On the Double Doppler Effect Generated by Scatterer Motion

Based upon coherent (amplitude and phase) received signal strength data collected over fixed wireless macrocell channels at almost 100 locations in residential, campus and open area environments near the University of British Columbia, we have shown that Thoen's model for fixed wireless Doppler spectra fits observed Doppler spectra remarkably well. This allows us to extract the equivalent maximum Doppler frequency for such channels and determine both: (1) its marginal distribution, which is surprisingly narrow, and (2) its joint distribution with Ricean K-factor and wind speed in typical suburban macrocell environments. Incorporating wind effects into the model helps us to improve the accuracy of the model by helping us account for the differences between the wind speed distributions observed during the measurement campaigns and those observed over the long term.

Frequency conversion from microwaves to millimetre waves using the Doppler effect in a slot line on an optically excited silicon-on-insulator (SOI) substrate has been experimentally demonstrated. Laser pulses with a wavelength of 532 nm and duration of 33 psec have generated electron-hole plasma periodically at the intervals of 1.2 mm and of 13.6 psec on the SOI surface along the slot line. The plasma acts as an rf-short which effectively moves at a relativistic velocity. The rf-short reflects counter propagating microwaves and up-shifts their frequency through the double Doppler effect. Experiments have shown that microwaves at the frequencies between 10 GHz-18 GHz in the slot line have been successfully converted to millimetre waves with a frequency up-ratio of about 3.9.

In this thesis, we cope with the fundamental mathematical and physical problems of the space-time-Doppler UWB system design for fading channels: multi-input multi-output (MIMO) wireless communication with adaptive filtering. The estimation algorithm from equalizer providing an accurate parameters estimate is investigated. UWB radio is a fast emerging technology with uniquely attractively features inviting major advances in wireless communications, networking, radar, imaging, and positioning systems. By its rule-making proposal in 2002, the Federal Communications Commission (FCC) in the United States essentially unleashed huge new bandwidth (3.6-10.6 GHz) at the noise floor, where UWB radios overlaying coexistence RF systems cerate using low-power ultra-short information bearing pulses. Right now, there are three basic types of UWB: multiband OFDM UWB (MB-OFDM UWB), impulse-UWB (I-UWB), and direct sequence UWB (DS-UWB). We focus on I-UWB and MB-OFDM-UWB, and compare their performance. A simple means for spreading the spectrum of low duty cycle pulse trains is time hopping (TH), with pulse position modulation (PPM) for data modulation at the rate of many pulses per data bit. The main contribution of this thesis for I-UWB is the design of leading edge detectors, coherent correlation detector (CCD), and pilot performance enhancement compared with different Rayleigh and Ricean fading conditions. For MB-OFDM UWB, we have considered the performance analysis and design criteria of MIMO OFDM UWB systems for high data-rate wireless transmission. The signal processing of frame detection, time synchronization, frequency synchronization, channel estimation, synchronization tracking using pilot subcarriers and 2-D MIMO detection algorithms is discussed. The main contributions of this thesis are 1) Compared with receiver employing the Maximum Likelihood (ML) detector, the receiver employing a low-complexity linear Minimum Mean Square Error (MMSE) demodulator can perform a limited performance loss in spatially uncorrelated channels. 2) Due to the operations of spreading and dispreading combined with MMSE-based frequency domain equalization, the adverse effects of the low-SNR subcarriers on the average BER performance are potentially improved. This is a direct consequence of spreading, because even if the signal corresponding to a specific chip is obliterated by a deep frequency domain channel fade, after dispreading these effects are spread over the Walsh-Hadamard Transform (WHT) length. Hence there is a high chance of still recovering all the partially affected subcarrier symbols without errors. 3) As a test case, the OFDM-based 200 Mb/s MB-UWB network (IEEE 802.15.3a) are considered, but the simulation results are shown above section. 4) The simulation channel can be easily applied to NOS and NLOS situation with WHT transformation from Simulink model. The fading channels of UWB with low/high signal to noise ratio (SNR), multipath effects, and multiuser interference may introduce large errors in location. The location engine performs the following tasks: █ Data fusion techniques: Different data fusion techniques are implemented using Time Of Arrival (TOA), Angle Of Arrival (AOA), or a combination of both. █ Channel modeling: A multipath, multiuser channel environment is created that models path loss, shadowing, Rayleigh fading, and Doppler frequency effects. █ Parameter estimation: TOA and AOA estimation algorithms are implemented as part of the location finding engine. Different variations of algorithms are implemented for performance and comparison purposes. █ Configuring the physical layer for different wireless networks. Among the programmable parameters are spreading factor, packet size, training length, constellation type, modulation technique, carrier frequency, level of transmitted signal power, and the number of antennas at the transmitter for both sides. █ Configuring the mobile user conditions. The wireless channel models depend on the Doppler frequencies present in the environment. The Doppler frequency depends on the mobile speed and carrier frequencies as input and generates a Rayleigh fading channel with the U-shape Doppler spectrum. █ Configuring the environmental parameters and network geographical structure. One of the factors affecting the performance of the wireless location system is the environment type (e.g., bad urban, urban, suburban, or rural area). For example, in a bad urban area with many blocking objects and buildings, non-line of sight (NLOS) effects plays an important role in the estimation accuracy.

