Anna University Regulation 2013 Computer Science & Engineering (CSE) CS6003 ASN Notes for all 5 units are provided below. Download link for CSE 7th SEM CS6003 AdHoc & Sensor Networks Lecture Handwritten Notes is listed down for students to make perfect utilization and score maximum marks with our study materials.

Many methods have been tried out for this frequency allocation among multiple competing carriers, some of which are described below.
x Each carrier would submit a proposal to the government explaining how it intends to use the frequency bands.
x The government, represented by officials, would go through the different proposals and come to a conclusion on which carrier would serve the public interest best, and accordingly allocate frequencies to that carrier.
x However, this method was often found to lead to bribery, corruption, and nepotism. Hence, this method was abandoned.
2) x The lottery system, where a lottery would be held among the interested companies.
x But this method too had a serious problem
x Companies which had no real interest in using the spectrum could participate in the lottery and win a segment of the spectrum.
x They would later resell the spectrum to genuine carriers and make huge profits. So this system also had to go.
x The third method, which is still used today, is the auctioning method.
x The frequency bands would be auctioned off to the highest bidder.
x This method overcame all the problems associated with the previous two methods.
Radio waves generally experience the following three propagation mechanisms:
• When the propagating radio wave hits an object which is very large compared to its wavelength (such as the surface of the Earth, or tall buildings), the wave gets reflected by that object. Reflection causes a phase shift of 180 degrees between the incident and the reflected rays.
• Diffraction:

This propagation effect is undergone by a wave when it hits an impenetrable object. The wave bends at the edges of the object, thereby propagating in different directions. This phenomenon is termed as The dimensions of the object causing diffraction are comparable to the wavelength of the wave being diffracted. The bending causes the wave to reach places behind the object which generally cannot be reached by the line-of-sight transmission. The amount of diffraction is frequency-dependent, with the lower frequency waves diffracting more.
• When the wave travels through a medium, which contains many objects with dimensions small when compared to its wavelength, scattering occurs. The wave gets scattered into several weaker outgoing signals. In practice, objects such as street signs, lamp posts, and foliage cause scattering.
x Path loss can be expressed as the ratio of the power of the transmitted signal to the power of the same signal received by the receiver, on a given path. It is a function of the propagation distance.
x Path loss is dependent on a number of factors such as the radio frequency used and the nature of the terrain.
x Since several of these factors (in particular, the terrain) cannot be the same everywhere, a single model may not be enough.
x So, several models are required to describe the variety of transmission environments.
x There are two path loss model,
1. Free propagation model
2. Two ray model or two path model
The simplest path loss model in which there is a direct-path signal between the transmitter and the receiver, with no atmospheric attenuation or multi-path components.

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