Gaussian Pulse-Based Two-Threshold Parallel Scaling Tone Reservation for PAPR Reduction of OFDM Signals

Tone Reservation (TR) is a technique proposed to combat the high Peak-to-Average Power Ratio (PAPR) problem of Orthogonal Frequency Division Multiplexing (OFDM) signals. However conventional TR suffers from high computational cost due to the difficulties in finding an effective cancellation signal in the time domain by using only a few tones in the frequency domain. It also suffers from a high cost of hardware implementation and long handling time delay issues due to the need to conduct multiple iterations to cancel multiple high signal peaks. In this paper, we propose an efficient approach, called two-threshold parallel scaling, for implementing a previously proposed Gaussian pulse-based Tone Reservation algorithm. Compared to conventional approaches, this technique significantly reduces the hardware implementation complexity and cost, while also reducing signal processing time delay by using just two iterations. Experimental results show that the proposed technique can effectively reduce the PAPR of OFDM signals with only a very small number of reserved tones and with limited usage of hardware resources. This technique is suitable for any OFDM-based communication systems, especially for Digital Video Broadcasting (DVB) systems employing large IFFT/FFT transforms

Peak-to-Average Power Ratio Reduction of DOCSIS 3.1 Downstream Signals

Tone reservation (TR) is an attractive and widely used method for peak-to-average power ratio (PAPR) reduction of orthogonal frequency division multiplexing (OFDM) signals, where both transmitter and receiver agree upon a number of subcarriers or tones to be reserved to generate a peak canceling signal that can reduce the peak power of the transmitted signals. The tones are selected to be mutually exclusive with the tones used for data transmission, which allows the receiver to extract the data symbols without distortions. This thesis presents two novel PAPR reduction algorithms for OFDM signals based on the TR principle, which do not distort the transmitted signals. The first proposed algorithm is performed in the time domain, whereas the second algorithm is a new clipping-and-filtering method. Both algorithms consist of two stages. The first stage, which is done off-line, creates a set of canceling signals based on the settings of the OFDM system. In particular, these signals are constructed to cancel signals at different levels of maximum instantaneous power that are above a predefined threshold. The second stage, which is online and iterative, reduces the signal peaks by using the canceling signals constructed in the first stage. The precalculated canceling signals can be updated when different tone sets are selected for data transmission, accommodating many practical applications. Simulation results show that the proposed algorithms achieve slightly better PAPR reduction performance than the conventional algorithms. Moreover, such performance is achieved with much lower computational complexity in terms of numbers of multiplications and additions per iteration. Among the two proposed algorithms, the time-domain algorithm gives the best peak reduction performance but the clipping-and-filtering algorithm requires considerably less number of multiplications per iteration and can be efficiently implemented using the fast Fourier transform (FFT)/inverse fast Fourier transform (IFFT) structure

Adjustable dynamic range for paper reduction schemes in large-scale MIMO-OFDM systems

In a multi-input-multi-output (MIMO) communication system there is a necessity to limit the power that the output antenna amplifiers can deliver. Their signal is a combination of many independent channels, so the demanded amplitude can peak to many times the average value. The orthogonal frequency division multiplexing (OFDM) system causes high peak signals to occur because many subcarrier components are added by an inverse discrete Fourier transformation process at the base station. This causes out-of-band spectral regrowth. If simple clipping of the input signal is used, there will be in-band distortions in the transmitted signals and the bit error rate will increase substantially. This work presents a novel technique that reduces the peak-to-average power ratio (PAPR). It is a combination of two main stages, a variable clipping level and an Adaptive Optimizer that takes advantage of the channel state information sent from all users in the cell. Simulation results show that the proposed method achieves a better overall system performance than that of conventional peak reduction systems in terms of the symbol error rate. As a result, the linear output of the power amplifiers can be minimized with a great saving in cost

