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Military Communications Conference, 1990. MILCOM '90, Conference Record, A New Era. 1990 IEEE

Date Sept. 30 1990-Oct. 3 1990

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Displaying Results 1 - 25 of 245
  • MILCOM 90. A New Era. 1990 IEEE Military Communications Conference. Conference Record (Cat. No.90CH2831-6)

    Publication Year: 1990
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    Freely Available from IEEE
  • Architecture selection for deployable local area networks

    Publication Year: 1990 , Page(s): 952 - 955 vol.3
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    Considerations for the selection of deployable local area networks (LANs) for use in a tactical environment are discussed. These considerations include the LAN components. LAN standards, and LAN performance issues. Recommendations for deployed users are presented, covering standards, future growth, fiber optics, topology and protocols, and the need for designing the system `smart' from the beginning View full abstract»

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  • On TCM schemes transparent to constant phase and frequency shifts

    Publication Year: 1990 , Page(s): 384 - 388 vol.1
    Cited by:  Papers (3)  |  Patents (1)
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    The problem of digital transmission over a channel with phase ambiguity generated by a constant phase shift or (Doppler) frequency shift is considered. To remove this phase ambiguity differential encoding/decoding techniques are used in systems with combined modulation and coding, provided that the transmitted sequence is transparent to the phase rotations of the signal space. Necessary and sufficient conditions for a trellis-coded modulation (TCM) scheme to be fully transparent rotationally invariant are derived. Procedures for the design of fully transparent phase-invariant trellis codes (PIC), Doppler-invariant trellis codes (DIC), and phase/Doppler-invariant trellis codes (PDIC) are proposed. Examples are given to clarify the design procedures View full abstract»

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  • Adaptive data compression for VLF communication system

    Publication Year: 1990 , Page(s): 1030 - 1035 vol.3
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    A proposed data compression method for text messages transmitted through the US Navy's fixed submarine broadcast system (FSBS). (a VLF/LF communication system) is discussed. The current and proposed FSBS), (a VLF/LF communication system) is discussed. The current and proposed FSBS systems, data compression methods in general, compression results on the FSBS, determination of a figure of merit for error analysis forward error correction (FEC) code requirements, preamble requirements, and system analysis results are described. After determining the overhead requirements, it is concluded that the arithmetic coding adaptive data compression technique can provide a substantial increase in throughput for the FSBS View full abstract»

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  • Interference suppression using a SAW-based adaptive filter

    Publication Year: 1990 , Page(s): 970 - 974 vol.3
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    The structure and performance of a transversal filter interference suppressor that has been constructed using a surface acoustic wave (SAW) delay line are described. The delay line operates at a center frequency of 300 MHz and has eight equally spaced taps with an intertap delay of 150 ns. In the programmable mode, the tap weights are externally controllable, and in the adaptive mode, the tap weights are adjusted using the Widrow-Hoff least-mean-squared algorithm. Experimental results are provided that illustrate the performance of the filter ill both the adaptive and programmable modes. Filter responses obtained in the adaptive mode are shown, along with spectra demonstrating the corresponding interference suppression. Bit-error-rate performance results for a single-tone jammer interfering with a direct sequence spread spectrum signal are presented View full abstract»

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  • Practical applications of TCM

    Publication Year: 1990 , Page(s): 380 - 383 vol.1
    Cited by:  Patents (1)
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    The first VLSI implementation of a decoder for multiple-signal (pragmatic) trellis-coded modulation (TCM) is described. Integrated on the same device is an encoder and a decoder for a variable rate binary code. The IC discussed is a 64-state rate 2/3 or 3/4 (used in conjunction with 8 and 16 PSK modulation) TCM decoder. The decoder is also accompanied by a K=7 trellis encoder. Integrated on the TCM decoder is a variable-rate Viterbi decoder (rates 1/2, 3/4, 7/8, 1/3). The chip has been manufactured and tested. The performance in rate 2/3 8 PSK and rate 3/4 16 PSK is shown graphically. Included in each figure is the uncoded performance in addition to the simulated and measured data of the chip. The performance of the chip in the rest of the models is shown. The die size is 320 mils on a side. The device contains 17800 transistors and was fabricated in a state-of-the art 1.0 μm process. The device has attained clock speeds above 30 MHz under nominal conditions. The power consumption at 10 Mbit/s is less than 0.75 W View full abstract»

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  • Trellis coded spread-spectrum for fading channels

