445 research outputs found
Binary Sequences With Low Aperiodic Autocorrelation for Synchronization Purposes
Cataloged from PDF version of article.An evolutionary algorithm is used to find three sets
of binary sequences of length 49–100 suitable for the synchronization
of digital communication systems. Optimization of the sets are
done by taking into consideration the type of preamble used in
data frames and the phase-lock mechanism of the communication
system. The preamble is assumed to be either a pseudonoise (PN)
sequence or a sequence of 1’s. There may or may not be phase ambiguity
in detection. With this categorization, the first set of binary
sequences is optimized with respect to aperiodic autocorrelation
which corresponds to the random (PN) preamble without phase
ambiguity case. The second and third sets are optimized with respect
to a modified aperiodic autocorrelation for different figures
of merit corresponding to the predetermined preamble (sequence
of 1’s) with and without phase ambiguity cases
Optimization Methods for Designing Sequences with Low Autocorrelation Sidelobes
Unimodular sequences with low autocorrelations are desired in many
applications, especially in the area of radar and code-division multiple access
(CDMA). In this paper, we propose a new algorithm to design unimodular
sequences with low integrated sidelobe level (ISL), which is a widely used
measure of the goodness of a sequence's correlation property. The algorithm
falls into the general framework of majorization-minimization (MM) algorithms
and thus shares the monotonic property of such algorithms. In addition, the
algorithm can be implemented via fast Fourier transform (FFT) operations and
thus is computationally efficient. Furthermore, after some modifications the
algorithm can be adapted to incorporate spectral constraints, which makes the
design more flexible. Numerical experiments show that the proposed algorithms
outperform existing algorithms in terms of both the quality of designed
sequences and the computational complexity
Binary matrices of optimal autocorrelations as alignment marks
We define a new class of binary matrices by maximizing the peak-sidelobe
distances in the aperiodic autocorrelations. These matrices can be used as
robust position marks for in-plane spatial alignment. The optimal square
matrices of dimensions up to 7 by 7 and optimal diagonally-symmetric matrices
of 8 by 8 and 9 by 9 were found by exhaustive searches.Comment: 8 pages, 6 figures and 1 tabl
Large Zero Autocorrelation Zone of Golay Sequences and -QAM Golay Complementary Sequences
Sequences with good correlation properties have been widely adopted in modern
communications, radar and sonar applications. In this paper, we present our new
findings on some constructions of single -ary Golay sequence and -QAM
Golay complementary sequence with a large zero autocorrelation zone, where
is an arbitrary even integer and is an arbitrary integer.
Those new results on Golay sequences and QAM Golay complementary sequences can
be explored during synchronization and detection at the receiver end and thus
improve the performance of the communication system
System performance criteria in CDMA networks using gold codes
First, we have presented the autocorrelation and crosscorrelation properties for periodic and aperiodic binary sequences. The generation of binary sequences using shift registers with feedback was reviewed. We have also included correlation properties for the Gold codes.
Next, we discussed Gold code generation for the balanced and unbalanced Gold codes.
Thirdly, we investigated the number of simultaneous users in a CDMA system using Gold codes for the worst case and the average case of mutual interference.
Finally, we simulated the probability of interference exceeding a threshold value, and the average crosscorrelation value caused by interference in a CDMA network which is using a Gold code. We compared probability and average crosscorrelation values simulated with theoretical bounds calculated. Here the simulation programs are done in C computer language
Parsing a sequence of qubits
We develop a theoretical framework for frame synchronization, also known as
block synchronization, in the quantum domain which makes it possible to attach
classical and quantum metadata to quantum information over a noisy channel even
when the information source and sink are frame-wise asynchronous. This
eliminates the need of frame synchronization at the hardware level and allows
for parsing qubit sequences during quantum information processing. Our
framework exploits binary constant-weight codes that are self-synchronizing.
Possible applications may include asynchronous quantum communication such as a
self-synchronizing quantum network where one can hop into the channel at any
time, catch the next coming quantum information with a label indicating the
sender, and reply by routing her quantum information with control qubits for
quantum switches all without assuming prior frame synchronization between
users.Comment: 11 pages, 2 figures, 1 table. Final accepted version for publication
in the IEEE Transactions on Information Theor
Development of a set of optimum synchronization codes for a unique decoder mechanization
Synchronization requirements are specified for and a unique decoder mechanization is associated with a particular communication system. Optimum synchronization codes, defined as codes which are the least susceptible to false synchronization indications, are sought. Existing sets of optimum codes are investigated for applicability. This Thesis shows how these sets were developed from selected criteria and demonstrates why their theoretical nature produces unsatisfactory results in the present application wherein all parameters are known. A computer program was written to examine code pattern performance in the specified decoder under actual operating conditions. From an analysis of the results, a recommended set of optimum synchronization codes was developed --Abstract, page ii
Wireless digital point to multipoint link utilizing wideband CDMA
One of the proposed techniques for multiple access communications for the third generation is code division multiple access (CDMA). This has been shown to be a viable alternative to both TDMA and FDMA. While there does not appear to be a single multiple accessing technique that is superior to others in all situations, there are characteristics of CDMA that give it a distinct advantage over the other multiple access techniques. In CDMA each user is provided with an unique, orthogonal code. If these K codes are orthogonal and uncorrelated with each other, than K independent users can transmit at the same time and in the same radio bandwidth. The receivers decorrelate the information and regenerate the original transmitted signal. It must be noted that the term "Wideband CDMA" is used comparatively to the only existing commercial CDMA system, IS-95 which uses a spectral bandwidth of only 1.2288 MHz. This thesis examines and evaluates a good set of orthonormal codes (orthogonal and normalized to have equal power) and their application to providing accessing for a point to multipoint (PMP) stationary system. The correlation properties, design and constellation properties of these codes are investigated. The system model is then simulated using Systemview and then evaluated in terms of it's bit error rate, user capacity and Erlang with addition of users to the system
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