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The classical way of extending an [ n , k , d ] linear code C is to add an overall parity-check coordinate to each codeword of the linear code C. This extended code, denoted by C ‾ (− 1) and called the standardly extended code of C , is a linear code with parameters [ n + 1 , k , d ¯ ] , where d ¯ = d or d ¯ = d + 1. This is one of the two extending techniques for linear codes in the literature. The standardly extended codes of some families of binary linear codes have been studied to some extent. However, not much is known about the standardly extended codes of nonbinary codes. For example, the minimum distances of the standardly extended codes of the nonbinary Hamming codes remain open for over 70 years. The first objective of this paper is to introduce the nonstandardly extended codes of a linear code and develop some general theory for this type of extended linear codes. The second objective is to study this type of extended codes of a number of families of linear codes, including cyclic codes and nonbinary Hamming codes. Four families of distance-optimal or dimension-optimal linear codes are obtained with this extending technique. The parameters of certain extended codes of many families of linear codes are settled in this paper. [ABSTRACT FROM AUTHOR]

The punctured binary Reed–Muller code is cyclic and was generalised into the punctured generalised Reed–Muller code over GF ( q ) in the literature. The first objective of this paper is to present another generalisation of the punctured binary Reed–Muller code and the binary Reed–Muller code, and analyse these codes. The second objective of this paper is to consider two applications of the new codes in constructing LCD codes and 2-designs. The major motivation of constructing and studying the new codes and their extended codes is the construction of 2-designs, which is an interesting topic in combinatorics. It is remarkable that the family of newly generalised cyclic codes contains a subclass of optimal ternary codes with parameters [ 3 m − 1 , 3 m − 1 − 2 m , 4 ] for all m ≥ 2 . Their extended codes have parameters [ 3 m , 3 m − 1 − 2 m , 5 ] for all m ≥ 2 , and are also optimal. [ABSTRACT FROM AUTHOR]

A pair (n , q) with q a prime power and n a positive integer for which gcd ⁡ (n , q) = 1 is non-standard if one of the following properties holds, which we will show to be equivalent. − The group U n , q of n -th roots-of-unity in the splitting field F q m of x n − 1 over F q is fixed set-wise by an F q -linear map on F q m that is not of the form x ⟶ α x q j . − There is a non-cyclic linear recurring sequence s of period n (so with s not of the form s i = α ξ i for i ≥ 0) with associated characteristic polynomial being irreducible over F q , such that U n , q = { s 0 , ... , s n − 1 }. In that case, the group U n , q is called non-standard by Brison and Nogueira, who studied this phenomenon in a sequence of papers. − A q -ary irreducible cyclic code of length n has "extra" permutation automorphisms (some well-known examples are the (duals of the) Golay codes and binary simplex codes for n ≥ 7). We will refer to such codes as non-standard irreducible cyclic codes or NSIC-codes. We first investigate non-standard linear recurring sequence subgroups and establish the equivalence between the first and second of the above properties. Then we investigate permutation automorphisms of general (repeated-root) cyclic codes and irreducible cyclic codes and establish the equivalence between the first and third of these properties. We also introduce a notion of non-standardness for general cyclic codes, and relate it to our earlier definition of NSIC-codes. This paper is the first part of an expanded version of the arXiv paper [28]. [ABSTRACT FROM AUTHOR]

Let R be a finite commutative chain ring with unique maximal ideal 〈 γ 〉 , and let n be a positive integer relatively prime to the characteristic of R / 〈 γ 〉 . In this paper, some new necessary and sufficient conditions for the existence of nontrivial self-dual cyclic codes of length n over R are provided. Explicit enumeration formulas for self-dual cyclic codes over R are studied. In particular, several main results of [21] are special cases of the present paper. [ABSTRACT FROM AUTHOR]

Let p and q be odd primes and q be a cubic primitive modulo p u for some positive integer u. In this paper, we prove that the solutions of some Diophantine equations provide the weight enumerators of some cubic primitive irreducible cyclic codes of prime length. Bounds on the minimum distances of these codes are also given. [ABSTRACT FROM AUTHOR]

