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2007, Designs, Codes and Cryptography
We determine the minimum length n q (k, d) for some linear codes with k ≥ 5 and q ≥ 3. We prove that n q (k, d) = g q (k, d) + 1 for q k−1 − 2q k−1 2 −q + 1 ≤ d ≤ q k−1 − 2q k−1 2 when k is odd, for q k−1 − q k 2 − q k 2 −1 − q + 1 ≤ d ≤ q k−1 − q k 2 − q k 2 −1 when k is even, and for 2q k−1 − 2q k−2 − q 2 − q + 1 ≤ d ≤ 2q k−1 − 2q k−2 − q 2 .
IEEE Transactions on Information Theory, 2000
Designs, Codes and Cryptography, 2010
The shortest possible length of a q-ary linear code of covering radius R and codimension r is called the length function and is denoted by q (r, R). Constructions of codes with covering radius 3 are here developed, which improve best known upper bounds on q (r, 3). General constructions are given and upper bounds on q (r, 3) for q = 3, 4, 5, 7 and r ≤ 24 are tabulated.
Advances in Mathematics, 2007
In this paper we prove that a set of points (in a projective space over a finite field of q elements), which is incident with 0 mod r points of every hyperplane, has at least (r −1)q +(p−1)r points, where 1 < r < q = p h , p prime. An immediate corollary of this theorem is that a linear code whose weights and length have a common divisor r < q and whose dual minimum distance is at least 3, has length at least (r − 1)q + (p − 1)r. The theorem, which is sharp in some cases, is a strong generalisation of an earlier result on the non-existence of maximal arcs in projective planes; the proof involves polynomials over finite fields, and is a streamlined and more transparent version of the earlier one.
Ieee Transactions on Information Theory, 1998
k01 j=0 dd=q j e = N d + A + k 0 I d 0 2; so k n 0 N d + I d 0 A + 2: Comparing this inequality with Theorem 4, we completed the proof. In the following, we give two examples. Example 1: q = 2, d = 5. If n > 12, the new bound is tighter than the Griesmer bound. For instance, the Griesmer bound cannot prove the nonexistence [13; 6; 5], but the new bound can. Example 2: q = 3, d = 9. If n > 13, the new bound is tighter than the Griesmer bound. For instance, the Griesmer bound cannot prove the nonexistence [14; 4; 9], but the new bound can. IV. CONCLUSION In this correspondence, we gave some bounds for [n; k; d] codes with the method of coset partitions. These bounds are new in type and are derived from the basic properties of the parity-check matrix. Comparing these bounds with tables of the best codes known, it can be shown that these bounds are not strong for arbitrary n and d although, indeed, Theorem 4 improves on the Griesmer bound for a large range of code parameters. Comparing with [3, Table I] in the binary case, we list some results in the following. Case 1: d = 3. In this case, Theorem 1 shows that k bn 0 log 2 (n + 1)c: The equality holds for Hamming [n = 2 r 0 1; k = n 0 r; d = 3] codes and also for shortened Hamming [n = 2 r 010m; k = n 0r 0m; d = 3] codes, where 0 < m < n 0 r. This shows that Theorem 1 is tight for d = 3. This also shows that the Hamming codes and shortened Hamming codes are optimal linear block codes for a given codelength and minimum distance d = 3, a fact known earlier in coding theory. Case 2: d = 5. We compare Theorem 2 with [3, Table I ]. In this case, Theorem 2 shows that k bn 0 4 0 log 2 (n 0 4)c. The results obtained are listed in Table I. Case 3: d = 7. In this case, Theorem 3 can be written as k bn 0 7 0 log 2 (n 0 7)c: The results obtained are listed in Table II. Case 4: d = 9. In this case, Theorem 4 can be written as k bn 0 12 0 log 2 (n 0 13)c:
Discrete Mathematics, 2004
Let [n; k; d] q -codes be linear codes of length n, dimension k and minimum Hamming distance d over GF(q). In this paper, 32 new codes over GF(5) are constructed and the nonexistence of 51 codes is proved.
