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2017 Vol. 14, No. 8
Published: 10 August 2017

Guest Editorial
SIGNAL PROCESSING FOR COMMUNICATIONS
COMMUNICATIONS THEORIES & SYSTEMS
NETWORKS & SECURITY
 
   
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       Guest Editorial

Construction of Short-Block Nonbinary LDPC Codes Based on Cyclic Codes Hot!

Hengzhou Xu, Baoming Bai, Min Zhu, Bo Zhang, Yulong Zhang
China Communications, 2017, 14(8): 1-9
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In this paper, we focus on short-block nonbinary LDPC (NB-LDPC) codes based on cyclic codes. Based on Tanner graphs’ isomorphism, we present an efficient search algorithm for finding non-isomorphic binary cyclic LDPC codes. Notice that the parity-check matrix H of the resulting code is square and not of full rank, and its row weight and column weight are the same. By replacing the ones in the same column of H with a nonzero element of finite fields GF(q), a class of NB-LDPC codes over GF(q) is obtained. Numerical results show that the constructed codes perform well over the AWGN channel and have fast decoding convergence. Therefore, the proposed NB-LDPC codes provide a promising coding scheme for low-latency and high-reliability communications.
       Guest Editorial

LDPC Coding Scheme for Improving the Reliability of Multi-Level-Cell NAND Flash Memory in Radiation Environments

Guangjun Ge, Liuguo Yin
China Communications, 2017, 14(8): 10-21
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Utilizing commercial off-the-shelf (COTS) components in satellites has received much attention due to the low cost. However, commercial memories suffer severe reliability problems in radiation environments. This paper studies the low-density parity-check (LDPC) coding scheme for improving the reliability of multi-level-cell (MLC) NAND Flash memory in radiation environments. Firstly, based on existing physical experiment works, we introduce a new error model for heavy-ion irradiations; secondly, we explore the optimization of writing voltage allocation to maximize the capacity of the storage channel; thirdly, we design the degree distribution of LDPC codes that is specially suitable for the proposed model; finally, we propose a joint detection-decoding scheme based on LDPC codes, which estimates the storage channel state and executes an adaptive log-likelihood ratio (LLR) calculation to achieve better performance. Simulation results show that, compared with the conventional LDPC coding scheme, the proposed scheme may almost double the lifetime of the MLC NAND Flash memory in radiation environments.
       Guest Editorial

Polar Codes for Soft Decode-and-Forward in Half-Duplex Relay Channels

Fangliao Yang, Kai Niu, Chao Dong, Baoyu Tian
China Communications, 2017, 14(8): 22-32
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Soft decode-and-forward (DF) can combine the advantages of both amplify-and-forward and hard DF in relay channels. In this paper, we propose a low-complexity soft DF scheme based on polar codes, which features two key techniques: a low-complexity cyclic redundancy check (CRC) aided list successive cancellation (CALSC) decoder and a soft information calculation method. At the relay node, a low-complexity CALSC decoder is designed to reduce the computational complexity by adjusting the list size according to the reliabilities of decoded bits. Based on the path probability metric of the CALSC decoder, we propose a method to compute the soft information of the decoded bits in CALSC. Simulation results show that our proposed scheme outperforms the soft DF based on low-density parity-check codes and the soft DF with belief propagation or soft cancellation decoder, especially in the case when the source-relay channel is at the high signal-to-ratio region.
       Guest Editorial

Low Complexity SOVA for Turbo Codes

Ruilin Pei, Zulin Wang, Qin Huang, Jiaqing Wang
China Communications, 2017, 14(8): 33-40
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Recently, trimming Soft-output Viterbi algorithm (T-SOVA) has been proposed to reduce the complexity of SOVA for Turbo codes. In its first stage, a dynamic algorithm, lazy Viterbi algorithm, is used to indicate the minimal metric differences which brings obstacle on hardware implementation. This paper proposes a Viterbi algorithm (VA) based T-SOVA to facilitate hardware implementation. In the first stage of our scheme, a modified VA with regular structure is used to find the maximum likelihood (ML) path and calculate the metric differences. Further, local sorting is introduced to trim the metric differences, which reduces the complexity of trimming operation. Simulation results and complexity analysis show that VA based T-SOVA performs as well as lazy VA based T-SOVA and is easier to be applied to hardware implementation.
       Guest Editorial

