MIMO-OFDM Wireless Communication System Research Articles

Photonic parallel channel estimation of MIMO-OFDM wireless communication systems.

Channel estimation is a key technology in MIMO-OFDM wireless communication systems. Increasingly extensive application scenarios and exponentially growing data volumes of MIMO-OFDM systems have imposed greater challenges on the speed, latency, and parallelism of channel estimation based on electronic processors. Here, we propose a photonic parallel channel estimation (PPCE) architecture which features radio-frequency direct processing. Proof-of-concept experiment is carried out to demonstrate the general feasibility of the proposed architecture at different frequency bands (100 MHz, 4 GHz, and 10 GHz). The mean square errors (MSEs) between the experimental channel estimation results and the theoretically simulated ones lie on the order of 10-3. The bit error rates (BERs) are below the pre-forward error correction (pre-FEC) threshold. Besides, we analyze the performance of PPCE under different signal-to-noise ratios (SNRs), baseband symbol forms, and weight tuning precisions. The proposed PPCE architecture has the potential to achieve high-speed, highly parallel channel estimation in large-scale MIMO-OFDM systems after the photonic-electronic chip integration.

РАЗРАБОТКА НИЗКОРАНГОВЫХ ПРОСТРАНСТВЕННЫХ ВЕКТОРОВ ПРЕДВАРИТЕЛЬНОГО КОДИРОВАНИЯ ВО ВРЕМЕННОЙ ОБЛАСТИ

In this paper we consider the alternative way of development of spatial beamforming processing algorithm in time-domain under low-rank Massive-MIMO systems. It is well-known, that the telecommunication systems, which based on spatial multiplexing technology achieve following advantages: increase the spectral efficiency in many times due to spatial channel multiplexing gain, the beamforming technology implementation (effective energy distribution in the space). The organization of spatial filtering (the beamforming vector processing) – one of the most significant tools in MIMO-OFDM multiplexing. In this paper, we consider a new spatial filtering processing approach (precoding vectors calculation), which is a significant tool in large-scale antenna systems, due to the fact of smart processing of the radio narrow-beam implementation increases the efficiency of the communication system many times over. Nowadays, the spatial filter design algorithms with low computational complexity have attracted considerable attention from researchers seeking to improve existing MIMO-OFDM wireless communication systems. In the paper we developed basic algorithms for calculating precoding vectors in the frequency domain and proposed the time-domain precoder approach with aim to achieve the complexity reduction gain. The proposed method was tested on the geometric statistical simulation channel model QuAdRiGa according to the multipath channel scenario "3GPP-3D Uma-NLoS". We provide the assessment of whole presented methods and the evaluation range of discrepancies was revealed in the form of pictures of the correlation and integral metrics. The analysis of integral cumulative distribution function of simulation results shows the relation gap between accuracy of correlation metric and losses of beamforming processing recalculation approximately -0.5 dB for 1st layer. In conclusion of paper was revealed the fact that proposed SVD factorization for each impulse response did not take into account the beams and eigenvectors distribution over the whole frequency bandwidth

Ergodic Capacity Evaluation of Multi-Hop Decode-and-Forward MIMO-OFDM Relaying Network

Spatial diversity plays a significant role in wireless communication systems, including the Fourth Generation (4G) and Fifth Generation (5G) systems, and it is expected to be a fundamental part of the future wireless communication systems as well. The Multiple-Input Multiple-Output (MIMO) technology, which is included in the IEEE 802.16j standard, still holds the most crucial position in the 4G spectrum as it promises to improve the throughput, capacity, spectral, and energy efficiency of wireless communication systems in the 2020s. This makes MIMO a viable technology for delay constrained medical and health care facilities. This paper presents an approximate closed-form expression of the ergodic capacity for the Decode-and-Forward (DF) protocol MIMO-Orthogonal Frequency Division Multiplexing (OFDM) relaying network. Although MIMO-OFDM is highly valuable for modern high-speed wireless communication systems, especially in the medical sciences, its performance degrades in multi-hop relay networks. Therefore, in this paper, an approximate closed-form expression is derived for an end-to-end ergodic capacity of multi-hop DF MIMO-OFDM wireless communication system has been presented. Monte-Carlo simulations are conducted to verify the performance of the presented analysis regarding the capacity (bits/s/Hz) for different SNR-dB values for single, 2 × 2, 4 × 4, and multi-hop DF MIMO-OFDM systems. The presented results provide useful insights for the research on the end-to-end ergodic capacity evaluation.

