Ultra-wideband Channel Model Research Articles

UWB channel modeling and simulation with continuous frequency response

Ultra-wideband (UWB) technology is a prospective technology for high-rate transmission and accurate localization in the future communication systems. State-of-art channel modeling approaches usually divide the UWB channel into several sub-band channels and model them independently. By considering frequency-dependent channel parameters, a novel analytical UWB channel model with continuous frequency response is proposed. The composite effect of all frequency components within the UWB channel on the channel impulse response (CIR) of delay domain is derived based on the continuous channel transfer function (CTF) of frequency domain. On this basis, a closed-form simulation model for UWB channels and geometry-based parameter calculation method are developed, which can guarantee the continuity of channel characteristics on the frequency domain and greatly reduce the simulation complexity. Finally, the proposed method is applied to generate UWB channel with 2 GHz bandwidth at sub-6GHz and millimeter wave (mmWave) bands, respectively. The channel measurements are also carried out to validate the proposed method. The simulated CIR and power gain are shown to be in good agreement with the measurement data. Moreover, the comparison results of power gain and Doppler power spectral density (DPSD) show that the proposed UWB channel model achieves a good balance between the simulation accuracy and efficiency.

Performance Evaluation of an On-Body Wireless Body Network Based on an Ultra-Wideband Physical Layer under a Dynamic Channel Model

Wireless body area networks (WBANs) are attracting attention as an important technology for realizing the Internet of Medical Things (IoMT). In addition, ultra-wideband (UWB) is one of the wireless communication technologies suitable for the IoMT and WBANs. Our previous study investigated the feasibility of WBANs utilizing UWB under ideal and static wearable WBAN channel models. The present research applies a dynamic on-body UWB channel model to a WBAN as a more realistic channel model. The feasibility of a high-reliability UWB-WBAN is demonstrated by evaluating the physical layer performance. Numerical results reveal the maximum number of retransmissions needed to achieve the desired transmission failure ratio for each link type and the corresponding energy efficiency and average number of retransmissions. These findings contribute to the realization of a highly reliable IoMT utilizing UWB-WBANs in a practical environment.

A Statistical Lower UWB Channel Model for in Body Communications

Applications of implantable micro-level wireless devices in the instantaneous collection and observation of body potentials of patients is becoming prominent nowadays. The license free radio band that is reserved internationally for industrial, scientific, and medical purposes (ISM) is being used currently for the above telemedicine applications. However, for short distance higher bit rate applications such as capsule endoscopy, the ultra-wide band (UWB) of frequencies is found as much suitable, since base band communication with less complex transceivers is possible due to its noise like behavior. But before developing any wireless network, it is necessary to characterize the radio channel accurately. In Body Area Network (BAN) with implantable low power and high data rate transceivers, on site measurement is not practically feasible. Therefore, easy to use statistical models that are derived from the measurement data are preferred. In this paper, authors introduce honey as an easily available and less expensive base, through a study of its dielectric properties, for preparing body mimicking liquid phantoms. In addition, this paper proposes an empirical in-body UWB channel model to determine the possible pathloss in the human abdominal region. The empirical pathloss data, which have been collected with the above liquid phantoms that mimic the biological tissues in lower UWB i.e. 3.1 GHz – 9 GHz frequency range are used to derive the proposed model.

Time-Varying Ultra-Wideband Channel Modeling and Prediction

This paper considers the channel modeling and prediction for ultra-wideband (UWB) channels. The sparse property of UWB channels is exploited, and an efficient prediction framework is developed by introducing two simplified UWB channel impulse response (CIR) models, namely, the windowing-based on window delay (WB-WD) and the windowing-based on bin delay (WB-BD). By adopting our proposed UWB windowing-based CIR models, the recursive least square (RLS) algorithm is used to predict the channel coefficients. By using real CIR coefficients generated from measurement campaign data conducted in outdoor environments, the modeling and prediction performance results and the statistical properties of the root mean square (RMS) delay spread values are presented. Our proposed framework improves the prediction performances with lower computational complexity compared with the performance of the recommended ITU-R UWB-CIR model. It is shown that our proposed framework can achieved 15% lower prediction error with a complexity reduction by a factor of 12.