Design of a (480,240) CMOS Analog Low-Density Parity-Check Decoder

Hao Zheng, Zhe Zhao, Xiangming Li, Hangcheng Han
China Communications, 2017, 14(8): 41-53
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Digital low-density parity-check (LDPC) decoders can hardly meet the power-limits brought by the new application scenarios. The analog LDPC decoder, which is an application of the analog computation technology, is considered to have the potential to address this issue to some extent. However, due to the lack of automation tools and analog stopping criteria, the analog LDPC decoders suffer from costly handcraft design and additional decoding delay, and are not feasible to practical applications. To address these issues, a decoder architecture using reusable building blocks is designed to lower the handcraft design, and a probability stopping criterion that is specially designed for analog decoder is further planned and implemented to reduce the decoding delay. Then, a (480,240) CMOS analog LDPC decoder is designed and fabricated in a 0.35-μm CMOS technology. Experimental results show that the decoder prototype can achieve 50Mbps throughput when the power consumption is about 86.3mW, and the decoding delay can be reduced by at most 93% compared with using the preset maximum decoding delay in existing works.
       COMMUNICATIONS THEORIES & SYSTEMS

k-NN Based Bypass Entropy and Mutual Information Estimation for Incremental Remote-Sensing Image Compressibility Evaluation

Xijia Liu, Xiaoming Tao, Yiping Duan, Ning Ge
China Communications, 2017, 14(8): 54-62
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Incremental image compression techniques using priori information are of significance to deal with the explosively increasing remote-sensing image data. However, the potential benefits of priori information are still to be evaluated quantitatively for efficient compression scheme designing. In this paper, we present a k-nearest neighbor (k-NN) based bypass image entropy estimation scheme, together with the corresponding mutual information estimation method. Firstly, we apply the k-NN entropy estimation theory to split image blocks, describing block-wise intra-frame spatial correlation while avoiding the curse of dimensionality. Secondly, we propose the corresponding mutual information estimator based on feature-based image calibration and straight-forward correlation enhancement. The estimator is designed to evaluate the compression performance gain of using priori information. Numerical results on natural and remote-sensing images show that the proposed scheme obtains an estimation accuracy gain by 10% compared with conventional image entropy estimators. Furthermore, experimental results demonstrate both the effectiveness of the proposed mutual information evaluation scheme, and the quantitative incremental compressibility by using the priori remote-sensing frames.
       COMMUNICATIONS THEORIES & SYSTEMS

An Ant Colony Algorithm Based on Cross-Layer Design for Routing and Wavelength Assignment in Optical Satellite Networks

Guoli Wen, Qi Zhang, Houtian Wang, Qinghua Tian, Ying Tao
China Communications, 2017, 14(8): 63-75
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This paper introduces an ant colony routing and wavelength assignment algorithm based on cross-layer design (CL-ACRWA), which can overcome the adverse effects of Doppler wavelength shift on data transmission in optical satellite networks. Firstly, a cross-layer optimization model is built, which considers the Doppler wavelength shift, the transmission delay as well as wavelength-continuity constraint. Then an ant colony algorithm is utilized to solve the cross-layer optimization model, resulting in finding an optimal light path satisfying the above constraints for every connection request. The performance of CL-ACRWA is measured by the communication success probability, the convergence property and the transmission delay. Simulation results show that CL-ACRWA performs well in communication success probability and has good global search ability as well as fast convergence speed. Meanwhile, the transmission delay can meet the basic requirement of real-time transmission of business.
       COMMUNICATIONS THEORIES & SYSTEMS

Resource Allocation for Two-Way Amplify and Forward OFDM Relay Networks

Zhijun Liu, Xiaofeng Tao, Waheed ur Rehman
China Communications, 2017, 14(8): 76-82
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Physical-layer network coding (PNC) promises substantial theoretical gain to achieve the maximum system throughput in cooperative relay transmission. However, with the increasing global warming, how to reduce power consumption while satisfy system throughput requirement is becoming a vital issue. In this paper, we investigate energy-efficiency resource allocation (RA) based on PNC with amplify-and-forward (AF) protocol in orthogonal frequency division multiple (OFDM) bidirectional transmission. To minimize the overall transmit power consumption with required system throughput requirement, we consider joint subcarriers and power allocation and formulate the objective task into a constrained optimization problem where the best relay node is selected to minimize total transmit power. The closed form optimization power allocation solutions are acquired by analytical derivation. Based on derivation, we propose a novel optimal energy-efficient power allocation (OE-PA). Numerical results are given to evaluate the performance of the derived scheme as compared to other schemes and show that our scheme has significant improvement to energy saving.
       COMMUNICATIONS THEORIES & SYSTEMS

Energy Efficient Resource Allocation in Timesharing Multiuser Systems with Hybrid Energy Harvesting Transmitter

Jinming Hu, Wei Heng*, Guodong Zhang, Xiang Li
China Communications, 2017, 14(8): 83-92
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An energy efficient resource allocation scheme in timesharing multiuser system with a hybrid energy harvesting transmitter is studied in this paper. Specially, the operation energy of system is supplied by constant energy and energy harvesting, which harvests energy from external environment. Our goal is to maximize the energy efficiency of timesharing multiuser systems by considering jointly allocation of transmission time and power control in an off-line manner. The original nonconvex objective function is transformed into convex optimization problem via the fractional programming approach. Then, we solve the convex problem by Lagrange dual decomposition method. Simulation results show that the proposed energy efficient resource allocation scheme has a better performance than the scheme which decomposes optimization problem into two parts (power allocation, time allocation) to solve iteratively.
       COMMUNICATIONS THEORIES & SYSTEMS

