LDPC coded DFT/DCT-spread SC-FDMA for image communication: A compressed sensing approach

A compressed sensing (CS)-based detector is proposed for the low-density parity-check (LDPC) coded single carrier frequency division multiple access (SC-FDMA) scheme. The proposed CS-based detector can be employed at the receiver of LDPC-coded SC-FDMA systems for efficient image communications over vehicular channels. The proposed detector employs a suitable sparse recovery algorithm. We have considered both the discrete Fourier transform (DFT)-based and the discrete cosine transform (DCT)-based SC-FDMA for mitigating the channel-induced dispersion at a low peak to average power ratio (PAPR). Additionally, both the linear equalizer (LE) and the decision feedback equalizer (DFE)-based SC-FDMA have been considered for image communication. The performance of the proposed technique is investigated using a number of image quality metrics. The qualities of the received images are also compared visually. The complexity of the proposed detector and that of the benchmark detectors are quantified. Furthermore, the performance and the complexity of the proposed system using some of the sparse recovery techniques are investigated and compared. Our simulations demonstrate that LDPC coded SC-FDMA using the compressed sampling matching pursuit (CoSaMP)-based CS detector can significantly improve the performance of image communication over vehicular channels.     

Variable TDMA MAC Protocol For WDM EPON

A MAC(Media Access Control) protocol, one of the most important technologies for an EPON(Ethernet Passive Optical Network), contains a scheduling algorithm to avoid collisions in shared links and assigns an effective bandwidth when ONUs (Optical Network Units) transfer signals upward. The current paper proposes a MAC Protocol that operates a TDMA(Time method with a variable slot assignment to overcome short of bandwidth using by the number of n wavelength., the next generation access network. To verify the above, the current study also implements an EPON model using OPNET as the simulation tool.     

An efficient and secure authentication scheme based on NTRU for 10G ethernet passive optical

Ten gigabit ethernet passive optical network (10G EPON),which is viewed by many as an attractive solution to deliver very high-speed broadband access, is widely deployed in some data transmission areas with confusing security issues such as eavesdrop and masquerade caused by its point-to-multi-point topology. To solve the security problems, a new authentication scheme based on NSS signature algorithm using Hash is proposed. It possesses perfect mutual authentication of ONUs and OLTs as well as embedded session key. Besides, our new scheme can provide lower power dissipation, lower computing cost and better security attributes when comparing with RSA, ECC, and ElGamal in the literature.     

Improving quality of service in four-channel WDM ethernet passive optical network

Energy-efficiency and green communications have become dominant topics related to access network implementation, since their energy consumption is a major contributor of energy consumption within the Internet. In this paper we analyze an implementation of a new energy-efficient dynamic bandwidth algorithm in a four-channel Wavelength Division Multiplexing Ethernet Passive Optical Network (WDM EPON), in which wavelength assignments take place per service class and not per Optical Network Unit (ONU). The improved Dynamic Bandwidth Allocation (DBA) algorithm introduces independent bandwidth allocation for each wavelength, which results in efficient bandwidth management and utilization. The mathematical model for new DBA algorithm is described, as are changes to the Multi-Point Control Protocol (MPCP), necessary for its implementation. The obtained results show that the redefined DBA algorithm improves Key Performance Indicators (KPIs) and as a consequently enables delivery of enhanced services to end-users. Significant energy savings are achieved without Quality of Service (QoS) degradation, and without network or equipment architecture changes.     

Secure authentication scheme for 10 Gbit/s Ethernet passive optical networks

With the development of access network, 10G EPON has gained more and more attention. As its topology structure is point-to-multi-point and the downstream data is broadcasted, it will suffer from eavesdropping and masquerading attack. To eliminate these safety threats, this paper proposes an integrated security scheme including a bilateral authentication method and an encryption algorithm combined with one-way hash function. The authentication method can verify OLT and ONU during the registration process, preventing illegal users joining the network, and safely establish a secret key used for encrypting as well. The proposed scheme's security is based on the computational Diffie–Hellman assumption and the target collision resistant hash functions. The simulation results indicate that this mechanism is more suitable for practical use.     

