Minimum Peak-to-average Power Ratio Research Articles

Reducing the Peak to Average Power Ratio of MIMO-OFDM Systems

In this paper, we proposed a particle swarm optimization (PSO) based partial transmit sequence (PTS) technique in order to achieve the lowest Peak-to-Average Power Ratio(PAPR) in Multiple Input Multiple Output- Orthogonal Frequency Division Multiplexing (MIMO-OFDM) systems. Our approach consist of applying the PSO based PTS on each antenna of the system in order to find the optimal phase factors, which is a straightforward method to get the minimum PAPR in such a system. The simulation results demonstrate that the PSO based PTS algorithm when applied to MIMO-OFDM systems with a wide range of phase factors, tends to give a high performance. In addition, there is no need to increase the number of particles of the PSO algorithm to enhance the performance of the system. As a result of this, the complexity of finding the minimum PAPR is kept at a reasonable level.

Sliding the SLM-technique to Reduce the Non-Linear Distortion in OFDM Systems

In this paper, a novel technique that can be effectively used to reduce the peak-to-average power ratio (PAPR) of the orthogonal frequency division multiplexing (OFDM) system is proposed. The proposed technique, called sliding selected mapping (SSLM), is considered a modified version of the conventional selected mapping (CSLM) scheme. SSLM uses a window with a predefined size of less than N, which carries the phase rotation vector (PRV). In contrast to the CSLM, SSLM uses length-f·N PRV s (0< f <1). The window is shifted by a step size (sliding) on the data sequence. At each shift, the modified data sequence undergoes IFFT operations to check the PAPR, similar to the CSLM. Thereafter, the shift index that corresponds to the minimum PAPR is chosen as the side information. Meanwhile, for comparison, the CSLM uses the PRV index as side information. Simulation results and mathematical computations show that our proposed technique requires less computational complexity. In addition, the corresponding amount of side information is significantly reduced compared with that of CSLM. DOI: http://dx.doi.org/10.5755/j01.eee.19.5.2075

Chromatic Dispersion Estimation for Single-Carrier Coherent Optical Communications

We propose and demonstrate a blind chromatic dispersion (CD) estimation technique for single-carrier coherent optical communication systems. We show that the peak-to-average-power ratio (PAPR) of a signal is a good indicator of the amount of CD the signal experiences and the minimum PAPR typically corresponds to zero accumulated CD. By scanning CD values of a CD compensator in a coherent receiver and monitoring the PAPR after the CD compensator, CD can be estimated accurately. We experimentally demonstrate this technique in a non-dispersion-managed optical transmission system with mixed 130-Gb/s polarization-division-multiplexed quadrature-phase-shift-keying (PDM-QPSK) and 260-Gb/s PDM 16-ary quadrature-amplitude-modulation (PDM-16QAM) channels and show that the technique works well for both PDM-QPSK and PDM-16QAM even with Nyquist pulse shaping.

Analysis of Peak to Average Power Ratio Reduction Techniques in Sfbc Ofdm System

Orthogonal Frequency Division Multiplexing (OFDM) has become the most popular modulation echnique for high speed data transmission. But the great disadvantage of the OFDM technique is its high Peak to Average Power Ratio (PAPR). In this paper, the Selected Mapping (SLM) technique and Clipping and Differential Scaling is applied to Space Frequency Block Coded (SFBC) OFDM systems to reduce the PAPR with Alamouti coding scheme. In SLM technique, different representations of OFDM symbols are generated by rotation of the original OFDM frame by different phase sequences, and the signal with minimum PAPR is selected and transmitted. To compensate for the effect of the phase rotation at the receiver, it is necessary to transmit the index of the selected phase sequence as side information (SI). Additionally, a suboptimum detection method that does not need SI is introduced at the receiver side. In Clipping and Differential Scaling technique, the amplitude of complex OFDM signal is clipped and then scaled in such a way so that the PAPR is reduced without causing much degradation in bit error rate (BER). The threshold values for clipping and scaling is determined using Monte Carlo Simulations. Simulation results show that the SLM method and Clipping and Scaling method effectively reduce the PAPR. Keywords: Orthogonal frequency division multiplexing (OFDM), peak to average power ratio (PAPR), selected mapping (SLM), space frequency block coded (SFBC), Side information (SI), high power amplifiers (HPA), complementary cumulative density function (CCDF), inter-symbol interference (ISI).

