Receiver In Communication System Research Articles

Error analysis of OFDM‐IM systems for beyond 5G: The effect of IQI at transceiver

SummaryIt is well known that hardware impairments (HWIs) can worthy reduce the wireless system performance at high carrier frequencies by showing random effects. Most current researches for 5 GB systems assume that transmitters and receivers (transceivers) are perfectly equipped. But wireless transceivers ( ) are affected by HWIs in practice. Considering the previous studies in the literature, it is reported that HWIs have devastating effects on the performance of OFDM and OFDM‐index modulation (IM) systems with fading channels. In this paper, in‐phase and quadrature phase imbalance (IQI), which is the one of most HWIs between transmitter and receiver in wireless communication systems, is examined on OFDM‐IM system over Rayleigh and Nakagami‐ fading channels. Two well‐known detectors, the maximum likelihood (ML) detector and the log‐likelihood ratio (LLR) detector are used under the effect of the IQI at . Error performance analyzes over fading channels of the IQI effect on OFDM‐IM system are realized first theoretically and then by computer simulations. Results obtained for the presence of IQI at show that a performance evaluation based only on the presence of IQI in the receiver would be optimistic and misleading in terms of the performance of real‐life OFDM‐IM systems.

Inkjet-printed high-performance and mechanically flexible organic photodiodes for optical wireless communication

Emerging areas such as the Internet of Things (IoT), wearable and wireless sensor networks require the implementation of optoelectronic devices that are cost-efficient, high-performing and capable of conforming to different surfaces. Organic semiconductors and their deposition via digital printing techniques have opened up new possibilities for optical devices that are particularly suitable for these innovative fields of application. In this work, we present the fabrication and characterization of high-performance organic photodiodes (OPDs) and their use as an optical receiver in an indoor visible light communication (VLC) system. We investigate and compare different device architectures including spin-coated, partially-printed, and fully-printed OPDs. The presented devices exhibited state-of-the-art performance and reached faster detection speeds than any other OPD previously reported as organic receivers in VLC systems. Finally, our results demonstrate that the high-performance of the fabricated OPDs can be maintained in the VLC system even after the fabrication method is transferred to a fully-inkjet-printed process deposited on a mechanically flexible substrate. A comparison between rigid and flexible samples shows absolute differences of only 0.2 b s−1 Hz−1 and 2.9 Mb s−1 for the spectral efficiency and the data rate, respectively.

Prospects for visible color for underwater wireless broadband communications

Nowadays, underwater wireless communications are realized through communication systems based on acoustic waves, electromagnetic waves (radiofrequency waves and low frequency waves), magnetic induction and visible light. This paper provides a basic problems and key aspects in the development of underwater wireless optical communication systems. The latter attracts considerable interest from science, industry and ecology as an effective solution to satisfy the rapidly increasing demands of underwater high data-rate transmission on at any depth. However, severe aquatic channel conditions (absorption, scattering, turbulence, etc.) significantly reduce the attainable communication ranges. The second serious problem limiting the functioning of wireless optical communication systems is the difficulty of aligning the transmitter beam with the receiver's field of view. Two main types between transmitter and receiver are considered: diffuse line-of-sign (wide-beam) configuration and point-to-point light-of-sign (narrow-beam) configuration. Diffuse line-of-sign communication have reduced alignment requirements, but data rates and distances are noticeably lower than in narrow-beam systems. The main technical solutions for adjusting the receiver and transmitter in narrow-beam communication systems are discussed in this paper.

Selection Combining Over Log-Logistic Fading Channels With Applications to Underwater Optical Wireless Communications

We study the performance of a selection combining (SC) receiver operating over independent but non-identically distributed log-logistic ($\mathcal{LL})$ fading channels. We first characterize the statistics of the output instantaneous signal-to-noise ratio (SNR) of the SC receiver. Based on the SNR statistics, we derive exact analytical expressions, in terms of multivariate Fox H-functions, for the outage probability, the average bit error rate, and the ergodic capacity. We also derive exact expressions for such performance measures when all channels are independent and identically distributed, as a special case. Furthermore, we deduce simplified asymptotic expressions for these performance metrics assuming high values of average transmit SNR. To demonstrate the applicability of our theoretical analysis, we study the performance of an SC receiver in underwater optical wireless communication systems. Finally, we confirm the correctness of the derived analytical results using Monte Carlo Simulations.

