expert systems in telecommunications: prospects for china

TELEMATICS and

INFORMATICS

Vol. 7, No. 2, pp. 135-144, 1990 Copyright © 1990 Pergamon Press plc. Printed in the USA 0736-5853/90 $3.00 + .00

EXPERT SYSTEMS IN TELECOMMUNICATIONS: PROSPECTS FOR CHINA

Jianshi Wu Jay Liebowitz

Abstract- Expert Systems (ES) provide the possibility for improving the quality of telecommunications management. Considering the current telecommunications environment in China and its future development, this article discusses possible ES applications in telecommunications management in China.

I N T R O D U C T I O N

With the continued development in computer science, Expert Systems (ES) are receiving much attention in research, management and applications. An ES is a computer program that uses human expertise and knowledge to solve problems in a specific domain. Unlike conventional computer programs, ES can use incomplete data to solve ill-defined problems, answer relative questions, and explain the reasoning process (Kivan, 1986).

Although ES originate from Artificial Intelligence (AI), today's ES are much different from their progenitor. The goal of ES is to solve difficult problems in a human-like manner within a well-defined task. Today, many ES have been successfully used in some tightly defined areas for problem solving, such as switching systems fault diagnosis.

Components of expert systems

An expert system consists of several components that work together to solve the problems. Although there are different classifications for the components and definitions for their functions, generally the components of ES, can be divided into three parts: (1) knowledge base; (2) inference engine; and (3) dialogue structure.

Knowledge base. The knowledge base is a component that stores the knowledge from domain experts, such as facts and rules of thumb. According to Duda (1981): the power of expert systems lies in the specific knowledge, with potentially the most powerful systems being the ones containing the most knowledge. This means the knowledge base is a very important part of expert systems.

The knowledge engineer acquires the domain knowledge from the expert and makes it available on the computer. There are two ways commonly used for knowledge repre-

Jianshi Wu was a visiting Chinese scholar at George Washington University and can be contacted at 614 1 lth Street, Menomie, WI 54751.

Jay Liebowitz is an Associate Professor of the Department of Management Science, George Washington University, Washington, DC 20052.

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136 Jianshi Wu and Jay Liebowitz

sentation in ES. One is a production rule representation (or ruled-based representation), the other is a frame representation (frame-based representation) (Keim, 1986; Liebo- witz, 1988). In the production rule representation, the knowledge is represented in rules which take the IF (condition) THEN (consequent) form. To infer a conclusion, the ES checks the conditions of rules, when all conditions of a rule are met, the consequent will be reached by the rule. This representation is suitable for the knowledge given in the form of rules. By changing rules, the knowledge in the knowledge base can be adjusted. To deal with the data which involve some uncertainty, there are several ways for handling uncertainty, such as the Bayesian Approach, Belief Functions, Dempster-Shafer theory of evidence, and fuzzy logic (Liebowitz, 1988).

Another popular approach for knowledge representation is the frame-based representation. A frame is a description of the objects or situations which it deals with, including slots filled with objects, sets of rules and attached procedures (Keim, 1986). It is useful for declarative knowledge.

Inference engine. An inference engine functions to make logical inferences. The major inferencing methods are: forward chaining (data driven), backward chaining (goal driven), and forward and backward chaining combined.

Forward chaining, with no initial goal, starts with a subset of evidence and proceeds to invoke the production rules in a forward direction, and continues until no further rules can be used (Weiss, 1984).

Backward chaining, unlike forward chaining which starts from facts, starts with goals and checks the rules whose consequents are related to the goal to find which rules are applicable. Forward and backward chaining combined examines rules in both forward and backward ways. This method can raise search efficiency and reduce the response time.

Dialogue structure. The dialogue structure works as an interface between the user and ES. It not only makes the user and ES understand each other, but also allows the user to ask questions about the solution and explain the reasoning process.

BENEFITS OF EXPERT SYSTEMS

ES have various advantages that can be classified in the following ways:

1. Potential cost cutting and quality upgrading; 2. Knowledge preservation; 3. Professional training.

Cost cutting and quality improvement

The cost of telecommunication services has a great influence on the productivity of telecommunication enterprises. It is an important factor that greatly affects the development of these enterprises.

