Double Space-time Transmit Diversity System Research Articles

On Angle Feedback and Antenna Shuffling in Double Space-Time Transmit Diversity Systems

In this letter, we compare angle feedback and transmit antenna shuffling schemes for double space-time transmit diversity (DSTTD) systems with four transmit antennas and at least two receive antennas. We show that a DSTTD system with one bit of angle feedback does not provide better performance than the same system with one bit of transmit antenna shuffling. We also present a simplified general result about the selection of antenna shuffling matrix from six permutation matrices to facilitate our arguments. In simulation, we observe that antenna shuffling outperforms angle feedback in i.i.d. Rayleigh fading channels.

Antenna Selection with Superposition for 4 x 2 DSTTD Systems

From 1820 4 times 4 binary matrices, 253 binary preprocessing matrices are designed for double space-time transmit diversity (DSTTD) systems with two 2 times 2 space-time block code (STBC) encoders. Among them, six matrices yielding the highest average minimum-post-processing SNR are proposed from numerical experimentation under uncorrelated channel conditions. The proposed preprocessing performs a superposition of the first and second (second and first) STBC symbols and a selection of two transmit antennas. Simulation results show that the proposed method provides 1.7 dB (1.8 dB) SNR improvement in uncorrelated (correlated) channel environment at 10-3 bit error rate over the conventional antenna shuffling method.

Performance Analysis of the D-STTD Communication System with AMC Scheme

In this paper, we propose a Double-Space Time Transmit Diversity (D-STTD) communication system with Adaptive Modulation and Coding (AMC) scheme and analyze its performance using simulation experiments. The simulation results show that the probability of selecting a high Modulation and Coding Scheme (MCS) level increased as the Signal to Noise Ratio (SNR) improved. Furthermore, the D-STTD communication system with AMC scheme provided a more uniform throughput distribution throughout the entire SNR range compared to its counterpart which did not apply AMC scheme. Also, the maximum throughput of the D-STTD communication system with AMC scheme was twice that of a conventional AMC communication system or a Space Time Transmit Diversity (STTD) communication system with AMC scheme.

Approaching maximum-likelihood performance with reduced complexity for a double space–time transmit diversity system

A reduced-complexity detector approaching maximum-likelihood (ML) detection performance is presented for the double space–time transmit diversity system. The proposed scheme exploits both the special structure of equivalent channel matrix and decision-feedback detection. This accounts for accomplishing near-ML or ML performance with significantly relieved computational loads. Moreover, to moderate the average complexity, several distance metric selection criteria are proposed. We can control performance and computational savings according to different distance metric selection rules. Numerical results show that the proposed detector requires significantly fewer computations than that of the Schnorr–Euchner sphere-decoding algorithm in terms of both the worst-case and the average complexity.

Error Performance of Double Space Time Transmit Diversity System

The theoretical error performance of double space time transmit diversity (DSTTD) system with optimum combining receiver is analyzed in this paper. By employing both spatial multiplexing and transmit diversity in one system, DSTTD provides practical tradeoff between system spectral efficiency and diversity gain. We derive exact analytical expressions to describe the symbol error rate for DSTTD systems. The effects of both diversity gain and antenna interference introduced by spatial multiplexing are quantified in the results. In addition, the performance of DSTTD system with successive interference cancellation is also investigated. Simulation results are in excellent agreement with the theoretical results obtained in this paper.

A Computationally Efficient Criterion for Antenna Shuffling in DSTTD Systems

The application of double space-time transmit diversity (DSTTD) scheme to multicarrier systems, such as orthogonal frequency division multiplexing (OFDM) systems, requires calculating the determinations of the antenna permutation matrices for all subcarriers, resulting in a heavy computation load. In this paper, we show that the signal-to-noise ratio (SNR)-based antenna shuffling criterion for DSTTD systems can be reduced to a simple criterion that evaluates determinants of 2 times 2 submatrices of the 4 times 4 equivalent channel matrix. The new criterion can lighten the computational load by about 95%. Furthermore, it is shown that the minimum mean square error (MMSE)-based criterion for antenna permutation can also be reduced to the same criterion.

A simplified adaptive modulation scheme for D-STTD systems with linear receivers

In this letter, we consider D-STTD (Double Space Time Transmit Diversity) with an adaptive modulation (AM) scheme. The simple criteria for AM are proposed according to linear receivers and the corresponding AM schemes are derived to minimize bit error rate under the constraint of the total data rate and total transmit power. The D-STTD system using the proposed AM scheme requires low computational complexity and small feedback information. The performance of D-STTD system using the proposed scheme is improved by 7 dB or more in signal to noise ratio corresponding to 10/sup -4/ bit error rate.