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We present a novel Packet Type (PT)-based design framework for the finite-length analysis of Device-to-Device (D2D) coded caching. By the exploitation of the asymmetry in the coded delivery phase, two fundamental forms of subpacketization reduction gain for D2D coded caching, i.e., the subfile saving gain and the further splitting saving gain, are identified in the PT framework. The proposed framework features a streamlined design process which uses several key concepts including user grouping, subfile and packet types, multicast group types, transmitter selection, local/global further splitting factor, and PT design as an integer optimization. In particular, based on a predefined user grouping, the subfile and multicast group types can be determined and the cache placement of the users can be correspondingly determined. In this stage, subfiles of certain types can be potentially excluded without being used in the designed caching scheme, which we refer to as subfile saving gain. In the delivery phase, by a careful selection of the transmitters within each type of multicast groups, a smaller number of packets that each subfile needs to be further split into can be achieved, leading to the further splitting saving gain. The joint effect of these two gains results in an overall subpacketization reduction compared to the Ji-Caire-Molisch (JCM) scheme [1]. Using the PT framework, a new class of D2D caching schemes is constructed with order reduction on subpacketization but the same rate when compared to the JCM scheme.
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A New Design Framework on D2D Coded Caching with Optimal Rate and Less Subpacketizations
In this paper, we propose a new design framework on Device-to-Device (D2D) coded caching networks with optimal communication load (rate) but significantly less file subpacketizations compared to that of the well-known D2D coded caching scheme proposed by Ji, Caire and Molisch (JCM). The proposed design framework is referred to as the Packet Type-based (PTB) design, where each file is partitioned into packets according to their pre-defined types while the cache placement and user multicast grouping are based on the packet types. This leads to the so-called raw packet saving gain for the subpacketization levels. By a careful selection of transmitters within each multicasting group, a so-called further splitting ratio gain of the subpacketizatios can also be achieved. By the joint effect of the raw packet saving gain and the further splitting ratio gain, an order-wise subpacketization reduction can be achieved compared to the JCM scheme while preserving the optimal rate. In addition, as the first time presented in the literature according to our knowledge, we find that unequal subpacketizaton is a key to achieve subpacketization reductions when the number of users is odd. As a by-product, instead of directly translating shared link caching schemes to D2D caching schemes, at least for the sake of subpackeitzation, a new design framework is indeed needed.
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- PAR ID:
- 10188065
- Date Published:
- Journal Name:
- 2020 IEEE International Symposium on Information Theory (ISIT)
- Page Range / eLocation ID:
- 1699 to 1704
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/ISIT44484.2020.9174215