The Architectural Optimizations of a Low-Complexity and Low-Latency FFT Processor for MIMO-OFDM Communication Systems

Fast Fourier Transform (FFT) processor is a paramount signal processing component in MIMO-OFDM wireless communication systems. Furthermore, novel applications introduced in 5G incur much more rigorous requirements for FFT designs including complexity, latency, and re-configurability. This paper presents the VLSI architecture design and circuit implementation of a FFT processor that is jointly optimized for low-latency, low-complexity, and configurability. Specifically, the proposed architecture processes two data streams concurrently and supports power-of-two FFT sizes from 64 to 2048 symbols. Moreover, a novel data-processing sequence is presented so that data streams are processed in a time-multiplexing manner and an efficient hardware-sharing architecture can be designed. In addition, a highly efficient I/O reorder mechanism is proposed so that the memory elements are shared between processing stages and the efficiency for utilizing memory components is enhanced. Based on the architectural optimizations, two FFT processors are realized. The ultra-low latency design achieves a latency of 4 μs with 41% area reduction compared to the comparable designs. On the other hand, the ultra-low complexity structure achieves a latency of 25 μs with 24% area reduction compared to the state-of-the-art implementations.

Investigating the Performance of Various Channel Estimation Techniques for MIMO-OFDM Systems using Matlab

This paper simulates and investigates the performance of four widely-used channel estimation techniques for MIMO-OFDM wireless communication systems; namely, super imposed pilot (SIP), comb-type, spacetime block coding (STBC), and space-frequency block coding (SFBC) techniques. The performance is evaluated through a number of MATLab simulations, where the bit-error rate (BER) and the mean square error (MSE) are estimated and compared for different levels of signal-to-noise ratio (SNR). The simulation results demonstrate that the comb-type channel estimation and the SIP techniques overwhelmed the performance of the STFC and STBC techniques in terms of both bit-error rate (BER) and mean square error (MSE).

Performance Analysis of MIMO-OFDM System Based on SVD scheme under multi path selective fading channel

We consider in this paper a MIMO-OFDM wireless communication system based on pre-coding and SVD techniques, which the system has the feedback of CSI to the transmitted side. The multi path channel, delay spread, Rayleigh fading and channel noise are assumed in the simulation of the proposed system. The zero forcing method is applied for detection the data received. The goal of our study is to evaluate the BER performance and see it with different case. The BER resulted shows the improvement by using the SVD decomposition for the associated system of MIMO-OFDM. Particularly in the complex conditions of wireless channel where we considered ten paths for propagation the signals between transmitter and receiver sides. And also the contribution is appeared when the system studied keeps a good BER performance when the data rate is increased by using more transmit antenna. As we evaluated the BER of MIMO-OFDM system done for various sub-carriers and in two guard interval lengths for the OFDM system

Performance Evaluation of Encrypted Text Message Transmission in 5G Compatible Frequency-domain Subband Superposed Scheme Implemented MIMO OFDM Wireless Communication System

In this paper, an investigative study has been made on the performance evaluation of encrypted text message transmission in 5G compatible multiuser frequency-domain subband superposed (FDSS) scheme implemented MIMO OFDM wireless communication system. The 2×2 multiantenna configured simulated system under consideration incorporates modern channel coding (LDPC and Repeat and Accumulate (RA)) and signal detection (Cholesky decomposition based ZF detection, Group Detection (GD) approach aided Efficient Zero-Forcing (ZF) and Lanczos method based efficient signal detection) techniques. In the scenario of transmitting encrypted text message over AWGN and Rayleigh fading channels, it is noticeable that implementation of Repeat and Accumulate channel coding and Group Detection (GD) approach aided Efficient Zero- Forcing (ZF) signal detection techniques is very much robust and effective in retrieving transmitted text messages for all users.

Investigating the Performance of Various Channel Estimation Techniques for Mimo-Ofdm Systems Using Matlab

This paper simulates and investigates the performance of four widely-used channel estimation techniques for MIMO-OFDM wireless communication systems; namely, super imposed pilot (SIP), comb-type, spacetime block coding (STBC), and space-frequency block coding (SFBC) techniques. The performance is evaluated through a number of MATLab simulations, where the bit-error rate (BER) and the mean square error (MSE) are estimated and compared for different levels of signal-to-noise ratio (SNR). The simulation results demonstrate that the comb-type channel estimation and the SIP techniques overwhelmed the performance of the STFC and STBC techniques in terms of both bit-error rate (BER) and mean square error (MSE).

Analysis of a MIMO-OFDM Wireless Communication System Using a Binary Power Control Scheme with Radio Channel Uncertainties

Here a novel binary power control scheme is presented with radio channel uncertainty which includes path loss, Rayleigh fading, shadowing coefficient, and interference from other users to analyse the performance of MIMO-OFDM wireless communication system. From bit error rate (BER) point of view a two tier system with adjacent interference is taken into account to guarantee QoS. The main objective of this system is to optimize energy efficiency with QoS. Taking both energy efficiency and quality of service (QoS) an energy efficient binary power control with BER constraint algorithm is presented. The performance of this system is analyzed and results of the same are presented to show the effectiveness of the system presented.

