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Projeto de investigação
DETECÇÃO DE MÚLTIPLOS UTILIZADORES EM SISTEMAS CDMA CODE DIVISION MULTIPLE ACCESS
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Turbo multiuser detection for MC-CDMA signals with strongly nonlinear transmitters
Publication . Silva, Paulo; Dinis, Rui
In this paper we consider the uplink transmission in MC-CDMA (multicarrier -coded division multiple access) systems. Since MC-CDMA signals are OFDM-like multicarrier signals, they have high envelope fluctuations and a high PMEPR (Peak-to-Mean Envelope Power Ratio) which leads to amplification difficulties. To reduce the envelope fluctuations of the transmitted signals, while maintaining the spectral efficiency, the MC-CDMA signal associated to each MT (mobile terminal) is submitted to a clipping device, followed by a frequency-domain filtering operation. However, the nonlinear distortion effects can be high when an MC-CDMA transmitter with reduced envelope fluctuations is intended. In this paper, we define an iterative receiver that jointly performs a turbo-MUD (Multiuser Detection) and the estimation and cancellation of the nonlinear distortion effects. The set of simulation results presented shows that the proposed receiver structure allows good performances, very close to the linear receiver ones, even for high system load and/or when a low-PMEPR is intended for each MT.
Turbo equalization with cancellation of nonlinear distortion effects for CP-Assisted and Zero-Padded MC-CDMA signals
Publication . Dinis, Rui; Silva, Paulo; Araújo, Teresa
We consider MC-CDMA schemes, with reduced envelope fluctuations. Both CP-assisted (cyclic prefix) and ZP (zero-padded) MC-CDMA schemes are addressed. We develop turbo FDE (frequency-domain equalization) schemes, combined with cancelation of nonlinear distortion effects. The proposed turbo receivers allow significant performance improvements at low and moderate SNR, even when the transmitted signals have reduced envelope fluctuations.
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Fundação para a Ciência e a Tecnologia
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Número da atribuição
SFRH/BD/24520/2005