Space-time Transmit Diversity Scheme Research Articles

Novel polar-coded space-time transmit diversity scheme over Rician fading MIMO channels

In this paper, a polar-coded space-time transmit diversity (STTD) scheme is proposed in order to improve the performance of multiple-input multiple-output (MIMO) system. In Rician fading MIMO channels, the corresponding polar-coded STTD system can be equivalent to a single transmission channel for each polar code bit. Density evolutions for the polar-coded STTD systems are proposed based on the analyses of the single transmission channel. The proposed density evolutions provide preferable guidance to construct polar codes for the polar-coded STTD systems. Simulation results show that the BER performance of polar-coded STTD system is significantly improved as the number of antennas increases and the influence of the variable Rician K-factor of MIMO channels gradually vanishes. The proposed 2 × 2 polar-coded STTD system can provide better frame error rate (FER) performance than low-density parity-check (LDPC)-based system under low and mid code rates, and the average advantage is 0.3 dB approximately when the code rate is 0.25 and 0.2 dB when the code rate is 0.5.

BER Performance of MPSK and MQAM in 2x2 Almouti MIMO Systems

Almouti published the error performance of the 2x2 space-time transmit diversity scheme using BPSK. One of the key techniques employed for correcting such errors is the Quadrature amplitude modulation (QAM) because of its efficiency in power and bandwidth.. In this paper we explore the error performance of the 2x2 MIMO system using the Almouti space-time codes for higher order PSK and M-ary QAM. MATLAB was used to simulate the system; assuming slow fading Rayleigh channel and additive white Gaussian noise. The simulated performance curves were compared and evaluated with theoretical curves obtained using BER tool on the MATLAB by setting parameters for random generators. The results shows that the technique used do find a place in correcting error rates of QAM system of higher modulation schemes. The model can equally be used not only for the criteria of adaptive modulation but for a platform to design other modulation systems as well.

Performance Analysis of Alamouti Transmit Diversity with QAM in Imperfect Channel Estimation

In this paper, the performance of multi-level quadrature amplitude modulation (M-QAM) systems is studied analytically when Alamouti space-time transmit diversity (STTD) coding is used for transmission over Rayleigh fading channels. The effect of self-interference (interference from another simultaneously transmitted symbol in the STTD scheme for the same user) due to imperfect channel estimation is investigated. Based on the characteristic function method, a closed-form expression of the bit error rate (BER) is derived. Numerical results for 16/64-QAM show that, with the Alamouti STTD technique, the BER performance of the QAM system can be improved significantly. The effect of receive antenna diversity is also investigated. It is shown that high-order QAM constellations can be employed even in low signal to noise ratio (SNR) with the transmit diversity technique in conjunction with receive antenna diversity.

Analysis of MIMO Band-Limited DS-CDMA Systems in the Presence of Multitone Jamming Over Generalized-$K$ Fading Channels

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In this paper, we study the effects of different pulse shapes on the bit-error-rate (BER) performance of a space-time transmit diversity scheme for band-limited direct-sequence code-division multiple-access (DS-CDMA) systems in the presence of multitone jamming (MTJ) over generalized-<formula formulatype="inline"><tex Notation="TeX">$K$</tex> </formula> fading channels. We consider a space-time system with two transmitter and multiple receiver antennas. Two types of band-limited pulse shapes, namely, spectrum raised cosine (SRC) and Beaulieu–Tan–Damen (BTD) pulses, are considered in the BER performance of the conventional matched-filter receiver, the decorrelator receiver, and the minimum-mean-square-error (MMSE) receiver. Numerical results show that the system with BTD pulse outperforms the system with SRC pulse, and the MMSE receiver gives the best BER performance among the three receivers considered. </para>

Combining Orthogonal Space Time Block Codes with Adaptive Sub-group Antenna Encoding

An adaptive space time transmit diversity scheme with simple feedback is proposed for the next generation wireless communication systems. By combining orthogonal space time block codes with adaptive sub-group antenna encoding, this new diversity scheme can effectively exploit the diversity potential provided by multiple antenna arrays without introducing interference among the signals transmitted at different antennas. In order to reduce the amount of feedback information as well as the computational complexity, a new quadrant phase constraining method is introduced to formulate the feedback information. With simple operations at both the transmitter and the receiver, the new adaptive diversity scheme outperforms not only open loop space time block encoding techniques, but also some close loop transmit diversity techniques with the same amount of feedback.