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Selected Areas in Communications, IEEE Journal on

Issue 4 • Date May 1992

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Displaying Results 1 - 13 of 13
  • Perfect N-phase sequences and arrays [spread spectrum communication]

    Publication Year: 1992 , Page(s): 782 - 789
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    Perfect sequences and arrays have periodic autocorrelation functions whose out-of-phase values are zero. Time-discrete N-phase sequences and arrays have complex elements of magnitude one, and one of (2π/N)n, 0⩽n<N , different phase values. Existence conditions and construction methods for perfect N-phase sequences and arrays with a small alphabet of possible phase values are introduced. Combining the existence conditions with, methods of advanced computer search, new perfect N-phase arrays have been found. The resulting lowest number N of perfect N-phase sequences and arrays up to 40 elements are given in a table, after having applied the construction methods View full abstract»

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  • Sequential acquisition of PN sequences for DS/SS communications: design and performance

    Publication Year: 1992 , Page(s): 750 - 759
    Cited by:  Papers (24)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (752 KB)  

    The performance of sequential acquisition of m sequences, based on the sequential probability ratio test (SPRT), is studied. The authors consider a sliding correlator-type structure for the acquisition scheme, which the mean acquisition time is proportional to the average number of samples used for a synchronization test. Sequential acquisition requires the knowledge of the partial correlation of the pseudonoise (PN) sequence, however, as the partial correlation of an m sequence is difficult to model the authors propose an approximate upper bound. This is then piecewise linearized and used for designing the SPRT which is then compared to the fixed-dwell time technique, a scheme using the fixed sample size test. Numerical results show that the saving of acquisition time by the SPRT increases as the desired probabilities of errors and/or the input SNR decrease. Analytic results are verified by computer simulation View full abstract»

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  • Performance of fast frequency-hopped MFSK receivers with linear and self-normalization combining in a Rician fading channel with partial-band interference

    Publication Year: 1992 , Page(s): 731 - 741
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (820 KB)  

    An error probability analysis is performed for both self-normalized and conventional M-ary orthogonal frequency-shift-keying (MFSK) noncoherent receivers using fast frequency-hopped (FFH) spread-spectrum waveforms transmitted over a Rician fading channel with partial-band interference. The self-normalization receiver uses a nonlinear combination procedure to minimize performance degradation due to partial-band interference. The performance of the conventional receiver is significantly degraded by worst-case partial-band interference regardless of the modulation order or number of hops per data symbol used, while the self-normalization receiver can provide a significant immunity to worst-case partial-band interference for many channel conditions when diversity is used, provided the signal-to-thermal-noise ratio is large enough to minimize degradation due to nonlinear combining losses. The improvement afforded by higher modulation orders is dependent on channel conditions View full abstract»

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  • Analysis of a multiple-cell direct-sequence CDMA cellular mobile radio system

    Publication Year: 1992 , Page(s): 669 - 679
    Cited by:  Papers (41)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (796 KB)  

    The performance of a multiple-cell direct-sequence code division multiple-access cellular radio system is evaluated. Approximate expressions are obtained for the area-averaged bit error probability and the area-averaged outage probability for both the uplink and downlink channels. The analysis accounts for the effects of path loss, multipath fading, multiple-access interference, and background noise. Two types of differentially coherent receivers are considered: a multipath rejection receiver and a RAKE receiver with predetection selective combining. Macroscopic base station diversity techniques and uplink and downlink power control are also topics of discussion View full abstract»

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  • Modified SUGAR/DS: a new CDMA scheme

    Publication Year: 1992 , Page(s): 690 - 704
    Cited by:  Papers (3)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (948 KB)  

    The authors prove by analysis the possibility of gaining a minimum of 2 dB in signal-to-noise ratio by just, splitting the users to three or more groups and identifying each one by an orthogonal waveform (on top of his short Gold code) in a PSK/DS spread-spectrum network. User signals may arrive in a code-asynchronous fashion at the receiver, however, it is shown that by using the scheme the average code cross-correlation is minimal compared to the classic code division multiple access (CDMA) system. Both the chip-synchronous and asynchronous cases are investigated and the uniform and optimal cases of dividing the users into orthogonal groups are analyzed. The superior bit error and network data throughput results in the different fading and forward error correction environments make the system a strong candidate for competitive domestic applications View full abstract»

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  • Suppression of narrowband jammers in a spread-spectrum receiver using transform-domain adaptive filtering

    Publication Year: 1992 , Page(s): 742 - 749
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (680 KB)  

    The author investigates the use of transform-domain adaptive filtering for the suppression of narrowband jammers in a direct-sequence (DS) spread-spectrum receiver. An input signal consisting of the DS signal, white Gaussian noise, and a narrowband jammer is transformed into the frequency domain where adaptive filtering acts to suppress the jammer. Weight leakage is used to allow jammer suppression while preserving the desired DS signal. Bit error rate (BER) results obtained by computer simulation are presented to illustrate performance for a single-tone jammer and for a jammer consisting of a second DS signal with a lower chip rate. These results are compared to those for a transform-domain exciser. Expressions for the converged tap weights are derived and the results are verified via the simulation. Finally, the convergence properties of the adaptive suppressor are illustrated View full abstract»

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  • Performance of direct-sequence systems with long pseudonoise sequences

    Publication Year: 1992 , Page(s): 770 - 781
    Cited by:  Papers (58)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (808 KB)  

