Applications of Maximum Likelihood Algorithm in Asynchronous DS-CDMA Systems
Pei Xiao,Erik Str¨o m
Communication Systems Group,Dept.of Signals and Systems
Chalmers University of Technology,SE-41296,G¨o teborg,Sweden E-mail:pei.xiao@s2.chalmers.se,erik.strom@s2.chalmers.se
Abstract—In this paper,we treat the problems of propagation delay and channel estimation as well as data detection of orthogonally modulated signals in asynchronous DS-CDMA system over fading chan-nels using the maximum likelihood(ML)approach. The overwhelming computational complexity of the ML algorithm makes it unfeasible for implementa-tion.The emphasis of this paper is to reduce its com-plexity by some approximation methods.The de-rived approximative ML schemes are compared with conventional algorithms as well as some others,e.g., the PIC for data detection and the subspace-based algorithm for acquisition.
I.I NTRODUCTION
The considered system in this paper is an asyn-chronous DS-CDMA system with orthogonal modula-tion.The transmitted chip sequence from a particular user is the concatenation of one of possible Walsh codes(representing the transmitted symbol)and a long scrambling code used for user separation.The rationale for using orthogonal modulation is to avoid having to track the phase in a rapid fading environment[1]. Iterative methods for demodulating orthogonal sig-nalling formats in DS-CDMA systems were proposed in[2],[3].Perfect synchronization of the chip timing is required to achieve the low bit error rate by all the demodulation schemes.The impact of synchronization errors on data demodulation was studied in[3].It was shown that errors in the delay estimates would drasti-cally degrade the system performance.
Several synchronization schemes were proposed in[4]for orthogonally modulated signals, e.g., subspace-based estimator,MMSE delay estimator, whitened sliding correlator,etc..They all require a long periodic training sequence to derive an accurate esti-mate of the covariance matrix.
To provide substantial capacity gains,multiuser de-tectors also require estimation of the fading channels. Coherent detection always outperforms its non-coherent counterpart provided that the channel gains are accu-rately estimated[3].
In this paper,we treat all the above issues in an uni-form manner,i.e.,under the maximum likelihood(ML) framework,and compare the performance with the al-gorithms mentioned earlier.In section II,the system model is presented,and the general ML algorithm is formulated.The applications of the approximative ML algorithms with reduced complexity on delay estima-tion,channel estimation and data detection are intro-duced and evaluated with numerical results in section III and IV.Finally,the proposed algorithms are summa-rized and conclusions are drawn in section V.
II.S YSTEM M ODEL
The passband received signal due to the user is denoted by.The user’s symbol is denoted by,and the or-thogonal signal alternatives are de?ned by Walsh sequences of length. The Walsh chips are randomized by a scrambling code
.Hence,every symbol which repre-sents binary bits is spread by chips and each bit by chips.
The baseband signal is formed by pulse ampli-tude modulation with the unit-energy rectangular chip waveform,and the baseband signal is multiplied with a carrier with frequency and transmitted over the chan-nel,which is represented by the complex channel gain and assumed to be a slowly time-varying Rayleigh ?at fading channel with delay.
The total received signal is the sum of the users’signals plus additive white complex Gaussian noise with power spectral density.The complex enve-lope of the received signal is
where stands for the propagation delay of the th user.The vector is de?ned as
.Let us denote
(is one chip interval)such that
stands for the chip delay,
stands for the interchip delay,and denote, the transmitted chip sequence due to the th user as
(3) where is a diagonal matrix de?ned by the th user’s scrambling code,and
is the th column()of the Hadamard matrix.Then,each column of the matrix in(2)can be expressed as
(4) where,stand for the up-shift and down-shift operators respectively:
,
.All the delay estimators intro-duced in this paper need a periodic training sequence, which means remains unchanged at the delay es-timation stage.
In our case,the noise is complex Gaussian.Given observations of the received vector for
,the log-likelihood function of the received vector can be expressed as1
We denote the2-norm of a vector by Downmixing,
Chip-Matched
Filtering,
Sampling
Delay
Estimation
reformed as
Since is irrelevant to the choice of,so the decision is solely decided by,i.e.,the projection of onto the the subspace spanned by the vector. Therefore,the ML single user delay estimator(8)can be expressed alternatively as
The projection of onto the the subspace spanned by the vector is the same as the normalized correla-tion of the vectors and,therefore,in single user case,the ML delay estimator becomes identical to the conventional sliding correlator(SC)which is the stan-dard approach to delay estimation.The merit function for the SC is formed by correlating the received signal with time delayed versions of the known code se-quence
is the sample mean of the re-ceived vector.The estimated delay is the delay candi-date value that maximizes the correlation.
Like the standard receiver(i.e.,the single user matched?lter),the SC or the ML single user delay esti-mator is only optimal in the AWGN single user channel or in strict orthogonal synchronous channel.It is highly unreliable in the presence of MAI.The ML approach to delay estimation suitable for multiuser environment is presented below.
B.ML multiuser delay estimator
It is shown in[2]that the ML estimation of the fading channel vector is
(9) where denotes the left pseudoin-verse of,which is the data matrix with timing uncertainty denoted by.Substituting into(6),we yield the ML estimate of as
(10)
where is the orthogonal projection matrix onto the orthogonal complement to the subspace spanned by the columns of.
The ML multiuser delay estimator?nds the delays of
all the users simultaneously.The disadvantage of this algorithm is the unaffordable computational complex-ity because it has to search over points(is the number of users,is spreading factor,and we assume the delays are within one symbol interval).While the
ML single user estimator or the subspace-based estima-tor(see[4],[6])estimate the delay for one user at a time, the number of points to be searched goes down to. However,some approximations can be made to sim-plify the ML algorithm.The sub-optimum solutions with reduced complexity are discussed below.
