By Topic

Military Communications Conference, 1996. MILCOM '96, Conference Proceedings, IEEE

Date 24-24 Oct. 1996

Go

Filter Results

Displaying Results 1 - 25 of 80
  • IEEE Military Communications Conference - Milcom 96 [front matter]

    Page(s): i - xxiv
    Save to Project icon | Request Permissions | PDF file iconPDF (843 KB)  
    Freely Available from IEEE
  • A near optimum diversity combining method adapted to slow frequency hopping DPSK transmission

    Page(s): 984 - 987 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (370 KB)  

    Frequency hopping (FH) is used in communication systems to mitigate interference such as jamming. For low data rate, fast FH and MFSK are often used in combination with diversity, which consists in transmitting every symbol on several hops. It brings additional protection. Several robust diversity combining methods have been developed previously for fast FH. Much attention has been previously focused on slow FH, where several symbols are transmitted during each hop, in order to allow higher data rates. Moreover, for higher data rates, FH MPSK could be preferred as this waveform is more bandwidth efficient and may provide better performance on a gaussian channel. This paper presents an new efficient method derived from the maximum likelihood criterion to combine hops in a slow FH MPSK transmission with diversity. First, theoretical analysis yields the formulation of the optimal receiver. Then, several approximations are used to let the implementation of this algorithm be feasible. Finally, resorting to computer simulations, it is shown that the method introduced in this paper outperforms conventional techniques. Bit error rate performance is presented for a gaussian channel corrupted by partial band jamming. View full abstract»

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

    Page(s): 1084 - 1086
    Save to Project icon | Request Permissions | PDF file iconPDF (143 KB)  
    Freely Available from IEEE
  • A bandwidth reservation multiple access protocol for wireless ATM local networks

    Page(s): 954 - 958 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    A bandwidth reservation multiple access scheme (BRMA) is proposed to resolve contention and assign bandwidth among multiple users trying to gain access to a common wireless channel. The protocol is best suited to support variable-bit rate (VBR) traffic. The channel capacity is modeled as a time frame with a fixed duration. Each frame starts with mini-slots, to resolve contention and reserve bandwidth, followed by data-transmission slots. Every contending user places a request for data slots in one of the mini-slots and starts transmission in the assigned data slot(s). A speech activity detector is utilized to avoid wasting bandwidth. Due to its asynchronous nature, BRMA is rather insensitive to the burstiness of traffic from each mobile station. Due to the deterministic assignment of the mini-slots, the request channels are contention-free and the data channels are collision-free. BRMA provides better performance than conventional TDMA and PRMA for the same quality of service (QoS) View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Reduction of cosite interference for digital FM frequency hopping radios

    Page(s): 1036 - 1040 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    Digital FM frequency hopping radios closely located together on a platform or on nearby platforms may cause interference to each other. In this paper, the interference effects of cosited radios will be discussed. These effects include transmitter wideband noise, transmitter intermodulation and receiver intermodulation. The performance of the radio will be considered taking into account the interference from intermodulation products and multiple users. Potential solutions to reduce the interference from cosited radios will also be discussed. These solutions include the use of filters, orthogonal hopping, and coupling all cosited radios through a highly linear amplifier. Ways to achieve higher isolation between radios will also be discussed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Packet combining techniques for frequency-hop communication systems with partial-band interference

    Page(s): 1027 - 1031 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    Two methods for combining packets in frequency-hop spread-spectrum systems that employ interleaving and Reed-Solomon coding are presented and analyzed for the partial-band interference channel. Bounded distance errors-and-erasures decoding and erasure generation by means of Viterbi's (1982) ratio-threshold test are incorporated in the analysis. Results of the analysis show that both combining schemes provide significant gains in throughput View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance measures for adaptive antenna systems

    Page(s): 1050 - 1054 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (404 KB)  

