The Army Operations warfighting concept includes a need for reliable tactical communications worldwide. A line-of-sight (LOS) propagation reliability working group, convened by the U.S. Army Communications-Electronics Command, has developed a propagation reliability model that relates the reliability of an LOS link to path length, radio frequency, equipment capability, and geophysical and meteorological variables. The geophysical and meteorological variables are described in terms of a climate factor. The importance of climate on the reliability of communications links has been amply demonstrated by experience in Southwest Asia. The propagation reliability model has been incorporated in a new battlefield automated system, the Joint Tactical Area Communications Systems (Provisional) Network Planning Terminal (NPT). The NPT provides the U.S. Army with new capabilities for network planning and management, frequency management, communications engineering, and electronic warfare threat analysis of LOS tactical communications links for deployment anywhere in the world.
As military communications has evolved over the decades, spectrum management technique development has kept pace. A large portion of spectrum management technology involves spectrum planning, which is the process of cataloging the current use of the spectrum and the assignment of new frequencies within that environment to minimize interference while maximizing spectrum reuse. Spectrum planning has received considerable attention in recent years and today there are many state-of-the-art tools available. Another, less known aspect of spectrum management, the identification and resolution of interference, has not developed at a commensurate rate. As the available frequency resource decreases, and demand for that limited resource increases, interference is bound to occur, and the ability to identify and control occurrences of interference on the battlefield will present the next spectrum management challenge. This paper outlines an approach for the identification and resolution of interference events involving softwarebased radios in near-real time using principles and standards found in network management.
A line-of-sight propagation reliability working group, convened by the U.S. Army Communications-Electronics Command, has developed a propagation reliability model. The model includes a climate factor for fading to allow worldwide planning of reliable terrestrial communications links.This paper introduces a new application concept, a monthly climate factor, to meet tactical needs since the probability of fading can vary significantly from month to month. Climate factor estimation is described and illustrated with examples from the Arabian peninsula. The propagation reliability model, including monthly climate factors, has been incorporated in a new battlefield automated radio planning system, the Joint Tactical Area Communications Systems (Provisional) Network Planning Terminal.
The frequency-allotment function bridges the gap between the national and international frequency allocation tables and the actual frequency assignments for various radio networks. The tables of allocation define the permitted type of operation in various portions of the spectrum; assignments specify the specific frequency in use by a link or net. This paper discusses a scheme for determining the way to define the required frequency complement for a nethetwork and how the frequencies should be spread out to allow for optimum use of the spectrum by the radio system. TerminologyFrequency allotment differs from frequency allocation which differs from frequency assignment. Frequency allocation refers to the function(s) permitted in a portion of the spectrum. Frequency assignment refers to the specific frequency permitted on a particular link or for a net. Frequency allocation refers to use of the spectrum for such services as broadcasting, fixed, mobile, radiolocation, radio astronomy, etc. Figure 1 is an extract from a page of the U.S. Table of Frequency Allocation. Frequency assignment specifies the radio frequency (RF) carrier frequency in use with an associated bandwidth. Frequency allotment refers to the set of frequencies available for assignment for a given type of service in a given area.A frequency-allotment capability is a formulated of set rules and guidelines to effectively apportion the frequency resource among competing users to permit maximum reuse. This requires a knowledge of both the assignment rules/ algorithms and equipment characteristics. Current frequency allotments at the various Army locations are not very efficient This work has been sponsored by the Improved Spectrum Efficiency Modeling and Simulation (ISEMS) project of the Space and Terrestrial Communications Directorate (S&TCD) of the Research, Development and Engineering Center (RDEC), U.S. Army Communications-Electronics Command (CECOM).or necessarily supportive of the needs of the systems deployed; i.e., they have not kept up with the newer radios, systems, and deployment concepts.A recent study (Ref 1) commissioned by the U.S. Army Communications-Electronics Command (CECOM) Space and Terrestrial Communications Directorate (S&TCD) looked at the tables of allocations, the types of radios in use by the Army and the other military services, their characteristics, and the uses envisioned. The characteristics information was used to determine representative guardbands between the various equipment types; frequency-distance separation curves were generated based on the equipment characteristics and interference thresholds for each receiver/transmitter combination. These curves are valid for far-field situations, not for close cosite deployments. Worst-case situations were selected for detailed evaluation. For closely located radios (e.g. same mast, masts within 10 meters, etc.), FDR curves are not accurate.Multichannel line-of-sight (LOS) radios were the principal case investigated as they have the worst-case cosite situations and the most s...
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