氮化硅扩散阻挡层在采用HfON栅介质的Ge MOS 电容中的作用

MOS capacitors with hafnium oxynitride（HfON）gate dielectrics were fabricated on Ge and Si substrates using the RF reactive magnetron sputtering method.A large amount of fixed charges and interface traps exist at the Ge/HfON interface.HRTEM and XPS analyses show that Ge oxides were grown and diffused into HfON after post metal annealing.A Si nitride interfacial layer was inserted between Ge and HfON as diffusion barrier.Using this method,well behaved capacitance–voltage and current–voltage characteristics were obtained.Finally hystereses are compared under different process conditions and possible causes are discussed.     

基于Si3N4的电荷俘获型存储器中氧缺陷的第一性原理研究

Based on first principle calculations, a comprehensive study of substitutional oxygen defects in hexagonal silicon nitride （β-Si3N4） has been carried out. Firstly, it is found that substitutional oxygen is most likely to form clusters at three sites in Si3N4 due to the intense attractive interaction between oxygen defects. Then, by using three analytical tools （trap energy, modified Bader analysis and charge density difference）, we discuss the trap abilities of the three clusters. The result shows that each kind of cluster at the three specific sites presents very different abilities to trap charge carriers （electrons or holes）： two of the three clusters can trap both kinds of charge carriers, confirming their amphoteric property; While the last remaining one is only able to trap hole carriers. Moreover, our studies reveal that the three clusters differ from each other in terms of endurance during the program/erase progress. Taking full account of capturing properties for the three oxygen clusters, including trap ability and endurance, we deem holes rather than electrons to be optimal to act as operational charge carriers for the oxygen defects in Si3N4-based charge trapping memories.     

Software Radio——Software Radio： A Review of Design Considerations and Digital Hardware Choices

This paper reviews the requirements for Software Defined Radio （SDR） systems for high-speed wireless applications and compares how well the different technology choices available- from ASICs, FPGAs to digital signal processors （DSPs） and general purpose processors （GPPs） - meet them.     

EEFA： Energy Efficiency Frame Aggregation Scheduling Algorithm for IEEE 802.11n Wireless Network

Packet size is restricted due to the error-prone wireless channel which drops the network energy utilization. Furthermore, the frequent packet retransmissions also lead to energy waste. In order to improve the energy efficiency of wireless networks and save the energy of wireless devices, EEFA （Energy Efficiency Frame Aggregation）, a frame aggregation based energy-efficient scheduling algorithm for IEEE 802.11n wireless network, is proposed. EEFA changes the size of aggregated frame dynamically according to the frame error rate, so as to ensure the data transmission and retransmissions completed during the TXOP and reduce energy consumption of channel contention. NS2 simulation results show that EEFA algorithm achieves better performance than the original frame-aggregation algorithm.     

Survivable Virtual Network Mapping Using Optimal Backup Topology in Virtualized SDN

Software-Defined Network architecture offers network virtualization through a hypervisor plane to share the same physical substrate among multiple virtual networks. However, for this hypervisor plane, how to map a virtual network to the physical substrate while guaranteeing the survivability in the event of failures, is extremely important. In this paper, we present an efficient virtual network mapping approach using optimal backup topology to survive a single link failure with less resource consumption. Firstly, according to whether the path splitting is supported by virtual networks, we propose the OBT-I and OBT-II algorithms respectively to generate an optimal backup topology which minimizes the total amount of bandwidth constraints. Secondly, we propose a Virtual Network Mapping algorithm with coordinated Primary and Backup Topology （VNM-PBT） to make the best of the substrate network resource. The simulation experiments show that our proposed approach can reduce the average resource consumption and execution time cost, while improving the request acceptance ratio of VNs.     

Distributed Power Control for Energy Conservation in Hybrid Cellular Network with Device-to-Device Communication

Device-to-Device （D2D） com- munication has been proposed as a promising implementation of green communication to benefit the existed cellular network. In order to limit cross-tier interference while explore the gain of short-range communication, we devise a series of distributed power control （DPC） schemes for energy conservation （EC） and enhancement of radio resource utilization in the hybrid system. Firstly, a constrained opportunistic power control model is built up to take advantage of the interference avoidance methodology in the presence of service requirement and power constraint. Then, biasing scheme and admission control are added to evade ineffective power consumption and maintain the feasibility of the system. Upon feasibility, a non-cooperative game is further formulated to exploit the profit in EC with minor influence on spectral efficiency （SE）. The convergence of the DPC schemes is validated and their performance is confirmed via simulation results.     

