An intelligent multimode voice communications system for indoor communications

Hanzo, Lajos; Woodard, Jason

doi:10.1109/25.467957

Cited by 19 publications

(6 citation statements)

References 46 publications

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“…Then the channel decoder can attempt a second tentative decoding by passing the second most likely corrected message to the source decoder, which in turn subjects this again to the previously failed threshold test, etc. A variety of such techniques have successfully been used in robust source-matched source and channel coding [73], [74], [82], [83]. Another practical manifestation of the time-variant source statistics of speech signals is the fact that during silent speech spurts, some speech codecs do not surrender their reserved physical link; they reduce their output bit rate instead, which can reduce the interference inflicted to other users in CDMA systems, such as the American IS-95 system [43].…”

Section: Shannon's Message and Its Implications For Wireless Chanmentioning

confidence: 99%

Bandwidth-efficient wireless multimedia communications

Hanzo

1998

Proc. IEEE

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Section: Shannon's Message and Its Implications For Wireless Chanmentioning

confidence: 99%

Bandwidth-efficient wireless multimedia communications

Hanzo

1998

Proc. IEEE

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“…The error sensitivity of Codec F was improved using the techniques described in [31,32]. These techniques include a way to correct 25% of all bit errors that occur in the 34 bits representing the LPC coefficients of the codec and smoothing of the ACELP gains to correct errors that occur in these bits.…”

Section: A Forward Adaptive Acelp Codecmentioning

confidence: 99%

A Range of Low and High Delay CELP Speech Codecs between 8 and 4 kbits/s

Woodard

Hanzo

1997

Digital Signal Processing

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(1997), 37-46. In this paper we study the performance and the error sensitivities of six CELP [I] based codecs operating between 8 and 4 kbitsls. Codecs using both forward and backward adaption of the linear prediction coefficients and the long term predictor (LTP) are described. Initially we describe four low delay codecs which all use backward adaption of the LPC coefficients but which differ in their use of LTP. These codecs all have frame-lengths of 3 ms or less, and their performance at various bit rates between 8 and 4 kbitafs is examined. Next the error sensitivity of these codecs, and means of improving it, are described. Then an algebraic CELP (ACELP) [2] codec operating at 6.2 kbitsfs with a frame-length of 5 ms is described. Our final codec also uses ACELP and operates between 4.7 and 7.1 kbitsls, but it is forward adaptive and so it has a much longer frame-length of up to 30 ms. After describing this codec we compare the performance of our codecs in both error-he conditions and in the presence of channel errors. Surprisingly the error sensitivity of the low delay backward adaptive codec with no Lll' is similar to that of the forward adaptive, high delay,ACELP codec. e 1997 Academic Press

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“…Specific issues of low-rate voice coding are considered for example in [ 101, while an intelligent multimode voice transceiver is proposed in reference [14]. In our current system a programmable-rate 814 kbitls Code Excited Linear Predictive (CELP) speech codec is assumed [16] for the purposes of networking studies, but speech coding aspects are not considered here.…”

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confidence: 99%

Robust programmable‐rate wireless graphical correspondence

Hanzo

Yuen

1997

Trans Emerging Tel Tech

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Abstract. An adaptive fixed-length differential chain coding (FL-DCC) scheme is proposed for the transmission of line graphics, which canbe re-configured as a lower rate, lower resolution or higher rate. higher resolution source codec. Compared to Differential Chain Coding (DCC), the proposed FL-DCC codec has a lower coding rate in both of its lower-and higher-rate operating modes, while maintaining a similar subjective graphical quality.The dual-rate re-configurable FL-DCC codec is embedded in a voice, video multimedia communicator system, which allocates the FL-DCC graphics packets Lo idle speech packets with the aid of the Packet Reservation Multiple Access (PRMA) multiplexer. In a bandwidth of 200 kHz, which is characteristic of the Pan-European GSM system, nine speech, video and graphics multimedia users can be accommodated using bandwidth efficient 16-level Quadrature Amplitude Modulation (16QAM) over benign ~nicrocellular channels.Under less favourable propagation conditions the more robust, but less bandwidth efficient 3QAM mode of operation can be invoked. In the diversity-aided and automatic repeat request (ARQ) assisted I6QAM mode of operation the multimedia user bandwidth becomes 22.2 kHz and the minimum required channel signal to noise ratio ( S N R ) over AWCN and Rayleigh channels is about 11 and 15 dB, respectively. The most salient system features are summarised in Table 2. Telewriting is a multimedia telecommunication service enabling the bandwidth-efficient transmission of handwritten text and line graphics through fixed and wireless communication networks [2, 41. Differential chain coding (DCC) has been successfully used for graphical communications over E-mail networks or teletext systems [I], where bit rate economy is achieved by exploiting the correlation between successive vectors. A plethora of further excellent treatises were contributed to the literature of chain coding by R. Prasad and his colleagues from Delft University [I, 51. In this contribution an intelligent re-configurable graphical communications scheme is contrived, which is embedded in a voice, video multimedia system context. In the proposed fixed-length differential chain coding (FL-DCC) scheme the number of bits used to quantise the differential vectors of the so-called coding ring is dynamically adjusted under system's control, in ordei to match the prevailing bitrate, graphical quality andlor channel quality constraints. Our efforts are in line with the European Research in Advanced Communications Equipment (RACE) project's Advanced Communications Technologies and Services (ACTS) programme [6] to define a flexible third generation standard, backwardly compatible with second generation systems, while providing more advanced future features. The adaptivity of the transceiver can be exploited in numerous ways on a more static or dynamic basis, but these algorithms form part of the higher-level functions of the classic sevenlayer architechture. This contribution will concentrate on the physical layer functions, establis...

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An intelligent multimode voice communications system for indoor communications

Cited by 19 publications

References 46 publications

Bandwidth-efficient wireless multimedia communications

Bandwidth-efficient wireless multimedia communications

A Range of Low and High Delay CELP Speech Codecs between 8 and 4 kbits/s

Robust programmable‐rate wireless graphical correspondence

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