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Questions and Answers
What defines the far-field or Fraunhofer region in radio propagation?
What is the primary cause of diffraction in radio propagation?
Which of the following statements about reflection in refraction is true?
What causes scattering in radio propagation?
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Which of the following best describes path loss?
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What is the first step in the telephone call procedure to a mobile user?
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Which message does the base station send to alert the mobile user during an incoming call?
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What information does a mobile send to the base station when originating a call?
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What is the role of the MSC after receiving a call from a mobile user?
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What action does the MSC take to facilitate a conversation after validating a mobile user's call?
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What does a station class mark (SCM) indicate when a mobile sends it to the base station?
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What service do all cellular systems provide that allows users to use their mobile phones outside their home network?
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During the call setup, how does the mobile user respond to the paging message from the base station?
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What happens when a mobile device enters a new geographic area outside its home service area?
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How does the Mobile Switching Center (MSC) handle unregistered mobiles?
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What is the formula to calculate light speed?
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Which frequency range corresponds to the Very Low Frequency (VLF) band?
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What characteristic of the Ultra High Frequency (UHF) band is notable?
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What distinguishes small-scale propagation models from large-scale models?
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What is the frequency of FM radio broadcasts?
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What range of frequencies does the Extremely Low Frequency (ELF) band cover?
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Study Notes
Cellular Process
- A telephone call to a mobile user is received at the MSC
- The MSC dispatches the call request to all base stations in the cellular system and a paging message with the mobile's identification number (MIN) and telephone number is broadcast over the FCC
- The mobile receives the paging message and responds by identifying itself on the reverse control channel
- After, the base station informs the MSC of the acknowledgment and the MSC instructs the base station to move the call to a voice channel within the cell
- The base station signals the mobile to change frequencies to an unused forward and reverse voice channel pair and transmits a data message to instruct the mobile to ring
Roaming
- Cellular systems provide a roaming service that allows subscribers to operate in service areas other than their home service area
- When roaming, mobile users are registered in the new service area
- The MSC polls for unregistered mobiles and mobiles respond with their MIN
- The MSC queries the mobile's home for billing information
- The MSC controls the call and bills the mobile's home
Speed, Wavelength, and Frequency
- Light speed is calculated by multiplying wavelength and frequency: 3 x 108 m/s = 300,000 km/s
- Radio frequency (RF) is used for cellular, FM radio, satellite and much more.
Radio Frequency Bands
- Extremely low frequency (ELF) is < 300 Hz
- Infra low frequency (ILF) is 300 Hz - 3 kHz and is part of the ground wave
- Very low frequency (VLF) is 3 kHz - 30 kHz
- Low frequency (LF) is 30 kHz - 300 kHz
- Medium frequency (MF) is 300 kHz - 3 MHz and is part of the ground/sky wave
- High frequency (HF) is 3 MHz - 30 MHz and is part of the sky wave
- Very high frequency (VHF) is 30 MHz - 300 MHz
- Ultra high frequency (UHF) is 300 MHz - 3 GHz and is part of the space wave
- Super high frequency (SHF) is 3 GHz - 30 GHz
- Extremely high frequency (EHF) is 30 GHz - 300 GHz
- Tremendously high frequency (THF) is 300 GHz - 3000 GHz
Radio Propagation Mechanisms
-
Refraction
- Propagation wave impinges on an object which is large as compared to the wavelength
- This happens when the wave intersects with conductors and dielectric materials
- Examples of objects include buildings, walls, the earth's surface
-
Diffraction
- Radio path between transmitter and receiver is obstructed by a surface with sharp, irregular edges
- Waves bend around the obstacle, even when LOS (line of sight) does not exist
-
Scattering
- Objects are smaller than the wavelength of the propagation wave
- Examples of objects include foliage, street signs, lamp posts
- Scattering from small objects causes the wave to be scattered in many directions.
Refraction (Continued)
- Perfect conductors reflect waves with no attenuation
- Dielectrics reflect a fraction of incident energy
- Grazing angles result in maximum reflection
- Steep angles result in maximum transmission
- Reflection induces a 180 phase shift
Free Space Propagation Model
- Assumes far-field (Fraunhofer region)
- d >> D and d >> , where
- D is the largest linear dimension of the antenna
- is the carrier wavelength
- d >> D and d >> , where
- No interference, no obstructions
- Effective isotropic radiated power (EIRP)
- Effective radiated power (ERP)
- Path loss
- Fraunhofer region/far field
Relating Power to Electric Field
- Power is proportional to the square of the electric field
- Power is also proportional to the square of the magnetic field
Antenna Model
- Example 4.3
- The gain of an antenna is a measure of how well it focuses power in a particular direction.
- It's important to consider the antenna model in free space propagation.
Large-scale Small-scale Propagation
- Different scales
- Large scale (averaged over meters)
- Small scale (order of wavelength)
- Different environmental characteristics
- Outdoor, indoor, land, sea, space, etc.
- Different application areas
- Macrocell (2km), microcell(500m), picocell
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Description
This quiz covers the essential steps of cellular communication processes, including how calls are dispatched and received in a cellular network. Additionally, it explores the concept of roaming, explaining how mobile users can operate outside their home service areas and how they interact with the Mobile Switching Center (MSC).
