Tactical military communications

The evolution of Army tactical communications systems, starting with the formation of the Signal Corps in 1856, is outlined. The use of mobile subscriber equipment (MSE), the single channel ground and airborne radio system (SINCGARS), and the maneuver control system (MCS), among others, to support American troops in Operation Desert Storm is described, and a representative sample of signal unit employment is presented. The fundamental goals of near-term efforts at the Army Signal Center to complete the planned Army tactical command and control (ATCCS) architecture, to enhance the integration of the systems composing that architecture, to prepare for and maintain compatibility with developments in the strategic environment, sustaining base, and tactical user community are discussed     

An adaptive propagation prediction program for land mobile radiosystems

This paper describes the development of an adaptive RF propagation prediction program for land mobile radio systems. The program, which allows the user to specify transmitted signal strength, carrier frequency, base station antenna height, and mobile vehicle antenna height also provides the information necessary to determine a level of confidence for its predictions. In lieu of detailed topographical data (which is unavailable for many regions), the program makes use of data files containing the results of received signal strength measurements previously taken within the geographic region of interest at various locations, various carrier frequencies (measurements were taken at 453, 922, 1310, 1430, and 1920 MHz), and various base station antenna heights. This paper concludes by providing examples of results illustrating the performance of the adaptive propagation prediction program, showing that the proposed program yields significant improvement in propagation prediction and level of confidence when compared to currently available tools     

Army Fiber Optic Program: An Update

Modernization of Army tactical communication systems has placed emphasis on meeting new digital data handling requirements. An all digital transmission facility will require new radio systems and substantially improved cable systems which can overcome present length-bandwidth limitations. These new digital systems must have, in addition, superior reliability, freedom from electromagnetic countermeasures, and be highly mobile. These requirements are driving the development of new distributed multiplexed radio systems and an intensive investigation into the utilization of fiber optic cable systems. Fiber optic cables have the required capabilities of: EMI, RFI, and crosstalk immunity, substantially reduced deployment weight and volume, and freedom from electromagnetic pulse effects. Recent developments in fiber technology have significantly reduced the risk associated with the use of fiber cable in a tactical field Army installation. However, there are some problems that need to be resolved before fiber optic systems can be fielded. This paper will discuss Army application areas, components and system development efforts directed toward fielding tactical fiber optic systems.     

Theoretical and experimental investigation of feedforward signal regeneration as a means of combating multipath propagation effects in pilot-based SSB mobile radio systems

A technique is described, feedforward signal regeneration (FFSR), to combat the effects of multipath propagation on VHF and UHF pilot tone single sideband (SSB) mobile radio systems. Unlike feedforward automatic gain control (FFAGC), FFSR suppresses both the random amplitude and phase fluctuations in the received signal. Extensive laboratory and field tests have shown that the operation of SSB at UHF frequencies is a viable proposition for both speech and data communication.     

Spectral properties of signal fading and Doppler spectra distribution in urban mobile communication links

In this work, we continue the analysis of a probabilistic approach and the corresponding stochastic multi‐parametric model of wave propagation, in built‐up areas with randomly distributed buildings. We have concentrated on the spectral properties of signal strength spatial variations and on Doppler spread spectrum distribution of signal power. The analysis is based on a unified stochastic approach of radio wave propagation above the built‐up terrain with applications to mobile communications. We analyze the signal power spectrum of spatial frequencies and the signal power distribution in the Doppler domain for moving vehicles, taking into account a Doppler shift proportional to the vehicle antenna speed relative to the base station. The comparison between the theoretical prediction and experimental data was motivated by the proposed stochastic model and other existing statistical models to verify the signal power distribution in the Doppler domain for various urban environments and terminal heights with respect to building rooftops. New effects of terrain features on signal spectrum are obtained, examined and compared with existing models. Copyright © 2006 John Wiley & Sons, Ltd.     

Computer prediction of service areas for VHF and UHF land mobile radio services

A computer program written to predict the effective service area of a transmitter in a VHF or UHF mobile radio network is described. The computed results enable field strength contours to be determined, and hence provide more useful information than is possible by reference to standard statistical curves. Present manual methods of calculating the attenuation to be expected over transmission paths rely on the laborious extraction of essential ground profile information along the path joining the transmitter to the receiver. This difficulty may be overcome by using a topographical data base in a computerized method of service area prediction. With this scheme each data base entry represents the effective terrain height above sea level within each 0.5-km square. A high-speed computer can access the necessary information from the data base to reconstruct a close approximation of the radio path profile. The reconstructed profile is then processed to calculate the transmission loss. These computations are repeated for numerous points throughout the area and enable field strength contours to be deduced. The propagation model described forms part of a fully automated frequency assignment procedure for the private land mobile radio services in operation in the Directorate of Radio Technology, Home Office, UK.     

