A new approach for the assessment of hf channel availability under ionospheric disturbances

Download

index.pdf

Date

2006

Author

Sarı, Murat Özgür

Metadata

Show full item record

Item Usage Stats

152
views

66
downloads

High Frequency (3-30 MHz) (HF) Ionospheric Channel is used for military, civilian and amateur communications. By using Ionosphere, communication for distances beyond the line of sight is achieved. The main advantage of this type of communication is that it does not to require a satellite to communicate with a point beyond the line of sight. Actually the Ionosphere is used instead of a satellite. To use Ionosphere but not a satellite means independent communication for a country. The disadvantage of HF Ionospheric Communication is that the characteristics of the reflecting media (i.e. channel’s transfer function) depends on many variables, e.g. sun spot number, hour of the day, season, solar cycles etc., so that mathematically modeling the channel is very difficult. Since military standards like STANAG 4538, STANAG 4285, STANAG 4415, MIL-STD-188-110A and MIL-STD-188-141A define the required performance of an HF modem in terms of Signal to Noise Ratio (SNR), Doppler Spread and Delay Spread according to desired conditions, a new approach to characterize the channel in terms of these three parameters is presented. In this thesis, HF Channel is considered as a system which involves various physical and chemical processes. A new method to characterize the HF channel to be used for modem performance evaluation is presented. In this study, it is aimed to relate modem/channel availability with the magnetic indices, which may be considered as the disturbances to the system. For this purpose the data taken from an HF communication experiment is used to model the channel to be used for modem availability calculations. The aim of the study is to asses the HF Channel Availability under Ionospheric Disturbances. This new technique will be a useful tool for HF Modem operators to select the optimum data rate or modulation method during HF Communication.

Subject Keywords

Telecommunication (including telegraphy, telephone, radio, radar, television).

URI

http://etd.lib.metu.edu.tr/upload/12607686/index.pdf
https://hdl.handle.net/11511/16048

Collections

Graduate School of Natural and Applied Sciences, Thesis

Suggestions

OpenMETU
Core

Implementation of a digital signal synthesizer with high spurious free dynamic range Kılıç, Argun; Yılmaz, Ali Özgür; Department of Electrical and Electronics Engineering (2006) Today’s analog modulators and upconverters are inadequate to synthesize and modulate signals with high ‘Spurious Free Dynamic Range’ (SFDR). Thus, the main objective of this thesis is to design and implement a ‘Digital Signal Synthesizer’ (DSS) that is capable of synthesizing signals between 50-100 MHz with 60dB SFDR and to modulate them variable symbol rates and modulation techniques with very high phase/frequency resolution and switching speed while keeping the amplitude modulation occurring during a modu...
Range resolution improvement of fmcw radars Kurt, Sinan; Demir, Şimşek; Department of Electrical and Electronics Engineering (2007) Frequency Modulated Continuous Wave (FMCW) radar has wide application areas in both civil and military use. The range resolution is a critical concept for these FMCW radars as for the other radar types. There are theoretical restrictions in the range resolution. In addition, the non-ideal properties of the modules used in the systems negatively affects the range resolution. The transmitter leakage, non-linear frequency sweep, FM to AM distortion and measurement errors are some of the critical non-ideal prop...
Comparison of the intercarrier interference cancellation methods in OFDM systems Etiler, Burkay; Tuncer, Temel Engin; Department of Electrical and Electronics Engineering (2007) In OFDM systems carrier frequency offset is observed due to Doppler shift and transmitter-receiver frequency mismatches. This offset induces ICI (Intercarrier Interference). In this thesis, repeated data methods and pilot-aided carrier frequency offset(CFO) estimation methods and windowing techniques are used to mitigate the frequency offset problem and a performance comparison is made between these ICI cancellation techniques. Repeated data methods use only half of the bandwidth for information transmissio...
The feasibility, reliable communication and networking aspects of passive wireless sensor networks Yağlı, Mehmet; Baykal, Buyurman; Department of Electrical and Electronics Engineering (2006) The primary challenge in wireless sensor network (WSN) deployment is the limited network lifetime due to the finite-capacity batteries. In accordance with this challenge, the vast majority of research efforts thus far have focused on the development of energy-efficient communication and computing mechanisms for WSNs. In this thesis, a fundamentally different approach and hence completely new WSN paradigm, i.e., the Passive Wireless Sensor Network (PWSN), is introduced. The objective of PWSN is to eliminate ...
An investigation of jamming techniques through a radar receiver simulation Kırkpantur-Çadallı, Atiye Aslı; Koç, Seyit Sencer; Department of Electrical and Electronics Engineering (2007) In this study, various jamming techniques and their effects on detection and tracking performance have been investigated through a radar receiver simulation that models a search radar for target acquisition and single-target tracking radar during track operation. The radar is modeled as looking at airborne targets, and hence clutter is not considered. Customized algorithms have been developed for the detection of target azimuth angle, range and Doppler velocity within the modeled geometry and chosen radar p...

Citation Formats

M. Ö. Sarı, “A new approach for the assessment of hf channel availability under ionospheric disturbances,” M.S. - Master of Science, Middle East Technical University, 2006.