B.1Hierarchic ML delay estimator
In[7],a hierarchic way to construct an ML approx-imation for delay estimation was proposed.A revised version of this algorithm adopted to the system model in question is as follows:
1.Evaluate for
.Choose corresponding to the minimum trace value,which means we?x the delay es-timate for the user.
2.Form the matrices for
https://www.doczj.com/doc/8612397128.html,pute
,evaluate for
and.Choose cor-responding to the minimum trace value.
3.Form the matrices
for https://www.doczj.com/doc/8612397128.html,pute
,evaluate. Choose corresponding to the minimum trace value.
4.Repeat step3until all the users’delays are esti-mated and?xed.
The idea of this scheme is similar to that of successive interference cancellation(SIC).We?x the delay of one user at each step,that user’s signal is reconstructed and used for detecting the next user’s delay.
B.2Multistage parallel ML delay estimator
The complexity of ML algorithm can also be reduced in an iterative multistage manner like parallel interfer-ence cancellation(PIC).We use the ML single user de-lay estimator to get initial estimates of delays for all the users and enter the iteration loop.The subsequent stages differ from the hierarchic estimator introduced earlier. Instead of?xing one user’s delay at a time,we?x the delays of all the interfering users simultaneously(in par-allel),using the estimates derived from last iteration in order to estimate the delay for the user of interest,e.g., the th user.This multistage parallel ML delay estima-
tor can be expressed as
(11)
The matrix
is de?ned as
where are the estimated delays for the interfering user at the
iteration stage.
In contrast to the original ML algorithm which jointly detects all the users,these two approximative ML algo-rithms detect the delay of one user at a time,thus greatly reduce the computational complexity compared to a full search of the ML criterion function.Like the SC,they have the property of fast convergence,require much shorter training sequence than the subspace-based algo-rithm,thus reduce the overhead induced by the training.The results of the -stage parallel ML delay estima-tion are demonstrated in Fig.2.Clearly,the perfor-mance is improved at each iteration.However,it tends to get saturated at the th stage.The simulated system for this and all the following experiments is a -user system with chips per symbol and
signal alternatives.The signal to noise ratio is set to
,and perfect power control is
assumed in the sense that the average power is equal to all users.The channels are independent Rayleigh fad-ing channels.The channel gain
is complex cir-cular Gaussian process with auto-correlation function
where is the max-imum Doppler frequency and is the zeroth order
Bessel function of the ?rst kind.Simulation results are averaged over or Monte-Carlo runs with each MCrun representing a particular realization of the data sequences,noise,and fading processes,as well as prop-agation delays.
The comparison among different delay estimators is illustrated in Fig.3.The parallel ML estimator per-forms slightly better than the hierarchic one.They both achieve good acquisition performance with a short training sequence (approximately pilots).As ex-pected,the subspace-based estimator does not work with short training sequence.We anticipate the curve of the subspace-based algorithm would go down to the same level as the approximative ML algorithms when the number of pilots increases,e.g.,to around .
B.3Combined hierarchic and parallel ML delay esti-mator Since the hierarchic and parallel estimator have dif-ferent mechanisms for searching the optimum values of the propagation delays,we tend to think that when
estimator
these two are coupled together,the combined algorithm has better chance to get out of the local minimum and
converge to the global optimum attainable by the origi-
nal ML algorithm.That is indeed the case as shown in
Fig.4.In the experiment,the hierarchic scheme is used
as the?rst stage followed by-stage parallel scheme. The combined scheme performs better than each indi-
vidual one.For instance,with pilot symbols,the
acquisition error probability goes down to when these two methods are coupled together.While the ac-quisition error probability of each individual scheme is around.
IV.ML A PPROACH TO D ATA D ETECTION The ultimate goal of the receiver is to detect the sym-bols from all the users given the received signal vector ,i.e.,detect for(see Fig.1). The decision on the th user’s symbol at the th itera-tion stage(if multistage detection is applied)is denoted by and is found as
where is the soft decision function at the iteration stage.
It was shown in[8]that with proper synchronization (delay estimation)mechanism,an asynchronous system with random propagation delays approximates the per-formance of a synchronized and chip-aligned system (meaning is known and,i.e.,the received signal is aligned with chip matched?lter),for which in equation(4)reduces to
(12) In the following,we shall derive the soft decision
for the ML demodulation schemes based on this simpli-?ed setting.
A.ML single user detector
The extension of the ML single user delay estimation to data detection is straightforward.Instead of having different candidate values of delay for the th user in equation(7),we try the possible transmitted wave-forms,,,,,() when detecting the th transmitted symbol of the th user.The ML single user detector can therefore be for-mulated as
where,. The matrix is the instantaneous covariance matrix de?ned as.
Here again,the ML single user detector becomes identical to the conventional matched?lter(MF)which forms the soft decision by correlating the received sig-nal with the local reference signals,i.e.,
.This simple scheme is particularly useful in the beginning of the detection process,e.g.,at the?rst iteration stage,when the estimates of the fading chan-nels are lacking,we must therefore carry out the detec-tion in a noncoherent manner.
B.ML multiuser detector
Although optimum in the single user AWGN channel, the above mentioned detector has poor performance in multiuser environment.From equations(6)and(9),we know that the ML estimation of the data matrix
can be derived as the minimizer of
(13) This ML multiuser detection algorithm jointly detects the symbols transmitted by all the users,it requires a test of hypotheses,thus the com-plexity grows exponentially with the number of users .A sub-optimum solution that reduces the complex-ity from exponential to polynomial is the multistage ML detector.We use the ML single user detector,or equiva-lently,the conventional detector for the?rst stage to get initial estimates of the transmitted data.Then the ML algorithm switches to the decision directed mode.To detect the data transmitted by the th user,we replace in equation(13)with de?ned as
(14) where the vectors
are obtained by substituting
into equations(3),(12),and we assume the chip delay is known.