    As the desire for jamming-resistant satellite communication grows, adaptive antennas will soon enter service on satellite platforms. These antennas cancel received interference to a low level while preserving as much user coverage as possible. The specification of adaptive antenna performance has considerable subtlety. Such antennas need measures of quiescent and steady-state adapted performance, as well as the speed and quality of the adaptation. A set of measures are discussed for user coverage and jammer suppression View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Suboptimal Viterbi decoding metrics for channels with pulse jamming

    Page(s): 1032 - 1035 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    The tradeoff between complexity and performance of decoding metrics for use with Viterbi decoding has been studied for a channel with Gaussian pulse jamming. It is shown that a metric with three-bit quantization provides a good combination of robust performance and low complexity. In addition, a new variable rate coding scheme which utilizes soft information from the quantizer is described. The performance of this scheme is compared with that of a scheme which attempts to count corrected errors. It is shown that an improvement in performance may be obtained without significant increase in complexity by using this new scheme View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • MAC protocol for wireless networks in tactical environments

    Page(s): 923 - 927 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    A MAC protocol suitable for cellular wireless networks with motorized base stations operating in battlefield environments is described. The proposed scheme is a quasi-deterministic media access protocol based on disjunctive superimposed codes. Each wireless terminal is pre-assigned a unique code vector from a binary superimposed code whose parameters are computed from network specifications. A terminal transmits in slot κ of each fixed length frame only if the the κth component of its assigned code vector is non-zero. This scheme guarantees each active terminal at least one collision free packet transmission per time frame. Additionally, this scheme is robust, does not require reassignment of code vectors, and obviates the need for explicit association procedures when users cross cell boundaries. These properties are important in environments where the coverage areas and intersections between cells vary dynamically as a consequence of base station mobility View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance analysis of non-coherent DPSK receivers for medium data rate EHF frequency hopping systems .1. Analytical analysis of N-DPSK receivers .2. Simulations analysis of N-DPSK receivers

    Page(s): 1069 - 1073 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    This paper presents a new DPSK receiver matched to slow frequency-hopping and perturbated channels in the EHF band. Performance obtained with this non-coherent receiver are improved compared to the classical DPSK demodulator, either under thermal noise or partial-band noise jamming (PBNJ). This new receiver uses different metrics to improve the performance in terms of the BER under PBNJ. It is shown that this receiver can be very performant by using an L diversity associated with the frequency-hopping system. This is true particularly in the EHF band where the assumption that the jammed band is small (<0.5) compared to the hopping bandwidth. Moreover, this paper proposes the design of a square-law linear combining diversity detector (SLD) with an automatic gain control (AGC) which is very efficient to combat partial-band jammer. This receiver can work with any number of symbols per hop without increasing the design complexity View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Frequency estimation from short pulses of sinusoidal signals

    Page(s): 979 - 983 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (332 KB)  

    This paper treats the problem of estimating the frequencies of sinusoidal components from short, incoherent, noisy pulses. We formulate the problem in a stochastic framework and construct a generalized Yule-Walker solution by minimizing a cost function. This approach gives an improved estimate of the covariance matrix and is computationally efficient. Noise is mitigated by incorporating the principal component analysis algorithm. A computer simulation applying this algorithm to FSK data demonstrates that the proposed algorithm converges more rapidly and with more accuracy than a competing method View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Adaptive equalization of nonlinear digital satellite channels using a frequency-domain Volterra filter

    Page(s): 843 - 848 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (512 KB)  

    The objective of this paper is to present a new structure for an adaptive nonlinear equalizer for digital transmission over a nonlinear satellite channel with PSK modulation. The adaptive nonlinear equalizer is based on a discrete frequency-domain, third-order Volterra filter with the multidimensional overlap-save filtering technique, and on the block least mean square (BLMS) algorithm for updating the filter coefficients. Since the proposed equalizer performs fast convolution by blocks, in decision-directed mode, it provides potentially larger savings in computational complexity compared to the conventional time-domain Volterra equalizers. The feasibility and practicality of the proposed equalizer structure is demonstrated by utilizing it to equalize a nonlinear satellite channel View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A nine-tile algorithm for LPI signal detection using QMF filter bank trees

