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Cdma2000 network problem analysis with mobile station 20030212-a-v1.0
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Cdma2000 network problem analysis with mobile station 20030212-a-v1.0

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Keyword: CDMA, forward coverage, reverse coverage and connection ...

Keyword: CDMA, forward coverage, reverse coverage and connection
Abstract: This document describes how to use a Mobile Station (MS) to locate network problems. That is, judge the forward/reverse coverage by viewing the indices displayed on the Debug screen of MS. Then locate the network problems according to reverse Frame Error Rate (FER) and Received Signal Strength Indicator (RSSI) test on the background. This document uses H100 MS as an example for the description. For settings of other CDMA MSs, see the relevant document.
1.1
Displaying Debug Screen of H100 MS
1.2
1) 2) 3) 4)
Switch on the MS; Input password: ##27732726; Press the red Power-off key; Select 3.
The Debug screen is displayed.
Index Value on Debug Screen
Assume that the following information is displayed on the Debug screen:
P232 R085 C0210
03612-00001-1
PAGE Ec: -5.0
RX: -75 TX: NoTx

P232: PN of primary service sector
C0210: System operating frequency
03612: SID
00001: NID
PAGE: Channel mode
Ec: Ec/Io
Rx: Receive level of MS
TX: Transmit level of MS
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Cdma2000 network problem analysis with mobile station 20030212-a-v1.0 Document Transcript

  • 1. Document No. Product name Cdma2000User Product VersionCompiled by:Wireless Network SystemResearch DepartmentVersion 1.00Cdma2000 Network Problem Locationwith Mobile StationPrepared by: Li Jie Date: 2003/1/22Reviewed by: Ma Mingming Date: 2003/2/18Reviewed by: Xiong Qiang Date: 2003/2/18Approved by: Tao Maodi Date:Huawei Technologies Co., Ltd.All rights reserved.
  • 2. Revision RecordDate Revised version Description Author2003/1/22 V1.0 First draft finished. Li Jie
  • 3. Table of Content1 Introduction to MS Debug Screen ............................................................................................... 21.1 Displaying Debug Screen of H100 MS ................................................................................. 21.2 Index Value on Debug Screen.............................................................................................. 21.3 Debug Screen of S200 MS................................................................................................... 32 Judgment of Forward Coverage .................................................................................................. 42.1 Pilot Strength ........................................................................................................................ 42.2 Receive Level of MS............................................................................................................. 53 Judgment of Reverse Coverage .................................................................................................. 73.1 Transmit Level of MS............................................................................................................ 73.2 Reverse Frame Error Rate ................................................................................................... 74 Judgment of Connection Quality................................................................................................. 95 Judgment of Voice Quality......................................................................................................... 106 Summary ...................................................................................................................................... 11
  • 4. Cdma2000 Network Problem Location with Mobile Stationcdma2000 Network Problem Location with Mobile StationKeyword: CDMA, forward coverage, reverse coverage and connectionAbstract: This document describes how to use a Mobile Station (MS) to locate networkproblems. That is, judge the forward/reverse coverage by viewing theindices displayed on the Debug screen of MS. Then locate the networkproblems according to reverse Frame Error Rate (FER) and ReceivedSignal Strength Indicator (RSSI) test on the background. This documentuses H100 MS as an example for the description. For settings of otherCDMA MSs, see the relevant document.Abbreviations:Reference:Page 1 of 11
  • 5. Cdma2000 Network Problem Location with Mobile Station11.11)2)3)4)1.2Introduction to MS Debug ScreenDisplaying Debug Screen of H100 MSSwitch on the MS;Input password: ##27732726;Press the red Power-off key;Select 3.The Debug screen is displayed.Index Value on Debug ScreenAssume that the following information is displayed on the Debug screen:P232 R085 C021003612-00001-1PAGE Ec: -5.0RX: -75 TX: NoTxP232: PN of primary service sectorC0210: System operating frequency03612: SID00001: NIDPAGE: Channel modeEc: Ec/IoRx: Receive level of MSTX: Transmit level of MSThough the meanings of two indices (R085 and -1) are unavailable, the network qualitycan be evaluated without them, since the major indices of Um interface are given.Page 2 of 11
  • 6. Cdma2000 Network Problem Location with Mobile Station1.31)2)3)Debug Screen of S200 MSRemove the cell of a S200 MS, you will see “S/P NO”. Each “NO” corresponds to aService Processing Board (SPC). See the relevant attachment for details.To display the Debug screen:Select “Menu”;Press <0> key;Input the corresponding No. of SPC.The Debug screen is displayed.Assume that the following information is displayed on the Debug screen:s13842n0001i1c0210p036r057e04v489:224t116s00300 00 0s13842: SIDn0001: NIDc0210: System operating frequencyp036: PN of primary service sectorr057: Receive level of MSe04: Ec/IoThe transmit level of MS is not displayed on the Debug screen of S200 MS. Thus thejudgment of reverse coverage is affected more or less.Page 3 of 11
