A trained sparse conjugate codebook is proposed for improving the speech quality of CELP-based coding in a noisy environment. Although CELP coding provides high quality at a low bit rate in a silent environment (creating clean speech), it cannot provide a satisfactory quality in a noisy environment because the conventional fixed codebook is designed to be suitable for clean speech. The proposed codebook consists of two sub-codebooks; each sub-codebook consists of a random component and a trained component. Each component has excitation vectors consisting of a few pulses. In the random component, pulse position and amplitude are determined randomly. Since the radom component does not depend on the speech characteristics, it handles noise better than the trained one. The trained component maintains high quality for clean speech. Since excitation vector is the sum of the two sub-excitation vectors, this codebook handles various speech conditions by selecting a sub-vector from each component. This codebook also reduces the computational complexity of a fixed codebook search and memory requirements compared with the conventional codebook. Subjective testing (absolute category rating (ACR) and degradation category rating (DCR)) indicated that this codebook improves speech quality compared with the conventional trained codebook for noisy speech. The ACR test showed that the quality of the 8 kbit/s CELP coder with this codebook is equivalent to that of the 32 kbit/s ADPCM for clean speech.

We give an efficient shortest path algorithm on a mesh-connected processor array for nn banded matrices with bandwidth b. We use a b/2b/2 semisystolic processor array. The input data is supplied to the processor array from the host computer. The output from the processor array can be also supplied to itself through the host computer. This algorithm computes all pair shortest distances within the band in 7n4b/21 steps.

We analyze the error probability performance of multi-pulse pulse position modulation (MPPM) in noisy photon counting channel. Moreover we investigate the error perofrmance of convolutional coded MPPM and RS coded MPPM in noisy photon counting channel. We define a distance between symbols as the number of nonoverlapping pulses in one symbol, and by using the distance we analyze the error performance of MPPM in noisy photon counting channel. It is shown that MPPM has better performance than PPM in the error probability performance in noisy photon counting channel. For PPM in noisy photon counting channel, convolutional codes are more effective than RS codes to reduce the average transmitting power. For MPPM in noisy photon counting channel, however, RS codes are shown to be more effective than convolutional codes.

Japan's PARTNERS Project, one of the programmes of ISY advocated by UN, has just started. This letter is a brief introduction of the trials being carried out by the partners in the University of Electro-communications under the Project. The focus is on the distance education and training via ETS-V overcoming the geographical extent and the cultural diversity of the Asia-Pacific Region.