| 1. |
- Kumar, Siddhartha, 1991, et al.
(författare)
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Code Constructions for Distributed Storage With Low Repair Bandwidth and Low Repair Complexity
- 2018
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Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 66:12, s. 5847-5860
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Tidskriftsartikel (refereegranskat)abstract
- We present the construction of a family of erasure correcting codes for distributed storage that achieve low repair bandwidth and complexity at the expense of a lower fault tolerance. The construction is based on two classes of codes, where the primary goal of the first class of codes is to provide fault tolerance, while the second class aims at reducing the repair bandwidth and repair complexity. The repair procedure is a twostep procedure where parts of the failed node are repaired in the first step using the first code. The downloaded symbols during the first step are cached in the memory and used to repair the remaining erased data symbols at minimal additional read cost during the second step. The first class of codes is based on MDS codes modified using piggybacks, while the second class is designed to reduce the number of additional symbols that need to be downloaded to repair the remaining erased symbols. We numerically show that the proposed codes achieve better repair bandwidth compared to MDS codes, codes constructed using piggybacks, and local reconstruction/Pyramid codes, while a better repair complexity is achieved when compared to MDS, Zigzag, Pyramid codes, and codes constructed using piggybacks.
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| 2. |
- Pedersen, Jesper, 1984, et al.
(författare)
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Dynamic Coded Caching in Wireless Networks
- 2021
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Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 69:4, s. 2138-2147
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Tidskriftsartikel (refereegranskat)abstract
- We consider distributed and dynamic caching of coded content at small base stations (SBSs) in an area served by a macro base station (MBS). Specifically, content is encoded using a maximum distance separable code and cached according to a time-to-live (TTL) cache eviction policy, which allows coded packets to be removed from the caches at periodic times. Mobile users requesting a particular content download coded packets from SBSs within communication range. If additional packets are required to decode the file, these are downloaded from the MBS. We formulate an optimization problem that is efficiently solved numerically, providing TTL caching policies minimizing the overall network load. We demonstrate that distributed coded caching using TTL caching policies can offer significant reductions in terms of network load when request arrivals are bursty. We show how the distributed coded caching problem utilizing TTL caching policies can be analyzed as a specific single cache, convex optimization problem. Our problem encompasses static caching and the single cache as special cases. We prove that, interestingly, static caching is optimal under a Poisson request process, and that for a single cache the optimization problem has a surprisingly simple solution.
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| 3. |
- Pedersen, Jesper, 1984, et al.
(författare)
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Optimizing MDS Coded Caching in Wireless Networks with Device-to-Device Communication
- 2019
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Ingår i: IEEE Transactions on Wireless Communications. - 1558-2248 .- 1536-1276. ; 18:1, s. 286-295
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Tidskriftsartikel (refereegranskat)abstract
- We consider the caching of content in the mobile devices in a dense wireless network using maximum distance separable (MDS) codes. We focus on an area, served by a base station (BS), where mobile devices move around according to a random mobility model. Users requesting a particular file download coded packets from caching devices within a communication range, using device-to-device communication. If additional packets are required to decode the file, these are downloaded from the BS. We analyze the device mobility and derive a good approximation of the distribution of caching devices within the communication range of mobile devices at any given time. We then optimize the MDS codes to minimize the network load under a cache size constraint and show that using optimized MDS codes results in significantly lower network load compared to when caching the most popular files. We further show numerically that caching coded packets of each file on all mobile devices, i.e., maximal spreading, is optimal.
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