Ultra Wideband Radio Channel Research Articles

Ultra-wideband wireless channel and environment characterization assisted by dual optical frequency comb

In this work, a photonic technique based on dual optical frequency comb is proposed to perform ultra-wideband channel sounding that delivers high-resolution channel characterization and high-speed environment monitoring. The proof-of-concept experiments demonstrate the continuous sounding of non-line-of-sight wireless channels with > TS/s sampling resolution and the revealing of an electric fan rotating at up to 1100 rpm. A wireless channel of 12 GHz bandwidth is covered using electronics with less than 60 MHz bandwidth, showcasing the high practicality of the proposed technique in assisting the evolution towards the integration of communication and sensing essential in the next generation of wireless communication.

Ultra-Wideband Radio Channel Characteristics for Near-Ground Swarm Robots Communication

Ultra-Wideband (UWB) technology has great potential for the cooperation and navigation among near ground mobile robots in GPS-denied environments. In this paper, an efficient two-segment UWB radio channel model is proposed with considering the multi-path condition in very near-ground environments and different surface roughness. We conducted field measurements to collect channel information, with both transmitter and receiver antennas placed at different heights above the ground: 0cm-20cm. Signal frequency was chosen at 4.3GHz with bandwidth of 1GHz. Three ground coverings were tested in common scenarios: brick, grass and robber fields. The proposed model has enhanced accuracy achieved by careful assessment of dominant propagation mechanisms in each segment, such as diffraction loss due to obstruction of the first Fresnel zone and higher-order waves produced by ground roughness. It is realized that antenna height and distance are the most influential geometric parameters to affect the path loss model. Once the antenna height is known, there exists a breakpoint distance in UWB propagation, which separates two segmentation using the different path-loss mechanism. Different surface types can cause different signal attenuation. Monte Carlo simulations are used to investigate the effects of antenna height, distance, ground surface type on mobile robots swarm communication to find out the antenna height is also a dominant factor on connectivity and the average number of neighbors. Within a certain range, the higher the antenna height and the closer the communication distance, the better the communication performance will usually be. Cramér-Rao lower bound(CRLB) of path loss estimator based on the proposed model is derived to show the relationship between CRLB with height and distance.

Secret Key Generation from Common Randomness over Ultra-wideband Wireless Channels

We develop a secret key generation scheme using phase estimation in ultra-wideband (UWB) wireless fading channels. Based on the reciprocity theorem, two terminals extract the phase of the channel as a common random source to generate secret bits. Moreover, we study the secret key rate by a pair of nodes observing correlated sources and communicating to achieve secret key agreement over public communication channels. As our main results, we establish a more practical upper bound from Cramer-Rao bound (CRB) and compare it with a universally theoretical upper bound on the shared maximum key rate from mutual information of correlated random sources. Derivation and numerical examples are presented to demonstrate the bound. Simulation studies are also provided to validate feasibility and efficiency of the proposed scheme.

Capacity of UWB wireless channel for neural recording systems.

Ultra wide-band (UWB) short-range communication systems are valuable in medical technology, particularly for implanted devices, due to their low-power consumption, low cost, small size and high data rates. Monitoring of neural responses in the brain requires high data rate if we target a system supporting a large number of sensors. In this work, we are interested in the evaluation of the capacity of the ultra wide-band (UWB) channel that we could exploit using a realistic model of the biological channel. The channel characteristics are examined under two scenarios that are related to TX antenna placements. Using optimal power spectrum allocation (OPSA) at the transmitter side, we have computed this capacity by taking into account the fading characteristics of the channel. The results show the pertinence of the optimal power spectrum allocation for this type of channel. An improvement by a factor of 2 to 3 over a uniform power spectrum allocation (UPSA) when the SNR <; 0 dB was obtained. When the SNR is > 40 dB, both approaches give similar results. Antennas placement is examined under two scenarios having contrasting power constraints.

Experimental comparison between centimeter‐ and millimeter‐wave ultrawideband radio channels

AbstractThis paper analyzes radio wave propagation phenomena at two very different frequency bands: 2–10 GHz (centimeter wave) and 57–66 GHz (millimeter wave (mm‐W)). The two frequency bands have been measured using the same equipment and under similar propagation conditions, such as path loss, root‐mean‐square delay spread, maximum excess delay, and Rician K factor, and their respective correlations compared. Obstructed line of sight situations have also been considered by using metal and cardboard obstructions. The statistical distributions, main specular reflections, and decay factors have been found similar for the two bands. However, the measured path loss, correlation in terms of electrical distances, and the K factor are higher for the millimeter‐wave frequency band. Indeed, the importance of propagation mechanism changes from one band to the other, which must be considered in the design of future mm‐W systems.

Channel Characterization and Modulation Schemes of Ultra Wideband Systems

Channel measurements are generally the basis for channel models. Strictly speaking, channel models do not exclusively require measurements, but it is a fact that all standardized models are derived from measurements. This licentiate paper is focused on the characterization of ultra-wideband wireless channels. The paper presents the characterization of ultra wide band system with their benefits and drawbacks within the telecommunication industry. Furthermore with the advantages of Ultra wideband several modulation techniques for UWB are discussed in this paper.