For a simple-root λ -constacyclic code C over F q , let 〈 ρ 〉 and 〈 ρ , M 〉 be the subgroups of the automorphism group of C generated by the cyclic shift ρ , and by the cyclic shift ρ and the scalar multiplication group M , respectively. Let N G (C ⁎) be the number of orbits of a subgroup G of the automorphism group of C acting on C ⁎ = C ﹨ { 0 }. In this paper, we establish explicit formulas for N 〈 ρ 〉 (C ⁎) and N 〈 ρ , M 〉 (C ⁎). Consequently, we derive a upper bound on the number of non-zero weights of C. We present some irreducible and reducible λ -constacyclic codes, which show that the upper bound is tight. A sufficient condition to guarantee N 〈 ρ 〉 (C ⁎) = N 〈 ρ , M 〉 (C ⁎) is presented. [ABSTRACT FROM AUTHOR]

Cyclic codes are an interesting type of linear codes and have wide applications in communication and storage systems due to their efficient encoding and decoding algorithms. Inspired by the recent work on binary cyclic codes published in Tang and Ding (2022) [26] and the works in Liu et al. (2023) [15] and Liu et al. (2023) [16] , the objectives of this paper are the construction and analysis of four infinite families of ternary cyclic codes with length n = 3 m − 1 for odd m and dimension k ∈ { n / 2 , (n + 2) / 2 } whose minimum distances have a square-root-like lower bound. Their duals have parameters [ n , k ⊥ , d ⊥ ] , where k ⊥ ∈ { n / 2 , (n − 2) / 2 } and d ⊥ also has a square-root-like lower bound. These families of codes and their duals contain distance-optimal cyclic codes. [ABSTRACT FROM AUTHOR]

Cyclic codes are a subclass of linear codes and have applications in consumer electronics, data storage systems and communication systems as they have efficient encoding and decoding algorithms. In this paper, we settle an open problem about a class of optimal ternary cyclic codes which was proposed by Ding and Helleseth [5]. Let C (1 , e) be a cyclic code of length 3 m − 1 over GF (3) with two nonzeros α and α e , where m and e are given integers, and α is a generator of GF (3 m) ⁎. It is shown that C (1 , e) is optimal with parameters [ 3 m − 1 , 3 m − 1 − 2 m , 4 ] if one of the following conditions is met. 1) m ≡ 0 (mod 4) , m ≥ 4 , and e = 3 m 2 + 5. 2) m ≡ 2 (mod 4) , m ≥ 6 , and e = 3 m + 2 2 + 5. [ABSTRACT FROM AUTHOR]

Cyclic codes are an interesting type of linear codes and have wide applications in communication and storage systems due to their efficient encoding and decoding algorithms. Inspired by the recent work on binary cyclic codes published in Tang and Ding (2022) [14] , the objectives of this paper are the construction and analyses of five infinite families of binary cyclic codes with parameters [ n , k ] and (n − 6) / 3 ≤ k ≤ 2 (n + 6) / 3. Three of the five families of binary cyclic codes and their duals have a very good lower bound on their minimum distances and contain distance-optimal codes. The other two families of binary cyclic codes are composed of binary duadic codes with a square-root-like lower bound on their minimum distances. As a by-product, two infinite families of self-dual binary codes with a square-root-like lower bound on their minimum distances are obtained. [ABSTRACT FROM AUTHOR]

Abstract Under research for nearly sixty years, Bose–Chaudhuri–Hocquenghem (BCH) codes have played increasingly important roles in many applications such as communication, data storage and information security. However, the dimension and minimum distance of BCH codes have been seldom solved by now because of their intractable characteristics. The objective of this paper is to study the dimensions of some binary BCH codes with length n = 2 m + 1. Many new techniques are employed to investigate the coset leaders modulo n. For m = 2 t + 1 , 4 t + 2 , 8 t + 4 and m ≥ 10 , the first five largest coset leaders modulo n are determined, and the dimensions of some BCH codes of length n with designed distance δ > 2 ⌈ m 2 ⌉ are presented. These new skills and results may be helpful to study other types of cyclic codes over finite fields. [ABSTRACT FROM AUTHOR]

