Abstract: The trend of current development in telecommunications is toward systems which will allow a number of widely disparate traffic streams to share the same channel. Rapid growth demand for mobile communications services make it necessary to use the relevant part of electromagnetic spectrum in the most economic way. The purpose of the research is to investigate the different integrated network models, analyze their performances and study the optimization problems for efficient network planning.

Demand for international communications services is going on in the world. Often, however, the know how needed to meet demand is unavailable locally. Therefore, to link a country’s national communications to the world wide telecommunication network rapidly and cost-effectively, proper planning is required. More and more importance is being attached to the planning of telecommunications networks since networks must be designed so that they can be extended without difficulty. In order to make network investments future proof, capacity must also be designed for unexpectedly high growth rates. For any efficient manner, there is a requirement for systematic planning.

As the operation of telecommunications system involves considerable investment of plants having economic lives of several decades even recovery of equipment and network rearrangements normally involves heavy capital expenditure, hence the development pattern, however flexible, once fixed is expensive and difficult to change. Good network planning is therefore of paramount importance. To meet the rising demand and at the same time fulfill the requirements on transmission and traffic qualities, there is a need to install new equipment in the network. The problem is to make this at a cost as low as possible.

One of the fundamental problem met in the planning procedure, is the determination of the number and locations of new exchanges. This problem is an optimization one, which involves so many variables and is so intricate that it needs to be investigated in detail. Network planning process is a complex multi-task activity involving numerous interrelated and interactive tasks. There are different areas of planning. The problems involving in the planning of mobile and integrated network which are emerging into the presents days communications systems are described below.

The term Personal Communications Services (PCS) encompasses a broad range of services designed to allow people to access the public switched telephone network (PSTN) regardless of their physical location. As a set of telecommunications features supporting terminal personal and service mobility, PCS will combine many engineering "intelligent network" capabilities of the public networks (CCS, ISDN, AIN) with sophisticated wireless access technologies and related radio network mobility control capabilities. Hence, regardless of the many uncertainties, it is resonable to assume that large segments of the population will eventually have "anytime anywhere" wireless access to public switched networks and services. To plan for this situation, many challenging new teletraffic problems will need to be solved.

Personal Communications Services (PCS) will provide terminal mobility using wireless access arrangements, as well as personal mobility. Terminal mobility involves the ability of the users to be in continuous motion whilst accessing and using telecommunications services and the capability of the network to keep track of the user’s terminal. This requires the telecommunications service to be available as the terminal moves within the radio coverage and ideally at all times. Personal mobility is conferred by flexibility of the user’s access to telecommunications service provision which is available at any terminal, fixed or mobile, to meet the user’s requirements. These requirements may then be relocated from terminal to terminal. Personal mobility involves the network capability to locate the user on the basis of unique personal telecommunication identity (i.e. ‘personal’ number) for the purpose of addressing, routing and charging of the user’s calls.

Widespread personal communication services are expected to evolve from isolated islands of mobility that grow in size and number. A key factor in stimulating and sustaining the market demand for these service will be network capabilities that permit call routing, call delivery, acceptable blocking and delay performance, and high level of security to widely roaming users/terminals across multiple services, network operators and service providers. A widely accepted or global set of network standards including teletraffic standards will therefore be essential in the emerging PCS environment.

Possible reference architecture for future mobile services involve integration of mobile and fixed network function and operation. The FPLMS standard being developed in ITU-T and ITU-R will lead to an integrated system to support the complete range of terminal mobility/wireless applications using emerging advances in network intelligence and signaling. The IN (Intelligent Network) will support the database requirements and provide personal mobility and call and service management functions. For some wireless access application, the terminal mobility and terminal location functions may be provided within the specific application (e.g. cellular mobile systems) while for some other applications (like low power wireless) the IN infrastructure in ISDN/PSTN will play a significant role. In either case SS#7 network will be required to support the messaging needs for not only terminal locations and mobility management but also for basic functions as authentication, call set up, call supervision and call hand over for wireless access applications. The possible integration of future mobile networks with the terrestrial network (ISDN/B-ISDN) has implications on the distributed database architecture and sharing of data. These impact on the traffic GOS parameters such as post-selection delay, answer signal delay, call release delay, probability of end-to-end blocking, probability of connection cut-off due to unsuccessful land cellular hand over. Other parameters unique to mobile services (e.g. hand over delay, location registration delay, authentication delay etc.) should be considered in detail. In order to evaluate these GOS parameters, various factors have to be known like characteristics (e.g. mean and variance) of traffic offered to each cell, characteristic of hand over traffic into and out of each of the cells etc. Determining the number of radio channels needed for and acceptable GOS requires not only the consideration of traffic parameters and estimation of signal interference between cells, but also the assessment of factors such as cost/performance trade-off and potential impact on the fixed network (PSTN/ISDN). Traffic characterization in PLMN may differ considerably from those of fixed networks e.g. in high density areas, traffic variation may be quite large due to subscriber’s roaming. Measurement issues and methods for mobile traffic characterization should be studied further. The relationship between resource usage and user inconvenience is an important design issue which impacts traffic engineering and requires further study.

Increasing the capacity of a network by using mosaics of microcells, we will need an overlay of large cells. These will vary from macrocells upto the large satellite cells. In the future when passengers in trains have video displays and audio and data communications facilities, communications with train passengers will introduce intense peak of mobile radio traffic into the network as the train rush along. High concentration of rapidly moving mobile radio teletraffic will be generated by large passenger aircraft. One thing we can be relatively sure of is that the future teletraffic from PCN/PCS will eventually be vast, without the current time-space predictability of non-mobile traffic.

Recent developments in communication networks have led to much interest in system where traffic is widely differing characteristic is integrated together. The range of teletraffic issues that need to be addressed for personal communication services include characterization of traffic demand taking into account the spatial volatility of traffic, impact of database architecture (location and partitioning of database) for user/terminal authentication, location tracking and paging, identification of new grade of service (GOS) parameters to capture user’s perception of service quality and setting of suitable target values based on sound economic and service considerations. Additional traffic related activity is needed to address such areas as traffic demand estimation / forecasting, traffic routing, and network planning and design. Much more work is needed in order to refine our understanding of these issues, to prioritize specific problems, and to solve them. I would like to contribute in the investigation, performance analysis and planning of integrated mobile network. I believe my background knowledge is quite suitable to do research in this area.

Rabindra Shakya
Asian Institute of Technology