Multipath Delay Research Articles

Source Localization Using Multi-Path Time Delays Measured by Two Hydrophones in the Deep Ocean

Source Localization Using Multi-Path Time Delays Measured by Two Hydrophones in the Deep Ocean

DESIGN OF A HIGH-SPEED HIGH-ACCURACY 2048-POINT FFT USING SINGLE-PRECISION FLOATING-POINT ADAPTIVE CORDIC ON FPGA

In this paper, hardware design of a Fast Fourier Transform (FFT) core using Single-precision Floating-point Adaptive CORDIC is implemented on Altera Stratix IV FPGA. With FFT implementation, CORDIC is utilized for reducing the speed drawback of complex multiplication and the adaptive algorithm is proposed to decrease the iterations of conventional CORDIC. The experimental results of Adaptive CORDIC and 2048-point Radix-2 Multi-path Delay Commutator FFT designs are built and verified based on three kinds of Look-up Table that cost 16, 8 and 4 constant angles. As experimental results, there is a resource equivalence while it has a trade-off between speed performance and accuracy. In comparison, an adaptive CORDIC core based on Look-up Table of 16 constant angles, and 2048-point Radix-2 Multi-path Delay Commutator Fast Fourier Transform based on Adaptive CORDIC using Look-up Table of 16 constant angles are well responding to resource optimization, high-speed performance and high-accuracy of computations.

PRIDE: Path Integration Based Delay Estimation in Multi-Device Multi-Path Environments

Massive connectivity in the near future puts forward an urgent demand for the accurate time delay estimation (TDE). However, the accuracy of the traditional TDE methods is severely degraded by the multi-path interference (MPI) and multi-device interference. In this paper, we propose a path integration based delay estimation (PRIDE) method. For the first time, the unique delay structure of each device is utilized, and the MPI is converted to an assistance. Considering the practical case where multi-path delays are non-integer times of the sampling period, PRIDE is carried out in two steps to estimate the integer and fractional parts of the delay sequentially. Theoretical analysis and simulations show that the TDE accuracy in the multi-device multi-path environment can be greatly improved by the proposed PRIDE method with comparatively low computational complexity.

All MOS noise-shaped time-mode temperature sensor

All MOS smart temperature sensor is presented in this work using digital-intensive temperature to time converter and noise-shaped time-to-digital converter (TDC). The temperature to time converter is designed using novel delay elements, where the output of a proportional to absolute temperature (PTAT) sensor delay line having a temperature coefficient of 2037 ppm/C∘, is compared with a reference delay line having a temperature coefficient of 80 ppm/C∘. The proposed multipath delay cell is utilized in the design of a noise-shaped TDC, which achieves 8 ps raw resolution over 25 ns dynamic range(DR). Because of quantization and mismatch noise-shaping, the simulation error of the sensor is limited to ±0.71C∘ after two-point calibration, over a temperature range from 0C∘ to 100C∘. The design achieves a resolution of 0.032C∘ at a conversion rate of 5.5 MS/s in SCL 180 nm 1.8 V/3.3 V 1P4M CMOS process.

SS‐OFDM: an enhanced multicarrier transmission scheme based on variable granularity spectrum allocation for 5G

When oriented to the needs of the future fifth generation (5G) networks, orthogonal frequency division multiplexing (OFDM), as a modulation scheme, has some drawbacks: high out-of-band emission (OOBE) of power, relatively low spectrum efficiency, and poor flexibility for allocating resources. In this study, a subband superposed OFDM (OFDM) scheme, based on a variable granularity spectrum allocation, is proposed to divide the transmission channel into several subbands considering the compromises between single-carrier and multicarrier spectrum utilisation. For accommodating the diverse 5G scenarios, appropriate signalling parameters can be independently configured among the subbands. A multistage polyphase interpolator is developed in the transmitter to reduce the implementation cost of time-domain filter depressing the OOBE. Extremely narrow frequency guard intervals between subbands are realised by filtering to maximise the spectrum utilisation. At the receiver, a subband decision feedback and feedforward equaliser, relying on the subband's oversampling architecture, is designed to utilise the diversity gains in both the Doppler and the multipath delay domains. Simulation results indicate that the spectral efficiency, in terms of the spectrum utilisation rate, is increased up to 98.5 % and that the bit-error-rate performance is significantly improved for the subbands experiencing high-speed mobile channels while preserving a relatively low computational complexity.

