655 research outputs found
New Optimal Binary Sequences with Period via Interleaving Ding-Helleseth-Lam Sequences
Binary sequences with optimal autocorrelation play important roles in radar,
communication, and cryptography. Finding new binary sequences with optimal
autocorrelation has been an interesting research topic in sequence design.
Ding-Helleseth-Lam sequences are such a class of binary sequences of period
, where is an odd prime with . The objective of this
letter is to present a construction of binary sequences of period via
interleaving four suitable Ding-Helleseth-Lam sequences. This construction
generates new binary sequences with optimal autocorrelation which can not be
produced by earlier ones
Autocorrelation of a class of quaternary sequences of period
Sequences with good randomness properties are quite important for stream
ciphers. In this paper, a new class of quaternary sequences is constructed by
using generalized cyclotomic classes of . The
exact values of autocorrelation of these sequences are determined based on
cyclotomic numbers of order with respect to . Results show that the
presented sequences have the autocorrelations with at most values
Low Correlation Sequences over the QAM Constellation
This paper presents the first concerted look at low correlation sequence
families over QAM constellations of size M^2=4^m and their potential
applicability as spreading sequences in a CDMA setting.
Five constructions are presented, and it is shown how such sequence families
have the ability to transport a larger amount of data as well as enable
variable-rate signalling on the reverse link.
Canonical family CQ has period N, normalized maximum-correlation parameter
theta_max bounded above by A sqrt(N), where 'A' ranges from 1.8 in the 16-QAM
case to 3.0 for large M. In a CDMA setting, each user is enabled to transfer 2m
bits of data per period of the spreading sequence which can be increased to 3m
bits of data by halving the size of the sequence family. The technique used to
construct CQ is easily extended to produce larger sequence families and an
example is provided.
Selected family SQ has a lower value of theta_max but permits only (m+1)-bit
data modulation. The interleaved 16-QAM sequence family IQ has theta_max <=
sqrt(2) sqrt(N) and supports 3-bit data modulation.
The remaining two families are over a quadrature-PAM (Q-PAM) subset of size
2M of the M^2-QAM constellation. Family P has a lower value of theta_max in
comparison with Family SQ, while still permitting (m+1)-bit data modulation.
Interleaved family IP, over the 8-ary Q-PAM constellation, permits 3-bit data
modulation and interestingly, achieves the Welch lower bound on theta_max.Comment: 21 pages, 3 figures. To appear in IEEE Transactions on Information
Theory in February 200
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