Transmission Of Side Information Research Articles

Joint PAPR reduction and channel estimation in low-complexity VLC systems

In recent times, there has been a surge in interest surrounding visible light communication (VLC) as a compelling adjunct to radio frequency (RF) technology. This enthusiasm stems from deployments showcasing its efficacy in high-speed data transmission, characterized by low complexity, robust security, and high reliability. Among the variants of orthogonal frequency division multiplexing (OFDM), direct current-biased optical OFDM (DCO-OFDM) stands out in the realm of VLC systems, owing to its ability to furnish rapid data provisioning. However, a significant drawback of selective mapping (SLM) based DCO-OFDM transceivers lies in its computational complexity and practical implementation challenges. To address this limitation, this paper presents a modified SLM technique termed selective phase modulation (SPM) aimed at mitigating the peak-to-average power ratio (PAPR) in the transmitter section while simplifying the data decoding process at the receiver end. The SPM method utilizes a phase modulation and demodulation process based on clusters and assisted by pilot signals, streamlining the transceiver architecture. The SPM methodology offers reduced computational complexity at the transmitter by selectively applying phase sequences to data, circumventing the necessity for side information (SI) transmission and SI estimation at the receiver with a known pilot symbol inserted in the data. This dual-functionality mechanism not only achieves complexity reduction but also facilitates channel estimation at the receiver for proper data recovery. Based on complexity analysis and simulation outcomes, the computational complexity reduction strategy outperforms the conventional selective mapping (CSLM) technique, VLC-based pilot-assisted PAPR reduction systems, and embedded coded modulation (ECM). This allows for smooth incorporation of this technology into future VLC systems.

Optical-OFDM VLC System: Peak-to-Average Power Ratio Enhancement and Performance Evaluation.

Visible Light Communication (VLC) systems are favoured for numerous applications due to their extensive bandwidth and resilience to electromagnetic interference. This study delineates various constructions of Optical Orthogonal Frequency Division Multiplexing (O-OFDM) approaches employed in VLC systems. Various factors are elaborated within this context to ascertain a more effective O-OFDM approach, including constellation size, data arrangement and spectral efficiency, power efficiency, computational complexity, bit error rate (BER), and peak-to-average power ratio (PAPR). This paper seeks to assess these approaches' BER and PAPR performance across varying modulation orders. Regrettably, in VLC systems based on OFDM methodology, the superposition of multiple subcarriers results in a high PAPR. Therefore, this study aims to diminish the PAPR in VLC systems, enhancing system performance. We propose a non-distorting PAPR reduction technique, namely the Vandermonde-Like Matrix (VLM) precoding technique. The suggested technique is implemented across various O-OFDM approaches, including DCO-OFDM, ADO-OFDM, ACO-OFDM, FLIP-OFDM, ASCO-OFDM, and LACO-OFDM. Notably, this method does not affect the system's data rate because it does not require the mandatory transmission of side information. Furthermore, this technique can decrease the PAPR without impacting the system's BER performance. This study compares the proposed PAPR reduction technique against established methods documented in the literature to evaluate their efficacy and validity rigorously.

ASCO-OFDM based VLC system throughput improvement using PAPR precoding reduction techniques

The huge bandwidth and immunity to electromagnetic interference make visible light communication (VLC) systems the preferred technique for many applications. Unfortunately, the superposition of multiple subcarriers in VLC orthogonal frequency division multiplexing systems leads to a high peak-to-average power ratio (PAPR). So, in this study, we aim to reduce PAPR in VLC systems and improve the system performance by proposing non-distorting PAPR reduction techniques like precoding techniques as it doesn’t affect the system data rate because they do not require any obligatory transmission of side information. Moreover, it has a very good ability to reduce the PAPR without affecting the system BER performance. So, different precoding reduction techniques are proposed like discrete cosine transform (DCT), discrete sine transform (DST), discrete Hatley transform (DHT), and Vandermonde like matrix (VLM), to address the high PAPR and light-emitting diode-restricted linear range problems in VLC systems. The proposed technique using DHT, DCT, DST, and VLM provided a significant advantage in reducing the PAPR by 1.35 dB, 1.46 dB, 2.12 dB, and 2.17 dB, respectively. So the proposed technique is based on using the VLM precoding technique to achieve maximum reachable PAPR reduction value. Also, a comparison of the presented work and related literature reviews for PAPR reduction techniques are held to ensure the validity and effectiveness of the proposed scheme.