沉积温度对多元醇法制备硫化镉薄膜的影响

CdS thin films were successfully deposited onto glass substrates for the first time by the polyol method using cadmium acetate, thiourea and diethylene glycol as the raw materials. The effects of the deposition tempera- ture from 120 to 200 ℃ in steps of 20 ℃on the structure, morphology and optical properties of the resultant films were investigated. It was found that the crystallinity was improved and the value of the surface average roughness was decreased with increasing the deposition temperature. The average grain sizes of the CdS thin films were 77.16 and 76.61 nm at 140 and 180 ℃, respectively. All samples showed excellent transmittance and the band gaps were found to reduce from 2.55 to 2.45 eV with the increase of the deposition temperature, which was attributed to the improvement of crystallinity.     

On the Secrecy Rate of Limited Feedback Beamforming over Multiple-Input Single-Output Wiretap Channels

The secrecy rate of limited feedback beamforming is studied for a Multiple-Input Single-Output （MISO） wiretap channel with a multi-antenna eavesdropper. We first obtain the secrecy rate of limited feedback beamforming achieved at the legitimate receiver. We then derive a lower bound for the asymptotic secrecy rate in the large system limit, From this bound, we observe a threshold for the ratio of eavesdrop antennas to transmit antennas to obtain a positive secrecy rate. We further show that the secrecy rate loss due to limited feedback decays with the number of feedback bits per transmit antenna.     

应用于低中频和零中频DVB调谐器中8阶信道滤波器设计

An eighth order active-RC filter for low-IF and zero-IF DVB tuner applications is presented, which is implemented in Butterworth biquad structure. An automatic frequency tuning circuit is introduced to compensate the cut-off frequency variation using a 6-bit switched-capacitor array. Switched-resistor arrays are adopted to cover different cut-off frequencies in low-IF and zero-IF modes. Measurement results show that precise cut-off frequencies at 2.5, 3, 3.5 and 4 MHz in zero-IF mode, 5, 6, 7 and 8 MHz in low-IF mode can be achieved, 60 dB frequency attenuation can be obtained at 20 MHz, and the in-band group delay agrees well with the simulation. Two-tone testing shows the in-band IM3 achieves -52 dB and the out-band IM3 achieves -55 dB with -11 dBm input power. This proposed filter circuit, fabricated in a SMIC 0.18μm CMOS process, consumes 4 mA current with 1.8 V power supply.     

用于ZigBee的2.4GHz低功耗双增益低噪声放大器

This paper presents a fully differential dual gain low noise amplifier（DGLNA） for low power 2.45-GHz ZigBee/IEEE 802.15.4 applications.The effect of input parasitics on the inductively degenerated cascode LNA is analyzed.Circuit design details within the guidelines of the analysis are presented.The chip was implemented in SMIC 0.18-μm 1P6M RF/mixed signal CMOS process.The DGLNA achieves a maximum gain of 8 dB and a minimum gain of 1 dB with good input return loss.In high gain mode, the measured noise figure（NF） is 2.3-3 dB in the whole 2.45-GHz ISM band.The measured 1-dB compression point, IIP3 and IIP2 is-9, 1 and 33 dBm, respectively.The DGLNA consumes 2 mA of current from a 1.8 V power supply.     

具有频率调谐的GNSS接收机双模复数滤波器

A fifth/seventh order dual-mode OTA-C complex filter for global navigation satellite system receivers is implemented in a 0.18μm CMOS process.This filter can be configured as the narrow mode of a 4.4 MHz bandwidth center at 4.1 MHz or the wide mode of a 22 MHz bandwidth center at 15.42 MHz.A fully differential OTA with source degeneration is used to provide sufficient linearity.Furthermore,a ring CCO based frequency tuning scheme is proposed to reduce frequency variation.The measured results show that in narrow-band mode the image rejection ratio（IMRR）is 35 dB,the filter dissipates 0.8 mA from the 1.8 V power supply,and the out-of-band rejection is 50 dB at 6 MHz offset.In wide-band mode,IMRR is 28 dB and the filter dissipates 3.2 mA.The frequency tuning error is less than±2%.     