Successive Cancellation Integer Forcing via Practical Binary Codes

A new multiple-input multiple-output (MIMO) receiver scheme for practical binary codes is proposed that provides consistent gains over conventional linear receivers. We first develop a practical successive integer forcing (IF) scheme based on practical binary codes rather than lattice codes. We then present the successive cancellation integer forcing (SC-IF) scheme, which combines and enhances successive IF and minimum mean squared error successive interference cancellation (MMSE-SIC). In this scheme, the receiver first decides whether individual decoding or IF sum decoding is appropriate for each data stream, and then conducts successive IF sum decoding only for selected streams while decoding the remaining streams using MMSE-SIC. The proposed SC-IF methodology mitigates the performance loss caused by mismatched IF filtering in fading channels, while attenuating the noise amplification caused by MMSE filtering. Extensive link-level simulations demonstrate that the proposed successive IF significantly improves the basic IF, and the SC-IF improves both the successive IF and MMSE-SIC, offering uniform improvements over conventional linear receivers for most channel correlation and variation parameters and modulation orders at comparable computational costs. These results illustrate the viability of SC-IF as a fundamental building block for high-performance MIMO receivers in 5G-Advanced and/or subsequent-generation communication systems.

Study of Automatic Gain Control System in Broadband Radio Receiver

In modern times, almost all communication systems are digital. In the receivers of such communication systems, the analog signal is discretized and quantized using an analog-to-digital converter at an intermediate frequency. Automatic gain control is used to avoid overloading the analog-to-digital converter and to maintain intermediate frequency analog signals at a suitable fixed level. If the power of the received signals is much less than the load level of the analog-to-digital converter, the automatic gain adjustment increases the gain, reducing the quantization noise. If the received signal strength is high, the automatic gain adjustment lowers the gain so that the analog-to-digital converter is not overloaded. The accuracy of the adjustment of the transmission coefficient of the automatic adjustment of the digital amplification does not always satisfy the requirements given in real time. Based on the above, the article is devoted to the study of the digital automatic gain regulator of the broadband radio receiver.

An Enhanced Channel Estimation for IEEE 802.15.4 OFDM Receiver in High-Speed Mobile IoT Communication Systems

Currently, orthogonal frequency division multiplexing (OFDM), standardized in IEEE 802.15.4, has attracted attention as a transmission scheme for higher data rates, long-distance transmissions, and mobile communications for the expansion of IoT applications as well as for legacy IoT applications, such as smart metering systems and home-area networks. In particular, receiving schemes using IEEE 802.15.4-based OFDM have been actively examined to realize mobile communication. Previous studies used the long training field (LTF) and pilot subcarriers for channel estimation of multipath fading, achieving mobile communication with data rates of 100 kbps or above at moving speeds of up to 40 km/h in an urban environment. In a previous study, channel estimates were obtained by repeating channel estimates from the LTF and pilot subcarriers in the time domain and by interpolating the estimates in the frequency domain. This study proposes a receiving scheme for IEEE 802.15.4 OFDM aimed at high-speed mobile IoT communication systems. In the time axis direction, the proposed scheme obtains channel estimates in the same manner as previous schemes. However, in the frequency axis, the proposed scheme obtains the channel estimates by copying estimates of neighboring subcarriers according to the coherence bandwidth of the multipath fading channel to update the channel estimates frequently. Computer simulation results show that the proposed scheme including delay spread estimation can achieve mobile communication with a data rate of 100 kbps at moving speed of 200 km/h in the urban environment.

Mid-wave infrared optical receiver based on an InAsSb-nBn photodetector using the barrier doping engineering technique for low-power satellite optical wireless communication.

This paper proposes a new nBn photodetector (nBn-PD) based on InAsSb with a barrier doping engineering technique [core-shell doped barrier (CSD-B) nBn-PD] for utilization as a low-power receiver in satellite optical wireless communication (Sat-OWC) systems. In the proposed structure, the absorber layer is selected from an I n A s 1-x S b x (x=0.17) ternary compound semiconductor. The difference between this structure and other nBn structures is the placement of the top and bottom contacts in the form of a PN junction, which increases the efficiency of the proposed device through the creation of a built-in electric field. Also, a barrier layer is placed from the AlSb binary compound. The presence of the CSD-B layer with the high conduction band offset and very low valence band offset improves the performance of the proposed device compared to conventional PN and avalanche photodiode detectors. By applying -0.1V bias at 125K, the dark current is demonstrated at 4.31×10-5 A/c m 2 by assuming high-level traps and defect conditions. Examining the figure of merit parameters under back-side illumination with a 50% cutoff wavelength of 4.6µm shows that at 150K, the responsivity of the CSD-B nBn-PD device reaches about 1.8A/W under 0.05W/c m 2 light intensity. Regarding the great importance of using low-noise receivers in Sat-OWC systems, the results indicate that the noise, noise equivalent power, and noise equivalent irradiance are calculated as 9.98×10-15 A H z -1/2, 9.21×10-15 W H z 1/2, and 1.02×10-9 W/c m 2, respectively, at -0.5V bias voltage and 4µm laser illumination with the influence of shot-thermal noise. Also, D ∗ obtains 3.26×1011 c m H z 1/2/W without using the anti-reflection coating layer. In addition, since the bit error rate (BER) plays an essential role in the Sat-OWC systems, the effect of different modulations on the BER sensitivity of the proposed receiver is investigated. The results represent that the pulse position modulation and return zero on-off keying modulations create the lowest BER. Attenuation is also investigated as a factor that significantly affects BER sensitivity. The results clearly express that the proposed detector provides the knowledge to achieve a high-quality Sat-OWC system.

