An (n, d) permutation array (PA) is a subset of S-n with the property that the distance (under some metric) between any two permutations in the array is at least d. They became popular recently for communication over ...
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An (n, d) permutation array (PA) is a subset of S-n with the property that the distance (under some metric) between any two permutations in the array is at least d. They became popular recently for communication over power lines. Motivated by an application to flash memories, in this paper, the metric used is the Chebyshev metric. A number of different constructions are given, as well as bounds on the size of such PA.
Li et al. (Retransmission not equal repeat: simple retransmission permutation can resolve overlapping channel collisions, 2009) introduced a technique for resolving overlapping channel transmissions that used an inter...
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Li et al. (Retransmission not equal repeat: simple retransmission permutation can resolve overlapping channel collisions, 2009) introduced a technique for resolving overlapping channel transmissions that used an interesting new type of combinatorial structure. In connection with this problem, they provided an example of a 4 x 4 array having certain desirable properties. We define a class of combinatorial structures, which we term retransmission permutation arrays, that generalise the example that Li et al. provided. We show that these arrays exist for all possible orders. We also define some extensions having additional properties, for which we provide some partial results.
We give new lower bounds for M(n, d), for various positive integers n and d with n > d, where M(n, d) is the largest number of permutations on n symbols with pairwise Hamming distance at least d. Large sets of perm...
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We give new lower bounds for M(n, d), for various positive integers n and d with n > d, where M(n, d) is the largest number of permutations on n symbols with pairwise Hamming distance at least d. Large sets of permutations on n symbols with pairwiseHamming distance d are needed for constructing error correcting permutation codes, which have been proposed for power-line communications. Our technique, partition and extension, is universally applicable to constructing such sets for all n and all d, d < n. We describe three new techniques, sequential partition and extension, parallel partition and extension, anda modifiedKronecker product operation, which extend the applicability of partition and extension in different ways. We describe how partition and extension gives improved lower bounds for M(n, n - 1) using mutually orthogonal Latin squares (MOLS). We present efficient algorithms for computing new partitions: an iterative greedy algorithm and an algorithm based on integer linear programming. These algorithms yield partitions of positions (or symbols) used as input to our partition and extension techniques. We report many new lower bounds for M(n, d) found using these techniques for n up to 600.
A permutation array A is a set of permutations on a finite set Omega, say of size n. Given distinct permutations pi, sigma is an element of Omega, we let hd(pi, sigma) = vertical bar{x is an element of Omega : pi(x) n...
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A permutation array A is a set of permutations on a finite set Omega, say of size n. Given distinct permutations pi, sigma is an element of Omega, we let hd(pi, sigma) = vertical bar{x is an element of Omega : pi(x) not equal sigma(x)}vertical bar, called the Hamming distance between pi and sigma. Nowlet hd(A) = min{hd(pi, sigma) : pi, sigma is an element of A}. For positive integers n and d with d <= n we let M(n, d) be the maximum number of permutations in any array A satisfying hd(A) >= d. There is an extensive literature on the function M(n, d), motivated in part by suggested applications to error correcting codes for message transmission over power lines. A basic fact is that if a permutation group G is sharply k-transitive on a set of size n >= k, then M(n, n - k + 1) = vertical bar G vertical bar. Motivated by this we consider the permutation groups AGL(1, q) and PGL(2, q) acting sharply 2-transitively on GF(q) and sharply 3-transitively on GF(q) boolean OR {infinity} respectively. Applying a contraction operation to these groups, we obtain the following new lower bounds for prime powers q satisfying q equivalent to 1 (mod 3). 1. M(q - 1, q - 3) >= (q(2) - 1)/ 2 for q odd, q >= 7, 2. M(q - 1, q - 3) >= (q - 1)(q + 2)/3 for q even, q >= 8, 3. M(q, q - 3) >= Kq(2)log(q) for some constant K > 0 if q is odd. These results resolve a case left open in a previous paper (Bereg et al. in Des Codes Cryptogr 86(5):1095-1111, 2018), where itwas shownthat M(q-1, q-3) >= q(2)-q and M(q, q-3) >= q(3) - q for all prime powers q such that q not equivalent to 1 (mod 3). We also obtain lower bounds for M(n, d) for a finite number of exceptional pairs n, d, by applying this contraction operation to the sharply 4 and 5-transitive Mathieu groups.
