Noncoherent Demodulation Research Articles

Enabling cost-effective wireless THz communication through semiconductor optical amplifier’s direct/cross gain modulation for seamless integration of hybrid fiber-coaxial connectivity

We propose a cost-effective THz wireless communication scheme for future femtocell networks that leverages either direct gain modulation (DGM) or cross gain modulation (XGM) of a semiconductor optical amplifier (SOA) to convert coaxially or optically carried data into intensity-modulated THz waves, respectively. This architecture, based on an SOA and a uni-traveling-carrier photodiode (UTC-PD), has advantages over typical THz modulation schemes involving a resonant tunneling diode or an electro-optic modulator combined with a UTC-PD. Consequently, it facilitates the seamless convergence of hybrid fiber-coaxial networks to THz radio access networks with low cost, straightforward monolithic integration, and a more compact footprint. Furthermore, we experimentally verified the possibility of non-return-to-zero on–off keying wireless communication over 0.5 m in the 300 GHz band, achieving real-time transmission of 4 Gbit/s for coaxial access via an SOA’s DGM and 10 Gbit/s for fiber access via the SOA’s XGM. Notably, these data rates were attained by simple non-coherent THz intensity demodulation based on a Fermi-level managed barrier diode while meeting the 7% hard-decision forward error correction (HD-FEC) threshold (3.4×10−3). Finally, we conducted an analysis of the merits and drawbacks of the proposed THz communication scheme based on the combination of an SOA and a UTC-PD, discussed bottlenecks that hinder further rate improvement, and explored possibilities for optimization. In conclusion, this scheme is crucial for realizing future ultra-high-speed wireless networks that seamlessly connect to fiber-coaxial networks.

CPM modulation implementation using blind equalizer and non-coherent demodulation for 5G and beyond

CPM modulation implementation using blind equalizer and non-coherent demodulation for 5G and beyond

Toward RIS-Aided Non-Coherent Communications: A Joint Index Keying M-ary Differential Chaos Shift Keying System

In reconfigurable intelligent surface (RIS)-aided coherent communications, channel state information (CSI) is often assumed to be perfectly estimated at the receiver. However, perfect CSI cannot be available in practice. Furthermore, the complex and ever-changing channel makes the acquisition of accurate CSI unaffordable because of the large overhead in transmitting pilot signals. Motivated by these considerations, a novel non-coherent RIS-aided joint index keying <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> -ary differential chaos shift keying (RIS-JIK-MDCSK) scheme is proposed in this paper, where the receiver can retrieve information bits by performing non-coherent correlation demodulation without requiring CSI, thereby reducing the system complexity. In RIS-JIK-MDCSK, the states of the reference signal, RIS elements, and information-bearing subcarriers are jointly optimized to devise a joint index keying mechanism, where additional information bits are implicitly transmitted by these state indices, thus increasing the throughput and spectral efficiency. Furthermore, an effective joint index keying detection algorithm is proposed to recover information bits. The analytical bit error rate (BER) of RIS-JIK-MDCSK is derived over a Rayleigh fading channel. Other evaluation metrics, including the throughput, spectral efficiency, and system complexity are also analyzed and compared against benchmark schemes. Numerical simulations are performed to evaluate the superiority of RIS-JIK-MDCSK compared to existing schemes.

Response analyses on the drill-string channel for logging while drilling telemetry