Simultaneous minimization of side‐band power and PAPR in OFDM based cognitive radio without additional bandwidth requirement for sending SI

AbstractCognitive radio (CR) incorporating orthogonal frequency division multiplexing (OFDM) is an intelligent spectrum sharing technique that acquires high data rate in frequency selective fading environment. OFDM has been successfully used for 4G and specific version of OFDM is being considered as the multiple access technology for 5G as well. However OFDM signal is more likely to have high peak‐to‐average power ratio (PAPR). Similarly, the sideband power of secondary or temporary users (SU) in CR can lead to interference to the licensed or primary users of the neighboring bands. In this work, an improved technique for the joint minimization of sideband power and PAPR using Zadoff‐Chu (ZC) sequence is proposed for CR based on OFDM technology. Furthermore, we propose a detection algorithm based on a binary hypothesis testing problem to recover the chosen ZC sequence at the receiver side eliminating the requirement of side information (SI) transmission. Simulation studies of the proposed method exhibits the efficiency of the concurrent reduction of PAPR and sideband power along with a huge bandwidth saving by the omission of the SI transmission.

A Multichannel Wireless UAV Charging System With Compact Receivers for Improving Transmission Stability and Capacity

This article presents a multichannel wireless rotary-wing unmanned aerial vehicle (UAV) charging system with compact receivers for improving transmission stability and capacity. The multichannel scheme and associated landing structure are proposed according to the application challenges. It contains multiple null-cross-coupled transmission paths to improve charging capability, and the structure stabilizes the charging. Compact and shielding-free receivers are embedded to avoid affecting the airflow and the weight of the flight. Misalignment-tolerant unipolar coils are designed based on transmission and field characteristics, which cooperate with the scheme for efficient coupling and restrained leakage flux. The output characteristics of the multichannel system are analyzed based on theoretical modeling and simulation. A multichannel output estimation control strategy is implemented, based on the deduced mapping relations and transmitter-side information, to regulate output currents and eliminate circulating currents. It is realized without real-time massive communication or measuring on board, and the parallel channels avoid influences of faulty channels. A multichannel experimental prototype is established and tested to prove the feasibility of the design, which can be applied to rotary-wing UAV autonomous charging flexibly.

Inference in Turbulent Molecular Information Channels Using Support Vector Machine

Inference of transmitter side information is essential to communication. In Molecular Communication (MC), whilst the Bayesian inference of mass diffusion channel parameters is well established, turbulent diffusion (TD) channels are not well-understood. Cascading vortices rapidly transform transmitted momentum (molecular information puffs) into heat, which raises the challenge of receiver inferring transmitter information. Our initial results found that in TD channels, inferring transmitted molecular concentration or timing is challenging. As such, we were motivated to infer transmitter velocity from a flexible receiver sample area. In this paper, we consider an unbounded scenario of Molecular Communication via Turbulent Diffusion (MCvTD) where a transmitter injects several molecular puffs with different velocities. We first developed a time difference concentration (TDC) method based on large-scale support vector machine (SVM) to distinguish the injection velocities. To trade-off the prediction accuracy and number of receiver spatial samples, we propose the stepwise maximum variance (SMV) algorithm to select the limited dominant receiver sampling locations. The overall performance can achieve 100% accuracy in transmitter velocity information recovery, with excellent error vs. receiver size trade-off (e.g., 5% error for 74% area reduction). The research results indicate that velocity modulation at transmitter and TDC with SVM receiver should be used in MCvTD channels.

A New Selective Mapping Scheme for Visible Light Systems

The huge bandwidth and immunity to electromagnetic interference make Visible Light Communication (VLC) systems as preferred technique for designing the physical layer of 5G applications. Unfortunately, the superimposition of multiple subcarriers in DC-biased Optical Orthogonal Frequency Division Multiplexing (DCO-OFDM) system leads to a high peak to average power ratio (PAPR). The well-accepted nondistorting PAPR reducing schemes like selective mapping (SLM) require an obligatory transmission of side information (SI) reducing the bandwidth efficiency of the system. To address these issues, a simple SI cancellation algorithm using pilots associated with channel estimation is proposed in this work. In short, the DCO-OFDM system is presented with a modified cluster architecture and each cluster is assigned with at least one pilot. Every cluster is restricted to have same phase and this idea provides the pilots to perform joint channel estimation and SI cancellation. The experimental results obtained by using Universal Software Radio Peripheral (USRP) as hardware and LabVIEW as software indicate a significant reduction in PAPR without effecting the real-time channel response.

