15 research outputs found
Random Routing and Concentration in Quantum Switching Networks
Flexible distribution of data in the form of quantum bits or qubits
among spatially separated entities is an essential component of
envisioned scalable quantum computing architectures. Accordingly, we
consider the problem of dynamically permuting groups of quantum bits,
i.e., qubit packets, using networks of reconfigurable quantum
switches.
We demonstrate and then explore the equivalence between the quantum
process of creation of packet superpositions and the process of
randomly routing packets in the corresponding classical network. In
particular, we consider an n × n Baseline network for which we
explicitly relate the pairwise input-output routing probabilities in
the classical random routing scenario to the probability amplitudes of
the individual packet patterns superposed in the quantum output state.
We then analyze the effect of using quantum random routing on a
classically non-blocking configuration like the Benes network. We
prove that for an n × n quantum Benes network, any input
packet assignment with no output contention is probabilistically
self-routable. In particular, we prove that with random routing on the
first (log n-1) stages and bit controlled self-routing on the last
log n stages of a quantum Benes network, the output packet
pattern corresponding to routing with no blocking is always present in
the output quantum state with a non-zero probability. We give a lower
bound on the probability of observing such patterns on measurement at
the output and identify a class of 2n-1 permutation patterns for
which this bound is equal to 1, i.e., for all the permutation
patterns in this class the following is true: in every pattern
in the quantum output assignment all the valid input packets are
present at their correct output addresses.
In the second part of this thesis we give the complete design of
quantum sparse crossbar concentrators. Sparse crossbar concentrators
are rectangular grids of simple 2 × 2 switches or crosspoints,
with the switches arranged such that any k inputs can be connected
to some k outputs. We give the design of the quantum crosspoints for
such concentrators and devise a self-routing method to concentrate
quantum packets. Our main result is a rigorous proof that certain
crossbar structures, namely, the fat-slim and banded quantum crossbars
allow, without blocking, the realization of all concentration patterns
with self-routing.
In the last part we consider the scenario in which quantum packets are
queued at the inputs to an n × n quantum non-blocking
switch. We assume that each packet is a superposition of m classical
packets. Under the assumption of uniform traffic, i.e., any output is
equally likely to be accessed by a packet at an input we find the
minimum value of m such that the output quantum state contains at
least one packet pattern in which no two packets contend for the same
output. Our calculations show that for m=9 the probability of a
non-contending output pattern occurring in the quantum output is
greater than 0.99 for all n up to 64
New approaches to the analysis of connecting and sorting networks
10255788Originally issued as an Sc. D. thesis, Dept. of Electrical Engineering, Massachusetts Institute of Technology, 1971.Includes bibliographical references (p. 53-54).Michael J. Marcus
Size bounds and parallel algorithms for networks
SIGLEAvailable from British Library Document Supply Centre- DSC:D34009/81 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Customer premise service study for 30/20 GHz satellite system
Satellite systems in which the space segment operates in the 30/20 GHz frequency band are defined and compared as to their potential for providing various types of communications services to customer premises and the economic and technical feasibility of doing so. Technical tasks performed include: market postulation, definition of the ground segment, definition of the space segment, definition of the integrated satellite system, service costs for satellite systems, sensitivity analysis, and critical technology. Based on an analysis of market data, a sufficiently large market for services is projected so as to make the system economically viable. A large market, and hence a high capacity satellite system, is found to be necessary to minimize service costs, i.e., economy of scale is found to hold. The wide bandwidth expected to be available in the 30/20 GHz band, along with frequency reuse which further increases the effective system bandwidth, makes possible the high capacity system. Extensive ground networking is required in most systems to both connect users into the system and to interconnect Earth stations to provide spatial diversity. Earth station spatial diversity is found to be a cost effective means of compensating the large fading encountered in the 30/20 GHz operating band
Application of advanced on-board processing concepts to future satellite communications systems
An initial definition of on-board processing requirements for an advanced satellite communications system to service domestic markets in the 1990's is presented. An exemplar system architecture with both RF on-board switching and demodulation/remodulation baseband processing was used to identify important issues related to system implementation, cost, and technology development
Novel techniques in large scaleable ATM switches
Bibliography: p. 172-178.This dissertation explores the research area of large scale ATM switches. The requirements for an ATM switch are determined by overviewing the ATM network architecture. These requirements lead to the discussion of an abstract ATM switch which illustrates the components of an ATM switch that automatically scale with increasing switch size (the Input Modules and Output Modules) and those that do not (the Connection Admission Control and Switch Management systems as well as the Cell Switch Fabric). An architecture is suggested which may result in a scalable Switch Management and Connection Admission Control function. However, the main thrust of the dissertation is confined to the cell switch fabric. The fundamental mathematical limits of ATM switches and buffer placement is presented next emphasising the desirability of output buffering. This is followed by an overview of the possible routing strategies in a multi-stage interconnection network. A variety of space division switches are then considered which leads to a discussion of the hypercube fabric, (a novel switching technique). The hypercube fabric achieves good performance with an O(N.log₂N)²) scaling. The output module, resequencing, cell scheduling and output buffering technique is presented leading to a complete description of the proposed ATM switch. Various traffic models are used to quantify the switch's performance. These include a simple exponential inter-arrival time model, a locality of reference model and a self-similar, bursty, multiplexed Variable Bit Rate (VBR) model. FIFO queueing is simple to implement in an ATNI switch, however, more responsive queueing strategies can result in an improved performance. An associative memory is presented which allows the separate queues in the ATM switch to be effectively logically combined into a single FIFO queue. The associative memory is described in detail and its feasibility is shown by laying out the Integrated Circuit masks and performing an analogue simulation of the IC's performance is SPICE3. Although optimisations were required to the original design, the feasibility of the approach is shown with a 15Ƞs write time and a 160Ƞs read time for a 32 row, 8 priority bit, 10 routing bit version of the memory. This is achieved with 2µm technology, more advanced technologies may result in even better performance. The various traffic models and switch models are simulated in a number of runs. This shows the performance of the hypercube which outperforms a Clos network of equivalent technology and approaches the performance of an ideal reference fabric. The associative memory leverages a significant performance advantage in the hypercube network and a modest advantage in the Clos network. The performance of the switches is shown to degrade with increasing traffic density, increasing locality of reference, increasing variance in the cell rate and increasing burst length. Interestingly, the fabrics show no real degradation in response to increasing self similarity in the fabric. Lastly, the appendices present suggestions on how redundancy, reliability and multicasting can be achieved in the hypercube fabric. An overview of integrated circuits is provided. A brief description of commercial ATM switching products is given. Lastly, a road map to the simulation code is provided in the form of descriptions of the functionality found in all of the files within the source tree. This is intended to provide the starting ground for anyone wishing to modify or extend the simulation system developed for this thesis
Research and Technology 1990
A brief but comprehensive review is given of the technical accomplishments of the NASA Lewis Research Center during the past year. Topics covered include instrumentation and controls technology; internal fluid dynamics; aerospace materials, structures, propulsion, and electronics; space flight systems; cryogenic fluids; Space Station Freedom systems engineering, photovoltaic power module, electrical systems, and operations; and engineering and computational support
NASA Tech Briefs, Spring 1985
Topic include: NASA TU Services; New Product Ideas; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Life Sciences; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences