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PAPR Reduction in LTE Down Link using a Hybrid Repeated Clipping and SQRT Companding
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Tone injection (TI) mitigates the high peak-to-average power ratio problem without incurring data rate loss or extra side information. However, optimal TI requires an exhaustive search over all possible constellations, which is a hard optimization problem. In this paper, a novel TI scheme that uses the clipping noise to find the optimal equivalent constellations is proposed. By minimizing the mean error of the clipping noise and possible constellation points, the proposed scheme easily determines the size and position of the optimal equivalent constellations. The proposed scheme achieves significant PAPR reduction while maintaining low complexity.
One of major drawbacks of Orthogonal Frequency Division Multiplexing (OFDM) is the high Peak-to-Average Power Ratio (PAPR) of the transmit signal. Due to the non-linear characteristics of the power amplifier (PA), significant out-of- band and in-band distortions occur when high peak signals exceed the saturation level of the PA. In this paper we present a new PAPR reduction technique which exploits the use of unused- carriers as well as the phase information of pilot signals in OFDM systems to reduce the PAPR while not degrading channel estimation or frequency offset. Compared to conventional techniques such as clipping and windowing, this technique introduces much less out-of-band distortions and provides a lower bit-error-rate (BER) since there is no interference to the original data signals. There is also no requirement for side information to be transmitted to the receiver.
One of the challenging issues for Orthogonal Frequency Division Multiplexing (OFDM) system is its high Peak-to-Average Power Ratio (PAPR). In this paper, we review and analysis different OFDM PAPR reduction techniques, based on computational complexity, bandwidth expansion, spectral spillage and performance. We also discuss some methods of PAPR reduction for multiuser OFDM broadband communication systems.
This paper addresses the problem of peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. It also introduces a new PAPR reduction technique based on adaptive square-rooting (SQRT) companding process. The SQRT process of the proposed technique changes the statistical characteristics of the OFDM output signals from Rayleigh distribution to Gaussian-like distribution. This change in statistical distribution results changes of both the peak and average power values of OFDM signals, and consequently reduces significantly the PAPR. For the 64QAM OFDM system using 512 subcarriers, up to 6 dB reduction in PAPR was achieved by square-rooting technique with fixed degradation in bit error rate (BER) equal to 3 dB. However, the PAPR is reduced at the expense of only -15 dB out-ofband spectral shoulder re-growth below the in-band signal level. The proposed adaptive SQRT technique is superior in terms of BER performance than the original, non-adaptive, square-rooting technique when the required reduction in PAPR is no more than 5 dB. Also, it provides fixed amount of PAPR reduction in which it is not available in the original SQRT technique.
Communication is one of the important aspects of life. With the advancement in age and its growing demands, there has been rapid growth in the field of communications. Signals, which were initially sent in the analog domain, are being sent more and more in the digital domain these days. For better transmission, even single carrier waves are being replaced by multi carriers. Multi carrier systems like CDMA and OFDM are now a days being implemented commonly. In the OFDM system, orthogonally placed sub carriers are used to carry the data from the transmitter end to the receiver end. Presence of guard band in this system deals with the problem of ISI and noise is minimized by larger number of sub carriers. But the large Peak-to-Average Power Ratio (PAPR) of these signal have some undesirable effects on the system. This paper present different PAPR reduction techniques and conclude an overall comparison of these techniques.
This paper describes a new peak-to-average power ratio (PAPR)
reduction scheme for orthogonal frequency division multiplexing (OFDM).
A time domain version of the OFDM signal is generated using an oversized
inverse discrete Fourier transform (DFT). This results in trigonometric
interpolation. The interpolated signal is clipped. To remove the
resulting out-of-band components, the clipped signal is filtered through
the use of a forward and inverse DFT. The filter passes the wanted
in-band discrete frequencies while nulling the out-of-band components.
The new scheme gives lower PAPR than other clipping techniques. Results
are presented for the power spectral density and in-band distortion when
the scheme is followed by a non-ideal amplifier. No change to the
receiver is required so the scheme is compatible with existing
communications standards
Orthogonal frequency division multiplexing (OFDM) is an attractive technique for achieving high-bit-rate wireless data transmission. However, the potentially large peak-to-average power ratio (PAP) of a multicarrier signal has limited its application. Two promising techniques for improving the statistics of the PAP of an OFDM signal have previously been proposed: the selective mapping and partial transmit sequence approaches. Here, we summarize these techniques and present suboptimal strategies for combining partial transmit sequences that achieve similar performance but with reduced complexity
High peak-to-average power ratio of the transmit signal is a major drawback of multicarrier transmission such as OFDM or DMT. This article describes some of the important PAPR reduction techniques for multicarrier transmission including amplitude clipping and filtering, coding, partial transmit sequence, selected mapping, interleaving, tone reservation, tone injection, and active constellation extension. Also, we make some remarks on the criteria for PAPR reduction technique selection and briefly address the problem of PAPR reduction in OFDMA and MIMO-OFDM.
The repeated clipping and frequency domain filtering of an orthogonal frequency division multiplexing (OFDM) signal was studied to reduce peak-to-average power ratio (PAPR) of the transmitted signal. An oversize inverse fast Fourier transform (IFFT) was used to transform the input vector. The clipping was followed by filtering to reduce the out-of-band power. Analysis suggested that the clip-and-filter technique did not increase the out-of-band power and limited the PAPR reduction practical systems to in-band-distortion.
PAPR Reduction of OFDM Signals Using Selected Mapping Technique
- Sarita Singh Bhadhoria
- S Gupta
Sarita Singh Bhadhoria and S. Gupta, March 2013.
"PAPR Reduction of OFDM Signals Using Selected
Mapping Technique," Current Research in Engineering,
Science and Technology (CREST) Journals, vol.1,no.
1, pp 34-37.
Time domain statistical control for PAPR reduction in OFDM system
- F Wisam
- Borhanuddin M Al-Azzo
- Sabira Ali
- S M Khatun
- Bilfagih
Wisam F. Al-Azzo, Borhanuddin M. Ali, Sabira
Khatun, and S. M. Bilfagih, 2007. "Time domain
statistical control for PAPR reduction in OFDM
system", Proc. IEEE APCC 2007, Bangkok, Thailand,
pp.141-144.
PAPR Reduction in OFDM system Using Tone Reservation Technique
- M Chauhan
- A Chobey
M. Chauhan and A. Chobey, August 2012. "PAPR
Reduction in OFDM system Using Tone Reservation
Technique," International Journal of Computer
Technology and Electronics Engineering (IJCTEE),
vol. 2, no. 4, pp 57-60.
Peak Power Reduction in Orthogonal Frequency Division Multiplexing Transmitters
- Gavin Hill
Gavin Hill, March 2011 "Peak Power Reduction in
Orthogonal
Frequency
Division
Multiplexing
Transmitters," Ph.D. Thesis, Victoria University of
Technology.
Peak to Average Power Ratio Reduction Technique for OFDM Using Pilot Tones and Unused Carriers" Radio and Wireless Symposium
- Carole A Devlin
- Anding Zhu
- Thomas J Brazil
Carole A. Devlin, Anding Zhu, and Thomas J. Brazil
Jan. 2008. "Peak to Average Power Ratio Reduction
Technique for OFDM Using Pilot Tones and Unused
Carriers" Radio and Wireless Symposium, 2008 IEEE,
pp 33 -36, 22-24.