Selected Mapping Algorithm for PAPR Reduction of Space-Frequency Coded OFDM Systems Without Side Information

Selected mapping (SLM) is a well-known technique for peak-to-average-power ratio (PAPR) reduction of orthogonal frequency-division multiplexing (OFDM) systems. In this technique, different representations of OFDM symbols are generated by rotation of the original OFDM frame by different phase sequences, and the signal with minimum PAPR is selected and transmitted. To compensate for the effect of the phase rotation at the receiver, it is necessary to transmit the index of the selected phase sequence as side information (SI). In this paper, an SLM technique is introduced for the PAPR reduction of space-frequency-block-coded OFDM systems with Alamouti coding scheme. Additionally, a suboptimum detection method that does not need SI is introduced at the receiver side. Simulation results show that the proposed SLM method effectively reduces the PAPR, and the detection method has performance very close to the case where the correct index of the phase sequence is available at the receiver side.

PAPR Reduction in OFDM Via Separation of Complex Baseband Signal

system is the stronger base for the future wir eless c o m m u n i c a t i o n . The one w i t h the lowest peak to average power ratio (PAPR) among these OFDM signal sequences are selected for transmission. One major Disadvantage of OFDM is the high peak-to-average Power ratio (PAPR). One investigated technique Selected Mapping (SLM) is PAPR reduction techniques for Orthogonal Frequency Division Multiplexing (OFDM). By analyzing separation of complex baseband signal in this paper we proposed a Modernize SLM algorithm (MSLM) scheme to reduce the PAPR by using the complex signal to separate into real & imaginary parts and use as a individually phase sequence multiply real part as well as imaginary part of complex signal. Finally select the minimum PAPR signal which is achieved by real & imaginary part and then combine both of the approach and find one of the lowest peak to average power ratio among these OFDM signal sequences for transmission. After applying different simulation on the MATLAB software it produces less complexity and improved performance.

Combining of Cyclically Delayed Signals: A Low-Complexity Scheme for PAPR Reduction in OFDM Systems

Based on superposition of signals in the time domain, we propose a new low-complexity scheme for the reduction of the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. The proposed scheme first generates signal candidates by combining an OFDM signal and its cyclically delayed versions with different delays and phases, and then selects the candidate signal with minimum PAPR. It is shown that the complexity of the proposed scheme is significantly lower than that of the selective mapping (SLM) at the cost of some degradation in the bit error rate (BER) performance and, at similar PAPR and coded BER performance, is lower than that of the low-complexity SLM proposed recently.

Channel Estimation for Two-Way Relay OFDM Networks

We consider the channel estimation for two-way relay OFDM networks. We proposed an LS-based channel estimation algorithm under block-based training schemes. Based on the mean square error (MSE) criterion, the condition and the design method for optimal training sequences are discussed. To reduce peak-to-average power ratio (PAPR), a special sequence called Zadoff-Chu sequence is employed to design the optimal training sequence, which can achieve both minimum MSE performance and excellent PAPR performance.

Peak-to-Average Power Ratio (PAPR) Reduction by Pulse Shaping Using the K-Exponential Filter

A K-exponential filter is derived and utilized for pulse shaping to reduce peak to average power ratio (PAPR) without intersymbol interference (ISI). While keeping the same bandwidth, the frequency responses of the filters vary with different values of the parameter k. The minimum PAPR is associated with a value of the parameter k when the roll-off factor α is specified. Simulations show that the PAPR can be reduced compared with the raised cosine (RC) filter in various systems. The derived pulse shaping filters also provide better performance in PAPR reduction compared with the existing filters.

