4
votes
3answers
182 views
Bounded Hamming distance
Definition 1. For each $n\in\mathbb{Z}^+$, the $n$-dimensional Hamming cube is the set of ordered $n$-tuples of $\lbrace 0,1\rbrace$, denoted by $\lbrace 0,1\rbrace ^n$.
Definitio …
1
vote
1answer
173 views
Hamming codes from overlapping vectors
I am interested in whether the following problem is known.
For a given binary vector $V$ of length $n\geq m$, let $S$ be a subset of the possible subvectors of $V$ of length $m$ a …
0
votes
1answer
80 views
Isometry on a Hamming cube
Let $E^n$ be a Hamming cube of dimension $n$, and $\phi$ be a mapping from $E^n$ to $E^n$ that preserves Hamming distance, i.e. $d(x,y)=d(\phi (x),\phi (y))$. The question is the f …
2
votes
0answers
119 views
Matrix where every subset of rows has maximal rank
I am looking for a class of matrices $M(n(m), m, k(m), \phi)$ with the following properties:
M is $n \times m$ where $n(m) > m$.
Every subset of rows of size $k$ has (maximal) ra …
4
votes
1answer
130 views
Lower bound on the dimension of a subspace of $\mathbb Z_2^r$?
This question may be very trivial, I apologize if it is so.
I have subspace $V\subset \mathbb Z_2^r$ with the property that for every choice of a subset $I$ of $k$ elements in $\{ …
3
votes
1answer
297 views
Automorphisms of subgroup of hamming cube under distance constraint
Let $S$ be a subset of $\{0,1\}^n$ such that any two elements of $S$ are at least (Hamming) distance 5 apart. I'm looking for an upper bound on the size of the automorphism group o …
4
votes
1answer
123 views
Best upper bound on rate for q-ary codes
Among the many upper bounds for families of codes in $\mathbb F _2 ^n$, the best known bound is the one by McEliece, Rodemich, Rumsey and Welch which states that the rate $R(\delta …
3
votes
3answers
345 views
Good codes in practice for correcting combination of errors and erasures
In practice, both errors and erasures might be introduced in the channel. Could you point me to some good codes for correcting such combinations. Also what are their correction cap …
3
votes
1answer
230 views
If “force” is periodic does it imply “velocity” is periodic ? (or decoding tail-bited conv. codes)
I'll try to translate certain problem about convolutional codes to more common language of ODE, hope my translation is correct, but welcome to criticize.
Consider two given fun …
12
votes
3answers
521 views
Can you cover the Boolean cube {0,1}^n with O(1) Hamming-balls each of radius n/2-c*sqrt(n)?
(where c>0 and the balls need not be disjoint?)
This is an embarrassingly simple question, yet somehow I couldn't find an answer (not even, "this is a well-known open problem") …
1
vote
1answer
88 views
(A)periodicity and (In)dependence on the boundary condition for some discrete analog of ODE (convolutional codes)
(See also MO117508, MO116611). This post describes somewhat real problem with convolutional codes. Let me first try to give brief and vague formulation of the question, later give …
1
vote
1answer
142 views
What is matrix A such that Hamming weight of [x, Ax] is maximal ? (Min distance of 1/2 block code?)
Everything over F_2.
For any matrix $A$ define the number $N(A) = min_{x}$ HammingWeight $( [x , Ax])$.
Where $x$ is vector and [a,b] is just concatenation of vectors: (a_1,...a_ …
4
votes
1answer
177 views
Most orthogonal lattice basis
Let $n \in \mathbf{N}$ be a natural number and $v_1,\cdots,v_n$ a set of basis vectors in $\mathbb{R}^n$. How does one find the matrix $g \in \mathbf{GL}_n(\mathbb{Z})$ orthogonali …
3
votes
3answers
395 views
Structure of F_p[G], for finite group G ?
Consider group algebra k[G] of finite group G.
If k is alg.closed then every irrep lives there with multiplicity equal to dimension.
(More conceptually as bimodule over GxG it is m …
4
votes
2answers
494 views
Hot-topics in error correcting coding related to interesting math. ?
What are topics in error-correcting coding which are related to interesting math. ?
I am primarely interested in nowdays hot topics, but old days topics are also welcome.
Let me …

