GSM system-network maintenance optimization parameter extraction
Optimize some parameters, and on the basis of research on the signaling process, give the parameter extraction method. The extraction of parameters is realized on the basis of the signal acquisition instrument as the platform and on the basis of the analysis of the collected field signal data. Using the parameter extraction software to perform statistics on the data collected on site, the results basically reflect the network behavior and user behavior, and have a certain significance for the maintenance and optimization of the network.
1. Significance of parameter extraction and significance of possibility parameter extraction: 1) Parameter extraction is necessary for network maintenance monitoring and optimization, and network maintenance and optimization must have relevant parameters as reference. 2) The development of some network maintenance equipment and monitoring systems must be supported by network parameter theory, such as the implementation of signaling analyzers. Without these parameter theories, these devices or monitoring systems cannot be realized. 3) Network parameters can provide data support for some current network optimization theories.
Possibility of parameter extraction: The parameter extraction is based on the GSM signaling acquisition instrument (which has been successfully developed by the author's laboratory) as a platform and is obtained through research on the collected signaling data.
2. Parameter extraction software system and data structure
2. 1 Parameter extraction software The premise of the parameter extraction software is the realization of the signaling acquisition instrument. The basic function of the signal acquisition instrument is to collect and interpret signaling data, and attach time stamps and connection types (such as MS calling, MS called, etc.) and other information. After the parameter extraction software performs statistical processing on the initial signaling data file collected by the signaling acquisition instrument, the parameter output data file is obtained. The parameter extraction software can be used as a module of the signaling acquisition instrument, so that the parameters can be extracted online, but in this way, the processor speed is often insufficient. The parameter extraction software can also become a software package independently, and perform statistical processing on the collected initial signaling data files. The parameter output data file includes the most basic parameter information. If you post-process the parameter data file, you will get additional parameters. The post-processing of the parameter output data file can be implemented as an independent software or a module of the parameter extraction software package. We are taking the latter option. Of course, you can also use existing office software, such as MS-EXCEL.
2. 2 Data structure of parameter output data file Each parameter statistics corresponds to a parameter output data file, such as user CDR (CALL DATA RECORDS) output data file, call status statistics output data file, etc. The parameter output data file consists of records. The record consists of statistical intervals and statistical items. The statistical items are determined by specific parameters and extraction methods. For example, the statistical items of call status statistics include LAC, CI, connection type, and CC layer messages.
3. Several concept statistics for parameter extraction can be aimed at the first layer discussion, the second layer discussion and the third layer discussion. The low-level statistics reflect the network transmission performance, while the high-level statistics can obtain network parameters such as call control, mobility management, and handover status. This article is aimed at high-level statistics.
Statistical direction dependence: The so-called direction-dependent statistics refer to the counting of messages based on the physical or logical direction of the link. The physical direction means whether the transmission of the message is from MSC to BSC (downstream) or from BSC to MSC (upstream). The logic direction reflects the type of connection to which the message belongs. There are four types of connections that should be distinguished: MOC (mobile station initiated), MTC (mobile station called), LOC (location update), UNKNOW (no connection). The MOC message belongs to the message of the connection established by the GSM04 and 08 messages CM-Service Request, that is, the message of the connection established by the mobile station calling. The MTC message belongs to the message of the connection established by the GSM04.08 message Paging Response, that is, the message of the connection established by the mobile station being called. The LOC message is a message of the connection established by the GSM04.08 LocaTIon Update Request message. All messages transmitted by SCCP-UDT (messages that do not belong to any connection are marked with UNKNOWN. For an incoming Handover, handoverRequest message and Handover Request Acknowledge message should be classified as UNKNOWN type messages, and subsequent messages should be Count according to the connection type established in the serving cell.
