Nabiyev N. K.¹, Zhubanazarov D.M.²

¹Cand. of Eng. Sci., The JSC «National Company «Kazakhstan Gharysh Sapary», Kazakhstan

²Master's Degree student, L. N. Gumiliev Eurasian National University, Kazakhstan

The main stages of circuitry design of data transmission systems

Data transmission systems (DTS) widely applied the microprocessor equipment are the typical representative of territorially distributed information computation systems. Such systems provide improvement of automated systems of control, design, office activity and various systems in military area. DTS saturation by microprocessors causes increase of their "intelligence" in technical aspect and sharply expands areas of their use in the flexible automated structures.

The Microprocessor-based Data Transmission Systems (MDTS) represents a basis for creation the local computing systems with the distributed information processing. The last ones are created as a final stage of development of territorially dispersed computers complexes of different types covering small territories (to 10 km) in various buildings, the organizations, the enterprises etc. [1, 2].

At the present time there are two main directions in design process of MDTS. The first is guided by the theory concept of data transmission networks, the second defined by the physical concept of less difficult distributed MDTS. The first direction is characterized by the relation to efficiency and ways of its assessment. Thus, efficiency of MDTS is understood as that positive impact which MDTS has on internal and external indicators of a LAN. The concrete maintenance of MDTS fades into the background; superiority gets a way of an assessment of MDTS contribution in work of a LAN as a whole. The second direction is mainly characterized by the physically measured parameters of efficiency criteria in which users are interested, such as capacity, real time of information transfer, number of stations in a LAN, etc. Such real indicators are usually set in the form of basic data for design and allow defining a main objective of LAN creation. An additional point is that such indicators take into account the nature of interaction of elements, paths in and between stations on the scale of a LAN. In this behalf, physical contents and characteristics of MDTS and a LAN are the principal points.

According to abovesaid, the methods of the analysis and synthesis cover the complicated multilevel system containing thousands of functional knots interfaces, paths of a reception-transmission, the control of a monochannel condition, the management of access to the monochannel etc. Whereas it is quite complicated issue, now therefore it is solved because of multi-stage circuitry design of products.

Figure 1 depicts the scheme displaying the process of circuitry design of MDTS with the general communication channel. This process begins with setting the demanded technical and operational indicators of LAN, MDTS and stations. The right choice of indicators is extremely important, considering that mistakes lead to considerable material, temporary and other expenses in the course of creations and the subsequent operation of system.

At the level of design solutions of a LAN the following indicators have special value: cost index, temporary and sustainable indicators. Function of these indicators is to provide clarity and unambiguity of the formulations describing offered LAN. Therefore, at the first design stage it is possible to carry to cost indexes such, as the given costs of transfer and the information processing, full costs of introduction in operation and ensuring operability of a LAN, costs of MDTS creation and transformation of information in it, etc.

One of the methods of ensuring fault tolerance is the organization of optimum redistribution of resources at refusals in stations and subscriber systems. As assessment of functional degradation of a LAN the percent of reduction of represented resources and information losses owing to indistinct work of MDTS.

For estimating the dynamic properties of LAN such indicators, as time of delivery of information to destination, time of the solution of a task on this subscriber equipment with attraction of resources of other subscriber means, an answer waiting time at transfer of texts, transaction time at selection of a certain record of memory of the local database placed territorially on removal from this subscriber means, etc. are applied [3].

Fig. 1

On the basis of structural model functional and parametrical models of objects are developed. For example, on the most top stratum of model – MDTS stratum – the structural model represents the schedule with temporary indicators t describing interaction of stations A, B, C (fig. 2). In compliance with this structural model, on the same stratum formed the functional model that displays interaction process of elements of model by means of algorithm (fig. 3). Then transformation to the parametrical model displaying key parameters by which it is characterized the stratum at this level of the description of system is made. For the work with MDTS the following indicators of work quality are often used: the territorial dispersion which is expressing in length of connections between stations, number of actively working stations in MDTS, a ratio of stations cost and MDTS equipment as a whole and costs of the terminal subscriber equipment, information transfer time from the sender to the recipient taking into account the set method of service of the monochannel from station, the volume of turn of messages in each station.

Transferring time and volume of messages turn in paths of stations are interconnected and depend on a method of control over access to the monochannel and indicators of hardware means realizing it. It is the main dynamic quality criteria of stratums; it depends on two major factors of dynamics of influence a tractor in MDTS. The number of the conflicts belongs to the first factor in case of application of a method of the competition between stations and a waiting time of receipt of a marker of go-ahead transfer in case of application of the centralized form of government by LAN stations. The number of unserved stations belongs to the second factor owing to a monochannel overload. Thus the increase in transferring time of shots owing to growth of number of the conflicts and the related pauses of expectation or a waiting time of a marker of go-ahead transfer causes increase in number of unserved messages, i.e. eventually – turn lengths.

Fig. 2 Fig. 3

Further process of design is reduced to a choice of the next stratums of station, paths and station elements. On every such stratum, as in the previous case, functional, structural and parametrical models of objects are formed.

The whole process of design is considered as a process of introduction of structure in a certain functional model. On this aspect, two types of structures are considered: virtual and real. The virtual structure is set by means of the description in stratums and layers, and real one is the result of decomposition of virtual structure on real subsystems (schemes). It reflects the made structural decision in each design stage.

Though this technique is considered by authors for decision-making automation in the course of design of the stations equipment, it can be used in software design of stations regarding communication protocols at the top levels of interaction of subscriber systems.

Thus, the rational circuit decision of quite complicated system as MDTS can be received only on the basis of synthesis and the analysis of structural technical solutions and repeated modeling by means of the multilevel stratified model in the direction "from top to down" and vice versa. Recurrence of modeling causes wide using and application of computer facilities in a dialogue mode of the user with models on every stratum. Dialogue is caused by the fact that the majority of technical solutions on stratum borders is accepted on the basis of heuristic reasons, i.e. a creative career.

References:

1. Bertsekas D. Сети передачи данных / Bertsekas D., Gallager R. – пер. с англ. – М.: Мир, 2003. – С. 562. Bertsekas D., Gallager R. Data Networks. – Prentice Hall, 1987. – P. 486.

2. Grigoriev V.А., Lagutenko О.I., Raspaev Y.А. Сети и системы радиодоступа. – М.: Эко-Трендз, 2005. – С. 384.

3. Olifer V.G., Olifer N.A. Основы сетей передачи данных. – Интернет-университет информационных технологий, 2003. – С. 248.