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1、河南移动2007年网优中级培训第二批学员毕业考试一、填空题:20分(每空0.5分)1、A接口中,全速率语音编码方式为PCM编码,速率为64kbps;空中接口中语音编码方式为RPE-LTP,速率为13kbps,它们通过TC 互相转化。2、Blocking Rate = Lost Traffic/ Offered Traffic。3、DTX、功控、跳频等功能可降低网络整体干扰。4、A3算法用来鉴权,A5算法用来加密,加密用密钥由A8算法获得。5、DCR_3j公式一般用来确定区域的掉话率,它是在channel activation信令之前开始计算。6、SD掉话原因中一般SDCCH_ABIS_FAIL
2、最高、TCH掉话中TCH_RADIO_FAIL 最高。(填写COUTER名称)7、qual5级对应的BER是3.2%-6.4%。8、BSC中话务量每20s扫描一次。9、根据集团三方测试规范,高速路测中脚本语音持续时长为100s;铁路测试是100s;市区测试是900s。10、ABIS接口的LADP信令分为TRXSIG和OMUSIG(BCFSIG)信令。11、如使用手动分频,我们一般会使用MRP的频率规划方法,目前NOKIA使用的自动分频工具是optimizer。12、在容量规划的时候,TCH采用2%的GOS,SDCCH采用0.5%的GOS。13、切换的优先级要高于于功控;同样的切换原因,下行的切
3、换优先级要低于于上行;因干扰切换的优先级要高于于因上行质量引起的切换。14、GSM的无线接口的三层信令中手机处理RR 、MM、CM消息,而基站仅处理RR。15、在无线电波传播过程中,存在着两种衰落:快衰落(瑞利衰落)和慢衰落,其中快衰落 是由于多径传播所引起的电波损耗。16、鉴权三元组包括Rand、Signed Response、Kc。二、单项选择题:18分(每题1.5分)1、 如果将T3101设置抬高,可能会造成什么影响?aa. risk of SDCCH Congestionb. risk of PCH Congestionc. risk of TCH Congestiond. risk
4、of AGCH Congestion2、 1毫瓦与50瓦约相差多少? da. 50 dBb. 40 dBc. 43 dBd. 47 dB3. 以下哪个现象不存在模拟网,而只存在于数字无线网中? da. 瑞利衰落b. 拥塞c. 快衰落d. 码间干扰4. Locating是指:ca. 在多于一个小区的范围内对手机进行寻呼b. 选择最佳小区c. 对移动台进行定位d. Roaming5. 天线增益是如何获得的? ba. 在天线系统中使用功率放大器b. 使天线的辐射变得更集中c. 使用高效率的天馈线d. 使用低驻波比的设备6. A和B小区同属于一个LAC,PER参数分别设置1个小时和半个小时。10:00
5、,A小区一用户挂掉电话,驻留该小区,直至10:50,该用户由A小区走到B小区的覆盖范围下并停留下来,请问下一次该用户进行位置更新是在几点? ba. 10:50b. 11:00c. 11:20d. 12:307对于GSM系统,手机占用SDCCH时,每 ms向网络提供一次测量报告,其中包含了 个TDMA帧。da. 480、4b. 470、2c. 480、104d. 470、1028. 假设一个用户在一小时内分别进行了一个两分钟及一个四分钟的通话,那么他在这一小时内产生了多少话务? ca. 10 millierlangsb. 50 millierlangsc. 100 millierlangsd.
6、200 millierlangs9. Call Proceding是在以下哪个过程中被用到? aa. MOCb. MTCc. Location Updated. Handover10.HO利用 信道? CALL RELEASE利用 信道? da. SACCH、SDCCHb. FACCH、SACCH c. FCCH、FACCH d. FACCH、FACCH11. 被叫号码在哪条信令中传送? ca. Channel Requestb. CM Service Requestc. Setupd. Transfer IMSI Response12. Which of the following is r
7、adio criteria for site selection. aa. No surrounding high obstacles b. Space for equipmentc. Power supplyd. Rental cost三、不定项选择题:18分(每题3分)1. 下面关于信道表述正确的是? b c d e fa. 逻辑信道由物理信道构成b. SDCCH可以传送短消息、鉴权等信息c. TCH复帧中包括一个IDLE TDMA帧d. 如果使用MBCCHC信道组合,该小区的PCH Block最多有3个e. SACCH可传送系统信息f. SCH只在下行传送,并可以被邻小区用户解读2. 下
8、面关于功控表述正确的是? d ea. 整个BCCH载频上下行都不功控b. 功控和DTX不会同时发生c. 功控之后,小区Rx_Lev下降,手机容易切换到邻小区d. 功控可以降低网络干扰,但会牺牲质量e. GPRS/EDGE信道下行方向不进行功控3. 下面关于直放站说法正确的是?a b d ea. 按传输方式来分,直放站种类主要有:无线直放站、光纤直放站。b. 根据放大信号的频带宽度,无线直放站可以分为:宽待选择直放站(宽带直放站)、信道选择型直放站(窄带直放站或同频转发直放站)。c. 无论光纤直放站还是无线直放站,应用时都要注意直放站服务区域的半径加上直放站至基站的距离可以超过TA值。d. 宽带
9、直放站的最大好处是可以满足基站跳频的要求,但是它对整个频段内的信号都进行放大,因此比较容易给其它小区带来干扰。e. 直放站是同频放大,对信号的处理有一个时间,从而造成一定的时延。采用直放站进行级连时必须考虑直放站处理时延所带来的影响。4. 下面关于参数表述正确的是? a c a. 小区被BAR以后,本小区下面手机将无法起呼b. PER控制下行寻呼重试间隔c. Power budget切换由周期性检查触发d. 在任何切换中,目标小区电平不能低于源小区电平e. VDLS在FACCH中发送给手机5. 下面关于频率表述正确的是? a b d ea. 跳频可以进行干扰分集和频率分集b. 好的频率规划可以
10、提升容量降低干扰c. 8MHz共有32个频点可用d. MRP是指不同层使用不同的频率复用方式e. 频率规划一般从网络配置最高的区域向周围扩展6. 下面关于日常优化表述正确的是? a c d a. 一个小区dcr_3j有可能大于100%b. 路测中,我们习惯考察rx_lev_fullc. 为解决区域话务较高,可打开DR功能d. 铁路测试之前,需打开铁路SDCCH切换功能e. 切换失败后,手机将释放无线链路,记为一次掉话四、简答题:27分(每题5分)1请列出OSS/NMS中最重要的网络指标:(至少列出5个)(5分)答:DCR、TCH BLOCKING、TRX_QUAL_UL/DL、HOF、SDR2
11、请列出NOKIA支持的切换类型,并按照优先级排序。(6分)答:1. Uplink and downlink Interference干扰2. Uplink quality上行质量3. Downlink quality下行质量4. Uplink level 上行电平5. Downlink level下行电平6. Distance距离7. Rapid Field Drop快衰落8. Slow moving MS慢速移动9. Better cell i.e. Periodic check (Power Budget HO or Umbrella HO)周期性检查3NOKIA支持几种跳频方式,各自优缺
12、点是什么?(5分)答:BB HOP 和 RF HOP。对于BB跳频优点是:Less HW restrictions supported by all BTS generations all antenna combining methods feasible (RTC or AFE)Minimum number of antennas requiredEasy to Implement (switch on) existing planning tools the same interferers and frequency plan than with IUO缺点是:Limitations
