the paper, we define a new notion of performance in the network, called effective throughput, which captures the effect of arrival process in the network throughput, and maximize it for different cases of packet arrival process. It is proved that the effective throughput of the network asymptotically scales as $\frac{\log n}{\hat{\alpha}}$, with $\hat{\alpha} \triangleq \alpha \varpi$, regardless of the packet arrival process. In the second part of the paper, we present the delay characteristics of the underlying network in terms of the packet dropping probability. We derive the sufficient conditions in the asymptotic case of $n \to \infty$ such that the packet dropping probability tend to zero, while achieving the maximum effective throughput of the network. Finally, we study the trade-off between the effective throughput, delay, and packet dropping probability of the network for different packet arrival processes.

State Regulation and State Observation in Networked Control Systems

This paper discusses variable signal delays and stochastic packet dropouts within closed loop Networked Control Systems (NCS). A special focus is dedicated to uncertain or partly unknown transition probabilities and the solution of the bilinear controller design problem. In addition, this approach is extended to the design of state observers. A numerical example is given to demonstrate the effectiveness of the controller design, while the observer based approach is applied to an inverted pendulum experiment.

Exponentially Mean-square Stable Control for Uncertain Discrete Networked Control Systems with Stochastic Time Delay and Packet Dropout

Exponentially Mean-square Stable Control for Uncertain Discrete Networked Control Systems with Stochastic Time Delay and Packet Dropout

Mean square exponential stabilization of networked control systems with Markovian packet dropouts

This paper considers the mean square stabilization for a kind of network control system (NCS) in which there exist network-induced delay and stochastic packet dropout between sensor and controller. This kind of NCS is modelled as a Markovian switched system with two subsystems. Using the average dwell time method, we design a state feedback controller to guarantee that NCS be mean square exponentially stable. An illustrative example is provided to demonstrate the effectiveness of the proposed results.

Optimal Estimation for Multiple Packet Dropouts Systems Based on Measurement Predictor

The stochastic packet dropouts often occur in the networked control systems (NCSs), which can degrade performance or stability of the systems. An optimal estimation of the dropped data during the transmissions is often inevitable. This paper has proposed a new compensation method for NCSs with packet dropouts using measurement predictor, the estimated measurement values for the lost information are obtained by using all the weighted known measurement values instead of the latest one. Based on the estimated measurement values, the optimal estimators including filter, predictor, and smoother are developed via an innovation analysis approach for multiple packet dropouts systems with white and colored measurement noises. Simulations show that the proposed estimators based on all the known information improve the estimation accuracy of the lost information, the precision of state estimation can also be improved accordingly.

Optimal Linear State Estimator With Multiple Packet Dropouts

This technical note is concerned with the optimal linear estimation problem in the presence of multiple packet dropouts in both sensor-to-controller and controller-to-actuator channels. The considered stochastic packet dropouts are independent and Bernoulli distributed. Based on a linear packet dropout model with stochastic parameters, a linear-minimum-variance (LMV) filter is proposed using the orthogonality principle. A sufficient condition for convergence of the steady-state LMV filter under a dc controller output is also given. Simulation results show the effectiveness of the proposed filter.

Modelling and stabilisation of networked control system with packet loss and time-varying delays

The modelling and stabilising control of networked control systems (NCSs) with stochastic packet loss and time-varying delays are addressed. In specific, a novel Markovian jump linear system with time-varying delays is used to model the NCS. Without using the augmented state method, sufficient conditions for the stochastic stabilisation of the NCS with packet loss and time-varying delays are obtained via the mode-dependent Lyapunov function method. The mode-dependent controller for the closed-loop NCS is presented in the linear matrix inequalities formulation via the Shur complement theory. A numerical example is given to illustrate the effectiveness of the proposed method.

Predictive control and scheduling codesign in network control systems

A codesign approach combining predictive control compensation and network scheduling is presented in this paper to overcome the adverse influences of stochastic time delays and packet losses encountered in network-based real-time control systems. The state estimation and control prediction compensation algorithms are used for the random network delays in the feedback and forward channels, and the stability criteria are analyzed. The proper sampling rate is given with network scheduling to meet the desired system performance, while the network-induced delay is tolerated. Simulations show that the codesign approach works well with the bounded network delay.