Downhole acoustic telemetry (DAT), using a long drill string with periodical structures as the channel, is a prospective technology for improving the transmission rate of logging while drilling (LWD) data. Previous studies only focused on the acoustic property of a free drill string and neglected the coupling between pipes and fluid-filled boreholes. In addition to the drill-string waves, a series of fluid waves are recorded in the DAT channel, which has not been investigated yet. Unpredictable channel characteristics result in lower transmission rates and stability than expected. Therefore, a more realistic channel model is needed considering the fluid-filled borehole. In this paper, we propose a hybrid modeling method to investigate the response characteristics of the DAT channel. By combining the axial wavenumbers and excitation functions of mode waves in radially layered LWD structures, the channel model is approximated to the 1-D propagation, which considers transmission, reflection, and interconversion of the drill-string and fluid waves. The proposed 1-D approximation has been well validated by comparing the 2-D finite-difference modeling. It is revealed that the transmitted and converted fluid waves interfere with the drill-string wave, which characterizes the DAT channel as a particular coherent multi-path channel. When a fluid-filled borehole surrounds the drill string, the channel responses exhibit considerable delay as well as strong frequency selectivity in amplitude and phase. These new findings suggest that the complexity of the channel response has been underestimated in the past, and therefore channel measurements on the ground are unreliable. To address these channel characteristics, we apply a non-coherent demodulation strategy. The transmission rate for synthetic data reaches 15 bps in a 94.5 m long channel, indicating that the acoustic telemetry is promising to break the low-speed limitation of mud-pulse telemetry.

Noncoherent Demodulation and Decoding via Polynomial Zeros Modulation for Pilot-Free Short Packet Transmissions over Multipath Fading Channels

With the advent of the Internet of Things (IoT), short packet transmissions will dominate the future wireless communication. However, traditional coherent demodulation and channel estimation schemes require large pilot overhead, which may be highly inefficient for short packets in multipath fading scenarios. This paper proposes a novel pilot-free short packet structure based on the association of modulation on conjugate-reciprocal zeros (MOCZ) and tail-biting convolutional codes (TBCC), where a noncoherent demodulation and decoding scheme is designed without the channel state information (CSI) at the transceivers. We provide a construction method of constellation sets and demodulation rule for M-ary MOCZ. By deriving low complexity log-likelihood ratios (LLR) for M-ary MOCZ, we offer a reasonable balance between energy and bandwidth efficiency for joint coding and modulation scheme. Simulation results show that our proposed scheme can attain significant performance and throughput gains compared to the pilot-based coherent modulation scheme over multipath fading channels.

A Design of Analog Front-End with DBPSK Demodulator for Magnetic Field Wireless Network Sensors

This paper presents an on-chip fully integrated analog front-end (AFE) with a non-coherent digital binary phase-shift keying (DBPSK) demodulator suitable for short-range magnetic field wireless communication applications. The proposed non-coherent DBPSK demodulator is designed based on using comparators to digitize the received differential analog BPSK signal. The DBPSK demodulator does not need any phase-lock loop (PLL) to detect the data and recover the clock. Moreover, the proposed demodulator provides the detected data and the recovered clock simultaneously. Even though previous studies have offered the basic structure of the AFEs, this work tries to amplify and generate the required differential BPSK signal without missing data and clock throughout the AFE, while a low voltage level signal is received at the input of the AFE. A DC-offset cancellation (DCOC), a cascaded variable gain amplifier (VGA), and a single-to-differential (STOD) converter are employed to construct the implemented AFE. The simulation results indicate that the AFE provides a dynamic range of 0 dB to 40 dB power gain with 2 dB resolution. Measurement results show the minimum detectable voltage at the input of AFE is obtained at 20 mV peak-to-peak. The AFE and the proposed DBSPK demodulator are analyzed and fabricated in a 130 nm Bipolar-CMOS-DMOS (BCD) technology to recover the maximum data rate of 32 kbps where the carrier frequency is 128 kHz. The implemented DCOC, cascaded VGA, STOD, and the demodulator occupy 0.15 , 0.063 , 0.045 , and 0.03 of area, respectively. The AFE and the demodulator consume 2.9 mA and 0.15 mA of current from an external 5 V power supply, respectively.