To deploy effective communication systems in vehicle cavities, it is critical to understand the time variation of the in-vehicle channel. Initially, rapid channel variation is addressed, which is characterized in the frequency domain as a Doppler spread. It is then shown that, for typical Doppler spreads, the in-vehicle channel is underspread, and therefore, the information capacity approaches the capacity achieved with perfect receiver channel state information in the infinite bandwidth limit. Measurements are performed for a number of channel variation scenarios (e.g., absorptive motion, reflective motion, one antenna moving, and both antennas moving) at a number of carrier frequencies and for a number of cavity loading scenarios. It is found that the Doppler spread increases with carrier frequency; however, the type of channel variation and loading appear to have little effect. Channel variation over a longer time period is also measured to characterize the slower channel variation. Channel variation is a function of the cavity occupant motion, which is difficult to model theoretically; therefore, an empirical model for the slow channel variation is proposed, which leads to an improved estimate of the channel state.

A novel ultra‐bright high‐intensity source of X‐ray and gamma radiation is suggested. It is based on the double Doppler effect, where a relativistic flying mirror reflects counter‐propagating electromagnetic radiation causing its frequency multiplication and intensification, and on the inverse double Doppler effect, where the mirror acquires energy from an ultra‐intense co‐propagating electromagnetic wave. The role of the flying mirror is played by a high‐density thin plasma slab accelerating in the radiation pressure dominant regime. Frequencies of high harmonics generated at the flying mirror by relativistically strong counter‐propagating radiation undergo multiplication with the same factor as the fundamental frequency of the reflected radiation, approximately equal to the quadruple of the square of the mirror Lorentz factor.

The inverse synthetic aperture radar (ISAR) uses the Doppler effect caused by the rotation and translation of the target to improve the cross-range resolution. Usually, these two motions have not been distinguished and have been processed in one dimension in the cross-range compression of the ISAR. In this paper, it is shown that Doppler components caused by these two motions can be separated, so that two-dimensional cross-range compression by elevation compression due to rotation and azimuth compression due to translation is possible for a target such as a boat that moves slowly in translation with rolling. Further, the boundary condition is derived that enables image reconstruction from the Doppler effect caused by the two motions, rotational and translational. For radar parameters such as the transmission wavelength λ, the resolution Δ of the ISAR image, and the range D to be visualized, two-dimensional cross-range compression becomes possible if the relationships hold for target parameters such as the maximum rolling angle α, rolling period T0, translation speed v, and relative distance R0 from the radar. By computer simulation, an image reconstruction example using the two-dimensional cross-range compression algorithm is presented. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 82(9): 10–18, 1999