Estimation mothod of the figure of merit in Ultra-wideband radio channel

UWB(Ultra-WideBand) technology is considered to be the most suitable for indoor wireless location and IEEE802.15.4a is the first radio ranging and positioning physical layer IEEE standard.In order to let the sender know the quality of the ranging,FoM(Figure of Merit) is added in this protocol,but how to produce FoM is not given.On the basis of analyzing the statistical characteristics of the received signal energy block,a method based on the joint parameters of skewness and the maximum slope was proposed to estimate the FoM in UWB radio channel.The simulation finds that this method can provide reference for accurate ranging and positioning,and can improve the ranging accuracy about 30% in the CM1(Channel Model) channel.

Compressed sensing based deconvolution algorithm for time-domain UWB channel modeling

Extracting the parameters of the multipath with high accuracy can be achieved by using high-resolution algorithm for time-domain ultra wideband (UWB) channel modeling. The CLEAN algorithm has been used as such a high-resolution algorithm for UWB time-domain characterization. This paper presents a compressed sensing (CS) based high-resolution deconvolution algorithm for time-domain UWB channel modeling. UWB wireless channels are a prime example of long and sparse channel impulse response (CIR). Furthermore, the dictionary of parameterized waveforms that closely matches the waveform of multipath leads to that the UWB channel measurement signal is more compactly represented. By adjusting the parameter of dictionary, CIRs of different resolutions can be obtained. The matching pursuit (MP) algorithm is used as the signal reconstruction method for CS and outputs the CIR directly. We also demonstrated that if the dictionary of CS is designed specifically, MP is an equivalent of single template CLEAN. Finally, the computation complexity of CS-MP is analyzed and comparison of MP and CLEAN is performed. Simulation results show that compared to CLEAN, the proposed CS-MP deconvolution algorithm can achieve a comparable performance with much fewer samplings.

Beamforming Effects on Measured mm-Wave Channel Characteristics

Beamforming is an important feature of 60 GHz communications. We present an analysis of the influence of beamforming in indoor ultrawideband radio channels measured in the mm-wave 60 GHz band. The performance of narrowband and wideband direction-based beamformers is investigated in terms of improving channel metrics such as the delay spread, excess delay, and the signal-to-noise ratio (SNR). The performance of the direction-based beamformers is compared with dominant eigenmode transmission and statistical beamforming. Our analysis reveals that in line-of-sight (LOS) scenarios, the two direction-based beamformers have a similar performance that approaches the upper bound set by dominant eigenmode transmission. In non-LOS (NLOS) scenarios, the direction-based beamformers show a performance degradation in relation to the upper bound, with the narrowband beamformer worse off than the wideband variant. The array gain in our measured NLOS scenarios is observed to exceed the theoretical upper limit valid for a rich scattering environment. We show that this result follows from the spatial structure of the measured NLOS channels that has only a few strong reflected components. We investigate the influence of array size on beamforming performance; 5×5 planar arrays are observed to improve the channel's delay metrics as well as the larger 7×7 planar arrays.

Frequency-selective fading of ultrawideband wireless channels in confined environments

As a result of the recent ruling by the European Commission, ultrawideband (UWB) wireless communications can now pervade small confined environments such as cars or trains. This research studies frequency-selective fading experienced by UWB wireless channels in these confined environments. It focuses on the relationship between the severity of fading and the environment size using analytical modelling, simulation and measurement. The authors show that the frequency-selective fading is more severe in smaller environments because the bandwidth required to resolve all multipaths in time is inversely proportional to the cubic root of the volume of the environment. They show that the European Computer Manufacturers Association (ECMA) International standards for UWB proposed by the WiMedia alliance may not provide sufficient means of mitigating the issues associated with the frequency-selective fading in confined environments such as cars.

Exploration of Nakagami fading in ultra-wideband wireless channels

The parameters m and Ω of the Nakagami distribution for fading in ultra-wideband wireless channels are explored. In contrast to the IEEE 802.15.4a model, it shows the dependency of these parameters on bandwidth, which facilitates optimisation of UWB transceiver systems.

On-Body Radio Channel Characterization and System-Level Modeling for Multiband OFDM Ultra-Wideband Body-Centric Wireless Network

Given the trend towards a user-centric concept in mobile communications, body area networks have received increasing attention within the wireless personal and body area networks community. In this paper, an experimental investigation is presented to derive suitable radio propagation models for ultra wideband (UWB) body-centric wireless communications. The performance of the body-centric UWB radio channel is investigated by considering several on-body links, including different body postures. System-level modeling of potential multiband orthogonal frequency-division multiplexed UWB system has been conducted and system performance is measured using bit error rate (BER) and signal-to-noise ratio. The conducted system analysis demonstrated that for 78% in the static case and 75% and 61% for stable and unstable transmitter locations in the pseudodynamic in-motion scenarios (respectively) of the specified on-body radio links, the BER is equal to or less than 0.1%. This demonstrates promising applications of the proposed UWB body-centric radio system. Based on these results, clear recommendations are given for best on-body locations leading to optimal system performance.

