Single Channel Reception Research Articles

Source number of single-channel signals intelligent estimation via signal reconstruction

As wireless communication advances, the spectrum is becoming more crowded and overlapping, making it essential to determine the number of signal sources based on the received signal in signal processing. In various communication scenarios, single-channel reception is preferred over multi-channel reception due to its simplicity, reliability, and cost-effectiveness. However, most existing methods for estimating the number of sources in single-channel systems are adapted from multi-channel methods and require high signal-to-noise ratios (SNRs). To overcome this limitation, we explore a deep learning-based solution for estimating the number of sources in single-channel systems. Our method utilizes a signal reconstruction algorithm based on low-rank representation to recover the essential structure of the signal and suppress noise. The reconstructed signal is then transformed into a radio image, taking into account the correlation and feature completeness of the information. Moreover, we develop a lightweight hybrid classification (LHC) model capable of estimating source number by using small sample images, without the need for extensive data. Our experimental results demonstrate the effectiveness of this method in estimating the number of sources under low SNR and small samples conditions.

Forward Scatter Radar Meets Satellite: Passive Sensing of Aerial Target Using Satellite Communication Waveforms

The problem of single-channel reception of global positioning system (GPS) communication waveforms makes passive sensing of aerial target difficult because of forward scatter. This paper proposes a novel aerial target passive sensing method based on linear canonical transformation (LCT) using the forward scattered satellite communication waveforms. The proposed method firstly preprocesses the received signal based on the characteristics of the traditional satellite tracking loop and the forward scattered satellite communication waveforms to effectively suppress the interference of the direct wave through DC removal. Then, the Gaussian noise and multipath interference in the channel are suppressed by applying a rectangular window to its linear canonical domain. Finally, aerial target sensing is performed based on the peak value of signals in the linear canonical transform domain. The characteristic signal is constructed by analyzing the satellite communication waveforms. Combining the linear canonical transform with the matched filter (MF) to estimate the target parameter. Simulation results show that the proposed method can effectively perform the aerial target sensing by using satellite communication waveforms in the forward scatter scenario.

Performance of Selection Combining Diversity in <inline-formula> <tex-math notation="TeX">$\eta{-}\mu$</tex-math></inline-formula> Fading Channels With Integer Values of <inline-formula> <tex-math notation="TeX">$\mu$</tex-math></inline-formula>

An analytical study of selection combining (SC) diversity under η-μ multipath fading is presented, considering that the μ parameter takes integer values. Closed-form expressions are derived for the statistics of the signal-to-noise ratio (SNR) at the combiner output and for the error rate of some relevant M-ary modulation schemes. Additionally, closed-form expressions are also derived for the channel capacity, considering different adaptive transmission policies. It is shown that, if the number of receive branches is high enough, severe fading may result in an increased channel capacity for all the considered transmission strategies due to the branch selection and the higher channel variability. This is in sharp contrast to the behavior of capacity in single-channel reception schemes. Monte Carlo simulations have been carried out to validate the derived analytical expressions.

Distributed Multi-Interface Multichannel Random Access Using Convex Optimization

The aggregate capacity of wireless ad hoc networks can be increased substantially if each node is equipped with multiple network interface cards (NICs) and each NIC operates on a distinct frequency channel. Most of the recently proposed channel assignment algorithms are based on combinatorial techniques. Combinatorial channel assignment schemes may sometimes result in computationally complicated algorithms as well as inefficient utilization of the available frequency spectrum. In this paper, we analytically model channel and interface assignment problems as tractable continuous optimization problems within the framework of network utility maximization (NUM). In particular, the link data rate models for both single-channel reception and multichannel reception scenarios are derived. The assignment of both nonoverlapped and partially overlapped channels is also considered. We then propose two distributed multi-interface multichannel random access (DMMRA) algorithms for single-channel reception and multichannel reception scenarios. The DMMRA algorithms are fast, distributed, and easy to implement. Each algorithm solves the formulated NUM problem for each scenario. DMMRA requires each node to only iteratively solve a local, myopic, and convex optimization problem. Convergence and optimality properties of our algorithms are studied analytically. Simulation results show that our proposed algorithms significantly outperform utility-optimal combinatorial channel assignment algorithms in terms of both achieved network utility and throughput.

