WCDMA RF Optimization_Cases

WCDMA Radio Frequency Optimization www.huawei.com Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Foreword RF (Radio Frequency) optimization is the most important step to ensure the quality of the network. RF optimization will solve network problems related to neighbor cell list, coverage and interference. Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page2 Objectives Upon completion of this course, you will be able to: Know the steps of RF optimization Know how to solve the RF problems cased by neighbor cell list, poor coverage and interference Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page3 Contents RF Optimization Workflow Typical Problems Analysis in RF optimization Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page4 RF Optimization Workflow Start Preparation: Set the optimization target Divide the optimization cluster Draw out the test route line Prepare the DT tools Data Collection: DT test Indoor DT test RNC configuration data Adjustment: Engineering parameters adjust Neighbor cell list adjust The DT result is satisfied with optimization target? N Y RF optimization finished Problem Analysis neighbor cell list poor coverage pilot pollution handover interference Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page5 RF Optimization Workflow Set RF optimization target, for example: Target Item Coverage Probability CPICH Ec/Io ≥ -12dB CPICH RSCP ≥ -95dBm SHO Percentage Pilot pollution Percentage Reference Value ≥95% ≥95% ≥95% 30%-40% ≤5% Remark CPICH Ec/Io ≥ -12dB & RSCP ≥ -95dBm Scanner result Scanner result Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page6 RF Optimization Workflow RF optimization clusters division Cluster is the area for one time drive test One cluster should contains 15 to 25 sites Cluster division should consider the following factor, such as: Terrain Traffic Route line Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page7 RF Optimization Workflow Preparation for DT (drive test) Hardware Test phone Scanner GPS Software Drive test software, for example, GENEX Probe Drive test post process software, for example, GENEX Assistant Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page8 Contents Preparation of RF Optimization Typical Problems Analysis in RF optimization Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page9 Contents Typical Problems Analysis in RF optimization RF case related to neighbor cell list RF case related to bad coverage RF case related to interference Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page10 Case 1 Description In DT, call drop happened Check the signaling trace at UE side Call Drop After call drop, begin to read system information Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page11 Case 1 Data analysis Check cell information from UE active set and cell information from scanner at call drop points. From UE From Scanner No SC 170 cell!! Why? Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page12 Case 1 Data analysis Checking monitor set Check monitor set for the scramble measured by scanner SC 170 is not in monitor set Missing neighbor cell Delayed handover Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page13 Case 1 Data analysis Check the latest measurement control Search for the latest intrafrequency measurement control Call drop point Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page14 Case 1 Measurement ID is 1. It is Intrafrequency measurement control The primary scramble of the cell is 6 Check the list of intra-frequency neighbor cell in measurement control and no SC 170 Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page15 Case 1 Solution Add neighbor cells in neighbor cell list Summary In the beginning stage of network, it is very common that missing neighbor cell cased cause call drop. Analysis with signaling procedure is the common way to find and solve the problem Some problems can be avoided if the Combined Neighbor Cell Algorithm is switched on. Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page16 Case 2 Phenomenon description In DT, call drop happened at cell A Cell B (PSC277) Cell A (PSC58) Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page17 Case 2 Phenomenon description In Cell A, UE keeps reporting PSC 277 1A event. RNC received this event and send Active Set Update to UE according to the signaling trace record UE send Active Set Update complete to RNC Then, RNC send Active Set Update to delete PSC 277 from active set Finally call drop happened due to RL failure Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page18 Case 2 Problem Analysis From the signaling trace of DT, it looks like the handover is complete successfully. But, according to the signaling trace from CDT, the handover failed actually. Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page19 Case 2 Problem Analysis Signaling trace from CDT shows: UE NodeB Measurement control (1A Event for PSC 227) Radio Link Setup Radio Link Setup Response Active set update Active set update complete Radio Link Failure RNC Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page20 Case 2 Problem Analysis Cell C (PSC277) After checking the neighbor cell list, the following problem is found Cell C has the same PSC as Cell B Cell A (PSC58) Cell B (PSC277) Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page21 Case 2 Problem Analysis The neighbor cell list shows Cell ID A B C Missing configuring NCell PSC 58 277 277 Cell A (PSC58) Cell ID A C NCell ID C A Mistake for configuring NCell Cell B (PSC277) Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Cell C (PSC277) Page22 Case 2 Problem Analysis Based on the analysis above, the new NodeB is not the one of cell B, but the one of cell C Even the cell C prepared resource for UE according to the RNC command of “Radio Link Setup”, it can not find the UE uplink signal. That does why the “Radio Link Failure” is sent by NodeB Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page23 Case 2 Solution Change the wrong neighbor cell list Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page24 Case 2 Summary Phenomenon for wrong neighbor cell list From DT, radio link branch is added into active set, then deleted from active set repeatedly. SHO success rate is low Radio link failure is low in the wrong neighbor cell, for example, cell C in case 2 Call drop is high in the cell with wrong neighbor cell, for example, cell A in case 2 Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page25 Case 2 Summary About SHO event, UE will only report PSC to RNC in Measurement Report RNC will find the right cell according to the neighbor cell list between cell ID and PSC This problem is mainly happened in dense urban when is PSC is reused a lot Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page26 Case 3 Description 14605 (Frequency C) Call drop rate high 14603 (Frequency A) 14602 (Frequency B) 14031 (Frequency B) Inter-frequency handover based on capacity Inter-frequency handover based on coverage Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page27 Case 3 Description UE is in Cell 14602 with frequency B When 14602 is in high load level, UE will be handed over to 14603 with another frequency A When 14603 is in high load level, UE will be handed over to 14605 with frequency C Because frequency A and C are not used continuously at this area, UE has to be handed over to Cell 14031 with frequency B 14603 and 14605 can share the load level, but the call drop rate in 14603 is very high. Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page28 Case 3 Analysis Because it’s difficult to do drive test for collecting signaling trace, the IOS (Information of Subscriber) trace is used. Based on the analysis for the call dropped UE, there is one thing is common: Before call drop in 14603, all UEs initiated compress mode, and send Measurement Report to RNC periodically, but handover is not triggered. Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page29 Case 3 Analysis 2D Event Compress mode Inter-frequency measurement control Inter-frequency Measurement report Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page30 Case 3 Analysis Open “Inter-frequency Measurement Control”, the Cell 14605 with frequency C is put in the first place And in the following measurement report, UE only report Cell 14605 But the cell 14605 cell signal level is lower than -90dBm, which can not trigger handover, till call drop. Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page31 Case 3 Analysis Measurement Control Cell 14605 with Frequency C Cell 14031 with Frequency B Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page32 Case 3 Analysis Measurement Report Cell 14605 with Frequency C Cell 14605 CPICH & Ec/Io Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page33 Case 3 Question Why the handover can not be triggered? Since the network give UE the information of cell 14605 and cell 14031, Why UE only report cell 14605? Did UE measure cell 14031, just not report it? Or, UE never measure cell 14031, just 14605? Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page34 Case 3 Analysis UE report cell 14605 CPICH RSCP is 19, which is -96dBm. After checking the RNC configuration file, this CPICH RSCP level can not trigger inter-frequency handover Actually, because cell 14605 and 14603 are in one sector, their signal level should be same. Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page35 Case 3 Analysis If UE can report cell 14031, the handover may be triggered After analyze the compress mode principle, it is found that UE can only monitor 1 WCDMA frequency in the gap of compress mode. Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page36 Case 3 Analysis Because UE can not measure cell 14031 with frequency B, only monitor cell 14605 with frequency C, and meanwhile cell 14605 and 14603 signal level are the same, the call dropped due to the poor signal of 14605 and 14603 How to make UE monitor cell 14031 with frequency B instead of 14605 with frequency C? Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page37 Case 3 Solution Delete the neighbor relation from 14603 with frequency A to 14605 with frequency C Add the neighbor relation from 14602 with frequency B to 14605 with frequency C Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page38 Case 3 Solution 14605 (Frequency C) 14603 (Frequency A) 14602 (Frequency B) 14031 (Frequency B) Inter-frequency handover based on capacity Inter-frequency handover based on coverage Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page39 Case 3 Summary Do not configure two different frequency neighbor cells in WCDMA system Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page40 Contents Typical Problems Analysis in RF optimization RF case related to neighbor cell list RF case related to bad coverage RF case related to interference Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page41 Case 1 Description In drive test for RF optimization, call drop happened in the circle area Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page42 Case 1 Analysis After analyze the signal level of this area, the call drop is caused by discontinuous coverage of the cell with PSC 442 Problem Zone Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page43 Case 1 Analysis After checking the RF transmission environment, the signal is blocked by the glass wall Call drop Antenna The Wall Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page44 Case 1 Solution Solution 1: Decrease the downtilt to increase the signal level Maybe the problem area will become better, but due to the wall, this problem may still exist nearby. Solution 2:Increase the antenna height After checking the installation condition, it’s very hard to increase the height Even increased the height, the problem may still exist due to the wall. Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page45 Case 1 Solution Solution 3: Move the antenna position if possible, and the main direction antenna is parallel with the side of the wall Move the antenna position to right about 15 meters considering the installation condition Original Position New Position Wall Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page46 Case 1 Solution Solution 3: About the antenna downtilt, two strategies are designed. First, 10 degrees 10 Degree Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page47 Case 1 Solution Solution 3: Second, 5 degrees 5 Degree Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page48 Case 1 Summary Before RF adjustment, site survey should be done. Find the problem and the reason, design several strategies for the adjustment One time adjustment, and check the performance at the same time. Adjustment and performance checking should be done at the same to improve the work efficiency. Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page49 Case 2 Description In drive test for RF optimization, the area Ec/Io is bad Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page50 Case 2 Analysis Checking the cell distribution at this area PSC186 PSC184 PSC185 Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page51 Case 2 Analysis One site with 3 cells, PSC184, 185 and 186 cover this area Two cells, PSC 184 and 185, are separated to two sectors to cover different direction Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page52 Case 2 Analysis The area is covered by different cell – PSC 184 and 185 No dominant cell – PSC 184 and 185 is the best cell crossly in this area Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page53 Case 2 Solution Change the sector PSC, or combine some sector Previously, 3 cells PSC 184: sector 1 & sector 3 PSC 185: sector 2 & sector 4 PSC 186: sector 5 After adjustment, 2 cells: PSC184: sector1 & sector3 PSC185: sector4 & sector5 Delete sector 2 Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page54 Case 2 After adjustment, the drive test for PSC 184 and 185 Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page55 Case 2 The comparison result for scanner Ec/Io Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page56 Case 2 The comparison result for UE Ec/Io Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page57 Case 2 Summary In order to get better coverage performance at the place with complicated transmission environment, splitter is used to separate one cell into different sectors to cover different area. In this case, the sector should be designed reasonably to control the interference Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page58 Case 3 Description In drive test for RF optimization, bad Ec/Io is found on the bridge Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page59 Case 3 Analysis Check the RSCP value of scanner, the result shows the RSCP value is good. Based on this, pilot pollution need be considered in this area. Check the top N pilot RSCP and Ec/Io in scanner result Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page60 Case 3 Analysis From the DT result, it shows the RSCP value is strong, but the Ec/Io is bad. And the signal level of different cell are very similar. Find the cells which cover this area Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page61 Case 3 Analysis Site 2 Cell C Site 3 Cell C Site 1 Cell A Site 4 Cell C Site 5 Cell C Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page62 Case 3 Analysis On the bridge, the signal from different cell can cover this area due to reflection of the river and no building. From DT, following cell cover this area: Site 1 cell A Site 2 cell C Site 3 cell C Site 4 cell C Site 5 cell C Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page63 Case 3 Analysis Need to find the best cell Check the map, the site 6 is very near to the bridge. Site 4 Cell C Site 5 Cell C Site 1 Cell A Site 2 Cell C Site 3 Cell C Site 6 Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page64 Case 3 Analysis After checking site 6 RF environment, it is difficult to increase the antenna height or move site 6 position to avoid the blocking caused by the building The residence buildings are much higher than antenna, which block the signal of site 6 Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page65 Case 3 Analysis Then, site 1 cell A can be the best cell to cover this area Site 1 Cell A Site 2 Cell C Site 3 Cell C Site 4 Cell C Site 5 Cell C Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page66 Case 3 Analysis Then, try to increase the signal of site 1 cell A, and decrease other cells To confirm this, DT for site 1 cell A needs to be done Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page67 Site 5 Cell C Site 4 Cell C Site 1 Cell A Site 2 Cell C Site 3 Cell C Case 3 Solution Increase the signal of site 1 cell A Change the antenna downtilt from 10 to 7 Increase CPICH Tx power 1.5 dB higher Decrease other cell signal – change the antenna downtilt From 7 to 10 for site 2 cell C From 5 to 8 for Site 3 cell C From 9 to 11 for site 4 cell C From 9 to 11 for site 5 cell C Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page68 Case 3 Confirmation After the modification, the DT shows the pilot pollution area as below Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page69 Case 3 Confirmation The Ec/Io comparison After Before Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page70 Case 3 Summary To solve the pilot pollution, the following issues has be considered Find the reason caused