Mitsugu Ohkawa

COMETS 21-GHz advanced satellite broadcasting experiments-evaluation of trellis-coded 8-PSK performance

An advanced satellite broadcasting system using 21 GHz has been studied by using the high-power (200 W) and wideband (120 MHz) transponders on the Communication and Broadcasting Engineering Test Satellite (COMETS), which was launched 21 February 1998. A highly effective trellis-coded eight-phase-shift-keying (TC8PSK) modem was developed for the COMETS satellite broadcasting experiments, and this paper describes the degradation in the bit error performance of the TC8PSK modem due to the nonlinear amplification (AM/AM distortion and AM/PM conversion effects), group-delay distortion, and amplitude-frequency characteristics of the satellite transponder. The results of the COMETS experiments and computer simulations indicate that the performance degradation is due primarily to the nonlinear distortion and the amplitude-frequency characteristics of the traveling wave tube amplifiers in the transponder.

High-Speed Satellite Network Experiments using 622/1244 Mbps Modems

The National Institute of Information and Communications Technology (NICT) has developed a 622/1244 Mbps high-speed satellite communications network using the Wideband Internet Engineering Test and Demonstration Satellite (WINDS). A 622/1244 Mbps dual-rate burst modems were also developed. The high-speed dual rate burst modem is designed for the user data rates of 622 Mbps and 1244 Mbps with a single carrier of QPSK modulation. 622/1244 Mbps transmission test using the WINDS was conducted. The results showed that the Eb/No ratio required to achieve a BER at 10 -10 with FEC was less than 10 dB and 13 dB for 622 Mbps and 1244 Mbps respectively. They also showed that operation as a TDMA satellite communications system for using a 622/1244 Mbps burst modem and a three-dimensional 4KHDTV transmission experiment was successfully performed by this system.

EFFECT OF ADAPTIVE MODULATION AND ERROR CORRECTION ON MULTI-BAND OFDM-MIMO SYSTEM

We have devised a new system for forming the antenna beam in a com- bined OFDM and MIMO scheme. In this scheme, the OFDM signal is divided among multiple bands, and the divided signals are transmit- ted on an appropriate beam of each sub-band. In this paper, We have described the system configuration of the proposed multi-band OFDM- MIMO scheme for use over multipath wireless channels. And, we have discussed the performance of adaptive modulation and error correction of the system.