Constructions of Optimal and Near-Optimal Quasi-Complementary Sequence Sets from an Almost Difference Set

Compared with the perfect complementary sequence sets, quasi-complementary sequence sets (QCSSs) can support more users to work in multicarrier CDMA communications. A near-optimal periodic QCSS is constructed in this paper by using an optimal quaternary sequence set and an almost difference set. With the change of the values of parameters in the almost difference set, the near-optimal QCSS can become asymptotically optimal and the number of users supported by the subcarrier channels in CDMA system has an exponential growth

Linear complexity and trace representation of quaternary sequences over Z4\mathbb{Z}_4 based on generalized cyclotomic classes modulo pqpq

We define a family of quaternary sequences over the residue class ring modulo $4$ of length $pq$, a product of two distinct odd primes, using the generalized cyclotomic classes modulo $pq$ and calculate the discrete Fourier transform (DFT) of the sequences. The DFT helps us to determine the exact values of linear complexity and the trace representation of the sequences.Comment: 16 page

New Quadriphase Sequences families with Larger Linear Span and Size

In this paper, new families of quadriphase sequences with larger linear span and size have been proposed and studied. In particular, a new family of quadriphase sequences of period $2^n-1$ for a positive integer $n=em$ with an even positive factor $m$ is presented, the cross-correlation function among these sequences has been explicitly calculated. Another new family of quadriphase sequences of period $2(2^n-1)$ for a positive integer $n=em$ with an even positive factor $m$ is also presented, a detailed analysis of the cross-correlation function of proposed sequences has also been presented

Linear complexity of quaternary sequences over Z_4 derived from generalized cyclotomic classes modulo 2p

We determine the exact values of the linear complexity of 2p-periodic quaternary sequences over Z_4 (the residue class ring modulo 4) defined from the generalized cyclotomic classes modulo 2p in terms of the theory of of Galois rings of characteristic 4, where p is an odd prime. Compared to the case of quaternary sequences over the finite field of order 4, it is more dificult and complicated to consider the roots of polynomials in Z_4[X] due to the zero divisors in Z_4 and hence brings some interesting twists. We answer an open problem proposed by Kim, Hong and Song

Cyclic bent functions and their applications in codes, codebooks, designs, MUBs and sequences

Let $m$ be an even positive integer. A Boolean bent function $f$ on \GF{m-1} \times \GF {} is called a \emph{cyclic bent function} if for any a\neq b\in \GF {m-1} and \epsilon \in \GF{}, $f(ax_1,x_2)+f(bx_1,x_2+\epsilon)$ is always bent, where x_1\in \GF {m-1}, x_2 \in \GF {}. Cyclic bent functions look extremely rare. This paper focuses on cyclic bent functions on \GF {m-1} \times \GF {} and their applications. The first objective of this paper is to construct a new class of cyclic bent functions, which includes all known constructions of cyclic bent functions as special cases. The second objective is to use cyclic bent functions to construct good mutually unbiased bases (MUBs), codebooks and sequence families. The third objective is to study cyclic semi-bent functions and their applications. The fourth objective is to present a family of binary codes containing the Kerdock code as a special case, and describe their support designs. The results of this paper show that cyclic bent functions and cyclic semi-bent functions have nice applications in several fields such as symmetric cryptography, quantum physics, compressed sensing and CDMA communication