Binary Polarization Shift Keying With Reconfigurable Intelligent Surfaces

We propose a novel binary polarization shift keying modulation scheme for a line-of-sight environment by exploiting the polarization control ability of the reconfigurable intelligent surface (RIS). The RIS encodes the information data in terms of the polarization states of either the reflected wave from the RIS or the composite wireless channel between an RF source and receiver. In the first case, polarization mismatch correction becomes essential at the receiver. In the second case, the RIS pre-codes the reflected wave to compensate for the polarization mismatch which allows non-coherent demodulation at the receiver.

SSK-ICS LoRa: A LoRa-Based Modulation Scheme With Constant Envelope and Enhanced Data Rate

Long-range (LoRa) modulation is an orthogonal modulation scheme that uses linearly-modulated up chirps to represent information bits. Its constant envelope and good bit-error-rate performance make it one of the key players in establishing low-power wide-area networks for the Internet of things applications. However, LoRa modulation has low data rates. In this letter, we propose a new constant-envelope modulation scheme, named slope-shift-keying and interleaved-chirp spreading (SSK-ICS) LoRa modulation, that can deliver higher data rates than the conventional LoRa modulation scheme. Succinctly, the proposed SSK-ICS-LoRa modulation uses up chirps, down chirps, interleaved up chirps and interleaved down chirps to expand the signal set and hence can carry more bits per transmission symbol. For the same spreading factor and bandwidth consumption, the proposed scheme is able to improve the data rate of the conventional LoRa scheme up to 28.6%. We also present the optimal maximum-likelihood detectors for both coherent and non-coherent demodulators for the proposed scheme. Simulation results show that the proposed scheme outperforms LoRa modulation in both data rate and bit-error rate.

Time Domain Multiplexed LoRa Modulation Waveform Design for IoT Communication

Long-Range (LoRa) is one of the emerging technologies in low-power wide-area networks (LPWANs). In this letter, we proposed a Time Domain Multiplexed LoRa (TDM-LoRa) modulation to improve the throughput of conventional LoRa by using up-chirp and down-chirp simultaneously. A low complexity non-coherent algorithm for the TDM-LoRa modulation is also presented. We then derive an analytical expression for the bit error rate (BER) of non-coherent demodulation in the additive white Gaussian noise (AWGN) channel. In addition, a scheme that encodes information bits on both in-phase and quadrature components of the TDM-LoRa symbol is presented to further improve the system data rate. Performance analysis and simulation show that our proposed schemes can achieve better spectral efficiency (SE) and throughput without obvious bit error rate (BER) degradation compared to the LoRa Physical Layer (PHY) scheme.

Numerical modeling on the bit error rate of EHF communication in time-varying hypersonic plasma sheath

Plasma sheaths enveloping hypersonic vehicles could yield a communication blackout. Many previous studies have shown that the electromagnetic wave in an extremely high frequency (EHF) band could penetrate a hypersonic plasma sheath effectively. In other words, the EHF communication could be a potential solution to the communication blackout problem. Nevertheless, most of those works used to concern only the EHF signal attenuation. In addition, those works normally treated plasma sheaths as a static plasma layer. However, plasma sheaths always keep evolving. In the present study, the modulated EHF signal propagation in a time-varying plasma sheath was investigated numerically. The plasma sheath was obtained with a hypersonic hydrodynamical model that has been utilized in previous studies. The EHF signal propagation was modeled based on theories of geometrical optics. The frequencies studied are 94, 140, and 225 GHz. The investigation revealed that not only signal attenuation but also the phase shifts for carrier waves vary with time. Their impact on the bit error rate (BER) of the EHF communication system was studied numerically. The modulation modes concerned in the present study are 2ASK, 2PSK, 4QAM, and Non-Coherent demodulation 2FSK (NC-2FSK). According to the study, the BER keeps varying with time. This study also showed that the BER is impacted by the carrier frequency, modulation mode, and the demodulation method. According to the comparison and the analysis, the suggested modulation modes are 2PSK and 4QAM at the carrier frequency of 140 GHz, which could lead to smaller and more stable BER for the EHF communication system utilized by hypersonic vehicles.

