QAM Modulation Schemes Research Articles

Performance Analysis of Radio Over Fiber System Employing Photonics Antenna and Different Modulation Schemes

In today’s world of communication, the wireless access network is a rapidly growing technology. As upcoming generations of wireless communication require more number of diminished cells than that used in the current generation, photonic antenna and RoF are being considered as the key technologies for such futuristic applications. RoF technology has the special feature of combining the characteristics of both a free space radio and an optical fiber link. Due to the larger bandwidth, competitive cost and low propagation loss, optical fiber has become the best option for the backhaul. In this work, architecture (architecture in an uncountable noun, so no article is required) has been proposed for analyzing the structure of a 2.4 GHz photonic antenna for RoF system. The architecture has a significant importance in meeting the demand for higher bandwidth. The system provides an optimum performance at a data rate of 2.5 Gbps over a fiber length of 50 km, employing 16-QAM modulation scheme. The quality of the received signal has also been analyzed by varying fiber length and transmitted power for different types of fibers.

Performance evaluation of chaotic spreading codes in massive MIMO OFDM system

Background/Objectives: Wireless communication systems are growing towards the implementation of 5G communication systems to satisfy the demand of services in future. OFDMA has some shortcoming like one or more subcarriers of OFDM are completely affected due to the characteristic of the transmission channel. Spreading scheme has been introduced to combat the aforementioned issue. Furthermore, communication channels are affected by multipath fading which changes the amplitude of the received signal. This fading severely affects the communication systems. Therefore, it is essential to develop a more robust technique for higher data transmission and larger throughput. The main objective of this study is to design a massive MIMOOFDM system for secure transmission of data. Chaos based sequence is used to spread the data before transmission which will solve intercell interference and improve the security of data. Methods: This study presents a chaos based massive MIMO-OFDM communication system. The proposed chaos based massive MIMO-OFDM system is implemented and its efficacy is evaluated by computing bit error rate. The effectiveness of the proposed system is investigated by varying the parameters including modulation methods such as PSK and QAM, number of users 10, 20 and 30 and spreading factor of 5, 10 and 15. Findings: Results clearly proved that the proposed system provides exceptional performance with 16QAM modulation scheme, 10 users at high spreading factor value of 15. Novelty: The uniqueness of the proposed system is with enhanced performance and usage of novel modulation scheme by varying the spreading factor value, when compared to its peers. Keywords: Communication system; spreading code; chaotic code; massive MIMO-OFDM; bit error rate

128-QAM dual-polarization chaotic long-haul system performance evaluation

Abstract In this research work, performance of 128-quadrature amplitude modulation (QAM) modulation format along with dual polarization is investigated for long-haul communication in chaotic environment at data rate of 112 Gb/s and different fiber lengths. The prime objective of this work is the merger of QAM modulation scheme and optical chaos to acquire higher effective data rate with secure optical communication. The property of semiconductor laser for producing high bandwidth chaos is utilized to encrypt high data rate supported by 128-QAM signal. Chaos produced in this way is then applied to two states i.e., x and y-polarization of signal, at the same time to study results individually through constellation diagrams. The proposed model consisting of 128-QAM transmitter and receiver design, incorporating chaos is tested to investigate and combat the effects of different transmission impairments such as attenuation, dispersion, inline amplifiers effects, and message retrieval.

Blind Signal Modulation Recognition through Density Spread of Constellation Signature

Automatic recognition of modulation scheme in blind environment plays a key role in many communication applications. A hierarchical and local density (HLD) approach is proposed to classify eight modulation schemes in a two stage process. In the first stage, the domain of modulation schemes (FSK, ASK, PSK, and QAM) is identified. FSK is identified based on feature extracted through complex envelope of downconverted signal. ASK scheme is identified using linear regression error. PSK and QAM modulation schemes are recognized based on the ratio of sixth and fourth order cumulant. In the latter stage, the order of modulation (ASK, PSK, and QAM) is classified through its respective ideal constellation points. HLD can correctly identify 2ASK, 4ASK, and QPSK modulation schemes in AWGN channel above 8 dB SNR and the other modulation schemes (8ASK, 8PSK, 16QAM, and 64QAM) above 16dB SNR. HLD is implemented in NI labVIEW and validated on the signals generated through PXIe-5673 and received using NI PXIe-5661. The proposed HLD classifier does not require any training to set thresholds as compared to more complex SVM, KNN, and Naive Bayes Classifier based techniques and shows an improved accuracy.

