期刊文献+
共找到25,804篇文章
< 1 2 250 >
每页显示 20 50 100
连续Pilot体制CDMA高速移动台自适应信道估计器 被引量:2
1
作者 陈国安 尤肖虎 《东南大学学报(自然科学版)》 EI CAS CSCD 1999年第B11期1-5,共5页
提出了连续Pilot 信号体制CDMA系统中,高速移动台自适应信道估计的方法,它包括信道变化速率的检测和信道估计积分长度的自适应调整两个部分.仿真结果显示,该信道估计器有效拓展了移动台正常工作的运动速度范围,提高了R... 提出了连续Pilot 信号体制CDMA系统中,高速移动台自适应信道估计的方法,它包括信道变化速率的检测和信道估计积分长度的自适应调整两个部分.仿真结果显示,该信道估计器有效拓展了移动台正常工作的运动速度范围,提高了RAKE接收机的适应性. 展开更多
关键词 cdma 信道估计 高速移动台 连续pilot体制
下载PDF
TRAFFIC CHANNEL SIR ESTIMATION BASED ON REVERSE PILOT CHANNEL IN cdma2000
2
作者 ZhouHua YangDacheng 《Journal of Electronics(China)》 2004年第4期278-288,共11页
Signal-to-Interference Ratio(SIR) is a very important metric of communication link quality. For wireless cellular systems, several control mechanisms, such as power control mechanisms, rate control mechanisms, and all... Signal-to-Interference Ratio(SIR) is a very important metric of communication link quality. For wireless cellular systems, several control mechanisms, such as power control mechanisms, rate control mechanisms, and allocation of radio resource, are based on SIR estimation.In previous researches, most of researchers concentrated on WCDMA systems, in which pilot symbol is time-multiplexed with data symbol; the method developed in this case is not feasible for cdma2000 systems where pilot symbol is code-multiplexed with data symbol. This paper first develops the SIR estimators based on the reverse pilot channel and then derives the approximate analytic expression for its Mean Squared Error (MSE) function, the accuracy of which is validated through simulation. It is shown that the MSE of the new SIR estimator is significantly smaller than that of other widely used SIR estimators, especially in low SIR case. Finally, the estimate quality of the proposed method is further improved by long-termly averaging the sample interference. 展开更多
关键词 Wcdma cdma2000 Signal-to-lnterference Ratio(SIR) estimation pilot channel
下载PDF
Pilot Beacon在CDMA双载频间切换的应用
3
作者 刘海明 黄唯萍 《移动通信》 2003年第11B期202-206,共5页
本文论述了CDMA网络双载频间切换的几种方法,并就Pifot Beacon技术实现CDMA系统中双载频向切换的方式进行了相关实验和分析。
关键词 cdma网络 pilot Beacon技术 双载频 载频切换 更软切换 硬切换 实验分析
下载PDF
PilotFleet——全方位的TD-SCDMA无线测试解决方案 被引量:1
4
作者 陈春雄 《电信网技术》 2008年第3期51-53,共3页
介绍了珠海世纪鼎利通信科技股份有限公司自主研发的TD-SCDMA网络建设和运营的一种关键测试设备——TD-SCDMA无线网络自动监测系统Pilot Fleet,以及本系统的特点及其应用。
关键词 TD-Scdma 自动监测 pilot FLEET
下载PDF
W-CDMA连续Pilot专用导码功率动态调整
5
作者 陈国安 尤肖虎 《东南大学学报(自然科学版)》 EI CAS CSCD 2000年第1期32-36,共5页
对连续Pilot体制的宽带CDMA系统 ,提出了根据信道衰变速率对专用导码功率动态调整 ,从而提高系统容量的方法 .该技术使导码与数据码道功率之比下降 ,对不同业务模型的系统容量均有不同程度的增加 .文中对该方法的机理进行了阐述和推导 ... 对连续Pilot体制的宽带CDMA系统 ,提出了根据信道衰变速率对专用导码功率动态调整 ,从而提高系统容量的方法 .该技术使导码与数据码道功率之比下降 ,对不同业务模型的系统容量均有不同程度的增加 .文中对该方法的机理进行了阐述和推导 ,仿真和数值计算结果证实了该方法的正确性和有效性 . 展开更多
关键词 移动通信 码分多址 容量 功率控制 IMT-2000
下载PDF
基于CDMA网络优化之伪导频(Pilot Beacon)的换频切换技术探析
6
作者 龚葵花 雷赟 《科技广场》 2009年第5期60-61,共2页
随着当前3G无线网络的迅速商用化,原有2.5G网络CDMA1x网络也遇到了空前的挑战,因此CDMA网络优化成为当前非常热门的词。本文对于CDMA优化之伪导频的换频切换进行了简明厄要的概述,包括技术原理及与95系列手机使用的导频进行比较,最后说... 随着当前3G无线网络的迅速商用化,原有2.5G网络CDMA1x网络也遇到了空前的挑战,因此CDMA网络优化成为当前非常热门的词。本文对于CDMA优化之伪导频的换频切换进行了简明厄要的概述,包括技术原理及与95系列手机使用的导频进行比较,最后说明伪导频的优势。 展开更多
关键词 伪导频 CDHAlx 网络优化 换频切换
下载PDF
Interference in Complex CDMA-OFDM/OQAM for Better Performance at Low SNR
7
作者 Chrislin Martial Lélé 《International Journal of Communications, Network and System Sciences》 2024年第8期113-128,共16页