Factors that influence telecommunication costs will be either objective or subjective in nature. Objective factors are those that cannot easily be influenced by the managers of enterprises, such as traffic volume, natural circumstances, the technical level of the equipment, etc. Subjective factors are the ones that can be affected by human activity, such as enterprise's management, staff quality, and their sense of responsibility.

The subjective factors will have more and more influence on telecommunication

Prospects for China 137

costs. With the more investment and higher technical level for telecommunication systems, the telecommunications network becomes more complex and greater in value than before. To reduce the costs of telecommunications, one of the critical ways is to increase the operation rate of telecommunication systems and rationally use the equipment, which are largely dependent upon the telecommunications management level. In other words, the cost of telecommunications is directly affected by the quality of management. According to a survey for telecommunication enterprises in China (Min- istry of Posts and Telecommunications, 1988), the difference of average telecommunication costs among the enterprises which have similar objective environments can reach as high as 30%. It is believed that there is no reason except the poor management of some enterprises to explain this high difference.

Using ES will be helpful in aiding management in making more informed and better decisions. Higher quality in management can greatly reduce the cost of telecommunications. Although this reduction is hard to estimate, according to Carl Klahr (1985), the cost for long distance circuit facilities in many big American companies can be reduced by as much as 20% by employing proper economic optimization method and telecommunication technology for the selection, combination, and operation of circuits.

The ES has the nonhuman advantage of never feeling fatigue no matter how long it works. It can work at the same high performance level 24 hours-a-day. It is not influenced by time pressure, emotions, etc. This will be helpful for cost reduction and the improving of quality.

Knowledge preservation

Knowledge engineering involves acquiring domain knowledge from the expert to estab- lish the knowledge base for ES. This knowledge transformation between expert and engineer can preserve a lot of valuable knowledge. This knowledge, gained by the general acknowledged expert from many years of doing various tasks and shaped from refining, is the essence of domain knowledge.

There are several advantages for knowledge preservation. They are" keeping expertise from being lost, making the expertise systematized, and knowledge dissemination.

A tool for professional training

The aim of professional training is not only to help novices learn basic skills for their work, but also to help the current staff for their knowledge renewal and deepening. ES can give some assistance for such training. Using ES as a tool of professional training, one of the obvious advantages is that an ES can easily adjust the training program. Unlike the ordinary computer training software, some ES can find the specific weaknesses and advantages of the trainee to adjust the training program to deal with these weaknesses. This is sometimes called intelligent tutoring systems. By using ES, which can simulate the complex practical environment, we can provide the trainee with an environment which is similar to the practical work. This is helpful in raising the training level and reducing the training cost.

At the present time in China, most professional training is largely limited to theoreti- cal study. Since it is affected by the trainer's training skills and equipment, the training often cannot meet the requirements of practical work. The ES brings the possibility to improve it.


APPLICATIONS OF ES IN TELECOMMUNICATIONS

ES have a broad prospect for application in telecommunications. The application can be divided into two parts, i.e., the hardware and software of telecommunications. The hardware include terminal equipment, transmission equipment, and switching equipment. The software means the managerial regulation, instruction, control message, etc., which are necessary to make telecommunication systems operate smoothly. These conditions assure that each part works.

Hardware

The aim of ES applications in hardware is to prolong the useful life of the qualified equipment, assure that the equipment can work as required, reduce the faults and the mean time to repair, and ensure the maintenance quality. ES can be used for failure analysis, trouble shooting, and maintenance for equipment. It also can be used to predict the coming failure or give some suggestions, by analyzing unusual symptoms of equipment behavior.

Software

Unlike hardware, in the software's application, the aim of ES is in enhancing efficiency of equipment. At the present time, ES is being used in traffic management, route selecting, network control and monitoring, and planning. In traffic management, ES can be used to monitor and control traffic of the network by data collection and analysis. Since, in the telecommunications network, the traffic is random in nature and the capacity of network is fixed, they may cause the network to overload, especially the regional networks. An ES in traffic management can be used by adjusting the volume and selecting reasonable routes. An ES might also be used to approach nationwide network efficiency in network resource utilization because of the large amount of extra capacity in it. This can reduce the network congestion, transmit more messages at a high standard. In network planning and management, ES can monitor the network's performance, plan new routing strategy, or expand network capacity on the basis of historical data and performance trend (Liebowitz, 1988; Stach, 1985).