Frequency Modulated Signal’s Optimum Noncoherent Demodulator Performance

The article considers optimum noncoherent demodulator scheme. The symbol synchronization is key problem of demodulator’s performance. It is offered the resampler symbol synchronization sсhem. Modeling demodulator algorithm results is shown. The modeling results let to propose the optimum noncoherent demodulator scheme. It is shown that the demodulator provided near to ideal noncoherent performance. Based on the results presented in the paper, receivers of various broadband signals can be constructed.

A Batteryless RFID Sensor Architecture With Distance Ambiguity Resolution for Smart Home IoT Applications

In this article, a novel batteryless wireless sensor design is proposed and demonstrated. The proposed passive wireless sensor node integrates a ultrahigh-frequency (UHF) radio-frequency identification (RFID) chip, a filter, and a reactive sensor to enable the reading of environmental conditions wirelessly, without increasing the complexity of a typical RFID chip and substantial loss of the read range. The sensor changes the phase of the reflected RFID signal based on the sensed parameter; whereas, the filter helps in resolving any phase ambiguity that may arise due to the placement of the node at different distances. The phase change is detected at the reader using a noncoherent IQ demodulator. The design can easily integrate any type of sensors, such as temperature, humidity, and water-level sensor. A flood sensor and a temperature sensor were used to demonstrate the performance of the proposed design in a home and office environment.

2ASK System Modeling and Simulation

The communication network of our country is developing vigorously, and the digital communication system has a certain development prospect. However, for wireless signal transmission, signal modulation is needed to ensure the output results. To use the limited bandwidth to transmit digital signals more efficiently, the corresponding digital signals need to be modulated by the carrier. In this paper, the digital signal is transmitted by carrier modulation, and under the condition of Gaussian white noise, the modelling and simulation of 2ASK modulation and demodulation system are realized by using Simulink and m file respectively, and the anti-noise performance of the system can be seen. And through the m file to achieve non-coherent demodulation and coherent demodulation through the Simulink, we can see the advantages and disadvantages of the two ways. At the end of the paper, the bit error rate of the 2ASK signal is analyzed.

Performance Analysis of Typical Telemetry Modulation Methods Under Downlink Integrated Channel of Hypersonic Vehicles

Due to the severe impact of dynamic plasma sheath on electromagnetic (EM) waves, the communication quality of hypersonic vehicles deteriorates, even resulting in communication blackouts during the reentry process. In this article, the hypersonic vehicle downlink integrated channels that cascade the plasma sheath channel and Rice fading channel, i.e., the downlink telemetry channels, are first established, and then the demodulation method and performance of typical telemetry modulations including the M-ary phase shift keying (MPSK), M-ary amplitude shift keying (MASK), and M-ary frequency shift keying (MFSK) are studied. Considering the high dynamics of the plasma sheath, the pilot signals are used to detect the signal correctly for MPSK, and the non-coherent demodulation is adopted for MASK and MFSK. Especially, an adaptive maximum likelihood (ML) receiver for ASK is proposed based on a reduced reversible jump Markov chain Monte Carlo (RRJ-MCMC) algorithm to estimate the probability density function (pdf) of the received signal. The simulation results show that the communication performance of PSK and ASK is improved with the modulation order $M$ decreasing; the performance of non-coherent FSK is improved with the modulation order $M$ increasing. Meanwhile, the performance follows the order of NC-MFSK (M ≥ 8) > BPSK > NC-4FSK > NC-2FSK > 2ASK. For NC-8FSK, when the electron density peak value ${Ne}_{\mathrm {peak}}$ = {2, 4, 6, 8, 10} $\times 10^{18}\,\,\text{m}^{-3}$ , the signal to noise ratio (SNR) required to reduce the bit error rate (BER) to 10−6 are 17, 18, 19, 21, and 34 dB, respectively.

