Does Amplify-and-Forward Cooperative Relay Improve OFDM/OFDMA Ergodic Capacity？

The ergodic information rate for Orthogonal Frequency-Division Multiplexing / Orthogonal Frequency-Division Multiple Access with amplify-and-forward （AF） relaying systems in the presence of frequency offsets is evaluated. Unlike previous work, per-subcarrier adaptive power allocation is performed on each relay to optimize the system ergodic information rate. For a given frequency offset and total number of relays M, the AF ergodic information rate is proven to be a monotonically increasing function of α （the ratio of the power allocated to the source node and the total transmit power）, implying that the maximum ergodic information rate can be obtained at α=1 （i.e., there is no cooperative relay）. Furthermore, the proof of ＂cooperative relays cannot improve the AF ergodic information rate in a quasi-static wireless channel＂ is also provided in this letter.     

Hybrid Weighted l1-Total Variation Constrained Reconstruction for MR Image

Compressed sensing based Magnetic resonance （MR） image reconstruction can be done by minimizing the sum of least square data fitting item, the Total variation （TV） and ll norm regularizations. In this paper, inspired by the conventional constrained reconstruction model, we propose a hybrid weighted l1-TV minimization method to reconstruct MR image. We introduce the iterative mechanism to update the weights for l1 and TV norms adaptively. The weights vary at each element of the image matrix according to the presented weights selection strategy. Experiments on Shepp-Logan phantom and practical MR. images demonstrate the proposed method can preserve image details and obtain improved reconstruction quality compared to the traditional CS-MRI method and other weighted methods.     

Network Function Virtualization Technology： Progress and Standardization

Network innovation and business transformation are both necessary for telecom operators to adapt to new situations,but operatorsface challenges in terms of network bearer complexity,business centralization,and IT/CT integration.Network function virtualiza-tion(NFV)may inspire new development ideas,but many doubts still exist within industry,especially about how to introduceNFV into an operator’s network.This article describes the latest progress in NFV standardization,NFV requirements and hottechnology issues,and typical NFV applications in an operator networks.     

A 3.1-4.8 GHz transmitter with a high frequency divider in 0.18μm CMOS for OFDM-UWB

A fully integrated low power RF transmitter for a WiMedia 3.1-4.8 GHz multiband orthogonal frequency division multiplexing ultra-wideband system is presented. With a separate transconductance stage, the quadrature up-conversion modulator achieves high linearity with low supply voltage. The co-design of different resonant frequencies of the modulator and the differential to single （D2S） converter ensures in-band gain flatness. By means of a series inductor peaking technique, the D2S converter obtains 9 dB more gain without extra power consumption. A divided-by-2 divider is used for carrier signal generation. The measurement results show an output power between -10.7 and -3.1 dBm with 7.6 dB control range, an OIP3 up to 12 dBm, a sideband rejection of 35 dBc and a carrier rejection of 30 dBc. The ESD protected chip is fabricated in the Jazz 0.18μm RF CMOS process with an area of 1.74 mm^2 and only consumes 32 mA current （at 1.8 V） including the test associated parts.     

A RT Steganalytic Method for Optimal Parity Assignment Algorithm

Steganography is the art of transmitting a message by embedding it into multimedia data without drawing any suspicions. OPA （Optimal parity assignment） algorithm is one of the most secure steganographlc methods for palette format images. In this paper, we present RT （Replacement transfer） steganalytic algorithm for detecting the secret messages embedded by OPA and the improved algorithm. Based on the analysis of Replacementtransfer structure （RTS） of colors, we explore the singular statistics of core colors in OPA stego-images via replacement operation. In addition, we can estimate statistics of the cover-image from the corresponding stego-lmage by an average filtering operation. With the estimation of statistics of the cover image and the singular statistics of the stego-image, the length of secret messages embedded in palette format images with OPA and the improved algorithm can be estimated. The experimental results indicate that the RT steganalytic algorithm is eiTective and accurate.     

A 6.25 Gb/s equalizer in 0.18μm CMOS technology for high-speed SerDes

This paper presents a 0.18μm CMOS 6.25 Gb/s equalizer for high speed backplane communication. The proposed equalizer is a combined one consisting of a one-tap feed-forward equalizer （FFE） and a two-tap half-rate decision feedback equalizer （DFE） in order to cancel both pre-cursor and post-cursor ISI. By employing an active-inductive peaking circuit for the delay line, the bandwidth of the FFE is increased and the area cost is minimized. CML-based circuits such as DFFs, summers and multiplexes all help to improve the speed of DFEs. Measurement results illustrate that the equalizer operates well when equalizing 6.25 Gb/s data is passed over a 30-inch channel with a loss of 22 dB and consumes 55.8 mW with the supply voltage of 1.8 V. The overall chip area including pads is 0.3 × 0.5 mm^2.     