C.A comparison between PIC and ML algorithm Parallel interference cancellation(PIC)scheme de-tects all the users at the same iteration(in parallel)and then cancels the MAI at the next iteration stage.The soft decision of PIC can be formed as
(15) where and are obtained by substituting into(12),and is the estimate of the fading vector.
Let us denote as the MAI matrix formed as
The matrix is similar to except that the th user transmitted symbol is deleted.
Similarly,we delete the estimate of the th user’s channel coef?cient from the vector and form the channel vector corresponding to the MAI
Then the PIC algorithm can be reformulated as
(16) Meanwhile,the expression of the approximative ML algorithm–equations(13)and(14)can be expanded as
(17) The?rst term of the expression(17)is irrelevant to the choice of,and all the possible transmitted wave-forms for have the same energy, thus the third term is also common for the decision met-rics.Minimization of the decision function(17)is there-fore equivalent to maximization of
which is exactly the same as the PIC algorithm ex-pressed by the equation(16).We can conclude that the PIC is an approximative ML approach to data detection. We know that the channel gains are correlated in time,and the channel estimates can be improved by smoothing.A simple smoothing procedure[2]is to feed through an FIR?lter with impulse response which yields the smoothed channel vector as
.
The performance of the discussed data detectors is il-lustrated in https://www.doczj.com/doc/8612397128.html,ing the ML single user detector (conventional receiver)as the?rst stage,the ML mul-tiuser detector or equivalently,the PIC without channel smoothing achieves considerable gains compared to the conventional receiver as indicated by the dashed curve. The performance of the PIC can be further improved by channel smoothing(replacing with in equa-tion(15)or(16)),as illustrated by the dash-dot curve.
V.S UMMARY AND CONCLUSIONS
In this paper,some approximation methods to reduce the complexity of the ML algorithm are introduced and the applications of the derived approximative ML algo-rithms on the delay estimation and data detection of the orthogonally modulated signals in asynchronous DS-CDMA system are discussed.
The general principle is to use the single user ML algorithm as the?rst stage to get an initial estimates of the delays/transmitted data.In this case,the MAI is treated as additive noise.The ML single user delay estimator/data detector turns out to be identical to the
conventional SC/MF.Clearly,the SC/MF is optimal de-lay estimator/data detector in single user AWGN chan-nel.After obtaining the initial estimates,we switch to decision directed mode and improve the results at each iteration stage,using the ideas similar to SIC or PIC. The suggested approximative ML algorithms are eval-uated by computer simulations and found to have good performance with affordable complexity.
R EFERENCES
[1]S.Vembu,A.Viterbi.Two different philosophies
in CDMA-a comparision.Proc.VTC’1996,vol.
2,pages869-873,Jan.1996.
[2] E.G.Str¨o m,https://www.doczj.com/doc/8612397128.html,ler.Iterative demodulation
of orthogonal signalling formats for DS-CDMA.
Proc.ICC2000,vol.3,pages1457-1461,2000. [3]P.Xiao,E.Str¨o m.Performance of iterative DS-
CDMA M-ary demodulation in the presence of synchronization errors.Proc.VTC’2001spring, pages1703-1707,May,2001
[4]P.Xiao,E.Str¨o m.Acquisition of Orthogonal
Modulated Signals in Rayleigh-Fading Channels.
Proc.European Wireless,pages811-816,Feb.
2002.
[5] E.Str¨o m,F.Malmsten.A maximum likelihood
approach for estimating DS-CDMA multipath fad-ing channels.IEEE Journals on Selected Areas in Communications,vol.18,pages132-140,Jan.
2000.
[6] E.Str¨o m,S.Parkvall,https://www.doczj.com/doc/8612397128.html,ler, B.Ottersten.
Propagation delay estimation in asynchronous direct-sequence code-division multiple access systems.IEEE https://www.doczj.com/doc/8612397128.html,mun.,vol.44,pages 84-93,Jan.1996.
[7]J.Joutsensalo,J.Lilleberg, A.Hottinen,J.
Karkunen.A hiearchic maximum likelihood method for delay estimation in CDMA.Proc.
VTC’1996,vol.1,pages188-192,1996.
[8]P.Xiao,E.Str¨o m.Delay estimation and data de-
tection in long-code DS-CDMA system.Submit-ted to GLOBECOM’2002.
