Cdma2000 network problem analysis with mobile station 20030212-a-v1.0
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This document describes how to use a mobile station (MS) to locate network problems in CDMA2000 networks. It explains how to view debugging screens on different MSs to check indices like pilot strength, receive level, and transmit level, which can indicate issues with forward or reverse coverage. It also discusses using reverse frame error rate tests on the network side to evaluate connection quality and voice quality. The document provides guidance on interpreting these metrics and diagnosing potential problems based on the results, like interference issues affecting transmit levels or poor coverage in certain areas.
Cdma2000 network problem analysis with mobile station 20030212-a-v1.0
- 1. Document No. Product name Cdma2000 User Product Version Compiled by: Wireless Network System Research Department Version 1.00 Cdma2000 Network Problem Location with Mobile Station Prepared by: Li Jie Date: 2003/1/22 Reviewed by: Ma Mingming Date: 2003/2/18 Reviewed by: Xiong Qiang Date: 2003/2/18 Approved by: Tao Maodi Date: Huawei Technologies Co., Ltd. All rights reserved.
- 2. Revision Record Date Revised version Description Author 2003/1/22 V1.0 First draft finished. Li Jie
- 3. Table of Content 1 Introduction to MS Debug Screen ............................................................................................... 2 1.1 Displaying Debug Screen of H100 MS ................................................................................. 2 1.2 Index Value on Debug Screen.............................................................................................. 2 1.3 Debug Screen of S200 MS................................................................................................... 3 2 Judgment of Forward Coverage .................................................................................................. 4 2.1 Pilot Strength ........................................................................................................................ 4 2.2 Receive Level of MS............................................................................................................. 5 3 Judgment of Reverse Coverage .................................................................................................. 7 3.1 Transmit Level of MS............................................................................................................ 7 3.2 Reverse Frame Error Rate ................................................................................................... 7 4 Judgment of Connection Quality................................................................................................. 9 5 Judgment of Voice Quality......................................................................................................... 10 6 Summary ...................................................................................................................................... 11
- 4. Cdma2000 Network Problem Location with Mobile Station cdma2000 Network Problem Location with Mobile Station 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. Abbreviations: Reference: Page 1 of 11
- 5. Cdma2000 Network Problem Location with Mobile Station 1 1.1 1) 2) 3) 4) 1.2 Introduction to MS Debug Screen Displaying Debug Screen of H100 MS 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 Though the meanings of two indices (R085 and -1) are unavailable, the network quality can be evaluated without them, since the major indices of Um interface are given. Page 2 of 11
- 6. Cdma2000 Network Problem Location with Mobile Station 1.3 1) 2) 3) Debug Screen of S200 MS Remove the cell of a S200 MS, you will see “S/P NO”. Each “NO” corresponds to a Service 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: s13842n0001i1 c0210p036r057e04 v489:224t116s003 00 00 0 s13842: SID n0001: NID c0210: System operating frequency p036: PN of primary service sector r057: Receive level of MS e04: Ec/Io The transmit level of MS is not displayed on the Debug screen of S200 MS. Thus the judgment of reverse coverage is affected more or less. Page 3 of 11
- 7. Cdma2000 Network Problem Location with Mobile Station 2 2.1 Judgment of Forward Coverage Pilot Strength In CDMA 1X system, the pilot strength (Ec/Io) is one of the essential parameters that indicate network forward coverage and co-frequency interference. Due to the interference-restricted feature of CDMA system, it is crucial to properly control the pilot strength. 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 to eliminate the signal interference between cells is a major consideration in CDMA network construction. If a sector is assigned with a fixed Ec, the increment of signal level 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 the overlapped area of the cells. Meanwhile, check the connection sequence of antenna-feeder (for improper connection) and antenna engineering parameters of each BTS, based on network topological map, PN list, etc. If the coverage ranges of some BTSs are not properly controlled, the Ec/Io may be poor in the overlapped area of these cells. In addition, the serious interference in forward coverage may also degrade the Ec/Io. This frequently happens to the CDMA 450MHz network in China. Generally, the Ec/Io above -8dB is ideal. Some operators only requires 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 the BTS topological map. Page 4 of 11
- 8. Cdma2000 Network Problem Location with Mobile Station The above figure shows the BTS topological map of a CDMA network. The network covers a prosperous city in southern China. A newly-developed urban area is located in the 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 buildings closely-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 of Shanzhang 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 on field, the Ec/Io of this area is poor and the signals of the nearby BTSs are of the similar quality. 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 Waima Telecom, the dominant service cells come from Information Building and Jinsha Telecom rather than Waima Telecom. Then, observe the radio environment of Waima Telecom on top of the building. As a result, the area (about 20 m) around sector 1 and sector 2 of Waima BTS is surrounded by high buildings. So far, the cause is located for the poor coverage in this area. This problem can be temporarily eased by adjusting the pilot power ratio, and the azimuth and down tilt of the antenna. It is also recommended that new BTS(s) be added to this area in the subsequent engineering. In a large-scale network, the on-foot MS test will greatly increase the workload. In this case, use the BTS topological map and administrative map to locate the suspect areas and then test in these areas with extra attention. Particularly, the indoor environment of the overlapped area may be the blind-spot of the coverage. 2.2 Receive Level of MS The MS’s receive level (Rx) and pilot strength (Ec/Io) jointly indicate the effect of forward 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 antenna feeder system is properly designed. However, in rural areas or at the edges of the service 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 be used. Logically, the call service should be satisfactory if judged by Ec/Io only. However, since the attenuation can be up to 20dB, the strength of attenuated signals may be weaker than the receive sensitivity of the MS. Thus the forward bit error occurs to the MS. The Page 5 of 11
