1,721,042 research outputs found
Maximum likelihood decoding of uncoded and coded PSK signal sequences transmitted over Rayleigh flat-fading channels
No full textThe problem of maximum likelihood (ML) detection for uncoded and coded M-PSK signals on Rayleigh fading channels is investigated. It is shown that, if the received signal is sampled at baud-rate, a ML receiver employing per-survivor processing can be implemented. The error rate performance of this receiver is evaluated by means of computer simulations and its limitations are discussed. In addition, it is shown that, on a fast fading channel, the error floor in the BER curve can be appreciably lowered if more than one received signal sample per symbol interval is processed by the receiver algorithm, Finally, a sub-optimum two-stage receiver structure for interleaved coded PSK systems is proposed. Its error rate performance is assessed for simple trellis-coded modulation schemes and compared to that provided by other receiver structures
MULTISAMPLING RECEIVERS FOR UNCODED AND CODED PSK SIGNAL SEQUENCES TRANSMITTED OVER RAYLEIGH FREQUENCY-FLAT FADING CHANNELS
No full textAn algorithm, based on previous work [Vitetta and Taylor 1994, 1995], for the detection of coded and uncoded PSK sequences transmitted on a frequency-flat fading channel is investigated. It is based on the Viterbi algorithm and processes more than one signal sample per signaling interval. Its performance is evaluated by means of computer simulations for both uncoded and coded systems
Maximum likelihood detection of differentially encoded PSK signals transmitted over Rayleigh frequency-flat fading channels
No full textThe problem of maximum likelihood (ML) detection of differentially encoded M-PSK signals on Rayleigh fading channels is investigated. It is shown that the solution to this problem can be easily related to previous results [Vitetta and Taylor, 1994] and leads to the implementation of a receiver structure based on a Viterbi Algorithm. The error rate performance of this receiver is evaluated by means of computer simulations for both coded and uncoded systems
Noncoherent double-filter detection of FSK and DPSK signals with diversity
No full textLinearly time-varying fading models are used to investigate both noncoherent detection of FSK signals and differential detection of PSK signals over frequency-flat fading channels. The structure of the optimal FSK and DPSK detectors is derived and an analytical technique is proposed to compute their error performance in fast fadin
Maximum likelihood sequence estimation of uncoded and coded PSK signals transmitted over Rayleigh flat-fading channels
No full textThe problem of maximum likelihood (ME) detection for uncoded and coded M-PSK signals on Rayleigh fading channels is investigated. It is shown that, if the received signal is sampled at baud rate, a ML receiver can be implemented. The error rate performance of this receiver is evaluated by means of computer simulations and its limitations are discussed. Moreover, it is shown that, on a fast fading channel, the error floor in the BER curve can be appreciably lowered if more than one received signal sample per symbol interval is processed by the receiver decoder. Finally, it is proved that, on fast fading channels, the use of PSK trellis-codes without the interleaving-deinterleaving subsystems can provide substantial gains over uncoded PSK systems with the same information rat
Viterbi decoding of differentially encoded PSK signals transmitted over Rayleigh frequency-flat fading channels
No full textMaximum Likelihood (bit) detection of differentially encoded M-PSK signals on Rayleigh fading channels is investigated. It is shown that the solution to this problem can be related to previous results [Vitetta and Taylor, 1994] and leads to the implementation of a receiver structure based on the Viterbi algorithm and employing per-survivor processing. The error rate performance of this receiver is evaluated by means of computer simulations for both trellis-coded and uncoded systems
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
EXCESS BANDWIDTH IS NECESSARY FOR ISI-FREE DOUBLE-FILTER RECEIVERS
No full textPrevious work has indicated that highly effective double-filter receivers can be implemented for phase-shift keying (PSK) transmissions over linearly time-selective fading channels provided that the transmitter and receiver filters have root-raised-cosine transfer functions with unity rolloff factor. Revisiting the detection problem within the frame of maximum-likelihood (ML) sequence estimation we prove that this filter design is unique within the class of signaling pulses which are band limited to the symbol rate. It is concluded that some waste of bandwidth is inevitable for achieving ISI-free operation with double-filter receiver
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