Part One 宏观指导 彭青龙 上海交通大学外国语学院教授、副院长、博士生导师 研究领域：外语教学方法、专门用途英语、其他外国文学研究、其他外国社会文化 主持项目：独立主持课题十项，其中国家社科基金重大课题子项目一项、国家社科基金一般项目两项、教育部人文社科基金一般项目一项、澳大利亚政府基金项目两项等。 Q：如何更好地利用国家社科基金项目、教育部人文社会科学研究项目中的选题指南来进行选题？ a.课题申报者应仔细研究课题指南，深刻领会其内涵和外延，确定适合自己的选题。国家项目课题指南往往反映的是最前沿或者最基础却尚未解决好的研究问题。 b.国家项目课题指南每年都会有变化，课题申报者可以对比研究近两三年课题指南的变化，较往年有变化的地方通常是国家特别希望在这个领域内进行着力研究的问题。 Q：如何判断某一个课题是否具有学术价值或应用价值？可否举例说明？ 一个课题的学术价值体现在其理论价值和应用价值两方面。而课题的创新往往体现在观点创新或是方法创新两个主要方面。如，某课题一般运用定性研究的方法，而本人综合运用了定性和定量的两种方法，这从某种意义上来说就是一种创新，方法创新也可理解为新路径或新视角。创新往往是站在巨人的肩膀上的创新。Q：国家课题的选题与一般学术论文选题区别在哪里？ 国家课题往往是各领域亟待解决的问题。研究成果受众面大，具有广泛的应用价值或理论价值，也具有相当的示范性。国家课题一般是集中某一重要方面进行多维度的探讨，更具系统性和逻辑性，其成果至少应该是系列论文而非单篇文章。Q：课题申报书常见问题有哪些？ 申报书需要展示的是三个方面，即why, what, how, 即你为什么要做此项研究，研究的主要内容是什么，你将如何组织实施你的研究。同时，前期积累也很重要。总之，通过申报书，你要能说服评审专家可以将这个项目放心地交给你。 课题申报书中的常见问题有： a. 选题本身存在概念不清、逻辑混乱。申报者对基本概念应有明晰的判断，主概念和子概念之间关系要有逻辑性。 b. 选题过大或过小。有些选题太大，可写成大型系列丛书，但申报书中的论述不够详实，难以支撑。有些选题也很大，但仅以很小的案例做支撑，论证充分性不够，难以令人信服。 c. 文献综述，述而不论。一些申报书中文献综述仅罗列多方观点，却没有批判性的论述，或将自己的论述淹没在描述中，没有鲜明地提出自己的观点。文献综述在综合分析前人研究成果的同时，要对其进行评价和判断，即哪些观点是得到普遍认同的，哪些观点还存在不足，有待进一步研究。而本课题研究正是弥补不
How to manage time Time treats everyone fairly that we all have 24 hours per day. Some of us are capable to make good use of time while some find it hard to do so. Knowing how to manage them is essential in our life. Take myself as an example. When I was still a senior high student, I was fully occupied with my studies. Therefore, I hardly had spare time to have fun or develop my hobbies. But things were changed after I entered university. I got more free time than ever before. But ironically, I found it difficult to adjust this kind of brand-new school life and there was no such thing called time management on my mind. It was not until the second year that I realized I had wasted my whole year doing nothing. I could have taken up a Spanish course. I could have read ten books about the stories of successful people. I could have applied for a part-time job to earn some working experiences. B ut I didn’t spend my time on any of them. I felt guilty whenever I looked back to the moments that I just sat around doing nothing. It’s said that better late than never. At least I had the consciousness that I should stop wasting my time. Making up my mind is the first step for me to learn to manage my time. Next, I wrote a timetable, setting some targets that I had to finish each day. For instance, on Monday, I must read two pieces of news and review all the lessons that I have learnt on that day. By the way, the daily plan that I made was flexible. If there’s something unexpected that I had to finish first, I would reduce the time for resting or delay my target to the next day. Also, I would try to achieve those targets ahead of time that I planed so that I could reserve some more time to relax or do something out of my plan. At the beginning, it’s kind of difficult to s tick to the plan. But as time went by, having a plan for time in advance became a part of my life. At the same time, I gradually became a well-organized person. Now I’ve grasped the time management skill and I’m able to use my time efficiently.
广东省哲学社会科学“十三五”规划项目 外语专项 申请书 项目类别 项目名称 项目负责人 负责人所在单位 填表日期
广东省哲学社会科学规划领导小组办公室制 二О二О年六月 申请者的承诺： 保证如实填写本表各项内容。如果获准立项，承诺以本表为有约束力协议，遵守《广东省哲学社会科学规划项目管理办法》等有关规定，认真开展研究工作，取得预期研究成果。 申请者（签章）： 年月日 填表注意事项 一、本表请如实填写。 二、本表第一项“项目负责人、主要参加者情况”部分栏目填写说明： 1、研究类型：指本项目研究属基础理论研究、应用开发研究、综合研究等。 2、主要参加者：必须真正参加本项目研究工作，不含项目负责人，不包括科研、财务管理人员。 3、预期成果形式：指最终成果形式，含专著、研究报告、论文等。其中，论文指内容具有相关性、系统性的，已发表及未发表的论文若干篇。 4、项目完成时间：1-2年。 三、申请人具有副高以上（含副高）职称或具有博士学位者，不填“推荐人意见”。 四、本表内“申请者（签章）”和“推荐人姓名”处须手写，不能打印。
五、本表用A3纸双面印制，中缝装订成册。 六、本表由项目负责人所在单位加具单位意见，并统一报送省哲学社会科学规划领导小组办公室。 七、省哲学社会科学规划领导小组办公室地址：XX市天河北路618号广东社科中心B座9楼，邮编：******，电话：（020）********、********。 一、项目负责人、主要参加者情况
二、课题设计论证
三、项目负责人正在主持的其他项目 四、推荐人意见 五、项目负责人所在单位意见
Outlook中存储了日常工作所需的重要数据，因此，Outlook数据的及时备份也就显得尤为重要。一般情况下，Outlook中的数据都是通过PST文件进行存储 和备份的。 PST文件（Personal Folder File个人文件夹）在实质上是一组Outlook信息的集合，如：收件箱、发件箱、草稿、日历、任务、地址簿，但不包含邮件账户及规则。Outlook为每个用户都建立独立的PST文件。如果你使用的是Windows XP，那么，你会在“X:￥Documents and Settings￥用户名￥Local Settings￥Application Data￥Microsoft￥Outlook”目录下面找到名为“Outlook.pst”的文件，这就是属于你的PST文件，默认状态下，这个文件中存储了Outlook中与你的账户相关的所有信息。 1. 备份Outlook数据文件 执行【文件】菜单下的【导入和导出】命令，在弹出的“导入和导出向导”对话框中，选择“导出到一个文件”一项，单击【下一步】按钮。 接下来，在“创建文件的类型”中选择“个人文件夹文件(.pst)”一项，单击【下 一步】按钮。
在“选定导出的文件夹” 中，我们可以选择需要备份的内容，比如收件箱、联系人、日历等。如果想要将收件箱中所有的邮件都备份，记得要选择下面的“包括子文件夹”项。如果想要将当前Outlook中所有的信息全都备份在一个pst文件里，可以直接选择文件夹树形结构的最顶端——“个人文件夹”一项。 最后，指定好个人文件夹的保存位置，单击【完成】按钮，即可开始进行备份。
2. Outlook数据的还原 一旦Outlook数据有损失，或者需要对Outlook数据进行迁移，我们都可以将曾经备份好的Outlook数据文件还原回来。还原过程与备份是相逆的操作，其方法与备份是基本相同的。 我们同样要执行【文件】菜单下的【导入和导出】命令，在对话框中则要选择“从另一个程序或文件导入”这一项，单击【下一步】按钮。 选择导入文件的类型是“个人文件夹文件(.pst)”。 指定需要导入的pst文件的位置。
伊川县江左镇中基 础教育教研课题 立项申报书 学 科 分 类_____初中英语______________________ 课 题 名 称_多媒体课件优化中学生英语阅读的实践研究 课 题 主 持 人___ 刘志刚___________________________ 课 题 组 成 员_韩世伟 程会英 黄爱香 杨玉温 端木梦梦 主持人工作单位____ 伊川县江左镇初级中学_________ 申 请 日 期__ 2014年12月10日 伊川县教育局基础教育教研室 立项编号 ?yckt160803 学科代码 08?
