Cache-Aided Coded Multicast for Correlated Sources

The combination of edge caching and coded multicasting is a promising approach to improve the efficiency of content delivery over cache-aided networks. The global caching gain resulting from content overlap distributed across the network in current solutions is limited due to the increasingly personalized nature of the content consumed by users. In this paper, the cache-aided coded multicast problem is generalized to account for the correlation among the network content by formulating a source compression problem with distributed side information. A correlation-aware achievable scheme is proposed and an upper bound on its performance is derived. It is shown that considerable load reductions can be achieved, compared to state of the art correlation-unaware schemes, when caching and delivery phases specifically account for the correlation among the content files.Comment: In proceeding of IEEE International Symposium on Turbo Codes and Iterative Information Processing (ISTC), 201

Correlation-Aware Distributed Caching and Coded Delivery

Cache-aided coded multicast leverages side information at wireless edge caches to efficiently serve multiple groupcast demands via common multicast transmissions, leading to load reductions that are proportional to the aggregate cache size. However, the increasingly unpredictable and personalized nature of the content that users consume challenges the efficiency of existing caching-based solutions in which only exact content reuse is explored. This paper generalizes the cache-aided coded multicast problem to a source compression with distributed side information problem that specifically accounts for the correlation among the content files. It is shown how joint file compression during the caching and delivery phases can provide load reductions that go beyond those achieved with existing schemes. This is accomplished through a lower bound on the fundamental rate-memory trade-off as well as a correlation-aware achievable scheme, shown to significantly outperform state-of-the-art correlation-unaware solutions, while approaching the limiting rate-memory trade-off.Comment: In proceeding of IEEE Information Theory Workshop (ITW), 201

Le società finanziarie regionali nel contesto della riforma delle società partecipate pubbliche.

mercato del credito nelle Regioni esercita una funzione rilevante per il progresso armonioso dei territori di riferimento. Anche la Costituzione assegna al servizio del credito un ruolo di promozione dello sviluppo economico. Le Regioni, sia a statuto speciale sia a statuto ordinario, intraprendono delle azioni in tal senso, considerando il nesso di strumentalità tra le materie del credito e le materie di competenza regionale. Con la crisi economica che ha colpito i mercati internazionali e nazionali è emersa, in modo ancora più evidente, la necessità di una riflessione e di una proposta sul ruolo che il soggetto pubblico può svolgere per la crescita del sistema economico, con una crescente rilevanza e criticità del ruolo della finanza pubblica chiamata sia a contribuire allo sviluppo economico che a risanare i bilanci pubblici. In questo contesto assumono rilevanza le iniziative promosse dalle Regioni nel settore del mercato del credito. Tra gli strumenti a loro disposizione ci sono le società finanziarie regionali, soggetti partecipati dalle Regioni attraverso le quali queste ultime, molto spesso, gestiscono i fondi di garanzia costituiti proprio a servizio del credito. L’interesse per queste società, dunque, scaturisce dalla necessità delle Regioni di promuovere iniziative per lo sviluppo socio-economico del proprio territorio, anche attraverso questi soggetti, sovente creati con apposite leggi regionali e che sono lo strumento per l’attuazione delle politiche economiche e finanziarie delle Regioni e rappresentano un sistema alternativo al credito ordinario. Si tratta di soggetti che attualmente sono al centro di un importante processo di riordino, ex art. 106 del Testo unico bancario, in relazione al tema dei controlli da parte della Banca d’Italia. Inoltre, la materia è interessata dalla riforma delle società partecipate pubbliche prevista dalla legge delega 7 agosto 2015, n. 124: nella sua versione preliminare, il decreto legislativo 19 agosto 2016, n. 175 “Testo unico in materia di società a partecipazione pubblica”, se non fosse stato opportunamente emendato, avrebbe potuto avere un impatto negativo proprio sulle società finanziarie regionali e sulla loro operatività. Obiettivo del presente capitolo è analizzare tali tipologie di società partecipate pubbliche, indagando sui vari modelli operativi e sul loro ruolo di attori dello sviluppo nel panorama creditizio regionale in un’ottica di governo multilivello, mettendone in luce l’aspetto giuspubblicistico e la collocazione nel contesto della forma di stato regionale e della regolazione economica.The regional credit market plays a major role in the harmonious progress of the reference territories, and the Constitution also assigns credit to the role of promoting economic development. The Regions, both by special statute and by ordinary statute, undertake such actions, taking into account the link between instrumentalities and matters of regional competence. With the economic crisis affecting the international and national markets, the need for a reflection and a proposal on the role that the public bodies can play for the growth and development of the economic system emerged even more clearly, with growing relevance and criticality of the role of public finance called to contribute to economic development and to the rescue of public budgets. In this context, the initiatives promoted by the Regions in the credit market are relevant. Among the tools at their disposal are the regional finance companies, which are participants in the Regions and through which the latter, very often, manage the guarantee funds set up in the service of credit. The interest for these societies, therefore, derives from the need for the Regions to promote initiatives for the socio-economic development of their territory, even through these bodies, often created by specific regional laws. They are the instrument for the implementation of economic policies and financial services of the Regions and represent an alternative system to ordinary credit. These entities are currently at the center of an important reordering process, ex art. 106 of the Consolidated Law on Banking, in relation to the subject of controls by the Bank of Italy. In addition, the reform of the publicly-owned companies, led to the approval of the Legislative Decree No. 175/2016, "Consolidated Law on Publicly-Owned Companies". If its preliminary version was not been appropriately amended, it could have had a negative impact on the regional finance companies and their operation. The aim of this chapter is to analyze these types of publicly-owned companies, investigating the various operating models and their role as actors of development in the regional credit landscape in a multilevel governance perspective, highlighting the public-sector aspect and its location in the context of the form of regional status and of the government of the economy

