| 1. |
- Abbas, Taimoor, et al.
(författare)
-
A Measurement Based Shadow Fading Model for Vehicle-to-Vehicle Network Simulations
- 2015
-
Ingår i: International Journal of Antennas and Propagation. - : Hindawi Publishing Corporation. - 1687-5869 .- 1687-5877.
-
Tidskriftsartikel (refereegranskat)abstract
- The vehicle-to-vehicle (V2V) propagation channel has significant implications on the design and performance of novel communication protocols for vehicular ad hoc networks (VANETs). Extensive research efforts have been made to develop V2V channel models to be implemented in advanced VANET system simulators for performance evaluation. The impact of shadowing caused by other vehicles has, however, largely been neglected in most of the models, as well as in the system simulations. In this paper we present a shadow fading model targeting system simulations based on real measurements performed in urban and highway scenarios. The measurement data is separated into three categories, line-of-sight (LOS), obstructed line-of-sight (OLOS) by vehicles, and non-line-of-sight due to buildings, with the help of video information recorded during the measurements. It is observed that vehicles obstructing the LOS induce an additional average attenuation of about 10 dB in the received signal power. An approach to incorporate the LOS/OLOS model into existing VANET simulators is also provided. Finally, system level VANET simulation results are presented, showing the difference between the LOS/OLOS model and a channel model based on Nakagami-m fading.
|
|
| 2. |
- Abbas, Taimoor, et al.
(författare)
-
Line-of-Sight Obstruction Analysis for Vehicle-to-Vehicle Network Simulations in a Two Lane Highway Scenario
- 2013
-
Ingår i: International Journal of Antennas and Propagation. - : Hindawi Limited. - 1687-5869 .- 1687-5877. ; 2013
-
Tidskriftsartikel (refereegranskat)abstract
- In vehicular ad-hoc networks (VANETs) the impact of vehicles as obstacles has largely been neglected in the past. Recent studies have reported that the vehicles that obstruct the line-of-sight (LOS) path may introduce 10-20 dB additional loss, and as a result reduce the communication range. Most of the traffic mobility models (TMMs) today do not treat other vehicles as obstacles and thus can not model the impact of LOS obstruction in VANET simulations. In this paper the LOS obstruction caused by other vehicles is studied in a highway scenario. First a car-following model is used to characterize the motion of the vehicles driving in the same direction on a two-lane highway. Vehicles are allowed to change lanes when necessary. The position of each vehicle is updated by using the car-following rules together with the lane-changing rules for the forward motion. Based on the simulated traffic a simple TMM is proposed for VANET simulations, which is capable to identify the vehicles that are in the shadow region of other vehicles. The presented traffic mobility model together with the shadow fading path loss model can take in to account the impact of LOS obstruction on the total received power in the multiple-lane highway scenarios.
|
|
| 3. |
- Ahmad, Ikhlas, et al.
(författare)
-
Highly Compact GCPW-Fed Multi-Branch Structure Multi-Band Antenna for Wireless Applications
- 2022
-
Ingår i: International Journal of Antennas and Propagation. - : Hindawi Limited. - 1687-5869 .- 1687-5877. ; 2022, s. 1-9
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, we present a highly compact multi-branch structure multi-band antenna with a grounded coplanar waveguide (GCPW)-fed structure printed on 26 x 13 x 1.6 mm(3) sized FR-4 substrate having dielectric constant epsilon r of 4.3 and loss tangent delta of 0.02. In the proposed antenna, five branches are extended from the main radiator to provide multi-band behavior. Two branches are introduced at the upper end of the main radiator, effectively covering the lower bands, while the other three branches are introduced near the center of the main radiator to extend operation to higher bands. The designed antenna covers five different bands: 2.4 GHz, 4.5 GHz, 5.5 GHz, 6.5 GHz, and 7.8 GHz, with respective gain values of 1.34, 1.60, 1.83, 1.80, and 3.50 dBi and respective radiation efficiency values of 90, 88, 84, 75, and 89%. The antenna shows a good impedance bandwidth, ranging from 170 MHz to 3070 MHz. The proposed antenna is simulated in CST Microwave Studio, while its performance is experimentally validated by the fabrication and testing process. The antenna has potential applications for IoT, sub-6 GHz 5G and WLAN (both enablers for IoT), C-band, and X-band services.
|
|
| 4. |
- Barbosa, V.L., et al.
(författare)
-
Linear Array Design with Switched Beams for Wireless Communications Systems
- 2015
-
Ingår i: International Journal of Antennas and Propagation. - : Hindawi. - 1687-5869 .- 1687-5877. ; 2015
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents an analysis for optimal design of switched beamforming applied to a linear array for wireless communication systems. The beam switching scheme provides coverage of a given sector in azimuth and controls the sidelobe level simultaneously. The analysis was developed considering arrays composed of Quasi-Yagi elements. The model assumes a user moving in the azimuthal direction under a constant velocity and with an estimation of the signal-to-noise ratio (SNR) at the mobile user (MU). The radio base station applies the beam that yields the best performance during transmission. The decision is based on the feedback information received from the MU. The goal of the analysis is to determine the best trade-off between the array size and number of feedback bits necessary to maximize the SNR at the receiver. The results show that a compromise between the number of beam-pointing directions and the array size should be taken into consideration for a wireless communication system design.
|
|
| 5. |
- Björklund, Svante, et al.
