BY

1. Basic Electronics & Communication Engineering (21ELN14 / 24)
Mod 5 - Syllabus Copy
Text Book 3:
1

2. 2
Wireless Cellular Networks

3. Mobile Communication System
• In 1947, Bell Labs was the
first to propose a cellular
radio telephone network.
• InDecember
1947,
and
Douglas
William
H. Ring
Rae Young, Bell
Labs engineers, proposed
hexagonal cells for mobile
phones in vehicles.
William Rae Young
October 30, 1915 – March 7, 2008
3

4. 4
Cellular Telephone System
A cellular system comprises the following basic
components:
• Mobile Station (MS)
– This is the mobile handset.
• Cell
– A basic geographical unit of a cellular communication
system
• Base Station (BS)
– Each cell contain an antenna, which is controlled by a
small office.
• Mobile Switching Center (MSC)
– Each BS is controlled by a switching office, called
MSC.

5. Cellular Telephone System
Scheme diagram of a cellular telephone system
5

6. Cellular Concept
10
Cellular concept in wireless &
mobile networks
• Cellular concept was
proposed in 1970.
• Divide the coverage area
into number of smaller
areas called as cells.
• The groups of cells is
known as clusters.
• Frequencies used in one
cell cluster can be reused
in other cell clusters.

7. 7
Main features of cellular concept
• It employs variable low power transmitters.
• Cluster size is not fixed, it can be varied based
on the subscriber density & demand.
• Frequency reuse.
• Small cells will increase the network capacity.
Disadvantages:
• Co-channel interference (CCI)
• Increase in hardware cost as cluster size
increases.

8. Frequency Reuse
• Frequency reuse is the
core concept of cellular
system.
• Cells
with
alphabet use
the
same the
same
channel set.
• Reuse distance D is given
by: 𝐷 = 3𝑁 ∙ 𝑅
where, N = # of channel sets (in fig. N = 7)
R = Radius of a cell
8

9. 9
Reduction of Interference
• Reusing
differen
t
the
cells
same frequency
channel in is limited
by co-channel
interference (CCI).
• There are TWO ways to reduce this CCI:
– Sufficient distance between two co-channel cells.
– Use of directional antennas at the BS which is called
as cell sectoring.
• One more way is to avoid the assignment
of adjacent channels to the same cell.

10. 10
Transmitting involves the following steps:
1. A caller dials the 10-digit code (phone number)
& presses the send button.
2. The MS scans the band to select a free channel
& sends a strong signal to send the number
entered.
3. The BS communicates the number to the MSC.
4. The MSC in turn dispatches the request to all the
BS in the cellular system.
5. The Mobile Identification
broadcasted over all the
Number
(MIN)is forward
control
channels throughout the cellular system. It
is known as paging.

11. 11
6. The MS responds by identifying itself over
the reverse control channel.
7. The BS communicates the acknowledgement
sent by the mobile & informs the MSC about
the handshake.
8. The MSC then assigns a free voice channel to
the call.
And now the call is established.

12. 12
Receiving involves the following steps:
1. All the idle mobiles (MS) continuously listens to
the paging signal to detect messages directed at
them.
2. When a call is placed to a MS, a packet is sent to
the end user’s home MSC to find out where it is.
3. A packet is sent to the BS in its current cell, which
then sends a broadcast on the paging channel.
4. The called MS responds on the control channel.
5. In response, a voice channel is assigned and
Mobile (MS) starts ringing.

13. Mobility
Management
Handoff
Management
Location
Management
(Roaming
)
13

14. Mobility Management
• When an MS moves out of its current BS into another
BS, a procedure is performed to maintain service
continuity, known as Handoff management.
• The home agent keeps track of the current location of
MS. This procedure to keep track of the users current
location is referred to as Location Management.
14

15. Handoff Management
• Hard Handoff
– Break-before-Make
• Soft Handoff
– Make-before-Break
15

16. 16
Roaming
Two fundamental operations are associated with
location management:
1. Location update
• Done in association between the foreign agent & the
home agent.
• Home directory of the MS is updated with its current
location.
2. Paging
• When a home agent receives a message destined to
MS, it forwards the message via the foreign agent.

17. 17
Wireless Network Topologies
• Wireless network topology is defined as the
configuration in which a mobile terminal (MT)
communicates with other MTs.
• There are TWO types of topologies used in
wireless networks:
1. Ad – Hoc Network Topology
2. Infrastructure Network Topology

18. 18
Ad – Hoc Network Topology
• Ad-hoc wireless networks do not need
any infrastructure to work.
• Each node can communicate directly
with other nodes, so no Base Station is
necessary.
• Such networks are used by military services.

