A system and method for transmitting high speed data on fixed rate and for variable rate channels. The system and method provides the flexibility of adjusting the data rate, the coding rate, and the nature of individual retransmissions. Further, the system and method supports partial soft combining of retransmitted data with previously transmitted data, supports parity bit selection for successive retransmissions, and supports various combinations of data rate variations, coding rate variations, and partial data transmissions.

Hybrid ARQ schemes with soft combining in variable rate packet data applications

Microprocessors and microsystems

The techniques according to the present invention can be used to optimize signal transmission according to the quality of service (QOS) required or requested at the receiver/destination/client. Such optimization can take into account actual user requirements, human perception minimum requirement or application specific requirements. Scaling can also be provided based on the size of the network or the number of users on the network. The quality of service requirement seeks to trade off or balance quality, complexity, delay, and data rate. In other words, the QOS techniques of the present invention seeks to minimize delay and maximize throughput. That is, to maximize quality within constraints.

System and method of quality of service signaling between client and server devices

Computing solutions used in mobile communications equipment are similar to those in personal and mainframe computers. The key differences between the implementations at chip level are the low leakage silicon technology and lower clock frequency used in mobile devices. The hardware and software architectures, including the operating system principles, are strikingly similar, although the mobile computing systems tend to rely more on hardware accelerators. As the performance expectations of mobile devices are increasing towards the personal computer level and beyond, power efficiency is becoming a major bottleneck. So far, the improvements of the silicon processes in mobile phones have been exploited by software designers to increase functionality and to cut development time, while usage times, and energy efficiency, have been kept at levels that satisfy the customers. Here we explain some of the observed developments and consider means of improving energy efficiency. We show that both processor and software architectures have a big impact on power consumption. Properly targeted research is needed to find the means to explicitly optimize system designs for energy efficiency, rather than maximize the nominal throughputs of the processor cores used.

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Observations on power-efficiency trends in mobile communication devices

In this paper, we investigate the combination of complementary acoustic feature streams in large-vocabulary continuous speech recognition (LVCSR). We have explored the use of acoustic features obtained using a pitch-synchronous analysis, Straight, in combination with conventional features such as Mel frequency cepstral coefficients. Pitch-synchronous acoustic features are of particular interest when used with vocal tract length normalization (VTLN) which is known to be affected by the fundamental frequency. We have combined these spectral representations directly at the acoustic feature level using heteroscedastic linear discriminant analysis (HLDA) and at the system level using ROVER. We evaluated this approach on three LVCSR tasks: dictated newspaper text (WSJCAM0), conversational telephone speech (CTS), and multiparty meeting transcription. The CTS and meeting transcription experiments were both evaluated using standard NIST test sets and evaluation protocols. Our results indicate that combining conventional and pitch-synchronous acoustic feature sets using HLDA results in a consistent, significant decrease in word error rate across all three tasks. Combining at the system level using ROVER resulted in a further significant decrease in word error rate.

/pdf/combining-spectral-representations-for-large-vocabulary-2o8b6f6qgw.pdf

Combining Spectral Representations for Large-Vocabulary Continuous Speech Recognition

A variable bit rate coder, and an associated method, for encoding a frame of speech, such as frames of data generated during operation of a communication station operable in a cellular communication system. Selection of the coding rate is made responsive to indicia of actual coding performance of a coder at more than one coding rate.

Variable bit rate coder, and associated method, for a communication station operable in a communication system

A novel paradigm based on pitch-adaptive windows is proposed for solving the problem of encoding the fixed codebook excitation in low bit-rate CELP coders. In this method, the nonzero excitation in the fixed codebook is substantially localized to a set of time intervals called windows. The positions of the windows are adaptive to the pitch peaks in the linear prediction residual signal. Thus, high coding efficiency is achieved by allocating most of the available FCB bits to the perceptually important segments of the excitation signal. The pitch-adaptive method is adopted in the design of a novel multimode variable-rate speech coder applicable to CDMA-based cellular telephony. Results demonstrate that the adaptive windows method yields excellent voice quality and intelligibility at average bit-rates in the range of 2.5-4.0 kbps.

Pitch adaptive windows for improved excitation coding in low-rate CELP coders

Component-based development of DSP software for mobile communication terminals

A significant improvement in the efficiency of excitation coding with CELP at low bit rates is achieved by a new paradigm for encoding the fixed excitation. In the proposed scheme, the non-zero fixed-codebook excitation elements are substantially localized in a set of windows, with positions adaptive to the pitch peaks. Highly efficient coding is thus achieved by allocating most of the available excitation bits to capture the essential excitation events. The paradigm is validated by computer simulation of a variable-rate speech codec. The performance of the codec is evaluated by informal subjective tests and compared with TIA standard variable rate speech codecs. The results indicate that the proposed scheme can be used to reproduce speech at average bit rates from 2.3 to 3.4 kbps (i.e., in a two-way communication scenario) with very high quality and intelligibility.

A novel approach to excitation coding in low-bit-rate high-quality CELP coders

A new paradigm for efficient coding of the fixed-codebook excitation in CELP coders at low-bit rates is presented. In this scheme, the non-zero components of the fixed-codebook excitation are localized to a set of windows whose locations are dependent on the pitch frequency and on the energy contour of a modified residual signal. Highly efficient coding is thus achieved by allocating most of the fixed excitation bits to capture the essential excitation events. The paradigm is validated by computer simulation of a variable-rate speech codec. The performance of the codec is evaluated by informal subjective tests comparing it with TIA standard variable rate speech codecs. The results confirm that the proposed scheme can be used to reproduce speech at average bit rates from 2.3 to 3.4 kbps with very high quality and intelligibility.

Ryan Heidari

Papers

Variable bit rate coder, and associated method, for a communication station operable in a communication system

Pitch adaptive windows for improved excitation coding in low-rate CELP coders

Component-based development of DSP software for mobile communication terminals

A novel approach to excitation coding in low-bit-rate high-quality CELP coders

Adaptive window excitation coding in low-bit-rate CELP coders