Estimating Markov Model Parameters from Statistical Analysis of Speech Packets Transmitted over BWA Networks

The main problem encountered in the design of Markov models is in choosing the adequate mathematical model for their representation. Analysis of the mathematical models of speech packet sources was conducted on the basis of Markov chains. The specific characteristics of telephony dialogue and monologue were taken into consideration. These in their turn can be used in the design of methods of statistical companding of packet communication nodes. In this paper we show that the choice of the number of states of the Markov chain as well as their probabilistic characteristics can be estimated from the results of the statistical processing of speech packets transmitted over Broadband Wireless Access Networks (BWAN). Keywords: Markov models, Wireless network, Speech processing, Packet switching, Mathematical model

Estimating the Quality of Digitally Transmitted Speech over Satellite Communication Channels

Analogue speech signal is one of the most natural means used by humans for communication purposes. The emergence of digital modulation and coding techniques has made the transmission of analogue speech (as digital content) over various conduits possible, albeit with inevitable signal degradation as a result of errors inherent in the conversion process. A need naturally arises for determining the quality of speech received at the information sink, with a view to enhancing its robustness to degradation suffered in transit over the communication channel. We present in this paper analytic methods of qualitative assessment of the quality of recovered digitally transmitted speech. A methodology for determining the intelligibility of speech by using segmental SNR gotten by dividing the speech signal into M integer segments is proposed. This methodology has the following advantages: a) it allows for assessing the dynamics of change of speech quality in real-time through statistical modeling, b) it obviates the need for expensive, yet subjective experimental approaches like MOS, and c) it takes into consideration not only the signal power, but also its spectral characteristics which is a step above the use of Modulated Noise Reference Units (MNRUs). Using the obtained results, a procedure for analysis of speech intelligibility by means of statistical modeling is developed. Keywords: Speech processing, Mean opinion score, MOS, SNR, PCM, Quantization nois