Cellular Communication Concepts

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Cellular Communication Concepts

• CEC

Noise
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Contents

• Concept of Communication.
• Concept of a Cell.
• Frequency Reuse.
• Block Diagram Explanation.
• Hand Off.
• Roaming.
• Capacity Enhancement.

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Concept of Communication
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Concept of Communication
A ? B
A
Simplex or Duplex?
A ? B
B
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Concept of a Cell
Cluster A group of cells.
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Why Cellular Shape?
Spatial division into hexagonal cells, not
circles, Why cellular???
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GSM Network

• GSM - Global System for Mobile Communications.
• Idea developed at Bell Laboratories in 1970.
• Open and digital cellular technology to transmit
  voice and data.
• Uses 850 MHz, 900 MHz, 1800 MHz and 1900 MHz
  frequency bands.
• Different cell sizes macro, micro, pico, and
  umbrella.
• Each cell has it own frequencies (10 50).

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General Block Diagram
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Cellular Communication
Two way Duplex!
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Detailed Block Diagram
MS Mobile Station. BTS Base Transceiver
Station. BSC Base Station Controller. MSC
Mobile Switching Centre. VLR Visitor Location
Register. HLR Home Location Register. AUC
Authentication Centre. EIR Equipment Identity
Register.
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Block Functions

• Mobile Station (MS) A station in the cellular
  system intended for use while in motion, your
  mobile phone.
• Base Station (BTS and BSC) Fixed Station
  consisting of radio channels and transceiving
  antennas mounted on a tower located at the centre
  or on the edge of a coverage region.
• Mobile Switching Centre (MSC) Switching centre
  connects base stations and mobiles to public
  switched telephone network (PSTN), also called
  Mobile Telephone Switching Office (MTSO).

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Block Functions

• Mobile Switching Centre
• - responsible for routing voice calls and
  SMS.
• - sets up, releases end to end connection.
• - handles mobility, hand off requirements
• during the call.
• - real time prepaid account charging and
• monitoring.

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Block Functions

• Gateway MSC
• - determines which visited MSC subscriber
• being called is currently located.
• - routes calls to PSTN/mobiles.
• . Anchor MSC MSC from which hand off has been
  initiated.
• . Target MSC MSC to which handoff should take
  place.

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Block Functions

• Equipment Identity Register (EIR) maintains an
  account of all mobile equipments, each equipment
  identified by International Mobile Equipment
  Identity (IMEI) number.
• Location Registers Home Location Register (HLR)
  and Visitor Location Register (VLR) provides call
  routing and roaming capabilities.
• Authentication Centre (AUC) Identification and
  verification of SIM validity, ensures subscriber
  privacy by assigning a temporary mobile
  subscriber identity.

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Frequency Reuse
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Reuse to conserve bandwidth. No channel reuse in
a cluster.
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Frequency Reuse

• Communication within a cell at a given frequency.
• Same frequency for multiple conversations.
• Reuse of frequencies in non-adjacent cells.
• Minimum interference.
• Multiple frequencies per cell.

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Capacity Enhancement
Congested cell into smaller cells.
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Cell Splitting

• Subdividing a congested cell into smaller cells
  with each smaller cell having its own base
  station.
• Can be permanent or dynamic splitting.
• Cells to microcells and smaller.
• Utilizes allocated frequency spectrum in real
  time.
• Increase system capacity.
• Useful for capacity enhancement.

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Hand Off
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Hand Off
Make after Break
Make before Break
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Roaming

• A travelling cell phone to be connected to a
  network without breaking the connection.
• Ability to make and receive voice calls, send and
  receive data or access other services when
  travelling outside the geographical coverage area
  of the home network.
• Hop to another network if needed.

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Conclusions

• Integration of voice and data.
• Global coverage.
• Wireless!!!, need for physical copper eliminated.
• 2G, 3G, 4G, 5G, 6G..?
• CDMA has become extinct.
• New features every generation..

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References

• Aneesh P Thankachan, Basic Electronics
  Engineering, PHOENIX Book Publishers, 2017.
• Your standard reference text books
• Internet Sources.

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