scholarly journals An Effective Linear Precoding Scheme to Resolve High PAPR and High OOBE Problems of OFDM systems

2021 ◽  
Author(s):  
Hikaru Kawasaki ◽  
Takeshi Matsumura ◽  
Fumihide Kojima
Keyword(s):  
Mobile Communications ◽  
Orthogonal Frequency Division Multiplexing ◽  
Peak Power ◽  
Fourth Generation ◽  
High Peak Power ◽  
Linear Precoding ◽  
Ofdm Systems ◽  
Power Characteristics ◽  
Band Emission ◽  
Fifth Generation

Abstract In the fifth-generation of mobile communications, the use of orthogonal frequency-division multiplexing is agreed by the Third Partnership Project as it was in the fourth-generation. On the other hand, the major problems of its transmitted signals are high out-of-band emission (OOBE) that causes strong interference to adjacent frequency bands and high peak power characteristics that limit device costs and power savings. For future communications, this paper proposes an effective method to resolve the problems based on linear precoding with the theoretical analyses. Numerical experiments show that compared with the usual OFDM, the proposed method can achieve 25 dB lower OOBE, 2 dB lower peak power, no error rate degradation with a practical computational complexity simultaneously.

scholarly journals Análisis de la técnica UFMC en un canal multitrayecto y usando estimación de canal

2021 ◽  
Vol 9 (17) ◽  
pp. 26-39
Author(s):  
Hugo Wladimir Iza Benítez ◽  
Diego Javier Reinoso Chisaguano
Keyword(s):  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Filter Bank ◽  
Estimation Method ◽  
Wireless Communication Systems ◽  
Ofdm Systems ◽  
Matlab Simulation ◽  
Fifth Generation ◽  
Power Spectral ◽  
Filter Bank Multicarrier

UFMC (Universal Filtered Multi-Carrier) is a novel multi-carrier transmission technique that aims to replace the OFDM (Orthogonal Frequency Division Multiplexing) modulation technique for fifth generation (5G) wireless communication systems. UFMC, being a generalization of OFDM and FBMC (Filter Bank Multicarrier), combines the advantages of these systems and at the same time avoids their main disadvantages. Using a Matlab simulation, this article presents an analysis of the robustness of UFMC against fading effects of multipath channels without using a CP (cyclic prefix). The behavior of the UFMC system is analyzed in terms of the PSD (Power Spectral Density), BER (Bit Error Rate) and MSE (Mean Square Error). The results show that UFMC reduces the out-band side lobes produced in the PSD of the processed signal. Also, it is shown that the pilot-assisted channel estimation method applied in OFDM systems can also be applied in UFMC systems.

scholarly journals Discrete Multiwavelet Critical-Sampling Transform-Based OFDM System over Rayleigh Fading Channels

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Sameer A. Dawood ◽  
F. Malek ◽  
M. S. Anuar ◽  
Suha Q. Hadi
Keyword(s):  
Fading Channels ◽  
Mobile Communications ◽  
Orthogonal Frequency Division Multiplexing ◽  
Discrete Wavelet ◽  
Ofdm Systems ◽  
Ofdm System ◽  
Time Frequency ◽  
Wireless Mobile Communications ◽  
Time Frequency Localization ◽  
Multiwavelet Transform

Discrete multiwavelet critical-sampling transform (DMWCST) has been proposed instead of fast Fourier transform (FFT) in the realization of the orthogonal frequency division multiplexing (OFDM) system. The proposed structure further reduces the level of interference and improves the bandwidth efficiency through the elimination of the cyclic prefix due to the good orthogonality and time-frequency localization properties of the multiwavelet transform. The proposed system was simulated using MATLAB to allow various parameters of the system to be varied and tested. The performance of DMWCST-based OFDM (DMWCST-OFDM) was compared with that of the discrete wavelet transform-based OFDM (DWT-OFDM) and the traditional FFT-based OFDM (FFT-OFDM) over flat fading and frequency-selective fading channels. Results obtained indicate that the performance of the proposed DMWCST-OFDM system achieves significant improvement compared to those of DWT-OFDM and FFT-OFDM systems. DMWCST improves the performance of the OFDM system by a factor of 1.5–2.5 dB and 13–15.5 dB compared with the DWT and FFT, respectively. Therefore the proposed system offers higher data rate in wireless mobile communications.

