scholarly journals Uplink Multiuser MIMO-OFDM System in the Presence of Phase Noises, Power Imbalance, and Correlation

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
Xiaoming Chen ◽  
Andreas Wolfgang ◽  
Tommy Svensson
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Mimo Systems ◽  
Multiple Input Multiple Output ◽  
Base Station ◽  
Closed Form Expression ◽  
Ofdm System ◽  
Multiuser Mimo ◽  
Single Antenna ◽  
Input Multiple Output ◽  
Mimo Ofdm

The effects of phase noises (PNs), power imbalances, and correlations on multiuser orthogonal frequency division multiplexing (OFDM) multiple-input multiple-output (MIMO) systems are studied. It is assumed that each user is equipped with a single antenna, whereas the base station (BS) has multiple antennas and use zero-forcing (ZF) decoder for multiuser detection. Since each user has an independent oscillator, the received uplink (UL) signal at each BS antenna is corrupted by all of these independent PNs. Furthermore, there may be power imbalances and correlations (due to common scatterers) between different users. These impairments are jointly analyzed in this work. A closed-form expression of the mean square error (MSE) performance of the multiuser MIMO-OFDM system is derived. The analytical results are verified by simulations.

A companding approach for PAPR suppression in OFDM based massive MIMO system

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ajay Kumar Yadav ◽  
Pritam Keshari Sahoo ◽  
Yogendra Kumar Prajapati
Keyword(s):  
Massive Mimo ◽  
Orthogonal Frequency Division Multiplexing ◽  
Mimo System ◽  
Multiple Input Multiple Output ◽  
Average Power ◽  
Base Station ◽  
Convex Optimization Problem ◽  
Multiple Input ◽  
Input Multiple Output ◽  
Mimo Ofdm

Abstract Orthogonal frequency division multiplexing (OFDM) based massive multiuser (MU) multiple input multiple output (MIMO) system is popularly known as high peak-to-average power ratio (PAPR) issue. The OFDM-based massive MIMO system exhibits large number of antennas at Base Station (BS) due to the use of large number of high-power amplifiers (HPA). High PAPR causes HPAs to work in a nonlinear region, and hardware cost of nonlinear HPAs are very high and also power inefficient. Hence, to tackle this problem, this manuscript suggests a novel scheme based on the joint MU precoding and PAPR minimization (PP) expressed as a convex optimization problem solved by steepest gradient descent (GD) with μ-law companding approach. Therefore, we develop a new scheme mentioned to as MU-PP-GDs with μ-law companding to minimize PAPR by compressing and enlarging of massive MIMO OFDM signals simultaneously. At CCDF = 10−3, the proposed scheme (MU-PP-GDs with μ-law companding for Iterations = 100) minimizes the PAPR to 3.70 dB which is better than that of MU-PP-GDs, (iteration = 100) as shown in simulation results.

scholarly journals Covert Communication in MIMO-OFDM System Using Pseudo Random Location of Fake Subcarriers

2016 ◽  
Vol 4 (1) ◽  
pp. 150-163 ◽  
Author(s):  
Rizky Pratama Hudhajanto ◽  
I Gede Puja Astawa ◽  
Amang Sudarsono
Keyword(s):  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Random Sequence ◽  
Multiple Input Multiple Output ◽  
Ofdm System ◽  
Transmission Scheme ◽  
Sensitive Data ◽  
Input Multiple Output ◽  
Mimo Ofdm ◽  
Random Location

Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) is the most used wireless transmission scheme in the world. However, its security is the interesting problem to discuss if we want to use this scheme to transmit a sensitive data, such as in the military and commercial communication systems. In this paper, we propose a new method to increase the security of MIMO-OFDM system using the change of location of fake subcarrier. The fake subcarriers’ location is generated per packet of data using Pseudo Random sequence generator. The simulation results show that the proposed scheme does not decrease the performance of conventional MIMO-OFDM. The attacker or eavesdropper gets worse Bit Error Rate (BER) than the legal receiver compared to the conventional MIMO-OFDM system.

scholarly journals Channel capacity and performance evaluation of precoded MIMO-OFDM system with large-size constellation

2019 ◽  
Vol 9 (6) ◽  
pp. 5024
Author(s):  
Hussein A. Leftah ◽  
Huda N. Alminshid
Keyword(s):  
Fading Channels ◽  
Channel Capacity ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multiple Input Multiple Output ◽  
Ofdm System ◽  
Large Size ◽  
Multiple Input ◽  
Input Multiple Output ◽  
Mimo Ofdm ◽  
And Performance

<p>Multiple input-multiple output (MIMO) is a multipath diversity exploring approach which is emerged with orthogonal frequency division multiplexing (OFDM) to produce MIMO-OFDM that is widely used in wireless communications. This paper presents a discrete Hart-ley transform (DHT) precoded MIMO-OFDM system over multipath frequency-selective fading channel with large-size quadrature amplitude modulation (16-QAM, 64-QAM and 256-QAM). A mathematical models for the BER and channel capacity over mutlipath fading channels are also derived in this paper. Average Bit-error-rate (BER) and channel capacity of the presented system is considered and compared with that of the traditional MIMO-OFDM. Simulation results shows that the transmission performance and channel capacity of the proposed schemes is better than that of the traditional MIMO-OFDM without a pre-coder.</p>

scholarly journals A Survey on Massive MIMO Systems in Presence of Channel and Hardware Impairments