This article is about orthogonal frequency-division multiplexing with quadrature amplitude modulation combined with code division multiplexing access for complex data transmission. It aims to present a method which us... This article is about orthogonal frequency-division multiplexing with quadrature amplitude modulation combined with code division multiplexing access for complex data transmission. It aims to present a method which uses two interfering subsets in order to improve the performance of the transmission scheme. The idea is to spread in a coherent manner some data amongst two different codes belonging to the two different subsets involved in complex orthogonal frequency-division multiplexing with quadrature amplitude modulation and code division multiplexing access. This will improve the useful signal level at the receiving side and therefore improve the decoding process especially at low signal to noise ratio. However, this procedure implies some interference with other codes therefore creating a certain noise which is noticeable at high signal to noise ratio. 展开更多
关键词 cdma OFDM/OQAM Complex Data
下载PDF
Exploration of Operation and Maintenance Management Mode and Innovation Mechanism of Pilot Base of Chemical Park
8
作者 Shenggan ZHU Tengfei SHANG 《Asian Agricultural Research》 2024年第9期16-18,22,共4页
Based on the current situation of the operation and maintenance management of the pilot base in many chemical parks in China,this paper conducts an in-depth exploration of the operation and maintenance management and ... Based on the current situation of the operation and maintenance management of the pilot base in many chemical parks in China,this paper conducts an in-depth exploration of the operation and maintenance management and innovation mode of the pilot base from the aspects of the evaluation of the pilot project entering the park,safety and environmental protection supervision,pilot mode,and industrialization mode of the pilot test results,so as to provide solutions for accelerating the process and industrialization of the pilot project and realizing the innovation value of the pilot base. 展开更多
关键词 CHEMICAL parks pilot BASE Operation and maintenance Mode INDUSTRIALIZATION EXPLORATION
下载PDF
The"4+4"Medical Doctor(MD)Pilot Program at PUMC:Implementation,Performance,and Prospects
9
作者 Jing-Jing Yi Wei-Wei Xu +6 位作者 Chao Ma He Di Jing Jin Le Zeng Wen-Ji Tu Wen-Wen Sun Qin Zhang 《Chinese Medical Sciences Journal》 CAS CSCD 2024年第2期144-148,共5页
Peking Union Medical College(PUMC)launched the"4+4"Medical Doctor(MD)pilot program in 2018,admitting students with non-medical backgrounds from top universities,aligning with national medical talent training... Peking Union Medical College(PUMC)launched the"4+4"Medical Doctor(MD)pilot program in 2018,admitting students with non-medical backgrounds from top universities,aligning with national medical talent training policies to foster diverse and eager learners in medicine.On the occasion of the graduation of the first class of the"4+4"MD pilot class at PUMC in 2023,we reviewed the teaching reform in the pilot program and carried out a systematic survey and interviews with students,faculties,and management staff of the pilot class.This article reports on the measures taken by the pilot class at PUMC in enrollment and curriculum setting,and demonstrates the achievements of the pilot class in terms of student academic background structure,knowledge acquisition and skill learning,scientific research ability,and course evaluation.The results indicated that the pilot class had met the national demand for the"Medicine+X"talent training