- 9. Cdma2000 Network Problem Location with Mobile Station forward bit error may disable the MS transceiver, incur reverse bit error or even call drop. Please pay extra attention to it. This may also happen to the ground floors of high buildings in urban areas. The MS’s receive level can be viewed from the Debug screen of the MS. Generally, the areas with receive level above -60dB can receive good service, while those with receive level under -95dB are blind-spot of the coverage. The quality of forward coverage is jointly determined by Ec/Io and Rx. The signal strength displayed on the screen is directly related to the sum of absolute values of Ec/Io and RxAGC. Page 6 of 11
- 10. Cdma2000 Network Problem Location with Mobile Station 3 3.1 3.2 Judgment of Reverse Coverage Transmit Level of MS The transmit level (Tx) is the parameter that reflects the reverse coverage of the network. There are many factors affecting Tx, such as reverse interference and improper setting of search window. In the 450MHz network in China, the reverse interference is a serious problem. In areas near the BTS (within 1 km), the MS’s transmit level should be under -20dB. The high transmit level may result from the reverse interference. The reverse interference can be monitored by using RSSI. The interference is primarily judged based on the mean value of no-load RSSI. In a new office 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 measurement can be used to judge the interference. If a carrier is seriously interfered, use the Telnet command to connect a PC to the BTS so as to view the peak value of RSSI. Connect the PC to BTS via Telnet to trace the TRX resources. In this way, the RSSI mean value, peak value and other information can be reported every second. The command is Str infotrace:brdtp=btrm,brdid=XXX,item="rssi", where XXX is the board No. of resource allocation board (RMU) on Resource Module (RM) subrack. The MS transmit level can be viewed from the Debug screen of the MS. Note that the Debug screen of H100 MS only displays “TX: NoTx” in standby status. The actual Tx value is displayed only when a call is connected or when a call is in progress. Reverse Frame Error Rate The reverse FER cannot be obtained on MS side. It should be traced via the background. It can be used to judge the reverse coverage quality of the network. The background can only trace the FER of one (or more) MS in a given time. Normally, the reverse FER should be lower than 1%. Once the reverse FER exceeds 20%, the call will be frequently interrupted. Measurement of reverse FER Enable FER measurement function: Page 7 of 11
- 11. Cdma2000 Network Problem Location with Mobile Station a. 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 frame measurement 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 frame measurement 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 Station 4 Judgment of Connection Quality The connection quality is primarily reflected by the call completion rate and call connection time. The general connection quality of the network can be evaluated via dial test in a fixed position using the MS. The call completion rate can be obtained via traffic measurement. For methods of improving call completion rate, see M2000 Traffic Measurement Analysis Guide. Currently, Huawei system supports the call connection time 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 when signals are weak. For methods of shortening call connection time, see the relevant cases and guides. Page 9 of 11
- 13. Cdma2000 Network Problem Location with Mobile Station 5 Table 5-1 Judgment of Voice Quality The subjective opinion evaluation is widely applied since it complies with people’s sense of hearing. The major subjective opinion method is Subjective Opinion Scale or Mean Opinion Score (MOS). The MOS grades the voice quality in five scales. The method is that dozens of testing engineers listen to the voice calls in the same channel and grade the quality respectively. Then the average score is calculated based on these scores. The score of each subjective opinion test may vary with the subjective or objective factors. To minimize the inaccuracy of the scores, the number of testing engineers should be sufficient. Meanwhile, provide diversified voice materials and try to maintain the same environment for the test. In addition, note that the objective opinion upon voice quality is often related to people’s listening effect. Therefore, the objective opinion score should also cover the listening effect scale. The following table lists the quality level, score and description of corresponding listening effect scale of subjective opinion evaluation. Subjective opinion score table Quality level Score Description of listening effect scale Excellent 5 Relax without attention Good 4 With slight attention Fair (Normal) 3 With medium attention Poor 2 With concentrated attention Bad 1 Cannot follow even with extra attention Generally, 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 with MOS around 3.5 delivers acceptable communication quality and the audience is aware of the degraded voice quality. However, it does not affect the normal conversation and meets the requirements of most digital communication systems. Voice code with MOS under 3.0 is usually called synthesis voice. With such voice quality, the audience can only follow the conversation, but cannot distinguish the speaker, since the voice is distorted to some extend. It is essential to judge the voice quality as the subscriber will eventually evaluate the quality of network based on the voice. Page 10 of 11
- 14. Cdma2000 Network Problem Location with Mobile Station 6 Summary When drive test equipment is unavailable, the general network quality can be evaluated by viewing the Debug screen of the MS and originating calls with the MS. And the network problem can be located via tools such as traffic measurement and commissioning console. With the drive test equipment, the MS can be used to test the coverage 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 at early optimization stage is to construct a network with appropriate structure. As the backbone of a network, a sound network structure is the most essential factor in radio network. The software parameter should serve the network structure. The network structure determines the software parameters. Getting a perfect network structure makes up 80% of the network optimization work. In the latter stage of network optimization, the key areas should be optimized based on the traffic measurement. The optimization covers software parameters on the basis of the entire network, including power ratio, neighbor cell relation, search window and power control parameter. Page 11 of 11