scholarly journals A New-Trend Model-Based to Solve the Peak Power Problems in OFDM Systems

2008 ◽  
Vol 2008 ◽  
pp. 1-9 ◽  
Author(s):  
Ashraf A. Eltholth ◽  
Adel R. Mekhail ◽  
A. Elshirbini ◽  
M. I. Dessouki ◽  
A. I. Abdelfattah
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Peak Power ◽  
Dynamic Range ◽  
Average Power ◽  
Problem Definition ◽  
Ofdm Systems ◽  
Ofdm System ◽  
Ofdm Signal ◽  
Nonlinear Amplifier ◽  
Power Problem

The high peak to average power ration (PAR) levels of orthogonal frequency division multiplexing (OFDM) signals attract the attention of many researchers during the past decade. Existing approaches that attack this PAR issue are abundant, but no systematic framework or comparison between them exists to date. They sometimes even differ in the problem definition itself and consequently in the basic approach to follow. In this paper, we propose a new trend in mitigating the peak power problem in OFDM system based on modeling the effects of clipping and amplifier nonlinearities in an OFDM system. We showed that the distortion due to these effects is highly related to the dynamic range itself rather than the clipping level or the saturation level of the nonlinear amplifier, and thus we propose two criteria to reduce the dynamic range of the OFDM, namely, the use of MSK modulation and the use of Hadamard transform. Computer simulations of the OFDM system using Matlab are completely matched with the deduced model in terms of OFDM signal quality metrics such as BER, ACPR, and EVM. Also simulation results show that even the reduction of PAR using the two proposed criteria is not significat, and the reduction in the amount of distortion due to HPA is truley delightful.

scholarly journals Suitability of OFDM in 5G Waveform – A Review

2019 ◽  
Vol 12 (Issue 3) ◽  
pp. 66-75
Author(s):  
Pathuri Lavanya ◽  
Penke Satyanarayana ◽  
Afaq Ahmad
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Average Power ◽  
Fourth Generation ◽  
Future Research ◽  
Frequency Division ◽  
Major Drawback ◽  
Research Directions ◽  
Fifth Generation ◽  
Future Research Directions ◽  
Wireless Standards

Systematic pursuits are being developed to set forth the framework for the Fifth Generation (5G) wireless standards. This paper emphases on the most extensively deployed technology - Orthogonal Frequency Division Multiplexing (OFDM) that has outpaced other waveform aspirants for Fourth Generation (4G) communication standards. Irrespective of the beneficial features, it does possess a number of significant limitations that mark it as an incompatible candidate for the upcoming 5G standard. This paper highlights on its major drawback i.e high Peak-to-Average Power Ratio (PAPR). Results state that PAPR does cause sudden upsurge to the output signal envelope causing further other damages. There exists a need for more flexible waveforms to replace the conventional OFDM in order to address the unprecedented challenges. The future research directions in the domain are presented.

OFDM Transmission Technique

2009 ◽  
pp. 3561-3587
Author(s):  
Hermann Rohling
Keyword(s):  
Communication Networks ◽  
Mobile Communications ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multiple Access ◽  
Fourth Generation ◽  
Frequency Division ◽  
Carrier Synchronization ◽  
Radio Channels ◽  
Transmission Technique ◽  
Cellular Environment

The orthogonal frequency division multiplexing (OFDM) transmission technique can efficiently deal with multi-path propagation effects especially in broadband radio channels. It also has a high degree of system flexibility in multiple access schemes by combining the conventional TDMA; FDMA; and CDMA approaches with the OFDM modulation procedure; which is especially important in the uplink of a multi-user system. In OFDM-FDMA schemes carrier synchronization and the resulting sub-carrier orthogonality plays an important role to avoid any multiple access interferences (MAI) in the base station receiver. An additional technical challenge in system design is the required amplifier linearity to avoid any non-linear effects caused by a large peak-to-average ratio (PAR) of an OFDM signal. The OFDM transmission technique is used for the time being in some broadcast applications (DVB-T; DAB; DRM) and wireless local loop (WLL) standards (HIPERLAN/2; IEEE 802.11a) but OFDM has not been used so far in cellular communication networks. The general idea of the OFDM scheme is to split the total bandwidth into many narrowband sub-channels which are equidistantly distributed on the frequency axis. The sub-channel spectra overlap each other but the sub-carriers are still orthogonal in the receiver and can therefore be separated by a Fourier transformation. The system flexibility and use of sub-carrier specific adaptive modulation schemes in frequency selective radio channels are some advantages which make the OFDM transmission technique a strong and technically attractive candidate for the next generation of mobile communications. The objective of this chapter is to describe an OFDM-based system concept for the fourth generation (4G) of mobile communications and to discuss all technical details when establishing a cellular network which requires synchronization in time and frequency domain with sufficient accuracy. In this cellular environment a flexible frequency division multiple access scheme based on OFDM-FDMA is developed and a radio resource management (RRM) employing dynamic channel allocation (DCA) techniques is used. A purely decentralized and self-organized synchronization technique using specific test signals and RRM techniques based on co-channel interference (CCI) measurements has been developed and will be described in this chapter.