Optimum and Suboptimum Code Allocation for Peak Power Reduction in Down-Link MC CDMA

We develop an optimum code allocation scheme by investigating the peak to average power ratio (PAPR) characteristic of a down-link multi-carrier (MC)-CDMA system using Walsh-Hadamard code. It is shown that PAPR of a MC-CDMA system is highly dependent upon the selection of code combination. Based on this fact, we develop the allocation method which minimizes PAPR according to the number of active users. In addition, an efficient suboptimum code combination search scheme is also proposed for near minimum PAPR.

Control information transmission without resource consumption for PAPR reduction of OFDM signal

A peak-to-average power ratio (PAPR) reduction method for orthogonal frequency division multiplexing (OFDM) signals is proposed that requires no additional resources to transmit side information. The approach used to reduce PAPR is based on selected mapping (SLM). SLM produces several candidates of OFDM symbols, the subcarrier phases of which are rotated, and the OFDM symbol that yields the minimum PAPR is selected and transmitted to the receiver. To cancel the rotation used to generate the original signal at the receiver, transmission of side information using a time slot is usually required. This decreases the efficiency with which data can be transmitted. The proposal is to modify SLM so as to implant the side information into the OFDM data symbol. This results in no efficiency loss. Additionally, the error rate in estimating the side information is extremely low when enough subcarriers are used to carry the side information. The performance of the method is confirmed by numerical simulation. The PAPR improvement equals that of the original SLM. The implanted side information was transmitted with high reliability.

RBF Neural Network Based SLM Peak-to-Average Power Ratio Reduction in OFDM Systems

One of the major disadvantages of the orthogonal frequency division multiplexing system is high peak-to-average power ratio (PAPR). Selected mapping (SLM) is an efficient distortionless PAPR reduction scheme which selects the minimum PAPR sequence from a group of independent phase rotated sequences. However, the SLM requires explicit side information and a large number of IFFT operations. In this letter we investigate a novel PAPR reduction method based on the radial basis function network and SLM.

Minimizing the Peak-to-Average Power Ratio of OFDM Signals Using Convex Optimization

The main disadvantage of orthogonal frequency-division multiplexing (OFDM) is the high time-domain peak-to-average power ratio (PAR) that limits transmitter power efficiency. Assuming no changes in receiver structure, the transmitter can only reduce PAR by distorting the data carriers or by adding power to the free carriers. This paper shows that the OFDM signal with globally minimum PAR, subject to constraints on the allowed constellation error and the free carrier power, can be efficiently computed using convex optimization. Simulation results are presented for the 802.11a/g wireless local-area network standard. The globally minimum PAR, subject to the constellation error constraint, ranges from 0.7 dB for 6-Mbps binary phase-shift keying to 4.1 dB for 54-Mbps 64-QAM. Tradeoff analysis shows that the free carrier power can be drastically reduced by backing off from this globally minimum PAR by less than 1 dB. A customized interior-point method (IPM) is derived for solving the OFDM optimization problem. The IPM reaches the desired tradeoff between PAR and free carrier power within two iterations, where the main computational complexity per iteration is four fast Fourier transforms plus the solution of a linear system of equations. The customized IPM is about 100 times faster than a general-purpose optimization algorithm

The Minimum PAPR Code for OFDM Systems

In this letter, a block code that minimizes the peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals is proposed. It is shown that peak envelope power is invariant to cyclic shift and codeword inversion. The systematic encoding rule for the proposed code is composed of searching for a seed codeword, shifting the register elements, and determining codeword inversion. This eliminates the look-up table for one-to-one correspondence between the source and the coded data. Computer simulation confirms that OFDM systems with the proposed code always have the minimum PAPR.