Frequency Offset Compensation for Satellite Communication System with CE-OFDM

Gaofeng Cui, Cheng Wang, Weidong Wang, Yinghai Zhang
China Communications, 2017, 14(8): 93-104
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Constant envelope orthogonal frequency division multiplexing (CE-OFDM) is a waveform that can achieve 0dB peak-to-average power ratio and avoid the signal distortion caused by the nonlinear power amplifier. However, the carrier frequency offset (CFO) in CE-OFDM systems can cause errors at phase unwrapper module. In this paper, a CFO estimation scheme is proposed for CE-OFDM in satellite communication system. As the null subcarrier is inherent in the conjugate symmetric symbol structure at the transmitter, the proposed scheme uses the null subcarrier as prior information to estimate the CFO at the receiver. The ideal estimation range of normalized CFO is obtained by mathematical analysis. Simulation results show that the proposed scheme can estimate the CFO accurately under additive white Gaussian noise (AWGN) channel and multipath fading channel, especially for moderate and high signal-to-noise ratio (SNR).
       NETWORKS & SECURITY

Intelligent Resources Management System Design in Information Centric Networking

Hengyang Zhang, Shixiang Zhu, Renchao Xie, Tao Huang, Yunjie Liu
China Communications, 2017, 14(8): 105-123
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Information centric networking (ICN) is a new network architecture that is centred on accessing content. It aims to solve some of the problems associated with IP networks, increasing content distribution capability and improving users’ experience. To analyse the requests’ patterns and fully utilize the universal cached contents, a novel intelligent resources management system is proposed, which enables efficient cache resource allocation in real time, based on changing user demand patterns. The system is composed of two parts. The first part is a fine-grain traffic estimation algorithm called Temporal Poisson traffic prediction (TP2) that aims at analysing the traffic pattern (or aggregated user requests’ demands) for different contents. The second part is a collaborative cache placement algorithm that is based on traffic estimated by TP2. The experimental results show that TP2 has better performance than other comparable traffic prediction algorithms and the proposed intelligent system can increase the utilization of cache resources and improve the network capacity.
       NETWORKS & SECURITY

An Alternative-Service Recommending Algorithm Based on Semantic Similarity

Kun Guo, Yonghua Li, Yueming Lu
China Communications, 2017, 14(8): 124-136
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With the development of the Internet of Things (IoT), people’s lives have become increasingly convenient. It is desirable for smart home (SH) systems to integrate and leverage the enormous information available from IoT. Information can be analyzed to learn user intentions and automatically provide the appropriate services. However, existing service recommendation models typically do not consider the services that are unavailable in a user’s living environment. In order to address this problem, we propose a series of semantic models for SH devices. These semantic models can be used to infer user intentions. Based on the models, we proposed a service recommendation probability model and an alternative-service recommending algorithm. The algorithm is devoted to providing appropriate alternative services when the desired service is unavailable. The algorithm has been implemented and achieves accuracy higher than traditional Hidden Markov Model (HMM). The maximum accuracy achieved is 68.3%.
       NETWORKS & SECURITY

Multi-Domain Collaborative Recommendation with Feature Selection

Lizhen Liu, Junjun Cui, Wei Song, Hanshi Wang
China Communications, 2017, 14(8): 137-148
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Collaborative filtering, as one of the most popular techniques, plays an important role in recommendation systems. However, when the user-item rating matrix is sparse, its performance will be degenerate. Recently, domain-specific recommendation approaches have been developed to address this problem. The basic idea is to partition the users and items into overlapping domains, and then perform recommendation in each domain independently. Here, a domain means a group of users having similar preference to a group of products. However, these domain-specific methods consisting of two sequential steps ignore the mutual benefit of domain segmentation and recommendation. Hence, a unified framework is presented to simultaneously realize recommendation and make use of the domain information underlying the rating matrix in this paper. Based on matrix factorization, the proposed model learns both user preferences of multiple domains and preference selection vectors to select relevant features for each group of products. Besides, local context information is utilized from the user-item rating matrix to enhance the new framework. Experimental results on two widely used datasets, e.g., Ciao and Epinions, demonstrate the effectiveness of our proposed model.
       SIGNAL PROCESSING FOR COMMUNICATIONS