Microwave Doppler radar has been used to make non-contact river flow measurements and offers a high resolution and a wide range. However, discharge estimation with microwave Doppler radar is challenging due to the inability to measure flow velocity below the river surface based on the Doppler shift. To address this problem, a velocity distribution inversion method based on the Reynolds-Averaged Navier-Stokes (RANS) equations is proposed. A classical two-region model which divides the flow into the inner region and the outer region is applied. Velocity at the inner-outer boundary is estimated using surface velocity and the log law is used to estimate velocity distribution of the inner region. Taking velocities at the surface and the inner-outer boundary as boundary conditions, the velocity distribution in the outer region is derived by solving the RANS equations. Discharge is calculated by combining the proposed method with the velocity-area method. The results illustrated that the velocity distribution obtained by the proposed method and measured by an acoustic instrument are in reasonable agreement. Discharge estimated using the obtained velocity distribution has an error less than 10%. The work indicates the potential of microwave Doppler radar to retrieve the river cross section velocity distribution and estimate discharge.

One of the fundamental research areas in wireless communications is the development of realistic models that can efficiently and accurately describe the wireless propagation channel. In multi-path environments, the received signal frequency constantly varies as a result of the relative motion between the receiver and transmitter. In this paper, we bridged a novel 3D geometric channel model and the multiple-input and multiple-output (MIMO) antenna array, analyzed deeply the probability density functions (PDFs) of the Doppler shift (DS), its variance, and characteristic function and etc. For the particular channel model, analytical expressions for PDFs of the channel model and the DS of mobile station (MS) due to its motion, have been derived. Based on the analysis, we investigated MIMO receiving performance. Also developed a geometric channel model, and was firstly in the asymmetric geometry literature due to a directional antenna array employed at base station. For this channel model, it was assumed that each multi-path component of the propagating signal undergoes one bounce. It was also assumed that the scattering objects around MS, could be expressed as Gaussian and exponential density models, which are more suitable to simulate outdoor and indoor environments.

High-frequency (HF) communication is critical for applications such as over-the-horizon positioning and ionospheric detection. However, precise time-delay estimation in complex HF channels faces significant challenges from multipath fading, Doppler shifts, and noise. This paper proposes a Modulation Signal-based Adaptive Time-Delay Estimation (MATE) algorithm, which effectively decouples carrier and modulation signals and integrates phase-locked loop (PLL) and delay-locked loop (DLL) techniques. By leveraging the autocorrelation properties of 8PSK (Eight-Phase Shift Keying) signals, MATE compensates for carrier frequency deviations and mitigates multipath interference. Simulation results based on the Watterson channel model demonstrate that MATE achieves an average time-delay estimation error of approximately 0.01 ms with a standard deviation of approximately 0.01 ms, representing a 94.12% reduction in mean error and a 96.43% reduction in standard deviation compared to the traditional Generalized Cross-Correlation (GCC) method. Validation with actual measurement data further confirms the robustness of MATE against channel variations. MATE offers a high-precision, low-complexity solution for HF time-delay estimation, significantly benefiting applications in HF communication systems. This advancement is particularly valuable for enhancing the accuracy and reliability of time-of-arrival (TOA) detection in HF-based sensor networks and remote sensing systems.

In this paper, we propose a new method for blind carrier frequency and symbol rate estimation based on second order cyclostationary features for underwater acoustic communication. Followed by a coarse carrier frequency and symbol rate estimation via spectral analysis, a cyclostationary based estimation algorithm is developed to provide high resolution estimation of both parameters. Specifically, a short time varying resolution spectrum correlation function and spectrum coherence function algorithm is developed to obtain spectral lines in cyclic frequency domain to accurately estimate (1) varying carrier frequency and Doppler shift caused by relative motion and (2) symbol rate for single carrier communication. Simulations confirm the effectiveness, fast speed and low complexity of the proposed algorithm. The proposed method does not assume any a priori knowledge of the target signal.

