Dissertation of Andrey Hailo

          For performance of the problems laid on a guard service, it is necessary that the information acts in due time. Critical parameters for a guard service are the recognition time of a situation and an arrival time of mobile operative group. The maximal arrival time is 4 minutes, this time should consist both time of the situation estimation and time of decision-making. The variant of the notification with radio stations (portable radio sets) is not comprehensible because of the big intervals of the information transfer about object and because of the given method is not automated. There of there is a necessity for using of the automated system of the information gathering.
          The actuality of the given problem will be, that duly delivery of a trustworthy information to a guard service and on operators boards of items of the centralized guard allows to take measures on prevention of damage drawing to stationary objects, immediate helping at an attack on mobile protected objects more effectively.
          Now the increasing development of connection wireless systems allows to realize the given problem more effectively because modern systems of connection allow to transfer the necessary information during several seconds.
          In the given structure there are problem places which demand for theoretical research, modeling and skilled check. First of all, it is algorithm of protected object access to an area of data transmission. The problem is complicated that for the work of system only one frequency is allocated; hence, for the organization of multistation access probably use only time division of channels. There are three basic algorithms of such access: casual, markered and cyclic interrogation. Now first of them is used, and it results in characteristic losses of information packages; in process of system growth and increasing of protected objects quantity this problem will grow. Thus exactly during the greatest loading when in an operative range of one BS there is the greatest quantity of protected objects in a condition of an operative performance, there will be the greatest probability of the information loss that will lead to an exit of protected objects from under the control of a guard service. The problem is aggravated with a principle of the not guaranteed delivery: the sender has no information about the fact of the delivery datas to the addressee, he operates by a principle «allowed and forgot». Therefore the paramount task stands research and a method choice of access to a radio channel at which the least probability of loss of the information will be provided at required quantity of protection objects in operative range of BS. It is supposed to consider a various methods, and to apply dynamic optimization of their parameters: the basic criterion of optimization is the intensity maximum of transfer of the helpful information.
          The state-of-the-art review of various systems standards of data transmission has been lead, merits and demerits of this or that standard, their opportunity in a binding to the given theme are considered and for research of a service network the standard APCO 25 has been chosen.
          Standard АРСО 25 provides an opportunity of work in any of the frequencies standard ranges used by systems of mobile connection: (138-174, 406-512 or 746-869 MHz). The basic method of plural access to liaison channels is a frequency (FDMA). However the opportunity of plural access with time division of channels (TDMA) is included in the standard.
          The basic purpose of my work is research of two ways of plural access to the data transmission area of researched system of the information gathering, such as: plural access with frequency division of channels (FDMA) and plural access with time division of channels (TDMA).
          Two variants of network researches are possible. In a range of 160 MHz there is one licensed confidence channel. In a range of 450 MHz probably use several channels.
          In system FDMA the allocated general frequencies range is divided on separate stationary frequency channels. Each transmitter or the receiver uses separate frequency.
          The system of connection with TDMA uses division of users on time so that their transceivers could common use one carrying frequency. Such principle of the connection organization is used, for example, in simple duplex radio stations where the button is pressed when the subscriber speaks and is let off, when he listens to the interlocutor.
          As against systems of frequency division, all subscribers of system with TDMA work in the same frequencies range, but thus everyone has time restrictions on access in system.
          Thus all user's devices should be synchronized uniformly with base station, for this purpose on one of base broadcasting channels the uniform time is broadcast. Feature of a way of time division that in comparison with transfer speed in FDMA which is identical on all frequency ranges, in TDMA it increases in so much times how many users share the given range.
          Thus, to define, what way of access to the information transfer area in a researched network is more comprehensible, it is necessary to lead modeling of data transmission with the help of these two ways (FDMA and TDMA) to construct model and to lead its analysis.
          Searches in the Internet have not led to a positive results. It has not been found suitable applications or software packages for such modelling. Software packages for designing a cellular network in a general sense (installation of base stations, radio-frequency planning) have been found, etc.
          As a result of it the decision to lead modeling by own forces in available software packages, for example in such as MatLab (Simulink) was accepted.
          The operational environment allows to formulate problems and to receive decisions in the habitual mathematical form, not resorting to routine programming. Among packages of expansions it is possible to allocate packages for processing signals: Communicational and Signal Processing Toolbo-xes. These packages working in common are intended for the calculations connected with telecommunication systems modelling. Their functions are focused on systems of digital connection, but there are also functions of analog modulation and demodulation. To the possible application domains the modeling of communication of data behaves on the networks of telephones, radio channels (radiotelephones, cellular networks of GSM and other) and various physical environment of telecommunications network. The special place among expansions occupies SIMULINK - a package for modeling and the analysis of dynamic systems.
          In the rest of the work I am going to lead modeling of two ways of access to the data transmission environment, namely FDMA and TDMA.
          Also it will be necessary to lead the analysis, what way is more comprehensible for using in a researched network. As criteria of such analysis act: the maximal number of served objects of one BS, throughput of channels, the minimal losses.
          Result of modeling is such parameters getting:
          - The maximal throughput of liaison channels;
          - The minimal probability of the transferred data losses.

Department: Computer information technologies and automatics

Speciality: Telecommunication systems and networks

Subject of master's work:Research and construction of a network of gathering Information from mobile guarded objects.

Scientist organizer: associate prof., candidate, Popov Vladislav Alexandrovich

Abstract of master`s work "RESEARCH OF THE NETWORK OF GATHERING OF THE INFORMATION FROM MOBILE GUARDED OBJECTS"