The Enterprise File Sync and Share (EFSS) is one of the most important services to provide enterprises' employees with cloud file sync, share, and collaboration services. To take enterprises' concerns into account, such as security, privacy, compliance, and regulation, the existing EFSS solutions are either using private (on-premise) or hybrid cloud service model to provide their services. They usually emphasize that files stored in the solutions are encrypted on transfer and at rest and events occurred in the service are logged as the audit trail. However, support of data encryption and audit trail are not capable of protecting enterprise sensitive data from not well addressed security issues of the EFSS service. The security issues, including employee privacy protection, management of share links and synchronized cloud files, and the secure enterprise directory integration, are pointed out in this article. To address these issues, this work proposes and develops a scalable Secure EFSS service which can be deployed on the on-premise Open Stack cloud infrastructure to securely provide employees with EFSS service. Designs of an integrated security approach are introduced in this article, including data and metadata isolations, Distinct Share Link utility, encryption key management for personal and shared files, sandbox-based cloud file synchronization, and out-of-band authentication method.

A bi-directional fiber-radio network based on spectral-amplitude-coding (SAC) optical code-division multiple access (OCDMA) with interference elimination is proposed. This scheme uses hybrid ring/star topology with partial self-healing ability and its key feature is the elimination from the addition of direct current signal before the optical encoding process. Therefore, as compared to the previous SAC-based fiber-radio networks, both power efficiency and carrier-to-noise ratio at the decoder of the proposed scheme are improved. In addition, simple encoding/decoding structures with small sizes in the control base station is proposed to reduce the cost of todays mobile radio networks with a large number of remote base stations.

One approach for designing the one-coincidence sequence (OCS) low-density parity-check (LDPC) codes of large girth is investigated. These OCS-LDPC codes are quasi-cyclic, and their parity-check matrices are composed of circulant permutation matrices. Generally, the cycle structures in these codes are determined by the shift values of circulant permutation matrices, and the existence of cycles in the corresponding Tanner graph is governed by certain cycle-governing equations (CGEs). Therefore, finding the proper shift values is the key point to increase the girth of these codes. In this paper, we provide an effective method to systematically find out the CGEs for these codes of girth 6, 8, and 10, respectively. Then, one less computation-intensive algorithm is used to generate the proper shift values for constructing the OCS-LDPC codes of large girth. Simulation results show that significant gains in signal-to-noise ratio over an additive white-Gaussian noise channel can be achieved by increasing the girth of the OCS-LDPC codes.

One fiber radio network based on optical codedivision multiple access is proposed. This scheme has ring topology with self-healing ability and allows bi-directional communications between control base station and the remote base stations (RBSs). Two code families are proposed for this scheme and the corresponding correlation properties can be used for interference elimination. As compared to the conventional codes used in the spectral-amplitude-coding scheme, they not only have better carrier-to-noise ratio (CNR) in the decoder, but also alleviate the influence of splitting loss for the broadcasting of RBSs' signal. In addition, the encoding/decoding devices in the RBSs have smaller sizes than that of conventional codes. Thus the complexity and cost of RBSs are reduced and a large number of RBSs is allowed to deploy for future low power radio mobile communications.

In this paper the improved versions of quadratic congruence (QC) codes for cardinality enlargement are proposed for spectral-amplitude coding (SAC) optical code-division multiple-access (OCDMA) network. These codes can adopt two-code keying for performance enhancement and the interference can be eliminated in the decoder by our interference elimination scheme proposed previously. In addition, to mitigate the cardinality reduction in the two-code keying scheme, hybrid schemes using QC and/or stuffed QC (SQC) codes for differentiated service provision are proposed. These two code families are capable of using compact encoders and decoders for the application of passive optical networks.

A new two-dimensional frequency/spatial code for spectral-amplitude coding a optical code-division multiple-access system is proposed. The corresponding coder/decoder pairs are based on the tunable fiber-Bragg gratings cooperating with optical splitters/combiners, and multiple-access interference can be eliminated through the proposed decoding mechanism. For the performance analysis, the effects of phase-induced intensity noise, shot noise, and thermal noise are considered simultaneously. Bit-error rate (BER) performance is compared with that of the former system using M-matrix codes. It is shown that the system using these new code matrices not only maintains most advantages of the former one, but also allows larger number of active users under a given BER

Two codeword families and the corresponding encoder/decoder schemes are present for spatial/frequency optical code-division multiple-access communications. These 2-D codewords have multiple weights per row and can be encoded/decoded via compact hardware. With the proposed decoding mechanism, the intended user will reject interfering users and multiple-access interference is fully eliminated. In addition, the power of the same wavelength contributed by all interfering codewords is split and detected by distinct photodiodes in the decoder. Thus the performance degradation due to the beat noise arising in the photodetecting process is improved, as compared with the traditional 1-D coding scheme, and a larger number of active users is supported under a given bit-error rate.

A fiber Bragg grating (FBG) encoder/decoder scheme based on correlation subtractions of nearly orthogonal M-sequence codes is presented. With proper coder design, a receiver can reject interfering users and obtain quasi-orthogonality between optical code-division multiple-access (CDMA) users in the network. However, optical CDMA networks may be degraded by multiple-access interference (MAI) due to nonflattened incoherent sources and nonideal FBG coders. A compensating module is therefore proposed to compensate for such MAI effects. As a result, the MAI effects induced by nonideal FBG coders can be perfectly eliminated by the compensating module. With spectral width reduction on the incoherent source, the scheme can partly compensate the MAI effects induced by nonflattened sources and further reduce the average error probability in the system performance.