填表说明 一、本表须经课题主持人所在单位和中心校审核，签署明确意见，承担信誉保证并加盖公章后，方可上报。 二、封面左上方代码框申请人不填，其他栏目由申请人用中文填写。每项课题主持人限1人；主要参与者不包括课题主持人，至少2人，最多5人。 三、本表报送一式3份，请用A4纸双面打印、复印，于左侧装订成册。同时，须提供本表的电子版1份。 四、请用钢笔或电脑打印，准确如实填写各项内容，书写要清晰、工整。 五、伊川县教育局基础教育教研室课题管理办公室： 联系人：赵康卷电话：
?一、基本情况 ? 二、 课题 设计论证 课题名称 多媒体课件优化中学生英语阅读的实践研究? 主持人 姓 名 ?刘志刚 政治面貌 党员? 性别 男? 年龄 41 行政职务 教导主任 专业 职称 中一? 学科 专业 英语? 学历 学位 本科 起止时间 2014年 12 月 10 日至 2015 年 12 月 10日 工作单位 通讯地址 伊川县江左镇中 邮政 编码 471314? 固定电话 E-mail 移动电话 主 要 参 与 者 姓 名 性别 年龄 专业 职称 学科 专业 学历学位 工作单位 韩世伟 男? 48 中二? 初中英语 本科 伊川县江左镇中 程会英 女? 40 中二? 初中英语 专科 伊川县江左镇中 黄爱香 女? 37 中二? 初中英语 本科 江左教育? 杨玉温? 女? 41 中二? 初中英语 本科 伊川县电力中学 端木梦梦 女? 26 中二? 初中英语 本科 伊川县江左镇中 预 期 成 果 （在选项上打“√” 或加粗） A ．专着 B.研究报告 C.论文 D.其他
金蝶K/3 OA 服务器备份、恢复及迁移 指导手册 金蝶国际 2005年1月
目录 1金蝶K/3 OA服务器的备份与恢复 (3) 1.1情况介绍 (3) 1.2最佳的备份策略 (3) 1.3如何恢复系统 (3) 1.4OA系统恢复的最低条件 (3) 2金蝶K/3 OA服务器的迁移 (5) 2.1情况介绍 (5) 2.2如何迁移系统 (6)
*****以下所有的操作方案都要求以细心的数据备份为前提 1金蝶K/3 OA服务器的备份与恢复 1.1情况介绍 最糟糕的事情发生了，不幸的系统管理员某一天上班突然发现OA服务器已经无法开启了，这可怎么办？别担心，如果他做好了备份工作，他就可以在短时间内恢复系统。 1.2 最佳的备份策略 ●首先管理员应该每周进行一次对整个“Lotus”文件夹的备份。(建议采用磁带机或专业 配分软件备份) ●然后在OA系统中设置OA数据库的备份规则。设置过程如下： 1、在Notes中，打开系统设置库。 2、点击“工具→备份设置”按钮。 3、在“每日备份时间”中天日备份启动的时间。在“保存几个备份”中建议填入5。 这样在备份目录中可以始终保留下最近5天的备份数据。在“目的路径”中填入备 份的数据的存放目录。 4、之后，点击按钮“保存”，再点击按钮“定时备份”。 5、设置好之后，请注意保证Domino在设置好的每日备份时间时为开启状态。 1.3 如何恢复系统 按照以上的备份规则，可以采用如下操作恢复系统。 1、如果需要的话，可以将OA服务器的操作系统重装一下（注意服务器的机器名称和IP地 址设置为和原来一样）。 2、然后首先将每周备份的“Lotus”文件夹恢复到他原来的路径下。 3、再将最近一次的OA自动备份的“K3OA”目录恢复到Lotus\Domino\Data目录下,替换原 有的“K3OA”目录。 4、运行Lotus\Domino\nserver.exe启动Domino服务器。运行Lotus\notes\notes.exe 启动Notes客户端。 1.4 OA系统恢复的最低条件 如果他没有备份整个Lotus文件夹的话，那他至少需要备份了以下文件： Cert.id（验证字文件） Server.id（服务器ID文件） User.id（管理员ID文件） Name.nsf（Domino服务器通讯录数据库）
1.How to build a business that lasts100years 0:11Imagine that you are a product designer.And you've designed a product,a new type of product,called the human immune system.You're pitching this product to a skeptical,strictly no-nonsense manager.Let's call him Bob.I think we all know at least one Bob,right?How would that go? 0:34Bob,I've got this incredible idea for a completely new type of personal health product.It's called the human immune system.I can see from your face that you're having some problems with this.Don't worry.I know it's very complicated.I don't want to take you through the gory details,I just want to tell you about some of the amazing features of this product.First of all,it cleverly uses redundancy by having millions of copies of each component--leukocytes,white blood cells--before they're actually needed,to create a massive buffer against the unexpected.And it cleverly leverages diversity by having not just leukocytes but B cells,T cells,natural killer cells,antibodies.The components don't really matter.The point is that together,this diversity of different approaches can cope with more or less anything that evolution has been able to throw up.And the design is completely modular.You have the surface barrier of the human skin,you have the very rapidly reacting innate immune system and then you have the highly targeted adaptive immune system.The point is,that if one system fails,another can take over,creating a virtually foolproof system. 