(författare)
-
Measurement of Rank and Other Properties of Direct and Scattered Signals
- 2016
-
Ingår i: International Journal of Antennas and Propagation. - : Hindawi Publishing Corporation. - 1687-5869 .- 1687-5877. ; 2016
-
Tidskriftsartikel (refereegranskat)abstract
- We have designed an experiment for low-cost indoor measurements of rank and other properties of direct and scattered signals with radar interference suppression in mind. The signal rank is important also in many other applications, for example, DOA (Direction of Arrival) estimation, estimation of the number of and location of transmitters in electronic warfare, and increasing the capacity in wireless communications. In real radar applications, such measurements can be very expensive, for example, involving airborne radars with array antennas. We have performed the measurements in an anechoic chamber with several transmitters, a receiving array antenna, and a moving reflector. Our experiment takes several aspects into account: transmitted signals with different correlation, decorrelation of the signals during the acquisition interval, covariance matrix estimation, noise eigenvalue spread, calibration, near-field compensation, scattering in a rough surface, and good control of the influencing factors. With our measurements we have observed rank, DOA spectrum, and eigenpatterns of direct and scattered signals. The agreement of our measured properties with theoretic and simulated results in the literature shows that our experiment is realistic and sound. The detailed description of our experiment could serve as help for conducting other well-controlled experiments. © Copyright 2016 Svante Björklund et al.
|
|
| 6. |
- Bondarik, Alexander, et al.
(författare)
-
Pattern Reconfigurable Wideband Stacked Microstrip Patch Antenna for 60 GHz Band
- 2016
-
Ingår i: International Journal of Antennas and Propagation. - : Hindawi Limited. - 1687-5869 .- 1687-5877. ; 2016
-
Tidskriftsartikel (refereegranskat)abstract
- A beam shift method is presented for an aperture coupled stacked microstrip antenna with a gridded parasitic patch. The gridded parasitic patch is formed by nine close coupled identical rectangular microstrip patches. Each of these patches is resonant at the antenna central frequency. Using four switches connecting adjacent parasitic patches in the grid, it is possible to realize a pattern reconfigurable antenna with nine different beam directions in broadside, H-plane, E-plane, and diagonal planes. The switches are modeled by metal strips and different locations for strips are studied. As a result an increase in the antenna coverage is achieved. Measurement results for fabricated prototypes correspond very well to simulation results. The antenna is designed for 60 GHz central frequency and can be used in high speed wireless communication systems.
|
|
| 7. |
- Dayo, Zaheer Ahmed, et al.
(författare)
-
A Compact High-Gain Coplanar Waveguide-Fed Antenna for Military RADAR Applications
- 2020
-
Ingår i: International Journal of Antennas and Propagation. - : HINDAWI LTD. - 1687-5869 .- 1687-5877. ; 2020
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a new design of a compact, high-gain coplanar waveguide-fed antenna and proposes a multielement approach to attain enhanced characteristics. The proposed method overcomes the simulation and geometrical complexity and achieves optimal performance features. The antenna prototype is carefully designed, and simulation results have been analyzed. The proposed antenna was fabricated on a new WangLing TP-2 laminate with dimensions (0.195 lambda x 0.163 lambda x 0.0052 lambda) at the lowest resonance of 9.78 GHz. The results have been tested and experimentally verified. The antenna model achieved excellent performance including a peak realized gain better than 9.0 dBi, optimal radiation efficiency better than 87.6% over the operating band, and a good relative bandwidth of 11.48% at 10 dB return loss. Symmetrical stable far-field radiation pattern in orthogonal planes and strong distribution of current are observed. Moreover, a comparative analysis with state-of-the-artwork is presented. The measured and simulation result shows a good agreement. The high-performance antenna results reveal that the proposed model is a good contender of military airborne, land, and naval radar applications.
|
|
| 8. |
- Gustafsson, Mats, et al.
(författare)
-
Absorption Efficiency and Physical Bounds on Antennas
- 2010
-
Ingår i: International Journal of Antennas and Propagation. - : Hindawi Limited. - 1687-5869 .- 1687-5877. ; 2010
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract—The all spectrum absorption efficiency appears in the physical bounds on antennas expressed in the polarizability dyadics. Here, it is shown that this generalized absorption efficiency is close to 1/2 for small idealized dipole antennas and for antennas with a dominant resonance in their absorption. Also, the usefulness of this parameter is analyzed for estimation of antenna performance. The results are illustrated with numerical data for several antennas.
|
|
| 9. |
|
|
| 10. |
- Hosseinzadegan, Samar, 1987, et al.
(författare)
-
A discrete dipole approximation solver based on the COCG-FFT algorithm and its application to microwave breast imaging
- 2019
-
Ingår i: International Journal of Antennas and Propagation. - : Hindawi Limited. - 1687-5869 .- 1687-5877. ; 2019
-
Tidskriftsartikel (refereegranskat)abstract
- We introduce the discrete dipole approximation (DDA) for efficiently calculating the two-dimensional electric field distribution for our microwave tomographic breast imaging system. For iterative inverse problems such as microwave tomography, the forward field computation is the time limiting step. In this paper, the two-dimensional algorithm is derived and formulated such that the iterative conjugate orthogonal conjugate gradient (COCG) method can be used for efficiently solving the forward problem. We have also optimized the matrix-vector multiplication step by formulating the problem such that the nondiagonal portion of the matrix used to compute the dipole moments is block-Toeplitz. The computation costs for multiplying the block matrices times a vector can be dramatically accelerated by expanding each Toeplitz matrix to a circulant matrix for which the convolution theorem is applied for fast computation utilizing the fast Fourier transform (FFT). The results demonstrate that this formulation is accurate and efficient. In this work, the computation times for the direct solvers, the iterative solver (COCG), and the iterative solver using the fast Fourier transform (COCG-FFT) are compared with the best performance achieved using the iterative solver (COCG-FFT) in C++. Utilizing this formulation provides a computationally efficient building block for developing a low cost and fast breast imaging system to serve under-resourced populations.
|
|