model.More specifically,with a diverse academic backgrounds,the pilot class graduates had academic levels comparable to the eight-year medical education graduates,and their scientific research abilities were satisfactory.The pilot program at PUMC will optimize the curriculum setting,strengthen the construction of faculty,learning resources,and teaching facilities,and reform the academic evaluation methods,thus deepening the reform of medical education and improving the"4+4"MD program as a novel medical education model. 展开更多
关键词 "4+4"MD pilot program teaching reform medical education
下载PDF
Adverse Pregnancy Outcomes Following Cryotherapy, Thermal Ablation and Loop Electrosurgical Excision Procedure for Cervical Intraepithelial Neoplasia Treatment: A Pilot Study among Zambian Women
10
作者 Victoria Mwiinga-Kalusopa Johanna E. Maree +1 位作者 Concepta Kwaleyela Patricia Katowa-Mukwato 《Open Journal of Obstetrics and Gynecology》 2024年第1期7-17,共11页
Background: Cervical Intraepithelial neoplasia treatments have become essential interventions to manage cervical lesions. Majority of the recipients of these treatments are women within the reproductive age group, who... Background: Cervical Intraepithelial neoplasia treatments have become essential interventions to manage cervical lesions. Majority of the recipients of these treatments are women within the reproductive age group, who according to literature may be at risk of adverse pregnancy outcomes. This pilot study is part of a study investigating adverse pregnancy outcomes among women who received Cryotherapy, Thermal ablation and Loop Electrosurgical Excision Procedure compared to the untreated women in Zambia. Materials and Methods: This descriptive study analyzed records of 886 (n = 443 treated and n = 443 untreated) women aged 15 - 49 years. The women were either screened with Visual Inspection with Acetic Acid or treated for Cervical Intraepithelial neoplasia at the Adult Infectious Disease Centre between January 2010 and December 2020. Women meeting the criteria were identified using the Visual Inspection with Acetic Acid screening records and telephone interviews to obtain the adverse pregnancy outcome experienced. Data were analysed using STATA version 16 to determine the prevalence and obtain frequency distribution of outcomes of interest. Univariate and multivariable binary logistic regression estimated odds of adverse pregnancy outcomes across the three treatments. Results: The respondents were aged 15 to 49 years. Adverse pregnancy outcomes were observed to be more prevalent in the treatment group (18.5%) compared to the untreated group (5.4%). Normal pregnancy outcomes were lower in the treated (46.3%;n = 443) than the untreated (53.7%;n = 443). The treated group accounted for the majority of abortions (85.2%), prolonged labour (85.7%) and low birth weight (80%), whereas, the untreated accounted for the majority of still births (72.7%). Women treated with cryotherapy (aOR = 2.43, 95% CI = 1.32 - 4.49, p = 0.004), thermal ablation (aOR = 6.37, 95% CI = 0.99 - 41.2, p = 0.052) and Loop Electrosurgical Excision Procedure (aOR = 9.67, 95% CI = 2.17 - 43.1, p = 0.003) had two-, six- and ten-times higher odds of adverse pregnancy outcomes respectively, relative to women who required no treatment. Conclusion: Adverse pregnancy outcomes are prevalent among women who have received treatment in Zambia. The findings indicate that treating Cervical Intraepithelial Neoplasia has been linked to higher chances of experiencing abortion, delivering low birth weight babies and enduring prolonged labor that may result in a caesarean section delivery. Cervical neoplasia treatments, particularly Loop Electrosurgical Excision Procedure, are associated with significantly increased odds of adverse pregnancy outcomes. It is essential to include information about prior Cervical Intraepithelial neoplasia treatment outcomes in obstetric care. 展开更多