Positioning Performance of BDS Observation of the Crustal Movement Observation Network of China and Its Potential Application on Crustal Deformation.

The Crustal Movement Observation Network of China (CMONOC) has begun receiving BeiDou Navigation Satellite System (BDS) observations since 2015, and accumulated more than 2.5 years of data. BDS observations has been widely applied in many fields, and long-term continuous data provide a new strategy for the study of crustal deformation in China. This paper focuses on the evaluation of BDS positioning performance and its potential application on crustal deformation in CMONOC. According to the comparative analysis on multipath delay (MPD) and signal to noise ratio (SNR) between BDS and GPS data, the data quality of BDS is at the same level with GPS measurements in COMONC. The spatial distribution of BDS positioning accuracy evaluated as the root mean square (RMS) of daily residual position time series on horizontal component is latitude-dependent, declining with the increasing of station latitude, while the vertical one is randomly distributed in China. The mean RMS of BDS position residual time series is 7 mm and 22 mm on horizontal and vertical components, respectively, and annual periodicity in position time series can be identified by BDS data. In view of the accuracy of BDS positioning, there are no systematic differences between GPS and BDS results. Based on time series analysis with data volume being 2.5 years, the noise characteristics of BDS daily position time series is time-correlated and corresponding noise is white plus flicker noise model, and the derived mean RMS of the BDS velocities is 1.2, 1.5, and 4.1 mm/year on north, east, and up components, respectively. The imperfect performance of BDS positioning relative to GPS is likely attributed to the relatively low accuracy of BDS ephemeris, and the sparse amount of MEO satellites distribution in the BDS constellation. It is expectable to study crustal deformation in CMONOC by BDS with the gradual maturity of its constellation and the accumulation of observations.

An Iterative Receiver for OFDM With Sparsity-Based Parametric Channel Estimation

In this work we design a receiver that iteratively passes soft information between the channel estimation and data decoding stages. The receiver incorporates sparsity-based parametric channel estimation. State-of-the-art sparsity-based iterative receivers simplify the channel estimation problem by restricting the multipath delays to a grid. Our receiver does not impose such a restriction. As a result it does not suffer from the leakage effect, which destroys sparsity. Communication at near capacity rates in high SNR requires a large modulation order. Due to the close proximity of modulation symbols in such systems, the grid-based approximation is of insufficient accuracy. We show numerically that a state-of-the-art iterative receiver with grid-based sparse channel estimation exhibits a bit-error-rate floor in the high SNR regime. On the contrary, our receiver performs very close to the perfect channel state information bound for all SNR values. We also demonstrate both theoretically and numerically that parametric channel estimation works well in dense channels, i.e., when the number of multipath components is large and each individual component cannot be resolved.

Secure image transmission over wireless network

The advances recently seen in data compression, and communication systems, have made it viable to design wireless image transmission systems. For many applications such as confidential transmission, military and medical applications, data encryption techniques should be also used to protect the confidential data from intruders. For these applications, both encryption and compression need to be performed to transmit a message in a fast and secure way. Further, the wireless channels have fluctuating channel qualities and high bit error rates. In this paper, a new scheme based on encryption and channel coding has been proposed for secure image transmission over wireless channels. In the proposed scheme, the encryption process is based on keys generator and Chaotic Henon map. Turbo codes are utilized as channel coding to deal effectively with the channel errors, multipath signal propagation and delay spread. Simulation results show that the proposed system achieves a high level of robustness against wide different of attacks and channel impairments. Further, it improves image quality with acceptable data rates.

Modeling and measurement of microwave propagation multipath channels in drill pipe bore

AbstractIn this paper, the characteristics of microwave propagation channels in drill pipe bore are analyzed by regarding the drill pipe as an irregular lossy cylindrical waveguide. An attenuation law is modeled using multipath propagation theory and an experimental statistical method. It is shown from physical measurement results that 5″ and $5^{1/2 \prime \prime} $ drill pipe bores, widely applied in the field of air drilling, can be used as 2.4 GHz band microwave channels with the caveat that the numerous reflective surfaces in the joint section of the drill pipe produce a great deal of reflected waves. Hence, the drill pipe bore has the characteristics of a dual cluster multipath channel, and multipath fading and delay are the primary factors affecting propagation quality. The study's constructed microwave attenuation model, based on multipath channels, can be regarded as the average attenuation of the unit length in the drill pipe bore, and can be used as the basis for simulation and analysis of the longer drill pipe string. In addition, a large delay between the two clusters leads to a significant increase of the root mean square delay spread. Consequently, multipath fading and delay are the main factors affecting the channel transmission rate.

