Peak-to Average Power Research Articles

A Handy Dandy Doherty PA: A Linear Doherty Power Amplifier for Mobile Handset Application

As wireless communications progress from second to fourth-generation (4G) systems, the information content drastically increases, requiring high-data-rate transmissions. For efficient use of precious spectrum resources, the modulated signals have wider bandwidths (BWs) and higher peak-toaverage power ratios (PAPRs) than previous generations of systems. Therefore, the power amplifier (PA) operates at a less efficient backoff-power region to achieve the required linearity.

On the Optimization of Iterative Clipping and Filtering for PAPR Reduction in OFDM Systems

Orthogonal frequency division multiplexing (OFDM) offers spectral efficiency advantage, however, it is limited by peak-to-average power (PAPR) problem. The PAPR can be reduced using iterative clipping and filtering (ICF) scheme but requires that the same signals are iteratively clipped with a fixed clipping threshold at different clipping iterations. This method warrants that fast-Fourier transform (FFT)/inverse FFT (IFFT) blocks must be driven in the order of iterations many times to attain a desired PAPR threshold which expends the system power and expands the processing time. Using a second-order cone program, the number of iterations required to attain the desired PAPR threshold was reduced. This optimized ICF (OICF) was later simplified using Lagrange multiplier (LM). In this paper, we apply an adaptive clipping threshold to the LM scheme to improve the performance of the simplified OICF (SOICF). Our results show significant reduction of the PAPR problem compared with the earlier SOICF scheme albeit with some degradation in the bit error ratio (BER) performance that can be under 1.0 dB depending on the chosen clipping threshold. In addition, we also illustrate the results of the performances and the theoretical relationships between the error vector magnitude (EVM) and PAPR, between clipping ratio (CR) and EVM, and lastly the inter-dependencies of EVM, PAPR, the number of OFDM subcarriers, and the CR.

Efficient Nonlinear Companding Transform Scheme for Reducing PAPR of OFDM Signals

Efficient nonlinear companding transform (NCT) scheme for reducing peak-to-average power (PAPR) of orthogonal frequency division multiplexing (OFDM) signals is proposed. This scheme transforms the Gaussian-distributed signals into the specified statistics form defined as a piecewise function. By adjusting the transform parameters, it enables more design flexibility in companding form so that a favorable trade-off between PAPR and bit error rate (BER) can be offered. Compared to existing techniques, the scheme can achieve an effective reduction in PAPR as well as an improved BER performance simultaneously.

An Overview of Peak-to-Average Power Ratio Reduction Techniques for OFDM Signals

OFDM (Orthogonal Frequency Division Multiplexing) has been widely adopted for high data rate wireless communication systems due to its advantages such as extraordinary spectral efficiency, robustness to channel fading and better QoS (Quality of Service) performance for multiple users. However, some challenging issues are still unresolved in OFDM systems. One of the issues is the high PAPR (peak-toaverage power ratio), which results in nonlinearity in power amplifiers, and causes out of band radiation and in band distortion. This paper reviews some conventional PAPR reduction techniques and their modifications to achieve better PAPR performance. Advantages and disadvantages of each technique are discussed in detail. And comparisons between different techniques are also presented. Finally, this paper makes a prospect forecast about the direction for further researches in the area of PAPR reduction for OFDM signals.

Assessment of the peak-to-average power ratio in different channel organization strategies

The benefits of organizing multichannel communications by fragmenting the data in bonded or in aggregated channels have been usually assessed at the media access control layer, being the network traffic the purpose of the studies. Despite the importance of the different kinds of channel organizations over the transmit signal peak-to average power ratio (PAPR) to size the back-off value of the power amplifier, little attention has been paid to it. In this paper the key aspect is the PAPR, which is fundamental to face transmitter designs optimizing the trade-off between linearity and the time-of-life of the batteries. The results are of interest not only in ad hoc cognitive radio networks, but also in some of the latest European Telecommunications Standards Institute and Institute of Electrical and Electronics Engineers standards supporting mobility in either wireless local area network environments or in cellular communications. A standardized radio link is used to model a realistic scenario to study different settings of the aggregate channels and to compare them with channel bonding alternatives. Besides, the suitability of some crest factor reduction techniques is here considered for different channel organizations. The results show how the channel organization (contiguous, regular and random spaced), either with bonded or aggregated strategies, affects the PAPR.