Large-signal characterizations of DDR IMPATT devices based on group Ⅲ-Ⅴ semiconductors at millimeter-wave and terahertz frequencies

Large-signal （L-S） characterizations of double-drift region （DDR） impact avalanche transit time （IM- PATT） devices based on group III-V semiconductors such as wurtzite （Wz） GaN, GaAs and InP have been carried out at both millimeter-wave （mm-wave） and terahertz （THz） frequency bands. A L-S simulation technique based on a non-sinusoidal voltage excitation （NSVE） model developed by the authors has been used to obtain the high frequency properties of the above mentioned devices. The effect of band-to-band tunneling on the L-S properties of the device at different mm-wave and THz frequencies are also investigated. Similar studies are also carried out for DDR IMPATTs based on the most popular semiconductor material, i.e. Si, for the sake of comparison. A compara- tive study of the devices based on conventional semiconductor materials （i.e. GaAs, InP and Si） with those based on Wz-GaN shows significantly better performance capabilities of the latter at both mm-wave and THz frequencies.     

CMOS反相器在高功率微波下闩锁效应的温度影响

The temperature dependence of the latch-up effects in a CMOS inverter based on 0.5 μm technology caused by high power microwave （HPM） is studied. The malfunction and power supply current characteristics are revealed and adopted as the latch-up criteria. The thermal effect is shown and analyzed in detail. CMOS in- verters operating at high ambient temperature are confirmed to be more susceptible to HPM, which is verified by experimental results from previous literature. Besides the dependence of the latch-up triggering power P on the ambient temperature T follows the power-law equation P = ATβ. Meanwhile, the ever reported latch-up delay time characteristic is interpreted to be affected by the temperature distribution. In addition, it is found that the power threshold increases with the decrease in pulse width but the degree of change with a certain pulse width is constant at different ambient temperatures. Also, the energy absorbed to cause latch-up at a certain temperature is basically sustained at a constant value.     

Design of Anti-Collision Integrated Security Mechanism Based on Chaotic Sequence in UHF RFID System

Collision and security issues are considered as barriers to RFID applications. In this paper, a parallelizable anti-collision based on chaotic sequence combined dynamic frame slotted aloha to build a high-efficiency RFID system is proposed. In the tags parallelizable identification, we design a Discrete Markov process to analyze the success identification rate. Then a mutual authentication security protocol merging chaotic anti-collision is presented. The theoretical analysis and simulation results show that the proposed identification scheme has less than 45.1% of the identification time slots compared with the OVSF-system when the length of the chaos sequence is 31. The success identification rate of the proposed chaotic anti-collision can achieve 63% when the number of the tag is 100. We test the energy consumption of the presented authentication protocol, which can simultaneously solve the anti-collision and security of the UHF RFID system.     

The Data Age of Mobile Cellular Network in Germany and China： Policies,Technologies and Markets （Part I）

The UMTS auction in 2000 brought approximately 100 billion DM （Deutsche Mark） for the German National Treasury. T-Mobile （D1-Netz）, Vodafone （D2-Netz）, E-Plus （E1-Netz） and 02 （E2-Netz） have gradually evolved from GSM to full-fledged UMTS operators over the past years. The conglomerate of China Telecom was split twice. China acceded to WTO and promulgated the FITE Provisions. MIIT （Ministry of Industry and Information Technology） became the regulator and China Netcom was incorporated into China Unicorn in 2008. Most recently the layout of 3G future has been reconfirmed by MIIT. Voice service has remained the main source of income in both countries and operators have continued to focus on voice quality and network availability in their respective 2G networks. Because value-added and higher-speed data applications have been gaining market attention, 2.5G and 3G infrastructure has increasingly become the focal network strategy for the operators since the beginning of the new century. Germany has rolled out WCDMA/UMTS services on a large scale in the consumer market, while China has adopted all three 3G standards （TD-SCDMA, WCDMA/UMTS, CDMA2000）, which shall gradually capture a wider 3G subscriber base. The summary shows that the development of the cellular technology and market in Germany and China can be discussed in three distinct historical periods. The conclusion suggests that the case of the cellular technology appears to be consistent with and applicable to a number of arguments widely disputed in economics and management related to technology and innovation, such as dominant design, technology waves/ S-Curve, disruptive technologies, Technology Adoption Life Cycle.     