Localizing the Unknown Receiver in a Diffusive SIMO Molecular Communication System

This letter introduces a method to estimate the position of an unknown fully absorbing (FA) spherical receiver in a diffusive molecular communication (MC) system. This latter consists of a point transmitter and multiple FA spherical receivers in a three-dimensional space. The method relies on a temporal asymptotic single-input multiple-output (SIMO) channel model for diffusive MC systems that takes into account the interaction among receivers. By relying on the asymptotic model, a grid-based likelihood function is a priori created from each known receiver’s perspective. The likelihood function’s computation requires information about the number of molecules released by the transmitter, its position, and the position of known receivers. From the cumulative number of molecules absorbed by the known FA receivers, different likelihood maps are obtained, where each map corresponds to the likelihood of the position of unknown receiver from a specific known receiver’s perspective. By combining the receivers’ likelihood maps, which is equivalent to cooperation by sharing their knowledge, the position of the unknown receiver is estimated. The quality of the estimation is evaluated in terms of root mean squared error (RMSE) between the estimated position of the unknown receiver and its true position for different number of released molecules.

Базовые конструкции СВЧ балансных фильтров на оттекающих поверхностных акустических волнах

Ladder filters on leaky surface acoustic waves (LSAW) with electrical connection of resonators provide the lowest insertion loss IL=0.6-1.2 dB as compared with other types of LSAW filters, such as longitudinally coupled resonator filters. A drawback of ordinary nonsymmetrical ladder filters on LSAW is their limited selectivity (or minimal attenuation in the stop band) about UR=40-45 dB. In addition some problems arise when matching nonsymmetrical ladder filters to balanced or differential microcircuits. The present paper describes basic symmetric П-type and Т-type sections as well as various structures of ladder filters that allow to achieve a high selectivity thanks of parasitic electromagnetic signal (EMS) suppression. An extra advantage of balanced LSAW filters is their possibility to work with high impedance symmetric loads. The results of our study have been illustrated by few examples of balanced filters constructions on frequency 1217 MHz with selectivity UR=55-7- dB and low insertion loss IL=1,5-2,0 dB. Filters exhibiting high selectivity UR=55-70 dB and small insertion loss IL=1,2-4,0 dB. The described constructions may be used as basic for application on TV tuners, receivers of communication and navigation systems in frequency range 600-2000 MHz.

INTEGRATED RADAR AND COMMUNICATION SYSTEMS FOR HIGHLY AUTOMATED VEHICLES

The application of radar has spread to numerous civilian automotive purposes like adaptive cruise control, automotive emergency braking, blind spot detection, lane change assist, and so on. The need for ever-increasing rates in wireless communications has moved the frequency spectrum toward millimeter range, usually assigned to automotive radar. This has led to an integrated automotive radar and communication system, which results in limited electromagnetic pollution and lower cost, size, weight, and power. Improved massive multiple input, multiple output signal processing techniques are required as integration of these two systems will be based on large antenna arrays. Similar to the see-through technique of 3GPP Release 16, the authors have conducted a simulation experiment where data of multiple targets have been obtained with automotive radar and then sent to a gateway. From there, data are transmitted to a fifth-generation communication model. Final data obtained at a receiver of the communication system matches the original radar output, which proves that data have been successfully transferred from the radar system to the communication system, thus making it an integrated system. This system is very useful in the case of vehicle platooning.