A permutation array (PA) A is a set of permutations on Z(n) = (0, 1, ... , n - 1}, for some n. A PA A has pairwise Hamming distance at least d, if for every pair of permutations sigma and tau in A, there are at least ...
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A permutation array (PA) A is a set of permutations on Z(n) = (0, 1, ... , n - 1}, for some n. A PA A has pairwise Hamming distance at least d, if for every pair of permutations sigma and tau in A, there are at least d integers i in Z(n) such that sigma(i) not equal tau(i). Let M(n, d) denote the maximum number of permutations in any PA with pairwise Hamming distance at least d. Recently considerable effort has been devoted to improving known lower bounds for M(n, d) for all n > d > 3. We give a partition and extension operation that enables the production of a new PA A' for M (n + 1, d) from an existing PA A for M (n, d - 1). In particular, this operation allows for improvements for PA's for M(q + 1, q) for powers of prime numbers q, as well as for many other choices of n and d, where n is not a power of a prime. Finally, for prime numbers p, the partition and extension technique provides an asymptotically better lower bound for M(p + 1, p) than that given by current knowledge about mutually orthogonal Latin squares. We prove a new asymptotic lower bound for the set of primes p, namely, M(p + 1, p) >= p(1.5) / 2 - O(p).
permutation arrays under the Chebyshev metric have been considered for error correction in noisy channels. Let P(n, d) denote the maximum size of any array of permutations on n symbols with pairwise Chebyshev distance...
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permutation arrays under the Chebyshev metric have been considered for error correction in noisy channels. Let P(n, d) denote the maximum size of any array of permutations on n symbols with pairwise Chebyshev distance d. We give new techniques and improved upper and lower bounds on P(n, d), including a precise formula for P(n, 2).
In this paper we study the special class of equidistant constant composition codes of type CCC( n, d, mu(m)) ( where n = m mu), which correspond to equidistant frequency permutation arrays;we also consider related cod...
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In this paper we study the special class of equidistant constant composition codes of type CCC( n, d, mu(m)) ( where n = m mu), which correspond to equidistant frequency permutation arrays;we also consider related codes with composition "close to" mu(m). We establish various properties of these objects and give constructions for optimal families of codes.
We consider permutation rational functions (PRFs), V(x)/U(x), where both V(x) and U(x) are polynomials over a finite field F-q. permutation rational functions have been the subject of several recent papers. Let M (n, ...
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We consider permutation rational functions (PRFs), V(x)/U(x), where both V(x) and U(x) are polynomials over a finite field F-q. permutation rational functions have been the subject of several recent papers. Let M (n, D) denote the maximum number of permutations on n symbols with pairwise Hamming distance D. Computing lower bounds for M(n, D) is the subject of current research with applications in error correcting codes. Using PRFs of specified degrees d we obtain improved lower bounds for M (q, q - k) for prime powers q and k is an element of {5, 6, 7, 8, 9}, and for M (q + 1, q - k) for prime powers q and k is an element of {4, 5, 6, 7, 8, 9}.
Let M(n, d) be the maximum size of a permutation array on n symbols with pairwise Hamming distance at least d. We use various combinatorial, algebraic, and computational methods to improve lower bounds for M(n, d). We...
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Let M(n, d) be the maximum size of a permutation array on n symbols with pairwise Hamming distance at least d. We use various combinatorial, algebraic, and computational methods to improve lower bounds for M(n, d). We compute the Hamming distances of affine semilinear groups and projective semilinear groups, and unions of cosets of AGL(1, q) and PGL(2, q) with Frobenius maps to obtain new, improved lower bounds for M(n, d). We give new randomized algorithms. We give better lower bounds for M(n, d) also using new theorems concerning the contraction operation. For example, we prove a quadratic lower bound for for all such that is a prime power.
An (n,d)-permutation code is a subset C of Sym(n) such that the Hamming distance d(H) between any two distinct elements of C is at least equal to d. In this paper, we use the characterization of the isometry group of ...
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An (n,d)-permutation code is a subset C of Sym(n) such that the Hamming distance d(H) between any two distinct elements of C is at least equal to d. In this paper, we use the characterization of the isometry group of the metric space (Sym(n), d(H)) in order to develop generating algorithms with rejection of isomorphic objects. To classify the (n,d)-permutation codes up to isometry, we construct invariants and study their efficiency. We give the numbers of nonisometric (4,3)- and (5,4)- permutation codes. Maximal and balanced (n,d)-permutation codes are enumerated in a constructive way.
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