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...
The ersonal radio communication industry has spawned GHz fiequency spectrum, and has provided technological advances that create opportunities or military communications to capitalize on the use o f t R ese higherfiequencies for tactical communications. However, the interests of the civilian personal communication industry have focused upon propayt;?? gath c o n f i p t i o n s that can be considered 'high-ow in which one end is close to the ground (an individual user) and the other end is at a higher elevation and utilizes an antenna su port structure such as a tower or a building, an aircrajf or an orbital satellite. Tactical military communication, on the other hand, usually employs "low-low " path configuraaths between individual soldiers where the antenna tions-;P eights at both ends of each link will be 1.5 meters above the ground or less. In addition, most o the recent propagation research that has been sponsore f' in the I to 3 GHz frequency spectrum has centered on ropagation phenomena in urban settings to sup ort mi P itary operations in urban terrain (MOW) an dp the development of personal communication systems. There is a dearth of empirical propagation data in this region of the fiequency spectrum that is applicable to tactical military operations.The diference in geometry of a "high-low" and a "lowlow" path is rather obvious, but what is not so obvious is the di erence in propagation phenomena, especially fadlow" path in an urban area is usual y characterized by what is called "Rayleigh" ropagation in which there is no direct line-of-sight (LO$ i.e., optical path, and all of the energfiom radio transmitter to receiver is by forward scatter and reflections. A "low-low path between two soldiers is usually via a direct LOS propagation path, but with insuficient terrain clearance to support what is called "Gaussian" propagation. This path is called "Rician. " This paper reviews Rayleigh, Gaussian, and Rician propagation phenomena; describes the diferent factors that are associated with each of these three types of propa ation; and discusses the research and experimental Rician propagation loss and ex ected fading under diflertions.
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