This presentation would clear your basic concept on cellular network/communication....although it is recommend to read about various multiplexing techniques as prerequisites....For further knowledge please read more from books. I hope its useful in someway.

1. Cellular Networks
Introduction, Cellular communication , concepts of frequency reuse, Architecture , etc
Presented By: Rahul Pandey
M Tech (CSE), MZU
Date: 26/03/2019

2. Principles of Cellular Networks
• Underlying technology for mobile phones, personal
communication systems, wireless networking etc.
• Developed for mobile radio telephone
-- Replace high power transmitter/receiver systems
Typical support for 25 channels over 80km
-- Use lower power, shorter range, more transmitters

3. Cellular Network Organization
• Multiple low power transmitters
-- 100w or less
• Areas divided into cells
-- Each with own antenna
-- Each with own range of frequencies
-- Served by base station
Transmitter, receiver, control unit
-- Adjacent cells on different frequencies to avoid
crosstalk

4. A Cellular Network
Mobile
Telephone
Switching
Centre
(MTSC)
Cell 1
Cell 2
HLR VLR
Public
Switched
Telephone
Network
HLR = Home Location Register
VLR = Visitor Location Register
Base Transceiver Station (BTS)
Mobile User
Cordless Connection

5. Cellular Geometries
a) Square Pattern b) Hexagonal Pattern

6. Frequency Reuse
• Power of base transceiver controlled
-- Allow communications within cell on given frequency
-- Limit escaping power to adjust cells
-- Allow re-use of frequencies in nearby cells
-- Use same frequency for multiple conversations
-- 10-50 frequencies per cell
E.g.
-- N cells all using same number of frequencies
-- K total number of frequencies used in systems
-- Each cell has K/N frequencies
-- Advanced Mobile Phone Service (AMPS) K=395, N=7
giving 57 frequencies per call on average

7. Frequency Reuse Patterns
(a) Frequency Reuse for N=4 (b) Frequency Reuse for N=7
Circle with Radius D

8. Frequency Reuse Patterns
(c) Frequency Reuse for N=19

9. Frequency reuse pattern

10. Frequency Reuse factor/ Channel Capacity
Assuming hexagonal shape cells of
equal size
D/R=q=√3N
where:
D: Distance between the center’s of cells
R: Radius of the cell
q: Reuse ratio
N: Cluster size
Channel Capacity
C = MKN where,
C = Capacity
M = No. of clusters
K = Allotted channel to cell
N = No. of cells in a cluster

11. Increasing Capacity(1)
• Add New Channels
-- Not all channels used to start with
• Frequency borrowing
-- Taken from adjacent cells by congested cells
-- Or assign frequencies dynamically
• Cell Splitting
-- Non-Uniform distribution of topography and traffic
-- Smaller cells in high use areas

12. What is Cell Splitting?

13. Cell Splitting Demystified..!
• Smaller Cells in high use areas
-- Original Cells 6.5 – 13 km
-- 1.5 km in general
-- More frequent handoffs
-- More base stations

14. Clearer Picture for Cell Splitting
• Every Cell will have its own tower
even though it exists inside another
Cell

15. Increasing Capacity(2)
• Cell Sectoring
-- Cell divided into wedged shaped sectors
-- 3-6 sectors per cell
-- Each with own channel set
-- Subset of cell’s channels
• Directional antennas
• Microcells
-- Move antennas from top of hills and large buildings to top of small buildings
and sides of large buildings
 Even lamp posts
-- Form microcells
-- Reduced power
-- Good for city streets, along roads and inside large buildings

16. Important Issues in Cellular Communication
• Frequency allocation
• Licenced
• Many providers
• Multiple Access
• Many users
• Wide area of coverage
• Traffic management
• Location management
• High mobility (in cars, trains)
• Multiple suppliers
• Handoff management, roaming

17. Multiple Access TechniquesFrequency
Frequency
Frequency
Time
Time
Time
Frequency Division
Multiple Access (FDMA)
1G Cellular (AMPS)
2G CDMA (IS –(%)
3G CDMA
Code Division Multiple
Access (CDMA)
Time Division Multiple Access
(TDMA)
2G TDMA
3G TDMA

18. 2G(voice) network architecture
G
PublicTelephone
Network
Base Tower Station (BTS)
Base Station Controller (BSC)
Mobile Switching Center
Mobile Subscriber
Gateway MSC

19. Operation Of Cellular Systems
• Base Station (BS) at center of each cell
-- Antenna, controller, transceivers
• Controller handles call process
-- Number of mobile units may be in use at a time
• BS connected to mobile telecommunications switching Centre (MTSC)
-- One MTSC serves multiple BS
-- MTSC to BS link by wire or wireless
• MTSC:
-- Connects call between mobile units and from mobile to
fixed telecommunication network
-- Assigns voice channel
-- Performs handoffs
-- Monitors calls (billing)

20. Channels
• Control channels
-- Setting up and maintaining calls
-- Establish relationship between mobile unit and nearest BS
• Traffic channels
-- Carry voice and data

21. Handling Mobility in Cellular Networks
 Home Network: network of cellular provider you subscribe to
(e.g., Airtel, BSNL, etc)
 Home Location Register (HLR): database in home network containing
permanent cell phone #, profile information (services, preferences,
billing), information about current location (could be another network)
 Visited network: network in which mobile currently resides
 Visitor Location Register (VLR): database with entry for each user
currently in network
 could be home network

22. Mobile
switching
center
GSM: indirect routing to mobile
HLR
VLR
Public Switched
Telephone
Network
Home network
Mobile
switching
center
1
3
2
4
Call routed to
home network
Correspondent
Visited network
Home MSC consults HLR, gets
roaming number of mobile in
visited network
Home MSC sets up 2nd leg of call to MSC in
visited network
MSC in visited network completes call through base
station to mobile

23. GSM: handoff with common MSC
Mobile
switching
center
Old BSS New BSS
Center
Old routing New routing
 VLR
2
1
3
4
5 6
7
8
1. Old BSS informs MSC of impending
handoff, provides list of 1* new BSSs
2. MSC sets up path (allocates resources) to
new BSS
3. New BSS allocates radio channel for use by
mobile
4. New BSS signals MSC, Old BSS: ready
5. Old BSS tells mobile: perform handoff to
new BSS
6. Mobile, new BSS signal to activate new
channel
7. Mobile signals via new BSS to MSC:
handoff complete. MSC reroutes call
8. MSC-old-BSS resources released

24. Thank You