CS_04: WMC- April 15 2023

What is the purpose of modeling the radio channel in wireless communication systems?

• A) To determine the number of users in a network

• B) To optimize the transmission rate of the transmitter

• C) To predict how radio signals will behave under different conditions

• D) To reduce the cost of wireless devices

Answer explanation

Explanation: Modeling the radio channel involves creating a mathematical or computational model that describes how radio signals will travel through a particular environment. By doing so, we can predict how the signal will behave under different conditions, such as varying the transmitter power or antenna height. This information can be used to optimize the performance of wireless communication systems by determining the coverage area, transmitter power requirements, and battery lifetime.

At which frequency bands do ground waves tend to be absorbed by the earth, leading to the use of sky wave propagation in long-distance communication?

• A. VLF, LF, and MF bands

• B. HF and VHF bands

• C. UHF and microwave bands

• D. All frequency bands

Answer explanation

HF and VHF bands. At high frequency (HF) and very high frequency (VHF) bands, ground waves tend to be absorbed by the earth due to the higher frequency of the waves, leading to the use of sky wave propagation in long-distance communication.

Match the following electromagnetic wave behaviors with their definitions:

• medium with small obstacles

• Reflection

• path obstructed by edges

• Diffraction

• wave hits large object

• Scattering

What is the Fresnel Reflection Coefficient (Γ)?

• A. A measure of how much of a radio wave is absorbed when it encounters a boundary between two materials ls

• B. A measure of how much of a radio wave is transmitted when it encounters a boundary between two materials

• C. A measure of how much of a radio wave is reflected when it encounters a boundary between two materials

Answer explanation

The Fresnel Reflection Coefficient (Γ) is a measure of the amount of light that is reflected off a surface when light strikes it at a certain angle. It is calculated by taking the ratio of the reflected light intensity to the incident light intensity. The coefficient is dependent on the angle of incidence, the refractive indices of the two materials, and the polarization of the light.

The ability of a material to store electric charges is determined by its​ ​ (a)   ​​ ​ The ability of a material to support the formation of a magnetic field is determined by its ​ (b)   The ability of a material to conduct electricity is determined by its​ (c)  

• permittivity
• permeability
• conductance

Answer explanation

The ability of a material to store electric charges is determined by its dielectric constant, which is a measure of the material's ability to resist the flow of electric current. The ability of a material to support the formation of a magnetic field is determined by its permeability, which is a measure of the material's ability to support the formation of a magnetic field. The ability of a material to conduct electricity is determined by its electrical conductivity, which is a measure of the material's ability to allow the flow of electric current.

What is the effective isotropic radiated power (EIRP) defined as ​ ​ ​ (a)   ​ ?

• PtGt
• Pt/Gt
• Pt-Gt