Peak to average power ratio reduction and error control in MIMO-OFDM HARQ System

Currently, multiple-input multiple-output orthogonal frequency division multiplexing (MIMOOFDM) systems underlie crucial wireless communication systems such as commercial 4G and 5G networks, tactical communication, and interoperable Public Safety communications. However, one drawback arising from OFDM modulation is its resulting high peak-to-average power ratio (PAPR). This problem increases with an increase in the number of transmit antennas. In this work, a new hybrid PAPR reduction technique is proposed for space-time block coding (STBC) MIMO-OFDM systems that combine the coding capabilities to PAPR reduction methods, while leveraging the new degree of freedom provided by the presence of multiple transmit chairs (MIMO). In the first part, we presented an extensive literature review of PAPR reduction techniques for OFDM and MIMO-OFDM systems. The work developed a PAPR reduction technique taxonomy, and analyzed the motivations for reducing the PAPR in current communication systems, emphasizing two important motivations such as power savings and coverage gain. In the tax onomy presented here, we include a new category, namely, hybrid techniques. Additionally, we drew a conclusion regarding the importance of hybrid PAPR reduction techniques. In the second part, we studied the effect of forward error correction (FEC) codes on the PAPR for the coded OFDM (COFDM) system. We simulated and compared the CCDF of the PAPR and its relationship with the autocorrelation of the COFDM signal before the inverse fast Fourier transform (IFFT) block. This allows to conclude on the main characteristics of the codes that generate high peaks in the COFDM signal, and therefore, the optimal parameters in order to reduce PAPR. We emphasize our study in FEC codes as linear block codes, and convolutional codes. Finally, we proposed a new hybrid PAPR reduction technique for an STBC MIMO-OFDM system, in which the convolutional code is optimized to avoid PAPR degradation, which also combines successive suboptimal cross-antenna rotation and inversion (SS-CARI) and iterative modified companding and filtering schemes. The new method permits to obtain a significant net gain for the system, i.e., considerable PAPR reduction, bit error rate (BER) gain as compared to the basic MIMO-OFDM system, low complexity, and reduced spectral splatter. The new hybrid technique was extensively evaluated by simulation, and the complementary cumulative distribution function (CCDF), the BER, and the power spectral density (PSD) were compared to the original STBC MIMO-OFDM signal

Analysis and Implementation of PAPR reduction algorithms for C-OFDM signals

Nowadays multicarrier modulation has become a key technology for communication systems; for example C-OFDM schemes are used in wireless LAN (802.11a/g/n), terrestrial digital television (DVB-T) and audio broadcaster (DAB) in Europe, and discrete multitone (DMT) in x.DSL systems. The principal difficulty with OFDM is the occurrence of the coherent alignment of the time domain parallel signals at the transmitted side which forces system designer to introduce either additional hard computationally device or a suitable power back-off at the high power amplifier in order to cope with the large magnitude signal fluctuation. This leads to a significant increment in computational cost in the former case whereas in a worse allowable power utilization in the latter case with respect to the original system. However since both allowable power and computational cost are subject to a design as well as regulatory limit others solution must be accomplished. Peak reduction techniques reduce maximum-to-mean amplitude fluctuations nominating as a feasible solution. Peak-to-average power ratio is the key metric to measure this amplitude fluctuations at transmitter and to give a clear figure of merit for comparison among different techniques

PAPR Analysis in OFDM-IQ-IM Systems

One of the key disadvantages of OFDM system, implemented already in 4G and 5G is high PAPR. For this reason, it is very important to evaluate the PAPR performance of any potential multiplexing technique candidate for upcoming generations. Due to the superior performance over OFDM considering BER performance, spectral efficiency, energy efficiency, OFDM-IQ-IM is one of the promising multiplexing techniques for upcoming generations of wireless technology. Therefore, the PAPR performance of OFDM-IQ-IM system has been analysed here. In deterministic approach, subcarriers are considered to be modulated by symbols with highest power and the upper limit of the PAPR of OFDM-IQ-IM system has been formulated. Using statistical distribution, a probabilistic approach has been taken to determine the PAPR performance of the OFDM-IQ-IM and OFDM-IM systems. The distribution of PAPR of OFDM-IQ-IM and OFDM-IM systems has been evaluated considering the discrete time baseband signals for both in-phase and quadrature components as independent Gaussian random variables. A comparative analysis of the PAPR of OFDM, OFDM-IM and OFDM-IQ-IM systems has been made in both deterministic and probabilistic approach. Thus improved PAPR performance has been noticed in OFDM-IQ-IM system compared to OFDM-IM and OFDM systems for same spectral efficiency