  • 7. Cdma2000 Network Problem Location with Mobile Station22.1Judgment of Forward CoveragePilot StrengthIn CDMA 1X system, the pilot strength (Ec/Io) is one of the essential parameters thatindicate network forward coverage and co-frequency interference. Due to theinterference-restricted feature of CDMA system, it is crucial to properly control the pilotstrength.The Ec/Io value of the service area can be obtained from the Debug screen of the MS.Since the base stations (BTSs) of CDMA system operate in one frequency, how toeliminate the signal interference between cells is a major consideration in CDMAnetwork construction. If a sector is assigned with a fixed Ec, the increment of signallevel in any other sector may increase the Io. Hence the Ec/Io of this cell decreases.When judging the forward coverage effect via the MS, pay more attention to theoverlapped area of the cells. Meanwhile, check the connection sequence ofantenna-feeder (for improper connection) and antenna engineering parameters of eachBTS, based on network topological map, PN list, etc.If the coverage ranges of some BTSs are not properly controlled, the Ec/Io may be poorin the overlapped area of these cells. In addition, the serious interference in forwardcoverage may also degrade the Ec/Io. This frequently happens to the CDMA 450MHznetwork in China. Generally, the Ec/Io above -8dB is ideal. Some operators onlyrequires that the Ec/Io in 99% of the coverage area should be better than -12dB.The following example illustrates how to locate network problems using a MS and theBTS topological map.Page 4 of 11
  • 8. Cdma2000 Network Problem Location with Mobile StationThe above figure shows the BTS topological map of a CDMA network. The networkcovers a prosperous city in southern China. A newly-developed urban area is located inthe east of the city with a number of luxury residential communities and high buildings.The old urban area is located in the west of the city, with lower buildingsclosely-packed.As the above figure shows, area A is surrounded by the BTSs of Jinsha Telecom,Waima Telecom, Information Building and Chaoshan Telecom. The BTS antenna ofShanzhang Telecom is mounted high above the earth (75 m) and covers other areas.Thus the coverage of this area is under suspicion. According to the on-foot MS test onfield, the Ec/Io of this area is poor and the signals of the nearby BTSs are of the similarquality. Moreover, the signals from BTS in the south riverbank can also be received.There is no dominant service cell in area A. In nearby area to the east of WaimaTelecom, the dominant service cells come from Information Building and JinshaTelecom rather than Waima Telecom. Then, observe the radio environment of WaimaTelecom on top of the building. As a result, the area (about 20 m) around sector 1 andsector 2 of Waima BTS is surrounded by high buildings. So far, the cause is located forthe poor coverage in this area.This problem can be temporarily eased by adjusting the pilot power ratio, and theazimuth and down tilt of the antenna. It is also recommended that new BTS(s) beadded to this area in the subsequent engineering.In a large-scale network, the on-foot MS test will greatly increase the workload. In thiscase, use the BTS topological map and administrative map to locate the suspect areasand then test in these areas with extra attention. Particularly, the indoor environment ofthe overlapped area may be the blind-spot of the coverage.2.2 Receive Level of MSThe MS’s receive level (Rx) and pilot strength (Ec/Io) jointly indicate the effect offorward coverage and none of them can be absent. In densely-populated urban area,the BTSs are closely distributed. Therefore, the Rx can be ensured if only the antennafeeder system is properly designed. However, in rural areas or at the edges of theservice cells, the Rx of the MS is generally around -90dBm, while the Ec/Io is around-3dB. Obviously, though the signal strength is only -90dBm, half of them can still beused.Logically, the call service should be satisfactory if judged by Ec/Io only. However, sincethe attenuation can be up to 20dB, the strength of attenuated signals may be weakerthan the receive sensitivity of the MS. Thus the forward bit error occurs to the MS. ThePage 5 of 11
  • 9. Cdma2000 Network Problem Location with Mobile Stationforward bit error may disable the MS transceiver, incur reverse bit error or even calldrop. Please pay extra attention to it. This may also happen to the ground floors of highbuildings in urban areas.The MS’s receive level can be viewed from the Debug screen of the MS. Generally, theareas with receive level above -60dB can receive good service, while those withreceive level under -95dB are blind-spot of the coverage.The quality of forward coverage is jointly determined by Ec/Io and Rx. The signalstrength displayed on the screen is directly related to the sum of absolute values ofEc/Io and RxAGC.Page 6 of 11
  • 10. Cdma2000 Network Problem Location with Mobile Station33.13.2Judgment of Reverse CoverageTransmit Level of MSThe transmit level (Tx) is the parameter that reflects the reverse coverage of thenetwork. There are many factors affecting Tx, such as reverse interference andimproper setting of search window.In the 450MHz network in China, the reverse interference is a serious problem. In areasnear the BTS (within 1 km), the MS’s transmit level should be under -20dB. The hightransmit level may result from the reverse interference. The reverse interference can bemonitored by using RSSI.The interference is primarily judged based on the mean value of no-load RSSI. In a newoffice with few subscribers, the no-load RSSI level is generally less than -105dBm.According to the records of Cangzhou office, the mean value of RSSI will not exceed-95dBm in the presence of multiple services. The RSSI values in traffic measurementcan be used