This paper analyzes a finite buffer M/G/1 queue with two classes of customers who are served by a combination of head-of-the-line priority and push-out schemes. This combination gives each class of customers two different types of priorities with respect to both delay and loss. There are two models considered. The first one is that one class of customers has a higher priority over the other class with respect to both delay and loss; the second one is that one class has a higher priority with respect to loss and the other has high-priority with respect to delay. For both of these models, the joint probability distribution of the number of customers of both classes in the buffer is derived by a supplementary variable method. Using this probability distribution, we can easily calculate the loss probabilities of both classes, the mean waiting time for high-priority customers with respect to loss and the upper bound for mean waiting time for low-priority customers with respect to loss. Numerical examples demonstrate an effect of the combination of different types of priorities.

In this paper, we propose two mechanisms for the priority added automatic call gapping method under the fairness scheme and analyze the effect of those mechanisms. Both mechanisms provide good overload controllability and work well on the priority calls. We also define a measure of priority achievement. Both mechanisms show good performance on the pass probability and priority achievement.

In this paper, we derive the mean message waiting times in a local area network that uses the Demand-Priority Access Method. We model the system as a two-priority M/G/1 queue with switchover time between service periods. This switchover time accounts for the polling and port selection performed by the repeater after each message transmission. The service discipline is non-preemptive and the length of the switchover time is dependent upon the priority class of the preceding message served as well as that of the message to be served next. The dependency in the switchover times is motivated by the polling and port selection operation of the protocol and it makes the analysis much more involved. In order to avoid the complexities of an exact analysis, we make some independence assumptions and thus obtain an approximate solution. Laplace-Stieltjes transforms of the stationary probability distribution functions for the waiting time of high- and normal-priority messages are derived, and subsequently, the expressions for the mean message waiting times. Numerical results computed using these expressions are verified using simulations which model the actual protocol. These numerical results which are shown to be accurate can be easily computed with widely available mathematical software.

The present study investigated the human ability to selectively process pictures and words in free recall. We explored whether successful bias towards a subset of priority items occurs at the expense of the remaining items-i.e., whether successful priority item bias necessitates the dumping of information related to non-priority items. It has been shown that an increase in the percentage of correct recalls to items given priority in the pre-test instructions induces a decrease in the percentage of correct recalls for non-priority items. Even in a free recall experimental paradigm, the information dumping phenomenon was observed. However, there were no effects of stimulus presentation time and stimulus modality (picture vs. word) on the percentage of correct recalls detected.

In this paper, we propose a handoff scheme with two-level priority for the reservation of handoff request calls in mobile cellular radio systems. We assume two types of mobile subscribers with different distributions of moving speed, that is, users with low average moving speed (e.g., pedestrians) and high average moving speed (e.g., people in moving cars). A fixed number of channels in each cell are reserved exclusively for handoff request calls. Out of these number of channels, some are reserved exclusively for the high speed handoff request calls. The remaining channels are shared by both the originating and handoff request calls. In the proposed scheme, both kinds of handoff request calls make their own queues. The system is modeled by a three-dimensional Markov chain. We apply the Successive Over-Relaxation (SOR) method to obtain the equilibrium state probabilities. Blocking probabilities of calls, forced termination probabilities and average queue length of handoff calls of each type are evaluated. We can make the forced termination probabilities of handoff request calls smaller than the blocking probability of originating calls. Moreover, we can make the forced termination probability of high speed handoff request calls smaller than that of the low speed ones. Necessary queue size for the two kinds of handoff request calls are also estimated.

We propose two multipriority reservation protocols for wavelength division multiplexing (WDM) networks. The network architecture is a single-hop with control channel-based passive star topology. Each station is equipped with two pairs of laser and filter. One pair of laser and filter is always tuned to wavelength λ0 for control and the other pair of laser and filter can be tuned to any of data wavelengths, λ1, λ2, ..., λN. According to the access methods of the control channel, one protocol is called slotted ALOHA-based protocol and the other protocol is called TDM-based protocol. The two protocols have the following properties. First, each of them has its own priority control scheme which easily accommodates multipriority traffics. Second, they can be employed in the network with limited channels, i.e. the number of stations in the system is not restricted by the number of data channels. Third, they are conflict-free protocols. By using a reservation scheme and a distributed arbitration algorithm, channel collision and destination conflict can be avoided. For the performance point of view, the TDM-based protocol gives an optimal solution for the priority control. However it is less scalable than the slotted ALOHA-based protocol. The slotted ALOHA-based protocol also performs good priority control even though it is not an optimal solution. We analyze their performances using a discrete time Markov model and verify the results by simulation.