UHF propagation prediction for wireless personal communications

Propagation characteristics of radio signals in the UHF band place fundamental limits on the design and performance of wireless personal communications systems, such as cellular mobile radio (CMR), wireless LANs, and personal communication services (PCS). Because the radio link is direct to each subscriber, the prediction of signal characteristics is most important in urban areas where subscriber density is high, and the buildings have a profound influence on the propagation. The paper starts by reviewing the characteristic signal variations observed in CMR systems employing high base station antennas to cover macrocells having radius out to 20 km. Theoretical models incorporating diffraction are shown to explain the observed range dependence and shadow loss statistics. For the low base station antennas envisioned to cover microcells of radius out to 1 km for PCS applications, signal propagation is more strongly dependent on the building environment and on the location of the antennas in relation to the buildings. Various levels of theoretical modeling of this dependence are discussed in conjunction with measurements made in various building environments. Finally, the paper discusses advances in site specific prediction for outdoor and indoor propagation     

The AN/ARC-164 radio: life-cycle-cost savings

The AN/ARC-164, the new standard U.S. Air Force/Army 10-watt UHF radio, has been subjected to an extensive Life-Cycle-Cost Verification Test to determine whether the radio meets its specified reliability and maintainability criteria. This paper deals with the entire spectrum of the ARC-164 LCC Program, with emphasis on up-to-date test data and analysis, and recommendations for structuring future programs.     

A versatile wave propagation model for the VHF/UHF rangeconsidering three-dimensional terrain

A polarimetric wave propagation model for field strength forecasting and coverage prediction in the VHF/UHF frequency range is presented. The model uses a digital terrain data bank and considers multipath propagation. Based on the uniform geometrical theory of diffraction (UTD) and physical optics an approach is described for calculating the propagation effects in natural 3-D terrain, given by topological and morphographical data. The method for field strength forecasting is described and methods for the analysis of the predicted multipath signal are discussed. It is shown how the complex probability density function (PDF) for the receiver field strength and the field strength delay spectrum can be derived. Methods for further evaluation of the transmitting channel characteristics are discussed     

直接序列扩频通信系统研究及仿真

直接序列扩频通信系统因其抗干扰性强、隐蔽性好、易于实现码分多址(CDMA)、抗多径干扰、直扩通信速率高等众多优点,在个人通信网、无线局域网、第三代移动通信、卫星通信以及军事战术通信等领域得到广泛应用.本文以扩频通信理论为基础,用MATLAB工具箱中的Simulink通信仿真模块和MATLAB函数对直接序列扩频通信系统进...     

Propagation and coverage prediction for cellular radio systems

The development of a computerized UHF signal propagation and coverage prediction system for Singapore is described. This system consists of a terrain database, a propagation prediction model, and a subsystem to plot coverage patterns. The predicted results were verified by field strength measurements. The comparison showed that the errors of the prediction for two UHF bands have a standard deviation of less than 10 dB     

Terrestrial mobile communication train measurements in western India

Mobile train radio measurements were conducted in the UHF band in western India with a total distance of 140 km utilizing eight track side base stations in different environments. The observed path losses deduced from signal levels were compared with those deduced from several prediction methods and their standard deviations are discussed. Path loss exponents are derived from signal levels and their variation as a function of distance are also presented. Suitable prediction methods for this region are identified. These studies would be useful for designing future train mobile communication systems in this region, for spectrum management applications and in framing recommendations for the radio communication study group of ITU-R.     

Mobile satellite system fade statistics for shadowing and multipathfrom roadside trees at UHF and L-band

Field tests related to planned mobile satellite systems (MSS) were performed, and results that add to the existing database of propagation measurements at L-band (1.5 GHz) are described. They are considered particularly useful in that propagation effects were studied systematically with repeated and controlled runs pertaining to different path elevation angles, road types, and path geometries defining shadowing and line-of-sight modes. In addition, simultaneous L-band and UHF measurements were performed for the purpose of establishing scaling factors applicable to previous UHF (870 MHz) results. The control of the experimental parameters was made possible by using a helicopter as the source platform and a mobile van which housed the receiver     

Optical Fiber Transmission System Demonstration Over 32 km with Repeaters Data Rate Transparent Up to 2.3 Mbits/s

An initial optical fiber transmission system under development for Army long haul tactical communications is described and evaluated. The system interfaces with the 2.304 Mbit/s data input and output of an Army inventory multiplexer and its orderwire. The system includes transmitter and receiver end terminals, three data rate transparent repeaters, 8 km of graded index optical fiber, plus three optical attenuators and various optical connectors for simulating transmission up to 32 km. Long repeater spacing is achieved using low loss fiber, semiconductor lasers stabilized using optical feedback, and avalanche photodiodes. The system met all of the specified requirements and shows that optical fiber transmission systems have excellent prospects of meeting full military specifications. The versatility of data rate transparent repeaters is achievable even for transmission up to the 64 km distance desired for Army long haul tactical communications.     

