3 research outputs found
Low-Complexity Decoding for Symmetric, Neighboring and Consecutive Side-information Index Coding Problems
The capacity of symmetric, neighboring and consecutive side-information
single unicast index coding problems (SNC-SUICP) with number of messages equal
to the number of receivers was given by Maleki, Cadambe and Jafar. For these
index coding problems, an optimal index code construction by using Vandermonde
matrices was proposed. This construction requires all the side-information at
the receivers to decode their wanted messages and also requires large field
size. In an earlier work, we constructed binary matrices of size such that any adjacent rows of the matrix are linearly
independent over every field. Calling these matrices as Adjacent Independent
Row (AIR) matrices using which we gave an optimal scalar linear index code for
the one-sided SNC-SUICP for any given number of messages and one-sided
side-information. By using Vandermonde matrices or AIR matrices, every receiver
needs to solve equations with unknowns to obtain its wanted
message, where is the number of messages and is the size of the
side-information. In this paper, we analyze some of the combinatorial
properties of the AIR matrices. By using these properties, we present a
low-complexity decoding which helps to identify a reduced set of
side-information for each users with which the decoding can be carried out. By
this method every receiver is able to decode its wanted message symbol by
simply adding some index code symbols (broadcast symbols). We explicitly give
both the reduced set of side-information and the broadcast messages to be used
by each receiver to decode its wanted message. For a given pair or receivers
our decoding identifies which one will perform better than the other when the
broadcast channel is noisy.Comment: Some minor changes made in Algorithm 1. 11 Figures, 3 Table
Optimal Scalar Linear Index Codes for Symmetric and Neighboring Side-information Problems
A single unicast index coding problem (SUICP) is called symmetric neighboring
and consecutive (SNC) side-information problem if it has messages and
receivers, the th receiver wanting the th message and
having the side-information messages immediately after and
() messages immediately before . Maleki, Cadambe and Jafar
obtained the capacity of this SUICP(SNC) and proposed -dimensional
optimal length vector linear index codes by using Vandermonde matrices.
However, for a -dimensional vector linear index code, the transmitter needs
to wait for realizations of each message and hence the latency introduced
at the transmitter is proportional to . For any given single unicast index
coding problem (SUICP) with the side-information graph , MAIS() is used
to give a lowerbound on the broadcast rate of the ICP. In this paper, we derive
MAIS() of SUICP(SNC) with side-information graph . We construct scalar
linear index codes for SUICP(SNC) with length . We derive the
minrank() of SUICP(SNC) with side-information graph and show that the
constructed scalar linear index codes are of optimal length for SUICP(SNC) with
some combinations of and . For SUICP(SNC) with arbitrary and
, we show that the length of constructed scalar linear index codes are
atmost two index code symbols per message symbol more than the broadcast rate.
The given results for SUICP(SNC) are of practical importance due to its
relation with topological interference management problem in wireless
communication networks.Comment: 6 pages, 1 figure, 2 tables. arXiv admin note: text overlap with
arXiv:1801.0040
Groupcast Index Coding Problem: Joint Extensions
The groupcast index coding problem is the most general version of the
classical index coding problem, where any receiver can demand messages that are
also demanded by other receivers. Any groupcast index coding problem is
described by its \emph{fitting matrix} which contains unknown entries along
with 's and 's. The problem of finding an optimal scalar linear code is
equivalent to completing this matrix with known entries such that the rank of
the resulting matrix is minimized. Any row basis of such a completion gives an
optimal \emph{scalar linear} code. An index coding problem is said to be a
joint extension of a finite number of index coding problems, if the fitting
matrices of these problems are disjoint submatrices of the fitting matrix of
the jointly extended problem. In this paper, a class of joint extensions of any
finite number of groupcast index coding problems is identified, where the
relation between the fitting matrices of the sub-problems present in the
fitting matrix of the jointly extended problem is defined by a base problem. A
lower bound on the \emph{minrank} (optimal scalar linear codelength) of the
jointly extended problem is given in terms of those of the sub-problems. This
lower bound also has a dependence on the base problem and is operationally
useful in finding lower bounds of the jointly extended problems when the
minranks of all the sub-problems are known. We provide an algorithm to
construct scalar linear codes (not optimal in general), for any groupcast
problem belonging to the class of jointly extended problems identified in this
paper. The algorithm uses scalar linear codes of all the sub-problems and the
base problem. We also identify some subclasses, where the constructed codes are
scalar linear optimal.Comment: 9 page