A Novel PAPR Reduction Scheme for Polar-Coded OFDM Systems

A novel joint channel coding and peak-to-average power ratio (PAPR) reduction technique for polar-coded orthogonal frequency-division multiplexing (OFDM) systems is proposed. The main concept is to introduce shaping indices to polar encoder, and generate multiple OFDM symbol candidates according to various shaping bit patterns and then select the one with the lowest PAPR as a transmitted signal. Since information and shaping bits can be jointly decoded using the conventional decoding algorithm of polar codes, transmission of side information is not required. The polar code design algorithm for efficient PAPR reduction is also discussed. It is demonstrated that the proposed shaping method offers a gain of more than 4.5dB in terms of PAPR performance without affecting the decoding complexity.

Distortion-less PAPR reduction algorithm for multi-user MIMO system with linear precoding

High peak-to-average power ratio (PAPR) is a major factor degrading power efficiency of communication systems. In multi-user (MU) multiple-input multiple-output (MIMO) systems, the PAPR becomes even worse since the power efficiency of the system is determined by the transmission stream with the highest PAPR. In this paper, we propose two PAPR reduction algorithms based on linear precoding, which exploit extra degree-of-freedom of the channel state matrix in MU-MIMO systems. The basic idea is to generate candidate output signals by multiplying the input signal with a set of equivalent linear precoding matrices, and find the signal with the lowest PAPR for transmission. The proposed algorithms are distortion-less PAPR reduction algorithms that do not sacrifice the system performance. Comparing to other distortion-less PAPR reduction algorithms, the proposed algorithms do not need to transmit side information, thus comply with existing MU-MIMO systems. Numerical results further validate our designs.

PAPR Reduction in DCO-OFDM Visible Light Communication Systems Using Optimized Odd and Even Sequences Combination

This paper proposes a novel peak-to-average power ratio (PAPR) reduction scheme, which has several advantages, such as low-complexity candidate construction and no side information (SI) transmission in direct current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) visible light communication (VLC) systems. In the proposed scheme, the candidates can be generated by linearly combining time-domain even and odd sequences with cyclic shift and phase rotation. Even and odd sequences are obtained by adopting an inverse fast Fourier transform on the even and odd parts of a Hermitian symmetry encoded signal, respectively. Furthermore, a deterministic and efficient selection method of cyclic shift and phase rotation is derived to improve PAPR reduction performance and ensure that each candidate is unique, so that the receiver can recover the transmitted candidate signal without the use of SI. Simulation results show that the proposed scheme can achieve comparable PAPR reduction performance with the conventional selected mapping (CSLM) scheme with random and chaotic sequences, but at a considerably low computational complexity. Moreover, the proposed blind SI detection scheme provides almost the same bit error rate (BER) performance as that of the CSLM scheme with a perfect SI detection and symmetric selected mapping for a DCO-OFDM VLC system with 1024 subcarriers and 16-QAM. In contrast to other related time-domain sequences that combine methods used for DCO-OFDM systems, the proposed scheme improves BER performance with a slight increase in computational complexity and PAPR.

Multiple Parameters Estimation Based on Transmitter Side Information in Wireless Power Transfer System

Due to the electrical isolation nature of wireless power transfer (WPT) system, a method that can obtain the receiver side parameter only based on transmitter side information is desirable. However, typical estimation scheme assume that the coil inductance and compensation capacitance are constant, which will cause large estimation errors in high frequency system. Therefore, a multiple parameters estimation algorithm that can simultaneously identify load resistance, mutual inductance and receiver coil inductance is proposed in this paper, where only the input current and voltage are needed to be measured. Moreover, in order to cope with capacitor aging effect and manufacturing tolerance, compensation capacitance estimation algorithm is also presented. Mathematical model and algorithm procedure are depicted thoroughly and the gradient descent approach is adopted to obtain the optimal estimated parameter. The uniqueness of solution and the validity of this approach are strictly proved as well. Finally, a WPT experimental prototype with Class-D inverter is implemented and the experimental results are provided to verify the availability and accuracy of the proposed algorithm.