Performance Comparison of Proposed Scheme Coded DWT-OFDM System with that of Conventional OFDM

In this paper, we have investigated the Proposed scheme coded DWT-OFDM system in comparison to conventional OFDM system over AWGN channel. 16, 32, 64 – QAM and PSK modulation schemes have been considered to evaluate the system. Moreover, two different wavelets have been used for examining the system. Simulations are performed using MATLAB software. It is found that proposed scheme based DWT-OFDM system performs better than conventional OFDM system under all the considered modulation schemes

A multi-band high-efficiency envelope elimination and restoration CMOS power amplifier

A multi-band CMOS power amplifier has been realized to be used in high-efficiency handset applications. The proposed PA is based on class-E stage linearized using envelope elimination and restoration (EER) technique. In order to cover multiple frequency bands, a wide-band passive output matching network is designed and combined with band-select feature. This allows switching between two wide-band output matching networks; increasing frequency coverage and yet satisfying the criteria of high rejection of out-of-band emissions. A design methodology is introduced to optimize the values required for the wide-band passive network. The design has been implemented using CMOS 0.13 μm technology. Simulation results show frequency coverage from 800 MHz to 2.2 GHz with peak efficiency more than 60% (before taking the effect of supply modulator) and 47% after taking the losses of the supply modulator into account. The designed EER system achieves excellent linearity performance. The test and validation process includes LTE test signal with 16 QAM modulation scheme and signal bandwidth of 20 MHz.

Least Square Channel Estimation for Image Transmission with OFDM Over Fading Channel

Wireless communication is the most effective communication to convey audio or video information among the population. It enables the masses to connect throughout the world. Wireless technologies improve the lifestyle of individuals in rural and poor communication areas. In this view, the quality of a reliable signal can be enhanced by minimizing carrier interference. In this paper bit error rate of an image, signal is transmitted over fading channel is analyzed using orthogonal frequency multiplexing and channel estimation technique. An Orthogonal Frequency Multiplexing (OFDM) provides prominent bandwidth effectiveness and improved immunity to the fading environments. In OFDM, the data is modulated using multiple numbers of subcarriers that are orthogonal to each other. A cyclic prefix is infixed between OFDM symbols to annihilate the inter symbol interference (ISI) and inter-carrier interference (ICI). The least square channel estimation method is used to minimize the effect of multipath fading. An image, signal is modulated using BPSK, QPSK, 16QAM and 64QAM digital modulation schemes with OFDM and channel estimation and transmitted over AWGN and fading channel. The objective of this work is to improve the signal to noise ratio by reducing interference.

Deep Learning-Based Autoencoder for m-User Wireless Interference Channel Physical Layer Design

Deep learning (DL) based autoencoder (AE) has been proposed recently as a promising, and potentially disruptive approach to design the physical layer of beyond-5G communication systems. Compared to a traditional communication system with a multiple-block structure, the DL based AE approach provides a new paradigm to physical layer design with a pure data-driven and end-to-end learning based solution. In this article, we address the dynamic interference in a multi-user Gaussian interference channel. We show that standard constellation are not optimal for this context, in particular, for a high interference condition. We propose a novel adaptive DL based AE to overcome this problem. With our approach, dynamic interference can be learned and predicted, which updates the learning processing for the decoder. Compared to other machine learning approaches, our method does not rely on a fixed training function, but is adaptive and applicable to practical systems. In comparison with the conventional system using $n$ -psk or $n$ -QAM modulation schemes with zero force (ZF) and minimum mean square error (MMSE) equalizer, the proposed adaptive deep learning (ADL) based AE demonstrates a significant achievable BER in the presence of interference, especially in strong and very strong interference scenarios. The proposed approach has laid the foundation of enabling adaptable constellation for 5G and beyond communication systems, where dynamic and heterogeneous network conditions are envisaged.