Determination of service area for VHF/UHF land mobile and broadcast operations over irregular terrain

In this paper we define the service area of VHF/UHF land mobile and broadcast stations and demonstrate graphical and computer methods to determine and present such areas as a function of known equipment parameters and of a propagation model derived largely from an extensive measurement program over irregular terrain.     

Propagation of Wide-Band Signals at VHF/UHF

The experimental jam-resistant secure voice communications (JRSVC) system developed by M.I.T. Lincoln Laboratory was used to conduct a series of VHF/UHF (225-400 MHz) propagation measurements, representative of a veriety of tactical communications situations, both ground to ground and ground to low-flying aircraft. Results are unusual in two regards: they were made with the receiver in motion, covering many contiguous propagation paths, and the JRSVC system, by frequency-hopping over almost an octave and averaging the results, largely eliminated the effects of frequency-selective (multipath) fading that generally dominate VHF/UHF propagation measurements.     

Empirical formula for propagation loss in land mobile radio services

An empirical formula for propagation loss is derived from Okumura's report in order to put his propagation prediction method to computational use. The propagation loss in an urban area is presented in a simple form: A + B log10R, where A and B are frequency and antenna height functions and R is the distance. The introduced formula is applicable to system designs for UHF and VHF land mobile radio services, with a small formulation error, under the following conditions: frequency range 100-1500 MHz, distance 1-20 km, base station antenna height 30-200 m, and vehicular antenna height 1-10 m.     

Satellite spacing and frequency sharing for communication and broadcast services

Satellite relays complicate the problem of sharing a limited frequency spectrum that is in great demand. This paper reviews the problem and outlines a general approach for efficient use of orbits and spectrum. The protection of received signals, the equipment capabilities, and systems considerations pertinent to the problem are reviewed before systematically examining the principal direct and scatter modes of interference. Conclusions derived include the following. The full potential use of orbits and spectrum for satellite systems can provide enormous capacities greatly exceeding any current proposals, but it requires careful coordination of many system parameters. The use of spectrum for microwave or satellite relays to fixed terminals could evolve to intense full sharing by both types of service without seriously limiting either one or requiring unreasonable accommodation. The satellite down links for area coverage to small terminals (e.g., mobile and broadcast services) can share fully and intensively the spectrum above VHF that is used for terrestrial mobile and broadcast services without seriously limiting the potential of any of the services. Although the greatest potential capacity of the spectrum lies above 16 GHz, for most down-link applications propagation factors make it more attractive to share the spectrum below about 16 GHz much more intensively before making extensive use of the higher frequencies. Providing the satellite down-link spectrum for area coverage to small terminals deserves priority consideration. For this purpose the UHF band is most attractive; the merit of the spectrum rapidly diminishes for higher frequencies.     

Partitioning QoS management for secure tactical wireless ad hoc networks

Addressing quality of service in military wireless ad hoc communication networks involves unique challenges due to imposed tactical requirements and,conditions, such as heterogeneous traffic with stringent-real-time and survivability requirements, mobile wireless nodes in hostile environments, and limited spectrum availability. Encryption adds another layer of complexity because of the partitioning of the network into plain text (unencrypted) and cipher text (encrypted) parts that, by definition, cannot communicate QoS information to one another. A typical communication shelter is composed of unencrypted LANs connected to a packet-encrypted backbone network. This article presents a partitioned QoS approach, focusing on QoS management at the unencrypted LAN that complements QoS management done at the encrypted backbone. Some of the unencrypted LAN QoS techniques being considered for the Warfighter Information Network-Tactical (the future Army tactical backbone network) are outlined.     

Interference and propagation formulas and tables used in the federal communications commission spectrum management task force land mobile frequency assignment model

The computerized frequency assignment program developed by the FCC Spectrum Management Task Force utilizes monitoring van [1] measured occupancy data and models for propagation, interference, and noise. The propagation model was constructed by the Technical Division of the FCC Office of the Chief Engineer from measured FM and television data [2] and National Bureau of Standards measurements in the UHF/VHF range [3]. The co-channel interference model uses commonly accepted signal ratios between desired and interfering signals. The adjacent channel interference model is based on performance characteristics furnished by the major land mobile (LM) equipment manufacturers. The receiver and transmitter intermodulation interference models and the noise model were taken from the Report of the Advisory Committee for the Land Mobile Services [4]. None of the models is considered immutable. All will be continuously updated.