Multiuser Diversity OFDMA using Power Priority Selection and Adaptive Clipping

In recent, orthogonal frequency division multiple access (OFDMA) has been used for a multiuser wireless communication. In a wireless network, the transmitted signal of each user has independent channel fluctuation characteristic. By using this characteristic, OFDMA can achieve the multiuser diversity (MUDiv). Until this time, to achieve a low complexity and performance improvement, the adaptive subcarrier block (ASB) and frequency symbol spreading (FSS) methods have been proposed. However, the system performance in a low Eb/N0 is worse than that of maximal sum capacity (MSC) and peak to average power ratio (PAPR) does not decrease greatly. To solve these problems, in this paper, we propose the subcarrier allocation with the power priority selection (PSS) and the adaptive clipping (AC) with the peak reduction signal to improve the system and PAPR performance.

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NOVEL MULTIPLE LEVEL SUBCARRIER ALLOCATION SCHEME IN SC-FDMA FOR LTE-A UPLINK

Jurnal Teknologi ◽

10.11113/jt.v78.7432 ◽

2016 ◽

Vol 78 (8) ◽

Author(s):

Mohamed Melood A. Abdased ◽

Mahamod Ismail ◽

Rosdiadee Nordin

Keyword(s):

Multiple Access ◽

Average Power ◽

Frequency Division ◽

Robust Performance ◽

Frequency Allocation ◽

Single Carrier ◽

Term Evolution ◽

Lower Complexity ◽

Papr Performance

Long Term Evolution-Advanced (LTE-A) uses Single-Carrier Frequency Division Multiple Accesses (SC-FDMA) for uplink, because it has robust performance against the Peak Average Power Ratio (PAPR), compared to Orthogonal Frequency Division Multiple Access (OFDMA). SC-FDMA schemes include Interleaved FDMA (IFDMA) and Localized FDMA (LFDMA), both of which are commonly practiced in LTE-A uplink. IFDMA allocates distributed frequency carriers for users, whereas LFDMA allocates localized frequency carriers for users. The frequency allocation in an IFDMA scheme exhibits better PAPR performance, whereas the advantage of LFDMA is its lower complexity requirements. In this paper, a new scheme is introduced that integrates IFDMA and LFDMA by using a variable interleave allocation of subcarriers in the bandwidth. Here, Generalized Interleaved Frequency Division Multiple Accesses (GIFDMA), is used as a master key that controls the allocation for interleaved and localized FDMA, also known as L/I FDMA. This integration of IFDMA and LFDMA has been derived theoretically and empirically. Simulations are conducted to investigate the effect of different parameters on the GIFDMA PAPR performance, which is compared to that of conventional IFDMA and LFDMA. The simulation results revealed that the proposed GIFDMA provides PAPR performance comparable to that of both LFDMA and IFDMA.

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PAPR Performance Improvement in OFDM System Using DCT Based on Adjacent Symbol Grouping

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.550.204 ◽

2014 ◽

Vol 550 ◽

pp. 204-209

Author(s):

K. Muralibabu ◽

M. Sundhararajan

Keyword(s):

Performance Improvement ◽

Fading Channel ◽

Orthogonal Frequency Division Multiplexing ◽

Average Power ◽

Multipath Fading ◽

Frequency Division ◽

Ofdm System ◽

Multipath Fading Channel ◽

A New Technique ◽

Papr Performance

In wireless communication, Orthogonal Frequency Division Multiplexing (OFDM) is a promising scheme against the multipath fading channel .However, due multi-carrier transmission , OFDM system has a major draw back of Peak-to-Average Power Ratio (PAPR) problem that affect the efficiency of HPA in the transmitter side. In the proposed scheme, a new technique is discussed for reducing PAPR in the OFDM system by using Discrete Cosine Transform (DCT) and adjacent sub carriers grouping with companding technique.A computer simulation is used to evaluate the performance of the proposed PAPR scheme.

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Low-Complexity Distortionless Techniques for Peak Power Reduction in OFDM Communication Systems

Journal of Computer Networks and Communications ◽

10.1155/2012/929763 ◽

2012 ◽

Vol 2012 ◽

pp. 1-13

Author(s):

A. Ghassemi ◽

T. A. Gulliver

Keyword(s):

Computational Complexity ◽

Communication Systems ◽

Orthogonal Frequency Division Multiplexing ◽

Average Power ◽

Low Complexity ◽

Inverse Discrete Fourier Transform ◽

Peak Power Reduction ◽

And Performance ◽

Selective Mapping ◽

Papr Performance

A high peak-to-average power ratio (PAPR) is one of the major drawbacks to using orthogonal frequency division multiplexing (OFDM) modulation. The three most effective distortionless techniques for PAPR reduction are partial transmit sequence (PTS), selective mapping (SLM), and tone reservation (TR). However, the high computational complexity due to the inverse discrete Fourier transform (IDFT) is a problem with these approaches. Implementation of these techniques typically employ direct computation of the IDFT, which is not the most efficient solution. In this paper, we consider the development and performance analysis of these distortionless techniques in conjunction with low-complexity IFFT algorithms to reduce the PAPR of the OFDM signal. Recently, proposed IFFT-based techniques are shown to substantially reduce the computational complexity and improve PAPR performance.

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