Optimal PET Protection for Streaming Scalably Compressed Video Streams With Limited Retransmission Based on Incomplete Feedback

For streaming scalably compressed video streams over unreliable networks, Limited-Retransmission Priority Encoding Transmission (LR-PET) outperforms PET remarkably since the opportunity to retransmit is fully exploited by hypothesizing the possible future retransmission behavior before the retransmission really occurs. For the retransmission to be efficient in such a scheme, it is critical to get adequate acknowledgment from a previous transmission before deciding what data to retransmit. However, in many scenarios, the presence of a stochastic packet delay process results in frequent late acknowledgements, while imperfect feedback channels can impair the server's knowledge of what the client has received. This paper proposes an extended LR-PET scheme, which optimizes PET-protection of transmitted bitstreams, recognizing that the received feedback information is likely to be incomplete. Similar to the original LR-PET, the behavior of future retransmissions is hypothesized in the optimization objective of each transmission opportunity. As the key contribution, we develop a method to efficiently derive the effective recovery probability versus redundancy rate characteristic for the extended LR-PET communication process. This significantly simplifies the ultimate protection assignment procedure. This paper also demonstrates the advantage of the proposed strategy over several alternative strategies.

Tradeoffs between quantization and packet loss in networked control of linear systems

In this paper, we consider to derive the coarsest memoryless quantizer which can stabilize a single-input discrete-time linear time-invariant system with stochastic packet loss in the sense of stochastic quadratic stability. We show that the upper bound of the coarseness is strictly given by the packet loss probability and the unstable poles of the plants. We furthermore deal with permissible dead-zone width around the origin of the quantizers and time-varying finite quantizers in order to realize control using finite quantization steps.

Effects of network communications on a class of learning controlled non-linear systems†

In this article, an iterative learning control approach is proposed for a class of sampled-data non-linear systems over network communication channels. The effects of constant time delays and stochastic packet loss are discussed and demonstrated by simulation results. The focus of this article is to study the remote control problems when the environment is periodic or repeatable over iterations in a fixed finite interval. Because of the existence of time delays and packet loss in input and output signal transmissions, it is not trivial to accomplish the remote stabilisation task of any system. Moreover, to track a desired trajectory through a remote controller is even more difficult. Previous cycle-based learning method is incorporated into the network-based control for a class of non-linear systems which satisfies a global Lipschitz condition. The convergence property of this approach is proven. Furthermore, the convergence in the iteration domain is also discussed when there exists packet loss in both transmission channels of the system. Finally, one single-link rigid robot is given as an example to show the effectiveness of the proposed approach. †Final version for the International Journal of Systems Science.

Fault Detection and Isolation of discrete-time Markovian jump linear systems with application to a network of multi-agent systems having imperfect communication channels

This paper deals with the problem of Fault Detection and Isolation (FDI) for discrete-time Markovian Jump Linear Systems (MJLSs). A geometric property related to the unobservable subspace of an MJLS is first presented and the concept of unobservability subspace is introduced. Sufficient conditions for designing an H ∞ -based FDI algorithm for MJLSs subject to input disturbances and measurement noise are presented and developed. Our proposed approach is then applied to the problem of fault detection and isolation in a network of multi-agent systems when imperfect communication channels exist among the agents. A discrete-time communication link with a stochastic packet dropping effect is considered based on the Gilbert–Elliott model and the entire network is modeled as a discrete-time MJLS. Simulation results are presented for formation flight of satellites to demonstrate and verify the effectiveness and performance capabilities of our proposed FDI algorithm.

Cross-layer optimization for wireless multihop networks with pairwise intersession network coding

For wireless multi-hop networks with unicast sessions, most coding opportunities involve only two or three sessions as coding across many sessions requires greater transmission power to broadcast the coded symbol to many receivers, which enhances interference. This work shows that with a new flow-based characterization of pairwise intersession network coding (coding across two unicast sessions), an optimal joint coding, scheduling, and rate-control scheme can be devised and implemented using only the binary XOR operation. The new scheduling/rate-control scheme demonstrates provably graceful throughput degradation with imperfect scheduling, which facilitates the design tradeoff between the throughput optimality and computational complexity of different scheduling schemes. Our results show that pairwise intersession network coding improves the throughput of non-coding solutions regardless of whether perfect/imperfect scheduling is used. Both the deterministic and stochastic packet arrivals and departures are considered. This work shows a striking resemblance between pairwise intersession network coding and non-coded solutions, and thus advocates extensions of non-coding wisdoms to their network coding counterpart.

