Acquire data about cells with abnormal KPIs through the traffic statistics. If KPIs of these cells used to be normal, then the abnormal KPIs may be brought by software version, hardware, transmission, antenna, or data, then you can check these aspects based on the alarms.
If no obvious abnormal cells exist, the statistics can be classified based on the carrier in each sector, then cells with poor KPIs can be screened out. Further analyze the traffic statistics of these cells, such as analyzing more related KPIs, such as analyzing data at a shorter interval, or analyzing KPIs that are more likely to cause call drops, such as handover. Meanwhile, you can analyze the reasons for call drops based on system logs. It should be specified that the result of traffic statistics is meaningful only when the traffic volume reaches a certain amount.
This value is meaningful only when the calling number, succeed calling number, call drop times all make statistical significances. After several repetitions, the related KPI can be speedily converged. At the initial stage of network construction, there are few subscribers in the network. At this stage, the KPIs of many cells might be unstable, such as call drop rate. You can collect the data in seven days or longer periods, then select the top cell and then perform the optimization.
For example, optimization of call drop rate of CS services. When selecting top cells, you can select the cell with call drop numbers exceeding the specified threshold, and then arrange the priority based on the call drop rate. The procedures of top cell selection are the same as the procedures of handling input information from other team of engineers complains or single site acceptance , and are shown in the following figure.
While, speedy and accurate collection of the field data is essential to locate and solve the problem and to improve the KPIs. Data collection can be divided into multiple layers. At present, most field questions can be located through the data analysis at this layer.
Data at this layer can help to solve some deep layer problems. The following chapter focuses on the data collection tool and method for the first layer data, and only gives a brief introduction to that of the second layer. It should be emphasized that signaling tracing by cells can only trace the UE that initiates the call from this cell.
The UE can be traced as long as it remains in the same RNC, even if it is handed over to other cells. However, if a UE initiates the call from other cells and then is handed over this call, and its call drop happens in this cell, it cannot be traced. Therefore, when you trace the signaling of a cell with high call-drop rate, the signaling of cells in close handover relation with this cell should also be traced, then the result would be more comprehensive.
RNC Association Log This tool helps to record the context of the abnormal system flow, and then the context would be counted and analyzed to locate the network problem. It is usually used when the system is abnormal and no RNC signaling is traced. It can help to locate the problem by the time when the system exception happens. Different modules of the NodeB would record the information when exceptions happen, thus facilitating the location of problems.
However, specialized knowledge is required. You have to understand the functions and interfaces of different boards. CTS can trace the interactive signaling among different NEs within the CN, and can trace the signaling at the Iu and Uu interfaces, and this is called deep tracing. Many problems, signaling tracing at the network side and tracing of problems which are hard to be located, can be finally located after combining the UE logs.
The setting of TTT would influence timely handover. The adjustment of handover parameters should first ensure that this cell is overlapped by other cells, then you can adjust the related radio parameters to ensure that the time that the UE passes the handover area is longer than the handover delay of the whole system, thus ensuring the continuity of the services. The other is to ensure that the handover area ascertained by the signals and radio parameters cannot be too large to avoid the increase of handover overhead and reduction of resource utilization ratio.
For areas where the signals may change greatly, the trigger time of Event 1A must be reduced, and that of Event 1B must be increased. Meanwhile, the CIO of the corresponding neighbor cells should be adjusted so that Event 1A can happen earlier and Event 1B would happen later, thus ensuring successful handovers.
For highways, the cells are sparsely distributed. If the vehicles drive too quickly and cannot access the new cell in time, call drops would happen. The optimization is the same as that for the optimization for street corners in dense urban, which is to make cells with good signals join the active set speedily to ensure continuity of services.
For the adjustment of the related parameters, a whole new set of parameters must be assigned to the target cell.
The UE would use the original measurement value of this cell plus the CIO as the measurement result for the intra-frequency handover judgment. CIO can help to ascertain the cell edge. However, more resources are consumed. This smaller is parameter is set, the more difficult the soft handover is. CIO is valid only for the neighbor cell. Mi is the mean measurement result of cells exclude the best cell in an active set.
NA is the current cell number exclude the best cell in the active set. MBest is the measurement result of the optimal cell in the active set. W is the weight proportion of the best cell to the rest cells in the active set. R1a is the reporting range of Event 1A. H1a is the reporting hysteresis of Event 1A. R1bis the reporting range of Event 1B. H1b is the reporting hysteresis of Event 1B. In the current system, the compressed mode is started through Event 2D, and stopped through Event 2F.
