10 WCDMA Call Drop Problem Analysis HUAWEI TECHNOLOGIES CO , LTD www huawei com HUAWEI Confidential Internal WCDMA Call Drop Problem Analysis HUAWEI TECHNOLOGIES CO , LTD Page 2HUAWEI Confidential For[.]
Internal WCDMA Call Drop Problem Analysis www.huawei.com HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Foreword: Causes of Call Drop in GSM & UMTS GSM UMTS Neighbor cell problem No response after T3103 expiry Interference problem Interference problem Coverage problem Coverage problem Handoff problem Improper parameter setting Interactive process Equipment problem HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Page Objectives Upon completion of this course, you will be able to understand: Definition of the call drop Process for handling the call drop problem Various methods to analyze call drop data Solutions to call drop problems HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Page Contents Definition and classification Causes and handling process Solutions Case analysis Concerns in various network optimization phases Training.huawei.com HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Page Definition and Classification HUAWEI TECHNOLOGIES CO., LTD 1.1 Normal release procedure 1.2 Call drop over the Um interface 1.3 Call drop measurement - CS 1.4 Call drop measurement - PS HUAWEI Confidential Page Normal Release Procedure Procedure of CS service normal release HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Page Normal Release Procedure CS Normal Release Procedure The UE sends the RRC_UL_DIR_TRANSF message to the RNC If the nas message carried in this message is 0325, it indicates that the message is the disconnect message of the call control sublayer The RNC sends the RANAP_DIRECT_TRANSFER message to the CN If the nas pdu carried in this message is 0325, it indicates that the message is the disconnect message of the call control sublayer The CN sends the RANAP_DIRECT_TRANSFER message to the RNC If the nas pdu carried in this message is 832d, it indicates that the message is the release message of the call control sublayer The RNC sends the RRC_DL_DIRECT_TRANSF message to the UE If the nas message carried in this message is 832d, it indicates that the message is the release message of the call control sublayer The UE sends the RRC_UL_DIR_TRANSF message to the RNC If the nas message carried in this message is 032a, it indicates that the message is the release complete message of the call control sublayer The RNC sends the RANAP_DIRECT_TRANSFER message to the RNC If the nas pdu carried in this message is 032a, it indicates that the message is the release complete message of the call control sublayer HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Page Normal Release Procedure The CN sends the RANAP_IU_RELEASE_COMMAND message to the RNC to release resources of the Iu interface, including resources of the RANAP layer and the ALCAP layer The RNC sends the RANAP_IU_RELEASE_COMPLETE message to the CN The RNC sends the RRC_RRC_CONN_REL message to the UE to release the RRC connection 10 The UE sends the RRC_RRC_CONN_REL_CMP message to the RNC 11 The RNC sends the NBAP_RL_DEL_REQ message to the NodeB to release resources of the Iu interface, including resources of the NBAP layer and the ALCAP layer 12 The NodeB sends the NBAP_RL_DEL_RSP message to the RNC Then, the release procedure is complete HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Page Normal Release Procedure Procedure of PS service normal release HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Page Normal Release Procedure Procedure of PS service normal release The UE sends the RRC_UL_DIR_TRANSF message to the RNC The nas message carried in the message is 0a46, indicating that the message is the deactivate PDP context request message of the session management sublayer The RNC sends the RANAP_DIRECT_TRANSFER message to the CN The nas pdu carried in the message is 0a46, indicating that the message is the deactivate PDP context request message of the session management sublayer The CN sends the RANAP_DIRECT_TRANSFER message to the RNC The nas pdu carried in the message is 8a47, indicating that the message is the deactivate PDP context accept message of the session management sublayer The CN sends the RNC the RANAP_RAB_ASSIGNMENT_REQ message carrying the RAB list (to be released) with RAB IDs to be released The RNC sends the RRC_DL_DIRECT_TRANSF message to the UE The nas message carried in the message is 8a47, indicating that the message is the deactivate PDP context accept message of the session management sublayer The RNC sends the NBAP_RL_RECFG_PREP message to the NodeB HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Page 10 Cases of Call Drop Caused by Handoff As shown in this figure, the call drop does not occur at the edge of the 3G network coverage area HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Page 69 Cases of Call Drop Caused by Handoff The call drop occurs in