By Topic

Military Communications Conference, 1985. MILCOM 1985. IEEE

Date 20-23 Oct. 1985

Go

Filter Results

Displaying Results 1 - 25 of 44
  • [Cover]

    Page(s): C1
    Save to Project icon | Request Permissions | PDF file iconPDF (326 KB)  
    Freely Available from IEEE
  • 1985 IEEE Military Communications Conference

    Page(s): i
    Save to Project icon | Request Permissions | PDF file iconPDF (375 KB)  
    Freely Available from IEEE
  • Copyright page

    Page(s): ii
    Save to Project icon | Request Permissions | PDF file iconPDF (300 KB)  
    Freely Available from IEEE
  • General Chairman's welcome

    Page(s): iii
    Save to Project icon | Request Permissions | PDF file iconPDF (574 KB)  
    Freely Available from IEEE
  • Technical Program Chairman's Message

    Page(s): iv
    Save to Project icon | Request Permissions | PDF file iconPDF (630 KB)  
    Freely Available from IEEE
  • MILCOM '85 Executive Committee

    Page(s): v
    Save to Project icon | Request Permissions | PDF file iconPDF (117 KB)  
    Freely Available from IEEE
  • Patron Sponsors

    Page(s): v
    Save to Project icon | Request Permissions | PDF file iconPDF (117 KB)  
    Freely Available from IEEE
  • MILCOM '85 Unclassified Sessions - IEEE/AFCEA Sponsored

    Page(s): vi
    Save to Project icon | Request Permissions | PDF file iconPDF (104 KB)  
    Freely Available from IEEE
  • MILCOM '85 Classified Sessions - DOD Sponsored

    Page(s): vii
    Save to Project icon | Request Permissions | PDF file iconPDF (93 KB)  
    Freely Available from IEEE
  • Author index

    Page(s): viii - ix
    Save to Project icon | Request Permissions | PDF file iconPDF (254 KB)  
    Freely Available from IEEE
  • [Sessions - Table of Contents]

    Page(s): x - xvi
    Save to Project icon | Request Permissions | PDF file iconPDF (1025 KB)  
    Freely Available from IEEE
  • [Breaker pages]

    Page(s): 1
    Save to Project icon | Request Permissions | PDF file iconPDF (12 KB)  
    Freely Available from IEEE
  • A Comparison of Diversity Combining Techniques for Frequency-Hop Communications with Partial-Band Interference

    Page(s): 570 - 574
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (831 KB)  

    Several diversity combining techniques are considered for applications to frequency-hop communications with partial-band interference. These diversity combining schemes are based on Viterbi's ratio threshold technique. The frequency-hop system considered has binary orthogonal signaling and noncoherent demodulation. A quiescent noise level is included in the analysis to account for thermal noise in the receiver and other wideband noise sources. The goal of this work is to find diversity combining techniques that perform well in partial-band interference without the need for side information. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Multiple-Access Capability of Frequency-Hop Spread-Spectrum Communication

    Page(s): 575 - 579
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (677 KB)  

    The multiple-access capability of frequency-hop spread-spectrum communication is considered from an information theoretic viewpoint. The model adopted is that of an interference channel with T source-receiver pairs with ith receiver only interested in the message produced by the ith source. Different transmitters use different frequency-hopping patterns which we model as random hopping patterns. We propose some simple models for the resulting channels. We consider both the case where all users are synchronized and the totally asynchronous case. We also consider the cases when the receiver can detect when two or more transmitters hop to the same frequency at the same time. This allows for erasure correction in decoding. Without this information the channel is modeled as a noisy M-ary symmetric channel. when there is a hit and a noise-less M-ary symmetric channel in the absence of a hit. For this channel model we determine the capacity region. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Principles of Spread Spectrum Radar

    Page(s): 586 - 590
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (690 KB)  

    This paper presents a general class of ranging waveforms which utilize a code sequence as a means of achieving high range/Doppler resolution and good self clutter performance. The generalized waveform is defined and the primary analysis tools are developed. The concept of a random ambiguity function is introduced. System processing architectures and code waveform design guidelines are developed. Examples point out the effectiveness of this technique in a high clutter environment. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance of Selected Coded Direct-Sequence Receiver Structures in Pulsed Interference

    Page(s): 591 - 597
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1206 KB)  

    We consider the performance of short constraint-length convolutional codes in conjunction with coherent BPSK direct-sequence spread-spectrum modulation in a variety of pulsed interference scenarios. We explore the use of several types of imperfect interference estimation mechanisms and the resulting impact on Viterbi decoder bit error probability performance. Our digital receiver structures eliminate the need for a fast-acting analog AGC circuit which is often susceptable to spoofing. For the short constraint-length codes under consideration, we provide upper bounds on bit error probability performance under idealized channel modeling assumptions. Departures from these idealized assumptions are analyzed through extensive Monte-Carlo computer simulation. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Processing Gain Improvement by Means of Replica Subtraction in Code Division Multiple Access Systems

    Page(s): 598 - 602
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    The paper presents a performance evaluation of code division multiple access (CDMA) systems, using signal replica transmission and interference subtraction thereafter in the receiver. Asynchronous direct sequence systems, using two transmission channels, are discussed. The two incoming signals in the receivers are coherently multiplied by IF frequency quadrature components, enabling the elimination of the desired signal in the replica path. Additional low pass filtering, sideband frequency conversion and delay operations occur, prior to the interference subtraction process. System synthesis, parameter design and necessary conditions for adequate CDMA interference reduction are discussed. The results obtained indicate that an improved processing gain may be achieved on account of a 3dB degradation in signal to thermal noise ratio. The time delay in the receiver replica path is a major factor in processing gain determination. The CDMA interference subtraction requirements dictate an appropriate choice of carrier frequencies and strict frequency control in the various transmitters. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Development and Evaluation of an LPI Figure of Merit for Direct-Sequence and Frequency-Hop Systems