TELECOMMUNICATIONS ENVIRONMENT IN CHINA

The first appearance of telecommunications service in China was in 1871. At that time the Denmark Telegraph Company set up a telegraph line to connect Shanghai to Naga- saki (Japan). Six years later, 1877, the Chinese Qing Government established the first domestic telegraph line in China. After more than 100 years of development, the total number of telephones is over 11 million (Zhou, 1990). The telephone network reaches to every county and over 95.1% of small towns and 44.8% of villages (China Statistics Almanac, 1988). The telecommunications services include telephone, telegraph, telex, facsimile, cellular telephone, and data services, etc. The transmission systems include open wires, coaxial cable, 4380 channel medium-sized concentric cable, optical fiber systems, digital transmission systems, 7800 channel microwave carrier systems, satellite transmission systems, etc. (Chinese Academy of Social Sciences, 1989).

In China, major telecommunications systems can be classified into two areas, and the major telecommunications services can be divided into four categories, according to the communication range and customer.

There are two kinds of telecommunication systems: Private telecommunications sys-


tem and public telecommunications system. A private telecommunications system is a telecommunications system which is set up for special needs and is limited to a closed group of users. Those systems, that are state-owned, include railway communication systems, water conservancy and electric power telecommunications systems, radio and television communication systems, public security communication systems and military communication systems, etc.

A public telecommunications system is a system that meets the needs of users of different categories (private, professional, and general public). These systems are mainly state-owned, some are collectively owned or privately owned. The Ministry of Post and Telecommunication (MPT) is in charge of the public telecommunications. This article only deals with public telecommunications.

The public telecommunication system can be divided as international communications, long-distance communications (domestic), local communications, and rural communications, which is the communication in rural areas outside of county town (see Fig. 1 for administrative division [New World Press, 1985]). Usually, this communication system is collectively owned.

Telecommunications network and structure

Today in China, the telecommunications network structure is hierarchical, centralized in the Beijing network, which has four levels in the hierarchy (see Fig. 2). According to the political, economic, and administrative divisions, China is divided into six telecommunications regions, each is subdivided into provincial areas, which is similar to the

CENTRAL PEOPLE'S GOVERNMENT

MUNICIPALITIES DIRECTLY UNDER

CENTRAL GOVERNMENT(3)

AUTONOMOUS REGIONS(5)

I PROVINCES ( 22 )

CITIES DIRECTLY UNDER PROVINCIAL

GOVERNMENT

DISTRICTS I

AUTONOMOUS PREFECTURES I

ADMINISTRATIVE ][ UNITS DIRECTLY II

UNDER PROVINCIAL H JURISDICTION

I I I CITIES COUNTIES AUTONOMOUS COUNTIES ~ TOWNSHIP ~

Figure 1. Administration division of the People's Republic of China.


- - Final route - - Direct route

8eiling

Nodes of Class 1 (Regional centers)

Nodes of Class 2 (Provincial centers)

Nodes of Class 3 (District centers)

Nodes of Class 4 (County centers)

Figure 2. Telecommunications network structure.

states in the United States. These are then further subdivided into districts or prefectures and each district or prefecture is divided into counties. There are 10 nodes of class 1 in this network, which includes 6 regional centers, 4 auxiliary regional centers; 21 nodes of class 2, which are the provincial centers (not including Hainan, which is a newly established province, and Taiwan); about 150 nodes of class 3, which are the district centers; and over 2000 nodes of class 4, which are the toll centers usually situated at county towns. The basic structure of the telecommunications network is a compromise between mesh and star configurations. Among the regional centers, they are connected in a mesh network, and Beijing has direct routes to all the provincial centers. The centers below class 1 are connected in a star network and according to the political and economic needs set up the direct routes between different centers. In fact, according to the 1985 statistics, the total number of direct routes among the 30 nodes of class 1 and 2 was 62% of the total number of circuits of the mesh network (Shong, 1989).

Telecommunications management systems

The current telecommunications management systems are established by taking into account the telecommunications regulation and network structure and the special conditions in China, especially for long-distance telecommunications (Wang, 1983).