Computationally Efficient Modified PTS for PAPR Reduction in MIMO-OFDM

Nowadays wireless communication has taken its leap for a high data rate using the multi-carrier transmission technique.Orthogonal frequency division multiplexing(OFDM) is one of such popular method for achieving this high information rate.OFDM has several advantages,but one of the main drawbacks is its high peak-to-average power ratio(PAPR).This is due to a large number of the subcarrier,which leads to distortion problem at receiver. An OFDM signal with the high PAPR requires power amplifier’s(PAs)with large dynamic ranges.Such PAs are less efficient,costly to manufacture and very much difficult to design.There have been a large number of techniques are available in the literature to reduce the PAPR, such as Partial transmit sequence,Selective mapping,Block Coding, Tone rejection,etc.However,the challenging part is that most of the PAPR reduction schemes come with high computational complexity.Recent PAPR reduction techniques such as partial transmit sequence(PTS)has been considered as most popular for PAPR reduction.This research work explores to find a solution for the PAPR reduction by using PTS technique, which has been implemented by using sub-blocks partitioning.In sub-block partition consists of OFDM data frame which is partitioned into several sub-blocks.An adjacent partitioning(AP)method can be perceived as the best of the existing partitioning method when the cost and PAPR reduction performance are considered together.A new technique is based on modified PTS using phase rotation and circular shifting to attain the overall reduction of PAPR in MIMO-OFDM system, but computational complexity does not decrease for the same.A Co-operative PTS technique which is mainly based on alternative PTS technique is applied.In this technique although a slight loss of PAPR reduction performance is there but with much lower computational complexity

Spectral efficiency improvement of low peak-to-average power ratio complete complementary code division multiple access systems

An investigation into the peak-to-average power ratio (PAPR) performance of cyclic rotation complete complementary code division multiple access (CR-CC-CDMA) has been conducted. Additionally, a novel orthogonal signalling technique, referred to as complementary rotation keying (CRK), has been developed for improving the spectral efficiency (SE) of CC-CDMA whilst maintaining a low PAPR. The CRK system is based on the concept of CR of CC codes in order to allow interoperability with CR-CC-CDMA systems. To this end, both systems employ a similar transmitter and receiver structure. The CR-CC-CDMA technique suffers from increased PAPR as SE per user is increased. The CRK system offers an improvement in SE, while maintaining the PAPR of a CC-CDMA system. The bit error rates of both systems were unaffected in a joint system, indicating complete interoperability. This allows dynamic adjustment of the PAPR and SE of any user in the system, with users being able to switch between both systems without causing multi user interference.Dissertation (MEng)--University of Pretoria, 2018.Electrical, Electronic and Computer EngineeringMEn

OFDM based air interfaces for future mobile satellite systems

This thesis considers the performance of OFDM in a non-linear satellite channel and mechanisms for overcoming the degradations resulting from the high PAPR in the OFDM signal in the specific satellite architecture. It was motivated by new S-DMB applications but its results are applicable to any OFDM system via satellites. Despite many advantages of OFDM, higher PAPR is a major drawback. OFDM signals are therefore very sensitive to non-linear distortion introduced by the power amplifiers and thus, significantly reduce the power efficiency of the system, which is already crucial to satellite system economics. Simple power amplifier back-off to cope with high OFDM PAPR is not possible. Two transmitter based techniques have been considered: PAPR reduction and amplifier linearization.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Low Complex PAPR Reduction Schemes for OFDM Systems

In this thesis, three low-complex PAPR reduction schemes for OFDM systems are proposed. All the proposed schemes can be considered as modi ed versions of the conventional SLM scheme, which can signi cantly reduce high PAPR of OFDM signals with no distortion. In the rst proposed scheme, a new set of the candidate sequences is generated by partial phase weighting in the time domain and the combination of sub-blocks by applying IFFT properties. In the second scheme which is based on a combination of SLM and PTS, a simple phase optimization technique is introduced. The third scheme forms di erent 16-QAM signals from 2 QPSK signals. Also, the circular convolution part in TPPW-SLM, which is also a part of Class-III SLM, is applied