1:54I can see I'm losing you,Bob,but stay with me,because here is the really killer feature.The product is completely adaptive.It's able to actually develop targeted antibodies to threats that it's never even met before.It actually also does this with incredible prudence,detecting and reacting to every tiny threat,and furthermore, remembering every previous threat,in case they are ever encountered again.What I'm pitching you today is actually not a stand-alone product.The product is embedded in the larger system of the human body,and it works in complete harmony with that system,to create this unprecedented level of biological protection.So Bob,just tell me honestly,what do you think of my product? 2:47And Bob may say something like,I sincerely appreciate the effort and passion that have gone into your presentation,blah blah blah-- 2:56(Laughter) 2:58But honestly,it's total nonsense.You seem to be saying that the key selling points of your product are that it is inefficient and complex.Didn't they teach you 80-20?And furthermore,you're saying that this product is siloed.It overreacts, makes things up as it goes along and is actually designed for somebody else's benefit. I'm sorry to break it to you,but I don't think this one is a winner.
尊敬的领导，老师，亲爱的同学们， 大家好！我是5班的梁浩东。今天早上我坐车来学校的路上，我仔细观察了路上形形色色的人，有开着小车衣着精致的叔叔阿姨，有市场带着倦容的卖各种早点的阿姨，还有偶尔穿梭于人群中衣衫褴褛的乞丐。于是我问自己，十几年后我会成为怎样的自己，想成为社会成功人士还是碌碌无为的人呢，答案肯定是前者。那么十几年后我怎样才能如愿以偿呢，成为一个受人尊重，有价值的人呢？正如我今天演讲的题目是：自主管理。 大家都知道爱玩是我们孩子的天性，学习也是我们的责任和义务。要怎样处理好这些矛盾，提高自主管理呢？ 首先，我们要有小主人翁思想，自己做自己的主人，要认识到我们学习，生活这一切都是我们自己走自己的人生路，并不是为了报答父母，更不是为了敷衍老师。 我认为自主管理又可以理解为自我管理，在学习和生活中无处不在，比如通过老师，小组长来管理约束行为和同学们对自身行为的管理都属于自我管理。比如我们到一个旅游景点，看到一块大石头，有的同学特别兴奋，会想在上面刻上：某某某到此一游话。这时你就需要自我管理，你需要提醒自己，这样做会破坏景点，而且是一种素质低下的表现。你设想一下，如果别人家小孩去你家墙上乱涂乱画，你是何种感受。同样我们把自主管理放到学习上，在我们想偷懒，想逃避，想放弃的时候，我们可以通过自主管理来避免这些，通过他人或者自己的力量来完成。例如我会制定作息时间计划表，里面包括学习，运动，玩耍等内容的完成时间。那些学校学习尖子，他们学习好是智商高于我们吗，其实不然，在我所了解的哪些优秀的学霸传授经验里，就提到要能够自我管理，规范好学习时间的分分秒秒，只有辛勤的付出，才能取得优异成绩。 在现实生活中，无数成功人士告诉我们自主管理的重要性。十几年后我想成为一位优秀的，为国家多做贡献的人。亲爱的同学们，你们们？让我们从现在开始重视和执行自主管理，十几年后成为那个你想成为的人。 谢谢大家！
数据中心灾难恢复指南 （更新版）
数据中心灾难恢复指南（更新版） 当前，基于Web的应用不断普及深入，新一代的企业级数据中心建设已成为行业信息化的新热点。虚拟化、云计算等新技术和概念的提出更是为数据中心的发展开辟了新的道路。但是，无论数据中心怎样变化，企业对于数据中心容灾备份的需求是只会提高不会降低的。此外，在预算日益紧缺的情况下，灾难恢复成本也是企业考虑的重要因素之一。企业灾难因素应该考虑哪些因素？如何将虚拟化应用到灾难恢复中来？如何减少数据中心灾难恢复成本？本指南将对这些问题进行解答。 灾难恢复考虑因素 灾难恢复策略和基础架构本身就很复杂，对于大型企业来说更是这样。在这个过程中存在许多可变因素：需要确定许多标准和流程，需要对人力资源进行组织，需要对技术进行整合，需要辨别不同应用间的差异并为其排定优先次序。 数据中心灾难恢复需要考虑哪些因素？ 将IT变更管理作为灾难恢复的一部分 虚拟化与灾难恢复 现在，许多公司都在它们环境的某处使用虚拟化技术。但是，他们可能不知道如何使用虚拟化技术来进行数据中心灾难恢复规划。学习如何应用虚拟化到灾难恢复很有用，也会受到很多技术上的限制。 虚拟化在数据中心灾难恢复中的作用 利用虚拟化技术来进行数据中心灾难恢复
如何节省灾难恢复成本 如今否认经济形势迫使企业减少预算。尽管灾难恢复（DR）人员在极力劝阻对这个领域预算的削减，DR也无法躲过预算危机。那么对于DR站对站数据复制解决方案的创建和维护而言，有没有什么方法或工具可以降低总的成本呢？ 灾难恢复预算的头号挥霍者 使用开源复制工具来降低灾难恢复成本 你是不是在为了避免麻烦而浪费灾难恢复成本？
Dear teacher and colleagues: my topic is on “spare time”. It is a huge blessing that we can work 996. Jack Ma said at an Ali's internal communication activity, That means we should work at 9am to 9pm, 6 days a week .I question the entire premise of this piece. but I'm always interested in hearing what successful and especially rich people come up with time .So I finally found out Jack Ma also had said :”i f you don’t put out more time and energy than others ,how can you achieve the success you want? If you do not do 996 when you are young ,when will you ?”I quite agree with the idea that young people should fight for success .But there are a lot of survival activities to do in a day ,I want to focus on how much time they take from us and what can we do with the rest of the time. As all we known ,There are 168 hours in a week .We sleep roughly seven-and-a-half and eight hours a day .so around 56 hours a week . maybe it is slightly different for someone . We do our personal things like eating and bathing and maybe looking after kids -about three hours a day .so around 21 hours a week .And if you are working a full time job ,so 40 hours a week , Oh! Maybe it is impossible for us at
