scholarly journals Pilot-Aided Frame Synchronization in Optical OFDM Systems

2020 ◽  
Vol 10 (11) ◽  
pp. 4034 ◽  
Author(s):  
Funmilayo B. Offiong ◽  
Sinan Sinanović ◽  
Wasiu O. Popoola
Keyword(s):  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Average Power ◽  
Visible Light Communication ◽  
Low Complexity ◽  
Frame Synchronization ◽  
Ofdm Systems ◽  
Pilot Symbol ◽  
Pilot Signal ◽  
Symmetric Property

Efficient frame synchronization is essential for data recovery in communication systems. In this study, a single pilot sequence is used to achieve both frame synchronization and peak-to-average power ratio (PAPR) reduction. The two systems considered are direct-current biased optical orthogonal frequency division multiplexing (DCO-OFDM) and asymmetrically clipped O-OFDM (ACO-OFDM). The pilot symbol is allocated to odd indexed subcarriers only. Thus, the synchronization algorithm leverages the mirror symmetric property of the pilot symbol within a frame to detect the start of the pilot signal at the receiver. This scheme has low complexity and gives precise frame synchronization at signal-to-noise ratios as low as 4 dB in an indoor visible light communication (VLC) channel.

Combined Envelope Scaling with Modified SLM Method for PAPR Reduction in OFDM-Based VLC Systems

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Ridha Touhami ◽  
Djamal Slimani ◽  
Ayad Atiyah Abdulkafi ◽  
Yaseein Soubhi Hussein ◽  
Mohamad Yusoff Alias
Keyword(s):  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Average Power ◽  
Visible Light Communication ◽  
Low Complexity ◽  
Optical Communication Systems ◽  
High Spectral Efficiency ◽  
Low Complexity Implementation ◽  
Scaling Process ◽  
Selective Mapping

AbstractOrthogonal frequency-division multiplexing technique (OFDM) has been adopted widely as a modulation technique for radio frequency (RF) and optical communication systems such as visible-light communication (VLC) due to its high spectral efficiency and low-complexity implementation. VLC-OFDM is recommended in 5 G mobile communication. However, VLC-OFDM suffer from the high peak to-average power ratio (PAPR). In this paper, a modified selective mapping (MSLM) method is applied to the proposed system followed by a new envelope scaling process for further reductions in PAPR of VLC-OFDM system. Simulation results show that the proposed method reduces the PAPR by about 6.8 and 1.7 dB comparing with the original signal and the traditional SLM with a number of rotation vector U = 8, respectively.

scholarly journals PAPR Performance Analysis of low Complexity SLM for Various Phase Sequences in MIMO-OFDM System

2019 ◽  
Vol 8 (2) ◽  
pp. 4347-4353
Keyword(s):  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Average Power ◽  
Multipath Fading ◽  
Low Complexity ◽  
Superior Performance ◽  
Ofdm Systems ◽  
Phase Sequence ◽  
Mimo Ofdm ◽  
Papr Performance

Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing (MIMO OFDM) is a key technology for contemporary communication systems due to its spectral efficiency, higher data rates, better diversity gain, good link reliability and both inter symbol interference (ISI) and multipath fading free transmission. However, due to the presence of OFDM, MIMO-OFDM suffers from high peak to average power ratio (PAPR). Even though, several schemes are available to mitigate PAPR, there is no standard solution. Selective Mapping (SLM) significantly reduces the PAPR in OFDM systems at the cost of computational complexity (CC). The CC of SLM can be reduced by proper design of SLM. This paper considers a low complexity SLM (LC SLM) scheme in which both the CC and length of the index of selected phase sequence are significantly reduced. The PAPR of an SLM-OFDM depends on the number of subcarriers in OFDM, the number of candidate blocks in SLM and selected phase sequence and this paper investigate various phase sequences and analyses their PAPR performance. Simulation results show the superior performance of Riemann sequence over the other phase sequences.