IEEE Transactions on Information Theory, 1996
Let d, ( n k ) be the maximum possible minimum Hamming It is proved that d4 (33,5) = 22, d4(49 5 ) = 34, &(I31 5) = 96, d4(142,5) = 104, rla(147,5) = 108, &(I52 5 ) = 112, &(I58 5 ) = 116,d4(176,5) 2 129,d4(180,5) 2 132,&(190 5 ) 2 140,&(19j 5) = 144,d4(200,5) = 148,d4(205 5) = 132,d4(216 3 ) = 160,d4(22i 2) = = 180, and d4(247,5) = 184. A survey of the results of recent work on bounds for quaternary linear codes in dimensions four and five is made and a table with lower and upper bounds for drl ( n , 5) is presented. distance of a q-ary [ rt k , d] -code for given values of n and k 168, dq(232 5) = 172, d4(237,5) 176, d4(240 3 ) = 178, d4(242 3) Index Terms-Minimum distance bounds, quaternary linear codes. c-concatenation sh-shortened code r-nonexistence of an [ n~ k ; d ; 41-code via its residual code d-nonexistence of an [ n , k , d ; 41-code follows from the nonexistence of its dual code For all the others lower bounds ( 1 5 n 5 128 ) see [18]. B. Upper Bounds Res (C, 43) = [6,4,3; 41 Res (C, 45) = [4,4,2; 41 By [4], [lo] 34 5 &(49,5) 5 35. Theorem 12: d4(49,5) = 34. Proof Suppose there exists a [g4(5,35) = 49,5,35; 41-code C. codes. BY nom2 of these codes exist and so By Corollary 5.1, Bl = B2 = B3 = 0. By Lemma 3 A s , = A38 = -441 = A12 = A,, = A g g = 0.
be the smallest integer n for which there exists a linear code of length n, dimension IC, and minimum distance d, over a field of q elements. In this correspondence we determine n5 (4, d ) for all but 22 values of d. Index Terms-Optimal q-ary linear codes, minimum-length bounds. Publisher Item Identifier S 0018-9448(97)00108-9.
q code be a linear code of length n, dimension k and Hamming minimum distance d over GF(q). In this paper record-breaking codes with parameters [30, 10, 15]5, [
2017
The length function \(\ell _q(r,R)\) is the smallest length of a q-ary linear code of covering radius R and codimension r. New upper bounds on \(\ell _q(r,2)\) are obtained for odd \(r\ge 3\). In particular, using the one-to-one correspondence between linear codes of covering radius 2 and saturating sets in the projective planes over finite fields, we prove that $$\begin{aligned} \ell _q(3,2)\le \sqrt{q(3\ln q+\ln \ln q)}+\sqrt{\frac{q}{3\ln q}}+3 \end{aligned}$$ and then obtain estimations of \(\ell _q(r,2)\) for all odd \(r\ge 5\). The new upper bounds are smaller than the previously known ones. Also, the new bounds hold for all q, not necessary large, whereas the previously best known estimations are proved only for q large enough.
arXiv:1712.07078v5 [cs.IT], 2019
The length function q (r, R) is the smallest length of a q-ary linear code of codimension (redundancy) r and covering radius R. The d-length function q (r, R, d) is the smallest length of a q-ary linear code with codimension (redundancy) r, covering radius R, and minimum distance d. By computer search in wide regions of q, we obtained following short codes of covering radius R = 3: [n, n − 4, 5] q 3 quasi-perfect MDS codes, [n, n − 5, 5] q 3 quasi-perfect Almost MDS codes, and [n, n − 5, 3] q 3 codes. In computer search, we use the step-by-step lexi-matrix and inverse leximatrix algorithms to obtain parity check matrices of codes. These algorithms are versions of the recursive g-parity check matrix algorithm for greedy codes. The new codes imply the following new upper bounds (called lexi-bounds) on the length function and the d-length function: q (4, 3) ≤ q (4, 3, 5) < 2.8 3 ln q · q (4−3)/3 = 2.8 3 ln q · 3 √ q = 2.8 3 q ln q for 11 ≤ q ≤ 6607; q (5, 3) ≤ q (5, 3, 5) < 3 3 ln q · q (5−3)/3 = 3 3 ln q · 3 q 2 = 3 3 q 2 ln q for 37 ≤ q ≤ 839. Moreover, we improve the lexi-bounds, applying randomized greedy algorithms, and show that q (4, 3) ≤ q (4, 3, 5) < 2.61 3 q ln q if 13 ≤ q ≤ 4373; q (4, 3) ≤ q (4, 3, 5) < 2.65 3 q ln q if 4373 < q ≤ 6607; q (5, 3) < 2.785 3 q 2 ln q if 11 ≤ q ≤ 401; q (5, 3) ≤ q (5, 3, 5) < 2.884 3 q 2 ln q if 401 < q ≤ 839. The general form of the new bounds is q (r, 3) < c 3 ln q · q (r−3)/3 , c is a constant independent of q, r = 4, 5 = 3t. The codes, obtained in this paper by leximatrix and inverse leximatrix algorithms, provide the following new upper bounds (called density lexi-bounds) on the smallest covering density µ q (r, R) of a q-ary linear code of codimension r and covering radius R: µ q (4, 3) < 3.3 · ln q for 11 ≤ q ≤ 6607; µ q (5, 3) < 4.2 · ln q for 37 ≤ q ≤ 839. In the general form, we have µ q (r, 3) < c µ · ln q, c µ is a constant independent of q, r = 4, 5. The new bounds on the length function, the d-length function and covering density hold for the field basis q of an arbitrary structure, including q = (q) 3 where q is a prime power.