19. Ad – Hoc Network Topology
Single hop ad-hoc network Multi hop ad-hoc network
19

20. 20
Infrastructure Network Topology
• In this topology, there is a fixed infrastructure
that supports the communication between
the mobile terminals and between mobile &
fixed terminals.
• This topology is often designed for large
coverage areas.

21. Infrastructure Network Topology
21

22. 22

23. 23

24. 24
First Generation (1G) Technology
• 1G wireless networks used analog radio signals.
• 1G featured mobile radio telephones
& technologies such as:
– Mobile Telephone System (MTS)
– Advanced Mobile Telephone System (AMTS)
– Improved Mobile Telephone Service (IMTS)
– Push to Talk (PTT)
• 1G was designed for voice communication.
• One example is AMPS (Advanced Mobile Phone
System) used in North America. It was an analog
cellular phone system.

25. 31
Fig. (b) AMPS uses FDMA -
Frequency Division Multiple Access
Fig. (a) Frequency bands used in AMPS
system

26. 2G Technology
32
• 2G cellular telecom networks were
commercially launched on the GSM standard
in Finland in 1991.
• SMS service was made available.
• 2G can be divided into TWO standards based
on the type of multiplexing used.
2G Technologies
TDMA
(Time Division
Multiple Access)
CDMA
(Code Division
Multiple Access)

27. Three Major systems were evolved in 2G:
• IS – 136 (D – AMPS)
• IS – 95 (CDMA)
• Global System for Mobile (GSM)
D – AMPS uses both TDMA & FDMA medium access control techniques.
27

28. 28
Global System for Mobile (GSM)
Communications
• The first GSM system developed was GSM-
900 (Phase -1) – in 1990.
• It operated in 900 MHz band for voice only.
• Phase – 2 included facsimile, video &
data communication services – in 1995.
• GSM was the first totally digital
cellular telephone system.
• It solved the fragmentation problem which
inherent in 1G.

29. GSM System Architecture
GSM
Mobile Station
(MS)
Base Station
Subsystem (BSS)
Network &
Switching
Subsystem (NSS)
Operation &
Maintenance
Subsystem (OMSS)
29

30. GSM Architecture Diagram
ME – Mobile Equipment
BTS – Base Transceiver Station
BSC – Base Station Controller
MSC – Mobile Switching Center
30
HLR – Home Location Register
VLR – Visitor Location Register
EIR – Equipment Identity Register
AuC – Authentication Center

31. 31
3G Technology
• 3G systems support high speed packet switched
data (up to 2 Mbps).
• Smart phones are introduced.
• Two main 3G networks are:
– UMTS (Universal Mobile Telecommunication System)
– CDMA-2000
• Both these systems use CDMA technology.

32. CDMA Technology
• CDMA offers the following advantages:
• Error Control Coding
• Spreading of the spectrum
• Soft handoffs
• Strict power control
• Capacity of a Mobile Telecommunication System is given by
𝐶 = 𝐵 𝑙𝑜𝑔2(1 + 𝑆𝐼𝑁𝑅)
32

33. High Level Architecture of LTE
Evolution of the system architecture from GSM & UMTS to LTE 33

34. 34
4G Technology
• Long Term Evolution (LTE) is the brand
name 4th
given to the efforts of 3GPP
generation
technology.
• The high level requirements for a 4G technology
were identified as:
– High spectral efficiency
– Reduced cost per bit
– Increased services by increasing the efficiency
– Open interfaces
– Power efficiency
– Flexible usage of frequency bands

35. LTE – A System Architecture
35

36. LTE – A System Architecture

37. Evolution of Wireless Communication Technologies:
A quick summary
37

38. 38
Mobile Generations
• 1G – Analog transmission – 1981
• 2G – Digital transmission – 1992
• 3G – Multimedia transmission – 2001
• 4G – Mobile ultra-broadband transmission – 2012
• 5G – Internet-of-Things – 2020 / 2021
Future
• 6G – Integration with Satellite networks for global
coverage
• 7G – Space Roaming, Complete world will be
wireless

39. Wireless Local Area Network (WLAN)
• LAN is a way of connecting computers together within a
single organization, and usually in a single site.
• WLAN links two or more devices using a wireless
communication method.
• It usually provides a connection through an Access Point (AP) to the
wider internet.
39

40. 40
WLAN Specifications
• The IEEE 802.11 specifications were
developed specifically for WLANs by the IEEE.
• It includes the following 4 subsets:
 802.11 – operated in the 2.4 GHz range (1 to 2 Mbps)
 802.11a – operated in the 5 – 6 GHz range (6 Mbps,
12 Mbps or 24 Mbps)
 802.11b – also known as Wi-Fi, operates in
the 2.4 GHz range with up to 11 Mbps data rates.
 802.11g – operates in the 2.4 GHz range with
data rates as high as 54 Mbps over a limited
distance.