scholarly journals An Adaptive Power and Bit Allocation Algorithm for MIMO OFDM/SDMA System Employing Zero-Forcing Multi-user Detection

2006 ◽  
Vol 2 (2) ◽  
pp. 63
Author(s):  
Peerapong Uthansakul ◽  
Marek E Bialkowski
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Multiple Input Multiple Output ◽  
Zero Forcing ◽  
Space Division Multiple Access ◽  
Multiple User ◽  
Input Multiple Output ◽  
Mimo Ofdm ◽  
One Step ◽  
User Access ◽  
Adaptive Power

The paper describes an adaptive algorithm for power and bit allocations in a multiple user Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing (MIMO OFDM) system with Space Division Multiple Access, which operates in a frequency selective fading channel. The zero forcing (ZF) technique is applied to accomplish multi user detection (MUD). A Lagrange multiplier method is applied to obtain a one-step solution for optimal power and bit allocations in this system. The resulting algorithm is advantageous over an alternative Greedy algorithm, because it does not require a time-consuming iterative procedure for its implementation. The algorithm assigns bits and power for all users according to the channel state information (CSI), which is assumed to be fully or partially available to the transmitter. The simulation results show the proposed algorithm operates successfully in multiple user access scenarios.

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>

A New Method for MIMO-OFDM Channel Estimation Based on Discrete Wavelet Transform

2012 ◽  
Vol 182-183 ◽  
pp. 2066-2070
Author(s):  
Hui Shi ◽  
Ren Wang Song ◽  
Gang Fei Wang
Keyword(s):  
Wavelet Transform ◽  
Channel Estimation ◽  
Discrete Wavelet Transform ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multiple Input Multiple Output ◽  
Mimo Channel ◽  
Discrete Wavelet ◽  
Input Multiple Output ◽  
Estimation Scheme ◽  
Mimo Ofdm

This paper puts forward a suitable channel estimation scheme for multiple input multiple output and orthogonal frequency division multiplexing system (MIMO-OFDM) based on discrete wavelet transform. According to the least-squares standard (LS), this plan uses pilot to estimate the unit impulse response of MIMO channel firstly, then does wavelet denoising in changing domain, in order to reduce the frequency spectrum leakage and improve the estimation precision. At the same time, this method does not need to know channel information in advance, and can follow up the changes of channel on time with good error rate performance.

Joint Channel Estimation and Data Detection for STBC MIMO-OFDM Wireless Communication System

2015 ◽  
Vol 24 (04) ◽  
pp. 1550059 ◽  
Author(s):  
Gajanan R. Patil ◽  
Vishwanath K. Kokate
Keyword(s):  
Channel Estimation ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multiple Input Multiple Output ◽  
Data Detection ◽  
Channel Estimate ◽  
Multiple Input ◽  
Input Multiple Output ◽  
Mimo Ofdm ◽  
The Cost ◽  
Joint Channel

This paper presents a joint channel estimation and data detection technique for multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) system. Initial estimate of the channel is obtained using semi-blind channel estimation (SBCE). The whitening rotation (WR)-based orthogonal pilot maximum likelihood (OPML) method is used to obtain the channel estimate. The estimate is further enhanced by extracting information through the received data symbols. The performance of the proposed estimator is studied under various channel models. The simulation study shows that this approach gives better performance over training-based channel estimation (TBCE) and OPML SBCE methods but at the cost of higher computational complexity.

scholarly journals Phase Noise Effect on MIMO-OFDM Systems with Common and Independent Oscillators

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Xiaoming Chen ◽  
Hua Wang ◽  
Wei Fan ◽  
Yaning Zou ◽  
Andreas Wolfgang ◽  
...  
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Multiple Input Multiple Output ◽  
Spatial Multiplexing ◽  
Ofdm Systems ◽  
Error Vector Magnitude ◽  
Multiple Input ◽  
Input Multiple Output ◽  
Mimo Ofdm ◽  
Value Decomposition ◽  
Vector Magnitude

The effects of oscillator phase noises (PNs) on multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems are studied. It is shown that PNs of common oscillators at the transmitter and at the receiver have the same influence on the performance of (single-stream) beamforming MIMO-OFDM systems, yet different influences on spatial multiplexing MIMO-OFDM systems with singular value decomposition (SVD) based precoding/decoding. When each antenna is equipped with an independent oscillator, the PNs at the transmitter and at the receiver have different influences on beamforming MIMO-OFDM systems as well as spatial multiplexing MIMO-OFDM systems. Specifically, the PN effect on the transmitter (receiver) can be alleviated by having more transmit (receive) antennas for the case of independent oscillators. It is found that the independent oscillator case outperforms the common oscillator case in terms of error vector magnitude (EVM).

scholarly journals Overview of Beyond 4G-LTE Wireless Transmission Technologies

2019 ◽  
Vol 7 (6) ◽  
pp. 74-77
Author(s):  
Ms. Shalini ◽  
Anoop Tiwari
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Multiple Input Multiple Output ◽  
Point Of View ◽  
Wireless Transmission ◽  
Remote Transmission ◽  
Multiple Input ◽  
Input Multiple Output ◽  
Mimo Ofdm ◽  
4G Lte

Non-orthogonal multiple access (NOMA) is a promising applicant innovation for 5G cell systems. By and by MIMO-OFDM remote innovations are utilizing in 4G LTE development remote correspondence. This paper examine about the job of MIMO-OFDM and NOMA as principal contributing execution factors in past 4G LTE Remote Transmission Innovation from a specialized point of view. Long Term Evolution (LTE) utilizes Orthogonal Frequency Division Multiplexing (OFDM) along with MIMO (Multiple Input Multiple Output) reception apparatus innovation standard to accomplish high radio spectral efficiency and multicarrier approach for multiple accesses.

scholarly journals Fractional weighted ZF equalizer: A novel approach for channel equalization in MIMO-OFDM system under impulse noise environment

2021 ◽  
Vol 6 (1) ◽  
pp. 1-10
Author(s):  
S. P. Girija ◽  
Rameshwar Rao
Keyword(s):  
Error Rate ◽  
Orthogonal Frequency Division Multiplexing ◽  
Impulse Noise ◽  
Multiple Input Multiple Output ◽  
Symbol Error Rate ◽  
Mitigation Strategy ◽  
Ofdm System ◽  
Noise Mitigation ◽  
Zero Forcing ◽  
Mimo Ofdm

Impulse noise is the major factor degrading the performance of the wireless system, imposing the need for the impulse noise mitigation strategy. Mainly, in the multiple-input multiple-output (MIMO) and orthogonal frequency-division multiplexing (OFDM) system contaminated with the impulse noise creates a major impact in the performance as the conventional zero-forcing (ZF) equalizer as there is no satisfactory results. Thus, the paper concentrates on the impulse noise mitigation strategy based on the fractional weighed zero-forcing (FWZF) equalizer, which is the integration of the fractional concept in the Zero-Forcing equalizer. The noise impacts in the MIMO-OFDM system are minimized and the performance is enhanced due to the usage of the fractional theory in the ZF equalizer as the equalization values of the previous instances are interpreted for the formulation of the effective equalization value in the current instance of the ZF equalizer. The performance of the methods is done based on the valuation metrics, Bit Error Rate (BER), Mean Square Error (MSE), and Symbol Error Rate (SER) with respect to the Signal-to-Noise Ratio (SNR) and dissimilar antenna array size. It is found that the proposed Fractional Weighed Zero-Forcing equalizer outperformed the existing methods with a minimal BER and SER of 0.063, and 0.1038 while analyzing the methods in the Rayleigh environment.

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