Automatic Modulation Classification Using a Support Vector Machine-Based Pattern Recognition Algorithm

Modulation format recognition is an essential part of intelligent receivers of wireless communication systems, especially for adaptive radio systems (ARS). This paper presents a detailed investigation of automatic modulation classification (AMC) using pattern recognition classifiers (PRC) under fading and AWGN conditions. A variety of classifiers with different kernel functions and Support Vector Machine (SVM) classifiers have been developed for the classification of higher-order digital modulation signals. In addition, an extensive investigation of the extraction of various higher-order statistical features from each of the modulated classes and the choice of appropriate features for training classifiers are presented. In addition, the performance of the SVM classifier is evaluated under a variety of training rates and suboptimal channel conditions. Further, the performance of SVM classifiers is compared to that of existing techniques to demonstrate the effectiveness of the SVM classifiers for modulation categorization.

A Notch Filter-Based Coupling Circuit for UNB and NB PLC Systems

This paper introduces an analog notch filtering-based coupling circuit for receivers in ultra-narrowband and narrowband power line communication systems, which are connected to low-voltage electric power grids. It is composed of a twin-T notch analog filter, which is responsible for imposing a significant attenuation on the main frequency (i.e., f0∈{50,60} Hz) in cascade with an elliptic low-pass analog filter, designed with a 3 dB cut-off frequency of fc≫f0. For f0=60 Hz and fc=2 MHz, the prototype of the analog notch filtering-based coupling circuit attains attenuation values of 22 dB and less than 2 dB at the main frequency and in the rest of the frequency bandwidth, respectively, when practical scenarios are considered. Lastly, it shows that the analog notch filtering-based coupling circuit is more effective than a typical capacitive coupling circuit when frequencies lower than 3 kHz are considered for data communication and sensing purposes.

A 280 GHz 30 GHz Bandwidth Cascaded Amplifier Using Flexible Interstage Matching Strategy in 130 nm SiGe Technology

This paper presents a 280 GHz amplifier design strategy for a robust multistage amplifier in a sub-Terahertz (sub-THz) regime in 130 nm SiGe technology. The presented 280 GHz amplifier consists of 14 stages of the cascaded common emitter (CE) amplifier which offers a compact and improved-noise design due to the absence of the area-expensive and lossy baluns at such high frequencies. The interstage-matching network was flexibly constructed with two separate resonant tanks using metal–insulator–metal (MIM) capacitors and microstrip transmission lines (MSTLs) between each stage. The measured amplifier achieved a peak power gain of 10.9 dB at 283 GHz and a 3 dB gain of bandwidth of 30 GHz between 270 and 300 GHz. The peak output power of the amplifier was 0.8 dBm with an output of 1 dB gain compression point (OP1dB) of −3.6 dBm in simulation. The 14-stage amplifier consumes an area of 0.213 mm2, including all the pads. With the proposed interstage matching approach, a well-balanced 280 GHz amplifier has been demonstrated. The proposed design strategy is widely applicable to sub-THz receivers for future wireless communication systems.

High Speed and High Sensitivity InGaAs/InAlAs Single Photon Avalanche Diodes for Photon Counting Communication

A planar InGaAs/InAlAs single photon avalanche diode (SPAD) was fabricated and comprehensively characterized. At room temperature, the dark count rate is 3.1 MHz at 10.4% photon detection efficiency. The corresponding noise-equivalent power of 3.07 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−15</sup> W/Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> is achieved, which is the lowest value among reported InGaAs/InAlAs SPADs operated at room temperature. Moreover, it is the first time to report an InGaAs/InAlAs SPAD driven by a sine wave gate (SWG) quenching circuit as a receiver in the photon counting communication system. For achieving high-bit-rate transmission with high sensitivity, a high-frequency (1.8 GHz) SWG quenching circuit is developed and the time jitter for the system is reduced to 53 ps. At bit rates of 100 Mbit/s, 200 Mbit/s, and 400 Mbit/s, the sensitivities of −57.2 dBm, −53.42 dBm, and −51.06 dBm are experimentally demonstrated with a single InGaAs/InAlAs SPAD respectively. In addition, a theoretical sensitivity of −42.7 dBm is predicted at 1.8 Gbit/s with a 4 × 4 InGaAs/InAlAs SPAD array.

Over‐the‐air equalization with reconfigurable intelligent surfaces

Reconfigurable intelligent surface (RIS)-empowered communications is on the rise and is a promising technology envisioned to aid in 6G and beyond wireless communication networks. RISs can manipulate impinging waves through their electromagnetic elements enabling some sort of control over the wireless channel. In this paper, the potential of RIS technology is explored to perform a sort of virtual equalization over-the-air for frequency-selective channels whereas, equalization is generally conducted at either the transmitter or receiver in conventional communication systems. Specifically, with the aid of an RIS, the frequency-selective channel from the transmitter to the RIS is transformed to a frequency-flat channel through elimination of inter-symbol interference (ISI) components at the receiver. ISI is eliminated by adjusting the phases of impinging signals particularly to maximize the incoming signal of the strongest tap. First, a general end-to-end system model is provided and a continuous to discrete-time signal model is presented. Subsequently, a probabilistic analysis for the elimination of ISI terms is conducted and reinforced with computer simulations. Furthermore, a theoretical error probability analysis is performed along with computer simulations. It is analyzed and demonstrated that conventional RIS phase alignment methods, can successfully eliminate ISI and the RIS-aided communication channel can be converted from frequency-selective to frequency-flat.