Design o f “ 32 ” Point Split Radix b ased Multipath Delay Commutator FFT Architecture for Low Power Applications

<p>FFT is used in Modern high speed signal processing application. In aforementioned technologies that tends to operate in various operational modes. To implement FFT obviously it not only needs to meet high throughput demand and also it needed to scalable cater selectable N point FFT. Our contribution to this paper is two-fold of our existing method, as proposes for the split radix using Multipath Delay Commutator (MDC) algorithm has the least complex design and less multiplications comparing to radix-2 algorithm. So that it can able to reduce power consumption and area than our existing work. The implementation of power efficient hardware of split radix FFT (SRFFT) is built up by pruning excessive computation. Leveraging this potential, a new architecture of a configurable SRFFT processor is first developed so that unnecessary computations, which yield zeros at the output, are pruned. Simulations show that maximum power saving of around 20% is achieved. The proposed algorithm consists of mixed radix butterflies, whose structure is more regular. It has the conjugate-pair version, which requires less memory.</p>

Millimeter-wave propagation measurements and models at 28 GHz and 38 GHz in a dining room for 5G wireless networks

To meet 5G requirements, industries are looking forward to a new set of frequency allocation in the millimeter spectrum space, where there is huge amount of bandwidth for wireless gigabit communications. In this paper, the statistics of large-scale path loss and time dispersion parameters are investigated based on ultra-wideband measurements using a steerable directional horn antenna at transmitter (Tx) and omni-directional antenna at the receiver (Rx). The measurement was conducted in a dining room line-of-sight (LOS) scenario, which represents a typical closed-plan for in-building communication. The single-frequency, multi-frequency directional and omni-directional large-scale path loss models are evaluated at 28 GHz and 38 GHz bands based on data acquired from unique Tx and Rx antennas with combination pointing angles. The results show that the large-scale path loss models for indoor propagation developed in this paper is less complex, and yet more physically-based than those used in the third-generation partnership project (3GPP) systems, which involve additional model parameters but yield less accurate results. The time dispersion statistics for mmWave systems using directional antennas and omni-omni antennas configuration at both Tx and Rx are presented for co-polarization scenarios. We show that the multipath root mean square delay spread can be reduced when Tx and Rx antenna are pointed to each other, which results in the strongest received power.

Propagation Path Loss Modeling and Outdoor Coverage Measurements Review in Millimeter Wave Bands for 5G Cellular Communications

The global bandwidth inadequacy facing wireless carriers has motivated the exploration of the underutilized millimeter wave (mm-wave) frequency spectrum for future broadband cellular communication networks, and mmWave band is one of the promising candidates due to wide spectrum. This paper presents propagation path loss and outdoor coverage and link budget measurements for frequencies above 6 GHz (mm-wave bands) using directional horn antennas at the transmitter and omnidirectional antennas at the receiver. This work presents measurements showing the propagation time delay spread and path loss as a function of separation distance for different frequencies and antenna pointing angles for many types of real-world environments. The data presented here show that at 28 GHz, 38 GHz and 60 GHz, unobstructed Line of Site (LOS) channels obey free space propagation path loss while non-LOS (NLOS) channels have large multipath delay spreads and can utilize many different pointing angles to provide propagation links. At 60 GHz, there is more path loss and smaller delay spreads. Power delay profiles PDPs were measured at every individual pointing angle for each TX and RX location, and integrating each of the PDPs to obtain received power as a function of pointing angle. The result shows that the mean RMS delay spread varies between 7.2 ns and 74.4 ns for 60 GHz and 28 GHz respectively in NLOS scenario.

