scholarly journals A Model of OFDM based Maritime VHF Communication System for Data Exchange

2018 ◽  
Vol 25 (2) ◽  
pp. 27-36
Author(s):  
Sanjin Valčić ◽  
Tibor Pogány ◽  
Zoran Mrak
Keyword(s):  
Communication System ◽  
Orthogonal Frequency Division Multiplexing ◽  
Data Exchange ◽  
Simulation Models ◽  
Automatic Identification ◽  
Very High Frequency ◽  
Ofdm Modulation ◽  
Data Rates ◽  
Validation Parameters ◽  
Very High

Abstract In the maritime Very High Frequency (VHF) band, there are no systems for transmitting large amounts of data. Therefore, it is necessary to develop new systems that would modernize the Global Maritime Distress and Safety System (GMDSS), significantly relieve the Automatic Identification System’s (AIS) communication channels, and set guidelines for the development of communication infrastructure of the e-Navigation. In line with this, analytical and simulation models of the maritime VHF data transmission communication system using Orthogonal Frequency Division Multiplexing (OFDM) modulation are worked out in this paper. The achieved data rate, the spectral efficiency and the bit error rate (BER) represent validation parameters on which the results of the analytical and simulation models are evaluated. It is concluded that the application of the digital OFDM modulation in the maritime VHF band may improve the GMDSS system by achieving higher data rates compared to the current terrestrial mandatory systems for data exchange, i.e. Digital Selective Calling (DSC) and AIS.

A collision feedback based multiple access control protocol for very high frequency data exchange system in E-navigation

2021 ◽  
pp. 1-16
Author(s):  
Xu Hu ◽  
Bin Lin ◽  
Ping Wang ◽  
Hongguang Lyu ◽  
Tie-Shan Li
Keyword(s):  
Access Control ◽  
High Frequency ◽  
Multiple Access ◽  
Data Exchange ◽  
High Frequency Data ◽  
Frequency Data ◽  
Exchange System ◽  
Very High Frequency ◽  
Time Division ◽  
Very High

Abstract The very high frequency data exchange system (VDES) is promising in promoting electronic navigation (E-navigation) and improving navigation safety. The multiple access control (MAC) protocol is crucial to the transmission performance of VDES. The self-organising time division multiple access (SOTDMA) protocol, as the only access mode given by current recommendations, leads to a high rate of transmission collisions in the traditional automatic identification system (AIS), especially with heavy traffic loads. This paper proposes a novel feedback based time division multiple access (FBTDMA) protocol to address the problems caused by SOTDMA, such that collision of transmissions can be avoided in information transmission among vessels. Simulation results demonstrate that the proposed FBTDMA outperforms the traditional SOTDMA in terms of channel utilisation and throughput, and significantly reduces the transmission collision rate. The study is expected to provide insights into VDES standardisation and E-navigation modernisation.

Performance Bounds for VDES R-mode

2019 ◽  
Vol 73 (1) ◽  
pp. 92-114 ◽  
Author(s):  
Jan Šafář ◽  
Alan Grant ◽  
Paul Williams ◽  
Nick Ward
Keyword(s):  
Data Exchange ◽  
Estimation Error ◽  
Additive White Gaussian Noise ◽  
Automatic Identification ◽  
Identification System ◽  
Performance Bounds ◽  
Radio Communication ◽  
Very High Frequency ◽  
Radio Communication System ◽  
The Impact

The Very High Frequency (VHF) Data Exchange System (VDES) is a new radio communication system being developed by the international maritime community, with the principal objectives to safeguard existing Automatic Identification System (AIS) core functions and enhance maritime communication applications, based on robust, efficient and secure data transmission with wider bandwidth than the AIS. VDES is also being considered as a potential component of the R-mode concept, where the same signals used for communication are also used for ranging, thus mitigating the impact of disruptions to satellite positioning services. This paper establishes statistical performance bounds on the ranging precision of VDES R-mode, assuming an additive white Gaussian noise propagation channel. Modified Cramér-Rao bounds on the pseudorange estimation error are provided for all waveforms currently proposed for use in terrestrial VDES communications. These are then used to estimate the maximum usable ranges for AIS/VDES R-mode stations. The results show that, under the assumed channel conditions, all of the new VDES waveforms provide better ranging performance than the AIS waveform, with the best performance being achieved using the 100 kHz bandwidth terrestrial VDE waveforms.

Symbol Timing Sequence Structure for OFDM-CDMA Communication System under Low SNR

2015 ◽  
Vol 713-715 ◽  
pp. 1188-1192
Author(s):  
Zhen Yu Zhang ◽  
Feng Chun Tian ◽  
Fan Xin Zeng ◽  
Li Jia Ge ◽  
Gui Xin Xuan
Keyword(s):  
Communication System ◽  
Orthogonal Frequency Division Multiplexing ◽  
Average Power ◽  
Timing Synchronization ◽  
Computer Search ◽  
Sequence Structure ◽  
Symbol Timing ◽  
Symbol Timing Synchronization ◽  
Ofdm Modulation ◽  
Code Division Multiple

Symbol synchronization offset of orthogonal frequency division multiplexing (OFDM) communication system will cause the rotation of data constellation at receiver even if such offset falls in the range of the appended cyclic prefix. When OFDM modulation is combined with spread spectrum technique, e.g., OFDM code division multiple access (OFDM-CDMA), the problem becomes more serious since OFDM-CDMA communication system generally works under very low signal-to-noise ratio. This paper focuses on symbol timing synchronization of OFDM-CDMA communication system and proposes an effective sequence structure on the basis of circular conjugate-symmetric properties of discrete Fourier transform. The proposed frequency-domain sequence not only can generate real time-domain signal to reduce calculation complexity, but also can resist peak-to-average power ratio of OFDM modulation by exploiting suitable computer search algorithm. The simulation results show a sharp cross-correlation peak can be obtained, which is quite helpful for accurate symbol timing synchronization of OFDM-CDMA communication system.