scholarly journals Palm Date Leaf Clipping: A New Method to Reduce PAPR in OFDM Systems

Information ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 190 ◽  
Author(s):  
Brahim Bakkas ◽  
Reda Benkhouya ◽  
Idriss Chana ◽  
Hussain Ben-Azza
Keyword(s):  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
High Speed ◽  
Average Power ◽  
Papr Reduction ◽  
Frequency Division ◽  
Ofdm Systems ◽  
Leaf Clipping ◽  
Hyperbolic Cosine ◽  
Transmitted Signal

Orthogonal frequency division multiplexing (OFDM) is the key technology used in high-speed communication systems. One of the major drawbacks of OFDM systems is the high peak-to-average power ratio (PAPR) of the transmitted signal. The transmitted signal with a high PAPR requires a very large linear range of the Power Amplifier (PA) on the transmitter side. In this paper, we propose and study a new clipping method named Palm Clipping (Palm date leaf) based on hyperbolic cosine. To evaluate and analyze its performance in terms of the PAPR and Bit Error Rate (BER), we performed some computer simulations by varying the Clipping Ratio (CR) and modulation schemes. The obtained results show that it is possible to achieve a gain of between 7 and 9 dB in terms of PAPR reduction depending on the type of modulation. In addition, comparison with several techniques in terms of PAPR and BER shows that our method is a strong alternative that can be adopted as a PAPR reduction technique for OFDM-based communication systems.

scholarly journals A low complexity partial transmit sequence approach based on hybrid segmentation scheme

2020 ◽  
Vol 9 (6) ◽  
pp. 2371-2379
Author(s):  
Ali Hussein Fadel ◽  
Hasanain H. Razzaq ◽  
Salama A. Mostafa
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Average Power ◽  
Low Complexity ◽  
Frequency Division ◽  
Ofdm Systems ◽  
Wave Shape ◽  
Data Sequence ◽  
Practical Applications ◽  
Phase Rotation ◽  
Hybrid Segmentation

The partial transmit sequences (PTS) is regarded as a promising scheme for inhibiting ‎the high peak-to-average power ratio (PAPR) problem in the orthogonal frequency division ‎multiplexing (OFDM) systems. The PTS scheme relies on partitioning the ‎data sequence into subsets and weighting these subsets by a group of the phase rotation ‎factors. Although the PTS can efficiently reduce the high PAPR value, a great ‎computational complexity (CC) level restricts the utilization of the PTS scheme in practical ‎applications. In PTS, there are three common types of segmentation schemes; ‎interleaving (IL-PTS), pseudo-random (PR-PTS), and adjacent (Ad-PTS) schemes. This ‎paper presents a new algorithm named hybrid pseudo-random and interleaving cosine wave shape ‎‎(H-PRC-PTS) by combining the PR-PTS scheme and the symmetrical ‎interleaving cosine wave shape (S-IL-C-PTS) scheme which was proposed in our previous ‎work. The results indicate that the suggested algorithms can ‎diminish the PAPR value like the PR-PTS scheme, whereas the CC level is reduced significantly.

scholarly journals An Efficient Adaptive Technique with Low Complexity for Reducing PAPR in OFDM-Based Cognitive Radio

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Hefdhallah Sakran ◽  
Omar Nasr ◽  
Mona Shokair
Keyword(s):  
Cognitive Radio ◽  
Orthogonal Frequency Division Multiplexing ◽  
Average Power ◽  
Low Complexity ◽  
Papr Reduction ◽  
Modulation Scheme ◽  
Ofdm Systems ◽  
Cpu Time ◽  
Reduction Techniques ◽  
Selective Mapping