Development of Relay Selection Method for Audio Transmission in Cooperative Ad Hoc Networks

The quality of service parameters, such as Latency and Bit error rate for audio transmission in IEEE 802.11b Wireless ad hoc network are analyzed in this paper. The issue addressed here is that the quality of the audio, when transmitted directly from source to destination in ad hoc network is low. This can be improved by incorporating a relay between source and destination, where the relay uses decode and forward technique before forwarding the information to the destination. Destination applies Maximal ratio combining (MRC), to combine the signal received from the source and the relay. This concept is called Cooperative communication. A location aware channel estimation based relay selection strategy is proposed in this paper for a wireless ad hoc network. Audio is transmitted using 16 QAM modulation scheme over a Rayleigh fading channel in the presence of additive white Gaussian noise (AWGN). This paper focusses on the relay selection method for audio transmission in cooperative ad hoc networks where best relay is selected based on the average channel strength supported between the source and the destination. Audio quality at the destination is observed for the cases of relay presence and relay absence. Results showed that the measured audio quality with the presence of relay was far better than the measured quality in the absence of relay which stresses the importance of cooperative communication.

Frequency Interleaving IF Transmitter and Receiver for 240-GHz Communication in SiGe:C BiCMOS

This article presents a fully integrated modular wideband frequency interleaving (FI) transmitter and receiver for high data rate communication applications. At the transmitter side, three independent in-phase and quadrature-phase (IQ) baseband channels are upconverted to different intermediate frequencies (IFs) and then interleaved. At the receiver side, the interleaved signals are downconverted and separated back to each independent channel. Single-ended inputs and outputs are utilized to reduce the pin count, for a more practical realization and higher potential toward future system scaling. Special design techniques are followed to minimize crosstalk and intermodulation products between the channels. All circuits are manufactured and measured in a 130-nm SiGe:C BiCMOS technology with $f_{\textbf {T}}/f_{\textbf {max}}$ =300/500 GHz. The FI transmitter achieves a channel bandwidth of 2.5 GHz with less than 3-dB difference across different channels until 15-GHz IF. It consumes 560 mW from 2.5 and 3.3 V supplies and occupies a silicon area of 1.9 mm2. The FI receiver achieves a baseband channel bandwidth of 2.5 GHz with a 1-dB difference between the channels until the same IF. It consumes 860 mW from 2.5 and 3.3 V supplies and has a chip area of 1.55 mm2. The circuits are deployed in a communication experiment; first, in a back-to-back test with a direct cable connection, demonstrating a data rate of 15.6 Gb/s across the three IQ channels with a 16-QAM modulation scheme and a worst case transmitter-to-receiver error vector magnitude (EVM) of −18.6 dB. Then, a wireless experiment is performed with a 240-GHz front end with on-chip antenna, demonstrating a data rate of 7.8 Gb/s with QPSK modulation and a worst case EVM of −8.3 dB, across a wireless link of 15 cm. To the best of our knowledge, this is the first article that demonstrates a wireless transmission at sub-terahertz (sub-THz) carrier frequencies utilizing FI architectures.

Detecting and Receiving Phase-Modulated Signals With a Rydberg Atom-Based Receiver

Recently, we introduced a Rydberg-atom based mixer capable of detecting and measuring the phase of a radio-frequency field through the electromagnetically induced transparency (EIT) and Autler-Townes (AT) effect. The ability to measure phase with this mixer allows for an atom-based receiver to detect digital modulated communication signals. In this paper, we demonstrate detection and reception of digital modulated signals based on various phase-shift keying approaches. We demonstrate Rydberg atom-based digital reception of binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), and quadrature amplitude (QAM) modulated signals over a 19.626~GHz carrier to transmit and receive a bit stream in cesium vapor. We present measured values of Error Vector Magnitude (EVM, a common communication metric used to assess how accurate a symbol or bit stream is received) as a function of symbol rate for BPSK, QPSK, 16QAM, 32QAM, and 64QAM modulation schemes. These results allow us to discuss the bandwidth of a Rydberg-atom based receiver system.