    Publication Year: 1990 , Page(s): 389 - 393 vol.1
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    A direct-sequence spread-spectrum (DS/SS) communication system that uses a form of trellis coding is considered. In this system, the trellis code is used to select the signature sequence which is transmitted. This system is analyzed for a channel model which includes the effects of multiple-access interference, Gaussian noise, and Rician fading. Analytic performance results are reported for several systems in the form of bit error rate (BER). These results are shown to compare favorably with uncoded systems over a aide range of fading channels. The tradeoff is a modest increase in system complexity. The trellis coded system is shown to offer performance improvements over the uncoded system for a wide range of channels. The techniques presented can be adapted to the case of random signature sequences, but the results for a deterministic signal constellation are presented View full abstract»

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  • STU III operation over 2.4 kbps links

    Publication Year: 1990 , Page(s): 1043 - 1043 vol.3
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    The STU III phones are designed to work over public switched telephone networks and not over a digital link, such as a satellite 2.4-kb/s data link. Two interfaces, the STel 9610 and 9620, which enable two STU III phones to operate over synchronous 2.4 kb/s channels, are described. The STel 9610 STU III digital link interface unit provides an interface to the STU III phone that functions like a central office or PBX interface. It provides loop current, dial tone, ring back, busy signals, and can detect and process dual-tone multifrequency (DTMF) signals. The STel 9620 STU III Telco gateway interface is treated as a normal phone by the public switched network. The applications of these products are discussed View full abstract»

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  • 35-GHz monolithic GaAs FET power amplifiers

    Publication Year: 1990 , Page(s): 483 - 485 vol.1
    Cited by:  Papers (3)
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    A state-of-the-art 35-GHz monolithic GaAs power amplifier, based on metal semiconductor field-effect transistor (MESFET) technology, is developed for millimeter-wave communications and seeker applications. Both single-ended and balanced amplifier configurations, with on-chip DC-block and bias networks, are designed and evaluated. A cascaded four-stage amplifier exhibited 14.6 dB of linear gain and 300 mW of saturated output power at 35 GHz. These MMIC chips are very flexible and can easily be combined/cascaded to achieve even higher gains and greater output power using low-loss off-chip power combiner/dividers. These amplifiers are suitable for future military millimeter-wave systems applications View full abstract»

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  • Constrained total least squares applied to superresolution array processing

    Publication Year: 1990 , Page(s): 1129 - 1132 vol.3
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    The constrained total least squares (CTLS) method, a regularization technique for solving an overdetermined system of linear equations whose coefficients have been perturbed by noise, is described. The CTLS technique can be used to estimate the direction of arrival of planar wavefronts impinging on a uniform array. Simulation results are presented that show that the accuracy and resolution of the CTLS method, when applied to real or simulated data, are equal or superior to those of other techniques View full abstract»

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  • Some measured properties of the ionosphere reflection channel at high frequencies

    Publication Year: 1990 , Page(s): 1209 - 1214 vol.3
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    An HF sounder capable of continuous wave (CW) operation at 800 equally spaced discrete frequencies from 5 to 15 MHz, the hardware of which also allows ranging measurements to be performed, is described. Ranging data that possess periodic spikes which can be used to determine the propagation delay with resolution of up to 10 μs are presented. Based on these data, the dispersive bandwidth is estimated. In some cases the data clearly show the existence of multiple propagation modes. In CW operation the complex channel transfer function of up to six different frequencies was measured, from which a variety of statistics helpful to characterize the channel determined. Some cases are presented. The measured channel characteristics are discussed View full abstract»

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  • An investigation of the meteor channel for adaptive communication systems

    Publication Year: 1990 , Page(s): 873 - 877 vol.2
    Cited by:  Papers (2)
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    High resolution measurements have been carried out to characterize the time spread properties of overdense meteor trails. A number of other parameters of interest for adaptive communication systems have been examined for both underdense and overdense trails. It has been found that the time spread in the overdense trails is not severe for data rates up to 250-500 kbit/s. For the underdense trails, the exponential decay constant shows great variations, and a great number of the trails have significant risetime View full abstract»

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  • Acquisition of timing and Doppler-shift in a direct-sequence spread spectrum system