Variable pulse position modulation receivers for visible light communication systems without the knowledge of dimming level

AbstractThe dimming control is one of the most significant issues to provide both illumination and data transmission for visible light communication (VLC) systems. The receivers—such as variable pulse position modulation (VPPM) receiver—must know the dimming level of the received signal for the demodulation process. To provide a complete solution to this problem, we propose two VPPM receivers that can detect data bits without knowledge of dimming level (KDL). The first one, which is referred to as artificial neural network (ANN)‐VPPM, includes the ANN technique to achieve a proper step signal instead of traditional mask signals that are generated by using the perfect KDL. The ANN‐VPPM gives a successful bit error rate (BER) performance compared to the unsuitable traditional system (U‐TS), which is called the traditional system that decodes the VPPM signal using inappropriate mask signals. If the ANN‐VPPM is compared to traditional system (TS), which is the traditional system using a perfect mask signal, the TS has better BER performance than the ANN‐VPPM. Hence, the other one that is called the proposed estimation method (PEM) is improved to achieve the same BER performance compared to the TS. An estimation performance is given to indicate the 100% estimation rate and to prove that the BER performance of systems is the same at least signal‐to‐noise ratio of 22 dB. Additionally, the PEM is saving the optical power of the VPPM signal up to 23% at a BER of 10−3 when compared to U‐TS.

Tensor-Based Information Monitoring Receiver in UAV-Aided MIMO Communication Systems

In this letter, we consider an unmanned aerial vehicle (UAV)-aided information monitoring scheme in a multiple input multiple output (MIMO) communication system. According to the tensor structure of the communication links, an information monitoring receiver is proposed. The receiver is based on the generalized tensor contraction (GTC), which exploits a nested parallel factor (PARAFAC) model for the received signals, via an iterative least squares (LS) algorithm to jointly monitor the data symbols transmitted from the users via the base stations. Compared with some competing receivers, our simulation results demonstrate the superiority of the proposed GTC-LS receiver in terms of normalized mean square error and bit error rate.

Low Excess Noise of Al0.85Ga0.15As0.56Sb0.44 Avalanche Photodiode From Pure Electron Injection

Avalanche photodiodes (APDs) are used in optical receivers of high-speed optical communication systems to improve signal-to-noise ratio over conventional photodiodes. Low excess noise characteristics are crucial for APDs to preserve the benefits associated with high internal gains. In this work, we presented room temperature data of avalanche gain and excess noise factors of Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.85</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.15</sub> As <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.56</sub> Sb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.44</sub> APDs using pure and mixed carrier injection profiles. Using pure electron injection, the best possible excess noise performance for a given avalanche width was measured with an excess noise factor <; 2 for gains up to 25. This is the lowest excess noise reported for this material system at high gain. Two other injection profiles with increased portion of injected holes worsened the excess noise performance, confirming the need to use pure electron injection for the best possible APD noise performance. The data reported in this article is available from the ORDA digital repository (https://doi.org/10.15131/shef.data.15082455).

Evaluation and experimental comparisons of different photodetector receivers for visible light communication systems under typical scenarios

Positive-intrinsic-negative diode (PIN), avalanche photodiode (APD), and single photon avalanche diode (SPAD) are commonly used optoelectronic receivers with different characteristics in practical visible light communication system. To determine the most appropriate candidate, different signal and ambient light strength in the communication scenarios should be taken into account. APD and SPAD receivers have higher sensitivities than PIN, but there are still some defects that restrain their operation performance. APD receiver may generate excessive shot noise, whereas SPAD is limited by the dead time, afterpulsing, and smaller detection area. We initially analyze the noise characteristics of PIN, APD, and SPAD receivers. SNR models are established, and the main factors affecting the performance of APD and SPAD receivers are concluded. Then, the comparison experiments of three kinds of receivers in various transmission distances are conducted, respectively. Finally, the experimental results show that: short and mid distance conditions, PIN and APD are better choices, whereas SPAD performs better in long-distance communication. In addition, if a certain intensity of ambient light is introduced, APD is still better than SPAD even in long distance.