# NSU Research Contributions

### Title : High-Rate Full-Diversity Space-Time-Frequency Code for Multiuser MIMO-OFDM Systems over Frequency Selective Multiple Access Channels

**Authors : **R. Shelim, A.U.Alam, and M.A. Matin

**Abstract : **In this paper, we have proposed a new space-time-frequency (STF) code for multiuser multipleinput-multiple-output orthogonal-frequency-division-multiplexing (MIMO-OFDM) systems to increase the spectral efficiency. For each user, the proposed code can achieve high symbol rate (rate- ) with full diversity ( ), where denotes the number of transmit antenna for each user, denotes number of receive antenna at the receiver, represents the number of independent fading block in the codeword and L denotes the number of independent channel taps. This STF code has been constructed from a threaded algebraic layering concept, which combines the space-frequency layering with algebraic component codes. The component code is considered to be an algebraic number theoretic constellation. Each component code is assigned to a “thread” and interleaved over space time and frequency. Diophantine approximation theory is then used to make the threads transparent to each other. In addition, another approximation is used so that the users become transparent to each other. Our STF code does not require the cooperation among the users in uplink process and also does not
require zero-padding, which always ensures high symbol rate. The proposed coding schemes are bandwidth efficient as the data streams of all the users are sent simultaneously through all the OFDM sub-channels. Simulation results show that our proposed coding schemes achieve higher coding and diversity gain over recently proposed space-frequency codes.

Journal : Journal of Convergence Information Technology |
Volume : 6 |
Year : 2011 |
Issue : 8 |

Pages : pp. 8-22 |
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