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Journal ArticleDOI

Stereoscopic UWB Yagi–Uda Antenna with Stable Gain by Metamaterial for Vehicular 5G Communication

01 May 2023-Sensors-Vol. 23, Iss: 9, pp 4534-4534
TL;DR: In this article , a Yagi-Uda antenna with stable gain by near-zero-index metamaterial (NZIM) has been proposed for vehicular 5G communication, which consists of magneto-electric dipole structure and coaxial feed patch antenna.
Abstract: In this paper, a stereoscopic ultra-wideband (UWB) Yagi–Uda (SUY) antenna with stable gain by near-zero-index metamaterial (NZIM) has been proposed for vehicular 5G communication. The proposed antenna consists of magneto-electric (ME) dipole structure and coaxial feed patch antenna. The combination of patch antenna and ME structure allows the proposed antenna can work as a Yagi–Uda antenna, which enhances its gain and bandwidth. NZIM removes a pair of C-notches on the surface of the ME structure to make it absorb energy, which results in two radiation nulls on both sides of the gain passband. At the same time, the bandwidth can be enhanced effectively. In order to further improve the stable gain, impedance matching is achieved by removing the patch diagonally; thus, it is able to tune the antenna gain of the suppression boundary and open the possibility to reach the most important characteristic: a very stable gain in a wide frequency range. The SUY antenna is fabricated and measured, which has a measured −10 dBi impedance bandwidth of approximately 40% (3.5–5.5 GHz). Within it, the peak gain of the antenna reaches 8.5 dBi, and the flat in-band gain has a ripple lower than 0.5 dBi.

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Journal ArticleDOI
TL;DR: An analytical model is developed for analyzing the throughput performance of the fair channel access protocol in a non-saturated state and the minimum contention window size can be determined in order to achieve fair access among different vehicles.
Abstract: This paper considers the fair access problem in vehicular ad hoc networks and develops analytical models for analyzing the performance of an IEEE 802.11 distributed coordination function based fair channel access protocol in a non-saturated state. We first derive the relationship between the transmission probability and the minimum contention window size of a vehicle, and the relationship between the velocity and the minimum contention window size of a vehicle in a non-saturated state. Based on the analytical model, the minimum contention window size of a vehicle for a given velocity can be determined in order to achieve fair access among different vehicles. Moreover, an analytical model is also developed for analyzing the throughput performance of the fair channel access protocol in a non-saturated state. The effectiveness of the analytical models is justified through simulation results.

56 citations

Journal ArticleDOI
TL;DR: In this paper, a wideband and unidirectional loop antenna with enhanced and stable gain is presented, where the loop is loaded with three mu-negative (MNG) metamaterial unit-cells.
Abstract: A wideband and unidirectional loop antenna with enhanced and stable gain is presented. To reduce the size of the antenna, the loop is loaded with three mu-negative (MNG) metamaterial unit-cells. The proposed unit-cells consist of a series-gap capacitor and a shunt meandered floating inductor. The series capacitive loading is used to excite the zeroth order resonance (ZOR) of the MNG unit-cell, whereas the floating inductor is used to improve impedance matching. To enhance the front-to-back-ratio (FBR) of the antenna and widen its operating bandwidth, the loop is loaded with a tuning slot in the vicinity of the loaded unit-cells. To overcome the low gain of the antenna at frequencies above the ZOR and thus obtain a stable gain, two tightly coupled dumbbell and arc-shaped directors are proposed. The shape and operation of these directors are inspired by the cylindrical capacitor, which achieves higher coupling compared to a planar capacitor with the same area. The antenna achieves a compact size of $0.25\lambda _{0} \times 0.29\lambda _{0}$ with a wide fractional bandwidth of 34% at 0.76–1.07 GHz, and peak measured gain and FBR values of 4.5 dBi and 16 dB, respectively.