Algorithms and Architectures of Energy-Efficient Error-Resilient MIMO Detectors for Memory-Dominated Wireless Communication Systems

In a broadband MIMO-OFDM wireless communication system, embedded buffering memories occupy a large portion of the chip area and a significant amount of power consumption. Due to process variations of advanced CMOS technologies, it becomes both challenging and costly to maintain perfectly functioning memories under all anticipated operating conditions. Thus, Voltage over Scaling (VoS) has emerged as a means to achieve energy efficient systems resulting in a tradeoff between energy efficiency and reliability. In this paper we present the algorithm and VLSI architecture of a novel error-resilient K-Best MIMO detector based on the combined distribution of channel noise and induced errors due to VoS. The simulation results show that, compared with a conventional MIMO detector design, the proposed algorithm provides up-to 4.5 dB gain to achieve the near-optimal Packet Error Rate (PER) performance in the 4 × 4 64-QAM system. Furthermore, based on experimental results, when jointly considering the detector and memory power consumption, the proposed resilient scheme with VoS memory can achieve up to 32.64% savings compared to the conventional K-Best detector with perfect memory.

A Combined Time and Frequency Domain Approach to Channel Estimation for SFBC MIMO-OFDM Wireless Communication System

This paper presents a combined approach to channel estimation for multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM). It uses both time domain and frequency domain information in the received signal to estimate the channel. Initial estimate of the channel is obtained using pilot assisted least square (LS) channel estimation. The estimate is further enhanced by extracting information through the received data symbols. A frequency domain approach is used to estimate the channel using pilots whereas time domain approach is used to enhance the estimate of the channel. The performance of the proposed estimator is studied under various channel models. The simulation study shows that this approach outperforms the pilot assisted least square channel estimation method. General Terms Channel Estimation, MIMO-OFDM, Wireless Communication.

Different Channel Estimation and ICI Cancellation Techniques in MIMO-OFDM Wireless Communication Systems

MIMO OFDM is one of the prominence communication schemes with multi-carrier modulation. The MIMO combined with OFDM modulation technique provides the reliable high data rate transmission over the broadband wireless channels. They have been widely studied and employed for 4G systems such as Wi-Fi, DVB- T, Wi-MAX and LTE-A. The major challenge in MIMO-OFDM systems is how to estimate the channel. The estimation of the channel is done by various algorithms such as Least Square (LS) and Minimum Mean Square Error (MMSE). The main issue in OFDM systems is the problem of ICI (Inter carrier Interference) which is due to the loss of the orthogonality between the sub-carriers and the signal transmitted.ICI self-cancellation is one of the reduction methods to reduce the ICI effect in the signal.

Soft-input iterative channel estimation for bit-interleaved turbo-coded MIMO-OFDM systems

Bit-interleaved coded modulation (BICM) is a robust multiplexing technique for achieving multiplexing gain in multiple-input multiple-output (MIMO)-orthogonal frequency division multiplexing (OFDM) systems. However, in order to benefit maximally from the various advantages offered by BICM-based MIMO-OFDM systems, availability of accurate MIMO channel state information (CSI) at the receiver end of the system is essential. Without accurate MIMO CSI, accurate MIMO demapping and coherent detection and decoding of the transmitted message symbols at the system’s receiver would be impossible. In such cases, the multiplexing gain offered by the BICM technique, as well as the higher data rate made possible by the MIMO-OFDM system, is not benefitted from in full. In this paper, we propose a soft input based decision-directed channel estimation scheme for the provision of MIMO CSI for coherent detection of signals in MIMO-OFDM systems. The proposed channel estimator works in iterative mode with a MIMO demapper and a turbo decoder, and is based on the fast data projection method (FDPM) and the variable step size normalised least mean square (VSSNLMS) algorithm. Simulation results of the proposed estimator based on the FDPM and VSSNLMS algorithms indicate better performance in comparison with the same estimator employing minimum mean square error criteria and deflated projection approximation subspace tracking algorithms for both slow- and fast-fading channel scenarios. The proposed estimator would be suitable for use at the receiver end of MIMO-OFDM wireless communication systems operating in either slow- or fast-fading channels.