Transient Characteristics of Wearable Antennas and Radio Propagation Channels for Ultrawideband Body-Centric Wireless Communications

This paper presents transient characterization of ultrawideband (UWB) body-worn antennas and on-body radio propagation channels for body-centric wireless communications. A novel miniaturized CPW-fed tapered slot antenna is proposed and used for transient measurements of UWB radio channels for body area network (BAN) and personal area network (PAN) scenarios. Unlike conventional UWB CPW-fed antennas, the proposed antenna employs two diverging tapered slots to provide smooth and stable impedance matching. Fidelity analysis is applied to evaluate the time-domain behavior of body-worn antennas and it is found that average fidelity obtained is 88% and 86% for the conventional coplanar waveguide fed antenna and the tapered slot antenna, respectively. However, the tapered slot antenna shows a significant size reduction and hence is suited for body-centric wireless communications.

Isochronous Data Transfer between AV Devices Using Pseudo CMP Protocol in IEEE 1394 over UWB Network

This paper presented a new method to transfer isochronous data through an IEEE 1394 over UWB (ultra wideband) network. The goal of this research is to implement a complete heterogeneous system without commercial IEEE 1394 link chips supporting the bridge-aware function. The method resolving this dedicated chip-less situation, was employed a new bridge adapting a pseudo connection management protocol (CMP). This approach made a wired 1394 devices as an IEEE 1394 over UWB device. This method allowed an IEEE 1394 equipment to transfer an isochronous data using a UWB wireless communication network. The result of this approach was demonstrated successfully via an IEEE 1394 over UWB bridge module. The proposed CMP and IEEE 1394 over UWB bridge module can exchange isochronous data through an IEEE 1394 over UWB network. This method makes an IEEE 1394 equipment transfer an isochronous data using a UWB wireless channel.

Characterization of on‐human‐body UWB radio propagation channel

AbstractWireless body area network (WBAN) has begun to receive attention recently. Ultra wideband (UWB) is a promising technology for WBAN applications. This article presents the results of UWB radio channel measurements performed on human bodies from 3.1 to 10.6 GHz in indoor environments. The measurements were devised to generate the radiographs of path loss and delay spread for the first time. The radiographs contain both qualitative and quantitative information on the channel. They clearly display the influence of the body on the channel and thus reveal where the network nodes should be strategically placed on the body in the design of the UWB WBAN systems. They directly give such channel parameters as path loss and delay spread. They also reflect variations of the channel on and in close proximity to the body. In addition, the measurements were made in an anechoic chamber to expose the impact of the body and to study the effect of different environments on the channel. It is shown that for the UWB channel on the body the path loss exponent n = 2.7 can be used, while for the UWB channel through the body the path loss exponent increases to n = 3.7. The maximum value of the rms delay spread is 12 ns. The rms delay spread values are less than 6 ns 50% of the time. The number of multipath components increases with the separation between transmit and receive antennas. Because of the nonreflecting mechanism, the path loss is larger and the delay spread is smaller in the anechoic chamber environment. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1365–1371, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22411

Statistical modeling of the ultra wide band propagation channel through the analysis of experimental measurements

For the development of future Ultra Wide Band (UWB) communication systems, realistic modeling of the propagation channel is necessary. This article presents an experimental study of the UWB radio channel, based on an extensive sounding campaign covering the indoor office environment. We consider the main characteristics of the UWB channel by studying the propagation loss and wide band parameters, such as the delay spread and the power delay profile decay. From this analysis, we propose a statistical channel model reproducing the UWB channel effects over the frequency bandwidth 3.1–10.6 GHz. To cite this article: P. Pagani, P. Pajusco, C. R. Physique 7 (2006).

An overview of ultra wide band indoor channel measurements and modeling

In this paper, an overview of reported measurements and modeling of the ultra wide band (UWB) indoor wireless channel is presented. An introduction to UWB technology and UWB channels is provided. Different UWB channel sounding techniques are discussed and approaches for the modeling of the UWB channel are reviewed. The available indoor UWB channel measurement results are consulted and accordingly, the major UWB channel parameters are presented and compared to those of narrowband systems. The novelty of this work is the gathering of different UWB channel parameters, analysis, and comparison. Added with the influence of UWB antenna in channel-modeling as well as the frequency-dependency of the channel parameters, leading to a conclusion on the UWB radio channel modeling.

Relation between multipath and wave propagation attenuation

A theoretical multi-slope wave propagation model is proposed based on ultra-wideband radio channel impulse response measurements in a dispersive channel. The theory, which applies to radiowave and acoustic propagation, relates multipath delay spread, propagation attenuation exponent, and the maximum possible rake gain for the multipath propagation channel.