論文

Fiber-optic transmission of 256 quadrature amplitude modulation (QAM) signals at both 10 Mb/s and 50 Mb/s transmission rates are presented. Theoretical and preliminary experimental bit error rate (BER) performance results are described for two types of 256-QAM signals. Application of error correction coding using a BCH code is very effective in optical analog intensity modulation. It is feasible to use 256-QAM signals as subcarriers in fiber distribution networks. 12 Refs.

In tandem with the development of ISDN and high-speed digital leased circuit services, network digitization has also gone ahead at a very rapid　pace. As radio transmission that carries information in the microwave band has different advantages than physically wired media, it can thus serve to complement these other systems and lend greater stability to the network as a whole. The most cost-effective way to provide service on severe fading spans is by developing an array of sophisticated countermeasures that can be deployed on particular spans. The article describes theprogress achieved to dateon technologies engineered to improve the quality　of digital microwave radio.

ＮＴＴが実用化した４・５・６ＧＨｚ帯マイクロ波ディジタル無線中継方式について，開発のねらい，方式概要，主要技術などを総合的に報告した。本方式は世界で最初に２５６ＱＡＭという超多値変調を採用し，１中継器で４００Ｍｂｉｔ／ｓの大容量伝送を行うもので，従来のアナログＦＭ通信を超える周波数利用効率が達成率が達成できた。

マルチパス・フェージング時における１６値ＱＡＭディジタル無線方式のビット誤り率分布をエラー発生要因，受信条件，伝搬路種類別に明らかにした。つぎに，それらの分布に対してエラー発生をポアソン生起と仮定して６４ｋｂ／ｓ系におけるＥＳ（エラーセコンド）値を推定した。

既設のマイクロ波ルートに導入する条件のもとで，２５６ＱＡＭ方式の実現性に関 して検討した。まず，周波数利用効率の観点から，多値ＱＡＭ変調方式が優れていることを述べた。次に，フェージング伝搬路における２５６ＱＡＭ方式のクロック速度の上限を求め，マルチキャリア方式が有効であることを示した

The experiment the authors conducted for integrated digital satellite communications is aimed at realising integrated services digital networks by satellite communication. The experiment was carried out in 1980 using the Japanese experimental communication satellite 'CS'. This experiment uses 30/20 GHz small earth stations and demand-assignment time-division　multiple-access (TDMA) systems. Communications between customer terminals, which contain video conferencing, high-speed facsimile communication,high-speed computer communication, and packet-switching signal transmission, were carried out through the experimental digital satellite link. This paper describes the configuration of the experimental　integrated digital satellite communications system and the experimental results of communications between customer terminals.

Describes a concept of multibeam high capacity transmission possible with a 30/20 GHz and 50/40 GHz domestic satellite communication system. The relationship between satellite antenna pointing accuracy and　multi-satellite interference are looked at.

The demand-assigned time division multiple access (DAK-TDMA) system has remarkable advantages with regard to effective utilization ofsatellite traffic channels and network flexibility. The DA-TDMA system is one of key　technological developments for application to integrated services　satellite digital networks (ISSDN) which transmit digitally integrated　information signals between Earth stations. The experimental DA-TDMA system designed for an ISSDN experiment hasa 20 Mbps bit rate and operates　in a fully variable demand-assignment mode. The ISSDN experiment using the　Japanese 30/20 GHz band 'CS' satellite, which is planned as the first　stage of ISSDN study in Japan, is scheduled to start in 1980. The outline　of the DA-TDMA system and the ISSDN experimental plan are presented.

The demand assignment time division multiple access (DA-TDMA) system has remarkable advantages with regard to effective utilization of　satellite traffic channels and network flexibility. The DA-TDMA system is one of several key technological developments for application to　integrated digital satellite communications, which transmit digitally　integrated information signals between earth stations. The experimental　DA-TDMA system designed for a integrated digital satellite communication　experiment has a 20 Mbps bit rate and operates in a fully variable demand　assignment mode. This paper describes an outline of the DA-TDMA system and　the experimental plan.