附件1 1+X证书制度专项研究2020年度课题指南 为深入贯彻《国家职业教育改革实施方案》部署，落实《关于在院校实施“学历证书+若干职业技能等级证书”制度试点方案》等文件要求,着力通过专项课题研究、协同创新，为1+X证书制度目标任务实现、重点难点问题解决提供科研与智力支持，特制定本指南。申请人可结合自己的学术专长和研究基础选择申报，指南选题如下。 1.“放管服”改革背景下职业技能等级证书的功能、定位、效力和话语体系研究 主要内容：在“放管服”改革背景下，系统梳理技术技能人才评价制度、评价模式改革脉络，聚焦对技术技能人才评价维度、内容、方法等方面的改革，研究提出职业技能等级证书的功能、定位和效力，明晰职业技能等级标准、职业技能等级证书、复合型技术技能人才、国家资历框架、职业教育学分银行、培训评价组织等概念与内涵，建构1+X证书制度作为中国特色职业教育制度的话语体系和基本语境，为1+X证书制度理论体系的建构提供建议。 研究周期：1年 预期成果：论文3篇(在CSSCI核心库来源期刊发表至少1篇)；
专著（或合著）1部；研究报告1篇（不少于5万字）。 2.职业技能等级证书对接职业标准和教学标准的机制研究 主要内容：在技术技能人才培养培训中实行学历证书和职业技能等级证书相结合的理论依据、实践寻证和教育学价值；1+X证书制度与原“双证书”制度对比研究，德国、澳大利亚、新西兰等国家证书制度的比较研究；在职业院校实施“1+X”复合型技术技能人才培养模式研究；研究提出职业技能等级证书对接国际先进标准、对接职业标准、对接院校教学标准的运行机制和政策建议。 研究周期：10个月 预期成果：阶段性研究报告、总报告、论文、专著。论文3篇(在CSSCI核心库来源期刊发表至少1篇)；专著（或合著）1部；总研究报告1篇（不少于5万字），阶段性研究报告不少于2篇。 3.职业技能等级证书效力和待遇落实的实施路径研究 主要内容：梳理国外资历框架制度发展脉络，结合国内实际，通过调查分析，厘清实施中存在的主要问题，找准切入点和突破口，研究提出院校内和院校外实施的职业技能等级证书具备同等效力和待遇、行业企业和用人单位切实兑现相关待遇的具体政策与保障机制，相关学习成果认定、积累和转换等具有同一效能的具体实施路径。 研究周期：10个月
Oracle单机定时备份恢复配置指南 一、模块说明 1.1、文档适用范围 本文档适用于AnyBackup5.0.0~6.0版本 1.2、原理介绍 使用RMAN脚本进行备份， 1.3、备份介绍 支持完全备份和增量备份，备份时会备份数据库的数据文件，日志文件，参数文件，控制文件； 1.4、恢复介绍 1. Oracle 普通恢复 使用之前的数据库备份集来实现数据库的还原，然后使用归档日志及联机日志将数据库恢复到最新及指定时间点的状态，恢复时需要将停止数据库的生产业务； 2. Oracle 高级恢复 单独恢复不同类型的物理文件，包含控制文件、数据文件、日志文件、参数文件，在用户需要单独恢复各类型的文件时，可以选择此种恢复方式； 3. Oracle 表级恢复 可以在线进行表级恢复，并不影响数据库其它数据的正常业务使用；此种恢复方式主要针对用户误删除误操作，造成的表损坏或者数据丢失，不影响业务的正常运行；
二、环境说明 2.1、用户和客户端说明 2.1.1、用户权限 进行Oracle定时备份时，使用的用户必须是sysdba的权限，否则无法备份，如果使用的是不是sys用户，可以使用下面的命令将dba的权限赋予用户： grant sysdba to eisoo; //把dba的权限赋予用户eisoo 2.1.2、其他厂商库文件查询 其他厂商残留的库文件会影响到备份，Windows库文件名称为orasbt.dll，Linux下文件名为lilbobk.so，如果测试时环境上有其他厂商的客户端，建议先卸载掉，然后使用find命令查询库文件，如果还存在，就将该文件重命名 参考命令：find / -name orasbt.so 2.1.3、数据库位数 备份客户端时选择客户端的位数已Oracle数据库的位数为标准，最简单的检查数据库位数的方法就是在登录时查看输出信息，如下图，如标记有64bit则为64位数据库，如有没有则为32位数据库
关于时间的英语演讲稿范文_演讲稿 and organizing people to learn from advanced areas to broaden their horizons in order to understand the team of cadres working conditions in schools, the ministry of education has traveled a number of primary and secondary schools to conduct research, listen to the views of the school party and government leaders to make school leadership cadres receive attention and guidance of the ministry of education to carry out a variety of practical activities to actively lead the majority of young teachers work hard to become qualified personnel and for them to put up the cast talent stage, a single sail swaying, after numerous twists and turns arrived in port, if there is wind, a hand, and naturally smooth arrival and guide students to strive to e xcel, need to nazhen “wind” - teacher. teachers should be ideological and moral education, culture education and the needs of students organically combining various activities for the students or students to carry out their own. for example: school quiz competitions, essay contests, ke benju performances and other activities to enable students to give full play to their talents. teachers rush toil, in order to that will enable students to continue to draw nutrients, to help them grow up healthily and become pillars of the country before. for all students in general education, the government departments have also not forget those who cared about the
