共查询到20条相似文献,搜索用时 15 毫秒
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介绍V5接入网用户接入系统的ISDN接入模块硬件和软件设计方案。这个方案具有系统配置灵活的特点。另外,此方案主要采用西门子公司的芯片组。 相似文献
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首先说明传统电话网为了适应数据通信需要 ,在用户线上设置调制 -解调器 ,传送数据速率达5 0~ 6 0 kb/ s,又为了用户能够接入 Internet索取大量数据信息 ,在不对称数字用户线上设置调制 -解调器 ,在下行方向提供较高数据速率 1.5~ 9.0 Mb/ s。着重地介绍由光纤和同轴电缆混合组成的有线电视网 CATV,以及它除了广播电视信号外 ,还设置电缆调制 -解调器 cable modem,以便电视台与用户间能够互通电话和数据通信 ,并让用户接入 Internet索取信息 ,其数据速率高达 10~ 30 Mb/ s。 相似文献
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Ana Gomes Marcio Monteiro Boris Dortschy Aldebaro Klautau 《International Journal of Communication Systems》2016,29(1):194-209
This work describes and proposes the application of evolutionary algorithms on the multiuser spectrum and SNR margin optimization problem for multicarrier systems, such as digital subscriber line. The proposed method is designed such that it takes advantage of special characteristics of the well‐known power adaptation techniques and uses them to solve the broader and more challenging problem of multiuser margin adaptation. Simulations show that the proposed method provides Pareto‐optimal and diverse solutions when compared to a previous method to solve the same problem. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Meiqin Tang Chengnian Long Xinping Guan 《International Journal of Communication Systems》2008,21(9):971-985
This paper presents a new algorithm for optimal spectrum balancing in modern digital subscriber line (DSL) systems using particle swarm optimization (PSO). In DSL, crosstalk is one of the major performance bottlenecks, therefore various dynamic spectrum management algorithms have been proposed to reduce excess crosstalks among users by dynamically optimizing transmission power spectra. In fact, the objective function in the spectrum optimization problem is always nonconcave. PSO is a new evolution algorithm based on the movement and intelligence of swarms looking for the most fertile feeding location, which can solve discontinuous, nonconvex and nonlinear problems efficiently. The proposed algorithm optimizes the weighted rate sum. These weights allow the system operator to place differing qualities of service or importance levels on each user, which makes it possible for the system to avoid the selfish‐optimum. We can show that the proposed algorithm converges to the global optimal solutions. Simulation results demonstrate that our algorithm can guarantee fast convergence within a few iterations and solve the nonconvex optimization problems efficiently. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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分别介绍了 ADSL、Etherenet、HFC三种接入方式并进行了综合比较,探讨了发展用户宽带接入网的一些思路和需要注意的问题. 相似文献
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主速率ISDN(PrimaryRateISDN,简写为PRISDN)由于具有既高又灵活的带宽,被认为是实现局部网之间互连的一种较理想的媒介,而局部网与PRISDN之间的网关正是实现这种互连的关键设备。本文以笔者在国外的研究工作为基础,全面系统地介绍该种网关的总体结构,硬、软件设计以及通道管理等实现中所应解决的主要技术问题。 相似文献
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W. Margaret Amutha H. Harshini V. Rajini 《International Journal of Electronics》2018,105(11):1831-1854
Providing electricity to telecom tower can be realised by hybrid green energy systems than extending a power line from grid. For a hybrid energy system, it is important to develop a converter to integrate different power sources and storage elements. Conventional systems use an individual converter for individual source thus leading to a relatively complex configuration, larger component count and reduced system efficiency. To address these issues green energy interface (GEI) converter is used. In this paper, a detailed component wise analysis and performance comparison between conventional and GEI converter using Matlab/Simulink is presented. GEI converter has linear and non-linear components. So, small signal model based on state space averaged model of the GEI topology is obtained. A lab level prototype for the GEI converter with programmable interface controller is implemented and tested under various input conditions to study the performance of the converter during seasonal changes. The simulation and experimental results showed that effective operation and control strategy of the hybrid power supply system.
