Simple Transmit Diversity Scheme Research Articles

Coded OFDM-IM With Transmit Diversity

In this paper, we propose a simple transmit diversity scheme for orthogonal frequency division multiplexing (OFDM) with index modulation (IM) in order to achieve a diversity gain for index detection, which can significantly improve the performance of OFDM-IM at the cost of the spectral efficiency. An optimal approach for active index detection is derived, which has a complexity, growing linearly with the size of OFDM symbol. A salient feature of the proposed transmit diversity scheme is that it can be easily employed in conjunction with a conventional coding scheme for data symbols. Consequently, we can implement coded OFDM-IM together with the proposed transmit diversity scheme in a straightforward manner, which can provide a good performance under a frequency-fading environment.

I/Q-Imbalance Self-Interference Coordination

In this paper, we present a novel low-complexity scheme, which improves the performance of single-antenna multi-carrier communication systems, suffering from in-phase and quadrature (I/Q)-imbalance (IQI) at the receiver. We refer to the proposed scheme as I/Q-imbalance self-interference coordination (IQSC). IQSC does not only mitigate the detrimental effects of IQI, but, through appropriate signal processing, also coordinates the self-interference terms produced by IQI in order to achieve second-order frequency diversity. However, these benefits come at the expense of a reduction in transmission rate. More specifically, IQSC is a simple transmit diversity scheme that improves the signal quality at the receiver by elementary signal processing operations across symmetric (mirror) pairs of subcarriers. Thereby, the proposed transmission protocol has a similar complexity as Alamouti's space-time block coding scheme and does not require extra transmit power nor any feedback. To evaluate the performance of IQSC, we derive closed-form expressions for the resulting outage probability and symbol error rate. Interestingly, IQSC outperforms not only existing IQI compensation schemes but also the ideal system without IQI for the same spectral efficiency and practical target error rates, while it achieves almost the same performance as ideal (i.e., IQI-free) equal-rate repetition coding. Our findings reveal that IQSC is a promising low-complexity technique for significantly increasing the reliability of low-cost devices that suffer from high levels of IQI.

Channel Estimation for TDS-OFDM System with Transmit Diversity

A simple transmit diversity scheme based on cyclic-shift pseudo noise (PN) sequences for the time domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) system is proposed and the corresponding channel estimation algorithms are also investigated. Simulation results are presented to verify the effectiveness of the proposed method.

Performance sensitivity comparison of two diversity schemes

A recently proposed simple transmit diversity (STD) scheme was shown to have the same performance as the classical maximal-ratio combining (MRC) receiver under the assumption that the amplitude and phase of the Rayleigh faded channel are known exactly at the receiver. An analysis and comparison of the performance degradations of the STD scheme and MRC receiver due to errors in estimating the channel parameters are presented. It is shown that the bit error rate degradation for the STD scheme can be significantly worse than that of an MRC receiver.