2020年度粤港澳大湾区教育专项课题指南 2020年度粤港澳大湾区教育专项课题分为重大项目和一般项目两种类型。具体如下： 一、重点项目选题 围绕粤港澳大湾区国际教育示范区建设研究 二、一般项目参考选题 1、粤港澳大湾区高校合作办学体制机制研究 2、国际湾区高等教育协同创新发展指数评估研究 3、粤港澳高校学分互认、累计与转换体系研究 4、粤港澳高校科研成果分享转化机制研究 5、粤港澳大湾区特色学院建设研究 6、粤港澳大湾区高校课程开放共享研究 7、粤港澳大湾区大学集群发展研究 8、粤港澳大湾区高校创新创业体系研究 9、粤港澳大湾区高等教育提升国家身份认同的路径与机制 10、粤港澳大湾区高等教育规模、布局与类型优化研究 11、粤港澳大湾区职业教育体制机制创新研究
12、粤港澳大湾区职业教育资历框架研究 13、粤港澳大湾区现代职业教育体系建设研究 14、粤港澳大湾区职业教育1+X证书制度研究 15、粤港澳大湾区现代学徒制研究 16、粤港澳大湾区职业教育园区建设研究 17、粤港澳大湾区基础教育交流合作路径机制研究 18、粤港澳大湾区基础教育与社区教育结合研究 19、粤港澳大湾区基础教育质量标准比较研究 20、粤港澳大湾区学前教育优化发展研究 21、粤港澳大湾区儿童体质与健康促进研究 22、粤港澳大湾区特殊教育融合发展研究 23、广东省港澳子弟学校布局优化及管理机制研究 24、粤港澳大湾区教师资质互认研究 25、粤港澳大湾区家校共育研究 26、随迁子女在粤港澳大湾区平等接受高中教育和参加高考政策研究 27、粤港澳大湾区民办教育发展政策与机制研究 28、粤港澳大湾区教育信息化发展及合作模式研究
联通XXXX系统备份和恢复指南 数据库备份原则和周期 备份工作应遵循快速、有效原则。 各项数据的备份周期建议如下： 1、数据库：建议SYSDB每天做全量备份，同时做文本备份和exp导出备份 （1）文本备份每天做全量备份，备份时间为3:00，主机和磁阵上分别保留两份备份文件，主机上的保留周期为3天，磁阵上的保留周期为15天。 （2）exp导出备份每天做两次，备份时间为0点和12点，主机和磁阵上分别保留两份备份文件，主机上的保留周期为3天，磁阵上的保留周期为15天。 BILLDB每月做两次全量备份，备份时间为每月的1号和16号3:00。只在磁阵上保留备份文件，磁阵上的保留周期为3个月。 2、话单文件：建议每月做一次全量备份，备份时间为1号3:00，只在磁阵上保留备份文件，磁阵上的保留周期为3个月，本地只保留最新的备份。 3、配置文件：建议系统上线后备份一次，以后如果有修改则重新备份，只在主机保留备份文件。 自动备份篇 自动备份只备份数据库，配置文件和话单文件采取手动备份的方式进行。自动备份是在oracle的用户下进行的，需要将备份文件放置目录的权限赋予oracle用户。并设置oracle 用户的crontab。 # crontab –e 00 3 * * * /opt/oracle/backup/backup.sh > /dev/null 2>&1 00 0,12 * * * /opt/oracle/backup/backup.sh -L > /dev/null 2>&1 00 3 1,16 * * /opt/oracle/backup/backup.sh -B > /dev/null 2>&1 1.每天对sysdb进行自动备份： （1）每天3:00对sysdb进行文本备份，备份文件的目录： 本地目录：/export/home/backup/sysdb/exp 异地目录：/export/home/mps/sysdb/exp 文件命名格式为：AAABackup_2009080611_asc.tar.Z （2）每天0:00和12:00对sysdb进行二进制备份，备份文件放置的目录： 本地目录：/export/home/backup/sysdb/asc 异地目录：/export/home/mps/sysdb/asc 文件命名格式为：AAABackup_2009080600_exp.tar.Z 2.每月1号和16号的3:00对billdb进行自动备份 本地目录：/export/home/backup/billdb
---------------------------------------------------------------范文最新推荐------------------------------------------------------ 1 / 9 关于坚持的英语演讲稿 results are not important, but they can persist for many years as a commemoration of . many years ago, as a result of habits and overeating formed one of obesity, as well as indicators of overall physical disorders, so that affects my work and life. in friends to encourage and supervise, the participated in the team now considered to have been more than three years, neither the fine rain, regardless of winter heat, a day out with 5:00 time. the beginning, have been discouraged, suffering, and disappointment, but in the end of the urging of friends, to re-get up, stand on the playground. in fact, i did not build big, nor strong muscles, not a sport-born people. over the past few years to adhere to it, because i have a team behind, the strength of a strong team here, very grateful to our team, for a long time, we encourage each other, and with sweat, enjoying common health happy. for example, friends of the several run in order to maintain order and unable to attend the 10,000 meters race, and they are always concerned about the brothers and promptly inform the place and