PAPR Reduction Scheme using Precoding Evolutionary Adaptation for MIMO OFDM Data Communication

An extremely attractive procedure for fast airing over a dispersive correspondence channel is Multicarrier transmission. PAPR has a badly-behaved imperative concern to be spoken in evolving multicarrier broadcast systems. In this article PAPR reduction procedure has been designated for multicarrier transmission. In this developed technique a promising for the reduction of PAPR without loss of data transmit signal and BER of MIMO OFDM presented, but computational complexity has increased as increasing number of transmitter antennas Mt. A technique is used for finding of constant modulus (CMA) signal in such a way that beam forming weights have multiply with their orthonormal data matrix. That prime solution is an evolutionary adaptive constant modulus algorithm (EA-CMA) for optimal search of least PAPR signal. The results are simulated for QPSK, 16QAM and 64QAM modulation schemes with MATLAB 2013 version. This technique is compatible with PTS (Partial transmit sequence) scheme.

Application of Modified Bellman-Ford Algorithm for Cooperative Communication

Network lifetime of mobile ad hoc networks is limited by the battery power of the mobile nodes. Energy saving can be achieved by operating the nodes in power save mode (PSM). Cooperative communication provides the cooperative diversity and the performance of the network can be improved by using cooperative relays. A new cooperative modified Bellman ford algorithm (CMBFA) using PSM is proposed to improve the performance of the network. Distributed Bellman ford algorithm (DBFA) is considered as a basic routing protocol. A modified Bellman-ford algorithm (MBFA) also called as Non-cooperative MBFA (NCMBFA) is developed by modifying the DBFA. In NCMBFA, residual energy of a node is considered to select the optimal path for routing the packets. NCMBFA is energy efficient and suitable for Grid topology using PSM. In the proposed CMBFA, the nodes in the Grid topology are categorized into amplify-and-forward and decode-and-forward nodes using the received signal-to-noise ratio at the relay. All the DF nodes are considered for routing and the optimum route is calculated using the NCMBFA. For CMBFA and NCMBFA, the bit error rate performance of the network for BPSK, QPSK, and 64-QAM modulation schemes are analyzed. The performance metrics of the packet received, delay and the average jitter of CMBFA and NCMBFA are compared. Simulation results show clearly that CMBFA gives better performance over NCMBFA and CMBFA consumes less energy compared to NCMBFA using PSM.

Performance comparison of M-QAM and DQPSK modulation schemes in a 2 × 20 Gbit/s–40 GHz hybrid MDM–OFDM-based radio over FSO transmission system

This work is focused on the modeling and performance investigation of a 2 × 20 Gbit/s–40 GHz hybrid mode division multiplexing–orthogonal frequency division multiplexing-based radio over free space optics (RoFSO) transmission system under the influence of different weather conditions. The performance of the proposed system has been compared for 4-quadrature amplitude modulation (QAM), differential quadrature phase-shift keying, 16-QAM, and 32-QAM modulation schemes using error vector magnitude, optical signal-to-noise ratio requirement, and maximum link reach as the performance metrics. The results show that 4-QAM scheme demonstrates the best performance. The proposed RoFSO transmission system incorporating 4-QAM modulation demonstrates a successful transmission of 2 × 20 Gbit/s–40 GHz information over 104 km link range under clear weather conditions. Also, the maximum link range using the proposed system is reported as 4.52 km under light fog, 2.78 km under moderate fog, and 2.11 km under heavy fog conditions. Further, the performance of the proposed system has been compared with the previously reported literature which shows that the proposed system has a better figure of merit (information rate × transmission distance). The presented work can be used to implement a spectrum efficient, high-speed, long-haul information transmission system for future wireless networks.

PAPR reduction in OFDM using scaled particle swarm optimisation based partial transmit sequence technique

Partial transmit sequence (PTS) is one of the effective techniques for reducing the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. PTS technique has some issues such as higher computational complexity due to its exhaustive searching of optimal phase factors. In order to overcome this drawback, a scaled particle swarm optimisation algorithm is applied to PTS technique to find the optimal phase factors for reducing the PAPR at a faster convergence rate and lower computational complexity. A scaling factor has been introduced in the velocity updating equation of conventional particle swarm optimisation (PSO) to increase the inertia weight and velocity of the particle, thereby providing faster convergence to the optimum value as well as reducing PAPR effectively. From the simulation results obtained, it can be observed that the proposed scaled PSO-PTS algorithm reduces PAPR effectively and is most suitable for applications with the 64-QAM modulation scheme.