Abbreviations: BTS: base transceiver station; MSC: mobile switching centre; BSC: base station controller; CAPEX: capital expenditure; OPEX: operational expenditure; GEI: green energy interface 相似文献
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根据现代毫米波频段军民用电子信息系统并行多功能、全频带、集成化发展趋势,提出了毫米波综合化信道技术发展需求。综述了国内外宽带综合化信道架构和关键技术研究进展,提出了基于可配置宽带毫米波前端的信道架构、全信道单片集成、超导技术、宽带线性固态功放等毫米波综合化信道技术发展方向,给出了开展毫米波宽带综合化信道技术研究的建议。 相似文献
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用0.35μm CMOS工艺实现存储接口单元中的数模混合DLL 总被引:1,自引:0,他引:1
论述了一种利用0.35mm、双阱、双层金属、双层多晶硅的CMOS工艺所实现的延迟锁定环(DLL)。该DLL用于RISC处理器中存储接口部件的时钟同步。本文介绍了其应用背景,给出了DLL的系统结构,接着分别介绍了鉴相器、电荷泵以及压控延迟线的电路结构,最后给出相关仿真结果。 相似文献
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SHDSL接入技术特点及其发展趋势 总被引:1,自引:0,他引:1
SHDSL是在单对双绞线上提供传输双向对称带宽数据的一种技术,目前受到广泛关注。该技术采用16电平TC-PAM,与ADSL,HDSL技术相比具有明显的技术优势。本文首先介绍了SHDSL的结构、数据流程以及技术优势,然后分析了他的发展趋势。 相似文献
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采用磁控溅射方法,在不锈钢箔上制备多横向界 面Mo(M-Mo,multi-transverse interface Mo)和单横向界面Mo(S-Mo)薄 膜,并利用共蒸发三步法分别在M-Mo和S-Mo薄膜上制备Cu(In,Ga)Se2(CIGS)薄膜及 器件。通过二次离子质谱仪(SIMS)、X射线衍射仪(XRD)和扫描电子显微镜(SEM)研究了不同 结构的Mo薄膜对CIGS影响。通过I-V测试,表征M-Mo和S -Mo作为背电极的CIGS电池电学性能。XRD结果显示,M-Mo和S-Mo 薄膜均以(110)为择优取向。SEM结果显示,M-Mo薄膜相对 于S-Mo,薄膜晶粒 较小,粗糙度较大。J-V测试结果显示,M-Mo薄膜作为背 电极的电池的开路电压Voc、短路电流J sc和填充因子(FF)均有所提高。 相似文献
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We propose the physical-layer (PHY) air interface solutions for downlink and uplink transmissions in broadband high-speed
wireless cellular systems. A system based on low-density parity-check (LDPC) coded multiple-input-multiple-output (MIMO) orthogonal
frequency-division multiplexing (OFDM) time-division multiple-accessing (TDMA) (with scheduling) is proposed for downlink
transmission; and a system based on orthogonal space-time block coded (STBC) multi-carrier code-division multiple-accessing
(MC-CDMA) is proposed for uplink transmission. The proposed scheme can support ∼100 Mbps peak rate over 25 MHz bandwidth downlink
channels and ∼30 Mbps sum rate of multiple users over 25 MHz uplink channels. Moreover, the proposed solutions provide excellent
performance and reasonable complexity for mobile station and for base station.
Ben Lu received the B.S. and M.S. degrees in electrical engineering from Southeast University, Nanjing, China, in 1994 and 1997;
the Ph.D. degree from Texas A & M University in 2002. From 1994 to 1997, he was a Research Assistant with National Mobile
Communications Research Laboratory at Southeast University, China. From 1997 to 1998, he was with the CDMA Research Department
of Zhongxing Telecommunication Equipment Co., Shanghai, China. From 2002 to 2004, he worked for the project of high-speed
wireless packet data transmission (4G prototype) at NEC Laboratories America, Princeton, New Jersey. He is now with Silicon
Laboratories. His research interests include the signal processing and error-control coding for mobile and wireless communication
systems.
