Improved Lower Bounds for Coded Caching

Ghasemi, Hooshang; Ramamoorthy, Aditya

doi:10.1109/tit.2017.2705166

Cited by 108 publications

(98 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For this scenario, the best communication rate stated in prior works is achieved by the Amiri et al scheme [16]. The tightest prior converse bound in this scenario is provided by [45], [46], [49]. Our results strictly improve the prior arts in both achievability and converse, for both average rate and peak rate.…”

Section: B Exact Rate-memory Tradeoff For Decentralized Settingsupporting

confidence: 66%

“…5, both the achievability scheme and the converse provided in our paper strictly improve the prior arts, for both average rate and peak rate. , we compare our proposed achievability scheme with prior-art coded-prefetching schemes [14], [15], prior-art converse bounds [45], [46], [49], and two recent results [50], [53]. The achievability scheme proposed in this paper achieves the best performance to date in most cases, and is within a factor of 2 optimal as shown in [50], even compared with schemes that allow coded prefetching.…”

Section: B Exact Rate-memory Tradeoff For Decentralized Settingmentioning

confidence: 80%

“…Besides developing better achievability schemes, there have been efforts in tightening the outer bound of the rate-memory tradeoff [33], [45]- [49]. Nevertheless, in almost all scenarios, there is still a gap between the state-of-the-art communication load and the converse, leaving the exact rate-memory tradeoff an open problem.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The Exact Rate-Memory Tradeoff for Caching With Uncoded Prefetching

Maddah-Ali

Avestimehr

2018

IEEE Trans. Inform. Theory

306

278

View full text Add to dashboard Cite

Abstract-We consider a basic cache network, in which a single server is connected to multiple users via a shared bottleneck link. The server has a database of files (content). Each user has an isolated memory that can be used to cache content in a prefetching phase. In a following delivery phase, each user requests a file from the database, and the server needs to deliver users' demands as efficiently as possible by taking into account their cache contents. We focus on an important and commonly used class of prefetching schemes, where the caches are filled with uncoded data. We provide the exact characterization of the rate-memory tradeoff for this problem, by deriving both the minimum average rate (for a uniform file popularity) and the minimum peak rate required on the bottleneck link for a given cache size available at each user. In particular, we propose a novel caching scheme, which strictly improves the state of the art by exploiting commonality among user demands. We then demonstrate the exact optimality of our proposed scheme through a matching converse, by dividing the set of all demands into types, and showing that the placement phase in the proposed caching scheme is universally optimal for all types. Using these techniques, we also fully characterize the rate-memory tradeoff for a decentralized setting, in which users fill out their cache content without any coordination.

show abstract

Section: B Exact Rate-memory Tradeoff For Decentralized Settingsupporting

confidence: 66%

Section: B Exact Rate-memory Tradeoff For Decentralized Settingmentioning

confidence: 80%

See 1 more Smart Citation

The Exact Rate-Memory Tradeoff for Caching With Uncoded Prefetching

Maddah-Ali

Avestimehr

2018

IEEE Trans. Inform. Theory

306

278

View full text Add to dashboard Cite

show abstract

“…Several caching schemes have been proposed in [14]- [21], and converse bounds have also been introduced in [9], [22]- [26]. For the case, where the prefetching is uncoded, the exact rate-memory tradeoff for both peak and average rate (under uniform file popularity) and for both centralized and decentralized settings have been established in [20].…”