Statistical cell dependency: When a connection is established, the LAC (location area code) and CI (cell number) of a cell (CELL) will be sent as message elements. The statistics of many parameters are related to a specific cell. In statistics, the news related to a specific cell must be counted. For connected messages, the identity of a cell (LAC / CI) is a message element of the Complete layer 3 informaTIon message of the BSSMAP layer and is carried by the SC (CR continuation request) message. For BSC-controlled Handover, the LAC / CI of the new cell is included in the GSM08.08 HO Performed message, which indicates that a Handover was successfully completed. For messages sent in connectionless mode, the LAC and CI should be marked with 0.
Statistical methods can be divided according to the means and difficulty of implementation, and can be divided into message-oriented parameters, message-oriented parameters, and process-oriented parameters. Message-oriented parameters refer to the extraction of parameters as long as the related messages are counted. The parameter of the message element refers to that the extraction of the parameter involves not only the statistical processing message itself but also the elements of the statistical processing message, which is often filtered.
Process-oriented parameters refer to the specific process involved in the extraction of messages. For example, the implementation of user tracking, because the establishment of each CALL is associated with a connection, this connection implementation process is completed by SCCP, so the tracking of users involves not only the CC layer, but also the SCCP layer. When a connection is established, the identification of the connection is independently assigned by the SCCPs at both ends, and the transmission path is indicated by the identification later.
4. A port parameter statistics and post-processing Some parameters can be extracted on both the A interface and the Abis interface, such as call-through rate and call loss rate. Generally, when it is extracted from port A, the implementation is complicated. However, there is more information obtained and fewer devices are connected.
Different parameter extraction corresponds to different program branches, each branch is basically composed of the following modules: connection management module, used to manage the connection number that identifies a process; statistics and filtering module, used to obtain and count specific information; display Module, used to display related signaling process; save module, store related information; task scheduling module; resource management module, etc.
4.1 User CDR (CALL DATA RECORDS) and user tracking A basic user tracking is to record chronologically high-level messages about three basic signaling processes (mobile station call, mobile station call and location update) about the user It is enough to come down. The specific tracking process is as follows: Use the set IMSI, TMSI or IMEI to filter the BSSMAP Complete layer 3 informaTIon
The message-related message elements, when captured, can obtain the connection number from the SCCP message CR (of course, you must also obtain a part of the information from the subsequent message CC) that carries the message, and record all the messages of the connection. Another process parallel to the above process is to use the set MSISDN to filter the message element calling party BCD number or called party BCD number of the CC layer SETUP message. After capturing, the connection number is obtained from the SCCP message DTI that carries the message In one direction, the CC message of the corresponding connection can be further retrieved, so a complete connection number is obtained. Record all the messages of the connection.
User CDR is to record the relevant information of all users who have communicated within the test period within the jurisdiction of the BSC. The recorded user information can be more or less, which is related to the needs of users who use the software. Basic user information includes: user identity (IMSI, TMSI, IMIE), the identity of the other party to the call (MSISDN), the duration of the call (start time, end time, duration), release reason, signaling point code (OPC, DPC), the cell where it is (LAC / CI), the number of BSC internal handovers that occurred, the change of the cell sequence, and whether the handover that occurred out of the BSC occurred.
User CDR is similar to user tracking, except that user CDR is a record of all users' data within the jurisdiction of the BSC, and user tracking is to capture users of a given identity; user tracking also requires users outside the BSC's jurisdiction Tracking, but the user CDR only counts the users within the jurisdiction of the BSC; the user CDR can be implemented in an off-line mode, and the user tracking must be implemented in an online mode.
The realization of the user CDR can start with each connection (the SC and CR messages of the SCCP layer contain connection information), and organize the signaling data of all connections into a connected sequence, so that the user CDR is basically realized, of course, you can only choose Out some useful information.
The following applications can be obtained by post-processing the user CDR:
(1) According to the number of OPC and DPC calls.
(2) Distribution of call release reasons by time.
(3) The number of calls is distributed according to the reason of the call.
(4) The number of calls is distributed by time.
(5) Call records of specific users.
(6) The number of calls is distributed according to duration.
The above statistics are important for network planning and user behavior statistics.