    Page(s): 974 - 978 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    This paper describes a novel spread spectrum intercept receiver which uses orthogonal wavelet techniques and a quadrature mirror filter (QMF) bank tree to decompose a waveform into components representing the energy in rectangular “tiles” in the time-frequency plane. Specifically, a nine-tile algorithm is presented and discussed. By simultaneously examining multiple layers of the tree, the dimensions of concentrations of energy can be estimated with a higher resolution than is normally associated with linear transform techniques. This allows detection and feature extraction even when the interceptor's knowledge of the target signal is limited. For example, no prior knowledge of channelization or time segmentation is assumed. In addition, the receiver can intercept and distinguish between multiple signals View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fully digital joint phase recovery, timing synchronization and data sequence demodulation

    Page(s): 819 - 823 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    A joint estimator for carrier phase, symbol timing, and data sequence is proposed. This fully digital scheme is systematically derived from the maximum likelihood estimation (MLE) theory. The simulation and the analytical results demonstrate that the scheme is asymptotical to the optimum in AWGN channel View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance evaluation of a coded CDMA optical system

    Page(s): 908 - 912 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (340 KB)  

    The performance of a coherent code division multiple access (CDMA) optical fiber communication system is degraded by the phase noise of the semiconductor lasers and by multiple access interference (MAI). This paper examines the effects of phase noise on the performance of a CDMA optical system. Results show that the combined effects of MAI and laser phase noise impose a very low limit on the number of simultaneous users. We investigate the possibility of increasing the receiver sensitivity using convolutional coding with Viterbi decoding, and show that coding significantly improves system performance, and allows for relaxation of the laser linewidth View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A method for detecting a fine frequency deviation

    Page(s): 824 - 827 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    The paper considers the effect of a fine frequency deviation generated in a transmission channel on the performance of an adaptive equalizer. We describe a channel model with a frequency deviation and investigate how the equalizer is adapted to the channel. The test results show that even a small amount of frequency deviations can severely deteriorate the adaptation performance. The paper also proposes a method for detecting a fine frequency deviation. This method makes it possible to accurately detect a frequency deviation less than 1 Hz within a short estimation time View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fast self-healing for node failures in ATM networks

    Page(s): 750 - 754 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    Network restoration becomes an essential function for a high speed network since service disruption due to network failures can cause a huge tangible and intangible loss for customers and service providers. We propose a VP-based distributed self-healing to rapidly restore the disrupted VPs from node failures. The developed scheme can provide a priority restoration based on the survivability requirement of services. By simulation, we verify the features of the proposed scheme and the simulation results show that high priority VPs can be resorted in a high restoration rate for node failures and single link failure View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ray optical wave propagation models for the characterization of radio channels in urban outdoor and indoor environments

    Page(s): 718 - 722 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (728 KB)  

    A deterministic approach for the prediction of path loss and channel impulse response of UHF radio links in built-up areas, including building penetrating links, is presented. The wave propagation prediction is based on ray-tracing algorithms implemented in the URBAN-MICRO model. A brief description of this model is given and comparisons with path loss measurements are shown. Further an extension of the URBAN-MICRO model for in-building antenna locations, resulting in the new model URBAN-MICRO-I, is presented. Both models use vector oriented building data and raster based topography data. Arbitrary outdoor base station heights can be handled by the models, which is a very important feature from a practical point of view View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Noncoherent hybrid acquisition of DS/CDMA signals

    Page(s): 988 - 992 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    A noncoherent signal acquisition scheme using hybrid active correlation for a direct sequence code division multiple access (DS/CDMA) receiver is presented. A test based on sequential hypothesis testing called the M-ary sequential probability ratio test (MSPRT) and several fixed sample size (FSS) tests are considered for the testing stage. Continuous integration of in-phase and quadrature signal components is used to minimize noncoherent combining losses. The MSPRT is adapted accordingly to accommodate dependent samples from the integrator output. Results of analysis and simulation show that the IMSPRT provides significantly better performance than the FSS schemes. It has been found that use of the IMSPRT with continuous integration results in negligible noncoherent implementation loss (compared to coherent acquisition) when a moderate number of correlators are used View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The case for multiply-detected macrodiversity scheme in mobile systems