the area where the best cell changes rapidly HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Page 70 Cases of Call Drop Caused by Handoff Before the call drop, the Ec/Io measured by the UE is decreased to lower than -21 dB, whereas the Ec/Io measured by the scanner is still above -11 dB HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Page 71 Cases of Call Drop Caused by Handoff Before the call drop, the best cell measured by the UE is the SC009 cell, whereas the best cell measured by the scanner is the SC018 cell After the call drop, the UE camps on the SC018 cell rapidly HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Page 72 Cases of Call Drop Caused by Handoff Before the call drop, the SC018 cell is not measured in the monitored set of the UE The neighbor relation is found to be defined in the neighbor list Therefore, the possible call drop cause is that the best cell changes rapidly from the SC009 cell to the SC011 cell and SC018 cell, and thus the UE fails to perform the soft handoff timely HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Page 73 Cases of Call Drop Caused by Handoff The SC018 cell is not the best cell here Serious cross coverage exists in the SC018 cell Upon the call drop, the RSCP is over -75 dBm Therefore, you must increase the down tilt of the SC018 cell, control the coverage, and optimize the primary cell of the call drop location HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Page 74 Case analysis 4.1 Cases of call drop caused by poor coverage 4.2 Cases of call drop caused by interference 4.3 Cases of call drop caused by handoff 4.4 Cases of call drop caused by other reasons HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Page 75 Cases of Call Drop Caused by Other Reasons The material is not available HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Page 76 Contents Definition and classification Causes and handling process Solutions Case analysis Concerns in various network optimization phases Training.huawei.com HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Page 77 Concerns in Various Network Optimization Phases 5.1 Concerns in various network optimization phases HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Page 78 Concerns in Various Network Optimization Phases Network optimization procedure HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Page 79 Concerns in Various Network Optimization Phases The entire network optimization process consists of the following phases: Sign the project contract Optimize the network Generate the network optimization report Here, we focus on the causes of the call drop in phases from the single site test phase to the subsequent acceptance phase Single site test phase In the single site test phase, analyze the equipment problem to locate the abnormal call drop cause If the call drop occurs during the drive test, check whether the call drop is caused by the poor coverage HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Page 80 Concerns in Each Phase RF optimization phase Evaluation before the optimization During the evaluation phase, check the drive test results for call drop rate indexes and learn about the call drop rate of the entire network according to the measurement analysis In this phase, emphasize on and differentiate call drops caused by poor coverage, interference, or untimely handoff In addition, the call drops caused by the untimely handoff should be taken into account RF optimization The emphasis of this phase is to check whether call drops are caused by the poor coverage or strong interference Check whether such call drop problems can be solved by adjusting engineering parameters of the antenna In addition, call drops caused by the untimely handoff should be taken into account Check whether the corner or pinpoint effect can be avoided by adjustment of the antenna HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Page 81 Concerns in Each Phase Parameter optimization phase If certain call drops cannot be avoided by RF optimization or the RF optimization cannot be performed in some scenarios, optimize parameters to solve these problems after the RF optimization In this phase, lay special stress on call drops caused by the handoff, inter-frequency handoff, and inter-RAT handoff Generally, call drops due to latter causes occur in indoor area or subway In this case, carry out the walking dialing test accordingly and trace messages of the single user on the RNC for data analysis Acceptance phase To evaluate the optimization effect, collect drive test indexes and measurements related to the call drop rate during the optimization and acceptance phases Not all these call drop problems are required to be solved, but you are advised to analyze the detailed causes of each call drop and put forward further suggestions on the future optimization HUAWEI TECHNOLOGIES CO., LTD HUAWEI Confidential Page 82 Thanks! 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