Because of the different characteristics among the different kinds of communications, the management methods are different. For the local telecommunications, since it is limited in a small area, it is managed by the local telecommunications institution. Rural telecommunications is managed by the owner, but the local telecommunications institution provides technical assistance. For long-distance telecommunications, because of its cooperative operation characteristic, the management is more complex, and the basic regulation, "centralized direction, decentralized management," is used.

To reach the goal of centralized direction, the telecommunications directive system was established to monitor the telecommunications network, adjust the network according to the traffic pattern, organize and carry out important telecommunications tasks, and handle the problems in telecommunications.

There are two reasons to set up the telecommunications directive systems. They are:

1. Long-distance telecommunications is a cooperative work, which needs all the relative enterprises and departments to work together. Because there are no administrative leadership among these enterprises and departments, the problems in telecommunications can not be handled by management normally.

2. One of the important factors of telecommunications is that the telecommunication systems have to operate 24 hours-a-day. But the administrative personnel only work during office hours. This is not suitable for telecommunications management.

For these reasons, the telecommunications directive system was set up to deal with these problems.

The telecommunication system consists of two parts. One is to set up a control office in ministerial and provincial telecommunications institutions, for day-to-day opera- tions. The other is to appoint professional leading centers at different levels for circuit management.

The control offices at the ministerial or provincial institution, which represent the MPT or provincial institution, is in charge of daily management and control, such as handling the problem in telecommunications, monitoring the network performance, and adjusting circuits according to the traffic volume. The control office is the professional leader in telecommunications. It can direct any subordinate institutions irrespec- tive of an administrative relationship.

The professional leading center, which is a node of the network in different levels, has leadership in telecommunications circuits management. For every two centers in a circuit, there is one professional leading center. The professional leading center takes charge of circuit management, operation and maintenance, monitors the circuit, and coordinates the network operation.

The long-distance telecommunications network planning, building, expansion, adjusting and management, and different equipment are managed by different institutions. The equipment, at or between nodes of class 2 or above, and the equipment for international communication, are managed by MPT.

Evaluation for current telecommunications organization and management

The current telecommunications network was established more than 20 years ago. It will exist as a basic network structure for a certain period. The relevant telecommunications management system has been used for about 10 years. From the results of application, the telecommunication system cannot yet meet the need of economic and social


development. According to the 1988 statistics, in 1988, the telephone density was 0.75 per 100 and the local call connection rate was 63 %.

The telecommunication facilities are in short supply, the network structures are un- reasonable and the management needs to be modernized. For example, the current network has the less alternative route, too many links for a call, and network configura- tion and capacity for expansion is not conducive to economic development. For the current management system, there also exist some drawbacks for the new telecommunications services, especially in network operation, circuit management and control, maintenance, network planning, and design.

There are some objective factors that affect the telecommunications management system improvement. This is because the territory is large and there is a big difference in the economic development and the telecommunication service level. Some towns have Stored-Program Control (SPC) Exchanges and International Direct Dial service, while poor areas do not even have a telephone. These factors make it difficult to suit the practical situation.

Future applications of ES in telecommunications in China

According to the plan of telecommunications development in China, by the year 2000, the total number of telephones will reach more than 39.6 million and the telephone network throughout the county will be automatic. The SPC switching equipment, the optical fiber, digital microwave links, and the satellite links will be progressively introduced in the telecommunications network. The network will be digitized. During the Seventh Five-Year Plan period (1986-1990), 3 million telephones will be installed, in areas with high economic growth such as Yangtze River Delta, Zhujiang Delta, and in the Beijing-Tianjing-Tangshan area. The digital switching systems and the digital transmission systems will be progressively used in the telecommunications network to achieve the digital conversion of the telecommunications network and set up Integrated Digital Network (IDN), then toward Integrated Services Digital Network (ISDN). For the general areas, although the digital conversion is a bit slower than the former, the coexisting of digital and analog systems network will be accomplished (Ge and Zao, 1986; Chinese Academy of Social Sciences, 1989).

Today, the digital conversion of telecommunications networks has already begun. In many large cities, the digital switches have been introduced (such as in Beijing, the last electromechanical switching in local network was put into use in 1987. Since that time, the newly installed switching equipment are mainly digital switching systems).