13、with small configurations and small BW hopping may not be possible on both layers (IFH)Limited FH gain FH gain is limited with small configurations ( 3 TRX / cell)对于RF跳频优点是:Flexibility hopping with small configurations and small BW is possibleMaximum FH gain or easy allocation possible hopping enabl
14、ed over large number of frequencies缺点是:Number of antennas in large configurations the number of antennas increasesHW dependencies old BTS generations do not support RF-FH wideband antenna coupling equipment needed (AFEs)4请列出小区重选的条件。(5分)答:(1)移动台计算某小区(与当前小区属同一个位置区)的C2值超过移动台当前服务小区的C2值连续5秒。(2)移动台计算某小区(与
15、当前小区不属同一个位置区)的C2值超过移动台当前服务小区的C2值与小区重选滞后值(CELL_SELECTION_HYSTERESIS)之和连续5秒。(3)当前服务小区被禁止。(4)MS监测出下行链路故障。(5)服务小区的C1值连续5秒小于0。5网络存在哪些干扰,请分别解释?(6分)答:Internal、External and Inter-modulation InternalInternal interference, co-channel or adjacent channel interference, means that the problem exists within the o
16、wn network due to a bad frequency plan, bad site location, congestion or too high antenna location. ExternalExternal interference means that there is another transmitter or something else acting as a transmitter outside the network such as TV transmission, repeaters microwave links, or other mobile
17、systems like AMPS. To solve this problem the operator either has to change affected frequencies to avoid the disturbance or to negotiate with the owner of the source of the disturbance. Inter-modulationIf the interference is inter-modulation the signal is reflected in an undesired way.There might be
18、 problems with the combination of different transmitters on the same base station or faulty equipment.五、综合题:17分1 网络现象诊断(10分)Question 1.(5分)A cell with relatively low traffic figures (1.5 Erl) shows high congestion times of the SDCCH.background information: Cell has one TRX, combined configuration of
19、 BCCH and SDCCH DCR is not remarkably higher than other cells Hardware works without any problems Quality distribution is OK NMS data shows high number of Location Updates during day timeWhat is the possible cause of the problem, and briefly describe how would you solve the problem.Answer:-Cause of
20、the problem:Cell is located at a Location Area boundary and partly covers a motorway. Passing Mobiles perform a Location update when entering and leaving the Location Area. Similar problems occur on other cells on the Location Area border. Solution: Reparenting the cell/site to an other Location Are
21、a: Location Area borders should be designed to cut major roads at 90 degrees, and not run parallel to them. This will prevent ping-pong Location Updates between the two Location Areas.Preliminary solutions: increase CellReselect from 6dB to e.g. 10dB to reduce number of Location Updates change SDCCH
22、 configuration from combined to non-combinedQUESTION 2 (5分)A cell with relatively low traffic figures (1.5 Erl) shows high congestion times of the SDCCH.background information: Cell has one TRX, combined configuration of BCCH and SDCCH DCR is not remarkably higher than other cells Cell is not locate
23、d at a location area border Hardware works without any problems Analysis of HO cause distribution: Ul Qual 2%UL Level 2%DL Qual29%DL Level7%UL Interfer5%DL Interfer28%PwrBudget28% Observation on cell shows following ratio of RACCH retransmission:1 Retransmission16%2 Retransmissions8%3 Retransmission
24、s5%4 Retransmissions2%5 Retransmissions1%What is the possible cause of the problem, and briefly describe how would you solve the problem.Answer:-Cause of the problem:Cell suffers from heavy Downlink interference. This causes that mobiles can not decode the IMMEDIATE_ASSIGNMENT and sends another RACCH. Solution:Analysis of the frequency plan identified the interfering cell, change of frequency improved situation.2 请画出手机做被叫的呼叫建立信令流程图(只要空中接口部分,请标注信令是在哪些逻辑信道中传送的,不考虑鉴权和加密部分信令)(7分)