POWER AND BANDWIDTH-EFFICIENT CIRCULAR M-ARY APSK SCHEMES WITH LOW PAPR

This paper presents a class of circular M-ary Amplitude-Phase Shift Keying (APSK) signaling techniques with high bandwidth efficiency and low peak-to-average power ratio (PAPR) suitable for systems using nonlinear power amplifiers to achieve high power efficiency. For nonlinear amplification, good performance requires not only high squared minimum distance to average power ratio (DPR) but also low PAPR. A search algorithm for M-ary APSK schemes using circular constellations suitable for nonlinear amplification with minimum PAPR and maximum DPR is developed. Results for 8-, 16-, 32-, 64- and 128-APSK signalling schemes are presented. The effects of bandlimiting filter sharpness on the PAPR are examined and considered in the development. The analytical and simulation results show that this class of circular M-ary APSK signals outperforms the square and cross M-ary QAM schemes.

Spreading sequences for multi‐carrier CDMA systems with nonlinear amplifier

AbstractMulti‐carrier CDMA (MC‐CDMA) system with a nonlinear amplifier is evaluated in this study. This paper proposes to use the amplifier at the saturation by minimizing the degradation of MC‐CDMA signal due to the nonlinearity. Peak‐to‐average power ratio (PAPR) of MC‐CDMA signals for various spreading sequences is also evaluated for both up‐ and down‐links. As spreading sequences, M‐sequences and their variations are considered in this study. As a result, Golay complementary sequences are suitable for the up‐link and low‐traffic down‐link. Meanwhile, Hadamard sequences provide the minimum PAPR in the down‐link with heavy traffic. Copyright © 2004 AEI

Peak power reduction scheme based on subcarrier scrambling for MC-CDMA systems

A new PAPR (peak-to-average power ratio) reduction scheme is proposed for MC-CDMA (multicarrier-CDMA) using subcarrier scrambling. Based on the fact that the PAPR of the MC-CDMA signal is highly dependent on the scrambling pattern of the subcarriers irrespective of users&apos; data symbols, the optimum fixed scrambling patterns for each combination of user spreading codes are searched to achieve the minimum PAPR. This enables the system to dynamically allocate the optimum scrambling pattern during system operation. The proposed scheme achieves a significant reduction in PAPR compared to random scrambling, especially for a small number of users. A simple suboptimum scrambling scheme is also proposed where a common scrambling pattern is used irrespective of the code combinations.

Peak-to-average power control in OFDM using standard arrays of linear block codes

We propose an efficient scheme to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems by using the standard arrays of linear block codes. Our scheme may be regarded as a modified version of the selective mapping (SLM), which is a probabilistic method to reduce the PAPR by selecting a signal with minimum PAPR from several candidates as the transmit signal. Because the coset leaders of a linear code are used for scrambling in our scheme, no side information is required to be transmitted and the received signal can be easily decoded by syndrome decoding. Simulation results show that our scheme has good performance in PAPR reduction.

On the existence and construction of good codes with low peak-to-average power ratios

The first lower bound on the peak-to-average power ratio (PAPR) of a constant energy code of a given length n, minimum Euclidean distance and rate is established. Conversely, using a nonconstructive Varshamov-Gilbert style argument yields a lower bound on the achievable rate of a code of a given length, minimum Euclidean distance and maximum PAPR. The derivation of these bounds relies on a geometrical analysis of the PAPR of such a code. Further analysis shows that there exist asymptotically good codes whose PAPR is at most 8 log n. These bounds motivate the explicit construction of error-correcting codes with low PAPR. Bounds for exponential sums over Galois fields and rings are applied to obtain an upper bound of order (log n)/sup 2/ on the PAPRs of a constructive class of codes, the trace codes. This class includes the binary simplex code, duals of binary, primitive Bose-Chaudhuri-Hocquenghem (BCH) codes and a variety of their nonbinary analogs. Some open problems are identified.