2021
An arc and a blocking set are both geometrical objects linked with linear codes. In this paper, we use relations among these objects to prove the non-existence of linear codes over F53 of lengths s = (t − 1)p + t − (p + 1)/2, (p + 3)/2 < t < p and minimum Hamming distance d = s − t with dimension three. As a special case, no linear code of length 1864 exists. In addition, we determine the upper bounds of mt(2, 53).
1999
We deal with the minimum distances of q-ary cyclic codes of length q m -1 generated by products of two distinct minimal polynomials, give a necessary and sufficient condition for the case that the minimum distance is two, show that the minimum distance is at most three if q > 3, and consider also the case q = 3.
IEEE Transactions on Information Theory, 2000
Some new infinite families of short quasi-perfect linear codes are described. Such codes provide improvements on the currently known upper bounds on the minimal length of a quasi-perfect [n; n 0m; 4] -code when either 1) q = 16; m 5; m odd, or 2) q = 2 ; 7 i 15; m 4, or 3) q = 2 ;` 8; m 5; m odd. As quasi-perfect [n; n0m; 4] -codes and complete n-caps in projective spaces P G(m 01;q) are equivalent objects, new upper bounds on the size of the smallest complete cap in P G(m 01;q) are obtained.
Indagationes Mathematicae, 2001
We show that a code C of length n over an alphabet Q of size q with minimum distance 2 and covering radius 1 satisfies rc] >_ qn_ 1/( n _ 1). For the special case n = q = 4 the smallest known example has IC] = 31. We give a construction for such a code C with IC] = 28.
Discrete Applied Mathematics, 2013
Asymptotic bounds are given for the asymptotic exponent of the quantity in the title. Upper bounds follow from the theory of matroids. Lower bounds are derived by random coding. Constructive lower bounds are derived by considering the cycle code of special graphs. This choice is shown to be essentially optimal.
Discrete Mathematics, 2001
We consider the problem of ÿnding bounds and exact values of A5(n; d) -the maximum size of a code of length n and minimum distance d over an alphabet of 5 elements. Using a wide variety of constructions and methods, a table of bounds on A5(n; d) for n611 is obtained.
IEEE Transactions on Information Theory, 1985
Advances in Mathematics of Communications, 2010
In this work a heuristic algorithm for obtaining lower bounds on the covering radius of a linear code is developed. Using this algorithm the least covering radii of the binary linear codes of dimension 6 are determined. Upper bounds for the least covering radii of binary linear codes of dimensions 8 and 9 are derived.
Let an $[n,k,d]_q$ code be a linear code of length $n$, dimension $k$ and minimum Hamming distance $d$ over $GF(q)$. One of the most important problems in coding theory is to construct codes with optimal minimum distances. In this paper 22 new ternary linear codes are presented. Two of them are optimal. All new codes improve the respective lower bounds in [11].
IEEE Transactions on Information Theory, 1999
New constructions of linear nonbinary codes with covering radius R = 2 are proposed. They are in part modifications of earlier constructions by the author and in part are new. Using a starting code with R = 2 as a "seed" these constructions yield an infinite family of codes with the same covering radius. New infinite families of codes with R = 2 are obtained for all alphabets of size q 4 and all codimensions r 3 with the help of the constructions described. The parameters obtained are better than those of known codes. New estimates for some partition parameters in earlier known constructions are used to design new code families. Complete caps and other saturated sets of points in projective geometry are applied as starting codes. A table of new upper bounds on the length function for q = 4; 5; 7; R = 2; and r 24 is included.
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