WIRELESS BODY-AREA NETWORKS

The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless person-     

Matched Filter Based Spectrum Sensing When Primary User Has Multiple Power Levels

In this paper,we investigate the matched filter based spectrum sensing in a more reasonable cognitive radio(CR) scenario when the primary user(PU) has more than one transmit power levels,as regulated in most standards,i.e.,IEEE 802.11 Series,GSM,LTE,LTE-A,etc.This new multiple primary transmit power(MPTP) scenario is specialized by two different targets:detecting the presence of PU and identifying the power level.Compared to the traditional binary sensing where only the presence of PU is checked,SU may attain more information about the primary network(making CR more "intelligent") and design the subsequent optimization strategy.The key technology is the multiple hypothesis testing as opposed to the traditional binary hypothesis testing.We discuss two situations under whether the channel phase is known or not,and we derive the closed form solutions for decision regions and several performance metrics,from which some interesting phenomenons are observed and the related discussions are presented.Numerical examples are provided to corroborate the proposed studies.     

Design of 25 Gbit/s half-rate CDR with 1:2 demultiplexer for 100 GbE optical interconnects

A 25 Gbit/s clock and data recovery(CDR) circuit with 1:2 demultiplexer for 100 Gbit/s Ethernet(100 Gb E) optical interconnects has been designed and fabricated in Taiwan Semiconductor Manufacture Company(TSMC) 65 nm complementary metal-oxide-semiconductor(CMOS) technology. A novel quadrature voltage-controlled-oscillator(QVCO) structure adopts two pairs of transconductance cell and inverters to acquire rail-to-rail output swing. A half-rate bang-bang phase detector adopts four flip-flops array to sample the 25 Gbit/s input data and align the data phase, so the 25 Gbit/s data are retimed and demultiplexed into two paths 12.5 Gbit/s output data. Experimental results show that the recovered clock exhibits a peak-to-peak jitter of 7.39 ps and the recovered data presents a peak-to-peak jitter of 7.56 ps, in response to 312-1 pseudorandom bit sequence(PRBS) input. For 1.2 V voltage supply, the CDR circuit consumes 92 m W(excluding output buffers).     

国内煤机行业特征分析与预测

在分析国内煤矿机械行业基本特征的基础上,根据近5年来国内煤机的技术状况、国内煤炭市场环境、煤矿机械化程度及煤矿机械进出口情况,对"十二五"期间的煤矿机械市场需求进行预测与分析,分析结果能够帮助我国煤矿机械企业把握"十二五"期间煤机行业的变动趋势,并寻求最佳的发展方式.     

KKT-based iterative algorithm for beamforming in cognitive radio system

In this paper,we consider the downlink channel of multi-user multi-input single-output(MU-MISO)system in cognitive radio network,where the cognitive base station(CBS)resort to beamforming scheme to relief co-channel interference.The design criterion is to minimize the transmit power at CBS,subject to the signal-to-interference-plus-noise-ratio(SINR)constraints of cognitive users(CUs)and the interference constraints at primary users(PUs).Standard conic optimization packages can handle the problem,however,the...     

Service behavior modeling and service behavior convergence-based radio resource scheduling in wireless systems

With the development of wireless networks,the amount of multiple services increased sharply in recent years.High quality multiple services with low price are urgently needed especially in new generation mobile communication systems,e.g.,3G/LTE networks.It is important to enhance the availability of data service resources.Services have strong association which are used by clients with similar behavior habits in networks.Such feature results in service behavior convergence(SBC)and its utilization will enhance resource efficiency.This paper proposes two applications of service behavior:service prediction and a scheduling algorithm which enhances bandwidth efficiency.Convergence cells are classified according to SBC and hot-spot services are broadcasted separately in each convergence cell.It is demonstrated by stimulation that the bandwidth is saved 80% more than classical cellular system and nearly 20 % more than traditional broadcasting system.     

Analysis of secondary throughput and optimization in cooperative spectrum sensing

In cooperative spectrum sensing,more secondary user makes more opportunity for detecting the vacant spectrums,which resulting the spectrum utilization improved,however much bandwidth would be occupied for sending the local observation results,inducing the reduced secondary throughput.In this paper,an adaptive algorithm for selecting detection threshold was proposed,where the maximized secondary throughput can always be achieved while assuring sufficient protection to primary user,regardless of the number of...     

Precoding with interference suppression sequence scheme for OFDM-based cognitive radio systems

Orthogonal frequency division multiplexing(OFDM)is considered to be one of the promising schemes for cognitive radios(CR)systems,due to its flexibility in spectrum shaping.However,the traditional way of spectrum-notching failed to suppress out-of-band leakage enough,resulting in interference with licensed users(LUs).A novel spectrum shaping scheme is proposed in this article,where a precoder with interference suppression sequence(ISS)is for the first time introduced for shaping the spectrum of OFDM signals in OFDM-based CR systems.The precoder matrix together with ISS matrix is obtained by minimizing the power of out-of-band interference,which results in the sufficient interference suppression of OFDM signal to LUs.Analysis and simulation results show that the proposed scheme can significantly suppress the interference power to LUs at a little cost of precoding efficiency.Meanwhile,the peak-to-average-power-ratio(PAPR)is invariable and the bit-error-rate(BER)performance over Rayleigh fading channel is improved.     

Network selection policy in multi-radio access environment using stochastic control theory

Network selection is crucial in improving the performance of heterogeneous wireless access systems.Most of previous work on network selection or radio resource allocation concentrates on the capability of each available network and ignores the time-varying nature of wireless media due to channel fading.However,the channel condition determines the state of each wireless network and plays a vital role in ensuring quality of service in multi-radio access environment.In this article,we propose a network selection policy using stochastic control theory considering the time-varying and stochastic character of wireless channels.The proposed scheme selects one network among different alternatives in each decision epoch according to the channel state of each network,which is modeled as finite-state Markov channel,with the objectives of increasing the data-rate,decreasing the bit error rate and minishing the delay.The procedure of network selection is formulated as a stochastic control problem,which can be solved using linear programming and primal-dual index heuristic algorithm.Simulation results are presented to show that network selection has great impact on the system performance,and the proposed scheme can improve the performance significantly.     

Configuration Analysis of Metamorphic Mechanisms Based on Extended Adjacency Matrix Operations

The adjacency matrix operations,which connect with configuration transformation correspondingly,can be used for analysis of configuration transformation of metamorphic mechanisms and the corresponding algorithm can easily be simulated by computer.But the adjacency matrix based on monochrome topological graph is not suitable for the topological representation of mechanisms with multiple joints.The method of adjacency matrix operations has its own limitations for analysis of configuration transformation of me...