Developments in orthogonal frequency division multiplexing (OFDM) system-a survey
29 Dec 2011-pp 1-4
TL;DR: Challenges in Orthogonal frequency division multiplexing are presented and work done so far in channel equalisation and different transforms used in OFDM system are presented.
Abstract: In today's communication scenario, high data rate single-carrier transmission may not be feasible due to too much complexity of the equalizer in the receiver. To overcome the frequency selectivity of the wideband channel experienced by single-carrier transmission, multiple carriers can be used for high rate data transmission. Orthogonal frequency division multiplexing (OFDM) , is multicarrier system which has become a modulation in physical layer of next generation WiMAX, LTE system. In this paper effort is made to present challenges in OFDM and work done so far in channel equalisation and different transforms used in OFDM system.
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01 Dec 2015
TL;DR: In this paper, a new proposed technique is presented to further improve OFDM performance with varying Doppler shift error, which has significant improvements in the error performance and comparative analysis suggest that proposed technique has outperformed legacy Self Cancellation and Maximum Likelihood ICI cancellation scheme with huge gain.
Abstract: Orthogonal Frequency Division Multiplexing (OFDM), a most promising technique where multi-carrier modulation concept is implemented through splitting the signal into a number of signals, modulating each of these new signals to several orthogonal sub-carriers and combining the data received on the multiple channels at the receiver. Apart from delivering high spectrum efficiency, great channel robustness, immunity to impulse interferences, flexibility and easy equalization, OFDM is severely affected by undesirable effects of frequency offset errors (causes to generate inter carrier interface) due to Doppler shift in receiver frequency and Local oscillator frequency synchronization error. This paper describes some of the important ICI cancellation techniques, like Self Cancellation and Maximum Likelihood, and produces their performance comparative analysis with respect to BER and SNR. A new proposed technique is here by presented to further improve OFDM performance with varying Doppler shift error. The simulation results shows that proposed technique has significant improvements in the error performance and comparative analysis suggest that proposed technique has outperform legacy Self Cancellation and Maximum Likelihood ICI cancellation scheme with huge gain.
5 citations
Cites methods from "Developments in orthogonal frequenc..."
...Each data stream is modulated using any digital modulation scheme to get data X(m), however in this paper Quadrature Amplitude Modulation(QAM) is used [7] [8] to yield better results ....
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...Each stream is multiplexed with orthogonal frequency carriers, for this purpose NIFFT (N times Inverse Fast Fourier Transform) is used [7] [8]. x(n) = liN I:��X(m)exp j2nmn/ N...
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TL;DR: With intuitive mathematical analysis, it has been shown that with the reduced complexity that VFFT can offer, OFDM performance can be greatly improved in terms of calculations needed.
Abstract: In this paper, an intuitive comparison of the computational performance of orthogonal frequency division multiplexing (OFDM) system has been made in terms of complex calculations required using different Fourier transform techniques. The different transform techniques are introduced such as discrete Fourier transform (DFT) and various types of fast Fourier transform (FFT) as 2-radix FFT, 4-radix FFT etc. and the very recent very fast Fourier transform (VFFT). With intuitive mathematical analysis, it has been shown that with the reduced complexity that VFFT can offer, OFDM performance can be greatly improved in terms of calculations needed.
3 citations
01 Jan 2013
TL;DR: PTS technique for 4G wireless communication applications is analyzed and simulated and it is observed that the PTS techniques are more efficient, practical and attractive.
Abstract: At present for high data rate transmission, orthogonal frequency division multiplexing (OFDM) is the best and efficient modulation and multiplexing scheme adapted for 4G wireless communication applications. OFDM is an efficient method of data transmission for high speed communication system. OFDM is a multicarrier modulation technique that provides high band width efficiency because the carriers are orthogonal to each other and multiple carriers share the existing data. The main drawback of OFDM system is the high peak to average power ratio (PAPR) of the transmitted signal. OFDM consist of large number of independent sub carriers as a result of which amplitude of such a signal can have high peak valves .The Different PAPR reduction techniques available, such as Clipping, Companding, Selective Mapping (SLM), Interleaving, Tone reservation (TR) Tone Injection (TI) and Partial Transmit Sequence (PTS) and made comparison between them. In this paper, we analyzed and simulated PTS technique for 4G wireless communication applications. In this the data block to be transmitted is partitioned in to disjoint sub blocks. It is the combination of phase factors to minimize PAPR. It is observed that the PTS techniques are more efficient, practical and attractive.
1 citations
References
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Book•
16 Nov 2010TL;DR: In this article, the authors provide a comprehensive introduction to the theory and practice of wireless channel modeling, OFDM, and MIMO, using MATLAB programs to simulate the various techniques on a wireless network.