Xiaodong Wang received the B.S. degree in Electrical Engineering and Applied Mathematics (with the highest honor) from Shanghai Jiao Tong
University, Shanghai, China, in 1992; the M.S. degree in Electrical and Computer Engineering from Purdue University in 1995;
and the Ph.D degree in Electrical Engineering from Princeton University in 1998. From July 1998 to December 2001, he was an
Assistant Professor in the Department of Electrical Engineering, Texas A&M University. In January 2002, he joined the faculty
of the Department of Electrical Engineering, Columbia University. Dr. Wang’s research interests fall in the general areas
of computing, signal processing and communications. He has worked in the areas of digital communications, digital signal processing,
parallel and distributed computing, nanoelectronics and bioinformatics, and has published extensively in these areas. Among
his publications is a recent book entitled “Wireless Communication Systems: Advanced Techniques for Signal Reception”, published
by Prentice Hall, Upper Saddle River, in 2003. His current research interests include wireless communications, Monte Carlo-based
statistical signal processing, and genomic signal processing. Dr. Wang received the 1999 NSF CAREER Award, and the 2001 IEEE
Communications Society and Information Theory Society Joint Paper Award. He currently serves as an Associate Editor for the
IEEE Transactions on Communications, the IEEE Transactions on Wireless Communications, the IEEE Transactions on Signal Processing, and the IEEE Transactions on Information Theory.
Mohammad Madihian (S’78-M’83-SM’88-F’98) received his Ph.D in electronic engineering from Shizuoka University, Hamamatsu, Japan, in 1983. He
is presently the Chief Patent Officer and Department Head, NEC Laboratories America, Inc., Princeton, New Jersey, where he
conducts Microwave as well as PHY/MAC layer signal processing activities for high-speed wireless networks and personal communications
applications. He holds 35 Japan/US patents and has authored/co-authored more than 130 technical publications including 25
invited talks. He has received 8 NEC Distinguished R&D Achievement Awards, the 1988 IEEE MTT-S Best Paper Microwave Prize,
and 1998 IEEE Fellow Award. He has served as Guest Editor to the IEEE Journal of Solid-State Circuits, Japan IEICE Transactions
on Electronics, and IEEE Transactions on Microwave Theory and Techniques. He is currently serving on the IEEE Speaker’s Bureau,
IEEE Compound Semiconductor IC Symposium Executive Committee, IEEE Radio and Wireless Symposium Executive Committee, IEEE
International Microwave Symposium Technical Program Committee, IEEE MTT-6 Subcommittee, IEEE MTT Editorial Board, and Technical
Program Committee of International Conference on Solid State Devices and Materials. Dr. Madihian is an Adjunct Professor at
Electrical and Computer Engineering Department, Drexel University, Philadelphia, Pennsylvania. 相似文献
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Jacek Jasielski Stanisław Kuta Witold Machowski Wojciech Kołodziejski 《Microelectronics Journal》2014
In the paper we propose a novel architecture and implementation of 11-bit Digital Pulse Width Modulator (DPWM) circuit based on previously known building blocks. Linearized Class-AD Double-sided (LADD) algorithm has been used to calculate the DPWM signals of the 11-bit resolution hybrid DPWM for a Class-AD digital audio amplifier. Noise-shaping process is used to support high fidelity with practical values of time resolution. The proposed DPWM circuit is composed of 8-bit counter and Analog Delay Locked Loop (ADLL) using 4-bit tapped delay line. A dual ADLL employing coarse and fine programmable delay element is used to adjust the delay time of delay line and lock it to required time. The coarse- as well as fine-delay lines are implemented as a cascade of variable-delay elements based on shunt capacitor delay element or single-ended Schmitt trigger. The proposed 11-bit DPWM circuit, at a switching frequency of 352.8 kHz and clock generator frequency of 90.3 MHz allows us to attain SNR of 120 dB and THD of the output signal less than 0.1% within the audio baseband and modulation index M=0.95. Basic verification of circuit manufacturability and simulation results (Monte Carlo analysis) for real CMOS process are presented. 相似文献