A multi-level dynamic guard channels (MLDGC) scheme to efficiently provide priority access for handoff calls over new calls in cellular systems is proposed. The switch between levels is controlled by the number of dropped calls. Each additional level has an increasing number of guard channels as triggered by the number of dropped calls. An analytical formulation of the steady state probabilitie...

This paper proposes a prioritized real-time admission control algorithm to support soft handoff calls with QoS assurance in both uplink and downlink signal to interference ratio (SIR) requirement. Admission control is formulated as a performance optimization model, in which the objective is to minimize handoff forced termination probability. The algorithm is based upon dynamic reserved channels...

In this paper, we develop a performance model of a cell in a wireless communication network where the effect of handoff arrival and the use of guard channels is inlcuded. Fast recursive formulas for the loss probabilities of new calls and handoff calls are developed. Monotonicity properties of the loss probabilities are proven. Algorithms to determine the optimal number of guard channels and th...

Introduction In plants as in animals, K+ channel activity is the major determinant of cell membrane conductance [1,2]. Kt channels are therefore involved in central physiological processes such as setting the resting cell membrane potential, transducing signals and shaping action-potential waveforms. In addition, in plant cells, K t channel activity is thought to be involved in long-term fluxes...

Electrical properties of the plasma membrane of guard cell protoplasts isolated from stomates of Vicia faba leaves were studied by application of the whole-cell configuration of the patch-clamp technique. The two types of K+ currents that have recently been identified in guard cells may allow efflux of K+ during stomatal closing, and uptake of K+ during stomatal opening (Schroeder et al., 1987)...

Many signal-transduction processes in higher plant cells have been suggested to be triggered by signal-induced opening of Ca2+ channels in the plasma membrane. However, direct evidence for activation of plasma-membrane Ca2+ channels by physiological signals in higher plants has not yet been obtained. In this context, several lines of evidence suggest that Ca2+ flux into the cytosol of guard cel...

The phytohormone abscisic acid (ABA) induces stomatal closure in response to drought stress, leading to reduction of transpirational water loss. A thiol tripeptide glutathione (GSH) is an important regulator of cellular redox homeostasis in plants. Although it has been shown that cellular redox state of guard cells controls ABA-mediated stomatal closure, roles of GSH in guard cell ABA signaling...

Cytosolic Ca(2+) in guard cells plays an important role in stomatal movement responses to environmental stimuli. These cytosolic Ca(2+) increases result from Ca(2+) influx through Ca(2+)-permeable channels in the plasma membrane and Ca(2+) release from intracellular organelles in guard cells. However, the genes encoding defined plasma membrane Ca(2+)-permeable channel activity remain unknown in...

Abscisic acid (ABA) regulates vital physiological responses, and a number of events in the ABA signaling cascade remain to be identified. To allow quantitative analysis of genetic signaling mutants, patch-clamp experiments were developed and performed with the previously inaccessible Arabidopsis guard cells from the wild type and ABA-insensitive (abi) mutants. Slow anion channels have been prop...