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Radar and Signal Processing, IEE Proceedings F

Issue 3 • Date Jun 1988

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Displaying Results 1 - 11 of 11
  • Performance analysis of GMSK frequency detection with decision feedback equalisation in digital land mobile radio

    Page(s): 199 - 207
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    The bit-error-rate (BER) performance of premodulation Gaussian filtered MSK (GMSK) using frequency detection (FD) in conjunction with 1 bit decision feedback equalisation (DFE) is theoretically investigated. The introduction of the premodulation filter causes severe intersymbol interference (ISI) in the waveform of the input to the FM modulator. DFE is used for reducing the ISI effect and therefore improving the BER performance. Applying the analysis to additive white Gaussian noise (AWGN) channels (no fading) shows that a 1-bit DFE attains about 8.5 dB Eb/N0 improvement at BER=10-3 for the premodulation filter bandwidth-time product BbT=0.25 (typical for mobile radio applications) when the receiver predetection bandpass filter bandwidth-time product BT is optimised. It is shown that the effect of error propagation due to DFE is negligible and the exact BER can be well approximated by the BER that is obtained assuming the decision 1-bit prior is correct. The analysis is then extended to the case of Rayleigh fading channels. Both predetection and postdetection diversity reception are considered. When two-branch predetection maximal-ratio combining (MRC) is used, the 1-bit DFE attains about 6.3 dB Eb/N0 improvement at BER=10-3 for BbT=0.25. View full abstract»

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  • Outage probability calculations for multiple cochannel interferers in cellular mobile radio systems

    Page(s): 208 - 215
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    The calculation of outage probability is discussed in relation to cochannel interference problems inherent in mature cellular radio systems. Outage probability equations for coverage only and for single cochannel interferer situations are reviewed briefly, and examples of the application of these results to the estimation of the service area of a typical cellular base station are given. An analytical technique for multiple uncorrelated interferers in a Rayleigh fading environment is presented and the effect of several cochannel Rayleigh interferers on the service area of a cellular base station is examined. View full abstract»

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  • Transfer function parameters in multipath channel modelling

    Page(s): 262 - 264
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (196 KB)  

    Two alternative forms of representation of a multipath fading channel frequency response function are presented. Appropriate analytical expressions relating the two sets of characterisation parameters are derived. The results are applied to published data to illustrate their use. View full abstract»

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  • Theoretical performance prediction of the MUSIC algorithm

    Page(s): 216 - 222
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    The expected value of the MUSIC 'spectrum' is investigated for two situations. First the case when there are very few data samples available is investigated. The paper performs a second-order perturbation analysis, using the assumption that the data comes from a complex Gaussian distribution. The final expression which is obtained is shown to be very simple to compute, and gives very good agreement with results obtained by simulation. The paper also investigates the performance of the MUSIC algorithm when it is necessary to perform some pre-whitening. In practical situations, it is often necessary to estimate the background noise statistics from noise samples. The paper obtains analytic expressions for the expected value of the MUSIC spectrum under these conditions. Good agreement is obtained between the predicted spectra and results obtained by simulation. View full abstract»

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  • Effects of random sensor motion on bearing estimation by the MUSIC algorithm

    Page(s): 233 - 250
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1348 KB)  

    The MUSIC method of bearing estimation is a high resolution estimating method utilising the orthogonal relationship between the signal and noise subspaces which are spanned by the eigenvectors of the covariance or the cross-spectral density matrices. In the application of the MUSIC method to bearing estimation in a sonar environment, an important source of error is that the position of the array of sensors are under constant perturbation. The paper investigates the effect of this source of error on the bearing estimate. The Cramer-Rao bound of bearing estimation under the influence of this source of error is evaluated and the performance of the MUSIC method is compared with this lower bound. View full abstract»

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  • Performance of the greater-of and censored greater-of detectors in multiple target environments

    Page(s): 193 - 198
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    The greater-of (GO) constant false alarm rate (CFAR) detector selects the greater of the leading and lagging sets of the reference noise cells to minimise the effect of clutter and jamming. The performance of the GO detector is derived for the case where an arbitrary number of interfering targets are present in the leading and lagging reference noise cells. To improve its performance in this situation, the censored greater of (CGO) detector, which discards several of the largest samples on each side is analysed. Results presented show improvements for the CGO over the GO detector, especially when the number of interfering targets is less than the number of censored cells. View full abstract»