关键词 Adverse Pregnancy Outcomes Cervical Intraepithelial Neoplasia Cryothera-py Thermal Ablation Loop Electrosurgical Excision Procedure pilot Repro-ductive Age
下载PDF
The Tenth Anniversary of Free Trade Pilot Zones in China:Fundamental Experiences and Enhancement Strategies
11
作者 Pei Changhong 《China Economist》 2024年第3期2-20,共19页
Since the 18th National Congress of the Communist Party of China,the country has established 21 Free Trade Pilot Zones(FTZs),achieving significant pioneering results in reform and opening up and creating a strong demo... Since the 18th National Congress of the Communist Party of China,the country has established 21 Free Trade Pilot Zones(FTZs),achieving significant pioneering results in reform and opening up and creating a strong demonstrative effect nationwide.The basic experience from a decade of FTZs includes:adhering to the centralized and unified leadership of the CPC Central Committee;combining top-level design with encouragement of grassroots innovation;leveraging the distinct characteristics and strengths of FTZs to form a differentiated development pattern;maintaining the integration of opening up with domestic reforms;using openness to drive reforms;and organically combining openness with national security assurance.Under the current and future new circumstances,China’s FTZs face new challenges and tasks.In accordance with the directives of the 20th National Congress of the Communist Party of China,an enhancement strategy for the FTZs needs to be implemented.This involves the following:First,accurately understanding and responding to the changing situation to create strategic opportunities.Second,shifting paradigms to implement innovation-driven strategies,using the new development pattern concept to guide the reform experiments and construction of the FTZs.Third,granting more autonomy to FTZs for reforms,pursuing progress while maintaining stability,and solidly advancing the reform experiments in the FTZs.Fourth,orderly expanding the opening up of the service sector and cautiously advancing the internationalization of the renminbi.Fifth,promoting innovative development in trade to build a strong trade nation.Sixth,establishing synergy with bilateral FTZs,Belt and Road cooperation,and national diplomatic strategies to enhance the linkage effect. 展开更多
关键词 Tenth anniversary of Free Trade pilot Zones experience summary enhancement strategy conception
下载PDF
Hazardous Attitude Factors Influence Risk Perception in General Aviation Pilots
12
作者 Athina Holmes 《Advances in Aerospace Science and Technology》 2024年第3期85-93,共9页