Optimal beamforming in ultrasound using the ideal observer

Beamforming of received pulse-echo data generally involves the compression of signals from multiple channels within an aperture. This compression is irreversible, and therefore allows the possibility that information relevant for performing a diagnostic task is irretrievably lost. The purpose of this study was to evaluate information transfer in beamforming using a previously developed ideal observer model to quantify diagnostic information relevant to performing a task. We describe an elaborated statistical model of image formation for fixed-focus transmission and single-channel reception within a moving aperture, and we use this model on a panel of tasks related to breast sonography to evaluate receive-beamforming approaches that optimize the transfer of information. Under the assumption that acquisition noise is well described as an additive wide-band Gaussian white-noise process, we show that signal compression across receive-aperture channels after a 2-D matched-filtering operation results in no loss of diagnostic information. Across tasks, the matched-filter beamformer results in more information than standard delay-and-sum beamforming in the subsequent radio-frequency signal by a factor of two. We also show that for this matched filter, 68% of the information gain can be attributed to the phase of the matched-filter and 21% can be attributed to the amplitude. A 1-D matched filtering along axial lines shows no advantage over delay-andsum, suggesting an important role for incorporating correlations across different aperture windows in beamforming. We also show that a post-compression processing before the computation of an envelope is necessary to pass the diagnostic information in the beamformed radio-frequency signal to the final envelope image.

Capacity of Correlated Generalized Gamma Fading With Dual-Branch Selection Diversity

The capacity of correlated generalized gamma (GG) fading channels with dual-branch selection diversity (SD) reception and channel side information (CSI) available at both the transmitter and the receiver is studied and analyzed. In particular, the capacity is evaluated under four adaptive transmission policies defined according to the operational CSI: 1) optimal power and rate adaptation (OPRA); 2) constant power with optimal rate adaptation (ORA); 3) channel inversion with fixed rate (CIFR); and 4) truncated CIFR (TIFR). Under these four adaptation policies, fast converging infinite series expressions for the capacity are derived and evaluated. Furthermore, for the simplifying cases of independent GG fading channels and/or single-channel reception (i.e., no diversity), closed-form expressions have been obtained. Previously published expressions are shown to be special cases of the derived expressions. Performance evaluation results obtained by means of numerical analysis clearly demonstrate the usefulness and accuracy of the analysis.

A single-chip array of NMR receivers

We present the first single-chip array of integrated NMR receivers for parallel spectroscopy and imaging. The array, optimized for operation at 300 MHz, is composed of eight separate channels, with each channel consisting of a detection coil, a tuning capacitor, a low noise amplifier and a 50 Ω buffer. As all the integrated electronics are placed underneath the reception coils, the array is densely packed. Each single-channel reception coil has a diameter of 500 μm, resulting in a total active area of 1 mm by 2 mm for the array. The 1H time-domain spin sensitivity of a single channel is approximately 1 × 10 15 spins / Hz .

Effect of Channel Estimation Error on Bit Error Probability in OFDM Systems over Rayleigh and Ricean Fading Channels

A characteristic function-based method is used to derive closed-form bit error probability (BEP) expressions for orthogonal frequency-division multiplexing (OFDM) systems in the presence of channel estimation error over frequency-selective Rayleigh fading channels and frequency-selective Ricean fading channels. Both single channel reception and diversity reception with maximal ratio combining (MRC) are examined. The BEP expressions are shown to be sums of several conditional probability functions which can be calculated by using proper complex Gaussian random variable theory and a characteristic function method. The closed-form BEP expressions can be used to accurately investigate the bit error rate performance degradation caused by channel estimation error under different wireless channel environment models. The performances of two interpolation methods, a sine interpolator with Hamming windowing and a Wiener interpolator, are compared.