Stochastic Packet Loss Model to Evaluate QoE Impairments

SUMMARY The estimation of quality for real-time services over telecommunication netb4works requires realistic models for impairments and failures during transmission. We focus on the classical Gilbert-Elliott model whose second-order statistics is derived over arbitrary time-scales. The model is used to fit packet loss processes of backbone and DVB-H traffic traces. The results show that simple Markov models are appropriate to capture the observed loss pattern and to discuss how such models can be used to examine the quality degradations caused by packet losses.

Networked fault detection with random communication delays and packet losses

This article deals with the fault detection problem for a class of discrete-time networked systems with multiple state delays and unknown input. Two kinds of incomplete measurements, namely measurements with random communication delays and measurements with stochastic packet losses, are simultaneously considered. By properly augmenting the states of the original system and the fault detection filter, the fault detection filter design problem can be formulated as an H ∞ filtering problem. Attention is focused on the design of a fault detection filter such that, for all unknown input and incomplete measurements, the error between residual and weighted fault is made as small as possible. A sufficient condition for the existence of the desired fault detection filter is established in terms of a linear matrix inequality. A numerical example is provided to illustrate the effectiveness and applicability of the proposed techniques.

An optimum strategy for dynamic and stochastic packet routing problems by chaotic neurodynamics

The most important issue in real packet routing problem on a computer network is how to alleviate packet congestion, because it often leads to unstable and insecure communication. In order to resol...

An optimum strategy for dynamic and stochastic packet routing problems by chaotic neurodynamics

The most important issue in real packet routing problem on a computer network is how to alleviate packet congestion, because it often leads to unstable and insecure communication. In order to resolve the issue, various methods have already been propo

Feedback Control via AmI-Networks – Managing the Limited Resource Problem by QoS-Adaptive Control (Regelungen über ressourcenbeschränkte AmI-Netzwerke durch Adaption an die Quality of Service)

Ambient Intelligence (AmI) systems are typically based on low-energy and low-performance nodes which are connected by wireless ad-hoc networks. Due to these constraints communication is restricted as well, as can be seen from the quality of service (QoS) parameters. If feedback control is used in AmI systems, two main effects are limiting the control performance and threatening the control stability: the variable network delays and the stochastic packet losses. The paper describes an approach taking into account these crucial parameters at the same time. This problem is solved by adapting the control law to the measured QoS parameters of the ad-hoc network. An example is discussed to show the advantages of the proposed QoS-adaptive control.

Networked Real-Time Control Strategy Dealing With Stochastic Time Delays and Packet Losses

Abstract A novel model-predictive-control strategy with a timeout scheme and p-step-ahead state estimation is presented in this paper to overcome the adverse influences of stochastic time delays and packet losses encountered in network-based distributed real-time control. An open-loop unstable magnetic-levitation (maglev) test bed was constructed and employed for its experimental verification. The compensation algorithms developed in this paper deal with the network-induced stochastic time delays and packet losses in both the forward path and the feedback path simultaneously. With the p-sampling-period delay upper bound, the networked control system (NCS) can also accommodate up to p−1 successive packet losses. Experimental results demonstrate the feasibility and effectiveness of this networked real-time control strategy.

Optimal control of variable rate coding with incomplete observation in integrated voice/data packet networks

This paper investigates the design of dynamic voice coding rate control with doubly stochastic packet arrival processes to reduce traffic congestion in an integrated voice/data packet network. Incomplete observation is assumed. A control maximizes the average coding rate of voice packets subject to an average voice/data packet waiting time constraint on a finite horizon with incomplete observation. The optimal control has a simple structure and is a randomization of two linear feedbacks with input saturation. The general separation principle for the optimal control with incomplete observation, that is, the sufficiency of the posterior distribution for the optimal control, is derived. Since the complexity of the analytical results prevents us from obtaining an explicit control when observation is incomplete, an adaptive suboptimal control is proposed. This is also a random modification of two linear feedbacks with saturation and is easily implementable. The effectiveness of the suboptimal control is verified by simulations.