Abstract Due to their wide applications in consumer electronics, data storage systems and communication systems, cyclic codes have been an interesting research topic in coding theory. The objective of this paper is to present a family of optimal ternary cyclic codes from the Niho-type exponent. Specifically, for an odd integer m and a positive integer r with 4 r ≡ 1 (mod m) , a family of cyclic codes C (u , v) of length 3 m − 1 over GF (3) with two nonzeros β u and β v is studied, where β is a generator of GF (3 m) ⁎ , u = (3 m + 1) / 2 and v = 3 r + 2 is the ternary Niho-type exponent. The parameters of this family of cyclic codes are determined. It turns out that C (u , v) is optimal with respect to the Sphere Packing bound if 9 ∤ m and otherwise almost optimal. Thanks to a recent proof of the Dobbertin–Helleseth–Kumar–Martin conjecture by Katz and Langevin, the dual of this family of cyclic codes is shown to have at most five nonzero weights. [ABSTRACT FROM AUTHOR]

Linear codes with a few weights have many nice applications including combinatorial design, distributed storage system, secret sharing schemes and so on. In this paper, we construct two families of linear codes with a few weights based on special polynomials over finite fields. The first family of linear codes are extended primitive cyclic codes which are affine-invariant. The second family of linear codes are reducible cyclic codes. The parameters of these codes and their duals are determined. As the first application, we prove that these two families of linear codes hold t -designs, where t = 2 , 3. As the second application, the minimum localities of the codes are also determined and optimal locally recoverable codes are derived. [ABSTRACT FROM AUTHOR]

Binary odd-like duadic codes have parameters [ n , (n + 1) / 2 ] , where n is odd. It is well known that the minimum odd weight of odd-like duadic codes has the lower bound n. The binary quadratic-residue codes and the punctured binary Reed-Muller codes of certain order are two families of binary cyclic codes with parameters [ n , (n + 1) / 2 , d ≥ n ]. It is very hard to construct an infinite family of binary cyclic codes with length n and dimension near (n + 1) / 2 whose minimum distances have a square-root bound. Recently, Tang and Ding constructed an infinite family of binary cyclic codes with parameters [ 2 m − 1 , 2 m − 1 , d ] whose minimum distances have lower bounds close to the square-root bound. The objective of this paper is to construct several infinite families of binary cyclic codes of length 2 m − 1 and dimension near 2 m − 1 whose minimum distance d much exceeds the square-root bound. For m ≥ 9 being odd, an infinite family of binary cyclic codes with parameters [ 2 m , 2 m − 1 , d ≥ 3 ⋅ 2 m − 1 2 − 1 ] is presented. For m ≥ 8 being even, an infinite family of binary cyclic codes with parameters [ 2 m , 2 m − 1 − 1 + m 2 , d ≥ 3 ⋅ 2 m − 2 2 + 1 ] is presented. [ABSTRACT FROM AUTHOR]

Linear codes and t -designs are interactive with each other. It is well known that some t -designs have been constructed by using certain linear codes in recent years. However, only a small number of infinite families of the extended codes of linear codes holding an infinite family of t -designs with t ≥ 3 are reported in the literature. In this paper, we study the extended codes of the augmented codes of a class of binary cyclic codes with three zeros and their dual codes, and show that those codes hold 3-designs. Furthermore, we obtain some shortened codes from the studied cyclic codes and explicitly determine their parameters. Some of those shortened codes are optimal or almost optimal. [ABSTRACT FROM AUTHOR]

Let α be a primitive element of a finite field F r , where r = q m 1 m 2 and gcd ⁡ ( m 1 , m 2 ) = d , so α 1 = α r − 1 q m 1 − 1 and α 2 = α r − 1 q m 2 − 1 are primitive elements of F q m 1 and F q m 2 , respectively. Let e be a positive integer such that gcd ⁡ ( e , q m 2 − 1 q d − 1 ) = 1 , F q m 2 = F q ( α 2 e ) , and α 1 and α 2 e are not conjugates over F q . We define a cyclic code C = { c ( a , b ) : a ∈ F q m 1 , b ∈ F q m 2 } , c ( a , b ) = ( T 1 ( a α 1 i ) + T 2 ( b α 2 e i ) ) i = 0 n − 1 , where T i denotes the trace function from F q m i to F q for i = 1 , 2 . In this paper, we use Gauss sums to investigate the weight distribution of C , which generalizes the results of C. Li and Q. Yue in [13,14] . Furthermore, we explicitly determine the weight distribution of C if d = 1 , 2 . Moreover, we prove it is optimal three-weight achieving the Griesmer bound if d = 1 and gcd ⁡ ( m 2 − e m 1 , q − 1 ) = 1 . [ABSTRACT FROM AUTHOR]