    Page(s): 603 - 608
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (928 KB)  

    This paper investigates the performance evaluation problem associated with the design of a low probability of intercept system. Two general methods for evaluating the LPI performance are proposed and described: An interception-time figure of merit and a probability-of-intercept figure of merit. The latter of the two was favored and studied in detail. The performances of frequency-hop and direct-sequence systems are evaluated, using the chosen figure of merit, as functions of both constrained and adjustable system parameters. The direct-sequence signal is found to be more difficult to detect than the frequency-hop signal, in general. Comments are made regarding situations where the frequency-hop signal may be more difficult to detect. Design guidelines are specified for determining frequency-hop system parameters that optimize the LPI performance of a system being designed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A Comparison of Two Methods for Very-Low-Rate Speech Coding

    Page(s): 609 - 613
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (848 KB)  

    Vector quantization (VQ) has been used recently for developing vocoders operating below 800 b/s. We describe in this paper two systems that use VQ and transmit intelligible speech in the range of 300 to 600 b/s. The frame vocoder which uses VQ for quantizing the spectral parameters of a single frame of speech was found to be most effective at the higher rate of 600 b/s. The segment vocoder which uses VQ for quantizing the spectral parameters of a sequence of frames yielded better intelligibility at the lower 300 b/s rate. We present the quantization algorithms and bit allocation for the two vocoders and compare their performance for varying bit rates and different noisy speech conditions. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An Overview of Matrix Quantizer Design using the Generalized Lloyd Algorithm

    Page(s): 614 - 619
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (813 KB)  

    This paper gives a tutorial review of extensions of the Lloyd vector quantizer called matrit quantizers. The Lloyd matrix quantizer arises naturally from the minimization step in linear prediction, where the minimization takes place over a codebook of inverse filter models. Rate-distortion theory predicts possible bit-rate savings for increasing block length N when such a code-book is optimized. Experimental results on LPC speech indicate that this is the case. On single-speaker tests, a 3-vector matrix quantizer at 3 bits per frame for the LPC model achieved average distortion comparable to a vector quantizer at 7 bits per frame. However, such savings are obtained at the expense of exponentially rising complexity. Shape-gain matrix quantizers provide a compromise between complexity and very low bit rate. In this case, N-vector shape matrices are combined with K-dimensional gain vectors to form a generalized product codebook. We have simulated a shape-gain matrix quantizer operating at 6 bits per frame (or 300 bits per second) for the LPC model having average distortion comparable to a vector quantizer operating at 9 bits per frame (or 450 bits per second), with less than 1.7 times the complexity. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Transform Coding of Speech with Pyramid Vector Quantization

    Page(s): 620 - 623
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (593 KB)  

    The pyramid vector quantizer (PVQ) is a lattice quantizer that was motivated bv the geometric properties of a memoryless Laplacian source. For large rates and the cubic lattice. the PVQ provides improvements of 2.39, 5.64, and 8.40 dB for memoryless Gaussian, Laplacian, and gamma sources, respectivelv, compared to the corresponding optimum (noniuniform) scalar quantizer. The lattice basis of the PVQ allows simple encoding and decoding algorithms with a complexity that grows only linearly with the vector dimension. A correlated source such as speech has a geometric nature that is not well suited to the PVQ unless transform coding is used. It is demonstrated that an encoding system using a cosine transform, interleaving of the transform coefficients, and pyramid vector quantization can achieve signal-to-noise ratio (SNR) performance in excess of 20dB for an average rate of 2 bits/sample. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • New Technique for Combined Pixel and Frequency Domain Image Sequence Coding

    Page(s): 624 - 627
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    This paper describes a technique for producing an optimal set of linear basis function coefficients given a priori information about the image to be transmitted. In particular, when certain pixel domain data is known, the transmitted frequency coefficients can be adjusted to make use of this information. The algorithm utilizes successive projections onto two non-intersecting sets in order to determine the optimal frequency domain coefficients. This technique is best suited to fixed blocksize transform coders and builds on the techniques used in previous work (refs.2,4). View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Image Coding System - A Single Processor Implementation

    Page(s): 628 - 634
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1778 KB)  

    In this paper we present the design of a still image coder. The system is built around the TNS320 digital signal processor, and is based on the Adaptive Cosine Transform Coding (ACTC) algorithm presented by Chen and Smith [1]. The algorithm is simplified in order to overcome the TMS320 hardware limitations, and computational shortcuts are introduced to speed up coding and decoding processing time. The effect of these modifications on the image quality is discussed. We will also discuss an algorithm for achieving an improved quality on predefined areas of the image while preserving the image compression rate. The system is user-interactive, and it allows the selected output bit rate to be as low as 0.1 bits/pixel. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Applications of Integrated Service Digital Networks in the Defense Communications System

    Page(s): 635 - 639
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (714 KB)  

    Many of the characteristics of a commercial ISDN have counterparts in the Department of Defense plans for a military World Wide Digital Systems Architecture. This paper reviews a number of ISDN issues and discusses their potential impact on the development of the WWDSA. The ISDN architecture is discussed with emphasis on the user/network interface. Current ISDN status is summarized. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.