Wireless ad hoc network consists of inexpensive nodes that form a mobile communication network. Due to limitations of the transmission range, the nodes rely on each other to forward packets such that messages can be delivered across the network. The selection of the path along which a packet is forwarded from the source node to the destination node is done by the routing algorithm. Most commonly used routing algorithms, though effective for non-real time applications, cannot handle real-time applications that require strict delay bounds on packet delivery. In this thesis, we propose a routing protocol that ensures timely delivery of real time data packets. The idea is to route packets in such a way that irrespective of factors like traffic load and node density, the average delay remains within acceptable bounds. This is done by carefully accessing the resources available to a route before a session is admitted along that route. Each link in the route is checked for sufficient bandwidth not only for the new session to be admitted but also for the sessions that are already using that link. The new session is admitted only if the admission does not violate the delay bounds of any on-going sessions. This method of route selection coupled with per-hop link reservations allows us to provide bounds on the delay performance. Extensive simulation experiments have been conducted that demonstrate the performance of the proposed routing protocol in terms of throughput, session blocking probability, packet drop probability, average path length, and delay.

The issue of write-read contention is one of the most prevalent problems when deploying real-time data warehouses. With increasing load, updates are increasingly delayed and previously fast queries tend to be slowed down considerably. However, depending on the user requirements, we can improve the response time or the data quality by scheduling the queries and updates appropriately. If both criteria are to be considered simultaneously, we are faced with a so-called multi-objective optimization problem. We transformed this problem into a knapsack problem with additional inequalities and solved it efficiently. Based on our solution, we developed a scheduling approach that provides the optimal schedule with regard to the user requirements at any given point in time. We evaluated our scheduling in an extensive experimental study, where we compared our approach with the respective optimal schedule policies of each single optimization objective.

The design of an I/O Controller capable of processing data in real time in a tactical training simulator is presented. The controller consists of two microprocessor systems that communicate with peripherals by means of programmed I/O, and with the host computer by Direct Memory Access (DMA) and a serial RS232 link. This thesis addresses both the hardware and software aspects of the controller design.

Multitasking systems are becoming increasingly used for implementing real-time systems since they are well-suited to asynchronous, often overlapping, events. With the availability of kernels such as Hunter and Ready's VRTX Operating System components, multitasking becomes a good alternative to other implementations of real-time systems, such as interrupt-driven and polling systems. We developed a software design method and wrote a sample real-time system with many of the characteristics of typical real-time systems. This multitasking system uses a standard printer port to output bits which indicate the various activities of the tasks in the system. It also allows the user to interactively change the priorities of the tasks and to modify parameters which determine how long and how often the tasks execute. Through the use of the printer port connected to a logic analyzer and the ability to change various parameters in the system dynamically, the interaction between tasks was studied for different situations. The observed interaction between tasks was consistent with intuition. We observed task pre-emption, tasks waiting for results from other tasks and the system overhead required for context switching. When the timing restrictions were increased, we observed that data is lost during intertask communication and that higher priority tasks are the only tasks which run. This ability to observe the interaction between tasks has removed much of the mystery surrounding multitasking. / M.S.

The advent of synchronized phasor measurements allows the problem of real time prediction of instability and control to be considered. The use of direct methods for these on-line applications is assessed. The classical representation of a power system allows the use of two reference frames: Center of angle and one machine as reference. Formulae allowing transition between the two reference frames are derived. It is shown that the transient energy in both formulations is the same, and that line resistances do not dampen system oscillations. Examples illustrating the mathematical characterization of the region of attraction, exit point, closest u.e.p. and controlling u.e.p. methods are presented. Half-dimensional systems (reduced-order systems) are discussed. The general expression for the gradient system which accounts for transfer conductances is derived without making use of the infinite bus assumption. Examples illustrating the following items are presented: a) Effect of the linear ray approximation on the potential energy (inability to accurately locate the u.e.p.’s); b) Comparison of Kakimoto’s and Athay’s approach for PEBS crossing detection; c) BCU method and; d) One·parameter transversality condition. It is illustrated that if the assumption of the one-parameter transversality condition is not satisfied, the PEBS and BCU methods may give incorrect results for multi-swing stability. A procedure to determine if the u.e.p. found by the BCU method lies on the stability boundary of the original system is given. This procedure improves the BCU method for off~line applications when there is time for a hybrid approach (direct and conventional), but it does not improve it for on-line applications due to the following: a) It is time consuming and b) If it finds that the u.e.p. does not belong to the stability boundary it provides no information concerning the stability/instability of the system. / Ph. D. / incomplete_metadata

Demand for Data Transfer between computers has increased ever since the introduction of Personal Computers (PC). Data Communicating on the Personal Computer is much more productive as it is an intelligent terminal that can connect to various hosts on the same I/O hardware circuit as well as execute processes on its own as an isolated system. Yet, the PC on its own is useless for data communication. It requires a hardware interface circuit and software for controlling the handshaking signals and setting up communication parameters. Often the data is distorted due to noise in the line. Such transmission errors are imbedded in the data and require careful filtering. The thesis deals with the development of a Data Acquisition system that collects real time load and weather data and stores them as historical database for use in a load forecast algorithm in a load management system. A filtering technique has been developed here that checks for transmission errors in the raw data. The microcomputers used in this development are the IBM PC/XT and the AT&T 3B2 supermicro computer. / Master of Science

Serial or parallel data links have been the primary tools of data transfer across physical layer boundaries for point-to-point communication systems. However there exists a tradeoff between these two kinds of data transfer mechanisms based on their cost-effectiveness and complexity. A recent technological advancement has altered this trade-off considerations. A new chip-set from Advanced Micro Devices offers a high performance integrated alternative to traditional serial/parallel data transfer techniques. The Transparent Asynchronous Transmitter Receiver Interface chipset offers a new means to establish a transparent high speed serial link between two high performance parallel buses. The current TAXlchip set has a maximum effective data rate throughput of 140Mbps which is ten times faster than the RS-422 drivers and receivers. The TAXIchip set can be used in conjunction with the optical components and optical fiber to form a simple fiber optic communication link. The inherent advantages of optical communications can be combined with the versatility of the TAXIchip set to establish TAXI links using optical fiber to cover distances up to several kilometers. This thesis will systematically develop on the TAXI communication system Focus of the effort will be on understanding the functionality of the building blocks of the TAXIchip set and the encoding and decoding schemes of the chip set. On obtaining a complete understanding of the communication system fundamentals the communication system will be interfaced to the optical media with a specific reference to the development of the Optical Slip Ring. / Master of Science

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