Broadcast caching networks with two receivers and multiple correlated sources

IEEE Trans. Inform. Theory

Tulino

Llorca

et al. 2020

Self Cite

This paper studies the fundamental limits of content delivery in a cache-aided broadcast network for correlated content generated by a discrete memoryless source with arbitrary joint distribution. Each receiver is equipped with a cache of equal capacity, and the requested files are delivered over a shared error-free broadcast link. A class of achievable correlation-aware schemes based on a two-step source coding approach is proposed. Library files are first compressed, and then cached and delivered using a combination of correlation-unaware multiple-request cache-aided coded multicast schemes. The first step uses Gray-Wyner source coding to represent the library via private descriptions and descriptions that are common to more than one file. The second step then becomes a multiple-request caching problem, where the demand structure is dictated by the configuration of the compressed library, and it is interesting in its own right. The performance of the proposed two-step scheme is evaluated by comparing its achievable rate with a lower bound on the optimal peak and average rate-memory tradeoffs in a two-file multiple-receiver network, and in a three-file two-receiver network. Specifically, in a network with two files and two receivers, the achievable rate matches the lower bound for a significant memory regime and it is within half of the conditional entropy of files for all other memory values.In the three-file two-receiver network, 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 one for all other cache sizes.for the compression of requested files during the delivery phase. Alternatively, our work in [9] addresses the content dependency by first compressing the correlated library. A subset of the files, most representative of the library, are selected as references, referred to as I-files, and the remaining files are inter-compressed with respect to the selected files and referred to as P-files.This results in a compressed library where each file is made up of an I-file and a P-file, leading to a multiple-request caching problem. Differently from previous multiple-request schemes [4],[15]- [18], the demand in [9] has a specific structure dictated by the configuration of the resulting compressed library in terms of I-files and P-files. 3 The first information-theoretic characterization of the rate-memory trade-off in a cache-aided broadcast network with correlated content was studied in [10] for the setting of two files and two receivers, each equipped with a cache. This paper introduces an achievable two-step scheme that exploits content correlations by first jointly compressing the library files using the Gray-Wyner network [14], and then treating the compressed content as independent files. It is shown in [10] that this strategy is optimal for a large memory regime, while the gap to optimality is quantified for other memory values.Building on the idea introduced in [9] and [10], concurrent work i...

“…For γ K and λ K defined in (12), and forγ K defined in (14), when K ≥ 2 we have 2γ K ≤γ K ≤ γ ≤ λ ≤ λ K . Therefore, for a given = (ρ 0 , ρ 1 , ρ 2 ):…”

Section: Appendix D Proof Of Theoremmentioning

confidence: 99%

“…for γ K = 1 K min{ρ 1 , ρ 2 } defined in (12). Proof: For the purposes of our analysis we only provide the caching and delivery strategies for cache sizes…”

Section: Appendix D Proof Of Theoremmentioning

confidence: 99%

Section: Ii) Lower Bound Onr * (M)mentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Rate-Memory Trade-Off for Caching and Delivery of Correlated Sources

IEEE Trans. Inform. Theory

Tulino

Llorca

et al. 2020

Self Cite

“…A two-file system is studied in detail in [7], where the files are initially compressed using Gray-Wyner source coding, and an optimal caching scheme is derived for the two-receiver network. This scheme is generalized to more files in [6], which is shown to be optimal for large cache sizes. Arbitrary numbers of users and files are considered in [5], where each file is modeled as a collection of subfiles, each of which is shared by a different subset of files.…”

Section: Introductionmentioning

confidence: 99%

Centralized caching and delivery of correlated contents over a Gaussian broadcast channel

Yang

2018 16th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt)

Gündüz

et al. 2018

Self Cite

Content delivery in a multi-user cache-aided broadcast network is studied, where a server holding a database of correlated contents communicates with the users over a Gaussian broadcast channel (BC). The minimum transmission power required to satisfy all possible demand combinations is studied, when the users are equipped with caches of equal size. A lower bound on the required transmit power is derived, assuming uncoded cache placement, as a function of the cache capacity. A centralized joint cache and channel coding scheme is proposed, which not only utilizes the user's local caches, but also exploits the correlation among the contents in the database. This scheme provides an upper bound on the minimum required transmit power for a given cache capacity. Our results indicate that exploiting the correlations among the contents in a cache-aided Gaussian BC can provide significant energy savings.

On Coding for Cache-Aided Delivery of Dynamic Correlated Content

IEEE J. Select. Areas Commun.

Tulino

Llorca

et al. 2018

Cache-aided coded multicast leverages side information at wireless edge caches to efficiently serve multiple unicast demands via common multicast transmissions, leading to load reductions that are proportional to the aggregate cache size. However, the increasingly dynamic, 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 specifically account for the correlation among content files, such as, for example, the one between updated versions of dynamic data. It is shown that (i) caching content pieces based on their correlation with the rest of the library, and (ii) jointly compressing requested files using cached information as references during delivery, can provide load reductions that go beyond those achieved with existing schemes. This is accomplished via the design of a class of correlationaware achievable schemes, shown to significantly outperform state-of-the-art correlation-unaware solutions. Our results show that as we move towards real-time and/or personalized media dominated services, where exact cache hits are almost non-existent but updates can exhibit high levels of correlation, network cached information can still be useful as references for network compression.