scholarly journals Analysis of Doppler frequency shift response mechanism based on OFDM system

2018 ◽  
Vol 232 ◽  
pp. 04049
Author(s):  
Ke Li ◽  
Zhiguo Sun ◽  
Xiaoyan Ning ◽  
Ming Diao
Keyword(s):  
Spectral Efficiency ◽  
Doppler Frequency ◽  
Doppler Frequency Shift ◽  
Response Mechanism ◽  
Ofdm System ◽  
System Parameters ◽  
Shift Response ◽  
High Spectral Efficiency ◽  
High Dynamic ◽  
Response Formula

OFDM system is widely used in mobile communication because of its high spectral efficiency and strong anti-multipath capability. However, in high dynamic scenarios, the Doppler shift between the transmitter and the receiver destroys the orthogonality between the sub-carriers, resulting the interference between the sub-carriers and distortion of the signal, which greatly degrades the system performance. In this paper, a mathematical model of Offset-OFDM system was established and the Doppler response formula of OFDM system in high white channel was derived. Furthermore, we investigated the factors that influence the performance of OFDM. This study laid the foundation for determining OFDM system parameters in high dynamic scenarios.

An Improved Algorithm Based on Optimized PTS in MIMO-OFDM System

2013 ◽  
Vol 765-767 ◽  
pp. 2801-2804
Author(s):  
Ya Jing Wang ◽  
Ya Zhen Li ◽  
Li Qun Huang
Keyword(s):  
Spectral Efficiency ◽  
Communication System ◽  
High Speed ◽  
Fourth Generation ◽  
Ofdm System ◽  
Broadband Wireless ◽  
High Spectral Efficiency ◽  
Mimo Ofdm ◽  
Simulation Results ◽  
Improved Algorithm

The fourth generation mobile communication system is a high-speed broadband wireless communication system, it needs MIMO and OFDM technology which have high spectral efficiency and suitable for a multi-path fading channel. Because the MIMO-OFDM system is still an multi-carrier modulation system, the main drawback is the high PAPR value. This paper proposed an improved algorithm based on optimized PTS to reduce PAPR in STBC MIMO-OFDM system. The simulation results show that the improved algorithm can effectively reduce the PAPR value and do not increase the amount of computation in STBC MIMO-OFDM system.

Analysis of the Impact on Doppler Frequency Shift of the Signal Caused by Receiver’s High Dynamic Environment

2014 ◽  
Vol 568-570 ◽  
pp. 176-179
Author(s):  
Xiao Jing Du ◽  
Wen Bo Zhang ◽  
Song Bo Wang
Keyword(s):  
Frequency Shift ◽  
High Speed ◽  
Dynamic Environment ◽  
Doppler Frequency ◽  
Doppler Frequency Shift ◽  
Positioning Accuracy ◽  
High Acceleration ◽  
High Dynamic ◽  
The Impact ◽  
Changing Rate

The Doppler frequency shift of the signal received from receiver carrier in high dynamic environment which means high speed and high acceleration represents different changing rules. The changing rules can make the positioning accuracy become worse and even make the receiver unable to track the signal. On the basis of modeling and simulation of three high dynamic carriers including the aircraft, satellite and ballistic missile, the changing rules of Doppler frequency shift were analyzed using the calculation equation of the Doppler frequency shift. The results show that for the high dyanmic carriers, the larger the velocity of the carrier is, the larger corresponding Doppler frequency shift is and the larger the acceleration of the carrier is, the larger corresponding changing rate of Doppler frequency shift is.

scholarly journals WRELM based CO-OFDM system with improved performance, spectral efficiency and computational complexity

2021 ◽  
Author(s):  
Gurpreet Kaur ◽  
Gurmeet Kaur
Keyword(s):  
Phase Noise ◽  
Spectral Efficiency ◽  
Orthogonal Frequency Division Multiplexing ◽  
Fourier Transforms ◽  
Wavelet Packet ◽  
Discrete Wavelet ◽  
Ofdm System ◽  
High Spectral Efficiency ◽  
Improved Performance ◽  
Learning Machine

Abstract Coherent Optical Orthogonal Frequency Division Multiplexing (CO-OFDM) system with Pilot-free phase noise compensator was introduced in order to accomplish the need of high spectral efficiency in the optical communication. In CO-OFDM system Discrete wavelet packet transforms (DWPTs) in place of Fast Fourier Transforms (FFTs) had attracted more attention since it has removed the need of cyclic prefix used to compensate fiber dispersion. In this paper, a DWPT based CO-OFDM system with Wilcoxon Robust Extreme Learning Machine based pilot-free phase noise compensator using multi-level QPSK partitioning of 16-QAM has been proposed. From the results of this work it has been seen that the percentage improvement in performance (in terms of Q-Factor) and spectral efficiency over traditional pilot-aided techniques is approximately 6 and 21 respectively. Moreover, this proposed work will comparatively reduce the overall system complexity.

scholarly journals Generalized Complex Quadrature Spatial Modulation

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Manar Mohaisen
Keyword(s):  
Spectral Efficiency ◽  
Mimo System ◽  
Multiple Input Multiple Output ◽  
Spatial Modulation ◽  
System Parameters ◽  
Multiple Input ◽  
Generalized Complex ◽  
High Spectral Efficiency ◽  
Input Multiple Output ◽  
Single Input

Spatial modulation (SM) is a multiple-input multiple-output (MIMO) system that achieves a MIMO high spectral efficiency while maintaining the transmitter computational complexity and requirements as low as those of the single-input systems. The complex quadrature spatial modulation (CQSM) builds on the QSM scheme and improves the spectral efficiency by transmitting two signal symbols at each channel use. In this paper, we propose two generalizations of CQSM, namely, generalized CQSM with unique combinations (GCQSM-UC) and with permuted combinations (GCQSM-PC). These two generalizations perform close to CQSM or outperform it, depending on the system parameters. Also, the proposed schemes require much less transmit antennas to achieve the same spectral efficiency of CQSM, for instance, assuming 16-QAM, GCQSM-PC, and GCQSM-UC require 10 and 15 transmit antennas, respectively, to achieve the same spectral of CQSM which is equipped with 32 antennas.

A Novel Carrier Acquisition for HAPS Communication System in High Dynamic Scenario

2011 ◽  
Vol 204-210 ◽  
pp. 445-448
Author(s):  
Ming Xiang Guan ◽  
Xue Yuan Wan ◽  
Le Wang
Keyword(s):  
Great Influence ◽  
Doppler Frequency ◽  
Phase Lock Loop ◽  
Doppler Frequency Shift ◽  
Information Rate ◽  
Phase Lock ◽  
Dynamic Scenario ◽  
High Dynamic ◽  
Frequency Phase ◽  
High Information

To detect and receive the high dynamic and high information-rate signal for communication platform in the stratosphere, it is necessary to design digital system to acquire and track the carrier. In the high dynamic and high information-rate situation, the most important aspect is the great influence of Doppler frequency shift and high information rate on the carrier acquisition and track. Carrier acquisition and track in the high dynamic and high information-rate situation was implemented by means of the combination of FPGA and frequency, phase lock loop. A new algorithm using DQPSK for carrier acquisition and track was proposed and the validity of the design and algorithm was proved by means of trials and comparison with EKF method in the high dynamic and high information-rate situation.

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