Conventional learning algorithms are considered to be a sort of estimation of the true recognition function from sample patterns. Such an estimation requires a good assumption on a prior distribution underlying behind learning data. On the other hand the human being sounds to be able to acquire a better result from an extremely small number of samples. This forces us to think that the human being might use a suitable prior (called presupposition here), which is an essential key to make recognition machines highly flexible. In the present paper we propose a framework for guessing the learner's presupposition used in his learning process based on his learning result. First it is pointed out that such a guess requires to assume what kind of estimation method the learner uses and that the problem of guessing the presupposition becomes in general ill-defined. With these in mind, the framework is given under the assumption that the learner utilizes the Bayesian estimation method, and a method how to determine the presupposition is demonstrated under two examples of constraints to both of a family of presuppositions and a set of recognition functions. Finally a simple example of learning with a presupposition is demonstrated to show that the guessed presupposition guarantees a better fitting to the samples and prevents a learning machine from falling into over learning.

In this paper, we present an exact analysis and an efficient matrix-analytic procedure to numerically evaluate the performance of cellular mobile networks with hand-off. In high-capacity micro-cell cellular radio communication networks, a cell boundary crossed by moving users can generate many hand-off attempts. This paper considers such a priority scheme that some channels and buffers are reserved for hand-off calls to reduce the forced termination of calls in progress. Performance characteristics we obtained include blocking probability, channel utilization, average queue length and average waiting time for hand-off calls. Using the matrix-analytic solution for the stationary state probability distribution, we also derive the probability distribution of the waiting time of a hand-off call. Numerical results show how priority can be provided to hand-off calls according to the number of reserved channels and buffer size. They also clarify the effect of the hand-off priority scheme on the standard deviation of waiting time of a hand-off call.

This paper proposed a method of slot allocation in a multislot TDMA system when multiple service priorities are supported. The algorithm is tested both in Variable Rate Reservation Access (VRRA) and Advanced TDMA protocols. We exploit the multislot reservation capability to achieve the delay requirements of each priority level. The channel allocation algorithm assumed that all data terminals are capable of multislot reservation. In this case the delay variance can be controlled based on the packet length information and the accumulated delay of each data user. The performance of the system is evaluated using the cumulative delay distribution and mean overall delays for the different user types.

This paper presents some tighter bounds on universal noiseless coding, in particular, the lowerbound tighter than Davisson et al.'s for finite sequence and the upperbound for some typical universal data compression. We find that Davisson et al.'s bound satisfies some optimization in the case of using the Jeffreys prior and also that the derived upperbound in this paper is within O(1/n) from the Clarke and Barron asymptotics in the case of some restricted typical universal data compression defined in the paper.

The selection of an appropriate key search algorithm for a specific application field is an important issue in application systems development. This is because data retrieval is the most time-consuming part of many application programs. An automatic selection method for key search algorithms is presented in this paper. The methodology has been implemented in a system called KESE2 (KEy-SEarch ALgorithm SElection). Key search algorithms are selected according to the user's requirements through interaction with KESE2 which bases its inferences on an evaluation table. This evaluation table contains values rating the performance of each key search algorithm for the different searching properties, or characteristics. The selection algorithm presented is based on step by step reduction of unsuitable key search algorithms and searching properties. The paper also proposes assistance facilities that consist of both a support function and a program synthesis function. Experimental results show that the appropriate key search algorithms are effectively selected, and that the necessary number of questions asked, to select the appropriate algorithm, is reduced to less than half of the total number of possible questions. The support function is useful for the user during the selection process and the program synthesis function fully translates a selected key search algorithm into high level language in an average of less than 1 hour.

A queueing model suitable for multimedia packets with Poisson and batch Poisson arrivals is studied. In the queueing model, priority is given to the packets with batch Poisson arrival, and the packets with Poisson arrival, accumulated in a buffer, are routed by utilizing intervals of the packets with priority. The queueing performance of the proposed model is evaluated by the mean system delay. We also consider the effect of batch size and the ratio of the traffic with batch Poisson arrival and the one with Poisson arrival on the mean system delay. It is found that the proposed queueing model is useful to reduce the mean system delay of the packets with Poisson arrival, while maintaining the means system delay of the packets with batch Poisson arrival.

The double-stage threshold-type foreground-background congestion control for the common-store queueing system with multiple nonpreemptive priority classes is proposed to improve the transient performance, where the numbers of accepted priority packets in both foreground and background stores are controlled under the double-stage threshold-type scheduling. In the double-stage threshold-type congestion control, the background store is used for any priority packets, and some parts of the background store are reserved for lower-priority packets to accommodate more lower-priority packets in the background store, whereas some parts of the foreground store are reserved for higher-priority packets to avoid the priority deadlock. First, we derive the general set of coupled differential equations describing the system-state, and the expressions for mean system occupancy, throughput and loss probability. Second, the transient behavior of system performance is evaluated from the time-dependent state probabilities by using the Runge-Kutta procedure. It is shown that when the particular traffic class becomes overloaded, high throughputs and low loss probabilities of other priority classes can be obtained.

