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IEE Proceedings I - Communications, Speech and Vision

Issue 4 • Date Aug. 1992

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Displaying Results 1 - 11 of 11
  • Voice activity detection using a periodicity measure

    Publication Year: 1992, Page(s):377 - 380
    Cited by:  Papers (26)  |  Patents (15)
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (411 KB)

    The author describes a voice activity detector (VAD) that can operate reliably in SNRs down to 0 dB and detect most speech at -5 dB. The detector applies a least-squares periodicity estimator to the input signal, and triggers when a significant amount of periodicity is found. It does not aim to find the exact talkspurt boundaries and, consequently, is most suited to speech-logging applications whe... View full abstract»

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  • Spectral efficiency of M-QAM in frequency reuse radio systems

    Publication Year: 1992, Page(s):381 - 385
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (557 KB)

    The spectral efficiency of M-QAM has been investigated for frequency reuse radio systems under the propagation conditions of the land mobile radio environment. The results indicate that, under certain circumstances (of propagation and coverage requirements), increasing the number of levels can lead to an improvement in the spectral efficiency of interference limited systems, but that, as better co... View full abstract»

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  • Convolutionally encoded FFH-MFSK: demodulation and frequency tracking over frequency-varying jammed channels

    Publication Year: 1992, Page(s):386 - 394
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (819 KB)

    A novel soft decision metric for the Viterbi demodulation and decoding of convolutionally encoded fast-frequency-hopped M-ary frequency shift keying (FFH-MFSK) is described. The effectiveness of two possible hop-by-hop AGC methods is evaluated for use with metric calculation methods to optimise the worst-case partial-band-jamming performance. The metric is shown to improve the worst-case jamming b... View full abstract»

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  • A chirp modem incorporating interference excision

    Publication Year: 1992, Page(s):395 - 406
    Cited by:  Patents (5)
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (1012 KB)

    The authors describe an experimental 75-baud chirp modem designed to operate at high frequency (HF), which is able to reject interference from other HF users by adaptive filtering at the receiver. It also has inherently good performance in multipath propagation and in white noise, and is thus capable of robust digital communication. The system has been tested over a 170 km point-to-point HF skywav... View full abstract»

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  • Scheduling delay protocols integrating voice and data on a bus LAN

    Publication Year: 1992, Page(s):407 - 412
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (591 KB)

    Two new protocols integrating voice and data on a multiaccess broadcast bus LAN with reverse round robin service are presented. The protocols are based on a collision free scheduling delay access mechanism. According to this mechanism, each station computes its transmission time relying on the activity of the bus. In the first protocol, the authors use this mechanism for both voice and data traffi... View full abstract»

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  • Decoding delays of orchard codes

    Publication Year: 1992, Page(s):413 - 417
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (476 KB)

    To evaluate an orchard code, a standard measure of how well the orchard code works is necessary. The authors propose the decoding delay to replace the commonly used scheme length as a criterion for evaluating orchard codes. The ever approachable lower bound of the decoding delay is derived to be 2 tau for tau -error correcting orchard codes. With the help of the concept of the decoding delay, the ... View full abstract»

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  • Examination of an adaptive DFE and MLSE/near-MLSE for fading multipath radio channels

    Publication Year: 1992, Page(s):418 - 428
    Cited by:  Papers (3)  |  Patents (1)
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (1020 KB)

    The authors examine the performance over an HF channel of two adaptive equalisers; the decision feedback equaliser (DFE) and the maximum likelihood sequence estimator (MLSE), or an approximation to it (near-MLSE). It is shown that the superiority of the more complex MLSE/near-MLSE over the DFE is not great, and that this advantage is only due to error propagation in the DFE. In the absence of any ... View full abstract»

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  • Synchronised linear almost periodically time-varying adaptive filter

    Publication Year: 1992, Page(s):429 - 436
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (781 KB)

    Conventional adaptive filters only suit stationary and slowly time-varying nonstationary inputs. Based on the previous work on linear almost periodically time-varying adaptive filtering, the authors develop such an adaptive filter adopting the output-modulator structure. In addition to being capable of dealing with almost cyclostationary inputs (an important class of nonstationary signals), this s... View full abstract»

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  • Transmission of digitally encoded speech at 1.2 kbaud for PCN

    Publication Year: 1992, Page(s):437 - 447
    Cited by:  Papers (2)
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (969 KB)

    The transmission of digitally encoded speech at 1.2 kbaud for mobile personal communication networks (PCN) is investigated both analytically and by computer simulations. Speech was encoded at 4.8 kbit/s using a low complexity transformed binary pulse excited LPC codec. A 64-level QAM modem was used having three subchannels that operated with different BERs. The sensitivity of the encoded speech bi... View full abstract»

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  • Teletraffic performance of microcellular personal communication networks

    Publication Year: 1992, Page(s):448 - 461
    Cited by:  Papers (13)  |  Patents (3)
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (1301 KB)

    Teletraffic performance of a personal communication network (PCN) based on city street microcells catering for pedestrian mobile users is analysed. A teletraffic analysis is performed to determine the new and handover call rates as well as the channel holding time of the PCN. Next, a teletraffic model is established to determine the teletraffic performance parameters, such as the blocking probabil... View full abstract»

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  • Performance of 8-PSK trellis codes over nonlinear fading mobile satellite channels

    Publication Year: 1992, Page(s):462 - 471
    Cited by:  Papers (7)
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (920 KB)

    A new analytical bound for large effective code length codes (ECL) is derived. The accuracy of the analytical bounds is validated by simulation. Based on the new bound a trellis code design procedure for fading channels is defined. A quasi-analytical technique for BER estimation on nonlinear channels is proposed. This method is used to estimate the performance degradation of nonlinear communicatio... View full abstract»

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