    Publication Year: 1990 , Page(s): 1285 - 1289 vol.3
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    A model for acquisition of a spread-spectrum signal distorted by Doppler shifts is discussed. A joint acquisition of both the time delay and the distorting Doppler velocity, modeled by a Markov chain, is described. The received signal is assumed to undergo a compression/expansion as a function of time. It is shown that the simultaneous presence of the unknown Doppler shift and timing necessitates a modification of conventional serial acquisition strategies. A two-dwell system, using a short-duration correlation to acquire the timing information, with a subsequent longer correlation to acquire the Doppler velocity, is proposed. It is assumed that the system recovers from false alarms, and hence the performance of the system is given by the mean and variance of the synchronization time. Two systems of linear equations that can be solved for the mean and variance are developed. The large sparse matrices are solved numerically. As an example, the performance of such a system for a spread-spectrum signal having a period of 15 chips, a chip duration of tc=10-4 s, and operating over a range of 0.0 to 10.0 dB signal-to-noise ratio with v/c equal to 0.0024 is analyzed View full abstract»

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  • An evaluation of the Gaussian approximation technique applied to the multiple input signal case of an ideal hard-limiter

    Publication Year: 1990 , Page(s): 579 - 584 vol.2
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    The accuracy of the Gaussian approximation technique (GAT) is evaluated. The GAT involves representing the signal ensemble input into a nonlinear device, such as a hard limiter, as a Gaussian process. The results demonstrate that if the number of signals is greater than five and the power of each of the Gaussian approximated input signals contain less than 20% of the total power, then the results obtained by approximating the input signal ensemble by a Gaussian process will accurately represent actual system performance. It is also shown that the GAT is quite accurate as long as the ratio of Gaussian approximated input signal power to total signal power is no more than 50% View full abstract»

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  • On the weight distributions of m-sequences in AWGN

    Publication Year: 1990 , Page(s): 81 - 85 vol.1
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    An analysis and simulation is performed on the effect of additive white Gaussian noise (AWGN) on the weight distribution of the cross-correlation function between two maximal-length sequences (m-sequences) for direct-sequence spread-spectrum modulation, with specific examples cited for the m-sequences of linear span eight. The decimation, cross-correlation, and weight distribution properties of m-sequences are examined and integrated to characterize these functions in an efficient manner, requiring only O(N) functions instead of O(N2) to describe all possible weight distributions achievable for N m-sequences of a given length. Mean-squared difference (MSD) and skewness criteria to describe the degradation of weight distributions in noise are presented. The results of these criteria are summarized in weight distribution merge graphs, indicating that weight distributions in AWGN approach a Gaussian distribution at or above -15-dB signal-to-noise ratios View full abstract»

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  • Programmable demultiplexer/demodulator processor

    Publication Year: 1990 , Page(s): 230 - 234 vol.1
    Cited by:  Papers (1)  |  Patents (26)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    Low to medium bit rate digital transmission formats are increasingly being used for satellite communications to reduce the size and cost of earth stations. A combined demultiplexer and demodulator using digital signal processing is described which uses frequency domain filtering to separate the signals and a shared structure for the demodulation process. A special-purpose, high-speed fast Fourier transform (FFT) processor is designed which operates on a 20-MHz bandwidth that contains carriers ranging in bit rate from approximately 1.5 to 11.3 Mb/s. An interpolating filter is used between the demultiplexer and the demodulator to provide the two samples per symbol required for the demodulation process. The major components of the demultiplexer/demodulator are described. The implementation concentrated on designs using low-power complementary metal-oxide semiconductor (CMOS) circuitry. In addition, a testbed was designed and fabricated to provide the multicarrier inputs needed to demonstrates system capability View full abstract»

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  • Survivable planar internetwork (SPIN) for multimedia communications

    Publication Year: 1990 , Page(s): 311 - 317 vol.1
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (644 KB)  

    A survivable planar internetwork (SPIN) architecture to interconnect local area networks (LANs), wide area networks (WANs), and extended-area satellite networks (ESANs) by organizing them into various connectivity planes that extend tie range of survivable communications provided by each is proposed. The core of the SPIN architecture is a layer of gateways that interconnect purpose-specific networks or preexisting networks deployed for localized networking support to provide a much wider range of communications. An adaptive SPIN access protocol (ASAP) is proposed to handle both data and stream traffic in the proposed SPIN. According to ASAP, the reservation requests are handled by the terrestrial network and the data transmission will take place via satellite network or the ground segment, depending on the resources available. Other issues, such as routing and congestion control, are discussed View full abstract»

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  • Spread spectrum software simulation results