This paper presents an alternative traffic model for an ATM multiplexer providing video, voice, image, and data services. The traffic model classifies the input traffic into two types: real-time and non-real-time. The input process for realtime traffic is periodic and correlated, while that for non-realtime traffic is batch Poisson and independent. This multiplexer is assumed to be a priority queueing system with synchronous servers operating on time-frame basis and with separate finite buffers for each type of traffic. State probabilities and performance measures are successfully obtained using a Markov analysis technique and an application of the residue theorem in complex variable. The results can be applied in the design of an ATM multiplexer.

The connection admission control is one of preventive traffic control in ATM networks. The one objective of connection admission control is to keep the network load moderate so as to achieve a performance objective associated with quality of services (QOS). Because the cell loss rate is more sensitive to offered load than the average queuing delay in ATM networks, QOS requirement associated with cell loss rate is considered. The connection admission control acts as one of the major roles in traffic control. The job of connection admission control is to make an acceptance decision for connection set-up request to control the network load. This paper proposed and evaluated a connection admission control method. The proposed method is suitable for real time operation even in large diversity of connection types, because the amount of calculation for connection admission control is reduced remarkably compared to conventional algorithms. Moreover, the amount of calculation for the algorithm does not increase even when the number of connection types increases. The proposed method uses probability function for the number of cells transferred from multiplexed connections and uses recursive equations in estimating cell loss rate.

By a measure we mean a function µ from {0, 1}* (the set of all binary sequences) to real numbers such that µ(x)0 and µ({0, 1}*). A malign measure is a measure such that if an input x in {0, 1}n (the set of all binary sequences of length n) is selected with the probability µ(x)/µ ({0, 1}n) then the worst-case computation time tWOA (n) and the average-case computation time tav,µA(n) of an algorithm A for inputs of length n are functions of n of the same order for any algorithm A. Li and Vitányi found that measures that are known as a priori measures are malign. We prove that a priori" -ness and malignness are different in one strong sense.

Broadband ISDN, using asynchronous transfer mode, are expected to carry traffic of different classes, each with its own set of traffic characteristics and performance requirements. To achieve the quality of service in ATM networks, a suitable buffer management scheme is needed. In this paper, we propose a buffer management scheme using a priority service discipline to improve the delay time of delay-sensitive class and the packet loss ratio of loss-sensitive class. The proposed priority scheme requires simple buffer management logic and minor processing overhead. We also analyze the delay time and the packet loss ratio for each class of service. The results indicate that the required buffer size of the proposed priority scheme is reduced and the delay time of each class of service is controlled by a parameter. If the control parameter is appropriately chosen, the quality of service of each class is improved.

This paper investigates a two-class priority queue with decrementing service of a parameter (k1=, k2=k,1k) which operates as follows: Starting once a class-1 message service, a single server serves all messages in queue 1 until it becomes empty. After service completion in queue 1, the server switches over to queue 2 and continues serving messages in queue 2 until either queue 2 becomes empty, or the number of messages decreases to k less than that found upon the server's arrival at queue 2, whichever occurs first. It is assumed that arrival streams are Poissonian, message service times are generally distributed, and switch-over times are zero. We derive queue-length generating functions and LSTs of message waiting time distributions.

The subject of the paper is to propose two approximation algorithms FM_SPLA, FM_DPLA for priority-list scheduling in timed Petri nets. Their capability is compared with that of existing algorithms SPLA, DPLA through experimental results, where SPLA and DPLA have previously been proposed by the authors.

Asynchronous Transfer Mode (ATM) switching system is expected to handle various kinds of media (such as motion video, computer data, and voice), and traffic control becomes essential to satisfy various quality requirements and to maintain efficient utilization of system resources. Priority control is one possible solution for realizing such a traffic control. In priority control, cells from various media are scheduled for transmission with different priority according to the quality class to which they belong. In this paper, we propose a new priority control method in which cells from various media are stored in their own buffer, we call it class buffer, and priority assignments are carried out based on the number of cells in each class buffer and the delay time. The number of cells in each class buffer is maintained using the counter circuit. The delay time of the cell is checked by the timer circuit for cell group, each of which consists of cells arriving during a periodical time interval. For simulation model, we consider three kinds of traffic; video, computer data, and voice, of which quality requirements are quite different. We show performance results in terms of the cell delay and the cell loss probability in our method through simulation.