Physical Layer Security in MIMO Wiretap Channels with Antenna Correlation

Gangcan Sun, Zhuo Han, Jingbo Jiao, Zhongyong Wang, Dagang Wang
China Communications, 2017, 14(8): 149-156
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To investigate the impact of antenna correlation on secrecy performance in MIMO wiretap channels with Nakagami-m fading, the expressions of secrecy outage probability and positive secrecy probability were derived. Diversity order and array gain were also achieved for further insight. The study was based on the information theory that physical layer security can be guaranteed when the quality of the main channel is higher than that of the eavesdropper’s channel. Monte Carlo simulations well validated the numerical results of analytic expressions. It was shown that antenna correlation is detrimental to secrecy performance when average SNR of the main channel is at medium and high level. Interestingly, when average SNR of the main channel reduces to low level, the effect of antenna correlation becomes beneficial to secrecy performance.
       SIGNAL PROCESSING FOR COMMUNICATIONS

Relaying Strategy Based on Estimated Information for Multi-Antenna Cooperative Networks

Shuangshuang Han, Peng Zhang, Feijin Shi, Fei-Yue Wang
China Communications, 2017, 14(8): 157-165
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A sphere-based list forwarding scheme for multiple-input multiple-output (MIMO) relay networks is proposed and analyzed. Firstly, an estimate forwarding (EF) method is proposed, which forwards the minimum mean squared error (MMSE) estimate of the source data to the destination. Since it performs like amplify-and-forward (AF) and decode-and-forward (DF) for the low and high signal-to-noise ratio (SNR) regions, respectively, the EF relay thus outperforms conventional AF and DF across all SNRs without the need for switching algorithms for different SNRs. Because computational complexity is however high for relays with a large number of antennas (large MIMO) and/or high order constellations, list EF for large MIMO relay networks is proposed. It computes a list sphere decoder based MMSE estimate and retains the advantages of the exact EF relay at a negligible performance loss. The proposed list EF could offer a flexible trade-off between the performance and computational complexity.
       SIGNAL PROCESSING FOR COMMUNICATIONS

On Design of Conjugated Transmission Scheme for FBMC/OQAM Systems with Interference Cancellation

Chuanxue Jin, Su Hu, Yixuan Huang, Fan Li, Jing Zhang, Shiyong Ma
China Communications, 2017, 14(8): 166-175
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Compared to OFDM systems with cyclic prefix, filterbank multicarrier with offset quadrature amplitude modulation (FBMC/OQAM) system is considered as an alternative technology for next generation wireless communication systems. However, FBMC systems suffer from intrinsic imaginary interference caused by the real-field orthogonality destruction when passing through complex-valued fading channels. By analyzing the transmultiplexer’s response of FBMC/OQAM systems, in this paper, a simple conjugated transmission scheme is proposed for FBMC/OQAM systems. Following the specific conjugation design, the intrinsic imaginary interference including the intrinsic inter-symbol and the inter-carrier interference can be eliminated at the receiver side through linear signal processing operation. Meanwhile, the proposed conjugated transmission scheme is able to obtain extra linear combination diversity gains for improving the systematic performance of FBMC/OQAM. Simulation results show that the proposed scheme is more efficient than conventional methods, especially in practical application scenarios with large Doppler spread caused by high-speed movement.
       SIGNAL PROCESSING FOR COMMUNICATIONS

Decode-and-Forward Relay Based Bidirectional Wireless Information and Power Transfer

Ruirui Chen, Hailin Zhang
China Communications, 2017, 14(8): 176-183
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In this paper, we propose the decode-and-forward (DF) based bidirectional wireless information and power transfer (BWIPT) in two-hop relay systems, where the bidirectional relay can decode and forward information from the user to the access point (AP), and assist the wireless power transfer from the AP to the user. To maximize the information rate from the user to the AP, we derive the closed form expression of the optimal power splitting (PS) factor, and the time allocation scheme to obtain the optimal time switching (TS) factor. Simulation results show that for both PS and TS protocols, the proposed DF based bidirectional relay systems can improve the information rate as compared with the amplify-and-forward (AF) based bidirectional relay systems.
       SIGNAL PROCESSING FOR COMMUNICATIONS

Time-Frequency Bandwidth Product Estimation of Sinusoidal Non-Linear Chirp Keying Scheme

Zhiguo Sun, Xiaoyan Ning, Danyang Tian
China Communications, 2017, 14(8): 184-194
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Sine Non-linear Chirp Keying (SNCK) is a kind of high-efficient modulation scheme, which provides a potential new beamforming method in communication and radar systems. It has been proved to have advantages in some parameter estimation issues over conventional modulation schemes. In this paper, a novel transform termed as Discrete Sinusoidal Frequency Modulation transform (DSFMT) is proposed. Then, the DSFMT of SNCK signal is deduced and classified into three types, based on which, the time-bandwidth product is estimated by the proposed algorithm. Simulation results show that the noise has a significant impact on the localization of the peak value and the time-bandwidth product can be estimated by using local ratio values when SNR≥5db.
 
 
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