    Publication Year: 1990 , Page(s): 667 - 673 vol.2
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    A software program called SPREAD, developed for modeling and time/frequency domain simulation of spread spectrum systems, is discussed. It allows the representation of the very large bandwidth-time products that are characteristic of spread spectrum signals. Results of typical simulations of direct-sequence pseudonoise and frequency hopping (FH) signals are given. The program can be used to evaluate end-to-end bit error rate performance and to perform intermediate analysis of waveform characteristics that affect detectability. Results presented include the application of importance sampling to reduce the length of Monte Carlo simulations of FH systems, as well as preliminary results on the application of cyclic spectral analysis View full abstract»

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  • DS/SSMA amplitude and phase estimation with unknown bits using a correlation matrix

    Publication Year: 1990 , Page(s): 394 - 398 vol.1
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    An algorithm is proposed for the estimation of amplitude and phase in a spread-spectrum multiple-access (SSMA) environment in additive white Gaussian noise (AWGN) without prior knowledge of the data bits. The estimate is obtained from the autocorrelation of the matched filter outputs. Estimator complexity is O(K2) for fixed delay. Convergence is discussed, and simulation results that show that the estimator compares favorably with a maximum likelihood estimator with known bits are presented View full abstract»

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  • A system dynamics model of the standards development process

    Publication Year: 1990 , Page(s): 662 - 666 vol.2
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    An overall dynamic model of the standards development process that was developed to document savings potentially obtainable from standards improvements in the Defense Information System (DIS) is presented. DIS is defined as the aggregation of all US Department of Defense information systems, including sensors, data entry devices, displays, communications networks, and computer resources. The model provides a 20-yr view of the application of standards to DIS programs. Quantitative measures of performance are calculated, and standards resource allocation is optimized View full abstract»

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  • Rapid prototyping of message processor systems

    Publication Year: 1990 , Page(s): 1044 - 1048 vol.3
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    Two communication systems that are being developed through the reuse of government-owned Ada software are described. The systems are the advanced message processing system (AMPS), which provides advanced message processing capabilities along with other message processing systems for aircraft, and the submarine message processor (SMP), which performs standard message processing activities such as message editing, message parsing, database management, archiving, auditing, and scheduling for transmission on submarines. The technical requirements, development strategies, and selection of Ada software for the two systems are discussed View full abstract»

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  • An automatically driven beamformer

    Publication Year: 1990 , Page(s): 1138 - 1141 vol.3
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    Research into the performance of automatically driven beamformers is described, and the problems which must be investigated before their performance can be predicted with confidence are identified. Early simulation results support the idea that high-resolution direction finding algorithms can be used to generate dynamic steering vectors for Applebaum arrays View full abstract»

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  • Selfconsistent model for pseudomorphic MOSFETs

    Publication Year: 1990 , Page(s): 486 - 490 vol.1
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    A self-consistent charge control and current-voltage (I V) characteristics are presented for a pseudomorphic MODFET (AlGaAs/InGaAs/AlGaAs). Poisson's and Schrodinger's equations are solved self-consistently to calculate the areal charge distribution n s in the quantum well (QW). For simplicity, the QW formed in InGaAs is approximated by three straight lines. The gate voltage dependence of the two-dimensional electron gas gives the charged control expression View full abstract»

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  • Eigenstructure methods for direction-of-arrival estimation of frequency hop (FH) emitters

    Publication Year: 1990 , Page(s): 1133 - 1137 vol.3
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    The application of multiple signal classification (MUSIC) as a direction-of-arrival (DOA) estimator for the wideband, time varying frequency-hop spread-spectrum (FH/SS) signal environment is described. Both block and adaptive approaches are discussed for a multiple FH emitter environment. Results from simulation studies of the block and adaptive versions of MUSIC, which were performed in order to examine their resolution performance, are presented View full abstract»

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  • A tree-search algorithm for signal detection and parameter estimation in multi-user communications

    Publication Year: 1990 , Page(s): 796 - 800 vol.2
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    The problem of simultaneously detecting the information bits and estimating signal amplitudes and phases in a K-user asynchronous direct-sequence spread-spectrum multiple-access communication system is addressed. The joint maximum-likelihood (ML) estimator has a computational complexity that is exponential in the total number of bits transmitted, and thus does not represent a practical solution to the problem. An estimator that combines a suboptimum tree-search algorithm with a recursive least-squares estimator of complex signal amplitude is considered. The complexity of this estimator is O(K2) computations per decoded bit, and its performance is very close to that of the joint ML receiver. This receiver has the advantage that the transmitted signal powers and phases are extracted from the received signal in an adaptive fashion without the use of a test sequence View full abstract»

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