Reduction of PAPR in OFDM Signals by using Electromagnetism Optimization Algorithm

Orthogonal Frequency Division Multiplexing grown to be a trendy modulation process inside impressive tempo wirelesscommunications. It is more advantageous over remaining technologies, even though it has some problems also. The high PAPR (Peak toAverage Power Ratio) is the main difficulty which causes non linearity at the receiving end. To reduce the PAPR so many techniques areproposed in previous such as clipping and filtering, SLM, CE, SA, PTS and so on. PTS (Partial Transmit Sequence) is highly successive thananother. In this paper PTS technique is used to reduce the PAPR but there is one problem with PTS technique, it introduces a high amount of complexity. So that to reduce such complexity and get better PAPR we planned to implement a novel based stochastic optimization algorithm which is EM (Electromagnetism-like) algorithm. By using EM get the better PAPR than PTS

A Comparative Analysis of SC-FDMA and OFDMA over WiMAX Broadband Networks

WiMAX, is the modern technology for providing broadband wireless access over long distance communication here we are adopted orthogonal frequency division multiple access (OFDMA) and single carrier frequency division multiple access (SC-FDMA) scheme for the uplink transmissions, SCFDMA utilizes single carrier modulation and frequency domain equalization. In this paper, we are presenting a Raised Cosine and Root raised cosine scheme to reduce the peak-toaverage power ratio (PAPR) of SCFDMA signals. The current scheme can transform the original SC-FDMA signals into Raised Cosine and Root Raised Cosine like distributed. Moreover, the scheme use IFDMA for compress the large signals and repetition while DFDMA for allocating different subcarriers. Computer simulation results show that the proposed SC-FDMA scheme can offer better PAPR compare to OFDMA.

SLM and Clipping Joint Algorithm for PAPR Reduction in OFDM System

As one of the most appealing techniques, selective mapping (SLM) provides an efiective solution for Peakto-average Power Ratio (PAPR) reduction in Orthogonal Frequency Division Multiplexing (OFDM) systems, however, results in large computational complexity simultaneously. As compared to SLM, clipping provides a more simple way towards a better PAPR performance, whereas results in degradation of the Bit Error Rate (BER) performance. In this paper, we proposed a joint algorithm called SLM and Quantization Clipping (SLM-QC) scheme, which combined the conventional SLM technology with a modifled quantization clipping scheme. The proposed scheme achieves a better exploitation of advantages brought about by each technique alone, with the tradeofi between the PAPR performance and the BER performance being well balanced.

Dual Bias Modulator for Envelope Tracking and Average Power Tracking Modes for CMOS Power Amplifier

This paper presents a dual-mode bias modulator (BM) for complementary metal oxide semiconductor (CMOS) power amplifiers (PAs). The BM includes a hybrid buck converter and a normal buck converter for an envelope tracking (ET) mode for high output power and for an average power tracking (APT) mode for low output power, respectively. The dual-mode BM and CMOS PA are designed using a 0.18-㎜ CMOS process for the 1.75 ㎓ band. For the 16-QAM LTE signal with a peakto-average power ratio of 7.3 ㏈ and a bandwidth of 5 ㎒, the PA with the ET mode exhibited a poweradded efficiency (PAE) of 39.2%, an EVM of 4.8%, a gain of 19.0 ㏈, and an adjacent channel leakage power ratio of -30 ㏈c at an average output power of 22 ㏈m, while the stand-alone PA has a PAE of 8% lower at the same condition. The PA with APT mode has a PAE of 21.3%, which is an improvement of 13.4% from that of the stand-alone PA at an output power of 13 ㏈m.

English

In this paper a new scheme is proposed for image transmission over coded Orthogonal Frequency Division Multiplexing (COFDM) system with Low Density Parity Check Coding (LDPC). Trigonometric transforms are used in this scheme for improving the performance of the OFDM systems and reducing the Peakto-Average Power Ratio (PAPR) of OFDM signal. It improves the error resilience ability and transmission efficiency for progressive image transmission over Additive White Gaussian Noise (AWGN) channel. The Set Partitioning In Hierarchical Trees (SPIHT) algorithm is used for source coding of the images to be transmitted. In the proposed scheme the transmit data sequence of the OFDM signal after Inverse Fast Fourier Transform (IFFT) is grouped into in-phase and in-quadrature components, then each component is transformed using either the Discrete Cosine Transform (DCT) or the Discrete Sine Transform (DST). The simulation results show that adding the DST to the system improves the visual quality of reconstructed images and reduces the PAPR of OFDM signal more than the DCT.