Sensors ◽  
2019 ◽  
Vol 19 (1) ◽  
pp. 164 ◽  
Author(s):  
Zahra Mokhtari ◽  
Maryam Sabbaghian ◽  
Rui Dinis
Keyword(s):  
Massive Mimo ◽  
Orthogonal Frequency Division Multiplexing ◽  
Mimo Systems ◽  
Low Cost ◽  
Multiple Input Multiple Output ◽  
Base Station ◽  
Aging Effects ◽  
Hardware Impairments ◽  
Single Carrier ◽  
Input Multiple Output

Massive multiple input multiple output (MIMO) technology is one of the promising technologies for fifth generation (5G) cellular communications. In this technology, each cell has a base station (BS) with a large number of antennas, allowing the simultaneous use of the same resources (e.g., frequency and/or time slots) by multiple users of a cell. Therefore, massive MIMO systems can bring very high spectral and power efficiencies. However, this technology faces some important issues that need to be addressed. One of these issues is the performance degradation due to hardware impairments, since low-cost RF chains need to be employed. Another issue is the channel estimation and channel aging effects, especially in fast mobility environments. In this paper we will perform a comprehensive study on these two issues considering two of the most promising candidate waveforms for massive MIMO systems: Orthogonal frequency division multiplexing (OFDM) and single-carrier frequency domain processing (SC-FDP). The studies and the results show that hardware impairments and inaccurate channel knowledge can degrade the performance of massive MIMO systems extensively. However, using suitable low complex estimation and compensation techniques and also selecting a suitable waveform can reduce these effects.

Spectral Efficiency in Wireless Networks through MIMO-OFDM System

2017 ◽  
pp. 249-277
Author(s):  
Shuvabrata Bandopadhaya ◽  
Jibendu Sekhar Roy
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Multiple Input Multiple Output ◽  
Wireless Channel ◽  
Estimation Methods ◽  
Ofdm System ◽  
Spectrum Utilization ◽  
High Data ◽  
Rate Transmission ◽  
Input Multiple Output ◽  
Mimo Ofdm

The traffic in Wireless Sensor Network (WSN) is brusty in nature; when any incident takes place, the data load on the channel increases suddenly demanding large channel spectrum. The scarcity of spectrum is the major technical obstacle for high data rate transmission along with better quality of service in any kind of wireless network. Hence it is very essential to enhance the spectrum efficiency of wireless channel. The major technical advancement in the physical layer which brings feasibility of broadband data transmission without increasing the transmission bandwidth or transmitting power are implementation of Multiple Input Multiple Output (MIMO) communication system with Orthogonal Frequency Division Multiplexing (OFDM) as modulation schemes. This chapter includes the fundamental concept of MIMO-OFDM system along with the channel estimation methods and the spectrum utilization issues therein.

scholarly journals Experimental Evaluation of MIMO-OFDM System with Rateless Space-Time Block Code

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Ali H. Alqahtani ◽  
Khaled Humadi ◽  
Ahmed Iyanda Sulyman ◽  
Abdulhameed Alsanie
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Multiple Input Multiple Output ◽  
Block Code ◽  
Space Time ◽  
Ofdm System ◽  
Time Block ◽  
Space Time Block Code ◽  
Field Programmable ◽  
Input Multiple Output ◽  
Mimo Ofdm

Multiple-input multiple-output (MIMO) wireless technology in combination with orthogonal frequency-division multiplexing (MIMO-OFDM) is an attractive technique for next-generation wireless systems. However, the performance of wireless links is severely degraded due to various channel impairments which cause a decoding failure and lead to packet loss at the receiver. One technique to cope with this problem is the rateless space-time block code (RSTBC). This paper presents experimental results on the performance of a 2×2 MIMO-OFDM system with RSTBC as measured in a testbed implemented with field-programmable gate array (FPGA). The average bit error rate (BER) performance of the proposed scheme is evaluated experimentally, and the results agree closely with simulation and analytical upper bound. It has been shown that RSTBC can be implemented in real-world scenarios and guarantee the reliability of loss-prone wireless channels.

scholarly journals Wavelet Transform Application Based on Matlab Simulation

2020 ◽  
Vol 36 (1) ◽  
Author(s):  
Tan Nguyen Minh ◽  
Hua-Ming Chen ◽  
Binh Duong Giap ◽  
Hoang Le Quang Nhat
Keyword(s):  
Wavelet Transform ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multiple Input Multiple Output ◽  
Simulation Software ◽  
Discrete Wavelet ◽  
Matlab Simulation ◽  
Ofdm System ◽  
High Data ◽  
Input Multiple Output ◽  
Mimo Ofdm

Multiple Input Multiple Output (MIMO) and Orthogonal Frequency Division Multiplexing (OFDM) are two combined technologies to provide the spectral efficiency and high data rate required for 4G, 5G wireless systems. Discrete Wavelet Transform (DWT) is presented as an alternative for Fast Fourier Transform (FFT) since there is no necessity for Cyclic Prefix (CP) due to the overlapping properties of DWT. By a simple replacement of the FFT with DWT in MIMO OFDM system, an improvement of performances has been detected which leads to a new system scenario DWT-based MIMO-OFDM. In this thesis, such a system is simulated and the performance of Bit Error Rate (BER) is analyzed to determine the different types of wavelets in various channel condition with different modulations (4, 16, 64 -QAM). Therefore, DWT-based MIMO-OFDM in comparison with DFT-based MIMO-OFDM system was investigated using MATLAB simulation software. And besides, I would like to refer to use Neural Network algorithms to replace Wavelet transform in the next research.

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