pilot pollution – – Due to no strong signal Due to too much strong signal After the adjustment, the DT has to be done at this cluster to confirm that no new problem appeared Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page71 Case 4 Description In DT, video call quality is decreased at the problem area. Also, the PS call drop happened several times Problem Area 3G Antenna 2G Antenna Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page72 Case 4 Analysis RSCP distribution in DT Problem area Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page73 Case 4 Analysis Ec/Io distribution in DT Problem Problem area area Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page74 Case 4 Analysis Checking the RF environment, the antenna is installed on 10meter platform 2G and 3G antenna are installed at one platform, but 3G antenna is a little bit inner than 2G antenna. After finishing DT in 2G, signal level is very stable Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page75 Case 4 Analysis If 3G and 2G antenna are installed at the same place, the problem may be solved. The short wall of this platform may block the signal of 3G 3G Antenna Problem Area Wall Since 2G antenna is near to the border, the wall influence 2G little 2G Antenna Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page76 Case 4 Solution Solution 1 Increase the antenna height can solve this problem Solution 2 Move the installation place near to the border Solution 3 3G and 2G use the same place Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page77 Case 4 Solution Solution 3 is adopted Road T X / R R X X T X / R R X X 2G BTS 3G NodeB Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page78 Case 4 Question Do you have other methods? Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page79 Case 4 Summary Sharing the same installation place for 3G and 2G is very common, and several strategies can solve the problem In this situation, 3G and 2G can share the feeder system, or can only share the installation platform. Considering the factors of the installation and related resource, a easiest and simplest method should be adopted Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page80 Case 5 Description In DT, call drop happened a lot in the area Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page81 Case 5 Description Check the DT information, SC304 is in active set with the signal level – RSCP -76dBm and Ec/Io -18 Analysis Consider the pilot pollution But only 1 cell in active set and 1 Cell in monitor set Consider the missing neighbor cell But the cell in monitor set has very good quality – RSCP -65dBm and Ec/Io -6 Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page82 Case 5 Analysis Check the signaling trace at UE side Before call drop, UE sends measurement report to RNC with 1A event for cell 298 Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page83 Case 5 Analysis Check the signaling trace at RNC side RNC sent Active Set Update to UE, but no response. Then, RNC send release RRC connection – Call Drop Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page84 Case 5 Analysis Based on the DT and signaling trace, this call drop can be take as handover failure For example cell56 vs cell041 0 EcNo -10 -20 -30 time cell56 cell041 Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page85 Case 5 Analysis Around the corner, the original cell 304 signal level drop very quickly because of the building shadowing, and the neighbor cell 298 increase very quickly. After UE sent measurement report to RNC, cell 304 has become very bad when RNC sent active set update. Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page86 Case 5 Adjustment Since cell 298 has better coverage at this area, handover can happen earlier Decrease the coverage performance at this area – – Increase the downtilt from 5 to 9 Adjust the direction from 0 to 310 Increase the coverage performance at this area – – Decrease the downtilt from 5 to 4 Adjust the direction from 300 to 270 Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page87 Case 5 Adjustment Result after adjustment Handover area Before Handover area After Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page88 Case 5 Adjustment Comparison of Ec/Io of UE Before After Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page89 Case 5 Summary Confirm the corner effect by analyzing signaling trace at UE and RNC About corner effect, Taking the method make the handover happen earlier, such as RF optimization Other method can also adopted Modify 1A event Modify CIO (Cell Individual Offset) Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page90 Contents Typical Problems Analysis in RF optimization RF case related to neighbor cell list RF case related to bad coverage RF case related to interference Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page91 Case 1 Description From traffic statistic, the following RTWP problem is found RNCId 1 1 1 CellId 62501 62502 62503 CellName KwongYu1 KwongYu2 KwongYu3 Time(As hour) 2005-5-16 17:00 2006-5-16 17:00 2006-5-16 17:00 VS.MaxRTWP -74.5 -74.3 -82 VS.MeanRTWP -102.34 -94.89 -101.6 VS.MinRTWP -105.3 -105.5 -105.4 Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page92 Case 1 Analysis Connect to the problem NodeB, and monitor the RTWP Cell 62501 RTWP Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page93 Case 1 Analysis Cell 62502 RTWP Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page94 Case 1 Analysis Cell 62503 RTWP Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page95 Case 1 Analysis The main diversity antenna is interfered seriously Can not find any relation between interference and time, and the interference appears randomly Check the neighbor site, no interference Deduction Inter-modulation cause the