Correction of fractional cycle bias of pseudolite system for user integer ambiguity resolution

Synchronized pseudolite systems allow single-point positioning (SPP) using carrier-phase measurements with centimeter-level accuracy. Locata, developed by the Locata Corporation, emerged from the development of synchronized pseudolite technology. Numerous studies have claimed to achieve Locata SPP with centimeter-level accuracy; however, the ambiguities of Locata observations have been typically estimated as floating-point values. Similar to precise point positioning of global navigation satellite systems, pseudolite SPP that is based on ambiguity fixing can improve the positioning accuracy and shorten the convergence time, compared to the float solution. However, integer ambiguity fixing may be prevented due to the clock offset among the pseudolite transmitters. To recover the integer nature of single-difference ambiguity, a fractional cycle bias (FCB) correction method is proposed; this method is based on two-way time synchronization. The FCB correction method employed to estimate and correct the bias by a pseudolite network itself has two steps: two-way FCB measurement and half-cycle bias estimation. A ground-based testbed is constructed to test and verify the proposed method. It is shown that the FCB between the pseudolite transmitters have a stability better than 15 ps even considering the influence of variable multipath delay; the bias can be estimated with high precision and reliability. Statistical results support the theoretical findings that half-cycle bias may be caused by two-way clock offset measuring via carrier phase measurement. A two-dimensional positioning experiment is performed to evaluate the performance of the proposed FCB correction method. The single-difference ambiguities are fixed to integer values using the LAMBDA method with the fixed failure-rate ratio test. The results indicated that the positioning accuracy is at the sub-centimeters to centimeter-level compared with the real-valued solutions for all surveyed points.

Particle filter for multipath time delay tracking from correlation functions in deep water.

This paper presents a particle filtering-based approach for tracking multipath time delays from correlation function, such as autocorrelation, cross-correlation, and matched-filter output. The proposed approach exploits the continuous evolution with time of the correlations between multipath arrivals masked by the background noise to track time delays. The prominent feature of this approach is tracking the signal-related peaks (single points) instead of correlation pulses adopted in conventional approaches. To do so, the correlation function with only local peaks is introduced in the model of the measurement equation. This allows no assumption on the reference signal used to match the correlation pulse and no a priori knowledge of the covariance of the background noise. The time-evolving marginal posterior probability densities are also extracted by filtering to reveal the uncertainty of the time delays in every step of tracking. The approach is performed on both simulated data in reliable acoustic path propagation and experimental data collected during two deep water experiments; the results demonstrate significant advantages of the proposed method over a conventional state-space approach, the multiple hypothesis tracking, and a modified peak amplitude detection method.

Statistical multipath model comparative analysis of different GNSS orbits in static urban canyon environment

GNSS multipath channel characteristics research and modeling is an important but not well-solved topic. Therefore, we conducted a series of on-field research experiments from June 2015 to August 2017 at Shanghai Lujiazui area in China to study the multipath channel model of different satellite orbits for static urban canyon environment. A wideband GNSS intermediate frequency (IF) data sampling and recording platform are built up to capture real BDS B1 and GPS L1 signal. An advanced multipath estimation algorithm software is designed to extract multipath parameters from these real signal data. More than 16,400 multipath echoes are found in the on-field experiments. Based on the data, we analyze three core parameters about multipath - delay, power and lifetime. It is found that the multipath delay follows Gamma distribution. It is verified that the multipath power-delay profile follows a log-linear decline model, and the multipath lifetime follows a quasi-exponential decrease. The model feature parameters of different orbit satellite are analyzed and compared. This research deepens our insights into multipath channel characteristics in urban canyon environment and will be helpful for the design of both GNSS receivers and simulators.

Effects of Selective PPARα Modulator K-877 on Particle Numbers of Lipoprotein Subclasses in Dyslipidemic Patients: Analysis by GP-HPLC and NMR Lipoprofile 2 and 3

GNSS multipath channel characteristics research and modeling is an important but not well-solved topic. Therefore, we conducted a series of on-field research experiments from June 2015 to August 2017 at Shanghai Lujiazui area in China to study the multipath channel model of different satellite orbits for static urban canyon environment. A wideband GNSS intermediate frequency (IF) data sampling and recording platform are built up to capture real BDS B1 and GPS L1 signal. An advanced multipath estimation algorithm software is designed to extract multipath parameters from these real signal data. More than 16,400 multipath echoes are found in the on-field experiments. Based on the data, we analyze three core parameters about multipath - delay, power and lifetime. It is found that the multipath delay follows Gamma distribution. It is verified that the multipath power-delay profile follows a log-linear decline model, and the multipath lifetime follows a quasi-exponential decrease. The model feature parameters of different orbit satellite are analyzed and compared. This research deepens our insights into multipath channel characteristics in urban canyon environment and will be helpful for the design of both GNSS receivers and simulators.