    Page(s): 928 - 932 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    The multiply-detected macrodiversity (MDM) is based on post-detection combining; i.e., it is a macrodiversity scheme with a number of received signals being detected and a decision algorithm being employed to maximize the probability of correct decision. We compare the performance of the MDM scheme with the traditional S/I-diversity and show the achievable improvement. As a rule of thumb, improvement of two orders of magnitude in the BER is possible for small number of interferers View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An extremely robust turbo coded HF modem

    Page(s): 691 - 695 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    We propose an extremely robust, low rate HF modem for military radio communications. The modem design is based on the existing DSTO chirp modem which uses a half rate, memory length ten convolutional code together with a soft decision Viterbi decoder. The proposed modem replaces the current convolutional codec with a turbo codec. The problems of frame synchronisation, noise variance estimation and metric optimisation have been solved in order to implement the modem. The turbo coded chirp modem outperforms the convolutionally-coded chirp modem by more than one dB on the AWGN channel and more than two dB on HF test channels View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optimal baud-rate estimation

    Page(s): 1015 - 1019 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    This paper treats the problem of estimating the baud rate of digital communication signals with application to automatic signal recognition. We estimate the baud rate from short-duration data segments by seeking the baud period that is “most” commensurate with a set of transition measurements. A technique for generating a set of candidate baud periods is described. Next, the modified Euclidean algorithm is used to find the greatest common factor of this set. The greatest common factor is another candidate for the baud period and is appended to the set. Then a quality factor is calculated for each candidate baud period. Optimality is achieved by choosing the baud period with the maximum quality factor. The algorithm's performance is investigated by numerical simulations View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On majority-logic diversity combining in Rayleigh fading

    Page(s): 1055 - 1058 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB)  

    An interesting relationship between the bit error rate (BER) performance of majority-logic diversity combining and that of maximal-ratio combining in Rayleigh fading is derived. It is shown that, for the commonly-used binary modulation formats BPSK, DPSK, and BFSK, the BER of an L-diversity system using maximal-ratio combining (or equal-gain combining for the noncoherent modulation) identical to that of a (2L-1)-diversity system using majority-logic combining. The comparison is made based on equal branch signal-to-noise ratios (Ec /N0), which implies that to achieve the same performance, a system using majority-logic combining requires approximately 3 dB greater total energy-per-bit-to-noise-density-ratio, Eb/N0, than a system using maximal-ratio combining. As a related side note, it is also shown that for majority-logic combining, diversity of order 2L achieves the same performance as diversity of order 2L-1, assuming an unbiased tie resolution (i.e., when a tie occurs, the final output is randomly chosen) View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Concatenation of MLSE equalizer and Viterbi decoder for TDMA cellular systems

    Page(s): 723 - 727 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    The concatenation of a maximum likelihood sequence estimation (MLSE) equalizer and a Viterbi decoder is a powerful means for improving the performance of mobile communication system receivers. The best system performance is obtained when the Viterbi algorithm is used with soft decisions. The soft output MLSE equalizer enables the use of soft decision Viterbi decoding. This paper investigates the performance of a new time division multiple access (TDMA) cellular system that employs a soft output MLSE equalizer and a Viterbi decoder. Simulation results are presented for multipath Rayleigh fading channels having various delay profiles View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optimum and suboptimum 8D-4P2C receivers

    Page(s): 969 - 973 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    The performance (error probability vs. Eb/N0) of a suboptimum sampling receiver used for detecting the 8D-4P2C signals is compared with a matched filter receiver. In addition, formulas for a selected set of modulation waveforms are derived, and the joint optimization of the transmitter and receiver is carried out for binary communications over a bandlimited Gaussian channel View full abstract»

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