This manuscript presents a research proposal to investigate how hazardous attitudes among general aviation pilots influence pilot performance in aviation accidents. General aviation pilots train to maintain safe flyin... This manuscript presents a research proposal to investigate how hazardous attitudes among general aviation pilots influence pilot performance in aviation accidents. General aviation pilots train to maintain safe flying conditions, but accidents still occur, and human factors figure prominently among the causes of aviation accidents. The levels of hazardous attitudes among pilots may influence the likelihood of engaging in risky flight behaviors that can lead to accidents. This quantitative study aims to determine whether dangerous attitudes impact risk perception in general aviation pilots. The study will focus on two specific hazardous attitudes, “Anti-Authority” and Macho” behaviors. Among the hazardous attitudes identified by the Federal Aviation Administration (FAA), the two attitudes often stand out in accident investigations and pilot narratives. While all hazardous attitudes have inherent dangers, these two attitudes tend to be more frequently cited in accident reports and investigations. Despite rigorous training in safe flying conditions, general aviation accidents still transpire due to human factors. This research hypothesizes that the five attitudes from the hazardous attitude model, particularly Anti-Authority and Macho, significantly shape pilots’ risk perception. The insights from this study would benefit stakeholders, like the Aircraft Owners and Pilots Association (AOPA), Air Safety Institute, and aviation training programs, in creating training modules tailored to reduce such attitudes. 展开更多
关键词 General Aviation (GA) pilot Aviation Safety Hazardous Attitudes Anti-Authority Macho Risk Perception Flight Training
下载PDF
The Current Situation and Future Expectationsof China's Pilot Boatsl
13
作者 Haidong Zhan 《现代交通(中英文版)》 2023年第1期1-8,共8页
Pilots need to board the ship for pilotage,but there are risks or potential dangers in the transfer of pilot.The author reviewed the history of the development of pilot boats,analyzed the potential risks or dangers of... Pilots need to board the ship for pilotage,but there are risks or potential dangers in the transfer of pilot.The author reviewed the history of the development of pilot boats,analyzed the potential risks or dangers of transferring pilot,proposed that pilot boat shall have the function of ensuring the safety of pilot when embarking or disembarking the ships,some suggestions on the future design and manufacture of Chinese pilot boats are also given according to the advantages and disadvantages of domestic and foreign pilot boats. 展开更多
关键词 pilot Boat pilot Transfer of pilot SAFETY RISK Current Situation Future Expectations
下载PDF
TD-SCDMA进行时
14
作者 杨海峰 《通信世界》 2005年第31期14-16,共3页
2000年5月,TD—SCDMA被ITU批准为第三代移动通信国际标准,实现百年来中国电信发展史上的重大突破。2002年2月,TD-SCDMA被证明能够实现独立组网和全国覆盖。2002年10月,TD—SCDMA标准获得了总计155MHz的非对称频段。 2003年7月,世... 2000年5月,TD—SCDMA被ITU批准为第三代移动通信国际标准,实现百年来中国电信发展史上的重大突破。2002年2月,TD-SCDMA被证明能够实现独立组网和全国覆盖。2002年10月,TD—SCDMA标准获得了总计155MHz的非对称频段。 2003年7月,世界首次TD-SCDMA手持电话成功演示。 2004年12月,全球首款GSM/TD—SCDMA双模终端问世。 2005年,随着TD—SCDMA相关测试工作全面收尾,TD—SCDMA进入商用前的冲刺阶段。TD—SCDMA发展的每一步,部是产业链以及所有投入了力量在TD—SCDMA技术上的企业的共同努力。 无论是同类竞争企业还是不同领域的企业,其前所未有的联手合作模式,给TD—SCDMA的发展提供了独有的支持,使得TD-SCDMA相对于WCDMA和CDMA2000发展速度快了许多。2005年是TD—SCDMA发展速度大幅提升的一年,也是其独立组网和牌照颁发被讨论得最多的一年。TD—SCDMA的优势和劣势皆明显,随着产业链的不断壮大,其劣势必将逐渐化小,优势将逐渐上升,但在3G的现实环境中,只有加快产业链的成熟、获得更明朗的市场前景并为走向全球市场积极作好准备,TD-SCDMA才能在自身商用方式的问题上获得更主动的选择权。 展开更多
关键词 TD-Scdma 中国电信 3G cdma2000 第三代移动通信 Scdma技术 cdma标准 独立组网 发展速度 Wcdma
下载PDF
汉明码在多载波CDMA系统中的应用
15
作者 陆峰 曹开田 +1 位作者 钱卫星 郑义 《信息技术与信息化》 2006年第2期59-61,共3页