Precise BER analysis of π/4-DQPSK OFDM with carrier frequency offset over frequency selective fast fading channels

An exact closed-form bit error rate (BER) expression is derived for an orthogonal frequency-division multiplexing system with π/4-shifted differentially encoded quadrature phase shift keying (π/4-DQPSK) in the presence of carrier frequency offset over frequency-selective fast Rayleigh fading channels. Different system configurations, including time domain differential modulation, frequency domain differential modulation, single channel reception, and multi-channel reception with maximal ratio combining diversity, are considered in the exact BER analysis. For a small number of subcarriers, the BER expression can be calculated directly. A Monte Carlo method is designed to evaluate the BER for a large number of subcarriers. The analytical expression can be used to investigate the effect of several channel parameters, including mean delay spread and maximum Doppler spread, on the system BER performance. Particularly, the effect of carrier frequency offset on the system performance, and the differences and opportunities to use frequency domain differential modulation or time domain differential modulation, can be studied in a quantitative way for a more realistic wireless channel environment model. By using the exact closed-form BER expression, an optimum number of subcarriers can be found, and the allowable carrier frequency offset, Doppler spread, and mean delay spread for given operating conditions can be determined.

Performance of Digital Linear Modulations on Weibull Slow-Fading Channels

A closed-form expression is derived for the moment-generating function of the Weibull distribution, valid when its fading parameter assumes integer values. Expressions for average signal-to-noise ratio, signal outage, and average symbol-error rate are derived for single-channel reception and independent multichannel diversity reception operating on flat Weibull slow-fading channels.

Error rates for Nakagami-m fading multichannel reception of binary and M-ary signals

This paper derives new closed-form formulas for the error probabilities of single and multichannel communications in Rayleigh and Nakagami-m (1960) fading. Closed-form solutions to three generic trigonometric integrals are presented as part of the main result, providing a unified method for the derivation of exact closed-form average symbol-error probability expressions for binary and M-ary signals with L independent channel diversity reception. Both selection-diversity and maximal-ratio combining (MRC) techniques are considered. The results are generally applicable for arbitrary two-dimensional signal constellations that have polygonal decision regions operating in a slow Nakagami-m fading environments with positive integer fading severity index. MRC with generically correlated fading is also considered. The new expressions are applicable in many cases of practical interest. The closed-form expressions derived for a single channel reception case can be extended to provide an approximation for the error rates of binary and M-ary signals that employ an equal-gain combining diversity receiver.

A unified approach for calculating error rates of linearly modulated signals over generalized fading channels

We present a unified analytical framework to determine the exact average symbol-error rate (SER) of linearly modulated signals over generalized fading channels. The results are applicable to systems employing coherent demodulation with maximal-ratio combining multichannel reception. The analyses assume independent fading paths, which are not necessarily identically distributed. In all cases, the proposed approach leads to an expression of the average SER involving a single finite-range integral, which can be easily computed numerically. In addition, as special cases, SER expressions for single-channel reception are obtained. These expressions reduce to well-known solutions, give alternative (often simpler) expressions for previous results, or provide new formulas that are either closed-form expressions or simple to compute numerically.

The Incoherent-carrier Communication Systems

Possibilities of the use of incoherent carriers for transmission of analogue and digital signals have been established. It has been shown that for analogue signals a message SNR of 60–70 db, with incoherent carrier, can be obtained by using compound pulse modulation and carrier clipping. The use of incoherent carriers eliminates the fading distortion, normally very disturbing with the coherent-carrier systems.For On-Off digital transmission through noisy fading channels, an error rate of 1 × 10−5 has been obtained with incoherent carriers for a CNR of 17 db, the sine wave carriers under similar conditions require 53 db CNR for the single channel reception. Thus in effect, the noise carrier provides a signal gain of 36 db. Minimum noise-carrier bandwidths required to obtain fading protection have been obtained, and it was found to depend on the method of noise-carrier generation. Different methods of noise-carrier generation have been studied. The diversity effectiveness of noise-carrier systems has been e...

Stereo sound broadcasting now compatible with single channel reception

Stereo sound broadcasting now compatible with single channel reception