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  • Research Article
  • Open Access

Complexity-Reduced MLD Based on QR Decomposition in OFDM MIMO Multiplexing with Frequency Domain Spreading and Code Multiplexing

EURASIP Journal on Advances in Signal Processing20102011:525829

  • Received: 12 April 2010
  • Accepted: 19 August 2010
  • Published:


This paper presents a new maximum likelihood detection- (MLD-) based signal detection method for orthogonal frequency division multiplexing (OFDM) multiple-input multiple-output (MIMO) multiplexing with frequency domain spreading and code multiplexing. The proposed MLD reduces the computational complexity by utilizing signal orthogonalization based on QR decomposition of the product of the channel and spreading code matrices in the frequency domain. Simulation results show that when the spreading factor and number of code multiplexed symbols are 16, the proposed MLD reduces the average received signal energy per bit-to-noise spectrum density ratio (Eb/N0) for the average packet error rate (PER) of 10−2 by approximately 12 dB compared to the conventional minimum mean-squared error- (MMSE-) based filtering for 4-by-4 MIMO multiplexing (16QAM with the rate-3/4 Turbo code is assumed).


  • Orthogonal Frequency Division Multiplex
  • Turbo Code
  • Packet Error Rate
  • Spreading Code
  • Signal Orthogonalization

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Authors’ Affiliations

Department of Electrical Engineering, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
Radio Access Network Development Department, NTT DOCOMO, INC.,, 3-5 Hikari-no-oka, Yokosuka Kanagawa, 239-8536, Japan


© Kouji Nagatomi et al. 2011

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.