Alternative Spreading Code を用いたFractional Sampling OFCDM システム

摘要

高速・大容量通信を実現する方式として，直交周波数符号分軸多重（OFCDM）が注目されている．本報告ではOFCDMにおいて，シングルアンテナにてダイバーシチを得るFractional Sampling（FS）と呼ばれる技術の適用を考える．FSを用いたOFCDM受信機はパスダイバーシチにより特性を改善する．しかし，サブキャリア数とオーバーサンプリング比の増加によるノイズ間の相関はパスダイバーシチの効果に影響を与える．そこで提案システムでは，Alternative Spreading CodeをFSOFCDMシステムに適用しこの影響を軽減する．%The Orthogonal Frequency and Code Division Multiplexing (OFCDM) has received large attention as a modulation scheme to realize high data rate transmission. In this paper, the OFCDM system with Fraction Sampling (FS) is investigated. FS is a diversity scheme with a single antenna, which achieves path diversity through oversampling and parallel signal reception. However, the correlation among noise components may deteriorate the bit error rate (BER) performance at the receiver as the number of subcarriers and oversampling ratio increases. To overcome this problem, the alternative spreading code is used for the FS OFCDM system. Numerical results through computer simulation show that the proposed scheme can improve the performance of the receiver with large oversampling ratio.