scholarly journals 5G Wireless Networks Deployment with Emerging Technologies and Research Challenges

2018 ◽  
Vol 3 (1) ◽  
pp. 1-20
Author(s):  
Rajamohan Parthasarathy ◽  
◽  
Preethy Ayyappan ◽  
Seow Soon Loong ◽  
◽  
...  
Keyword(s):  
Wireless Networks ◽  
Mobile Communications ◽  
Wireless Access ◽  
Fourth Generation ◽  
Fifth Generation ◽  
Research Challenges ◽  
New Business ◽  
New Applications

Over the last couple of decades the world has witnessed gradual, yet steady evolution of mobile wireless communications towards second, third and fourth generation wireless networks. Introduction of digital modulations, effective frequency reuse, penetration of packetbased Internet and rapid advancement in physical layer technologies. Currently all IP based 4G Long Term Evolution (LTE/4G) networks have become a part of everyday life. As a result, a set of new, user-oriented mobile multimedia applications, like mobile video conferencing, streaming video, e-healthcare and online gaming are coming up. These new applications are not only satisfying users’ requirements, but also opening up new business horizons for wireless operators to increase their revenue. Fifth generation mobile communications (5G) are expected to accommodate rapidly increasing mobile traffic aiming at the realization of a “Hyper Connected World” in which all people and surrounding things are connected and information is exchanged between them, and to play the role of a basis of the Internet of everything. The 5G wireless network is expected to become a “Heterogeneous Network” where new wireless access technologies incompatible with 4G and the wireless access technologies for unlicensed band are incorporated with the enhanced technology of 4G (e.g. IMT-advanced). This paper introduces the vision and emerging technology trends of 5G, shows key directions of the research challenges and development of 5G in the future.

scholarly journals Comparing f-OFDM and OFDM Performance for MIMO Systems Considering a 5G Scenario

2019 ◽  
Author(s):  
Felipe Augusto Pereira de Figueiredo ◽  
Nathália F. T. Aniceto ◽  
Jorge Seki ◽  
Ingrid Moerman ◽  
Gustavo Fraidenraich
Keyword(s):  
Mobile Communications ◽  
Orthogonal Frequency Division Multiplexing ◽  
Error Probability ◽  
Mimo Systems ◽  
Radio Spectrum ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Primary Users ◽  
Band Emission ◽  
Spectral Localization

The advances mobile communications has seen in recent years has rendered the radio spectrum a limited and, hence, an expensive resource. Therefore, technologies that support unlicensed access to spectrum are needed. Therefore, the adoption of novel modulation schemes becomes of utmost importance to obtain better spectral-localization and reduce the OOBE (\textit{Out of Band Emission}) inherent to OFDM (\textit{Orthogonal Frequency Division Multiplexing}) and, consequently, mitigating the interference between secondary (\textit{unlicensed}) and primary users. In this scenario, we assess the gain in the bit error probability using f-OFDM (\textit{filtered-OFDM}) in MIMO systems, both used in the 5G RANGE project.

scholarly journals Comparing f-OFDM and OFDM Performance for MIMO Systems Considering a 5G Scenario

2019 ◽  
Author(s):  
Felipe Augusto Pereira de Figueiredo ◽  
Nathália F. T. Aniceto ◽  
Jorge Seki ◽  
Ingrid Moerman ◽  
Gustavo Fraidenraich
Keyword(s):  
Mobile Communications ◽  
Orthogonal Frequency Division Multiplexing ◽  
Error Probability ◽  
Mimo Systems ◽  
Radio Spectrum ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Primary Users ◽  
Band Emission ◽  
Spectral Localization

