The Alamouti Scheme with CDMA-OFDM/OQAM

This paper deals with the combination of OFDM/OQAM with the Alamouti scheme. After a brief presentation of the OFDM/OQAM modulation scheme, we introduce the fact that the well-known Alamouti decoding scheme cannot be simply applied to this modulation. Indeed, the Alamouti coding scheme requires a complex orthogonality property; whereas OFDM/OQAM only provides real orthogonality. However, as we have recently shown, under some conditions, a transmission scheme combining CDMA and OFDM/OQAM can satisfy the complex orthogonality condition. Adding a CDMA component can thus be seen as a solution to apply the Alamouti scheme in combination with OFDM/OQAM. However, our analysis shows that the CDMA-OFDM/OQAM combination has to be built taking into account particular features of the transmission channel. Our simulation results illustrate the 2×1 Alamouti coding scheme for which CDMA-OFDM/OQAM and CP-OFDM are compared in two different scenarios: (i) CDMA is performed in the frequency domain, (ii) CDMA is performed in time domain

On the decoding of single delay STTC using filter bank based multicarrier modulation

Filter bank based multi-carrier (FBMC) is a multi-carrier modulation scheme that can be considered as an alternative to conventional OFDM with cyclic prefix (CP-OFDM) for transmission over multi-path fading channels. Compared to CP-OFDM, FBMC can provide a higher information bit rate, since it operates without the addition of a CP. Furthermore, FBMC enables the use of different pulse shapes therefore; it can provide better frequency localization than CP-OFDM. Since FBMC is based on real orthogonality, the association with MIMO techniques needs specific decoding schemes. In this paper we consider the combination of FBMC with a single delay space time trellis code (STTC). We propose an iterative decoding based on interference estimation and cancellation which does not require any channel coding or decoding block. We show that if we omit the CP loss of CP-OFDM and by using this FBMC decoding scheme we outperform CP-OFDM in single delay STTC context, this with only a slight increase in complexity