4.2 Call status statistics Call status statistics mainly deal with the messages of the CC layer. The statistics of the call status depend on the specific cell and logic connection. The extraction of this parameter is process-oriented. The SCCP layer protocol is involved in the statistical process. Statistical items include LAC, CI connection types and various CC layer messages.
The statistical process is as follows: First, capture CR and CC messages to obtain the identification number of the connection to be established, and at the same time obtain the cell identity in the Completelayer 3 information message carried by the CR message. All subsequent messages of the connection are messages concerning the cell. Of course, within the statistical interval, there is more than one connection related to a particular cell, and all messages related to the connection must be counted.
Post-processing it can get the following applications:
(1) Number of mobile phone calls and number of calls and ratio of mobile phone calls: Number of mobile phones = Number of SETUP messages with connection type MOC Number of mobile phones called: Ratio of mobile phones called / Number of mobile phones called (2 ) Mobile phone call connection rate, call loss rate and called miss rate Mobile phone call connection rate = number of CONNECT messages with connection type MOC / mobile phone call number mobile phone call loss rate = (mobile phone call number- Number of CONNECT messages with connection type MOC) / Number of cell phone calls Cell phone missed call rate = 1-Cell phone call connection rate-Cell phone call loss rate = (Number of ALERTING messages with connection type MOC-Connection type is Number of CONNECT messages of MOC) / Number of mobile phone calls (3) Connected call rate, call loss rate and missed call rate of mobile phones Called call rate of mobile phones = number of CONNECT messages with connection type MTC / number of mobile phones called Mobile phone call loss rate = (number of mobile phone calls-number of CONNECT messages with connection type MTC) / number of mobile phone calls missed rate of mobile phone call = 1-mobile phone call connection rate-mobile phone call loss rate = (Number of ALTERING messages with connection type MTC-Number of CONNECT messages with connection type MTC) / The phone is called Number (4) call connection rate, call loss rate and called missed rate call connection rate = mobile phone call connection rate + mobile phone call connection rate call loss rate = mobile phone call call loss rate + mobile phone call Call Loss Rate Called Missed Rate = Mobile Phone Called Missed Rate + Mobile Phone Called Missed Rate (5) Mobile Phone Called and Called Connected Ratio Compared to Mobile Phone Called and Called Connected Ratio = Mobile Phone Called and Connected Ratio Called connection rate (6) Number of mobile phone emergency call establishments Number of mobile phone emergency call establishments = Number of EMERGENCY SETUP messages (7) Number of mobile phone on-hook and network side on-hook ratios DISCONNECT number of connection type MOC / DISCONNECT number of connection type MTC (8 ) Statistical distribution and statistical average If the above parameters are generated every statistical interval, the result will be a statistical distribution; if the statistical results of the above parameters are from the entire measurement period, the result will be a statistical average.
(9) Cell parameters and BSC parameters If the statistics of the above parameters use LAC and LAC / CI as the filtering conditions, the parameters obtained are the parameters that measure the area or the cell at that location; if they are not used as filtering conditions, the obtained The parameters measure all cells under the jurisdiction of the entire BSC.
4.3 Call release statistics The reason for call release statistics is a parameter that counts the cause of call release, including normal release and abnormal release. By counting the value of the message element CAUSE of the message RELEASE COMPLETE in the CC layer, the statistics of this parameter can be realized. The call release statistics are dependent on the specific cell and logical connection, and are process-oriented. The SCCP layer protocol is involved in the statistical process. The statistical items are: LAC, CI connection type and the number of various release reasons.
You can distinguish whether the message belongs to MOC or MTC according to the physical connection direction of the RELEASE COMPLETE message. If the message sending direction is upstream, it is MOC; if the message sending direction is downstream, it is MTC. The connection where the message is located is obtained by checking the connection identifier of the UDT1 of the SCCP layer carrying the RELEASE COMPLETE message of the CC layer.
