Feasibility evaluation of satellite VPFDM modem

摘要

NTT研究所では将来のKu帯移動衛星通信システムとして偏波周波数可変多重通信（VPFDM）を用いた偏波無追尾衛星通信を提案している。WFDMは1ユーザが両偏波を同時に利用し、偏波追尾を一切せず、偏波間干渉を受信機で補償することを特徴とする。1ユーザが両偏波を使用するため、従来課題とされたユーザ間の偏波間干渉は原理的に生じない。また、偏波追尾機構そのものが不要になり，衛星追尾アンテナの経済化・薄型化に貢献できる。NTT研究所ではVPFDMを実現するモデムを開発し、その性能評価を行った。評価の結果、0.5dB以下の特性劣化で開発モデムが偏波間干渉を補償できることを確認した。%NTT Lab. has been proposing a polarization-tracking-free Ku broadband mobile satellite communications with variable polarization frequency division multiplexing (VPFDM) for future mobile satellite communications. In VPFDM system, a single user utilizes dual polarization simultaneously and does not track the polarization status at all. Therefore, cross-polarization interference should be entailed, but it is cancelled by interference canceller in the receiver. Since different users don't share the same frequency with different polarization, the problem of mutual interference between users does not occur in the proposed VPFDM system. This means that it can eliminate the function of polarization-tracking from a user earth station and VPFDM is exceedingly preferable for an antenna that can hardly track the linear polarization status in the mobile environment. This paper overviews the concept of VPFDM and introduces a newly developed modem for VPFDM systems, and then, its feasibility is also discussed. As a result, it is confirmed that the developed modem can cancel the cross-polarization interference within the degradation of less than 0.5 dB.