Currently, the default value is RSCP. Generally, the quality and other related information of the target cell inter-frequency or inter-RAT must be acquired for the compressed mode. Meanwhile, the moving of the UE would lead to the deteriorate of the quality of the cell, therefore, the start threshold of the compressed mode should satisfy the condition that the UE can finish the measurement of the target cell and report for handover before call drops happens. Coverage overlap.
The coverage of service cell is overlap with another cell B, and there is handover relationship between cell B and cell A but not between the service cell and cell A. Then the call in cell A will drop for no suitable handover target cell according to the original configuration. Obvious coverage holes in the areas. Signal fading. Serious signal fading leads to call drop for too late to handover during signal transmission. Not all the neighbor cells are configured in the data configuration.
Limited neighbor cells configuration leads to keep MS staying in the current service cell and hard to start handover and cause call drop finally. Uplink-and-Downlink unbalance problem. When uplink signal strength is higher than downlink signal strength, the downlink signal receiving level on the edge the cell is lower and easy to cover by the other stronger signals. When downlink signal strength is higher than uplink signal strength, MS will be kept to stay in the current service cell with bad voice quality and call drop for too weak uplink signal strength.
Troubleshooting Procedure Procedure 1. Adjust the network parameters to optimize handover relationship and handover speed. Build new site to cover the deficient coverage area.
Control the coverage scope of BTS. Check the configuration of neighbor cells. Check Uplink-and-Downlink Balance Measurement with tower amplifier, antenna feeder and couplers. Check the actual antenna direction with design direction. Uplink signal strength will be much lower if diversity antenna connection is installed inversely.
In addition, if the BSC-level parameters are set incorrectly, call drops may occur in some or all of the cells under the BSC. Besides , parameters shown as follow are also important with call drop. If the value of this parameter is 0, the BTS assumes that the uplink radio link is faulty.
In this case, set this parameter to a larger value. Do not set this parameter to a small value during light congestion. Call Reestablishment Forbidden Blind spots caused by tall buildings or abrupt interference may lead to radio link failures and call drops. This parameter specifies whether an MS can initiate a call re-establishment procedure to re-establish a dropped call in such a scenario.
To reduce the call drop rate, set this parameter to No to allow call reestablishment. Handover-related Parameters If handover-related parameters are not set correctly, handovers may not be performed in time, leading to call drops. Power Control Parameters If the power control level and quality thresholds are set to small values, call drops are likely to occur because of low signal level and poor signal quality.
Troubleshooting Procedure Neighboring Relationship If only some neighboring cells are configured in the BA2 list, no neighboring cells may be suitable for handovers and signal levels may deteriorate, resulting in call drops.
When this parameter is not configured, after being handed over to a target cell, an MS cannot hang up because it does not receive a release acknowledgment message, leading to call drops. Configuring this parameter enables the MS to hang up in this scenario. Do not set this parameter to a small value.
If this parameter is set to a small value, some MSs with low signal levels may attempt to access the network and call drops are likely to occur. To reduce the call drop rate, set this parameter to a large value. A large value, however, may affect the call setup success rate and traffic volume. A large value, however, may decrease the call setup success rate and paging success rate.
View the traffic statistics and operation logs to check whether the call drop rate significantly increases when an MSC cutover is performed or when the related parameters are modified on the MSC or the BSC.
Check whether an MSC cutover is performed. Ensure that the parameters are set to the same values. Check whether related parameter settings were modified on the MSC. View the parameter description to check whether parameter setting modification may cause call drops. If the parameter setting modification causes any call drops, undo the parameter setting modification.
Check whether any of the relevant parameter settings are modified on the BSC. The frequency band of the two cells was M. After the operation, call drop rate for the two cell both increased and cell A worked normally. Questions 1. Please list the information you need to analyze this problem. What is the possible cause for the increasing call drop? What about he solution to this problem? After the two sites broke Abis transmission and recovered normally, the call drop rate counter still increased and CSSR decreased.
What is the possible cause for this problem, and any information you need to support the analysis result? If you think the transmission problem is the main cause, how to test and prove it?
Open navigation menu. Close suggestions Search Search. User Settings. Skip carousel. Carousel Previous. Save to Library Save. Create Alert Alert. Share This Paper. Figures, Tables, and Topics from this paper. Artificial neural network Quality of service Computer engineering X. Citation Type. Has PDF. Publication Type. More Filters. Internet traffic can be described as a general term that includes the transmission of internet data between different devices and systems.
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