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Congestion control in multi-source connection-oriented networks with aperiodic feedback

Ignaciuk P., Bartoszewicz A.

Systems Science

2008

Vol. 34, no 1

59-66

In this paper, the congestion control problem in a mutli-source connection-oriented network is addressed. The network considered employs control units, generated by each source once every M data packets, to deliver feedback information used to regulate the transfer speed of the sources. Since the sources adjust the transmission rate only upon the control unit arrival, the interval between successive rate modifications is input dependent and varies with time. A new, nonlinear strategy effectively combining the Smith principle with the proportional controller with saturation is proposed. Conditions for no data loss and full bottleneck link bandwidth utilization are presented and strictly proved with explicit consideration of the aperiodic feedback information availability. Moreover, since the controller saturation limits are fully adjustable, the algorithm performance may be easily tuned according to the existing system resources. Special attention is given to the analysis of the algorithm robustness with respect to imprecise delay time estimation, and it is shown that all of the favorable properties of the proposed scheme are preserved, even though the propagation delays are estimated by the controller with decreased accuracy.

Optimal flow control strategies for a single virtual circuit in a connection-oriented communication network

Ignaciuk P., Bartoszewicz A.

Systems Science

2007

Vol. 33, no 4

93-101

In this paper, the congestion control problem in a single virtual circuit of a connection-oriented network is addressed. The network is modeled as a discrete time, n-th order system. On the basis of the state space description of the plant a feedback control law is derived by minimizing linear quadratic cost functional. Two controllers are proposed. The first one is obtained when the whole state vector is considered in the optimization procedure, while in the latter case the emphasis is placed on the output variable, with its influenceon the cost functional moderated by a weighting coefficient. Closed loop system stability is demonstrated, and conditions for no data loss and full bottleneck link bandwidth utilization in the network are presented, and strictly proved. Since the rates generated by the controller are always nonnegative and bounded, the proposed scheme can be implemented in real systems.

Congestion control in multi-source connection-oriented networks with rate dependent sampling period

Ignaciuk P., Bartoszewicz A.

Systems Science

2006

Vol. 32, no 3

45-53

Congestion control in multi-source connection-oriented networks with rate dependent sampling period Keywords: congestion control, connection-oriented communication networks, variable sampling period In this paper, flow control in a generic multi-source connection-oriented network is considered. A new, nonlinear controller based on the Smith principle is proposed. In the system under examination, the feedback information is received by each source once every M data unit sent by this source Round Trip Time (RTT) earlier. Since the rate is modified only when this information becomes available, the transfer speed changes at irregularly spaced time instants. A thorough mathematical description of the network model with variable sampling period is given. Subsequently, conditions for data loss elimination and full bottleneck link bandwidth utilization are formulated and strictly proved. Finally, the system robustness with respect to the imprecise RTT delay estimation is discussed and modified conditions, which allow favourable properties of the principal control scheme to be preserved, are presented. Since the rates generates by the controller are always nonnegative and bounded, the proposed strategy can be directly applied in real telecommunication systems.