MIMO Interleaved SC-FDMA繰り返し受信方式における球内復号による演算量削減の検討

摘要

本稿では，MIMO Interleaved SC-FDMA(MIMO Interleaved Single Carrier-Frequency Division Multiple Access)方式の受信機構成につき，まず周波数領域等化(FDE: Frequency Domain Equalization)による仮判定後に，ISI(Inter-Symbol Interference)キャンセラーでISIを除去し，次にMLDを用いて送信アンテナストリーム間の空間多重分離を行って復調信号を得て，さらにこれを改善された仮判定値として用いISIキャンセルとMLD(Maximum Likelihood Detection)を繰り返す受信機構成を提案する.さらにMLDの演算量を削減するため，MLDの代わりに最尤解の得られるSD(Sphere Decoding)を適用し，計算機シミュレーションによりBER特性と演算量削減効果を検証する.また，提案受信機構成をLDPC符号化した場合に対し，信頼度の高いLDPC復号結果を再びISIキャンセラーにフィードバックし，これを繰り返すことで，更なるBER特性の改善を図った.%In this paper, we propose the receiver structure for MIMO Interleaved SC-FDMA (MIMO Interleaved Single Carrier-Frequency Division Multiple Access) where the FDE (Frequency Domain Equalization) is firstly done for obtaining the tentative decision results and secondly using the tentative results the ISI (Inter-Symbol Interference) is cancelled by ISI canceller and then the MLD is made for separating the spatially multiplexed signals. Furthermore the output from MLD is fed back to ISI canceller and this feedback is iteratively repeated. In order to reduce the complexity of the proposed receiver structure, we replace the MLD by SD (Sphere Decoding). We examine the BER characteristics and the complexity reduction through computer simulations. Also, we apply LDPC encoding to the proposed receiver and the LDPC decoding results with high reliability are fed back to ISI canceller and this feedback is repeated for further improving the BER.