Cognitive radio (CR) is considered nowadays as a strong candidate solution for the spectrum scarcity problem. On standards level, many cognitive radio standards have chosen Non-Contiguous Orthogonal Frequency Division Multiplexing (NC-OFDM) as their modulation scheme. Similar to OFDM, NC-OFDM suffers from the problem of having a high Peak to Average Power Ratio (PAPR). If not solved, either the transmitted signal will be distorted, which will cause interference to primary (licensed) users, or the effeciency of the power amplifier will be seriously degraded. The effect of the PAPR problem in NC-OFDM based cognitive radio networks is worse than normal OFDM systems. In this paper, we propose enhanced techniques to reduce the PAPR in NC-OFDM systems. We start by showing that combining two standard PAPR reduction techniques (interleaver-based and selective mapping) results in a lower PAPR than using them individually. Then, an “adaptive number of interleavers” will be proposed that achieves the same performance of conventional interleaver-based PAPR reduction while reducing the CPU time by 41.3%. Finally, adaptive joint interleaver with selective mapping is presented, and we show that it gives the same performance as conventional interleaver-based technique, with reduction in CPU time by a factor of 50.1%.

scholarly journals Ciphered BCH Codes for PAPR Reduction in the OFDM in Underwater Acoustic Channels

2022 ◽  
Vol 10 (1) ◽  
pp. 91
Author(s):  
Mohsin Murad ◽  
Imran A. Tasadduq ◽  
Pablo Otero
Keyword(s):  
Secure Communication ◽  
Orthogonal Frequency Division Multiplexing ◽  
Average Power ◽  
Low Complexity ◽  
Bch Codes ◽  
Papr Reduction ◽  
Ofdm Systems ◽  
Computational Power ◽  
Underwater Acoustic ◽  
Underwater Acoustic Channels

We propose an effective, low complexity and multifaceted scheme for peak-to-average power ratio (PAPR) reduction in the orthogonal frequency division multiplexing (OFDM) system for underwater acoustic (UWA) channels. In UWA OFDM systems, PAPR reduction is a challenging task due to low bandwidth availability along with computational and power limitations. The proposed scheme takes advantage of XOR ciphering and generates ciphered Bose–Chaudhuri–Hocquenghem (BCH) codes that have low PAPR. This scheme is based upon an algorithm that computes several keys offline, such that when the BCH codes are XOR-ciphered with these keys, it lowers the PAPR of BCH-encoded signals. The subsequent low PAPR modified BCH codes produced using the chosen keys are used in transmission. This technique is ideal for UWA systems as it does not require additional computational power at the transceiver during live transmission. The advantage of the proposed scheme is threefold. First, it reduces the PAPR; second, since it uses BCH codes, the bit error rate (BER) of the system improves; and third, a level of encryption is introduced via XOR ciphering, enabling secure communication. Simulations were performed in a realistic UWA channel, and the results demonstrated that the proposed scheme could indeed achieve all three objectives with minimum computational power.

scholarly journals OFDM PAPR Reduction via Time-Domain Scattered Sampling and Hybrid Batch Training of Synchronous Neural Networks

Electronics ◽  
2021 ◽  
Vol 10 (14) ◽  
pp. 1708
Author(s):  
Ahmad Gendia ◽  
Osamu Muta
Keyword(s):  
Neural Network ◽  
Orthogonal Frequency Division Multiplexing ◽  
Average Power ◽  
Computational Cost ◽  
Low Complexity ◽  
Critical Issue ◽  
Papr Reduction ◽  
Ofdm Systems ◽  
Comparable Performance ◽  
Increasing Demand