Support Recovery with Sparsely Sampled Free Random Matrices

Consider a Bernoulli-Gaussian complex $n$-vector whose components are $V_i = X_i B_i$, with X_i \sim \Cc\Nc(0,\Pc_x) and binary $B_i$ mutually independent and iid across $i$. This random $q$-sparse vector is multiplied by a square random matrix \Um, and a randomly chosen subset, of average size $n p$, $p \in [0,1]$, of the resulting vector components is then observed in additive Gaussian noise. We extend the scope of conventional noisy compressive sampling models where \Um is typically %A16 the identity or a matrix with iid components, to allow \Um satisfying a certain freeness condition. This class of matrices encompasses Haar matrices and other unitarily invariant matrices. We use the replica method and the decoupling principle of Guo and Verd\'u, as well as a number of information theoretic bounds, to study the input-output mutual information and the support recovery error rate in the limit of $n \to \infty$. We also extend the scope of the large deviation approach of Rangan, Fletcher and Goyal and characterize the performance of a class of estimators encompassing thresholded linear MMSE and $\ell_1$ relaxation

Distortion-Memory Tradeoffs in Cache-Aided Wireless Video Delivery

Mobile network operators are considering caching as one of the strategies to keep up with the increasing demand for high-definition wireless video streaming. By prefetching popular content into memory at wireless access points or end user devices, requests can be served locally, relieving strain on expensive backhaul. In addition, using network coding allows the simultaneous serving of distinct cache misses via common coded multicast transmissions, resulting in significantly larger load reductions compared to those achieved with conventional delivery schemes. However, prior work does not exploit the properties of video and simply treats content as fixed-size files that users would like to fully download. Our work is motivated by the fact that video can be coded in a scalable fashion and that the decoded video quality depends on the number of layers a user is able to receive. Using a Gaussian source model, caching and coded delivery methods are designed to minimize the squared error distortion at end user devices. Our work is general enough to consider heterogeneous cache sizes and video popularity distributions.Comment: To appear in Allerton 2015 Proceedings of the 53rd annual Allerton conference on Communication, control, and computin

Broadcast Caching Networks with Two Receivers and Multiple Correlated Sources

The correlation among the content distributed across a cache-aided broadcast network can be exploited to reduce the delivery load on the shared wireless link. This paper considers a two-user three-file network with correlated content, and studies its fundamental limits for the worst-case demand. A class of achievable schemes based on a two-step source coding approach is proposed. Library files are first compressed using Gray-Wyner source coding, and then cached and delivered using a combination of correlation-unaware cache-aided coded multicast schemes. The second step is interesting in its own right and considers a multiple-request caching problem, whose solution requires coding in the placement phase. A lower bound on the optimal peak rate-memory trade-off is derived, which is used to evaluate the performance of the proposed scheme. It is shown that for symmetric sources the two-step strategy achieves the lower bound for large cache capacities, and it is within half of the joint entropy of two of the sources conditioned on the third source for all other cache sizes.Comment: in Proceedings of Asilomar Conference on Signals, Systems and Computers, Pacific Grove, California, November 201

Caching and Coded Multicasting: Multiple Groupcast Index Coding

The capacity of caching networks has received considerable attention in the past few years. A particularly studied setting is the case of a single server (e.g., a base station) and multiple users, each of which caches segments of files in a finite library. Each user requests one (whole) file in the library and the server sends a common coded multicast message to satisfy all users at once. The problem consists of finding the smallest possible codeword length to satisfy such requests. In this paper we consider the generalization to the case where each user places $L \geq 1$ requests. The obvious naive scheme consists of applying $L$ times the order-optimal scheme for a single request, obtaining a linear in $L$ scaling of the multicast codeword length. We propose a new achievable scheme based on multiple groupcast index coding that achieves a significant gain over the naive scheme. Furthermore, through an information theoretic converse we find that the proposed scheme is approximately optimal within a constant factor of (at most) $18$.Comment: 5 pages, 1 figure, to appear in GlobalSIP14, Dec. 201

Hypergraph-Based Analysis of Clustered Cooperative Beamforming with Application to Edge Caching

The evaluation of the performance of clustered cooperative beamforming in cellular networks generally requires the solution of complex non-convex optimization problems. In this letter, a framework based on a hypergraph formalism is proposed that enables the derivation of a performance characterization of clustered cooperative beamforming in terms of per-user degrees of freedom (DoF) via the efficient solution of a coloring problem. An emerging scenario in which clusters of cooperative base stations (BSs) arise is given by cellular networks with edge caching. In fact, clusters of BSs that share the same requested files can jointly beamform the corresponding encoded signals. Based on this observation, the proposed framework is applied to obtain quantitative insights into the optimal use of cache and backhaul resources in cellular systems with edge caching. Numerical examples are provided to illustrate the merits of the proposed framework.Comment: 10 pages, 5 figures, Submitte

Luci ed ombre della recente riforma delle società partecipate pubbliche

nel corso dell’ultimo ventennio la realtà delle società a partecipazione pubblica si è affermata come un fenomeno complesso, caratterizzato da una crescita convulsa, finendo per incidere sempre più significativamente sulla nostra legislazione e, allo stesso tempo, generando molteplici dubbi interpretativ