Application of NO. 7 Signaling System in GSM

This article is excerpted from: Communication Technology

1 Introduction

The No. 7 signaling system is one of the key technologies of modern communication networks and the neural hub of communication networks. It has become an indispensable part of communication networks such as telephone networks, mobile networks, and intelligent networks. As the nerve hub of modern network communication, the No. 7 signaling network plays an increasingly important role in mobile communication, and has higher requirements on the management and maintenance of the No. 7 signaling network. How to better monitor the No. 7 signaling network, improve the operational service quality and maintenance level, improve the call rate, and monitor abnormal calls has become an urgent problem for telecom operators. Traditional network management systems, monitoring instruments, and other maintenance methods alone cannot meet the maintenance requirements for the increasingly complex and evolving 7th signaling network. The centralized signaling Detection System No. 7 can obtain signaling information accurately and effectively, providing effective support for signaling network management, maintenance, and service quality monitoring and analysis.

2 monitoring interface and protocol model of GSM digital mobile system

GSM digital mobile system consists of four parts: Mobile Station (MS), Base Station Subsystem (BSS), network and exchange subsystem (NSS), Operation and Maintenance Subsystem (OSS. The Base Station Subsystem (BSS) is composed of two types of devices: The base station transceiver (BTS) and the Base Station Controller (BSC. The network and exchange subsystem (NSS) includes the mobile exchange center (MSC), visit Location Register (vlr), belonging Location Register (HLR), Monitoring Center (AUC), MSC Gateway (gmsc).

The um interface is the communication interface between the mobile station and the base station receiving and sending station (BTS). The signaling transmission protocol is the unique lapdm of GSM. The Abis interface is the communication interface between the base station controller (BSC) and the base station receiver (BTS). The signaling transmission protocol is LAPD. The interface between BSS and the Mobile Business Exchange Center MSC is the interface. The A interface is based on the 2 Mbit/s digital interface and adopts the 14-Bit Coding No. 7 signaling method. It mainly transmits information including call processing, mobility management, base station management, and mobile station management. The interface between MSC and the visit Location Register vlr is the B interface, which is used by MSC to ask vlr about the current location information of the mobile station, or to notify vlr about the location update information of the Mobile Station. The interface between MSC and HLR is the C interface, which is used to pass the information of the called mobile customer and obtain the roaming number of the called mobile customer. The D interface is an interface between HLR and vlr. It exchanges location information and customer information. The interface between MSC is an E interface, which is a 2 Mbit/s digital interface. It adopts the 24-bit encoded No. 7 signaling method, and the bits keep the call continuously, while switching the situation.

3 monitoring system architecture and functional requirements

* Architecture

The No. 7 signaling centralized monitoring system adopts a modular architecture, which is divided into two levels: the center and the remote station. They are interconnected through the WAN. The Central Station and the remote station are composed of their local LAN and adopt the Client/Server mode, moreover, the system can be flexibly built and expanded based on users' network needs. Data is collected by the data collection module of each front-end machine from the 2 Mbit/s port of the No. 7 Signaling Link. After preprocessing, after entering the remote station processing system, the corresponding data and call details (CDR) are generated and stored in the remote station database. At the same time, the relevant data is stored in the central station database through the WAN, the operating terminal can directly access the database through the network.

* Functional requirements

As a network maintenance optimization platform, the signaling centralized monitoring system should have certain functions, including real-time application and comprehensive statistical analysis.

3.1 real-time application

3.1.1 Real-time Monitoring and Management of Signaling Link Status and Performance

The system provides real-time monitoring of the status and load of inter-network signaling links, and displays various link faults collected by the system in real time in an audible and visualized manner, color changes are used to reflect the alert type and level. At the same time, it can display the available status and load of the signaling link in real time, query, statistics, and sort the link load during a certain disconnection period, and provide various charts to analyze the link performance, provides technical basis for network optimization.