基于纳米多晶硅薄膜晶体管分裂漏MAGFET制作和特性

A split-drain magnetic field-effect transistor （MAGFET） based on a nano-polysilicon thin film transistor （TFT） is proposed, which contains one source, two drains and one gate. The sensor chips were fabricated on （100） high resistivity silicon substrate by CMOS technology. When drain-source voltage equals 5.0 V and length and width ratio of the TFT channel is 80 μm/160 μm, the current and voltage magnetic sensitivities of the split-drain MAGFET based on the TFT are 0.018 mA/T and 55 mV/T, respectively. Through adopting nano-polysilicon thin films and nano-polysilicon thin films/high resistivity silicon heterojunction interfaces as the magnetic sensing layers, it is possible to realize detection of the external magnetic field. The test results show that magnetic sensitivity of the split-drain MAGFET can be improved significantly.     

Recommending Friends Instantly in Location-based Mobile Social Networks

Differently from the general online social network （OSN）, location- based mobile social network （LMSN）, which seamlessly integrates mobile computing and social computing technologies, has unique characteristics of temporal, spatial and social correlation. Recommending friends instantly based on current location of users in the real world has become increasingly popular in LMSN. However, the existing friend recommendation methods based on topological structures of a social network or non-topological information such as similar user profiles cannot well address the instant making friends in the real world. In this article, we analyze users＇ check-in behavior in a real LMSN site named Gowalla. According to this analysis, we present an approach of recommending friends instantly for LMSN users by considering the real-time physical location proximity, offline behavior similarity and friendship network information in the virtual community simultaneously. This approach effectively bridges the gap between the offline behavior of users in the real world and online friendship network information in the virtual community. Finally, we use the real user check-in dataset of Gowalla to verify the effectiveness of our approach.     

SDN-Based Data Offioading for 5G Mobile Networks

The rapid growth of 3G/4G enabled devices such as smartphones and tablets in large numbers has created increased demand formobile data services.Wi-Fi offloading helps satisfy the requirements of data-rich applications and terminals with improved multi-media.Wi-Fi is an essential approach to alleviating mobile data traffic load on a cellular network because it provides extra capaci-ty and improves overall performance.In this paper,we propose an integrated LTE/Wi-Fi architecture with software-defined net-working(SDN)abstraction in mobile backhaul and enhanced components that facilitate the move towards next-generation 5G mo-bile networks.Our proposed architecture enables programmable offloading policies that take into account real-time network condi-tions as well as the status of devices and applications.This mechanism improves overall network performance by deriving real-time policies and steering traffic between cellular and Wi-Fi networks more efficiently.     

Improving MapReduce Performance by Balancing Skewed Loads

MapReduce has emerged as a popular computing model used in datacenters to process large amount of datasets.In the map phase,hash partitioning is employed to distribute data that sharing the same key across data center-scale cluster nodes.However,we observe that this approach can lead to uneven data distribution,which can result in skewed loads among reduce tasks,thus hamper performance of MapReduce systems.Moreover,worker nodes in MapReduce systems may differ in computing capability due to（1） multiple generations of hardware in non-virtualized data centers,or（2） co-location of virtual machines in virtualized data centers.The heterogeneity among cluster nodes exacerbates the negative effects of uneven data distribution.To improve MapReduce performance in heterogeneous clusters,we propose a novel load balancing approach in the reduce phase.This approach consists of two components：（1） performance prediction for reducers that run on heterogeneous nodes based on support vector machines models,and（2） heterogeneity-aware partitioning（HAP）,which balances skewed data for reduce tasks.We implement this approach as a plug-in in current MapReduce system.Experimental results demonstrate that our proposed approach distributes work evenly among reduce tasks,and improves MapReduce performance with little overhead.     

Differentiating Data Collection for Cloud Environment Monitoring

In a growing number of information processing applications, data takes the form of continuous data streams rather than traditional stored databases. Monitoring systems that seek to provide monitoring services in cloud environment must be prepared to deal gracefully with huge data collections without compromising system performance. In this paper, we show that by using a concept of urgent data, our system can shorten the response time for most ＇urgent＇ queries while guarantee lower bandwidth consumption. We argue that monitoring data can be treated differently. Some data capture critical system events; the arrival of these data will significantly influence the monitoring reaction speed which is called urgent data. High speed urgent data collections can help system to react in real time when facing fatal errors. A cloud environment in production, MagicCube, is used as a test bed. Extensive experiments over both real world and synthetic traces show that when using urgent data, monitoring system can lower the response latency compared with existing monitoring approaches.