Low-Complexity Blind Selected Mapping Scheme for Peak-to-Average Power Ratio Reduction in Orthogonal Frequency-Division Multiplexing Systems

Orthogonal frequency-division multiplexing (OFDM) is an attractive multicarrier technique for the simplicity of equalization and high data throughput. However, the transmitted OFDM signal has a very high peak-to-average power ratio (PAPR), which severely degrades the performance of practical OFDM systems and reduces the efficiency of high-power amplifiers (HPA). The selected mapping (SLM) scheme is an effective PAPR reduction method of OFDM signals. However, this approach usually requires side information (SI) transmission, which increases the difficulty of the hardware implementation with high complexity and reduces the data transmission rate. In this paper, based on designing phase rotation vectors in the time domain, a novel blind SLM method with low complexity is proposed to reduce the PAPR of OFDM signals. At the transmitter, the proposed method properly designs the phase rotation vectors in the time domain, which can be considered as an equivalent wireless channel without SI transmission. At the receiver, the effect of phase rotation vectors can be removed by the conventional channel estimation method, and the data demodulation processing can be easily performed by the frequency domain equalization. Simulation results show that the proposed scheme can achieve low complexity in PAPR reduction and has great robustness in bit error rate (BER) performance compared to the other low-complexity SLM PAPR schemes.

Joint channel mitigation and side information estimation for GFDM systems in indoor environments

Generalized frequency division multiplexing (GFDM) is the foremost contender for physical layer of 5G communication. The flexible nature of GFDM allows multiple symbols in time domain to superimpose, thereby creating high peak to average power ratio (PAPR). The idea of selective mapping (SLM) is to use a sequence of phase rotation vectors for generating alternatives using original GFDM signal. Among them, signal with lowest PAPR is selected for transmission. This procedure requires mandatory side information (SI) estimation or transmission which in turn decreases data reliability or efficiency. To address these issues, authors present a modified approach of pilot-assisted GFDM SLM system without need of SI transmission and to enable joint PAPR reduction and data recovery. In the proposed approach, we utilize a common modulating phase to modulate all subcarriers in a subsymbol assuming that each subsymbol consists of at least two pilots. This creates an inherent SI cancellation mechanism using the pilots which are employed for channel estimation. For practical validation of proposed concepts, we used software-defined radio (SDR) experimental setup employing universal software radio peripheral USRP) 2953R as hardware and Labview as software. Experimental results show a significant reduction in out-of-band spectral leakage without disturbing the estimated channel response.

SLM‐based ACO‐OFDM VLC system with low‐complexity minimum amplitude difference decoder

A novel low-complexity minimum amplitude difference (MAD) decoder is proposed for selected mapping (SLM)-based asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) visible light communication (VLC) system. With the proposed scheme, a specific set of symmetric vectors is designed to minimise the peak-to-average power ratio (PAPR) of signal without the transmission of side information (SI) and recover SI blindly by the proposed MAD decoder. Simulation results show that the proposed scheme reduces the PAPR effectively and the bit error rate performance of ACO-OFDM system with MAD decoder is very close to that of conventional selected mapping (CSLM) scheme with maximum likelihood decoder, but at much lower complexity.

Blind selective mapping for single-carrier frequency division multiple access system

Single-Carrier Frequency Division Multiple Access (SC-FDMA) signals have a Peak-to-Average Power Ratio (PAPR) problem. So, there is a need for PAPR reduction techniques to be implemented on these signals. The PAPR becomes larger as the modulation order increases. Recently, Conventional Selective Mapping (C-SLM) has been used to reduce the PAPR of SC-FDMA signals. Unfortunately, the standard C-SLM technique requires the transmission of Side Information (SI) to the receiver side. In this paper, a Blind Selective Mapping (B-SLM) technique is proposed to reduce the PAPR in the SC-FDMA system, where there is no change in the C-SLM algorithm at the transmitter and no necessity for SI transmission. Our simulation results show that the PAPR performance of the proposed B-SLM technique is approximately the same as that of the C-SLM technique. The proposed technique is applied to the SC-FDMA system for Single-Input Single-Output (SISO) and Multiple-Input Multiple-Output (MIMO) scenarios. The proposed B-SLM technique provides a reduction in bandwidth without a significant degradation in the Bit-Error Rate (BER) performance. Also, we present a comparison in the PAPR performance between the B-SLM and the other PAPR reduction techniques such as the Partial Transmit Sequence (PTS) and the C-SLM.

A Low Complexity PTS Technique Using Minimal Trellis in OFDM Systems

In this paper, we present a novel algorithm for peak-to-average power ratio (PAPR) reduction of OFDM signals by executing partial transmit sequence (PTS) in minimal trellis of block codes. The proposed method uses a linear code with good minimal trellis to select the transmitted OFDM signal with minimum PAPR and to transmit side information with error correction. The goals of combining strategy of trellis and PTS are twofold: to provide a low complexity PTS for weighting vector search and to highlight error protection capability for side information. Simulation results show that the proposed scheme achieves good PAPR reduction with lower complexity, compared to other PTS approaches.