Sec ured Text Message Transmission i n Pre - Channel Equalization Based Mimo - O fdm System With Implementation of Concatenated Ecb and Cfb Cryptographic Algorithm

In this paper, we made a comprehensive performance evaluative study of a secured MIMO Orthogonal FrequencyDivision Multiplexing wireless communication system with implementation of two pre channel equalization techniques such as Pre-Minimum Mean Square Error (Pre-MMSE) and Pre-Zero Forcing (Pre-ZF) under QPSK and QAM digital modulations. The simulated system deploys three channel coding techniques (1/2-rated Convolutional, CRC and BCH). In the present simulated system, text message transmission has been secured with concatenated implementation of Electronic Codebook (ECB) and Cipher Feedback (CFB) cryptographic algorithm. It is anticipated from the numerical results that the pre-ZF channel equalization based MIMO OFDM wireless communication system outperforms in QAM digital modulation and BCH channel coding under AWGN and Raleigh fading channels .In Pre-MMSE/pre-ZF channel equalization scheme, the system shows comparatively worst performance in convolutional channel coding scheme with QAM/QPSK digital modulation. It has been observed from the present study that the system performance deteriorates with increase in noise power as compared to signal power.

Performance of MIMO-OFDM system using Linear Maximum Likelihood Alamouti Decoder

A MIMO-OFDM wireless communication system is a combination of MIMO and OFDM Technology. The combination of MIMO and OFDM produces a powerful technique for providing high data rates over frequency-selective fading channels. MIMO-OFDM system has been currently recognized as one of the most competitive technology for 4G mobile wireless systems. MIMO-OFDM system can compensate for the lacks of MIMO systems and give play to the advantages of OFDM system.In this paper , the bit error rate (BER) performance using linear maximum likelihood alamouti combiner (LMLAC) decoding technique for space time frequency block codes(STFBC) MIMO-OFDM system with frequency offset (FO) is being evaluated to provide the system with low complexity and maximum diversity. The simulation results showed that the scheme has the ability to reduce ICI effectively with a low decoding complexity and maximum diversity in terms of bandwidth efficiency and also in the bit error rate (BER) performance especially at high signal to noise ratio.

Modeling and Performance Analysis of Energy Efficiency Binary Power Control in MIMO-OFDM Wireless Communication Systems

The energy efficiency optimization of the binary power control scheme for MIMO-OFDM wireless communication systems is formulated, and then a global optimization solution of power allocation is derived. Furthermore, a new energy efficiency binary power control (EEBPC) algorithm is designed to improve the energy efficiency of MIMO-OFDM wireless communication systems. Simulation results show that the EEBPC algorithm has better energy efficiency and spectrum efficiency than the average power control algorithm in MIMO-OFDM wireless communication systems.

A Virtual Channel-Based Approach to Compensation of I/Q Imbalances in MIMO-OFDM Systems

Multiple-input multiple-output (MIMO)-orthogonal frequency-division multiplexing (OFDM) scheme has been considered as the most promising physical-layer architecture for the future wireless systems to provide high-speed communications. However, the performance of the MIMO-OFDM system may be degraded by in-phase/quadrature-phase (I/Q) imbalances caused by component imperfections in the analog front-ends of the transceivers. I/Q imbalances result in inter-carrier interference (ICI) in OFDM systems and cause inaccurate estimate of the channel state information (CSI), which is essential for diversity combining at the MIMO receiver. In this paper, we propose a novel approach to analyzing a MIMO-OFDM wireless communication system with I/Q imbalances over multi-path fading channels. A virtual channel is proposed as the combination of multi-path fading channel effects and I/Q imbalances at the transmitter and receiver. Based on this new approach, the effects of the channel and I/Q imbalances can be jointly estimated, and the influence of channel estimation error due to I/Q imbalances can be greatly reduced. An optimal minimal mean square error (MMSE) estimator and a low-complexity least square (LS) estimator are employed to estimate the joint coefficients of the virtual channel, which are then used to equalize the distorted signals. System performance is theoretically analyzed and verified by simulation experiments under different system configurations. The results show that the proposed method can significantly improve system performance that is close to the ideal case in which I/Q are balanced and the channel state information is known at the receiver.

VLSI architecture of a K-best detector for MIMO–OFDM wireless communication systems

The K-best detector is considered as a promising technique in the MIMO-OFDM detection because of its good performance and low complexity. In this paper, a new K-best VLSI architecture is presented. In the proposed architecture, the metric computation units (MCUs) expand each surviving path only to its partial branches, based on the novel expansion scheme, which can predetermine the branches' ascending order by their local distances. Then a distributed sorter sorts out the new K surviving paths from the expanded branches in pipelines. Compared to the conventional K-best scheme, the proposed architecture can approximately reduce fundamental operations by 50% and 75% for the 16-QAM and the 64-QAM cases, respectively, and, consequently, lower the demand on the hardware resource significantly. Simulation results prove that the proposed architecture can achieve a performance very similar to conventional K-best detectors. Hence, it is an efficient solution to the K-best detector's VLSI implementation for high-throughput MIMO-OFDM systems.