Physical Layer Network Coding in Network MIMO: A New Design for 5G and Beyond

Physical layer network coding (PNC) has been studied to serve wireless network MIMO systems with much lower backhaul load than approaches such as Cloud Radio Access Network (Cloud-RAN) and coordinated multipoint (CoMP). In this paper, we present a design guideline of engineering applicable PNC to fulfil the request of high user densities in 5G wireless RAN infrastructure. We show that the proposed design criteria guarantee that: 1) the whole system operates over binary system; 2) the PNC functions utilized at each access point overcome all singular fade states; and 3) the destination can unambiguously recover all source messages, while the overall backhaul load remains at the lowest level. We then develop a two-stage search algorithm to identify the optimum PNC mapping functions which greatly reduces the real-time computational complexity. The impact of estimated channel information and reduced number of singular fade states in different QAM modulation schemes are studied in this paper. Numerical results show that the proposed schemes achieve low outage probability with reduced backhaul load.

Performance Analysis of Two Way All Optical Relay Assisted PM-FSO over Different Weather Conditions

This paper proposes a novel method of relaying in Polarization Multiplexing (PM) in Free Space Optical (FSO) networks using amplify and forward and decode and forward relays with and without fixed gain. The idea of multiplexing scheme combined with relay helps in improving the channel capacity and the link distance. To mitigate the inter channel crosstalk that occurs in Wavelength Division Multiplexing, PM is proposed. To avoid the degrading performance of the system due to atmospheric turbulence, QAM modulation scheme is used. The performance of the system is analyzed by considering various parameters like BER, link distance and the transmitted and received power. Monte Carlo simulations are used to validate the results.

Fast-Fading Channel Environment Estimation Using Linear Minimum Mean Squares Error-Support Vector Regression

In this article, we propose a Linear Minimum Mean Squares Error-Support Vector Machine regression (LMMSE-SVR) approach which is applied to Long Term Evolution (LTE) downlink channel environment estimation under high mobility conditions. LMMSE-SVR is employed to track and estimate the rapid variations of a realistic Extended Vehicular A model channel according to 3GPP specifications. This contribution assimilates both channel estimation at reference signals and interpolation at data signals into the LMMSE-SVR method. Performances of our channel environment estimation proposal in terms of Bit Error Rate and Mean Squares Error are established via simulation for both normal and extended Cyclic Prefix scenarios in LTE downlink system with 64-QAM modulation scheme under 350 km/h mobile speed.

A Comprehensive Performance Analysis of MIMO-OFDM Technology Using Different MIMO Configurations and M-QAM Modulation Schemes for LTE Cellular Network

MIMO-OFDM (Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing) uses multiple antennas at transmitter and receiver side to facilitate high throughput performance without needing additional bandwidth or transmission power. But frequency synchronization, Inter Carrier Interference (ICI) minimization and antenna diversity are the main challenges for MIMO-OFDM wireless technology. In this paper, a MIMO-OFDM hybrid model is designed with proper frequency synchronization and antenna diversity that minimizes ICI with improved signal strength. Using the model a comprehensive analysis in terms of Bit Error Rate (BER) performance with respect to Signal to Noise Ratio (SNR) and Bit Rate for different M-ary QAM modulation schemes and different MIMO configurations are presented over Rayleigh fading and AWGN channel. After an extensive analysis, it is found that the propose OFDM scheme shows better Bit Error rate (BER) performance for 64-QAM than any other M-ary QAM modulation schemes and the optimum MIMO configuration for this good quality performance is found to be 3×2 configuration.

New closed-form expressions for SNR estimates of Nakagami fading channels by the method of moments

Method of moments has been a parameter estimation technique appropriate to calculate signal-to-noise ratio (SNR) estimates in fading channel models in which an optimal technique like maximum likelihood estimation is not mathematically tractable. In this article, the ratio of the second moment squared to the fourth moment of the received signal envelope is considered to calculate an exact expression for the SNR estimate in Nakagami-m fading channel for M-QAM and $$\theta $$ -MQAM modulations as well as expressions to evaluate the variance and the mean of the estimate. The paper presents two useful contributions for SNR estimation theory on Nakagami fading. Besides the exact algebraic expression for the estimate for a generalized QAM modulation scheme, its performance is evaluated through a statistical linearization argument.