Bandwidth Allocation Method by Service for WDM EPON

A WDM(Wavelength Division Multiplexing) EPON(Ethernet Passive Optical Network) is an economical and efficient access network that has attracted significant research attention in recent years. A MAC(Media Access Control) Protocol of PON is based on TDMA(Time Division Multiple Access) basically, we can classify this protocol into a fixed length slot assignment method suitable for leased line supporting Qos(Quality of Service) and a variable length slot assignment method suitable for LAN/MAN with the best efforts. In this paper, we present bandwidth allocation method by service for WDM EPON and verify this method by simulation results.     

Adaptive dynamic bandwidth allocation algorithm supporting multi-services over Ethernet passive optical networks

In order to ensure fairness of each optical networks unit (ONU) in access network and meet quality of service (QoS) requirements of differentiated service such as voice, video and data, Ethernet passive optical network (EPON) dynamic bandwidth allocation (DBA) algorithm should avoid light load penalty, choose different scheduling scheme according to light loading or heavy loading circumstances, adaptively adjust the order of ONUs at the case heavy loading in order to guarantee QoS. Aiming at this problem, an adaptive dynamic bandwidth allocation algorithm supporting multi-services is presented. The algorithm guarantees QoS through dividing service into voice, video and data putting them into different queues, optical line terminal (OLT) collects all requests of different services from different ONUs, divides the adopted scheduling scheme according to loading, adaptively adjusts the order of ONUs queue based on minimum delay at the case heavy load. Therefore, it can really guarantee QoS. Simulation results of the algorithm show that the algorithm not only can support multi-service and avoid light load penalty, but also can guarantee the fairness of each ONUs and QoS. It has a better performance than other algorithms particularly at the case of heavy loading.     

一种改进的EPON动态带宽分配算法

 在分析了现有带宽分配算法的基础上,结合已有算法的优缺点,提出一种新的区分业务等级的、保证服务质量的动态带宽分配算法。新算法动态确定轮询周期,分配给高优先级业务请求带宽,按权重对中、低优先级业务进行带宽分配,并考虑到了剩余带宽的再分配。经仿真验证：该方案充分保证了高优先级业务的带宽需求,考虑到了低等级业务可能分不到带宽的情况,体现了带宽分配的公平性,全面提高了上行带宽的利用率,提高了系统的服务质量保证。     

An algorithm for encryption of secret images into meaningful images

Image encryption algorithms typically transform a plain image into a noise-like cipher image, whose appearance is an indication of encrypted content. Bao and Zhou [Image encryption: Generating visually meaningful encrypted images, Information Sciences 324, 2015] propose encrypting the plain image into a visually meaningful cover image. This improves security by masking existence of encrypted content. Following their approach, we propose a lossless visually meaningful image encryption scheme which improves Bao and Zhou's algorithm by making the encrypted content, i.e. distortions to the cover image, more difficult to detect. Empirical results are presented to show high quality of the resulting images and high security of the proposed algorithm. Competence of the proposed scheme is further demonstrated by means of comparison with Bao and Zhou's scheme.     

Hybrid multiplexed OFDM-DWDM-EPON access network

For bottleneck problem of the broadband access networks, Ethernet-PON comes out as a striking and promising solution. Even though, EPON nodes necessitate a cost-effective up-gradation, WDM based topology proves to be a vigilant up-grading approach that deals with the deployment of multiple wavelengths in the upstream/downstream directions. Furthermore, only EPON nodes with privileged traffic can be WDM-upgraded. Accordingly, we propose and demonstrate a hybrid multiplexed OFDM/DWDM-EPON access network employing OSSB modulation scheme. Case A demonstrates a single channel OFDM-OSSB-EPON system and achieves a fiber link of 27 km with split ratio of 16. Afterwards, a contrast between OFDM-EPON and conventional EPON (C-EPON) after a fiber link of 20 km with split ratio of 16 is carried out. Case B targets the transmission of two channels with channel spacing of 0.1 nm to realize OFDM-DWDM-OSSB-EPON system and achieves a fiber link of 20 km with split ratio of 32.     