Routing Protocols for Underwater Wireless Sensor Networks: Taxonomy, Research Challenges, Routing Strategies and Future Directions.

Recent research in underwater wireless sensor networks (UWSNs) has gained the attention of researchers in academia and industry for a number of applications. They include disaster and earthquake prediction, water quality and environment monitoring, leakage and mine detection, military surveillance and underwater navigation. However, the aquatic medium is associated with a number of limitations and challenges: long multipath delay, high interference and noise, harsh environment, low bandwidth and limited battery life of the sensor nodes. These challenges demand research techniques and strategies to be overcome in an efficient and effective fashion. The design of routing protocols for UWSNs is one of the promising solutions to cope with these challenges. This paper presents a survey of the routing protocols for UWSNs. For the ease of description, the addressed routing protocols are classified into two groups: localization-based and localization-free protocols. These groups are further subdivided according to the problems they address or the major parameters they consider during routing. Unlike the existing surveys, this survey considers only the latest and state-of-the-art routing protocols. In addition, every protocol is described in terms of its routing strategy and the problem it addresses and solves. The merit(s) of each protocol is (are) highlighted along with the cost. A description of the protocols in this fashion has a number of advantages for researchers, as compared to the existing surveys. Firstly, the description of the routing strategy of each protocol makes its routing operation easily understandable. Secondly, the demerit(s) of a protocol provides (provide) insight into overcoming its flaw(s) in future investigation. This, in turn, leads to the foundation of new protocols that are more intelligent, robust and efficient with respect to the desired parameters. Thirdly, a protocol can be selected for the appropriate application based on its described merit(s). Finally, open challenges and research directions are presented for future investigation.

An improved channel estimation method using doubly reduced matching pursuit over fractional delay multipath channel

Owing to the inherent sparse channel feature in multi-carrier modulation systems, compressed sensing (CS)-based techniques have been used for channel estimation with less pilot subcarriers for orthogonal frequency division multiplexing (OFDM) systems. Because of a sparse multipath channel’s characteristic of fractional delay, the channel measurement matrix that is generated by conventional time-domain sampling approaches cannot perfectly recover the channel impulse response (CIR), especially in the case of two adjacent paths that both have with non-negligible power. In this study, a fractional delay multipath channel model is used to simulate the wireless multipath channel. In addition, a time-domain oversampling based doubly reduced matching pursuit (DRMP) algorithm at the receiver is proposed to improve the estimation accuracy while reducing the computational complexity. Simulation results show that the proposed method can improve both the bit error rate (BER) performance and estimation time compared to conventional methods in an environment with fractional delay.

Statistical Multipath Model Based on Experimental GNSS Data in Static Urban Canyon Environment.

A deep understanding of multipath characteristics is essential to design signal simulators and receivers in global navigation satellite system applications. As a new constellation is deployed and more applications occur in the urban environment, the statistical multipath models of navigation signal need further study. In this paper, we present statistical distribution models of multipath time delay, multipath power attenuation, and multipath fading frequency based on the experimental data in the urban canyon environment. The raw data of multipath characteristics are obtained by processing real navigation signal to study the statistical distribution. By fitting the statistical data, it shows that the probability distribution of time delay follows a gamma distribution which is related to the waiting time of Poisson distributed events. The fading frequency follows an exponential distribution, and the mean of multipath power attenuation decreases linearly with an increasing time delay. In addition, the detailed statistical characteristics for different elevations and orbits satellites is studied, and the parameters of each distribution are quite different. The research results give useful guidance for navigation simulator and receiver designers.

Throughput of underwater acoustic networks with significant multipath delays

All existing works regarding the throughput of underwater acoustic networks (UWANs) explicitly ignore multipath effect of underwater acoustic channels (UWACs), which, however, is a prominent feature in underwater environments. In this paper, we investigate the throughput of UWANs with significant multipath delays. We extend the popular delay matrix model to make it suitable for analysis of throughput in UWANs with multipath delays. We differentiate between two cases of successful transmissions corresponding to different channel models. With the extended model, we derive the upper bounds of throughput for UWANs under different channel models with various fair constraints. We also show the necessary conditions for achieving these upper bounds under different scenarios. In addition, with derived upper bounds and necessary conditions, we offer designing rules for optimal schedules in UWANs with different channel models. Some examples of optimal schedules which could achieve the upper bounds under different scenarios are also provided.