Low-Power Wireless Data Transfer System for Stimulation in an Intracortical Visual Prosthesis.

There is a growing interest to improve the quality of life of blind people. An implanted intracortical prosthesis could be the last resort in many cases of visual impairment. Technology at this moment is at a stage that implementation is at sight. Making the data communication to and from the implanted electrodes wireless is beneficial to avoid infection and to ease mobility. Here, we focus on the stimulation side, or downlink, for which we propose a low-power non-coherent digital demodulator on the implanted receiver. The experimentally demonstrated downlink is on a scaled-down version at a 1 MHz carrier frequency showing a data rate of 125 kbps. This provides proof of principle for the system with a 12 MHz carrier frequency and a data rate of 4 Mbps, which consumes under 1 mW at the receiver side in integrated circuit (IC) simulation. Due to its digital architecture, the system is easily adjustable to an ISM frequency band with its power consumption scaling linearly with the carrier frequency. The tested system uses off-the-shelf coils, which gave sufficient bandwidth, while staying within safe SAR limits. The digital receiver achieved a reduction in power consumption by skipping clock cycles of redundant bits. The system shows a promising pathway to a low-power wireless-enabled visual prosthesis.

Detecting Relative Amplitude of IR Signals with Active Sensors and Its Application to a Positioning System

Nowadays, there is an increasing interest in smart systems, e.g., smart metering or smart spaces, for which active sensing plays an important role. In such systems, the sample or environment to be measured is irradiated with a signal (acoustic, infrared, radio-frequency…) and some of their features are determined from the transmitted or reflected part of the original signal. In this work, infrared (IR) signals are emitted from different sources (four in this case) and received by a unique quadrature angular diversity aperture (QADA) sensor. A code division multiple access (CDMA) technique is used to deal with the simultaneous transmission of all the signals and their separation (depending on the source) at the receiver’s processing stage. Furthermore, the use of correlation techniques allows the receiver to determine the amount of energy received from each transmitter, by quantifying the main correlation peaks. This technique can be used in any system requiring active sensing; in the particular case of the IR positioning system presented here, the relative amplitudes of those peaks are used to determine the central incidence point of the light from each emitter on the QADA. The proposal tackles the typical phenomena, such as distortions caused by the transducer impulse response, the near-far effect in CDMA-based systems, multipath transmissions, the correlation degradation from non-coherent demodulations, etc. Finally, for each emitter, the angle of incidence on the QADA receiver is estimated, assuming that it is on a horizontal plane, although with any rotation on the vertical axis Z. With the estimated angles and the known positions of the LED emitters, the position (x, y, z) of the receiver is determined. The system is validated at different positions in a volume of 3 × 3 × 3.4 m3 obtaining average errors of 7.1, 5.4, and 47.3 cm in the X, Y and Z axes, respectively.

Energy Efficient Parallel Concatenated Index Modulation and $M$-ary PSK Aided OFDM-DCSK Communications With QoS Consideration

In this paper, we propose a parallel concatenated index modulation and $M$ -ary phase shift keying (MPSK) to integrate with carrier interferometry (CI) codes into the orthogonal frequency division multiplex (OFDM) differential chaotic shift keying (DCSK) communication system. Our objective is to meet different quality of service (QoS) user demands while achieving higher energy efficiency and retaining reliable communications with low peak-to-average power ratio (PAPR). In our design, one input bit set is modulated by the index of the CI codes matrix whose rows are rotated circularly, another bit set is mapped to the MPSK symbols to realize the $M$ -ary modulation. Subsequently, the resultant MPSK symbols are modulated by reference chaotic sequences and spread by the information-bearing rotated CI codes matrix at the transmitter. After the OFDM modulations, the information bearing symbols are transmitted over multiple subcarriers. At the receiver, after the non-coherent chaotic correlation demodulation, the maximum likelihood detection method is firstly applied to attain the estimates of the index modulated bit set, which are then used to recover the phases of chaotic sequences for further evaluation of another MPSK modulated symbols. Since no additional energy is required while more bits can be transmitted via the $M$ -ary modulation and index modulation, the energy efficiency can be improved. In addition, thanks to the orthogonality of the CI codes matrix and the spreading in the frequency domain, the PAPR could be suppressed and reliability performances can be improved. Then theoretical analysis is conducted and simulation results validate the theoretical analysis. Moreover, the results demonstrate the superior bit error rate (BER) performances to benchmarks and flexible data rate could be provided for user terminals via different combinations of the index modulation and the $M$ -ary modulation.