Multispectrum Signal Transmitters: Advances in Broadband High-Efficiency Power Amplifiers for Carrier Aggregated Signals

The growing demand for broadband mobile access drives the deployment of sophisticated and increasingly spectrum-efficient modulation techniques and access technologies resulting in communication signals with highly varying envelopes and increasing peakto-average power ratios (PAPRs). These communication signals call for advanced transmitter architectures and design techniques. This is particularly the case for the constituent radio frequency (RF) power amplifiers (PAs), which are required to amplify communication signals efficiently while maintaining signal quality and minimizing out-of-band emissions in adjacent channels. The Doherty [1] technique has been successfully applied to develop highly efficient solid-state PAs for wireless communication applications. Benefiting from recent advancements in laterally diffused metal oxide semiconductors (LDMOSs), and taking advantage of the advent of gallium nitride (GaN) technology, Doherty PA (DPA) demonstrators with average drain efficiencies approaching 50% were reported in [2]-[4]. Unfortunately, the underlying narrow bandwidth of these demonstrators currently restricts their use to infrastructure supporting third-generation (3G) wireless networks. Communication signals required by the 3G Partnership Project (3GPP) specifications for long-term evolution (LTE) will have to utilize carrier aggregation to meet the need for transmission bandwidth. Carrier aggregation refers to the use of more than one spectrum portion to deploy multiple component carriers to yield aggregated channels of wider transmission bandwidth (up to 100 MHz). Figure 1 illustrates the three carrier aggregation scenarios that are envisaged: 1) intraband contiguous carrier aggregation (contiguous component carriers aggregated in the same operating band), 2) intraband noncontiguous carrier aggregation (noncontiguous carriers aggregated in the same operating band), and 3) interband carrier aggregation (carrier aggregation of component carriers in different operating bands that may be contiguous or noncontiguous within each band).

A New Approach to Enhance Performance of OFDM using BCH and Newly Designed Filter

Orthogonal frequency division multiplexing (OFDM) is a multicarrier communication technique and it has capability to rise above the frequency-selective fading problem, which is common in wireless broadband communications. This has made it popular since last few years. The OFDM system suffers from a number of drawbacks such as the high peak-toaverage power ratio (PAPR). Many PAPR reduction techniques used either destroy the system performance, which is the clipping technique or increases the overall complexity of the system, such as the selective mapping (SLM). In this paper a unique approach has been proposed to obtain a new code from the existing codes in order to reduce the bit error rate (BER), to mitigate the gap between the performance and Shannon limit while the bounded peak average power ratio (PAPR) of OFDM symbol is guaranteed. A new code based on the BCH with a Barthannwin Wave Filter has been proposed to achieve the desired results. General Terms BCH with Barthannwin Wave Filter

PAPR Reduction in LTE Down Link using a Hybrid Repeated Clipping and SQRT Companding

The Orthogonal Frequency Division Multiplexing is one of the widely used modulation techniques in the broadband wireless technology. One of the main problems of the OFDM is the high peak-to-average power ratio of transmitting signal due to the superposition of many subcarriers. This paper presents a new hybrid peak-toaverage power ratio reduction technique, which repeated clipping and frequency domain filtering with SQRT companding over LET channel. The paper highlights the performance and advantages of the mixed technique. The simulations show that the proposed technique realizes an improved PAPR With acceptable BER.

Reduction of Papr in Ofdm Systems Using Clipping and Differential Scaling

Orthogonal Frequency Division Multiplexing (OFDM) has grown to a popular communication technique for high speed communication in the last decade. OFDM is an important member of the multicarrier modulation (MC) techniques and it has been adopted as a standard for various high data rate wireless communication systems due to its spectral bandwidth efficiency, robustness to frequency selective fading channels, etc. Although it is having many advantages it has two major drawbacks namely high PAPR and inter carrier interference (ICI). This paper is aimed to reduce the effect of PAPR and we proposed two techniques for the reduction of high Peak to Average Power Ratio (PAPR) based on Clipping, Differential Scaling. keywords: Orthogonal frequency division multiplexing (OFDM), partial transmit sequences (PTS), peak-toaverage power ratio(PAPR), selected mapping (SLM), tone reservation (TR), inter carrier interference (ICI), Companding, Active constellation, Multi carrier(MC).