interference, could be Inter-modulation caused by bad connectors Inter-modulation by GSM Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page96 Case 1 Analysis Check the RF environment Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page97 Case 1 Analysis Check the RF environment No blocking or any reflection due to the glass wall The site RF condition is very good Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page98 Case 1 Analysis 2G and 3G share the feeder system Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page99 Case 1 Analysis Check 2G frequency planning Sector 1 – 544 with hopping frequency 821 – 544 – 1811.6MHz & 821 – 1867MHz Sector 2 – 538 with hopping frequency 821 – 538 – 1808.6MHz & 821 – 1867MHz Sector 3 – 858 with hopping frequency 821 – 858 – 1874.4MHz & 821 – 1867MHz Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page100 Case 1 Analysis Calculate the third order intermodulation Cell 1 – 1922.4MHz Cell 2 – 1925.4MHz Cell 3 – 1859.6MHz Check cell 2 uplink interference The interval of 2 interference is 821-544 Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page101 Case 1 Analysis Conclusion The third intermodulation of cell 1 and cell 2 is just in WCDMA uplink band Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page102 Case 1 Solution Change the hopping frequency of DSC Confirmation Check the RTWP again, the values are normal Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page103 Case 1 Summary Characteristics of inner system interference The RTWP result are not same at the main and diversity antenna The amplitude of interference is big, and the difference is more than 10 dB High RTWP will appear in a duration, and will not change so frequently High RTWP will not show in a certain time each day, but randomly Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page104 Case 2 Description In a commercial network of country U, the following RTWP problem is found from traffic statistic RNCId 201 201 201 201 201 201 CellId 11912 11942 11932 11623 11461 11643 CellName Aguada_C Centenario_C Centro_C Ciudad Vieja_C Palacio_C Pocitos_C Time(As hour) 2005-11-15 4:00 2005-11-15 4:00 2005-11-15 17:00 2005-11-15 0:00 2005-11-15 20:00 2005-11-15 2:00 RTWP_MEAN -93.94 -95.86 -96.62 -96.74 -97.1 -97.72 RTWP_MAX -88.65 -87.65 -93.65 -91 -96 -92.65 RTWP_MIN -105.66 -105.66 -97.65 -105.65 -104.65 -105.65 Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page105 Case 2 Analysis Connect to the problem NodeB, and monitor the RTWP Take one site as example Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page106 Case 2 Analysis The main and diversity antenna have the same interference trend The different between main and diversity is less than 10dB Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page107 Case 2 Analysis Check the location of the sites with high RTWP High Medium Low Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page108 Case 2 Analysis All the problem cells are in the third sector of the NodeB, and the direction is to the northwest Many cells at this area show high interference, and the cells with low RTWP are at low place Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page109 Case 2 Analysis Analyze the RTWP in the nearly one month, the interference shows randomly, but if appears, usually one whole day, or several days The interference shows with high traffic, and also with low traffic. No evidence shows it is related to the traffic Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page110 Case 2 Analysis Maybe the interference comes from outside and the northwest direction Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page111 Case 2 Analysis Use YBT250 to do the interference checking Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page112 Case 2 Analysis All the test results show the interference comes from the same direction – to the country A But the distance to country A from the test place is around 50Km to 200Km Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page113 Case 2 Analysis Frequency analysis U Country UMTS frequency – 1900MHz A country GSM frequency – 1900MHz Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page114 Case 2 Analysis Maybe the interference comes from A country, but looks like impossible because the distance (50 to 200Km) is beyond the transmission To confirm this problem, use A country cell phone at the area with high RTWP The result shows the phone does receive the A country DSC Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page115 Case 2 Conclusion The interference comes from A country GSM Even the distance is very far, the area between the border is covered by a large water area Due to reflection the water, the signal can be transmitted far away Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page116 Case 2 Conclusion After known the reason, the following character of this kind of interference is found Related to the weather – – – Rain day, no interference Cloudy day, less interference Sunny day, high interference Related to the seasons also – Problems show at Summer more than Winter Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page117 Case 2 Summary Characteristics of external interference The RTWP result are same at the main and diversity antenna The amplitude of interference is small, and the difference is less than 10 dB The interference exists at large area, not just one cell, also including neighbor cells The direction of external interference is obvious The cell with high antenna is easier to be interferenced Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page118 Summary RF optimization Neighbor cell list optimization Coverage performance optimization Interference optimization Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. Page119 Thank you www.huawei.com