3.1.2 message filtering

Filter events that are stored and allow users to query signaling messages with special content. Use sequential filtering to form the complete sequence of event processing. Event Recognition and sequence recognition can be used as filter conditions. You can select multiple predefined events and sequence identification. 3.1.3 Management of busy household numbers

The system detects and provides the number, number, and user information of a busy user in real time, this information enables telemarketing and other business departments to address the low connection rate caused by busy users. Through the specific loose management, we can greatly improve the call rate of long-distance and domestic networks, and improve the service quality.

3.1.4 call tracking

Call tracking is used to track the complete signaling process of a call in real time, so as to quickly identify the problem of signaling coordination between entities, the specified call number tracking test function enables dynamic and real-time tracking of ISDN numbers, mobile users imsi, and msisdn numbers. The system should be able to automatically track and cooperate with specified call-related signaling, real-time display of trace messages or call process records, and quick query of call failure causes, user business reasons, and user location environment causes. The system also has the ability to track calls of multiple user numbers at the same time, automatically tracks multi-segment and multi-protocol signaling coordination processes, and saves tracking process data.

3.1.5 protocol analysis capability

The centralized monitoring system for signaling No. 7 provides protocol analysis for the entire network, and provides complete decoding and protocol analysis for MTP, Tup, ISUP, and map. This function makes inter-Bureau signaling analysis very convenient and fast, and maintenance personnel can conveniently observe the protocols of any links in the network, it facilitates compatibility testing between various vswitches and finds and solves problems when new services such as ISDN and intelligent network are introduced.

3.2 Comprehensive statistical analysis

The comprehensive statistical analysis module conducts in-depth data mining and statistics on the data stored in the database, and reports, histograms, pie charts, and graphs. Provides effective decision support data for network management, business analysis, and network planning. Including:

3.2.1 Fault Analysis

Fault analysis provides detailed statistics on the frequency and duration of failures in links, link groups, routing groups, and subsystems, as well as horizontal and vertical comparisons. Supports flexible query conditions for alarm records and queries, including Alarm types, alarm levels, alarm occurrence time, clearing time, and alarm source.

3.3.2 statistical analysis of network performance

Statistical Analysis of signaling link performance refers to the comprehensive statistical analysis of the performance indicators of a specified link within a specified time range. The analysis includes:

---- Integrity rate of the signaling link (failure rate, long congestion time, long blocking time, etc)

---- Availability of the signaling link (unavailable duration and blocking duration)

---- Utilization of signaling links (number of MSU receiving and receiving, number of link congestion, etc)

---- Performance of MTP bearer services (MTP carries load of services such as Tup, ISUP, INAP, and map)

3.2.3 statistical analysis of signaling routing performance

Signaling routes are composed of different signaling link groups. The performance of Signaling routes is derived from the statistical analysis of the performance of each link group. The analysis includes:

---- Unavailable duration of the signaling link group

---- Number of times a signaling link group fault occurs

---- Number of times a route group unavailable event occurs to one or more dpcs

---- The duration of the routing group to one or more dpcs is unavailable.

3.2.4 Statistical Analysis of the Performance of signaling points (STP/SP)

Statistical Analysis of the Performance of signaling points refers to the comprehensive statistical analysis of the performance indicators of a specified signaling point (STP/SP) within a specified time range. The analysis includes:

---- The accessibility of signaling points (the number of times that cannot be accessed and the length of time that cannot be accessed at the signaling points)

---- Load Status of signaling points (number of MSU receiving and transmitting, distribution of load imbalance between pairs of STPS, etc)

---- Service processing capability of signaling points (number of messages sent and received, such as Tup, iuup, INAP, and map)

3.2.5 statistical analysis of signaling services (Tup, ISUP, SCCP, etc.) and their corresponding calls

Statistical Analysis of signaling services (Tup, ISUP, SCCP, etc.) and their corresponding calls includes:

Call count, access rate, usage, Response count, call duration, call loss distribution, ultra-short call count, and ultra-long call count.

