Seung-Jun Yu

Enhanced Lattice-Reduction aided detection for MIMO systems with QRD-M detector

In this letter, an efficient MIMO detection scheme combined with a QRD-M and a complex LR-aided detection scheme is proposed. For the first T stages, the QRD-M detection is executed, and then the complex LR-aided detection is executed for the last Nt-T stages. Simulation results show that the proposed scheme provides the comparable detection performance to the QRD-M. Also, the proposed scheme can significantly reduce the computational complexity compared with the QRD-M because the computations for the QRD-M is limited by the parameter T. The value of T is determined by the required system performance.

A Combination of STBC and SM Scheme with Iterative Detection in LTE Systems

This paper proposes an adaptive iteration detection scheme for a combination of STBC and SM scheme in LTE systems. The hybrid space-time block code system is a combination of STBC and SM scheme. It obtains both diversity gain and spectral efficiency gain. The conventional combination of STBC and SM scheme can’t achieve good BER performance of STBC symbols due to interference from other symbols. The iterative V-BLAST detection scheme improves BER performance but has complex iterative detection process. The proposed scheme applies the adaptive iterative detection scheme by channel condition and can reduce complexity of LTE systems. LTE systems require high speed. Therefore, this scheme can be applied effectively in LTE systems.

Smart Cooperative System Using Orthogonal Signaling with Signal Space Diversity

In this paper, an efficient cooperative transmission scheme with signal space diversity is proposed for two-user cooperative systems. In contrast with the conventional cooperative scheme based on orthogonal signaling, the proposed scheme obtains signal space diversity by utilizing rotated constellation. Because the proposed scheme provides much information to receiver in decoding process, a receiver can decode information more accurately. Therefore, the proposed scheme improves the bit error rate performance in severe fading channel environments. Simulation results demonstrate that the performance of the proposed scheme is especially superior to the performance of the conventional scheme in low inter-user channel quality.

Efficient Decoding Scheme for Cooperative Communication Using Hierarchical Modulation in the Mobile Communication Systems

In this paper, an efficient decoding scheme for cooperative communication using hierarchical modulation in the mobile communication systems is proposed to obtain better bit error rate performance than conventional scheme. Inevitably, superimposed low priority stream has worse performance than high priority stream in hierarchical modulation. A new approach on hierarchical modulation as a diversity scheme is proposed. The proposed scheme includes two key ideas. The first one is signal separation of hierarchically modulated symbol to eliminate noisy factor. The second one is the combination of signal after process of signal separation to obtain diversity gain. Simulation results show that the proposed scheme outperforms conventional scheme on bit error rate performance without loss of rate.

Hybrid MIMO Cooperative Scheme for Improved Throughput in Wireless OFDM Systems

In this paper, a new hybrid multiple-input multiple-output (MIMO) cooperative scheme is proposed in wireless orthogonal frequency division multiplexing (OFDM) systems. MIMO–OFDM systems have allowed the improvement of the system performance as reliability and data rate. However, MIMO–OFDM systems have limitations of supporting reliable transmission and high data rate due to size, cost and complexity limitation of device. So, the hybrid MIMO cooperative communication has been studied to compensate the defects. The hybrid MIMO cooperative scheme has advantages of MIMO and cooperative communication. But the conventional hybrid MIMO cooperative scheme has a few defects under particular environments. So, the proposed hybrid MIMO cooperative scheme supplements the defects of the conventional schemes.

A Multi-relay Cooperative Communication Using Space Time Spatial Phase Coding Based on OFDM

Among schemes to obtain diversity gain, space-time block code (STBC) and spatial phase coding (SPC) have been widely studied for the cooperative wireless relaying system. However, conventional STBC has a problem that cannot deal with change in the number of relays due to low throughput. In this paper, we propose a SPC that multi-relay transmission is possible and a space-time spatial phase coding (STSPC) using the proposed SPC scheme and STBC. The STSPC scheme provides improved bit error rate performance and full rate.