Modified SC-Type Turbo Detection Using SISO-MLD for CCI Suppression in SDM-OFDM Systems

Shoichi SASAHARA  Takahiko SABA  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E90-A    No.9    pp.1854-1861
Publication Date: 2007/09/01
Online ISSN: 1745-1337
DOI: 10.1093/ietfec/e90-a.9.1854
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Information Theory and Its Applications)
SDM,  OFDM,  CCI,  turbo detection,  

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In space division multiplexing with orthogonal frequency division multiplexing (SDM-OFDM) systems, since co-channel interference (CCI) degrades the demodulation performance, CCI suppression is essential. For CCI suppression, the turbo detector using the soft-input soft-output maximum likelihood detector (SISO-MLD) is proposed. Although SISO-MLD can deal with soft information, SISO-MLD updates only a priori information of code bits at each iteration. This prevents the performance to be improved. Meanwhile, a turbo detector with soft cancellation (SC) followed by minimum mean square error (MMSE) filter, in which the variance of the residual interference components as well as a priori information can be updated at each iteration, is well known. However, the performance of SC/MMSE detector is also limited because it is proposed to reduce the computational complexity at the cost of performance degradation. In this paper, we propose an SC-type turbo detector which uses SISO-MLD for SDM-OFDM systems. In our proposed detector, the soft cancellation unit of the SC-type turbo detector is modified to cope with the SISO-MLD. From the simulation results, the proposed SC/MLD provides a better BER performance than the turbo detector using SISO-MLD. Furthermore, the proposed SC/MLD can attain the bit error rate (BER) equivalent to that of the SC/MMSE detector with a smaller computational complexity.