4 Implementation Scheme of centralized monitoring of Mobile 7 Signaling

The Mobile 7 signaling centralized monitoring system consists of the following subsystems: (1) signaling data access; (2) signaling data collection and processing; (3) Data processing and application; (4) wan section.

(1) signaling data access section. There are two methods to connect signaling data:

---- High-impedance span access method

---- STP switch internal convergence termination Access Mode

For direct link (F-chain), the high-impedance span method can be used to converge to the centralized monitoring platform through dxc. Because all types of hstp and lstp switches in the current network support internal convergence, you can use the internal convergence termination access mode of the STP switch for the chain or D chain. The STP switch switches the signaling time slots on each E1 to a certain E1, so that the 31 time slots of the E1 carry the signaling data and then output the data to the centralized monitoring system, this function can be implemented through human-machine commands of STP switches. Human-Machine commands allow you to easily select the monitored Signaling Link.

For the signaling data access part, each hstp (lstp) can connect several E1 lines to the centralized monitoring platform. The E1 data is determined based on the construction scale of the monitoring platform. Each hstp (lstp) must be connected to at least four 2 m connections to ensure that at least one pair of link groups can be monitored.

The signaling data access part should support both 64 K and 2 m signaling links.

(2) signaling data collection and processing. Signaling data collection and processing is an important part of the No. 7 signaling centralized monitoring platform, which is generally composed of signaling monitoring equipment, servers and LAN. It should be able to collect, process and store signaling data, and provide statistics on signaling messages, call message records (CDRs), and transaction details records (TDR) for data processing and application) and the signaling message data that meets the matching conditions required for data processing and application.

At the same time, the signaling data collection and processing part should support good scalability in quantity, support expansion in the modular stack mode, and the system does not have a major bottleneck.

(3) Data processing and application. Data processing and application must implement the following functions:

---- Comprehensive data analysis and processing

---- Data Storage

---- Business logic implementation

---- Various applications

The Data Processing Layer mainly includes the processing of signaling messages, CDR/TDR, basic statistics, alarm processing, and system backup. the application layer mainly includes real-time and comprehensive statistics. The real-time part should be able to monitor the network and service quality in real time, and the comprehensive statistical analysis part should be able to fully and reasonably use the data collected by the system.

(4) Wan section. The Wan part connects the data processing applications of signaling data collection and processing, and can be networked in the following ways:

---- DCN

---- DDN

---- X.25

---- Frame Relay

Vrouters are available for network devices. Today, all the signaling data is connected to the same physical location through the transmission network. Then, the signaling data collection and processing part and the Data Processing Application Part are in the same LAN, and the WAN can be omitted.

When the X.25 leased line is used, the transmission rate is 64 KB/s and 2 Mb/s. At the same time, for the sake of security, all X. The 25 link must be placed under a closed user group (gug. To avoid network congestion, permanent virtual circuit (PVC) is used.

The ddnleased line is used, and the data transmission rate is 64 KB/s and 2 Mb/s. Because DDN adopts a point-to-point approach, if the collection devices are large and scattered, the routers on one side of the centralized monitoring platform must have multiple Wide Area Network Ports.

Frame Relay is used, and the data transmission rate is 2 Mb/s.

The DCN method is used, and the 10/100 m should be adaptive.

5 conclusion

In the GSM system, with the rapid development of mobile services and the improvement and promotion of the centralized monitoring system for signaling No. 7, the maintenance methods of telecom operators will be more comprehensive and the maintenance capability will be greatly improved, it will make China's telecom communication system more powerful, stable and sturdy, and provide more powerful support for the development of the national economy. With the continuous improvement of GPRS, VoIP, and WAP monitoring functions, the No. 7 signaling monitoring platform is bound to win a wide market with the continuous development of mobile services.