Improved Multiband Excitation Research Articles

Application of auditory masking in improved multiband excitation model

Modifications to improve the performance of the improved multiband excitation (IMBE) model in coding narrow-band speech are presented in this paper. The first modification is based on the phenomenon of auditory masking which helps the model to focus on the perceptual aspect of the coder by eliminating components that are inaudible to human ears during the analysis process of the IMBE model. In addition, a spectral amplitude enhancement stage is added. Preliminary results indicate that the proposed modifications improve the objective and subjective performances of the IMBE model in coding narrow-band speech at 4.15 kbps.

Multiresolution joint source-channel coding appliedto Fourier magnitudes ofvoice spectrum

Application of multiresolution joint source-channel coding to the Fourier magnitudes of the improved multi band excitation speech coder when transmitted through a Rayleigh fading channel is described. A multiresolution algorithm was developed for a vector source and a solution proposed for the empty cell problem.

Capacity of a wireless LAN with voice and data services

The capacity of a carrier sense multiple-access wireless LAN with voice and data services using the TCP/IP protocol is analyzed to obtain a lower bound for the capacity of the wireless networks with voice and data services. The voice traffic is given a higher priority over the data traffic to accommodate the delay requirement for an acceptable quality of service. This is implemented by assigning the TCP protocol for data and the UDP protocol for voice. The relationship between the data throughput and the number of the voice users supported in this environment is analyzed by using a nonpreemptive queuing model. While the analysis in this paper can be applied to any voice encoding system, the improved multiband excitation voice encoding technique is adopted to provide a low transmission rate with an acceptable quality.

Pitch synchronous multi-band (PSMB) coding of speech signals

A novel speech coding algorithm, named pitch synchronous multi-band (PSMB), is proposed. The new coding algorithm uses the multi-band excitation (MBE) model to generate a representative pitch-cycle waveform (PCW) for each frame. The representative PCW of a frame is encoded by two out of three codebooks depending upon whether the frame is related or unrelated to the previous frame. When a frame is related to its previous frame, the PCW is encoded by a length-converted-excitation (LCE) codebook and a stochastic codebook. The codevectors of the LCE codebook are derived from the previous PCW. When a frame is unrelated to its previous frame, it is encoded by a bandlimited single pulse excitation (BSPE) codebook and the stochastic codebook. The new speech coder introduces a pitch-period-based coding feature. It overcomes some weaknesses existing in the improved MBE (IMBE) speech coder. The PSMB coder operating at 4 kbps outperforms the Inmarsat 4.15 kbps IMBE coder by a clear margin. Our listening tests also indicate that it is slightly better than the FS1016 4.8 kbps code excited linear predictive (CELP) coder in terms of perceptual quality. Fast search algorithms for the three codebooks used in PSMB are also developed. The fast algorithms render the new speech coder comparable to the FS1016 CELP coder, in terms of computational complexity.

Experimental quantification of voice transmission quality of mobile-satellite personal communications systems

The design and analysis of an experiment, which was conducted in order to assess the subjective impact of transmission delay on mobile voice communications via a satellite, are presented. This study was conducted using simulated end-to-end propagation delays representative of low Earth orbit (LEO) and geostationary Earth orbit (GEO) networks (single and double-hop) in combination with three different speech coding technologies: 64 kb/s pulse code modulation, 8 kb/s vector-sum excited linear prediction, and 4.15 kb/s improved multiband excitation (representing wireline, cellular, and mobile satellite technologies, respectively). Subsequent analysis included computation of the cross-correlation between the delay and coding method, from which it was concluded that for "wireline-quality" and "communications-quality" circuits the transmission performance somewhat degraded as the propagation delay increased to that of a double-hop GEO circuit. However, for "communications quality" circuits employing the 4.15 kb/s speech coding algorithm, the transmission performance remained constant as propagation delay increased.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Magnetic tape recording of television pictures

Modifications to improve the performance of the improved multiband excitation (IMBE) model in coding narrow-band speech are presented in this paper. The first modification is based on the phenomenon of auditory masking which helps the model to focus on the perceptual aspect of the coder by eliminating components that are inaudible to human ears during the analysis process of the IMBE model. In addition, a spectral amplitude enhancement stage is added. Preliminary results indicate that the proposed modifications improve the objective and subjective performances of the IMBE model in coding narrow-band speech at 4.15 kbps.