![]() ![]() Majority of existing works however, assume the presence of replicated databases, each storing all the K messages. PRIVATE CACHE TYPE DOWNLOADThere has been significant recent progress on understanding fundamental information-theoretic limits of PIR, and in particular the download cost of PIR for several variations. ![]() Private information retrieval (PIR) allows a user to retrieve a desired message out of K possible messages from N databases without revealing the identity of the desired message. The product design embeds the well-known Sun-Jafar PIR scheme into coded caching, in order to benefit from the coded caching gain while preserving the privacy of the users’ demands. In addition, the product design can achieve the optimal load when the cache memory is large enough. First, we characterize the optimal memory-load trade-off for a system with N = 2 databases, K = 2 messages and K u = 2 users demanding distinct messages Second, a product design with order optimality guarantee is proposed. Besides the formulation of the MuPIR problem, the contribution of this paper more » is two-fold. ![]() The goal is to find the optimal memory-load trade-off while preserving the demand privacy. The load of this problem is defined as the average number of downloaded bits per desired message bit. Privacy of the users’ demands requires that any individual database can not learn anything about the demands of the users. This paper formulates the cache-aided multi-user Private Information Retrieval (MuPIR) problem, including K u cache-equipped users, each of which wishes to retrieve a desired message efficiently from N distributed databases with access to K independent messages. Computer-aided investigation also shows that the proposed schemes are optimal in general when N=2,3. We prove that the proposed scheme is optimal if the cache placement is uncoded (i.e., users directly cache a subset of the library bits). In this paper, for the MuPIR problem with more » K=2 messages, Ku=2 users and N≥2 databases, we provide achievability for the memory-load pairs (N−12N,N+1N) and (2(N−1)2N−1,N+12N−1) by constructing specific achievable schemes based on the novel idea of Private Cache-aided Interference Alignment (PCIA). The goal is to find the optimal memory-load trade-off under the constraint of user demand privacy, which ensures that any individual database learns nothing about the demands of the users. The communication load of this problem is defined as the total number of bits downloaded (normalized by the message length) by the users. In the problem of cache-aided Multiuser Private Information Retrieval (MuPIR), a set of K u cache-aided users wish to download their desired messages from a set of N distributed non-colluding databases each holding a library of K independent messages. Computer-aided investigation also shows that the proposed schemes are optimal in general when N = 2, 3. In this paper, for the MuPIR problem with K = 2 messages, K u = 2 users and N ≥ 2 databases, we provide achievability for the memory-load pairs (N-1/2N, N+1/N) and(2(N-1)/2N-1,N+1/2N-1) by constructing specific achievable schemes based on the novel idea of Private Cacheaided Interference Alignment (PCIA). In the problem of cache-aided Multiuser Private Information Retrieval (MuPIR), a set of Ku cache-aided users wish to download their desired messages from a set of N distributed non-colluding databases each holding a library of K independent messages. ![]()
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