A complex orthogonal WCP circular filtered multi-carrier (COW-CFMC) scheme
Résumé
In this paper, we propose a scheme that preserves the advantages of Windowed Cyclic Prefix FBMC/Circular Offset Quadrature Amplitude Modulation (WCP-COQAM) while guaranteeing the complex orthogonality. Indeed, WCP-COQAM is based on block processing and uses circular filtering in order to remove time overheads. However, like FBMC/OQAM scheme, WCP-COQAM suffers from the presence of intrinsic interference that prevents the combination with some Multiple Input Multiple Output (MIMO) techniques such as Alamouti Coding. This intrinsic interference results from the non-complex orthogonal property of WCP-COQAM and Filter Bank MultiCarrier (FBMC). In this work, we show that circular filtering makes the transmultiplexer impulse response circulant. Our proposed scheme, called COW-CFMC, exploits this circularity to restore the complex orthogonality by precoding the data symbols in each subcarrier. Thus, we show by simulation that our proposed scheme can enable Alamouti coding in a straightforward manner.