In wireless distributed storage systems, storage nodes are connected by wireless channels, which are broadcast in nature. This paper exploits this unique feature to design an efficient repair mechanism, called broadcast repair, for wireless distributed storage systems in the presence of multiple-node failures. Due to the broadcast nature of wireless transmission, we advocate a new measure on repair performance called repair-transmission bandwidth. In contrast to repair bandwidth, which measures the average number of packets downloaded by a newcomer to replace a failed node, repair-transmission bandwidth measures the average number of packets transmitted by helper nodes per failed node. The storage system we considered can undergo an unlimited number of repair rounds. We obtain an upper bound on the maximum file size that can be supported by a cut analysis of a finite graph. The achievability is shown by codes constructed over a refined information flow graph, which is unbounded. In addition, the optimal storage-bandwidth tradeoff is obtained. The performance of broadcast repair is compared both analytically and numerically with that of cooperative repair, the basic repair method for wired distributed storage systems with multiple-node failures. While cooperative repair is based on the idea of allowing newcomers to exchange packets, broadcast repair is based on the idea of allowing a helper to broadcast packets to all newcomers simultaneously. We show that broadcast repair outperforms cooperative repair, offering a better tradeoff between storage efficiency and repair-transmission bandwidth.

The classical threshold secret sharing scheme by Shamir requires high computation complexity. Many fast secret sharing schemes have been proposed to reduce the computation cost. Another problem of perfect secret sharing scheme is the large share size. Ramp sharing schemes were proposed as a solution to reduce the share size with sacrificing secrecy to some extent. This paper proposes a new ramp scheme, which is adapted from the zigzag-decodable erasure codes for data storage systems. The scheme is shown to approach a linear ramp scheme when the secret size grows to infinity. It is conceptually easy to understand, and has low computation cost, since both its encoding and decoding algorithms are based only on the XOR and bitwise-shift operations.

For a user to store data in the cloud, using services provided by multiple cloud storage providers (CSPs) is a promising approach to increase the level of data availability and confidentiality, as it is unlikely that different CSPs are out of service at the same time or collude with each other to extract information of a user. This paper investigates the problem of storing data reliably and securely in multiple CSPs constrained by given budgets with minimum cost. Previous works, with variations in problem formulations, typically tackle the problem by decoupling it into sub-problems and solve them separately. While such a decoupling approach is simple, the resultant solution is suboptimal. This paper is the first one which considers the problem as a whole and derives a jointly optimal coding and storage allocation scheme, which achieves perfect secrecy with minimum cost. The analytical result reveals that the optimal coding scheme is the nested maximum-distance-separable code and the optimal amount of data to be stored in the CSPs exhibits a certain structure. The exact parameters of the code and the exact storage amount to each CSP can be determined numerically by simple 2-D search.

The problem of storing data reliably and securely in multiple cloud storage providers (CSPs) with minimum cost is investigated. A jointly optimal coding and storage allocation scheme, which achieves perfect secrecy with minimum cost, is derived. The optimal coding scheme is shown to be the nested maximum-distance-separable code and the optimal amounts of data to be stored in the CSPs is proven to exhibit a three-level structure. The exact parameters of the code and the exact storage amount to each CSP can be determined numerically by simple one-dimensional search.

The fundamental theorem of distributed storage systems characterizes the maximum file size that can be stored with certain assumptions on file retrieval and node repair. The result is composed of two parts, namely, the min-cut bound and that the bound can be achieved by linear network code with bounded field size. The derivation of the min-cut bound is reexamined and illuminated by making an implicit step explicit. Furthermore, a simple alternative proof for the achievability of the min-cut bound is presented, which is based on the construction of the generic storage code, a restricted form of generic network code. The proof techniques in this paper are expected to be extensible to other more complex models of distributed storage systems.

The achievable outage probability of the diamond relay network under Rayleigh fading is investigated. Two existing transmission protocols are considered, namely, the Alamouti-Coded Amplify-and-Forward (ACAF) and the Alamouti-Coded Decode-and-Forward (ACDF). For ACAF, a distributed optimal power control rule for the two relays is analytically derived. Simulation results show that with this power control rule, the diversity gain of ACAF increases from one to two, and its performance approaches that of ACDF in the high signal-to-noise ratio (SNR) regime. For ACDF, a performance bound is analytically obtained: for any outage probability e, its SNR offset is bounded above by 3 dB and its e-outage rate is within 1 bit of the e-outage capacity of the diamond relay network.