Direct modes line-of-sight [ edit ] Line-of-sight refers to radio waves which travel directly in a line from the transmitting antenna to the receiving antenna. It does not necessarily require a cleared sight path; at lower frequencies radio waves can pass through buildings, foliage and other obstructions. This is the most common propagation mode at VHF and above, and the only possible mode at microwave frequencies and above. This is the method used by cell phonescordless phoneswalkie-talkieswireless networkspoint-to-point microwave radio relay links, FM and television broadcasting and radar.
Download 4MB Preview Abstract This thesis investigates and analyses the performance of terrestrial free-space optical communication FSO system based on the phase shift keying pre-modulated subcarrier intensity modulation SIM. The results are theoretically and experimentally compared with the classical On-Off keying OOK modulated FSO system in the presence of atmospheric turbulence.
The performance analysis is based on the bit error rate BER and outage probability metrics. Optical signal traversing the atmospheric channel suffers attenuation due to scattering and absorption of the signal by aerosols, fog, atmospheric gases and precipitation.
The effect of atmospheric turbulence on the symbol detection of an OOK based terrestrial FSO system is presented analytically and experimentally verified. It was found that atmospheric turbulence induced channel fading will require the OOK threshold detector to have the knowledge of the channel fading strength and noise levels if the detection error is to be reduced to its barest minimum.
This poses a serious design difficulty that can be circumvented by employing phase shift keying PSK pre-modulated SIM. The results of the analysis and experiments showed that for a binary PSK-SIM based FSO system, the symbol detection threshold level does not require the knowledge of the channel fading strength or noise level.
As such, the threshold level is fixed at the zero mark in the presence or absence of atmospheric turbulence. Also for the full and seamless integration of FSO into the access network, a study of SIM-FSO performance becomes compelling because existing networks already contain subcarrier-like signals such as radio over fibre and cable television signals.
The intermodulation distortion can impose a BER floor of up to on the system error performance. In addition, spatial diversity and subcarrier delay diversity techniques are studied as means of ameliorating the effect of atmospheric turbulence on the error and outage performance of SIM-FSO systems.
The three spatial diversity linear combining techniques analysed are maximum ratio combining, equal gain combining and selection combining. The system performance based on each of these combining techniques is presented and compared under different strengths of atmospheric turbulence.
On the other hand, retransmitting the delayed copy of the data once on a different subcarrier frequency was found to result in a gain of up to 4.Type or paste a DOI name into the text box.
Click Go. Your browser will take you to a Web page (URL) associated with that DOI name. Send questions or comments to doi. CO-OFDM Elastic Optical Networks - Issues on Transmission, Routing, and Bandwidth Allocation by Bo Wang A thesis presented to the University of Waterloo in ful llment of the PON Passive optical network OLT Optical line terminal LTE Long-term evolution C-RAN Cloud radio access network.
This thesis investigates and analyses the performance of terrestrial free-space optical communication (FSO) system based on the phase shift keying pre-modulated subcarrier intensity modulation (SIM). The results are theoretically and experimentally compared with the classical On-Off keying (OOK) modulated FSO system in the presence of atmospheric turbulence.
(Click here for bottom) P p p, P Momentum. Utility of the concept of momentum, and the fact of its conservation (in toto for a closed system) were discovered by . Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another, or into various parts of the atmosphere.
As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. Understanding the effects of varying conditions on radio. resulted in a high-data-rate at lower cost in the last mile of wireless networks.
This paper investigates the use of the OFDM as a modulation technique for radio over fiber (RoF) in passive optical .