Rate-Memory Trade-off for Multi-Access Coded Caching With Uncoded Placement
| Autor: | Kota Srinivas Reddy, Nikhil Karamchandani |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
FOS: Computer and information sciences
Discrete mathematics 060102 archaeology Computer science Information Theory (cs.IT) Computer Science - Information Theory 020206 networking & telecommunications 06 humanities and the arts 02 engineering and technology Upper and lower bounds Computer Science - Information Retrieval Computer Science - Distributed Parallel and Cluster Computing Server FOS: Mathematics 0202 electrical engineering electronic engineering information engineering Mathematics - Combinatorics 0601 history and archaeology Distributed Parallel and Cluster Computing (cs.DC) Combinatorics (math.CO) Electrical and Electronic Engineering Multi access Algorithm Information Retrieval (cs.IR) |
| Zdroj: | ISIT |
| ISSN: | 1558-0857 0090-6778 |
| DOI: | 10.1109/tcomm.2020.2980817 |
| Popis: | We study a multi-access variant of the popular coded caching framework, which consists of a central server with a catalog of $N$ files, $K$ caches with limited memory $M$, and $K$ users such that each user has access to $L$ consecutive caches with a cyclic wrap-around and requests one file from the central server's catalog. The server assists in file delivery by transmitting a message of size $R$ over a shared error-free link and the goal is to characterize the optimal rate-memory trade-off. This setup was studied previously by Hachem et al., where an achievable rate and an information-theoretic lower bound were derived. However, the multiplicative gap between them was shown to scale linearly with the access degree $L$ and thus order-optimality could not be established. A series of recent works have used a natural mapping of the coded caching problem to the well-known index coding problem to derive tighter characterizations of the optimal rate-memory trade-off under the additional assumption that the caches store uncoded content. We follow a similar strategy for the multi-access framework and provide new bounds for the optimal rate-memory trade-off $R^*(M)$ over all uncoded placement policies. In particular, we derive a new achievable rate for any $L \ge 1$ and a new lower bound, which works for any uncoded placement policy and $L \ge K/2$. We then establish that the (multiplicative) gap between the new achievable rate and the lower bound is at most $2$ independent of all parameters, thus establishing an order-optimal characterization of $R^*(M)$ for any $L\ge K/2$. This is a significant improvement over the previously known gap result, albeit under the restriction of uncoded placement policies. Finally, we also characterize $R^*(M)$ exactly for a few special cases. Accepted in Transactions on Communications. Preliminary works appeared and presented in SPCOM and ISIT |
| Databáze: | OpenAIRE |
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