We analyze an efficient medium access control (MAC) protocol for use in a single cell of a wireless local area network (LAN). A fixed frame structure with two periods is used; one period for making reservations using a slotted Aloha protocol and a second period for data transmission. The MAC protocol operates in a centralized manner in which a single station, the base station, accepts reservations (transmission or data requests) that are made by the remote stations, and then schedules the times in which they will transmit or receive data. We consider two different types of client-server traffic models, an open-loop and a closed-loop model. In the open-loop model, a remote station can generate reservation requests for the base station whether or not it has received a response from the base station. In the closed-loop case, the remote station waits for a response before generating a new request. The performance of the MAC protocol was analyzed exactly for both the open and closed-loop traffic models and for cases in which transmission errors and a mean-value type of radio capture model are included. In addition, different policies were considered for the transmission strategy that is used by the remote stations when they attempt to make reservations. We derive exact results for the mean throughput and waiting times as well as for the queue length distributions. We also derive an approximate Markov chain to treat a case in which a fixed-position capture model is used. Several types of behavior are illustrated through the use of numerical examples.>

An efficient medium access control (MAC) protocol for use in a single cell of a wireless local area network (LAN) is analyzed. A fixed frame structure with two periods is used, one period for making reservations using a slotted Aloha protocol and a second period for data transmission. The MAC protocol operates in a centralized manner in which a single station, the base station, accepts reservations (transmission or data requests) that are made by the remote stations, and then schedules the times in which they will transmit or receive data. Two different types of client-server traffic models, open loop and closed loop, are considered. Exact results are derived for the mean throughput and waiting times as well as for the queue length distributions. Several types of behavior are illustrated by numerical examples.>

The authors present an analysis of a rate-based access control mechanism for high-speed networks that is based on the buffered leaky bucket scheme. The analysis assumes a discrete time environment representative of asynchronous transfer mode (ATM) networks and a batch arrival process that captures cell arrivals generated by segmentation of large user packets or superposition of a number of arrival streams. The solution method is based on matrix analytic techniques, but the particular structure of the system allowed for a number of important improvements. It is shown that the problem can be partitioned and that the matrix G, central to the matrix analytic technique, can be computed using exact recursive procedures instead of the traditional iterative approach. These improvements not only extend the range of systems that can be handled, but also eliminate computational issues such as convergence rate and stopping criterion.>

MetaRing is a Gigabit/second local area network architecture based on a dual(bi-directional) optical fiber ring with spatial reuse mechanism. The paper uses simulation to study the performance of MetaRing in the buffer insertion mode with variable length packets. It shows through various delay-throughput curves the major performance aspects of the MetaRing architecture. The results indicate that the combination of a full-duplex ring spatial reuse, and a simple and reliable fairness mechanism of the MetaRing architecture exhibit an excellent delay-throughput performance.>

The authors propose a computationally simple approximate expression for the equivalent capacity or bandwidth requirement of both individual and multiplexed connections, based on their statistical characteristics and the desired grade-of-service (GOS). The purpose of such an expression is to provide a unified metric to represent the effective bandwidth used by connections and the corresponding effective load of network links. These link metrics can then be used for efficient bandwidth management, routing, and call control procedures aimed at optimizing network usage. While the methodology proposed can provide an exact approach to the computation of the equivalent capacity, the associated complexity makes it infeasible for real-time network traffic control applications. Hence, an approximation is required. The validity of the approximation developed is verified by comparison to both exact computations and simulation results.>

The arbitrage pricing theory (APT) offers an alternative to the traditional asset pricing model in finance. In almost all of the literature, a statistical methodology called factor analysis is used to test or estimate the APT model. The major shortcoming of this procedure is that it identifies neither the number nor the definition of the factors that influence the assets. A unique solution to this problem is offered. It uses a simple back-propagation neural network with a generalized delta rule to learn the interaction of the market factors and securities return. This technique can be used to investigate the effect of several variables on one another simultaneously without being plagued with uncertainty of probability distributions of each variable

A survey of high-performance switch fabric architectures which incorporate fast packet switching as their underlying switching technique to handle various traffic types is presented. A descriptive overview of the major activities in this rapidly evolving field of telecommunications is given. The switch fabrics are classified into the following categories: banyan and buffered banyan-based fabrics, sort-banyan-based fabrics fabrics with disjoint-path topology and output queuing, crossbar-based fabrics, time division fabrics with common packet memory, and fabrics with shared medium.>

An architecture is described for a high-performance switching fabric that can accommodate circuit-switched and packet-switched traffic in a unified manner. The switch fabric is self-routing and uses fixed-length minipackets within the switching fabric for all types of connections. Its architecture provides full input/output connectivity paths with FIFO (first-in-first-out) queueing at each output. The connection paths are non-overlapping, so there is no internal blocking. Because of output queueing, there is also practically no output port blocking. The uniformity in architecture allows the construction of any size fabric from a single basic module which could be realized on a single chip. Larger-size configurations can be realized either as single-stage configuration.>

The authors present and solve a discrete-time G/sup (X)//D/1-S queuing system with a finite queue size and batch arrivals with a general batch size distribution. The motivation for this model arises from performance modeling of a statistical multiplexer with synchronous transmission of fixed-size data units in synchronous time slots. The arrival process to the multiplexer, for example, may originate from a number of independent sources with packets of variable lengths. Hence, a packet arrival corresponds to an arrival of a batch of data units. Different performance measures such as percentage of packet loss and data-unit loss are considered under two different admission policies of packets into the queue.>