The advances mobile communications has seen in recent years has rendered the radio spectrum a limited and, hence, an expensive resource. Therefore, technologies that support unlicensed access to spectrum are needed. Therefore, the adoption of novel modulation schemes becomes of utmost importance to obtain better spectral-localization and reduce the OOBE (\textit{Out of Band Emission}) inherent to OFDM (\textit{Orthogonal Frequency Division Multiplexing}) and, consequently, mitigating the interference between secondary (\textit{unlicensed}) and primary users. In this scenario, we assess the gain in the bit error probability using f-OFDM (\textit{filtered-OFDM}) in MIMO systems, both used in the 5G RANGE project.

OFDM Transmission Technique

2011 ◽  
pp. 151-177
Author(s):  
Hermann Rohling
Keyword(s):  
Communication Networks ◽  
Mobile Communications ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multiple Access ◽  
Fourth Generation ◽  
Frequency Division ◽  
Carrier Synchronization ◽  
Radio Channels ◽  
Transmission Technique ◽  
Cellular Environment

The orthogonal frequency division multiplexing (OFDM) transmission technique can efficiently deal with multi-path propagation effects especially in broadband radio channels. It also has a high degree of system flexibility in multiple access schemes by combining the conventional TDMA, FDMA, and CDMA approaches with the OFDM modulation procedure, which is especially important in the uplink of a multi-user system. In OFDM-FDMA schemes carrier synchronization and the resulting sub-carrier orthogonality plays an important role to avoid any multiple access interferences (MAI) in the base station receiver. An additional technical challenge in system design is the required amplifier linearity to avoid any non-linear effects caused by a large peak-to-average ratio (PAR) of an OFDM signal. The OFDM transmission technique is used for the time being in some broadcast applications (DVB-T, DAB, DRM) and wireless local loop (WLL) standards (HIPERLAN/2, IEEE 802.11a) but OFDM has not been used so far in cellular communication networks. The general idea of the OFDM scheme is to split the total bandwidth into many narrowband sub-channels which are equidistantly distributed on the frequency axis. The sub-channel spectra overlap each other but the sub-carriers are still orthogonal in the receiver and can therefore be separated by a Fourier transformation. The system flexibility and use of sub-carrier specific adaptive modulation schemes in frequency selective radio channels are some advantages which make the OFDM transmission technique a strong and technically attractive candidate for the next generation of mobile communications. The objective of this chapter is to describe an OFDM-based system concept for the fourth generation (4G) of mobile communications and to discuss all technical details when establishing a cellular network which requires synchronization in time and frequency domain with sufficient accuracy. In this cellular environment a flexible frequency division multiple access scheme based on OFDM-FDMA is developed and a radio resource management (RRM) employing dynamic channel allocation (DCA) techniques is used. A purely decentralized and self-organized synchronization technique using specific test signals and RRM techniques based on co-channel interference (CCI) measurements has been developed and will be described in this chapter.

A Low Complex Modified Grey Wolf Optimization Model for OFDM Peak Power Reduction

2021 ◽  
Vol 36 (3) ◽  
pp. 259-265
Author(s):  
Radhakrishnan Suriavel Rao ◽  
Ramakrishnan Menaka ◽  
Rajan Alexciyaa Winslet
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Peak Power ◽  
Average Power ◽  
Processing Technique ◽  
Grey Wolf Optimizer ◽  
Ofdm Systems ◽  
Grey Wolf ◽  
Signal Processing Technique ◽  
Sequence Method ◽  
Low Complex

Orthogonal frequency division multiplexing (OFDM) or multicarrier modulation is an essential signal processing technique in new generation wireless gadgets owing to its potential to support fast and spectrally efficient transmission. One of the major limitations of OFDM systems is the peak-to-average power ratio (PAPR) of transmit data. In this article, a novel meta heuristic algorithm called modified grey wolf optimizer is used to boost the computing performance of subcarrier phase factor search in the undisputed partial transmit sequence method. The proposed modified grey wolf optimizer (mGWO) has a balancing between exploration and exploitation phases while searching for peak power carriers and brings out a nearly optimal performance but with less number of iterations. The objective is to propose low complex computing algorithm without compromising the output quality. The simulation results of proposed mGWO-PTS model assure improvements around 20 to 25 percent from that of the comparative counterparts such as GWO-PTS, PSO-PTS, and etc.

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