Cyclic codes have attracted a lot of research interest for decades as they have efficient encoding and decoding algorithms. In this paper, for an odd prime p , we investigate two classes of p -ary cyclic codes for special cases and determine their weight distributions explicitly. The results show that both codes have at most five nonzero weights. [ABSTRACT FROM AUTHOR]

In this paper, a class of binary cyclic codes with three generalized Niho-type nonzeros is introduced. Based on some techniques in solving certain equations over finite fields, the proposed cyclic codes are shown to have six nonzero weights and the weight distribution is also completely determined. [ABSTRACT FROM AUTHOR]

Let GF (p 2 m) be the finite field with p 2 m elements, where p is a prime number and m is a positive integer. Let F (x) = x 2 p m − 1 be a power function over GF (p 2 m). When p m ≢ 2 (mod 3) , the Walsh transform of F was first studied in [15] , and the value distribution of its four-valued Walsh transform was determined in [6]. In this paper, we prove that the Walsh transform of F is also four-valued when p m ≡ 2 (mod 3). Moreover, the value distribution of the Walsh transform of F is determined. This result is a complement of the works shown in [15] and [6]. Furthermore, a class of four-weight p -ary cyclic codes are obtained. [ABSTRACT FROM AUTHOR]

The (Euclidean) hull of a linear code is defined to be the intersection of the code and its Euclidean dual. It is clear that the hulls are self-orthogonal codes, which are an important type of linear codes due to their wide applications in communication and cryptography. Let C be an [ n , k ] cyclic code over F q , where F q is the finite field of order q. In this paper, we will employ the defining set of the code C to present a general characterization when its hull has dimension k − ℓ. Furthermore, we mainly focus on the primitive q -ary BCH codes C (q , n , δ , b) when b = 0 and b = 1 based on the general characterization. Especially for binary and ternary cases, we will present several sufficient and necessary conditions that the hulls of the codes C (q , n , δ , b) have dimensions k − 2 and k − 3 by giving lower and upper bounds on their designed distances, which extends the results of [17]. In addition, several classes of binary and ternary self-orthogonal codes are proposed via the hulls of BCH codes and their parameters are investigated in some special cases. [ABSTRACT FROM AUTHOR]

Cyclic codes are a subclass of linear codes and have applications in consumer electronics, data storage systems, and communication systems as they have efficient encoding and decoding algorithms. Let m = 2 ℓ + 1 for an integer ℓ ≥ 1 and π be a generator of GF ( 3 m ) ⁎ . In this paper, a class of cyclic codes C ( u , v ) over GF ( 3 ) with two nonzeros π u and π v is studied, where u = ( 3 m + 1 ) / 2 , and v = 2 ⋅ 3 ℓ + 1 is the ternary Welch-type exponent. Based on a result on the non-existence of solutions to certain equation over GF ( 3 m ) , the cyclic code C ( u , v ) is shown to have minimal distance four, which is the best minimal distance for any linear code over GF ( 3 ) with length 3 m − 1 and dimension 3 m − 1 − 2 m according to the Sphere Packing bound. The duals of this class of cyclic codes are also studied. [ABSTRACT FROM AUTHOR]

For two positive integers m and k , let C e be a class of cyclic code of length 2 m − 1 over F 2 with three nonzeros γ − 1 , γ − ( 2 k + 1 ) and γ − ( 2 e k + 1 ) for e = 2 or 3, where γ is a primitive element of F 2 m . When m gcd ⁡ ( m , k ) is odd, Kasami in 1971 determined the weight distributions of cyclic codes C 2 and C 3 , which is the same as that of the dual of the triple error-correcting BCH code. This paper obtains the weight distributions of C 2 and C 3 for the case of m gcd ⁡ ( m , k ) being even. [ABSTRACT FROM AUTHOR]