Section: Introductionmentioning

confidence: 99%

Characterizing the rate-memory tradeoff in cache networks within a factor of 2

Maddah-Ali

Avestimehr

2017

2017 IEEE International Symposium on Information Theory (ISIT)

163

View full text Add to dashboard Cite

We consider a basic caching system, where a single server with a database of N files (e.g. movies) is connected to a set of K users through a shared bottleneck link. Each user has a local cache memory with a size of M files. The system operates in two phases: a placement phase, where each cache memory is populated up to its size from the database, and a following delivery phase, where each user requests a file from the database, and the server is responsible for delivering the requested contents. The objective is to design the two phases to minimize the load (peak or average) of the bottleneck link. We characterize the rate-memory tradeoff of the above caching system within a factor of 2.00884 for both the peak rate and the average rate (under uniform file popularity), where the best proved characterization in the current literature gives a factor of 4 and 4.7 respectively. Moreover, in the practically important case where the number of files (N ) is large, we exactly characterize the tradeoff for systems with no more than 5 users, and characterize the tradeoff within a factor of 2 otherwise. We establish these results by developing novel information theoretic outer-bounds for the caching problem, which improves the state of the art and gives tight characterization in various cases. I. INTRODUCTIONCaching is a common strategy to mitigate heavy peak-time communication load in a distributed network, via duplicating parts of the content in memories distributed across the network during off-peak times. In other words, caching allows us to trade distributed memory in the network for communication load reduction. Characterizing this fundamental rate-memory tradeoff is of great practical interest, and has been a research subject for several decades. For single-cache networks, the ratememory tradeoff has been characterized for various scenarios in 80th [1]. However, those techniques were found insufficient to tackle the multiple-cache cases. There has been a surge of recent results in information theory that aim at formalizing and characterizing such rate-memory tradeoff in cache networks [2]- [13]. In particular, the peak rate vs. memory tradeoff was formulated and characterized within a factor of 12 in a basic cache network with a shared bottleneck link [2]. This result has been extended to many scenarios, including decentralized caching [3] Essentially, many of these extensions share similar ideas in terms of the achievability and the converse bounds. Therefore, if we can improve the results for the basic bottleneck caching network, the ideas can be used to improve the results in other cases as well.In the literature, various approaches have been proposed for improving the bounds on rate-memory tradeoff for the bottleneck network. Several caching schemes have been proposed in [14]-[21], and converse bounds have also been introduced in [9], [22]-[26]. For the case, where the prefetching is uncoded, the exact rate-memory tradeoff for both peak and average rate (under uniform file popularity) and for both centra...

show abstract

“…Their coded caching scheme has a significant improvement over traditional caching schemes and was also proven to be optimal under the constraint of uncoded cache placememnt [5], [6]. This fundamental understanding of caching networks heralded a series of interesting results ranging from proposing improved lower bounds [7]- [9], and achievability schemes to the application of coded caching scheme on different topologies [10], changing parameters such as different cache [11], [12], and file size [13], investigating caching in Device-to-Device (D2D) communication networks [14] as well as decentralized variations [15]. Some of the notable developments, results and challenges in these directions are summarized in [16].…”

Section: Introductionmentioning

confidence: 99%

Towards the exact rate-memory trade-off for uncoded caching with secure delivery

Bahrami

Attia

Tandon

et al. 2017

2017 55th Annual Allerton Conference on Communication, Control, and Computing (Allerton)

View full text Add to dashboard Cite

Abstract-We consider the problem of secure delivery in a single-hop caching network with a central server connected to multiple end-users via an insecure multi-cast link. The server has a database of a set of files (content) and each user, which is equipped with a local cache memory, requests access one of the files. In addition to delivering users' requests, the server needs to keep the files (information-theoretically) secure from an external eavesdropper observing the underlying communications between the server and users. We focus on an important class of content placement strategies where the prefetching is required to be uncoded and caches are filled with uncoded fragments of files. In this paper, we establish the exact characterization of secure rate-memory trade-off for the worstcase communication rate through a matching converse under the constraint of uncoded cache placement where the number of users is no larger than the number of files in the database.

show abstract

Improved Lower Bounds for Coded Caching

Cited by 108 publications

References 34 publications

The Exact Rate-Memory Tradeoff for Caching With Uncoded Prefetching

The Exact Rate-Memory Tradeoff for Caching With Uncoded Prefetching

Characterizing the rate-memory tradeoff in cache networks within a factor of 2

Towards the exact rate-memory trade-off for uncoded caching with secure delivery

Contact Info

Product

Resources

About