PAPR reduction in ECMA‐368 UWB communication systems using parametric discrete sliding norm transform

SummaryECMA‐368 Standard adopts multiband orthogonal frequency division multiplexing (MB‐OFDM) for high rate ultra‐wideband (UWB) communication systems as a possible candidate for indoor wireless personnel area networks. One of the main drawbacks of MB‐OFDM modulation is the high peak‐to‐average power ratio (PAPR), which limits the power efficiency of the digital‐to‐analog converter and the high power amplifier due to nonlinear distortion. In this paper, a post inverse discrete Fourier transform nonlinear transformation called parametric discrete sliding norm transform (PDSNT) is proposed to reduce the PAPR in MB‐OFDM systems. The PDSNT method in addition to its much lower computational complexity than other schemes recently proposed for ECMA‐368 UWB systems introduces an efficient controlling parameter to obtain a good tradeoff between PAPR reduction and bit error rate (BER) performance degradation. Simulation results show that the proposed PDSNT‐based MB‐OFDM scheme can achieve better performance in PAPR reduction than conventional solutions with affordable BER performance degradation in UWB channel models.

An extension of the RiMAX multipath estimation algorithm for ultra-wideband channel modeling

This work presents an extension of the high-resolution RiMAX multipath estimation algorithm, enabling the analysis of frequency-dependent propagation parameters for ultra-wideband (UWB) channel modeling. Since RiMAX is a narrowband algorithm, it does not account for the frequency-dependency of the radio channel or the environment. As such, the impact of certain materials in which these systems operate can no longer be considered constant with respect to frequency, preventing an accurate estimation of multipath parameters for UWB communication. In order to track both the specular and dense multipath components (SMC and DMC) over frequency, an extension to the RiMAX algorithm was developed that can process UWB measurement data. The advantage of our approach is that geometrical propagation parameters do not appear or disappear from one sub-band onto the next. The UWB-RiMAX algorithm makes it possible to re-evaluate common radio channel parameters for DMC in the wideband scenario, and to extend the well-known deterministic propagation model comprising of SMC alone, towards a more hybrid model containing the stochastic contributions from the DMC’s distributed diffuse scattering as well.Our algorithm was tested with synthetic radio channel models in an indoor environment, which show that our algorithm can match up to 99% of the SMC parameters according to the multipath component distance (MCD) metric and that the DMC reverberation time known from the theory of room electromagnetics can be estimated on average with an error margin of less than 2 ns throughout the UWB frequency band. We also present some preliminary results in an indoor environment, which indicate a strong presence of DMC and thus diffuse scattering. The DMC power represents up to 50% of the total measured power for the lower UWB frequencies and reduces to around 30% for the higher UWB frequencies.

An Off-Body Narrowband and Ultra-Wide Band Channel Model for Body Area Networks in a Ferryboat Environment

In the article an off-body narrowband and ultra-wide band channel model for body area networks in a ferryboat environment is described. Considering the limited number of publications there is a need to develop an off-body channel model, which will facilitate the design of radio links, both from the multimedia services provider and the security point of view, for body area networks in this atypical environment. A mobile heterogeneous measurement stand, using radio distance measurements, which consists of three types of devices: miniaturized mobile nodes, stationary reference nodes, and a data acquisition server, was developed. A detailed analysis of both radio channels’ parameters was carried out. An analysis of system loss for off-body communication, including mean system loss, large-scale fading (corresponding to body shadowing), and small-scale fading (associated with the multipath phenomenon), both for 868 MHz narrowband and for 6489 MHz ultra-wide band channels, was performed. A statistical analysis of the obtained system loss model parameters was also carried out; good fit to the empirical data is observed.

UWB channel measurements and modelling for hurricanes

Maintaining communications during major hurricanes is critically important for public safety operations by first responders. This requires accurate knowledge of the propagation channel during hurricane conditions. In this work, the authors have carried out ultra-wideband (UWB) channel measurements during hurricane conditions ranging from Category-1 to Category-4, generated at the wall of wind facility of Florida International University. Time-domain P410 radios are used for channel measurements. From the empirical data analysis in time domain, they developed an UWB statistical broadband channel model for hurricanes. In particular, they characterise the effects of rain and wind speed on large-scale and small-scale UWB propagation parameters considering both line-of-sight (LOS) and non-LOS (NLOS) links. Their experimental results show that number of multipath components reduce considerably with wind driven rain (WDR) and with link obstruction (NLOS scenario). Several remarks are also provided that can help explain the behaviour of UWB propagation characteristics under WDR.