Let p be an odd prime, and m , k be positive integers with m ≥ 3 k . Let C 1 and C 2 be cyclic codes over F p with parity-check polynomials h 2 ( x ) h 3 ( x ) and h 1 ( x ) h 2 ( x ) h 3 ( x ) , respectively, where h 1 ( x ) , h 2 ( x ) and h 3 ( x ) are the minimal polynomials of γ − 1 , γ − ( p k + 1 ) and γ − ( p 3 k + 1 ) over F p , respectively, for a primitive element γ of F p m . Recently, Zeng et al. (2010) obtained the weight distribution of C 2 for m gcd ( m , k ) being odd. In this paper, we determine the weight distribution of C 1 , and the weight distribution of C 2 for the case that m gcd ( m , k ) is even. [ABSTRACT FROM AUTHOR]

MDS codes and almost MDS (AMDS) codes are special classes of linear codes, and have important applications in communications, data storage, combinatorial theory, and secrete sharing. The objective of this paper is to present a class of AMDS codes from some BCH codes and determine their parameters. It turns out the proposed AMDS codes are distance-optimal and dimension-optimal locally repairable codes. The parameters of the duals of this class of AMDS codes are also discussed. [ABSTRACT FROM AUTHOR]

Let C (u , v) denote the ternary cyclic code with two nonzeros α u and α v , where α is a generator of F 3 m ⁎ and 0 ≤ u , v ≤ 3 m − 2. In this paper, we present a sufficient condition such that C (u , v) is an optimal ternary cyclic code. Based on this condition, we get several classes of optimal ternary cyclic codes by choosing the proper u and v. Moreover, we show that C ( 3 m + 1 2 , 3 m − 1 2 + v) and C (1 , v) have the same optimality. [ABSTRACT FROM AUTHOR]

In this paper, we give the dimension and the minimum distance of two subclasses of narrow-sense primitive BCH codes over F q with designed distance δ = a q m − 1 − 1 (resp. δ = a q m − 1 q − 1) for all 1 ≤ a ≤ q − 1 , where q is a prime power and m > 1 is a positive integer. As a consequence, we obtain an affirmative answer to two conjectures proposed by C. Ding in 2015. Furthermore, using the previous part, we extend some results of Yue and Hu [16] , and we give the dimension and, in some cases, the Bose distance for a large designed distance in the range a q m − 1 q − 1 , a q m − 1 q − 1 + T for 0 ≤ a ≤ q − 2 , where T = q m + 1 2 − 1 if m is odd, and T = 2 q m 2 − 1 if m is even. [ABSTRACT FROM AUTHOR]

Let F 2 m be a finite field of cardinality 2 m , R = F 2 m + u F 2 m (u 2 = 0) and s , n be positive integers such that n is odd. In this paper, we give an explicit representation for every self-dual cyclic code over the finite chain ring R of length 2 s n and provide a calculation method to obtain all distinct codes. Moreover, we obtain a clear formula to count the number of all these self-dual cyclic codes. As an application, self-dual and 2-quasi-cyclic codes over F 2 m of length 2 s + 1 n can be obtained from self-dual cyclic code over R of length 2 s n and by a Gray map preserving orthogonality and distances from R onto F 2 m 2. [ABSTRACT FROM AUTHOR]

Cyclic codes are an interesting type of linear codes and have wide applications in communication and storage systems due to their efficient encoding and decoding algorithms. The objective of this paper is to investigate the parameters of some q -ary cyclic codes of length n = q 2 m − 1 q + 1. The dimensions of these codes are settled and the lower bounds on their minimum distances are presented by employing the Hartmann-Tzeng bound or BCH bound. Moreover, when q = 2 , 3 , we give the largest coset leaders δ 1 modulo n and investigate the parameters of the BCH codes C (q , n , δ 1 , 1). [ABSTRACT FROM AUTHOR]