本文讨论了GMCCDMA技术。GMCCDMA提供了全数字、统一的结构,包含了单载波和多载波CDMA系统。然后,本文用信道编码对GMCCDMA技术改进,采用在GMCCDMA系统前先进行编码来确保低误码率。仿真结果会表明:经过编码后的系统能取得更低的误码率... 本文讨论了GMCCDMA技术。GMCCDMA提供了全数字、统一的结构,包含了单载波和多载波CDMA系统。然后,本文用信道编码对GMCCDMA技术改进,采用在GMCCDMA系统前先进行编码来确保低误码率。仿真结果会表明:经过编码后的系统能取得更低的误码率。图像在编码的GMCCDMA和未编码的GMCCDMA两个系统中的不同传输效果进一步验证了这一结论。 展开更多
关键词 MC-cdma MT-cdma MC-DS-cdma OFDM GMC-cdma
下载PDF
对多载波CDMA方案的分析
16
作者 王建 李方伟 《中国无线通信》 2004年第8期22-24,共3页
目前,第三代移动通信的主流标准(包括TD-SCDMA、WCDMA和cdma2000)都是采用扩频码分多址(CDMA)方式作为其空中接口的技术,由于CDMA技术可以提供比传统多址技术(例如:TDMA、FDMA)更大的系统容量,并且具有抗信道频率选择性衰落的良好... 目前,第三代移动通信的主流标准(包括TD-SCDMA、WCDMA和cdma2000)都是采用扩频码分多址(CDMA)方式作为其空中接口的技术,由于CDMA技术可以提供比传统多址技术(例如:TDMA、FDMA)更大的系统容量,并且具有抗信道频率选择性衰落的良好特性,该技术就成为未来支持无线移动通信中高速数据多媒体业务的有力竞争者。 展开更多
关键词 多载波cdma 多址技术 扩频码 频率选择性衰落 无线移动通信 码分多址(cdma) 空中接口 竞争者 cdma技术 TD-Scdma
下载PDF
三种改进的LMS算法应用于宽带CDMA中的窄带干扰抑制 被引量:2
17
作者 杜丽冰 朱宏涛 《电路与系统学报》 CSCD 1996年第4期25-28,共4页
本文应用三种改进的LMS算法,采用最简单的自适应线性预测器(ALP),抑制码分多址(CDMA)中的窄带干扰(NBI),以实现CDMA系统与现有模拟和数字窄带系统兼容运行。通过计算机模拟,从跟踪能力和运算量等方面对三种... 本文应用三种改进的LMS算法,采用最简单的自适应线性预测器(ALP),抑制码分多址(CDMA)中的窄带干扰(NBI),以实现CDMA系统与现有模拟和数字窄带系统兼容运行。通过计算机模拟,从跟踪能力和运算量等方面对三种改进的LMS算法进行比较分析,得出了一些结论。 展开更多
关键词 LMS算法 宽带cdma 窄带干扰抑制 窄带系统 码分多址(cdma) cdma系统 线性预测 自适应 跟踪 兼容
下载PDF
基于OFDM的多载波CDMA系统的研究 被引量:2
18
作者 李一兵 赵洁 李呈杰 《信息技术》 2004年第3期59-60,63,共3页
MC-CDMA系统是将CDMA和OFDM技术的优点结合在一起的多址方案。首先介绍了OFDM的基本原理,并据此给出MC-CDMA系统的模型,通过对MC-CDMA和DS-CDMA的性能比较,MC-CDMA能提供更高的系统容量,结构更简单,抗干扰性更强,更适用于未来移动通信... MC-CDMA系统是将CDMA和OFDM技术的优点结合在一起的多址方案。首先介绍了OFDM的基本原理,并据此给出MC-CDMA系统的模型,通过对MC-CDMA和DS-CDMA的性能比较,MC-CDMA能提供更高的系统容量,结构更简单,抗干扰性更强,更适用于未来移动通信的需要。 展开更多
关键词 OFDM 多载波cdma MC—cdma DS—cdma
下载PDF
TD-SCDMA、cdma2000和WCDMA无线网络设计和规划比较 被引量:2
19
作者 陈曦 杨福慧 《电信科学》 北大核心 2005年第11期59-62,共4页
本文介绍了WCDMA、cdma2000、TD-SCDMA等三种3G标准无线网络设计的特点,重点分析了TD-SCDMA与WCDMA规划设计的不同之外,并介绍了上海贝尔阿尔卡特的规划工具的特点。
关键词 3G 网络规划 TD-Scdma cdma2000 Wcdma
下载PDF
Low PAPR Channel Estimation for OTFS with Scattered Superimposed Pilots 被引量:2
20
作者 Wei Liu Liyi Zou +1 位作者 Baoming Bai Teng Sun 《China Communications》 SCIE CSCD 2023年第1期79-87,共9页
Orthogonal time frequency space(OTFS)modulation has been proven to be superior to traditional orthogonal frequency division multiplexing(OFDM)systems in high-speed communication scenarios.However,the existing channel ... Orthogonal time frequency space(OTFS)modulation has been proven to be superior to traditional orthogonal frequency division multiplexing(OFDM)systems in high-speed communication scenarios.However,the existing channel estimation schemes may results in poor peak to average power ratio(PAPR)performance of OTFS system or low spectrum efficiency.Hence,in this paper,we propose a low PAPR channel estimation scheme with high spectrum efficiency.Specifically,we design a multiple scattered pilot pattern,where multiple low power pilot symbols are superimposed with data symbols in delay-Doppler domain.Furthermore,we propose the placement rules for pilot symbols,which can guarantee the low PAPR.Moreover,the data aided iterative channel estimation was invoked,where joint channel estimation is proposed by exploiting multiple independent received signals instead of only one received signal in the existing scheme,which can mitigate the interference imposed by data symbols for channel estimation.Simulation results shows that the proposed multiple scattered pilot aided channel estimation scheme can significantly reduce the PAPR while keeping the high spectrum efficiency. 展开更多
关键词 OTFS channel estimation superimposed pilots PAPR interference mitigation
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部