4.4 Mobile management analysis (excluding handover process)
Mobility management involves identification procedure, TMSI redistribution procedure, authentication management, IMSI release (detach) procedure, abort procedure (Abort procedure), location update management, IMSI attach (attach) procedure, MM connection management procedure, etc. The mobile management analysis will extract the parameters that reflect these management processes. The extraction of all these parameters is cell-dependent and direction-dependent. Statistical items include LAC, CI, connection type and all MM layer messages.
The following applications can be obtained by post-processing the output data file:
(1) Location update status statistics Location update request number = LOCATION UPDATING REQUEST message number location update rejection number = LOCATION UPDATING REQUEST message number location update acceptance number = LOCATION UPDATING ACCEPT message number location update success rate = location update acceptance rate / location update request Location update failure rate = Location update rejection number / Location update request number = 1-Location update success rate (2) Authentication status statistics Authentication request number = AUTHENTICATION REQUEST message number Authentication success number = AUTHENTICATION RESPONSE message number Authentication rejection Number = AUTHENTICATION REJECT message number Authentication success rate = Number of authentication successes / Number of authentication requests Illegal user rate = Number of authentication rejections / Number of authentication requests Number of authentication success rate = 1- Authentication success rate-Illegal user rate (this The parameter indicates that the user is legal, but due to the network or other factors, the proportion of user authentication failures caused)
(3) MM connection management process business request number = CM SERVICE REQUEST message number service reconstruction request number = CM REESTABLISHMENT REQUEST message number business request success number = CM SERVICE ACCEPT message number business request rejection number = CM SERVICE REJECT message number business request success rate = Number of business request successes / Number of business request failures of business requests = Number of business request rejections / Number of business requests (4) Statistical distribution and statistical average If the above parameters are generated every statistical interval, the result will be a statistical distribution; if The statistical results of the above parameters come from the entire measurement period, and the result obtained is a statistical average.
(5) Cell parameters and BSC parameters If the statistics of the above parameters use LAC and LAC / CI as the filtering conditions, the parameters obtained are the parameters that measure the area or the cell at that location; if they are not used as filtering conditions, the obtained The parameters measure all cells under the jurisdiction of the entire BSC.
4.5 Abnormal Causes of Mobile Management Process Abnormal statistics location update may be caused by various reasons. The location updating reject message contains a message element reject cause, which reports in detail the reasons for the failure of the location update. The statistics of these causes will have a reference for network maintenance and optimization. Similarly, the cause value of the MM connection establishment failure is reported by a message element CAUSE of the message CMSERVICE REJECT. In addition, the ABORT message is used by the network to terminate an MM connection being established. The message element CAUSE of this message contains the reason why the network startup was aborted. For example, if the mobile phone has no roaming rights in this area, this process occurs.
4.6 Handover status statistics Handover status statistics are statistics related to the handover of the BSC. There are three possible handovers for the BSC: handover inside the BSC, MS outside the BSC enters the cell under the jurisdiction of the BSC, and MS inside the BSC moves out of the BSC. Handover status statistics involve messages from the BSSMAP protocol layer. The statistical items are: serving location area, serving cell, target location area, target cell, and various BSSMAP layer messages related to handover.