Peak-to-average power ratio (PAPR) reduction in multiplexed signals in orthogonal frequency division multiplexing (OFDM) systems has been a long-standing critical issue. Clipping and filtering (CF) techniques offer good performance in terms of PAPR reduction at the expense of a relatively high computational cost that is inherent in the repeated application of fast Fourier transform (FFT) operations. The ever-increasing demand for low-latency operation calls for the development of low-complexity novel solutions to the PAPR problem. To address this issue while providing an enhanced PAPR reduction performance, we propose a synchronous neural network (NN)-based solution to achieve PAPR reduction performance exceeding the limits of conventional CF schemes with lower computational complexity. The proposed scheme trains a neural network module using hybrid collections of samples from multiple OFDM symbols to arrive at a signal mapping with desirable characteristics. The benchmark NN-based approach provides a comparable performance to conventional CF. However, it can underfit or overfit due to its asynchronous nature which leads to increased out-of-band (OoB) radiations, and deteriorating bit error rate (BER) performance for high-order modulations. Simulations’ results demonstrate the effectiveness of the proposed scheme in terms of the achieved cubic metric (CM), BER, and OoB emissions.

Effect of Controlling Parameters of Tone Reservation Based on Null Subcarriers (TRNS) on the Performance of OFDM Systems

2020 ◽  
Vol 12 (2) ◽  
pp. 45-62
Author(s):  
Mohamed Mounir ◽  
Mohamed Bakry El Mashade
Keyword(s):  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Average Power ◽  
Threshold Value ◽  
Papr Reduction ◽  
Ofdm Systems ◽  
Peak Reduction ◽  
High Data ◽  
Tone Reservation ◽  
Number Of Iterations

High data rate communication systems usually implement Orthogonal Frequency Division Multiplexing (OFDM) to face frequency selectivity. High Peak to Average Power Ratio (PAPR) is an OFDM disadvantage that causes Bit Error Rate (BER) degradation and out-of-band (OOB) radiation when OFDM signal pass through nonlinear Power Amplifier (PA). In order to overcome this problem larger Input Back-Off (IBO) is required. However, large IBO decreases the PA efficiency. PAPR reduction techniques are used to reduce the required IBO, so that PA efficiency is saved. Several PAPR reduction methods are introduced in literature, among them Tone Reservation based on Null Subcarriers (TRNS) is downward compatible version of Tone Reservation (TR) with small excess in the average power and low computational complexity compared to others. As will be shown, TRNS is the best practical one of the four downward compatible techniques. Performance of TRNS is controlled by three parameters; number of peak reduction tones (PRTs), predefined threshold (Amax), and number of iterations (Itr). In order to increase PAPR reduction gain, enhance BER performance, and reduce the required IBO to follow the given power spectral density (PSD), we have to choose the values of these parameters adequately. Results showed that, we have to reduce the threshold value to the average (i.e. Amax =0 dB). Also, we have to increase number of PRTs. However, we have to maintain the spectrum shape. Finally, we have to choose moderate number of iterations (e.g. Itr ≈50), as excessive increase in number of iterations is not useful, especially at high PAPR values.

scholarly journals Design of an Adaptive Predistorter for Solid State Power Amplifier in Wireless OFDM Systems

2009 ◽  
Vol 2009 ◽  
pp. 1-5 ◽  
Author(s):  
Rui J. P. de Figueiredo ◽  
Lin Fang ◽  
Byung Moo Lee
Keyword(s):  
Performance Improvement ◽  
Power Amplifier ◽  
Communication Systems ◽  
Power Efficiency ◽  
Orthogonal Frequency Division Multiplexing ◽  
Average Power ◽  
Wireless Communication Systems ◽  
Ofdm Systems ◽  
High Power Amplifier ◽  
Ofdm Signals

Orthogonal frequency division multiplexing (OFDM) is a powerful modulation choice for wideband wireless communication systems. However, its high peak-to-average power ratio greatly limits the high power amplifier (HPA) power efficiency. Here, we present the design of an adaptive predistorter to compensate the distortion caused by the HPA. Specifically, we deal with the implementation issue of the proposed predistorter in Lee and de Figueiredo's work (2006). The performance improvement by predistorter is verified by both floating-point simulation and fixed-point simulation, where the latter includes the distortion effects from the hardware. The bit widths for OFDM signals, ADC, and DAC are evaluated, and the bit width of 10 is shown to be sufficient for the hardware design.

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