Performance of Polar Codes for OFDM-Based UWB Channel

A multiuser Ultra Wide Band (UWB) channel suffers seriously from realistic impairments. Among this, multipath fading and interferences, such as Multiple Access Interference (MAI) and Inter Symbol Interference (ISI), that significantly degrade the system performance. In this paper, a polar coding technique, originally developed by Arikan, is suggested to enhance the BER performance of indoor UWB based Orthogonal Frequency Division Multiplexing (OFDM) communications. Moreover, Interleave Division Multiple Access (IDMA) scheme has been considered for multiuser detection depending on the turbo type Chip-By-Chip (CBC) iterative detection strategy. Three different models as Symmetric Alpha Stable (SαS), Laplace model and Gaussian Mixture Model (GMM), have been introduced for approximating the interferences which are more realistic for UWB system. The performance of the proposed Polar-coded IDMA OFDM-based UWB system is investigated under UWB channel models proposed by IEEE 802.15.3a working group and compared with Low Density Parity Check (LDPC)-coded IDMA OFDM-based UWB system in terms of BER performance and complexity under the studied noise models. Simulation results show that the complexity of the proposed polar-coded system is much lower than LDPC-coded system with minor performance degradation. Furthermore, the proposed polar-coded system is robust against noise and interferences in UWB indoor environment and gains a significant performance improvement by about 5 dB compared with un-coded IDMA-OFDM-UWB system under the studied noise models.

Cluster-head based feedback for simplified time reversal prefiltering in ultra-wideband systems

Time-reversal prefiltering (TRP) technique for impulse radio (IR) ultra wide-band (UWB) systems requires a large amount of feedback to transmit the channel impulse response from the receiver to the transmitter. In this paper, we propose a new feedback design based on vector quantization. We use a machine learning algorithm to cluster the estimated channels into several groups and to select the channel cluster heads (CCHs) for feedback. In particular, CCHs and their labels are recorded at both side of the UWB transceivers and the label of the most similar CCH to the estimated channel is fed back to the transmitter. Finally, the TRP is applied using the feedback CCH. The proposed digital feedback provides three main advantages: (1) it significantly reduces the dedicated bandwidth required for feedback; (2) it considerably improves the speed of transceivers; and, (3) it is robust to noise in the feedback channel since few bytes are required to send the codes that can be heavily error protected. Numerical results on standard UWB channel models are discussed, showing the advantage of the proposed solution.

Integration interval determination and decision threshold optimization for improved TRPC-UWB communication systems

Integration interval and decision threshold issues were investigated for improved transmitted reference pulse cluster (iTRPC-) ultra-wideband (UWB) systems. Our analysis shows that the bit error rate (BER) performance of iTRPC-UWB systems can be significantly improved via integration interval determination (IID) and decision threshold optimization. For this purpose, two modifications can be made at the autocorrelation receiver as follows. Firstly, the IID processing is performed for autocorrelation operation to capture multi-path energy as much as possible. Secondly, adaptive decision threshold (ADT) instead of zero decision threshold (ZDT), is used as estimated optimal decision threshold for symbol detection. Performance of iTRPC-UWB systems using IID and ADT was evaluated in realistic IEEE 802.15.4a UWB channel models and the simulation results demonstrated our theoretical analysis.