For BSC-controlled handover, the LAC / CI of the new cell is included in the GSM08.08 HO Performed message, which indicates that a handover was successfully completed. For handovers that require handover out of this BSC, the LAC / CI of the candidate new cell is included in the HANDOVER REQURIED message. For handover to this BSC, the LAC / CI of the target cell and the original cell is included in the HANDOVER REQUEST. The following applications can be obtained by post-processing the output data file:
(1) The number of MSs required to switch out of this BSC, the number of handovers that occurred within the jurisdiction of this BSC, the number of MSs requested to switch to this BSC, and the total number of handovers:
Number of MSs required to switch out of this BSC = Number of HANDOVER REQUIRED messages Number of handovers that occurred within the scope of this BSC = Number of HANDOVER PERFORMED messages Number of MSs requested to switch to this BSC = Number of HANDOVER REQUEST messages Total number of switches = Request to switch out of this BSC The number of MSs in BSC + the number of MSs requesting to switch to this BSC + the number of handovers that occurred within the jurisdiction of this BSC (2) The number of successful handovers and the cost of handover to this BSC
Number of successful BSC handovers: Number of successful handovers after switching out this BSC = CLEAR COMMAND CAUSE
(0B) The number of messages successfully switched into the BSC = the number of HANDOVER COMPLETE messages (3) the success rate of switching out of the BSC and the success rate of switching into the BSC: the success rate of the switching out of the BSC = the rate of switching out Number of successful handovers of this BSC / Number of MSs required to switch out of this BSC The rate of handover success of switching into this BSC = Number of successful handovers into this BSC / Number of MSs requesting to switch to this BSC (4) Statistical distribution and statistical average If the above parameters are generated every statistical interval, the result obtained is a statistical distribution; if the statistical results of the above parameters are derived from the entire measurement period, the obtained results are a statistical average.
(5) Cell parameters and BSC parameters If the statistics of the above parameters use LAC and LAC / CI as the filtering conditions, the parameters obtained are the parameters that measure the area or the cell at that location; if they are not used as filtering conditions, the obtained The parameters measure all cells under the jurisdiction of the entire BSC.
4.7 Switching Cause Statistics and Switching Failure Statistic Switching statistics can be achieved by counting the message element CAUSE value of HANDOVER REQUIRED message and HANDOVER PERFORMED message.
The following applications can be obtained by post-processing the output data files:
(1) The reason for BSC internal handover;
(2) The cause of the switchover from BSC;
(3) Measure the performance of a specific cell, such as whether there is a shortage of wireless resources in the cell;
(4) Statistical distribution and statistical average: If the above parameters are generated every statistical interval, the result will be a statistical distribution; if the statistical results of the above parameters are derived from the entire measurement period, the result will be a statistical average;
(5) Cell parameters and BSC parameters: If the statistics of the above parameters use LAC and LAC / CI as the filtering conditions, the obtained parameters are the parameters of the area or the cell that measure the location; if they are not used as the filtering conditions, the obtained The parameters are measured for all cells under the jurisdiction of the entire BSC.
The reason for the handover failure can be achieved by counting the value of the message element CAUSE of HANDOVER FAILURE. This message is generated when the MSC requests the new BSC to allocate resources for the handover and the BSC has no resource allocation. In addition, when the MS switches to the new cell and finds that it cannot communicate normally on the new wireless resources, it sends the air interface message HANDOVER FAILURE through the old channel. Notify the old BSS, and then the old BSC sends a BSSMAP HANDOVER FAILURE message to the old BSS.
4.8 Statistics of TCH failure cause allocation, CLEAR REQUEST cause and CLEAR COMMAND cause statistics MSC requests the allocation of TCH by sending BSSMAP ASSIGNMENT REQUEST message, and BSS responds by ASSIGNMENT COMPLETE and ASSIGNMENT FAILURE messages. Calculate the cause value of the message element CAUSE of the ASSIGNMENT FAILURE message, and you can find the cause of the TCH allocation failure.
When the resource is released due to the cause of the BSS, the BSS will send a CLEAR REQUEST message to the MSC. The specific reason is given by the message element CAUSE. When the resources are released due to a successful handover or after completing a transaction, the MSC will send a CLEAR COMMAND to the BSS, the specific reason is given by the message element CAUSE.
5. Conclusion and application By applying the implemented system to the Guangdong GSM mobile communication network, satisfactory results have been achieved. As a subsystem of the signaling analyzer, it passed the identification of Guangdong Mobile Communications Bureau and has been applied in Guangdong GSM network. Specific applications are:
6) Maintenance of the existing network;
7) Optimization of the existing network;
8) Provide direct data for the study of network optimization theory;
9) Provide data support for the development of the third generation mobile communication network.
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