Toshio Miki

5.6 kbits/s PSI-CELP of the half-rate PDC speech coding standard

A pitch synchronous innovation-CELP (PSI-CELP), proposed by NTT DoCoMo in 1993, is adopted as the Japanese half-rate PDC (personal digital cellular) speech codec standard. This algorithm is based on CELP (code excited linear prediction) with a pitch synchronized excitation source. It uses 3.45 kbit/s out of 5.6 kbit/s for speech coding and the remaining 2.15 kbit/s for error protection. The paper summarizes the standardized PSI-CELP algorithm. The techniques used to improve speech quality, to reduce computational complexity, and to reduce memory requirements are mentioned. A real time operating prototype based on this algorithm is also described.<<ETX>>

End-to-end QoS provisioning in mobile heterogeneous networks

The ability to provide seamless and adaptive quality of service (QoS) in a heterogeneous environment is the key to the success of the next generation wireless communication systems. There has been a considerable amount of QoS research going on recently but the main portion still occurred in the context of individual architecture components and much less progress has been made in addressing the issue of an overall QoS architecture for the mobile Internet. In this article the state-of-the-art QoS techniques and standardization activities are summarized. Important challenges in building a ubiquitous QoS framework over the heterogeneous environment are examined in detail. Then a three-plane QoS framework based on QoS signaling architecture and policy framework is proposed to provide seamless support for future applications.The remarkable advances in information technologies bring a heterogeneous environment for mobile users and service providers. This heterogeneity exists in wireless access technologies, networks, user terminals, applications, service providers, and so on. The ability to provide seamless and adaptive quality of service in such a heterogeneous environment is key to the success of next-generation wireless communications systems. There has been a considerable amount of QoS research recently. However, the main part of this research has been in the context of individual architectural components, and much less progress has been made in addressing the issue of an overall QoS architecture for the mobile Internet. This article first summarizes the state-of-the-art QoS techniques and standardization activities, then examines in detail important challenges in building a ubiquitous QoS framework over the heterogeneous environment, and finally proposes a QoS framework integrating a three-plane network infrastructure and a unified terminal cross-layer adaptation platform to provide seamless support for future applications.

QoS framework for mobile heterogeneous networks

The ability to provide seamless and adaptive quality of service (QoS) in heterogeneous environment is the key to the success of the next generation wireless communication systems. There has been a considerable amount of QoS research going on recently but the main portion still occurred in the context of individual architecture components and much less progress has been made in addressing the issue of an overall QoS architecture for the mobile Internet. In this article, the state-of-the-art QoS techniques and standardization activities are summarized. Important challenges in building ubiquitous QoS framework over the heterogeneous environment are examined in detail. Then a three-plane QoS framework based on QoS signaling architecture and policy framework is proposed to provide seamless support for future applications.

The Overview of the 4 th Generation Mobile Communication System

In order to satisfy the expectation of the users to have more advanced wireless access even in the mobile environments, research and development efforts for realizing the fourth-generation (4G) mobile communication system has been discussed. This paper outlines the requirements for the system, technical challenges to be solved, and finally describes the activities related to the standardization of the 4G mobile communication system

Joint optimization of model and excitation in parametric speech coders

This paper presents a new Analysis-by-Synthesis (AbS) technique for joint optimization of the excitation and model parameters based on minimizing the closed loop synthesis error instead of the linear prediction error. By minimizing the synthesis error, the analysis and synthesis stages become more compatible. Using a gradient search in the root domain, model parameters for a given excitation are optimized to minimize the error between the original and the synthesized speech. Since the optimization starts from the LPC solution, the synthesis error is guaranteed to be lower than that obtained using the LPC coefficients. For multipulse LPC, there is a 0.5–1 dB improvement in the segmental SNR for male and female speakers over 4 to 6 second long sentences. Listening tests and objective MOS scores confirm the improved speech quality. By adding an extra optimization step, the technique can be incorporated into the LPC, multi-pulse LPC and CELP-type speech coders.

Enhanced-reality multimedia communications for 4G mobile networks

4G mobile networks are expected to provide advanced media communications services. The paper proposes three enhanced-reality technologies (3D audio, 3D video and biological information), and introduces a prototype reality audio/visual communications system. Finally, the requirements placed on future networks, that are to provide reality media services, are discussed.

Joint optimization of model and excitation in CELP-type speech coders

This paper presents a new analysis-by-synthesis (AbS) technique for joint optimization of the excitation and model parameters based on minimizing the closed loop synthesis error instead of the linear prediction error. By minimizing the synthesis error, the analysis and synthesis stages become more compatible. Using a gradient search in the root domain, model parameters for a given excitation are optimized to minimize the error between the original and the synthesized speech. Since the optimization starts from the LPC solution, the synthesis error is guaranteed to be lower than that obtained using the LPC coefficients. For the ITU G.729 speech codec there is about 1dB of improvement in the segmental SNR for male and female speakers over 4 to 6 second long sentences. By adding an extra optimization step, the technique can be incorporated into any parametric coder such as LPC, multi-pulse LPC and CLEP-type speech coders in a bit stream compatible manner.

An Error Protected Transform Coder for Cellular Mobile Radio

Recently, medium bit rate speech waveform coders have been receiving much attention for use in digital mobile radios. 13 kbit/s RPE-LTP ( Regular Pulse Excitation with Long Term Prediction) [1] with 9.8 kbit/s error correction coding has been standardized for the Pan-European digital mobile radio systems to be introduced in 1991. 13 kbit/s speech coding, including 5 kbit/s error correction, has been investigated for the next digital cellular radio systems in the USA.

Evaluation system for mobile radio speech codec

A multifunctional speech quality evaluation system has been developed to test the performance of mobile radio speech codecs. This system is characterized by a simple hardware configuration, a variety of software functions, and general interface specifications. Major degradation factors in mobile radio communications are taken into account, e.g., Rayleigh fading channel errors and background noise. The effects of PSTN, including transmission loss, noise, delay, and echo, are also considered. This evaluation system was used in the full-rate speech codec standardization for the Japanese digital cellular system in 1990.<<ETX>>