Cache-enabled broadcast packet erasure channels with state feedback

Abstract

Abstract-We consider a cache-enabled K-user broadcast erasure packet channel in which a server with a library of N files wishes to deliver a requested file to each user who is equipped with a cache of a finite memory M . Assuming that the transmitter has state feedback and user caches can be filled during off-peak hours reliably by decentralized cache placement, we characterize the optimal rate region as a function of the memory size, the erasure probability. The proposed delivery scheme, based on the scheme proposed by Gatzianas et al., exploits the receiver side information established during the placement phase. Our results enable us to quantify the net benefits of decentralized coded caching in the presence of erasure. The role of state feedback is found useful especially when the erasure probability is large and/or the normalized memory size is small.

Adding Transmitters Dramatically Boosts Coded-Caching Gains for Finite File Sizes

“…This gain -which is close to the theoretic optimal [1] -was shown to persist under a variety of settings that include uneven popularity distributions [2]- [4], uneven topologies [5], [6], a variety of channels such as erasure channels [7], MIMO broadcast channels with fading [8], a variety of networks such as heterogeneous networks [9], D2D networks [10], and in other settings as well.…”

“…Note that for the settings in[1],[22],[23], the aforementioned subpacketization costs in (1),(7) and(8)do not account for the extra subpacketization costs due to memory sharing.…”

Content Delivery in Erasure Broadcast Channels With Cache and Feedback

“…However, if the underlying wireless channels enjoy some degrees of freedom to convey simultaneously both private messages and common messages, the delivery phase of coded caching can be further enhanced. In the context of multi-antenna broadcast channel and erasure broadcast channel, the potential gain of coded caching in the presence of channel state feedback has been demonstrated [18], [25], [26]. The key observation behind [18], [26] is that opportunistic multicasting can be performed based on either the receiver side information established during the placement phase or the channel state information acquired via feedback.…”

“…However, such proof exploits the specific structure of the rate region of symmetric networks, and unfortunately cannot be applied to a general network setting considered here. Our current work provides a non-trivial extension of [18] to such networks. Furthermore, we show that our results can be extended in a straightforward manner to the centralized content placement [1] as well as the multi-antenna broadcast channel with state feedback.…”

Fundamental Limits of Cache-Aided Wireless BC: Interplay of Coded-Caching and CSIT Feedback

“…In this setting, whenever the requested data resides within the pre-filled caches, the data-transfer load of the backhaul link is alleviated, thus allowing for these links to be instead used for exchanging CSIT that supports interference alignment. An even more recent concurrent work can be found in [45] where Ghorbel et al studied the capacity of the cacheenabled broadcast packet erasure channel with ACK/NACK feedback. In this setting, Ghorbel et al cleverly showedinterestingly also using a retrospective type algorithm, this time by Gatzianas et al in [46] -how feedback can improve performance by informing the transmitter when to resend the packets that are not received by the intended user and which are received by unintended users, thus allowing for multicast opportunities.…”