Problem of Retention of Radio Frequency Resource for Military Communication Systems

Military Thought, March, 2001 by G.I. Azarov, O. Yu. PERFILOV, B.G. Telezhniy

Successful performance of combat assignments by forces in the course of armed conflicts is impossible unless they use modern systems of military communication, which are the material basis of command and control. They should rationally combine radio, radio relay, tropospheric and satellite communication equipment and function reliably in a difficult electromagnetic environment (influence of radio interference, both unintentional and jamming, including one induced by enemy RW countermeasures).

The problem is that different economic sectors have been rapidly expanding the use of foreign-made mobile radio communication systems (cell, trunk, pager, etc.), which operate within frequency bands that have been long used by the domestic military communication systems. For this reason, it is particularly urgent to retain the radio frequency resource for military communication systems during implementation of the governmental program envisaging conversion of the radio frequency spectrum. The only correct way to deal with the problem, as we see it, is finding technical and organizational methods of coordinated functioning of different communication systems, which provide for a joint use of the radio frequency resource, rather than introduction of administrative bans and restrictions. The main effort in this context ought to be focused on ensuring electromagnetic compatibility (EMC) of complexes of electronic facilities (EF).

The concept of "radio frequency resource" implies not only electronic facilities' working frequency bands but also that part of space where they function as well as the time when they function. It makes sense, therefore, to split all EF complexes into two main types in accordance with the degree to which they use frequency, space and time resources.

The first one includes complexes comprising relatively few EF that are positioned within a restricted space (technical buildings, motor vehicles, armored facilities, aircraft, etc.) and characterized by some enhanced requirements to EMC of radio facilities. On account of the restricted space, it is only the frequency and time resources that can be used with efficiency to ensure the EMC of such complexes.

The characteristic features of the second type of complexes are a relatively big number of EF and considerable distances between them. They may be represented as a totality of complexes of the first type as placed in restricted territories (communication centers, radio centers, etc.) and forming a system of communications that embraces an entire area under consideration.

This classification proves useful when one confronts concrete EMC problems in EF complexes, because knowing the type of a complex one may identify the main varieties of unintentional interference and methods of combating them.

The essential signs of unintentional interference in complexes of the first type are a wide band of a disturbance that results from non-linear distortion of signals in the input section of a receiver, the formation of a wide spectrum of secondary emissions sent by a transmitter (extraband, noise, etc.), and the presence of a considerable number of narrow-band interferences due to side and intermodulation emissions originating in transmitters and reception channels of receivers. Besides, such complexes are prone to an impact by wide-band unintentional interferences (contact, electrostatic, industrial, etc.), which are created by traffic, electric equipment of moving facilities, and power supply sources, and influence a receiver section not only via a receiving antenna but also via a receiver's low-frequency power-supply, control and commutation circuits.

A distinguishing feature of unintentional interference in complexes of the second type is their narrower band and lower levels, as well as fewer side and intermodulation interferences.

Efforts to provide EMC should follow two main directions. The first one is developing technical solutions helping to improve EMC characteristics of complexes and separate EF and identifying the degree of impact of unintentional interferences. The second one is connected with putting through organizational measures directed at increasing the spacing of assigned working frequencies, dispersing EF, introducing temporary restrictions on parameters of the flow of signals and unintentional interferences, etc.

Upgrading technical characteristics of EF complexes that are responsible for the effectiveness of the use of frequency resource is the principal method of ensuring their electromagnetic compatibility. For this reason, designers should focus their efforts on reduction of non-linear frequency sections of EF, optimization of signal-forming processes in transmitters, enhancement of frequency selectivity and noise immunity in receivers and space selectivity in antenna devices, this in addition to the removal of designing inadequacies in communication centers, technical buildings, and mobile facilities.

There are regularly held international and national assemblies, conferences and symposia devoted to the problem of rational use of the frequency resource. The activity of the International Telecommunication Union, the State Commission on Radio Frequencies and other standing committees and commissions is aimed at ensuring international legal recognition and protection of interests of different states, as well as at shaping state policies vis-a-vis the use of the frequency resource with account taken of EMC of different EF. The main legal documents regulating allocation of frequencies between radio services are Radio Regulations (at the international level) and the Frequency Bands Allocation Table (at the state level).