Sequential Adaptive Predictors for ADPCM Speech Encoders

The sequential gradient estimation predictor is compared in detail to the stochastic approximation predictor, and both are evaluated in an ADPCM codec. A switched predictor having two coefficients is then described for use in a DPCM-AQF codec. This predictor divides the range of the correlation coefficient of the speech signal into zones, and as the correlation coefficient changes zones, the predictor coefficients undergo a substantial modification. By this method the adaptation rate of the predictor is improved, particularly during transitions between unvoiced and voiced sounds.     

Air interface access schemes for broadband mobile systems

High bandwidth everywhere is a key requirement of future communication systems. The big challenge is that the mobile user also be able to benefit. The UMTS, a member of the IMT-2000 family of systems, will offer global universal services up to 2 Mb/s for the mass market in the near future. For users demanding more capacity for “bit-hungry” high-quality applications, broadband mobile radio access systems are being developed, such as wireless LANs and the Mobile Broadband System. In this article broadband mobile systems are classified, taking into account services and quality, spectrum, and standardization issues. The practical experiences gained in two European research projects-ATM Wireless Access Communication System (AWACS) and System for Advanced Mobile Broadband Applications (SAMBA)-are described. Finally, a realistic look at possible future deployment is given     

Effect of welding wire and groove angle on mechanical properties of high strength steel welded joints

Mechanical properties of high strength steel welded joints strictly depend on the welding process, the filler material composition and the welding geometry. This study investigates the effects of using cored and solid welding wires and implementing various groove angles on the mechanical performance of weld joints which were fabricated employing the gas metal arc welding process. It was found that weld joints of low alloy, high strength steels using low alloy steel cored welding wires exhibited higher tensile strength than that of low alloy steel solid wire and chromium‐nickel steel bare welding wire when the method of gas metal arc welding is employed. The effect of groove angle on the strength and toughness of V‐groove and double V‐groove butt‐joints was investigated. V‐groove joints, with higher tensile strength than double V‐groove joints in the whole range of groove angles, were superior in toughness for small groove angles, but impact toughness values of both joints were comparable for large angles. The effect of heat input and cooling rate on the weld microstructure and weld strength was also investigated by performing thermal analysis employing the commercial software ANSYS. It was concluded that cooling rate and solidification growth rate determined the microstructure of the weld zone which had great consequences in regard to mechanical properties.     

Effect of instant controlled pressure drop process on some physicochemical and nutritional properties of snacks produced from chickpea and wheat

The chickpea and wheat seeds were processed using laboratory‐scale equipment of instant controlled pressure drop process (DIC) to produce nutritious snack products. In this study, we present the results concerning the effect of various DIC‐processing variables, moisture content, steam pressure and processing time on some physicochemical (water absorption (WAI) and water solubility (WSI) indices) and nutritional properties (total phenolic and phytic acid contents, starch gelatinisation and digestibility values). Among the DIC‐processing conditions, processing pressure and time had the highest significance rather than the moisture content. DIC process increased the total phenolic content of chickpea by approximately twofold, whereas it usually decreased in that of wheat. Severe processing conditions such as long processing time and high steam pressures generally led to an increase in WAI, WSI and starch gelatinisation as well as phenolic content, but a decrease in the antinutritional factor of phytic acid content within the working limit of the study. DIC treatment significantly increased the level of starch gelatinisation and digestibility of snack products.     

Race-UMTS for third generation wireless communications

Universal mobile telecommunication system (umts) is a projected European standard of the ccir defined future public land mobile telecommunication systems (fplmts) for third generation mobile communications. Race mobile project is studying issues related to umts. Race is the European Commission’s programme on research and development in advanced communications in Europe. The main purpose of this programme is to introduce an integrated broadband communications network (ibcn) so that it provides an universal standard telecommunications system across Europe, with the capacity to meet demand in the early 21st. century. The purpose of this paper is two fold. The first one is to make the reader familiar with the Race mobile project which is partially funded by Commission of European Community (cec). The second one is devoted to the activities in the project since its start in 1988 and major results up to now. Further, the paper describes many techniques investigated within the project with respect to umts requirements.     

Overview of the mobile communications programme of RACE II

The paper provides a general overview of the main research activity on the Universal Mobile Telecommunications System (UMTS) and the Mobile Broadband System (MBS) within the European Union's RACE II programme. The main characteristics, innovations and trends with regard to cell types, services, network architectures and radio interfaces are discussed. Evolutionary aspects of interworking with other existing and emerging terrestrial networks are also discussed     

Spectrum management, pricing, and efficiency control in broadbandwireless communications

The radio spectrum is a unique, ubiquitous natural resource shared by various types of services. Unlike many other natural resources, it can be repeatedly reused. In practice, though, it remains a finite resource, and it can only accommodate a limited number of simultaneous users. This restriction requires careful planning and management for maximizing its value for all services. This is especially true since the demand for communication spectrum worldwide is rapidly increasing. As the pressure on spectrum increases with a generalized image of radio techniques, traditional ways to assess the merits of new technical solutions and to allocate as well as to tax frequencies appear to be adapted less and less. This paper reviews the present situation and stresses the need for more proactive, harmonized, and dynamic approaches linking technical and regulatory aspects in order to introduce broadband wireless communications systems     

Simplified fast least-squares algorithms for speech predictors

The letter deals with the development of a simplified fast least-squares algorithm which is free of roundoff error accumulation. The simplified algorithm requires 9N MADPR (multiplications and divisions per recursion) rather than 10N MADPR as in the fast least squares or fast Kalman (FLS) case where N is the order of predictor. The superiority of SFLS over FLS and LMS approaches is illustrated by prediction gain performance curves for various speech signals