超小型衛星通信用端末装置

Abstract

近年、社会生活における情報通信の重要性がますます認識され、またサービスの多様化が急速に進む中、衛星通信を利用した通信ネットワークの構築は現代社会に不可欠なものとなりつつある。また、阪神・淡路大震災では、耐災害性、広域性、回線設定の容易性などの特長を十分に生かし、臨時用の通信手段として衛星通信が大活躍した。これを機に、通信サービス業者やガス・電力会社などの公的な機関を中心に、VSAT(Very Small Aperture Terminal:超小型地球局)システムを初めとする衛星通信ネットワーク導入の機運が高まっている。三菱電機では、音声、ファクシミリまたはデータ伝送が可能で、容易に持ち運びができ、設置および運用が簡単な重さ約30kgの可搬型VSAT装置を開発した。音声符号化には16kbpsLD-CELP(低遅延符号励振線形予測)方式を採用し、衛星回線の効率化を図った。また、32kbpsADPCM(適応差分パルス符号変調)方式への切換えが可能であり、従来システムにも適用できる。VSAT装置はアンテナ、ODU(Out Door Unit:屋外装置)とIDU(In Door Unit:屋内装置)からなるが、今回は特に小型で軽く、可搬性に優れたIDUを開発したので、その構成と主な特長について述べる。

In recent years, the importance of info-communication in social life get more and more recognized so that configuring communication networks which use satellite communication is just into indispensable for modern society. Furthermore, at the time when Hanshin-Awaji Earthquake occurred, satellite communication played active roles as communication means in an emergency, making full use of its features characterized by disaster resistance, expanded service area, ease of cross connection. On this occasion, tendency to introduce satellite communication network including VSAT (Very Small Aperture Terminal) are growing in these days mainly among communication service providers and public enterprise like gas or electric power corporation. Mitsubishi Electric Corporation has developed transportable VSAT equipment which is capable of voice, data or facsimile transmission, is easily transportable, and weighs about 30kg so as to ease installation and operation. The 16 kbps LD-CELP (Low Delay-Code Excited Linear Prediction) method is applied for speech coding, which improves the efficiency of satellite link. Further it allows to switchover to 32 kbps ADPCM (Adaptive Differential Pulse Code Modulation) and applicable to existing system. As IDU (In Door Unit) unit of the VSAT equipment comprising of antenna, ODU (Out Door Unit) and IDU was developed so small-sized, light and transportable, the composition and main features of IDU unit are described.