End-to-End Simulations of Coded Transmissions in Space Links Affected by Solar Scintillation

In this article, coded space communication links impaired by solar scintillation are investigated followed by a comprehensive end-to-end approach. With respect to baseband analyses, this allows for a more realistic modeling of actual communication links in these scenarios, though at the cost of longer simulation times and higher minimum values of the error rates assessable. The effect of solar scintillation on both signal amplitude and phase is studied, by considering the potential use of noncoherent demodulation to withstand phase synchronization impairments. This article allows optimizing some receiver parameters, such as the phase-locked loop bandwidth, in a way to face critical contingency scenarios as well.

Multiple Range and Vital Sign Detection Based on Single-Conversion Self-Injection-Locked Hybrid Mode Radar With a Novel Frequency Estimation Algorithm

This article presents a single-conversion self-injection-locked (SIL) (SCSIL) hybrid mode radar with a novel frequency estimation algorithm, which improves the range resolution in a frequency-modulated continuous-wave (FMCW) mode and simultaneously detects the vital signs of multiple subjects in the CW mode. The system architecture includes an SIL oscillator (SILO), a frequency converter, two antennas, and a noncoherent frequency demodulator. Due to the frequency–phase relationship in the spectrum of the beat signal in the FMCW mode, the distance to the closely spaced subjects can be determined. Moreover, the algorithm will identify the most dominant component and remove it from the input signal, and the steps are repeated until the residual-to-input energy ratio is less than the threshold value. This iterative method can thus distinguish multiple signals whose frequencies are close to each other and can support a superresolution analysis in both FMCW and CW modes. In an experiment, the radar with a 150-MHz bandwidth and a sensing period of 20 s can simultaneously provide accurate range and vital sign information of two adjacent subjects with radial and azimuth spacings of 60 cm and 5°, respectively.

Complex-Valued Neural Networks for Noncoherent Demodulation

Noncoherent demodulation is an attractive choice for many wireless communication systems. It requires minimal protocol overhead for carrier synchronization, and it is robust to radio impairments commonly found in low-cost transceivers. Machine learning techniques, such as neural networks and deep learning, offer additional benefits for these systems. Practical communication systems often include nonlinearities, non-stationarity, and non-Gaussian noise, which complicate mathematical derivation of optimum demodulators. Learning approaches can optimize demodulator performance directly from simulated or measured radio data, which is often plentiful in the design and verification of today’s integrated transceivers. This paper examines several candidate neural network topologies for use in noncoherent demodulation and provides a mathematical framework for their comparison. Each is based on a complex-valued feature detection layer, which may be characterized as coherent or noncoherent, followed by one or more real-valued classification layers. Backpropagation equations for the noncoherent feature layer include a synchronization term that facilitates training with noncoherent input data. The coherent layer does not synchronize training data, however a noncoherent demodulator can still be constructed by increasing the coherent layer capacity and adding a max pooling layer to marginalize the unknown signal phase. A frequency classification example highlights the differences between the topologies and confirms that optimum noncoherent demodulation can be learned in the presence of AWGN and random phase offsets. The topologies considered here are suitable for noncoherent demodulation of power-efficient modulations such as FSK and ASK, which are typical in today’s short-range wireless communication systems. It is hoped that such topologies will lead to a future common architecture that can support the wide range of modulation formats in this space.