Providing voice and data communications to people away from their wireline telephones has become a major communication frontier. This frontier is being penetrated by evolving approaches to portable communications, e.g., cordless telephones, mobile radiotelephone, and radio paging. However, these approaches have many limitations; none can provide universal portable communications services. This paper discusses limitations of the evolving approaches and considers objectives and approaches for providing more universal digital portable communications as an integrated part of telephone exchange networks. These more universal communications could be accomplished by using demand-assigned radio links for the last thousand feet or so of telephone loops and sharing the remainder of the fixed distribution facilities. Fixed radio ports as integrated parts of telephone distribution networks could be placed throughout service regions. Efficient use of the radio spectrum could be insured by the planned reuse of radio frequencies throughout the regions. The severe multipath radio propagation environment within and around buildings that strongly influences the design of portable communications systems is described in the paper. System configurations and radio link techniques, that can provide reliable communications in the multipath environment, are discussed. Radio system calculations are illustrated for radio ports with 30-ft-high antennas in residential areas. The calculations indicate that radio link availability would be greater than 99 percent for 2000-ft port separations and 5-mW portable transmitters. Reuse of frequencies would require dividing the allocated frequency band into segments for use at adjacent ports. Calculations suggest that link availability in the cochannel interference environment would be greater than 99 percent, if 25 to 35 segments were used in residential areas.

Universal digital portable radio communications

Fast algorithms for computation of the discrete cosine transform (DCT) are evaluated. Implementation via the fast Fourier transform and also by the direct method are considered. DCT algorithms for arbitrary sequence lengths are also included.

http://ieeexplore.ieee.org/iel4/5502/14788/00671464.pdf

Fast computational algorithms for the discrete cosine transform

Design of a real-time French text-to-speech system

This report discusses quality–of–service (QOS) issues for telephone networks. Deregulation and divestiture have fostered increased competition in the United States in the telephone equipment and service industries. There are many economic, policy, and technical issues that remain to be solved as the result of the plethora of equipment and services now available. This report addresses the technical problems associated with the interconnection of equipment from many vendors. In order to maintain a satisfactory quality of service to the end user, performance standards must be developed, approved, and implemented. The work of IEEE, CCITT, and ANSI–accredited standards groups responsible for telephone QOS is reviewed. The problem of interconnecting different national networks in the international community is seen to be analogous, in part, to the problem of interconnecting the numerous public and private networks within the United States. Although progress has been made by both national and international telephone QOS standards groups, unsolved issues remain. Principal among these are the development of objective measures of voice quality, the mapping of these objective measures into five levels of quality, enhancement of IEEE and CCITT telephony QOS standards (including the development of standards for the transmission of data on voiceband networks), and the development of QOS standards for Integrated Services Digital Networks. These are discussed in this report along with recommendations for new programs that would contribute to their resolution.

Voiceband Quality–Of–Service Issues in the Post Divestiture Environment

This paper considers the possibility of introducing packetized voice traffic into a packet-switched network. It is well known that the network must assure voice packets sufficient delay characteristics for conversational speech, i.e., low delay between speaker and listener and low delay jitter or variance. To reach these goals, simplified protocols and priority rules for voice handling are proposed and evaluated. A model of a packet switching node structure capable of handling both data and voice is derived for both analytical and simulation approaches. The use of low bit rate voice encoders is considered. The necessity of avoiding the transmission of silent intervals is discussed in relation to the behavior of packet voice receivers. Proposed strategies are compared by means of analytical tools and simulation experiments considering the presence of voice, interactive, and batch data packets.

Coded Speech in Packet-Switched Networks: Models and Experiments

THE field of digital speech is rapidly coming to fruition as an area of opportunity for commercial application. In this paper we attempt to give a broad tutorial overview of some of the key aspects of this technology. We briefly outline some of the basic properties of speech and the techniques of coding that use these properties and point to areas of current research and areas of practical hardware implementation. We also attempt to outline some of the potential application areas for this new technology.

Current perspectives in digital speech

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Current perspectives in digital speech