TIME DOMAIN AND FREQUENCY DOMAIN DETERMINISTIC CHANNEL MODELING FOR TUNNEL/MINING ENVIRONMENTS

Understanding wireless channels in complex mining environments is critical for designing optimized wireless systems operated in these environments. In this paper, we propose two physics-based, deterministic ultra-wideband (UWB) channel models for characterizing wireless channels in mining/tunnel environments - one in the time domain and the other in the frequency domain. For the time domain model, a general Channel Impulse Response (CIR) is derived and the result is expressed in the classic UWB tapped delay line model. The derived time domain channel model takes into account major propagation controlling factors including tunnel or entry dimensions, frequency, polarization, electrical properties of the four tunnel walls, and transmitter and receiver locations. For the frequency domain model, a complex channel transfer function is derived analytically. Based on the proposed physics-based deterministic channel models, channel parameters such as delay spread, multipath component number, and angular spread are analyzed. It is found that, despite the presence of heavy multipath, both channel delay spread and angular spread for tunnel environments are relatively smaller compared to that of typical indoor environments. The results and findings in this paper have application in the design and deployment of wireless systems in underground mining environments.

Joint Estimation of TOA and PPM Symbols Using Sub-Nyquist Sampled IR-UWB Signal

Impulse radio ultra wideband (UWB) signals are used in various applications which require joint localization and communication. Due to the large bandwidth of the UWB signal, the estimation of time of arrival (TOA) and data symbols requires high sampling rates. This letter describes a sub-Nyquist rate receiver, which can jointly estimate TOA and data symbols. We first represent the received UWB signal in a new domain in which it is sparse. Then, we design physical layer waveforms and estimation algorithms to exploit this sparsity for joint estimation of TOA and pulse position modulation data symbols. The performance of the receiver is compared against the maximum likelihood (ML)-based receiver using an IEEE 802.15.4a CM1 line of sight UWB channel model. The proposed algorithm yields performance similar to the ML-based algorithms with only a fraction of sampling rate at high SNRs (> 25 dB).

Statistical Modeling of Indirect Paths for UWB Sensors in an Indoor Environment.

In this paper, we present a statistical model of an indirect path generated in an ultra-wideband (UWB) human tracking scenario. When performing moving target detection, an indirect path signal can generate ghost targets that may cause a false alarm. For this purpose, we performed radar measurements in an indoor environment and established a statistical model of an indirect path based on the measurement data. The proposed model takes the form of a modified Saleh–Valenzuela model, which is used in a UWB channel model. An application example of the proposed model for mitigating false alarms is also presented.

Analysis of Ultrawideband Pulse Distortion Due to Lossy Dielectric Walls and Indoor Channel Models

Ultrawideband (UWB) communication channels cause pulse distortion and result in many multipath components arriving at the receiver in clusters. In this paper, the effects of lossy dielectric walls on UWB pulses are analyzed. The frequency-dependent parameters of commonly used building materials are used to analyze the effects of multiple reflections and transmissions, material distortion, and interpulse interference on the UWB pulse waveform. The possibility of polarization-dependent distortion is discussed. Various thicknesses of walls and angles of incidence are considered. The distortion due to each effect is quantified in terms of maximum correlation coefficients (MCCs). The overall effect of the wall is modeled as a tapped-delay-line filter based on the MCC. The results are used to specify the multicluster structure of UWB channel models for indoor communication.

Frequency-Domain In-Vehicle UWB Channel Modeling

This paper aims to present a simple but robust model characterizing the frequency-dependent transfer function of an in-vehicle ultrawideband (UWB) channel. A large number of transfer functions spanning the UWB (3–11 GHz) are recorded inside the passenger compartment of a four-seated sedan. It is found that the complex transfer function can be decomposed into two terms, the first term being a real-valued long-term trend that characterizes frequency dependence with a power law and the second term forming a complex correlative discrete series that may be represented via an autoregressive (AR) model. An exhaustive simulation framework is laid out based on empirical equations characterizing trend parameters and AR process coefficients. The simulation of the transfer function is straightforward as it involves only a handful of variables; however, it is in good agreement with the actual measured data. The proposed model is further validated by comparing different channel parameters, such as coherence bandwidth, power delay profile, and root-mean-square delay spread, obtained from raw and synthetic data sets. It is also shown how the model can be compared with existing time-domain Saleh–Valenzuela-influenced models and related IEEE standards.