Abstract: MIMO-OFDM is a key technology for next-generation cellular communications (3GPP-LTE, Mobile WiMAX, IMT-Advanced) as well as wireless LAN (IEEE 802.11a, IEEE 802.11n), wireless PAN (MB-OFDM), and broadcasting (DAB, DVB, DMB). In MIMO-OFDM Wireless Communications with MATLAB, the authors provide a comprehensive introduction to the theory and practice of wireless channel modeling, OFDM, and MIMO, using MATLAB programs to simulate the various techniques on MIMO-OFDM systems. One of the only books in the area dedicated to explaining simulation aspects Covers implementation to help cement the key concepts Uses materials that have been classroom-tested in numerous universities Provides the analytic solutions and practical examples with downloadable MATLAB codes Simulation examples based on actual industry and research projects Presentation slides with key equations and figures for instructor use MIMO-OFDM Wireless Communications with MATLAB is a key text for graduate students in wireless communications. Professionals and technicians in wireless communication fields, graduate students in signal processing, as well as senior undergraduates majoring in wireless communications will find this book a practical introduction to the MIMO-OFDM techniques. Instructor materials and MATLAB code examples available for download at www.wiley.com/go/chomimo
1,413 citations
TL;DR: A new frequency-domain decision feedback equalizer for single carrier modulation, which makes use of a data block transmission format similar to that of the orthogonal frequency-division multiplexing with cyclic prefix, with the result that FD-DFE and OFDM have a similar computational complexity in signal processing.
Abstract: Most comparisons between single carrier and multicarrier modulations assume frequency-domain linear equalization of the channel. We propose a new frequency-domain decision feedback equalizer (FD-DFE) for single carrier modulation, which makes use of a data block transmission format similar to that of the orthogonal frequency-division multiplexing with cyclic prefix (OFDM). The scheme is a nonadaptive DFE where the feedforward part is implemented in the frequency domain, while feedback signal is generated by time-domain filtering. Through simulations in a HIPERLAN-2 scenario, we show that FD-DFE yields a capacity very close to that of OFDM. This result is also confirmed by analytical derivations for a particular case. Furthermore, when no channel loading is considered, FD-DFE performs closely to OFDM for the same averaged frame error rate in a coded transmission. Design methods of the FD-DFE are investigated and a reduced complexity technique is developed, with the result that FD-DFE and OFDM have a similar computational complexity in signal processing.
344 citations
TL;DR: The flexibility and adaptation provided by wavelets have made wavelet technology a strong candidate for future wireless communication.
Abstract: Wavelets have been favorably applied in almost all aspects of digital wireless communication systems including data compression, source and channel coding, signal denoising, channel modeling and design of transceivers. The main property of wavelets in these applications is in their flexibility and ability to characterize signals accurately. In this paper recent trends and developments in the use of wavelets in wireless communications are reviewed. Major applications of wavelets in wireless channel modeling, interference mitigation, denoising, OFDM modulation, multiple access, Ultra Wideband communications, cognitive radio and wireless networks are surveyed. The confluence of information and communication technologies and the possibility of ubiquitous connectivity have posed a challenge to developing technologies and architectures capable of handling large volumes of data under severe resource constraints such as power and bandwidth. Wavelets are uniquely qualified to address this challenge. The flexibility and adaptation provided by wavelets have made wavelet technology a strong candidate for future wireless communication.
222 citations
TL;DR: This scheme is shown to be overall quite similar to OFDM but with some interesting additional features and improved characteristics and a detailed analysis of the system's implementation complexity as well as an evaluation of the influence of implementation-related impairments.
Abstract: As proven by the success of OFDM, multicarrier modulation has been recognized as an efficient solution for wireless communications. Waveform bases other than sine functions could similarly be used for multicarrier systems in order to provide an alternative to OFDM.
In this paper, we study the performance of wavelet packet transform modulation (WPM) for transmission over wireless channels. This scheme is shown to be overall quite similar to OFDM but with some interesting additional features and improved characteristics. A detailed analysis of the system's implementation complexity as well as an evaluation of the influence of implementation-related impairments are also reported. Copyright © 2004 John Wiley & Sons, Ltd.
184 citations
TL;DR: This paper reviews the conventional PAPR reduction schemes and their modifications for achieving the low computational complexity required for practical implementation in wireless communication systems.
Abstract: Orthogonal frequency division multiplexing (OFDM) has been adopted as a standard for various high data rate wireless communication systems due to the spectral bandwidth efficiency, robustness to frequency selective fading channels, etc. However, implementation of the OFDM system entails several difficulties. One of the major drawbacks is the high peak-to-average power ratio (PAPR), which results in intercarrier interference, high out-of-band radiation, and bit error rate performance degradation, mainly due to the nonlinearity of the high power amplifier. This paper reviews the conventional PAPR reduction schemes and their modifications for achieving the low computational complexity required for practical implementation in wireless communication systems.
178 citations