The majority of prior coded computation works treat stragglers as erasures over an erasure channel and ignore their partial computations. The whole speed of a computation network will still be limited due to different processing speeds of worker nodes. This paper presents a novel coded scheme for this problem to effectively leverage partial stragglers. It simultaneously embeds the maximum distance separable (MDS) codes and codes in the universally decodable matrices (UDMs) into the system. By imposing constraints on coding parameters, the coefficient matrix corresponding to any first kAkBproducts of encoded submatrices from worker nodes is full rank, when two input matrices are partitioned into kAand kBblock-columns, respectively. Thus, it only requires the minimum kAkBproducts performed by worker nodes (including stragglers). Analysis results show that our scheme can achieve not only the optimal utilization of partial computations of worker nodes, but also the optimal straggler resilience capability.

This paper analyzes and explicitly constructs quasi-cyclic (QC) codes for correcting multiple bursts via matrix transformations. Our analysis demonstrates that the multiple-burst-correction capability of QC codes is determined by sub-matrices in the diagonal of their transformed parity-check matrices. By well designing these sub-matrices, the proposed QC codes are able to achieve optimal or asymptotically optimal multiple-burst-correction capability. Moreover, it proves that these codes can be QC low-density parity-check (QC-LDPC) codes, if the diagonal sub-matrices of their transformed parity-check matrices are Hadamard powers of base matrices. Analysis and simulation results show that our QC-LDPC codes perform well over not only random symbol error/erasure channels, but also burst channels.

Quantum secure direct communication (QSDC) is capable of direct confidential communications over a quantum channel, which is achieved by dispensing with the key agreement channel of the well-known quantum key distribution (QKD). However, to make QSDC a practical reality, we have to mitigate its reliance on quantum memory, its immediate communication interruption caused by eavesdropping and its low transmission reliability due to the heavy qubit losses. Hence a new QSDC protocol is proposed based on a sophisticated coded single-photon DL04 QSDC protocol to tackle the open challenges. In particular, quantum memory is dispensed with and a high-accuracy secrecy capacity estimate is derived for this protocol by conceiving dynamic joint encryption and error-control (JEEC) coding. We demonstrate that this quantum-memory-free DL04 QSDC (QMF-DL04 QSDC) protocol inches closer to the quantum channel's capacity and significantly improves the original DL04 QSDC's robustness. Moreover, a rate-compatible low-rate JEEC coding scheme is designed for the proposed framework, and the JEEC code advocated is shown to approach the secrecy capacity, despite tolerating an extremely high loss of qubits in the time-varying wiretap channel. Our simulations and experimental results demonstrate that the QMF-DL04 QSDC scheme significantly increases both the secure information rate and the communication distance of the original DL04 protocol.

Recently, several remarkable works [1]-[5] constructed regenerating codes to offer intermediate tradeoffs between storage and bandwidth. Unlike regenerating codes, this paper proposes to graft codes together to provide various such intermediate tradeoffs. It shows that the linear relations in the generator matrices of grafting codes can be transferred to those of grafted codes without any loss of reconstruction capability. A construction based on minimum storage regenerating codes shows that the resulted graftage codes may provide better tradeoffs than space-sharing and approach cut-set bounds, with the cost of fixed access of helper nodes.

This paper proposes to construct a class of multiple-burst-correction quasi-cyclic (QC) codes via matrix transformations. Due to the diagonal structure of the transformed parity-check matrix of a QC code, multiple bursts can be corrected in the transform domain. By well designing the diagonal submatrices, the constructed QC codes are able to achieve optimal or asymptotically optimal multiple-burst-correction capability. In particular, a subclass of our constructed QC codes are QC low-density parity-check (QC-LDPC) codes which also perform very well over random channels. Simulation results show that our QC-LDPC codes outperform the existing QC-LDPC codes over burst channels.

In the check node (CN) update of non-binary message-passing algorithms, each element of reliability vectors takes the same computational complexity. However, our analysis indicates that various elements in the same vector have various correct probabilities, thus have different contributions to error performance. In order to match computational complexity with correct probability, all elements in a vector are partitioned into different sets. For the extended min-sum (EMS) decoding, various strategies are applied for sets according to their correct probability. For the trellis-based EMS decoding, it is interesting that set partition only involves fixed paths, thus it does not need to search over the whole trellis of a CN. Complexity analysis and simulation results show that the proposed algorithms efficiently decode non-binary low-density parity-check codes, including ultra-sparse ones.

This paper reduces the complexity of decoding non-binary low-density parity-check (LDPC) codes by set partition. In the check node update, the input vectors are partitioned into several sets such that different elements in the virtual matrix enjoy various computational strategies. As a result, the proposed algorithm achieves high computational efficiency by setting strategies according to the correct probability of these elements. Simulation results indicate that it significantly decreases the complexity of check node update with negligible performance loss.

The weighted bit-reliability-based (wBRB) algorithm for nonbinary LDPC codes suffers certain loss of symbol-reliability. Thus, this paper enhances its soft-decision version by passing multiple symbol-reliability instead of bit-reliability. Furthermore, it demonstrates that plurality robustly indicates symbol-reliability of extrinsic information-sums. Thus, this paper enhances the hard-decision version by introducing symbol-reliability from plurality. Analysis results show that these two enhanced decoding algorithms significantly outperform the wBRB algorithm with reasonable overhead.

The traditional majority-logic decoding (MLgD) based algorithms suffer error-floors for decoding non-binary LDPC codes with small column weights. This paper presents a bit-reliability based MLgD (BRB-MLgD) algorithm with low error-floors for non-binary LDPC codes. The proposed algorithm is carried out based on the binary representations of non-binary symbols. The reliability update along each edge of the Tanner graph of a non-binary LDPC code is in terms of bits rather than symbols. Thus, its computational complexity and memory consumption are less than those of the existing MLgD based algorithms. Simulation results indicate that the proposed algorithm can significantly reduce error-floors with small performance degradation in the waterfall region.

In wireless body area networks (WBAN), energy efficiency is one of the most important issues to be addressed. In this paper, researches on efficiency optimization in WBAN are carried out. Based on the quality of service (QoS) required from each sensor node, intelligent time and power resource allocation is performed for energy saving. First, global energy minimization (GEM) model is proposed as a general target for optimization. Due to the special requirements of typical WBAN applications (e.g. health monitoring), network lifetime is defined and then handled as the objective function to be maximized. Both problems are proved to be geometric programming, which can be solved by many off the shelf solvers efficiently. Numeric results show that, compared to the sub-optimal resource allocation schemes, the proposed methods are able to improve the energy efficiency obviously. Furthermore, they also provide a performance benchmark for developing low complexity distributed algorithms in the future.