to judge the interference.If a carrier is seriously interfered, use the Telnet command to connect a PC to the BTSso as to view the peak value of RSSI. Connect the PC to BTS via Telnet to trace theTRX resources. In this way, the RSSI mean value, peak value and other informationcan be reported every second. The command is Strinfotrace:brdtp=btrm,brdid=XXX,item="rssi", where XXX is the board No. ofresource allocation board (RMU) on Resource Module (RM) subrack.The MS transmit level can be viewed from the Debug screen of the MS. Note that theDebug screen of H100 MS only displays “TX: NoTx” in standby status. The actual Txvalue is displayed only when a call is connected or when a call is in progress.Reverse Frame Error RateThe reverse FER cannot be obtained on MS side. It should be traced via thebackground. It can be used to judge the reverse coverage quality of the network. Thebackground can only trace the FER of one (or more) MS in a given time. Normally, thereverse FER should be lower than 1%. Once the reverse FER exceeds 20%, the callwill be frequently interrupted.Measurement of reverse FEREnable FER measurement function:Page 7 of 11
  • 11. Cdma2000 Network Problem Location with Mobile Stationa. Connect to the FMR board;b. Enable the print functions of RMM and DBG modules;c. Input the command FMR DEBUG. The command code is ERASURE framemeasurement startup, and the parameter is the last 10 digits of IMSI of the MS.Disable FER measurement:1)2)3)Connect to the FMR board;Enable the print functions of RMM and DBG modules;Input the command FMR DEBUG. The command code is ERASURE framemeasurement stop, and the parameter is the last 10 digits of IMSI of the MS.Page 8 of 11
  • 12. Cdma2000 Network Problem Location with Mobile Station4 Judgment of Connection QualityThe connection quality is primarily reflected by the call completion rate and callconnection time. The general connection quality of the network can be evaluated viadial test in a fixed position using the MS. The call completion rate can be obtained viatraffic measurement. For methods of improving call completion rate, see M2000 TrafficMeasurement Analysis Guide. Currently, Huawei system supports the call connectiontime of 3 ~ 4 seconds. The call connection in 450MHz network usually takes longer time.That is, the average call connection time is 6 ~ 8 seconds or even 10 seconds whensignals are weak. For methods of shortening call connection time, see the relevantcases and guides.Page 9 of 11
  • 13. Cdma2000 Network Problem Location with Mobile Station5Table 5-1Judgment of Voice QualityThe subjective opinion evaluation is widely applied since it complies with people’ssense of hearing. The major subjective opinion method is Subjective Opinion Scale orMean Opinion Score (MOS). The MOS grades the voice quality in five scales. Themethod is that dozens of testing engineers listen to the voice calls in the same channeland grade the quality respectively. Then the average score is calculated based onthese scores. The score of each subjective opinion test may vary with the subjective orobjective factors. To minimize the inaccuracy of the scores, the number of testingengineers should be sufficient. Meanwhile, provide diversified voice materials and try tomaintain the same environment for the test.In addition, note that the objective opinion upon voice quality is often related to people’slistening effect. Therefore, the objective opinion score should also cover the listeningeffect scale. The following table lists the quality level, score and description ofcorresponding listening effect scale of subjective opinion evaluation.Subjective opinion score tableQuality level Score Description of listening effect scaleExcellent 5 Relax without attentionGood 4 With slight attentionFair (Normal) 3 With medium attentionPoor 2 With concentrated attentionBad 1 Cannot follow even with extra attentionGenerally, the subscriber may consider that the voice code with MOS between 4.0 ~4.5 is of high quality and meets the requirement of toll network. The voice code withMOS around 3.5 delivers acceptable communication quality and the audience is awareof the degraded voice quality. However, it does not affect the normal conversation andmeets the requirements of most digital communication systems. Voice code with MOSunder 3.0 is usually called synthesis voice. With such voice quality, the audience canonly follow the conversation, but cannot distinguish the speaker, since the voice isdistorted to some extend.It is essential to judge the voice quality as the subscriber will eventually evaluate thequality of network based on the voice.Page 10 of 11
  • 14. Cdma2000 Network Problem Location with Mobile Station6 SummaryWhen drive test equipment is unavailable, the general network quality can be evaluatedby viewing the Debug screen of the MS and originating calls with the MS. And thenetwork problem can be located via tools such as traffic measurement andcommissioning console. With the drive test equipment, the MS can be used to test thecoverage blind-spots of the network.The cellular network should be structured during the network planning phase. However,since the ideal network structure may not be achieved in the network plan, the goal atearly optimization stage is to construct a network with appropriate structure. As thebackbone of a network, a sound network structure is the most essential factor in radionetwork. The software parameter should serve the network structure. The networkstructure determines the software parameters. Getting a perfect network structuremakes up 80% of the network optimization work. In the latter stage of networkoptimization, the key areas should be optimized based on the traffic measurement. Theoptimization covers software parameters on the basis of the entire network, includingpower ratio, neighbor cell relation, search window and power control parameter.Page 11 of 11