11 research outputs found
Constructions of Batch Codes via Finite Geometry
A primitive -batch code encodes a string of length into string
of length , such that each multiset of symbols from has mutually
disjoint recovering sets from . We develop new explicit and random coding
constructions of linear primitive batch codes based on finite geometry. In some
parameter regimes, our proposed codes have lower redundancy than previously
known batch codes.Comment: 7 pages, 1 figure, 1 tabl
Lifted Multiplicity Codes and the Disjoint Repair Group Property
Lifted Reed Solomon Codes (Guo, Kopparty, Sudan 2013) were introduced in the context of locally correctable and testable codes. They are multivariate polynomials whose restriction to any line is a codeword of a Reed-Solomon code. We consider a generalization of their construction, which we call lifted multiplicity codes. These are multivariate polynomial codes whose restriction to any line is a codeword of a multiplicity code (Kopparty, Saraf, Yekhanin 2014). We show that lifted multiplicity codes have a better trade-off between redundancy and a notion of locality called the t-disjoint-repair-group property than previously known constructions. More precisely, we show that, for t <=sqrt{N}, lifted multiplicity codes with length N and redundancy O(t^{0.585} sqrt{N}) have the property that any symbol of a codeword can be reconstructed in t different ways, each using a disjoint subset of the other coordinates. This gives the best known trade-off for this problem for any super-constant t < sqrt{N}. We also give an alternative analysis of lifted Reed Solomon codes using dual codes, which may be of independent interest
Locality via Partially Lifted Codes
In error-correcting codes, locality refers to several different ways of quantifying how easily a small amount of information can be recovered from encoded data. In this work, we study a notion of locality called the s-Disjoint-Repair-Group Property (s-DRGP). This notion can interpolate between two very different settings in coding theory: that of Locally Correctable Codes (LCCs) when s is large - a very strong guarantee - and Locally Recoverable Codes (LRCs) when s is small - a relatively weaker guarantee. This motivates the study of the s-DRGP for intermediate s, which is the focus of our paper. We construct codes in this parameter regime which have a higher rate than previously known codes. Our construction is based on a novel variant of the lifted codes of Guo, Kopparty and Sudan. Beyond the results on the s-DRGP, we hope that our construction is of independent interest, and will find uses elsewhere
PIR Array Codes with Optimal Virtual Server Rate
There has been much recent interest in Private information Retrieval (PIR) in
models where a database is stored across several servers using coding
techniques from distributed storage, rather than being simply replicated. In
particular, a recent breakthrough result of Fazelli, Vardy and Yaakobi
introduces the notion of a PIR code and a PIR array code, and uses this notion
to produce efficient PIR protocols.
In this paper we are interested in designing PIR array codes. We consider the
case when we have servers, with each server storing a fraction of
the bits of the database; here is a fixed rational number with . A
PIR array code with the -PIR property enables a -server PIR protocol
(with ) to be emulated on servers, with the overall storage
requirements of the protocol being reduced. The communication complexity of a
PIR protocol reduces as grows, so the virtual server rate, defined to be
, is an important parameter. We study the maximum virtual server rate of a
PIR array code with the -PIR property. We present upper bounds on the
achievable virtual server rate, some constructions, and ideas how to obtain PIR
array codes with the highest possible virtual server rate. In particular, we
present constructions that asymptotically meet our upper bounds, and the exact
largest virtual server rate is obtained when .
A -PIR code (and similarly a -PIR array code) is also a locally
repairable code with symbol availability . Such a code ensures
parallel reads for each information symbol. So the virtual server rate is very
closely related to the symbol availability of the code when used as a locally
repairable code. The results of this paper are discussed also in this context,
where subspace codes also have an important role
Bounds and Constructions for Generalized Batch Codes
Private information retrieval (PIR) codes and batch codes are two important
types of codes that are designed for coded distributed storage systems and
private information retrieval protocols. These codes have been the focus of
much attention in recent years, as they enable efficient and secure storage and
retrieval of data in distributed systems.
In this paper, we introduce a new class of codes called \emph{-batch
codes}. These codes are a type of storage codes that can handle any multi-set
of requests, comprised of distinct information symbols. Importantly,
PIR codes and batch codes are special cases of -batch codes.
The main goal of this paper is to explore the relationship between the number
of redundancy symbols and the -batch code property. Specifically, we
establish a lower bound on the number of redundancy symbols required and
present several constructions of -batch codes. Furthermore, we extend
this property to the case where each request is a linear combination of
information symbols, which we refer to as \emph{functional -batch
codes}. Specifically, we demonstrate that simplex codes are asymptotically
optimal functional -batch codes, in terms of the number of redundancy
symbols required, under certain parameter regime.Comment: 25 page