60GHz Radio over Fiber System with 5Gb/s 32QAM-OFDM Downlink Signals Using Self-Mixing Homodyne Detection Technique

A novel self-mixing homodyne detection 60GHz radio over fiber (RoF) scheme with 5Gb/s 32QAM-OFDM downlink signals using discrete multitone (DMT) modulation is proposed and demonstrated by experiment. 5Gb/s 32QAM-OFDM downstream signals are transmitted over 42km SMF-28. The peak-to average power ratio (PAPR) characteristic, and the BER performance of 5Gb/s 32QAM-OFDM signals with different subcarriers generated DMT modulation and self-mixing homodyne detection are analyzed. The experimental results show the transmission performance of 5Gb/s 32QAM-OFDM signals with different subcarriers, and this RoF scheme is a suitable method for future 60GHz access system applications.

A PAPR reduction scheme with residue number system for OFDM

The peak-to-average power (PAPR) is one of the main challenges in multicarrier transmissions. Aiming at reducing the PAPR, we propose a residue number system (RNS)-based OFDM parallel transmission scheme. The key idea of the proposed scheme is to utilize the parallel property of RNS to convert the input signals into the parallel smaller residue signals while utilizing the characteristic of RNS modular operation to effectively limit the output in each residue subchannel after inverse fast Fourier transform, which is smaller than the corresponding modulus. The main contribution of the proposed scheme is to reduce the dynamic range of the transmitted signal without nonlinear distortion so as to reduce the PAPR during the transmission. A generalized performance of the proposed scheme is analyzed in this paper, including the PAPR reduction, the complexity, the transmission bandwidth, etc. Also, an approximate formula to calculate the transmission bandwidth of the proposed scheme is derived, which simplifies design procedure in practice and implies that a minor increase of the dynamic range of RNS will bring comparative improvement of the transmission bandwidth consumption. Theoretical analysis and simulation results demonstrate that the proposed scheme has the ability to achieve desirable PAPR reduction and low computational complexity without nonlinear distortion.

PTS and Companding Transform for PAPR Reduction in OFDM

A combined model of Partial Transmit Sequence (PTS) and a Companding Transform is proposed to reduce Peak-toAverage Power Ratio (PAPR) in Orthogonal Frequency Division Multiplexing (OFDM). Simulation results demonstrate that the proposed scheme can substantially offer better PAPR reduction and BER performance.

A Study of Performance Enhancement Schemes for Multicarrier Transmission

OFDM allow the transmission of high data rates over broadband channel due to the spectral bandwidth efficiency, robustness to the multipath delay etc. However OFDM signal are very sensitive to nonlinear effects due to the high peak-toaverage power radio (PAPR), which is one of the major drawback of OFDM system. The high PAPR results, high inband distortion and out-of- band radiation ,inter-carrier interference(ICI) and degradation of bit error rate (BER) performance, all these losses occur due to the non-linearity of HPA(high power amplifier). The complexity of analog-todigital converter (ADC) and digital-to- analog converter (DAC) also get increased if the PAPR of OFDM signal is high. Thus in OFDM system one of the important research areas is reduction of PAPR . This paper reviews the conventional PAPR reduction schemes for achieving the low computational complexity in wireless communication systems.

Bessel Companding Transform for reducing PAPR, OBI and BER in OFDM Systems

Orthogonal Frequency division multiplexing (OFDM) is a very popular technique in wireless communications which provides excellent robustness to channel fading and immune to interference. OFDM is one of a popular modulation technique for transmitting large amounts of digital data over radio carriers. One of the major problems that had been observed in this is the Peak-To Average power Ratio (PAPR). PAPR is a distortion that had occurred due to large number of sub carriers that are used in OFDM for modulating the digital data. Many techniques were available to reduce the PAPR in OFDM systems, among them the companding technique can be used to enhance the OFDM transmission performance by decreasing the PAPR effectively and hence BER. Here we proposed "Bessel Companding Algorithm" to reduce this significant drawback in OFDM Systems.

Comparison and analysis of PAPR reduction techniques in OFDM

In this paper, different techniques for reducing Peak To Average Power Ratio (PAPR) is discussed. The performance of an orthogonal frequency division multiplexing(OFDM) system is degraded if the peak-toaverage power ratio(PAPR) is high. An OFDM system dynamic range is typically two or four times larger than a single carrier system increasing value of the dynamic range will lead to an increased cost, power consumption of transmitter amplifier and also lead to high peak to average power ratio (PAPR). This is one of the major drawbacks of OFDM system. A serious problem of large PAPR presents when energy-inefficient nonlinear power amplifiers are used. Several techniques have been proposed to reduce PAPR in OFDM system, out of that few are selective mapping (SLM), tone reservation and partial transmit sequence. SLM method could be used to reduce PAPR, however, it causes the BER degradation and increases computational complexity. The good improvement in PAPR given by the present techniques permits the reduction of the complexity and cost of the transmitter significantly.