Showing papers in "IEICE Transactions on Communications in 1997"

A Hierarchical Image Transmission System for Multimedia Mobile Communication

Abstract: This paper proposes a new mobile image transmission system based on the hierarchical modulation scheme for achieving a high quality and high speed digital image transmission in a band-limited fading channel. The proposed system uses a hierarchical QAM (quadrature amplitude modulation) scheme to give unequal transmission reliability depending on the significance of DCT (discrete cosine transform) based compressed images. Computer simulation results show that the proposed system is an effective high-quality and high-speed image transmission technique in the band-limited fading channel.

Throughput Improvement of CDMA Slotted ALOHA Systems

Abstract: An electrical connector having a deformable tubular shell between a cable and fitting manufactured by a process of magnetically deforming the shell at one end to the underlying cable and at the other end to the underlying fitting to provide a superior EMI and shielding integrity as well as a good water tight seal without the need of potting the connection or providing special seal elements.

A Modified Code Tracking Loop for Direct-Sequence Spread-Spectrum Systems on Frequency-Selective Fading Channels

Abstract: A modified fully-digital code tracking loop is proposed in this paper for direct-sequence spread-spectrum signaling on a frequency-selective fading channel. A data-modulated channel estimator is used to cope with the time-varying Rayleigh fading effect and the data modulation effect, and extract the desired error signal from each path independently in the multipath environments. By taking advantage of the inherent diversity with the maximal ratio combining (MRC) or a proposed Even/odd maximal ratio combining (EMRC) technique, this modified code tracking loop can avoid the problem due to the drift or flutter effects of the error characteristics, and provide better performance on frequency selective fading channels. Extensive computer simulation has verified the analysis and indicated very attractive behavior of the proposed digital tracking loop.