DRL-Assisted Resource Allocation for NOMA-MEC Offloading with Hybrid SIC

Multi-access edge computing (MEC) and non-orthogonal multiple access (NOMA) are regarded as promising technologies to improve the computation capability and offloading efficiency of mobile devices in the sixth-generation (6G) mobile system. This paper mainly focused on the hybrid NOMA-MEC system, where multiple users were first grouped into pairs, and users in each pair offloaded their tasks simultaneously by NOMA, then a dedicated time duration was scheduled to the more delay-tolerant user for uploading the remaining data by orthogonal multiple access (OMA). For the conventional NOMA uplink transmission, successive interference cancellation (SIC) was applied to decode the superposed signals successively according to the channel state information (CSI) or the quality of service (QoS) requirement. In this work, we integrated the hybrid SIC scheme, which dynamically adapts the SIC decoding order among all NOMA groups. To solve the user grouping problem, a deep reinforcement learning (DRL)-based algorithm was proposed to obtain a close-to-optimal user grouping policy. Moreover, we optimally minimized the offloading energy consumption by obtaining the closed-form solution to the resource allocation problem. Simulation results showed that the proposed algorithm converged fast, and the NOMA-MEC scheme outperformed the existing orthogonal multiple access (OMA) scheme.     

A joint shape evolution approach to medical image segmentation using expectation-maximization algorithm

This study proposes an expectation–maximization (EM)-based curve evolution algorithm for segmentation of magnetic resonance brain images. In the proposed algorithm, the evolution curve is constrained not only by a shape-based statistical model but also by a hidden variable model from image observation. The hidden variable model herein is defined by the local voxel labeling, which is unknown and estimated by the expected likelihood function derived from the image data and prior anatomical knowledge. In the M-step, the shapes of the structures are estimated jointly by encoding the hidden variable model and the statistical prior model obtained from the training stage. In the E-step, the expected observation likelihood and the prior distribution of the hidden variables are estimated. In experiments, the proposed automatic segmentation algorithm is applied to multiple gray nuclei structures such as caudate, putamens and thalamus of three-dimensional magnetic resonance imaging in volunteers and patients. As for the robustness and accuracy of the segmentation algorithm, the results of the proposed EM-joint shape-based algorithm outperformed those obtained using the statistical shape model-based techniques in the same framework and a current state-of-the-art region competition level set method.     

Computational ghost imaging with deep compressed sensing

Computational ghost imaging (CGI) provides an elegant framework for indirect imaging, but its application has been restricted by low imaging performance. Herein, we propose a novel approach that significantly improves the imaging performance of CGI. In this scheme, we optimize the conventional CGI data processing algorithm by using a novel compressed sensing (CS) algorithm based on a deep convolution generative adversarial network (DCGAN). CS is used to process the data output by a conventional CGI device. The processed data are trained by a DCGAN to reconstruct the image. Qualitative and quantitative results show that this method significantly improves the quality of reconstructed images by jointly training a generator and the optimization process for reconstruction via meta-learning. Moreover, the background noise can be eliminated well by this method.     

稀疏信道条件下正交多载波扩频水声通信无导频信道估计算法

提出了一种无导频信道估计算法,该算法首先利用水声信道的稀疏特性对扩频信号进行识别,再利用扩频信号识别结果对水声信道响应进行判决反馈估计,从而实现对稀疏水声信道响应的可靠重建。仿真和湖上试验结果证实:无导频信道估计算法可以在不降低通信质量的前提下,实现对水声通信信号的稳健均衡,提升水声通信速率。      

An image compression method for space multispectral time delay and integration charge coupled device camera