PAPR Reduction in MIMO-OFDM System Using SLM Without SI

AbstractMIMO-OFDM is a key technology being widely used these days for 4 G communication systems but its main drawback is high PAPR. Selected mapping is commonly used approach for PAPR reduction but in SLM there is requirement of side information (SI) to be sent along with the input data signal and leading to the loss in data rate and increased complexity. In this article, we have come up with a technique for PAPR reduction in which there is no requirement of transmission of side information and therefore preserves the data rate and also provides sufficient reduction in the PAPR. In this technique, SI embedding is performed in the form of subcarrier location (index) by increasing its power. The simulation results demonstrate that the scheme which has been proposed provides the favorable response in terms of bit error rate (BER), PAPR reduction and SI detection capability.

PAPR effect remedy in OFDM-based wireless systems

An enhancement proposition for a Terrestrial Digital Video Broadcasting (DVB-T) systems is discussed in this work. DVB-T physical layer uses a powerful technique namely Orthogonal Frequency Division Multiplexing (OFDM) technique, which has been used to combat the channel’s effect. However, it has a major drawback that degrades its efficiency; namely Peak-to-Average Power Ratio (PAPR). Two criteria have been used for this purpose; BER curves and CCDF curves in order to distinguish the powerfulness of those propositions in reducing the PAPR effect. In fact, a powerful special averaging technique results are compared to previously published propositions, namely based on wavelet transformations and the one that is based on the pulse width modulation. A mathematical model has been drawn in order to check both of the CCDF and the BER curves, and simulated at same channel limitations and specifications. The proposition gives extra 35% noise immunity over our previously published work that is based on entropy wavelet, and an enhancement of over 25% from the CCDF point of view in combatting the PAPR. Furthermore, a complexity reduction has been attained by decreasing the side information transmission in compared with the work in the literature.

PAPR Reduction for Visible Light Communication Systems Without Side Information

It is well known that visible light communication (VLC) systems with the direct current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) scheme suffers from high peak-to-average power ratio (PAPR), which leads to serve distortion and degradation of the output of light emitting diodes. Selected mapping (SLM) technique is an attractive PAPR reduction technique for radio frequency OFDM systems. However, conventional SLM (CSLM) techniques cannot be adopted directly in DCO-OFDM VLC systems because DCO-OFDM VLC signals are restricted to have positive real values. Moreover, CSLM requires transmission of side information (SI) to identify which candidate signal is selected. To avoid the transmission of SI, a novel phase sequence is proposed for the SLM scheme with blind SI detection in DCO-OFDM VLC systems. The proposed phase sequences consist of the magnitude extension and phase rotation factors, where the former factors enable the blind detection of SI, and the latter factors aim to decrease the PAPR. Particularly, the magnitude extension factors are designed to have the symmetry and periodicity. Compared with basic DCO-OFDM with no PAPR reduction scheme, the proposed scheme achieved significant PAPR reductions of 2.1 dB, 3.4 dB, 4 dB, and 4.2 dB for a complementary cumulative distribution function of $10^{-3}$ and $V=4$ , $V=8$ , $V=16$ , and $V=31$ , respectively. Simulation results show that the proposed schemes achieve comparable PAPR reduction performance with the CSLM scheme without the need for SI. Moreover, the proposed SI detection scheme achieves almost the identical bit error rate performance as the CSLM scheme with perfect SI detection with a slight increase in transmitted average power and lower computational complexity.

Reduction of PAPR in coded OFDM using fast Reed-Solomon codes over prime Galois fields

ABSTRACTIn this work, two new techniques using Reed–Solomon (RS) codes over GF(257) and GF(65,537) are proposed for peak-to-average power ratio (PAPR) reduction in coded orthogonal frequency division multiplexing (OFDM) systems. The lengths of these codes are well-matched to the length of OFDM frames. Over these fields, the block lengths of codes are powers of two and we fully exploit the radix-2 fast Fourier transform algorithms. Multiplications and additions are simple modulus operations. These codes provide desirable randomness with a small perturbation in information symbols that is essential for generation of different statistically independent candidates. Our simulations show that the PAPR reduction ability of RS codes is the same as that of conventional selected mapping (SLM), but contrary to SLM, we can get error correction capability. Also for the second proposed technique, the transmission of side information is not needed. To the best of our knowledge, this is the first work using RS codes for PAPR reduction in single-input single-output systems.