When an amplitude modulator that is asymmetric in time is applied to a sinusoid, the direction of the asymmetry affects the timbre of the sound. If the modulator is a decaying exponential with a 4-ms half-life and a repetition period of 25 ms, the resulting ‘‘damped’’ sinusoid does not have the sound quality of a sinusoid. But if the modulator is reversed in time to produce a ‘‘ramped’’ sinusoid, the sound of a sinusoid returns [R.D. Patterson, J. Acoust. Soc. Am. (1994)]. This paper extends the domain of the phenomenon with an experiment in which the modulator period varies with the carrier frequency to fix the number of carrier periods per envelope period. This fixes the shape of the wave within a cycle of the sound across carrier frequencies, and it fixes the shape of the main peak in the spectrum of the sound. When presented with pairs of damped and ramped sounds having the same half-life, listeners choose the ramped sound as having the stronger sinusoidal component provided the sinusoids are discriminable. Discrimination is limited to conditions where the half-life is 1 ms or more. At longer half-lives, performance is near ceiling for carrier frequencies up to 1600 Hz; above this, performance falls off as carrier frequency increases. The sound quality differences in damped and ramped sinusoids are explained in terms of a time-interval model of hearing that simulates our auditory images of sounds. The number of carrier periods in the auditory image is greater for the ramped sinusoid in most conditions where the ramped perception is judged to have a stronger sinusoidal quality. Many of these carrier-period intervals are in channels well away from the carrier channel indicating that the sound of a sinusoid is more closely associated with time intervals at the carrier period than with energy in the carrier channel.

As wind turbines operate within the atmospheric boundary layer (ABL), the study of their interaction with the ABL flow can help us better understand and predict their performance. In addition to the performance of wind turbines, this interaction has an effect on the flow both upwind and downwind (i.e., wake region) of the turbines. In particular, the study of turbine wakes is of great importance because they are the main cause of power losses and fatigue loads in wind farms. In the current thesis, four studies are conducted to fully examine the turbine interaction with the ABL flow, with an emphasis on turbine wakes. In the first study, a new analytical wake model is proposed and validated to predict the wind velocity distribution in the far-wake region, where downwind turbines usually operate. The proposed model is derived by applying the conservation of mass and momentum and assuming a Gaussian distribution for the velocity deficit in the wake. This simple model only requires one parameter to predict the velocity distribution in the far wake of a wind turbine. In general, it is found that the velocity deficit in the wake predicted by the proposed analytical model is in good agreement with the experimental and numerical data. Furthermore, the results show that the new model predicts the power extracted by downwind wind turbines more accurately than other common analytical models, some of which are based on less accurate assumptions like considering a top-hat shape for the velocity deficit. In the second study, wind tunnel measurements are carried out to systematically investigate turbine wakes under yawed conditions. The detailed experimental data are used to perform a budget study of the continuity and Reynolds-averaged Navier-Stokes equations. This theoretical analysis reveals some notable features of the wakes of yawed turbines, such as the asymmetric distribution of the wake skew angle with respect to the wake center. Under highly yawed conditions, the formation of a counter-rotating vortex pair in the wake cross-section as well as the vertical displacement of the wake center are also shown and analyzed. Finally, this study enables us to develop general governing equations upon which a simple and computationally inexpensive analytical model is built. The proposed model aims at predicting the wake deflection and the far-wake velocity distribution for yawed turbines. The findings of this study can be especially useful to assess the possibility of optimizing wind-farm power production by controlling the yaw angle of the turbines. In the third study, comprehensive wind tunnel experiments are performed to study the interaction of a turbulent boundary layer with a wind turbine operating under different tip-speed ratios and yaw angles. Force and power measurements are performed to characterize the wind turbine performance. Moreover, a high-resolution stereoscopic particle-image velocimetry (S-PIV) system and hot-wire anemometry are used to study the flow in the upwind, near-wake and far-wake regions. This study provides new insights on the turbine and flow characteristics such as the evolution of tip vortices and wake meandering. Finally, the last study concerns the design and the performance analysis of a new three-bladed horizontal-axis miniature wind turbine with a rotor diameter of $15$ cm. Due to its small size, this turbine is particularly suitable for studies of wind farm flows and the interaction of the turbine with an incoming boundary-layer flow. Special emphasis is placed on accurate measurements of the mechanical power extracted by the miniature turbine from the incoming wind. In order to do so, a new setup is developed to measure the torque of the rotor shaft. The thrust and power coefficients of the miniature turbine are found to be around $0.8$ and $0.4$ in optimal conditions, respectively, which are close to the ones of large-scale turbines in the field.