    A performance analysis of direct-sequence systems with long pseudonoise sequences is presented. The assessment of the symbol error probability in the presence of multiple-access interference is stressed, but other types of interference are also considered for completeness. Both binary and quaternary spreading waveforms are treated. The analysis, which uses a nonstandard Gaussian approximation, makes transparent the answers to a number of technical issues. Approximate error probabilities that are relatively simple computationally are derived. The approximations are accurate to within at least one decibel and, more typically, a few tenths of a decibel View full abstract»

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  • On the distribution function of the spread-spectrum code acquisition time

    Publication Year: 1992 , Page(s): 760 - 769
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (688 KB)  

    By using the direct approach to the analysis of the serial-search spread-spectrum code acquisition, the author presents the approximate analysis of the cumulative probability density function (CDF) of the acquisition time. This approach is based on the binomial approximation to the distribution of the partial acquisition times, instead of the Gaussian one used previously. The binomial approximation gives very accurate results but, more importantly, it shows that the analysis of the arbitrary detection/verification scheme can be reduced to the much simpler analysis of the equivalent single-dwell system, whose parameters depend only on the mean test times and not on their distribution. Based on the exact results, simple closed-form approximations are derived for the CDF in the case of the straight-line serial search with uniform a priori distribution, which might be useful in practice View full abstract»

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  • Limiter-differential detection of a frequency-hopped CPFSK diversity system in partial-band jamming

    Publication Year: 1992 , Page(s): 724 - 730
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (568 KB)  

    The error probability achieved by a differential detector with a bandpass limiter preceding the receiver is analyzed for a slow-frequency-hopped CPFSK diversity waveform transmitted over a partial-band noise jamming channel, and is compared to the system's performance without the bandpass limiter. The system's thermal noise is not neglected in the analysis. In principle, each bit is repeated on L different hops, and for the FH/CPFSK system analyzed, these repetitions are combined to yield a soft decision. The main result is that a diversity gain for error rate improvement in worst-case partial-band jamming is realized with the detector preceded by a limiter, but not without the limiter. This is shown by considering the error probability for L=2 in comparison with that for L=1 View full abstract»

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  • Performance evaluation for cellular CDMA

    Publication Year: 1992 , Page(s): 680 - 689
    Cited by:  Papers (80)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (580 KB)  

    The authors consider the performance of a cellular radio, direct-sequence code-division multiple access, (CDMA) system. The base-to-mobile link is modeled as a flat Rayleigh fading channel, with all signals transmitted from a given base station fading in unison. For the mobile-to-base link, the authors use a similar model, except that the waveforms from all users are assumed to experience independent fading. The effects of imperfect power control are shown View full abstract»

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  • Error probabilities of fast frequency-hopped FSK with self-normalization combining in a fading channel with partial-band interference

    Publication Year: 1992 , Page(s): 714 - 723
    Cited by:  Papers (37)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (740 KB)  

    Error probability analysis is performed for a binary orthogonal frequency-shift-keying (FSK) receiver using fast frequency-hopped (FFH) spread-spectrum waveforms transmitted over a frequency-nonselective slowly fading channel with partial-band interference. Diversity is performed using multiple hops per data, bit. A nonlinear combination procedure referred to as self-normalization combining is used by the receiver to minimize partial-band interference effects. Diversity is found to completely negate degradation of the self-normalized receiver caused by partial-band interference and offers definite receiver performance improvement when the direct signal component is weak. The self-normalized receiver is sensitive to fading channels. For severe channel fading, the performance of a conventional noncoherent binary FSK receiver is generally either equivalent or superior to that of the self-normalized receiver View full abstract»

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  • On the feasibility of a CDMA overlay for personal communications networks

    Publication Year: 1992 , Page(s): 655 - 668
    Cited by:  Papers (165)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1384 KB)  

    Because of the continually increasing demand for mobile communications, it has been suggested that personal communication networks (PCNs) be established in the 1850-1990 MHz range. However, that band of frequencies is currently occupied by various microwave signals transmitted by users ranging from utility companies to state and local agencies. In order to allow both sets of users to occupy these frequencies as well as improve the spectral efficiency of this band, a spread-spectrum overlay is proposed, whereby a code-division multiple-access (CDMA) PCN would share the spectral band with the existing narrowband microwave traffic. The results of several field tests which have been designed to demonstrate the feasibility of an overlay of this type are discussed View full abstract»

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  • Hybrid DS/SFH spread-spectrum multiple access with predetection diversity and coding for indoor radio

    Publication Year: 1992 , Page(s): 705 - 713
    Cited by:  Papers (48)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (732 KB)  

    The authors derive close upper and lower bounds on the average bit error probability for hybrid direct-sequence/slow-frequency-hopped spread-spectrum multiple-access (DS/SFH-SSMA) systems with noncoherent DPSK demodulation, using predetection diversity (selection combining and equal gain combining) in conjunction with interleaved channel coding (Hamming (7,4) code and BCH (15,7) code) operating through indoor radio channels. A multipath Rayleigh fading model is assumed for the indoor radio channel. The results show that the DS portion of the modulation combats the multipath interference, whereas the FH portion is a protection against large multiaccess interference. It is shown that, for the considered types of channel coding, the use of predetection diversity is still essential for obtaining satisfactory error performance View full abstract»

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Aims & Scope

IEEE Journal on Selected Areas in Communications focuses on all telecommunications, including telephone, telegraphy, facsimile, and point-to-point television, by electromagnetic propagation.

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Editor-in-Chief
Muriel Médard
MIT