A Secure Adaptive Routing Strategy Using Immune Mechanism in MANET

Many protocols have been proposed to in- crease efficiency and security of traditional protocols in Mobile ad-hoc networks （MANET）, but they are all facing the problem of computation overhead which leads to im- practicability. Adaptive routing strategy （ARS） is a novel routing strategy that switches routing protocol according to the network condition. Though this method alleviates the problem of efficiency, it doesn＇t cover the secure issues. We integrate our security mechanism based on Artificial immune system （AIS）, with adaptive routing strategy to enhance efficiency and security. First we presented a more appropriate definition to the measurement of network con- dition, then we designed a secure adaptive routing strategy based on the definition. At last, we gave a performance analysis to validate the correctness and reliability of our scheme.     

A Sensor Anonymity Enhancement Scheme Based on Pseudonym for Clustered Wireless Sensor Network

Security problem is an important issue for Wireless Sensor Network. The paper focuses on the privacy protection of WSN applications. An anonymity enhancement tactic based on pseudonym mechanism is presented for clustered Wireless Sensor Network, which provides anonymity for both the sensors within a cluster and the cluster head nodes. Simulation experiments are launched through NS2 platform to validate the anonymity performance. The theoretical analysis and empirical study imply that the proposed scheme based on pseudonym can protect the privacies of both the sensor nodes and the cluster head nodes. The work is valuable and the experimental results are convincible.     

一种应用于超宽带（UWB）的CMOS五次微分高斯脉冲发生器

A CMOS fifth-derivative Gaussian pulse generator is presented for ultra-wideband （UWB） applications. The design exhibits low power consumption, low circuit complexity, and a precise pulse shape to inherently comply with the FCC spectrum mask for indoor UWB applications without the need for a filter. The pulse generator is implemented with a 1.8-V, 0.18-μm CMOS process. The small core chip size of the pulse generator is only 217 ×121 #m2 because of its all digital circuit design. The measured fifth-derivative Gaussian pulse has a peak-to-peak amplitude of 158 mV and a pulse width of 800 ps. The average power dissipation is 0.6 mW with a pulse repetition frequency of 50 MHz.     

A Hierarchical Virus Immunization Method for Community Networks

Due to the enormous harm of virus propagation, research regarding virus immunizations still absolutely necessary. In comparison to current researches, a new virus immunization method the hierarchical virus immunization method （HVIM） for community networks is proposed. Based on the virus transmission dynamic model Susceptible- Infectious-Removed and Susceptible- Removed （SIRSR）, HVIM considered the influence of external factors on the spread of viruses and only needs a portion of the network structure to be able to carry out immunization. Another pro for HVIM is that it is scalable and suitable for parallel computing which is a requirement in the big data era. Finally, a simulation dataset and a real dataset were used to run experiments, and the results of simulation showed that HVIM obviously is superior to others on the aspect of immunity.     

Adaptive Method of Velocity Control for Cardiac CT

The image for cardiac CT is blurred because the heart is in motion. Currently, fixed scan velocity for cardiac CT is used and approximate projection can only be achieved due to the non-synchronism between the heartbeat and scan velocity. In order to achieve ideal projection, the control method for selectable scan velocity is proposed according to heartbeat. The velocity varies with the heart beat, temporal resolution and control parameters to achieve a desirable temporal resolution in nonperiodic heartbeat. The selectable scan velocity can provide ideal projection with uniform distribution and the same phases. The simulation result shows that the variable velocity method outperforms the current fixed velocity method.     

Analytical modeling of subthreshold current and subthreshold swing of Gaussiandoped strained-Si-on-insulator MOSFETs

This paper presents the analytical modeling of subthreshold current and subthreshold swing of short- channel fully-depleted （FD） strained-Si-on-insulator （SSOI） MOSFETs having vertical Gaussian-like doping pro- file in the channel. The subthreshold current and subthreshold swing have been derived using the parabolic approx- imation method. In addition to the effect of strain on silicon layer, various other device parameters such as channel length （L）, gate-oxide thickness （tox）, strained-Si channel thickness （ts_Si）, peak doping concentration （Np）, project range （Rp） and straggle （op） of the Gaussian profile have been considered while predicting the device characteris- tics. The present work may help to overcome the degradation in subthreshold characteristics with strain engineering. These subthreshold current and swing models provide valuable information for strained-Si MOSFET design. Ac- curacy of the proposed models is verified using the commercially available ATLASTM, a two-dimensional （2D） device simulator from SILVACO.     

Amended Truncated Union Bounds on the ML Decoding Performance of Binary Linear Codes over AWGN Channels

In this paper＇s simple upper bounds are derived on the frame and bit error probabilities of binary linear codes over Additive white Gaussian noise （AWGN） channels. The conventional union bound is first truncated and then amended, which can be justified by invoking Gallager＇s first bounding technique （GFBT）. Different from most other works, the ＂good region＂ is specified by a suboptimal list decoding algorithm. The error probability caused by the good region can be upper-bounded by the union bounds using pair-wlse error probability and tripletwise error probability, which can be further tightened by exploiting the independence between the error events and certain components of the receiving signal vector. The proposed bounds are simple since they involve only the Q-function. The proposed bounds improve our recently proposed bounds. Numerical results are also presented to compare the proposed bounds with the Divsalar bound, which is a simple tight upper bound with closed-form, and the Tangential-sphere bound （TSB）, which is considered as one of the tightest upper bounds.     

