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This paper describes a novel approach to the problems of state estimation in linear, discrete-time systems which switch randomly between two sets of parameters, indicated by a random switching variable. A non-linear approximate model for the switching variable is developed and used for the joint estimation of the state vector and the switching variable via a single extended Kalman filter. The performance of the filter is compared with that of other suboptimal filters known to date. The proposed approach provides comparable accuracy, and saves computational effort in systems of order three or more. In large systems the computational effort is halved.

Interrupted service, which may occur in fading radio channels, in low-priority channels which can be preempted or in systems with failures may make severe demands on buffer size if overflow is to be avoided. This paper analyzes a buffer with a Markov-interrupted timeslotted server, generalizing earlier work on independent random interruptions. An equivalent service distribution is defined for use in an approximate M/G/1 model, which in turn gives buffer probabilities and overflow probabilities. For very small overflow probabilities, the necessary buffer size is found from a further analytic approximation to the tail of the buffer size distribution. The accuracy of the two approximations together is good, shown by an example of a fading radio channel.

The execution workload of a protocol often limits the data communications throughput in local area and wide area networks. The handling of buffers is one of the implementation factors that affects the execution workload of a protocol implementation: if possible, copying of user data should be avoided. Two buffer cut-through strategies for avoiding copying higher-level data are described, with some of the mechanisms necessary to implement them. The resulting execution workload in a transport protocol (similar to the ISO class 4 protocol) is studied in detail. Individual protocol actions are modeled for a wide range of data-stream parameters. The improvement when copying is avoided is shown to be relatively insensitive to the parameter values and to be as high as 80% when the checksum is not computed at the transport level. >

A second-order nonlinear model of steel refining in an electric are furnace is formulated and optimized. Iterative computation using steepest descent shows the existence of an optimal singular arc, which is then found more precisely by directly applying necessary conditions for such an arc. When a soft (penalty-function) constraint on state is replaced by a hard constraint, a state-constrained arc is found which corresponds directly to the singular arc. The dependence of the singular arc on problem parameters is explored.

An algorithm is described by which TDM slots in many links of a network can be optimally allocated between voice and data. It is an adaptation of a convex-programming method due to Fox, by which a pool of resources is allocated to minimize a convex separable criterion function such as blocking probability for voice subject to a single convex separable constraint such as specified maximum mean delay to data. In our case the single pool of resources is the total of the available slots. The necessary adaptation of Fox's algorithm is described for the minimum blocking problem, and for minimum data delay subject to a blocking constraint.