Review of antenna technologies for very high frequency Data Exchange Systems

2021 ◽  
Author(s):  
Victoria Gómez‐Guillamón Buendía ◽  
Salvatore Liberto ◽  
George Goussetis ◽  
Nelson J. G. Fonseca
Keyword(s):  
High Frequency ◽  
Data Exchange ◽  
High Frequency Data ◽  
Frequency Data ◽  
Very High Frequency ◽  
Very High

Experimental Investigation of very High Frequency Slot Antenna on M-60A-1 Tank

1977 ◽  
Author(s):  
D. V. Campbell ◽  
William Kennebeck ◽  
A. Zanella ◽  
Paul Sexton
Keyword(s):  
Experimental Investigation ◽  
High Frequency ◽  
Slot Antenna ◽  
Very High Frequency ◽  
Very High

Evaluation of the mechanical properties of Inconel 718 to SCM 440 dissimilar friction welding through real-time monitoring of the acoustic emission system

2021 ◽  
pp. 146442072199383
Author(s):  
Yu Sik Kong ◽  
Muralimohan Cheepu ◽  
Jin-Kyung Lee
Keyword(s):  
Acoustic Emission ◽  
Friction Welding ◽  
Inconel 718 ◽  
Low Voltage ◽  
Dissimilar Materials ◽  
Average Frequency ◽  
Very High Frequency ◽  
Cumulative Count ◽  
Emission System ◽  
Very High

Friction welding was chosen for its versatility in the joining of dissimilar materials with high quality. The aim of this study is to determine the optimal welding conditions for attaining quality joints by using online monitoring of acoustic emission system signals. During friction welding, the formation of cracks, defects, or any abnormalities in the joining process which have a detrimental effect on the joints quality was identified. The most widely used materials in the aerospace industry—Inconel 718 and molybdenum steel—were joined by friction welding. The precision of the joints, internal defects, and quality are major concerns for aerospace parts. The results of the present research determined the optimal welding conditions for high tensile strength by nondestructively inducing acoustic emission signals. During friction time and upset time periods, the typical waveforms and frequency spectrum of the acoustic emission signals were recorded, and their energy level, average frequency, cumulative count, and amplitude were analyzed. Both cumulative count and amplitude were found to be useful parameters for deriving the optimal welding conditions. In the initial stage of friction welding, a very high voltage of continuous form was generated with frequency characteristics of 0.44 MHz and 0.54 MHz. The signals generated during the upset stage had a low voltage, but a very high frequency of 1.56 MHz and 1.74 MHz with a burst-type signal. The amplitude of the signal generated for the optimally welded joints was about 100 dB at the friction time and about 45 dB at the upset time.

scholarly journals Measurement of Electrical Properties of Superconducting YBCO Thin Films in the VHF Range

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3360
Author(s):  
Yakir Dahan ◽  
Eldad Holdengreber ◽  
Elichai Glassner ◽  
Oz Sorkin ◽  
Shmuel E. Schacham ◽  
...  
Keyword(s):  
Thin Films ◽  
Theoretical Model ◽  
Quality Factor ◽  
High Frequency ◽  
Unit Length ◽  
Superconducting Thin Films ◽  
Electrical Parameters ◽  
Very High Frequency ◽  
Production Constraints ◽  
Very High

A new measurement technique of electrical parameters of superconducting thin films at the Very High Frequency (VHF) range is described, based on resonators with microstrip (MS) structures. The design of an optimal resonator was achieved, based on a thorough theoretical analysis, which is required for derivation of the exact configuration of the MS. A theoretical model is presented, from which an expression for the attenuation of a MS line can be derived. Accordingly, simulations were performed, and an optimal resonator for the VHF range was designed and implemented. Production constraints of YBa2Cu3O7 (YBCO) limited the diameter of the sapphire substrate to 3″. Therefore, a meander configuration was formed to fit the long λ/4 MS line on the wafer. By measuring the complex input reflection coefficients of a λ/4 resonator, we extracted the quality factor, which is mainly affected by the dielectric and conductor attenuations. The experimental results are well fitted by the theoretical model. The dielectric attenuation was calculated using the quasi-static analysis of the MS line. An identical copper resonator was produced and measured to compare the properties of the YBCO resonator in reference to the copper one. A quality factor of ~6·105 was calculated for the YBCO resonator, three orders of magnitude larger than that of the copper resonator. The attenuation per unit length of the YBCO layer was smaller by more than five orders of magnitude than that of the copper.

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