503 research outputs found
Crosstalk-free Conjugate Networks for Optical Multicast Switching
High-speed photonic switching networks can switch optical signals at the rate
of several terabits per second. However, they suffer from an intrinsic
crosstalk problem when two optical signals cross at the same switch element. To
avoid crosstalk, active connections must be node-disjoint in the switching
network. In this paper, we propose a sequence of decomposition and merge
operations, called conjugate transformation, performed on each switch element
to tackle this problem. The network resulting from this transformation is
called conjugate network. By using the numbering-schemes of networks, we prove
that if the route assignments in the original network are link-disjoint, their
corresponding ones in the conjugate network would be node-disjoint. Thus,
traditional nonblocking switching networks can be transformed into
crosstalk-free optical switches in a routine manner. Furthermore, we show that
crosstalk-free multicast switches can also be obtained from existing
nonblocking multicast switches via the same conjugate transformation.Comment: 10 page
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
Upper Bound Analysis and Routing in Optical Benes Networks
Multistage Interconnection Networks (MIN) are popular in switching and communication applications. It has been used in telecommunication and parallel computing systems for many years. The new challenge facing optical MIN is crosstalk, which is caused by coupling two signals within a switching element. Crosstalk is not too big an issue in the Electrical Domain, but due to the stringent Bit Error Rate (BER) constraint, it is a big major concern in the Optical Domain. In this research dissertation, we will study the blocking probability in the optical network and we will study the deterministic conditions for strictly non-blocking Vertical Stacked Optical Benes Networks (VSOBN) with and without worst-case scenarios. We will establish the upper bound on blocking probability of Vertical Stacked Optical Benes Networks with respect to the number of planes used when the non-blocking requirement is not met. We will then study routing in WDM Benes networks and propose a new routing algorithm so that the number of wavelengths can be reduced. Since routing in WDM optical network is an NP-hard problem, many heuristic algorithms are designed by many researchers to perform this routing. We will also develop a genetic algorithm, simulated annealing algorithm and ant colony technique and apply these AI algorithms to route the connections in WDM Benes network
A system for routing arbitrary directed graphs on SIMD architectures
There are many problems which can be described in terms of directed graphs that contain a large number of vertices where simple computations occur using data from connecting vertices. A method is given for parallelizing such problems on an SIMD machine model that is bit-serial and uses only nearest neighbor connections for communication. Each vertex of the graph will be assigned to a processor in the machine. Algorithms are given that will be used to implement movement of data along the arcs of the graph. This architecture and algorithms define a system that is relatively simple to build and can do graph processing. All arcs can be transversed in parallel in time O(T), where T is empirically proportional to the diameter of the interconnection network times the average degree of the graph. Modifying or adding a new arc takes the same time as parallel traversal
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