UKF-based channel estimation and LOS/NLOS classification in UWB wireless networks

The paper addresses ultra-wideband (UWB) channel estimation and line-of-sight (LOS) vs. non-line-of-sight classification based on the application of the unscented Kalman filter (UKF) and the analysis of the multipath channel response characteristics. For non-linear models, the UKF provides an efficient recursive minimum mean squared error estimation technique that is successfully applied in this work, and supported by numerical results demonstrating its effectiveness in UWB multipath channel gain and time delay estimation. The multipath channel response obtained from a limited number of channel taps is subsequently characterized in terms of relevant statistical parameters including kurtosis and mean excess delay. This characterization reveals clear differences in the statistics of these parameters under LOS and NLOS propagation conditions for various channel types in residential, office, outdoor and industrial environments. Based on the estimated parameters probability density functions under LOS/NLOS conditions, a likelihood ratio test (LRT) for hypothesis classification is performed for the different UWB channel models, and numerical results show that highly reliable LOS vs. NLOS classification is achievable, with accuracy exceeding 90% for most cases of practical interest. These results can then be further exploited in enhancing the performance of positioning applications.

Optimal Receiver Scheme for Transmitted-Reference Ultra-Wideband System in Coal Mine

An average Transmitted-Reference (TR) receiver scheme based on orthogonal codes is proposed for improving the bit error rate (BER) performance and the transmitting rate of Ultra-wideband (UWB) TR receiver systems in coal mine. Orthogonal codes are used for modulating the reference pulses and the data pulses in each frame of every bit. Since the orthogonality of the two codes, the inter-pulse interference (IPI) is greatly reduced. Then the decoding reference pulses and the data pulses are averaged in a frame, which decreases the noise in the reference pulses and the data pulses. Finally, I demonstrate this optimal receiver scheme by the simulation in the coal mine roadway ultra-wideband channel model. Detailed simulation experiments are presented to validate the effectiveness of this proposed method. The experimental results show that this method can not only efficiently reduce the noise interference in receiving signals, but also can provide higher transmission rate, which make UWB signal receiving in coal mines more accurately. Index Terms—Coal mine, Ultra-wideband, Transmitted- Reference receiver, bit error rate

Bayesian compressive sensing for ultra-wideband channel estimation: algorithm and performance analysis

Due to the sparse structure of ultra-wideband (UWB) channels, compressive sensing (CS) is suitable for UWB channel estimation. Among various implementations of CS, the inclusion of Bayesian framework has shown potential to improve signal recovery as statistical information related to signal parameters is considered. In this paper, we study the channel estimation performance of Bayesian CS (BCS) for various UWB channel models and noise conditions. Specifically, we investigate the effects of (i) sparse structure of standardized IEEE 802.15.4a channel models, (ii) signal-to-noise ratio (SNR) regions, and (iii) number of measurements on the BCS channel estimation performance, and compare them to the results of $$\ell _1$$l1-norm minimization based estimation, which is widely used for sparse channel estimation. We also provide a lower bound on mean-square error (MSE) for the biased BCS estimator and compare it with the MSE performance of implemented BCS estimator. Moreover, we study the computation efficiencies of BCS and $$\ell _1$$l1-norm minimization in terms of computation time by making use of the big-$$O$$O notation. The study shows that BCS exhibits superior performance at higher SNR regions for adequate number of measurements and sparser channel models (e.g., CM-1 and CM-2). Based on the results of this study, the BCS method or the $$\ell _1$$l1-norm minimization method can be preferred over the other one for different system implementation conditions.

A New Universal Approach to Time-Domain Modeling and Simulation of UWB Channel Containing Convex Obstacles Using Vector Fitting Algorithm

The paper presents a new approach to time-domain modeling of ultra-wideband (UWB) channels with multiple convex obstacles. Rational approximation exploiting the vector fitting algorithm (VF) is used for deriving the closed-form impulse response of a multiple diffraction ray creeping on a cascade of convex obstacles. The VF algorithm is performed with respect to new generalized variables proportional to frequency but also taking into account geometrical parameters of the obstacles. The limits of the approximation domain for the VF algorithm reflect the range of UWB channel parameters that can be met in practical UWB channel scenarios. The results of VF approximation have the form of a finite series of partial fractions in the frequency domain, which then is easily transformed to the time domain. Obtained in this way, impulse response is a sum of exponential functions. As a consequence, in simulations of electromagnetic (EM) wave propagation, we can implement very fast and effective convolution algorithms with any input signal or perform simulations implementing SPICE-like programs.