40 citations

Journal ArticleDOI
TL;DR: The impact of disturbance is focused on and models to analyze the time-dependent performance of 802.11p-based platooning communications are constructed and it is validated that 802.
Abstract: Platooning is a critical technology to realize autonomous driving. Each vehicle in platoons adopts the IEEE 802.11p standard to exchange information through communications to maintain the string stability of platoons. However, one vehicle in platoons inevitably suffers from a disturbance resulting from the leader vehicle acceleration/deceleration, wind gust and uncertainties in a platoon control system, i.e., aerodynamics drag and rolling resistance moment etc. Disturbances acting on one vehicle may inevitably affect the following vehicles and cause that the spacing error is propagated or even amplified downstream along the platoon, i.e., platoon string instability. In this case, the connectivity among vehicles is dynamic, resulting in the performance of 802.11p in terms of packet delay and packet delivery ratio being time-varying. The effect of the string instability would be further deteriorated once the time-varying performance of 802.11p cannot satisfy the basic communication requirement. Unlike the existing works which only analyze the steady performance of 802.11p in vehicular networks, we will focus on the impact of disturbance and construct models to analyze the time-dependent performance of 802.11p-based platooning communications. The effectiveness of the models is validated through simulation results. Moreover, the time-dependent performance of 802.11p is analyzed through numerical results and it is validated that 802.11p is able to satisfy the communication requirement under disturbance.

29 citations

Journal ArticleDOI
TL;DR: In this paper, a novel shared aperture planar quasi-Yagi antenna with complementary pattern diversity performance is presented for 5G-NR application, where a shared aperture antenna with high port isolation and a compact size is first proposed by the even-odd mode feedings.
Abstract: A novel shared aperture planar quasi-Yagi antenna with complementary pattern (as well as polarization) diversity performance is presented for fifth generation (5G)-new radio (NR) application. A shared aperture antenna with high port isolation and a compact size is first proposed by the even–odd mode feedings. Then, by combining the monopole and dipole modes, the novel pattern reconfigurable method is studied step by step using the surface current distribution. By controlling the feeding states of the monopole and dipole elements, a pattern reconfigurable Yagi antenna with four modes (omnidirectional, broadside, and two tilted patterns) is realized. The quasi-Yagi antenna, which exhibits a compact size of $0.511\lambda _{0} \times 0.244\lambda _{0} \times 0.005\lambda _{0}$ , is fabricated and measured for experimental verification. The measured −10 dB bandwidth of the four modes all basically covers the 5G-N78 band 3.3–3.8 GHz (14.1%). The measured peak radiation efficiency is greater than 80%. The proposed compact antenna, with the advantages of low-cost, simple design, good bandwidth, and radiation performance, and pattern/polarization reconfigurability, is well situated for 5G-NR communication.

29 citations

Journal ArticleDOI
30 Nov 2018-Sensors
TL;DR: A fair-access scheme to ensure that vehicles with different velocities successfully transmit the same amount of data by adaptively adjusting the minimum contention window of each vehicle according to its velocity is proposed.
Abstract: Platooning strategy is an important component of autonomous driving technology. Autonomous vehicles in platoons are often equipped with a variety of on-board sensors to detect the surrounding environment. The abundant data collected by autonomous vehicles in platoons can be transmitted to the infrastructure through vehicle-to-infrastructure (V2I) communications using the IEEE 802.11 distributed coordination function (DCF) mechanism and then uploaded to the cloud platform through the Internet. The cloud platform extracts useful information and then sends it back to the autonomous vehicles respectively. In this way, autonomous vehicles in platoons can detect emergency conditions and make a decision in time. The characteristics of platoons would cause a fair-access problem in the V2I communications, i.e., vehicles in the platoons moving on different lanes with different velocities would have different resident time within the infrastructure's coverage and thus successfully send different amounts of data to the infrastructure. In this case, the vehicles with different velocities will receive different amounts of useful information from the cloud. As a result, vehicles with a higher velocity are more likely to suffer from a traffic accident as compared to the vehicles with a lower velocity. Hence, this paper considers the fair-access problem and proposes a fair-access scheme to ensure that vehicles with different velocities successfully transmit the same amount of data by adaptively adjusting the minimum contention window of each vehicle according to its velocity. Moreover, the normalized throughput of the proposed scheme is derived. The validity of the fair-access scheme is demonstrated by simulation.

24 citations