Multispectral time delay and integration charge coupled device （TDICCD） image compression requires a low- complexity encoder because it is usually completed on board where the energy and memory are limited. The Consultative Committee for Space Data Systems （CCSDS） has proposed an image data compression （CCSDS-IDC） algorithm which is so far most widely implemented in hardware. However, it cannot reduce spectral redundancy in mukispectral images. In this paper, we propose a low-complexity improved CCSDS-IDC （ICCSDS-IDC）-based distributed source coding （DSC） scheme for multispectral TDICCD image consisting of a few bands. Our scheme is based on an ICCSDS-IDC approach that uses a bit plane extractor to parse the differences in the original image and its wavelet transformed coefficient. The output of bit plane extractor will be encoded by a first order entropy coder. Low-density parity-check-based Slepian-Wolf （SW） coder is adopted to implement the DSC strategy. Experimental results on space multispectral TDICCD images show that the proposed scheme significantly outperforms the CCSDS-IDC-based coder in each band.     

Novel Multi-AP Coordinated Transmission Scheme for 7th Generation WLAN 802.11be

The demand for high-data-rate and time-sensitive applications, such as 4k/8k video streaming and real-time augmented reality (AR), virtual reality (VR), and gaming, has increased significantly. Addressing the inefficiency of distributed channel access and the fairness problem between uplink and downlink flows is crucial for the development of wireless local area network (WLAN) technologies. In this study, we propose a novel transmission scheme for IEEE 802.11be networks that addresses the fairness problem and improves the system throughput. Utilizing the concept of multi-AP coordinated OFDMA introduced in the 7th-generation WLAN IEEE 802.11be, the proposed transmission scheme allows an AP to share a granted transmission opportunity (TXOP) with nearby APs. A mathematically analysis of the throughput performance of the proposed schemes was performed using a Markov chain model. The simulation results verify that the scheme effectively improves the downlink fairness and the system throughput. Combined with the advanced multiuser (MU) features of IEEE 802.11ax, such as TUA, MU cascading sequence, and MU EDCA, the proposed scheme not only enhances downlink AP transmission, but also guarantees improved control over the medium. The scheme is carefully designed to be fully compatible with conventional IEEE 802.11 protocols, and is thus potentially universal.     

Minimizing performance loss of MMSE algorithm for CDMA-based O-MIMO-OFDM

This paper presents an algorithm to minimize the performance loss (PL) of minimum mean square error (MMSE) in code division multiple access (CDMA) based optical multiple input multiple output orthogonal frequency division multiplexing (O-MIMO-OFDM) systems over 1200 km of standard single mode fiber (SSMF). The performance of the system using proposed algorithm scheme is compared to MMSE scheme by simulation results. It shows the superior performance of proposed algorithm.     

Ring-based PON supporting multiple optical private networks using OCDMA technique

This work is a novel attempt to provide local communications for multiple optical private networks (PNs) within ring-based passive optical network (PON). In order to improve network throughput performance, PNs traffic is decentralized from PON traffic let no extra traffic management into optical line terminal (OLT). To achieve multiple secure optical private networking over ring-based PON layout, optical code division multiple access (OCDMA) technique is applied. This technique leads to interconnect optical network units (ONUs) in the same PN sharing the same codeword while other PNs benefiting from different codewords. This scheme can be used in access networks to establish discrete communications between different sites in an enterprise or a university campus or even a residential accommodation. The proposed network architecture is then set up and its bit error rate performance is experimentally demonstrated. Finally, the network scalability and throughput performance of the proposed scheme are analyzed.     

Four-dimensional scheduling for uplink dynamic bandwidth allocation in OFDM-PON

Orthogonal frequency division multiplexing passive optical network (OFDM-PON) has been considered a promising access solution to meet the variable bandwidth demand. In this paper, a novel scheduling for dynamic bandwidth allocation (DBA) at medium access control (MAC) layer is proposed for uplink transmission of OFDM-PON. In order to utilize the bandwidth efficiently, scheduling in four dimensions is adopted in the proposed DBA algorithm. Four dimensions stand for frequency domains, time domains, modulation formats and power allocations. The algorithm is quite flexible. Simulation results and analysis show that the proposed algorithm can efficiently utilize the OFDM bandwidth and make the system highly energy-efficient.