A Method of Peak Detecting for Nanosecond Pulse in Optical Performance Monitoring System

In optical performance monitoring system, the analog to digital converter is needed to detect the peak of nanosecond pulse and get the signal envelope. A scheme based on a designed anti-aliasing filter and analog to digital converter is proposed to broaden the nanosecond pulse and make it easier for the analog to digital converter to catch the peak of the nanosecond pulse. The experimental results demonstrate that, with the proposed scheme, the optical performance system needs less time to get the recovered eye-diagram of high speed optical data signal, and is robust to phase mismatch in the analog to digital converter circuit.     

Query Expansion with Statistical Machine Translation

In practical applications of information retrieval, such as the search engine, the query user submitted contains only several keywords usually. This will cause unmatched issues of words between relevant files and the user＇s query, and result in more seriously negative effects on the performance of information retrieval. On the basis of analyzing the process of producing query, this paper puts forward a new method of query expansion based on the model of statistical machine translation. The approach extract related terms between documents and query through statistical machine translation model, then expand the query with them. The experiment on TREC data collection shows that our method achieved 4 - 17% of the improvement all the time more than the language model method without expanding. Compared to pseudo feedback, our method has the competitive average precision.     

Service Parameter Exposure and Dynamic Service Negotiation in SDN Environments

Software-defined networking(SDN)is a generic term and one of the major interests of the telecoms industry(and beyond)over thepast two years.However,defining SDN is a somewhat controversial exercise.The claimed flexibility,as well as other presumed as-sets of SDN,should be carefully investigated.In particular,the use of SDN to dynamically provision network services suggests theintroduction of a certain level of automation in the overall network service delivery process,from service parameter negotiation todelivery and operation.This paper aims to clarify the SDN landscape and focuses on two main aspects of the SDN framework:net-work abstraction,and dynamic parameter exposure and negotiation.     

Integrating IPsec within OpenFlow Architecture for Secure Group Communication

Network securityprotocolssuch as IPsechave been used for many years to ensure robust end-to-end communication and are impor-tant in the context of SDN.Despite the widespread installation of IPsec to date,per-packet protection offered by the protocol isnot very compatible with OpenFlow and flow-like behavior.OpenFlow architecture cannot aggregate IPsec-ESP flows in transportmode or tunnel mode because layer-3 information is encrypted and therefore unreadable.In this paper,we propose using the Secu-rity Parameter Index(SPI)of IPsec within the OpenFlow architecture to identify and direct IPsec flows.Thisenables IPsec to con-form to the packet-based behavior of OpenFlow architecture.In addition,by distinguishing between IPsec flows,the architectureis particularly suited to secure group communication.     

Virtualized Wireless SDNs： Modelling Delay Through the Use of Stochastic Network Calculus

Software-defined networks(SDN)have attracted much attention recently because of their flexibility in terms of network manage-ment.Increasingly,SDN is being introduced into wireless networks to form wireless SDN.One enabling technology for wirelessSDN is network virtualization,which logically divides one wireless network element,such as a base station,into multiple slices,and each slice serving as a standalone virtual BS.In this way,one physical mobile wireless network can be partitioned into multi-ple virtual networks in a software-defined manner.Wireless virtual networks comprising virtual base stations also need to provideQoS to mobile end-user services in the same context as their physical hosting networks.One key QoS parameter is delay.This pa-per presents a delay model for software-defined wireless virtual networks.Network calculus is used in the modelling.In particu-lar,stochastic network calculus,which describes more realistic models than deterministic network calculus,is used.The model en-ables theoretical investigation of wireless SDN,which is largely dominated by either algorithms or prototype implementations.     

光模块SMT工艺简霸

本文介绍了用于光模块产品的PCB’A在sMT过程中的工艺难点及其解决方案,希望给业界的同行提供一些借鉴。     

A New Process and Framework for Direct Anonymous Attestation Based on Asymmetric Bilinear Maps

For the problem of security properties scale badly of the Direct anonymous attestation （DAA） scheme based symmetric bilinear pairing, a new DAA scheme based on asymmetric bilinear pairing, which gives a new practical solution to ECC-based TPM in protecting the privacy of TPM,is presented. The scheme takes on new process and framework in sign protocol, of which the TPM has only to perform three exponentiations, moreover, the signature which isn＇t knowledge of signature, is a signature of the ordinary ecliptic curve system itself. Compared to other schemes, the whole performance of the scheme is the best,and the scheme not only satisfies the same proper- ties, but also is more simple and efficient. This paper gives not only a detailed security proof of the proposed scheme which shows that the scheme meets the security require- ments of anonymity and unlinkability,but also a careful performance analysis by comparing with the existing DAA schemes.