This thesis introduces some topics about initial downlink synchronization, algorithm derivations, and program simulations of IEEE 802.16m system. When a mobile station entering to the network, it needs to perform initial synchronization, including of symbol timing offset, carrier frequency offset and preamble index. We utilize the trait which the power of preamble is larger than it of the common data symbol to compute the moving power sum, and then estimate the left boundary of preamble by finding out the peak value of moving power sum. A symbol period from this estimated boundary is regarded as the estimated preamble, which has a phase noise with the exact preamble. We derive the quasi maximum likelihood estimation from the likelihood function of the estimated preamble to obtain fractional carrier frequency offset (FCFO) and the formula of channel estimation. After compensating the estimated fractional carrier frequency offset to the formula of channel estimation, we substitute several reasonable integral carrier frequency offsets (ICFOs) and primary advanced preambles (PA-Preambles) into this formula and obtain channel impulse responses (CIRs). After that, we compute different fine timing offset index 64-points power sum of these CIRs and find out the peak value whose ICFO, PA-Preamble index, and fine timing offset index are regarded as the result of the joint estimation. In terms of simulations, above all, we present a reasonable received signal model of IEEE 802.16m, and then simulate our algorithm in floating point under AWGN (additive white Gaussian noise) channel to verify its performance. Moreover, we test this algorithm under different multipath fading channels, Pedestrian B and SUI-5, at different speed which cause Doppler shifts, and signal to noise ratio (SNR) to observe the effect on this algorithm.

Wimax is the wireless technology providing link of broadband in distance which far. Wimax is technology of broadband having high speed access and the wide reach. Such as system communications of previous nirkabel, wimax also have model of different propagation. Propagation models of wimax involve variation of delay (μs), power (dB), Factor K (dB), Doppler frequency (Hz). This Model called SUI (Stanford University Interim) channel. Variation of Parameters SUI channel determine performance of communications wimax. In this final project, analysed SUI channel use simulation where parameter of SUI channel of variation into 6 condition of channel SUI - 1 up to SUI-6. While performance of channel presented in comparison of graph of BER and Eb/No. For wimax communication used type of IEEE 802.16d with digital modulation 16 QAM and 64 QAM, include the variation of cylic prefix and bandwidth. Simulation test result show that simulation of SUI channel with type of modulation 16 QAM with cylic prefix 1/8, bandwidth 1.5MHz can repair almost entirety of performance SUI channel. Five SUI channel show best performance when at gyration of Eb/No 5dB up to 15 dB. While result of simulation SUI channel with type of modulation 16QAM with cylic prefix 1/16, bandwidth 20MHz showing bad performance, when improvement Eb/No of gyration BER between 10 -1 dan 10 0 for channel SUI-2, SUI-3, SUI-4, SUI-5, SUI-6. Result of simulation SUI channel with type of modulation 64 QAM with cylic prefix 1/8, bandwidth 1.5MHz showing best performance. Result of simulation SUI channel with type of modulation 64 QAM with cylic prefix 1/16, bandwidth 20MHz showing bad performance. Keyword : 802.16d, SUI channel, WiMAX, cylic prefix, bandwidth.

The time-sensitive network paradigm envisions the integration of operation technology and information technology in the same network. One of the requirements for building time-sensitive networks is sharing a global time along the network. This requirement is especially critical in wireless systems, where there are few robust methods to perform accurate time transfer. In this article, the problem of time transfer over realistic wireless channels is studied, and a time distribution scheme is proposed. The time distribution scheme has three components: Precision time protocol, a novel timestamping method (enhanced timestamps) and an algorithm to implement the enhanced timestamps. The performance of the proposed scheme has been evaluated in MATLAB using the IEEE 802.11n Standard under several standard wireless local area network channel models. The results show that the system can reach subnanosecond time transfer accuracy under non-line-of-sight and time-variant conditions, but its performance greatly depends on the signal-to-noise ratio and on the channel variation rate.