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  • New technique for speaker-independent isolated-word recognition

    Page(s): 251 - 257
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (636 KB)  

    In a speech recognition system based on dynamic time warping (DTW) the DTW operation is used to time-align two words while calculating the distance between them. The DTW operation is repeated many times as the number of the reference templates in the system. As a result the processing becomes time-consuming. The generation of a single pattern to be used as a time aligning pattern (TAP) for all the words in the system (references and unknowns) is proposed. The unknown word is first time-aligned with the TAP only. Then the distance between the time-aligned version of the unknown word and any of the reference templates (which have already been time-aligned with the TAP in the training mode) is directly calculated without any further need for DTW operations. Thus a great reduction in the processing time results. Two methods for generating TAPs are proposed. The approach is extended to using more than one TAP. In both cases, the processing time saving, when compared with conventional DTW systems, is in the range of 95% for comparable recognition accuracy. View full abstract»

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  • Class of optimum signal shapes in data transmission

    Page(s): 272 - 276
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    An efficient method is given for the optimal design of band-limited, Nyquist-type signal shapes for data transmission, which maximises its energy in a time interval and which generates no intersymbol interference at the periodic sampling instants. The computation is straightforward and the constraint for intersymbol interference is shown to be easy to include in the problem. A numerical example is given and performance of the optimal signal shapes is compared with that resulting from the use of the 'raised-cosine' and the 'modified triangular' types of signals. It is also concluded that the optimal signal shapes thus obtained are almost immune to small timing offsets at the sampling instants. View full abstract»

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  • Cochannel interference between point-to-point urban microwave radio systems

    Page(s): 225 - 232
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (620 KB)  

    Low-cost point-to-point radio systems are available at a number of frequencies in both the centimetre and millimetre wavebands for local business applications. In urban areas a high degree of cochannel operation is predicted, both for reasons of spectral efficiency, and because forecast demands greatly exceed the number of available channels. The paper presents an initial probabilistic study of the limiting cochannel interference effects, based on an idealized flat circular locality model. The study indicates that high system populations, or area capacities, should be achievable. For example in a typical large metropolitan area, the predicted capacities for one way systems sharing a single channel, are several hundred for centimetre wave (13 GHz) systems, and several thousand for millimetre wave (39 GHz) systems. It is demonstrated furthermore that the area capacity is proportional to the square of the antenna diameter to wavelength ratio. There is thus a high incentive to employ equipment with relatively large antennas, and to operate wherever possible in the millimetre wavebands. View full abstract»

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  • Analytical expression for the performance bounds of 16-QAM signalling in non-Gaussian products environment

    Page(s): 265 - 271
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    The error performance of 16-QAM schemes operating in nonlinear satellite channels where additive white Gaussian noise (AWGN) appears on the down link has already been evaluated. However, it is well known that in realistic nonlinear satellite transmission systems, additive channel noise appears on both the up- and the downlink; and indeed it is mostly the presence of uplink Gaussian channel noise that creates severe system performance degradation. A theoretical analysis is carried out by formulating upper and lower bounds of the 16-QAM system error performance, considering that Gaussian channel noise appears at both the input (uplink) and the output (downlink) of the space bandpass nonlinearity (BPNL). This creates AM/AM distortion and AM/PM conversion products, whose origin may be demonstrated by quadrature modelled nonlinear processing of the signal and the uplink Gaussian noise. The analysis described offers a technique for evaluating M-ary QAM system performance appraisals in a complex nonlinear satellite environment. View full abstract»

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  • Autocorrelation and power spectrum of Hadamard signalling

    Page(s): 258 - 261
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    Presents results for the autocorrelation and power spectrum of digital modulation for M-ary orthogonal and biorthogonal signal sets based on binary Hadamard matrices. Such signal sets provide easily-mechanised orthogonal (and related) constructions, and are important in coded signalling for jammed and/or fading channels using large-alphabet codes. View full abstract»

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Aims & Scope

The latest version of this title is Radar, Sonar & Navigation, IET.

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