Because of the progressive introduction of digital equipment, there are new requirements for the network structure, management systems, network planning, equipment maintenance, etc. To suit the new requirement, some changes in these aspects have to be made. These also bring some possibility for ES application.

There are several ways for possible application of ES in telecommunications, such as training, equipment maintenance, and network management.

Training. Training is a learning process for the technicians. Since the telecommunications equipment becomes more and more complex, the training also becomes more important. The more complex the equipment, the more integrated functions are needed for operation and maintenance. The technician will have to be more knowledgeable and be more skillful than ever before. Take switching systems as an example. The electronic switch has fewer faults than the electromechanical switch, but trouble influence is greater than the latter (Sun, 1984). If the technicians get good training, there will


probably be fewer mistakes for operation or mishandling of problem fixing, and the breakdown will occur less often.

ES have some clear advantages in this area. For example, today, China has imported several SPC switches. There is a possibility for system failure. This means the whole system is paralyzed, because the stoppage is so serious that jeopardizes the whole communication, and the technician will have to fix it as soon as possible. Such problem solving is an important part of training. In fact, today there are only two ways for this kind of training. One is to let the technician perform simulated problem solving practice on the SPC switch before it begins to be used (there is only a limited time); the other way is to use the model equipment for problem solving practice (Wen, 1986). This is not economic. If we can use ES as a training tool, it could simulate the breakdown in many ways.

Network control In the current hierarchical network structure, the nodes of class 1 and 2 are the points in which the major traffic is carried. According to the telecommunications development plan, during 1990s, several hundred thousand lines of local digital switches and tens of thousands of lines of long-distance digital switching equipment will be installed in these points. These provide the condition for a digital switching network, using high-rank centers as a basis, giving full play to the digital switching equipment in these centers. The nonhierarchical digital network can be set up, which will bring the high quality telecommunication services, possible cost reduction, and greater reliability.

Traffic varies randomly in nature and it is affected by the time, economic, political, weather factors, or natural disasters. It changes so drastically that in the normal work- day the variation between the busy hour and the hour with less traffic can exceed 100 • 1 (Freeman, 1980). Since the capacity of the network is fixed, if we want to improve the transmission efficiency of the network, we should select the proper route according to the traffic volume. In the current hierarchical network, because of the strict regulation for route selection, the network flexibility is poor. The utilization ratio of the network is low. In the nonhierarchical network, since there is no classification for network centers, there are more routes for selection. The flexibility and reliability of the network are improved. But the management becomes more complex.

ES can be used for route selection for this network. It can choose the qualified and economic route for transmission depending on the network operation status, reducing the telecommunication costs, and improving the utilization of network. Compared with traditional routing methods, the ES can take more of available information into account, such as information on cpu, queue lengths, link occupancy and so on. These information are regularly sent to the ES, which use these data to choose the proper route and maintain the network efficiently (Stach, 1985).

Equipment maintenance. The function of maintenance is to keep telecommunications equipment in good condition. Equipment maintenance is an important part of telecommunications management. The quality of equipment maintenance affects not only the quality of communication, but also the communication costs.

In China, there are three kinds of equipment maintenance in use. They are: corrective maintenance, fixed interval preventive maintenance (FIPM) and control preventive maintenance (CPM). The first two methods are the major methods currently used for equipment maintenance. Since corrective maintenance is to repair the equipment after it breaks down, the technicians often lack preparation for the repair. Today, it is hard to


ensure the maintenance quality and the time for repair. FIPM, as a kind of preventive maintenance, can avoid some disadvantage of corrective maintenance.

ES have some advantage to this effect. They can collect and analyze data from the monitoring system, which is very tedious, and forecast the possible fault and give suggestions for maintenance. For instance, in the local cable maintenance, ES can analyze the detail data from monitoring systems, tracking maintenance records and maintenance trends to forecast or locate trouble spots in local loops and derive rehabili- tation decision. At the same time, it also can provide evidence from databases that support its conclusion.

CONCLUSIONS

Although ES are a relatively new technology, there have been many applications of expert systems, such as in physical detection, VLSI design, and program syntactic errors debugging, etc. ES will play an important role in telecommunications in China. Some practical ES applications in telecommunications already exist in the United States. Perhaps some day, ES will become an indispensable part of telecommunications worldwide.

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