Novel Design and Implementation of MIMO Antenna for LTE Application

The quest for achieving high bandwidth connectivity that renders a complete wireless system ideal for video-intensive applications at very low power consumption using multiple inputs/multiple outputs (MIMO) dual-band combo chip with high-speed is ever-growing. A newly designed structure of the MIMO antenna four ports is implemented for efficient bandwidth broadening. The bandwidth and Sparameters of the antenna are simulated and determined. The dual-band MIMO micro-strip patch antenna comprised of four ports where the ground plane is extruded on a substrate having area 125x128 mm2 and thickness 1.6 mm. The antenna is fabricated on an inexpensive FR4 with the dielectric constant of 4.5, loss tangent ~0.019 and patch thickness of 0.035 mm. The MIMO antenna with dimension 53.5x38.25 mm2 operates at 1.8 and 2.6 GHz. The proposed antenna is found to achieve good pattern diversity, low correlation coefficient, high gain, excellent directivity, and quite reasonable bandwidth in the abovementioned range, highly suitable for LTE bands application with 10 dB return loss. The CST microwave studio program is used for the simulation, and real experimental measurements are made using Agilent Technologies E5071B VNA and the equipment inside the anechoic chamber. Measurements on the prototype antenna are carried out, and characteristic evaluations are performed for comparison. The admirable features of the results suggest that our systematic approach may constitute a basis for the design and implementation of MIMO antenna for diverse LTE applications

Design and analysis of large MIMO systems with Krylov subspace receivers

This paper studies large multiple-input multiple-output (MIMO) communication systems with line ar precoding and reduced-rank Krylov subspace receivers. We design precoders and analyze their performance by exploiting large-dimensional random matrix theory. We first devise low-complexity precoding schemes that can improve performance of low-rank Krylov subspace receivers in the regime of high signal-to-noise ratio (SNR). We then introduce a potential theory-based method for analyzing the convergence behavior of the mean-squared error (MSE) for various transmission schemes. This method can be applied to a broader range of problems compared to previous analytical tools. The analysis reveals that the MSE decreases superexponentially with the rank of the receiver. Numerical examples show that the proposed precoders can outperform conventional precoders when low-rank Krylov subspace receivers are used, and that the performance of such receivers can be accurately predicted

Reduced complexity detection for massive MIMO-OFDM wireless communication systems

PhD ThesisThe aim of this thesis is to analyze the uplink massive multiple-input multipleoutput with orthogonal frequency-division multiplexing (MIMO-OFDM) communication systems and to design a receiver that has improved performance with reduced complexity. First, a novel receiver is proposed for coded massive MIMO-OFDM systems utilizing log-likelihood ratios (LLRs) derived from complex ratio distributions to model the approximate effective noise (AEN) probability density function (PDF) at the output of a zero-forcing equalizer (ZFE). These LLRs are subsequently used to improve the performance of the decoding of low-density parity-check (LDPC) codes and turbo codes. The Neumann large matrix approximation is employed to simplify the matrix inversion in deriving the PDF. To verify the PDF of the AEN, Monte-Carlo simulations are used to demonstrate the close-match fitting between the derived PDF and the experimentally obtained histogram of the noise in addition to the statistical tests and the independence verification. In addition, complexity analysis of the LLR obtained using the newly derived noise PDF is considered. The derived LLR can be time consuming when the number of receive antennas is very large in massive MIMO-OFDM systems. Thus, a reduced complexity approximation is introduced to this LLR using Newton’s interpolation with different orders and the results are compared to exact simulations. Further simulation results over time-flat frequency selective multipath fading channels demonstrated improved performance over equivalent systems using the Gaussian approximation for the PDF of the noise. By utilizing the PDF of the AEN, the PDF of the signal-to-noise ratio (SNR) is obtained. Then, the outage probability, the closed-form capacity and three approximate expressions for the channel capacity are derived based on that PDF. The system performance is further investigated by exploiting the PDF of the AEN to derive the bit error rate (BER) for the massive MIMO-OFDM system with different M-ary modulations. Then, the pairwise error probability (PEP) is derived to obtain the upper-bounds for the convolutionally coded and turbo coded massive MIMO-OFDM systems for different code generators and receive antennas. Furthermore, the effect of the fixed point data representation on the performance of the massive MIMO-OFDM systems is investigated using reduced detection implementations for MIMO detectors. The motivation for the fixed point analysis is the need for a reduced complexity detector to be implemented as an optimum massive MIMO detector with low precision. Different decomposition schemes are used to build the linear detector based on the IEEE 754 standard in addition to a user-defined precision for selected detectors. Simulations are used to demonstrate the behaviour of several matrix inversion schemes under reduced bit resolution. The numerical results demonstrate improved performance when using QR-factorization and pivoted LDLT decomposition schemes at reduced precision.Iraqi Government and the Iraqi Ministry of Higher Education and Scientific researc